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Ask Dr Clark - Cement Industry Help Desk Cement company personnel, or anyone involved in the cement industry, are free to use this "Ask Dr Clark" facility. Dr Clark will do his best to answer those questions, calling on his more than 30 years of cement industry experience. Name: Email Address: Question: Previous Questions Question: We have thee kilns of same capacity (3000 TPD) Earliar we was using ptcoke (Sulpher -6.00 % )and getting 1.80 % in clinker but now we are using South afican coal (sulphe 0.80 % ) and getting .80 % in clinker. I want to now the impact on clinker properties i.e strength ,setting,grindability petcoke Vs South african coal . And how can i get more literature on this topic. Answer: There will be many affects on clinker properties. I expect that the nodulisation of the clinker will improve due to improved viscosity of the flux with lower SO3 content. The strength potential could also imporve as less CaO will be combined as CaSO4 and therefore be available for combination in the clinker minerals. In general petcoke is more difficult to grind than coal. Question: Dear Mr. Clark, What are the main causes of flushing of Kiln Feed in Kiln (Dry Process). Is the flushing is operational or material problem? Answer: Flushing can be both an operational and/or a material problem. Question: Dear Mr. Clark, What are the main causes of flushing of Kiln Feed in Kiln (Dry Process) Answer: Failure to combine the feed in the burning zone. This might be caused by variability of

the composition of delivery rate of the kiln feed, variation of the calorific value or delivery rate of the fuels to the kiln, or otherwise inadequate control of the kiln process. Question: What are the other reasons for declining in C.V of coal during grinding beside addition of dust coming with hot gas? Answer: Evaporation of volatiles during the drying of the coal in the grinding mill. Question: hello i have three question, many thanks for your answer before 1-which parameter(s) has(or have ) effect on liquid phase viscosity? 2-How can we calculate liquid phase viscosity? 3- what is the effect of liquid phase viscosity in cement production process? Answer: Clinker liquid phase viscosity is affected by the alumina modulus and the SO3 content of clinker. I am not aware of a calculation of a viscosity index. It is a qualitative consideration. Changes in clinker liquid phase viscosity will affect the tendency to form coating and also the nodulisation of the clinker. Question: As a consultant to government regulators, I note that some jurisdictions have established the same numerical emissions limits for particulate matter (PM)for the exhaust gas from kilns as the exhaust from clinker coolers when the latter are vented through a separate stack. Yet, when hot clinker cooler air is ducted to the raw mill of a in-line kiln/raw mill system and the combined gases exhaust through a common control device and stack, some jurisdictions adjust the PM limit allowing for the dilution by the clinker cooler air (i.e. this results in a higher PM emission limit value). The latter makes no sense to me. Your thoughts? Thank you. Answer: I've not come across this. However, most emission limits are quoted reference to a certain percentage of oxygen in the exhaust air to prevent reduction of the emission simply by dilution. As cooler exhaust is pure air then with a combined exhaust stack there is automatically a rise in the oxygen content. That would have to be allowed for. Question: For good quality clinker, how much the maximum size (in mm) of clinker. & How the colour defines the quality of clinker. Answer: Normally well nodulised clinker would be up to 20mm in size with not too many fines. Colour does not define the quality of clinker.

Question: Dear sir what r van der walls forces and where r these forces applying .thx sir Answer: Van der Waals forces are intermolecular forces so they are applying between molecules. They have no particular significance in the cement industry other than perhaps the tendency to cause agglomeration of powders. Question: Dear sir we r facing problams during last 20day our c5 cyln b side and its feed pipe chowke twoice we r using poultary waste and sugarcane mud as alternative fuel plz sir tell me whats reasons their r.thx sir Answer: That might be associated with the volatile content of the poultry waste or the sugarcane mud. But there is no reason why the problem should only be encountered in the B-side stage 5 cyclone. That needs on-site investigation. Question: DEAR SIR, PLEASE TELL ME THE RANGE OF So3 % FOR PPC & OPC CEMENT. REGARDS SPLAL JAGDAMBA CEMENT (NEPAL) Answer: Normally 2 to 3%. Question: Dear sir, our open circuit mill have three chember having capacity 250 mt per day. we want to know how much area of it should remain empty for suitable grinding/ out put. Regards splal Answer: Normally the volume filling of a cement mill is around 30%. Question: Dear sir, Thanks for ur reply.My open grinding cement mill is 250 TPD based on OPC but We are grinding ppc with this . Dear sir plz let me know regarding the max capacity of it in ppc. Warm Regards splal jagdamba cement Answer: That can't be answered without knowing more about the mill and the fineness of grinding of the OPC and the PPC. Question: What are the effects of NOX and SOX on kiln operation and also quality of product? Answer:

NOx and SOx don't themselves affect kiln operation or product quality. The formation of NOx and SOx can be caused by the cement kiln process and give rise to emission problems. Question: R/sir, if MgO conc.is high in lime stone than in what form it remains in clinker ( the limit of MgO is given 6% max. than if MgO exeed beyond this than what will happen. can we still use this cement) Answer: The MgO will be present as periclase in the clinker. This will potentially cause expansion and cracking of hardened concrete. Cement with MgO content greater than 6% cannot be used. Question: Dear sir, pls explaine reason for dioxin and furan emmission from cement plant. thank you Answer: This is a very rare occurence. I can arise from homogenous gas phase pyrolytic reactions of chlorinated organic compounds in the temperature range 200~800°C. Alternatively by De Novo synthesis which arises from the chlorination of non-chlorinated organic compounds by inorganic chloride compounds (HCl or NaCl) via a suitable transition metal catalyst (usually Cu). This can take place in the temperature range 200~450°C by heterogeneous reaction between combustion gases and particle surfaces. Question: respected sir, pls explaine.. where excess sulpher goes when using pet coke ..is this sulphur emmited in the form of SO2 and causing environment pollution Answer: No, it normally exits the kiln in the clinker either as alkali or calcium sulphate. Question: If the GYPSUM is heated above than 120 deg C then what are changes in Gypsum properties. Answer: The gypsum is dehydrated to hemihydrate and anyhdrite. These have different solubilities to gypsum and therefore the retardation of the cement setting is affected. Question: If the burner momemtum is very high,more than 10N/Mw then it will create any problem on kiln refractory.

Answer: No. Question: What are effects of high burner momemtum i.e around 2300 % m/s or 8.5 N/Mw. Answer: You should aim for a minimum of 10 N/MW to achieve good mixing of the fuel with the combustion air in the main burner flame. Question: what is the (return dust/kiln feed) ratio for Elex Filter in 3500 TPD FLS kiln with FIFEER VRM 350 TPH,in compound and direct mode? Answer: That depends on the collection efficiency of the top stage cyclones of the preheater. Typically 95% so around 15 tonnes per hour. Question: Dear Sir, In which temperature should gypsum dehydrates inside the mill and what is the maximum temperature to be maintained inside the mill? Answer: The rate of gypsum dehydration will become significant as the temperature in the mill rises above 80 degrees C. You should control the temperature to less than 120 degrees C. Question: Dear Dr. Clark, Thank you very for your support in advance, The plants using TDF as alternative fuel in preheater. Zinc present in TDF ,which retards setting time of cement. My question is 1: Maximum upper allowable limit of Zinc you will reccoment which will not distrub the setting time of cement? 2: Zinc Oxide only effect the setting time of cement or or it also effect other Properties ? Answer: The amounts of zinc added from the galvanising of the reinforcement of motor tyres will be insignificant. You should not expect any adverse affects on the physical properties of cement made from the clinker. Question: Dear Sir,I am just thinking to retain the residue of raw meal/Kilnfeed to 13% from 15% to see the change and improvement in the burnability. So, how to do that.Kindly, advice. Answer: By adjusting the separator of the raw mill.

Question: Respected Sir,If the alumina is more than the specified limit in the raw meal/kilnfeed, how can we minimise the content of same, so that it does not affect the quality. Answer: The only way is to use raw materials with lower alumina content. With correct proportioning of the kiln feed to lime saturation, silica modulus and alumina modulus targets the alumina content of the kiln feed will be controlled. Question: Dear Sir, One week back we start using pure sand as raw material to produce SRC after 3 days of operation red spot appear at 9.8 m n once we enter the kiln we found out that all previous coating has been washed out.Sand % was only 2 % and raw meal residue was 13 on 90 mic. Sand is the reason of coating wash out? Answer: Most probably. Question: what is theorticaly formula for secondary air calculation formula Answer: That relies on stoichiometric calculations from the elemental composition of the fuel. Question: What should be axial,radial,& stablize air. Answer: That depends on many things: (i) the capacity of the kiln, (ii) the amount of fuel delivered through the kiln main burner, (iii) the velocity of the primary air, (iv) the temperature of the primary air, etc. Question: Sir,thank you for reply my question to exceed MgO,if it is increased above 2% than remaing Mgo convert to pareclause after 2% Mgo and might be expension occur in cement.Can it possible to increase Mgo in clinker to change colour from gray to black as more mgo in cement also produced gray may I write sir. Please answer my question for which I am grateful to you. Regards .Iqbal Shaikh Answer: International standards limit MgO content of clinker to 5to 6%. There will be no problems of delayed expansion if the MgO content rises slightly above 2%. Increased MgO will not turn the cement black (nothing will), but it will darken the colour. Question: How to reduce coal consumption from 17.5% .kiln 54mts length,3.4 dia ,coal resdiue 212

& 90 micron as 3.5~4.0% & 20.0 ~22.0%,IM -5.8 TO 6.8%,COAL CALORIFIC VALUE AROUND 4910 Kcals.Clinkerproduction around 2650 ~2700 tpd coming ,coal mill o/l temp 58 ~ 63 deg maintaining ,hot air from cooler of 280 ~ 340 deg .please sugesst me how can we reduce to 15~ 16%. Answer: We need much more information to able to make such a suggestion. What is the excess oxygen in the preheater exhaust gases? What is the temperature of the preheater exhaust gas? What is the chemistry of the kiln feed? Question: Dear sir please let me know that what is the relation between residue & blaine value for ppc.And secondly what will be maintained value of these for ppc Thanking u sir Regards splal Answer: There is not a direct relationship between residue and Blaine. Both are related to particle size distribution so are indirectly related. Question: Dear sir i request u, please tell me the process/ methods in detail to find out blaine value of ppc. Thanks & Warm Regards splal Answer: Blaine is measured with an air permeability cell. These can be purchased from laboratory equipment suppliers. Question: Dear Dr.we are oprating a kiln 550tpd raw mix LSF-95+/- 2 SM-2.2+/-.1 AM 1.7+/-.1 but we are always facing ring formation in burning zone thats leading frequentstoppage of our kiln Dear DR, we are using natural gas for fuel Answer: There is no obvious reason that can be diagnosed on the basis of this information. Question: sir, what to do by the burner besides reducing kiln fuel when the kiln is about to melt or already have in melt condition of kiln feed ? Answer: You must reduce the fuel supply drastically. Question: sir, what should be the important actions w.r.t kiln operation that should be taken when the kiln shell temperature is very high or high above normal temp. ?

Answer: You can try the application of shell cooling fans to protect the kiln shell and try to build coating. If unsuccessful you will have to stop the kiln and repair the refractory lining. Question: dear sir, can you please give me the thumb rule of cooling air required in grate cooler ? Answer: About 1.8 kg/kg of clinker. Question: Dear Dr.we are oprating a kiln 550tpd raw mix LSF-95+/- 2 SM-2.2+/-.1 AM 1.7+/-.1 but we are always facing ring formation in burning zone thats leading frequentstoppage of our kiln Answer: There could be many reasons. But as you say the ring is in the burning zone I would suspect that the fuel is not being ground finely enough if you are firing the kiln with solid fuel. Question: We are using imported and local coal,with 22%ash,residue on 212&90micronaround 3.6&20.0 coming.IM 6.8% & CV 4910 coming. Kiln o/p sir,we are getting coal consumption 17.5%.kiln production,operating conditions normal.please send me how to reduce coal consumption. Answer: I presume the CV is kcal/kg? In which case the CV is low. I am not surprised that you need 17.5% of the kiln clinker output. Question: Dear Dr. Clark: We are considering to convert Raymond Coal Mill 923 into a raw mill. In this regard we seek your guidance that which of the parameters should be considered as the most critical to evaluate the technical viability. Thanks and Best Regards Answer: The potential output would be the main consideration. Raw meal requirements being much higher than fine coal requirements. Apart from that I know of mo technical reason why not. Question: What are all the factors that affect the setting time of OPC cement? Answer: Fineness of grinding. Gypsum addition rate. Gypsum dehydration in the cement mill. C3A content and reactivity.

Question: What happens if the % of Fe2O3 increases in OPC cement? Answer: There is more C4AF and less C3A present in the cement. Question: What happens if percentage of Al2O3 increases in OPC cement? Answer: There is more C3A present in the clinker and cement. Question: Sir, portland cement called gray portland cement because it has gray in colour of type1 which is natural colour,but now a days contractors like black in colour of same type with Fe2O3 content 3.0% to 3.5%.Sir kindly advise me how to improve its colour in black without changing chemistry. Iqbal Shaikh. Regards. Answer: Perhaps you need more MgO in the clinker. Question: what reason raw mill & cement mill chamber sample residue cheque in different sieve. Answer: Because cement is finer than raw meal. Question: In your opinion is possible to grind High Volatiles Content(ab. 52%)Coal, using a tubular ball mill and Electrostatic Precipitator? There is any relation between Blaine and Residue? It is possible to produce Fine Cement , with 4000cm2/ gram and residue 12% on 45 microns sieve? Please, I wait your opinion Thanks Answer: No, I would not favour that. There would be a danger of coal dust explosions in the electrostatic precipitator. Yes, there is a relationship between Blaine and residue. I see no reason why a 4000 Blaine cement could not have a 12% residue on a 45 micron sieve. This would be achieved by adjustment of the separator and the recirculating load. Question: cement temperature is high maximum 140c what effect in cement give me reson. Answer: The gypsum will be fully dehydated to anhydrite. This is likely to affect the setting and workability characteristics of the cement.

Question: Respected Sir, How to measure or calculate secondary air flow? Regards. Answer: It is difficult to measure. You need to calculate the combustion air requirements stoichiometrically to estimate the secondary air requirements. Question: sir, im chemical engineer and have experience of 2 year training at attock cement Pakistan my question is that how amount of air required to cool the clinker in grate cooler, can we calculate this by simple heat balance of cooler? or other parameters Answer: Yes, a mass and energy balance of the cooler is the way to do that. Question: Dear Sir, I wpuld like to know the fan capacities of our raw mill (Air swept ball mill double fan circuit).Mill effective dia 2.6m Circulating air fan(Separtator Fan) 69000 m3/hr @ 750mm wc, Bag filter fan 35000 m3/hr @ 250 mm wc, If I took velocity of air through mill is 2 m/sec, our air requirement will be 38232 m3/hr, I wanted to know how to determine the circulating air fan (Separator Fan) capacity, We have already 69000 m3/hr which is quite sufficient to handle bag filter, Shall we use single fan for the same Out put to reduce power consumption,Kindly give your feed back. Answer: This requires development of a mass and energy balance of the milling system to determine the actual volumes at different points. Then the application of fan equations to predict the fan capacity requirements. It is not something that can be done without a detailed understanding of the process. Question: Kindly explain mTBF & mtbr with example ???? Answer: Mean time between failure is the total operating time a period divided by the number of failures. I presume MTBR is the mean time between repairs. That would be the total operating time divided by the number of repairs. Question: Dear sir, what is KH and its relationship with LSF ? . Am just 1yr in cement industry and seeing KH for the first time. Answer: I've not seen it myself.

Question: Dear sir, At my Kiln plan, there is often got problem on Kiln Inlet (Draft), many articles said that it caused by alkali, actually what is the source of this alkali?, the fuel (coal) or from the raw material?, and what is the solving way to solve this problem recently....thanks so much before Answer: There will be alkalis and other volatile compounds in the feed and the fuel. These evaporate in the burning zone and recondense in the preheater building up into an "alkali" cycle between the rotary kiln and the preheater. These materials are sticky in the kiln inlet, causing build-up and loss of draft. The alkali cycle must be controlled by monitoring the alkalis in the hot meal and careful control of the temperature regime in the kiln. Question: dear sir how can we prove that kiln main drive current is the kiln torque or how can kiln torque is related with the kiln main drive amps waiting for your answer thanks Muhammad Arshad Answer: Torque is the moment or force required to rotate an object, i.e. in this case the kiln. The current drawn by an electric motor is a function of the force which must be ammplied to rotate of the machine being driven. In this case the kiln. As the weight of the kiln rises, i.e. with filling degree, so the resistance rises. Equally as the flux content of the material rises so the material adheres to the walls of the kiln and "climbs" with the rotation of the kiln. This means more force, or torque, must be applied compared with the material slipping in the bottom of the kiln. Question: dear sir, we have ball formation problem in our kiln from last two weaks.there is no variation in kiln feed.we also increase silica ratio in kiln but problem is no reactified.is any other problem instend of feed. Answer: What about the fuels used to fire the kiln? Are you using solid fuels? Is the fineness of the solid fuel constant? Question: Do I need to process the pyrolysis carbon black before can be used? It will have small quantities of steel, ash and maybe other impurities. V Answer: That depends on the other impurities. Small quantities of steel or ash should not cause any problems.

Question: Could carbon black from the pyrolysis of waste tyres/rubber be added to coal in the heating process of cement production? Or in any other way? It will be in powder form. Thank you for your time, Regard, V Answer: Yes, it can. Question: R/Sir, which material is suitable valconic pozzalan or granulated blast furnace slag ground with clinker in mill quality point of view and bulk usage if so why. Regards M.I.Shaikh Answer: Both are suitable supplementary cementitious materials. Question: Dear sir, What is the basic difference b/w inline and off-line calciner ? Answer: The fuel in a in-line calciner is burnt in the presence of the vitiated gas exiting the kiln, while in an off-line calciner the fuel is burnt in pure tertiary air. Question: Dear sir, what are the advantages and disadvantages of dynamic separator over static separator ? Answer: A dynamic separator will cut at a lower fineness than a static separator. Question: Dear Dr. Clark, in our kiln that burns natural gas, we have mainly found spurrite in the tertiary air duct coating samples. How could we explain that and how could we prevent it? In addition, in one of the samples-that was grayish-black-we have found a high TOC content(~6%) and no spurrrite. Any ideas about that? Thanks in advance, Dimitris Answer: This is strange. For spurrite to form there usually needs to be a mixture of uncalcined CaCO3 together with partially combined clinker. I can understand combined clinker being in the dust carried in the tertiary air, but not how uncalcined CaCO3 would be there? Unless there is some dropout of feed material entering the calciner into the tertiary air duct? The high TOC is even more strange unless some of the calciner fuel is dropping into the tertiary air duct? None of these things should happen as the air velocity through the tertiary air duct should be too high. Unless there is variable draft at some stages of the kiln operation?

Question: sir, what could be the possible effects of increase in residue in kiln coal besides the high fuel consumption ? (i mean on quality of clinker or anything else) Answer: Reducing burning conditions, heavy sulphur circulation, dusty clinker, ring and build-up formation, inhomogeneity in the clinker, etc. Question: Dear sir, Could you please tell me all the major or important reasons of hogh free lime in clinker ? Answer: There are many: (i) too high lime saturation of the kiln feed, (ii) insufficient temperature in the burning zone of the kiln, (iii) breakdown of calcium sulphate due to reducing burning conditions, etc. Question: what are the reasons for ring formation inside the kiln? and solutions for the same problem? Answer: I suggest you read my article in the October 2011 issue of International Cement Review. Question: what are the advantages of automatic fan control for cooling the kiln shell? what are the disadvantages of of manual control of the fans from a plant field panel? Answer: Automatic control linked to an infra-red shell scanner will give more reactive control and better kiln shell protection. Question: Dear Sir, please guide me, what is the acceptable criteria of water inj., cement mill? which is maximum limit as well as minimum limit? Answer: Water injection of up to 5% of the total mass flow into the mill should create no problems. Only maximum of 40% of the total should be injected into the first chamber. Question: Dear Sir, please explaine me,what is the reactions in the finall product(silo feeding cement)temperature is less than 90 celsius? Answer:

At 90 degrees celcius there is the possibility of continued gypsum dehydration in the silo and lump formation. Question: dear sir, what is the acceptable velocity in tube mill? which is designed for 75tph Answer: The air sweeping velocity over an end-discharge mill is normally limited to 2 m/s. Question: Resp.Sir.. Thank you For your kind answer. sir pls explaine which kind of cement mill is better , Ball mill type or Vertical mill and why so. Answer: A vertical roller mill will have a significantly lower unit electricity consumption. Question: Dear Sir, Normally, we maintain OPC blaine to 3500cm2/gm but of late blaine of same has rose to 4000 plus which is beyond control and despite cleaning slots inside the mill did not work. Please suggest how to get back to normal. Answer: The normal method would be to increase the feed rate to the mill or reduce the speed of the separator. Question: resp.sir. . .pls reply m . .is it possible that LSF in -ve value or zero. .and very high value. 3000- 5000 Answer: This is just maths. LSF cannot be zero as the %CaO, SiO2, Al2O3 or Fe2O3 cannot be zero. A pure limestone with high %CaO and low %SiO2, Al2O3 and Fe2O3 could have an LSF in the thousands. Question: is opc the type of hydraulic cement? Answer: Certainly ordinary Portland cement (OPC) is a type of hydraulic cement. It reacts with water. Question: dear sir Recently i joined a cement co as a ccr operator in production dept. Please guide me . Answer:

This forum can only answer specific questions. I suggest you enrol in CemNet Training, http://training.cemnet.com/, on-line training courses. Question: Dear sir, What are the effect/influence of clinker quality, process operation, and mechanical aspect for directly water contact on hot clinker? (if it installed/sprayed on section 1/2/3 of grate cooler)....by the way thanks a lot for your attention sir. Answer: That depends whether the water actually comes into contact with the clinker, in which case there will be some prehydration. Most likely the water is fully evaporated before reaching the clinker and is just used for evaporative cooling. If the evaporated water vapour enters the kiln then the overall thermal energy consumption of the kiln will rise. If it is drawn through the cooler exhaust then there should be no adverse affect on the process. Question: Dear Sir, What is the optimum size of clinker to maintain the temperature for Waste Heat Recovery (AQC Boiler)? Best regards Anwar Hussain Answer: There is no direct relationship between clinker particle size and waste heat recovery. the relationship is with the volume and temperature of the cooler excess air. That will be to some extent affected by clinker particle size distribution. Question: Dear Sir, The % Analysis of Kiln Feed: SiO2=13.940, Al2O3=3.672, Fe2O3=2.232, CaO=42.875, MgO=1.023, MA=1.660, MS=2.369, LSF=0.953 Residue on 90Micron sieve=13% We are using coal in PC and Main burner. Is it hard or soft material? Best regards, Anwar Hussain Answer: It is typical, neither hard nor soft, burning kiln feed. Question: We are experiencing high so2 values inside our rotary cement kiln which is fed by lepol grate system, is there anyway of reducing it Answer: High SO2 in the kiln suggests that you have reducing conditions at some point in the kiln. This will be associated with the fuels burnt in the kiln and the settings of the kiln main burner. Question: Dear Sir, Does the ASR happen only with aggregates or also with all types of reactive silica , for example Fly Ash? If ASR does not take place with fly ash then why? Does the

fineness of the fly ash have any role in avoiding / limiting ASR? Answer: Alkali silica reaction derives from reactive silica in aggregates. The silica in fly ash is pozzolanic and reacts with the calcium hydroxide from hydration of clinker to form additional hydrated calcium silicate. Question: Can we grind 100 % flyash in standerd ball mill which is design for OPC cement grinding which is design for 70 Tons FLS mill for 3200 blaine Answer: You can but why would you want to? Fly ash is normally already sufficiently fine and is delivered to the separator of the mill and passes straight to the finished product without ever going through the mill. Question: Sir,What is the role of Insoluable residue(IR)If is is mor than the limit prescribed in opc cement, can it be possible to affect the compressive strength, Regards. Answer: The insoluble residue has no role. It is inert material. That is why it is limited in international specifications. If it is higher than the allowed limit then it can reduce compressive strength due to dilution. Question: Dear Sir, we are using HFO for kiln firing, our raw meal LSF is 89-91 while clinker LSF is comming 93-96 How this is possible with OIL firing and also our bag house return dust LSF is only 75-80 and it is going to homo silo not mixing with kiln feed. Looking for your guidance Answer: That can only be explained if the baghouse dust is being mixed with the raw mill product before the sample is being taken. Question: Dear Dr Clark, Please, what is the meaning of 'curing time of the cement'? 2. What is the different between setting time and curing time? Answer: Curing time is the time required before the formwork can be removed from concrete, i.e. the length of time required for the concrete to develop enough strength to be selfsupporting. Setting time is the time required for concrete to stiffen and begin to develop strength. It is shorter than the curing time.

Question: Dear sir what is mean degree of atomization,whats ideal velocity of primry fan(kiln) Answer: The degree of atomisation is the fineness of the droplets of heavy fuel delivered into the kiln through the main burner. The ideal velocity of the primary air depends on the capacity of the kiln and the fuel consumption. Question: sir,what is the difference between vdz specification and iso specification of the refractory. which one is the best for kiln lining Answer: ISO are bigger than VDZ so heavier to install. Both have their advantages. Question: sir lime stone me high sio2 , high so3, high chloride , & high mgo ka Kya effect kiln mai hoga. Answer: The effect on the kiln will be to cause process, operational and product quality problems. Question: Sir cement mill chamber sample cheque in 45 micron, 90 micron , 212 micron what reson , And 45 micron sieve is main give me reson. Answer: Because the residues would be too high on 45 micron at the beginning of the mill chamber. The 45 micron residue is most important for the finished cement because it is the fine particles that develop the strength of the cement. Question: sir,i have two silly questions.(1)WHAT WILL HAPPEN IF WE ADD FLYASH INSIDE KILN OR COOLER OR AT DBC? WHAT IF WE ADD FLYASH ALONG WITH KILN FEED? o(2) WHAT WILL HAPPEN IF WE ADD LIMESTONE,IRON ORE AND KILN FEED ALL TOGETHER INSIDE PREHEATER PRECALCINER ROTARY KILN? Answer: These are not silly questions. What is DBC? (i) There are cement factories where fly ash is used as a component of the kiln feed instead of clay. The fly ash will act just as clay. (ii) There are also cement fatories that add raw material components at the precalciner. This is normally done to avoid emissions of SO2 or CO due to sulphides or organic materials in the raw material.

Question: Sir , what is the typical ratings of fans used in a cement mill like Raw mill ( Circulating fan , filter fan , Raw mill fan) , Pre heater fan , Clinker cooler fans, Primary air fan , clinker cooler exhaust fan, Coal mill filter fan , cement mill filter fan etc.. for a dry 5-6 stage cyclone PH with pre calciner , 5000 tpd clinker production plant ? Answer: That requires the calculation of a mass and energy balance for the whole process and then calculations using the volume of gases and the fan equations. Question: CAN YOU GIVE ME REASONS FOR CYCLONES JAMING IN CEMENT INDUSTRY Answer: There are many, but they are often associated with the recirculation of volatile materials between the rotary section of the kiln and the preheater. Question: please tell me exact % component of set point of iorn and silica to maintain lsf 106 Answer: There is not exact setpoint. That depends on the chemical composition of the raw materials being mixed to form the kiln feed and the targets for LSF, silica modulus and alumina modulus. Question: sir can you please explain the exact difference between clinkerization factor & raw meal to cliker ratio ? Answer: The raw meal to clinker factor (and I presume the clinkerisation factor) allow the amount of clinker to be produced from the raw meal to be calculated using the loss on ignition of the raw meal. The kiln feed to cliner factor also takes into consideration the dust losses from the kiln feed to the kiln. Question: Sir,gnetised water enhance strength. i used magnetised water for casting mortar cubes of opc cement.The compressive strength of 3 and 7 days dicreased by 3% against normal water the pH of normal water and megnetised was 7 and 7.8 respectively.why it has happen. regards. Answer: 3% is not a significant difference in my experience of physical testing.

Question: dear sir, Thank you for the answer about cement mill motor Kw (99% nominal Kw).I would say this motor Kw is unusual for our cement mill because in past 6 month with the mentioned process condition ,motor Kw was about 5000(+-100 kw) and before that kw was even less and we never saw kw>5200 for our mill in different condition. suddenly after changing 50% intermediate diaphragm liners(between chamber 1,2 which blocked and worn)and replacing mill vent fan impeller with new one ,motor Kw went up to 5390 kw(at the same time mill feed increased from 120t/h to 140t/h).according to fls instruction for our cement ball mill,in nominal condition with parameters defined for us(present parameters in mill),main motor kw must be 5000 and for at least recently 2 years (untill changing blocked diaphragm ...)our motor kw was so(5000kw).we want to know when mill charge and mill feed are constant why has Kw been increased about 300kw. Answer: You are saying that the mill feed went up from 120 t/h to 140 t/h so the mill feed is not constant. The greater throughput of the mill will mean more weight and the mill motor drawing more power. Question: we have 3.5% residue of Raw meal on 212 Micron. How to find what would be the % residue on 90 Micron. Answer: You need the residue at two different sieve sizes to be able to predict the residue at any sieve size using the osin ammler distribution. Question: Sir! Already discussed with you that we have the quenching facility at the outlet of the kiln,our burner pipe tip is just above this area, due to water showering in this area steam generates and damages the castable of the burner pipe tip from bottom with in 20-25 days and after that the burner pipe tip metallic plate started wearing, we have to change the whole tip area of the burner pipe after one and a half month,we have used High alumina castable, silicon carbide castable there at tip area but the life of the tip remains same. Your precious suggestions required for any improvement of the life of the burner pipe tip. Regards Answer: You could try steel fibres in the castable, but this sounds to be a very demanding application. Question: Sir! We are using Hunter scale apparatus for measuring the whiteness of the clinker and cement, the L value is the whiteness of the sample and the b value is the parameter showing how yellowish shade is there in the sample,normal B value for the white cement clinker is between +1 to +2. If it goes towards -ve then the sample has bluish shade.

Answer: This will be dependent on the trace elements in the clinker. Question: Dear Sir, Thank you for the answer,the C3S content 52~58% calculated by XRF, SM=2.25%, AM=1.6%,LSF=96.5% ,liq. phase 27% , free lime 1.45% but litre wt.1100 ~1150 (low) , how i can increase the litre wt.and improve the C3S , Also how i can decrease the dust ( S03 in clinker 0.6 , Total Alkali 0.7%),We added 0.3% SO3 in raw mix to control the Alkali(0.65% in raw mix) where S03 IN COOL is 0.3% also i have problem the shell temp increased to 395 °C FROM 320°C in kiln in 30 m ( kiln is 104 m), please advise Answer: XRF does not tell you anything about the actual C3S content of clinker. You need XRD for that. To increase the LSF calculated from the oxide analysis you need to increase the lime saturation factor and the silica modulus.What do you mean by COOL? Question: Dear Dr Clark, Please could you advice for the reason of a very dusty clinker in a wet process when adding more coal sludge. Sulfur are saturated by alklaine and the ratio is close to 1. The free lime is around 1.2 to 1.5 as usual. Could it be related to the Oxygen level in the kiln, around 1. 2 to 1.5% ? Thanks for yoru answer, Best regards, Sylvie G. Answer: Certainly it could be associated with the coal sludge and the low excess oxygen content in the kiln if either is impairing the combustion in the main burner flame. Question: Dear sir,we have cement ball mill 2 chambers, nominal capacity=145t/h(ums50*14 fls company).liners condition and charge percent in both chambers are ok. we are working with following parameters :feed=140,separator reject=170,inlet and outlet press=-1,-8 mbar but motor Kw is high(99% rated Kw ,0.99*5450=5390Kw).can it be a process problem and how can we decrease Kw by changing process parameters? Answer: Why is that a problem? It is normal for a mill main motor to draw it's nominal power if it is charged to capacity with grinding media. Question: Daer Sir, Thanks for your prompt reply. Now advise us how can we increase 1 day and 28 day strength of cement with same quality of clinker and how can we reduse residue ? By applying grinding pressure or by increasing RPM of classifier ? Answer: Increasing the speed of the classifier.

Question: Dear Sir, While reply to my question you mentioned the term "False Surface".Would you please elaborate the meaning false surface and how it is generated in the mill as ours is VRM. Answer: The prehydrated calcium silicate and calcium hydroxide in the clinker will provide a very high surface are in any type of mill, be it a ball mill or a VRM. The actual clinker will remain coarse resulting the high residues. The prehydrated clinker is giving the "false" impression that the cement has been ground finely enough, when in fact it has not. Question: SIR EXPLAIN CONTROL THE C3S BY PRIMARY AIR AND GRATE COOLER ALSO HOW TO INCREASE THE LITRE WT. OF THE CLINKER AND DECREASE THE DUSTY INSIDE THE KLIN Answer: The first step is to monitor the actual C3S content of the clinker. How are you doing that? By X-ray diffraction or microscopy? The temperature profile in the kiln is critical for controlling the C3S mineral form. This is adjusted by the main burner flame, which is turn is adjusted by the primary air and the recuperation of energy to the secondary air in the cooler. A dusty kiln can have many causes. Excess sulphur circulation caused by the main burner flame can be one of those causes. Question: Sir! Our experiment to fire carbon black in our white kiln is successful, Thanks to God & after that our seniors especially our GM (Works) & DGM (Process) who has guided & motivated the white plant team to make the process successful. Thanks you also for making you available for everybody in this profession. We are getting enough whiteness for clinker to make the production acceptable under production targets. Sir can you explain the B value of clinker & the parameters effecting B value? What would be the side effects of high B values? Regards Answer: Good news Wahab and thank you. Please explain what you mean by "B value of clinker"? Question: Dear Sir, we are a grinding unit and in rainy season we receive some what wet clinker from our main plant.What impact the wet clinker will put on our quality ? Does in wet clinker chemical composition remains the same and only physical properties is affected ? Will it increase the redidue on 45 and 90 micron seive ? Answer: The wet clinker will reduce the quality of the cement you produce due to partial prehydration of the clinker. Chemical composition will remain the same but the mineral

composition will change with some hydrated calcium silicate and calcium hydroxide being present. It is very likely to increase the residue of the ground cement because "false surface" will be generated in the cement mill. Question: Earlier we were maintaining the blaine 380 m2/kg and residue on 45 micron was 12 14%. Now we are maintaining the blaine 400 or 410 m2/kg ,but the residue on 45 micron is 20 to 25%. How is it possible when we are grinding more but the residue is more. Is it possible that if baline is incresed residue also increases ? Kindly give your comments. Answer: It is possible. My suspicion is that the clinker is partially prehydrated and that that is causing some "false surface" to be generated in the mill. You should control the mill to residue targets rather than Blaine. Question: Dear Dr. Clark please advice me about the formula to be use to calculate the electrical power saving when increasing the amount of additives from 5 to 25% Regards Sayed Answer: Dear Sayed, The electricity consumed in manufacturing clinker is diluted by the amount of additives ground with the clinker in the cement mill. So the formula is: kWh/t cement = kWh/t cement milling + kWh/t clinker x (1 - %additives) However, there are many other considerations. Will the cement be ground to exactly the same fineness with 25% additives compared with 5% additives? Question: Blaine relationship with KWh in the cement mill?( graph or table) Answer: There will be a direct relationship with kWh/t of cement rising with Blaine. But there are other variables such as the type of mill, the grindability of the clinker and the recipe of the cement. A graph or table cannot be produced without more information. Question: Dear Sir, We have 5 stage preheater, the velocity in the Cyclone inlet & outlet are in the range of 18-22 m/s, where as the Twin cyclone inlet raiser duct velocity is around 7 m/s because of higher duct area. Is it the cause of excess dust generation in PH fan, high power consumption in PH fan & low pressure developed by the fan?. Shall we reduce the size of the duct to match 18 m/s? Answer: I need to know more about the design of the preheater. Is it a Polysius Dopol preheater? I doubt that low gas velocity in a riser duct can cause the problems you describe with the preheater fan.

Question: Dear Dr. Clark. INTRODUCTION. We have two cement mills dim 4,2x14,5m. Cement cooling is with water injection is into 2nd chamber and with fresh air in separator circuit. Set point of water injection is at 105°C. What means diction: ''The water vapor-dew point temperature in the mill air must not exceed about 70°C, otherwise cement quality will be affected above this level''? For cement stored in small steel and concrete silos additive Iron-II Sulphate (always monohydrate) is added between the mill and classifier. Metering point of chromate reducer for cement stored in three big silos from concrete is before cement loading. QUESTION: In last two years in cement storage silos increased problems with worse cement discharging and lump formation. As you can read above monohydrate is not in all cases mixed with cement in storage silos. What could be the reason for problems in silos? Maybe water injection, moisture from air for aeration and cement cooling, monohydrate, clinker property or combination. We still haven’t bypass kiln dust extraction. With best regards Boris Benedejcic Answer: I doubt that the ferrous sulphate monohydrate is the cause of the problems. All clinker contains some alkalis and those can react with moist air forming syngenite which causes flow problems with the cement. The dew point of the air is the temperature at which condensation of evaporated water from the air will take place. That depends on the amount of water injection in the mills and the volume of air sweeping the mills. Do you know those quantities? It is also an important consideration for the type of dust filter fitted to the mills. Is this a baghouse or an electrostatic precipitator? Most likely the problem is caused by the high storage temperature of the cement and the incomplete dehydration of the gypsum ground in the cement with the clinker in the cement mills. This will cause the gypsum to continue to dehydrate in the silos. At the walls of the silos the dehydrated water will condense reacting with the cement and forming lumps. There are two potential solutions: (i) cement should be cooled to less than 65°C before storing in the silos, or (ii) the calcium sulphate added to the mill for setting control should be in the hemihydrate form rather than as gypsum. Question: pl. help me out from material having mgo, alkalies(Alkali Expansion) but need strength give the suggetion on use of coal firing in kiln & maitaining litr. wt. of clk Answer: MgO content of cement is limited by international specifications to avoid unsoundness in concrete made from the cement. You must select raw materials that will limit the MgO content to below these specifications. There is no such phenomena as "alkali expansion". There is an alkali-aggregate reaction but that is not expansion. Many cement kilns are fired with coal. The technology is well documented. Maintaining litre weight is achieved by consistent kiln operation and combination of the clinker. Question: Dear Sir, Thank you for the answer. In continuation of the earlier question, How do we reverse the affect of high Alkali sulfates and high C3A (Al2O3)in the clinker. Due to this,

the gain in compressive strength over a period of 3,7 & 28 days is less. Answer: The only way to change these fundamental aspects of the chemistry of your clinker is to change the raw materials so that there are less alkalis, sulphate and alumina in the clinker. This clinker with its high early reactivity should be ideal for producing blended cements with pozzolanic additions such as fly ash. Question: Sir Please explain details and difference between following(in kiln or pyro section) 1. False air 2. Cooling air 3. Dosing air 4. Primary air 5. Secondary air 6. Tertiary air with respect to their source of generation, location , purpose of use, quantity, necessity and temperature. Answer: False air is ambient air being drawn into the process through gaps in seals, etc. Cooling air is ambient air blown or drawn into the cooler to cooling the clinker. Dosing air is the ambient air used to transport solid fuels or sometimes kiln feed into the process. Primary air is ambient air blown into the kiln through the main burner with the fuel. Secondary air is preheated cooling air drawn into the kiln from the cooler. Tertiary air is preheated cooling air drawn into the precalciner from the cooler via the tertiary air duct. Question: sir main reason of boulder formation in kiln. Answer: The main reasons are high sulphur recirculation in the kiln, variations in the flux content and properties or misadjustment of the kiln main burner. Without knowing more information it is impossible to say which one applies in your case. Question: respected sir, where High Pressure cyclones are used and where Low Pressure cyclones are used ?, please tell me. Answer: Low pressure drop cyclones are used in preheaters to reduce the resistance to drawing the exhaust gas out of the kiln. Question: respested sir, what are the basic differences between High Presuure and Low Pressure cyclones ? Answer: The pressure drop across the cyclones due to the dimensions and geometry of the gas inlets and outlets.

Question: Does wet process kiln possess any advantage as regards quality and cost effectiveness over a dry process kiln?? Answer: Some minor advantages: lower alkali content of clinker; lower electricity consumption in grinding. But these are far outweighed by the disadvantage of the higher kiln fuel consumption. Question: Sir,how much air requried for combustionof coal in clinker burning in normal cubic meter per kilogram of clinker and its calculation for refrence. Regards Answer: About 1 Nm3/kg clinker. The calculation relies on stoichiometry. Question: Dear Dr. Clark. We have a high sulfur load in our kiln. The hot meal SO3 is at 1.5%. This resulted in dusty kiln & high free lime. By increasing the A/F ratio to 1.6, we have reduced the effect of sulfur, with good nodulization. What could be the reason? Has liquid viscosity any role in it? Answer: For sure liquid viscosity has a major role to play. Calcium sulphate melt reduces the viscosity and surface tension of the flux leading to smaller particle size distribution and high dust content in the clinker. Increasing the A/F increases the viscosity so combating the effect of the high SO3 in the flux. The high free lime is caused by late breakdown of CaSO4 to CaO and SO2. Question: Dear Sir,Thanks for your reply.Now I want to ask another question.We are a grinding unit and receive clinker from our mother integrated plant. The problem is that when we test clinker for 1 day or 28 days strength, the results are lower than the PPC made from the same clinker with 25% addition of Fly Ash. Is it possible that the strength of 28 days is lower than the PPC?If yes then why and if not then what could be the possible mistakes we are committing? Answer: It is possible that the early reactivity of the cement due to the high coontent of alkali sulphate is activating the pozzolanic reaction of the fly ash in the PPC and boosting the 28-day strength of the PPC. Particularly if the fly ash is a high calcium fly ash. Question: Sir, we are using magnetite as Iron input in raw mix for our kiln. Is it that reactivity of magnetite is poor compare to hematite? If magnetite is used (used in % 1.0), what will be the effect in kiln. As tested magnetite contains Fe2O3 above 88%.

Answer: I am not aware of any difference between the reactivity of magnetite and hematite. Question: With respected Sir, I have a question for you, about saving electricity and energy consumption in cement plant, especial cooler fans. In my cement plant, I don’t know why they used damper for adjusting the flow rate into cooler chambers, maybe the cheaper costs than inverters. And I don’t know if I want to retrofit them by replacing inverters for dampers(which used to use specific for pumps such as ABB inverters ACS550, ACS310…) If have a similar project in some cement plants you know, pls share me some pros and cons or any your experiment about that.Or the procedure of this project, now I just think and did something, such as collect electrical consumption of fans in three months with highest capacity of kiln... Pls give me some advices about replacing inverter for damper… Answer: Certainly there will be electricity savings by replacement of damper controlled cooler fans with variable speed drives. I suggest you contact Urban Scheupp, [email protected]. Question: Question: Dear sir, We have 2 FLS Kilns- 5000 TPD each.The burner used is douflex burner(Oil fired).The maxm brick life here is only 3 months. The coating is unstable & the brick always gets damaged only between 10-13 m area (that to only 3-4 lines). The increase in retraction (inner pipe movement)& free silica problem was sorted out which showed some improvement. What could be the major reason?. Burner is kept 400 mm inside from the kiln tip, aligned in the centre of kiln c/s. Answer: It is unusual to have such a localised refractory lining problem. The mechanical situation regarding the shells of the kilns needs to be considered. Where does the problem area lie in relation to the riding tyres? Sir, Both are new kilns, one year & five year old. Shell is perfectly alright. Answer: Why do you say the shell is perfectly alright? Do you know the stiffness of the shell? Do you know the magnitude of the deflection forces acting on the shell at all points along the shell? Question: Give standard heat balance data for 1700tpd and 2500 tpd cement kiln with SLC Answer: Whitehopleman can provide such a service, but there would be a charge made. Question: When we analyse cement for prticle size distribution by using Particle size Distributor Analyser, the results is appx.30% but by doing wet seiving it is 20%.Why?

Answer: The wet sieving causes some reaction with the cement affecting the residue. Question: Thanks Dr clark,can u please give me the average cost of a wet kiln drive that has a capacity of 400000tonnes/yr....and what is the density of LPFO at room temperature? Answer: Whitehopleman does not supply drives for wet kilns. I suggest you contact rban Scheupp, [email protected]. Question: Does carbon black give same heating ( temperature ) in cement plant instead of coal and gas? Answer: Certainly carbon black will burn in a cement kiln relaesing thermal energy. Question: Dear Sir, Thanking you for the answer. Our initial compressive strength is good but the gain over the remaining periods is not appreciable. Our clinker SO3 is 1% & total alkalis at about 1.5%. We are maintaining the cement SO3 at 2.6%. What could be the reason for less gain in compressive strength? Answer: It is a well known phenomena that high alkali sulphate content in cement promotes early strength but means that strength growth to later ages is reduced. The soluble alkali causes the hydration of the cement clinker minerals to be speeded up, but there is no increase in ultimate strength. Question: Dear sir, In recently days we have clinker ball formation in our kiln so there are two or three times a day. Those clinker ball have about 1 to 1.5 m diameter.Sometimes in these days, material leakage from kiln inlet has been seen.It's interesting,that event cause just after refractory maintenance.The pile that has used before and after maintenance was the same. Thank you. Answer: Both sound to be symptoms of heavy sulphur cycling in the kiln. What is the sulphur input levels in feed and fuel, output in clinker and sulphate content in hot meal? It is interesting that this has arisen just after refractory maintenance. The new refractory lining will be retaining more heat within the kiln therefore the internal wall temperatures will have changed.

Question: what is the use of carbon black in cement plant? which type of carbon black is used in cement plant? Answer: There is no use of carbon black in a cement plant to my knowledge. Residues from carbon black manufacture could be used as an alternative fuel. Question: Is there any realtionship between dusty clinker and the degree of calcination. In addition please describe how the dust retured of a grate cooler impedes on flame shape. Thanks in advance Answer: There might be some indirect relationship between dusty clinker and degree of calcination but more likely they are both symptoms of some other underlying process problem. Dust returned from the grate cooler in the secondary air can affect the efficiency of mixing of that air into the flame therefore impeding the flame shape. The dust will also need to be reheated which will absorb some energy from the flame. Question: Hello,whats qty of Lpfo will give the same energy output as a litre of natural gas?? Answer: A litre of natural gas is not very much natural gas. The LPFO equivalent would be 0.8 to 0.9 millilitres. Question: Please,whats the energy content of LPFO Answer: Typically 40,000 MJ/t of LPFO, net. Question: Dear sir plz tell me why some time kiln back come out with great velocity and kiln &cooler chamney remain very dusty about 20 to 30 minute.thx sir Answer: I'm sorry I don't really understand this. The kiln back come out with great velocity? The kiln and cooler chimneys remaining very dusty implies that the process is disturbed and the dust filters are not doing their job. Question: Dear sir plz tell what is differential pressure &how it works in raw mill operation.thx sir. Answer:

The differential pressure is the gas pressure at the outlet of the mill minus the gas pressure at the inlet of the mill. As the load of material in the mill rises the pressure differential will rise. Therefore the differential pressure across the mill is a measure of the loading on the mill. Question: Dear sir, We have 2 FLS Kilns- 5000 TPD each.The burner used is douflex burner(Oil fired).The maxm brick life here is only 3 months. The coating is unstable & the brick always gets damaged only between 10-13 m area (that to only 3-4 lines). The increase in retraction (inner pipe movement)& free silica problem was sorted out which showed some improvement. What could be the major reason?. Burner is kept 400 mm inside from the kiln tip, aligned in the centre of kiln c/s. Answer: It is unusual to have such a localised refractory lining problem. The mechanical situation regarding the shells of the kilns needs to be considered. Where does the problem area lie in relation to the riding tyres? Question: Dear Sir, Our kiln feed has a residue of 3 to 6% with sandstone as one of the additives for silica. We are balancing hot meal molar ratio where the SO3 & chloride are about 1.5% & 1.2% respectively.The kiln feed chloride is 0.15% max with bypass system. The clinker SM is 2.5, AM is 1.6 with 5.8% Al2O3, 3.5% Fe2O3 & SO3 at about 1.0%. LSF is 0.90 to 0.93. What would be the role of increased Al & low Fe in clinker on the early compressive strength of cement & possible deterioration of concrete? What should be done to increase 1 day strength? Also what should be done for stable liter weight & free lime. Regards, Ajay Trivedi Answer: Increased alumina content and lower iron oxide content will have virtually no affect on early compressive strength. Higher alumina content impies higer C3A content and therefore more susceptibility to sulphate attack on concrete, but this should not be a problem except in acid ground waters. Increasing 1-day strength can be achieved by finer grinding, increased silica modulus, real clinker mineralogy control or fluoride mineralisation of the clinker. Question: Sir, what is the max; percentage of sulphur cycle(sulphatisation of alkalies)for the un interepted operation ofkiln, and at what percentage the sulphur ring formed in kiln and or buildup in preheater Answer: The rule of thumb is that the alkali:sulphate ratio should be between 0.8 and 1.2. You cannot state a %sulphur that will cause rings or build-up in the preheater because it depends on many factors. Mosst important is to avoid reducing burning conditions at any point in the kiln.

Question: dear sir,we have douflex burner and inside the kiln in length of 7-22m we have stable coating .some times part of brick liner in the length of 24-25m became week(decrease on brick thickness) and we want to protect this zone by creating coating on it and keep the kiln running further(increasing kiln refractory lifetime).what is your suggestion to increase length of coating(about 2-3 m)? Answer: I suggest pushing the burner into the kiln by 0.25m. You should do this in small steps and carefully observe the effects on the kiln and clinker. Question: cause of snowman formation in cement kiln Answer: Snowmen are caused by the presence of some liquid phases in the clinker entering the cooler from the kiln. In part they are a consequence of the higher secondary air temperature achieved by modern grate coolers. ou can try to combat these by adjusting the kiln burner to create a cooling zone within the kiln and reduce the dust content of the clinker. Question: Dear Sir, In a previous question I have briefed about our raw mill, Dia 2.8x7.32L,Our feed size on -10mm sieve is 50-60% & -15mm sieve is 70-80%, and also we are feeding 5-10% on +20 to 25mm, we don't have secondary crusher arrangement. Our separator return residue is 25-40% on 212 mic & 50-60% on 90 mic,Product residue is also higher 18-20% on 90 mic, Suppose if we close the separator blade 45 -60 Deg our residue improves but TPH drastically comes down by around 4-5. My question is to improve our mill potential 45-50 TPH which is bottleneck for our kiln requirement, and also to improve product residue. 1. Is it essential to change the mechanical Grit separator to higher size or to change with other separator. 2. Is it essential to put secondary crusher with vibrating screen arrangement to reduce & keep feed size 100% below 10mm. Kindly give your valuable suggestion. Answer: My suggestions would be to add precrushing ahead of the raw mill and also to replace the grit separator with a dynamic separator. Question: Dear Sir,I wanted to brief about our raw mill, our mill potential is 45 TPH & we are getting around 30 to 34 TPH. We have air swept ball mill having Dia 2.8*7.32L having Dia 3.2 grit separator & 3.2 dia cyclone separator,CA fan capacity 70000 m3/hr & 650mm wc & Bag filter fan 35000 m3/hr & 250mm wc.In previous few months we have operated our mill by disconnecting Bag filter fan by making exhaust opening above Bag filter at that time we are getting around 28 to 30TPH & later this month we have again connected the bag filter fan to the circuit, operated for one month our TPH remains same

TPH.We have fully opened the separator blade our TPH increase to 32-34, parallely residue on 90 mic increases from 16-17% to 18-19%.My question is whether we need to operate with/without bag filter fan due to increase in KWH,as we are getting enough volume & pressure on Circulating air fan. Answer: I presume the filter fan is required to keep the filter under negative pressure? If the filter fan is not running then I imagine the filter must be pressurised by the mill fan? Question: dear sir,our kiln dimension is 4.8*75 m with ILC ,4 stage. arrangement of brick in the first 36 meters of kiln is as follows: 1) Ring 1-36(7.2 meters length) in lower transition zone ,magnesite-spinel bricks 2)Ring 37-136 (19.8 meters length)in central burning zone ,chromite-magnesite bricks 3) Ring 137-182(9 meters length) in upper transition zone magnesite-spinel bricks whenever we go inside the kiln to do some repairing activity,we see burning zone coating up to 23 meters length from kiln outlet and about 4 meters of kiln length in burning zone have no coating.can we replace this 4 meters length of kiln(or part of it) by magnesite-spinel bricks and increase the upper transition zone length?(lifetime of magnesite-spinel bricks against heat of flame is more than chromitemagnesite bricks) . Answer: Coating formation should be better on magnesite chromite bricks. However, magnesia spinel bricks are often used throughout the burning zone of the kiln so there should be no problems extending the zone over which they are installed. Ideally magnesite chrome bricks should be phased due to the health implications associated with their use. Question: Thenk you sir for king help, pls tell me sir what are the main differences between dry and wet process of cement manufacturing. Answer: In the dry process of cement clinker manufacture the kiln feed is a dry powder. In the wet process the kiln feed is a slurry containing 30 to 40% water. This means the fuel consumption of a wet process kiln is much higher because the water must be evaporated in the kiln. Question: effect of alkali in kiln operation Answer: There are many affects on kiln operations and clinker and cement quality. I suggest you enrol on the CemNet Kiln Chemistry course. Question: how can we decide coal mill residue target . .and othr raw mill kiln feed residue target?

Answer: The coal mill residue target should be less than 50% of the volatile content on a 90 micron sieve and less than 2% on a 150 micron sieve. The kiln feed residue target depends on the mineral content of the kiln feed and the free CaO content of clinker after burning. Around 13% on a 90 micron sieve would be a median target. Question: Respected Sir, We want to increase the addition of fly ash from 18% to 22%.We tried to increase the LSF in clinker from 91.5 to 93 but at the same time Free CaO also increased from 1.80% to 2.80%.We have also tried to replace sandstone which is having high quartz with marl around 2.0%.Is it the raw meal residue on 212 mic below 2.00% from 3.5% can help? Please suggest the way of increasing of clinker LSF by keeping same free Cao at same cement strength. Regards Answer: Finer grinding of kiln feed should help, but that is not necessarily the solution. There can be other causes of high free CaO in clinker. If the kiln is hot enough and there are oxidising conditions then there should be no problems combining a kiln feed with lime saturation of 93%. I suggest you investigate the combustion conditions and the recirculation of sulphur in the kiln. Question: Dear Sir, Would you tell me about how important of flow or volume gas/air in Operating, which pros and cons when you know these parameters inlet or outlet from a VRM ( Vertical Roller Mill)? Thank you so much! Answer: A vertical roller mill is normally controlled via the gas inlet and outlet temperature and also the pressure drop across the mill. These are related to the gas volume and flow, of course, but you don't need to know the actual flow to control the operation of the mill. Question: How we can used followin fuel combination at opc and src clinker coal A containsash12%v matters39.6%sulphur1.81% cv 6670kcal/kg and coal B contains ash 24% v matters38.95% sulphur 6.67% cv 5570kcak/kg without any problem in burning in kiln Answer: You will need to blend the coals to have a constant ash content and adjust the kiln feed chemistry accordingly to give the required clinker composition. Both coals have similar volatile content so you can grind to 18% residue on a 90 micron sieve, less than 2% on a 150 micron sieve. ou must ensure there is sufficient excess oxygen due to the high sulphur content of one of the coals.

Question: Dear Dr.Clark, How to control C3S phase by kiln operation? Answer: First you must monitor it's real content in clinker by XD or microscopy. Then you have to adjust either the chemistry or the combustion conditions. Chemistry can be adjusted by additions of corrective materials at the kiln inlet. Combustion relies on adjustment o[f the primary air and the grate cooler. Question: Dear sir plz tell me What afèct of ALM in kiln feed if his ratio is low and what is standard of ALM in kiln feed. Answer: Low alumina modulus can lead to heavy coating and ring formations in the kiln. An alumina modulus of 1.60 is typical. Question: Hello Sir, i have a query about VRM our mill capacity is 75 tph recenty we are facing problem in increasing its feed, when we increase the feed to 65 dp and mill kw attains to 460 and 360 res. all of sudden dp and kw inc to 490 and 400 but the feed is constant also rest of the parameters are constant and we also facing high residue kindly help us. thanks reg Sarav Answer: Your question is not clear. The mill capacity is 75t/h. When you increase the feed to 65 dp?......what do you mean? Question: What is tromp curve and it's effect on cement quality. Regards Answer: The Tromp Curve plots the particle size recovery to the rejects of a separator. It is a means of assessing the efficiency of a separator in a grinding circuit. Question: Sir!We have succeeded to transport carbon black to pfister feeder bin after passing it through coal mill. Carbon black residue after mill is 1.5 % on 90 micron. At start we used 1.3 tph carbon black along with gas to achieve 95 % production with clinker whiteness 88.5 %. Now we have increased the carbon black to max. with no gas firing, but clinker whiteness dropped to 86 & we have to take kiln production to reject side. Clinker has brown shade on it. What could be the reasons?is it ash?can we use full carbon black to achieve full production with acceptable whiteness? Regards Answer: Have you determined the ash content of the carbon black and the ash composition?

Question: I am a landowner looking to build earth-sheltered some architecture from limestone I will quarry from my land. I am looking to build a hoffman kiln. I was wondering if you knew of a corporation that builds these or could build them. HOFFMAN KILN: http://collections.infocollections.org/ukedu/collect/ukedu/index/assoc/h2385e/p120.gif EARTH-SHELTERED ARCHITECTURE: http://radioweblogs.com/0119080/images/Gallery/wells2.gif Answer: That is an unusual question Jared. The short answer is that I don't know a corporation who builds these kilns. My brother is involved in heritage projects in the North of England. I will ask him if he knows of an organisation. Question: Dear Sir, Can we design a cyclone immersion tube (dip tube) with its bottam closed & give the opeings by vertical slots to improve the collection efficiency.This is for twin cyclone Preheater cyclones. Answer: The critical factor will be the pressure drop across the cyclone. Hurrivanes supplied bt ATEC sound similar to this. Question: Dear Sir, In a PH cyclone, what is the relation between 1. cyclone collection efficiency vs cyclone discharge opening(diameter). 2. Pressure drop vs cyclone discharge opening(diameter). Will the wrongly designed (more or less than the required)cycone discharge opening makes any difference? Thanks. Answer: The cyclone discharge dimensions are critical for determining the pressure drop across the cyclone. The power drawn by the induced draft fan will be releted to the square of the pressure drop which must be achieved across the fan. Therefore, yes, a wrongly designed discharge opening will make a huge difference. Question: Respected Sir, Thank you for your answer, but i dont understand more. You can explain the way you answer me more detailer, "calculating the volume and flow of exhaust gas using stoichiometry and the Ideal Gas Laws". You can share me an examples about this calculation. I will wait your answer, many thanks. Answer: You need the calorific value and ultimate analysis of the fuel used to fire your kiln, i.e. the carbon, hydrogen, sulphur, nitrogen and oxygen content. Also the amount of fuel burnt per tonne of clinker produced. Also the composition of your kiln feed. If you can tell me those then I will make a calculation.

Question: About flow meter in duct, especial cement industry, Dear Admin, Your answer always help me to increase my knowleadge in cement industry. Now i want to ask you some question, pls help me: I wondering about the importance of gas/air flow in operating cement plant. In Vietnam, i know some cement plant but i cant find a flow meter in any cement plant (besides some equipments in cement procedure). If ferfect diffirent, you know, the temperature of gas exhaust recovery for cement grinding has low (about 100oC) so i can find many flow meters for collecting data. But in clinker producing, that be ignored. I dont know the reason, pls help me to understand more clearly about that. I see, we must depend on the temperature and volume of gas/air (m3/h) for optimise or normal operation. Why some cement plant only depend on temperature, sensible, the volume is not important for producing a high quality clinker or cement, and saving energy, so on. Now if i want to know about some equipments for monitoring gas flow in high-temperature duct ( which temperature more than 600oC), could you help me find a or more solutions for carrying out that. Thanks much for your support! Kindly! Answer: You are right that the gas flow and volume is very important in cement kilns. It is also very difficult to measure due to the high temperatures. For that reason the normal method is to calculate the volume and flow of exhaust gas using stoichiometry and the Ideal Gas Laws. Question: Dear Dr Clark, please tell me the difference between refractory life for white cemen kiln and OPC kiln, beacuse there is a diference in thermal load. Answer: Yes, the thermal load on white cement kilns is usually much higher than grey cement kilns due to the higher unit thermal energy consumption and the small diameter of white kilns. You could refractory life to be reduced by 50% compared with grey cement kilns. However, there are many contributing factors beyond thermal load. Question: Dear sir plz tell me why cyclone chowke Answer: There could be many reasons. Most likely connected with the circulation of alkalis, sulphates and chlorides in the kiln. Question: Dear Sir, In a VRM of 75 TPH (380-420KW main motor and 480 to 500 kw fan), recently table liners were replaced after facing huge power consumption in mill main motor. now we are starting and increasing feed gradually to mill. but residue is very high and not able to control. could you help on this?

Answer: I am not sure that I can help. It sounds as if you have mechanical problems with the mill. Question: sir,In our kiln 3.4*54 ,coal ash 24%,lsf 1.08-1.12 varies,sm 2.65,al2o3 2.7, kf residue 1922 and 2.9-3.6, sulpur % in coal 3-4.5% varies .due to these resons fuel varies.small ring present at 25mts and heavy coating from outlet to 18th mts,dia approx.2.0 .kiln inlet and orfice area coating coming and pc u bend area also coating forming. problem is ltwts have to maintain 1220-1280,fcao 1.3-2.5 variations coming ,kiln condition is normal,but dust generation is higher side,higherfaco,and unburnt showing inside clinker.please give me suggestion for control of FCao,dustgeneration. Answer: You must consider the total alkali, sulphur and chloride inputs to the kiln and also their concentration in the hot meal. I suspect your problem is the high sulphur inputs but we must know the Na2O, K2O, SO3 and Cl content in the hot meal. Question: thanks for your answers, her is several time (mor than 5 time)killn stop for ballring problem and condition of material is:LSF of killnfeed=91-95 ,SM=2.55-2.60 ,AM=1.151.20 ,liquid phase=25.5-26 .if any information else need to say exactly what is the reason of ballring formed ,i will write . thanks a lot. Answer: You must consider the alkali, sulphate and chloride inputs to the kiln and their concentration levels in the hot meal. Also the detailed adjustment of the main burner of the kiln. Question: Respected Sir, We are using high grade,feedable grade and low grade total three grade of lime stone.We are finding difficulty in making longitudnal lime stone pile. What should be the blending efficiency of the pile? What is the method of calculating blending efficiency of pile based on LSF. Regards Answer: The blending efficiency is the ratio of the standard deviation of the material stacked on the pile to the material reclaimed from the pile. You should expect a blending efficiency in excess of 5. Question: What is the effect of high residue of coal to burning and thermal efficiency.What is the recommended residue levels on 90micron sieve. rgds kibii Answer: The recommended target for coal finess is a 90 micron residue of less than 50% of the

volatile content of the coal. High residue can lead to many problems due to incomplete combustion of the coal in the main burner flame of the kiln. Question: Sir! At our white plant, We are trying carbon black as fuel at main burner but facing lot of problems in its transportation especially after grinding mill because of its very light weight. We are not getting enough carbon black in the pfister bin to fire in the kiln & check its effects on our product parameters especially whiteness. Please suggest us something which can help us in this task & can carbon black can be used in white kilns as a main burner fuel? Regards Answer: Carbon black should cause no problems when used to fire a white cement kiln. However, nothing can be done about its density. Question: hi, what reasons cause inform ballring in killn of cement factory. Answer: There are many potential reasons. The causes are usually unstable operation, variation in the quantity and properties of the liquid phase in the kiln, dust return from the cooler, or a poorly adjusted main burner flame. Question: We are using high VM coal (Indonesian coal) VM 47-48%. SOme times during shutdown of coal mills ,explosions also occured. We are maintaining following parameters. Residue 22-27% on 90 micron ,2 % on 212 micron Mill outlet temp 54 deg C ESP inlet temp 58 deg C O2 at ESP outlet 13-16% based on condition. we are mixing 25% south african coal with 75% indo with separate feed tables. FIne coal VM around 40%. Pl suggest standard operating procedures for high VM coal grinding with safety. Answer: There are many preventive and protective measures that have to be employed when grinding coal. My comments on the data you have sent would be that (i) the coal mill exit temperature seems to be low - I suggest you construct a coal dewatering curve, (ii) the O2 content at ESP outlet is high enough for coal dust explosions to occur - you should have 12.5 %. We need your comments. liquid contenT in clinker=? and use of construction sand? Answer: The construction sand should be no problem provided there are no harmful trace components in the sand (there shouldn't be). You should aim for 22 to 24% liquid content including 2% from the MgO and the alkalis. Question: what is the effect of raw mill fluctuations on burnabilty Answer: Burnability varies with varying kiln feed granulometry and chemistry. If raw mill fluctuations are causing fluctuations in kiln feed granulometry or cheemistry then they will cause fluctuations in burnability. Question: what is the effect of raw mill composition fluctuation on the clinkering process Answer: It increases variability demanding higher fuel consumption and resulting in lower production rate.

Question: what are the causes of high fCaO in clinker Answer: There are many: too high lime saturation of the kiln feed; too coarse grinding of the kiln feed; insufficient burning temperature; high sulphate content in hot meal; high K2O content of clinker; etc. Question: sir, why we check coal fineness on 90 mic. and raw mill 90 mic and 212 mic. Answer: You should check coal fineness on both 90 and 212 micron sieves. Question: Has a permanent solution been found to the snowmen problem? How are the manufacturers taking care of this problem currently?In what stage are the researchers in this regard? Answer: No, there's no premanent solution. People install "pushers" or air cannons. I'm not aware of any reserach going on. Question: Dear Sir, How do we decide / distribute the grinding media/balls sizes in a single chamber closed ckt ball mill? Like if we would like to fill 250 MT grinding media,then how much balls of 12 mm,17 mm ,20 mm & 25 mm should be filled inside the media? Answer: This depends on the residues of the feed to the mill and the type of lining. Whether it is classifying or not. If there is a high residue on a 1mm sieve of the feed to the mill then more 25mm balls would used. Typically equal tonnages of 12mm, 17mm, 20mm & 25mm balls would be used. Question: Our kiln diameter is 3000 mms*42000 mms long. We have 5 stage preheater with secondary firing arrangement, Bottommost cyclone material temp.=820 Deg.C. We have 6/30 grate cooler with first 5 row as CFG(static). Our preheter fan flow is 35000 nm3/hr. Our kiln production varries from 300 TPD to 380 TPD. Our coal ash is varrying from 26 to 28 %. Our preheater cyclone dia=3500 mms(inside bricks) . Our clinker MgO is 4.5% to 5 %. What could be the reasons for such wide varriations of kiln output? Answer: It is a very small kiln. That doesn't explain the wide variation in output though. Perhaps the coating thickness varies a lot due to the high MgO content.

Question: Could you please make an animation on snowman formation in grate coolers? Answer: I don't understand what an animation would be? Snowmen are caused by liquid content remaining in the clinker after it falls from the rotary kiln into the cooler. They are a consequence of high thermal energy recovery by modern coolers and the attendant high secondary air temperatures. Question: Dear Sir, Our limestone contains on an average 5 % MgCO3. Our kiln feed MgO =3%. We are using coal as fuel with ash=28%. What alumina modulus we need to maintain sothat our clinkerisation temperature is optimum? We are not able to maintain more than 63.5 % CaO in clinker. What could be the reasons? Answer: The MgO in clinker must be approaching 5%? This is at the upper limits as allowed by international specifications. This will lead to high liquid content in clinker and might lead to problems of clinker ball formation. Regarding the inability to maintain more than 63.5% CaO in clinker I presume you mean that there is free CaO present at higher levels? MgO will substitute in the clinker minerals to some extent. The rule of thumb is up to 2% with the remainder being present as free MgO (periclase). The actual levels of solid solution would need to be verified by scanning electron microscopy. I suspect there will be other explanations. What are the K2O, Na2O, SO3 and Cl levels in hot meal and clinker? Question: DearMr clark Thank you very much for your prompt reply SO3in hotmeal 2-2.2% chloride 1.1-1.2% running by pass 20% kiln feed CHLORIDE 0.15-0.20% FINE CLINKER GENERATION IS very high -1mm 30-40 give solution kilnfeed residue on 90micrn 24-25%on 212Micrn 1.2-1.8%freelime of clinker under control is this can be a reason for high generation of fines in clinker Answer: We need to know the K2O, Na2O, SO3 and Cl levels in hot meal and clinker in order to determine whether the SO3 is in excess of the alkalis after taking into consideration combination with chloride. Question: what is bottom dead centre of kiln tire? what is its significance?? Answer: I suppose it is what it says it is. When in position the bottom in the centre of the tyre. When the kiln is turning it would have no significance at the tyre would be moving through it continuously. However, when standing the weight of the kiln would be borne by the bottom dead centre of the tyre.

Question: Dear Sir, What will happen if we paint the outer surface of preheater cyclones by black coloure. (black body absorption law) What abt the heat losses in this case? It could b a funny question but creating some confusion in mind. Answer: The heat losses would rise because the radiation is greatest from a black body. Preheater cyclones are normally painted silver as the emissivity from a silver body is lowest. That is also the reason why some rotary kilns are coated with lime wash, which has a lower emissivity than rough oxidised steel. Question: we are facing problem of fine clinker generation of clinker in our kiln some time we get less clinker littreweight free Cao under control quality parameter kiln feed Lsf 103-104 S/m 1.9-2.2 clinker liquid 30-31% kf residue on 90micron 16-17% please send your comment Answer: The clinker liquid phase is very high. I suggest raising the silica modulus. The situation might be made worse by a heavy recirculation of sulphate in the kiln. What is the sulphate content of the hot meal and the clinker? Question: Dear sir, We are having open circuit cement mill with three chamber having size 2.4m Dia X 9.57 m Long. We are grinding mixture of clinker and granulated slag. slag 40 % gypsum 3 % and clinker 57 %. We have planned to conver the three chmaber cement mill to two chamber cement mill. By this any advantages? prouduction improvement ? better residue control? any other improvements do you anticipate? Answer: I doubt that there will be any improvement. You need the long path length through the mill because it is open circuit. It would only make sense to convert to two chambers if you are also introducing a separator and a classifying lining. Grinding such a mixture on an open circuit mill will be very inefficient. It would be much better to separately grind the clinker and granulated slag and then to blend them together in whatever ratios you want. Question: Hi, we have a problem with our tertiary air damper tongue on our cement kiln not lasting the full year between shut downs. We have recently installed a new design tongue to see if it will last but i am also looking in to changeing the tongue in a mini mid year shut down. Is there any pointers you can give as to the best cooling down and warming up processes? what is the main effect the loss of the damper tongue will have on the kiln effeciency? Cheers! Answer:

For the rate of warming up the first guide would be the refractory suppliers data sheets. For the rotary kiln usually 25 to 30 degrees per hour up to 900C then it can be faster, perhaps 50 degrees per hour. For preheater, cooler then it depends how much castable work has been done and how much curing is required. The problem with the loss of the tertiary air damper tongue will be balancing the draft between the rotary kiln and the tertiary air duct, particularly at times when the feed rate is reduced. Question: Dear Sir, We are mixing power plant fly ash(silica=55 %) in south african coal to maintain kiln fired coal ash=27%. South african coal has ash=15 %. Calorific value of south african coal =6400 kcals/kg of coal. After mixing power plant ash with soth african coal the calorific value of as fired coal in kiln =4900 kcals/kg. The power plant ash mixed is to tune of 20 %. This is being practiced to reduce the heat intensity of as fired coal so as to safeguard the alumina bricks used in the kiln. Is this correct practice? Any advverse effects w.r.t to coal consumption in kiln? Any effects on kiln production?Any effects o clinker quality? Answer: I don't like this practice. There must be problems of inhomogeneity in the clinker introduced by having to combine the extra ash with residual lime so late in the process. The best clinker is produced by a short intense flame. Deliberately degrading the flame must be detrimental for clinker quality. A more refractory lining should be used for the burning zone of the kiln. Question: dear dr.clark, what are the factors that may lead to very dusty clinker from a coal (imported coal from indonesia) fired cement kiln? the kiln is also producing a low freelime clinker 0.5 to 1.1 with litreweights not exceeding 1150-1220. regards. Answer: I would suspect that dusty clinker arises from a high sulphate content in the hot meal. Do you have any hot meal analysis? Question: Dear Dr. Clark I would like to ask about the possible reasons of clinker ball formation ( boulder )because we are suffering from this phenomena . Here the chemical analysis for a sample taken from one boulder (1.5 m Di. ) LSF=94.76, SM=2.7, AM=0.9, Fcao=1.09, C3S=53.6, C3A=2.77 , regards. Answer: Clinker ball formation is usually related to premature flux formation and formation of balls of meal in the inlet of the kiln. These then grow like a snowball due to the rotation of the kiln. The premature flux formation can be caused by excessive temperature at the kiln inlet or heavy recirculation of sulphur in the kiln. Clinker balls can also be caused by increases in the MgO content of the kiln feed.

Question: Is there any equipment or device to measure the hight or range of jamming occurd inside the cyclones?? and how to reduce power consumption of kiln, preheater section??? regards Answer: Question: Dear Dr. Clark? What does the word "recarbonation of calcined meal" mean? Answer: The CaCO3 in the kiln feed is calcined to form CaO and CO2 in the lower preheater stages and precalciner of a cement kiln. Poor collection efficiency of the lower stage cyclones can lead to the calcined meal, i.e. the meal containing free CaO being carried back up the preheater. There it can recarbonate - the CaO recombines with CO2 to once again form CaCO3. This is an exothermic reaction and liberates energy raising the temperature in the upper stages of the preheater and the thermal losses in the preheater exhaust gas. The recarbonated meal then has to be calcined again when it passes down the preheater wasting energy. Question: Dear Dr/ Clark, Would you please tell me if there are limits for free silica in both Kiln Feed and Clinker as a criterion to assess the burnability. Thanks Answer: The limits are not on the amount of free silica but the grain size of the free silica. The silica content of the residue on a 45micron sieve is one of the variables in the FL Smidth burnability equation. Question: First of all I would be sincerely offering my thanks to you for all your prompt and perfect answers to my questions raised earlier. I have acted on your suggestions and taken actions suitably. I am glad to state that my all problems got solved by your help. To state a few 1) Kiln inlet build up disappeared 2) Kiln inlet draft reduced to below 10 mms 3) all undesired build ups/coatings inside kiln eliminated 4) Kiln production restored to normalself 5) Clinker quality improved after adjustment of liquid content 6) Lastly my tensions eased out and life is cool. I am feeling proud to have good assocition with a fantastic process engineer i.e Michael Clark Answer: Nice to be able to assist! Question: Dear Sir, ihad a problem in my kiln , kiln look very bright ,but clinker liter weight normal around 1050 , Kiln feed LSF is 100.9 ,AM 1.38 , Mgo : 1.49 Kiln feed residue is 23 % on

90 mic ,6.4 % on 212 mic, tell me reason for low liter weight Answer: The kiln feed residues seem to be very coarse. Question: This is related to my previous question about boulders formation,and your question, if there is uncombined material when the boulder is broken? My answer is yes, there is brown coulor inside. It is observed also boulder formation starts from the area of kiln inlet,develops and proceeds forwards. I hope what I sayed is usefull for complete diagnosis ? Just today kiln is stopped 5-hour to break boulders stuck at cooler crusher inlet. best regards. Answer: This must be connected with early flux formation in the kiln. How long is the kiln? What fuel is being used to fire the kiln? Question: In our kiln -5000t/d clinker-76mx4.8m diameter-5 stages cyclones with precalciner,gas fired , It is started after shutdown without cyclone -5 dip tube as its damaged and removed.we can not go up to nominal feed as before and excessive dust is arriving at the cooler, causing under cooler pan conveyor to trip with over load fault and tertiary air duct dedusting cyclone-just after intake area- is jamming with dust material. Wil you pl;ease Dr. Clark explain such relation between cyclone -5 dip tube and execessive cooler dust? Answer: That is difficult to explain without more information. I would expect the gas consumption to rise due to heavy recirculation of hot meal around the bottom stage cyclones and recarbonation of the calcined meal. How long has the kiln been gas fired? Are these new problems or have they just arisen? My suspicion is that the problem is poor mixing of the combustion air and the gas at the main burner. Question: In our kiln-56m x φ3.8m-2000t/d clinker, 5-stages cyclones with precalciner,gas fired and equipped with bypass system , we are facing the problem of continuous boulders formation sizes φ1.0-1.5m , rolling to cooler and stuck at cooler crusher inlet.This leads to kiln stoppage for breaking boulders manually. Will you please, Dr. Clark suggest/give the expected causes/reasons for this phenomenon ? Answer: Clinker boulders formation is normally associated with heavy recirculation of sulphates in the kiln. The cause of that is usually the combustion conditions at the main burner. Sometimes it can be secondary firing at the kiln inlet. When you break the clinker boulders are they uncombined raw meal inside?

Question: Dear Sir, We have secondary firing in kiln inlet riser duct. PD blower with 0.2 kg/cm2 air pressure is used for secondary coal conveying. The temperature at kiln inlet is widely changing/is not stable. Is there any other way to make secondary firing more effective. Answer: It sounds as if some of the secondary fuel is falling into the charge at the kiln inlet and burning there. What type of secondary fuel is it? If solid is it a powder or in lump form? Question: Dear Sir, In our kiln kiln inlet draught is widely fluctuating from 10 mms to 40 mms. This is creating kiln disturbances quiet often.Kiln inlet spillage problem is observed. Our preheater fan flow is 2.2 nm3/kg clinker. Please suggest. Answer: It sounds as if you have a ring in the back section of the kiln causing the feed to be dammed up behind the ring. Question: Dear Sir, we are currently experiencing problems of high Litre weight(Ranges of 1400 and above) and very low FCaO (0.45). We recently shifted to coal as fuel but before, we were using HFO(Heavy furnace oil). Our strengths are though very good(OPC 2days=1518mpa). Our ball mills sometimes experience hard grinding and so we are thinking that we r overburning or hard burning. Please help me sort out the issue coz i think am confused. Regards Answer: All the symptoms are consistent with over-burning the clinker. Presumably the burner has been changed with the fuel switch? You need to either: (i) increase the feed rate to the kiln and/or the rotational speed, (ii) reduce the coal supply to the main burner. Question: dear dr.i have two question : 1-why reducing condition at rotary kiln caused to dusty clinker. 2-caused to limitation C3A