Plant Design-Biscuit Manufacturing
A process plant to produce one thousand kilograms or one tonne per day on a single eight-hour shift basis has been carri...
DESIGN OF A PLANT TO PRODUCE ONE TONNE OF BISCUIT PER DAY
EXECUTIVE SUMMARY A process plant to produce one thousand kilograms or one tonne per day on a single eight-hour shift basis has been carried out with much precision and consideration given to the most optimum process route. An increase of 10% was given to the product so as to take care of losses along the production line and also to the plant producing under capacity. The materials needed for the production of the biscuit and their approximate percentages are: Flour -- 50%, water--30%, sugar--2%, salt --2%, baking powder--2%, additives --14%. The materials or equipment design are: one mixer, one extruder and conveyor tunnel oven.Other equipments are sealing machines, water pump, filter, tables, pre-printed nylon etc. 1492.96 kg of dough is mixed per day and 1000 kg of biscuit is the target to be produced with a 10% increase to account for losses in the production line. The heat generated over the whole production process is 650,358.92 kJ/hr. The profit at 75% and 100% capacities are N12.678m and N 17.7135 m respectively. The recommended sales price is estimated at N3.60. The feasibility and technological requirement for the production of a biscuit plant of total capacity of one tonne or 30,000 thousands packs per day running only one eight hour shift.
The approach used for the design of this process technology starts with the
selection of the process route that will give optimum yield and low cost. The route was chosen after considering the existing routes industrially and modifying it to suite the capacity of this plant. The equipment for the plant were also chosen based on their ability to carry out the expected functions of the plant, putting into consideration the working characteristics, capacity and area. They are also chosen based on the characteristics of the materials. The best were chosen and the process flow route with the equipment was determined. The material and energy balance for the whole process units were done, to determine the flow of material in and out of the system and to determine the heat generated over the whole system. Each of the basic equipment like the oven, the extruder were selected or modified using the material and energy balance, and some design parameters from design books and companies. Analysis of the cash flow for profitability of the plant was then looked into using high expenditure ratio to low revenue rate of return. The analysis covers, the costing of machinery and equipments, the working capital, factory and building cost, pre-operational
expenses, contingency, cost of utilities and tax. The revenue generated at a selling rate of 3.60 per pack was determined. The depreciation of equipments (20 years), office building and furniture (5 years each) and the trading profit was used to generate a good profit. Site selection and plant location was also done, by looking into the market areas available to the product, the nature of competition, rate of consumption of the product, source of raw material, transportation of raw material and product, availability of both skilled and unskilled labour, nature of utilities that will be needed for process and recreation, environmental impact of process effluent (if any), climatic effect, topography, and strategic economic consideration. Suggestion of the plant layout, safety of both material/ product and man/machinery was also looked into, suggestion on waste management and services was done. After all the above consideration the results obtained during the study and design show some very interesting results for any investor. The type of biscuit chosen for the production plant is the southern type biscuit (trade name) with a simple recipe of flour, sugar, salt, baking powder, additives and water with its own percentages by weigh. The ingredients are readily available in the market locally or by importation. This type of biscuit are already enjoying good acceptance in the market. The process route selected is such that only one mixer is used and the paste or dough is poured into an extruder below, from where the dough is extruded through a mould, placed at the nozzles of the extruder which are then placed in trays for a two-in-one cutter stamp to cut and stamp the company logo. A conveyor then conveys these trays through a drying zone with three compartments for the final drying (baking) of the biscuit. Products are then packed and sealed and cartooned for the market. The equipments for the plant are mainly the mixer, extruder and the oven, the choice of the mixer after careful consideration of material amount, characteristics and efficiency expected is the sigma z-blade which belongs to the double arm kneading mixing equipment group. It has good mixing action, readily discharges material, relatively easy to clean and does not allow sticking of material. By the nature of extruders, a total design is needed therefore, no choice was made, however the design follows the basic principle. The choice of drying is the tunnel continuous dryer due to the amount of heat expected to be generated and the nature of the product to be dried and also due to the nature of drying medium, steam. It is very suitable for materials that form bed with open structure. High drying rate
is achieved, with good quality of product, high thermal efficiency, usage of steam as during medium as low as 1.5 kg/kg of water for evaporation, and good recycle of steam, which gives cost effectiveness. The only disadvantage here is the cost for mechanical belt maintenance for the conveyor. The source of heat is chosen to be steam, from plant boiler and cooling water in the extruder nozzle as compared with electric heater which are expensive, difficult to maintain and heating which is not uniform. The capacity of the oven designed is 1m by 11.21m, the resident time in the drying/cooking zone is 15 min, the amount of material per day is 1,306 kg/day, heat generated as 99,990.82 kJ/hr and the process dynamic is subject to a pilot test. The capacity for the extruder designed is 0.1103 m3, with the internal specification of 1m by 0.5 m long by 0.22 m high, resident time of 0.052 kg/s, the extrusion time is 0.141s, the amount of material extruded per hour is 186.6 kg/hr, heat generated is 469,800 kJ/hr, which is very high, about 70% of which is lost to the environment, thus adequate need for cooling water at the nozzle. The mixer capacity is designed to handle 622 kg/hr over 20 min of mixing for homogeneity, tank diameter is 0.622 m, blade diameter is 0.25 m, the blade tip velocity is 1.44 m/s, the power consumption per unit volume is 118.225 kN/m2s, the design blade number is 2,700. The material in is also 186.6 kg/hr and the heat generated is 80,568 kJ/hr, with a loss of 73, 641.28 kJ/hr. For every 1,492.8 kg of feed material 1.1 tonne of product is produced which is estimated 10% above target to take care of losses of materials that may occur along process line e.g. burnt products or loss during mixing, extruding and cutting. The heat generated over the whole system is 650,358.82KJ/hr, most of which are lost, thus the mixer will be properly lagged and extruder cooled. The cooling water from the extrusion unit is sent to the boiler to generate treated water for oven i.e. conservation of energy. The projected income and expenses evaluated is done with 75% capacity production for the starting year, 2002 with 10% increase until the fourth year 2005. The total product for the first year of production is 210 tonne of biscuit, with a market sales of N 3.60 gives a revenue of N 22.50 million less than the yearly expenditure of N 9.022 million and loan on interest at 0.8% gives a yearly net profit of N 12.678 million, and this increases as the plant grows to operate at full capacity. Due to the market available for biscuit, the site of the plant should be close to the market within a reasonable radius. The raw material, flour can be sourced locally from the
northern part and transported. Transportation by road and rail are safe. Other additives are more concentrated in the western part.
CHAPTER ONE INTRODUCTION 1.1 GENERAL Biscuit like bread is a bakery wheat or wheat composite product of valuable food nutrition. Biscuit came to Nigeria through the colonialists but have become popular among our people, especially children of school age. Its acceptance is based on the ready for consumption nature of the product. It can also be eaten alone or with other foods like milk, tea, butter, stew, pap (ogi) etc (Adeniyi, 1998; Onyia, 1997). Biscuit is food and food is man's basic need. Being a food producer in a society where food is not only very expensive but scarce, it certainly has a ready market for investors. In the cities where there is little time for detailed cooking due to socio-economic factors, ready-for-consumption foods like biscuits come to the rescue. This product is often taken as breakfast, or taken to offices or schools for lunch by children and adult alike. The use of biscuit for hospitality has become popular thereby creating huge demand for the product. The unit packaging available make it affordable even by the poor. With a good quality publicity as well as price, biscuit production can be a good profit-earning business.
1.1.1 RAW MATERIALS  FLOUR: This is the most important raw material, which can be made of whole wheat or composite from maize, cassava, millet etc. It takes not less than 50% of all ingredients required. A small packet of biscuit of 30 g contains at least 15 g of flour. Wheat flour is produced locally (Ogunsola, 1999, Adeniyi, 1998).  SUGAR: Sugar is essential for sweet taste which biscuit is known for. Sugar is produced locally and allot is also imported to meet the huge national demand. Nevertheless, there are other natural sweeteners like honey, sweet potato and some native extracts that can be carefully incorporated as substitute or filler for sugar.  ADDITIVES: These include flavouring, shortening, colourants and modifiers like salt, eggs, milk, glucose, fat etc. They are added in very small quantities depending on the type of biscuit needed.  WATER: Water is essential for mixing the ingredients to a workable level. Water takes up to 30% of the components. This however, must be hygienic and clean.
 BAKING POWDER (AND/OR YEAST): Baking powder or yeast is important, for biscuit making. Where fermentation is not done like in wafers, yeast is not needed. The extent of swelling or rising of biscuits during production depends on the baking powder or yeast as the case may be. All raw materials must of necessity be food grade and hygienic (Ogunsola, 1999, Adeniyi, 1998).
1.1.2 EQUIPMENT/TOOLS FOR PRODUCTION The following equipment/tools are necessary for commercial production of biscuits (Crenan and Butter, 1990).  OVEN (DRYER): This can fired by wood, electricity or gas depending on the design.  MIXER: This can be manually operated or motorized to make mixing efficient.  MOULD/STAMP: The various designs that will appear on a biscuit depend on the mould and stamp. There are manual and motorised types.  CUTTER: The cutter cuts mixed and flattened biscuit parts into the desired sizes. It can be manual or motorized too.  Other tools such as wrapping and sealing machines, storage tanks, trolleys, packing racks etc can be provided. These equipments and tools can be fabricated locally to any desired standard.
1.2 DESIGN PROBLEM The plant to be designed will have a capacity to produce one tonne (one thousand kilograms) of biscuit per day. The manufacturing operation is to comprise of the following units: mixing, extrusion, drying and packaging. The entire technological process is to be a semi continuous operation where materials are only manually operated during transfer from the horizontal drier to the packaging. Services available are normal services with cooling water at a temperature of thirty degrees centigrade (30oC). A detailed chemical engineering design is required with a flow diagram for the process accompanied with the mass and energy balance for the equipments and units. At optimum operation the technology is to produce a minimum of thirty thousand packs (30,000 packs or 1 tonne) of biscuit per day or one for one eight our shift.
CHAPTER TWO MANUFACTURING OPERATIONS 2.1 INTRODUCTION The process of making biscuit comprises of various unit operations. Following the formulation, the raw materials are carefully measured out and mixed in the dough mixer. The dough when formed is passed through the moulds. This is then stamped either before or after cutting depending on the design of the plant. The dough pieces are taken to the oven where they are baked for at least 10-15 minutes at 200-250 oC temperatures. This however depends on the type and thickness of the biscuit to be produced. The baked biscuits are removed and sorted out. They are then packed in polyethylene or waxed paper previously printed and finally sealed on the sealing machine. The wrapped biscuits are in turns packed in cartons and taken to the market.
2.2 SELECTION OF PROCESS ROUTE Basically, the technology of biscuit production involves the thorough mixing of the wheat four or other cereals (that can serve the same purpose) with other ingredients and additives. After the mixing operation the dough is extruded and shaped to fancy, how be it with some restriction in size and thickness. These shaped dough are then dried to reduce the water content and invariably browning. The biscuits are then packaged as desired and ready for market (Crenan and Butter, 1990). This process demand the following unit operations and auxiliary services:  Surface tanks
 mixing equipment
 Cutting equipment
 stamping equipment
 drying oven
 Sealing machines
 trays, rollers or conveyor
The flow of material through this equipment (units) is determined with the aim of having optimum production cost and best quality of products. This influences the choice of optimum process route (Fig. 2.1). This route is chosen after answering the following questions:  Is the flow diagram logical, are the units compatible?  Is the technique feasible and logical?
 What are the possible flows, can they be corrected and controlled?  Which of the different kinds of the unit is the best considering cost, efficiency, durability, capacity, energy consumption?  Are the equipments readily available?  How safe are the units to operate?
2.3 CHOICE OF PROCESS ROUTE The choice of process route for the biscuit plant is basically dependent on the size of the plant i.e. capacity. The basic process route (arrangement) of mixer, extruder, stamp, drying and packaging is universally well known and documented. However, depending on plant capacity, the type of unit used becomes important. The use of other equipment such as pumps for supply of water to mixer, the need for continuous flow of materials, recycling e.t.c. are factors to be considered. Therefore in the design of the best process route, the route chosen should be seem to be at par with other known good techniques used in the biscuit industries, it is safe from both operational, human and environmental hazards, the technique is not technologically demanding. The only improvement may be the use of sophisticated equipment, which is not wise considering the economy of the proposed plant capacity. Therefore the choice of the optimum route has been done based on breaking down the technology in unit operations. The choice of the required equipment was done after answering the questions stated above. Each unit is properly examined to choose the best that will be compatible with others. This is to ensure the optimal operation of the processing technique as shown on Fig 2.1 (Adeniyi, 1998).
Fig. 2.1: Block diagram of biscuit production
2.4 PRODUCTION MACHINERY A full list of the major production machinery needed for the production of one tonne of biscuit per day is presented in Appendix A. The
minimum of one tonne of biscuit per day, per technological line. Water used for mixing must pass through filters. The cooling system is necessary to avoid rapid evaporation of water as well as the blockage of the nozzle of extruder. The dryer stage comprises of: 1 horizontal oven with complete accessories. Baking is a very important stage as it greatly determines the quality of the final products. The packaging department consist of: 6 wooden silos 6 weighing machines Nylon sealing machines
2.5 ANCILLARY OPERATIONS In addition to the main production processes outlined above, several ancillary units must be established for efficient operation of the factory. They include among others:  QUALITY CONTROL UNIT: A unit responsible for quality control at every stage of production will be set up to ensures compliance with set National Standards for food and beverages by the National Agency for Food, Drug Administration and Control (NAFDAC).  MAINTENANCE UNIT: A maintenance unit must be set up to ensure early fabrication of worn out parts It should be equipped with the necessary workshop machines. The workers are under the indirect production list, which is given in Appendix C. 2.6 FACTORY PERSONNEL Manning levels have been estimated fairly generously in comparison with those, which would be expected in a more developed industrial environment. The factory will operate a single eight-hour shift system. The distribution of personnel along the technological line is given in Appendix C under the direct production worker. It requires a total of fifteen people. The indirect factory personnel are also given in Appendix C also with a total of fifteen people.
CHAPTER THREE MASS AND ENERGY BALANCES 3.1 OVERALL BALANCE The percentage compositions of the feed is known, what is not known is the masses of the feed but the masses of the product is 1000 kg of biscuit. A detailed calculation is in Appendix B and a computer program has been written to solve the material and energy balances. The computer program is in Appendix D (Adeniyi, 1998). The percentage compositions of the feed materials are:  Flour 50%
 Sugar 2.0%
 Water 30%
 Baking powder 2.0%
 Additives/modifiers 16% Additives includes flavouring, shortening (about 14%), colourants and modifiers includes salts (about 1.0%), eggs, milk, glucose and fat (They are added in very small quantities depending on the types of biscuits)[Adeniyi, 1998, Ogunsola, 1999)]
3.1.1 MATERIAL BALANCE From the material balance carried out it can be seen that to get a product of 1000 kg (1 tonne) of biscuit, a feed mass of 1357.15 kg of the raw material is required. This will require the following mass of feed:  Flour 678.58 kg
 Sugar 27.14 kg
 Water 407.15 kg
 Baking powder 27.14 kg
 Addition/modifier 217.14 kg
3.1.2 HEAT BALANCE At a moisture content of 30% the heat capacity of biscuit is estimated at 1.845 kJ/kgoC, the latent heat is 100.50 kJ/kgoC. The heat required to bake 1kg of biscuit in the oven is 715.97 kJ (kW). The heat required to bake 1357.15 kg of biscuit in the oven is 1331960.46 kJ. The overall heat balance across the oven is calculated to be 1198766.35kJ, this is different from the heat required to bake 1357.15 kg because some moisture will
already be lost before the dough enters the oven. About 10% of moisture is expected to be lost before the dough enters the oven and this amount to about 321.453 kg. Detailed calculation of the heat balance is given in Appendix B. The results are summarised in Tables 3.1-3.9.
Table 3.1: Overall material balance. Mass In
Table 3.2: Unit material balance over the mixer. Mass In
Table 3.3: Unit material balance over the extruder. Mass In
Table 3.4: Unit material balance over the dryer (oven). Mass In
Table 3.5: Overall energy balance Equipment
Heat load (kJ/hr)
Table 3.6: Unit energy balance over the mixer Heat generated
Heat load (kJ/hr)
Heat load in dough
Heat loss in mixer
Table 3.7: Unit energy balance over the extruder Heat generated
Heat load (kJ/hr)
Heat load in dough
Heat loss in extruder
The unit energy balances across the dryer or oven is given in three zones namely: the heating zone, the constant rate zone and the falling rate zone.
Table 3.8: Unit energy balance over the dryer (oven)- Zone 1: Heating zone Heat generated
Heat load (kJ/hr)
Heat load for dough
Heat load for liquid
Zone 2 is the constant rate change zone and the heat in is equal to the heat out which is estimated as 40953.265 kJ/hr using the computer program developed (Appendix D).
Table 3.9: Unit energy balance over the dryer (oven)- Zone 3: falling rate zone Heat generated
Heat load (kJ/hr)
Heat load in dough
Heat load in evaporated liquid
Heat loss in dryer
Table 3.10: Total Heat balance over the Dryer (Oven) Heat generated
Heat load (kJ/hr)
Zone 1: Heating
Zone 2: Constant rate change
Zone 3: Falling rate
CHAPTER FOUR EQUIPMENT DESIGN 4.1 CHOICE OF EQUIPMENT In any production process, the choice of the equipment from the different types is very important, so as to meet the production capacity target, ensure good quality of product, maximise cost, durability, safety to life and property and cost of production. Equipment are built with different sizes and shapes, they are designed on different working principle or operation, which are therefore characteristic of the use to which it will be applied. It is therefore important to know the nature of the material in the process and the equipment type that will serve ones purpose.
4.2 DOUGH AND PASTE Dough and paste are mixed in machines, which have of necessity, to be heavy and powerful. Because of the large power requirements, it is particularly desirable that the motor posses reasonable efficiency; as the power dissipated in the form of heat may cause substantial heating of the product. Such machines may require jacketing mixer to remove as much heat as possible with cooling water (Richardson and Peacock, 1994). The most commonly used mixers for these heavy material are the (1) Z-blade mixers (2) The pan mixers (3) The Kneader, which employs two contra rotating arms of special shape, which fold and shear the material across a cusp, or division, in the bottom The blade of these mixers rotates at differential speeds, often in the ratio of 3:2. Mixing action of the Z-blade mixers combines shearing and kneading which is brought about by the specially shaped blades enabling it to mix, whip and knead materials ranging from low viscosity paste to stiff dough. Other types of machines employ very heavy contra-rotating paddles, whilst a modern continuous mixers consist of an interrupted screw which oscillate with both rotary and reciprocating motion between pegs in an enclosing cylinder. The important principle in these machines is that the material has to be divided and folded and also displaced so that fresh surfaces recombine as often as possible (Meyer, 1992; Perry and Green, 1997).
4.2.4 DESIGN OF MIXER SPECIFICATION N= Rotational speed s-1 D=blade diameter
Np= Power number V=volume
1 =mixing (blending) time s Nb= Blend number PHYSICAL DATA Based on laboratory unit data and scale up exponent n see Appendix F N=108 s-1 e=2200 kg/m3 µ=200 Ns/s2 P=22.38 kgm2/s3 v=0.1893 m3 L=laboratory unit data DETERMINATION OF PARAMETERS (1) SIZE OR CAPACITY c=m/1 where m= mass of dough 1 =blend time c=622 kg/h (2) BLADE DIAMETER D=sqr(PPL.NL3.DL5/PL.µ.N3)5 D = 0.2549 (3) TANK DIAMETER
T=sqr(TL3.V/VL)3 T=0.622 m (4) TIP VELOCITY Vt=Β ND=86.50 m/min =1.44 m/s (5) POWER PER UNIT VOLUME P/V=118.23 kg/ms3 (6) POWER NUMBER Np = P / eN3D5 = .1 (7) BLEND NUMBER NB=N1 =162000 4.3
EXTRUDER Extrusion is an operation in which a mass of plastic or semi soft material inside a
heavy walled cylindrical container is forced to flow through an orifice (die or mould) at one end of the container as a result of pressure applied to the material by a piston (ram) acting at the other end of the container. The process is often successful on materials, which are too brittle to work by other shaping methods such as rolling. The instruments for this process are generally called extruders. They may come in many shapes and work with different principles e.g. the extrusion mixer, presses the material via a kneader. Extrusion is well suited to producing long bars of constant cross section. The shape of the cross section, which is determined by the die opening, may be quite complex. The force required for extrusion may be supplied by a hydraulic cylinder, which drives the ram. The material to be extruded must have sufficient plasticity so that it begins to flow through the die at a pressure less than the breaking point of the material. The ram pressure should not be above 180,000lb/m2. The die is another limiting feature of the process since it may lose its shape if pressure and temperature becomes excessive and abrasive wear may occur. The pressure (force/area) required for extrusion is a function of the stiffness of the material, surface friction and changes in cross sectional are from the billet to the rod or shaped material (Perry and Green, 1997). A useful expression is P = KlnR. Where R = Ratio of the initial to final cross sectional area
K = Constant which is a function of temperature
TABLE 4.1: EXTRUSION CONSTANT K OF SOME METALS METAL TEMPERATURE K (lb/in2) 2S Aluminium
Powerful presses up to 15,000 tonnes capacity are used for extrusion, but the most common size is about 2,500 tonnes. Suitable lubricants (ground nut oil) must be used to reduce extrusion force, increase die life and give better surface on the extruded product. In general the force required to overcome friction, even in well-lubricated operation is about 25% of total force (Richardson and Peacock, 1994). Extruded product are usually or sometimes used as extruded, but it is more common practice to employ a subsequent cold working operation, such as drawing to improve the surface finish and to get greater dimensional accuracy or desired thickness.
4.3.1 DESIGN OF EXTRUDER SPECIFICATION e=Density of dough kg/m3 m=mass dough kg Ut=Total volume of dough m3 T=extrusion time F=Force of extrusion A=Area of piston P=Pressure
s N m2 N/m2
VE=Volume of dough extruded per sec m3 Ut=velocity of piston
H=height of extruder chamber
L=length of extruder surface m
W=thickness of extruded surface m DATA e=2200 kg/m3 m=186.608 kg L=0.97 m W=0.40m H=0.05m
4.4 OVEN (DRYER) Drying (baking) is the removal of volatile substances (moisture) by heat from a mixture that yields a solid product (biscuit). Dryers are classified by: (1) HEATING METHOD: The manner whereby the moist material removes heat i.e. by conduction heating from the sheets or very wet material. Convective heating is the most common, where mild heating is necessary to avoid heavy degraded product, and radiation drying is used in the microwave oven (Macrea and Robbinson, 1997). (2) PROCESS CONDITION: The pressure and temperature of operation which are constrained however by the nature of the materials to be dried. The thermal sensitivity of the material fixes the maximum temperature to which the material may be heated. The temperature rises with the time the material is held in the dryer. (3) CONVEYING METHOD: The way the material is loaded or supported in the dryer. The outward appearance of the dryer depends largely upon the way the drying material moves through the equipment. Free flowing granules can be handled in many ways (conveyor, rolling, trays etc), but more awkward materials often require special techniques. Most modern dryers are operated continuously or semi-continuously over the working tray, as a continuous dryer will require less labour, fuel and floor space than the batch dryers. Certain factors are considered in the selection of dryer for particular purpose, they are: (1) Feed Condition: is it solid, liquid, paste powder, crystals (2) Feed Concentration, the initial liquid content. (3) Product Specification, dryers required, physical form. (4) Throughput Required. (5) Heat Sensitivity of The Product. (6) Nature of Vapour, toxicity and flow ability.
(7) Nature of the Solid: flammability (dust explosion hazard), toxicity.
4.4.1 CONVEYOR DRYERS(CONTINUOS CIRCULATION BAND DRYERS) The conveyor dryer (oven) has been chosen for the production of one tonne of biscuit per day, because of the complete accessories it has to offer. In this type the solids are fed onto the endless, perforated conveyor belt, through which hot air is forced. The belt is housed in a long rectangular cabinet, which is divided into zones, so that the flow pattern and temperature of the drying air can be controlled. The relative movement through the dryer of the solids and drying air can be parallel or more usually counter-current (Marcel and Dekkar, 1987). This type of dryer is clearly only suitable for materials that form a belt with an open structure. High drying rate can be achieved with good product quality control. Thermal efficiency are high and with steam heating, steam usage can be as low as 1.5 per Kg of water evaporated.
4.4.2 DESIGN OF DRYERS (OVENS) There may be more than one type of dryers suitable for a particular job, therefore the choice based on optimal cost, fuel or power rating and space comes to mind during the design for a process dryer. The design Engineer chooses for a given dryer conditions which enable the specified properties of the product to be obtained. In this way performance characteristics of alternative system can be expressed as a basis for the ultimate choice of the specified plant (Ulrich, 1986). Almost always some small scale are needed to determine the materials drying characteristics required to predict the way which the shift will be in the commercial plant.
SPECIFICATION A=Total surface area of dryer m2 AH=surface area of heating zone m2 AC=surface area of concentred drying zone AF=surface area of falling rate zone m2 DTMF= log. mean temperature difference in the falling rate zone oC DTMH= log. mean temperature difference in the falling zone oC
Ti= zone heating medium (steam) inlet temperature To=zone heating medium (steam) outlet temperature ti=zone in process material, inlet temperature in a zone to=zone in process material, outlet temperature in a zone
DATA THi=270K (543oC) THo=270K (543oC) ο
tHi=80K (353 C) tHo=180K (453oC) QH=33407.994 kJ/h QC=40953.265 kJ/h QF=25629.565 kJ/h UH = 142 UC = 227.13 UF = 852.2 LH = 1 LC = .8 LF = .6 Moisture drying ratios 25:40:15 5:8:3 142:227.2:85.2 DTMH = (543 - 453) - (543 - 353) / In((543 - 453) / (543 - 353)) =183.83 =133.83 DTMF = (543 - 513) - (543 - 453) / In((543 - 513) / (543 - 453)) =39.15 =54.61 AH=Q/UTL=33407.994/142x133.83x1=1.76m2 AF=Q/UDTL=25629.565/85.2x54.61x.6=9.18 AC=4953.265/227.13x(543-453)x0.8=0.267m2
CHAPTER FIVE ECONOMIC SURVEY 5.1 ECONOMIC ANALYSIS 5.1.1 ESTIMATED PROJECT COST The following are the estimated costs of the project based on the prevailing economy of the country.
TABLE 5.1: ESTIMATED PROJECT COST DESCRIPTION
COST (N m)
MACHINERY & EQUIPMENT
FACTORY & OFFICE BUILDING
AUXILIARY ITEMS (UTILITIES)
VALUE ADDED TAX (VAT, 5%)
The sales turnover is estimated at about thirty-million naira (N 30.0m) in the first year of operation while a profit margin of four million-naira (N 4.0m) is obtainable from the project. The project can be financed through a mixture of equity contribution, term loan and overdraft from commercial or merchant banks.
5.1.2 FIXED CAPITAL Fixed capital refers to buildings, industrial plants, machinery and tools, motor vehicles, office equipment (Max and Klaus, 1973). The cost of machinery and equipment
is estimated at about five million naira (N 4.90 m) and that of factory space is estimated at about two million (N 2.0m).
5.1.3 WORKING CAPITAL Working capital is mostly referred to as circulating capital which are nonrenewable goods, such as raw materials, fuel and the funds required to pay wages and other claims against the company ( Bauman, 1984; Ulrich, 1986). The estimated working capital required for this project is two million naira (N 2.0m). The raw materials are estimated for four months requirements including goods-intransit already paid for. The salary for the personnel should also be enough for three months pay. Proper arrangement should also be made for contingencies.
TABLE 5.2: THE BREAKDOWN OF THE WORKING CAPITAL ITEM
4 MONTHS RAW MATERIALS
3 MONTHS SALARY
5.1.4 NET COST The net cost of the biscuit production plant including provision for working capital and the value added tax (VAT) at 5% is estimated at about ten million naira (N 10.5 m).
5.2 COST OF PRODUCTION 5.2.1 RAW MATERIALS The main raw materials for the production of biscuit are flour, sugar, additives, water, baking powder and yeast. Wheat flour and sugar are produced locally and this will reduce the overall cost of production. Additives include; flavouring, shortening, colourants and modifiers, which are also obtained locally while water, baking powder and yeast, are readily available.
Most of these materials are locally produced (although most of them are still imported to meet the demand of the populace) and thus help reduce the overall cost of production and consequently produce biscuit at a cheaper rate, but putting into consideration that they must of necessity be good food grade and hygienic.
5.2.2 LABOUR COST In estimating the labour requirement and cost for plant personnel, a one eight hour shift was assumed for the direct production workers. The indirect production workers will also operate a single shift for eight hours. The full labour requirement which are detailed in Appendix C are summarised below:
TABLE 5.3: LABOUR COST DESCRIPTION
COST (N m)
DIRECT PRODUCTION WORKERS
INDIRECT PRODUCTION WORKERS
5.2.3 OVERHEAD COST The estimated overhead cost are enumerated in Appendix C. They are allocated between production, administration and sales as follows:
TABLE 5.4: OVERHEAD COST DESCRIPTION
ADMIN & SALES
In estimating the depreciation charges, the plant and building were written off over a 20 years period, the equipment over 10 years, the office equipment and furniture over 5 years. The charges arrived at are as follows:
TABLE 5.5: DEPRECIATION ASSETS
VALUE (N m)
DEPREC. RATE %
ANNUAL DEP. (N m)
OFFICE & FACTORY BUILDING
PLANT & EQUIPMENT
OFFICE FURNITURE & EQUIPMENT
5.4 PROJECTED INCOME AND EXPENSES STATEMENT (2002-2005) Based on the production capacity of one tonne of biscuit per day, the total annual output (allowing 30 days for planned maintenance work) is 280 tonnes. The average output of 210 tonnes has been estimated for the plant first year of operation (working at 75% capacity).
TABLE 5.6: PROJECTED INCOME AND EXPENSES STATEMENT
RAW MATERIAL (N m)
FACTORY LABOUR (N m)
DEPRECIATION (N m)
OVERHEAD (N m)
TOTAL (N m)
BEFORE INTEREST(N m)
LOAN INTEREST (N m) NET PROFIT (N m)
REVENUE NET SALES (N m) EXPENDITURE
CHAPTER SIX SAFETY,SITE & CONCLUSION
6.1.1 SANITATION In the biscuit industries, sanitation is the planned control of the production environment, equipment and personnel to prevent or minimize loss, product contamination and condition offensive to the aesthetic senses of the discriminating consumer and to provide clean, healthful and safe working conditions. Some of the broad areas of sanitation concern are(Meyer, 1992):  GOOD MANUFACTURING PRACTICES: This implies orderliness and freedom from refuse in all areas.  RODENT ELIMINATION: It involves knowledge of rodent
recognition of problems and permanent control through structural changes, removal of harbourages and food supplies, and supplementary poisoning and trapping.  INSECT ELIMINATION: Insect elimination from finished products and ingredients in the factory requires recognition of serious or incipient infestations, identification and knowledge of habits and ecology. Control methods may involve changes in structure, equipment or process and safe use of insecticide chemicals.  MICRO-ORGANISMS: The type and significance of which vary with product and type of operation, must often be controlled by process and equipment change, cleaning and sanitising chemicals. Construction and maintenance of buildings and equipment are of major importance in sanitation. New units can be planned to simplify sanitation maintenance, reduce costs and eliminate the hazards of contamination and spoilage. Cleaning of plant and equipment involves careful organisation, training, work scheduling and the use of the best available equipment, methods and materials. The trend is to clean processing equipment in place, without dismantling. This is done by an automatic system that circulates and sprays cleaning and sanitizing solutions inside equipment in time sequence. Employment facilities, such as rest room, locker rooms, drinking water, eating facilities and working environment, must be well maintained for the comfort and safety of the workers if they are to remain happy and maintain production efficiency and product quality.
Laboratory tests, of importance to the sanitation program in the biscuit plant, must be understood to be utilized to the best advantages. Water supply quality and plant distribution systems, as well as waste treatment and disposal, lighting and ventilation are often a part of sanitation. Inspection techniques tailored to the specific sanitation situation must be taught, learned and applied for efficient functioning and adjustment of the sanitation program.
6.1.2 WASTE MANAGEMENT This is a newer approach to cost-effective food-processing waste disposal. Through waste management, modifications are applied to biscuit plant operation and manufacturing processes. These modifications reduce the amount of solid and liquid wastes, recover more product and by-products, often reduce energy consumption and exhibit other benefits. In general, the principle is to convert waste liabilities into profitable assets. One major objective of waste management is to eliminate or at least lessen the dependence upon end-of-the-pipe sanitary engineering methods. This is achieved by reducing both the amount of waste solids generated and the volume of the waste water discharged (Adeniyi, 1998). The following are examples of modifications, which can be made to biscuit plant operations:  Incorporating good manufacturing practices  collecting culls and other solid wastes into containers rather than discharging to the floor drain,  recycling water  reusing spent process water in another plant operation and  using less or no water in plant operations that formerly used a fair to a large amount of water. Good manufacturing practices that reduce water usage and waste require good personnel management and employee awareness of conservation practices. Such practices as needless use of water or overloading of containers, thereby causing spillage, should be discouraged. Recycling of water in the same plant operation can be achieved by treating spent process water with activated charcoal or sand filter or by ion-exchange columns, chemical
treatment, pH adjustment, temperature adjustment, pasteurisation, or a combination of these and other methods. Counter currents water reuse systems can be established in many plant operations. For example, spent wash water can be used again to initiate wash down of dirty floors or to flume solid waste away from the process line.
6.1.3 HUMAN SAFETY Any organisation has a legal and moral obligation to safeguard the health and welfare of its employees and the general public safety is also good business; the good management practices needed to ensure safe operation will also ensure efficient operation. The term "loss prevention" is an insurance term, the loss being the financial loss caused by an accident. This loss will not be the cost of replacing damaged plant and third party claims but also the loss of earnings from lost production and lost sales opportunity. Safety and loss prevention in biscuit industries can be considered under the following broad headings; 1) Identification and assessment of hazards. 2) Control of the hazards. 3) Control of the process. Prevention of hazardous deviation in (pressure, temperature, flow), by provision of alarms, trips together
automatic control systems, interlocks,
with good operating practices and management.
4) Limitation of loss. The damage and injury caused if an accident occurs; pressure relief, plant layout, provision of fire fighting equipment.
6.1.4 THRESHOLD LIMIT VALUE This is the most commonly used guide for controlling the long-term exposure of workers to contaminated air. The threshold limit value is defined as the concentration to which it is believed the average worker could be exposed to day to day, for eight hours a day, five days a week, without suffering harm (Odigure, 1995).
Excessive noise is a hazard to health and safety. Long exposure to high noise level can cause permanent damage to hearing. At lower levels, noise is a distraction and causes fatigue. Excessive plant noise can lead to complains from neighbouring factories and local residents. Due attention should be given to noise levels when specifying and when laying out equipment that is likely to be excessively noisy and such as compressors, fans, barriers and steam relief valves.
6.2 PLANT LOCATION AND SITE SELECTION The location of the plant can have a crucial effect on the profitability of a project, and the scope for future expansion. The principal factors are: (1) Location with respect to the marketing area (2) Raw material supply (3) Transport facility (4) Availability of labour (5) Availability of utilities (water, fuel, power etc.) (6) Availability of suitable land (7) Environmental impact and effluent disposal (8) Climate (9) Political and strategic consideration
6.2.1 MARKETING AREA For a product such as biscuit in which case the product per tonne is low the plant should be located close to the primary market.
6.2.2 RAW MATERIALS The availability of suitable raw materials will often determine the site location. A plant that will produce biscuit should be sited close to where the major raw materials are available.
The transport of materials and products to and from the plant is an overriding consideration in site location. The plant should be located close to at least two major forms of transport: road, rail, waterway (canal and river) or airport. Choosing at least two will be an added advantage for the two cannot be out of service at the same time.
6.2.4 AVAILABILITY OF LABOUR Labour will be needed for construction of the plant and its operation. Skilled workers will be brought in from outside the site area, but there should be an adequate pool of unskilled labour locally and labour suitable for training, to operate the plant. Skilled tradesmen will be needed for plant maintenance.
6.2.5 UTILITIES A biscuit plant invariably requires large quantities of water for its operation (process and general use). Hence the plant must be located near a source of water of suitable quality. Process water may be drawn from borehole or purchased from local authority. Electrical power will be needed for the plant production process (mixer, electric pumping machine, oven heater etc.) and also for lightings.
6.2.6 ENVIRONMENTAL IMPACT Full consideration must be given to the difficulties and cost of disposal of biscuit plant's by-product.
6.3 LAND (SITE) CONSIDERATION Sufficient suitable land must be available for the proposed plant and for future expansion, the land should be ideally flat, well drained and have suitable load bearing characteristics.
6.4 CLIMATE Since weather in Nigeria is neither too hot nor too cold, the site consideration in form of climate can be neglected since the raw materials will not degrade in quality over the little time for storage and production. Also the country is not situated within the earthquake region of the world.
6.5 POLITICAL AND STRATEGIC CONSIDERATION Capital grants and other inducement are often given by government to direct new investment to preferred area or locations such as high unemployment prone zone. The availability of such grants can be the overriding consideration in site selection.
6.6 SITE LAYOUT The biscuit industry and ancillary building should be laid out to give the most economical flow of material and personnel around the site. Consideration must also be given to the future expansion of the biscuit factory. The ancillary buildings and services required on a site in addition to the main processing units (buildings) will include: (1) Storage for raw materials and products (2) Maintenance workshop (3) Stores for maintenance and operating supplies (4) Laboratory for process control (5) Fire station and other emergency services (6) Utilities (storage tank, cooling water, steam) (7) Effluent disposal plant (8) Offices for general administration (9) Canteens, car park, security post etc. When roughing out the biscuit factory layout the process unit will normally be sited first and arranged to give a smooth flow of material through the various processing steps, from raw material to final step. The location of principal ancillary buildings should then be decided. They should be arranged so as to minimize the time spent by personnel in travelling between buildings. The sitting of the main process route will determine the layout of the plant roads, pipe alleys and drains. Access roads will be needed to each building for construction, operation and maintenance. Utility buildings should be sited to give the most economical runs of pipes to and from the process units. The main storage area should be placed between the loading and unloading.
REFERENCES Adeniyi O.D. (1998) “ Design of a plant to produce one tonne of Biscuit per day” Plant
Design Thesis, Federal University of Technology, Minna, pp. 1-63 Bauman H.C. (1984) “Fundamental of cost engineering in the chemical industry” Reinhold Publishing corporation, New York, pp. 16-67, 415-516 Crenan J.G. and Butter J.R. (1990) “ Food engineering operation,” George Godwin Inc., Vol. 3, London, pp. 571-603 Macrea J.A. and Robbinson D.K. (1987) “ Drying principles and practice,” Pergamon Press, Oxford, pp. 14-21, 115, 231,412 Marcel and Dekkar (1987) “ Handbook of industrial drying” Munjar Inc., 4th edition, New York, pp. 393-412 Max P. and Klaus D.T. (1973) “ Plant design and economics for chemical engineers” McGraw Hill Book company, New York, 3rd edition, pp. 11-24 Meyers R.A. (1992) “Encyclopaedia of physical science and technology” vol. 15, 2nd Edition, academic press Inc., London, pp, 519-520 Odigure J.O. (1995) “General chemical engineering technology” Jodigs and associate, Minna, pp. 19-24, 129 Ogunsola V. (1999) “Food preparation recipes for Nigerians schools and homes” Update Media ltd., Ilorin, pp. 116-128 Onyia C. (1997) “ Make your money producing biscuits” Success digest magazine, Lagos Perry R.H. and Peacock D.G. (1994) “Coulson and Richardosn chemical engineering” Vol. 3, 3rd edition, Pergamon Press, Great Britain, pp. 71-103 Ulrich G.D. (1986) “ A guide to chemical engineering process design and economics” Wiley & sons company, New York, pp. 33,46,105
APPENDIX A LIST OF PRODUCTION PLANT MACHINERY
A list of the production machinery needed for the production of one tonne of biscuit per day is (Adeniyi, 1998): [A] THE MIXING UNIT (a) 2 water tanks (b) 1 mixer (c) 1 weighing machine (d) 1 measuring/regulating device for water (e) 1 water pump [B] THE EXTRUDER UNIT (a) 1 extruder fitted with mould, cutting and stamping device [C] THE DRYING UNIT (a) 1 horizontal dryer with conveyor belt (b) 1 collection table (c) trays [D] THE PACKAGING UNIT (a) 6 wooden silos (b) 6 tables (c) 6 weighing machines (d) Nylon sealing machines
APPENDIX B CALCULATION OF MASS & ENERGY BALANCE
B1.1 OVERALL BALANCE The composition of the feed is as listed in chapter three. From the material balance carried out it can be seen that to get a product of 1000 kg (1 tonne) of biscuit, a feed mass of 1357.15 kg of the raw material is required. This will require the following mass of feed:  Flour 678.58 kg
 Sugar 27.14 kg
 Water 407.15 kg
 Baking powder 27.14 kg
 Addition/modifier 217.14 kg
B1.1.1 MATERIAL BALANCE Taking a basis of 1000 kg of feed; the masses of the feed based on the composition is: (a) Flour = 50%=500 kg (b) Sugar = 2.0%=20 kg (c) Water = 30%=300 kg (d) Baking powder = 2.0%=20 kg (e) Additives = 16%=160 kg Initial moisture content = 30%=300 kg Final moisture content = 5% = 50kg 300 kg of moisture is associated with 700 kg of dough 300 kg ---> 700 kg (i.e. 300 kg + 700 kg = 1000 kg) 50 kg ---> 950 kg of dry matter (i.e. 50 + 950 =1000 kg) ==> (50 x 700)/950 =36.84 kg moisture associated with 700 kg 1000kg of original matter must loss (300-36.84)=263.16 kg of moisture ==> weight of dried matter leaving the dryer =1000-263.16 =736.84 kg Working backward, 0.30T ---> 0.70T 0.05T ---> 0.95T Y=(0.05T x 0.70T) / 0.95T =0.0368T x of the original matter must loss (407.15-49.998) = 357.15kg 0.3T - 0.0368T = 357.15 kg
T(0.3-0.0368) = 357.15 kg T= 357.15/0.2632=1356.95 kg The difference (1000-736.84) =263.16 kg of moisture lost The difference (1356.95-357.15)= 999.8 kg of biscuit, this value is 0.2 short of the expected 1000kg. This means that the original feed must be (1356.95 + 0.2)= 1357.15 kg.
B1.1.2 HEAT BALANCE Heat capacity = ((4.19 P) +(0.84(100-P)))/100 where P= moisture content of biscuit dough =30% Heat capacity=((4.19x30)+(0.84(100-30)))/100=1.845 kJ/kgoC Latent heat = 335P/100= 335x30/100=100.50 kJ/kgoC Heat required for 1kg original material: = Heat energy to raise temp. to 100oC + Latent heat to vaporise
water = m1Cp0 + m2L
=1 x 1.845(100-30) + (357.17 x 2257)/1357.15 = 715.97 kJ (kW/s) The heat required in baking 1357.15kg = 1357.15x1.845(240-30) + 357.17 x 2257 = 525827.77+806132.69 = 1331960.46 kJ Since 10% of moisture is lost the overall heat balance over the oven is: m1=(1357.15-(1357.15x10)/100 = 1221.44 kg me
=(357.17 - (357.17x10)/100 = 321.453 kg
Heat = 1221.44 x 1.845 (240-30)+ 321.453x2257 =1198766.35 kJ From the material balance carried out, to get a product of 1000kg (1 tonne) of biscuit we will need to feed a mass of about 1492.96 kg of the raw material. This will require the following mass of feed:  Flour 746.48 kg
 Sugar 298.59 kg
 Water 447.84 kg
 Baking powder 29.86 kg
 Addition/modifier 238.87 kg The loss is estimated at 134.85 kg to make up to 1492.96 (1357.15 + 134.85)
B1.1.3 OVERALL MATERIAL BALANCE In a hourly basis:
Mass in Total material in = (1492.96/8) =186.62 kg/hr Total dry solid in = (1045.12/8) =130.64 kg/hr Total water in
= (447.84/8)= 55.98 kg/hr
Mass out Total material out = (1100/8) = 137.5 kg/hr Total dry solid out = (1045/8) = 130.63 kg/hr Total water out
= (55/8) = 6.875 kg/hr
Loss = 49.11 kg/hr 3.1.2 UNIT MATERIAL BALANCE 18.104.22.168 MIXER Mass in Total material in = 1492.96 kg Water in
= (30% of 1492.96) = 447.84 kg
= (70% of 1492.96) = 1045.12 kg
Since there is no loss in the mixer Material in = material out 1492.96 kg = 1492.96 kg On an hourly basis: Total material in = Total material out Water in = Water out = 55.98 kg/hr Solid in =
Solid out = 130.64 kg/hr
22.214.171.124 EXTRUDER Mass in Water in Solid in
= 447.84 kg =
Total material in = (447.84 + 1045.12)=1492.96 kg Mass out Water out Solid out
= 261.25 kg =
Losses = 186.71 kg Total material out =(1045 +261.25)= 1306.25 kg
On a hourly basis: Water in
= (447.84/8) = 55.98 kg/hr
= (1045.12/8) =130.64 kg/hr
Material in (total) =(55.98 + 130.64)= 186.62 kg/hr Water out = (261.25/8)= 32.66 kg/hr Solid out =(1045/8)= 130.63 kg/hr ; Losses = (186.71)/8=23.34 kg/hr Total material out =32.66 + 130.63 = 163.29 kg/hr 126.96.36.199 DRYER Basis: 1000kg/hr of product Water in
= 261.25 kg
= 1045.00 kg
Total material in = (261.25 + 1045)=1306.25 kg Water out
= 55 kg
= 1045 kg
Total material out =(55+1045) = 1100 kg On a hourly basis: Material in = 1306.25/8= 163.28 kg/hr Material out =1100/8= 137.50 kg/hr Dry solid in = 1045/8=130.63 kg/hr Dry solid out =1045/8=130.63 kg/hr Water in = 261.25/8= 32.656 kg/hr Water out =55/8= 6.875 kg/hr 3.2
3.2.1 OVERALL ENERGY BALANCE HEAT
GENERATED FOR THE MIXER + HEAT GENERATED FOR THE
+ HEAT GENERATED FOR THE DRYER = TOTAL HEAT LOAD
80568 + 469800 + 99990.824 = 650358.824 kJ/hr 3.2.2 UNIT ENERGY BALANCES Most of the energy balances were done using the computer program developed (Appendix D) 188.8.131.52
Heat in = 80568 kJ/hr
Heat load in dough = 4226.72 kJ/hr Heat loss in mixer = 76341.28 kJ/hr 184.108.40.206
Heat in = Heat out Heat generated in extruder = Heat load in dough + heat loss
Heat generated = 469800 kJ/hr Heat loss in extruder = 448516.8 kJ/hr Heat load in dough = 21283.2 kJ/hr 220.127.116.11 DRYER The dryer zone has three zones: Zone 1 (heating zone) Heat generated for solid = 19725.13 kJ/hr Heat generated for liquid = 13682.864 kJ/hr Total heat load for zone 1 19725.13 + 13682.864 = 33407.994 kJ/hr Zone 2 (constant rate change zone) Heat in = Heat out Heat generated = 40953.265 kJ/hr ZONE 3 (falling rate zone) Heat load for solid = 3944.12 kJ/hr Heat load for evaporated water = 21109.32 kJ/hr Total heat load in the filling rate zone = Heat in solid + Heat in evaporated liquid = 3944.12 + 21109.32 + 576.125 = 25629.565 kJ/hr Total load for the dryer = 33407.994 + 40953.265 + 25629.565 =
99990. 824 kJ/hr
APPENDIX C FINANCIAL EVALUATION
C1.0 LABOUR REQUIREMENT AND COST The total labour requirements were estimated on the basis that the direct production workers will work one eight hour shift and the indirect production workers also a single eight hours shift. C1.1 DIRECT PRODUCTION WORKERS NUMBER
PACKAGING UNIT TOTAL
C1.2 INDIRECT PRODUCTION WORKERS
C1.3 OVERHEAD COST
ADM. & SALES
FUEL,POWER & WATER
GROUND RATE & RENT
POSTAGE & PHONE
C1.4 PROJECTED INCOME AND EXPENSES STATEMENT 1 Tonne of biscuit/day, in 1 year = 1x365 tonnes Less 30 days of maintenance =365-30=326 tonnes Less 48 days of non-working days in a year = 326-48= 278 .
Based on capacity the following tonnes are evaluated: (a) 75%=0.75x280=210
C1.4.1 REVENUE Total sales revenue of N30m is expected on 100% capacity. So for other capacities: (a) 75%=0.75x30= N 22.50m (b) 85%=0.85x30= N 25.50m (c) 95%=0.95x30= N 28.50m (d) 100%=1.00x30= N 30.00m C1.4.2 Depreciation 1st year (2002)=0.365 2nd year (2003) a. Factory= 0.1 – (5/100 x 0.1)=0.0950 b. Equipment= 0.245 – (5/100 x 0.245)=0.2328
c. Furniture = 0.02 – (10/100 x 0.02)=0.018 Depreciation = 0.0950 + 0.2328 + 0.018 = 0.3458 3rd Year (2004) d. Factory= 0.0950 – (5/100 x 0.0950)=0.0903 e. Equipment= 0.2328 – (5/100 x 0.2328)=0.2212 f. Furniture = 0.018 – (10/100 x 0.018)=0.0162 Depreciation = 0.0903 + 0.2212 + 0.0162 = 0.3277 4th Year (2005) g. Factory= 0.0903 – (5/100 x 0.0903)=0.08579 h. Equipment= 0.2212 – (5/100 x 0.2212)=0.2101 i. Furniture = 0.0162 – (10/100 x 0.0162)=0.01458 Depreciation = 0.08579 + 0.2101 + 0.01458 = 0.3105 C1.4.3 Overhead Overhead = total – depreciation 1st year = 1.292 – 0.365= 0.927 2nd year = 0.927 x 85/75= 1.0506 3rd year = 0.927 x 95/75 =1.1742 4th year = 0.927 x 100/75 = 1.2360 C1.4.4 Trading profit Trading profit before interest = revenue - expenditure 1st year = 22.50 – 9.022= 13.478 2nd year = 25.50 – 10.0564 =15.4436 3rd year = 28.50 – 11.2819 =17.2181 4th year = 30.00 – 12.0865 = 17.9135 C1.4.6 Net profit: net profit = trading profit – loan interest 1st year = 13.478 – 0.8 = 12.6780 2nd year = 15.4436 – 0.6 = 14.8436 3rd year = 17.2181 – 0.4 = 16.8181 4th year = 17.9135 – 0.2 = 17.7135
APPENDIX D COMPUTER PROGRAM A computer program was written in basic to solve the material and energy balance, the program is listed below (Adeniyi, 1998): CLS LOCATE 2, 20: PRINT "PLANT DESIGN PROJECT" LOCATE 4, 2: PRINT "DESIGN OF A BISCUIT PLANT WITH 1 TONNE CAPACITY PER DAY" LOCATE 6, 20: PRINT "COMPILED BY GROUP TWO" LOCATE 8, 20: PRINT "FEBRUARY 1998" 'A$ = INPUT$(1) 20 : INPUT "Mass of feed (Kg)"; F MA = .3 * F MB = .7 * F MC = .05 * F MD = .95 * F ML = (MC * MB) / MD MM = MA - ML WB = F - MM HC = ((4.19 * 80) + (.84 * (100 - 80))) / 100 LH = (335 * 80) / 100 HR = ((100 - 80) * HC) + (.25 * 2257) HR2 = HR / 3600 PRINT "OVERALL MATERIAL AND HEAT BALANCES" PRINT "Weight of moisture lost by wet dough in dryer="; MM; "Kg" PRINT "Weight of dried biscuit leaving the drier ="; WB; "Kg" PRINT "Heat capacity of biscuit ="; HC PRINT "Latent heat of biscuit="; LH; "KJ/KgΕ C" PRINT "Heat required to dry 1Kg of biscuit="; HR; "KJ"; "or"; HR2; "KW/h" HH = ((240 - 80) * HC * F) + (MM * 2257) PRINT "Heat required to dry"; F; " Kg ="; HH; "KJ"
PRINT "IS THE MATERIAL BALANCE SATISFACTORY" PRINT "THEN PRESS Y FOR YES AND N FOR NO" 30 : A$ = INKEY$: IF A$ = "" THEN 30 IF A$ = "Y" THEN 50 IF A$ = "y" THEN 50 IF A$ = "N" THEN 20 IF A$ = "n" THEN 20 50 : WIN = .3 * F ASIN = .7 * F TIN = WIN + AASIN PRINT "MASS BALANCE OVER MIXER" PRINT "Weight of water in is equal to weight of water out="; WIN; "Kg" PRINT "Weight of solid in is equal to weight of dough out="; ASIN; "Kg" A$ = INPUT$(1) 60 : AD = (.95 * WB) / .8 WOUTD = .05 * WB SOUTD = WB - AD ASIND = .8 * AD WIND = .2 * AD
PRINT "MASS BALANCE OVER DRYER" PRINT "Weight of moisture entering dryer="; WIND; "Kg" PRINT "Weight of moisture leaving dryer="; WOUTD; "Kg" PRINT "Weight of dough entering dryer="; ASIND; "Kg" PRINT "Weight of dough leaving dryer="; SOUTD; "Kg" A$ = INPUT$(1)
WINE = .3 * F WOUTE = WIND WRE = WIN - WOUTE ASINE = .7 * F SOUTE = .2 * AD PRINT "MASS BALANCE OVER THE EXTRUDER" PRINT "Weight of moisture entering extruder="; WINE; "Kg" PRINT "Weight of moisture leaving extruder="; WOUTE; "Kg" PRINT "Weight of moisture removed from extruder="; WRE; "Kg" PRINT "Weight of dough entering extruder="; ASINE; "Kg" PRINT "Weight of dough leaving extruder="; SOUTE; "Kg" A$ = INPUT$(1) 80 :
HEE = 22.38 * 3600 HLD = WRE * 1.57 * 15 HLM = HLD - HEE
PRINT "HEAT BALANCE OVER THE DRYER" PRINT "Heat load in dough="; HLD; "KJ/h" PRINT "Heat loss in extruder"; HEE; "KJ/h" 90 : PRINT "HEAT BALANCE OVER THE DRYER" PRINT "Balance is estimated over 3 zones of the dryer" PRINT "ZONE 1- HEATING ZONE" PRINT "Inlet temperature =80Ε C" PRINT "Outlet temperature=180Ε C" QHL = (WIND * 4.19 * 100) / 8 QHS = (ASIND * 1.5 * 100) / 8 QH1 = QHL + QHS PRINT "The heat load in liquid="; QHL; "KJ/h" PRINT "The heat load on dough="; QHS; "KJ/h" PRINT "The total heat load for zone 1="; QH1; "KJ/h" A$ = INPUT$(1) PRINT "ZONE 2- CONSTANT RATE ZONE"
PRINT "Inlet temperature =180Ε C" PRINT "Outlet temperature=220Ε C" QC = 2257 * 18.145 PRINT "The total heat load for zone 2="; QC; "KJ/h" A$ = INPUT$(1) PRINT "ZONE 3- FALLING RATE ZONE" PRINT "Inlet temperature =220Ε C" PRINT "Outlet temperature=240Ε C" QFS = 130.6 * 1.51 * (240 - 220) QFE = 7.635 * (2769 - 4.19) QFV = 6.875 * 4.19 * (240 - 220) Q3 = QFS + QFE + QFV QT = Q1 + QC + Q3 QM = 469800 PRINT "The Heat load for the dough ="; QFS; "KJ/h" PRINT "The heat load for the evaporated liquid="; QFE; "KJ/h" PRINT "The heat load for the unevaporated liquid="; QFV; "KJ/h" PRINT "The heat load for zone 3="; Q3; "KJ/h" PRINT "The total heat load for the dryer= "; QT; "KJ/h" PRINT "IS THE UNIT BALANCE SATISFACTORY" PRINT "THEN PRESS Y FOR YES AND N FOR NO" 120 :
A$ = INKEY$: IF A$ = "" THEN 120
IF A$ = "Y" THEN 200 IF A$ = "y" THEN 200 IF A$ = "N" THEN 20 IF A$ = "n" THEN 20 200 :
QQT = QT + HEE + QM
PRINT "THE OVERALL HEAT GENERATED OVER THE WHOLE PROCESS="; QQT; "KJ/h" END
APPENDIX E TYPICAL SUPPLIED HORSEPOWER FOR SIGMA BLADE Table E1: Typical supplied horsepower (Hp) for sigma blade
Floor space (ft2)
8 x 10
9 x 11
9 x 13
9 x 14
11 x 16
12 x 16
12 x 17
14 x 18
Conversion rating 1 Gallon = 0.003785 m2 = 3.785 litres 1 ft = 0.3048 m 1 Hp = 0.746 kW