Understanding Refractory API 936 Reading V
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Understanding Refractory API 936 Reading V...
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Understanding REFRACTORY For API936 Personnel Certification Examination Reading 5 My Pre-exam Self Study Notes 1st October 2015
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Steel Mill
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BODY OF KNOWLEDGE FOR API936 REFRACTORY PERSONNEL CERTIFICATION EXAMINATION API certified 936 refractory personnel must have knowledge of installation, inspection, testing and repair of refractory linings. The API 936 Personnel Certification Examination is designed to identify applicants possessing the required knowledge. The examination consists of 75 multiple-choice questions; and runs for 4 hours; no reference information is permitted on the exam. The examination focuses on the content of API STD 936 and other referenced publications.
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REFERENCE PUBLICATIONS: A. API Publications: API Standard 936; 3rd Edition, Nov 2008 - Refractory Installation Quality Control Guidelines - Inspection and Testing Monolithic Refractory Linings and Materials.
B. ACI (American Concrete Institute) Publications: 547R87 - State of the art report: Refractory Concrete 547.1R89 - State of the art report: Refractory plastic and Ramming Mixes
C. ASTM Publications: C113-02 - Standard Test Method for Reheat Change of Refractory Brick C133-97 - Standard Test Methods for Cold Crushing Strength and Modulus of Rupture of Refractories C181-09 - Standard Test Method for Workability Index of Fireclay and High Alumina Plastic Refractories C704-01 - Standard Test Method for Abrasion Resistance of Refractory Materials at Room Temperatures
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闭门练功
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http://independent.academia.edu/CharlieChong1 http://www.yumpu.com/zh/browse/user/charliechong http://issuu.com/charlieccchong
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http://greekhouseoffonts.com/
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The Magical Book of Refractory
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Fion Zhang at Shanghai 1st October 2015
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Video Time- shotcrete refractory
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https://www.youtube.com/watch?v=s81LE7XXZ4A&list=PLey7s_Oct4OK9-7tMIx5cp9-RjSdetDTq
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Reading V Content:
Study note One : Introduction to refractory and insulating materials Study note Two : Study note Three : Study note Four :
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Reading 1: Introduction to refractory and insulating materials
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http://materialrulz.weebly.com/uploads/7/9/5/1/795167/refractory_materials.pdf
ZONES OF BLAST FURNACE (WITH AVG TEMPERATURE)
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2732°F
3452°F
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ZONES OF BLAST FURNACE (WITH AVG TEMPERATURE)
1292°F
Blast Furnace
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1.0 REFRACTORY MATERIALS A material having the ability to retain its physical shape and chemical identity when subjected to high temperatures. Refractories, bricks of various shapes used in lining furnaces. (castable, refractory concrete, refractory plastid) Refractories are inorganic, nonmetallic (the oxide?) , porous (a necessity?) and heterogeneous materials composed of thermally stable mineral aggregates, a binder phase and additives. ASTM C71 defines refractories as "non-metallic materials having those chemical and physical properties that make them applicable for structures or as components of systems that are exposed to environments above 1,000°F (811 K; 538°C)".
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Refractories are heat resistant materials used in almost all processes involving high temperatures and/or corrosive environment. These are typically used to insulate and protect industrial furnaces and vessels due to their excellent resistance to (1) heat, (2) chemical attack and (3) mechanical damage (erosion). Any failure of refractory could result in a great loss of production time, equipment, and sometimes the product itself. The various types of refractories also influence the safe operation, energy consumption and product quality; therefore, obtaining refractories best suited to each application is of supreme importance.
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2.0 Refractories perform four basic functions: 1. They act as a thermal barrier between a hot medium (e.g., flue gases, iquid metal, molten slags, and molten salts) and the wall of the containingvessel; 2. They insure a strong physical protection, preventing the erosion of walls by the circulating hot medium; 3. They represent a chemical protective barrier against corrosion; 4. They act as thermal insulation, insuring heat retention. The principal raw materials used in the production of refractories are: 1. the oxides of silicon, aluminum Al2O3 , magnesium MgO, calcium CaO and zirconium ZrO2 and 2. some non-oxide refractories like carbides MC, nitrides MN, borides MB, silicates MSiO2 and graphite C. Where: M is the metallic radical
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3.0 What are Refractories used for? Refractories are used by the metallurgy industry in the internal linings of furnaces, kilns, reactors and other vessels for holding and transporting metal and slag. In non-metallurgical industries, the refractories are mostly installed on fired heaters, hydrogen reformers, ammonia primary and secondary reformers, cracking furnaces, utility boilers, catalytic cracking units, coke calciner, sulfur furnaces, air heaters, ducting, stacks, etc. Majority of these listed equipment operate under high pressure, and operating temperature can vary from very low to very high (approximately 900°F to 2900°F). The refractory materials are therefore needed to withstand temperatures over and above these temperatures. Due to the extremely high melting point of common metals like iron, nickel and copper, metallurgists have to raise furnace temperatures to over 2800°F.
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4.0 Requirements of Right Refractory The general requirements of a refractory material can be summed up as: 1. Its ability to withstand high temperatures and trap heat within a limited area like a furnace; 2. Its ability to withstand action of molten metal, hot gasses and slag erosion etc; 3. Its ability to withstand load at service conditions; 4. Its ability to resist contamination of the material with which it comes into contact; 5. Its ability to maintain sufficient dimensional stability at high temperatures and after/during repeated thermal cycling; 6. Its ability to conserve heat.
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5.0 Properties of Refractories Important properties of refractories are: chemical composition, bulk density, apparent porosity,apparent specific gravity (= bulk density?) and strength at atmospheric temperatures (compressive strength, MOF). These properties are often among those which are used as “control points” in the manufacturing and quality control process. Some of the important characteristics of refractories are:
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1) Melting Point: Melting temperatures (melting points) specify the ability of materials to withstand high temperatures without chemical change and physical destruction. The melting point of few elements that constitute refractory composition in the pure state varies from 3100°F– 6300°F as indicated in the table below: (The melting point serves as a sufficient basis for considering the thermal stability of refractory mixtures and is an important characteristic indicating the maximum temperature of use.)
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2) Size and Dimensional Stability: The size and shape of the refractories is an important feature in design since it affects the stability of any structure. Dimensional accuracy and size is extremely important to enable proper fitting of the refractory shape and to minimize the thickness and joints in construction.
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3) Porosity: Porosity is a measure of the effective open pore space in the refractory into which the molten metal, slag, fluxes, vapors etc can penetrate and thereby contribute to eventual degradation of the structure. The porosity of refractory is expressed as the average percentage of open pore space in the overall refractory volume. High porosity materials tend to be highly insulating as a result of high volume of air they trap, because air is a very poor thermal conductor. As a result, low porosity materials are generally used in hotter zones, while the more porous materials are usually used for thermal backup. Such materials, however, do not work with higher temperatures and direct flame impingement, and are likely to shrink when subjected to such conditions. Refractory materials with high porosity are usually NOT chosen when they will be in contact with molten slag because they cannot be penetrated as easily. (?)
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4) Bulk Density: The bulk density is generally considered in conjunction with apparent porosity. It is a measure of the weight of a given volume of the refractory. For many refractories, the bulk density provides a general indication of the product quality; it is considered that the refractory with higher bulk density (low porosity) will be better in quality. An increase in bulk density increases the volume stability, the heat capacity, as well as the resistance to abrasion and slag penetration.
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5) Cold Crushing Strength: The cold crushing strength, which is considered by some to be doubtful relevance as a useful property, other than it reveals little more than the ability to withstand the rigorous of transport. It can be seen as a useful indicator to the adequacy of firing and abrasion resistance in consonance with other properties such as bulk density and porosity.
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6) Pyrometric Cone Equivalent (PCE) Refractories due to their chemical complexity melt progressively over a range of temperature. Hence refractoriness or fusion point is ideally assessed by the cone fusion method. The equivalent standard cone which melts to the same extent as the test cone is known as the pyrometric cone equivalent (PCE). According to ASTM C24 -01, PCE is measured by making a cone of the material and firing it until it bends to 3 oclock.
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Pyrometric cones are small triangular ceramic prisms that when set at a slight angle (known as self-supporting cones)bend over in an arc so that the tip reaches the level of the base at a particular temperature if heated at a particular rate. The bending of the cones is caused by the formation of a viscous liquid within the cone body, so that the cone bends as a result of viscous flow. The endpoint temperature when the tip of the cone touches the supporting plate is calibrated for each cone composition when heated at a standard rate. Values of endpoint temperatures for Orton cones (the U.S. name) are listed in Table for the higher temperatures. Since pyrometric cones are sensitive to both time and temperature, the actual temperatures associated with each cone can vary, but this is also one of the reasons why they are very useful for ceramic processing. Sintering, for example, depends on both time and temperature. PCE can be useful for quality control purposes to detect variations in batch chemistry that result from changes or errors in the raw material formulation.
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The Orton Cone
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https://www.youtube.com/watch?v=0iZn9HvXF8E
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PCE- Before Reading Further….fun time!
https://www.youtube.com/results?search_query=Pyrometric+Cone+Equivalent+
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Standard Test Method for Pyrometric Cone Equivalent (PCE) of Fireclay and High Alumina Refractory Materials
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1. Scope 1.1 This test method covers the determination of the Pyrometric Cone Equivalent (PCE) of fire clay, fireclay brick, high alumina brick, and silica fire clay refractory mortar by comparison of test cones with standard pyrometric cones under the conditions prescribed in this test method. 1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are for information only. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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2. Referenced Documents 2.1 ASTM Standards: C 71 Terminology Relating to Refractories E 11 Specification for Wire-Cloth Sieves for Testing Purposes E 220 Method for Calibration of Thermocouples by Comparison Techniques
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3. Terminology 3.1 Definitions—For definitions of terms used in this test method, see Terminology C 71.
4. Summary of Test Method 4.1 This test method consists of preparing a test cone from a refractory material and comparing its deformation end point to that of a standard pyrometric cone. The resultant PCE value is a measure of the refractoriness of the material. 4.2 Temperature equivalent tables for the standard cones have been determined by the National Institute of Standards and Technology when subjected to both slow and rapid heating rates.
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Keypoints: This test method consists of preparing a test cone from a refractory material and comparing its deformation end point to that of a standard pyrometric cone. The resultant PCE value is a measure of the refractoriness of the material. Keywords: comparing deformation end point standard pyrometric cone PCE value is a measure of the refractoriness
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5. Significance and Use 5.1 The deformation and end point of a cone corresponds to a certain heatwork condition due to the effects of time, temperature, and atmosphere. 5.2 The precision of this test method is subject to many variables that are difficult to control. Therefore, an experienced operator may be necessary where PCE values are being utilized for specification purposes. 5.3 PCE values are used to classify fireclay and high alumina refractories. 5.4 This is an effective method of identifying fireclay variations, mining control, and developing raw material specifications. 5.5 Although not recommended, this test method is sometimes applied to materials other than fireclay and high alumina. Such practice should be limited to in-house laboratories and never be used for specification purposes.
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6. Procedure 6.1 Preparation of Sample: 6.1.1 Clay or Brick— Crush the entire sample of fire clay or fireclay brick, in case the amount is small, by means of rolls or a jaw crusher to produce a particle size not larger than ¼ in. (6 mm). If the amount is large, treat a representative sample obtained by approved methods. Then mix the sample thoroughly and reduce the amount to about 250 g (0.5 lb) by quartering (see Note 1). Then grind this portion in an agate, porcelain, or hard steel mortar and reduce the amount again by quartering. The final size of the sample shall be 50 g and the fineness capable of passing an ASTM No. 70 (212 μm) sieve (equivalent to a 65-mesh Tyler Standard Series). In order to avoid excessive reduction to fines, remove them frequently during the process of reduction by throwing the sample on the sieve and continuing the grinding of the coarser particles until all the sample passes through the sieve (see Note 2). Take precautions to prevent contamination of the sample by steel particles from the sampling equipment during crushing or grinding. Comment: passed sieve ASTM No.75, retained ?
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NOTE 1— Take care during the crushing and grinding of the sample to prevent the introduction of magnetic material. NOTE 2— The requirement to grind the coarser particles is particularly important for highly siliceous products; excessively fine grinding may reduce their PCE by as much as two cones (two cone? 2 adjacent cone or numerically from cone (X-2) e.g. cone 20 to cone 18? ) .
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6.1.2 Silica Fire Clay (see 3.1)—In the case of silica fire clay, test the sample obtained by approved methods as received without grinding or other treatment. 6.2 Preparation of Test Cones: 6.2.1 After preparing samples of unfired clays (Note 3), or of mixes containing appreciable proportions of raw clay, in accordance with 6.1.1, heat them in an oxidizing atmosphere in the temperature range from 1700°F to 1800°F (925 to 980°C) for not less than 30 min. NOTE 3—Some unfired clays bloat 膨胀 when they are formed into cones and are carried through the high-temperature heat treatment prescribed in 5.4.1 without preliminary calcining. The substances that cause bloating can, in most cases, be expelled by heating the clay samples before testing.
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6.2.2 The clay sample may be given the heat treatment prescribed in 6.2.1 after it has been formed into a cone (see 6.2.3), but this procedure has been found not as effective as the treatment of the powdered material. If cones so prepared bloat during the PCE test, heat a portion of the original sample in its powdered condition as prescribed in 6.2.1 and then retest it. 6.2.3 Thoroughly mix the dried sample, and after the addition of sufficient dextrine 糊精, glue, gum tragacanth 树胶, or other alkali-free organic binder and water, form it in a metal mold into test cones in the shape of a truncated trigonal pyramid with its base at a small angle to the trigonal axis, and in accordance with dimensions shown in Fig. 1. In forming the test cone use the mold shown in Fig. 2.
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FIG. 1 Standard Pyrometric Test Cone NOTE 1—Dimensions are in inches.
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FIG. 2 Split Mold for ASTM Pyrometric Test Cone
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FIG. 2 Split Mold for ASTM Pyrometric Test Cone
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FIG. 2 Split Mold for ASTM Pyrometric Test Cone
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6.3 Mounting: 6.3.1 Mount both the test cones and the Standard Pyrometric Cones on plaques of refractory material that have a composition that will not affect the fusibility of the cones (see Note 4). Mount both (1) test and (2) PCE cones with the base embedded so that the length of the sloping face of the cone above the plaque shall be 15/16 in. (24 mm) and the face of the cone (about which bending takes place) shall be inclined at an angle of 82° with the horizontal. Arrange the test cones with respect to the PCE cones as shown in Fig. 3, that is, alternate the test cones with the PCE cones in so far as is practical (see Note 5). The plaque may be any convenient size and shape and may be biscuited before using, if desired.
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FIG. 3 Method of Mounting Test Cones and Appearance After Testing
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NOTE 4—A satisfactory cone plaque mix consists of 85 % fused alumina and 15 % plastic refractory clay. For tests that will not go above Cone 34, the plastic refractory clay may be increased to 25 % and the alumina may be replaced with brick grog containing over 70 % alumina. The alumina or grog should be ground to pass an ASTM No. 60 (250 μm) sieve (equivalent to a 60-mesh Tyler Standard Series), and the PCE of the refractory plastic clay should be not lower than Cone 32. NOTE 5—The number of cones and their mounting facing inward as shown in Fig. 3 is typical for gas-fired furnaces of relatively large dimensions and gases moving at high velocity. The practical bore of the muffle tubes in most electric furnaces does not permit cone pats of this size. The static atmosphere prevailing permits the cones being mounted to face outward, if so desired.
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6.4 Heating: 6.4.1 Perform the heating in a suitable furnace, operating with an oxidizing atmosphere, at rates to conform to the following requirements (see Note 6 and Note 7). It is advisable, but not mandatory that the furnace temperature be controlled with a calibrated thermocouple or radiation pyrometer connected to a program-controlled recorder. 6.4.1.1 For PCE tests expected to have an end point of PCE Cone 12 or above, but not exceeding Cone 26, heat at the rate prescribed in Table 1. 6.4.1.2 For PCE tests expected to have an end point above Cone 26, heat at the rate prescribed in Table 2. 6.4.2 The furnace atmosphere shall contain a minimum of 0.5 % oxygen with 0 % combustibles. Make provisions to prevent any external forces from being exerted on the cones or cone plaque, such as from flames or gases. Test the furnace at intervals to determine the uniformity of the distribution of the heat.
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NOTE 6—The heating rate through the cone series in both Table 1 and 2 is at 270°F (150°C)/h. NOTE 7—Following a test run, the cone pat may be removed at 1830°F (1000°C) and a new pat may be put in without cooling the furnace to below red heat. The time interval to bring the furnace, using Table 1, up to Cone 12 shall be not less than 20 min, and using Table 2, the time interval up to Cone 20 shall be not less than 25 min.
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6.5 Pyrometric Cone Equivalent: 6.5.1 The softening of the cone will be indicated by the top bending over and the tip touching the plaque. Always report the bloating, squatting, or unequal fusion of small constituent particles. Report the Pyrometric Cone Equivalent (PCE) in terms of Standard Pyrometric Cones and the cone that most nearly corresponds in time of softening with the test cone. If the test cone softens later than one Standard Pyrometric Cone but earlier than the next Standard Pyrometric Cone and approximately midway between, report the PCE as Cone 33–34. 6.5.2 If the test cone starts bending at an early cone but is not down until a later cone, report this fact. 6.5.3 The temperatures corresponding to the end points of the Standard Pyrometric Cones are frequently of interest and are shown in Appendix X1.
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7. Precision and Bias 7.1 Precision and bias are based on four participating laboratories. Although six labs are preferred, further participation is not anticipated or perceived possible. 7.2 Interlaboratory Data—An interlaboratory round robin 轮询/合作 was conducted in which four laboratories each tested specimens from four different types of refractory materials. Each laboratory performed three trials on each sample to determine the pyrometric cone equivalent (PCE). The cone differences are adjacent cones, not numeric cones. The components of variance from this study expressed as standard deviation and relative deviation are given in Table 3. Refer to Practice E 691 for calculation of the components of variance.
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7.3 Precision—Repeatability and reproducibility statistics were calculated at the 95% confidence level. The relative repeatability statistic means that two 7.4 test results of PCE obtained in one laboratory should not vary by more than about 1.47% for silica brick, for example. The relative reproducibility statistic means that two laboratories each obtaining a test result of PCE of silica brick should not differ by more than about 4.86 %, for example. Bias—No justifiable statement on bias is possible since the true physical property values of refractories cannot be established by an acceptable reference material.
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8. Keywords 8.1 PCE; pyrometric cone; pyrometric cone equivalent; refractories
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APPENDIX (Nonmandatory Information) X1. TEMPERATURES CORRESPONDING TO STANDARD PYROMETRIC CONE END POINTS
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X1.1 The approximate temperature equivalents corresponding to the end points of those Standard Pyrometric Cones that are used in connection with refractory testing are as shown in Table X1.1. X1.2 Heating Rate: X1.2.1 Cones 12 to 37, inclusive - 270°F (150°C)/h. X1.2.2 Cone 38 - 180°F (100°C)/h. X1.2.3 Cones 39 to 42, inclusive - 1080°F (600°C)/h. X1.3 Standard Pyrometric Cones 28 and 30 are manufactured but are not used in the PCE test.
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X1.4 Temperatures for Cones 12 to 37 were reported at the National Institute of Standards and Technology. Temperatures for Cones 38 to 42 were determined by C. O. Fairchild and M. F. Peters. These temperatures apply satisfactorily for all the conditions of this test method, but do not apply to the conditions of commercial firing of kilns and use of refractory materials. X1.5 Temperature values were determined in degrees Celsius; Fahrenheit temperature values were calculated.
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30⁰
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https://www.youtube.com/embed/m2zmY4SQkl8
90⁰
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https://www.youtube.com/embed/m2zmY4SQkl8
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https://www.youtube.com/embed/m2zmY4SQkl8
7) Refractoriness under load: Refractoriness points to the resistance of extreme conditions of heat (temperature >1800 °F) and corrosion when hot and molten materials are contained while being transported and/or processed. The ability to withstand exposure to elevated temperatures without undergoing appreciable deformation is measured in terms of refractoriness. The refractoriness under load test (RUL test) gives an indication of the temperature at which the bricks will collapse, in service conditions with similar load. However, under actual service where the bricks are heated only on one face, most of the load is carried by the relatively cooler rigid portion of the bricks. Hence the RUL, test gives only an index of the refractory quality, rather than a figure which can be used in a refractory design. Under service conditions, where the refractory used is heating from all sides such as checkers, partition walls, etc. the RUL test data is quite significant. Keywords: RUL- refractoriness under load
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8) Creep at high temperature: Creep is a time dependent property which determines the deformation in a given time and at a given temperature by a material under stress. Refractory materials must maintain dimensional stability under extreme temperatures (including repeated thermal cycling) and constant corrosion from very hot liquids and gases. The criterion of acceptance usually adopted is; that compressive creep (deformation at a given time and temperature under stress) for normal working conditions of load and temperature shall not exceed 0.3% in the first 50 hours of the test. This figure has been found to indicate that the creep rate falls by a negligible amount at the end of the stipulated period, and therefore the refractory can be considered safe to use for a much longer time.
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9) Volume stability, expansion and shrinkage at high temperature: The contraction or expansion of the refractories can take place during service. Such permanent changes in dimensions may be due to: 1. The changes in the allotropic forms which cause a change in specific gravity 2. A chemical reaction which produces a new material of altered specific gravity. 3. The formation of liquid phase 4. Sintering reactions 5. It may also happen on account of fluxing with dust and slag or by the action of alkalies on fireclay refractories, to form alkali-alumina silicates, causing expansion and disruption. This is an example which is generally observed in blast furnaces. Keywords: specific gravity, allotropic forms, liquid phase alkali-alumina silicates, Sintering reactions
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While it is desirable that all these changes are effected during manufacturing, it is not possible due to economic reasons, as the process is time dependent. Permanent Linear Change (PLC) on reheating and cooling of the bricks give an indication on the volume stability of the product as well as the adequacy of the processing parameters during manufacture. It is particularly significant as a measure of the degree of conversion achieved in the manufacture of silica bricks. Wiki: Allotropy or allotropism, is the property of some chemical elements to exist in two or more different forms
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10) Reversible Thermal Expansion: Any material when heated expands, and contracts on cooling. The reversible thermal expansion is a reflection on the phase transformations that occur during heating and cooling. The PLC and the reversible thermal expansion are followed in the design of refractory linings for provision of expansion joints. As a general rule, those with a lower thermal expansion co-efficient are less susceptible to thermal spalling. Comments: Provision of expansion needs to consider both PLC (why?) & reversible thermal expansion.
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11) Thermal Conductivity: Thermal conductivity is defined as the quantity of heat that will flow through a unit area in direction normal to the surface area in a defined time with a known temperature gradient under steady state conditions. It indicates general heat flow characteristics of the refractory and depends upon the chemical and mineralogical compositions as well as the application temperature. High thermal conductivity refractories are required for some applications where good heat transfer is essential such as coke oven walls, regenerators, muffles and water cooled furnace walls. However, refractories with lower thermal conductivity are preferred in industrial applications, as they help in conserving heat energy. Porosity is a significant factor in heat flow through refractories. The thermal conductivity of a refractory decreases on increasing its porosity. Although it is one of the least important properties as far as service performance is concerned, it evidently determines the thickness of brick work.
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Application where high heat conductivity refractories are required: High thermal conductivity refractories are required for some applications where good heat transfer is essential such as (1) coke oven walls, (2) regenerators, (3) muffles and water cooled furnace walls.
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6.0 Classification of Refractories Refractories are classified into number of ways on the basis of chemical properties of their constituent substances, their refractoriness, method of manufacture and physical form. Classification Based on 1. 2. 3. 4. 5.
Chemical Composition Method of Manufacture Physical Form refractoriness oxide content
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1) Classification Based on Chemical Composition Refractories are typically classified on the basis of their chemical behaviour, i.e. their reaction to the type of slags. Accordingly the refractory materials are of three classes - Acid, Basic & Neutral. Acid Refractories: Acid refractories are those which are attacked by alkalis (basic slags). These are used in areas where slag and atmosphere are acidic. Examples of acid refractories are: 1) Silica (SiO2), 2) Zirconia (ZrO2),
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Neutral Refractories: Neutral Refractories are chemically stable to both acids and bases and are used in areas where slag and atmosphere are either acidic or basic. The common examples of these materials are: 1) Carbon graphite (most inert), 2) Chromites (Cr2O3), (?) 3) Alumina Al2O3, Out of these graphite is the least reactive and is extensively used in metallurgical furnaces where the process of oxidation can be controlled.
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Basic Refractories: Basic refractories are those which are attacked by acid slags but stable to alkaline slags, dusts and fumes at elevated temperatures. Since they do not react with alkaline slags, these refractories are of considerable importance for furnace linings where the environment is alkaline; for example non-ferrous metallurgical operations. The most important basic raw materials are: 1) Magnesia (MgO) - caustic, sintered and fused magnesia 2) Dolomite (CaO*MgO) - sintered and fused dolomite 3) Chromite -main part of chrome ore (neutral or basic?) Chemical characteristics of the furnace process usually determine the type of refractory required. Theoretically, acid refractories should not be used in contact with basic slags, gases and fumes whereas basic refractories can be best used in alkaline environment. Actually, for various reasons, these rules are often violated.
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2) Classification Based on Method of Manufacture The refractories can be manufactured in either of the following methods: a) Dry Press Process b) Fused Cast c) Hand Molded d) Formed (Normal, Fired or chemical bonded) e) Unformed (Monolithic – Plastics, Ramming mass, Gunning, Castable, Spraying
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3) Classification Based on Physical Form Refractories are classified according to their physical form. These are the shaped and unshaped refractories. The shaped is commonly known as refractory bricks and the unshaped as “monolithic” refractories. Shaped Refractories: Shaped refractories are those which have fixed shaped when delivered to the user. These are what we call bricks. Brick shapes maybe divided into two: standard shapes and special shapes. Standards shapes have dimension that are conformed to by most refractory manufacturers and are generally applicable to kilns and furnaces of the same type. Special shapes are specifically made for particular kilns and furnaces. This may not be applicable to another furnaces or kiln of the same type. Shaped refractories are almost always machine-pressed, thus, high uniformity in properties are expected. Special shapes are most often hand-molded and are expected to exhibit slight variations in properties.
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Unshaped Refractories: Unshaped refractories are without definite form and are only given shape upon application. It forms joint less lining and are better known as monolithic refractories. These are categorized as Plastic refractories, ramming mixes, castables, gunning mixes, fettling mixes 涂炉材料 and mortars.
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4) According to their refractoriness
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5) Based on the oxide content, they are also classified as: 1. Single oxide refractories Example: Alumina Al2O3 , Magnesia MgO , Zirconia ZrO2 2. Mixed oxide refractories Example: Spinel (MgAl2O4), Mullite (3Al2O32SiO2 or 2Al2O3SiO2 (Wiki)) 3. Non-oxide refractories Example: borides, Carbides, Silicates. (SiO2?)
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Spinel
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Spinel
Charlie Chong/ Fion Zhang
7.0 TYPES OF REFRACTORIES Refractories are classified as dense or insulating types. The most high-temperature refractories, such as firebricks, are highdensity (>120 lb/ft3). They offer excellent resistance in challenging operating environments, such as slags with different chemical compositions, fumes, dust, and gases. Insulating refractories have lower densities (4 to 70 lb/ft3) and provide insulating properties, while offering resistance to corrosion and chemical reactions with the operating environment. The following is the discussion of the outstanding characteristics of the various types of refractories :
Charlie Chong/ Fion Zhang
1) Fire-clay brick Refractories Fire-clay brick comprise about 75% of the production of refractories on a volume basis and are essentially hydrated aluminum silicates with minor proportions of other minerals. Typical composition consists of Silicon dioxide SiO2
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