THE DIRECT FIRED CAR TUNNEL KILN ON ROOFING TILE1

The pioneer car tunnel kiln for the firing of roofing tile is described. The kiln is 324 feet, 11 1/2 inches long and holds 52 cars each of which carries 2.3 tons of fired ware. Ten furnaces equipped with Maxon Premix combination oil and gas burners arc used. A schedule of one car every 65 minutes is in operation, 56 hours and 20 minutes being required for a trip through the kiln. The ware reaches a maximum temperature of 1820°F and is drawn from the kiln at 400°F. Additional cooling is accomplished with a portable fan. The kiln has a capacity equal to ten 30-foot round down-draft kilns and shows a fuel saving over the latter of 64.2%. A total of 15 h. p. is required. A saving in setting and drawing labor of 29.2% and 45.8% respectively is effected.     

Cause-And-Effect Relations with Respect to Defects in Brick Firing in Tunnel Kilns

The cause-and-effect relations in firing brick in tunnel kilns are investigated and the causes of defects depending on the rate of heat treatment of brick in the kiln are identified. Current gas burners do not satisfy the requirements imposed on firing velocity regimes. The kiln has to be upgraded: Vulkan-gaz burners should be replaced by state-of-the-art gas burners with automatic control of the heat regime of the kiln, and the thermal regime in the preparation zone of the tunnel kiln has to be improved.__________Translated from Steklo i Keramika, No. 3, pp. 26 – 28, March, 2005.     

Increasing the thermal efficiency of a rotary kiln for firing dolomites from various deposits

Conclusions More uniform firing of dolomite of various fractions can be achieved by reducing the upper limits of the dolomite particle size to 10–12 mm and excluding fractions < 5mm. Considering the low resistance of chrome-magnesite brick in the firing zone it is necessary to use periclase-spinel brick.The use of GVM burners for burning natural gas in rotary kilns increases the output of the kiln and reduces the consumption of fuel when burning dolomite. These burners can be recommended for installation in rotary kilns for firing magnesite, chamotte, lime, etc.Translated from Ogneupory, No. 4, pp. 23–26, April, 1973.     

水泥窑铅镉等重金属的污染及防治

利用原子吸收分光光度法、振荡溶出等方法,研究了水泥窑铅镉等重金属污染的防治.氟会促进Pb,Cd,Zn和Cu的逸放.无论何种水泥窑,Hg逸放率高达89%～96%.Pb,Cd,Zn和Cu在不同类型水泥窑中其逸放率有明显差别,立窑的逸放率较高,Pb和Cd为84%～90%,Zn和Cu为36%～47%;湿法回转窑次之;新型干法窑的逸放率最低.使用高效的除尘设备,不仅可减少粉尘的污染,还可减少Pb等重金属的逸放.把Pb等重金属含量较高的窑灰用作水泥混合材既可使Pb等重金属被固封于水泥混凝土中不会产生二次污染,又能减少因窑灰循环入窑而导致Pb等重金属的再次逸放.     

An ejection system for firing a small high-temperature tunnel kiln

Conclusions An ejection system for firing a tunnel kiln differs from an ejection system for firing metallurgical and machine building industry furnaces.Investigations were conducted on a model of the ejection equipment of small high temperature kilns.Results were obtained on the change in the coefficient of ejection in relation to the geometric parameters of the ejectors and the burners, the distance between them, the pressure in the ejection channel and the working space of the kiln, and the temperature of the air ejected.A method of calculation of ejectors used in tunnel kilns is proposed.Translated from Ogneupory, No. 2, pp. 40–43, February, 1984.     

Automation of high-temperature tunnel-type kilns at Zaporozh'ye Refractory Plant

Conclusions For effective automation of high-temperature tunnel-type kilns it is essential to redesign them so that the gas and air supply to individual burners can be automatically controlled.The representative measurement points selected and the trial devices worked out and tested make it possible to control automatically all the essential parameters for the heat conditions in the kiln.There has been constructed and tested a system for automatically controlling the heat conditions at one point using an extremal regulator (optimizer) and regulator for analyzing combustion products in terms of oxygen yield in order to control the air supplied for combustion. This system may be successfully employed in reconstructed kilns in which the temperature and set combustion conditions at a point ensure optimum combustion conditions.An automatic unit has been worked out for regulating temperature at separate points in the firing zone, as well as a remote-control device for feeding gas to each burner with automatic control of pressure in the injector channel. This unit makes it possible to maintain a set temperature with a high degree of accuracy in tunnel-type kilns in which there are to be separate gas and air supplies to each working burner.     

Operating high-temperature tunnel kilns with a 700-mm-high charge

Conclusions In low tunnel kilns, periclase-spinel brick should be fired in columns about 700 mm in height in an arrangement which leaves an effective cross section of 47–48%.Injectors for feeding air at low pressure to the burners serve no useful purpose. A 45-m-long firing zone (15 positions) is not required.Ways must be found of further improving the heat insulation properties of the lining of the kiln trucks.Translated from Ogneupory, No. 2, pp. 12–15, February, 1976.     

Conditions of operation of a tunnel kiln with injection burners

Conclusions The injection burners ensure jet combustion of the gas with the generation of an oxidizing atmosphere in the tunnel kiln. The firing of dense ladle brick and brick for blast furnaces in such kilns must last for 50–60 h.In discussion series [see Ogneupory, No.5, 11 (1968)].Translated from Ogneupory, No. 5, pp. 10–13, May, 1969.     

Numerical Simulation of a Solar Kiln Design for Drying Timber with Different Geographical and Climatic Conditions in Australia

A numerical simulation for the modeling of solar kilns for hardwood timber drying with different boundary conditions has been developed in this work. This simulation has been used to predict the key behavior of the wood and the kiln itself under different geographical and weather conditions in Australia. This work, therefore, enables a site to be suggested that is likely to give the best kiln performance both in terms of the productivity and the quality of the end-use product. As test cases, realistic climatic conditions for three representative geographical locations in Australia, including Sydney (latitude 33.86°S), Melbourne (37.81°S), and Brisbane (27.46°S), have been considered in this simulation. Out of the three sites considered in this work, the fastest drying rates (and highest diffusion coefficients) were predicted in Brisbane. The highest level of instantaneous strain in the timber for this location was also predicted to be 0.0075 m/m, which is much less than the failure value (0.02 m/m). The moisture content distribution profile within the boards toward the end of the drying period was found to be almost uniform, which is likely to cause low degrade in the dried timber.     

SILLIMANITE KILN REFRACTORIES MADE FROM AN ANDALUSITE BASE1

Some andalusite refractories are high in transverse strength. Bars 12 inches long, 2 inches wide, and 1/2 inch thick tested across an 11-inch span supported a 45-pound load with 13/32-inch sag at cone 16^1/4 and a 1/2-pound load at cone 34 down with 1/16-inch sag. A standard 9-inch brick tested under a load of 50 pounds per square inch at 1525°C showed no deformation. They are relatively constant in volume, are not affected by kiln gases, and tend to improve rather than to deteriorate under continued heating owing to the formation of an increased amount of mullite. Andalusite saggers used at cone 12 are estimated to have stood 180 cycles and are still in good condition. Saggers in continuous use at cone 16^1/4 have an estimated average age of 1^1/2 years and many are four years old. The andalusite lining of a periodic kiln being fired regularly at 3000 to 3200°F is still serviceable after 110 firings. Cars built of andalusite refractories have given five years of continuous service in tunnel kilns operating at cone 16^1/4, whereas cars built of fireclay refractories were unfit for use after three to four months. Side walls, damper boxes, expansion sleeves, and flame shields of Dressler tunnel kilns operating at cone 16^1/4 have proved satisfactory.     

Choosing burners for tunnel kilns

Conclusions Double-duct burners fitted to tunnel kilns have proved themselves. Subsequently, it will be necessary to improve the design of burners and to carry out research into the most rational economic combustion of natural gas.Hot-air injection into burners is undesirable in tunnel kilns heated with natural gas and used for firing chamotte and dinas products.A discussion.Translated from Ogneupory, No. 5, pp. 11–13, May, 1968.     

The ratio of zone lengths in high-temperature tunnel kilns

Conclusions The ratios of the heating zone lengths existing in high-temperature tunnel kilns for firing magnesia refractories are not optimal. There are reserves for improving the operation of the kilns by optimizing the ratio of the zone lengths.The operation of the preheat zone in a high-temperature tunnel kiln is characterized by perfect heat-exchange and the presence of a reserve section. This zone can be reduced without damage to the furnace operation, as a result of which it is possible to elongate the cooling zone.Further treatment of the question of optimization of the ratio of zone lengths in a high-temperature tunnel kiln should be continued in the new kiln design developed by the All-Union Institute of Refractories, which is equipped with burner assemblies from the 19th position.Translated from Ogneupory, No. 3, pp. 8–15, 1970.     

Performance Comparison of Two Solar Kiln Designs for Wood Drying Using a Numerical Simulation

The predicted performances of the two different timber-drying solar kiln designs (Oxford and Boral kilns) have been compared by using the climatic and geographical conditions of Brisbane (27.46°S) in Australia. The dimensions of the original Boral kiln have been scaled down in order to compare the kilns’ performances on the basis of same load capacity. The comparison was made in terms of the key performance indicators, including drying rates, drying qualities (i.e., the level of strains developed within the timber boards during drying), energy gains, and major elements of the energy losses (i.e., the convection and radiation losses) while drying timber from an average initial moisture content of 53% (dry basis) to a final moisture content of 15% (dry basis) in both kilns. The relative performances for the two designs were discussed in more detail by using the typical climatic conditions (spring season 2013), when the days and nights are of approximately equal length. Finally, an analysis of the seasonal effects on the kiln performances was also carried out in this article. More effective orientation of the solar absorbers with respect to sun, together with faster heat transfer rates between the circulating air and the timber stack for the Oxford design, were likely to give consistently better predicted performance for the Oxford design than for the Boral kiln throughout the year.     

Influence of the secondary air parameters on the combustion conditions of a tunnel kiln

Conclusions The operating effectiveness of the cooling zone has a significant influence on the fuel consumption in a tunnel kiln, which increases with an increase in the temperature level of firing of the refractories. Acceleration of heat exchange in the cooling zone with improvement in its thermal and gas insulation is an important step in reducing the fuel consumption in kilns.With identical effectiveness of the thermal operation of the cooling zone the parameters of the secondary air supplied for combustion do not have a significant influence on the total fuel consumption in the furnace but do determine to a significant degree the operating conditions of its burners.Translated from Ogneupory, No. 3, pp. 41–43, March, 1987.     

再论新型超短窑的应用及在我国的发展

新型超短窑对原燃料的适应性更强，既可以烧劣质烟煤，也可以烧劣质无烟煤；同时还可以实现两档支承，使回转窑的结构简化、机重减轻；可使检修维护和土建费用降低，运转率提高等，特别是降低基本建设投资的作用更为显著。建议大力开发并发展处在预分解技术领先地位的新型超短窑，以便尽快赶上世界先进水平。     

PROTOTYPE HIGH TEMPERATURE/HIGH PRESSURE KILN FOR THE EVALUATION OF WOOD DRYING SCHEDULES

ABSTRACT

A new laboratory kiln was developed and built to perform over a very wide range of drying conditions. For example, the dry bulb temperature can vary from 30°C to 150°C and the dew point can be adjusted between 20°C and 130°C. Obviously, with such a high level of dew point, pressures over atmospheric pressure may be induced inside the chamber. For this reason, the kiln has been designed to withstand pressure of up to 3 bars. This kiln can also perform vacuum drying.

A programmable controller allows the temperature levels to be maintained within ± 0.2°C. Because the whole kiln can be heated only through the agitated water present at the bottom of the kiln, the load temperature can be increased up to 130°C in saturated conditions, without any change of moisture content.

The kiln has various sensors attached and is capable of withstanding severe conditions (high temperature, saturated vapour and elevated pressures). At present, air and water temperatures as well as temperature at different locations within the board can be collected during the drying process. A load cell and pressure gauges are also available. The first tests performed using this equipment are presented at the end of the paper.     

CALCINATION OF TOPAZ ORE IN A ROTARY KILN*

Reports have indicated that calcined topaz might be useful as substitute material for Indian kyanite in high aluminous, mullite-type refractories. Tests were conducted to determine the value of calcining and defluorinating raw topaz. Fifteen tons of minus 1-in. topaz ore were calcined in a 25-ft. rotary kiln of 20-in. in inside diameter, at 2600° to 2950°C., with feed rate of 200 to 400 1b. per hour and feed retention in the kiln of 70 to 120 minutes. The best operating conditions were found to be 2700°F. and a feed rate of 300 1b. per hour at 0.90 r.p.m. of kiln rotation. The average fluorine content was 0.24% and the apparent porosity was 19%. A dust loss of 11% occurred during calcination, but no serious reduction in particle size occurred from the heat-treatment. It seems to be practicable, therefore, to calcine and defluorinate raw topaz in a rotary kiln and to obtain a product suitable for the manufacture of mullite-type refractories.     

Evolution of fluorine emissions during the fast firing of ceramic tile

The present paper examines the emission–adsorption phenomena of fluorine compounds in various ceramic tile body compositions with different fluorine and calcium contents, processed by fast firing cycles in an electric laboratory batch kiln and in continuous fast-cycle industrial combustion kilns (roller kilns). In the roller kilns, fluorine emission was monitored by analysing the fluorine content in both solid and gas samples throughout the kilns.It was found that fluorine emission during firing in air atmosphere in the laboratory batch kiln began at temperatures above 800 °C and increased progressively up to peak firing temperature. In the roller kilns, however, the emissions started at lower temperatures and decreased in certain kiln zones. This decrease indicates that there are regions in these kilns in which fluorine is adsorbed rather than emitted by the material being processed.A fluorine adsorption process is thus shown to occur in the preheating stage in the roller kilns, despite the rapid heating rate. However, encouraging this adsorption process in order to foster the formation of crystalline phases is ineffective in abating fluorine emissions when ceramic tiles are fired at peak temperatures exceeding 1100 °C.     

Firing lightweight Dinas in a tunnel-type kiln

Conclusions The best type of stacking has been ascertained for lightweight dinas on tunnel-type kiln cars.The dinas can be fired in tunnel-type kilns together with ordinary dinas without altering the firing conditions.The lightweight dinas fired in the tunnel-type kilns included the larger types PM-17 and PM-20, so there is no doubt that standard size lightweight dinas can also be fired in these kilns.The satisfactory results of the experiments have enabled the plant to begin firing this dinas in tunnel-type kilns.