Mass transfer through the gas phase during the firing and service of periclase refractories in a tunnel kiln

Conclusions There is a substantial transfer of material through the gas phase during the firing of periclase articles at 750–1800°C in a tunnel kiln. From the investigation of the condensate deposits on the lining surface and in the pores of the bricks, we detected both the typical (ordinary) and the new phases and compounds for these conditions: thenardite, meta-thenardite, Na₂SO₄ of forms I and III, langbeinite, vanthoffite, 3Na₂SO₄·MgSO₄, sulfates of magnesium and calcium, chromates of potassium, sodium and calcium, their solid solutions, periclase, spinel, of variable composition, chromium oxide (III). The mass transfer through the gaseous phase affects the structure change in the refractories and the character of their wear in service, which must be considered in the development of new refractories for the linings of high-temperature tunnel kilns.Translated from Ogneupory, No. 7, pp. 23–28, July, 1981.     

Conversion of a tunnel kiln for firing of mullite-corundum refractories to firing with natural gas

Conclusions At Zaporozhe Refractory Plant the tunnel kiln of the High-Alumina Part Shop has been converted to firing with natural gas with replacement of the single-passage burners with doublepassage ones equipped with individual supply of primary eold air. Subsequent improvement in the design parameters of the burners and the accomplishment of measures directed toward increasing the effectiveness of combustion of natural gas made it possible to stabilize the thermal operation of the kiln with respect to production of mullite-corundum refractories of the specified quality and reduce fuel consumption by 3%.Translated from Ogneupory, No. 4, pp. 42–45, April, 1988.     

A circular tunnel kiln for firing of refractories

Conclusions The first high-temperature circular tunnel kiln in the country, in which firing of mullite-corundum refractories with a phosphate binder at 1400–1500°C has been introduced, has been placed in service.The operation of the kiln is characterized by the high service reliability of its design elements, including the hearth system, and insignificant costs for routine repairs of the kiln equipment.Translated from Ogneupory, No. 2, pp. 40–44, February, 1985.     

A small tunnel kiln for firing corundum refractories

Conclusions The special features of the small (working volume capacity 6. 8 m³) tunnel kiln for firing corundum refractories are: firing with a gas-air mixture, absence of combustion chambers between the charges, absence of end doors, and slow kiln truck speed (13 cm/h). The corundum bricks are fired in the kiln for 136 h at 1660°C.The gaseous medium of the firing zone contains oxidizing and reducing components.The faults of the kiln are: nonuniformity of the firing of the bricks, inadequate firing temperature level, and unsatisfactory performance of the first six positions of the heating zone where heating takes the form mainly of a thermal shock in the region of the last two (in the direction of the gas flow) pairs of connections for the extraction of the combustion productsTo improve the quality and economics of the firing process, it will be necessary to improve the heat insulation of the kiln channel, to provide channels in the floor, and to modify the heating and gas extraction systems.Translated from Ogneupory, No. 7, pp. 8–15, July, 1977.     

A new tunnel kiln for the high-temperature firing of magnesian refractories

An updated microprocessor-based version of a tunnel kiln for production of high-grade magnesian refractories is presented. Improvements achieved in engineering and economic figures are discussed. __________ Translated from Novye Ogneupory, No. 5, pp. 18–20, May, 2006.     

Drying magnesia refractories with the flue gas of the tunnel kiln

Conclusions Experiments at the Magnezit Plant confirmed the feasibility of drying magnesia refractories with the flue gas in the first positions of a tunnel kiln. Drying the refractories in the section where the flue gas is tapped off does not result in more rejects or in degradation of the properties of the fired products.Compounding the processes of drying and firing magnesia refractories in a single unit, viz., the tunnel kiln, makes it possible to dispense with the driers the freed floorspace of which can be used for installing equipment for mechanizing the loading of the products on the kiln trucks.Translated from Ogneupory, No. 4, pp. 15–21, April, 1976.     

Study of magnesite-chromite brick after service in a tunnel kiln roof

Conclusions During the service of magnesite-chromite brick in constant temperature conditions (1700°C) and an oxidizing gaseous atmosphere in the absence of corrosive agents in the furnace space (silicates, iron oxides), fusion melts developed in the brick migrate to the colder sections, forming dense silicate-iron subzone.The hot end of the brick is enriched with magnesia and consists of coarse grains of recrystallized periclase. The grains of chromite in these sections have a direct bond with the grains of periclase, as a result of which the thermal properties of the hot section on the whole are improved [4] despite the high porosity of the brick in the subzone.Investigation of the structure of the pores confirms the capilliary mechanism of migration of melts. Recrystallization of periclase in the subzones adjacent to the hot zone is accompanied not by sintering and shrinkage but by coalescence (coarsening) of the pores.Movement of the melts over the pore channels is accompanied by corrosion of the walls of the pores.Translated from Ogneupory, No. 8, pp. 36–41, August, 1966.     

A system for firing a small tunnel kiln operating on natural gas

Refractories and Industrial Ceramics - An improved method of firing corundum refractories in the small high-temperature tunnel kiln of Snigirevka Division of Vnukovo Refractory Part Plant has been...     

Heat losses in a tunnel kiln for brick firing

The results of experimental studies of heat losses via the enclosing structures of an operating brick-firing kiln using a thermal imager are described. __________ Translated from Steklo i Keramika, No. 4, pp. 24–25, April, 2006.