Heat treatment of bottom pouring tubes in a roller kiln

Abstract

The high multilayer charge in which refractory parts are fired is frequently the reason for formation of scrap and significant variations in the properties of refractories. In connection with this possibility of use of a roller kiln with single-layer firing for bottom pouring tubes was studied.In our country roller kilns are used primarily for firing of ceramic plates. Designs of such kilns are known [i, for example].At Konstantinovka Refractory Plant an SMK-158 roller kiln produced in Constructional Material Production Machinery Plant, Mogilev-Podol'skii has been built. The necessary changes and additions taking into consideration the product being fired have been introduced into the design of the roller kiln. The kiln includes a dryer. A single roller conveyer driven in sections by six drives was the means of movement. The rollers are driven on both sides by sprocket chains. To each roller is fastened a drive sprocket. The driving branch of the chain is located above the sprockets. Above the chain are located clamping strips. The rollers rotate in sleeves.The roller dryer consists of four similar sections with a length of 9 m each. Each section is a metal frame covered on the outside with steel plate. The lining of the walls, the hearth, and the roof is made of thermal insulation materials and chamotte brick. In the walls in a checkerboard arrangement on both sides there are hatches with doors for cleaning the hearth. Each section is equipped with 12 inj'ection burners located under the conveyer in checkerboard order. There is also a system for utilization of the stack gas heat, for which the manifold of each section is connected by an individual pipe with a controlling slide valve to the centrifugal fan removing the stack gases from the kiln. To remove the stack gases in the roof of each section there are exhaust manifolds connected by a pipe with a controlling slide valve to the common stack.The roller kiln consists of 24 3-m sections (positions) located on the frame of the roller conveyer. Between the sections there is a 20 mm gap filled with asbestos cord serving as a temperature joint. Rollers with a length of 2150 mm, a diameter of 32 mm, and a spacing of 70 mm pass through holes in the walls. The width of the kiln channel is 1150 mm and the height in the firing zone from the learth level to the peak of the roof 750 mm.To fire the kiln channel 157 gas injection burners are located over the whole length of the roller kiln in both sides in the walls in checkerboard order. In the heating and firing zones the burners are located above and below the roller conveyer. Under normal conditions the consumption of natural gas is ii0 m3/h. The stick gases are removed from the kiln through holes in the roof and directed to the dryer. The quantity of gases removed by positions of the kiln is regulated by slide gates.At the level of the hearth in each section there are four hatches, two on a side, in checkerboard order and two peepholes above the rollers to observe the working space.Lightweight and normal chamotte mater...