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Show CONVERSION TO COAL-OIL MIXTURE The combustion of C O M by means of ultrasonic burners was first conducted on a large scale in a rotary kiln at Kali-Chemie A.G., Germany. The rotary kiln produced crude phosphate and was fired originally with heavy oil through a pressure-atomizing burner. The flow schematic diagram of the entire COM system is shown in Figure 4. The coal is transported via a conveyor belt, elevator and drag chain conveyor into a storage bin. It is then pulled into the mixing tank by means of a proportioning conveyor type scale. Depending on the amount of coal, heavy oil is continuously pumped into the mixing tank. The mixture is then ground in a wet grinding mill and transported to the storage tank, where a uniform consistency is maintained by the use of an agitator. The storage tank contains sufficient supply of C O M for three hours of operation. The C O M is pumped to the burner via a variable speed positive displacement pump. The waste gas flows through the rotary kiln, the electro-static precipitator and finally out the stack. Production and Transportation of the Coal-Oil Mixture A total of 1300 tons of fine grain bituminous coal (less than 30 m m ) was burned in the course of the testing period. The preferred mixing ratio for the mixture was 6 0 % solids and 4 0 % oil by weight. Oil additives were not used. The coal supply for the mixing tank was regulated with a proportioning conveyor type scale, as shown in Figure 5. The content of solids in the mixture was not limited by the burner, but by the pumpability of the mixture. An important characteristic of the COM production in the system presented here is the grinding of coal together with oil inside the wet grinding mill. Since the coal enters the oil in a lumpy form, the explosion problems are hereby omitted. Water contained in coal does not present a problem during the grinding process or the combustion. The wet-grinding system is small and its capacity can be directly coordinated with the burner throughput, so that only the required amount of mixture is produced. Therefore, manifestations of separation are prevented. Two toothed-ring mills with a throughput capacity of 5 to 10 t/h were tested as wet grinding mills. Figure 6 shows one of the mills in an installed condition. The 16-6 |