Coal Gasification Pilot Plant Support Studies. Subtask 4-2. Liquid-Phase Treatment to Reduce the Agglomerating Properties of Caking Coals

摘要

The pretreatment of caking bituminous coals to prevent agglomeration is necessary for most proposed or existing coal conversion processes. Although partial oxidation has been shown to be effective, an alternative method is being investigated and is reported here: treatment of clal with liquids or supercritical fluids. The IGT Agglomeration Test, which classifies samples on a scale (AN) from 0 to 5 according to their agglomerating character upon heating in a hydrogen atmosphere, was used as the basic criterion of success. Another measure, the product condition index (PCI), was formulated to gauge the degree of caking occurring during treatment. Pyridine was reacted with Illinois No. 6 coal under atmospheric pressure to reduce the AN to zero at 200 exp 0 F. Solvent retention of up to 11% cast doubt on the practicability of this method. Treatment with phenanthrene was partially effective at a temperature of 480 exp 0 F, but the difficult separation of solvent and extract was noted as a drawback. The agglomeration number of Illinois coals was lowered to a range of 0 to 1 by treating the coal at supercritical conditions, 670 exp 0 to 700 exp 0 F and 1000 to 1500 psig, with benzene and toluene. Run-of-mine Illinois No. 6 coal can be effectively pretreated at a residence time of less than 30 minutes and a temperature of 700 exp 0 F. A noncaking feed can be obtained over a wide range of extraction levels (11% to 23%), depending on the thermal history of the sample as well as the original composition of the coal. In conclusion, the method of pretreatment by extraction with supercritical benzene, toluene, or phenol/benzene is technically feasible at the laboratory level for mildly caking bituminous coals. (ERA citation 06:001828)