Refining of fossil resin flotation concentrate from Western coal. Ninth quarterly report, January 1--March 31, 1995

摘要

Heptane showed a consistently higher extraction than hexane even through heptane contains only one more methylene group in its molecular structure. However economic factors must also be considered in the overall evaluation of the process. In this regard a simple economic evaluation was carried out taking into consideration the operating costs for the resin concentrate refining process. First of all, the price of industrial grade heptane is about the same as hexane. Because the process operates in a recycle mode, the initial cost would be about the same for both solvents. But in order to obtain the final resin product, the extracted resin has to be recovered from solution using evaporation techniques, which consume energy. Due to the significant difference in boiling points between the two solvents, approximately 25--35% more energy will be required for resin recovery by evaporation if heptane is used as the solvent for extraction. This represents a very significant increase of the operating cost. Secondly, based on bench scale tests the same yield can be achieved with hexane if the average residence time is increased. Such an increase in retention time only increases the capital cost by a small amount. It appears then from an economic perspective that hexane is the most appropriate solvent.