ABSTRACT
Besides gasication, the direct liquefaction (and extraction) of coal, biomass, and waste to generate synthetic liquids is a very valuable and commercially viable thermochemical transformation technology. Unlike combustion, gasication, and pyrolysis, liquefaction (or extraction) generally involves multiple fuels, solid (coal, biomass, or waste), and liquid (oil or water). Coal, biomass, and waste materials can be liqueed (generally in the presence of a donor solvent) to produce a host of liquid products. The quality of liquid product depends on the nature of feedstock; nature of operating conditions such as temperature, pressure, and reaction time; and the presence of a catalyst. While coal, biomass, or waste can be liqueed on their own at high temperatures, the best results to produce desirable liquids involve liquefaction in the presence of a donor solvent, which actively interacts with solid feedstock in producing the liquid. The quality of the donor solvent is an important parameter in the production of both quantity and quality of liquid products as well as for the economics of the process. The liquid can also be produced by the extraction of various useful components of the solid feedstock (such as extraction of coal by supercritical water [SWC]).
