| OCR Text |
Show filtration. The resulting liquid can be distilled to form the process solvent and SRC products, which may be directly used as boiler fuel. In SRC-II process, part of the mineral matter is recycled into the dissolver which facilitates the coal conversion. The process uses more hydrogen and produces a variety of liquid products, namely naphtha, middle and heavy distillates, and vacuum bottom products. While naphtha and middle distillate are suitable for production of transportation fuels, middle and heavy distillates may be used as turbine fuel, and heavier products may be burned in boilers (Robertson and Hicks, 1982). Both SRC-I and SRC-II are considered as noncatalytic processes, whereas H-Coal and EDS processes use molybdenum based hydroprocessing catalysts. In the H-Coal process the coal slurry is liquefied in an ebul1ated-bed catalytic reactor, whereas in EDS process, the recycle solvent is catalytically hydroprocessed to produce the hydrogen donor solvent. Both EDS and H-Coal processes can produce boiler fuels and synthetic crudes for refineries. Coal-derived liquids are complex mixtures of aromatic and non-aromatic hydrocarbons, nitrogen, oxygen and sulfur containing heterocyclic compounds, and trace elements. Their composition varies significantly depending on the coal type, the liquefaction process, and liquefaction conditions. Most coal-derived liquids, in their original form, do not meet the specifications for direct combustion or refining. They are often upgraded by catalytic hydrotreatment to suitable products. As a result, their hydrogen content increases while their aromaticity, sulfur, nitrogen, oxygen and trace element contents decrease (Crynes, 1981). 1.5.6 |
