State-of-the-Art Assessment of Coal Feeding for Coal Conversion Plants

摘要

Coal Feeding is one of the critical steps common to all coal conversion processes such as gasification, liquefaction and fluidized bed combustion. For liquefaction in processes such as H-Coal and SRC I and II, reciprocating slurry pumps are primarily used in current practice. The dry coal must be slurried with recycle oils or water. In first generation gasifiers such as the Lurgi installations at Sasol, lockhoppers are used. The demonstration sized plants such as ICGG COGAS and Concoco Slagging Lurgi also are slated to use lockhopper type systems. In atmospheric fluidized bed combustors combination mechanical feeding with pneumatic assist is used at the Rivesville Installation. Overfeed stokers are used at Georgetown. Flow splitting to achieve uniformity of feed to the bed has been a problem. If we have satisfactory feeders such as lockhoppers, why is DOE sponsoring feeder development. High installation costs and high power consumptions have been indicated by several studies when compared to projected costs of developmental feeders. There are several advanced technology feeders being developed by the private sector both with and without DOE support. These feeders can be broken down into types such as screw extruders, rotary or drums, cavity, centrifugal, and pneumatic. The various feeders of each type are discussed, giving maximum pressure obtained to date, coal types and sizes handled, and operational hours obtained to date giving an indication of progress in development. A table of feeders versus application for current DOE major coal conversion projects is presented. The feeder currently proposed for each project as well as possible applications of newer feeders is given. (ERA citation 06:001803)