Molten-Caustic-Leaching (MCL or Gravimelt) System Integration Project

Abstract

The objectives of the task covered in this document are to operate an integrated MCL test circuit to demonstratethe technical capabilityof the process for producing a demineralizedand desulfurizedcoal that meets New Source Performance Standards (NSPS),to test process conditionsaimed at lower costs, and to deliver product coal. These objectiveswere met by the operation of the integrated test circuit during a 54-test process matrix that resulted in the productionof 3,000 pounds of treated coal. Product MCL coal might be used to displace oil in some turbine and diesel engines and may be used in the retrofit of oil-fired boilers to coal-fired boilers. Two high sulfur, high ash coals representativeof the Eastern United States coal production were processed: Pittsburgh No. 8 and Kentucky No. g. Although mild kiln conditions(325 to 415°C and I to 2.3 hours residence time) and low caustic to coal ratios (1:1 to 3:1) were used, the combination of continuousoperation and rigorous exclusion of air from the system allowed the productionof MCL coal that had product sulfur content well below NSPS standards,very low carbonate production, very little volatiles loss, and low alkali retention by the product MCL coal. Optimization testing resulted in a product coal containing 0.4 percent sulfur (0.6 Ibs SO2/millionBtu) and 0.15 percent ash with more than gO percent organic sulfur removal, g5 percent SO2 reduction from run-of-mine coal, gi percent SO2 reduction from precleanedprocess feed coal, and with heat content of about 14,000 Btu per pound.