Coal liquefaction and deashing studies of the CSF and SRC processes

Abstract

Continuous bench-scale studies on the deashing of coal liquefaction products by gravity settling were conducted in a 10 lb coal/hour unit. The donor solvent Consol Synthetic Fuel (CSF) process and the Solvent Refined Coal (SRC) process were simulated. Steady-state liquefaction solvents were used to give as good a simulation as possible. The SRC data were used in a conceptual design for the solvent deashing unit of a commercial coal liquefaction plant. Anti-solvent (deasphalting or precipitating solvent) screening was done in a batch system before continuous runs using anti-solvent were made. Deashed CSF product contained 0.22 wt % ash; using anti-solvent did not improve settling efficiency. The upflow velocity of the settler was 0.3 in/min, which is about 25% of the value obtained in a previous study using non-steady-state liquefaction solvent. SRC with 0.1 wt % ash was produced using an anti-solvent/liquefaction solvent weight ratio of 0.3 to 0.5. The recovery of SRC was 85% in this single-stage operation. The upflow velocity was 0.4 in/min. Deashing was sensitive to the amount of Soltrol 130 (a paraffinic naphtha) used as anti-solvent. Equilibrium liquefaction solvent from the Ft. Lewis SRC pilot plant was used. Performance of the 10 lb/hr liquefaction reactor matched Ft. Lewis results. Moderate contamination of recycled Soltrol 130 significantly decreased the settling rate. Kauri-butanol value was a good indicaton of anti-solvent purity. A conceptual design of a two-stage solvent deashing unit for a commercial (20,000 TPSD) SRC plant shows that thirty-five 40' diameter primary settlers (600/sup 0/F, 77 psig) and twenty wash settlers (550/sup 0/F, 54 psig) of the same diameter are required to produce specification SRC (0.18% ash). The SRC recovery in the two-stage system is estimated at 97% of the entering SRC.