THE AIM OF THE PROJECT IS TO IDENTIFY THOSE PETROLEUM DERIVED FEEDSTOCKS WHICH ARE MOST SUITED TO CO-PROCESSING WITH HARD COAL IN DIRECT LIQUEFACTION PROCESSES.
A United Kingdom bituminous coal (84.1% carbon, 5.2% hydrogen, 7.9% oxygen) has been coprocessed with a set of 5 petroleum residues, of varied composition, under conditions simulating the extraction stage of 2-stage coal liquefaction. The aim of the work is to test the feasibility of replacing a coal derived solvent with a petroleum derived solvent in the extraction stage.
The petroleum solvents used consisted of 2 atmospheric and 3 vacuum residues. These have been extensively characterised and shown to vary widely in their structural properties. Optimum coal extraction rates were obtained at a coprocessing temperature of 410 C and at coal to solvent ratios of between 1 to 3 and 1 to 1. Coal conversions, measured as quinoline soluble material, varied from 16.6% to 37.4%. The coal petroleum interaction was enhanced by a high carbon aromaticity value in the petroleum solvent, but no simple correlations between solvent structure and extraction efficiency have as yet been identified.
THIS IS A COOPERATIVE PROJECT INVOLVING SEPARATE CONTRACTS WITH THE UNIVERSITY OF LEEDS AND THE UNIVERSITY OF HERIOT-WATT. AS EMPHASIS IS PLACED ON CO-PROCESSING APPLIED TO THE BRITISH LSE PROCESS, BRITISH COAL HAS AGREED TO CO-ORDINATE THE OVERALL PROJECT AND TO SUPPLY THE COAL AND COAL LIQUID FEDDSTOCKS. THE OVERALL PROJECT IS DIVIDED INTO THREE OVERLAPPING PHASES SPANNING A TOTAL OF THREE YEARS.
IN PHASE I TWELVE PETROLEUM DERIVED FEEDSTOCKS WILL BE CHARACTERIZED AND THE LIQUEFACTION REACTOR WILL BE COMMISSIONED. THE SAME 'BASHERVILLE' STIRRED BATCH REACTOR, LOCATED AT HERIOT-WATT, WILL BE USED FOR EXTRACTION AND HYDROCRACKING; OPERATION OF THE REACTOR WILL BE DEMONSTRATED IN EACH MODE.
IN PHASE II AN ASSESSMENT WILL BE MADE OF THE EFFICIENCY OF COAL EXTRACTION WITH THE PETROLEUM FEEDSTOCKS BOTH USED ALONE AND MIXED WITH LSE DERIVED SOLVENTS. THE EXTRACTION TIME, TEMPERATURE AND SOLVENT: COAL RATIO WILL BE VARIED AND IN EACH CASE PRODUCT YIELDS AND STRUCTURE WILL BE ANALYSED AND FILTERABILITY ASSESSED.
IN PHASE III ATTENTION WILL BE FOCUSED ON THE HYDROCRACKING OF EXTRACT SOLUTIONS. THE TIME AND TEMPERATURE OF REACTION WILL BE VARIED AND MEASUREMENTS WILL BE MADE OF PRODUCT YIELDS, PRODUCT STRUCTURE, CATALYST DEACTIVATION AND EXTRACTION YIELDS WITH RECYCLE SOLVENT. PRODUCT YIELD WILL ALSO BE ASSESSED FOR ONE STAGE LIQUEFACTION.
HEROT-WATT WILL CARRY OUT THE EXTRACTION AND HYDROCRACKING EXPERIMENTS AND WILL CHARACTERIZE LIGHT ENDS. LEEDS WILL PREPARE THE PETROLEUM FRACTIONS AND CHARACTERIZE HEAVY ENDS.
STATE OF ADVANCEMENT:
TWO PROGRESS REPORTS HAVE BEEN RECEIVED. CO-PROCESSING RUNS OF POINT OF AYR COAL WITH VACUUM RESIDUES DID NOT SHOW A SUBSTANTIAL INCREASE OF THE TOTAL OIL YIELD. ADDITION OF ANTHRACENE OIL SHOWS A SIGNIFICANT POSITIVE INTERACTION. REACTION CONDITIONS WILL FURTHER BE OPTIMIZED TO IMPROVE YIELDS.