COAL-GAS MULTIPLE CONTAMINANT POLISHING

THE OBJECTIVE OF THIS PROJECT IS EXAMINATION OF THE FEASIBILITY OF REMOVING TRACE CONTAMINANTS FROM HOT COAL-GAS. AFTER DESULFURIZATION BY PRELIMINARY HOT-GAS CLEANING, COAL-GAS MUST BE FURTHER POLISHED TO REMOVE A NUMBER OF TRACE CONTAMINANTS TO LEVELS OF LESS THAN 1 PPM. SUCH POLISHING BY GAS SCRUBBING CAN BE ACHIEVED BY VERY INTIMATE CONTACT OF FUEL WITH A NONCONTAMINATING, HIGH TEMPERATURE LIQUID SORBENT IN A FINAL GUARD REACTOR. SOLID SORBENTS SUCH AS ZINC FERRITE WORK WELL FOR INITIAL HOT DESULFURIZATION OF COAL-GAS, BUT THEY ARE NOT SUFFICIENTLY ACTIVE TO COMPLETELY CLEAN VERY HIGH SULFUR GASES DOWN TO THE FRACTIONAL PPM LEVELS REQUIRED IN ALMOST ALL APPLICATIONS. ZINC FERRITE ALSO CANNOT REMOVE SUBSTANTIAL AMOUNTS OF HYDROCHLORIC ACID (HC1), WHICH IS THE SECOND MOST DETRIMENTAL TRACE SPECIES AT UP TO 500 PPM IN COAL-GAS. UNTIL NOW, THE PRODUCTION OF A COAL-GAS COMPATIBLE WITH GAS TURBINE, DIESEL ENGINE, AND FUEL CELL SYSTEMS HAS REQUIRED THE USE OF EITHER COLD-GAS CLEANUP SCRUBBERS OR THE SELEXOL SYSTEM, BOTH OF WHICH USE AMINE SOLVENTS. HOWEVER, COLD SCRUBBING ALWAYS ENTAILS THE EXPENSE OF ENORMOUS HEAT EXCHANGERS TO REHEAT THE CLEANED GAS FOR MOST EFFICIENT USE. THE POLISHING METHOD BEING STUDIED IS EXPECTED TO REACTIVELY ABSORB HYDROGEN SULFIDE (H2S), HC1, AND MANY OTHER TRACE CONTAMINANTS SUCH AS MERCURY, ARSENIC, AND LEAD. PHASE I ATTEMPTS TO SHOW UNEQUIVOCALLY THAT THIS CONCEPT REPRESENTS A VIABLE APPROACH TO THE COMPLETE HOT CLEANUP AND POLISHING OF COAL-DERIVED FUEL. THIS WILL BE DONE BY THERMOGRAVIMETRIC ANALYSIS OF THE SORBENT DURING THE CLEANUP OF THE COAL-GAS.