FLUID BED COMBUSTOR COMPLIANCE COAL PRODUCTION

MANY LOW RANK COALS (ESPECIALLY LIGNITES) HAVE ONLY MARGINALLY HIGH SULFUR CONTENTS, RESULTING IN EMISSIONS OF 2 TO 3 POUNDS OF SULFUR DIOXIDE (SO2) PER MILLION BTU. THIS SULFUR IS PRESENT IN ABOUT EQUAL AMOUNTS OF PYRITIC, SULFATIC, AND ORGANIC SULFUR. THEREFORE, PHYSICAL CLEANING METHODS ARE TYPICALLY NOT APPLICABLE. HOWEVER, THESE COALS HAVE HIGH OXYGEN CONTENTS, AND MUCH OF THIS OXYGEN IS PRESENT IN CARBOXYLIC ACID FUNCTIONALITIES THAT COULD PROVIDE SITES FOR CALCIUM ION EXCHANGE. CALCIUM COULD BE INCORPORATED INTO THE COAL STRUCTURE, CLOSE TO THE SULFUR, WHERE IT COULD EFFICIENTLY TRAP SULFUR DURING FLUID BED COMBUSTION. THUS, THE CALCIUM-EXCHANGED MATERIAL WOULD BE COMBUSTIBLE AS A COMPLIANCE COAL, ELIMINATING THE NEED FOR MECHANICALLY INTENSIVE SCRUBBING OR SORBENT INJECTION TECHNIQUES. THE ASH CONTENT OF THE COAL MAY BE SOMEWHAT HIGHER, BUT THE TOTAL PLANT SOLIDS WOULD BE LESS AND SOLIDS HANDLING WOULD BE SIMPLER. IN PHASE I, THE METHOD OF ION EXCHANGING COAL WITH CALCIUM IN A SIMULATED STOCKPILE WILL BE INVESTIGATED, AS WELL AS THE PERFORMANCE OF THE PRODUCT IN A SMALL FLUID BED COMBUSTOR (FBC).