Sulfur Capture during Combustion of High Sulfur CoalsImpregnated with Calcium Acetate as a Desulfurization Sorbent

摘要

Combustion of Datong coal,with impregnation of calcium acetate onto it,was carried outin a drop tube furnace.Its pyrolysis was first conducted to study the morphology of theresultant chars,and the mode of occurrence of calcium,sulfur and their association withinchar were studied as well.Secondly,combustion of chars was carried out to reveal theemission of sulfur,transformation of char structure and that of calcium- and sulfur-basedcompounds in this process.For the raw coal,the sulfur emission during its combustion wascontinued until all the carbon burnt out.The thick wall was formed for the pyrolyzing char.The SO2 emission during combustion of impregnated coals was decreased considerablycompared to that in the cases of raw coals.More than half the emitted sulfur was capturedby added calcium in coal pyrolysis.The sulfur removal in the following char compoundsvaried with both reaction temperature and coal type.During coal pyrolysis,the addedcalcium,which penetrated into coal due to the impregnation,moved to the surface ofporous char,where it met the emitted sulfur,capturing it quickly.Little calcium reactedwith the inherent aluminosilicate in this step.In the beginning of char combustion,thereaction of oxygen with volatile and char led to the increase of char temperature,as a result,the sulfation of calcium was inhibited to certain extent;whilst the formation of calciumaluminosilicate was facilitated.With char combustion progressed,the porous calciumnetwork consisting of unreacted calcium and the molten calcium aluminosilicate wasformed as the consequence,which reacted with SO2 readily,hence,the sulfur removalefficiency was increased eventually.