Comparison of sulphur retention by coal ash in different types of combustors

During coal combustion, a part of the total sulphur in coal will be retaine d as solid compounds in ash, In the present paper, the retention of sulphur by ash of typical Chinese coal used for electric power generation was corr elated with the contents of alkaline elements relative to sulphur in the pa rent coal. Comparison was performed among the capabilities of sulphur reten tion by coal ashes in laboratory ashing procedure, pulverised coal-fired co mbustor and fluidised bed combustor (FBC), It was shown that calcium plays a dominant role in sulphur retention of laboratory-prepared ash and the sul phur retention percentage increases with the increase of Ca/S molar ratio o f the parent coal, while the contributions of other elements are limited. T he sulphur retention behaviour in pulverised coal-fired combustor is signif icantly different from that in laboratory ashing procedure. The contributio n of calcium is reduced markedly, while the roles of the other alkaline ele ments are obviously enhanced. Using the literature data from foreign coals, it was found that the sulphur retention in FBC is comparable with that in laboratory ashing procedure. It was suggested from the results obtained in this study that the sulphur retention of laboratory-prepared ash can be app lied to fluidised bed combustion because the behaviour of calcium is simila r to that of lime in FBC. (C) 2000 Elsevier Science B.V. All rights reserve d.