Aspects on the Flue Gas Chemistry of KCl, NO and CO During Injection of Ammonium Sulphate - An Experimental Approach

Abstract

Sulphate containing additives, such as ammonium sulphate (AS, (NH4)2SO4), are used for sulphation of KCl during biomass combustion. Another aspect with injection of AS is that a significant NOx reduction is achieved but it may also have an impact on other flue gas components such as CO. The concentration of oxygen and the presence volatile combustibles could also have an effect on the flue gas chemistry involving KCl, NO and CO. This paper is based on results obtained from two measurement campaigns during co-combustion of wood chips and straw pellets in a 12 MW circulating fluidised bed (CFB) boiler. In the first campaign, the NO reduction performance of AS, ammonia and urea was compared. In the second one, AS was injected at three positions in the boiler i.e. in the upper part of the combustion chamber, in the cyclone inlet, and in the cyclone. The impact of AS on the flue gas chemistry was investigated at three air excess ratios (λ= 1.1, 1.2 and 1.4). Several measurement tools including, IACM (on-line measurements of gaseous alkali chlorides) and gas analysis were applied. The position for injection of AS as well as the different air excess ratios had a great impact on the flue gas chemistry for especially KCl and NO