Modelling of N2O Reduction in a Circulating Fluidized Bed Boiler

Jan Erik Johnsson, Lars Erik Åmand, Kim Dam-Johansen, Bo Leckner

Research output: Chapter in Book/Report/Conference proceedingArticle in proceedingsResearchpeer-review

Abstract

The addition of limestone for sulphur retention in Fluidized Bed Combustion (FBC) has been observed to influence the emission of N2O, and in many cases a lower emission was observed. The catalytic activity of a Danish limestone (Stevns Chalk) for decomposition of N2O in a laboratory fixed bed quartz reactor was measured. It was found that calcined Stevns Chalk is a very active catalyst for N2O decomposition in an inert atmosphere compared to bed material, i.e. a mixture of ash and sand. However, in FBC the limestone is exposed to a mixture of gases, including CO, CO2 and SO2, and sulphation of the limestone will take place. The influence of these gases was investigated in the laboratory reactor. The presence of 3 vol% CO increased the rate of N2O destruction by a factor of 5 due to the catalytic reduction of N2O by CO. The activity decreased with increasing CO2 concentration, and uncalcined or recarbonated limestone had negligible activity. Sulphation of the calcined limestone under oxidizing conditions lowered the activity, however sulphidation under reducing conditions showed that CaS is an active catalyst for the reduction of N2O by CO. Without CO present a gas solid reaction between N2O and CaS takes place and SO2 is released. Kinetic rate expressions for the decomposition and reduction of N2O were developed.
Original languageEnglish
Title of host publicationCirculating Fluidized Bed Technology V, Proceedings of the Fifth International Conference on Circulating Fluidized Beds, May 28 to 31, 1996, Beijing
Place of PublicationBeijing
PublisherScience Press
Publication date1997
Pages338-343
Publication statusPublished - 1997
Event5th International Conference on Circulating Fluidized Beds - Beijing, P.R. China
Duration: 1 Jan 1996 → …

Conference

Conference5th International Conference on Circulating Fluidized Beds
CityBeijing, P.R. China
Period01/01/1996 → …

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