Nitrogen Containing Additives for Simultaneous Reduction of KCl and NOx during Biomass Combustion in a CFB Boiler
Paper in proceeding, 2009

High levels of alkali chlorides in the flue gas can cause enhanced deposit formation and superheater corrosion during combustion of biofuels. These alkali chlorides mainly originate from potassium chloride (KCl). A challenge during combustion of biofuels is to simultaneously reduce NOx and KCl. The ChlorOut concept has been developed by Vattenfall to minimise deposit formation and corrosion. It consists of IACM, an instrument for on-line measurements of gaseous alkali chlorides, and a sulphate-containing additive that converts alkali chlorides to less corrosive alkali sulphates. The sulphate-containing additive is often ammonium sulphate, (NH4)2SO4, and, therefore, a significant NOx reduction is also achieved. This paper presents the results from a comparison of the conventional SNCR additives (ammonia or urea) and (NH4)2SO4 for reduction of NOx and/or KCl during combustion in a CFB boiler. The fuel consisted of either a mixture of wood chips and wood pellets with added PVC or with straw pellets. Of special interest was the influence of sulphation of KCl in parallel to the reduction of NO and if these processes interact. The results show that there are rather small differences in performance concerning NOx reduction between the additives.

nitrogen oxides

fluidized bed combustion

alkali chlorides

alkali monitor


ammonium sulphate


Håkan Kassman

Chalmers, Energy and Environment, Energy Technology

Magnus Holmgren

Elin Edvardsson

Lars-Erik Åmand

Chalmers, Energy and Environment

Johannes Öhlin

Chalmers, Energy and Environment

Proceedings of the 9th International Conference on Circulating Fluidized Beds, May, 13 - 16, 2008, Hamburg, Germany

Driving Forces

Sustainable development

Areas of Advance


Subject Categories

Other Environmental Engineering

More information