Countermeasures against alkali-related problems during combustion of biomass in a circulating fluidized bed boiler
Artikel i vetenskaplig tidskrift, 2008

The purpose of this work was to study different ways to mitigate alkali-related problems during combustion of biomass in circulating fluidized beds. Wood chips and wood pellets were fired together with straw pellets, while the tendency to agglomerate and form deposits was monitored. In addition to a reference case, a number of countermeasures were applied in related tests. Those were addition of elemental sulphur, ammonium sulphate and kaolin to a bed of silica sand, as well as use of olivine sand and blast-furnace slag as alternative bed materials. The agglomeration temperature, composition and structure of bed-ash samples were examined. The flue-gas composition, including gaseous alkali chlorides, was measured in the hot flue gases and in the stack. Particles in the flue gas were collected and analysed for size distribution and composition. Deposits were collected on a probe in hot flue gases and their amount and composition were analysed. Addition of kaolin was found to be the best method to counteract the agglomeration problem. The deposition problem is effectively counteracted with addition of ammonium sulphate, while kaolin is too expensive to be used commercially against deposits, and sulphur is less effective than ammonium sulphate.

Particulate processes

Deposition

Gases

Combustion

Agglomeration

Biofuels

Författare

Kent Davidsson

Chalmers, Energi och miljö, Energiteknik

Lars-Erik Åmand

Chalmers, Energi och miljö, Energiteknik

Britt-Marie Steenari

Chalmers, Kemi- och bioteknik, Oorganisk miljökemi

Anna-Lena Elled

Chalmers, Energi och miljö, Energiteknik

David Eskilsson

Bo G Leckner

Chalmers, Energi och miljö, Energiteknik

Chemical Engineering Science

Vol. 63 5314-5329

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