Countermeasures against alkali-related problems during combustion of biomass in a circulating fluidized bed boiler

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

Subject headings

TEKNIK OCH TEKNOLOGIER  -- Maskinteknik -- Energiteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering -- Energy Engineering (hsv//eng)

TEKNIK OCH TEKNOLOGIER  -- Naturresursteknik -- Annan naturresursteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Environmental Engineering -- Other Environmental Engineering (hsv//eng)

Keyword

Particulate processes

Deposition

Gases

Combustion

Agglomeration

Biofuels

Publication and Content Type

art (subject category)

ref (subject category)