Sulfation of alkali halides in a bench-scale bubbling fluidized bed reactor

A1 Journal article (refereed)


Internal Authors/Editors


Publication Details

List of Authors: Hao Wu, Patrik Yrjas, Pasi Vainikka, Daniel Lindberg, Mikko Hupa
Publication year: 2016
Journal: Fuel
Volume number: 177
Start page: 173
End page: 179
eISSN: 1873-7153


Abstract

During biomass and waste combustion, high levels of alkali halides in the flue gas often lead to increased
deposit formation and accelerated superheater corrosion. These problems can be reduced either by cocombustion
or by the use of sulfur-containing additives. A measurement campaign was carried out in
a 20kWth bubbling fluidized bed (BFB) bench-scale reactor to characterize the sulfation behaviors of
alkali chloride and alkali bromide. Spruce bark was used as the base fuel – serving as a source of alkali
metals (mainly K). HCl and HBr gases were fed with the fluidization air to simulate co-firing of a
halide-rich fuel with bark. SO2 and elemental S powder were used as additives to convert the alkali halide
aerosols to less corrosive alkali sulfates. The sulfation behavior of alkali halides was evaluated by means
of several measurements including: FTIR (flue gas measurement), a low-pressure impactor (particle size
distribution and chemical composition of extracted aerosol particles) and deposit probe sampling
(deposit growth rate and chemical composition of the windward, 90 side and leeward deposits). The
results indicated a higher tendency for sulfation of alkali chloride than of alkali bromide.

During biomass and waste combustion, high levels of alkali halides in the flue gas often lead to increased deposit formation and accelerated superheater corrosion. These problems can be reduced either by cocombustion or by the use of sulfur-containing additives. A measurement campaign was carried out in a 20kWth bubbling fluidized bed (BFB) bench-scale reactor to characterize the sulfation behaviors of alkali chloride and alkali bromide. Spruce bark was used as the base fuel – serving as a source of alkali metals (mainly K). HCl and HBr gases were fed with the fluidization air to simulate co-firing of a halide-rich fuel with bark. SO2 and elemental S powder were used as additives to convert the alkali halide aerosols to less corrosive alkali sulfates. The sulfation behavior of alkali halides was evaluated by means of several measurements including: FTIR (flue gas measurement), a low-pressure impactor (particle size distribution and chemical composition of extracted aerosol particles) and deposit probe sampling (deposit growth rate and chemical composition of the windward, 90 side and leeward deposits). The results indicated a higher tendency for sulfation of alkali chloride than of alkali bromide.


Keywords

alkali halides, bubbling fluidized bed combustion, sulfation

Last updated on 2019-19-08 at 05:34