Abstract


SULPHATION OF ESTONIAN AND ISREALI OIL SHALE ASHES UNDER ATMOSPHERIC AND PRESSURIZED COMBUSTION CONDITIONS

I. KÜLAOTS
A. OTS
Tallinn Technical University
Thermal Engineering Department
Tallinn, Estonia
 
P. YRJAS
M. HUPA
P. BACKMAN
Åbo Akademi University
Department of Chemical Engineering
Turku, Finland

The main problems in conventional combustion boilers firing pulverized oil shale are the high SO2 emission and intensive fouling of heat transfer surfaces with ash deposits. One alternative to lower the SO2 and CO2 concentration in flue gas is the use of the pressurized combustion technologies. The capture of sulphur dioxide by oil shale ashes as material with high calcium oxide content in atmospheric and pressurized fluidized bed combustion condition has been studied using a thermo-
gravimetric apparatus. Four different materials have been tested: Estonian oil shale fractions 125-
-180 µm and 56-200 µm, Israeli oil shale fraction 125-180 µm and cyclone ash from an Estonian pulverized oil shale boiler. The experiments were carried out in SO2 containing ambient at two pressures 0.1 MPa (atmospheric) and 1.5 MPa, and at temperatures 750 and 850 C. In pressu-
rized conditions CaCO3 does not calcine due to the high partial pressure of CO2. As a result, the SO2 will be captured in oil shale ashes' conversion characteristics to CaSO4. The results of studies of the ashes after the sulphation with a Scanning Electron Microscope are also presented.

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