EFFECT OF BIOMASS BLENDING AND DESULPHURIZATION ON FLUE GAS EMISSIONS OF NIGERIAN SUB BITUMINOUS COAL BRIQUETTES

Abstract

The effect of blending, briquetting and desulphurization of coal and biocoal briquettes of Nigerian sub bituminous coal is discussed. The flue gas of the coal and biocoal samples were analyzed to study the emission characteristics of nitrogen oxide (NO2), sulphur dioxide (SO2) and carbon monoxide (CO) due to environment concern with the use of coal as either domestic or industrial fuel. Sub bituminous coal sample from eight coal mines and sites in five states in Nigeria were collected. The states and sites included Kogi (Ogboyoga, Okaba), Benue(Owukpa),Nassarawa (Lafia/Obi), Ebonyi (Afikpo) and Enugu (Okpara,Onyeama and Ezinmo).The samples were pulverized and blended with sawdust at various constituent ratios of 0:100, 10:90, 20:80, 30:70, 40:60, 50:50 and 100:0 sawdust : coal. Cassava starch was used as binding material while calcium hydroxide was used as desulphurizing agent for the briquettes. Emission tests for various compositions of the briquettes were carried out and the O2, CO2, CO, NO2 and SO2 of the briquettes were compared. Results showed reduction in combustion emission with increase in sawdust concentration with the reduction in smoke and noxious gas emission. The sulphur dioxide range of the coal briquettes is between 0.018ppm and 0.028ppm which decreased to between 0.025and 0.005 ppm in biocoal briquettes. Same for nitrogen oxide which range between 0.034ppm and 0.038ppm but decreased to between 0.025 and 0.019 ppm and carbon monoxide range of between 0.3ppm and 0.48ppm which decreased to between 0.43ppm and 0.12 ppm in the biocoal briquettes. The 50:50 blends of sawdust to coal for Ogboyaga has the lowest carbon monoxide emission of 0.12 ppm; Okpara has the lowest sulphur dioxide emission of 0.005ppm while Onyeama has the lowest nitrogen oxide emission of 0.019 ppm. These are below the national ambient air quality standards which put sulphur dioxide at 1.4 x 10-1 ppm. The biocoal briquette emits less sulphur dioxide because it contains desulphurizing agent which fixes some of the sulphur that would have gone to the atmosphere to ash. Keywords: biocoal briquettes, blending, flue gas emissions, sub - bituminous coal.