| The biomass activated carbon from the raw material of renewable resources, was used to absorb multi-kind of pollutants in flue gas, including SO2, Nitrogen oxides and heavy metal elements such as mercury, with economic superiority and excellent performance.The flue gas cleaning technologies were summarized firstly in this paper, especially the research status of the activated carbon method. In order to reduce the production and running cost, the raw materials of biomass were chosen to product the activated carbon for the simultaneously removal. A vertical energy conservation furnace was developed; the pyrolysis and activation processes could continuously be preceded in the furnace. The pellets made from Wood dust, wheat straw, wheat straw added 10% coal powder and cotton seeds skin were used in this paper to produce the activated carbon. The pyrolysis heating rate was 5K/min and the terminal temperature was 450℃. The activation heating rate was 10K/min, and its terminal temperature was 800℃. The characteristics of the carbon pellets were analyzed by Gas Adsorption Analyzer and SEM-EDS. The BET specific surface area of wood dust activated carbon can reach to 810 m2/g. But there was a different characteristic that more alkali metal oxide loaded on the carbon surface of crop pellets than wood dust, so more alkaline functional groups formed on the carbon surface, which was beneficial for the removal of acidic contaminants gas.The biomass activated carbon pellets were used step by step for the research on the simultaneously removal performance of gas pollutants. The single-layer/multi-layer layout of activated carbon were designed in the fixed-bed reactor. The activated carbon was suitable for physical adsorption and removal of sulfur dioxide gas; and the carbon soaked with ammonia could improve the catalytic denitration performance. The third carbon layer was layout after the water cooling coiler; the lower gas temperature was benefit for higher efficiency of physisorption of the remainder SO2 and Hg.A comprehensive analysis was made for the simultaneously removal tests. The wood dust activated carbon showed a desulphurization efficiency of more than 90% and de-nitrogen efficiency of more than 80% in a working period about 2 hours. It was suitable to work under the lower temperature (70-90℃). The activated carbon immersed with ammonia water could increase the deNOx efficiency at a higher working temperature (130℃). The regeneration did not reduce the deSO2 efficiency. And the carbon of straw with 10% coal could maintain higher desulphurization efficiency over 95% and higher de-nitrogen efficiency over 85% in most of working time. Comparatively, the mechanical strength, physical adsorption (at 70℃) and chemical adsorption (at 110℃) of the carbon of straw with 10% coal showed an unique advantages. For the Cotton seed skin activated carbon, the performance on the associated removal performance was desirable when both low (70℃) and medium (110℃) working temperature. Its desulfurization efficiency was above 95%, denitration efficiency over 70% and mercury removal efficiency above 43% at low temperature. And the desulfurization efficiency was above 99%, the denitration efficiency was above 80% and the mercury removal efficiency was above 30% at medium temperature.The experimental study was under the actual engineering background, the dry flue gas contaminants was simultaneously removed by the biomass activated carbons, some significant conclusions were drawn. The cotton seed skin activated carbon had not only excellent physisorption but also better chemisorptions performance with the high level of desulfurization, associated denitration and mercury removal efficiency. The study of this paper presented the important significance and supplied more guidance for the industrial reactor design of activated carbon to remove the flue gas pollutants. |
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