Research On Preparation Of Activated Carbon For Flue Gas Desulfurization By Blending Coal Method

Compared with other flue gas cleaning technology with high competitiveness and larger space for development, dry desulfurization method with activated carbon is simple and has a higher desulfurization efficiency. Besides, activated carbon can be regenerated for cycling and sulfur resources can be recycled.Therefore it is a prospect better flue gas desulphurization technology.In this study, Shaanxi weakly caking coal, Shaanxi semi-coke and Shandong gas-fat coal as main raw material, coal tar as a binder, an orthogonal experiment and a single factor experiment are designed to study the four properties of activated carbon for flue gas desulfurization, including abrasion resistance, compressive strength, saturated sulfur capacity, penetrable sulfur capacity. In the range of influence level, the independence impact of changes of LOI rate to each indicator is relatively large. The effect of carbonization time to abrasion resistance, saturated sulfur capacity and penetrable sulfur capacity is consistent.While, the effect of activation temperature to compressive strength, saturated sulfur capacity and penetrable sulfur capacity is consistent. Also, the compressive strength and saturated sulfur capacity are two most important performance indicators, so we can draw a conclusion that: the greatest impact on the property of activated carbon for flue gas desulfurization is activation temperature, followed by carbonization time, and finally LOI rate. According to the results of the orthogonal experiment and single factor experiment, we derive that the best preparation conditions of activated carbon for flue gas desulfurization are 50% of Shaanxi weakly caking coal, 40% of Shaanxi semi-coke, 10% of Shandong gas-fat coal, 40% of coal tar, 700?C of carbonization temperature, 20 min of carbonization time, 900?C of activation temperature, 25% of LOI rate. The performance indicators of activated carbon under the conditions are 96.81% of abrasion resistance, 547.2 N/cm of compressive strength, 29.71 mg/g of saturated sulfur capacity, 13.45 mg/g of penetrable sulfur capacity.In order to further improve the compressive strength of activated carbon, Henan meager coal, Shandong gas-fat coal, Shanxi weakly caking coal as main raw material, adding a certain percentage of asphalt, solution based on a synthetic polymer as blinder, by changing the proportion of blending coal, asphalt and the diameter of activated carbon, we analyze the changes of the compressive strength. Finally, an optimal solution is obtained: Henan meager coal: Shandong gas-fat coal: Shanxi weakly caking coal = 3:3:4, 8% of asphalt, 5 mm of diameter, 700?C of carbonization temperature, 20 min of carbonization time, 900?C of activation temperature, 25% of LOI rate. The performance indicators of activated carbon under the conditions are 862.8 N/cm of compressive strength, 98.6% of abrasion resistance, 27.64 mg/g of saturated sulfur capacity, 18.38 mg/g of penetrable sulfur capacity.The trends of breakthrough curve and desulfurization rate curve are completely opposite and appear relationship of axial symmetry. By observing the trends of multi-group breakthrough curves, we find that before reaching the breakthrough concentration 100 ppm of sulfur dioxide, concentration datas continue very small and tend to be straight. After reaching the breakthrough concentration, breakthrough curves become rising faster and between breakthrough concentration 100 ppm and saturation concentration 3000 ppm, there will appear several peaks; During the initial stages of adsorption, larger adsorption rate cause sulfur capacity to increase rapidly. As the time goes on, adsorption rate decreases and sulfur capacity increases slowly until it reaches a maximum. At this point, the adsorption reaches saturation and adsorption rate is reduced to a minimum.Through linear fitting, we find that it is no significant linear relationship between the saturated sulfur capacity and specific surface area and total pore volume of activated carbon. The pore size of activated carbon is concentrated in the 0.6-1.5 nm of micropore range and the 2.6-4 nm of mesopore range. After linear fitting between the pore volume of different aperture range and the saturated sulfur capacity of activated carbon, we find that the slope of fitting curves are all negative. The linear correlation in 1.83-2.38 nm, 2.38-3.39 nm, 3.39-4.41 nm three aperture range is overall large and increases with increasing aperture, indicating that the larger the aperture, the less help to improve the saturated sulfur capacity of activated carbon. R2 in 1.42-1.83 nm range is relatively large, indicating that the fewer the holes in this aperture range, the more help to improve the saturated sulfur capacity of activated carbon. R2 in 3.39-4.41 nm is a maximum, indicating that the fewer the holes in this aperture range, the most help to improve the saturated sulfur capacity of activated carbon.