Study On Low-cost Preparation Technology Of Activated Carbons For Flue Gas Mercury Removal

Pollutants control of coal-fired flue gas has been one of the main problems faced by national environmental protection department, coal-fired mercury pollution has become the fourth largest after dust, SOX, NOX. Currently the most effective method of coal-fired flue gas mercury is activated carbons injection method. However, the price of activated carbons has affected the application of this technology, how to significantly reduce the cost of activated carbons has important significance.In this paper, activated carbons are prepared from Taixi anthracite, used the processing without binder, no binder and carbonization processing and coal with high ash. The effect of conditions, such as particle sizes of coal, carbonization temperature, carbonization heating rate, activation temperature, feed temperature, burn off and ash of coal on the adsorption properties, pore size distribution and the capability of mercury removal are investigated, so as to find out the optimum operation conditions at which the performance of mercury adsorption is the best. At the same time, studied on the relationship between various indicators of activated carbons and find out the best aperture for mercury adsorption.For the processing without binder, when prepared under the conditions of 3-4mm of particle sizes of coal, investment directly of carbonization heating rate, 450℃ of carbonization temperature, 970℃ of activation temperature and 64% of burn off, the adsorbent achieves the highest mercury adsorption capacity within 60 min. For the processing without binder and carbonization, when prepared under the conditions of 4-5mm of particle sizes of coal, 700℃ of carbonization temperature, 910℃ of activation temperature and 71% of burn off, the adsorbent achieves the highest mercury adsorption capacity within 60 min. By comparison, activated carbons without binder is better for mercury removal. The higher the content of coal ash, the higher the mercury penetration, the lower the accumulated mercury adsorption quantity per unit mass of adsorbent. The results show that ash affects the ability of activated carbons for mercury removal, the inorganic constituents of ash don’t act as a catalyst for the adsorption of mercury.Linear regression analysis is used to analyze the relationship between the various indicators of activated carbons. The study shows that correlation between iodine number and specific surface area is best, methylene blue adsorption and the total pore volume has correlation. However, there exists no obvious linear relationship between iodine number and adsorption of mercury, so is methylene blue adsorption. The pores ranging from 0.61 nm to 1.30 nm were in favor of iodine number, which about 1.09-2.32 times larger than the diameter of iodine molecule; The pores ranging from 1.30 nm to 2.18 nm were in favor of methylene blue adsorption, which about 1.19-2.02 times as large as the diameter of methylene blue. The pores ranging from 0.61 nm to 0.67 nm were in favor of mercury adsorption.