Experimental Study On Mercury Removal Process Of Coal - Fired Flue Gas

With the increasingly stringent environmental protection requirements, mercury pollution control in China has been gradually put on the agenda. As a large source of mercury pollution, coal-fired power plants will be the focus of mercury emission control. This paper is based on the Guodian scientific research project, depending on the equipment in the laboratory of Heavy Metal Pollution Control of National Energy Bureau, exploring the formula of mercury removal adsorbent, building the fixed bed mercury adsorption platform and laboratory scale in-duct mercury capture equipment, carrying out study on the process parameters of mercury removal.Through the experimental study of the adsorption properties of various types of activated carbon in fixed bed mercury adsorption platform,the surface physical properties of activated carbon has great influence on the adsorption efficiency,the result indicates that larger specific surface area and micropore volume activated carbon perform excellent in mercury adsorption; By modifying raw material activated carbon using same concentration HNO3 and NaOH solution,the result indicates the activated carbon surface area and micropore volume was not significantly improved, the number of carboxyl、phenolic hydroxyl and carbonyl functional group on activated carbon surface increase after modified by HNO3, carboxyl on the surface of activated carbon slightly increases and carbonyl functional group change little after modified by NaOH. Activated carbon modified by HNO3 perform better in mercury adsorption. After modified by the same concentration solution of CaCl2、CaBr2、 CaI2, the mercury adsorption of activated carbon improved obviously, of which the activated carbon modified by calcium bromide perform best in mercury adsorption. In the conclusion, the paper selects the coconut shell activated carbon, modifying it by nitric acid and CaBr2 solution, the result indicates that activated carbon surface area and micropore volume decreased slightly, the oxygen, nitrogen element content in the surface of the active carbon increased, the layered structure is more obvious, calcium bromide load on the surface of activated carbon as non crystal morphology.As the system reaction temperature increases, the mercury removal efficiency of raw activated carbon decreases, however the temperature change does not affect mercury removal efficiency of brominated activated carbon, for the reason that the chemical adsorption occupies a dominant position; As the residence time prolongs, the contact opportunities of the active carbon and mercury molecular increases, the utilization rate of activated carbon improves. And with the increase of residence time, the speed of improvement of mercury removal efficiency delays. Different particle size of activated carbon has a great influence on the removal efficiency of mercury, mercury removal efficiency of 325 objective raw coconut shell activated carbon was significantly higher than that of 200 orders and 50 objective activated carbon; When the activated carbon injection amount is 310mg/h, mercury removal efficiency of 1.6%,4.1%,5.5% amount of brominated activated carbon reached 99%,so the brominated amount of 1.6% is very good; Mercury removal efficiency of activated carbon will improve with the increase of initial concentration of mercury, the increase of mercury concentration in the entrance brings about the advance of number of molecules in flue gas and promotes the adsorption of mercury molecular and activated carbon.The increase of the initial concentration of Hg has great effect on the raw material of activated carbon and has little effect on efficiency of bromized activated carbon. After loading bromine on the surface of raw activated carbon, mercury removal efficiency greatly enhance.As the C/Hg increases,the mercury removal of activated carbon increases. When the figure of C/Hg similar, the mercury removal of modified activated carbon is much higher than raw activated carbon.