Study On Dioxins Adsorption By Powder Activated Carbon

Control of dioxin emissions from municipal solid waste flue gas has been paid attention toboth in domestic and overseas. The most simple and effective method is to make use of activatedcarbon, which has the ability of strong adsorption with trace-level organic compounds. Duing toboth crude process and serious secondary pollution of the traditional semi-dry process which usingactivated carbon adsorption technology, this Research group put forward a novel integrativetechnology which contained dual-layered granular bed, activated carbon and bag filter.Dibenzofuran(simulacrum of dioxin) adsorption experiments were conducted, experimentalresearch on adsorption efficiency by only PAC attached to the bag filter was carried to investigatethe effects of such factors as material of PAC, adsorption temperature, quantity of PAC, inlet DBFconcentration. The results indicated that wood-derived AC has higher adsorption efficiency thancoal-derived AC, when adsorption temperature was403.15K. The adsorption efficiency decreasedwith the rise of temperature, when adsorption temperature raised from363.15K to403.15K, theaverage adsorption efficiency of wood-derived AC decreased from91.73%to82.37%within100min, and coaled-derived AC was from87.9%to80.83%. As the PAC addition amount increasedfrom0.1507g to0.2504g, the average adsorption efficiency of wood-derived AC raised from74.18%to89.81%within200min, when adsorption temperature was383.15K. At the sameadsorption temperature, when the inlet DBF concentration rise from0.5007g/m~3to0.9061g/m~3,the average adsorption efficiency of wood-derived AC decreased from77.87%to62.51%,byabout15percentage points within400mins, so dropped with penetration time.Yoon-Nelson model was used to fit with the curve of penetrate process when inlet DBFconcentration ranged from0.5007g/m~3to0.9061g/m~3. The results showed that the model fit wellwith the experiment data, and absolute value of average relative error was in15%range. It takes along time to reach to penetrate in the PAC adsorption on DBF. PAC had a saturation capacity of0.1863g/g at temperature of383.15K.DBF adsorption and repeat adsorption experiments were conducted on a small-scale bag filterwith the mixture of PAC and fly ash as sorbent, which PAC proportion was5%,0%, thencompared with pure PAC. The results indicated that the first adsorption of pure PAC’s averageadsorption efficiency was85.17%within140mins, the first time repeation was76.28%, the secondwas69.03%,and the third was56.28%,which was28.92%lower than the first adsorption, whichstill24.08%higher than pure fly ash’s first adsorption. And the first adsorption of the mixture with 5%PAC’s average adsorption efficiency was66.21%within100min, the first time repeation was48.43%, the second was34.7%. it was believed that adsorption ability of the mixture with5%PACsharply declined with the repeation times. The average adsorption efficiency of the mixture with5%PAC was64.69%within200min，which was20.48%lower than pure PAC.Compared with the semi-dry desulphurization and PAC injection in baghouse filters in MSW,the feasibility of adsorption removal by PAC injection in bag filter was analyzed. The resultshowed that the novel process has advantages such as low operation cost, high removal efficiencyand high utilization ratio, without seconday pollution, et al. So it has a broad application prospect.