The Study On Removing SO₂ And Hg⁰ Simultaneously From Simulated Flue Gas By Waste Coal Gas Desurfurizer

The sulfur dioxide and mercury emissions from coal-fired power plants are the main source of sulfur pollution and mercury pollution in the atmosphere. In recent years, the controlling emission concentration of sulfur dioxide and mercury is becoming more and more strict. According to the " air pollutants emission standards of power plant " in 2011, the emission limits of sulfur dioxide and mercury are respectively 100 mg/m3 and 0.03 mg/m3. The semi-coke sorbents prepared by ultrasound-assisted high-pressure impregnation method show better removing capacity for H2 S. because it is difficult for regeneration, so it is called waste desulfurizer. But the waste desulfurizer loading Zn, Mn and Cu still has developed pore structure and abundant surface functional groups. According to the literature, these features should be useful. Combined with the emission limits sulfur dioxide and mercury from coal-fired flue gas, the waste desulfurizer DZMCSC was used for removing SO2 and Hg0. It not only can process waste desulfurizer but also find a kind of cheap sorbent for cleaning flue gas. At last, the purpose can be achieved of using waste treat waste.In this paper, the removing capacities of SO2 and Hg0 of the waste desulfurizer DZMCSC were tested using fixed-bed evaluation device. As comparing samples, the ultrasonic hydration semi-coke sorbent(USC) and semi-coke sorbent loading Zn, Mn, and Cu(ZMCSC) were prepared and also were tested. In order to reveal desulfurization and demercuration mechanism of DZMCSC, The changes of physical and chemical properties were detected By BET, XRD, XPS, FTIR methods. Main conclusions are as follows:Fixed bed experimental results show that the waste desulfurizer DZMCSC can simultaneously remove the SO2 and Hg0 from the simulated flue gas at 120 ℃. The functional groups-OH, C=O and COOH are the common active site of SO2 and Hg0, and the competitive adsorption will happen between SO2 and Hg0.Waste desulfurizer DZMCSC exhibits better mercury removal ability and the order is DZMCSC>ZMCSC>USC through comparison experiment. DZMCSC removing mercury includes physisorption and chemisorption and the latter plays an important role in demercuration. Chemical adsorption is embodied in two aspects. On the one hand,-OH, C=O and COOH are main chemisorption mercury functional groups, on the other hand, ZnO MnO2 and ZnS are the main active component. Among them, ZnS is crucial. Under oxygen atmosphere, ZnS can be oxidated into the element S, and then the stable HgS may be generated with element S and Hg0. With the increas ing adsorption amount of H2 S, the capacity of mercury removal is also enhanced.Aim at the low SO2 removal ability, the waste desulfurizer DZMCSC was modified by ultrasonic assisted impregnating ammonia. The results show that the SO2 removal capacity of the modified sorbent increased significantly. The increasing ammonia concentration leads to higher removing ability. But the demercuration capacity is lower than that of DZMCSC. The modified sorbent has more developed pore structure. The reason is that physisorption H2 S on the surface of DZMCSC react with the alkaline ammonia, which opens the holes blocked by H2 S molecules. More developed pore structure is beneficial to physisorption of Hg0 and SO2. But XRD results show that the metal sulfide ZnS content decreases for DZMCSC after being modified with ammonia, which makes the modified sorbent decrease its mercury removal capacity slightly.