Elemental mercury removal from flue gas using modified tonstein: Performance of adsorbent injection at an entrained flow reactor system and 50-MW coal-fired power plant in China

Abstract

The application of mercury removal technology in coal-fired power plants has attracted much attention. In this paper, performances of CuBr2-modified tonstein from coal seams (MTCS) injection at an entrained flow reactor system and a 50-MW coal-fired power plant and their corresponding mechanisms were studied. The results showed that the increase of the injection rate, the reduction of the particle size, the extension of the residence time, and the increase of the initial Hg0 concentration were all conducive to mercury removal. At an entrained flow reactor, SO2 and H2O obviously inhibited mercury removal, but this inhibition could be reduced with the increase of the residence time or the participation of NO and HCl. Specifically, with the participation of 1200 ppm SO2, the Hg0 removal efficiency was 56.9% and 82.8% at 0.6 s and 1.2 s, respectively. In the temperature range of 30–150 °C, the Hg0 removal efficiency in the flue gas at the simulated flue exit was approximately 83–93%. In addition, at a 50-MW coal-fired power plant, the injection of MTCS was beneficial to Hg0 removal. In this process, most Hg0 was converted to Hg2+ by active substances, and then captured using fabric filter (FF) and wet flue gas desulfurization (WFGD) device. Injecting MTCS with a particle size of 300 mesh and concentration of 0.31 g/m3 can result in a relative mercury removal efficiency of up to 82.9% in the flue gas at the WFGD outlet, indicating that the low-cost mineral adsorbent MTCS is a suitable choice for mercury control in coal-fired power plants.