Chemical-mechanical bromination of biomass ash for mercury removal from flue gases

Current approaches for mercury removal have been focusing on injection of powdered activated carbon sorbents into the flue gas stream. In particular, brominated activated carbon has been proven at pilot scale and plant trials to be effective at removing mercury from flue gases of coal-fired power plants. However, activated carbon is a costly source material. Using an industrial solid waste from biomass combustion as an alternative source material to produce sorbents for mercury emission control is an attractive option. This paper describes a novel chemical-mechanical bromination process for production of mercury sorbent from a biomass combustion ash, which is normally considered a solid waste. The chemical-mechanical brominated ash was characterized and tested for mercury capture and release at high temperatures. The brominated biomass ash was found to effectively capture mercury up to 390 °C in lab scale tests. The tests of the new brominated sorbent in a 375 MW coal fired power plant showed promising performance.