(421c) The Design and Analysis of Activated Biochar Material for the Control of Elemental Mercury Emission From Industrial Facilities Into the Global Atmospheric Pool

     Mercury in the environment is a global environmental issue.  One of the main sources of elemental mercury into the atmospheric environment is coal burning electricity generating power plants.  Mercury is a trace contaminant in the burning of coal. Essentially, this anthropogenic elemental mercury is emitted into the earth’s atmospheric environment.  It then mixes globally.  Once it deposits to the earth’s surface, it is the aquatic systems of planet earth that are the most sensitive to the elemental mercury.  The deposited mercury methylates the aquatic systems of the planet with the accumulation of this material occurring in selective fish tissue and then subsequently into the human being with the consumption of fish tissue.

     Biological carbon or biochar has been prepared and used by the University of Saskatchewan Chemical Engineering Department, the Saskatchewan Research Council (SRC) and SaskPower in a research program over the years, to test its effectiveness as a capture agent for elemental mercury gas in Saskatchewan’s coal-fired power plant flue gas streams.

     The source of the biological carbon products for these programs has come from Advanced BioRefinery, which is a commercial firm that acquires its biological carbon from Canada’s forest industry and other similar venues.

     The biochar material is then activated at the University of Saskatchewan and prepared into an appropriate particle size range at SRC for injection into a coal-fired power plant’s flue gas stream within the province of Saskatchewan, Canada.  After activation, this biochar material is ground into a series of small aerosol particles in the size range of approximately 50 microns in diameter for direct in-stack injection into an operational coal-fired power plant’s flue gas stream.  Once in the flue gas stream, these biochar aerosols capture elemental mercury atoms which are subsequently sequestered from emission into the environment.

      In this presentation we will discuss the need for the activation process of the raw biochar product.  It has been discovered in this research that it is the surface aerosol microporosity that is the primary agent responsible for the elemental stack gas mercury capture efficiency. Various procedures have been employed to enhance the biochar elemental mercury capture effectiveness within an operational setting.

     We have prepared two levels of aerosol microporosity described as an optimum level at 287 m²/g and a reference level at 207 m²/g.  Once these various levels of biochar aerosol microporosity were injected into a coal burning power plan’s flue gas stream, it was discovered that the optimum level of biochar aerosol microporosity reduced the elemental mercury emission rate into the environment by approximately 88 per cent.  The reference level of aerosol microporosity reduced the elemental mercury emission rate in to the environment by approximately 60 per cent.

     The primary conclusion of this research work with biochar is that it is the aerosol surface microporosity that is the main capture agent for in-stack elemental mercury atoms.  Biochar aerosols can be prepared and sold into the international market as a sorbent-based emission control agent for in-stack elemental mercury emissions control for the coal burning power stations of the world.