System and method for reducing halogen levels necessary for mercury control, increasing the service life and/or catalytic activity of an SCR catalyst and/or control of multiple emissions

A method for reducing the amount and/or concentration of one or more halogen-containing compounds used to achieve mercury capture in a flue gas while simultaneously controlling both gas phase selenium speciation and one or more of gas phase sodium, gas phase sodium compounds, gas phase potassium, and/or gas phase potassium compounds, the method comprising the steps of:

• (i) providing at least one coal-based fuel to the furnace, or boiler;
• (ii) subjecting the at least one coal-based fuel to a staged combustion process, wherein the staged combustion process produces gaseous mercury;
• (iii) providing one or more halogen-containing compounds to a combustion zone or flue gas stream of a furnace, or boiler, prior to entry of the flue gas into an SCR, wherein the halogen portion of the one or more halogen-containing compounds are liberated in the combustion zone or flue gas stream of the furnace or boiler and are converted to one or more corresponding gaseous hydrogen halide compounds;
• (iv) providing one or more first metal-bearing compounds to a combustion zone or flue gas stream of a furnace, or boiler, at one or more points selected from injection points A through G that is both prior to entry of the flue gas into an SCR as well as after a point where the majority of the one or more halogen-bearing compounds have been converted to the corresponding gaseous hydrogen halides;
• (v) providing one or more second metal-bearing compounds to a combustion zone or flue gas stream of a furnace, or boiler, at a point that prior to entry of the flue gas into an SCR;
• (vi) providing one or more kaolin-bearing compounds to a combustion zone or flue gas stream of a furnace, or boiler, at one or more points selected from injection points M, N, O, P or Q that is both prior to entry of the flue gas into an SCR as well as after the points at which both the one or more first metal-bearing compounds and the one or more second metal-bearing compounds have been provided;
• (vii) permitting the one or more first metal-bearing compounds to catalyze the conversion of the corresponding one or more hydrogen halides to one or more corresponding elemental halogen compounds;
• (viii) permitting the resulting one or more corresponding elemental halogen compounds to react with the gaseous mercury present in the combustion zone or flue gas stream of the furnace, or boiler, thereby resulting in the oxidation of the gaseous mercury so as to convert the gaseous mercury into one or more corresponding mercury halides;
• (ix) permitting the one or more second metal-bearing compounds to react with one or more gaseous selenium compounds or gaseous selenium-containing compounds thereby resulting in the reduction of any gaseous selenium ions to a lower oxidation state;
• and
• (x) permitting the one or more kaolin-bearing compounds to react with one or more of gas phase sodium, gas phase sodium compounds, gas phase potassium, and/or gas phase potassium compounds so as to reduce or prevent the poisoning and/or contamination of a catalyst in the SCR,
• wherein the metal portion of the one or more first metal-bearing compounds and the metal portion of the one or more second metal-bearing compounds are different metals.