Sorbents for the oxidation and removal of mercury

Abstract

A promoted activated carbon sorbent is described that is highly effective for the removal of mercury from flue gas streams. The sorbent comprises a new modified carbon form containing reactive forms of halogen and halides. Optional components may be added to increase reactivity and mercury capacity. These may be added directly with the sorbent, or to the flue gas to enhance sorbent performance and/or mercury capture. Mercury removal efficiencies obtained exceed conventional methods. The sorbent can be regenerated and reused. Sorbent treatment and preparation methods are also described. New methods for in-flight preparation, introduction, and control of the active sorbent into the mercury contaminated gas stream are described.

1 . A method of treating coal for combustion in a combustion chamber at a coal-combustion facility comprising a sorbent injection system for injecting activated carbon into a flue gas formed by the combustion, the method comprising:
 adding an additive to the coal, wherein the adding of the additive to the coal is performed at the coal-combustion facility before the coal enters the combustion chamber, and the additive comprises Br2, I2, a bromide compound, an iodide compound, HBr, HI, or a combination thereof;   wherein a weight ratio of the Br2, I2, bromide compound, iodide compound, HBr, HI, or combination thereof in the additive added to the coal to an amount of the activated carbon injected into the flue gas is from about 1:100 to about 30:100.   
     
     
         2 . The method of  claim 1 , wherein the adding of the additive to the coal at the coal-combustion facility comprises adding the additive to the coal during conveyance of the coal to the combustion chamber. 
     
     
         3 . The method of  claim 1 , wherein the additive comprises the Br2, I2, or combination thereof. 
     
     
         4 . The method of  claim 1 , wherein the additive comprises the bromide compound, HBr, or combination thereof. 
     
     
         5 . The method of  claim 1 , wherein the additive comprises the bromide compound. 
     
     
         6 . The method of  claim 1 , wherein the additive comprises the iodide compound, HI, or a combination thereof. 
     
     
         7 . The method of  claim 1 , wherein the additive comprises the iodide compound. 
     
     
         8 . The method of  claim 1 , wherein the coal-combustion facility comprises a system that measures mercury content and modifies, in response to the measured mercury content, an injection rate of injecting the activated carbon into the flue gas, an amount of the additive added to the coal, or a combination thereof. 
     
     
         9 . The method of  claim 1 , wherein the additive is added to the coal at the coal-combustion facility between a coal pulverizer and the combustion chamber. 
     
     
         10 . The method of  claim 1 , wherein the additive is added to the coal at the coal-combustion facility in a pulverizer. 
     
     
         11 . The method of  claim 1 , wherein the additive is added to the coal before the coal enters a pulverizer. 
     
     
         12 . A method of treating coal for combustion in a combustion chamber at a coal-combustion facility comprising a sorbent injection system for injecting activated carbon into a flue gas formed by the combustion, the method comprising:
 adding an additive to the coal, wherein the adding of the additive to the coal is performed at the coal-combustion facility before the coal enters the combustion chamber, and the additive comprises Br2, a bromide compound, HBr, or a combination thereof.   
     
     
         13 . The method of  claim 12 , wherein a weight ratio of the Br2, bromide compound, HBr, or combination thereof in the additive added to the coal to an amount of the activated carbon injected into the flue gas is from about 1:100 to about 30:100. 
     
     
         14 . The method of  claim 12 , wherein the additive comprises the Br2. 
     
     
         15 . The method of  claim 12 , wherein the additive comprises the bromide compound, HBr, or combination thereof. 
     
     
         16 . The method of  claim 12 , wherein the additive comprises the bromide compound. 
     
     
         17 . The method of  claim 12 , wherein the coal-combustion facility comprises a system that measures mercury content and modifies, in response to the measured mercury content, an injection rate of injecting the activated carbon into the flue gas, an amount of the additive added to the coal, or a combination thereof. 
     
     
         18 . The method of  claim 12 , wherein the additive is added to the coal at the coal-combustion facility between a coal pulverizer and the combustion chamber. 
     
     
         19 . The method of  claim 12 , wherein the additive is added to the coal at the coal-combustion facility in a pulverizer. 
     
     
         20 . The method of  claim 12 , wherein the additive is added to the coal before the coal enters a pulverizer. 
     
     
         21 . A method of treating coal, the method comprising:
 adding an additive to the coal, the additive comprising Br2, I2, a bromide compound, an iodide compound, HBr, HI, or a combination thereof;   wherein the adding of the additive to the coal is performed before the coal enters a combustion chamber at a coal-combustion facility comprising a sorbent injection system that injects activated carbon into a flue gas formed by the combustion, and the adding of the additive to the coal is sufficient such that a weight ratio of the Br2, I2, bromide compound, iodide compound, HBr, HI, or combination thereof in the additive added to the coal to an amount of the activated carbon injected into the flue gas is from about 1:100 to about 30:100.   
     
     
         22 . A method of treating coal, the method comprising:
 adding an additive to the coal, wherein the additive comprises Br2, a bromide compound, HBr, or a combination thereof;   wherein the adding of the additive to the coal is performed before the coal enters a combustion chamber at a coal-combustion facility, the coal-combustion facility comprising a flue gas activated carbon injection system.   
     
     
         23 . The method of  claim 22 , wherein a weight ratio of the Br2, bromide compound, HBr, or combination thereof in the additive added to the coal to an amount of the activated carbon injected into flue gas formed by combustion of the coal in the combustion chamber is from about 1:100 to about 30:100.