Staged-coal injection for boiler reliability and emissions reduction

Abstract

A staged-coal injection procedure for coal-fired boilers used in power generation. The procedure includes the steps of combusting a first type of coal in a first zone of a furnace; and combusting a second type of coal in a second zone of the furnace. The second zone is at a position separate from the first zone.

1 . A coal combustion method, comprising the steps of:
 (a) combusting a first type of coal in a first zone of a furnace; and   (b) combusting a second type of coal in a second zone of the furnace, the second zone being at a position separate from the first zone.   
   
   
       2 . The coal combustion method according to  claim 1 , wherein the first type of coal has a substantially higher alkali content than the second type of coal. 
   
   
       3 . The coal combustion method according to  claim 1 , wherein the second type of coal has a substantially higher chlorine content than the first type of coal. 
   
   
       4 . The coal combustion method according to  claim 1 , and further including the steps of feeding the first type of coal to fed to a first burner for combustion in the first zone of the furnace and feeding the second type of coal to a second burner for combustion in the second zone of the furnace. 
   
   
       5 . The coal combustion method according to  claim 4 , wherein the first burner is adapted to combust the first type of coal and the second burner is adapted to combust the second type of coal. 
   
   
       6 . A coal combustion method, comprising the steps of:
 (a) providing a first type of coal including a selected first compound;   (b) providing a second type of coal including a selected second compound;   (c) combusting the first type of coal in a first zone of a furnace;   (d) combusting the second type of coal in a second zone of the furnace; and   (e) positioning the first and second zones in relation to each other so as to substantially prevent the first compound from combining with the second compound during combustion of the first and second types of coal.   
   
   
       7 . The coal combustion method according to  claim 6 , wherein the first compound is an alkali compound and the second compound is a chloride compound. 
   
   
       8 . The coal combustion method according to  claim 6 , and further including the steps of feeding the first type of coal to a first burner for combustion in the first zone and feeding the second type of coal to a second burner for combustion in the second zone. 
   
   
       9 . The coal combustion method according to  claim 8 , and further including the step of providing combustion air to the first burner and second burner. 
   
   
       10 . The coal combustion method according to  claim 9 , wherein the amount of combustion air provided to the first burner is less than the amount of air provided to the second burner. 
   
   
       11 . The coal combustion method according to  claim 6 , and further including the step of providing overfire air in a third zone of the furnace to aid in complete combustion of the first type of coal and second type of coal. 
   
   
       12 . A coal combustion method, comprising the steps of:
 (a) providing a boiler having:
 (i) a furnace section; 
 (ii) a first burner positioned in a first zone of the furnace section; and 
 (iii) a second burner positioned in a second zone of the furnace section; 
   (a) feeding a first type of coal including a selected first compound to the first burner;   (b) combusting the first type of coal in a first zone of the furnace section; (c) feeding a second type of coal to the second burner;   (d) combusting the second type of coal in a second zone of the furnace section; and   (e) wherein the first compound is consumed in the first zone so as to be substantially unavailable for reaction in the second zone.   
   
   
       13 . The coal combustion method according to  claim 12 , wherein the first type of coal is a Powder River Basin coal. 
   
   
       14 . The coal combustion method according to  claim 12 , wherein the first compound is an alkali compound. 
   
   
       15 . The coal combustion method according to  claim 12 , wherein the second type of coal is an eastern bituminous coal. 
   
   
       16 . The coal combustion method according to  claim 12 , wherein the second compound is a chloride compound. 
   
   
       17 . The coal combustion method according to  claim 12 , and further including the step of feeding the first type of coal from a first storage hopper to a first pulverizer where the first type of coal is pulverized. 
   
   
       18 . The coal combustion method according to  claim 12 , and further including the step of feeding the second type of coal from a second storage hopper to a second pulverizer where the second type of coal is pulverized. 
   
   
       19 . The coal combustion method according to  claim 12 , and further including the step of providing a combustion air to the first burner, second burner, and an overfire port. 
   
   
       20 . The coal combustion method according to  claim 19 , wherein the amount of combustion air provided to the first burner is less than the amount of air provided to the second burner. 
   
   
       21 . The coal combustion method according to  claim 19 , wherein the overfire port is adapted to introduce combustion air into a third zone of the furnace to aid in complete combustion of the first and second types of coal.