Patent EA-002327-B1 (EA)
Title: Process for producing highly reactive lime in a furnace
Inventor: LAVELY LLOYD L JR
IPC: C01F11/04
Filed: 1998-07-21
Abstract: 1. A process for producing highly reactive lime in a furnace and removing sulfur dioxide from the flue gas of a furnace, the furnace being of a type in which the flue gas including sulfur dioxide is produced from the combustion of sulfur-containing fuels; said process comprising injecting finely divided particles of limestone into said furnace at a location at which the temperature of said flue gas passing therethrough exceeds the minimum calcination temperature and is below the minimum effective quicklime utilization/sulfation temperature. 2. The process of claim 1 wherein the injecting step comprises injecting limestone particles having a maximum particle size between of approximately 1 to 100 microns in diameter into said furnace. 3. The process of claim 1 wherein the injecting step comprises injecting limestone particles having a maximum particle size of approximately 10 microns in diameter into said furnace. 4. The process of claim 3 wherein the injecting step comprises injecting finely divided particles of limestone into said furnace at a location at which the temperature of said flue gas passing therethrough exceeds 1365 degree F (740,5 degree C) and below 1800 degree F (982,2 degree C) for at least approximately 100 milliseconds after said limestone particles are injected. 5. The process of claim 3 wherein the injecting step comprises injecting finely divided particles of limestone into said furnace at a location at which the temperature of said flue gas passing therethrough exceeds 1365 degree F (740,5 degree C) and below 1800 degree F (982,2 degree C) for at least approximately 100 and 600 milliseconds after said limestone particles are injected. 6. The process of claim 1 wherein the injecting step comprises injecting finely divided particles of limestone into said furnace at a location at which the temperature of said flue gas passing therethrough exceeds 1365 degree F (740,5 degree C) and below 1600 degree F (871,1 degree C). 7. A process for positioning nozzles in a furnace for injecting limestone in producing a highly reactive lime for use in downstream flue gas desulfurization processes, the furnace being of a type in which flue gas including sulfur dioxide is produced from the combustion of sulfur-containing fuels, said process comprising the steps of: (a) identifying a first set of operating conditions of said furnace including the concentration of sulfur dioxide, carbon dioxide and water vapor in the flue gas; (b) identifying a first minimum calcination temperature and a first minimum effective quicklime utilization/sulfation temperature for available limestone under said first set of operating conditions of said furnace; (c) identifying a first location within said furnace wherein the temperature of said flue gas passing therethrough approximately equals said first minimum effective quicklime utilization/sulfation temperature; (d) identifying a second location within said furnace wherein the temperature of said flue gas passing therethrough is approximately equal to said first minimum calcination temperature; and (e) positioning said first nozzle through which finely divided particles of said available limestone may be injected into said furnace relative to said first location such that when said furnace is operated under said first set of conditions infection of limestone through said first nozzle results in the calcination of a substantial portion of said limestone to lime while limiting quicklime sulfation of said lime in said furnace. 8 The process of claim 7 wherein positioning said first nozzle such that limestone injected therethrough does not significantly impinge upon or erode any heat exchangers extending into said furnace. 9. The process of claim 7 wherein positioning said first nozzle such that after said flue gas passes said second location, said flue gas is rapidly cooled to a temperature below a minimum hydrated lime sulfation temperature. 10 The process of claim 7 wherein the step of positioning said first nozzle comprises positioning said first nozzle such that the temperature of said flue gas is maintained above the minimum calcination temperature for at least approximately 100 milliseconds after said limestone particles are injected through said first nozzle. 11. The process of claim 7 wherein the step of positioning said first nozzle comprises positioning said first nozzle such that the temperature of said flue gas is maintained above the minimum calcination temperature for approximately 100 to 600 milliseconds after said limestone particles are injected through said first nozzle. 12. The process of claim 7 further including the steps of: (a) identifying a second set of operating conditions of said furnace including the concentration of sulfur dioxide, carbon dioxide and water vapor in the flue gas; (b) identifying a second minimum calcination temperature and a second minimum effective quicklime utilization/sulfation temperature for available limestone under said second set of operating conditions of said furnace; (c) identifying a third location within said furnace wherein the temperature of said flue gas passing therethrough approximately equals said second minimum effective quicklime utilization/sulfation temperature; (d) identifying a fourth location within said furnace wherein the temperature of said flue gas passing therethrough is approximately equal to said second minimum calcination temperature; and (e) positioning said second nozzle through which finely divided particles of said available limestone may be injected into said furnace nozzle relative to said third location such that when said furnace is operated under said second set of conditions, infection of limestone through said second nozzle results in the calcination of a substantial portion of said limestone to lime while limiting quicklime sulfation of said lime in said furnace, and (f) providing means for selectively injecting said limestone through said first nozzle when said furnace operating conditions approach said first set of conditions and through said second nozzle when said furnace operating conditions approach said second set of conditions. 13. A process for producing a highly reactive lime in a furnace for use in downstream flue gas desulfurization processes, said furnace being of a type in which flue gas including sulfur dioxide is produced from the combustion of sulfur-containing fuels, said process comprising the steps of: (a) identifying a first set of operating conditions of said furnace including the concentration of sulfur dioxide, carbon dioxide and water vapor in the flue gas; (b) identifying a first minimum calcination temperature and a first minimum effective quicklime utilization/sulfation temperature for available limestone under said first set of operating conditions of said furnace; (c) identifying a first location within said furnace wherein the temperature of said flue gas passing therethrough approximately equals said first minimum effective quicklime utilization/sulfation temperature; (d) identifying a second location within said furnace wherein the temperature of said flue gas passing therethrough is approximately equal to said first minimum calcination temperature; (e) providing a first array of nozzles through which finely divided particles of said available limestone may be injected into said furnace and positioning said first array of nozzles relative to said first location such that  (i) when said furnace is operated under said first set of conditions, injection of limestone through said first array of nozzles results in the calcination of a substantial portion of said limestone to lime while limiting quicklime sulfation of said lime in said furnace; and  (ii) limestone injected through said first array of nozzles does not significantly impinge upon or erode any heat exchangers extending into said furnace; (f) identifying a second set of operating conditions of said furnace including the concentration of sulfur dioxide, carbon dioxide and water vapor in the flue gas; (g) identifying a second minimum calcination temperature and a second minimum effective quicklime utilization/sulfation temperature for available limestone under said second set of operating conditions of said furnace; (h) identifying a third location within said furnace wherein the temperature of said flue gas passing therethrough approximately equals said second minimum effective quicklime utilization/sulfation temperature; (i) identifying a fourth location within said furnace wherein the temperature of said flue gas passing therethrough is approximately equal to said second minimum calcination temperature; and (j) providing a second array of nozzles through which finely divided particles of said available limestone may be injected into said furnace and positioning said second array of nozzles relative to said third location such that (i) when said furnace is operated under said second set of conditions, injection of limestone through said second array of nozzles results in the calcination of a substantial portion of said limestone to lime while limiting quicklime sulfation of said lime in said furnace; and (ii) limestone injected through said second array of nozzles does not significantly impinge upon or erode any heat exchangers extending into said furnace; and (k) selectively injecting said limestone through said first nozzle when said furnace operating conditions approach said first set of conditions and through said second nozzle when said furnace operating conditions approach said second set of conditions. 14. A process for removing sulfur dioxide from the flue gas of a furnace, the furnace being of a type in which the flue gas including sulfur dioxide is produced from the combustion of sulfur-containing fuels, said process comprising the steps of: (a) injecting finely divided particles of limestone into said furnace directly into the flue gas in close proximity to a location at which the temperatu