System and Method for Improved Heat Recovery from Flue Gases with High SO3 Concentrations

Abstract

Disclosed is a power generation system for high sulfur fuel combustion and a method of generating power from high sulfur fuel. The system includes a boiler for combusting a sulfur containing fuel to form a sulfur containing flue gas, a heat exchanger arranged and disposed to transfer heat from the sulfur containing flue gas to combustion air, a sorbent injector arranged and disposed to inject sorbent into the sulfur containing flue gas, and a second stage heat recovery mechanism arranged and disposed to transfer heat from the sulfur containing flue gas.

1 . A power generation system for high sulfur fuel combustion, the system comprising:
 a boiler for combusting a sulfur containing fuel to form a sulfur containing flue gas;   a heat exchanger arranged and disposed to transfer heat from the sulfur containing flue gas to combustion air;   a sorbent injector arranged and disposed to inject sorbent into the sulfur containing flue gas;   a second stage heat recovery mechanism arranged and disposed to transfer heat from the sulfur containing flue gas;   wherein the heat exchanger maintains a temperature of the sulfur containing flue gas above a predetermined temperature, the predetermined temperature relating to the acid condensation temperature, and   wherein the sorbent reduces concentration of sulfur in the sulfur containing flue gas, thereby reducing the acid condensation temperature of the sulfur containing flue gas.   
     
     
         2 . The system of  claim 1 , wherein the second stage heat recovery mechanism is arranged and disposed to transfer heat from the sulfur containing flue gas to air directed to the heat exchanger. 
     
     
         3 . The system of  claim 1 , wherein the predetermined temperature is a sulfuric acid dew point in the sulfur containing flue gas. 
     
     
         4 . The system of  claim 1 , wherein the predetermined temperature corresponds to a sulfuric acid dew point. 
     
     
         5 . The system of  claim 1 , wherein the predetermined temperature is correlated to a sulfuric acid dew point. 
     
     
         6 . The system of  claim 1 , wherein the predetermined temperature is correlated to a sulfuric acid dew point based upon a Kiang correlation. 
     
     
         7 . The system of  claim 1 , further comprising a selective catalytic reduction unit arranged and disposed to receive the sulfur containing flue gas from the boiler and to apply a reductant to the sulfur containing flue gas. 
     
     
         8 . The system of  claim 5 , further comprising an additional sorbent injection location positioned between the selective catalytic reduction unit and the heat exchanger. 
     
     
         9 . The system of  claim 6 , wherein the additional sorbent injection location applies a second sorbent, the second sorbent being configured for reducing fouling. 
     
     
         10 . The system of  claim 1 , further comprising a particulate removal mechanism arranged and disposed to remove particulate from the sulfur containing flue gas. 
     
     
         11 . The system of  claim 1 , further comprising a flue gas desulfurization unit arranged and disposed to apply oxidation air and reagent to the sulfur containing flue gas to remove SO2 and form a waste product, and to release the waste product. 
     
     
         12 . The system of  claim 1 , wherein the heat exchanger is configured to operate in the presence of particulate. 
     
     
         13 . The system of  claim 1 , wherein the sorbent is selected from the group consisting of limestone, lime, trona, sodium bisulfate, magnesium hydroxide, and combinations thereof. 
     
     
         14 . The system of  claim 1 , wherein the application of the sorbent results in the sulfur containing flue gas having a SO3 concentration of less than about 50 ppm volume. 
     
     
         15 . The system of  claim 1 , wherein the application of the sorbent lowers SO3 concentration in the sulfur containing flue gas by at least 80%. 
     
     
         16 . A power generation system for high sulfur fuel combustion, the system comprising:
 a boiler for combusting a sulfur containing fuel to form a sulfur containing flue gas;   a heat exchanger arranged and disposed to transfer heat from the sulfur containing flue gas to combustion air;   a sorbent injector arranged and disposed to inject sorbent into the sulfur containing flue gas; and   a second stage heat recovery mechanism arranged and disposed to transfer heat from the sulfur containing flue gas to air directed to the heat exchanger;   wherein the heat exchanger maintains a temperature of the flue gas above a predetermined temperature, the predetermined temperature relating to the acid condensation temperature,   wherein the predetermined temperature corresponds to a sulfuric acid dew point or is based upon a correlation,   wherein the sorbent is selected from the group consisting of limestone, lime, trona, sodium bisulfate, magnesium hydroxide, and combinations thereof,   wherein the application of the sorbent results in the sulfur containing flue gas having a SO3 concentration of less than about 50 ppm volume, and   wherein the application of the sorbent lowers SO3 concentration in the sulfur containing flue gas by at least 80%.   
     
     
         17 . A method of generating power, the method comprising:
 combusting a sulfur containing fuel to form a sulfur containing flue gas;   in a heat exchanger, transferring heat from the sulfur containing flue gas to combustion air;   maintaining a temperature of the sulfur containing flue gas leaving the heat exchanger above a predetermined temperature, the predetermined temperature relating to the acid condensation temperature;   injecting sorbent into the sulfur containing flue gas, wherein the sorbent reduces concentration of sulfur in the sulfur containing flue gas, thereby reducing the acid condensation temperature of the sulfur containing flue gas; and   transferring heat from the sulfur containing flue gas in a second stage heat recovery mechanism.   
     
     
         18 . The method of  claim 17 , further comprising directing the air in the second stage heat recovery mechanism to the heat exchanger. 
     
     
         19 . The method of  claim 17 , further comprising reducing fouling by applying an additional sorbent. 
     
     
         20 . The method of  claim 17 , wherein the predetermined temperature corresponds to a sulfuric acid dew point.