APPLYING OZONE NOx CONTROL TO AN HRSG FOR A FOSSIL FUEL TURBINE APPLICATION

Abstract

A method for reducing NOx and recovering waste heat from a stream of exhaust gas from a fossil fuel fired turbine includes contacting the stream of exhaust gas between an economizer and an evaporator with ozone gas to convert the NO to nitrogen dioxide (NO 2 ) thereby forming a stream of exhaust gas comprising NO 2 and residual NO. The method further includes, contacting the stream of exhaust gas comprising NO 2 and residual NO with water mist to create an exhaust stream comprising nitric acid (HNO 3 ) and residual NO. The method further includes cooling the stream of exhaust gas comprising HNO 3 and residual NO, collecting a first residual water film on a first condensing medium to capture the HNO 3 and removing the first water film and HNO 3 .

What is claimed is: 
     
         1 . A system for reducing NOx and recovering waste heat from a stream of exhaust gas from a fossil fuel fired turbine, the system comprising:
 a superheater configured to recover heat from the stream of exhaust gas;   an evaporator configured to recover heat from the stream of exhaust gas, wherein the evaporator is located downstream from the superheater;   an economizer configured to recover heat from the stream of exhaust gas, wherein the economizer is located downstream from the evaporator;   an ozone aspirator, located between the evaporator and economizer, wherein the ozone aspirator is configured to receive the stream of exhaust gas comprising nitric oxide (NO) from the evaporator and contact the stream of exhaust gas comprising NO with ozone to convert the NO to nitrogen dioxide (NO 2 ) thereby forming a stream of exhaust gas comprising NO 2  and residual NO;   a heat reclaim coil configured to capture heat from the stream of exhaust gas comprising NO 2  and residual NO to produce hot water;   a first misting stage configured to receive the stream of exhaust gas comprising NO 2  and residual NO and contact the stream of exhaust gas comprising NO 2  and residual NO with water mist to create an exhaust stream comprising nitric acid (HNO 3 ) and residual NO; and   a first condensing medium configured to cool the stream of exhaust gas comprising HNO 3  and residual NO and to collect a first residual water film thereon to capture the HNO 3 , thereby creating an exhaust stream comprising residual HNO 3  and residual NO.   
     
     
         2 . The system of  claim 1 , further comprising:
 a second misting stage configured to receive the exhaust stream comprising residual HNO 3  and residual NO and contact the exhaust stream comprising residual HNO 3  and residual NO with water mist to further create residual exhaust stream comprising HNO 3 ; and   a second condensing medium configured to cool the residual exhaust stream comprising HNO 3  and collect a second residual water film thereon to capture the HNO 3 , thereby creating a saturated exhaust stream.   
     
     
         3 . The system of  claim 2 , further comprising:
 a reheat coil configured to reheat the saturated exhaust stream to remove moisture from the saturated exhaust stream thereby creating a clean exhaust stream wherein the NOx and water has been removed.   
     
     
         4 . The system of  claim 3  further comprising a fan configured to direct the clean exhaust gas stream out of the system. 
     
     
         5 . The system of  claim 3  further comprising a wastewater facility configured to receive a water film comprising the first and second water films. 
     
     
         6 . The system of  claim 3  further comprising an exhaust stack configured to receive the clean exhaust gas stream. 
     
     
         7 . The system of  claim 1 , wherein the first condensing medium comprises a coating of one selected from a group consisting of Teflon and critical polyvinal chloride (CPVC). 
     
     
         8 . The system of  claim 2 , wherein the second condensing medium comprises a coating of one selected from a group consisting of Teflon and critical polyvinal chloride (CPVC). 
     
     
         9 . The system of  claim 1 , wherein the ozone aspirator is further configured to contact the stream of exhaust gas with a mixture of ozone and hydrogen peroxide. 
     
     
         10 . A method for reducing NOx and recovering waste heat from a stream of exhaust gas from a fossil fuel fired turbine, the method comprising:
 recovering heat from the stream of exhaust gas by passing the stream of exhaust gas through a superheater, an evaporator located downstream from the superheater, and an economizer located downstream from the evaporator;   contacting the stream of exhaust gas between the economizer and the evaporator with ozone gas to convert the NO to nitrogen dioxide (NO 2 ) thereby forming a stream of exhaust gas comprising NO 2  and residual NO;   recovering heat from the stream of exhaust gas comprising NO 2  and residual NO to produce hot water;   contacting the stream of exhaust gas comprising NO 2  and residual NO with water mist to create an exhaust stream comprising nitric acid (HNO 3 ) and residual NO;   cooling the stream of exhaust gas comprising HNO 3  and residual NO;   collecting a first residual water film on a first condensing medium to capture the HNO 3 , thereby creating an exhaust stream comprising residual HNO 3  and residual NO; and   removing the first water film and HNO 3 .   
     
     
         11 . The method of  claim 10  further comprising:
 further contacting the stream of exhaust gas comprising residual HNO 3  and residual NO with water mist thereby creating an exhaust stream comprising HNO 3 ; 
 cooling the stream of exhaust gas comprising HNO 3 ; 
 collecting a second residual water film on a second condensing medium to capture the HNO 3 , thereby creating a saturated exhaust stream comprising HNO 3 ; and 
 removing the second water film and HNO 3 ; and 
 reheating, the saturated exhaust stream to dry the saturated exhaust stream thereby creating a clean exhaust stream wherein the NOx and water has been removed. 
 
     
     
         12 . The method of  claim 10 , further comprising directing the hot water from a reclaim coil to a reheat coil. 
     
     
         13 . The method of  claim 12 , further comprising directing the hot water from the reheat coil to a cooling tower and directing the hot water from the cooling tower to the heat reclaim coil. 
     
     
         14 . The method of  claim 10 , further comprising directing the hot water from the reclaim coil to a heat exchanger and directing the hot water from the heat exchanger to a building process heating system. 
     
     
         15 . The method of  claim 10 , further comprising directing the hot water from a reclaim coil to a deaerator and directing the hot water from the deaerator to a low pressure economizer. 
     
     
         16 . The method of  claim 11 , further comprising directing the clean exhaust gas stream out of the system. 
     
     
         17 . The method of  claim 11 , further comprising providing a wastewater facility with wastewater comprising the first and second water films. 
     
     
         18 . The method of  claim 11 , further comprising exhausting the clean exhaust gas stream from a stack. 
     
     
         19 . The method of  claim 10 , further comprising contacting the stream of exhaust gas between the economizer and the evaporator with a mixture of ozone and hydrogen peroxide.