Nox hg and so2 removal using ammonia

Abstract

A process and apparatus for removing SO?2#191, NO, and NO?2#191 from a gas stream having the steps of oxidizing ( 60 ) a portion of the NO in the flue gas stream to NO?2#191, scrubbing ( 62 ) the SO?2#191, NO, and NO?2#191 with an ammonia scrubbing solution, and removing ( 64 ) any ammonia aerosols generated by the scrubbing in a wet electrostatic precipitator. The process can also remove Hg by oxidizing it to HgO and removing it in the wet electrostatic precipitator. Ammonium sulfate, a valuable fertilizer, can be withdrawn from the scrubbing solution.

1 . A process for removing SO 2 , NO, and NO 2  from a gas stream comprising the steps of 
 a. oxidizing at least a portion of NO in a gas stream to NO 2  with an oxidizing means resulting in a mole ratio of SO 2  to NO 2  of between 2.5 to 1 and 4 to 1, followed by    b. scrubbing at least a portion of SO 2 , NO, and NO 2  from the gas stream with a scrubbing solution 
 comprising ammonia, and  
 having a pH between 6 and 8, and  
   c. removing at least a portion of any ammonia aerosols generated from the scrubbing step from the gas stream with an aerosol removal means.    
     
     
         2 . The process of  claim 1 , wherein said oxidizing means is an electrical discharge reactor.  
     
     
         3 . The process of  claim 2 , wherein said electrical discharge reactor is a dielectric barrier discharge reactor.  
     
     
         4 . The process of  claim 3 , further comprising the step of oxidizing at least a portion of the NO to HNO 3  with said dielectric barrier discharge reactor.  
     
     
         5 . The process of  claim 1 , wherein said oxidizing means comprises injecting ethylene or propylene.  
     
     
         6 . The process of  claim 1 , wherein said oxidizing step is adapted to result in a mole ratio of SO 2  to NO 2  of at least four to one.  
     
     
         7 . The process of  claim 1 , said scrubbing solution 
 comprising ammonia, ammonium sulfite, ammonium sulfate, and water, and    having a pH between 6 and 8.    
     
     
         8 . The process of  claim 1 , wherein said aerosol removal means is a wet electrostatic precipitator.  
     
     
         9 . The process of  claim 1 , wherein said scrubbing step results in the formation of ammonium sulfate, the process further comprising the step of withdrawing ammonium sulfate from the scrubbing solution.  
     
     
         10 . The process of  claim 4 , wherein said scrubbing step results in the formation of ammonium nitrate, the process further comprising the step of withdrawing ammonium nitrate from the scrubbing solution.  
     
     
         11 . A process for removing SO 2 , NO, NO 2 , and Hg from a gas stream comprising the steps of 
 a. oxidizing at least a portion of the NO in a gas stream to NO 2 , and at least a portion of the Hg in a gas stream to HgO, with an oxidizing means resulting in a mole ratio of SO 2  to NO 2  of between 2.5 to 1 and 4 to 1, followed by    b. scrubbing at least a portion of the SO 2 , NO, and NO 2  from the gas stream with a scrubbing solution 
 comprising ammonia, and  
 having a pH between 6 and 8, and  
   c. removing at least a portion of any ammonia aerosols generated from the scrubbing step, and HgO, from the gas stream with an aerosol removal means.    
     
     
         12 . The process of  claim 11 , wherein said oxidizing means comprising a dielectric discharge reactor.  
     
     
         13 . The process of  claim 11 , wherein said oxidizing means comprising injecting ethylene or propylene.  
     
     
         14 . The process of  claim 11 , wherein said aerosol removal means is a wet electrostatic precipitator.  
     
     
         15 . The process of  claim 11 , said scrubbing solution comprising ammonia, ammonium sulfite, ammonium sulfate, and water, and having a pH between 6 and 8.  
     
     
         16 . The process of  claim 15 , wherein said scrubbing step results in the formation of ammonium sulfate, the process further comprising the step of withdrawing ammonium sulfate from the scrubbing solution.  
     
     
         17 . An apparatus for removing SO 2 , NO, and NO 2  from a gas stream comprising 
 a. an oxidizing means for oxidizing at least a portion of the NO in a gas stream to NO 2 , followed by    b. a scrubber suitably adapted to scrub at least a portion of the SO 2 , NO, and NO 2  from the gas stream with a scrubbing solution 
 comprising ammonia, and  
 having a pH between 6 and 8, and  
   c. an aerosol removal means for removing at least a portion of any ammonia aerosols generated by the scrubber from the gas stream.    
     
     
         18 . The apparatus of  claim 17 , wherein said oxidizing means is at least one electrical discharge reactor.  
     
     
         19 . The apparatus of  claim 18 , wherein said electrical discharge reactor is at least one dielectric barrier discharge reactor.  
     
     
         20 . The apparatus of  claim 19 , wherein said dielectric barrier discharge reactor is adapted to oxidize at least a portion of the NO to NO 2  and HNO 3 .  
     
     
         21 . The apparatus of  claim 17 , said scrubbing solution  
       comprising ammonia, ammonium sulfite, ammonium sulfate, and water, and having a pH between 6 and 8.  
     
     
         22 . The apparatus of  claim 17 , wherein said aerosol removal means is at least one wet electrostatic precipitator.  
     
     
         23 . An apparatus for removing SO 2 , NO, NO 2 , and Hg from a gas stream comprising 
 a. an oxidizing means for oxidizing at least a portion of the NO in a gas stream to NO 2 , and at least a portion of the Hg in a gas stream to HgO, followed by    b. a scrubber suitably adapted to scrub at least a portion of the SO 2 , NO, and NO 2  from the gas stream with a scrubbing solution 
 comprising ammonia, and  
 having a pH between 6 and 8, and  
   c. an aerosol removal means for removing at least a portion of any ammonia aerosols generated by the scrubber, and HgO, from the gas stream.    
     
     
         24 . An apparatus for removing SO 2 , NO, and NO 2  from a gas stream comprising 
 a. an NO oxidizer adapted to oxidize at least a portion of the NO in a gas stream to NO 2 , followed by    b. a scrubber adapted to scrub at least a portion of the SO 2 , NO, and NO 2  from the gas stream with a scrubbing solution 
 comprising ammonia, and  
 having a pH between 6 and 8, and  
   c. an aerosol remover adapted to remove at least a portion of any ammonia aerosols generated by the scrubber from the gas stream.    
     
     
         25 . The apparatus of  claim 24 , wherein said NO oxidizer is at least one electrical discharge reactor.  
     
     
         26 . The apparatus of  claim 25 , wherein said electrical discharge reactor is at least one dielectric barrier discharge reactor.  
     
     
         27 . The apparatus of  claim 26 , wherein said dielectric barrier discharge reactor is adapted to oxidize at least a portion of the NO to NO 2  and HNO 3 .  
     
     
         28 . The apparatus of  claim 24 , said scrubbing solution comprising ammonia, ammonium sulfite, ammonium sulfate, and water, and having a pH between 6 and 8.  
     
     
         29 . The apparatus of  claim 24 , wherein said aerosol remover is at least one wet electrostatic precipitator.