System for recovering water from flue gas

Abstract

A power plant may include a combustion apparatus ( 11 ) producing an exhaust gas ( 12 ), an absorber ( 20 ) receiving the exhaust gas ( 12 ), the absorber ( 20 ) including a desiccant and producing a first stream of desiccant solution containing water and a first concentration of desiccant, and an apparatus ( 29, 70, 94 ) for dehydrating the first stream of desiccant solution while maintaining the water in a liquid phase. The apparatus ( 29, 70, 94 ) may include one or more reverse osmosis apparatus ( 30, 40 ) that receive the first stream of desiccant solution and produce a second stream of desiccant solution containing a second concentration of desiccant greater than the first concentration of desiccant. The apparatus ( 29, 70, 94 ) may include a heat exchanger ( 71, 110 ), a crystallizing heat exchanger ( 74, 96 ), a separator ( 78, 98 ) and a flash tank ( 112 ) for dehydrating the desiccant solution while maintaining water in a liquid phase and subsequently recovering water from the solution.

1 ) A power plant comprising: 
 a combustion apparatus producing an exhaust gas;    an absorber receiving the exhaust gas, the absorber comprising a desiccant and producing a first stream of desiccant solution containing water and a first concentration of desiccant; and    means for dehydrating the first stream of desiccant solution while maintaining the water in a liquid phase.    
     
     
         2 ) The power plant of  claim 1 , the means for dehydrating comprising a first reverse osmosis apparatus receiving the first stream of desiccant solution and producing a second stream of desiccant solution containing water and a second concentration of desiccant greater than the first concentration of desiccant.  
     
     
         3 ) The power plant of  claim 2 , the means for dehydrating further comprising a second reverse osmosis apparatus receiving the second stream of desiccant solution and producing a third stream of desiccant solution containing water and a third concentration of desiccant greater than the second concentration of desiccant.  
     
     
         4 ) The power plant of  claim 1 , the absorber comprising a media directly contacting the desiccant with the exhaust gas.  
     
     
         5 ) The power plant of  claim 1  further comprising: 
 a main fluid connection between an outlet of the absorber and an inlet of the absorber;    a fluid connection between the main fluid connection and the means for dehydrating; and    valving for selectively regulating a flow of the first stream of desiccant solution between the means for dehydrating and the inlet of the absorber.    
     
     
         6 ) The power plant of  claim 1 , the means for dehydrating comprising a crystallizing heat exchanger receiving and cooling the first stream of desiccant solution and producing a second stream of desiccant solution comprising desiccant crystals and a second concentration of desiccant greater than the first concentration of desiccant.  
     
     
         7 ) The power plant of  claim 6  further comprising a separator receiving the second stream of desiccant solution and separating a quantity of the desiccant crystals from the second stream of desiccant solution, the separator producing a desiccant slurry containing the second concentration of desiccant.  
     
     
         8 ) The power plant of  claim 7  further comprising a heat exchanger receiving and heating the desiccant slurry to melt at least a portion of the desiccant crystals.  
     
     
         9 ) The power plant of  claim 6  further comprising: 
 a heat exchanger receiving and cooling the first stream of desiccant solution upstream of the crystallizing heat exchanger.    
     
     
         10 ) The power plant of  claim 1  further comprising a flash tank receiving a second stream of desiccant solution from the means for dehydrating.  
     
     
         11 ) The power plant of  claim 1 , the means for dehydrating comprising: 
 a heat exchanger receiving and cooling the first stream of desiccant solution from the absorber;    a desiccant sub-cooler receiving and further cooling the cooled first stream of desiccant solution and producing a second stream of desiccant solution comprising desiccant crystals; and    a separator receiving the second stream of desiccant solution and separating a quantity of the desiccant crystals from the second stream of desiccant solution, the separator producing a slurry containing desiccant crystals and dissolved desiccant in solution, and a flow of desiccant solution containing a concentration of desiccant lower than a concentration of desiccant in the slurry.    
     
     
         12 ) The power plant of  claim 11  further comprising a flash tank for receiving the flow of desiccant solution from the separator, the flash tank producing water vapor and a return stream of desiccant solution.  
     
     
         13 ) The power plant of  claim 12  further comprising a return fluid connection for directing the return stream of desiccant from the flash tank to the absorber.  
     
     
         14 ) The power plant of  claim 13  further comprising a desiccant cooler receiving the return stream of desiccant from the flash tank upstream of the absorber.  
     
     
         15 ) The power plant of  claim 13  further comprising a fluid connection for directing the slurry to the return fluid connection upstream of the absorber.  
     
     
         16 ) A power plant comprising: 
 a combustion apparatus producing an exhaust gas;    an absorber receiving the exhaust gas, the absorber comprising a desiccant and producing a first stream of desiccant solution containing water and a first concentration of desiccant; and    a reverse osmosis circuit receiving the first stream of desiccant solution and producing a stream of recovered water and a second stream of desiccant solution having a second concentration of desiccant greater than the first concentration of desiccant.    
     
     
         17 ) The power plant of  claim 16 , the reverse osmosis circuit comprising: 
 a first reverse osmosis apparatus receiving the first stream of desiccant solution and producing an intermediate stream of desiccant solution having an intermediate concentration of desiccant greater than the first concentration of desiccant; and    a second reverse osmosis apparatus downstream of the first reverse osmosis apparatus and receiving the intermediate stream of desiccant solution, the second reverse osmosis apparatus producing the second stream of desiccant solution.    
     
     
         18 ) The power plant of  claim 16  further comprising: 
 a main fluid connection between an outlet of the absorber and an inlet of the absorber;    a fluid connection between the main fluid connection and the primary osmosis apparatus; and    valving for selectively regulating a flow of the first stream of desiccant solution between the primary reverse osmosis apparatus and the inlet of the absorber.    
     
     
         19 ) A power plant comprising: 
 a combustion apparatus producing an exhaust gas;    an absorber receiving the exhaust gas, the absorber comprising a desiccant and producing a first stream of desiccant solution containing water and a first concentration of desiccant; and    a crystallization circuit receiving the first stream of desiccant solution and producing a second stream of desiccant solution having a second concentration of desiccant greater than the first concentration of desiccant.    
     
     
         20 ) The power plant of  claim 19 , the crystallization circuit comprising: 
 a recuperative heat exchanger receiving the first stream of desiccant solution;    a desiccant crystallizer downstream of the recuperative heat exchanger receiving the first stream of desiccant solution from the recuperative heat exchanger, the desiccant crystallizer producing a stream of desiccant solution comprising desiccant crystals; and    a separator downstream of the desiccant crystallizer receiving the stream of desiccant solution comprising desiccant crystals and producing the second stream of desiccant solution.    
     
     
         21 ) The power plant of  claim 20  further comprising the separator producing the second stream of desiccant solution and a stream of recovered water.  
     
     
         22 ) The power plant of  claim 21  further comprising: 
 a fluid connection directing the second stream of desiccant solution from the separator to the recuperative heat exchanger; and    a fluid connection directing the second stream of desiccant solution from the recuperative heat exchanger to the absorber.    
     
     
         23 ) The power plant of  claim 20  further comprising the separator producing a third stream of desiccant solution and the second stream of desiccant solution as a slurry containing desiccant crystals and dissolved desiccant in solution.  
     
     
         24 ) The power plant of  claim 23  further comprising a flash tank for receiving the third stream of desiccant solution from the separator, the flash tank producing water vapor and a return stream of desiccant solution.  
     
     
         25 ) The power plant of  claim 24  further comprising: 
 a condenser receiving the water vapor and producing a flow of recovered water;    a fluid connection directing the return stream of desiccant solution from the flash tank to the absorber; and    a fluid connection directing the slurry containing desiccant crystals and dissolved desiccant in solution from the separator to the absorber.    
     
     
         26 ) A system for use with a fossil fuel burning power plant producing an exhaust gas, the power plant including a water absorber receiving the exhaust gas and producing an aqueous desiccant solution containing water and a first concentration of desiccant, the system comprising: 
 means for dehydrating the aqueous desiccant solution while maintaining the water in a liquid phase, the means for dehydrating producing a second stream of desiccant solution having a second concentration of desiccant greater than the first concentration of desiccant.    
     
     
         27 ) The system of  claim 26 , the means for dehydrating comprising a reverse osmosis apparatus receiving the aqueous solution from the water absorber and producing the second stream of desiccant solution.  
     
     
         28 ) The system of  claim 26 , the means for dehydrating comprising: 
 a recuperative heat exchanger receiving the aqueous solution;    a desiccant crystallizer downstream of the recuperative heat exchanger receiving the aqueous desiccant solution from the recuperative heat exchanger, the desiccant crystallizer producing a stream of desiccant solution comprising desiccant crystals; and    a separator downstream of the desiccant crystallizer receiving the stream of desiccant solution comprising desiccant crystals and producing the second stream of desiccant solution.    
     
     
         29 ) The system of  claim 28  further comprising the separator producing a third stream of aqueous desiccant solution and the second stream of desiccant solution as a slurry containing desiccant crystals and dissolved desiccant in solution.  
     
     
         30 ) The system of  claim 29  further comprising a flash tank for receiving the third stream of desiccant solution from the separator, the flash tank producing water vapor and a return stream of desiccant solution.