Recuperative combustion system

Abstract

The methods and systems described herein relate to a recuperative combustion system that recuperates energy from fuel combustion that would otherwise be lost. The recuperative combustion system minimizes or eliminates the need for an air separator unit through the use of a clean water splitter section, consisting of a thermochemical cycle or high-temperature electrolysis. Water is split into its component hydrogen and oxygen, primarily with process heat from the combustion process. The oxygen produced by the water splitter provides oxygen necessary for oxy-fuel combustion, thereby reducing or eliminating the need for the power intensive air separator unit and/or external oxygen source, significantly increasing the efficiency of the oxy-fuel combustion cycle. Hydrogen produced by the water splitter may be used for a variety of industrial uses, or combined with carbon dioxide (captured from the flue gases produced by said combustion process) to produce methanol. Methanol can further be refined in a methanol to gasoline reactor to produce dimethyl ether, olefins or high grade gasoline. Described herein are methods and systems that 1) increase oxy-fuel combustion efficiency, 2) produce hydrogen for a suite of industrial/energy uses, and 3) capture carbon dioxide and convert it to high value hydrocarbons.

1 . A method for oxy-fuel combustion, comprising:
 providing a system comprising a combustion chamber arranged and disposed to receive fuel, oxygen and recycled flue gas and combust said fuel, oxygen and recycled flue gas to produce heat and heated flue gas;   capturing heat produced by the oxy-fuel combustion;   using a portion of the heat to power a water splitter, thereby generating hydrogen gas and oxygen gas; and   transferring the oxygen gas from the water splitter to the combustion chamber for use in said oxy-fuel combustion.   
     
     
         2 . The method of  claim 1 , further comprising providing an air separator unit, or another external oxygen supply, wherein the combustion chamber is arranged and disposed to receive oxygen from the air separator unit and/or external oxygen supply and/or the water splitter. 
     
     
         3 . The method of  claim 1 , further comprising one or more heat exchangers for the capture and transfer of heat from the heated flue gas to the water splitter. 
     
     
         4 - 5 . (canceled) 
     
     
         6 . The method of  claim 1 , wherein the amount of oxygen required from the air separator unit and/or external oxygen supply, is reduced or eliminated in proportion to the amount of oxygen provided by the water splitter. 
     
     
         7 . (canceled) 
     
     
         8 . The method of  claim 1 , wherein the oxy-fuel comprises any hydrocarbon-based fuel. 
     
     
         9 . The method of  claim 8 , wherein the oxy-fuel comprises a coal/water slurry. 
     
     
         10 . (canceled) 
     
     
         11 . The method of  claim 1 , wherein the water splitter produces hydrogen gas and oxygen gas by means of high-temperature electrolysis. 
     
     
         12 . The method of  claim 1 , wherein the water splitter produces hydrogen gas and oxygen gas by means of a thermochemical cycle. 
     
     
         13 . The method of  claim 12 , wherein the thermochemical cycle is selected from: a hybrid copper-chlorine cycle; a sulfur-iodine cycle; and a hybrid sulfur cycle. 
     
     
         14 - 15 . (canceled) 
     
     
         16 . The method of  claim 13 , wherein the thermochemical cycle is a hybrid copper-chlorine cycle. 
     
     
         17 . The method of  claim 16 , wherein the hybrid copper-chlorine cycle is selected from: a 3-step cycle, a 4-step cycle, and a 5-step cycle. 
     
     
         18 . The method of  claim 17 , wherein the hybrid copper-chlorine cycle is the 4-step cycle. 
     
     
         19 . The method of  claim 18 , wherein the 4-step cycle of the hybrid copper chlorine cycle may be represented by the following steps:
 Step I: Cu(s)+2HCl(g)→2CuCl(molten)+H 2 (g)   Step II: 4CuCl(s)→2Cu(s)+2CuCl 2 (aq)+HCl(aq)   Step III: CuCl 2 (aq)+n f H 2 O(l)→CuOCuCl 2 (s)+2HCl(g)+(n f −1)H 2 O(g)   Step IV: CuOCuCl 2 (s)→2CuCl(molten)+0.50 2 (g)   
     
     
         20 . (canceled) 
     
     
         21 . The method of  claim 19 , wherein n f  is 5-30. 
     
     
         22 . (canceled) 
     
     
         23 . The method of  claim 1 , wherein the hydrogen from the water splitter is used directly or indirectly in a subsequent process. 
     
     
         24 . (canceled) 
     
     
         25 . The method of  claim 1 , wherein the hydrogen from the water splitter and the carbon dioxide from the combustion flue gas are reacted to form methanol and water. 
     
     
         26 - 29 . (canceled) 
     
     
         30 . The method of  claim 1 , wherein the amount of oxygen that the combustion chamber requires from an air separator unit and/or external oxygen supply, is reduced or eliminated in proportion to the amount of oxygen received from the water splitter, resulting in increased efficiency. 
     
     
         31 . The method of  claim 30 , wherein the increased efficiency is measured in terms of increased gross power output of the combustion process. 
     
     
         32 . The method of  claim 31 , wherein the gross power output of the combustion process is increased by 1-20%. 
     
     
         33 - 35 . (canceled) 
     
     
         36 . An oxy-fuel combustion system, comprising:
 a combustion chamber arranged and disposed to receive fuel, oxygen and recycled flue gas and combust said fuel, oxygen and recycled flue gas to produce heat and heated flue gas containing carbon dioxide;   one or more heat exchangers arranged and disposed to capture heat produced by the oxy-fuel combustion and transfer said heat to a water splitter; and   a water splitter, for the conversion of heat and electricity into hydrogen gas and oxygen gas.   
     
     
         37 . The system of  claim 36 , further comprising an air separator unit, or another external oxygen supply, wherein the combustion chamber is arranged and disposed to receive oxygen from the air separator unit, or external oxygen supply, and/or the water splitter. 
     
     
         38 . The system of  claim 36 , wherein one or more heat exchangers serve as the means to capture the heat produced by the oxy-fuel combustion and to transfer said heat to the water splitter. 
     
     
         39 - 62 . (canceled)