Process and apparatus for high energy efficiency chemical looping combustion

Abstract

Process and apparatus are provided for a high energy efficiency chemical combustion process. The process provides two reaction steps, both of which are exothermic. First, a reduced oxygen carrier is contacted with oxygen in a reactor to form an oxidized oxygen carrier, such as metal oxide or metal suboxide, and then the oxidized oxygen carrier is fed to a second reactor and combusted with a fuel. The reaction produces the reduced oxygen carrier and carbon dioxide. The reduced oxygen carrier from the second reactor is recycled back to said first reactor. Carbon monoxide can also be produced during the process depending on stoichiometric amounts of the reactants. Though the process can be performed in various types of reactor systems, one preferred embodiment is the flash furnace with the production of fly ash during combustion. The process is highly efficient and produces a large amount of usable work.

1 . A process for chemical looping combustion comprising:
 (a) contacting a reduced oxygen carrier with oxygen to form an oxidized oxygen carrier, and   (b) contacting said oxidized oxygen carrier and a fuel to produce said reduced oxygen carrier and carbon dioxide,   wherein both steps are exothermic.   
     
     
         2 . A process for chemical looping combustion in a furnace comprising:
 (a) a first step wherein a reduced oxygen carrier is contacted with oxygen to form an oxidized oxygen carrier, and   (b) a second step wherein an ash-containing fuel is contacted with said oxidized oxygen carrier to produce a reaction product comprising said reduced oxygen carrier, carbon dioxide and fly ash,   wherein both the first step and the second step are exothermic.   
     
     
         3 . A process for chemical looping combustion comprising the steps of:
 (c) contacting at least one reduced oxygen carrier with oxygen in a first reactor to form at least one oxidized oxygen carrier,   (d) passing the at least one oxidized oxygen carrier from said first reactor to a second reactor receivably connected to said first reactor,   (e) contacting said at least one oxidized oxygen carrier with at least one fuel in said second reactor to produce said at least one reduced oxygen carrier and carbon dioxide, and   (f) passing said at least one reduced oxygen carrier from said second reactor to said first reactor,   wherein both reaction steps are exothermic.   
     
     
         4 . A process for chemical looping combustion in a flash furnace, said flash furnace comprising a first reactor and a second reactor receivably connected to said first reactor, said process comprising the steps of:
 (a) feeding oxygen and a reduced oxygen carrier into the first reactor having a first reactor temperature at a location that is not a reaction zone, said oxygen and said reduced oxygen carrier each having a temperature that is lower than said first reactor temperature, and said first reactor temperature being sufficient to ignite the oxygen and the reduced oxygen carrier as they pass through the first reactor and create a reaction that is sufficiently exothermic to form a self-sustaining reaction zone having a first flash temperature, said reaction producing an oxidized oxygen carrier;   (b) feeding said oxidized oxygen carrier and a fuel into said second reactor at a location that is not a reaction zone having a second reactor temperature, said oxidized oxygen carrier and said fuel each having a temperature that is lower than said second reactor temperature, and said reactor temperature being sufficient to ignite the oxidized oxygen carrier and the fuel as they pass through the second reactor and create a reaction that is sufficiently exothermic to form a self-sustaining reaction zone having a second flash temperature, said reaction producing the reduced oxygen carrier and carbon dioxide; and   (c) optionally, feeding said reduced oxygen carrier from said second reactor to said first reactor.   
     
     
         5 . A process for chemical looping combustion comprising the steps of:
 (g) feeding a reduced oxygen carrier and oxygen into a first reactor;   (h) contacting the reduced oxygen carrier with the oxygen source in said first reactor to form an oxidized oxygen carrier;   (i) passing the oxidized oxygen carrier from said first reactor to a second reactor receivably connected to said first reactor;   (j) feeding a fuel into said second reactor for contact with said oxidized oxygen carrier within said second reactor to produce a reaction product comprising said reduced oxygen carrier, carbon dioxide and carbon monoxide; and   (k) passing said reduced oxygen carrier from said second reactor to said first reactor;   wherein the reaction in the first reactor and the reaction in the second reactor are both exothermic.   
     
     
         6 . The process of  claim 4  wherein the fuel is an ash-containing fuel and wherein the reaction in the second reactor further produces fly ash. 
     
     
         7 . The process of  claim 4  wherein the reduced oxygen carrier and the oxygen are preheated before being fed into the first reactor of the furnace. 
     
     
         8 . The process of  claim 4  wherein the fuel and the oxidized oxygen carrier are preheated before being fed into the second reactor of the furnace. 
     
     
         9 . The process of  claim 3  wherein the oxygen and the reduced oxygen carrier are fed into the first reactor at a rate that is substantially constant and the first reactor temperature and the second reactor temperature remain substantially constant. 
     
     
         10 . The process of  claim 4 , wherein after step (b), the fuel and the oxidized oxygen carrier are blended prior to being passed into the second reactor. 
     
     
         11 . The process of  claim 1  or  claim 2  wherein said process is performed in a flash furnace. 
     
     
         12 . The process of  claim 1  wherein said process is performed in a rotary kiln, a multiple hearth furnace, a vertical tube furnace or a fluidized bed reactor. 
     
     
         13 . The process of  claim 1  wherein said process is continuous. 
     
     
         14 . The process of  claim 1  further comprising recycling the reduced oxygen carrier produced during said second step into said first step of the process. 
     
     
         15 . The process of  claim 1  further comprising the step of separating and sequestering the carbon dioxide produced during the second step. 
     
     
         16 . The process of  claim 2  wherein at least a portion of the reduced oxygen carrier together with at least a portion of the fly ash are removed from the furnace. 
     
     
         17 . The process of  claim 16  wherein the amount of reduced oxygen carrier is fed into the furnace in an amount that is substantially the same as the amount of reduced oxygen carrier being removed from the furnace. 
     
     
         18 . The process of  claim 2  wherein at least a portion of the reduced oxygen carrier together with at least a portion of the fly ash are removed from the furnace and subsequently utilized as a ferroalloy addition in a process to produce an alloy material containing iron and slag. 
     
     
         19 . The process of  claim 5  further comprising the step of separating the carbon monoxide produced during the second step. 
     
     
         20 . The process of  claim 1  or  claim 2  wherein the reduced oxygen carrier is a metal or a metal suboxide. 
     
     
         21 . The process of  claim 1  wherein the reduced oxygen carrier is a metal selected from the group consisting of rhenium, platinum, rhodium, palladium, copper, barium, manganese, molybdenum, vanadium, bismuth, lead, mercury, sodium, potassium, rubidium, and cesium. 
     
     
         22 . The process of  claim 2  wherein the oxygen carrier is substantially free-flowing. 
     
     
         23 . The process of  claim 1  wherein the fuel is selected from carbon, coal, hydrogen, hydrocarbon, biofuel, methane, natural gas, petroleum, crude oil, tar sands, oil shale, biomass, algae, fuel-rich waste gases from fuel cells, other fossil fuel or synthetic fuel. 
     
     
         24 . The process of  claim 2  wherein the ash-containing fuel is coal. 
     
     
         25 . The process of  claim 1  wherein the fuel is a carbon, a hydrocarbon, or hydrogen in the form of a solid, a liquid or a gas. 
     
     
         26 . The process of  claim 1  wherein the oxygen carrier is in the form of a powder. 
     
     
         27 . The process of  claim 26  wherein the oxygen carrier powder has a particle size of from 100 nanometers to 1 mm as determined by laser light scattering. 
     
     
         28 . The process of  claim 1  wherein the oxygen carrier is in the form of a powder having a particle size of from 20 microns to 250 microns as determined by laser light scattering. 
     
     
         29 . The process of  claim 1  wherein the fuel is a coal in the form of a powder. 
     
     
         30 . The process of  claim 29  wherein the coal powder has a particle size of from 100 nanometers to 10 mm as determined by laser light scattering. 
     
     
         31 . The process of  claim 1  wherein the fuel is a coal in the form of a powder having a particle size of from 20 microns to 250 microns as determined by laser light scattering. 
     
     
         32 . The process of  claim 1  wherein the fuel is coal having a particle size that is substantially similar to the particle size of the oxygen carrier. 
     
     
         33 . The process of  claim 1  wherein said oxidized oxygen carrier is at least partially vaporized during said second step of the process. 
     
     
         34 . The process of  claim 4  wherein the difference between said first reactor temperature and said first flash temperature in the first reactor is at least 300° C. 
     
     
         35 . The process of  claim 4  wherein the difference between said second reactor temperature and said second flash temperature in the second reactor is at least 300° C. 
     
     
         36 . The process of  claim 4  wherein the difference between said first reactor temperature and said first flash temperature in the first reactor is at least 800° C. 
     
     
         37 . The process of  claim 4  wherein the difference between said second reactor temperature and said second flash temperature in the second reactor is at least 800° C. 
     
     
         38 . The process of  claim 4  wherein the reduced oxygen carrier and the oxygen are fed into the first reactor at a rate sufficient to substantially off-set the heat loss of the first reactor and create a stable self-sustaining reaction zone within the first reactor. 
     
     
         39 . The process of  claim 4  wherein the oxidized oxygen carrier and the fuel are fed into the second reactor at a rate sufficient to substantially off-set the heat loss from the second reactor and create a stable self-sustaining reaction zone within the second reactor. 
     
     
         40 . The process of  claim 2  wherein the temperature within the first reactor is above the solid/liquid phase transition temperature of the reduced oxygen carrier. 
     
     
         41 . The process of  claim 2  wherein the temperature within the first reactor is above the solid/gas phase transition temperature of the reduced oxygen carrier. 
     
     
         42 . The process of  claim 2  wherein the temperature within the first reactor is above the liquid/gas phase transition temperature of the reduced oxygen carrier. 
     
     
         43 . The process of  claim 2  wherein the temperature within the second reactor is above the solid/liquid phase transition temperature of the oxidized oxygen carrier. 
     
     
         44 . The process of  claim 2  wherein the temperature within the second reactor is above the solid/gas phase transition temperature of the oxidized oxygen carrier. 
     
     
         45 . The process of  claim 2  wherein the temperature within the second reactor is above the liquid/gas phase transition temperature of the oxidized oxygen carrier. 
     
     
         46 . The process of  claim 3  wherein the residence time of the oxygen and the reduced oxygen carrier in the first reactor is from 0.01 to 1.0 minute. 
     
     
         47 . The process of  claim 3  wherein the residence time of the oxygen and the reduced oxygen carrier in the first reactor is from 0.01 to 10 seconds. 
     
     
         48 . The process of  claim 3  wherein the process is performed in a flash furnace and the residence time of the fuel and the oxidized oxygen carrier in the second reactor is from 0.01 seconds to 1.0 minute. 
     
     
         49 . The process of  claim 3  wherein the process is performed in a flash furnace and the residence time of the fuel and the oxidized oxygen carrier in the second reactor is from 0.01 seconds to 10 seconds. 
     
     
         50 . The process of  claim 4  wherein the reduced oxygen carrier flows concurrently in the same direction with the flow of the oxygen in the first reactor. 
     
     
         51 . The process of  claim 4  wherein the oxidized oxygen carrier flows concurrently in the same direction with the flow of the fuel in the second reactor. 
     
     
         52 . The process of  claim 5  wherein the fuel and the oxidized oxygen carrier are fed into the second reactor in substantially stoichiometric amounts. 
     
     
         53 . The process of  claim 5  wherein the fuel and the oxidized oxygen carrier are fed into the second reactor in less than stoichiometric amounts in order to produce carbon monoxide. 
     
     
         54 . A process for generating useful work comprising the process of  claim 1 . 
     
     
         55 . A process for generating useful work comprising the first step of the process of  claim 1 . 
     
     
         56 . A process for generating useful work comprising the second step of the process of  claim 1 . 
     
     
         57 . The process of  claim 1  further comprising utilizing the energy produced during the exothermic process in a generator for generating electricity. 
     
     
         58 . The process of  claim 1  further comprising converting the energy produced during the exothermic process into steam that is used to rotate a turbine engine. 
     
     
         59 . The process of  claim 1  wherein the steps can be performed in either order. 
     
     
         60 . The process of  claim 4  further comprising (d) feeding carbon dioxide into said second reactor.