Process for Gas/Vapor Separation by Cryogenic Froth Flotation

Abstract

A process for separating a vapor from a gas is disclosed. A cryogenic liquid is provided to an inlet of a froth flotation device. A carrier gas is provided to a gas distributor of the froth flotation device. The carrier gas comprises a product vapor. Bubbles of the carrier gas are produced and passed through the cryogenic liquid in the froth flotation device. A portion of the product vapor desublimates, condenses, crystallizes, or a combination thereof to produce a solid product and a product-depleted carrier gas. Bubbles of the product-depleted carrier gas collect the solid product as a froth concentrate. The froth concentrate is removed by overflowing out of the froth flotation device.

1 . A process for separating a vapor from a gas comprising:
 providing a cryogenic liquid to an inlet of a froth flotation device;   providing a carrier gas to a gas distributor of the froth flotation device, the carrier gas comprising a product vapor;   producing bubbles of the carrier gas and passing the bubbles of the carrier gas through the cryogenic liquid in the froth flotation device, wherein:
 a portion of the product vapor desublimates, condenses, crystallizes, or a combination thereof to produce a solid product and a product-depleted carrier gas, wherein the solid product is cryogenic liquidphobic; and, 
 bubbles of the product-depleted carrier gas collect the solid product as a froth concentrate; and, 
   removing the froth concentrate by overflow out of the froth flotation device, wherein the froth concentrate comprises the solid product, the product-depleted carrier gas, and a first portion of the cryogenic liquid;   
       whereby the product vapor is separated from the carrier gas. 
     
     
         2 . The process of  claim 1 , further comprising removing a second portion of the cryogenic liquid from the froth flotation device as a used cryogenic liquid, wherein the second portion of the cryogenic liquid is substantially larger than the first portion of the cryogenic liquid 
     
     
         3 . The process of  claim 1 , providing the product vapor comprising carbon dioxide, nitrogen oxide, sulfur dioxide, nitrogen dioxide, sulfur trioxide, hydrogen sulfide, hydrogen cyanide, water, hydrocarbons, mercury, other heavy metals, condensed organics, salts, water ice, particulates, soot, dust, or combinations thereof. 
     
     
         4 . The process of  claim 1 , providing the cryogenic liquid comprising any compound or mixture of compounds with a freezing point below the temperature at which the solid melts. 
     
     
         5 . The process of  claim 1 , providing the cryogenic liquid comprising mercaptans, ionic liquids, salt solutions, hydrocarbons, or a combination thereof. 
     
     
         6 . The process of  claim 5 , providing the hydrocarbons comprising 1,1,3-trimethylcyclopentane, 1,4-pentadiene, 1,5-hexadiene, 1-butene, 1-methyl-1-ethylcyclopentane, 1-pentene, 3,3,3,3-tetrafluoropropene, 3,3-dimethyl-1-butene, 3-chloro-1,1,1,2-tetrafluoroethane, 3-methylpentane, 3-methyl-1,4-pentadiene, 3-methyl- 1 -butene, 3-methyl-1-pentene, 3-methylpentane, 5-methyl-1-hexene, 5-methyl-1-pentene, 5-methylcyclopentene, 5-methyl-trans-2-pentene, bromochlorodifluoromethane, bromodifluoromethane, bromotrifluoroethylene, chlorotrifluoroethylene, cis 3-hexene, cis-1,3-pentadiene, cis-2-hexene, cis-2-pentene, dichlorodifluoromethane, difluoromethyl ether, trifluoromethyl ether, dimethyl ether, ethyl fluoride, ethyl mercaptan, hexafluoropropylene, isobutane, isobutene, isobutyl mercaptan, isopentane, isoprene, methyl isopropyl ether, methylcyclohexane, methylcyclopentane, methylcyclopropane, n,n-diethylmethylamine, octafluoropropane, pentafluoroethyl trifluorovinyl ether, propane, sec-butyl mercaptan, trans-2-pentene, trifluoromethyl trifluorovinyl ether, vinyl chloride, bromotrifluoromethane, chlorodifluoromethane, dimethyl silane, ketene, methyl silane, perchloryl fluoride, propylene, vinyl fluoride, methanol, ethanol, 1-propanol, 2-propanol, aqueous mixtures thereof, or combinations thereof. 
     
     
         7 . The process of  claim 1 , providing the carrier gas comprising combustion flue gas, syngas, producer gas, natural gas, steam reforming gas, light gases, hydrocarbons with a freezing point above the temperature of the cryogenic liquid, or combinations thereof. 
     
     
         8 . The process of  claim 1 , further comprising separating the product-depleted carrier gas from the froth concentrate. 
     
     
         9 . The process of  claim 8 , further comprising passing the product-depleted carrier gas through further froth flotation devices. 
     
     
         10 . The process of  claim 8 , further comprising separating the solid product from the first portion of the cryogenic liquid and passing the first portion of the cryogenic liquid to combine with the used cryogenic liquid. 
     
     
         11 . The process of  claim 10 , further comprising reconstituting the used cryogenic liquid by heat exchange to produce the cryogenic liquid. 
     
     
         12 . The process of  claim 1 , further comprising providing a frother, a collector, a modifier, or a combination thereof to the froth flotation device. 
     
     
         13 . The process of  claim 1 , further comprising providing a controller to receive inputs from instruments and output commands to drives and valves. 
     
     
         14 . The process of  claim 13 , providing the gas distributor further comprising an agitator. 
     
     
         15 . The process of  claim 14 , further comprising driving the agitator with a variable frequency drive. 
     
     
         16 . The process of  claim 15 , providing the froth flotation device further comprising a skimmer, a level sensor, a turbidity meter, or combinations thereof. 
     
     
         17 . The process of  claim 16 , providing the froth flotation device further comprising controlling a flow rate of the carrier gas with a control valve and a flow rate of the cryogenic liquid with a variable frequency drive on a pump. 
     
     
         18 . The process of  claim 1 , providing the gas distributor comprising a cryogenically-stable material. 
     
     
         19 . A process for separating a vapor from a gas comprising:
 providing n froth flotation banks in series, a bank B 1  being associated with a first bank and a bank Bn being associated with an nth bank, n representing the number of banks, wherein each bank comprises one or more flotation cells;   providing a cryogenic liquid to the banks Bn through B 1  in reverse series, passing the cryogenic liquid through the one or more flotation cells;   providing a carrier gas to the banks B 1  through Bn in series, passing the carrier gas through gas distributors in the one or more flotation cells of the banks, producing bubbles of the carrier gas and passing the bubbles of the carrier gas through the cryogenic liquid in the froth flotation device, wherein:
 the product vapor desublimates, condenses, crystallizes, or a combination thereof to produce a solid product and a product-depleted carrier gas, wherein the solid product is cryogenic liquidphobic; and, 
 bubbles of the product-depleted carrier gas collect the solid product as a froth concentrate; 
   removing the froth concentrate by overflow out of the banks B 1  through Bn, wherein the froth concentrate comprises the solid product, the product-depleted carrier gas, and a first portion of the cryogenic liquid;   separating froth concentrate into the product-depleted carrier gas, the solid product, and the first portion of the cryogenic liquid, removing the product-depleted carrier gas and the solid product as a final gas product and a final solid product, respectively;   removing a second portion of the cryogenic liquid from the bank B 1 , combining the second portion of the cryogenic liquid with the first portion of the cryogenic liquid to form a used cryogenic liquid, wherein the second portion of the cryogenic liquid is substantially larger than the first portion of the cryogenic liquid; and,   reconstituting the used cryogenic liquid by heat exchange to produce the cryogenic liquid;   
       whereby the product vapor is separated from the carrier gas. 
     
     
         20 . The process of  claim 19 , further comprising:
 providing a controller to receive inputs from instruments and output commands to drives and valves;   providing the gas distributors further comprising agitators, the agitators comprising variable frequency drives; and,   providing the banks B 1  through Bn with skimmers, level sensors, turbidity meters, control valves for controlling flow rates of the carrier gas, and variable frequency drives on pumps for controlling flow rates of the cryogenic liquid.