Radial counterflow carbon capture and flue gas scrubbing

Abstract

Carbon capture is effected by mechanical means, producing out of flue gas a concentrated, cleaned, and cooled stream of carbon dioxide. This is a new method of carbon capture which avoids the limitations of known cryogenic, membrane, or chemical capture methods. A mechanically assisted turbulent flue gas scrubber comprises counter-rotating coaxial centrifugal impellers and a shrouding tank for receiving the flow from between the impellers. Feed is at the axis of rotation. Axial extraction of nitrogen and water vapor is driven by an axial pump and by back pressure from the tank while radially outward flow of carbon dioxide and scrubbing targets is driven by the impellers. Scrubbing of the concentrated targets is in high turbulence during a long residence time. Tiny centrifugation effects of innumerable turbulent eddy vortices in a shear layer between the impellers and in the tank are integrated by the forcing regime of the impellers and the axial pump. Radial vortices caused by shear between the counter-rotating impellers provide coherent sink flow conduits for axial extraction of nitrogen ballast. Fine fly ash (PM-2.5) scrubbing is concurrent with NOx and SOx scrubbing and with carbon capture. Mechanically assisted and highly turbulent wet scrubbing shear thickens fine fly ash and precipitates into clumps of sludge, so the wastewater stream is easily treatable and requires no large storage tank.

1 . A method of mechanical carbon capture to separate carbon dioxide gas from a gaseous emission stream, the gaseous emission stream comprising light fractions and heavy fractions, the method comprising the simultaneous steps of:
 feeding the gaseous emission stream axially into a work space between coaxial counter-rotating centrifugal impellers,   causing flow of heavy fractions, including carbon dioxide gas, radially outward through the work space and into a tank,   causing flow of light fractions, including nitrogen gas, radially inward through the work space, and   axially extracting light fractions from between the impellers.   
     
     
         2 . The method of  claim 1 , additionally including the further simultaneous steps of injecting scrubbing liquid into the gaseous emission stream and purging liquid and agglomerated solids from the tank. 
     
     
         3 . Apparatus for separating a gaseous fluid mixture, the mixture comprising light fractions and heavy fractions, the apparatus comprising:
 an impeller assembly, the impeller assembly comprising:
 coaxial counter-rotatable centrifugal impellers connected to mechanical means for causing counter-rotation and defining between them a work space, the impellers providing means for advecting heavy fractions radially outward, 
 an axial feed port providing means for introducing the gaseous fluid mixture into the work space while the impellers are counter-rotating, and 
 an axial exhaust port communicating with means for axially extracting light fractions from the work space; 
   means for advecting fluid radially inward through the work space to the axial exhaust port while the impellers are counter-rotating; and   a static tank communicating with the work space and disposed about the impeller assembly, the tank providing means for pressurizing and collecting heavy fractions, including carbon dioxide gas.   
     
     
         4 . The apparatus of  claim 3 , additionally comprising a baffle connected by vanes to an impeller having an axial feed port. 
     
     
         5 . The apparatus of  claim 3 , wherein the impellers of the impeller assembly vary in their separation distance radially outward from the impeller axis of rotation, forming a pinch section and a flare section. 
     
     
         6 . The apparatus of  claim 5  wherein the impellers comprise vanes. 
     
     
         7 . The apparatus of  claim 3  wherein the tank comprises a gas vent for evacuating gaseous carbon dioxide and a purge pump for evacuating liquids and agglomerated solids. 
     
     
         8 . The apparatus of  claim 3  additionally comprising means for injecting scrubbing liquid into the gaseous emission stream. 
     
     
         9 . Apparatus for separating a gaseous mixture, the mixture comprising light fractions and heavy fractions, the apparatus comprising:
 a casing comprising an axial feed port and an axial exhaust port, the casing also comprising at its periphery a gas vent for evacuation of non-condensible gases and a purge pump for evacuation of liquids and solids,   a centrifugal impeller connected to mechanical means for causing rotation, the impeller being disposed within the casing and defining a flow path radially outward between the impeller and the casing on the side of the casing having the axial feed port and a flow path radially inward between the impeller and the casing on the side of the casing having the axial exhaust port, the centrifugal impeller and its drive means providing means for advecting heavy fractions radially outward, and   means for advecting light fractions through said radially inward flow path and through the axial exhaust port while the impeller rotates within the casing.   
     
     
         10 . The apparatus of  claim 9 , additionally comprising means for injection of scrubbing liquid into the gaseous mixture. 
     
     
         11 . The apparatus of  claim 9 , wherein the impeller comprises vanes on both sides. 
     
     
         12 . Apparatus for natural gas separation, comprising:
 an impeller assembly, the impeller assembly comprising:
 coaxial counter-rotatable centrifugal impellers connected to means for causing counter-rotation thereof and defining between them a work space, the impellers providing means for advecting natural gas radially outward, 
 an axial feed port providing means for introducing natural gas to the work space while the impellers are counter-rotating, and 
 an axial exhaust port communicating with means for axially extracting methane from the work space while the impellers counter-rotate; and 
   a static tank communicating with the work space and disposed about the impeller assembly, the tank being pressurized by flow through the work space and providing means for collecting concentrated heavy fractions including condensible vapors, water, mercury, mercaptans, hydrogen sulfide, and carbon dioxide.   
     
     
         13 . Apparatus for turbulent scrubbing of a gaseous mixture, the gaseous mixture comprising scrubbing targets and light fractions including nitrogen gas, the apparatus comprising
 means for injecting scrubbing sorbents and/or liquid into the gaseous mixture;   an impeller assembly, the impeller assembly comprising
 coaxial counter-rotatable centrifugal impellers connected to mechanical means for counter-rotation thereof and defining between them a work space, the impellers providing means for advecting fluid radially outward, 
 an axial feed port providing means for introducing the gaseous fluid mixture to the work space while the impellers are counter-rotating, and 
 an axial exhaust port communicating with means for axially extracting light fractions from the work space while the impellers counter-rotate; 
   means for advecting light fractions radially inward to the axial exhaust port while the impellers are counter-rotating; and   a static tank having an interior communicating with the work space, the tank being disposed about the impeller assembly and the tank being pressurized by flow through the work space, and the back pressure from the tank in combination with shear from the impeller assembly providing means for causing high turbulence in concentrated scrubbing targets, the tank comprising a gas vent for evacuating non-condensible gases and a purge pump for evacuating liquids and solids.   
     
     
         14 . The turbulent scrubber of  claim 13 , comprising means for shear thickening of fly ash slurry.