Carbon dioxide capture system and methods of capturing carbon dioxide

#This disclosure generally relates to systems and processes for capturing carbon dioxide (CO2) from gas streams, and more particularly to a solids delivery system to handle solid material containing the captured CO2.

#The emission of carbon dioxide into the atmosphere from industrial sources such as power plants is now considered to be a principal cause of the “greenhouse effect”, which contributes to global warming. In response, efforts are underway to reduce emissions of CO2. Many different processes have been developed to attempt to accomplish this task. Examples include polymer and inorganic membrane permeation; removal of CO2 by adsorbents such as molecular sieves; cryogenic separation; and scrubbing with a solvent that is chemically reactive with CO2, or which has a physical affinity for the gas.

#One technique has received much attention for removing CO2 from flue gas streams, e.g., exhaust gas produced at power plants. In this technique, aqueous monoethanolamine (MEA) or hindered amines like methyldiethanolamine (MDEA) and 2-amino-2-methyl-1-propanol (AMP) are employed as the solvents in an absorption/stripping type of regenerative process. The technique has been demonstrated commercially, using pilot plant and/or slipstream units, for CO2 capture from coal-fired power plants and gas turbines. Commercial CO2 capture has been practiced in gas sweetening processes for chemical production and in the food and beverage industry.

#Referring now to the figures, which are exemplary embodiments and wherein like elements are numbered alike:

#FIG. 1 is a schematic of an exemplary system for recovering CO2 from a gas stream;

#FIG. 2 is a schematic of an exemplary embodiment of a GE Posimetric™ solids pump for use as the transport mechanism of the system of FIG. 1; and

#CO2 sorbents can comprise liquid, nonaqueous CO2-reactive material that is liquid through a large range of temperatures, is non-volatile, is thermally stable, and does not require a nonabsorbing carrier fluid or solvent. These liquid sorbents can solidify in the presence of CO2. Disclosed herein are systems and methods for treating gas streams which contain CO2 and which use these types of liquid sorbents. The system have would a method of pressurizing the solid CO2-sorbent complex formed from the chemical reaction between the liquid sorbent and the CO2. Moreover, the system includes a transportation mechanism for transporting the solid CO2-sorbent complex to downstream components of the system, such as for treatment with related system equipment, e.g., regeneration units, and the like.

#In capturing the CO2 from the gas stream, the present system advantageously combines the use of a liquid sorbent that forms a solid in the presence of CO2 and a dry solids pressurization system for handling the solid material and transporting it to a desorption unit or other downstream unit operation. The utilization of a dry solids pressurization system means no carrier fluid is required and hence the CO2-containing solids and the liquid sorbent are not diluted. Not only does this allow the system size to be minimized, but it also saves the energy that would otherwise be required to pressurize the carrier fluid to create a high pressure desorption condition. Further, because the solids remain dry, there is no need to separate a carrier fluid from the CO2 after the sorbent has been removed.

#Carbon dioxide is present in a wide variety of gas streams that can be treated with the systems described herein. Non-limiting examples include gas streams originating from a combustion process; a gasification process; a landfill; a furnace (e.g., blast furnace or chemical reduction furnace); a steam generator; a boiler; and combinations comprising at least one of the foregoing. In one embodiment, the CO2 gas stream is a flue stream originating in a coal-fired plant.