System and method for capturing carbon dioxide from a humidity adjusted air stream
The present invention relates to a system for capturing carbon dioxide from an air stream. The system includes a carbon dioxide capturing unit that includes a humidity/temperature adjusting unit with an evaporative cooling unit and a CO 2 adsorbing unit. The CO 2 adsorbing unit includes a sorbent column made of polyamine-Cu (II) complex resin. The humidity/temperature adjusting unit receives air stream from ambient atmosphere and process the air stream to obtain a humidity-adjusted air stream. The CO 2 adsorbing unit receives the humidity-adjusted air stream to pass through the sorbent column. The sorbent column selectively adsorbs the CO 2 from the humidity-adjusted air stream. The sorbent column is regenerated using an alkaline stream to separate the adsorbed CO 2 from the sorbent column.
1 . A system for capturing carbon dioxide from a humid-adjusted air stream, wherein the system comprising: a carbon dioxide capturing unit comprising a humidity/temperature adjusting unit that comprises an evaporative cooling unit and a CO2 adsorbing unit, wherein the carbon dioxide adsorbing unit comprises a sorbent column made of polyamine-Cu (II) complex resin, wherein the humidity/temperature adjusting unit is configured to (a) enhance the humidity of the air stream by utilizing the air stream for evaporative cooling in the evaporative cooling unit to obtain a high humidity-low temperature air stream and (b) adjust the humidity of the high humidity-low temperature air stream as appropriate by drawing additional air and mixing the additional air with the high humidity-low temperature air stream, wherein the air stream comprises a humidity of about 75 to 95% and the humidity-adjusted air stream comprises a humidity of about 50 to 75%, wherein the CO2 adsorbing unit is configured to receive the humidity-adjusted air stream from the humidity/temperature adjusting unit and allow the humidity-adjusted air stream to pass through the sorbent column to selectively adsorb the CO2 from the humidity-adjusted air stream, thereby capturing the CO2 from the humidity-adjusted air stream, wherein the sorbent column is regenerated to separate the adsorbed CO2 from the sorbent column by (a) passing a source of NaCl to the sorbent column and displacing the captured CO2 in the resin with chloride (cl—) ion and releasing the captured CO2 in the NaCl solution as a bicarbonate ion (HCO3-); and (b) passing an alkaline stream to the sorbent column upon passing the source of NaCl, thereby replacing the chloride species (Cl—) in the resin with hydroxide ion (OH—); wherein the polyamine-Cu (II) complex resin is Polyam-N-Cu2+ resin; wherein the sorbent column is regenerated using NaOH produced through electro-dialysis of NaCl in a bipolar Electro-dialysis reversal (EDR) unit; and wherein the spent NaCl solution comprising adsorbed CO2 as a bicarbonate ion (HCO3-) is used to regenerating resins of a water softening unit comprising a Strong Acid Cation (SAC) resin unit and a Weak Acid Cation (WAC) resin unit.
2 . The system of claim 1 , wherein the evaporative cooling unit is a Peltier hybrid cooling system.
3 . The system of claim 1 , wherein the sorbent column is conditioned using spent alkali with a pH in a range of 11-13 or fresh batch of 0.5% weight by weight (w/w) of NaOH before allowing the humidity-adjusted air stream to pass through.
4 . The system of claim 1 , wherein the source of NaCl comprises at least one of sea water, spent brine or fresh brine, wherein the alkaline stream comprises at least one of NaOH solution or lime regenerant.
5 . The system of claim 4 , wherein around 60-bed volumes of the source of NaCl and 20 bed volumes of the alkaline stream are passed through the sorbent column in a down-flow mode.
6 . The system of claim 1 , wherein the sorbent column is regenerated by exposing the sorbent column to hot water at a temperature of 80° C. or any waste heat source to produce pure CO2 gas.
7 . The system of claim 1 , wherein the evaporative cooling unit is an empty box, a vegetable cooler, a gymnasium which has been air cooled in arid environment or a pigsty cooler for animals in arid and hot environment.
8 . The system of claim 1 , wherein the CO2 adsorbing unit are provided as modular cartridges.
9 . A method for capturing carbon dioxide from a humidity-adjusted air stream, wherein the method comprises the steps of: providing the carbon dioxide capturing unit as recited in claim 1 ; receiving the air stream from ambient atmosphere by the humidity/temperature adjusting unit, wherein the humidity/temperature adjusting unit is configured to (a) enhance the humidity of the air stream by utilizing the air stream for evaporative cooling in the evaporative cooling unit to obtain the high humidity-low temperature air stream and (b) adjust the humidity of the high humidity-low temperature air stream as appropriate by drawing additional air and mixing the additional air with the high humidity-low temperature air stream; performing selective adsorption of the carbon dioxide by the CO2 adsorbing unit, wherein the CO2 adsorbing unit comprises the sorbent column that selectively adsorbs the CO2 from the humidity-adjusted air stream that is passed through the sorbent column; and regenerating the sorbent column to separate the adsorbed CO2 from the sorbent column by (a) passing the source of NaCl to the sorbent column, and displacing the captured CO2 in the resin with chloride (Cl—) ion and releasing the captured CO2 in the NaCl solution as the bicarbonate ion (HCO3-); and (b) passing the alkaline stream to the sorbent column upon passing the source of NaCl, thereby replacing the chloride species (Cl—) in the resin with hydroxide ion (OH—).
10 . The method of claim 9 , wherein the method comprising conditioning the sorbent column using spent alkali with a pH in a range of 11-13 or fresh batch of 0.5% weight by weight (w/w) of NaOH before allowing the humidity-adjusted air to pass through.
11 . The method of claim 9 , wherein the method comprising regenerating the sorbent column by (i) passing around 60-bed volumes of a source of NaCl to the sorbent column and displacing the captured CO 2 in the resin with chloride (Cl—) ion and releasing the captured CO 2 in the NaCl solution as the bicarbonate ion (HCO3-); and (ii) passing around 20 bed volumes of the alkaline stream to the sorbent column in a down-flow mode, upon passing the source of NaCl, thereby replacing the chloride species (Cl—) in the resin with hydroxide ion (OH—).
12 . The method of claim 9 , wherein the method comprises regenerating resins of a water softening unit comprising a Strong Acid Cation (SAC) resin unit with primary resins and a Weak Acid Cation (WAC) resin unit with polishing resins, wherein the method comprises introducing the spent NaCl solution comprising CO 2 bicarbonate ion (HCO3-) from the CO 2 adsorbing unit into the Strong Acid Cation (SAC) resin unit of the water softening unit to regenerate the Strong Acid Cation (SAC) resin unit.
13 . The method of claim 12 , wherein the method comprises regenerating the Weak Acid Cation (WAC) resin unit of the water softening unit using NaOH and HCl produced from NaCl by performing electrodialysis in the bipolar Electrodialysis reversal (EDR) unit.
14 . The method of claim 13 , wherein the method comprises regenerating the sorbent column of the CO 2 adsorbing unit simultaneously using the NaOH produced from the bipolar Electrodialysis reversal (EDR) unit.