Method for the removal of carbon dioxide from a process gas
First Claim
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1. A method of continuously removing carbon dioxide from a process gas which includes the method steps of:
- contacting the process gas under pressure in an absorption stage with an aqueous solution containing dissolved therein, potassium carbonate as a reagent, potassium bicarbonate as a reaction product, diethanol amine as a catalyst and potassium vanadate as a corrosion inhibitor, the carbon dioxide in the process gas being absorbed by the aqueous solution and reacting therein with the potassium carbonate according to the reaction K2CO3+CO2+H2O →
2KHCO3;
increasing the temperature of the aqueous solution and decreasing the pressure thereon to cause desorption, in a desorption stage separate from the absorption stage, of the carbon dioxide from the aqueous solution according to the reaction
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Abstract
The invention relates to the absorption of carbon dioxide from a process gas using a solution of potassium carbonate, potassium bicarbonate, diethanolamine and potassium vanadate, followed by desorption of the carbon dioxide from the solution and recycling the regenerated solution. Organic acid salts of potassium build up in the aqueous solution is diluted with aqueous diluent, and then passed over a semi-permeable membrane such as a nanofiltration membrane, and ultrafiltration membrane or a reverse-osmosis membrane using a pressure drop to remove the organic acid salts of potassium from the side stream.
46 Citations
16 Claims
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1. A method of continuously removing carbon dioxide from a process gas which includes the method steps of:
- contacting the process gas under pressure in an absorption stage with an aqueous solution containing dissolved therein, potassium carbonate as a reagent, potassium bicarbonate as a reaction product, diethanol amine as a catalyst and potassium vanadate as a corrosion inhibitor, the carbon dioxide in the process gas being absorbed by the aqueous solution and reacting therein with the potassium carbonate according to the reaction K2CO3+CO2+H2O →
2KHCO3;
increasing the temperature of the aqueous solution and decreasing the pressure thereon to cause desorption, in a desorption stage separate from the absorption stage, of the carbon dioxide from the aqueous solution according to the reaction - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
- contacting the process gas under pressure in an absorption stage with an aqueous solution containing dissolved therein, potassium carbonate as a reagent, potassium bicarbonate as a reaction product, diethanol amine as a catalyst and potassium vanadate as a corrosion inhibitor, the carbon dioxide in the process gas being absorbed by the aqueous solution and reacting therein with the potassium carbonate according to the reaction K2CO3+CO2+H2O →
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10. A method of treating an aqueous solution which contains dissolved potassium carbonate, potassium bicarbonate, diethanol amine, potassium vanadate and organic salts of potassium, so as to remove said organic salts of potassium from the aqueous solution while retaining the potassium vanadate in the aqueous solution, the method comprising the method steps of:
- withdrawing part of the aqueous solution from the remaining aqueous solution;
diluting the withdrawn part of the aqueous solution with an aqueous diluent;
passing the withdrawn part of the solution of the aqueous solution over a semi-permeable membrane at a pressure differential across the membrane that is in the range of about 1,000 kPascals to 3,500 kPascals to prevent vanadate anions from passing through the semi-permeable membrane while allowing small proportions of potassium carbonate, potassium bicarbonate and diethanol amine to pass through the semi-permeable membrane such that the aqueous solution containing the organic salts of potassium passing through the semi-permeable membrane contains at most 0.5 g/l potassium carbonate, at most 0.5 g/l potassium bicarbonate and at most 0.5 g/l diethanol amine;
optionally adding potassium carbonate and diethanol amine to the solution in the circuit, and after the withdrawn part has passed over the semi-permeable membrane, returning the withdrawn part to the remaining aqueous solution. - View Dependent Claims (11, 12, 13, 14, 15, 16)
- withdrawing part of the aqueous solution from the remaining aqueous solution;
Specification