Method for carbon dioxide capture and concentration by partitioned multistage circulation based on mass transfer-reaction regulation

A method for carbon dioxide capture and concentration by partitioned multistage circulation based on mass transfer-reaction regulation, comprising:

• introducing flue gas into a multistage circulating absorption tower, performing impurity removal and cooling on the flue gas through a pre-washing device disposed in a front of the multistage circulating absorption tower and then successively introducing the flue gas into a first stage carbon dioxide absorption system to (n−1)th stage carbon dioxide absorption system and nth stage washing system, wherein n is greater than or equal to 3;
• introducing a rich solution into a carbon dioxide desorption tower through a rich solution and lean solution heat exchanger, and discharging a lean solution out of the carbon dioxide desorption tower and introducing the lean solution into the rich solution and lean solution heat exchanger;
• introducing regenerated gas from the carbon dioxide desorption tower into a carbon dioxide concentration device, and introducing the regenerated gas into a gas-liquid separator through a cooler;
• connecting an intelligent regulation system respectively to the first to (n−1)th stages carbon dioxide absorption systems, the nth stages washing system, and the carbon dioxide desorption tower;
• and connecting in series the first to (n−1)th stages carbon dioxide absorption systems and the nth stage washing system in the multistage circulating absorption tower stage by stage from bottom to top;
• wherein the pre-washing device is a venturi pre-washing section or a vertical pre-washing tower;
• washing, impurity removal and cooling water of the pre-washing device is softened water, which is sprayed by an atomizing nozzle, and the washing, impurity removal and cooling water is recycled, and regularly discharged to a wet desulfurization slurry-preparing system as slurry preparing water;
• wherein the pre-washing device is the venturi pre-washing section, and the multistage circulating absorption tower is a four-stage circulating absorption tower with n equal to 4;
• and the method comprises the following steps:
• (1) introducing flue gas into the four-stage circulating absorption tower, and performing impurity removal and cooling on the flue gas through the venturi pre-washing section disposed in the front and then introducing the flue gas into the first-stage carbon dioxide absorption system, a second-stage carbon dioxide absorption system, a third-stage carbon dioxide absorption system, and a fourth-stage washing system in sequence,
• wherein an absorbent circulates in the first-stage carbon dioxide absorption system with pH of 7.7-9.0 at 49-60° C.;
• an absorbent circulates in the second-stage carbon dioxide absorption system with pH of 8.0-10.0 at 44-53° C.;
• an absorbent circulates in the third-stage carbon dioxide absorption system with pH of 9.5-11.5 at 40-48° C.;
• and
• softened water circulates in the fourth-stage washing system with pH of 8.5-10.0 at 40-48° C.:
• (2) heating the rich solution through rich solution and lean solution heat exchanger to 90-98° C. and then introducing the rich solution into the carbon dioxide desorption tower;
• after the absorption liquid is heated to 105-115° C., enhancing carbon dioxide desorption by the rich solution under a coupling action of a plurality of fields including thermal field, ultrasonic field, and electric field;
• and using composite catalyst that is one or more of a γ-Al2O3/zeolite molecular sieve, an SO42−/ZrO2-zeolite molecular sieve, a shell-coated SO42−/ZrO2-zeolite molecular sieve, shell-coated SO42−/ZrO2—TiO2, shell-coated SO42−/CoO—TiO2 to improve stability and reduce desorption energy consumption;
• and discharging the lean solution out of the carbon dioxide desorption tower and introducing the lean solution into the rich solution and lean solution heat exchanger for cooling to 60-68° C., and then introducing the lean solution to the second-stage carbon dioxide absorption system;
• (3) introducing regenerated steam of the carbon dioxide desorption tower into the carbon dioxide concentration device, cooling the regenerated steam by the cooler to the boiling point of carbon dioxide or below, and introducing the regenerated steam into gas-liquid separator to obtain high-purity carbon dioxide;
• and
• (4) connecting the intelligent regulation system to the first-stage carbon dioxide absorption system, the second-stage carbon dioxide absorption system, the third-stage carbon dioxide absorption system, the fourth-stage washing system, and the carbon dioxide desorption tower, and establishing a global optimization parameter model of carbon dioxide absorption and carbon dioxide desorption by partitioned multistage circulation based on key parameters comprising pH, temperature, and circulation quantity in each stage to implement stable, efficient and low-cost operation of the system.