Patent DE-102009056660-A1 (DE)
Title: Method for chemisorptive separation of carbon dioxide from bio- or sewage gas by amine-containing washing solution, comprises introducing bio- or sewage gas in a washing column in contact with washing solution
Inventor: GUENTHER LOTHAR
IPC: B01D53/14
Filed: 2009-12-02
Abstract: The method for chemisorptive separation of carbon dioxide from bio- or sewage gas by amine-containing washing solution, comprises introducing bio- or sewage gas in a washing column (K1, K2) in contact with washing solution, separating carbon dioxide from the loaded washing solution in single- or multi steps and recirculating cleaned, regenerated washing solution again into the washing column. The separation of carbon dioxide is carried out in two washing stages, where the first washing stage is preliminary cleaning and the second washing stage is final cleaning. The method for chemisorptive separation of carbon dioxide from bio- or sewage gas by amine-containing washing solution, comprises introducing bio- or sewage gas in a washing column (K1, K2) in contact with washing solution, separating carbon dioxide from the loaded washing solution in single- or multi steps and recirculating cleaned, regenerated washing solution again into the washing column. The separation of carbon dioxide is carried out in two washing stages, where the first washing stage is preliminary cleaning and the second washing stage is final cleaning. Each washing stage is associated to the washing column. A part quantity of carbon dioxide is separated in the first washing stage by loaded washing solution that is drawn-off at the sump of the second washing column, from the supplied raw gas. The raw gas pre-cleaned in the second washing column at the head of the first washing column is supplied to second washing column and is finally cleaned and discharged by fresh and/or finally cleaned washing solution brought in counter flow. The first and second partial quantity of the loaded washing solution are subjected to the sump of the first washing column, where the partial quantity is supplied to main regeneration stage (R1). The chemically bound and physically dissolved portion of carbon dioxide and further impurities are separated through desorption. The another part quantity is supplied to a sub-regeneration stage (R2) in which carbon dioxide of the loaded washing solution is separated under pressure and heating. The loaded partial stream of the regenerated washing solution is again recirculated into cleaning circuit. The loaded washing solution is supplied before the regeneration to stripping stage at the sump of the first washing column, where methane contained in the washing solution and another hydrocarbon are separated from carbon dioxide as stripping gas. The stripping gas mixture of the raw biogas is supplied to a stage of the biogas production. The carbon dioxide separated as stripping gas in the sub-regeneration stage is used from the washing solution. The separation of carbon dioxide is carried out in the washing stage under different irrigation density and loading factors. The ratio of the irrigation density of the second washing stage to the first washing stage is 1:1.5. The washing stage is processed with identical pressure or the pressure in the second washing column is greater than in the first washing column, where the pressure is 50 mbar to 15 bar. The regeneration of the loaded washing solution is carried out in the main regeneration stage on the pressure of 4-20 bar at 120-180[deg] C. The loaded washing solution in circulation is pumped in the sub-regeneration stage in circulation over a first heat exchanger, a separator and a second heat exchanger on a pressure of 0.1-4 bar at 85-125[deg] C. The loaded washing solution is pumped in the sub-regeneration stage in circulation over a first heat exchanger, a second heat exchanger, a separator and a third heat exchanger on a pressure of 0.1-4 bar at 85-125[deg] C. The washing solution is used as heat carrier for the first heat exchanger from the separator. The partial quantity of the loaded washing solution that is supplied to sub-regeneration stage is greater than the partial quantity supplied to the main regeneration stage. Waste heat from a thermal power station is used for heat supply for the regeneration of the washing solution in the sub-regeneration stage. The washing solution consists of an absorber component based on a tertiary amine or mixture of tertiary amine in a concentration of 30-60 wt.% related to total weight of the washing solution, a first activator from monoalkyl amine and/or dialkylamine in a concentration of 1-10 wt.% related to the total weight of the washing solution, a second activator from compounds of piperazine and/or piperazine derivatives with a free hydrogen atom on one of both nitrogen atoms in a concentration of 0.01-10 wt.% related to the total weight of the washing solution, if necessary an inhibitor based on silicon in a quantity of 1-100 ppm, and water as residue, where the portion of the water is 60 wt.% related to the total weight of the washing solution. The actual-temperature of the washing solution continuously measured and monitored in the washing stage over the column dumping height and one of both activators and if necessary inhibitors are pre-dosed during rising over a given boundary value. An independent claim is included for a plant for chemisorptive separation of carbon dioxide from bio- or sewage gas by amine-containing washing solution.