NO20093124A1 - Process for ammonia-based separation of CO2 from combustion gas from power generation - Google Patents

Description

Description

The present invention relates to a method for ammonia-based separation of CO2 from the combustion gas from power generation. The procedure includes CO2 pressurization of a slurry mixture consisting of ammonia water, ammonium urncarbonate and ammonium bicarbonate to about 7 kg/cm at about 2-40 °C, where the slurry mixture is formed from a first reaction step at approximate atmospheric pressure between ammonia water and CO2 from polluted waste gas from power generation. During CO2 pressurization of the slurry mixture, a large part of the ammonium carbonate portion will split into ammonium bicarbonate and cause ammonium bicarbonate to precipitate as a solid and thereby can be filtered from the slurry mixture as a solid. At atmospheric pressure, solid ammonium bicarbonate splits at around 60-80 °C into water, ammonia gas and CO2 gas, where the water is separated out first. When ammonia gas and CO2 gas are pressurized, the ammonia gas condenses into a liquid while the CO2 is in gaseous form. Ammonia is then separated out as a liquid, while an almost pure CO2 gas goes on to further pressurization and condensation to liquid for intermediate storage in a pressure tank. Prior to condensation, the CO2 gas is pressurized in a first step to approx. 7 kg/cm<2>, where part of the CO2 amount is used for pressurizing and reacting with the slurry mixture from the first reaction step. After further pressurization and condensation of the separated CO2, the CO2 liquid after intermediate storage can be further transported under pressure to, for example, geological storage. Ammonia and water from the splitting process, as well as that filtrate from slurry filtration is circulated to the output reactor for reaction between ammonia and CO2 from polluted exhaust gas. The method will contribute to the production costs for CO2 liquid from power-generated waste gas being reduced compared to "mature" technology, in that the energy costs will be relatively low and that recovery of the absorption liquid, i.e. ammonia, will be very high.

Focus on CO2 emissions from power production as a climate threat has been increasing strongly in recent years. "Mature" technology for CO2 handling from power generation appears to be very expensive with high energy costs and a relatively high loss of harmful absorption liquid. The need for alternative and cheaper methods is therefore very relevant

Ammonia-based CO2 separation from combustion waste gas from power generation is based on the production of a slurry mixture consisting of ammonia water, ammonium urncarbonate and ammonium bicarbonate. The slurry mixture occurs as a reaction product after a first reaction step in an ammonia-C02 reactor, where ammonia water and CO2 from impure combustion exhaust gas react at atmospheric pressure according to the following chemical equation:

After the reaction course of the first reaction step has ended in about 10 seconds, there will still be about 50% unreacted ammonia (NH3) left in the solution. About 85-90% of the CO2 content in the exhaust gas will be absorbed and converted to ammonium bicarbonate and ammonium urncarbonate. Mole-based distribution between ammonium bicarbonate (HNH4CO3) and ammonium carbonate ((NH^COa) in the mixture will be about HNH4C03/(NH4)2C03 = 5/4. By pressurizing the mixture with C02 to about 7 kg/cm<2>at about 2 -40 °C, large parts of the ammonium carbonate will be converted into ammonium bicarbonate according to the following chemical equation:

In practice, this will mean that almost all CO2 will be precipitated as ammonium bicarbonate under pressure. The precipitation will take place in a separate crystallizer, after which the slurry mixture is filtered on a pressurized filter. Filtered off ammonium bicarbonate is then heated and decomposed at about 60

- 80 °C, for water, ammonia gas and CO2 gas. Water is separated first and ammonia-CCh

the gas mixture is then pressurized to separate out condensed ammonia liquid. The gas phase, which then mainly consists of pure CO2 gas, is first pressurized to approx. 7 kg/cm<2> and then further until the CO2 condenses out as a pressurized liquid and is then intermediately stored for transport to final landfill. At the first pressurization to approx. 7 kg/cm<2>, part of the C02 quantity is led to the crystallizer for pressurization and reaction with the slurry mixture from the first reaction stage. The slurry mixture is then filtered and the filtrate from the filtration, as well as water and ammonia from the cleavage of ammonium bicarbonate, are circulated back to the ammonia CChreactor in the first reaction stage.

The present invention relates to a method for ammonia-based separation of CO2 from combustion waste gas from power generation, characterized in that ammonium bicarbonate is produced from a slurry mixture, which is generated from a first reaction step where ammonia water and CO2 from polluted waste gas from power generation and at approximately atmospheric pressure react to form a slurry mixture of ammonia water, ammonium bicarbonate and ammonium bicarbonate, after which the slurry mixture is pressurized with CO2 gas to approx. 7 kg/cm<2> at approx. 2 - 40 °C, which leads to the ammonium bicarbonate being converted into ammonium bicarbonate, and so that the ammonium bicarbonate solid is precipitated and filtered out, after which the ammonium bicarbonate solid at atmospheric pressure is decomposed by approx. 60 - 80 °C to water, ammonia gas and CO2 in gaseous form, after which water is separated out first and the gas phase is then pressurized so that ammonia is separated out as a liquid, after which C02 gas is then first pressurized to approx. 7 kg/cm and where part of The amount of CO2 is directed to ty coagulation and reaction with the slurry mixture from the first reaction stage, after which the remaining part of the CO2 gas is further pressurized and condensed into a pressurized liquid, which can thereby be stored geologically, so that the method can be used in an economically favorable way for the capture, regeneration and storage of CO2 from combustion exhaust gas from, among other things, coal-fired power plants and gas-fired power plants.

In what follows, an example of how to carry out the method is given.

Example

The starting point is handling 100,000 tonnes of CO2 per year, which constitutes 90% of CO2

the quantity in the exhaust gas from a 40 MW Coal-fired power plant, The exhaust gas to the handling facility will amount to 70,000 m<3>/hour of exhaust gas with 15 tonnes/hour of CO2, i.e. that the net captured CO2 in the process will amount to 13.5 tonnes/hour of CO2. The exhaust gas from the coal-fired power plant and regenerated ammonia from the process go to the CC>2 reactor, where 90% of the CO2 amount after about 10 seconds. at approximately atmospheric pressure, reacts to ammonium bicarbonate and ammonium carbonate in a slurry mixture with ammonia water. The slurry mixture is then pumped to a pressurized crystallizer where ammonium carbonate at about 2-40 °C and a CO2 pressure of about 7 kg/cm<2>is converted into ammonium bicarbonate, with the result that ammonium bicarbonate is precipitated as a solid. The slurry mixture then goes to a filter where ammonium bicarbonate is filtered off and then stored in an intermediate silo. The filtrate from the filtration is circulated back to the CO2 reactor. The ammonium bicarbonate product in the intermediate silo then undergoes thermal decomposition at a temperature of approximately 60-80 °C in a rotary kiln, where ammonium bicarbonate is decomposed into water, ammonia gas and CO2 in gaseous form. The water is led out separately from the rotary kiln and circulated

back to the CO2 reactor, while CCfe gas and ammonia gas are pressurized in the pressure tank, whereby ammonia condenses into liquid which is drained off separately from the pressure tank and circulated back to the CO2 reactor. The CCtø gas is tapped from the pressure tank in gaseous form and then first pressurized to approx. 7 kg/cm<2>, where part of the C02 gas is led to pressurize and react with the slurry mixture in the crystallizer. The remaining part of the C02 gas is further pressurized whereby the CO2 condenses into liquid and is then temporarily stored as a liquid in a pressurized storage tank. This achieves the separation of approximately 90% of the CO2 amount from the incineration exhaust gas from a 40 MW coal-fired power plant in an energy-efficient and competitive manner.

A process flow chart is attached as an appendix to the application.

Claims (1)

1. Process for ammonia-based separation of CO2 from combustion waste gas from power generation, characterized in that ammonium bicarbonate is produced from a slurry mixture, which is generated from a first reaction step in which ammonia water and CO2 from polluted waste gas from power generation and at approximately atmospheric pressure react to form a slurry mixture of ammonia water, ammonium bicarbonate and ammonium carbonate, after which the slurry mixture pressurized with CO2 gas to approx. 7 kg/cm<2> at approx. 2-40 °C, which causes ammonium carbonate to be converted into ammonium bicarbonate, and so that solid ammonium bicarbonate is precipitated and filtered out, after which solid ammonium bicarbonate is decomposed at atmospheric pressure at approx. 60 - 80 °C to water, ammonia gas and CO2 in gaseous form, after which water is separated out first and the gas phase is then pressurized so that ammonia is separated out as a liquid, after which CCV gas is then first pressurized to approx. 7 kg/cm<2> and where part of the CO2 amount is led for pressurizing and reaction with slurry mixture none from the first reaction step, and after which the remaining part of the CO2 gas is further pressurized and condensed into a pressurized liquid, which can thereby be stored geologically, so that the method can be used in an economically favorable way for the capture, regeneration and deposition of CO2 from combustion exhaust gas from, among other things, coal power plants and gas power plants.