Development of Carbon Dioxide Removal System from the Flue Gas of Coal Fired Power Plant

Post-combustion carbon dioxide capture is the technique that can be rapidly and safely employed for substantially reducing carbon dioxide emissions from existing and near future power plants. The key question of the absorption/desorption technique for carbon dioxide removal is process economics. Toshiba is pushing through the post-combustion carbon dioxide capture because it can be employed in rather short period and applied for both retrofit and new power plants. In this work, we evaluated the seven amine-based absorbents as new solvents, which was selected from about 900 amines, in terms of energy consumption for CO2 desorption using a thermodynamic absorption and desorption cycle simulation. We estimated the consumed energy in the stripper when the flue gas contains 12 % CO2 and the capture ratio of CO2 from the flue gas is 90 %. It was found that the lowest energy consumption in the stripper was about 2.5 GJ/t-CO2 when one mixed amine-based aqueous solution (Toshiba Solvent 2, TS-2) was used as the solvent. The value was much lower than that for the general 30 wt. % monoethanolamine (MEA) aqueous solution. And it is lower than our former solvent (Toshiba Solvent 1, TS-1) which was presented at GHGT-9. Then we evaluated the new solvent TS-2 using the bench-scale test facility which contains a complete absorption/desorption process with the absorber and the stripper. At this test TS-2 showed lower consumed energy, less than 2.5 GJ/t-CO2, by optimizing the space velocity of the simulated flue gas and so on, while TS-1 showed about 2.7 GJ/t-CO2 which is nearly equal of the value of the thermodynamic simulation. Parallel to these activities the pilot plant of 10 t-CO2/day recovery was constructed and commenced in September 2009 with a complete absorption/desorption supplied with the flue gas of a coal fired power plant. In the demonstration tests CO2 capture ratio and captured CO2 rate exceeded the planning values of 90% and 10t-CO2/day each during continuous 3,000 hour operation. Furthermore the energy consumption for CO2 recovery at the stripper had been kept between 3.2 and 3.3 GJ/t-CO2. These results prove that Toshiba CO2 capture system using TS-1 solvent is a promising system which has been realizing good and stable performances. Toshiba will utilize the results of these studies to further improve and optimize the performance of the system, towards implementation and integration of the system to a larger scale thermal power plant system. (C) 2011 Published by Elsevier Ltd.