Potential of Amine-based Solvents for Energy-saving CO_2 Capture from a Coal-fired Power Plant

摘要

The potential of amine-based solvents was investigated by a thermodynamic analysis for low-energy CO_2 capture from the flue gas of a thermal power plant. The solubility of CO_2 into the amine-based solvent was predicted by the vapor-liquid equilibrium model on the basis of absorption reactions between CO_2 and amine. The model was covered for developed and developing amine-based solvents. Considering the energy consumptions of CO_2 capture and compression, the power output of the coal-fired power plant with a post-combustion CO_2 capture was estimated. The results showed that the solvent characteristics of high CO_2 cyclic capacity and low absorption heat had an important effect on reducing the thermal energy requirement for CO_2 capture. In the case of CO_2 capture from a 12% CO_2-containing flue gas, the lowest thermal energy requirement was estimated at approximately 2 GJ/ t-CO_2， and the efficiency penalty of power generation was reduced to 7.2%pt. Also, concerning the impact of CO_2 capture and compression on the power generation system, l%pt. of power generation efficiency could be recovered by lowering 0.6 GJA-CO_2 of the thermal energy requirement of CO_2 capture. These results mean that the amine-based solvents still have high capability to improve energy performance of post-combustion CO_2 capture. However, lowering the regeneration temperature in the range of 90 ℃ to 130 ℃ did not have a significant advantage in reducing energy consumption. This comprehensive analysis for the CO_2 capture and compression integrated with a coal-fired power plant is useful for process evaluation, and the desire will be to extend the analysis to other applications.%アミン吸収液による火力発電所燃焼排ガスからのCO_2分離回収について，所要エネルギ—削減に向けたアミン系吸収液の可能 性を検討した。具体的には，アミン系吸収液のCO_2溶解度をCO_2吸収反応をもとに気液平衡をモデル化し，CO_2分離回収プロセ スおよびCO_2回収型石炭火力発電システムを対象にエネルギー収支を解析した。その結果，CO_2分離回収の所要熱エネルギーの削減には吸収液のCO_2回収容量や吸収熱を小さくすることが効果があった。また，CO_2濃度1296の燃焼排ガスに対して，所要 熱エネルギー2 GJ/t-CO_2の可能性が示され，その場合の発電効率の低下は7.296pt.となった。CO_2回収型発電システムに対する CO_2分離回収の影響は,化学吸収液の所要熱エネルギーを0.6 GJ/t-CO_2下げることにより,発電効率をl%pt改善することができる。 これら結果は化学吸収液の更なる高性能化の可能性を示している。一方，吸収液の再生温度については90℃〜130℃の範囲にお いて発電効率への影響は小さかった。今回の解析手法はCO_2回収技術の実施に向けた検討に有益であり，様々なCO_2排出源へ の展開が期待できる。