化學溶劑吸收再生法回收廢氣中二氧化碳之溶劑使用成本分析

Abstract

本研究針對處理廢氣中二氧化碳所使用的各種醇胺溶劑之溶劑使用成本分析，研究考慮溶劑消耗成本及再生熱成本，並假設SOx濃度對溶劑之二氧化碳去除效率影響很小。 研究結果顯示，影響二氧化碳吸收溶劑成本之關鍵因子以SOx濃度的影響最大，其也影響最佳溶劑之選擇；其次為再生熱能成本，尤其是在低SOx濃度下，再生熱能佔整個溶劑使用成本的比例最大，惟其值只隨溶劑之組成不同才有所改變。當SOx濃度高(如500 ppm)時，30%MEA為最具經濟效益之醇胺溶劑，其溶劑使用成本為1.97 kTWD/tonne-CO2，此時之去除率約95%；若SOx濃度在54ppm以下時，則溶劑受SOx毒化之影響較不顯著，此時使用18%MEA+12%AMP應較為經濟；而SOx濃度若能降低至10ppm時，則18%MEA+12%AMP之溶劑使用成本可降低至0.87 kTWD/tonne-CO2，此時之去除率約90%。因此廢氣之淨化前處理效果將為決定最佳醇胺溶劑，以降低分離回收二氧化碳成本之主要影響關鍵。 此外本研究亦進行非醇胺溶劑之溶劑使用成本評估，由於NaOH-CaO再生法及氨水再生法不受SOx濃度所影響，又加上價格低廉，使NaOH-CaO再生法之溶劑使用成本可低至0.9 kTWD/tonne-CO2，而氨水再生法之溶劑使用成本可低至0.5~0.72 kTWD/tonne-CO2，因此以非醇胺溶劑來回收煙道氣中二氧化碳具有相當高之應用潛力。但本研究係採用非醇胺之理論熱能損耗來得到溶劑使用成本，因此未來研究需探討實際之再生熱損耗，以了解其實際應用價值。

This study aimed at solvent utilization costs by chemical absorption of carbon dioxide recovery from flue gas. Both of the solvent consumption costs and the heat of regeneration costs are principal items to affect solvent utilization costs. The costs are estimated based on the assumption that influence of SOx concentration (under 500 ppm) on CO2 removal efficiency are negligible. The results show that the concentration of SOx, the solvent purchase price, and the L/G ratio are the major factors influence the solvent utilization costs. Using 30%MEA as the chemical solvent appears to be the most economical amine at high SOx concentration (as 500 ppm), it’s solvent utilization costs is 1.97 kTWD /metricton-CO2 at removal efficiency of about 95%. When the SOx concentration is lower than around 54 ppm, the solvent consumption by SOx poison is less significance and 18%MEA+12%AMP appears to be more economical than 30%MEA. If SOx concentration can be reduced to 10 ppm, the solvent utilization costs of 18%MEA+12%AMP can be reduced to 0.87 kTWD/metricton-CO2, at 90% CO2 removal efficiency. Therefore, the best amine solvent will be determined by the pretreatment of flue gases to remove SOx and other gases that may poison the chemical solvent. The solvent utilization costs of non-amine solvent is estimated in this study also. Due to NaOH-CaO and ammonia regeneration methods are not affected by SOx concentration, and they have cheaper purchase prices, the solvent utilization costs can be lower to 0.9 kTWD/metricton-CO2 for NaOH-CaO solvents,and 0.5~0.72 kTWD/metricton-CO2 for ammonia solvent. So non-amine solvents have high potential to replace amine solvent on recovery from CO2 of flue gas. But it needs to confirm their field applications.