以混合醇胺溶液(MEA+AMP)吸收二氧化碳之填充式吸收塔設計及成本評估

Abstract

CO2的分離回收技術主要包括化學溶劑吸收法、物理吸附法、冷凍分離法、膜分離法、生物固定法及氧氣與CO2燃燒的排氣直接回收法等。在眾多分離回收技術當中，以化學溶劑吸收法的技術最多也最成熟。其中又以醇胺溶劑來去除CO2之應用最廣泛。 本研究分成三個主要部分，包括吸收塔之連續流實驗、吸收塔設計以及吸收塔成本之估算。在連續流實驗方面，以改變進流氣體流量及吸收液流量等參數，藉此求出不同溫度條件下總質傳係數之經驗式與液氣比。在填充塔設計方面，利用實驗所得結果，由總質傳單位高度(HTU)之觀念，設計吸收塔填充高度，而使用氾濫曲線(flooding line)求得吸收塔直徑。在成本分析方面，利用設計參數可求取吸收塔總設置成本及去除每噸二氧化碳所需之成本。 研究結果顯示，操作溫度越高時CO2吸收效率越佳，但溫度過高(>40℃)時則會出現反效果。而在操作溫度35℃下，液氣比由1.5增至4.5(ml/l)時，二氧化碳去除率由50％增加為98％。本研究亦由實驗結果回歸求得總質傳係數回歸式。在廢氣風量由200增加至1000 m3/min之間，吸收塔直徑設計值約由1m增加至5m，填充高度則由5m增加30m。而成本評估之結果顯示，在風量大於200 m3/min，去除每噸二氧化碳之價格漸趨穩定，其值約為20至40美元左右。

There are various technologies used to separate CO2 from stack gas. These include chemical solvent methods, physical adsorption methods, cryogenic methods, membrane systems, biological fixation and O2/CO2 combustion process. The chemical solvent methods are generally recognized as the most efficient technologies at present. This study aims at a design of the packed tower using mixed amines solution for scrubbing CO2. The research work includes three main parts: continuous flow experiments, packed tower design and cost evaluation. In continuous flow experiments, a mixed MEA/AMP solvent with ratio of 18/12(% wt / % wt) was used to obtain performance data that are required for the packing tower design. In packed tower design, packed height and diameter of tower were calculated by theory of height of transfer units (HTUs) and flooding concept. The cost of a full-scale packed tower was then evaluated and the costs of a packed tower as well as the marginal cost of CO2.removal were presented. The results indicate that the CO2 removal increases with an increase of operation temperature when operated bellow 40℃. At 35℃, the CO2 removal changes from 50% to 98% for the L/G ratios from 1.5 to 4.5 (ml/l). The overall mass transfer coefficient was obtained from a regression analysis of the experiment data and used for the design of packed tower. It is show that at gas flow rate between 200 and 1000 m3/min, design values of packing height range from 5 to 30 m, and diameter of tower are from about 1 to 5 m. The costs per ton of CO2 removal are about 40 to 20 U.S.D. at the gas flow rates between 200 to 1000m3/min. Keywords: greenhouse affect, packed tower, MEA, AMP, alkanolamines, absorber, cost evaluation.