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標題: | 二氧化碳轉化為碳酸二甲酯、碳酸二乙酯以及二甲醚之減碳與經濟效益評估 Environmental and Economic Analysis for Processes of CO2 Conversion to Dimethyl Carbonate, Diethyl Carbonate and Dimethyl Ether |
作者: | Tsai-Wei Wu 吳采薇 |
指導教授: | 錢義隆(I-Lung Chien) 錢義隆(I-Lung Chien | ilungchien@ntu.edu.tw | ), |
關鍵字: | CO2再利用,碳酸二甲酯,碳酸二乙酯,二甲醚,製程強化, CO2 Utilization,Dimethyl Carbonate,Diethyl Carbonate,Dimethyl Ether,Process Intensification, |
出版年 : | 2022 |
學位: | 博士 |
摘要: | 本研究以二氧化碳為原料,合成其他含碳之高值化產品,以探討減碳效益及經濟可行性。碳酸二甲酯與碳酸二乙酯皆具有多重功能,包含燃料添加劑、溶劑以及重要的反應中間體等,於本研究中被選擇為二氧化碳轉化產品;另考量到替代能源的發展迫切性,此研究亦探討二氧化碳轉化為二甲醚的製程。本研究於製程模擬之前皆有針對熱力學模型與反應動力式模型進行驗證,接著進行嚴謹的製程單元模擬、製程最佳化、製程強化技術應用及熱整合,並計算不同產物最佳製程之淨碳排放與經濟效益,最後為了合理評估二氧化碳轉化產品是否真的能夠對於減少大氣中碳排放有幫助,也進行了搖籃至大門(Cradle-to-gate)的生命週期碳排放分析。研究結果顯示,三種不同產物以大門至大門(Gate-to-gate, or battery limit)的範疇計算最低淨碳排放量之結果分別為:每噸碳酸二甲酯產生-0.232 噸CO2、每噸碳酸二乙酯產生 0.097 噸 CO2,以及每噸二甲醚產生-1.704 噸 CO2。經濟評估結果則顯示,碳酸二甲酯製程若要有經濟效益,則需取得合理價格的環氧乙烷,以作為反應之除水劑;碳酸二乙酯製程則由於產物及副產物丙二醇的市場價格都很不錯,計算出的投資報酬率> 100%,顯示出很高的獲利潛能;二甲醚製程的經濟效益評估結果顯示目前尚無投資利益,歸因於現階段價格仍然居高不下的原料綠氫。經濟評估最後亦納入碳稅計算,以目前美國政府所提出的45Q政策而言,每噸用於其他產品合成的CO2即使有$35鎂的補貼,亦無法對經濟評估結果產生決定性的影響,尤其是用到綠氫的二甲醚製程,其獲利關鍵仍是落在綠氫價格。三種產物的搖籃至大門生命週期碳排放分析結果分別為:每噸碳酸二甲酯產生0.841噸CO2、每噸碳酸二乙酯產生1.417噸CO2,以及每噸二甲醚產生-1.314噸CO2。與碳酸二甲酯的傳統製程碳排放量1.329相比較,證明本研究所提出之新穎性碳酸二甲酯製程相較於其商用傳統製程,每生產一噸碳酸二甲酯能夠節省36.72%碳排放,若能夠使用新穎製程取代傳統製程,的確能夠對於邁向淨零碳排的社會有所助益;二甲醚製程的生命週期碳排放分析也顯示,若是使用綠氫作為其原料,本研究所提出之製程每製造一噸二甲醚即可消耗1.314噸二氧化碳,若未來綠氫的價格能夠因為技術更成熟而降低,則此二甲醚製程仍值得成為減碳技術的參考製程。 Processes of CO2 converting to other valuable products were investigated in this study in order to discover their ability of CO2 emission mitigation and economic feasibility. Dimethyl carbonate (DMC) and diethyl carbonate (DEC) are two versatile compounds, which can be used as fuel additives, solvents for Li-ion batteries, and reaction intermediate. Thus, they were chosen as the products of CO2 conversion in this work. Moreover, considering the urgency of developing alternative fuels, processes of CO2 converting to dimethyl ether (DME) have also been studied. To rigorously simulate the chemical processes, thermodynamic models and reaction kinetic models were validated before the simulation of the plant-wide processes. Subsequently, rigorous simulation of process units, optimization of operating and design variables, application of process intensification, and process heat integration were executed. Performances of CO2 emission mitigation for each product were evaluated by calculating their gate-to-gate (or battery limit) process net CO2 emission, and the results showed that the lowest net CO2 emission for each product is as follows: -0.232 ton CO2/ton DMC, 0.097 ton CO2/ton DEC, and -1.704 ton CO2/ton DME. From the results of economic analysis, DMC production process is only economically attractive when the price of dehydrating agent EO is reasonable. DEC production process shows great potential economically because of the higher price of products DEC and PG, resulting in ROI > 100%. As for DME process, there is no economic interest under the current circumstance of the extremely high price of the raw material – green hydrogen. Carbon tax credit was considered in the procedure of economic analysis; unfortunately, no decisive changes can be made for all products discussed in this work by introducing a credit of $USD 35/ton CO2 utilized based on the 45Q policy proposed by the US government. In the case of producing DME, the key to making profit still lies in the price of green hydrogen. Last but not least, cradle-to-gate carbon emission had been analyzed to reasonably evaluate the effect of carbon emission mitigation throughout the life cycle of the products, and the results are as follows: 0.841 ton CO2/ton DMC, 1.417 ton CO2/ton DEC, and -1.314 ton CO2/ton DME. Compared to cradle-to-gate carbon emission of the commercial and conventional process of DMC production (1.329 ton CO2/ton DMC), the novel process proposed in this study emits 36.72% less CO2 per unit production of DMC. Therefore, by substituting the novel process for the traditional transesterification process, it will be beneficial for achieving a society with net-zero emissions. This life-cycle carbon emission analysis has also shown that the proposed novel DME process in this study can consume 1.314 tons of CO2 per ton of DME production. Such a prominent effect in CO2 emission mitigation should be taken into consideration in the long-term development of CO2 utilization, under the premise of a more reasonable price of green hydrogen along with matured electrolysis technology. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/86257 |
DOI: | 10.6342/NTU202202953 |
全文授權: | 同意授權(全球公開) |
電子全文公開日期: | 2022-09-02 |
顯示於系所單位: | 化學工程學系 |
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