二氧化碳回收再利用技術之製程研究 : 二甲醚與碳酸乙烯酯

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Title:	二氧化碳回收再利用技術之製程研究 : 二甲醚與碳酸乙烯酯
Other Titles:	Process research on the recovery and utilization of carbon dioxide : dimethyl ether and ethylene carbonate
Authors:	徐明煌;Hsu, Ming-Huang
Contributors:	淡江大學化學工程與材料工程學系碩士班陳錫仁;Chen, Hsi-Jen
Keywords:	二氧化碳回收再利用;二氧化碳捕獲;二甲醚製程;碳酸乙烯酯製程;Recovery and Utilization of Carbon dioxide;CO2 Capture;Dimethyl Ether;Ethylene carbonate
Date:	2016
Issue Date:	2017-08-24 23:49:36 (UTC+8)
Abstract:	工業革命以來，溫室氣體大量的排放造成了全球暖化，溫室氣體中的二氧化碳更是造成全球暖化的主因之一，因此二氧化碳回收再利用的技術也成為各先進國科技發展的主要方向。本研究的目的在回收二氧化碳為原物料，藉以產製高經濟價值的化學品：二甲醚 (DME) 與碳酸乙烯酯程 (EC)。針對兩種化學品之製造進行程序合成與設計，最後並進行製程內部之熱能整合。值得一提的，研究中並針對二甲醚製程的分離段所排放的高濃度二氧化碳進行MEA (單乙醇胺) 的吸收設計。二甲醚製程分成兩個部份，第一部份為甲烷乾式重組反應製造合成氣，第二部份則為合成氣製造二甲醚之程序。首先經由程序軟體Aspen Plus的敏感度分析後，吾人採用的反應器操作條件為：(1)甲烷乾式重組反應之操作條件：進料比為二氧化碳/甲烷 = 1.2、操作壓力1.3 bar、反應器之入口進料溫度為900℃；(2)二甲醚製程反應器的操作條件：操作壓力為40 bar，操作溫度為200℃。二甲醚程序以年產量為19萬噸純度達99.5 mol%的二甲醚為設計目標，進料為甲烷與二氧化碳，先經乾式法反應生成合成氣後，再經由單階段反應合成二甲醚。分離程序中之蒸餾塔皆利用吾人提出的「蒸餾塔設計三步驟」做節能設計，最後並對二甲醚整廠進行熱能整合。在MEA 的吸收設計中，採用兩座蒸餾塔進行二氧化碳的捕獲，分別為二氧化碳之吸收塔與二氧化碳之氣提塔，以二氧化碳回收率達99%、純度達99 mol%為設計目標。碳酸乙烯酯之製程亦分成兩個部份，第一部份為環氧乙烷之合成反應，第二部份則為碳酸乙烯酯之合成反應。碳酸乙烯酯製程的反應器操作條件亦先利用Aspen Plus中的敏感度分析，決定出最後之操作條件為：操作壓力為98 bar，操作溫度為100℃，二氧化碳/環氧乙烷之反應器入口進料比為1.8的狀態下進行反應。碳酸乙烯酯程序是以年產量為1.5萬噸、純度為99.5 mol%的碳酸乙烯酯為目標。碳酸乙烯酯是以環氧乙烷與二氧化碳作為原物料，因此在進行碳酸乙烯酯的合成之前，須先以乙烯氧化程序，製得99.5 mol%的環氧乙烷，再將部分環氧乙烷與二氧化碳反應產生碳酸乙烯酯。最後並針對碳酸乙烯酯整廠進行熱能整合設計。本論文中甲烷乾式重組反應器與環氧乙烷反應器以化工動力學為基礎，而二甲醚反應器與碳酸乙烯酯反應器則以化工熱力學為基礎進行模擬。製程主要使用 “Aspen Plus” 與 “SuperTarget” 兩種化工程序軟體；前者用於程序合成與設計，後者則用於狹點分析及換熱器網路合成。 Since the Industrial Revolution, more and more greenhouse gases have been released into the atmosphere and resulting in global warming. The technology to recover and utilize CO2 has become an ever important technique the worldwide. The aim of this study is to transform the recovered CO2 into high-value-added chemicals: dimethyl ether (DME) and ethylene carbonate (EC). It is noteworthy that in the study we also design an MEA absorption unit to recover CO2 flue gas in the DME process. The DME process consists of two sections: one is the dry methane reforming process, the other is the dimethyl ether synthesis. Having carried out the sensitivity analysis using Aspen Plus software for the process, we are able to select the reactor operation conditions: (1) dry methane reforming: feed temperature is set at 900oC, feed pressure is set 1.3 bar and the feed ratio of carbon dioxide to methane is 1.2:1; (2) DME synthesis: pressure is set at 40 bar and temperature is set at 200℃. The DME process simulates a plant capacity of 190,000 metric tons per year of 99.5 mol% purity of dimethyl ether. To minimize the reboiler’s heat duty for the distillation towers in the DME process, we used a “three-step design procedure” for energy savings. In addition, pinch technology is used to heat-integrate the plant-wide DME synthesis. Ultimately, we also simulate the CO2-capture process which targets at 99% of recovery and 99 mol% of CO2 concentration. Note that there are two towers in the capture process: an absorber and a stripper. The EC process also consists of two sections: the first is to produce ethylene oxide (EO) and the second is the ethylene carbonate synthesis. Similarly, we are able to select the EC reactor operation conditions according to the sensitivity results in using Aspen Plus: pressure is set at 98 bar, temperature is set at 100℃ and the feed ratio of carbon dioxide to ethylene oxide is 1.8. We used the ethylene oxidation process to produce 99.5 mol% of ethylene oxide (EO). Then parts of EO flows into the EC reactor and reacts with CO2 to obtain 99.5 mol% of ethylene carbonate. The capacity of this EC process is 15,000 metric tons per year. Similarly, the pinch technology is also applied to heat-integrate the plant-wide ethylene carbonate synthesis. It should be mentioned that, in this thesis, the methane dry reforming and the EO reactors system are designed on the basis of the chemical kinetic principle, and both of DME and EC reactors system are based on the chemical thermodynamic principle. Two kinds of software are utilized in the research－Aspen Plus and SuperTarget. The first is applied to implement the process synthesis and design; the second is applied to perform the pinch analysis and the synthesis of heat exchanger network.
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