各類煤炭氣化多聯產化學品程序之設計、最適化與經濟分析

Design, Optimization and Economical Evaluation of Coal-based Poly-generation Process to Produce Chemicals

余柏毅(Bor-Yih Yu)

指導教授 ： 錢義隆

國立臺灣大學/工學院/化學工程學研究所/博士(2017年)

https://doi.org/10.6342/NTU201701683

摘要

本研究旨在探討各類煤炭氣化以多聯產製化學品的製程設計、最適化與經濟評估研究。由於國內缺少能源來源，因此逾98%的能源來源仰賴進口。而煤炭價格便宜、全球存量豐、且易於運送，因此為國內最主要的能源來源之一，未來煤炭在國內仍將扮演重要的角色。
氣化過程為此類研究的核心，而本研究以此為起點。首先，本研究提出一維的氣化爐模型，探討煤炭與生質能源在不同條件下的操作情形。接續探討的是煤炭氣化以合成天然氣生產程序、以及合成天然氣與氨的多聯產生產與操作。由於進口天然氣需要經過壓縮與液化等步驟，導致價格昂貴(11.3~11.7 USD/MMBTU)，因此由煤炭以產合成天然氣頗具經濟效益(10.336 USD/MMBTU)。若以多聯產的方式生產，則可提升經濟效益，但若其中一產物的產量相對過小時，經濟效益的提升即不明顯。
再來探討的是新穎的甲醇產製烯烴程序的整廠製程，以產製乙烯與丙烯產物為主要目標。本研究針對此程序進行完整嚴密的模擬，並仔細探討各個變數所造成的影響。由於丙烷與丙烯沸點相近，不易分離，因此本研究亦特別針對丙烷與丙烯分離系統進行探討。所探討的分離方法有以下四種，分別為使用蒸氣作熱源的傳統單塔分離、使用熱廢水作熱源的傳統單塔式分離、利用蒸氣再壓縮循環做熱整合的傳統單塔式分離、以及利用乙腈溶液作挾帶劑的萃取蒸餾分離。分析結果得知使用熱廢水作熱源的傳統單塔式分離、以及萃取蒸餾分離皆能大幅改善成本以及分離使用的塔板數目。
本文最後探討的合成氣產製乙二醇程序的設計與最適化。此程序包含兩階段，第一階段為將合成氣中一氧化碳轉化為草酸二甲酯，第二階段則將草酸二甲酯氫化成乙二醇。於第一階段中，甲醇於系統中的循環量為最具決定性的變數，其主要由填充床反應器進料中，甲醇與一氧化氮及二氧化氮的總和之莫耳比例(MeOH/NOs)來影響。於第二階段中，最重要的變數為混合進料中氫氣與草酸二甲酯莫爾進料比(HDMR)。
總括而言，本文針對各類煤炭氣化的下游化學品生產程序進行的完整與嚴密的模擬，輔以最適化、熱整合、經濟與能量分析，以仔細探討各程序的內部行為。透過本研究，對於此類程序有了更透徹的了解。

關鍵字

煤炭氣化 ； 多聯產 ； 合成天然氣 ； 甲醇製烯烴 ； 乙二醇 ； 設計與最適化 ； 經濟分析

並列摘要

In this work, the design, optimization, and economic evaluation of coal-based poly-generation processes to produce different kind of chemicals are investigated. We lack energy sources in Taiwan, thus over 98% of the energy sources come from importation. Among those energy sources, coal has several advantages such as its relative low proce, abundance, and easy transportation. Therefore, coal has been one of the most important energy sources in Taiwan, and it is expected that its role will be retained in the future.
Gasification is the center of this kind of processes, which is also the starting point of this work. Firstly, a 1-dimension gasifier model is established to investigate the gasification performance of coal or biomass under different operating conditions. After that, the coal-to-synthetic natural gas (SNG) and coal-based poly-generation process to produce SNG and ammonia are followed. Because importation of natural gas required liquefaction and compression, thus the importation price is quite expensive in Taiwan (11.3~11.7 USD/MMBTU). Thus, converting coal into SNG can be economically attractive (10.336 USD/MMBTU). If the poly-generation configuration is adopted, the economic performance can be further enhanced. But the enhancement of economic performance may be not obvious once one of the product flowrate is too small.
The next topic to investigate is the novel methanol-to-olefin (MTO) process, and the main products are ethylene and propylene. In this work, the rigorous simulation of this process is studied, and the influences from variables are carefully investigated. Besides, due to the close boiling point between propylene and propane, separating them through distillation is not easy. Thus, four method for separation propane with propylene are studied. They are traditional single-column separation using steam as the heat source (case 1), using waste hot water as the heat source (case 2), distillation with the vapor recompression cycle (case 3), and the extractive distillation using acetonitrile solution as the entrainer (case 4). From the results, it is found that case 2 and case 4 may be economically attractive.
The final topic is the syngas-to-ethylene glycol (EG) process. There are two stages in this process. In the first stage, CO in syngas is converted into dimethyl oxalate (DMO) as an intermediate, while in the second stage, DMO is hydrogenated to become EG. In the first stage, the circulation rate of methanol inside the process is the most important one. It is mainly determined by the ratio of methanol to the combined nitric oxide and nitric dioxide flowrate into the packed-bed reactor. In the second stage, the most influential variable is the molar ratio of hydrogen and DMO in the combined feed.
In short, many coal-based poly-generation processes for producing chemicals are rigorously studied in this work. The analysis methods include optimization, heat integration, economic and energetic evaluation. Through this work, a better understanding toward these processes can be obtained.

並列關鍵字

Coal Gasification ； Poly-generation ； Synthetic Natural Gas (SNG) ； Methanol-to-Olefin ； Ethylene Glycol ； Process Design and Optimization ； Economical Evaluation

參考文獻

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