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  • 學位論文

結晶程序之設計、控制、最適化與經濟分析

Design, control, optimization, and economic analysis of crystallization processes

指導教授 : 吳哲夫

摘要


本論文主要探討批式結晶程序之設計與最適化、連續式結晶程序之設計與控制、及各類結晶程序之經濟分析。 基於硫酸鋇與谷氨酸之案例,本論文描述批式反應結晶之操作策略與設計概念,並使用晶種與批式操作曲線對不同的目標函數進行最適化。結果顯示使用晶種能有效抑制谷氨酸之成核,而硫酸鋇則較無效果;早期的成長曲線能最小化硫酸鋇之成核,而晚期的成長曲線則能最小化谷氨酸之成核,其中的不同皆因兩案例之長晶速率與成核速率不同所致。 本文亦探討連續式反應結晶控制架構以及穩定操作區間之設計。結果顯示,以流量控制晶體產量,並以液位高度控制晶體粒徑分布而架設以IMC方法調整參數後之PI控制器,此控制架構能有效處理10%擾動變數及設定點之改變。而穩定操作區間之決定亦十分重要,對硫酸鋇而言,持續震盪的區間相對不明顯,但對谷氨酸來說其區間較明顯而需特別注意,穩定操作區間係由長晶速率對過飽和度之敏感度與成核速率對過飽和度之敏感度決定。 此外,本文呈現多孔性疏水膜結晶、逆滲透膜結晶、共熔冷凍結晶程序之設計,並與傳統蒸發結晶程序做比較。基於氯化鉀與己二酸之案例,分為小規模批式程序(產量2×105 kg/yr)及大規模連續式程序(產量2×107 kg/yr),並分別考慮是否有低成本之廢熱源做能量來源之情況。結果顯示,當無低成本熱源時,逆滲透膜結晶程序最為經濟,因其程序無須提供相變化所需潛熱。然若結晶系統在操作濃度下之逆滲透壓超出逆滲透膜可承受範圍,則一個先將進料用逆滲透膜濃縮過後再接續共熔冷凍結晶之程序將是最為經濟。當有低成本熱源可用時,傳統單效蒸發結晶程序則最具優勢。除了逆滲透壓之限制,此經濟分析與結晶產品之物理化學性質較無關聯,其成本幾乎只由質量平衡所算出之除水量有關,故本研究成果對大部分結晶系統皆適用。

並列摘要


This thesis is concerned with the design and optimization of batch crystallization processes, the design and control of continuous crystallization processes, and the economic analysis of several types of crystallization processes. Conceptual methods are illustrated for the development of operating policies for batch reactive crystallization processes using barium sulfate and L-glutamic acid production process as case studies. The method of optimizing several objective functions by seeding policy and operation trajectory of batch crystallization process is presented. The control structure and stable operation region of continuous reactive crystallization process is determined, which provides good performance under 10% disturbance and set point changes and guidelines for designing operating zone of continuous crystallization processes. Several types of crystallization have attracted researcher’s attention as alternatives to conventional evaporative crystallization. The processes for hydrophobic membrane, reverse osmosis membrane, and eutectic freeze crystallization are designed and costs are compared with those of conventional multiple-effect vacuum evaporative crystallization processes. Two process scales, a small-scale batch process (2×105 kg/yr) and a large-scale continuous process (2×107 kg/yr), and two chemical products, potassium chloride and adipic acid, are considered. Finally, the situation where free or low-cost waste heat is available is also considered. When waste heat is not available, reverse-osmosis processes are shown to be the least expensive because the pumping costs, while significant, are more than offset by the fact that it is not necessary to provide the enthalpy of vaporization or enthalpy of crystallization of the solvent. If the osmotic pressure of a saturated solution of the solute exceeds the feasible operating pressure of a RO membrane, then the least expensive process alternative is to concentrate the feed up to the osmotic pressure limit using RO membranes and then remove the remaining water by a eutectic freeze crystallization process. When waste heat is available, a single-stage conventional evaporation process is favorable because it can also be powered by the waste heat and does not require the capital cost for the membranes. With the exception of the osmotic pressure limitation, the economics of the design alternatives do not depend strongly on the physical and chemical properties of the substance to be crystallized. The capital and operating costs depend almost entirely on the amount of water that must be removed, which is determined completely by an overall material balance. Therefore the results developed in this work are likely to be applicable to most crystallization processes. Although porous hydrophobic membranes were never found to be the lowest-cost alternative, they may offer advantages such as reduced equipment size.

參考文獻


[24] L.D. Shiau, T.S. Lu, Programmed cooling of a batch crystallizer in the presence of growth rate dispersion, J Chin Inst Chem Eng, 35 (2004) 677-682.
[1] C. Wibowo, W.C. Chang, K.M. Ng, Design of integrated crystallization systems, Aiche J, 47 (2001) 2474-2492.
[2] D. Jagadesh, N. Kubota, M. Yokota, A. Sato, N.S. Tavare, Large and mono-sized product crystals from natural cooling mode batch crystallizer, J Chem Eng Jpn, 29 (1996) 865-873.
[3] N. Doki, N. Kubota, A. Sato, M. Yokota, O. Hamada, F. Masumi, Scaleup experiments on seeded batch cooling crystallization of potassium alum, Aiche J, 45 (1999) 2527-2533.
[4] N. Doki, N. Kubota, A. Sato, M. Yokota, Effect of cooling mode on product crystal size in seeded batch crystallization of potassium alum, Chem Eng J, 81 (2001) 313-316.

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