As an alternative to gasoline, bioethanol can be produced from lignocellulosic biomass through hydrolysis using an ionic solution containing zinc chloride (ZnCl₂). This method allows for a high yield of glucose from lignocellulose, but entails the removal of ZnCl₂ from the hydrolysate using multiple nanofiltration membranes before the fermentation of glucose. This paper presents a mathematical technique for designing such a multistage membrane separation system. The optimization model for the synthesis of membrane networks is based on a superstructure with all feasible interconnections between the membrane units, and consists of mass balances, logical constraints and product specifications. A case study of the separation of a bagasse hydrolysis solution is used to demonstrate the application of the proposed model. Results show that using both types of nanofiltration membranes allows higher ZnCl₂ removal ratios at each membrane unit, hence a decrease in the number of membrane units required and a reduction of about 35% in capital cost compared to the cases in which only one membrane type is used. Further analysis is performed to examine the effect of membrane performance on the economics of the separation system.

中文翻译：

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基于上层结构的水解糖膜净化系统的优化设计

作为汽油的替代物，可以使用含有氯化锌（ZnCl ₂）的离子溶液通过水解由木质纤维素生物质生产生物乙醇。该方法可以从木质纤维素中获得较高的葡萄糖产量，但需要去除ZnCl ₂在葡萄糖发酵之前，使用多个纳滤膜从水解产物中分离得到。本文提出了一种设计这种多级膜分离系统的数学技术。膜网络合成的优化模型基于上部结构，其中膜单元之间具有所有可行的互连，并且由质量平衡，逻辑约束和产品规格组成。以甘蔗渣水解液分离为例，证明了该模型的应用。结果表明，使用两种类型的纳滤膜均可获得更高的ZnCl ₂与仅使用一种膜类型的情况相比，每个膜单元的去除率高，因此所需膜单元的数量减少，并且投资成本减少约35％。进行进一步分析以检查膜性能对分离系统经济性的影响。