高效节能型生物质水解糖液浓缩纯化综合过程研究

The production of bioalcohols from straws has been recognized as an effective means to address today's global energy issues, however its industrial process is severely restricted by low sugar yield rate，low sugar concentration, impurities-inhibition to fermentation, high energy consumption, and huge amount of wastewater. Based on our preliminary work that used multiple-effect membrane distillation (MEMD) to concentrate aqueous sugar solution in a high-efficient and energy-saving way, the theoretical and experimental study will be carried out on the separation，purification and enrichment of the sugar/acid solution obtained from the biomass hydrolysis，by integrating various energy-saving methods including ion retardation, liquid-liquid extraction and MEMD. It will be emphatically studied to remove fermentative-inhibition impurities including organic acids, aldehydes and phenols from the sugar solution，and to recover and reuse the inorganic acid used as the catalyst during the straw hydrolysis. As a feasible approach, it can effectively solve the critical problems such that sugar loss，acid loss，too low concentration of sugar solution used for fermentation, impurity-inhibition to fermentation, high energy consumption during distillation, and causing large amount of effluent. The situation of low efficiency, high energy consumption and high sugar-lost rate during the removal of impurities by using traditional method should be much improved, which would provide a new idea and a novel approach for the high-efficiency production of bio-alcohol from straws.

秸秆制燃料乙醇/丁醇被公认为解决全球能源和环境等问题的有效方式，但其生产过程中仍存在糖得率低、糖液浓度低、杂质抑制发酵、能量消耗高和废水产量大等一系列问题，从而制约了其工业化发展。本课题在我们首次运用高效节能的多效膜蒸馏技术用于糖水溶液深度浓缩的基础上进一步进行理论和实验研究。利用多种高效节能型技术包括离子阻滞、液液萃取、多效膜蒸馏等相结合的方式对中低浓度酸催化所得水解糖/酸液进行分离、纯化、浓缩处理，着重研究水解糖液中的酸类、醛类和酚类等发酵抑制物的脱除规律，探究无机酸回收利用的可行性; 有效解决水解糖液后处理过程中糖损失、酸损失，发酵液中糖浓度过低、杂质抑制发酵、精馏过程能耗高、废水产量大等关键问题; 突破传统法生物质水解糖液中抑制物脱除的低效率、高能耗、可发酵糖损失率高等缺陷，为秸秆制生物乙醇或丁醇的高效生产提供一种新思路和新手段。

秸秆制燃料乙醇是缓解能源危机和环境压力的有效方式之一。本项目着重研究解决生物质转化过程中糖酸分离、产物抑制等关键科学问题，以及设备能耗高、酸催化剂无回收等技术瓶颈问题。主要研究成果如下：.提出了一种高效利用玉米秸秆的绿色工艺，利用离子阻滞、多效膜蒸馏等多种高效节能型技术相结合的方式对秸秆酸水解液进行分离、纯化和浓缩处理，有效解决了水解糖液后处理过程中糖损失大、酸损失大、发酵液中糖浓度过低、杂质抑制发酵等关键问题。由于预处理过程有效分离了秸秆中的纤维素、半纤维素和木质素，故还可以充分利用半纤维素和木质素制备糠醛、酚类或其他高附加值化学品。.系统地研究了离子阻滞过程用于水解液的糖酸分离，研究发现该过程不仅能够有效分离水解液中的糖和酸，还能够脱除水解液中大部分的发酵抑制物，而且糖酸的回收率也保持在较高水平，最高可达99%以上。.系统地研究了多效膜蒸馏过程用于非挥发性溶质水溶液的浓缩。建立了温差极化、浓差极化影响下多效膜蒸馏过程用于非挥发性溶质水溶液浓缩过程的传热传质理论模型，建立的理论模型可很好地描述多效膜蒸馏浓缩非挥发性溶质水溶液过程中的性能变化规律。研究发现该过程能够有效实现水解糖液和酸液的浓缩和回收，在模拟秸秆水解液的浓缩过程中还发现该过程能够脱除大部分的挥发性抑制物。.验证了以所得浓缩水解糖液为碳源进行乙醇发酵的可行性，最终得到与对照组（葡萄糖为碳源）实验结果相近的乙醇产量和得率，为酸解法秸秆制乙醇的高效生产提供了一定的基础数据。.另外，针对液体硫酸直接催化高酸值油脂生产生物柴油过程中存在的酸催化剂难以回收利用的问题，提出一种新的研究思路用于分离甘油相中的甲醇、甘油和硫酸，并采用多效膜蒸馏过程分别进行催化剂硫酸和副产品甘油的脱水浓缩回收，有效提高了生物柴油生产的经济性和环保效益。