乙醇发酵过程模型及模拟优化研究进展

综述了乙醇发酵模型及模拟方面的研究,总结了各种模型的特点以及模拟的难点.Monod方程能较好地描述乙醇发酵的各种竞争性抑制作用,模拟的难点在于模型的优化求解;反应器中的乙醇发酵模型包括传质模型,模拟的难点在于采用总传质系数简化求解过程,并涉及非稳态平衡计算;纤维素发酵是大量制取廉价乙醇的方向,发酵模型中需综合考虑酶解、发酵及抑制作用等,模拟计算过程复杂.结果说明,对发酵过程进行模拟优化,是降低乙醇生产成本、促进乙醇大规模工业化生产的有效途径.提出乙醇发酵模型模拟方面的发展方向为:解决纤维素发酵的关键问题,并形成应用软件,有利于后续工业化中的优化控制等过程.     

自絮凝颗粒酵母表观生长动力学

首先利用激光聚焦反射颗粒测量系统在线监测了自絮凝颗粒酵母粒径分布,通过提高发酵罐搅拌速率减小了颗粒粒径,消除了内扩散影响,获得了本征动力学模型。进而基于颗粒内部薄壳物料衡算理论,建立了表观动力学模型,并通过不同底物浓度和自絮凝酵母颗粒粒径分布条件下发酵实验数据拟合,获得了模型的参数。在此基础上,分析了内扩散效应导致颗粒内部可能出现死区的影响,绘制了发酵培养基初始糖和自絮凝颗粒酵母粒径影响的操作图,分析了这一发酵体系的性能。结果表明对于工业生产中普遍采用的多级串联连续乙醇发酵系统,主发酵罐和后发酵罐由于残糖水平差别较大,使颗粒内部因底物枯竭而导致内扩散效应的可能性显著不同：主发酵罐适宜于较大粒径自絮凝颗粒酵母体系,以利于固定化,提高发酵罐中细胞密度和生产强度;而后发酵罐适宜于较小粒径自絮凝颗粒酵母,以减轻底物内扩散影响,保持所需的发酵活性。因此需要综合考虑工程操作和动力学行为,对自絮凝颗粒酵母粒径分布进行优化控制。     

蒸汽渗透技术在乙醇发酵原位分离耦合过程中的应用研究

利用5L发酵罐分别对乙醇流加发酵、分批发酵蒸汽渗透耦合过程和流加发酵蒸汽渗透耦合过程进行了研究,并对过程进行了优化。当发酵液中ρ(乙醇)70g/L时,乙醇产率明显减慢;相对于分批发酵,蒸汽渗透耦合可使乙醇产率提高25%;相对于流加发酵,蒸汽渗透耦合可使乙醇产率提高44%;发酵与蒸汽渗透耦合最佳料液体积与膜面积比V∶A=0.053m,一级冷凝温度为-20℃,在以上条件下,整个过程乙醇回收率可达92.80%,发酵与蒸汽渗透能够较好耦合。     

氯丁二烯精馏过程的模拟计算

本文通过选用适当的汽液平衡数学模型和根据实验数据回归模型参数，应用流程模拟软件对氯丁二烯精馏过程进行全面、系统的模拟计算，其计算结果与生产实际对照，经验证是正确的。该模拟计算适用于氯丁二烯精馏过程设计，也可用于工厂操作优化和工况研究等方面。     

L-赖氨酸发酵罐搅拌器的改造

针对300 m3 L-赖氨酸发酵罐搅拌器不能满足发酵工艺传质混合要求的实际情况,提出改造方案,并采用CFD软件对改造前后搅拌效果进行了数值模拟,模拟结果显示改造后的搅拌器强化了混合效果,改善了气液传质.改造后经过46批发酵实验,L-赖氨酸的糖酸转化率相比未改造发酵罐高2%,且产量更稳定.最后提出搅拌器继续改造的方向.     

玻璃纤维窑炉玻璃液流场数学模拟研究

玻璃纤维窑炉作为玻璃纤维生产最重要的热工设备之一,被称为玻璃纤维生产的心脏.为了实现玻璃液熔制的高效节能和玻璃液高质量的输出,需掌握窑炉中高温玻璃液的运动轨迹,对生产过程实现实时控制.通过对窑炉内玻璃液的流动状态进行模拟,可以在提高产品质量、节约能源、降低废物排放、提高单位产出率等方面得到优化.以年产8万t玻璃纤维窑炉玻璃液为研究对象,通过使用ANSYS软件对窑炉生产状态进行数值模拟,分析了模型中温度场分布、速度场分布和电功率场分布情况,同时计算了不同电助熔参数设置对窑炉内玻璃液温度场分布以及速度场分布的影响,结合生产实际提出了窑炉内部实际的玻璃液流动场优化情况.     

燃料乙醇生产工艺的节能减排研究

高能耗、高污染是制约燃料乙醇行业发展的主要因素。为实现节能减排,本公司对木薯燃料乙醇生产中的精馏过程进行模拟和优化,并研究了浓醪发酵工艺。优化后的精馏系统操作稳定性和能量利用率得以提高,酒精发酵醪浓度提升到18.21%,为乙醇工业生产降低能耗、节约工业用水和提高设备利用率提供科学依据,实现绿色化生产工艺。     

煤气化废水萃取脱酚过程的模拟研究与应用

煤气化含酚废水处理的达标排放一直是限制行业发展的一个瓶颈,萃取脱酚过程容易酚含量超标,而直接影响污水处理过程,为了准确模拟研究这一萃取过程,采用实际生产中的工艺参数和实验测定的水-二异丙基醚-苯酚-对苯二酚四元液液平衡数据,用Aspen软件对该过程进行了模拟,并对模拟参数进行了回归,得到了新的工艺模型。结果表明,新模型结果与实际数据误差在0.5%之内,非常准确;将模拟应用于指导工业生产,为实际生产操作和工艺改造提供了很好的技术支持。     

燃料乙醇系统模拟平台开发及应用

对典型燃料乙醇系统进行了分析,阐述了目前该系统相关全流程模拟模型的不足以及由非线性和复杂性等特征导致的系统建模难点。在此基础上,运用VC#编程工具和SQLSERVE开发了全新的燃料乙醇系统模拟平台,该平台可模拟燃料乙醇实际生产过程,能够从物质流、能量流、水流、价值流等方面对系统开展工业生态学分析。最后利用实际生产过程中出现的两个问题案例对平台进行了检验。     

用于发酵系统的减速传动装置设计探讨

在轻工和化工许多产品生产过程中,发酵是一个重要的生产过程,在带有搅拌装置的发酵系统中,发酵罐和减速传动装置是主要关键设备,由于我国旧式发酵罐用减速传动装置大部分采用三角皮带轮传动,不仅效率低,而且结构庞大,从而限制了发酵罐容积的增大。正是基于这一情况,我厂根据市场需要研制生产出了立式减速器,这些减速传动装置已广泛地用于我国许多味精相制药厂家,收到了良好的经济效益。本文将介绍这些减速器及其传动装置的设计要点。     

Continuous ethanol production by the synchronous saccharification and fermentation using food wastes

The synchronous saccharification and fermentation (SSF) by continuous fill and draw method was investigated in order to develop a continuous ethanol fermentation process using the food wastes (FW) available among Korea’s organic wastes. The activity of the hydrolytic enzymes was maintained constantly in the continuous culture by their intermittent addition together with medium exchange. The concentrations of reducing sugar in the culture were maintained at a steady state by regulating supplemented enzyme concentration and exchange rate of medium, reflecting on the consumption rate of reducing sugar caused by the fermentation. When the temperature of the SSF was maintained at the fixation of 35 °C, which enabled us to perform both enzymatic hydrolysis and enzyme fermentation simultaneously, the rate of reducing sugar consumption was 3.61 g/L-hr. For the enzymatic saccharification of FW, when 0.01 BGU as Viscozyme/g-FW and 0.05 AGU as Spirizyme Plus/g-FW were used, the production rate of reducing sugar was 3.93 g/L-hr, indicating a little higher rate of production than that of consumption. A decompression device with ethanol condensing ability was used to continuously pull out ethanol from the culture broth at −600 mmHg, where the ethanol evaporation ability would be maximized and the water evaporation minimized during the process. As a result of the continuous SSF performance, the reducing sugar concentration was maintained at around 30 g/L. The amylase activity was maintained at 8.93±2.17 U/mL. During a 352 hour culture, the whole ethanol productivity was 2.24 g/L-hr, indicating a considerable productivity compared with the other result reported in the continuous SSF.     

自絮凝颗粒酵母发酵菊芋汁生产乙醇

分别采用分批和连续发酵方式,对自絮凝颗粒酵母Saccharomyces cerevisiae flo发酵菊芋汁生产乙醇的条件进行了优化. 与先酶解菊芋汁后再用自絮凝酵母发酵的分步糖化发酵相比,分批发酵过程中同时加入菊粉酶和自絮凝酵母的同步糖化发酵乙醇得率高,发酵时间短. 当菊芋汁总糖浓度分别为105和179 g/L时,同步糖化发酵的最高乙醇浓度达50和82.5 g/L,比分步糖化发酵高6.4%和13.8%. 在连续发酵过程中应用同步糖化发酵法,当稀释率为0.02 h-1时,乙醇浓度约为90 g/L时达到稳定状态,乙醇得率达到理论值的90%,生产强度达2.12 g/(L×h).     

Dynamic modelling,simulation and optimization of an extractive continuous alcoholic fermentation process

The conventional alcoholic fermentation is a typical inhibitory process, leading to low productivity and yield. The ethanol produced inhibits yeast cells, causing a reduction in the alcohol production rate and cell growth rate. In this work, modelling and simulation have shown that continuous extractive fermentation, coupling a fermenter with an extractive vacuum flash chamber, is technically possible. In this case, the ethanol is partially removed, increasing drastically the productivity. Additionally, temperature control can be performed without using heat exchangers. The optimization was carried out using the method of factorial design and response surface analysis, leading to the determination of the most relevant variables, which were: 1.2 h residence time, 0.4 flash recycle rate, 180 g dm⁻³ sugar concentration and 0.35 cell recycle rate. The results, using optimized variables, were 98% conversion and 23 g dm⁻³ h⁻¹ productivity, which represent a three times higher productivity than in a conventional continuous process. © 1999 Society of Chemical Industry     

农业秸秆类生物质制取生物燃料的研究进展

为了缓解全球能源危机和解决环境污染问题,将农业秸秆类生物质,通过微生物发酵将它们转化为能源及高附加值的化学品,具有重要意义。介绍农业秸秆类生物质的结构成分;综合评述物理和化学预处理方法;重点介绍由农业秸秆类生物质生产乙醇、丁醇的研究现状。指出农业秸秆发酵制取生物燃料工业化进程的关键所在。     

气提法弱化超高浓度乙醇发酵过程中自絮凝酵母振荡行为

超高浓度(very high gravity,VHG)连续乙醇发酵过程中的振荡行为会导致发酵终点的乙醇浓度振荡和降低,是VHG连续乙醇发酵面临的主要问题。研究表明,游离酵母Saccharomyces cerevisiae 4126和自絮凝酵母BHL01在VHG连续乙醇发酵过程中,生物量、残糖、乙醇、甘油等发酵参数都呈现130～145 h的周期性振荡,且絮凝酵母发酵体系的平均乙醇浓度和乙醇生产强度都明显高于游离酵母体系。在絮凝酵母VHG连续乙醇发酵过程中利用发酵尾气气提分离乙醇,酵母细胞振荡行为被明显弱化,达到拟稳态状态,并且使发酵液中的残糖浓度控制在0.1 g·L^-1以下,平均乙醇浓度为110.87 g·L^-1,乙醇产率达到2.99 g·L^-1·h^-1。因此,本研究为弱化VHG连续乙醇发酵中的参数振荡行为提供了新的技术手段。     

Development of real-time state estimators for reaction–separation processes: A continuous flash fermentation as a study case

The development of reliable on-line state estimators applicable to reaction–separation processes is addressed in this work. Artificial Neural Network-based software sensors (ANN-SS) are proposed to allow on-line measurement of key variables, with an estimation algorithm that uses secondary variables as inputs. A continuous laboratory-scale flash fermentation for bioethanol production is considered as a case study. The process consists of three interconnected units: fermentor, filter (tangential microfiltration for cell recycling) and vacuum flash vessel (for the continuous separation of ethanol from the broth). The concentrations of ethanol in the fermentor and of ethanol condensed from the flash are successfully monitored on-line using ANN-SS. The proposed model contributes to improve the understanding of the complex relationships between process variables in the reaction and separation units, which is of major importance to allow the operation of the ethanol production process near its optimum performance.     

纤维素燃料乙醇技术经济分析

考察了以玉米秸秆为原料生产燃料乙醇的工艺流程,对年产5万t燃料乙醇的生产工艺进行了技术经济和敏感性分析. 蒸馏能耗分析表明,当发酵醪中乙醇浓度高于4%(w)时蒸馏的能耗比较低. 年产5万t燃料乙醇的直接固定成本约1.37亿元,乙醇的最低成本为8425 ￥/t. 该工艺能副产3.75万t CO2和215 t杂醇油,可带来额外收益2386万元. 经济敏感性分析表明,纤维素酶价格对生产成本的影响较显著,副产物CO2的回收利用可明显增加收益.     

乙醇浓醪发酵技术研究进展

乙醇浓醪发酵具有高细胞密度、高产物浓度和高生产速率等特点,是乙醇工业的发展目标和方向。采用乙醇浓醪发酵技术,具有节约工艺用水、提高设备利用率、降低能耗等优势,是提高乙醇发酵工业效益的重要途径。研究乙醇浓醪发酵具有十分重要的现实意义。本文综述了乙醇浓醪发酵技术研究进展,介绍了乙醇浓醪发酵定义、优势以及影响乙醇浓醪发酵的因素。指出降低发酵醪液黏度、筛选高耐性酿酒酵母、改变发酵工艺模式、添加适宜酶制剂以及营养物质是实现乙醇浓醪发酵技术的主要途径,其中筛选高耐性的酿酒酵母是实现乙醇浓醪发酵技术的关键。     

酒精-沼气双发酵耦联工艺中丙酸对酿酒酵母酒精发酵的影响(英文)

Propanoic acid accumulated in an ethanol-methane coupled fermentation process affects the ethanol fermentation by Saccharomyces cerevisiae. The effects of propanoic acid on ethanol production were examined in cassava mash under different pH conditions. Final ethanol concentrations increased when undissociated propanoic acid was <30.0 mmol·L-1 . Propanoic acid, however, stimulated ethanol production, as much as 7.6% under proper conditions, but ethanol fermentation was completely inhibited when undissociated acid was >53.2 mmol·L-1 . Therefore, the potential inhibitory effect of propanoic acid on ethanol fermentation may be avoided by controlling the undissociated acid concentrations through elevated medium pH. Biomass and glycerol production decreased with propanoic acid in the medium, partly contributing to increased ethanol concentration.