机械蒸汽再压缩系统的流程模拟及性能研究

为使得整个机械蒸汽再压缩(MVR)蒸发系统的稳定性、节能性更好,借助Aspen Plus软件学习版,根据MVR运行原理,构建了MVR性能分析模型,并通过改变MVR节点的参数,模拟研究了蒸发量、补充新鲜蒸汽量与进料温度、蒸发压强的关系;蒸发量、沸点与进料浓度(NaCl质量分数)、蒸发压强的关系;蒸发器换热量、COP与蒸发压强、压缩机压力升的关系。通过分析模拟结果得出:适当减小压缩比,可以提高蒸发系统的COP;原料液应该加热到沸点后,再进入蒸发器中进行换热;从节能效果看,MVR蒸发系统更适合在低温低压下运行;在蒸发前,应对浓度较大的原料液进行适当的稀释。     

机械蒸汽再压缩系统的设计及其在食品工业中的应用

从热力学的角度对MVR系统进行了分析,并主要对蒸发器、蒸汽压缩机、预热器进行数学模型的构建。综述MVR技术在国内外食品工业上的应用。     

滩田饱和卤水机械式蒸汽再压缩蒸发工艺研究

文章以热力学第一定律和朗肯循环原理对二次蒸汽经压缩机加压(以下简称MVR工艺)后进行换热工艺的原理分析,阐述了二次蒸汽在压缩过程中的参数变化及滩田饱和卤水单效蒸发的低品位二次蒸汽经压缩提高压力后返回该效加热室作为加热热源的经济性.表明滩田饱和卤水及岩盐卤水为原料生产精制盐的蒸发工艺中,采用MVR蒸发工艺必将是节能减排、提高经济效益的极好途径.     

MVR技术在液态奶蒸发系统中的应用

针对目前液态奶蒸发浓缩领域的能耗高、热效率低等缺点,提出了基于MVR技术的液态奶蒸发浓缩系统,设计了基于MVR技术的蒸发工艺流程,介绍了MVR热泵系统的蒸发工作原理;采用单效MVR热泵蒸发系统,对系统主要工作部件进行了设计计算;采用火用分析模型对系统及各个部件进行了能效分析;并对影响系统性能的主要参数:压缩比、蒸发温度进行了分析。应用结果表明该系统具有运行稳定、能耗低等特点;火用分析结果指出了系统在用能方面的薄弱环节及改进系统性能的方向;参数分析表明,当压缩比增大时系统的性能系数η和火用效率减小,而当蒸发温度升高时呈相反的变化趋势,因此,MVR乳品蒸发系统应尽量采用较小压缩比的压缩机和维持较高的蒸发温度。     

甘蔗糖厂热力系统节能改造工程技术

分析甘蔗糖厂传统蒸发系统存在问题及热力方案节能潜力,对热力方案进行优化并提出技改实施方案,减少蒸发末效二次蒸汽进入冷凝器,减少制糖一次蒸汽消耗量。本文以某糖厂节能技改为例,提出节能技术改造方案。通过采用低真空蒸发热力方案,提高各效汁汽压力,使蒸发系统各效汁汽抽取尽量推后;增加物料加热级数及用汽种类,Ⅴ效汁汽用于混合汁加热,回收利用汽凝水预热混合汁;提升供煮糖的Ⅲ效汁汽温度等节能措施,达到了降低全厂耗汽的目的。     

混合油负压蒸发工艺探讨

浸出毛油的品质随着加热温度的升高和时间的延长显著降低,混合油负压蒸发工艺是使一蒸、二蒸、汽提在负压状态下操作,同时,利用蒸脱机的二次蒸汽作为一蒸的热量来源.一方面在负压状态下可以减少油脂与空气中氧分子的接触;另一方面可以降低混合油中溶剂的沸点,以达到降低蒸发温度的目的.可以节约能源、节省钢材、提高毛油质量.在负压蒸发工艺设计中要注意合理配备冷凝面积,降低冷却循环水的温度,防止蒸脱机气相产生正压,控制蒸脱机二次蒸汽量,合理操作第二蒸发器,使用湿式粕末捕集器,加大第一蒸发器面积,列管适当加长加大,并选用不锈钢材质,选择蒸汽喷射泵,合理选择真空度,搞好余热利用和尾气回收.     

离心式与旋涡式压缩机驱动的MVR系统运行效果比较

从理论上分析植物提取液浓缩用MVR系统的运行原理,并比较不同类型压缩机的特点。结合实例,对比离心式与旋涡式压缩机驱动的MVR系统的运行效果。通过统计方法计算运行半年内,两套系统累计的蒸发量与用电量。结果发现:在相同设计蒸发量下,离心式压缩机平均蒸发量为2 545.3kg/h,最大能效比(COP)为15.3,单位蒸发量电耗为0.040kW·h/kg;旋涡式压缩机平均蒸发量为1 908.3kg/h,最大COP为11.0,单位蒸发量电耗为0.058kW·h/kg。证明在保证气密性的前提下,离心式压缩机比旋涡式压缩机更适用于含乙醇植物提取液的浓缩,节能效果更佳。     

Energy use and conservation in concentrated and dried milk production

The importance of providing energy supplies in the most efficient way possible is stressed. Reductions in specific energy consumption for the concentration step can be achieved by using multiple-effect evaporation and thermal and mechanical vapor recompression or by the use of reverse osmosis followed by evaporation. Significant reductions in specific energy consumption for the drying process can be achieved by recovering the heat from the hot exhaust gases using suitable heat exchangers, by using a fluidized bed for the final water removal step, and by altering the process conditions. Freeze concentration, freeze dying, dielectric dying, and roller dying are also discussed .     

机械蒸汽再压缩（MVR）技术在制浆废液蒸发中的应用

以制浆废液为研究对象,提出了机械蒸汽再压缩（MVR）技术与多效蒸发相结合的组合蒸发工艺,并以化学浆黑液及化机浆废水的蒸发为例,比较了组合蒸发与多效蒸发两种工艺。     

Systematic approach to study temperature and time effects on yield of pasta filata cheese

A batch cooker‐stretcher for pasta filata cheese production was developed based on the kitchen machine ‘Thermomix’. With this batch model system, the effect of kneading time (180, 420 and 600 s) and temperature (55, 60 and 70 °C) on the chemical composition of the pasta filata cheese and the yield was investigated. An increase in temperature from 55 to 70 °C reduced the yield of the pasta filata cheese production from 0.88 to 0.59 g/g, compared to initial curd weight. A correlation between process temperature and the water‐holding properties of protein (casein micelles) is proposed.     

麦汁煮沸节能技术探讨

啤酒生产过程的热能消耗除CIP和热水制备外，主要耗能集中在醪液升温、麦汁升温以及麦汁煮沸等工段。实现麦汁煮沸工段节能降耗的技术措施有：回收煮沸乏汽节能，包括采用乏汽冷凝器回收乏汽和采用乏汽压缩机节能；采用新型煮沸系统节能，可采用Merlin煮沸系统节能，或采用柔和煮沸系统节能，或采用Stromboli煮沸系统节能。     

MVR热泵技术及其在国内制盐工艺上的应用

机械热压缩(MVR)是利用热泵节能技术的一种目前世界上较先进的节能蒸发技术。文章简要介绍了机械热压缩技术的原理及其在工业上的应用。重点介绍了机械热压缩在国内制盐上的应用情况,旨在引起人们对机械热压缩技术的重视,促进机械热压缩在国内制盐行业中的推广及开发应用。     

Comparison of direct steam injection and steam-jacketed heating in squid protein hydrolysis for energy consumption and hydrolysis performance

Direct steam injection (DSI) and conventional steam-jacketed (SJ) heating systems were compared for energy consumption and hydrolysis performance in producing squid hydrolysates (SH). Hydrolysis was carried out with endogenous enzymes at 55 °C for 90 min and native pH (6.5 ± 0.2), followed by pasteurization at 75 °C for 30 min. Hydrolysis performance was evaluated by monitoring the changes in viscosity, degree of hydrolysis (DH), and protein profile during the course of hydrolysis. The DSI heating process was more energy efficient than SJ heating with significantly less energy usage (∼30% energy reduction), shorter come-up times, and total processing time. While considerable fouling was evident with SJ heating, no fouling was observed with DSI heating. No appreciable differences in hydrolysis performance were observed between DSI and SJ heating, although the DSI-treated hydrolysate exhibited slightly lower values in viscosity and DH, as well as weaker protein band intensities due to dilution caused by steam condensation. The use of a steam filtration unit in DSI not only filtered the incoming steam, but also reduced condensation. Results suggest that DSI heating with steam filtration is an energy efficient and fouling-free process for preparing SH and potentially for other type of enzymatic protein hydrolysates.     

利用分散染料废水的硫酸铵自动连续化制备

针对分散染料酸性废水难处理、易再次污染等问题,以分散蓝291∶3滤饼生产过程中产生的酸性母液废水为例,研究了酸性分散染料废水综合循环利用及资源化技术,并探索染料废水节能减排技术的工艺过程。分散蓝291∶3酸性母液废水经中和、脱色和分离、精滤、机械蒸汽再压缩(MVR)浓缩结晶、离心分离等工艺处理后,残余染料等有机物基本脱除,得到了氮含量在20.92%以上,游离酸(硫酸)含量低于0.1%的硫酸铵产品,从而实现了染料废水的循环利用和资源化。整个处理工艺实现了硫酸铵的自动连续化和清洁高效生产,同时MVR蒸发浓缩技术循环利用了它自身产生的二次蒸汽能量,提升了制备硫酸铵的经济效益和环保效益。     

MODELING of VENTING TIME, TEMPERATURE DISTRIBUTION and STEAM CONSUMPTION DURING VENTING of RETORTS

A model to predict the temperature history of the slowest heating point during venting of steam retorts is proposed. the theoretical analysis was based on a physical interpretation of the system behavior. the model was used to evaluate the influence of steam flow rate and initial temperature on venting time, steam consumption and temperature distribution in a pilot scale horizontal retort.     

Mathematical modelling of vacuum ohmic evaporation process

Ohmic evaporation is a complex process in which heat and mass transfers take in place simultaneously. In this study, finite difference-FD and finite volume-FV models simulating the changes of temperature and water removed from tomato juice during the vacuum ohmic evaporation process (VOEP) were developed. Models considering the heat and mass transfer equations were combined. Experimental effective electrical conductivity and specific heat capacity relations were taken into account. For heating period, final temperature was predicted with errors of 3.4 ± 1.3 °C and 0.7 ± 1.3 °C, while the evaporation time prediction errors were 1.3 ± 1.6 min and − 2.1 ± 1.6 min for FV and FD models, respectively. It was concluded the effect of mixing was not important on temperature distribution for such a high consistency tomato paste compared to the heat generation effect during the ohmic evaporation process. The developed models could be used to predict process time, temperature history, and volume fraction at any time during the ohmic evaporation process.     

大型纸机干燥部温湿参数动态特征及热能节约原理的研究

为了降低纸机干燥部热能消耗、提高水分蒸发效率,根据气压分布原理,通过各温湿参数内在关联机理和Matlab编程分析,从理论上系统地对干燥部温湿参数动态特征及热能节约原理进行了研究。研究表明,纸幅干燥曲线受烘缸蒸汽和进风状况共同影响,烘缸蒸汽消耗受进风状况影响;许多纸机干燥部虽运行正常,但是蒸汽消耗并非最低,可通过优化工艺参数,大大减少蒸汽用量;在保证产品质量的前提下,对热风交换系统零位进行优化调节与控制,可达到最佳节能效果。     

浸出车间蒸脱机结构及关键操作参数控制

蒸脱机(DT)是浸出车间最为关键的大型设备之一,蒸脱机蒸汽耗量占整个浸出车间的75%,电耗(含主驱动和DC风机)占整个浸出车间的75%。蒸脱机通常由预脱层、混脱层和直接汽层组成,DT层数和直径根据产量大小确定。在生产过程中,控制好DT的气相温度、料层高度、料层温度和直接汽量尤为重要。气相温度由直接汽量控制,反映DT的蒸汽利用效率;料层高度决定豆粕在DT中的停留时间,停留时间和料层温度影响豆粕的脲酶活性和蛋白溶解度,从而影响豆粕品质。     

超声波辅助提取佛手精油的工艺研究

以佛手果为原料,研究了超声波辅助水蒸汽蒸馏法提取佛手果精油的方法。通过单因素实验优化工艺条件,所得最优工艺条件为:水蒸馏流量为1.30 mL/min,超声波的功率180 W,辅助工作时间30 min,水馏汽蒸馏时间75 min。在此条件下,佛手精油的提取率为0.763%。     

An efficient approach for the extraction of anthocyanins from Lycium ruthenicum using semi-continuous liquid phase pulsed electrical discharge system

Lycium ruthenicum is regarded as a good source of natural anthocyanins. In this work, we proposed a novel semi-continuous liquid-phase pulsed discharge (LPD) system for the extraction of anthocyanins from Lycium ruthenicum. The optimized conditions for this method were: 20% ethanol concentration, 7 pH value, 8 kV input voltage, 27 mL/min volume flow, and 8 min treatment time. Under these conditions, a maximum anthocyanins recovery rate (95.69%) was obtained. Compared with batch LPD and heat-assisted extraction (HAE), semi-continuous LPD showed higher anthocyanins yield, shorter time, and lower energy consumption. The antioxidant activity of extracts was determined by scavenging ability of DPPH and ABTS radicals and, reducing ability of Fe³⁺. The results indicated that the antioxidant activity of batch LPD, HAE, and semi-continuous LPD were similar. Besides, the HPLC chromatograms showed that three methods had similar anthocyanins composition. Thus, semi-continuous LPD was an good and promising method for the extraction of natural anthocyanins.