高浓度尿素废水泠冻浓缩极限

冷冻浓缩技术是处理尿素厂废水和尿液等高浓度尿素废水的有效方法之一,浓缩极限的确定则是预测和评价该工艺最高水回收率和工作效率的必要条件.以尿素溶液为研究对象,采用差示扫描量热技术分析了溶液在冷冻过程中的相态变化规律,通过冷冻试验确定了溶液发生尿素共晶析出时的浓度;以尿液为对象,研究了确定高浓度尿素废水冷冻浓缩极限的方法.研究结果表明：尿素废水在达到浓缩极限之前,当尿素浓度高于26.3%时,继冰晶析出之后会共晶析出尿素;尿素废水在浓缩极限处呈玻璃态,由差示扫描量热分析可确定废水玻璃化转变温度、推算冷冻浓缩工艺最高水回收率;尿液的玻璃化转变温度为-108.33 ℃,相应的溶液浓度为57.92%,冷冻浓缩可达到的最高水回收率为97.75%.     

吸波材料辅助的初始非饱和物料微波冷冻干燥

为了强化冷冻干燥过程,制备咖啡溶液的初始饱和与非饱和2种冷冻样品,分别使用石英与碳化硅底盘进行常规和微波冷冻干燥实验,同时采用电阻法测定溶液的共晶温度.结果表明,在温度为25℃、压力为22 Pa时采用石英底盘,初始非饱和物料冷冻干燥时间比饱和物料缩短了14.9％,适当提高操作温度可以强化冷冻干燥过程.在25℃、22 P...     

Keggin结构杂多酸盐结晶方法的探究

Keggin结构杂多酸盐的结晶方法：应用冷冻浓缩法,是将稀溶液中的水冻结并分离冰晶从而使溶质增浓的操作。应用不同浓度的氯化钠盐溶液凝点的不同,以控制冷冻浓缩过程的温度。探究对Keggin结构杂多酸盐浓度的设定,从而根据实验过程得到随温度降低的浓度变化曲线。分析各曲线,绘制非饱和溶液与饱和溶液浓度变化曲线图,最终得到最低温度相交点为此Keggin结构杂多酸盐的低共熔点,即结晶点。     

冷冻浓缩在去除黄河水体中重金属元素的研究

室内模拟黄河水的结冰过程,探讨冷冻浓缩对黄河水体中各重金属元素的去除效应。结果表明,冷冻浓缩对实验水样中各重金属都有一定的去除效应,且其受到冷冻温度、冷冻时间、溶液浓度和种冰的影响。各重金属的去除率随着冷冻温度的降低而下降,-15℃为该实验水样的最佳冷冻温度;冷冻时间的增加,可以提高各重金属的去除率,24 h作为实验水样的最佳冷冻时间;去除率随着溶液浓度的升高而逐渐降低;加入种冰可以提高冷冻浓缩对各重金属的去除率。     

大鲵糖肽润肤霜的制备及性能评价

通过添加大鲵糖肽制备了润肤霜,探讨了大鲵糖肽的吸湿性与抗氧化性,大鲵糖肽润肤霜的抗紫外线性与豚鼠皮肤涂抹的变态反应。结果表明：在低湿度条件下,大鲵糖肽的吸湿率达3.8%,在高湿度条件下,大鲵糖肽的吸湿率达15.6%;羟基自由基清除率为50.85%;添加了大鲵糖肽在260～315 nm下具有较强紫外线吸收能力;涂抹大鲵糖肽润肤霜和大鲵糖肽的豚鼠皮肤没有出现任何的红斑和水肿,与对照组的豚鼠的皮肤一致。     

列管式真空蒸发器的快速取样装置

<正> 浓缩工序是明胶生产中的一个重要工序,其主要作用是利用减压蒸发器将水分从过滤后的稀明胶溶液中蒸发除去,提高明胶溶液的浓度,为明胶冷冻干燥创造有利条件,缩短干燥过程中的时间,达到节     

费托合成水的冷冻浓缩处理及能耗估算

为提高费托合成水中有机物浓度,降低废水处理量,以冷冻浓缩处理费托合成水,主要采用2种不同进料方式考察冷冻浓缩后的结果.一是以费托合成水作为进料直接浓缩,考察不同浓缩倍率时浓缩液组分和产水水质;二是以NaOH中和费托合成水至pH=6-7,进行冷冻浓缩,考察浓缩倍率和产水水质.结果表明:冷冻浓缩可以对有机物和羧酸盐溶液进行...     

杂质离子对共晶冷冻结晶过程中冰晶结晶特性的影响

以硝酸钾水溶液为研究对象,考察了杂质离子对共晶冷冻结晶过程中冰晶结晶特性的影响。首先,建立并验证了共晶冷冻结晶过程冰点的测定方法,并基于Extend-UNIQUAN模型对硝酸钾体系的冰点进行模拟计算。同时考察了不同种类杂质离子对硝酸钾水溶液冰点、结晶点、以及冷冻介稳区宽度的影响,实验研究结果表明:硝酸钾水溶液中离子杂质浓度越高,冰点、结晶点的温度越低,介稳区宽度越宽;杂质离子浓度相同的硝酸钾水溶液其冰点温度随着杂质离子半径减小而减小,结晶点温度和介稳区宽度与阳离子杂质价态成反比,与阴离子杂质价态成正比。并利用基于经典成核理论所推导的介稳区宽度模型方程对实验数据进行模拟计算,模拟结果与实验值符合较好,计算得到硝酸钾水溶液的冰晶成核级数为1.46。     

具有初始孔隙的多孔物料冷冻干燥

实验研究了具有一定孔隙的非饱和多孔物料对液体物料冷冻干燥过程的影响。以甘露醇为主要溶质的待干料液采用“液氮制冰激凌法”制备非饱和物料进行冷冻干燥,并与常规饱和的冷冻物料相比较。结果表明,非饱和冷冻物料确实能够显著地强化液体物料的冷冻干燥过程。干燥产品SEM形貌分析显示,初始非饱和冷冻物料具有连续均匀的固体骨架和孔隙,固体基质更加纤细,孔隙空间更大,可以大大减小传质阻力。考察物料内部各点的温度变化发现,初始非饱和物料内部冰晶确实发生整体升华,但仍然存在主要升华区域;非饱和多孔物料的冷冻干燥过程主要是传热控制,而常规饱和物料冷冻干燥主要是传质控制。操作压力对过程的影响可以忽略。采用辐射/导热组合加热方式可改善初始非饱和多孔物料冷冻干燥过程的传热,进一步缩短干燥时间。     

高强度多孔聚乙烯醇水凝胶的制备

为制备兼顾多孔性和高强度的水凝胶,本研究利用循环冷冻和冷冻干燥联用设计和制备了一系列聚乙烯醇水凝胶。从聚乙烯醇溶液的浓度、循环冷冻次数、单次冷冻时长三个方面对水凝胶的力学性能、内部微观形貌、含水量进行了研究。结果表明:以质量分数14%浓度的聚乙烯醇水溶液经过3次循环冷冻过程(16h冷冻,8h解冻)和液氮冷冻冰干后的支架,再经溶胀平衡后得到的PVA水凝胶具有最佳的力学性能,此时PVA水凝胶的拉伸强度为5.74MPa,断裂伸长率为347%;改变循环冷冻次数可有效地调节PVA水凝胶的含水量;水凝胶力学性能提高来源于体系结晶度的增大。     

Spray Freeze Drying in a Fluidized Bed at Normal and Low Pressure

The aim of this study is to develop the spray freeze drying process and its hardware and to investigate its capabilities to dry thermosensible substances such as pharma-proteins at normal and low pressures. As the result, the spray freeze fluidized-bed dryer was constructed. During the study, the drying kinetic comparison between classical and spray freeze-drying technologies was done. Spray freeze drying has shown short process times and allows advanced control, product particle shape and size uniformity, and high solubility. This shows that the fluidized-bed freeze-drying process could be an alternative for classical freeze-drying processes. Identified problems are the low yield of the primary drying phase and the strong electrostatic effects during the secondary drying step. However, the innovative process has shown an excellent capability to dry and stabilize the thermosensitive substances, such as pharma-proteins.     

Spray Freeze Drying in a Fluidized Bed at Normal and Low Pressure

The aim of this study is to develop the spray freeze drying process and its hardware and to investigate its capabilities to dry thermosensible substances such as pharma-proteins at normal and low pressures. As the result, the spray freeze fluidized–bed dryer was constructed. During the study, the drying kinetic comparison between classical and spray freeze–drying technologies was done. Spray freeze drying has shown short process times and allows advanced control, product particle shape and size uniformity, and high solubility. This shows that the fluidized-bed freeze-drying process could be an alternative for classical freeze-drying processes. Identified problems are the low yield of the primary drying phase and the strong electrostatic effects during the secondary drying step. However, the innovative process has shown an excellent capability to dry and stabilize the thermosensitive substances, such as pharma-proteins.     

Microwave Freeze Drying of Sea Cucumber Coated with Nanoscale Silver

To develop an improved dehydration method for sea cucumber, microwave freeze drying was tested as a potential method. According to our experimental results, microwave freeze drying can reduce drying time to about half of the traditional vacuum freeze-drying process. To ensure a high degree of sterilization, a novel nanoscale silver coating technique was combined with microwave freeze drying. Microwave freeze drying combined with nanoscale silver coating treatment leads to a much lower microorganism number with no significant effect on drying efficiency and sensory quality.     

Microwave Freeze Drying of Sea Cucumber Coated with Nanoscale Silver

To develop an improved dehydration method for sea cucumber, microwave freeze drying was tested as a potential method. According to our experimental results, microwave freeze drying can reduce drying time to about half of the traditional vacuum freeze-drying process. To ensure a high degree of sterilization, a novel nanoscale silver coating technique was combined with microwave freeze drying. Microwave freeze drying combined with nanoscale silver coating treatment leads to a much lower microorganism number with no significant effect on drying efficiency and sensory quality.     

A Novel Atmospheric Freeze-Drying System Using a Vibro-Fluidized Bed with Adsorbent

Atmospheric freeze drying (AFD) in a vibro-fluidized bed dryer coupled with an adsorbent and multimode heat input is proposed for dehydration of food products at lower cost than the traditional freeze-drying process under vacuum. The aim of this project is to study the proposed AFD system using a vortex tube to produce low-temperature dry air, an alternative for producing dried food products of high quality. An experimental setup was designed and built to permit simultaneous application of convection, conduction, and radiation heat input to the drying material above its freezing point to ensure sublimation. A parametric evaluation over a broad range of possible parameter values was carried out using cubic-shaped potato and carrot as model heat-sensitive products. The influence of various system parameters on drying kinetics, quality, and functional properties of the dried products (color, rehydration properties, and morphology) were investigated. Comparison between physical quality and drying characteristics of the AFD system with AFD using fixed bed, fluidized bed dryer, and also with traditional vacuum freeze drying were carried out to investigate the viability of this new system. Results indicate that proposed system is an alternative to reduce the process time as well as to maintain the product quality at lower cost.     

A Novel Atmospheric Freeze-Drying System Using a Vibro-Fluidized Bed with Adsorbent

Atmospheric freeze drying (AFD) in a vibro-fluidized bed dryer coupled with an adsorbent and multimode heat input is proposed for dehydration of food products at lower cost than the traditional freeze-drying process under vacuum. The aim of this project is to study the proposed AFD system using a vortex tube to produce low-temperature dry air, an alternative for producing dried food products of high quality. An experimental setup was designed and built to permit simultaneous application of convection, conduction, and radiation heat input to the drying material above its freezing point to ensure sublimation. A parametric evaluation over a broad range of possible parameter values was carried out using cubic-shaped potato and carrot as model heat-sensitive products. The influence of various system parameters on drying kinetics, quality, and functional properties of the dried products (color, rehydration properties, and morphology) were investigated. Comparison between physical quality and drying characteristics of the AFD system with AFD using fixed bed, fluidized bed dryer, and also with traditional vacuum freeze drying were carried out to investigate the viability of this new system. Results indicate that proposed system is an alternative to reduce the process time as well as to maintain the product quality at lower cost.     

Effect of freeze-drying process on the physical stability and properties of Voriconazole complex system

This paper studied the effect of lyophilization together with annealing on the physical properties, such as critical micelle concentration, particle size, differential scanning calorimetry, and eutectic point. The freeze-drying method had successfully set up the Voriconazole complex system. Samples processed by lyophilization had slightly superiority compared to those without the lyophilization in terms of surface properties. Furthermore, this paper also investigated the physical stabilities of Voriconazole complex system related to cloud point thermodynamic and insoluble particles. Samples processed by lyophilization with annealing achieved better performance of physical stabilities than those without any process.     

Concentration of aqueous dye solution by freezing and thawing

The concentration phenomena during freezing and thawing were investigated to study the feasibility of freeze–thaw process as a concentration operation. An aqueous dye solution was employed as a model binary eutectic solution. The localised concentration in the frozen matrix was determined, and the concentration profile of the melting solution during thawing was examined. It was found that the solution obtained during thawing showed higher concentration than the original solution, and the concentration did not correspond to the amount of solute localised in the frozen matrix. It was suggested that the concentration phenomena during thawing would be governed by the melting droplet growth rate at the melting interface and by the diffusion rate of solute from eutectic phases to the droplet.