高通量二氧化硅复合膜的制备及其渗透汽化性能研究

二氧化硅复合膜展现出的耐酸性和稳定性在渗透汽化领域有着广阔的应用前景。本文采用真空抽吸浸渍法制备二氧化硅复合膜的支撑层,得到高通量二氧化硅复合膜。本文对支撑层真空抽吸的最优条件进行探究,并采用扫描电镜对膜层的表面、截面形貌结构进行表征。结果表明,当支撑层溶胶质量浓度为2%,真空抽吸时间为10 s,真空抽吸压力为0.10 MPa时制备出致密的二氧化硅复合膜,其膜层厚度为6~7 μm。将本文制备的二氧化硅复合膜应用于异丙醇水溶液渗透汽化中,该膜显示出优异的分离性能,其中异丙醇的渗透通量为6.42 kg/(m²·h)。     

Dewatering of drinking water treatment sludge by vacuum electro-osmosis

The objective of this research was to evaluate the dewatering of drinking water treatment sludge (DWTS) by vacuum electro-osmosis dewatering (VEOD) technology. DWTS has a high moisture content, with the water existing as free water, pore water, surface adhesion water and internal combined water. Vacuum filtration of 0.05 MPa can quickly dewater sludge and has low energy consumption, but can only remove free water and some pore water. The moisture content of the DWTS was reduced to below 79% by vacuum filtration technique alone. At this moisture content, all free water had been expelled by vacuum filtration. Electro-osmosis optimized for the experimental conditions (0.05 MPa, 2.5 V/cm) began after vacuum filtration ceased, and drew pore water and surface adhesion water to the cathode, where it was expelled through vacuum filtration. The VEOD process removed all free water. In addition, pore water and surface adhesion water were reduced by 60.2% and 15.9%, respectively.     

Optimizing Drying Conditions for the Microwave Vacuum Drying of Enzymes

The aim of this study was the methodological use of experimental planning for the optimization of microwave vacuum drying of enzymes using α-amylase as a model. A factorial in star designwas used to optimize the microwave vacuum–drying process, and the variables were power output and vacuum pressure. The material dehydrated by this technique was analyzed with regard to its enzymatic activity, water activity, and moisture content. Response surface methodology was used to estimate the main effects of vacuum pressure and power on the enzymatic and water activities. The experimental in star design revealed that microwave vacuum drying is influenced mainly by power. The dehydrated product showed high enzymatic activity and low water activity.     

蒸汽喷射真空泵的影响因素及测试罩的应用

实际生产中的影响因素很多 ,诸如蒸汽压力、蒸汽干燥度、冷却水量、冷却水温、冷却水喷嘴堵塞、真空泵泄漏、拉瓦尔蒸汽喷嘴堵塞、泵前工艺设备冷却效果不好等等。但主要的是冷却量、拉瓦尔蒸汽喷嘴和泵前工艺设备的冷却。测试罩安装在真空泵的吸入真空管道上 ,在测试罩上选择不同直径的空气流量喷嘴 ,可以测得真空泵的空气流量喷嘴、抽气量、真空度之间的关系 ,从而可指导正确操作。     

Dampfstrahlvakuumpumpen in der Speiseöl-Industrie Auslegungsmerkmale und Betriebsverhalten

Steam Jet Vacuum Pumps in the Edible Oil Industry – Layout Characteristics and Operational Behaviour For vacuum generation in distillation and deodorization multiple stage steam jet vacuum pumps are preferred in conjunction with mixed condensers. The working range of the steam jet pump should be adapted to the various materials processed and the cooling water available, and, a minimum of energy requirement should be aimed. The relevant considerations are presented in the form of diagrams and layout plans. The unavoidable mixing of suction current, ejector current and cooling water and its consequence on the waste water pollution are discussed.     

Stepwise Development of a Mathematical Model for Air Flow in Vacuum Dewatering of Paper

Part of the dewatering in a paper machine takes place via vacuum suction boxes situated below the moving web. In addition to the removal of liquid water, considerable amounts of air are sucked through the paper. The air flow that accompanies dewatering is a crucial parameter for the electricity consumption of a vacuum system. The present study models this air flow, combining differential conservation equations with fiber characterization. Measured air flow rates for different vacuum levels, basis weights, and pulp types are compared to model predictions. More than 70% of the data agree within the range of experimental error.     

Use of capillary suction apparatus for estimating the averaged specific resistance of filtration cake

A method for estimating the averaged specific resistance of filtration cake, which avoids the necessity of measuring the liquid invasion volume in capillary suction apparatus (CSA) experiments, is proposed. When insufficient slurry is used, the slurry will exhaust during an experiment and the curve of wet front radius versus time shows transition. The transition point shifts according to the slurry concentration, cake specific resistance and the CSA parameters. Based on the wet front radius and the capillary suction time (CST) of the transition point, the liquid saturation under the inner cylinder can be estimated and the averaged specific resistance of cake calculated without the liquid invasion volume data. The proposed method agrees well with vacuum filtration data.     

一种混合防腐技术在水环真空泵上的应用

从技术经济角度出发,对耐腐蚀水环真空泵过流零件表面处理的现状及各工艺方案的特点进行了分析,提出了能够满足使用需要的混合防腐工艺方案,达到使用寿命延长,防腐成本降低。     

Cause and effect of void formation during vacuum bag curing of epoxy film adhesives

Void formation during vacuum bag curing of epoxy film adhesives arises from extraneous volatile products. Potential sources of volatiles were found to include organic solvents and/or water remaining in the adhesive from manufacture, water picked up by the adhesive prior to curing, and water retained in various forms on the prepared adherend surface. Using a novel FTIR spectroscopy technique, water and methyl ethyl ketone (MEK) were identified as the principal volatiles formed during curing, and quantitative estimations showed batch-to-batch variations and the tendency of uncured adhesive to rapidly absorb atmospheric water. An estimation of void content was obtained from video images of fractured, adhesively bonded joints using a computerized pixel-counting technique. The conclusions drawn from tensile shear, peel, and wedge durability tests suggest that a void content in excess of 25% lowers T-peel and honeycomb peel strengths and may affect bond durability. Void content can be minimized using an in situ heat/vacuum outgassing treatment.     

Dampfstrahl-Vakuumpumpen in der Öl- und Fettindustrie Energieverbrauch und Abwassertechnik

Steam Ejectors in Oil and Fat Industry: Energy Consumption and Waste Water Technology Steam ejectors convey gases and vapours from distillation and deodorization columns via intermediate condensers to atmospheric pressure. Inspite of utmost care taken for the separation of liquid or solid particles at the point of suction, some of these particles are carried over into the vacuum lines and are deposited at the cold surfaces of the vacuum system. Measures to prevent this carry over by scrubbing, freezing or heating need additional energy. Minimizing such energy requirements is one of the tasks of the processing engineer, plant manufacturer and plant operator. In the presented work, the influences of suction pressure, intermediate pressure, boosting steam pressure, cooling water temperature and temperature of the surroundings were correlated. Different possibilities of connection are shown, which can be chosen depending upon local requirements in order to minimize environmental pollution.     

Slip casting molds produced by hot isostatic process

Slip casting can produce large green bodies of fairly complex shape with high homogeneity. In this work, porous alumina produced by hot isostatic process (HIP) is evaluated to apply as slip casting molds. HIPed porous alumina molds have higher water suction rate than conventionally sintered ones with a same open porosity. The high water suction rate of HIPed molds is due to the low specific surface area of HIPed porous materials. The high water suction rate of HIPed porous alumina molds allows high casting rates.     

The effect of oxygen on the chemisorption on polycrystalline silver surface

The adsorption of oxygen(O₂) and the effect of oxygen on the chemisorption of water(D₂O) and hydrogen(D₂) on polycrystalline silver surface have been studied using the technique of thermal desorption spectroscopy(TDS) under ultra-high vacuum(UHV) condition. Three different states of adsorbed oxygen are observed on the surface. The adsorptions and reactions of water and hydrogen on the oxygendosed surface are strongly affected by the pre-adsorbed oxygen. Water on the oxygen-dosed surface shows a maximum desorption at 430K. During the adsorption of hydrogen on the oxygen-dosed surface, hydrogen is rapidly oxidized by a stepwise reaction in which hydrogen reacts first with O(a) to yield hydroxyl intermediate[OD(a)] and then this intermediate reacts to form water. The rate-determining step in this reaction is desorption of water.     

Water-induced effects on the adsorption on polycrystalline platinum (II. Interaction of carbon monoxide and water)

The adsorption and desorption of carbon monoxide and water as well as interaction between them on polycrystalline platinum has been studied using the technique of thermal desorption spectroscopy (TDS) under ultrahigh vacuum (UHV) conditions. A small amount of water adsorbs on the surface of the platinum at 310K and desorbs readily and steadily in the temperature range of 350-450 K. When exposure of water by more than 100 L is followed by saturation exposure of carbon monoxide, the height of carbon monoxide desorption peak appeared at 790 K becomes higher. It suggests that preadsorbed water dissociates a small part of carbon monoxide to atomic carbon and oxygen on the surface of the sample. And, interaction of water and carbon monoxide (or atomic carbon) results in the water-gas shift reaction.     

THE CAPILLARY SUCTION OF SOME CERAMIC MATERIALS1

The forces which act when clay is mixed with water and when water is removed from wet clay by evaporation have received little study. For this reason, very little definite information regarding the internal mechanism of the drying of clayware is available. In this paper, the writer reviews the experiments and theories of Pukall, Terzaghi, Dixon, etc., lists some of the forces which may act when ware is drying, and defines an important force which he calls “capillary suction.” A simple experiment is described, by means of which this force can be readily demonstrated. The development and final form of an apparatus for measuring the capillary suction of ceramic materials is described and data obtained from measurements on a ball clay, a kaolin, flint, feldspar and mixtures of these substances are reported. Capillary suction decreases rapidly with increase in the flint and feldspar of a ceramic body. By utilizing the capillary suction produced by evaporation of water from a clay surface, water at atmospheric pressure has been made to enter a steel bomb in which the gas pressure was maintained at 200 lbs. per square inch.     

压缩气体吹吸式尘源控制技术实验研究

对于冷轧带钢尘源的控制,提出了一种新型控制技术——压缩气体吹吸式尘源控制技术。通过对其进行静态实验研究并确定相关的实际运行参数,结果表明,该技术能有效促进带钢表面松动的氧化铁皮的捕集,且易于在现有除尘系统上进行改造,降低车间粉尘浓度和系统能耗。     

Influence of vacuum pressure,pH, and potential gradient on the vacuum electro-osmosis dewatering of drinking water treatment sludge

This paper describes research that evaluated the influence of vacuum pressure, pH, and potential gradient on the vacuum electro-osmosis dewatering (VEOD) of drinking water treatment sludge (DWTS). In the first phase of the VEOD process, a vacuum pressure of ?0.05 MPa was applied alone to DWTS for 30 min, removing almost all free water and part of pore water. In phase two, electro-osmosis was applied in combination with intermittent vacuum filtration, further reducing pore water and surface adhesion water in DWTS. However, statistical analysis indicated that the optimum dewatering parameter values were vacuum pressure at ?0.06 MPa, pH at 6.2, and potential gradient at 2.5 V/cm, which resulted in a relevant energy consumption of 0.35 kW.h/kg removed water.     

DEM and experimental analysis of the water retention curve in polydisperse granular media

We investigate the water distribution and the link between suction and water content in granular media. Firstly, we examine the effect of suction on the shape and the volume of the liquid bridge by four different methods. Method I is based on the local expression of the capillary force coupled with the gorge method and Method II is based on the Laplace law. These two methods use the toroidal approximation. Methods III and IV are based on the integration of the differential equation that defines the liquid bridge shape (established from the Laplace law). This local behaviour is then used in a discrete element study of a sample composed of several thousands of grains. We focus our study on the pendular state. A liquid film around the grains involving the continuity of the liquid phase is assumed. The water distribution and the water content associated with a given suction are calculated. Then retention curves of the granular media are built. A parametric study is made to bring to light the effect of macroscopic parameters (grain-size distribution) and physical parameters (liquid/air surface tension and contact angle) on the water retention curve. Finally, numerical data are compared to experimental results.     

The role of silanol groups on the reaction of SiO2 and anhydrous hydrogen fluoride gas

It is essential to etch SiO₂ for producing silica glass components, semiconductor devices, and so on. Although wet-etching with hydrogen fluoride (HF) solutions is usually employed for this purpose, it faces a drawback that microstructures stick during the drying of the solution. To overcome this problem, we have developed a dry-etching technique with gaseous HF at high temperatures. In the present study, an interesting phenomenon was found that silicon thermal oxides were much less etched than vitreous silica by gaseous HF. Such difference had not been found in wet- or humid HF gas etching. Because their bulk chemical formulae are the same (SiO₂), it was suggested that the surface species affected the reaction rate. In fact, preprocessing with water vapor plasma remarkably increased the etching rate on the thermal oxides layer, and vacuum heating almost completely suppressed the reaction on the vitreous silica and the plasma-treated thermal oxides. These results indicate that the surface silanol groups enhance the reaction between SiO₂ and gaseous HF. Based on the results, a model of chain reaction for SiO₂ and gaseous HF was proposed, where the surface silanol groups act as the reaction center.     

MHD flow of a micropolar fluid towards a vertical permeable plate with prescribed surface heat flux

The problem of a steady mixed convection stagnation point flow towards a permeable vertical plate with prescribed surface heat flux immersed in an incompressible micropolar fluid is studied numerically. The governing partial differential equations are first transformed into a system of ordinary differential equations using a similarity transformation, before being solved numerically by a finite-difference scheme known as the Keller-box method and the Runge–Kutta–Fehlberg method with shooting technique. The effects of the material parameter, buoyancy parameter, suction/injection parameter and the Prandtl number on the fluid flow and heat transfer characteristics are discussed. It is found that dual solutions exist for both assisting and opposing flows. The skin friction coefficient and the local Nusselt number increase in the presence of suction and magnetic field. Moreover, suction as well as fluids with larger Prandtl number widens the range of the buoyancy parameter for which the solution exists.