低温吸湿复合吸附剂的制备及吸湿性能

针对冷库结霜严重制约其经济性的问题,化学固体吸附除湿防霜技术逐渐得到重视。本文将对水吸附能力较强的金属卤化物与容易定型且传热传质性能较好的分子筛相结合,制成复合吸附剂,建立了低温情况下吸附材料的吸湿性能测试系统,并进行了大量测试,给出了多种材料在-5℃、-10℃、-15℃下的吸湿量及吸湿速率变化,实验结果表明复合吸附剂的吸附性能与单纯的分子筛相比有了明显的改善,13X型分子筛浸渍浓度20%的Na Br溶液所得试样吸湿量和吸湿速率性能优越,复合过程中损失较少,成本低,可作为复合吸附剂应用于冷库除湿系统中。     

硝酸铵吸湿点测定方法的改进及影响因素

吸湿点是硝酸铵在用作固体推进剂时的重要指标之一。通过实验对吸湿处理的方法进行了改进,并从温度、称样量及样品表面积3个方面对硝酸铵吸湿点测定的影响进行了分析。依据实验得出的数据,将吸湿处理的方法改进为在25℃的恒温环境中、90%的相对湿度下吸湿3 h。在影响因素中,温度对其影响最明显;称样量对吸湿点的测定影响比较小,但使称样量尽量接近会减小平行差;表面积对吸湿点测定的影响较大。     

复合固体干燥剂的研究进展

近年来，固体除湿材料受到广泛关注，研究表明，固体干燥剂可以应用于固定床、转轮与吸附式制冷系统，替代传统空调除湿系统，提高除湿效率以降低空调能耗。本文首先对固体干燥剂进行分类，简要阐述了传统干燥剂（如硅胶、活性炭、沸石等）的特点，然后详细介绍了各类复合干燥剂的特征参数测试结果（如吸附速率、吸附量、再生温度、再生速率、再生效率、再生量等），综合比较其优缺点。指出聚丙烯酸、聚丙烯酸钠等高分子材料和金属有机骨架MOFs具备再生温度低、吸湿量高、稳定性好等特点，是未来研究固体除湿材料的主要方向。接着总结了复合干燥剂的制备与表征方法，给出了改善孔隙结构、提高结构稳定性和防止液解的方法，指出了制备方法的改进也是改善固体干燥剂物性的重要方向。最后总结了各种复合干燥剂的特征参数对比情况。     

管翅式换热器离子交换树脂涂层

采用浸渍法将离子交换树脂(IER)浸渍于饱和氯化锂或氯化镁溶液中,并依次经过滤、洗涤及干燥得改性离子交换树脂。经粉碎后的改性离子交换树脂粉与固体粉末涂料混合成喷涂料,对管翅式换热器铝箔表面进行静电喷涂、热固化得吸湿涂层。XRD分析表明,改性前后树脂结构没有发生根本性改变;SEM表明,吸湿涂层能够均匀紧密地分散在铝箔表面,涂层厚达120um;EDS显示出吸湿涂层各成分组成及含量;TG曲线表明,吸湿涂层失重主要集中在30~150℃及400~600℃区域,前者与吸附剂脱附有关,后者与涂料及树脂粉热分解有关;静态和动态吸附曲线显示,吸湿涂层经改性后,其吸湿性能明显提高;吸湿涂层重复性测试显示,涂层具有较高吸附及脱附稳定性。     

管翅式换热器离子交换树脂涂层

采用浸渍法将离子交换树脂（IER）浸渍于饱和氯化锂或氯化镁溶液中,并依次经过滤、洗涤及干燥得改性离子交换树脂。经粉碎后的改性离子交换树脂粉与固体粉末涂料混合成喷涂料,对管翅式换热器铝箔表面进行静电喷涂、热固化得吸湿涂层。XRD分析表明,改性前后树脂结构没有发生根本性改变;SEM表明,吸湿涂层能够均匀紧密地分散在铝箔表面,涂层厚达120 mm;EDS显示出吸湿涂层各成分组成及含量;TG曲线表明,吸湿涂层失重主要集中在30～150℃及400～600℃区域,前者与吸附剂脱附有关,后者与涂料及树脂粉热分解有关;静态和动态吸附曲线显示,吸湿涂层经改性后,其吸湿性能明显提高;吸湿涂层重复性测试显示,涂层具有较高吸附及脱附稳定性。     

球形ADN的吸湿机理

用动态吸湿性分析法和扫描电镜研究了球形二硝酰胺铵(ADN)的吸湿过程和吸湿过程中ADN形貌的变化,探讨了ADN的吸湿机理。结果表明,ADN吸湿过程可分为平缓吸湿(Ⅰ),急剧增强吸湿(Ⅱ)和潮解(Ⅲ)三个阶段,Ⅰ、Ⅱ阶段是水蒸汽与ADN固体表面的作用,Ⅲ阶段是水蒸汽与ADN液化膜表面的作用。Ⅰ阶段吸湿过程为多分子层吸附,符合BET理论模型;该阶段水与ADN之间的作用力对ADN吸湿性能起主导作用;Ⅱ阶段吸湿机理可用毛细孔凝聚理论解释,影响该阶段ADN吸湿性能的主要因素是ADN表面的光滑程度。     

聚合物基复合材料吸湿性能研究进展

综述了聚合物基复合材料吸湿性能的研究进展,阐述了复合材料吸湿行为的机理和影响复合材料吸湿的主要因素,并对复合材料吸湿有关的模型进行了介绍,主要集中在吸湿扩散模型、脱湿行为及其使用寿命预测模型等方面。     

吸附式空气取水系统用吸湿材料研究进展

吸附式空气取水技术因其适用环境范围广、低碳环保的特性，被认为是解决全球水资源短缺问题的重要技术之一。吸湿材料的特性决定着该技术的取水性能。本文对吸湿材料的最新研究进行了系统的归纳与总结。重点介绍了吸湿性聚合物和复合吸湿剂（多孔材料-盐、聚合物-盐、聚合物-聚合物和多孔材料-聚合物），并对各类吸湿剂的性能特点以及在吸附式空气取水系统的应用展开详细介绍。发现复合吸湿剂的吸湿性能更强，特别是聚合物类复合吸湿剂，满足宽领域吸附的要求，进而提高了在干旱地区的取水效果，在未来具有很好的应用前景。最后，指出了吸湿材料需要进一步研究和解决的相关问题，以期为推进吸附式空气取水技术早日实现从实验室研究到规模化工业应用提供有价值的借鉴和参考。     

吸湿介质对碳纤维增强铸型尼龙复合材料的吸湿行为及力学性能的影响

本文对碳纤维增强铸型尼龙(CF／MC 尼龙)复合材料在不同吸湿介质中的吸湿行为进行了研究。结果表明，对于纤维体积分数为10％的碳纤维增强铸型尼龙复合材料(10％CF／MC尼龙复合材料)，随着吸湿介质的PH值减小，它的吸湿率增大。同时，经过吸湿后，10％CF／MC尼龙复合材料的弯曲强度有明显的下降。随着吸湿介质的PH值减小，试样的弯曲强度下降。使用环境扫描电子显微镜观察在10％HCl溶液中吸湿的试样的剪切断口形貌，得到的结果与吸湿实验的结果一致。     

吸湿多孔介质冷冻干燥传质传热模型

本研究在作者提出的吸附—解吸平衡关系的基础上,建立了一个全新的考虑吸湿效应的多孔介质冷冻干燥数学模型。模型用有限差分法进行求解,并带有一个移动边界,以模拟介电材料辅助的微波冷冻干燥过程。介电材料选用碳化硅（SiC）,原料液为脱脂奶。模拟结果表明：介电材料能够有效强化微波冷冻干燥过程。在典型操作条件下,介电材料辅助的微波冷冻干燥所用的时间比普通微波冷冻干燥减少33.1%。当料液中固体含量较低或者固体产品的损耗因子较小时,介电材料对微波加热的效果不明显。基于冰饱和度、温度和水蒸气浓度的分布,本文分析了干燥过程中的传质传热机理,并对干燥速率控制因素进行了讨论。     

EQUILIBRIUM MOISTURE CONTENT OF DRIED BLOOD FLOUR FN THE TEMPERATURE RANGE OF 20 - 50°C

ABSTRACT

The paper presents results of water sorption tests of dried blood flour carried out tinder laboratory conditions and mathematical analyses of sorption isotherms obtained. Moisture equilibrium data were investigated at air temperatures in the range of 20–50°C and water activity ranging from 0 4 to 0 99. The experimental procedure used was a gravimetric dynamic method with continuous registration of sample weight changes. Sorption capacity decreases as temperature increases. Rehydration of the dried material results in hysteresis but this phenomenon was small. Four models of equilibrium moisture content/equilibrium relative air humidity (Chung—Pfost. Halsey. Henderson, and Oswin) were evaluated for their ability to fit data for the samples of dried blood. The modified Henderson equation was a good model for moisture adsorption and desorption of dried blood flour     

印尼褐煤干燥和水分再吸收特性的试验研究

利用热重分析仪(TGA)和等温吸湿实验装置对一种印尼褐煤干燥和水分再吸收过程进行了试验研究.结果表明干燥过程的平均表观活化能为25.77 kJ/mol,脱去吸附水的表观活化能为33.14 kJ/mol.吸湿等温线的形状为S型等温线,Chung Pfost数学模型更适合于拟合印尼褐煤的等温吸湿过程.     

Production of desiccants from Turkish bentonites

Representative samples of three Turkish bentonites were investigated with the aim of producing moisture adsorbents, so-called desiccants, of commercial grade: 1) Ca-bentonite from Lalapaşa–Edirne region (LLP), 2) Na/Ca-bentonite from Çankırı region (CNK), and 3) Na-bentonite from Reşadiye–Tokat region (RSD). The samples were composed of smectite and small amounts of quartz, feldspar, calcite and opal-CT and minor amounts of zeolite and dolomite. The clay mineral contents of the raw samples were estimated at 75–80% for LLP, 50–55% for CNK and 75–80% for RSD.The bentonites were upgraded by mineral processing techniques and modified by addition of calcium chloride. The effect of particle size, heat treatment conditions such as drying temperature and drying time were examined. A maximum moisture adsorption capacity of 17.1% was obtained after heating at 150–200 °C for LLP Ca-bentonite. The mixed bentonite (CNK) achieved a maximum moisture adsorption capacity of 8.3% at 105 °C and the Na-type bentonite (RSD) exhibited the lowest adsorption capacity of 6.4% at 105 °C. In addition to the standard tests and parameters, chemical additives such as calcium chloride which is known as a hygroscopic material were mixed with the bentonites. Moisture adsorption capacities of the bentonites were raised to a level about 20% above required as standards. The results obtained in this study together with the standard specifications were compatible with the commercial counterparts.     

高温干燥对褐煤孔隙结构及水分复吸的影响

利用卧式固定床实验炉制得不同温度下干燥处理的煤样,采用低温氮吸附法测试煤样的比表面积、孔体积和孔径分布等孔隙特征参数,使用复吸实验装置测定不同干燥程度褐煤煤样的平衡含水量,探索了高温干燥处理后褐煤孔隙结构的演变与其复吸特性之间的关联规律。结果表明：褐煤原煤及不同干燥温度(600~800℃)下半焦的等温吸附曲线均属于第Ⅱ类吸附等温线,褐煤原煤、600℃和700℃干燥半焦的吸附回线均属于L1型,800℃干燥半焦的吸附回线有从L1型转变为L2型的趋势;随着干燥温度的增加,干燥半焦的比表面积先增大后减小,介孔峰值的孔径微分同样先增大后减小,而大孔孔径微分基本保持不变;分形维数D₁和D₂呈相反的变化趋势,且D₂>D₁;不同干燥程度半焦的复吸曲线变化趋势相同,且平衡含水量随着干燥温度的升高而减小;半焦复吸特性与孔隙结构有关,平衡含水率与其孔容积之间呈较好的线性关系。     

Moisture Adsorption Isotherms and Glass Transition Temperature of Xanthan Gum

The moisture adsorption isotherms of the xanthan gum were determined at 30–70°C over water activity ranging from 0.11 to 0.94. The moisture adsorption isotherms revealed that the equilibrium moisture content increased with water activity. Increased temperature, in general, resulted in decreased equilibrium moisture content. However, in some cases equilibrium moisture content values increased with temperature. Selected sorption models were tested to describe the adsorption isotherms. Parameters of each sorption model were determined by nonlinear regression analysis. The modified Oswin model gave the best fit for xanthan gum. The isosteric heat of sorption decreased with increase in moisture content and varied between 1.66 and 7.61 kJ/mol. The glass transition temperature decreased with increase in moisture content for xanthan gum.     

Moisture Adsorption Isotherms and Glass Transition Temperature of Xanthan Gum

The moisture adsorption isotherms of the xanthan gum were determined at 30-70°C over water activity ranging from 0.11 to 0.94. The moisture adsorption isotherms revealed that the equilibrium moisture content increased with water activity. Increased temperature, in general, resulted in decreased equilibrium moisture content. However, in some cases equilibrium moisture content values increased with temperature. Selected sorption models were tested to describe the adsorption isotherms. Parameters of each sorption model were determined by nonlinear regression analysis. The modified Oswin model gave the best fit for xanthan gum. The isosteric heat of sorption decreased with increase in moisture content and varied between 1.66 and 7.61 kJ/mol. The glass transition temperature decreased with increase in moisture content for xanthan gum.     

Evolvement behavior of microstructure and H2O adsorption of lignite pyrolysis☆

The effect of pyrolysis on the microstructure and moisture adsorption of lignite was investigated with low field nuclear magnetic resonance spectroscopy. Changes in oxygen-containing groups were analyzed by Fourier transform infrared spectroscopy(FTIR), and H2 O adsorption mechanism on the surface of lignite pyrolysis was inferred. Two major changes in the pore structure of lignite char were observed as temperature increased in 105–200 °C and500–700 °C. Pyrolysis temperature is a significant factor in removing carboxyl and phenolic hydroxyl from lignite.Variation of ether bond content can be divided into three stages; the content initially increased, then decreased,and finally increased. The equilibrium adsorption ratio, content of oxygen-containing groups, and variation of pore volume below 700° were closely correlated with each other. The amount of adsorbed water on char pyrolyzed at700 °C increased. Moreover, the adsorption capacity of the lignite decreased, and the adsorption state changed.     

Modeling of Diffusion with Shrinkage and Quality Investigation of Banana Foam Mat Drying

A diffusion model including shrinkage has been developed for predicting the change of moisture content in banana foam mats during drying. Two solution methods, moving boundary using variable grid and immobilizing boundary using the Lagrangian referential coordinate, were used in exploring their capabilities to predict the moisture change. Banana foam mats with initial foam densities of 0.3, 0.5, and 0.7 g/cm³ were dried at 60, 70, and 80°C and superficial air velocity of 0.5 m/s. The qualities of the final products in terms of texture and microstructure were determined. The moving boundary method can predict the moisture content more accurately than the immobilizing boundary method especially in the case of low-density foam. The quality determinations showed that the initial foam density strongly affected hardness, crispness, and morphology of dried banana foam mats, whereas the drying temperature had no significant effect on those qualities.     

原油/水/壁面界面吸附特性及应用研究

原油/水/壁面三相界面特性存在于接触式传感器测量原油含水率当中,通过探针与原油的接触时间与原油掠过探针的速度,及Langmuir等温吸附模型得出特性吸附曲线,表明温度是影响含水率传感器测量精度的主导因素,现场应用结果表明,根据温度影响趋势,对传感器标定可减小传感器的测量误差。     

EQUILIBRIUM MOISTURE CONTENT OF DRIED BLOOD FLOUR FN THE TEMPERATURE RANGE OF 20 - 50°C

The paper presents results of water sorption tests of dried blood flour carried out tinder laboratory conditions and mathematical analyses of sorption isotherms obtained. Moisture equilibrium data were investigated at air temperatures in the range of 20-50°C and water activity ranging from 0 4 to 0 99. The experimental procedure used was a gravimetric dynamic method with continuous registration of sample weight changes. Sorption capacity decreases as temperature increases. Rehydration of the dried material results in hysteresis but this phenomenon was small. Four models of equilibrium moisture content/equilibrium relative air humidity (Chung—Pfost. Halsey. Henderson, and Oswin) were evaluated for their ability to fit data for the samples of dried blood. The modified Henderson equation was a good model for moisture adsorption and desorption of dried blood flour