微波—对流干燥技术在聚丙烯酰胺生产中的应用

采用微波－对流干燥技术对高含水、粘度较大、过热表面易结壳的热敏性物料进行烘干试验,取得了较好的效果,解决了干燥领域的一大难题,并给出了烘干曲线及微波－对流干燥原理图,可供设计参考。     

微波加热在毛条烘干中的应用研究

介绍了应用微波加热烘干毛条的基本原理,研究了微波干燥设备的烘干效率、节能效果及烘干效果,结果表明,微波加热可以应用于纺织印染行业,为微波加热在纺织印染行业的推广应用提供了研究基础。通过生产应用,在计算微波加热毛条烘干工艺参数时,微波烘干机的干燥效率可取1.1kg/kW﹒h,微波干燥后,毛条含水率均匀,颜色前后色差无变化,纤维的强度和手感得到改善,微波干燥节能效果,比射频烘干节能约20%。     

不同干燥方式对天然胶性能影响研究

为探讨干燥方式对天然胶性能影响,采用了烟熏烘干,微波烘干,直接烘干,絮胶烘干等不同干燥方式,探讨了不同干燥方式下产品特性、动态力学性能以及机械性能。结果表明：微波烘干烘干时间远远短于其他几种方式,天然胶产品中几乎不存在烘干过程中的夹生胶情况。四种方式中微波烘干纯胶、碳黑胶配方、白炭黑配方均得到优越的物理性能,絮胶烘干方式次之。动态力学性能测试中,可得碳黑配方的硫化胶中,絮胶烘干得到的天然橡胶产品tanδ值最小,而在白炭黑配方的硫化胶中,微波烘干所得天然胶产品tanδ值最小。     

干燥方式对天然橡胶性能的影响

探讨直接烘干、絮胶烘干、微波烘干和烟熏烘干4种干燥方式对天然橡胶(NR)性能的影响。结果表明:微波烘干时间远远短于其他3种干燥方式,且几乎不存在夹生胶现象;微波烘干NR纯胶、炭黑和白炭黑填充NR硫化胶物理性能均较优,絮胶烘干NR次之;絮胶烘干炭黑填充NR硫化胶的损耗因子(tanδ)最小,微波烘干NR白炭黑填充配方硫化胶的tanδ最小。     

多孔物料微波对流干燥模化实验装置设计探讨

根据微波对流干燥法的特点，建立多孔物料微波对流干燥过程的物理模型和数学模型，通过数学方式的无因次化处理和分析，获得进行微波对流干燥模化实验研究所遵循的条件，讨论了模化实验装置设计应考虑的因素。     

不粘煤的微波－对流干燥研究

从不粘煤的特性出发，讨论了不粘煤工业干燥的要求；从微波－对流综合干燥传热传质原理分析，论证了这种干燥方式用于不粘煤干燥，在降低温度、控制负荷、提高经济性等方面都有显著成效，并以翔实的试验数据为理论分析作了辅证。     

不粘煤的微波－对流干燥研究

从不粘煤的特性出发，讨论了不粘煤工业干燥的要求；从微波－对流综合干燥传热传质原理分析，论证了这种干燥方式用于不粘煤干燥，在降低温度、控制负荷、提高经济性等方面都有显著成效，并以翔实的试验数据为理论分析作了辅证。     

集装箱水性涂料的微波烘干工艺研究

根据微波在集装箱水性涂料干燥成膜过程中对水分挥发的特殊作用原理,研发了集装箱水性涂料的微波烘干设备,并开展了样机验证测试和能耗分析,确认了微波烘干工艺对降低集装箱水性涂料烘干能耗的效果,从而开发出一项针对集装箱水性涂料的新型节能烘干工艺。     

干燥方式对天然橡胶性能的影响

天然橡胶的性能在很大程度上会受烘干方式的影响,常见的烘干方式有直接烘干、微波烘干、烟熏烘干、絮胶烘干。其中烘干时间比较短的是微波烘干,在使用该种干燥方法时不容易出现夹生胶的情况。使用微波烘干的方法对天然纯橡胶进行烘干,能够保证橡胶的物理性能,絮胶烘干以及炭黑和白炭黑填充的处理方法次之。     

企业讯息

<正>嘉宝莉研究水性木器漆微波红外干燥技术随着人们对环境污染的日益重视,更具环保性能的水性木器漆逐渐得到家具行业、企业的关注,但是干燥难等技术问题却成为了该产品发展中的难题,对此嘉宝莉涂料公司新近研发出一种微波红外干燥技术。据公司介绍,红外和微波都具有穿透性,红外加热能温和地烘干水分,而微波则可以快速而彻底地完成对水分的烘干,二者相结合既能够满足对水性漆干燥速度的要求也     

高湿物料真空连续复合管束烘干设备研制初步探讨

从分析影响烘干设备干燥效果的烘干时间、加热温度、运行距离、物料与加热系统的接触面积入手，研制出高湿物料真空连续复合管束烘干设备。干燥主机采用三个不同直径的同心圆筒组成多级干燥室，各个干燥室内设有一定数量的加热管束，利用真空连续干燥、热能按需分配的原理，延长物料在干燥主机内的烘干时间、运行距离，加大物料与加热系统的接触面积，提高烘干设备的空间利用率。从而有效踺提高了烘干效率，降低烘干成本，改善了物料品质；改变了传统管束烘干设备采用一级干燥室的空间利用率低、热能不被充分利用的局面。     

微波真空组合干燥技术的研究

微波真空干燥是综合微波干燥和真空干燥各自优点的一项新技术,将微波干燥的快速高效性和真空干燥的低温高质相结合,在真空条件下利用微波对物料进行干燥处理,从而实现物料的快速低温干燥。着重阐述了微波真空组合干燥技术的机理、特点、干燥动力学以及影响微波真空干燥的重要因素,并对微波真空组合干燥的应用研究进行了介绍。     

A novel preparation of superhydrophobic silica aerogels via the combustion drying method

Silica aerogels with prominent physical, thermal, optical, and acoustic properties are considered to be highly promising materials. However, owing to the high cost and the complex production processes associated with existing drying technologies, the application of silica aerogels is limited in many fields. In this study, a novel combustion drying method (CDM) was successfully used in the synthesis of superhydrophobic silica aerogels for the first time. It was confirmed that silica aerogel prepared by CDM has a typical aerogel structure with low density, high porosity, high specific surface area, high total pore volume, superhydrophobicity and high thermal stability. Compared with supercritical fluid drying, freeze drying and ambient pressure drying, CDM possesses significant advantages in the drying efficiency and low-cost production due to its active drying mode. Finally, the mechanism of the combustion drying method is proposed based on the combustion of organic solvents. The results will be meaningful for the design and production of aerogel materials in the future.     

A Study of the Power Density Distribution generated during the Combined Microwave and Convective Drying of Softwood

ABSTRACT

Investigations into new and innovative drying strategies can lead to the development of more efficient and effective drying processes. The commercialisation of these processes would prove invaluable to the drying industry as a whole and the associated technology would generate worldwide interest. Combined microwave and convective drying is one such process which offers great potential, with benefits that include : reduced drying times and increased drying rates; volumetric heating; higher fluxes of liquid to the drying surface; high temperature and internal pressure buildup within the material which enhances the overall moisture migration rate; and preferential heating of wetter areas. Numerical simulation can elucidate on the intricate details of the heat and mass transfer henomena that occur during the drying process, thus eliminating the need for performing numerous time consuming and expensive experiments. The simulations can predict the evolutionary behaviour of the moisture, temperature and pressure distributions, and can provide a detailed analysis of how microwaves interact with materials during drying and heating operations at a fundamental level. The research presented in this paper uses a comprehensive mathematical model to study the behaviour of the iniernal microwave power density distribution that is generated during the microwave enhanced convective drying of softwood. The configuration understudy concerns a plane wave microwave source irradiating the wood in the transverse direction.     

Selected chemical and physico-chemical properties of microwave-convective dried herbs

The purpose of the presented study was to describe kinetics of microwave-convection drying of basil (Ocimum basilicum), lovage (Levisticum officinale), mint (Mentha sp.), oregano (Origanum vulgare), parsley (Petroselinum crispum), and rocket (Eruca vesicaria) by means of different mathematical models, as well as to describe changes of polyphenols content, color and sorption properties after drying. The analyzed leaves were dried using microwaves power level of 300 W, in a temperature of 40 °C. Logistic model provided best fit to the experimental data. No significant differences in the drying kinetics could be discerned, while significant influence of herbs species on polyphenols contents, color and sorption properties was noted. The highest retention of phenolic compound, good resistance to color degradation and the highest water vapor adsorption concerned Apiaceae family (lovage, parsley), while worse properties in terms of these parameters were noted in Lamiaceae (basil, oregano, mint) and Brassicaceae (rocket).     

Encapsulation Efficiency of Food Flavours and Oils during Spray Drying

Microencapsulation is a rapidly expanding technology which is a unique way to package materials in the form of micro- and nano-particles, and has been well developed and accepted within the pharmaceutical, chemical, food and many other industries. Spray drying is the most commonly used encapsulation technique for food products. A successful spray drying encapsulation relies on achieving high retention of the core materials especially volatiles and minimum amounts of the surface oil on the powder particles for both volatiles and non-volatiles during the process and storage. The properties of wall and core materials and the prepared emulsion along with the drying process conditions will influence the efficiency and retention of core compounds. This review highlights the new developments in spray drying microencapsulation of food oils and flavours with an emphasis on the encapsulation efficiency during the process and different factors which can affect the efficiency of spray drying encapsulation.     

Carbon aerogels, cryogels and xerogels: Influence of the drying method on the textural properties of porous carbon materials

Carbon materials with tailored texture can be obtained from drying and pyrolysis of resorcinol-formaldehyde gels. The pore texture of both dried and pyrolyzed material depends on the drying process. Several more or less expensive methods (supercritical drying, freeze-drying, evaporative drying) were tested in order to determine which process is the most suitable for the synthesis of a porous carbon with a definite texture. Supercritical drying leads to the highest pore volume and the widest texture range, but residual surface tensions and shrinkage are not avoided when the pore size is small or when the material density is low; this hampers to fix both the pore volume and the pore size easily. Monoliths are very difficult to obtain by freeze-drying, and the appearance of huge channels due to ice crystal growth at high dilution ratio hinders the fabrication of low density materials. Moreover, gels with small pores do not remain frozen throughout drying, which leads to surface tensions and shrinkage. Although generally replaced by more complicated techniques, evaporative drying is suitable when dense carbons are needed or when the only selection criterion is the pore size: all pore sizes are reachable, but this parameter is in this case strongly correlated to the pore volume.     

Effect of Drying Methods on Dyeing Capacity of Dyestuff Plant Materials

This article presents a study of the effect of drying methods on dyeing capacity of widespread European flora dyestuff plant materials. The natural colorants, derived from the selected plant materials, were applied on chemical pulp in order to examine their dyeability. In this work, three different drying methods were examined—the natural, the air-, and the freeze-drying method—in various conditions. The plant materials that were dried naturally show weak dyeing results in comparison with the air- and freeze-dried materials. Freeze drying significantly improved the dyeing capacity of dyestuff plant materials with high initial moisture content. On the other hand, air drying at low temperature and high relative humidity improved the dyeing capacity of plant materials with low initial moisture content.     

Diffusive Model with Shrinkage in the Thin-Layer Drying of Fish Muscles

Fish fillets present large variation in volume during drying, due to their high initial moisture content. A kinetical study on the drying of fish muscles in slabs shaped with constant air conditions at three temperature levels is presented. For the modeling of the drying process of these materials, a diffusive model can be used, assuming a one-dimensional volume change. A linear correlation was considered between the thickness of the material and its moisture content, where the linear shrinkage coefficient has been determined. The resulting dimensionless nonlinear partial differential equation was solved numerically by the finite differences technique.     

内热式惰性粒子流化床中膏状物料干燥模型

通过对惰性粒子流化床中膏状物料干燥机理的分析,得到了干燥时间及单位面积床层水分汽化量的数学计算式,可对干燥器的性能进行预测。采用带浸没加热管的惰性粒子流化床对膏状钛白物料进行干燥中试研究,采用气流式喷嘴将膏状物料分散成200～400μm的小液滴喷洒在惰性粒子表面进行干燥,探索了适宜的干燥条件,测定和确定了最佳的干燥工艺参数、操作参数和设备参数。结果表明:该干燥工艺能强化床内传热传质,促进高黏性膏糊状物料很好地分散,床层温度分布均匀,干燥器的操作弹性大,热量消耗低,干燥强度高,传热系数可达300W·m-2·K-1以上。