R&D OPPORTUNITES IN DRYING OF ADVANCED ELECTRO-CERAMICS

ABSTRACT

This article presents an inaoduction to the various drying processes operational in the ceramic processing industry, with special emphasis on electro ceramics. An attempt is made to arouse the interest of drying specialists in fields other than ceramics to participate in a concentrated group effort to solve a number of existing problems related to ceramics drying. The importance of materials education is highlighted by referring to a few examples depicting the effect of the drying process on the final product quality. It is argued that with more research, conventional processes like spray drying, rotary drum drying, etc. can be improved or replaced with alternative processes like freeze drying, microwave drying, infrared drying and vibrated fluidized bed drying.     

DRYING AND DEWATERING R&D IN JAPAN

Presently, it has become an urgent and important concern worldwide to reduce the volume of waste and rationally use the waste for electric power generation. Sludge is a dominant part in the family of wastes. Drying of sludge, not only for volume reduction but also for further utilization, is becoming an essential and integral process. On the other hand, as the requirement of new materials production, for example, fine particles of micron or sub-micron scale for advanced materials, some new drying technologies and techniques have emerged. The market-pull may be the direct and active impetus to drying research and development (R&D). In this paper, drying technologies for sludges, fine particles, coatings as well as advanced dewatering are discussed to reflect the “hot” points of drying and dewatering R&D in Japan. And some novel dryers are also presented.     

DRYING R& D IN P.R. CHINA

A survey has been made of r6cent R& D activities in drying of solids in the People's Republic of China. Overall, the interest level appears to be rising in view of the increase in industrial development in the chemical, food, and other industries. Synopses are provided of selected recent publications     

STEAM DRYING TECHNOLOGIES: JAPANESE R&D

This report reviews some fundamental and practical aspects of steam drying technologies based mainly on studies published in Japan. Steam drying kinetics, and some industrial technologies particularly for drying of foods, textiles and sludges are reviewed with focus on quality of dried material, drying time, dryer selection and energy recovery from steam dryer exhaust. For energy recovery, heat pump technologies are outlined along with characteristics of different types of steam compressors. A new process is proposed for steam drying; it combines a direct-indirect dryer followed by a direct steam dryer for internal moisture removal.     

R&D Needs-Drying of Sludges

Sludge management is very important subject for the environmental issue in many industrialized countries, because its generated volume is the largest in all generated wastes. In sludge management field, role of drying is becoming more needful as increase of difficulty for sludge disposal and need for sludge drying is expected in the future.

In this paper, the present status of drying of construction sludge, food industry sludge and municipal sludge are mentioned as concrete examples.

To respond these needs, it is necessary to advance further R & D     

Global R&D Needs in Drying

This paper summarizes some recent advances and general trends in drying technologies of industrial interest. The process of innovation is applied to drying R&D. The conventional drying techniques are compared with the innovative technologies. Numerous emerging technologies are listed and some examples are discussed in detail. Potential application areas for the new technologies are identified.     

R&D Needs in the Drying of Coatings

The key technologies involved in the drying of coatings are first reviewed and then the factors that influence the drying process are identified, leading to a discussion uf future R&D needs. The drying mechanisms in the constant and falling rate periods are discussed. Present and nticipated estrictions on the use of solvents will result in aqueous systems replacing some solvent systems. and in wider use of high solids coatings and 100% solids coatings. Cross-linking reactions to solidify monomers and low-molecular polymers now become important. Dryers will become chemical reactors. Further development of models of drying, of diffusion, of surface solvent levels, and of solvent vapor pressures will be needed, along with those of dryer defects and drying stresses. To accurately simulate a wide range of coating systems more physical property data is needed. Nan-convection heating and environmental concerns complete the discussion.     

Recent R&D on Drying Technology in Japan

This article presents the outlook of the energy situation in Japan and reviews the recent R&D on innovative drying technologies performed in Japan. The overview of drying includes fundamentals as well as industrial technologies. The topics considered are drying characteristics of several materials, drying of hard-to-handle powders, drying of coatings, drying-induced strain-stress problems, drying modeling, and drying of agricultural wastes for functional recycling and noble dryers. An appropriate combination of heating methods and dryer type can result in significant enhancement of efficiency, drying rate, and/or material quality. The final goal of this article to contribute to providing an idea for development and evaluation of precise drying systems with a high performance and an effect of energy saving in drying.     

Review of R&D in Drying of Refractories

This article reviews the published research and development work on refractory drying. Current practice and potential problems are analyzed. Some selected important research results are presented. It is shown that significantly improved drying procedures can be achieved through computer simulation of the drying process.     

DRYING AND DEWATERING R&D IN JAPAN

Presently, it has become an urgent and important concern worldwide to reduce the volume of waste and rationally use the waste for electric power generation. Sludge is a dominant part in the family of wastes. Drying of sludge, not only for volume reduction but also for further utilization, is becoming an essential and integral process. On the other hand, as the requirement of new materials production, for example, fine particles of micron or sub-micron scale for advanced materials, some new drying technologies and techniques have emerged. The market-pull may be the direct and active impetus to drying research and development (R&D). In this paper, drying technologies for sludges, fine particles, coatings as well as advanced dewatering are discussed to reflect the “hot” points of drying and dewatering R&D in Japan. And some novel dryers are also presented.     

DRYING R& D IN P.R. CHINA

A survey has been made of r6cent R& D activities in drying of solids in the People's Republic of China. Overall, the interest level appears to be rising in view of the increase in industrial development in the chemical, food, and other industries. Synopses are provided of selected recent publications     

EFFECT OF DRYING ON PULP & PAPER PROPERTIES: A BIBLIOGRAPHY

Papermaking is a massive dehydration operation. Thermal removal of moisture which can not be removed mechanically is a key process stage in papermaking. It is well known that it is a highly energy intensive step. However, it is less readily recognized that it also influences some of the most important physical, optical or functional properties of the product. With the advent of new drying technologies- some already commercialized while some still at pilot or laboratory stage - it is increasingly important to devote attention to the interaction between the drying conditions and the final product quality as measured by generally accepted standard test results. Aside from the drying parameters one must also examine paper/pulp parameters in the hope of achieving in the long term some predictive capability as well as drying-quality effects. This bibliography is selective in coverage and is compiled to ease the task of the interested reader in locating appropriate references covering his/her areas of interest.. Some general observations are made on the basis of the literature cited.

important problem.This is influenced by the composition and characteristics of the coating colour and raw stock and also by the type and rate of drying.

The following selected bibliography covers the effect of drying on pulp, paper and paperboard properties. Some available literature on coated paper drying is also included. It is encouraging to note a trend towards considering the effect of drying on the product quality as an integral part of drying R&D projects. Earlier, the drying work was confined to optimising only the heat and mass transfer parameters. It should be noted also that this bibliography includes a substantial number of publications which are not in english. The availability of their translations into english is not known to the authors.

It is noteworthy that an international symposium - The Helsinki Symposium on Alternate Drying Technologies will be held in Helsinki in June 1991 to discuss the competing new drying technologies from the papermakers viewpoint.     

RATE OF DRYING AND STRESSES IN THE FIRST PERIOD OF DRYING

The paper presents a computer simulated processes and illustrate how the drying induced stresses are influenced by the rate of drying. It is shown that the moisture transport coefficient, and thus the rate of drying, depends on the thermal state of the drying material, defined by the wet-bulb temperature. Through these simulated processes one can observe the evolution of the moisture content and stress distributions during drying at constant, but in each process different, wet-bulb temperatures. A convective drying process of a bar with rectangular cross-section is considered as example, and a two-dimensional initial-boundary value problem is solved numerically with the use of the finite element method. The numerical results are visualised in spatial diagrams.     

先进复合材料中主要缺陷分析

本文重点介绍了复合材料中主要缺陷的各类,分析了缺陷产生的原因,对主要缺陷对性能的影响、缺陷的控制方法、缺陷的无损检测方法及其进展进行了综述。     

ESTIMATION OF FUNCTIONS IN DRYING EQUATIONS

In drying problem, particularly for drying foodstuff, modelling is very difficult. Many physical effects have to be taken into account for mass transfer ; then mass transfer coefficient varies

In different models unknown functions must be estimated. It is particularly the case in simple models of drying using average values of water content, where the mass transfer varies versus mean water content in falling rate period. On the other hand in the “diffusion model” we have the same problem concerning the diffusion coefficient which must be also estimated

The method we propose in this paper for these two models : simple and “diffusion model” of drying consists from measurements of temperature and water content of the product to search a numerical approach of the unknown function. This method uses optimization techniques on computer and least squares criterion between model values and experimental data

Results are given for the “diffusion model” applied to shelled corn drying to find the diffusion coefficient and for a simple 11107 del applied to plum drying to find the mass transfer coefficient.     

新技术在电泳涂装中的应用

介绍阳极膜和高红外固化技术在电泳涂装中的应用、特点及要求。     

国内外尼龙增韧研究进展

介绍了近年来尼龙增韧的最新研究进展，并对尼龙增韧的发展前景进行了展望，把尼龙增韧的研究划分为6类，即不同尼龙品种之间的共混、尼龙／聚烯烃、尼龙／聚烯烃弹性体、尼龙／高性能工程塑料、尼龙／无机物、尼龙／有机低分子物，列举了主要的研究工作。