Powder Technology Handbook edited by Keishi Gotoh,Hiroaki Masuda and Ko Higashitani Marcel Dekker,Inc., Cimarron Rd., Monticello,NY 12701 Second Edition. 1997, 944 pages.

Abstract:

In 2000, the U.K. government's Energy Efficiency Best Practice Programme commissioned a survey to determine the energy consumption of spray dryers within the chemicals, foods, and ceramics industries. The results of this survey, which included dryers having evaporation rates ranging from 0.1 to 12 t/h, revealed values of the specific energy consumption E _s varying from around 3 to 20 GJ/t water evaporated. The average for all dryers included in the survey was 4.87 GJ/t. The fuel-to-electricity consumption ratio averaged around 27. The data obtained in the survey were interpreted with the aid of a newly developed model that enabled the performance of a particular dryer to be compared with that of its ideal adiabatic counterpart. Using the model, it was estimated that around 29% of the energy supplied to the dryers included in the survey was being wasted.     

Numerical Modeling of Moisture and Temperature Distribution within a Rectangular Bagasse Layer Undergoing Drying

In this work, a numerical two-dimensional model using the finite volume method, which predicts the temperature and moisture distribution of the moist rectangular bagasse layer undergoing drying, is developed. During the drying process, variable heat and mass transfer coefficients are considered. The flow fields are numerically predicted using a commercial CFD package, Fluent. The temperature and moisture distributions under transient conditions are obtained, which determine both heat and moisture transport inside the material. The validation of the model is carried out by comparing the predicted mean moisture content values with those obtained experimentally. The comparison of the numerical and experimental result shows good agreement up to 8%.     

Availability and reliability considerations in the design and optimisation of flexible utility systems

Industrial utility plants are usually comprised of many interconnected units that must constitute a flexible and reliable system capable of meeting process energy requirements under different circumstances (e.g. varying prices, demands, or equipment shutdowns). Also, in order to avoid large economic penalties, the design and operation of a utility plant should consider that the equipment is not fully reliable and that each item needs to receive preventive and corrective maintenance. Conventionally, these issues are handled by installing additional units according to rules of thumb or heuristics, which usually imply excessive capital costs and might even result in designs that cannot satisfy the specified demands for certain situations. In contrast, during the present work a systematic methodology has been developed to address the design and operation of flexible utility plants incorporating reliability and availability considerations. The suggested method is based on a novel modelling and optimisation framework that can address grassroots design, retrofit, or (pure) operation problems in which design and operational parameters are optimised simultaneously throughout several scenarios. Thereafter, it is possible to define maintenance and failure situations in different operating periods to ensure that the plant will be able to cope with them, while meeting process requirements at minimum cost. Hence, for design cases, the most cost-effective elements of redundancy can be determined without pre-specifying any structural options in the final configuration (e.g. equipment sizes, types, and number of units). Furthermore, the proposed (multiperiod) MILP formulation is robust enough to tackle problems of the size and complexity commonly found in industry, and has the potential of yielding significant economic savings.     

利用螺杆膨胀动力机回收蒸汽余热发电

简述茂名石化利用螺杆膨胀机回收高压聚乙烯装置副产低压蒸汽余热发电工艺,本文介绍了螺杆膨胀机发电的工作原理、结构及技术特点、应用范围、应用方式及经济、节能效益。利用螺杆膨胀机回收蒸汽余热进行发电,发电后产生的凝液达到循环利用,最大程度地提高余热综合利用率。达到节能减排、节电、获得高效益的目的。并认为螺杆膨胀动力机将在石油化工行业有广泛的应用前景。     

DRYING OF SUGAR BEET PULP USING A LABORATORY AIR DRIER

ABSTRACT

Drying curves for sugar beet pulp were obtained in a laboratory-scale air drier. Dehydration conditions were: temperatures in the range of 35 to 90 ^°C, air flow velocities of 0.5 to 2.0 m/s, and air moisture content of 0.005 to 0.06 kg water/kg air. Using data from thin layer experiments, a mathematical model was derived to describe the dehydration behaviour under the described conditions. The model was able to predict data obtained from deep bed experiments. Results from this work could be used to develop a design methodology for dryers that operate at relatively low temperatures (<90^°C).     

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.     

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.     

INFLUENCE OF PROCESS CONDITIONS ON THE DRYING RATE OF CASSAVA CHIPS IN A SOLAR SIMULATOR

ABSTRACT

Experiments were carried out in a solar simulator to study the influence of air temperature (25-40°C), air relative humidity (40-80%), air velocity (0.95-2.2 m/s), radiation intensity (0-916 W/m²), and loading density (10-30 kg/m²) on the drying rate of a bed of cassava chips (2×2×2 cm). Well-known thin-layer drying equations were fitted to the experimental data, and the empirical constants were used in a statistical analysis of the influence of process conditions on the drying rate. The air temperature, air velocity, radiation intensity, and loading density influenced the drying rate significantly (p=0.05). The effects of the air temperature and the radiation intensity were attributed to the temperature-dependent diffusion of moisture within the chips, while the effect of the air velocity was ascribed to the resistance to mass transfer at the air-chip interface. Equations were presented to express the empirical constants as functions of the process variables.     

A DRYING HEAT PUMP USING CARBON DIOXIDE AS WORKING FLUID

The application of carbon dioxide as working fluid in refrigeration and heat pump systems is regaining increasingly importance in view of the chlorofluorocarbon (CFC) substitution problem. It is both under ecological and economical aspects an attractive alternative to the hydrofluorocarbon (HFC) working fluids being in practical use. The thermophysical properties and characteristics of carbon dioxide are quite different from those of refrigerants used in conventional vapour compression cycles. Its application in conventional vapour compression refrigerating systems is limited by its critical parameters (t_c = 31.1°C and p_c = 73.8 bar). The possibility to use carbon dioxide also beyond these limits in high temperature processes, e.g., heat pumps, is given by the application of a trans-critical process. The design and construction of a commercial drying heat pump system (batch type cabinet dryer with 12 kW heating capacity and closed air circuit) using the natural working fluid carbon dioxide is shown and experimental results of investigations carried out are presented. Possible energy savings calculated theoretically are given for comparison.     

A DRYING HEAT PUMP USING CARBON DIOXIDE AS WORKING FLUID

ABSTRACT

The application of carbon dioxide as working fluid in refrigeration and heat pump systems is regaining increasingly importance in view of the chlorofluorocarbon (CFC) substitution problem. It is both under ecological and economical aspects an attractive alternative to the hydrofluorocarbon (HFC) working fluids being in practical use. The thermophysical properties and characteristics of carbon dioxide are quite different from those of refrigerants used in conventional vapour compression cycles. Its application in conventional vapour compression refrigerating systems is limited by its critical parameters (t _c = 31.1°C and p _c = 73.8 bar). The possibility to use carbon dioxide also beyond these limits in high temperature processes, e.g., heat pumps, is given by the application of a trans-critical process. The design and construction of a commercial drying heat pump system (batch type cabinet dryer with 12 kW heating capacity and closed air circuit) using the natural working fluid carbon dioxide is shown and experimental results of investigations carried out are presented. Possible energy savings calculated theoretically are given for comparison.     

我国粮食干燥节能途径

能耗是衡量粮食干燥机技术性能好差的一项经济指标。介绍了粮食干燥能耗情况，分析了粮食干燥的节能途径，供设计粮食干燥机时合理选用。     

Experimental Study on Energy Consumption of Combined Conventional and Dehumidification Drying

Conventional drying, dehumidification drying, and combined conventional-dehumidification drying of wood were experimentally studied in this article. The results showed that the energy consumption in the dehumidification drying is the least but its drying time is the longest. The energy consumption in the combined drying is more than that in the dehumidification drying but less than that in the conventional drying, and the drying time is half of that in the dehumidification drying. The advantages of the combined conventional and dehumidification drying are discussed from the experiments results.     

Experimental Study on Energy Consumption of Combined Conventional and Dehumidification Drying

Conventional drying, dehumidification drying, and combined conventional-dehumidification drying of wood were experimentally studied in this article. The results showed that the energy consumption in the dehumidification drying is the least but its drying time is the longest. The energy consumption in the combined drying is more than that in the dehumidification drying but less than that in the conventional drying, and the drying time is half of that in the dehumidification drying. The advantages of the combined conventional and dehumidification drying are discussed from the experiments results.     

我国木材干燥设备制造业概况与存在的问题

介绍了我国木材干燥的市场需求与设备制造企业的概况,指出了我国木材干燥设备制造企业目前存在着技术规范还不够健全、缺乏质量监督机构、检测控制系统精度差、零部件质量差及干燥设备的能耗偏高等问题,并对提高木材干燥设备质量提出了几点建议。