干燥技术的进展和应用

文章侧重与化学工业关系较密切的方面，以各种干燥机的开发、改进和应用为主要线索，简要评述干燥技术２０多年来的进展与应用、技术发展趋势和存在的问题、以及我国的基本情况。     

COMPARISON OF TIMBER DRYING USING SOLAR ENERGY,ELECTRICAL HEATING AND DEHUMIDIFIER.

ABSTRACT

The performance of three different types of dryers for the hot air drying of sawn-limber planks are compared. These were the electric resistance dryer, solar dryer, and the dehumidifier dryer. Whilst the electric and solar dryers depended only upon hot air for drying, the dehumidifier dryer relied on hot dehumidified air. The results of investigations carried out on timber drying employing these three types of dryers in the Engineering Faculty are compiled and compared here in this paper. The results showed that the electric dryer produced the fastest drying lime and lowest moisture content, followed by dehumidifier drying. The solar dryer achieved a lower moisture content and a faster drying rate compared to natural drying, although the difference in drying times was marginal.     

薄层干燥技术的研究进展

简要介绍了各种类型的薄层干燥方程,并对薄层干燥技术在农产品、水产品、中药材及其他产品干燥特性研究中的应用进行综合评述。     

应用涂装设备改善水性木器涂料的干燥瓶颈

从不同条件及各种涂装现场的角度来探讨水性木器涂料与不同涂装干燥设备的搭配的效果,寻找出适合水性木器涂装的设备,改善水性木器干燥瓶颈,促使水性木器涂料能广被采用。     

干燥动力学研究综述

对现有的几种干燥速率定义及其数学表达式进行了分析和比较。简述了多孔介质的干燥动力学特性及其湿分迁移机理。对薄层干燥的半理论模型、半经验模型和经验模型作了评述。     

Through Drying of Paper

Through drying of paper of basis weight 25 to 50 g/m² was studied through 89 experiments with 22 to 90°C air at mass flow rates from 0.125 to 1.45 kg/m²s. The complete drying rate curves are represented with five quantitative parameters:moisture contents at the end of the increasing and constant rate periods, the constant drying rate, and exponents for the increasing and falling rate period relations. The constant drying rate period disappears at higher drying intensities leaving the increasing rate period accounting for as much as 37% of the drying. The constant drying rate may be controlled by thermodynamics or by transport phenomena. The critical moisture content depends on effects from the intrinsic local nonuniformity of through drying as well as on sheet average conditions. A universal set of relations was obtained for representation of the complete drying rate curve and was verified for prediction of drying rate and drying time. Through drying rates cannot be increased significantly by providing the drying air as an impingement flow.     

DRYING RATES AND DRYER CAPACITIES OF DIFFERENT SEED GRAINS

ABSTRACT

The three most commonly occurring grains --maize, rice and wheat --are compared for single kernel and deep bed drying rates. The grains are dried in a concurrent-flow (CCF) dryer; high grain temperatures are avoided to prevent deterioration of seed viability.

Wheat dries the fastest of the three grains as an individual kernel as well as in the CCF grain dryer, maize the slowest; the throughput with wheat is 23% larger than with maize, and 15% larger than with rice.     

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.     

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.     

Structure of Drying Costs

ABSTRACT

Cost structures of lumber and coal drying processes together with an application of the factor method for prediction of the drying cost are presented.     

从软泥状到粉末

描述了旋转瞬时干燥设备利用机械能与热能，对糊状物与滤饼进行高效干燥的过程、设备的设计与干燥的成本，以及与之相关的其它方面。     

不同加热功率下含油污泥的干燥

辽河油田的含油污泥含有大量的水分,为了更有效地进行油泥热解和减少热解过程中的能耗,需运用干燥技术处理油泥。实验考察了不同干燥功率对油泥干燥速率、湿分比的影响。实验结果表明:油泥干燥可以分成3个阶段,即恒速干燥阶段、第1降速干燥阶段和第2降速干燥阶段;加热功率越大,达到平衡含水质量分数所用的时间越短,恒速干燥速率越大。然后运用干燥方程求得干燥时间。最后运用热分析动力学对实验数据进行处理,得到干燥动力学的数学模型。模拟结果表明修正Page模型符合油泥干燥过程。     

Microwave-Assisted Atmospheric Freeze Drying of Green Peas: A Case Study

Atmospheric freeze drying (AFD) is based on the sublimation of ice due to a pressure gradient (convective drying), and is a dehydration process for temperature-sensitive products. Since the process is slow in general, microwave radiation (MW) was applied in order to increase the sublimation in fluid and fixed bed conditions at drying temperatures of ?6°C, ?3°C, and 0°C. The modified Weibull model was used to describe the drying behavior for all investigations. With 280 Watt power supplied to the magnetrons, it was possible to reduce drying time by approximately 50%. The drying efficiency was approximately 30%, while the SMER was increased by 0.1 to 0.3 kg_waterkWh^?1, which gives better energy efficiency for the microwave drying system used in this investigation. The product quality (color reduction and particle size/porosity) was well preserved in fixed bed drying at ?6°C and ?3°C, while the product quality was reduced significantly in microwave AFD experiments at 0°C and in a fluid bed. The drying rates of AFD in a fluid bed condition were not as high as those in a fixed bed. MW-AFD in a fixed bed condition at temperatures of ?6°C and ?3°C performed best regarding product quality, drying time, and process control.     

气凝胶制备的干燥技术

气凝胶是一种新型轻质的三维纳米多孔固态材料,由于其独特的物理化学性能,在许多领域存在潜在的应用价值而备受关注。本文简要介绍了湿凝胶的干燥理论和气凝胶的超临界干燥制备技术,评析了气凝胶的亚临界干燥、常压干燥、常压阶梯干燥及真空冷冻干燥等非超临界干燥制备技术。     

USE OF NEW APPLICATOR DESIGN IDEAS TO IMPROVE UNIFORMITY OF PAPER DRYING VIA MICROWAVE ENERGY

Previous studies of microwave drying of paper have employed slotted waveguides having the slots along the centerlines of the waveguide broad walls. It has now been recognized that a slot height that varies with cross-machine position can be designed to achieve better heating uniformity. This configuration can compensate for the reduction in peak electric field strength due to absorption in the paper web as the waves propagate across the width of the paper machine. In this paper, we present a model that facilitates design for uniformity. We then investigate the tradeoff between efficiency and heating/drying intensity, and present preliminary model results indicating the ranges and combinations of basis weight and moisture content which are most compatible with the goals of achieving uniform microwave energy absorption, high efficiency, and high drying rate.     

USE OF NEW APPLICATOR DESIGN IDEAS TO IMPROVE UNIFORMITY OF PAPER DRYING VIA MICROWAVE ENERGY

Previous studies of microwave drying of paper have employed slotted waveguides having the slots along the centerlines of the waveguide broad walls. It has now been recognized that a slot height that varies with cross-machine position can be designed to achieve better heating uniformity. This configuration can compensate for the reduction in peak electric field strength due to absorption in the paper web as the waves propagate across the width of the paper machine. In this paper, we present a model that facilitates design for uniformity. We then investigate the tradeoff between efficiency and heating/drying intensity, and present preliminary model results indicating the ranges and combinations of basis weight and moisture content which are most compatible with the goals of achieving uniform microwave energy absorption, high efficiency, and high drying rate.     

我国干燥技术和装备的研究及应用

介绍我国干燥设备的开发、研究和应用情况。情况表明：我国干燥技术有很大的进步，大批进口干燥器的时代已经结束。     

EXPERIMENTAL INVESTIGATIONS OF BEET PULP DRYING IN SUPERHEATED STEAM UNDER PRESSURE

ABSTRACT

Beet pulp drying in superheated steam under pressure makes it possible to save energy in sugar factories. A new concept of a two-stage convective steam drier is presented. To obtain kinetic data on beet pulp drying, an experimental setup was built. Beet pulp samples were dried at steam pressure up to 4 bar and temperature up to 220° C.