提高对流干燥系统热效率方法的研究

阐述了提高对流干燥系统热效率的三种有效方法，即强化干燥器内的传热性质过程、采用部分排气再循环和回收排气余热，并进行了理论分析，给出了相应的计算实例。     

塑料原料的干燥系统

<正> 一、引言 可把塑料分为非吸湿性与吸湿性两类。湿气只粘附在非吸湿性塑料颗粒的表面,PE、PP与PS等是常见的非吸湿性塑料;吸湿性塑料会把湿气吸至其内部,形成分子键,常见的吸湿性塑料有PET及多数工程塑料。     

传导干燥与对流干燥的能耗与成本对比分析

干燥作业是各行业中能耗较大的处理方法之一,我国干燥能耗约占全部工业能耗的12%。传导干燥比对流干燥节能20%—50%,但传导设备往往耗用金属材料较多,结构较复杂,主机造价较高,用户有时会因不能综合分析对比,只因主机投资较大,放弃节能产品的选用。文中利用通用的Excel程序,建立了一种定量的能耗及干燥成本综合对比分析方法,可方便迅速地对不同干燥方法定量比较,给出节能对投资的回报率,从而优选出节能干燥设备,对推动节能产品的应用、降低干燥成本具有重要意义。     

竹条干燥特性的实验研究

对竹条的热风对流干燥特性进行了系统的实验研究。讨论了干燥方式, 热风速度和温度等因素对干燥过程的影响; 从干燥过程的基本原理出发, 导出了干燥过程的数学模型; 利用此模型对实验结果进行回归整理, 得到了反映竹条干燥特性的实验关系式。     

管线系统设计前的压降预测

<正> 在工艺及能源工厂的设计中,在得到全部所需条件之前,往往必须预测管路的压降。例如在工厂设计的初始阶段,在工艺流程图和布置图已经确定后,而管线系统还未开始详细设计时,工程师必须及时地、合理地对各条工艺管线和公用管线的压降作出精确的估算。管线的总长度可以通过布置图来确定,但管件数目是未知的,而这些管件所引     

立式干燥工艺系统与回转干燥工艺系统比较

电石、铁合金等行业需要用干燥的焦丁做原料。早期焦丁价格在500~700元/吨左右,成本比较低;近年来,焦丁价格现在已经达到了1500元/吨以上,焦丁和焦末的差价已达500元/吨以上。随着项目规模大型化的发展趋势,原来传统的回转干燥工艺系统焦炭丁在干燥过程中的破损率过大对生产成本的影响已经不容忽视,立式干燥工艺系统由于其低破损率在电石等行业日渐倍受青睐。     

氧化铁红干燥系统的改进

氧化铁红辊筒干燥系统，经改进采用ＱＤ型旋转接头和ＳＴ型疏水阀后，提高了蒸汽利用率和设备干燥能力，又保证产品质量。     

氯乙酸分离干燥系统的改造

对氯乙酸生产中分离干燥工序进行改造，采用HR400—N型双级活塞推料离心机，作为氯乙酸分离干燥设备，离心机投用后，产品质量得到提高。与改造前相比，成本可降低126．9元／t。     

基于量纲分析的气力输送压降模型研究

量纲分析法是建立数学计算模型的一种重要的方法。以实验室气力输送数据为基础,结合量纲分析法,建立了管道压降计算准数关联式,同时将计算结果与实验数据进行对比分析,实验值与计算值总体变化趋势基本相同,偏差较小,并对其中误差相对较大的公式进行了修正,所得准数关联式对化工气力输送中压降的估算具有实际意义。     

组合干燥系统在浆料干燥中的应用

介绍了应用于浆料干燥的两种桨叶组合干燥系统，重点阐述了工艺流程及关键设备，分析了两种组合形式的特点及经济性，并列出了两种具有代表性浆料的工业应用参数。     

真空连续干燥系统抽气量的计算

介绍了真空连续干燥装置真空系统—抽气量的计算方法,通过与实际实验装置操作情况的比较,验证了该计算方法的可行性。     

木材真空干燥设备加热系统理论计算的探讨

将过热蒸汽作为干燥介质,推导了木材真空干燥设备加热系统的理论计算方程,并以厚度为40mm,初含水率从60%干至10%的红松为标准材,对真空干燥设备的加热系统进行了理论计算,比较分析了绝对压力对计算结果的影响。     

太阳能相变储热在木材干燥中应用的初步研究

针对木材太阳能干燥间歇性的不足,在原有太阳能干燥装置的基础上,增设了多管道叉排石蜡相变储热系统。研究结果表明,随着储热系统管排数的增加（5、7、9、11排）,其放热时间逐渐缩短,换热系数呈现增加趋势,平均值分别为17．8、22．1、24．7、26．4W／（m^2·℃）;在其它参数相同的条件下,当管排数不大于5时,储热温度对换热系数的影响不大,但当管排数大于11,储热系统显热储存的热量就不能够忽略;在其它参数相同的条件下,随着风速的增加,换热系数呈现增长趋势,风速为1．0、1．5和2．0m／s时,放热速率的比值为0．89：0．94：1。     

多喷头压力喷雾干燥塔喷嘴的设计

压力喷雾干燥塔生产能力大到一定量时,单喷头喷雾干燥就难以满足生产的需要,这时应考虑采用多喷头进行喷雾干燥。以RGYP03-1000型压力喷雾干燥塔在奶粉生产中的应用为例,对多喷头和热风分布器的结构设计进行了阐述。     

Variation in Drying Behavior and Final Moisture Content of Wood during Conventional Low Temperature Drying and Vacuum Drying of Betula pendula Timber

Conventional and vacuum drying experiments were conducted on Betula pendula timber, which was sawn from trees felled during three different seasons. The influence of the wood procurement season on drying behavior differed, on the one hand, between the drying phases above and below 30% moisture content in the conventional drying, and, on the other hand, between the conventional and vacuum drying methods. During the first steps of the conventional drying process, relative humidity in the kiln, as well as drying time and drying rate, varied according to the felling season. Variations in environmental conditions outside the kiln and the seasonal variation in the physical properties of the wood were presumed to be the reasons for differences in drying behavior. The difference in moisture content gradient, i.e., the difference in final moisture content between the inner wood and the surface layer of boards, was greater in conventionally dried timber than in vacuum-dried timber. In conventionally dried timber there was a clear seasonal variation in the gradient of final moisture content, which was greatest for winter-felled wood. The premature drying of the surface layer during the first steps of the conventional drying process of winter-felled wood was the reason for the higher gradient of moisture content. Storage of wood as logs decreased the standard deviation of the final moisture content.     

Variation in Drying Behavior and Final Moisture Content of Wood during Conventional Low Temperature Drying and Vacuum Drying of Betula pendula Timber

Conventional and vacuum drying experiments were conducted on Betula pendula timber, which was sawn from trees felled during three different seasons. The influence of the wood procurement season on drying behavior differed, on the one hand, between the drying phases above and below 30% moisture content in the conventional drying, and, on the other hand, between the conventional and vacuum drying methods. During the first steps of the conventional drying process, relative humidity in the kiln, as well as drying time and drying rate, varied according to the felling season. Variations in environmental conditions outside the kiln and the seasonal variation in the physical properties of the wood were presumed to be the reasons for differences in drying behavior. The difference in moisture content gradient, i.e., the difference in final moisture content between the inner wood and the surface layer of boards, was greater in conventionally dried timber than in vacuum-dried timber. In conventionally dried timber there was a clear seasonal variation in the gradient of final moisture content, which was greatest for winter-felled wood. The premature drying of the surface layer during the first steps of the conventional drying process of winter-felled wood was the reason for the higher gradient of moisture content. Storage of wood as logs decreased the standard deviation of the final moisture content.     

Drying Characteristics In Superheated Steam Drying at Reduced Pressure

Abstract

The superheated steam drying at reduced pressure is performed, and the effects of operational conditions such as drying pressure and temperature on the drying characteristics are examined. In order to obtain the basic guideline for the design of the superheated steam dryer at reduced pressure, the heat flux to sample was calculated and the optimal conditions were estimated.

After the sample temperature reached at the boiling point, the temperature was maintained at the boiling point and the drying rate became almost constant. Once the sample was dried out, the temperature suddenly increased up to the drying gas temperature. From the calculation of combined heat flux, the followings were found. The contribution of radiative heat transfer to the combined heat flux became larger as the drying pressure was lower. The combined heat flux had a maximum value against the drying pressure. The optimum drying pressure, which gave the maximum heat flux, became lower as the drying gas temperature decreased. It was found that reduction in the drying pressure is effective for the enhancement in drying performance.     

Drying Characteristics In Superheated Steam Drying at Reduced Pressure

The superheated steam drying at reduced pressure is performed, and the effects of operational conditions such as drying pressure and temperature on the drying characteristics are examined. In order to obtain the basic guideline for the design of the superheated steam dryer at reduced pressure, the heat flux to sample was calculated and the optimal conditions were estimated.

After the sample temperature reached at the boiling point, the temperature was maintained at the boiling point and the drying rate became almost constant. Once the sample was dried out, the temperature suddenly increased up to the drying gas temperature. From the calculation of combined heat flux, the followings were found. The contribution of radiative heat transfer to the combined heat flux became larger as the drying pressure was lower. The combined heat flux had a maximum value against the drying pressure. The optimum drying pressure, which gave the maximum heat flux, became lower as the drying gas temperature decreased. It was found that reduction in the drying pressure is effective for the enhancement in drying performance.     

牡丹花干燥过程中色变机理分析

在牡丹花红色素理化性质研究的基础上，对品种为“洛阳红”的牡丹花在干燥过程和干花自然存放过程色变的机理作了探讨。研究发现，牡丹花干燥过程中细胞内水分去除引起的pH值变化和细胞内酶的作用是导致牡丹花干燥过程花瓣变色的两个决定性因素。在牡丹干花自然存放过程中引起花材色变的主要因素是紫外线和氧气。     

天然气长输管道干燥剂干燥投产工艺分析

干燥剂法干燥投产在陆上和海底输气管道投产中应用较为普遍。清管器的运行控制是干燥过程的一个重点和难点,必须准确的估算清管器运行压降,同时干燥剂的窜漏量也是一个十分关注的参数。概述了干燥剂法干燥工艺过程,重点分析清管器运行压降和窜漏量的理论计算方法,为干燥设计和施工操作提供了理论指导与依据。