吸水树脂-冷冻复合干燥法制备纳米碳酸钙粉体

湿法工艺制备的纳米材料悬浮液在后处理过程中常发生团聚现象,严重影响纳米粉体材料的性能。本文提出了一种吸水树脂脱水与冷冻干燥相耦合的复合干燥方法,以纳米碳酸钙浆料的干燥过程为研究对象,考察了复合干燥方法对制备的纳米粉体材料性能的影响。研究结果表明,采用该复合干燥方法,可以制得无团聚、分散性能好的粉体产品,且在吸水树脂处理阶段,浆料的脱水率最大可达到78%左右,可以大幅降低后续冷冻干燥过程的能耗。本文同时研究了吸水树脂干燥时间、外部压力、吸水树脂用量和吸水袋面积等因素对干燥过程脱水率的影响规律。     

WG-800离心机异常振动问题的解决

在聚氯乙烯生产过程中，氯乙烯单体在聚合釜中进行悬浮聚合，生成聚氯乙烯悬浮液，聚氯乙烯浆料含有70％-85％的水份，在物料进入干燥工序前要进行脱水处理，使聚氯乙烯含水量控制在25％以下，再进入干燥工序进行干燥。目前，我公司聚氯乙烯车间有2台WG-800离心机，用于从含固量约20％的PVC浆料中分离出含水量为20％-25％的PVC树脂湿料，以便进一步干燥。其中2#离心机由于机体振动严重，从一开始投入使用就没有正常过，开开停停，严重影响我公司PVC树脂的生产。     

对位芳纶浆粕的制备方法及产品（CN：200810225082．4）

一种对位芳纶浆粕的制备方法，包括以下步骤：（1）对位芳纶长丝经机械切割机切成3～13mm的短纤，然后分散在水中配成0．1％～5％的悬浮液；（2）悬浮液经盘磨机疏解、切断、帚化10～30min，制成单纤长度O．8～3mm、比表面积5～10m^2／g的充分微纤化的浆料；（3）浆料经造纸机脱水、干燥制成纸；（4）纸经碎纸机切碎，然后经开纤机疏松制成对位芳纶浆粕，最后压缩包装。     

国外聚氯乙烯树脂干燥技术

本文报导国外悬浮法聚氯乙烯(粉状)树脂的干燥技术,干燥装置的结构型式,推荐一种单级卧式(连续)内加热管型的流态化干燥装置。 前言 聚氯乙烯树脂(简称PVC)系仅次于聚烯烃的塑料品种,目前世界产量已达1000万吨/年以上。其主要生产工艺由氯乙烯单体聚合、未聚合单体回收、悬浮液浆料中残留氯乙烯单体的汽提、离心脱水、滤饼干燥、产品过筛及贮存包装几个过程组成。由石油乙烯为原料生产氯     

惰性粒子流化床干燥器的研究

本文在以内径为145mm、粒径为1．5mm的玻璃珠作为惰性粒子的流化床中对钛白粉浆料进行了干燥实验研究．实验结果表明，惰性粒子流化床能有效地对浆状物料进行脱水干燥，与其它几种浆状物料干燥器相比，具有容积传热系数大、热效率高、对物料适应性大等优点．实验发现浆料在情性粒子流化床内干燥，其过程可能表现为两种操作状态：’稳定操作和非稳定操作．在系统参数和操作条件给定时，干燥器存在一最大干燥能力．若加入的浆料速率超出其干燥能力而得不到及时的干燥脱水，湿料粘结在壁和玻璃珠的表面上，导致玻璃珠聚结成团，最终会形成死床…     

TRH050型离心机的使用与检修

近年来,国内PVC行业发展很快,PVC的产量有较大提高,大多数厂家采用的是悬浮聚合工艺,这就涉及到浆料的脱水干燥。齐化集团有限公司悬浮法PVC生产能力为8万t／a,离心干燥采用的是两台日本巴工业株式会社生产的TRH050型离心机,每台产干基7．5t／h。浆料经汽提后进入离心机,经离心机脱水后浆料含水质量分数为21％～23％,然后进气流塔等设备进一步干燥。     

湿法制造热塑性片材的工艺技术研究Ⅲ.湿片成型工艺研究

本文研究了湿法制造热塑性片材工艺过程中的湿片成型工艺技术,包括“固－液相系”浆料的搅拌和流送方式;浆料的上网布浆,脱水制片及湿片从成型网向干燥网过渡传递等工艺技术和相关设备。     

万华化学集团开发出聚酰亚胺制备新方法

正万华化学集团股份有限公司开发出一种聚酰亚胺制备新方法,包括以下步骤:二元伯胺溶解于弱水溶性溶剂中,逐渐加入有机酸酐发生缩聚反应生成聚酰胺酸;然后升温回流,聚酰胺酸发生脱水反应得到半亚胺化的聚酰亚胺悬浮液;过滤悬浮液得到半亚胺化的聚酰亚胺固体,干燥后得到聚酰亚胺粉末产品;或     

卧式螺旋卸料过滤离心机

卧式螺旋卸料过滤离心机是利用过滤原理分离悬浮液，对固相颗粒在0．06-10MM的母液均可作固液分离或离心脱水，并可配备洗涤功能，其特性具有：连续进料、连续出料、固相脱水率高、结构紧凑、占地面积小、安装简便、维护成本较低、本机采用先进的变频调速器，工作转速无级可调、螺旋体与转鼓具有相对可调整的差转速、操作容易等特点，它能大大地降低物料热干燥的成本，甚至可省去干燥程序，对易损部分可用耐磨材料保护，因此广泛适用于化工、食品、化纤、冶矿、制药、轻工等行业作悬浮液的固液分离和脱水。     

氧化锆水悬浮液的分散

通过考察多元共聚物分散剂对氧化锆zeta电位和浆料流变性的影响,研究了氧化锆浓悬浮液的分散性.结果表明: 多元共聚物分散剂的加入增加了氧化锆zeta电位的绝对值,等电点移至2.4以下.随分数剂加入量的增加,悬浮液的流变性出现复杂的情况:低剪切速率下(100s-1以下),悬浮液粘度略微增加;高剪切速率下(100s-1以上),悬浮液的粘度明显降低;4种分散剂中,二元共聚物分散的氧化锆浆料流动性最好,加入质量分数为0.14%,pH值为9.6左右.并制备了体积分数54%的氧化锆浆料,粘度为0.91Pa·s(100s-1).     

Ozone Mass Transfer in Stirred Vessel

A method is proposed and a model is developed which are capable of providing a correlation of the mass transfer coefficient k_La, with stirrer speed and gas superficial velocity. The method can be adopted for deriving a correlation which can be profitably used for ozone gas–liquid reaction both for assessing the absorption regime and for the simulation of oxidation processes which evolve according to slow reaction regime.     

对化工原理三传类比教学方法的探讨

本文把三传类比方法用实例作了解析,从传递本质、基础定律数学模型、有效膜模型、物性系数四个方面介绍了化工原理传递过程的研究方法,目的是使繁杂的知识简练清晰,希望能引起化工原理初学者及相关教学人士的借鉴,从不同的角度来学习掌握化工原理这门理论。     

Heat transfer by radiation and convection in fire testing

Fire safety engineers, especially those experts writing fire test standards, often have different understandings of the concepts of heat transfer from a fire to a surface by radiation and convection. The concepts are therefore often not very well defined, in e.g. ISO and CEN standards, leading in many cases to confusions, misunderstandings and considerable errors. This paper is an effort, in a very simple way, to make the issue a little clearer, particularly for use in international standardization work. ISO/TC92 and the International FORUM of Fire Research Directors are currently endorsing very important work on procedures to calibrate heat flux meters. The two entities, heat transfer by radiation and convection, may be treated independently. The presentation below is deliberately very short and basic avoiding many phenomena that are not immediately needed in most fire standardization work. Recommendations are reached on how to define and measure heat transfer in fire testing. Copyright © 2004 John Wiley & Sons, Ltd.     

间歇釜传热时间和传热面积的计算

通过对间歇釜传热过程的分析,推导出间歇釜传热时间和传热面积的计算公式。附有说明计算方法的实例。     

化工原理课程中三传相似性教学要点分析

单元操作从本质上讲可以分解为动量传递、热量传递、质量传递这三种传递过程或者它们的结合。学习和掌握三传相似性在加强学生对化工原理知识的深入认识、融会贯通方面有着重要的意义。文章就三传相似性的一些教学要点进行了深入剖析,并对教学方法进行了简要探讨。     

Enhancement of oxygen mass transfer rate in the presence of nanosized particles

Absorption of gases into a liquid is essentially important for two- or three-phase reactions, because the diffusion of a sparingly soluble gas, like oxygen, across a gas-liquid interface generally limits the reaction rates. Using a third, dispersed phase, the mass transfer rate could be significantly increased. The question arises how the absorption rate can be described in the presence of very fine, nanometer size particles or droplets. Its mathematical model should take into account the specific properties of the nanoparticles, e.g. the Brownian motion of particles, its effect on the diffusion of the bulk phase molecules, the mass transfer rate into the nanoparticles, its dependency on the particle size, etc. The mass transfer rate of oxygen, in the presence of nanometer size, organic droplets, has been investigated both experimentally, using organic submicron n-hexadecane droplets, and theoretically. The effect of the Brownian motion of the nanoparticles as well as its effect on the diffusivity in the nanofluid has been discussed. Accordingly, the enhanced diffusion coefficient, due to the convective motion of the continuous liquid phase induced by the moving particles, has been predicted and its effect on the mass transfer enhancement has been calculated using both homogeneous and heterogeneous mathematical models. The predicted data were compared to the measured ones.     

Nonbuoyancy density‐driven convective mass and heat transfer: Scaling analysis and solution methodology

Density change during mass or heat transfer can cause convection in the absence of buoyancy forces. Prior studies have shown that this convection can be significant in the determination of diffusion coefficients and in the casting of polymeric membranes. Including this effect is challenging even for advanced numerical codes. A general methodology for obtaining the mass‐average velocity for unsteady‐state, one‐dimensional, multicomponent mass and/or heat transfer circumvents the problem of numerically solving the coupled continuity equation. Scaling analysis permits assessing the importance of this convection for a generic equation‐of‐state. Numerical predictions for evaporation from a liquid layer for components having density ratios of 1:1 and 0.7:1 indicate that ignoring convection results in errors of 34% and 24% in the evaporation time and final thickness, respectively. This convection also influences the evaporation in the percutaneous application of cosmetics, medications, and insecticides, curing of paints, varnishes, and lacquers, and formation of thin films. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

MODELLING THE INFRARED RADIATIVE HEATING OF AGRICULTURAL CROPS

Simultaneous heat and mass transfer equations were developed to simulate the infrared radiative heating of agricultural crops. The equations assume that moisture diffuses to the outer boundaries of the material in liquid form and evaporation occurs at the surface of the kernel. Energy for moisture evaporation is supplied by the infrared radiant energy. The equations were validated with experimental data on surface temperature and average moisture content of barley kernels. Average deviations of predicted surface kernel temperature and average kernel moisture from experimental data were 3.9°C and 0.6%(w.b.), respectively. These comparisons were performed using kernels having initial moisture contents of 12.2%, 17.C% and 23.17%.

Sensitivity analysis of process parameters showed that infrared burner temperature, distance of infrared burner from the grain bed, grain initial moisture content and grain heating time significantly affected kernel temperature. Burner temperature and burner height had no significant effect on grain final moisture content.     

MODELLING THE INFRARED RADIATIVE HEATING OF AGRICULTURAL CROPS

ABSTRACT

Simultaneous heat and mass transfer equations were developed to simulate the infrared radiative heating of agricultural crops. The equations assume that moisture diffuses to the outer boundaries of the material in liquid form and evaporation occurs at the surface of the kernel. Energy for moisture evaporation is supplied by the infrared radiant energy. The equations were validated with experimental data on surface temperature and average moisture content of barley kernels. Average deviations of predicted surface kernel temperature and average kernel moisture from experimental data were 3.9°C and 0.6%(w.b.), respectively. These comparisons were performed using kernels having initial moisture contents of 12.2%, 17.C% and 23.17%.

Sensitivity analysis of process parameters showed that infrared burner temperature, distance of infrared burner from the grain bed, grain initial moisture content and grain heating time significantly affected kernel temperature. Burner temperature and burner height had no significant effect on grain final moisture content.     

恒热流工况下管内对流换热(火用)传递特性

从管内传热与流动的特点出发,基于热力学第一、第二定律和非平衡热力学理论,对壁面恒热流工况下,管内充分发展段对流换热的火用传递过程进行了研究,定义了对流换热传火用系数、火用流密度、传火用Nusselt数和对流换热火用传递方程,并导出相应的计算式;讨论了Reynolds数、量纲1热通量和不同截面位置等参数对对流换热火用传递过程的影响;最后将传火用和传热的结果进行了比较.