三效蒸发器的设计.doc

化工原理课程设计–––––三效蒸发器的设计 南通大学化学化工学院轻化工程073 目 录符号说明·····································································2第一节 概述·································································3一、蒸发及蒸发流程··················································3二、蒸发操作的分类··················································3三、蒸发操作的特点··················································3四、蒸发设备························································3五、蒸发器选型· ·······················································4第二节 蒸发装置设计任务 ····················································4一、设计题目· ·····················································4 二、设计任务及操作条件···············································4第三节 三效蒸发器得工艺计算·················································5一、估计各效蒸发量和完成液浓度······································5二、估计各效溶液的沸点和有效总温差··································6 （一）各效由于溶液的蒸汽压下降所引起的温度差损失/ ···············7（二）各效由于溶液静压强所因引起的温度差损失· ··················7（三）流体阻力产生压降所引起的温度差损失 ······················8（四）各效料夜的温度和有效总温差· ································8三、加热蒸汽消耗量和各效蒸发水量的计算·······························8四、蒸发器的传热面积的估算 ··········································9 五、有效温差的再分配················································10 六、重复上述计算步骤 ·············································10 （一）计算各效溶液浓度 ··········································10（二）计算各效溶液沸点 ···········································10（三）各效焓衡算 ·················································11（四）蒸发器传热面积的计算 ·······································12七、计算结果·························································12第四节 蒸发器的主要结构尺寸计算一、加热管的选择和管数的初步估计·····································12二、循环管的选择·····················································13三、加热室直径及加热管数目的确定·····································13 四、分离室直径与高度的确定···········································13五、接管尺寸的确定···················································14 (一)溶液的进出口 ················································14（二）加热蒸气进口与二次蒸汽出口 ································14（三）冷凝水出口 ················································14第五节 蒸发装置的辅助设备 ····················································14一、气液分离器·······················································14二、蒸汽冷凝器·······················································15（一）冷却水量 ···············································15（二） 冷凝器的直径 ··············································16（三）淋水板的设计 ···························16第六节 主要设备强度计算及校核···························17一、蒸发分离室厚度设计························17二、加热室厚度校核···················································18符号说明 第一节 概述一、 蒸发及蒸发流程蒸发是采用加热的方法，使含有不挥发性杂质（如盐类）的溶液沸腾，除去其中被汽化单位部分杂质，使溶液得以浓缩的单元操作过程。

蒸发操作广泛用于浓缩各种不挥发性物质的水溶液，是化工、医药、食品等工业中较为常见的单元操作化工生产中蒸发主要用于以下几种目的：1获得浓缩的溶液产品；2、将溶液蒸发增浓后，冷却结晶，用以获得固体产品，如烧碱、抗生素、糖等产品；3、脱除杂质，获得纯净的溶剂或半成品，如海水淡化进行蒸发操作的设备叫做蒸发器蒸发器内要有足够的加热面积，使溶液受热沸腾溶液在蒸发器内因各处密度的差异而形成某种循环流动，被浓缩到规定浓度后排出蒸发器外蒸发器内备有足够的分离空间，以除去汽化的蒸汽夹带的雾沫和液滴，或装有适当形式的除沫器以除去液沫，排出的蒸汽如不再利用，应将其在冷凝器中加以冷凝蒸发过程中经常采用饱和蒸汽间壁加热的方法，通常把作热源用的蒸汽称做一次蒸汽，从溶液蒸发出来的蒸汽叫做二次蒸汽二、 蒸发操作的分类按操作的方式可以分为间歇式和连续式，工业上大多数蒸发过程为连续稳定操作的过程按二次蒸汽的利用情况可以分为单效蒸发和多效蒸发，若产生的二次蒸汽不加利用，直接经冷凝器冷凝后排出，这种操作称为单效蒸发若把二次蒸汽引至另一操作压力较低的蒸发器作为加热蒸气，并把若干个蒸发器串联组合使用，这种操作称为多效蒸发多效蒸发中，二次蒸汽的潜热得到了较为充分的利用，提高了加热蒸汽的利用率。

按操作压力可以分为常压、加压或减压蒸发真空蒸发有许多优点：（1）、在低压下操作，溶液沸点较低，有利于提高蒸发的传热温度差，减小蒸发器的传热面积；（2）、可以利用低压蒸气作为加热剂；（3）、有利于对热敏性物料的蒸发；（4）、操作温度低，热损失较小在加压蒸发中，所得到的二次蒸气温度较高，可作为下一效的加热蒸气加以利用因此，单效蒸发多为真空蒸发；多效蒸发的前效为加压或常压操作，而后效则在真空下操作三、 蒸发操作的特点从上述对蒸发过程的简单介绍可知，常见的蒸发时间壁两侧分别为蒸气冷凝和液体沸腾的传热过程，蒸发器也就是一种换热器但和一般的传热过程相比，蒸发操作又有如下特点 :(1) 沸点升高 蒸发的溶液中含有不挥发性的溶质，在港台压力下溶液的蒸气压较同温度下纯溶剂的蒸气压低，使溶液的沸点高于纯溶液的沸点，这种现象称为溶液沸点的升高在加热蒸气温度一定的情况下，蒸发溶液时的传热温差必定小于加热唇溶剂的纯热温差，而且溶液的浓度越高，这种影响也越显著2) 物料的工艺特性 蒸发的溶液本身具有某些特性，例如有些物料在浓缩时可能析出晶体，或易于结垢；有些则具有较大的黏度或较强的腐蚀性等如何根据物料的特性和工艺要求，选择适宜的蒸发流程和设备是蒸发操作彼此必须要考虑的问题。

3) 节约能源 蒸发时汽化的溶剂量较大，需要消耗较大的加热蒸气如何充分利用热量，提高加热蒸气的利用率是蒸发操作要考虑的另一个问题四、蒸发设备   蒸发设备的作用是使进入蒸发器的原料液被加热，部分气化，得到浓缩的完成液，同时需要排出二次蒸气，并使之与所夹带的液滴和雾沫相分离   蒸发的主体设备是蒸发器，它主要由加热室和蒸发室组成蒸发的辅助设备包括：使液沫进一步分离的除沫器，和使二次蒸气全部冷凝的冷凝器减压操作时还需真空装置兹分述如下：  由于生产要求的不同，蒸发设备有多种不同的结构型式对常用的间壁传热式蒸发器，按溶液在蒸发器中的运动情况，大致可分为以下两大类：（1）循环型蒸发器   特点：溶液在蒸发器中做循环流动，蒸发器内溶液浓度基本相同，接近于完成液的浓度操作稳定此类蒸发器主要有   a.中央循环管式蒸发器，   b.悬筐式蒸发器 c.外热式蒸发器， d.列文式蒸发器 e.强制循环蒸发器其中，前四种为自然循环蒸发器2）单程型蒸发器   特点：溶液以液膜的形式一次通过加热室，不进行循环。

  优点：溶液停留时间短，故特别适用于热敏性物料的  蒸发；温度差损失较小，表面传热系数较大  缺点：设计或操作不当时不易成膜，热流量将明显下降；不适用于易结晶、结垢物料的蒸发  此类蒸发器主要有     a.升膜式蒸发器，     b.降膜式蒸发器，     c.刮板式蒸发器五、蒸发器选型本次设计采用的是外加热式。