NaOH水溶液蒸发装置的设计

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····················································4三、蒸发操作的特点····················································4四、蒸发设备··························································4五、蒸发器选型························································5第二节工艺流程草图···························································5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/···············6（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·lV···············································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2)./(////)./(22CmWKkgJhmhsmgfhkgFhkgDmDmdCkgkJcmb总传热系数，二次蒸汽的焓，高度，重力加速度，校正系数，无因次原料液流量，加热蒸汽消耗量，直径，加热管的内径，比热容，管壁厚度，英文字母误差，无因次温度损失，对流川热系数，希腊字母质量，单位体积冷却水的蒸汽次溶质的质量分率，无因质量流量，蒸发量，分离室的体积，流体得体积流量，蒸发体积强度，CCmWmkgXxhkgWhkgWmVsmVsmmUS)./(////)./(233333饱和的秒污垢的压力流速，温度，管心距，溶液的温度（沸点），传热面积，污垢热阻，气话潜热，雷诺系数，无因次总传热速率，热通量，普兰特准数，无因次绝对压力，蒸发系统总效数，管数，溶液质量，子周边上的单位时间内通过单位管长度，SsspsmuCTmtCtmSWCmRkgkJrRWQmWqPPapnnsmkgMmLer//).(//)../(222壁面的水的体积的蒸汽的外侧的最小的最大的平均的液体的冷凝器的内侧的沸腾的平均的下标水流收缩系数，无因次因次管材质的校正系数，无密度，表面张力，粘度，导热系数，热利用系数，无因次wwuvomLKiBavmkgmNsPaCmWminmax//.)./(3第一节概述一、蒸发及蒸发流程3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，4b.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中央循环管式蒸发器：结构和原理：其下部的加热室由垂直管束组成，中间由一根直径较大的中央循环管。当管内液体被加热沸腾时，中央循环管内气液混合物的平均密度较大；而其余加热管内气液混合物的平均密度较小。在密度差的作用下，溶液由中央循环管下降，而由加热管上升，做自然循环流动。溶液的循环流动提高了沸腾表面传热系数，强化了蒸发过程。这种蒸发器结构紧凑，制造方便，传热较好，操作可靠等优点，应用十分广泛，有标准蒸发器之称。为使溶液有良好的循环，中央循环管