陕西科技大学毕业论文 IV
目 录
第1章 绪论 ································································································································································ 1
急救措施： ··················································································································································· 4 第2章 精馏塔的计算 ················································································································································ 8 第2.1节 精馏塔的物料衡算 ·························································································································· 8 2.1.1 物料液及塔顶、塔底产品的摩尔分数 ··························································································· 8 2.1.2
原料液及塔顶、塔底产品的平均摩尔量····················································································· 8
2.1.3 塔板数的确定 ····································································································································· 9 第2.2节 热量衡算 ········································································································································ 12 2.2.1 塔顶、塔底汽化潜热的计算 ········································································································· 12 第2.3节 精馏塔的工艺条件及有关物性数据的计算 ················································································ 13 2.3.1 以精馏段为例进行计算 ················································································································· 13 2.3.2 精馏塔的塔体工艺尺寸计算 ········································································································· 16 2.3.3 塔板主要工艺尺寸的计算 ············································································································· 17 2.3.4浮阀塔板的流体力学验算 ················································································································ 19 第2.4节 精馏塔的工艺条件及有关物性数据的计算 ················································································ 25 2.4.1 以提馏段为例进行计算 ················································································································· 25 2.4.2 精馏塔的塔体工艺尺寸计算 ········································································································· 27 2.4.3 塔板主要工艺尺寸的计算 ············································································································· 28 2.4.4浮阀塔板的流体力学验算 ················································································································ 30 第2.5节 辅助设备 ········································································································································ 36 2.5.1 管道规格 ········································································································································· 36 第3章 结论与讨论 ········································································································································ 39 第3.1节 结论 ················································································································································ 39 第3.2节 讨论 ················································································································································ 39 符号说明 ······································································································································································· 40 参考文献 ······································································································································································· 42 致 谢 ············································································································································································· 43 附图 ··············································································································································································· 44
年产15万吨乙苯的精馏装置工艺设计
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第1章 绪论
第1.1节 精馏的概述
一种利用回流使液体混合物得到高纯度分离的蒸馏方法，是工业上应用最广的液体
混合物分离操作，广泛用于石油、化工、轻工、食品、冶金等部门。精馏操作按不同方法进行分类。根据操作方式，可分为连续精馏和间歇精馏；根据混合物的组分数，可分为二元精馏和多元精馏；根据是否在混合物中加入影响汽液平衡的添加剂，可分为普通精馏和特殊精馏（包括萃取精馏、恒沸精馏和加盐精馏）。若精馏过程伴有化学反应，则称为反应精馏。双组分混合液的分离是最简单的精馏操作。典型的精馏设备是连续精馏装置，包括精馏塔、再沸器、冷凝器等。精馏塔供汽液两相接触进行相际传质，位于塔顶的冷凝器使蒸气得到部分冷凝,部分凝液作为回流液返回塔顶,其余馏出液是塔顶产品。位于塔底的再沸器使液体部分汽化，蒸气沿塔上升，余下的液体作为塔底产品。进料加在塔的中部,进料中的液体和上塔段来的液体一起沿塔下降,进料中的蒸气和下塔段来的蒸气一起沿塔上升。在整个精馏塔中，汽液两相逆流接触，进行相际传质。液相中的易挥发组分进入汽相，汽相中的难挥发组分转入液相。对不形成恒沸物的物系，只要设计和操作得当，馏出液将是高纯度的易挥发组分，塔底产物将是高纯度的难挥发组分。进料口以上的塔段，把上升蒸气中易挥发组分进一步提浓，称为精馏段；进料口以下的塔段，从下降液体中提取易挥发组分,称为提馏段。两段操作的结合,使液体混合物中的两个组分较完全地分离，生产出所需纯度的两种产品。当使 n组分混合液较完全地分离而取得n个高纯度单组分产品时，须有n-1个塔。
精馏之所以能使液体混合物得到较完全的分离，关键在于回流的应用。回流包括塔顶高浓度易挥发组分液体和塔底高浓度难挥发组分蒸气两者返回塔中。汽液回流形成了逆流接触的汽液两相，从而在塔的两端分别得到相当纯净的单组分产品。塔顶回流入塔的液体量与塔顶产品量之比，称为回流比，它是精馏操作的一个重要控制参数，它的变化影响精馏操作的分离效果和能耗.
化工生产中常需进行液体混合物的分离达到提纯或回收有用组分的目的。互溶液体混合物的分离有多种方法，精馏是其中最常用的一种。
混合物的分离，总是根据混合物中各组分间某中物理和化学性质的差异而进行的。精馏操作是根据混合物中各组分挥发度的不同而达到分离的目的。
精馏是指利用液体混合物中各组分的挥发性（沸点）的差别，将互溶的液体混合物
分离提纯的单元操作。将液体混合物加热部分汽化时所产生的气相组成与液相组成必将有差异，利用这一差异，就可将液体混合物分离。例如，这次设计是将甲苯和乙苯的混合液在精馏中分离，在加热（或换热）的条件下，使混合溶液部分汽化，由于甲苯的沸
陕西科技大学毕业论文 2
点比乙苯的沸点低则易于从液相中汽化出来，将部分汽化所得的蒸汽全部冷凝，可得到甲苯含量高于原料中的产品，从而是甲苯和乙苯得以分离。他是目前使用最广的液体混合物分离方法。习惯上，混合液中的易挥发组分称为轻组分，对难挥发组分称为重组分。 精馏过程是化工中常用的液体混合物分离操作。它虽然不能将液体混合物彻底分离。但却说明经过一次部分汽化和一次部分冷凝能使馏出液中易挥发组分的含量有所提高，这里全部汽化或全部冷凝不可能达到。若将这种部分汽化，部分冷凝反复多次地进行下去，就可能使混合液得到较彻底的分离。
塔设备是化工、石油化工、制药、生活用品等生产过程中广泛采用的传质设备，根据它内气液接触形式，可分为板式塔和填料塔。
精馏操作其基本原理是利用互溶液体混合物的相对挥发度不同实现各组分分离的
单元操作。由于浮阀可根据气量的大小而上下浮动，故操作弹性大，而且浮阀在塔板上安排的很紧凑，因此，由于高气量时阀片能自动浮动，从而降低了高气速时的压降，塔板效率较高。该塔板的主要缺点是浮阀使用久后会被卡住、锈住或黏住，与你共享其自由度。
精馏过程的节能:精馏过程的核心在于回流，而回流必须消耗大量能量。降低能耗是精馏过程发展的重大课题。除了选择经济上合理的回流比外，主要的节能措施有：①热泵精馏。将塔顶蒸气绝热压缩（见热力学过程）升温后，重新作为再沸器的热源(见热泵蒸发)；②多效精馏。精馏装置由压力依次降低的若干个精馏塔组成，前一精馏塔塔顶蒸气用作后一精馏塔再沸器的加热蒸气（见多效蒸发）；③采用高效精馏塔，可用较小的回流比；采用高效换热器，可降低传热温度差，这样就可以减少有效能损失。④采用电子计算机对过程进行有效控制，减小操作裕度，确保过程在最低能耗下进行。
评价精馏操作的主要指标是：①产品的纯度。板式塔中的塔板数或填充塔中填料层高度，以及料液加入的位置和回流比等，对产品纯度均有一定影响。调节回流比是精馏塔操作中用来控制产品纯度的主要手段。②组分回收率。这是产品中组分含量与料液中组分含量之比。③操作总费用。主要包括再沸器的加热费用、冷凝器的冷却费用和精馏设备的折旧费，操作时变动回流比，直接影响前两项费用。此外，即使同样的加热量和冷却量，加热费用和冷却费用还随着沸腾温度和冷凝温度而变化，特别当不使用水蒸气作为加热剂或者不能用空气或冷却水作为冷却剂时，这两项费用将大大增加。选择适当的操作压力，有时可避免使用高温加热剂或低温冷却剂（或冷冻剂），但却增添加压或抽真空的操作费用。
第1.2节 甲苯 乙苯性质和用途
甲苯(Toluene）是最简单，最重要的芳烃化合物之一。在空气中，甲苯只能不完全燃烧，火焰呈黄色。甲苯的熔点为-95 ℃，沸点为111 ℃。甲苯带有一种特
年产15万吨乙苯的精馏装置工艺设计
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殊的芳香味（与苯的气味类似），在常温常压下是一种无色透明，清澈如水的液体，密度为0.866 g／cm³，对光有很强的折射作用（折射率：1.4961）。甲苯几乎不溶于水(0,52 g/l)，但可以和二硫化碳，酒精，乙醚以任意比例混溶，在氯仿，丙酮和大多数其他常用有机溶剂中也有很好的溶解性。甲苯的粘性为0.6 mPa·s，也就是说它的粘稠性弱于水。甲苯的热值为40.940 kJ/kg，闪点为4 ℃，燃点为535 ℃。化学性质有：甲苯是有机化合物，属芳香烃，结构简式为C6H5CH3。在常温下呈液体状，无色、易燃。它的沸点为110.8℃，凝固点为－95℃，密度为0.866 g／cm³。甲苯温度计正是利用了它的凝固点比水很低，可以在高寒地区使用；而它的沸点又比水的沸点高，可以测110.8℃以下的温度。因此从测温范围来看，它优于水银温度计和酒精温度计。另外甲苯比较便宜，故甲苯温度计比水银温度计也便宜。
甲苯不溶于水，但溶于乙醇和苯的溶剂中。甲苯容易发生氯化，生成苯—氯甲烷或苯三氯甲烷，它们都是工业上很好的溶剂；它可以萃取溴水中的溴，但不能和溴水反应；它还容易硝化，生成对硝基甲苯或邻硝基甲苯，它们都是染料的原料；一份甲苯和三份硝酸硝化，可得到三硝基甲苯（俗名TNT）；它还容易磺化，生成邻甲苯磺酸或对甲苯磺酸，它们是做染料或制糖精的原料。甲苯与硝酸取代的产物三硝基甲苯是爆炸性物质，因此它可以制造梯恩梯(TNT)炸药。
甲苯与苯的性质很相似，是工业上应用很广的原料。但其蒸汽有毒，可以通过
呼吸道对人体造成危害，危害等级为乙类，使用和生产时要防止它进入呼吸器官。
甲苯是重要的化工原料。也是燃料的重要万分，使用甲苯的工厂、加油站，汽车尾气是主要污染源。城市空气中的甲苯，主要来自与汽油有关的排放及工业活动造成的溶剂损失和排放。贮运过程中的意外事故是甲苯的又一个污染源。甲苯能被强氧化剂氧化，为一级易燃品。进入人体的甲苯，可迅速排出体外。甲苯易挥发，在环境中比较稳定，不易发生反应。由于空气的运动，使其广泛分布在环境中。水中的甲苯可迅速挥发至大气中。甲苯毒性小于苯，但刺激症状比苯严重，吸入可出现咽喉刺痛感、发痒和灼烧感；刺激眼粘膜，可引起流泪、发红、充血；溅在皮肤上局部可出现发红、刺痛及泡疹等。重度甲苯中毒后，或呈兴奋状：躁动不安，哭笑无常；或呈压抑状：嗜睡，木僵等，严重的会出现虚脱、昏迷。甲苯微溶于水，当倾倒入水中时，可漂浮在水面，或呈油状分布在水面，会引起鱼类及其它水生生物的死亡。受污染水体散发出苯系物特有刺鼻气味。甲苯为一级易燃物，其蒸气与空气的混合物具爆炸性。发生爆炸起火时，冒出黑烟，火焰沿地面扩散。进入现场，眼睛、咽喉会感到刺痛、流泪、发痒，并可闻到特殊的芳香气味。
危险特性：易燃，其蒸气与空气可形成爆炸性混合物。遇明火、高热极易燃烧爆炸。与氧化剂能发生强烈反应。流速过快，容易产生和积聚静电。其蒸气比空气
陕西科技大学毕业论文 4
重，能在较低处扩散到相当远的地方，遇明火会引着回燃。油站、汽车尾气是主要污染源。城市空气中的甲苯主要来源与汽甲苯是重要的化工原料。也是燃料的重要成分，使用甲苯的工厂、加油有关的排放及工业活动造成的溶剂损失和排放。贮运过程中意外事故是甲苯的有一个污染源。甲苯能被强氧化剂氧化为一级易燃品。进入人体的甲苯，可以迅速排出体外。甲苯易挥发，在环境中比较稳定，不易发生反应。由于空气的运动，使其广泛分布在化境中。水中的甲苯可迅速挥发至大气中。甲苯毒性小于苯，但刺激症状比苯严重，吸入可以出现咽喉刺痛感、发痒和灼伤感；刺激眼粘膜，可以引起流泪、发红、充血；溅在皮肤上局部可出现发红、刺痛及疱疹等。
泄漏应急处理：迅速撤离泄漏污染区人员至安全区，并进行隔离，严格限制出入。切断火源。建议应急处理人员戴自给正压式呼吸器，穿消防防护服。尽可能切断泄漏源，防止进入下水道、排洪沟等限制性空间。小量泄漏：用活性炭或其它惰性材料吸收。也可以用不燃性分散剂制成的乳液刷洗，洗液稀释后放入废水系统。大量泄漏：构筑围堤或挖坑收容；用泡沫覆盖，降低蒸气灾害。用防爆泵转达移至专用收集器内，回收或运至废物处理场所处置。如有大量甲苯洒在地面上，应立即用砂土、泥块阴断液体的蔓延；如倾倒在水里，应立即筑坝切断受污染水体的流动，或用围栏阴断甲苯的蔓延扩散；如甲苯洒在土壤里，应立即收集被污染土壤，迅速转移到安全地带任其挥发。事故现场加强通风，蒸发残液，排除蒸气。
防护措施：呼吸系统防护：空气中浓度超标时，应该佩戴自吸过滤式防毒面罩(半面罩)。紧急事态抢救或撤离时，应该佩戴空气呼吸器或氧气呼吸器。 眼睛防护：戴化学安全防护眼镜。 身体防护：穿防毒渗透工作服。 手防护：戴乳胶手套。
其它：工作现场禁止吸烟、进食和饮水。工作毕，淋浴更衣。保持良好的卫生习惯。 急救措施：
皮肤接触：脱去被污染的衣着，用肥皂水和清水彻底冲洗皮肤。
眼睛接触：提起眼睑，用流动清水或生理盐水冲洗。就医。
吸入：迅速脱离现场至空气新鲜处。保持呼吸道通畅。如呼吸困难，给输氧。如呼吸停止，立即进行人工呼吸。就医。 食入：饮足量温水，催吐，就医。
灭火方法：喷水保持火场容器冷却。尽可能将容器从火场移至空旷处。处