苯-甲苯精馏浮阀塔设计【含4张CAD图纸+文档全套资料】
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摘要：在化工、炼油、医药、食品及环境保护等工业部门，塔设备是一种重要的单元操作设备。它可以实现气（汽）-液相或液-液相之间的充分接触，从而达到相际间进行传质及传热的目的。苯和甲苯都是化工生产中的重要原料。因此，将苯和甲苯从其混合物中分离出来意义重大。设计一座连续浮阀塔，通过对原料，产品的要求和物性参数的确定及对主要尺寸的计算，工艺设计和附属设备结果选型设计，完成对苯-甲苯精馏工艺流程和主体设备设计关键词：精馏塔；浮阀塔；苯；甲苯Abstract: The tower equipment is an important unit operation equipment in industry sectors,for instrance, chemical industry, refinery, medicine, food , environmental protection,and so on.It can realize the steam between the liquid phase or the fluid - liquid phase contect deeply, thus achieveing the border carries on the mass transfer and the heat transfer goal.The distillation is the separation of liquid mixtures most commonly used as an. unit operation in chemical industry, oil refining, petrochemical and other industries. The design mission is to produce an important chemical raw material from a mixture of benzene and toluene, it will be a great significance if the material can be separated from its mixture of benzene and toluen. The design of a continuous distillation valve column, in the material, product requirements and the main physical parameters and to determine the size, process design and selection of equipment and design results, completion of the benzene-toluene distillation process and equipment design themeKeywords : rectification column； valve tower； Benzene；Toluene目录绪论10.1设计题目10.2精馏及精馏流程10.3精馏的分类10.4精馏操作的特点20.5塔板的类型与选择2一、设计方案的选择和论证31.1 设计流程31.2 设计思路3二、浮阀塔结构设计62.1基础物性数据62.1.1原料液及塔顶，塔底产品的摩尔分率62.1.2原料液及塔顶，塔底产品的平均摩尔分率72.2塔板数的确定72.2.1理论层数NT的求取72.2.2实际板数Np的求取102.3.1操作压力的计算102.3.2操作温度的计算102.3.3平均摩尔质量的计算102.3.4平均密度的计算112.4精馏塔的工艺尺寸的计算122.4.1塔径的计算122.4.2精馏塔有效高度的计算132.5塔板主要工艺尺寸的计算132.5.1降液管的选择与计算132.5.2溢流堰的选择与计算142.5.3受液盘和底隙152.5.4塔盘及其布置15三、塔板流动性能校核183.1液沫夹带量校核183.2塔板阻力hf的计算183.3降液管液泛校核193.4液体在降液管内的停留时间193.5严重漏夜校核193.6塔板负荷性能图203.6.1过量液沫夹带线关系式203.6.2液相下限线关系式203.6.3严重漏夜线关系式203.6.4液相上限线关系式213.6.5降液管液泛线关系式21四、浮阀塔载荷分析及强度校核234.1筒体和封头厚度计算234.2载荷分析244.2.1塔设备质量载荷计算244.2.2自振周期的计算274.2.3地震载荷与地震弯矩的计算274.2.4风载荷与风弯矩的计算294.2.5最大弯矩334.3强度校核344.3.1圆筒轴向力校核和圆筒稳定性校核344.3.2塔设备压力试验时的应力校核354.3.3裙座轴向应力校核364.3.4基础环和地脚螺栓设计及校核384.3.5筋板设计及校核404.3.6盖板设计及校核414.3.7裙座与塔壳的对接焊缝424.3.8接管的计算与选择434.4开孔及开孔补强设计444.4.1补强结构444.4.2开孔补强设计准则454.4.3允许不另行补强的最大开孔直径454.4.4等面积补强计算46五、英文文献翻译53主要符号说明96参考文献98结束语99第v页绪论0.1设计题目苯甲苯连续精馏塔的工艺设计（浮阀塔）0.2精馏及精馏流程精馏是多级分离过程，即同时进行多次部分汽化和部分冷凝的过程。因此可是混合物得到几乎完全的分离。精馏可视为由多次蒸馏演变而来的。精馏操作广泛用于分离纯化各种混合物，是化工、医药、食品等工业中尤为常见的单元操作。化工成产中，精馏主要用于以下几种目的:获得馏出液塔顶的产品；将溶液多级分离后，收集馏出液，用于获得甲苯，氯苯等；脱出杂质获得纯净的溶剂或半成品，如酒精提纯，进行精馏操作的设备叫做精馏塔。精馏过程中采用连续精馏流程，原料液经预热器加热到指定温度后，送入精馏塔的进料板，在进料板上与自塔顶上部下降的回流液体汇合后，逐板溢流，最后流入塔底再沸器中。在每层板上，回流液体与上升蒸汽互相接触，进行热和质的传递过程。操作时，连续地从再沸器取出部分液体作为塔底产品，部分汽化，产生上升蒸汽，依次通过各层塔板。塔顶蒸汽进入冷凝器中被全部冷凝，并将部分冷凝液用泵送回塔顶作为回流液体，其余部分经冷却器后被送出作为塔顶产品。根据精馏原理可知，单有精馏塔还不能完成精馏操作，必须同时拥有塔底再沸器和塔顶冷凝器，有时还有配原料液，预热器、回流液泵等附属设备，才能实现整个操作。0.3精馏的分类按操作方式可分为:间歇式和连续式，工业上大多数精馏过程都是采用连续稳定的操作过程。化工中的精馏操作大多数是分离多组分溶液。多组分精馏的特点：能保证产品质量，满足工艺要求，生产能力大；流程短，设备投资费用少；耗能量低，收率高，操作费用低；操作管理方便。0.4精馏操作的特点从上述对精馏过程的简单介绍可知，常见的精馏塔的两端分别为汽化成分的冷凝和液体的沸腾的传热过程，精馏塔也就是一种换热器。但和一般的传热过程相比，精馏操作又有如下特点： （1)沸点升高 精馏的溶液中含有沸点不同的溶剂，在相同的压力下溶液的蒸汽压较同温度下纯溶剂的汽化压低，使溶液的沸点高于醇溶液的沸点，这种现象称为沸点的升高。在加热汽化温度一定的情况下，汽化溶液时的传热温差必定小于加热纯溶剂的纯温差，而且溶液的浓度越高，这种影响也越显著。 （2)物料的工艺特性精馏溶液本身具有某些特性，如某些物料在加入到溶液中时可与溶液中的某一组分或几组分形成恒沸液等。如何利用物料的特性和工艺要求，选择适宜的精流流程和设备是精馏操作彼此需要知道和必须考虑的问题。 （3)节约能源精馏汽化的溶剂量较大，需要消耗较大的加热蒸汽。如何充分利用热量提高加热蒸汽的利用率是精馏操作需要考虑的另一个问题。0.5塔板的类型与选择 塔板是板式塔的主要构件，分为错流式塔板和逆流式塔板两类 ，工业应用以错流式 塔板为主，常用的错流式塔板有：泡罩塔板、筛孔塔板和浮阀塔板。我们应用的是浮阀塔板，因为它是在泡罩塔板和筛孔塔板的基础上发展起来的，它吸收了两种塔板的优点。它具有结构简单，制造方便，造价低；塔板开孔率大，生产能力大；由于阀片可随气量变化自由升降，故操作弹性大，因上升气流水平吹入液层，气液接触时间较长，故塔板效率较高。一、设计方案的选择和论证1.1 设计流程本设计任务为分离苯_甲苯混合物。对于二元混合物的分离，采用连续精馏流程。设计中采用泡点进料，将原料液通过预热器加热至泡点后送入精馏塔内。塔顶上升蒸气采用全凝器冷凝，冷凝液在泡点下一部分回流至塔内，其余部分经产品冷凝器冷却后送至储罐。该物系属易分离物系，最小回流比较小，故操作回流比取最小回流比的2倍。塔釜采用间接蒸汽加热，塔底产品经冷却后送至储罐。 连续精馏塔流程流程图 连续精馏流程附图图1-1 流程图1.2 设计思路在本次设计中，我们进行的是苯和甲苯二元物系的精馏分离，简单蒸馏和平衡蒸馏只能达到组分的部分增浓，如何利用两组分的挥发度的差异实现高纯度分离，是精馏塔的基本原理。实际上，蒸馏装置包括精馏塔、原料预热器、蒸馏釜、冷凝器、釜液冷却器和产品冷却器等设备。蒸馏过程按操作方式不同，分为连续蒸馏和间歇蒸馏，我们这次所用的就是浮阀式连续精馏塔。蒸馏是物料在塔内的多次部分汽化与多次部分冷凝所实现分离的。热量自塔釜输入，由冷凝器和冷却器中的冷却介质将余热带走。在此过程中，热能利用率很低，有时后可以考虑将余热再利用，在此就不叙述。要保持塔的稳定性，流程中除用泵直接送入塔原料外也可以采用高位槽。塔顶冷凝器可采用全凝器、分凝器-全能器连种不同的设置。在这里准备用全凝器，因为可以准确的控制回流比。此次设计是在常压下操作。 因为这次设计采用间接加热，所以需要再沸器。回流比是精馏操作的重要工艺条件。选择的原则是使设备和操作费用之和最低。在设计时要根据实际需要选定回流比。塔板工艺计算流体力学验算塔负荷性能图全塔热量衡算塔附属设备计算 图1-2 设计思路流程图1、本设计采用连续精馏操作方式。2、常压操作。3、泡点进料。4、间接蒸汽加热。5、选R=2.0Rmin。6、塔顶选用全凝器。7、选用浮阀塔。在此使用浮阀塔，浮阀塔塔板是在泡罩塔板和筛孔塔板的基础上发展起来的，它吸收了两者的优点，其突出优点是可以根据气体的流量自行调节开度，这样就可以避免过多的漏液。另外还具有结构简单，造价低，制造方便，塔板开孔率大，生产能力大等优点。浮阀塔一直成为化工生中主要的传质设备，其多用不锈钢板或合金 。近年来所研究开发出的新型浮阀进一步加强了流体的导向作用和气体的分散作用，使气液两相的流动接触更加有效，可显著提高操作弹性和效率。从苯甲苯的相关物性中可看出它们可近似地看作理想物系。而且浮阀与塔盘板之间的流通面积能随气体负荷的变动而自动调节，因而在较宽的气体负荷范围内，均能保持稳定操作。气体在塔盘板上以水平方向吹出，气液接触时间长，雾沫夹带量少，液面落差也较小。二、浮阀塔结构设计2.1基础物性数据 表1-1 苯、甲苯的粘度温度020406080100120苯0.6380.4850.3810.3080.2550.215甲苯0.7580.580.4590.3730.3110.2640.228 表1-2 苯、甲苯的密度温度020406080100120苯-877.4857.3836.6815.0792.5767.9甲苯885.6867.0848.2829.3810.0790.3770.0 表1-3 苯、甲苯的表面张力温度020406080100120苯 31.6028.8026.2523.7421.2718.8516.49甲苯30.8928.5426.2223.9421.6919.4917.34 表1-4 苯、甲苯的摩尔定比热容温度050100150苯 72.789.7104.8118.1甲苯93.3113.3131.0146.6 表1-5 苯、甲苯的汽化潜热温度20406080100120苯 431.1420.0407.7394.1379.3363.2甲苯 412.7402.1391.0379.4367.1354.22.1.1原料液及塔顶，塔底产品的摩尔分率苯的摩尔质量 MA=78kg/kmol甲苯的摩尔质量 MB=92kg/kmolXF=0.282XD=0.983XW=0.0122.1.2原料液及塔顶，塔底产品的平均摩尔分率 MF=0.28278(10.282)92=88.05 kg/kmol MD=0.98378(10.983)92=78.24 kg/kmol MW=0.01278(10.012)92= 91. 83kg/kmol2.1.3物料衡算 原料处理量 F=141.96kmol/h 总物料衡算 141.96=D+W苯物料衡算 141.960.282=0.983D+0.012W联立解的 D=39.474kmol/h W=102.486kmol/h2.2塔板数的确定2.2.1理论层数NT的求取苯甲苯是理想物系，可以用逐板法求取理论板数。 已知：XF =0.282； XD =0.983； XW =0.012； q=1； 查得苯甲苯的相对挥发度=2.5 由q=1时Xe =XF 1) 操作回流比的确定 =0.495苯甲苯是理想物系,在最小回流比时，精馏段操作线的斜率为 最小回流比 =2.291取操作回流比为 R=1.6Rmin=1.62.291=3.662) 逐板法塔板数的求取相平衡方程 （a）精馏段操作线方程 （b）提馏段操作线方程 代入得 即 （c）泡点进料 q=1 第一块塔板上升蒸汽组成 从第一块板下降的液体组成由式（a）求得 由第二块板上升的气相组成由式（b）求得 由第二块板下降的液体组成 由此反复计算得 = 0.9666 =0.9205 = 0.9336 =0.8490 =0.8775 =0.7413 = 0.7929 =0.6050=0.6859 =0.4662= 0.5770 =0.3530=0.4881 0.2761=0.4277 =0.23010.25因为,从第十一块板上升的气相组成由提馏段操作方程（c）计算 由第十一块板下降的液体组成 由此反复计算得= 0.2701 =0.1289= 0.1963 =0.0890= 0.1316 =0.0572= 0.0821 =0.0345= 0.0467 =0.0192 = 0.0229 =0.00930.01所需总理论板数为17块，第块11加料，精馏段需10块，板提馏段需6块板 2.2.2实际板数Np的求取 全塔效率 =0.544实际塔板数 精馏段塔板数 =18.3819 提留段塔板数 所需实际塔板数为31块，第19块加料，精馏段需18块，提馏段需12块板2.3精馏塔的工艺条件及有关物性数据的的计算2.3.1操作压力的计算塔顶操作压力 PD=101.3kPa每层塔板压降 P=0.8 kPa进料板压力 PF=101.3+0.819=116.5kPa精馏段平均压力 Pm=（101.3+116.5）/2=108.9kPa2.3.2操作温度的计算 由泡点方程通过试差法计算出泡点温度塔顶温度 =82.2进料板温度 =99.5精馏段平均温度 =（82.2+99.5）/2=90.82.3.3平均摩尔质量的计算1) 塔顶摩尔质量的计算由 由上面计算得 0.958 0.98378+（1-0.983）92=78.23kg/kmol 0.95878+（1-0.958）92=78.59kg/kmol2) 进料板平均摩尔质量的计算由以上计算的0.4277 0.2301 0.427778+（1-0.4277）92=86.01 kg/kmol 0.230178+（1-0.2301）92=88.78 kg/kmol3) 精馏段平均摩尔质量（78.23+86.01）/2=82.12kg/kmol （78.59+88.78）/2=83.69 kg/kmol2.3.4平均密度的计算1)气相平均密度的计算由理想气体状态方程计算，即 kg/m32)液相平均密度的计算a)塔顶液相平均密度 由tD=82.2，查手册得812.7 kg/m3 802.9 kg/m3812.502 kg/m3b)进料液相平均密度 由tF=99.5，查手册得812.7 kg/m3 786.7 kg/m3 则进料液相的质量分率 kg/m33)精馏段液相平均密度（812.502+727.466）/2=769.984 kg/m32.4精馏塔的工艺尺寸的计算2.4.1塔径的计算根据液相流量参考课本选取单溢流型塔板，则精馏段的气液相负荷 L=RD=3.6639.474=144.47 V=（R+1）D=(3.66+1)39.474=183.95精馏段的气液相体积流率 =1.42m3/s=0.0041 m3/s由 其中 其中 =0.092取板间距HT=0.6m，板上液层高度hL=0.06m则 HT- hL=0.60-0.06=0.54m查图=0.075 =0.0753带入得 =1.21m/s取设计泛点率为0.75，则空塔气速为 m/s则汽相通过的塔截面积 A=（m2）塔截面积为汽相流通截面积A与降液管面积Ad之和。D= m圆整后为D=1.6m塔截面积2.011m2 实际空塔气速 u=1.42/2.011=0.706m/s2.4.2精馏塔有效高度的计算精馏段有效高度为 （18-1）0.60=10.2m提馏段有效高度为 （12-1）0.60=6.6m在进料板上方开一人孔，其高度为0.8m故精馏塔的有效高度为 10.2+6.6+0.8=18m2.5塔板主要工艺尺寸的计算由于塔径为1600mm,所以选用分块式塔板，塔板结构示意图如图2.1 图2.1单溢流分块式弓型塔板2.5.1降液管的选择与计算1)降液管的选择根据工艺条件，选取使用弓形降液管，又由考虑到塔径为一般塔径，所以选择如下图2.2所示的降液管。图2.2降液管2)降液管主要尺寸的选择由塔经D=1.6m，查资料得以下数据降液管宽度Wd=表2.1塔板的参数 塔经D/mm塔截面积/m2(/)/%/D弓形降液管降液管面积/m2堰长/mm堰宽/mm16002.01110.30.73211712550.2072.5.2溢流堰的选择与计算1)堰长 因/D=0.732，D=1.6 故 =1171m2)堰高选用平直堰，堰上液层高度 E近似为1则 =0.0161m取板上清液层高度83mm故 =0.083-0.0161=0.0669m2.5.3受液盘和底隙根据工艺参数与工艺操作条件选取平行受液盘底隙选为35mm。2.5.4塔盘及其布置1)塔板分块 由于塔经D=1.6m故采用分块式塔板，根据表2.2，塔板分为四块。 表2.2塔径/mm8001200140016001800200022002400塔板分块数34562)边缘区宽度的确定取塔板上液体进、出口安定区宽度m m3)有效传质面积计算传质面积 其中 =0.1913=0. 75故 =0.206m 24)浮阀数及其排列浮阀数 由工艺和物料操作特点选取F1重型浮阀如图2.3所示，阀孔直径d0=0.039m图2.3初选阀孔动能因子F0=11，计算阀孔气速=6.40m/s浮阀个数 =185.83186浮阀排列方式开孔所占面积 =0.222m2采用等腰三角形叉排，计算孔心距由开孔区内阀孔所占面积分数解得 其中 =0.3134m根据估算提供孔心距t进行布孔，并按实际可能的情况进行调整来确定浮阀的实际个数n，按t=300mm进行布孔，实际阀数n=120 如图2.4所示图2.4 开孔区内 重新计算塔板以下参数阀孔气速 =9.91 m/s动能因子 =17塔板开孔率 =0.13由于物料的腐蚀性较小，故塔板材料选Q235，通常，钢板的厚度为34mm，不锈钢塔板的厚度是22.5mm。所以塔板厚度去=3mm三、塔板流动性能校核3.1液沫夹带量校核为控制液沫夹带量过大，应使泛点。由 其中CF由塔板上气相密度v及塔板间距HT，查图的系数CF=0.16根据表5-11所提供数据，本物系参数K值可选取1，带入可得 =0.625所得泛点率低于0.8，故不会产生过量的液沫夹带3.2塔板阻力hf的计算1)干板阻力ho临界气速 =5.79,故不会发生液泛。3.4液体在降液管内的停留时间必须保证液体在降液管内的停留时间必须大于3-5s才能保证液体所夹带气体的释出 =21.65855故所夹带气体可以释出。3.5严重漏夜校核当阀孔的动能因子低于5时将发生严重漏夜，故漏夜点的孔速可取5的相应孔流气速=2.907m/s稳定系数 =3.41.5故不会发生严重漏夜3.6塔板负荷性能图3.6.1过量液沫夹带线关系式根据资料一般的大塔，F10.8-0.82,另F1=0.8则根据前面计算液沫夹带的式子可以整理出 即 此为一线性方程，在图上表示过量液沫夹带线（1）3.6.2液相下限线关系式对于平直堰，其堰上液头高度how必须要大于0.006，取how=0.006，即可确定液相流的下限线 该线是垂直于Lh轴的直线，在图上表示（2）3.6.3严重漏夜线关系式因为动能因子小于5时发生严重漏夜，故取Fo=5，计算相应的气相流率 =7920.072该线是平行于Lh轴的直线，为漏夜线，在图上表示（3）3.6.4液相上限线关系式 当t=5s时，降液的最大流量是 = =4550.688该线是平行于Vh轴的直线，在图上表示（4）3.6.5降液管液泛线关系式根据降液管液泛的条件，得以下降液管液泛工况下的关系 为避免降液管液泛的发生，应使 整理得 其中 分别带入可整理得： 将前面的计算结果带入上式的： =0.196计算降液管上液泛线上点得如下表3.1表3.1Ls(m2/h)102030405060Vs(m2/h)352.3681346.5938333.7652321.483299.8364278.7567由图表数据做出降液管的液泛线，记做线（5）将以上的各条线绘制在同一个直角坐标系中得塔板负荷性能图因为设计压力P=0.11Mpa,属于低压化工设备，一类容器；塔内物料苯和甲苯对钢材的腐蚀性较轻微，故塔体和封头材料选用低合金钢板16MnR。 四、浮阀塔载荷分析及强度校核4.1筒体和封头厚度计算根据设计压力和液柱静压力确定计算压力塔内液柱高度仅考虑塔底至液封盘液面高度=2.34m，液柱静压力=，可忽略。P=(1.05-1.10) =(1.05-1.10) 0.1013=（0.108-0.113）MPa 取p=0.11MPa计算压力低压容器的圆筒厚度计算式为：查【5】表D1钢板许用应力在设计温度为150时，16MnR的许用应力为=170，查【5】表4-3 钢制压力容器的焊接接头系数值，在制造中采用双面焊对接接头和相当于双面焊的全熔透对接接头，故焊接接头系数值取0.85。将、 值代入上式得mm圆筒设计厚度式中 为腐蚀裕量，在无特殊腐蚀情况下，对于碳素钢和低合金钢，不小于1mm，故取=2mm。为钢材负偏差，使用中钢板厚度超过5mm时（如20R、16MnR和16MnDR等）可取=0，故=2+0=2mm圆筒设计厚度根据刚度要求，筒体所需最小厚度 =3.2 ； 且 不小于3 ，故按刚度条件，筒体厚度仅需4 ；考虑到此塔较高，风载荷较大，而塔的内径不太大，故应适当增加厚度，现假设塔体厚度12，刚假设的塔体有效厚度 C1C212-0-210 ；圆整并根据【4】附表4-1所以取圆筒名义厚度为=12mm,则圆筒有效厚度=-=封头厚度计算公式为：封头设计厚度=+=0.605+mm封头名义厚度与圆筒一样，取为12mm封头有效厚度=-=4.2载荷分析4.2.1塔设备质量载荷计算质量载荷示意如图4.1塔设备的操作质量:塔设备的最大质量:塔设备的最小质量 图4.1 :塔体总质量1)筒体质量塔板总间距=(塔板总数N-1)HT=30600=18000mm筒体顶部空间高度（即第一块塔板到上封头切线处距离）取为1200mm；筒体底部空间高度（即最后一块塔板到下封头切线处距离）取为3000mm;筒体总高H=18000+4800+1200+3000=25400mm=25.4m。查【4】附表4-1得一米高筒节理论质量为199筒体质量=19925.4=5054.62)封头质量查【4】附表4-3得公称直径为1600mm厚度为8mm的椭圆封头的质量为229.63，查【4】附表4-2 以内径为公称直径的椭圆封头的型式和尺寸得曲边高度为400mm封头质量=2229.63=459.263)裙座质量取裙座高度为3060mm，裙座材料选Q235-A，一米高裙座理论质量为199裙座质量=1993.06=608.94所以塔体总质量=筒体质量+封头质量+裙座质量 即=+=5054.6+459.26+608.94=6123塔段内件质量：查【4】表5-4 塔设备部分零件质量载荷估算表得 浮阀塔塔盘质量载荷为75所以 保温层质量：取保温层厚度为=100mm查【4】表5-4 塔设备部分零件质量载荷估算表得 保温层质量载荷为300，查【4】附表4-2 以内径为公称直径的椭圆封头的型式和尺寸 得封头的容积为0.5864,以保温层外径为内径的椭圆型封头的容积为0.8652。所以=式中 为封头保温层质量平台、扶梯质量（）：查【4】表5-4 塔设备部分零件质量载荷估算表得 平台质量，笼式扶梯质量塔设备总高=筒体总高+单个封头曲边高度+裙座高度=25400+400+3060=28860mm=28.86m塔设备总高取为29m, 笼式扶梯总高取为HF=28m，平台数量n取4则=3428操作时塔内物料质量（）：查【4】附表4-2 得封头容积=0.5864m3 则=6595人孔、接管、法兰等附件质量，按经验取附件质量为=0.25=0.256123=1531充液质量=52213塔设备的操作质量=6123+4872+4295+3428+6595+1531=26844塔设备的最大质量=6123+4872+4295+3428+52213+1531=72462塔设备的最小质量=6123+0.24872+4295+3428+1531=163514.2.2自振周期的计算分析塔设备的振动时，一般情况下不考虑平台及外部接管的限制作用以及地基变形的影响，而将塔设备看成是顶端自由，底部刚性固定，质量沿高度连续分布的悬臂梁，其基本震型的自振周期按【5】 （7-5）式第一振型计算式：其中为塔单位高度上的质量即所以=4.2.3地震载荷与地震弯矩的计算当发生地震时，塔设备作为悬臂梁，在地震载荷作用下产生弯曲变形。安装在七度或七度以上地震烈度地区的塔设备必须考虑它的抗震能力，计算出它的地震载荷。其计算示意图如图4.2 图4.2首先，选取计算截面（包括危险截面）。该课题中将全塔分为5段。其计算截面分别为0-0、1-1、2-2、3-3、4-4，其中0-0、1-1、2-2为危险截面。由【5】表7-9取第二组类场地土的特性周期为=0.3由【4】7-10取设防烈度为7时地震影响系数最大值为=0.23。地震影响系数根据场地土的特性周期及塔的自振周期由分析设计方法确定 且不得小于=0.230.2=0.046即=0.052设等直径、等壁厚塔设备的任意截面距地面的高度为，基本振型在截面处产生的地震弯矩为式中为塔单位高度上的质量即当塔设备H/D15时，还需考虑高振型的影响，这时应根据第一、二、三振型，分别计算其水平地震力及地震弯矩。然后根据振型组合的方法确定作用于质点处的最大地震力及地震弯矩。这样的计算方法很复杂，所以在进行稳定和其他验算时，可按一种简化的由第一振型的计算结果估算地震弯矩的近似算法即计算由此可得底截面处地震弯矩=1.250.50.052268449.8129000=1.13截面1-1处地震弯矩 2.83截面2-2处地震弯矩 =2.374.2.4风载荷与风弯矩的计算各计算段的外径均为=1600+212=1624mm塔顶管线外径：塔顶管线是气体的出口，已知设计压力： 0.11MPa设计温度： 150 气体密度： 2.956kg/m3气体流量： 0.0041 m3/s 图4.3计算示意图如图4.3由气体状态方程可计算出设计温度和设计压力下的气体流量 即：求得=0.025 m3/s操作气速为=1.21m/s则，塔顶管线外径=385.38mm,圆整后取=400mm第段保温层厚度已知为100取管线保温层厚度=100mm笼式扶梯当量宽度=400取各段平台构件的投影面积 为，操作平台当量宽度塔设备迎风面的有效直径是该段所有受风构件迎风面的宽度总和。当笼式扶梯与塔顶管线布置成180时当笼式扶梯与塔顶管线布置成90时,取下列两式中的较大值风压高度变化系数可根据各计算段顶截面距地面高度查【5】7-5。体型系数 风压在不同体型的结构表面分布亦不相同，对细长的圆柱形塔体结构，体型系数=0.7.风振系数 风振系数是考虑风载荷的脉动性质和塔体的动力特性的折算系数。对塔高的塔设备，取1.70。而对于塔高时，则按下式计算已求出塔设备自振周期，查【6】表17-2，近似取衡阳地区基本风压值为350=400=998.56假设土地粗糙度类别为B类，则由值查【5】表7-6得脉动增大系数=2.53，查表7-7得，脉动影响系数分别为=0.72，=0.72，=0.72，=0.79=0.82第段振型系数可根据/查7-8得到各计算段的水平风力将以上讨论数据整理如表4.1表4.1风载荷与风弯矩的计算计算内容数据011223344顶各计算段的外径()1624塔顶管线外径()400第段保温层厚度()100管线保温层厚度()100笼式扶梯当量宽度400各计算段长度()100020007000100009000操作平台所在计算段长度()100020007000100009000平台数00121操作平台当量宽度00257.1360200各计算段的有效直径()2224222424812584242424242424268127842624各计算段顶截面距地面高度()13102029风压高度变化系数1.001.001.001.251.42体型系数0.7风振系数1.041.091.691.942.46塔设备自振周期()1.58400998.56脉动增大系数2.53脉动影响系数0.720.720.720.790.820.0530.1580.5260.6891第段振型系数0.020.050.380.591.00各计算段的水平风力679149388001890323099塔设备任意截面处的风弯矩按下式计算：塔设备底截面的风弯矩为+ 代入数值得=679+1493（）+8800（）+18903（）+23099（1000+2000+7000+10000+）=9.101-1截面的风弯矩为 +代入数值的得=1493（）+8800（）+18903（）+23099（2000+7000+10000+）=8.632-2截面的风弯矩为+ 带入数值得=8800（）+18903（）+23099（7000+10000+）=7.58偏心弯矩该塔设备中无再沸器，故偏心弯矩为04.2.5最大弯矩最大弯矩取和两者中的较大值计算数据如表4.2表4.2最大弯矩选择计算内容计算公式及数据00截面11截面22截面9.10 8.637.583.414.984.27最大弯矩9.108.637.584.3强度校核4.3.1圆筒轴向力校核和圆筒稳定性校核由设计压力引起的轴向应力=4.4此应力只存在于筒体，裙座上由设计压力引起的轴向力为0操作质量引起的轴向应力=5.24最大弯矩引起的轴向应力，由此式可计算出：0-0截面上最大弯矩引起的轴向应力72.41-1截面上最大弯矩引起的轴向应力68.72-2截面上最大弯矩引起的轴向应力60.4查【5】附表D1的设计温度下16MnR的许用应力为170，Q235的许用应力为113载荷组合系数等于1.2系数=0.001175根据A值查【5】图4-7得16MnR在设计温度下的系数B=118，Q235在设计温度下的系数B=93，许用轴向压应力取KB和K中较小值对内压容器圆筒最大组合压应力，最大组合拉应力K就满足要求数据整理如表4.3表4.3圆筒组合应力计算及校核计算内容计算数据001122KB 111.6111.6141.6K 135.6135.6204 135.6135.6204圆筒最大组合压应力（）77.6473.9465.64满足要求圆筒最大组合拉应力（）71.5667.8659.56K满足要求4.3.2塔设备压力试验时的应力校核进行压力试验时，试验压力=1.250.11=0.1375查过程设备设计第二版附表D1得 筒体常温屈服点=3452-2截面=0.91.2345=372.62-2截面=1.2118=141.6筒体的许用轴向压应力取及中较小值即=141.6由试验压力引起的周向应力当试验介质为水时，=0.001，单位转换成的液柱静压力为，式中为2900，所以=0.296=3.28（满足要求）试验压力引起的轴向应力=5.5重力引起的轴向应力=14.15弯矩引起的轴向应力=11.32压力试验时最大组合压应力=14.15+11.32=25.5=141.6压力试验时最大组合拉应力=5.5-14.15+11.32=2.67=141.64.3.3裙座轴向应力校核塔设备常采用裙座支承。该设计中选择圆筒形裙座，圆筒形裙座轴向应力校核首先选取裙座危险截面。危险截面的位置，一般取裙座底截面（0-0）或裙座检查孔（人孔）和较大管线引出孔（）界面处。然后按裙座有效厚度验算危险截面的应力。（0-0）截面处（0-0）截面积=160010=5.024（0-0）截面系数=2.0由前面计算知，=111.6，=135.6裙座许用轴向应力取以上两者中较小值为111.6（1） 座体操作时底截面的最大组合轴向压应力应满足如下条件：裙座许用应力，其中仅在最大玩具为地震弯矩参与组合时计入此项。故，在此，=50.74111.6，满足要求检查孔加强管长度取为120，检查孔加强管水平方向的最大宽度取为450检查孔加强管厚度取与筒体壁厚一致为12=212012=28801-1截面处裙座筒体截面积=4.65=1.841-1截面处裙座筒体截面系数=1.651-1截面组合应力操作时底1-1截面的最大组合轴向压应力应满足如下条件裙座许用应力，其中仅在最大玩具为地震弯矩参与组合时计入此项。故，在此，=-57.96111.6，满足要求水压试验时，最大组合轴向压应力应满足如下条件：裙座许用应力=30.97111.6，满足要求4.3.4基础环和地脚螺栓设计及校核图4.4地脚螺栓群座内径=1600裙座外径=1600+212=1624基础环内外径计算公式分别为=1600+300=1900=1600-300=1300基础环伸出宽度=140地脚螺栓承受的最大拉应力取=和=中的较大值。其中仅在最大玩具为地震弯矩参与组合时计入此项。其中基础环截面系数=基础环面积=1.63=0.47故基础环地脚螺栓承受的最大拉应力=1.630，塔设备必须设计地脚螺栓。先将地脚螺栓个数取为16（4的倍数）材料选择Q235。对于Q235，取许用应力=147地脚螺栓腐蚀裕量取为3则地脚螺栓螺纹小径=+3=28.82故取地脚螺栓满足要求基础环伸出部分平均周长为=5526.416个地脚螺栓均布排列，每一个地脚螺栓两侧，基础环与盖板之间要设置筋板，相邻两筋板最大外侧间距取为160基础环材料许用应力：对于低碳钢材料取为140。水压试验时的压应力=1.56操作时压应力=0.989混凝土基础上的最大压力取以上两者中的最大值 即：=1.56=0.875，故对轴的弯矩=负号表示方向对轴的弯矩=计算力矩取以上两者中大值 即：=4341.8故，有筋板时基础环厚度无论有筋板或无筋板侧基础环厚度都不得小于，故 此设计中取基础环厚度4.3.5筋板设计及校核筋板的许用应力按如下公式计算当时，当时筋板细长比，且不大于250式中为惯性半径，对长方形截面的筋板取， 筋板长度=205，故筋板细长比=16.38临界细长比，式中为筋板材料的许用应力，对低碳钢材料取140E为近半材料弹性模量，E=2.1所以=15.7， 故=35.63筋板的压应力可按下式计算 ，式中为一个地脚螺栓承受的最大拉力，可用式计算，=为对应一个地脚螺栓的筋板个数，取=2故选支座号为3的型筋板，筋板宽度=125，筋板厚度为=8，筋板长度=205故=筋板的压应力筋板的许用应力，满足要求。4.3.6盖板设计及校核环形盖板的最大应力按下式计算计算示意图如图4.5无垫板时 图4.5有垫板时式中-垫板上地脚螺栓孔直径，；=27盖板上地脚螺栓直径，；=40筋板宽度，；=125筋板内侧间距，；=140垫板宽度，；=50盖板厚度，；=16垫板厚度，。=12一般环形盖板厚度不小于基础环厚度。无垫板时=37.10有垫板时=32.20盖板最大应力应等于或小于盖板材料的许用应力，即。对低碳钢盖板的许用应力=140，由计算结果可知=140，满足要求。4.3.7裙座与塔壳的对接焊缝截面2-2即裙座与塔壳对接焊缝截面，此处的剪应力按下式校核：其中仅在最大弯矩为地震弯矩参与组合式计入此项。式中-裙座顶截面内直径，=1600-设计温度下焊接接头的许用应力，取两侧母材许用应力的小值，即=113=37.7=0.61.2113=81.36，满足要求。4.3.8接管的计算与选择（1）由前面计算已知，塔顶管线外径为400，即进气口与排气口的公称直径为400。（2）回流液管径DR冷凝器安装在塔顶时，冷凝液靠重力回流，一般流速为0.20.5m/s，速度越大，则冷凝器的高度也相应增加。用泵回流时，速度可取1.52.5m/s。取u=0.5m/s 则DR=0.07m.查文献4附录取管规格765. （3）进料管径dF料液由高位槽进塔时，料液流速取0.40.8m/s。由泵输送时，流速取为1.52.5 m/s。取u=0.5m/s, VS=320kmol/h. dF=0.0858m查文献4附录取管规格895（4）釜液排除管径dW釜液流出的速度一般取0.51.0m/s。取u=0.5m/s,方法同上dW=0.0732m查文献4附录取管规格=765（5）饱和水蒸气管饱和水蒸气压力在295kPa（表压）以下时，蒸气在管中流速取为2040m/s；表压在785 kPa以下时，流速取为4060m/s；表压在2950 kPa以上时，流速取为80m/s。现u=30m/s,D=236mm.查标准取管规格为=245104.4开孔及开孔补强设计由于各种工艺和结构上的要求，不可避免地要在容器上开孔并安装接管。开了以后，除削弱器壁的强度外，在壳体和接管的连接处，因结构的连续性被破坏，会产生很高的局部应力，给容器的安全操作带来隐患，因此压力容器设计必须充分考虑开孔补强问题。4.4.1补强结构 压力容器接管补强结构通常采用局部补强，主要有补强圈补强、厚壁接管补强和整体煅件补强三种形式。a.补强圈补强 补强圈补强是中低压容器应用最多的补强结构，补强圈贴焊在壳体与接管连接处。它结构简单，制造方便，使用经验丰富，但补强圈与壳体金属之间不能完全贴合，传热效果差，在中温以上使用时，二者存在较大的热膨胀差，因而使补强局部区域产生较大的热应力；另外，补强圈与壳体采用搭接连接，难以与壳体形成整体，所以抗疲劳能力差。这种补强结构一般使用在静载、常温、中低压、材料的标准抗拉强度低于540、补强圈厚度小于或等于1.5、壳体名义厚度不大于38的场合。b.厚壁接管补强 即在开也处焊上一段厚壁接管。由于接管的加厚部分正处于最大应务区域内，故比补强圈更能有效地降低应力集中系数。接管补强结构简单，焊缝少，焊接质量容易检验，因此补强效果较好。高强度低合金钢压力容器由于材料缺口敏感性较高，一般都采用该结构，但必须保证焊缝全熔透。c.整体锻件补强 该补强结构是将接管和部分壳体连同补强部分做成整体锻件，再与壳体和接管焊接。其优点是：补强金属集中于开孔应力最大部位，能最有效地降低应力集中系数；可采用对接焊缝，并使焊缝及其热影响区离开最大应力点，抗疲劳性能好，疲劳寿命只降低10%15%。缺点是锻件供应困难，制造成本较高，所以只在重要压力容器中应用，如核容器，材料屈服点在500以上的容器开孔及受低温、高温、疲劳载荷容器的大直径开孔等。4.4.2开孔补强设计准则开孔补强设计就是指采取适当增加壳体或接管厚度的方法将应力集中系数减小到某一允许数值。目前通用、也是最早的开孔补强设计准则是基于弹性失效设计准则的等面积补强法。但随着各国对开孔补强研究的深入，出现了许多新的设计思想，形成了新的设计准则，如建立了以塑性失效准则为基础的极限分析方法。设计时，对于不同的使用场合和载荷性质可采用不同的设计方法。a.等面积补强 认为壳体因开也被削弱的承载面积，须有补强材料在离孔边一定距离范围内给予等面积补偿。该方法是以双向受拉伸的无限大平板上开有小孔时孔边的应力集中作为理论基础的，即仅考虑壳体中存在的拉伸薄膜应力，且以补强壳体的一次应力强度作为设计准则，故对小直径的开孔安全可靠。由于补强法未计及开孔处的应力集中的影响，也没有计入容器直径变化的影响，补强后对不同接管会得到不同的应力集中系数，即安全裕量不同，因此有时显得富裕，有时显得不足。等面等补强准则是优点是有长期的实践经验，简单易行，当开孔较大时，只要对其开孔尺寸和形状等予以一定的配套限制，在一般压力容器使用条件下能够保证安全，因此不少国家的容器设计规范主要采用该方法，如ASMEVII1和GB150等。b.极限分析补强 该法要求带有某种补强结构的接管与壳体发生塑性失效时的极限压力和无接管时的壳体极限压力基本相同。4.4.3允许不另行补强的最大开孔直径压力容器常常存在各种强度裕量，例如接管和壳体实际百度往往大于强度需要的厚度；接管根部有填角焊缝；焊接接头系数小于1但开孔位置不在焊缝。这些相当于对壳体进行了局部加强，降低了薄膜应力从而也降低了开孔处的最大应力。因此，对于满足一定条件了开孔接管，可以不予补强。GB150规定，当在设计压力小于或等于2.5的壳体上开孔，且相邻开孔中心的间距（对曲面间距以弧长计算）大于两孔直径之和的两倍，且接管公称外径小于或等于89时，只要接管最小厚度满足下表4.4要求，就可不另行补强。表4.4不另行补强的接管最小厚度接管公称外径253238454857657689最小厚度3.54.05.06.04.4.4等面积补强计算 等面积补强设计方法主要用于补强圈结构的补强计算。基本原则如前所述，就是使有效强的金属面积等于或大于开孔所削弱的金属面积。 a.允许开孔的范围 等面积补强法是以无限大平板上开小圆孔的孔边应力分析作为其理论依据。但实际的开孔接管是位于壳体而不是平板上，壳体总有一定的曲率，为减少实际应力集中系数与理论分析结果之间的差异，必须对开孔的尺寸和形状给予一定的限制。GB150对开孔最大直径作了如下限制。 (1)圆筒上开孔的限制，当其内径时，开孔最大直径，且；当其内径时，开孔最大直径，且。 (2)凸形封头或球壳上开孔最大直径。 (3)锥壳（或锥形封头）上开孔最大直径，为开孔中心处的锥壳内径。 (4)在椭圆或碟形封头过渡部分开孔时，其孔的中心线宜垂直于封头表面。 b.所需最小补强面积A 对受内压的圆向或球壳，所需要的补强面积A为 Ad+ 式中 A 开孔削弱所的补强面积， ； D 开孔直径，圆形孔等于接管内直径加2倍厚度附加量，椭圆形或长圆形孔取所考虑平面上的尺寸（弦长，包括厚度附加量），； 壳体开孔处的计算百度，； 强度削弱系数，等于设计温度下接管材料与壳体材料许用应力之比，当该值大于1.0时，取1.0 。 c.有效补强范围 在壳体上开孔处的最大应力在孔边，并随离孔边距离的增加而减少。如果在离孔边一定距离的补强范围内，加上补强材料，可有效降低应力水平。壳体进行开孔补强时，其补强区的有效范围按WXYZ确定，超过此范围的补强是没有作用的。 有效宽度B按下式计算，取二者中的较大值 式中 B 补强有效宽度，； 壳体开孔处有名义厚度，； 接管名义厚度，； 内外径有效高度按下式计算，分别取式中较小值 外侧高度 内侧高度 d.补强范围内补强金属 在有效补强区WXYZ内，可作为有效补强的金属面积有以下几部分。 壳体有效厚度减去计算厚度之外的多余金属面积。 接管有效厚度减去计算百度之处的多余面积。 有效补强区内焊缝金属的截面积。 有效补强区内另处再增加的补强元件的金属截面积。式中 壳体开孔处有有效厚度，； 接管计算厚度，。 若 =+ +A式中 有效补强范围内另加的补强面积，； 则开孔后不需要另行补强。 若=+ +A则开也需要另外补强，所增加的补强金属截面积应满足 A-补强材料一般需与壳体材料相同，若补强材料许用应力小于壳体材料许用应力，则补强面积按壳体材料与补强材料许用应力之比而增加。若补强材料许用应力大于壳体材料许用应力，则所需补强面积不午减少。以上介绍的是壳体上单个开孔的等面积补强计算方法。当存在多个开孔，且各相邻孔之间的中心距小于两孔平均直径两倍时，则这些相邻孔就不能再以单孔计算，而应作为并联开孔来进行联合补强计算。承受内压的壳体，有时不可避免地要出现大开孔。当开孔直径超过标准中允许的开孔范围时，孔周边会出现较大的局部应力，因而不能采用等面积补强法进行补强计算。目前，对大开孔的补强，常采用分析设计标准中规定的方法和压力面积法等方法进行分析计算。 由已经计算出的条件，内径1600，采用标准椭圆封头，在封头中心位置设置的内平齐管，封头名义厚度12，设计压力0.11，设计温度，接管外伸高度，封头和补强圈材料为，其许用应力，接管材料为10号钢，其许用应力112，封头和接管的厚度附加量C均取2.焊接接头系数。补强及补强方法的判别，由上表知，允许不另行补强的最大接管外径为。本开孔外径等于400，故需另行考虑其补强。补强计算方法判别开孔直径d=+2C=400+22=404本凹形封头开孔直径d=404A故开人孔后不需另行补强 五、英文文献翻译ExxonMobil Research & Engineering Company (P.O. Box 900, 1545 Route 22 East, Annandale, NJ, 08801-0900, US)Claims:What is claimed is:1. A de-entrainment baffle for location in a distillation tower having a feed zone, a flash zone and a wash zone, the baffle comprising a plurality of radial fins with openings between the fins to permit the upward passage of vapors from the portion of the tower below the baffle.2. A baffle according to claim 1, wherein each fin is angularly inclined with respect to a plane passing through a central axis of the baffle such that an upper edge of the fin is displaced relative to the lower edge in the direction of flow of incoming feed to the tower.3. A baffle according to claim 2, wherein each fin is angularly inclined with respect to the plane passing through the central axis of the baffle such that the upper edge of the fin is displaced relative to the lower edge in the direction of flow of incoming feed to the tower by an angle from 0 to 180.4. A baffle according to claim 3, wherein the angle is between 30 to 60.5. A baffle according to claim 3, wherein the inclination of each fin relative to the central axis of the baffle is constant along the radial length of the fin.6. A baffle according to claim 1, further comprising at least one liquid downcomer to permit downward passage of liquid past the baffle.7. The baffle according to claim 6, wherein the at least one liquid downcomer is located in a central portion of the baffle.8. The baffle according to claim 6, wherein the at least one liquid downcomer is offset from the center of the baffle.9. The baffle according to claim 6, wherein the at least one liquid downcomer comprises two spaced apart liquid passageways.10. The baffle according to claim 6, wherein the at least one liquid downcomer comprises at least two downcomers, wherein one downcomer is disposed at an angle with respect to another dowcomer.11. The baffle according to claim 1, further comprising: a central circular hub; a peripheral collar spaced from the central circular hub, wherein the plurality of radial fins extend between the central hub and the peripheral collar.12. A baffle according to claim 11, wherein the central hub comprises an open collar providing a liquid downcomer for passage of liquid downwards through the baffle.13. A baffle according to claim 11, wherein the central hub comprises an upstanding circular wall member and a cover over the top of the wall member.14. The baffle according to claim 11, further comprising: at least one intermediate collar spaced between the central circular hub and the periperhal collar.15. The baffle according to claim 14, wherein a first set of fins extends between the central circular hub and one intermediate collar and a second set of fins extends between the intermediate collar and the peripheral collar.16. The baffle according to claim 11, further comprising at least one liquid downcomer to permit downward passage of liquid past the baffle.17. The baffle according to claim 16, wherein the at least one liquid downcomer being formed from at least one plate extending from a portion of the peripheral collar to another portion of the peripheral collar.18. The baffle according to claim 17, wherein the at least one plate includes two plates.19. The baffle according to claim 18, wherein the two plates extend parallel to each other.20. The baffle according to claim 18, wherein one plate extends at an angle with respect to another plate.21. A distillation tower comprising: a feed zone, a flash zone, a lower stripping zone located below the flash zone, a rectification zone above the flash zone, and a de-entrainment baffle located below the flash zone and above the stripping zone.22. A distillation tower according to claim 21, wherein the baffle comprises a plurality of radial fins with openings between the fins to permit the upward passage of vapors from the portion of the tower below the baffle.23. The distillation tower according to claim 22, wherein each fin is angularly inclined with respect to a plane passing through a central axis of the baffle such that an upper edge of the fin is displaced relative to the lower edge in the direction of flow of incoming feed to the tower.24. The distillation tower according to claim 23, wherein each fin is angularly inclined with respect to the plane passing through the central axis of the baffle such that the upper edge of the fin is displaced relative to the lower edge in the direction of flow of incoming feed to the tower by an angle from 0 to 180.25. The distillation tower according to claim 24, wherein the angle is between 30 to 60.26. The distillation tower according to claim 24, wherein the inclination of each fin relative to the central axis of the baffle is constant along the radial length of the fin.27. The distillation tower according to claim 22, further comprising at least one liquid downcomer to permit downward passage of liquid past the baffle.28. The distillation tower according to claim 27, wherein the at least one liquid downcomer is located in a central portion of the baffle.29. The distillation tower according to claim 27, wherein the at least one liquid downcomer is offset from the center of the baffle.30. The distillation tower according to claim 27, wherein the at least one liquid downcomer comprises two spaced apart liquid passageways.31. The distillation tower according to claim 27, wherein the at least one liquid downcomer comprises at least two downcomers, wherein one downcomer is disposed at an angle with respect to another dowcomer.32. The distillation tower according to claim 22, wherein the baffle further comprising: a central circular hub; a peripheral collar spaced from the central circular hub, wherein the plurality of radial fins extend between the central hub and the peripheral collar.33. The distillation tower according to claim 32, wherein the central hub comprises an open collar providing a liquid downcomer for passage of liquid downwards through the baffle.34. The distillation tower according to claim 32, wherein the central hub comprises an upstanding circular wall member and a cover over the top of the wall member.35. The distillation tower according to claim 32, further comprising: at least one intermediate collar spaced between the central circular hub and the periperhal collar.36. The distillation tower according to claim 35, wherein a first set of fins extends between the central circular hub and one intermediate collar and a second set of fins extends between the intermediate collar and the peripheral collar.37. The distillation tower according to claim 32, further comprising at least one liquid downcomer to permit downward passage of liquid past the baffle.38. The distillation tower according to claim 37, wherein the at least one liquid downcomer being formed from at least one plate extending from a portion of the peripheral collar to another portion of the peripheral collar.39. The distillation tower according to claim 38, wherein the at least one plate includes two plates.40. The distillation tower according to claim 39, wherein the two plates extend parallel to each other.41. The distillation tower according to claim 39, wherein one plate extends at an angle with respect to another plate.42. A distillation tower according to claim 24, wherein each fin is angularly inclined with respect to a plane passing through the longitudinal axis of the tower in such a manner that the upper edge of each fin is displaced relative to the lower edge in the direction of rotational movement of the rotating vector of the incoming feed by an angle from 40 to 50.43. A vacuum distillation tower comprising: a stripping zone having stripping trays, a flash zone located above the stripping zone, a feed zone located above the flash zone, a feed director located in the feed zone for introducing an incoming feed into the feed zone with a rotating vector, a rectification zone above the feed zone, a radially-louvered liquid de-entrainment baffle located above the top of the stripping zone and below the feed zone, comprising a central circular hub, a peripheral collar and a plurality of radial fins extending between the central hub and the peripheral collar, with openings between the fins to permit the upward passage of vapors from the stripping zone of the tower, each fin being angularly inclined with respect to a plane passing through the longitudinal axis of the tower in such a manner that the upper edge of each fin is displaced relative to the lower edge in the direction of rotational movement of the rotating vector of the incoming feed by an angle from 30 to 60.Description:CROSS REFERENCE TO RELATED APPLICATIONThis application relates and claims priority to U.S. Provisional Patent Application Ser. No. 60/763,925, entitled “Distillation Tower Baffle” filed on Feb. 1, 2006, the disclosure of which is hereby incorporated specifically herein in its entirety.FIELD OF THE INVENTIONThis invention relates to a baffle for use in a distillation tower used for separating liquids into fractions of different boiling points. It is particularly applicable to vacuum distillation towers used for the fractionation of petroleum liquids but it may also be used in towers and units of other types where re-entrainment of a component separated from the incoming feed liquid presents problems, typically in atmospheric towers and fractionators in other applications.BACKGROUND OF THE INVENTIONSeparation units, such as atmospheric distillation units, vacuum distillation units and product strippers, are major processing units in a petroleum refinery or petrochemical plant. Atmospheric and vacuum distillation units are used to separate crude oil into fractions according to boiling point for downstream processing units which require feedstocks that meet particular specifications. In the initial fractionation of crude oil, higher efficiencies and lower costs are achieved if the crude oil separation is accomplished in two steps: first, the total crude oil is fractionated at essentially atmospheric pressure, and second, a bottoms stream of high boiling hydrocarbons (the atmospheric resid) is fed from the atmospheric distillation unit to a second distillation unit operating at a pressure below atmospheric, referred to as a vacuum distillation tower. The reduced pressure in the vacuum tower allows the unit to separate the bottoms fraction from the atmospheric tower into fractions at lower temperature to avoid thermally-induced cracking of the feed.The vacuum distillation unit typically separates the bottoms stream coming from the atmospheric unit into various gas oil streams which may be categorized according to the needs of the refiner as light vacuum gas oil, heavy vacuum gas oil or vacuum distillate. The undistillable residual or bottoms fraction leaves the vacuum distillation unit as a liquid bottoms stream. Additional information concerning the use of distillation in petroleum refining is to be found in Petroleum Refining Technology and Economics, Gary, J. H. and Handwerk, G. E., pp. 31-51, Marcel Dekker, Inc. (1975), ISBN 0-8247-7150-8 as well as Modern Petroleum Technology, 4 thEd., Hobson, Applied Science Publishers, 1973, ISBN 0-8533-4487-6 and numerous other works.In atmospheric or vacuum distillation, lighter hydrocarbons are vaporized and separated from relatively heavier hydrocarbons. Although the heavier hydrocarbons may not vaporize, they may be carried into the lighter hydrocarbons because of entrainment. This is particularly the case within many commercial designs of vacuum towers in which the two phase feed stream to the tower is generally under turbulent conditions so that the separated resid droplets are easily entrained in the vapors that are being flashed off from the incoming feed stream. Entrainment is undesirable because first, the presence of high boiling or undistillable fractions may be undesired for their physical properties, e.g. viscosity, and second, because the entrained heavier hydrocarbons are typically contaminated with metal-containing compounds such as vanadium or nickel compounds, that can poison the catalysts used in downstream processing. While some metal contaminants enter the lighter fractions by vaporization, reduction of entrainment is a more effective method of reducing metals contamination as it is the heavier fractions in which these contaminants are concentrated. For this reason, the present invention may be applied to fractionation or distillation towers regardless of the operating pressure if the construction of the towers or their operating regimes have led to re-entrainment problems; it may be applied to atmospheric towers, vacuum towers and high pressure towers or any unit in which reduction of re-entrainment is desirable.Distillation towers often use various tangential entry devices to impart centrifugal force to the two-phase feed entering the tower. The droplets not captured in the feed zone are entrained with ascending vapors from the flash zone immediately underneath the feed zone and pass to the wash zone above the feed zone. If stripper trays are positioned at the bottom of the flash zone, the swirling feed vortex will tend to entrain resid from the top stripper tray and increase the extent of liquid entrainment, depending in part, by the shear force of the feed vapors on the liquid/froth surface of the liquid pool on the tray.Various steps have previously been used or proposed to reduce entrainment in vacuum distillation. Demisters or wire mesh pads may be installed at some point between the flash zone and a liquid draw-off point. Demister or wire mesh pads may not, however, be completely satisfactory because they may have a tendency to plug with heavy oil and other material, have a tendency to corrode, with holes resulting from the corrosion or simply be ineffective in reducing entrainment.Methods other than demister pads have also met with only limited success in many applications. Conventional bubble-cap trays above the flash zone may cause the vapor to pass through liquid on the bubble-cap tray, thereby allowing vapor to re-entrain liquid droplets besides creating a pressure drop which may be excessive, particularly in a vacuum tower in which the total tower pressure drop (top to bottom) should be maintained as low as is feasible.Chimney trays having a number of risers attached to a plate having holes, with a baffle attached to the top of each riser have also been used. Chimney trays are available that use two direction changes in the flow of the vapor/liquid to improve liquid/vapor separation have a lower pressure drop than bubble-caps but they may still not be completely effective in reducing entrainment.U.S. Pat. Nos. 4,698,138 (Silvey) and 5,972,171 (Ross) describe de-entrainment trays for vacuum towers which are based upon risers to effect improved liquid/vapor separation. Another type of de-entrainment device which has been used in various applications has taken the form of a conical baffle with vertical sides which sits over a large diameter riser located at the top of the stripper section of the vacuum tower. While this device has been effective it is relatively large and may not be suitable for installation in existing units which do not have adequate vertical clearances.A further problem may be encountered in vacuum towers used for petroleum distillation. The bottoms stream from the atmospheric tower is passed into the flash zone of the vacuum tower where a portion of the stream is vaporized and travels up into the rectification or wash section in the upper portion of the tower. The liquid (non-vaporized) portion of the feed falls onto the trays in the stripper zone in the lower portion of the tower and may be agitated into a froth by the ascending vapor stream from the lower stripper zone as well as by the turbulent incoming feed stream; the liquid elements of the froth may then be picked up and entrained by the ascending vapors and taken up with the lighter fractions into the upper portion of the tower.A need therefore exists to devise an improved device to reduce the degree of re-entrainment of separated liquids into the vapor stream of a distillation tower or column, particularly in vacuum and atmospheric distillation columns between the flash zone and the stripper zone. The improved device should, at the same time, cause a minimal pressure drop appropriate to use in vacuum distillation units.SUMMARY OF THE INVENTIONThe present invention provides an improved device for distillation towers or columns which effectively reduces the extent to which separated liquids are re-entrained into the vapor streams in the columns. The device is particularly suitable for use in towers which have a feed inlet located above a zone which contains liquid separated from the feed and whose entrainment is to be reduced to the extent feasible. The device is especially adapted to use in vacuum distillation towers used for fractionating petroleum atmospheric resids. In this application, it has the capability of reducing the entrainment of the liquid resid fraction into the vapor stream while, at the same time, occupying a smaller volume of the tower as compared to known types of de-entrainment device. Its simplicity of construction also makes it economical to build and install as well as providing the potential for trouble-free operation. It may be applied to towers or columns regardless of the type of feed device and so may be applied both with tangential and radial feed devices although in its preferred form described below, it is of special utility with tangential feed inlets.According to the present invention, the distillation tower has a lower stripping zone, upper rectification zone, and a flash zone between the stripping zone and the rectification zone. An inlet for the feed to be distilled is located between the stripping zone and the rectification zone, usually within and towards the top of the flash zone. An inlet for a stripping medium, usually steam, is located in the lower part of the stripping zone so that the stripping medium passes up through the stripping zone to remove the more volatile components from the high boiling residual material which enters the stripping zone from the flash zone above it. In order to reduce the degree of re-entrainment of residual material from the stripping zone into the vapor stream ascending through the flash zone into the rectification zone, a re-entrainment reduction device is provided at the top of the stripping zone in the form of a baffle which allows the upward passage of vapor from the stripping zone but inhibits the downward flow of vapor from the flash zone into the stripping zone. This baffle may be in the form of a simple apertured plate or it may be in the form of a fabricated baffle with passages for upward vapor flow defined by upwardly directed vapor flow passages, for example, in the form of an “egg crate” baffle.In its most preferred form, the re-entrainment reduction device takes the form of a radially-louvered baffle which is located in the portion of the tower below the feed zone. The baffle is in the form of a number of radial fins or blades, resembling a static fan with openings between the fins to permit vapors from the stripping zone in the lower portion of the tower to pass upwards through the baffle with a minimal pressure drop. The fins of the baffle are preferably oriented so that the incoming feed stream skims over the top surfaces or edges of the fins but they may be oriented at any angle with respect to the plane of the baffle, as described below.It is an aspect of the present invention to provide a de-entrainment baffle for location in a distillation tower having a feed zone, a flash zone and a wash zone. The baffle includes a plurality of radial fins with openings between the fins to permit the upward passage of vapors from the portion of the tower below the baffle. Each fin is angularly inclined with respect to a plane passing through a central axis of the baffle such that an upper edge of the fin is displaced relative to the lower edge in the direction of flow of incoming feed to the tower. Preferably, each fin is angularly inclined with respect to the plane passing through the central axis of the baffle such that the upper edge of the fin is displaced relative to the lower edge in the direction of flow of incoming feed to the tower by an angle from 0 to 180. More preferably, the angle is between 30 to 60 and the inclination of each fin relative to the central axis of the baffle is constant along the radial length of the fin.The baffle includes a central circular hub and a peripheral collar spaced from the central circular hub. The plurality of radial fins extend between the central hub and the peripheral collar. The central hub comprises an open collar providing a liquid downcomer for passage of liquid downwards through the baffle. The central hub includes an upstanding circular wall member and a cover over the top of the wall member. The baffle may further include at least one intermediate collar spaced between the central circular hub and the periperhal collar. A first set of fins extends between the central circular hub and one intermediate collar and a second set of fins extends between the intermediate collar and the peripheral collar.Each de-entrainment baffle has at least one liquid downcomer to permit downward passage of liquid past the baffle. The downcomer may be located in a central portion of the baffle. Alternatively, the downcomer may be offset from the center of the baffle. It is also contemplated that multiple downcomers may be provided. The downcomers may extend parallel to each other. The downcomers may extend at an angle with respect to each other.BRIEF DESCRIPTION OF THE DRAWINGSThe invention will now be described in connection with the following drawings in which like reference numerals designate like elements and wherein:FIG. 1 is a simplified cross sectional view of vacuum tower illustrating the location of the radial louver baffle in the vacuum tower;FIG. 2 is an isometric schematic of a radial louver baffle according to an embodiment of the present invention;FIG. 3 is an isometric schematic of a radial louver baffle with a modified liquid downcomer in accordance with another embodiment of the present invention;FIG. 4 is an isometric schematic of a radial louver baffle with a modified liquid downcomer in accordance with yet another embodiment of the present invention;FIG. 5 is an isometric schematic of a radial louver baffle with an intermediate fin support ring in accordance with the present invention;FIG. 6 is an isometric schematic of a radial louver baffle in accordance with another embodiment of the present invention;FIG. 7 is a simplified cross sectional view of a radial louver baffle in accordance with the present invention having a conical cap covering an opening in the central collar; andFIG. 8 is a simplified cross sectional view of a variation of the radial louver baffle of FIG. 7 having a plate covering an opening in the central collar.DETAILED DESCRIPTIONThe present invention will now be described in greater detail in connection with the figures. FIG. 1 shows the location of a baffle 10in a vacuum tower 20, with only the lower portion of the tower illustrated for simplicity. The feed F enters tower 20through two radial inlets 21, 22which feed into tangential inlet horns 23, 24in the form of inverted channels which direct the feed in a downward direction into flash zone 25where vaporization commences in the flow of heated, ascending vapors from below. While two inlets are shown, the present invention is not intended to be so limited. It is contemplated that a single inlet or multiple inlets may be provided. The configuration of the inlet horns 23, 24confers a rotating vector of motion to the incoming feed so that its path can be considered as a downward helix. The feed enters the feed/flash zone of the tower with a rotating vector of motion imparted by the feed inlet system, the direction of flow of the entering feed (with respect to the tower axis) being indicated by arrows 17, shown in FIG. 2. Various alternative inlet horn configurations are known and may be used, for example, the configurations shown in U.S. Pat. No. 4,770,747 and U.S. Pat. No. 4,315,815. The feed maintains its characteristic rotating flow pattern within the feed and flash zone of the tower and mixes with the ascending vapor stream in flash zone 25. Liquid droplets from the feed are spun outwards by the rotating motion within these zones and collect on walls 26in the flash zone. The liquid droplets then coalesce and pass downwards to a circular channel 27formed between the sloping walls 26of the flash zone 25and an outer peripheral collar 11of baffle 10located on the top of the stripper zone 30. The liquid then passes down through downcomer 16, as shown in FIG. 2, formed by a gap or gaps in the outer collar of the baffle 10onto the top stripper tray 31in the stripping zone and then onto the next tray 32and successively to any additional stripper trays. An inlet for the steam stripping medium is provided in the reboil section 33at the bottom of the tower. Alternative pathways for the liquid into the stripper zone 30may be provided, for example, by conduits formed externally of the tower 20or by having a higher peripheral collar to the baffle with a number of ports below the level of the fins through which the liquid may pass from channel 27to the stripper zone 30. Vapors coming up from the region below the baffle join with the vapors flashed from the incoming feed and move into the rectification zone of the tower.As noted above, baffle 10may be in the form of a simple apertured plate. The total cross-sectional area of the apertures should be sufficient to allow the upward passage of the vapors from the stripping zone, comprising the stripping medium and the stripped vapors from the feed. The plate may be planar or non-planar, for example, in the form of an apertured wide cone. The upward flow of the vapors from the stripping zone tends to prevent the rotating mass of fluid in the flash zone from passing down through the apertures into the stripping zone and so serves to reduce the extent to which the liquid on the top stripper tray is re-entrained in the rotating mass of vapor/liquid in the flash zone. In order to promote desirable flow patterns in the two-phase fluids in the flash zone, flow vanes may be provided on the baffle for the vapors passing through the apertures. These flow vanes may be provided in the manner of a jet tray simply by punching U-shaped cuts in the baffle and bending the metal tabs upwards to form flow vanes with longitudinal slots to permit the vapor flow. The flow vanes may be directed in the same or different directions, for example, all the same way or in two opposing directions. Another possibility is to form the flow vanes in groups, e.g. in repetitive squares with the vanes directed to provide a desirable flow pattern in the flash zone.Alternatively, the slots may be configured as radial slots extending from the central area of the plate out towards the circumference. Again, the total area of the apertures will be sufficient to allow upward vapor flow from the stripper zone; the unperforated areas between the radial slots will serve to inhibit downward flow of vapor onto the top stripper tray. In this form, the baffle is similar to the preferred Radial Louver Baffle described below.Another form of baffle is an “egg crate” type baffle composed of two groups of elongated strips or flat plates which intersect with one another to form a series of upwardly directed flow passages for the vapors from the stripping zone. The plates may be secured to a surrounding collar to fix them in place and hold them at the correct angle relative to the plane of the baffle. The intersecting plates readily allow the upward flow of vapors from the stripping zone while protecting the liquid on the top stripper tray from being caught up and entrained by the rotating mass of vapor/liquid in the flash zone.While these baffles are suitable for the reduction of re-entrainment, a preferred construction will now be described in connection with the figures. The basic structural elements of a baffle 10in accordance with an embodiment of the present invention, referred to as a Radial Louver Baffle, are shown in FIG. 2. The complete baffle 10resembles a fan, albeit one which does not rotate. It comprises a peripheral collar 11which is sized to fit the interior of the tower 20in which the baffle 10is to be used. A central, inner collar 12forms a central hub. A number of radial fins 13, similar to the blades of a fan, extend between central collar 12and the outer peripheral collar 11. A single fin 13is illustrated in FIG. 1. Each of the fins 13has a similar construction. Each fin 13has a generally planar construction, as shown in FIGS. 2-5. The present invention, however, is not intended to be limited to a planar construction; rather, it is contemplated that other configurations including the corrugated construction shown in FIG. 6 are contemplated and considered to be well within the scope of the present invention. The corrugations or bends in fin 113increase the stability of the fins and may serve to enhance the collection of the entrained component. The fins 13or 113extend outwardly from the inner collar 12. It is preferable that the uppermost portion of the fins are located below the top edge of the collar 12, but the above the uppermost edge of the peripheral collar 11.As shown in FIG. 2, a pair of parallel plates 18, 19extend across the baffle 10from one side to the other below the level of fins 13and central collar 12to form a centrally located, radial liquid downcomer 16with radially opposed liquid inlets at each end to allow liquid to flow from the circular channel 27in flash zone 25to the stripper tray 31under the baffle 10. The peripheral collar 11is interrupted in the regions where it meets plates 18, 19to allow the entry of liquid there through from channel 27. The central collar, 12, may be left open, as shown in FIGS. 2-6 to provide an additional path for vapor to pass upwards from the region below the baffle or, alternatively, it may be sealed by a circular plate if the open area of the baffle is otherwise adequate for the required vapor flow capacity.If the central collar 12is left open for vapor flow, it may be covered with a plate or cap having openings or slots formed therein, which permits the flow of vapor there through and prevents any liquid droplets, e.g. in the form of spray, from passing down into the stripper zone. The cover may be provided by a flat, circular plate 300, as shown in FIG. 8 that is supported by the top edge of the collar 12by rods or struts 301, which allow a path for vapor flow between the top edge of the collar 12and the cover 300. The plate 300may include openings therein to permit the passage of vapor therethrough. The cover may be provided by a domed or conical cap or hat 200supported above the top edge of collar 12by rods or flat struts 201which allow a path for vapor flow between the top edge of the collar and the lower peripheral edge of the cover, as shown in FIG. 7. The cover or hat may have slots or openings 302formed therein to permit the passage of additional vapor therethrough.The present invention is not intended to be limited to the arrangement disclosed in FIG. 2, other downcomer arrangements as disclosed, for example, in FIGS. 3-6 are considered to be well within the scope of the present invention. FIG. 3, for example, shows a radial louver baffle similar to that of FIG. 2 (reference numerals for similar elements omitted for clarity) with a single chordal downcomer 40located at one point around the periphery of collar 11. In this case, a flat plate 41extends chordally form one point on the circumference of collar 11to another point, below the level of the fins 13to define the downcomer between plate 41and the inner curved surface of the column such that liquid can pass there through. The chordal arrangement may be duplicated on radially opposite sides of the baffle as shown in FIG. 4 (similar element references again omitted) where flat plates 42, 43, extend across the circumferential path of collar 11to form two chordal downcomers, 44, 45between the plates and the inner curved surface of the column. The formation of multiple downcomers is considered to be well within the scope of the present invention. The flat plates may be disposed at an angle with respect to an adjacent flat plate. The plates may be parallel, as shown in FIG. 4. The plates may be orthogonal with respect to each other, as shown in FIG. 6. Other angles of orientation are contemplated and considered to be well within the scope of the present invention.The fins 13, 113in the radial louver baffle may be directed at an angle anywhere between 0 and 180 relative to the plane of the baffle, that is, they may lie in the plane of the baffle (in which case the baffle becomes a radially-slotted baffle as described above) or they may be directed to provide upward vapor flow passages either facing into or away from the direction of rotation of the two-phase vapor/liquid system in the flash zone. The preferred configuration is for the fins to impart a rotation to the vapors ascending from the stripper zone in the same direction as the rotation in the flash zone. In this case, the fins are angularly disposed so that the feed “skims” over the top of the fins in the course of its rotational movement in the flash zone. While the fins may be facing into the direction of rotation of the two-phase vapor/liquid system, it is not preferable because the rotating flow could enter the chamber below the baffle and disturb the liquid surface causing further entrainment.In general terms, the angular disposition of the fins can be described by reference to a characteristic angle between the plane of each fin and the radial plane passing vertically through the central axis of the baffle (which corresponds to the vertical axis of the tower). This angle will vary between 90 and +90 with a characteristic angle of 0 representing a vertical fin and angles of 90 representing fins parallel to the plane of the baffle, equivalent to the radially slotted baffle. The sense of the angle (or + values) can be expressed relative to the direction of rotation of the vapor/liquid system in the flash zone The fins define flow passages for the ascending vapors from the stripper and it is preferred that these flow passages direct the ascending vapors in the same rotational sense as the rotation in the flash zone, i.e. in the direction of flow of the two phase system in the flash zone. Reverse inclination of the fins (vapor flow counter to the flash zone rotation) is not generally favored because in such cases, the fins may tend to “peel off” the lower layer of incoming feed and direct it down onto the top stripper tray where it will agitate the liquid and induce re-entrainment. Low characteristic angles, for example, from 0 to 30, in the desired direction will allow good vapor flow since the axial or near-axial disposition of the fins will allow good upward flow from the region below the baffle, assuming a reasonable spacing between the fins. Normally, the characteristic angle will be from 30 to 60 relative to the central vertical axis of the baffle, with a value of 45 being most preferred. Within this range, the fins will act to preclude or, at least, impede flow of the feed stream downwards through the baffle to the region of the top stripper tray while, at the same time, providing an adequate area for upward flow of vapors from the stripper below. This preferred angular disposition will also be effective to remove vapors from the region below the baffle by an eductor-type effect as the feed blows over the angled baffles to entrain upcoming vapors but since downward passage of feed vapors is impeded by the fins, re-entrainment of residual liquid from the stripper tray is largely precluded.The optimum characteristic angle for a baffle in any given service is dependent upon a number of variables such as the physical composition of the feed (vapor/liquid ratio under prevailing tower conditions), feed rate, stripping gas (steam) rate relative to feed rate, tower diameter, location of inlet horns relative to the baffle, location of baffle relative to top stripper tray, with the relationship between these variable being extraordinarily complicated. In most cases, computational fluid dynamics will indicate the appropriate characteristic angle (or range of angles) for a given case but in most cases, it will normally be sufficient to select an angle within the preferred range for adequate results.The characteristic angle need not be constant along the radial length of the fin and, indeed, there may be an advantage to be gained by imparting a “twist” to the fins, in the manner or an airplane propeller, with the characteristic angle varying from the inner end of the fin to the outer end. The characteristic angle may either increase or decrease along the length of the fins, again depending on the tower design and operational variables. Computational fluid dynamics or experiments may be used to reveal an optimum value of radial variation for the characteristic angle in any given case.One problem that may be encountered with baffles for columns of relatively large diameter is that the radial fins require support along their length; also, as the radius increases, the distance between each fin increases correspondingly and the open area may increase beyond the amount necessary for vapor flow out of the stripper zone. A form of baffle which addresses both these problems is shown in FIG. 5. This variant of the baffle is similar to the one shown in FIG. 2 (reference numerals for similar elements omitted for clarity) but has an intermediate fin support ring 60which is located between central collar 51and outer peripheral collar 50. A number of inner radial fins 52similar to one another extend between the central hub and intermediate collar 60, fastened to the hub and the collar at each end. It is contemplated that more than one intermediate collar 60may be provided, which will produce multiple rings of fins. Multiple intermediate collars may be necessary for larger diameter baffles such that the fins have the necessary rigidity. A number of outer fins 63, again similar to one another, extend between intermediate collar 60and peripheral collar 50, fastened to the two collars at their respective ends. The number of outer fins may differ from the number of inner fins and, if so, the number of outer fins will usually be greater in view of the larger area between the intermediate collar and the peripheral collar. Similarly, the outer fins may be sized or shaped differently to the inner fins since the larger outer area will permit fins with a larger transverse dimension to be accommodated. The liquid downcomer is of the single chordal type, similar to that shown in FIG. 3. A flat plate 64extends across the circumference of collar 50to form the downcomer inlet between plate 64and the inner curved surface of the column.克森美孚研究与工程公司（邮政信箱900，1545年22路由东安南岱尔，新泽西州08801-0900，美国） 声明： 什么是声称是： 1。一个位置去夹带在精馏塔进料区有一区，一洗流入区塔挡板，挡板组成开口之间的散热翅片多元化的径向允许从塔部分的蒸气上升通道下面的挡板。 2。挡板根据权利要求1，其中每个散热翅片方位相对于一个平面通过挡板，这样一对散热翅片上边缘是流离失所相对于在对传入的原料，以较低的边缘流向中心轴通过倾斜塔。 3。根据权利要求一个挡板2，其中每个散热翅片方位相对于平面通过挡板的中轴线等顺便指出，散热翅片的上边缘是相对于流离失所的传入原料流向下缘斜由塔从一个角度0 180 。 4。挡板根据权利要求3，其中的角度为30 60 。 5。挡板根据权利要求3，其中，每个散热翅片相对于挡板的中轴线倾角沿径向长度不变的散热翅片。 6。挡板根据权利要求1，还包括至少一个液体下降管允许液体通过过去的挡板向下。 7。根据权利要求的挡板6，其中至少有一个液体的下水管是在一个位于中央部分的挡板。 8。根据权利要求的挡板6，其中至少有一个液态下水管是从挡板中心偏移。 9。根据权利要求的挡板6，其中至少有一个液体下降区分为两个间隔开的液体通道。 10。根据权利要求的挡板6，其中至少有一个液态下水管至少包括两个下降管，其中一降液管是一个针对另一角度处理。 11。挡板根据权利要求1，进一步包括：中央圆形的枢纽，周边轴环从中央圆形枢纽间距，其中多数的径向翅片之间的中心枢纽及周边轴环扩展。 12。根据权利要求一个挡板11，其中包括一个中央枢纽开领提供了一个向下的液体通过液体通过挡板下水管。 13。根据权利要求一个挡板11，其中包括一个中央枢纽墙直立圆形部件和在墙的部件顶盖。 14。根据权利要求的挡板11，进一步包括：至少一个中间领中央圆形之间的枢纽和轴环间隔。 15。根据权利要求的挡板14，其中一首套翅片之间的枢纽中心和一个圆形中间领和第二组的散热翅片之间延伸的中间领领口和周边延伸。 16。根据权利要求的挡板11，还包括至少一降液管液的液体，允许过去的挡板向下通道。 17。根据权利要求的挡板16，其中至少有一个下水管被液体从至少一人领部分的周边延伸到周边的另一部分领板组成。 18。根据权利要求的挡板17，其中至少包括两个板块一个板块。 19。根据权利要求的挡板18，其中两个板块彼此平行延伸。 20。根据权利要求的挡板18，其中一个板块的角度延伸到另一个板块方面。 21。蒸馏塔，包括：一进料区，一个流入区，区以下的低剥离闪存区，位于上方的流入区整治区域，一个去夹带挡板下面的流入区及以上的剥离开发区。 22。蒸馏塔根据要求21，其中包括一个与挡板之间的径向散热翅片散热翅片开口允许从下面的挡板塔部分的蒸气上升通道的多元化。 23。蒸馏塔根据权利要求22个，其中每个散热翅片方位相对于一个平面通过挡板，这样一个上缘的散热翅片是流离失所相对较低的优势在对传入的原料流向A中轴通过倾斜到塔。 24。蒸馏塔根据权利要求23，其中每个散热翅片方位相对于平面通过挡板的中轴线等顺便指出，散热翅片的上边缘是相对于流离失所的传入原料流向下缘斜要通过从0 到180 转角塔。 25。蒸馏塔根据权利要求24个，其中，角度为30 60 。 26。蒸馏塔根据权利要求24个，其中，每个散热翅片相对于挡板的中轴线倾角沿径向长度不变的散热翅片。 27。蒸馏塔根据权利要求22，还包括至少一降液管液的液体，允许过去的挡板向下通道。 28。蒸馏塔根据权利要求27，其中至少有一个液体的下水管是在一个位于中央部分的挡板。 29。蒸馏塔根据权利要求27，其中至少有一个液态下水管是从挡板中心偏移。 30。蒸馏塔根据权利要求27，其中至少有一个液体下降区分为两个间隔开的液体通道。 31。蒸馏塔根据权利要求27，其中至少有一个液态下水管至少包括两个下降管，其中一降液管是一个针对另一角度处理。 32。蒸馏塔根据权利要求22，其中，该挡板还包括：中央圆形的枢纽，周边轴环从中央圆形枢纽间距，其中多数的径向翅片之间的中心枢纽及周边轴环扩展。 33。蒸馏塔根据权利要求32个，其中包括一个中央枢纽开领提供了一个向下的液体通过液体通过挡板下水管。 34。蒸馏塔根据权利要求32个，其中包括一个中央枢纽直立圆形墙部件和在墙的部件顶盖。 35。蒸馏塔根据权利要求32，进一步包括：至少一个中间领中央圆形之间的枢纽和periperhal领间隔。 36。蒸馏塔根据权利要求35岁，其中一首套翅片之间的枢纽中心和一个圆形中间领和第二组的散热翅片之间延伸的中间领领口和周边延伸。 37。蒸馏塔根据权利要求32，还包括至少一降液管液的液体，允许过去的挡板向下通道。 38。蒸馏塔根据权利要求37个，其中至少有一个下水管被液体从至少一人领部分的周边延伸到周边的另一部分领板组成。 39。蒸馏塔根据权利要求38个，其中至少包括两个板块一个板块。 40。蒸馏塔根据权利要求39个，其中两个板块彼此平行延伸。 41。蒸馏塔根据权利要求39个，其中一个板块的角度延伸到另一个板块方面。 42。蒸馏塔根据权利要求24个，其中每个散热翅片方位相对于一个平面通过这样的方式传递塔纵轴倾斜，每个散热翅片上边缘是相对于在流离失所的转动方向的下缘运动传入原料从40 旋转载体用角为50 。 43。一个真空蒸馏塔，包括：一剥剥区有托盘，上面的剥离区，原料区以上的流入区，原料在原料中区主任位于引进具有一到进料区位于位于传入原料旋转载体，一个以上的进料区，一个环状，液体去夹带挡板高于剥离带顶部和下方的进料区位于由一个中央圆形枢纽，周边轴环和散热翅片多元化的径向延伸，整治区之间的中心枢纽和外围之间的散热翅片领开口，允许从塔剥离区的蒸气向上推移，每个方位倾斜散热翅片正就通过转轴在这样的塔纵轴传递方式，每个散热翅片上边缘是相对于流离失所在对传入的原料旋转矢量旋转运动方向的下缘，从一个角度30 60 。 说明： 相互参照相关应用 这关乎的要求优先权的申请向美国临时专利申请辑。第七百六十三分之六十零，925，题为“蒸馏塔墩”2月1日提出，2006年，披露，现明确纳入其全部责任。 领域的发明 本发明涉及一种用于分离成不同沸点的组分液体用蒸馏塔使用挡板。它特别适用于真空分馏的石油液体用蒸馏塔，但它也可用于在塔和地方再从传入的料液的分离组件夹带其他类型单位提出的问题，大气和分馏塔的典型在其他应用程序。 发明背景 分离单位，如常压蒸馏装置，真空蒸馏装置和产品除沫，在一个石油炼油厂或石化厂主要处理单元。常减压蒸馏装置用于将原油馏分分离根据煮沸下游加工装置原料的需要，满足特殊规格点。在原油，更高的效率和更低的成本取得初步分馏是，如果原油分离为两个步骤来完成：首先，总原油分馏在本质上的大气压力，二是对高沸点烃底流（大气重油）是美联储从常压蒸馏装置在低于常压蒸馏装置运行第二个，称为真空蒸馏塔。在真空减压塔分离装置允许在较低温度下从常压塔底部成各种馏分分数为避免热引起的原料开裂。 通常的真空蒸馏装置分离成各种石油天然气流从底部来流的大气单位可根据分类轻减压瓦斯油，重减压瓦斯油或真空蒸馏炼油的需要。残留或底部部分叶片底部流液体的真空蒸馏装置。更多信息关于在石油精炼蒸馏的用途是在石油精炼技术与经济，加里，JH和H和werk，通用电气，页31-51，马塞尔德克尔公司（1975），书号0-8247-7150发现-8以及现代石油技术，4 thEd。，霍布森，应用科学出版社，1973年，书号0-8533-4487-6和许多其他作品。 在大气或真空蒸馏，蒸发和轻碳氢化合物从相对较重碳氢化合物分离。虽然重烃不得汽化，他们可能会带入因夹带打火机碳氢化合物。这是特别是在真空塔很多商业设计案，其中两相进料流塔一般在动荡的条件，使分离重油中的水滴很容易闪现正在从传入的流过蒸汽夹带的原料。夹带是不可取的，因为第一，高沸点组分存在可能会为他们不需要的物理特性，如粘度，二是因为通常夹带污染较重的碳氢化合物，如钒或镍化合物金属化合物，可以毒化下游加工过程中使用的催化剂。虽然有些金属污染物进入了汽化较轻组分，减少了夹带是减少金属污染，因为它是重中，这些污染物都集中分数更有效的方法。出于这个原因，本发明可应用于分馏或蒸馏塔的操作压力，无论如果塔或他们的经营体制建设，导致重新夹带的问题，它可应用于大气塔，塔，高真空压力塔或任何单位，其中重夹带减少是可取的。 蒸馏塔经常使用各种切线输入装置传授离心力两阶段原料进入塔。不是在进料区捕获的液滴夹带与上升蒸气从闪存区立即下的进料区，并通过上方的进料区洗区。如果剥离托盘在流入区域的底部位置时，涡漩原料将倾向于乘火车从顶部剥离托盘重油，增加了液体夹带的程度，取决于部分，由原料蒸气对液体的剪切力/泡沫表面上的托盘液池。 各种步骤先前已采用或建议，以减少在真空蒸馏夹带。除雾器或铁丝网片，可安装在闪存之间的一些区和一个液体画过的点点。丝网除沫器或垫可能，但不能完全令人满意，因为它们可能有一种倾向，插头重油和其他材料，有孔的腐蚀造成腐蚀的倾向，或仅仅是在减少夹带无效。 其他方法，而不是除雾器垫还借鉴了在许多应用中只有有限的成功。传统的泡罩区盘以上的流入灯可能会导致蒸气通过液体传递的泡罩托盘，从而使蒸气重新创造压降这可能是多余的液体滴，特别是在中，减压塔塔的总压降（从上到下）应维持低至是可行的。 烟囱托盘有一个连接到板孔立管有多少，附加到每个立管的顶部挡板也被使用。烟囱托盘可使用两个在蒸气/液体流动方向发生变化，提高液体/气体分离具有比泡沫上限较低的压力下降，但他们仍然不能完全有效地减少夹带。 美国专利。第4698138（西尔维）和5972171（罗斯）描述真空塔去夹带是在立管效应的改进的基础，以液体/气体分离盘。另一个去夹带设备类型，已采取了各种应用的一个垂直边锥形挡板大直径超过一在真空塔顶部的冒口剥离部分位于形式。当该设备已被有效，它是比较大的，不得在现有单位没有足够的垂直间隙适合安装。 另一个问题可能会遇到使用石油蒸馏塔真空。从常压塔底部流被传递到了真空塔下的一个流部分汽化和旅行将在塔的上半部分条文修正或洗流入灯区。进料液体（非汽化）的一部分属于中上，在塔的下部卸料区的托盘，并可能成为泡沫的处理，从下蒸汽汽提塔升流区，以及由动荡传入进料流;液体的泡沫成分，可能再被拾起并夹带上升的蒸汽通过，进入塔的上部采取与较轻组分了。 因此，存在着需要改进，设计出一套装置，减少进入蒸馏塔或柱子的蒸气流的转口夹带液体分离，特别是在真空度之间的流入区和除沫区常压蒸馏列。改进后的设备应在同一时间，造成最小压降适合使用真空蒸馏装置。 本发明的概要 本发明提供了一种蒸馏塔或列有效降低的程度，分离液体重新进入蒸汽夹带在列流改善设备。该设备特别适用于塔进料口有一个以上的区域包含分离液从进料，其夹带是要减少到尽可能位于使用。该设备尤其适合使用在真空蒸馏石油分馏塔的大气使用。在此应用中，它具有降低到蒸气流液体的重油分数夹带的同时，在同一时间，占领了塔相比，体积较小撤销夹带设备已知类型的能力。它的简单性也使得它的建设对经济建设和安装提供了无故障运行潜力良好。它可用于塔或列无论原料设备类型等都可能适用，切向和径向进给两个设备的首选形式，尽管在其所述，它与切向进料口的特殊效用。 根据本发明，具有较低的蒸馏塔汽提区，上整治区域，区域之间的剥离和整改区流入区域。一种是在进料口位于蒸馏区之间的剥离和区域通常在整改和对流入灯的带顶部。剥离中的一种，通常是蒸汽，入口位于该剥离的剥离，使区中传递了通过剥离区下部去除高沸点残留物质的进入从剥离区的挥发性成分多流
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