应用化学专业文献原文及翻译.doc

本科毕业设计文献翻译Operation of plate rectification towerWU Chang-xiang(Harbin Gasification Plant,Harbin 154864,China)Abstract:The influencing factors,abnoimal phenomenon and rectification process were analyzed to direct actual operationKey words: rectification tower,recification,reboiler,operationDistillation column is a multi-stage partial vaporization and partial condensation according to the different components in the mixture volatility in each floor tower board to achieve the separation of a mixture of various components of the tower gas-liquid contact device, also known as distillation. A plate column and packed column types. According to mode of operation are divided into continuous distillation and batch distillation. Steam from the bottom of the column entry, and the decline in liquid countercurrent contact with the two in contact, the drop in the volatile liquid (low boiling point) components is continuously transferred to the steam. The difficulty of steam volatile (high boiling) component continued to decline in the transfer of liquid, steam the closer the top of the tower, the higher the concentration of its volatile components, while the decline in the closer tower bottom liquid, its hard to be more volatile components rich set, to achieve component separation. Steam rising from the top of the tower into the condenser, the liquid part of the condensate as reflux liquid to return into the distillation tower, the rest is removed as distillate. Tower bottom outflow of liquid, some of which into the reboiler, thermal evaporation, the steam back to tower, and the other part of the liquid as residua release.Compared with other chemical unit operations,distillation unit,although relatively simple,single production run that often appear in a variety of problems affecting the operation of the distillation unit,leading to tower top orbottom of product failure,severe constraints of production equipmentthe operation resulting in product loss.1.Regular changes in process conditions of distillation column1.1 Reboiler temperatureUnder the same operating pressure,raising the temperature of the reboiler,the volatile components in the tower liquid to reduce,at the same time,the rising vapor velocity increases,and help to improve the efficiency of mass transfer.If products from the top of the tower,the tower reactor discharge of difficult volatiles volatile components to reduce and reduce losses.If the tower reactor effluents for the product,it can improve product quality tower discharge of volatile components entrained difficult nolatile components increased,thereby increasing the losses.In balanced operation,the reactor temperature is suddenly increased,and it too late to adjust the pressure and temperature will inevitably lead to the reboiler fluid is steam-air, the pressure increased.At this time,the tower gas,liquid composition changes,the restructuring were likely to be steamed to the top of the tower,so that the failure of top product.1.2 Operating pressureIn the case of certain operating temperature,increasing the operating pressure can increase the productive capacity of the tower,so that stable operation,but the content of volatile group in the tower reactor products.In distillation,often provides for the adjustment range of the operating pressure.When the fallout of the operating pressure by extmrnal factors,were destroyed,the normal operation of the tower will be completely destroyed.1.3 Feeding temperature1.3.1 Condensate feed,the feed temperature is lower than the temperature of the feeding board,and added if all the material into the stripper segment,stripping segment load increases,the reboiler consumption increase in the amount of steam,and the top of the tower is difficult volatile group were lower.1.3.2 Saturated steam feed,the feed material temperature is higher than the temperature of feed board,all the material of the feed into the rectifying section and stripping section of the load reduction,and increased load of the rectifying section,make the top product quality reduce.1.4 Feeding quantity and composition changesChanges in the feedstock of a direct impact on the change of the amount of steam,the latter increase will produce entrained,even flooding.The feedstock is too low,the operation is not good to maintain the balance of the tower,the steam velocity decreases,the plate is prone to leakage,the rectification efficiency is low.Inthe low-load operation,may be appropriate to increase the reflux ratio,the tower operating in a load lower limit above normal and stable operation in order to maintain the tower.Feeding component of the changes directly affect the product quality.Increased restructuring concentration increase in the rectifying section load separation is not good,the results of restructuring were brought to the top of tower,causing the top of the tower of inferior quality.Product from the reboiler,the top of the tower losses increase.If the concentration of the volatile group in the feeding group were increased,and the stripping section of the load increases,may be poor due to the separation caused by the tower reactor products of inferior quality,which entrained volatile components increased.Feeding restructuring concentration increased,the feeding mouth move down and vice versa,then move up.The same time,operating temperature,back flow and operating pressure must be adjusted accordingly in order to ensure the stability of the distillation operation.Distillation,increasing the reflux ratio,can improve the quality of the product,but the reflux ratio is too large,the inner loop of the tower increased,increasing energy consumption.Reduction of the reflux ratio,the tower gas-liquid contact is not good,the balance to damaged and therefore the mass transfer efficiency decreased.The same time,the operating pressure drop,difficult volatile components easily brought to the top of the tower,resulting in a substandard product.2 Anomalies in the distillation column during operation2.1 Plate capacityRectifying section tray downcomer overflow liquid transportation,however,that the tower upper part of the beginning of flooding,a phenomenon known as downcomer obstruction or liquid flooding.Its causes is to block the liquid leaving the tower board level rise in the downcomer plate between mist entrained excessive leaving the tray efficiency to reduce entrainment of this phenomenon is known as the excessive fog or steam flooding,the reason is the relativein the gas while the tower board bubbling area is too small.2.2 Plate foulingSediment cumulative to the board of board of the tower is an important issue,trays of dirt will tower premature flooding will reduce the plate efficiency.Plate scaling phenomenon:(1)The reflux ratio is not high on liquid pan;(2)The pressure drop increase between the tray;(3)Increase the reflux ratio on the bottom of the column temperature,flow or reboiler load does not have any impact,if the reflux ratio to the heat balance and material balance of 20% to 30%,while the tower did not change significantly,then the tower must be completely full of liquid.The amount of returning tower direct stream gas pipeline through the top of the tower back to the reflux tank.2.3 Slug flows in the riserSlug flow in the riser is a distillation column running unstable,may be caused due to an unstable gas-liquid mixture flow in the vertical pipeline.Reflux tank is elevated at the of the condenser by the condenser discharge logistics is that part of the pipeline between the gas-liquid two-phase mixture,the condenser and reflux tank is called the riser.Generate a liquid column in the riser flow rate is too low will result in two-phase separation,the distillation column to produce a back pressure,this liquid column intermittently be introduced after the riser,back pressure will weaken,then the risergradually being filled with liquid,such slug flow will cause the tower pressureperiodic pulse of change.Abnormal factors cause distillation column plate was washed away,condenser corrosion,clogged caondenser,not condensable gas influence condenser.3.ReboilerReboiler in the distillation column occupies a very important position,it used to bebottom after the vaporization of the liquid part of the back to the distillation column,two phases of the tower gas-liquid contact and mass transfer to proceed.Which used the vertical thermal siphon reboiler,which is a vertical placement of the shell and tube heat exchanger.Partial vaporization of liquid in the bottom-up tube passes through the heat exchanger,heating the heat carrier in the shell.Vertical thermal siphon reboiler features:(1)cycle driving force:the density of the reactor liquid and the heat exchanger tube gas-liquid mixture;(2)compact,small footprint,high heat transfer coefficient;(3)of the shell can not be mechanically cleaned,not suitable for hightower reactor,heat transfer medium viscosity,or dirty;(4)provide the space and buffer zones of the gas-liquid separator.Factors that determine the distillation column capacity restricted,find the reboiler failure is the most laborious,the distillation column by steam reboiler.(1)gas-barrier drain valve failure;(2)steam condensate collected indoor pressure is too large;(3)the condensate liquid seal failure.Hydrophobic failure caused by hydrophobic failure factors:3.1 Thermosiphon rebiler failureReboiler liquid inlet pipe and outlet pipe cold liquid mixture exists between the density difference is the density difference driving the process of processing liquid flow through the reboiler.When tower humoral bit elevated to the reboiler back to the liquid nozzle height,siphon circulation will be impeded.The circulation rate reduction will result in the reduction of heat transfer,thus the cover back to the fluid nozzle is clearly an important reason for fluctuations in the reboiler duties.3.2 Non-condensable gas in the water vaporSteam reboiler to run the process,water vapor may be non-condensable gases,or the reboiler leak,the hydrocarbon vapor or other non-condensable gas into the reboiler,the non-condensable gas into the reboiler pipingthereby reducing the heat transfer capacity of the reboiler with the distillation column within a circulating fluid,thus causing the reboiler heat transfer efficiency decreased.4 ConclusionIn view of these problems often appear in a production run affect the operation of the distillion unit,leading ton the top of the tower or the bottom of product failure,seriously restricting the production device to run resulting in product loss.In order to avoid such things from bappening,the operator should do the following:4.1 storage and transportation of materials Plate column distillation process must be set in place a number of different volume raw material storage tanks,pumps and all kinds of heat exchanger has been temporarily stored,transported and preheating(cooling)of materials used,in order to protect the device can be a continuous and stable operation.4.2 Necessary means of detection In order to facilitate the resolution of the problem in the operation shall be the appropriate place in the process to set the necessary instrumentation,as well as to obtain the pressure,temperature and other parameters.In addition,often set in a particular place manholes and hand holes,so that regular testing and maintenance.4.3 Adjustment device State parameters are not in the actual production value should be placed in the appropriate location of a certain number of the valve to be adjusted to achieve the production requirements,can be a double adjustment,that is both automatic and manual adjustment coexist,and at any timeswitch.板式精馏塔的操作吴昌祥（哈尔滨气化厂，黑龙江 哈尔滨 154864）摘要：本文通过对影响精馏塔因素的分析及异常现象剖析，分析精馏过程从而指导实际操作。关键词：精馏塔，精馏，再沸器，操作中国分类号：TB657.6 文献标识码：A精馏塔是根据混合物中各组分挥发度的不同，在每层塔板上进行多级部分汽化和部分冷凝，从而达到使混合物各组分分离的一种塔式气液接触装置，又称蒸馏塔。有板式塔和填料塔两种类型。根据操作方式又分为连续精馏塔与间歇精馏塔。蒸汽从塔底进入，与下降液进行逆流接触，两相接触中，下降液中的易挥发（低沸点）组分不断地向蒸汽中转移，蒸汽中的难挥发（高沸点）组分不断地向下降液中转移。蒸汽愈接近塔顶，其易挥发组分浓度愈高，而下降液愈接近塔底，其难挥发组分愈富集，达到组分分离的目的。由塔顶上升的蒸汽进入冷凝器，冷凝的一部分作为回流液返回塔顶进入精馏塔中，其余的部分则作为馏出液取出。塔底流出的液体，其中的一部分送入再沸器，热蒸发后，蒸汽返回塔中，另一部分液体作为釜残液放出。与其它化工单元操作相比，精馏装置虽然比较简单，但生产运行中经常出现各种各样的问题而影响精馏装置的操作，从而导致塔顶或塔底产品不合格，严重制约生产装置的运行从而造成产品损失。1 精馏塔的常规工艺条件变化1.1 塔釜温度在操作压力不变的情况下，提高塔釜温度，则使塔内液相中易挥发的组分减少，同时，使上升蒸气的速度增大，有利于提高传质效率。如果由塔顶得到产品，则塔釜排出难挥发物中易挥发组分减少，减少损失。如果塔釜排出物为产品，则可提高产品质量，但塔顶排出的易挥发组分中夹带的难挥发组分增多，从而增大损失。在平衡操作中，釜温突然升高，来不及调整相应的压力和温度时，必然导致塔釜液被蒸空，压力升高。这时，塔内气、液相组成变化很大，重组份容易被蒸到塔顶，使塔顶产品不合格。1.2 操作压力在操作温度一定的情况下，提高操作压力，可以提高塔的生产能力，使操作稳定，但在塔釜产品中易挥发组份含量增加。在精馏操作中，常常规定了操作压力的调节范围。当受到外界因素的影响而使操作压力受到破坏时，塔的正常操作就会完全破坏。1.3 加料温度1.3.1 冷凝进料，则进料温度低于可加料板上的温度，则加入的物料全部进入提馏段，使提馏段负荷增加，塔釜消耗蒸汽量增加，塔顶难挥发组份降低。1.3.2 饱和蒸汽进料，则进料温度高于加料板上的温度，所进物料全部进入精馏段，提馏段的负荷减少，精馏段的负荷增加，会使塔顶产品质量降低。1.4 加料量及组份的变化加料量的变化直接影响蒸汽量的改变，后者的增大会产生夹带，甚至液泛。加料量过低，塔的平衡操作不好维持，蒸汽速度减小，塔板容易漏液，精馏效率较低。在低负荷操作时，可适当增大回流比，使塔在负荷下限之上操作，以维持塔的操作正常稳定。加料组分的变化直接影响到产品质量。重组份浓度增高使精馏段负荷增加，分离效果不好，结果重组份被带到塔顶，造成塔顶质量不合格。若从塔釜得到产品，则塔顶损失增加。如果加料组份中易挥发组份浓度增加，使提馏段的负荷增加，可能因分离不好而造成塔釜产品质量不合格，其中夹带的易挥发组份增多。加料中重组份浓度增高时，加料口往下移，反之，则向上移动。同时，操作温度、回流量和操作压力都须相应地调整，才能保证精馏操作的稳定性。在精馏操作中，提高回流比，可以提高产品的质量，但回流比过大，塔内的内循环量增加，增加能耗。回流比减少时，塔内气液接触不好，使平衡受到破坏，因而传质效率下降。同时，操作压力下降，难挥发组份易被带到塔顶，导致产品质量不合格。2 精馏塔操作过程中的异常情况2.1 塔板能力精馏段塔板降液管输送不过来溢流液，亦即塔上部开始液泛，这种现象称为降