应用化学专业文献原文及翻译Lt
D
Operation of plate rectification tower
WU Chang-xiang
(Harbin Gasification Plant,Harbin
154864,China)
Abstract:The influencing factors,abnoimal phenomenon and rectification process were analyzed to direct actual operation
Key words: rectification tower,recification,reboiler,operation
Distillation 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 a
nd 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 column 1.1 Reboiler temperature
Under 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 pressure
In 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 temperature
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.
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 changes
Changes 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 operation
2.1 Plate capacity
Rectifying section tray downcomer overflow liquid transportation,however,that the tower upper part of t
he 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 fouling
Sediment 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.
reactor 翻译
2.3 Slug flows in the riser
Slug flow in the riser is a distillation column running unstable,may be caused due to an unstable gas-li
quid 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.Reboiler

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