机械外文翻译--精馏操作基本知识

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1、外文原文： Basic knowledge of distillation operation The principle of rectificationThe liquid mixture of times and partial vaporization, multiple partial condensation of the steam produced again at the same time, separate the mixture process called distillation for the operation of the required component

2、s For a vaporization, condensation, due to the boiling point of liquid mixture contained components are different, when partial vaporization under a certain temperature, due to the low boiling point is easy to gasification, so it is in the liquid phase in the gas phase concentration is high, and the

3、 concentration of the liquid high boiling point material is the gas phase. Its changed the composition of gas liquid two phase. When condensation for the steam from partial vaporization parts, due to the high boiling point material easy to condensate, to make the concentration of high boiling point

4、material, the condensate gas phase is high, and for condensate gas of low boiling point matter concentration is higher than in the condensate. So after a part vaporization and condensation, make the change of mixture concentration of components in a preliminary separation. If multiple go on like thi

5、s, will eventually left in the liquid phase is basically high boiling components, in the gas phase is basically a low boiling point components. Thus, multiple partial vaporization and partial condensation simultaneously for many times, can separate the mixture of pure or relatively pure components.

6、Rectification tower is composed of a number of plate, the upper is called the top of the tower, the bottom is called the tower of the tower kettle. Tower a tray is only a part vaporization and condensation, tray number, the more the more the number of parts vaporization and condensation, separation

7、effect is better. Through the distillation process, the final high purity of volatile components are obtained by the tower, tower kettle is basically difficult volatile components. entrainment Entrainment is refers to the gas entrainment from the lower plate belt to the upper plate of liquid droplet

8、s. In mass transfer process, a large number of smuggled with foam fog makes should not be on the top of a restructuring reached into products, so as to reduce the quality of the products, at the same time can reduce the concentration difference in the process of mass transfer, is only plate efficien

9、cy decline. For a given tower, the maximum allowable amount of smuggled with foam fog will restrict the rising velocity of the gas. There are many factors which can influence the entrainment entrainment quantity, such as plate spacing, superficial velocity, high weir, the flow velocity and material

10、physical and chemical properties, etc. At the same time, you have to point out that smuggled with foam fog and capture device structure also has a lot to do. Although many factors affect the amount of smuggled with foam fog, but the main influence factor is the superficial velocity and gas liquid se

11、paration space between the two pieces of plate. For fixed tower, entrainment entrainment quantity increases with the increase of superficial velocity and mainly. If, however, increase the distance between the plate and enlarge the separation space, the corresponding improve superficial velocity. The

12、 structure of the float valve tray Float valve tower is widely used in the past ten years in our country a new enterprise mass transfer equipment. Now it is widely used in petrochemical industry, and have achieved satisfactory results. Float valve tower structure is simple, the main structure of the

13、 tray, downcomer, overflow weir, the float valve and plate. The advantages and disadvantages of float valve tray The performance of the float valve tray with blister tray and the advantages of porous plate, and improved their shortcomings. Bubble column plate because of the opening of the slot is fi

14、xed, so its to adapt to the bad performance of steam load change. Steam speed hours, gas-liquid contact is bad, when the gas velocity is big, and easy to make steam liquid. Although the perforated plate structure is simple, processing capacity is big, but smaller, elasticity of operation for float v

15、alve tower, steam valve opening, along with the speed. Low gas velocity, the valve plate under the action of gravity automatic fall, in order to reduce leakage. So, float valve tower of high efficiency, large elasticity of operation, can better adapt to the change of feed rate, with the experimental

16、 results show that the minimum load and maximum load ratio can reach about 7 9. Float valve tower structure is simple, free cross-sectional area is larger, than bubble column 12 15% lower cost, higher than that of bubble column plate processing capacity about 20 40%. Because the float valve tray is

17、the level of the steam blowing into the liquid layer, therefore, better gas liquid agitation, entrainment placing small, contact Float valve tray are the main disadvantages of steam rising along the hole of the surrounding, there is still a liquid back, thus reduces the mass transfer efficiency. In

18、addition, the valve is easy to get stuck, rusty, or stick to open. The influence factors of distillation operation In addition to equipment problems, the influence factors of distillation operation process basically has the following several aspects: temperature and pressure of the tower (including

19、the tower, tower kettle, and some have a special meaning of plate). Feeding status; Feed rate. Feed composition; Feed temperature; The tower rises steam evaporation speed and kettle and heat; Back to the traffic; The tower cold dose; The amount and bottom at the top of the column can withdrawl. The

20、operation of the tower is composed of overhead and bottom products in accordance with the requirements for this a few factors. Distillation column pressure changes on the effect of distillation operation Design and operation of the tower are based on certain pressure, thus the general rectification

21、column, I always want to maintain a constant pressure. Tower pressure fluctuations will produce the following effect to the operation of the tower 1 ring the quality of the products change operating pressure and material balance, will lead to gas-liquid phase balance on each plate of change. Pressur

22、e, the gas phase of restructuring, the corresponding improved the concentration of light component in the gas phase; Light component content in liquid phase, but also change the weight of the gas liquid ratio, increase the amount of liquid phase, reduce gas phasor. Concentration of light component i

23、n the overall result is: the overhead fraction increased, but the number is less; Reactor, such as concentration of light component in the increase, reactor fluid volume increases. By the same token, the pressure is reduced, the number of overhead fractions increase, concentration of light component

24、; Still reduced the volume of liquid, concentration of light component. Should maintain a constant pressure in the normal operation, but if the operation is not normal, the cause of the overhead product restructuring concentration increases, the higher can adopt appropriate operating pressure, make

25、the product quality qualified, but the loss of light components in the liquid phase increase at this time. 2 variable components increase the relative volatility between pressure, relative volatility between components is reduced, the separation efficiency decreases, and vice versa. 3 change tower p

26、ressure increases, the capacity of components of the severe increase, increase processing capacity of the tower. 4 column pressure fluctuation which will cause temperature and composition of the corresponding relationship between chaos. We often with temperature in the operation as the indirect meas

27、ure of the quality of the product, but it only in the tower under the condition of constant pressure is correct. When the pressure changes, the mixture of dew point and bubble point change, change caused the temperature distribution of the tower, the corresponding relation of temperature and product

28、 quality will also change. From the above analysis, change the operating pressure, will change the working conditions of the tower, so should maintain a constant pressure in the normal operation, only in the normal operation of the tower is damaged, can according to the above analysis, the technical

29、 index, to the extent permitted to appropriate adjust pressure of the tower. It should be pointed out that in the process of distillation operation, the feed rate and feed composition and the change of feed temperature, column reactor heating steam change, back flow, reflux temperature, tower cold d

30、ose of change and clogging of plate, are likely to cause tower pressure fluctuations, at this time we should analyze the reason of pressure fluctuation, timely processing, make the operation back to normal. The influence of the installation of the tower of distillation operationDifferent materials a

31、nd different process, the tower equipment demands are different. But generally always hope the separation ability of high tower equipment, large production capacity, stable operation. For a tower of finalize the design of the equipment, because there is something wrong with the installation, you wil

32、l probably could not reach the requirements of the above. Such as the tower, tower board, the overflow mouth, if do not conform to the requirements when installation, are likely to impact on distillation operation. 1) the tower the tower for vertical, generally of no more than one over one thousand,

33、 otherwise it will cause dead zone in the plate, for small diameter of column, if the installation is first section plate, and then to assemble, is not vertical tower will directly affect the whole tower all the levelness of the plate, reduce the efficiency of the tower 2) plate plate requirements,

34、its levelness level determination for no more than plus or minus 2 mm. If the plate is not level, will cause the liquid on the surface layer height, the tower rising steam easily from the liquid layer height through smaller, thus reducing the efficiency of the plate. (3) the overflow mouth overflow

35、mouth and the distance of the lower plate, use according to the production capacity and lower on the height of the overflow weir plate. But must meet the overflow mouth insert the tray in the liquid, to seal up steam. If the overflow mouth and the lower plate too close to the distance, may cause the

36、 upper plate back cannot smoothly into the lower plate, make higher liquid layer of the upper plate, the lower the pressure plate, serious when cause flooding. The overflow mouth is too high, more than the height of the overflow weir, rising steam short circuit, straight from the overflow tube to th

37、e upper plate, no liquid seal effect, influence the plate efficiency. When installation, for all kinds of concrete plate type has different levels of demand, if not required to install, may make the production efficiency of the tower. The operation of the rectifying column should grasp the three bal

38、ance (1) the material balance embodies the production capacity of the tower, it mainly depends on the feed rate and storage overhead, bottom to adjust. When the operation of the tower does not conform to the overall material balance, this can see from tower on the change of pressure difference, into

39、 more, get less, the differential pressure rise. For a fixed rectification tower, the tower pressure difference should be within a certain range. Tower pressure difference is too big, that the tower rising steam too fast, entrainment entrainment is serious, even causing flooding and damage the norma

40、l operation of the tower; Tower pressure difference is too small, which indicates that the tower of the vapor rising speed is too small, the gas and liquid on the plate of the turbulent level is too low, the mass transfer effect is poor, make the plate produces leakage, reduce the plate efficiency.

41、If the column is not in conformity with the material balance the components of a certain type, there will be two kinds of performance: If the column is not in conformity with the material balance the components of a certain type, there will be two kinds of performance: Another case is the restructur

42、ing of the recovery of more than the amount of material balance, the material composition of the tower will be as for the operation gradually became light, the tower temperature drop, especially kettle temperature decreased obviously, still increased the concentration of light component in the liqui

43、d Thus, material balance master is bad, will make the whole operation of the tower is in chaos, can not reach the expected goal. In addition, if the material balance of the normal, so, gas-liquid phase balance and can not meet the expected effect, also need to adjust the resulting heat balance. So t

44、he material balance is a key link of tower operation. (2) the gas-liquid balance mainly reflected the quality of the product and damage. It is by adjusting operating conditions (pressure, temperature) of the tower and tower plate gas-liquid contact to achieve. Because, only in the fixed temperature,

45、 pressure, in order to determine the gas-liquid equilibrium composition. Operating temperature and pressure of rectification tower is according to the separation of the tower task (that is, the key components of the separation and concentration). When the temperature and pressure changes, the compos

46、ition of gas liquid equilibrium determined by the changes, the quality of the product or loss situation has changed. However, the composition of gas-liquid phase balance and depend on each plate of gas and liquid contact each other for mass transfer and heat transfer. That is to say, is closely rela

47、ted to the gas-liquid phase balance and material balance. Material balance control of good, the tower of the vapor rising speed, good gas-liquid contact, high mass transfer efficiency, every board composition of gas and liquid is close to balance, is often said that plate of high efficiency, and vic

48、e versa. Of course, temperature, (3) the heat balance is the basis of material balance and gas liquid equilibrium are realized. No vapor rising column reactor heating, no, no overhead condensing backflow, the whole distillation process is unable to realize. The heat balance is attached to the materi

49、al balance of gas and liquid phase equilibrium. Feed rate or composition changed, for example, column reactor heat consumption and the top of the tower cold dose should be correspondingly changed. Operating pressure, temperature of the tower has changed (that is, the gas-liquid equilibrium compositi

50、on changes), the gas phase on every board of condensing heat and liquid absorbs heat of gasification will also change. Heating kettle heating is not enough, for example, can cause the tower kettle temperature can not meet the specified value, that: (1) material balance, kettle liquid discharge incre

51、ases, the tower distillate volume reduction, for the tower to get product process, production capacity of the tower fell; (2) the gas-liquid balance, the tower rises reduced the volume of steam, gas and liquid contact, mass transfer efficiency drops, restructuring of the gas content at the same time

52、 Known from the analysis of the above: grasp the material balance, gas-liquid balance, heat balance is the key to distillation operation. The three balance is to be able to influence each other, restrict each other, the operation is usually given priority to with the change of material balance, acco

53、rdingly adjusting the heat balance to achieve the goal of gas-liquid phase balance.译文：精馏操作基本知识 精馏的原理把液体混合物进行多次部分汽化，同时又把产生的蒸汽多次部分冷凝，使混合物分离为所要求组分的操作过程称为精馏。对于一次汽化，冷凝来说，由于液体混合物中所含的组分的沸点不同，当其在一定温度下部分汽化时，因低沸点物易于气化，故它在气相中的浓度较液相高，而液相中高沸点物的浓度较气相高。这就改变了气液两相的组成。当对部分汽化所得蒸汽进行部分冷凝时，因高沸点物易于冷凝，使冷凝液中高沸点物的浓度较气相高，而为冷凝

54、气中低沸点物的浓度比冷凝液中要高。这样经过一次部分汽化和部分冷凝，使混合液通过各组分浓度的改变得到了初步分离。如果多次的这样进行下去，将最终在液相中留下的基本上是高沸点的组分，在气相中留下的基本上是低沸点的组分。由此可见，多次部分汽化和多次部分冷凝同时进行，就可以将混合物分离为纯或比较纯的组分。液体气化要吸收热量，气体冷凝要放出热量。为了合理的利用热量，我们可以把气体冷凝时放出的热量供给液体气化时使用，也就是使气液两相直接接触，在传热同时进行传质。为了满足这一要求，在实践中，这种多次部分汽化伴随多次部分冷凝的过程是逆流作用的板式设备中进行的。所谓逆流，就是因液体受热而产生的温度较高的气体，自下

55、而上地同塔顶因冷凝而产生的温度较低的回流液体（富含低沸点组分）作逆向流动。塔内所发生的传热传质过程如下1）气液两相进行热的交换，利用部分汽化所得气体混合物中的热来加热部分冷凝所得的液体混合物；2）气液两相在热交换的同时进行质的交换。温度较低的液体混合物被温度较高的气体混合物加热二部分汽化。此时，因挥发能力的差异（低沸点物挥发能力强，高沸点物挥发能力差），低沸点物比高沸点物挥发多，结果表现为低沸点组分从液相转为气相，气相中易挥发组分增浓；同理，温度较高的气相混合物，因加热了温度较低的液体混合物，而使自己部分冷凝，同样因为挥发能力的差异，使高沸点组分从气相转为液相，液相中难挥发组分增浓。精馏塔是由

56、若干塔板组成的，塔的最上部称为塔顶，塔的最下部称为塔釜。塔内的一块塔盘只进行一次部分汽化和部分冷凝，塔盘数愈多，部分汽化和部分冷凝的次数愈多，分离效果愈好。通过整个精馏过程，最终由塔顶得到高纯度的易挥发组分，塔釜得到的基本上是难挥发的组分。 浮阀塔板的结构 浮阀塔是我国近十余年来广为使用的一种新型企业传质设备。目前它广泛应用在石油化工中，并取得了令人满意的效果。浮阀塔的结构较为简单，主要结构有受液盘，降液管，溢流堰，浮阀和塔板。 浮阀塔板的优缺点 浮阀塔板的性能兼有泡罩塔板与多孔塔板的优点，并改进了它们的缺点。泡罩塔板由于齿缝开度是固定的，因此其对蒸汽负荷变动的适应性能不好。汽速小时，气液接触

57、不好，气速大时，又易使蒸汽吹开液体。多孔塔板虽然结构简单，处理能力大，但操作弹性比较小，对于浮阀塔来说，阀片的开度则随汽速而变。低气速时，阀片在重力作用下自动落下，以减少泄漏。所以，浮阀塔的效率较高，操作弹性大，能较好的适应进料量的变化，有实验表明，其最大负荷与最小负荷的比可达到79左右。浮阀塔结构简单，自由截面积较大，造价比泡罩塔降低1215%，处理能力比泡罩塔板提高2040%左右。由于浮阀塔板的蒸汽是水平吹入液层，因此，气液搅动较好，雾沫夹带小，接触时间长，传质效果好，其效率比泡罩塔板药膏15%。浮阀塔板的主要缺点是蒸汽沿上升蒸汽气孔的周边喷出，仍然有液体的逆向混合，因而会降低传质效率。另

58、外，阀片容易被卡住、锈住或粘住，影响开启。 精馏操作的影响因素 除了设备问题以外，精馏操作过程的影响因素主要有以下几个方面：塔的温度和压力（包括塔顶、塔釜和某些有特殊意义的塔板）；进料状态；进料量；进料组成；进料温度；塔内上升蒸汽速度和蒸发釜的加热量；回流量；塔顶冷剂量；塔顶采出量和塔底采出量。塔的操作就是按照塔顶和塔底产品的组成要求来对这几个影响因素进行调节。 精馏塔操作压力的变化对精馏操作的影响 塔的设计和操作都是基于一定的压力下进行的，因此一般的精馏塔总是先要保持压力的恒定。塔压波动对塔的操作将产生如下的影响。 1 响产品质量和物料平衡改变操作压力，将使每块塔板上的气液相平衡的组成发生改

59、变。压力升高，则气相中的重组份减少，相应的提高了气相中的轻组分的浓度；液相中的轻组分含量增加，同时也改变了气液相的重量比，使液相量增加，气相量减少。总的结果是：塔顶馏分中的轻组分浓度增加，但数量却相对减少；釜液中的轻组分浓度增加，釜液量增加。同理，压力降低，塔顶馏份的数量增加，轻组分浓度降低；釜液量减少，轻组分浓度减少。正常操作中应保持恒定的压力，但若操作不正常，引起塔顶产品中重组分浓度增加时，则可采用适当升高操作压力的办法，使产品质量合格，但此时液相中轻组分的损失增加。 2 变组分间的相对挥发度压力增加，组分间的相对挥发度降低，分离效率下降，反之亦然。 3 改变塔的生产能力压力增加，组分的重

60、度增大，塔的处理能力增大。 4 塔压的波动这将引起温度和组成间对应关系的混乱。我们在操作中经常以温度作为衡量产品质量的间接标准，但这只有在塔压恒定的情况下才是正确的。当塔压改变时，混合物的露点、泡点发生改变，引起全塔的温度分布发生改变，温度和产品质量的对应关系也将发生改变。从以上分析来看，改变操作压力，将改变整个塔的工作状况，因此在正常操作中应维持恒定的压力，只有在塔的正常操作受到破坏时，才可以根据上述分析，在工艺指标允许的范围内，对塔的压力进行适当的调整。应当指出，在精馏操作过程中，进料量、进料组成和进料温度的改变，塔釜加热蒸汽量的改变、回流量、回流温度、塔顶冷剂量的改变以及塔板的堵塞等，都

61、有可能引起塔压的波动，此时我们应先分析塔压波动的原因，及时处理，使操作恢复正常。 塔的安装对精馏操作的影响 不同的物料和不同的工艺过程，对塔设备提出的要求是不同的。但是，一般总希望塔设备的分离能力高，生产能力大，操作稳定。对于一个定型的塔设备来说，由于安装上有问题，就可能会达不到以上的要求。如塔身、塔板、溢流口等，在安装时若不符合要求，都有可能对精馏操作带来影响。（1）塔身 塔身要求垂直，一般的倾斜度不能超过千分之一，否则将会在塔板上造成死区，对于小直径的精馏塔来说，如果塔板的安装是先分节安装，然后再组装的话，则塔身的不垂直将直接影响全塔的所有塔板的水平度，使塔的效率降低。（2）塔板 塔板要求

62、水平，其水平度用水平仪测定不能超过2毫米。如果塔板不水平，将造成板面上的液层高度不均，塔内上升蒸汽易从液层高度较小的浅处穿过，从而降低塔板的效率。（3）溢流口 溢流口与下层塔板的距离，用根据生产能力和下层塔板的溢流堰的高度而定。但必须满足溢流口插入受液盘的液体中，以封住上升蒸汽。如果溢流口与下层塔板的距离太近，则可能造成上层塔板的回流也不能顺利流入下层塔板，使上层塔板的液层增高，下层塔板的压力增大，严重时造成液泛。溢流口过高，超过溢流堰的高度时，上升的蒸汽“走短路”，从溢流管直接上升到上层塔板，起不到液封作用，影响塔板效率。安装时，对于各种具体的塔板类型都有不同程度的要求，如果不按要求去安装，

63、将可能使塔的生产效率大大下降。 精馏塔的操作应该掌握好三个平衡 （1）物料平衡体现了塔的生产能力，它主要是靠进料量和塔顶、塔底采储量来调节。当塔的操作不符合总的物料平衡式时，这可以从塔压差的变化上看出，进得多，取得少，则塔压差上升。对于一个固定的精馏塔来说，塔压差应该在一定范围内。塔压差过大，说明塔内上升的蒸汽速度过快，雾沫夹带严重，甚至发生液泛，破坏塔的正常操作；塔压差过小，表明塔内上升蒸汽的速度过小，塔板上的气液湍动的程度过低、传质效果差，使塔板产生漏液，降低塔板效率。如果精馏塔不符合对某组分的物料平衡式时，将有两种表现：A、轻组分的采出量超过了物料平衡的量，在这种情况下，将使塔内的物料组

64、成变重，全塔的温度逐步升高，塔顶馏分中重组份的浓度增加，以致使质量不合格。B、另一种情况是重组份的采出量超过了物料平衡的量，全塔的物料组成将随着操作的进行而逐渐变轻，塔身温度下降，特别是釜温明显下降，釜液中轻组分的浓度增加。由此可见，物料平衡掌握不好，将使整个塔的操作处于混乱状况，达不到预期的目的。另外，如果正常的物料平衡受到破坏，那么，气液相平衡也达不到预想的效果，随之而来的热量平衡也得重新调整。所以物料平衡是塔操作中的一个关键环节。（2）气液平衡主要体现了产品的质量和损失情况。它是靠调节塔的操作条件（温度、压力）及塔板上气液接触的情况来达到的。因为，只有在温度、压力固定时，才能确定气液平衡

65、组成。精馏塔的操作温度和压力是根据塔的分离任务（即关键组分的分离浓度）决定的。当温度、压力发生变化时，气液平衡所决定的组成就发生了变化，产品的质量或损失情况也发生了变化。但是，气液相平衡的组成又是靠在每块塔板上的气液互相接触进行传质和传热而实现的。这就是说，气液相平衡和物料平衡密切相关。物料平衡掌握的好，塔内上升蒸汽的速度合适，气液接触好，则传质效率高，每块板上的气液组成就愈接近于平衡组成，也就是常说的板效率高，反之亦然。当然，温度、压力也会随着物料平衡的改变而变化。总之，汽液平衡的组成与物料平衡有着密不可分的关系。反过来，温度、压力的改变又可造成塔板上气相和液相相对量的改变，从而破坏原来的物料平衡。例如，釜温低于规定值，会使塔板上的液相量增加，蒸汽量减少，釜液量增加，顶部产物量减少；当顶温高于规定值时，就会使塔板上的气相量增加，液相量减少，顶部产物量增加，釜液量减少。这些都会破坏原来的物料平衡。（3）热量平衡是物料平衡和气液相平衡得以实现的基础。没有塔釜供热就没有上升蒸汽，没有塔顶冷凝就没有回流液，整个精馏过程就无法实现。而热量平衡又是依附于物料平衡和