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2014 屆畢業(yè)設計外文翻譯 院 、 部： 機械工程學院 學生姓名： 朱業(yè)煌 外聘教師： 陳志剛 職 稱 副教授 指導教師： 鄒芝芳 職 稱 副教授 專 業(yè)： 機械設計制造及其自動化班 級 機本 1004 班 學 號： 10201440441 2014 年 5 月外文原文：Basic knowledge of distillation operationThe 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 componentsFor 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 concentration of the liquid high boiling point material is the gas phase. It's 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 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 this, 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.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 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.entrainmentEntrainment is refers to the gas entrainment from the lower plate belt to the upper plate of liquid droplets. 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 efficiency 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 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 separation 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 structure of the float valve trayFloat 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 tray, downcomer, overflow weir, the float valve and plate.The advantages and disadvantages of float valve trayThe 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 fixed, 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 valve 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 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 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 addition, the valve is easy to get stuck, rusty, or stick to open.The influence factors of distillation operationIn addition to equipment problems, the influence factors of distillation operation process basically has the following several aspects: temperature and pressure of the tower (including 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 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 operationDesign and operation of the tower are based on certain pressure, thus the general rectification column, I always want to maintain a constant pressure. Tower pressure fluctuations will produce the following effect to the operation of the tower1 ring the quality of the products change operating pressure and material balance, will lead to gas-liquid phase balance on each plate of change. Pressure, 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 in 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; 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 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 pressure 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 measure 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 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 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 dose 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 and 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 will 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, 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 tower2) plate plate requirements, 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 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 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 the 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 balance(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 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 normal 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.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 restructuring 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 liquid 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 the 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, 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 composition 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 related 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 vice 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 material 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 composition 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 increases, 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 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, accordingly adjusting the heat balance to achieve the goal of gas-liquid phase balance.