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In the area dedicated to technical exchanges in production, many questions related to distillation have been raised. To make it easier for everyone to refer to these issues, this post has been compiled! Distillation column control systems: http://bbs.hcbbs.com/thread-77888-1-1.html. Problem of repeated flooding in the distillation column: Question: The distillation column in our facility floods repeatedly. Using oil slurry to regulate the temperature of the gas phase at the bottom of the column does not work well; the temperature of that gas phase can easily rise to 400 degrees, forcing us to use pressure to bring it down. Several washes with water have also been ineffective. What solutions exist for this problem? http://bbs.hcbbs.com/thread-54773-1-1.html. Issues with distillation control: My distillation column functions fine when operating in full reflux mode, but it starts to experience flooding as soon as feeding begins. I would appreciate it if experts could explain what might be causing this issue http://bbs.hcbbs.com/thread-77804-1-1.html Why is the temperature in the distillation section of the tower low, and why is there no temperature difference between the different tray levels? What are the conditions required for vapor-liquid equilibrium inside a distillation tower? Why is the temperature in the distillation section of the tower low, and why is there no temperature difference between the tray levels? http://bbs.hcbbs.com/thread-76181-1-1.html Urgent! Urgent! Urgent! The distillation tower won’t start; it just won’t function. Later, by increasing the reflux rate, one of the towers gradually started working properly. Now, a new problem has arisen ； Top of tower pressure: around 50–60 KPA; normal value is around 200 KPA. Bottom of tower pressure: 150–160 KPA; normal value is around 300 KPA. Steam percentage: 30%; any increase in this percentage poses a risk of flooding. Condenser opening: 0%; there is slight internal leakage. Liquid level is full; feeding has just been completed. Purity is over 90%; no nitrogen present. Some light components are present. Full reflux is used; the material from the top of the tower is returned to the system as appropriate. Issues exist ； The steam flow is increased from 0% to 30%. The pressure at the top of the tower remains around 50 KPA; it’s not possible to activate the condenser when the pressure at the top of the tower is low. A pressure of around 100 KPA would be sufficient. But no matter how much steam is supplied, the pressure at the top of the tower still doesn’t increase. http://bbs.hcbbs.com/thread-75016-1-2.html http://bbs.hcbbs.com/thread-71569-1-3.html How is the pressure difference in a distillation tower generated? How to control the pressure difference in a distillation tower? How is it generated? How to control it? Besides being related to the reboiler, what else is it related to? http://bbs.hcbbs.com/thread-52377-1-2.html Distillation operating procedures http://bbs.hcbbs.com/thread-72119-1-2.html The purpose of filling N2 during distillation. Our company’s methanol distillation system uses a 4-tower process, namely a pre-tower, a pressurized tower, an atmospheric pressure tower, and a recovery tower. Each tower is equipped with N2 pipelines; the pressurized tower and the atmospheric pressure tower are both double-effect towers, with the reflux liquid from the pressurized tower serving as the heat source for the atmospheric pressure tower. In actual production, we often encounter such a problem: the fundamental principle of operation is to strive for stability in the operating conditions and minimize fluctuations as much as possible. When the pressure at the top of the atmospheric pressure column is low (below the specified value but still above 0 MPa(G)), and adjustments such as changing the reflux rate or the cooling water flow in the reflux cooler fail to bring the pressure at the top of the column within the specified range, the workers in the control room do not resort to indirectly adjusting the pressure at the top of the atmospheric pressure column by modifying the already stable pressurized column or the recovery column. Instead, they ask the operators to increase the N2 supply to the atmospheric pressure column in order to raise its pressure. Interestingly, after introducing N2, the top temperature of the atmospheric pressure column rose rapidly, but the temperature of the reflux liquid remained almost unchanged. When the N2 was then turned off, the top pressure of the column could again reach the specified value. My question is: I believe it is only necessary to introduce N2 when the pressure at the top of the tower is negative. Introducing N2 in this case is different from vacuum distillation; it is not done to reduce the partial pressures of methanol and water at the top of the tower, but rather to ensure that the pressure there is not negative. Therefore, there is no need to introduce N2 when the pressure at the top of the tower is low. But in practice, doing this does have a certain effect? N2 has a significant impact on cooling due to its non-condensable nature, but why doesn’t the temperature of the reflux liquid change much, while the temperature at the top of the tower increases? http://bbs.hcbbs.com/thread-75272-1-3.html The acid value of the methanol distillation products is above the specified limit; crude methanol is acidic, and if no alkali is used for adjustment during the distillation process, the quality of the distilled product can still be of top grade ； However, after adjusting the pH value with alkali, the acid value of the distilled product exceeds the standard, rendering it a non-conforming product. How can we handle this situation while ensuring both product quality and the service life of the equipment? Please share your opinions! ! http://bbs.hcbbs.com/thread-69538-1-3.html The function of the balance line in the reboiler: On the PID diagram of the distillation process, there is a balance line running from the heat source inlet to the outlet of the reboiler; I’m not sure what its purpose is or when it would be used http://bbs.hcbbs.com/thread-67986-1-3.html This post was last edited by yeep123 on 2007-8-21 21:34 ]
Manufacturers of tray trays: There are now many companies that produce tray trays and packing materials, but the majority of them are small-scale manufacturers; large-scale enterprises with a significant scale seem to be rare. Companies like Sulzer in Shanghai are fairly well-known, but their products are also relatively expensive. Is it possible to find products that are both affordable and of good quality? http://bbs.hcbbs.com/thread-59452-1-3.html Strange phenomena in our distillation tower. We have a xylene distillation tower; its feed consists of C6-C10 hydrocarbons. Previously, the temperature at the top of the tower was generally maintained at around 144 degrees, while the temperature at the bottom was kept between 240 and 255 degrees. We recently conducted major maintenance on the tower. Now, the temperature difference between the top and bottom of the tower is less than 20 degrees. Our supervisors are very worried as they can’t figure out the reason behind this. The pressure on us is immense; if this continues, it will affect our annual production plan. Please help us analyze the cause! http://bbs.hcbbs.com/thread-74342-1-4.html Key points for operating an ADV floating valve tower. It’s my first time operating a floating valve tower, and with the use of highly efficient ADV floating valves, I really don’t know where to start. Could some expert give me some guidance? http://bbs.hcbbs.com/thread-76651-1-4.html What are the processes of mass and heat transfer inside a distillation tower? What is the essence of the distillation process? What are the main factors that affect distillation operations? What is the difference between distillation and rectification? http://bbs.hcbbs.com/thread-76167-1-4.html How is a reboiler tested for pressure and leaks? http://bbs.hcbbs.com/thread-75310-1-5.html What do AGO and HGO stand for? Thank you! More specifically, for example, where do AGO and HGO come out from on the tower’s sides respectively? Thank you! http://bbs.hcbbs.com/thread-46423-1-5.html What is the effect of heat carried away by the side stream of the distillation column? Are all distillation columns designed to use side-stream reflux to remove some of the heat in order to achieve distillation? I remember that this is the case for constant-pressure and reduced-pressure columns; is it the same for the xylene column and the xylene re-distillation column in aromatic compound processing units? http://bbs.hcbbs.com/thread-39489-1-6.html What knowledge should distillation workers acquire? http://bbs.hcbbs.com/thread-75311-1-6.html Concepts of tower pressure and reactor pressure: 1. If the tower pressure is high, is the reactor temperature necessarily high? 2. If the reactor temperature is high, is the tower pressure necessarily high? 3. If the reactor temperature is high, is the reactor pressure necessarily high? 4. If the tower pressure is high, is the reactor temperature necessarily high? 5. If the tower pressure is high, is the reactor pressure necessarily high? I would appreciate advice from experts on these questions. Could you first tell me how tower pressure is measured? Where is it measured? How is reactor pressure measured? Where is it measured? The tower pressure gauge I’ve come across was located 20 centimeters above the liquid level gauge. There’s one more small issue: why is the tower pressure gauge reading slightly higher than the level gauge? I would appreciate some advice from those who are more experienced; I’m new here. Thank you for your guidance. http://bbs.hcbbs.com/thread-73056-1-6.html Selection of Distillation Column Packing: There are various types of packing for distillation columns, including wire mesh corrugated packing and perforated plates. What are the characteristics of each of these fillers, and how should they be selected? http://bbs.hcbbs.com/thread-75986-1-6.html Solvent foaming occurs in the coking dry gas desulfurization unit. My unit has been in operation for 8 months, and recently foaming has appeared at the top of the solvent regeneration tower; the reflux tank at the top of the tower filled up rapidly within a short time, the pressure at the top of the tower dropped to zero quickly, and the temperatures at the top and bottom of the regeneration tower increased slightly, resulting in a brief situation of overpressure in the tower. Could that expert help with the analysis? http://bbs.hcbbs.com/thread-74814-1-8.html This post was last edited by yeep123 on 2007-8-21 17:49 ]
Special topic on the operation and control of distillation towers: The attachment to this post is a summary of my responses to questions from some netizens over the recent period. These answers to the questions are all derived from my own practical experience and have been verified through practice. It can be used to guide the resolution of operational issues related to distillation columns, as well as to provide designers with guidance on the design aspects of such columns. We welcome criticism and suggestions from netizens. Netizens are also asked to indicate the source when reposting. There are no restrictions on the level for reading and downloading; access is free. The file format is .doc.rar; after downloading, remove the .rar extension. I also suggest that the moderator mark it as a featured post. http://bbs.hcbbs.com/thread-73916-1-9.html Solutions to the problem of excessive resistance in the benzene washing tower in the benzene washing unit. The benzene washing tower in our plant has excessive resistance; after replacing the packing, the production volume decreased. What’s going on? http://bbs.hcbbs.com/thread-67177-1-9.html What are the wastewater parameters for three-column distillation? Our company plans to install a new methanol production plant with a capacity of 2,000 tons per day. I would like to know what the volume of wastewater generated per hour would be using a three-column distillation process What are the typical main pollutant indicators in wastewater? Due to environmental regulations, our company intends to achieve “zero emissions” as a solution; we would appreciate your valuable suggestions! Key process points to note. http://bbs.hcbbs.com/thread-74640-1-9.html How is the height of the flare determined when burning methanol distillation off-gases? http://bbs.hcbbs.com/thread-72127-1-9.html Word version of the distillation operating procedures
http://bbs.hcbbs.com/thread-73862-1-10.html What is the maximum allowable difference between the diameters of the upper and lower sections of a distillation column? http://bbs.hcbbs.com/thread-73738-1-10.html Operation and adjustment of distillation towers http://bbs.hcbbs.com/thread-26148-1-11.html Liquid flooding in towers In factory production, the reflux rate and pressure difference of purification towers are well below the set values, but liquid flooding still occurs frequently in these towers? Who knows how to operate it so that flooding occurs as little as possible in the tower? How to control it? http://bbs.hcbbs.com/thread-71948-1-11.html What are the advantages of combining the top condenser of a distillation tower with the tower body? The overhead condenser of the distillation column is installed together with the column body. What are the advantages of this? Moreover, a level gauge is also installed between the tower body and the top condenser; I think it’s necessary to control this liquid level during the operation of the tower. However, since we have never seen tower equipment installed in this way before, we don’t know how to operate it. We hope everyone can help us! Thank you! Thank you! http://bbs.hcbbs.com/thread-72979-1-11.html Questions regarding the application of reflux ratio controllers: What properties of the product to be distilled are related to the reflux ratio controlled by such controllers? http://bbs.hcbbs.com/thread-72787-1-12.html This post was last edited by yeep123 on 2007-8-21 at 18:00.]
http://bbs.hcbbs.com/thread-73862-1-10.html What is the maximum allowable difference between the diameters of the upper and lower sections of a distillation column? http://bbs.hcbbs.com/thread-73738-1-10.html Operation and adjustment of distillation towers http://bbs.hcbbs.com/thread-26148-1-11.html Liquid flooding in towers In factory production, the reflux rate and pressure difference of purification towers are well below the set values, but liquid flooding still occurs frequently in these towers? Who knows how to operate it so that flooding occurs as little as possible in the tower? How to control it? http://bbs.hcbbs.com/thread-71948-1-11.html What are the advantages of combining the top condenser of a distillation tower with the tower body? The overhead condenser of the distillation column is installed together with the column body. What are the advantages of this? Moreover, a level gauge is also installed between the tower body and the top condenser; I think it’s necessary to control this liquid level during the operation of the tower. However, since we have never seen tower equipment installed in this way before, we don’t know how to operate it. We hope everyone can help us! Thank you! Thank you! http://bbs.hcbbs.com/thread-72979-1-11.html Questions regarding the application of reflux ratio controllers: What properties of the product to be distilled are related to the reflux ratio controlled by such controllers? http://bbs.hcbbs.com/thread-72787-1-12.html This post was last edited by yeep123 on 2007-8-21 at 18:00.]
Fractionation Unit 1: Operating procedures for the coking fractionation unit 2: Operation of the fractionation tower in hydrogenation units. http://bbs.hcbbs.com/thread-71145-1-12.html The time required for steaming the tower – Everyone has experienced maintenance periods, during which the towers are steamed; especially for these towers, the steaming process can last up to 48 hours. However, with an emphasis on energy conservation these days, there is a push to use as little steam as possible. This creates a conflict with the need to steam the towers for safety reasons. Please discuss: how long does it take to steam the towers when a refinery unit is shut down? Are there any specific regulations regarding this? And how do people balance energy considerations with safety needs? http://bbs.hcbbs.com/thread-71254-1-12.html Differences between Bauer rings and structured packing in the installation of desulfurization towers http://bbs.hcbbs.com/thread-72287-1-13.html Issues related to the distillation separation of binary components; there are binary components in the laboratory that need to be separated. Please design an experimental setup using the principles of distillation (the instruments provided include: a distillation flask, an alcohol lamp, a thermometer, a condenser, a receiving flask, etc.). I think a fractional distillation flask should be used instead of a distillation flask. How many thermometers do we need? Are there two? How should it be assembled? I drew one; I’m not sure if it’s correct. If you know, please help me out. Thanks! There are two vertical bars in the image, which represent a thermometer: http://bbs.hcbbs.com/thread-72260-1-13.html. The process flow diagram for the triple-column distillation of methanol can be found here: http://bbs.hcbbs.com/thread-72189-1-13.html. Where can I find the manual on packing materials? http://bbs.hcbbs.com/thread-71975-1-13.html. I’m looking for basic knowledge on organic distillation as well as technical questions related to distillation; if anyone has this information, please upload it: http://bbs.hcbbs.com/thread-71033-1-15.html. The composition of the gas inside the tower: In my facility, the final step involves using a drying tower to remove moisture from 98% CO gas. The CO gas also contains small amounts of H2, CO2, N2, and H2S. The packing used in the drying towers is Al2O3; there are two towers in total, one for dehumidification and the other for regeneration. The high-temperature CO gas (220 degrees Celsius) in the regeneration system removes moisture through the original dehumidifier tower and is then cooled by a heat exchanger. The problem now is that the heat exchanger used for cooling is severely corroded and needs to be replaced frequently. Sampling analyses show that there is no H2S in the regeneration system; only large amounts of H2 and CO2 are present. What could be the reason for this? http://bbs.hcbbs.com/thread-70346-1-15.html Refluxer renovation: The bottom refluxer of the distillation tower in one of our plant’s units is heated by 10 kilograms of steam. The current process involves using 1.0 MPa steam to heat the material at the bottom of the tower, which then turns into process condensate water. I would like to ask if it is possible to convert steam at 1.0 MPa into steam at 0.35 MPa through heat exchange for reuse, thereby reducing energy consumption. How exactly should this be calculated? http://bbs.hcbbs.com/thread-63955-1-15.html Reflux issues in distillation columns: I would like to ask about the differences between internal reflux and external reflux in distillation columns, and under what circumstances each is used http://bbs.hcbbs.com/thread-69914-1-16.html This post was last edited by yeep123 on 2007-8-21 18:01 ]
What is the performance of CTST trays in methanol distillation units? Our company currently has a methanol distillation capacity of 70,000 tons, and we plan to expand production. I would like to know what the performance of CTST trays is in methanol distillation units http://bbs.hcbbs.com/thread-70140-1-16.html What extent can the differences be between the reflux ratio, operating time, and actual calculations during intermittent distillation trials? What aspects need to be taken into consideration during such trials? http://bbs.hcbbs.com/thread-68425-1-17.html What is the direct impact of pressure in a distillation column on its separation efficiency? http://bbs.hcbbs.com/thread-69034-1-17.html Issues related to pressure difference in refining columns; in a plate-type refining column, which pressure is usually higher, the pressure at the top of the column or that at the bottom? When I came into contact with it before, I didn’t study it in detail; it seems that the pressure in the tower bottom needs to be a bit higher. Could someone explain this to me theoretically? http://bbs.hcbbs.com/thread-37911-1-17.html Regarding the issue of reflux in towers: In the chemical industry, many towers utilize reflux systems, such as top reflux and mid-tower reflux; there is more than one type of reflux device. What are the main functions of these reflux systems? Is it to lower temperatures? I hope everyone can explain this to me. Thank you. http://bbs.hcbbs.com/thread-68141-1-18.html Investment and returns in crude phenol refining: I know that phenol, cresol, and dimethylphenol can be extracted from crude phenol. But it’s unknown how to refine it, how much investment is required, and what the benefits will be. Please ask an expert for help. You can contact them directly at: macj1988@163.com. Relevant links: http://bbs.hcbbs.com/thread-67036-1-18.html – Issues related to the operation of methanol-water distillation towers; http://bbs.hcbbs.com/thread-66778-1-18.html – Problems with the water coolers at the top of distillation towers. I am currently working on a design, and there is disagreement with the client regarding whether it is necessary to install control valves to regulate the flow rate of water in the cooling system of these water coolers. In my opinion, usually, a constant flow of cooling water is sufficient; if needed, the process valves for supplying or removing water can be reduced. However, the client insists on installing flow control valves for the cooling water. I would appreciate it if everyone could share their opinions on this matter. http://bbs.hcbbs.com/thread-55795-1-21.html Is a plate tower or a packed tower better for distillation towers? For a single-series methanol distillation plant with an annual capacity of 600,000 tons, it is worth considering whether to use a plate tower or a high-efficiency packed tower; please discuss the advantages and disadvantages of each type of tower. Does anyone else know what type of columns are used in the distillation units of domestic methanol manufacturers with an annual production capacity of 600,000 tons? http://bbs.hcbbs.com/thread-64472-1-21.html What are the types of solid packing materials used in packing towers and what are their applications? http://bbs.hcbbs.com/thread-64781-1-22.html This post was last edited by yeep123 on 2007-8-21 18:02 ]
How is the amount of azebestic added in azeotropic distillation determined? How is the amount of benzene to be used as an azeotrope to separate ethanol and water determined? http://bbs.hcbbs.com/thread-64204-1-23.html Questions regarding some challenging operations in the acetaldehyde distillation tower: 1. When unqualified concentrated acetaldehyde is sent back to the acetaldehyde distillation tower for re-distillation, how can the stability of the tower be improved? 2. When the recovered alcohol is not up to standard and needs to be sent back to the acetaldehyde distillation tower for re-distillation, how can the stability of the tower be improved? 3. Is there a simple way to determine whether the acetaldehyde concentration is above 99%? Can anyone help me? I’ve just started working with these devices, and these are the problems I’ve encountered; they really drive me crazy every time. It takes over 6 hours to get everything adjusted properly, which is a waste of so much time. I hope experienced users can teach me how to do this. Thank you! http://bbs.hcbbs.com/thread-64031-1-23.html Is it a good idea to use automatic reflux control in the middle section of an atmospheric pressure tower? For the first extraction in my unit, the temperature is controlled automatically, while for the second extraction and the return flow rate of the second stage, a cascade control system is used. I’d like to know how other factories are, as well as the advantages and disadvantages of adopting automation. http://bbs.hcbbs.com/thread-63137-1-24.html Are the fluctuations in the atmospheric pressure tower severe? Production conditions: naphtha, 0# diesel; first and second distillation columns. Temperature fluctuations: atmospheric column: 10; first column: 10; second column: 20. This has never happened before; I don’t know how to handle it. I kindly request guidance from experienced colleagues who have worked with atmospheric distillation processes. http://bbs.hcbbs.com/thread-62847-1-25.html Series operation of distillation columns Currently, the capacity of one of the distillation columns in our plant is insufficient; we intend to operate two columns in series for distillation. However, we lack any experience in this area. I would appreciate any advice from everyone. http://bbs.hcbbs.com/thread-57530-1-25.html Types of overhead condensers http://bbs.hcbbs.com/thread-57830-1-25.html Questions regarding the operation of distillation columns I’m new to the chemical industry. My question is: if the feed condition changes from cold liquid feed to saturated steam feed, will the position of the feed inlet be higher or lower compared to its original position when using cold liquid feed? http://bbs.hcbbs.com/thread-51841-1-25.html The separation performance of the rectifying tower is deteriorating. Our factory uses a rectifying tower to separate oleic acid, and the separation efficiency is inconsistent; previously this was due to blockages in the distribution tray. After resolving that issue, the same problem has arisen again. I’m not sure what other causes there might be. http://bbs.hcbbs.com/thread-61613-1-26.html What are the reasons for little or no water output from the oil-water separator between coking debenzene towers? http://bbs.hcbbs.com/thread-57983-1-27.html Issues with the distribution of circulating cooling water in the condenser at the top of the distillation tower. Our company has recently installed a new set of equipment, and the distribution of circulating cooling water in the condenser at the top of the distillation tower is not optimal. If the total circulation water pipeline, the total amount of circulation water, and the circulation water pressure all meet the design values, then there is a problem with the distribution; the material outlet on the process side of the distillation column’s top condenser does not reach the set value. The overhead condensers of the distillation columns are located on the 21-meter platform of the plant. The water consumption of these condensers accounts for over 70% of the total water usage. May I ask how experts handle such situations? http://bbs.hcbbs.com/thread-57921-1-27.html This post was last edited by yeep123 on 2007-8-21 at 18:03.]
Distillation operations: http://bbs.hcbbs.com/thread-60095-1-28.html. Issues regarding the selection of methanol distillation towers. For newly constructed methanol plants, currently available distillation processes include two-tower and three-tower distillation. As for tower internals, there are both packing-based and sieve tray-based options. We invite everyone to share their opinions on how to scientifically and economically select the appropriate distillation process and equipment for a new methanol plant with a capacity of 200,000 tons per year. http://bbs.hcbbs.com/thread-40865-1-28.html Water splashing sound coming from the feed inlet of the distillation tower. The feed inlet of our company’s distillation tower has been producing a water splashing sound during operation; the feed is a liquid at its bubble point. The pipeline downstream of the valve has been enlarged, from DN100 to DN200, and a tubular distributor is installed at the feed inlet. Could anyone help me analyze the cause of this issue? http://bbs.hcbbs.com/thread-48962-1-32.html Regarding the temperature of heat transfer oil in distillation: if the temperature at the bottom of the distillation column is below 200 degrees, is it more economical to use heat transfer oil or steam? Can the recycling of heat transfer oil be considered a fixed investment? http://bbs.hcbbs.com/thread-22737-1-32.html What is the difference between placing the heat transfer oil heating automatic control unit at the inlet and outlet of the reboiler? http://bbs.hcbbs.com/thread-50785-1-33.html Question: Distillation columns are classified by pressure into atmospheric columns, vacuum columns, etc. So, is this pressure based on the design pressure or the operating pressure? http://bbs.hcbbs.com/thread-55553-1-33.html Sensitive plate in a distillation column. I have a question regarding the sensitive plate in a distillation column. Under normal circumstances, how is the position of the sensitive plate determined? What does it matter to keep track of the material location? http://bbs.hcbbs.com/thread-55893-1-33.html New methods for increasing diesel production through atmospheric and vacuum distillation http://bbs.hcbbs.com/thread-52588-1-35.html Techniques for controlling ethylene distillation towers http://bbs.hcbbs.com/thread-52777-1-36.html Water circulation in packed towers; I would like to ask whether it is allowed for water to enter the packed tower during water circulation http://bbs.hcbbs.com/thread-49848-1-36.html This post was last edited by yeep123 on 2007-8-21 18:04 ]
How is the operational flexibility of the tower determined? Our company is preparing to put a distillation unit into operation. There is disagreement regarding the minimum load at which the unit should operate. Is the operational flexibility of the tower equivalent to the range of operating loads for the unit? If so, how can this operational flexibility be determined? http://bbs.hcbbs.com/thread-35286-1-37.html How can a distillation tower be optimized? The company has two distillation towers; the feed materials for these towers are mainly C4, C5, and MTBE (with certain differences in the materials used in each tower). It is required that the MTBE product be obtained from the bottom of the towers, with the purity level to be above 95%. The temperature of the reactor in Tower A is 127 degrees, while that in Tower B is 140 degrees. Tower A achieves a better separation efficiency, remaining around 97%, whereas Tower B’s efficiency often falls below 95% recently. What measures can be taken to optimize the operation of Tower B? I would appreciate some advice on how to address the issue of high energy consumption and poor separation efficiency in Tower B. Tower A has more trays than Tower B. http://bbs.hcbbs.com/thread-48964-1-37.html There is also a problem with the temperature distribution in the methanol pre-distillation tower. Our plant uses a three-tower distillation process for methanol distillation, and it seems that the temperature distribution in the pre-distillation tower isn’t correct. In a normal distillation tower, the temperature should increase from the top to the bottom; however, in our pre-distillation tower, the temperature remains roughly the same at the top and bottom, while it decreases as one moves downward along the tower – this is confusing. I’d like to ask everyone for their insights: what are the reasons why the temperature at the top of the methanol pre-distillation tower is higher than that at the bottom? http://bbs.hcbbs.com/thread-50746-1-37.html Difficulties in molten salt distillation technology!! The price of industrial-grade LiCl in the world differs by tens of thousands of yuan from that of high-purity LiCl; how to purify LiCl has long been a challenge for lithium companies around the world. I would like to ask whether it is feasible to use molten salts of LiCl and KCl for distillation at high temperatures in order to obtain LiCl with a high purity level. http://bbs.hcbbs.com/thread-50937-1-38.html Why is the pressure difference in the distillation tower much lower than the set value? (I’m very happy to be part of the distillation industry; I also enjoy learning more, and I hope my seniors can offer me lots of guidance.) The pressure difference in the distillation column is much lower than the set value; the top pressure can reach the set value, but the difference in pressure between the reactor and the top of the column is too large. However, the top temperature, middle temperature, and reactor temperature are all roughly at the set values. I’m not sure what the reason is; could it be a problem in the design of the tower? http://bbs.hcbbs.com/thread-47164-1-40.html I have a question regarding the steam pressure between the tubes of a reboiler. Could you please help me figure out how to calculate the pressure between the tubes of a reboiler in this situation, where 5 kgf of steam enters the distillation column reboiler, and the drain from the reboiler’s trap is directly discharged into the sewer? http://bbs.hcbbs.com/thread-47462-1-42.html What is the relationship between internal reflux, mid-stage reflux, and side reflux? http://bbs.hcbbs.com/thread-47355-1-42.html How to operate an ammonia stripping distillation tower: The wastewater feed contains 0.09% ammonia, and the output from the bottom of the tower should have less than 0.01% ammonia. Equipment used: two-stage Pall ring packing, with a falling film evaporator for heating. http://bbs.hcbbs.com/thread-47342-1-42.html Stripping is commonly used in oil refining units; there are wet and dry types of stripping. Wet stripping usually employs superheated steam, so what medium is used in dry stripping? http://bbs.hcbbs.com/thread-46192-1-43.html Liquid carryover in pre-distillation. There is currently a fully circulating urea production line; its original design capacity was 450 tons per day. After expansion and renovation, the daily production capacity increased to around 800 tons. However, recently the pre-distillation stage of this system has been experiencing liquid carryover problems when the amount of ammonia added to the urea tower ranges from 45 to 50 cubic meters per hour. Prior to the expansion and renovation, the system operated normally with an ammonia addition rate between 42 and 53 cubic meters per hour. Recent shutdowns were carried out to inspect the pre-distillation tower, the first absorption tower, etc., and the medium-pressure system was cleaned via thermal washing, but the problem of liquid carryover still persists (although its frequency has decreased somewhat). I would like to seek advice from everyone here so that I can gain some insights. http://bbs.hcbbs.com/thread-45965-1-44.html How to deal with foaming in the desulfurization tower – a tough problem? Recently, the amine solution in the desulfurization tower of our unit has been foaming frequently. This leads to an increase in the tower’s load. Let’s all discuss how to deal with the foaming in the desulfurization towers of our own installations http://bbs.hcbbs.com/thread-28487-1-44.html Negative pressure issue in distillation columns: In the atmospheric pressure column used for methanol, negative pressure persists at the top of the column as well as in the reflux tank; moreover, water hammer phenomena occur in the reflux lines. I would like to ask: why is this happening? http://bbs.hcbbs.com/thread-40154-1-46.html What are the definitions of separation equipment such as distillation columns and fractionation towers, and what are their similarities and differences? http://bbs.hcbbs.com/thread-40538-1-46.html I would like some advice on the operation of the butane removal tower. We have recently put a new natural gas processing unit into operation, and the butane removal tower is difficult to regulate properly; the temperature at the top of the tower fluctuates greatly. Increasing the reflux can bring the temperature back to normal levels; however, after about 20 minutes, the liquid level in the reflux drum drops to zero. Once the liquid level in the reflux drum returns to normal, the temperature at the top of the tower rises again. http://bbs.hcbbs.com/thread-35821-1-48.html How to control the product temperature in atmospheric and vacuum distillation towers? I’ve never worked with distillation before. How does one control the temperature of the products drawn off from atmospheric and vacuum distillation towers (at the side draws prior to entering the stripper)? http://bbs.hcbbs.com/thread-36172-1-48.html Problems with alcohol distillation using four columns; I would like to ask experts why the loss of alcohol during distillation is so severe in plants with an annual production capacity of 150,000 tons. http://bbs.hcbbs.com/thread-30613-1-49.html Last edited by yeep123 on 2007-8-21 18:05]
Several concepts: 1) Reflux: The vapor stream that rises to the top of the tower, after condensing in the condenser, has only a portion released as the product at the top of the tower; the remaining portion returns to the top of the tower as a liquid stream, and this liquid stream is known as reflux. 2) Rectification – the section above the feed plate (rectifying section). Function: It serves to recover and concentrate the volatile components in the feed. 3) Stripping – the section below the feed plate (stripping section), including the feed plate itself. Function: It also serves to recover the volatile components in the feed. 4) Distillate: The portion of the overhead product that is obtained after distillation and subsequent condensation. 5) Role of reflux: Rectification is a process of mass transfer between the vapor phase and the liquid phase; without either vapor phase or liquid phase present on any given tray, the process cannot proceed. For the first tray at the top of the column, there is steam rising from the tray below it; liquid flowing downward is lacking, and reflux serves precisely to provide the liquid that flows downward for the first tray. The vapor concentration rising from the second tray is already quite high; according to the principle of phase equilibrium, the concentration of the liquid phase in contact with it should also be high. Obviously, using a portion of the tower top condensate as the flow liquid is the simplest approach. Although the lowest tray at the bottom of the tower is supplied with liquid flowing down from the tray above it, rising steam is also required to ensure proper operation. According to the principles of phase equilibrium, the concentration of steam in contact with the liquid on the tray should also be very low. Therefore, the vapor partially vaporized in the reboiler is introduced to the lowest tray. Reflux at the top of the tower and rising vapor at the bottom are the necessary and sufficient conditions to ensure a continuous and stable distillation process.
Our distillation column is a vacuum distillation column; during the production process, the vacuum level (absolute pressure) is around 20 KPa. However, it keeps rising to around 30 KPa or even higher, before dropping back to around 20 KPa, with continuous fluctuations. Please give your support, everyone! ! Thank you! ! This post was last edited by BlueDot on 2008-3-29 17:31]