Distillation tower problem?

This should be easily solved by finding a relevant professional book.

The performance indicators of evaluation tower equipment mainly include the following aspects:: ①production capacity ； ②Separation efficiency ； ③Tower pressure drop ； ④Operational flexibility ； ⑤Structure, manufacturing and cost, etc. (1) Production capacity The liquid flow and mass transfer mechanisms of plate towers and packed towers are different. Mass transfer in a plate tower is achieved by rising gas passing through the liquid layer on the plate. The opening ratio of the plate generally accounts for 7% to 10% of the cross-sectional area of ​​the tower. ； The mass transfer in the packed tower is achieved through the contact between the rising gas and the liquid flow that descends along the packing surface by gravity. The opening rate of packed tower internals is usually above 50%, while the void ratio of the packing layer is over 90%. Generally, the flooding point is higher, so the production capacity of packed towers per unit tower cross-sectional area is generally higher than that of plate towers. (2) Separation efficiency Generally, packed towers have higher separation efficiency. The theoretical levels per meter of packed towers commonly used in industry are 2 to 8. For commonly used plate towers, the number of theoretical plates per meter does not exceed 2 levels at most. Research shows that under reduced pressure, normal pressure and low pressure (pressure less than 0.3 MPa) operations, the separation efficiency of packed towers is significantly better than that of plate towers, and under high-pressure operations, the separation efficiency of plate towers is slightly better than packed towers. (3) Pressure drop The pressure drop of a packed tower is much smaller than that of a plate tower due to its high void ratio. Under normal circumstances, the pressure drop of each theoretical stage of a plate tower is about 0.4~1.1kPa, and that of a packed tower is about 0.01~0.27 kPa. Usually, the pressure drop of a plate tower is about 5 times higher than that of a packed tower. The pressure drop can not only reduce operating costs and save energy consumption, but also reduce the temperature of the tower kettle during the distillation process, which is beneficial to the separation of heat-sensitive substances. (4) Operational elasticity Generally speaking, the packing itself is very adaptable to changes in gas and liquid loads. ； Therefore, the operating elasticity of the packed tower depends on the design of the tower internals, especially the design of the liquid distributor. Therefore, the operating elasticity of the packed tower can be determined according to actual needs. The operating flexibility of plate towers is limited by the tray's liquid flooding, liquid foam entrainment and downcomer capabilities. Generally, the operating flexibility is small. (5) Structure, manufacturing and cost Generally speaking, the structure of packed towers is simpler than that of plate towers, so manufacturing and maintenance are more convenient. However, the cost of packed towers is usually higher than that of plate towers. It should be pointed out that the liquid holding capacity of the packed tower is smaller than that of the plate tower. The large liquid holding capacity can make the operation of the tower stable and not easy to cause rapid changes in the product. Therefore, the plate tower is easier to operate than the packed tower. The plate tower is easy to realize line feeding and discharging, while the packed tower is not suitable for complicated situations such as side line feeding and discharging. For high-performance packing with a large specific surface area, the packing layer is easily blocked, so the packed tower is not suitable for directly processing materials with suspended solids or easy polymerization. In the traditional design of tower equipment selection, plate towers are mostly used in the distillation process, while packed towers are mostly used in the absorption process. In recent years, with the improvement of tower equipment design level and the emergence of new tower components, the above tradition has gradually been broken. For a specific separation process, the choice of tower type in design should be based on production capacity, separation efficiency, tower pressure drop, operating flexibility and other requirements, as well as factors such as manufacturing, maintenance, and cost. For example, for the separation of heat-sensitive substances, the tower pressure drop is required to be as low as possible, and a packed tower is more suitable. ； For processes with side feeds and discharges, a plate tower is more suitable. ； For the separation of suspended solids or easy polymer systems, in order to prevent clogging, a plate tower should be used. ； For processes with extremely low liquid spray density, if a packed tower is used, the packing layer will not be fully wetted, which will significantly reduce the separation efficiency. Therefore, a plate tower should be used. ； For the separation of easily foaming materials, a packed tower should be used because the packing layer has the function of breaking foam.

You can refer to this forum: Comparison between packed tower and plate tower http://bbs.hcbbs.com/viewthread.php?tid=240493 What are the differences between packed towers and plate towers used for distillation? http://bbs.hcbbs.com/viewthread.php?tid=140962&highlight=%CC%EE%C1%CF%CB%FE%2B%B0%E5%CA%BD%CB%FE Is it better to use a plate tower or a packed tower for the distillation tower? http://bbs.hcbbs.com/viewthread.php?tid=64472&highlight=%CC%EE%C1%CF%CB%FE%2B%B0%E5%CA%BD%CB%FE

(1) When the tower diameter is large, a plate tower should be used. Because the plate tower has low cost, high tower efficiency, and easy maintenance and cleaning (2) When the tower height is very high, a plate tower should be used. Because the packed tower requires multiple liquid redistributions (3) when heat is removed from the tower, a plate tower should be used. Because the tower is suitable for installing a cooler (4) when the liquid flow rate is small, a plate tower should be used. Because packed towers easily lead to insufficient wetting of the packing (5) plate towers are suitable for handling liquids with suspended solids, while packed towers are prone to clogging. (6) The plate tower facilitates side discharge. (7) Packed towers are suitable for handling corrosive materials. (8) The pressure drop of the packed tower is small, and the packed tower is commonly used in vacuum distillation. (9) The amount of liquid retained in the packed tower is small and the residence time is short, which is suitable for intermittent distillation and heat-sensitive materials. (10) Packed towers are suitable for handling liquids that are prone to foaming

Comparison between plate tower and packed tower? ⑴When the tower diameter is large, a plate tower should be used. because: ①The cost of a plate tower based on unit plate area decreases as the tower diameter increases. The cost of a packed tower is proportional to its volume. The cost of a small diameter packed tower (below 0.8m) is generally lower than a plate tower. ②The larger the diameter of the plate tower, the more efficient it can be. The larger the diameter of the packed tower, the more difficult it will be to distribute the liquid evenly, and the efficiency will decrease. ③Maintenance of large trays is easier than cleaning of packed towers. ⑵When the required number of mass transfer units or theoretical plates is relatively large and the tower is very high, a plate tower is more suitable. In this case, the packed tower must be divided into many sections, and the liquid must be redistributed multiple times. Otherwise, the liquid will be unevenly distributed and channel flow will occur in the liquid or gas, which will affect the heat transfer efficiency. ⑶If heat must be removed from the tower, a plate tower is preferred because it is easier to install cooling tubes on the tower. ⑷The plate tower can adapt to relatively small liquid flow, but if a packed tower is used at this time, it will easily lead to insufficient wetting of the packing. ⑸The plate tower is suitable for handling liquids with suspended solids, and the packing layer is easily blocked by suspended solids. ⑹The plate tower facilitates side discharge. ⑺Packed towers are suitable for handling corrosive materials. If the trays are made of corrosion-resistant metal materials, the cost will be much higher. ⑻The pressure drop of packed tower is relatively small. During vacuum distillation, the pressure drop in the tower needs to be controlled to a very small value, and a packed tower can usually meet the requirements. ⑼The amount of liquid retained in the packed tower is relatively small, and the material stays in the tower for a short time, so it is suitable for intermittent distillation and the distillation of heat-sensitive materials. ⑽Packed towers are suitable for handling liquids that are prone to foaming.