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PINGXIANG JINGJUN CHEMICAL INDUSTRY CO LTD

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Address:Pingxiang city, Jiangxi Province


Structure and working principle of a packed column

Packed column is to play the role of absorption, it is one of the chemical, petrochemical and refining production in the most important equipment.

The following talk about the structural characteristics of the packed column:

Packed tower is tower packings as the gas-liquid contact member between the two phases of mass transfer equipment. The tower is packed column has a vertical cylinder, the bottom with packing support plate, filler huddle or the whole puzzle set in a support plate. Install the packing above the filler plate to avoid being blown updraft. Liquid from the top through the liquid distributor sprayed onto the filler, and flow along the surface of the filler. Gas is fed from the bottom, through the gas distribution system (small diameter column generally no gas distribution device) after the distribution, and continuous countercurrent liquid through the gap filler layer was on the filler surface, in close contact with the two-phase gas-liquid mass transfer . Packed tower belonging continuous contact liquid mass transfer equipment, two phases along the tower height changes continuously under normal operating conditions, the gas phase is a continuous phase, liquid phase to the dispersed phase.

When the liquid flows downward along the filler layer, there is a gradual trend towards centralized tower wall, making the fluid flow near the wall of the tower increases, a phenomenon known as wall flow. Wall liquid two-phase flow effects caused by the uneven distribution of the filler layer, so that the mass transfer efficiency. Thus, when a high packing layer, the need for segmentation, intermediate redistribution device settings. Liquid redistribution device comprises a liquid collector and liquid redistribution of two parts, a top packing shed liquid after the liquid collector to collect, to liquid redistributors, after redistribution sprayed onto the lower filler.

Packed tower having large capacity, high separation efficiency, pressure drop, holding a small amount of liquid, operating flexibility and other advantages.

Packed column, there are some shortcomings, such as packing high cost; when the liquid load is small can not be effectively wetting of the filler surface, so that the mass transfer efficiency is reduced; it can not be directly used for suspended solids or easily polymeric materials; contralateral line feed and the material is not suitable for complex distillation and the like.

Classification filler

Many types of fillers, depending on the filling mode can be divided into bulk packing and structured packing.

1. Bulk Packing

Bulk Packing is one with a certain geometry and size of granules, generally stacked in a random manner in the tower, also known as random packing or particulate filler. Bulk packing according to different structural characteristics, can be divided into the ring packing, saddles, saddle-shaped packing ring and ball packing. Now introduce some more typical bulk packing:

Raschig ring Pall ring packing Ladder ring arc saddle saddle saddle packing filler metal ring spherical packing

(1) Raschig ring packing in 1914 by the Rasi (F.Rashching) invention, the diameter and height equal to the ring. Raschig ring packing gas and liquid distribution is poor, low mass transfer efficiency, resistance, small flux, the current industry has been rarely used.

(2) Pall rings Raschig rings packing is an improvement on the side wall Raschig rings out two rows of rectangular apertures, the side wall of the ring to be cut still connected with the wall, the other side curved inner ring, formed in extending the blade, all sides of the blade center of the ring with the ride. Pall rings due to the ring wall openings, greatly improving the utilization of space inside the ring and the inner ring surface, air resistance, liquid distribution. Compared with Raschig rings, Pall rings of gas flux increased more than 50%, the mass transfer efficiency of about 30%. Pall ring filler is a wider application.

(3) ladder ring packing Pall Ring is an improvement compared with the pall ring, ladder ring height is reduced by half and added a taper at one end flange. Because of the high aspect ratio reduced, making the gas filler outer wall around the average path is much shorter, reducing the gas through the packing layer resistance. Conical flange not only increases the mechanical strength of the filler, and so dominated by the line contact between the filler becomes the main point contact, it will not only increase the gap between the filler, the same time as the liquid flows along the surface of the filler dispersed collection point can promote the liquid film surface renewal, in favor mass transfer efficiency. Overall performance is better than Pall ring ring ladder, becoming annular filler currently used in the most excellent kind.

(4) arc saddle packing a case of saddles, saddle-like shape, usually made of ceramic material. Saddle filler arc is characterized by an open surface all, regardless of internal and external, uniform flow of liquid on both surfaces, surface high utilization, runner curved, small flow resistance. The drawback is prone to intussusception, causing a portion of the filler surface is coincident mass transfer efficiency. Arc saddle filler strength is poor, broken container, much industrial production applications.

(5) saddle packing will saddle filler arc curved surface at both ends to a rectangular surface and sides vary in size, it becomes saddle packing. Intalox filler accumulation will not intussusception, liquid distribution is more uniform. Saddle packing generally made of ceramic material, its performance is better than Raschig rings. Currently, the vast majority of applications domestic porcelain Raschig rings occasions, have been replaced by ceramic saddle packing.

(6) metal ring saddle packing ring saddle packing (abroad called Intalox) are both ring and saddle structural characteristics of the design of a new type of filler, which is generally made of metal material, it is also referred to as metal ring Intalox filler. Ring saddle packing filler both advantages and saddle ring packing set in one, its overall performance is better than pall ring and stepped ring, in bulk packing in more applications.

(7) general spherical packing plastic injection molded, and its structure has a variety. Spherical filler is characterized as a hollow sphere, can allow gas and liquid from the inside through. Because even symmetry, filler loading density spherical structure, easy to produce holes and bridges, so good liquid dispersion properties. Spherical packing generally apply only to certain situations, the application of less engineering.

In addition to the several more typical bulk filler, in recent years there have been a unique new packing configuration developed, such as conjugated ring packing, Haier ring packing, Nat ring packing. Characteristics of the industry commonly used bulk packing several documented manual.

2. Structured Packing

Structured packing is a certain geometry arranged neatly dumped packing. Many different types of structured packing, according to its geometry can be divided into a grid packing, packing, packing and other pulses.

(1) grill packing unit body composition is strip made by certain rules, with a variety of structural forms. The first application for the wood grill grill packing packing industry. There are currently more general Geli Qi grill packing, packing mesh grille, honeycomb grille filler, of which the most representative Geli Qi grill packing.

Lower than the surface area of the grill packing, primarily for applications requiring low pressure drop, load large and blockades and other occasions.

(2) the application of the packing industry is currently structured packing when assembled with the vast majority of packing, which is disc-shaped filler composed of many corrugated sheet, corrugated and column axis inclination has 30 ° and 45 ° are two, two adjacent corrugated plates stacked against reverse. Each dish filler mounted perpendicular to the tower, between two adjacent disc packing 90 ° staggered arrangement.

Packing according to the structure can be divided into net corrugated board packing and packing into two categories, the material but also metals, plastics and ceramics, etc. points.

Metal gauze packing is the main form of net packing, which is made of a metal mesh. Metal gauze packing pressure to reduce high separation efficiency, especially for sophisticated distillation and vacuum distillation unit, difficult isolate system, heat-sensitive materials rectification system provides an effective means. Despite its high cost, but because of its excellent performance it is still widely used.

Metal plate packing is a major form of corrugated board packing. Corrugated sheet of the filler has many f5mm about punching holes, can play rough liquid distribution plate on strengthening the role of the lateral mixing. Rolling corrugated board sheet into small grooves, can play a fine distribution of liquid on the plate, enhancing the role of surface wetting properties. High strength metal plate packing, corrosion resistance, especially for larger diameter columns and a large gas-liquid load applications.

Metal rolling corrugated plate packing is another typical plate packing. The main difference between it and the metal plate corrugated packing sheet surface is not punched holes, but a puncture, with jarring manner to the sheet rolling out very dense pore size of 0.4 ~ 0.5mm small puncture. Its separation capability similar to net packing, but the anti-blocking ability than the net packing, and cheap, is widely used.

Advantages packing is compact, small resistance, high mass transfer efficiency, large capacity, large surface area (such as several commonly used 125,150,250,350,500,700). Packing drawback is not suitable for handling high viscosity, easy polymerization or suspension of the material, and loading and unloading, cleaning difficulties and high cost.

(3) Pulse filler is hollow prismatic individual by the band constriction, assembled from a certain way of a structured packing. Pulse filler assembly, will form a porous prismatic channel with the constriction of the longitudinal passage in alternating contraction and expansion of a strong turbulent gas-liquid two-phase through. In constriction segment, the highest gas velocity, turbulent violent, thereby strengthening the mass transfer. Expanding segment, the gas velocity is minimized, to achieve the separation of the two phases. Runner shrink, expand the alternately repeated to achieve a "pulse" mass transfer process.

Pulse filler is characterized by large capacity, low pressure drop, is the ideal filler vacuum distillation. Liquid distribution because of its excellent performance makes the amplification effect reduction, it is particularly suitable for large column diameter occasions.


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