Demister Pad
Demister pad, also called wire mesh demister, mister pad, mesh mist eliminator, catching mist, mist eliminator, is used in gas entrained mist separation column to guarantee the filtering efficiency.
History of demister pad
The late fifties, the foreign used an apparatus which made of the special wrinkle woven mesh to remove inclusions of tiny liquid foam in the gas. Then it is found that is very efficient and the resistance is very small, which is unmatched by other gas-liquid separation device, so it is widely accepted and used in a wide range of applications.
Wire demister standard was formulated by the Ministry of Chemical Industry in China on December 20, 1982, the basic implementation of the Shanghai municipal government standards Q/YSZZ-88-91 wire mesh industry was in 1991, began to fully implement HG/T21618-1998 national unity standard after the year 1998. The new standard demisters are divided into HG5-1404-81 riser type, HG5-1405-81 necking type and HG5-1406-81 full bore wire mesh device.
Demister pad is commonly placed at the top of the packing tower, which can not only ensure the mass transfer efficiency, but also reduce the board spacing. Demister pad is widely used in chemical, petroleum, pharmaceutical, light industry, metallurgy and other industrial production in the vertical cylindrical equipment vapor-liquid separation device. It can also be used in the desulfurization and other productions to remove oil mist, toxic and poisonous gas.
Working principle of demister pad
When the gas with mist rises at a constant speed and passes through the wire mesh, the rising mist will collided with the mesh filament and attached to the surface filament due to the inertia effect. The mist will be diffuse on the filament surface and the droplet will follow along the filaments of the two wire intersection. The droplet will grow bigger and isolate from the filament until the droplets gravity exceeding gas rising force and liquid surface tension force while there is little gas passing through the demister pad.
Separate the gas in the droplets can improve the operating condition, optimize process indicators, reduce corrosion of the equipment, extend equipment life, increase the amount of processing and recovery of valuable materials, protect the environment, and decrease air pollution.
Features of demister pad
Specifications of standard type demister pad
| Item | Wire type | Wire size (mm) |
Wire width tolerance (mm) |
Bulk density (kg/m3) |
Specific surface area (m2/m3) |
porosity |
|---|---|---|---|---|---|---|
| STWM-01 | Flat wire | 0.1 × 0.4 | +10/-0 | 150 | 475 | 0.981 |
| STWM-02 | Round wire | 0.23 | 320 | |||
| Note: every 100 mm thick mat has 25 layers wire mesh. | ||||||
Specifications of efficient type demister pad
| Item | Wire type | Wire size (mm) |
Wire width tolerance (mm) |
Bulk density (kg/m3) |
Specific surface area (m2/m3) |
porosity |
|---|---|---|---|---|---|---|
| ETWM-01 | Flat wire | 0.1 × 0.3 | +10/-0 | 182 | 626 | 0.977 |
| ETWM-02 | Round wire | 0.19 | 484 | |||
| Note: every 100 mm thick mat has 32 layers wire mesh. | ||||||
Specifications of high-penetration type demister pad
| Item | Wire type | Wire size (mm) |
Wire width tolerance (mm) |
Bulk density (kg/m3) |
Specific surface area (m2/m3) |
porosity |
|---|---|---|---|---|---|---|
| HTWM-01 | Flat wire | 0.1 × 0.4 | +10/-0 | 98 | 313 | 0.9875 |
| HTWM-02 | Round wire | 0.23 | 4217 | |||
| Note: every 100 mm thick mat has 20 layers wire mesh. | ||||||
Mesh pad installation
There are two kinds of wire mesh demister pad, which are disk shaped demister pad and bar type demister pad.
According to different using condition, it can be divided into upload type and download type. When the opening is located in the above of the demister pad or when there is no opening but has flange, you should choose the upload demister pad.
When the opening is in the below of the demister pad, you should choose the download type demister pad.
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