I. Profile, working principle and characteristics of demister pad
Profile
Wire mesh demister (also known as mesh mist eliminator, mist, catching mist) is used for gas entrained mist separation column, in order to guarantee the efficiency of the filter, can increase productivity by 5%. 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 that such an apparatus in the study of the gas-liquid separation process and found that is very efficient, and the gas drop through the resistance of the device is very small, which is unmatched by other gas-liquid separation device, so quickly get a lot of promotion and 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 generally set at the top of the tower, setting it, not only can ensure the mass transfer efficiency of the tray, but also to reduce the board spacing. Demister standard applicable for chemical, petroleum, pharmaceutical, light industry, metallurgy and other industrial production in the vertical cylindrical equipment vapor-liquid separation device, is currently in the imports of ethylene, ammonia and chemical fiber production equipment used demister pad, has been applied in the desulfurization, remove oil mist, toxic and hazardous industrial gases and other fields.
Demister Pad working principle
When gas with mist rises at a constant speed through the wire mesh, due to the inertia effect, the rising mist collides with the mesh filaments and attached to the filament on the surface. Mist on the filament surface diffusion, gravity settling mist make the entrainment form larger droplets flow along the filaments of the two wire intersections. The wettability of filaments, the surface tension of the liquid and the capillary action of the filaments make the droplets grow bigger, until the droplets together to produce its own gravity exceed gas rising force and liquid surface tension force, droplets isolate from the filaments on the whereabouts. Basically it does not contain the entrainment after gas goes through the demister pad.
Separate the gas in the mist, in order to improve the operating conditions, 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
Simple structure, lightweight.
High porosity, less pressure drops.
Big surfaces area, high demisting efficiency.
Easy installation, operation and maintenance.
Long service life.
II. The selected wire mesh form of wire mesh demister and domestic standards
Selected wire mesh form
Selected demister pad forms have four categories: standard type, efficient type, high-penetration type and shock absorber type.
The standard type wire mesh
Wire size (mm) Wire width tolerance (mm) Bulk density
(kg/m3) Specific surface area
(m2/m3) Porosity
Flat wire Round wire diameter +10 -0 150 475 320 0.981
0.1*0.4 0.23
Note: Every 100mm thick mat have 25 layers wire mesh
The efficient type wire mesh
Wire size (mm) Wire width tolerance (mm) Bulk density
(kg/m3) Specific surface area
(m2/m3) Porosity
Flat wire Round wire diameter +10 -0 182 626 484 0.977
0.1*0.3 0.19
Note: Every 100mm thick mat have 32 layers wire mesh
The high-penetration type wire mesh
Wire size (mm) Wire width tolerance (mm) Bulk density
(kg/m3) Specific surface area
(m2/m3) Porosity
Flat wire Round wire diameter +10 -0 98 313 217 0.9875
0.1*0.4 |
