Demister Pad

Place of Origin:	Hebei

Company Profile

Daheng Demister Pad Co., Ltd.

Location:	Hengshui, Hebei, China (Mainland)
Business Type:	Manufacturer
Main Products:	Demister Pad

Product Description

I. Profile, working principle and characteristics of demisterpad

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 theefficiency of the filter, can increase productivity by 5%. The late fifties, theforeign used an apparatus which made of the special wrinkle woven mesh to removeinclusions of tiny liquid foam in the gas that such an apparatus in the study ofthe gas-liquid separation process and found that is very efficient, and the gasdrop through the resistance of the device is very small, which is unmatched byother gas-liquid separation device, so quickly get a lot of promotion and a widerange of applications.

Wire demister standard was formulated by the Ministry of Chemical Industry inChina on December 20, 1982, the basic implementation of the Shanghai municipalgovernment standards Q/YSZZ-88-91 wire mesh industry was in 1991, began to fullyimplement HG/T21618-1998 national unity standard after the year 1998. The newstandard demisters are divided into HG5-1404-81 riser type, HG5-1405-81 neckingtype and HG5-1406-81 full bore wire mesh device.

Demister pad is generally set at the top of the tower, setting it, not onlycan ensure the mass transfer efficiency of the tray, but also to reduce theboard spacing. Demister standard applicable for chemical, petroleum,pharmaceutical, light industry, metallurgy and other industrial production inthe vertical cylindrical equipment vapor-liquid separation device, is currentlyin the imports of ethylene, ammonia and chemical fiber production equipment useddemister pad, has been applied in the desulfurization, remove oil mist, toxicand hazardous industrial gases and other fields.

Demister Pad working principle

When gas with mist rises at a constant speed through the wire mesh, due tothe inertia effect, the rising mist collides with the mesh filaments andattached to the filament on the surface. Mist on the filament surface diffusion,gravity settling mist make the entrainment form larger droplets flow along thefilaments of the two wire intersections. The wettability of filaments, thesurface tension of the liquid and the capillary action of the filaments make thedroplets grow bigger, until the droplets together to produce its own gravityexceed gas rising force and liquid surface tension force, droplets isolate fromthe filaments on the whereabouts. Basically it does not contain the entrainmentafter 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 equipmentlife, 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 domesticstandards

Selected wire mesh form

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 wiremesh

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	0.23
Note: Every 100mm thick mat have 20 layers wiremesh

The shock absorber type

Type	Specification	Filaments specifications (mm)
Shock absorber type	33-30 type	Φ0.08
	38-40 type	Φ0.08
	20-40 type	Φ0.22
	30-40 type	Φ0.10Φ0.12
	30-50 type	Φ0.16
	40-60 type	Φ0.12
	30-80 type	Φ0.22
	50-120 type	Φ0.22
	40-120 type	Φ0.22

Wire mesh demister domestic standardsare divided into HG5-1404 (1405, 1406) -81, HG/T21618-1998, HG/T21586-98 andother non-standard mesh demister.

● HG5-1404 (1405,1406) -81
The standards are divided into the riser-type(1404), the necking (1405) and full bore type (1406). The diameter of demisteris from 300mm to 6400mm and height is 100mm and 150mm. When ordering need tooffer a figure number and use of the material.

Mark example: HG5-1406-81-11, 304/304 It means that the gratings and wiremesh are made of 304 stainless steel, full bore coat type, diameter 1600mm,height 100mm demister pad.

● HG/T21618-1998
New standards merged riser type, reducing neckingtype and full bore type installation form; proposed SP, HP, DP and HR four kindsof network types and expanded the types of material selection; and increased theset specifications size interval density.

	DP	HR/HP
The standard wire specification:0.1+0.03*0.4	The standard wire specification:0.1+0.02*0.3	The standard wire specification: φ0.23(φ0.275)\0.1+0.03*0.4mm

Mark example: HG/T21618 wire mesh demister S1600-100 SP 304/304 it indicatesthat the gratings and wire mesh are made of 304 stainless steel, coat type,diameter 1600mm, height 100mm, SP screen demister grid.

● HG/T21586-98(drawer mesh demister device)
This standard is principally applied to thedemister element often needs to be cleaned or replaced occasions, for examplesulfuric acid drying tower and absorber device. Its selection of nominaldiameter has 56 kinds ranging from DN300mm ~ DN5000mm. When ordering simply needto provide a figure number and choice of materials (316L, NS-80 and RS-2 wiremesh material is commonly used in sulfuric acid plant).

Mark example: HG/T21586.11-98 WME-1600-100 NS-80/Q235-A it means that thewire mesh using the NS-80, grill carbon steel diameter 1600mm, height 100mmdrawer demister pad.

● Other non-standard wire mesh demister
Wavelike type, embedded type, external loading type, SWD1 type, square,rectangular and irregular, and so on.

III. Using method of demisters:

1, Mesh Block Installation

Mesh block structures of demister pad havetwo types: disk-shaped mesh block and bar mesh block.

It has upload typeand download type two structures. When the location of the manhole opened in theabove of the wire demister, or unmanned hole but equipment flange, choose theupload type wire demister; the manhole location opened in the below of it, thenchoose the download type wire mesh demister.

2, Demister Schematic

IV. Maintenance:

After using for some time because of the gas containing particles (such assublimated sulfur, etc.), the wire mesh is partially clogged and prone toflooding, the pressure drop also increased, therefore, the demister pad needsfor proper maintenance.
During the stop of a long time, air will enter thetower body, the moisture in the air and mesh acid are easily formed sweet sour,since the metal mesh generally are intolerant to dilute acid, therefore, itneeds to seize the opportunity to maintain the demister.
The way ofmaintenance is to clean with water, but remember: to avoid the dilute acid onthe demister wire mesh to affect service life, after flushing the demister pad,mesh block must be drying (in the natural state, also can in the sun). Put itinside the tower before the equipment works. Choose to use a constant efficiencyor the innovative adjustable mist eliminator in the production and smeltingenterprises.