Exploration of Mist Eliminator

Mist eliminator consists of upper grid, middle strut, bottom grid, connection rod, cross strut, and metal/plastic knitted mesh pad.

Metal/Plastic knitted mesh pad is a kind of gas-liquid filter metal/plastic knitted mesh pad made of metal or non-metal wires.

Basic parameters:

• Mist eliminator diameter: 200 mm – 6000 mm
• Metal/Plastic knitted mesh pad thickness: 100 mm – 350 mm
• Connection rod diameter: 6 mm
• Grid size: 25 mm × 3 mm (metal) or 25 mm × 10 mm (plastic)

• Materials
  The common materials of gas-liquid filter metal/plastic knitted mesh pad are PP, stainless steel and PE + stainless steel.
  

  PP

  

  Stainless steel

  

  PE + stainless steel

• Types
  Generally, we have 3 types of gas-liquid filter metal/plastic knitted mesh pad for you to choose from: standard type (SP), efficient type (DP), and high penetration type (HP/HR).

  Table 1: HG/T21618-1998 Gas-Liquid Filter Metal/Plastic Knitted Mesh Pad

  Type	Volume (kg/m3)	Surface Area (m2/m3)	Voidage ɛ
  SP	168	529.6	0.9788
  DP	186	625.5	0.9765
  HP	128	403.5	0.9839
  HR	134	291.6	0.9832

  

  SP gas-liquid filter metal/plastic knitted mesh pad

  

  DP gas-liquid filter metal/plastic knitted mesh pad

  

  HR/HP gas-liquid filter metal/plastic knitted mesh pad

  Table 2: SP Gas-Liquid Filter Metal/Plastic Knitted Mesh Pad

  Wire Size (mm)		Mesh Width Tolerance (mm)	Density (kg/m3)	Surface Area (m2/m3)		Voidage ɛ
  Flat Wire	Round Wire	± 20	150	Flat Wire	Round Wire	0.981
  0.1 × 0.4	0.23			475	320
  Note: Every 100 mm thick mesh mat is made up of 28 layers of wire mesh.

  Table 3: DP Gas-Liquid Filter Metal/Plastic Knitted Mesh Pad

  Wire Size (mm)		Mesh Width Tolerance (mm)	Density (kg/m3)	Surface Area (m2/m3)		Voidage ɛ
  Flat Wire	Round Wire	± 20	182	Flat Wire	Round Wire	0.977
  0.1 × 0.3	0.19			626	484
  Note: Every 100 mm thick mesh mat is made up of 32 layers of wire mesh.

  Table 4: HP/HR Gas-Liquid Filter Metal/Plastic Knitted Mesh Pad

  Wire Size (mm)		Mesh Width Tolerance (mm)	Density (kg/m3)	Surface Area (m2/m3)		Voidage ɛ
  Flat Wire	Round Wire	± 20	98	Flat Wire	Round Wire	0.9875
  0.1 × 0.4	0.23			313	217
  Note: Every 100 mm thick mesh mat is made up of 28 layers of wire mesh.

Mist Eliminator – Grid

The grid of the mist eliminator is often made of stainless steel or PP. When using the mist eliminator, if the area of the tray in the tower supporting the mist eliminator is large, the grid should be used. Because the mesh pad is softer and easy to fall off from the larger gap of the tray without grid.

Stainless steel grids

PP grids

When the gas with mist rises at a constant speed and passes through the metal/plastic knitted mesh pad, the rising mist collides with the mesh filament and is attached to the surface filament due to the inertia effect. The mist on the surface of the filament diffuses further, and the gravity of the mist itself settles to form large droplets. The larger droplets flow towards the filaments at the intersection of the two wires. Due to the wettability of the filament, the surface tension of the liquid and the capillary action of the filament make the droplets grow larger and larger until their own gravity exceeds the combined force of the rising buoyancy of the gas and the surface tension of the liquid, separating the drop and flowing into the vessel's downstream equipment. As long as the gas speed and other conditions are properly selected, after the gas passes through the mist eliminator, the mist elimination efficiency can reach more than 97%, and can even achieve the purpose of completely removing the mist.

Mist eliminator working principle

Mist eliminator working principle flow chart

When Maintenance Is Required?

• The mesh aperture can be partially blocked and liquid flooding can easily occur due to the gas containing particles (such as sublimated sulfur, etc.), after a period of use, the pressure drop can also increase a lot, so the mist eliminator needs to be properly maintained according to the use situation.
• During a long-term parking of the equipment, the air can enter the tower, and the moisture in the air can easily neutralize with the acid foaming in the wire mesh to form sweet acid substance. However, the wire mesh is generally not resistant to dilute acid, so the mist eliminator needs to be removed for maintenance.

How to maintain?

The maintenance method is to rinse with clean water, but it should be noted that in order to avoid the production of dilute acids on the mesh pad, affecting the service life, the mesh pad of the mist eliminator must be dried after rinsing (in its natural state, drying can also be done). Install the mesh pad in the tower before starting operation.

• Materials
• Size
• Density
• Grids required or not
• Sections required or not & number of sections

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