Demisters
Demisters separate up to 100% of 2-5µm droplets in a gas flow.
A demister consists of multiple layers of mesh fabric knitted from metal or plastic monofilaments, crimped and then assembled so that the crimps cross in successive layers forming a pad.
The space between the wires is very evenly distributed throughout the demister and the surface area is extremely high per volume unit. The large volume of space in a demister means that the pressure drop is relatively low.
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Separation efficiency 100% for droplets >5µm
Demister design
A demister is a droplet separator made of a mesh knitted from metal or plastic wires. The mesh is assembled in several layers and forms a demister pad, which is always oversized in width to avoid the gas bypassing the demister pad along the vessel wall.
Demister design, function and efficiency is determined by wire diameter, number of wires, number of mesh layers, mesh size and overall demister height.
The space between the wires is very evenly distributed throughout the demister and the surface area is extremely high per unit volume.
A smaller demister is manufactured as a unit with a support grid on each side of the demister pad. A larger demister consists of several sections to allow for insertion and removal through the manhole during installation and maintenance.
The mesh in each section is larger than the support grid to ensure a tight installation between the different segments and the vessel wall.
Separation efficiency
As the process gas passes through the demister, the liquid is trapped in the space between the wires, the droplets grow in size and are drained by the force of gravity.
The large volume of space in a demister means that the pressure drop is relatively low. Separation efficiency is 100% for droplets >5µm, provided that the demister design is based on correct process and operating data.
The illustration shows the separation refficienct for droplets >5µm at a given gas flow rate in % of the calculated maximum allowable gas flow velocity.
Choice of material
Choice of material depends on temperature and composition of the gas stream, among other things. Demisters are made in a variety of materials in different types of plastic or metal, such as
- 304L, 316L
- Polypropylene, PP
- Other special materials on request
Checklist important parameters
In order to offer an effective and sustainable solution, below are a number of process parameters that are important to consider when selecting and designing a droplet separator.
Sometimes it is difficult or even impossible to obtain information and data regarding the specific process. Together with our suppliers, we have extensive experience and we can make sound assumptions as a basis for designing the best solution for the process.
| Operating data | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Gas | Unit | ||||||||||
| Maximum gas volume flow | m³/h | ||||||||||
| Gas density (operating conditions) | kg/m³ | ||||||||||
| Kinematic gas viscosity | mm²/s (cSt) | ||||||||||
| Operating pressure | bar (a) | ||||||||||
| Operating temperature | °C | ||||||||||
| Operating data | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Liquid | Unit | ||||||||||
| Liquid content | kg/h | ||||||||||
| Liquid density | kg/m³ | ||||||||||
| Surface tension | nM/m | ||||||||||
| Dynamic viscosity of the liquid | mPass | ||||||||||
| Geometrical data | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Data | Info/unit | ||||||||||
| Flow direction | horizontal or vertical | ||||||||||
| Installed in column | column or pipe | ||||||||||
| Column diameter or dimension | mm | ||||||||||
| Opening for installation | manhole or vessel flange | ||||||||||
| Requirements | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Data | Info/unit | ||||||||||
| Type of mist eliminator | wire mesh or vane type | ||||||||||
| Type of material | Please specify | ||||||||||
| Separation efficiency | % | ||||||||||
| Separation efficiency/Limit drop size | µm | ||||||||||
| Maximum pressure drop | mbar | ||||||||||
| Other requirements | Please specify | ||||||||||
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Choose the right product for effective and optimised droplet separation
Every process is unique. The Knowledge base provides information on how droplet separation works and what questions need to be answered to achieve an effective and sustainable solution.
Founded in 1976, RVT Process Equipment is a leading supplier and manufacturer of droplet separators, packings, column internals and other products for mass and heat transfer processes.
RVT Process Equipment offers advanced engineering and technical support and has extensive experience in various processes and applications in the chemical and petrochemical industry, refineries, power plants, and pulp and paper. The R&D department houses fully equipped test units, available to carry out customer-specific tests when needed.
RVT Process Equipment has subsidiaries and manufacturing facilities in Knoxville, USA and in Kunchan, China.
Begg Cousland Envirotec has vast know-how and experience in the field of droplet separation with a complete range of demisters, coalescers and candle filters.
Many applications may be similar at a first glance, but there are often small differences that are crucial to consider for an optimal solution. With an extensive experience in many industries, Begg Cousland's technical team are able to deliver the most effective solution for a specific problem and process.
Our customer promise
Right solution, technical expertise and commitment is what you can expect from us as your partner or supplier.
Support & service
We offer the support you need to optimise your droplet separation and provide a sustainable solution.
Right solution, delivered on time
Delivering the right solution on time requires co-operation, structure, attention to detail and following a process throughout the project.