Mist eliminators, or demisters, play an essential role in removing mists and other liquids generated during industrial and manufacturing processes. During these processes, droplets of water and other molecules may become trapped in the air or gas, resulting in entrapment.
As environmental protection regulations have increased, the use of mist eliminators has risen to meet these new requirements and reduce pollutants that gases may otherwise carry. Understanding how mist elimination works will help you choose a suitable mist eliminator for wet scrubber systems.
The Role of Mist Eliminators in Wet Scrubbers
The wet scrubbing process is designed to remove solid or liquid particles from a gas stream. This is done by merging the gas stream with a liquid like water to control the particulate matter. In environments where machines are used, it is essential to use moisture eliminators and control systems.
For a wet scrubber to work effectively, inertia and dispersion must apply. Wet scrubbers incorporate mist eliminators that help manipulate the gas to control these particulates and remove them from the air.
The mist eliminator’s role is to remove liquid contaminants from gas streams. Eliminating these contaminants helps improve plant emissions, promote product integrity, prevent equipment corrosion and reduce possible employee health risks. The design of a wet scrubber incorporates mist eliminators to remove liquid droplets. Contaminants and pollutants can become trapped if gas and liquid streams make contact.
In combination with mist eliminators, wet scrubbers can remove both particulate matter and gases. Additionally, a wet scrubber’s ability to collect droplets is directly proportionate to how much power the scrubber receives and how well the mist eliminator functions per its design.
3 Common Mist Eliminators Used in Wet Scrubbers
The three most common types of mist eliminators for wet scrubbers are mesh pads, vanes and fiber beds.
1. Wire Mesh Mist Eliminator
Wire mesh is the most common type of mist eliminator. They incur a low installation cost and provide high separation efficiency. These eliminators are usually made of several compressed layers of metal wire or thermoplastic held together by support grids. They can deliver great results in a variety of conditions, and you can set them up in vertical or horizontal airflow arrangements. Wire mesh mist eliminators work by dirty air being forced through the media, where the droplets coalesce and continue to push the now-clean air to the outlet. The droplets are removed from the dirty air by direct interception, inertial impaction and Brownian diffusion.
Brownian diffusion — or Brownian motion — occurs when particles and molecules bounce off one another in an airstream in an irregular motion rather than a straight line. The eliminator may use multiple layers of mesh wire filters to create multiple stages of droplet collection. When choosing a wire mesh eliminator, some variables to consider include surface area, mesh thickness, wire diameter and the surface tension between the captured liquid and fiber.
2. Vane Mist Eliminator
Vane eliminators, also known as chevron or baffle-type mist eliminators, are needed to remove larger droplets from gas streams. This type of mist eliminator uses inertial impact to separate particulate droplets from the airflow. Rows of parallel plates, or chevrons, are placed in a zigzag formation to attract droplets. There are plates in each of these rows that allow the gas to flow through once it is rid of the droplets. Vane mist eliminators can be used for vertical or horizontal airflow.
You can combine vane mist eliminators with wire mesh to provide a more efficient system for capturing particulates. The wire mesh serves as a precursor for the fine mist and forms large particulate droplets for the vane mist eliminator. When these are combined, you can expect improved performance and the benefits of each type of equipment to be optimized.
3. Fiber Bed Mist Eliminator
For industrial processes that generate finer particulate droplets, consider a fiber bed mist eliminator. These work very similar to wire mesh mist eliminators but are only built for horizontal gas streams.
Filter bed mist eliminators are cylindrical. An inner and outer screen is rolled to form the cylinder, and plates or flanges are attached to either end for draining and mounting. This type of mist eliminator is best used for removing sub-micron particulates from gas streams.
Like mesh wire mist eliminators, the fiber bed type utilize Brownian diffusion to impinge the droplets onto the media before reaching the outlet. The air stream’s velocity and media density both play a factor in removing most contaminated droplets in this method.
Advantages of Mist Eliminator Considerations for Wet Scrubbers
Mist eliminators are a perfect addition to wet scrubbers and help enhance the cleaning of contaminated air. The three types of mist eliminators can be made to meet the specifications that you require for your wet scrubber system.
Mesh mist eliminators are relatively inexpensive and are efficient at removing small particles.
Filter bed mist eliminators filter smaller droplets extremely efficiently. Due to the large surface area of this type of mist eliminator, you can also filter a high volume of contaminated air.
Vane mist eliminators work across various applications, and the blade spacing can be adjusted for specific cases. You can arrange this type horizontally or vertically for high-capacity filtering. Out of the three mist eliminators, the vane-type creates the lowest pressure drop as gas is forced through.
If you’re unsure which type of mist eliminator would be best for your facility, or if you need a custom wet scrubber system engineered for a specialized application, MACH Engineering can help.
Contact MACH Engineering for Custom Mist Eliminators
If you’re interested in learning more about mist eliminators, contact MACH Engineering. At MACH Engineering, we design state-of-the-art odor and emission control systems for specific industry applications. We use multiple construction materials, sizes and other elements to create the most effective possible solutions.
We stand behind the quality of our products and our service. For more information about the benefits of our mist elimination systems or to request a quote for a mist eliminator for a new or existing process tower, contact us using our online form.