What is the purpose of the mist eliminator?

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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.

Fiber 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.

With competitive price and timely delivery, ZHUAN LV sincerely hope to be your supplier and partner.

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.

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.

Related Blogs

Date: -07-07 | Author: Christine McAniff

In a world of online information, you will find many options when searching for mist elimination solutions. While many companies can sell you a mist eliminator, it is a wise choice to find a company that will design the right mist eliminator for your process. Below we will talk about the basics of mist eliminators, also known as demister pads.

In the manufacturing of fertilizers, chemicals, and other processes, liquid will encounter flowing gas, as a result, the entrainment of liquid droplets will generate a mist. Mist is corrosive and can result in process inefficiencies and damage your equipment.

A properly designed and installed mist eliminator will collect and remove droplets from the gas stream. Removal happens when droplets within the flowing gas strike the mist eliminator and are then captured. The material coalesces on the surface of the demister pad, causing larger droplets to form. The droplets will join and flow by gravity into the drainage area below where they are recovered or removed.

One major concern in mist elimination is plugging. This occurs when a substance builds upon the surface of the mist eliminator causing a blockage and then pressure drop. It is common for process and gas stream problems to result from plugging of the demister pad. Plugging can result in product loss, excessive energy use, corrosion, reduction of equipment life, plant run times being affected, and not meeting output requirements. Structured media mist eliminators are less prone to plugging than conventional knitted mesh.

When choosing a mist eliminator, it is important to choose a company that will understand your chemical process and design a mist eliminator for your system and process needs. Being a retrofit or a new design, many considerations will come into play for the design of the demister pad. Particle size will determine the type of mist elimination for the application, such as Fiber Bed Filters vs. Structured Mesh Pads. Definition of the droplets size in the current system will be necessary to determine the proper design. Droplets definition are based on diameter. For example Sprays are larger than 10 microns. Mist are 10 microns to 1 micron. Aerosols are smaller than 1 micron.

Droplets are collected on the mist eliminator media by three different methods. Inertial Impaction, Interception, and Brownian diffusion.

For larger droplets, inertial impaction happens when droplets &#; 20-30 travel in a straight line, away from the gas flow, and then they strike the surface of the media and stick together.

Interception happens when droplets down to 1 to 3 microns in diameter travel along the path but are caught or intercepted because they cannot pass through the fibers of the media.

Brownian diffusion happens when particles smaller than 1 micron collide with gas molecules, then the molecules gain momentum and random motion, therefore likelihood increases that the molecules will contact the fibers.

Mist Eliminators Are Available in Several Different Styles:

Vane packs, also known as chevron or plate-type mist eliminators are composed of corrugated plates that are spaced close together. This creates a tortuous path for the gas to follow. Vanes are more effective for larger droplets and can be quite costly.

Fiber bed Filters are made of fine fibers, typically glass or plastic, and packed or wound around a cylinder. Fiber bed filters can be repacked and replaced. They should not be used where solids exist.

Wire mesh also known as knitted mesh is composed of multiple layers of mesh that is knitted of metals or plastic monofilaments. These pads can be cleaned and reused.

Structured mesh mist eliminators are made of interlocking plastic monofilaments. These pads can also be cleaned and reused. When designed properly, larger diameter polypropylene mesh pads can easily handle particulates that would usually cause pressure drop.

Poorly designed mist eliminators can lead to corrosion of downstream equipment, product waste, and shutdown times that are longer than desired.

Properly designed mist eliminators can reduce plugging and mist carryover, have lower pressure, reduced energy consumption, less cleaning and maintenance, less damage to downstream equipment, reduced corrosion, and longer equipment life and reduced atmospheric emissions. All which will lead increased profitability.

Contact us to discuss your requirements of fiber bed mist eliminators. Our experienced sales team can help you identify the options that best suit your needs.