What is the Advantage and Disadvantage of fiber bed mist eliminators

Mist eliminators are designed to remove vapor and other liquids that are contained in air or gas streams produced during manufacturing or industrial processes. When molecules and very small droplets of liquid are trapped in air or gas, this is known as entrainment.

You will get efficient and thoughtful service from ZHUAN LV.

Removing liquid contaminants from industrial exhaust streams prevents corrosion of equipment, improves plant emissions, prevents slippery floors, reduces worker health risks, and improves overall product integrity. Some of the types of liquid contaminants that may be removed from process gas include oil mist, mist from machine coolant, aerosols, and mist from chromic or sulfuric acid.

Mist eliminators may be designed to remove entrained droplets from 3mm to less than 1 µm in size.

How does mist elimination work?

In simplest terms, the exhaust gas is forced into a constrained area, where filters separate the condensate from the gas.

The three most common types of mist eliminators are mesh, vane (sometimes known as Chevron), and fiber bed demisters. These three types of mist collection can be used separately or in conjunction with one another, depending on the setup.

These varieties of mist eliminators mechanically separate miniscule droplets of liquid from vapor streams, though they do it in slightly different ways.

Wire mesh mist eliminators

The most prevalent type of mist eliminator is wire mesh. These types of demisters are most effective for removing droplets from 3mm to less than 1 micron in diameter.

Mesh mist eliminators have either a vertical or horizontal airflow. Vertical mist eliminators are very common. Horizontal mist eliminators are commonly used in applications like battery manufacturing, chrome or nickel plating, and chromic anodizing.

Here’s how a mesh pad filter works: a random woven mesh of wire made from metal, polyester, polypropylene, or glass fibers sits between the gas stream inlet and the clean air outlet. The dirty air moves through the filter media, where liquid droplets coalesce on the filter mesh. The liquid is collected in a reservoir, and a fan pushes the clean air to an outlet.

The droplets are removed from the air by three forces: inertial impaction, direct interception, and Brownian diffusion.

Inertial impaction is when the droplets in the air stream hit the fibers in the mesh filter. Some of the air flows around the mesh. But for the vapor particles that hit fibers in the mesh, the droplet is removed from the air stream.

Direct interception is when a particle, in this case a droplet in a gas stream, attaches to a fiber in the mesh filter. As a droplet moves in the air flow, if it’s distance to a fiber is less than its diameter, it will be intercepted by the fiber and attach to the filter fiber.

In cases where the air flow is faster, or the droplets are larger, the efficiency of the filtering mechanism becomes greater. As droplets attach to the fibers, the fiber effectively has a greater reach, and more droplets are impacted or intercepted, removing them from the air flow.

When the air flow is slower, or the particles are much smaller, Brownian diffusion comes into play. Brownian motion is when particles in a flow of air or liquid have random motion (not in a straight line) due to impact from smaller particles and molecules.

The more vapor particles attach to a filter, the greater the filtering efficiency, but the greater the pressure drop.
Most mesh pad filters are several inches thick, usually about six inches.

In many applications, like in oil and petroleum mist collection, there will sometimes be multiple layers of wire mesh filters. This allows for successive collection of droplets from the gas stream with different filter sizes.

Advantages and disadvantages of mesh mist eliminators

The main advantages of mesh pad mist eliminators: they are relatively inexpensive, and efficient at removing particles down to a certain size.

Some disadvantages: efficiency decreases as the droplet size increases, the pressure drop is greater than other mist filtration methods.

Fiber bed mist eliminators

Fiber bed mist eliminators work in a similar fashion as wire mesh pad mist collection. This type of mist filter is built for horizontal gas streams. The filters are in a cylindrical shape, sometimes known as candle filters. These filters can be anywhere from 2 feet to 20 feet in height. Most often, the gas stream is forced through an enclosed area where the filter bed filters are contained. The droplets are removed from the air stream through inertial impaction, direct interception, and Brownian diffusion.

The inner and outer part of the filter are rolled screens, and the filter media is in between these two layers. The removed liquid is collected and either disposed of or used for other purposes, depending on the application.
Filter bed mist collection is used in many different industries where filtration of sub-micron particulate is necessary. This mist collection method is efficient up to 99.9% for removing contaminant from emissions.

Advantages and disadvantages of fiber bed mist eliminators

Advantages of fiber bed mist eliminators: Filters very small droplets less than one micron extremely efficiently. Large contact surface means high volumes of gas stream can be filtered.

Disadvantages of fiber bed mist filtration: Designed for horizontal airflow, not vertical. Large pressure drop and poor drainage compared to other methods. Not suited for simultaneous high volume and high-speed air flow.

Vane (aka chevron) mist eliminators

Vane, also known as baffle-type, or chevron mist eliminators are effective at removing larger droplets from a gas stream. In a vane mist eliminator, inertial impaction is used to mechanically separate the vapor droplets from the air flow.

A vane mist eliminator can be used for either horizontal or vertical air flow. This type of filtration uses a series of blades inserted in the path of the air flow. Each blade has a series of zig-zagging plates parallel to each other, separated by spacers, so the vaporized air flows through the plates.

The vapor droplets in the air are usually denser than the air itself, and as the air moves through the zig-zagging plates, the droplets adhere to the plates, as the liquid cannot traverse the air flow path as easily as the gas stream.

Droplets condense on the walls of the plates, and flow into a drainage reservoir. The density of the gas vs the density of the vaporized liquid should be calculated, as the angle of the “chevrons” can affect the rate of impaction. Another factor to consider is the speed of the air flow. If the gas stream is too fast for the vane pattern, the vapor droplets can be reabsorbed to the gas stream. This is known as re-entrainment. Many vane mist eliminators have capture hooks and drainage hooks to prevent re-entrainment.

Most vane mist eliminators are made from stainless steel or carbon steel, though other materials are common as well. The recommended design and spacing of the vane blades depend on the specific application, and the droplets that are being filtered.

Advantages and disadvantages of vane plate mist eliminators

Some advantages of vane mist eliminators: Can be used for vertical or horizontal air flow. High capacity filtering. Removes entrained solids from gas streams. Can be used along with mesh pad demisters for more efficiency. Low pressure drop. Blade spacing can be designed for specific use cases.

Disadvantages of vane mist eliminators: Not designed for sub-micron mist elimination. Gas stream velocity must be controlled to prevent re-entrainment.

Applications of mist elimination

Mist eliminators are used to remove vapor and particulate such as the following:

• Organic vapors
• Chemical mist
• Oil mist
• Acidic or caustic mist
• Soluble particulates

Some industries that use mist elimination include:

• Oil and petroleum
• Metalworking
• Battery manufacturing
• Plating and Anodizing
• Chemical processing
• Power plants / cooling towers
• Circuit board manufacturing

If you need professional consultation for mist eliminators or wet scrubber systems in your manufacturing plant or industrial facility, contact IAF using the link below.

Demisters: Clearing the Air (and Water) in Environmental & Water Treatment

In various industrial processes, the presence of mist – tiny liquid droplets suspended in a gas stream – can be problematic. It can lead to inefficiencies, product contamination, and even environmental hazards. This is where demisters, also known as mist eliminators, come into play.

If you are looking for more details, kindly visit stainless steel filter cartridges.

What are Demisters?

Demisters are specialized devices designed to remove mist from gas streams. They operate by utilizing various physical principles to capture the droplets and separate them from the gas, effectively "clearing the air" (or gas) for a cleaner and more efficient operation.

Types of Demisters:

Demisters come in various types, each tailored for specific applications:

• Mesh Pad Demisters: These consist of a tightly woven mesh of fine wire or fiber, creating a labyrinthine path that forces the gas to change direction, causing the droplets to collide and coalesce. This allows larger droplets to be easily separated from the gas stream.
• Wire Mesh Demisters: Similar to mesh pad demisters but with a more robust construction, often used in harsh environments.
• Vaned Demisters: These use a series of curved vanes to change the gas flow direction, forcing droplets to collide with the vanes and coalesce.
• Packed Bed Demisters: Employ a bed of packed materials like ceramic beads or metal rings to enhance droplet collision and coalescence.
• Cyclone Demisters: Utilize centrifugal force to separate mist from the gas stream.

Mist Eliminator by Koch-Otto York

Koch-Otto York is a renowned manufacturer of high-quality mist eliminators, known for their innovative design and robust construction. Their mist eliminators boast several features that make them a reliable choice for various industrial applications:

• High Efficiency: Koch-Otto York mist eliminators achieve exceptionally high removal efficiency, often exceeding 99%, ensuring minimal mist carryover.
• Durability: Their mist eliminators are built to withstand demanding conditions, featuring corrosion-resistant materials and robust construction.
• Low Pressure Drop: They are designed for minimal pressure drop across the device, optimizing efficiency and minimizing energy consumption.
• Customization: Koch-Otto York offers a wide range of mist eliminator designs and materials to meet specific application requirements.

Applications in Environmental & Water Treatment:

Demisters play a crucial role in environmental and water treatment applications, helping to:

• Reduce Air Emissions: In industries like power plants, chemical processing, and waste management, demisters help capture and remove mist from exhaust gases, minimizing particulate matter emissions and improving air quality.
• Improve Water Treatment Efficiency: Demisters are used in various water treatment processes to remove mist from air streams, preventing contamination of the water.
• Optimize Process Performance: Demisters ensure a cleaner and more efficient operation by preventing mist buildup and potential blockages, improving overall process performance.

Conclusion:

Demisters are essential components in environmental and water treatment systems, playing a vital role in enhancing efficiency, minimizing emissions, and safeguarding the environment. Koch-Otto York's mist eliminators offer robust and efficient solutions, ensuring reliable performance and minimizing environmental impact. By embracing technology like demisters, we can effectively address mist-related challenges and strive towards a cleaner and more sustainable future.

Test Your Knowledge

Demisters Quiz:

Instructions: Choose the best answer for each question.

1. What is the primary function of a demister?

a) To remove dust particles from gas streams. b) To separate mist droplets from gas streams. c) To filter out harmful chemicals from water. d) To purify air by removing bacteria.

b) To separate mist droplets from gas streams.

2. Which of the following is NOT a type of demister?

a) Mesh Pad Demister b) Wire Mesh Demister c) Vaned Demister d) Steam Turbine Demister

d) Steam Turbine Demister

3. How does a Mesh Pad Demister work?

a) By using a centrifugal force to separate droplets. b) By forcing gas through a tightly woven mesh, causing droplets to coalesce. c) By filtering gas through a bed of packed materials. d) By using a series of curved vanes to change the gas flow direction.

b) By forcing gas through a tightly woven mesh, causing droplets to coalesce.

4. Which of the following is a benefit of using Koch-Otto York mist eliminators?

a) High efficiency and low pressure drop. b) Low cost and minimal maintenance requirements. c) Easy installation and minimal space requirements. d) Ability to remove all types of pollutants from air.

a) High efficiency and low pressure drop.

5. How do demisters contribute to environmental and water treatment?

a) By reducing air emissions and improving water treatment efficiency. b) By cleaning up oil spills and preventing water pollution. c) By purifying contaminated water sources and making them drinkable. d) By capturing and removing greenhouse gases from the atmosphere.

a) By reducing air emissions and improving water treatment efficiency.

Demisters Exercise:

Scenario: You are working at a chemical processing plant. The exhaust gases from a particular process contain a significant amount of mist, leading to inefficient operation and potential environmental concerns. You are tasked with recommending a suitable demister solution.

Task:

1. Identify two types of demisters that could be suitable for this application.
2. Explain the advantages and disadvantages of each type based on the specific scenario.
3. Recommend which type of demister would be most appropriate and justify your choice.

**Possible Solutions:**

1. **Mesh Pad Demister:** * **Advantages:** High efficiency, relatively low cost, and wide availability. * **Disadvantages:** May be prone to clogging with high mist concentrations, may require frequent cleaning.

2. **Wire Mesh Demister:** * **Advantages:** Robust construction, more resistant to clogging, suitable for harsh environments. * **Disadvantages:** Higher cost than mesh pad demisters, may have a slightly higher pressure drop.

**Recommendation:** The **Wire Mesh Demister** would be the more appropriate choice for this scenario. Given the high mist concentration and potentially harsh environment of a chemical processing plant, the Wire Mesh Demister offers a combination of high efficiency and robust performance, making it a reliable and long-lasting solution.