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Wet Scrubber: What It Is, How It Works, Types, Advantages and Disadvantages

What is a wet scrubber? This device is designed to remove various impurities from gases by washing the gas medium with liquid.

How does a wet scrubber work? This process is based on the wet cleaning method, where the gas medium in the working chamber is mixed with water or another process fluid. As a result, water droplets envelop dust particles or other contaminants, after which the clean flow is released into the atmosphere, and the waste water is drained from the working chamber. Thanks to this operating principle, a wet scrubber can purify air up to 99%.

Horizontal BOREAS-P3 Wet Scrubber

A Detailed Description

To understand what is a wet scrubber and how does it work, it's important to understand what this unit is and examine it in more detail. It captures solid and impurities from a mixture using the familiar properties of water.

Where is wet scrubber operation used? The device has proven itself in a variety of industrial and scientific applications. Among the most popular are:

The chemical and metalworking industries use equipment to remove inorganic impurities from exhaust gases and capture various harmful substances, including ammonia. They are often used to remove ash from flue gases and to conduct chemical reactions at the gas/fluid interface.
In the pharmaceutical and metallurgy industries, they are used to filtering substances with a viscous, oily, or greasy consistency (sulfur oxides, nitrogen oxides, hydrogen sulfide, and various acid vapors).
The food and energy industries require chemical gas treatment systems because they remove dust, acid and alkali mists, SO₂, HCl, HF, NH₃, and volatile organic compounds from gases. They can remove up to 99% of acidic gases or organic compounds and are resistant to solid particles in the stream.
Medical facilities and laboratories rely on these devices, as they ensure a high level of safety for the environment and employees.

Case Study: Wet Gas Cleaning System for a Pigment Manufacturer

In the client’s production process, a metallic salt is oxidized by spraying a ~40% nitric acid solution into a furnace to evaporate HNO₃ and water. To capture NOx (NO and NO₂), a two-stage scrubbing system is proposed: first, a scrubber with an H₂O₂ solution, which allows for nitric acid recovery, followed by a second scrubber with NaOH for complete purification. The NOx removal efficiency of the two-stage system reaches up to 99%. Read more.

How It Works?

A wet scrubber working with water or an active absorbent solution. In different types of dust and collectors, this fluid can exist in different states:

Fluidized bed.
Foam.
Aerosol or microfog.
Microfilm.

Wet scrubber meaning is a mass transfer process involving gas-solution contact. Water (or a solution) is liberally sprayed onto the gas-air mixture. The liquid is supplied through a chemical pump. After passing through the pipeline and nozzles, the water wets the substances in the housing, thoroughly washing out solid particles and dissolving gases and aerosols. The dirty water, containing dust particles, moves to a settling tank and from there to the cleaning device.

The dust-laden stream flow inside the device is forced to change direction abruptly, but particles with significant mass are unable to change direction and collide either with the water column or with structural components or the device walls.

A dynamic contact effect is also used. The purification process occurs using nozzles that spray water under pressure into the interior of the housing.

Wet Scrubber Dust Collector

The working principle of wet scrubber consists of capturing various harmful substances, including ammonia, and can be more effective than their dry-technology counterparts. The device operates by bringing contaminant particles into contact with a wet surface or moisture droplets, followed by their binding and removal via drainage.

This type of equipment differs from dry and semi-dry purification methods in its greater efficiency and performance.

Now we sorted it out about wet scrubber definition and can consider other aspects in more detail.

Classification by Type of Construction

Devices can be divided into several types: packed, hollow, bubble, and Venturi. Each of these types has its own characteristics and is used depending on specific emissions' purification tasks.

Packed
Uses special packing to improve the performance of the device. This increases the contact area between the air and the cleaning fluid, improving cleaning efficiency. However, packing increases the hydraulic resistance of the gases and quickly becomes clogged, limiting their use.

TORNADO FB Fluidized Packed Bed Scrubber

Performance:
100 — 175 000 cfm

BOREAS-P3 Horizontal Packed Bed Scrubber

Performance:
100 — 175 000 cfm

TORNADO SP Packed Bed Scrubber

Performance:
600 — 30 000 cfm

Venturi
It consists of two cone-shaped sections connected by a narrow throat where the gas migration meets the liquid flow. The operating principle is based on the Bernoulli equation, whereby as the cross-sectional area decreases, the velocity of the gas increases, reaching its maximum velocity at the throat. A disadvantage of this type of equipment is rapid wear of the section walls.

Wet Venturi Scrubber

Performance:
100 — 175 000 cfm

TORNADO FB Venturi Packed Bed Scrubber

Performance:
600 — 30 000 cfm

Hollow and Spray Wet Gas Cleaning Systems
Have a hollow vessel equipped with nozzles installed inside for water injection. The gas mixture is introduced into the unit through a nozzle at the bottom, passes through a water curtain, and is purified. Purified substances exit the system via a nozzle at the top of the vessel, and wastewater flows into a special tank before being released to the sewer.

TORNADO ST Spray Tower Wet Scrubber

Performance:
600 — 30 000 cfm

BOREAS-P1 Horizontal Wet Scrubber

Performance:
100 — 175 000 cfm

Tray-Type Gas Treatment Systems
Are classified as bubble or foam types, depending on the flow rate. In bubble liquid gas cleaners, the mixture passes through the liquid layer as bubbles, which is effective against large particles. Foam aqueous gas treatment systems are more effective due to their higher gas flow rate.

TYPHOON Tray Tower Scrubber

Performance:
100 — 175 000 cfm

Pros and Cons

Essential Data for Selecting a Wet Scrubber or Dust Collector

Chemical gas treatment systems are widely used in various industries, including hydrometallurgy, chemical industry, and mineral fertilizer production. They are used to capturing various harmful substances and can be more effective than their counterparts using dry contaminant capture technology.

This equipment is essential for the safe and efficient operation of many enterprises, including industrial plants and pharmaceutical companies. Torch-Air offers modern filtration systems for use in any environment. High-quality materials extend their service life, and state-of-the-art electronics significantly reduce energy consumption. By choosing our equipment, you can forget about replacing them for a long time.

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We always perform precise calculations and offer expert assistance in selecting the optimal dust collection or gas cleaning systems, typically completing this process within 1 to 2 days

Head of Engineering,
Vladimir Nikulin

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