Venturi scrubber

Types of Venturi scrubbers

A Venturi scrubber is a kind of wet scrubber. While wet scrubbers are usually defined as apparatuses that remove pollutants from gas streams or flue gases using liquid-based solvents or solutions, the Venturi scrubber works on the effect of pressure drops as water flows through a Venturi tube to make use of the driving force behind such pressure drops. Hence, these are also known as pressure drop scrubbers.

The following are some common types of Venturi scrubbers:

• Basin type: Normally used for larger flue gas volumes, a basin Venturi scrubber incorporates a basin or reservoir where the liquid solvent is kept. The contaminated gas enters the Venturi throat, where the cross-section of the channel decreases. The water level in the basin is usually above the lower basin throat, which forms a physical barrier to the water in the basin. Due to pressure drop, water is sucked up into the throat and comes into contact with contaminants inside the gas, thus purging the latter.
• Bypass channel: This kind of channel refers to a segregated passageway in parallel with the Venturi throat. The gas can go through this passage to avoid contact with the liquid in the Venturi throat. Bypass channels are usually used for scrubbers designed to handle gas streams with variable flow rates. When gas volume is low, the stream can go through the bypass channel, thus improving liquid consumption efficiency. When gas volume is large, the stream can go through the Venturi throat to improve pollutant removal.
• Multitube: A multitube Venturi scrubber incorporates several small-diameter tubes or channels to replace the large Venturi throats in conventional tube scrubbers. Gas passes through the throat of each channel, and liquid is sprayed or injected into each channel to remove pollutants. The multitube design increases pollutant removal efficiency in compact scrubber designs.
• Single-stage scrubbers: They include a venturi-nozzle scrubber and a venturi-throat scrubber that consists of only one pollutant-removing unit as described above.
• Multi-stage scrubbers: In contrast to single-stage Venturi scrubbers, multi-stage ones are constructed with many pollutant-removing units connected serially. They are usually effective against huge pollutant loads and corrosive or harmful contaminants.

Specification & Maintenance

• Efficiency: Venturi scrubbers are highly efficient in removing various pollutants, including particulate matter, gases, and vapours. Efficiency rates often exceed 90%, making them effective for compliance with environmental regulations.
• Design: The design specifications of venturi scrubbers can vary depending on the intended application. Some venturi scrubbers are designed for high gas flow rates, while others focus on maximizing liquid-gas contact area.
• Pressure Drop: A critical design consideration for venturi scrubbers is the pressure drop across the unit. Typically, the pressure drop ranges from 1,500 to 3,000 Pascals (15 to 30 mmHg). A higher pressure drop indicates more efficient cleaning but may result in greater energy costs due to fan capacity.
• Liquid flow rate: The volumetric liquid flow rate is an important specification, usually ranging from 0.05 to 2 m3/h per scrubber. This affects the amount of recycled water used and the overall operating costs.
• Materials: Venturi scrubbers are made from corrosion-resistant materials like stainless steel or certain alloys. This ensures that they can withstand the chemical properties and corrosion of the pollutants being treated.

Maintenance

• Regular inspections: Monthly or quarterly inspections are vital for venturi scrubbers. First, operators should check the appearance of the scrubber, the inlet and outlet pipes, and the water distribution device to ensure there are no leaks, blockages, or damages.
• Cleaning: Clean the interior of the venturi scrubber periodically to remove deposits, grime, and other contaminants. The cleaning frequency and methods should be based on the specific operating conditions and pollutant types.
• Filter replacement: For venturi scrubbers with pre-filters or other filtering devices, the filters should be replaced or cleaned according to the prescribed schedule. This ensures that the scrubber operates effectively and maintains its filtration efficiency.
• Pump maintenance: If the venturi scrubber is equipped with a cooling or washing liquid pump, it should be maintained periodically. This includes inspecting the pump for any leaks, adjusting pump flow rates, and more.
• Fan maintenance: For venturi scrubbers with fans, they should be maintained regularly as per the manufacturer's instructions. This may include cleaning the fan blades, replacing bearings, and more.

Industry applications of the Venturi scrubber

Industrial Venturi scrubbers are used in many industries to control air pollution and improve environmental sustainability.

• Chemical manufacturing

  A Venturi scrubber is commonly used to remove toxic chemicals in the air in chemical production factories to protect workers' health and the surrounding environment. Chemical factories frequently use Venturi scrubbers to eliminate harmful gases, fine particulate matter, and solid nucleuses generated during chemical processes. For instance, in the pesticide industry, a pesticide Venturi scrubber is used to capture and treat waste gas containing pesticide residue and other organic pollutants, preventing them from being released into the atmosphere and polluting the air. By using Venturi scrubbers, chemical manufacturing companies can reduce air pollution caused by chemical production processes, ensuring compliance with environmental regulations and improving the quality of life for nearby residents.

• Cement production

  In the cement production process, a large amount of dust and particulate matter is generated, polluting the air. A cement Venturi scrubber is an air purification device specifically designed for cement production. It utilizes the Venturi effect and water to capture dust and particulate matter from the cement production process, preventing it from being directly released into the air. This not only improves the air quality but also enhances the environmental sustainability of cement production. Furthermore, the captured dust can be treated and potentially reused, contributing to resource conservation and recycling.

• Construction

  The Venturi scrubber is a widely used air purification device in the construction industry. During the construction process, a large amount of dust and particulate matter are generated, seriously polluting the air and impacting the health of construction workers and nearby residents. By using Venturi scrubbers, the construction industry can effectively control dust pollution, improve air quality, and provide a healthier working and living environment for workers and residents. Meanwhile, it complies with relevant environmental standards and regulations.

• Metallurgy

  Metallurgy industries, such as steel and non-ferrous metal smelting, are known to produce significant amounts of dust and particulate matter, negatively impacting air quality. Consequently, the metallurgy industry places great importance on air pollution control and dust collection. A Venturi scrubber serves as an effective tool for dust collection and air purification in metallurgy industries. By utilizing the Venturi effect and water, it captures dust and particulate matter generated during metallurgy processes, preventing them from being released into the atmosphere. This not only mitigates the environmental impact of metallurgy industries but also safeguards the health of nearby residents.

• Power generation

  The power generation industry faces the prominent problem of air pollution. Power generation processes, especially those relying on fossil fuels, generate significant amounts of dust and harmful gases, including sulfur dioxide, nitrogen oxides, and other pollutant gases. These emissions contribute to environmental degradation and pose health risks to nearby communities. Power plants utilize Venturi scrubbers to effectively remove dust and harmful gases from the emissions, significantly reducing air pollution. The implementation of Venturi scrubbers in power plants demonstrates a commitment to sustainable energy production and environmental stewardship.

• Textile

  During the textile production process, a variety of harmful gases, such as ammonia, methane, and volatile organic compounds (VOCs), are emitted, posing significant risks to the health of workers and the surrounding environment. Furthermore, the production of dust and particulate matter can contribute to air pollution. To address this issue, Venturi scrubbers have been widely applied in the textile industry to effectively control air pollution. By utilizing the Venturi effect and water, these scrubbers capture and remove harmful gases, dust, and particulate matter, thereby improving air quality and ensuring a safer working environment. The implementation of Venturi scrubbers in the textile industry represents a step towards more sustainable and environmentally friendly production practices.

How to choose Venturi scrubbers

When buying a Venturi scrubber, buyers should focus on selecting the ideal venturi scrubber for their specific industrial needs. To begin with, buyers should evaluate their gas stream composition and flow rate. They need to determine the type of pollutants they need to remove, such as particulate matter, gases, or vapors, and the characteristics of the gas stream, including its composition, temperature, pressure, and presence of particulates. Additionally, buyers should consider the liquid phase they can use and the correct flow rate for effective scrubbing.

Next, buyers should identify the pollutants they need to remove and choose a Venturi scrubber designed for that specific pollutant. Also, buyers should assess the physical properties of the gas stream, such as pressure drop constraints and particle sizes, which determined the scrubber's design and operating parameters. Some industrial processes might have pressure drop constraints that limit the permissible pressure drop across the scrubber. In such cases, buyers need to select a scrubber with a design that meets the pressure drop requirement.

Moreover, buyers should ensure the Venturi scrubber can handle the expected dust loading in the gas stream. High dust loading may lead to increased liquid consumption and the need for frequent water recirculation.

Finally, buyers should ensure the Venturi scrubber can be easily maintained. Considered maintenance-friendly scrubbers can reduce operational costs and ensure proper handling.

Venturi scrubber Q&A

Q1. Why does a venturi scrubber need a demister?

A1. The venturi demister performs an important function in a venturi scrubber. It removes a large quantity of water droplets from the gas stream before it enters the fan for subsequent treatment. The venturi demister improves the efficiency of the scrubber and reduces the quantity of water used in the process.

Q2. What are the strengths and weaknesses of venturi scrubbers?

A2. The main strength of a venturi scrubber is its ability to remove a large percentage of pollutants from gas streams. Moreover, venturi scrubbers can be used to treat gas streams with low pollutant concentrations. When faced with a high concentration of pollutants, the scrubber can be operated in by-passed mode so that only a portion of the gas stream is treated. On the other hand, venturi scrubbers are energy-consuming devices. High pressure and fan speed are required to treat gas streams effectively, which may result in the creation of noise pollution.

Q3. What types of pollutants can venturi scrubbers remove?

A3. Venturi scrubbers are multipurpose devices that can remove various types of pollutants. They are commonly used to remove particulate matter, such as dust, smoke, and aerosols, from gas streams. Moreover, venturi scrubbers can be used to remove specific gaseous pollutants, including sulfur dioxide, nitrogen oxides, hydrogen chloride, ammonia, volatile organic compounds (VOCs), and other hazardous gases. The design of the scrubber may need to be modified to improve the removal efficiency of specific gaseous pollutants.

Q4. What is the operating principle of a venturi scrubber?

A4. The venturi scrubber combines the high level of absorption of gas-liquid contact with the throat of the venturi nozzle. The venturi scrubber operates in three stages. The feed gas first enters the scrubber's inlet section. The downward high-pressure water spray then forms a mist of water droplets before the water and pollutants are captured in the scrubber's bottom section.

Q5. What are the main components of a venturi scrubber?

A5. A venturi scrubber usually has a spray nozzle, venturi throat, and scrubber hopper. Besides, a venturi scrubber may have other components, such as a blower or fan, upstream electrostatic precipitators, downstream bag filters, water recycling systems, demisters, and ducting systems that connect the scrubber to other pollutants removal or recycle systems.