How to Design an Efficient Gas Scrubbing System

Designing an efficient gas scrubbing system is essential for industries handling harmful gases such as hydrochloric acid, sulphuric acid, sulphur trioxide and ammonia. These systems play a vital role in protecting workers, ensuring compliance with environmental standards, reducing reagent losses through vapour loss, and maintaining the integrity of industrial equipment. A well-designed gas scrubber not only improves air quality but also contributes to sustainable and safe operations. These systems are widely used across industries such as mining and minerals, infrastructure, manufacturing, energy, and processing, where controlling harmful gases and fumes is critical for both safety and environmental compliance, and potential reduction in operating costs.

In this article, we’ll explore the key elements of a gas scrubber design, including system components, performance considerations, and the overall benefits of effective gas scrubbing.

Understanding Gas Scrubbers

A gas scrubber (also known as a gas scrubbing column or mass transfer column) is a type of device designed to efficiently capture specific gas components into a liquid phase stream, and if required neutralise the liquid phase components to an inert form. Commonly used in chemical processing, mineral processing, metal finishing, and manufacturing industries, these systems are crucial for managing emissions of substances like sulphuric acid and sulphur trioxide. A gas scrubbing column can also be an integral part of the processing plant, wherein an important reagent can be susceptible to losses due to vaporisation, such as is seen with ammonia-based solutions.

Gas scrubbers work by bringing the gas stream into contact with a liquid phase solution selected to readily absorb the target gas phase components, and where necessary neutralise the absorbed species.

Key Components of a Gas Scrubber System

An effective gas scrubber system includes several critical components, each of which contributes to the overall efficiency and reliability of the design:

• Scrubbing Tower (or Column): The vertical chamber where the gas stream contacts the scrubbing liquid. Packed bed towers are commonly used to increase the contact surface area and improve mass transfer.
• Packing Material: Enhances the interaction between gas and liquid. High surface area packings are utilised, with material of construction like polypropylene, ceramic or stainless steel(s) commonly used, dependent on the gas and liquid phase composition and properties..
• Liquid Distribution System: Ensures uniform distribution of the liquid solution across the packing media.
• Demister or Mist Eliminator: Captures entrained droplets from the gas stream before it exits the system.
• Recirculation Pump: Maintains the flow of the liquid solution within the system.
• Monitoring & Control Equipment: Sensors and instruments to monitor the system and control to optimal performance, such as pressure, pH, conductivity and flow rate.

Design Considerations for an Efficient Gas Scrubber

When developing a high-performing gas scrubber design, consider the following principles:

1. Gas Flow Rate and Composition

Determine the volume and chemical makeup of the gas phase to size the system appropriately. A hydrochloric acid scrubber, for example, may require different specifications compared to systems handling ammonia capture.

2. Choice of Liquid Phase Solution

The liquid phase solution must effectively absorb the target gas phase components, and if necessary neutralise the liquid phase species to an inert form. For example, in sulphuric acid/sulphur trioxide applications, an acidic liquid phase solution could be utilised if the requirement is to capture and reuse the acid gas within the process to minimise reagent losses. Alternatively, an alkaline solution like sodium hydroxide can be utilised if the requirement is to neutralise the captured sulphuric acid gas before discharging downstream.

3. Mass Transfer Efficiency

Improve gas-liquid contact by using high-efficiency packing materials and optimised liquid distribution. This is key to effective gas phase capture.

4. Pressure Drop Minimisation

A low-pressure drop ensures energy efficiency. This can be achieved by selecting the right packing and maintaining a clean operation.

5. Corrosion Resistance

Select materials suitable for the chemical composition of the system, maintaining a focus on cost effectiveness, such as FRP, PVC, or other non-metallic options for long-lasting performance.

6. System Footprint and Integration

Design the system to fit existing plant layouts without disrupting operations, ensuring ease of access for maintenance.

Benefits of a Well-Designed Gas Scrubber System

An efficiently designed gas scrubber offers numerous operational and environmental benefits:

• Enhanced Emission Control: Achieves high removal efficiencies for hazardous gases that would otherwise be emitted to the environment.
• Regulatory Compliance: Meets strict local and national environmental standards.
• Workplace Safety: Reduces exposure to toxic and corrosive gases.
• Reduced Equipment Corrosion: Protects the surrounding infrastructure from potential chemical corrosion.
• Operational Efficiency: Minimises energy consumption and maintenance downtime.
• Operational Cost Reduction: Minimise the loss of reagent due to volatilisation from the reagent liquid stream or process equipment that would otherwise report to the local atmosphere..

Innovent Engineering: Your Partner in Gas-Phase Capture and Control

Designing an efficient gas scrubbing system is a critical step in maintaining compliance, protecting infrastructure, reducing reagent losses from your process, and ensuring a safe working environment in industrial and mining operations. By considering key design elements such as gas flow, liquid media, and material selection, you can achieve both performance and longevity.

At Innovent Engineering, we specialise in designing and delivering custom gas scrubbing systems for Australia’s most demanding industrial environments. If you’re looking for a reliable partner to support your air pollution control strategy or recover a gas-side reagent, get in touch with our team today.