HCl Scrubber: Operation, Review of Types, Efficiency, Cost and Selection

Author: Michael Klepik, Chief Executive Officer

In various industrial sectors, hydrochloric acid is applied as a versatile chemical. It functions as a pickling agent for removing oxides in metal processing, and acts as a catalyst in the production of PVC. The petrochemical industry employs it in refining processes, showcasing its extensive usage. However, the extensive applications of hydrochloric acid also underscore the need for cautious handling and efficient containment systems to mitigate the associated risks and ensure workplace safety.

Wet scrubbing equipment remains one of the most common and effective methods for purifying air from caustic components in the industry, offering a balanced approach to efficiency and environmental sustainability.

A Venturi scrubber is an equipment designed to remove not only HCl but also NaOH, organic acids, Cl2, H2S, HCN, and other pollutants from industrial vapor streams.

It operates on the principle of generating a high-velocity, turbulent zone within a Venturi throat, where the vapor stream is blended with a cleaning liquid.

In this configuration, the contaminated air is compelled through a narrowed Venturi section, inducing a pressure drop and elevating gas velocity. At the same time, a fluid, typically water, is introduced through spray nozzles into the vapor stream. The turbulence generated in the Venturi throat facilitates the absorption of contaminants into the solution.

This HCl caustic scrubber incorporates a two-stage cleaning setup, comprising a Venturi pressure tube and a mass-exchanging column with random packing, along with an automatic irrigation system.

The efficiency of the Venturi scrubber for HCl lies in its capacity to achieve high gas-liquid contact and facilitate mass transfer, effectively capturing and neutralizing caustic components.

The purified atmosphere exits through the outlet, while the solution, now containing absorbed contaminants, may undergo further treatment or be recycled within the system.

A spray chamber or tower is a crucial component of a wet scrubber for hydrochloric acid, designed to eliminate pollutants such as corrosive agents or particulate matter from industrial vapor streams. In this configuration, contaminated vapors are introduced into the chamber, where they encounter a fine mist or spray of liquid.

The primary purpose of the spray chamber is to maximize the surface area of the liquid in interaction with the air, facilitating the absorption or capture of pollutants. Spray nozzles or atomizers disperse the solution into small droplets, creating an efficient interface for chemical reactions or physical absorption to occur.

As the vapor passes through the spray chamber, the pollutants are either dissolved or captured by the aqueous mixture droplets. The purified air exits the chamber, while the solution, now containing the absorbed contaminants, is collected for further processing or recycling within the setup.

The well-thought-out design of the hydrochloric acid scrubber facilitates the passage of a substantial airflow for purification. Vapor entry occurs tangentially, allowing pollutants to be directed straight down into the hopper (water-setting tank). The cleaning equipment is based on mass-exchanging processes in a hollow column.

The cleaning equipment relies on mass-exchanging processes within a column that incorporates special plates and stabilizers. A foam layer is generated on these elements, serving as a settling area for all contaminants.

Spray chambers are integral to wet technologies, providing an effective means of removing harmful substances from industrial emissions and ensuring environmental compliance.

A packed bed wet scrubber for HCl is an air pollution control device utilized for the removal of contaminants, such as corrosive substances and particulate matter, from industrial vapor streams. The HCl gas acidic scrubber consists of a vertical tower filled with packing material, typically made of plastic, ceramic, or metal, arranged to create a large surface area.

In operation, the contaminated substances ascend through the packed bed, while a cleaning fluid is introduced from the top and allowed to trickle downward over the packing material. The contaminants and solution undergo close contact, promoting mass transfer and the absorption of pollutants. The packing material enhances the interaction surface between the vapor and liquid phases, facilitating the removal of contaminants.

As the vapor rises through the packed bed, chemical reactions or physical absorption take place, capturing and neutralizing the pollutants. The cleaned air exits the HCl scrubber, and the fluid, now containing the absorbed contaminants, is collected for further treatment or recycling within the setup.

This HCl gas scrubber system features a horizontal mass-exchange chamber with random packing, incorporating rings such as Raschig, Palia, Intalox, and others. It is a compact piece of equipment with easy maintenance, suitable for purifying atmospheres containing various corrosive agents, alkali, and their mixtures.

The BOREAS-P3 is a packed-bed absorption tower with a watering and multi-stage droplet elimination setup design. The enlarged column provides better cleaning, and an additional ion-exchange cassette may be inserted. This hydrochloric acid scrubber system is designed for vapors that require a longer cleaning time and, consequently, a longer contact with the liquid. The packings and droplet elimination chamber are enlarged for more delicate multicomponent cleaning.

Packed bed absorption towers are recognized for their effectiveness in handling high flow rates of gaseous substances and are commonly employed across various industries to meet emission control standards.

Recirculating hydrochloric acid scrubbers involve the process of returning a portion of the purified gas back into the production process, subjecting it to cleaning once again. Key components include absorption devices, filters, and, in some cases, heat exchangers.

Application in Industrial Processes

• Returning purified vapors can be crucial in the production of chemical substances.
• Applied for capturing and reusing metallurgical waste.
• Gas recirculation in power plants can enhance the efficiency of electricity generation.
• Returning purified vapors can reduce raw material consumption in polymer production.

Recirculation configurations provide an innovative solution, mitigating the adverse effects of industrial processes on the environment and improving the efficiency of HCl scrubbers.

In short, the efficiency of an HCl gas scrubber is determined by:

• Contact duration,
• Surface area of interaction between gas and liquid,
• Diffusion length in the vapor phase,
• Difference in concentrations between the gas and liquid phases or added reagent,
• Temperature,
• Pressure.

Let's break down the key points in more detail.

Measurement of HCl Concentration:
Monitoring mechanisms can be employed for the continuous measurement of hydrochloric substance concentration in emissions, both before and after passing through the cleansing device.
Analysis of Liquid Waste:
Regular analysis of the solution waste used in the cleaning device provides information on the amount of substances adsorbed or dissolved in the liquid.
Measurement of Liquid and Gas Flow:
Measuring the flow of the utilized fluid and vapor before and after passing through the device provides insights into the volumes of pollutants that have been removed.
Monitoring Process Factors:
Monitoring temperature, pressure, pH, and other parameters in the setup assists in optimizing the operation of the cleaning device and evaluating its effectiveness.
Testing in Real Conditions:
Conducting tests in actual operating conditions, followed by the analysis of results, is also a method for evaluating effectiveness.

How can the efficiency of the caustic scrubber for HCl removal be increased? It can be increased by:

• increasing the contact duration,
• enlarging the washing area using special nozzles, interaction elements,
• more active mixing of media inside the equipment,
• decreasing the concentration in the liquid phase by employing a larger quantity of it,
• lowering the temperature,
• increasing the pressure.

The results of these measurements and analyses enable operators and engineers to optimize the operation of the apparatus, ensuring compliance with regulations and standards.

Approximate prices for HCl scrubber system in the USA can start from several thousand dollars and reach substantial amounts depending on the scale, complexity of technical specifications, and additional options, such as monitoring and control systems. The HCl scrubber cost for small laboratory setups typically ranges from $5,000 to $10,000, whereas larger and more complex installations for industrial enterprises may incur expenses in the hundreds of thousands or even millions of dollars. However, to obtain an exact cost based on the specific needs of your project, it is recommended to contact manufacturers or equipment suppliers, conduct detailed consultations, and obtain an individualized proposal.

Choosing the Appropriate System Involves Several Key Steps:
Pollution Analysis
Assess the composition of emissions, concentration, and other characteristics to determine the requirements for the setup.
Technical Specifications
Consider the specifics of the production process, emission volumes, and temperature conditions to choose suitable technical characteristics.
Budget Constraints
Assess the cost of installation, maintenance, and operation, taking into account the budget constraints of the enterprise.

We are always ready to assist you with the calculation and manufacturing (utilizing our factory) of purification systems. Since the equipment is custom-made to meet the client's requirements, the pricing is also tailored individually. Feel free to contact us to inquire about the cost and delivery timelines.