Sulfur Scrubber: Design and Principle of Operation – Sulfuric Acid and Tank Vent Scrubbers

Author: Michael Klepik, Chief Executive Officer

Inhaling vapors of these substances can lead to serious health effects, with the most common being damage to the mucous membranes of the respiratory tract, potentially causing asthma. It is also important to note that sulfur emissions are a major cause of acid rain, which harms soil, forests, and aquatic life. Therefore, implementing sulfuric acid fume scrubber in industrial processes has become a crucial step towards environmentally sustainable production.

There are several modern methods for addressing purification challenges, with the most effective being the use of a wet sulfur removal scrubber. This device is specifically designed to remove pollutants from industrial gases.
At the core of the unit is its column. The incoming stream enters the equipment housing, where a liquid phase is sprayed inside via specialized nozzles, ensuring uniform distribution. This promotes contact between the phases. Typically, airstream enters at the tower's base and ascend, while liquid is sprayed from above and descends, creating a counterflow. This enhances both the duration and intensity of phase contact. The example describes a vertical design, but there is also a horizontal sulfur oxide scrubber which is more compact and suitable for indoor applications.

During purification, contaminated gas dissolves in the liquid, where its components undergo chemical or physical interactions. Clean air exits the apparatus, passing through a droplet separator before being discharged into the environment or reintroduced indoors. Undesirable components remain inside in a neutralized state. The resulting solution, now containing not only initial reactants but also reaction by-products, is collected in a reservoir and can be recirculated, further purified, or disposed of appropriately.

Typically, water or a mixture thereof with specific reagents is used as the scrubbing solution, tailored individually to the pollutant at hand. In caustic scrubber sulfuric acid systems, for instance, solutions of sodium hydroxide, lime, or limestone are employed due to their effective interaction with sulfur-containing pollutants.

Additionally, sulfuric acid scrubber design may incorporate packing or grids to enhance the contact area between gases and liquid. The efficiency of purification depends significantly on the contact time, droplet size, and the chemical composition of the contaminants involved.

Let's take a closer look at some specific examples of devices and their features.
As mentioned earlier, special packing is often used in a sulfur gas scrubber. This packing consists of large or small bodies with specific shapes that collectively form the filler material for the column. The optimal parameters, shape, size, and quantity of the material are calculated based on the specific task, required efficiency, and operating conditions. This filler is placed on a grid with small holes or on a mesh made of intersecting rods arranged at right angles. The grid is designed so that its openings are smaller than the packing size, preventing it from falling to the bottom of the apparatus.

There are several main types of packing. Raschig rings are one of the most commonly used types for a sulfur scrubber. These ceramic rings with holes enhance the mixing efficiency of gases and liquids and provide a large contact surface area. Additionally, other types of the material used by sulfur scrubber companies include partition rings, cross-partition rings, Berl saddles, Pall rings, Intalox rings, and Torch-Air rings. Each of these media has unique characteristics and is chosen based on the specific requirements of the equipment.

Additionally, the material can be applied in two configurations.

• Structured packing has a uniform shape and size, ensuring even distribution of liquid and creating a stable air flow through the scrubber. This type of media includes various plates, as well as spherical and ring-shaped bodies.
• Random packing features non-uniform shapes and sizes, promoting an unstable gas and liquid flow within the device. This results in more complex phase interactions and can be more effective for certain types of pollutants. Random packing includes mesh materials, porous elements, or a heterogeneous mix of different structured packing.

Here are some examples of effective models from Torch-Air for removing sulfur-containing impurities, utilizing random packing:

These models also differ in column orientation. The first two have a vertical design, while the latter two have a horizontal design. Horizontal bodies with sludge removers along the bottom edge reduce the likelihood of clogging the air inlet pipes. This design is recommended for applications with high foam-forming sludge.

Let's delve into another type of chemical plant sulfur scrubber: the Venturi scrubber. This equipment is employed for purging impurities from gas streams. Its defining structural feature is the conical narrowing section known as the Venturi tube. The contaminated mixture enters the device where liquid (either water or a reagent solution) is concurrently injected into the gas stream via nozzles or a spray system, generating a mist that breaks the liquid into droplets. Subsequently, the mixture passes through the narrowing section of the apparatus. Here, due to changes in gas velocity and pressure within the Venturi tube's narrow section, condensation and agglomeration of contaminants occur. These are then collected in the liquid phase. Cleaned air exits the equipment, while the contaminated liquid undergoes further treatment or disposal.

A sulfur scrubber pricelist from manufacturers often features spray tower models. These systems rely on specialized spray towers distributed evenly throughout the device's interior. Water is delivered through them, forming a fine film on the inner surfaces. This process facilitates vigorous mixing of gases and liquids, effectively removing pollutants from the air stream. Such a design of hollow spray tower units is highly efficient and widely adopted across various industries for purifying emissions before their release into the atmosphere.

Sulfuric acid tank vent scrubber is designed to treat vapors emitted from storage tanks. Such tanks often contain hazardous chemicals or materials capable of releasing them. One example includes tanks used for storing and transporting sulfuric acid. Therefore, tank ventilation scrubbers effectively capture and neutralize sulfuric acid vapors that may be emitted during storage.

The operational principle of this equipment is akin to that of other wet devices. Gas from the tank passes through a ventilation system into the unit, where volatile acid vapors come into contact with an alkaline reagent solution and are neutralized. This process prevents the escape of hazardous chemical gases into the environment, ensuring that only clean air is allowed to exit freely.

Reducing sulfur dioxide emissions from power plants is critical for meeting environmental standards. Sulfur dioxide is a primary pollutant released during fuel combustion, contributing to acid rain and health issues. The implementation of scrubbing equipment significantly mitigates these emissions.

Unlike other industrial sectors where SO₂ emissions may vary, power plants face distinct challenges due to large-scale coal combustion and high pollutant concentrations in exhaust gases. Power plant air purifiers are specifically engineered to operate under varying temperatures and pressures, ensuring effective sulfur removal, which is essential for this application.

In this field, wet scrubbers with lime solutions are widely used. Solutions of caustic soda, limestone, or oxidizers like hydrogen peroxide can also be utilized. Venturi scrubbers effectively remove sulfur from power plant flue gases by exploiting the changes in gas velocity and pressure within the Venturi tube, making this method another form of wet scrubbing. When wet methods are not desirable, dry adsorbers are employed. These use adsorbents such as activated carbon or sodium bicarbonate to capture sulfur gases. In some cases, a combination of wet and dry cleaning methods is used to enhance efficiency.

If you are unsure about the best type of scrubber for your facility, feel free to reach out to us. Our sulfur scrubber company offers expert consultation tailored to your needs.