Spray Tower Scrubber: Design, Operation, Models, and Calculation

The simplest wet scrubbing device is the spray tower scrubber or spray chamber scrubber. It is designed for capturing coarse dust particles larger than 10–15 µm, as well as for cooling and conditioning. The specific liquid consumption is low — from 0.5 to 8 liters per cubic meter of cleaned air. It is effective for eliminating odors, sulfur compounds, phenol, formaldehyde, and other impurities.

The spray tower scrubber design features a cylindrical vessel equipped with inlet and outlet pipes for the flow of air, along with nozzles or sprayers for liquid distribution. One or more tiers of nozzles for spraying the wash fluid are located in the upper part of the housing. The fluid, with droplet sizes of 0.025 – 0.04 inches, effectively washes the gas being cleaned, which moves countercurrently (from bottom to top) at a velocity of 2.3 – 5 ft/s. At higher velocities, moisture carryover occurs, and dust deposits on the internal surfaces of the scrubber's outlet pipe.

The spray tower wet scrubber working principle involves the injection of liquid at high pressure through special nozzles, creating a mist in which pollutants are absorbed. The cleaned air is then discharged from the system.

Spray scrubbers are widely used in various industries, such as energy, chemical production, and steel manufacturing, to ensure compliance with environmental standards and reduce the negative impact on the environment.

Spray scrubbers are classified based on the direction of gas and liquid flow into counter-current, co-current, and crossflow types. The simplest type of hollow scrubber spray tower is the irrigated flue, which features a series of nozzles or sprayers installed in a gas pipeline or smokestack to create water curtains in the path of the dust-laden stream. To avoid significant droplet carryover, the air flow velocity in the irrigated flue should not exceed 3 m/s. The washing chamber is typically made of metal, reinforced concrete, or brick. Inside the chamber, sprayers are arranged in several rows to create water curtains along the path of the gas being cleaned.

A classic hollow scrubber has a central hollow opening through which water or another solvent passes. Nozzles are evenly distributed across the entire surface of the device, spraying liquid into fine droplets that interact with the gases. This interaction causes a physical-chemical reaction between the pollutants and the liquid, resulting in either the precipitation or dissolution of harmful substances. The cleaned air is then discharged from the device.

A Venturi-type hollow scrubber is an effective solution for removing dust, soot, smoke, and aerosols. This technology operates based on the Venturi principle. The core of the system is a Venturi nozzle, into which dust-laden gas is introduced at the constricted section (the throat) and liquid is injected through centrifugal nozzles for washing. As the gas accelerates in the throat, dust particles are captured by the droplets due to their mass, the large surface area of the droplets, and the high relative speed between the droplets and the dust particles in the throat.

The cleaning efficiency largely depends on the uniform distribution of the liquid across the throat's cross-section. Venturi equipment is widely used in industries to remove pollutants such as sulfur dioxide or nitrogen oxides.

The high-pressure wet scrubber venturi spray tower can capture particles as small as 0.5 µm and larger.

The Venturi scrubber quench tower is designed to rapidly cool and neutralize exhaust before it enters the main filtration system.

The type of irrigation depends on the wet scrubber spray tower design.

Note: 1 – distribution plate; 2 – groove with side slits; 3 – groove with long tubes; 4 – multi-tube sprayer; 5 – perforated cup; 6 – slot sprayer; 7 – socket sprayer; 8 – multi-cone sprayer; 9 – spraying star.

For the design calculation of a spray tower scrubber, the following parameters need to be considered:

• Gas Flow Rate (Q): Determines the size of the chamber and the efficiency of cleaning.
• Pollutant Concentration: Affects the choice and consumption of the washing solution.
• Air Velocity: Should be optimal for effective phase contact.
• Chamber Diameter: Calculated based on the volume and velocity of the air flow.
• Spray Zone Height: Must provide sufficient phase contact time for complete cleaning.
• Liquid Droplet Velocity: Affects the efficiency of pollutant absorption.
• Mass Balance: Determines the required amount of fluid for pollutant absorption.
• Hydraulic Resistance: Important for selecting fans and pumps.

Key parameters for equipment calculation include the gas flow volume, pollutant concentration, type of fluid used, and cleaning efficiency.