Venturi scrubber Totally Explained

Everything about Venturi Scrubber totally explained

A venturi scrubber is designed to effectively use the energy from the inlet gas stream to atomize the liquid being used to scrub the gas stream. This type of technology is a part of the group of air pollution controls collectively referred to as wet scrubbers. Venturi devices have also been used for over 100 years to measure fluid flow (Venturi tubes derived their name from Giovanni Battista Venturi, an Italian physicist).
   About 35 years ago, Johnstone (1949) and other researchers found that they could effectively use the venturi configuration to remove particles from gas streams. Figure 1 illustrates the classic venturi configuration.
   A venturi scrubber consists of three sections: a converging section, a throat section, and a diverging section. The inlet gas stream enters the converging section and, as the area decreases, gas velocity increases (in accordance with the Bernoulli equation). Liquid is introduced either at the throat or at the entrance to the converging section.
   The inlet gas, forced to move at extremely high velocities in the small throat section, shears the liquid from its walls, producing an enormous number of very tiny droplets.
   Particle and gas removal occur in the throat section as the inlet gas stream mixes with the fog of tiny liquid droplets. The inlet stream then exits through the diverging section, where it's forced to slow down.
   Venturis can be used to collect both particulate and gaseous pollutants, but they're more effective in removing particles than gaseous pollutants.
    Liquid can be injected at the converging section or at the throat. Figure 2 shows liquid injected at the converging section.

Maintenance problems

The primary maintenance problem for venturi scrubbers is wear, or abrasion, of the scrubber shell because of high gas velocities. Gas velocities in the throat can reach speeds of 430 km/h (270 mph). Particles and liquid droplets traveling at these speeds can rapidly erode the scrubber shell.
   Abrasion can be reduced by lining the throat with silicon carbide brick or fitting it with a replaceable liner. Abrasion can also occur downstream of the throat section. To reduce abrasion here, the elbow at the bottom of the scrubber (leading into the separator) can be flooded (for example filled with a pool of scrubbing liquid). Particles and droplets impact on the pool of liquid, reducing wear on the scrubber shell.
   Another technique to help reduce abrasion is to use a precleaner (for example, quench sprays or cyclone) to remove the larger particles.
   The method of liquid injection at the venturi throat can also cause problems. Spray nozzles are used for liquid distribution because they're more efficient (have a more effective spray pattern) for liquid injection than weirs. However, spray nozzles can easily plug when liquid is recirculated. Automatic or manual reamers can be used to correct this problem. However, when heavy liquid slurries (either viscous or particle-loaded) are recirculated, open-weir injection is often necessary.

Summary

Venturi scrubbers can have the highest particle collection efficiencies (especially for very small particles) of any wet scrubbing system.
   They are the most widely used scrubbers because their open construction enables them to remove most particles without plugging or scaling. Venturis can also be used to absorb pollutant gases; however, they're not as efficient for this as are packed or plate towers.
   Venturi scrubbers have been designed to collect particles at very high collection efficiencies, sometimes exceeding 99%. The ability of venturis to handle large inlet volumes at high temperatures makes them very attractive to many industries; consequently, they're used to reduce particulate emissions in a number of industrial applications.
   This ability is particularly desirable for cement kiln emission reduction and for control of emissions from basic oxygen furnaces in the steel industry, where the inlet gas enters the scrubber at temperatures greater than 350 °C (660 °F).
   Venturis are also used to control fly ash and sulfur dioxide emissions from industrial and utility boilers.
The operating characteristics of venturi scrubbers are listed in Table 1.

Table 1. Operating characteristics of venturi scrubbers
Pollutant	Pressure drop (Δp)	Liquid-to-gas ratio (L/G)	Liquid-inlet pressure (p_L)	Removal efficiency
Gases	13-250 cm of water (5-100 in of water)	2.7-5.3 l/m³ (20-40 gal/1,000 ft³)	< 7-100 kPa (< 1-15 psig)	30-60% per venturi, depending on pollutant solubility
Particles	50-250 cm of water (50-100 cm of water is common) 20-100 in of water (20-60 in. of water is common)	6.7-13.4 l/m³(50-100 gal/1,000 ft³)	< 7-100 kPa (< 1-15 psig)	90-99% is typical

Bibliography

Anderson 2000 Company. Venturi scrubbing equipment. Engineering Manual with Operating and Maintenance Instructions. Atlanta: Anderson Company.

Bethea, R. M. 1978. Air Pollution Control Technology. New York: Van Nostrand Reinhold.

Brady, J. D., and L. K. Legatski. 1977. Venturi scrubbers. In P. N. Cheremisinoff and R. A. Young (Eds.), Air Pollution Control and Design Handbook. Part 2. New York: Marcel Dekker.

Buonicore, A. J. 1982. Wet scrubbers. In L. Theodore and A. J. Buonicore (Eds.), Air Pollution Control Equipment, Design, Selection, Operation and Maintenance. Englewood Cliffs: Prentice-Hall.

Calvert, S. 1977. How to choose a particulate scrubber. Chemical Engineering. 84:133-140.

Johnstone, H. F., and M. H. Roberts. 1949. Deposition of aerosol particles from moving gas streams. Industrial and Engineering Chemistry. 41:2417-2423.

Kelly, J. W. 1978, December 4. Maintaining venturi-tray scrubbers. Chemical Engineering.

McIlvaine Company. 1974. The Wet Scrubber Handbook. Northbrook, IL: McIlvaine Company.

Richards, J. R. 1995. Control of Particulate Emissions (APTI Course 413). U.S. Environmental Protection Agency.

Richards, J. R. 1995. Control of Gaseous Emissions. (APTI Course 415). U.S. Environmental Protection Agency.Further Information

Get more info on 'Venturi Scrubber'.

External Link Exchanges

Do you know how hard it is to get a link from a large encyclopaedia? Well we're different and will prove it. To get a link from us just add the following HTML to your site on a relevant page:

<a href="http://venturi_scrubber.totallyexplained.com">Venturi scrubber Totally Explained</a>

Then simply click through this link from your web page. Our crawlers will verify your link, extract the title of your web page and instantly add a link back to it. If you like you can remove the words Totally Explained and embed the link in article text.
As long as your link remains in place, we'll keep our link to you right here. Please play fair - our crawlers are watching. Your site must be closely related to this one's topic. Any kind of spamming, dubious practises or removing the link will result in your link from us being dropped and, potentially, your whole site being banned.