Venturi scmbbers

Venturi scmbbers can be operated at 2.5 kPa (19 mm Hg) to coUect many particles coarser than 1 p.m efficiently. Smaller particles often require a pressure drop of 7.5—10 kPa (56—75 mm Hg). When most of the particulates are smaller than 0.5 p.m and are hydrophobic, venturis have been operated at pressure drops from 25 to 32.5 kPa (187—244 mm Hg). Water injection rate is typicaUy 0.67—1.4 m of Hquid per 1000 m of gas, although rates as high as 2.7 are used. Increasing water rates improves coUection efficiency. Many venturis contain louvers to vary throat cross section and pressure drop with changes in system gas flow. Venturi scmbbers can be made in various shapes with reasonably similar characteristics. Any device that causes contact of Hquid and gas at high velocity and pressure drop across an accelerating orifice wiU act much like a venturi scmbber. A flooded-disk scmbber in which the annular orifice created by the disc is equivalent to a venturi throat has been described (296). An irrigated packed fiber bed with performance similar to a... 

Decomposition by Caustic Scrubbing. The waste gas stream is led through packed towers where a sodium hydroxide solution is introduced at the top of the towers. Venturi scmbbers can also be used. Makeup sodium hydroxide is added under pH control (32). 

Venturi scrubbers. In a venturi scmbber, a liquid jet issues from a nozzle. The jet induces cocurrent gas flow into the throat of the jet. Mass transfer takes place between the gas and the atomized liquid downstream of the nozzle. Mass transfer is usually poor and depends on the throat velocity or pressure drop, the liquid/gas ratio, and the liquid atomization pattern. Because of the cocurrent nature of contacting, the maximum solute removal does not exceed a single theoretical stage. Venturi scmbbers are used primarily for separation of fine particulate matter or... 

Type of pollution control (e.g., venturi scmbber, baghouse). 

The overhead gases from the venturi scmbber are then passed tluough an additional particulate filter. The particulate filter medium constitutes a secondary waste stream from the venturi scmbber and is one of the larger secondary waste streams. The filtered venturi offgas is heated to 120°F to lower the relative humidity and then sent to the munitions demilitarization building HVAC, where it flows through activated carbon filters. ... 

Absorption processes are often technically realized in packed columns or, more scarcely, in tray columns. For chemical absorption, however, many other types of equipment are used in industiy, e.g., spray tower, venturi scmbber, bubble columns, etc. 

Venturi scmbbers, packed columns, ESP (dry and wet types), ejector scrubbers (Fig. 7.5). 

Packed towers are used for further scmbbing after the venturi scmbber. 

Scmbbers wash the particles out of the dusty gas by ava-riety of mechanisms, including contact with water droplets created by spray nozzles and breakup of hquid streams (venturi scmbbers) or contact with wetted solid surfaces. 

Typical mechanisms for aerosol removal from gas streams by filters are diffusion to surfaces, interception and impaction. Very large particles can be removed by gravitational settling. These mechanisms are quite dependent on the particle size and it is usually found that conventional filters have a minimum in filter efficiency for particles in a narrow size range less than 1 im. When the gas is hot relative to the filter, thermophoresis can enhance particle removal. When the aerosol laden gas stream contains elevated concentrations of steam that condenses within the filter, difflisiophoresis will enhance particle removal. These phoretic enhancements of filtration are attractive because filtration efficiencies by these mechanisms are not especially dependent on the aerosol particle size. Washed Venturi scmbbers involve the injection of water droplets into the aerosol laden gas and these water droplets act much like spray water droplets to remove aerosol particles. Electrostatic precipitation is, in principle, a very attractive decontamination process, but it is difficult to assure that the necessary power will be available to operate the precipitators under accident conditions. 

A separate scmbbing liquor circulation tank should be installed, on which the venturi scmbber can be mounted. 

If a completely separate tank is provided, it will need a U-seal for the gases which means some additional piping and separate civil foundations for the tank and venturi scmbber. 

Calculate the mass of particulates leaving the venturi scmbber using an overall efficiency of 99.0% ... 

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