Q1: Which of the following equipments is used for liquid dispersion ?

ANS:B - Venturi scrubber

A Venturi scrubber is a type of air pollution control device used to remove particulate matter and aerosols from industrial exhaust gases or flue gases. It operates on the principle of gas-liquid contact and utilizes the Venturi effect to achieve efficient particle removal. Here's how a Venturi scrubber works:

1. Principle of the Venturi Effect: A Venturi scrubber consists of a converging section, a throat, and a diverging section. As the exhaust gas flows through the converging section, its velocity increases while the pressure decreases due to the constriction of the flow area. This creates a low-pressure zone in the throat of the scrubber.
2. Introduction of Liquid: A liquid (usually water) is introduced into the Venturi scrubber either at the throat or at the entry point of the converging section. The liquid is typically sprayed or atomized into the gas stream in the form of fine droplets.
3. Gas-Liquid Contact: The high-velocity gas stream entrains the liquid droplets, causing them to collide with the particulate matter and aerosols present in the gas stream. This collision results in the capture of the particles by the liquid droplets through mechanisms such as impaction, interception, and diffusion.
4. Particle Removal: The gas-liquid mixture containing captured particles then passes through the throat of the Venturi scrubber, where the high-velocity gas stream helps to disperse the liquid droplets and particles evenly throughout the gas stream. This increases the chances of particle capture by the liquid droplets.
5. Separation of Captured Particles: The gas-liquid mixture containing captured particles then enters a separation chamber or demister section, where the liquid droplets are separated from the gas stream. This can be achieved through gravity settling, centrifugal force, or the use of demister pads.
6. Clean Gas Discharge: The cleaned gas is discharged from the Venturi scrubber, while the captured particles are collected in a liquid reservoir or removed from the system for further treatment or disposal.

Venturi scrubbers are widely used in various industries, including power plants, chemical plants, and manufacturing facilities, to control emissions of particulate matter and aerosols and to comply with environmental regulations. They are effective for removing fine particles, especially those with diameters less than 10 micrometers (PM10), from gas streams. However, they may not be as efficient for removing gases or vapors.