Question

Give details about some devices which are helpful in the reduction of pollution from industries.

Answer 1

1. Fabric filters: These are the devices which are used to capture and recycle the escaped gases from the engines. The particulate-containing gases are allowed to pass through the porous fabric bags, which act as filters. The particulate matter is trapped by the filter while the clean gases are passed out. This method works like common vacuum cleaners, which trap the dust. The dust collected in the fabric bags can be periodically shaken out of the bags. The efficiency of these filters is greater than 99%.
2. Cyclone separator: The particles present in the gas strike the walls of a cylindrical-shaped collector, from where they drop into a hopper at the bottom. The clean gas then comes out from the top of the collector.
3. Gravity settling chamber: This is the most basic technique for arresting particulate matter. It consists of a chamber in which dust is separated from gas by reducing gas velocity. The dust particles settle down and are removed. A settling chamber best serves as a pre-chamber to prevent logging of the main small particle collection.
4. Scrubbers: The air scrubbers remove pollutants from gas emissions. These scrubbers consist of a throat through which harmful gas and water both are passed at very high velocities where they get completely mixed, and hence, dust particles are removed. Dust particles surrounded by the liquid are carried to another cylinder. As the gas moves upwards, the liquid-covered particles drop from the gas in the contaminated liquid reservoir.
5. Electrostatic precipitator: This device removes suspended impurities like dust, mist, fumes, etc. from gases or air. An electrostatic precipitator is fitted on the exhaust pipes of the industries. When gaseous waste passes through these pipes, the pollutants are absorbed. This device can also remove very fine particles. But this is a very costly device, and it also needs regular cleaning. Electrostatic precipitators are extensively used in thermal power plants, pulp and paper industries, mining and metallurgical industries, iron and steel plants, and chemical factories.
6. Plate tower: This unit works on the principle of transforming gaseous pollutants to liquid phase. These devices are effectively used for the removal of gaseous pollutants. Their effectiveness depends on the solvent used during the transformation process.