Techniques of Air Pollution Control

Air Pollution is defined as the presence of certain substances in the form of particles or gases in concentrations high enough and for durations long enough to cause harm or undesirable effects. Most air contaminants originate from combustion or reduction processes.

Each year the numbers of possible sources increase rapidly with the accelerating trends of population growth, urbanization, industrialization and increased affluence.

Air pollutants are many and have differing physical and chemical characteristics, as also a vast number of sources. Common pollutants include dust, soot, ash, carbon monoxide, carbon dioxide, sulphur dioxide, oxides of nitrogen, hydrocarbons, chlorofluorocarbons (CFC), lead compounds, asbestos & cement dust, pollens, and radioactive rays.

The techniques of air pollution control is used to reduce the gaseous & particulate emissions of harmful substances that can affect not only human health but also the environment.

Therefore, a good understanding of the pollutants and their sources is necessary before a particular control technology is implemented and applied to any particular situation.

To effectively clean the pollutants would require an increased application of control procedures as well as the adoption of new techniques. The selection of control technologies depends on environmental, engineering, economic factors and pollutant type.

Latest techniques of air pollution control are:

  • Combustion – This method is applied when the pollutants are organic gases or vapours. The organic air pollutants are exposed to ‘flame or catalytic combustion’ when they are converted to less harmful product carbon dioxide and product water.
  • Absorption – In this technique, the polluted air containing gaseous pollutants is passed through a scrubber carrying a suitable liquid absorbent, which absorbs the harmful gaseous pollutants present in the air.
  • Adsorption – In this technique, the polluted air is passed through porous solid adsorbents kept in suitable containers. The gaseous pollutants are adsorbed at the surface of the porous solid, and clean air passes through.
  • Means of controlling particulate emissions -The air pollution caused by particulate matter such as dust, soot, ash, etc. can be controlled by using fabric filters, wet scrubbers, electrostatic precipitators, and certain mechanical devices, that work on the basis of the following:
    • Gravity – In this process, the particulate settles down by the action of gravitational force and gets removed.
    • Rapid change in the direction of air flow – This brings about separation of particles due to greater momentum.
    • Fabric Filters – The particulate matter is passed through a porous medium made of woven or filled fabrics. The particulate present in the polluted air is filtered and gets collected in the fabric filters, while the gases are discharged. The process of controlling air pollution by using
      fabric filters is called &’bag filtration’
    • Wet Scrubbers – They are used to trap SO2, NH3 and metal fumes by passing the fumes through the water.
    • Electrostatic Precipitators – When the polluted air containing particulate pollutants is passed through an electrostatic precipitator, it induces an electric charge on the particles, and then the aerosol particles get precipitated on the electrodes.

Thermax Group provides a range of engineering solutions that are sustainable and environmentally friendly in nature. Thermax is among the top five manufacturers of industrial pollution control equipment in India and offers innovative and sustainable solutions that solve problems of air pollution. They offer single-source expertise for several areas of protection of the environment. These include products and systems for air pollution control, services for equipment that specializes in dealing with gaseous and particulate emissions.

Thermax focuses on resource recovery which is advantageous to process focused industries and provides several customized products for controlling air pollution:

  • Ash control after combustion in Boiler: The ash being generated after combustion of Fossil fuel or any biomass like rice husk, wood chips, Bagasse, Spent Wash, Palm Fiber, Empty fruit bunch (EFB), Coal, Anthracite, Lignite, inside a Boiler is called as Suspended Particulate Matter (SPM). This ash creates various size of particulates that are emitted from the Stack or Chimney after the Boiler. To control this SPM (ash) of variety suitable Air Pollution control device are selected like Electrostatic Precipitator (ESP), Pulse Jet bag Filter (PJBF), Scrubber, High Efficiency Cyclone, Electrostatic Fabric Filter(ESFF). Major industry that needs to focus like Power, Textile, Food, Brewery, Agro, Palm, Edible Oil, Cement, Steel, Sponge Iron.
  • Fume Extraction and De-dusting Systems – These systems are installed to seize fumes from all kind of electric arc (EAF), induction, ladle, submerged arc furnace. The right product and solution that will help protect the environment and safe disposal can help attain clean air in the operating zone. The process is completely safe and takes place without formation of dust or deposition due to the optimized air velocity in these systems. Major industries are Secondary steelmaking from Sponge Iron, Scrap, Alloy steel, Steel Rolling, Continuous Casting Machine, Ferroalloy like Ferro-manganese, Ferro Silicate, Ferro Chrome, Cast House, Stock House, Gas Cleaning
    plant etc.
  • Pushing Emission Control Systems – These systems control emissions that are produced from hot coke being discharged from an oven of a coke battery from the beginning of the discharge to the time the coke reaches the quenching station. This system is designed to capture solid emissions that result from coke pushing and cleans
    them. Major Industry are primary Steel Making.
  • Flue Gas Desulphurisation [FGD] – Oxides of Sulphur (SOx) adversely affects the environment. Desulphurisation helps in reducing the harmful effects of SOx through dry, semi-dry and wet systems. Major Industries Power plant, Glass furnaces, Oil Fired boiler and Turbines
  • Sinter Plant and Pellet Plant De-Dusting – Sintering is the process that is conducted to fuse the constituent materials of iron ore to make a single porous mass that can be used in a blast furnace. Pelletizing is used to turn fine iron-ore grains into pellets that can be used in blast furnaces and are suitable for direct reduction
  • Coal Preparation Plants – These plants consist of equipment for storing and handling raw coal. They also have a section for pulverizing, grinding, drying and collection of coal through a bag filter.Coal preparation plants convert coal to fine dust for faster combustion inside the Blast Furnace. It also can replace the use of Coking Coal thereby making it safe and at times cost-effective solution to be used by major steel plants, Cement plants for firing in Kiln Thermax is one of the rare chemical companies in Pune that offers all these efficient and eco-friendly services under one roof. This makes them reliable partners who provide solutions to critical energy challenges of their clients.
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