Flue Gas Desulphurisation (FDG)

Syllabus: General Studies Paper 3

A recent study has found that not a single coal-based thermal power plant in West Bengal has installed flue gas desulphurisation (FDG), a technology to eliminate sulphur compounds from exhaust emissions.

• Plants that contribute to 40% of coal-based power generation capacity in the State have not yet been awarded the contracts for FDG units whereas the remaining power production facilities were not able to complete the installation of the technology within the allotted time frame.
• The total coal-based electricity generation capacity of plants in the State is 13,686 megawatts (MW). None of the major plants connected to the power grid has installed FGD units or direct sorbent injection (DSI) technology to control sulphur dioxide emissions.
• The country’s first emission norms for control of sulphur dioxide, nitrogen oxide, and mercury from coal-fired power plants were notified in December 2015 and since then the deadline for installation of pollution control equipment has been extended three times by the Ministry of Environment, Forest and Climate Change.
• Data from the Central Electricity Authority (CEA) shows that till February 2021, of the 600 units contributing the total thermal power of 211. 6 GW (gigawatts) in the country; only 20 units contributing 8.2 GW have installed FDGs.

Particulate Matter

• A significant portion of the overall Particulate Matter (PM) concentration in ambient air is made up of secondary particles, which are created when sulphur dioxide combines with other contaminants. 
• Well-known dangerous particulate matter PM2.5 causes millions of fatalities each year both globally and in India. 
• Controlling sulphur dioxide emissions from coal-based power plants at the source will significantly reduce the overall amount of air pollution in the State and beyond.

Flue Gas Desulphurisation(FGD)

• Flue-gas desulfurization(FGD) is a set of technologies used to remove sulfur dioxide (SO2) from exhaust flue gases of fossil-fuel power plants and from the emissions of other sulfur dioxide-emitting processes such as waste incineration.
• FGD systems may involve wet scrubbing or dry scrubbing.
• In wet FGD systems, flue gases are brought in contact with an absorbent, which can be either a liquid or a slurry of solid material. The Sulphur dioxide dissolves in or reacts with the absorbent and becomes trapped in it.
• In dry FGD systems, the absorbent is dry pulverized lime or limestone; once absorption occurs, the solid particles are removed by means of baghouse filters.

About Sulphur Dioxide

• It is an inorganic compound, heavy, colourless, and poisonous gas. It is produced in large quantities in intermediate steps of sulphuric acid manufacture.
• It has a pungent, irritating odour, similar to the smell of a just-struck match.
• In nature, it occurs in volcanic gases and in a solution of some water warm springs.
• Usually, it is prepared industrially by the burning in air or oxygen of sulphur or such compounds of sulphur as iron pyrite or copper pyrite.
• In large quantities, sulphur dioxide is formed in the combustion of sulphur-containing fuels.
• It can combine in the atmosphere with water vapour to form sulphuric acid which is a major component of acid rain.
• Under moderate pressures at room temperatures, sulphur dioxide can be liquified and the liquid freezes at -73 degree Celsius and boils at -10 degree Celsius under atmospheric pressure.

Sulphur Dioxide uses are:

• It is used in the preparation of sulphuric acid, sulphur trioxide, and sulphites.
• It is also used as a disinfectant.
• It is used in a refrigerant, a reducing agent, a bleach, and food preservation mainly in dried fruits.

Sulphur Dioxide (SO2) and Air Pollution:

• SO2 emissions are a significant contributor to air pollution. High concentrations of SO2 in the air generally lead to the formation of other Sulfur Oxides (SOx).
• SOx can react with other compounds in the atmosphere to form small particles. These particles contribute to Particulate Matter (PM) pollution.
• Small particles may penetrate deeply into the lungs and in sufficient quantity can contribute to health problems.
• Air Pollution is a huge public health concern, with 91% of the world’s population living in areas where outdoor air pollution exceeds guideline limits by the World Health Organization (WHO) and as a result, 4.2 million people die prematurely every year.
• The greatest source of SO2 in the atmosphere is the burning of fossil fuels in power plants and other industrial facilities.
• Other sources include industrial processes such as extracting metal from ore, natural sources such as volcanoes, and locomotives, ships and other vehicles and heavy equipment that burn fuel with high sulphur content.

Question: Define Flue Gas Desulphurisation. Why is it important to installed in thermal power station? Also shed the light on government guidline about it.