India produced 129.09 million tons more fly ash in the first half of 2019–20 than it did in the same period in 2018–19 (93.26 million tons vs. 120.9 million tons). Fly ash, also known as flue ash, coal ash, or pulverised fuel ash, is the collective name for the particulates (fine particles of burned fuel) and flue gases that are ejected out of coal-fired boilers. In contemporary coal-fired power plants, fly ash is often collected by electrostatic precipitators or other particle filtration equipment before the flue gases reach the chimneys. Bottom ash is the term used to describe ash that settles to the bottom.
A Fly Ash Is Exactly What?
• Ash is produced each time a solid material burns. Fly ash is one such deposit that ascends into the atmosphere with the gases.
• A very little particle called fly ash spreads widely across the atmosphere.
• 90% of India's installed thermal power generation capacity is coal-based, with the remaining 10% coming from steam, diesel, wind, gas, and other sources.
• Fly ash is typically finer than lime and Portland cement.
• Fly ash consists of silt-sized, frequently spherical particles between 10 and 100 microns in size.
Fly Ash - Constituents
• The main constituents of fly ash are assumed to be SiO2, Al2O3, Fe2O3, and maybe CaO.
• Fly ash solidifies as it floats in exhaust fumes.
• Many different minerals can also be found in fly ash. They consist of the iron oxide minerals hematite, magnetite, and/or maghemite, as well as quartz and mullite.
• Fly ash is divided into two classifications by the American Society for Testing and Materials: Class F and Class C.
• It differs depending on how much calcium, aluminium, and iron are present in each of them.
• The chemical makeup of the fly ash is significantly influenced by the chemical makeup of the coal that was burned.
Effects On The Environment
• Contamination of Groundwater: Most of the elements found in coal, which is a component of fly ash, are poisonous to both people and animals. These elements include arsenic, barium, boron, selenium, and mercury.
• Fly ash, which is created when coal is burned, may therefore contaminate groundwater.
• The type of enterprise involved and the nature of the thermal power plant discharge determine the influence of fly ash on the environment.
• This is due to coal's variable chemical makeup, which depends on the local geology.
• Therefore, the fly ash that will be spread over the topsoil will have an effect on the nearby plants and animals.
Worries About Exposure To Fly Ash
• Heavy metals and other compounds that are known to be detrimental to human health are present in significant concentrations in fly ash.
• Traces of coal that may be hazardous include arsenic, beryllium, cadmium, barium, chromium, copper, lead, mercury, molybdenum, nickel, radium, selenium, thorium, uranium, vanadium, and zinc.
• Hazardous substances, crystalline silica, and lime all pose exposure dangers to the environment and human health.
• Fly ash contains crystalline silica, which is known to cause lung problems when inhaled, most notably silicosis.
• Crystalline silica is a documented human carcinogen according to the US National Toxicology Programme and the IARC.
• Lung Damage: Due to the production of calcium hydroxide [Ca(OH)2], which is created when lime (CaO) and water (H2O) interact, fly ash has a pH range of 10 to 12, making it a mild to strong base. This can affect the lungs as well if it's present in high enough concentrations.
• Radiation: For a given amount of electricity generated, fly ash has 100 times higher radiation than nuclear waste kept in a dry cask or water.
• The material safety data sheets recommend a number of safety precautions when handling or dealing with fly ash.
• These include avoiding agitating the fly ash to lessen the amount that is released into the air as well as putting on protective gear including disposable clothing, goggles, and respirators.
• The National Academy of Sciences declared in 2007 that "the presence of high pollutant levels in some CCR (coal combustion residue) leachates may raise human health and ecological issues."
Why Does Fly Ash Contain Pollutants?
• Ash concentration ranges from 30-45% in low-grade coal used in thermal power generation.
• The low ash level of the imported high-grade coal is between 10% and 15%.
• Since low-grade coal makes up the majority of the fuel used in thermal plants, a sizable area must be set aside as a landfill or pond for the disposal of the ash that is produced.
• Fly ash is typically disposed of in ponds that are not well-maintained.
• As the temperature rises, fly ash dries out and becomes airborne.
• As a result, it becomes a significant source of water and air pollution.
• In addition to contributing to a number of ailments, it decreases groundwater recharge.
• As a result, fly ash pollutes the air in communities near coal-fired power stations.
Applications For Fly Ash
• Building of Embankments: Fly ash is a rare material, yet it is utilized to construct embankments.
• Fly ash has a high homogeneity coefficient and clay-sized particle size.
• Engineering characteristics of fly ash embankments include compaction properties, shear strength, compressibility, permeability, and frost susceptibility.
• Stabilization of Soil: Stabilization of soil entails permanently altering the chemical and physical properties of the soil.
• The ability of a soil to contract and expand can be enhanced by the granular form of fly ash, allowing the development of subgrade pavements and foundations.
• Concrete for Asphalt Construction: Roads are typically paved with asphalt concrete, a composite material comprised of asphalt binder and mineral aggregate.
• Fly ash is widely used as a mineral filler in asphalt concrete mixtures to fill holes and establish contact points between larger aggregate particles.
• Waste stabilization and treatment: Fly ash can be used in combination with other alkaline materials to transform sewage sludge into organic fertilizer or biofuel due to its capacity to absorb water and alkalinity.
• Being a Catalyst Fly ash appears to function efficiently as a catalyst for converting polyethylene into a substance similar to crude oil when treated with sodium hydroxide in pyrolysis, a high temperature process used in wastewater treatment.
Moef Fly Ash Policy Measures
• All thermal power plants had until that point to guarantee 100% utilization in order to be in compliance.
• Later revisions issued in 2003 and 2009 raised the compliance deadline to 2014.
• According to the Central Electricity Authority in New Delhi, as of 2015, just 60% of the produced fly ash was being utilized.
• Due to this, the most current notification, released in 2015, established a new deadline of December 31, 2017.
• Only about 0.74% of the approximately 55.7% fly ash utilized is put to concrete, the majority of it (42.3%) is used to create cement.
• The use of fly ash-based products is required in all construction projects, road embankment works, and low lying land filling projects within a 100 km radius of a thermal power station, according to the Ministry of Environment and Forests.
• Additionally required was the use of fly ash in mine filling operations within a 50-kilometer radius of thermal power plants.
Mission of Management And Utilization
• In addition to monitoring the disposal of annual stock of unutilized fly ash, the Fly Ash Management and Utilization Mission will look at how 1,670 million tons of residual (accumulated) fly ash can be used in the least dangerous manner and how the power plants can implement all necessary safety measures.
• Aim: "Coordinate and monitor concerns related to the treatment and disposal of fly ash and associated difficulties" is its stated purpose.
• Agency Head & Nodal: Together with the chief secretaries of the individual states where the mission is being carried out, the mission will be jointly headed by the union's secretaries of coal and power and environment, forests, and climate change (MoEF&CC).
• Provisions: The new fly ash notification from December 2021 calls for the "forcing, monitoring, audit and reporting" of the advancement of fly ash utilization and implementation by coal thermal power plants and user agencies.
• The Notification assigns the CPCB and the State Pollution Control Boards (SPCB) / Pollution Control Committees (PCC) the duty of ensuring that its mandates are carried out properly.
• However, in addition to these statutory authorities, the Mission also grants the chief secretaries of the state’s extra authority over fly ash reduction.
• The Notification mandates that each thermal power plant post information on ash generation and use once per month on its internet portal.
Initiatives Relating To Fly Ash
• National Thermal Power Corporation: Earlier in 2021, NTPC (National Thermal Power Corporation Limited) published an EOI request for the sale of fly ash.
• Additionally, NTPC has supplied fly ash to cement manufacturers all around the country.
• Pradhan Mantri Awas Yojana: The Pradhan Mantri Awas Yojana (Urban) has strongly emphasized the use of modern, environmentally friendly construction methods, such as the use of fly ash bricks.
• State Governments: Maharashtra was the first state to announce its plans for utilizing fly ash. Even the state governments have since followed suit.
• For tracking the production and usage of fly ash, the government has released the "ASHTRACK" mobile application and web portal.
• Fly ash and associated products are now only subject to a 5 percent Goods and Services Tax (GST).
Researchers in India are working on activated pozzolanic cement such as geopolymer and fly ash as an additive for concrete to help achieve the goal of utilizing fly ash. Without a sure, the subject of increasing the quantity of fly ash used in concrete has the greatest potential. India produced 280 million tons of cement in 2016. Given that the housing industry utilizes 67 percent of the cement, there is a ton of opportunity for fly ash integration in both the expanding percentage of PPC and low to moderate strength concrete.