In the early years of thermal energy, coal-fired power plants used to release the entire fly ash (almost 25-30% of pulverized coal by weight) along with the smoke into the atmosphere via their enormous chimneys. A few years back, strict regulations on managing coal-combustion waste came into effect in an attempt to combat pollution, and hence people had to explore various commercial applications of fly ash.

Today fly ash is used in so many industrial and commercial applications this has become a complete industry by itself.

• Brick making: Interestingly, fly ash bricks were invented by 2 Indian inventors, who used lime, fly ash, and gypsum to create a brick that did not need natural clay at all. Their process also did away with the requirement for kiln firing. Today, the fly ash bricks industry in India is projected to grow at a compound annual growth rate (CAGR) of around 7% by 2026.One of the best qualities of fly ash is that it has excellent insulation capability. Since it also absorbs much less heat than clay bricks, fly ash bricks are considered a more energy-efficient as well as an eco-friendly option. Fly ash bricks come in several load-bearing grades, and to encourage and ensure consistency of quality, the Indian Standard, IS 16720: 2018 has been formulated for the same. According to their official statement, “The standard lays down essential requirements of finish, dimensions, strength, water absorption, etc. with a view to achieving quality and uniformity in the manufacture of such bricks.”

 

• Cement: Fly ash is a pozzolanic substance, which means it contains silicates and aluminum compounds that turn into cement when combined with water. When fly ash is added to the concrete as a partial replacement for cement, it can improve the durability and strength of the concrete. This is because the cementitious compounds in fly ash react with the calcium hydroxide in the concrete to form additional cementitious compounds, which fill in the gaps in the concrete and make it stronger.Moreover, using fly ash as a partial replacement for cement has several environmental benefits. First, it reduces the amount of cement needed in concrete, which in turn reduces the demand for natural resources like limestone and clay that are used to make cement. Second, fly ash is a waste product that would otherwise be sent to landfills, so using it in concrete reduces the amount of waste that needs to be disposed of. Third, using fly ash in concrete reduces the amount of CO2 emissions associated with cement production, which is a major contributor to greenhouse gas emissions.

 

• Roads and Embankments: If fly cement is used in road construction, it allows for much-reduced permeation of concrete, which keeps the aggressive expansive minerals from damaging the concrete from the inside. Also, since it is lighter than traditional concrete, it causes lesser settlements. Fly Ash is particularly relevant in making stabilization projects and embankments over places with weak sub-soils, as it puts lesser pressure on the retaining walls.

 

• Mine Backfilling: When areas are mined, and exhausted, backfilling is required to reclaim that land, otherwise, such vast tracts of land will be rendered useless. Since mines require deep or shallow excavation, mostly in embedded carbonate rocks, they leave behind numerous hollows and shafts. If these gaps are not filled in properly they may open up large sinkholes or elongated fractures or other deformations in the future. To avoid such calamities that could possibly affect human lives, it is important to fill the mines with a material that is the ability to fill tight spaces, has a high resistance to water permeation or compression, and is eco-friendly.Fly ash has all these qualities and lends itself beautifully as a filler for Mine Void Filling.

 

• Fly ash Coagulant: Water pollution is one of the biggest ecological concerns today. If on one hand, we encourage rapid industrialization, which results in greater productivity, and therefore more effluents and pollutants, then we must also have measures to manage these wastes so that we are able to reduce our carbon footprint and protect our environment. Fly has proved useful in Wastewater Treatment, where modified or activated fly ash acts like a coagulant and traps and absorbs various types of organic compounds. Textiles, Handmade paper, Tanning & Dyeing etc. are all industries that benefit from using Fly in significantly reducing their contribution towards wastewater.

 

The Indian economy has seen enormous economic growth in terms of infrastructure development and manufacturing. Given the number of natural resources that will be used in either creating this infrastructure or in the services provided by them, it is very important that environment-friendly, cost-effective options be considered very seriously.  The Fly Ash industry has received a lot of impetus from the government, but if more and more people are educated about its benefits and enough attention is directed to its positive ecological impact, we are pretty sure that fly ash will see a lot of research and technological innovation in the coming years.

The term “green coal” may sound like an oxymoron, but it’s a viable form of renewable energy.

In recent years, green coal has become increasingly popular among businesses and individuals as an alternative energy source. But what is green coal, and how is it different from traditional coal?

In this blog post, we’ll explore the mysterious world of green coal and uncover the facts you need to know.

What is green coal?

Green Coal is a type of eco-friendly coal briquette made from Biowaste or Municipal Solid Waste,. Burning Green Coal decreases sulfur emissions by large while boosting combustion efficiency. Using biochar in the production process qualifies as a renewable energy source, as it replaces fossil fuels.  Green coal is an innovative technology that can help reduce the environmental impact of burning coal while still producing usable energy. It is a form of clean coal technology that involves segregation, mixing & Heating processes to convert municipal waste into charcoal.

It is produced by using heating MSW inside rotating cylinders.  This process converts a variety of organic materials, such as municipal solid waste, into a high-energy, low-ash, low-sulfur coal substitute.

It is often called ‘clean’ coal, as it produces fewer toxic emissions than ordinary coal. It can substantially reduce air pollution from coal-fired power plants. In addition, green coal can help reduce the cost of electricity generation, as it is much more efficient than traditional coal-fired plants.

The technology behind green coal is still relatively new, but it is gaining traction in the energy industry. Many countries are investing in green coal technologies to reduce reliance on traditional coal-fired power plants. This is because green coal has the potential to provide a cleaner, cheaper, and more reliable source of energy.

Green coal is a promising form of clean coal technology that can reduce the environmental impact of burning coal while still providing usable energy. It is still in its early stages, but it has the potential to revolutionize the energy industry and help reduce the environmental impact of coal burning.

How Green coal is produced?

Green coal is produced by Waste to coal (WTC) facilities using the Heating process. The process begins with the conversion of Raw waste into Refused Drive Fuel (RDF). They are heated into Reactor. During this process, it breaks down the RDF  molecules and converts them into liquid fuels and Charcoal. Liquid fuels are used as an energy source to heat the dryer & reactor and Charcoal l is used to produce green coal.

The reaction inside the Reactor is relatively simple and cost-effective. The process does not require any chemical additives or hazardous processes and is much more efficient than traditional coal-burning processes. In addition, green coal is produced from waste materials, which are available in abundance, making it a much more sustainable energy source.

How is green coal different from traditional coal?

Green coal differs from traditional coal in its production and use.

Traditional coal production methods involve coal extraction from mines, which can lead to the destruction of natural habitats and release pollutants such as sulfur and nitrogen oxides, particulate matter, and carbon dioxide (CO2).

In contrast, green coal is produced through processes such as Waste to coal (WTC) which makes it environment-friendly and cost-effective.

Green coal can be used in various applications such as power generation, steel plants,  dying industries, cement industry, and industrial use more cleanly and efficiently than traditional coal.

Applications of green coal

Power Generation

In power generation, green coal can be used to generate electricity more cleanly and efficiently than traditional coal-fired power plants.

Industrial use

Green coal can also produce chemicals, fertilizers steel, cement, and other industrial products.

Conclusion

Green coal is a clean and efficient way of utilizing waste resources while minimizing the negative environmental impact. It can be used in various applications such as power generation, steel, cement, and industrial use, making it a valuable addition to the energy mix as we transition to a more sustainable future.

While it may have its challenges, such as cost, the scale of production, and environmental impact, the potential benefits of green coal must be addressed, and further research and development are needed to make it a viable option in the long term.

Frequently Asked Questions (FAQs)

What is green coal?

Green coal, also known as clean coal, is a term used to describe coal produced in a way that is more environmentally friendly than traditional coal production methods.

What are the challenges and limitations of green coal?

One of the main challenges is the cost of production. The equipment and technology required for green coal production are expensive, making it difficult for countries with limited financial resources to adopt this technology.

Is green coal a renewable energy source?

Green coal can be considered a renewable energy source because it is not a fossil fuel, meaning it is a renewable resource. Green coal production methods aim to reduce emissions and pollutants associated with traditional coal mining and use, making it a cleaner and more environmentally friendly option than traditional coal.

 

Excessive mining activities and deforestation cause a rise in global temperatures and release large amounts of CO2, which pose a significant threat to life on our planet. As a result, many countries are shifting towards eco-friendly ways of energy management and carbon-neutral methods of energy production. One such method that has gained a lot of attention recently is Green Coal technology.

Green coal, also known as bio-coal is an eco-friendly alternative to fossil fuels and is made from a combination of waste materials, such as agricultural residue and municipal solid waste (MSW). One of the key benefits of green coal is that it reduces the amount of CO2 emissions produced.

For example, using 1 kg of bio-coal as solid fuel, instead of fossil coal, can bring about a reduction of approximately 2 kg of CO2 produced per kg of fossil coal. This is a significant step in reducing the carbon footprint of industries that rely on fossil fuels, such as thermal power plants, petrochemical refining, cement plants, etc.

 

How is Green Coal made?

Waste-to-Coal plants turn municipal solid waste (MSW), often called garbage or trash, into the high calorific value of charcoal by means of a ‘Charcoal Reactor’,  which involves the thermal treatment of MSW at a temperature of 200-300°C, resulting in a solid fuel that has properties similar to fossil coal. Not only does bio-coal provide a sustainable and fossil-free alternative to traditional coal, but it also offers a solution to the problem of waste management.

The process of waste to energy starts with the collection of MSW from various sources such as households, institutions, and commercial establishments. The waste is then transported to an energy conversion facility, where it is sorted, processed, and treated to remove contaminants and impurities. The processed waste is then subjected to high temperatures which break down into volatile matter.

It is important to note that MSW contains a diverse range of materials that are not typically found in biomass feedstock, due to this reason, the process of Charcoal generation is more complex and requires a different approach to the process.

The charcoal that is discharged is further cleaned using a sieve. The pure char is mixed with exacting proportions of binder & water in a mixer. The mixture is then fed into a pelletizing machine, which creates pellets of Green Coal.

 

Why should fossil-fuel-consuming industries consider Green Coal?

• Cost-effective: Green coal is a renewable resource, which means that it is not subject to the same price volatility and supply chain issues as fossil fuels. It is produced from waste materials such as agricultural residue and municipal solid waste, which makes it a cost-effective alternative to fossil coal, which is becoming increasingly expensive.
• Reduced transportation costs: Since green coal can be produced locally, it reduces the need for long-distance transportation. This results in lower transportation costs and helps reduce carbon emissions associated with transportation. It is also easy to store and transport, as it is a solid fuel that can be stored and transported in bulk.
• Cleaner combustion: Green coal has a lower sulphur content compared to fossil coal, which makes it a cleaner fuel. This means that when it is burned, it produces fewer pollutants, such as sulphur dioxide and particulate matter.
• Improved waste management: The production of green coal provides a sustainable solution for waste management. It allows for the conversion of waste materials into a valuable energy source, reducing the amount of waste sent to landfills, etc.
• Utilisation of non-biodegradable components: Larger components nowadays in MSW are plastics including bottles & cans which take centuries to decompose. In this process, it gives an immediate solution as it is 100% broken into the volatile matter.
• Improved energy security: By using green coal, industries, and thermal power plants can reduce their dependence on fossil fuels, which are finite resources. This can help improve energy security and provide a more stable energy supply.
• Reduced environmental impact: Green coal has a lower carbon footprint and produces fewer pollutants than fossil coal. The production of green coal from MSW reduces greenhouse gas emissions and does not emit harmful pollutants.

Macawber Beekay has been making conscious and consistent efforts toward the protection of our environment so that CO2 emissions reduce significantly. We have done this by creating a better, sustainable alternative to fossil coal in the form of ‘Green Coal’. Though the waste-to-coal initiative is at a nascent stage, we are confident that our efforts are in the right direction & in line with India’s promise at the COP26 Glasgow summit on cutting its emissions to net zero by 2070.

We firmly believe that waste to energy will play an important role in shaping the future of the energy sector. The benefits of using green coal are many, and industries and thermal power plants can take advantage of them to reduce their environmental impact, lower their costs, and improve their energy security. By making the switch to this eco-friendly alternative, you too can help create a more sustainable future for generations to come.

Reach us today at https://www.mbl.in/greencoal to know more about Green Coal.

BROADLY SPEAKING, ALL ASH HANDLING SYSTEMS HAVE THE FOLLOWING SEQUENCE OF PROCESSES:

• Ash handling collection
• Ash Handling System Conveying
• Storage
• Dry or wet out-loading

Depending upon the quantity of fuel, type of boiler, the usability of ash, etc, the right ash handling systems are chosen to ensure the highest efficiency and utilization. Below are different types of boilers that determine the type of ash handling systems that need to be used:

1. Stoker Fired Boilers

Stoker firing is a power-operated fuel feeding mechanism and grate. This self-cleaning system allows for burning large quantities of fuel with ease, gives us greater control over the combustion process with higher efficiency. It also requires less labor of handling ash.

2. Atmospheric Fluidized Bed Combustor (AFBC)

FBC is atmospheric fluidized bed combustion, where the furnace pressure is atmospheric pressure. The combustion exhaust gas from the furnace goes through a cyclone, Bag Filters or ESP for arresting the ash particulates and are let out into the atmosphere. This kind of a system has comparatively lesser residence time, turbulence and lower combustion efficiency and lower desulfurization.

If there is less headspace under the boiler, then a mechanical dry bottom ash handling system is more suitable as it requires no water but still offers continuous ash removal, otherwise pneumatic ash handling may be used to convey ash out into an ash storage silo for interim holding prior to load out for disposal or reuse.FBC is atmospheric fluidized bed combustion, where the furnace pressure is atmospheric pressure. The combustion exhaust gas from the furnace goes through a cyclone, Bag Filters or ESP for arresting the ash particulates and are let out into the atmosphere. This kind of a system has comparatively lesser residence time, turbulence and lower combustion efficiency and lower desulfurization.

3. Circulating Fluidized Bed Combustor (CFBC) Boiler

In Circulating fluidized bed combustion boilers, the furnace is pressurized and the flue gas is re-circulated to capture the unburnt carbon, and to increase the thermal efficiency of the boiler, hence this is the next evolved version of the AFBC. CFBC boilers are particularly suitable for Indian coal as it has a higher percentage of ash than other types. Due to ash recirculation, the unburnt carbon percentage in exhaust gases can be reduced considerably, which in turn increases the quality of ash produced.

All fluidized combustors operate on either mechanical, pneumatic or a combination ash handling system, depending upon the type of fuel used, availability of ash disposal area, and the need for ash utilization.

4. Pulverized fuel Fired Boilers (PF Fired B)

In boilers with pulverized firing systems, about 80% of ash released is fly ash, and the rest gets collected as bottom ash. Since Indian coal has a significantly higher amount of ash, it needs an efficient ash handling system.

5. Waste Heat Recovery Boilers

WHRB boilers recover ‘waste’ heat, generated during the production process by way of fuel combustion or chemical reaction. This heat can be reused by supplementing it with additional heat to raise the boiler inlet gas temperature to a level commensurate with the desired steam conditions.

One of the biggest advantages of WHRB boilers is that they save a substantial amount of primary fuel that otherwise would have been consumed to generate the same amount of steam.

In the early years of thermal energy, coal fired power plants used to dispose-off entire fly ash in slurry form to ash dykes or otherwise, fly ash’s utilization avenues were not available. A few years back development of fly ash’s utilization technologies lead to strict regulations on managing coal-combustion waste to combat pollution and to maximise the applications of fly ash.

Today fly ash is used in so many industrial and commercial applications that it has become a complete industry by itself.

1. BRICK MAKING

Interestingly, a number of technologies are in vogue to manufacture good quality fly ashes bricks.  These are fly ashes-lime-gypsum, fly ash-cement, fly ash mineralization, fly ashes geopolymerization and fly ash-clay bricks, etc.  All types of fly ash bricks except fly ash-clay bricks, do away with kiln firing as well as requirement of clay. Today, India produces over 20 billion fly ash bricks per annum.

One of the best qualities of fly ashes are that it has insulation capability. Since it requires much less heat and energy to manufacture than clay bricks, fly ash bricks are energy-efficient as well as eco friendly. Fly ashes bricks come in several load-bearing grades, and to encourage and ensure consistency of quality, BIS has formulated standards and specifications for all types of fly ashes bricks. According to their official statement, “The standards lay down essential requirements of finish, dimensions, strength, water absorption, etc. in addition to quality of raw materials to be used with a view to achieve quality and uniformity in the manufacture of such bricks.”

2. CEMENT

Fly ashes are a pozzolanic material, it contains silicates & aluminates in amorphous form  and behaves like cement when combined with lime and water. Partial replacement of cement with fly ashes are not only a more viable prospect commercially, it also saves on naturals resources, reduces CO2 emissions and ensures longer durability.

3. ROADS AND EMBANKMENTS

If fly ash cement is used in construction of concrete roads, it reduces the permeability of concrete and also keeps the aggressive expansive minerals from damaging the concrete from the inside. Also, since fly ash is lighter than traditional soils, it causes lesser settlements. It is particularly relevant in stabilization projects and embankments over weak sub-soils.  Further, it exerts lesser pressure on the retaining walls.

4. MINE BACKFILLING

When areas are mined and exhausted, backfilling is required to reclaim that land, otherwise such vast tracts of land will be rendered useless. Since mines require deep or shallow excavation, they leave behind numerous hollows and shafts. If these gaps are not filled in properly, they may open large sinkholes or elongated fractures or other deformations in the future. To avoid such calamities that could possibly affect human lives, it is important to fill the mines with a material that has the ability to fill tight spaces, has a high resistance to water permeation or compression, and is eco-friendly.

Fly ashes has all these qualities and lends itself beautifully as a filler for Mine Void Filling.

5. FLY ASH COAGULANT

Water pollution is one of the biggest ecological concerns today. If on one hand we encourage rapid industrialization, which results in greater production, and therefore more effluents and pollutants, then we must also have measures to manage these wastes so that we are able to reduce our carbon footprint and protect our environment.

Fly ashes has proved useful in Wastewater Treatment, where modified or activated fly ashes traps and adsorbs various types of organic compounds. Textiles, Handmade paper, Tanning & Dyeing etc. are all industries that can benefit from using Fly ash in significantly reducing their contribution towards wastewater.

Indian economy has seen an enormous economic growth in terms of infrastructure development and manufacturing. Given the amount of natural resources that will be used in either creating this infrastructure or in the services provided by them, it is very important that environment-friendly, cost-effective options be considered very seriously. The Fly Ashes handling system industry has received a lot of impetus from the government, but if more and more people are educated about its benefits and enough attention is directed to its positive ecological impact, we are pretty sure that fly ashes will see a lot of research and technological innovation in the coming years.

Across the globe, countries that have presence in coal based plants, and therefore have huge coal ash production, are expressing interest in extracting value out of this potential gold “dust” mine, instead of just dumping it in landfills. India, which ranks 4th in the world in coal ash production, may possibly quadruple the quantum is fly ash generated when it switches to super critical technologies for thermal power. With that situation looming large in our near future, it is critical that countries fast track research on fly ashes utilisation.

Eventually, the choice for finding innovative uses for fly-ashes wins out in the end because not only does one minimize the harsh impact of fly ashes on the soil and ground water, but also helps in recycling an existing, and abundantly available resource that brings commercial benefits too.

Here are some of the ways that countries have found used Of fly ashes :

The use of one tonne of fly ashes replacement in cement production typically saves one tonne of CO2. Perhaps the most important advantage for cement firms, though, is that fly ash is about one-third the price of cement – which is why some cement companies and power plants have entered into joint venture projects to recover fly ash.

A team from the UWC University in South Africa has been trying to completely replace cement with fly ash. Their aim is to create a prototype that can turn fly ash lower-cost roof tiles, bricks, paving stones, building elements like lintels, fire-retardant panels and insulation material, which could offer important solutions in low-cost housing to replace chipboard and gypsum board, or so-called drywall, which are highly flammable. This way, construction material will become cheaper and also result in huge energy savings.

One research from an agricultural university indicates that they have found that a certain composition of fly ash effectively increases yield of some crops and in reclaiming fallow land.

Universities and laboratories in India, South Africa, the USA and Australia etc. alike have been running funded research experiments for extraction of desirable rare earth metals from coal ash like Alumina, Vanadium etc. ‘Beneficiation’ is a term that refers to the process by which carbon is removed from fly ash to produce a higher-value material. Power plants can increase their revenue stream by adding the beneficiation step to their ash handling process.

In South Africa, CSIR researchers are converting fly ash, a by-product of the South African pulp and paper industry, into heat-resistant geo-polymers that can be used in the protection of metal surfaces against high temperatures in furnaces or kilns. The conversion of fly ash into valuable products such as heat resistant geo-polymers offers alternative options that could help the pulp and paper industry to reduce its environmental footprint and waste management costs.

In summary, it does seem that identifying applications of coal ash re-use will be extremely beneficial, offering an enhanced revenue stream for power plants and also be a means of significantly decreasing the carbon footprint.

Fly ash recovery and disposal trends around the world.The World Energy Outlook 2017, Southeast Asia, cited that India, along with other developing economies in Asia, would helm the global demand for coal in years to come. In the next 20 years, power plants are expected to be responsible for almost 75% of the additional coal consumption.

And when there is so much coal, there is of course, a lot of fly ash recovery, coal ash. Globally, the most popular and the most economical solution for coal ash disposal is storage. Cost of disposal plays a big factor and can be curbed to a minimum if there are disposal sites available that are near a power plant.

Considering the ecological impact of coal ash on our environment, almost all countries have developed stringent regulations on its recovery, disposal and usage. In USA for example, the US Environmental Protection Agency (EPA) laid out the first-ever federal rules for coal ash disposal, where America’s coal-fired power plants are required to store coal ash only in landfills and disposal sites that meet minimum structural standards. In China, Fly ash is a Type II Class C general industrial solid waste. Currently, Chinese regulations allow for the fly ash to be stockpiled temporarily if it cannot be comprehensively utilized.

In Germany, where around 10 million tonnes of coal ash is produced per year, around 97% is re-used, and the rest stored only on a temporary basis. Other countries like the Netherlands are doing even better by having a zero landfill policy, which subsequently means that they are required to recycle 100% of the coal ash generated.

In the UK and US, the recent downward market trend in the coal industry has resulted in an increased interest by cement companies in mining landfill storage sites to fly ash recover the ash. There are recent studies and research papers that suggest that fly ash recovery landfills have enormous untapped value and potential that, when unlocked, can bring tremendous ecology-friendly and economically viable opportunities for re-use applications.

In Malaysia, the coal consumption is set to increase by over three times. It already has very stringent pollution targets, therefore it prefers towards using HELE technologies, mainly USC, for new projects. In Vietnam, a recent resurgence of interest in nuclear power could offset coal’s share in the medium-term. “The availability of sufficient capacity from coal plants now being built means that it is only when plants are retired and additional power is needed from 2035 onwards, that AUSC units may be introduced and emissions of CO2 will fall.