What is Coking Coal?
Steel is made from coke, also known as metallurgical coal. Coke is one of the most important inputs for steel production. In the world, there are many different types of coal, such as brown coal, lignite, and anthracite. It is the property of coking coals that sets them apart from other coals--they have the caking ability necessary to make coke suitable for steelmaking. A coke oven heats coke coals in a reducing atmosphere to produce coke. Coal becomes plastic when it is heated, fusing before resolidifying into coke particles. The process is known as caking.
What is Metallurgical Moal? How Does it Differ from the Other Types of Coal?
Metallurgical coal (or coking coal) is a sedimentary rock that occurs naturally in the earth's crust. Hard coking coal, semi-hard coking coal, semi-soft coking coal, and pulverized coal for injection are all types of met coal (PCI). These terms refer to the various grades of met coal that are used to create steel. Thermal coal, which is used to make power, has a higher carbon content, less ash, and less moisture than met coal.
What is the Purpose of Metallurgical Coal?
Steel manufacture requires metallurgical coal, which is one of the most commonly used building resources on the planet. One tonne of steel requires approximately 770 kilos of coal, with basic oxygen blast furnaces producing over 70% of world steel. The challenge for steelmaking is to produce this crucial commodity in a way that allows for long-term expansion while lowering the production process's greenhouse gas emissions. BHP expects to produce roughly 70 million tonnes of met coal in 2020. That's enough steel to construct the Burj Khalifa (the world's tallest structure) 1,600 times over!
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What Methods are Used to Mine Metallurgical Coal?
Depending on how deep the coal is buried beneath the Earth's surface, several mining methods are used.
Underground
Coal is extracted by a longwall shearer deep below at our Broadmeadow mine in Central Queensland. On a conveyor belt, the coal is subsequently brought to the surface and stacked. At a coal handling and preparation factory, impurities are removed by washing and treatment. It is then carried to port by train, loaded into ships, and shipped to our customers.
Open Cut
We collect coal from seams that are relatively near to the surface in our open-cut mines. Excavators, draglines, shovels, and trucks are used to blast and remove the top layers of soil and rock to expose the coal, which is then mined with excavators, draglines, shovels, and trucks. After that, the coal is transferred to stockpiles. At a coal handling and preparation factory, impurities are removed by washing and treatment. It is then carried to port by train, loaded into ships, and shipped to our customers.
Coking Coal Meaning
Coke is a hard grey cellular material that softens and agglomerates when heated and after volatile stuff has been driven out at high temperatures. It is the meaning of coking coal. Coking coal is defined as coal of a quality that enables the creation of coke appropriate for use in blast furnaces. On an ash-free yet moist basis, it has a gross calorific value of more than 23 865kJ/kg (5 700 kcal/kg). It is the coking coal definition.
Uses of Coke Coal
Coke is mostly used as a fuel for stoves, furnaces, and blacksmithing. Because coke creates very little smoke, it is sometimes favoured over coal.
In a blast furnace, it's also used to make iron.
Coke is used to make steel and a range of other items as per the uses of coke coal.
Did You Know
The quality of the resulting coke is governed by the coking coals utilised and the working parameters of the coke plant. Coke quality is influenced mostly by coal rank, composition, mineral content, and the capacity to soften, become flexible and resolidify into a cohesive mass when heated. Coking coals are bituminous class coals with the high, medium, or low volatile ranks that have these qualities. Steel companies are in high demand for high-quality coking coals, which they need to make high-quality coke to increase the productivity of their blast furnace operations.
Even though metallurgical and thermal coal has the same origin, their economic markets and industrial applications are quite different.
FAQs on Coking coal
1. What is coking coal, and how is it different from thermal coal?
Coking coal, also known as metallurgical coal, is a high-grade type of coal with specific properties that allow it to be converted into coke. The primary difference between coking coal and thermal coal (used for power generation) is its chemical composition and behaviour when heated. Coking coal has low sulphur and phosphorus content and, when heated in an oxygen-free environment, it melts, swells, and re-solidifies into a hard, porous block called coke. Thermal coal, in contrast, simply burns to ash and does not have these caking properties.
2. What are the main applications of coking coal?
The primary application of coking coal is in the iron and steel industry. After being converted into coke, it serves two critical functions in a blast furnace:
- It acts as a fuel source, providing the intense heat required to melt iron ore.
- It serves as a reducing agent, chemically removing oxygen from iron ore to produce molten iron.
3. How is coke produced from coking coal?
Coke is produced from coking coal through a process called carbonisation or pyrolysis. In this process, the coal is heated to extremely high temperatures (over 1,100°C) inside a series of ovens without any oxygen. This intense heat drives off volatile matter like water, coal gas, and tar. What remains is coke, a material that is almost pure carbon, strong, and porous, making it ideal for use in a blast furnace.
4. Why is coking coal considered essential for primary steel production?
Coking coal is essential for primary steel production via the blast furnace route because the resulting coke provides the unique combination of heat, chemical reactivity, and structural support needed. The coke bed in a blast furnace must be strong enough to support the heavy layers of iron ore and limestone above it, while also being porous enough to allow hot gases to pass through. No other material can cost-effectively provide all these functions simultaneously in the large-scale production of iron.
5. What are the major coking coal-producing regions in India?
In India, high-grade coking coal deposits are primarily concentrated in the Damodar Valley. The most significant producing areas are located in the state of Jharkhand. The key coking coalfields include:
- Jharia Coalfield, the largest reserve of prime coking coal in India.
- Bokaro and Giridih coalfields.
- Raniganj Coalfield in West Bengal, which also has some coking coal reserves.
6. Which are the leading countries in coking coal production globally?
The world's largest producer of coking coal is China, which uses most of its production for its domestic steel industry. Other major global producers include Australia, Russia, the United States, and Canada. Australia is the world's largest exporter of metallurgical coal, playing a crucial role in the global steel supply chain.
7. Can modern steel manufacturing exist without coking coal?
Yes, steel can be manufactured without coking coal through alternative methods. The most common alternative is the Electric Arc Furnace (EAF), which primarily uses electricity to melt recycled steel scrap or Direct Reduced Iron (DRI). While the EAF method is growing, the traditional blast furnace route using coking coal still accounts for the majority of the world's primary steel production from iron ore.
8. Why does India need to import coking coal despite having large coal reserves?
India faces a quality and quantity deficit when it comes to coking coal. While the country has vast reserves of coal, the majority is of the non-coking or thermal grade with high ash content. The domestic reserves of high-quality coking coal are limited and insufficient to meet the demands of India's large and growing steel industry. To ensure operational efficiency and produce high-quality steel, India imports a significant volume of coking coal, mainly from countries like Australia.
9. What are the environmental impacts of using coking coal in industries?
The use of coking coal has significant environmental consequences. The primary impact is the emission of large amounts of carbon dioxide (CO₂), a potent greenhouse gas, during the coking process and in the blast furnace. This contributes heavily to climate change. Additionally, the process releases other air pollutants like sulphur dioxide and nitrogen oxides. Mining activities can also cause deforestation, water pollution, and habitat destruction. These concerns are driving innovation towards 'green steel' technologies that aim to reduce or eliminate dependence on coal.
