KOMPAS.com – Coal is a non-renewable fossil fuel that is burned and generally used to produce electricity.
Quoted from National Geographic, coal is a black or brownish black sedimentary rock consisting of carbon and hydrocarbons.
This high content makes it flammable or contains energy that can be released through combustion.
Coal is found in underground formations called “coal seams”. This layer can be 30 meters thick and stretches for 1,500 kilometers.
Coal seams exist on every continent, and the largest coal reserves are in the United States, Russia, China, Australia and India.
Coal is classified as a non-renewable energy source because it takes millions of years to form.
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So, how is new coal formed?
The process of forming coal
Coal contains energy stored by plants that lived hundreds of millions of years ago in swamp forests.
Layers of soil and rock covered the plants for millions of years, then the resulting pressure and heat turned the plants into a substance known as coal.
Reporting from the Science Focus page, around 300 million years ago, in the Carboniferous era, the earth’s climate was warm and humid, so there were many large swamps.
When plant material (and other organic matter) from dense swamp forests accumulates and rots on the swamp floor, it becomes buried and then becomes solid.
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From some of this decomposed organic material, anaerobic conditions due to lack of oxygen then form peat.
When this peat is buried at a relatively shallow depth, heat and pressure continue to squeeze it between layers of sediment, turning it into lignite (lignite).
Lignite is a soft, brownish black coal-like material with a high water content.
With continuous burial, heat, and structural deformation, this lignite metamorphoses into sub-bituminous and bituminous coal (soft coal).
Until finally over time it becomes anthracite (hard coal), and the more metamorphism, the harder and richer the carbon content of the coal.
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Types of coal
iStockphoto/small smiles
Illustration of types of coal.
According to the United States Energy Information Administration, coal is classified into four main types or grades: anthracite, bituminous, sub bituminous, and lignite.
The ranking of a coal deposit depends on the type and amount of carbon the coal contains and the amount of heat energy it can produce.
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1. Lignite
Lignite or lignite contains 25 to 35 percent carbon and has the lowest energy content of all grades of coal.
Lignite coal deposits tend to be relatively young and have not experienced extreme heat or pressure.
Lignite is brittle and has a high water content, resulting in a low heating value.
2. Sub-bitumen
Sub-bituminous coal usually contains 35 to 45 percent carbon, and has a lower heating value than bituminous coal.
This type of coal is about 100 million years old. In many parts of the world, sub-bituminous coal is considered “brown coal” along with lignite.
Like lignite, sub-bituminous coal is primarily used as a fuel for power plants.
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3. Bitumen
Bituminous coal contains 45 to 86 percent carbon, and is generally used to generate electricity.
Yes, it is also an important fuel as a raw material for making coke or used in the iron and steel industry.
Bituminous coal is formed due to greater heat and pressure, and is 100 to 300 million years old.
4. Anthracite
Anthracite is a type of coal that contains 86 to 97 percent carbon and generally has the highest calorific value among all types of coal.
This coal is harder, denser, and shinier than other types of coal.
Almost all the water and carbon dioxide have been removed, and it does not contain the soft or fibrous parts found in bituminous coal or lignite.
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2023-10-02 00:45:00
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