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WHAT IS COAL? UNDERSTANDING THE PROPERTIES OF COAL AND ITS SIGNIFICANT APPLICATIONS

Coal is a vital source of energy worldwide, playing a pivotal role in the industrial revolution and the socio-economic development.

Coal stands as a crucial global energy source, having played a pivotal role in the industrial revolution and socio-economic development. It is currently the most widely utilized fossil fuel, supplying up to 25% of the world's primary energy needs. Energy derived from coal serves various aspects of daily life and plays a critical role in numerous industrial sectors. So, what exactly is coal? How is it formed? And in which areas is it applied? Let's delve into these questions in the following article.

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1. What is Coal?

Coal is a type of sedimentary rock, typically dark brown or black, found in multi-layered rock strata or veins. It is discovered worldwide, primarily originating from prehistoric forests and swamps, which were buried over millions of years.

2. The Formation Process of Coal

Coal is derived from the remains of ancient plants buried underground. Over millions of years, heat and pressure have altered its chemical properties. This transformation involves several stages, beginning with the decomposition of plant matter into peat under anaerobic conditions. Subsequently, it evolves into brown coal (lignite), semi-bituminous coal, and eventually, into bituminous coal, ultimately becoming anthracite. This process encompasses complex biological and geological renewal.

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3. Characteristics and Properties of Coal

- Characteristics of Coal

  • Coal primarily consists of carbon, along with other elements like hydrogen, oxygen, nitrogen, and sulfur.
  • Coal's color is typically black, although it can exhibit variations depending on the source, appearing as brown, silver, yellow, or dull.
  • It has a high calorific value, ranging from approximately 5500 to 7500 kcal/kg.
  • Coal's appearance varies based on age, mining methods, and refining equipment.
  • Coal can absorb toxins and retain gases, substances dissolved in solutions, or vapor on its surface.

- Properties of Coal

  • Coal is characterized by high hardness and weight, with carbon content ranging from 75% to 95%, varying based on its origin. Lower impurity content typically results in higher hardness.
  • Moisture content in coal is typically around 5-6%, and higher moisture levels lead to reduced heat generation.
  • Coal ash, a product of mineral components when burned, greatly impacts its combustion properties. A higher ash content diminishes the heat output, causing fouling on heat-absorbing surfaces and decreasing efficiency.
  • Volatile matter (Vk%) represents the gases produced during coal's thermal decomposition in the absence of oxygen, including hydrogen, carbon dioxide, hydrogen carbide, and carbon monoxide. The younger the coal, the higher the volatile matter percentage.
  • The calorific value Q (Cal/g, Kj/kg) indicates the heat released when 1kg of coal completely burns. Higher calorific values denote more efficient combustion.

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4. Classification of Coal

- Classification According to Intended Use

  • Metallurgical coal: Primarily used in steel production.
  • Thermal coal: Utilized for electricity generation when burned or in the cement production industry.

- Classification Based on Morphological Characteristics

  • Peat: peat has physical characteristics such as high moisture content of about 42.1%, fine and fine texture, average level of resolution is 35.3%, the deeper the mines, the higher the resolution ability. Peat that has been sifted and crushed to meet the standards of microbial organic fertilizer production is divided into 3 types:
      Type 1 Type 2 Type 3
    Color Black Black and brown Umber
    Sieve pass fineness 3.5mm 3.5mm 5.5mm
    Humidity 20-30% 20-30% 20-35%
    Organic content 30-35% 17-25% <16%
  • Coal dust: coal dust 2a, coal dust 2b, coal dust 32, coal dust 3c, coal dust 4a, coal dust 4b,...
  • Cabcoal: coal bucket, two bucket coal, three bucket coal, four bucket coal, five bucket coal, six bucket coal, seven bucket coal, eight bucket coal

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5. Applications of Coal

- Electricity production: Coal is crucial for generating electricity, accounting for 37% of global electricity production.

- Metallurgy: Coal, when processed into coke, is used to produce steel, aluminum, and copper.

- Construction materials: Coal is the primary energy source for cement production, and by-products from coal combustion play a vital role in the cement and concrete industry.

- Energy industry: Used as a solid fuel for electricity production and combustion.

- Gasification technology: Coal gasification produces syngas, used for electricity generation, fuel production, and chemical products.

- Chemistry: Coal is employed in pharmaceuticals, plastics, and artificial fibers.

- Other industries: Coal serves industries like paper, textiles, glass, and water purification, owing to its toxin-absorbing properties.

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6. Benefits and Limitations of Using Coal

- Benefits

  • Safety: Coal is safer to transport and store compared to other fossil fuels.
  • Flexibility: Coal is versatile, and used in a wide range of industrial and technological processes.
  • Convenience: Coal is readily usable upon extraction, unlike other energy sources that require extensive processing.
  • Low cost: Abundant reserves and low transportation expenses make coal a relatively inexpensive energy source.

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- Limitations

  • Depletion of fossil energy: Fossil fuel resources, including coal, are being rapidly depleted.
  • Environmental pollution: Burning fossil fuels, especially coal, contributes to environmental pollution and climate change.
  • Health impacts: Coal mining and combustion result in pollution that can harm human health.

 

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