Question

Steel is made in a process in which iron is combined with carbon at extremely high temperatures. Which of the following types of coal might be most useful in this process? A. peat B. lignite C. subbituminous coal D. anthracite

Short answer

The most useful type of coal in the steelmaking process, where iron is combined with carbon at high temperatures, would be anthracite (option D) due to its highest carbon content and high-energy value.

Step-by-step solution

Understanding the types of coal

Peat, lignite, subbituminous coal, and anthracite are all types of coal. They differ in their carbon content, hardness, and energy content. In general, the higher the carbon content, the harder the coal and the greater its energy content. Anthracite has the highest carbon content, while peat has the lowest. Let's analyze each type: 1. Peat: Peat is the least mature form of coal, with the lowest carbon content and energy value. It is formed from partially decayed plant material and is often considered more of a precursor to coal than a true coal. 2. Lignite: Lignite, also known as brown coal, has a higher carbon content than peat, but still has a relatively low energy value compared to other coals. It is a soft, brown, crumbly material and is typically used in power generation. 3. Subbituminous coal: Subbituminous coal has a higher carbon content and energy value than lignite. It is a dark brown to black coal that is used primarily for electricity production and industrial applications. 4. Anthracite: Anthracite is the highest grade of coal, containing the most carbon and having the highest energy content. It is a hard, black, and shiny material, often called "stone coal". Anthracite is used in various applications, including heating, industrial processes, and steelmaking.

Determining the type of coal for steelmaking

In the steelmaking process, coal plays an essential role as it is the source of carbon, which is combined with iron at extremely high temperatures. The coal with the highest carbon content would be the best choice for this process, as it would provide the most carbon and energy to facilitate the high-temperature process.

Comparing the carbon content of the coal types

When we compare the carbon content of the four types of coal, we find that anthracite has the highest carbon content, followed by subbituminous coal, lignite, and peat.

Conclusion

Based on the carbon content and high-energy value, the most useful type of coal in the steelmaking process, where iron is combined with carbon at high temperatures, would be anthracite (option D).

Key concepts

Types of Coal

Coal, a natural resource mined from the earth, is a combustible black or brownish-black sedimentary rock which has been utilized as a fuel source for centuries. It forms from plant remains that have been compacted, hardened, and chemically altered by heat and pressure over millions of years.

Coal is categorized based on its physical and chemical properties, particularly its carbon content, which influences its energy output when burned. Here are the primary types of coal:

• Peat - Not truly coal yet, peat is the precursor to coal, consisting of soft organic material that is only partially decomposed.
• Lignite - Often referred to as 'brown coal,' lignite is the lowest rank of coal used mainly for electricity generation.
• Subbituminous coal - This type has a higher carbon content than lignite; it's used mostly for steam-electric power generation.
• Anthracite - With the highest carbon content, anthracite is the most efficient and hardest coal type, often used in heating and metallurgy.

The different types of coal are essential in various industries, depending on their properties. For the high temperatures required for industrial processes like steelmaking, a coal type with a higher carbon content would be preferable due to its higher energy value and efficiency.

Steelmaking Process

The process of transforming iron into steel is a complex and high-temperature operation that involves several stages. The basic oxygen steelmaking (BOS) process is one of the most common methods, utilizing a high-carbon coal-derived substance known as coke. The key steps in the BOS method include:

1. Charging the furnace with iron ore, coke, and limestone.
2. Blowing oxygen through the mixture to reduce the carbon content to the desired level.
3. Tapping off the molten steel and slag.
4. Secondary processes for refining, including alloying to achieve specific steel properties.

During the steelmaking process, the interaction between iron and carbon is crucial in defining the quality and characteristics of the final steel product. The selection of coal type is vital as it contributes carbon to the mix and should be highly efficient to sustain the extreme temperatures required for melting and refining the iron ore.

Carbon Content in Coal

The carbon content in coal is a definitive factor in its grade and usage, particularly in the context of the steelmaking process. The variation in carbon content is a result of the coalification process, which includes the geological and chemical changes that organic material undergoes to become coal. The stages include the conversion from peat, progressing through lignite and subbituminous, and finally to anthracite, the form with the highest carbon content.

High carbon content correlates with increased hardness and higher energy content, making the coal more valuable for certain applications, notably in producing the high temperatures required for steelmaking. Anthracite, with its superior carbon content, is thus the most suitable type of coal for this purpose. It provides ample carbon to combine with iron and generates the necessary heat efficiently. The knowledge of carbon content and its implications is fundamental for industries that require specific energy outputs and carbon contributions, like the metallurgical sector.