Understanding Coal Types and Their Heat Content Ranking

Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. It is primarily composed of carbon along with variable quantities of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. The quality and energy content of coal are often determined by its rank, which reflects the degree of transformation from the original organic plant material to coal. Heat content, typically measured in kilojoules per kilogram ($\\text{KJ}/\\text{kg}$), is a crucial indicator of coal's energy potential.

Explaining the Different Coal Types

The question asks us to arrange specific types of coal based on their increasing heat content. These types represent different stages in the coalification process:

• Peat (A): This is the youngest type of coal, essentially partially decayed plant matter. It has a high moisture content and the lowest carbon content, resulting in the lowest heat value.
• Lignite (B): Also known as brown coal, lignite is a low-rank coal with a high moisture content. It has more carbon than peat but is still considered a low-energy fuel source compared to higher ranks.
• Sub-bituminous Coal (E): This is an intermediate rank coal between lignite and bituminous coal. It has lower moisture content and higher carbon content than lignite, thus a higher heat value.
• Bituminous Coal (D): This is a mid-rank coal. It has undergone further compression and heating compared to sub-bituminous coal, leading to lower moisture and higher carbon content, and consequently, a higher heat content.
• Anthracite (C): This is the highest rank of coal. It is hard, black, and has the highest carbon content and the lowest moisture content among the listed types. This makes it the most efficient fuel source with the highest heat content.

Comparing Heat Content of Coal Types

The heat content generally increases as the rank of coal increases, due to higher carbon content and lower moisture/volatile matter content. Here's a general comparison:

Arranging Coal by Increasing Heat Content

Based on the typical heat content ranges and coal ranks, we can arrange the given coal types in increasing order:

• Step 1: Start with the lowest heat content. Peat (A) has the lowest heat value.
• Step 2: The next lowest is Lignite (B).
• Step 3: Following Lignite is Sub-bituminous Coal (E), which has a higher heat content than Lignite.
• Step 4: Bituminous Coal (D) comes next, offering a significantly higher heat output than Sub-bituminous coal.
• Step 5: Finally, Anthracite (C) has the highest heat content among the options.

Therefore, the correct order of coal types in increasing order of their heat content is: Peat (A), Lignite (B), Sub-bituminous Coal (E), Bituminous Coal (D), Anthracite (C).

This corresponds to the sequence: (A), (B), (E), (D), (C).