Science, asked by Dharmpalsingh, 1 year ago

why is coke more porous than bituminious coal?

Answers

Answered by Jenny1981
8
An optimal coking coal is in the rank range of high volatile A bituminous to medium volatile bituminous, and can include low vol bituminous, when blended with lower rank coals. When coal is heated in a coke oven (which must have a deficiency of oxygen, or the coal would simply burn up), it softens, and partially melts. Volatile gases are formed within the coal through thermal cleavage of chemical bonds. These gases combine with any gaseous and low molecular weight hydrocarbons naturally present within the coal and expand to form large gas-filled vesicles (bubbles). The entire coal structure expands (swells) substantially, but then but then re-solidifies as volatile substances escape from the structure. After it cools and hardens, the residual coke has a high porosity, with a strong framework structure enriched in carbon.

Coke is a better fuel for smelting iron ore than coal, because its high porosity allows gases to circulate through the blast furnace. It is also structurally stronger than coal, which prevents it from being crushed by the heavy mixture of coke, limestone, and iron ore in the furnace. During smelting, chemically reduced molten iron flows down to the bottom of the blast furnace, where it is released into molds, to form ingots of “pig iron”, which are eventually refined and converted to make steel.

Good quality “metallurgical grade” coal (“met coal”) fetches the highest price of any coal on the market, costing between USD$100 and USD$150 per ton over the past year.

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