Properties
The bulk specific gravity of coke is typically around 0.77. It is highly porous.
The most important properties of coke are ash and sulfur content, which are linearly dependent on the coal used for production. Coke with less ash and sulfur content is highly priced on the market. Other important characteristics are the M10, M25, and M40 test crush indexes, which convey the strength of coke during transportation into the blast furnaces; depending on blast furnaces size, finely crushed coke pieces must not be allowed into the blast furnaces because they would impede gas dynamics. A related characteristic is the Coke strength after reaction (CSR) index; it represents coke's ability to withstand the violent conditions inside the blast furnace before turning into fine particles.
The water content in coke is practically zero at the end of the coking process, but coke is often water quenched to reduce its temperature so that it can be transported inside the blast furnaces. The porous structure of coke absorbs some water, usually 3-6% of its mass. In some more modern coke plants an advanced method of coke cooling is by air quenching.
Bituminous coal must meet a set of criteria for use as coking coal, determined by particular coal assay techniques. See Section "Production".
The volatility of coke reaches minimum levels at the end of the coking process.
Read more about this topic: Coke (fuel)
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