Editing Coke (fuel) (section)

==Properties==
[[File:Siegelfurnace1.jpg|left|thumb|[[M. A. Hanna Company|Hanna furnaces]] of the Great Lakes Steel Corporation, [[Detroit]]. Coal tower atop coke ovens. November 1942]]

Before bituminous coal is used as coking coal, it must meet a set of criteria determined by particular [[coal assay]] techniques.{{cn|date=October 2024}}

The bulk [[specific gravity]] of coke is typically around 0.77. It is highly [[porous]]. Both the chemical composition and physical properties are important to the usefulness of coke in blast furnaces. In terms of composition, low ash and sulphur content are desirable. 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 the blast furnace's size, finely crushed coke pieces must not be allowed into the furnace because they would impede the flow of gas through the charge of iron and coke. 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. Pieces of coke are denoted with the following terminology: "bell coke" (30 - 80 mm), "nut coke" (10 - 30 mm), "coke breeze" (< 10 mm).<ref>{{Ullmann |doi=10.1002/14356007.a14_461.pub2|title=Iron|year=2006|last1=Oeters|first1=Franz|last2=Ottow|first2=Manfred|last3=Meiler|first3=Heinrich|last4=Lüngen|first4=Hans Bodo|last5=Koltermann|first5=Manfred|last6=Buhr|first6=Andreas|last7=Yagi|first7=Jun-Ichiro|last8=Formanek|first8=Lothar|last9=Rose|first9=Fritz|last10=Flickenschild|first10=Jürgen|last11=Hauk|first11=Rolf|last12=Steffen|first12=Rolf|last13=Skroch|first13=Reiner|last14=Mayer-Schwinning|first14=Gernot|last15=Bünnagel|first15=Heinz-Lothar|last16=Hoff|first16=Hans-Georg}}</ref>

The water content in coke is practically zero at the end of the coking process, but it is often water quenched so that it can be transported to the blast furnaces. The porous structure of coke absorbs some water, usually 3–6% of its mass. In more modern coke plants an advanced method of coke cooling uses air quenching.{{cn|date=October 2024}}