Review of Research on Coke Gasification in the Blast Furnace with Elevated Hydrogen Content and Determination of Coke’s Postreactive Strength. 4. Evolution of Coke’s Microstructure on Gasification in the Presence of H₂ and H₂O

In recent decades, hydrogen-bearing blast additives have been widely used to improve blast furnace smelting. Universities and steelmakers have conducted experiments to study the behavior of metallurgical coke in blast furnaces with an elevated hydrogen content. Although research on the high-temperature reaction of coke with atmospheres containing H₂O at different enterprises has employed different experiment designs, some basic conclusions may be drawn. The presence of atmospheric moisture significantly intensifies the gasification of coke, especially in the surface layers. The influence of H₂O on gasification becomes pronounced above 1000°C (1273 K). If the porosity of coke after reaction with the atmosphere is studied separately in the external and internal regions, the influence of H₂O on the internal region is found to be significantly lower. Higher moisture content of the atmosphere is associated with greater conversion of the coke to graphite in the final sample. Evidently H₂O reacts more actively than CO₂ with disordered carbon structures. One study demonstrated that the initial coke contains matrices of two types: with lower and higher elastic modulus. The matrix with the higher elastic modulus is mainly consumed on reaction with H₂O.