Mineral Related CO2 and H2O Emissions during the Production of Metallurgical Coke

During coking processes, certain coal-associated minerals undergo various chemical changes, amongst which are dehydration, dehydroxylation, and decarbonation. In order to evaluate the character of CO2 and H2O emission by a particular mineral, thermodynamic calculations for theoretical gas production were performed. Observations showed that the behavior of carbonates in respect of CO2 emission vary substantially and, for that reason, their influence on the properties of coke differ. The amount of mineral-associated CO2 released during the coking process is smaller than that which is produced by a carbon-based matrix. For each ton of coal, containing 1wt% of carbonates, there will be c. 17.6-22.0m(3) of CO2 present at the stabilization stage of the coking process. However, the impact of a mineral-related gas phase should not be underestimated (in particular, for porosity development and cracks formation), mostly when the grain size of the minerals is quite large. The major CO2-related impact on coke properties can be referred to dolomite, magnesite, and calcite. The amount of H2O released by each ton of coal containing 1wt% of phyllosilicates, can be approximately 0.88-9.68m(3) at the stabilization stage of a coking process. The presence of OH- and H2O-bearing minerals, especially montmorillonite, can affect coke reactivity, pores formation, and cause formation of micro cracks.