Fundamentals of Coal Carbonization Reactions

The reactions involved in the process of carbonization are disproportionate in nature, and are guided primarily by the chemical constitution and physical structure of coal and secondarily by varying operational conditions and pre-treatment of the coal charge. Low rank coals cannot attain high degree of freedom on heating due to their highly disorganized structure; besides, preponderance of reactive oxygen groups in them initiates a cross-linked, immobile structure at an early stage of carbonization. Very high rank coal also cannot soften due to their very large immobile molecules. Medium rank coal are more orderly than the low rank coals; their molecular sizes are not very large and they do not contain large amounts of reactive oxygen groups. They can, therefore, attain plasticity on heating. Major devolatilization takes place after the plastic stage and the semi-coke during its conversion into true coke is not weakened by severe strains. No absolute limit can be set to the coking potentiality of coal