Destruction of caking properties of bituminous coal by jetting pre-oxidation in a fluidized bed

Jetting pre-oxidation was proposed to destroy the caking property of bituminous coal in a fluidized bed (FB) gasifier. By defining an index ω to characterize the degree or realized effect of caking destruction, experiments were conducted in an electrically heated laboratory FB reactor under different conditions to investigate the feasibility and required conditions for effectively destroying the caking propensity of a kind of bituminous coal. The tested major parameters were the equivalence air ratio (ER) of jetting gas and the temperature in the jetting zone. At relatively lower temperatures it was hard to completely destroy the caking propensity of the tested coal particles. Without oxygen inside the jetting gas, it was also impossible to fully destroy the caking propensity of the coal even at sufficiently high temperatures. Thus, oxidation of coal particles at suitably high temperatures was essential to the expected good destruction of their caking propensity. For the tested bituminous coal this was achieved at temperatures above 1000 °C in the jetting zone and an equivalent oxygen ratio above 0.1 for the jetting gas (up to 0.3 considering gasification applications). For coal pre-oxidation in a FB, the agglomeration state of char particles due to caking adherence in the reactor could be anticipated via the unsteady variations in the bed temperature and H2/CO concentrations in the effluent gas with reaction time.