This paper describes a model called “FC-CBK” developed to represent the combustion histories of individual coal particles with a minimum amount of laboratory support. The FC-CBK model is a combination model of FLASHCHAIN model, one of the network depolymerization devolatilization models, and CBK8 model, a mechanism for char oxidation that quantitatively represents the latest stages of combustion. Each simulation represents the entire combustion history of particles injected into hot oxidizing gas, including drying, devolatilization, volatiles combustion with energy feedback to the particle, heterogeneous char ignition, thermal annealing, quasi-steady char oxidation with simultaneous reductions in particle density and size, and mineral effects during the char combustion. Whereas these mechanisms involve numerous reaction rate constants and physical properties, all the parameters in FC-CBK model may be specified from the proximate and ultimate analyses of the coals. In this paper, the outline of FC-CBK model, the result of the test predictions and the required input data are described.
A model called “FC-CBK” is developed to predict the coal burnout profiles in a lot of furnaces. “FC-CBK” combines FLASHCHAIN, one of the network depolymerization devolatilization models, with CBK8, a mechanism for char oxidation that quantitatively represents the latest stages of burnout. Whereas these mechanisms involve numerous reaction rate constants and physical properties, all the parameters in “FC-CBK” may be specified from the coal's proximate and ultimate analyses. In this study, an evaluation of “FC-CBK” was carried out to compare the predictions with the experimental data in an electrically heated drop-tube furnace. Firstly, the particle temperature histories in this furnace under various conditions were calculated by using a computational fluid dynamic code. Next, the obtained temperature histories were given to “FC-CBK” as the input data of the furnace conditions. Finally, the coal burnout profiles of eight coals were predicted by “FC-CBK” with the above-mentioned procedure. As a result of these verifications, we found “FC-CBK” can predict the accurate coal burnout profiles with giving the particle temperature histories. The advanced features describing the late stages of burnout are hereby validated in conceptual terms, while the estimation of initial char reactivities still represents a major hurdle to any predictive capabilities based on only the basic coal analyses.
Chlorine content of bituminous coal was determined and its behavior during carbonization was investigated. The chlorine content in the metallurgical coals used in this experiment was between 100 and 1, 500ppm. Most chlorine in coal and coke was removed by washing with water. CaO addition to coal increased the chlorine residue ratio in coke. The residue ratio of chlorine in coke increased with increasing Ca content in coal. This is considered because chlorine in coal is released as HCl, which is trapped in coke again in the form of CaCl2. The chlorine residue ratio of coke produced in actual coke oven was higher than that of coke produced in laboratory scale tube furnace. This is considered because released gas from coal has more chances to contact with calcium in the actual coke oven than in the tube furnace. Furthermore the removal of chlorine from NaCl was promoted by co-carbonization of NaCl with coal. This implies that H2O derived from coal decomposition may help chlorine to be released.