Thermochemical Process Study on a Jet-Fluidized-Bed Gasifier Reaction System by an Equivalent Chemical Reactor Network

Abstract

To study the effects of operational parameters on gasifying characteristics in the jet-fluidized-bed reactor and illustrate the scaling relationships of jet-fluidized-bed coal gasifier in a scale-up process, we established an equivalent reactor network model for the gasifier using CHEMKIN 4.1 software. The model is based on hydrodynamic properties in the gasifier and knowledge of the burning zone and gasifying zone of the reactor. It involves two-phase flow between materials, heat and mass transfer, as well as the coal gasification process in the presence of mixed gases, most notably H2O, O2, N2, etc. The model was validated by comparing it to the experimental data of outlet gas compositions. To optimize characteristics of the jet-fluidized-bed coal gasifier, the influence of the oxygen feed rate into the center nozzle and the coal feed rate on the gasification process and gas composition were studied by the equivalent established reactor network. Within the calculation range, with the increase of the oxygen feed rate into the center nozzle, the jet region nearly doubled, the temperature increased by 306 K, carbon conversion efficiency rose from 68 to 97%; however, the temperature of the jetting region should be controlled within the coal ash-softening temperature, and in generated gases, the CO and H2 contents had clearly changed. With the increase of the coal processing capacity, the jet region temperature decreased by 252 K, the gasifier overall temperature decreased, and carbon conversion reduced from 98 to 74%.