Modeling study on the external heated entrained flow reactor in Shengli lignite mild gasification process:Model development and description

Shengli brown coal in 150-180 μm was gasified at 800 ℃ / 900 ℃ in a simulated entrained-flow reactor, ϕ80 mm× 3 000 mm. Kinetics of main reactions and flow characteristics of gas / solid were discussed to build a coal mild gasification model. The results show that,firstly,the gas phase flow was divided into 3 zones,including jet zone, recirculation zone and downstream zone. The height of downstream zone was 95% of that of reactor. Secondly,pyroly- sis,combustion and gasification could be considered running in order as a result of different reaction rates. Thirdly,the rate equations of oxidation reaction (OR) and steam gasification reaction (SGR) derived were in good agreement with the experimental data. The OR rate was in membrane diffusion controlled regime,and SGR rate was in chemical con- trolled regime. Moreover,the apparent rate constant of SGR increased obviously after adding O2 to steam. Therefore,the kinetic equation derived was suitable with the experimental conditions. Fourthly,the reactions of H2 ,CO,CH4 combustion,char-CO2 / H2 gasification,CO-H2 methanation,and water-gas shift reaction were considered,while the reactions of tar combustion,char-H2 O methanation,CO2 -H2 methanation were ignored. Fifthly,due to the difference of char mi- crostructure,the effective contact (collision) area between gas and solid in different temperatures and atmospheres is different significantly. Based on those,a numerical model of en-trained-flow reactor was built,and its predicted values were in good agreement with the experimental values,with the error of less than 20% for 92% predicted values and less than 10% for 75% predicted values.