Kinetics of Co-Ca catalyzed coal char hydrogasification in a pressurized fluidized bed
The coal catalytic hydrogasification is a highly promising technology for converting coal to natural gas.It consists of coal catalytic hydropyrolysis and char catalytic hydrogasification.The char catalytic hydrogasification is the rate-controlling step of the whole process be-cause its rate is much less than that of coal catalytic hydropyrolysis.Therefore,it is critical to establish a reasonable kinetic model of Co-Ca catalyzed char hydrogasification in pressurized fluidized bed for the technology's future development.The variations of particle density and pore characteristics with carbon conversion were investigated during Co-Ca catalyzed char hydrogasification in a lab-scale pressurized fluidized bed.The results show that the char particle density decrease as the carbon conversion,and there is linear correlation between the total pores specific surface area and reaction rate.These phenomena confirm that the conversion of char should follow the random pore model during Co-Ca catalyzed char hydrogasification.The effects of reaction temperature,hydrogen pressure,and Co loading on the carbon conversion were researched.It is found that the reaction is controlled by dynamics in the range of 650-850 ℃.The reaction rate is dramatically increased when the temperature is over 750 ℃,and the carbon conversion increase from 16.32％to 95.32％when reaction temperature is elevated from 650 ℃ to 850 ℃.The carbon conversion is elevated to 94.11％with increasing the hydrogen partial pressure from 0.6 MPa to 2.5 MPa.Raising the Co loading from 1％to 3％resultes in the continous increase in carbon conversion,but it has lit-tle change when the Co loading is furtherly increased to 5％.The experiment data was analyzed adopting an extended random pore model with the introduction of empirical parameters c and p.The results indicate that the activation energy of coal char catalytic hydrogasification is 122.7 kJ/mol,and the reaction order is 1.54.The average deviation between the predicted and experimental reaction rate is 4.81％.
coal charcatalytic hydrogasificationpressurized fluidized bedreaction kineticrandom pore model
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