Effects Of Composite Potassium-iron Catalyst On Coal Char Gasification

The high dependence of China on natural gas imports demands more efficient coal utilization. Coal catalytic gasification technologies play a significant role in improving China’s energy structure. Efficient, economical and environmentally friendly catalysts dramatically facilitate this technology and have important industrial applications. This work experimentally studies the performance and properties of K-Fe composite catalysts during coal char gasification and provides research foundation and technical guidance for the coal char gasification technology.The performance of K, Fe single and composite catalysts during coal char gasification was studied with Thermal Gravimetric Analysis (TGA). The effects of catalyst type, catalyst quantity/ratio and gasification temperature on the carbon conversion efficiencies were investigated. The results indicate that both single and composite catalysts significantly improved the gasification rate. K2CO3 showed better catalytic performance than iron-based catalysts. Potassium-based catalyst (K2CO3) played a major role in determining the gasification efficiency, while adding 1% FeCO3 gave rise to an additional synergistic effect, which further improved the catalytic performance. In summary, the sorted performances of different catalysts are:K2C03+Fe(NO3)3>K2CO3+FeS04>K2CO3+FeCO3 >K2CO3+Fe>K2CO3>FeCO3>Fe(NO3)3>Fe>FeCl3>FeSO4>None.The effects of catalyst type, catalyst quantity/ratio and gasification temperature on product gas composition (i.e., ratios of H2, CO and CO2) during coal char gasification was studied with a fixed-bed reactor. The results indicate that K-Fe composite catalysts exhibited excellent catalytic performance by combining the merits of individual constituents. Iron-based catalysts dominated the product gas composition and raised the H2 productivity. With the combination of potassium and iron based catalysts, the productivity of high quality product gas such as H2 and CO was significantly improved (by 6.4-12.6% and 5.8-22.3%, respectively). Besides, high temperature accelerated the gasification process and increased the CO but lowered the H2 and CO2 productivity.Random pore model demonstrated better fitting of the gasification process than Homogeneous model and Shrinking core model, indicating that the change of pore structure during the gasification process has a significant impact on gasification rate. Activation energy was closely related to gasification rate. The abilities of different catalysts to lower the activation energy are as follows:5% K2CO3>2% K2CO3+2% FeCO3>5% FeCO3.