Numerical simulation investigation of pyrolysis characteristics, bubble evolution and CRI reduction mechanism under the hot tamping coking condition

Abstract

Superior quality coke with low reactivity and high strength is indispensable for the safe operation of blast furnaces and is beneficial for reducing carbon emissions. The hot tamping operation could effectively reduce the coke reactivity and increase the coke strength. The CPD (Chemical Percolation Devolatilization) and bubble evolution models were used to investigate the influences of hot tamping on pyrolysis characteristics and bubble evolution in the coking process. Results show that hot tamping operation significantly affects the yield of metaplast at the plastic stage. The variation of the metaplast fraction is more drastic when the holding temperature is higher. The tamping operation could effectively squeeze out the bubbles in the coal particles. However, the compact structure produced by tamping impedes the escaping of bubbles. Tamping at the proper time with a suitable holding temperature could effectively reduce the bubble number and escape resistance. Coke with low porosity could be produced when the hot tamping operation is conducted at a higher temperature with a longer holding time before total resolidification. The diffusion of CO2 could be effectively resisted in the coke gasification reaction when the coke has a small pore size, thicker pore wall and poor pore connectivity, resulting in a low coke reactivity.