The process and mechanism of coke gasification dissolution loss in hydrogen-rich blast furnace

Abstract

Blast furnace (BF) hydrogen-rich smelting has become an important way for low-carbon ironmaking. The coke gasification dissolution loss will be accelerated by H2O generated through hydrogen reduction, which is the fundamental reason for the limited injection rate of hydrogen-rich gas in BF. The gasification dissolution loss experiments of coke were carried out under different conditions. Experimental results indicate that: The pore size of coke containing H2O is larger under the same gasification time. The quantitative relationship between pore size and gasification time, flow rate of H2O is obtained. The pore wall around the inner hole will gradually be eroded, the pore wall gradually dissolves along the edge of the inner hole. The connectivity between two pores starts from the deep layers of the pores, the pore walls in the deep layers of pores are first connected. The carbon layer spacing slightly decreases with gasification time, which indicates that the microcrystalline cells inside the coke have contracted in the vertical direction. The carbon layer stacking height shows an overall upward trend with the increase of temperature and gasification time, and it will reach a maximum value for a certain temperature. The carbon layer diameter increases with the prolongation of gasification time, the aromatic carbon layers continue to grow as gasification progresses. The dynamic model of H2O diffusion is established, the effective internal diffusion coefficients of H2O under different conditions are calculated, the diffusion ability of H2O is stronger than that of CO2. The mechanism of H2O dissolution loss of coke based on surface active sites is summarized, whether the gasification dissolution loss reaction can occur depends on whether there are active sites on the adsorbed surface. The competitive gasification always occurs vigorously at active sites, the gasification reaction between H2O and C is easier and the reaction rate is higher.