| The requirement for the coke's quality is more and more serious, especially for the thermal performance (CRI and CSR), along with the scaling up of blast furnace and increasing of the quantity of pulverized coal injection. The passivation of coke is to adopt the method of insufflation or infusion to dispose the coke under cold condition, to improve the thermal performance of coke.In this paper, the raw coke is from the industrial production and is infused in the H3BO3 solution whose concentration is 3 %. Then the determination of CRI and CSR of coke is carried out according to the GB/T 4000—1996, and the results show that the CRI and CSR are both improved in some extent. The solution loss reaction rate of coke before and after passivation is determined by using the thermo-gravimetry analyzer, and then the every step resistance of coke's solution loss reaction before and after passivation is calculated according to unreacted shrinking core model, including external diffusion, interfacial chemical reaction and internal diffusion. The calculated results show: when the reaction temperature is between 900℃and 1000℃, the processes of coke solution loss reaction before and after passivation are both controlled by the internal diffusion and the mechanism of passivation after addition of boric acid is increasing the resistance of internal diffusion during the solution loss reaction process, so the entire rate of reaction is decreased.The field emission SEM is used to observe the superficial structure change of coke before and after passivation (after solution loss reaction). The results prove the conclusion from kinetic calculation to be right and they also show that when the reaction temperature is above 1100℃, the process of coke solution loss reaction after passivation is controlled by the interfacial chemical reaction and the mechanism of passivation is restrianing the interfacial chemical reaction. |
