【摘要】 讨论了回转窑直接还原的两个主要反应。研究证明,直接还原用煤的气化反应符合“拟均相反应模型”,CO 对球团矿的还原反应符合未反应核模型。两个反应均处于反应动力学控制阶段。最后探讨了固体碳对球团矿还原的动力学计算问题。更多还原

【Abstract】 In this paper, an experimental investigation is carried out on the reduction process in rotary kilns. The gasification reaction of the fixed carbon of lignitous coal charged into the rotary kiln usually takes place on the interface between the gaseous phase and the solid phase. The solid reactant under reaction is such a porous substance that its surface area may be considered of no account as compared to the total inner surface areas of all its pores. Thus, the reaction can be considered as taking place in pores only and so the reaction rate also may be refered to as proportional to the total inner surface areas of all the pores. Based on this assumption, a kinetics model of quasi-homogeneous reaction describing the gasification reaction is proposed, i. e.where θ =M/M0, M is the amount of carbon and M0 is M when t = 0, t the time and k the proportionality constant and CCO is the CO2 concentration. The experimental verification shows that such a model of quasi-homogeneous reaction is applicable for describing the gasification reaction of carbon in rotary kilns. The reduction reaction of iron ore pellets with CO is the other reaction on the interface between the gaseous phase and the solid phase. The unreacted core model describing this reaction is expressed as follows.where Rd is the degree of reduction, fi(T) a function of T(temperature), CCo the concentration of CO and r0 the radius of the iron ore pellet. In addition the influence of the external diffusion on the reaction rate has been discussed. Kinetics calculations performed here for the pellet’s reduction by solid carbon conform to the experimental results.更多还原