Gasification Reactivity And Kinetics Of Blast Furnace Coke/Tuyere Coke

As the main fuel of blast furnace,the scientific evaluation of coke quality and performance should not be ignored before use.The decrease of coke’s mechanical strength and particle size in the blast furnace and the coke powder will reduce the permeability of the charging column and affect the furnace condition.The increasingly large blast furnace and low coke ratio increase the deterioration of coke,which is mainly due to coke gasification reaction with CO₂ at high temperature and mechanical and thermal stress failure.There are many factors affecting with the gasification reaction of coke in blast furnace,and the complex gas environment is also difficult to simulate in the laboratory,the primary and secondary relationship and the connect with each other of the factors is not clear.In this paper,the gasification reactivity of the same batch of coke and tuyere coke into the same blast furnace when it rests twice in a certain steel mill was studied.The coke was sampled radially,and SEM-EDS,XRD,XRF,N₂ adsorption were used to characterize and test the sample,so as to explore the microstructure,carbonization structure,alkali metal enrichment degree,pore structure change process and rules of the coke sample from the furnace to the tuyere.The gasification reactivity and gasification reaction process of coke were studied by means of thermogravimetric analysis at different heating rates and temperatures.And the unreacted core model,volume model and random pore model were used to calculate the kinetics of coke gasification reaction.The influence of gas diffusion on the gasification reaction of coke block was studied by simulating gasification experiment of coke block with tube furnace.The main conclusions are as follows:（1）In the process of coke from entrance to tuyere,its properties change as follows:the specific surface area increases,the degree of carbon structure increases and the alkali metal content increases.It is proved that the surface of the coke block and its internal reaction in the blast furnace are different,from the tuyere coke edge,midpoint and centre of the properties of all parts are reflected.（2）In the non-isothermal gasification reaction,the metal content of K is the main factor affecting the reactivity of coke gasification,and also the main reason for the increase of the reactivity of coke in tuyere.In the model selection,VM and RPM models have better fitting for the gasification reaction of the in-furnace coke,while the RPM model has the best fitting degree for the gasification reaction of the tuyere coke.The overall activation energy of the tuyere coke is lower than that of the in-furnace coke,corresponding to the gasification reactivity shown.（3）In the isothermal gasification reaction,at 1100℃,the content of metal K was still the main factor affecting the gasification reaction,while at 1500℃,the specific surface area of coke was the main factor affecting the gasification reaction.In the model selection,the URCM,VM and RPM models all have good fitting effects on the furnace coke,while the fitting effects on the tuyere coke,VM and URCM models are better.The total activation energy of tuyere coke is lower than that of furnace coke.Because it affects the change of control conditions of gasification reaction at different temperatures,the activation energy values of each part calculated by different calculation methods are different.（4）During the gasification reaction of coke block,there are reactions on its surface and inside.The reaction model changes from gradient model to homogeneous model as the reaction progresses by the change of pore structure of coke during the gas diffusion and gasification reaction.