Nondestructive Analysis of Coke with/without Iron Catalyst Using μ-X-ray CT

摘要

The performance of coke in blast furnace (BF)used to prefer a high strength and low reactivity,generally.One of the reasons is in the importance of gas and liquid permeability in the lower part of BF,which are related to the stable operation of BF.On the other hand,the energy saving in the BF process will contribute the decrease of CO2 emission,because the proportion of CO2 emission in the ironmaking field is quite large.To decrease the reducing agent ratio the reaction efficiency in the BF should increase more and more.It is recognized that the reactivity and the strength of coke contradict each other.The high reactivity coke generally has a low strength.To overcome the contradiction,the use the catalyst on the coke gasification will be effective.Since the gasification reaction occurs on the surface of inner wall of pore,the change of pore structure should be clarified.In this study,the coke structures before and after gasification were analyzed using μ-X-ray CT (Computer Tomograph).The optimum conditions for the image processing of data from the μ-X-ray CT were elucidated through the comparison with the image of cross section of coke using an optical microscope,which was embedded in the resin with a fluorescent agent.It was found that a nondestructive observation of coke using μ-X-ray CT was possible.In the case of no addition of iron catalyst,relatively larger structure(～0.5mm) was almost the same between the μ-X-ray CT and the optical microstructure,however,the smaller structure less than 0.5mm could not be observed appropriately.The causes of the discrepancy were come both from μ-X-ray CT and optical microscope observations.The μ-X-ray CT has a lower image resolution in comparison with optical microscope,on the other hand,the plane of cross section for the observation of optical microscope had a lower flatness because of the problem of polishing technique.In the case of iron catalyst addition,the resolution of μ-X-ray CT decreased significantly with the increase of catalyst addition.To overcome this problem,the higher intensity of X-ray will be necessary.Although the observation by μ-X-ray CT has some limit,a macroscopic observation before and after gasification can be performed appropriately.The nondestructive analysis of coke before and after gasification was carried out and the structure change after gasification was elucidated.