摘要
H2 injection through the shaft into blast furnace (BF) is a key technology for further reduction of CO2 emission from BF.It is well known that H2 accelerates reduction of burdens,but not well known of the effect on their reduction disintegration behavior.Therefore,we have investigated it with sinter,self-fluxed and acid pellet and estimated a dominant factor of disintegration behavior.Experiments: we measured mass fraction under 3mm (-3mm) after each burden was reduced at 823K for 30 minutes with gas mixture of CO-N2 system and H2-N2 system in an electrical furnace,and observed products after reduction with optical-microscopic and Electron Probe Microanalysis (EPMA).Results: -3mm of pellets increased with H2 contents and reached 15 mass% when self-fluxed pellet reduced with gas mixture of 70%N2-30%H2.The increase is beyond expectation that the standard RDI test (without H2) gave to the pellet.The optical and EPMA observation related the reaction mode to the generation of -3mm; that is,the fraction of -3mm increased as the reduction mode changed from topochemical to non-topochemical.This relationship can be explained by the manner of crack initiation and propagation: In case of topochemical mode,cracks generated in a concentric reducing zone; meanwhile,reduction with non-topochemical mode tended to generate radial cracks,which cause pellet chipping and further disintegration.
