Fundamental Study On Two-stage Gasification Of Coal And Iron Ore For High-grade Gas And Iron Ore

Removal and conversion of tar produced during gasification has important significance on development and application of coal gasification technology. In conventional tar catalytic cracking process, catalysts usually are expensive, volatile live, and difficult to recycle, this thesis proposes a new process that coal and iron ore are both used to produce clean gas and high-grade iron ore. This process can remove and converse the tarproduced during process of coal gasification to get clean gas,meanwhile iron ore after reduction reaction and with carbon can also be used as high-grade raw material for iron making. In this paper, the mechanism and experimental research primarily related to this process were carried out.Firstly, steam gasification and pyrolysis characteristics of coal under different reaction conditions were studied with TGA, the results showed that:the main pyrolysis zone of Mengdong coal is300-600℃, the lowest temperature of gasification reaction is900℃, the gasification reaction activity is effected by the deposition thickness of the sample, the vaporization temperature and water vapor concentration. Coal gasification reactivity index of different raws are effecte by volatile matter, fixed carbon, ash content and composition.2D-PCIS method was used to study infrared functional groups evolution during coal pyrolysis under different temperature, reveals the mechanism of coal pyrolysis process, the results showed that:Polyhydroxy I in Xiaolongtan and Mengdong coal, molecular hydrogen in Lu’an coal, Functional groups of symmetric and asymmetric-CH2-is very sensitive to pyrolysis temperature, changes easily occurred during the pyrolysis process. Free hydroxyl groups are not found in chars after demineralization of Mengdong coal, the order of hydroxyl groups is not changed after demineralization and adding K2CO3as catalyst. The aromatic CH functional groups had a little change with addtion K2CO3as catalyst, but change is limited. Demineralization has great impact on the aromatic area, the order of aromatic and fatty areas of functional groups is changed.In the study of carbon skeleton structure evolution during coal gasification, reveals the mechanism on catalytic gasification of coal gasification, it was found that K-based catalysts both had a significant effect on the efficiency of the steam gasification, and could significantly reduce the gasification reaction temperature and increase the carbon conversion. Gasification active intermediates C(O) of original coal was structures as aromatic ring of small (3-5rings) and crosslinked structure. With the rank of coal increasing, the formation of active intermediates C(O) decreased. With the gasification temperature increasing, the formation of active intermediates C(O) increased. After addition of catalyst (K-base and CaCl2), the active intermediates consisted of C (O)(small aromatic ring structure (3to5rings)) and M-O-C (smaller aromatic ring structures (more than3to5rings) and part of the M-O-C formed from crosslinked structure). After addition of catalyst (FeCl3), the active intermediates consisted by C (O)(small aromatic ring structure (3to5rings)) and M-O-C (smaller aromatic ring structures (more than3to5K-ring) were less than K-base and CaCl2).Study on characteristics of catalytic cracking of tar with iron ore, it was found that the reaction of decomposition tar into carbon firstly occurred in catalytic cracking of tar by iron ore, and then the carbon reacted with iron ore. Iron ore was reduced by carbon at400℃, and could be completely reduced to Fe3O4. With temperature increasing, the reactivity of tar and iron ore increased, amount of carbon content and other Fe (Fe, Fe2C and Fe3C) increased.Study on the advanced systems of gasification of coal and iron ore, indicated that H2yield was greatly effected by the water vapor concentration. H2yield increased as water vapor concentration increased. CO yield was greatly impacted by the ratio of iron ore to coal, CO yield decreased as the ratio of iron ore to coal increased. With concentration of water vapor increasing, the amount of Fe3O4, FeO, Fe and C in iron ore decreased. With gasification temperatur increasing, the amount of Fe, FeO, Fe2C and Fe3C in iron ore decreased, the content of C first increased and then decreased.