| Description |
In an effort to develop a novel flash ironmaking process, to be called the Sohn process in this dissertation, with the potential of steelmaking in a single continuous process, the phase equilibria involved and the chemistry of selected slag systems were investigated. The Sohn process is an ecofriendly flash ironmaking process for producing iron from iron oxide concentrates in a flash reactor using fuels and reductants that help reduce energy consumption and minimize greenhouse gas emissions. Amongst the proposed reductants and fuels are H2, natural gas, and coal gas. The molten bath (ironslag bath) is expected to equilibrate with gas atmospheres of mainly H2/H2O, CO/CO2/H2/H2O, and CO/CO2 corresponding to H2, natural gas/coal gas (NG/CG), and coke/coal (blast furnace, BF), respectively. The latter was investigated to allow comparison with the blast-furnace conditions. The slag composition was selected to resemble that of the blast furnace, which consisted of the CaO-MgO-SiO2-Al203-FeOMnO-P2O5 system with CaO/SiO2 in the range 0.8 to 1.4. The temperature range was 1550 to 1650°C encompassing a wide range of expected ironmaking temperatures for the Sohn process. The oxygen partial pressure was maintained in the reducing range 10-10 to 10-9 atm in the three gas atmospheres. It was found that H2O dramatically affects the chemistry of the slag and strongly affects the phase equilibria in the slag as well as the equilibrium distribution of elements between slag and molten metal. It was found that the slags under H2O-containing (H2 and NG/CG) atmospheres had a moderately higher degree of polymerization as compared to that under the blast furnace conditions. H2O in the gas atmosphere also increased the activity coefficient of FeO in the slag and accordingly lowered the FeO content. The FeO content in the slag of H2 (FeO wt% = 10) and NG/CG (11) was significantly less than under the BF (16) conditions. On the other hand, the average MgO solubility (22 wt%) under the NG/CG was higher than under the BF (18%) conditions, whereas MgO solubility showed no change under H2 (18 wt%) relative to the BF. Moreover, H2O causes the highest L s in the case of H2 as compared with all the other reducing agents. H2 showed 400% (Ls = 5.0) enhancement in Ls, whereas NG/CG exhibited 130% (Ls = 2.3) improvement compared with the BF (Ls = 1.0). Under H2 (Lp = 9) and NG/CG (Lp = 17), Lp was 50 and 6 % lower than under the BF (18) conditions, respectively. In addition, H2O in the gas atmosphere depressed LMn. LMn under H2 (LMn = 5) and NG/CG (4) conditions was, respectively, 29 and 43% lower than under the BF (7) conditions. The findings from this work suggest that the Sohn process will produce high quality iron with lower impurity levels and less FeO in the slag than the blast furnace. |
