1995 Volume 38 Issue 6 Pages 390-398
The iron manufacturing industry has been required to reduce emission of carbon dioxide and exergy consumption for the protection of the global environment. For the purpose, to resolve this problem, partial replacement of coke by auxiliary fuels in the energy source of blast furnaces and the conversion of CO and CO2 in the blast furnace stack-gas into methanol were investigated over 25.7Cu-60ZnO-14.3Al2O3(mol%) catalyst. The performance of a blast furnace fired with natural gas, coal water mixture (CWM), coal oil mixture (COM) and pulverized coal was predicted by a mathematical model, based on heat and mass balances. In the prediction, firing rate of auxiliary fuels was determined to keep the theoretical flame temperature unchanged in the raceway region of the blast furnace.
As a result, the auxiliary fuel firing led to hydrogen enriched and lean nitrogen concentration in the blast furnace stack-gas. In the methanol synthesis experiment, forty fold higher yield of methanol on the carbon basis was observed by increasing the H2/(CO+CO2) ratio in the reactant gas from 0.05 to 0.5, where 0.05 corresponds to the value for the conventional blast furnace. The methanol yield was also increased with decreased nitrogen. This implied that controlled firing auxiliary fuels into the blast furnace is advantageous from the view of subsequent methanol synthesis.
The greenhouse gas emission was reduced by the auxiliary fuel injection. The exergy consumption was also decreased by the injection of CWM, COM and pulverized coal. In particular, COM was the most effective for the reduction of GHG emission and exergy consumption, and for methanol synthesis from the blast furnace stack-gas. In the blast furnace operation where 384kg-coke/tHM and 100kg-COM/tHM were supplied, the total amount of GHG emission was reduced from 535 to 501kg-C/tHM and the sum of exergy consumption also decreased from 9.0 to 8.3GJ/tHM, when compared to that of the operation without COM injection.
