Validation of Calculated Thermal Parameters with Experimental Results in SOFCs

Eleven steel grades were designed to be used as metallic interconnects for Solid Oxide Fuel Cells (SOFC). Low carbon, high chromium steel with different additives of niobium, vanadium, aluminum, molybdenum, silicon, manganese and titanium were produced. Phase transformation temperatures;eutectoid temperature (Ac1) and temperature at which transformation of ferrite to austenite is completed during heating (Ac3) were measured by L75-76 dilatometer. The influence of the alloying elements on transformation temperatures was analyzed using MATLab. Considering the interaction between different alloying elements two equations for predicting Ac1 & Ac3 were obtained. The obtained Ac1 & Ac3 by these equations showed more compatibility than that obtained by traditional ones. In addition, the coefficients of thermal expansion of these steel grades were detected. The influences of chemical composition and temperature on the thermal expansion coefficient were analyzed;the obtained equations were verified to certain extent by using several kinds of steels. The predicted values were in good accordance with the experimental results which proof the validation of calculation model.

Parameters Affecting the Production of High Carbon Ferromanganese in Closed Submerged Arc Furnace

This study has been performed to investigate the different parameters affecting on the production of high carbon ferromanganese in closed submerged arc furnace. The analysis of industrial data revealed that using manganese ores with low Mn/Fe ratio necessitates higher amount of Mn-sinter in the charge. Using Mn-blend with higher Mn/Fe ratio reduces the coke consumption and this leads to reducing the electrodes consumption. The recovery of Mn ranges between 70 and 80 %. Much higher basic slag has slight effect on Mn- recovery. However, as slag basicity increases, the MnO- content of slag decreases. The manganese content of produced HCFeMn depends mainly on Mn/Fe ratio of Mn-blend. For obtaining HCFeMn alloy containing minimum 75%Mn, it is necessary to use Mn-blend with Mn/Fe ratio of higher than 6. A model for determination of the amount and composition of off-gases has been derived based on the chemical composition and material balance of the input raw materials and the produced alloy and slag. By using this model, the amount of off-gases was found to increase by increasing both Mn-blend and coke consumption.

Parameters Affecting Energy Consumption for Producing High Carbon Ferromanganese in a Closed Submerged Arc Furnace

The power consumption is considered to be the most important factor affecting the production cost of fer romanganese alloy. Different parameters affecting the energy consumption for industrial production of high carbon ferromanganese HCFeMn were investigated in a closed submerged arc furnace. The analysis of industrial data revealed that the most energy consumed factors were the direct reduction by solid carbon, Boudouard reaction, metal and slag formation, and decomposition of fluxing materials （limestone and dolomite）. To reduce the energy con- sumption and minimize the energy losses in the production process of HCFeMn, it was recommended to use Mn blend with minimum Mn to Fe ratio of 6 and lower SiO2 content or higher basicity. The added coke must be adjusted according to the material balance to prevent the over-coke and to minimize the highly endothermic ＂Boudouard reac tion＂. In addition, it was recommended to work at basic slags with the ratio of （CaO＋MgO） to Si（）2 equal to 1.0- 1.2 instead of much higher slag basicity. Furthermore, the mass losses had to be minimized through adjusting the handling and charging process and to take care of all metal produced.