Numerical analysis of the carbon containing pellets direct reduction process

In view of the carbon-containing composite pellets direct reduction process in rotary hearth furnace, a mathematical model coupling heterogeneous chemical reaction kinetics, heat and mass transfer of this process was established. The effects of furnace temperature (from 1273.15 K to 1673.15 K) and pellet radius (from 6 mm to 16 mm) on the direct reduction of carbon-containing composite pellets were studied by adopting computational fluid dynamics software. The pellet temperature and composition changes under different operating conditions were analyzed. CO and CO2 fluxes, heat fluxes on the pellet surface were especially studied. Total heat absorption by the pellet, CO and CO2 overflow from the pellet surface together with pellet degree of metallization (DOM) and zinc removal rate (ZRR) were calculated. Results show that with the increasing of furnace temperature or the decreasing of the pellet radius, the temperature difference between pellet surface and its center and the final DOM, ZRR increased. The larger the pellet radius, the smaller the heat absorption, also the smaller CO and CO2 overflow. But heat absorption and CO overflow per unit volume are higher. There is an optimal pellet radius with high CO utilization efficiency. Pellet porosity decreases at first and then increases with reducing time. It is also found that effective thermal conductivity is a major factor limiting the pellets temperature increasing. The reduction sequence of the pellets is Fe2O3→Fe3O4→FeO→Fe.

Numerical Analysis of Radiative Heat Transfer and Direct Reduction of Three-Dimensional Multilayer Ellipsoidal Carbon-Containing Pellet Unit in the Rotary Hearth Furnace

It is very important for a multilayer pellet bed to have a proper description of the radiant heat transfer and direct reduction process in the rotary hearth furnace. Ellipsoidal pellets may also be used in industrial production. The research on this ellipsoidal pellet bed will provide comprehensive data support for the production process. Besides, the view factor is one of the important factors affecting the heat transfer of the multilayer pellet bed. It is of great significance to study its value and distribution. In this study, the effects of the gas field and the bottom of the furnace on the direct reduction of multilayer ellipsoidal pellets were considered. The local environmental viewing angle coefficient in the model was obtained through the mechanism calculation method, which is more accurate than the calculation through the radiation exchange network. Furthermore, the porosity variation in the pellet during the direct reduction process was also considered. According to the calculation, it was found that the higher initial temperature at the furnace bottom is beneficial to increase the degree of metallization (DOM) and zinc removal rate (ZRR) for all pellets, and is more advantageous to the lower pellets in the material bed. Nevertheless, the reduction degree of the lower pellets is still smaller than that of the upper pellets. The results also show that increasing the offset ξ has a greater effect on increasing the ambient view factor and each position reduction degree in the ellipsoidal pellets layer. Results can be applied for the optimization of pellets distribution in a rotary hearth furnace.

Study on Direct Reduction Process of Cylindrical Briquetting Hematite

There are two types of iron resources such as primary iron ore and iron sand. In general, primary iron ores use as raw materials in iron and steel making and can reduce directly. In Direct reduction process, Fe2O3 (hematite) is converted to metallic iron by the removal of oxygen. This work presents a heat transfer rate study for direct reduction process of iron ore cylindrical briquette. An investigation has been carried out of different reduction parameter such as different sizes cylindrical geometry over temperatures ranging from 700°C to 1100°C for reaction time from 10 minutes to 1 hour. The result was indicated that the value of the heat transfer rate decreases in the core and outer parts of the cylinder briquettes.

Carbon Impact Mitigation of the Iron Ore Direct Reduction Process through Computer-Aided Optimization and Design Changes

The steel industry is known to have one of the highest environmental impacts on the industrial sector, especially in terms of CO2 emissions. The so-called direct reduction route, which makes use of reformed natural gas along with top gas recycling to reduce iron oxide pellets with H2 and CO, is responsible for lower CO2 emissions than the classic blast furnace route and is currently under development. The present article focuses on the direct reduction process and discusses means to further decrease the CO2 emission rate. A set of 10 operating parameters were simultaneously changed according to computer-aided optimization. The results provide about 15% improvement over original emissions for comparable output values.

Analysis of Cylindrical Briquette Dimension on Total Iron Content and the Degree of Metallization in Direct Reduction Process of Iron Ore and Iron Sand Mixture

Indonesia has abundant resources or raw materials, especially the iron sand raw materials. But, the iron sand processing in Indonesia is still low. Even though, the steel demand in Indonesia is still high. So, the iron sand processing product as raw materials in steelmaking is the solution of it. In this research, the study was conducted by using the variation of briquette dimension of mixture of iron sand and iron ore in Direct Reduction process. The aim of this research is to study the effect of briquette dimension on Fe content and degree of metallization of the Direct Reduced Iron (DRI). First, the iron sand and iron ore were crushed and shieved until pass the 50 mesh standar size. Then, iron sand and iron ore were mixed and briquetted based on the variation of dimension. There are three variations of briquette dimension. Then, the briquettes was reduced at 1250°C for 12 hours. The reduced briquettes then were analyzed using XRD, XRF and degree metallization calculation. The result showed that the dimension of briquette affect the Fe content and the degree metallization of DRI. The dimension of briquette will affect the reductor gas flow in the crucible, so the rate and direction of reduction process of iron oxide will be affected too. The best briquette is Briquette B (7.9 cm for inside diameter, 15.1 cm for outer diameter and 19.5 cm for the height), with 75.02% for Fe total content and 66.52% for degree of metallization. This was due to The briquette B has the most evenly diffused dimension either vertically and horizontally.