Detailed comments on governing equations and boundary conditions on which numerical results of gas flow in porous media should rely are presented. Numerical results are shown for the gas flow through a large blast furnace with designed layered structure of burdens. Not only the effects of radial and vertical distributions of resistance to flow but also the effects of different top profiles of burden, such as V-, M-shapes and V-shape with a side terrace, on the resultant gas flow are discussed in relation to the properties of burden, such as repose angle, particle size, voidage and different charging sequence. For the gas flow in a coaxial annulus bed, which is expected to appear in the lower part of blast furnace during a start-up or a blow-out operation, numerical predictions are compared with analytical ones based on a simple yet convenient gas flow model.

With the raw materials for ironmaking are becoming increasingly complex, more accurate control of blast furnace operation is essential to reduce the energy cost and CO2 emission. CaO–SiO2–Al2O3–MgO is a basic system of ironmaking slag in which CaO and MgO are mainly come from the flux, SiO2 and Al2O3 are mainly from the raw materials. Effect of raw material composition on phase equilibrium of the slag can be described by a pseudo-ternary system (CaO + MgO)–SiO2–Al2O3 at a fixed MgO/CaO ratio of 0.2. High-temperature experiments have been carried out in this system, and the quenched samples were analyzed by an electron-probe microanalyzer. The results are presented in a pseudo-ternary phase diagram (CaO + MgO)–SiO2–Al2O3 with a fixed MgO/CaO weight ratio of 0.2. Dicalcium silicate (Ca2SiO4), Melilite (2CaO·MgO·2SiO2–2CaO·Al2O3·SiO2), spinel (MgO·Al2O3), merwinite (3CaO·MgO·2SiO2), and anorthite (CaO·Al2O3·2SiO2) are the major primary phases in the composition range investigated. A series of pseudo-binary phase diagrams have been constructed to demonstrate the applications of phase diagram on blast furnace operation. CaO-rich cordierite solid solution has been first time reported with the accurate compositions and microstructure. The liquidus temperatures and solid solution compositions are compared between the experimental data and FactSage predictions to provide useful information for optimization of the thermodynamic database.

The use of pellet with low SiO 2 content in blast furnace (BF) will reduce the slag amount as well as fuel rate and increase the productivity. In this paper, the effect of the firing temperature and the added MgO on the reduction swelling index (RSI) and the compressive strength of the reduced pellet with low SiO 2 content was investigated, and the microstructure of the fired and reduced pellets was analysed by means of the electron microscopy. It was found that the decrease of SiO 2 content will raise the RSI and reduce the compressive strength of reduced pellet. When the SiO 2 content of pellet is 4.8%, the RSI is 16.5% and compressive strength of reduced pellet is 423 N/P. When the SiO 2 content is 2.8 and 1.8% fired at 1280°C, the RSI of the reduced pellet will increase to 34.5 and 55.8% and the compressive strength is reduced to less than 200 and 80 N/P. However, if some MgO was added, the RSI and the compressive strength of the reduced pellet could be improved significantly. When pellet's MgO content was over 1.7% and SiO 2 content was 2.8% or MgO content was 2.5% and SiO 2 content was 1.8% fired at 1280°C, the RSI of the two pellets could drop to less than 20% and the compressive strength could increase to more than 300 N/P. Then, the technical index of pellet will meet the requirement of the charging in large BF. The added MgO pellet with low SiO 2 content have been used in 5500 m 3 BF in Shougang Jingtang Corporation and delivered sustainable improvement of cost reduction.

With the raw materials for ironmaking becoming increasingly complex, more accurate phase equilibrium information on the slag is needed to refine the blast furnace operation to reduce the energy cost and CO2 emissions. CaO–SiO2–Al2O3–MgO is a basic system of ironmaking slag in which CaO and MgO mainly come from the flux, SiO2 and Al2O3 are mainly from raw materials. The effect of flux additions on the phase equilibrium of the slag can be described by a pseudo-ternary system CaO–MgO–(Al2O3+SiO2) at a fixed Al2O3/SiO2 ratio of 0.4. Liquidus temperatures and solid solutions in the CaO–MgO–Al2O3–SiO2 system with Al2O3/SiO2 weight ratio of 0.4 have been experimentally determined using high temperature equilibration and quenching techniques followed by electron probe microanalysis. Dicalcium silicate (Ca2SiO4), cordierite (2MgO·2Al2O3·5SiO2), spinel (MgO·Al2O3), merwinite (3CaO·MgO·2SiO2), anorthite (CaO·Al2O3·2SiO2), mullite (Al2O3·SiO2), periclase (MgO), melilite (2CaO·MgO·2SiO2-2CaO·Al2O3·SiO2) and forsterite (Mg2SiO4) are the major primary phases in the composition range investigated. A series of pseudo-binary phase diagrams have been constructed to demonstrate the application of the phase diagrams on blast furnace operation. Composition of the solid solutions corresponding to the liquidus have been accurately measured and will be used for the development of the thermodynamic database.

The variation in soil organic carbon density (SOCD) has been widely documented at various spatial and temporal scales. However, an accurate method for examining the attribution of explanatory factors for change in SOCD is still lacking. This study aims to attribute and quantify the key climatic factors, anthropogenic activities, and soil properties associated with SOCD change in the native grasslands of Inner Mongolia, China, by comparing data between the 1960s and the 2010s. In 2007 and 2011, we resampled 142 soil profiles which were originally sampled during 1963-1964 in the native grasslands of Inner Mongolia. SOCD was determined in A horizon (eluvial horizon) of the soil. We selected the explanatory factors based on a random forest method, and explored the relationships between SOCD change and each of the explanatory factors using a linear mixed model. Our results indicated that the change in SOCD varied from the east to the west of Inner Mongolia, and SOCD was 18% lower in the 2010s than in the 1960s. The lower SOCD in the 2010s may primarily be attributed to the increasing in mean annual water surface evaporation, which explained approximately 10% and 50% of the total variation and explainable variation in the change in SOCD, respectively. The sand content of the soil is also a significant explanatory factor for the decrease in SOCD, which explained about 4% and 21% of the total variation and explainable variation in the change in SOCD, respectively. Furthermore, the collection of quantitative information on grazing frequency and duration may also help to improve our understanding of the anthropogenic factors that govern the change in SOCD.