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A novel smelting reduction process called pre-reduction in rotary kiln and total oxygen melting pool is a promising route to reduce environmental pollution from the ironmaking industry. In this paper, the process parameters and appropriate efficiency of reduction in the pre-reduction process of the rotary kiln were investigated via the detection of the metallization rate, phase composition, and internal morphology of the product combining with the analysis of the off-gas. The results indicated that the parameters of reduction temperature, reduction holding time, and coal ratio have a remarkable influence on the metallization rate. The reduction temperature has the most significant effect, followed by the reduction time and the coal ratio. Furthermore, under the condition of reduction temperature 1000 &deg, C, holding time 30 min, coal ratio = 1, a product with a metallization rate of more than 70% can be obtained, which meets the requirements of the rotary kiln process, and its CO2/CO value of the pre-reduction endpoint is appropriate. Continue to increase the temperature, holding time, and coal ratio can raise the metallization rate of the pellets, but only a little improvement and may cause reoxidation of the product.

To estimate the thermodynamic properties of a multi-component system using traditional geometric models, lack of a physical meaning generates many puzzles during choosing a concrete method. In this paper, we introduced a perspective in terms of the molar quantity of the components in the sub-binary of a ternary system affected by the third component and deduced a new model to unify all other traditional geometric models (e.g. Kohler, Muggianu, Toop-Kohler, etc.) into one model. The effects could be represented by so-called contribution coefficients, whose values only depend on the degree of identity between the thermodynamic properties of the third component and those of the selected components in the sub-binary, and which gives the physical meaning for the present model.

The partition behavior of alloying elements between the γ’ and γ phases in Nickel-based alloys was investigated by using infinite dilution activity coefficient and activity interaction parameter. The results showed that the preferential partition behavior of elements in the γ’ and γ phases is related to its infinite dilution activity coefficient ( ln γ i 0 \ln \gamma _i^0 ). When ln γ i 0 ≪ 0 \ln \gamma _i^0 \ll 0 , the element i has a strong tendency to partition in the γ’ phase; When ln γ i 0 \ln \gamma _i^0 approaches to zero, the element i has preferentially partition to the matrix γ phase. In addition, the partition behavior of element i in the γ’ and γ phases is also affected by the third element j in Nickel-based alloys, and this effect can be distinguished by the sign of the second-order activity interaction parameter ρ i i j \rho _i^{ij} .

In order to explore a reasonable way for the efficient utilization of coal resources in the ironmaking process. In this paper, lignite and bituminous coal are used as reducing agents, and two types of vanadium-titanium magnetite composite reducing agent pellets are prepared for different content ratios and mixed forms of the two coal powders. Under the simulated rotary kiln pre-reduction conditions, the influence of the ratio and mixing of pulverized coal on the metallization rate and tail gas composition of the reduction process was explored. The results show that increasing the proportion of high volatile lignite is beneficial to the reduction of pellets and can obtain pellets with a higher metallization rate. Under the new pre-reduction process conditions of the rotary kiln, the vanadium-titanium magnetite double-layer pellet with 75wt% lignite inside and 25wt% bituminous coal outside has the highest metallization rate of about 76%. At the same time, this new type of composite reducing agent pellets reduced gas emissions. This pellet is of great significance to the coal-based ironmaking process.

Catalyst can enhance the reduction effect and promote the reduction of vanadium titanomagnetite. In this paper, the carbon-containing pellets of vanadium titanomagnetite were prepared by using highly volatile coal as the reducing agent under the background of a novel process of pre-reduction in the rotary kiln. The effects of CaO, CaCO3, B2O3 and borax (Na2B4O7·10H2O) on the tail gas characteristics of carbon-containing pellets in the prereduction process were studied by using a simulated rotary kiln and flue gas analyzer. The results showed that the enhanced reduction effect of boron catalysts was slightly stronger than that of calcium catalysts, among which CaO catalyzed the least and borax the best. With the increase of metallization rate, the CO utilization in the tail gas is generally reduced, while when using CaCO3 as the catalyst, the CO utilization is significantly increased. Due to different reduction mechanism, the boron catalysts have little effect on the tail gas, and the calcium catalysts have a great effect on the tail gas. Based on the experimental results and the characteristics of the tail gas from the reduction process, we put forward the idea of using CaCO3 as the best catalyst and using CaO to absorb CO2 in the tail gas to form CaCO3.

With an attempt to improve the thermoelectric properties of type I clathrates in the Ba-Ga-Si system, we introduce Cu into the framework of the crystal structure. Single crystals are prepared in Ga-flux and characterized by X-ray diffraction techniques and transport measurements for the structural and thermoelectric properties. Our composition analyses show that only a small amount of Cu is determined in the clathrates. The single crystal X-ray diffraction data refinements confirm that Ga atoms prefer the 6c and 24k sites and avoid the 16i sites in the crystal structure. The small amount of Cu affects the crystal structure by compressing the tetrakaidecahedral cage along the direction perpendicular to the six-atom-ring plane. This could be the reason for the high charge carrier concentration, and low electrical resistivity and Seebeck coefficient. We analyze the principal mechanism for our observation and conclude that the Cu substitution can adjust some subtle details of the structure, maintaining the Zintl rule in the type I clathrates.

As an important method to estimate the thermodynamic properties of a multi-component system from the sub-binary systems, many extrapolation models have been proposed in the past. However, lacking a clear rule to distinguish the applicability leads to much confusion in practice. Recently, a Unified Extrapolation Model (UEM) that can cover all traditional extrapolation models was built by introducing a contribution coefficient which depends on the property difference between two components in a multi-component system. In this paper, the definition of property difference between any two components was discussed and presented a new mathematical expression to describe it. The performance of the new mathematical expression was tested for prediction of the mixing enthalpy in multicomponent alloy systems. The results revealed that the new mathematical expression for the property difference between components makes the performance of the UEM stand out among all traditional extrapolation models.

As an important method to link the thermodynamic properties of a binary system to that of a multicomponent system, many extrapolation models have been proposed in the past. However, lacking clear rules to distinguish the applicable systems of these extrapolation models led to much confusion during choosing a concrete model. Recently, a unified extrapolation model has been proposed by introducing a contribution coefficient, which is correlated to the difference in properties between the third component and a component from the selected sub-binary system. In this paper, two ways to treat this difference were discussed and their performances were tested by predicting the integral enthalpy of mixing in multicomponent systems. The results showed that when the properties difference is confined to the considered two components, the predicted values are in perfect agreement with the experimental data both in symmetric systems and in asymmetric systems; when this difference is defined by considering the interaction of the two components with the other one from the sub-binary system, the obtained results are in good agreement with the experimental data only in the symmetric systems. The reason is in the latter consideration, the treatment may exaggerate the properties difference in components.

With an attempt to improve the thermoelectric properties of type I clathrates in the Ba-Ga-Si system, we introduce Cu into the framework of the crystal structure. Single crystals are prepared in Ga-flux and characterized by X-ray diffraction techniques and transport measurements for the structural and thermoelectric properties. Our composition analyses show that only a small amount of Cu is determined in the clathrates. The single crystal X-ray diffraction data refinements confirm that Ga atoms prefer the 6c and 24k sites and avoid the 16i sites in the crystal structure. The small amount of Cu affects the crystal structure by compressing the tetrakaidecahedral cage along the direction perpendicular to the six-atom-ring plane. This could be the reason for the high charge carrier concentration, and low electrical resistivity and Seebeck coefficient. We analyze the principal mechanism for our observation and conclude that the Cu substitution can adjust some subtle details of the structure, maintaining the Zintl rule in the type I clathrates.

It is important to know the activity interaction parameters between components in melts in the process of metallurgy. However, it&rsquo, s considerably difficult to measure them experimentally, relying still to a large extent on theoretical calculations. In this paper, the first-order activity interaction parameter ( e s j ) of j on sulphur in Fe-based melts at 1873 K is investigated by a calculation model established by combining the Miedema model and Toop-Hillert geometric model as well as considering excess entropy and mixing enthalpy. We consider two strategies, with or without using excess entropy in the calculations. Our results show that: (1) the predicted values are in good agreement with those recommended by Japan Society for Promotion of Science (JSPS), and (2) the agreement is even better when excess entropy is considered in the calculations. In addition, the deviations of our theoretical results from experimental values | e S ( exp ) j &minus, e S ( cal ) j | depend on the element j&rsquo, s locations in the periodic table.