A novel method for modeling the phase change of iron ore particles in the cohesive zone of a blast furnace

Cohesive zone plays a vital role in the stable operation of a blast furnace(BF),yet the complex phase change process of iron ore particles in this zone is still not well understood.In this study,a novel one-dimensional(1D)unsteady phase change model was developed to elucidate the heat transfer and melting mechanisms of iron ore particles.After model validation,the effects of several key operating parameters(e.g.,particle diameter,gas velocity,initial temperature)on the phase change behavior of iron ore particles were analyzed,and the joint effect of multiple parameters was discussed.The results show that larger-sized iron ore particles possess lower specific surface areas,which in turn reduces their convective heat absorption capacity.Consequently,the distance from the solid-liquid phase interface to the particle surface increases,thereby slowing down the movement of the phase interface and pro-longing the melting duration of the particles.Increasing the gas velocity and the initial temperature does not have a significant impact on reducing the duration of the complete melting process.Under the specified conditions,it is observed that increasing the gas velocity by 3-fold and 9-fold results in a reduction of the melting duration by 2.4%and 8.3%,respectively.Elevating the initial temperature of iron ore particles results in a decrease in the core-to-surface temperature difference,a slower heating rate,and a shorter duration to achieve melting.Among the factors affecting the melting process,the particle diameter is found to be the most significant in terms of the liquid phase precipitation,mushy zone thickness,and core-to-surface temperature difference of iron ore particles.

Particle shape effect on hydrodynamics and heat transfer in spouted bed:A CFD-DEM study

Spouted bed has drawn much attention due to its good heat and mass transfer efficiency in many chemical units.Investigating the flow patterns and heat and mass transfer inside a spouted bed can help optimize the spouting process.Therefore,in this study,the effects of particle shape on the hydrodynamics and heat transfer in a spouted bed are investigated.This is done by using a validated computational fluid dynamics-discrete element method(CFD-DEM)model,considering volume-equivalent spheres and oblate and prolate spheroids.The results are analysed in detail in terms of the flow pattern,microstruc-ture,and heat transfer characteristics.The numerical results show that the prolate spheroids(Ar=2.4)form the largest bubble from the beginning of the spouting process and rise the highest because the fluid drag forces can overcome the interlocking and particle-particle frictional forces.Compared with spherical particles,ellipsoidal spheroids have better mobility because of the stronger rotational kinetic energy resulting from the rough surfaces and nonuniform torques.In addition,the oblate spheroid system exhibits better heat transfer performance benefiting from the larger surface area,while prolate spheroids have poor heat transfer efficiency because of their orientation distribution.These findings can serve as a reference for optimizing the design and operation of complex spouted beds.

Effects of Bacillus subtilis and Saccharomyces cerevisiae inoculation on soil bacterial community and rice yield under combined irrigation with reclaimed and fresh water

In order to save fresh water and reduce soil salt accumulation,reclaimed water-fresh water combined irrigation,i.e,irrigation with reclaimed water for 50 d and then with fresh water till harvest,was used in rice planting.Bacillus subtilis and Saccharomyces cerevisiae were inoculated into the soil at the end of reclaimed water irrigation.The inoculation weight per pot of these microorganisms was as follows:0 g and 0 g(J0),5 g and 0 g(J1),3.75 g and 1.25 g(J2),2.5 g and 2.5 g(J3),1.25 g and 3.75 g(J4),and 0 g and 5 g(J5),respectively.Treatment using reclaimed water in the whole stage was used as the control(CK).The plant height,tiller,physical and chemical properties of the soil,and soil bacterial diversity were measured.It was found that the plant height of rice was increased significantly by J1-J5 treatments.The dry weight of rice root,stem,and panicle and the 1000-grain weight increased significantly,while the leaf dry weight decreased.Microorganism inoculation significantly increased the nutrient absorption capacity of the crops.J1,J2,and J4 treatments significantly increased the amount of nitrate-nitrogen,ammonium nitrogen,available phosphorus,and available potassium,while J3,J4,and J5 treatments increased the soil organic matter,and microbial inoculation significantly decreased the EC of soil.J4 treatment induced the largest reduction in EC,and microorganisms treatments increased soil pH.Bacterial function prediction based on the KEGG(Kyoto Encyclopedia of Genes and Genomes)pathway indicated that soil metabolic function was not significantly disturbed by the treatments.Organic matter and pH are the two main factors affecting the structure of the bacterial community in soil.3.75 g of B.subtilis and 1.25 g of S.cerevisiae per pot is the best inoculation ratio.