Fuyong Su

CFD Modeling of Flow, Temperature, and Concentration Fields in a Pilot-Scale Rotary Hearth Furnace

A three-dimensional mathematical model for simulation of flow, temperature, and concentration fields in a pilot-scale rotary hearth furnace (RHF) has been developed using a commercial computational fluid dynamics software, FLUENT. The layer of composite pellets under the hearth is assumed to be a porous media layer with CO source and energy sink calculated by an independent mathematical model. User-defined functions are developed and linked to FLUENT to process the reduction process of the layer of composite pellets. The standard k–ε turbulence model in combination with standard wall functions is used for modeling of gas flow. Turbulence-chemistry interaction is taken into account through the eddy-dissipation model. The discrete ordinates model is used for modeling of radiative heat transfer. A comparison is made between the predictions of the present model and the data from a test of the pilot-scale RHF, and a reasonable agreement is found. Finally, flow field, temperature, and CO concentration fields in the furnace are investigated by the model.

Mathematical simulation of direct reduction process in zinc-bearing pellets

A one-dimensional unsteady mathematical model was established to describe direct reduction in a composite pellet made of metallurgical dust. The model considered heat transfer, mass transfer, and chemical reactions including iron oxide reductions, zinc oxide reduction and carbon gasification, and it was numerically solved by the tridiagonal matrix algorithm (TDMA). In order to verify the model, an experiment was performed, in which the profiles of temperature and zinc removal rate were measured during the reduction process. Results calculated by the mathematical model were in fairly good agreement with experimental data. Finally, the effects of furnace temperature, pellet size, and carbon content were investigated by model calculations. It is found that the pellet temperature curve can be divided into four parts according to heating rate. Also, the zinc removal rate increases with the increase of furnace temperature and the decrease of pellet size, and carbon content in the pellet has little influence on the zinc removal rate.

Numerical simulation and parameters optimisation of direct reduction process of iron ore–carbon composite pellet

Abstract A mathematical model considering heat transfer, mass transfer, porosity change, stepwise reductions of iron oxides and carbon gasification has been developed to investigate the direct reduction process of iron ore–carbon composite pellet. The governing equations were discretised in fully implicit form based on control volume method and numerically solved using tri-diagonal matrix algorithm. The model has been validated by comparison with experimental data from the literature. The effects of some operational parameters have been investigated, and the optimal combination of these parameters is determined by orthogonal test. The results show that the reduction rate increases with the decrease of pellet diameter initially. However, the final degree of reduction increases with the increase of pellet diameter ranging from 5 to 15 mm. Chemical reaction rates increase significantly with the increase of furnace temperature. The degree of reduction for pellet with C/O ratio of 0·8 is lower than pellets with C/O ratio of 1·0 and 1·2 after reduction for 900 s. The degree of reduction is 95·84%, which is high enough in engineering, when furnace temperature, reduction time, C/O mole ratio, and pellet diameter are 1473 K, 10 min, 1·2, and 20 mm, respectively.