The raceway has been studied extensively both theoretically and experimentally. In this study, particle velocity contours have been developed to define the raceway boundary. The raceway boundary is coarse and fragmentised, but all of the previous studies are based on Euclidean geometry, which regard the dimension of the raceway as an integer. In this paper, the fractal method of calculating raceway size, which describes the boundary with extremely irregular or fragmented characteristics, is on the data from a cold physical model of the raceway. The results show that the precise raceway boundary can be obtained by the particle velocity contours, that the surface area of the ellipsoidal raceway based on fractal theory is larger than that based on Euclidean geometry and that the data can be used as original boundary conditions of the flow and chemical reaction in the raceway region.

COREX shaft furnace (SF) is a typical screw hopper with eight screws evenly distributed at bottom. The design of screws plays an important role in moving behaviors of burdens and interaction between solid. Therefore, a three‐dimensional cylindrical COREX SF model at full scale of Baosteel is established based on the Discrete Element Method to study the influences of the design of screws, and comparisons are made between the old and modified screws of Baosteel. The measure implemented to the modified screw is to decrease screw flight diameters from the pitch 1 to 3 to obtain greater increment withdraw volume along the screw length. The results show that the profile coefficient, increases dramatically at pitch 4 and 5 than that of the old screw. Compared to old screw, descending velocities and flow patterns of modified screw are more uniform in the lower part of SF. The force distributions are similar in the upper part of SF between the two screws, but the small force area in the lower part for the modified screw expands from screw tip to furnace wall, which is much bigger than that of old screw. The abrasive screw wear at the third and fourth pitches are alleviated with the implement of the modified screw, which is consistent with the force distribution in the lower part of SF. Additionally, the total power draw also decreases after the modification. The findings of this work should be useful for the design, control, and optimization of the SF operation.

A three-dimensional mathematical model is developed to describe the influence of AGD beams on gas distribution in COREX-3000 shaft furnace. The calculated result shows that with AGD beams installed, the pressure drop in furnace is decreased while the volume of low velocity zone at bottom of furnace is enlarged. AGD channels can lead reduction gas into shaft center, and increase the gas velocity at slots level, but it have little effect on gas distribution at upper part of the furnace. AGD beams are also good at restraining down pipe gas, and the volume fraction of down pipe gas declines from 9.89 % to 6.41 %, decreases about 35.2%. 2#COREX furnace with AGD beams is better at achieving uniform gas distribution.

The freeboard, which is an important region in COREX melter gasifier, has drawn more and more attentions, and as a key parameter for COREX melter gasifier operation, the temperature in freeboard must be within a certain range. In this paper, the temperature field of freeboard is simulated with computational fluid dynamics(CFD). The results show that the temperature in bottom is lower than that in upper. The temperature when oxygen nozzles are open is higher than that when oxygen nozzles are off, and the temperature under different operation conditions is all about 1000 °C.

A physical thermal model was established in this study, and the gas temperature in the model was measured with temperature sensors under different experimental conditions. The results show that the packed bed, cohesive zone, dripping zone and raceway in melter gasifier can be roughly distinguished by temperature gradient analysis along the vertical direction. The changes of different zones in the COREX melter gasifier were also investigated in this paper under different operation conditions.