Application of multiphase experimental and numerical methods to investigate the trickle flow behavior in the lower part of blast furnace

Abstract

The trickle flow behavior in the lower part of blast furnace is studied using multiphase computational method and high temperature experimental method. Previous studies for decades do not agree each other and have limitations caused by computational limitation and experimental difficulties. Based on multiphase approach, 2 dimensional and 3 dimensional phase field method and volume of fluid method are used to simulate and visualize the liquid flow behavior in the packed bed. Residence time of liquid material in packed bed is calculated and a correlation equation is obtained as: (log t’ = 2.8 - 10/7 log Rem + 1/4 log Gam + 2/7 log Cps). In 3dimesional calculation, the liquid hold-up characteristic of different liquid materials which have different physical properties are analyzed by using closely packed bed system in which the particle diameter is 20mm. The result shows that viscosity, surface tension and contact angle highly influence on the liquid hold-up and liquid flow velocity. As increasing viscosity, the liquid hold-up increases from 0.05Pa•s to 1.0Pa•s. the liquid hold-up increases but the static hold-up does not change much after the full drainage. Increasing surface tension from 0.05N/m to 1.0N/m increases the liquid hold-up and it also increases the static hold-up after the drainage. On the other hand, the increasing contact angle decreases the hold-up and the static hold-up as well. According to the high temperature experimental result, liquid high carbon iron can pass through the coke bed of which the diameter is in the range of 5mm~9mm, but, it cannot pass through the coke bed in the range of 3.35mm~5mm. This result basically shows that the capillary force dominantly interrupts the liquid iron flow in the small sized coke bed. Considering that capillary force is determined by surface tension and contact angle, 3 phase computation and experiment are performed to see how the liquid iron and slag behave in the coke bed. The liquid iron can pass through the 3.33mm~5mm sized coke bed when it has a contact with slag drop. The enhanced liquid iron flow contacting with slag is simulated by Volume of Fluid method and it confirmed that the contact angle change of the liquid metal enhanced the flow behavior by changing the capillary force direction. Based on the experimental and numerical results, an analytic model is developed to illustrate the capillary force effect on the dripping flow of a liquid drop in a three dimensional packed bed.