Study of gas fine flow in a packed bed with an application to the ironmaking blast furnace

Abstract

The iron and steelmaking industry uses coal as the primary reducing agent. The carbon that is the major component of coal is finally released into the environment as carbon dioxide. One of the effective ways to reduce the coke consumption and thus the reduction in greenhouse gases is to introduce coal or other carbonaceous materials through the tuyere. However, this can be done only up to some extent as injection of these materials reduces the bed permeability which in turn affects the operation and productivity of the blast furnace (BF). Previous studies have shown that at a higher pulverised coal injection (PCI) rate and depending on the operating conditions of the furnace, some amount of coal remains unburnt and consequently the ashes and coal particles, in the form of powders, may be entrained in the gas stream or be deposited into the lower zones of the BF. However, the physics of the pulverised coal within the furnace is still not well understood, especially in presence of raceway and tuyere protrusion. Raceway is very important in iron-making BF as its size and shape determines the aerodynamics of BF and thus the heat and mass transfer. Therefore, the study of fine flow in a packed bed is a necessary precursor to understand the above-mentioned processes/phenomena. For the validation purpose, two-dimensional experimental studies were performed at room temperature on the various packed bed such as a rectangular bed with and without a cohesive zone and a cylindrical bed without a cohesive zone. Both the packing and fine particles were made of glass material. Steady state of experiment with fines was achieved based on the recently developed accurate mass balance method which dictates that fines into the system must be equal to fines out of the system. Most research neglect vital characteristics of BF, such as lateral inflow, presence of tuyere protrusion, the raceway s shape and size, and cohesive zone leading to a significant incongruence with the BF being modelled. The present work incorporates these feat...