Despite measures to increase pulverised coal (PC) conversion, part of the injected PC leaves the raceway as char, particularly at high injection rates. The coke/PC replacement ratio and, consequently, the blast furnace (BF) operation efficiency depends on the consumption of char by reactions of secondary gasification and added burden. This contribution focuses on the change in streaming conditions in different BF zones when coal particles leave the raceway. To investigate this, a 2-D physical BF cold model was used. Tests were conducted after injecting various amounts of PC and under various gas flow rates. Particle movement and accumulation were examined by measuring the pressure drop at different positions in the model. To evaluate the effect of PC on the gas permeability in vertical and horizontal directions, calculations using the Darcy-Weisbach/ Ergun equation were performed. The results will be used to improve CFD-modelling and the prediction of char behaviour in the BF.

Counter current flow reactors are the most efficient metallurgical vessels. This is why the blast furnace (BF) remains since more than 700 years No. 1 aggregate for primary metal production. It is anticipated that also in the future, shaft furnaces operating on this principle will dominate the direct reduction (DR) production. Consequently, the gas permeability is a crucial issue for shaft furnaces. In the BF, required gas permeability, as well as a drainage ability in the dripping zone, is ensured, primarily, by a certain amount and quality of coke.The injection of solid auxiliary reducing agents (ARA) may negatively affect the gas permeability and the drainage ability by two means: decrease of thickness of coke layers due to lower coke rates─and accumulation of unburnt injected particles outside the raceway─in dripping zone (DZ), cohesive zone (CZ), and shaft. Concerning the first reason, the burden-coke layer thickness ratio was increased, for example, from 0.93 for only coke operation to 1.54 while injecting 200 kg t HM À1 pulverized coal (PC) according to the calculations conducted. [1] Effects of layer thickness on the pressure drop in the BF "dry" zone and in the cohesive zone become apparent at increasing Reynolds number and flow rate. [2] Concerning the second reason, the mathematical modeling showed that char accumulates mainly in cohesive zone, deadman, and hearth. [3] The effect of accumulation of unburnt PC on the specific pressure drop is examined experimentally in this work.Factors affecting the BF operation efficiency while injecting PC can be divided into four major groups: 1) characteristics and conversion behavior of coal and formed char; 2) characteristics of charged materials and liquid products, and their change caused by PC injection; 3) BF operation parameters; and 4) design of tuyere and injection lance.These factors are also considered vital important by the current trend of PC co-injection with hydrogen-containing gases such as coke oven gas [4,5] or pure hydrogen. [6] Chemical, physical, mechanical, and petrographic characteristics of injected coals and their effect on the conversion behavior in the raceway, reducing gas, and heat generation and, consequently, on the coke replacement ratio are well known and summarized in Ref. [7,8] This also applies to the effect of BF operation parameters such as blast temperature, oxygen