Extended use of helium tracing technique and assessment of blast furnace shaft permeability

Abstract

The blast furnace is a countercurrent reactor in which a reducing gas is produced by coke gasification with the oxygen blown in via tuyeres. The reducing gas flows upwards, reducing the iron ores charged at the top of the furnace. It is a very complex process with many influencing and correlating factors. Its productivity is the quotient between possible gas throughput per unit of time and required specific gas generation for 1 tonne of hot metal obtained, and its permeability is a measure of the gas ability to pass through the bed of solid materials. The objective of 'high levels of injection of pulverised coal' is not only compatible with productivity, but also even necessary to increase blast furnace productivity. In this sense the helium tracing technique consists of injecting He at the tuyeres with its arrival at the blast furnace top being detected by a mass spectrometer. With this measurement it is possible to define the transfer time as the delay between the injection moment and the time when the helium concentration reaches 10% of the maximum detected level. Calculated variables from the measurements allow a concise characterisation of the blast furnace state. These gas transfer measurements can be considered as a new tool to evaluate the state of a furnace at a specific moment. The main advantage will be that by employing only one measurement it will be possible to evaluate the furnace state.