Monitoring the Blast furnace working state by a combination of innovative measurement techniques

At blast furnace B at Salzgitter Flachstahl a series of innovative measuring techniques are installed to monitor the processes at the blast furnace top, making this furnace one of the best equipped furnaces in Europe. These techniques comprise full 2D measurement of the temperature profile of the top gas shortly above the burden surface, 3D radar scan of the whole burden surface and online measurement of the dust concentration in the top gas. After more than 5 years’ experience with most of these techniques, they enable to better understand the complex chemical and physical interrelations occurring in the BF stack between the ascending process gas and the descending solid burden. A couple of examples of incidents that were monitored are presented in this article, including influences of charging programmes on top gas temperature profiles and influences of disturbed gas solids interaction on the BF working state. The new measuring techniques with tailor-made data processing enable the operators to gain a better picture of the processes currently occurring in the blast furnace, consequently supporting them in keeping the blast furnace operation as stable and efficient as possible.

Calculation of Coke Layers Situation in the Cohesive Zone of Blast Furnace

Coke is the only batch component that does not soften in blast furnace thermal conditions. It is especially important at the temperatures of the cohesive zone forming because coke layers are the only gas-permeable charge. The aim of the work described in this article is the identification of individual coke layers situation in the cohesive zone. Numerical calculations of the cohesive zone situation are based on the horizontal below burden probe measures, however, coke layers are calculated using analytical geometry. The results can be presented as a bitmap; the individual and total area of the coke layers passing gases through the cohesive zone is also calculated. This form of results allows for subjective but quick assessment of the blast furnace operation by its crew.

Attempts to replace nut coke with semi-coke for blast furnace ironmaking

Low coke rate for blast furnace operation has been required in response to the rising cost of coking coals. To extend the utilisation of coal resources, semi-coke has been introduced to blast furnace ironmaking process in recent years, however, there are still many issues unclear about the effect of semi-coke on ironmaking process. In this study, the possibilities of using semi-coke as alternative fuel for nut coke were studied. The characteristics of semi-coke including mechanical strength, high-temperature strength/reactivity, carbon gasification as well as direct reduction were studied and compared with small size metallurgical cokes (nut cokes). The results showed that semi-coke has higher CRI values, especially at higher temperatures and in a mix-charging pattern. Semi-coke was found to have a higher gasification reaction rate and depleted at lower temperatures. The reduction results showed that with participating of semi-coke the reaction starts at lower temperatures. In addition, the study suggested that semi-coke exhibits the advantages of low ash and sulphur contents, although it has lower mechanical strength, it would protect the lump coke by shifting the carbon gasification to itself, therefore, mixing semi-coke would benefit the blast furnace operation and lower the coke rate.