EUROPEAN STEEL TECHNOLOGY AND APPLICATION DAYS 2017 - ESTAD 2017

To achieve minimal coke rates in blast furnace operation it is crucial to obtain optimal burning of additional fuels like e.g. pulverized coal (PC). However, there are operating conditions, where an optimal burning is not possible and it is beneficial to shut down the PC supply on one or more injection lances. The frequent case of raceway blockages can lead to reduced wind throughput on the effected tuyere. If PC is injected in that tuyere the unburned coal might lead to locally reduced permeability of the burden. Thus it is necessary to have reliable information of the current raceway condition to be able to shut down PCI lances if beneficial and to do so with short latency. This study aims to find an optimal blockage detection based on the combination of hot blast flow rates and additional tuyere cameras. A usual implementation of triggering the shutdown of PCI lances is to use a threshold value for a minimum wind flow rate through the individual tuyere sections. However, a blast furnace never shows exact axially symmetric behavior, thus the hot blast flow rates vary between the tuyeres. So applying the same threshold level to all tuyeres is not an optimal solution to trigger the shutdown of PCI lances. Thus, we tested various approaches for the signal processing of hot wind data. To allow an efficient testing of various algorithms and parameter sets a modular software test bench was implemented in Matlab/Octave. To assess the results of signal processing, it is also necessary to visually check the raceway conditions. For this we collected image data on various tuyeres. As the flow rate data needs to be tested over many hours of plant data, also the tuyere images need to cover these time spans. Hence, we have thousands of raceway images, which cannot be checked manually for blockage assessment. This inherently leads to the need of fully automated image processing to detect blockages from the raceway images. The software test-bench was therefore extended to allow also the testing of image processing algorithms. This additional effort does pay off in a way that also combined methods of using available plant data of the hot blast flow rates plus the optical information of tuyere cameras can be evaluated for an optimal implementation in the blast furnace process control system.