This paper deals with model-based pressure and flow control of a fine coal injection vessel for the use of the blast furnace process. A control system should be in place to maintain a constant coal mass flow from the injection vessel to the blast furnace, since irregularities in the coal mass flow cause significant variations in the hot metal quality. By means of system modeling, the structure and behavior of the coal injection vessel are analyzed. It is shown that by use of a model-based design, the control objectives can be reached and the control performance can be significantly improved compared to the proportional integral (PI) controllers. Alternative control strategies are discussed and compared with the conventional design. The linear quadratic Gaussian (LQG) design method is used to design a multi-input multi-output (MIMO) controller which is validated through experiments on the coal injection plant at SSAB Tunnplat, Lulea, Sweden.
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