Improvement of operation of the second generation shaft preheaters

After commissioning of the shaft furnaces of the second generation (with retaining fingers) some technological and design disadvantages appeared which reduce the effectiveness during preheating of scrap in the shaft preheater and the off gas units. The results of these disadvantages were an uneven and incomplete preheated scrap and a one-sided emission of harmful substances in the shop building ("chimney effect"). The thermal and mechanical design of the shaft preheater caused also additional losses of heat. The existing construction of the shaft hood and the movable sleeve piece created extreme conditions for the off gas system units. This article discusses the causes of the mentioned disadvantages of the shaft preheater and provides the measures which will remove them and stabilize the operation of the post combustion and off gas cleaning systems significantly.