Drain Rate and Liquid Level Simulation in Blast Furnace Hearth Based on Plant Data

Abstract

Proper understanding and control of drainage of hot metal and slag from hearth is essential for a stable and efficient blast furnace operation. Due to irregular drainage, liquid level in the hearth may exceed to a critical limit where the hearth coke and deadman start to float and thereby causing irregular casting intervals, low blast intake, damage to refractory lining, and furnace pressurization etc. Carrying out any direct measurement of liquid level inside hearth is extremely difficult due to the hostile conditions. In order to provide a tool for the furnace operators to examine and control the tapping, drain rate and liquid level in hearth required to be estimated based on the available operating parameters. Here a dynamic mathematical model based on Bernoulli's principle has been developed considering blast furnace hearth as a pressurized vessel with liquid supply from top and a drain at bottom. The fluid flow from the tap hole is assumed to be dynamic and depends on the hot metal and slag production rate, furnace pressure, quality of metal, slag, mud gun clay used and the erosion behaviour of taphole. These parameters were studied over a large number of castings and their relationship is established in term of tuneable flow factors. The predicted slag-out time (ts) and tapping closure time (tc) from this simulation are in good agreement with the plant data. A real time view of liquid levels in blast furnace hearth is also provided.