The process of a blast furnace starting up a furnace is a complex one. In order to have a successful startup, all of the parts of the blast furnace must work together flawlessly.
First, the furnace must be preheated with cooling mediums such as nitrogen, water, or air. This process is vital to prevent damage to the furnace and its components. Preheating is done in stages, beginning with the hearth and then continuing with the bosh, stack, and nose. As the temperature is increasing, the valves in the furnace are opened one-by-one in order to release pressure. The pressure must be monitored carefully in order to ensure proper and safe functioning of the furnace.
Then, the blast of forced air is initiated, which is the key to melting the iron ore in the furnace. The heat created by the forced air along with the preheated components quickly raises the temperature inside the furnace. The blast is maintained at a constant level and monitored by shifts in order to maintain the desired temperatures.
Next, the charge of iron ore, coke, and flux are loaded into the furnace. The coke provides a layer of insulation between the hearth and the ore, allowing for more efficient heat production. The flux is necessary in order to reduce any impurities in the ore and create good quality steel. The charge is carefully tamped down in order to ensure that there are no holes that could prevent the gases from passing through it and melting the ore.
Then, the tuyers, which are long tubes that introduce oxygen into the furnace, are tapped to allow oxygen to enter. This results in an increase in temperature and helps in speeding up the process of melting the ore. Once the ore has fully melted, the tap is closed and the slightest amount of oxygen is added to keep the furnace burning.
At this point, the furnace is ready to go and only requires continuous monitoring of gas levels and temperatures in order to provide optimal working conditions. The rate of production and the temperature of the furnace is manipulated in order to create the desired product, either pig iron or steel. When the desired ratio of carbon in the waste gases is achieved, the furnace is tapped and the molten iron runs into a receptacle where it will harden and become useable.
The entire process from start up to finished steel takes many hours and requires strict adherence to safety protocols and procedures. This is why the process of starting up a blast furnace is a complex one and everything must be planned out carefully beforehand. A successful startup takes practice and knowledge of the furnace systems and the science behind them.
