Steel production is vital to many industries around the world. Some industries include general construction, machinery manufacturing, automotive, marine, and transportation. The world needs large volumes of high-quality steel to sustain the high demand. This is especially true during times of economic growth.The blast furnace is a key component of many integrated steel mills. A chemical reduction process occurs within the blast furnace. Carbon dioxide converts iron oxides into “pig iron,” an elemental iron with carbon and sulfur containing impurities. Pig iron undergoes additional processing to make a variety of commercial steel products.

In Indonesia, a tier one steel producer uses REXA actuators in multiple applications, for the blast furnace. One application is positioning the cold blast mixing valve. This valve’s purpose is to blend cold blast air with hot blast main air, so the feed air temperature is constant. Constant air volume and temperature enables the reactions in the blast furnace to occur in a controlled manner. The outcome is a reliable blast furnace production of pig iron. A simplified process diagram is illustrated in Figure 1.

Two or three stoves are used to preheat the air to around 1200°C (2190°F). The stoves are cylindrical steel structures lined with insulation and filled with checker brick. This is where the heat is stored and then transferred to the cold blast air. Air blowers feed 200°C (392°F) air to the ovens. The ovens cycle between preheating the air and being in reheat mode. Air entering a preheated oven exits at higher temperatures that dissipate over time until the next heated oven is utilized. The complex sequencing of the three stoves, switching modes, is illustrated in Figure 2. The actuator needs to position the mixing valve, without delay, so the mixed air has a constant temperature.