Sponge Iron Manufacturing Process

Sponge iron is formed through the reduction of iron ore to metallic iron through reaction with carbon in the form of coal, etc. at approx. 1100 degree Celsius. Sponge iron is also referred to as direct reduced iron, metalized iron, or hot briquetted iron.

Sponge iron is used in the iron and steel industry as a substitute for scrap in induction and electrical arc furnaces. Over the years, the shortage of expensive melting scrap has made sponge iron a significant raw material for manufacturing high quality steel. 

This process is one of the oldest direct reduction methods, and its structure is based on a horizontal cement kiln. In this method, heat coal (as a reducing agent) is mixed with iron ore and sponge iron is produced in a horizontal furnace.

• Input iron ore: In the Midrex or HYL process, it is generally recommended to use high-quality cooked pellets with a maximum of about 30% iron ore lumps. Up to 100% of the lumps can be used in this process, and some types of raw pellets will also be used. The use of magnetite rock is not recommended as it requires high-grade hematite iron ore.
• Reducing agent: The advantage of this method is the possibility of using relatively low-quality thermal coal as the reducing agent. Coal in the furnace produces carbon monoxide gas, which reduces iron oxide. Despite the relatively high temperature in the furnace, the reaction rate is relatively low, and the furnace will have low capacity. There is no hydrogen gas in this process.
• Type of Reduction Furnace: Rotary Horizontal Furnace that operates at slightly above atmospheric pressure. The main rotary furnace consists of the preheating section, and the reduction area, with the gases caused by the reaction being discharged at a temperature of about 1000 °C and recycling systems are not anticipated, which is why this energy is generally used to generate electricity. The cooling part of the furnace is a completely separate chamber that is cooled by water from the outside.
• Reduction temperature: about 1000 to 1100 °C.
• Process history: since 1980.
• Process position: Stabilized and commercialized.
• Optimum Capacity: Approximately 100 to 150 thousand tons per module.
• Market share: About 23% of sponge iron total production.