The bituminous coal used in the production of metallurgical coke is found in small quantities in the United States but in larger quantities in Asian and Far Eastern countries, such as India and China. Large reserves have been found in Turkey, especially on the western coastal region of the Black Sea.
The purification process is performed in coke batteries, which are platforms of large enclosed ovens. Once bituminous coal is loaded into the ovens (in a vacuum), it is heated to approximately 1,000 degrees Celsius for more than 22 hours. During the heating process, the unstable components are released, and the remaining solid coal endures a partial melting and subsequent resolidification to a hard carbon. The unstable components include ammonia, coal tar and dozens of other waste products.
The resulting solid is a stable carbon known as metallurgical coke. Due to the elimination of unstable components and volatile gasses, and also due to the partial melting, "met coke," as it is sometimes called, has an open, porous structure and may appear glassy in some samples. Met coke has a very low waste product content; however, the "ash" elements that were part of the original bituminous coal remain trapped in the resultant coke. Met coke is available in a variety of sizes, from basketball-sized chunks to fine powder.
Metallurgical coke is used in applications requiring strong-wearing carbon of high performance, high quality and resilience. Some applications for met coke include foundry coatings, drilling applications, heat treatment, oxygen exclusion, electrolytic processes, conductive flooring, friction materials, foundry carbon raiser, corrosion materials, reducing agents, iron ore refining and ceramic packing media. Metallurgical coke is also an agent in the production of ferro-alloys, calcium carbide, elemental phosphorus and carbon electrodes.
The key characteristic of met coke is its stable burning temperature while producing little or no smoke. It is used as the critical reducing agent in smelting iron ore into pig iron, making it a key ingredient in the production of steel. More than 90 percent of the met coke produced is used in the iron and steel industries.