Not wasting any energy
Nippon Steel & Sumitomo Metal Corporation (NSSMC) is committed to reduction of the environmental burden created by production activities and manufacturing processes. We make continuous efforts in all processes to not waste limited resources and energy.
NSSMC uses iron ore mined overseas, coal as an iron ore reductant, and scrap generated by society as its main raw materials for steel production. By-product gases, such as coke oven gas generated by dry distillation of coal in the coke manufacturing process and blast furnace gas generated from blast furnaces, are fully utilized as fuel gas for steel heating furnaces or energy sources for power generation plants on the premises of steelworks.
In addition, NSSMC itself generates 88% of the electricity it uses at steelworks, 78% of which is from internally generated energy sources such as waste heat and by-product gases. 90% of water used for cooling and cleaning products and manufacturing equipment is repeatedly re-used.
When one ton of iron is produced, the amount of by-products generated exceeds 600 kg, but the steel slag, dust, and sludge are reused in-house as raw materials, or are used by society or other corporations as raw materials for cement, construction materials, and so forth. These efforts have resulted in the achievement of a very high recycling rate of approximately 99%. In fiscal 2017, with the objective of promoting preservation of resources by an expanded use of steel by-products, “KATAMA™ SP (special),” an environmentally-friendly and instantly-available road bed materials, expanded its application as a low-cost pavement material for forest roads and farm roads.
We are also engaged in the recycling of various types of by-products generated by society or other industries by utilizing our steelmaking processes that are carried out at high temperature and high pressure. In recent years, we have been actively recycling waste plastics, waste tires, and other waste materials.
NSSMC’s share in Japan’s total energy
Blast furnaces are huge reactors, using coal
Iron ore and coal are the main raw materials fed into a blast furnace. Iron ore is melted in a huge furnace (height, about 100 meters) and steel is reduced and extracted, but what kind of role does coal play? The main ingredient of coal is carbon, but before it is fed into a blast furnace, it is thermally decomposed in the absence of oxygen (carbonized), effective ingredients such as hydrocarbon oil and gas are separately extracted, and it is turned into coke with high strength and high carbon purity. However, the iron included in iron ore is present as iron oxides. In the blast furnace, a chemical reaction called reduction, which removes oxygen from these iron oxides, occurs, and the carbon in the coke functions as a reducing agent. Coal is not burned as a fuel but rather is the ingredient used to cause a chemical reaction.
At present, as there is no reducing agent to replace coal in the industrial production of steel, the generation of CO2 resulting from the reduction reaction caused by carbon cannot be avoided (iron oxide + carbon g iron + CO2).
Nevertheless, as the Japanese steel industry, including NSSMC, has promoted energy-saving measures such as making effective use of the by-product gases and heat generated in the steelmaking process, it has realized the highest energy efficiency in the global steel industry and at the same time is controlling the CO2 emissions. We may therefore conclude that making steel in Japan is ecologically wise.
Furthermore, for the above-mentioned COURSE50, we are engaged in R&D activities aimed at using hydrogen as a reducing agent partially replacing coal in industrial production (iron oxide + hydrogen g iron + water).
Coke Dry Quenching (CDQ)
NSSMC recovers high-temperature waste heat and by-product gases generated in blast furnaces, coke ovens, converters, and so forth, and efficiently uses them as a source of self-generated electric power. The company uses CDQ and other facilities located in the steelworking facilities to generate 84% of the total electric power that it needs, and purchases the remaining 16% from outside. A total of 88% of the total electric power generated in the steelworking facilities is obtained from recovered waste heat and by-product gas.
Rotary Hearth Furnace (RHF)
This is a facility to recover iron and zinc, etc., and recycle them into resources. In these facilities, dust, sludge and other ferric oxide-rich by-products produced during the steelmaking process are mixed with coal or other reducing materials, and then continuously processed at a high-temperature.