Promotion of in-house zero emissions
Promotion of In-House Zero Emissions By-products generated and their final disposal amount
In the iron and steel-making process, over 600 kg of by-products, such as steel slag, dust, sludge, and used refractory bricks, are generated for each ton of crude steel produced. In fiscal 2020, Nippon Steel produced 33.34 million tons of crude steel and generated 20.38 million tons of by-products.
As a result of efforts to reduce most of by-products, such as by recycling, the final disposal amount was decreased to 229,000 tons, falling below the national target of 276,000 tons. The recycling rate has been maintained at a very high level of 99%. Going forward, we will strive to further reduce the amount of waste by setting the target in the final disposal amount for fiscal 2025 at 263,000 tons – approximately 10,000 tons of incremental reduction from the target for fiscal 2020.
By-products and Recycling
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|By-product||Process of generation||Amount generated
(wet weight million tons)
|Recycling application||Recycling rate|
|Blast furnace slag||Components other than iron melted in blast furnace||12.16||12.78||10.14||Blast furnace cement, concrete, fine aggregate, road base, etc.||100%||100%||100%|
|Steelmaking slag||Substances other than steel generated in the steelmaking process||5.40||5.65||4.39||Road base, civil engineering materials, fertilizer, etc.||99%||99%||99%|
|Dust||Fine dust collected with a dust collector||3.17||3.13||2.70||Raw materials for use in-house and also zinc refining||88%||88%||100%|
|Sludge||Water treatment sludge, residue from plating solution, road cleaning sludge||0.48||0.43||0.40||Raw materials for in-house use||100%||100%||89%|
|Coal ash||Ash from coaled-fired power plants||0.50||0.52||0.46||Cement raw materials||100%||100%||100%|
|Waste furnace materials||Refractories from steelmaking facilities and furnace facilities||0.35||0.35||0.27||Reuse, road base, etc.||76%||81%||64%|
|Others||Scale, etc.||2.30||2.07||2.02||In-house use, others||99%||100%||99%|
|Total||24.35||24.93||20.38||Total recycling rate||99%||99%||99%|
By-product recycling rate
Nippon Steel’s final disposal amounts
Effective use of steel slag
Steel slag Slag is a by-product that is separated and recovered from molten metal during metal refining. It is used as road base material and raw material for cement. is almost entirely utilized. Approximately 70% of blast furnace slag is used for cement, while steelmaking slag is used for materials for road bases, civil engineering work, fertilizer, soil improvement, etc.
“Blast furnace cement,” a mixture of pulverized blast furnace slag and ordinary portland cement Hydraulic cement. Gypsum is added to clinker produced by calcinating raw materials containing silica, alumina, iron oxide and lime, and then the mixture is made into powder., contributes to a 40% reduction of CO2 emissions during manufacturing, since the cement-making process can be omitted. It also exhibits superior long-term strength and is registered as an Eco Mark product. Due to the effects of reduction in mining of natural crushed stone and less energy consumption in the cement making process, steel slug products are designated as a “designated procurement item” under the Green Purchasing Law, and included in the Common Specifications for Civil Engineering Work compiled by the Ministry of Land, Infrastructure, Transport and Tourism.
Nippon Steel’s pavement materials, KATAMA™ SP, taking advantage of characteristics of steel slag, are used for forest roads and farm roads, as well as for weed preventive pavement to be installed near mega-solar panel installations and other locations.
Granulated blast furnace slag
Geo-Tizer™ made of steel slag can be mixed with soft soil (mud, such as surplus excavated soil from construction sites or farmland soil) to reform the soil to make it usable. Unlike conventional soil-improvement materials (i.e., cement and lime), this soil produces less dust, construction cost. The remediated soil is outstanding in compacting and can also be easy to be dug again, without being excessively solidified.
Calcia modified soil, a mixture of steelmaking slag and dredged soil, has the beneficial effects of improving the strength and inhibiting the elution of phosphorus, the generation of hydrogen sulfide, etc. in dredged soil. It has also been used to improve the marine environment, including restoration of seaweed beds and creation of wetlands and tideland. In addition, Nippon Steel’s Beverly™ iron supply units, which are composed of steel slag and humus made from waste wood, provides iron needed for seaweeds to flourish, promoting regeneration of an area of the sea bed that had lost much of its living organisms.
Moreover, as steel slag contains nutrition that helps plants grow, it is also widely used as fertilizer, contributing to improving farming productivity.
Geo-Tizer™ is in the granular form and easy to handle with less dust.
Conventional modified materials
Recycling of dust and sludge
To recycle the dust1 and sludge2 generated in the iron and steelmaking processes, for them to be used as raw materials, Nippon Steel operates a dust reduction kiln (RC: Resource circulating oven) at East Nippon Works Kashima Area and a rotary hearth reduction furnace (RHF) at East Nippon Works Kimitsu Area, Setouchi Works Hirohata Area, and Kyushu Works Oita Area (Hikari). This enables us to recycle all internally-generated dust.
In March 2009, we obtained special approval for RHF under the Waste Disposal Act to carry out recycling of externally-generated dust as well.