Promotion of In-House Zero Emissions

By-products generated and their final disposal amount

In the iron-making process, over 600 kg of by-products are generated for every ton of iron produced. In fiscal 2017, NSSMC produced 40.67 million tons of crude steel and generated 23.29 million tons of by-products. We strove to reduce the final disposal to less than 260,000 tons, an amount based on the government’s target, such as by recycling the majority of these by-products inside and outside the company. As a result, our final disposal of industrial wastes amounted to approximately 230,000 tons and we maintained a very high recycling rate of 99%.

By-products and Recycling

By-product Process of generation Amount generated
(wet weight million tons)
Recycling application Recycling rate
FY2014 FY2015 FY2014 FY2015
Blast furnace slag Components other than iron melted in blast furnace 13.46 12.65 Blast furnace cement, concrete, fine aggregate, road base, etc. 100% 100%
Steelmaking slag Substances other than steel generated in the steelmaking process 6.28 5.65 Road base, civil engineering materials, fertilizer, etc. 99% 98%
Dust Fine dust collected with a dust collector 3.38 3.41 Raw materials for use in-house and also zinc refining 100% 100%
Sludge Water treatment sludge, residue from plating solution, road cleaning sludge 0.39 0.51 Raw materials for in-house use 90% 87%
Coal ash Ash from coaled-fired power plants 0.53 0.51 Cement raw materials 100% 100%
Waste furnace materials Refractories from steelmaking facilities and furnace facilities 0.28 0.28 Reuse, road base, etc. 71% 65%
Others Scale, etc. 1.73 1.82 In-house use, others 96% 94%
  Total 26.05 24.71 Total recycling rate 99% 99%

NSSMC’s final disposal amounts

1 Including waste (97,000 tons) generated due to a large-scale construction work in FY2015

Recycling of steel slag

Steel slagSlag 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. For example, 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. NSSMC’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.

“Blast furnace cement,” a mixture of pulverized blast furnace slag and ordinary portland cementHydraulic 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 product are designated as a “designated procurement itemAn Eco-friendly item that the government, independent administrative institution, etc. takes the lead in procuring.” 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.

NSSMC’s Use of Recycled Steel Slag

NSSMC’s Use of Recycled Steel Slag

Message from Innovators

Chika Kosugi
Sea Laboratory (marine environment simulator)

Sea Laboratory
(marine environment simulator)

Development of “iron” supply unit to prevent ocean desertification

NSSMC promotes the “creation of marine forest” to counteract the “rocky-shore denudation,” which has been a nation-wide environmental concern in recent years.

One of the causes of the “rocky-shore” phenomenon is the decreased supply of iron hich is necessary for kelp and seaweed to grow hrough rivers as a result of deforestation and upstream development. To cope with this problem, in 2004, we developed an iron supply unit containing humic substances made of iron/ steel slag and waste wood. Since then, we have been working on creating a seaweed bed (marine forest).

NSSMC also opened a “Sea Laboratory” (marine environment simulator) at the Technical Development Bureau in Futtsu City, Chiba Prefecture. We are working to scientifically clarify the usefulness and safety of using steel slag to create marine forest.

Recycling of dust and sludge

To recycle the dust and sludge generated in the iron manufacturing process to be used as raw materials, NSSMC has a dust reduction kiln (RC: Resource circulating oven) at Kashima Works and a rotary hearth reduction furnace (RHF: Refer to note 2, page 9) at Kimitsu Works, Hirohata Works, and Hikari WorksTransferred to Nippon Steel & Sumikin Stainless Steel Corporation.. 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.

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