NKK CORPORATION: Annual Report 1998
Home Up Back Next
Research and Development

Our long-term involvement with developing environmental technologies again produced significant results, most notably in the fields of environmental preservation and resource recycling.

W aste plastics recycling and blowing system

We recycled 30,000 tons of industrial waste plastics at the world's first integrated waste plastics recycling and blowing system, which we launched at the Keihin Works No. 1 blast furnace in October 1996 and began fully operating in fiscal 1997. The system blows processed industrial waste plastics into a blast furnace and reuses them as a coke substitute in ironmaking. Several R&D projects carried out during the year will enable us to increase annual capacity to approximately 200,000-300,000 tons in the near future.

Chlorine-containing polyvinyl chlorides (PVCs) must be separated from the waste plastic to prevent corrosion and other possible damage to blast furnace facilities. To simplify this process, we developed a new technology for removing the chlorine and began achieving good results with a test plant that started operating shortly after the fiscal year ended. Research at the test plant, which has a treatment capacity of 100 kg per hour, was conducted jointly with the PVC Environmental Affairs Council and the Plastic Waste Management Institute.

We also developed a pretreatment process for municipal waste plastics, which removes PVCs by exploiting differences in the specific gravities of plastics. The effort was a national project assigned to us by the New Energy and Industrial Technology Development Organization.

 

photo
Thermal-decomposition dehydrochlorination and granulation test plant at NKK's Keihin Works

n ew slag-less steelmaking process

To promote effective resource recycling, we developed a "slag-less" blowing method for basic oxygen furnaces (BOFs) that lowers the amount of slag formed during steelmaking. Under the process, low-silicon hot metal is dephosphorized at low temperature by adding a small amount of burnt lime, which minimizes the need for burnt lime during BOF decaburization, thereby greatly reducing slag formation.

In 1995, our Fukuyama Works launched low-silicon blast furnace (BF) operations after we improved the quality of sintered ores, and hot metal dephosphorization in BOFs, in addition to conventional hot metal dephosphorization in BF ladles.

In March 1998, we began operating a desiliconization station at our Fukuyama Works to supply BOFs stably with hot metal containing ultra-low amounts of silicon. With this highly efficient pretreatment station in place, the Works is set to begin steelmaking operations that will reduce the volume of slag to a mere 30 kilograms or less per ton of steel output, down substantially from the conventional level of about 100 kg/ton.


 

photo
New slag-less steelmaking process

T itanium-clad steel sheet

We commercialized a new hot-rolled titanium-clad steel sheet, which is one of the more environmentally friendly steel materials. The composite sheet comprises a base steel sheet and a titanium layer bonded to the steel's surface.

The sheet's excellent bonding characteristics result in superior bending workability. In addition, the sheet can be welded onto other steel products, which promises to find a wide variety of applications in the linings of, for example, chemical tanks, offshore steel-hull structures, bridges and other structures requiring excellent corrosion resistance.

We first commercialized a titanium-clad steel plate at the Fukuyama Works in 1986, applying original technology such as slab assembling under high vacuum, accurately controlled rolling and use of a special agent to separate the clad plates after rolling. Based on these same technologies, the company has now produced a new sheet in total thicknesses of 4 mm to 6 mm. NKK is now the world's first company to offer a full range of hot-rolled titanium-clad steel products, from sheets to plates.

 

photo
Titanium-clad steel sheets after bending tests

G asifying & direct-melting furnace for wastes

Responsible handling of solid waste requires strict control of dioxin and other toxic substance generation, as well as control of waste volume to prolong the life of disposal sites. In 1992, we began researching next-generation technology for waste treatment, which led to our development of a high-temperature gasifying and direct-melting process, and in 1995 we set up a furnace-size pilot plant with a 24 tons/day processing capacity at our Tsurumi Works. A variety of wastes, including municipal waste, car shredder dust, plastics waste and incineration ash -- 2,000 tons of material in total -- were disposed of in 200 days of testing during the year, bringing the development phase to a close. The next step is commercialization.

A primary achievement realized during the testing was the reduction of harmful substances in gas emissions, including dioxin, to a level of below 0.1ng-TEQ/Nm3. This was achieved through high-temperature combustion in the reducing atmosphere, without using activated-carbon treatment. A second important achievement was the realization of a method for continuous discharging of molten slag, which saves labor by simplifying the discharging process.

 

photo
Schematic drawing of direct waste melting furnace



  Copyright (C)2000 NKK Corporation. All Rights Reserved.  Terms and Conditions