Part 2 CCT Overview
Iron Making and General Industry Technologies (General Industry Technologies)

3B2. New Scrap Recycling Process (NSR)
Research and development: Japan Coal Energy Center; Nippon Sanso Corp.; and JFE Steel Corp.
Project type: Coal Production and Utilization Technology Promotion Grant
Period:1992-1997 (6 years)

Technology overview

1. Background
In Japan, approximately 30 million tons of iron scrap are recycled

melting process. In response, the NSR process employs technology

annually, and most is melted in arc furnaces, which consume athat melts metals such as iron scrap utilizing high-temperaturesignificant amount of electric power. The energy efficiency of an arc

energy from the direct combustion of pulverized coal by oxygen

furnace is as low as approximately 25% (converted to primaryinstead of electric power. The NSR process was developed with theenergy, taking into account power generation and transmission

objective of significantly increasing the energy efficiency of theefficiency). Given this, there is a need for a more energy-efficientmelting process relative to that of conventional technology.

2. Development timetable
Development was promoted by a joint team from Japan Coalefficiency melting. The study began with a batch smelter. With theEnergy Center, Nippon Sanso Corp., and NKK Corp. (now JFE

results of the batch smelter, a continuous melting furnace wasSteel Corporation). The main subjects of development were thedeveloped, with the objective of improving the energy efficiency.

furnace structure and the burner arrangement to attain highTable 1 Development timetable
1992

1993

1994

1995

1996

1997

SurveyBatch-furnace

Bench scale (1 t/batch)
Pilot plant scale (5 t/batch)Continuous furnace (pilot plant scale: 6 t/hr)

3. Overview of process and results of study
Figure 1 shows the process overview of the continuous melting

Using the above-described system, even slow-burning pulverized

furnace. The melting furnace consists of three sections: melting,coal can be rapidly combusted, with efficiency similar to that ofbasin, and holding, each of which functions separately. Eachliquid fuels, such as heavy oil. Raw materials fed from the top of

section has a pulverized coal oxygen burner. The oxygen

the furnace are directly melted by the burner in a shaft-shaped

osupplied to the burner is preheated to temperatures of 400-600 C

melting section in the lower part of the furnace. The melted raw

by an oxygen preheater to combust the pulverized coal.

material flows through the basin section and enters the holding
Bag filter
Flue gas

BlowerRaw material
Oxygengenerator

Open/close damper

Burnercontroller

Slide gate

Oxygen preheater

Pulverizedcoal tank

Pulverized coal
oxygen burner

Pulverizedcoal charge
unit
TuyereNitrogengenerator

Molten steel

Fig. 1 NSR process flowchart

Fig. 2 Pilot plant (6t/hr)
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Clean Coal Technologies in Japan

section. The molten steel is soaked in the basin section. The

Furthermore, the process achieved highly superior results relative

carbon content of the molten steel in the basin section can beto the conventional process from an environmental perspective,

controlled by injecting powder coke into the furnace. The holding

such as a significant suppression of dust (excluding the ash insection stores the molten steel for a specified period, and rapidly

pulverized coal) and of dioxins, due to the control of theheats the molten steel to approximately 1,600oC, and then taps

intrafurnace atmosphere.

the molten steel through an EBT system. Molten steel agitation
gas is injected from the bottom of the respective furnaces to thebasin section and the holding section to accelerate the heattransfer from flame to molten steel, thereby enhancing the slag-1600
Coke

metal reaction. All the combustion gas coming from the individual
1400

sections passes through the melting section, and is vented from
Melting energy (Mcal/T)

the furnace top after being used to preheat the raw material in
the melting section. The raw material is continuously fed from thefurnace top and melted in the furnace. Tapping from the holding
section is conducted intermittently.
The process effectively utilizes the heat transfer characteristics ofoxygen burners, and achieves high-efficiency melting. Figure 3
shows a comparison of melting energy between the NSR process

Oxygen

1200
1000
800

Electric power

600
400
Pulverized coal

200

and the arc furnace. Electric power (oxygen is also added

0because it is produced by electricity) is included in the primary

EAF(380Wh/T)

energy and includes power generation and transmission losses.
Compared with a standard arc furnace, melting energy wasNSR

Fig. 3 Comparison of melting energy

reduced by 40%, dramatically improving energy efficiency.

4. Toward practical application
The study team completed the design for actual scale facilities.

power melting technology, which, even globally, is quite rare, andDue to the influence of the current poor economy in the electricbecause of the strong advantage of being unaffected by thefurnace industry, however, the process has not been brought into

electric power infrastructure, the study team continues to makepractical application. Nevertheless, since the process is a non-efforts toward commercialization in Japan and abroad.
Fig. 4 Schematic for commercial scale plant (50 t/hr)

Fig. 4 Schematic for commercial-scale plant (50 t/hr)

References

1) Hiroshi Igarashi, Toshio Suwa, Yukinori Ariga, and Nobuaki Kobayashi: ZAIRYO TO PROCESS (Materials and Processes), Vol. 12, No. 1, p. 135, 1999.
2) Hiroshi Igarashi, Nobuaki Kobayashi, and Hiroyuki Nakabayashi: Technical Bulletin of Nippon Sanso Corp., (19) pp. 30-37, 2000.

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