Mark
September 28, 1998    

Fukuyama Sets Record for Pulverized Coal Injection

Pulverized coal injection system Pulverized coal injection system (left) in operation
at the Fukuyama Works' No.3 blast furnace
(below)

The Fukuyama Works' No.3 blast furnace (BF) (inner volume: 3,223m3) set a new world record for pulverized coal injection (PCI) in June with an injection rate of 266kg per ton of hot metal. This milestone was reached just three months after the PCI facility was commissioned in late April.

The PCI facility began operations with a relatively high injection rate exceeding 150kg/ton of hot metal from the start, and raised it to 184kg/ton in May. Higher PCI operations continued with the aim of injecting 250kg/ton, a level thought to be the theoretical upper limit PCI rate. But in June, a new world record was set by achieving a monthly average of 266kg/ton (coke rate: 289kg/ton). This surpasses the previous record of 254kg/ton set by Kobe Steel's Kakogawa No.1 BF in March this year. The realization of this record-high PCI rate enabled the Fukuyama Works to halve the coke charged into the BF.

Integrated steelmakers around the world have been working to realize higher PCI rates to prolong the service life of existing coke ovens and reduce the costs of producing hot metal by increasing the use of cheaper non-or soft-coking coal in place of hard coking coal needed for coke production. At present, Japan's average PCI rate is holding steady at around 120kg/ton of hot metal because increased injection volume blocks in-furnace permeability and hinders stable BF operations.

Since achieving the then world PCI record of218kg/ton at the No.4 BF in October 1994, the Fukuyama Works has aggressively sought the250kg/ton level by incorporating a number of advanced technical improvements in its PCI system.

The factors that contributed to achieving the new PCI record at the Fukuyama No.3 BF include:

  1. Employment of a special lance to inject pulverized coal through tuyeres: an improved model of a unique NKK-developed eccentric double lance greatly improved the combustion efficiency of pulverized coal in the tuyeres.

  2. Establishment of highly accurate BF burden distribution control technology: use of an advanced movable armor to control burden distribution greatly improved in-furnace gas flow.Also, the use of coke featuring excellent mechanical and thermal properties assured good permeability even in high PCI operations.

  3. Establishment of low-silica ore sintering technology:by using sintered ores with a greatly reduced silica (SiO2) content, in-furnace reducing and melting characteristics were greatly enhanced.

  4. Effective use of an NKK-developed FIMPIT (fiber in metallic tube for pig iron temperature)thermometer at the tapping hole: this new device enabled accurate, prompt measurement and monitoring of in-furnace temperatures,which, combined with the latest artificial intelligence-based heat control technology, contributed to stable BF operation even with high PCI rates.

PCI operations are well under way at all of NKK's BFs now in operation at Fukuyama and Keihin. By fully utilizing its operational achievements,NKK intends to further promote technical developments and the realization of even higher PCI rates.

Fukuyama Works'No.3 blast furnace

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