Mr T. Fukishma of F-TeCon Pty Ltd carried out the modeling (
Bennett & Fukushima, 2003) to
investigate the impact of PCI coal quality on the operation of a blast furnace. The model was used
for a quantitative study on the influence of ash content of the PCI coal on blast furnace operation,
particularly focusing on the impact on operating costs. For this study the blast furnace process
parameters shaft efficiency, reserve zone temperature, heat losses of upper shaft and lower shaft
and theoretical flame temperature at raceway were constant for all calculations. One coal was used
in all calculations with different amounts of ash – 8, 9, and 10 % ad. These calculations indicated
that the change in coke requirements (kg/tHM) per 1 percent ash change in the PCI coal varies
with injection rate as:
For an injection rate of 150 kg/tHM, an increase of 1% in the ash of the injected coal would result
in a 1.2 kg/tHM increase in the coke rate. In addition to this increase in coke rate there is also a
need to adjust BF operating parameters (e.g. blast volumetric rate, temperature and oxygen, and
slag chemistry), which results in a net increase in BF energy requirements and other raw
materials. Therefore, the cost impact of an increase in ash of the injected coal is dependent on the
coke costs and the cost of auxiliary fuel used within the plant.
The increase in coke rate per 1% increase in ash determined by this study is significantly less
than that suggested by other authors. Poveromo [1] suggests that for furnaces with total fuel rates
of 500 kg/tHM every reduction of coke ash (or injected coal ash ) of 1 % would reduce coke rate
by 6 kg/tHM. Xi Ping and Suen [2] state that for each one percent of ash will increase the blast
furnace fuel rate by two percents. Therefore, the ash content of the PCI coal must be at least 1.5
percent lower than that of met coke.
Brouwer and Toxopeus [3] in summarising the PCI operating results at Hoogovens IJmuiden blast
furnace derived a relationship between replacement ratio and the properties of the coal injected
(given in Appendix A). This relationship shows that ash increases replacement ratio and therefore
would lower coke rate.
There is a value-in-use penalty for increased ash, but for the majority of coals traded as PCI coals
the ash differences are small and the composition of the ash may be more of a concern in the
future.
[1] Poveromo, J., 2004, Blast furnace fuel injection trends, Met Coke World Summit, Chicago,
October 2004.
[2] Xi Ping, P., Suen H., 2003, PCI Application in blast furnace operation and market trend in
China, McCloskey’s 8th Annual Australian Coal Forecast 2004 Conference, 24 – 25 November
2003.
[3] Brouwer, R.C., Toxopeus, H.L., 1991, Massive coal injection at Hoogovens IJmuiden BFs,
Revue de Metallurgie. Cahiers d'Informations Techniques, V88, N4, Apr 1991
