Effect of Large Amount of Co-injected Gaseous Reducing Agent on Combustibility of Pulverized Coal Analyzed with Non-Contact Measurement

Abstract

Nowadays, reduction of amounts of CO₂ from ironmaking process is important from the aspect of prevention of the global warming. COURSE50 is Japanese national project which aims to reduce the amount of CO₂ emission from ironmaking process by 30% by 2050. In COURSE50, we try to reduce iron oxide with H₂ to decrease amounts of carbon use, by injecting large amount of gas containing H₂ and pulverized coal (PC) from tuyere. In that case, PC combustibility can be different from that in general blast furnace condition, due to high co-injected reducing gas ratio. Though a large number of researches about PC combustion around tuyere of blast furnace has been carried out, the effect of large amounts of co-injected reducing gas on PC combustibility was hardly investigated. To evaluate that, we conducted experiments with two experimental furnaces equipped with various non-contact measurement apparatus and found that;

1) The larger amounts of co-injected reducing gas were, the faster O₂ and CO₂ consumption, and CO and H₂ generation in the raceway.

2) The amounts of co-injected reducing gas should be optimized for higher PC combustibility.

3) Co-injected reducing gas activated PC combustion by raising PC temperature, and that resulted in acceleration of PC.

4) Trade-off relationship between rapid heating effect and O₂ consumption of co-injected reducing gas could determine the optimum amounts of reducing gas.

Consequently, we elucidated how we could co-inject reducing gas with PC as reducing agents without deteriorating PC combustibility.