Abstract
The injection of large quantities of auxiliary fuels to reduce the coke rate at blast furnaces is an economic necessity because of the shortage of coke and its increasing cost. One of the reasons of the limitation of the amount of injected heavy oil is incomplete combustion with unacceptable soot formation.
Firstly, the authors observed the phenomena in the raceway by using the experimental model and, secondly, they analyzed the combustion process in the real raceway on the basis of the gas composition measured by the probe inserted through the tuyere.
The heavy oil is generally injected from the tip of oil nozzle settled near the tuyere at the oxygen excess ratio (μ) over 1.1. A great part of injected oil burns simultaneously with coke in the raceway and soot formation begins with increasing the amount of injected oil.
In order to gasify the heavy oil in the blowpipe and tuyere before the beginning of the coke combustion, the nozzle tip was moved backward 1.75 or 0.75m away from the tuyere nose. The test of the new injection system was carried out at No. 6 tuyere of No. 2 blast furnace in Chiba Works and its results were also discussed. Much quantity of heavy oil could be gasified without soot formation on the condition of μ=0.9.
