Experiments on Pulverized Coal Combustion Under Conditions Simulating a Blast Furnace Environment

Combustion of pulverized coal under conditions simulating injection into a blast furnace was studied. Four coals were tested and the effects of coal flow rate, blast temperatures from 900°C to 1200°C, coal fineness, injection position and momentum, on the combustion of these coals were characterized through visualization and measurements. The performance of the coals was very dependent on the coal rank. The other parameters, particularly coal flow rate, also had a strong influence on the combustion rate. Indications are that the early combustion (< 10 ms) is determined by the devolatilization process with total volatile yields significantly in excess of the proximate analysis being measured for the bituminous coals. The combustion of the expelled volatile matter was found to be mixing limited, leading to soot formation. This problem was amplified with a high coal rate. The trial results indicate that the optimum method of achieving a high burnout level with pulverized coal in the raceway zone of a blast furnace, particularly with the current injection system, is through a judicious selection of coal type and coal rate.