Quality of charcoal submitted to different cooling rates with heat exchanger

Abstract

Charcoal is an important material in the national steelmaking industry and its use has many benefits over coal and coke, since it is renewable, less polluting and with lower contents of sulfur and phosphorus. The aim of this study was to evaluate the performance of the artificial cooling of the charcoal in a rectangular kiln. It was evaluated the influence of the variation of the velocity of the gas flow through the porous bed of charcoal in the final quality of the product. Four flow velocities were used, in three repetitions, totalizing 12 carbonization tests in a rectangular kiln. The used of heat exchanger provided a reduction from 76 to 28 hours in the cooling time. The highest reduction in cooling time was obtained with lower flow velocity. It was observed that, at higher velocities, part of the charcoal closed to the exhaust section of the kiln was burned, which resulted in an increase in the cooling time. However, these partial burns did not cause the significant difference in gravimetric yield in relation to the control. For the velocities adopted, it was verified that there was no significant difference between the treatments and the control in the quality parameters of the charcoal. Therefore, for the dimensioning of heat exchangers, the pressure difference between the suction openings and the gas injection should be considered to minimize the infiltration of air into the kiln.

Keywords:
Artificial cooling; Fluid flow in porous media; Charcoal steelmaking