Rod coal briquette is a kind of porous material consisting of solid coal particles, liquid phase moisture, stream and air, and study of drying process of coal briquette is that of porous material.
Most researchers proposed some mathematical models of drying inside porous material by convective heat. They are classified into diffusion model, theory model based on osmosis evaporation, and models based on Whitaker’s continuum theory and non-equilibrium thermodynamics.
Study on heat and mass transfer in porous material was conducted for a long period and it developed from the basic theory of heat and moisture transfer mechanism into the modern comprehensive and logical scientific theory. However, most studies were focused on the drying of wood, grain and paper, and not on rod coal briquette.
Pak Kyong Il, a researcher at the Faculty of Metal Engineering, designed a tunnel-type dryer for reducing coal consumption while reducing the cracking of briquettes and increasing their strength by improving the thermal working state of a tunnel dryer with low recovery and high coal consumption required for drying.
Compared to the conventional dryers, the newly-designed one has many advantages. First, drying time per batch is reduced by 4h from 24h to 20h. Second, 48kg of coal is saved for drying a ton of coal briquettes. Third, cracking rate is reduced by 23%.
In addition, cold compressive strength and hot compressive strength, and hot abrasive strength are raised by 10-11% and 4-5%, respectively, to improve the quality of briquettes used for iron production in small blast furnaces.