PFTR, Shaft Furnace

Phases Gas plus reacting solid. Solid particle diameter 8-300 mm. Gapacity 0.2-1 kg/s. Can operate as a shaft furnace where the product is a solid, the furnace has countercurrent gas-solid flow and the blast furnace where the product is hot metal liquid the furnace has countercurrent gas liquid solid flow. Blast fur- 

Fundamentals productivity is limited by the gas flow. Ergun equation for pressure drop through a packed bed of particles of equivalent volume diameter D, and sphericity = rp. 

For turbulent conditions with Re 1000 this becomes the Burke-Plummer equation  

Some suggest that for wind flow in the blast furnace the factor 1.75 should be double or triple this value. In the blast furnace literature, the term k/1.75 is called the burden permeability with values of 0.15-0.35 cm. 

Solid residence time, 20000-360000 s gas residence time, about 5 s. For fast reactions, bulk phase film diffusion may control and pore diffusion may control if the solid diameter 1.5 mm. 

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