Method and apparatus for heat treatment of materials

Claim 2

A continuous method of heat treating granular and pelleted materials, comprising the steps of heating moist raw material to a temperature of at least 700* C. on a traveling grate, discharging the material at such temperature directly from the traveling grate into the top of a vertical shaft portion of constant cross section having a firing zone therein, maintaining such shaft portion filled with the material, while causing the material to settle therein by withdrawing material continuously below such shaft portion, and firing the material in such shaft portion, whereby a uniform temperature is maintained throughout the cross section at each level in such shaft portion.

Claim 3

A method according to claim 1 comprising the step of causing the material to settle through an unheated soaking zone below the vertical shaft portion.

Claim 4

A method according to claim 1 comprising the step of cooling the material on a second traveling grate as it is withdrawn.

Claim 5

A method according to claim 3 comprising the step of firing a burner to heat the material on a portion of the first traveling grate.

Claim 6

A method according to claim 4 comprising the steps of supplying cooling air to cool the material on the second traveling grate, and conducting the spent cooling air partly as combustion air to the vertical shaft portion, partly as combustion air for heating the material on a portion of the first traveling grate, and partly as a drying medium for drying the material on a preceding portion of the first traveling grate.

Claim 7

A method according to claim 5 comprising the step of supplying the products of combustion from the vertical shaft portion to heat the material on the first traveling grate.

Claim 8

Apparatus for heat treating granular and pelleted materials, comprising a first traveling grate which travels through a drying zone and then through a heating zone, a vertical shaft portion of constant cross section, arranged to permit material to fall directly off the end of the first traveling grate into the top of the vertical shaft portion, a soaking zone below such shaft portion, a second traveling grate which is arranged to withdraw material at the lower end of such soaking zone and which travels through a cooling zone, a burner which fires into the lower end of such shaft portion, of constant cross section above the soaking zone, and means for supplying products of combustion to the heating zone of the first traveling grate to preheat the material to such a degree that a uniform temperature is maintained throughout the cross section at each level in the vertical shaft portion.

Claim 9

Apparatus for heat treating granular and pelleted materials, comprising a first traveling grate which travels through a drying zone and then through a heating zone, a vertical shaft portion of constant cross section, arranged to permit material to fall directly off the end of the first traveling grate into the top of the vertical shaft portion, a soaking zone below such shaft portion, a second traveling grate which is arranged to withdraw material at the lower end of such soaking zone and which travels through a cooling zone, a burner which fires into the lower end of such shaft portion, of constant cross section above the soaking zone, and means for supplying products of combustion to the heating zone of the first traveling grate to preheat the material to such a degree that a uniform temperature is maintained throughout the cross section at each level in the vertical shaft portion.

Claim 10

Apparatus according to claim 7 comprising a supplemental burner which fires into the heating zone of the first traveling grate, and air passages for supplying cooling air to the second traveling grate and for conducting the spent cooling air partly as combustion air to the vertical shaft portion, partly as combustion air for the supplemental burner, and partly as a drying medium to the drying zone of the First traveling grate.