Method and apparatus for indirectly drying and preheating fine material

An apparatus for drying and preheating fine material, comprising:

• an outer rotary drum defining a space therein:
• drum drive means connected to said rotary drum for rotating said rotary drum;
• a plurality of heating tubes extending through and closed with respect to the space of said rotary drum, a pair of heads connected to opposite ends of said rotary drum for rotatably receiving said rotary drum with said heating tubes connected between said pairs of heads;
• feed means connected at one end of said rotary drum for applying moist fine material to said rotary drum;
• discharge means at an opposite end of said rotary drum for the removal of dried and preheated fine material from said rotary drum;
• vapor takeoff means connected to said rotary drum for removing vapor, from the moist material, out of said rotary drum;
• and
• a return line connected between said discharge means and said feed means, at a location outside said rotary drum space, for recycling a portion of the preheated and dried fine material to said rotary drum with said moist fine material seals between opposite ends of said rotary drum and each of said heads respectively, said heads being stationary with respect to said rotary drum and rotatably receiving said rotary drum at said seals, each of said seals comprising a smooth ring surface on said rotary drum and a unilateral labyrinth gland on said respective stationary head associated with said smooth ring surface.

An apparatus for drying and preheating fine material, comprising:

• an outer rotary drum defining a space therein:
• drum drive means connected to said rotary drum for rotating said rotary drum;
• a plurality of heating tubes extending through and closed with respect to the space of said rotary drum, a pair of heads connected to opposite ends of said rotary drum for rotatably receiving said rotary drum with said heating tubes connected between said pair of heads, said heating tubes having diameters which increase, in stepwise fashion, in a direction of travel of the fine material moving said rotary drum;
• feed means connected at one end of said rotary drum for supplying moist fine material to said rotary drum;
• discharge means at an opposite end of said rotary drum for the removal of dried and preheated fine material from said rotary drum;
• vapor takeoff means connected to said rotary drum for removing vapor, from the moist material, out of said rotary drum;
• and
• a return line connected between said discharge means and said feed means, at a location outside said rotary drum space, for recycling a portion of the preheated and dried fine material to said rotary drum with said moist fine material.

An apparatus for drying and preheating fine material, comprising:

• an outer rotary drum defining a space therein;
• drum drive means connected to said rotary drum for rotating said rotary drum:
• a plurality of heating tubes extending through and closed with respect to the space of said rotary drum, a pair of heads connected to opposite ends of said rotary drum for rotatably receiving said rotary drum with said heating tubes connected between said pairs of heads, a number of said heating tubes being larger and the spacing between adjacent heating tubes being smaller at a discharge side of said rotary drum adjacent said discharge means, that the number and spacing of said heating tubes at an opposite feed side of the rotary drum adjacent said feed means;
• discharge means at an opposite end of said rotary drum for the removal of dried and preheated fine material from said rotary drum;
• vapor takeoff means connected to said rotary drum for removing vapor, from the moist material, out of said rotary drum;
• and
• a return line connected between said discharge means and said feed means, at a location outside said rotary drum space, for recycling a portion of the preheated and dried fine material to said rotary drum with said moist fine material.