Multi-stage drying apparatus and method

Claim 2

Apparatus for treating material with a gas comprising: first and second treatment devices, said first device having an inlet for receiving the material and a generally horizontally disposed conveyor deck having a plurality of openings, means for supplying a gas under pressure for passage through said openings for treating the material, said openings being configured such that the gas issuing therethrough forms jets having horizontal flow components for conveying the material from said inlet in a direction generally parallel to said deck to said second treatment device, said second device including a generally cylindrical drum defining a chamber, said drum having an inlet to said chamber adjacent one end thereof for receiving the material from said first device and an outlet from said chamber adjacent its opposite end for discharging the material, said drum having a plurality of openings through at least a portion of the cylindrical wall defining the same, said conveyor deck forming a substantially tangential extension of the drum wall at its inlet, means for supplying a gas under pressure for passage through said openings into said chamber for treatment of the material therein, each of said latter openings being configured such that the gas issuing therethrough forms jets having flow components for conveying the material in a generally circumferential direction about said chamber, and means for conveying the material in an axial direction along said drum for discharge through said outlet.

Claim 3

Apparatus according to claim 1 including means adjacent the inlet of said first device for forming a gas jet having flow components predominantly parallel to and adjacent said deck wherein, in conjunction with the gas jets issuing through the openings in said deck, the material against which the gas jets impinge is adapted for conveyance in spaced relation to said deck.

Claim 4

Apparatus according to claim 1 including first and second plenums underlying said deck and said drum, said inlet to said first conveyor including a chute having an inclined wall spaced from said deck and defining a slot therewith, said slot lying in communication with the gas under pressure in said first plenum and being configured to form a high velocity gas jet having flow components predominantly parallel to and adjacent said deck.

Claim 5

Apparatus according to claim 1 including means for supplying heated gas for passage through the openings in each of said deck and said drum.

Claim 6

Apparatus according to claim 1 including first and second plenums underlying said deck and said drum, said inlet to said first device including a chute having an inclined wall spaced for said deck and defining a slot therewith, said slot lying in communication with said first plenum and being configured to form a gas jet having flow components predominantly parallel to and adjacent said deck, said deck forming a generally Horizontal and tangential extension of the wall defining a portion of said drum, the gas issuing through said slot and the openings in said deck being adapted to maintain the material in spaced relation to said deck, and means for supplying heated gas for passage through said slot and the openings in said decks.

Claim 7

Apparatus for drying wetted material comprising; a predryer, a primary dryer, said predryer including a generally horizontally disposed deck having a plurality of openings and an inlet adjacent one end of said deck for receiving the wetted material, a plenum underlying said deck, a source of heated air under pressure in communication with said plenum for supplying heated air through said openings, said openings being configured such that the air issuing therethrough dries the wetted material and forms jets having horizontal flow components for conveying the wetted material from said inlet in a direction generally parallel to said deck to said primary dryer, said primary dryer including a generally cylindrical drum defining a chamber having an inlet and an outlet adjacent opposite ends of said chamber, for respectively receiving the material from said predryer and discharging the material, said drum having a plurality of openings through at least a portion of the cylindrical wall defining the same, said conveyor deck forming a substantially tangential extension of the drum wall at its inlet, a second plenum surrounding at least the portion of the drum containing said openings, means for communicating the heated air from said source to said second plenum for issuance through said drum openings into said chamber, said drum openings being configured such that the air issuing therethrough dries the wetted material received from said predryer and forms jets having circumferential flow components for conveying the wetted material in a generally circumferential direction about said chamber, and means for conveying the material in an axial direction along said drum for discharge through said outlet.

Claim 8

Apparatus for drying wetted material comprising; a predryer, a primary dryer, said predryer including a generally horizontally disposed deck having a plurality of openings and an inlet adjacent one end of said deck for receiving the wetted material, a plenum underlying said deck, a source of heated air under pressure in communication with said plenum for supplying heated air through said openings, said openings being configured such that the air issuing therethrough dries the wetted material and forms jets having horizontal flow components for conveying the wetted material from said inlet in a direction generally parallel to said deck to said primary dryer, said primary dryer including a generally cylindrical drum defining a chamber having an inlet and an outlet adjacent opposite ends of said chamber, for respectively receiving the material from said predryer and discharging the material, said drum having a plurality of openings through at least a portion of the cylindrical wall defining the same, said conveyor deck forming a substantially tangential extension of the drum wall at its inlet, a second plenum surrounding at least the portion of the drum containing said openings, means for communicating the heated air from said source to said second plenum for issuance through said drum openings into said chamber, said drum openings being configured such that the air issuing therethrough dries the wetted material received from said predryer and forms jets having circumferential flow components for conveying the wetted material in a generally circumferential direction about said chamber, and means for conveying the material in an axial direction along said drum for discharge through said outlet.

Claim 9

Apparatus according to claim 6 wherein the inlet to said pre-dryer includes a chute having an inclined wall, the lower end of said wall being spaced above said deck to define a slot therewith in communication with the plenum underlying said deck, said slot being configured to form an air jet having flow components predominantly parallel to and adjacent said deck whereby, in conjunction with said inclined wall and the air jets issuing through the openings in said deck, the material is adapted to conveyance along said deck in spaced relation thereto.

Claim 10

Apparatus according to claim 6 wherein the inlet to said pre-dryer includes a chute having an inclined wall, the lower end of said wall being spaced above said deck to define a slot therewith in communication with the plenum underlying said deck, said slot being configured to form an air jet having flow components predominantly parallel to and adjacent said deck whereby, in conjunction with said inclined wall and the air jets issuing through the openings in said deck, the material is adapted for conveyance along said deck in spaced relation thereto, the opposite end of said deck from its inlet end forming a substantially tangential extension of the wall defining a portion of said drum at its inlet, the openings in the wall of said drum being distributed in a wall portion of said drum which extends circumferentially from said deck and in a predetermined circumferential extent of the drum wall for the full distance between the drum inlet and drum outlet.

Claim 11

Apparatus according to claim 6 wherein the plurality of openings in the wall of said drum are provided at least in a wall portion of said drum which extends circumferentially from said deck.

Claim 12

A two-stage method of drying wetted material utilizing a predryer comprised on a conveyor deck having a plurality of openings and a primary dryer comprised of a drum having a plurality of openings through a predetermined area of the cylindrical wall defining said drum comprisinG the steps of delivering the wetted material to the predryer, passing heated air through the openings in said deck for drying the wetted material and conveying it toward said primary dryer, delivering the predried wetted material to said primary dryer, in a direction substantially tangential to said cylindrical wall, passing heated air through the openings in said primary dryer drum for imparting circumferential movement to said material about said chamber and for drying the material and conveying the air and material axially along said drum to discharge the dried material at the outlet to said drum.

Claim 13

A two-stage method of drying wetted material utilizing a predryer comprised on a conveyor deck having a plurality of openings and a primary dryer comprised of a drum having a plurality of openings through a predetermined area of the cylindrical wall defining said drum comprisinG the steps of delivering the wetted material to the predryer, passing heated air through the openings in said deck for drying the wetted material and conveying it toward said primary dryer, delivering the predried wetted material to said primary dryer, in a direction substantially tangential to said cylindrical wall, passing heated air through the openings in said primary dryer drum for imparting circumferential movement to said material about said chamber and for drying the material and conveying the air and material axially along said drum to discharge the dried material at the outlet to said drum.

Claim 14

The method according to claim 10 wherein the material has an initial wetted content above a predetermined wetted level at which the material will clog or otherwise impair the efficiency of the primary dryer including the step of predrying the material in said pre-dryer such that the wetted level of the material delivered to the primary dryer is below the predetermined level.

Claim 15

The method according to claim 11 including the step of providing an air jet along said deck in the direction of movement of the material whereby the air jet and the air issuing through the openings entrains the material in a cushion of air flowing above the deck.

Claim 16

The method according to claim 12 including the step of delivering the wetted material into said pre-dreyer along an inclined chute.