Method for drying adherent particulate matter such as a polyvinyl chloride resin

Claim 1

A METHOD FOR DRYING COHESIVE PARTICULATE MATERIALS IN AN ELONGATED SUBSTANTIALLY CYLINDRICAL DRUM WHICH IS ROTATABLE ABOUT A SUBSTANTIALLY HORIZONTAL AXIS, WHICH HAS A FEED END AND A DISCHARGE END THROUGH WHICH HEATED DRYING GASES ARE FED COCURRENTLY WITH SAID PARTICULATE FROM SAID FEED END TO SAID DISCHARGE END, WHEREIN THE METHOD COMPRISES: A. FEEDING WET COHESIVE PARTICULATE AND SUFFICIENT AT LEAST PATIALLY DRIED RECYCLE PARTICULATE TO A FEED AND MIXING ZONE AT THE FEED END OF SAID DRUM AND MIXING TO PROVIDE A SUBSANIALLY NON-ADHEREN AND RELATIVELY FREE-FLOWING FEED. B. ADVANCING SAID FEED TO THE BED OF A PRIMARY DRYING ZONE PROVIDED WITH A PLURIY OF CIRCUMFERENTIALLY SPACED FLIGHTS. C. LIFTING A PORTION OF SAID BED ON SAID FLIGHTS TO AN UPPER PORTION OF SAID PRIMARY DRYING ZONE AND RELEASING SAID PORTION TO FREEFALL INTO SAID BED THROUGH A STREAM OF HEATED GASES,

Claim 2

A METHOD FOR DRYING COHESIVE PARTICULATE MATERIALS IN AN ELONGATED SUBSTANTIALLY CYLINDRICAL DRUM WHICH IS ROTATABLE ABOUT A SUBSTANTIALLY HORIZONTAL AXIS, WHICH HAS A FEED END AND A DISCHARGE END THROUGH WHICH HEATED DRYING GASES ARE FED COCURRENTLY WITH SAID PARTICULATE FROM SAID FEED END TO SAID DISCHARGE END, WHEREIN THE METHOD COMPRISES: A. FEEDING WET COHESIVE PARTICULATE AND SUFFICIENT AT LEAST PATIALLY DRIED RECYCLE PARTICULATE TO A FEED AND MIXING ZONE AT THE FEED END OF SAID DRUM AND MIXING TO PROVIDE A SUBSANIALLY NON-ADHEREN AND RELATIVELY FREE-FLOWING FEED. B. ADVANCING SAID FEED TO THE BED OF A PRIMARY DRYING ZONE PROVIDED WITH A PLURIY OF CIRCUMFERENTIALLY SPACED FLIGHTS. C. LIFTING A PORTION OF SAID BED ON SAID FLIGHTS TO AN UPPER PORTION OF SAID PRIMARY DRYING ZONE AND RELEASING SAID PORTION TO FREEFALL INTO SAID BED THROUGH A STREAM OF HEATED GASES,

Claim 9

A method for drying polyvinyl chloride resin drum dryer rotatable about a substantially horizontal axis which has a feed end and a discharge end through which heated drying gases are fed cocurrently with said particulate from said feed end to said discharge end, comprising: a. feeding wet polyvinyl chloride resin having a moisture content in the range of 20-30 percent by weight and sufficient recycle polyvinyl chloride resin having a moisture content of 1.0 to 5 percent by weight of a feed and mixing zone at the feed end of said dryer and mixing to provide a non-adherent relatively free-flowing feed to a primary drying zone, said feed having a moisture content in the range of 5-20 percent by weight, b. advancing said feed to a primary drying zone provided with a plurality of circumferentially spaced flights and depositing the same in a bed of partially dried polyvinyl chloride resin, c. lifting a portion of said bed on said flights to an upper portion of said primary drying zone and releasing said portion to free-fall through a stream of heated gases fed at temperature in the range of 200* to 350*F, d. entraining a portion of said free-falling portion having a moisture content below about 5 percent by weight in said stream of heated gases and advancing the entrained portion of the bed of a flight-free secondary drying zone of said drum, e. maintaining the bed of said secondary drying zone in rolling motion in contact with said strEam of heated gases permitting diffusion drying to occur while said resin is retained in said secondary drying zone, f. recycling a portion of said resin from said secondary drying zone to step (a), and g. removing dried resin having a moisture content below about 0.5 percent by weight from the discharge end of said dryer.

Claim 10

A method for drying polyvinyl chloride resin drum dryer rotatable about a substantially horizontal axis which has a feed end and a discharge end through which heated drying gases are fed cocurrently with said particulate from said feed end to said discharge end, comprising: a. feeding wet polyvinyl chloride resin having a moisture content in the range of 20-30 percent by weight and sufficient recycle polyvinyl chloride resin having a moisture content of 1.0 to 5 percent by weight of a feed and mixing zone at the feed end of said dryer and mixing to provide a non-adherent relatively free-flowing feed to a primary drying zone, said feed having a moisture content in the range of 5-20 percent by weight, b. advancing said feed to a primary drying zone provided with a plurality of circumferentially spaced flights and depositing the same in a bed of partially dried polyvinyl chloride resin, c. lifting a portion of said bed on said flights to an upper portion of said primary drying zone and releasing said portion to free-fall through a stream of heated gases fed at temperature in the range of 200* to 350*F, d. entraining a portion of said free-falling portion having a moisture content below about 5 percent by weight in said stream of heated gases and advancing the entrained portion of the bed of a flight-free secondary drying zone of said drum, e. maintaining the bed of said secondary drying zone in rolling motion in contact with said strEam of heated gases permitting diffusion drying to occur while said resin is retained in said secondary drying zone, f. recycling a portion of said resin from said secondary drying zone to step (a), and g. removing dried resin having a moisture content below about 0.5 percent by weight from the discharge end of said dryer.