US 4,346,523 AGranted

Method and apparatus for recovering heat in product dehydration system

AssigneeRonning Engineering Company, Inc.

InventorRichard L. Ronning

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Abstract

An improved, fuel efficient crop drying system and method is disclosed which makes use of the waste heat from a primary rotary drum dryer in order to predry the crop in a two-pass, indirect heat exchange dryer. The predryer and primary dryer are coupled in a pneumatic (negative pressure) conduit loop so that crop is conveyed in serial order through the dryers. The predryer includes respective, adjacent, two-pass air and crop paths disposed within a tubular shell, and the entire predryer is axially rotated during operation thereof. The ultimate volumetric air discharge from the system is significantly reduced as compared with conventional rotary dryers, and the saturated wet scrubbing which occurs in the predryer displaces a high percentage of particulate matter from the gaseous discharge to the water discharge, thereby reducing atmospheric pollution.

Claims7

Dependent claims

A crop drying system, comprising:

a primary dryer having a direct heat exchange zone and structure operatively coupled and in communication with said zone including an air inlet, a crop inlet, and outlet-defining means for exhaust air and crop;
a predryer having an indirect heat exchange zone comprising means defining separate, adjacent, noncommunicating passages therethrough for crop and air respectively, an air inlet and an air outlet respectively operatively coupled and in communication with said air passage, and a crop inlet and outlet respectively operatively coupled and in communication with said crop passage;
means operatively coupled with said primary dryer air inlet for supplying initially hot, dry air thereto;
means operatively coupled with said predryer crop inlet for directing initially moist crop thereto;
crop moving means including conduit means operatively coupling said crop outlet of said predryer and said crop inlet of said primary dryer for passage of predried crop from said predryer to said primary dryer;
and
air moving means including conduit means operatively coupling said air outlet-defining means of said primary dryer and said predryer air inlet, for passage of exhaust air from said primary dryer to said predryer in order to provide a source of heating air to said predryer.

4 more elements

A crop drying method comprising the steps of:

a. passing a first quantity of predried moisture-containing crop into a primary drying zone;
b. introducing a quantity of initially hot, relatively dry air into said primary drying zone, and bringing said air and said predried crop into direct intimate contact for effecting a direct heat exchange between said air and said predried crop, thereby transferring at least a portion of said moisture of said predried crop to said air to produce a relatively dry crop and hot, moist air;
c. exhausting said hot moist air and said dry crop from said primary drying zone;
d. directing said hot moist air to a predrying zone;
e. introducing a second quantity of moisture-containing crop into said predrying zone, said second quantity of crop having a higher moisture content than the moisture content of said first quantity of predried crop, separating said second quantity of crop and said hot moist air in said predrying zone by directing the second quantity of crop and said hot moist air along, separate, adjacent, noncommunicating paths, and causing an indirect heat exchange between said hot, moist air and said second quantity of crop within said predrying zone to thereby predry said second quantity of crop;
f. exhausting said hot moist air and said predried crop from said predrying zone;
g. passing said predried crop to said primary drying zone;
and
h. repeating steps b through g.

6 more elements

Dependencies are inferred from the claim text.

Facts

Application: 06/207,216Filed 17 Nov 1980
Granted: 31 Aug 1982
Term ends: Not estimatedThe source records don’t support an estimate.

Classification8 codes

F26B 11/0436
Rotating about a horizontal or slightly-inclined axis: comprising multiple stages, e.g. multiple rotating drums subsequently receiving the…
F26B 3/00
Drying solid materials or objects by processes involving the application of heat
F26B 3/22
By conduction, i.e. the heat is conveyed from the heat source, e.g. gas flame, to the materials or objects to be dried by direct contact: the heat…
F26B 11/0413
With internal subdivision of the drum, e.g. for subdividing or recycling the material to be dried: the subdivision consisting of concentric walls,…