# US 5,341,576 A · Method and apparatus for drying granular materials

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- Number: US 5,341,576 A
- Document ID: US5341576A
- Status: Granted
- Kind: A
- Application number: 07/720,193
- Filed: 1991-06-25
- Granted: 1994-08-30
- Earliest claimed: 1990-06-29
- Assignees: Matsui Manufacturing Co., Ltd.
- Inventors: Ono Tsutomu; Nosaka Masaaki
- Web page: https://patentgrep.com/patent/US5341576A

## CPC

- B29B 13/021: {Heat treatment of powders}
- B29B 13/065: {of powder or pellets}
- F26B 5/041: {for drying flowable materials, e.g. suspensions, bulk goods, in a continuous operation, e.g. with locks or other air tight arrangements for charging/discharging}
- F26B 5/048: {in combination with heat developed by electro-magnetic means, e.g. microwave energy}
- B29C 2035/0855: {using microwave}
- B29K 2067/00: Use of polyesters {or derivatives thereof}, as moulding material
- B29K 2995/0041: Crystalline
- B29B: PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
- F26B: DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM (drying devices for combines A01D41/133; racks for drying fruit or vegetables A01F25/12; drying foodstuffs A23; drying hair A45D20/00; body-drying implements A47K10/00; drying household articles A47L; drying gases or vapours B01D; chemical or physical processes for dewatering or like separating liquids from solids B01D43/00; centrifugal apparatus B04; drying ceramics C04B33/30; drying yarns or fabrics in association with some other form of treatment D06C; drying frames for laundry without heating or positive air circulation, domestic laundry-or spin-driers, wringing or hot pressing laundry D06F; furnaces, kilns, ovens F27)
- B29C: SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING (making preforms B29B11/00; making laminated products by combining previously unconnected layers which become one product whose layers will remain together B32B37/00 - B32B41/00)
- B29K: INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR {MOULDS, } REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS

## Abstract

The present invention discloses a method and an apparatus for drying granular materials by submitting them to dielectric heating by means of electromagnetic waves such as microwave, high frequency, etc. The granular materials to be dried are heated to the prescribed temperature with electromagnetic waves under a reduced pressure of a range not producing any glow discharge and then dried to the prescribed moisture percentage while passing through a pressure reducing process of a vacuum of higher degree. An apparatus for it is provided with a reduced pressure drying tank (1) having an electromagnetic wave generator (2), a main drying tank (30) communicated with said reduced pressure drying tank (1), and suction air sources (20), (20') which are provided respectively in the reduced pressure drying tank (1) and the main drying tank (30).

## Claims

### Claim 1

A method for drying granular materials intended to dry the granular materials to be dried through a heating process which heats the granular materials with electromagnetic waves under a reduced pressure lower than the atmospheric pressure and a pressure reducing process which performs final drying by producing a vacuum of a higher degree compared with the state of pressure reduction in said heating process in the absence of electromagnetic waves.

### Claim 2

An apparatus for drying granular materials comprising:
a reduced pressure drying tank (1) having an electromagnetic wave generator (2) which submits the granular materials fed through the material inlet (4),
a main drying tank (30) communicated with the material outlet (6) of said reduced pressure drying tank (1) through a communicating tube (7), and a heater (33) also being provided, and
suction air sources (20), (20') connected respectively to said reduced pressure drying tank (1) and the main drying tank (30).

### Claim 3 (depends on 2)

An apparatus for drying granular materials as defined in claim 2, wherein a spare reduced pressure tank (9) is provided upstream of the reduced pressure drying tank (1), said spare reduced pressure tank (9) also being depressurizable with a suction air source.

### Claim 4 (depends on 3)

An apparatus for drying granular materials as defined in claim 3, wherein the suction air source for the spare reduced pressure tank (9) is common with the suction air source (20) for the reduced pressure drying tank (1).

### Claim 5 (depends on 2, 3, 4)

An apparatus for drying granular materials as defined in any of claims 2 to 4, wherein an agitating means (5) is provided inside the reduced pressure drying tank (1).