Drying and gas or vapor contact with solids – Material treated by electromagnetic energy – Infrared energy
Patent
1998-10-23
2000-03-14
Gravini, Stephen
Drying and gas or vapor contact with solids
Material treated by electromagnetic energy
Infrared energy
34147, 34179, F26B 334
Patent
active
060355468
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a device by means of which bulk materials can be thermally treated.
A great number of technical variations of screw conveyors is known used to solve the problem of thermal treatment. Likewise many devices are known wherein also bulk materials are thermally treated during continuous transport due to an input of heat radiation. The transport devices used thereby operate according to the principles of belt conveyors, chain conveyors or vibratory conveyors (according to DIN 15 201).
The combination of screw feeding with the input of radiated heat is known from DE-OS 19 06 278, DE-OS 19 22 230, U.S. Pat. Nos. 5,143,626 A and 5,497,562 A. All mentioned specifications show infrared heat radiators mounted outside the perimeter of the effective screw conveyor. This leads on the one hand to a disadvantageous irradiation of the screw parts, on the other hand the distance to the bulk materials equals at least the radius of the screw, whereby the efficiency of the heat transmission remains extremely limited.
The U.S. Pat. No. 4,430,057 A proposes to move a part of the material to be irradiated closer to the infrared radiation source by means of paddles arranged in a screw-like manner.
The DE 23 41 331 A describes a drum drier, wherein the screw shaft is heated by hot combustion gases, whereby it acts as a heat radiation source. The total radiation output is radially radiated over the entire periphery of the screw shaft. The efficiency of this radiation source remains always limited by their low output density in comparison to the electrically powered infrared radiators, as well as by their characteristic peak wave length in the long-wave infrared range (according to the IEC Classification).
It is the object of the present invention to make possible a machine-operated heat treatment with depth penetration of bulk materials in a continuous operation, so that a targeted and quick tempering of the bulk materials can take place in the shortest possible process times, by observing the temperature ranges as closely as possible. The heat treatment can thereby serve for drying and/or for producing targeted changes of further physical or chemical characteristics of the material.
According to the invention this object is achieved due to the features of patent claims 1 or 2, whereby for the transport of the bulk material the principle of screw conveyors is used and heat input for the tempering of the conveyed goods takes place through heat radiation during the transport in the screw conveyor or the screw-tube conveyor.
Further developments and advantages of the invention are the object of the dependent claims.
Due to the invention, especially for the following specific uses, advantages of the screw conveyors can be developed:
Due to the fact that the conveying is based on thrust an overturning of the material takes generally place, at least in the contact area between the bulk material and the thrust-effecting screw flank. This overturning effect is particularly strong in screw-tube conveyors, since here in addition the trough wall is also moved. This overturning supports a uniform thermal irradiation of the conveyed goods and thereby supporting an even tempering.
Due to a zoned layout of the construction of the screw conveyor, process steps preceding or following the actual tempering process can be technically connected into one unit. This way for instance the most accurate and even feeding of the tempering zone in all tempering processes can be attempted. In the concept of vibratory conveyors this is made possible for instance by providing a preceding star valve (see GB-A-1 313 203). In addition to a skillfully provided dosage zone, in the following description other screw conveyor zones advantageous to the invention will also be disclosed.
As advantages specific to the use of tempering by thermal radiation the following can be counted: material is at least partially heated.
This advantage of the thermal radiation is widely used for instance in the technology of plastic materials, since the plastic mater
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patent: 4794011 (1988-12-01), Schumacher
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patent: 5127347 (1992-07-01), Cheetham
patent: 5143626 (1992-09-01), Nugent
Siebert Martin
Stricker Klaus
Stricker Urban
Dubno Herbert
Gravini Stephen
Stricker Urban
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