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Patent Searching and Data


Title:
PLANT FOR DRYING ANIMAL OR VEGETABLE MATERIAL
Document Type and Number:
WIPO Patent Application WO/1984/003935
Kind Code:
A1
Abstract:
A plant for heat treating animal or vegetable material comprises apparatuses for two-stage or multi-stage heat treatment. A heat medium which is used in a second heat treatment apparatus (2), which follows a first heat treatment apparatus (1), consists of uncontaminated water/steam which is circulated in a closed circuit, that is to say separated from the heat medium of the first apparatus and from the treatment material of the second apparatus. The closed circuit extends from heat exchanger surfaces, which are supplied with heat energy from exhaust gas/exhaust steam from the first apparatus (1), via heat surfaces of the second apparatus (2) back to said heat exchanger surfaces. The closed circuit includes one or more steam compressor(s) (17) in order to bring in a manner known per se the heat medium of the circuit up to the process steam pressure before it is supplied to the heat surfaces of the second apparatus (2).

Inventors:
ALSAKER JON (NO)
Application Number:
PCT/NO1984/000018
Publication Date:
October 11, 1984
Filing Date:
April 05, 1984
Export Citation:
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Assignee:
STORD BARTZ AS (NO)
International Classes:
F26B21/00; F26B20/00; F26B23/00; (IPC1-7): F26B23/00
Foreign References:
US4312136A1982-01-26
US4205456A1980-06-03
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Claims:
CLAIM:
1. Plant for drying animal or vegetable material, comprising apparatuses for twostage or multistage heat treatment, preferably separate apparatuses (1, 2) for successive heat treatment of the material, characterised in that a heat medium which is used in a second heat treatment apparatus (2),whic follows a first heat treatment apparatus (1) , consists of uncontami¬ nated water/steam which is circulated in a closed circuit, that is to say separated from the heat medium of the first apparatus and from the treatment material of the second apparatus the circuit extending from heat exchanger surfaces, which are supplied with heat energy from exhaust gas/exhaust steam from the first apparatus (1) , via heat surfaces in the second apparatus (2) back to said heat ex¬ changer surfaces, and the closed circuit includes one or more steam compressor(s) (17) in order to bring in a manner known per se the heat medium of the circuit up to the process steam pressure before it is supplied to the heat surfaces of the second appa¬ ratus (2) . OMPI.
Description:
PLANT FOR DRYING ANIMAL OR VEGETABLE MATERIAL

1 The present invention relates to a plant for drying animal or vegetable material, comprising appa¬ ratuses for two-stage or multi-stage heat treatment, preferably separate apparatuses for successive heat treatment of the material.

It is well known within various branches of industry to employ waste heat from a first heat treat¬ ment apparatus - in the form of recompressed exhaust steam - in a subsequent heat treatment apparatus. In known process techniques the waster heat is usually employed in the form of impure exhaust gas or impure process exhaust steam, and such known, secondary heat medium as a consequence of the impurities in the exhaust steam or exhaust gas from the first heat treatment apparatus place special material technical demands on compressor(s) and on remaining process apparatus for the said subsequent heat treatment apparatus. These special demands involve complicated and expensive apparatus. The main object of the plant according to the invention is to obtain a possibility for employing compressors and other apparatus which is simple and inexpensive in procurement as well as in use. The plant according to the invention is characterised, in that a hea medium which is used in a second heat treatment apparatus ' , which follows a first heat treatment apparatus, consists of uncontami- nated water/steam which is circulated in a closed circuit, that is to say separated from the heat medium of the first apparatus and from the treatment material of the second apparatus the circuit extending from heat exchanger surfaces, which are supplied with heat energy from exhaust gas/exhaust steam from the first apparatus, via heat surfaces in the second apparatus back to said heat exchanger surfaces, and the closed circuit includes one or more steam compressor(s) in order to bring in a

manner known per se the heat medium of the circuit up to the process steam pressure before it is supplied to the heat surfaces of the second apparatus.

By employing according to the invention a secondary heat medium circuit, based on uncontami- nated water which is circulated in a closed circuit, the problems with the impurities in the exhaust steam or the exhaust gas from the first heat treatment apparatus are avoided, and equipment of conventional construction materials, such as soft steel,can there¬ by be employed in the second apparatus. In other words, corrosion of the material can be avoided at the surfaces which are only exposed to uncontami- nated water and uncontaminated water vapor, respe- tively. In addition, such process-associated disturbances are avoided which are due to carried along particles, carried along impure fluid drops, scum formations, and the like.

Even if the plant requires extra energy for operating pump and compressor in the closed circuit, there are obtained operatively economic favorable results as a consequence of the advantages of using uncontaminated water/steam in said closed circuit.

The invention will be further described in the following description having regard to the accom¬ panying drawing, which illustrates a process diagram according to the invention.

The plant according to the invention, as illu¬ strated in the accompanying drawing comprises two heat treatment apparatuses 1 and 2. By broken lines there is shown, respectively, a feed conduit 3 for the material which is to be treated in the apparatus 1, a transfer conduit 4 for the material between the apparatus 1 and the apparatus 2 together with a discharge conduit 5 from the apparatus 2 for the material. If desired, there can be present in series with the apparatus 2 or in series with the apparatus . '

one or more additional apparatuses (not shown further) . The apparatus 2 and possible further appa¬ ratuses effect heating of the material or portions of the latter by means of waste heat from the appa- ratus 1.

In the illustrated embodiment is a conduit 6 for exhaust gas or exhaust steam or a mixture of exhaust gas and exhaust steam from the apparatus 1. The conduit 6 leads the gas/steam via a primary duct 7 in a heat exhanger 8 to a discharge conduit 9 to a collection location not shown further.

The heat exchanger 8 has a secondary duct 10 which is included in a separate, closed circuit for uncontaminated water/water vapor which is supplied heat in the heat exchanger 8 from the gas/steam waste heat duct of the primary side. From the secondary duct 10 in the heat exchanger 8 there extends a conduit 11, in which there is inserted a regulating valve 12, and there is supplied water heated in the heat exchanger to the upper portion of a flash tank 13. From the bottom of the flash tank 13 there extends a return conduit 14 via a pump 15 back to the secondary duct 10 in the heat exchanger 8, so that by repeated circulation of water from the tank 13 to the heat exchanger duct 10 the temperature of the circulating water can be increased. From the top of the flash tank water vapor is drawn outwardly via a conduit 16 which passes to a compressor 17 which brings the pressureof the water vapor upwards from a pressure of below 1.5 bar (absolute pressure) to process steam pressure.

In the conduit 6 between the heat treatment apparatus 1 and the heat exchanger one operates with an exhaust gas temperature of between 80 and 100 C at a pressure of 0.3 to 1.5 bar (dependent upon which medium one dries in the heat treatment appa¬ ratus 1) . In the conduit 16 between the flash tank

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13 and the compressor one operates correspondingly with a temperature of betwen 60 and 100 C an at a pressure of 0.2 to 1 bar. In a conduit 18 between the compressor 17 and the second heat treatment apparatus 2 one operates at a pressure of between 1.0 and 4.0 bar, depending upon the type and number of compressors.

Water vapor at process steam pressure is thus led from .the compressor via the conduit 18 to the heat treatment apparatus 2 and - still in a closed circuit - through the apparatus 2 and outwardly from the latter in the form of exhaust steam and condensate via a conduit 19 back to the tank 13. By means of the closed heat medium circuit, in which uncontaminated water and steam circulate respec¬ tively, conduits 11, 14, 16, 18, 19 together with valve 12, tank 13, pump 15 and compressor 17 can be made of conventional construction materials (for example soft steel) . The metal in or the contact surfaces in the heat exchanger 8 and in the appa¬ ratus 2, respectively, can on the other hand be of special construction with respect to the contacts with the medium in the primary duct 7 and the con¬ tact with the material which is to be heat treated in the apparatus 2, respectively.

There is shown a ventilation conduit 20 with associated ventilation valve 21 for venting the secondary heat medium circuit of the plant.