Drying and gas or vapor contact with solids – Process – With fluid current conveying or suspension of treated material
Patent
1999-04-07
2000-12-05
Gravini, Stephen
Drying and gas or vapor contact with solids
Process
With fluid current conveying or suspension of treated material
34364, 34371, 34487, 34167, 34169, 34174, F26B 308
Patent
active
061549797
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a method for the removal of liquid from particulate material by evaporation through the supply of heat transferred mainly by superheated vapours or steam of the liquids existing in the particulate material, said method taking place in a substantially closed system.
The invention also concerns an apparatus for the execution of such a method, said apparatus consisting of a substantially closed container which has means for the introduction of the particulate material from which liquid is to be removed, means for the removal of dried particulate material, means for the circulation of superheated vapours in the container, means for the supply of thermal energy to these vapours and means for the separation of dust particles from the vapours.
The particulate material can contain particles which can be uniform in size as well as particles which in size can differ considerably from each other. The material can contain several different volatile and liquefied components which are desired to be removed, which is effected in an atmosphere of superheated vapours of the same volatile liquids. If the liquid which is to be removed is water, the process involved is a drying process where the drying takes place in a superheated water vapour. It will be understood, however, that where drying processes are referred to in the following, these could equally well involve similar processes where liquids other than water are removed from the particulate material.
A method and an apparatus of the kind mentioned in the introduction are known, for example from EP Patent Application no. 82 850018.1(publication no. EP 0.058.651 A1). With this known technique, the drying process is effected by the particles to be dried flowing through series-connected vertical pipes or heat exchangers while suspended in the super-heated water vapour. This method gives a uniform retention time which is relatively short, since in practice it is possible to build sufficiently high and sufficiently many vertical pipes and heat exchangers. For example, when the flow rate is 20 m/sec., a retention time of only a few minutes can be achieved with the use of 30 vertical processing zones, each of which is 40 m high. This means that the particles must be of a very uniform particle size and have a very short drying time, which is why this method is suitable only for small, uniform particles,
A method and an apparatus are also known from EP 0.153.704, which comprises a series of vertical, rather long processing zones, up through which superheated steam is supplied. Above the processing zones there is a common zone to which particles with reduced moisture content are transferred, in that from here the particles are conveyed further to the removal zone or removal zones. At the lower ends of the processing zones, at least some of the particles can be led through connection channels from one processing zone to the next.
With this known technique, the configuration of the long, vertical processing zone means that a considerable part of the medium-sized particles receive a retention time which is too long. Consequently, they are dried to an undesirably high drystuff content which lowers the product quality, since where many products are concerned the re-absorption of water is hereby reduced. Moreover, the high construction involves relatively high building and installation costs. Finally, by the division of the processing zones there is a relatively great risk that wet, particulate material will block the first zones of the apparatus, partly by adhesion of the product and partly by steam condensing on the product, hereby making it so much heavier that it can no longer be held in movement by the flow of steam.
The object of the invention is to provide a method and an apparatus which avoids the above-mentioned disadvantages in connection with the use of several processing zones, and in that an optimum processing time is achieved for particles of all sizes in the particulate material.
In that use is made only of horizontal chambers, a suitably low con
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ASJ Holding ApS
Gravini Stephen
Sapone William J.
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