Drying and gas or vapor contact with solids – Apparatus – With means to treat gas or vapor
Patent
1985-10-23
1987-09-01
Makay, Albert J.
Drying and gas or vapor contact with solids
Apparatus
With means to treat gas or vapor
34 26, 34 27, 34 35, 34 86, F26B 302
Patent
active
046898948
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a closed intermittent process for drying moist material distributed to expose a large area to a gas flowing through the material and stacked in such a manner that a moderate gas flow resistance is obtained. The material to be dried may be, for example, grain, fibre crops, timber, granulates or liquid products which are spread on horizontal metal sheets.
The process utilizes, in a known manner, a circuit integrated with the drying process and having a cooling surface for cooling a moisture-carrying gas flow and for condensing water vapour. In contrast to prior art processes, the material is dried intermittently by means of a gas flow which is colder than the material and which is progressively heated by heat exchange when flowing through the material. During heating, the gas flow takes up an increasing amount of vapour which is expelled from the goods to the gas because of the vapour pressure difference between warmer material and colder gas. Also the requisite heating and evaporation heat is supplied intermittently to the material by means of a substantially greater gas flow which is warmer than the material. According to the invention, cycling between cooling/drying and reheating is effected between at least two preferably gastight chambers within which the total amount of the material to be dried is distributed in two substantially equal lots, the enthalpy flow from the cooling/drying in one chamber preferably being transferred by a refrigerating machine for reheating the other chamber, simultaneously as condensate is precipitated on the cooling surface of the refrigerating machine. In other words, an enthalpy quantity is moved back and forth between the chambers at a given frequency during cyclic heat storage in the lots of material to be dried.
If the process is combined with efficient cooling, for example by means of a refrigerating machine, thermodynamically highly efficient drying is accomplished at low drying temperatures. Drying may be effected at a temperature level and in a closed gas environment in which the nutrient value and taste of, for example, different crops are maintained remarkably well.
The process according to the invention makes it possible, at low investment cost, to combine long-term storage of a moist organic material at a quality-preserving temperature level and in gaseous environment with a progressive slow drying-out which is extended during the storage period.
Atmospheric moisture may also in itself be regarded as a material to be dried. Furthermore, the drying process is applicable to moisture control in moisture-producing environments, for example in greenhouses, the air volume being divided in a similar manner into at least two separate parts which have substantially the same size and which are alternately cooled/dried and reheated, respectively.
The invention will be described in more detail below, reference being had to the accompanying drawings.
FIG. 1a illustrates a plant which is intended to be used with the process according to the invention and which comprises two chambers, one of which is cooled/dried and the other of which is heated.
FIG. 1b shows the chambers according to FIG. 1a when subjected to the inverse treatment.
FIGS. 2a and 2b illustrate a cooling/heating device comprised by the plant.
FIG. 3 illustrates an embodiment comprising a storing/drying device.
FIGS. 4a-c illustrate, as a further embodiment, and in plan and sectional views, the moisture control in closed cultivation chambers, such as greenhouses.
The material to be dried, which in the embodiment illustrated in FIGS. 1a and 1b is timber, is stacked in two equally large lots 31, 32, each in one gastight and preferably heat-insulated chamber 1 and 2, respectively. Stacking is carried out according to the type of the material to be dried and by methods which need not be explained in detail, to provide for fairly uniform distribution of a gas flow across the surface of the material.
In accordance with the invention, cooling/drying and heating are conducted alternately
REFERENCES:
patent: 3086533 (1963-04-01), Touton
patent: 3939573 (1976-02-01), Berti
patent: 3965696 (1976-06-01), Thomason
patent: 4020562 (1977-05-01), Wevermann
patent: 4255870 (1981-03-01), Malmquist
Makay Albert J.
Westphal David W.
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