The present invention relates to a drying apparatus lO for batchvise drying of material stacked in lots, in known manner arranged penetrable to a gas flow. The invention relates further to such known closed cycle drying processes that include precipitation of condensate against a cooler or absorb vapour by a 15 sorbtion process.

Objects of the invention are as follows.

An apparatus that ensures an essentially gas tight SO and heat insulated environment during drying.

An apparatus that allows improved access for loading or unloading drying lots and minimizes damage during handling of lots to the drying chamber structure.

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These objects and other listed below are according to the invention achieved by a drying apparatus further characterized in that it comprises a platform positioned in a shallow water bath; to said

30 platform attached drying equipment; means to load to or unload from said platform said lots; an heat insulated and essentially gas tight hood dimensioned to cover said lots, said drying equipment, perimeter of said platform and for said closed gas circulation

35 necessary gas space and means for withdrawal of said hood during loading or unloading of said lots to a

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space apart from a space reserved for loading/unloading.

One further object of the invention is an apparatus 5 where the gas environment may be modified to prevent deterioration during drying of organic material, due to growth of fungi or bacteria.

Such modification may also include a reduced oxygen 10 content to prevent fire hazard and minimize oxidation processes of drying material or drying equipment.

Another further object of the invention is an 15 apparatus provided with. simple and effective means for sealing the surfaces of lots, that are parallell to gas flows, thus preventing shortcuts of interior gas circulation.

SO The invention will be described in more detail in the following reference being made to accompanying drawings, where fig 1 and fig S illustrate plan and section of an apparatus and fig 3, fig ** illustrate in plan and section a lumber drying plant.

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Referring to fig 1 and fig S a platform 11 is positioned in a shallow bath 3 of water. On said platform is mounted drying equipment IS, that includes the necessary machinery for a drying

30 process i. e. circulation fans, a cooler, a heater, necessary regulation equipment etc. Lots S to be dried are parked on the platform 11 by a handling equipment in a handling space 6, that may be an overhead telpher conveyor 5 and hoist block 8. A

35 heat insulated and essentially gas tight hood 13 is dimensioned to cover the perimeter of the platform

11, the lots 2, the drying equipment IS and gas spaces 14- for gas circulation through the lots 2. During treatment of the lots, i.e. curing or drying, the hood is positioned with bottom parts of its sidewalls immersed in the bath 3. The interior gas space will thus be effectively sealed against the atmosphere.

During loading or unloading of the lots the hood is withdrawn to a storage space 7 apart from said handling space 6. Obviously this procedure faciliates the handling of the lots, especially in case of heavy, bulky material like lumber, compared to known rigid structure drying chambers, using ports.

Damage to chamber structure from loading procedure is also highly diminished with the present invention.

Design criteria for the hood 13 is high heat insulation, low gas diffusion, lightness and enough stiffness to be hoisted. Preferably the hood is constructed in sandwhich technique, using thin metal skins and a polyuretane foam core.

The air entrapped under the hood 13, positioned for a curing/drying cycle, may according to the invention be chemically modified or substituted by a different gas or gas mixture in order to prevent degradation of products or equipment as mentioned. Thus an evident and simple modification may as example be oxidation of oxygen to carbondioxide by means of a burner. Both a low oxygen content and an increased concentration of carbondioxide will halter the growth of fungi.

The apparatus may thus be equipped with a burner 9, with an amount of a suitable hydrocarbon agent, dimensioned for the burning out of the oxygen content of the entrapped air . This air is slowly circulated through the burner at the start of the curing/drying cycle.

By the mentioned burning process and by precipation of condensate out of the closed apparatus system, the enclosed gas volume will shrink, causing an underpressure and a level of water from the bath to raise inside the hood. To prevent this an additional gas, for instance carbondioxide, may be added to the interior space through a conduit 16. A small underpressure versus the atmosphere may be preferred in order to prevent tilting of the hood , othervise caused by local" overpressures in the interior gas circulation.

The efficiency of closed condensation processes in for instance lumber drying is in known chamber structures often severely affected by shortcuts of the air circulation, i.e. a high percentage of the air flow passes besides the lots instead of through the lots. Known seals like flaps etc are not very efficient and may be out of place or damaged as a cause of the loading practise of these structures.

With the invention inflatable seals of thin plastic hoses efficiently solves the mentioned sealing problem. Thus thin, flat and wide plastic hoses .• are tape glued on one flat side to the interior skin of the hood 13 at appropriate sections.

These hoses - are inflated during drying thus .

efficiently sealing betweeen the hood 13 and the lots 2 and the drying equipment 13 against gas shortcuts. The hoses are deflated in the withdrawal procedure of the hood. Due to the working mode of the invention the thin hoses thus never will be submitted to any rough handling from loading etc and may have a long lifetime.

The invention may be utilized in a wide range of 10 applications and scope as from a small apparatus for drying fruit or vegetables to a large scale lumber drying.

Referring to fig 3 and fig •*> an efficient handling 15 of lumber in large scale is exemplified by poisitioning individual apparatus stations 10 according to the invention in a row in a common bath 3 beneath a common overhead telpher conveyor 5. Said handling space 6 is dimensioned for transport of 20 lots to and fro any of the stations above the other stations being in drying operation. Any hood 13 not in operation is as previously mentioned stacked at a storage space 6 above the conveyor 5. As illustrated in fig .• the apparatus stations 10 may well be Ξ5 positioned below ground which saves overground structure and faciliates overall handling of the lumber.