FI70321C - FOERFARANDE OCH ANORDNING FOER TORKNING AV VIRKE - Google Patents

Description

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(51) Kv.lk. * / Lnt.CI. «F 26 B 3/0 * 4 (21) Patent application - Patentansöknlng 761 0 ^ 40 (22) Application date - Ansöknlngsdag 1 5.0 * 4. 76 (23) Start date - Giltighetsdag 15 · 0 * 4.76 (41) Become public - Bllvlt offentllg 1 8.1 0.76

National Board of Patents and Registration of Finland Nihtäväk, (date of the hearing) - 28.02.86

Patent and registration authorities '' Ansökan utlagd och utl.skriften publlcerad (32) (33) (31) Privilege requested - Begird prloritet 17-0 * 4.75 Sweden-Sweden (SE) 750 * 4 * 47 * 4-3 (71) (72) Erik Ruben Wallman, Backvindeln 36, 126 57 Hägersten,

Gunnar Ernfrid Stargren, Hälleskaran 53, 126 57 Hägersten,

Sweden i-Sver ige (SE) (7 * 4) Oy Koister Ab (5 * 0 Method and apparatus for drying timber -Förfarande och anordning för torkning av virke

The invention relates to a method for drying timber in a dryer, in which the timber in the form of loads is fed continuously or intermittently first through at least one heating zone and then through at least one drying zone, while passing heated drying air through the timber loads, discharging wet air or extracting air. , in connection with a drop in temperature and water precipitation while maintaining a shared flow path, whereby part of the flow is recycled.

Timber drying usually takes place in four stages, which are heating, pre-drying, pre-drying and cooling. Each step can be performed in the corresponding zone of the dryer. The total transit time of the timber is normally 5-6 days, in which case the dryer has a total varying amount, e.g. 20 - 24, of timber loads.

The use of a different heating and preheating zone in said timber dryer provides several advantages. One advantage is that a drying operation is obtained which is not disturbed by the new timber. By using a different heating zone, it is also possible to recover heat. In addition, it is not necessary to increase the heating surface or or the used boiler, etc. to obtain the additional heat required for the supply of new timber.

Swedish patent publication 130,363 describes a timber dryer which takes advantage of such a preheating zone. However, such a dryer operates with practically insufficient drying capacity.

U.S. Patent No. 1,729,675 describes a different type of dryer with two similar, partitioned zones, both equipped with radiators and fans, each of which can be used separately for preheating and which can be connected to a single circulation. This system is completely obsolete and its capacity is completely inadequate for a modern drying plant.

It is an object of the present invention to increase the overall power of the dryer by making more efficient use of such a heating zone.

The method according to the invention is characterized in that the new wood is heated by means of exhaust wet or exhaust air until the temperature of the wood has reached or approached the wet temperature of the drying air, and that the circulating air flow is then changed so that substantially all of the circulating air passes through the zone. the new timber is heated, which zone is then included in the drying zone.

The application of the method according to the invention thus results in a different heating zone which offers such the above-mentioned advantages, but in which part of the "useless" heating time is used for pure drying. This increases the efficiency of the entire dryer.

Changes in the recirculating air flow are preferably achieved by closing and opening the openings between the drying zone and the associated recirculation duct, or by opening the outlet area associated with the zone to which new timber is fed (i.e. the heating zone) and the recirculation duct.

In this case, changes in the recirculated air flow can be effected 3 70321 in practice very simply by using a damper in two positions, which in its second position keeps one opening open and closes the other and vice versa.

The control of closing and opening the openings can take place in different ways. The change of position can be performed, for example, after a certain time has elapsed since the timber load was fed into the dryer.

Alternatively, the change can occur after the timber has reached a predetermined temperature. This can be registered by a sensor that is suitably attached to the timber, e.g. by drilling a hole in the timber and inserting a sensor or by allowing the sensor to sense the temperature on the surface of the timber.

Another way is to sense the wet temperature gradient of the circulating air over the new wood, and when this has dropped to a certain value near 0 ° C, to bring about a change.

The invention also relates to a wood drying device with which said method is carried out. The essential features of this device are stated in the characterizing part of claim 6.

An embodiment of the invention will now be described in more detail with reference to the accompanying drawing, in which: Figure 1 shows a schematic plan view of the inside of a timber dryer during drying of several timber loads; and Figures 2 and 3 show, on a larger scale, different views of a sheet metal device according to the invention.

In Figure 1, the number 1 indicates a dryer for drying timber fed inside in the form of unit loads. The dryer is divided into zones where the drying of timber loads takes place in stages. The dryer thus includes a heating zone 2, a first drying zone 3, a second drying zone 4 and a cooling zone 5.

The first drying zone 3 is associated with a recirculation duct 7 with a recirculation opening 12 and a fresh air opening 9. Several fans, one of which 10 is shown in Figure 1, co-operate with a plurality of radiators 11 to circulate the flow of heated, non-saturated air as indicated by arrows. Most of this flow is diverted through the recirculation opening 12 to the recirculation duct 7 of the drying zone, while a smaller part of the flow 70321 passes through the heating zone 2 and enters the associated outlet area 15 through the outlet 16. From the exhaust area 15, air is discharged through the exhaust duct 17. Between the outlet area 15 and the recirculation duct 7 there is a wall 18 with an opening 8. A number of thermometers 19 and thermostats 20 register and regulate the temperatures of the circulating air. Ventilation is controlled by thermostats using dampers (items 9, 17 and 23). The magnitude of the supplied heat medium flow is controlled via the valve center 21.

In the second part of the dryer, which includes the drying zone 4 and the cooling zone 5, a corresponding air circulation takes place as indicated by the arrows. This part of the dryer can be made in a conventional manner and does not form a po. part of the invention. Therefore, it is not described in more detail here. However, it may be mentioned that a control room 22 is connected to the cooling belt zone 5.

The timber loads 25 are fed intermittently into the heating zone 2 and move in stages between the different zones of the dryer.

There are several sealing means 26 between the timber loads and the walls of the drying duct, i.e. the roof. The circulating flow of warm air then passes the timber loads so as to provide efficient drying and heating.

Drying of timber in a heating zone usually takes only part of the time that the timber remains standing in said zone.

This disadvantage is eliminated by the fact that the opening 12 between the drying zone 3 and the recirculation channel 7 is provided with a damper 27 which is suitably manually or automatically turned from the dashed position to the intact dashed position (Fig. 1) when the heating of the timber in the heating zone is completed. In this case, the entire flow fed to the drying zone 3 will also pass through the heating zone 2, which is temporarily given the operation of the extended part of the nearby drying zone. This gives the dryer a higher drying power.

When the timber loads in the extended drying zone move to the "actual" drying zone 3 and new wood spare loads are fed inside the heating zone 2, the position of the damper 27 is changed to open the opening 12 and instead close the opening 8 in the discharge area 15 and recirculation 7. Most of the flow fed to the drying zone 3 is then recycled through the opening 12 and only a smaller part of the flow, namely the amount of exhaust air, passes through the heating zone, heating the new, fed timber.

The damper 27 is rotatable about a shaft 28 and its position is changed manually or by a motor, preferably automatically, by means of an impulse provided by a suitable sensor or control device. The change in the position of the damper can thus take place after a certain time has elapsed since a new load of timber has been fed into the heating zone 2. Alternatively, the change in the position of the damper can take place after a suitable temperature in the timber has been reached.

Another alternative control device can be obtained by means of two thermostats which sense the wet temperature gradient above the heating zone and the timber loads therein, and when this temperature gradient has dropped to a suitable value close to 0 ° C, they give an impulse to change the position of the damper 27.

Other ways of controlling and distributing the circulating air flow through the drying and heating zones are also conceivable within the scope of the invention. The embodiment shown as an example in the drawing has the special advantage that it is easy to install and apply to drying plants already in use.

Claims (8)

A method of drying timber in wood dryer (1), which timber in the form of loads during continuous or discontinuous motion is measured primarily by eating at least one heating zone (2) and then by eating at least one drying zone (3), while: a flow of heated drying air is caused to pass through the timber loads (25), whereby newly added wood is heated with leaving hydrogen or evacuating air during temperature lowering and precipitation with maintaining a divided flow process, whereby part of the flow is recirculated therewith, which is recirculated, or evacuation air for such a long time that the timber temperature approaches or approaches the drying temperature of the drying air, and the circulating air flow thereafter changes so that substantially all of the circulating airflow passes through the zone (2) where fresh wood is heated, which zone is thereby incorporated into the drying zone (3). 2. A method according to claim 1, characterized in that the change in the circulation air flow is effected by closing and closing respectively. releasing openings (12 and 8, respectively) between the drying zone (3) and a recirculation channel (7) in connection with this, respectively. between an evacuation area (15) adjacent to the zone (2) where newly inserted wood is heated and said recirculation duct (7). Method according to claim 2, characterized in that an evacuation opening (12) between the drying zone and the recirculation duct (7) is closed for some time after new wood is introduced into the dryer. Method according to claim 2, characterized in that an opening (12) between the drying zone and the recirculation duct is closed after freshly added wood has reached a predetermined temperature. 5. A method according to claim 2, characterized in that an opening (12) between the drying zone (3) and the recirculation duct (7) is closed, where the wet temperature gradient of the circulating air over newly inserted wood is reduced to a predetermined value in the vicinity of 0 ° C. A device for wood drying, which at least primarily comprises a heating zone (2) and an adjacent drying zone (3), which