METHOD AND APPARATUS FOR TREATING A BOARD-LIKE MATERIAL WITH A GASEOUS AGENT

Abstract: The present invention is related to a method of treating a board-like material with a gaseous treatment agent, in which method the gaseous treatment agent is passed through the material (1) being treated. The board material (1) being treated is taken into at least one treatment zone (2), where the gaseous treatment agent is contacted with at least one wall of the board and is caused to pass through the thickness of the board material (1) and that, if required, the state of the gaseous treatment agent including its temperature, moisture content and/or composition is/are controlled in order to achieve a desired effect on the material (1) being treated.

Description: Method and apparatus for treating a board-like material with a gaseous agent The present invention relates to a method according to the preamble of claim 1. The invention further concerns an apparatus according to claim 11. In the manufacture of planar materials such as wood-based boards, it is necessary to cool the boards exiting from the press, prior to their further processing. Today, the cooling is performed in a board turner/cooler also called a cooling wheel, which is a massive rotary unit having a diameter of 7 m typical comprised of radial slots into which the cut boards are inserted. In the turner, each board can cool freely from both sides during one revolution of the turner, for instance. The capacity of cooling turners is often a bottleneck limiting the production speed or board length in continuously operating board manufacturing lines. The cooling capacity of conventional coolers cannot be varied during operation. Also the emission of obnoxious VOC gases, that is volatile organic carbo compounds has been freely admitted to the ambient air. It is an object of the present invention to provide a novel method and apparatus capable of overcoming the disadvantages of prior-art techniques. More specifically, the invention is characterized by what is stated in the appended claims . The arrangement according to the invention has a number of significant benefits. Particularly, the cooling time of the board material being processed can be shortened essentially. The properties of the board may also be affected during the treatment process. The cooling process of the board can be controlled more accurately and the obnoxious VOC emissions can be confined into a closed space. Moreover, the method may be applied prior to the cutting of the board blank into separate board products. In the following, the invention will be examined in more detail with the help of an example by making reference to the attached drawings in which Figure 1 shows schematically a simplified cooler arrange- ment according to the invention; Figure 2 shows an apparatus according to the invention in a partially sectioned end view illustrating the travel of board material therein; and Figure 3 shows an apparatus according to the invention in a side view partially sectioned along line III-III of Fig. 2. The method is suited for treating a board-like material with a gaseous agent, whereby the method is implemented as illustrated in the drawings by passing a gaseous agent through the material 1 being treated. The method is based on the concept that the board material 1 being treated is taken into at least one treatment zone 2, where the gaseous treatment agent is contacted with at least one wall of the board and caused to pass through the thickness of the board material 1 and that, if required, the state of the gaseous treatment agent including its temp- erature, moisture content and/or composition is/are controlled in order to achieve a desired effect on the material 1 being treated. In the method, the material 1 being treated is moved through at least one treatment zone 2. The material being treated is moved continuously or cyclically through at least one treatment zone. In Fig. 1 is shown diagrammatically an arrangement suitable for implementing the method. Therein the board-like material 1 such as a pressed wood-based particle board blank is moved by means of a gas-transmissive conveyor 5 to a treatment zone 2. The treatment zone 2 is divided into two compartments 3, 4 separated by the board material 1 to be treated. To the first compartment 3 of the treatment zone (in the diagram located principally above the board material) , the gaseous agent is introduced via at least one nozzle 6, wherefrom at least a portion of the gas is directed to pass through the board material 1 into the second compartment 4 of the treatment zone that is situated on the opposite side of the board material. The passage of the gaseous agent from first compartment through the board material to the opposed second compartment is chiefly attributable to the pressure difference which is provided between the separate compartments formed on the opposite sides of the board material. In the arrangement shown in the diagrams, the pressure dif- ference is achieved by forming a vacuum to the underside of the board material with the help of at least one suction pump means 9 such as a rotary vacuum pump. The opposite side of the board material is provided with means 6, 7 for introducing the gaseous agent into the first compartment 3 of the treatment zone. Preferably, the first compartment of the treatment zone is also equipped with means 10 for discharging a portion, typically the excess portion, of the gaseous agent away from the treatment zone. By altering the state of the gaseous treatment agent including its composition, temperature, moisture content and the pressure difference between the treatment zone compartments surrounding the two sides of the board material, it is possible to exert a desired treatment effect on the board material. In the arrange- ment of Fig. 1, the gas inlet nozzle 6 is provided with a nozzle 11 serving, e.g., to introduce steam into the flow of the gaseous treatment agent . The second compartment of the treatment zone is provided with means 8, 9 for discharging the gaseous treatment agent from the second compartment of the treatment zone. The discharged gas can be recycled back to the treatment process according to the invention, or alternatively, passed to postprocessing such as gas scrubbing or incineration. All gas-transmissive board-like materials are suited for treatment in the method according to the invention. Obviously, the treatment process parameters such as the required pressure difference are affected by the qualities of the board material to be treated and the desired treatment effect. Typical board materials to be treated include different kinds of wood-based particle boards such as MDF boards, flake boards, fiber boards, OSB boards and others. For certain board materials, the required pressure difference may be in the order of 20 kPA when the board thickness is, e.g., 30 mm. Then, the volu- metric gas flow through the board is about 0.1 m 3 /s, while for a 4 mm board the gas flow is about 0.4 m 3 /s. An advantageous implementation of the method according to the invention is to affect the temperature of the board material via the treatment according to the method. Principally, this goal is achieved by cooling the board material by directing onto the board material a gas flow of lower temperature than that of the board material . The cooling process can be complemented with other treatment effects through varying the moisture content of the treatment gas, for instance. In this manner, the properties of the board material such as its VOC content, moisture and temperature can be affected, or alternatively, it is possible to introduce chemicals into the board, for instance. The cooling effect can be controlled by altering the temperature and moisture content of the treatment gas . Furthermore, it is possible to use a plurality of the treatment zones 2, arranged in series and/or parallel, whereby each treatment zone can be used separately for affecting the properties of the board material via indi- vidually adjusted treatment gas compositions, temperature, moisture content or other parameters and/or pressure differences and volumetric flow rates. In an arrangement comprising a plurality of treatment zones, it is advantageous to pass the gaseous agent in at least one treatment zone through the material being treated so that the pass-through flow direction is essentially opposite to that used in the adjacent zone. In a preferred embodiment, at least a portion of the gas used in the preceding treatment zones is passed on to the next treatment zone, and so forth. For instance, one practical arrangement of the zones is such that the treatment gas is first introduced into the last zone of the cooling line and therefrom successively through the zones countercurrent to the board travel direction until reaching the first zone of the cooling line, whereby an optimally graded cooling effect on the board is attained. In a preferred embodiment, the heat of the treatment gas is recovered after the gas has been passed through the board material . The heat recovery may be implemented using, e.g., a heat exchanger placed on a pipe 8 shown in Fig. 1, or alternatively, in a chamber 4, for instance. The recovered heat can be utilized in a conventional manner, e.g., for the heating of a building. Advantageously, the treatment zone is complemented with sensor devices such as pressure sensors 13, temperature sensors 12, moisture content sensors 14 and/or flow rate sensors 15, whose output signals are utilized in the control of the treatment process . In the arrangement of Fig. 1, the temperature sensors are placed into the treatment zone at the entry end and the exit end of the board material into and away from treatment zone, respectively, whereby it is possible to monitor, e.g., the change of temperature drop in the cooling zone and to control the cooling rate of the board material, for instance . An apparatus suited for implementing the method comprises a chamber space 2 including a first compartment 3 and means 6, 7 for passing a gaseous treatment agent into said first compartment, a second compartment 4 and means 8, 9 for forming a vacuum into said second compartment of the chamber space, and further means 5, 16 for supporting the board- like material in the chamber space, whereby the board-like material 1 under treatment itself forms at least a portion of the wall separating the first compartment from the second compartment of said chamber space. The apparatus is further characterized in that it is equipped with sensor elements 12, 13, 14, 15 for monitor- ing the status of the material 1 being treated and/or of the gaseous treatment agent, that the apparatus is controlled as required on the basis of sensor element output signals and that the apparatus includes means for controlling the state parameters of the gaseous treatment gas including its temperature, moisture content and/or composition. Accordingly, the apparatus needs means for conveying the board material within the treatment zone. Such a means may be, e.g., a roller conveyor 5 similar to the one shown in Figs . 2 and 3 , or any other type of conveyor permitting free passage of gas through its structure. The conveyor 5 or its immediate vicinity is provided with sealing means 16 adapted to seal against the surface of the board 1, whereby the board material can form a portion of the intercompartmental wall which separates the at least one first compartment 3 from the at least one second compartment 4 of the treatment zone. Advantageously, the seal means 16 are adapted to form a sealing perimeter which is in intimate contact with the surface of the board material. Advantageously, the apparatus also includes a second seal means 17 adapted above the board material as shown in Fig. 2. Advantageously, the seal means 17 forms a sealing perimeter and is lower- able onto the surface of the board material. The seal means 17 serves to enclose the gaseous emissions evaporating from the top surface of the board material into a closed space, thus preventing the emissions from escaping into the ambient air. Thence, the treatment zone is advantageously designed into a closed construction, whereby the treatment gas and the obnoxious emissions possibly evaporating from the board are effectively collected and passed to further processing or incineration, for instance. The apparatus may also be complemented with a heat- recovering means such as a heat exchanger, whereby the heat transferred from the board material into the gas can be utilized in some other process such as heating of buildings, for instance. To those versed in the art it is obvious that the invention is not limited by the exemplifying embodiments described above, but rather, can be varied within the scope and spirit of the appended claims.

Claims: Claims : 1. A method of treating a board-like material with a gaseous treatment agent, in which method the gaseous treatment agent is passed through the material (1) being treated, c h a r a c t e r i z e d in that the board material (1) being treated is taken into at least one treatment zone (2), where the gaseous treatment agent is contacted with at least one wall of the board and is caused to pass through the thickness of the board material (1) and that, if required, the state of the gaseous treatment agent including its temperature, moisture content and/or composition is/are controlled in order to achieve a desired effect on the material (1) being treated. 2. A method as defined in claim 1, c h a r a c t e r i z e d in that the material (1) being treated is moved via at least one treatment zone (2) . 3. A method as defined in claim 1 or 2 , c h a r a c t e r i z e d in that the material (1) being treated is moved continuously via at least one treatment zone (2) . 4. A method as defined in any of claims 1 - 3, c h a r a c t e r i z e d in that the material (1) being treated is moved cyclically via at least one treatment zone (2) . 5. A method as defined in any of claims 1 - 4, c h a r a c t e r i z e d in that in an arrangement comprising a plurality of treatment zones, the gaseous treatment agent is passed in at least one treatment zone through the material being treated so that the pass- through flow direction is essentially opposite to that used in the adjacent zone. 6. A method as defined in any of claims 1 - 4, c h a r a c t e r i z e d in that the gaseous treatment agent is used to cool the board material. 7. A method as defined in any of claims 1 - 6, c h a r a c t e r i z e d in that the gaseous treatment agent is used to heat the board material. 8. A method as defined in any of claims 1 - 7, c h a r a c t e r i z e d in that the moisture content of the gaseous treatment agent is controlled. 9. A method as defined in any of claims 1 - 8, c h a r a c t e r i z e d in that the method is also used for collecting the obnoxious emissions such as VOC gases released by the board material and for passing them to further processing. 10. A method as defined in any of claims 1 - 9, c h a r a c t e r i z e d in that the heat of the gaseous treatment agent passed through the board material is recovered. 11. An apparatus suitable for implementing the method defined in claim 1, said apparatus comprising a chamber space (2) including a first compartment (3) and means (6, 7) for passing a gaseous treatment agent into said first compartment, a second compartment (4) and means (8, 9) for forming a vacuum into said second compartment of the chamber space, and further means (5, 16) for supporting the board-like material in the chamber space, whereby the board- like material (1) under treatment itself forms at least a portion of the wall separating the first compartment from the second compartment of said chamber space, c h a r a c t e r i z e d in that said apparatus is equipped with sensor elements (12, 13, 14, 15) for monitoring the state of the material (1) being treated and/or of the gaseous treatment agent, that the apparatus is controlled as required on the basis of sensor element output signals and that the apparatus includes means for controlling the state parameters of the gaseous treatment gas including its temperature, moisture content and/or composition . 12. An apparatus as defined in claim 10, c h a r a c t e r i z e d in that the apparatus includes seal means (16, 17) adapted to form an intimate contact with the board material from both sides thereof. 13. An apparatus as defined in claim 10 or 11, c h a r a c t e r i z e d in that at least one side of the board material (1) is provided with a seal means (17) , advantageously of a type forming a sealing perimeter, which among other things serves to prevent the gaseous emissions evaporating from the top surface of the board material (1) from escaping into the ambient air.

Inventors: SIMOLIN KARI, TULONEN ERNO, SIMOLIN, KARI, TULONEN, ERNO
Applicants: SIMOLIN KARI, SUNDS DEFIBRATOR PANELHANDLING, TULONEN ERNO, SIMOLIN, KARI, SUNDS DEFIBRATOR PANELHANDLING OY, TULONEN, ERNO
Application year: 1998
Main classification: B27N7
IPC codes: B27N3, B27N7