Method for manufacturing a wood material and wood material manufacturing device

Abstract

The invention relates to a method for manufacturing a wood material in which exhaust air (45) is produced which contains volatile organic substances, in particular terpene and / or aldehyde, and which is discharged into the environment, wherein as a result of introducing an oxidation agent (56) into the exhaust air, volatile organic substances contained in the exhaust air (45) are oxidised and purified exhaust air (45.2) is produced.

Description

[0001] Method for producing a wood-based material and wood-based material production device

[0002] The invention relates to a process for producing a wood-based material in which exhaust air is produced which contains volatile organic substances, in particular terpenes and / or aldehydes, and which is released into the environment.

[0003] According to a second aspect, the invention relates to a wood material manufacturing device for producing a wood material, comprising (a) a shredder for shredding wood and (b) a dryer for drying shredded wood, so that exhaust air is produced which contains volatile organic substances, in particular terpenes and / or aldehydes,

[0004] Wood-based materials are made from wood, as described, for example, in EP 2 974 841 A1, and are used, for example, in the production of particleboard, OSB, wood fiberboard, or insulation material. During the production, particularly drying, of shredded wood, especially wood chips or wood fibers, volatile organic compounds (VOCs) are released, which are released into the exhaust air. Such VOCs pollute the environment; therefore, there are limits for VOCs in exhaust air that must not be exceeded. Terpenes are particularly relevant in this regard.

[0005] If the material is wood fiber, the production of this wood material requires large quantities of steam, some of which is diverted and used to heat or cook the wood chips, as is known from US 4,925,527. To prevent volatile organic substances contained in the wood from accumulating in the wood material, part of the steam is condensed, the terpene-rich components are separated, and the heat released during condensation is used to evaporate water. This process is complex and not very energy-efficient. US 2007 / 0081933 A1 describes a process for removing formaldehyde using hydrogen peroxide, in which terpenes are washed out before the formaldehyde is removed, for example using an alkaline solution.

[0006] US 3882612 describes a process for reducing the concentration of volatile organic substances by thermal oxidation in air using a high-temperature heat source.

[0007] The invention is based on the object of reducing VOCs in the exhaust air.

[0008] The invention solves the problem by a generic method comprising the step of introducing an oxidizing agent into the exhaust air so that volatile organic substances contained in the exhaust air are oxidized and purified exhaust air is produced.

[0009] The invention also solves the problem by means of a generic wood material manufacturing device which has an exhaust air purifier which is designed to introduce an oxidizing agent into the exhaust air so that volatile organic substances contained in the exhaust air are oxidized and purified exhaust air is produced.

[0010] The advantage of the invention is that predetermined limit values ​​for the release of volatile organic substances into the environment can be kept within predetermined limit values ​​with comparatively little technical effort.

[0011] For the purposes of this description, an exhaust air purifier is understood to mean a device by which a VOC concentration, in particular terpenes and / or aldehydes, can be reduced by at least 50%, in particular at least 70%, through a chemical reaction of the volatile organic compounds with an oxidizing agent. This represents the maximum possible reduction in volatile organic substances. Exhaust air is understood to be a mixture of air, possibly particles, possibly gaseous water, and possibly liquid droplets, in particular water droplets.

[0012] A wood fiber is understood, in particular, to mean a lignin-containing wood fiber. In particular, the process for producing the wood fiber is carried out as part of the production of a wood-based panel, wherein the wood fiber is used to produce the wood fiber panel.

[0013] The manufacture of the wood-based material does not include, in particular, burning, pyrolyzing or other decomposition of the wood-based material.

[0014] The feature of introducing the oxidizing agent into the exhaust air so that volatile organic substances contained in the exhaust air are oxidized means, in particular, that the volatile organic substances are removed by oxidation. In particular, the volatile organic substances are not separated by adsorption. In particular, the exhaust air is generated before the wood-based material is processed, for example, into a wood-based panel.

[0015] The oxidizing agent is preferably a flameless oxidizing agent. According to one embodiment, the oxidizing agent contains oxygen. It is advantageous if the oxidizing agent releases elemental oxygen upon reaction with terpenes and / or aldehydes. In particular, the oxidizing agent is not molecular oxygen, especially not atmospheric oxygen. In other words, this is not combustion. Combustion is understood to mean oxidation using gaseous oxygen (O2), especially air.

[0016] Preferably, the oxidizing agent is introduced into the exhaust air in such a way that the oxidation products resulting from the oxidation of the volatile organic substances contained in the exhaust air are transferred into the exhaust air. This specifically means that the oxidation products become part of the exhaust air and are removed with the exhaust air.

[0017] The oxidation of the volatile organic substances preferably takes place in the gas phase, for example in liquid droplets. The oxidation preferably does not take place in a liquid phase. According to one embodiment, the oxidizing agent is introduced into the exhaust air in such a way that the terpenes are oxidized in the gas phase. Oxidation in the gas phase is understood in particular to mean that the oxidation does not take place at a solid interface of a component of the system used to purify the exhaust air. In particular, this is understood to mean that the oxidizing agent is introduced into the exhaust air in such a way that the particulate terpenes, in particular terpene particles, are oxidized in the gas phase, in particular not in the adsorbed state. In particular, the particulate terpenes are oxidized directly, i.e. without catalysis.

[0018] The oxidizing agent is preferably liquid. For example, the oxidizing agent is hydrogen peroxide. Alternatively, the oxidizing agent is ozone. When referring to hydrogen peroxide, this also includes an aqueous solution of hydrogen peroxide. The hydrogen peroxide may contain an Fe(II) salt, ammonium persulfate, cytochrome P450, monooxygenases, or ammonium peroxide. In particular, the oxidizing agent is not molecular oxygen or air.

[0019] According to a preferred embodiment, the process comprises the steps of (a) heating wood chips in a precooker using water or steam, (b) subsequently cooking the wood chips using steam in a cooker, and (c) subsequently defibrating the wood chips in a refiner to produce fiber material and exhaust air. In this case, the exhaust air contains steam or condensed steam, i.e., air with liquid droplets.

[0020] Cooking wood chips specifically means heating the wood chips with water and / or steam. The wood chips are preferably first placed in the precooker and then in the cooker.

[0021] The invention also relates to a method for producing a wood fiberboard, in which the above-mentioned method is carried out. A wood fiberboard is understood, in particular, to be LDF, MDF, or HDF. The fiber material is wood fibers. The invention also relates to a method for producing insulation material or plant substrate for plant cultivation, in which the above-mentioned method is carried out.

[0022] The invention also relates to a method for producing a particle board, in which the above-mentioned method is carried out. In this case, the method preferably comprises the steps of (a) chipping round wood, wood scraps, and / or waste wood to produce wood chips, (b) drying the wood chips, (c) applying glue to the wood chips, (d) scattering the glued wood chips and shaping them into a particle board, and (e) pressing the particle board into a particle board. It is possible for the wood chips to be scattered in multiple layers.

[0023] Also according to the invention is a method for producing an OSB board, in which the above-mentioned method is carried out. In this case, the method preferably comprises the steps of (a) chipping round wood, wood residues, and / or waste wood to produce coarse chips, (b) drying the coarse chips, (c) applying glue to the coarse chips, (d) scattering the glued coarse chips to form a chip mat, and (e) pressing the chip mat into an OSB board.

[0024] It is possible for the coarse chips to be scattered in multiple layers. Preferably, the preferred orientations of the coarse chips in at least two adjacent layers differ. For example, the preferred orientation of the second layer runs perpendicular to the preferred orientation of the first layer, onto which the second layer is applied. For example, if the preferred orientation of the first layer runs along the conveying direction in which the chip mat moves, the preferred orientation of the second layer preferably runs perpendicular to the direction of travel. The preferred orientation is the direction in which most of the longitudinal axes of the (elongated) coarse chips extend.

[0025] It is advantageous if the VOC concentration cvoc.i, i.e., the concentration of volatile organic substances, particularly terpenes and / or aldehydes, in the exhaust air is measured. The VOC concentration cvoc.i is preferably measured regularly, preferably continuously. For example, the VOC concentration cvoc.i is measured at least once a week, in particular at least once a day, in particular at least once an hour, and in particular at least once a minute. The VOC concentration cvoc.i is expressed, for example, as mass per exhaust air volume or as a mass fraction of the exhaust air.

[0026] VOC concentration is defined as a concentration that can be used to determine the concentration of volatile organic components. In particular, the TOC concentration of all organic carbon compounds is also a VOC concentration when it comes to compliance with an upper limit. When referring to VOC concentration in the following, the TOC concentration (TOC = total organic carbon) could also be used in general terms.

[0027] Preferably, the introduction of the oxidant into the exhaust air is controlled based on the VOC concentration. In other words, the amount of oxidant, namely the oxidant flow, introduced into the exhaust air is increased when the VOC concentration rises. Additionally, the amount of oxidant introduced into the exhaust air can be reduced when the VOC concentration decreases. In this way, on the one hand, sufficient oxidant is always introduced into the exhaust air and, on the other hand, the consumption of oxidant is minimized. It is advantageous if this VOC concentration is measured in the direction of exhaust gas flow upstream of an introduction point at which the oxidant is introduced into the exhaust air. Control can be achieved by regulating it to a predetermined target VOC concentration, but this is not necessary.

[0028] The introduction of the oxidizing agent into the exhaust air based on the VOC concentration can also be a recording of a measured variable from which the VOC concentration can be indirectly determined. Thus, controlling the introduction of the oxidizing agent into the exhaust air based on the VOC concentration can also be a control of the introduction of the oxidizing agent into the exhaust air based on an oxidizing agent concentration. The more oxidizing agent is measured, the lower the VOC concentration. Preferably, the method comprises the steps of (a) comparing the VOC concentration cvoc.i with a limit value concentration CVOC.G and (b) if the VOC concentration cvoc.i falls below the limit value concentration CVOC.G, introducing an idle flow of oxidizing agent, in particular of no oxidizing agent. In this way, oxidizing agent is saved since it is not necessary to fall below the limit value concentration CVOC.G in the exhaust air.However, it is possible to introduce an idle flow of oxidant into the exhaust air, for example, to quickly increase the oxidant flow if necessary. The idle flow is a volume flow of oxidant that is smaller than the oxidant flow required to reduce the amount of VOC. For example, the idle flow is at most one-fifth, especially one-tenth, of the flow introduced when the limit concentration is exceeded.

[0029] If the VOC concentration cvoc.i does not fall below the limit concentration (CVOC.G), an oxidant stream is preferably introduced into the exhaust air. The oxidant stream is selected such that the discharged VOC concentration (CVOC.A) in the exhaust air, which is released into the environment, is below a specified exhaust air limit concentration CVOC.BREV. The exhaust air limit concentration is, for example, a legal requirement. For example, CVOC.BREV = 400 pg / m 3 The volume is preferably measured in standard cubic meters, i.e. the volume of the gas under standard conditions (23 °C, 1013 hPa).

[0030] According to one embodiment, a second VOC concentration of volatile organic substances, in particular terpenes and / or aldehydes, is continuously measured in the exhaust air. This occurs in particular in the exhaust air flow direction downstream of an introduction point at which the oxidizing agent is introduced into the exhaust air. Preferably, the introduction of the oxidizing agent into the exhaust air is also or exclusively controlled or regulated based on the second VOC concentration.

[0031] If, for example, the second VOC concentration rises above the exhaust air limit concentration CVOC.BREV, SO, according to a preferred embodiment, the amount of oxidant introduced per unit of time (oxidant flow) is increased. This occurs, in particular, even if the first VOC concentration remains unchanged.

[0032] If the second VOC concentration falls below a predetermined minimum concentration, the oxidant flow is reduced according to a preferred embodiment. This occurs especially even if the first VOC concentration remains unchanged.

[0033] It is possible that only the second VOC concentration is measured, which then does not have to be called a second VOC concentration, but can be called a general VOC concentration.

[0034] According to one embodiment, the method comprises the step of irradiating the oxidizing agent with UV light. This results, for example, in the formation of radicals by the oxidizing agent, if a suitable oxidizing agent is used. If the oxidizing agent is hydrogen peroxide, for example, hydroxyl radicals are formed. These react particularly rapidly with VOCs.

[0035] Preferably, the oxidizing agent is irradiated with UV light immediately before being introduced into the exhaust air. In particular, the distance between the point at which the oxidizing agent is irradiated with UV light and the point at which the oxidizing agent first comes into contact with the diverted steam is no more than 10 m, in particular no more than 5 m.

[0036] According to one embodiment, the oxidizing agent is introduced into the exhaust air so that the volatile organic substances react directly with the oxidizing agent. The feature that the volatile organic substances react directly with the oxidizing agent is understood in particular to mean that they react with each other without catalysis. In particular, the oxidizing agent reacts with the volatile organic substances without the need for contact with a solid-state interface. In particular, the oxidizing agent therefore reacts with volatile organic substances in the gas phase and in particular not with volatile organic substances bound to an interface. Preferably, the exhaust air has an exhaust air temperature of at least 40°C when the oxidizing agent is introduced.At higher temperatures, the oxidizer reacts more quickly with the volatile organic substances, resulting in lower concentrations of volatile organic substances in the purified steam. However, high exhaust air temperatures result in energy loss, so it is best to keep the exhaust air temperature below 80°C.

[0037] Preferably, the exhaust air has a pressure of at least 1.2 bar and / or at most 5 bar.

[0038] The method preferably comprises the step of drying the wood-based material, in particular the wood chips, coarse shavings, or wood fibers. Exhaust air generated during the drying process is preferably purified, as described above, by introducing the oxidizing agent before the exhaust air is released into the environment. In particular, the exhaust air into which the oxidizing agent is introduced consists of at least 20 percent by weight, in particular at least 40 percent by weight, preferably at least 60 percent by weight, and more preferably at least 80 percent by weight, of exhaust air generated during the drying of the wood-based material.

[0039] If the wood-based material is wood chips, coarse shavings, or wood fibers, the method preferably comprises the step of applying glue to the wood-based material, in particular using a blow line. According to one embodiment, the glued fiber material is dried.

[0040] It is advantageous if the method comprises the steps of scattering the, in particular dried and / or glued, fiber material into a fiber cake and pressing the fiber cake into a wood-based panel, in particular a particle board, an MDF, an MDF or an HDF board, or an OSB board. The pressing is carried out, for example, using a belt press.

[0041] A wood-based material production device according to the invention preferably has a chimney connected to the exhaust air purifier for discharging the purified exhaust air into the environment. The exhaust air purifier can have an oxidant tank filled with oxidant, for example, hydrogen peroxide. The exhaust air purifier preferably also has a pump for conveying the oxidant to the introduction device. Alternatively or additionally, the exhaust air purifier can have an oxidant generator by means of which oxidant can be produced. For example, the oxidant generator can be an ozone generator. Alternatively or additionally, the exhaust air purifier can have an oxidant container in which oxidant can be stored. For example, the oxidant container is filled with hydrogen peroxide.

[0042] It is advantageous if the wood fiber board manufacturing device has a VOC concentration meter for measuring a (first) VOC concentration of volatile organic substances, in particular terpenes or aldehydes, and / or the total concentration of organic carbon compounds in the exhaust air in the exhaust gas flow direction upstream of an introduction point at which the oxidizing agent is introduced into the exhaust air.

[0043] The dosing device is preferably designed to automatically introduce the oxidizing agent into the exhaust air based on the measured VOC concentration. In other words, the dosing device controls or regulates the oxidizing agent flow. For example, the dosing device contains a controllable pump and / or a controllable valve for this purpose.

[0044] The VOC concentration meter comprises, for example, a gas chromatograph with a flame ionization detector. The VOC concentration meter is preferably designed to automatically measure the VOC concentration at regular intervals, for example, more frequently than once per hour, in particular more frequently than once every half hour, and most preferably more frequently than once every 10 minutes.

[0045] In a preferred embodiment, the dosing device is designed to detect the VOC concentration from the VOC concentration meter and to automatically introduce the oxidizing agent into the exhaust air based on the VOC concentration and the exhaust air flow. In other words, the volume flow of oxidizing agent introduced into the exhaust air per unit of time is calculated, in particular based on the VOC concentration and, if applicable, the exhaust air flow, and the oxidizing agent is then introduced accordingly.

[0046] The wood material manufacturing device preferably has a first introduction device for introducing the oxidizing agent into the exhaust air at a first introduction point.

[0047] It is particularly advantageous if the exhaust air purifier is designed to regulate the VOC concentration to a predefined VOC target concentration. If the measured VOC concentration deviates from the VOC target concentration, the oxidant flow rate is adjusted so that the measured VOC concentration approaches the VOC target concentration. If the measured VOC concentration is above the VOC target concentration, the oxidant flow rate is increased. If the measured VOC concentration is below the VOC target concentration, the oxidant flow rate is reduced.

[0048] According to a preferred embodiment, the wood-based material production device has a second VOC concentration meter for measuring a second VOC concentration (or a second TOC concentration) in the exhaust air downstream of the introduction point in the exhaust gas flow direction. The feeder is preferably designed to automatically introduce the oxidizing agent into the exhaust air based on the first VOC concentration and the second VOC concentration, as well as optionally the exhaust air flow. In other words, the feeder is designed to control or regulate the oxidizing agent volume flow based on the first and second VOC concentrations. It is possible for the wood-based material production device to have a VOC concentration meter downstream of the introduction point in the exhaust gas flow direction. In this case, the second VOC concentration meter can simply be called a VOC concentration meter.

[0049] The wood-based material production device preferably has a second introduction device for introducing the oxidizing agent into the exhaust air at a second introduction point located downstream of the first introduction point in the exhaust gas flow direction. The second introduction point is preferably located downstream of the second VOC concentration meter. It is advantageous if the exhaust air purifier is designed to control a second oxidizing agent volume flow rate, which is introduced at the second introduction point, depending on the second VOC concentration.

[0050] It is particularly advantageous if the exhaust air cleaner is designed to regulate the second VOC concentration to a predetermined second VOC target concentration. If the measured second VOC concentration deviates from the second VOC target concentration, the first and / or second oxidant volume flow is adjusted so that the measured second VOC concentration approaches the second VOC target concentration. If the measured second VOC concentration is above the second VOC target concentration, the first and / or second oxidant volume flow is increased. If the measured second VOC concentration is below the second VOC target concentration, the first and / or second oxidant volume flow is reduced. For example, the VOC target concentration is below the exhaust air limit concentration CVOC.BREV.

[0051] The wood-based material production device preferably has a gluing device for applying glue to the fiber material. A gluing device is understood to be a device by means of which the fiber material can be glued. The gluing device can also be referred to as a binder.

[0052] Also according to the invention is a wood-based panel manufacturing device for producing a wood-based panel, which comprises a wood-based material manufacturing device according to the invention. The wood-based panel manufacturing device is, for example, a wood fiberboard manufacturing device for producing lightweight, medium-density fiberboards (LDF), medium-density fiberboards (MDF), and / or high-density fiberboards (HDF), which comprises the wood-based material manufacturing device according to the invention. Alternatively, the wood-based panel manufacturing device is a chipboard manufacturing device for producing chipboards. Again alternatively, the wood-based panel manufacturing device is an OSB manufacturing device for producing coarse particle boards.

[0053] The wood fiber board manufacturing device preferably has (a) a cooker for cooking wood chips by means of steam so that cooked wood chips are produced, (b) a refiner, which is arranged downstream of the cooker in the wood material flow direction, for defibrating the cooked wood chips so that fiber material is produced and optionally (c) a gluing device, in particular a blow line, arranged downstream of the refiner in the wood material flow direction for gluing the fiber material so that glued fiber material is produced.

[0054] The wood fiberboard production device preferably has a spreader for spreading dried fiber material into a fiber cake. It is advantageous if the wood fiberboard production device has a press, in particular a belt press, for compressing the fiber cake into wood fiberboard.

[0055] A wood fiberboard is a board made from wood. The wood fiberboard preferably has a thickness between 2 mm and 60 mm. The density of the wood fiberboard is preferably between 600 kg per cubic meter and 1000 kg per cubic meter.

[0056] Insulation material refers, in particular, to insulation in the form of panels. This can have a density between 50 and 400 kg per cubic meter. The thickness of the insulation panels is preferably between 2 and 800 mm.

[0057] A chipboard manufacturing device preferably has a spreader for spreading a fiber cake of glued wood material in the form of wood chips into a fiber cake and a hot press for pressing the fiber cake into the chipboard.

[0058] An OSB manufacturing device or a particleboard manufacturing device preferably has a spreader configured to spread a first cover layer, a middle layer onto the first cover layer, and a second cover layer onto the middle layer. It is advantageous if the median size distribution of the chips in the middle layer is smaller, in particular at least 15% smaller, than the median size distribution of the chips in the first cover layer and / or the second cover layer.

[0059] It is advantageous if a sifter is arranged upstream of the spreader in the direction of wood material flow, by means of which wood material particles whose size lies outside a predetermined target size range are removed. The invention is explained in more detail below with reference to the attached drawings.

[0060] Figure 1 shows a flow diagram of a wood material manufacturing device according to the invention as part of a wood fiber board manufacturing device according to the invention for carrying out a method according to the invention according to a first embodiment,

[0061] Figure 2 shows a flow diagram of a wood material manufacturing device according to the invention as part of an OSB manufacturing device according to the invention for carrying out a method according to the invention according to a second embodiment,

[0062] Figure 3 shows a flow diagram of a wood material manufacturing device according to the invention as part of a chipboard manufacturing device according to the invention for carrying out a method according to the invention according to a third embodiment and

[0063] Figure 4 shows a flow diagram of a wood material manufacturing device according to the invention as part of a wood fiber board manufacturing device according to the invention for carrying out a method according to the invention according to a second embodiment.

[0064] Figure 1 shows a flow diagram of a wood-based material production device 10 according to the invention for producing wood-based material 11. The wood-based material production device 10 has a cooker 14 that receives heated wood chips 18 from a pre-cooker 16. The wood chips 18 were cleaned in the pre-cooker 16, so that the pre-cooker 16 functions as a washing system. Alternatively, the wood-based material production device can have a separate washing system 24.

[0065] A refiner 32 is arranged downstream of the digester 14 in the wood material flow direction H. This refiner 32 defibres the wood chips 18 emerging from the digester 14. Combined with steam 26, this produces a steam-fibre mixture 38. The steam-fibre mixture 38 can be fed to a gluing device 40, which is preferably designed as a blow line, but this is not necessary. The steam-fibre mixture 38 can also be fed to a dryer 44, from which exhaust air 45 and dried wood material 11 leave, but the dryer is also not necessary. Exhaust air 45 generated in the dryer 44. The particle load of the exhaust air 45 can be reduced by means of an optional wet electrostatic precipitator 47.

[0066] The wood-based material 11 is used, for example, for the production of insulation material, medium-density fiberboards (MDF), lightweight medium-density fiberboards (LDF), high-density fiberboards (HDF), plant substrate for plant cultivation, for example potting soil, or packaging material.

[0067] An exhaust air purifier 52, arranged in the exhaust gas flow direction D downstream of the dryer 44 and, if applicable, the wet electrostatic precipitator 47, reduces the VOC content in the exhaust air 45 before it is discharged into a stack 67 for release to the environment. The exhaust air purifier 52 is described in detail below in connection with Figure 4.

[0068] The wood-based material production device 10 is part of a wood-based panel production device 76, in this case in the form of a wood-fiber panel production device. The wood chips 18 can be produced from fresh wood 22, fresh wood chips 23, or recycled wood 25 using a shredder 20.

[0069] The wood-based panel manufacturing device 76 has a separator 78 that removes wood-based particles outside a predetermined target size range. A fiber cake 48 is scattered from the wood-based material 11 by means of a spreader 46 and pressed into the wood-based panel 12 by means of a press 50, in particular a hot press.

[0070] Figure 2 shows a second wood-based material production device 10, which is part of a wood-based panel production device 76 in the form of an OSB production device. Using the shredder 20, for example a chipper, the wood chips 18 are produced and dried in the dryer 44. The resulting exhaust air 45 is purified by the exhaust air purifier 52 described below and then flows into the chimney 67.

[0071] The sifter 78 and the spreader 46 are arranged downstream of the dryer 44 in the wood flow direction H. The sifter 78 classifies the particles of the wood-based material 11 into surface layer particles and middle layer particles. The spreader 46 spreads a first surface layer D1 of surface layer particles, a middle layer M of middle layer particles arranged on the surface layer D1, and a second surface layer D2 of surface layer particles arranged on the middle layer M. These layers are pressed by the press 50 into an OSB 80.

[0072] Figure 3 shows a third wood material manufacturing device 10, which is part of a wood material panel manufacturing device 76 in the form of a chipboard manufacturing device for producing a chipboard 82. The chips 18 produced by the shredder 20 are dried in the dryer 44 and the resulting exhaust air 45 is cleaned in the exhaust air cleaner 52 described below before it reaches the chimney 67.

[0073] Downstream of the dryer 44 in the wood flow direction H, the classifier 78 classifies the particles of the wood-based material 11 into surface layer particles and middle layer particles. The spreader 46 spreads a fiber cake 48 consisting of a first surface layer D1 of surface layer particles, a middle layer of middle layer particles arranged on the first surface layer D1, and a second surface layer D2 of surface layer particles arranged on the middle layer M. The fiber cake 48 is pressed into the particleboard 82 by means of the press 50.

[0074] Figure 4 shows a further wood-based material production device 10 according to the invention and a wood-based panel production device 76 according to the invention. The wood chips 18 produced by the shredder 20 are heated with steam 26 from a steam generator 28 in the pre-cooker and then cooked in the cooker 14. They are then defibrated in the refiner 32, the steam-fiber material mixture 38 is coated with glue in the gluing device 40, and then dried in the dryer 44. The exhaust air cleaner 52 is arranged downstream of the dryer 44 in the material flow direction M. This introduces an oxidizing agent 56 into the exhaust air 45 at an introduction point 54. In the present case, the oxidizing agent is hydrogen peroxide (H2O2).

[0075] The exhaust air purifier 52 comprises an oxidant source 58, which in this case has an oxidant container 58 and a dosing device 60 in the form of an oxidant pump. Using a VOC concentration meter 62, the exhaust air purifier 52 measures a first VOC concentration cvoc.i of volatile organic components in the exhaust air 45. Depending on the VOC concentration, an oxidant volume flow Qse of oxidant 56 is introduced, for example, by spraying, into the exhaust air 45 by means of an introduction device 57 at the introduction point 54. The oxidant 56 reacts with volatile organic components in the exhaust air 45.

[0076] The exhaust air purifier 52 can have a second VOC concentration meter 64, which is located downstream of the introduction point 54 in the exhaust gas flow direction D. The second VOC concentration meter measures a second VOC concentration cvoc,2. In this case, this is the TOC concentration of the total concentration of organic compounds. If the second VOC concentration cvoc,2 is above a predetermined maximum concentration CVOC,max, the oxidant volume flow Q56 is increased.

[0077] For example, the maximum concentration corresponds to a specified exhaust air limit concentration CVOC.BREV, which is, for example, a legal requirement. However, it is also possible that the maximum concentration is lower than the exhaust air limit concentration CVOC.BREV. This ensures that the exhaust air limit concentration CVOC.BREV is definitely not exceeded. For example, cvoc.max = f* CVOC.BREV with a safety factor fe [0.75, ... ,1]. The smaller the safety factor, the lower the probability that the exhaust air limit concentration CVOC.BREV will be exceeded at any time, but the higher the oxidant consumption.

[0078] The exhaust air cleaner 52 regulates the second VOC concentration cvoc,2 to a VOC target concentration cvoc.soii by increasing or decreasing the oxidant volume flow Q56.

[0079] Alternatively, it is possible for the exhaust air purifier 52 to have an introduction device, for example a nozzle 66, for introducing oxidizing agent at a second introduction point 54.2 downstream of the second VOC concentration meter 64 in the exhaust gas flow direction D. Alternatively, it is possible for the oxidizing agent volume flow Q56 to be increased if the second VOC concentration cvoc,2 is above the maximum concentration CvOC,max. It is possible, but not necessary, for the same oxidizing agent to be introduced at both introduction points 54, 54.2. In particular, it is possible for two different oxidizing agents to be used.

[0080] It is also possible for the exhaust air cleaner 52 to have only one VOC concentration meter 64, which is arranged behind the introduction point 54 in the steam flow direction D, wherein oxidizing agent is introduced into the exhaust air 45 only at this one introduction point 54.

[0081] By introducing the oxidizing agent, purified exhaust air 45.2 is produced, which is released into the environment via a chimney 67.

[0082] The exhaust air cleaner 52 can have a light source 74 by means of which the oxidizing agent 56 can be irradiated with UV light. This creates hydroxyl radicals that particularly effectively destroy the volatile organic substances in the diverted vapor 26.

[0083] An exhaust air temperature T45 is, for example, 45°C ± 5°C. The first VOC concentration meter 62 measures a first VOC concentration of, for example, cvoc,i = 200 pg / standard cubic meter. The oxidant volume flow is then set to, for example, Q56 = 50 liters / hour. The oxidant 56 in this case is a 5 percent (by weight) hydrogen peroxide solution. The second VOC concentration meter 64 then measures a second VOC concentration of cvoc,2 = CTOC,2 = 90 pg / standard cubic meter. One standard cubic meter is the amount of gas that occupies 1 cubic meter under standard conditions of 1013 hPa and 23°C.

[0084] The wood-based material manufacturing device 10 can be part of a wood-based panel manufacturing device 76, which includes a spreader 46 for spreading glued wood-based material 11 onto a conveyor belt, forming a fiber cake 48. A press 50 compresses the fiber cake 48 into a wood-based panel 12. Reference Symbol List

[0085] 10 Wood material 57 insertion device, first nozzle

[0086] Manufacturing device 58 oxidizer container

[0087] 11 Wood-based material

[0088] 12 wood fiber board 60 dosing devices

[0089] 14 Kocher 62 first VOC concentration measurement

[0090] 16 pre-cookers

[0091] 18 (wood) chips 64 second VOC concentration meter

[0092] 20 shredders, chippers 66 second feeding device,

[0093] 22 round wood second nozzle

[0094] 24 car wash 68 purified steam

[0095] 26 Steam 69 Exhaust air duct

[0096] 28 Steam generator 70 Branch valve

[0097] 72 Capacitor

[0098] 30 Steam-fiber material mixture 74 Light source

[0099] 32 Refiner 76 Wood-based panel manufacturing

[0100] 34 Fiber material device

[0101] 36 steam branch 78 classifier

[0102] 38 steam-fiber material mixture 80 OSB

[0103] 82 chipboard

[0104] 40 blow line, gluing device

[0105] 42 glued fiber material cvoc,i first VOC concentration

[0106] 44 Dryer cvoc,2 second VOC concentration

[0107] 45 Exhaust air CvOC,max Maximum concentration of vo¬

[0108] 45.2 purified exhaust air latile organic compounds

[0109] 46 spreaders (VOC)

[0110] 48 Fiber cake cvoc.soii VOC target concentration

[0111] D Steam flow direction

[0112] 50 Press H Wood flow direction

[0113] 52 exhaust air cleaner eyelet oxidant volume flow

[0114] 54 Placement point T45 Exhaust air temperature

[0115] 54.2 second insertion point T26 exhaust air temperature

[0116] 56 Oxidizing agents

Claims

Patent claims 1. A method for producing a wood-based material in which exhaust air (45) is produced which contains volatile organic substances, in particular terpenes and / or aldehydes, and which is released into the environment, characterized by the step of introducing an oxidizing agent (56) into the exhaust air so that volatile organic substances contained in the exhaust air (45) are oxidized and purified exhaust air (45.2) is produced.

2. Method according to claim 1 , characterized by the steps: (a) measuring a VOC concentration (cvoc ) of volatile organic Substances in the form of terpenes in the exhaust air (45) and (b) controlling the introduction of the oxidizing agent (56) into the exhaust air (45) based on the VOC concentration (cvoc ).

3. Method according to claim 2, according to one of the preceding claims, characterized in that controlling the introduction of the oxidizing agent (56) into the exhaust air (45) based on the VOC concentration (cvoc ) comprises the following steps: (a) comparing the VOC concentration (cvoc ) with a limit value concentration (CVOC.G) and (b) if the VOC concentration (cvoc ) falls below the limit concentration (CVOC.G), introducing an idle current of oxidizing agent (56), in particular no oxidizing agent (56), and (c) if the VOC concentration (cvoc ) does not fall below the limit concentration (CVOC.G), introducing an oxidant stream selected such that a discharge VOC concentration (CVOC.A) of the exhaust air (45) discharged into the environment is below a predetermined exhaust air limit concentration (CVOC.BREV).

4. Method according to one of claims 2 or 3, characterized by the steps: (a) continuously measuring a second VOC concentration (cvoc,2) of volatile organic substances, in particular terpenes and / or aldehydes, in the exhaust air (45) in the exhaust air flow direction behind an introduction point (54) at which oxidizing agent (56) is introduced into the exhaust air (45), and (b) controlling the introduction of the oxidizing agent (56) into the exhaust air (45) based on the second VOC concentration (cvoc,2).

5. Method according to one of claims 2 to 4, characterized by the step of irradiating the oxidizing agent (56) with UV light so that the oxidizing agent (56) forms radicals.

6. Method according to one of the preceding claims, characterized in that (a) the volatile organic substances react directly, in particular uncatalyzed, with the oxidising agent and / or (b) the oxidising agent is not molecular oxygen, in particular atmospheric oxygen.

7. Method according to one of the preceding claims, characterized in that the oxidizing agent (56) is introduced into the exhaust air in such a way that oxidation products resulting from the oxidation of the volatile organic substances contained in the exhaust air (45) pass into the exhaust air.

8. Method according to one of the preceding claims, characterized in that the oxidizing agent (56) is introduced into the exhaust air in such a way that the terpenes are oxidized in the gas phase.

9. Method according to one of claims 2 to 6, characterized by the steps (a) heating wood chips in a pre-cooker (16) by means of water or steam (26), (b) then cooking the wood chips by means of steam (26) in a cooker (14) and (c) then defibrating the wood chips in a refiner (32) to produce fiber material (34) and exhaust air (45).

10. Method according to one of claims 2 to 9, characterized in that the wood material is a wood fiber material (11) and the wood fiber material (11) is further processed into insulation material, plant substrate for plant cultivation, a medium-density fiberboard, a high-density fiberboard or packaging material made from the fiber material (34).

11. Method according to one of claims 1 to 10, characterized in that (a) the wood-based material is wood chips and the process comprises the following steps: (i) chipping of round wood, wood residues and / or waste wood to produce wood chips, (ii) drying the wood chips, (iii) gluing the wood chips, (iv) scattering the glued wood chips and forming them into a chip mat and (v) pressing the chipboard mat into a chipboard or (b) the wood-based material is coarse chips and the process comprises the following steps: (i) Chipping of round wood, wood residues, waste wood to produce coarse chips, (ii) drying the coarse chips, (iii) gluing the coarse chips, (iv) Spreading the glued coarse chips into a chipboard mat and pressing the chipboard mat into an OSB board.

12. Wood material manufacturing device (10) for producing a wood material, with (a) a shredder for shredding wood, (b) a dryer for drying shredded wood to produce exhaust air containing volatile organic substances, in particular terpenes and / or aldehydes, characterized by (c) an exhaust air purifier (52) which is designed to introduce an oxidizing agent (56) into the exhaust air (45) so that volatile organic substances contained in the exhaust air (26) are oxidized and purified exhaust air (45.2) is produced.

13. Wood material manufacturing device (10) according to claim 12, characterized by (a) a VOC concentration meter for measuring a VOC concentration (cvoc ) of volatile organic substances, in particular terpenes and / or aldehydes, in the exhaust air (45) in the exhaust gas flow direction (D) upstream of an introduction point (54) at which the oxidizing agent (56) is introduced into the exhaust air, and (b) a dosing device (60) which is designed to automatically introduce the oxidizing agent (56) into the exhaust air (45) based on the VOC concentration (cvoc ).

14. Wood material manufacturing device (10) according to claim 13, characterized by (a) a second VOC concentration meter for measuring a second VOC concentration (cvoc,2) in the exhaust air (45) in the exhaust gas flow direction (D) behind the introduction point (54), (b) wherein the dosing device (60) is designed to automatically introduce the oxidizing agent (56) into the exhaust air (45) based on the first VOC concentration and the second VOC concentration.

15. Wood material manufacturing device (10) according to claim 14, characterized by an introduction device which is designed to introduce oxidizing agent (56) into the exhaust air (45) at a second introduction point (54.2) which is located in the exhaust gas flow direction (D) behind the point at which the second VOC concentration (cvoc.2) is measured.

16. Wood fiber board manufacturing device according to one of claims 13 to 15, characterized by (a) a gluing device (40), in particular a blow line, arranged behind the refiner (32) in the wood material flow direction (H) for gluing the fiber material (34) so ​​that glued fiber material (42) is produced, (b) a dryer (44) arranged downstream of the gluing device in the wood material flow direction (H) for drying the glued fiber material (42), (c) a spreader (46) for spreading dried fiber material (34) into a fiber cake (48) and (d) a press (50), in particular a belt press, for pressing the fiber cake (48) into the wood fiber board (12).

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