WO2024227566A1 - Method for manufacturing a wood material and wood material manufacturing device - Google Patents

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

Method for producing a wood-based material and wood-based material manufacturing device

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.

According to a second aspect, the invention relates to a wood material manufacturing device for producing a wood material, with (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,

Wood materials are made from wood, as described in EP 2 974 841 A1, for example, and are used, for example, to manufacture chipboard, OSB boards, wood fiber boards or insulation material. During the production, especially drying, of shredded wood, especially wood chips or wood fibers, volatile organic substances (volatile organic compounds, VOCs) are released, which pass into the exhaust air. Such VOCs pollute the environment, so there are limits for VOCs in the exhaust air that must not be exceeded. Terpenes are particularly relevant here.

If the material is wood fiber, the production of this wood material requires large amounts 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 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 discloses a process for removing formaldehyde using hydrogen peroxide, in which terpenes are washed out before the formaldehyde is removed, for example by means of an alkaline solution.

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

The invention is based on the task of reducing VOCs in the exhaust air.

The invention solves the problem by a generic method with 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.

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.

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.

In the context of the present description, an exhaust air purifier is understood to mean a device by means of which a VOC concentration, in particular terpenes and/or aldehydes, can be reduced by at least 50%, in particular at least 70%, through chemical reaction of the volatile organic compounds with an oxidizing agent. This is 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.

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

The manufacture of the wood-based material does not include any burning, pyrolysis or other decomposition of the wood-based material.

The feature of introducing the oxidizing agent into the exhaust air so that volatile organic substances contained in the exhaust air are oxidized is understood in particular to mean 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 created before the wood material is processed, for example to make a wood material panel.

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

Preferably, the oxidizing agent 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 pass into the exhaust air. This is understood in particular to mean that the oxidation products become part of the exhaust air and are discharged with the exhaust air.

Preferably, the oxidation of the volatile organic substances takes place in the gas phase, for example in liquid droplets. The oxidation takes place preferably not 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 clean 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. uncatalyzed.

The oxidizing agent is preferably liquid. For example, the oxidizing agent is hydrogen peroxide. Alternatively, the oxidizing agent is ozone. When we talk about hydrogen peroxide, we also mean an aqueous solution of hydrogen peroxide. The hydrogen peroxide can contain an Fe(II) salt, ammonium persulfate, cytochrome P450, monooxygenases or ammonium peroxide. In particular, the oxidizing agent is not molecular oxygen or air.

According to a preferred embodiment, the method comprises the steps of (a) heating wood chips in a pre-cooker using water or steam, (b) then cooking the wood chips using steam in a cooker, and then (c) defibrating the wood chips in a refiner so that fiber material and exhaust air are produced. In this case, the exhaust air contains steam or condensed steam, i.e. air with liquid droplets.

Cooking the wood chips means in particular that the wood chips are heated with water and/or steam. The wood chips are preferably first placed in the pre-cooker and then in the cooker.

The invention also relates to a method for producing a wood fiber board, in which the above-mentioned method is carried out. A wood fiber board is understood to mean in particular an LDF, MDF or HDF. The fiber material is wood fibers. The invention also relates to a method for producing insulating material or plant substrate for plant cultivation, in the context of which the above-mentioned method is carried out.

The invention also relates to a method for producing a chipboard, in the context of 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 wood chips, (b) drying the wood chips, (c) applying glue to the wood chips, (d) spreading the glued wood chips and shaping them into a chip mat and (e) pressing the chip mat into a chipboard. It is possible for the wood chips to be spread in several layers.

Also according to the invention is a method for producing an OSB board, in the context of 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) spreading the glued coarse chips to form a chip mat and (e) pressing the chip mat to form an OSB board.

It is possible for the coarse chips to be scattered in several 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 transversely 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 transversely to the direction of travel. The preferred orientation is the direction in which most of the longitudinal axes of the (elongated) coarse chips extend.

It is beneficial to measure the VOC concentration cvoc.i, i.e. the concentration of volatile organic substances, especially terpenes and/or aldehydes, in the exhaust air. Preferably, the VOC concentration cvoc.i is 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, in particular at least once a minute. The VOC concentration cvoc.i is given, for example, in mass per exhaust air volume or in mass fraction of the exhaust air.

The VOC concentration is understood to be 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 complying with an upper limit. When the VOC concentration is mentioned below, it could generally also be referred to as the TOC concentration (TOC = total organic carbon).

Preferably, the introduction of the oxidizing agent into the exhaust air is controlled based on the VOC concentration. In other words, the amount of oxidizing agent, namely the oxidizing agent flow, that is introduced into the exhaust air is increased when the VOC concentration increases. In addition, the amount of oxidizing agent that is introduced into the exhaust air can be reduced when the VOC concentration decreases. In this way, on the one hand, enough oxidizing agent is always introduced into the exhaust air and, on the other hand, the consumption of oxidizing agent 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 oxidizing agent is introduced into the exhaust air. The control can be a regulation to a predetermined target VOC concentration, but this is not necessary.

The introduction of the oxidizing agent into the exhaust air based on the VOC concentration can also be a recording of a measured value from which the VOC concentration can be determined indirectly. Thus, controlling the introduction of the oxidizing agent into the exhaust air based on the VOC concentration can also be a controlling 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 concentration CVOC.G and (b) if the VOC concentration cvoc.i falls below the limit concentration CVOC.G, introducing an idle flow of oxidizing agent, in particular no oxidizing agent. In this way, oxidizing agent is saved since it is not necessary to fall below the limit concentration CVOC.G in the exhaust air. However, it is possible for an idle flow of oxidizing agent to be introduced into the exhaust air, for example in order to be able to quickly increase the oxidizing agent flow if this becomes necessary. The idle flow is a volume flow of oxidizing agent that is smaller than the oxidizing agent flow that is necessary if the amount of VOC is to be reduced. For example, the idle flow is at most one fifth, in particular one tenth, of the flow that is introduced when the limit concentration is exceeded.

If the VOC concentration cvoc.i does not fall below the limit concentration (CVOC.G), an oxidizing agent stream is preferably introduced into the exhaust air, whereby the oxidizing agent stream is selected such that a discharge VOC concentration (CVOC.A) in the exhaust air that is discharged 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 can apply. The volume is preferably measured in standard cubic meters, i.e. the volume of the gas under standard conditions (23 °C, 1013 hPa).

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 takes place in particular in the exhaust air flow direction behind an introduction point at which 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.

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 oxidizing agent introduced per unit of time (oxidizing agent flow) is increased. This occurs especially when the first VOC concentration does not change.

If the second VOC concentration falls below a predetermined minimum concentration, the oxidizing agent flow is reduced according to a preferred embodiment. This occurs in particular even if the first VOC concentration does not change.

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

According to one embodiment, the method comprises the step of irradiating the oxidizing agent with UV light. This results in the oxidizing agent forming radicals, for example, when a suitable oxidizing agent is used. If the oxidizing agent is hydrogen peroxide, for example, hydroxyl radicals are formed. These react particularly quickly with VOCs.

Preferably, the oxidizing agent is irradiated with UV light immediately before it is 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 at most 10 m, in particular at most 5 m.

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 in an uncatalyzed manner. In particular, the oxidizing agent reacts with the volatile organic substances without contact with a solid interface being necessary. In particular, the oxidizing agent therefore reacts with volatile organic substances in the gas phase and in particular not with volatile organic substances that are 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 oxidizing agent reacts more quickly with the volatile organic substances, so that lower concentrations of volatile organic substances can be achieved in the purified steam. However, high exhaust air temperatures mean a loss of energy, so it is beneficial if the exhaust air temperature is at most 80°C.

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

The method preferably comprises the step of drying the wood material, in particular the wood chips, the coarse chips or the wood fibers. Exhaust air produced during drying is preferably cleaned, 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, preferably at least 80 percent by weight, of exhaust air that was produced during drying of the wood material.

If the wood material is wood chips, coarse chips or wood fibers, the method preferably comprises the step of applying glue to the wood material, in particular by means of a blow line. According to one embodiment, the glued fiber material is dried.

It is advantageous if the method comprises the steps of spreading the, in particular dried and/or glued, fiber material to form a fiber cake and pressing the fiber cake to form a wood-based panel, in particular a chipboard, an MDF, an MDF or an HDF panel or an OSB panel. The pressing is carried out, for example, by means of a belt press.

A wood material manufacturing device according to the invention preferably has a chimney which is connected to the exhaust air cleaner for releasing the cleaned exhaust air into the environment. The exhaust air cleaner can have an oxidizing agent tank that is filled with oxidizing agent, for example hydrogen peroxide. Preferably, the exhaust air cleaner also has a pump for conveying the oxidizing agent to the introduction device. Alternatively or additionally, the exhaust air cleaner can have an oxidizing agent generator by means of which oxidizing agent can be produced. For example, the oxidizing agent generator can be an ozone generator. Alternatively or additionally, the exhaust air cleaner can have an oxidizing agent container in which oxidizing agent can be stored. For example, the oxidizing agent container is filled with hydrogen peroxide.

It is advantageous if the wood fibre 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 oxidising agent is introduced into the exhaust air.

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

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 per half hour, particularly preferably more frequently than once per 10 minutes.

In a preferred embodiment, the feeder 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, an oxidizing agent volume flow of oxidizing agent that is introduced into the exhaust air per unit of time, in particular calculated based on the VOC concentration and, if applicable, the exhaust air flow and then the oxidizing agent is introduced accordingly.

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.

It is particularly advantageous if the exhaust air cleaner is designed to regulate the VOC concentration to a predetermined VOC target concentration. If the measured VOC concentration deviates from the VOC target concentration, the oxidizing agent volume flow 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 oxidizing agent volume flow is increased. If the measured VOC concentration is below the VOC target concentration, the oxidizing agent volume flow is reduced.

According to a preferred embodiment, the wood material manufacturing device has a second VOC concentration meter for measuring a second VOC concentration (or a second TOC concentration) in the exhaust air in the exhaust gas flow direction behind the introduction point. 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, and 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 the second VOC concentration. It is possible for the wood material manufacturing device to have a VOC concentration meter in the exhaust gas flow direction behind the introduction point. In this case, the second VOC concentration meter can simply be called a VOC concentration meter.

The wood material manufacturing device preferably has a second introduction device for introducing the oxidizing agent into the exhaust air at a second introduction point, which is located behind the first introduction point in the exhaust gas flow direction. The second introduction point is preferably located behind the second VOC concentration meter. It is advantageous if the exhaust air cleaner is designed to control a second oxidant volume flow of oxidant introduced at the second introduction point, depending on the second VOC concentration.

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 oxidizing agent 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 oxidizing agent volume flow is increased. If the measured second VOC concentration is below the second VOC target concentration, the first and/or second oxidizing agent volume flow is reduced. For example, the VOC target concentration is below the exhaust air limit concentration CVOC.BREV.

The wood material manufacturing device preferably has a gluing device for gluing 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 gluing bucket.

The invention also relates to a wood-based panel manufacturing device for manufacturing a wood-based panel, which has a wood-based panel manufacturing device according to the invention. The wood-based panel manufacturing device is, for example, a wood fiberboard manufacturing device for manufacturing light, medium-density fiberboard (LDF), medium-density fiberboard (MDF) and/or high-density fiberboard (HDF), which has the wood-based panel manufacturing device according to the invention. Alternatively, the wood-based panel manufacturing device is a chipboard manufacturing device for manufacturing chipboard. Again alternatively, the wood-based panel manufacturing device is an OSB manufacturing device for manufacturing coarse chipboard.

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 behind the cooker in the direction of wood material flow is arranged for defibrating the cooked wood chips so that fiber material is produced and optionally (c) a gluing device, in particular a blow line, arranged behind the refiner in the direction of wood material flow, for gluing the fiber material so that glued fiber material is produced.

The wood fiber board manufacturing device preferably has a spreader for spreading dried fiber material to form a fiber cake. It is advantageous if the wood fiber board manufacturing device has a press, in particular a belt press, for pressing the fiber cake to form wood fiber boards.

A wood fiber board is a board that is made using wood. The wood fiber board preferably has a thickness of between 2 mm and 60 mm. The density of the wood fiber board is preferably between 600 kg per cubic meter and 1000 kg per cubic meter.

Insulation material is understood to mean, in particular, panel-shaped insulation material. This can have a density of between 50 and 400 kg per cubic meter. The thickness of the panel-shaped insulation material is preferably 2 to 800 mm.

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

An OSB manufacturing device or a chipboard manufacturing device preferably has a spreader which is designed to spread a first cover layer, a middle layer on the first cover layer and a second cover layer on the middle layer. It is advantageous if the median of the size distribution of the chips in the middle layer is smaller, in particular at least 15% smaller, than the median of the size distribution of the chips in the first cover layer and/or the second cover layer.

It is advantageous if a sifter is arranged in front 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 interval are removed. The invention is explained in more detail below with reference to the accompanying drawings.

Figure 1 is a flow chart 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,

Figure 2 shows a flow chart 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,

Figure 3 is a flow chart 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

Figure 4 is a flow chart 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.

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

A refiner 32 is arranged behind the cooker 14 in the wood material flow direction H, by means of which the wood chips 18 coming from the cooker 14 are shredded. Together with steam 26, a steam-fiber material mixture 38 is thus created. The steam-fiber material 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-fiber material 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 that is created in the dryer 44. The particle load of the exhaust air 45 can be reduced by means of an optional wet electrostatic precipitator 47.

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

An exhaust air cleaner 52 arranged in the exhaust gas flow direction D behind the dryer 44 and, if applicable, the wet electrostatic precipitator 47 reduces the VOC content in the exhaust air 45 before it is introduced into a chimney 67 for discharge into the environment. The exhaust air cleaner 52 is described in detail below in connection with Figure 4.

The wood material manufacturing device 10 is part of a wood material panel manufacturing device 76, in the present case in the form of a wood fiber panel manufacturing device. The wood chips 18 can be produced from fresh wood 22, fresh wood chips 23 or recycled wood 25 by means of a shredder 20.

The wood-based panel manufacturing device 76 has a sifter 78 which removes wood-based particles outside a predetermined target size interval. A fiber cake 48 is spread from the wood-based material 11 by means of a spreader 46 and pressed into the wood fiber panels 12 by means of a press 50, in particular a hot press.

Figure 2 shows a second wood material manufacturing device 10, which is part of a wood material panel manufacturing device 76 in the form of an OSB manufacturing device. The wood chips 18 are produced by means of the shredder 20, for example a chipper, and dried in the dryer 44. The resulting exhaust air 45 is cleaned by means of the exhaust air cleaner 52 described below and reaches then into chimney 67.

The sifter 78 and the spreader 46 are arranged behind the dryer 44 in the direction of wood flow H. The sifter 78 classifies the particles of the wood material 11 into top layer particles and middle layer particles. The spreader 46 spreads a first top layer D1 made of top layer particles, a middle layer M made of middle layer particles arranged on the top layer D1 and a second top layer D2 made of top layer particles arranged on the middle layer M. These layers are pressed by the press 50 to form an OSB 80.

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.

In the direction of wood flow H behind the dryer 44, the classifier 78 classifies the particles of the wood material 11 into cover layer particles and middle layer particles. The spreader 46 spreads a fiber cake 48 consisting of a first cover layer D1 of cover layer particles, a middle layer of middle layer particles arranged on the first cover layer D1 and a second cover layer D2 of cover layer particles arranged on the middle layer M. The fiber cake 48 is pressed into the chipboard 82 by means of the press 50.

Figure 4 shows a further wood material manufacturing device 10 according to the invention and a wood material panel manufacturing 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 shredded in the refiner 32, the steam-fiber material mixture 38 is glued in the gluing device 40 and then dried in the dryer 44. The exhaust air cleaner 52 is arranged behind 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.

The exhaust air cleaner 52 comprises an oxidant source 58, which in the present case an oxidizing agent container 58 and a feeder 60 in the form of an oxidizing agent pump. The exhaust air cleaner 52 measures a first VOC concentration cvoc.i of volatile organic components in the exhaust air 45 by means of a VOC concentration meter 62. Depending on the VOC concentration, an oxidizing agent volume flow Qse of oxidizing agent 56 is introduced, for example sprayed, into the exhaust air 45 by means of an introduction device 57 at the introduction point 54. The oxidizing agent 56 reacts with volatile organic components in the exhaust air 45.

The exhaust air cleaner 52 can have a second VOC concentration meter 64, which is located behind the introduction point 54 in the exhaust gas flow direction D. The second VOC concentration meter measures a second VOC concentration cvoc,2. In the present 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 C V O C, max , the oxidizing agent volume flow Q56 is increased.

For example, the maximum concentration corresponds to a specified exhaust air limit concentration CVOC.BREV, which is a legal requirement, for example. However, it is also possible that the maximum concentration is smaller 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 f e [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 consumption of oxidizing agent.

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

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

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 only introduced into the exhaust air 45 at this one introduction point 54.

The introduction of the oxidizing agent produces purified exhaust air 45.2, which is released into the environment via a chimney 67.

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. In this way, hydroxyl radicals are formed, which particularly effectively destroy the volatile organic substances in the diverted steam 26.

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 oxidizing agent volume flow is then set to, for example, Q56 = 50 liters/hour. The oxidizing agent 56 in this case is a 5 percent (weight percent) 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. A standard cubic meter is the amount of gas that occupies 1 cubic meter under standard conditions of 1013 hPa and 23°C.

The wood material manufacturing device 10 can be part of a wood material panel manufacturing device 76, which comprises a spreader 46 for spreading glued wood material 11 on a conveyor belt so that a fiber cake 48 is formed. The fiber cake 48 is pressed into a wood fiber panel 12 by means of a press 50. list of reference symbols

10 Wood material 57 insertion device, first nozzle

Manufacturing device 58 oxidizer container

11 wood-based material

12 wood fiber board 60 feeders

14 Kocher 62 first VOC concentration measuring

16 pre-cookers

18 (wood) chips 64 second VOC concentration meter

20 shredder, chipper 66 second feeding device,

22 round wood second nozzle

24 car wash 68 purified steam

26 Steam 69 Exhaust air duct

28 Steam generator 70 Branch valve

72 capacitor

30 Steam-fiber material mixture 74 Light source

32 refiners 76 wood-based panel manufacturing

34 fiber material device

36 steam branch 78 sifter

38 steam-fiber material mixture 80 OSB

82 chipboard

40 blow line, gluing device

42 glued fiber material cvoc,i first VOC concentration

44 Dryer cvoc,2 second VOC concentration

45 Exhaust air CvOC,max Maximum concentration of vo¬

45.2 purified exhaust air latile organic compounds

46 spreaders (VOC)

48 Fiber cake cvoc.soii VOC target concentration

D Steam flow direction

50 Press H Wood flow direction

52 exhaust air cleaner eyelet oxidant volume flow

54 Place of entry T45 Exhaust air temperature

54.2 second introduction point T26 exhaust air temperature

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 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 oxidizing agent 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 fibre 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 of 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) spreading the glued wood chips and forming them into a chip mat and (v) pressing the chipboard 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 to form a chip mat and pressing the chip mat to form 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 claims 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 feeder (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 behind 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).