Method and processing system for reducing volatile organic compounds in wood chips

Abstract

The present invention relates to a method for reducing volatile organic compounds (VOCs) in wood chips for wood fiber production in a processing system (1), comprising at least the following successive steps: a first heat treatment (100) of the wood chips in a first heat treatment device (10), which first heat treatment device (10) is designed to receive exhaust gas (G1) containing VOCs; a cleaning (200) of the wood chips in a cleaning device (20); a second heat treatment (300) of the wood chips in a second heat treatment device (30), which second heat treatment device (30) is designed to receive exhaust gas (G2) containing VOCs and to separate exhaust gas (G3) containing VOCs; a cooking (400) of the wood chips in a cooker (40), which cooker (40) is designed to receive exhaust gas (G4) containing VOCs and to separate exhaust gas (G5) containing VOCs; and a comminution (500) of the wood chips in a refiner (50), which refiner (50) is designed to separate exhaust gas (G6) containing VOCs. This allows for an effective, and thus energy-optimized or environmentally friendly, and thus also cost-optimized, method for reducing volatile organic compounds in wood chips.

Description

Technical Field

[0001] The present invention relates to a method for reducing volatile organic compounds in wood chips used in a processing system for the production of wood fibers.

[0002] The present invention also relates to a processing system for reducing volatile organic compounds in wood chips used in the production of wood fibers. Background Art

[0003] The continuous manufacturing process of wood fibers based on lignocellulosic materials such as wood, straw or bagasse, in particular, includes crushing the raw materials into free fibers or fiber aggregates, and in subsequent steps, coating with adhesives, drying, shaping and pressing into a final product, namely a so-called board or wood fiber board. Nowadays, the release of fibers from the raw materials is preferably carried out in a so-called thermomechanical process in one step, or in a thermal processing step and a mechanical processing step in two independent stages.

[0004] Before the first heat treatment, the wood chips are usually washed to remove contaminants such as dirt or stones therein. The heat treatment, i.e., the heating of the raw materials, is carried out especially in a first heat treatment device at a preferred temperature up to about 100°C, especially at atmospheric pressure, and then in a second heat treatment device under pressure, for example, at a temperature of about 150 to 190°C, especially at a pressure of about 4 to 13 bar. The residence time of the wood chips in the heat treatment device can be adjusted according to the existing processing conditions, for example, it can be in the range of about 1 to 10 minutes. According to the prior art, the heating in the second heat treatment device is preferably carried out by steam. Then, mechanical processing is carried out in a refiner. The residence time of the wood chip raw material in the refiner is very short. The energy converted into mechanical energy related to the mechanical processing is converted into heat in the reduction zone and appears as exhaust gas, especially steam, generated by the moisture in the raw materials in the processing system.

[0005] Typically, after the wood fibers are refined in a refiner, they are pneumatically conveyed to a fiber dryer, in which the drying process is carried out at a large air volume and a controlled inlet air temperature of about 140 to 200°C according to the current fiber moisture content. The dried fibers are then further conveyed to the forming, pre-pressing and final pressing of the board.

[0006] In the prior art, during processing, mainly in the second heat treatment device, the released wood emissions are conveyed from the first heat treatment device via a refiner together with the fibrous loose material to a dryer, where most of them are separated from the fibers, and finally the moist drying air is discharged from the dryer to the atmosphere. These emissions mainly contain volatile organic substances, namely so-called volatile organic compounds (VOCs). The remaining substances that do not leave the dryer flow downstream to the processing unit with the fiber stream, are continuously released into the surrounding atmosphere or appear as residual products in the finished board. Therefore, the emission of emissions into the atmosphere also occurs in the finished product.

[0007] It is known from WO99 / 10594 that the second heat treatment device is equipped with an upper outlet for degassing the organic emissions released at the upper outlet. At this time, steam is introduced into the lower part of the first heat treatment device, and the wood chips entering the upper part of the first heat treatment device are washed in the countercurrent steam during condensation. This is achieved by the steam moving upward through the wood chip column to the cooler wood chips at the upper part of the first heat treatment device. The released emissions, waste gas, and steam generated by the evaporation of moisture in the wood chips are separated and processed through the outlets of the corresponding devices. According to this publication, it is also known that the wood chips are conveyed from the first heat treatment device to the refiner by a screw conveyor, and the screw conveyor compresses and dehydrates the wood chips during conveyance.

[0008] According to the published patent application EP1597427 A1, a method is known in which the waste gas generated during compression in the screw conveyor is treated through an outlet provided in the compression zone. According to the previously known invention, the system is characterized in that the waste gas outlet is provided in the compression zone for discharging the evaporated moisture, which is generated during the compression of the wood chips and includes the waste gas containing VOCs.

[0009] During the compression of the wood chips in the screw conveyor, the moisture is extruded, which contains most of the remaining wood emissions. The outlet in the compression zone allows the water to evaporate, and the released emissions are discharged through the outlet. By directly and locally collecting and redirecting the emissions released in the compression zone, a much higher emissions concentration is achieved compared to the case where the emissions have to be further conveyed together with the fibrous material and mixed with the drying air. According to other prior art, the drying air represents a very large air flow and thus has a lower concentration. Therefore, more effective treatment of the waste gas from the first heat treatment is achieved thereby.

[0010] However, in terms of environmentally friendly wood processing, it is necessary to more effectively extract VOCs from the wood chips, and for the same environmental reasons, it should also be carried out in an energy-saving manner. Summary of the Invention

[0011] According to the present invention, its object is achieved by a method for reducing volatile organic compounds in wood chips for wood fiber production and a processing system for implementing the method including the features of the independent claims. Preferred embodiments of the present invention are disclosed in the dependent claims and the subsequent description, and these embodiments can respectively constitute aspects of the present invention alone or in any combination.

[0012] Therefore, the present invention relates to a method for reducing volatile organic compounds (VOCs) in wood chips for wood fiber production in a processing system, the method comprising at least the following consecutive steps:

[0013] - A first heat treatment of the wood chips in a first heat treatment device, the first heat treatment device being configured to receive exhaust gas containing VOCs;

[0014] - Cleaning the wood chips in a cleaning device;

[0015] - A second heat treatment of the wood chips in a second heat treatment device, the second heat treatment device being configured to receive and discharge exhaust gas containing VOCs;

[0016] - Cooking the wood chips in a cooker, the cooker being configured to receive and discharge exhaust gas containing VOCs; and

[0017] - Crushing the wood chips in a refiner, the refiner being configured to discharge exhaust gas containing VOCs.

[0018] Therefore, the basic idea of the present invention is to feedback exhaust gas containing VOCs, especially exhaust gas containing VOCs generated by the heat treatment steps of wood chips, into the processing system in different ways. As a result, compared with previously known methods or processing systems, the wood chips of the method according to the present invention have an increased number and duration of contact between the wood chips and the VOC release temperature in the corresponding processing system, where the processing system feedbacks highly temperature-controlled exhaust gas containing VOCs back into the processing system or recovers it as effectively as possible. This means that the wood chips are heated in an environmentally friendly manner and are free of VOCs. Although the exhaust gas containing VOCs is recycled to the previous processing stage, the wood chips do not absorb the VOCs that have been discharged, but use the existing processing heat to discharge other VOCs. These VOCs are removed from the processing system in further processing steps.

[0019] The processing system according to the present invention includes three heat treatment stages, and thus more than the prior art known before. These heat treatment stages occur in the first heat treatment device, the second heat treatment device, and the cooker. This makes it possible to introduce further heat treatment stages without significant additional costs, and thus preferably provides three heat treatment stages, ensuring the effective discharge of VOCs from the wood chips.

[0020] In principle, in the context of the present invention, it is envisaged that the waste gas containing VOCs has a high temperature. In particular, this means a temperature above the boiling temperature of water, i.e., 100 °C.

[0021] The first heat treatment of the wood chips in the first heat treatment device causes the wood chips to be heated for the first time. The first heat treatment device is designed to receive the waste gas containing VOCs. The heating can be achieved by a heating device and / or by the waste gas containing VOCs from subsequent, especially heat treatment steps. The first heat treatment is carried out on further non-wood particles between the wood chips, such as soil or stones. These non-wood particles are indeed washed out in the next step by washing, so the heating appears uneconomical. However, it has been found that if the wood chips and other non-wood particles are introduced into the washing device at a high temperature, then the washing of the wood chips in the washing device will be more thorough. The high temperature may cause the release of VOCs from the wood chips. It is possible to discharge the waste gas containing VOCs from the first heat treatment device. Preferably, the first heat treatment of the wood chips is carried out with an aqueous medium, especially a water-based medium.

[0022] Exemplarily and independently of other features, it is possible that the first heat treatment of the wood chips in the first heat treatment device is carried out by using steam, preferably water vapor. At this time, a part of the VOCs may be transferred from the wood chips to the steam. This steam containing VOCs can be discharged from the first heat treatment device, preferably from its upper part, for example, through a pipeline arranged at the top. Optionally, or in addition to discharging the steam containing VOCs, some or all of the steam may condense and release VOCs from the wood chips as condensate. This condensate containing VOCs may be conveyed to, for example, a washing device and / or a water conditioning system.

[0023] The washing of the wood chips in the washing device is carried out especially at a temperature above room temperature and below or equal to the boiling temperature of water, especially between 80 and 100 °C. The high temperature allows for better separation of the wood chips and impurities. Therefore, the impurities that are not wood chips are filtered out of the processing system and discharged. Preferably, the washing of the wood chips is carried out with an aqueous medium, especially a water-based medium.

[0024] A favorable option is that the washing device receives the aforementioned condensate containing VOCs from the first heat treatment device. This condensate containing VOCs can be discharged from the processing system together with the VOCs released during washing.

[0025] The second heat treatment of the wood chips in the second heat treatment device is configured to receive and discharge VOC-containing exhaust gas, in particular into the first heat treatment device. The second heat treatment is carried out without pressure at a temperature above room temperature, in particular at a temperature below or equal to the boiling point of water, i.e., below or equal to 100 °C. The high temperature allows the VOCs to be released better from the wood chips. The VOC-containing exhaust gas is discharged from the second heat treatment device and / or conveyed to the first heat treatment device. In addition, the VOC-containing exhaust gas from the devices subsequently used for carrying out the processing can be fed into the second heat treatment device to further heat the wood chips and / or release VOCs.

[0026] Exemplarily and independently of other features, it is possible for the second heat treatment of the wood chips in the second heat treatment device to be carried out by steam, preferably water vapor. In this process, a part of the VOCs can be transferred from the wood chips to the steam. This VOC-containing steam can be discharged from the second heat treatment device, preferably from its upper part, for example through a pipeline arranged at the top. Optionally, or in addition to discharging the VOC-containing steam, some or all of the steam can be condensed and the VOCs are released from the wood chips as condensate. This VOC-containing condensate can be conveyed, for example, to a stuffing screw and / or a digester and / or a water conditioning system.

[0027] The cooking of the wood chips in the digester, which is designed to receive and discharge VOC-containing exhaust gas, takes place at a temperature above room temperature, in particular between 3 bar and 15 bar, preferably between 5 bar and 13 bar, preferably 9 bar, at a temperature above the boiling temperature of water, i.e., 100 °C. The high temperature allows the VOCs to be released better from the wood chips. Preferably, the wood chips are washed with an aqueous medium, in particular an aqueous-based medium. The first and second heat treatments have heated and softened the wood chips so that the VOCs contained in the wood chips are released from the digester in an effective manner. Preferably, a droplet separator is provided downstream of the digester.

[0028] Advantageously, the stuffing screw upstream of the digester and / or the digester receive the aforementioned VOC-containing condensate from the second heat treatment device. The VOC-containing condensate can be discharged from the processing system via the stuffing screw and / or via the digester together with any VOCs optionally released during cooking.

[0029] Subsequently, the wood chips are shredded in a refiner, which is configured to discharge VOC-containing exhaust gas. These VOC-containing exhaust gases can be recycled to the processing system in the refiner and / or to the system downstream of the refiner, thereby utilizing waste heat and saving energy costs.

[0030] According to a preferred embodiment of the present invention, a first heat treatment device is provided, which is configured to receive the VOC-containing exhaust gas discharged from a second heat treatment device, a digester, and / or a refiner. Compared with the embodiment without such an exhaust gas supply pipeline, the additional energy required to heat the first heat treatment device in the processing system is reduced. It is possible to heat the wood chips only by the VOC-containing exhaust gas. Therefore, the fed VOC-containing exhaust gas promotes the discharge of VOCs from the wood chips already in the first heat treatment device. Therefore, the wood chips heated in this way are more effectively cleaned in the cleaning device compared to the unheated wood chips.

[0031] According to a preferred embodiment of the present invention, a second heat treatment device is provided, which is configured to receive the VOC-containing exhaust gas discharged from a digester and / or a refiner. Compared with the embodiment without such an exhaust gas supply pipeline, the additional energy required to heat the second heat treatment device in the processing system is reduced. It is also possible to heat the wood chips only by the VOC-containing exhaust gas. Therefore, the fed VOC-containing exhaust gas promotes the discharge of VOCs from the wood chips already in the first heat treatment device. Therefore, the wood chips heated in this way are more effectively cleaned in the cleaning device compared to the unheated wood chips.

[0032] According to a preferred embodiment of the present invention, VOCs are discharged from the processing system through the first heat treatment device, the second heat treatment device, the digester, and / or the refiner. It is possible to discharge the VOCs from only one of these sites. For example, it may be carried out in the first heat treatment device, the second heat treatment device, and / or the refiner in the gas phase. It is also possible to discharge the VOC-containing liquid flowing out of the processed wood chips from the refiner. In the digester, when the cooking medium flows out of the digester, the VOCs can be removed in the gas phase and / or removed from the cooking medium. In addition, the VOCs can float on the water surface as an oily medium and be discharged from the digester. The discharge in the gas phase is carried out through the discharge port at the upper part of the container. The discharging is carried out by gravity from the lower region of the container. For example, if a discharge screw or a stuffing screw is provided between the digester and the refiner, at least part of the VOCs can leave the processing system via the water in the digester or as an oil phase on the water. Preferably, a large part of the VOCs, for example, more than 50%, leave the processing system via the water in the cleaning device or as an oil phase on the water. The basic idea herein is that the VOCs are first concentrated and then disposed of, particularly by cleaning and squeezing water.

[0033] According to a preferred embodiment of the present invention, there is provided that VOC from the processing system is discharged from the cleaning device. Optionally or additionally, there is provided a processing system that includes a filling screw along the material flow of the wood chips between the second heat treatment device and the digester. In particular, the filling screw is designed such that VOC can be discharged from the processing system via the filling screw. Further optionally or additionally, there is provided a processing system that includes a discharge screw along the material flow between the digester and the refiner, wherein VOC from the processing system is discharged from the discharge screw. The discharge screw can be designed as a filling screw. It has been found that VOC in these areas can be removed from the processing system with favorable efficiency through the cleaning device, the filling screw, and the discharge screw without having a significant negative impact on the processing, such as an adverse temperature development.

[0034] According to a preferred embodiment of the present invention, there is provided:

[0035] The first heat treatment of the wood chips is carried out at 80 °C for 5 to 10 minutes; and / or

[0036] The second heat treatment of the wood chips is carried out at 100 °C for 5 to 10 minutes; and / or

[0037] The cooking of the wood chips is carried out between 140 and 180 °C for 2 to 5 minutes. Both the temperature data and the time data include a variation of plus or minus 10% each. It has been found that in each processing step, the wood chips can be particularly advantageously reduced in terms of VOC to these ranges. In this regard, each preferred range can be advantageous in itself and becomes even more advantageous with further preferred ranges that can be freely combined with each other.

[0038] According to a preferred embodiment of the present invention, there is provided that the first heat treatment device is at least partially, preferably completely, heated by the exhaust gas from the digester. This exhaust gas is also referred to as heating steam. It has proven to be energy-saving, where sufficient energy is introduced to support the reduction of VOC in the processing.

[0039] According to a preferred embodiment of the present invention, there is provided that the VOC-containing exhaust gases from the digester and the refiner are conveyed in a combined manner. In this way, the temperatures of the exhaust gases from the digester and the refiner are averaged, so that the necessary proportion of self-heating of the container receiving the mixed exhaust gas can be reliably determined and the unwanted temperature fluctuations in the receiving container can be reduced. The receiving container is in particular the first heat treatment device, the second heat treatment device, and / or the digester.

[0040] According to a preferred embodiment of the present invention, the VOC-containing exhaust gases from the second heat treatment device, the digester, and the refiner are conveyed in a combined manner. In this way, the temperatures of the exhaust gases from the second heat treatment device, the digester, and the refiner are averaged, so that the necessary proportion of self-heating of the container receiving the mixed exhaust gas can be reliably determined, and the undesired temperature fluctuations in the receiving container are reduced. The receiving container is in particular the first heat treatment device.

[0041] According to a preferred embodiment of the present invention, a digester is provided which is configured to receive the VOC-containing exhaust gas discharged from the digester and / or the refiner. The exhaust gas heat can thus be returned to the digester. The exhaust gas heat can thus be returned to the digester. In addition, the exhaust gas heat can be increased by using the exhaust gas of the refiner. Therefore, the discharge of VOC from the wood chips can be promoted in an energy-saving manner.

[0042] According to a preferred embodiment of the present invention, the VOC-containing exhaust gas is introduced into the bottom of the digester, the first heat treatment device, and / or the second heat treatment device. Thus, the heated wood chips come into contact with the gas stream along the longest possible longitudinal axis of the digester, the first and / or second heat and / or second heat treatment device, so as to absorb the VOC in the gas stream in the liquid. Thus, the VOC-containing exhaust gas is effectively utilized. This measure aims to heat the wood chips as effectively as possible and ensure the complete discharge of VOC.

[0043] According to a preferred embodiment of the present invention, a material flow of wood chips is generated:

[0044] From the first heat treatment device into the cleaning device;

[0045] From the cleaning device into the second heat treatment device;

[0046] From the second heat treatment device into the digester; and

[0047] From the digester into the refiner. It has been found that through this material flow related to the measures of the foregoing method, the effective discharge of VOC is achieved. This means that as much VOC as possible can be removed from the wood chips with the minimum energy consumption. Heating the still contaminated wood chips in the first heat treatment device before feeding them into the cleaning device improves the efficiency, because the dirt heated together with the wood chips can be easily released from the wood chips.

[0048] Furthermore, the present invention relates to a processing system for reducing volatile organic compounds VOC in wood chips for wood fiber production, for implementing the method according to at least one of the foregoing items, comprising:

[0049] - A first heat treatment device adapted to receive the VOC-containing exhaust gas for the first heat treatment of wood chips;

[0050] - A cleaning device for cleaning wood chips;

[0051] - A second heat treatment device, adapted to receive and discharge VOC-containing waste gas for the second heat treatment of wood chips;

[0052] - A digester, configured to receive and discharge VOC-containing waste gas for cooking wood chips;

[0053] - A refiner, which is designed to discharge VOC-containing waste gas for crushing wood chips. The processing system can economically and effectively and environmentally friendly discharge VOCs from wood chips, and the foregoing embodiments, especially the embodiment according to claim 1, are equally applicable.

[0054] The term pipeline system or pipeline section used hereinafter preferably refers to a conveying device for waste gas and / or liquid. The conveying device can be a closed or open pipeline.

[0055] If the terms "heating system" or "heating medium pipeline section" are used hereinafter, preferably it refers to a conveying device for hot waste gas and / or hot liquid.

[0056] The term wood chip material flow system or material flow line used hereinafter preferably refers to a conveying device for the wood chips to be processed.

[0057] According to a preferred embodiment of the present invention, a processing system is provided, which includes a pipeline system having a pipeline section. The pipeline section is arranged and configured to convey the VOC-containing waste gas discharged from the second heat treatment device, the digester and / or the refiner into the first heat treatment device. Compared with the embodiment without this waste gas supply pipeline, the additional energy required to heat the first heat treatment device in the processing system is reduced. It is possible to heat the wood chips only by the VOC-containing waste gas. Therefore, these fed VOC-containing waste gases have promoted the precipitation of VOCs from the wood chips in the first heat treatment device. Therefore, the wood chips heated in this way are more effectively cleaned in the cleaning device compared with the unheated wood chips.

[0058] According to a preferred embodiment of the present invention, a processing system is provided, which includes a pipeline system having a pipeline section. The pipeline section is arranged and configured to transfer the VOC-containing waste gas discharged from the digester and / or the refiner into the second heat treatment device. Compared with the embodiment without this waste gas supply pipeline, the additional energy required to heat the second heat treatment device in the processing system is reduced. It is possible to heat the wood chips only by the VOC-containing waste gas. Therefore, these fed VOC-containing waste gases have promoted the precipitation of VOCs from the wood chips in the first heat treatment device. Therefore, the wood chips heated in this way are more effectively cleaned in the cleaning device compared with the unheated wood chips.

[0059] According to a preferred embodiment of the present invention, there is provided a processing system, which includes a conduit system having a conduit portion, the conduit portion being arranged and configured to discharge VOCs from a first heat treatment device, a second heat treatment device, a digester, and / or a refiner. It is possible to discharge VOCs from only one of these sites. For example, it may be discharged in the gas phase in the first heat treatment device, the second heat treatment device, and / or the refiner. It is possible for the liquid containing VOCs to flow out of the refiner from the processed wood chips. In the digester, when the cooking medium flows out of the digester, the VOCs can be removed in the gas phase and / or removed from the cooking medium. In addition, the VOCs can float on the water surface as an oily medium and be discharged from the digester. The discharge in the gas phase is carried out through the discharge port at the upper part of the container. The discharging is carried out by gravity from the lower region of the container. For example, if a discharge screw, especially a plug screw, is provided between the digester and the refiner, at least part of the VOCs can leave the processing system through the water of the digester or as an oil phase on the water. Preferably, a large part of the VOCs, for example more than 50%, leave the processing system via the water of the cleaning device or as an oil phase on the water. The basic idea herein is that the VOCs are first concentrated and then disposed of, especially by cleaning and squeezing water treatment.

[0060] According to a preferred embodiment of the present invention, there is provided a processing system, which includes a conduit system having a conduit portion, wherein the conduit portion is arranged and configured to discharge VOCs from a cleaning device, and / or

[0061] A processing system, which includes a stuffing screw along the material flow between the second heat treatment device and the digester, wherein the VOCs can be removed from the processing system via the conduit portion of the conduit system through the stuffing screw and / or

[0062] A processing system having a discharge screw along the material flow between the digester and the refiner, wherein the VOCs can be discharged from the processing system via the conduit portion of the pipeline system through the discharge screw. The discharge screw can be in the form of a plug screw. It has been found that the VOCs in these parts can be removed from the processing system with favorable efficiency through the cleaning device, the stuffing screw, and the discharge screw without having a significant negative impact on the processing, such as an adverse temperature development.

[0063] According to a preferred embodiment of the present invention, there is provided a processing system, which includes a heating system having a heating medium conduit portion, wherein the heating medium conduit portion is arranged and formed to at least partially, preferably completely, heat the first heat treatment device by the exhaust steam of the digester. This exhaust steam is also called sweat vapours. It has been proven to be energy-saving, introducing sufficient energy to help reduce the VOCs in the processing.

[0064] According to a preferred embodiment of the present invention, there is provided a processing system comprising a duct system having a duct portion, the duct portion being arranged and configured to convey together the VOC-containing exhaust gases from a digester, a refiner. In this way, the temperatures of the exhaust gases from the digester and the refiner are equalized, so that the necessary proportion of self-heating of the container receiving the mixed exhaust gas can be reliably determined and undesired temperature fluctuations in the receiving container are reduced. The receiving container is in particular a first heat treatment device, a second heat treatment device and / or a digester.

[0065] According to a preferred embodiment of the present invention, there is provided a processing system comprising a duct system having a duct portion, the duct portion being arranged and configured to convey in a combined manner the VOC-containing exhaust gases from a digester, a refiner and a second heat treatment device. In this way, the temperatures of the exhaust gases from the second heat treatment device, the digester and the refiner are equalized, so that the necessary proportion of self-heating of the container receiving the mixed exhaust gas can be reliably determined and undesired temperature fluctuations in the receiving container are reduced. The receiving container is in particular a first heat treatment device.

[0066] According to a preferred embodiment of the present invention, there is provided a processing system comprising a duct system having a duct portion, wherein the digester and the duct portion are arranged and configured to introduce the VOC-containing exhaust gas discharged from the digester and / or the refiner into the digester. The exhaust gas heat can thus be returned to the digester. This exhaust gas heat can also be increased with the exhaust gas from the refiner. Thus, the separation of VOC from the wood chips can be promoted in an energy-saving manner.

[0067] According to a preferred embodiment of the present invention, there is provided a digester comprising a bottom portion, which is configured to receive the VOC-containing exhaust gas from the digester, a first heat treatment device and / or a second heat treatment device via the duct portion of the duct system. Thus, the heated wood chips are in contact with the gas stream along the longest possible longitudinal extension axis of the digester, the first heat treatment device and / or the second heat treatment device to absorb the VOC in the gas stream in the liquid. Thus, the VOC-containing exhaust gas is effectively utilized. This measure aims to heat the wood chips as effectively as possible and ensure the complete discharge of VOC.

[0068] According to a preferred embodiment of the present invention, there is provided a processing system comprising a wood chip material flow system having a material flow line, wherein the material flow line for the wood chip material flow is arranged between:

[0069] a first heat treatment device and a cleaning device;

[0070] a cleaning device and a second heat treatment device;

[0071] a second heat treatment device and a digester; and

[0072] Cooking vessel and refiner. It has been found that by combining such a material flow with the aforementioned processing measures, effective VOC removal is achieved. This means that under low energy input, VOCs are separated from the wood chips as comprehensively as possible. Heating the still contaminated wood chips in the first heat treatment device before introducing them into the cleaning device also improves efficiency, because the dirt heated with the wood chips can be well dissolved from the wood chips. Description of the Drawings

[0073] Hereinafter, based on preferred exemplary embodiments, the present invention is exemplarily explained with reference to the drawings, wherein the features shown hereinafter individually and in combination may represent aspects of the present invention. In the drawings:

[0074] Figure 1 A method for reducing volatile organic compounds in wood chips for wood fiber production in a processing system is shown, and a material flow and an exhaust gas flow are shown. Detailed Description of the Invention

[0075] Figure 1 A schematic diagram of a processing system 1 for implementing a method for reducing volatile organic compounds VOC in wood chips for wood fiber production is shown.

[0076] Structurally, the processing system 1 at least includes a first heat treatment device 10, a cleaning device 20, a second heat treatment device 30, a cooking vessel 40 and a refiner 50.

[0077] In this regard, according to Figure 1 the processing system 1 for reducing VOC in wood chips performs the following processing steps:

[0078] In the first heat treatment device 10, a first heat treatment 100 of the wood chips is carried out.

[0079] Subsequently, in the cleaning device 20, wood chip cleaning 200 is carried out.

[0080] After the wood chip cleaning 200, a second heat treatment 300 of the wood chips is carried out in the second heat treatment device 30.

[0081] Subsequently, the wood chips that have completed the second heat treatment 300 in the second heat treatment device 30 are cooked 400 in the cooking vessel 40.

[0082] After the wood chip cooking 400 is carried out in the cooking vessel 40, the wood chips are crushed 500 in the refiner 50.

[0083] In the processing system 1, according to Figure 1 , in order to reduce VOC from wood chips energy-efficiently and environmentally friendly, the gas flow is as follows:

[0084] Receiving the VOC-containing waste gas G1 by using the first heat treatment device 10.

[0085] Receiving the VOC-containing waste gas G2 by using the second heat treatment device 30.

[0086] In addition, the second heat treatment device 30 discharges the VOC-containing waste gas G3.

[0087] The digester 40 receives the VOC-containing waste gas G4.

[0088] In addition, the digester 40 discharges the VOC-containing waste gas G5.

[0089] The refiner 50 is at least configured to discharge the VOC-containing waste gas G6. Optionally, it is possible to receive the VOC-containing waste gas from the digester 40.

[0090] The wood chips releasing VOC follow the following material flow in the processing system:

[0091] Entering the cleaning device 20M1 from the first heat treatment device 10,

[0092] Entering the second heat treatment device 30M2 from the cleaning device 20,

[0093] Entering the digester 40M3 from the second heat treatment device 30 and entering the refiner 50M4 from the digester 40.

[0094] In other words, the processing system 1 for reducing volatile organic compounds VOC in wood chips for wood fiber production and performing the foregoing processing includes:

[0095] - The first heat treatment device 10, configured to receive the VOC-containing waste gas G1 and perform the first heat treatment 100 of the wood chips;

[0096] - The cleaning device 20 for wood chip cleaning 200;

[0097] - The second heat treatment device 30, configured to receive the VOC-containing waste gas G2 and discharge the VOC-containing waste gas G3 and perform the second heat treatment 300 of the wood chips;

[0098] - The digester 40, configured to receive the VOC-containing waste gas G4 and discharge the VOC-containing waste gas G5 and perform wood chip cooking 400; and

[0099] - The refiner 50, configured to discharge the VOC-containing waste gas G6 and perform wood chip refining 500.

[0100] In other words, the method for reducing volatile organic compounds VOC in wood chips for wood fiber production in the processing system 1 at least includes the following consecutive steps:

[0101] - The first heat treatment 100 of the wood chips in the first heat treatment device 10, which is configured to receive the waste gas G1 containing VOC;

[0102] - Cleaning the wood chips 200 in the cleaning device 20;

[0103] - The second heat treatment 300 of the wood chips in the second heat treatment device 30, which is configured to receive the waste gas G2 containing VOC and discharge the waste gas G3 containing VOC;

[0104] - Cooking the wood chips 400 in the cooker 40, which is configured to receive the waste gas G4 containing VOC and discharge the waste gas G5 containing VOC; and

[0105] - Crushing the wood chips 500 in the refiner 50, which is configured to discharge the waste gas G6 containing VOC.

[0106] According to a preferred embodiment of the present invention, according to Figure 1 , a first heat treatment device 10 is provided, which is configured to receive the waste gas G1 containing VOC, and the waste gas is discharged from the second heat treatment device 30G3, the cooker 40G5 and the refiner 50G6.

[0107] According to a preferred embodiment of the present invention, according to Figure 1 , a second heat treatment device 30 is provided, which is configured to receive the waste gas G2 containing VOC, and the waste gas is discharged from the cooker 40G5 and the refiner 50G6.

[0108] According to a preferred embodiment of the present invention, VOC is discharged from the first heat treatment device 10, the second heat treatment device 30, the cooker 40 and / or the refiner 50. This is not shown in more detail in Figure 1 .

[0109] According to a preferred embodiment of the present invention, a processing system 1 is provided, which preferably includes a stuffing screw along the material flow between the second heat treatment device 30 and the cooker 40, wherein VOC is discharged from the processing system 1, especially from the cleaning device M2X and / or especially from the stuffing screw M3X. Further optionally or additionally, a processing system 1 is provided, which includes a discharge screw along the material flow between the cooker 40 and the refiner 50, wherein VOC from the processing system 1 is discharged from the discharge screw M4X. The discharge screw can be designed as a stuffing screw.

[0110] According to a preferred embodiment of the present invention, there is provided:

[0111] The first heat treatment 100 of the wood chips is carried out at 80 °C for 5 to 10 minutes; and / or

[0112] The second heat treatment 300 of the wood chips is carried out at 100 °C for 5 to 10 minutes; and / or

[0113] The wood chip cooking 400 is carried out between 140 and 180 °C for 2 to 5 minutes; the temperature data and the time data preferably each include an upper and / or lower deviation of 10%.

[0114] According to a preferred embodiment of the present invention, the first heat treatment device 10 is at least partially, preferably completely, heated by the exhaust gas from the digester 40.

[0115] According to a preferred embodiment of the present invention, according to Figure 1 The VOC-containing exhaust gases from the digester 40 and the refiner 50 are conveyed in a combined manner.

[0116] According to a preferred embodiment of the present invention, according to Figure 1 It is further provided that the VOC-containing exhaust gases from the second heat treatment device 30, the digester 40 and the refiner 50 are conveyed in a combined manner.

[0117] According to a preferred embodiment of the present invention, according to Figure 1 , a digester 40 is provided, which is configured to receive the VOC-containing exhaust gas G4 discharged from the digester 40 G5 and the refiner 50 G6.

[0118] According to a preferred embodiment of the present invention, according to Figure 1 The VOC-containing exhaust gas is introduced into the bottoms of the digester 40, the first heat treatment device 10 and the second heat treatment device 30.

[0119] According to a preferred embodiment of the present invention, according to Figure 1 A material flow of the wood chips occurs:

[0120] From the first heat treatment device 10 into the cleaning device 20 M1;

[0121] From the cleaning device 20 into the second heat treatment device 30 M2;

[0122] From the second heat treatment device 30 into the digester 40 M3; and

[0123] From the digester 40 into the refiner 50 M4.

[0124] List of reference numerals:

[0125] 1 Processing system

[0126] 10 First heat treatment device

[0127] 20 Cleaning device

[0128] 30 Second heat treatment device

[0129] 40 Steamer

[0130] 50 Refiner

[0131] 100 First heat treatment of wood chips

[0132] 200 Wood chip cleaning

[0133] 300 Second heat treatment of wood chips

[0134] 400 Wood chip cooking

[0135] 500 Wood chip crushing

[0136] G1 Receive waste gas containing VOC through the first heat treatment device

[0137] G2 Receive waste gas containing VOC through the second heat treatment device

[0138] G3 Discharge waste gas containing VOC through the second heat treatment device

[0139] G4 Receive waste gas containing VOC through the steamer

[0140] G5 Discharge waste gas containing VOC through the steamer

[0141] G6 Discharge waste gas containing VOC through the refiner

[0142] M1 Wood chip material flow entering the cleaning device from the first heat treatment device

[0143] M2 Wood chip material flow entering the second heat treatment device from the cleaning device

[0144] M2X Discharge VOC from the processing system through the cleaning device

[0145] M3 Wood chip material flow entering the steamer from the second heat treatment device

[0146] M3X Discharge VOC from the processing system through the stuffing screw

[0147] M4 Wood chip material flow entering the refiner from the steamer

[0148] M4X Discharge VOC from the processing system through the discharging screw

[0149] VOC Volatile Organic Compounds

Claims

1. A method for reducing volatile organic compounds (VOCs) in wood chips used for wood fiber production in a processing system (1), comprising at least the following consecutive steps: - A first heat treatment (100) of the wood chips in a first heat treatment device (10), the first heat treatment device (10) being adapted to receive exhaust gas G1 containing VOCs, where G1 is the exhaust gas containing VOCs received through the first heat treatment device (10); - Cleaning (200) the wood chips in a cleaning device (20); - A second heat treatment (300) of the wood chips in a second heat treatment device (30), the second heat treatment device (30) being designed to receive exhaust gas G2 containing VOCs and separate exhaust gas G3 containing VOCs, where G2 is the exhaust gas containing VOCs received through the second heat treatment device (30), and G3 is the exhaust gas containing VOCs discharged through the second heat treatment device (30); - Cooking (400) the wood chips in a cooker (40), the cooker (40) being adapted to receive exhaust gas G4 containing VOCs and remove exhaust gas G5 containing VOCs, where G4 is the exhaust gas containing VOCs received through the cooker (40), and G5 is the exhaust gas containing VOCs discharged through the cooker (40); and - Pulverizing (500) the wood chips in a refiner (50), the refiner (50) being adapted to remove exhaust gas G6 containing VOCs, where G6 is the exhaust gas containing VOCs discharged through the refiner (50).

2. The method for reducing volatile organic compounds (VOCs) in wood chips used for wood fiber production according to claim 1, characterized in that the first heat treatment device (10) is designed to receive exhaust gas G1 containing VOCs, and the exhaust gas G1 is separated from the second heat treatment device (30), the cooker (40), and / or the refiner (50).

3. The method for reducing volatile organic compounds (VOCs) in wood chips used for wood fiber production according to claim 1 or 2, characterized in that the second heat treatment device (30) is adapted to receive exhaust gas G2 containing VOCs, and the exhaust gas G2 is discharged from the cooker (40) and / or the refiner (50).

4. The method for reducing volatile organic compounds (VOCs) in wood chips used for wood fiber production according to claim 1 or 2, characterized in that VOCs are discharged from the processing system (1) via the first heat treatment device (10), the second heat treatment device (30), the cooker (40), and / or the refiner (50).

5. The method for reducing volatile organic compounds (VOCs) in wood chips used for wood fiber production according to claim 1 or 2, characterized in that VOCs from the processing system (1) are discharged from the cleaning device (20) and / or the processing system (1) includes a stuffing screw along the material flow between the second heat treatment device (30) and the cooker (40), where VOCs from the processing system (1) are discharged from the stuffing screw and / or the processing system (1) includes a discharge screw along the material flow between the cooker (40) and the refiner (50), where VOCs from the processing system (1) are discharged from the discharge screw.

6. A method for reducing volatile organic compounds (VOCs) in wood chips for wood fiber production according to claim 1 or 2, characterized in that, the first heat treatment (100) of the wood chips is carried out at 80 °C for 5 to 10 minutes; and / or the second heat treatment (300) of the wood chips is carried out at 100 °C for 5 to 10 minutes; and / or the wood chips are cooked (400) at a temperature between 140 and 180 °C for 2 to 5 minutes.

7. A method for reducing volatile organic compounds (VOCs) in wood chips for wood fiber production according to claim 1 or 2, characterized in that, the first heat treatment device (10) is at least partially heated, or completely heated, by the exhaust steam from the digester (40).

8. A method for reducing volatile organic compounds (VOCs) in wood chips for wood fiber production according to claim 1 or 2, characterized in that, the exhaust gas containing VOCs from the digester (40) and the refiner (50) and also from the second heat treatment device (30) is conveyed together.

9. A method for reducing volatile organic compounds (VOCs) in wood chips for wood fiber production according to claim 1 or 2, characterized in that, the digester (40) is designed to receive the exhaust gas G4 containing VOCs, which is separated from the digester (40) and / or the refiner (50).

10. A method for reducing volatile organic compounds (VOCs) in wood chips for wood fiber production according to claim 1 or 2, characterized in that, the exhaust gas containing VOCs is introduced into the bottom of the digester (40), the first and / or second heat treatment devices (10, 30).

11. A method for reducing volatile organic compounds (VOCs) in wood chips for wood fiber production according to claim 1 or 2, characterized in that, the material flow of the wood chips is: entering the cleaning device (20) from the first heat treatment device (10); entering the second heat treatment device (30) from the cleaning device (20); entering the digester (40) from the second heat treatment device (30); and entering the refiner (50) from the digester (40).

12. A processing system (1) for reducing volatile organic compounds (VOCs) in wood chips for wood fiber production, which is used to carry out the method according to claim 1 or 2, comprising: - a first heat treatment device (10), which is adapted to receive the exhaust gas G1 containing VOCs for the first heat treatment (100) of the wood chips; - a cleaning device (20) for cleaning the wood chips (200); - a second heat treatment device (30), which is adapted to receive the exhaust gas G2 containing VOCs and discharge the exhaust gas G3 containing VOCs for the second heat treatment (300) of the wood chips; - a digester (40), which is adapted to receive the exhaust gas G4 containing VOCs and discharge the exhaust gas G5 containing VOCs for cooking the wood chips (400); and - a refiner (50), which is adapted to remove the exhaust gas G6 containing VOCs for crushing the wood chips (500).

13. The processing system (1) for reducing volatile organic compounds (VOCs) in wood chips for wood fiber production according to claim 12, characterized in that, The processing system (1) includes a duct system having a duct portion, the duct portion being arranged and configured to transfer the VOC-containing exhaust gas G1 to the first heat treatment device (10), the exhaust gas G1 being discharged from the second heat treatment device (30), the digester (40), and / or the refiner (50).

14. The processing system (1) for reducing volatile organic compounds VOC in wood chips for wood fiber production according to claim 12 or 13, wherein, the processing system (1) includes a duct system having a duct portion, the duct portion being arranged and formed to transfer the VOC-containing exhaust gas G2 to the second heat treatment device (30), the exhaust gas G2 being discharged from the digester (40) and / or the refiner (50).

15. The processing system (1) for reducing volatile organic compounds VOC in wood chips for wood fiber production according to claim 12 or 13, wherein, the processing system (1) includes a duct system having a duct portion, the duct portion being arranged and configured to discharge VOC from the first heat treatment device (10), the second heat treatment device (30), the digester (40), and / or the refiner (50).

16. The processing system (1) for reducing volatile organic compounds VOC in wood chips for wood fiber production according to claim 12 or 13, wherein, the processing system (1) includes a duct system having a duct portion, the duct portion being arranged and configured to discharge VOC from the cleaning device (20), and / or the processing system (1) includes a stuffing screw along the material flow between the second heat treatment device (30) and the digester (40), wherein VOC can be discharged from the processing system (1) through the stuffing screw via a pipeline portion of the pipeline system, and / or the processing system (1) includes a discharge screw along the material flow between the digester (40) and the refiner (50), and it is possible for VOC to be discharged from the discharge screw of the processing system (1) via a pipeline portion of the pipeline system.

17. The processing system (1) for reducing volatile organic compounds VOC in wood chips for wood fiber production according to claim 12 or 13, wherein, the processing system (1) includes a heating system having a heating medium pipeline portion, wherein the heating medium pipeline portion is arranged and formed to at least partially or completely heat the first heat treatment device (10) via the exhaust steam from the digester (40).

18. The processing system (1) for reducing volatile organic compounds VOC in wood chips for wood fiber production according to claim 12 or 13, wherein, the processing system (1) includes a pipeline system having a pipeline portion, the pipeline portion being arranged and formed to convey the VOC-containing exhaust gases of the digester (40), the refiner (50), and the second heat treatment device (30) in a combined manner.

19. The processing system (1) for reducing volatile organic compounds VOC in wood chips for wood fiber production according to claim 12 or 13, wherein, The processing system (1) includes a duct system having a duct portion, wherein the digester (40) and the duct portion are arranged and configured to introduce exhaust gas G4 containing VOCs into the digester (40), and the exhaust gas G4 is discharged from the digester (40) and / or the refiner (50).

20. The processing system (1) for reducing volatile organic compounds VOCs in wood chips used for wood fiber production according to claim 12 or 13, characterized in that the digester (40) includes a bottom adapted to receive exhaust gas containing VOCs from the digester (40), the first and / or second heat treatment devices (10, 30) via the duct portion of the duct system.

21. The processing system (1) for reducing volatile organic compounds VOCs in wood chips used for wood fiber production according to claim 12 or 13, characterized in that the processing system (1) includes a wood chip material flow system having a material flow line, wherein the material flow line for the wood chip material flow is arranged between: the first heat treatment device (10) and the cleaning device (20); the cleaning device (20) and the second heat treatment device (30); the second heat treatment device (30) and the digester (40); and the digester (40) and the refiner (50).

Images