Method and system for recycling white water in fibre molding product manufacturing

Abstract

The present invention relates to a system and a method for recycling white water during production of fibre molded products. The method comprises: a) forming a wet fibre molded product in a forming unit (1) using a furnish comprising white water; b) dewatering the wet fibre product and producing a dewatered fibre molded product and a white water stream (4*); c) drying the dewatered fibre molded product and producing a dried fibre molded product and a steam stream (5*); d) condensing the steam stream (5*) by mixing the steam stream (5*) and the white water stream (4*) and producing a mixed white water stream (6*); e) reducing the temperature of the mixed white water stream (6*) to 50 °C or less; f) storing the mixed white water stream (7*) in a white water tank (8); and g) providing the white water (8*) from the white water tank (8) to the forming unit (1) for preparation of the furnish.

Description

Field of the Invention

[0001] This invention generally relates to the production of fibre molded products and more particularly the recycling of white water produced during production of the fibre molded product. A corresponding prior art method and system is known from CN 110 846 940 A.Background of the Invention

[0002] There is a strong desire in today's society to replace plastic packages with more sustainable alternatives that are made from renewable sources, recyclable and degradable should they end up in nature.

[0003] Packages made of fibre molded products have emerged as one sustainable alternative to plastic packages. Fibre molded products are made of cellulosic fibres and are hence made from biobased and renewable sources. In addition, the fibre molded products can be recycled after use or may be degraded should they end up in nature.

[0004] Due to the many advantages of packages made of fibre molded products, there is a desire to further improve the production of fibre molded products to facilitate the transition from plastic packaging materials to fibre molded materials.Summary

[0005] An object of the present invention is to provide an improved method and system for production of fibre molded products.

[0006] According to a first aspect of the present invention, it is provided a method for recycling white water during the production of fibre molded products, the method comprising: a) forming a wet fibre molded product in a forming unit using a furnish comprising white water; b) dewatering the wet fibre product and producing a dewatered fibre molded product and a white water stream; c) drying the dewatered fibre molded product and producing a dried fibre molded product and a steam stream; d) condensing the steam stream by mixing the steam stream and the white water stream and producing a mixed white water stream; e) reducing the temperature of the mixed white water stream to 50 °C or less, such as 40 °C or less; f) storing the mixed white water stream in a white water tank; and g) providing the white water from the white water tank to the forming unit for preparation of the furnish.

[0007] The present inventors have realized that the production of fibre molded products can be improved by reducing the temperature of the white water produced during manufacturing, prior to storing and reusing it.

[0008] Recycling the white water and steam produced during manufacturing of fibre molded products may lead to problems during manufacturing. Recycling the steam produced during drying of the dewatered fibre molded products, leads to a temperature increase in the white water tank where the white water is stored prior to reuse. The temperature increase may lead to precipitation of chemical additives present in the white water. Chemical additives such as AKD are sensitive to temperature and precipitate at elevated temperatures. Depending of the type of chemical additive, precipitation may occur above 40 °C, such as above 50 °C. The precipitation will eventually reach a critical mass where the precipitated chemical additives are found as remarking spots on the final products. The spots are considered as defects and deteriorate the quality of the final product. The reduction of temperature of the mixed white water stream prior to storing and reusing the mixed white water significantly reduces the appearance of remarking spots on the final fibre molded products. The mixed white water stream can in the present context be seen as a mixture of white water streams and steam streams produced during production. Preferably, all white water and steam resulting from the production are recycled. However, advantageous effects can be achieved also if only part of used white water is recycled. The method according to the first aspect enables the use of white water during production of the fibre molded products without deteriorating the quality of the final products while simultaneously reducing the amount of waste water and the need for fresh water. Hence, a more sustainable process is obtained.

[0009] The dewatering may comprise compression molding of the wet fibre molded product which enables an improved dewatering.

[0010] The drying of the dewatered fibre molded product may comprise vacuum assisted heating. Vacuum assisted heating improves the drying the dewatered fibre molded products.

[0011] The white water stream and the steam stream may be combined in a water tank wherein the condensing of the steam occurs.

[0012] The reduction in temperature of the mixed white water stream may comprise heat-exchanging. Energy may be generated during heat-exchanging and provided to a heating arrangement. The heat in the mixed white water stream may be transferred to a media such as water during heat-exchanging which may be used for district heating and / or heating buildings such as the building where the manufacturing process takes place. It would also be possible to generate electricity from the heated media. By taking advantage of the energy generated during the reduction in temperature, a less energy-consuming production of fibre molded products and hence a more sustainable and improved production is obtained.

[0013] During the production of fibre molded products more than one stream of white water and stream may be present. The white water tank may be a storage tank for all white water and steam produced during the fibre molding process.

[0014] The white water may in addition to fibres, such as fines, also comprise chemical additives such as alkyl ketene dimer (AKD).

[0015] The forming of the wet fibre molded product may further comprise: a1) preparing the furnish by diluting a pulp in a dilution unit with white water obtained from the white water tank in one or more dilution steps; a2) submersing a mold into the furnish in a forming tank; and a3) applying vacuum to the mold and forming the wet fibre molded product.

[0016] White water from the white water tank may be provided to the dilution unit. The dilution unit may comprise a pulper. The pulper may be able to disintegrate, refine and / or agitate the pulp present in the pulper. The white water from the white water tank may be provided to the pulper in the dilution unit.

[0017] The use of white water during the preparation of the furnish may reduce the need for fresh water. It may further reduce the amount of fresh chemical additives that needs to be added in order to achieve a desired effect as the white water may comprise chemical additives that were not retained in the previously produced fibre molded products. Hence, an overall reduction in the amount of needed chemical additives such as AKD may be obtained.

[0018] The white water from the white water tank may further be provided to a spray system used for cleaning the forming unit. This provides an additional use of the white water and a further reduction in the amount of fresh water needed to be provided to the production system.

[0019] According to a second aspect, it is provided a system for recycling white water during production of a fibre molded product comprising: a forming unit configured to form a wet fibre molded product from a furnish comprising white water; a dewatering unit configured to dewater the wet fibre product and produce a dewatered fibre molded product and a white water stream; a drying unit configured to dry the dewatered fibre molded product and produce a dried fibre molded product and a steam stream; a water tank configured to condense the steam stream by mixing with the white water stream and producing a mixed white water stream; at least one heat-transfer unit configured to lower the temperature of the mixed white water stream to a temperature of 50 °C or less; a white water tank configured to receive and store the mixed white water stream.

[0020] This system enables the reduction of temperature of the mixed white water stream prior to storing and reusing it during subsequent forming of fibre molded products. As a result, a reduction of the amount of defects, e.g. spots, on the final fibre molded products is obtained. That is, fibre molded products with a higher quality can be produced with a system according to the second aspect.

[0021] The forming unit may further comprise: a dilution unit configured to dilute a pulp to the furnish with white water obtained from the white water tank, in one or more dilution steps; a forming tank configured to form a wet fibre molded product from the furnish obtained in the dilution unit.

[0022] The dilution unit may comprise a pulper.

[0023] The dewatering unit may comprise a compression molding unit.

[0024] The system further comprises a water tank arranged between the drying unit and the heat-transfer unit.

[0025] The drying unit may comprise a vacuum assisted heater.

[0026] The heat-transfer unit may comprise a heat-exchanger.

[0027] Further features of, and advantages with, the present invention will become apparent when studying the appended claims and the following description. The skilled person realize that different features of the present invention may be combined to create embodiments other than those described in the following, without departing from the scope of the present invention.Brief Description of the Drawings

[0028] These and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing an example embodiment of the invention, wherein: Fig. 1 schematically illustrates a system for producing fibre molded products and recycling of white water; and Fig. 2 shows a flow chart outlining the steps of a method for recycling white water during production of fibre molded products. Detailed Description of Example Embodiments

[0029] The present invention provides a method and a system for recycling white water during the production of fibre molded products. The present invention minimizes the need for fresh water and hence enables a more sustainable production and system while simultaneously improving the quality of the fibre molded products.

[0030] In the present detailed description, various aspects and embodiments of the present invention are described with reference to a manufacturing assembly for producing a fibre molded product.

[0031] Fig. 1 schematically illustrates a system for recycling white water. The system comprises a forming unit 1 for forming the wet fibre molded product. The forming unit may further be divided into a dilution unit 2 for diluting the pulp to obtain the furnish and a forming tank 3 were forming of the wet fibre molded product occurs. The dilution unit 2 may comprise a pulper. The wet fibre molded product is transferred to a dewatering unit 4 where the wet fibre product is dewatered by compression molding to obtain a dewatered fibre molded product and a white water stream 4*. The dewatered fibre molded product is transferred to a drying unit 5 wherein it is dried using a vacuum assisted heater to obtain a dried fibre molded product and a steam stream 5*. The white water stream 4* and the steam stream 5* are directed to a water tank 6 wherein the two streams are mixed and the steam is condensed. The mixed white water stream 6* from the water tank 6 is directed to a heat-transfer unit 7 and the temperature of the mixed water stream 7* out from the heat-transfer unit is 50 °C or less. The heat-transfer unit may be a heat-exchanger. The mixed white water stream 7* is directed to a white water tank 8 where it is stored. Once stored in the white water tank 8, the mixed white water stream 7* is considered to be white water. The white water is, when needed, redirected to the forming unit 1 for the preparation if the furnish or to a spray system 9 used to clean the forming unit by spraying with white water.

[0032] Fig. 2 is a flow chart outlining the steps of a method for recycling white water during production of fibre molded products. The method will be described with reference to the system of Fig. 1. The method comprises the steps a) to f) which will be described in the following.

[0033] The method for recycling white water comprises a) forming of a wet fibre molded product in a forming unit 1 using a furnish comprising white water.

[0034] The furnish may be prepared by diluting a pulp with white water in a dilution unit 2. The dilution may be performed in one or more dilution steps in order to obtain a furnish with a desired consistency such as 0.1-1 wt.%. At least one of the dilution steps may occur during pulping of the pulp in a pulper. An example of a suitable pulp is chemi-thermomechanical pulp (CTMP), such as softwood CTMP. The pulp preferably has a Canadian Standard Freeness (CSF) of 375-475 ml. The CSF is measured according to ISO 5267 / 2-1980 after repulping according to ISO 5263-2:2204. White water is preferably used as the dilution media in all dilution steps; hence, no fresh water may be needed during dilution. In addition to fibres, the furnish may further comprise chemical additives such as alkyl ketene dimer (AKD) in order to induce certain properties such as hydrophobicity to the final product. The AKD may be added in an amount required in order to achieve desired properties such as a specific Cobb values.

[0035] After a furnish is produced, it is transferred to a forming tank 3. A mold in the desired shape of the final product is lowered into the forming tank 3 comprising the furnish. The mold preferably comprises a wire mesh and outlets for white water. By applying vacuum to the mold, a wet fibre molded product may be obtained on the mold. The wet fibre molded product is a wet layer of fibres and chemical additives, if present, formed on the surface of the mold. Once the wet fibre molded product has been formed, the mold is withdrawn from the forming tank 3 and transferred to a dewatering unit 4. The wet fibre molded product is than b) dewatered and a dewatered fibre molded product is obtained. The dewatering may comprise compression molding of the wet fibre molded product. During b) the dewatering a white water stream 4* is produced alongside the dewatered fibre molded product. The white water stream 4* may comprise fibres such as fines and chemical additives such as AKD.

[0036] The dewatered fibre molded product is c) dried in a drying unit 5 to a moisture content of approximately 80-95 wt.%. The drying preferably comprises vacuum assisted drying. The c) drying procedure produces a dried fibre molded product and a steam stream 5*.

[0037] The removed water, in form of white water 4* and steam 5*, is recycled in order to minimize the amount of waste water produced as well as to minimize the need to add fresh water and chemical additives. Hence, a more sustainable production of the fibre molded products is obtained.

[0038] The recycled water (mixed white water stream) is directed to and f) stored in a white water tank 8. Prior to being directed to the white water tank 8, the white water and steam are mixed in order to d) condense the steam and produce a mixed white water stream 6*. The mixing may occur in a water tank 6. When there is a need for water in the manufacturing process, the white water may be directed from the white water tank 8 to the place requiring water. As an example, the white water is g) directed to the forming unit 1 when new furnish needs to be prepared. The white water may further be directed to a spray system 9 that is used for cleaning of the forming unit 1.

[0039] In order to solve the above-mentioned problem, the present inventors have realized that by e) reducing the temperature of the recycled water streams, i.e. mixed white water stream, to a temperature of 50 °C or less, a significant reduction in precipitation of the chemical additives will be obtained. As a result, a significant reduction of remarking spots on the final products that deteriorate their quality will be obtained.

[0040] The reduction in temperature occurs prior to entering the white water tank 8 where the mixed white water is f) stored and after d) the white water stream and steam stream have been mixed. It is advantageous if all produced white water and steam is recycled, however, it is not necessary.

[0041] The reduction in temperature e) of the mixed white water stream 6* may comprise heat-exchanging. Energy may be generated during heat-exchanging and provided to a heating arrangement. The heat in the mixed white water stream 6* may be transferred to a more suitable media during heat-exchanging which may be used for district heating and / or heating buildings such as the building where the manufacturing process takes place. It would also be possible to generate electricity from the heated media. The utilization of the generated energy further decreases the environmental impact of the production method as little energy is lost during production.

[0042] Even though the invention has been described with reference to specific exemplifying embodiments thereof, many different alterations, modifications and the like will become apparent for those skilled in the art. art, as long as they fall within the scope of the claims.

[0043] Additionally, variations to the disclosed embodiments can be understood and effected by the skilled person in practicing the claimed invention, as defined in the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage.

Examples

Embodiment Construction

[0029]The present invention provides a method and a system for recycling white water during the production of fibre molded products. The present invention minimizes the need for fresh water and hence enables a more sustainable production and system while simultaneously improving the quality of the fibre molded products.

[0030]In the present detailed description, various aspects and embodiments of the present invention are described with reference to a manufacturing assembly for producing a fibre molded product.

[0031]Fig. 1 schematically illustrates a system for recycling white water. The system comprises a forming unit 1 for forming the wet fibre molded product. The forming unit may further be divided into a dilution unit 2 for diluting the pulp to obtain the furnish and a forming tank 3 were forming of the wet fibre molded product occurs. The dilution unit 2 may comprise a pulper. The wet fibre molded product is transferred to a dewatering unit 4 where the wet fibre product is dewat...

Field of the Invention

[0001] This invention generally relates to the production of fibre molded products and more particularly the recycling of white water produced during production of the fibre molded product. A corresponding prior art method and system is known from CN 110 846 940 A.Background of the Invention

[0002] There is a strong desire in today's society to replace plastic packages with more sustainable alternatives that are made from renewable sources, recyclable and degradable should they end up in nature.

[0003] Packages made of fibre molded products have emerged as one sustainable alternative to plastic packages. Fibre molded products are made of cellulosic fibres and are hence made from biobased and renewable sources. In addition, the fibre molded products can be recycled after use or may be degraded should they end up in nature.

[0004] Due to the many advantages of packages made of fibre molded products, there is a desire to further improve the production of fibre molded products to facilitate the transition from plastic packaging materials to fibre molded materials.Summary

[0005] An object of the present invention is to provide an improved method and system for production of fibre molded products.

[0006] According to a first aspect of the present invention, it is provided a method for recycling white water during the production of fibre molded products, the method comprising: a) forming a wet fibre molded product in a forming unit using a furnish comprising white water; b) dewatering the wet fibre product and producing a dewatered fibre molded product and a white water stream; c) drying the dewatered fibre molded product and producing a dried fibre molded product and a steam stream; d) condensing the steam stream by mixing the steam stream and the white water stream and producing a mixed white water stream; e) reducing the temperature of the mixed white water stream to 50 °C or less, such as 40 °C or less; f) storing the mixed white water stream in a white water tank; and g) providing the white water from the white water tank to the forming unit for preparation of the furnish.

[0007] The present inventors have realized that the production of fibre molded products can be improved by reducing the temperature of the white water produced during manufacturing, prior to storing and reusing it.

[0008] Recycling the white water and steam produced during manufacturing of fibre molded products may lead to problems during manufacturing. Recycling the steam produced during drying of the dewatered fibre molded products, leads to a temperature increase in the white water tank where the white water is stored prior to reuse. The temperature increase may lead to precipitation of chemical additives present in the white water. Chemical additives such as AKD are sensitive to temperature and precipitate at elevated temperatures. Depending of the type of chemical additive, precipitation may occur above 40 °C, such as above 50 °C. The precipitation will eventually reach a critical mass where the precipitated chemical additives are found as remarking spots on the final products. The spots are considered as defects and deteriorate the quality of the final product. The reduction of temperature of the mixed white water stream prior to storing and reusing the mixed white water significantly reduces the appearance of remarking spots on the final fibre molded products. The mixed white water stream can in the present context be seen as a mixture of white water streams and steam streams produced during production. Preferably, all white water and steam resulting from the production are recycled. However, advantageous effects can be achieved also if only part of used white water is recycled. The method according to the first aspect enables the use of white water during production of the fibre molded products without deteriorating the quality of the final products while simultaneously reducing the amount of waste water and the need for fresh water. Hence, a more sustainable process is obtained.

[0009] The dewatering may comprise compression molding of the wet fibre molded product which enables an improved dewatering.

[0010] The drying of the dewatered fibre molded product may comprise vacuum assisted heating. Vacuum assisted heating improves the drying the dewatered fibre molded products.

[0011] The white water stream and the steam stream may be combined in a water tank wherein the condensing of the steam occurs.

[0012] The reduction in temperature of the mixed white water stream may comprise heat-exchanging. Energy may be generated during heat-exchanging and provided to a heating arrangement. The heat in the mixed white water stream may be transferred to a media such as water during heat-exchanging which may be used for district heating and / or heating buildings such as the building where the manufacturing process takes place. It would also be possible to generate electricity from the heated media. By taking advantage of the energy generated during the reduction in temperature, a less energy-consuming production of fibre molded products and hence a more sustainable and improved production is obtained.

[0013] During the production of fibre molded products more than one stream of white water and stream may be present. The white water tank may be a storage tank for all white water and steam produced during the fibre molding process.

[0014] The white water may in addition to fibres, such as fines, also comprise chemical additives such as alkyl ketene dimer (AKD).

[0015] The forming of the wet fibre molded product may further comprise: a1) preparing the furnish by diluting a pulp in a dilution unit with white water obtained from the white water tank in one or more dilution steps; a2) submersing a mold into the furnish in a forming tank; and a3) applying vacuum to the mold and forming the wet fibre molded product.

[0016] White water from the white water tank may be provided to the dilution unit. The dilution unit may comprise a pulper. The pulper may be able to disintegrate, refine and / or agitate the pulp present in the pulper. The white water from the white water tank may be provided to the pulper in the dilution unit.

[0017] The use of white water during the preparation of the furnish may reduce the need for fresh water. It may further reduce the amount of fresh chemical additives that needs to be added in order to achieve a desired effect as the white water may comprise chemical additives that were not retained in the previously produced fibre molded products. Hence, an overall reduction in the amount of needed chemical additives such as AKD may be obtained.

[0018] The white water from the white water tank may further be provided to a spray system used for cleaning the forming unit. This provides an additional use of the white water and a further reduction in the amount of fresh water needed to be provided to the production system.

[0019] According to a second aspect, it is provided a system for recycling white water during production of a fibre molded product comprising: a forming unit configured to form a wet fibre molded product from a furnish comprising white water; a dewatering unit configured to dewater the wet fibre product and produce a dewatered fibre molded product and a white water stream; a drying unit configured to dry the dewatered fibre molded product and produce a dried fibre molded product and a steam stream; a water tank configured to condense the steam stream by mixing with the white water stream and producing a mixed white water stream; at least one heat-transfer unit configured to lower the temperature of the mixed white water stream to a temperature of 50 °C or less; a white water tank configured to receive and store the mixed white water stream.

[0020] This system enables the reduction of temperature of the mixed white water stream prior to storing and reusing it during subsequent forming of fibre molded products. As a result, a reduction of the amount of defects, e.g. spots, on the final fibre molded products is obtained. That is, fibre molded products with a higher quality can be produced with a system according to the second aspect.

[0021] The forming unit may further comprise: a dilution unit configured to dilute a pulp to the furnish with white water obtained from the white water tank, in one or more dilution steps; a forming tank configured to form a wet fibre molded product from the furnish obtained in the dilution unit.

[0022] The dilution unit may comprise a pulper.

[0023] The dewatering unit may comprise a compression molding unit.

[0024] The system further comprises a water tank arranged between the drying unit and the heat-transfer unit.

[0025] The drying unit may comprise a vacuum assisted heater.

[0026] The heat-transfer unit may comprise a heat-exchanger.

[0027] Further features of, and advantages with, the present invention will become apparent when studying the appended claims and the following description. The skilled person realize that different features of the present invention may be combined to create embodiments other than those described in the following, without departing from the scope of the present invention.Brief Description of the Drawings

[0028] These and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing an example embodiment of the invention, wherein: Fig. 1 schematically illustrates a system for producing fibre molded products and recycling of white water; and Fig. 2 shows a flow chart outlining the steps of a method for recycling white water during production of fibre molded products. Detailed Description of Example Embodiments

[0029] The present invention provides a method and a system for recycling white water during the production of fibre molded products. The present invention minimizes the need for fresh water and hence enables a more sustainable production and system while simultaneously improving the quality of the fibre molded products.

[0030] In the present detailed description, various aspects and embodiments of the present invention are described with reference to a manufacturing assembly for producing a fibre molded product.

[0031] Fig. 1 schematically illustrates a system for recycling white water. The system comprises a forming unit 1 for forming the wet fibre molded product. The forming unit may further be divided into a dilution unit 2 for diluting the pulp to obtain the furnish and a forming tank 3 were forming of the wet fibre molded product occurs. The dilution unit 2 may comprise a pulper. The wet fibre molded product is transferred to a dewatering unit 4 where the wet fibre product is dewatered by compression molding to obtain a dewatered fibre molded product and a white water stream 4*. The dewatered fibre molded product is transferred to a drying unit 5 wherein it is dried using a vacuum assisted heater to obtain a dried fibre molded product and a steam stream 5*. The white water stream 4* and the steam stream 5* are directed to a water tank 6 wherein the two streams are mixed and the steam is condensed. The mixed white water stream 6* from the water tank 6 is directed to a heat-transfer unit 7 and the temperature of the mixed water stream 7* out from the heat-transfer unit is 50 °C or less. The heat-transfer unit may be a heat-exchanger. The mixed white water stream 7* is directed to a white water tank 8 where it is stored. Once stored in the white water tank 8, the mixed white water stream 7* is considered to be white water. The white water is, when needed, redirected to the forming unit 1 for the preparation if the furnish or to a spray system 9 used to clean the forming unit by spraying with white water.

[0032] Fig. 2 is a flow chart outlining the steps of a method for recycling white water during production of fibre molded products. The method will be described with reference to the system of Fig. 1. The method comprises the steps a) to f) which will be described in the following.

[0033] The method for recycling white water comprises a) forming of a wet fibre molded product in a forming unit 1 using a furnish comprising white water.

[0034] The furnish may be prepared by diluting a pulp with white water in a dilution unit 2. The dilution may be performed in one or more dilution steps in order to obtain a furnish with a desired consistency such as 0.1-1 wt.%. At least one of the dilution steps may occur during pulping of the pulp in a pulper. An example of a suitable pulp is chemi-thermomechanical pulp (CTMP), such as softwood CTMP. The pulp preferably has a Canadian Standard Freeness (CSF) of 375-475 ml. The CSF is measured according to ISO 5267 / 2-1980 after repulping according to ISO 5263-2:2204. White water is preferably used as the dilution media in all dilution steps; hence, no fresh water may be needed during dilution. In addition to fibres, the furnish may further comprise chemical additives such as alkyl ketene dimer (AKD) in order to induce certain properties such as hydrophobicity to the final product. The AKD may be added in an amount required in order to achieve desired properties such as a specific Cobb values.

[0035] After a furnish is produced, it is transferred to a forming tank 3. A mold in the desired shape of the final product is lowered into the forming tank 3 comprising the furnish. The mold preferably comprises a wire mesh and outlets for white water. By applying vacuum to the mold, a wet fibre molded product may be obtained on the mold. The wet fibre molded product is a wet layer of fibres and chemical additives, if present, formed on the surface of the mold. Once the wet fibre molded product has been formed, the mold is withdrawn from the forming tank 3 and transferred to a dewatering unit 4. The wet fibre molded product is than b) dewatered and a dewatered fibre molded product is obtained. The dewatering may comprise compression molding of the wet fibre molded product. During b) the dewatering a white water stream 4* is produced alongside the dewatered fibre molded product. The white water stream 4* may comprise fibres such as fines and chemical additives such as AKD.

[0036] The dewatered fibre molded product is c) dried in a drying unit 5 to a moisture content of approximately 80-95 wt.%. The drying preferably comprises vacuum assisted drying. The c) drying procedure produces a dried fibre molded product and a steam stream 5*.

[0037] The removed water, in form of white water 4* and steam 5*, is recycled in order to minimize the amount of waste water produced as well as to minimize the need to add fresh water and chemical additives. Hence, a more sustainable production of the fibre molded products is obtained.

[0038] The recycled water (mixed white water stream) is directed to and f) stored in a white water tank 8. Prior to being directed to the white water tank 8, the white water and steam are mixed in order to d) condense the steam and produce a mixed white water stream 6*. The mixing may occur in a water tank 6. When there is a need for water in the manufacturing process, the white water may be directed from the white water tank 8 to the place requiring water. As an example, the white water is g) directed to the forming unit 1 when new furnish needs to be prepared. The white water may further be directed to a spray system 9 that is used for cleaning of the forming unit 1.

[0039] In order to solve the above-mentioned problem, the present inventors have realized that by e) reducing the temperature of the recycled water streams, i.e. mixed white water stream, to a temperature of 50 °C or less, a significant reduction in precipitation of the chemical additives will be obtained. As a result, a significant reduction of remarking spots on the final products that deteriorate their quality will be obtained.

[0040] The reduction in temperature occurs prior to entering the white water tank 8 where the mixed white water is f) stored and after d) the white water stream and steam stream have been mixed. It is advantageous if all produced white water and steam is recycled, however, it is not necessary.

[0041] The reduction in temperature e) of the mixed white water stream 6* may comprise heat-exchanging. Energy may be generated during heat-exchanging and provided to a heating arrangement. The heat in the mixed white water stream 6* may be transferred to a more suitable media during heat-exchanging which may be used for district heating and / or heating buildings such as the building where the manufacturing process takes place. It would also be possible to generate electricity from the heated media. The utilization of the generated energy further decreases the environmental impact of the production method as little energy is lost during production.

[0042] Even though the invention has been described with reference to specific exemplifying embodiments thereof, many different alterations, modifications and the like will become apparent for those skilled in the art. art, as long as they fall within the scope of the claims.

[0043] Additionally, variations to the disclosed embodiments can be understood and effected by the skilled person in practicing the claimed invention, as defined in the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage.

Examples

Embodiment Construction

[0029]The present invention provides a method and a system for recycling white water during the production of fibre molded products. The present invention minimizes the need for fresh water and hence enables a more sustainable production and system while simultaneously improving the quality of the fibre molded products.

[0030]In the present detailed description, various aspects and embodiments of the present invention are described with reference to a manufacturing assembly for producing a fibre molded product.

[0031]Fig. 1 schematically illustrates a system for recycling white water. The system comprises a forming unit 1 for forming the wet fibre molded product. The forming unit may further be divided into a dilution unit 2 for diluting the pulp to obtain the furnish and a forming tank 3 were forming of the wet fibre molded product occurs. The dilution unit 2 may comprise a pulper. The wet fibre molded product is transferred to a dewatering unit 4 where the wet fibre product is dewat...

Claims

1. A method for recycling white water during production of fibre molded products, the method comprising: a) forming a wet fibre molded product in a forming unit (1) using a furnish comprising white water; b) dewatering the wet fibre product and producing a dewatered fibre molded product and a white water stream (4*); c) drying the dewatered fibre molded product and producing a dried fibre molded product and a steam stream (5*); d) condensing the steam stream (5*) by mixing the steam stream (5*) and the white water stream (4*) and producing a mixed white water stream (6*); e) reducing the temperature of the mixed white water stream (6*) to 50 °C or less; f) storing the mixed white water stream (7*) in a white water tank (8); and g) providing white water (8*) from the white water tank (8) to the forming unit (1) for preparation of the furnish.

2. The method according to claim 1, wherein the dewatering comprises compression molding of the wet fibre molded product.

3. The method according to any one of the preceding claims, wherein the drying comprises vacuum assisted heating.

4. The method according to any one of the preceding claims, wherein the mixing of the steam stream (5*) and the white water stream (4*) occurs in a water tank (6) to produce the mixed white water steam (6*).

5. The method according to any one of the preceding claims, wherein reducing the temperature of the mixed white water stream (6*) comprises heat-exchanging.

6. The method according to claim 5, further comprising generating energy during heat-exchanging and providing the generated energy to a heating arrangement.

7. The method according to any one of the preceding claims, wherein the white water tank (8) is a storage tank for white water and condensed steam produced during the fibre molding process.

8. The method according to any one of the preceding claims, wherein forming the wet fibre molded product comprises: a1) preparing the furnish by diluting a pulp in a dilution unit (2) with white water (8*) obtained from the white water tank (8) in one or more dilution steps; a2) submersing a mold into the furnish in a forming tank (3); and a3) applying vacuum to the mold and forming the wet fibre molded product.

9. The method according to claims 1-7, comprising providing the white water (8*) from the white water tank to a dilution unit (2).

10. The method according to any one of the preceding claims, further comprising providing the white water (8*) from the white water tank (8) to a spray system (9) used for cleaning the forming unit (1).

11. A system for recycling white water during production of a fibre molded product comprising: - a forming unit (1) configured to form a wet fibre molded product from a furnish comprising mixed white water (8*); - a dewatering unit (4) configured to dewater the wet fibre product and produce a dewatered fibre molded product and a white water stream (4*); - a drying unit (5) configured to dry the dewatered fibre molded product and produce a dried fibre molded product and a steam stream (5*); - a water tank (6) configured to condense the steam stream (5*) by mixing with the white water stream (4*) and producing a mixed white water stream (6*); - at least one heat-transfer unit (7) configured to lower the temperature of the mixed white water stream (6*) to a temperature of 50 °C or less; and - a white water tank (8) configured to receive and store the mixed white water stream (7*).

12. The system according to claim 11, wherein the forming unit comprises: - a dilution unit (2) configured to dilute a pulp to the furnish with white water (8*) obtained from the white water tank (8) in one or more dilution steps; and - a forming tank (3) configured to form a wet fibre molded product from the furnish prepared in the dilution unit (3).

13. The system according to any one of the claims 11-12, wherein the dewatering unit (4) comprises a compression molding unit.

14. The system according to any one of the claims 11-13, wherein the drying unit (5) comprises a vacuum assisted heater.

15. The system according to claims 11-14, wherein the heat-transfer unit (7) comprises a heat-exchanger.

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