A method for producing foam glass

Abstract

Disclosed is a method for producing foam glass (1). The method comprises the steps of:  grinding a glass material (2) into glass powder (3),  grinding a waste composite material (4) comprising fiberglass (5) and resin 5 (6) into a composite powder (8), wherein the waste composite material has an ultimate tensile strength above 20 MPa,  mixing said glass powder (3), said composite powder (8) and a foaming agent (9) to form a foam glass feedstock (7), and  heating said foam glass feedstock (7) to a temperature of at least 600⁰C.10

Description

[0001] A METHOD FOR PRODUCING FOAM GLASS

[0002] Background of the invention

[0003] The invention relates to a method for producing foam glass by adding a foaming agent to a glass material, and foam glass produced by means of this method.

[0004] Description of the Related Art

[0005] Foam glass - also called cellular glass - is a porous glass foam material. Its advantages as a building material include its light weight, high strength, and thermal and acoustic insulating properties. Foam glass is made by heating a mixture of crushed or granulated glass and a chemical foaming agent (also called a blowing agent). Near the melting point of the glass, the foaming agent releases a gas, producing a foaming effect in the glass. After cooling the mixture hardens into a rigid material with gas-filled closed-cell pores or sometimes open-cell pores forming a large portion of the foam glass’s volume.

[0006] Even though foam glass is moisture-proof, fireproof, and anti-corrosive, and given the foam glass material has many advantages particularly in relation to long-term use performance, it is not used particularly often in the building industry or other industries and one of the main reasons for this is the cost, in that it takes much energy to melt the glass.

[0007] From the international patent applications WO 2012 / 139550 Al and WO 2020 / 242407 Al it is known to make the foam glass by means of a waste glass mixture which could reduce the cost of foam glass. However, the production costs are still too high.

[0008] From the Chinese patent application CN 102643013 A it is known to use waste glass fiber reinforced phenolic resin molding compound to produce foam glass. The glass fiber reinforced phenolic resin molding compound is subjected to heat treatment up to 500°C before being crushed and pulverized. The carbonized powder phenolic resin is then mixed with waste glass powder, a foaming agent, a stabilizing agent, a fluxing agent, a binder and other before the mixture is heated to up to 1000°C to form foam glass. However, this method is still not particularly cost- and energy effective.

[0009] An object of the invention is therefore to provide for a more cost-efficient method for producing foam glass.

[0010] The invention

[0011] The invention provides for a method for producing foam glass. The method comprises the steps of:

[0012] • grinding a glass material into glass powder,

[0013] • grinding a waste composite material comprising fiberglass, and resin into a composite powder, wherein said waste composite material has an ultimate tensile strength above 20 MPa,

[0014] • mixing the glass powder, the composite powder and a foaming agent to form a foam glass feedstock, and

[0015] • heating the foam glass feedstock to a temperature of at least 600°C.

[0016] Grinding the waste composite material directly from its original state where it has an ultimate tensile strength above 20 MPa - i.e., without first embrittling the waste composite material through heat treatment or similar - is advantageous in that the full heating value or calorific value of the waste composite material is hereby preserved. Most resins - like polyester resin, polyurethane resin, vinyl ester resin or epoxy resin - has a heating value or calorific value of around 30 MJoule per kg. Compared to this wood has a heating value of around 15 MJoule per kg and coal has a heating value of around 25 MJoule per kg and carbonized composite material will inevitably have a significantly lower calorific value than uncarbonized composite material because some of the combustible components in the composite material will combust or evaporate during the carbonization process thereby inevitably reducing the calorific value of the composite material. Thus, adding a composite powder comprising fiberglass and resin - made from composite material with an ultimate tensile strength above 20 MPa, i.e., composite material which has not been embrittled through heat treatment - to the foam glass feedstock, before the heating process, is advantageous, in that resin is flammable and highly energy dense and the resin hereby is a thermal energy source that will at least aid in driving the heating process in which the glass material and the fiberglass is heated during the manufacturing of the foam glass. Hereby a much more cost- and energy effective way of heating the foam glass feedstock is provided. The energy contribution from the uncarbonized resin also enables that the cost of the foam glass manufacturing plant can be reduced in that the demand for external heating means such as gas heaters, electrical heaters or other for generating the foam glass can be severely reduced. And the cost and complexity of the overall foam glass manufacturing process is reduced because the manufacturing process only includes a single heating step - i.e., the step in which the foam glass feedstock is heated to a temperature of at least 600°C to form the foam glass.

[0017] Furthermore, waste composite material is problematic because it is very expensive and complicated to reuse it, and because waste composite material often comprises additional problematic compounds and chemicals such as heavy metals, fluorine- containing substances - particularly Per- and polyfluoroalkyl substances (PF AS) - e.g., in the form of PFAS surface treatments of wind turbine blades, circuit boards and the like - and other. Likewise, the glass material can comprise additional problematic compounds and chemicals such as PFAS on worn-out solar panels or other. However, since the foam glass feedstock is heated to a temperature of at least 600°C, many or all of these problematic additional substances are combusted and degraded and those that are not - such as some heavy metals - are embedded or bonded in the produced foam glass. And given the high temperatures any problematic tar, dioxin or other e.g., generated during the heating process by the additional problematic compounds and chemicals are also combusted and degraded. Thus, the present method ensures that the production costs of the foam glass is reduced while at the same time providing a safe, environmentally friendly, and efficient way of disposing of problematic waste composite material.

[0018] Ultimate tensile strength (also called UTS, tensile strength, TS, or ultimate strength) is the maximum stress that a material can withstand while being stretched or pulled before breaking. In brittle materials, the ultimate tensile strength is close to the yield point. The ultimate tensile strength is found by performing a tensile test and recording the engineering stress versus strain. The highest point of the stress-strain curve is the ultimate tensile strength and has units of stress. Ultimate tensile strength may be determined by taking a small sample of the material with a fixed cross- sectional area, and then pulling it with a tensometer at a constant strain (change in gauge length divided by initial gauge length) rate until the sample breaks. The ultimate tensile strength of a material is an intensive property; therefore its value does not depend on the size of the test specimen. Ultimate tensile strength is defined as a stress, which is measured as force per unit area. Standardized methods for determining ultimate tensile strength may also be found in DIN 53455 and ASTM D638.

[0019] In this context the term “foaming agent” should be understood as an additive that facilitate the release of the gaseous phase upon heat treatment. I.e., the term includes any kind of redox and neutralization agents - such as nonoxide materials, e.g., carbides or nitrides, or decomposing agents such as sulphates, e.g., calcium sulphate (CaSO4»(nH2O)), organic compounds, and carbonates, e.g., calcium carbonate (CaCO3).

[0020] In this context the term “glass” should be understood as non-crystalline solid amorphous materials formed from a melt by cooling to rigidity without crystallization to form a usually transparent or translucent material consisting typically of a mixture of silicates. Glass is in most cases based on or at least includes a large amount of the chemical compound silica (silicon dioxide, or quartz) being the primary constituent of sand. However, during the process of forming the foam glass crystallization may occur leading to a foam glass also containing ceramic parts.

[0021] In an aspect of the invention, the glass material is grinded into glass powder having a particle size of between 10 and 900 microns, preferably between 30 and 600 microns, and most preferred between 50 and 300 microns.

[0022] If the particle size of the glass material is too big the glass material will not mix as evenly with the composite powder and the foaming agent and the sintering process will not run properly, and the resulting foam glass will become denser with a more uneven foam structure. However, if the particle size of the glass material is too little it takes too much time and energy to grind the glass material without any significant improvement in the quality of the resulting foam glass. Thus, the present particle size ranges present an advantageous relationship between product quality and cost.

[0023] In an aspect of the invention, the waste composite material is grinded into composite powder having a particle size of between 10 and 900 microns, preferably between 30 and 600 microns, and most preferred between 50 and 300 microns.

[0024] If the particle size of the waste composite material is too big the waste composite material will not mix as evenly with the glass material and the foaming agent, and the resulting foam glass will not heat evenly and will therefore form a more uneven foam structure. However, if the particle size of the waste composite material is too little it takes too much time and energy to grind the waste composite material without any significant improvement in the quality of the resulting foam glass. Thus, the present particle size ranges present an advantageous relationship between product quality and cost.

[0025] In an aspect of the invention, the method further comprises screening the glass powder and / or the composite powder before mixing the glass powder, the composite powder and the foaming agent. It is advantageous to screen the glass powder and / or the composite powder through a screen, a sieve, a strainer or the like before mixing the glass powder, the composite powder and the foaming agent in that hereby the foam glass feedstock becomes more uniform and larger particles - e.g., in the form of fibreglass strands - are removed for ensure a better foam glass quality. Screening can e.g. be performed by means of a screen, a sieve, a strainer or the like having an opening size of less than 300 pm, preferably less than 200 pm, and most preferred less than 100 pm.

[0026] In an aspect of the invention, the foam glass feedstock comprises between 40% and 97%, preferably between 50% and 94%, and most preferred between 60% and 90% glass powder by weight before the foam glass feedstock is heated.

[0027] If the foam glass feedstock comprises too much glass powder it is not possible for the remaining composite powder to efficiently aid in the heating process and if the foam glass feedstock comprises too little glass powder, too little foam glass is formed in relation to the amount of foam glass feedstock. Thus, the present content ranges regarding glass powder present an advantageous relationship regarding efficiency and output.

[0028] In an aspect of the invention, the foam glass feedstock comprises between 3% and 60%, preferably between 7% and 50%, and most preferred between 10% and 40% composite powder by weight before the foam glass feedstock is heated.

[0029] If the foam glass feedstock comprises too much composite powder, the composite powder will produce more heat than needed during the heating process and the process becomes inefficient - and / or the manufacturing process could become so hot that it could damage the manufacturing facilities. However, if the foam glass feedstock comprises too little composite powder, the composite powder is not able to efficiently aid in the heating process. Thus, the present content ranges regarding composite powder are advantageous regarding efficiency. In an aspect of the invention, the foam glass feedstock comprises between 0.2% and 10%, preferably between 0.5% and 8%, and most preferred between 1% and 5% foaming agent by weight before the foam glass feedstock is heated.

[0030] If the foam glass feedstock comprises too much foaming agent, the excess foaming agent will have no effect on the resulting foam glass, or it could even produce a too porous foam glass. However, if the foam glass feedstock comprises too little foaming agent, the desired porous structure will not be formed in all the foam glass. Thus, the present content ranges regarding foaming agent present an advantageous relationship regarding cost and foam glass quality.

[0031] In an aspect of the invention, the foam glass feedstock is heated to a temperature of between 600°C and 1600°C, preferably between 700°C and 1500°C, and most preferred between 800°C and 1400°C.

[0032] If the foam glass feedstock is heated too much, no further advantageous effects are obtained, and energy is just wasted. However, if the foam glass feedstock is heated too little, the desired porous structure will not be formed. Thus, the present temperature ranges present an advantageous relationship regarding cost and foam glass quality.

[0033] In an aspect of the invention, the waste composite material comprises between 1% and 80%, preferably between 4% and 70%, and most preferred between 10% and 60% resin by weight.

[0034] If the waste composite material comprises too much resin, the composite material will produce more heat than needed during the heating process and the process becomes inefficient. However, if the composite material comprises too little resin, the composite material is not able to efficiently aid in the heating process. Thus, the present content ranges regarding resin are advantageous regarding efficiency. The resin content may be determining by a chemical analysis of the waste composite material or through a calorific value measurement as will be described in the following.

[0035] In an aspect of the invention, the waste composite material comprises Per- and polyfluoroalkyl substances (PF AS).

[0036] PF AS can lead to health problems such as liver damage, thyroid disease, obesity, fertility issues and cancer, and PF AS is also environmentally damaging. However, PF AS is a very hard to break down or decompose but by using waste composite material comprising PFAS in the foam glass production process, an additional advantage is obtained, in that the PFAS decompose in the procedure due to the very high temperature necessary for forming foam glass. Thereby adding additional value to the present foam glass production method.

[0037] In an aspect of the invention, the glass material comprises Per- and polyfluoroalkyl substances (PFAS).

[0038] PFAS can lead to health problems such as liver damage, thyroid disease, obesity, fertility issues and cancer and PFAS is also environmentally damaging. However, PFAS is a very hard to break down or decompose but by using glass material comprising PFAS in the foam glass production process, an additional advantage is obtained, in that the PFAS decompose in the procedure due to the very high temperature necessary for forming foam glass. Thereby adding additional value to the present foam glass production method.

[0039] In an aspect of the invention, the glass powder, the composite powder and the foaming agent is mixed so that said resulting foam glass feedstock comprises between 1% and 50%, preferably between 3% and 40%, and most preferred between 5% and 30% resin by weight. If the foam glass feedstock comprises too much resin, the resin will produce more heat than needed during the heating process and the process becomes inefficient - and / or the manufacturing process could become so hot that it could damage the manufacturing facilities. However, if the foam glass feedstock comprises too little resin, the resin is not able to efficiently aid in the heating process. Thus, the present content ranges regarding resin are advantageous regarding efficiency.

[0040] The resin content may be determining by a chemical analysis of the waste composite material or through a calorific value measurement as will be described in the following.

[0041] In an aspect of the invention, the method further comprises determining the resin content of the waste composite material, composite powder and / or of the foam glass feedstock before heating the foam glass feedstock.

[0042] Determining the resin content (absolute or relative) of the waste composite material before it is mixed with the other components to form the foam glass feedstock, determining the resin content (absolute or relative) of the composite powder before it is mixed with the glass powder and the foaming agent and / or determining the resin content (absolute or relative) of the foam glass feedstock after the waste composite material has been mixed with the other components to form the foam glass feedstock is advantageous in that when the resin content is known and the subsequent heating process hereby can better be controlled to run more efficiently.

[0043] The resin content of the waste composite material, the composite powder and / or of the foam glass feedstock can be determined through a chemical analysis, or directly or indirectly by determining the calorific value of the waste composite material, the composite powder and / or of the foam glass feedstock. The calorific value can be measured by use of a calorimeter. A specific amount of the waste composite material, composite powder and / or of the foam glass feedstock is first combusted with Oxygen, under pressure, in a sealed “bomb”. Then, the heat of the subsequent reaction is measured from the temperature rise of a surrounding water bath. By calibration of the calorimeter system with, for example, thermochemical grade Benzoic Acid, the Gross Calorific value at constant volume is determined. The calorific value can also be measured by use of Dulong's Formula or in one of the other ways known to the skilled person.

[0044] In an aspect of the invention, the method further comprises determining the calorific value of the waste composite material, the composite powder and / or of the foam glass feedstock before heating the foam glass feedstock.

[0045] Determining the calorific value (absolute or relative) of the waste composite material before it is mixed with the other components to form the foam glass feedstock, determining the calorific value (absolute or relative) of the composite powder before it is mixed with the glass powder and the foaming agent and / or determining the calorific value (absolute or relative) of the foam glass feedstock after the waste composite material has been mixed with the other components to form the foam glass feedstock is advantageous, in that the calorific value (absolute or relative) is hereby known and the subsequent heating process hereby can better be controlled to run more efficiently based on this information.

[0046] In an aspect of the invention, the method further comprises obtaining the waste composite material from wind turbine blade parts formed by a fiberglass and resin material before grinding the waste composite material into a composite powder.

[0047] As more and more wind turbines are erected the problem of getting rid of the environmentally hazardous wind turbine blades - when the wind turbines have served their time - is growing and it is therefore advantageous if the waste composite material is obtained from wind turbine blade parts formed by a fiberglass and resin material.

[0048] In an aspect of the invention, the method further comprises obtaining at least a portion of the glass material from solar panels before grinding the glass material into glass powder.

[0049] The glass from solar panels typically comprises a PF AS containing coating. PFAS can lead to health problems such as liver damage, thyroid disease, obesity, fertility issues and cancer and PFAS is also environmentally damaging. However, PFAS is a very hard to break down or decompose but by using solar panel glass comprising PFAS in the foam glass production process, an additional advantage is obtained, in that the PFAS decompose in the procedure due to the very high temperature necessary for forming foam glass. Thereby adding additional value to the present foam glass production method.

[0050] In an aspect of the invention, the resin comprises polyester resin, polyurethane resin, vinyl ester resin and / or epoxy resin.

[0051] Polyester resin, polyurethane resin, vinyl ester resin and epoxy resin - reinforced by fiberglass - is widely used in wind turbine blades, circuit boards, ship hulls, airplane parts, car parts, flooring and other products that are problematic to get rid of after end of use. Furthermore, these specific resins have a very high heating value making them particularly suited for the method according to the present invention.

[0052] In an aspect of the invention, the foaming agent comprises a sulphate or a carbonate, such as CaCO3.

[0053] Sulphate or carbonate - such as CaCO3 - is particularly suited as a foaming agent when producing foam glass in that they are inexpensive and efficient at generating the desired cellular structure in the foam glass. In an aspect of the invention, the waste composite material being grinded has an ultimate tensile strength between 20 and 5000 MPa, preferably between 30 and 4500 MPa, and most preferred between 40 and 4000 MPa.

[0054] Hereby is achieved an advantageous embodiment of the invention.

[0055] In an aspect of the invention, the waste composite material has not been heated to a temperature above 100°C before the waste composite material is grinded into composite powder.

[0056] Using waste composite material that has not been heated to a temperature above 100°C before the waste composite material is grinded into composite powder is advantageous, in that this simplifies foam glass production - no extra heating process, simpler logistics, less production equipment, etc. - and in that the waste composite material will maintain its very high calorific value so that the resin in the waste composite material better reduces the energy needed to generate the necessary high temperatures needed for producing foam glass.

[0057] The invention provides for foam glass produced by means of a method according to any of the preceding methods.

[0058] Hereby is achieved an advantageous embodiment of the invention.

[0059] Figures

[0060] The invention will be described in the following with reference to the figures in which fig. 1 illustrates a simplified embodiment of a method for producing foam glass, and fig. 2 illustrates a simplified table of a method for producing foam glass.

[0061] Detailed description of related art

[0062] Fig. 1 illustrates a simplified embodiment of a method for producing foam glass 1. In this embodiment glass material 2 is obtained from broken windows but in another embodiment the glass material 2 could be obtained from solar panels, food jars, bottles, computer screens or other or any combination thereof. The broken glass material 2 is fed into a grinder 10 in which the glass material 2 is grinded into a glass powder 3 having a particle size of around 100 microns, which means that the largest particles in the resulting glass powder 3 is around 100 microns but most particles are smaller than 100 microns and a very few are bigger. Once the glass material 2 has been grinded into the desired particle size, the resulting glass powder 3 is in this embodiment led into a mixing container 12.

[0063] In this embodiment the waste composite material 4 is obtained from decommissioned wind turbine blades comprising a mix of fiberglass 5 and epoxy resin 6 but in another embodiment the waste composite material 4 could be obtained from furniture, building materials, car parts, boat hulls or other things comprising fiberglass 5 held together in a resin 6 matrix. Thus, in another embodiment the resin 6 could also or instead comprise polyester resin, polyurethane resin, vinyl ester resin and / or another type of resin 6 or any combination thereof. In this embodiment the waste composite material 4 has first been broken down to smaller pieces before the waste composite material 4 is fed into a grinder 10 in which the waste composite material 4 is grinded into a composite powder 8 having a particle size of around 100 microns. In this embodiment the glass material 2 and the waste composite material 4 is grinded in two separate grinders 10 but in another embodiment the glass material 2 and the waste composite material 4 could be grinded in the same grinder 10 or in several separate grinders 10. Once the waste composite material 4 has been grinded into the desired article size, the resulting composite powder 8 is in this embodiment led into a mixing container 12.

[0064] After the grinding process and before the composite powder 8 is led into the mixing container 12, the resin 6 content of the composite powder 8 is in this embodiment determined by drawing a sample of the composite powder 8 which is analyzed in a laboratory after which the laboratory provides a percentage by weight of resin in the sample. However, in another embodiment the resin 6 content could be established as a separate semi- or fully automated process step somewhere in the process before the composite powder 8 is led into a mixing container 12 or in another embodiment information regarding the resin 6 content could be obtained form the supplier of the waste composite material 4, from the original manufacturer of the waste composite material 4, from empirical studies, from other studies and / or other. Or in another embodiment the resin 6 content of the waste composite material 4 would not be determined and a fixed amount of composite powder 8 would always be included in the foam glass feedstock 7 and / or composite powder 8 would be added to the heating process in response to the temperature during the heating process or other.

[0065] In this embodiment the glass powder 3 and the composite powder 8 is led into the same mixing container 12. A foaming agent 9 - in this case in the form of calcium carbonate - is in this embodiment also led into the mixing container 12, and the three ingredients are mixed by means of a mixer 11 to form the foam glass feedstock 7. However, in another embodiment the foaming agent 9 could be added to the glass powder 3 or the composite powder 8 before the mixing step in the mixing container 12 or in another embodiment the system would not comprise a mixing container 12 and / or a mixer 11 and the components 5, 8, 9 could also or instead be mixed in the subsequent moulds 13, during a transportation process or other.

[0066] In this embodiment the laboratory tests have shown that the resin content of the wind turbine blades forming the waste composite material 4 is around 40% by weight. In this embodiment the desired amount of resin 6 in the resulting foam glass feedstock 7 should be around 17% by weight and in this embodiment 4% by weight of foaming agent is desired in the resulting foam glass feedstock 7. Thus, in this embodiment the foam glass feedstock 7 is mixed so that it contains around 50% by weight of glass powder 3 and around 46% by weight of composite powder 8 to make the resulting foam glass feedstock 7 have a resin content around the desired 17% by weight. However, in another embodiment the desired amount of resin 6 in the resulting foam glass feedstock 7 could be lower - such as 15%, 11%, 8% or even lower - or higher - such as 19%, 22%, 27% or even higher - e.g., depending on the specific type of resin 6, heat loss during the heating process, the desired maximum temperature during the heating process or other.

[0067] In another embodiment additional additives - such as foam promoters, pigments, activators or other - could also be added to the foam glass feedstock 7 before the heating process - e.g., during the mixing process - to alter or enhance properties of the foaming agent 9, to dye the resulting foam glass 1, to provide additional qualities to the foam glass 1 or other.

[0068] After the foam glass feedstock 7 has been mixed the foam glass feedstock 7 is in this embodiment placed in moulds 13 and led into a heating device 14 where the foam glass feedstock 7 is heated to sinter the glass powder 3 and the fibre glass 5 in the composite powder 8, to ignite and burn the resin 6 in the composite powder 8, and to activate the foaming agent 9 to generate the desired cellular structure in the resulting foam glass 1. However, in another embodiment foam glass feedstock 7 would not be arranged in moulds 13 during the heating process - i.e., in another embodiment the foam glass feedstock 7 would simply be pre-shaped or the foam glass feedstock 7 would be placed on pans, plates, trays or the like and after the heating process the heating process the foam glass would be cut or by other means given its desired shape.

[0069] In this embodiment the foam glass feedstock 7 is heated to a temperature of 1300°C in the heating device 14, in that in this embodiment the wind turbine blades - which in this case is forming the waste composite material 4 - are surface treated with a PF AS containing substance and to ensure that all the PF AS has been degraded it is in this embodiment advantageous that the foam glass feedstock 7 is heated to 1300°C. However, in another embodiment the foam glass feedstock 7 could be heated to a lower temperature - such as 1200°C, 1100°C, 1000°C or even lower - or the foam glass feedstock 7 could be heated to a higher temperature - such as 1450°C, 1550°C, 1700°C or even higher, e.g., depending on the specific waste composite material 4, the specific heating device 14, desired properties of the resulting foam glass, the specific foaming agent 9 or other.

[0070] Once the foam glass feedstock 7 has been turned into foam glass 1 in the heating device 14 the foam glass 1 is led out of the heating device 14 to cool down and be removed from the moulds 13. Subsequently, the foam glass 1 can e.g., be cut into desired shapes and sizes.

[0071] Fig. 2 illustrates a simplified table of a method for producing foam glass 1. In this embodiment the first method step 15 comprises breaking the glass material 2 into smaller pieces before grinding the glass material 2 into glass powder 3 in a second method step 16. However, in another embodiment the current first method step 15 could be omitted, and the first method step 15 would instead be the grinding of the glass material 2 which is currently the second method step 16. After the grinding process in the second method step 16 the glass powder 3 is in this embodiment subjected to a screening process in a third method step 17 to remove substantially all particles in the glass powder 3 having a size over a predetermined size. However, in another embodiment the screening process in the third method step 17 could be formed integrally with the grinding process in the second method step 16 or the screening process in the third method step 17 could be omitted if the grinding process in the second method step 16 produced glass powder 3 of a satisfactory quality.

[0072] In this embodiment the fourth method step 18 comprises shredding the waste composite material 4 into smaller pieces before grinding the waste composite material 4 into composite powder 8 in a fifth method step 19. However, in another embodiment the current fourth method step 18 could be omitted, and the fourth method step 18 would be the grinding of the waste composite material 4 which is currently the fifth method step 19. After the grinding process in the fifth method step 19 the composite powder 8 is in this embodiment subjected to a screening process in a sixth method step 20 to remove substantially all particles in the composite powder 8 having a size over a predetermined size. However, in another embodiment the screening process in the sixth method step 20 could be formed integrally with the grinding process in the fourth method step 19, the sixth method step 20 could be formed integrally with the grinding process in the second method step 16 and the fifth method step 19 if the glass material 2 and the waste composite material 4 was grinded in a common process, or the screening process in the sixth method step 20 could be omitted if the grinding process in the fifth method step 19 produced composite powder 8 of a satisfactory quality. And / or in another embodiment larger fibreglass strands could be included in the composite powder 8 in that these fibers can have a positive effect on the generation of the desired foam glass quality during the sintering process.

[0073] After the glass powder 3 has been screened in the third method step 17 and the composite powder 8 has been screened in the sixth method step 20, the glass powder 3 and the composite powder 8 is in this embodiment mixed in a seventh method step 21. In an eighth method step 22 foaming agent 9 is added to the mixing process - i.e., the seventh method step 21 - to form the foam glass feedstock 7. However, in another embodiment the foaming agent 9 could be added to the composite powder 8 and / or the glass powder 3 in a previous step.

[0074] After mixing, the foam glass feedstock 7 is heated in a ninth method step 23 - in this embodiment to a temperature of 1000°C. During the heating process the foam glass feedstock 7 is transformed into foam glass 1 and after the foam glass has been made, the foam glass 1 is cooled down in a tenth method step 24 - in this case to a temperature of 20 - 40°C so that the foam glass 1 can be handled. However, in another embodiment the foam glass 1 is cooled down to another temperature e.g., depending on the specific process, the ambient temperatures, the specific foam glass feedstock 7 or other.

[0075] It should be noted that in another embodiment the method could include further method steps - such as quality testing steps, resin content determining steps, weighing step, steps comprising addition of further ingredients and other. It should also be noted that some of the method steps 15-24 could be performed in another order or simultaneously. I.e., in another embodiment the first step would be to grind the waste composite material 4, in another embodiment the addition of the foaming agent 9 could be performed during or after steps 15-20 and so on.

[0076] The invention has been exemplified above with reference to specific examples of glass material 2, waste composite material 4, foaming agents 9 and other. However, it should be understood that the invention is not limited to the particular examples described above but may be designed and altered in a multitude of varieties within the scope of the invention as specified in the claims. List

[0077] 1. Foam glass

[0078] 2. Glass material

[0079] 3. Glass powder

[0080] 4. Composite material

[0081] 5. Fiberglass

[0082] 6. Resin

[0083] 7. Foam glass feedstock

[0084] 8. Composite powder

[0085] 9. Foaming agent

[0086] 10. Grinder

[0087] 11. Mixer

[0088] 12. Mixing container

[0089] 13. Mould

[0090] 14. Heating device

[0091] 15. First method step

[0092] 16. Second method step

[0093] 17. Third method step

[0094] 18. F ourth method step

[0095] 19. Fifth method step

[0096] 20. Sixth method step

[0097] 21. Seventh method step

[0098] 22. Eighth method step

[0099] 23. Nineth method step

[0100] 24. Tenth method step

Claims

Claims1. A method for producing foam glass (1), said method comprising the steps of:• grinding a glass material (2) into glass powder (3),• grinding a waste composite material (4) comprising fiberglass (5) and resin (6) into a composite powder (8), wherein said waste composite material has an ultimate tensile strength above 20 MPa,• mixing said glass powder (3), said composite powder (8) and a foaming agent (9) to form a foam glass feedstock (7), and• heating said foam glass feedstock (7) to a temperature of at least 600°C.

2. A method according to claim 1, wherein said glass material (2) is grinded into glass powder (3) having a particle size of between 10 and 900 microns, preferably between 30 and 600 microns, and most preferred between 50 and 300 microns.

3. A method according to claim 1 or 2, wherein said waste composite material (4) is grinded into composite powder (8) having a particle size of between 10 and 900 microns, preferably between 30 and 600 microns, and most preferred between 50 and 300 microns.

4. A method according to any of the preceding claims, wherein said method further comprises screening said glass powder (3) before mixing said glass powder (3), said composite powder (8) and said foaming agent (9).

5. A method according to any of the preceding claims, wherein said method further comprises screening said composite powder (8) before mixing said glass powder (3), said composite powder (8) and said foaming agent (9).

6. A method according to any of the preceding claims, wherein said foam glass feedstock (7) comprises between 40% and 97%, preferably between 50% and 94%,and most preferred between 60% and 90% glass powder (3) by weight before said foam glass feedstock (7) is heated.

7. A method according to any of the preceding claims, wherein said foam glass feedstock (7) comprises between 3% and 60%, preferably between 7% and 50%, and most preferred between 10% and 40% composite powder (8) by weight before said foam glass feedstock (7) is heated.

8. A method according to any of the preceding claims, wherein said foam glass feedstock (7) comprises between 0.2% and 10%, preferably between 0.5% and 8%, and most preferred between 1% and 5% foaming agent (9) by weight before said foam glass feedstock (7) is heated.

9. A method according to any of the preceding claims, wherein said foam glass feedstock (7) is heated to a temperature of between 600°C and 1600°C, preferably between 700°C and 1500°C, and most preferred between 800°C and 1400°C.

10. A method according to any of the preceding claims, wherein said waste composite material (4) comprises between 1% and 80%, preferably between 4% and 70%, and most preferred between 10% and 60% resin (6) by weight.

11. A method according to any of the preceding claims, wherein said waste composite material (4) comprises Per- and polyfluoroalkyl substances (PF AS).

12. A method according to any of the preceding claims, wherein said glass material(2) comprises Per- and polyfluoroalkyl substances (PF AS).

13. A method according to any of the preceding claims, wherein said glass powder(3), said composite powder (8) and a foaming agent (9) is mixed so that saidresulting foam glass feedstock (7) comprises between 1% and 50%, preferably between 3% and 40%, and most preferred between 5% and 30% resin (6) by weight.

14. A method according to any of the preceding claims, wherein said method further comprises determining the resin (6) content of said waste composite material (4), said composite powder (8) and / or of said foam glass feedstock (7) before heating said foam glass feedstock (7).

15. A method according to any of the preceding claims, wherein said method further comprises determining the calorific value of said waste composite material (4), said composite powder (8) and / or of said foam glass feedstock (7) before heating said foam glass feedstock (7).

16. A method according to any of the preceding claims, wherein said method further comprises obtaining said waste composite material (4) from wind turbine blade parts formed by a fiberglass (5) and resin (6) material before grinding said waste composite material (4) into a composite powder (8).

17. A method according to any of the preceding claims, wherein said method further comprises obtaining at least a portion of said glass material (2) from solar panels before grinding said glass material (2) into glass powder (3).

18. A method according to any of the preceding claims, wherein said resin (6) comprises polyester resin, polyurethane resin, vinyl ester resin and / or epoxy resin.

19. A method according to any of the preceding claims, wherein said foaming agent (9) comprises a sulphate or a carbonate, such as CaCO3.

20. A method according to any of the preceding claims, wherein said waste composite material (4) being grinded has an ultimate tensile strength between 20 and5000 MPa, preferably between 30 and 4500 MPa, and most preferred between 40 and 4000 MPa.

21. A method according to any of the preceding claims, wherein said waste composite material (4) has not been heated to a temperature above 100°C before said waste composite material (4) is grinded into said composite powder (8).

22. Foam glass (1) produced by means of a method according to any of the preceding claims.

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