SE2200045A1 - A composition for a sleeper and methods to produce sleepers based on used wind turbine blades - Google Patents

Abstract

Summary:This invention concerns recycling of composite materials such as used wind power blades, novel compositions of articles-ofuse such as railway sleepers or construction or architectural elements, and methods to produce such articles. Said articles comprise sections of used wind power blades, other materials made from used wind power blades in powder or fiber form, and thermoplastic polymers such as polyolefins, e.g. polyethylene (PE) and polypropylene (PP) and polyesters, e.g. polyethyleneterephtalate (PET) as binder material.Preferred embodiments, designs and production methods are described in detail.

Description

Definitions: Composites: shall be understood as materials comprising inorganic and organic materials including glass fibre or carbon fibre and wood, and binder materials, including thermosets such as epoxy or polyurethane or thermoplastics, see below. In particular, wind power blades or sections thereof are composites according to the invention, and sections cut-to-size for use in this invention may comprise carbon or glass fibres, wooden support or beam structures, epoxy or polyurethane coatings and binders and hard foam sections.

Thermoplastics: shall be considered as the group of polymers which melt at a temperature in the range 60 - 200 OC, specifically comprising polyolefins, including polyethylene (PE), polypropylene (PP), polyesters including polyethyleneterephtalate (PET) and polylactic acid (PLA), polystyrene, polyvinylchloride (PVC), thermoplastic elastomers such as SBS, SIS, SEBS and other plastics and mixtures or compounds of said plastic types, also collectively called "polymer" or "thermoplastics" below, which can be processed in compounding devices such as twin-screw compounding machines or in extruders. Compounding device(s): shall denote any intensive mixer, such as kneaders, batch mixers, continuous mixers, extruders capable of mixing materials, such as planetary extruders and twin-screw compounders which are able to mix polymer blends under pressure. Venting and removal of gases such as water vapour in a controlled manner, e.g. by pressure relief valves or extruder sections which allow controlled gas removal, are advantageous in this invention as some raw materials for the articles-of-use described later may be humid.

Field of the invention: This invention relates to recycling of composites, specifically used wind power turbine blades and Sections thereof. The invention also relates to articles~of-use such as railway sleepers or construction or architectural elements such as load-carrying beams, and to methods to produce such articles.

Background and prior art: A limited number of disclosures and scientific articles describe the recycling of wind power blades. The issue is relatively new as the expansion of wind power in the past 20 years only now generates a predictable and sizeable flow of used wind power blades of known composition and known properties. Blades have a lifetime of about 15 years. In Scandinavia and Germany alone, a total of >40 000 installed turbines generates a flow of about 40 000 tons of used blades annually (at 5 ton/blade).

Typically, wind power blades are cut and ground to powder form. To the extent possible, fractions such as glass fibre, wood, plastics etc are separated according to methods known in the art of recycling. Some powder streams are used as fillers for railway sleepers, see e.g. an initiative by Eneco in The Netherlands: https://news.eneco.com/old-wind-turbines~become- railwav-sleepers/ In a recent article (2018), J.P. Jensen et al. describe "Wind turbine recycling: Experiences, challenges and possibilities in a circular economy", see https://www.researchqate.net/publication/329342l50_Wind_turbin e_blade_recVclinq_Experiences_challenges_and_possibilities_in_ a_circular_economv In general, separating and recirculating raw materials directly to identical or similar applications is considered most appropriate in circular economy thinking. Use of materials in new applications is considered "down-cycling". This invention is an example that "down cycling" can be highly appropriate, better for the environment and cheaper for all stakeholders such as wind power blades suppliers, recycling companies, customers for long-lived articles of use such as railway sleepers, and society.

In fact, Geiger et al., in their 2020 article "Composite wind turbine blade recycling - value creation through Industry 4.0 to enable circularity in repurposing of composites", describe cases where whole sections of used wind blades are used as roofs or architectural components for bridges and the like. These examples are very convincing, however, they are difficult to scale, i.e. difficult to apply in a mass production of articles for industries under cost pressure. See https://iovëcience.ioD~orG/article/10.1088/1757- 899X/942/1/012016/pdf Korniejenko et al., in their review article "Tackling the circular economy challenges - composites recycling: used tyres, wind turbine blades and solar panels" (see J. Compos. Sci. 2021, 5, 243. httpsz//doi.org/lO.3390/ics5090243, describe the various options for recycling of blades such as material recovery, chemical recovery, incineration.

Industrial companies are active in the field of recyling wind power blades. Typically, they cut blades and grind the materials to powder or fiber form. An example is the German company Roth, see: https://www.roth-international.de/en/recVcling- recoverv/recvcling-of-rotor- blades/?gclid=EAIaIQobChMI79SsoMv38wIVisSvCh2bQQetEAMYASAAEgL6 KfD_BwE Regarding articles-of-use, in particular railway sleepers, reference is made to general publications: A Wikipedia article gives a general overview over the field, see https://en.wikipedia.org/wiki/Railroad_tie , and, more specifically on concrete sleepers: https://en.wikipedia.org/wiki/Concrete_sleeper There is a demand in the railway industry for functional, cheap and sustainable railway sleepers. Functional demands relate to hardness, stability in use, mechanical properties, ease of application etc. The industry has to be cost- competitive, therefore prices are a prime selection criterion. Public purchasing has to take environmental arguments seriously in consideration, therefore concrete sleepers with their inherently high carbon footprint will be de-selected by public (and privatel) purchasing provided that equally performing alternatives are available.

Railway sleepers, one of the target application of this invention, are caracterized by these general facts: Typical dimensions l x b x h (cm) 260 x 26 x 16 (heavy haul track sleeper), typical weight wood (creosote impregnated): 80-115 kg, in the case of steel reinforced concrete: 360 kg. Typical distance between sleepers is 0,70 m. 6 mill.

Sleepers, EU: 208.000 km railways giving about 297 mill.

Market demand Norway: 4.200 km railways giving about Sleepers, WORLD: 1.307.000 km railways giving about 1.867 mill. sleepers. Market demand for sleepers is in a similar order of magnitude as the potential supply of components from used wind turbine blades which makes this invention highly attractive on the market place.

A railway sleeper is but one example of a useful application of used composites from the wind industry. In the building industry, beams and load-carrying components are required, typically in the form of steel, wood. The invention allows to replace steel and wood, and as composites can be cut-out to meet specific requirements, the invention meets an existing market demand.

General characteristics of wind turbine blades are as follows: Typical blades of 37 m length weight 5.000 kg per blade, of 47 m length: 12.500 kg per blade, >47 m length > 15.000 kg per blade. Typical composite materials are: - 40 % Thermoset resin systems and gelcoats (epoxy, vinylester, polyester), - 35 % Glass fiber reinforcement (multiaxial, uni-directional and woven mats, optimized for overall max stiffness and strength control, - 25 % Sandwich core materials for increased stiffness and weight reduction (PVC, BALSA, PET).

Given the prior art, the objective of this invention is to provide novel architectural components, especially but not limited to railway sleepers, based on recycled wind power blade parts and binders, with excellent or very acceptable properties regarding strength, processability, ability to manufacture cheaply, and other properties, all allowing to use waste such as used wind power blades in a better and more sustainable manner. It is also an objective of this invention to provide methods to produce such sleepers for standardized mass applications. The term "sleeper" or "sleepers" is, for simplicity, being used for all architectural or structural components with dimensions of a minimum / maximum length of 30 cm / 6 meter, and a minimum / maximum weight of l kg / 500 kg, said "sleepers" being suitable in mass applications. The invention shall, however, not be limited by said minimum and maximum values.

Description of figures: Fig. l is a schematic drawing of a sleeper according to the invention, made of used wind turbine blade sections and other materials in typical dimensions 3 m length, 0,16 m height and O,25m width. The following figures show examples of possible cross sections.

Fig 2 is an example of a possible cross section. The different materials, laminates, blocks, binders are explained.

Figures 3-5 are further examples or configurations of cut-out sections, fillers and binders.

Fig. 6 is a schematic drawing of the production process for sleepers. 2= extruder, capable of extruding binder and optionally binder mixed with granulated solid waste. 6= form or mould already containing sections of wind blades into which binder is pressed or injected in liquid form. Note that this figure is just one potential embodiment as described below. Various modifications of injection moulding, inlet moulding, 2-component moulding and even semi-continuous or continuous processes similar to pultrusion are conceivable and within the spirit of this invention.

Fig. 7 shows suitable areas for cutting out elements from used wind turbine blades for stable sleepers. Other areas (highlighted) are more suitable for grinding to powder or fibres, these materials are more suitable as fillers, mixed with thermoplastics.

Fig. 8 shows product examples, profiles prepared from strong laminate (A) and reinforced thermoplastic profiles with high fiber content (B) Fig 9 shows an example of an I-beam made of composite parts (red) which are placed into a matrix (right part of the picture). Subsequently, these elements may be connected using further composite parts to form the article or beam shown in the left part of the figure.

Fig l0 shows a pillar produced by placing composite sections (red) into a matrix which may consist of fiber-reinforced thermoplastic polymer (ideally recycled). The composite parts may be fastened by glue, and the final pillar may be covered by an extra protective layer, such as a film or as extruded polymer.

Brief description of the invention: The general idea is to dis-assemble used wind turbine blades mechanically into suitable sections and to produce new, strong construction elements for long-life applications such as railway sleepers or building elements. The process includes a) cutting blades in appropriate pieces for easy logistics, b) selecting pieces with documented strength properties and suitable geometry (essentially flat), c) disassemble core materials and grind, slice and surface-treat multiaxial reinforced laminate products that have high modulus and strength properties, d) grind other laminate into small particles, e.g. 2-5 mm, mix with about 50% (range 25-75%) thermoplastics, and produce appropriate beam elements or blocks with high fiber / solids content by extrusion or injection moulding, d) handle other excess waste such as polymer dust, foams etc, according to relevant instructions.

In detail, the invention describes improved compositions and production methods for structural elements for building applications, in particular but not limited to railway sleepers, comprising the following general steps: a)Suitable composite sections of 0,3 to 22 m length are cut out from used wind power blades, kn At least one section is placed in a mould which reflects the dimensions of the desired finished article, c) Other sections and materials may be added, and the sections are connected by glueing or binder systems, d)A.final article is obtained which is useful as architectural element such as load-bearing beam or a railway sleeper.

In a more advanced version, the method may comprise the following steps: a) suitable sections are cut out from used wind power blades, b) at least one section is placed in a mould or vessel defining the dimensions of the desired article, whereby said mould whereby said mould can be an open or closed vessel or a pre-fabricated matrix, e.g. made of fibre-reinforced plastic, ll c) optionally, other sections and other solid materials are placed in said mould, and these sections are optionally glued together to achieve mechanical stability during the subsequent injection of, as the case may be, molten binder or during the application of other type of bonding systems, d) a binder formulation, comprising at least one thermoplastic polymer and optionally up to 50% by weight solid waste particles such as grinded composite material from used wind power blades, is prepared in a kneading device such as an extruder, e) said binder formulation is transported into the mould or vessel to fill the volume to the desired degree, f) said mould is allowed to cool until the binder solidifies, g) the article such as the sleeper is subjected to finishing steps which may include mechanical treatment, fastening of further elements, drilling of holes and the like, said methods, compositions and steps further characterized by: - The cut-out sections from used wind blades are typically limited in length by the interval 0,3 m up to 6 m, but may be up to 22 m, - The finished article is limited in weight by the interval 1 kg up to 500 kg per meter, - The weight content of used wind power blade sections in the finished article is at least 30%, more preferable above 40%, even more preferable above 50%.

Embodiments of the invention: Methods and compositions and finished products are described in the following section. Example l: Example 1 relates to a sleeper consisting of 40% by weight wind power blade cut-out section, the remainder 12 being thermoplastic polymer comprising 40% by weight solid waste, mainly consisting of granulate and fibers from grinded wind power blades. The cut-out sections are selected from certain areas of the wind turbine blade, see figure 7. Essentially, flat geometries are preferred for standardized processes and Certification. If several sections are used, these may be glued together, e.g. using a polyurethane based glue which exhibits good adhesion to composite materials. The glueing may be performed in an open mould at atmospheric pressure.

Example 2: Example 2 relates to construction of buildings, such as commercial greenhouses. Load-carrying pillars, 4-10 m in height, and horizontal beams e.g. to carry the roof, 5-22 m in length, are made by combining cut-out sections from wind power blades and matrices e.g. made by extrusion. Figures 9 and 10 show possible configurations.

In one embodiment, thermoplastics are mixed with solid powders and fibres prepared from wind turbine blades in a kneading or mixing device such as an extruder, in particular a planetary roll extruder, and injected into a form already containing at least one composite element, i.e. a cut-out turbine blade section or a plurality of such sections.

In one embodiment, one or more of polyethylene, polypropylene, polyolefins, polyester is used as thermoplastic binder.

In one embodiment, elastic materials such as styrene-butadiene block copolymers or polyvinylbutyrate (PVB) is added, among others to improve binding of solid materials.

In one embodiment, structural elements of thermoplastic binder mixed with solid powders or fibres are prepared independently and used in the same manner as cut-out sections from turbine 1,5 13 blades. Optionally, the plurality of cut-out sections and binder / solids beams or sections is glued together prior to filling the mould with additional binder material.

In one embodiment, glues and adhesives based on polyurethane, epoxy or acryl, i.e. thermosetting or permanently cross- linking adhesives are used as binder materials. Some of these adhesives, notably polyurethane, can expand during hardening, sometimes generating a structural foam. When composite parts are filled in a pre-fabricated matrix (se below), they may not fill the whole cavity, and it may be difficult to produce parts which exactly fit a cavity such as shown in figures, see e.g. 9 and 10. An expanding adhesive will fill out the whole cavity and provide excellent adhesion between matrix and composite part.

In one embodiment, bio-based fibers such as wood fibers or olive residues are used as fillers.

In one embodiment, minerals are used as additional fillers. In one embodiment, flame-retarding materials are used as additional fillers.

In one embodiment, the mould is formed such that sensors, mechanical fastening elements, cable ducts and the like can easily be connected to the final products, e.g. by leaving holes or cavities in the otherwise bar-like geometry.

In one embodiment, the finished sleeper is encapsulated in a protective outer layer which may be thermoplastic or a thermoset.

In one embodiment, hollow sections are left in the final product for easier cooling of the final product, or as functional cavity, e.g. serving as cable duct. 14 In one embodiment, see in particular figures 9 and 10, a matrix is produced, e.g. based on fibers and other residues from the inner parts of wind turbine blades and e.g. a thermoplastic binder. By extrusion of these materials, pre- fabricated matrices in many geometries can be provided. Cavities in this matrix can be filled with wind turbine sections such as rods, plates or other geometries. These sections can be glued to the matrix using adhesives such as described above. Different sections can be glued together, using even more wind turbine sections. Beams and pillars can be produced in this manner. In particular thermosetting adhesives which expand slightly upon hardening are useful, as the complete cavities will be filled, resulting in strength of the finished article. The matrix may contain thermoplastic binder such as LDPE (low density polyethylene) and elastic materials such as EVA (ethylvinylacetate) which accommodate deformation of the finished article in use.

The following table shows materials to be used in an embodiment: MATERIALS FOR ONE (260cm x 26cm x 16cm) SLEEPER VVEKSHT 96 (ke) OF (estimated) TOT The density of a sleeper will be the weighted average of the components, it will thus be in the range of 0,8-1,2 g/cm3, to be compared with 1,4 for wood/creosote and >2 for concrete, at comparable strength and reduced brittleness (versus concrete).

In one embodiment, the finished article such as shown in fig 9 and 10, is used as load-carrying beam for construction of private or commercial buildings. Load-carrying beams need to be able to carry heavy loads, and the downward deflection of a beam must typically be lower than O,5% of its length, i.e. a beam of 10 m length may not deform downwards more than 50 mm. This is achievable using wind power sections according to this invention.

In one embodiment, beams designed according to one of the attached figures can be used as vertical pillars or as horizontally (plus or minus inclination for roof construction, e.g. 4 to 30%) placed beams. In this case, the same connection devices for connecting beams and pillars as known in the prior art may be used.

In one embodiment, the articles according to the invention can be used for construction purposes in wet environments where there would be a risk for corrosion of metal or degradation of wood. As an example, the walls of swimming pools, district or solar heating tanks or fish pools can be constructed using articles of this invention, together with suitable fastening elements, insulation materials, liners to prevent water leakage etc. In this sense, the articles of this invention can replace significant amounts of concrete. 16 In one embodiment, wood-plastic-composites (WPC) are improved in the following manner: WPC are used as flooring material e.g. for terraces. Often, WPC flooring material is provided as long extrudates, and they can be produced with cavities. Composite sections from used wind turbines can be inserted into these cavities, and the remaining volume can be filled with binder such as polyurethane or hotmelting glues based e.g. on thermoplastic elastomers. The resulting flooring slabs are significantly more stable than the ones with cavities. This technique is cheaper, easier and C02 saving compared to the alternative where shredded wind turbine blade powder is used to fill the cavities or the WPC as such.

The C02 footprint is drastically reduced by utilizing both larger cut~out sections as well as grinded powder and fibres based on used wind turbine blades.

Mechanical stability is, in general, increasing with maximising the content of sections and power / fibre residues. Some preferred final products, as apparent from above table, will be characterized by the following weight ratios of components whereby these ratios depend on the intended use: % weight cut-out sections in sleeper: range 10 -50%, possibly more, % weight solid powder/fibre in sleeper: 10 - 60% % weight thermoplastic polymer in sleeper: lO- 50%

Claims (11)

Claims:

1. A composition and a method to produce structural elements for building applications, such as railway sleepers, comprising the following steps: a)Suitable composite sections of 0,3 to 22 m length are cut out from used wind power blades, b)At least one section is placed in a mould which reflects the dimensions of the desired finished article, c) Other sections and materials may be added, and the sections are connected by glueing or binder systems, d)A final article is obtained which is useful as architectural element such as load-bearing beam or a railway sleeper.

2. A composition and a method to produce structural elements for building applications, such as railway sleepers, comprising the following steps: a) suitable sections are cut out from used wind power blades, b) at least one section is placed in a mould or vessel defining the dimensions of the desired article, whereby said mould whereby said mould can be an open or closed vessel or a pre-fabricated matrix, e.g. made of fibre-reinforced plastic, c) optionally, other sections and other solid materials are placed in said mould, and these sections are optionally glued together to achieve mechanical stability during the subsequent injection of, as the case may be, molten binder or during the application of other type of bonding systems, d) a binder formulation, comprising at least one thermoplastic polymer and optionally up to 50% by weight solid waste particles such as grinded composite material from used wind power blades, is prepared in a kneading device such as an extruder, 18 e) said binder formulation is transported into the mould or vessel to fill the volume to the desired degree, f) said mould is allowed to cool until the binder solidifies, g) the article such as the sleeper is subjected to finishing steps which may include mechanical treatment, fastening of further elements, drilling of holes and the like, said methods, compositions and steps further characterized by: - The cut~out sections from used wind blades are typically limited in length by the interval 0,3 m up to 6 m, but may be up to 22 m, - The finished article is limited in weight by the interval 1 kg up to 500 kg per meter, The weight content of used wind power blade sections in the finished article is at least 30%, more preferable above 40%, even more preferable above 50%.

3. The method according to claim 1 where the components of the final sleeper product are characterized by the following ratios: a) % weight cut-out sections in sleeper: range 10 -50%, possibly more, b) % weight solid powder/fibre in sleeper: 10 - 60%, c) % weight thermoplastic polymer i sleeper: 10- 50%

4. The method according to claim l or 2 where at least 2 cut- out sections from used wind turbine blades are part of the compositions, said sections covering at least 80% of the length of the sleeper.

5. The method according to one of the preceding claims where the sleeper or architectural element consists of both at least one cut-out section and at least one pre-formed bar, said bar 19 comprising grinded wind turbine blade waste in powder or fibre form and thermoplastic.

6. The method according to one of the preceding claims where thermoplastics such as polyethylene, polypropylene, polyolefin, polyesters, polyurethanes, elastomers such as SBS, SEBS, PVB are used, either as recycled material or Virgin polymer or mixture.

7. The method according to one of the preceding claims where polymer is extruded or injected into a mould comprising at least one cut-out section of a used wind turbine blade, and where said polymer may comprise more than 10% by weight solids in powder or fibre form, preferably more than 20% by weight.

8. The method according to one of the preceding claims where the bio-based solids such as wood fibres are mixed into the polymer.

9. A composition of the final sleeper product according to one of the preceding claims, which is characterized by the following ratios: a) % weight cut~out sections in sleeper: range 10 -50%, possibly more, b) % weight solid powder/fibre in sleeper: 10 - 60%, c) % weight thermoplastic polymer i sleeper: 10- 50%

10. A composition according to claim 7 where polymer is selected from recycled polyolefins, polyesters, polyurethanes and additives for elasticity, adhesion between solid and thermoplastic components.

11. 11. 11.ll. An article such as a composite article, or an extruded or injection-moulded article, and use of said ërticle as railway sleeper or general construction element with a length between 0,3-22 m, more often l-6 m, more preferably between 2,5-3,5 m.