Man-made vitreous fibre (MMVF) as mineral additive to high temperature energy conversion processes

Abstract

The invention is directed to a heat generation process, comprising the step of combusting biomass as fuel in a boiler, wherein the biomass or an admixture of the biomass and at least one other fuel, preferably coal, is combusted in the presence of an additive comprising man-made vitreous fibers (MMVF), in particular man-made vitreous fiber (MMVF) waste. The additive can avoid or mitigate slagging and fouling in boilers. Moreover, the use of waste materials provides a more sustainable and cost effective process.

Description

[0001] Man-Made Vitreous Fibre (MMVF) as mineral additive to high temperature energy conversion processes

[0002] Description

[0003] Field of the Invention

[0004] The present invention relates to a heat generation process, wherein biomass is combusted in the presence of an additive comprising mineral fibers, in particular mineral fiber waste, the respective use of the additive and a biomass fuel containing the additive. The biomass combustion may be co-firing of a fuel mixture comprising biomass and at least one other fuel.

[0005] Background of the Invention

[0006] Biomass fuels may contain high concentrations of alkalis, especially potassium, compared to coal and lignite. During combustion, these alkalis are vaporized depending on the combustion temperatures. After release, the alkaline components are deposed on boiler walls, heat exchangers etc. This phenomenon of so-called slagging and fouling leads to operational problems, reduction of the efficiency of the boiler and deactivation of the SCR (selective catalytic reduction) catalysts in the plant. These operational problems occur in different type of biomass-fired boilers.

[0007] Additives added to the combustion process are known to mitigate the effects by one or more of the following mechanisms: chemical sorption and interaction, physical adsorption, dilution effect and inert element enrichment, restraining and powdering effects (abrasion). Thus according to the literature, aluminosilicate-based additives have proven to be effective in mitigating the concentration of vaporized alkalis and / or reducing deposit formation in suspension-combustion conditions. Examples of such additives are kaolin, clay minerals (bentonite) and coal fly ash. Other additives based on sulphur and phosphor-calcium are also mentioned in literature.

[0008] Kaolin and clay minerals are primary materials and coal fly ash is a by-product of power generation, which is widely used for the production of cement and concrete.

[0009] Thus, primary materials are consumed in biomass-fired boilers for power and heat generation in large quantities to enhance performance and to reduce slagging, deposition, corrosion and emissions of both particulate as well as volatile compounds. The use of these primary materials as an additive in heat generation processes has a substantial impact on sustainability and operational costs.

[0010] Summary of the invention

[0011] In view of the above, it was an object of the present invention to provide means to avoid or mitigate slagging and fouling in boilers where biomass is combusted, which is sustainable and cost effective.

[0012] The inventors surprisingly found that this object could be solved by using mineral fibers, in particular mineral fiber waste, as an additive for the combustion of biomass in a boiler.

[0013] Accordingly, the present invention relates to a heat generation process, comprising the step of combusting biomass as fuel in a boiler, wherein the biomass or an admixture of the biomass and at least one other fuel, preferably coal, is combusted in the presence of an additive comprising man-made vitreous fibers (MMVF), in particular man-made vitreous fiber (MMVF) waste.

[0014] The inventive process enables the substitution of primary materials such as kaolin or clay minerals used as additives in the prior art processes by industrial waste. This has clear advantages from the point of sustainability. Primary resources are saved and voluminous industrial wastes can be utilized. Further, the final product (fly ash) can be used for production of construction materials like concrete.

[0015] Without wishing to be bound to any theory it is assumed that the achieved slagging and fouling in biomass combustion boilers by the use of the man-made vitreous fibers (MMVF), in particular the MMVF waste, as additive is mainly due to the capability of the mineral fibers in the waste to act as scavenger of alkali metals, especially potassium, in particular the ions thereof, under the conditions of the combustion process.

[0016] The use of MMVF as mineral additive or reagent for combustion processes has not yet been described in the prior art.

[0017] MMVF are amorphous and have a high specific surface which is advantageous for alkali scavenging, in particular potassium scavenging. Moreover, MMVF waste typically comprises a binder, often an organic binder, which can also have a beneficial effect in the inventive process as a secondary fuel and possibly as a de-NOx compound.

[0018] The main benefits of the additives comprising MMVF, in particular MMVF waste, used in the inventive process can be summarized as follows:

[0019] - The addition of the additive mitigates deposition (slagging and fouling) in the boiler during operation compared to combustion of biomass without the additive. The anti-deposition effect of the additive is similar to that of prior art additives used such as kaolin or clay minerals.

[0020] - The substitution of primary materials by waste (secondary material) saves primary sources.

[0021] Reduction of costs for recycling of recycled or reclaimed MMVF products by providing a valuable application

[0022] Increasing focus on sustainability image of power and heat generation - The intrinsic properties (amorphous and high specific surface) of MMVF results in effective potassium capture.

[0023] - The fly ash resulting from the additives used in the invention has comparable reactivity compared to regular coal fly ash for use in construction materials

[0024] - Organic binder typically present in MMVF waste can serve as a secondary fuel. In addition, such organic binders often includes nitrogen-containing compounds such as urea and / or ammonia or reaction products thereof which can act as de-NOx compounds.

[0025] - It is not necessary to remove the binder content from the MMVF before application, which is often necessary in order to re-use the MMVF waste or the MMVF thereof.

[0026] Fig. 1 shows a schematic process scheme in a plant for heat generation according to an example of the inventive process.

[0027] Description of the preferred embodiments

[0028] The invention relates to a heat generation process, comprising the step of combusting biomass as fuel in a boiler, wherein the biomass or an admixture of the biomass and at least one other fuel, preferably coal, is combusted in the presence of an additive comprising man-made vitreous fibers (MMVF), in particular man-made vitreous fiber (MMVF) waste.

[0029] MMVF is a common abbreviation for man-made vitreous fibers. Other designations for MMVF are "mineral fibers" or "mineral wool". All these terms are used here interchangeably with each other.

[0030] Man-made vitreous fibers (MMVF) can be selected e.g. from stone fibers, glass fibers, ceramic fibres, basalt fibres, slag fibers or a combination thereof. The MMVF are preferably stone fibers.

[0031] Particularly low alkali and / or low earth alkali content of stone wool, in comparison to glass wool, results in high refractoriness (high-temperature resistance) and low fluxing, while the amorphous character of MMVF ensures well defined melting without energy loss typical of phase transformation of crystalline additives.

[0032] In the present invention, the term "fiber" such as stone fibers and "wool" such as stone wool are used interchangeably with each other.

[0033] A common procedure for producing MMVF includes the fiberisation of a melt of a respective raw material. Mineral fiber products typically comprise man-made vitreous fibres (MMVF) such as, e.g., glass fibres, stone fibers, ceramic fibres, basalt fibres, slag fibers, which are bonded together by a cured binder such as a cured thermoset polymeric binder material. A typical process for preparing a MMVF product such as a bonded mineral fibre mats for use as a thermal or acoustical insulation product includes converting a melt made of suitable raw materials to fibres in conventional manner, for instance by a spinning cup process or by a cascade rotor process. The fibres are blown into a forming or spinning chamber and, while airborne and while still hot, are sprayed with a binder solution and randomly deposited as a mat or web onto a travelling conveyor. The fibre mat is then transferred to a curing oven where heated air is blown through the mat to cure the binder and rigidly bond the mineral fibres together.

[0034] The additive comprises man-made vitreous fibers (MMVF) or man-made vitreous fiber (MMVF) waste, wherein it is preferred that the additive comprises man-made vitreous fiber (MMVF) waste.

[0035] MMVF waste may be generated during the production of MMVF or MMVF products. After usage of a MMVF product, the MMVF product remains as MMVF waste. Hence, the MMVF waste may be selected from recycled MMVF, reclaimed MMVF products, waste generated during production of MMVF or MMVF products (production waste), or a combination thereof.

[0036] The MMVF waste is usually subjected to a treatment, wherein the treatment is e.g. at least one of drying, milling, crushing, cleaning and granulating. The cleaning treatment may be suitable to remove components with which the MMVF products are provided such as plastic wrapping, and / or contaminations resulting from the use of the MMVF product. The cleaning may include common washing and separation procedures such as classifying or sifting. The MMVF waste is preferably a crushed, milled and / or granulated MMVF waste.

[0037] The MMVF waste may be, for instance, milled, crushed, granulated or loosely manufactured fibres, or derived from production waste or used MMVF products, including reclaimed products from market. Reclaimed MMVF products and / or production waste may be subjected to a treatment selected from at least one of at least one of drying, milling, crushing, cleaning and granulating to provide the MMVF waste in a suitable form for use as the additive. The MMVF waste employed is preferably a size reduced MMVF waste.

[0038] Examples of MMVF products from which the MMVF waste is derived are horticultural substrates such as growing media, or insulation products such as thermal and acoustic insulation products, including fagade, vibration as composite applications, such as insulation batts for walls, roof boards, ceiling tiles, insulation coverings for pipes, and the like, as well as production waste, or any combination of these sources.

[0039] The MMVF waste is a solid waste, usually in a particulate form. The MMVF waste is in preferably in form of fibers, powder or granules, preferably powder or granules.

[0040] In a preferred embodiment, the MMVF waste is selected from Reusable Substrate Granulate (RSG), reclaimed MMVF products, waste generated during production of MMVF products, stone wool waste, glass wool waste, or a combination thereof. In a preferred embodiment, the MMVF waste is derived from used horticultural substrates such as growing media.

[0041] Reusable Substrate Granulate (RSG) is also called Recycling Substrate Granulate (RSG). Reusable Substrate Granulate (RSG) is a MMVF waste obtained from used stone wool growing media by Grodan. In order to obtain the RSG, the used stone wool media are subjected to a treatment including crushing of the used stone wool growing media, a separation process, e.g. by means of a drum sifter, to remove components such as plastic wrapping and or contaminates such as soil. The main component of the RSG is stone fibers. Other fraction included are organic binder (e.g. about 1.5%) and contaminants such as roots and stems (e.g. about 10%). Ignition loss of RSG may be up to 15 wt.-%, which is mainly due to the organic binder and roots / stems included. Typical mean fiber diameter of RSG are, for instance, 4 to 7 pm, and fiber length up to 1.5 mm or more.

[0042] A man-made vitreous fiber waste or MMVF waste obviously includes MMVF which may be in crushed, milled and / or granulated form. As discussed above, the production of MMVF products typically involves application of a binder.

[0043] In a preferred embodiment, the MMVF waste further comprises a binder. The binder may be in an uncured state or in a cured state, typically in a cured state. The binder may be selected from an organic binder, an inorganic binder or a combination thereof. The binder is preferably an organic binder. The organic binder included in the MMVF binder can act as a secondary fuel in the combustion process, which is an additional advantage of the additive used in the inventive process.

[0044] In a further preferred embodiment, the MMVF waste comprises MMVF and a nitrogen-containing organic binder. The nitrogen-containing components of the binder results from nitrogen compounds such as urea and / or ammonia or salts or reaction products thereof which are often included as raw materials in binders used for the production of MMVF products.

[0045] Surprisingly, MMVF waste comprising nitrogen-containing organic binder can act as a de-NOx compound in the heat generation process of the invention. NOx generation is a general problem in combustion processes since the resulting NOx emission are most relevant air pollutants. In order to reduce NOx emission, it is known to use so called de-NOx compounds. For instance, technologies such as selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR) reduce post combustion NOx by reacting the exhaust with urea or ammonia to produce nitrogen and water. Thus, the MMVF waste acting as a de-NOx compound can reduce the NOx emission of the combustion process which is an additional advantage of the inventive process.

[0046] The MMVF waste may include further components such as organic matter as contaminants such as roots and stems resulting from the use of the MMVF products, and / or inorganic material such as phosphate minerals. The relatively high phosphate content in MMVF waste such as reclaimed RSG may have its origin from deposited nutrients minerals, which can be considered a kind of contamination. Such phosphate materials can have a beneficial effect by mitigating the risk of pollution / slagg ing during the combustion process.

[0047] For instance, in the case of RSG phosphate minerals, like whitlockite (Ca3[PO4]2), and possible other phosphate minerals crystallizing from the captured moisture in RSG, either dissolve into the molten glass droplets (increasing Tsoiidus) and / or create surface crystallization onto the molten glass droplets, both mitigating the risk of pollution / slagging. The molten glass droplets are generated from the MMVF included in the MMVF waste during the combustion process.

[0048] The amount of MMVF in the MMVF waste may be for instance 50 to 100% by weight, preferably 70 to 100 % by weight, and more preferably 90 to 100% by weight, based on the dry weight of the MMVF waste.

[0049] Usually, the additive consists of the MMVF or the MMVF waste or essentially consists of the MMVF or the MMVF waste, i.e. the amount of MMVF or MMVF waste in the additive is usually 95 to 100% by weight, based on the dry weight of the additive. However, one or more auxiliary agents may be added to form the additive. Examples for such auxiliary agents are organic or inorganic binders.

[0050] The amount of the MMVF in the additive may be, for instance, 80 to 100% by weight, preferably 90 to 100 % by weight, and more preferably 95 to 100% by weight, based on the dry weight of the additive. In a preferred embodiment, the amount of the MMVF waste in the additive may be, for instance, 80 to 100% by weight, preferably 90 to 100 % by weight, and more preferably 95 to 100% by weight, based on the dry weight of the additive.

[0051] The additive may be used alone or in combination or in admixture with other additives. In a preferred embodiment, the additive is mixed into the biomass, and the admixture comprising the additive and the biomass is fed into the boiler for combustion.

[0052] The additive may be dry or humid, wherein the additive is preferably humid, i.e. the additive includes moisture to a certain extent. The additive can be completely dry. When the additive is humid, the water content may be in the range of 0.1 to 70% by weight, preferably 0.5 to 30% by weight, preferably 1 to 20% by weight, more preferably 10 to 20% by weight, of water, based on the dry weight of the additive.

[0053] It is preferred that the moisture content of the additive is controlled. The moisture content may support at least one of mixing with other additives, regulating the reactivity, capturing of volatiles such as HF, HCI, SO2 among others.

[0054] In the following table, normalized (estimated) chemical compositions of various fly ash and mineral additives used in the prior art as alkali scavengers for biomass combustion in boilers and of a particular stone wool and RSG suitable for the present invention are given. Possible organic material in RSG is excluded from the chemical compositions. The table refers to the oxide components. Stone wool and RSG have different coating resulting in different moisture. Higher phosphorous in RSG is due to deposition of nutrients onto fibres.

[0055] Coal Fly ash Wood fly ash Kaolin Bentonite Stone wool RSG

[0056] SiO2 55.8 25.1 57.5 74.4 42.4 40.0

[0057] Al 203 27.1 2.8 41.4 18.3 18.9 16.9

[0058] TiO2 1.1 0.0 0.0 0.0 1.8 1.6

[0059] Fe2O3 7.0 5.6 1.1 0.0 6.7 6.9

[0060] CaO 4.0 24.6 0.0 1.2 17.2 19.0

[0061] MgO 1.5 8.9 0.0 2.4 9.3 8.1

[0062] Na2O 0.6 1.7 0.0 2.4 2.5 2.3

[0063] K2O 1.6 17.1 0.0 1.2 0.8 1.1

[0064] P2O5 0.8 9.0 0.0 0.0 0.2 2.8

[0065] SO3 0.5 5.1 0.0 0.0 0.2 1.4

[0066] Another effect of using mineral additives in combustion systems is the abrasion effect on heat exchangers and catalysts to keep these clean from deposition, e.g. from boiler walls, heat exchangers or catalytic reactors. MMVF have median abrasiveness level (6 Mohs hardness), comparable to that of coal fly ash but higher than that of kaolinite (2-21 / 2 Mohs hardness). Therefore, MMVF of the additive is also effective for cleaning by abrasion. In a preferred embodiment, the additive is admixed to the biomass before it is introduced into the boiler. Then, an admixture of the biomass and the additive is introduced into the boiler. In order to obtain such admixture of the additive and the biomass, the additive is preferably admixed to the biomass prior to milling the biomass to obtain a pulverized biomass containing the additive. This ensures a good distribution of the additive within the biomass. The pulverized biomass containing the additive may be further converted to chips, pellets or granules before entering the boiler, but this is usually not preferred.

[0067] In an alternative embodiment, the additive is introduced into the boiler during the combustion of the biomass, for instance by injection. In this embodiment, the additive and the biomass are introduced into the boiler separately.

[0068] A suitable ratio of the MMVF to the biomass to be implemented in the boiler may be, for instance in a range of 0.1 to 20% MMVF per ton biomass, preferably 0.5 to 10% MMVF per ton biomass, more preferably 1 to 5% MMVF per ton biomass. In a preferred embodiment, a suitable ratio of the MMVF waste to the biomass to be implemented in the boiler may be, for instance in a range of 0.1 to 20% MMVF waste per ton biomass, preferably 0.5 to 10% MMVF waste per ton biomass, more preferably 1 to 5% MMVF waste per ton biomass. Of course, this ratio also applies to the admixture where the additive is admixed to the biomass before it is introduced into the boiler. For instance, 20% MMVF waste per ton biomass means 0.2 tons MMVF waste per ton biomass.

[0069] The usual forms of biomass used in conventional combustion processes can be used (e.g. chips, pulverized, pellets, granules). The suitable shape of the biomass usually depends on the type of boiler. In a fluidised bed boiler, for instance, a chip can be used, but in a pulverised coal boiler chips are too large and has to be reduced in size.

[0070] Biomass is a renewable organic material is derived from living organisms (plants and animals). All types of biomass which are commonly used for heat generation processes can be used. Examples of suitable biomass are wood, wood residues, crops, agricultural residues, biogenic residues and waste from municipal waste, industry, farms or households, or a combination thereof. Examples of wood residues are firewood, wood pellets, wood chips, lumber, sawdust, and black liquor from pulp and paper mills. Examples of agricultural residues are straw, sugar cane, switchgrass, algae, crop and food processing residues, agricultural waste and animal manure. Examples for biogenic residues and biogenic waste from municipal waste (SRF=solid recovered fuel), industry, farms or households are paper products; cotton wool products; food, yard, wood wastes, vegetable oils and animal fats.

[0071] According to the heat generation process of the invention, the biomass is combusted as a fuel in a boiler, optionally in admixture with at least one other fuel. Direct combustion is the most common method for converting biomass to useful energy. All biomass or the admixture of biomass and the at least one other fuel can be burned directly for heating buildings and water, for providing industrial process heat, and for generating electricity in steam turbines.

[0072] In a particularly preferred embodiment, the biomass is combusted in the boiler in admixture with at least one other fuel. The combustion of more than one type of fuel is also called co-combustion or co-firing and a conventional combustion method. When biomass is one of the fuels, it is also designated biomass cocombustion. The biomass and the at least one other fuel, preferably coal, can be fed to the boiler separately or as a mixture.

[0073] The at least one other fuel, which is combusted in admixture with the biomass in the boiler, can be selected e.g. from coal, lignite, biogas, natural gas or combinations thereof. Natural gas is often used during start-up of the combustion process.

[0074] In a particular preferred embodiment, the at least one other fuel is coal. That is, the biomass is combusted in the boiler in admixture with coal.

[0075] The proportion of the biomass, based on the total mass of the biomass and the at least one other fuel, preferably coal, if present, in the boiler may be e.g. 30 to 100 wt.-%, preferably 50 to 100 wt.-%, more preferably 70 to 100 wt.-%. Hence, if the biomass is co-fired with at least one other fuel, the proportion of the biomass, based on the total mass of the biomass and the at least one other fuel, preferably coal, in the boiler may be at least 30 wt. -%, preferably at least 50 wt.- %, more preferably at least 70 wt.-%. The proportion refers to the dry weight of biomass and the at least one other fuel.

[0076] The biomass and the at least one other fuel, preferably coal, may be fed to the boiler separately or in admixture. In embodiments, where the biomass is combusted in the boiler in admixture with the at least one other fuel, preferably coal, the additive may be admixed with the biomass as described above or may be admixed with the at least one other fuel or with both the biomass and the at least one other fuel, before it is introduced into the boiler. The additive may be also introduced into the boiler separately during the co-combustion of the biomass and the at least one other fuel, preferably coal.

[0077] Typical co-firing combustion methods for admixtures of biomass and at least one other fuel are direct co-firing, indirect co-firing and parallel firing.

[0078] Direct co-firing is the commonly applied approach. The biomass is directly fed to the boiler furnace after being passed through the same mills - crushers, bunkers and pulverisers as the at least other fuel, preferably coal. The biomass can be mixed with the coal in the fuel yard or can be fed to the boiler separately. In indirect co-firing, biomass is first gasified, and the fuel gas is then co-fired in the main boiler with the at least other fuel, preferably coal. Parallel co-firing refers to a method where the biomass is burnt in a separate boiler for steam generation. The steam is used in a power plant together with the main fuel, preferably coal.

[0079] According to the heat generation process, the combustion of the biomass in the presence of the additive takes place in a boiler, preferably in admixture with at least one other fuel, in particular coal. The boiler can be any boiler typically used for the combustion of biomass or for the co-combustion of an admixture of biomass and at least one other fuel. The boiler is preferably a pulverized fuel boiler or a fluidized bed boiler. The boiler can be for instance a boiler of a heat and power generation plant. The boiler usually includes means for feeding oxygen or an oxygen containing gas such as air into the boiler.

[0080] The boiler typically includes one or more heat exchangers in order to collect the heat generated. The boiler may include one or more catalyst elements, for instance to catalyze NOx reduction. Biomass boilers produce fly ash and particulate matter that may require the installation of additional abatement equipment. In addition, nitrogen oxide (NOx) emissions and other emissions may require additional flue-gas abatement equipment. The common equipment may be used for such abatement equipment.

[0081] Thus, the boiler may be equipped with means for removing fly ash such as electrostatic precipitators (ESP). The boiler may additionally or alternatively be equipped with a flue-gas abatement equipment such as a de-NOx reactor including catalysts and / or flue-gas desulfurization means (FGD).

[0082] The combustion may be carried out in any suitable combustion mode belonging to the boiler design.

[0083] In general, the combustion of biomass or the admixture of biomass and at least one other fuel such as coal in the boiler proceeds in several stages including warming up, drying, pyrolysis, gasification of the material and oxidation of the combustible gases generated. The combustion temperature during the oxidation of the combustible gases may vary and depends e.g. on the type of fuel (biomass or biomass and at least one other fuel). The burner and process is tuned to specific composition of fuel mixture.

[0084] For the heat generation process of the invention, the temperature in the boiler may be, for instance, in the range of 700 °C to 2000°C, preferably 800°C to 1800°C.

[0085] Without wishing to be bound to any theory, it is assumed that in the inventive process during the combustion process in the boiler, the mineral fibres or the mineral fibres of the MMVF waste, respectively, will melt and their shape will change from fibre to a spherical shape. The particles that will be formed (based on the volume of the fibres) corresponds with an average fly ash particle.

[0086] The melting point of the MMVF or the MMVF included in the MMVF waste may be in the range of e.g. 1150 °C to 1800 °C. The melting temperature of glass fibers is generally lower than that of stone fibers. Since a rapid melting of the fibers may result in clumping, stone fibers are more preferably. The fibres are preferably well distributed through the biomass and through the boiler. Otherwise, bigger particles can be formed, which may catch fewer alkalis during combustion. These bigger particles may fall to the bottom of the boiler and become a part of the bottom ash.

[0087] The additives or MMVF, in particular MMVF waste, respectively, may be milled before use. If the additive is added to the biomass and / or the at least one other fuel, preferably coal, before introduction into the boiler, it is preferred to mill the admixture of biomass and additive and / or the admixture of the at least one other fuel and the additive, to obtain a pulverized biomass with a good distribution of the additive in the biomass and / or a milled at least one other fuel with a good distribution of the additive in the at least one other fuel, preferably coal. The milling of the additive and the biomass or the at least one other fuel such as coal can be carried out e.g. in coal mills.

[0088] The invention is also directed to the use of an additive comprising man-made vitreous fibers (MMVF), in particular man-made vitreous fiber (MMVF) waste, as an additive for the combustion of biomass or an admixture of biomass and at least one other fuel, preferably in a boiler. The at least one other fuel is preferably coal.

[0089] The additive, the biomass, the at least one other fuel, the boiler and the details of the heat generating process such as combustion or co-combustion and the technical effects and merits achieved have been described above for the inventive heat generating process. All indications discussed above with respect to the inventive heat generating process also apply to the use according to the invention so that reference is made thereto.

[0090] Accordingly, the additive is preferably used in a heat generation process of the invention as described above. The additive used is preferably as described above for the heat generation process of the invention.

[0091] With respect to the use of the invention, the additive is preferably used as at least one of an alkali scavenger, in particular a potassium scavenger, an anti - deposition agent, a corrosion inhibitor, a de-NOx compound and thereby an emission reducer. The additive is in particular suitable as an alkali scavenger, in particular a potassium scavenger, and / or as an anti-deposition agent. Such deposition is generally generated during biomass combustion in the boiler, e.g. deposition on boiler walls, heat exchangers or catalytic elements.

[0092] The invention is also directed to a biomass fuel, comprising biomass and an additive comprising man-made vitreous fibers (MMVF), in particular man-made vitreous fiber (MMVF) waste.

[0093] The additive, the biomass, the boiler and the details of the heat generating process such as combustion or co-combustion and the technical effects and merits achieved have been described above for the inventive heat generating process. All indications discussed above with respect to the inventive heat generating process also apply to the biomass fuel according to the invention, where applicable, so that reference is made thereto.

[0094] In particular, it is preferred that the biomass containing the additive of the biomass fuel of the invention is pulverized biomass or biomass in form of chips, pellets or granules, wherein the biomass containing the additive is preferably pulverized biomass.

[0095] As described above, the biomass is selected from wood, wood residues, crops, agricultural residues, biogenic residues and waste from municipal waste, industry, farms or households, or a combination thereof. Examples thereof have been described above.

[0096] The additive included in the biomass fuel of the invention is preferably as described above for the heat generation process of the invention.

[0097] As described above, the ratio of the MMVF to the biomass in the biomass fuel of the invention is preferably in a range of 0.1 to 20% MMVF per ton biomass, preferably 0.5 to 10% MMVF per ton biomass, more preferably 1 to 5% MMVF per ton biomass. As described above, in a preferred embodiment, the ratio of the MMVF waste to the biomass in the biomass fuel of the invention is preferably in a range of 0.1 to 20% MMVF waste per ton biomass, preferably 0.5 to 10% MMVF waste per ton biomass, more preferably 1 to 5% MMVF waste per ton biomass. The biomass fuel of the invention is preferably a pulverized or size reduced biomass fuel containing the additive, which is preferably obtainable by size reduction of an admixture of the additive and the biomass. Size reduction may be effected e.g. by milling or crushing.

[0098] In the following, the invention is illustrated by drawings and an example which should however not limit the scope of the invention.

[0099] Fig. 1 shows a schematic process scheme in a plant for heat generation according to an example of the inventive process.

[0100] The boiler shown in Fig. 1 is a pulverized fuel boiler (conversion of coal-fired boiler). Basically, also other conventional boiler combustion systems can be used, for instance fluidized bed boilers. The boiler may include heat exchangers (not shown) to collect the heat energy generated. The boiler is equipped with flue gas treatment means including a de-NOx reactor with catalysts for NOx reduction, an electrostatic precipitator (ESP) for capture of fly ash generated and flue-gas desulfurization means (FGD). The ESP may also be absent. Instead, a combination of a cyclone and a bag filter may be installed.

[0101] MMFV or preferably a MMVF waste can be used. The MMFV waste used can be Recycling Substrate Granulate (RSG). The MMVF or the MMVF waste as mineral additive can be added to the solid biomass (fuel) prior to milling the admixture of MMVF, in particular MMVF waste, and biomass (fuel milling) as shown in Fig. 1. Alternatively, MMVF, in particular MMVF waste, can be directly injected into the boiler. The milled (pulverized) admixture of biomass and additive (MMVF or MMVF waste) is then introduced into the boiler where the biomass is combusted to generate heat energy in form of a cloud combustion.

[0102] Without wishing to be bound to any theory, it is assumed that the following mechanism occur. During combustion of biomass, organically bound alkalis evaporate in the boiler due to the high temperatures. During this stage, different reactions take place more or less simultaneously. One of these reactions is the uptake of alkalis by minerals phases present in the boiler due to the addition of the additive (the chemical sorption as mentioned above). Especially molten vitreous phases are able to 'catch' these alkalis. Preliminary thermodynamic calculations of stone wool and Recycling Substrate Granulate (RSG) was performed to assess the temperature-viscosity behaviour and compare these with other additives according to the prior art, given the circumstance that released potassium will be taken up by stone wool and RSG. These calculations show that (1) RSG has a T(solidus) of about 1510-1520 °C. Some additives have higher values (like coal fly ash) or lower (bentonite) and (2) that the potassium can be taken up in the molten phase. With respect to potassium uptake, a thermodynamic software was used starting with the chemistry given in the above table and addition of K2O was simulated till solid phase formation appears in specific material. The high moisture content of RSG may be advantageous for the reaction:

[0103] KCI + H2O + Alumina-silicate(liquid) K2O-Alumina-silicate(liquid) + 2HCI(gas)

[0104] Based on this, mineral waste exemplified by RSG is suitable for using as mineral additive. The additive based on the MMVF waste RSG including stone wool is expected to act as alkali scavenger during biomass combustion and to mitigate deposition in the boiler during operation.

[0105] The present invention also relates to the following items.

[0106] Item 1. A heat generation process, comprising the step of combusting biomass as fuel in a boiler, wherein the biomass or an admixture of the biomass and at least one other fuel, preferably coal, is combusted in the presence of an additive comprising man-made vitreous fiber (MMVF) waste.

[0107] Item 2. The heat generation process according to item 1, wherein the MMVF are stone fibers, glass fibers, ceramic fibres, basalt fibres, slag fibers or a combination thereof, preferably glass fibers and / or stone fibers, more preferably stone fibers.

[0108] Item 3. The heat generation process according to any of the preceding items, wherein the MMVF waste is selected from recycled MMVF, reclaimed MMVF products, waste generated during production of MMVF or MMVF products, or a combination thereof. Item 4. The heat generation process according to any of the preceding items, wherein the MMVF waste is selected from Reusable Substrate Granulate (RSG), reclaimed MMVF products, waste generated during production of MMVF products, stone wool waste, glass wool waste, or a combination thereof.

[0109] Item 5. The heat generation process according to any of the preceding items, wherein the MMVF waste comprises MMVF and a binder selected from an organic binder, an inorganic binder or a combination thereof, preferably an organic binder; and / or wherein the MMVF waste comprises MMVF and a nitrogen-containing organic binder.

[0110] Item 6. The heat generation process according to any of the preceding items, wherein the amount of MMVF in the MMVF waste is 50 to 100% by weight, preferably 70 to 100 % by weight, and more preferably 90 to 100% by weight, based on the dry weight of the MMVF waste, and / or wherein the amount of MMVF waste in the additive is 80 to 100% by weight, preferably 90 to 100 % by weight, and more preferably 95 to 100% by weight, based on the dry weight of the additive.

[0111] Item 7. The heat generation process according to any of the preceding items, wherein the additive is humid, wherein the water content may be in the range of 0.1 to 70% by weight, preferably 0.5 to 30% by weight, more preferably 1 to 20% by weight of water, more preferably 10 to 20% by weight, based on the dry weight of the additive.

[0112] Item 8. The heat generation process according to any of the preceding items, wherein the MMVF waste is a treated MMVF waste, wherein the treatment is at least one of drying, milling, crushing, cleaning and granulating, and / or wherein the MMVF waste is in form of a fibers, powder or granules.

[0113] Item 9. The heat generation process according to any of the preceding items, wherein the additive is admixed to the biomass before it is introduced into the boiler, wherein the additive is preferably admixed to the biomass prior to milling the biomass to obtain a pulverized biomass containing the additive, and / or wherein the additive is admixed to the at least one other fuel, preferably coal, before it is introduced into the boiler, wherein the additive is preferably admixed to the at least one other fuel prior to milling the at least other fuel to obtain a pulverized at least one other fuel containing the additive, and / or wherein the additive is introduced into the boiler during the combustion of the biomass.

[0114] Item 10. The heat generation process according to any of the preceding items, wherein the ratio of the MMVF waste to the biomass in the boiler is in a range of 0.1 to 20% of MMVF waste per ton biomass, preferably 0.5 to 10% MMVF waste per ton biomass, more preferably 1 to 5% additive per ton biomass.

[0115] Item 11. The heat generation process according to any of the preceding items, wherein the biomass is pulverized or size reduced biomass or biomass in form of chips, pellets or granules, and / or wherein the biomass is selected from wood, wood residues, crops, agricultural residues, biogenic residues and waste from municipal waste, industry, farms or households, or a combination thereof.

[0116] Item 12. The heat generation process according to any of the preceding items, wherein the boiler is a pulverized fuel boiler or a fluidized bed boiler, and / or wherein the boiler is a boiler of a heat and power generation plant, and / or wherein the boiler includes one or more heat exchangers and / or one or more catalyst elements.

[0117] Item 13. The heat generation process according to any of the preceding items, wherein the biomass is combusted in the boiler in admixture with the at least one other fuel, preferably coal, wherein the proportion of the biomass, based on the total mass of the biomass and the at least one other fuel, in the boiler is preferably at least 30 wt. -%, more preferably at least 50 wt.-%, still more preferably at least 70 wt.-%. Item 14. Use of an additive comprising man-made vitreous fiber (MMVF) waste as an additive for the combustion of biomass or an admixture of biomass and at least one other fuel, preferably in a boiler.

[0118] Item 15. The use according to item 14, wherein the additive is used as at least one of an alkali scavenger, in particular a potassium scavenger, an anti-deposition agent, a corrosion inhibitor, a de-NOx compound and an emission reducer.

[0119] Item 16. The use according to item 14 or item 15, wherein the additive is used in a heat generation process according to any one of claims 1 to 13 or wherein the additive is defined as in any one of claims 2 to 8.

[0120] Item 17. A biomass fuel, comprising biomass and an additive comprising man-made vitreous fiber (MMVF) waste.

[0121] Item 18. The biomass fuel according to item 17, wherein the biomass is pulverized biomass or biomass in form of chips, pellets or granules, and / or wherein the biomass is selected from wood, wood residues, crops, agricultural residues, biogenic residues and waste from municipal waste, industry, farms or households, or a combination thereof.

[0122] Item 19. The biomass fuel according to any of items 17 to 18, wherein the additive is defined as in any one of claims 2 to 8.

[0123] Item 20. The biomass fuel according to any of items 17, 18 and 19, wherein the ratio of the MMVF waste to the biomass is in a range of 0.1 to 20% MMVF waste per ton biomass, preferably 0.5 to 10% MMVF waste per ton biomass, more preferably 1 to 5% MMVF waste per to biomass.

[0124] Item 21. The biomass fuel according to any of items 17 to 20, wherein the biomass fuel is a pulverized or size reduced biomass fuel containing the additive, preferably obtainable by milling an admixture of the additive and the biomass.

Claims

Claims1. A heat generation process, comprising the step of combusting biomass as fuel in a boiler, wherein the biomass or an admixture of the biomass and at least one other fuel, preferably coal, is combusted in the presence of an additive comprising man-made vitreous fibers (MMVF), in particular manmade vitreous fiber (MMVF) waste.

2. The heat generation process according to claim 1, wherein the MMVF are stone fibers, glass fibers, ceramic fibres, basalt fibres, slag fibers or a combination thereof, preferably glass fibers and / or stone fibers, more preferably stone fibers.

3. The heat generation process according to any of the preceding claims, wherein the MMVF waste is selected from recycled MMVF, reclaimed MMVF products, waste generated during production of MMVF or MMVF products, or a combination thereof.

4. The heat generation process according to any of the preceding claims, wherein the MMVF waste is selected from Reusable Substrate Granulate (RSG), reclaimed MMVF products, waste generated during production of MMVF products, stone wool waste, glass wool waste, or a combination thereof.

5. The heat generation process according to any of the preceding claims, wherein the MMVF waste comprises MMVF and a binder selected from an organic binder, an inorganic binder or a combination thereof, preferably an organic binder; and / or wherein the MMVF waste comprises MMVF and a nitrogen-containing organic binder.

6. The heat generation process according to any of the preceding claims, wherein the amount of MMVF in the MMVF waste is 50 to 100% by weight, preferably 70 to 100 % by weight, and more preferably 90 to 100% by weight, based on the dry weight of the MMVF waste, and / orwherein the amount of MMVF in the additive is 80 to 100% by weight, preferably 90 to 100 % by weight, and more preferably 95 to 100% by weight, based on the dry weight of the additive, and / or wherein the amount of MMVF waste in the additive is 80 to 100% by weight, preferably 90 to 100 % by weight, and more preferably 95 to 100% by weight, based on the dry weight of the additive.

7. The heat generation process according to any of the preceding claims, wherein the additive is humid, wherein the water content may be in the range of 0.1 to 70% by weight, preferably 0.5 to 30% by weight, more preferably 1 to 20% by weight of water, more preferably 10 to 20% by weight, based on the dry weight of the additive.

8. The heat generation process according to any of the preceding claims, wherein the MMVF waste is a treated MMVF waste, wherein the treatment is at least one of drying, milling, crushing, cleaning and granulating, and / or wherein the MMVF waste is in form of a fibers, powder or granules.

9. The heat generation process according to any of the preceding claims, wherein the additive is admixed to the biomass before it is introduced into the boiler, wherein the additive is preferably admixed to the biomass prior to milling the biomass to obtain a pulverized biomass containing the additive, and / or wherein the additive is admixed to the at least one other fuel, preferably coal, before it is introduced into the boiler, wherein the additive is preferably admixed to the at least one other fuel prior to milling the at least other fuel to obtain a pulverized at least one other fuel containing the additive, and / or wherein the additive is introduced into the boiler during the combustion of the biomass.

10. The heat generation process according to any of the preceding claims, wherein the ratio of the MMVF to the biomass in the boiler is in a range of 0.1 to 20% of MMVF per ton biomass, preferably 0.5 to 10% MMVF per ton biomass, more preferably 1 to 5% additive per ton biomass, and / orwherein the ratio of the MMVF waste to the biomass in the boiler is in a range of 0.1 to 20% of MMVF waste per ton biomass, preferably 0.5 to 10% MMVF waste per ton biomass, more preferably 1 to 5% additive per ton biomass.

11. The heat generation process according to any of the preceding claims, wherein the biomass is pulverized or size reduced biomass or biomass in form of chips, pellets or granules, and / or wherein the biomass is selected from wood, wood residues, crops, agricultural residues, biogenic residues and waste from municipal waste, industry, farms or households, or a combination thereof.

12. The heat generation process according to any of the preceding claims, wherein the boiler is a pulverized fuel boiler or a fluidized bed boiler, and / or wherein the boiler is a boiler of a heat and power generation plant, and / or wherein the boiler includes one or more heat exchangers and / or one or more catalyst elements.

13. The heat generation process according to any of the preceding claims, wherein the biomass is combusted in the boiler in admixture with the at least one other fuel, preferably coal, wherein the proportion of the biomass, based on the total mass of the biomass and the at least one other fuel, in the boiler is preferably at least 30 wt. -%, more preferably at least 50 wt.-%, still more preferably at least 70 wt.-%.

14. Use of an additive comprising man-made vitreous fibers (MMVF), in particular man-made vitreous fiber (MMVF) waste, as an additive for the combustion of biomass or an admixture of biomass and at least one other fuel, preferably in a boiler.

15. The use according to claim 14, wherein the additive is used as at least one of an alkali scavenger, in particular a potassium scavenger, an anti deposition agent, a corrosion inhibitor, a de-NOx compound and an emission reducer.

16. The use according to claim 14 or claim 15, wherein the additive is used in a heat generation process according to any one of claims 1 to 13 or wherein the additive is defined as in any one of claims 2 to 8.

17. A biomass fuel, comprising biomass and an additive comprising man-made vitreous fibers (MMVF), in particular man-made vitreous fiber (MMVF) waste, wherein the ratio of the MMVF to the biomass is in a range of 0.1 to 20% MMVF per ton biomass, preferably 0.5 to 10% MMVF per ton biomass, more preferably 1 to 5% MMVF per to biomass, or wherein the ratio of the MMVF waste to the biomass is in a range of 0.1 to 20% MMVF waste per ton biomass, preferably 0.5 to 10% MMVF waste per ton biomass, more preferably 1 to 5% MMVF waste per to biomass.

18. The biomass fuel according to claim 17, wherein the biomass is pulverized biomass or biomass in form of chips, pellets or granules, and / or wherein the biomass is selected from wood, wood residues, crops, agricultural residues, biogenic residues and waste from municipal waste, industry, farms or households, or a combination thereof.

19. The biomass fuel according to any of claims 17 to 18, wherein the additive is defined as in any one of claims 2 to 8.

20. The biomass fuel according to any of claims 17 to 19, wherein the biomass fuel is a pulverized or size reduced biomass fuel containing the additive, preferably obtainable by milling an admixture of the additive and the biomass.

Images