ARRANGEMENT FOR AND A METHOD OF RECYCLING MINERAL WOOL WASTE

Abstract

A method of and an arrangement for recycling mineral wool waste to mineral wool production includes at least one melting furnace for melting virgin mineral wool raw material, the melting furnace including an inlet for virgin mineral wool raw material and an outlet for molten mineral wool material, a production line connected to the outlet for molten mineral wool material for producing a mineral wool product from the molten mineral wool material. The production line includes a curing oven, a fluidized bed reactor including an exhaust gas duct, an inlet for predetermined primary fuel, an inlet for predetermined bed material, and an outlet for an ash material, the ash material including bottom ash discharged via a bottom outlet from the fluidized bed reactor or fly ash separated by a particle separator from exhaust gas in the exhaust gas duct or a mixture of the bottom ash and the fly ash.

Claims

1. An arrangement for recycling mineral wool waste to mineral wool production, the arrangement comprising: at least one melting furnace for melting virgin mineral wool raw material, the melting furnace comprising an inlet for virgin mineral wool raw material and an outlet for molten mineral wool material; a production line connected to the outlet for molten mineral wool material for producing a mineral wool product from the molten mineral wool material, wherein the production line comprises a curing oven; a fluidized bed reactor comprising an exhaust gas duct, an inlet for predetermined primary fuel, an inlet for predetermined bed material, and an outlet for an ash material, the ash material comprising bottom ash discharged via a bottom outlet from the fluidized bed reactor or fly ash separated by a particle separator from exhaust gas in the exhaust gas duct or a mixture of the bottom ash and the fly ash, together with particles of bed material removed from the fluidized bed reactor, the fluidized bed reactor comprising an inlet for mineral wool waste, whereby the ash material comprises fine mineral wool material powdered from the mineral wool waste in the fluidized bed reactor, wherein the melting furnace has a further inlet for the ash material so as to use the ash material as a further mineral wool raw material.

2. The arrangement for recycling mineral wool waste in accordance with claim 1, wherein the arrangement comprises means for providing a material quality analysis of at least one of the mineral wool product, the mineral wool waste and the further mineral wool raw material, and means for determining the material quality of at least one of the primary fuel and the bed material on the basis of the result of the material quality analysis.

3. The arrangement for recycling mineral wool waste in accordance with claim 1, wherein the arrangement comprises a reactor for sintering or briquetting the ash material so as to produce an ash product.

4. The arrangement for recycling mineral wool waste in accordance with claim 1, wherein the curing oven comprises an inlet for air and means for heating the air, and the arrangement comprises a line for conveying hot flue gas from the curing oven to the fluidized bed reactor.

5. The arrangement for recycling mineral wool waste in accordance with claim 1, wherein the arrangement comprises means for conducting heat extracted from exhaust gas in the exhaust gas duct to the mineral wool production line.

6. The arrangement for recycling mineral wool waste in accordance with claim 1, wherein the melting furnace is a cupola furnace having an inlet for coke and the arrangement comprises means for leading coke particles having a particle size smaller than a predetermined limit from the inlet for coke to the fluidized bed reactor.

7. The arrangement for recycling mineral wool waste in accordance with claim 6, wherein the arrangement comprises means for leading CO-comprising flue gas from the melting furnace to the fluidized bed reactor.

8. The arrangement for recycling mineral wool waste in accordance with claim 1, wherein the fluidized bed reactor is a fluidized bed gasifier generating combustible gas, wherein the arrangement comprises means for leading a portion of the combustible gas to be combusted for producing heat in at least one of the melting furnace and the curing oven in the mineral wool production line.

9. The arrangement for recycling mineral wool waste in accordance with claim 1, wherein the fluidized bed reactor is a fluidized bed boiler generating steam to a steam turbine to generate electrical power that is used in at least one of the melting furnace and the curing oven in the mineral wool production line.

10. The arrangement for recycling mineral wool waste in accordance with claim 9, wherein the melting furnace is an electrical arc furnace and the electrical power is used to power the melting furnace.

11. The arrangement for recycling mineral wool waste in accordance with claim 10, wherein the arrangement comprises a coke firing cupola furnace as a second melting furnace, means for leading undersized coke to be used as a further fuel in the fluidized bed reactor, and means for leading CO-comprising flue gas from the cupola furnace to the fluidized bed reactor.

12. A method of recycling mineral wool waste to mineral wool production, the method comprising the steps of: feeding virgin mineral wool raw material into a melting furnace and melting the virgin mineral wool raw material therein; discharging molten mineral wool material from the melting furnace to a production line; treating the molten mineral wool material as a flexible mat in the mineral wool production line, which comprises a curing oven, for producing a mineral wool product from the molten mineral wool material; providing an energy containing product in a fluidized bed reactor, wherein the fluidized bed reactor comprises an exhaust gas duct; feeding predetermined primary fuel and predetermined bed material into the fluidized bed reactor; discharging ash material from the fluidized bed reactor, the ash material comprising bottom ash or fly ash or a mixture of fly ash and bottom ash together with bed material removed from the fluidized bed reactor; feeding mineral wool waste into the fluidized bed reactor, whereby the ash material comprises fine mineral wool material powdered from the mineral wool waste in the fluidized bed reactor; and feeding a portion of the ash material to the melting furnace for using the ash material as a further mineral wool raw material.

13. The method of recycling mineral wool waste to mineral wool production in accordance with claim 12, further comprising the steps gf providing a material quality analysis of at least one of the mineral wool product, the mineral wool waste and the further mineral wool raw material, and determining the material quality of at least one of the primary fuel and the bed material on the basis of the result of the material quality analysis.

14. The method of recycling mineral wool waste to mineral wool production in accordance with claim 12, further comprising the steps of leading a stream of air to the curing oven, heating the stream of air, conveying the stream of heated air through the flexible mat so as to generate hot flue gas, and conveying the hot flue gas from the curing oven to the fluidized bed reactor.

15. The method of recycling mineral wool waste to mineral wool production in accordance with claim 12, further comprising the steps of spinning and sizing of mineral wool material, and the mineral wool waste fed to the fluidized bed reactor comprises at least one of demolition waste mineral wool and process waste mineral wool from the spinning step or the sizing step.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG. 1 schematically illustrates an arrangement according a first preferred embodiment of the present invention.

[0033] FIG. 2 schematically illustrates an arrangement according a second preferred embodiment of the present invention.

[0034] FIG. 3 schematically illustrates an arrangement according a third preferred embodiment of the present invention.

[0035] FIG. 4 schematically illustrates an arrangement according a fourth preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0036] The diagram of FIG. 1 schematically illustrates an arrangement 10 for recycling mineral wool waste to mineral wool production according to an embodiment of the present invention. The arrangement comprises a melting furnace 12, which is, in this embodiment, a cupola furnace, for melting virgin mineral wool raw material. The melting furnace comprises an inlet 14 for feeding in virgin mineral wool raw material and an outlet 16 for discharging molten mineral wool material to further processing in a mineral wool production line 22. The virgin raw material is generally a mixture of minerals, selected so as to obtain a desired mineral composition in the final mineral wool product. Mineral wool may, for example, comprise the following main mineral components: CaO (14.7%), SiO.sub.2 (41.9%), Al.sub.2O.sub.3 (16.5%), Fe.sub.2O.sub.3 (11.2%), Na.sub.2O (1.6%), MgO (12.2%). The inlet 14 for feeding in virgin mineral wool raw material comprises usually, although not shown in the Figures, means to render possible the selection of the virgin raw material components to be used. Such means comprises usually multiple bins for different raw materials and means to weight and control the flow of the components.

[0037] In a cupola furnace, the melting of the minerals, which generally takes place in a temperature of 1200 to 1500° C., is brought about by burning coke in the melting furnace in a flow of air, so-called blast air. Thus, the melting furnace 12 comprises an inlet for coke 18 and an inlet for blast air 20. The outlet for molten mineral wool material 16 leads to a production line 22 for producing the mineral wool product from a flexible mat of the mineral wool material, which production line generally comprises well-known stages for spinning 24, collecting 26, curing 28, and sizing 30 of the material for the product.

[0038] An element of the arrangement according to the present invention is a fluidized bed reactor 32, such as a fluidized bed boiler. As conventional, the fluidized bed reactor comprises an exhaust gas duct 34, an inlet for preheated fluidizing gas 36, usually, air, an inlet for primary fuel 38, such as biofuel, an inlet for bed material 40, such as sand, and a bottom outlet 42 for discharging bottom ash from the reactor. The exhaust gas duct 34 comprises a particle separator 44, such as a cyclone or a bag filter, for separating fly ash from the exhaust gas.

[0039] Ash material, comprising a portion of the bottom ash or the separated fly ash or a mixture of the fly ash and the bottom ash, is advantageously conducted along a line 66, together with coarse bed material removed from the bottom of the fluidized bed reactor 32 or fine bed material emanating with the exhaust gas, to a reactor 46 for sintering or briquetting the ash material to form so-called ash product.

[0040] A key element of the embodiment is that the fluidized bed reactor 32 also comprises an inlet 48 for shredded mineral wool waste. The mineral wool waste can be, for example, demolition mineral wool waste and/or mineral wool waste transported via a waste return line 64 from the spinning 24 and sizing 30 stages of the mineral product line 22. In the fluidized bed reactor 32, the binder of the mineral wool waste, typically, organic resin binder, is burned out and the fibers in the mineral wool are reduced into powder by the mechanical abrasive nature of the fluidized bed 32. Therefore, the ash product also comprises fine mineral wool material powdered from the mineral wool waste in the fluidized bed reactor 32.

[0041] If the composition of the ash is suitable, the ash can be fed as a further mineral wool raw material to the melting furnace 12. Therefore, the fuels are advantageously chosen so as to get an optimal composition for the ash. Then, the formed ash product can be lead as a further mineral wool raw material to the melting furnace 12 via an inlet for the ash product 50.

[0042] Because the ash product is generally mixed with particles of bed material removed or discharged from the fluidized bed reactor 32, it is advantageous to feed into the fluidized bed reactor via the inlet 40 bed material that has a composition that is close enough to the final composition of the desired raw material for the mineral wool making. As mineral wool is made from a mix of minerals, the composition of the bed material or the ash product does not have to precisely match the final melt composition as deviations from the normal recipes can, in many cases, be compensated for also by adjusting the ratios of components of the virgin raw material fed via the inlet 14 to the melting furnace 12.

[0043] According to a preferred embodiment of the present invention, the arrangement comprises means 52, 52′, 52″ for providing a material analysis of the produced mineral wool product, or the mineral wool waste to be fed to the fluidized bed reactor 32, and/or the further mineral wool raw material to be conveyed to the melting furnace 12, respectively. The results of the material analysis are then used, by means 54, 54′ to determine the quality of the primary fuel and/or the bed material to be fed to the fluidized bed reactor 32. Each of the means 54, 54′ may comprise, for example, a desired number of bins for alternative primary fuels and alternative bed materials and means to weight and to control the flows of the material components.

[0044] The arrangement may advantageously also comprise heat transfer means, such as heat exchangers 58, 58′ connected to a piping 56 for circulating water or other suitable heat transfer medium, between the exhaust gas duct 34 and the mineral wool production line 22. By the heat transfer means, heat extracted from exhaust gas in the exhaust gas duct 34 is transferred to the curing oven 28 to provide energy needed for the curing. Heat extracted from the exhaust gas of the fluidized bed reactor can also, or alternatively, be utilized for other purposes in the mineral wool production, such as for drying draw materials before the melting.

[0045] In the curing oven 28, the energy is advantageously used for heating a stream of air that is conveyed, in a conventional way, through a flexible mat of the mineral wool material, for the polymerization of the binder, to give to the mineral wool product its density and shape. Curing by hot air produces exhaust gas comprising mainly air but also, e.g., some phenols. Conventionally the exhaust gas is heat treated in a gas fired incinerator. According to an embodiment of the present invention, the exhaust gas from the curing oven 28 is conveyed along a line 82 to the fluidized bed reactor 32 to heat treat the gas, and also to be used as additional fluidizing gas, i.e., to replace some of the primary or secondary air. The temperature of the flue gas is typically about 200 to 300° C. when it leaves the curing oven. Thus, leading the hot flue gas to the fluidized bed reactor reduces the need for preheating fluidizing gas of the reactor. Leading flue gas from a hot air using curing oven to the fluidized bed reactor can be performed in any embodiment of the present invention, independent of the way of producing the hot air.

[0046] Coke material that is used as a fuel in a cupola furnace 12 comprises often under-size particles that cannot be used because they would deteriorate the operation of the cupola furnace, for example, by escaping from the furnace. The under-size coke, such as coke having a diameter less than 50 mm, is conventionally separated to a waste stream. However, such an under-size coke can be usable fuel in a fluidized bed reactor. Thus, in the present arrangement, the separated under-size coke is advantageously fed to the fluidized bed reactor 32. According to the present invention, when the melting furnace is a cupola furnace having an inlet for coke, the arrangement advantageously comprises means 60 for leading coke particles having a particle size smaller than a predetermined limit from the inlet for coke 18 to the fluidized bed reactor 32.

[0047] Usually, a cupola-furnace produces exhaust gas with a high CO-content, such as 10%, and a low oxygen content. The exhaust gas is conventionally combusted in an incinerator. The present arrangement provides a possibility for further synergy between the melting furnace 12 and the fluidized bed reactor 32 by using the exhaust gas from the cupola furnace as a further fuel 12 in the fluidized bed reactor 32. Therefore, the arrangement advantageously comprises means 62 for leading CO-comprising flue gas from the melting furnace 12 to the fluidized bed reactor 32.

[0048] The diagram of FIG. 2 schematically illustrates an arrangement 10′ for recycling mineral wool waste to mineral wool production according to another embodiment of the present invention. The arrangement shown in FIG. 2 differs from that shown in FIG. 1 mainly in that the melting furnace 12′ is an electrical arc furnace instead of a cupola furnace. All reference numbers of devices or elements that are identical to or at least similar with corresponding devices or devices in FIG. 1, are referred, in FIG. 2, as well as in FIGS. 3 and 4, with the same reference numbers.

[0049] As the melting furnace 12 in the embodiment of FIG. 1, the melting furnace 12′ comprises an inlet 14 for virgin mineral wool raw material and an outlet 16 for molten mineral wool material. Because the mineral material is melted in an electrical arc furnace by electrical power, instead of heat from a combustion process, there is no need to feed coke or other fuel to the electric arc furnace of the melting furnace 12′. Correspondingly, there is no means for leading under-size coke from an inlet of the melting furnace to the fluidized bed reactor, as in FIG. 1. However, there may be a need to feed in, for example, steel scrap to the melting furnace 12′ to initiate the melting process. The melting furnace 12′ also does not generate a significant amount of CO-rich flue gas, and generally there is no means for leading flue gas from the melting furnace 12′ to the fluidized bed reactor 32.

[0050] As in the arrangement shown in FIG. 1, the fluidized bed reactor 32 comprises an inlet 48 for shredded mineral wool waste, and the ash product from bottom ash and/or fly ash comprises fine mineral wool material powdered from the mineral wool waste in the fluidized bed reactor 32. The ash product is lead to the melting furnace 12′, i.e., to the electrical arc furnace 12′, via an inlet for the ash product 50, whereby the ash product is used as a further mineral wool raw material. Because no blast air is introduced into the electrical arc furnace 12′, it may in some applications be possible to use the ash material from the fluidized bed reactor 32 as a further mineral wool raw material without sintering or briquetting it in the corresponding reactor 46.

[0051] Advantageously, the fluidized bed reactor 32 is a fluidized bed boiler that generates steam, which steam is lead via a steam line 68 to a steam turbine 70, which is connected to a generator 72 to generate electrical power. According to a preferred embodiment, at least a portion of the electrical power is transmitted via line 74 to the electrical arc furnace 12′ to be used for melting the mineral wool raw material. The generated electrical power can advantageously also be transmitted via line 74′ to in the curing oven 28 of the mineral wool production line 22, to be used for generating heat, usually, hot air, therein. However, it is also possible that the curing oven is heated by other means, for example, by heat extracted from the flue gas as in the embodiment shown in FIG. 1.

[0052] The diagram of FIG. 3 schematically illustrates arrangement 10″ for recycling mineral wool waste to mineral wool production according to a still another embodiment of the present invention. The arrangement shown in FIG. 3 differs from those shown in FIGS. 1 and 2 in that the arrangement comprises a first melting furnace 12″ and a second melting furnace 12′″. The first melting furnace 12″ is a cupola furnace and the second melting furnace 12′″ is an electric arc furnace. All reference numbers of devices or elements that are at least principally identical with corresponding devices or devices in FIGS. 1 and 2, are referenced with the same reference numbers as therein.

[0053] As in the arrangement shown in FIG. 1, coke is fed as fuel to the first melting furnace, the cupola furnace 12″, and CO-rich flue gas is advantageously led from the first melting furnace, i.e., the cupola furnace 12″ via line 62 to the fluidized bed reactor 32. On the other hand, since no fuel is fed to the second melting furnace, the electrical arc melting furnace 12′″, the furnace 12′″ does not generate CO-rich flue gas to be led to the fluidized bed reactor 32. Both the first 12″ and the second 12′″ melting furnaces comprises an inlet 14 for virgin mineral wool raw material and an outlet 16 for molten mineral wool material. Stages of the production lines 22 of the first and second melting furnaces 12″, 12′″ are similar to that shown in FIG. 1, although not shown in FIG. 3. In the embodiment shown in FIG. 3, ash product or ash product from the fluidized bed reactor 32 is lead, via line 66′, only to the electrical arc melting furnace 12′″ so as to use it as a further mineral wool raw material in the electrical arc melting furnace 12′″.

[0054] However, it is also possible that the ash material or ash product from the fluidized bed reactor 32 is lead only to the first melting furnace, i.e., cupola furnace 12″, or that the ash material or ash product from the fluidized bed reactor 32 is lead to both the first melting furnace 12″ and to the second melting furnace 12′″, to be used as a further mineral wool raw material. As is clear to a person skilled in the art, the number of melting furnaces can be even higher than two, and their types and connections to the fluidized bed reactor may vary according to the need.

[0055] FIG. 3 does not show a reactor for sintering or briquetting the ash material, but naturally, such can be used, if needed. The way to provide power to the electrical arc furnace described in connection with FIG. 2 can naturally also be used for the embodiment of FIG. 3. The curing oven can be heated by heat extracted from the flue gas, as in FIG. 1, or by generated electrical power, as shown in FIG. 2. FIG. 3 does not show determining the type of fuel or bed material to be fed to the fluidized bed reactor on the basis of material analysis of the produced mineral wool product, the mineral wool waste fed to the fluidized bed reactor, and/or further mineral wool raw material conveyed to the melting furnace, but, as is clear to a person skilled in the art, the procedures described in connection with FIGS. 1 and 2 can also be used in the embodiment of FIG. 3.

[0056] FIG. 4 shows an arrangement 10′″ representing still another type of embodiment of the present invention, wherein the melting furnace 12 is a cupola furnace as in the embodiment shown in FIG. 1 above, but the fluidized bed reactor is a gasifier 76, that produces combustible gas. The arrangement comprises gas flow dividers 78 and a gas pipe 80 for leading at least a portion of the produced combustible gas to the cupola furnace 12 and/or to the curing oven 28 in the mineral wool production line 22.

[0057] While the invention has been described herein by way of examples in connection with what are at present considered to be the most preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but is intended to cover various combinations or modifications of its features and several other applications included within the scope of the invention as defined in the appended claims.