Feeder assembly for molten mineral material with energy recovery

Abstract

A feeder assembly (1) arranged in connection with a melting furnace (4), arrangement for producing fibrous insulation material (13) and a method for improving energy efficiency of a melting furnace producing molted mineral material (3). The feeder assembly comprises a feeder (2) for conveying the molten mineral material from the melting furnace to a forming machine (5) following the melting furnace. The feeder assembly further comprises an extraction ventilation system (6) for collecting high temperature extraction gases (7) from the feeder. The extraction ventilation system is provided with an energy recovery unit (8) for harvesting energy from the extracted gases.

Description

[0001]Feeder assembly, arrangement for producing insulation material, and method Background of the invention The invention relates to a feeder assembly compris- ing a feeder for conveying molten mineral material from a melting furnace to a forming machine following the melting furnace. The invention further relates to an arrangement for producing fibrous insulation material and to a method for recovering energy of a melting furnace wherein mineral ma- terial is molted. The field of the invention is defined more specif- ically in the preambles of the independent claims. Different types of melting furnaces are used for melting mineral materials when producing fibrous insulation materials and other products wherein molten mineral mate- rial is used as one raw material component. The molten mineral material is conveyed by means of a feeder from the melting furnace to next process steps wherein the molten mineral material is shaped and further processed. The known solutions have shown to contain some disadvantages. Brief description of the invention An object of the invention is to provide a novel and improved feeder assembly for conveying molten mineral material. A further object is to provide a new and improved arrangement and method utilizing the feeder assembly. The feeder assembly according to the invention is characterized by the characterizing features of the first independent apparatus claim. The arrangement according to the invention is char- acterized by the characterizing features of the second in- dependent apparatus claim. The method according to the invention is character- ized by the characterizing features of the independent method claim. An idea of the disclosed solution is that a feeder assembly comprises a feeder for conveying molten mineral material from a melting furnace to a forming machine fol- lowing the melting furnace. The feeder assembly further comprises an extraction ventilation system connected to the feeder for collecting high temperature extraction gases from the feeder. The extraction ventilation system comprises one or more energy recovery units for harvesting energy from the extracted gases. In other words, the feeder assembly is provided with an energy recovery arrangement for recovering heat energy which can be utilized in the following processes. The feeder assembly is advantageously part of an arrangement for producing fibrous insulation material. The feeder is arranged at the outlet of the melting furnace and is adapted to receive the molten mineral mate- rial from the melting furnace. An advantage of the solution is that significant amount of energy can be saved whereby CO2emissions can be reduced and production costs of end products can be kept tolerable despite of constantly rising energy prices. Uti- lizing waste heat is an environmental accomplishment and is also economically beneficial. According to an embodiment, the feeder is heated to maintain the molten mineral material in defined temperature and viscosity to be further processed in following process devices. However, the temperature of the molten mineral ma- terial can be allowed to be decreased during the convey from the initial temperature provided at the melting furnace so that it matches with the required process temperature of the following forming machine. In one example setting, the temperature at the melt- ing furnace may be 1300°C and the temperature at the end of the feeder may be 1100°C, whereby the molten mineral mate- rial is allowed to be cooled down intentionally for 200°C during the convey in the feeder. According to an embodiment, the feeder may be heated by electrical heating apparatuses. According to an embodiment, the feeder may alterna- tively be heated by gas-fired burners. According to an embodiment, the disclosed feeder is utilized in a production line producing mineral wool insu- lation material, such as glass wool or stone wool insulation material. Any of these insulation materials comprises min- eral fibers. According to an embodiment, the disclosed feeder can also be utilized in ceramic fiber production lines. According to an embodiment, the disclosed feeder is utilized in a production line producing flat glass, or any other glass products. In other words, the solution can be also implemented in other factories and processes forming molten mineral materials than in the insulation production lines. According to an embodiment, the feeder is an elon- gated structure comprising a bottom part provided with a longitudinal canal having material contact surfaces for conveying the molted mineral material, and a top part form- ing a superstructure for the bottom part whereby the bottom part and the top part define together an inner space of the feeder. Further, there is one or more ventilation ducts which are part of the extraction ventilation system and are in gas connection with the inner space of the feeder. In other words, hot fumes can be extracted from the feeder. An advantage is that hot fumes including waste heat can now be utilized in the following processes or elsewhere. A further advantage is that fumes and gases detrimental to health, such as boran fumes, can be gathered in a controlled way and led to a gas washer. Thus, the extraction of fumes can improve safety and energy efficiency of the process. According to an embodiment, the at least one venti- lation duct is connected to the top part of the feeder. There may be several separate ventilation ducts, or alter- natively a manifold may be mounted on the top part of the feeder for collecting the gases. According to an embodiment, the feeder is an elon- gated structure comprising a bottom part provided with a longitudinal canal having material contact surfaces for conveying the molted mineral material, and a top part form- ing a superstructure for the bottom part. Further, the top part of the feeder is provided with cooling air flow from one or more cooling fans for cooling the feeder. The ex- traction ventilation system comprises at least one overhead extractor hood for capturing the fed cooling air flow after being heated by the feeder. According to an embodiment, the solution relates also to an arrangement for producing fibrous insulation material wherein the arrangement comprises: a melting fur- nace for melting mineral material and producing molted min- eral material; a fiberizing device for shaping the received molted mineral material into fibres; a curing oven for cur- ing at elevated temperature at least one binder, which is added to the produced fibres; and a feeder for conveying the molted mineral material from the melting furnace to the fiberizing device. Further, the curing oven is provided with a gas-fired and / or oil-fired heating system comprising a combustion air feed system. Alternatively, the curing oven may be equipped with an electric means heating. The feeder is in accordance with the features and embodiments disclosed in this document and is connected to an extraction venti- lation system for collecting high temperature extraction gases from the feeder. The extraction ventilation system is provided with one or more energy recovery units for har- vesting energy from the extracted gases and are connected to the combustion air feed system for pre-heating combustion air fed to the gas-fired and / or oil-fired heating system of the curing oven, and / or the extraction ventilation system of the feeder assembly is connected to the fiberizing device for preheating a gas flow sent to the fiberizing device. In other words, the waste heat produced at the feeder is utilized for pre-heating air fed to gas and / or oil burners of the curing oven. An advantage is that consumption of natural gas, or oil can be decreased when temperature of the burning air is elevated. Less burned gas or oil means lower CO2emissions. An overall energy efficiency of the insulation material plant can be improved, and the implementation of the solu- tion is relatively easy and inexpensive to implement. Fur- ther, the solution can be retrofitted to the existing in- sulation plants producing mineral wool insulation materi- als. According to an embodiment, the energy recovery unit comprises at least one heat exchanger for transferring heat from the extracted high temperature extraction gases of the feeder to combustion air conveyed to the burners of the curing oven. According to an embodiment, in the melting furnace the mineral material is melted by electrical energy and in which the molten mineral material itself acts as the re- sistance element in which heat for melting the batch is generated. However, the disclosed solution is equally ap- plicable to other types of electric furnaces and to fuel- fired furnaces. According to an embodiment, the arrangement relates to production of mineral insulation material. Then the fi- berizing device comprises spinning elements for shaping the molten mineral material into fibres, and further, small quantities of binding agents are added to keep the fibres together and add to strength and mechanical properties. The added one or more binding agents, or binders, are cured in the curing oven at elevated temperature. According to an embodiment, the disclosed solution relates also to a method for recovering energy of a melting furnace wherein mineral material is molted, and the produced molted mineral material is conveyed via a feeder to a form- ing machine following the melting furnace. The method fur- ther comprises collecting high temperature extraction gases from the feeder and harvesting energy from the extracted gases. According to an embodiment, the method further com- prises: directing the collected gases as a first gas flow to at least one heat exchanger; pre-heating a separate sec- ond gas flow in the at least one heat exchanger; and con- veying the pre-heated second gas flow to the forming ma- chine. According to an embodiment, the method further com- prises implementing the harvested energy in a production of insulation material containing mineral material fibres. According to an embodiment, the method further com- prises implementing the harvested energy for heating indus- trial real estates. According to an embodiment, the method further com- prises collecting fumes from the feeder and directing them via at least one heat exchanger to a gas washer. According to an embodiment, the method further com- prises harvesting energy from the extracted gases by means of at least one heat pump. According to an embodiment, the method further com- prises implementing in the method the feeder assembly dis- closed in this document. The above disclosed embodiments may be combined in order to form suitable solutions having those of the above features that are needed. Brief description of the figures Some embodiments are described in more detail in the accompanying drawings, in which Figure 1 is a schematic diagram of a feeder assembly wherein a feeder is conveying molten mineral material from a melting furnace to a forming machine, Figure 2 is a schematic diagram of possible use cases of a feeder assembly in different production lines, Figure 3 is a schematic diagram of an arrangement for producing fibrous insulation material, Figure 4 is a schematic diagram of an arrangement for treating extraction gases gathered from a feeder, Figure 5 is a schematic diagram of possible energy recovery devices, Figure 6 is a schematic view of a structure of feeder connected to an extraction ventilation system, and Figure 7 is a schematic view of a feeder provided with a cooling system and an overhead extractor hood. For the sake of clarity, the figures show some em- bodiments of the disclosed solution in a simplified manner. In the figures, like reference numerals identify like ele- ments. Detailed description of some embodiments Figure 1 discloses a feeder assembly 1 comprising a feeder 2 for conveying molten mineral material 3 from a melting furnace 4 to a forming machine 5. The forming ma- chine 5 can be any type of machine treating the molten mineral material 3 and is selected in accordance with the produced product and implemented process. The feeder 2 is connected to an extraction ventilation system 6 for col- lecting high temperature extraction gases 7 from the feeder 2. In connection with the extraction ventilation system 6 there is an energy recovery unit 8 for harvesting energy 9 from the extracted gases 7. The harvested energy 9 can be utilized in following process steps 10 or submitted further for external use 11. Figure 2 shows that the disclosed feeder assembly may be part of an insulation production line 12 for produc- ing different mineral wool insulation materials 13, such as glass wool or stone wool. Alternatively, the disclosed feeder assembly may be utilized in ceramic fiber production lines 14 and also in glass production lines 15. Figure 3 discloses an arrangement for producing fi- brous insulation material and differs from the arrangement shown in Figure 1 in that the forming machine 5 is a fiber- izing device 16 for shaping the received molten mineral material into fibres. The fiberizing device 16 may comprise for example a rotating flywheel or other spinning elements for shaping the molten mineral material 3 into desired fi- bres. In the fiberizing device 16 one or more binders can be added 17 to the produced fibres to form a mat of fibres. Thereafter the mat of fibers is transferred to a curing oven 18 for curing the added binder at elevated temperature. The binder may comprise a thermosetting material, such as a thermosetting resin. Depending on the implemented binder, curing temperatures are typically in the range of 180°C up to 300°C. When the mat of fibers is cured in the curing oven for a designed curing time at designed circumstances, the mat of fibres is then transferred to one or more finishing processes 19 which are selected in accordance with the pro- duced insulation material. The finishing processes 19 may comprises different cutting, covering and packing measures, for example. The curing oven 18 is provided with a gas-fired and / or oil-fired heating system 20 comprising a combustion air feed system 21 for providing needed combustion air for gas and / or oil burners. Typically, the curing oven comprises an enclosure constituting a closed chamber in which are arranged a series of boxes supplied with hot gas generated by burners. The curing oven comprises means for conveying the mat of fibers through the plurality of boxes. Typically, a stream of hot gas generated by the burners is designed to flow inside the boxes through the mat of fibers to cure the binder. A feeder 2 between a melting furnace 4 and the fi- berizing device 16 is connected to an extraction ventilation system 6 for collecting high temperature extraction gases 7 from the feeder. The extraction ventilation system 6 is provided with at least one energy recovery unit 8 for har- vesting energy 9 from the extracted gases 7. The harvested energy 9 may be utilized for providing the gas-fired and / or oil-fired heating system 20 of the curing oven 18 with pre- heated combustion air 22. The energy recovery unit 8 may comprise one or more heat exchangers for transferring heat from the extracted gases 7 to air inflow. An advantage of the combustion air pre-heating feature is that consumption of the used natural gas, or oil can be decreased when tem- perature of the burning air director to the burners is elevated. Lower amount of burned gas and oil makes it pos- sible to have a significant decrease in CO2emissions. Alternatively, or in addition to, the recovered en- ergy of the extracted gases 7 can be utilized for heating real estate 23, such as industrial halls, factory buildings, and office facilities at or nearby the plant producing the fibrous mineral material. Figure 4 discloses that fumes 24 and gases detri- mental to health, such as boran fumes, can be collected from a feeder 2 and can be directed via one or more heat ex- changers 25 to on or more gas washers 26. This way the fumes can be treated in a controlled and safe way, and still, heat energy of the fumes is recovered. The heat exchanger 25 is part of an energy recovery unit 8 which is connected to an extraction ventilation system 6 of the disclosed arrange- ment. The heat exchanger 25 is configured to transfer re- covered heat energy to air fed 27 as an inlet flow to process steps following the feeder 2. Thus, the heat energy can be utilized for example to pre-heat burning air of burners 39 of a curing oven 18, as is disclosed above in this document. However, the heat energy recovered by the heat exchanger and arranged to pre-heat the inlet air flow can be addi- tionally, or alternatively, be implemented in other purposes and can be conveyed to a forming machine 5 to be utilized therein. For example, the heat energy recovered can be uti- lized to pre-heat burning air of burners of the forming machine 5 when the forming machine 5 is a fiberizing device. A further possibility is that the feeder 2 is heated by means of gas- or oil-fired burners whereby the pre-heated inlet air flow can be utilized therein as pre-heated burning air. Thus, there are several possible ways to utilize the recovered heat energy in the manufacturing process of fi- brous mineral material. Figure 5 discloses that an energy recovery device 8 for recovering heat energy from extracted gases 7 being collected from a feeder may comprise a heat exchanger 25, or a heat pump 28, or both. Coefficient of performance of the heat pump 28 utilizing a compressor, refrigerant and heat exchangers may be high i.e., the heat pump can further boost the heat recovery. Figure 6 discloses a structure of a feeder 2 in simplified cross-sectional manner. The feeder 2 comprises a bottom part 29 provided with a longitudinal canal having material contact surfaces 30 for conveying the molted min- eral material 3, and a top part 31 forming a superstructure for the bottom part 29. The bottom part 29 and the top part 31 define together an inner space 32 of the feeder 2. The inner space 32 is connected to an extraction ventilation system 6 by means of at least one ventilation duct 33 so that hot extraction gases 7 can be collected therefrom. Figure 7 discloses a solution which differs from the one shown in Figure 6 in that a feeder 2 is provided with a cooling system 34. Then, cooling air flow 35 is directed from one or more cooling fans 36 to a top part 31 of the feeder 2 for cooling the feeder 2 to a desired process temperature. Further, one or more overhead extractor hoods 37 are arranged above the feeder 2 for capturing the fed cooling air flow 35 after being heated by the feeder 2. The overhead extractor hood 37 is connected to an extraction ventilation system 6 by means of a ventilation duct 38. The extraction ventilation system 6 is connected to a heat re- covery unit 8. It is also possible to combine the solutions dis- closed in Figures 6 and 7 and to thereby collect heat energy both from inside and outside of the feeder 2. The detailed description refers to a gas- and / or oil-fired heating system. Alternatively, or in addition to, the heating system may comprise electric heating means, such as at least one electrical heat exchanger in communication with the inside of the curing oven so as to feed the boxes of the enclosure of the curing oven with heated air. The drawings and the related description are only intended to illustrate the idea of the invention. In its details, the invention may vary within the scope of the claims.

Claims

Claims 1. A feeder assembly (1) comprising a feeder (2), wherein the feeder (2) is configured to convey mol- ten mineral material (3) from a melting furnace (4) to a forming machine (5) following the melting furnace (4); ch a r a c t e r i z e d in thatthe feeder assembly (1) further comprises an ex- traction ventilation system (6), the feeder (2) being con- nected to the extraction ventilation system (6) for col- lecting high temperature extraction gases (7) from the feeder (2); and wherein the extraction ventilation system (6) is provided with at least one energy recovery unit (8) for harvesting energy from the extracted gases (7).

2. The feeder assembly as claimed in claim 1,c h a r a c t e r i z e d in thatthe feeder (2) is an elongated structure comprising a bottom part (29) provided with a longitudinal canal having material contact surfaces (30) for conveying the molted mineral material (3), and a top part (31) forming a super- structure for the bottom part (29) whereby the bottom part (29) and the top part (31) define together an inner space (32) of the feeder (2); and wherein at least one ventilation duct (33) of the extraction ventilation system (6) is in gas connection with the inner space (32) of the feeder (2).

3. The feeder assembly as claimed in claim 1 or 2,c h a r a c t e r i z e d in thatthe feeder (2) is an elongated structure comprising a bottom part (29) provided with a longitudinal canal having material contact surfaces (30) for conveying the molted mineral material (3), and a top part (31) forming a super- structure for the bottom part (29);and wherein the top part (31) of the feeder (2) is provided with cooling air flow (35) from at least one cool- ing fan (36) for cooling the feeder (2); and the extraction ventilation system (6) comprises at least one overhead extractor hood (37) for capturing the fed cooling air flow (35) after being heated by the feeder (2).

4. An arrangement for producing fibrous insulation material (13) wherein the arrangement comprises: a melting furnace (4) for melting mineral material and producing molted mineral material (3); a fiberizing device (16) for shaping the received molted mineral material (3) into fibres; and a curing oven (18) for curing at elevated tempera- ture at least one binder added (17) to the produced fibres; ch a r a c t e r i z e d in thatthe arrangement further comprises a feeder assembly (1) according to any one of claims 1 to 3, the feeder (2) of the feeder assembly (1) being configured to convey the molted mineral material (3) from the melting furnace (4) to the fiberizing device (16); the curing oven (18) is provided with a gas-fired and / or oil-fired heating system (20) comprising a combus- tion air feed system (21); and wherein the extraction ventilation system (6) of the feeder assembly is connected to the combustion air feed system (21) for pre-heating combustion air (22) fed to the gas-fired and / or oil-fired heating system (20) and / or the extraction ventilation system (6) of the feeder assembly is connected to electrical heating means of the curing oven (18), such as at least one electrical heat exchanger, and / or the extraction ventilation system (6) of the feeder assembly is connected to the fiberizing device (16)for preheating a gas flow sent to the fiberizing device (16).

5. A method for recovering energy of a melting fur- nace (4) wherein mineral material is molted, and the pro- duced molted mineral material (3) is conveyed via a feeder (2) to a forming machine (5) following the melting furnace (4); ch a r a c t e r i z e d bycollecting high temperature extraction gases (7) from the feeder (2) and harvesting energy from the extracted gases (7).

6. The method as claimed in claim 5, c h a r a c t e r -i z e d bydirecting the collected gases as a first gas flow to at least one heat exchanger (25); pre-heating a separate second gas flow in the at least one heat exchanger (25); and conveying the pre-heated second gas flow to the forming machine (5).

7. The method as claimed in claim 5 or 6, c h a r -a c t e r i z e d byimplementing the harvested energy in a production of insulation material (13) containing mineral material fi- bres.

8. The method as claimed in claim 5, c h a r a c t e r -i z e d byimplementing the harvested energy for heating in- dustrial real estates (23).

9. The method as claimed in any one of the precedingclaims 5 - 8, c h a r a c t e r i z e d bycollecting fumes (24) from the feeder (2) and di- recting them via at least one heat exchanger (25) to a gas washer (26).

10. The method as claimed in any one of the preced-ing claims 5 - 9, c h a r a c t e r i z e d byharvesting energy from the extracted gases (7) by means of at least one heat pump (28).

11. The method as claimed in any one of the preced-ing claims 5 - 10, c h a r a c t e r i z e d bycarrying out the method by means of the feeder as- sembly (1) being in accordance with any one of the preceding claims 1 - 3.

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