Furnace lining for mineral smelting

Abstract

Embodiments herein provide a furnace wall for a furnace system for melting mineral materials to produce mineral melt, wherein the mineral melt is at least one of stone melt, rock melt, or slag melt. The furnace wall includes: a solid refractory layer (201), e.g. bricks comprising alumina and chromium oxide, a solid conductive layer (202), e.g. comprising graphite, and conductive paste (203) therebetween. The conductive paste (203) may comprise graphite and transfers heat from the exterior surface of the solid refractory layer (201) to the interior surface of the solid conductive layer (202). A method of maintaining a furnace with said wall further having aperture(s) for introducing conductive paste into the furnace wall is described.

Description

[0001] FURNACE LINING FOR MINERAL SMELTING

[0002] FIELD OF THE INVENTION

[0003] The invention relates to improvements to systems and methods for melting mineral materials in a furnace. In particular, the systems and methods are well suited for the melting of mineral material, such as rock, stone, slag and other similar materials, to form a mineral melt suitable for use in the formation of manmade vitreous fibres (MMVF).

[0004] BACKGROUND

[0005] Furnace systems (also referred to as smelters), including electric furnace systems (also referred to as e-furnaces), may be used for melting mineral material, which may, in turn, be used for purposes such as the production of man-made vitreous fibres (MMVF) and manufacturing mineral wool insulation for buildings as well as other applications.

[0006] Electric furnace systems include a submerged arc furnace (SAF). In an SAF, current is transmitted through melt material (or slag), between two or more (such as three) electrodes submerged in the melt material. Heat can be generated through the Joule effect. Electric furnace systems also include an electric arc furnace (EAF). In an EAF, electrodes are generally not submerged, and act to arc towards a melt material surface. The melt material is melted by heat radiation from the arc / plasma. Further electric furnace systems include immersed arc furnace, brush arc furnaces and shielded arc furnaces.

[0007] Existing furnaces in glass and ferrometals industries, by way of example, are poorly suited to form mineral melts in the stone mineral industry as temperatures required are much hotter.

[0008] A particular issue facing furnaces, and furnace components, with respect to their suitability for mineral materials including stone and slag, is the durability of furnace walls or furnace linings. During furnace operation with stone, and slag mineral material and mineral melts, molten iron, Fe(0), often collects at a base of thefurnace. This iron erodes or wears away refractory bricks lining of the furnace, moving outwards through cracks in the bricks. The rate of wear of the wall or lining has been found to increase rapidly for melt temperatures above 1500 degrees Celsius (°C) which are common when melting mineral materials including stone, and slag. The rate of wear of the wall or lining has also been found to be higher for stone, and slag melt, as these compositions of melt can be highly corrosive. Furthermore, the rate of erosion may be increased at interfaces between different liquids (e.g. melt material and waste metal) due to the Marangoni Effect. Failure of the wall or lining can be extremely dangerous as molten material breaches the wall of the furnace and may possibly come into contact with a liquid cooling system disposed around the furnace. Such failures can cause damage with high material cost and can pose a serious risk to life or health of human operators.

[0009] As such, there is an ongoing desire for the provision of furnaces, methods of operating furnaces, and furnace components, that are suitable for mineral materials including rock, stone, and slag. Additionally, there is an ongoing desire for such furnaces, methods of operating furnaces, and furnace components which benefit from increased safety and durability, particularly at the furnace temperatures and melt compositions required in rock and stone mineral industry.

[0010] SUMMARY OF INVENTION

[0011] The object of the invention is addressed by the features of the appended independent claims. Further aspects of the invention are defined in the appended dependent claims. Aspects of the invention herein provide furnaces (e.g. electric furnaces), components thereof, and their methods of operation, which are suitable for rock, stone, and slag. These aspects provide substantially increased safety and durability, when compared to furnaces, components thereof, and their methods of operation, which are already available. Furnace walls, furnaces and methods in accordance with the invention are well suited for melting mineral materials to form mineral melts. These mineral melts may be stone, rock or slag melts. The mineral melts may be suitable for creating man-made vitreous fibres (MMVF) such as stone wool, rock wool and slag wool among others.In accordance with an aspect of the invention , there is provided a furnace wall for a furnace system for forming a mineral melt suitable for forming man-made vitreous fibres (MMVF), the furnace wall comprising a solid refractory layer comprising an interior surface and an exterior surface, wherein in use at least a portion of the interior surface is in contact with the mineral melt, a solid conductive layer comprising an interior surface arranged to face the exterior surface of the solid refractory layer, and a conductive paste between the interior surface of the solid conductive layer and the exterior surface of the solid refractory layer, wherein the conductive paste is configured to transfer heat from the exterior surface of the solid refractory layer to the interior surface of the solid conductive layer.

[0012] The solid refractory layer advantageously provides high heat and wear resistance, allowing the furnace to contain and melt mineral material at high temperatures. The solid refractory layer may define part of the boundary of an internal cavity in the furnace, the internal cavity being configured to receive and hold mineral material and mineral melt in use. Additionally, the internal cavity may contain any waste metal (e.g. iron) formed by the melting of the mineral material.

[0013] The conductive paste allows for effective thermal conduction between the solid refractory layer and the solid conductive layer. As such, the conductive paste transfers heat outwards from the inner solid refractory layer, which contacts mineral melt and waste metal, to the surrounding solid conductive layer.

[0014] The solid conductive layer also allows for effective thermal conduction and helps transfer heat from the furnace. Advantageously the solid conductive layer provides, in conjunction with the other layers, increased safety in the case that molten material breaches the solid refractory layer or substantially wears down the solid refractory layer. If molten material were to breach or substantially wear down the solid refractory layer, the solid conductive layer will rapidly distribute the heat throughout the solid conductive layer. As such, rapid cooling of the molten material is facilitated, prompting the molten material to solidify or freeze on contact with the solid conductive layer. The solid conductive layer is therefore a “last line of defence” in preventing molten mineral material from breaching the wall of the furnace completely and possibly coming into contact with a liquid cooling system(if present). In addition, the rapid distribution of heat throughout the solid conductive layer may be detected by a temperature detection system, such as a thermometer, temperature sensor, thermocouple, thermal camera or optical fibre sensors and thus may be used to detect wear to or a breach of the solid refractory layer. The solid conductive layer and conductive paste enable the size of the furnace wall and cost of the furnace wall to be reduced when compared to alternative arrangements which use relatively thick layers of refractory materials.

[0015] The conductive paste is advantageously flowable, and therefore, fills and bridges gaps and cavities between the solid refractory layer and the solid conductive layer. Preferably the exterior surface of the solid refractory layer and the interior surface of the solid conductive layer face one another and the conductive paste is provided therebetween (e.g. in contact with both layers). As such, the conductive paste may provide strong thermal contact between the opposing solid layers. The conductive paste accommodates variations in positioning of the solid refractory layer and the solid conductive layer. The paste may additionally or alternatively accommodate imperfections, variations, or gaps between component parts of the solid refractory layer and / or the solid conductive layer, for example, bricks or tiles making up these layers. Where the furnace system has a cylindrical form and the solid refractory layer is formed of cuboidal or substantially cuboidal bricks and / or tiles, the conductive paste ensures good thermal connection between the bricks and / or tiles and the cylindrical solid conductive layer. Indeed, using a conductive paste helps ensure a strong thermal connection between the solid refractory layer and the solid conductive layer, regardless of the shapes of the furnace system, solid refractory layer (and any constituent bricks or tiles) and the solid conductive layer. Thus, the construction and assembly of the furnace may be simplified without any loss in safety.

[0016] Preferably the exterior surface of the solid refractory layer and the interior surface of the solid conductive layer face one another and the conductive paste is provided therebetween (e.g. in contact with both layers). As such, the conductive paste may provide strong thermal contact between the opposing solid layers. Duringinstallation the paste may be tamped to remove any gaps and ensure good physical and thermal contact with the refractory and solid conductive layer.

[0017] Herein, the term “conductive” will be understood to refer to thermal or heat conduction. The conductive paste and solid conductive layer are materials which offer high thermal conductivity and may easily and effectively transfer heat from the inside the furnace towards the outside of the furnace. For instance, the conductive pastes (i.e. the thermally conductive pastes) used herein may have a thermal conductivity of at least 5 W / mK, preferably at least 10 W / mK, more preferably still at least 20 W / mK at 20 degrees Celsius. Similarly, the solid conductive layers (i.e. the solid thermally conductive layers) used herein may have a thermal conductivity of at least 25 W / mK, preferably at least 50 W / mK, more preferably still at least 70W / mK, more preferably still 100 W / mK at 20 degrees Celsius.

[0018] Herein, the term “interior” will be understood to refer the surfaces of the respective components and layers which are positioned closer to, and are arranged to face towards the centre of the furnace. Whereas, the term “exterior” will be understood to refer to the surfaces of the respective components and layers understood to refer the surfaces of the respective components and layers which are positioned further from, and are arranged to face away from the centre of the furnace.

[0019] Optionally, the furnace wall is provided with temperature sensors of a temperature detection system. The temperature detection system is configured to measure a temperature of, changes of temperature in, and / or heat flux through, the solid refractory layer, conductive paste and / or solid conductive layer. In particularly preferred examples, the temperature detection system may be configured to measure the temperature of an exterior surface of the solid conductive layer and / or the internal temperature within the solid conductive layer. Optionally, the temperature detection system and its temperature sensors may be coupled to the solid conductive layer, although non-contact systems may also be used. The combination of the solid conductive layer and the temperature detection system allows for effective detection of, for example, high temperatures of the solid conductive layer or rapid increases in temperature of the solid conductive layer.Additionally or alternatively, the temperature detection system may be configured to measure temperatures and temperature changes of or within any of the other components of the furnace walls described herein or heat flux through the furnace. For example, the temperature detection system may comprise temperature sensors in contact with the external surface of the solid refractory layer, within the solid refractory layer, and / or in contact with or within the conductive paste. Equally the temperature detection system may be configured to detect one or more temperatures of a liquid cooling system of the furnace and / or any liquid from said system.

[0020] In some embodiments, the temperature detection system is configured to detect wear or a breach of the solid refractory layer by mineral melt, based on a change in temperature of the solid conductive layer. Detection of high temperatures of the solid conductive layer or rapid increases in temperature of the solid conductive layer may be indicative of increased wear or a breach of the solid refractory layer by mineral melt or liquid metal. Therefore, the solid conductive layer performs an additional safety function of providing a warning system that may be used, for example, for alerting a user of a breach or informing a control system of a breach. Equally, wear or a breach of the solid refractory layer by mineral melt, based on a change in temperature of the solid refractory layer or conductive paste. In some preferable embodiments, increased wear is detected before a breach is detected. Detection of increased wear and / or a breach may result from detecting a difference in the rate of change of temperature and / or a change in the magnitude of the measured temperature of the components of the furnace. Mounting the temperature sensors on or within the solid conductive layer may offer easier maintenance than sensors that are mounted within the interior of the furnace wall (e.g. on or within the solid refractory layer or conductive paste).

[0021] Optionally, the temperature detection system is configured to issue a warning based on the detected wear or breach of the solid refractory layer by mineral melt. Advantageously, responsive action may then be taken, such as turning off the furnace and / or performing maintenance. The warning may be electronic, audible (e.g. an alarm), visual (a visual alert), or any other suitable means of providing awarning. An electronic warning may alert a computer system, for example, a computer system controlling aspects of the furnace system. Responsive action may then be automatic.

[0022] The temperature detection systems, its sensors, any controllers of the temperature detection systems and any warning or notification unit may form part of the furnace wall or may be comprised in a wider system that includes the furnace and its walls.

[0023] In some embodiments, the furnace wall is further provided with a cooling system configured to cool an exterior surface of the solid conductive layer. Cooling systems are advantageous (and sometimes possibly necessary) for rock, stone, and slag smelting due to the high temperatures involved. Furthermore, a cooling system at the exterior of the furnace wall may allow the overall dimensions of the furnace walls to be reduced. The present invention is particularly advantageous when applied to a furnace wall including a cooling system, as breaching molten material coming into contact with the cooling system can cause catastrophic structural failures, such as explosions, particularly given the large difference in temperatures of each of these entities. The safety provided by the present invention is therefore enhanced.

[0024] Optionally, the cooling system includes a liquid cooling jacket coupled to the exterior surface of the solid conductive layer. The present invention is particularly advantageous when applied to a furnace wall including a liquid cooling jacket. On contact with molten material from the furnace, liquid in the liquid cooling jacket is likely to rapidly change state, thus possibly causing a dangerous explosion. Thus, the solid conductive layer provides enhanced safety benefits for systems with liquid cooling jackets. Preferably, the liquid in the liquid cooling jacket is water or a water-salt solution. In some embodiments, the liquid cooling jacket comprises or requires a pump to circulate the liquid through jacket and transfer heat away from furnace wall. As alternative to a liquid cooling jacket, a furnace system such as those described below may include a liquid (e.g. water) mist or sprayer system to cool the outer surface of the solid conductive layer.In some embodiments, the solid refractory layer comprises at least 20% chromium oxide by weight, preferably in a range from 30% to 70%, although alternative compositions are possible. Advantageously, compositions comprising chromium oxide provide enhanced durability of the solid refractory layer. Enhanced durability of the refractory layer also provides enhanced safety of the furnace wall overall. The solid refractory layer may additionally comprise alumina or other materials suitable for use in refractory layers.

[0025] Preferably, at least a portion of the solid refractory layer that is in contact with the mineral melt when in use, has a higher amount of chromium oxide by weight than a further portion of the solid refractory layer. For instance, a lower portion of the solid refractory layer may have a higher content of chromium oxide than an upper portion of the solid refractory layer. Thus, the upper portion may be arranged above the lower portion along a vertical direction. Advantageously, such an arrangement provides enhanced durability to the portion of the furnace which is most susceptible to wear from molten iron or other byproducts. As before, enhanced durability of the refractory layer also provides enhanced safety of the furnace wall overall.

[0026] In some embodiments, the solid refractory layer comprises bricks comprising alumina and chromium oxide. Preferably the bricks comprise at least 50% by combined weight of alumina and chromium oxide, more preferably at least 75%. Advantageously, such bricks provide enhanced durability of the solid refractory layer. As before, enhanced durability of the refractory layer also provides enhanced safety of the furnace wall overall.

[0027] In further examples the solid refractory layer may be formed of a castable refractory.

[0028] Optionally, the solid conductive layer comprises graphite. Preferably, the solid conductive layer comprises pure graphite, or greater than 90%, 95%, or 99% graphite by weight. Advantageously, such compositions provide enhanced conductivity of the solid conductive layer. Consequently, the solid conductive layer may more rapidly distribute the heat throughout the solid conductive layer. Assuch, the aforementioned safety advantages are enhanced. More preferably still, the solid conductive layer comprises sheets or tiles. More preferably still, the solid conductive layer (possibly comprising sheets or tiles) is formed of pure graphite or greater than 90%, 95%, or 99% graphite by weight. Alternatively, the solid conductive layer may comprise other materials with high heat resistance, such as silicon carbide.

[0029] In some embodiments, the conductive paste comprises graphite. Advantageously, such compositions provide enhanced conductivity of the conductive paste. As such, conductivity between layers is enhanced, improving safety, durability, and cooling. Alternative conductive pastes with high heat conductivity may also be used, for instance, pastes comprising silicon carbide.

[0030] Optionally, the furnace wall includes one or more apertures extending from an exterior surface of the furnace wall, to between the solid conductive layer and the solid refractory layer, wherein said apertures are configured to facilitate introduction of conductive paste into the furnace wall. As such, these apertures may extending from an exterior surface of the furnace wall (e.g. the exterior surface of the solid conductive layer or the exterior surface of a liquid cooling jacket), to between the interior surface of the solid conductive layer and the exterior surface of the solid refractory layer. Advantageously, providing one or more apertures through the outer sections of the wall to a gap or cavity between the opposing solid conductive layer and the solid refractory layer facilitates the injection (introduction) of conductive paste through the aperture(s) and may substantially increase the durability and lengthen the life of the furnace wall, since, in use, conductive paste may be lost (e.g. it is “burnt off’) due to the high temperatures, and / or sink down the furnace under gravity. Where present, the apertures may pass through the cooling system, for example a liquid cooling jacket. Where the aperture is to pass through a liquid cooling jacket, the liquid cooling jacket should be configured to include walls surrounding the aperture, so as to prevent the mixing of cooling liquid and conductive paste.

[0031] In some embodiments, the conductive paste is comprised in a conductive paste layer. The conductive paste layer is in contact with the interior surface of the solidconductive layer and the exterior surface of the solid refractory layer. In some embodiments, the conductive paste layer may completely separate the solid conductive layer and the solid refractory layer. A conductive paste layer may improve the strong thermal connection between the solid refractory layer and the solid conductive layer. In some embodiments, the conductive paste layer may cover more than 25% of the total external surface of the refractory layer; more preferably, it may cover more than 50%; or more preferably still, it may cover more than 75%. The conductive paste layer may therefore be prioritised such that it corresponds to the hottest part of the furnace, while saving on material costs.

[0032] Some embodiments herein provide a furnace system configured to produce mineral melt, wherein the mineral melt is suitable for forming man-made vitreous fibres. For instance the mineral melts may be at least one of stone melt, rock melt, or slag melt and may be suitable for forming stone wool, rock wool or slag wool.

[0033] In accordance with an aspect of the invention there may be provided a furnace system forming a mineral melt suitable for forming MMVF, the system comprising a furnace body for receiving the mineral material, the furnace body comprising a furnace wall in accordance with the preceding aspect, and one or more heating apparatuses for heating the mineral material to form the mineral melt.

[0034] This system may include any of the optional or preferable features discussed above with respect to the preceding aspect of the invention, and offer corresponding benefits. In particular, .a furnace wall with enhanced safety and durability may lead to a furnace system with enhanced safety and durability, when said wall is incorporated into said system.

[0035] Preferably, the system comprises a temperature detection system configured to measure a temperature of the solid conductive layer. The temperature detection system may be the system discussed above with reference to the preceding aspect of the invention. Additionally, or alternatively, the temperature detection system may be configured to measure a temperature of the solid refractory layer, conductive paste and / or any liquid cooling system such as a jacket (if present). The temperature detection system may include the sensors discussed abovewhich are configured to detect a temperature of the solid refractory layer, conductive paste, solid conductive layer and / or liquid cooling system such as a jacket (if present), a controller configured to receive and analyse detection results from the sensors and a warning or notification unit configured to send a warning or notification to a user or other system based on the detection results.

[0036] Preferably, the temperature detection system is configured to detect wear or a breach of the solid refractory layer by mineral melt, based on a change in temperature of the solid conductive layer (e.g. a change in the internal or surface temperature of the solid conductive layer). Such a system is easily maintained from the exterior of a furnace and does not require any sensing equipment to pass around or through the solid conductive layer. Additionally, or alternatively, the temperature detection system is configured to detect wear or a breach of the solid refractory layer by mineral melt, based on a change in the temperature of the solid refractory layer or conductive paste, or in a temperature of a liquid cooling system or the liquid therein (if such a system is present). More preferably still the temperature detection system may be configured to issue a warning based on the detected wear or breach of the solid refractory layer by mineral melt.

[0037] In further examples, preferably the system comprises a fiberizer configured to form man-made vitreous fibres (MMVF) from a mineral melt. Additionally, the system may be configured to discharge mineral melt from the furnace, convey the discharged mineral melt to the fiberizer and / or to collect the man-made vitreous fibres (MMVF) formed by the fiberizer. Any suitable known fiberizers and mineral melt handling systems may be used in such a system.

[0038] A further aspect of the invention herein provides a method for maintaining the furnace wall or the furnace system according to the preceding aspects, wherein the furnace wall comprises one or more apertures extending from an exterior surface of the furnace wall, to between the solid conductive layer and solid refractory layer, wherein said apertures are configured to facilitate introduction of conductive paste into the furnace wall, and wherein the method comprises introducing additional conductive paste between the interior surface of the solid conductive layer and the exterior surface of the solid refractory layer through atleast one aperture of the one or more apertures. As such the method may include injecting or piping additional conductive paste into a gap or cavity defined between the interior surface of the solid conductive layer and the exterior surface of the solid refractory layer through at least one aperture of the one or more apertures. Advantageously, introducing extra conductive paste through an aperture, during use of the furnace or furnace wall, may substantially increase the durability and lengthen the life of the furnace wall, since, in use, conductive paste is often lost (e.g. it is “burnt off”) due to the high temperatures.

[0039] The additional conductive paste may be a graphite paste such as GrafTech Smart Ram (RTM) RP20 ramming paste or a graphite grout such as Ecogrout 050RN supplied by TRB Refractaires of Nesles, France. Alternative pastes such as those comprising silicon carbide may also be used. The additional conductive paste may have the same formulation as the conductive pastes discussed above with reference to the preceding aspects of the invention, and may in some embodiments be the same paste as a conductive paste provided during construction of the furnace. Alternatively, the additional conductive paste may have a different formulation and / or properties to the conductive paste provided between the interior surface of the solid conductive layer and the exterior surface of the solid refractory layer during construction of the furnace. For instance, the additional conductive paste introduced during the maintenance methods discussed above of a less viscous and more flowable composition than the conductive paste provided between the interior surface of the solid conductive layer and the exterior surface of the solid refractory layer, so that the additional paste can spread out and fill cavities within the lining. The additional conductive pastes (i.e. any additional thermally conductive pastes) may have a thermal conductivity similar to the previously described conductive pastes. Equally, the additional conductive pastes may have a thermal conductivity of at least 2 W / mK, preferably at least 5 W / mK, more preferably still at least 10 W / mK at 400 degrees Celsius.

[0040] Optionally, where the furnace wall or furnace system includes a temperature detection system configured to measure a temperature of the solid conductivelayer, the method further includes detecting, by the temperature detection system, a change in temperature of the solid refractory layer, conductive paste and / or solid conductive layer. The introduction of additional conductive paste then takes place in response to or based on a detection of a change in temperature of the solid refractory layer, conductive paste or solid conductive layer. Advantageously, automated introduction of additional conductive paste may be provided when changes in temperature indicate that conductive paste has been lost or burnt off. Equally, the temperature(s) of any liquid cooling system such as a liquid cooling jacket and the liquid or liquids therein may be measured and used to trigger the injection of additional conductive paste.

[0041] In alternative examples, additional conductive paste may be provided between the solid refractory layer and the solid conductive layer without the detection of wear of the solid refractory layer. For example, the additional conductive paste may be injected periodically according to a predetermined schedule as a preventative measure. Additional conductive paste could be provided at least once per day, week, month, quarter (three month calendar period), or at least once in a time period in the range from one day to 6 months.

[0042] According to a further aspect of the invention there may be provided a method of manufacturing man-made vitreous fibres (MMVF) using a furnace system according to the preceding aspects of the invention, wherein the method comprises introducing mineral material into the furnace body, heating the mineral material to form a mineral melt, removing the mineral melt from the furnace, fiberizing the mineral melt, and collecting the fibres. These methods may be performed using any of the furnace systems discussed above, using furnaces comprising any of the furnace walls discussed above. As such, the methods offers corresponding benefits as the preceding aspects and in particular offers enhanced safety and durability when manufacturing MMVF.

[0043] Furthermore, providing improved durability leads to reduced need for the furnace to be shut down and maintained. As such, the methods and systems discussed above offer increased output over the life of a furnace.BRIEF DESCRIPTION OF DRAWINGS

[0044] One or more embodiments will now be described, purely by way of example, with reference to the accompanying figures, in which:

[0045] Figure 1 schematically depicts a furnace system for melting mineral materials according to embodiments of the present invention;

[0046] Figures 2A and 2B depict portions of furnace walls in schematic cross section according to embodiments of the present invention;

[0047] Figure 3 depicts a portion of a furnace wall in schematic cross section according to embodiments of the present invention;

[0048] Figures 4A and 4B depict portions of furnace walls with apertures in schematic cross section according to embodiments of the present invention;

[0049] Figure 5 depicts a flowchart showing a method according to embodiments of the present invention; and

[0050] Figure 6 depicts a flowchart showing a method according to embodiments of the present invention.

[0051] DETAILED DESCRIPTION

[0052] In the following description and accompanying drawings, corresponding features may preferably be identified using corresponding reference numerals to avoid the need to describe said common features in detail for each and every figure and / or embodiment.

[0053] Embodiments herein refer to furnace systems, for example, including electric furnace systems. Furnace systems, including electric furnace systems, referred to herein may be as described, and / or operate according to principles, as outlined above. Furnace systems herein may be particularly suited to a melt material of mineral melt suitable for forming man-made vitreous fibres (MMVF) and may be especially well suited for handling one or more of stone melt, rock melt, or slagmelt. Furnace systems particularly suited for mineral melt such as rock, stone, or slag melt may be configured substantially differently to furnace systems particularly suited to other purposes, such as used for ferro-alloys.

[0054] The furnaces are configured to receive and melt a material that has a high electrical and low electrical conductivity. This is typical of rock, stone and slag melts. Thus, the furnaces discussed herein can be contrasted with those used in the metals industries. In particularly preferred examples, electric furnace systems are configured to supply immersed electrodes with a (relatively low) current of less than 60 kA (60000 Amps), a (relatively high) voltage in the range of 50 to 1000 V, typically between 150 and 450 V, and / or to handle mineral melt with an impedance of less than 50 mQ (0.05 Ohms), typically between 20 to 40 mQ. The furnaces may operate in a high resistive mode. The furnaces may generate low quantities of metal products.

[0055] The furnace systems discussed herein may be configured to produce internal furnace temperatures herein that are high, for example, more than 1400 degrees Celsius. These high temperatures may be required for melting rock, stone, or slag material. The furnace may be provided with thick outer walls and / or a cooling system, in order that the furnace and its surroundings are not damaged during use at such temperatures.

[0056] Furnace systems as described herein may be provided with one or more computing devices configured to control aspects of a furnace system during use.

[0057] Mineral melt referred to herein may include stone melt, rock melt, or slag melt. This mineral melt may comprise raw materials including mineral fibres and mineral fines or powders. The raw materials may be nonmelted, melted, or partially melted, for example, depending on the stage of the furnace melting process.

[0058] The furnaces and methods discussed herein may be used within wider systems and methods that produce man-made vitreous fibres (MMVF). The mineral melt may be continuously or periodically discharged (e.g. tapped) from the furnaces and formed into MMVF using known methods. For instance, the mineral melt maybe formed into stone fibres, rock fibres, slag fibres, glass fibres, glass wool, ceramic fibres, basalt fibres, and others. The mineral fibres may be formed as a wool product such as rock, stone or slag wool. Forming mineral fibres into a MMVF wool product may be performed by a known fiberizer.

[0059] In particular the furnaces and methods described herein may be used as part of a wider process to produce MMVF with the following levels of elements, calculated as oxides in mass percentages: SiC>2, at least 30, 32, 35 or 37 % and / or not more than 51, 48, 45 or 43 %; AI2O3, at least 12, 16 or 17 %, and / or not more than 30, 27 or 25 %; CaO, at least 8 or 10 %, and / or not more than 30, 25 or 20 %; MgO, at least 2 or 5 % and / or not more than 25, 20 or 15 %; FeO and Fe2C>3, at least 4 or 5 %, and / or not more than 15, 12 or 10; FeO+MgO, at least 10, 12 or 15 %, and / or not more than 30, 25 or 20 %; Na2O+K2O, 0 or at least 1 %, and / or not more than 10; CaO+MgO, at least 10 or 15 % and / or not more than 30 or 25 %; TiC>2, 0 or at least 1 %, and / or not more than 6, 4 or 2 %; TiO2+FeO, at least 4 or 6 %, and / or not more than 18 or 12 %; B2O3, 0 or at least 1 %, and / or not more than 5 or 3 %; P2O5, 0 or at least 1 %, and / or not more than 8 or 5; and other oxides at 0 or at least 1 % and / or not more than 8 or 5 %. The furnaces and methods described herein may be used as part of a wider process to produce stone fibres that comprise any or all of the following components in the following ranges of mass percentages: SiC>2, at 30 to 51%; AI2O3, at 12 to 25%; CaO, at 8 to 30%; MgO, at 2 to 25%; iron oxides (FeO and Fe2O3), at 2 to 15%; Na2O and / or K2O, at less than 10%; and CaO and / or MgO, at 10 to 30%. The furnaces and methods described herein may be used as part of a wider process to produce glass fibres that comprise the following oxides, in percent by mass: SiO2, 50 to 70 %; AI2O3, 10 to 30 %; CaO, not more than 27 %; MgO, not more than 12 %. Some glass fibres can also contain the following oxides in percent by weight: Na2O+K2O 8 to 18 %, and in particular Na2O+K2O in greater amounts by mass than CaO+MgO; B2O3, 3 to 12 %; and / or AI2O3 less than 2%.

[0060] Figure 1 depicts a furnace system 1000 for melting mineral materials according to embodiments of the present invention. The furnace system 1000 is an electric furnace system (i.e. including electrodes). However, in further embodiments afurnace may be powered in other ways. For instance, the furnace may be a gas-powered furnace system and comprise a plurality of gas-burners.

[0061] The system 1000 includes a furnace body 1002 that comprises an internal cavity 1004, configured to contain a mineral melt 1006. According to embodiments of the invention, the mineral melt 1006 may be stone melt, rock melt, or slag melt. As a result of the melt process, a layer of sediment 1008 may accumulate on the floor of the furnace body, for example, containing byproducts such as iron.

[0062] The system may include one or more heating apparatuses configured to heat the mineral melt. As mentioned, in electric furnaces, heating is carried out by electrodes, which are electrically charged and which heat mineral material / mineral melt through Joule heating and / or arcing. In other furnaces, heating may be carried out using oil or gas burners (e.g. a Kaldo furnace), coke combustion burners (e.g. a Cupola furnace), electrical induction apparatuses (e.g. an induction furnace), etc. In the embodiment of Fig. 1 , heating apparatuses are shown as one or more electrodes 1014, and in preferred examples the heating apparatuses may comprise two or three electrodes 1014, but the system may include an alternative means for heating the mineral melt.

[0063] The furnace system may optionally be provided with other components, such as a bubbling lance for releasing fluids into the mineral melt within the furnace body.

[0064] The furnace system 1000 and / or furnace body 1002 are provided with a layered furnace wall 100. The furnace wall 100 may be any furnace wall as described herein.

[0065] Figures 2A and 2B depict portions of furnace walls 200A and 200B according to embodiments of the present invention in cross-section. The wall may extend above and below the portion shown in Figures 2A and 2B, for example, as shown by the dashed lines.

[0066] Furnace walls include an interior surface (to the left in Figures 2A and 2B) which may be arranged in use to face a furnace system interior 205 (e.g. equivalent to furnace cavity 1004). Indeed, the interior surface of the furnace wall defines atleast a portion of the boundary of the internal cavity within the furnace that is configured to receive and hold mineral material and mineral melt in use Furnace walls include an exterior surface (to the right in Figures 2A and 2B) which may be arranged in use to face a furnace system exterior 206 (e.g. away from the furnace system). The relative sizes of each furnace wall layer shown in these figures are not necessarily to scale.

[0067] For clarity and consistency, in the depictions of furnace walls and their components in Figures 2 to 4, the interior of all components is shown to the left and the exterior of all components is shown to the right. This arrangement is merely a depiction and does not limit the present invention.

[0068] Furnace walls 200A and 200B include a solid refractory layer 201. The solid refractory layer 201 includes an interior surface and an exterior surface, wherein the interior surface of the solid refractory layer 201 is arranged in use to be an interior surface of the furnace wall (i.e. the interior surface of the solid refractory layer 201 may be arranged to face the furnace system interior 205). As such, the interior surface of the solid refractory layer 201 defines at least part of the boundary of an internal cavity in the furnace, the internal cavity being configured to receive and hold mineral material and mineral melt in use. Hence, the interior surface of the refractory layer 201 is configured such that at least a portion of the interior surface may be in contact with the mineral melt and any waste metal (e.g. iron) received in the furnace during use.

[0069] The solid refractory layer 201 may be constructed from refractory bricks, for example, alumina-chromium bricks, or a castable refractory. The solid refractory layer 201 optionally comprises at least 20% chromium by weight, preferably in a range from 30% to 50%. A lower portion of the solid refractory layer 201 may have a higher content of chromium than an upper portion of the solid refractory layer 201, the upper portion being above the lower portion. Herein the term brick is understood to refer to any block-shaped component such as a brick, block or tile.

[0070] Furnace walls 200A and 200B include a solid conductive layer (i.e. a solid thermally conductive layer) 202. The solid conductive layer 202 includes aninterior surface and an exterior surface, wherein the interior surface of the solid conductive layer 202 is arranged in use to face the exterior surface of the solid refractory layer 201. As such, the interior surface of the solid conductive layer 202 and exterior surface of the solid refractory layer 201 are opposed.

[0071] The solid conductive layer 202 optionally includes or comprises graphite, for example, in predominantly graphite or graphite-based sheets or tiles. In some embodiments, the graphite sheets or tiles are formed of pure graphite (e.g. greater than 90%, 95%, or 99% graphite). The solid conductive layer 202 additionally or alternatively comprises silicon carbide. The solid conductive layer 202 additionally or alternatively comprises any other material that has high thermal conductivity and maintains its structural properties at high temperatures.

[0072] Furnace walls 200A and 200B include a conductive paste (i.e. a thermally conductive paste) 203 between the interior surface of the solid conductive layer 202 and the exterior surface of the solid refractory layer 201. The conductive paste 203 is also referred to as the conductive paste layer 203 herein. The conductive paste 203 is configured to transfer heat from the exterior surface of the solid refractory layer 201 to the interior surface of the solid conductive layer 202. The conductive paste 203 is flowable, and therefore fills and bridges gaps and cavities between the solid refractory layer 201 and the solid conductive layer 202. As such, the conductive paste 203 accommodates variations in positioning of the solid refractory layer 201 and the solid conductive layer 202. The paste may additionally or alternatively accommodate imperfections, variations, or gaps between component parts of the solid refractory layer 201 and / or the solid conductive layer 202, for example, bricks or tiles making up these layers. Where the furnace system has a cylindrical form and the solid refractory layer is formed of bricks and / or tiles (e.g. with cuboid form), the conductive paste ensures good thermal connection between the square bricks and / or tiles and the cylindrical solid conductive layer.

[0073] As shown in Figures 2A and 2B, in these embodiments, the conductive paste 203 is disposed in a layer, which may be referred to as a conductive paste layer. Thisconductive paste layer is in contact with the interior surface of the solid conductive layer 202 and the exterior surface of the solid refractory layer 201.

[0074] The conductive paste 203 optionally comprises graphite. One example of a suitable graphite paste is GrafTech Smart Ram (RTM) RP20 ramming paste. The conductive paste 203 additionally or alternatively comprises silicon carbide. The conductive paste 203 additionally or alternatively comprises any other material that has high thermal conductivity and such that the paste remains flexible and / or flowable such that it can fill the gap or cavity between the solid refractory layer 201 and the solid conductive layer 202.

[0075] The conductive paste 203 may provide strong thermal contact between the solid refractory layer 201 and the surrounding solid conductive layer 202 (and possibly a cooling system 204). In addition, the conductive paste 203 may close gaps between refractory bricks which optionally form the solid refractory layer 201 , may allow for small variations in positioning of said bricks, and may accommodate thermal expansion of the furnace 1000 in use.

[0076] The conductive pastes 203 has a thermal conductivity of at least 5 W / mK, preferably at least 10 W / mK, and more preferably still at least 20 W / mK.. Similarly, the solid conductive layers has a thermal conductivity of at least 25 W / mK, preferably at least 50 W / mK, more preferably still at least 70 W / mK, and more preferably still at least 100 W / mK.

[0077] Conductive paste 203 may have limited wear resistance, in which case, solid conductive layer 202 increases the durability of the layered wall lining.

[0078] Furnace walls 200A and 200B and any furnace including these walls 200A, 200B include optional temperature detection system 210 configured to detect a temperature of the conductive layer 202. The temperature detection system 210 may be configured to detect wear or a breach of the solid refractory layer by mineral melt, based on a change in temperature of the solid conductive layer. The temperature detection system 210 may include one or more thermocouples, thermistors, infrared temperature sensors, thermal cameras, optical fibre sensorsor any other suitable temperature sensor(s). The temperature detection system 210 may be further configured to issue a warning based on the detected wear or breach of the solid refractory layer by mineral melt. This warning may be provided to a user or a control system (computer system). The warning may be electronic, audible (e.g. an alarm), visual (a visual alert), or any other suitable means of providing a warning or notification. Therefore, the temperature detection system 210 may comprise a controller configured to receive and analyse temperature measurements from the one or more temperature sensors, and a warning unit or notification unit configured to issue warnings and / or notifications to a user or other systems based on the temperature measurements.

[0079] Optionally, the temperature detection system 210 may include a plurality of temperature detectors at different known furnace wall locations (e.g. regularly spaced around a furnace system), such that a location of wear or a breach in the solid refractory layer by mineral melt may be identified based on the differences in measurements from different temperature sensors.

[0080] In further embodiments, the temperature detection system 210 may also be provided with one or more temperature sensors configured to measure temperatures of the solid refractory layer 201, conductive paste 203 and / or the cooling system 204 (if present). For example, temperature sensors may be mounted within blocks of the solid refractory layer 201 , to the exterior surface of the solid refractory layer 201 and / or may measure liquid exiting a liquid cooling jacket of the cooling system 204. Similar sensors as discussed above may be used. The temperature detection system 210 may be configured to detect wear or a breach of the solid refractory layer 201 by mineral melt, based on a change in temperature of the solid refractory layer 201, conductive paste 203 and / or the cooling system 204 and issue warnings as discussed above.

[0081] Furnace wall 200B of Figure 2B additionally includes an optional cooling system (also referred to as the cooling system layer). The cooling system includes a liquid cooling jacket 204 coupled to the exterior surface of the solid conductive layer 202. The cooling system is configured to convey liquid through the liquid cooling jacket 204, such that the liquid absorbs heat from the solid conductive layer 202and transfers this heat away from the furnace. As such, the cooling system 204 may comprise a pump (not shown) configured to push liquid through the liquid cooling jacket 204 and a heat exchanger (not shown) external to the furnace configured to remove heat from the liquid such that the cooled liquid can be recirculated through the liquid cooling jacket 204. The liquid used within the liquid cooling jacket 204 may include water, ionic salt solution, an oil coolant, or any other suitable liquid (e.g. with high heat capacity and conductivity).

[0082] In alternative examples, the cooling system may comprise a liquid spraying system, configured in use to spray liquid on to the exterior surface of the furnace (e.g. on the exterior surface of the solid conductive layer 202). The spraying liquid may again include water, ionic salt solution, or any other suitable liquid (e.g. with high heat capacity and conductivity). Additionally or alternatively, the cooling system may comprise a trickle cooling system, configured to supply a liquid such as water that flows down the exterior surface of the furnace (e.g. the exterior surface of the solid conductive layer 202).

[0083] The cooling system may help to ensure that damage to the furnace body, and its surroundings, is avoided or reduced during use. The cooling system may additionally be configured to cool the floor of the furnace and / or the roof of the furnace. The cooling system and any liquid cooled jacket 204 may surround and cool the part of the furnace 1000 or furnace wall 200 which experience the highest temperatures. Where the cooling system is a liquid cooled jacket 204 a thin layer of heat-conductive glue (e.g. graphite-based glue) may be used to connect the solid conductive layer 202 to the liquid cooled jacket 204. Alternatively, the solid conductive layer 202 may directly contact a wall of the liquid cooled jacket 204. The walls of the liquid cooled jacket 204 may be formed from steel or another suitable metal.

[0084] Figure 3 depicts a portion of a furnace wall in cross section according to embodiments of the present invention. As Figures 2A and 2B, the wall may extend above and below the portion shown.Components in Figure 3 with the same last two digits as in Figure 2 are substantially the same as described in Figure 2, and, for brevity, description of these components is not duplicated here.

[0085] The cross-sectional view of Figure 3 shows an interface between the solid refractory layer 301 and the solid conductive layer 302 in an exemplary close-up view. Each of the solid layers may have irregular surfaces, for example with uneven portions or undulations 308 and / or cracks 309 (e.g. at an interface between two refractory bricks).

[0086] The conductive paste 303 arranged between the interior surface of the solid conductive layer 302 and the exterior surface of the solid refractory layer 301 may compensate for the irregular surfaces (e.g. by filling them in) ensuring that there is high heat conductivity between the solid conductive layer 302 and the solid refractory layer 301.

[0087] As shown in Figure 3, the conductive paste 303 is disposed in a layer, which may be referred to as a conductive paste layer. This conductive paste layer is in contact with the interior surface of the solid conductive layer 302 and the exterior surface of the solid refractory layer 301.

[0088] Figures 4Aand 4B depict portions of furnace walls with optional apertures in cross section according to embodiments of the present invention. As in Figures 2A, 2B, and 3, the wall may extend above and below the portion shown in Figures 4Aand 4B, for example, as shown by the dashed lines.

[0089] Components with the same last two digits as in Figures 2 and 3 are substantially the same as described in Figures 2 and 3, and, for brevity, description of these components is not duplicated here.

[0090] An aperture 407 may be provided, extending from an exterior surface of the furnace wall, to between the interior surface of the solid conductive layer 402 and the exterior surface of the solid refractory layer 401. For example, the aperture 407 may be provided through the solid conductive layer 402, as shown in figure4A, or through both the solid conductive layer 402 and the cooling system 404 (where one is present), as shown in figure 4B.

[0091] The aperture may be configured to facilitate introduction of the conductive paste (e.g. graphite paste), from an exterior of the furnace wall, to between the interior surface of the solid conductive layer 402 (e.g. comprising graphite tiles) and the exterior surface of the solid refractory layer 401 (e.g. comprising refractory bricks), for example, into a gap therebetween.

[0092] Additional conductive paste 403 may be introduced (e.g. injected or piped) through an aperture 407 into the gap between the solid refractory layer 401 and the solid conductive layer 402 during use, for example, in order to fill cavities in the gap and / or the paste 403 and / or replace the originally provided conductive paste 403 as it is used or burnt up. The additional conductive paste 403 introduced through the aperture 407 may be of a less viscous and more flowable composition, so that it can spread out and fill cavities within the lining. This approach further extends the durability and lifespan of the furnace. The additional conductive paste may be a graphite paste or grout such as GrafTech Smart Ram (RTM) RP20 ramming paste or Ecogrout 050RN, a silicon carbide paste, or any other suitable paste.

[0093] As mentioned, the additional conductive paste may have a different formulation and / or properties to the conductive paste provided between the interior surface of the solid conductive layer and the exterior surface of the solid refractory layer during construction of the furnace. The additional conductive pastes (i.e. an additional thermally conductive pastes) may have a thermal conductivity of at least 2 W / mK, preferably at least 5 W / mK, more preferably still at least 10 W / mK. However, this is not essential and in further examples the additional conductive paste may be the same as the conductive paste originally provided during construction.

[0094] In preferred examples, the furnace wall 400A, 400B preferably comprise a plurality of apertures 407 positioned at a plurality of wall locations (e.g. regularly spaced around the furnace system). As such, the conductive paste 403 may be replenished from a variety of points around the furnace body. Each aperture 407in this array of apertures 407 may correspond to (e.g. be positioned consistently in relation to) a respective temperature sensor within the temperature detection system 410. However, this is not essential.

[0095] As shown in Figures 4A and 4B, the conductive paste 403 is disposed in a layer, which may be referred to as a conductive paste layer. This conductive paste layer is in contact with the interior surface of the solid conductive layer 402 and the exterior surface of the solid refractory layer 401. The aperture 407 extends from the exterior surface to this conductive paste layer.

[0096] Figure 5 depicts a flow chart for process for adaptively introducing paste according to embodiments of the invention. The process may be operable with furnace walls described elsewhere herein.

[0097] In optional operation 511, a change in temperature of the solid refractory layer, conductive paste and / or solid conductive layer may be detected by the temperature detection system.

[0098] In operation 512, additional conductive paste (additional thermally conductive paste) may be introduced into a gap between the interior surface of the solid conductive layer and the exterior surface of the solid refractory layer through at least one aperture of the one or more apertures, based on (e.g. in response to) a detection of a change in temperature of the solid refractory layer, conductive paste or solid conductive layer. The additional conductive paste may be injected using any suitable tool such as a syringe or caulking gun, or supplied by pipe into this gap.

[0099] During use, conductive paste is often lost or “burnt off’ due to the high temperatures. Therefore, injecting extra conductive paste through an aperture, during use of the furnace or furnace wall, may substantially increase the durability and lengthen the life of the furnace wall. Temperature detection, as in operation 511 allows for introduction of additional paste to be provided when changes in temperature indicate that conductive paste has been lost or burnt off.In optional embodiments, in which a number of temperature detectors are provided at different known furnace wall locations (e.g. regularly spaced around a furnace system), injection 512 of additional conductive paste may be through an aperture at or near a location of a temperature detector the measurements from which indicate that conductive paste has been lost or burnt off.

[0100] According to further examples the additional conductive paste may be injected between the solid conductive layer and the solid refractory layer as a preventative measure and without detecting a change in the temperature of any component of the furnace. For example, additional conductive paste may be injected periodically - e.g. on average once a day, once a week, once a month, or once every 3 to 6 months. This additional conductive paste may replace any paste that has been lost or burnt off since the previous injection of paste and ensure high levels of safety throughout the operation of the furnace.

[0101] Figure 6 depicts a flow chart for process for manufacturing man-made vitreous fibres (MMVF) using any of the furnaces or furnace walls discussed elsewhere herein.

[0102] In operation 611 mineral material is introduced into the furnace body. The mineral material may be suitable for forming MMVF. In preferred examples the mineral materials comprise rock, stone or slag, and may comprise these minerals in any of the compositions discussed above. The mineral material may be provided in a powdered or particulate form. The mineral material may comprise waste materials such as used scrubbing material from emission gas scrubbers or waste from MMVF manufacturing processes. The mineral material may be introduced continuously or periodically.

[0103] Operation 612 comprises heating the mineral material to form a mineral melt. Any of the heating mechanisms discussed above may be used to melt the mineral material. For example, where the furnace is an electric furnace this may comprise supplying power to the electrode(s) of the furnace. Through the use of the furnaces and furnace walls discussed above the safety and overall output of the manufacture process may be improved.In operation 613, the mineral melt is removed from the furnace. The mineral melt may be tapped from the furnace using a taphole. However, alternative ways of discharging the mineral melt is also possible (e.g. using a ladle or by tipping the furnace). The mineral melt may be removed periodically or continuously.

[0104] During operation 614, the mineral melt is fiberized to form mineral fibres. This fiberization process may be performed by any suitable known fiberizer such as a rotary fiberizer.

[0105] During operation 615, the fibres (i.e. the man-made vitreous fibres) may be collected. The fibres may be collected into a mineral wool product such as rock, stone or slag wool. Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised.

Claims

28CLAIMS1. A furnace wall for a furnace system for forming a mineral melt suitable for forming man-made vitreous fibres, MMVF, the furnace wall comprising:a solid refractory layer comprising an interior surface and an exterior surface, wherein in use at least a portion of the interior surface is in contact with the mineral melt;a solid conductive layer comprising an interior surface arranged to face the exterior surface of the solid refractory layer; anda conductive paste between the interior surface of the solid conductive layer and the exterior surface of the solid refractory layer, wherein the conductive paste is configured to transfer heat from the exterior surface of the solid refractory layer to the interior surface of the solid conductive layer.

2. The furnace wall of claim 1, comprising a cooling system configured to cool an exterior surface of the solid conductive layer.

3. The furnace wall of claim 2, wherein the cooling system comprises a liquid cooling jacket coupled to the exterior surface of the solid conductive layer.

4. The furnace wall of any preceding claim, wherein the solid refractory layer comprises at least 20% chromium oxide by weight based upon the weight of the solid refractory layer, preferably from 30% to 50% chromium oxide by weight.

5. The furnace wall of claim 4, wherein at least a portion of the solid refractory layer that is in contact with the mineral melt when in use, has a higher amount of chromium oxide by weight than a further portion of the solid refractory layer, wherein preferably a lower portion of the solid refractory layer has a higher amount of chromium oxide by weight than an upper portion of the solid refractory layer.

6. The furnace wall of any preceding claim, wherein the solid refractory layer comprises bricks comprising alumina and chromium oxide.

7. The furnace wall of any preceding claim, wherein the solid conductive layer comprises graphite.

8. The furnace wall of claim 7, wherein the solid conductive layer comprises graphite tiles or sheets.

9. The furnace wall of claims 7 or 8, wherein the solid conductive layer is greater than 90% graphite by weight, preferably greater than 95% graphite by weight, and more preferably greater than 99% graphite by weight.

10. The furnace wall of any preceding claim, wherein the conductive paste comprises graphite.

11. The furnace wall of any preceding claim, comprising:one or more apertures extending from an exterior surface of the furnace wall, to between the solid conductive layer and the solid refractory layer, wherein said apertures are configured to facilitate introduction of conductive paste into the furnace wall.

12. The furnace wall of any preceding claim, wherein the conductive paste is comprised in a conductive paste layer in contact with the interior surface of the solid conductive layer and the exterior surface of the solid refractory layer.

13. A system for forming a mineral melt suitable for forming man-made vitreous fibres, MMVF, the system comprising:a furnace body for receiving the mineral material, the furnace body comprising the furnace wall of any preceding claim; andone or more heating apparatuses for heating the mineral material to form the mineral melt.

14. The system of claim 13, comprising a temperature detection system configured to measure a temperature of the solid refractory layer, conductive paste and / or solid conductive layer.

15. The system of claim 14, wherein the temperature detection system is configured to detect wear or a breach of the solid refractory layer by mineral melt,based on a change in temperature of the solid refractory layer, conductive paste or solid conductive layer;and wherein preferably the temperature detection system is configured to issue a warning based on the detected wear or breach of the solid refractory layer by mineral melt.

16. A method for maintaining the furnace wall according to any of claims 1 to 12, or the furnace system according to claims 13 to 15, wherein the furnace wall comprises one or more apertures extending from an exterior surface of the furnace wall, to between the solid conductive layer and solid refractory layer, wherein said apertures are configured to facilitate introduction of conductive paste into the furnace wall, and wherein the method comprises:introducing additional conductive paste between the interior surface of the solid conductive layer and the exterior surface of the solid refractory layer through at least one aperture of the one or more apertures.

17. The method according to claim 16, wherein:the furnace system comprises a temperature detection system configured to measure a temperature of the solid conductive layer;the method further comprises:detecting, by the temperature detection system, a change in temperature of the solid refractory layer, conductive paste and / or solid conductive layer;wherein the introduction of additional conductive paste is performed in response to a detection of a change in temperature of the solid refractory layer, conductive paste or solid conductive layer.

18. A method of manufacturing man-made vitreous fibres, MMVF, using a furnace system according to any of claims 13 to 15, the method comprising: introducing mineral material into the furnace body;heating the mineral material to form a mineral melt;removing the mineral melt from the furnace;fiberizing the mineral melt; andcollecting the fibres.

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