Introduction of fine materials into a furnace

Abstract

There are provided methods and systems for melting mineral materials in a furnace system to produce mineral melt, wherein the mineral material comprises at least one of stone, rock, or slag, the method comprising: receiving the mineral material in a furnace body of the furnace; heating the mineral material to form the mineral melt; and injecting, using an insertion device, a fluid and a fine solid material into the mineral melt, wherein the fluid and the fine solid material are injected at a position below a free surface of the mineral melt.

Description

[0001] INTRODUCTION OF FINE MATERIALS INTO A FURNACE

[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 rock, stone, slag and other similar materials during production of man-made 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 materials, 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.

[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 electrodes submerged in the melt material. Heat can be generated through the Joule effect.

[0007] 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.

[0008] Existing furnaces in glass and ferrometals industries, by way of example, are poorly suited to rock and stone mineral industry as temperatures required are much hotter.

[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.

[0010] Additionally, there is an ongoing desire for such furnaces, methods of operating furnaces, and furnace components which benefit from increased efficiency of melting mineral materials, reduced production of unwanted byproducts, an increased proportion of a melt that may be comprised of recycled materials, and increased safety of operation.

[0011] SUMMARY OF INVENTION

[0012] 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 mineral material melting efficiency and safety, reduced unwanted byproducts production, and an increase to the proportion of a melt that may be comprised of recycled materials, when compared to furnaces, components thereof, and their methods of operation, which are already available.

[0013] In a first aspect of the invention, a method of melting mineral materials in a furnace system to produce mineral melt is provided. The mineral material comprises at least one of stone, rock, or slag. The method includes the steps of: receiving the mineral material in a furnace body; heating the mineral material to form the mineral melt; and injecting, using an insertion device, a fluid and a fine solid material into the mineral melt, wherein the fluid and the fine solid material are injected at a position below a free surface of the mineral melt.

[0014] This invention offers a safer and more efficient approach to melting rock, stone and slag within a wider process for manufacturing rock, stone and slag wools. In particular, the invention offers significant improvements in proportion of recycled and waste material that can be used during a smelting process and / or in the reduction of the production of harmful pollutants during use (e.g. depending on the type of fine solid material that is injected).

[0015] Previously, it has not been possible to safely and easily introduce waste materials, such as slag, or waste or defective mineral wool, into a working furnace. During the operation of a furnace a crust of solid slag tends to form on the free surface of a melt - i.e. at the transition between the melt (molten mineral material) and the gas (air) above. If relatively large pieces of waste material are dropped into the furnace they will pierce the crust, exposing the high temperature melt to the surrounding gas which can lead to violent bubbling and ejection of melt. These so-called “volcanisms” are dangerous and erratic. Alternatively, if small or fine pieces of waste material are added to the furnace they may fail to pass through the crust, in which case the material will not enter the melt. The invention overcomes these issues and offers a safe and efficient way to incorporate additional waste material into a mineral melt.

[0016] Injecting fine solid material below a free surface of the mineral melt bypasses the crust of solid slag formed on the free surface of the mineral melt, without causing dangerous volcanisms.

[0017] In addition, injecting the fluid and the fine solid material directly into the mineral melt advantageously provides a means of agitating the melt in the electric furnace. This can, in turn, spatially homogenise the temperature of the mineral melt. This enables an increase in the energy transfer by heating elements or electrodes and a corresponding reduction in energy requirements for the furnace. Moreover, this approach provides increased melt capacity, reduces the production of unwanted secondary products (e.g., iron), and aids in breaking apart agglomerated (stuck-together) portions of mineral melt. “Melt” or “mineral melt” as used herein refers to mineral material which has become fully or partially molten through heating.

[0018] Agitating the mineral melt may be particularly advantageous for mineral melt derived from small fibres of material (as small fibres are more prone to agglomeration), such as those injected in the present invention. Increasing the efficacy of breaking apart agglomerated portions of mineral melt may allow for greater proportions of the mineral melt to be comprised of fine solid material, which may include recycled fibres.

[0019] The stone, rock and slag materials used in the invention may comprise compositions with less than 75% silica by weight, and more typically will comprise between 30 and 65% silica by weight. In some embodiments, the fine solid material includes at least one of: powdered stone, powdered rock, powdered slag, waste stone wool, waste rockwool, waste stone wool, recycled stone wool, recycled rock wool, recycled slag wool, fly-ash, a dry scrubber powder, a de-SOx residue, lime powder, and sodium bicarbonate powder. The fine solid material (also referred to as “fines”) may be obtained in a recycling step from a wider process of manufacturing or using man-made vitreous fibre. As such, the method may comprise the steps of receiving waste or recycled stone wool, rock wool or slag wool and processing said materials to form the fine solid material - e.g. by cutting, grinding and / or crushing. The use of any of a dry scrubber powder, a de-SOxpowder (any material configured to react to sodium oxides to reduce their production), lime powder, and sodium bicarbonate powder may beneficially reduce the production of harmful pollutants, while the method is carried out. Dry scrubbers are commonly installed in factories using the furnaces discussed here - e.g. factories producing rock, stone, or slag wool or other manmade vitreous fibres. Therefore, it is particularly valuable to inject the used material from these dry scrubbers (e.g. dry scrubber powder, de-SOx residue, lime powder and sodium bicarbonate powder) into the mineral melt, as the waste material can be directly incorporated into the final product rather than requiring a separate process or means for recycling or disposal of these materials. Herein the term “de-SOxresidue” is understood to refer to the solid or semi-solid (slurry) material in which sulphur oxides (SOX) have been captured in an exhaust flue gas scrubber. For instance, de-SOxresidue may comprise calcium sulfite, calcium sulfate dihydrate (also commonly referred to as gypsum, or flue gas desulfurization gypsum) or any other compound in which sulphur from exhaust gases has been fixed.

[0020] As discussed, the fine solid material may be formed from pre-existing or waste rock, stone or slag wool. For example, the recycled rock, stone or slag wool may comprise rock, stone or slag wool that has been reclaimed as waste from previous installations. For example, rock, stone and slag wool is commonly used as insulation in buildings or as a growth medium for hydroponic agriculture. However, the rock, stone and slag wool will typically last longer than the building in which it is installed or the plants grown therein. Therefore, collecting and remelting the used waste rock, stone or slag wool to form new products is particularly environmentally friendly. Alternatively, or additionally, the recycled rock, stone or slag wool may comprise waste rock, stone or slag wool from a factory for manmade vitreous fibres that has not been formed into useful products. For instance, the recycled wool may be scraps or offcuts of wool left behind after a production process or defective wool.

[0021] Optionally, the method may comprise the steps of receiving recycled or waste rock, stone or slag wool (e.g. reclaimed or waste rock, stone or slag wool) and compacting the wool to form fine solid material to be injected into a mineral melt using the insertion devices discussed above. The wool may therefore be compacted into pellets that can be more easily handled and delivered into the furnace through an insertion device. In this way compact pellets of reclaimed or waste wool may be used in the production of new man-made vitreous fibres MMVF). Optionally, the method may comprise the step of cutting or tearing the received rock, stone or slag wool into smaller pieces prior to the step of compacting the wool into the fine solid material.

[0022] Optionally, each piece of the fine solid material has a maximum dimension of 2 mm, and preferably a maximum dimension of 1 mm. Such dimensions allow the fine solid material to be quickly melted as it enters the mineral melt within the furnace without affecting the properties of the surrounding melt significantly. For instance, the pellets produced from reclaimed or waste rock, stone or slag wool as described above may have a maximum dimension of 2 mm, and preferably a maximum dimension of 1 mm.

[0023] In some embodiments, the fluid is air or nitrogen. Alternatively other suitable gases or mixtures of gases may also be used.

[0024] Optionally, the fluid has a pressure of less than 1000 kPa, typically in the range from 25kPa to 200 kPa, and more typically in the range from 50 kPa to 100 kPa. Additionally or alternatively, the fluid may have a speed of at least 10 m / s and more preferably at least 20 m / s to help it carry the fine solid material through the insertion device. Advantageously, the injection of fluid into a furnace (particularly according to the above provided pressures) provides a means of carrying or conveying the fine solid material into the melt and / or material. Additionally, the fluid agitates the melt in the furnace, which can, in turn, spatially homogenise the temperature of the mineral melt, enabling an increase in the energy transfer by the electrodes heating apparatuses and a corresponding reduction in energy requirements for the furnace. Moreover, this agitation can provide increased melt capacity, reduce the production of unwanted secondary products (e.g., iron), and aid in breaking apart agglomerated (stuck-together) portions of mineral melt.

[0025] In some embodiments, the furnace system is an electric furnace system and the heating of the mineral material to form the mineral melt is carried out by one or more electrodes. Electric furnaces may advantageously provide, when compared to alternatives, higher energy efficiency, greater control over temperature, lower emissions of greenhouse gases and other pollutants, such as particulates, and improved safety.

[0026] Various approaches for injecting the fine solid material and fluid are possible. These include hollow electrodes, screw feeders (also known as augers), and bubbling lances.

[0027] In some embodiments, particularly where the furnace system is an electric furnace system, the insertion device is a hollow electrode, wherein the hollow electrode is one of the one or more electrodes of an electric furnace system. Preferably, the electrode includes a hollow pipe comprising an inlet at a proximal end of the electrode and an outlet at a distal end of the electrode, wherein the inlet is disposed outside the furnace body and the outlet is disposed inside the furnace body and is submerged in the mineral melt.

[0028] Advantageously, this solution may provide enhanced space efficiency, since an electrode is already usually required for heating the mineral material / melt in the furnace. Moreover, the body electrode surrounding the hollow pipe helps insulate the hollow pipe, prolonging its working lifespan. Optionally, the insertion device is screw feeder. Optionally, the screw feeder includes a screw portion comprising an inlet at a proximal end of the screw feeder and an outlet at a distal end of the screw feeder, wherein the inlet is disposed outside the furnace body and the outlet is disposed inside the furnace body and is submerged in the mineral melt.

[0029] The screw feeder may be arranged in any number of different positions. Preferably, the screw feeder may pass through the wall or roof of the furnace, such that it does not pass through a furnace cooling system.

[0030] Advantageously, this solution may provide enhanced mechanical simplicity, with minimal points of failure.

[0031] In some embodiments, the insertion device is a bubbling lance.

[0032] The lance may be arranged in any number of different positions. Preferably, the lance may pass through the wall or roof of the furnace, such that it does not pass through a furnace cooling system.

[0033] Optionally, the bubbling lance includes a hollow pipe comprising an inlet at a proximal end of the bubbling lance and an outlet at a distal end of the bubbling lance, wherein the inlet is disposed outside the furnace body and the outlet is disposed inside the furnace body and is configured to be submerged in the mineral melt during use.

[0034] Advantageously, the bubbling lance embodiment may allow for enhanced flexibility over the placement of the lance and therefore over the location of the inserted fluid and fine solid material (e.g. compared to an electrode). Additionally, this embodiment may improve agitation of the melt, leading to associated benefits, such as improved melting efficiency.

[0035] In some embodiments, the bubbling lance includes a cooling jacket surrounding the hollow bubbling pipe and extending to the distal end of the lance. Advantageously, a cooling jacket may protect the lance from damage, for example, insulating the lance from the high temperatures inside the electric furnace.

[0036] Optionally, the cooling jacket includes a coolant flow path defined from a coolant inlet to a coolant outlet, and the coolant flow path includes an inflow path extending along the lance from the coolant inlet to the distal end of the lance, and an outflow path extending from the distal end of the lance to the coolant outlet.

[0037] In some examples each bubbling lance or hollow electrode may comprise a single fluid outlet and the fluid outlet may direct fluid in a direction of a longitudinal axis of a portion comprising the distal end of the lance. However, this is not essential. In further examples, the lance or hollow electrode may comprise a plurality of fluid outlets through which fluid may be released into the surrounding mineral melt. For example, each fluid outlet may be arranged to expel fluids at an angle or lateral offset relative to the longitudinal axis of the distal end of the lance or hollow electrode. Each fluid outlet of the plurality of fluid outlets may be laterally offset and / or angularly offset to the remaining fluid outlets within the plurality of fluid outlets. In still further examples, two or more bubbling lances and / or hollow electrodes may be used to release fluid and fine solid material at different locations within a furnace.

[0038] Where a lance or hollow electrode comprises multiple fluid outlets, a gas supply system may be configured to supple air or nitrogen to the lance at a mass flow rate of 0.08 g / s to 17.5 g / s per fluid outlet, preferably 0.1 g / s to 8.0 g / s per fluid outlet, and more preferably in the range of 0.6 g / s to 2.0 g / s per fluid outlet. Additionally, or alternatively, the gas supply unit may be configured to supply air, nitrogen or another suitable gas at a rate of 250 litres per hour to 50,000 litres per hour per fluid outlet, and preferably 500 litres per hour to 10,000 litres per hour per fluid outlet.

[0039] Additionally or alternatively, where a lance comprises multiple fluid outlets, the furnace system may be configured to supply fine solid material to the lance at a mass flow rate of 1.4 g / s to 55.6 g / s (5 to 200 kg / hr) per fluid outlet, preferably 1.4 g / s to 20.8 g / s (5 to 75 kg / hr) per fluid outlet, and more preferably in the range from 8.3 g / s to 13.9 g / s (30 to 50kg / hr) per fluid outlet. Similarly, where a hollow electrode comprises multiple fluid outlets, the furnace system may be configured to inject fine solid material to each hollow electrode at a mass flow rate in the range from 1.4 g / s to 55.6 g / s (5 to 200 kg / hr), preferably in a range from 13.9 to 41 ,7g / s (50 to 150 kg / hr), and more preferably still in a range from 20.8 to 34.7 g / s (75 to 125 kg / hr).

[0040] The fluid injected by the insertion device may be conveyed or provided to the insertion device by a fluid supply device, such as a pump or compressor. The fine solid material injected by the insertion device may be conveyed or provided to the insertion device by a fines supply device, such as a hopper. The fluid and fine solid material may be provided to the insertion device having already been mixed together.

[0041] In some embodiments, mineral melt may be discharged or tapped from the furnace body, for example, when it is suitably melted and / or of the correct mineral composition. The furnace may be provided with a discharging means, such as a tap, for carrying out the discharging step.

[0042] In some embodiments, the mineral melt may subsequently be used in manufacturing processes, such as producing man-made vitreous fibres (MMVF) and / or mineral wool. Moreover, the electric furnace system may form part of a wider system for manufacturing rock wool, stone wool or slag wool. Known devices and systems for converting molten materials into these wools may be used.

[0043] The method may comprise operating the furnace system in an initial (or start-up) operation mode in which the furnace body is filled with mineral material and this mineral material is melted to form a pool of mineral melt as discussed above and in a normal operation mode. In the normal operation mode, the furnace system may be operated to continuously operate to produce mineral melt. In the normal operation mode, the mineral melt may be discharged (e.g. tapped) from the furnace body continuously or periodically and the contents of the furnace body may be replenished with new mineral material. In the normal operation mode of the furnace system, at least 10% of mineral material supplied into furnace to be melted to form a mineral melt may be supplied as fine solid material through an insertion device as described herein, preferably at least 20%, more preferably at least 30%. For example, in a normal (regular) mode of operation of the furnace, from 10% to 50% of the mineral material supplied into the furnace system to be melted to form a mineral melt may be supplied through an insertion device as described herein, preferably 20 to 40%, more preferably 30 to 40%. The remainder of the mineral material supplied into the furnace may be deposited onto a free surface of the mineral melt. For instance, the remainder of the mineral material may be dispensed into the furnace through one or more apertures, hatches or gates arranged in a roof or wall of the furnace above the free surface of the mineral melt. However, this is not essential and in further methods in a normal operation mode substantially all mineral material may be supplied through one or more insertion devices. When operating in the normal operation mode the furnace system may be supplied with mineral material may be continuously or periodically into the furnace through the insertion device and / or through the apertures, hatches or gates (if present).

[0044] In preferred methods, at least 10% of the mineral material received in or supplied to the furnace in the normal operation mode is waste rock, stone or slag wool, preferably at least 25%, more preferably at least 40%, more preferably still at least 50%. The remainder may be previously unused (virgin) stone, rock or slag. For example, at least 10% of the fine solid material injected through the insertion devices described above may be formed from waste rock, stone or slag wool preferably at least 25%, more preferably at least 40%, more preferably still at least 50%. The method may involve the steps of receiving the waste wool, optionally dividing the waste wool into smaller pieces, and compacting the waste wool to form the fine solid material (e.g. pellets with an average diameter in the range from 0.25 to 2 mm). Similar proportions of waste rock, stone or slag wool may also be supplied to a previously empty furnace in an initial (start-up) operation mode to create an initial pool of mineral melt. Of the mineral material comprising waste rock, stone or slag wool supplied through an insertion device or through any aperture, hatch or gate (if present), approximately half may be formed from used stone, rock or slag wool that has previously been sold before being reclaimed from users, whilst the other half may be factory waste from a facility producing man-made vitreous fibres (MMVF). The factory waste may include (for example) defective or offcut wool. For example: the fine solid material may be formed from waste wool comprising at least 25% used stone, rock or slag wool, preferably at least 40%; and / or the fine solid material may be formed from waste wool comprising at least 25% factory waste from a facility producing man-made vitreous fibres (MMVF), preferably at least 40%.

[0045] According to a further aspect of the invention, a furnace system for melting mineral materials to produce mineral melt is provided. The mineral material is at least one of stone, rock, or slag. The system includes: a furnace body and an insertion device. The system is configured to receive the mineral material in a body of the furnace and heat the mineral material to form the mineral melt. The insertion device is configured to inject a fluid and a fine solid material into the mineral melt, wherein the fluid and the fine solid material are injected at a position below a free surface of the mineral melt.

[0046] Preferably the system is configured to perform the method according to the preceding aspect of the invention.

[0047] The system of this aspect of the invention may provide substantially the same advantages as the corresponding first aspect of the invention and may perform any of the methods discussed above with reference to the previous aspect of the invention. The system may also include any of the optional or preferable steps and features discussed above. For example, the system may be configured to operate in a plurality of operating modes including the initial and normal operating modes discussed above. The system of this aspect of the invention may be implemented, at least in part, by one or more computing devices. In some embodiments, the insertion device comprises a hollow electrode. The electrode is configured to heat the mineral material to form the mineral melt. Optionally, the insertion device comprises screw feeder. In further embodiments, the insertion device comprises a bubbling lance.

[0048] BRIEF DESCRIPTION OF DRAWINGS

[0049] One or more embodiments will now be described, purely by way of example, with reference to the accompanying figures, in which:

[0050] Figure 1 depicts a flowchart of a mineral melting method according to embodiments of the invention.

[0051] Figure 2 depicts an electric furnace system, including a hollow electrode, for melting mineral materials according to embodiments of the present invention.

[0052] Figure 3 depicts an electric furnace system, including a screw feeder, for melting mineral materials according to embodiments of the present invention.

[0053] Figure 4 depicts an electric furnace system, including a bubbling lance, for melting mineral materials according to embodiments of the present invention.

[0054] Figures 5A and 5B depict cross-sectional views of a bubbling lance according to embodiments of the present invention.

[0055] DETAILED DESCRIPTION

[0056] 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.

[0057] 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, wherein the mineral melt may be one or more of stone melt, rock melt, or slag melt. 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.

[0058] In some embodiments herein, electrodes of electric furnace systems may each be submerged in mineral melt and heating of the furnace may be provided through the Joule effect.

[0059] The furnaces herein are configured to receive and melt a material that has a high electrical impedance and / or 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.

[0060] 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.

[0061] Furnace systems as described herein may be provided with one or more computing devices configured to control aspects of a furnace system during use.

[0062] 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 non-melted, melted, or partially melted, for example, depending on the stage of the furnace melting process. The insertion devices discussed herein may be suitable for injecting fine solids (e.g. powders or mineral fibres) with a largest dimension that is less than 2 mm, and preferably less than 1 mm in length. In turn, the furnaces discussed herein may be suitable to receive and melt material with a wide range of dimensions and fibre lengths, for example from 0.5-40.0 mm. Each of these properties may be particularly prevalent in recycled mineral material, and thus embodiments herein may allow for the melt material to comprise a large proportion of recycled material.

[0063] 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 may be 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.

[0064] 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: SiO2, 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 Fe2<D3, 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 %; TiO2, 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: SiO2, at 30 to 51%; AI2O3, at 12 to 25%; CaO, at 8 to 30%; MgO, at 2 to 25%; iron oxides (FeO and Fe2Os), 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%.

[0065] Figure 1 depicts a flowchart of a mineral melting method 1000 according to embodiments of the invention. The method relates to melting mineral materials in a furnace system to produce mineral melt, wherein the mineral melt is at least one of stone melt, rock melt, or slag melt.

[0066] In operation 1001, mineral material may be received or contained in a furnace body of the furnace. For example, the mineral material is received in an interior cavity of the furnace. Typically, in an initial step the furnace is charged or filled with solid mineral material to be melted. However, additionally or alternatively, the method may comprise providing mineral melt into the furnace body of the furnace. The mineral material preferably comprise at least one of rock, stone or slag, which are common ingredients used for the production of man-made vitreous fibres (MMVF) such as rock wool, stone wool and slag wool.

[0067] In operation 1002, the mineral material may be heated to form mineral melt. Additionally or alternatively, mineral material may be heated to form hotter mineral material, and / or mineral melt may be heated to form hotter mineral melt. “Melt” or “mineral melt” may refer to mineral material which has become fully or partially molten through heating. Mineral melt and non-melted mineral material may coexist in the furnace at the same time.

[0068] Heating may be carried out through a number of means. 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 (e.g. a Cupola furnace), electrical induction (e.g. an induction furnace), etc. The means through which mineral material and mineral melt is heated is not limited in most embodiments of the present invention.

[0069] In operation 1003, a fluid and a fine solid material may be injected into the mineral melt (and possibly non-melted mineral material), wherein the injection is below a free surface of the mineral melt. Operation 1003 may be carried out by an insertion device, as will be discussed further below. The fine solid material will melt, forming part of the liquid mineral melt.

[0070] A mass ratio of the fine solid material to the fluid may be less than 50, more preferably less than 20, and more preferably still less than 10.

[0071] The fine solid material may be injected into the mineral metal through each insertion device at a mass flow rate in a range from 1.4 g / s to 55.6 g / s (5 to 200 kg / hr). For example, when using one or more bubbling lances as insertion devices as discussed in Figure 4 and discussed below, the furnace system may be configured to inject fine solid material through each lance at a mass flow rate in the range from 1.4 g / s to 20.8 g / s (5 to 75 kg / hr), and more preferably in the range from 8.3 g / s to 13.9 g / s (30 to 50kg / hr). Similarly, when using a hollow electrode as shown in Figure 2 and discussed below, the furnace system may be configured to inject fine solid material through each hollow electrode at a mass flow rate in the range from 1.4 g / s to 55.6 g / s (5 to 200 kg / hr), preferably in a range from 13.9 to 41.7g / s (50 to 150 kg / hr), and more preferably still in a range from 20.8 to 34.7 g / s (75 to 125 kg / hr).

[0072] In preferred examples, from 1 to 40% of the mineral melt discharged or tapped off from the furnace may be formed from fine solid material injected into the melt during the smelting process, preferably 10 to 40%, more preferably 20 to 40% and more preferably still 30 to 40%. In some examples, approximately 16,000 kg of mineral melt may tapped off from the furnace each hour and approximately 5,000 kg of fine solid material may be injected into the melt each hour, such that the proportion of the mineral melt that is formed from the injected fine solid material is in the range from 30 to 40%. The remainder of the mineral melt discharged or tapped off from the furnace may be formed from material supplied onto the free surface of the mineral melt - e.g. through one or more apertures, gates or chutes arranged in a roof or wall of the furnace body.

[0073] In other words, during regular operation of the furnace (after an initial start-up of the furnace) at least 10% of mineral material supplied into furnace to be melted to form a mineral melt may be supplied as fine solid material through an insertion device as described herein, preferably at least 20%, more preferably at least 30%.

[0074] For example, in a normal (regular) mode of operation of the furnace, from 1% to 50% of the mineral material supplied into the furnace system to be melted to form a mineral melt may be supplied through an insertion device as described herein, preferably 1% to 40%, preferably 20 to 40%, and more preferably 30 to 40%. The remainder of the mineral material supplied into the furnace may be deposited onto a free surface of the mineral melt. For instance, the remainder of the mineral material may be dispensed into the furnace through an aperture, hatch or gate arranged in a roof or wall of the furnace above the free surface of the mineral melt.

[0075] In preferred examples of steps 1001 and 1003, at least 10% of the mineral material received in or supplied to the furnace - whether this be via the insertion device or through an aperture, hatch or gate (if present) - is waste rock, stone or slag wool, preferably at least 25%, more preferably at least 40%, more preferably still at least 50%. For example, at least 10% of the fine solid material injected into the furnace in step 1003 may be formed from waste rock, stone or slag wool preferably at least 25%, more preferably at least 40%, more preferably still at least 50%. More specifically, of the proportion of fine solid material formed from waste rock, stone or slag wool, approximately half (e.g. in the range from 40 to 60%) may be formed from used stone, rock or slag wool that has previously been sold before being reclaimed from users and / or approximately half (e.g. in the range from 40 to 60%) may be formed from factory waste from a facility producing man-made vitreous fibres (MMVF).

[0076] Steps 1001 and 1002 may be performed during the start-up of the furnace system to generate a pool of mineral melt within the furnace. Subsequently, step 1003 may be performed during subsequent regular operation of the furnace where mineral melt is continuously or periodically discharged from the furnace, and the contents of the furnace is replenished, at least in part, by injecting fine mineral material into the melt using the insertion devices described herein. The injection of fine mineral material with fluid in step 1003 may be performed continuously or periodically.

[0077] Fine solid materials may be obtained in a number of different ways. For example, where fine solid materials are of a same or similar material to the mineral material or mineral melt in the furnace, the fine solid materials may be obtained by recycling mineral material or mineral melt (e.g. from another or an earlier process) or processing mineral material or mineral melt into small fines or powder (e.g. mineral material that which would otherwise be mineral material in the furnace). For example, at least part of the fine solid material may be formed from waste rock, stone or slag wool, such as reclaimed rock, stone or slag wool (e.g. wool that has previously been used in the construction industry, hydroponic industry or other sector). Additionally or alternatively, at least part of the fine solid material may be formed from defective or waste wool from a factory producing man-made vitreous fibres. Therefore, the method may comprise as optional preparatory steps before step 1003, the steps of receiving any of the waste wools discussed above, optionally separating the waste wool into smaller sections (e.g. by cutting or tearing) and compacting the waste wool to form relatively dense pellets, the relatively dense pellets subsequently being used as the fine solid material in step 1003.

[0078] In some embodiments, mineral melt may be discharged or tapped from the furnace body, for example, when it is suitably melted and / or of the correct mineral composition. The furnace may be provided with a discharging means, such as a tap, for carrying out the discharging step.

[0079] In some embodiments, the mineral melt may subsequently be used in manufacturing processes, such as producing man-made vitreous fibres (MMVF) and / or mineral wool. Moreover, the electric furnace system may form part of a wider system for manufacturing rock wool, stone wool or slag wool. Known devices and systems for converting molten materials into these wools may be used.

[0080] This method offers a safer and more efficient approach to melting rock, stone and slag within a wider process for manufacturing rock, stone and slag wools. In particular, the method and the systems and devices performing it offer significant improvements in proportion of waste material that can be used during a smelting process.

[0081] During the operation of a furnace a crust of solid slag tends to form on the free surface of a melt - i.e. at the transition between the melt (molten mineral material) and the gas (air) above. If relatively large pieces of waste material are dropped into the furnace they will pierce the crust, exposing the high temperature melt to the surrounding gas which can lead to violent bubbling and ejection of melt. These so-called “volcanisms” are dangerous and erratic. Alternatively, if small or fine pieces of waste material are added to the furnace they may fail to pass through the crust, in which case the material will not enter the melt. The invention overcomes these issues and offers a safe and efficient way to incorporate additional waste material into a mineral melt. Injecting fine solid material below a free surface of the mineral melt bypasses the crust of solid slag formed on the free surface of the mineral melt, without causing dangerous volcanisms.

[0082] The bubbles of fluid released by the insertion device agitate the melt within the furnace. This can, in turn, spatially homogenise the temperature of the mineral melt, increase energy transfer by the means for heating the mineral melt, increase melt capacity, reduce the production of unwanted secondary products (e.g., iron), and aid in breaking apart agglomerated portions of mineral melt. Breaking apart agglomerated portions of mineral melt may be particularly advantageous for mineral melt derived from fine solid material and small fibres of material, as fines and small fibres are more prone to agglomeration. For example, material components of less than 1 mm in length may particularly benefit from fluid released by the insertion device. Such lengths may be particularly prevalent in recycled mineral material. Increasing the efficacy of breaking apart agglomerated portions of mineral melt may therefore allow for greater proportions of the mineral melt to be comprised of recycled fibres.

[0083] The method 1000 may be carried out using any applicable furnace system, such as those disclosed herein. Three suitable furnaces systems 100A, 100B, 100C will now be discussed with reference to Figures 2 to 5.

[0084] Figure 2 depicts an electric furnace system 100A, including a hollow electrode 244, for melting mineral materials according to embodiments of the present invention. The system 10 includes a furnace body 102 that comprises an internal cavity 104, configured to contain a mineral melt 106. According to embodiments of the invention, the mineral melt 106 may be stone melt, rock melt, or slag melt. The melt may include recycled fibres. As a result of the melt process, a layer of sediment 108 may accumulate on the floor of the furnace body, for example, containing byproducts such as iron.

[0085] The system may include a means of cooling the furnace body, for example, cooling system 110. This helps ensure that damage to the furnace body, and its surroundings, is avoided or reduced during use. The cooling system may be a liquid cooling system. The cooling system may be configured to cool one or more of: the walls of the furnace, the floor of the furnace, and the roof of the furnace. The cooling system may surround the part of the furnace which experience the highest temperatures. The cooling system may be liquid cooled, wherein the liquid may include water, ionic salt solution, or any other suitable liquid. Additionally, the system may comprise a lining surrounding the furnace to absorb heat and protect its surroundings. The lining may comprise a plurality of ceramic tiles or bricks which have high thermal resistance, such as tiles formed of alumina and chromium oxide.

[0086] The furnace system may be provided with a bubbling lance or pipe (not depicted), e.g. for releasing fluids into the mineral melt within the furnace body. Injecting fluid into a furnace using a bubbling lance provides a means of agitating the melt in the furnace. This can, in turn, spatially homogenise the temperature of the mineral melt. This enables an increase in the energy transfer by the heating apparatuses and a corresponding reduction in energy requirements for the furnace. Moreover, this approach provides increased melt capacity, reduces the production of unwanted secondary products (e.g., iron), and aids in breaking apart agglomerated (stuck-together) portions of mineral melt.

[0087] The system may include one or more electrodes for heating the mineral melt. Alternatively any other suitable means of melting mineral material within the furnace may be used.

[0088] In electric furnace system 100A of Fig. 2, one or more of the electrodes (one as shown) are hollow electrodes 244 configured to for injecting a fluid 118 and a fine solid material 120 into the mineral melt below a free surface 146 (i.e. an upper surface) of the mineral melt. As such, said hollow electrodes are each insertion devices for injecting fluid and fine solid material into the melt. The fluids may form into bubbles when released into the mineral melt.

[0089] The electrode may include a hollow pipe 244a comprising an inlet at a proximal end of the electrode and an outlet at a distal end of the electrode, wherein the inlet is disposed outside the furnace body and the outlet is disposed inside the furnace body and, in use, is submerged in the mineral melt below the free surface. The electrode further comprises electrode body 244b surrounding the hollow pipe 244a that may be formed of carbon, graphite or any other suitable material.

[0090] Figure 3 depicts a furnace system 100B, including a screw feeder 346, for melting mineral materials according to embodiments of the present invention.

[0091] A number of components, such as the furnace body and related components, (e.g., with preceding number “1”) are substantially the same as described in Figure 2, and, for brevity, description of these components is not duplicated here. These components comprise corresponding features and offer corresponding advantages to the corresponding features discussed above.

[0092] The furnace system 100B may be provided with a bubbling lance or pipe (not depicted), e.g. for releasing fluids into the mineral melt within the furnace body. The system may include one or more electrodes (not depicted) for heating the mineral melt.

[0093] The system may include one or more electrodes for heating the mineral melt. Alternatively any other suitable means of melting mineral material within the furnace may be used.

[0094] In furnace system 100B of Fig. 3, a screw feeder 346 (an insertion device) is provided, for injecting a fluid 118 and a fine solid material 120 into the mineral melt below a free surface 146 (i.e. an upper surface) of the mineral melt during use. The fluids may form into bubbles when released into the mineral melt.

[0095] The screw feeder may comprise an auger positioned within a pipe or tube. The screw feeder may include a screw portion comprising an inlet at a proximal end of the screw feeder and an outlet at a distal end of the screw feeder, wherein the inlet is disposed outside the furnace body and the outlet is disposed inside the furnace body and is submerged in the mineral melt below the free surface of the melt during use.

[0096] The screw feeder may be arranged in any number of different positions. For example, while the screw feeder of Fig. 3 is shown angled, and entering the furnace body through its side at a location without a cooling system, the screw feeder may alternatively be inserted through the roof of the furnace, through the floor of the furnace, inserted horizontally, inserted vertically, and / or inserted through a gap in the cooling system.

[0097] Figure 4 depicts a further furnace system 100C, including a bubbling lance, for melting mineral materials according to embodiments of the present invention.

[0098] A number of components, such as the furnace body and related components, (e.g., with preceding number “1”) are substantially the same as described in Figure 2 (and 3), and, for brevity, description of these components is not duplicated here. These components comprise corresponding features and offer corresponding advantages to the corresponding features discussed above. The system may include one or more electrodes (not depicted) for heating the mineral melt. Alternatively any other suitable means of melting mineral material within the furnace may be used.

[0099] The furnace system may be provided with bubbling lances or pipes for releasing fluids into the mineral melt within the furnace body.

[0100] The furnace system is provided with at least one bubbling lance (or pipe apparatus) 412 for releasing a fluid 118 and a fine solid material 120 into the mineral melt within the furnace body. Fluids may include gases and liquids. The fluids may form into bubbles when released into the mineral melt.

[0101] According to embodiments of the present invention, the at least one bubbling lance includes a hollow bubbling pipe with a fluid inlet at a proximal end 114 of the lance and a fluid outlet at a distal end 116 of the lance. The fluid inlet and fluid outlet are also an inlet and outlet for the fine solid material, however, they will be referred to as fluid inlet and fluid outlet for brevity. In use, the fluid inlet may be disposed outside the furnace body and the fluid outlet may be disposed inside the furnace body. The distal end of the lance and the fluid outlet are configured to be submerged in the mineral melt during use.

[0102] The at least one bubbling lance may be provided with a cooling jacket surrounding the bubbling pipe, which may preferably extend to the distal end of the lance and at least along the portion of the lance that is inserted into the mineral melt in use.

[0103] Cooling the lance protects the lance from damage caused by the mineral melt (e.g., from the high heat of the mineral melt).

[0104] Dimensions, materials, or thicknesses of lance, and / or quantities or flowrates of coolant, may be selected or designed such that the heat transfer from the mineral melt to the coolant is not sufficient to vaporise the coolant during use (i.e. the coolant remains in liquid form). Vaporisation may lead to reduced cooling and increased pressure which can reduce safety and efficiency of operation. In some embodiments, additives may be added to the coolant to increase its boiling / vaporisation temperature. Further, dimensions, materials, or thicknesses of lance, and / or quantities or flowrates of coolant, may be selected or designed such that the heat transfer from the mineral melt to the coolant is sufficient to solidify mineral melt immediately surrounding the lance, such that a crust may form on the exterior surface of the lance, protecting the lance from damage.

[0105] Further, dimensions, materials, or thicknesses of lance, and / or quantities or flowrates of coolant, may be selected or designed such that the heat transfer from the mineral melt to the coolant is sufficient to maintain the temperature of the lance below a melting point of the materials making up the lance.

[0106] The lance material may include steel, copper, or refractory metal, or an alloy of these materials. In some embodiments, additives may be added to the lance materials to increase its melting temperature.

[0107] The lance may be arranged in any number of different positions. For example, while the lance feeder of Fig. 4 is shown vertical, and entering the furnace body through its roof at a location without a cooling system, the lance may alternatively be inserted through the side of the furnace, through the floor of the furnace, inserted horizontally, inserted at an angle, and / or inserted through a gap in the cooling system.

[0108] In some embodiments, the lance is arranged such that it extends at an offset angle to a vertical axis of the furnace body. The offset angle increases dispersion of the fluid from the distal end of the bubbling lance, thereby increasing the effectiveness of the agitation of the melt and helping to ensure a consistent temperature throughout the furnace. The offset angle directs bubbles of fluid to away from the body of the lance, preventing them from simply travelling directly up and along the lance under buoyancy, and increasing the agitation.

[0109] The lance may be configured to be movable in use (e.g. pivoting around an insertion point in the furnace body) in order to allow for the increase in efficacy of breaking apart agglomerated portions of mineral melt. The lance may comprise a handle at its proximal end by which they may be moved through the melt manually. Equally, the system may comprise a motor or mechanism to automatically move the lance through the mineral melt so as to increase the mixing and agitation applied to the melt.

[0110] Figures 5A and 5B depict cross-sectional views of a bubbling lance (or “lance”) 412 according to embodiments of the present invention, wherein Figure 5B shows a close-up cross sectional view of a distal end 416 of the lance. The bubbling lance 412 may be incorporated into any of the systems and methods, as disclosed herein, and may be particularly applicable to the system 100C comprising a bubbling lance for releasing a fluid and a fine solid material into the mineral melt within the furnace body, as disclosed with respect to Figure 4.

[0111] The lance includes a proximal end 414 and a distal end 416. The lance includes a bubbling pipe 521 with a fluid inlet 524 and fluid outlet 530

[0112] The lance may include a cooling jacket 522. The cooling jacket may include a coolant flow path defined from a coolant inlet 526 to a coolant outlet 528.

[0113] The coolant flow path includes an inflow path extending along the respective lance from the coolant inlet to the distal end of the lance, and an outflow path extending from the distal end of the lance to the coolant outlet.

[0114] In more detail, the cooling jackets shown in Figures 5A and 5B include a coolant inflow pipe 536 defining the inflow path and a coolant outflow pipe 538 defining the outflow path.

[0115] Exemplary solid portions 543 may be seen inside the pipes. These solid portions are structural components for maintaining the structure of the lances and appropriate separation between the various pipes within the lances. They do not significantly impede the flow of fluid through the pipes on account of not being present around the full circumference of the pipes.

[0116] The bubbling lance as shown in Figures 5Aand 5B (particularly as shown in Figure 5A) may not be to scale; in particular, lances tend to be considerably more elongated than depicted but have been altered in the figures for clarity. In some embodiments, the hollow bubbling pipe, coolant inflow pipe, and / or coolant outflow pipe may be manufactured from a material which has a high melting point. One or more of the pipes may be manufactured from a metal such as steel, copper, or refractory metals, or an alloy of these materials.

[0117] As shown in both embodiments, the coolant inflow pipe 536 is arranged within the coolant outflow pipe 538. In turn, the bubbling pipe 412 is arranged within the coolant inflow pipe 536. These three pipes are arranged concentrically, such that the bubbling pipe is centred within the coolant inflow and outflow pipes and the cooling jacket as a whole. However, further arrangements of these pipes are possible. For instance, the order of the coolant inflow pipe and outflow pipe may be reversed or the coolant inflow and outflow pipes may not fully surround the bubbling pipe.

[0118] The inflow path may be separated from the outflow path by an intermediate wall 541 , the intermediate wall defining a transition opening 540 at the distal end of the lance between the inflow path and the outflow path. The cross-sectional area of flow through the transition opening may be less than the cross-sectional area of flow through the inflow path. Consequently, the flow of coolant fluid through the cooling jacket is accelerated at the distal end of the lance, and the transfer of heat away from this sensitive portion of the lance increased. This prolongs the lifespan of the lance and increases safety.

[0119] The system is further provided with an optional flow restrictor 532 mounted in the fluid outlet of the bubbling tube at the distal end 416. The flow restrictor advantageously increases the speed of outflowing fluid and fine solid material, thereby increasing the agitation of the surrounding melt. The flow restrictor is preferably comprises copper, but may also be formed of steel, a refractory metal or any other suitable material.

[0120] In each of the systems 100A, 100B, 100C discussed above, the furnace system is preferably configured to maintain the temperature of the melt at a range between 1400 degrees Celsius and 2000 degrees Celsius. As such, the furnace system will be well suited for use with stone rock and slag materials. The furnace systems 100A, 100B, 100C may further include a tapping apparatus or tap (not depicted) for extracting mineral melt from the furnace body. The mineral melt may subsequently be used in manufacturing processes, such as producing man-made vitreous fibres (MMVF) and / or mineral wool. Moreover, the furnace system may form part of a wider system for manufacturing rock wool, stone wool or slag wool. Known devices and systems for converting molten materials into these wools may be used.

[0121] The furnace systems 100A, 100B, 100C may further comprise one or more apertures, hatches or gates (not shown) formed in the roof or wall of the furnace body 102, and through which mineral material may be supplied onto a free surface of a mineral melt within the furnace body 102. As discussed, a portion of the mineral material supplied into the furnace body 102 may be supplied through the one or more apertures, hatches or gates during normal operation of the furnace systems 100A, 100B, 100C, whilst a portion of the mineral material supplied into the furnace body 102 may be supplied as fine solid material through one or more of the insertion devices described above. The furnace systems 100A, 100B, 100C may comprise further mineral material supply systems (e.g. chutes or hoppers) configured to supply mineral material into the furnace body 102 through said one or more apertures, hatches or gates.

[0122] The systems 100A, 100B, 100C may comprise a fluid supply unit (not depicted) configured to supply fluid to a fluid inlet of the insertion device (the hollow electrode, screw feeder and / or bubbling lance). Preferably, the fluid supply unit may be configured to supply a gas, for example air or nitrogen, at a flow rate of at least 0.6 g / s and preferably in the range from 1.0 g / s to 8.0 g / s. In further examples the fluid supply system may be configured to supply air or nitrogen at a flow rate in the range from 0.08 g / s to 17.5 g / s, preferably 0.1 g / s to 8.0 g / s, and more preferably in the range of 0.6 g / s to 2.0 g / s. The fluid supply unit may include a pump, fan, or compressor. The supplied gas may include any suitable gas. The fluid supply unit may be configured to supply a gas (e.g. air or nitrogen) with a pressure of less than 1000 kPa, preferably in the range from 25kPa to 200 kPa, and more preferably in the range from 50 kPa to 100 kPa. Additionally the fluid supply unit may be configured to supply a gas (e.g. air or nitrogen) with a velocity of at least 10 m / s and more preferably at least 20 m / s. Additionally, or alternatively, the gas supply unit may be configured to supply air, nitrogen or another suitable gas at a rate of 250 litres per hour to 50,000 litres per hour, and preferably 500 litres per hour to 10,000 litres per hour. The flow rate of fluid should be selected so as to ensure that sufficient agitation of the melt is provided by the fluid released by the lance, and such that the fluid outlet is not closed in use as melt solidifies at the distal end of the lance.

[0123] The systems 100A, 100B, 100C may further comprise a fines supply unit (not depicted) configured to supply fine solid material to the respective insertion device (the hollow electrode, screw feeder and / or bubbling lance). The fines supply unit is preferably configured to supply solid fine material substantially continuously. Preferably, the fines supply unit is configured to supply the fine solid material such that the mass ratio of the fine solid material to the fluid or gas is between 0 to 50, more preferably between 0 to 20 and more preferably still between 0 to 10 (e.g. preferably less than or equal to 50, 20 or 10). These ratios allow the fine solid material to be carried easily by a fluid. However, in further examples fine solid material may be supplied periodically in batches. The fines supply unit may be a hopper or other feed device. The fines supply unit may comprise a hopper in which fine solid material is received, an auger placed at the base of the hopper which is configured to convey fine solid material from the hopper, and a mixing chamber through which fluid passes as it travels towards the respective insertion device and into which an auger discharges the fine solid material from the hopper. Fine solid material discharged into the mixing chamber by the auger may be carried downstream by the moving fluid to the bubbling lance and into the melt. Control of the ratio of fine solid material to fluid that is received by the insertion device and injected into the mineral melt may be effected by controlling the speed at which the auger turns and / or the mass flow rate of fluid (e.g. the mass flow rate at which any of the fluid supply units discussed above operate at).

[0124] The fines supply unit and wider systems 100A, 100B, 100C may be configured so that the fine solid material injected into the mineral metal through each insertion device is injected at a mass flow rate in a range from 1.4 g / s to 55.6 g / s (5 to 200 kg / hr). For example, when using one or more bubbling lances as insertion devices as shown in the system 100C of Figure 4, the fines supply unit may be configured to inject fine solid material through each lance at a mass flow rate in the range from 1.4 g / s to 20.8 g / s (5 to 75 kg / hr), and more preferably in the range from 8.3 g / s to 13.9 g / s (30 to 50kg / hr). Similarly, in examples using a hollow electrode such as in the system 100A of Figure 1, the fines supply unit may be configured to inject fine solid material through each hollow electrode at a mass flow rate in the range from 1.4 g / s to 55.6 g / s (5 to 200 kg / hr), preferably in a range from 13.9 to 41.7g / s (50 to 150 kg / hr), and more preferably still in a range from 20.8 to 34.7 g / s (75 to 125 kg / hr). In preferred examples, the system may be configured such that 30 or 40% of the mineral melt discharged or tapped off from the furnace may be formed from fine solid material injected into the melt during the smelting process. In preferred examples, the systems discussed above are configured such that up to 5,000 kg of fine solid material is injected into the melt each hour, and that approximately 16,000 kg of mineral melt is tapped off from the furnace each hour, such that the proportion of the mineral melt that is formed from fine solid material is in the range from 20 to 40%. As previously discussed, the fine solid material may comprise one or more of powdered stone, powdered rock, powdered slag, waste stone wool, waste rock wool, waste stone wool, recycled stone wool, recycled rock wool, recycled slag wool, fly-ash, a dry scrubber powder (i.e. used or waste material from a dry scrubber that is in powder form or has been powdered), a de-SOxpowder, lime powder, and sodium bicarbonate powder. For example, the fine solid material may be formed by compacting waste stone, rock and / or stone wool collected from previous users and / or waste or defective stone, rock and / or stone wool collected from a man-made vitreous fibre factory.

[0125] Where the systems 100A, 100B, 100C include a bubbling lance with a cooling jacket, the system may comprise a coolant supply unit (not depicted) configured to supply coolant to the cooling jacket around the bubbling lance. Preferably, the coolant supply unit may be configured to supply water at a flow rate of at least 0.0008 m3 / s and preferably in the range from 0.001 to 0.002 m3 / s. The coolant supply unit may include a pump or compressor. The supplied coolant may include any suitable coolant. It may not be necessary to cool the coolant before use, as it may already be substantially cooler than the temperature inside an furnace. In the examples shown above, the systems 100A, 100B, 100C each include a single insertion device. However, this is not essential and in further examples furnace systems may be provided that comprise a plurality of insertion devices and multiple different types of insertion devices (e.g. one or more hollow electrodes, screw feeders and bubbling lances).

[0126] In system 100C shown in Figure 4 a straight bubbling lance is shown being inserted vertically through a roof of the furnace into the mineral melt. However, this is not essential. In further examples, the lance may be modified, such that the system is arranged such that a portion of the lance, said portion including the distal end of the lance, extends at an offset angle to a vertical axis of the furnace body. For example, the lance may pass through a side wall of the furnace body, such that it is angled into the mineral melt. Additionally, or alternatively, the bubbling lance (and any bubbling pipe and cooling jacket therein) may comprise a bend, such that the fluid outlet of the lance is laterally offset from a portion of the lance extending from the proximal end of the lance to the bend. As such, the distal end of the lance and the fluid outlet may be offset from a longitudinal axis of the lance. Preferably such a bend is located closer to the distal end of the lance than the proximal end of the lance. For instance, the fluid outlet may be laterally offset from a longitudinal axis of the lance by at least 50mm, more preferably at least 60mm, more preferably still at least 75mm. Additionally or alternatively, the length of the portion of the lance between the bend and the distal end of the lance is preferably at least 75 mm, more preferably at least 100mm.

[0127] The offset angle can help increase dispersion of the fluid and fine solid material from the distal end of the bubbling lance, thereby increasing the effectiveness of the agitation of the melt, the speed at which fines melt and helping to ensure a consistent temperature throughout the furnace. The offset angle also helps direct bubbles of fluid away from the body of the lance, preventing them from simply travelling directly up and along the lance under buoyancy, and increasing the agitation. Additionally, cooling the fluid to be released by the lance through use of the cooling jacket may advantageously increase the efficacy of the agitation of the melt, thereby increasing the effects discussed above. Preferably, the offset angle is in a range from 20 to 135 degrees, preferably from 30 to 90 degrees, more preferably from 30 to 60 degrees, more preferably still from 40 to 50 degrees.

[0128] The preferred angle ranges and dimensions the offset provided above are particularly effective at dispersing the fluid released by the lance over as broad a volume of the melt as possible. This may improve the efficacy of the breaking apart of agglomerated portions of mineral melt. Other lateral offset or bend sizes are possible.

[0129] The combination of the offset angle and a bubbling lance with the optional cooling jacket is particularly valuable. Without an offset angle, as mentioned, bubbles tend to rise up the surface of a cooling jacket under buoyancy. This can prevent or interrupt the formation of the protective layer of solid material around the outside of the cooling jacket. With the offset angle this protective layer is quickly and consistently formed. Therefore, the lifespan of the bubbling lance is improved.

[0130] These preferred offset angles are particularly effective at dispersing the fluid released by the lance over as broad a volume of the melt as possible. This may improve the efficacy of the breaking apart of agglomerated portions of mineral melt.

[0131] The above invention benefits (for example, due to the injection of a fluid and a fine solid material into the mineral melt), from increased efficiency of melting mineral materials, reduced production of unwanted byproducts, an increased proportion of a melt that may be comprised of recycled materials, and increased safety of operation.

Claims

32CLAIMS1. A method of melting mineral materials in a furnace system to produce mineral melt, wherein the mineral material comprises at least one of stone, rock, or slag, the method comprising:receiving the mineral material in a furnace body of the furnace; heating the mineral material to form the mineral melt; andinjecting, using an insertion device, a fluid and a fine solid material into the mineral melt, wherein the fluid and the fine solid material are injected at a position below a free surface of the mineral melt.

2. The method according to claim 1, wherein the fine solid material comprises at least one of: powdered stone, powdered rock, powdered slag, waste stone wool, waste rockwool, waste stone wool, recycled stone wool, recycled rock wool, recycled slag wool, fly-ash, a dry scrubber powder, a de-SOxpowder, lime powder, and sodium bicarbonate powder.

3. The method according to any previous claims, wherein each piece of the fine solid material has a maximum dimension of 2 mm, and preferably a maximum dimension of 1 mm.

4. The method according to any previous claims, wherein the fluid is air or nitrogen.

5. The method according to any previous claims, wherein the fluid has a pressure of less than 1000 kPa, preferably in the range from 25kPa to 200 kPa, and more preferably in the range from 50 kPa to 100 kPa; and / or wherein the fluid has a velocity of at least 10 m / s and more preferably at least 20 m / s.

6. The method according to any previous claims, wherein the furnace system is an electric furnace system and wherein heating the mineral material to form the mineral melt is carried out by one or more electrodes.

7. The method according to claim 6, wherein the insertion device comprises a hollow electrode, wherein the hollow electrode is one of the one or more33electrodes, and wherein preferably the hollow electrode includes a hollow pipe comprising an inlet at a proximal end of the electrode and an outlet at a distal end of the hollow electrode, wherein the inlet is disposed outside the furnace body and the outlet is disposed inside the furnace body and is submerged in the mineral melt.

8. The method according to any of claims 1 to 6, wherein the insertion device comprises a screw feeder.

9. The method according to any of claims 1 to 6, wherein the insertion device comprises a bubbling lance.

10. The method according to claim 9, wherein the bubbling lance comprises:a hollow pipe comprising an inlet at a proximal end of the bubbling lance and an outlet at a distal end of the bubbling lance, wherein the inlet is disposed outside the furnace body and the outlet is disposed inside the furnace body and is submerged in the mineral melt.

11. The method according to claim 9, wherein the bubbling lance comprises:a cooling jacket surrounding the hollow bubbling pipe and extending to the distal end of the lance.wherein the cooling jacket comprises a coolant flow path defined from a coolant inlet to a coolant outlet, andthe coolant flow path comprises an inflow path extending along the lance from the coolant inlet to the distal end of the lance, and an outflow path extending from the distal end of the lance to the coolant outlet.

12. A furnace system for melting mineral materials to produce mineral melt, wherein the mineral material is at least one of stone, rock, or slag, the system comprising: a furnace body and an insertion device, wherein the system is configured to:receive the mineral material in the furnace body;heat the mineral material to form the mineral melt; andwherein the insertion device is configured to:inject a fluid and a fine solid material into the mineral melt, wherein the fluid and the fine solid material are injected at a position below a free surface of the mineral melt.

13. The system according to claim 12, wherein the system is configured to perform the method of any of claims 1 to 11.

14. The system according to claim 12 or claim 13, wherein the insertion device is a hollow electrode, wherein the electrode is configured to heat the mineral material to form the mineral melt.

15. The system according to claim 12 or claim 13, wherein the insertion device comprises a screw feeder or a bubbling lance.

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