Melting of vitrifiable materials using biomass-type fuels

Abstract

Providing a mixture of biomass and vitrifiable raw materials. The present invention provides a mixture of biomass and vitrifiable raw materials for introduction into a fuel-fired furnace for melting glass or vitrifiable inorganic materials such as rock or silicates, the biomass being particularly oily, and its use reduces damage to equipment for metering and transporting the vitrifiable raw materials.

Description

[Technical Field]

[0001] The invention relates to the field of melting of vitrifiable materials such as glass or rock or silicates, in particular in the context of the production of mineral wool. [Brief explanation of the drawings]

[0002] (No original text) DETAILED DESCRIPTION OF THE INVENTION

[0003] Melting vitrifiable materials involves introducing vitrifiable raw materials into a furnace and heating them therein until molten. The high temperatures used (typically above 1300°C) subject the furnace and its accessories to severe testing, and it is desirable to extend their service life as long as possible. This objective is easier to achieve if the temperature of the molten material is completely homogenous within the furnace. In particular, a homogenous temperature of the molten mass makes it possible to minimize the temperature required to melt the majority of the solid particles without creating excessively hot zones that would cause wear and tear on the furnace and its accessories.

[0004] In the context of the present invention, heating in the furnace is carried out by burning a fuel (biomass acting as fuel). Since biomass generally has a non-zero ash content, it is not excluded that it also plays the role of a raw material that influences the composition of the vitrifiable material produced. Biomass is organic material of plant, animal, bacterial or fungal origin that can be used as an energy source.

[0005] Combustion of the fuel is achieved in the presence of an oxygen-containing oxidizer, such as air, oxygen-enriched air, or pure oxygen (i.e., containing more than 90% or even more than 99% oxygen). Biomass is usually not the only fuel used; gaseous or liquid hydrocarbon-type fuels, so-called hydrocarbon fuels, are also used. The hydrocarbon fuel and oxidizer can be introduced separately into the furnace or mixed in a burner mixing chamber before introduction into the furnace. The oxidizer and fuel can be introduced above the surface of the molten material or below the surface of the molten material. The furnace can include walls cooled by a water flow. The furnace can, in particular, be an immersion combustion furnace. As described in WO2013186480, this furnace can, in particular, include metal walls cooled by water circulation (furnaces referred to as "water jacket" by those skilled in the art) and can include one or two consecutive tanks. As described in WO2013117851, for the combustion of hydrocarbon fuels, the furnace can be equipped with immersion burners, in particular burners each including multiple in-line injectors.

[0006] The present invention relates to a method for melting vitrifiable inorganic materials, such as glass or rock or silicates, which method comprises introducing a pre-composed mixture of vitrifiable raw materials and biomass into a fuel-fired furnace, followed by heating of said mixture, which results in melting of the vitrifiable material. The mixture of raw materials and biomass is pre-composed, meaning that the mixture is prepared prior to introduction into the furnace and is not formed in situ in the furnace by separate introduction. Of course, separate introduction of the raw materials and / or biomass is not excluded.

[0007] Several beneficial effects were observed from the introduction of biomass: - the temperature in the furnace is much more homogeneous; this is certainly due to the fact that the biomass, like the raw material, is distributed uniformly in the furnace and therefore acts as fuel in every area of ​​the furnace; therefore, the combustion is not limited to the burner only, which usually tends to create very hot areas; therefore, the burner power can be reduced in order to partly replace it with the power coming from the combustion of the biomass, which power is spread over the entire furnace; thereby, the use of biomass provides a great stability of temperature and power output; - the presence of biomass in the pre-formed mixture prevents the premature formation of agglomerates under the influence of heat when the mixture approaches the point of introduction into the furnace; in particular, this type of agglomerates can form real plugs that block the channels for the introduction of raw materials, which then cause interruptions in production; this type of agglomerates appear to be a mixture of molten and non-molten material and form a bit like sintering; the presence of biomass prevents the formation of agglomerates under the influence of biomass decomposition, possibly with the formation of gases, so that the raw materials can be dispersed quickly and very homogeneously as soon as they are introduced into the furnace.

[0008] Advantageously, the pre-formed mixture is introduced into the furnace below the surface of the molten material. Thus, most of the volatile material (raw material or biomass) is trapped in the molten mass and cannot escape via the combustion flue gases. Submerged combustion furnaces provide very efficient mixing of all materials contained in the furnace. The pre-formed mixture introduced below the surface of the molten material is immediately mixed with everything the furnace contains and dispersed throughout the furnace.

[0009] The preformed mixture is introduced into the furnace by flow or extrusion, for example, using an endless screw or piston. In the case of introduction below the surface of the molten material, a plug forms near the point of introduction into the furnace. This plug is a mixture of solidified inorganic material (glass, rock, or silicate) chunks emerging from the furnace mixed with the incoming raw material. This plug forms where there is a large temperature change between the hot interior of the furnace and the cold exterior of the furnace. This temperature gradient is even greater in the case of "water-jacketed" furnaces. The formation of this plug is beneficial because it prevents the molten mass inside the furnace from leaking out of the furnace and into the sleeve housing the endless screw. However, if the plug is too viscous, it risks braking or blocking the screw, and applying too high a driving torque to the screw to rotate it can still destroy it. The presence of biomass mixed with the raw material reduces the viscosity of the plug. The invention is particularly suitable for melting inorganic materials in a submerged combustion furnace comprising walls cooled by a flow of water, and the vitrifiable raw materials mixed with biomass are introduced into the furnace below the surface of the molten material.

[0010] The present invention further relates to a mixture of biomass and vitrifiable raw materials for introduction into a furnace for melting vitrifiable inorganic materials, in particular glass or rock or silicates, the mixture being formed before its introduction into the furnace, in which the biomass typically accounts for 1% to 50% by weight, preferably 10% to 40% by weight, of the mass of the mixture.

[0011] The biomass may be plant material such as miscanthus or algae. Particularly effective biomass includes oily seeds and / or seed husks of oily seeds, referred to as oleaginous biomass. Oilseeds are plants cultivated for their seeds or fruits, rich in fatty substances, from which oil is extracted for food, energy, or industrial uses. The oleaginous biomass is particularly the seed or seed husk of at least one of the following plant species: sunflower, rapeseed, soybean, palm, peanut, olive, or pumpkin, and is particularly sunflower husk. The term "seed husk" refers to the material that surrounds and protects the seed itself, and may be a pod, husk, or skin, depending on the plant species. The excellent behavior of oleaginous biomass is due to its fatty nature. It acts as a true lubricant not only for the endless screw but also for the entire mechanical system that transports the mixture to the furnace. Therefore, the presence of the biomass serves to prevent damage to the equipment used to measure and transport the vitrifiable raw materials. The present invention further relates to the use of oleaginous biomass in addition to vitrifiable raw materials to reduce damage to equipment used to measure and transport the vitrifiable raw materials. A particularly effective oleaginous biomass is sunflower husk, which is also an inexpensive waste product from the food processing industry. Therefore, the use of this by-product is particularly advantageous and even ecological because it is a non-fossil fuel that is not known what to do with, is inedible (either as human food or animal feed), and does not require the substitution of specific crops for human consumption. The oleaginous biomass can account for more than 50%, preferably more than 80%, preferably more than 90%, or even 100% of the biomass mass.

[0012] To demonstrate the beneficial effect of introducing oily biomass on the service life of the feedstock feeder, two series of tests were carried out in a pilot furnace with an immersion burner. In the first series, called "without biomass," a biomass-free vitrifiable material composition was introduced into the furnace. In the second series, called "with biomass," an oily biomass consisting of sunflower seed husks was introduced into the vitrifiable material composition at a rate of 100 kg of biomass per 1,300 kg of vitrifiable material (i.e., approximately 7.7% by mass). Other process parameters (glass bath temperature, feed flow rate by mass, etc.) remained unchanged between the two series. For each test, the service life of the charge screw and sleeve, respectively, was noted. The average values ​​of these service lives are shown in Table 1 below.

[0013] [Table 1]

[0014] The results in Table 1 show that the introduction of oily biomass from sunflower seed husks, even at a relatively small proportion of 7.7% by mass, makes it possible to significantly increase the service life of the feeder, resulting in an average increase in the service life of the charge screw of 575% and an average increase in the service life of the sleeve of 123%.

[0015] The biomass is a fuel, as is the hydrocarbon fuel fed to the burner. The amount of oxidizer introduced into the furnace, usually by the burner, is adequate to incinerate all of the fuel introduced into the furnace. Thus, more oxidizer is fed to the burner than is necessary to incinerate the hydrocarbon fuel fed to the burner, with the excess oxidizer serving to incinerate the biomass fed outside the burner.

[0016] Biomass can provide between 5% and 80% of the net heating value of the total fuel used to heat the furnace.

[0017] The molten material in the furnace typically has a temperature of 1200°C to 1700°C.

[0018] The vitrifiable materials produced by the method according to the invention are usually inorganic materials of the oxide type, such as glass or rock or silicates, which usually contain at least 30% by weight of silica, for example alkali metal silicates and / or alkaline earth metal silicates.

[0019] The glass or rock typically contains: SiO2: 30% by mass to 75% by mass, CaO+MgO: 5% by mass to 40% by mass, Na2O+K2O: 0% by mass to 20% by mass, Al2O3: 0% by mass to 30% by mass, Iron oxide: 0% to 15% by mass.

[0020] When glass is the objective, the composition of the vitrifiable material produced typically includes: SiO2: 50% by mass to 75% by mass, CaO+MgO: 5% by mass to 20% by mass, Na2O+K2O: 12% by mass to 20% by mass, Al2O3: 0% by mass to 8% by mass, Iron oxide: 0% to 3% by mass, B2O3: 2% to 10% by mass.

[0021] If rock (also called "black glass" by those skilled in the art) is the objective, the composition of the vitrifiable material thus produced usually comprises: SiO2: 30% by mass to 50% by mass, CaO+MgO: 20% by mass to 40% by mass, Al2O3: 10% by mass to 26% by mass, Iron oxide: 3% to 15% by mass.

[0022] A pre-formed mixture of biomass and vitrifiable raw materials is introduced into the furnace. The vitrifiable raw materials introduced into the furnace contain compounds that make it possible to obtain the desired inorganic composition (glass, rock, or silicate). These compounds may be those commonly used by those skilled in the art, such as sand (silica source), oxides, hydroxides, or carbonates of alkali metals, oxides, hydroxides, or carbonates of alkaline earth metals, and feldspar (alumina source). The vitrifiable raw materials usually contain silica and at least one of the following compounds (oxides, hydroxides, or carbonates of alkali metals, oxides, hydroxides, or carbonates of alkaline earth metals). The raw materials may also contain cullet. The raw materials are usually a mixture of powders or a mixture of powders and cullet fragments. The term "raw material" is therefore a generic term that generally refers to a mixture containing various powdered compounds. This "raw material" is vitrifiable, and its melting results in a glass, rock, or silicate-type inorganic material.

[0023] The molten vitrifiable inorganic material produced by the present invention is withdrawn from the furnace to solidify by cooling in a suitable form. In particular, it can be withdrawn from the furnace in a molten state and directly used in a fiberization device to form reinforcing strands or mineral wool. Thus, the vitrifiable inorganic material can be withdrawn from the furnace and converted into fibers in the fiberization device. In fiberization applications, the vitrifiable material is usually glass or rock.

[0024] FIG. 1 illustrates a furnace with an immersion burner that can be used in the context of the present invention, seen in cross section from the side. Furnace 1 is shown containing burner 2, which is submerged in vitrifiable material 3 during melting. An endless screw 13 extrudes a mixture of raw material and biomass 5 below the surface 6 of the molten material in the furnace. A dispenser 17 of the mixture feeds a feed hopper 7, which in turn feeds the endless screw 13, which rotates within a sleeve 4. A more or less viscous plug 12, a mixture of solidified raw material and raw material, tends to form at the end of sleeve 4 as it approaches the temperature of the molten mass. The interior of the furnace contains two tanks 8 and 9, which operate according to the principles taught in WO2013186480. The endless screw first feeds tank 8, which is relatively cold; the resulting molten vitrifiable material then spills over a partition 10 and enters tank 9, whose temperature is higher than that of tank 8. The formed vitrifiable material exits through an outlet 11 below the level of the molten material. The combustion gases exit through an exhaust stack 16. The present disclosure also encompasses the following: [Aspect 1] 1. A mixture of biomass and vitrifiable raw materials for introduction into a furnace for melting vitrifiable inorganic materials, characterized in that the biomass comprises oleaginous seeds and / or seed husks of oleaginous seeds, called oleaginous biomass. [Aspect 2] The mixture according to aspect 1, wherein the biomass accounts for 1% to 50% by mass, preferably 10% to 40% by mass, of the mass of the mixture. [Aspect 3] 3. The mixture according to any one of the preceding aspects, wherein the oleaginous biomass comprises more than 50%, preferably more than 80%, preferably more than 90%, or even 100% of the mass of the biomass. [Aspect 4] The oleaginous biomass is derived from at least one of the following plant species: Sunflower, rapeseed, soybean, palm, peanut, olive or pumpkin 4. The mixture according to claim 2 or 3, characterized in that the seeds or seed husks are sunflower seeds or sunflower husks. [Aspect 5] The vitrifiable raw material comprises silica and the following compound: Oxides, hydroxides, or carbonates of alkali metals, oxides, hydroxides, or carbonates of alkaline earth metals and at least one of the following: [Aspect 6] 10. A method of melting vitrifiable inorganic material, the method comprising introducing a pre-composed mixture according to any of aspects 1-5 above into a fuel-fired furnace, followed by heating the mixture to result in melting of the vitrifiable inorganic material, particularly glass or rock or silicate. [Aspect 7] 7. The method of claim 6, wherein the furnace is an immersion combustion furnace. [Aspect 8] 8. The method of any one of claims 6 to 7, wherein the preformed mixture is introduced into the furnace below the surface of the molten material. [Aspect 9] 9. The method of any one of aspects 6 to 8, wherein the preformed mixture is introduced into the furnace by flow or extrusion. [Aspect 10] 10. The method of claim 9, wherein the introducing of the preformed mixture is performed by extrusion through an endless screw. [Aspect 11] 11. The method according to any one of aspects 6 to 10, wherein the biomass provides 5% to 80% of the net heating value of the fuel. [Aspect 12] 12. The method according to any one of the above-mentioned aspects 6 to 11, wherein the molten material in the furnace has a temperature of 1200°C to 1700°C. [Aspect 13] 13. The method of any one of aspects 6 to 12, wherein the vitrifiable inorganic material is withdrawn from the furnace and converted into fibers in a fiberizing device. [Aspect 14] 14. The method of any one of the aforementioned aspects 6 to 13, wherein the furnace comprises walls cooled by flowing water. [Aspect 15] The use of oily biomass in addition to vitrifiable raw materials to reduce damage to equipment for weighing and transporting said vitrifiable raw materials.

Claims

1. A mixture of biomass and vitrifiable raw materials for introduction into a furnace for melting vitrifiable inorganic material, said biomass comprising oleaginous seeds and / or seed husks of oleaginous seeds, referred to as oleaginous biomass, wherein the biomass accounts for 1% to 50% by mass of the mass of the mixture.

2. 10. The mixture of claim 1, wherein the oleaginous biomass comprises greater than 50% of the mass of the biomass.

3. The oleaginous biomass is derived from at least one of the following plant species: Sunflower, rapeseed, soybean, palm, peanut, olive or pumpkin 3. A mixture according to claim 1 or 2, characterized in that it is a seed or seed husk of

4. The vitrifiable raw materials comprise silica and the following compound: Oxides, hydroxides, or carbonates of alkali metals, oxides, hydroxides, or carbonates of alkaline earth metals The mixture according to any one of claims 1 to 3, characterized in that it contains at least one of:

5. 10. A method of melting a vitrifiable inorganic material, the method comprising introducing a pre-composed mixture of any one of claims 1 to 4 into a fuel-fired furnace, followed by heating the mixture to result in melting of the vitrifiable inorganic material.

6. 6. The method of claim 5, wherein the furnace is an immersion combustion furnace.

7. 7. A method according to claim 5 or 6, characterized in that the pre-composed mixture is introduced into the furnace below the surface of the molten material.

8. 8. The method according to any one of claims 5 to 7, characterized in that the pre-formed mixture is introduced into the furnace by flow or extrusion.

9. 9. The method of claim 8, wherein the introduction of the pre-composed mixture is carried out by extrusion through an endless screw.

10. 10. The method according to any one of claims 5 to 9, characterized in that the biomass provides between 5% and 80% of the net heating value of the total fuel.

11. A method according to any one of claims 5 to 10, characterized in that the molten material in the furnace has a temperature of between 1200°C and 1700°C.

12. 12. A method according to any one of claims 5 to 11, characterized in that the vitrifiable inorganic material is extracted from the furnace and converted into fibres in a fibreising device.

13. A method according to any one of claims 5 to 12, characterized in that the furnace comprises walls cooled by a flow of water.

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