Method for manufacturing a batch of a homogeneous pulverulent composition for ceramic welding comprising refractory filler particles and metallic particles

Abstract

Method for manufacturing a batch of a homogeneous pulverulent composition for ceramic welding comprising refractory filler particles and metallic particles. Method for manufacturing a batch of a homogeneous pulverulent composition for ceramic welding comprising refractory filler particles and metallic particles, comprising the steps of feeding the refractory filler particles and the particles into a first vessel, which is then gripped by a robotic arm and inverted to form a homogeneous mixture. The homogeneous mixture is transferred to a bagging hopper arranged to dispense a predetermined quantity of homogeneous mixture into n airtight and watertight bags forming said batch. The bags are then pierced and flattened before being placed on a transport pallet.

Description

[0001] A method for manufacturing a batch of a homogeneous powder composition for ceramic welding comprising refractory filler particles and metallic particles

[0002] The present invention relates to a method for manufacturing a batch of a homogeneous powder composition for ceramic welding comprising refractory filler particles and metallic particles.

[0003] The use of a powder composition containing refractory filler particles and metallic particles for ceramic welding in industrial furnaces allows the furnaces to be maintained while retaining high heat resistance and optimal durability in these demanding environments.

[0004] The presence of refractory filler particles increases the density and robustness of the ceramic, while improving its resistance to wear and abrasion. These particles help minimize shrinkage and the risk of cracking during the ceramic's cooling process.

[0005] Metallic particles play a crucial role in the formation of ceramic and metallic compounds, as they can react with various elements, such as oxygen, to form stable, high-temperature-resistant metal oxides. During welding or repair processes, these metallic particles can interact with other components to form solid phases, strengthening the material structure and improving its resistance to extreme conditions, such as intense heat or mechanical wear. Their ability to reinforce welds or coatings makes them essential components in the repair and protection of industrial furnaces.

[0006] In industrial furnaces, this powder composition is applied as a coating or bonding layer to refractory surfaces. It is used to repair existing ceramic coatings. In particular, it allows for the repair of cracks inside furnaces without having to shut them down. When heated inside the furnaces, often to temperatures exceeding 1000°C, the composition reacts to form a strong and durable bond with the surface being repaired.

[0007] This combination of materials makes it possible to create ceramic welds that resist not only intense heat, but also chemical corrosion and mechanical wear, thus significantly extending the service life of refractory components in industrial furnaces. The use of such powdered compositions for ceramic welding requires that the composition be homogeneous to ensure uniform material distribution during application. The reason for perfect homogeneity lies in the need to ensure that, during ceramic welding, each part of the composition reacts coherently. If the particles are not well mixed, some areas may lack critical components, which could lead to defects in the weld, such as structural weaknesses or uneven melting points.For example, if the metallic particles, which are responsible for the formation of refractory compounds at high temperatures, are not uniformly distributed, some parts of the weld may not achieve the properties necessary to withstand the extreme conditions inside industrial furnaces. The homogeneity of the powder composition is important to ensure its flowability. When used to fill cracks in an operating industrial furnace, the composition is projected at high speed onto the furnace walls. This projection speed depends directly on the homogeneity of the powder, and a homogeneous composition guarantees stable and controlled projection. It is crucial that this projection be controlled to allow for proper interaction between the composition and the furnace wall.The reactivity of the composition is directly linked to its homogeneity: a uniform composition ensures uniform reactivity. Conversely, any inhomogeneity can lead to reactivity problems, ranging from insufficient reactivity to excessive reactivity, the latter potentially causing serious incidents, such as the explosion of the projection device.

[0008] Achieving this homogeneity in the powder composition is complicated by the size difference between the refractory filler particles and the metallic particles. Indeed, particle size is determined by the specific roles each type of particle plays in the ceramic weld composition and by the weld's performance requirements in industrial environments. The larger refractory filler particles act primarily as aggregates or structural fillers within the composition. Their large size improves the weld's robustness and mechanical stability. These particles form the basic matrix that gives the weld its resistance to wear, thermal shock, and other mechanical stresses to which it might be exposed in an industrial furnace.The large size of the refractory filler particles also ensures that the composition remains porous, allowing for some flexibility while preventing cracking or breakage under thermal stress. The metallic particles are much smaller and play a different role in the composition. The metal reacts with oxygen at high temperatures to form a metal oxide, which helps create a refractory glassy phase, essential for the strength and chemical stability of the weld. The small size of these particles is crucial for enabling rapid and uniform chemical reactivity. The smaller the particles, the greater their specific surface area, which promotes efficient and rapid chemical reactions when heat is applied.

[0009] The size of the refractory charge particles is generally a few hundred micrometers and the size of the metallic particles is generally a few tens of micrometers.

[0010] Metallic particles, being much smaller, are also lightweight and can easily remain suspended in the air when handled. These fine particles can be inhaled deep into the lungs. Once inhaled, they can reach the alveoli, the tiny air sacs where gas exchange takes place. Their small size allows them to bypass the body's natural defense mechanisms, such as the cilia in the airways, which are less effective at filtering these minute particles. Regular inhalation of these fine particles can cause serious lung diseases.

[0011] For example, prolonged exposure to metallic particles can cause irritation of the respiratory tract and, in the long term, scarring of the lungs (chronic bronchitis). The permitted respirable fraction is 5 mg / m³ 3 for a working environment lasting 8 hours. Prolonged exposure can lead to a disease called silicosis.

[0012] Powdered compositions comprising refractory filler particles and metallic particles are well known in the prior art; see, for example, document EP2176192, which describes a dry mixture for treating refractory substrates and the process for producing it. Document EP3083523 describes a siliceous composition and the process for obtaining it. Document EP2171118 describes a process and apparatus for spraying powdered material into a carrier gas for use in a furnace.Document WO2015 / 091126 describes a two-step process for manufacturing a powdered ceramic solder composition: first, flint stones are heated to a high temperature to transform them into porous aggregates, primarily cristobalite; then, these are ground and sieved to isolate porous silica particles; and finally, this particle phase is mixed with one or more common additives to form the binding phase, resulting in a ready-to-use ceramic solder composition. Document US5202090 describes an apparatus for repairing a refractory body (e.g., a furnace wall) by projecting combustible particles in an oxygen-rich carrier gas against the body, causing their oxidation in an adjacent reaction zone and generating the heat required for straightening or forming a mass of refractory solder.

[0013] Unfortunately, although the exothermic nature of the reaction of the powder composition with atmospheric oxygen and moisture is known, as well as the need to obtain a homogeneous mixture, none of the previous documents provide any indication of how to produce this composition industrially, i.e., in a way that allows for the production of large homogeneous batches that preserve the reactivity of the materials and the health of the workers.

[0014] The invention aims to overcome the drawbacks of the prior art by providing a process for the industrial production of a homogeneous powder composition for ceramic welding comprising refractory filler particles and metallic particles, while limiting the contact between the powder composition and the outside in order to minimize the reaction of the composition with oxygen and humidity in the air, but also to prevent the suspension of fine particles which can cause health problems.

[0015] To solve this problem, the invention provides a method for manufacturing a batch of a homogeneous powder composition for ceramic welding, comprising refractory filler particles and metallic particles, comprising the steps of:

[0016] a) bringing refractory charge particles into a first feed hopper and pouring a predetermined quantity of these refractory charge particles chosen from the group comprising aluminium oxide particles, silicon carbide particles, zirconium oxide particles, silicon oxide particles, magnesia particles, chromium oxide particles, iron oxide particles, and mixtures thereof, from the first feed hopper into a first tank placed on load cells, said refractory charge particles having an average particle size measured by sieving d50 of between 350 and 800 µm, preferably between 400 and 500 µm and a d5 of between 150 µm and 200 µm,

[0017] b) bringing selected metallic particles from the group comprising aluminium particles, silicon particles, magnesium particles, calcium particles, iron particles and mixtures thereof, into a second feed hopper and pouring a predetermined quantity of these metallic particles from the second feed hopper into said first tank placed on load cells at the top of which dust is extracted, said metallic particles having an average particle size measured by optical particle size analysis d50 of between 10 and 50 µm, preferably between 15 and 40 µm, preferably between 20 and 30 µm, a d5 of between 1 and 10 µm, preferably between 3 and 7 µm and a d95 of between 35 and 65 µm, preferably between 45 and 55 µm, c) closing said first tank and transferring said closed first tank from the load cells to a robotic mixing arm,said robotic arm being arranged to grasp the first tank and perform a series of inversions of said first tank in order to form said powdered composition in the form of a homogeneous mixture during a time interval of between 15 and 45 minutes, d) a transfer of said homogeneous mixture from said first tank to a bagging hopper arranged to discharge a predetermined quantity of homogeneous mixture into n airtight and watertight bags forming said batch,

[0018] e) a horizontal deposit of an n ième airtight and watertight bag of said n airtight and watertight bags after closure on a conveyor belt, f) an inlet of said n ième airtight and watertight bag closed in a flattening device with a perforation of an orifice with a diameter between 0.1 and 0.5 mm, with formation of an n ième flattened and punctured bag

[0019] (g) horizontal placement on a transport pallet of the nième flattened and perforated waterproof bag, with said opening facing upwards

[0020] (h) a plugging of the hole of said orifice of the n ième a flattened and perforated waterproof bag on said transport pallet

[0021] and in which, between steps d) and h) there is a period of time of less than 4 hours, preferably less than 3 hours, preferably less than 2 hours, preferably less than 1 hour, said homogeneous mixture of the n sealed bags being a mixture in which, where appropriate, the metallic particles form a layer of metallic particles greater than 0.01 centimeter and less than 1 centimeter in the bottom of each of the n sealed bags, after 30 minutes at rest.

[0022] According to the invention, the process involves introducing refractory filler particles with an average size (d50) between 350 and 800 µm, preferably between 400 and 500 µm, and a particle size distribution (d5) ranging from 150 to 200 µm, which significantly improves the robustness and mechanical stability of the weld. For the purposes of this invention, refractory filler particles are defined as particles of aluminum oxide, silicon carbide, zirconium oxide, silicon oxide, magnesia, or chromium oxide. These particles form an essential base matrix that provides the weld with increased resistance to wear, thermal shock, and the various mechanical stresses encountered in an industrial furnace.Their relatively large size also ensures that the composition retains optimal porosity, thus offering the necessary flexibility while minimizing the risk of cracks or breaks under the effect of thermal variations.

[0023] The process further involves introducing metallic particles with an average size (d50) between 30 and 60 µm, preferably between 35 and 55 µm, and ideally between 40 and 50 µm, which allows for high reactivity. Indeed, the small size of these particles maximizes the surface area to volume ratio, which, for an equivalent mass, results in significantly higher reactivity than that of larger particles. For the purposes of this invention, metallic particles are defined as particles of aluminum, silicon, magnesium, calcium, or a mixture thereof. The size of these particles is measured by optical particle size analysis as described in BE1023760B1 and BE1023800B1.

[0024] The notation dX represents an average particle diameter measured by sieving or optical particle size analysis, expressed in pm, relative to which X% of the measured particles or grains are smaller.

[0025] Despite using particles of widely varying sizes to form the composition, the process according to the invention surprisingly yields a homogeneous batch. This result is achieved through homogenization by a robotic arm, which mixes the composition for 15 to 45 minutes in a first sealed tank, isolating the contents from the ambient atmosphere and thus ensuring a uniform distribution of the particles of varying sizes.

[0026] It is important to process this composition quickly using the method described above to prevent natural segregation. When a homogenized powder is left to stand, the different particles that compose it can begin to separate due to differences in size, density, or shape. This natural segregation is caused by gravitational forces and possible vibrations, which cause denser or larger particles to settle to the bottom of the mass, while lighter or finer particles may rise to the surface. This natural separation compromises the uniform distribution of the powder's components, thus affecting the quality and performance of the final product.Processing the homogenized composition immediately using the method described above reduces the risk of dehomogenization by maintaining a uniform particle distribution until the next processing step, including the welding operation at the industrial site. This ensures that each unit of the powder composition retains the desired properties, which is essential for obtaining a high-quality final product with predictable and repeatable characteristics.

[0027] Surprisingly, despite using particles with an average size of 50 µm, the quantity of particles suspended in the work environment remains low, thus ensuring the safety of workers operating the process according to the invention. This is made possible by the dust extraction system at the top of the first tank during the emptying of said particles. Extracting the dust at the top of the first tank, which is mounted on load cells, prevents any distortion in the measurement of the mass of material present in the tank. This arrangement thus protects the health of workers by maintaining accurate and reproducible measurements on an industrial scale.

[0028] The process according to the present invention comprises a first feed hopper and a second feed hopper which allow the discharge of a predetermined quantity of refractory charge particles and metallic particles into a first tank placed on load cells. This equipment makes it possible to handle a significant quantity of material, on the order of a few tens of kilograms to several hundred kilograms.

[0029] Next, the mixture is bagged, and the filled bags are flattened by removing the air inside, thus eliminating air pockets that could cause internal particle movement. These combined steps result in a homogeneous batch with reduced segregation, ensuring optimal quality and performance of the final product, even in the presence of particles of widely varying sizes.

[0030] Indeed, the bagging hopper is designed to dispense a predetermined quantity of mixture into airtight and watertight bags. The use of airtight and watertight bags limits the risk of the mixture heating up due to the exothermic reaction between the mixture and atmospheric humidity and / or water, by restricting the entry of air and water.

[0031] Once filled, the bags are hermetically sealed and placed on a conveyor belt to be fed into a flattening device. This flattening device flattens the bag and expels any residual air present after sealing through an orifice with a diameter between 0.1 and 0.5 mm. This orifice is located either within or upstream of the flattening device.

[0032] Piercing the bag during or before flattening expels any residual air. This expulsion minimizes the presence of air and moisture within the powdered composition inside the bag. This step helps limit unwanted reactions between the powdered composition and oxygen and / or water. The shelf life of powdered compositions packaged in such flattened bags with air expulsion is thus improved.

[0033] The flattened bags are then transported horizontally and stacked on a transport pallet with the opening facing upwards. Surprisingly, the dimensions of the perforated opening are small enough to prevent air and water from entering, thus avoiding degradation of the powdered composition inside the bags. Stacking the filled bags allows the opening of one bag to be sealed with the bag covering it. This sealing also prevents anything from entering the sealed bag. The opening can also be sealed using a piece of cardboard, preferably covered with plastic film.The use of such a cardboard plate makes it possible to cover the openings of the bags placed at the top of the stack on the transport pallet and is sufficient to prevent air from entering the last bag in the stack, which could otherwise cause some particles to react with the humidity in the air and allow some particles to move relative to others of a different size.

[0034] Preferably, the refractory filler particles are chosen from the group consisting of aluminum oxide particles, silicon carbide particles, zirconium oxide particles, silicon oxide particles, magnesia particles, chromium oxide particles, iron oxide particles, and mixtures thereof.

[0035] Preferably, the metallic particles are chosen from the group consisting of aluminum particles, silicon particles, magnesium particles, calcium particles, iron particles and mixtures thereof.

[0036] Preferably, through homogeneity, and without being bound to any theory, the alternating layers of large and small particles break apart and mix. The small particles fill the voids left between the large particles, which reduces the risk of segregation by gravity.In one particular embodiment, the process for manufacturing a powder composition for ceramic welding according to the invention further comprises a step of feeding additive particles selected from the group comprising lime particles, glass particles, magnesia particles, dolomite particles, calcium carbonate particles, magnesium carbonate particles, and mixtures thereof into a third feed hopper and a discharge of a predetermined quantity of these additive particles from the third feed hopper into said first tank placed on weights at the top of which a dust aspiration is carried out, said additive particles having an average particle size measured by optical particle size d50 of between 30 and 60 µm, preferably between 35 and 55 µm, preferably between 40 and 50 µm.Additive particles may be lime particles, preferably quicklime particles, glass particles, magnesia particles, preferably quicklime particles, dolomite particles, preferably quicklime and / or partially hydrated dolomite particles, calcium carbonate particles, or magnesium carbonate particles. The size of these particles is measured by optical particle size analysis as described in BE1023760B1 and BE1023800B1. These particles are used to control the reactivity of the homogeneous mixture. For example, additive particles may have lower reactivity than metallic particles, thus slowing the reaction and reducing the risk of explosion when using the powdered composition through a dilution effect.

[0037] Preferably, the additive particles are chosen from the group consisting of lime particles, glass particles, magnesia particles, dolomite particles, calcium carbonate particles, magnesium carbonate particles, and mixtures thereof.

[0038] Advantageously, the refractory charge particles are siliceous particles.

[0039] Even more advantageously, the metallic particles are silicon particles.

[0040] Preferably, the additive particles are quicklime particles.

[0041] Preferably, in which the predetermined quantity of refractory filler particles is between 70 and 90%, preferably between 80 and 90% by weight relative to the weight of said homogeneous mixture, the predetermined quantity of metallic particles is between 10 and 30% by weight relative to the weight of said homogeneous mixture.

[0042] Advantageously, the predetermined quantity of refractory filler particles is between 70 and 90%, preferably between 80 and 90% by weight relative to the weight of said homogeneous mixture, the predetermined quantity of metallic particles is between 5 and 25% by weight relative to the weight of said homogeneous mixture, and the predetermined quantity of additive particles is between 5 and 10% by weight relative to the weight of said homogeneous mixture.

[0043] Advantageously, the refractory charge particles are siliceous particles comprising at least 80% by weight of cristobalite and at most 20% by weight of tridymite, preferably at most 17% by weight of tridymite relative to the weight of refractory charge particles.

[0044] Advantageously, the refractory charge particles brought into the first feed hopper are brought into a first material receiving structure, they then pass into a first feed conduit by means of the vibrations of a first vibrating motor, the metallic particles brought into the second feed hopper are brought into a second material receiving structure, they then pass into a second feed conduit by means of the vibrations of a second vibrating motor and the refractory charge particles and the metallic particles move within said first and second conduit over a distance of at least one meter and up a slope whose angle of slope is between 1 and 10°.

[0045] Using a feed duct at least one meter long, with an incline between 1 and 10°, and in combination with a vibrating motor, allows for efficient control of the amount of material dispensed into the first hopper. Without vibration, the particles accumulate at the base of the duct. When the motor is activated, the vibrations reorganize the particles, which then move along the duct until they fall into the hopper. Stopping the vibrations immediately halts the flow of particles. This precise control mechanism is made possible by the specific incline of the duct, which is oriented upwards at 1 to 10°, ensuring optimal particle movement.

[0046] In a particular embodiment, the first tank comprises several parts of the first tank, at least one part of which has a diameter that decreases downwards. Preferably, the process takes place in a manufacturing building comprising a feeding area, a mixing area, and a bagging area, each separated from the others by at least 5 meters, and wherein the discharge of a predetermined quantity of particles into said first tank, which is placed on load cells, is carried out in the feeding area and when the first tank is in a feeding position, said feeding position being a position in which the first tank is opened from the top and the closure of said first tank is carried out in said feeding area.

[0047] Advantageously, said robotic arm is located in said mixing zone into which said first closed tank is transferred.

[0048] Preferably, the opening of the first closed tank is carried out in the bagging area.

[0049] Advantageously, the application of a predetermined quantity of refractory filler particles is followed by the application of a predetermined quantity of metallic particles. This second application of metallic particles is followed by a second application of a predetermined quantity of refractory filler particles. This second application of a predetermined quantity of refractory filler particles is followed by the application of a predetermined quantity of additive particles. Alternating particles with a d50 between 350 and 800 µm (the refractory filler particles) and particles with a d50 between 30 and 60 µm improves the subsequent homogenization by facilitating the mixing of the materials. The larger particles create wider interstitial spaces, into which the smaller particles can easily fit.This arrangement allows for a more uniform distribution of particles of different sizes within the overall mixture. During the homogenization process, the alternating layers break down and mix more easily, as the smaller particles fill the voids between the larger ones, reducing the risk of segregation due to gravity. This minimizes density variations within the mixture and ensures that the different components are evenly distributed throughout the process. Consequently, the final homogeneity of the mixture is improved.

[0050] These discharges can be, for example, an initial discharge of a predetermined quantity of refractory charge particles into the bottom of the first tank. This initial discharge is followed by a second discharge of a predetermined quantity of metallic particles, forming a layer of metallic particles above the refractory charge particles. This second discharge is followed by a third discharge of a predetermined quantity of refractory charge particles, forming a layer of refractory charge particles above the metallic particles. This third discharge is followed by a fourth discharge of a predetermined quantity of additive particles, forming a layer of additive particles above the refractory charge particles.

[0051] Advantageously, the discharge of the predetermined quantity of refractory charge particles from the first feed hopper to the first tank placed on load cells, the discharge of the predetermined quantity of metallic particles from the second feed hopper to the first tank placed on load cells, and the transfer of said homogeneous mixture from said first tank to an arranged bagging hopper is carried out by means of a series of butterfly valves.

[0052] Other embodiments of the process for manufacturing a ceramic welding composition according to the invention are indicated in the attached claims.

[0053] Other features, details and advantages of the invention will become apparent from the description given below, by way of non-limitation and with reference to the drawings and examples.

[0054] In the drawings, figure 1 shows a diagram of a process for manufacturing a batch of a homogeneous powder composition for ceramic welding according to the invention.

[0055] In the figures, identical or analogous elements bear the same references; pumping systems, valves, etc., are generally not shown. Only mass transfers are highlighted.

[0056] The process according to the present invention makes it possible to produce safely and industrially a batch of a homogeneous powder composition for ceramic welding comprising refractory filler particles and metallic particles.

[0057] As can be seen in Figure 1, the process first comprises a step of feeding refractory filler particles, for example silica particles (1), into a first feed hopper (2). The process also includes a step of feeding metallic particles, for example silicon particles (5), into a second feed hopper (12). The process includes a step of feeding additive particles, for example quicklime particles (7), into a third feed hopper (13). These feeding steps can be simultaneous or sequential. The silica particles are then fed into a first material receiving structure, from where they pass into a first feed duct by means of vibrations from a first vibrating motor. The motor's vibrations allow the particles to advance in the first feed duct, which rises at an angle of 1 to 10° and has a length of at least 1 meter.Similarly, the silicon particles are fed into a second material receiving structure, then into a second feed duct driven by the vibrations of a second vibrating motor. The motor's vibrations propel the particles through this second feed duct, which rises at an angle of 1 to 10° and is at least 1 meter long. The first and second vibrating motors can generate distinct vibrations, as the size difference between silica and silicon particles influences their behavior at the same vibration frequency. Therefore, it is advantageous to tailor the vibrations to the size of the particles being transported, optimizing their movement and ensuring efficient transport. Adapting the vibration frequency to the particle type thus improves the accuracy and performance of the transport process.

[0058] A predetermined quantity of silica particles (3) is dispensed via a butterfly valve into a first tank (4) on load cells. A predetermined quantity of silicon particles (6) is dispensed via a butterfly valve into a first tank (4) on load cells. A predetermined quantity of quicklime particles (8) is dispensed via a butterfly valve into a first tank (4) placed on load cells. These steps take place in a feed area of ​​a manufacturing shed.

[0059] The order and number of these discharges may vary, for example, a discharge of a predetermined quantity of silica particles followed by the discharge of a predetermined quantity of silicon particles, followed by a second discharge of a predetermined quantity of silica particles and followed by the discharge of a predetermined quantity of quicklime particles.

[0060] During the pouring of silicon particles and quicklime particles, dust is extracted from the top of the first tank.

[0061] The siliceous particles have an average particle size measured by sieving d50 of between 350 and 800 µm, preferably between 400 and 500 µm, and a d5 of between 150 and 200 µm. The silicon particles have an average particle size measured by optical particle size analysis d50 of between 10 and 50 µm, preferably between 15 and 40 µm, preferably between 20 and 30 µm, a d5 of between 1 and 10 µm, preferably between 3 and 7 µm, and a d95 of between 35 and 65 µm, preferably between 45 and 55 µm.

[0062] The quicklime particles have an average particle size measured by optical particle size analysis d50 of between 30 and 60 pm, preferably between 35 and 55 pm, preferably between 40 and 50 pm.

[0063] The tank is then sealed, removed from the load cells, and transported (9) to a robotic mixing arm (10) in a mixing area within the manufacturing building. The robotic arm grasps the sealed tank and performs a series of inversions (11) to homogenize the tank's contents over a period of 15 to 45 minutes.

[0064] The tank is then moved to a bagging area in the manufacturing shed. It is then opened and the homogeneous mixture is transferred to a bagging hopper (14). This bagging hopper (14) will discharge a predetermined quantity of homogeneous mixture (15) into a series of airtight and watertight bags (16).

[0065] The bags, after being filled with a predetermined quantity of homogeneous mixture, are closed and placed horizontally on a conveyor belt (17). Horizontal placement helps to limit the segregation of the mixture particles according to their size.

[0066] The horizontal bags are pierced with an orifice between 0.1 and 0.5 mm and enter a flattening device (18) allowing the air (19) contained in said airtight bags to be expelled.

[0067] Once flattened, the bags are placed on a transport pallet (20) with the opening facing upwards. The bags are spread evenly on the transport pallet (20) to optimize load distribution and achieve a stable stack. They are also arranged so that the bags on one layer cover the openings of the bags on the layer below. All openings, except those in the topmost layer of bags, are covered with an airtight and waterproof bag. The openings in the topmost layer of bags are plugged with a sheet of cardboard. The pallet is then wrapped in plastic film, including the top section containing the cardboard sheet. Example 1

[0068] 420 kg of silica particles (D50 = 450 µm; D5 = 175 µm), 40 kg of silicon particles (D5 = 5 µm, D50 = 45 µm, D95 = 50 µm), and 40 kg of quicklime particles (D50 = 45 µm) were used in the process according to the invention. This process produced 50 bags of 10 kg each. The following observations were made during the analysis of a bag stored on a shipping pallet for one month:

[0069] Homogeneity of the mixture: Homogeneity was verified by measuring the particle size distribution through sieving. This analysis showed that the mixture is indeed homogeneous, with a uniform distribution of particles throughout the bag.

[0070] Mixture Reactivity: Reactivity was measured by a spray test in an 800°C oven, similar to that used in the industrial application. The results indicated that the mixture reacts optimally, as expected for use in ceramic welding.

[0071] During spraying in a furnace, we observed that the application temperature was as expected (800°C) and that the resulting weld exhibited low open volume porosity (<10%), confirming the quality of the powder composition for ceramic welding. The apparent density, open porosity, and total porosity were determined according to ISO 5017:2013.

[0072] Finally, the particulate matter present during the manufacturing of this batch was measured using the airborne particle counting method (optical method), and remained below 0.1 mg / m³. 3 , thus complying with current safety standards.

[0073] It is understood that the present invention is in no way limited to the embodiments described above and that many modifications can be made to it without departing from the scope of the attached claims.

Claims

DEMANDS 1. A process for manufacturing a batch of a homogeneous powder composition for ceramic welding comprising refractory filler particles and metallic particles, comprising the steps of: a) bringing refractory charge particles (1) selected from the group comprising aluminium oxide particles, silicon carbide particles, zirconium oxide particles, silicon oxide particles, magnesia particles, chromium oxide particles, iron oxide particles, and mixtures thereof, into a first feed hopper (2) and pouring a predetermined quantity of these refractory charge particles (3) from the first feed hopper (2) into a first tank (4) placed on load cells, said refractory charge particles having an average particle size measured by sieving d50 of between 350 and 800 µm, preferably between 400 and 500 µm and a d5 of between 150 µm and 200 µm, b) feeding metallic particles (5) selected from the group comprising aluminum particles, silicon particles, magnesium particles, calcium particles, iron particles and mixtures thereof, into a second feed hopper (12) and discharging a predetermined quantity of these metallic particles (6) from the second feed hopper (12) into said first tank (4) placed on load cells at the top of which dust is extracted, said metallic particles having an average particle size measured by optical particle size analysis d50 of between 10 and 50 µm, preferably between 15 and 40 µm, preferably between 20 and 30 µm, a d5 of between 1 and 10 µm, preferably between 3 and 7 µm and a d95 of between 35 and 65 µm, preferably between 45 and 55 µm, c) closing said first tank (4) and transferring (9) from said closed first tank extracted from leaning towards a robotic mixing arm (10),said robotic arm being arranged to grasp the first tank and perform a series of inversions (11) of said first tank in order to form said powdered composition in the form of a homogeneous mixture during a time interval of between 15 and 45 minutes, d) a transfer of said homogeneous mixture from said first reservoir to a bagging hopper (14) arranged to discharge a predetermined quantity of homogeneous mixture (15) in n airtight and watertight bags (16) forming said batch, e) a horizontal deposit (17) of an n ième airtight and watertight bag of said n airtight and watertight bags after closure on a conveyor belt, f) an inlet of said n ième airtight and watertight bag closed in a flattening device (18) with a hole of diameter between 0.1 and 0.5 mm, with formation of an n ième flattened and punctured bag (g) horizontal placement on a transport pallet (20) of the n ième flattened and perforated waterproof bag, with said opening facing upwards (h) a plugging of the hole of said orifice of the n ième flattened and perforated waterproof bag on said transport pallet (20), and in which, between steps d) and h), a period of time elapses of less than 4 hours, preferably less than 3 hours, preferably less than 2 hours, preferably less than 1 hour, said homogeneous mixture of n sealed bags being a mixture for which, where applicable, the metallic particles form a layer of metallic particles greater than 0.01 centimeter and less than one centimeter in the bottom of each of the n sealed bags, after 30 minutes at rest.

2. A method for manufacturing a batch of a homogeneous powder composition for ceramic welding according to claim 1, further comprising a step of feeding additive particles (7) selected from the group comprising lime particles, glass particles, magnesia particles, dolomite particles, calcium carbonate particles, magnesium carbonate particles, and mixtures thereof, into a third feed hopper (13) and a discharge of a predetermined quantity of these additive particles (8) from the third feed hopper (13) into said first tank (4) placed on weights at the top of which a dust aspiration is carried out, said additive particles having an average particle size measured by optical particle size d50 of between 30 and 60 µm, preferably between 35 and 55 µm, preferably between 40 and 50 µm.

3. Method of manufacturing a batch of a homogeneous powder composition for ceramic welding according to claim 1 or 2, wherein the refractory filler particles are siliceous particles.

4. A method for manufacturing a batch of a homogeneous powder composition for ceramic welding according to any one of the preceding claims, wherein the metal particles are silicon particles.

5. Method of manufacturing a batch of a homogeneous powder composition for ceramic welding according to claim 2, wherein the additive particles are quicklime particles.

6. A method for manufacturing a batch of a homogeneous powder composition for ceramic welding according to any one of the preceding claims, wherein the predetermined quantity of refractory filler particles is between 70 and 90%, preferably between 80 and 90% by weight relative to the weight of said homogeneous mixture, the predetermined quantity of metallic particles is between 10 and 30% by weight relative to the weight of said homogeneous mixture.

7. A method for manufacturing a batch of a homogeneous powder composition for ceramic welding according to claim 2, wherein the predetermined quantity of refractory filler particles is between 70 and 90%, preferably between 80 and 90% by weight relative to the weight of said homogeneous mixture, the predetermined quantity of metallic particles is between 5 and 25% by weight relative to the weight of said homogeneous mixture and the predetermined quantity of additive particles is between 5 and 10% by weight relative to the weight of said homogeneous mixture.

8. A method for manufacturing a batch of a homogeneous powder composition for ceramic welding according to any one of the preceding claims, wherein the refractory filler particles are siliceous particles comprising at least 80% by weight of cristobalite and at most 20% by weight of tridymite, preferably at most 17% by weight of tridymite relative to the weight of refractory filler particles.

9. A method for manufacturing a batch of a homogeneous powder composition for ceramic welding according to any one of the preceding claims, wherein the refractory filler particles fed into the first feed hopper are introduced into a first material receiving structure, then pass through a first feed conduit by means of vibrations from a first vibrating motor; the metallic particles fed into the second feed hopper are introduced into a second material receiving structure, then pass through a second feed conduit by means of the vibrations of a second vibrating motor and refractory charge particles and metallic particles move within said first and second conduit over a distance of at least one meter and up a slope whose angle of slope is between 1 and 10°.

10. A method for manufacturing a batch of a homogeneous powder composition for ceramic welding according to any one of the preceding claims, wherein the first reservoir comprises several parts of the first reservoir, at least one part of the first reservoir has a diameter that tapers downwards.

11. A method for manufacturing a batch of a homogeneous powder composition for ceramic welding according to any one of the preceding claims, taking place in a manufacturing shed comprising a feeding area, a mixing area and a bagging area, each separated from each other by at least 5 meters, and wherein the discharge of a predetermined quantity of particles into said first tank placed on load cells is carried out in the feeding area and when the first tank is in a feeding position, said feeding position being a position in which the first tank is opened from the top and the closing of said first tank is carried out in said feeding area.

12. Method of manufacturing a batch of a homogeneous powder composition for ceramic welding according to claim 11, wherein said robotic arm is located in said mixing zone into which said first closed reservoir is transferred.

13. Method of manufacturing a batch of a homogeneous powder composition for ceramic welding according to claim 12, wherein said opening of the first closed reservoir is made in said bagging zone.

14. A method for manufacturing a batch of a homogeneous powder composition for ceramic welding according to any one of claims 2 to 13, wherein the pouring of a predetermined quantity of refractory filler particles is followed by the pouring of a predetermined quantity of metallic particles, the pouring of said predetermined quantity of metallic particles is followed by a second pouring of a predetermined quantity of refractory filler particles, said second pouring of a predetermined quantity of refractory filler particles is followed by the pouring of a predetermined quantity of additive particles.

15. A method for manufacturing a batch of a homogeneous powder composition for ceramic welding according to any one of the preceding claims, wherein the discharge of the predetermined quantity of refractory filler particles from the first feed hopper to the first tank placed on load cells, the discharge of the predetermined quantity of metallic particles from the second feed hopper to the first tank placed on load cells and the transfer of said homogeneous mixture from said first tank to an arranged bagging hopper is carried out by means of a series of butterfly valves.

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