Classifications

• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B11/00—Pressing molten glass or performed glass reheated to equivalent low viscosity without blowing
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B19/00—Other methods of shaping glass
  • C03B19/08—Other methods of shaping glass by foaming
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C11/00—Multi-cellular glass ; Porous or hollow glass or glass particles
  • C03C11/007—Foam glass, e.g. obtained by incorporating a blowing agent and heating
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C8/00—Enamels; Glazes; Fusion seal compositions being frit compositions having non-frit additions
  • C03C8/14—Glass frit mixtures having non-frit additions, e.g. opacifiers, colorants, mill-additions

Definitions

• the invention relates to foamed glass, more particularly to a mold casted foam glass product in the form of pipe insulation, more particularly to a method of mold casting of foamed glass for prefabricated pipe insulation with an outer protective crust.
• Foamed glass is traditionally produced by mixing ground or crushed glass together with one or more foaming agents, for instance coal as the main reactive ingredient, in an open mold made of heat-resistant steel or other heat resistant material. When heated, the mixture expands to form foamed glass. The foamed glass is thereafter removed from the open mold, and cut into blocks, which are thereafter further cut into desired shapes, for example shapes to be used as pipe insulation.
• foaming agents for instance coal as the main reactive ingredient
• open cells arise on all cut faces whatever shape the final product has. This results in the final product having sharp edges that lead to increased friction against the pipe sections they come into contact with.
• the open cells on the surface are directly exposed to moisture, which causes the product to absorb water into the surface.
• foamed glass produced with coal as the main reactive ingredients is electrically conductive due to the high content of carbon residuals.
• the combination of friction, water, and electric conductivity increases the risk of corrosion of the pipes under isolation (CUI) substantially.
• the carbon residuals will contribute with chemical energy in a fire scenario - and thereby reduce the fire resistance of the insulation.
• foamed glass produced by the traditional method has relatively low compression strength (600 kPa), which limits the thinness of the profiles of insulation products that can be manufactured from the foamed glass without breaking up.
• foamed glass produced by the traditional method will release sulfur when crushed, e.g.., as a consequence of vibration or direct pressure. This released sulfur, in contact with available moisture will cause a change in pH value. Consequently, in direct contact with pipes, the risk of CUI is substantially increased.
• the present invention concerns a method of producing mold casted, sealed foam glass components with an outer protective crust, as insulation and fire protection for pipes and structural components, building panels and other uses.
• the method is based on mixing a reactive ingredient (foaming agent) with one or more oxidants, and then adding this into crushed or milled glass, blending it, and then this is again added into a closed mold/casting die made from titanium, graphite or another suitable material, and heated until the glass melts and the reactive ingredient and the oxidant react and decompose and produce bubbles of gas in the melted mixture.
• the method is based on blending a calculated quantity of reactive mixture (foaming agent + oxidants) with the crushed/milled glass, filling the mixture into a closed mold/casting die (made from a material such as titanium, graphite, ceramic or metal alloy) with suitable thermal durability and expansion properties, and heating the mold until the glass melts and the reactive ingredients release gas bubbles producing a foamed material of the desired density and mechanical strength.
• a closed mold/casting die made from a material such as titanium, graphite, ceramic or metal alloy
• the reactive ingredients release gas bubbles producing a foamed material of the desired density and mechanical strength.
• the reactive ingredient is SiC and the oxidant is Mn0 2 , which react and produce C0 2 bubbles.
• the reactive ingredient is Si 3 N 4 or AIN
• the oxidant is Mn0 2, which react to produce N 2 bubbles.
• the following reaction equations are applicable: 1 ⁇ 2 Si 3 N 4 +3Mn0 2 -> 3 / 2 Si0 2 +3MnO+N 2
• the reactive ingredient A1N has a fraction size of 0.5 micron to 12 micron and may constitute between 0-15wt% of the mixture.
• the reactive ingredient SiC has a fraction size from 3 micron to 40 micron and may constitute between 0-15wt% of the mixture.
• the milled glass has a fraction size from 0.001 mm to 1.6 mm, preferably from 0.001 - 0.7mm.
• ranges should be understood to also express intermediate ranges, as if these had been specifically expressed.
• a range of 0-15 shall also include ranges such as 1-14, 1-13, 1-12, 2-14, 2-13 etc.
• the mold/casting die according to one aspect is designed to produce a semi- cylindrical pipe insulation profile adapted to a specific pipe size and shape.
• the size and/or design of the profile may however be varied to produce pre-cast profiles of different shapes for different applications, for instance building panels.
• the amount of finely milled glass and foaming agent is adapted to the internal volume of the mold/casting die, such that the amount of foamed glass, after heating and expansion, at least corresponds to the same volume as in the casting die.
• a mold with an internal volume of 8 liters and a desired density of 200 kg/m3, 1.6 kg of glass mixture is filled into the mold before heating.
• the expansion of the foamed glass inside the closed mold will result in a positive pressure inside the mold/casting die in the range from just above atmospheric pressure to 3 bar above atmospheric pressure (herein expressed as 0-3 bar), according to one aspect 1-3 bar, and according to yet another aspect 2-3 bar.
• any excess foam glass can be drained/vented out through a narrow overflow channel, for example a hole or slit located at the top of the die.
• the size of the channel will be determined by the viscosity of the foamed glass at the given process temperature and the desired inside pressure in the mold, for example an overflow channel of lmm high x 600mm wide and 5mm deep will be able to hold back the glass foam at a temperature of 880°C at 1 bar.
• the casting die is closed and inserted into a hot zone, in which it is heated to a temperature of normally between 750°C and 1000°C, dependent on the selection of reactive ingredients and desired internal pressure given by the viscosity and size of the overflow channel.
• the heat source may consist of radiate heating, airflow heating, induction heating or another suitable indirect heat source, e.g., gas.
• the working principle of the overflow channel is that it has a configuration of cross section area (given as length X width) and depth (usually equal to the wall thickness) which together define a pressure and viscosity dependent barrier, capable of containing the foam inside the mold cavity up to a given differential pressure - for any given viscosity (defined by the temperature for each unique formula of glass and additives). If the pressure inside the mold exceeds this limit, the channel will function as a safety valve, releasing superfluous foam before the excessive pressure can damage the mold.
• the channel is preferably narrow enough to allow a certain pressure buildup (of at least 3 bar) relative to the ambient - to provide an overpressure useful in preventing the component from shrinking while cooling down, and thus provide dimensional stability.
• the pressure buildup starts when the expanding foam has displaced all the air from the mold cavity, and no further expansion is allowed until the pressure is high enough to extrude foam trough the overflow channel.
• the extent of the expansion and pressure buildup is given by the quantity and composition of the raw materials mixture of glass and reactive additives.
• the pressure limit (at which further expansion will happen by extruding foam through the channel and prevent further pressure buildup) is given by the geometry of the channel (cross section vs. depth) and the glass formula's viscosity as a function of the temperature (depending on the additives). After a sufficient volume of foam has escaped through the channel, the pressure drops to just below the extrusion pressure - and further extrusion will not take place until the pressure again has reached the limit.
• This feature provides the benefit of not having to worry about overfilling the mold - since any excess material will escape through the overflow channel.
• the internal pressure in the foam can be kept at a high and stable level during the reaction phase, providing dimensional stability by preventing shrinkage and deformations during the cool down phase.
• the controlled overpressure in the reaction phase also contributes to a more predictable and homogenous cell size distribution in the foam.
• the foam glass When the foaming process is almost finished, and when the gas bubbles are formed and expanded to their desired size, the foam glass will have filled the casting die completely.
• the casting die is slowly cooled to a temperature where the viscosity is sufficiently high to stabilize the cell structure of the component and limit the further shrinkage or deformations - in a manner similar to metallurgical annealing.
• the die is cooled further down, to a temperature where the glass foam is sufficiently rigid to be removed from the die without being damaged, such as known to one skilled in the art of glass making.
• the foam glass expands inside a closed die to reach a predetermined size and form, identical to the end product, makes cutting and adaptation of the foamed glass semi-cylinder before it is used unnecessary.
• the foamed glass expands, the cells in direct contact with the die walls collapse, making the outer cell walls thicker, and the foamed glass profile is given a smooth and substantially sealed crust.
• This sealed outer surface essentially forms a sealed crust, almost a glassy surface, wherein the cells directly on the inside of the crust are intact. This creates a smooth surface, with low friction, that is gentler to the structure it is later to insulate. Because the crust is sealed, the profile does not absorb moisture into the surface. Combined with low electrical conductivity in the product, this significantly reduces the risk of CUI.
• An advantage of the method according to the invention is that the reaction is substantially chemically neutral, and only creates N 2 or C0 2 gas together with small amounts of 02, substantially reducing the risk of corroding the pipes compared to traditionally produced foamed glass insulation profiles made from coal as the reactive ingredient, where a small portion of S0 2 is released and blended with water in the case damage of the cell structure of the surface should arise.
• Another advantage of the invention is that tests performed with microwave scanner show that the product is transparent when scanned with microwaves, and thus suitable for detecting moisture in the insulation as well as corrosion under insulation at an early stage, using micro wave scanning. Said scanning can be performed in the longitudinal direction of the pipe based on a non-destructive method. Traditionally produced foamed glass contains large amounts of non- combusted carbon, and consequently, is not transparent upon micro wave scanning. For this reason, scanning the insulation semi-cylinders for moisture based on micro waves is not possible, and neither is detection of CUI at an early stage without an inspection based on a destructive method.
• Fig. 1 is perspective view of a semi-circular foam glass product
• Fig. 2 is a cross sectional view of a semi-circular foam glass product with chamfered edge
• Fig. 3 is a cross sectional view of a semi-circular foam glass product with groove for a gasket
• Fig. 4 is a perspective view of a mold for a semi-circular foam glass product
• Fig. 5A and B are cross sectional view of the mold
• Fig. 6 is a perspective view of a lower semi-circular profile
• Fig. 7 is a perspective view of an upper semi-circular profile
• Fig. 8 is a cross sectional view of a lower mold section filled with a glass mixture
• Fig. 9 is a perspective view of a mold for a semi-circular foam glass product with a glass mixture distributed along its length
• Fig. 10 is a cross sectional view of a semi-circular mold
• Fig. 1 1 A, B and C are detail views of a locking mechanism
• Fig. 12A and B illustrate a T-shaped foam glass product
• Fig. 13 A and B illustrate a bend-shaped foam glass product
• Fig. 14A-D illustrate a curved segment foam glass product
• Fig. 15 A, B and C illustrate a panel-shaped foam glass product
• Fig. 16 is a cross sectional view of a semi-circular mold with expanded foam glass
• Fig. 17A is plan view of an upper mold section and T-flange reinforcements
• Fig 17 B shows a T-flange reinforcement member
• Fig. 18 is a photograph that shows outer sealed crust on a precasted C02 based 4" 600 mm semi cylindrical foam glass component.
• Fig. 19 is a photograph that shows the inside sealed crust on a precasted C02 based 4" 600mm semi cylindrical foam glass component
• Fig. 20 is a photograph that shows the inside cell structure on a precasted C02 based 4" 600mm cylindrical foam glass component
• Fig. 21 is a photograph that shows N 2 and 0 2 based precasted foam glass with an outer crust cell strucure from 0 - 2mm
• Fig. 22 is a photograph that shows N2 based precasted foam glass with an outer crust cell structure 0-1 mm
• Fig. 23 is a photograph that shows C0 2 based precasted foam glass with an outer crust.
• Fig. 24 is a photograph showing precasted N2 based 200mm x 98mm x 20mm foam glass with an outer crust.
• Fig. 25 is a photograph showing a sintered tablet of glass mixture at 650-750°C.
• Fig 26 shows a crescent shaped sintered glass mixture at 650-750°C
• Fig 27 shows the sintered glass mixture re-heated to 850°C.
• Fig 28 is a photograph showing the inner cell structure N 2 based precasted foam glass 0-2mm
• a method for producing foamed glass components with an outer smooth crust is described.
• This aspect of the invention will be described with reference to a preferred embodiment comprising a die for casting semi-cylindrical insulation sections for pipes and the like, as shown in Figs 1 , 2 and 3. While a semi-circular profile is shown, it should be understood that other shapes are possible within the scope of the invention.
• the casting die comprises a lower mold section 1 having a lower semi-circular profile 2, as seen in detain in Fig 6, which extends in the longitudinal direction in a certain length, normally from 200 mm to 600 mm; however, it can be made longer if desired.
• Lower section 1 may have longitudinal cut outs 3 to provide better heat distribution and to reduce the weight of the mold.
• the mold further comprises an upper mold section 4 having a corresponding upper semi-circular profile 5 and lid portion 6, seen in detail in Fig 7.
• upper section 4 When upper section 4 is attached to lower section 1 , a cavity 7 as shown in Fig 4 is formed, having the shape of the component to be produced.
• Upper section 4 may have longitudinal cut outs 8 to provide better heat distribution and to reduce the weight of the mold.
• the upper and lower mold sections are provided with T-flange reinforcements 9 and 10 respectively.
• the mold is preferably made from titanium; however, it may also be made from another heat resistant material, for example graphite.
• the radius of the semi-circular profiles, as well as the distance between the semicircular surfaces 2 and 5 is decided by the diameter of the pipe to be insulated and by the thickness of desired insulation; normally between 20 and 50 mm.
• a measured mixture of milled glass and foaming agent is added into the lower mold section 1 , and evenly distributed along its length as shown in Fig 9.
• the upper mold section 4 is attached to lower mold section 1 and locked in place by the mechanism shown in Figs 10 and 1 1 A, B and C. The locking
• Locking pins 1 1 that engage openings 12 in a locking channel 13.
• Locking channel 13 may be arranged in a groove 14 as shown in Fig 17A.
• Openings 12 in the locking channel correspond to holes 15 in profile 5, as seen in Fig 5A.
• the locking mechanism is activated by inserting the pins in the openings, and sliding the channel in locking direction 17, or released by sliding in opening direction 18.
• a release agent for instance kaolin powder and water has been applied to the inside surfaces of the mold cavity, and more preferably to all surfaces of the mold.
• the purpose of the release agent is to prevent adhesion between the cast component and the mold wall.
• the kaolin powder is mixed with water to form a slurry, then dried at 100-300°C for two hours.
• the mold when made from Titanium, may also preferably be treated on its surfaces with a bond coat 19 as shown in Fig 4, comprising CoNiCrAlY to protect the mold from oxidation at high temperature.
• the bond coat preferably has the same thermal expansion ratio as the mold.
• End plates 20 having tabs 21 as shown in Fig 9 are attached, the tabs engaging slots 22 seen in Fig 6 thus sealing the mold.
• the casting die can be mounted onto a device which makes it possible to rotate the die in the heating zone during the casting phase.
• channels 23 are arranged between the lower and upper mold sections.
• the channels are made for venting out over-pressure, allowing excess foam glass to escape, or to supply pressure during the casting phase, by pressurizing the whole furnace.
• the channels are illustrated as a gap between the upper and lower sections, but the channels may also be positioned at another location in the mold, so long as the gases may freely escape and also allowing excess foam glass to escape during the casting phase.
• the die is filled with an evenly blended mixture consisting of finely milled glass having a fraction which may vary from 0.005 mm to 1.6 mm, and up to 15wt% foaming agent comprising a reactive ingredient and an oxidant.
• the amount of foaming agents and fraction size of the milled glass are decided from the desired density of the foam glass.
• the weight to be filled into the die is calculated from expected density of the completed foam glass and the internal volume of the casting die.
• the casting die is sealed, and is inserted into the heating zone; e.g., a radiation furnace or an air circulation furnace, and then heated to a first temperature plateau, at least equal to the melting temperature of the glass to form a glass melt.
• the first plateau temperature is maintained for a sufficient time to allow the reactive ingredient and the oxidant to become substantially evenly distributed in the glass melt.
• the mold is heated to a second temperature plateau in the range of 750°C to 1000°C, whereby the reactive ingredient and oxidant react to form bubbles of gas inside the glass melt, thereby forming the desired glass foam 28 as shown in Fig 16.
• the reaction temperature is maintained until foamed glass expands to fill the cavity in the mold.
• the inside pressure of the mold is in the range of 0-3 bar.
• the mold is then gradually cooled to a third temperature plateau of from 730° C to 650° C, allowing the viscosity of the foam to increase and stabilize the shape and size of the component before a larger temperature drop inside the gas bubbles causes them to shrink and deform the component.
• the mold is cooled to the third temperature at a rate of 3°C /min or lower.
• the foam also forms a strong and durable crust 29, 30 and 31 on the surfaces in contact with the mold, as seen in Fig 1.
• This crust gives the component extra strength and constitutes a gas and water tight membrane, offering extra protection against condensation, water penetration and Corrosion Under Insulation (CUI).
• the mold is then cooled to a fourth temperature plateau of from 400° C to 250° C, releasing internal tensions in the component before demolding.
• the mold is then cooled to a fifth temperature plateau, the demolding temperature, at which the foamed glass has solidified sufficiently to not deform or crack upon demolding.
• the foamed glass component may be removed from the mold.
• the raw materials mixture can be sintered together into prefabricated tablet portions, in a prebake process at a temperature between 640°C and 750°C, as seen in Fig 25, for then to be either cut into crescent shaped pieces as shown in Fig. 26 or crushed down into sand with a fraction size in the range 0-10mm before filling the die - in order to prevent uneven mass distribution in the early melting stage due to heat induced powder contraction.
• the crescent shape of the sintered mixture portions will thus align with the curved profile of the mold. This method makes it easier to fill out peripheral details of more complex die geometries, and to secure a uniform density and mass
• the heat source may consist of air circulation heat as in this case or radiated heat; however, it may also consist of an induction furnace into which the casting die is inserted between induction coils, for there to be heated to the desired temperature.
• Other suitable indirect heating sources may also be employed if appropriate, e.g., a gas burner.
• the gas Due to the low viscosity of the melted glass, the gas will be evenly distributed into the liquid and form small bubbles. Because of evenly distributed reactive ingredients in the glass powder during heating, and because of the pressure from the surrounding walls and pressure made from foam glass trying to enter through the narrow overflow channels, the bubble formation will be substantially homogenous. The inside pressure of gas inside the bubbles will try to expand the size of the bubbles. The higher the temperature and lower the viscosity of the glass mass, the faster the expansion occurs and the bigger the bubbles will become.
• a seeding/nucleation agent may be added to the mixture before blending; e.g., 0.1-2% finely ground kaolin powder.
• an insulation product is described.
• the product is made of a foamed glass material, having the following physical properties:
• the foamed glass material is, according to the invention, molded into the following types of products:
• a casted insulation product for pipes comprising a semicircular profile, made of foamed glass with a smooth crust on the outer and inner surfaces of which are substantially sealed and water tight, having inner pore size in the range of 0,2mm to 4mm, outer pore size 14,15, 17 from 0-lmm, density below 240 kg / m3, compression strength (ASTM D695) higher than 2MPa, Tensile strength (ISO 527) higher than 0.22 MPa, Flexural strength ((ISO 178) higher than 0.72 MPa, heat conductivity at 20°C less than 0.060 W/mK and a solidus point higher than 850°C.
• the pipe insulation profiles can be molded with a chamfered edge 32 or a groove 33, arranged to receive a sealing gasket.
• a casted fire protection and insulation product for boxes, walls and roofs comprising a flat profile/panel with a thickness from 15-40mm made of foamed glass with a smooth crust on all sides 25,26 of which are substantially sealed and water tight, having inner pore size in the range of 0,2mm - 4mm, outer pore size 0- lmm, density below 240 kg/m3, compression strength (ASTM D695) higher than 2MPa, Tensile strength (ISO 527) higher than 0.22 MPa, Flexural strength ((ISO 178) higher than 0.72 MPa, heat conductivity at 20°C less than 0.060 W/mK and a solidus point higher than 850°C.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Life Sciences & Earth Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Geochemistry & Mineralogy (AREA)
• Manufacturing & Machinery (AREA)
• Glass Compositions (AREA)
• Laminated Bodies (AREA)
• Joining Of Glass To Other Materials (AREA)

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Citations (6)

• 2015
  • 2015-09-14 EA EA201790483A patent/EA033664B1/ru not_active IP Right Cessation
  • 2015-09-14 EP EP15762635.9A patent/EP3194344A1/en not_active Withdrawn
  • 2015-09-14 WO PCT/EP2015/070948 patent/WO2016041899A1/en active Application Filing

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