Ceramic shell expanded perlite as well as preparation method and application thereof

Abstract

The invention provides ceramic shell expanded perlite as well as a preparation method and application thereof, and the preparation method comprises the following steps: pretreating perlite ore to obtain first perlite particles; proportioning the first perlite particles and a binder according to a mass ratio, and uniformly mixing the first perlite particles and the binder to obtain second perlite particles; respectively adding vitreous cladding powder and ceramic cladding powder into the second perlite particles in sequence, and granulating to obtain A-type third perlite particles and B-type third perlite particles in sequence; carrying out drying and preheating treatment on the B-type third perlite particles to obtain fourth perlite particles; and carrying out high-temperature expansion treatment on the fourth perlite particles to obtain the ceramic shell expanded perlite. Compared with common expanded perlite, the expanded perlite with the ceramic shell has higher expansion times, mechanical strength and sound absorption rate and lower water absorption rate, slurry absorption rate and heat conductivity coefficient, and can be used for producing light materials, heat preservation and insulation materials, sound absorption and insulation materials and fireproof and flame-retardant materials and replacing floating beads, light or expanded ceramsite and the like.

Description

Technical Field

[0001] This invention relates to the field of mineral and rock material processing and new materials, specifically to a ceramic-shell expanded perlite, its preparation method, and its application. Background Technology

[0002] Perlite minerals, including perlite type, obsidian type, and resinstone type, are acidic silicate glasses formed by the rapid cooling of acidic volcanic lava. Due to the rapid cooling rate, the water in the lava is uniformly sealed in the glass.

[0003] Under suitable high-temperature conditions (generally 1000–1300℃), perlite ore particles can rapidly expand several times their original size, forming lightweight, porous expanded perlite with properties such as thermal insulation, sound insulation, and fire resistance. This is because the acidic silicate glass melts during high-temperature firing, and the water within it expands as gas within the molten glass. Expanded perlite demonstrates broad application potential in multiple fields, especially as a raw material for the production of lightweight and insulating materials, occupying an important position in the construction and manufacturing industries.

[0004] However, expanded perlite produced by traditional methods suffers from drawbacks such as open cavities left by gas escape during the expansion process, irregular shape, low strength, and hygroscopicity. These problems often lead to a decline in product performance during preparation and use. For example, open cavities can easily allow the inclusion of cementitious / bonding material slurry, reducing its lightweight and thermal insulation properties, thus limiting its application range. To overcome these defects, researchers have tried various improvement methods, including organic modification and surface coating techniques. However, these methods often introduce new problems, such as affecting bond strength.

[0005] In recent years, with technological advancements, breakthroughs have been achieved in producing closed-cell expanded perlite using an electric expansion furnace under precise temperature control, addressing the porous structure of expanded perlite. This method, through precise temperature control, melts the glassy layer on the surface of expanded perlite particles, causing the surface to collapse and form closed-cell expanded perlite, sealing the open pores. This significantly improves the material's strength and water resistance while maintaining good thermal and sound insulation properties. However, this method is limited by the precise control of the furnace temperature, and the surface collapse of the expanded perlite particles affects the bulk density, thermal conductivity, and final product performance of the expanded perlite.

[0006] Therefore, it is of great significance to explore new production methods for closed-cell expanded perlite and overcome the defects of traditional methods, such as the open pores on the surface of expanded perlite, which easily lead to a reduction in the lightweight and thermal insulation properties of expanded perlite after the injection of cementitious / bonding material slurry.

[0007] This invention utilizes a bonding and coating method to coat the surface of perlite-like ore particles with a heterogeneous material that can form a glassy and ceramic outer shell. When the coated perlite-like ore particles are expanded, the coated glassy heterogeneous material first melts and traps the gas released during the expansion process, forming a glassy shell layer on the surface of the expanded perlite, creating closed-cell expanded perlite, and further improving the expansion ratio, sphericity, and overall performance. The coated ceramic heterogeneous material forms a ceramic shell layer on the outer surface of the expanded perlite, facilitating a high-strength bond with cementing materials. This novel shell / core structure of expanded perlite material exhibits excellent properties such as low bulk density, low thermal conductivity, high sphericity, and high strength. Especially in the molding process of lightweight, thermally insulating materials, the closed-cell structure of the expanded perlite not only prevents the infiltration of cementing / bonding material slurry, but also allows for a higher degree of compact packing due to its high sphericity, thus reducing the amount of cementing / bonding material used. At the same time, the ceramic outer shell can form a tight bond with the cementitious material, thereby giving the resulting composite material products higher mechanical strength, better lightweight, and better thermal insulation properties. Summary of the Invention

[0008] The purpose of this invention is to address at least one of the aforementioned deficiencies in the prior art. For example, one objective of this invention is to provide a method for preparing ceramic-shell expanded perlite; a second objective of this invention is to provide ceramic-shell expanded perlite; and a third objective of this invention is to provide an application of ceramic-shell expanded perlite.

[0009] To achieve the above objectives, the present invention provides a method for preparing ceramic-shell expanded perlite, the method comprising: 1) pretreating perlite ore to obtain first perlite particles; 2) mixing the first perlite particles and a binder in a mass ratio and mixing them evenly to obtain second perlite particles; 3) adding glassy shell powder and ceramic shell powder to the second perlite particles sequentially for granulation to obtain type A third perlite particles and type B third perlite particles; 4) drying and preheating the third perlite particles to obtain preheated fourth perlite particles; 5) subjecting the preheated fourth perlite particles to high-temperature expansion treatment to obtain ceramic-shell expanded perlite.

[0010] Alternatively, the perlite ore may include one or more of four types of ore: perlite-type, obsidian-type, resinstone-type, and pumice-like perlite.

[0011] Optionally, the pretreatment includes crushing, screening, and dust removal; the crushing is crushing with an inspection screening section, which further crushes the coarse perlite ore on the inspection screening screen to avoid over-crushing of perlite ore; the screening and dust removal include separating the crushed perlite ore into different particle sizes by screening, and collecting the micro powder with a particle size of less than 100 mesh from the perlite ore for use as raw material for preparing glassy coating powder;

[0012] The first perlite particle is perlite ore sand with a particle size range of +100 mesh to -10 mesh; the particle size specifications of the first perlite particle include multiple types from -10 mesh to +20 mesh, -20 mesh to +30 mesh, -30 mesh to +50 mesh, -50 mesh to +80 mesh, and -80 mesh to +100 mesh.

[0013] Alternatively, the mass ratio described in step 2) is 100:(3-8);

[0014] The process of uniform mixing includes: spraying the binder onto the first perlite particles being stirred using a spraying method, and uniformly coating the surface of the first perlite particles with the binder; the second perlite particles are perlite particles with the binder coated on their surface.

[0015] Alternatively, the adhesive may include one or more of inorganic and organic adhesives in an aqueous solution or hydrosol prepared with water;

[0016] The inorganic binder comprises one or more of water glass, sodium silicate, and potassium silicate with a modulus of 1.0 to 2.9, and is prepared as an aqueous solution with a density of 1.36 to 1.50 g / cm3 and a Baume degree of 38.4 to 48.3.

[0017] The organic binder includes one or more of carboxymethyl cellulose, sodium carboxymethyl cellulose, acrylic emulsion, vinyl acetate emulsion, polyvinyl alcohol acetal, emulsion glue, animal glue, and plant glue, and is formulated into a water-soluble adhesive with a solid content of 0.5% to 2.0% by mass.

[0018] Alternatively, the granulation described in step 3) is a process of weighing and granulating the second perlite particles with glassy coating powder and ceramic coating powder. First, the glassy coating powder is mixed with the second perlite particles and bonded by the surface binder of the second perlite particles to form a glassy component coating layer. Then, ceramic coating powder is added to continue granulation to form a ceramic component coating layer.

[0019] The specific steps include:

[0020] 1) Weigh the second perlite particles, glassy coating powder and ceramic coating powder at a mass ratio of (90-77):(2-8):(8-20);

[0021] 2) Place the weighed second perlite particles into a granulator, and then evenly add the weighed glassy coating powder into the running granulator so that the glassy coating powder evenly coats the second perlite particles to obtain type A third perlite particles.

[0022] 3) The weighed ceramic coating powder is evenly added to the granulator containing type A third perlite particles and is in operation, so that the ceramic coating powder is evenly coated on the type A third perlite particles to obtain type B third perlite particles.

[0023] Alternatively, the term "completely uniformly coated" means that when the coating is completed, the coating powder does not exist independently, but is completely coated on the surface of the perlite particles, with a dense texture and a tendency to be spherical; wherein, when the coating component powder exists independently, water is sprayed onto the perlite particles using a sprayer until the coating component powder is completely coated on the perlite particles and no particles stick together.

[0024] Alternatively, the preparation method of the glassy coating powder in step 3) includes: mixing perlite-like mineral powder with a particle size of less than 100 mesh, sodium / potassium feldspar, kaolin, and borax in a mass ratio of (50-70):(20-35):(5-10):(5-10), and obtaining the glassy coating powder by selective crushing, mixing and grinding. The particle size of the glassy coating powder is -200 mesh to -600 mesh.

[0025] Alternatively, the method for preparing the ceramic coating powder includes: mixing refractory clay, shale, potassium feldspar, and quartzite in a mass ratio of (30-60):(20-40):(10-25):(5-15), and obtaining the powder after selective crushing, mixing, and grinding. The particle size of the ceramic coating powder is -200 mesh to -600 mesh.

[0026] Alternatively, the drying described in step 4) is a drying process of type B third perlite particles in a drying-preheating device, where the temperature is increased from the ambient temperature section to the drying section at a rate of 8°C to 20°C to 200°C.

[0027] The preheating treatment is a process in which the third type of perlite particles are preheated in a drying-preheating device by heating the drying section to a heating section at a rate of 50°C to 80°C to 500°C to 850°C; the fourth type of perlite particles have a moisture content of 2 to 3%.

[0028] Optionally, the high-temperature expansion treatment in step 5) includes: uniformly sprinkling the fourth perlite particles while they are still hot onto a high-temperature flame in an expansion furnace where the temperature is maintained at 1100-1250°C, or uniformly spreading the fourth perlite particles and directly feeding them into a high-temperature section in an electrically heated expansion furnace where the temperature is maintained at 1100-1350°C, so that the fourth perlite particles are rapidly heated and expand quickly.

[0029] The fourth perlite particle's residence time in the high-temperature flame or the high-temperature section of the electric heating furnace, i.e., the rapid expansion time, is 2s to 80s, to obtain the ceramic-shell expanded perlite.

[0030] Optionally, the ceramic-shell expanded perlite has a shell / core composite structure; the inner layer of the shell is a glassy shell, mainly composed of a glassy body formed by melting the encapsulating glassy shell components, with a thickness of 0.01–0.2 mm; the outer layer of the shell is a ceramic shell, mainly composed of a ceramic body formed by high-temperature firing of the encapsulating ceramic shell components, with a thickness of 0.05–0.5 mm; the core is the expanded perlite body formed by the expansion of the first perlite particles, and the diameter of the core is determined by the particle size and expansion ratio of the first perlite, generally ranging from 2 mm to 28 mm; the bonding and composition between the ceramic outer layer, the glassy inner layer, and the expanded perlite body are in a gradual transition relationship.

[0031] Another aspect of the present invention provides a ceramic-shell expanded perlite, which can be prepared by the above method.

[0032] Alternatively, the ceramic-shell expanded perlite has the advantages of high expansion ratio, lightweight, high mechanical strength, good thermal insulation performance, low water absorption, and good chemical stability; the properties of the ceramic-shell expanded perlite include: expansion ratio of 3.8 to 6.5, and bulk density of 210 to 350 kg / m³. 3 The cylinder compressive strength is 0.9–2.1 MPa, the thermal conductivity is 0.043–0.075 W / (m·K), the water absorption rate is less than 1%–1.5%, the acid corrosion rate is less than 5%, and the alkali corrosion rate is less than 1%.

[0033] In another aspect, the present invention provides an application of ceramic-shell expanded perlite, wherein the ceramic-shell expanded perlite is the aforementioned ceramic-shell expanded perlite.

[0034] Alternatively, the ceramic-shell expanded perlite may be used in the production of lightweight materials, thermal insulation materials, sound-absorbing and sound-insulating materials, fire-retardant materials, and as a substitute for cenospheres, lightweight or expanded ceramsite.

[0035] Compared with the prior art, the beneficial effects of the present invention include at least one of the following:

[0036] (1) The present invention uses coating granulation technology to perform composite coating on the surface of perlite particles. The coating is a glassy shell with a melting temperature lower than the expansion temperature of perlite. It melts and forms a viscous glass melt before the perlite particles expand, which can effectively trap and encapsulate the gas generated during the expansion of perlite particles, thereby significantly improving the expansion ratio of perlite. The ceramic shell gives the expanded perlite higher mechanical strength and good bonding with organic binders or inorganic cementitious materials.

[0037] (2) The ceramic-coated expanded perlite prepared by this invention not only retains the original lightweight, heat insulation, sound insulation and sound absorption properties of traditional expanded perlite, but also further reduces the density and thermal conductivity by trapping and encapsulating the gas generated during the expansion of perlite particles. Moreover, the glassy layer seals the open pores of traditional expanded perlite. At the same time, the coating of perlite particles by the glassy and ceramic coating components improves the sphericity of the particles, increases the degree of compact packing when preparing composite materials, and reduces the amount of binder or cementing material used. While reducing costs, it greatly improves the comprehensive performance of expanded perlite products.

[0038] (3) In the process of preparing ceramic-shell expanded perlite, this invention cleverly utilizes the micro (tail) powder generated during the processing of the first perlite particles as an ingredient, thereby realizing the reuse of waste and reducing resource waste. At the same time, ceramic-shell expanded perlite generates almost no dust during production, transportation and use because its surface is covered by a shell, making it environmentally friendly and in line with the concept of sustainable development.

[0039] (4) The present invention adopts a shell / core composite structure design to prepare ceramic shell expanded perlite. The composite material or product prepared by ceramic shell expanded perlite with shell / core structure has its pores or voids sealed during use. Unlike traditional expanded perlite with open pores and cracks that lose their lightweight, heat insulation and heat insulation properties due to water absorption and moisture absorption, ceramic shell expanded perlite has better lightweight, heat insulation and heat insulation and sound absorption properties. This multifunctionality makes it perform well in various environments and makes it a more ideal choice for building materials and new materials.

[0040] (5) Through the design of the shell / core composite structure, this invention improves the sphericity and expansion ratio of the ceramic shell expanded perlite, reduces the density and thermal conductivity of expanded perlite, and enhances its mechanical strength, lightweight, thermal insulation and sound insulation performance, making the ceramic shell expanded perlite an ideal alternative to traditional materials. It provides more choices and possibilities for different application scenarios, greatly expanding the application field and market scope of expanded perlite. For example, it can replace a variety of traditional materials such as ceramsite and cenospheres to meet a variety of application needs. Attached Figure Description

[0041] The above and other objects and / or features of the present invention will become clearer from the following description taken in conjunction with the accompanying drawings, in which:

[0042] Figure 1 A flowchart illustrating the preparation process of the ceramic-shell expanded perlite described in this invention is shown.

[0043] Figure 2 A photograph of traditional expanded perlite is shown.

[0044] Figure 3 A photograph of the ceramic-shell expanded perlite described in this invention is shown.

[0045] Figure 4 An optical microscope image of conventional expanded perlite is shown.

[0046] Figure 5 An electron microscope image of conventional expanded perlite is shown.

[0047] Figure 6 An optical microscope image of the ceramic-shell expanded perlite described in this invention is shown.

[0048] Figure 7 An electron microscope image of the ceramic-shell expanded perlite described in this invention is shown.

[0049] Figure 8 Another electron microscope image of the ceramic-shell expanded perlite described in this invention is shown. Detailed Implementation

[0050] In the following description, an expanded perlite with a ceramic shell, its preparation method, and its application will be explained in detail with reference to exemplary embodiments.

[0051] It should be noted that terms such as "first," "second," "third," and "fourth" are merely for ease of description and distinction, and should not be interpreted as indicating or implying relative importance. Terms such as "up," "down," "front," "back," "left," "right," "inner," and "outer" are merely for ease of description and to establish relative orientations or positional relationships, and do not indicate or imply that the component referred to must have that specific orientation or position.

[0052] Exemplary Example 1

[0053] This invention provides a method for preparing expanded perlite with a ceramic outer shell, the method comprising:

[0054] S1. Pre-treat perlite ore to obtain the first perlite particles.

[0055] In this embodiment, the perlite ore includes one or more of four types of ore: perlite type, obsidian type, resinstone type, and pumice perlite.

[0056] In this embodiment, the pretreatment includes crushing, screening, and dust removal; the crushing is a crushing process with an inspection screening section, which further crushes the coarse perlite ore on the inspection screening screen to avoid over-crushing of perlite ore; the screening and dust removal include separating the crushed perlite ore into different particle sizes using a screening method, and collecting the micro powder with a particle size of less than 100 mesh from the perlite ore for use as raw material for preparing glassy coating powder;

[0057] The first perlite particle is perlite ore sand with a particle size range of +100 mesh to -10 mesh; the particle size specifications of the first perlite particle include multiple types from -10 mesh to +20 mesh, -20 mesh to +30 mesh, -30 mesh to +50 mesh, -50 mesh to +80 mesh, and -80 mesh to +100 mesh.

[0058] S2. Mix the first perlite particles and the binder according to the mass ratio and mix them evenly to obtain the second perlite particles.

[0059] In this embodiment, the mass ratio is 100:(3-8), such as 100:3, 100:3.7, 100:5.2, 100:6.5, 100:7.2 and 100:7.9, etc.;

[0060] The process of uniform mixing includes: spraying the binder onto the first perlite particles being stirred using a spraying method, and uniformly coating the surface of the first perlite particles with the binder; the second perlite particles are perlite particles with the binder coated on their surface.

[0061] In this embodiment, the adhesive includes one or more of inorganic and organic adhesives in an aqueous solution or hydrosol prepared with water;

[0062] The inorganic binder comprises one or more of water glass, sodium silicate, and potassium silicate with a modulus of 1.0 to 2.9, and is prepared as an aqueous solution with a density of 1.36 to 1.50 g / cm3 and a Baume degree of 38.4 to 48.3.

[0063] The organic binder includes one or more of carboxymethyl cellulose, sodium carboxymethyl cellulose, acrylic emulsion, vinyl acetate emulsion, polyvinyl alcohol acetal, emulsion glue, animal glue, and plant glue, and is formulated into a water-soluble adhesive with a solid content of 0.5% to 2.0% by mass.

[0064] S3. Glassy coating powder and ceramic coating powder are added to the second perlite particles in sequence for granulation, thereby obtaining type A third perlite particles and type B third perlite particles.

[0065] In this embodiment, the granulation is a process of weighing and granulating the second perlite particles with glassy coating powder and ceramic coating powder. First, the glassy coating powder is mixed with the second perlite particles and bonded by the surface binder of the second perlite particles to form a glassy component coating layer. Then, ceramic coating powder is added to continue granulation to form a ceramic component coating layer.

[0066] The specific steps include:

[0067] 1) Weigh the second perlite particles, glassy coating powder and ceramic coating powder in a mass ratio of (90-77):(2-8):(8-20), such as 90:2.1:8.1, 85:3:9.5, 80.5:4.2:15.4 and 78:7.5:19.5, etc.;

[0068] 2) Place the weighed second perlite particles into a granulator, and then add the weighed glassy coating powder evenly into the running granulator so that the glassy coating powder is evenly coated on the second perlite particles to obtain composite particles of glassy coating component / second perlite particles, namely type A third perlite particles.

[0069] 3) The weighed ceramic coating powder is evenly added to the granulator containing type A third perlite particles and is in operation, so that the ceramic coating powder is evenly coated on the type A third perlite particles to obtain type B third perlite particles.

[0070] In this embodiment, "complete and uniform coating" means that when the coating is completed, the coating powder does not exist independently, but is completely coated on the surface of the perlite particles, with a dense texture and a tendency to be spherical. When the coating component powder exists independently, water is sprayed onto the perlite particles using a sprayer until the coating component powder is completely coated on the perlite particles and no particles stick together.

[0071] In this embodiment, the preparation method of the glassy coating powder in step 3) includes: mixing perlite-like mineral powder with a particle size of less than 100 mesh, sodium / potassium feldspar, kaolin, and borax in a mass ratio of (50-70):(20-35):(5-10):(5-10), such as 51:21.5:5.2:5.1, 56:25:6.5:7.1, 62.5:29:7.2:8, and 69:34.5:9.2:9, etc., after selective crushing and mixed grinding. The glassy coating powder has a particle size of -200 mesh to -600 mesh.

[0072] In this embodiment, the method for preparing the ceramic coating powder includes: mixing refractory clay, shale, potassium feldspar, and quartzite in a mass ratio of (30-60):(20-40):(10-25):(5-15), such as 31:21:10.5:5.2, 35.5:25:12.5:6.5, 42:31:18.5:10.2, and 59:38.5:24:14; and obtaining the ceramic coating powder after selective crushing, mixing, and grinding. The particle size of the ceramic coating powder is -200 mesh to -600 mesh.

[0073] S4. The third type of perlite particles of type B are dried and preheated to obtain the preheated fourth type of perlite particles.

[0074] In this embodiment, the drying process is the drying of type B third perlite particles in a drying-preheating device, where the temperature is increased from the ambient temperature section to a drying section of 200-300°C at a heating rate of 8°C to 20°C.

[0075] The preheating treatment is a process in which the B-type third perlite particles are preheated in the drying-preheating device by heating the drying section to a heating section of 500-850°C at a heating rate of 50°C-80°C. During the drying-preheating process, the airflow in the drying-preheating device automatically flows from the heating section to the room temperature section. The moisture content of the fourth perlite particles is 2-3%.

[0076] Drying and preheating are essential steps in the process. Drying reduces the surface moisture of the perlite particles, while preheating reduces the internal moisture. Without these processes, excessive moisture on the surface and inside the perlite particles will cause them to absorb a large amount of heat during expansion due to excessive evaporation. This reduces the temperature difference required for rapid heating and prolongs the expansion time, preventing the perlite from expanding instantly and affecting its expansion ratio. Conversely, preheating increases the temperature of the material before the perlite particles enter the expansion furnace, allowing them to quickly reach their expansion temperature and expand instantly, thus increasing the expansion ratio.

[0077] S5. The preheated fourth perlite particles are subjected to high-temperature expansion treatment to obtain expanded perlite with a ceramic shell.

[0078] In this embodiment, the high-temperature expansion treatment includes: uniformly sprinkling the fourth perlite particles while they are still hot onto a high-temperature flame in an expansion furnace where the temperature is maintained at 1100-1250°C, or uniformly spreading the fourth perlite particles and directly feeding them into a high-temperature section in an electrically heated expansion furnace where the temperature is maintained at 1100-1350°C, so that the fourth perlite particles are rapidly heated and expand quickly.

[0079] The fourth perlite particle's residence time in the high-temperature flame or the high-temperature section of the electric heating furnace, i.e., the rapid expansion time, is 2s to 80s, to obtain the ceramic-shell expanded perlite, which has a shell / core composite structure.

[0080] During the high-temperature expansion process, the inner glassy coating powder material covering the outer surface of the first perlite ore particles (i.e., the shell) melts first, forming a viscous glassy melt that coats the perlite particles. This viscous glassy melt coating layer thins into a continuous coating layer as the first perlite particles rapidly expand, while simultaneously trapping the gas released during the expansion process. As a result, not only is an inner glassy layer of shell formed on the surface of the expanded perlite, but closed-cell expanded perlite is also formed, significantly increasing the expansion ratio of the expanded perlite. Meanwhile, the ceramic coating component covering the surface of the glassy coating powder material can be fired into a ceramic body during the high-temperature expansion process without melting, thus forming a cracked surface firing layer during the expansion of the first perlite particles. This cracked, non-melting firing layer better prevents adhesion between expanded perlite particles and facilitates good bonding with cementing materials when preparing expanded perlite composite materials.

[0081] Exemplary Example 2

[0082] This exemplary embodiment provides a ceramic-shell expanded perlite, which can be prepared by the method described in Exemplary Embodiment 1.

[0083] In this embodiment, the inner layer of the shell is a glassy shell, mainly composed of a glassy body formed by melting the encapsulating glassy shell components, with a thickness of 0.01 to 0.2 mm; the outer layer of the shell is a ceramic shell, mainly composed of a ceramic body formed by high-temperature firing of the encapsulating ceramic shell components, with a thickness of 0.05 to 0.5 mm; the core is the expanded perlite body formed by the expansion of the first perlite particles, and the diameter of the core is determined by the particle size and expansion ratio of the first perlite, with a diameter range of 2 mm to 28 mm; the combination of the shell (fired ceramic layer - molten glassy layer) and the core (surface part of the expanded product of the first perlite) in the shell / core composite structure is a gradient-gradient combination relationship of mutual penetration of components during the sintering-melting-expansion process, that is, the combination and composition between the ceramic outer layer - the glassy inner layer - the expanded perlite body is a gradual relationship.

[0084] In this embodiment, the ceramic-shell expanded perlite has the advantages of high expansion ratio, lightweight, high mechanical strength, good thermal insulation performance, low water absorption, and good chemical stability. The properties of the ceramic-shell expanded perlite include: expansion ratio of 3.8 to 6.5, bulk density of 210 to 350 kg / m3, cylinder compressive strength of 0.9 to 2.1 MPa, thermal conductivity of 0.043 to 0.075 W / (m·K), water absorption of less than 1.5%, acid corrosion of less than 5%, and alkali corrosion of less than 1%.

[0085] To better demonstrate the characteristics of the product of this invention, the applicant has provided, as follows: Figure 2 , Figure 4 , Figure 5 The images shown are photographs of ordinary expanded perlite, optical microscope images, and electron microscope images, and also include images of... Figure 3 , Figure 6-8 The photographs shown are optical microscope images and electron microscope images of the glassy expanded perlite of the present invention. Figure 2 Ordinary expanded perlite is uncoated expanded perlite.

[0086] from Figure 2 and Figure 3 It can be observed that traditionally obtained expanded perlite particles have low sphericity, while the expanded perlite with a ceramic shell prepared by this invention has high sphericity; from Figure 4 and Figure 5 It can be observed that the surface of traditional expanded perlite contains pores and voids formed by the escape of gas during the expansion process, resulting in an uneven surface with sharp edges. Therefore, these pores easily absorb binders (such as cement paste, water glass, etc.).

[0087] from Figure 6 Optical microscope photographs and Figure 7-8 Electron micrographs reveal that the ceramic-like outer shell of the expanded perlite prepared in this invention has an uneven surface, forming a cracked, fired layer that covers the outer surface of the expanded perlite. The cracks expose the inner glassy layer, sealing the pores of the expanded perlite. Therefore, in addition to the properties of traditional expanded perlite, it also exhibits excellent moisture-proof and waterproof properties, as well as better bonding with adhesives.

[0088] Exemplary Example 3

[0089] This exemplary embodiment provides an application of ceramic-shell expanded perlite, wherein the ceramic-shell expanded perlite is the ceramic-shell expanded perlite described in Exemplary Embodiment 2.

[0090] In this embodiment, the applications of the expanded perlite with ceramic shell include the production of lightweight materials, thermal insulation materials, sound-absorbing and sound-insulating materials, fire-retardant materials, and its use as a substitute for cenospheres, lightweight or expanded ceramic particles.

[0091] Example 1

[0092] A ceramic-shell expanded perlite and its preparation and application methods, such as Figure 1 As shown, the preparation method includes the following steps:

[0093] (1) Pre-treat the perlite ore, i.e. crush, screen and remove dust to obtain the first perlite particles.

[0094] (2) Select first-grade perlite particles with a mesh size of -10 to +20, and choose a binder with a modulus of 2.2 and a density of 1.42 g / cm³. 3 The water glass adhesive solution has a Baume degree of 43. The first perlite particles and the adhesive are mixed in a mass ratio of 100:5. The adhesive is sprayed onto the surface of the first perlite particles using a sprayer and mixed evenly to obtain the second perlite particles.

[0095] (3) The pre-treated micro powder (smaller than 100 mesh), sodium / potassium feldspar, kaolin, and borax are mixed in a mass ratio of 50:35:5:10 and selectively crushed and mixed-grinded to obtain a glassy coating powder with a particle size of -500 mesh to +600 mesh. Refractory clay, shale, potassium feldspar, and quartzite are mixed in a mass ratio of 30:30:25:15 and selectively crushed and mixed-grinded to obtain a ceramic coating powder with a particle size of -400 mesh to +500 mesh. Then, according to the mass ratio of the second perlite particles, glassy coating powder, and ceramic coating powder, the second perlite and glassy coating powder are added to a granulator and granulated to obtain type A third perlite particles. During the granulation process of type A perlite particles, ceramic-coated powder is added simultaneously to ultimately obtain type B third perlite particles.

[0096] (4) The third type of perlite particles of type B were placed in a drying device and heated to 220°C at a heating rate of 18°C / min. Then, they were placed in a high-temperature furnace and heated to 700°C at a heating rate of 60°C. They were then preheated at this temperature for 13 minutes to obtain the fourth type of perlite particles with a water content of 2.4%.

[0097] (5) The preheated fourth perlite particles are evenly sprinkled onto a high-temperature flame maintained at 1200℃ in an expansion furnace for high-temperature expansion treatment. The expansion time is 20s, which causes the fourth perlite particles to be rapidly heated and expanded to obtain the ceramic-shell expanded perlite. The obtained ceramic-shell expanded perlite has a shell / core composite structure, including a shell and a core. The inner layer of the shell is a molten glass layer of glassy shelling components with a thickness of 0.1mm; the outer layer of the shell is a ceramic layer made of ceramic shelling components with a thickness of 0.35mm; the core is the expansion product of the first perlite, and the diameter of the core is determined by the particle size and expansion ratio of the first perlite, ranging from 10mm to 28mm.

[0098] The bulk density of the expanded perlite with a ceramic outer shell is 220 kg / m³. 3 The compressive strength of the cylinder is 1.1 MPa; the thermal conductivity is 0.045 W / (m·K); the water absorption rate is 0.68%; the acid corrosion rate is 3.53%; and the alkali corrosion rate is 0.79%.

[0099] Example 2

[0100] A ceramic-shell expanded perlite and its preparation and application methods, the preparation method comprising the following steps:

[0101] (1) Pre-process the obsidian-type ore, namely crushing, screening and dust removal, to obtain the first perlite particles.

[0102] (2) Select first-grade perlite particles with a mesh size of -30 to +50, and choose a binder with a modulus of 2.2 and a density of 1.36 g / cm³. 3 A sodium silicate adhesive solution with a Baume degree of 38.4 was prepared. The first perlite particles and the binder were mixed at a mass ratio of 100:8. The binder was sprayed onto the surface of the first perlite particles using a sprayer and mixed evenly to obtain the second perlite particles.

[0103] (3) The pre-treated micro powder (smaller than 100 mesh), sodium / potassium feldspar, kaolin, and borax are mixed in a mass ratio of 70:20:5:5 and selectively crushed and mixed-grinded to obtain a glassy coating powder with a particle size of -400 mesh to +500 mesh. Refractory clay, shale, potassium feldspar, and quartzite are mixed in a mass ratio of 45:30:20:5 and selectively crushed and mixed-grinded to obtain a ceramic coating powder with a particle size of -500 mesh to +600 mesh. Then, according to the mass ratio of the second perlite particles, glassy coating powder, and ceramic coating powder, the second perlite and glassy coating powder are added to a granulator and granulated to obtain type A third perlite particles. During the granulation process of type A perlite particles, ceramic-coated powder is added simultaneously to ultimately obtain type B third perlite particles.

[0104] (4) The third type of perlite particles of type B were placed in a drying device and heated to 300°C at a heating rate of 12°C / min. Then, they were placed in a high-temperature furnace and heated to 850°C at a heating rate of 50°C. They were then preheated at this temperature for 9 minutes to obtain the fourth type of perlite particles with a water content of 2.0%.

[0105] (5) The preheated fourth perlite particles are evenly sprinkled onto a high-temperature flame maintained at 1150℃ in an expansion furnace for high-temperature expansion treatment. The expansion time is 5s, which causes the fourth perlite particles to be rapidly heated and expanded to obtain the ceramic-shell expanded perlite. The obtained ceramic-shell expanded perlite has a shell / core composite structure, including a shell and a core. The inner layer of the shell is a molten glass layer of glassy shelling components with a thickness of 0.03mm; the outer layer of the shell is a ceramic layer made of ceramic shelling components with a thickness of 0.21mm; the core is the expansion product of the first perlite, and the diameter of the core is determined by the particle size and expansion ratio of the first perlite, ranging from 8mm to 25mm.

[0106] The bulk density of the expanded perlite with a ceramic outer shell was 302 kg / m³. 3 The compressive strength of the cylinder is 1.5 MPa; the thermal conductivity is 0.063 W / (m·K); the water absorption rate is 1.13%; the acid corrosion rate is 2.71%; and the alkali corrosion rate is 0.68%.

[0107] Example 3

[0108] A ceramic-shell expanded perlite and its preparation and application methods, the preparation method comprising the following steps:

[0109] (1) Pre-treat the pumice-shaped ore, i.e. crush, screen and remove dust to obtain the first perlite particles.

[0110] (2) Select first-grade perlite particles with a mesh size of -20 to +30, and choose a binder with a modulus of 2.2 and a density of 1.50 g / cm³. 3 A potassium silicate adhesive aqueous solution with a Baume degree of 48.3 was prepared. The first perlite particles and the binder were mixed at a mass ratio of 100:3. The binder was sprayed onto the surface of the first perlite particles using a sprayer and mixed evenly to obtain the second perlite particles.

[0111] (3) The pre-treated micro powder (smaller than 100 mesh), sodium / potassium feldspar, kaolin, and borax are mixed in a mass percentage ratio of 58:27:10:5, and then selectively crushed and mixed-grinded to obtain a glassy coating powder with a particle size of -325 mesh to +400 mesh. Refractory clay, shale, potassium feldspar, and quartzite are mixed in a mass percentage ratio of 60:20:10:10 and then selectively crushed and mixed-grinded to obtain a ceramic coating powder with a particle size of -325 mesh to +400 mesh. Then, according to the mass ratio of the second perlite particles, glassy coating powder, and ceramic coating powder of 80:2:18, the second perlite and glassy coating powder are first added to a granulator, and then granulated to obtain type A third perlite particles. During the granulation process of type A perlite particles, ceramic-coated powder is added simultaneously to ultimately obtain type B third perlite particles.

[0112] (4) Place the third type of perlite particles in a drying device and heat them to 200°C at a heating rate of 8°C / min. Then place them in a high-temperature furnace and heat them to 500°C at a heating rate of 80°C. Preheat them at this temperature for 15 minutes to obtain the fourth type of perlite particles with a water content of 2.5%.

[0113] (5) The preheated fourth perlite particles are evenly sprinkled onto a high-temperature flame maintained at 1300℃ in an expansion furnace for high-temperature expansion treatment. The expansion time is 35s, which causes the fourth perlite particles to be rapidly heated and expanded to obtain the ceramic-shell expanded perlite. The obtained ceramic-shell expanded perlite has a shell / core composite structure, including a shell and a core. The inner layer of the shell is a molten glass layer of glassy shelling components with a thickness of 0.06mm; the outer layer of the shell is a ceramic layer made of ceramic shelling components with a thickness of 0.49mm; the core is the expansion product of the first perlite, and the diameter of the core is determined by the particle size and expansion ratio of the first perlite, ranging from 5mm to 20mm.

[0114] The bulk density of the expanded perlite with a ceramic outer shell is 335 kg / m³. 3The compressive strength of the cylinder is 2.0 MPa; the thermal conductivity is 0.072 W / (m·K); the water absorption rate is 1.38%; the acid corrosion rate is 4.69%; and the alkali corrosion rate is 0.46%.

[0115] Example 4

[0116] The overall process flow and raw material selection in this example are the same as in Example 1. The process parameters involved are shown in Tables 1 and 2, and the performance parameters of the resulting product are shown in Table 3.

[0117] Example 5

[0118] The overall process flow and raw material selection in this example are the same as in Example 1. The process parameters involved are shown in Tables 1 and 2, and the performance parameters of the resulting product are shown in Table 3.

[0119] Example 6

[0120] The overall process flow and raw material selection in this example are the same as in Example 1. The process parameters involved are shown in Tables 1 and 2, and the performance parameters of the resulting product are shown in Table 3.

[0121] Example 7

[0122] The overall process flow and raw material selection in this example are the same as in Example 1. The process parameters involved are shown in Tables 1 and 2, and the performance parameters of the resulting product are shown in Table 3.

[0123] Table 1 shows the preparation parameters for the ceramic-shell expanded perlite prepared in Example 4-7; Table 2 shows the parameters for the drying, preheating, and thermal expansion processes in Example 4-7; and Table 3 shows the characteristics of the ceramic-shell expanded perlite prepared in Example 4-7. From the parameters in Tables 1-3, it can be seen that the ceramic-shell expanded perlite prepared in Example 4-7 expands by 3.8 to 6.8 times, with a bulk density of 210 to 350 kg / m³. 3 The cylinder compressive strength is 1.1–2.1 MPa, the thermal conductivity is 0.043–0.075 W / (m·K), the water absorption rate is 0.61%–1.42%, the acid corrosion rate is 2.39%–4.15%, and the alkali corrosion rate is 0.35%–0.73%.

[0124] Table 1. Process parameters involved in the preparation of Example 4-7

[0125]

[0126]

[0127] Table 2 Parameters of the drying, preheating and thermal expansion processes in Example 4-7 of the preparation

[0128]

[0129] Table 3 Properties of expanded perlite with ceramic shell prepared in Example 4-7

[0130]

[0131] Although the present invention has been described above in conjunction with exemplary embodiments and accompanying drawings, those skilled in the art should understand that various modifications can be made to the above embodiments without departing from the spirit and scope of the claims.

Claims

1. A method for preparing expanded perlite with a ceramic outer shell, characterized in that, The preparation method includes: 1) Pre-treat perlite ore to obtain the first perlite particles; 2) Mix the first perlite particles and the binder according to the mass ratio and mix them evenly to obtain the second perlite particles; 3) Glassy coating powder and ceramic coating powder were added to the second perlite particles in sequence for granulation, and type A third perlite particles and type B third perlite particles were obtained in sequence. 4) The type B third perlite particles are dried and preheated to obtain preheated fourth perlite particles; 5) The preheated fourth perlite particles are subjected to high-temperature expansion treatment to obtain expanded perlite with a ceramic shell.

2. The method for preparing expanded perlite with a ceramic outer shell according to claim 1, characterized in that, The perlite ore includes one or more of four types of ore: perlite type, obsidian type, pitchstone type, and pumice perlite. The pretreatment includes crushing, screening, and dust removal; the crushing is crushing with a screening section for inspection; the screening and dust removal include separating the crushed perlite sand into different particle sizes by screening, and collecting the micro powder with a particle size of less than 100 mesh from the perlite sand for use as raw material for preparing glassy coated powder.

3. The method for preparing expanded perlite with a ceramic outer shell according to claim 1, characterized in that, The mass ratio mentioned in step 2) is 100:(3-8); The uniform mixing includes: spraying the binder onto the first perlite particles being stirred using a spraying method, and uniformly coating the surface of the first perlite particles with the binder to obtain the second perlite particles.

4. The method for preparing expanded perlite with a ceramic outer shell according to claim 1, characterized in that, The adhesive includes one or more of inorganic and organic adhesives in aqueous solutions or hydrosols prepared with water; The inorganic binder comprises one or more of water glass, sodium silicate, and potassium silicate with a modulus of 1.0 to 2.9, and is configured to have a density of 1.36 to 1.50 g / cm³. 3 The aqueous solution has a Baumé degree of 38.4–48.3; The organic binder includes one or more of carboxymethyl cellulose, sodium carboxymethyl cellulose, acrylic emulsion, vinyl acetate emulsion, polyvinyl alcohol acetal, emulsion glue, animal glue, and plant glue, and is formulated into a water-soluble adhesive with a solid content of 0.5% to 2.0% by mass.

5. The method for preparing expanded perlite with a ceramic outer shell according to claim 1, characterized in that, The granulation process described in step 3) is the weighing and granulation of the second perlite particles with glassy coating powder and ceramic coating powder. First, the glassy coating powder is mixed with the second perlite particles and bonded by the surface binder of the second perlite particles to form a glassy component coating layer. Then, ceramic coating powder is added to continue granulation to form a ceramic component coating layer. The specific steps include: The second perlite particles, glassy coated powder and ceramic coated powder were weighed at a mass ratio of (90-77):(2-8):(8-20); The weighed second perlite particles are placed in a granulator, and then the weighed glassy coating powder is evenly added to the running granulator so that the glassy coating powder is evenly coated on the second perlite particles to obtain type A third perlite particles. The weighed ceramic-coated powder is evenly added to a granulator containing type A third perlite particles and is in operation, so that the ceramic-coated powder is evenly coated on the type A third perlite particles to obtain type B third perlite particles.

6. The method for preparing expanded perlite with a ceramic outer shell according to claim 1, characterized in that, The preparation method of the glassy coating powder in step 3) includes: mixing perlite-like ore powder with a particle size of less than 100 mesh, sodium / potassium feldspar, kaolin, and borax in a mass ratio of (50-70):(20-35):(5-10):(5-10) after selective crushing and mixed grinding, and obtaining the glassy coating powder with a particle size of -200 mesh to -600 mesh; The method for preparing the ceramic coating powder includes: mixing refractory clay, shale, potassium feldspar, and quartzite in a mass ratio of (30-60):(20-40):(10-25):(5-15), and obtaining the powder after selective crushing, mixing, and grinding. The particle size of the ceramic coating powder is -200 mesh to -600 mesh.

7. The method for preparing expanded perlite with a ceramic outer shell according to claim 1, characterized in that, The drying process described in step 4) is the drying process of type B third perlite particles in a drying-preheating device, where the temperature is increased from the ambient temperature section to the drying section at a rate of 8℃~20℃ to 200~300℃. The preheating treatment is a process in which the third type of perlite particles are preheated in a drying-preheating device by heating the drying section to a heating section at a rate of 50°C to 80°C to 500°C to 850°C; the fourth type of perlite particles have a moisture content of 2 to 3%.

8. The method for preparing expanded perlite with a ceramic outer shell according to claim 1, characterized in that, The high-temperature expansion treatment in step 5) includes: while the fourth perlite particles are still hot, they are evenly sprinkled onto a high-temperature flame in an expansion furnace where the temperature is maintained at 1100-1250°C; or, the fourth perlite particles are evenly spread out and directly fed into a high-temperature section in an electrically heated expansion furnace where the temperature is maintained at 1100-1350°C, so that the fourth perlite particles are rapidly heated and expand quickly. The residence time of the fourth perlite particles in the high-temperature flame or the high-temperature section of the electric heating furnace, i.e. the rapid expansion time, is 2s to 80s, to obtain the ceramic shell expanded perlite. The expanded perlite with a ceramic outer shell has a shell / core composite structure. The inner layer of the shell is a glassy shell, mainly composed of a glassy body formed by melting the encapsulating glassy shell components, with a thickness of 0.01–0.2 mm. The outer layer of the shell is a ceramic shell, mainly composed of a ceramic body formed by high-temperature firing of the encapsulating ceramic shell components, with a thickness of 0.05–0.5 mm. The core is the expanded perlite body formed by the expansion of the first perlite particles. The diameter of the core is determined by the particle size and expansion ratio of the first perlite, and the diameter range is generally 2 mm–28 mm. The bonding and composition between the ceramic outer layer, the glassy inner layer, and the expanded perlite body are in a gradual transitional relationship.

9. A type of expanded perlite with a ceramic outer shell, characterized in that, The ceramic-shell expanded perlite is obtained by the method described in any one of claims 1-8. The ceramic-shell expanded perlite has the advantages of high expansion ratio, lightweight, high mechanical strength, good thermal insulation performance, low water absorption, and good chemical stability. The properties of the ceramic-shell expanded perlite include: an expansion ratio of 3.8 to 6.5 and a bulk density of 210 to 350 kg / m³. 3 The cylinder compressive strength is 0.9–2.1 MPa, the thermal conductivity is 0.043–0.075 W / (m·K), the water absorption rate is less than 1%–1.5%, the acid corrosion rate is less than 5%, and the alkali corrosion rate is less than 1%.

10. An application of expanded perlite with a ceramic outer shell, characterized in that, The ceramic-shell expanded perlite is the ceramic-shell expanded perlite as described in claim 9. The applications of the ceramic-shell expanded perlite include the production of lightweight materials, thermal insulation materials, sound-absorbing and sound-insulating materials, fire-retardant materials, and its use as a substitute for cenospheres, lightweight or expanded ceramsite.

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