CN110818442B

CN110818442B - CaO-MgO-SiO using asbestos tailings as raw material2Is a foamed ceramic

Info

Publication number: CN110818442B
Application number: CN201911189597.8A
Authority: CN
Inventors: 孙红娟; 郑文苗; 彭同江; 丁文金
Original assignee: Southwest University of Science and Technology
Current assignee: Southwest University of Science and Technology
Priority date: 2019-11-28
Filing date: 2019-11-28
Publication date: 2022-03-18
Anticipated expiration: 2039-11-28
Also published as: CN110818442A

Abstract

The invention provides CaO-MgO-SiO taking asbestos tailings as raw materials₂Is a ceramic foam. The foamed ceramic comprises the following components in percentage by mass: 35-48% SiO₂、28～40％MgO、8～20％CaO、5～12％Fe₂O₃、3～12％Al₂O₃、3～8％Na₂O、2～5％B₂O₃、2～4％K₂O, 0.5-1% MnO and 0.02-0.08% BaO. The beneficial effects of the invention can include: the low-cost, high-utilization rate and high-added-value utilization of asbestos tailing waste residues and waste glass can be realized, and meanwhile, the foamed ceramic is excellent in performance and high in safety in the using process.

Description

CaO-MgO-SiO using asbestos tailings as raw material2Is a foamed ceramic

Technical Field

The invention relates to the field of inorganic non-metallic functional materials, in particular to CaO-MgO-SiO taking asbestos tailings as raw materials₂Is a ceramic foam.

Background

Asbestos tailings are tailings produced during the exploitation and beneficiation of chrysotile tailings. The stockpiling of the asbestos tailings not only occupies a large amount of land and causes waste of resources, but also causes harm to the environment and human health due to asbestos fibers. Waste glass is an important solid waste. Therefore, the utilization of the asbestos tailings and the waste glass has important significance for resource and environmental protection.

The foamed ceramic is a novel light functional material, has a pore structure with certain size and quantity, and combines the high specific surface area of a porous material and the physical and chemical stability of a ceramic material. The foamed ceramic is composed of a large number of crystal grains and a large number of open three-dimensional communicated air holes, so that the foamed ceramic is endowed with good filtering performance and has the advantages of good chemical stability, high porosity, uniform and controllable pore diameter, high strength, good thermal stability, large specific surface area, strong reproducibility and the like. The material is widely applied to the aspects of heat insulators, sound insulation materials, thermal barrier coatings, light heat insulation materials, catalyst carriers, biological materials and the like.

The existing production process of foamed ceramics mainly comprises the following steps: particle stacking, organic foam impregnation, gel injection molding, direct foaming, and pore-forming additive methods. Among them, the organic foam impregnation method requires an organic additive as a template for forming pores, and then burns off the template at a high temperature, which causes energy consumption and environmental problems. The gel injection molding method utilizes in-situ polymerization of organic monomers to stabilize foam, has simple and flexible process and can prepare the foamed ceramic material with complex shape, but the process is consistent and not industrially adopted due to the toxicity of the used monomers. The particle stacking method utilizes the characteristic that fine particles are easy to sinter, the fine particles with the same components are added into the aggregate, and the fine particles are melted at a certain temperature to connect large particles together. The direct foaming method introduces air into the slurry by using a foam stabilizer, and prepares a porous material through drying and sintering, but has the defects of complex drying process flow and easy fragmentation of a sample.

Most of foamed ceramics are prepared by adding pore-forming agents into raw materials and performing a powder sintering method, wherein the pore-forming agents are decomposed at high temperature to release gas, and the gas stays or escapes out of a blank after undergoing thermal expansion so as to form holes, so that the foamed ceramics with complex shapes can be prepared, and the foamed ceramics have high porosity and simple process. However, it is very difficult to select the type and amount of pore-forming agent required for the raw materials of the different components. In addition, for foamed ceramics, the presence of pores tends to result in a reduction in the mechanical properties of the sample, making it difficult to prepare a sample having both high porosity and high mechanical properties.

Disclosure of Invention

In view of the deficiencies in the prior art, it is an object of the present invention to address one or more of the problems in the prior art as set forth above. For example, one of the objects of the present invention is to provide CaO-MgO-SiO using asbestos tailings as raw material₂Is foamed ceramic to realize the waste utilization of asbestos tailings and waste glass.

In order to realize the purpose, the invention provides CaO-MgO-SiO taking asbestos tailings as raw materials₂Is a ceramic foam. The foamed ceramic may comprise the following components in mass fraction: 35-48% SiO₂、28～40％MgO、8～20％CaO、5～12％Fe₂O₃、3～12％Al₂O₃、 3～8％Na₂O、2～5％B₂O₃、2～4％K₂O, 0.5-1% MnO and 0.02-0.08% BaO.

In an exemplary embodiment of the present invention, the raw materials for preparing the ceramic foam may include the following components in parts by mass:

30-70% of asbestos tailing roasted mixture, 15-50% of waste glass, 0-15% of kaolin, 0-15% of bentonite, 0-12% of potash feldspar, 0-12% of nepheline, 0-8% of perlite, 0-5% of quartz sand and 0-3% of borax.

In an exemplary embodiment of the invention, the asbestos tailings may comprise chrysotile tailings, and the asbestos tailings calcination mixture comprises, in mass fractions: 40-75% of forsterite, 15-40% of hematite and 8-25% of amorphous components.

In an exemplary embodiment of the present invention, the waste glass may include the following components in mass fraction:

45～80％SiO₂、10～28％CaO、3～10％Na₂O、1～5％MgO、0.5～1.6％Al₂O₃、 0.2～0.8％Fe₂O₃and 0.06 to 0.25K₂O。

In an exemplary embodiment of the invention, the phase composition of the foamed ceramic may include mass ratio of 48-72: 25-60 parts of forsterite and diopside.

In an exemplary embodiment of the present invention, the phase composition of the ceramic foam may include the following components in mass fraction:

35-60% of forsterite, 15-38% of diopside and 12-30% of akermanite.

35-50% of akermanite, 20-45% of forsterite and 15-35% of forsterite.

28-50% of quartz, 20-38% of enstatite, 15-30% of forsterite and 12-20% of forsterite.

In an exemplary embodiment of the present invention, the ceramic foam is prepared without adding a foaming agent and a pore-forming agent.

In an exemplary embodiment of the invention, the porosity of the foamed ceramic may be 32.56-78.48%, and the compressive strength may be 14.21-86.56 Mpa.

In an exemplary embodiment of the present invention, the bulk density of the ceramic foam may be 0.75 to 2.65g/cm³The thermal conductivity coefficient can be 1.08-5.45W/(m)²·K)。

In one exemplary embodiment of the invention, the ceramic foam surface is a water impermeable enamel layer.

Compared with the prior art, the beneficial effects of the invention can include: the preparation of the foamed ceramic realizes the utilization of asbestos tailings and waste glass, and the prepared foamed ceramic has good performance.

Drawings

The above and other objects and features of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1 illustrates CaO-MgO-SiO in an exemplary embodiment of the invention₂A flow chart of a preparation method of the foamed ceramic;

FIG. 2 shows an XRD pattern of a baked mixture of asbestos tailings in an exemplary embodiment of the invention;

FIG. 3 shows CaO-MgO-SiO prepared in example 1 of the present invention₂An XRD pattern of the ceramic foam;

FIG. 4 shows CaO-MgO-SiO prepared in example 1 of the present invention₂An SEM image of the ceramic foam;

FIG. 5 shows CaO-MgO-SiO prepared in example 2 of the present invention₂An XRD pattern of the ceramic foam;

FIG. 6 shows CaO-MgO-SiO prepared in example 2 of the present invention₂An SEM image of the ceramic foam;

FIG. 7 shows CaO-MgO-SiO prepared in example 3 of the present invention₂An XRD pattern of the ceramic foam;

FIG. 8 shows CaO-MgO-SiO prepared in example 3 of the present invention₂An SEM image of the ceramic foam;

FIG. 9 shows CaO-MgO-SiO prepared in example 4 of the present invention₂An XRD pattern of the ceramic foam;

FIG. 10 shows CaO-MgO-SiO prepared in example 4 of the present invention₂Is an SEM image of the ceramic foam.

Detailed Description

Hereinafter, a CaO-MgO-SiO raw material of asbestos tailings according to the present invention will be described in detail with reference to the accompanying drawings and exemplary embodiments₂Is a ceramic foam.

The invention provides CaO-MgO-SiO taking asbestos tailings as raw materials₂Is a ceramic foam.

For example, in terms of mass fraction: 50% of a roasted mixture, 35% of waste glass, 5% of kaolin, 3% of bentonite, 2% of potash feldspar, 2% of nepheline, 1% of perlite, 1% of quartz sand and 1% of borax.

Further, only one of kaolin and bentonite may be selected, and only one of potash feldspar and nepheline may be selected.

In the embodiment, the kaolin or the bentonite is added to improve the viscosity and plasticity of the product, the potash feldspar and the nepheline are added to reduce the sintering temperature of the product, the borax is added to reduce the sintering temperature of the product, so that the green body can be sintered at a lower temperature to form a high-strength foamed ceramic framework structure, and the perlite and the quartz sand are added to improve the sintering temperature range of the product.

In this embodiment, the asbestos tailings may include chrysotile tailings, and may include the following components in terms of mass fractions:

40～50％MgO、30～50％SiO₂、8～15％CaO、5～12％Fe₂O₃、0.5～1.2％ Al₂O₃、0.1～0.3％K₂o, 0.1-0.2% MnO and 0.02-0.08% BaO, and the balance of the loss on ignition (for example, the loss on ignition can be 12.46-15.65%), wherein the loss on ignition is mainly volatile components in the asbestos tailings and can comprise adsorbed water and hydroxyl structural water.

In this embodiment, the asbestos tailing roasting mixture may include a roasting product of the asbestos tailing, as shown in fig. 2, and the roasting mixture may include forsterite, hematite, and an amorphous component, wherein the amorphous component may include periclase and quicklime; the calcined mixture may include, in mass fractions: 40-75% of forsterite, 15-40% of hematite and 8-25% of amorphous components.

In this embodiment, the waste glass may include the following components in mass fraction:

45～80％SiO₂、10～28％CaO、3～10％Na₂O、1～5％MgO、0.5～1.6％Al₂O₃、 0.2～0.8％Fe₂O₃and 0.06 to 0.25K₂O, the balance may be loss on ignition, for example, 0.05 to 0.38%.

In this embodiment, the ceramic foam may include the following components in mass fraction: 35 to 48 percent of SiO₂、28～40％MgO、8～20％CaO、5～12％Fe₂O₃、3～12％Al₂O₃、3～ 8％Na₂O、2～5％B₂O₃、2～4％K₂O, 0.5-1% MnO and 0.02-0.08% BaO.

In addition, the foamed ceramic can be prepared from 35-48 parts by mass of SiO₂28-40 parts of MgO, 8-20% of CaO, 5-12 parts of Fe₂O₃3 to 12 parts of Al₂O₃3-8 parts of Na₂O, 2-5 parts of B₂O₃2 to 4 parts of K₂O, 0.5-1 part of MnO and 0.02-0.08 part of BaO.

The main performance parameters of the ceramic foam may include: the bulk density is 0.75 to 2.65g/cm³The porosity is 32.56-78.48%, the compressive strength is 14.21-86.56 Mpa, and the heat conductivity coefficient is 1.08-5.45W/(m)²K), the pore diameter may be 30 to 1600 μm, further, the porosity may be 32.56 to 56.7%, the compressive strength may be 46.7 to 86.56MPa, and further, the porosity may be 77 to 78%.

In this embodiment, the phase composition of the ceramic foam may include:

(1) forsterite and diopside, wherein the mass ratio of the forsterite to the diopside can be 48-72: 25-60;

in addition, the foamed ceramic of the phase (1) can be composed of 48-72 parts of forsterite and 25-60 parts of diopside by mass;

the phase composition of the foamed ceramic can further comprise the following components in percentage by mass:

(2) 35-60% of forsterite (main crystal phase), 15-38% of diopside (auxiliary crystal phase) and 12-30% of akermanite (auxiliary crystal phase);

in addition, the foamed ceramic of the phase (2) may be composed of, by mass, 35 to 60 parts of forsterite (primary crystal phase), 15 to 38 parts of diopside (secondary crystal phase), and 12 to 30 parts of akermanite (secondary crystal phase);

or (3) 35-50% of akermanite (main crystal phase), 20-45% of forsterite (auxiliary crystal phase) and 15-35% of forsterite (auxiliary crystal phase);

in addition, the foamed ceramic of the phase (3) may be composed of 35 to 50 parts by mass of akermanite (primary crystal phase), 20 to 45 parts by mass of forsterite (secondary crystal phase) and 15 to 35 parts by mass of forsterite (secondary crystal phase);

or (4)28 to 50% of quartz (main crystal phase), 20 to 38% of enstatite (main crystal phase), 15 to 30% of forsterite (auxiliary crystal phase) and 12 to 20% of forsterite (auxiliary crystal phase);

in addition, the ceramic foam of the phase (4) may be composed of, by mass, 28 to 50 parts of quartz (main crystal phase), 20 to 38 parts of enstatite (main crystal phase), 15 to 30 parts of forsterite (secondary crystal phase), and 12 to 20 parts of forsterite (secondary crystal phase).

Wherein, the raw materials for preparing the foamed ceramic with the phase composition (1) can comprise the following components in percentage by mass: 45-60% of asbestos tailing roasted mixture, 15-38% of waste glass, 5-12% of kaolin or bentonite, 3-10% of potash feldspar or nepheline, 2-8% of perlite, 2-5% of quartz sand and 1-3% of borax;

in addition, the foamed ceramic of the phase composition (1) can be prepared from 45-60 parts of asbestos tailing roasted mixture, 15-38 parts of waste glass, 5-12 parts of kaolin or bentonite, 3-10 parts of potassium feldspar or nepheline, 2-8 parts of perlite, 2-5 parts of quartz sand and 1-3 parts of borax by mass.

The raw materials for preparing the ceramic foam of the phase composition (2) may include the following components in mass fraction: 38-55% of a roasted mixture, 20-40% of waste glass, 5-15% of kaolin or bentonite, 3-8% of potash feldspar or nepheline, 2-6% of perlite, 2-5% of quartz sand and 1-3% of borax;

in addition, the foamed ceramic of the phase composition (2) can be prepared from 38-55 parts of a roasted mixture, 20-40 parts of waste glass, 5-15 parts of kaolin or bentonite, 3-8 parts of potash feldspar or nepheline, 2-6 parts of perlite, 2-5 parts of quartz sand and 1-3 parts of borax by mass.

The raw materials for preparing the ceramic foam of the phase composition (3) may include the following components in mass fraction: 30-48% of a roasted mixture, 25-40% of waste glass, 3-15% of kaolin or bentonite, 3-8% of potash feldspar or nepheline, 2-6% of perlite, 2-5% of quartz sand and 1-3% of borax;

in addition, the foamed ceramic of the phase composition (3) can be prepared from 30-48 parts by mass of a roasted mixture, 25-40 parts by mass of waste glass, 3-15 parts by mass of kaolin or bentonite, 3-8 parts by mass of potash feldspar or nepheline, 2-6 parts by mass of perlite, 2-5 parts by mass of quartz sand and 1-3 parts by mass of borax.

The raw materials for preparing the ceramic foam of the phase composition (4) may include the following components in mass fraction: 50-70% of a roasted mixture, 18-35% of waste glass, 3-15% of kaolin or bentonite, 3-8% of potash feldspar or nepheline, 2-6% of perlite, 3-5% of quartz sand and 1-3% of borax;

in addition, the foamed ceramic of the phase composition (4) can be prepared from 50-70 parts of a roasted mixture, 18-35 parts of waste glass, 3-15 parts of kaolin or bentonite, 3-8 parts of potash feldspar or nepheline, 2-6 parts of perlite, 3-5 parts of quartz sand and 1-3 parts of borax by mass.

In this example, as shown in FIG. 1, CaO-MgO-SiO of the present invention, which uses asbestos tailings as raw materials₂The raw materials for preparing the series foamed ceramics can comprise the raw materials, and the preparation method can comprise the following steps:

s01: mixing the prepared raw materials and grinding to obtain biscuit powder.

In this example, the fired mixture is mainly based on forsterite refractory phase, during the formation of ceramic foam, the low melting point waste glass forms a gas-tight glass melt network between the particles with forsterite as central skeleton and encloses the gas in the gaps of the green body, and as the temperature rises, the gas expands to push the melt film to grow larger, eventually leading to pore formation of the sample. When the content of the fired mixture is less than 30%, it is difficult to form a skeleton structure at the high-temperature pore-forming stage, and when the content is more than 70%, it is difficult to form a sufficiently closed glass melt network when the biscuit is heated, and the formation of pores will be affected. The auxiliary raw materials can comprise 15-50% of waste glass in the biscuit powder according to the mass fraction, in the process of forming the foamed ceramic, the low-melting-point waste glass forms a glass melt network of closed gas between particles taking forsterite as a central framework and encapsulates the gas in gaps of a biscuit body, and as the temperature rises, the gas expands to push the volume of a melt film to be continuously increased, and finally, the sample is formed into holes. When the content of the waste glass is less than 15%, it is difficult to form a sufficiently closed glass melt network, and when the content of the waste glass is more than 50%, the forsterite is insufficient to form a skeleton structure at a high-temperature pore-forming stage. Within the mass fraction range of the waste glass provided by the invention, the product porosity is increased along with the increase of the content of the waste glass.

In this embodiment, the particle size of the green body powder may be not greater than 80 μm, and further may be 10 to 80 μm, for example, 50 μm.

S02: uniformly mixing the biscuit powder with the adhesive and then granulating to obtain biscuit granules.

In this embodiment, the adhesive may comprise an aqueous suspension or solution of one or both of starch, polyvinyl alcohol and carboxymethylcellulose, and the adhesive is selected for reasons including: the adhesive is organic and can be completely decomposed into gas at low temperature (below 400 ℃), and the decomposition temperature of the adhesive is far lower than the melting temperature of waste glass in the green body and the sintering temperature of the green body, so that the gas formed by decomposition of the adhesive can escape through pores in the green body, and the high-temperature pore-forming process of the green body cannot be influenced. The addition amount of the adhesive can be 3-5% of the mass of the biscuit powder, when the addition amount of the adhesive is less than 3%, the obtained biscuit particles are fragile, and when the addition amount of the adhesive is more than 5%, the biscuit particles are prone to crack due to glue discharge in the heating process.

In this embodiment, the granulation method may include dry rotary granulation and slurry spray granulation.

In this embodiment, the particle size of the biscuit particles may be not greater than 2mm, and further may be 0.5-2 mm, for example, 1mm, and the particle size of the biscuit particles has an influence on the sintering effect of the sample, and the smaller the particle size is, the lower the sintering temperature is, which is beneficial to the densification and sintering of the sample, and vice versa, is not beneficial to the sintering of the sample.

S03: and pressing and forming the biscuit particles to obtain the biscuit.

In this embodiment, optionally, the biscuit particles are spread in a forming mold, a blank forming press is used for dry pressing, pressure is maintained for 2-20 s under the pressure of 20-100 Mpa, and the biscuit is obtained after demolding. When the pressure is lower than 20Mpa, the formed biscuit is low in strength and fragile, and when the pressure is higher than 100Mpa, the pressure is too high and exceeds the bearable load of the biscuit, the biscuit is broken; when the dwell time is less than 2s, the biscuit is difficult to form, and when the dwell time is more than 20s, the dwell time is too long, and the cost is increased.

S04: and heating the biscuit to 600-850 ℃, preserving heat to remove volatile components, then heating to 1050-1250 ℃, expanding to form holes, and naturally cooling to obtain the foamed ceramic. Under the condition of high temperature, the low-melting-point waste glass forms a glass melt network for sealing gas among particles taking forsterite as a central framework, air holes in gaps of a blank body are sealed, and the gas expands to push the volume of a melt film to be continuously increased along with the rise of the temperature, so that the pore forming of a product is finally caused. The first stage heating is to fully remove volatile components in the blank and remove the influence of the volatile components on the structural performance of a final product, when the temperature is lower than 600 ℃, the volatile components cannot be completely removed, and when the temperature is higher than 950 ℃, the volatile components of the blank are trapped in the blank and cannot be removed due to the fact that the temperature exceeds the melting temperature of the waste glass. The second stage heating is to form the holes through high temperature self-expansion of the blank, when the temperature is lower than 1050 ℃, the waste glass is difficult to melt to form a closed melt network, which is not beneficial to the expansion and the hole forming of the blank, and when the temperature is higher than 1250 ℃, the blank can generate an overburning phenomenon, which is not beneficial to the structure of the product.

In the embodiment, the biscuit is heated to 600-850 ℃ at a heating rate of 5-10 ℃/min and is subjected to heat preservation for 30-60 min, the biscuit is heated to 1050-1250 ℃ at a heating rate of 3-5 ℃/min and is subjected to heat preservation for 30-90 min, thermal stress in the product at a low temperature stage has small influence on the structure of the product, and thermal stress in the product at a high temperature stage has large influence on the structure of the product, so that time can be saved and energy consumption can be reduced by adopting a faster heating rate at a low temperature stage, thermal stress in the product can be reduced by adopting a slower heating rate at a high temperature stage, and the product is prevented from being broken due to overlarge stress.

In this embodiment, before step S01, the preparation method may further include the steps of: and roasting the asbestos tailings to obtain a roasted mixture.

In this embodiment, the asbestos tailings are roasted before the blank is made to remove volatile components, so that the asbestos is defibrinated to facilitate subsequent uniform mixing and reaction, and the influence of the escape of the volatile components on the pore structure of the product is avoided.

In this embodiment, the temperature of the baking treatment may be 650 to 950 ℃, for example: when the temperature is lower than 650 ℃, volatile components in the asbestos tailings cannot be completely removed, such as serpentine and other phases may not completely remove hydroxyl, the volatile components which are not removed escape in the biscuit heat treatment process can affect the product structure, and meanwhile, the fiber structure of the asbestos tailings cannot be completely destroyed, so that the asbestos tailings cannot be fully and uniformly mixed with auxiliary raw materials during grinding; when the temperature is higher than 950 ℃, the purpose of roasting can be achieved, and the energy consumption is overhigh by increasing the temperature. The time of the calcination treatment may be 30 to 90min, for example: 50min, when the time is less than 30min, the volatile components in the asbestos tailings cannot be completely removed, the subsequent uniform mixing reaction of the raw materials and the fired sample void structure are affected, when the time is more than 90min, the purpose of roasting can be achieved, the roasting time is prolonged, and the energy consumption is overhigh.

In this example, CaO-MgO-SiO in accordance with the present invention₂The series foamed ceramics can also comprise the ceramic prepared by the preparation methodThe foamed ceramic does not contain a foaming agent and a pore-forming agent in the preparation process, and can comprise a plate-shaped product, the surface of the foamed ceramic can be an impermeable enamel layer, and the back of the foamed ceramic can be a rough surface, so that the product has the functions of decoration, water and gas tightness, the construction and decoration requirements can be met without facing or coating treatment, the construction difficulty can be reduced, and the construction cost can be saved.

In order to better understand the above exemplary embodiments of the present invention, the following further explains it with reference to specific examples.

Example 1

The raw materials comprise: 48% of asbestos tailing roasted mixture, 28% of waste glass, 8% of kaolin or bentonite, 6% of potash feldspar or nepheline, 5% of perlite, 3% of quartz sand and 2% of borax.

The preparation process comprises the following steps:

(1) and (3) matching the roasted mixture with auxiliary raw materials and then grinding to obtain biscuit powder, wherein the granularity of the biscuit powder is 75 microns.

(2) Uniformly mixing the biscuit powder with a binder, and granulating to obtain biscuit granules, wherein the binder comprises one or two aqueous suspensions or solutions of starch, polyvinyl alcohol and carboxymethyl cellulose, the granulation method comprises dry-method rotary granulation and pulping spray granulation, and the average particle size of the biscuit granules is 1.5 mm.

(3) Spreading the biscuit particles in a forming die, and performing dry pressing forming by using a blank forming press to obtain the biscuit, wherein the pressure of the dry pressing forming is 80Mpa, and the pressure maintaining time is 10 s.

(4) And placing the foamed ceramic in a tunnel kiln for sectional heating treatment, cooling along with the kiln, taking out, and then cutting edges to obtain the foamed ceramic product. The heat treatment method comprises the following steps: and in a tunnel kiln, heating the biscuit to 800 ℃ from room temperature at a heating rate of 8 ℃/min, preserving heat for 30min, continuing heating to 1200 ℃ at a heating rate of 4 ℃/min, preserving heat for 60min, and naturally cooling to obtain the foamed ceramic.

The structure and properties of the obtained ceramic foam:

as shown in fig. 3, the phase composition of the ceramic foam product in this example includes forsterite and diopside. Wherein the mass fraction ratio of forsterite (main crystal phase) and diopside (secondary crystal phase) is 65% and 35%;

the bulk density is 1.98g/cm³Porosity of 72.05%, compressive strength of 75Mpa, and thermal conductivity of 3.56W/(m)²·K)。

As shown in fig. 4, the ceramic foam described in this example has a pore structure with different pore sizes, mainly including closed pores, and an average pore size of about 350 μm.

Example 2

The raw materials comprise: 45% of roasted mixture, 32% of waste glass, 10% of kaolin or bentonite, 5% of potash feldspar or nepheline, 3% of perlite, 3% of quartz sand and 2% of borax.

The preparation process comprises the following steps:

The structure and properties of the obtained ceramic foam:

as shown in fig. 5, the phase composition of the ceramic foam product in this example includes forsterite, diopside, and akermanite. Wherein the mass fraction ratio of forsterite (main crystal phase), diopside (secondary crystal phase) and akermanite (secondary crystal phase) is 55%, 25% and 20%;

the bulk density was 2.32g/cm³72.26 percent of porosity, 73.51Mpa of compressive strength and 3.98W/(m) of thermal conductivity coefficient²·K)。

As shown in FIG. 6, the internal pore structure of the ceramic foam in this example is uniform, mainly comprising closed pores, and the average pore size is about 208 μm.

Example 3

The raw materials comprise the following components in percentage by mass: 45% of roasted mixture, 28% of waste glass, 8% of kaolin or bentonite, 8% of potash feldspar or nepheline, 6% of perlite, 3% of quartz sand and 2% of borax.

The preparation process comprises the following steps:

The structure and properties of the obtained ceramic foam:

as shown in fig. 7, the phase composition of the ceramic foam product in this example includes akermanite, forsterite, and forsterite. Wherein the mass fraction ratio of the akermanite (main crystal phase), the forsterite (auxiliary crystal phase) and the forsterite (auxiliary crystal phase) is 42%, 38% and 20%;

the bulk density was 1.68g/cm³72.65 percent of porosity, 70.85MPa of compressive strength and 3.58W/(m) of thermal conductivity coefficient²·K)。

As shown in FIG. 8, the internal pore structure of the ceramic foam in this example is uniform, most of the internal pore structure is closed pores, and the average pore size is about 420 μm.

Example 4

The raw materials comprise the following components in percentage by mass: 60% of roasted mixture, 18% of waste glass, 8% of kaolin or bentonite, 5% of potash feldspar or nepheline, 4% of perlite, 3% of quartz sand and 2% of borax.

The preparation process comprises the following steps:

The structure and properties of the obtained ceramic foam:

as shown in fig. 9, the phase composition of the ceramic foam product in this example includes forsterite, enstatite, forsterite, and quartz. Wherein the mass fraction ratio of forsterite (main crystal phase), enstatite (main crystal phase), forsterite (secondary crystal phase) and quartz (secondary crystal phase) is 40%, 25%, 20% and 15%;

the bulk density was 2.20g/cm³61.85 percent of porosity, 82.12MPa of compressive strength and 5.21W/(m) of thermal conductivity coefficient²·K)。

As shown in fig. 10, the internal pore structure of the ceramic foam in this example is different in size, small-sized pores are present on the pore walls between the large pores, and the overall average pore size is about 320 μm.

In conclusion, the CaO-MgO-SiO of the invention which takes the asbestos tailings as the raw material₂Advantages of the ceramic foam may include:

(1) CaO-MgO-SiO of the invention₂The foamed ceramic uses asbestos tailings and waste glass which are hazardous solid wastes as raw materials for preparation, so that waste utilization is realized, meanwhile, asbestos fibers are decomposed into harmless olivine and amorphous components in the roasting treatment process in the preparation process, no harmful gas is discharged in the roasting treatment process and the roasting process of the foamed ceramic, no three wastes are discharged in the whole production process, and the technical requirements of green manufacturing processes are met.

(2) CaO-MgO-SiO of the invention₂The surface of the series foamed ceramic product is an enamel layer, so that the foamed ceramic product has the functions of decoration, water and gas tightness, can meet the requirements of construction and decoration without veneering or coating treatment, can reduce the construction difficulty, save the construction cost and has high safety in the using process.

(3) The preparation raw materials of the invention do not comprise pore-forming agent and foaming agent, and different solid wastes and auxiliary raw materials are directly utilized to carry out in-situ sintering and crystallization reaction at high temperature, thus self-expanding and pore-forming. The problem of selecting the types and the dosage of the pore-forming agent and the foaming agent in the traditional preparation method of the foamed ceramic is thoroughly solved.

(4) CaO-MgO-SiO of the invention₂The foamed ceramic product has good performance and can meet the requirements of light heat-insulating materials for buildings. In particular, body densityThe degree of the inorganic filler can be 0.75 to 2.65g/cm³The porosity can be 32.56-78.48%, the compressive strength can be 14.21-86.56 Mpa, and the heat conductivity can be 1.08-5.45W/(m)²K) and the pore diameter may be 30 to 1600 μm. In particular, the bulk density can be 1.5 to 2.4g/cm³The porosity can be 60-80%, the compressive strength can be 60-80 Mpa, and the thermal conductivity can be 2-4W/(m)²K) and an average pore diameter of 200 to 400 μm.

Although the present invention has been described above in connection with exemplary embodiments, it will be apparent to those skilled in the art that various modifications and changes may be made to the exemplary embodiments of the present invention without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. CaO-MgO-SiO using asbestos tailings as raw material₂The foamed ceramic comprises the following components in percentage by mass:

35～48％SiO₂、28～40％MgO、8～20％CaO、5～12％Fe₂O₃、3～12％Al₂O₃、3～8％Na₂O、2～5％B₂O₃、2～4％K₂o, 0.5-1% MnO and 0.02-0.08% BaO; the preparation raw materials of the foamed ceramic comprise the following components in parts by mass:

30-70% of asbestos tailing roasted mixture, 15-50% of waste glass, 0-15% of kaolin, 0-15% of bentonite, 0-12% of potash feldspar, 0-12% of nepheline, 0-8% of perlite, 0-5% of quartz sand and 0-3% of borax;

the asbestos tailing roasting mixture comprises forsterite, hematite and amorphous components;

and a foaming agent and a pore-forming agent are not added in the preparation process of the foamed ceramic.

2. The CaO-MgO-SiO raw material using asbestos tailings as claimed in claim 1₂Is a foamed ceramic characterized in that,

the preparation raw materials of the foamed ceramic comprise the following components in parts by mass:

50% of a roasted mixture, 35% of waste glass, 5% of kaolin, 3% of bentonite, 2% of potash feldspar, 2% of nepheline, 1% of perlite, 1% of quartz sand and 1% of borax.

3. The CaO-MgO-SiO raw material using asbestos tailings as claimed in claim 2₂The foamed ceramic is characterized in that the asbestos tailings comprise chrysotile tailings, and the asbestos tailing roasting mixture comprises the following components in percentage by mass: 40-75% of forsterite, 15-40% of hematite and 8-25% of amorphous components.

4. The CaO-MgO-SiO raw material using asbestos tailings as claimed in claim 2₂The foamed ceramic is characterized in that the waste glass comprises the following components in percentage by mass:

45～80％SiO₂、10～28％CaO、3～10％Na₂O、1～5％MgO、0.5～1.6％Al₂O₃、0.2～0.8％Fe₂O₃and 0.06 to 0.25K₂O。

5. The CaO-MgO-SiO raw material using asbestos tailings as claimed in claim 1₂The ceramic foam is characterized in that the phase composition of the ceramic foam comprises, by mass, 48-72: 25-60 parts of forsterite and diopside.

6. The CaO-MgO-SiO raw material using asbestos tailings as claimed in claim 1₂The ceramic foam is characterized in that the phase composition of the ceramic foam comprises the following components in percentage by mass:

35-60% of forsterite, 15-38% of diopside and 12-30% of akermanite.

7. The CaO-MgO-SiO raw material using asbestos tailings as claimed in claim 1₂The ceramic foam is characterized in that the phase composition of the ceramic foam comprises the following components in percentage by mass:

35-50% of akermanite, 20-45% of forsterite and 15-35% of forsterite.

8. The CaO-MgO-SiO raw material using asbestos tailings as claimed in claim 1₂The ceramic foam is characterized in that the phase composition of the ceramic foam comprises the following components in percentage by mass:

9. The CaO-MgO-SiO raw material using asbestos tailings as claimed in claim 1₂The ceramic foam is characterized in that only one of kaolin and bentonite is selected, and only one of potash feldspar and nepheline is selected.

10. The CaO-MgO-SiO raw material using asbestos tailings as claimed in claim 1₂The foamed ceramic is characterized in that the porosity of the foamed ceramic is 32.56-78.48%, and the compressive strength is 14.21-86.56 MPa.