CN106518138A - Preparation method for foam ceramic thermal insulation building block - Google Patents

Abstract

The invention discloses a preparation method of a foam ceramic thermal insulation block. The uniformly mixed foam ceramic blanks are added with water, stirred, aged, and piled on the porous refractory pallet; the porous body is pressed with a special molding die together with the refractory pallet; the molding die is made of punching needles. The bottom mold and porous pressing plate are composed. After the pressing is completed, the bottom mold and the porous pressing plate are separated, and the porous green body is taken out together with the porous refractory supporting plate; it is dried until the moisture content is <2%, and the temperature is raised in a high-temperature furnace at 3-5°C/min. To 1050～1200℃, keep warm for 0.5～1.5h, so that the blowing agent decomposes to form pores; after cooling in the furnace, cut into foam ceramic blocks. The porous green body structure designed by the invention accelerates the permeation and discharge of gas, promotes the oxidation and decomposition of minerals inside the green body, realizes the rapid firing of large-volume foam ceramics, and effectively reduces the temperature difference between the inside and outside of the product, solving the problem of large volume and thickness. Quality foam ceramic cooling cracking problem.

Description

A kind of preparation method of foam ceramic insulation block

technical field

The invention belongs to the technical field of composite materials, and in particular relates to a preparation method of a foamed ceramic block.

Background technique

As a new type of inorganic porous insulation material, ceramic foam has been widely used in the field of wall insulation materials due to its light weight, heat insulation, fire resistance, waterproof, sound insulation and other properties. At present, in order to reduce the preparation cost of foam ceramics, it has become the development trend of foam ceramics to use solid waste in large quantities and to sinter large-volume and thick green bodies rapidly. For example: use polished brick slag, fly ash, coal gangue and metal tailings and other solid wastes in a large amount to burn large-volume foam ceramic test blocks with a size greater than 2000*1000*300mm at one time, and shorten the firing cycle as much as possible ,reduce manufacturing cost. However, due to the complex mineral composition of tailings waste residue, more oxidation and decomposition reactions are involved at high temperatures, and these reactions are greatly affected by firing conditions (such as: firing atmosphere), plus the penetration and removal of gas inside large-volume foam ceramics Difficulties lead to different foaming effects inside and outside the foam ceramics prepared by using tailings waste residue, and the performance is significantly reduced. At present, this problem is mainly solved by reducing the utilization rate of tailings and prolonging the heating rate to increase the time of gas penetration and discharge. However, this measure reduces production efficiency and increases production costs.

In addition, the cooling cracking of large-volume foam ceramics is also one of the difficult problems in the production of foam ceramics. Due to the low thermal conductivity of foamed ceramics, the internal heat is only dissipated through conduction during the cooling process, and the efficiency is low. The cracking of the green body caused by temperature stress is more significant in large-volume foamed ceramics. Therefore, the limitation of product size and cooling rate has become an urgent problem to be solved in the industrial production of large-volume thick foam ceramics.

Contents of the invention

The purpose of the present invention is to provide a preparation method of foam ceramic insulation material, which solves the problems of slow heat and mass transfer speed, large temperature difference inside the green body, and difficulty in gas penetration and discharge in the production of large-volume and thick foam ceramics. The problem of volume and thick foam ceramic production is solved, and the problem of foam ceramic cooling and cracking is solved.

In order to achieve the above purpose, the following technical solutions are adopted:

A method for preparing a foam ceramic insulation block, comprising the following steps:

The uniformly mixed foam ceramic blanks are piled on porous refractory pallets after adding water, stirring, aging;

Press the special molding die together with the refractory plate to form a porous green body; the forming die is composed of a bottom mold with punching needles and a porous pressing plate. Take out the pallet together;

Dry until the moisture content is <2%, raise the temperature in a high-temperature furnace to 1050-1200°C at 3-5°C/min, and keep it warm for 0.5-1.5h to decompose the foaming agent to form pores; take off the porous refractory support after cooling in the furnace plates, cut into foam ceramic blocks.

According to the above scheme, the dry basis of the ceramic foam blank contains SiO ₂ +Al ₂ O ₃ : 65-85 wt%, CaO+MgO: 5-20 wt%, Na ₂ O+K ₂ O: 2-15 wt%, Fe ₂ O ₃ : 1-10 wt%.

According to the above scheme, the foam ceramic blank uses any one or a mixture of CaCO ₃ , SiC, CaSO ₄ , graphite as a foaming agent, and the particle size of the powder is less than 80 μm.

According to the above scheme, the amount of water added is 6-12wt%, and the aging time is 24-48h.

According to the above scheme, cylindrical upright holes with a diameter of 15-25 mm are distributed in a staggered arrangement in the porous body; the porosity is 18-26%.

According to the above scheme, cylindrical upright holes with a diameter of 5-15mm arranged in parallel are distributed in the porous body; the porosity is 12-22%.

Use forming dies together with refractory pallets to press into porous blanks. When the compressed porous blanks are distributed with staggered cylindrical vertical holes with a diameter of 15-25 mm and the porosity is 18-26%, A-type foam ceramics can be obtained after firing. Porous blocks with staggered vertical holes, the diameter of the vertical holes is 10-20mm, the porosity is 12-26%, and the volume density is 350-500kg/m ³ . When parallel cylindrical vertical holes with a diameter of 5-15mm are distributed in the porous body, and the porosity is 12-22%, the B-type foam ceramics obtained after firing are solid blocks without vertical holes, and the volume density is 150-350kg/ ^m3 .

The preparation method of the foam ceramic block proposed by the patent of the present invention, through the design of the foam ceramic body with communicating holes, accelerates the penetration and discharge rate of the gas inside the body, and effectively solves the problem of internal and external performance of the product caused by the firing atmosphere. One problem, and shorten the firing cycle of foam ceramics.

Through the design of hole diameter and firing temperature, the retention form of green body vertical holes in the product can be controlled, and A-type blocks with vertical holes and B-type blocks without holes can be prepared respectively.

During the cooling process, the A-type porous block can use the convection method to quickly discharge the heat inside the green body, effectively reduce the temperature difference between the inside and outside of the product, and solve the problem of large-volume thick foam ceramics cooling and cracking. At the same time, compared with traditional porous bricks, the porous foam ceramic blocks prepared by this method have lower bulk density, outstanding thermal insulation performance, and lower water absorption rate. Material.

The positive effects of the present invention are:

1) The porous green body structure designed by the present invention accelerates the permeation and discharge of gas, promotes the oxidation and decomposition of minerals inside the green body, and realizes the rapid firing of large-volume foam ceramics.

2) The A-type porous ceramic foam block prepared by the method of the present invention quickly discharges the heat inside the green body through the airflow channel formed by the upright holes, reduces the temperature difference between the inside and outside of the foam ceramic during the cooling process, and effectively solves the problem caused by the temperature difference stress. cooling cracking problem.

3) The preparation method of the foamed ceramic block proposed by the present invention improves the production efficiency and product quality, and is beneficial to the large-volume application of tailings waste slag in the foamed ceramics. The prepared product integrates the advantages of foamed ceramics and porous bricks, and has the advantages of light weight, heat preservation, fire prevention, frost resistance, and aging resistance.

Description of drawings

Figure 1: Schematic diagram of the structure of the A-shaped green body;

Figure 2: Schematic diagram of the structure of the B-type green body;

Figure 3: Schematic of the pressure forming die.

detailed description

The following examples further illustrate the technical solutions of the present invention, but are not intended to limit the protection scope of the present invention.

Example 1

1) Take evenly mixed ceramic foam blanks with a particle size of less than 80 μm, spray evenly with 10wt% water, stale and homogenize for 48 hours, and lay them on a porous refractory pallet with a thickness of 150mm.

2) Place the refractory pallet covered with blanks on the bottom mold of the pressure forming machine, make the punching needle pass through the holes of the refractory pallet and the blank, and then apply a pressure of 1.0MPa with the porous pressing plate to place the blank in the refractory pallet Press to form the A-type porous body with a pore diameter of 20mm and a porosity of 21.3% as shown in Figure 1, and then remove the forming bottom mold and the porous pressing plate downwards and upwards respectively. The pressure forming mold used is shown in Figure 3. The forming mold consists of a bottom mold with punching needles and a porous pressing plate. After the pressing is completed, the bottom mold and the porous pressing plate are separated, and the porous green body is taken out together with the porous refractory supporting plate.

3) Dry the porous body at 60°C until the moisture content is <2%, and then place it in a high-temperature furnace together with the porous refractory plate, raise the temperature to the firing temperature at 5°C/min, and keep it warm for 40 minutes. After controlled cooling, the cooling rate is 1-10°C/min, and the cooling time is 6-10h.

4) After cooling down to below 50°C, remove the side plates and porous supporting plates, cut them into demoulding and cutting, and prepare A-type porous ceramic foam blocks with regularly arranged upright holes. The diameter of the upright holes is 16mm, the porosity rate is 13.6%.

Example 2

1) Take the foamed ceramic blanks that have been uniformly mixed and have a particle size of less than 80 μm, spray them with 8wt% water evenly, and after being stale and homogenized for 36 hours, lay them on a porous refractory pallet with a thickness of 200mm.

2) Put the refractory pallet covered with blanks on the bottom mold of the pressure forming machine, let the punching needle pass through the holes and blanks of the refractory pallet, and then apply a pressure of 0.5MPa with a porous pressing plate to place the blank in the refractory pallet Press it into a B-type porous body with a pore diameter of 10mm and a porosity of 16.2% as shown in Figure 2, and then remove the forming bottom mold and the porous pressing plate downwards and upwards, respectively. The pressure forming mold used is shown in Figure 3. The forming mold consists of a bottom mold with punching needles and a porous pressing plate. After the pressing is completed, the bottom mold and the porous pressing plate are separated, and the porous green body is taken out together with the porous refractory supporting plate.

3) Dry the porous green body together with the porous refractory pallet at 80°C until the moisture content is <2%, then place it in a high-temperature furnace, raise the temperature to the firing temperature at 5°C/min, and keep it warm for 1.5h. After controlled cooling, the cooling rate is 1-10°C/min, and the cooling time is 8-12h.

4) After cooling down to below 50°C, remove the side plates and porous support plates, cut them into demoulding and cutting, and prepare B-type foam ceramic blocks without vertical holes.

Claims (6)

1. A preparation method for ceramic foam insulation block, is characterized in that comprising the following steps: The uniformly mixed foam ceramic blanks are piled on porous refractory pallets after adding water, stirring, aging; Press the special molding die together with the refractory plate to form a porous green body; the forming die is composed of a bottom mold with punching needles and a porous pressing plate. Take out the pallet together; Dry until the moisture content is <2%, raise the temperature in a high-temperature furnace to 1050-1200°C at 3-5°C/min, and keep it warm for 0.5-1.5h to decompose the foaming agent to form pores; after cooling in the furnace, the porous layer will be removed from the refractory support plates, cut into foam ceramic blocks. 2. The preparation method of the ceramic foam insulation material according to claim 1, characterized in that the dry basis of the ceramic foam blank comprises SiO ₂ +Al ₂ O ₃ : 65-85wt%, CaO+MgO: 5-20wt%, Na ₂ O+K ₂ O: 2-15 wt%, Fe ₂ O ₃ : 1-10 wt%. 3. The preparation method of foamed ceramic insulation material as claimed in claim 1, characterized in that the foamed ceramic blank adopts foaming agent CaCO ₃ , SiC, CaSO ₄ , graphite or a mixture thereof, and the particle size of the powder particles is <80 μm . 4. The preparation method of the ceramic foam thermal insulation material according to claim 1, characterized in that the amount of water added is 6-12 wt%, and the aging time is 24-48 hours. 5. The preparation method of the foamed ceramic thermal insulation material according to claim 1, characterized in that cylindrical upright holes with a diameter of 15-25 mm are distributed in a staggered arrangement in the porous body; the porosity is 18-26%. 6. The preparation method of the foamed ceramic thermal insulation material according to claim 1, characterized in that cylindrical upright holes with a diameter of 5-15 mm are arranged in parallel in the porous body; the porosity is 12-22%.