CN102276239A - Heat exchanger ceramic material for bulk tobacco flue-curing house and preparation method thereof - Google Patents

Abstract

The invention relates to a heat exchanger ceramic material for a dense flue-cured room and a preparation method thereof. A heat exchanger ceramic material for dense flue-cured rooms, characterized in that it is prepared from batch materials, water and dispersants, and the mass percentages of each component are: batch materials 64.25-75%, water 24.25-35%, Dispersant 0.75-1.25%; The batching material includes Yuan'an soil, bauxite, purple wood knot, wollastonite and talc, and the mass percentage of each raw material in the batching material is: Yuan'an soil 10-23%, bauxite 33-50%, purple wood knot 34-42%, wollastonite 1-3%, talc 5-8%. The heat exchanger ceramic material has the characteristics of high strength, high density, high thermal conductivity and good thermal shock resistance.

Description

A kind of heat exchanger ceramic material for intensive flue-cured tobacco room and its preparation method

technical field

The invention relates to a heat exchanger ceramic material for a dense flue-cured room and a preparation method thereof.

Background technique

As an advanced form of tobacco leaf curing at present and in the future, intensive curing barns will be fully promoted, and the scale will reach 810,000 in the country within three years. At present, my country's intensive flue-cured tobacco rooms mainly use steel heat exchangers with poor corrosion resistance, and the fuel is mainly coal. The sulfur-containing flue gas produced after coal combustion is extremely corrosive to the heat exchanger, so the use of steel heat exchangers Shorter lifespan. However, if an acid-resistant alloy steel heat exchanger is used, its price is high, and the comprehensive cost of flue-cured tobacco is greatly improved. The high-temperature creep performance of the metal heat exchanger is poor, which also makes the heat of the flue gas in the high-temperature section unusable, thereby reducing the thermal efficiency.

Among the ceramic materials, silicon carbide, silicon nitride and boron nitride have been reported to be used as heat exchanger materials, but the cost of raw materials is high, the sintering temperature is high, the molding is complicated, and the requirements for production equipment are high. At the current stage of my country's economic and technological level If it is still low, it cannot be used in large-scale production.

Alumina ceramics is a material that has been widely used. People know very well about its microstructure and production process. Although its thermal conductivity is lower than that of silicon carbide and other ceramics, it is also lower than that of metal materials, but alumina ceramics has its unique characteristics. advantage. Compared with ceramics such as silicon carbide, its raw materials have a wide range of sources, low cost, simple molding, and low firing temperature; compared with metal materials, it has good chemical stability and strong oxidation and corrosion resistance, so maintenance and management costs are low, and excellent high temperature creep The performance enables it to make full use of the heat of the flue gas in the high temperature section, thereby greatly improving the heat utilization efficiency.

The disadvantage of alumina ceramics as heat exchangers is their poor thermal shock resistance, but this can be compensated by introducing materials with low expansion and good thermal stability. The thermal expansion coefficient of cordierite is 2.04×10 ^-6 (20～800℃), and its thermal shock resistance is very good. It is a good thermal shock resistant material, but the price of industrial cordierite is relatively high, and the synthesis cost of using natural minerals is relatively low. .

Contents of the invention

The object of the present invention is to provide a heat exchanger ceramic material for dense flue-cured tobacco room and its preparation method. The heat exchanger ceramic material has the characteristics of high strength, high density, high thermal conductivity and good thermal shock resistance.

In order to achieve the above object, the technical solution adopted by the present invention is: a kind of heat exchanger ceramic material for intensive flue-cured tobacco room, it is characterized in that it is prepared from batch material, water and dispersant, and the mass percentage that each component accounts for is : Batch material 64.25-75%, water 24.25-35%, dispersant 0.75-1.25%;

The batching materials include Yuan'an soil, bauxite, purple wood knot, wollastonite and talc, and the mass percentages of each raw material in the batch are: Yuan'an soil 10-23%, bauxite 33-50%, purple wood Knot 34-42%, wollastonite 1-3%, talc 5-8%.

The said Yuan'an soil is the soil of Yuan'an County, Hubei Province.

The dispersant is hexametaphosphoric acid.

The above-mentioned preparation method of a heat exchanger ceramic material for a dense flue-cured room is characterized in that it comprises the following steps:

1) Preparation of batch materials: according to the mass percentage of each raw material in the batch materials: Yuan'an soil 10-23%, bauxite 33-50%, purple wood knot 34-42%, wollastonite 1-3%, Talc 5-8%, select Yuan'an soil, bauxite, purple wood knot, wollastonite and talc;

The Yuan'an soil, bauxite, purple wood knot, wollastonite and talc are all ground in a ball mill with water, dried and passed through a 300-mesh sieve, and then mixed to obtain batch materials;

2) Preparation of slurry: according to the mass percentage of each component: batch material 64.25-75%, water 24.25-35%, dispersant 0.75-1.25%, select batch material, water and dispersant; mix the batch material in Add water and dispersant to ball mill and mill for 3-5 hours to obtain slurry;

3) Molding: After ball milling and mixing are completed and the slurry is stale for 24 hours, inject the stale slurry into the plaster mold for grouting (control the slurry to obtain a product of a certain shape). After the moisture content of the body is lower than 20%, the mold is demoulded to obtain a green body after demoulding;

4) Drying: place the demoulded green body in a drying chamber and dry at a constant temperature of 80-100°C for 12 hours to obtain a dried green body;

5) Firing: The dried green body is fired in a tunnel kiln with an oxidizing flame, the firing temperature is 1150-1300°C, the firing cycle is 9-11 hours, and it is stacked out of the kiln to obtain heat exchange for a dense flue-cured room. ceramic materials.

The present invention uses purple wood knot, bauxite, faran soil, wollastonite and talc as main raw materials, and obtains a green body with high strength and good plasticity through traditional ball mill mixing and grouting molding, and obtains it through reasonable heat treatment after drying. Ceramic products of all sizes and shapes. For the heat exchanger ceramic material, the heat conduction base is alumina, which is provided by aluminum-containing raw materials; the thermal shock resistance base is cordierite, which is synthesized in situ by various raw materials during heat treatment, and is firmly combined with the alumina crystal microscopically, so that it can effectively guarantee High thermal conductivity and excellent thermal shock resistance of ceramic materials.

The advantages of the present invention are:

1) The prepared ceramic heat exchanger products for intensive flue-cured tobacco rooms have high strength (bending resistance 220-250Mpa), high density (2.70-2.98g/cm ³ ), and high thermal conductivity (research and testing of materials in Wuhan University of Technology The central test thermal conductivity is: 3.1-5.52W/m·℃), the thermal expansion coefficient is small, the thermal shock resistance is good, the high temperature creep performance is good, the maximum working temperature can reach 1200 ℃, and the comprehensive performance far exceeds that of the currently used metals. heat exchanger material.

2) Most of the required raw materials are natural minerals, the cost is low, and the molding process is simple. There is no special requirement for the production equipment. The firing temperature is consistent with that of ordinary daily-use ceramics. It can be mass-produced in the daily-use ceramic production line, so its The comprehensive cost is low, which is conducive to extensive popularization and application under the current national conditions.

The invention effectively overcomes the disadvantages of poor corrosion resistance and oxidation resistance, high thermal expansion coefficient, short service life and high production cost of existing metal heat exchanger materials.

Detailed ways

In order to better understand the present invention, the content of the present invention is further illustrated below in conjunction with the examples, but the content of the present invention is not limited to the following examples.

Example 1:

A method for preparing a heat exchanger ceramic material for a dense flue-cured room, comprising the steps of:

1) Preparation of batch materials: according to the mass percentages of each raw material in the batch materials: Yuanan soil 15%, bauxite 40%, purple wood knot 38%, wollastonite 2%, talc 5%, select Yuanan soil, bauxite, purple wood knot, wollastonite and talc;

The said Yuan'an soil is the soil of Yuan'an County, Hubei Province.

The dispersant is hexametaphosphoric acid.

The raw material source used in the present invention and main chemical composition are shown in Table 1:

The chemical composition (mass percentage composition) of each raw material of table 1

chemical components SiO ₂ Al ₂ O ₃ MgO CaO _{Fe2O3 _} TiO ₂ Loss on ignition origin Far Antu 46.23 41.78 0.11 0.19 0.20 0.20 11.29 Hubei Yuan'an Bauxite 8.69 73.00 0.23 - 1.06 2.45 14.57 Shanxi Xiaoyi Purple Wood Festival 45.22 34.67 0.06 0.64 1.46 1.46 16.49 Hubei Yichang wollastonite 50.34 0.46 1.00 44.90 0.82 0.01 2.47 Hubei Daye Talc 45.85 0.08 24.68 10.47 1.21 1.21 16.5 Guangxi Third Ring Road

The Yuan'an soil, bauxite, purple wood knot, wollastonite and talc are all ground in a ball mill with water, dried and passed through a 300-mesh sieve, and then mixed to obtain batch materials;

2) Preparation of slurry: according to the mass percentage of each component: batch material 74.25%, water 25%, dispersant 0.75%, select batch material, water and dispersant; add water and dispersant to the batch material in a ball mill Ball milling for 5 hours to obtain slurry;

3) Molding: After ball milling and mixing are completed and the slurry is stale for 24 hours, inject the stale slurry into the plaster mold for grouting (control the slurry to obtain a product of a certain shape). After the moisture content of the body is lower than 20%, the mold is demoulded to obtain a green body after demoulding;

4) Drying: place the demoulded green body in a drying chamber to dry for 12 hours (dry at a constant temperature of 90°C) to obtain a dried green body;

5) Firing: The dried green body is fired in a tunnel kiln with an oxidizing flame at a firing temperature of 1300°C and a firing cycle of 9 to 11 hours. It is stacked out of the kiln to obtain heat exchanger ceramics for dense flue-cured rooms. Materials (finished product).

Carry out firing under following firing system:

The obtained heat exchanger ceramic material for dense flue-cured rooms has high strength (bending resistance 220-250Mpa), density 2.86g/cm ³ , thermal conductivity 4.82W/m·℃, and thermal shock resistance up to YB/T376.3 standard Requirements, indicating that the thermal shock resistance is good. The maximum working temperature can reach 1200℃.

In this example, a ceramic factory in Yidu City, Hubei Province relied on the existing production equipment to carry out industrialized pilot production of various components of the heat exchanger. During production, it was found that its forming performance was good, the sintering was thorough, and the bending deformation of large-sized products was extremely small. Afterwards, each component was installed in a tobacco leaf company in Lichuan City, Hubei Province and a two-week flue-cured tobacco test was carried out. The test proved that the heat exchanger operated normally and the flue-cured tobacco effect was good, achieving the established goal of reducing fuel consumption while maintaining a high level of flue-cured tobacco. Target.

Example 2:

A method for preparing a heat exchanger ceramic material for a dense flue-cured room, comprising the steps of:

1) Preparation of batch materials: According to the mass percentages of each raw material in the batch materials: Yuanan soil 10%, bauxite 50%, purple wood knot 34%, wollastonite 1%, talc 5%, select Yuanan soil, bauxite, purple wood knot, wollastonite and talc;

The Yuan'an soil, bauxite, purple wood knot, wollastonite and talc are all ground in a ball mill with water, dried and passed through a 300-mesh sieve, and then mixed to obtain batch materials;

Described Yuan'an soil is the soil of Yuan'an County, Hubei Province;

Described dispersant is hexametaphosphoric acid;

2) Preparation of slurry: according to the mass percentage of each component: batch material 64.25%, water 35%, dispersant 0.75%, select batch material, water and dispersant; add water and dispersant to the batch material in a ball mill Ball milling for 3 hours to obtain slurry;

3) Molding: After ball milling and mixing are completed and the slurry is stale for 24 hours, inject the stale slurry into the plaster mold for grouting (control the slurry to obtain a product of a certain shape). After the moisture content of the body is lower than 20%, the mold is demoulded to obtain a green body after demoulding;

4) Drying: place the demoulded green body in a drying chamber to dry for 12 hours (dry at a constant temperature of 80°C) to obtain a dried green body;

5) Firing: The dried green body is fired in a tunnel kiln with an oxidizing flame at a firing temperature of 1150°C and a firing cycle of 9 hours, and is stacked out of the kiln to obtain ceramic materials for heat exchangers for dense flue-cured rooms.

The prepared ceramic heat exchanger products for dense flue-cured rooms have high strength (bending resistance 220-250Mpa), high density (2.98g/cm ³ ), high thermal conductivity (5.52W/m·℃), and thermal shock resistance Meet the requirements of the YB/T376.3 standard, the maximum working temperature can reach 1200 ℃, and the comprehensive performance far exceeds the currently used metal heat exchanger materials.

Example 3:

A method for preparing a heat exchanger ceramic material for a dense flue-cured room, comprising the steps of:

1) Preparation of batch materials: according to the mass percentages of each raw material in the batch materials: Yuanan soil 14%, bauxite 33%, purple wood knot 42%, wollastonite 3%, talc 8%, select Yuanan soil, bauxite, purple wood knot, wollastonite and talc;

The Yuan'an soil, bauxite, purple wood knot, wollastonite and talc are all ground in a ball mill with water, dried and passed through a 300-mesh sieve, and then mixed to obtain batch materials;

Described Yuan'an soil is the soil of Yuan'an County, Hubei Province;

Described dispersant is hexametaphosphoric acid;

2) Preparation of slurry: according to the mass percentage of each component: batch material 75%, water 24.25%, dispersant 0.75%, select batch material, water and dispersant; add water and dispersant to the batch material in a ball mill Ball milling for 5 hours to obtain slurry;

3) Molding: After ball milling and mixing are completed and the slurry is stale for 24 hours, inject the stale slurry into the plaster mold for grouting (control the slurry to obtain a product of a certain shape). After the moisture content of the body is lower than 20%, the mold is demoulded to obtain a green body after demoulding;

4) Drying: place the demoulded green body in a drying chamber to dry for 12 hours (dry at a constant temperature of 80°C) to obtain a dried green body;

5) Firing: The dried green body is fired in a tunnel kiln with an oxidizing flame at a firing temperature of 1300°C and a firing cycle of 11 hours. It is stacked out of the kiln to obtain ceramic materials for heat exchangers for dense flue-cured rooms.

The prepared ceramic heat exchanger products for dense flue-cured rooms have high strength (bending resistance 220-250Mpa), high density (2.70g/cm ³ ), high thermal conductivity (3.1W/m·℃), and thermal shock resistance Meet the requirements of the YB/T376.3 standard, the maximum working temperature can reach 1200 ℃, and the comprehensive performance far exceeds the currently used metal heat exchanger materials.

Example 4:

A method for preparing a heat exchanger ceramic material for a dense flue-cured room, comprising the steps of:

1) Preparation of batch materials: according to the mass percentages of each raw material in the batch materials: Yuanan soil 23%, bauxite 33%, purple wood knot 36%, wollastonite 2%, talc 6%, select Yuanan soil, bauxite, purple wood knot, wollastonite and talc;

The Yuan'an soil, bauxite, purple wood knot, wollastonite and talc are all ground in a ball mill with water, dried and passed through a 300-mesh sieve, and then mixed to obtain batch materials;

Described Yuan'an soil is the soil of Yuan'an County, Hubei Province;

Described dispersant is hexametaphosphoric acid;

2) Preparation of slurry: according to the mass percentage of each component: batch material 69.5%, water 29.25%, dispersant 1.25%, select batch material, water and dispersant; add water and dispersant to the batch material in a ball mill Ball milling for 4 hours to obtain slurry;

3) Molding: After ball milling and mixing are completed and the slurry is stale for 24 hours, inject the stale slurry into the plaster mold for grouting (control the slurry to obtain a product of a certain shape). After the moisture content of the body is lower than 20%, the mold is demoulded to obtain a green body after demoulding;

4) Drying: place the demoulded green body in a drying chamber to dry for 12 hours (dry at a constant temperature of 100°C) to obtain a dried green body;

5) Firing: The dried green body is fired in a tunnel kiln with an oxidizing flame at a firing temperature of 1200°C and a firing cycle of 10 hours, and is stacked out of the kiln to obtain ceramic materials for heat exchangers for dense flue-cured rooms.

The prepared ceramic heat exchanger products for dense flue-cured rooms have high strength (bending resistance 220-250Mpa), high density (2.70g/cm ³ ), high thermal conductivity (3.1W/m·℃), and thermal shock resistance Meet the requirements of the YB/T376.3 standard, the maximum working temperature can reach 1200 ℃, and the comprehensive performance far exceeds the currently used metal heat exchanger materials.

Claims (4)

1. A heat exchanger ceramic material for dense flue-cured rooms, characterized in that it is prepared from batch materials, water and dispersants, and the mass percentages of each component are: batch materials 64.25-75%, water 24.25-35% %, dispersant 0.75~1.25%; The batching materials include Yuan'an soil, bauxite, purple wood knot, wollastonite and talc, and the mass percentages of each raw material in the batch are: Yuan'an soil 10-23%, bauxite 33-50%, purple wood Knot 34-42%, wollastonite 1-3%, talc 5-8%. 2. A heat exchanger ceramic material for a dense flue-cured room according to claim 1, characterized in that: said Yuan'an soil is the soil of Yuan'an County, Hubei Province. 3. A heat exchanger ceramic material for a dense tobacco flue-curing room according to claim 1, characterized in that: said dispersant is hexametaphosphoric acid. 4. the preparation method of a kind of intensive tobacco flue-cured room heat exchanger ceramic material as claimed in claim 1, is characterized in that it comprises the steps: 1) Preparation of batch materials: according to the mass percentage of each raw material in the batch materials: Yuan'an soil 10-23%, bauxite 33-50%, purple wood knot 34-42%, wollastonite 1-3%, Talc 5-8%, select Yuan'an soil, bauxite, purple wood knot, wollastonite and talc; The Yuan'an soil, bauxite, purple wood knot, wollastonite and talc are all ground in a ball mill with water, dried and passed through a 300-mesh sieve, and then mixed to obtain batch materials; 2) Preparation of slurry: according to the mass percentage of each component: batch material 64.25-75%, water 24.25-35%, dispersant 0.75-1.25%, select batch material, water and dispersant; mix the batch material in Add water and dispersant to the ball mill and mill for 3-5 hours to obtain the slurry; 3) Molding: After ball milling and mixing are completed and the slurry is stale for 24 hours, inject the stale slurry into a gypsum mold for grouting molding, demoulding, and obtain a green body after demoulding; 4) Drying: place the demoulded green body in a drying room at a constant temperature of 80-100°C and dry for 12 hours to obtain a dried green body; 5) Firing: The dried green body is fired in a tunnel kiln with an oxidizing flame, the firing temperature is 1150-1300°C, the firing cycle is 9-11 hours, and it is stacked out of the kiln to obtain heat exchange for a dense flue-cured room. ceramic materials.