CN115504803A - A kind of fly ash-based cordierite honeycomb ceramic and its preparation method - Google Patents

Abstract

The invention relates to a fly ash based cordierite honeycomb ceramic and a preparation method thereof. The invention has the beneficial effects that: the invention has high fly ash mixing amount, low additive introduction amount and low sintering temperature, thereby having lower cost; in addition, the added binder dispersant and the like remarkably improve the dispersibility of the pug through the effects of steric hindrance and the like on all components in the powder, so that the pug has excellent and stable plasticity and water retention, high solid content, easy extrusion and high yield; and the rare earth fluoride auxiliary agent is added, so that the thermal and mechanical properties of the ceramic are excellent.

Description

A kind of fly ash-based cordierite honeycomb ceramic and its preparation method

technical field

The invention relates to the field of high-value application of coal-based solid waste and the preparation of ceramic regenerators, more precisely, it relates to a fly ash-based cordierite honeycomb ceramic and a preparation method thereof.

Background technique

At present, electric energy mainly comes from thermal power generation. The coal used for thermal power generation is mostly pulverized coal after mechanical crushing, and these pulverized coal will produce a certain amount of fly ash after full combustion. Although some progress has been made in the resource utilization of fly ash in recent years, most of the fly ash can only be piled up around power plants, occupying a large amount of land resources. In addition, waste fly ash can also cause dust pollution, water pollution and soil pollution.

The main chemical components of fly ash are SiO ₂ , Al ₂ O ₃ and Fe ₂ O ₃ , accounting for about 70% of the total, and other components such as CaO, MgO and trace elements account for about 30%. Obviously, fly ash is a secondary resource with rich application potential. At present, fly ash is often used as building materials, soil improvement, and backfilling of pits/shafts, etc., and the comprehensive utilization technology and level are relatively low. At the same time, with the gradual saturation of the building materials market, the improvement of agricultural soil standards, and the serious constraints of regional factors on backfilling of mine pits, the comprehensive utilization rate of fly ash has always been low. Utilizing fly ash to develop new structural functional materials with high added value is an important way and research hotspot to realize the high value utilization of fly ash.

The molecular formula of cordierite is 2MgO·2A1 ₂ O ₃ ·5SiO ₂ , which is an important ceramic material with advantages such as large specific heat capacity, low thermal expansion coefficient and good thermal shock resistance. Cordierite is widely used as regenerator material, high-temperature structural ceramics, catalyst carrier, bioceramics, etc. Fly ash can be used to synthesize cordierite because of its rich Al and Si resources. However, fly ash contains a variety of impurities. On the one hand, these impurity ions may replace the Mg ²⁺ or Al ³⁺ ions in cordierite, inhibiting the formation of cordierite phase, and on the other hand, excessive The glass phase reduces the thermal and mechanical properties of the material. In addition, as a barren material, fly ash has poor formability, so it is difficult to obtain high-quality ceramic blanks by extrusion.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies in the prior art and provide a fly ash-based cordierite honeycomb ceramic and a preparation method thereof.

In the first aspect, a fly ash-based cordierite honeycomb ceramic is provided, which is made of fly ash and other inorganic ingredients plus binder, plasticizer, dispersant and water; the fly ash is pretreated , the other inorganic ingredient powders include talc, alumina, silicon oxide and rare earth additives; the total mass content of fly ash and other inorganic ingredient powders is 100%, wherein pre-treated fly ash accounts for 20-70% %, talc 10-40%, alumina 5-20%, silicon oxide 0-30%, rare earth additives 0.2-3.0%; binder, plasticizer, dispersant and water are added It is 2-10%, 3-10%, 0.1-3% and 13-30% of the total mass of fly ash and other inorganic ingredient powders.

Preferably, the rare earth additive is one or more of lanthanum fluoride, cerium fluoride, europium fluoride and yttrium fluoride; the binder is starch, dextrin, methyl cellulose, hydroxyl One or more of propyl cellulose, hydroxymethyl cellulose, and paraffin; the plasticizer is one or more of glycerin, dibutyl phthalate, and oxalic acid; the dispersant is oil One or more of acid, simethicone, polyvinyl alcohol, polyacrylic acid and its salt, citric acid and its salt, sodium dodecylbenzenesulfonate, triethanolamine, and ethylene glycol.

The second aspect provides a method for preparing fly ash-based cordierite honeycomb ceramics as described in the first aspect, including:

S1. Treat fly ash in 1-30wt% hydrochloric acid or nitric acid solution for 0.5-3h, wash with water until neutral, and dry;

S2. Mix the pretreated fly ash with other inorganic ingredient powders in proportion, and perform dry ball milling;

S3, mixing the mixed powder in S2 in a strong mixer, and then adding a binder, a plasticizer, a dispersant and water, and kneading;

S4. After the kneaded material is stale and smelted, it is continuously extruded at 8-25MPa, and the vacuum degree is 0.09-0.1MPa;

S5. After drying the obtained honeycomb ceramic green body at 40-120° C., sintering at 1200-1450° C., the heating rate is 1-5° C./min, and the holding time is 1-4 hours.

The beneficial effects of the present invention are:

(1) Low raw material cost, stable process and high yield. In the present invention, the amount of fly ash is high, the amount of additives is low, and the sintering temperature is low, so the cost is low; in addition, the added binder dispersant etc. can significantly affect the steric hindrance of each component in the powder. Improve the dispersibility of the mud, so that the mud has excellent plasticity and water retention, high solid content, easy extrusion, and high yield.

(2) Excellent thermal and mechanical properties of ceramics. The rare earth fluoride additive added in the present invention, due to the special lattice distortion produced by rare earth ions, can promote the stepwise phase transition in the process of generating cordierite from fly ash; in addition, some decomposition products can also be combined with specific elements in other raw materials The reaction takes place to generate a high temperature liquid phase which facilitates mass transfer and sintering. The above mechanisms work together to significantly increase the material density, increase the compressive strength, and reduce the coefficient of thermal expansion.

Description of drawings

Fig. 1 is a flow chart of a preparation method of fly ash-based cordierite honeycomb ceramics.

detailed description

The present invention will be further described below in conjunction with the examples. The description of the following examples is provided only to aid the understanding of the present invention. It should be pointed out that for those skilled in the art, some modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

The embodiment of the present invention adopts the fly ash of a domestic coal-fired power plant. The chemical composition of the fly ash is: SiO ₂ : 48.77%, Al ₂ O ₃ : 31.56%, Fe ₂ O ₃ : 5.57%, CaO: 5.98%, TiO ₂ : 1.64%, MgO: 0.75%, SO ₃ : 0.19%.

Example 1

Weigh 12kg of fly ash, add 40L of 2mol/L HCl solution, stir and react at 80°C for 2h, wash and dry. Prepare a total of 20kg of powder with the treated fly ash, talc, alumina, silicon oxide, and lanthanum fluoride at a mass ratio of 50:33:15:2:0.5, and add zirconia balls according to the material-ball ratio of 3:1 Mix and ball mill for 1h. Add 1 kg of binder (hydroxypropyl methylcellulose), 0.6 kg of plasticizer (dibutyl phthalate), 0.04 kg of citric acid, and 4 kg of water to the above mixture, and mix vigorously for 30 minutes.

After aging the above mud overnight, extrude it with a vacuum mud mixer with a vacuum degree of 0.095 MPa, use a square-hole honeycomb ceramic mold, continuously extrude it at 20 MPa, and cut it with a molybdenum wire to obtain a honeycomb ceramic green body.

After the above-mentioned shaped blanks were left at room temperature overnight, they were dried in an oven at 60°C and 110°C for 2 hours to remove the remaining moisture.

Place the dried green embryo above in a muffle furnace, raise the temperature to 60°C at a rate of 2°C/min and keep it for 2 hours in an air atmosphere, then raise the temperature to 1300°C at a rate of 2°C/min and hold it for 2 hours, and sinter to obtain cordierite Honeycomb ceramics.

According to tests, the cordierite ceramics of the present invention has a bulk density of 2.05g/cm ³ and an average thermal expansion coefficient of 2.36×10 ^-6 /°C at RT-800°C, showing good overall performance.

Example 2

The introduction amount of lanthanum fluoride was increased to 1.0 wt.%, and the process of Example 1 was repeated.

After testing, the cordierite ceramics of the present invention has a bulk density of 2.23 g/cm ³ .

Example 3

The introduction amount of lanthanum fluoride was increased to 1.5wt.%, and the process of Example 1 was repeated.

After testing, the cordierite ceramics of the present invention has a bulk density of 2.26 g/cm ³ . Comparing Comparative Examples 1-3, it can be seen that with the increase of the added amount of lanthanum fluoride, the densification degree of cordierite ceramics gradually increases.

Comparative example 1

The amount of lanthanum fluoride introduced was reduced to 0wt.%, and the process of Example 1 was repeated.

After testing, the cordierite ceramics of the present invention has a bulk density of 2.01g/cm ³ and a thermal expansion coefficient of 2.98×10 ^-6 /°C. Compared with Comparative Example 1, the bulk density of Examples 1-3 has increased, and the average thermal expansion coefficient of Example 1 has increased by 20.81% compared with Comparative Example 1 at RT-800 ° C, indicating that the addition of lanthanum fluoride can promote sintering and reduce Average coefficient of thermal expansion.

Comparative example 2

Replace lanthanum fluoride with aluminum fluoride, and repeat the process of Example 1.

After testing, the cordierite ceramics of the present invention has a bulk density of 2.02 g/cm ³ and a thermal expansion coefficient of 2.89×10 ^-6 /°C. The bulk density of Comparative Example 2 is higher than that of Comparative Example 1, but lower than that of Example 1. The coefficient of thermal expansion of Comparative Example 2 is also between Comparative Example and Example 1. This shows that the addition of aluminum fluoride has an effect on promoting sintering and improving thermal performance, but at the same addition amount, its effect is lower than that of lanthanum fluoride.

In summary, the present invention provides a method for preparing high-quality cordierite honeycomb ceramic regenerator by continuous extrusion of fly ash. The method has simple process, low raw material cost, good process repeatability, and the prepared cordierite honeycomb ceramic Excellent thermal and mechanical properties.

Claims (3)

1. A fly ash-based cordierite honeycomb ceramic is characterized in that it is made of fly ash and other inorganic ingredient powders with external binding agent, plasticizer, dispersant and water; the fly ash is pretreated , the other inorganic ingredient powders include talc, alumina, silicon oxide and rare earth additives; the total mass content of fly ash and other inorganic ingredient powders is 100%, wherein pre-treated fly ash accounts for 20-70% %, talc 10-40%, alumina 5-20%, silicon oxide 0-30%, rare earth additives 0.2-3.0%; binder, plasticizer, dispersant and water are added It is 2-10%, 3-10%, 0.1-3% and 13-30% of the total mass of fly ash and other inorganic ingredient powders. 2. The fly ash-based cordierite honeycomb ceramics according to claim 1, wherein the rare earth additives are one or more of lanthanum fluoride, cerium fluoride, europium fluoride and yttrium fluoride species; the binder is one or more of starch, dextrin, methyl cellulose, hydroxypropyl cellulose, hydroxymethyl cellulose, paraffin; the plasticizer is glycerin, phthalic acid One or more of dibutyl ester and oxalic acid; the dispersant is oleic acid, simethicone, polyvinyl alcohol, polyacrylic acid and its salt, citric acid and its salt, sodium dodecylbenzenesulfonate , triethanolamine, ethylene glycol in one or more. 3. a preparation method of fly ash base cordierite honeycomb ceramics as claimed in claim 1, is characterized in that, comprises: S1. Treat fly ash in 1-30wt% hydrochloric acid or nitric acid solution for 0.5-3h, wash with water until neutral, and dry; S2. Mix the pretreated fly ash with other inorganic ingredient powders in proportion, and perform dry ball milling; S3, mixing the mixed powder in S2 in a strong mixer, and then adding a binder, a plasticizer, a dispersant and water, and kneading; S4. After the kneaded material is stale and smelted, it is continuously extruded at 8-25MPa, and the vacuum degree is 0.09-0.1MPa; S5. After drying the obtained honeycomb ceramic green body at 40-120° C., sintering at 1200-1450° C., the heating rate is 1-5° C./min, and the holding time is 1-4 hours.

Images