CN107032809B

CN107032809B - Preparation method of composite ceramic slurry for preventing slag formation on heating surface of boiler

Info

Publication number: CN107032809B
Application number: CN201710355004.5A
Authority: CN
Inventors: 池作和; 潜培豪; 王进卿; 张光学; 李锦�
Original assignee: China Jiliang University
Current assignee: China Jiliang University
Priority date: 2017-05-19
Filing date: 2017-05-19
Publication date: 2020-02-18
Anticipated expiration: 2037-05-19
Also published as: CN107032809A

Abstract

The invention discloses a preparation method of composite ceramic slurry for preventing slag formation on a heating surface of a boiler, belonging to the technical field of special coating. The method comprises the steps of mixing hexagonal boron nitride, silicon nitride and a binder according to a certain proportion, and then placing the mixture in an environment of 700 ℃ to sinter the mixture into blocks. And then putting the product into a ball mill for crushing, mixing the obtained crushed material and the adhesive according to a certain proportion, then putting the mixture into an environment at 600 ℃ again for sintering into blocks, then putting the blocks into the ball mill for crushing again, finally mixing the crushed material and the adhesive according to a certain proportion, adding an auxiliary agent and deionized water, grinding the mixture by using a planetary ball mill, filtering and packaging. The slurry prepared by the method can form a compact ceramic coating after being coated on the heating surface of the boiler and sintered and cured, and can effectively prevent the heating surface from slagging.

Description

Preparation method of composite ceramic slurry for preventing slag formation on heating surface of boiler

Technical Field

The invention belongs to the technical field of special coatings, and particularly relates to a preparation method of a composite ceramic slurry for preventing slag formation on a heating surface of a boiler.

Background

Boiler slagging is a common problem encountered in the operation process of a coal-fired boiler and can seriously affect the stability and the economical efficiency of the operation of the boiler. The slagging can cause the increase of thermal resistance, the smoke temperature at the outlet of the hearth is higher, the phenomena of tube explosion and the like caused by overheating of a heating surface in a horizontal flue are easily caused, and meanwhile, the smoke discharge loss can be increased, so that the thermal efficiency of the boiler is reduced. The direct and indirect economic losses due to slagging are enormous each year.

At present, the technology for preventing the boiler from slagging mainly comprises optimizing the arrangement of a burner, increasing soot blowing, optimizing operation parameters and the like, but the method cannot fundamentally solve the problem of slagging of the boiler. The composite ceramic coating is a novel nano ceramic material, and can effectively prevent the heating surface from being polluted, corroded and abraded when being used on the heating surface of a boiler. However, its ability to prevent boiler slagging has yet to be improved.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide the preparation method of the composite ceramic slurry for preventing the slag from forming on the heating surface of the boiler.

The invention realizes the aim through the following technical scheme:

a preparation method of composite ceramic slurry for preventing slag formation on a heated surface of a boiler is characterized in that hexagonal boron nitride, silicon nitride and a binder are mixed according to a certain proportion, then the mixture is placed in an environment at 700 ℃ to be sintered into blocks, then a product is placed in a ball mill to be crushed, the obtained crushed material and the binder are mixed according to a certain proportion, then the mixture is placed in an environment at 600 ℃ again to be sintered into blocks, then the blocks are placed in the ball mill again to be crushed, finally the crushed material and the binder are mixed according to a certain proportion, an auxiliary agent and deionized water are added, and the mixture is ground by the ball mill and then filtered and packaged.

Preferably, the hexagonal boron nitride, the silicon nitride and the binder are uniformly mixed according to the mass ratio of 5:1:3, and are placed in a muffle furnace at 700 ℃ to be burned for 4 hours to form blocks. Cooling the mixture to room temperature along with a furnace, placing the product in a ball mill for crushing, uniformly mixing the obtained crushed material and a binder according to a mass ratio of 5:3, then placing the mixture in a muffle furnace at 600 ℃ again for firing for 4 hours to form blocks, cooling the mixture to room temperature along with the furnace, then placing the product in the ball mill for crushing, finally uniformly mixing the crushed material and the binder according to a mass ratio of 5:3, adding an auxiliary agent and deionized water, grinding for 4 hours by using a planetary ball mill, filtering and packaging.

In the preparation method, the binder is added and fully mixed for three times, so that the mixture of the hexagonal boron nitride and the silicon nitride is uniformly wrapped by the binder for three times. This enables the particles to be distributed more evenly in the slurry, greatly improving the structural strength of the coating.

The mixture is sintered into blocks at 700 ℃, the binder is added after ball milling and crushing, then the blocks are sintered at 600 ℃, and then ball milling and crushing are carried out, so that the cyclic sintering and crushing process can effectively strengthen the chemical bonds in the mixture, ensure that the mixture is combined with a metal matrix more firmly, and ensure that a coating is more compact.

As a preferable scheme, the preparation method uses hexagonal boron nitride and silicon nitride in a mass ratio of 5:1, the hexagonal boron nitride can effectively improve the anti-slagging capacity, and the silicon nitride is the aggregate of the composite ceramic slurry.

Preferably, in the above production method, the hexagonal boron nitride has an average particle size of 1 μm and the silicon nitride has an average particle size of 500 nm.

Preferably, in the above production method, the binder component is sodium water glass having a modulus of 3.0, and the sodium water glass has good adhesiveness.

In the preparation method, the used auxiliary agents preferably comprise a dispersant of stearamide, a defoaming agent of n-octanol and a rheological agent of organic bentonite. The stearamide can effectively prevent particles from settling, the n-octanol can effectively inhibit the generation of foam in the preparation process of the slurry, and the organic bentonite serving as a rheological agent can improve the stability of the slurry.

Preferably, in the preparation method, the dispersant stearamide accounts for 0.2-0.3% by mass, the defoamer n-octanol accounts for 0.15-0.25% by mass, and the rheological agent organobentonite accounts for 0.25-0.4% by mass.

Compared with the prior art, the invention has the following beneficial effects:

in the preparation method, the mixture of the hexagonal boron nitride, the silicon nitride and the adhesive is burned and crushed twice, the temperature of each burning is gradually reduced, the repeated process can ensure that the filler particles are uniformly coated with a plurality of layers of adhesives, and the slurry prepared by the method can strengthen the chemical bond between the coating particles and the matrix after being coated on the surface of the metal, so that the combination is firmer and is not easy to fall off. The ceramic aggregate is superfine powder, has larger specific surface area, and can enable the structure of the coating to be more compact after sintering and curing, thereby effectively preventing the erosion and the abrasion of the fly ash to the coating. The hexagonal boron nitride has stable chemical property and is inert to all molten metal chemistry, and the anti-slagging capability of the composite ceramic coating can be greatly improved.

In addition, the preparation method of the anti-slagging composite ceramic slurry provided by the invention is simple and feasible, has lower cost, and has better economical efficiency and operability compared with the ceramic coating which is expensive in price and complex in preparation method on the market. In the specific construction aspect, the slurry prepared by the invention is simple and convenient to spray, and the coating can be sintered and cured by using the heat generated during combustion of a boiler, so that the economy is greatly improved.

Drawings

FIG. 1 shows the surface contact angle of the materials characterized by the present invention

Schematic representation of (a).

FIG. 2 is a graph showing the alignment of two comparative examples of the present invention.

Detailed Description

The present invention will be described in further detail with reference to examples, but the present invention is not limited to the following examples.

Example 1:

uniformly mixing 100g of hexagonal boron nitride, 20g of silicon nitride and 60g of sodium silicate, placing the mixture in a muffle furnace at 700 ℃ to sinter into blocks, naturally cooling the blocks along with the furnace, and then carrying out ball milling and crushing in a ball mill for 1 hour. 170g of crushed powder is taken, 102g of sodium silicate is added, the mixture is uniformly mixed and then placed in a 600 ℃ muffle furnace to be sintered into blocks, and the blocks are naturally cooled along with the furnace and then are ball-milled and crushed in a ball mill for 1 hour. 260g of the secondarily crushed powder is taken, 156g of sodium water glass, 2.1g of stearamide, 1.6g of n-octanol, 2.6g of organic bentonite and 633.5g of deionized water are added, and the mixture is ground for 4 hours by a planetary ball mill, filtered and packaged.

The anti-slagging composite ceramic slurry prepared in the example 1 is coated on the surface of a 20G steel substrate commonly used for a boiler heating surface, and the anti-slagging performance of the composite ceramic slurry is tested.

The specific operation process of coating is as follows:

firstly, 20G sample steel sheet with the thickness of 20 multiplied by 2mm is subjected to surface sand blasting treatment, and then the composite ceramic slurry prepared in the embodiment 1 is uniformly sprayed on the surface of the sample, wherein the spraying thickness is about 60-80 μm. After the spraying is finished, placing the sample in a muffle furnace for heating and curing, wherein the specific heating process is as follows: heating from room temperature to 120 ℃ at the speed of 5 ℃/min, keeping the temperature for 2 hours, heating from 120 ℃ to 500 ℃ at the speed of 5 ℃/min, keeping the temperature for 4 hours, and cooling to room temperature along with the furnace. The purpose of using this heat curing method is to simulate the temperature rise process of the water wall when the boiler is started.

The contact angle is an important parameter for characterizing the surface energy of a material, and the surface energy is a main factor influencing slag bonding. Therefore, the contact angle measurement method is adopted to carry out the anti-slagging performance test on the coating sample after heating and curing, and the larger the contact angle is, the better the anti-slagging performance of the material is.

Lower view of

I.e. the contact angle.

The specific test process is as follows:

2 parts of glass powder with the mass of 1G are respectively pressed into cylinders with the same shape, the cylinders are respectively placed on a coating sample and a 20G substrate with the size of 20 multiplied by 2mm and the surface subjected to sand blasting, the samples are simultaneously placed in a muffle furnace for heating, and the change condition of contact angles at different temperatures is observed. Soot is simulated herein with glass soot because the composition of glass soot is similar to soot.

The results of the test are shown in FIG. 2 below:

it can be obviously seen that the contact angle of the molten liquid drop on the coating sample on the right side is larger than that of the molten liquid drop on the left side, which indicates that the nano ceramic slurry prepared by the method has excellent anti-slagging property.

The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of composite ceramic slurry for preventing slag formation on a heated surface of a boiler is characterized by uniformly mixing hexagonal boron nitride, silicon nitride and a binder in a mass ratio of 5:1:3, then placing the mixture in a muffle furnace at 700 ℃ for sintering for 3-5 hours to form a block, placing the sintered product in a ball mill for crushing, uniformly mixing the obtained crushed material and the binder in a mass ratio of 5:3, then placing the mixture in the muffle furnace at 600 ℃ for sintering for 3-5 hours to form a block, placing the block in the ball mill for crushing, finally uniformly mixing the crushed material and the binder in a mass ratio of 5:3, adding an auxiliary agent and deionized water, grinding for 4 hours, and then filtering and packaging.

2. The method according to claim 1, wherein the block is sintered in a muffle furnace at 700 ℃ for 4 hours, and sintered in a muffle furnace at 600 ℃ for 4 hours.

3. The method of preparing a slag bonding-preventing composite ceramic slurry according to claim 1, wherein the average particle size of the hexagonal boron nitride is 1 μm, and the average particle size of the silicon nitride is 500 nm.

4. The method according to claim 1, wherein the binder used is sodium water glass having a modulus of 3.0.

5. The preparation method according to claim 1, wherein the auxiliary agent comprises 0.2-0.3% by mass of stearamide as a dispersant, 0.15-0.25% by mass of n-octanol as a defoaming agent, and 0.25-0.4% by mass of organobentonite as a rheological agent.

6. The method according to claim 1, wherein the deionized water is 60% by mass.