CN113004724A

CN113004724A - Coating for inhibiting furnace tube coking and preparation method thereof

Info

Publication number: CN113004724A
Application number: CN202110248355.2A
Authority: CN
Inventors: 刘京雷; 王响响; 王浩; 徐宏
Original assignee: East China University of Science and Technology
Current assignee: East China University of Science and Technology
Priority date: 2021-03-08
Filing date: 2021-03-08
Publication date: 2021-06-22

Abstract

The invention relates to a coating for inhibiting furnace tube coking and a preparation method thereof, in particular to a silica coating prepared on the surface of a material by a sol-gel method. The coating prepared by the invention effectively isolates the direct contact of materials and the furnace tube substrate, inhibits the occurrence of metal vulcanization reaction and coke adhesion reaction, has lower surface energy and smaller roughness, ensures that the coke is not easy to deposit on the surface of the coating, and has obvious effect of inhibiting coking.

Description

Coating for inhibiting furnace tube coking and preparation method thereof

[ technical field ] A method for producing a semiconductor device

The invention relates to the technical field of workpiece surface coatings, in particular to a coating for inhibiting furnace tube coking and a preparation method thereof.

[ background of the invention ]

In petrochemical industry, hydrocarbon materials and the like are coked and deposited on the inner wall surface of a pipe under high temperature conditions due to free radical coking, intermediate phase coking, vulcanization coking and the like. Coking can cause the temperature of the tube wall of the furnace tube to rise and the heat transfer coefficient to be reduced, and the coke cleaning needs to be carried out by periodically stopping production, thereby influencing the long-period continuous operation of the device, increasing the energy consumption and influencing the economic benefit of the device.

In response to the coking phenomenon, techniques such as adding inhibitors to the feedstock, feedstock upgrading, optimizing furnace tube structure, etc., have been used to inhibit furnace tube coking. The patent discloses a coating for inhibiting furnace tube coking and a preparation technology thereof.

[ summary of the invention ]

The invention aims to overcome the defects of the prior art and provides a coating for inhibiting furnace tube coking and a preparation method thereof.

The purpose of the invention is realized by the following technical scheme:

a coating for inhibiting furnace tube coking is mainly composed of silicon-oxygen-silicon cross-linked silicon dioxide.

A preparation method of a coating for inhibiting furnace tube coking comprises the following specific steps:

1) mixing 200-600 parts of siloxane and 5-30 parts of acid, standing at normal temperature for hydrolysis,

2) adding the standing hydrolysis mixture into 100-300 parts of silica sol, adding 15-30 parts of deionized water and 20-60 parts of isopropanol, and stirring at normal temperature to obtain a gel solution;

3) polishing the workpiece to remove surface oxides, then placing the workpiece in absolute ethyl alcohol for ultrasonic cleaning, and drying the workpiece by hot air for later use;

4) dipping the workpiece into the gel liquid, standing and then pulling out the gel liquid;

5) and (3) placing the workpiece in an oven at the temperature of 60-80 ℃ for 5-10 min, then heating to 550-600 ℃ in a muffle furnace at the speed of 2-5 ℃/min, preserving heat for 1-3 h, and taking out after naturally cooling to obtain the workpiece with the coating.

In step 1), the siloxane can be selected from organic siloxane or tetraethyl orthosilicate.

In said step 1), the acid that can be used is a weak acid such as acetic acid.

In the step 1), the hydrolysis time is 30-120 minutes.

In the step 2), the stirring time at normal temperature is 24-72 hours.

In the step 3), the ultrasonic cleaning time is 5-20 minutes.

In the step 4), the dipping speed is 10-60 mm/min; standing for 30-120 s;

in the step 4), the pulling speed is 10-60 mm/min.

In said step 4), one or more silica coatings may be impregnated according to actual requirements.

The prepared coating can be used for heating occasions of easily coked gas-liquid materials, such as furnace tubes of delayed coking heating furnaces, slurry bed heating furnaces, quenching boilers and the like. Can also be used in high-temperature corrosion-resistant occasions.

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

the coating is inert and can be used as an isolating layer to effectively prevent the furnace tube matrix material elements such as Fe from directly contacting with sulfur elements in the material. Meanwhile, the surface energy of the furnace tube coating is low, the surface roughness is small, and coke is not easy to adhere to the surface of the furnace tube. The inert coatings to which the present invention relates exhibit excellent anti-coking properties.

[ description of the drawings ]

FIG. 1 is a flow chart of the preparation of the silica coating of the present invention.

FIG. 2 is a scanning electron micrograph of the surface of a silica coating according to the present invention.

FIG. 3 is a scanning electron micrograph of a cross-section of a silica coating of the present invention.

FIG. 4 is a scanning electron microscope image of an uncoated sample after being coked for 1 hour.

FIG. 5 is a scanning electron microscope image of a coating sample after coking for 1 h.

[ detailed description ] embodiments

The following provides a specific embodiment of the coating for inhibiting furnace tube coking and the preparation method thereof.

Example (b):

in the embodiment, the surface of the Cr9Mo alloy is subjected to dip-coating to obtain a silica coating, and the coking inhibition performance is evaluated in a delayed coking heating furnace simulation experimental device.

The preparation method comprises the following steps: the silica coating is prepared on the surface of the Cr9Mo matrix material by adopting a sol-gel technology, and the specific preparation process comprises the following steps:

1) mixing 200 parts of methyltriethoxysilane and 5 parts of acetic acid, standing and hydrolyzing for 30 minutes;

2) adding 200 parts of alkaline silica sol, 15 parts of deionized water and 20 parts of isopropanol into the standing hydrolysis mixture, and then placing the mixture on a magnetic stirrer to stir for 24 hours at normal temperature to obtain gel liquid;

3) taking a furnace tube material Cr9Mo, processing the furnace tube material into a sample with the size of 10mm multiplied by 3mm, and polishing the sample to be flat by 2000-mesh water abrasive paper;

4) placing the sample in absolute ethyl alcohol, ultrasonically cleaning for 5 minutes, and drying by hot air for later use;

5) soaking the sample in the gel solution at 30mm/min with a program-controlled vertical elevator, standing for 30s, and pulling out the gel solution at 15 mm/min;

6) and placing the sample in a 60 ℃ oven for 5min, then placing the sample in a muffle furnace, raising the temperature to 550 ℃ at the speed of 5 ℃/min, preserving the temperature for 2h, and taking out the sample after the sample is naturally cooled to obtain a coating sample.

As can be seen from FIG. 2, the prepared coating is flat, compact and uniform, and has no defects such as cracks and the like.

As can be seen from fig. 3, the coating thickness was prepared to be about 5 um.

The coking of the furnace tube of the delayed coking heating furnace is simulated in the reaction kettle. In order to further analyze the coking mechanism and the anti-coking performance of the coating, the uncoated sample and the coating sample are contrasted and characterized. It can be seen from fig. 4 that the uncoated coupon was full of carbon and that the coke was hard to remove. FIG. 5 shows that the coke on the surface of the coated sample is brittle and is not adhered to the surface of the coating, so that the coke is easy to remove. Therefore, the coating can be used as an isolating layer to effectively prevent elements in the matrix material from directly contacting with the coking precursor, and the coating shows good coking inhibition performance.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and decorations can be made without departing from the concept of the present invention, and these modifications and decorations should also be regarded as being within the protection scope of the present invention.

Claims

1. A coating for inhibiting furnace tube coking is characterized in that the coating mainly comprises silicon-oxygen-silicon cross-linked silicon dioxide.

2. A preparation method of a coating for inhibiting furnace tube coking is characterized by comprising the following specific steps:

3. The method for preparing a coating for inhibiting furnace tube coking according to claim 2, wherein in the step 1), the selected siloxane is organic siloxane or tetraethyl orthosilicate.

4. The method for preparing a coating for suppressing furnace tube coking according to claim 2, wherein in the step 1), the selected acid is a weak acid such as acetic acid.

5. The method for preparing the coating for inhibiting the coking of the furnace tube according to claim 2, wherein in the step 1), the hydrolysis time is 30-120 minutes.

6. The method for preparing the coating for inhibiting the coking of the furnace tube according to claim 2, wherein in the step 2), the stirring time at normal temperature is 24-72 hours.

7. The method for preparing the coating for inhibiting the coking of the furnace tube according to claim 2, wherein in the step 3), the ultrasonic cleaning time is 5-20 minutes.

8. The method for preparing the coating for inhibiting the coking of the furnace tube as claimed in claim 2, wherein in the step 4), the dipping speed is 10-60 mm/min, the standing time is 30-120 s, and the pulling speed is 10-60 mm/min.

9. The method for preparing the coating for inhibiting furnace tube coking according to claim 2, characterized in that in the step 4), one or more silica coatings can be impregnated according to actual requirements.

10. The use of the coating for inhibiting furnace tube coking according to claim 1, wherein the prepared coating can be used in heating occasions of easily coked gas-liquid materials, such as furnace tubes of delayed coking heating furnaces, slurry bed heating furnaces, quenching boilers and the like. Can also be used in high-temperature corrosion-resistant occasions.