Binder asphalt for special graphite and preparation method thereof

Abstract

The invention discloses binder asphalt for special graphite and a preparation method of the binder asphalt, and the preparation method comprises the following steps: S1, conveying purified asphalt to a pressurized reaction kettle through a pipeline, stopping feeding after a set feeding amount is reached, adding a carburant according to the feeding amount of the purified asphalt, introducing nitrogen under a stirring condition, and carrying out pressurized polymerization reaction after the temperature is raised by adopting electric heating; s2, conveying asphalt obtained after the pressurized polymerization reaction to a reduced pressure reaction kettle, heating by adopting electric heating, carrying out reduced pressure polymerization reaction under a stirring condition after vacuumizing, and ending the reduced pressure polymerization reaction after the weight of materials in the reduced pressure reaction kettle meets a discharging requirement; and S3, sending the asphalt obtained by the reduced pressure polymerization reaction to a cooler for cooling, and then granulating to obtain the binder asphalt for the special graphite. According to the invention, the purified asphalt and a proper amount of carburant are adopted, and the binder asphalt with a high coking value and a low softening point is obtained through a pressurized polymerization reaction and a reduced pressure polymerization reaction, so that the requirement of a binder in a special graphite process is met.

Description

Technical Field

[0001] The present invention relates to the technical field of coal chemical industry, and in particular to a binder asphalt for special graphite and a preparation method thereof. Background Art

[0002] Binder asphalt plays two main roles in the production of carbon materials: (1) When coal tar pitch is in liquid form, it wets, bonds and kneads carbonaceous aggregates and powders into a plastic paste. After the paste is pressurized and cooled, the binder asphalt hardens, consolidating the aggregates and powders into green billets; (2) When the green billets are roasted, the binder coal tar pitch is heated to a certain temperature and melts. The molten asphalt is thermally decomposed and condensed in the billet, and finally carbonized into asphalt coke with adhesive properties, which firmly combines the aggregate particles and powders into a whole, giving the roasted billet mechanical and thermal properties; It can be seen from this that the binder asphalt needs to have a suitable softening point and coking value. A high softening point of asphalt will result in the kneading process requiring high-temperature melting, which is difficult to operate, while a low softening point asphalt corresponds to a low coking value, which affects the volume density of the product.

[0003] Special graphite mainly refers to high-strength, high-density, and high-purity graphite products, which are widely used in chemical, metallurgical, nuclear energy and other fields. In recent years, the domestic special graphite industry has developed rapidly, and the technical level has been continuously improved. It is capable of producing various large-size, high-purity, fine-structured, and isotropic high-end special graphites. At present, the process of special graphite industry is being optimized. In order to shorten the preparation process, the previous process of crushing toner powder - kneading - isostatic pressing - primary roasting - impregnation - secondary roasting - graphitization - finished product is changed to crushing toner powder - kneading - isostatic pressing - roasting - graphitization process; but during the roasting and carbonization heat treatment process, coal tar will pyrolyze and release a large amount of volatile matter, resulting in a large number of micropores in the roasted blank, which is generally compensated by impregnation and then roasting process. However, the current special graphite process cancels the impregnation-secondary roasting process, so it is necessary to improve the requirements of the binder asphalt used in the kneading process, and use coal tar with high coking value and low softening point, which can be directly graphitized into finished products after roasting. Therefore, it is necessary to develop a new preparation method for binder asphalt to meet industry needs.

[0004] Chinese patent application number CN201210541359.0 proposes a method for producing coal tar pitch, comprising the following steps: directly adding medium-temperature coal tar pitch into a stirred reactor, continuously introducing air, an air-nitrogen mixture, or a nitrogen-air mixture, heating to 200-210°C at a rate of 15-25°C / min, keeping warm for 0.5-1.5 hours, then heating to 330-340°C at a rate of 5-10°C / min, and keeping warm for 1-20 hours, thereby obtaining a high-softening-point coal tar pitch; using the medium-temperature coal tar pitch to be oxidized by air to produce a coal tar pitch with a softening point of 260-280, a coking value ≥75%, quinoline insolubles 30±5%, toluene insolubles ≥50%, and an ash content ≤0.4%.

[0005] Chinese patent application number CN201610765770.4 discloses a method for producing coal tar pitch with high coking value and low quinoline insolubles: high-purity impregnating agent asphalt is used as raw material, first passing through a self-cleaning reactor, fully reacting at 280-300°C, and oxidizing with air; then passing through a thin film evaporator, devolatilizing at 260-300°C, and producing a product with a softening point of 115-125°C and a coking value of 55-65%.

[0006] Chinese patent application number CN202010453635.2 provides a method for producing high-softening-point asphalt: a carboxylic anhydride component containing a cyclic structure and a base asphalt with a softening point of 70-130°C are added to a reactor equipped with a reflux system in a weight ratio of 1:100 to 50:100. The reaction is carried out under an inert atmosphere at a temperature of 200-370°C for 1-10 hours. The resulting product has a softening point of 283°C and a coking value of 81%. The coking value at a softening point of 215°C is 62%, and the coking value at a softening point of 153°C is only 52%.

[0007] Chinese patent application number CN202210080147.0: Using asphalt as raw material and coumarone resin as modifier, a coated asphalt material with good wettability is obtained through air oxidation, pressure polymerization, and molecular distillation processes. In the embodiment, the obtained asphalt has a softening point of 198.5℃-212.3℃ and a coking value of 61.8-66.2%.

[0008] The above technologies use air oxidation or add modifiers to increase the softening point and coking value of asphalt. However, when the coking value reaches 70%, the softening point exceeds 200°C, which cannot meet the requirements of high coking value and low softening point at the same time. Summary of the Invention

[0009] In view of the defects existing in the prior art, the purpose of the present invention is to provide a binder asphalt for special graphite and a preparation method thereof, by using purified asphalt and an appropriate amount of recarburizer, through pressurized polymerization reaction and reduced pressure polymerization reaction, to obtain a binder asphalt with high coking value and low softening point, which meets the requirements of the binder in the special graphite process.

[0010] In order to achieve the above object, the present invention adopts the following technical solutions:

[0011] A first aspect of the present invention provides a method for preparing a binder pitch for special graphite, comprising the following steps:

[0012] S1, the purified asphalt is transported to the pressurized reactor via a pipeline. When the set feed volume is reached, the feed is stopped. A recarburizer is added according to the feed volume of the purified asphalt. Nitrogen is introduced under stirring conditions, and the temperature is raised by electric heating before a pressurized polymerization reaction is carried out.

[0013] S2, sending the asphalt obtained after the pressure polymerization reaction to a vacuum reactor, heating it by electric heating, vacuuming it and carrying out the vacuum polymerization reaction under stirring conditions. The vacuum polymerization reaction is terminated when the weight of the material in the vacuum reactor reaches the discharge requirement;

[0014] S3, sending the asphalt obtained by the reduced pressure polymerization reaction to a cooler for cooling, and then obtaining the binder asphalt for special graphite through granulation.

[0015] Preferably, in step S1, the softening point of the purified asphalt is 70-90° C., the TI content is 8-10%, and the QI content is less than 1%.

[0016] Preferably, in step S1:

[0017] The recarburizer is selected from one or more of calcined petroleum coke, pitch coke, natural graphite, artificial graphite, coke, and anthracite, and has a D50 particle size of 0.5 to 5 μm; and / or

[0018] The recarburizer is added at 0.5-2% of the purified asphalt feed amount.

[0019] Preferably, in the step S1, during the pressurized polymerization reaction, the reactor temperature is 320-330° C., the reactor pressure is 0.2-0.3 MPa, the reaction time is 6-8 h, and the stirring speed is 10-100 r / min.

[0020] Preferably, in step S1, a circle of nitrogen inlet pipes is provided at the bottom of the pressurized reactor, and the nitrogen inlet pipes are provided with vent holes of 1 to 3 mm.

[0021] Preferably, the pressurized reactor and the decompressed reactor both use far-infrared electric heaters and are equipped with weighing modules for monitoring weight changes of the reactors.

[0022] Preferably, in the step S2, during the reduced pressure polymerization reaction, the reactor temperature is 350-360° C., the reactor pressure is controlled at an absolute pressure of 30-50 KPa by vacuum, the reaction time is 4-5 h, and the stirring speed is 10-100 r / min.

[0023] Preferably, in step S2, the discharge requirement is: the weight of the material in the vacuum reactor is reduced to 70-75% of the feed amount of the vacuum reactor.

[0024] Preferably, in step S3, the asphalt obtained by the reduced pressure polymerization reaction is cooled to 240±10° C. in a cooler and then granulated.

[0025] The second aspect of the present invention provides a binder asphalt for special graphite prepared by the preparation method of the binder asphalt for special graphite as described in the first aspect of the present invention, which has a softening point of 150-165°C, a coking value ≥70%, a QI content of 20-30%, and a TI content of 40-50%.

[0026] The beneficial effects of the present invention are:

[0027] 1. The present invention utilizes purified asphalt, adds an appropriate amount of recarburizer, selects a far-infrared electric heating reactor with precise temperature control to prevent coking, and undergoes pressurized polymerization and reduced pressure polymerization to obtain a binder asphalt with a softening point of 150-165°C and a coking value of ≥70%. The binder asphalt has a moderate softening point and a high coking value, making it suitable for use as a binder in the field of specialty graphite.

[0028] 2. The reactor used in the pressurized polymerization reaction and the reduced pressure polymerization reaction of the present invention adopts far-infrared electric heating technology, which can avoid coking of the reactor and accurately control the reaction temperature;

[0029] 3. The pressurized reactor and the reduced pressure reactor used in the present invention are both equipped with a weighing module, which can determine the discharge time by monitoring the weight change of the reactor. The material is discharged when the weight loss meets the requirement to ensure qualified quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic flow chart of the method for preparing the binder asphalt for special graphite of the present invention. DETAILED DESCRIPTION

[0031] The present invention will be described in detail below with reference to specific examples. The following examples will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form.

[0032] Combine Figure 1 As shown, the present invention provides a method for preparing a binder pitch for special graphite, comprising the following steps:

[0033] S1, the purified asphalt is transported to the pressurized reactor via a pipeline. When the set feed volume is reached, the feed is stopped. A recarburizer is added according to the feed volume of the purified asphalt. Nitrogen is introduced under stirring conditions, and the temperature is raised by electric heating before a pressurized polymerization reaction is carried out.

[0034] Specifically, the purified asphalt is piped into a pressurized reactor. After adding an appropriate weight, feeding is stopped and 0.5-2% recarburizer is added based on the feed amount of the purified asphalt. With the reactor agitator rotating at a speed of 10-100 r / min, nitrogen is introduced to control the pressure in the reactor to 0.2-0.3 MPa. The materials in the reactor are heated electrically (e.g., at a heating rate of 30-50°C / hour) to 320°C. The reactor temperature is maintained at a constant temperature of 320-330°C, and a pressurized polymerization reaction is conducted for 6-8 hours. The softening point of the purified asphalt is 70-90°C, the toluene insoluble matter (TI) content is 8-10%, and the quinoline insoluble matter (QI) content is less than 1%. The recarburizer is selected from one or more of calcined petroleum coke, pitch coke, natural graphite, artificial graphite, coke, and anthracite, with a D50 particle size of 0.5-5 μm. Nitrogen enters the pressurized reactor through a ring of nitrogen inlet pipes at the bottom of the reactor. The nitrogen inlet pipes are equipped with 1-3mm vents to improve nitrogen distribution. The pressurized reactor uses a far-infrared electric heater to prevent coking in the reactor. The far-infrared electric heater is divided into three stages: reactor preheating (for example, turning on the electric heating of the reactor in advance to raise the temperature to 150±10°C), heating, and constant temperature. The heating power can be automatically adjusted according to the set temperature of the corresponding stage, and the maximum heating temperature is set to no more than 400°C. The pressurized reactor is intermittently fed and is equipped with a weighing module to monitor the weight change of the reactor. The discharge time is determined by monitoring the weight change of the reactor. When the set feed amount is reached, the feed is stopped.

[0035] S2, sending the asphalt obtained after the pressure polymerization reaction to a vacuum reactor, heating it by electric heating, vacuuming it and carrying out the vacuum polymerization reaction under stirring conditions. The vacuum polymerization reaction is terminated when the weight of the material in the vacuum reactor reaches the discharge requirement;

[0036] Specifically, after the pressure polymerization reaction in step S1 is completed, the asphalt in the pressure reactor is delivered to the vacuum reactor using an asphalt pump, and the material in the reactor is electrically heated by the electric heater of the vacuum reactor (for example, the heating rate can be 30-50°C / hour), and the temperature of the vacuum reactor is controlled at 350-360°C. The vacuum is turned on to control the pressure of the reactor to an absolute pressure of 30-50 kPa. Under the condition that the stirring speed of the reactor agitator is 10-100 r / min, the vacuum polymerization reaction is carried out for 4-5 hours. The reaction is terminated after the weight of the material in the vacuum reactor reaches the discharge requirement. Among them, the discharge requirement is: the weight of the material in the vacuum reactor is reduced to 70-75% of the weight of the vacuum reactor feed amount, at which time the asphalt quality meets the requirements, that is, the softening point is 150-165°C and the coking value is ≥70%. The above-mentioned vacuum reactor also uses a far-infrared electric heater to prevent coking in the reactor. The far-infrared electric heater is also divided into three stages, namely reactor preheating (for example, turning on the reactor electric heating in advance to raise the temperature to 150±10℃), heating, and constant temperature. The heating power is automatically adjusted according to the set temperature of the corresponding stage, and the maximum heating temperature is set not to exceed 400℃. The vacuum reactor is equipped with a weighing module to monitor the weight change of the reactor. By monitoring the weight change of the reactor, it is determined whether to discharge the material. When the discharge requirements are met, the reaction is completed and the material is discharged to ensure qualified quality.

[0037] S3, sending the asphalt obtained by the reduced pressure polymerization reaction to a cooler for cooling, and then obtaining the binder asphalt for special graphite through granulation.

[0038] The qualified asphalt in the vacuum reactor is sent to a cooler. After the vacuum reactor is emptied, the next reactor can be produced. The qualified asphalt is cooled to 240±10°C in the cooler, producing steam as a by-product. The cooled asphalt is sent to a pelletizer for pelletization. The resulting binder asphalt for specialty graphite is then fed into a silo via a tube chain conveyor. This binder asphalt for specialty graphite has a high coking value and a low softening point, making it suitable for use as a binder asphalt in the specialty graphite industry. Its softening point is 150-165°C (GB / T 2294), coking value ≥70% (GB / T 8727), QI content is 20-30% (GB / T 2299), and TI content is 40-50% (GB / T 2292).

[0039] The binder pitch for special graphite and its preparation method of the present invention are further introduced below with reference to specific examples.

[0040] Example 1

[0041] The preparation method of the special graphite binder pitch of this embodiment adopts the following steps:

[0042] Turn on the far-infrared electric heater of the reactor in advance for electric heating, preheat the reactor wall temperature to 150°C, and transport liquid purified asphalt (softening point 82.5°C, QI: 0.85%, TI: 9.5%) with a temperature of 200°C into the reactor through a pipeline. When the weighing module on the pressurized reactor shows that the feed reaches 3 tons, the feed is stopped. Add 30kg of artificial graphite powder with a D50 particle size of 3um, introduce nitrogen, start the stirrer, set the stirring speed to 35r / min, adjust the power of the electric heater, increase the kettle temperature to 320℃ at 30℃ / h, stabilize the kettle temperature between 320 and 330℃, control the reactor pressure at 0.25MPa during this period, and carry out pressurized polymerization for 6 hours; after the reaction time is up, send the asphalt in the pressurized reactor into the reduced pressure reactor through the asphalt pump at the bottom of the reactor, set the reduced pressure reactor heater, control the temperature to rise at 10℃ / h, control the temperature of the reduced pressure reactor at 350-360℃, start the vacuum control absolute pressure of 50KPa, and carry out reduced pressure polymerization for 4 hours. When the weight of the reduced pressure reactor is displayed as 2.2 tons, stop the reactor heater, send the asphalt to the cooler, and send the asphalt cooled to 240℃ to the granulator. The binder asphalt for special graphite after granulation is sent to the silo. Product Analysis: The softening point of the asphalt binder for special graphite is 155℃, the coking value is 70.6%, QI: 22%, TI: 46%, and it can be used as a binder in the field of special graphite.

[0043] Example 2

[0044] The preparation method of the special graphite binder pitch of this embodiment adopts the following steps:

[0045] The reactor's far-infrared electric heater was pre-activated to preheat the reactor wall to 150°C. 200°C purified liquid asphalt (softening point 82.5°C, QI: 0.85%, TI: 9.5%) was piped into the reactor. Feeding was stopped when the weighing module on the pressurized reactor registered 3 tons. 30kg of graphite powder (D50 particle size 1µm) was added, nitrogen was introduced, and the agitator was activated at 35 rpm. The electric heater power was adjusted to increase the reactor temperature at a rate of 30°C / h to 320°C, stabilizing the temperature between 320-330°C. The reactor pressure was maintained at 0.25 MPa, and the pressurized polymerization reaction was continued for 6 hours. After the reaction time expires, the asphalt in the pressurized reactor is pumped into the vacuum reactor via the bottom asphalt pump. A heater is installed in the vacuum reactor, controlling the temperature to rise at a rate of 10°C / hour, maintaining the reactor temperature at 350-360°C. A vacuum is then activated to maintain an absolute pressure of 45 kPa, and the polymerization reaction is carried out for 4.5 hours. When the vacuum reactor weight reaches 2.15 tons, the heater is stopped and the asphalt is transferred to a cooler. Once cooled to 240°C, the asphalt is fed into a pelletizer. The pelletized specialty graphite binder asphalt is then fed into a silo. Product Analysis: This specialty graphite binder asphalt has a softening point of 158°C, a coking value of 71.2%, a QI of 23%, and a TI of 47%, making it suitable for use as a binder in the specialty graphite industry.

[0046] Example 3

[0047] The preparation method of the special graphite binder pitch of this embodiment adopts the following steps:

[0048] The reactor's far-infrared electric heater was preheated to 150°C. 200°C liquid purified asphalt (softening point 82.5°C, QI: 0.85%, TI: 9.5%) was piped into the reactor. Feeding was stopped when the weighing module on the pressurized reactor reached 3 tons. 30kg of carbon black powder with a D50 particle size of 0.5µm was added, nitrogen was introduced, and the agitator was started at 35 rpm. The electric heater power was adjusted to increase the reactor temperature at 30°C / h to 320°C and stabilized between 320-330°C. The reactor pressure was maintained at 0.25 MPa, and the pressurized polymerization reaction was continued for 6 hours. After the reaction time expires, the asphalt in the autoclave is pumped into the vacuum reactor via the bottom asphalt pump. A heater is installed in the vacuum reactor, controlling the temperature to rise at a rate of 10°C / hour, maintaining the reactor temperature at 350-360°C. A vacuum is then activated to maintain an absolute pressure of 40 kPa, and the polymerization reaction is carried out under reduced pressure for 5 hours. When the vacuum reactor weight reaches 2.1 tons, the heater is stopped and the asphalt is transferred to a cooler. Once cooled to 240°C, the asphalt is fed into a pelletizer. The pelletized specialty graphite binder asphalt is then fed into a silo. Product Analysis: This specialty graphite binder asphalt has a softening point of 162°C, a coking value of 73.8%, a QI of 25%, and a TI of 48%, making it suitable for use as a binder in the specialty graphite industry.

[0049] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, and all of these should be included in the scope of the claims of the present invention.

Claims

1. A method for preparing a binder pitch for special graphite, characterized in that: The following steps are involved: S1, the purified asphalt is transported to the pressurized reactor via a pipeline. When the set feed volume is reached, the feed is stopped. A recarburizer is added according to the feed volume of the purified asphalt. Nitrogen is introduced under stirring conditions, and the temperature is raised by electric heating before a pressurized polymerization reaction is carried out. S2, sending the asphalt obtained after the pressure polymerization reaction to a vacuum reactor, heating it by electric heating, vacuuming it and carrying out the vacuum polymerization reaction under stirring conditions. The vacuum polymerization reaction is terminated when the weight of the material in the vacuum reactor reaches the discharge requirement; S3, sending the asphalt obtained by the reduced pressure polymerization reaction to a cooler for cooling, and then obtaining the binder asphalt for special graphite through granulation.

2. The method for preparing the binder pitch for special graphite according to claim 1, wherein In the step S1, the softening point of the purified asphalt is 70-90° C., the TI content is 8-10%, and the QI content is less than 1%.

3. The method for preparing the binder pitch for special graphite according to claim 1, wherein: In the step S1: The recarburizer is selected from one or more of calcined petroleum coke, pitch coke, natural graphite, artificial graphite, coke, and anthracite, and has a D50 particle size of 0.5 to 5 μm; and / or The recarburizer is added at 0.5-2% of the purified asphalt feed amount.

4. The method for preparing the binder pitch for special graphite according to claim 1, wherein: In the step S1, during the pressurized polymerization reaction, the reactor temperature is 320-330° C., the reactor pressure is 0.2-0.3 MPa, the reaction time is 6-8 h, and the stirring speed is 10-100 r / min.

5. The method for preparing the binder pitch for special graphite according to claim 1, wherein: In the step S1, a circle of nitrogen inlet pipes is provided at the bottom of the pressurized reactor, and the nitrogen inlet pipes are provided with vent holes of 1 to 3 mm.

6. The method for preparing the binder pitch for special graphite according to claim 1, wherein: The pressurized reactor and the decompressed reactor both use far-infrared electric heaters and are equipped with weighing modules for monitoring weight changes of the reactors.

7. The method for preparing the binder pitch for special graphite according to claim 1, wherein: In the step S2, during the reduced pressure polymerization reaction, the reactor temperature is 350-360° C., the reactor pressure is controlled to be 30-50 KPa by vacuum, the reaction time is 4-5 h, and the stirring speed is 10-100 r / min.

8. The method for preparing the binder pitch for special graphite according to claim 1, wherein: In step S2, the discharge requirement is: the weight of the material in the vacuum reactor is reduced to 70-75% of the feed amount of the vacuum reactor.

9. The method for preparing the binder pitch for special graphite according to claim 1, wherein: In the step S3, the asphalt obtained by the reduced pressure polymerization reaction is cooled to 240±10° C. in a cooler and then granulated.

10. A binder pitch for special graphite prepared by the method for preparing a binder pitch for special graphite according to any one of claims 1 to 9, characterized in that: Its softening point is 150-165°C, the coking value is ≥70%, the QI content is 20-30%, and the TI content is 40-50%.

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