An impregnated bitumen, its preparation and use

Abstract

The present application relates to the field of pitch, and discloses a kind of impregnated pitch and its preparation method and application, which comprises: (1) oil slurry I is separated, and the intermediate distillate oil with initial boiling point 390-420 DEG C and final boiling point 450-470 DEG C is obtained;(2) in the presence of inert gas I, the intermediate distillate oil is carried out first heating reaction, and heavy distillate oil is obtained;(3) in mixed gas, the heavy distillate oil is carried out second heating reaction, and impregnated pitch is obtained;The volume ratio of inert gas II and air in the mixed gas is 1:2-5;The temperature of the second heating reaction is at least 30 DEG C lower than that of the first heating reaction;The pressure of the first heating reaction and the second heating reaction is independently 0.05-1 MPa respectively.The impregnated pitch prepared by the method of the present application has the advantages of low softening point, low quinoline insoluble content and high coking value, and can enhance the bulk density of graphite electrode when applied to graphite electrode.

Description

Technical Field

[0001] This invention relates to the field of asphalt, and more specifically to an impregnated asphalt, its preparation method, and its application. Background Technology

[0002] With the adjustment of my country's steel industry, the demand for large electric arc furnaces has increased, and the performance requirements for graphite electrodes have become more stringent. They are required to have high density, high strength, high thermal conductivity, low thermal expansion, and good oxidation resistance. However, graphite products have varying degrees of porosity during the batching and extrusion molding process, with porosity accounting for about 25% of the product volume. The presence of pores reduces the mechanical strength of graphite products and worsens their thermal and electrical conductivity. In order to improve the various properties of graphite electrodes, high-pressure impregnation is usually used to densify graphite products with impregnating agent asphalt.

[0003] Currently, existing technologies for preparing impregnated bitumen mainly use coal tar pitch as raw material. Although the resulting product has a high coking value, its softening point is too high, making the impregnation operation difficult. Furthermore, the preparation process requires reaction under high temperature and high pressure conditions and the addition of certain modifiers, which often leads to the formation of other impurities, such as an increase in the content of quinoline insolubles. This results in high requirements for equipment and high investment costs for industrial production.

[0004] Most impregnating bitumen used in carbon products is prepared using coal-based medium-temperature bitumen. However, this type of bitumen contains impurities such as zinc, aluminum, titanium, and iron, with impregnating bitumen products containing these impurities reaching 2% to 10%. Furthermore, due to the high relative molecular mass and viscosity of coal-based bitumen, its wetting ability is weak, making it difficult to penetrate into the pores of the material blank. Consequently, its effect on improving the weight gain and wettability of carbon products is not significant. This seriously hinders the development of the carbon industry and the graphite electrode industry.

[0005] CN114702978A discloses a method for preparing impregnated bitumen by using the residue from direct coal liquefaction as raw material, which undergoes centrifugal separation, filtration, distillation, and nitrogen thermal condensation, and then blending it with decrystalline anthracene oil or waste tire pyrolysis oil. This method requires repeated filtration of the liquid after coal liquefaction, and the raw materials have low flash points and poor chemical stability during the blending process, resulting in high operational risks. In addition, the raw materials contain a strong pungent odor, and long-term exposure can harm human health.

[0006] CN110540855A discloses a method for preparing impregnated bitumen using purified reduced-triple-line furfural extract oil or reduced-quad-line furfural extract oil mixed with purified catalytic cracking slurry as raw material, followed by distillation to remove light components. However, this method requires the addition of butane or pentane solvents. When the solvents used in this process need to be recovered and reused, the high volatility and low auto-ignition point of the solvents may pose difficulties and risks during the recovery process. Furthermore, such equipment requires high-pressure and high-temperature operating conditions, resulting in high equipment investment costs. Moreover, the raw materials used in this preparation come from fuel-lubricating oil refineries, resulting in a limited number of related enterprises and a narrow application scope. Summary of the Invention

[0007] The purpose of this invention is to provide an impregnated bitumen for graphite electrodes that can improve the bulk density of graphite electrodes.

[0008] To achieve the above objectives, a first aspect of the present invention provides a method for preparing impregnated bitumen, the method comprising:

[0009] (1) Separate oil slurry I to obtain middle distillate oil with an initial boiling point of 390-420℃ and a final boiling point of 450-470℃; the sulfur content, nitrogen content, heavy metal content and ash content in oil slurry I are <0.5wt%, <0.5wt%, <0.1wt%, and <0.02wt%.

[0010] (2) In the presence of inert gas I, the middle distillate oil is subjected to a first heating reaction to obtain heavy distillate oil;

[0011] (3) The heavy distillate oil is subjected to a second heating reaction in the mixed gas to obtain impregnated asphalt; the volume ratio of inert gas II to air in the mixed gas is 1:2-5;

[0012] The temperature of the second heating reaction is at least 30°C lower than the temperature of the first heating reaction;

[0013] The pressures of the first heating reaction and the second heating reaction are each independently 0.05-1 MPa.

[0014] A second aspect of the invention provides impregnated bitumen prepared by the method described in the first aspect.

[0015] A third aspect of the invention provides the application of the impregnated pitch described in the second aspect in a graphite electrode.

[0016] The present invention has at least the following advantages:

[0017] (1) The method for preparing impregnated bitumen provided by the present invention has a simple process flow, does not require the introduction of chemical additives, has low corrosivity to equipment, and is suitable for large-scale production;

[0018] (2) When the impregnated bitumen prepared by the present invention is used in graphite electrodes, it can effectively improve the bulk density and mechanical strength of graphite electrodes, which is beneficial to reduce the resistivity of graphite electrodes, alleviate the electrode wear problem caused by oxidation under high temperature use, and further improve the life of graphite electrodes.

[0019] (3) The impregnated bitumen prepared by the present invention has the advantages of low quinoline insoluble content, moderate softening point and high coking value. Detailed Implementation

[0020] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0021] As previously stated, a first aspect of the present invention provides a method for preparing impregnated bitumen, the method comprising:

[0022] (1) Separate oil slurry I to obtain middle distillate oil with an initial boiling point of 390-420℃ and a final boiling point of 450-470℃; the sulfur content, nitrogen content, heavy metal content and ash content in oil slurry I are <0.5wt%, <0.5wt%, <0.1wt%, and <0.02wt%.

[0023] (2) In the presence of inert gas I, the middle distillate oil is subjected to a first heating reaction to obtain heavy distillate oil;

[0024] (3) The heavy distillate oil is subjected to a second heating reaction in the mixed gas to obtain impregnated asphalt; the volume ratio of inert gas II to air in the mixed gas is 1:2-5;

[0025] The temperature of the second heating reaction is at least 30°C lower than the temperature of the first heating reaction;

[0026] The pressures of the first heating reaction and the second heating reaction are each independently 0.05-1 MPa.

[0027] The technical solution of this invention adopts a two-stage heating process and reacts under specific conditions to prepare impregnated pitch with low quinoline insoluble content and high coking value. When used in graphite electrodes, it can effectively improve the bulk density of graphite electrodes.

[0028] Preferably, in step (1), the separation is carried out by vacuum distillation.

[0029] More preferably, the conditions for the vacuum distillation treatment include a temperature of 260-300°C and a pressure of -0.1 MPa to 0.1 MPa. The inventors of this invention have discovered that under these preferred conditions, decomposition, oxidation, and polymerization of the desired middle distillate oil before reaching its boiling point are avoided, preventing its removal. Based on this, the impregnated asphalt prepared using the method of this invention has a lower content of quinoline-insoluble matter and a higher coking value.

[0030] Preferably, in step (2), the temperature of the first heating reaction is 380-450°C. More preferably, it is 400-440°C. The inventors of this invention have discovered that the impregnated bitumen prepared under these preferred conditions has a lower content of quinoline insolubles and a higher coking value, while effectively increasing the bulk density of the graphite electrode.

[0031] More preferably, the first heating reaction takes 1-10 hours.

[0032] Preferably, the stirring speed of the second heating reaction is 30-180 rpm, and the time is 1-10 hours. The inventors of this invention have discovered that when the stirring speed of the second heating reaction is 30-180 rpm, it can increase the contact area of ​​the material reaction process, improve the reaction rate, and help raise the softening point of the material. Furthermore, conducting the reaction for 1-10 hours on this basis can promote the intermolecular cross-linking reaction, ensuring that the material reaches the target softening point. If the stirring speed is too high or too low, the material will be heated unevenly, which is not conducive to raising the softening point and will also cause uneven product quality.

[0033] Preferably, in step (2), the flow rate of the inert gas I introduced is 1-10 m³ per 1 kg of the middle distillate oil. 3 / h, more preferably 1-8m 3 / h. The inventors of this invention have discovered that, in the technical solution of this invention, when the flow rates of the intermediate distillate and the inert gas satisfy the above-mentioned relationship, it is beneficial to promote the polymerization of materials, generate compounds with higher molecular weights, and thus result in lower quinoline insoluble content and higher coking value in the prepared impregnated asphalt.

[0034] More preferably, in step (3), the flow rate of the mixed gas introduced is 1-10 m³ per 1 kg of the heavy distillate oil. 3 / h.

[0035] Preferably, in step (2), the conditions of the first heating reaction are controlled such that the softening point of the heavy distillate oil is 30-70°C.

[0036] According to a preferred embodiment, the method further includes: purifying the raw material oil slurry to obtain the oil slurry I before performing the separation in step (1).

[0037] This invention does not impose any particular limitation on the specific method of purification treatment, as long as the oil slurry I meets the following requirements: sulfur content < 0.5 wt%, nitrogen content < 0.5 wt%, heavy metal content < 0.1 wt%, and ash content < 0.02 wt%. Those skilled in the art can select the appropriate method based on known techniques. However, to further improve purification efficiency and obtain graphite electrode products with higher bulk density, this invention provides a preferred embodiment. Specifically, the purification treatment is carried out by filtration, preferably using ceramic membrane filtration. The conditions for ceramic membrane filtration include: a filter membrane diameter of 6-8 mm and a filtration temperature of 120-300℃.

[0038] Preferably, the raw material slurry contains 50-75 wt% aromatics, <25 wt% gums, and <17 wt% asphaltenes, and has a density of 800-1360 kg / m³ at 20°C. 3 .

[0039] Preferably, the inert gas I and the inert gas II in this invention are each independently selected from at least one of nitrogen, helium, and argon. More preferably, both the inert gas I and the inert gas II are nitrogen.

[0040] According to a particularly preferred embodiment 1, in step (1), the conditions for the vacuum distillation treatment include: a temperature of 290-300°C and a pressure of -0.1 MPa to 0.1 MPa; in step (2), the conditions for the first heating reaction include: a temperature of 380-450°C and a time of 1-8 h; the softening point of the heavy distillate oil is 50-70°C; in step (3), the temperature of the second heating reaction is 280-330°C. The inventors of this invention have discovered that under these preferred conditions, the prepared impregnated bitumen has a lower content of quinoline insolubles and a higher coking value, while effectively increasing the bulk density of the graphite electrode.

[0041] According to another particularly preferred embodiment 2, in step (1), the conditions for the vacuum distillation treatment include: a temperature of 260-280℃ and a pressure of -0.1MPa to 0.1MPa; in step (2), the conditions for the first heating reaction include: a temperature of 380-450℃, a time of 2-10h, and a stirring speed of 50-120rpm; the softening point of the heavy distillate oil is 40-50℃; in step (3), the conditions for the second heating reaction include: a temperature of 280-300℃, a time of 1-6h, and a pressure of 0.05-0.1MPa. The inventors of this invention have discovered that under these preferred conditions, the impregnated asphalt prepared has a lower content of quinoline insolubles and a higher coking value, while effectively increasing the bulk density of the graphite electrode.

[0042] According to a particularly preferred embodiment 3, in step (2), the conditions for the first heating reaction include: a temperature of 400-440°C, a stirring speed of 50-150 rpm, and a pressure of 0.15-0.5 MPa; the softening point of the heavy distillate oil is 40-60°C; in step (3), the conditions for the second heating reaction include: a temperature of 290-330°C, a time of 2-8 h, and a pressure of 0.5-1 MPa; in the mixed gas, the volume ratio of the inert gas II to the air is 1:2-3. The inventors of this invention have discovered that under these preferred conditions, the impregnated asphalt prepared has a lower content of quinoline insolubles and a higher coking value, while effectively increasing the bulk density of the graphite electrode.

[0043] According to a particularly preferred embodiment 4, in step (2), the flow rate of the inert gas I introduced is 1-8 m³ per kilogram of the intermediate distillate oil. 3 / h; The conditions for the first heating reaction include: a stirring speed of 50-120 rpm and a pressure of 0.05-0.1 MPa; In step (3), the conditions for the second heating reaction include: a temperature of 290-300℃, a stirring speed of 80-150 rpm, a time of 1-6 h, and a pressure of 0.05-0.1 MPa, wherein the volume ratio of the inert gas II to the air in the mixed gas is 1:4-5. The inventors of the present invention have found that under these preferred conditions, the impregnated asphalt prepared has a lower content of quinoline insolubles and a higher coking value, while effectively increasing the bulk density of the graphite electrode.

[0044] According to a particularly preferred embodiment 5, in step (4), the volume ratio of the inert gas II to air in the mixed gas is 1:4-5; in step (3), the conditions for the second heating reaction include: a temperature of 340-350°C, a time of 1-5 h, and a pressure of 0.05-1 MPa. The inventors of this invention have discovered that under these preferred conditions, the prepared impregnated bitumen has a lower content of quinoline insolubles and a higher coking value, while effectively increasing the bulk density of the graphite electrode.

[0045] As previously stated, a second aspect of the present invention provides impregnated bitumen prepared by the method described in the first aspect.

[0046] Preferably, the softening point of the impregnated bitumen is 85-115℃, the quinoline insoluble content is ≤0.5wt%, and the toluene insoluble content is 8-16wt%.

[0047] More preferably, the softening point of the impregnated bitumen is 85-100°C.

[0048] More preferably, the impregnated bitumen has a coking value ≥47wt% and an ash content <0.05wt%.

[0049] As previously stated, a third aspect of the present invention provides the application of the impregnated bitumen described in the second aspect in a graphite electrode.

[0050] In the following embodiments, unless otherwise specified, all raw materials are commercially available products.

[0051] The composition of the raw material oil slurry is shown in Table 1.

[0052] Impregnated bitumen A: Model: softening point 80-90℃, quinoline insolubles 8-12%, toluene insolubles 15-25%, coking value ≥48%, purchased from Deri New Materials Technology Co., Ltd.

[0053] Impregnated bitumen B: Model: Medium-temperature bitumen No. 1, purchased from Yaotan Chemical Technology Co., Ltd.

[0054] Table 1

[0055]

[0056]

[0057] Preparation Example 1

[0058] The raw oil slurry was purified to obtain oil slurry I. The purification process was carried out by ceramic membrane filtration (the filter membrane diameter was 7 mm and the filtration temperature was 200℃).

[0059] The slurry I contained 0.27 wt% sulfur, 0.23 wt% nitrogen, 0.01 wt% ash, and 0.08 wt% heavy metals.

[0060] Example 1

[0061] (1) The oil slurry I was subjected to vacuum distillation to obtain the middle distillate oil;

[0062] (2) In an inert gas I, 1 kg of middle distillate oil is subjected to a first heating treatment to obtain heavy distillate oil;

[0063] (3) In the mixed gas, 1 kg of heavy distillate oil is subjected to a second heating treatment to obtain impregnated asphalt;

[0064] The process parameters are shown in Table 2.

[0065] Examples 2-10

[0066] Examples 2-10 follow the same process as Example 1, except that the process parameters are different, as detailed in Table 2.

[0067] Comparative Examples 1-4

[0068] Comparative Examples 1-4 were carried out using the same process as Example 1, except that the process parameters were different, as detailed in Table 3.

[0069] Table 2

[0070]

[0071] Continued from Table 2

[0072]

[0073]

[0074] Table 3

[0075]

[0076] Test Example 1

[0077] The impregnated bitumen prepared in the examples and comparative examples was tested with commercially available impregnated bitumen A and impregnated bitumen B according to the GB / T 35074-2018 standard. The specific results are shown in Table 4.

[0078] Test Example 2

[0079] The impregnated bitumen prepared in the examples and comparative examples, along with commercially available impregnated bitumen A and impregnated bitumen B, were used as impregnating agents to impregnate graphite electrodes to obtain graphite electrode I. Graphite electrode I was then tested according to the YB / T 4090-2000 standard, and the specific performance data are shown in Table 5.

[0080] The impregnation treatment conditions include: melting the impregnation bitumen at 240°C, mixing the molten impregnation bitumen with the graphite electrode at a weight ratio of 1:2 and a pressure of 1 MPa, and then subjecting the mixed graphite electrode to a secondary carbonization treatment (temperature of 800°C and time of 10 h) to obtain graphite electrode I.

[0081] Table 4

[0082]

[0083] Table 5

[0084]

[0085] As can be seen from the above, the impregnated bitumen prepared by this method has low quinoline insoluble content and toluene insoluble content; and when applied to graphite electrodes, the graphite electrodes have advantages in weight gain and calcined bulk density, and are superior to impregnated bitumen products used in the market.

[0086] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A process for the preparation of impregnated bitumen, characterized in that, The method comprises: (1) separating oil slurry I to obtain intermediate distillate oil with an initial boiling point of 390-420℃ and a final boiling point of 450-470℃; the oil slurry I has a sulfur content of <0.5wt%, a nitrogen content of <0.5wt%, a heavy metal content of <0.1wt%, and an ash content of <0.02wt%; (2) performing a first heating reaction on the intermediate distillate oil in the presence of inert gas I to obtain heavy distillate oil; (3) performing a second heating reaction on the heavy distillate oil in a mixed gas to obtain impregnated pitch; the volume ratio of inert gas II to air in the mixed gas is 1:2-5; The temperature of the second heating reaction is at least 30℃ lower than that of the first heating reaction; The pressure of the first heating reaction and the second heating reaction is independently 0.05-1MPa.

2. The method of claim 1, wherein, In step (1), the separation is performed by vacuum distillation treatment; And / or, the vacuum distillation treatment has a temperature of 260-300℃ and a pressure of -0.1MPa to 0.1MPa.

3. The method according to claim 1 or 2, characterized in that, In step (2), the temperature of the first heating reaction is 380-450℃.

4. The method according to claim 1 or 2, characterized in that, In step (3), the second heating reaction has a stirring speed of 30-180rpm and a time of 1-10h.

5. The method according to claim 1 or 2, characterized in that, In step (2), the flow rate of the inert gas I is 1 to 10 m3 / h per 1 kg of the middle distillate oil 3 / h; and / or, in step (3), the flow rate of the mixed gas is 1 to 10 m 3 / h per 1 kg of the heavy distillate oil.

6. The method of claim 1 or 2, wherein, In step (2), the conditions of the first heating reaction are controlled so that the softening point of the heavy distillate oil is 30-70℃.

7. The method according to claim 1 or 2, characterized in that, The method further comprises: before performing the separation in step (1), purifying raw oil slurry to obtain the oil slurry I; And / or, the purification treatment is performed by filtration.

8. The method of claim 7, wherein, The raw oil slurry has a content of aromatics of 50 to 75 wt%, a content of gum of < 25 wt%, a content of asphaltenes of < 17 wt%, and a density of the raw oil slurry at 20°C of 800 to 1360 kg / m 3 .

9. Impregnated pitch prepared by the method of any one of claims 1-8.

10. Use of the impregnated pitch of claim 9 in graphite electrodes.

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