Method for preparing coal-based needle coke from heavy coal pitch

Abstract

The invention belongs to the technical field of coal-based needle coke, and particularly relates to a method for preparing coal-based needle coke from heavy coal pitch, and the method comprises the following steps: S1, water injection; s2, oil feeding: mixing and stirring heavy coal pitch and low-temperature asphalt to prepare asphalt mixed oil, then mixing coking heavy oil serving as circulating oil with the asphalt mixed oil through a feeding pipeline to form mixed oil, and then feeding the mixed oil into a heating furnace; s3, pulling tar; and S4, generating the needle coke. According to the method, the heavy coal pitch and the low-temperature pitch are mixed in proportion to form the pitch mixed oil, the pitch mixed oil is mixed with the circulating oil to reduce the softening point of the heavy coal pitch so as to prepare the needle coke, the coal-based needle coke of which the calcined coke index is similar to that of high-quality raw material refined pitch is prepared, the green coke yield is high, and the true density and the tap density are far superior to those of high-quality coal-based needle coke standards; the thermal expansion coefficient is close to a superior index; the scorching index meets the related standard of the lithium battery negative electrode raw material, the comprehensive utilization rate of the heavy coal pitch is improved, and the economic benefit is increased.

Description

Technical Field

[0001] The invention belongs to the technical field of coal-based needle coke, and in particular is a method for preparing coal-based needle coke from heavy coal tar pitch. Background Art

[0002] Needle coke is a carbon material with a special structure. Ultra-high power graphite electrodes produced with needle coke have the advantages of low resistivity, high density, high mechanical strength, small thermal expansion coefficient, and good thermal shock resistance. It is used in high-power or ultra-high power electric furnace steelmaking, which can greatly shorten the smelting time and save electricity. Therefore, in recent years, affected by the market, the production capacity of needle coke has increased dramatically. It is not only used in high-power and ultra-high power graphite electrodes, but also the demand for needle coke for carbon negative electrode materials of lithium-ion batteries has increased significantly. In order to seize the market, many companies have expanded their factories and invested in construction as soon as possible, but the lack of basic research and development work and the "rote copy" production operation have made the quality of needle coke produced by domestic companies not very ideal, and also caused the phenomenon of product homogeneity among companies.

[0003] Coal tar pitch is a mixture of highly condensed aromatic ring compounds. Solvent separation is usually used to separate coal tar pitch into α resin, β resin and γ resin with similar structures and properties. Heavy coal tar pitch is rich in β resin and is a byproduct of preparing refined soft asphalt from coal tar by solvent extraction. It is also called heavy coal tar pitch and is usually used as a raw material for preparing mesophase carbon microspheres, electrodes for metallurgy, structural materials and many other carbon materials. However, the preparation of lithium battery negative electrode materials from heavy coal tar pitch has not been reported so far, and it is difficult to directly prepare needle coke due to its high softening point.

[0004] Therefore, the present invention develops a method for preparing coal-based needle coke from heavy coal tar pitch in order to reduce the softening point of heavy coal tar pitch and improve the utilization rate of the by-product heavy coal tar pitch. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing coal-based needle coke from heavy coal tar pitch, by using heavy coal tar pitch as aggregate and low-temperature asphalt as a blending agent, mixing heavy coal tar pitch and low-temperature asphalt in a certain proportion to prepare asphalt mixed oil as raw material, and mixing with circulating oil to lower the softening point of heavy coal tar pitch to prepare needle coke, and preparing coal-based needle coke with cooked coke indicators similar to those of refined asphalt of high-quality raw materials, thereby improving the comprehensive utilization rate of heavy coal tar pitch, a by-product in the preparation process of soft asphalt, and increasing economic benefits.

[0006] In order to solve the above technical problems, the present invention provides a method for preparing coal-based needle coke from heavy coal tar pitch, the method comprising the following steps:

[0007] S1, water injection

[0008] Water is injected into the steam regenerator at a certain water injection rate, heated by the steam regenerator, and then sent to the heating furnace through the delivery pipeline;

[0009] S2, oil inlet

[0010] The heavy coal tar and low temperature asphalt are mixed and stirred to form asphalt mixed oil, and then the coking heavy oil is used as circulating oil and mixed with the asphalt mixed oil to form mixed oil, and then the mixed oil is added into the conveying pipeline and sent to the heating furnace;

[0011] S3, tar pulling

[0012] The water vapor and the mixed oil mixed and heated in the heating furnace are sent to the coking tower together. After the mixed oil is fed, the tar is pulled through the coking tower;

[0013] S4. Preparation of needle coke

[0014] Preparation of needle coke green coke by air flow coke pulling;

[0015] S5. Preparation of needle coke

[0016] The needle coke is prepared by calcining in a vacuum atmosphere furnace at 1400-1500°C.

[0017] Preferably, in S1, before water injection, the steam regenerator, the heating furnace and the coke drum are preheated, and water injection is started after the preheating temperature reaches 200°C.

[0018] Preferably, the water injection rate in S1 before oil feeding is 10-50% of the asphalt mixture feed rate; after the oil feeding is stabilized, when the furnace temperature rises to the target value, the water injection rate is reduced to 5%-10% of the asphalt mixture feed rate, and the asphalt mixture feed rate is 3-4kg / h.

[0019] Preferably, in S2, heavy coal tar and low temperature asphalt are mixed and stirred at a ratio of 1:0.05-0.5 to form asphalt mixed oil; coking heavy oil is used as circulating oil and is mixed with the above asphalt mixed oil at a ratio of 1:0.8-1.4 to form mixed oil.

[0020] Preferably, the feeding time of the mixed oil in S2 is 24-48h.

[0021] Preferably, the outlet temperature of the heating furnace in S3 is divided into two stages, wherein the first stage is 450-490°C, and the control time is 2 / 3 of the mixing oil feeding time; the second stage is 480-520°C, and the control time is 1 / 3 of the mixing oil feeding time.

[0022] Preferably, during the tar pulling process in S3, coking heavy oil and water vapor continue to be fed, the feeding time of coking heavy oil and water vapor is controlled to be 2-6h, and the feeding rate of coking heavy oil and water vapor is 1.1-2.4 times the feeding rate of asphalt mixed oil; the furnace outlet temperature after tar pulling is heated to 500-520°C.

[0023] Preferably, the pressure of the coking tower in S3 is maintained at 0.1-1.0 MPa.

[0024] Preferably, in S4, small steam blowing and large steam blowing are used in the process of airflow coke pulling, wherein the small steam blowing is 1-2h, and the water injection rate is 5%-15% of the coking heavy oil feed rate; the large steam blowing is 2-4h, and the water injection rate is increased to 10%-30% of the coking heavy oil feed rate, and at the same time, the coke tower is depressurized to 0.01MPa during the large steam blowing.

[0025] Preferably, the method further comprises S6, decoking analysis: cleaning the prepared pre-calcined coke from the coke tower, weighing and calculating, and performing analysis on the true density, sulfur, nitrogen, ash, volatile matter, and moisture content on a dry basis for the pre-calcined coke.

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

[0027] 1. The present invention uses heavy coal tar as aggregate and low-temperature asphalt as a blending agent. The heavy coal tar and low-temperature asphalt are mixed in a certain proportion to prepare asphalt mixed oil as raw material. Under the mixing effect of circulating oil, the softening point of heavy coal tar can be reduced to prepare needle coke. The method of the present invention can prepare coal-based needle coke with a cooked coke index similar to that of high-quality raw material refined asphalt, and the green coke yield is high, and the true density and tap density are far better than the high-quality coal-based needle coke standard, and the thermal expansion coefficient is close to the excellent grade index; the cooked coke index meets the relevant standards of lithium battery negative electrode raw materials, improves the comprehensive utilization rate of heavy coal tar, a by-product in the preparation process of soft asphalt, and increases economic benefits.

[0028] 2. The present invention controls the outlet temperature of the heating furnace and sets it into two stages, wherein the first stage is 490°C and the second stage is 505°C. The temperature can be increased to 490°C and 505°C in stages, respectively. The advantage is that the temperature can be increased slowly to avoid coking, and the reaction temperature can be gradually reached, giving the intermediate phase spheres enough reaction time to grow and fuse, thereby generating high-quality green coke and improving the quality of needle coke.

[0029] 3. After the mixed oil feeding is completed, the present invention uses a coking tower to pull tar, and the coking heavy oil and water vapor continue to be fed for a period of time during the tar pulling process. This operation can use a large amount of oil and vapor to pull the intermediate phase spheres gradually formed in the coking tower, so that they can better form complete fibers, thereby improving the quality of needle coke production. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solution of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 The present invention is a preparation flow chart of a method for preparing coal-based needle coke from heavy coal tar pitch;

[0032] In the figure: 1-water injection tank, 2-steam regenerator, 3-heating furnace, 4-oil tank 1, 5-oil tank 2, 6-coking tower, 7-transport pipeline, 8-feeding pipeline, 9-discharging pipeline, 10-distillation tower, 11-flash tank 1, 12-flash tank 2, 13-heavy oil tank, 14-light oil tank. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the specification of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] like Figure 1 The present invention is a preparation flow chart of the method for preparing coal-based needle coke from heavy coal tar pitch;

[0035] Embodiment 1

[0036] The present invention adopts a system for preparing coal-based needle coke from heavy coal tar pitch. The system for preparing coal-based needle coke from heavy coal tar pitch comprises a water injection tank 1, a steam regenerator 2, a heating furnace 3, an oil tank 1 4, an oil tank 2 5 and a coking tower 6. The water injection tank 1 is connected to the feed port of the steam regenerator 2. The discharge port of the steam regenerator 2 is connected to the feed end of the heating furnace 3 through a conveying pipeline 7. A feeding pipeline 8 is connected to the conveying pipeline 7. The feeding pipeline 8 is respectively connected to the oil tank 1 4 and the oil tank 2 5. The discharge end of the heating furnace 3 is connected to the coking tower 6 through a discharge pipeline 9. The coking tower 6 is sequentially connected to a fractionation tower 10, a flash tank 1 11 and a flash tank 2 12 through pipelines. Two heavy oil tanks 13 are connected to the bottom of the fractionation tower 10. Two light oil tanks 14 are respectively connected to the bottoms of the flash tank 1 11 and the flash tank 2 12.

[0037] Specifically, in this embodiment, the water injection tank 1 is filled with pure water, the oil tank 1 4 is filled with asphalt mixed oil in which heavy coal tar and low-temperature asphalt are mixed in a certain proportion, and the oil tank 2 5 is filled with coking heavy oil as circulating oil;

[0038] The method for preparing coal-based needle coke from heavy coal tar pitch of the present invention comprises the following steps:

[0039] S1, water injection

[0040] Before water injection, the steam regenerator 2, the heating furnace 3 and the coke tower 6 are preheated, and water injection is started after the preheating temperature reaches 200°C;

[0041] The water in the water injection tank 1 is injected into the steam regenerator 2 at a certain injection rate and heated by the steam regenerator 2, and then sent to the heating furnace 3 through the conveying pipeline 7; the water injection rate is 1200g / h before oil feeding, and when the furnace temperature (furnace setting temperature 380℃) rises to the target value after the oil feeding is stable, the water injection amount is reduced to 250g / h of the feed amount;

[0042] S2, oil inlet

[0043] In the oil tank 14, heavy coal tar and low temperature asphalt are mixed and stirred in a ratio of 1:0.3 to form asphalt mixed oil, which is then pumped out from the oil tank 14 at a feeding rate of 3.0 kg / h; at the same time, the coking heavy oil in the oil tank 25 is pumped out from the oil tank 25 as circulating oil at a rate of 3.0 kg / h, and the asphalt mixed oil is mixed with the coking heavy oil through the feeding pipeline 8 to form mixed oil, which is then fed into the heating furnace 3 through the conveying pipeline 7, and the feeding time of the mixed oil is 36 hours;

[0044] S3, tar pulling

[0045] The water vapor and mixed oil mixed and heated in the heating furnace 3 are sent to the coking tower 6 together. After the mixed oil feeding is completed, the tar is pulled through the coking tower 6; during the tar pulling process, the coking heavy oil and water vapor continue to be fed, and the feeding time of the coking heavy oil and water vapor is 3h, and the feeding amount is 6.0kg / h; the outlet temperature of the heating furnace 3 is controlled, which is mainly divided into two stages, wherein the first stage is heated to 490℃, the control time is 24h, and the second stage is heated to 505℃, the control time is 12h, and the pressure of the coking tower 6 is maintained at 0.5Mpa;

[0046] S4. Preparation of needle coke

[0047] After the feeding is completed, the needle coke is obtained by air flow pulling. Specifically, the steam is blown at a low speed for 2 hours, the water injection rate is increased to 450g / h, and the steam is blown at a high speed for 2 hours, the water injection rate is increased to 1000g / h, and the pressure is reduced to 0.01MPa by using a variable pressure operation mode;

[0048] S5. Preparation of needle coke

[0049] The needle coke is prepared by calcining in a vacuum atmosphere furnace at 1400-1500°C;

[0050] S6. Decoking test

[0051] The prepared pre-calcined coke is cleaned out from the coke tower, weighed and calculated, and the true density, sulfur, nitrogen, ash, volatile matter and dry basis moisture of the pre-calcined coke are tested and analyzed.

[0052] By cooling and decoking, the green coke yield was calculated to be 65.53%. The green coke was calcined to obtain coal-based needle coke calcined coke (cooked coke), and its physical and chemical indicators are shown in Table 5 below.

[0053] The present invention prepares cooked coke under the same conditions with high-quality raw material refined asphalt (Comparative Example 1), pure heavy coal tar pitch (Comparative Example 2) and low-temperature asphalt (Comparative Example 3), and compares the indicators, as shown in Table 5 below.

[0054] The physical and chemical properties of the crude oil are as follows:

[0055] Table 1 Physical and chemical properties of circulating oil

[0056]

[0057] Table 2 Physical and chemical properties of heavy coal tar

[0058]

[0059] Table 3 Physical and chemical properties of low temperature asphalt

[0060]

[0061] Table 4 Physical and chemical properties of refined asphalt

[0062]

[0063] Comparative Example 1

[0064] The difference from the present embodiment is that high-quality raw material refined asphalt is selected, coking heavy oil is used as circulating oil, the feed mass ratio is 1:1, and the refined asphalt is pumped out from oil tank 1 4 at a feed rate of 3.0 kg / h, and the circulating oil is simultaneously pumped into the heating furnace 3 from oil tank 2 5 according to the same feed amount.

[0065] By cooling and decoking, the green coke yield is calculated to be 59.84%. The green coke is calcined to obtain coal-based needle coke calcined coke (cooked coke). Its physical and chemical indicators are shown in Table 5 below, and all the indicators can meet the high-quality indicators of coal-based needle coke.

[0066] Comparative Example 2

[0067] The difference from this embodiment is that heavy coal tar is used as raw material, coking heavy oil is used as circulating oil, the feed mass ratio is 1:1, heavy coal tar is pumped out from oil tank 1 4 at a feed rate of 3.0 kg / h, and circulating oil is pumped into heating furnace 3 from oil tank 2 5 at the same feed amount;

[0068] By cooling and decoking, the coke yield is calculated to be 68.84%. The raw coke is calcined to obtain coal-based needle coke calcined coke (cooked coke). Its physical and chemical indicators are shown in Table 5. Its indicators are far from those of coal-based needle coke and cannot meet the indicator requirements, but the coke yield is relatively high.

[0069] Comparative Example 3

[0070] The difference from this embodiment is that low-temperature asphalt is selected as raw material, coking heavy oil is used as circulating oil, the feed mass ratio is 1:1, the low-temperature asphalt is pumped out from oil tank 1 4 at a feed rate of 3.0 kg / h, and the circulating oil is synchronously pumped into the heating furnace 3 from oil tank 2 5 according to the same feed amount.

[0071] By cooling and decoking, the coke yield is calculated to be 37.95%. The raw coke is calcined to obtain coal-based needle coke calcined coke (cooked coke), and its physical and chemical indicators are shown in Table 5. Among the indicators, the true density and the coefficient of thermal expansion (CTE) are far from the indicators, and the coke yield is low.

[0072] Table 5 Needle coke implementation case data statistics

[0073]

[0074]

[0075] The present invention prepares cooked coke under the same conditions with high-quality raw material refined asphalt (Comparative Example 1), pure heavy coal tar pitch (Comparative Example 2) and low-temperature asphalt (Comparative Example 3). Combined with the comparison of indicators in Table 5, it can be seen that the present invention uses heavy coal tar pitch as aggregate and low-temperature asphalt as a blending agent, and mixes heavy coal tar pitch and low-temperature asphalt in a certain proportion to prepare asphalt mixed oil as raw material, and mixes with circulating oil to reduce the softening point of heavy coal tar pitch to prepare needle coke. The method of the present invention can prepare coal-based needle coke with cooked coke indicators similar to those of high-quality raw material refined asphalt, and the green coke yield is high, the true density and tap density are far better than the high-quality coal-based needle coke standard, and the thermal expansion coefficient is close to the excellent index; the cooked coke index meets the relevant standards of lithium battery negative electrode raw materials, improves the comprehensive utilization rate of heavy coal tar pitch, and increases economic benefits.

[0076] The above disclosure is only the preferred embodiment of the present invention, which certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for preparing coal-based needle coke from heavy coal tar pitch, characterized in that: The method comprises the following steps: S1, water injection Water is injected into the steam regenerator at a certain water injection rate, heated by the steam regenerator, and then sent to the heating furnace through the delivery pipeline; S2, oil inlet The heavy coal tar and low temperature asphalt are mixed and stirred to form asphalt mixed oil, and then the coking heavy oil is used as circulating oil and mixed with the asphalt mixed oil to form mixed oil, and then the mixed oil is added into the conveying pipeline and sent to the heating furnace; S3, tar pulling The water vapor and the mixed oil mixed and heated in the heating furnace are sent to the coking tower together. After the mixed oil is fed, the tar is pulled through the coking tower; S4. Preparation of needle coke Preparation of needle coke green coke by air flow coke pulling; S5. Preparation of needle coke The needle coke is prepared by calcining in a vacuum atmosphere furnace at 1400-1500°C.

2. The method for preparing coal-based needle coke from heavy coal tar pitch according to claim 1, characterized in that: In S1, before water injection, the steam regenerator, the heating furnace and the coke drum are preheated, and water injection is started after the preheating temperature reaches 200°C.

3. The method for preparing coal-based needle coke from heavy coal tar pitch according to claim 1, characterized in that: In S1, the water injection rate before oil feeding is 10-50% of the asphalt mixture feeding rate; after the oil feeding is stable, when the furnace temperature rises to the target value, the water injection rate is reduced to 5%-10% of the asphalt mixture feeding rate, and the asphalt mixture feeding rate is 3-4kg / h.

4. The method for preparing coal-based needle coke from heavy coal tar pitch according to claim 1, characterized in that: In S2, heavy coal tar pitch and low temperature asphalt are mixed and stirred at a ratio of 1:0.05-0.5 to form asphalt mixed oil; coking heavy oil is used as circulating oil and is mixed with the asphalt mixed oil at a ratio of 1:0.8-1.4 to form mixed oil.

5. The method for preparing coal-based needle coke from heavy coal tar pitch according to claim 1, characterized in that: The feeding time of the mixed oil in S2 is 24-48h.

6. The method for preparing coal-based needle coke from heavy coal tar pitch according to claim 1, characterized in that: The outlet temperature of the heating furnace in S3 is divided into two stages, wherein the first stage is 450-490°C, and the control time is 2 / 3 of the mixing oil feeding time; the second stage is 480-520°C, and the control time is 1 / 3 of the mixing oil feeding time.

7. The method for preparing coal-based needle coke from heavy coal tar pitch according to claim 1, characterized in that: During the tar pulling process in S3, coking heavy oil and water vapor continue to be fed, and the feeding time of coking heavy oil and water vapor is controlled to be 2-6 hours, and the feeding rate of coking heavy oil and water vapor is 1.1-2.4 times the feeding rate of asphalt mixed oil; the furnace outlet temperature after tar pulling is heated to 500-520°C.

8. The method for preparing coal-based needle coke from heavy coal tar pitch according to claim 1, characterized in that: The pressure of the coking tower in S3 is maintained at 0.1-1.0Mpa.

9. The method for preparing coal-based needle coke from heavy coal tar pitch according to claim 1, characterized in that: In the S4, small steam blowing and large steam blowing are used in the process of airflow coke pulling, wherein the small steam blowing is 1-2 hours, and the water injection rate is 5%-15% of the coking heavy oil feed rate; the large steam blowing is 2-4 hours, and the water injection rate is increased to 10%-30% of the coking heavy oil feed rate. At the same time, the coke tower is depressurized to 0.01MPa during the large steam blowing.

10. The method for preparing coal-based needle coke from heavy coal tar pitch according to claim 1, characterized in that: The method further comprises S6, decoking test: cleaning the prepared pre-calcined coke from the coke tower, weighing and calculating, and performing test and analysis on the true density, sulfur, nitrogen, ash, volatile matter, and dry basis moisture of the pre-calcined coke.

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