CN1069681C - Process for preparing carbon fibre asphalt and acicular petroleum coke simultaneously - Google Patents

Abstract

A process for simultaneously producing carbon fiber pitch and needle petroleum coke, which uses ethylene tar, a by-product of steam cracking to produce ethylene, as raw material, and converts alkenyl aromatics in ethylene tar into carbon fiber pitch through heat treatment and decompression flash evaporation. , the remaining ethylene tar fraction undergoes delayed coking to obtain needle petroleum coke. This process converts most of the ethylene tar into carbon fiber pitch and needle petroleum coke products with high added value, so that the ethylene tar can be better comprehensively utilized.

Description

A process for simultaneously producing carbon fiber pitch and needle petroleum coke

The invention belongs to a process for simultaneously producing carbon fiber pitch and needle-shaped petroleum coke, more specifically, a process for simultaneously producing carbon fiber pitch and needle-shaped petroleum coke using ethylene tar as a raw material.

Needle petroleum coke is a new type of carbon material developed in the late 1960s. Carbon products made of it have the characteristics of high crystallinity, high purity, low ablation, and low thermal expansion coefficient, so they are widely used in In important national economic sectors such as steelmaking and aerospace, especially with the widespread use of ultra-high-power electric furnace steelmaking, the demand for needle-shaped petroleum coke is becoming increasingly serious. So far, the annual output of needle coke in the world is 800,000 tons, mainly from the United States. The production of needle petroleum coke adopts delayed coking process, but its operating conditions and raw materials are different from general delayed coking, because any heavy oil can be used As a raw material for delayed coking, not all heavy oils can be used to produce needle petroleum coke.

According to the research on the coking mechanism of needle coke, the raw materials for producing needle coke must have high content of aromatics, low content of impurities such as sulfur, nitrogen, and metals, and have a high mesophase formation temperature and a wide range of temperature during thermal conversion. The mesophase formation temperature range is capable of forming a wide-area mesophase. Researches at home and abroad have shown that the ideal raw materials for producing needle petroleum coke are certain thermal cracking residues and catalytic cracking clarified oils.

With the development of catalytic cracking technology, in today's oil refining industry, thermal cracking has been almost completely replaced by catalytic cracking process, so it is no longer possible to obtain thermal cracking residue in refineries. In addition, with the improvement of catalytic cracking technology, heavy oil As the conversion depth increases, the catalytic cracking clear oil discharged from the catalytic cracking unit becomes less and less. At the same time, due to the increasing proportion of sulfur-containing crude oil in crude oil, the sulfur content of catalytic cracking raw materials is increasing day by day. Therefore, it is necessary to obtain Low-sulfur FCC decant oils are also increasingly difficult, so other sources of feedstock suitable for the production of needle petroleum coke must be developed.

According to statistics, my country's current steam cracking ethylene production capacity reaches 3 million tons per year, and the annual by-product ethylene tar is more than 1 million tons. Ethylene tar contains a large amount of aromatics, and the raw materials for steam cracking ethylene production are naphtha and light diesel oil. , its sulfur, nitrogen and metal content is low, so the impurity content of by-produced ethylene tar is not high. The disadvantage of using ethylene tar as a raw material to produce needle petroleum coke is that it contains more easily condensed alkenyl aromatics, which are easy to coke in the heating furnace tube and block the furnace tube. In addition, due to the rapid condensation of these substances , the mesophase small spheres formed by their condensation are not easy to merge, grow up and arrange in an orientation, so it is impossible to obtain high-quality needle-shaped petroleum coke with low thermal expansion coefficient from ethylene tar.

In order to overcome the above shortcomings, USP3,547,804 proposed to mix ethylene tar with some light fractions with a boiling point of about 380-410°C, and use these light fractions to flush the heating furnace tubes to prevent ethylene tar from coking in the delayed coking furnace tubes. The thermal expansion coefficient of the needle petroleum coke obtained by this method is low.

USP3,817,853 proposes that ethylene tar is hydrotreated to remove highly reactive substances therein before delayed coking. Although this method can produce high-quality needle-shaped petroleum coke from ethylene tar, due to the construction of hydrotreating units and The operating cost is very high, so the production cost of needle petroleum coke produced by this method is very high.

USP4,624,775 discloses a method for blending 10-40% coal tar in ethylene tar to produce needle petroleum coke. For oil refineries, a large amount of coal tar needs to be purchased outside for the production of needle coke. very inconvenient.

The purpose of the present invention is to provide a more economical and effective process for producing needle petroleum coke from ethylene tar, and to make better comprehensive utilization of ethylene tar.

The process provided by the invention is: after ethylene tar is heat-treated, the alkenyl arene polycondensate produced is decompressed and flashed to obtain a carbon fiber pitch product, and the remaining ethylene tar fraction undergoes delayed coking to obtain a needle-shaped petroleum coke product.

The process provided by the present invention is specifically implemented as follows: use ethylene tar, a by-product of steam cracking to produce ethylene, as a raw material, heat-treat for 20 to 60 minutes under normal pressure, and then decompress and flash separate to obtain alkenyl aromatic hydrocarbon condensation polymers, that is, carbon fiber pitch Products and fractions with a boiling point lower than 520°C, which are subjected to delayed coking together with light fractions obtained from heat treatment to obtain needle petroleum coke products.

In the present invention, the heat treatment temperature can neither be too low nor too high, preferably 320-360°C.

In the present invention, the decompression flash temperature does not exceed 350°C, and the obtained carbon fiber pitch product does not contain fractions with a boiling point lower than 520°C.

Delayed coking in the present invention is a prior art known to those skilled in the art, and the temperature is 400-550°C.

The technical process of the present invention will be described in detail below in conjunction with the accompanying drawings.

Fig. 1 is a schematic diagram of the technological process of heat treatment of ethylene tar.

The ethylene tar raw material from the pipeline 11 is sent to the heating furnace 2 for heating through the pump 1, and then enters the heat treatment reactor 3, and is condensed under normal pressure, 320-360°C, and staying for 20-60 minutes. The light fraction flows out from the top of the heat treatment reactor 3 through the pipeline 8, while the heavy fraction in ethylene tar and the condensation polymer of alkenyl aromatic hydrocarbons flow out from the bottom of the heat treatment reactor 3, and enter the heater 4 to be further heated with steam, and enter the flash evaporation Tower 5, under the decompression of the vacuum generator 7, the heavy fraction of ethylene tar with a boiling point lower than 520°C flows out from the top of the flash tower, enters the receiver 6, and mixes with the light fraction of ethylene tar from line 8 through line 9 The pre-treated ethylene tar is used as the raw material for the production of needle petroleum coke, and the product that flows out from the bottom of the flash tower is the polycondensation product of alkenyl aromatics - carbon fiber pitch.

Fig. 2 is a schematic flow chart of producing needle petroleum coke from pretreated ethylene tar through delayed coking.

The raw material of the needle-shaped petroleum coke from the pipeline 12, that is, the pre-treated ethylene tar enters the convection chamber of the heating furnace 15 and is heated to 350° C., and then enters the intermediate tank 13. After the oil is mixed, it enters the radiant section of the heating furnace 15 through the pipeline 14 to be heated, and then enters the coke tower 16 or 17 for coking. Decoking is carried out to obtain needle-shaped petroleum coke products. The oil gas generated by coking enters the fractionating tower 19 through the pipeline 18, and the oil gas generated by coking in the fractionating tower is separated into coked dry gas, coked gasoline, coked diesel oil, and coked wax oil.

The process provided by the invention adopts the method of heat treatment and flash evaporation to pre-treat ethylene tar. Compared with hydrogenation treatment or solvent treatment method, the process and equipment are simple, the operation cost is low, and it is practicable, and two kinds of carbon fibers with high added value can be obtained at the same time. Pitch and needle-shaped petroleum coke products, needle-shaped petroleum coke meet the requirements for the production of high-power graphite electrodes, so that ethylene tar can be better comprehensively utilized.

Fig. 1 is a schematic diagram of the technological process of heat treatment of ethylene tar.

Fig. 2 is a schematic flow chart of producing needle petroleum coke from pretreated ethylene tar through delayed coking.

The numbers in the accompanying drawings are explained as follows: 1 represents the pump, 2 and 15 represent the heating furnace, 3 represents the heat treatment reactor, 4 represents the heater, 5 represents the flash tower, 6 represents the receiver, 7 represents the vacuum generator, 8 and 9 , 10, 11, 12, 14, 18, and 20 all represent pipelines, 13 represents a tundish, 16, 17 represents a coke tower, and 19 represents a fractionation tower.

The following examples will further illustrate the method provided by the present invention.

So far, China has not yet established a unified quality standard and evaluation method for needle-shaped petroleum coke. When researching and developing the technology of producing needle-shaped petroleum coke, the Petrochemical Research Institute of China Petrochemical Corporation refers to the specifications and standards of foreign needle-shaped petroleum coke. In consultation with the Ministry of Metallurgy, the needle coke is divided into three grades. Those whose thermal expansion coefficient is less than 2.3×10 ^-6 /℃ are ultra-high power needle cokes, and those whose thermal expansion coefficient is 2.3～2.6×10 ^-6 /℃ are High-power needle coke with a thermal expansion coefficient of 2.6 to 3.0×10 ^-6 /℃ is called secondary needle coke. The test temperature of thermal expansion coefficient is 25～600℃.

Example 1

After the ethylene tar raw material is heat-treated for 30 minutes under normal pressure and a temperature of 320°C, it is flashed and separated under reduced pressure to obtain an alkenyl aromatic hydrocarbon condensation polymer, that is, a carbon fiber pitch product, and a fraction with a boiling point lower than 520°C. The distillates are subjected to delayed coking at 450-500°C to obtain needle-shaped petroleum coke products. The raw materials and product properties are shown in Table 1.

Example 2

After the ethylene tar raw material is heat-treated for 20 minutes under normal pressure and a temperature of 360°C, it is flashed and separated under reduced pressure to obtain an alkenyl aromatic hydrocarbon condensation polymer, that is, a carbon fiber pitch product, and a fraction with a boiling point lower than 520°C. The distillates are subjected to delayed coking at 450-500°C to obtain needle-shaped petroleum coke products. The raw materials and product properties are shown in Table 1.

Comparative example 1

The raw material of ethylene tar was directly delayed coking without heat treatment, and only one product was obtained, and the quality of needle petroleum coke was unqualified, and the coefficient of thermal expansion was 3.95×10 ^-6 /℃. The raw materials and product properties are shown in Table 1.

Table 1 Heat treatment temperature, residence time in °C, delayed coking temperature in minutes, needle coke raw material property density in °C (20 °C), g/ ^cm3 viscosity (100 °C), ^mm2 /s carbon residue, weight % sulfur, weight % nitrogen, weight % chemical group composition, weight % saturated hydrocarbon aromatic colloidal pitch carbon fiber pitch yield, weight % carbon fiber pitch properties softening point, ℃ quinoline insoluble matter, weight % needle petroleum coke properties true density, g/cm ³ coefficient of thermal expansion ( 25～600℃), 10 ^-6 /℃ Embodiment 132030450～5001.0042.313.40.010.00324.948.620.06.5162280.552.122.05 Example 236020450～5001.0012.23.20.0080.00226.248.518.37.0192700.682.101.97 Comparative example 1--450～5001.0253.359.80.020.00411.065.29.414.40--2.143.95

Claims (2)

1, a kind of technology of producing carbon fibre asphalt and acicular petroleum coke simultaneously, it is characterized in that ethylene bottom oil is after 320～360 ℃, the residence time are to heat-treat under 20～60 minutes the condition in normal pressure, temperature, the alkenyl aromatic hydrocarbon polycondensate that generates obtains the carbon fibre asphalt product after carrying out vacuum flashing under 350 ℃ the temperature being no more than, do not contain the cut that boiling point is lower than 520 ℃ in the carbon fibre asphalt product, remaining ethylene bottom oil cut carries out delayed coking and obtains the acicular petroleum coke product under 400～550 ℃ temperature.

2,, it is characterized in that described ethylene bottom oil is the by product of preparing ethylene by steam cracking according to the technology of claim 1.

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