RU2761201C1 - Method for producing coke with a pseudoisotropic microstructure - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to methods for producing coke with a pseudoisotropic microstructure and can be used in the technology for producing raw materials for manufacture of certain grades of carbon-based construction materials (CCM) widely applied in metallurgy, mechanical engineering, chemical and electrical industry, aviation and rocket technology, nuclear power engineering, medicine. The method is implemented from raw materials containing a mixture of medium-temperature coal tar pitch and an anthracene fraction, and includes stages wherein the raw materials are subjected to thermal oxidation at a temperature from 260 to 340°C, in the course whereof reaction air is supplied with a specific flow rate of 50 to 100 l/(kg∙h); and the oxidised raw materials are coked, wherein the content of anthracene fraction in the mixture is 50 to 80 wt.%.

EFFECT: production of coke with a pseudoisotropic microstructure, suitable for producing carbon-based construction materials.

2 cl, 1 dwg, 13 ex

Description

TECHNICAL FIELD OF THE INVENTION

The invention relates to methods for producing coke with a pseudoisotropic microstructure and can be used in the technology of obtaining raw materials for the production of certain grades of carbon structural materials (CCM), which are widely used in metallurgy, mechanical engineering, chemical and electrical industries, aviation and rocket technology, nuclear power, medicine.

LEVEL OF TECHNOLOGY

The coke in the UKM technology acts as a filler, and the binder is coal tar pitch. To ensure high physical and mechanical properties of CCM, coke must have a certain microstructure. One of the most accessible and informative methods for assessing the microstructure of cokes is GOST 26132-84. The essence of the method is to assess the microstructure of cokes based on a comparison of the microstructures of the tested coke samples with the control microstructure scale. According to GOST 26132-84, the structural components of the microstructure of coke are divided into isotropic (point) with a size of no more than 3 microns (1 point), very fine-fibrous - 3-10 microns (2 points), fine-fibrous - 10-15 microns (3 points), medium-fibrous - 15-35 microns (4 points), coarse-fibrous (petal) - 35-70 microns (5 points), fine-needled - 70-200 microns (6 points), medium-needled - 200-400 microns (7 points), medium-needled with a large size fibers - 400-600 microns (8 points) and larger structural components. The analysis is carried out on a polished section of coke using an optical microscope and using polarized light. The assessment of the microstructure is carried out for each field of view in terms of the prevailing or weighted average value. The number of fields of view must be at least 60. The average score of the microstructure of cokes is calculated by the arithmetic mean of the points of the microstructure of all fields of view.

When using cokes with a predominant content of isotropic structural components (no more than 3 microns) - isotropic coke, the strength properties of the obtained CCM will be high, however, the required electrical and thermophysical properties will not be provided, since such cokes are poorly graphitized. The average score of the microstructure of such cokes is in the range of 1.0-1.7.

When using cokes with a predominant content of anisotropic structural components (more than 15 microns) - anisotropic coke, the required electrical and thermophysical properties will be provided due to the high degree of graphitability of this coke, however, the strength properties of the obtained CCMs will turn out to be unacceptable. The average grade of such coke is above 2.5.

To obtain the main grades of UKM, cokes are used, which are characterized by a predominant size of structural components of 3-10 microns (very fine-fiber). With this size of coke crystallites, the optimum physical and mechanical properties (strength in compression, bending and torsion) and electrical and thermophysical properties obtained by CCM (thermal and electrical conductivity, coefficient of thermal expansion, thermal strength, etc.) are provided. Very fine-fiber structural components are not isotropic, but close to them. In connection with this, coke, in the microstructure of which very fine-fiber structural components prevail, is called pseudo-isotropic. The average grade of pseudo-isotropic coke should be 1.8-2.5.

A known method of producing pseudo-isotropic coke, including pyrolysis of kerosene-gas oil fractions to obtain a hydraulic resin and its subsequent coking [Sabanenkov SA and other Production, properties and use of petroleum pyrolysis coke. - Overview information. Series: Oil Refining, vol. 9, M., 1989]. The disadvantage of this method is the use of scarce and expensive distillate oil fractions as raw materials, which is economically inexpedient, low coke yield for feedstock, the frequency of the pyrolysis process due to coking of the reaction apparatus.

The known method, according to which pitch cokes are obtained from high-temperature pitches (HCP), having a softening temperature of 135-150 ° C. ECP is obtained by thermal oxidation of raw materials, which includes medium-temperature pitch (STP) and a mixture of pitch coking resins and pitch distillates - resin-distillate mixture (SDS) [Privalov, V.E. Coal tar pitch / V.E. Privalov, M.A. Stepanenko. - M .: Metallurgy. 1981. - 208 p.]. In this case, thermal oxidation of SDS can be carried out in a separate oxidizing cube to bring SDS to the values of STP. The content of SDS in a mixture with STP varies in the range of 21.6-23.6%. Thermal oxidation is carried out in a still battery, and coking is carried out in oven chambers. The microstructure of cokes obtained by this method is higher than 2.5 points, therefore, cokes are not pseudo-isotropic and cannot be a high-quality raw material for the production of artificial graphites. At coke-chemical plants, the addition of SDS to STP is not aimed at regulating the microstructure of the produced cokes, but for utilizing SDS, or to increase the yield of pitch coke, or to reduce the viscosity of the reaction mass. A known method for producing high-temperature pitch [Method for producing high-temperature pitch for the production of pitch coke / Tesalovskaya TM, Zhilyaev Yu.A., Andreikov EI, Stepanova LA, Akulov PV, Malkov N.N. // Patent RU 2176657, publ. 10.12.2001] by thermal oxidation of a mixture of STP and polymers of the benzene compartment. The content in the feedstock of polymers of the benzene section is 5-10% of the weight of STP. The resulting ECP has a softening point in the range of 135-150 ºС, assessed by the "Ring and rod" method. Cokes from ECP obtained by this method do not have a pseudo-isotropic microstructure and, therefore, cannot be used as a high-quality raw material for the production of structural graphites.

According to the method [Method of obtaining pitch-binder for electrode materials / Tesalovskaya TM, Karpin GM, Andreikov EI, Grabovskiy AE, Egorov VN, Tverskov AA, Slepova V M., Dmitrieva N.S., Mochalov V.V., Anikin G.Ya. // Patent RU 2119522] The invention relates to a method for producing pitch-binder for electrode materials. A mixture of medium-temperature coal tar pitch with absorption or anthracene fractions of coal tar in a pitch: fraction ratio equal to (9.9: 0.1) - (9.1: 0.9) is treated with air at 280 - 350 ° C. The technology of obtaining pitch allows to reduce the rate of formation of α ₁ -fraction, to reduce the softening temperature of pitch, and shortens the duration of the process. In this invention, the content of the anthracene fraction in the mixture with pitch is 1-9%. After oxidation of this mixture and further coking, no coke is formed with a predominant content of structural components of 3-10 microns.

The closest to the proposed technical solution is the method (taken as a prototype), according to which ECP for coking is obtained by thermal oxidation of a mixture of coal tar pitch (STP) and anthracene fraction, pitch tar, pitch distillates, or crude anthracene [Obtaining pitch for coking from high-boiling products of coal resin. E.A. Sukhorukova, L.A. Kogan, V.V. Epiphany // Collection of articles of the Institute of VUKHIN "Preparation and coking of coal", 1969, issue. 8, p. 204-213]. The amount of additive to STP should not exceed 30%, the specific air consumption is 15 l / (kg⋅h), the temperature of the reaction mixture is not higher than 340 ° C. In the description of the method it is indicated that it is most expedient to carry out the processing of raw materials at a gradually increasing temperature from 300 to 340 ° C, until a pitch with a softening temperature of 145 ± 5 ° C is obtained. The main disadvantages of this method include the low quality of the resulting coke, both in terms of the average microstructure score and the level of its homogeneity, determined by the distribution of structural elements in the coke.

DISCLOSURE OF THE INVENTION

The challenge faced by the developers of the present invention is to obtain coke of a pseudo-isotropic microstructure suitable for the production of carbon structural materials based on available and inexpensive raw materials - coal tar pitch (STP) and high-boiling coke products.

To solve the problem, a method has been developed for producing coke with a pseudo-isotropic microstructure from a feedstock containing a mixture of medium-temperature coal tar pitch and high-boiling coke products;

including the stages at which perform

thermal oxidation of feedstock at temperatures from 260 ° C to 340 ° C; and

coking oxidized feedstock;

characterized in that

the content of high-boiling coke-chemical products in the mixture is 50-80 wt%.

The technical result of the disclosed invention is to obtain a pseudo-isotropic microstructure coke suitable for the production of carbon structural materials based on coal tar pitch and high-boiling coke products.

BRIEF DESCRIPTION OF FIGURES DRAWINGS

FIG. 1 shows a table of the influence of the composition of raw materials on the average score of the microstructure of the resulting coke in each of examples 1-13.

CARRYING OUT THE INVENTION

In accordance with the present invention, the production of coke with a pseudo-isotropic microstructure is carried out from a feedstock containing a mixture of medium-temperature coal tar pitch and high-boiling coke products (VCPC). As high-boiling coke-chemical products, the mixture may contain at least one of: anthracene fraction of coal tar, pitch distillate, pitch coking tars and coke-chemical raw materials for the production of technical carbon. The use of an anthracene fraction of coal tar (AP) as VKPC is preferable, since AP has a more stable (predictable) composition and properties, which makes it possible to more accurately determine the parameters of the method in accordance with the present invention.

Due to the fact that high-boiling coke-chemical products, such as anthracene fraction of coal tar, pitch distillates, pitch coking tars, coke-chemical raw materials for the production of carbon black, have a similar composition, in the present invention, as high-boiling coke-chemical products, the mixture may contain at least one from: anthracene fraction of coal tar, pitch distillate, pitch coking tars and coke-chemical raw materials for the production of technical carbon.

The degree of isotropy of cokes is determined by the size of the mesophase, which is formed during carbonization in the temperature range 380-500 ° C. An increase in the size of mesophase formations during carbonization leads to an increase in the anisotropy of the obtained cokes and, accordingly, to an increase in the microstructure score of the cokes. In the disclosed invention, the method of controlling the size of the mesophase is the addition of VKPK. In contrast to coal tar pitch, the VKPC components have a lower molecular weight, a lower C / H atomic ratio and consist mainly of three to five annular condensed aromatic, heterocyclic compounds and their alkyl derivatives. Entering into polycondensation reactions initiated by atmospheric oxygen, the VKPC components form compounds with biphenyl, methylene and oxygen bridges, or other more complex cross-linked structures. In the process of carbonization, such compounds form an extremely small mesophase, or they are not at all capable of forming a mesophase. This is due to several factors: some of the compounds with low thermal stability decompose without participating in the formation of the mesophase and are removed with the gas phase, while the other part of the compounds as a result of thermal destruction forms nonplanar radicals that experience steric hindrance during the formation of the layered structure of mesophase spherulites.

The method in accordance with the present isorbeton includes the step of performing thermal oxidation of the feedstock at a temperature of 260 ° C to 340 ° C. Since 50% or more of VKPK boil away up to 360 ° C [Handbook of a coke chemist in 6 volumes. Volume 3. Catching and processing of chemical coking products / Under total. ed. Dr. tech. sciences E.T. Kovalev. - Kharkov: Publishing house "INZHEK", 2009. - 432 p.], It is advisable to carry out thermal oxidation at relatively low temperatures - 260-340 ° C. At temperatures below 260 ° C, the conversion depth of the components of the feedstock significantly decreases during thermal oxidation, and at temperatures above 340 ° C, the light part of the feedstock is intensively distilled off without participation in thermal oxidation reactions, which leads to a decrease in the yield and increased viscosity of ECP.

STP consists mainly of 4–10-ring condensed aromatic compounds, most of which, after low-temperature thermal oxidative treatment (260–340 ° C), do not lose the ability to form a mesophase during carbonization. Thus, in the process of thermooxidation of the mixture, STP acts as a source of mesogenic components, and VKPC functions as a restrictor of the growth of the mesophase during carbonization. Varying the composition of the mixture allows you to very finely control the microstructure of the resulting cokes and provide the required level of isotropy of properties. At the same time, with the content of VCPC below 50% (wt.) In the mixture, the average score of the microstructure increases (the degree of isotropy decreases), and with the content above 80% (wt.), A completely isotropic, non-graphitizing (sooty) coke is formed with an average score of the microstructure below 1.8. The optimal content of VCPK in the mixture is 50-80% (the optimal range at which the balance between mesogenic components and mesophase growth inhibitors is maintained) and depends on the temperature and duration of the thermal oxidation process. The higher the temperature and duration of the thermal oxidation process, the less VCPK is required to provide a pseudo-isotropic microstructure of the resulting coke. In this regard, it is preferable to carry out thermal oxidation at a temperature range of 300-340 ° C.

ECP obtained by the claimed method is characterized by a reduced viscosity associated with a high content of distillates in the feedstock. HPP and cokes based on them contain 0.2–0.4% sulfur, 1–1.5% nitrogen and trace amounts of ash impurities.

INDUSTRIAL APPLICABILITY

To implement the disclosed method for producing coke with a pseudoisotropic microstructure, the feedstock containing a weighed portion of a mixture of STP and VKPK weighing 600 g is loaded into a steel thermal oxidation reactor equipped with electric heating. In the process of thermal oxidation, compressed air is supplied to the reactor by a compressor, with a specific flow rate of 50-100 l / (kg⋅h), for the prototype - 15 l / (kg⋅h) (example 13). The specific consumption of the reaction air during thermal oxidation of the feedstock should not exceed 100 L / (kg⋅h), since above this value the pitch peroxidation is intensified, resulting in the formation of completely isotropic, non-graphitizing coke, and the device for supplying air to the reactor is coked. In addition, with an increase in the air flow rate above 100 l / (kg⋅h), the softening temperature of the resulting ECP can exceed 200 ° C. In this regard, the most preferable is the flow rate of the supplied reaction air in the process of thermal oxidation not more than 100 l / (kg⋅h). When the flow rate of the reaction air is less than 50 l / (kg⋅h), the required quality of the oxidized pitch is achieved, however, the thermal oxidation time increases significantly. The temperature is raised to values of 260-340 ° C at a rate of 20-25 ° C / min and holding at this temperature is ensured. The specific consumption of the reaction air and the duration of the thermal oxidation process are selected in such a way that the resulting ECP has a softening temperature not higher than 200 ° C, preferably not higher than 150 ° C.

The method also includes the step of coking the oxidized feedstock. During this stage, the resulting oxidized feedstock is coked in a porcelain crucible with a tightly closed lid under a coke bed to provide an inert environment. A sample of ECP weighing 100 g is loaded into the crucible and the temperature is gradually raised to 550 - 600 ° C. The final temperature is chosen to ensure the yield of volatile substances in the coke in the range of 3–6%, which is necessary for the CCM production technology. The heating rate is 0.5 ° C / min, the exposure at the final temperature is 1 hour.

Thermooxidation of feedstock on an industrial scale can be carried out in standard oxidation cubes, and coking - in a chamber furnace, coking cubes, or in unheated chambers (delayed coking). The softening point of the resulting ECP should be no higher than 200 ° C, more preferably no higher than 150 ° C. The softening temperature of ECP above 150 ° С will lead to difficulties with its pumping by pumps through process pipelines, and above 200 ° С - to the complete impossibility of pumping under the conditions of standard equipment of coke plants.

The possibility of carrying out the invention is confirmed by examples 1-12. Example 13 illustrates the implementation of the method in accordance with the prototype. The obtained results of the implementation of the invention in comparison with the prototype are presented in the table in figure 1.

Example 1. ECP and coke were obtained using the method in accordance with the disclosed invention.

A weighed portion of STP and AF weighing 600 g was loaded into a thermooxidation reactor, and the temperature was raised to 260 ° C using electric heating at a rate of 20 ° C / min. The duration (τ) and specific air consumption (G _c ) of the thermal oxidation process were 12 hours and 100 l / (kg⋅h), respectively. A weighed portion of the obtained ECP with a mass of 100 g was loaded into a porcelain coking reactor, the space above the lid was filled with coke breeze, the temperature was raised to 570 ° C at a rate of 0.5 ° C / min and held for 1 hour.

Examples 2-12. The experiments were performed in a similar way, but the temperature, duration, and flow rate of the reaction air during thermal oxidation were varied, and the AF content in the initial mixture was also changed. The parameters of the examples are shown in the table in Fig. 1.

Example 13. The temperature during thermal oxidation was raised gradually from 300 to 340 ° C at a rate of approximately 3.3 ° C / h, the specific air consumption was 15 l / (kg · h).

Example 13 shows data on the microstructure of coke and ECP obtained according to the prototype. The value of the average score of the microstructure shows that the coke is not pseudo-isotropic.

The content of AF in the feedstock in examples 1 is 60%, 2 is 80%, 4 is 50%, 5 is 60%, 6 is 70%, 9 is 60%, 12 is 50%. In these examples, a high quality homogeneous pseudo-isotropic coke was obtained, with an average microstructure score in the range of 1.8-2.5.

In examples 3, 8, the AP content was 40%, the microstructure of pseudo-isotropic coke was not provided due to the excessive content of mesogenic components of STP. In examples 7, 10, when the AF content in the initial mixture was 80%, a completely isotropic coke was formed with an average microstructure score of 1.1 and 1.2, respectively. This is due to an excess of nonplanar secondary compounds - products of AP oxidation, which have low mesogenic activity. In example 11, the content of AP was 30%, the microstructure of pseudo-isotropic coke was not provided due to the excess content of mesogenic components of STP.

Thus, when the AP content in the initial mixture is below 50%, the microstructure of pseudo-isotropic coke is not provided in all cases. At temperatures above 300 ° C (300-340 ° C), the AF content should be in the range of 50-70%, since high temperatures contribute to the deepening of the thermal oxidation process. At temperatures below 300 ° C, the AF content should be in the range of 50-80%.

Cokes with pseudo-isotropic microstructure are characterized by an average microstructure score of 1.8 to 2.5. Thus, the results of experiments in examples 1, 2, 4, 5, 6, 9, 12 confirm that the disclosed invention provides for the production of cokes with pseudo-isotropic microstructure.

Thus, the disclosed method makes it possible to obtain coke with a pseudo-isotropic microstructure suitable for the production of carbon structural materials based on coal tar pitch (STP) and high-boiling coke products.

The present invention has been disclosed in detail with reference to certain variants of its implementation, however, it is obvious that it can be implemented in various ways, without going beyond the claimed scope of legal protection defined by the claims.

Claims (8)

1. Method for producing coke with pseudoisotropic microstructure from a feedstock containing a mixture of medium-temperature coal tar pitch and anthracene fraction, including the stages at which perform thermal oxidation of the feedstock at a temperature of 260 to 340 ° C, during which the reaction air is supplied with a specific flow rate of 50-100 l / (kg⋅h), and coking oxidized feedstock, characterized in that the content of the anthracene fraction in the mixture is 50-80 wt%. 2. The method according to claim 1, characterized in that the thermal oxidation of the feedstock is carried out at a temperature of 300 to 340 ° C.

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