RU2586139C1 - Method of producing binder for making carbon materials and articles therefrom - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, particularly, to production and preparation of electrode pitch intended for production of anode mass, coal and graphite products, structural-graphite materials and can be used in coke-chemical industry. According to disclosed method starting material used is oxidised resin of low temperature pyrolysis of coal. Process involves oxidation of resin from low temperature pyrolysis of coal at a temperature of 100-250 °C and air supply in an amount of 20-60 l/kg and subsequent mixing at a ratio of 90:10 to 10:90 wt% of oxidised resin from low temperature pyrolysis of coal with coal-tar resin or fractions of coal-tar resin and pitch distillates or liquid oil refining products having an aromatic structure, and thermal treatment of obtained mixture at 350-430 °C in liquid phase with separation of distillate fractions and undistilled distillation residue.

EFFECT: technical result is expansion of raw material base for producing binder electrode pitch and reduced carcinogenicity of binder by reducing amount of benz(a)pyrene.

3 cl, 7 tbl, 17 ex

Description

The invention relates to the field of metallurgy, in particular to methods for producing and preparing electrode pitch intended for the production of anode paste, coal and graphite products, structural carbon and graphite materials, and can find application in the coke industry.

The main type of binder for the production of the anode paste is coal tar pitch - the non-distillable residue of the distillation of coal tar.

The most widespread in industry for the production of the anode paste was the B grade coal-tar electrode pitch according to GOST 10200-83, the quality indicators of which are shown in Table 1.

Coal tar is a by-product of the process of producing metallurgical coke from coal, so the scale of its production and qualitative characteristics are determined by the need for metallurgical coke and the existing state of the technology of coal coking.

Currently, due to a decrease in the production of metallurgical coke, used mainly for the production of pig iron, the production of coal tar and the production of coal tar associated with it are declining. This forces us to look for new ways to increase binder resources for the anode mass. The use of oil pitch to reduce the deficit of coal tar pitch is not widely used. Oil sands, obtained on the basis of heavy fractions and refining residues, have a low coke residue and do not allow to obtain high-quality anode mass. An acceptable way to involve oil pitch in the production of anodes is to obtain a combined binder from coal and oil pitch [McHenry E.R. Coal-tar / petro industrial pitches. Light Metals. 1997. P. 543-548; Wombles R.H., Kiser M.D. Developing coal tar / petroleum pitches. Light Metals. 2000. P. 537-541].

The second reason for the desired reduction in the use of coal tar pitch for the production of anode paste is its high content of polycyclic aromatic hydrocarbons (PAHs), some of which are carcinogenic. In practice, the concentration of benz (a) pyrene in the binder pitch or in emissions during coking is used as an indicator of the PAH content. Coal tar pitch is the main source of PAH emissions at aluminum plants with self-baking Soderberg anodes. It has been shown that the use of oil-tar pitch with a low PAH content, compared with coal tar pitch, can significantly reduce the emission of PAHs from industrial Soderberger electrolyzers [Boenigk W. et al. Production of low PAH pitch for use in Soederberg smelters. Light Metals. 2002. P. 519-524].

The production of oil-coal tar pitch new to the industry in the above cited works was carried out by mixing coal tar and oil pitch.

In the patent US 5746906, IPC C10C 3/00, publ. 05/05/1998, a method for producing a hybrid oil-tar pitch with a softening temperature in the range of 107-114 ° C and a low PAH content by mixing coal tar pitch with an increased softening temperature and oil pitch with a reduced softening temperature in the ratio of 60:40 is proposed.

In the patent RU No. 2080418, IPC С25С 3/12, publ. 05/27/97, it is proposed in the production of the anode paste as a carbon-containing binder to use a homogeneous mixture obtained by mixing coal tar pitch with oil pitch at a ratio of 19: 1-2: 1. Mixing coal tar pitch with oil pitch is carried out by pumping the mixture from the lower zone of the tank to the upper zone at the rate of 1-3-fold exchange of the total flow in a turbulent mode.

The disadvantage of methods for producing oil-tar pitch, using a mixture of oil and coal, is the need for industrial production of oil pitch. In addition, the stage of mixing coal and oil pitch requires capital and energy costs associated with the creation of the installation, including heated containers for the pitch and equipment for mixing.

Closest to the proposed invention in technical essence and the achieved result is a method of producing a binder for the manufacture of carbon materials and products from them (patent RU No. 20133416, IPC C1 C04 35/52, publ. 05/30/94.). According to this patent, a binder is obtained on the basis of coal tar pitch by heat treatment of coal tar. Before the heat treatment, a heavy oil pyrolysis resin or a distillate cracking residue in an amount of 10-35 masses is added to the coal tar resin. % The method allows to reduce the amount of benz (a) pyrene in the binder and expand the raw material base for its production. The distillate cracking residue, or heavy gas oil of catalytic cracking, is the bottom product of thermal cracking of petroleum products formed in catalytic oil refining processes at 350-480 ° C, designed to produce motor fuels.

The disadvantage of this method is the low quality of the obtained pitch and the high content of benz (a) pyrene in it. According to this method, a pitch is obtained with a benz (a) pyrene content of 1.32 to 1.84%, an α-fraction of up to 25% and a softening temperature of not higher than 81 ° C, which does not meet modern requirements for the quality of electrode pitch according to GOST 10200 and the characteristics of oil-tar pitch used to obtain the anode mass, are shown in table 1.

The objective of the present invention is to expand the raw material base to obtain a binder pitch.

The technical result is to improve the quality characteristics of the binder pitch and reduce the content of benz (a) pyrene.

            The technical result is achieved by the fact that the method of producing a binder pitch for the manufacture of carbon materials and products from them includes the oxidation of the resin of low-temperature pyrolysis of coal at a temperature of 100-250 ° C and with an air supply of 20-60 l / kg of resin and subsequent mixing in a ratio of 90:10 to 10:90 mass. % of oxidized resin of low-temperature pyrolysis of coal with coal tar or fractions of coal tar and pitch distillates or liquid refined petroleum products having an aromatic structure, and heat treatment of the resulting mixture at 350-430 ° C in the liquid phase with separation of the distillate fractions and the non-distillable distillation residue.

The proposed method is complemented by private distinctive features that contribute to the achievement of the specified technical result.

As a resin of low-temperature pyrolysis of coal, a heavy semi-coking resin of coal (coal oil) can be used, which is a liquid product of low-temperature coking of coal, satisfying the conditions:

Density at 20 ° C from 1020 kg / m ³ to 1100 kg / m ³ _.

Viscosity at 60 ° C no more than 5 ° U,

Mass fraction of substances insoluble in toluene, from 0.5 to 5%.

Mass fraction of moisture no more than 5%.

Ash content is not more than 0.2%.

Flash point at least 95 ° C.

As a resin of low-temperature coal pyrolysis, a heavy coal gasification resin can be used, which is a liquid product that satisfies the conditions:

Density at 20 ° C more than 1000 kg / m ³ _.

Mass fraction of substances insoluble in toluene, more than 0.2%.

Mass fraction of moisture no more than 5%.

Coking property (coke number) not less than 3%.

Ash content is not more than 0.2%.

Resin of low-temperature pyrolysis of coal has a minimum content of benz (a) pyrene, so that its use as a raw material can reduce the carcinogenic danger of binder pitch for anodes.

Coal tar is a liquid product of coal coking upon receipt of metallurgical coke, satisfying the conditions:

Density at 20 ° C from 1180 to 1240 kg / m ³ _.

Mass fraction of water no more than 4%.

Mass fraction of substances insoluble in toluene, no more than 12%.

Mass fraction of substances insoluble in quinoline, not more than 6%.

Mass fraction of ash is not more than 0.1%.

The anthracene fraction and pitch distillates are the heaviest distilled fractions of coal tar, satisfying the conditions:

Density at 20 ° C not less than 1100 kg / m ³ _.

The volume fraction of water is not more than 1.5%.

Coking property (coke number) not less than 1%.

Mass fraction of ash is not more than 0.1%.

The distillation of the fraction boiling up to 300 ° C, not more than 30%.

Liquid petroleum products must have an aromatic structure, since saturated and unsaturated hydrocarbons and naphthenes do not mix with coal tar and semi-coking tar. Such products include heavy hydrocarbon pyrolysis resins and heavy catalytic or thermal cracking gas oils. Moreover, the liquid oil product must satisfy the conditions:

Density at 20 ° C not less than 1020 kg / m ³ _.

Viscosity at 100 ° C no more than 20 cSt.

Coking ability not less than 5%.

The distillation of the fraction boiling up to 300 ° C, not more than 5%.

The proposed method allows to obtain a binder pitch with quality indicators similar to those for a coal-tar electrode pitch, while the content of benz (a) pyrene is lower than for oil-coal tar pitch obtained by mixing and prototype, see table 1.

Based on the experimental results, the following technological parameters were selected to obtain pitch suitable for the manufacture of the anode mass. At the first stage, the resin is oxidized by low-temperature pyrolysis of coal with atmospheric oxygen in the temperature range of 100-250 ° C and an air flow rate of 20-60 l / kg.

In the second stage, the thermal oxidation product is mixed in a ratio of 90:10 to 10:90 with one of the components: a) coal tar; b) anthracene fraction of coal tar or pitch distillates; c) liquid refined products.

The resulting mixture is subjected to heat treatment at a temperature of the liquid phase of 350-430 ° C with separation of the distillate fractions and the non-distillable distillation residue.

The first stage of thermal oxidation of the resin of low-temperature pyrolysis of coal at temperatures below 100 ° C does not lead to a change in the parameters of the starting materials. Thermal oxidation at temperatures above 250 ° C leads to premature polymerization of the molecules of the starting resin, which negatively affects the subsequent stage of joint heat treatment with other products. When the air flow at the stage of thermal oxidation is below 20 l / kg in the resin of low temperature pyrolysis, polymerization reactions are not initiated. An air flow rate of more than 60 l / kg is excessive, since the rate of oxidation reactions is limited by the diffusion rate of air bubbles.

The second stage - mixing - involves the use of at least 10% and not more than 90% of the products of thermal oxidation from the first stage. An amount of less than 10% is impractical to use, since this will not lead to a significant reduction in the content of benz (a) pyrene in the finished binder pitch. An amount of more than 90% is also undesirable, since the finished binder pitch will have a low softening temperature and a coke residue. Heat treatment of the resulting mixture is carried out at a temperature of the liquid phase 350-430 ° C. Conducting the process at temperatures above 430 ° C reduces the yield of binder pitch and causes undesirable formation of mesophase particles (secondary α ₁ fraction). At temperatures below 350 ° C, not all volatile substances are distilled off, which results in a binder pitch with a high content of volatile substances.

The proposed method can be carried out both in batch and continuous mode on existing coal tar processing plants.

The invention is illustrated by the following examples.

Example 1. The resin semi-coking coal (coal oil) has the following properties: density at 20 ° C 1,033 g / cm ³ ; coke residue 4.9%, ash 0.2%, mass fraction of substances distilled to 360 ° C, 16.3%, benz (a) pyrene content 0.2 mg / g resin.

The semi-coking resin was thermally oxidized at 227 ° C for 1 hour. Air consumption was 23 l / kg resin. The resulting oxidized resin sample had a density of 1.072 g / cm ³ _.

Coal tar corresponds to TU 2453-203-00190437-2005 “Coal tar for processing”, density at 20 ° C 1182-1202 kg / m ³ , content of α-fraction 6.8-9.4%, α ₁ -fraction 1, 9-3.1%. A mixture of coal tar and oxidized semi-coking resin in the ratio of coal tar: semi-coking resin 40:60 mass. % is placed in a round bottom glass flask with a capacity of 0.5 l. 200 g of the mixture are distilled at a final temperature of the liquid phase of 380 ° C with exposure at this temperature for 1 hour. A binder pitch is obtained with a yield of 52.0%.

Example 2. Mix coal tar and oxidized semi-coking resin, as in example 1, in a ratio of 50:50 mass. % 203 g of the mixture are distilled at a final temperature of the liquid phase of 380 ° C and holding for 1 h, a binder pitch is obtained with a yield of 55.5%.

Example 3. Mix coal tar and oxidized semi-coking resin, as in example 1, in a ratio of 60:40 mass. % 202 g of the mixture are distilled at a final temperature of the liquid phase of 380 ° C and holding for 1 h, a binder pitch is obtained with a yield of 60.6%.

Example 4. Mix coal tar and oxidized semi-coking resin, as in example 1, in the ratio of 70:30 mass. % 203 g of the mixture are distilled at a final temperature of the liquid phase of 380 ° C and holding for 1 h, a binder pitch is obtained with a yield of 55.5%.

Example 5. 200 g of oxidized semi-coking resin, as in example 1, is distilled at a final temperature of the liquid phase 364 ° C and exposure for 1 h, get a binder pitch with a yield of 46.2%.

Example 6. 200 g of coal tar, as in example 1, is distilled at a final temperature of the liquid phase of 380 ° C and exposure for 1 h, get a binder pitch with a yield of 48.0%.

The characteristics of the binder pitch obtained in examples 1-6 are shown in table 2.

Example 7. The anthracene fraction of coal tar corresponds to GOST 11126 “Coke-chemical raw materials for carbon production”, density 1.13 g / cm ³ , coke number 1.2%, ash content 0.04%, fraction distillation up to 300 ° C 15.5% . The anthracene fraction is mixed with an oxidized semi-coking resin, as in example 1, in a ratio of 85:15 mass. % 800 g of the mixture are distilled at a final temperature of the liquid phase of 400 ° C, and a binder pitch is obtained with a yield of 25.4%.

Example 8. The anthracene fraction, as in example 7, is mixed with an oxidized semi-coking resin, as in example 1, in a ratio of 66:34 mass. % A distillation of 800 g of the mixture is carried out at a final temperature of the liquid phase of 413 ° C., a binder pitch is obtained with a yield of 30.9%.

Example 9. A distillation of 800 g of the anthracene fraction is carried out, as in Example 7, at a final temperature of the liquid phase of 390 ° C., a binder pitch is obtained with a yield of 29.7%.

The characteristics of the binder pitch obtained in examples 7-9 are shown in table 3.

Example 10. The pitch distillate has the following properties: density 1.15 g / cm ³ , coke number 2.6%, ash 0.03%, distillation of fractions to 300 ° C 3.5%. The pitch distillate is mixed with an oxidized semi-coking resin, as in example 1, in a ratio of 66:34 mass. % 200 g of the mixture are distilled at a final temperature of the liquid phase of 425 ° C, and a binder pitch is obtained with a yield of 32.8%.

The characteristics of the binder pitch obtained in example 10 are shown in table 4.

Example 11. A heavy coal gasification resin has the following properties: density at 20 ° C 1.008 g / cm ³ ; coke residue 3.0%, ash 0.2%, water content 2.4%, benz (a) pyrene content 0.2 mg / g resin.

The heavy coal gasification resin was thermally oxidized at 230 ° C. for 1 hour. Air consumption was 23 l / kg resin. The resulting sample of oxidized heavy gasification resin had a density of 1.035 g / cm ³ . Coal tar, as in example 1, is mixed with an oxidized gasification resin in a ratio of 80:20 mass. % 200 g of the mixture are distilled at a final temperature of the liquid phase of 363 ° C, and a binder pitch is obtained with a yield of 49.4%.

Example 12. The coal tar resin, as in example 1, is mixed with an oxidized gasification resin, as in example 10, in a ratio of 90:10 mass. % 200 g of the mixture are distilled at a final temperature of the liquid phase of 364 ° C, and a binder pitch is obtained with a yield of 50.3%.

The characteristics of the binder pitch obtained in examples 11 and 12 are shown in table 5.

Example 13. Heavy catalytic cracking gas oil has a density at 20 ° C of 1078 kg / m ³ , coking ability of 6.8%, viscosity at 100 ^o C of 16 cSt; the content of the a fraction is 0.8%, and the ₁ fraction is absent. The oxidized semi-coking resin, as in example 1, is mixed with heavy gas oil in a ratio of 20:80 mass. % 200 g of the mixture are distilled at a final temperature of the liquid phase of 420 ° C with holding at this temperature for 2 hours, a binder pitch is obtained with a yield of 48%.

Example 14. The oxidized semi-coking resin, as in example 1, is mixed with heavy gas oil, as in example 12, in a ratio of 40:60 mass. % 200 g of the mixture are distilled at a final temperature of the liquid phase of 430 ° C with holding at this temperature for 2 hours, a binder pitch is obtained with a yield of 44%.

Example 15. The oxidized semi-coking resin, as in example 1, is mixed with heavy gas oil, as in example 12, in a ratio of 50:50 mass. % 200 g of the mixture are distilled at a final temperature of the liquid phase of 436 ° C with holding at this temperature for 1.5 hours, a binder pitch is obtained with a yield of 40%.

Example 16. The oxidized semi-coking resin, as in example 1, is mixed with heavy gas oil, as in example 12, in the ratio of 70:30 mass. % 200 g of the mixture are distilled at a final temperature of the liquid phase of 436 ° C with holding at this temperature for 3 hours, a binder pitch is obtained with a yield of 34%.

The characteristics of the binder pitch obtained in examples 13 to 16 are shown in table 6.

Example 17. A sample of binder pitch obtained under the conditions of example 3 weighing 2 kg was tested upon receipt of the anode mass. The characteristics of the anode mass produced on the pitch in example 3 are shown in table 7.

The results obtained indicate the possibility of obtaining a binder electrode pitch with a reduced content of benz (a) pyrene. Moreover, for the manufacture of pitch is used resin low-temperature pyrolysis of coal. The test results of the anode paste based on the binder obtained by the proposed method correspond to the quality of a conventional anode paste on grade B coal tar pitch, while the release of carcinogenic pyrolysis products, such as benzo (a) pyrene, will be reduced. Thus, the proposed method allows to obtain a binder pitch suitable for the manufacture of the anode mass, but with reduced carcinogenic activity.

Claims (3)

1. A method of producing a binder pitch for the manufacture of carbon materials and products from them, including the oxidation of the resin of low-temperature pyrolysis of coal at a temperature of 100-250 ° C and with an air supply of 20-60 l / kg of resin and subsequent mixing in a ratio of 90:10 up to 10:90 wt.% oxidized resin of low-temperature pyrolysis of coal with coal tar or fractions of coal tar and pitch distillates, or liquid petroleum products having an aromatic structure, and heat treatment of the resulting mixture at 350-430 ° C in liquid phase with separation of the distillate fractions and the non-distillable distillation residue. 2. The method according to claim 1, characterized in that as the resin of low-temperature pyrolysis of coal, a heavy semi-coking resin of coal (coal oil) is used, having physical and chemical properties: density at 20 ° C from 1020 kg / m ³ to 1100 kg / m ³ ; viscosity at 60 ° C not more than 5 ° C; mass fraction of substances insoluble in toluene, from 0.5 to 2.5%; mass fraction of moisture not more than 5%; ash content not more than 0.2%; flash point not less than 95 ° C. 3. The method according to claim 1, characterized in that as the resin of low-temperature coal pyrolysis, a heavy coal gasification resin is used, having physical and chemical properties: density at 20 ° C more than 1000 kg / m ³ ; mass fraction of substances insoluble in toluene, more than 0.2%; mass fraction of moisture not more than 5%; coking ability (coke number) not less than 3%; ash content not more than 0.2%.