RU2224003C1 - Oil coke production process - Google Patents

Abstract

FIELD: petroleum processing. SUBSTANCE: needle coke manufacture consists in fractionation of coil distillate cracking residue followed by coking of fractionation residue preceded by adding heavy pyrolysis tar in amount 5-20% based on the weight of feedstock. EFFECT: improved quality of needle coke due to improved degree of anisotropy and reduced content of sulfur and increased yield of coke. 2 tbl, 6 ex

Description

 The invention relates to the field of oil refining, in particular to methods for producing needle coke used to produce large graphite electrodes.

 A known method of producing needle coke by fractionation of an oil distillate cracking residue to obtain a fractionation residue and its subsequent coking (Sunyaev Z. I. Production, refinement and use of petroleum coke. M .: Chemistry, 1973).

The disadvantage of this method is to obtain coke with a high sulfur content (above 0.8-1.0 wt.%) When using raw materials with insufficiently low sulfur content, which with further heat treatment leads to cracking of the finished form of the electrode due to the intense release of sulfur in the temperature range 1400- 1600 ^o C.

 In order to obtain needle coke with the necessary sulfur content (not higher than 0.5-0.6%), mixtures of distillate cracked residues with low-sulfur residues are usually used as raw materials.

 Closest to the claimed method is a method for producing needle coke by mixing oil distillate cracking residue with a heavy pyrolysis resin, followed by fractionation of the mixture and coking of the fractionation residue (Kolesnikova T.A., Slutskaya S.M., Rozanova A.P., etc. On the rational use of heavy pyrolysis resins for ethylene production. Oil Refining and Petrochemicals, 1978, 10, pp. 39-41).

The disadvantages of this method are as follows. The heavy pyrolysis resin, which is part of the raw material, has a lightweight fractional composition. When a mixture of a distillate cracking residue and a heavy pyrolysis resin is fed into the lower part of the fractionation column, where the temperature is maintained at 400 ^° C, most (up to 70 wt.%) Of the heavy pyrolysis resin evaporates and does not get coked. This significantly reduces the microstructure index of the obtained needle coke, as it is known (P. Pappel, J. Tuebel. "Karbonisierung von Pyrolyseteer und semen Jnhaltsstoffen zu hochanisotropen Koksen". - Freiberger Forschungshefte, 1980, A, N618, s. 79-97) that light- and especially medium-boiling fractions, which just evaporate, provide the most anisotropic coke. In addition, the sulfur content in the resulting coke is reduced to a lesser extent than would be expected by additivity.

 The invention is aimed at increasing the yield of coke while improving the anisotropy index and reducing the sulfur content.

 This is achieved by the fact that in the method for producing needle coke by fractionating an oil distillate cracking residue followed by coking the fractionation residue before coking, a heavy pyrolysis resin in an amount of 5-20 wt.% On the feedstock is added to the residue.

 The addition of a heavy pyrolysis resin to the fractionation residue immediately before coking will make it possible to optimally use its properties when forming the structure of acicular coke during coking. The light and medium boiling fractions that make up the heavy pyrolysis resin during coking contribute to the formation of acicular coke with a high microstructure rating.

 In addition, the involvement of the entire hydrocarbon composition of the heavy pyrolysis resin in the coking reaction increases the yield of coke, and since the proportion of low-sulfur feedstock in the formation of coke increases, its sulfur content decreases.

 The proposed method is as follows.

The feedstock — petroleum distillate cracking residue — is heated in a furnace coil to 340-370 ^° C and fed to the bottom of the distillation column for fractionation (bottom temperature of the column is 380-400 ^° C). A boiling component is removed from the top of the column, and the remainder of fractionation from the bottom. To the residue of fractionation add a heavy pyrolysis resin in an amount of 5-20 wt. % of the feedstock, the mixture is heated in an oven to a temperature of 495-510 ^o C and served in a coking reactor.

 Example 1 (prototype method).

The distillate cracking residue obtained by thermal cracking of hydrotreated vacuum gas oil was mixed with a heavy pyrolysis resin (characteristics of the raw material components are given in table 1) at a ratio, wt. % 90:10. The mixture was heated in a furnace coil to a temperature of 350 ^o C and served in the lower part of the distillation column. The low boiling components of the feedstock are removed from the top of the column, and the fractionation residue from the bottom. The remainder of the fractionation was heated in an oven to 495-510 ^{° C.} and fed to a coking reactor. The yield of acicular coke was 27.5 wt.%, The coke sulfur content was 0.74 wt.%, And the microstructure was estimated to be 5.0 points.

 Example 2 (by the proposed method).

The distillate cracking residue obtained by thermal cracking of hydrotreated vacuum gas oils, the characteristics of which are shown in Table 1, was heated in an oven to 350 ^° C and fed to the bottom of the distillation column. The low boiling components of the feedstock are removed from the top of the column, and the fractionation residue from the bottom. A heavy pyrolysis resin was added to the fractionation residue (the characteristics are given in table 1) in an amount of 10 wt.% For the feedstock, the mixture was heated in an oven to a temperature of 495-510 ^{° C.} and fed to a coking reactor. The yield of acicular coke was 29.0 wt.%, The sulfur content in coke was 0.65 wt.%, The microstructure was estimated at 5.6 points.

 Examples 3-6 (by the proposed method).

 Needle coke is obtained analogously to example 2, but a heavy pyrolysis resin is added in an amount of 5, 20, 30 and 50 wt.%, Respectively, of the feedstock.

 The results of the examples are summarized in table 2.

 As can be seen from the table, when adding heavy pyrolysis resin to the fractionation residue in an amount of 5-20 wt.% (Examples 2-4), the degree of anisotropy of the obtained needle coke is significantly improved - the microstructure estimate increases to 5.4-5.6 points (in the prototype 5.0 points), the sulfur content decreases to 0.58-0.65 wt.% (In the prototype 0.74 wt.%) And the yield of coke is increased by 1.2-1.8 wt.% Compared with the method prototype. When adding a heavy pyrolysis resin of less than 5 wt.%, Its influence is not significant, and when added in an amount of more than 20 wt.% (Examples 5, 6), the evaluation of the needle coke microstructure is reduced.

 Thus, the proposed method will improve the quality of needle coke by improving the degree of anisotropy and reducing the sulfur content in it with a simultaneous increase in its yield.

Claims (1)

A method of producing needle coke by fractionation of an oil distillate cracking residue followed by coking of the fractionation residue, characterized in that before coking, a heavy pyrolysis resin is added to the fractionation residue in an amount of 5-20 wt.% On the feedstock.

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