Petroleum Coking Additive

Abstract

The quality of coke is improved by increasing the coking properties of a component of a coking feedstock (a coking additive) and by ensuring stability of the coking properties of a component when the coking additive constitutes up to 99% of the total volume of the coking feedstock. The result is an increase in the stability of a coking additive and in the coking properties of said coking additive. It is achieved by a petroleum coking additive consisting of a product of the delayed low temperature carbonization of heavy petroleum residues at temperatures of up to 500 C., said product being characterized by a 14 to 28% volatile substance content, the product of the delayed low temperature carbonization of heavy petroleum residues obtained at a recycle ratio of from 1.05 to 1.2 in the coking chamber is characterized by coking properties of not less than G on the Gray-King scale.

Claims

1. A petroleum coking additive comprising a product of a delayed low temperature carbonization of heavy petroleum residues at temperatures of up to 500 C., the product having a content of volatile substances from 14% to 28%, the product being obtained in the coking chamber at a recycle ratio from 1.05 to 1.20 and having a coking property of no less than G on a Gray-King scale.

Description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Petroleum caking additives produced at various oil-processing plants differ considerably from each other, depending on the volatile substances yield. Table 1 shows parameters of caking of the additives achieved at various oil-processing plants, and indexes of quality of the coke produced from them.

[0012] Caking properties were determined by the method GOST R ISO 15585-2009 Determining of caking index; coking of the additives was performed in a Nikolayev furnace until the temperature in the middle of the charge was achieving 1000 C.

TABLE-US-00001 TABLE 1 Caking Manufacturer Volatiles properties, G, No. plant yield, % units CSR, % CRI, % 1 Novoil 16.82 56.5 23.9 2 Novoil 15.42 66.2 26.0 3 Novoil 15.82 68.8 20.5 4 Ufaneftekhim 16.30 74.0 19.0 5 Ufaneftekhim 19.40 77.1 19.7 6 Ufaneftekhim 20.24 76.2 20.5 7 Lukoil 15.72 74.1 23.0 8 Lukoil 18.71 76.1 20.8 9 Lukoil 19.41 77.0 20.0

[0013] Instability of caking additives quality, in the authors' view, is explained by the fact that they are manufactured on different equipment and at different technologies.

[0014] In process of work with coking additives produced according to the known technologies, it was found that they do not always possess good coking properties (as it is known, coking and caking properties differ from each other), which also does not make possible to produce a good furnace coke with the stable quality.

[0015] Thus, as it turned out, stability of properties of the coke produced with the content of the known coking additives will depend, to a large extent, not only upon the additive composition and the method of its producing but also upon the equipment and definite technologies which are used for producing the coking additives, upon the original (inherent) properties of the raw stock for producing the additive which are conditioned, among others, by the locality of the raw stock origin. In a word, the stability of the additive properties occurred to be to a large extent dependable on factors which seem to be second-rate, at first sight, and do not influence the additive properties in an obvious way.

[0016] According to the claimed method, a mixture of heavy oil residues is held for 14-24 hours at temperature 450-470 C., with the recycle ratio K.sub.p=1.051.2. The recycle ratio is a proportion of the newly-generated low-boiling coking products in relation to the total mass of the raw stock fed for coking which is returned back into the reactor. Involving of recycle fractions into the coking original stock wherefrom the coking additive is produced will contribute to improving of composition stability of the obtained product due to the fact that the recycle is a product of coking (more exactly, delayed carbonization, as it is realised at temperatures up to 500 C.) which has already passed thermal conversions and, consequently, possesses improved thermal stability, and when it is recycled into the coking process it will be subject to the cracking (disintegration) reactions to a lesser extent. But increasing of the recycle ratio above 1.2 (i.e. when the coking process involves large amounts of thermally stable recycling fractions which have already passed thermolysis) results in receiving of a coking additive with a lesser percentage of volatiles. On the contrary, decreasing of the recycle ratio below 1.05 contributes to receiving of a coking additive with too large amount of volatiles. In the both cases, it will deteriorate coking properties of the additive.

[0017] The petroleum semi-coke produced at temperature 450-470 C. with the recycle ratio K.sub.p=1.051.2 is characterised with high coking property values, which makes it possible to add in into a coal feedstock in any weight proportionsup to 99 wt %.

[0018] For conducting tests, samples of petroleum semi-coke were taken which were obtained at temperature 465 C. with the recycle ratio K.sub.p=1.051.2, with different value of volatile substances yield (in %).

[0019] It is known that the index of coking property of hard coals is defined by Gray-King method (GOST 16126-91 (ISO 502-82)).

[0020] It is also known that the index of coking property defined by Gray-King method does not possess exact (direct or other) correlation with the volatiles percentage index or free swelling index. At various values of volatiles percentage the coking property index on the Gray-King scale can be identical, e.g. G.

[0021] In such a case, the authors of the invention believe that the index of coking property on the Gray-King scale characterizes not only the additive coking property but also the qualitative composition of volatile substances. In particular, caking and coking properties of volatiles in the petroleum coking additive (PCA) will be defined by their aromaticity. The more aromatic volatile substances are the higher is extent of their caking and coking properties, even at their lesser percentage in PCA, and vice versa. In this connection, by increasing of the recycle ratio we will increase the extent of volatiles aromatising and thus improve caking and coking properties of the PCA itself. On the contrary, due to decreasing of the recycle ratio, substances remain in the coke which have not been completely subjected to cracking, consequently, the PCA will posses lesser caking and coking properties.

[0022] Samples of petroleum semi-coke obtained with various values of the recycle ratio and with various values of volatiles yield (within 11.2-28.5%) were taken for analysis. Identification of the type of petroleum semi-coke by Gray-King method was conducted in a tubular furnace per GOST 16126-91 (ISO 502-82). Results of the experiment are presented in

TABLE-US-00002 TABLE 2 Volatiles Recycle Coke type by Gray- Sample No. yield, % ratio King method 1 11.0 1.05 C 2 11.0 1.20 C 3 12.0 1.05 C 4 12.0 1.20 D 5 13.0 1.05 D 6 13.0 1.20 G 7 14.0 1.05 G 8 14.0 1.20 G 9 15.0 1.05 G1 10 15.0 1.20 G2 11 17.0 1.05 G3 12 17.0 1.20 G4 13 20.0 1.05 G5 14 20.0 1.20 G5 15 23.0 1.05 G3 16 23.0 1.20 G5 17 25.0 1.05 G3 18 25.0 1.20 G4 19 27.0 1.05 G1 20 27.0 1.20 G2 21 28.0 1.05 G 22 28.0 1.20 G

[0023] The following consistent pattern has been found during investigation: the semi-coke type per Grey-King scale improves as the value of volatiles yield increases and, tentatively, when the value of volatiles yield is equal to 14%, the coke residue of the petroleum coking additive will melt into strong or normal coke (of G type). It means that the coking additive with the volatiles yield over 14% can be added into coal feedstock without any quantitative limits.

[0024] When the volatiles value is equal to 28%, the coking property value per Grey-King becomes equal to G again (like at the volatiles percentage equal to 14%). As the volatiles percentage grow again, we observe decrease of the coking additive coking property below the normal G level.

[0025] As a result of conducted investigation related to identification of factors influencing stability of properties of the coke produced from such coking additive, it was found that of significance is not only the quantitative content of volatiles in the cocking additive but their qualitative composition as well which, in this case, is characterized by the coking property per Grey-King.

[0026] The quality of furnace coke produced from the mixture of industrial coal feedstock of Mechel PJSC with the offered petroleum coking additive is presented in Table 3. The coal feedstocks were coked in a Nikolayev furnace until the temperature in the middle of the charge was achieving 1000 C.

TABLE-US-00003 TABLE 3 Coke type by Grey- Feedstock King method CRI, CSR, CBS, No. composition from PCA % % % 1 Coal feedstock - 100% 32.0 52.0 84.0 2 Feedstock 95% + PCA G4 31.2 54.6 84.2 5% 3 Feedstock 85% + PCA G3 29.1 56.0 84.7 15% 4 Feedstock 70% + PCA G3 27.5 58.9 85.2 30% 5 Feedstock 50% + PCA G4 26.1 63.6 85.8 50% 6 Feedstock 30% + PCA G3 23.6 66.7 86.0 70% 7 Feedstock 5% + PCA G3 19.7 72.1 87.3 95%

[0027] The obtained results show that use of the petroleum coking additive with the coking property value per Grey-King scale not lower than G will allow to produce furnace coke of high and stable quality at any weight proportion coking additivecola in feedstock.

[0028] Under stability we mean, first of all, mechanical strength of the coke: in all cases it is higher than that of the coke from a 100% coal feedstock. As for reacting power and hot strength, they both can be varied depending on certain needs of the coke consumers.

[0029] The price of a petroleum coking additive is lower than that of coking hard coals, so use of large amounts of the additive for producing of furnace coke (without deterioration of its quality) will make it possible to significantly improve economic efficiency indexes of by-product coke industry and metallurgical plants.

[0030] A product of the delayed coking of oil processing residues with the content of volatiles from 14 to 28% and the coke type not less than G on the Gray-King scale is applied as a petroleum coking additive (PCA) to coal feedstocks which are used for producing of furnace coke. The invention makes it possible to create an additive to coal feedstocks ensuring joint coking in coal feedstocks with adding in any weight proportions without the coke quality deterioration.