JPH02212593A - Method of conversion of heavy hydrocarbon feedstock - Google Patents

Abstract

PURPOSE: To enhance a conversion ratio of a heavy asphaltene-containing hydrocarbon feedstock to a product having a lower b.p. by pyrolyzing the raw material under a specific condition.

CONSTITUTION: A hydrocarbon feedstock containing heavy asphaltene composed of 25 wt.% or more of a hydrocarbon with a b.p. of 520°C or higher pref. being a vacuum residual oil of crude oil is preheated to be passed through a pyrolyzing zone held to a condition setting a conversion ratio of hydrocarbon with a b.p. of 520°C or higher to 35-70 wt.% and, subsequently, the effluence from the pyrolyzing zone is separated into one or more kinds of a distillation fraction (e.g.; gas, gasoline, intermediate fraction, vacuum distillate) and a residual fraction, and the residual fraction is deasphalted to be separated into asphalt and deasphalted oil.

COPYRIGHT: (C)1990,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a process for converting a heavy asphaltene-containing hydrocarbon feedstock consisting of at least 25% by weight of hydrocarbons having a boiling point of at least 520° C. to a lower boiling point product. be.

Pyrolysis is a suitable method for converting heavy asphaltene-containing hydrocarbon feedstocks into products with lower average boiling points. Pyrolysis is a fairly simple method,
It consists of preheating the feedstock to a suitable temperature and transporting the preheated feedstock to a pyrolysis zone where pyrolysis occurs. At the outlet of the pyrolysis zone, the effluent is generally quenched to stop the pyrolysis reaction, and the effluent is fractionated to provide one or more distillate fractions and a residue. The residue, which contains nearly all of the asphaltenes present in the pyrolysis products, is generally no longer processed and disposed of in refineries or as commercial fuel.

An important feature of this process is that the pyrolysis residue after blending with suitable diluents gives the resulting fuel the desired product properties such as viscosity, sulfur content, density and Conradson carbon number. Regarding the stability of If thermal decomposition becomes excessive,
It is known that the properties of asphaltenes and oils change to form sludge. Sludge formation occurs particularly during thermal decomposition of asphaltene-containing feedstocks. If the feedstock is deasphalted and the deasphalted oil is pyrolyzed, only at very high conversions
A considerable amount of sludge is formed. Basically, sludge is
It consists of coke particles that do not dissolve in cracked oil and/or fuel when fuel is produced by blending cracked residual oil. Once a certain limit of sludge formation is exceeded, the fuel no longer meets commercial fuel specifications.

A way to prevent sludge is to moderate the degree of pyrolysis treatment. Therefore, depending on the type of feedstock, the degree of pyrolysis is selected such that the conversion of heavy hydrocarbons (ie, hydrocarbons with boiling points above 520° C.) is about 30% by weight or less.

Sludge formation problems are avoided at this conversion level. In this case it would be clear that the yield with respect to the distillate is not optimal; other methods of preventing sludge formation are
The feedstock is deasphalted prior to pyrolysis treatment. In this case, conversion levels higher than 30% by weight are obtained. However, the removed asphaltenes no longer contribute to the formation of the distillate, so that in this case too the yield with respect to the distillate is not optimal.

Batch processes that attempt to maximize yield on distillate retard coke formation. In this process, the feedstock remains in a so-called coker drum where it decomposes and produces distillate and coke. When the heavy product is circulated and the coker drum is filled with coke,
Processing continues with other coker drums. Therefore, the coker drums are filled/drained in batches. It is clear that the retardation of coke formation, the batchwise operation and the more or less solid coke that must be disposed of, is a disadvantage of this process.

The present invention provides a method for increasing conversion without the problems of unstable residues and batchwise operation, and increasing distillate yield.

The present invention therefore provides a method for preheating a hydrocarbon feedstock in converting a heavy asphaltene-containing hydrocarbon feedstock consisting of at least 25% by weight of hydrocarbons having a boiling point of at least 520°C to a product having a lower boiling point. passing said preheated feedstock through a pyrolysis zone to obtain a conversion of at least 35% by weight of hydrocarbons having a boiling point above 520'C; A method is provided for converting a heavy asphaltene-containing hydrocarbon feedstock by separating it into a distillation fraction and a residual fraction, and deasphalting the residual fraction to obtain asphalt and deasphalted oil.

The resulting asphalt contains solid coke particles that may be formed during the pyrolysis reaction, and the deasphalted oil contains almost no asphaltenes and is less than the residual fraction obtained by separating the effluent from the pyrolysis zone. It has low viscosity, low density and low Conradson carbon number. Deasphalted oils do not exhibit any stability problems and can be used directly as a formulation component in the production of commercial fuels, or can be used for different purposes.

The heavy hydrocarbon feedstock used in the process of the invention consists of a small amount (25% by weight) of hydrocarbons having a boiling point of at least 520°C (520°C hydrocarbons).5
When the proportion of 20°C hydrocarbons is low, stability problems seem less likely to occur.

A convenient feedstock is the atmospheric residue of crude oil (so-called long residue).
including. Preferably, the feedstock contains more than 37.5% by weight, more preferably more than 75% by weight, particularly advantageously more than 9% by weight.
Consists of more than 0% by weight of 520°C hydrocarbons. A very convenient feedstock is the vacuum residue of crude oil (so-called short residue).

Of course, different feedstock atmospheric or vacuum residues obtained, for example, in the production of synthetic crude oil from synthesis gas, can be used in the process of the invention.

If desired, the heavy feedstock can be comprised of cycle oils obtained by catalytic pyrolysis and/or residual oils obtained from tar sands and shale oils.

The feedstock contains asphaltenes. Unless otherwise specified, the term "asphaltene" herein refers to I
Refers to C3-asphaltenes, which are determined similarly to the method of P143 but using C3 hydrocarbons.

Another way to express asphaltene content is IP143
According to C? -ECS using asphaltene-Is the numerical value for asphaltene C? -It will be understood that it is larger than asphaltene.

Although this process can be carried out using asphaltene-free feedstocks, it has been observed that pyrolysis of asphaltene-free feedstocks is less prone to stability problems and/or sludge formation. Typical deasphalted oils have an asphaltene content of less than 5% by weight. The asphaltene content in the feedstock of the process of the invention may vary depending on the raw material from which it is derived.

Preferably, the C3-asphaltene content in the feedstock is between 5 and 50% by weight as determined by a modified IP143 method.
is within the range of

The feedstock is preheated before being transferred into the pyrolysis zone. Generally, this is done in one or more furnaces or furnace sections, provided with heat exchange tubes or coils, through which the feedstock to be preheated passes.

The temperature at which the feedstock is preheated is preferably 350-600°C
It is.

The feedstock thus preheated is passed to the pyrolysis zone. The feedstock can be passed upwardly or downwardly into the cracking zone. Preferably the flow is in an upward direction. Feedstocks are described, for example, in U.S. Patent No. 1.899.
It can be passed through a decomposition zone configured as an empty vessel as described in the '889 publication. Preferably, the pyrolysis zone is located in an immersion vessel with internals. The internals are preferably in the form of perforated plates.

In this type of immersion vessel, the internals provide compartmentalization, thereby reducing the occurrence of backmixing.

A very suitable dipping vessel is described in European Patent Application No. 7656
listed in the number. For more detailed information regarding the internals, reference is made to this patent application.

The present invention provides high conversion of 520°C hydrocarbons. This means that the yield for the distillation fraction is high. Preferably, the conversion of 520"C+ hydrocarbons is between 35 and 70% by weight. Conversions below 30% by weight pose little stability problems, whereas higher than 70" polymerization results in residual fractions. becomes viscous and produces a large amount of coke, making its handling extremely difficult. Very good results were obtained at 520 DEG C. hydrocarbon conversions of 40-60% by weight.

Pyrolysis is generally carried out in the absence of reducing gases such as hydrogen. Thermal decomposition can be carried out in the presence of water vapor. The conditions under which pyrolysis can occur can vary. Temperature, pressure and residence time could be adjusted arbitrarily to obtain the desired conversion, on the one hand at high temperature and short residence time, and on the other hand at lower temperature but longer residence time. It will be clear to the person skilled in the art that the same conversion rate can be obtained over time.Moreover, the decomposition reaction is endothermic and thus in the case of immersion decomposition there is a tendency for the temperature to decrease across the decomposition zone. therefore,
A person skilled in the art will be able to select the conditions in the decomposition band to obtain the desired conversion level. Suitable pyrolysis conditions include temperatures of 350-600°C, pressures of 1-100 bar and residence times of 0.5-60 m1n. Residence times are for cold feedstocks.

After the effluent from the pyrolysis zone has been quenched, it is advantageous to separate it into one or more distillation fractions and a residual fraction. Quenching can be accomplished by contacting the effluent with a colder quenching liquid. Suitable quench liquids include relatively light hydrocarbon oils, such as gasoline, or recycled quench residual fractions obtained from effluents.

After optionally quenching the effluent, the effluent is separated into one or more MWI fluxigone and a residual fraction. The distillation fraction is, for example, a gas (C
+-4 hydrocarbons), gasoline, middle distillates and optionally one or more vacuum distillates. The residual fraction obtained contains heavy 520°C hydrocarbons.

As mentioned above, the residual fraction obtained is extremely viscous. If desired, the residual fraction can be combined with a diluent to facilitate handling of the resulting mixture. Suitable diluents include cutter oils such as gasoline, gas oil and other hydrocarbon streams obtained from both straight run and catalytic pyrolysis. Although the mixture is easier to handle, the disadvantage of adding this diluent is that it increases the volume that must be subjected to the deasphalting process. To assess whether adding a diluent is beneficial or not,
Economic considerations are decisive.

The residual fraction can be deasphalted by conventional methods. Solvent deasphalting is known in the art. In this process, the residual fraction is generally
Self-flow treatment with an extraction medium which is a light hydrocarbon solvent containing paraffinic compounds, preferably a C5-8 paraffinic hydrocarbon, more preferably butane, pentane and/or hexane, especially pentane. A rotating disk contactor or a plate column can be used, with the residual fraction entering from the top and the extraction medium entering from the bottom. The paraffinic compounds are dissolved in the extraction medium and withdrawn from the top of the device. Asphaltone, which is insoluble in the extraction medium, is withdrawn from the bottom of the apparatus. The conditions for deasphaltization are preferably a total solvent to residual fraction ratio of 1.5 to 8.0 w/w, a pressure of 1 to 50 bar, and a temperature of 160 to 230°C. These conditions allow the production of very heavy asphalt. To enable handling of this type of heavy asphalt, the addition of cutter oil to the asphalt is desirable.

Preferably, the deasphaltization is carried out such that at least 35% by weight of asphaltone in the residual fraction is removed. Preferably, 50% by weight or more, more preferably 80% by weight or more of asphaltenes are removed.

Preferably, at least 15% by weight of the residual fraction is recovered as asphalt. This ensures complete removal of all solid particles and removal of most asphaltenes. The deasphalted oil thus obtained has excellent properties with respect to density, Conradson carbon number and viscosity and therefore does not pose any problems when used in the production of fuels, depending on the type of feedstock and the conversion rate of pyrolysis. Depending on the level, conveniently a residual fraction of 15 to 50% by weight, preferably 20 to 45% by weight, is separated off as asphalt.

As mentioned above, the deasphalted oil obtained from the deasphalting process can be used as a residual fuel or can be used as a blending component for a residual fuel. The details of the fuel are preferably such that the deasphalted oil is blended with a so-called cutter oil so that the resulting mixture meets the desired product specifications. The details are not only about stability, but also about, for example, Conradson carbon content,
It also concerns other properties such as viscosity and density.

Other useful uses of deasphalted oil include the use of the oil as a feed for hydroprocessing or hydropyrolysis, catalytic pyrolysis or pyrolysis processes.

Suitably the asphalt can be combusted, for example in a fluidized bed combustion unit or in the form of a vaporized fuel.

Another useful use for asphalt is as a feed to a gasifier to produce synthesis or fuel gas.

The present invention will be further explained below with reference to Examples.

Thermal cracking experiments were conducted in a pilot plant apparatus equipped with a heated coil and the feedstock passed through the coil and the dip vessel. The feed rate was chosen such that the residence time in the heating coil (for cold feedstock) was 2 minutes and the residence time in the dip vessel was 38 minutes. In these experiments, the temperature was varied depending on the desired conversion. A heat exchanger is placed after the dip vessel and a fractionator is placed to cool the effluent from the dip vessel, and then the effluent is separated into a gaseous (C4-4) fraction, a gasoline (Cs-165°C) fraction and a gas fraction. Oil (165-3
It was separated into a fraction (50°C) and a residual (350°C) fraction.

Deasphalting experiments were carried out in a rotating disc contactor operating at a pentane:residual fraction weight ratio of 2.0 to 2.2, a feed rate of approximately 2.0 kg residual fruccidine/h, and a pressure of 40 bar.

The temperature in the contactor was varied in the range of 170-210°C.

In these experiments, different feedstocks were used:
Namely, short residue oil from the Middle East (feedstock ■), short residue oil from Venezuela (feedstock H), and short residue oil from the North Sea (feedstock III). Some characteristics of these feedstocks are described below. It is shown in Table 1.

Real JiLL A pyrolysis experiment was conducted using the feedstock 1 described above.

Thermal decomposition conditions and the results of these experiments are shown in Table ①.

2.0 kg of the obtained 350'C" residual fruccidin
/h feed rate and weight ratio of pentane/350 °C 0 residual flux and 40 bar pressure and 180 °C
When subjected to the deasphalting process at an average temperature of
Deasphalted oil (DAO) and asphalt (ASP) were obtained with the following yields and properties shown in Table 1.

; ω Example 111 - Pyrolysis experiments were conducted using other feedstocks and the results shown in Table 1 above were obtained.

Experiments according to the invention, namely experiments klO,
ii, 13. and deasphalting the 350°C residual fraction obtained in step 14 at a feed rate of 2.0 kg/h and a pentane/350°C three fraction weight ratio of 2.0 at a pressure of 40 bar and an average temperature of 185°C. When subjected to the process, deasphalted oil (DAO) and asphalt (A
sP) was obtained.

, Milo: of the eyes.

Claims (1)

[Scope of Claims] (1) At least two having a boiling point of at least 520°C
In converting a heavy asphaltene-containing hydrocarbon feedstock consisting of 5% by weight hydrocarbons to a product with a lower boiling point, the hydrocarbon feedstock is preheated to 520°C.
The preheated feed is passed through a pyrolysis zone to obtain a conversion of at least 35% by weight of hydrocarbons having a boiling point of at least 35%, and the effluent from the pyrolysis zone is divided into one or more distillate fractions and a residual fraction. A method for converting a heavy asphaltene-containing hydrocarbon feedstock, comprising separating it into fractions and de-asphalting the remaining fraction to obtain asphalt and de-asphalted oil. 2. The method of claim 1, wherein the hydrocarbon feedstock is vacuum residue of crude oil. 3. The method of claim 1 or 2, wherein the feedstock is preheated to a temperature of 350 to 600C. 4. A process as claimed in claim 1, in which the preheated feedstock is passed upwardly into the pyrolysis zone. (5) The method according to any one of claims 1 to 4, wherein the pyrolysis zone is located in an immersion vessel containing the internal matter. (6) The method according to claim 5, wherein the internal material comprises a perforated plate. (7) Conditions existing in the pyrolysis zone are 350-600℃
temperature, pressure from 1 to 100 bar and from 0.5 to 60 m
in. 7. A method according to any one of claims 1 to 6, wherein the average residence time is . (8) The conversion of hydrocarbons with a boiling point of at least 520 °C in the pyrolysis zone is between 35 and 70% by weight, in particular 40% by weight.
8. A method according to any one of claims 1 to 7, wherein the amount is ~60% by weight. (9) The method according to any one of claims 1 to 8, wherein the residual fraction is deasphalted using a C_3_ to_8 paraffinic hydrocarbon. 10. The process according to claim 9, wherein the paraffinic hydrocarbon comprises butane, pentane and/or hexane, in particular pentane. (11) The deasphalting is carried out at a total solvent/residual fraction ratio of 1.5 to 8 w/w, a pressure of 1 to 50 bar and a temperature of 160 to 230°C.
The method described in any one of the above. (12) The method according to any one of claims 1 to 11, wherein the deasphalted oil is blended with cutter oil. (13) Claims 1 to 1 which involve catalytic pyrolysis of deasphalted oil.
12. The method according to any one of 11. (14) The method according to any one of claims 1 to 11, wherein the deasphalted oil is subjected to hydrogen treatment or hydrogen pyrolysis. (15) Claims 1 to 1 in which the deasphalted oil is thermally decomposed.
1. The method according to any one of 1. (16) The method according to any one of claims 1 to 15, wherein the asphalt is combusted in a fluidized bed combustion unit. (17) The method according to any one of claims 1 to 15, wherein synthesis gas is obtained by gasifying asphalt. (18) The method according to any one of claims 1 to 15, wherein asphalt is used for producing emulsified fuel.