KR0148566B1 - Process for the conversion of a heavy hydrocarbonaceous feedstock - Google Patents

Abstract

No content

Description

How to convert heavy hydrocarbonaceous feedstock

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

Pyrolysis is a suitable method for converting heavy asphaltene-containing hydrocarbonaceous feedstock to products with lower average boiling points. Pyrolysis is a very simple method consisting of preheating the feedstock to the appropriate temperature and transferring the preheated feedstock to the pyrolysis zone. Decomposition takes place there. At the outlet of the pyrolysis zone, the effluent is usually quenched to stop the decomposition reaction and the effluent is fractionated to produce one or more distillates and residues. The residue contains substantially all asphaltenes present in the degraded product and is usually disposed of as refined or commercial fuel, although not further processed.

An important aspect of the present invention relates to the safety of the degraded residue after being combined with a suitable diluent, which gives the resulting fuel details of the desired product such as viscosity, sulfur, content, density and Conradson carbon number. . If the degradation is too severe, it is known that the properties of asphaltenes and oils change to form sludge. Sludge formation especially occurs upon pyrolysis of asphaltene-containing feedstocks. If the feedstock is deasphalted and the deasphalted oil is thermally decomposed, some sludge is formed only at very high conversions. Sludge basically consists of coke particles that are insoluble in the cracked oil and / or fuel when the cracked residue is combined to produce a fuel. If the sludge formation exceeds certain limits, the fuel will not meet the specifications of commercial fuels.

The method of preventing sludge is to relax the stringency of the pyrolysis process. Thus, depending on the type of feedstock, the stringency of the pyrolysis is chosen such that the conversion of heavy hydrocarbons, ie hydrocarbons having a boiling point of at least 520 ° C., is about 30% by weight or less. The problem of sludge formation will be avoided at this level of conversion. It is clear, however, that the yield for distillate is not optimal. Another way to prevent sludge formation is to deasphalt the feedstock prior to the pyrolysis process. A conversion level higher than 30% by weight can then be obtained. However, the removed asphaltenes can no longer contribute to the production of the distillate, so in this case also the yield for the distillate is not optimal.

The batch process attempted to maximize yield for distillate is delayed coking. In this process the feedstock remains in a so-called coker drum which is broken down to produce distillate and coke. If the heavy products are recycled and the coker drum is filled with coke, the process continues in another coke drum. Thus, the cocker drum is filled / empty in the batch direction. It will be evident that the fact that delayed coking is operated in a batch direction and that some solid coke has to be processed creates a drawback of this method.

The present invention provides a method by which the conversion rate can be increased while improving the yield of distillate without causing problems of unstable residues and batch operation.

Thus, the present invention provides a process for converting a heavy asphaltene-containing hydrocarbonaceous feedstock into a lower boiling product consisting of at least 25% by weight hydrocarbon having a boiling point of at least 520 ° C., wherein the hydrocarbon Preheating the feedstock, passing the preheated feedstock through a pyrolysis zone to convert at least 35% by weight of hydrocarbons having a boiling point of at least 520 ° C., and effluent from the decomposition zone with one or more distillates and residues. And the residue is deasphalted to obtain asphalt and deasphalted oil.

The resulting asphalt contains solid coke particles that would have formed during the decomposition reaction, and the deasphalted oil is substantially free of asphaltenes and has a lower viscosity, lower density and lower conerad than the residue obtained when separating the effluent from the pyrolysis zone. Hand has carbon number Deasphalted oils do not have any stability issues and can be used directly as blending ingredients in the manufacture of commercial fuels or for other purposes.

The heavy hydrocarbonaceous feedstock used in the process according to the invention consists of at least 25% by weight hydrocarbons (520 ° C. ⁺ hydrocarbons) having a boiling point of at least 520 ° C. If the 520 ° C ⁺ % of hydrocarbons is lower, stability problems will occur less. Convenient feedstocks include atmospheric residues of crude oil, so-called long residues. Suitably, the feedstock consists of at least 37.5% by weight of 520 ° C ⁺ hydrocarbons, more preferably at least 75% by weight, most preferably at least 90% by weight of 520 ° C ⁺ hydrocarbons. A very convenient feedstock is the vacuum residue of the crude oil, the so-called short residues.

Of course, atmospheric or vacuum residues of other origin, such as obtained when producing synthetic crude oil from synthesis gas, can also be used in the process of the invention.

If desired, the heavy feedstock may be composed of circulating oils obtained by catalytic cracking and / or residual oils obtained from tar sands and shale oils.

The feedstock contains asphaltenes. Unless otherwise noted, the asphaltenes in this specification, except that using the C ₅ hydrocarbon C ₅ similarly measured with the method of IP 143 - refers to the asphaltenes. Another way to indicate asphaltene content is to use C ₇ -asphaltene according to IP 143. It is recognized that the number for C ₅ -asphaltene is higher than for C ₇ -asphaltene.

Although the process can be carried out with feedstock free of asphaltenes, pyrolysis of the feedstock without asphaltenes results in less stability problems and / or sludge formation. The asphaltene content of a typical deasphalted oil is up to 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 originates. Suitably the C ₅ -asphaltene content in the feedstock is between 5 and 50% by weight, as measured according to the modified IP 143 method.

The feedstock is preheated before being passed to the pyrolysis zone. Typically this is done in one or more furnaces or furnace regions fed with heat exchange tubes or coils through which the feedstock to be preheated is passed. The temperature at which the feedstock is preheated is preferably 350 to 600 ° C.

This preheated feedstock is passed to the pyrolysis zone. The feedstock can be passed upstream or downstream through the cracking zone. Preferably the flow is upstream. The feedstock may be passed through a cracking zone consisting of an empty container as described, for example, in US-A 1,899,889. Preferably the pyrolysis zone is located in an immersion vessel containing the interior. The interior is preferably in the form of a porous plate. In such immersion vessels, the interior provides a compartment such that backmixing is reduced. Suitable dipping vessels are described in EP-A 7656. Reference is made to the above specification for more detailed information on the internals.

The present invention provides a high conversion of 520 ° C. hydrocarbons. This means that the yield for distillate is high. The conversion of 520 ° C. ⁺ hydrocarbons is preferably 35 to 70% by weight. Safety problems rarely occur at conversions below 30% by weight, but at conversions above 70% by weight the residues are too viscous and coke rich and handling them will be very cumbersome. Very good results were obtained with a conversion of 40-60% by weight of 520 ° C. ⁺ hydrocarbons.

Pyrolysis is generally carried out in the absence of a reducing gas such as hydrogen. Pyrolysis can be carried out in the presence of steam. The conditions under which pyrolysis is carried out may vary. The temperature, pressure and residence time may be arbitrarily adjusted to achieve the desired conversion. It will be apparent to those skilled in the art that the same conversion can be obtained on the one hand at high temperatures and short residence times and on the other hand at low temperatures and long residence times. In addition, since the decomposition reaction is an endothermic reaction, the temperature tends to decrease over the decomposition zone in case of soaker cracking. Those skilled in the art will therefore be able to select conditions within the decomposition zone to achieve the desired level of conversion. Suitable decomposition conditions include a temperature of 350 to 600 ° C., a pressure of 1 to 100 bar and a residence time of 0.5 to 60 minutes. The residence time is related to the cold feedstock. The residence time according to the present invention is considerably shortened compared to the residence time in the prior art. This shortened residence time allows the process to be carried out by reducing the volume of the reactor such as a pyrolysis reactor required to process a certain amount of feedstock. This is advantageous in that it can significantly reduce the capital investment for the company.

It will be useful to quench the effluent from the pyrolysis zone before separating it into one or more distillates and residues. Quenching can be performed by contacting the effluent with the cooler quench fluid. Suitable quench fluids include recycled cooling residues obtained from relatively light hydrocarbon oils such as gasoline or effluents.

After selective quenching of the effluent, the effluent is separated into one or more distillates and residues. The distillate consists, for example, of gas (C _1-4 hydrocarbons), gasoline, middle distillate and optionally one or more vacuum distillates. The residue obtained will contain heavy 520 ° C. ⁺ hydrocarbons.

As mentioned above, the residue obtained will be very viscous. If desired, the residue can be combined with a diluent to facilitate handling of the resulting mixture. Suitable diluents include cutter oils such as gasoline, gas oil and hydrocarbon streams from other straight run and catalytic cracking origins. Although handling of the mixture will be easier, the disadvantage of adding this diluent is that the volume must be increased to undergo a deasphalting step. Economic factors will be critical in assessing whether the addition of diluents is advantageous.

Deasphalting of the residue can be carried out in a typical manner. Solvent deasphalting is known in the art. In this step, the residue is usually subjected to countercurrent with an extraction medium, which is a light hydrocarbon containing paraffinic compounds, preferably C _3-8 paraffinic hydrocarbons, more preferably butane, pentane and / or hexanes, in particular pentane. . A rotating disk contactor or plate column may be used with the upper residue inlet and the lower extraction medium inlet. Paraffinic compounds are dissolved in the extraction medium and recovered at the top of the device. Aspartene, which is insoluble in the extraction medium, is recovered at the bottom of the apparatus. The deasphalting conditions are suitably a ratio of total solvent to residue of 1.5-8.0 weight / weight, pressure 1-50 bar and temperature 160-230 ° C.

These conditions allow very heavy asphalt to form. Among them, it is preferable to add cutter oil to the asphalt in order to enable the handling of the asphalt.

Deasphalting will suitably be carried out such that at least 35% by weight of asphaltenes of the residue are removed from them. Preferably at least 50% by weight, more preferably at least 80% by weight, of asphaltenes are removed.

Preferably at least 15% by weight of the residue is recovered as asphalt. This ensures complete removal of all solid particles and almost all asphaltenes. The resulting deasphalted oil will then have excellent properties in density, coneradone carbon number and viscosity, and therefore will not cause any problems when used in the manufacture of fuels. Depending on the type of feedstock and the level of conversion of pyrolysis, conveniently 15-50% by weight, preferably 20-45% by weight of the residue is separated as asphalt.

As mentioned above, the deasphalted oil resulting from the deasphalting step may be used as the residual fuel or may be used as a blending component for the residual fuel. The specifications for the fuel will be that the deasphalted oil is preferably combined with the so-called cutter oil so that the resulting mixture in the desired product specification is obtained. The statement relates not only to stability but also to other properties such as Conradson carbon content, viscosity and density.

Other useful uses for deasphalted oils include using the oil as a feed for a hydrotreatment or hydrocracking process, catalysis process or pyrolysis process.

Asphalt may suitably be burned, for example in a fluidized bed combustion unit or in the form of emulsified fuel. Another useful use for asphalt is as a feed for gasification units to obtain syngas or fuel gas.

The invention will be further illustrated by the following examples.

EXAMPLE

Pyrolysis experiments were performed in a pilot plant device consisting of a heated coil and an immersion vessel while the feedstock was passed. The feed rate of the feedstock was chosen such that the residence time in the heating coil (based on the cold feedstock) was 2 minutes and the residence time in the immersion vessel was 38 minutes. In the experiment, the temperature was changed according to the desired conversion rate. Arrange the heat exchanger next to the immersion vessel, cool the effluent from the immersion vessel and then drain the effluent to the gas (C _1-4 ) fraction, gasoline (C ₅ -165 ° C.) fraction, gas oil (165-350 ° C.). ) Fractionator is arranged to separate the fractions and residues (350 ° C.).

Deasphalting experiments were performed in a rotating disk contactor operating at a pentane: residue weight ratio of 2.0-2.2, feed rate of about 2.0 kg residue / hour, and pressure 40 bar. The temperature of the contactor varied between 170-210 ° C.

Different feedstocks were used in the experiments: Middle Eastern Short Residue (Feedstock I), Venezuela Short Residue (Feedstock II) and North Sea Short Residue (Feedstock III). Some properties of the feedstock are indicated in Table 1 below.

Example 1

Pyrolysis experiments were carried out with the feedstock I. Pyrolysis conditions and experimental results are described in Table II.

Obtained 350 ℃ residue feed rate 2.0 kg / hour, pentane / 350 ℃ By deasphalting at a weight ratio of 2.0, a pressure of 40 bar and an average temperature of 180 ° C., deasphalted oil (DAO's) and asphalt (ASP's) are obtained in the following yields, which have the properties as indicated in Table III.

Example 2

Pyrolysis experiments were carried out with different feedstocks to obtain the results in Table IV.

350 ° C. obtained in the experiments according to the invention, namely in experiments 10, 11, 13 and 14 Residue at feed rate 2.0 kg / hr, pentane / 350 ° C Deasphalting at fractionated weight ratio 2.0, pressure 40 bar and average temperature of 185 ° C., deasphalted oil (DAO's) and asphalt (ASP's) are obtained in the following yields, which have the properties as indicated in Table V.

Claims (18)

A method for converting a heavy asphaltene-containing hydrocarbonaceous feedstock consisting of at least 25% by weight of hydrocarbon having a boiling point of at least 520 ° C. to a lower boiling product, the method comprising preheating the hydrocarbonaceous feedstock and subjecting the preheated feedstock to Passed through a pyrolysis zone to allow 35 to 70% by weight of hydrocarbons having a boiling point of at least 520 ° C. to be converted, separating the effluent from the decomposition zone into one or more distillates and residues and deasphalting the residue And deasphalted and oil, wherein the average residence time in the pyrolysis zone is 0.5-60 minutes. The process of claim 1 wherein the hydrocarbonaceous feedstock is a vacuum residue of crude oil. The process of claim 1, wherein the feedstock is preheated to a temperature of 350-600 ° C. 4. The process of claim 1 or 2, wherein the preheated feedstock is passed upwardly through the pyrolysis zone. A process according to claim 1 or 2, wherein said pyrolysis zone is located in an immersion vessel containing internals. 6. The process of claim 5, wherein said internals are comprised of porous plates. The process of claim 1 or 2, wherein the main conditions in the pyrolysis zone are temperatures of 350-600 ° C. and pressures of 1-100 bar. The process according to claim 1 or 2, wherein the conversion rate of the heavy asphaltene-containing hydrocarbonaceous feedstock is 40-60% by weight of the hydrocarbon having a boiling point of at least 520 ° C in the pyrolysis zone. The process of claim 1 or 2, wherein the residue is deasphalted using C _3-8 paraffinic hydrocarbons. 10. The process of claim 9, wherein said paraffinic hydrocarbon is comprised of butane, pentane, hexane or mixtures thereof. 3. The asphaltene-containing medium of claim 1 or 2, wherein the deasphalting is carried out at a ratio of total solvent to residue of 1.5-8 weight / weight, pressure of 1-50 bar and temperature of 160-230 ° C. Method of converting hydrocarbonaceous feedstock. 3. The process of claim 1 or 2, wherein the asphalted oil is combined with cutter oil in the asphaltene-containing hydrocarbonaceous feedstock. The process of claim 1 or 2, wherein the deasphalted oil is catalytically cracked. The process of claim 1 or 2, wherein the deasphalted oil is hydrotreated or hydrocracked. The process of claim 1 or 2, wherein the deasphalted oil is pyrolyzed. The process of claim 1 or 2, wherein the asphalt is combusted in a fluidized bed combustion unit. The process of claim 1 or 2, wherein the asphalt is gasified to produce a synthesis gas. The process of claim 1 or 2, wherein the asphalt is used in the production of emulsified fuels.