FI99022C - Process for converting a raw material mixture consisting of heavy hydrocarbons - Google Patents

Description

99022

The present invention relates to a process for converting heavy asphalt-5 and a hydrocarbon feedstock containing at least 25% by weight of hydrocarbons having a boiling point of at least 520 ° C to products having a lower boiling point. .

Thermal cracking is a suitable method for converting heavy as-10 phaltene-containing leachate feedstocks into products with a lower average boiling point. Thermal cracking is a fairly simple method and involves preheating the feedstock to a suitable temperature and sending the preheated feedstock to the thermal cracking zone.

Cracking takes place in it. At the outlet of the thermal cracking zone, the effluent is usually turned off to stop the cracking reactions and the effluent is fractionally distilled to give one or more distillate fractions and a residue.

20 The residue contains essentially all the asphaltenes present in the cracked product and is not normally further processed but is removed as a refinery or commercial fuel.

An important feature of the process relates to the stability of the cracked residue 25 after mixing with suitable diluents to obtain the desired product specifications for the resulting fuel, such as viscosity, sulfur content, density, and Conradson carbon number. It is known that if the cracking is too severe, the nature of the asphaltenes and oils changes so that sludge formation occurs. Sludge formation takes place especially in the thermal cracking of asphaltene-containing feedstocks. If the asphaltenes have been removed from the feedstock and the asphaltene-free oil is thermally cracked, only very high conversions will form some sludge. The slurry basically contains coke particles that are insoluble in the cracked oil and / or fuel when the cracked residue is blended to obtain the fuel. If the sludge formation exceeds a certain specified limit, the fuel does not meet commercial fuel specifications.

One way to prevent sludge is to alleviate the severity of the thermal cracking process. Therefore, depending on the type of feedstock, the severity of thermal cracking is selected so that the conversion of heavy hydrocarbons, i.e., hydrocarbons having a boiling point of 520 ° C and higher, is less than about 30% by weight. The problem of sludge formation is avoided at this conversion level. It is obvious that in this case the yield of distillates is not optimal. Another way to prevent the formation of sludge 15 is to remove the asphaltenes from the feedstock prior to the thermal cracking process. Conversion levels of more than 30% by weight are then achievable. However, the removed asphalt tens can no longer be used in the production of distillates and therefore, in this case too, the yield of 20 distillates is not optimal.

The batch process, which attempts to maximize the yield of distillates, is delayed coking. In this process, the feedstock is allowed to stand in so-called coking drums to crack and produce distillates and coke.

25 Heavy products are recycled and when the coking drum is filled with coke, the process continues in another coking drum.

Thus, the coking drums are filled and emptied in batches. It is obvious that the fact that delayed coking is carried out in batches and that more or less solid coke has to be treated constitutes a disadvantage of this process.

This invention relates to a process in which the conversion can be increased without facing the problems of unstable residue and batch operation while improving the yield of distillates.

3 99022 Accordingly, this invention relates to a process for converting a heavy asphaltene-containing hydrocarbon feedstock containing at least 25% palno by weight of hydrocarbons having a boiling point of at least 520 ° C into products having a lower boiling point in the process of preheating the hydrocarbon feedstock. passing the preheated feedstock through a thermal cracking zone to achieve a conversion of at least 35% by weight to hydrocarbons having a boiling point of 520 ° C or higher, separating the cracking zone effluent into one or more distillates and residual fractions and removing asphaltenes residues and to obtain an asphalt-free oil, the method being characterized in that the cracking conditions include a residence time of 0.5 to 60 minutes for the cold feedstock.

The resulting asphalt contains solid coke particles that may have formed during the cracking reactions, and the asphaltene-free oil contains substantially no asphaltenes and has a lower viscosity, lower density, and lower Conradson carbon number than the residual fraction obtained in the thermal crack zone separation stream. Asphaltene-free oil has no stability problems and can be used directly as a blending component in the production of commercial fuel or for other purposes.

The heavy hydrocarbon feedstock used in the process of this invention contains at least 25% by weight of hydrocarbons having a boiling point of at least 30,520 ° C (520 ° C * hydrocarbons). When the percentage of 520 ° C * hydrocarbons is lower, the stability problem is less likely to occur. Suitable feedstocks are the residues from the normal distillation of crude oils, the so-called long remains. The feedstock suitably contains more than 35 37.5% by weight of 520 ° C + hydrocarbons, more preferably more than 75% by weight of 99022% and most preferably more than 90% by weight. A very suitable feedstock is the vacuum distillation residue of crude oil, the so-called short residue.

Naturally, normal pressure-5 or vacuum distillation residues of different origins, e.g. those obtained in the production of synthetic crude oils from synthesis gas, can be used in this process. If desired, the heavy feedstock may consist of recycled oil derived from tar sands and shale oils.

10 The feedstock contains asphaltenes. Unless otherwise stated, the term asphaltenes in this patent refers to C5 asphaltenes as defined analogously to method IP 143, but using C5 hydrocarbons. Another way to express the asphaltene content is to use C7-as-15 phthalenes according to method IP 143. It can be estimated that the number of C5 asphaltenes is higher than that of C7 asphaltenes.

Although the process can be carried out with a feedstock that does not contain asphaltenes, it is found that thermal cracking of asphalt-free feedstocks is less prone to stability problems and / or sludge formation. A typical asphaltene-free oil has an asphaltene content of less than 5% by weight. The asphaltene content of the feedstock for this process can vary depending on the source of the pendant. Suitably, the content of C5 asphaltenes in the feedstock varies between 5 and 50% by weight, determined according to a modified IP 143 method,

Before the feedstock is passed to the thermal cracking zone 30, it is preheated. This is usually done in one or more furnaces or parts of a furnace equipped with heat exchange tubes or coils through which the preheated feedstock is passed. The temperature at which the feedstock is preheated is preferably 350 to 600 ° C.

5 99022 The feedstock thus preheated is passed through a thermal cracking zone. The feedstock can be passed up or down through the cracking zone.

Preferably, the flow is upward. The feedstock can be passed through a cracking zone consisting of an empty vessel, as described, for example, in U.S. Pat. No. 1,899,889. Preferably, the thermal cracking zone is located in a soaking cracking vessel containing core pieces. The inner pieces are preferably in the form of perforated plates.

10 In such a soaking cracking vessel, the inserts provide compartments to increase the incidence of backmixing. A very suitable soaking cracking vessel is described in EP-A 7 656. For more detailed information on the inserts, reference is made to that EP-15 patent publication.

This invention provides a high conversion of 520 ° C * hydrocarbons. This means that the yield of distillate fractions is high. The conversion of 520 ° C + hydrocarbons is preferably 35-70% by weight. With a conversion of less than 30% by weight, there is hardly any stability problem, while with a conversion of more than 70% by weight, the residual fraction is so viscous and its coke content is so high that it is very cumbersome to handle. Very good results have been obtained with a conversion of 40-60% by weight of 520 ° C * hydrocarbons.

Thermal cracking is usually carried out without reducing gases such as hydrogen. Cracking can be performed in the presence of steam. The conditions under which thermal cracking can be performed can be varied. The temperature, pressure, and residence time could be adjusted as desired to provide the desired conversion. It will be apparent to one skilled in the art that the same conversion can be achieved on the one hand at a high temperature and a short residence time and on the other hand at a lower temperature but with a longer residence time. Furthermore, the cracking reactions are endothermic and therefore the temperature tends to drop in the cracking zone in the case of soaking cracking. As a result, one skilled in the art will be able to select the conditions for the cracking zone so that the desired level of conversion is achieved. Suitable escape 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. This residence time applies to the cold feedstock.

It may be useful to quench the effluent from the thermal cracking zone before separating it into one or more distillate fractions and residual fractions. Extinguishing can be accomplished by contacting the effluent with a colder extinguishing fluid. Suitable extinguishing fluids include relatively light hydrocarbon oils, such as gasoline or recycled, cooled residual fraction from the effluent.

After optional quenching of the effluent, it is separated into one or more distillate fractions and a residual fraction. Distillate fractions consist of, for example, gas (C 1 -C 6 hydrocarbons), gasoline, middle fractions and optionally one or more vacuum distillates. The residual fraction obtained contains heavy 520 ° C * hydrocarbons.

The residual fraction obtained as described above can be very viscous. If desired, a diluent may be added to the residual fraction to facilitate handling of the resulting mixture. Suitable diluents include cutting oils such as gasoline, gas oil or other hydrocarbon streams from both direct distillation and catalytic cracking. Although the handling of the mixture is made easier, the disadvantage of adding this diluent is that the increased volume must be brought to the asphaltene removal step. Economic motives may be crucial in deciding whether or not to add diluent is advantageous.

The removal of the asphaltenes from the residual fraction can be carried out in a conventional manner. The removal of asphaltenes as solvent 35 is known in the art. At this stage, the residual fraction is treated upstream with an extraction medium, which is usually a light hydrocarbon solvent containing paraffinic compounds, preferably paraffinic C 3-8 hydrocarbons, more preferably butane, pentane and / or hexane, especially pentane. A rotary disk contactor or plate column can be used, into which the residual fraction enters from above and the extraction medium enters from the bottom. The paraffinic compounds dissolve in the extraction medium and are removed from the top of the apparatus. Asphaltenes that are soluble in the 10-tower extraction medium are removed from the bottom of the device. The asphaltene removal conditions suitably include a weight ratio of total solvent to residual fraction of 1.5 to 8.0, a pressure of 1 to 50 bar and a temperature of 160 to 230 ° C. These conditions allow the production of very heavy asphalt.

15 In order to be able to handle such heavy asphalts, it may be desirable to add cutting oils to the asphalt.

The removal of the asphaltenes is suitably carried out in such a way that more than 35% by weight of the asphaltenes of the residual fraction are removed therefrom. Preferably more than 50% by weight and even more preferably more than 80% by weight of the asphaltenes are removed.

Preferably more than 15% by weight of the residual fraction is recovered as asphalt. This guarantees complete removal of all solid particles and a clear majority of asphaltenes. The resulting asphalt-free oil then has excellent properties in terms of density, Conradson carbon number and viscosity and therefore does not pose any problem when used in the manufacture of fuel. Depending on the type of feedstock and the conversion level of thermal cracking, suitably 15 to 50% by weight and preferably 20 to 45% by weight of the residual fraction are separated as asphalt.

As mentioned above, the asphaltene-free oil obtained from the asphaltene removal step can be used as a residual-35 fuel or can be used as a blend component of the residual fuel 8 99022. The fuel specifications may be such that it is preferable to mix the so-called cutting oil with the asphaltene-free oil to bring the resulting mixture to the desired product specifications. Spe-5 specifications apply not only to stability but also to other properties such as Conradson carbon content, viscosity and density.

Other useful uses for asphaltene-free oil include the use of the oil as a feed to a hydrotreating or hydro-10 cracking process, a catalytic cracking process, or a thermal cracking process.

The asphalt can be suitably burned, for example, in a fluidized bed incinerator or in the form of emulsified fuel. Another useful area of operation for asphalt is to use it as a feed to a gasification unit to produce synthesis gas or fuel gas.

The present invention is further illustrated by the following examples.

Examples 20 Thermal cracking experiments were performed in a pilot plant equipment consisting of a coil heated while passing feedstock and a soaking cracking vessel. The feed rate of the feedstock was selected so that the residence time (based on cold feedstock 25) in the heating coil was 2 min and the residence time in the soaking cracker was 38 min. In the experiments, the temperature was varied according to the desired conversion. After the soa-king cracker, a heat exchanger and fractionator were placed to cool the effluent from the soaking cracker and then to separate the effluent into a gaseous (C1-4) fraction, a gasoline fraction (C5-165 ° C), a gas oil fraction (165-350 ° C). ) and to a residual fraction (350 ° C +).

Asphaltene removal tests were carried out in a rotary disk contactor operating at a weight ratio of 2.0 to 2.2 between pentane and the residual fraction of 9,99022, at a feed rate of about 2.0 kg of residual fraction / h and a pressure of 40 bar. The temperature in the touch device was varied between 170 and 210 ° C.

Different feedstocks were used in the experiments: 5 Middle East short residue (feedstock I), Venezuelan short residue (feedstock II) and North Sea short residue (feedstock III). Some properties of the feedstocks are shown in Table I below.

10

Table I

Feedstock I II III

Viscosity at 100 ° C, mm2 / s 2347 - 555 15 Viscosity at 150 ° C, mm2 / s - 1224 61.8

Conradson carbon number, wt% 21.7 26.7 13.5 C5-asphaltenes (IP 143 mod.), Wt% 19.9 31.9 8.0

Insoluble in toluene, (ASTM D 593), wt% <0.01 <0.01 <0.01 Insoluble in 1-methylnaphthalene (ASTM D 593), wt% <0.01 <0.01 <0.01 350-520 ° C fraction, wt% 7.0 4.6 5.0 520 ° CT fraction, wt% 93.0 95.0 95.0 Example 1

Thermal cracking experiments were performed on the above-mentioned feedstock I. The thermal cracking conditions and experimental results are shown in Table II.

Table II

10 99022

Experiment No. 1234

Feedstock No. I I I I

5 Pressure, bar 5555

Coil outlet temperature, ° C 450,465,475,481

Product distribution, wt% CX.A 1.3 2.6 2.8 3.6 10 C5-165 ° C 2.4 5.1 6.7 7.5 165-350 ° C 6.0 12.7 16 Δ 16.4 350-520 ° C 19.3 22.2 22.4 22.8 520 ° C * 71.0 57.4 51.6 49.7 520 ° C * - conversion, 15 wt% 23 .7 38.2 44.4 46.5 3 Properties of the 50 ° C * residue fraction

Density 25/25 g / ml 1.037 1.053 1.063 1.069

Viscosity at 150 ° C, 20 mm 2 / s 98.7 108.0 105.3 126.3

Conradson carbon number, wt% 21.3 28.2 28.5 29.6 C5 asphaltenes, wt% 24.0 27.8 31.8 31.5 25 Insoluble in toluene, wt% <0.01 0 .52 0.54 0.48 520 ° C * content, wt% 78.6 70.2 67.6 66.2 30 When the obtained 350 ° C * residual fractions are subjected to an asphaltene removal step at a feedstock rate of 2, 0 kg / h, with a weight ratio of pentane to a residual fraction of 350 ° C * of 2.0, at a pressure of 40 bar and an average temperature of 180 ° C, asphaltene-free oils (DAO) and asphalts 35 (ASP) are obtained in the following yields and according to Table III features.

Table III

11 99022

Experiment No. 5678 350 ° C * fraction from Experiment No. 1 2 3 4 5 DAO yield, wt% of total fraction 78 78 78 78 ASP yield, wt% of total fraction 22 22 22 22 10 DAO properties

Density 25/25, g / ml 0.977 0.992 1.002 1.007

Viscosity at 100 ° C, nun2 / g 64.4 68.8 67.5 77.4

Conrad son - hi i 1 i 1 uku, 15 wt% 6.82 9.02 9.12 9.47 C5 asphaltenes, wt% 3.1 3.6 4.1 4.1

Toluene insoluble, wt% <0.01 <0.01 <0.01 <0.01 20 Properties of ASP

Insoluble in toluene, wt% <0.01 2.33 2.42 2.15

Example 2 Thermal cracking experiments were performed on other feedstocks to give the results in Table IV.

Table IV

12 99022

Experiment No. 9 10 11 12 13 14

Feedstock No. II II II III III III

5 Pressure, bar 555555

Coil outlet temperature, ° C 440 471 480 470 500 510

Product distribution, wt% 10 1.7 3.7 5.3 1.1 3.0 3.3 C3-165 ° C 2.9 6.5 8.2 2.8 7.7 10.1 165-350 ° C 7.8 14.1 17.4 7.2 17.1 23.4 350-520 ° C 14.7 18.2 15.4 17.8 22.9 26.1 520 ° C * 72.9 57.5 53.7 71.1 49.3 37.1 15 520 ° C + conversion, wt% 23.6 39.6 43.7 25.0 48.1 61.0 350 ° C * residue j Properties of the device 20 Viscosity at 150 ° C, mm2 / s 839 1744 1300 35.5 30.4 29.3

Conradson carbon number, wt% 31.5 34.3 38.9 16.0 20.8 22.6 C5 wood content, 25 wt% 36.0 36.9 35.8 12.4 19.8 27.0 Insoluble in 1-methylnaphthalene, w / w 0.12 1.08 1.12 -

Insoluble in toluene, wt% - - <0.01 0.34 0.84 520 ° C * content, wt% 82.9 74.0 77.1 79.6 64.6 55.0 13 99022

When the 350 ° C * residual fractions obtained in the experiments according to the present invention, i.e. experiments Nos. 10, 11, 13 and 14, are subjected to an asphaltene removal step at a feedstock rate of 2.0 kg / h, between the pentane and the 350 ° C * fraction. at a weight ratio of 2.0, at a pressure of 40 bar and a temperature of 185 ° C, asphaltene-free oils (DAO) and asphalt (ASP) are obtained in the following yields and with the results shown in Table V.

10 Table V

Experiment No. 15 16 17 18 350 ° C * fraction from Experiment No. 10 11 13 14 DAO yield, wt% of total 15 fractions 75 75 76 76 ASP yield, wt% of total fraction 25 25 24 24 DAO properties

Density 25/25, g / ml 1.030 1.044 0.937 0.941 20 Viscosity at 150 ° C, mm 2 / s 55.6 134.1 24.0 27.6

Conradson carbon number, wt% 11.3 12.8 6.7 7.2 C5 asphaltenes, wt% 4.76 4.62 2.53 3.46 insoluble in 1-methylnaphthalene, wt% <0, 01 <0.01

Insoluble in toluene, w / w - <0,01 <0,01 Properties of ASP Insoluble in 30 - 1-methylnaphthalene, w / w 4.29 4.45 - toluene, w / w - 1.39 3.47

Claims (10)

99022 A process for converting a heavy asphaltene-containing hydrocarbon feedstock containing at least 25% by weight of hydrocarbons having a boiling point of at least 520 ° C into products having a lower boiling point, the process comprising preheating the hydrocarbon feedstock. preheated feedstock through a thermal cracking zone to achieve a conversion of at least 10 35% by weight to hydrocarbons having a boiling point of 520 ° C or higher, separating the cracking zone effluent into one or more distillates and residual fraction and removing asphaltenes and residues to obtain an asphaltene-free oil, characterized in that the cracking conditions include a residence time of 0.5 minutes to 60 minutes for the cold feedstock. Process according to Claim 1, characterized in that the hydrocarbon feedstock is a vacuum distillation residue of crude oil. Process according to Claim 1 or 2, characterized in that the feedstock is preheated to a temperature of 350 to 600 ° C. A method according to any one of claims 1 to 3, characterized in that the preheated feedstock is passed upwards through a thermal cracking zone. Method according to any one of claims 1 to 4, characterized in that the thermal cracking zone is placed in a soaking cracking vessel containing inserts. Process according to any one of Claims 1 to 5, characterized in that the conversion of hydrocarbons having a boiling point of at least 35 520 ° C in the thermal cracking zone is from 35 to 70% by weight and in particular from 40 to 60% by weight. 99022 Method according to one of Claims 1 to 6, characterized in that cutting oil is mixed with the asphalt-free oil. Process according to one of Claims 1 to 6, characterized in that the asphaltene-free oil is catalytically cracked. Process according to any one of Claims 1 to 6, characterized in that the asphaltene-free oil is hydrotreated or hydrocracked. Process according to any one of Claims 1 to 6, characterized in that the asphaltene-free oil is thermally cracked. : 99022