EP2867339A1

EP2867339A1 - Method for producing olefins by thermal steam-cracking

Info

Publication number: EP2867339A1
Application number: EP13747796.4A
Authority: EP
Inventors: Gunther Schmidt; Helmut Fritz; Stefanie Walter
Original assignee: Linde GmbH
Current assignee: Linde GmbH
Priority date: 2012-08-09
Filing date: 2013-08-06
Publication date: 2015-05-06
Anticipated expiration: 2033-08-06
Also published as: CN104540925A; US20150315484A1; EP2867339B1; MY173254A; HUE027415T2; CA2877163A1; RU2015105404A; PH12015500279A1; KR20150042211A; JP2015524451A; CA2877163C; AU2013301898B2; US9670418B2; RU2627663C2; WO2014023418A1; IN2014DN11047A; CN104540925B; ZA201500937B; ES2558588T3; KR102117730B1

Abstract

The invention relates to a method for reacting hydrocarbon feedstocks by thermal steam-cracking to form at least one olefin-containing product stream that contains at least ethylene and propylene, wherein a hydrocarbon feedstock is reacted at least partially in at least one cracking furnace (2), wherein the hydrocarbon feedstock is reacted in the cracking furnace (2) under mild cracking conditions, mild cracking conditions meaning that propylene is present in a ratio of 0.81 to 1.6 kg/kg of ethylene at the cracking furnace outlet and wherein the hydrocarbon feedstock contains primarily hydrocarbons with a carbon number of at most 6, preferably at most 5.

Description

description

Process for producing olefins by thermal vapor cracking

The present invention relates to a method for the implementation of

Hydrocarbon inserts by thermal vapor cracking to at least one olefin-containing product stream containing at least ethylene and propylene, wherein a hydrocarbon feed is at least partially reacted in at least one cracking furnace.

Thermal steam cracking (also known as steam cracking or steam cracking) is a long-established petrochemical process. The classic target compound in the thermal

Steam columns is the ethylene (also: ethene), which is an important starting material for a number of chemical syntheses. As an insert for the thermal vapor cracking both gases such as ethane, propane or butane and corresponding mixtures as well as liquid hydrocarbons, such as naphtha, and hydrocarbon mixtures can be used.

For details of the devices and reaction conditions used in thermal steam cracking and the reactions that occur, as well as details of the refining technology, refer to corresponding articles in reference works such as

Zimmermann, H. and Walzl, R .: Ethylene. In: Ullmann's Encyclopedia of Industrial Chemistry. 6th ed. Weinheim: Wiley-VCH, 2005, and Irion, W.W. and Neuwirth, O.S .: Oil Refining. In: Ullmann's Encyclopedia of Industrial Chemistry. 6th edition Weinheim: Wiley-VCH 2005, referenced. Methods for producing olefins are

for example, also in US 3 714 282 A and US 6 743 961 B1.

Furthermore, mention should be made here of US 2008/0194900, which discloses a method for steam-splitting an aromatics-containing naphtha insert, wherein the pretreated naphtha insert before the thermal vapor cracking in the

Extracting aromatics from the steam cracker, the aromatics are removed and the raffinate obtained in the aromatics extraction is fed into the kiln with six to eight carbon hydrocarbons. For thermal vapor cracking cracking furnaces are used. The cracking furnaces, together with Quechenheit and downstream facilities for the processing of the product mixtures formed, in corresponding larger plants

Integrated olefin production, which are referred to in this application as "steam cracker".

An important parameter in thermal steam cracking is the so-called

Splitting severity (English: Cracking Severity), which determines the cleavage conditions. The cracking conditions are particularly influenced by the temperature and the

Residence time and the partial pressures of hydrocarbons and water vapor.

The composition of the hydrocarbon mixtures used as a feed and the type of cracking furnaces used also influence the cracking conditions.

Due to the mutual influences of these factors, the fission condition is usually increased by the ratio of propylene (also called propene)

Ethylene defined in the fission gas.

Thermal vapor cracking occurs depending on the feed mixture and

Cleavage conditions in addition to the classical target compound ethylene sometimes considerable amounts of by-products, which can be separated from a corresponding product stream. These include, but are not limited to, lower alkenes such as e.g. Propylene and butenes, as well as dienes such as butadienes, and aromatics such as e.g. Benzene, toluene and xylenes. These have a comparatively high economic value, so that their formation as so-called value-added products (English High Value Products) is desired.

The present invention therefore has as its object the possibilities for

Recovery of olefin-containing product mixtures from hydrocarbons by thermal vapor cracking.

Disclosure of the invention

Against this background, the invention proposes a process for the conversion of hydrocarbon feedstocks by thermal vapor cracking. to at least one olefin-containing product stream containing at least ethylene and propylene, wherein a hydrocarbon feed is at least partially reacted in at least one cracking furnace, having the features of the independent claims.

Preferred embodiments are the subject of the dependent claims and the

following description.

Advantages of the invention

According to the invention, a method is proposed in which the

Hydrocarbon use in the cracking furnace is reacted under mild cleavage conditions, wherein mild cleavage conditions mean that at the cracking furnace exit propylene to ethylene in a ratio of 0.81 to 1, 6 kg / kg are present, and wherein the

Hydrocarbon use predominantly hydrocarbons having a carbon number of not more than 6, preferably of at most 5 contains. For the purposes of this invention, cracking furnace is understood to mean a splitting unit in which the cracking conditions are defined. It is possible that there is a subdivision into two or more cracking furnaces in a total furnace. One speaks often of

Oven cells. Several furnace cells belonging to a total furnace generally have independent radiation zones and a common convection zone as well as a common smoke outlet. In these cases, each furnace cell can be operated with its own gap conditions. Each furnace cell is thus one

Column unit and is therefore referred to here as cracking furnace. The total furnace then has several column units or, in other words, it has several

Cracking ovens on. If there is only one furnace cell, this is the splitting unit and thus the cracking furnace. Cracking furnaces can be grouped together, which

For example, be supplied with the same use. The fission conditions within a furnace group will usually be set the same or similar.

In the thermal cracking of hydrocarbons of conventional composition, such as naphtha, under mild cleavage conditions produces a very large amount of pyrolysis gasoline, which is very difficult to handle due to the large amount. This is a result of the comparatively lower implementation of the use in the cracking furnace under mild cracking conditions. However, mild cleavage conditions are desirable because a larger cleavage under mild conditions Ratio of propylene to ethylene is present as in a cleavage under normal cleavage conditions, as they are commonly used.

With the method according to the invention, it becomes possible to operate a cracking furnace under mild cracking conditions, since the use and the cracking conditions are adapted to one another. Only by adjusting the use and fissure conditions is it possible to circumvent the disadvantages described above. These disadvantages and the solution shown were recognized within the scope of the invention. With the method according to the invention, it is thus possible to operate a plant for steam cracking in such a way that more propylene is produced in relation to the fresh feed than in a conventional plant in which the

inventive method is not used. The higher the ratio of propylene to ethylene for the cracking conditions in the second cracking furnace, the more propylene is produced in relation to the fresh feed. This is within the scope of the invention advantageous. However, a higher ratio of propylene to ethylene is accompanied by a lower conversion of the use, so that for the values upwards technical and economic limits occur. Within the limits specified in the claims, it is ensured that on the one hand adjust the inventive advantages and on the other hand, the steam cracker is technically manageable and economically operable.

For the specified limit values for the cracking conditions in the cracking furnace which converts under mild gap conditions, it is true that within these crackers a technically and economically advantageous steam cracking is possible in which

Propylene arise as primary value products.

The term "predominantly" is used in this application to make it clear that the insert or fraction does not consist exclusively of

Hydrocarbons having the specified carbon number, but in addition to the hydrocarbons of the specified carbon number also hydrocarbons with different carbon numbers and other impurities may be present. In the separation and work-up of the product stream, an output stream and / or the fractions and / or fresh-use fractionation always remains the remains Component (s) in the product stream or in the fraction. Other impurities remain, so that a processed product or

Fraction stream always contains residues. Since the effort for separation and

Working up with the purity to be achieved increases extremely sharply, it depends on economic factors, which proportion of residues may be contained in a stream. How high this proportion is, must be weighed from economic point of view. As a rough guideline for the proportion of unwanted

Hydrocarbons and other impurities will generally be considered to be contained in the product stream and / or in the fraction with a maximum of 40% by weight. Usually even a maximum value of 20% by weight or less is achieved. Ideally, a maximum value of 10% by weight is achieved. The just said applies to all process plants, not only in steam crackers but also in oil refineries. Consequently, for the hydrocarbon feed which is conducted into the cracking furnace which converts under mild cracking conditions, this is at least 60% by weight, preferably at least 80%

Weight percent and more preferably at least 90 weight percent and more preferably at least 95 weight percent and most preferably at least 98 weight percent hydrocarbons having a carbon number of at most 6, preferably of at most 5 contains. Also, for the recycled fractions and fractions recovered from the fresh feed fractionation (see below), these will be the desired hydrocarbons having at least 60

Percent by weight, preferably at least 80 weight percent and more preferably at least 90 weight percent and most preferably at least 95

Weight percent and most preferably at least 98 weight percent included.

In a particularly advantageous embodiment of the invention, one or more fractions, which are obtained from the product stream and which predominantly contains hydrocarbons having a carbon number of at most 5, are used as the cracking furnace which converts under mild cleavage conditions

Hydrocarbon used. By returning such fractions increases the amount of suitable use for the second cracking furnace or such a fraction is a suitable hydrocarbon feed for the reaction in mild gap conditions cracking furnace. Also, a fraction with hydrocarbons having a carbon number of 4 and a fraction with a Carbon number of 5 obtained in the workup of the product stream in steam crackers, which can be recycled after the separation of the desired products directly or after further treatment steps. In an advantageous embodiment of the invention, the recycled fractions are largely free of diolefins when they are fed to the cracking furnace which converts under mild cracking conditions as a hydrocarbon feed. Diolefins have an adverse effect in the cracking furnace. For this purpose, the diolefins are predominantly removed from the fractions which are recycled to the second cracking furnace by preceding conversion processes or separation steps. The removal can take place either before or after the separation of the fractions which are recycled.

The procedures that are necessary for separation and workup are known in the art. These are conventional measures in steam crackers for separating and working up product and fraction streams.

With particular advantages, saturated hydrocarbons are used as the hydrocarbon feed to the cracking furnace which converts under mild cracking conditions. Saturated hydrocarbons are particularly suitable for thermal vapor columns.

Advantageously, the hydrocarbon feed is reacted in the cracking furnace under mild cleavage conditions resulting in a ratio of propylene to ethylene of from 0.82 to 1.4 kg / kg, more preferably from 0.85 to 1.2 kg / kg at

Lead slit furnace exit.

In an advantageous embodiment of the invention, a hydrocarbon feed is reacted under normal cracking conditions in a further cracking furnace, wherein normal cracking conditions mean that at the cracking furnace exit propylene to ethylene in a ratio of 0.25 to 0.85 kg / kg, preferably from 0.3 to 0 , 75 kg / kg, more preferably from 0.4 to 0.65 kg / kg, wherein the ratio of propylene to ethylene for the cracking furnace operating under mild cracking conditions always has a value greater than the value for the ratio of propylene to ethylene for the cracking furnace which converts under normal conditions. In particular, lie the Values for the ratio of propylene to ethylene at least 0.1 kg / kg, preferably at least 0.15 kg / kg, more preferably at least 0.2 kg / kg apart, so that adjust the benefits of the invention in particular.

With special advantages, the steam cracker therefore has at least one cracking furnace which converts under normal cracking conditions. These are used as the insert those hydrocarbons out, which are disadvantageous for the cracking furnace which converts under mild cleavage conditions. Owing to the presence of at least one cracking furnace which converts under normal cracking conditions, the operation of the cracking furnace which converts under mild gap conditions becomes economically advantageous if

Fresh use is a mixture of hydrocarbons, which does not meet the condition mentioned in claim 1. With particular advantage is so for the under normal conditions

a cracking furnace using a hydrocarbon feed which deviates in composition from the hydrocarbon feedstock used for the cracking furnace which reacts under mild cracking conditions. Since the cracking furnace, which reacts under normal conditions, is very well suited for the conversion of long-chain hydrocarbons, this is normal

Cleavage furnace which converts cleavage conditions is supplied with at least one fraction separated off from the product stream and recycled, which comprises predominantly hydrocarbons having a carbon number of at least 6. Since certain hydrocarbons accumulate in recirculated fractions through the circulation, hydrocarbons having a carbon number of 6 under normal cracking conditions are recommended for recycled fractions. However, it is also possible to recycle these into the cracking furnace which converts under mildly cleavage conditions. In a particularly advantageous embodiment of the invention, a fresh use is used, which is fractionated into at least a first and a second fresh-use fraction and the first fresh-use fraction at least partially,

Advantageously complete, at least partially, advantageously completely, into the cracking furnace which converts under mild gap conditions into the cracking furnace which converts under normal cracking conditions and the second fresh feed fraction becomes. Fractionation of the fresh feed makes it possible to provide, in particular for the cracking furnace which converts under mild cracking conditions, an insert with which the advantages according to the invention are set in an outstanding manner.

At this point it should be emphasized once again that the aforementioned operations recirculated fractions, fresh-use fraction and fresh operations

Hydrocarbons having a carbon number of at most 6, preferably of a maximum of 5, are particularly suitable as an insert for the cracking furnace which converts under mild cleavage conditions. To achieve the advantages of the invention, the inserts proposed herein may be used alone or as a mixture in mild ones

Be performed gap conditions converting cracking furnace. When

Hydrocarbon use can thus one or more recirculated fractions or a fresh feed fraction or another use of hydrocarbons having a carbon number of at most 6, preferably a maximum of 5, are used. Also recycle fraction (s) and a fresh feed fraction or recycle fraction (s) and another feed may be hydrocarbons having a maximum carbon number of 6 or a fresh feed fraction and another use of hydrocarbons having a maximum carbon number of 6 or a mixture from all possible uses as a hydrocarbon feed to the cracking furnace operating under mild cracking conditions.

As explained in the beginning, the ratio of propylene to ethylene in thermal vapor cracking results from a number of different influencing factors in which the cracking furnace exit temperature, i. the temperature of a product stream as it leaves the reactor coil (coil output temperature) plays an important role. The cracking furnace exit temperature for the reaction in the cracking furnace operating at mild cracking conditions is advantageously between 680 ° C and 820 ° C, preferably between 700 ° C and 800 ° C and more preferably between 710 ° C and 780 ° C and more preferably between 720 ° C and 760 ° C. The

A cracking furnace exit temperature for the reaction in the cracking furnace which converts under normal cracking conditions is advantageously between 800 ° C and 1000 ° C, preferably between 820 ° C and 950 ° C and more preferably between 840 ° C and 900 ° C. The cracking furnace outlet temperature is below normal

Cleavage conditions implementing gap oven by at least 10 ° C, preferably in order at least 20 ° C, above that of under mild cleavage conditions

Cracking furnace.

Furthermore, in the cracking furnace which converts under mild cleavage conditions, a lower vapor dilution can be achieved than in the case of normal cracking conditions

implementing cracking furnace can be used. This reduces the necessary

Dilution steam and saves energy. However, a lower vapor dilution in the second cracking furnace is not necessary to show the significant advantage of the invention. Advantageously 0.3 to 1.5 kg of steam per kg of hydrocarbon feed and in the cracking furnace operating under mild cracking conditions 0.15 to 0.8 kg of steam per kg of hydrocarbon feed are used in the cracking furnace which converts under normal cracking conditions.

Also, with particular advantage in the product stream contained, in particular saturated hydrocarbons having a carbon number of 2 to 3 with advantage by means

thermal vapor columns are implemented in a cracking furnace for gaseous use. For this purpose, the saturated gaseous hydrocarbons are recovered from the product stream and recycled to the cracking furnace for gaseous use and implemented there.

Advantageously, as a fresh use in the under mild cleavage conditions

converting fissure gas condensates or / and one or more partial cuts from a petroleum refinery and / or synthetic and / or biogenic hydrocarbons and / or mixtures derived therefrom.

As fresh use for the cracking furnace which converts under normal cracking conditions and / or as fresh feed for fresh fractionation, both gases or gas fractions such as ethane, propane or butane and corresponding mixtures and condensates as well as liquid hydrocarbons and hydrocarbon mixtures can be used. The gas mixtures and condensates mentioned include in particular so-called natural gas condensates (English: Natural Gas Liquids, NGL). The liquid hydrocarbons and hydrocarbon mixtures can originate, for example, from the so-called gasoline fraction of crude oil. Such crude naphthas (NT) and kerosene are mixtures of preferably saturated compounds with boiling points between 35 and 210 ° C. The invention is but also advantageous when using middle distillates, atmospheric

Residues and / or mixtures thereof derived from crude oil processing. Middle distillates are so-called light and heavy gas oils, which can be used as starting materials for the production of light heating and diesel oils as well as heavy fuel oil. The compounds contained have boiling points of 180 to 360 ° C. Preferably, these are predominantly saturated compounds which can be reacted during thermal vapor cracking. Furthermore, by known distillation separation methods

won fractions and corresponding residues, but also the

Use thereof, for example, by hydrogenation or hydrocracking, derived fractions can be used. Examples are light, heavy and vacuum gas oils (English: Atmospheric Gas Oil, AGO, or Vacuum Gas Oil, VGO) and mixtures and / or residues treated by the hydrogenation processes mentioned (English Hydrotreated Vacuum Gas Oil, HVGO, Hydroeracker Residue, HCR or Unconverted Oil, UCO).

In particular, natural gas condensates and / or crude oil fractions and / or mixtures derived therefrom are used as fresh feed.

Advantageously, the invention thus encompasses the use of

Hydrocarbon mixtures with a boiling range of up to 600 ° C as

Hydrocarbon use as a fresh use for the reaction under normal cracking conditions hydrocarbon use. Within this total range it is also possible to use hydrocarbon mixtures with different boiling ranges, for example with boiling ranges of up to 360 ° C. or up to 240 ° C. The reaction conditions in the cracking furnace are matched to the hydrocarbon mixtures used in each case.

However, the invention can be used to advantage with any other fresh inserts, which have comparable properties, such as biogenic and / or synthetic hydrocarbons.

Short description of the drawing

The inventive method in a particularly advantageous embodiment is based on the process diagrams, which show the essential process steps schematically be explained in more detail. For a better understanding, the known method will first be explained with reference to FIG.

1 shows a schematic representation of a known procedure for

Olefin production. Figure 2 shows a schematic representation of the essential steps of the method according to the invention in a particularly advantageous embodiment and Figure 3, 4 and 5 show, also schematically, the essential steps of a particularly advantageous embodiment of the invention. In the figures wear each other

corresponding elements identical reference signs.

The schematic process diagram 100 of FIG. 1 for the known process includes a cracking furnace 1, in which the fresh feed A (for example naphtha) and the recycled fractions S and P are conducted as a hydrocarbon feed. In cracking furnace 1, the use of hydrocarbons in convection and

Radiation zone heated and reacted. In the cracking furnace water vapor is added, usually 0.5 to 1 kg of process steam per kg of hydrocarbon. From the cracking furnace 1, a product stream C exits, which is also referred to as a fission product stream directly at the outlet from the cracking furnace. When leaving the cracking furnace, this cracking product stream has a temperature which is normally between 840 ° C and 900 ° C. The ratio of propylene to ethylene is usually 0.35 to 0.6 kg / kg. After a first quench (not shown), the product stream is processed in a processing unit 4. From the

Working-up unit are obtained as essential product fractions E to N the following fractions: hydrogen E, spent liquor F, methane G, ethylene H, propylene I, gaseous hydrocarbons L having a carbon number of 4, pyrolysis gasoline M and pyrolysis N. The gaseous hydrocarbons L with a

Hydrocarbon numbers of 4 are further treated in a C4 workup unit 5 which is used to process hydrocarbons having a carbon number of 4. Such a C4-processing unit 5 further treats the fraction having a carbon number of 4 such that butadiene O can be discharged. The remaining hydrocarbons having a carbon number of 4 represent a fraction P, which is recycled to the cracking furnace 1. The pyrolysis gasoline M, which

Hydrocarbons having a carbon number of 5 and more, is further processed in a pyrolysis gasoline processing unit 6 and there are aromatics Q and hydrocarbons R having a carbon number of, for example, more than 9 dissipated. The remaining hydrocarbons having a carbon number of 5 or more are recycled as fraction S into the cracking furnace 1. The workup unit 4 and the C4 workup unit 5 and the pyrolysis gasoline workup unit 6 comprise conventional units for further processing of the product stream

or the product fractions which are used to carry out various

Process steps are used, such as compression, condensation and cooling, drying, distillation and fractionation, extraction and hydrogenation. The

Process steps are common in olefin plants and known in the art.

The schematic process diagram 10 of FIG. 2 now shows the method according to the invention in its essential steps. In the cracking furnace 2, which converts under mild conditions, a fresh feed BL is fed. From the cracking furnace 2 enters the product stream X, which has a temperature which is advantageously between 700 ° C and 800 ° C. The ratio of propylene to ethylene is thereby

advantageously between 0.7 to 1.5 kg / kg. The product stream X is further processed in the processing unit 4. The processes for further treatment and work-up in the processing unit 4 are known and have just been described. Thus, the processing unit 4 also, as just described, to the

Product fractions E to N. Likewise, the product fractions L and M are further treated in the special workup units 5 and 6. In contrast to the method described in FIG. 1, the fraction P which contains hydrocarbons having a carbon number of 4 is now advantageously recycled to the cracking furnace 2. In the pyrolysis gasoline working-up unit 6, in addition to the above-mentioned fractions Q and R, the fraction T is recovered. The fraction T, which contains hydrocarbons having a carbon number of 5, is advantageously recirculated to the cracking furnace 2, which reacts under mild cracking conditions.

The schematic process diagram 10 of FIG. 3 now shows the method according to the invention in a particularly advantageous embodiment and its essential process steps. In addition to the cracking furnace 1, which reacts under normal conditions, there is a cracking furnace 2 which converts under mild cracking conditions, and advantageously a fresh fractionation unit 7. A fresh batch B (for example naphtha) is now fractionated in the fresh fractionation unit 7 and the first freshly used fraction B1 is fed into the cracking furnace 1, while the second fresh-use fraction B2 in the cracking furnace second to be led. The fresh fraction fractionation processes use the usual methods of separating and treating hydrocarbon streams known from refinery olefin plants. This knows the expert and he knows how to use it. In the cracking furnace 1 in addition a fraction U and in the cracking furnace 2 in addition the fractions T and P are recycled (for more details see below). Furthermore, the slit furnace 2, which converts under mild cracking conditions, is supplied with a further feedstock BL comprising hydrocarbons having a maximum carbon number of 6, preferably a maximum of 5, as fresh feed. From the cracking furnace 1, in turn, the cleavage product stream C exits with the above-mentioned properties. From the cracking furnace 2, the cleavage product stream X exits. The cleavage product stream X has a temperature which is advantageously between 700 ° C and 800 ° C. The ratio of propylene to ethylene is thereby

advantageously between 0.7 to 1.5 kg / kg. The product streams C and X are further processed in the workup unit 4 and combined at a suitable point to a common product stream. The processes for further treatment and work-up in the processing unit 4 are known and have just been described. Thus, the workup unit 4 also leads, as just described, to the product fractions E to N. The product fractions L and M are further treated, as just described, in the special workup units 5 and 6. In contrast to the method described in FIG. 1, the fraction P which contains hydrocarbons having a carbon number of 4 is now advantageously not recycled into the cracking furnace 1 but into the cracking furnace 2. In the pyrolysis gasoline processing unit 6, the fractions T and U are recovered in addition to the above-mentioned fractions Q and R. The fraction T, which contains hydrocarbons having a carbon number of 5, is advantageously returned to the cracking furnace 2, while the fraction U, which contains hydrocarbons having a carbon number of 6 and more, in particular between 6 and 9, advantageously recycled to the cracking furnace 1 becomes. In Figure 3, various inserts are performed for the cracking furnace. These then form the second hydrocarbon feed. It should be mentioned that the list of different missions is not exhaustive and

In particular, that the inserts shown in Figure 3 for the second cracking furnace B2, BL, T and P does not always have to be guided all in the cracking furnace 2, but that it is sufficient in many cases, a portion of the possible uses in the mild

To lead gap conditions implementing gap furnace 2, for example a

recycled fraction T of hydrocarbons having a carbon number of 5 and a fresh feed BL from hydrocarbons having a maximum carbon number of 6, preferably a maximum of 5 or for example recycled fractions T and P with hydrocarbons having carbon numbers of 5 and 4 and LPG BL. Briefly, the following operations are possible in the second cracking furnace: B2, BL, T, P, B2 + BL, B2 + T, B2 + P, BL + T, BL + P, T + P, B2 + BL + T, B2 + BL + P, B2 + P + T, BL + P + T or B2 + BL + P + T.

FIG. 4 also has a particularly advantageous embodiment of the invention. FIG. 4 has the same schematic process diagram as FIG. 3 shows. This is supplemented by a cracking furnace 3 for gaseous use, in which a fraction V is performed as an insert. The fraction V contains saturated gaseous hydrocarbons having a carbon number of 2 or 3, which are also obtained in the workup unit 4.

Also in Figure 5, an advantageous embodiment of the invention is shown. FIG. 5 contains the same schematic process diagram as FIG. 3, but here the fresh-use fractionation is missing. Fresh use is here as Frischseinsatz B the first cracking furnace 1 added and the second cracking furnace 2, a fresh use BL of hydrocarbons having a carbon number of at most 6, preferably a maximum of 5 added. The further process steps were already in the

Figure description to Figure 2 and 3 explained.

LIST OF REFERENCE NUMBERS

1 cracking furnace (normal cracking conditions)

2 cracking furnace (mild cracking conditions)

3 cracking furnace for gaseous use

4 workup unit

5 C4 workup unit

6 pyrolysis gasoline workup unit

7 fresh-use fractionation unit

10 schematic process diagrams for a known method schematic process diagrams for the inventive method in particularly advantageous embodiments

A, B, BL Fresh use

B1, B2 fresh-use fractions

C, D, X product streams

E-V product fractions

Claims

claims

1. A process for the implementation of hydrocarbon feedstocks by thermal vapor cracking to at least one olefin-containing product stream containing at least ethylene and propylene, wherein a hydrocarbon feed in at least one cracking furnace (2) is at least partially reacted, characterized in that the hydrocarbon feed in the cracking furnace (2) under mild cleavage conditions mean that at the cracking furnace exit, propylene to ethylene is present in a ratio of 0.81 to 1.6 kg / kg, and wherein the hydrocarbon feed is predominantly

Hydrocarbons having a maximum carbon number of 6, preferably a maximum of 5 contains.

2. Process according to claim 1, characterized in that the cracking furnace (2) which reacts under mild cracking conditions comprises one or more recirculated fractions (P, T) which are obtained from the product stream and which predominantly contain hydrocarbons having a maximum carbon number of 5 , are fed as hydrocarbon feed.

3. The method according to claim 1 or 2, characterized in that the

recycled fractions (P, T) are largely free of diolefins, if they are the cracking furnace (2) acting under mild cleavage conditions as

Hydrocarbon used to be supplied.

4. The method according to any one of claims 1 to 3, characterized in that predominantly saturated hydrocarbons are fed as a hydrocarbon feed to the cracking furnace (2) which converts under mild cracking conditions.

5. The method according to any one of claims 1 to 4, characterized in that the hydrocarbon feed in the cracking furnace (2) is reacted under mild cleavage conditions, to a ratio of propylene to ethylene from 0.82 to 1, 4 kg / kg, particularly preferably from 0.85 to 1.2 kg / kg at the Spaltofenaustritt.

6. The method according to any one of claims 1 to 5, characterized in that in a further cracking furnace (1) a hydrocarbon feed under normal Cleavage conditions are implemented, wherein normal cleavage conditions mean that at the cracking furnace exit propylene to ethylene in a ratio of 0.25 to 0.85 kg / kg, preferably from 0.3 to 0.75 kg / kg, particularly preferably from 0.4 to 0.65 kg / kg, the ratio of propylene to ethylene always being greater for the cracking furnace (2) reacting under mild cracking conditions than the value for the ratio of propylene to ethylene for the cracking furnace (1) reacting under normal cracking conditions. ,

Process according to Claim 6, in which the propylene / ethylene ratio is at least 0.1 kg / kg, preferably at least 0.15 kg / kg, and more preferably at least 0.2 kg / kg.

Method according to one of claims 1 to 7, characterized in that for the converting under normal conditions gap cracking furnace (1) a

Hydrocarbon used, which deviates in its composition from the hydrocarbon feed, which is used for the cracking furnace under mild conditions (2), is used.

Method according to one of claims 1 to 8, characterized in that at least one separated from the product stream and recycled fraction (U), which converts under normal cracking conditions cracking furnace (1)

predominantly hydrocarbons having a carbon number of at least 6, is supplied.

Method according to one of claims 1 to 9, characterized in that a fresh use is used, which is fractionated into at least a first and a second fresh-use fraction (B1, B2) and the first fresh-use fraction (B1) at least partially in the under slit furnace (1) and the second fresh-use fraction (B2) are at least partially guided into the cracking furnace (2) which converts under mild gap conditions.

A process according to any one of claims 1 to 10, wherein the cracking furnace exit temperature for the reaction in the under mild cracking conditions

converting cracking furnace (2) between 680 ° C and 820 ° C, preferably between 700 ° C and 800 ° C and more preferably between 710 ° C and 780 ° C and more preferably between 720 ° C and 760 ° C and the cracking furnace exit temperature for the reaction in the cracking furnace (1) (1) (1) which converts under normal cracking conditions is between 800 ° C and 1000 ° C, preferably between 820 ° C and 950 ° C and more preferably between 840 ° C and 900 ° C, wherein the

The cracking furnace exit temperature of the cracking furnace (1) which converts under normal cracking conditions is at least 10 ° C., preferably at least 20 ° C., above that of the cracking furnace (2) which converts under mild cracking conditions.

12. The method according to any one of claims 1 to 1 1, wherein in the under

cracking furnace (1) 0.3 to 1.5 kg

Water vapor per kg of hydrocarbon use and in the mild under

Crevice furnace (2) used 0.15 to 0.8 kg of water vapor per kg of hydrocarbon feed is used.

13. The method according to any one of claims 1 to 13, wherein from the

Product stream at least one fraction (V), which predominantly

Hydrocarbons having a carbon number of 2 or 3, is recovered and is at least partially reacted in a cracking furnace (3) for gaseous use.

14. The method according to any one of claims 1 to 13, characterized in that as Frischseinsatz (BL) in the under mild gap conditions converting cracking furnace (2), or natural gas condensates and / or one or more partial sections of a

Petroleum refinery and / or synthetic and / or biogenic hydrocarbons and / or mixtures derived therefrom.

15. The method according to any one of claims 1 to 14, characterized in that as Frischseinsatz (B) for the under normal cleavage conditions implementing

Cracking furnace (1) or / and for the fresh use for the fresh-use fractionation (7) natural gas condensates and / or crude oil fractions, in particular naphtha, and / or synthetic and / or biogenic hydrocarbons and / or mixtures derived therefrom.