DE1922665A1 - Process for converting hydrocarbons to olefins - Google Patents

Description

Process for converting hydrocarbons to olefins.

The invention relates to a method for converting hydrocarbons in olefins, and the invention is based on the object of producing olefins from hydrocarbons boiling in the gas oil range, in particular containing aromatics, to improve. To solve this problem, the feed of hydrocarbons is treated selectively to remove the aromatic To remove compounds and the raffinate thus obtained fed to a hydrocarbon cracking.

The invention particularly relates to an improved process for making olefins, particularly ethylene, from one in the field the gas oil boiling and containing substantial quantities of aromatic compounds; following this procedure will selectively treating the feed to remove aromatic compounds, mixing the treated feed with steam and feeding the mixture to a cracking furnace operated under cracking conditions such that light olefins selectively and then the effluent mixture is rapidly cooled and the cracked products are separated out.

The known for the production of olefins, particularly light olefins from petroleum distillates boiling in the gas oil range Processes have several disadvantages such as large amounts of coke settling in the cracking coils and on the cracking furnace following quench boilers clog quickly, a large ratio of water vapor to carbon and a large one Furnace power required to produce a certain amount of olefins

st 27/9 909847/1213

1922865

im forget to make the oven power that for lower boiling feeds is required.

It has been found that those associated with the cracking or pyrolysis of petroleum distillates boiling in the range of gas oil high coke deposition and clogging of the heat exchangers essentially affect the In such distillates in general Aromatic compounds present are attributable. The removal of the aromatic compounds is a special one difficult problem as these compounds generally boil and within the full range of the distillate feed consequently cannot be easily removed by distillation. The aromatic compounds result when oiled little, if any, olefins. The presence of aromatic compounds in the feed requires use an additional amount of steam for dilution, thereby increasing the overall throughput and the fit of the oven and the others Device that is in the downstream direction of the furnace, is increased significantly.

It has been found that after an operation of only 28 days in cracking relatively light in the range of about 210-350 ⁰ C boiling gas oil in the conventional cracking process, ie, without prior removal of the aromatic compounds, the furnace'd clog up so quickly that check the Pressure drop in the furnace of about

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1.01 kg / cm had increased to about 1.8 ^ kg / cm, i.e. by about $ 81 and that the pollution in the Abs ehre ck boiler, i.e. in the heat exchanger, happened so quickly that the pressure drop

if increased from about 0.42 to about 1.27 kg / cm, i.e. by about three times.

Similarly, it has been found that cracking another relatively light gas oil, i.e. that in the range of boiled around 232 to 3! 50 ° C, the heat exchangers dirty so quickly, that a significantly longer operation than 50 days is not would have been possible.

It is thus proven that the known methods take place The cracking of such distillates has an economic

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From a point of view of this, uninterrupted operation of a system for a longer period of time is not possible, regardless of whether quenching steam boilers are used or not, since without a quenching steam boiler, the pollution of the cracking furnace is a limiting factor in dissolution. The removal of aromatic compounds from these charges and / οα'άϊ ⁵ W-Qh, and preferably practically all of the <3β2 aromatic compounds. heavier loads of the present invention result in a substantial reduction in pollution and pressure drop.

An essential object of the present invention is therefore a cracking of oils, a low deposition of coke and a Reduced clogging of the heat exchangers by the gases leaving the furnace and thus a longer operating time between the decoking of the furnace coil a and the cleaning of the heat exchangers to achieve.

Another object of the invention in the manufacture of olefins from petroleum distillates that boil in the range of gas oil to achieve a reduction in the total capacity of the furnace is required to obtain a certain amount of olefins.

Another object of the invention is to reduce the amount of dilution required ?! Amount of steam that the crack oven for the production of a certain confinement of olefins fed must become.

Another object of the invention is to reduce the feed of hydrocarbons to the cracking furnace by one produce equivalent amount of olefin.

Another task is to reduce the sulfur content in the feed intended for the cracking furnace.

Another object of the invention is to reduce the fuel required to heat the Craekofens by one to produce an equivalent amount of oil.

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BATH ORIGINAL

Further objects of the invention and advantages thereof emerge from the following description.

To solve the problems on which the present invention is based, a method is used in which boiling in the region of the gas oil Petroleum distillates are treated to remove aromatic compounds, the treated feed to steam dilution is added and the mixture is fed to a cracking furnace to remove the paraffinic and cracking naphthenic hydrocarbon to produce olefins. The gases leaving the furnace containing the cracked products are rapidly cooled, preferably in such a way that it leads through a quenching boiler, i.e. through a indirect heat exchanger to generate steam at high pressure.

By the term light olefins are 2 to 4 carbon atoms To understand containing mono- or diolefins, such as ethylene, propylene, butylenes and butadiene. Preferred olefins made by the process of the invention are ethylene, propylene and Butadiene and especially ethylene.

Petroleum distillates which are boiling in the gas oil range and which can be worked up by the process of the present invention are light gas oil, heavy gas oil and vacuum gas oil, and catalytic ⁺ recycled Cr-by products, such as light catalytic recycled cracked oil (LCCO) and heavy catalytic recycled oils (HCCO). + in

The essential hydrocarbons contained in the distillates mentioned are paraffins, cycloparaffins, polycyclic paraffins, aromatic compounds, polyaromatic compounds, and compounds that are both cycloparaffinic and aromatic Contain ingredients. The connections that are mainly used to Clogging of the furnace tube chings and the quenching steam boiler and which contribute little or nothing to the formation of olefins, are aromatic, polyaromatic and mixed aromatic and cyoloparaffinic compounds. The distillates also contain a considerable amount of sulfur compounds that

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is reduced by removing the aromatic compounds. The alkylbenzenes containing more than one carbon atom Side chains, however, can contribute to the production of olefins by cracking the side chains and they count therefore not to the aromatic compounds whose removal is desired. Whether alkylbenzenes with the other aromatics removed or not depends on the length and number of alkyl substituents. The methylbenzenes, for example, tend to with the aromatics to be extracted, while the ethyl and propyl benzenes, i.e. those which are more paraffinic, tend to to stay in the raffinate.

The removal, i.e. the separation of aromatic compounds from the petroleum distillates boiling in the range of gas oil, the paraffinic and naphthenic compounds in these distillates remain, can be done according to known methods, e.g. by solvent extraction and adsorption, for which e.g. adsorbents such as silica gel and molecular sieves used.

To carry out the process of the present invention, for the thermal cracking or pyrolysis of hydrocarbons, e.g. naphtha, conventional methods and ovens for the production of olefins can be used. In such processes and ovens, the Hydrocarbon feed mixed with steam for dilution and the mixture continuously through lines in the reaction zone of the furnace at an elevated temperature for a short residence time, with a relatively low partial pressure of the reacting hydrocarbon to convert part of the hydrocarbon content is maintained in olefins.

The specific working conditions of the steam dilution, the cracking temperatures and residence times depend mainly on the characteristics of the feed and the products desired.

The furnace generally has a radiant pre-heating zone which the has lines serving to preheat the charge.

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■ '■ "■■" "■"' ■ 9 D 90 47/121 3 '

The hydrocarbon feed is contained in the cracking zone within heated lines. To get the Burners on the walls or on top of the room to obtain heat placed at the bottom of the cracking zone of the furnace. The conduits may have a coil that consists of 2 or more in series there are pipes connected by U-bends. The tubes can be inside the crusting room, i.e. inside the cracking zone of the furnace can be arranged vertically or horizontally. Two or more coils can be grouped together. The tubes can in the furnace in one plane or in general parallel to two opposite walls of the furnace Levels be arranged, with one in the Peuerungsrauin itself Row of burners are provided.

The method of the invention provides for rapid quenching or cooling of the hot gaseous reaction products. The quenching zone is located close to the outlet of the reaction zone and enables rapid cooling of the products from the Reaction zone temperature to a temperature at which the Reaction is practically interrupted. Pure cooling or deterrence Common facilities can be used, e.g. quenching steam boilers with one or more tubes, i.e., heat exchangers, in which high pressure steam is generated. After quenching of the reaction mixture leaving the furnace, this can be further cooled by injecting it directly deterred by oil. If high pressure steam is not desired * can to achieve complete cooling and thus termination of the reaction in the products of the reaction zone immediately oil can be injected for quenching. After cooling, the reaction products coming from the cooling zone can be used in a known manner Processed in a way to separate the different products from each other, e.g. a fuel gas, ethylene, propylene, a C ^ fraction, a gasoline fraction and fuel oil.

The removal of the undesirable aromatic compounds from the feed boiling in the gas oil range Petroleum distillate according to the method of the present invention leads to the following * advantagesϊ significantly longer service life of the furnace and / or the quenching steam boiler until it is shut down

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Si Γ. Π ^r \ '1 ι ι ν s 1

for the purpose of removing the coke and cleaning it; reduced clogging in those following the furnace in the direction of flow of the reaction products lying facilities! a significant increase in the yield of light olefins, i.e. ethylene, propylene and Butadiene based on the unit weight of the feed for the Qfenj decrease in the steam to hydrocarbon ratio; a significant reduction in the capacity of the furnace required and the equipment downstream of the furnace, to produce a certain amount of olefins; A be- . eighth reduction in the amount required to heat the cracking furnace Fuel because of the removal of undesirable aromatics and the smaller amount used for dilution Steam; a reduction in the sulfur content of the feed used for the Craokofen, so that the life of the furnace tubes is extended and the risk of corrosion in the Furnace following devices located in the direction of flow of the reaction products is reduced and, as a result, the distance of sulfur in the furnishing system following the furnace is simplified.

The invention is explained below with reference to the drawing; it mean:

Fig. 1 is a flow diagram;

Fig. 2 is a schematic representation of the end portion of a thermal Cracking furnace and a heat recovery device following this furnace and

Fig. 3 is a schematic representation of a side view of the Fig. 2.

For the method of the invention are in the field of gas oil boiling petroleum distillates containing aromatic compounds used. These can be light and heavy gas oils, vacuum gas oils, light and heavy catalytic recycled crack oils and the like.

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Hydrocarbon distillates containing 15-60 percent by weight of aromatics can be used in the range from 149-593 ° C. Kohlenwasserstoffdestaillate in the range of 177 - 510 ⁰ C and boiling 20 - 50 wt .- # contain aromatics are preferred.

The term gas oils is understood to mean directly distilled off and / or treated petroleum distillates. The gas oils are generally referred to as light, heavy, and vacuum gas oils. Typical gas oils are shown in Table 1 below listed.

Table 1

Light gas
oil before
moreover
area Heavy
oil Gas- Vacuum gas oil before
moreover
area greater
area 177-
343
0.80-
0.88 greater
area prefer-
ter
area greater
area 343-
510
0.85-
0.92 c °
Boil
area
Speci
fish
weight 166-
343
0.80-
0.88 20-40 288-
399
0.82-
0.93 316-
399
0.83-
0.93 343-
593
0.85-
0.95 20-50 salary
to Aro
mate in
Gew.-Ji 15-45 0.01-
2.0 15-60 20-50 15-70 0.05-
2.0 Content of 0.01
S in Ge 2.0
weight % 0.05-
4.0 0.05-
2.0 0.05-
5.0

For the purposes of the invention, light and heavy cycle catalytic cracking oils produced by catalytic cracking processes are particularly suitable in the petroleum industry. With such there is a tendency that the aromatic content of the distillate is increased. The circulation supplies therefore contain one relatively larger amount of aromatic compounds than immediately distillates. Typical catalytic Recycle oils are described in Table 2 below.

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a Table 2 Preferred
Ready 1 922665 Preferred
area Light kmtalyti-
sones circulatory oil
(LCCO) 204-
343 316-
399 * Groler
Ready 0.85-
0.92 Heavy catalyti
circuit oil
(HCCO) 0.89-
0.96 204-
343 20-60 Greater
area 25-50 Boiling range ⁰ C 0.85-
0.92 0.03-
2.0 232-
454 0.05-
2.0 Specific
weight 20-60 0.87-
0.96 Aro content
mates in wt 0.03-
4.0 25-70 Content at 3 in
Oew. -% 0.05-
5.0

The petroleum distillates given in Tables 1 and 2 form a complex mixture of hydrocarbon compounds. Certain types of these compounds include paraffins, cyoloparaffins, polyoyoloparaffins, benzocyoloparaffins, benzopolycyoloparaffins, and both mononuclear and polynuclear aromatics. Sulfur can be present in considerable amounts, predominantly in the form of heterocyclic compounds such as the benzothiophenes.

The aromatic compounds contained in the distillates include polycyolisohe compounds that are completely aromatic are such as naphthalene, anthracene, phenanthrene and the like; alkylated polyoxyethylene aromatics such as methylnaphthalenes and the like; as well as polyoyolisohe compounds that are partly aromatic and partly naphthenic, such as indane, tetralin and Aoenathphenyi Fluoran and its alkylated compounds. Such Distillates can also contain alkylbenzenes. The aromatic compounds boil in the whole boiling range of the distillates.

The amount of aromatic compounds present in the respective petroleum distillate and their type and the amounts of the individual aromatic compounds depends on the boiling range of the Distillates, the previous work-up, e.g. hydrogenation and / or catalytic cracking, and the source of the crude oil from which the distillate was obtained, «b ·.

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The Big amount of separated out in the Craok Coils coke and the clogging of the heat exchanger by asm Reaktionsgemisoh occur "when boiling in the Bereloh of OasSls distillates oraokt, Sm Vergleloh to the quantities" welohe leg Craoken lower boiling Besohiokungen occur "is hauptslohlioh attributable to the aromatic compounds contained in the distillates.

The aromatic compounds, especially the polynuclear compounds, when exposed to high temperatures in the cracking ovens, are the main cause of coke separation in the coils of the cracking oven and the contamination of the heat exchangers, i.e. reaction gases.

Although the polynuclear compounds are relatively stable at the cracking temperatures used, a small part will be the compounds cracked with the formation of hydrogen, high-boiling tars and coke. The aromatic compounds with the exception the alkylbenzenes, as described below, do not contribute significantly to the production of olefins.

The selective removal of the aromatic compounds in the feed according to the process of the present invention has three main beneficial results. First will the main source of coke separation and pollution is largely eliminated. The second benefit is the reduction in furnace size required to obtain an equivalent amount of olefins from the same distillate. The third benefit lies in reducing the total amount of steam required for dilution, resulting in the processing of a smaller amount Hydrocarbon and duroh a considerable reduction in steam in the steam-to-hydrocarbon ratio that is achieved for the processing of the treated hydrocarbon tank is necessary. Require untreated loads not only require a greater amount of steam for dilution but also require a higher steam to hydrogen ratio for the hydrocarbon to be processed · Even if the higher Steam to hydrocarbon ratios are applied «leads 3t 27/9 · -10-

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this is not »as stated above, to the desirable length Operating times with the untreated charges of distillate.

Depending on the source of the crude oil, the petroleum distillates can contain up to 5% by weight of sulfur as sulfur, for example about 0.01-5.0 % . Based on the weight of the feed, particular distillate feeds contain approximately 0.5-4.0 # of sulfur as sulfur. A considerable amount of sulfur is in the form of aromatic compounds, such as benzothiophenes. The removal of the aromatic constituents results in the removal of a considerable amount of the sulfur, for example an amount of 40-80 $ of the sulfur present. The removal of the sulfur results in a significant reduction in corrosion in the equipment following the cracking furnace, enables the use of less expensive / highly corrosion-resistant metals, and also reduces the cost of separating the sulfur from the reaction products.

Considering the petroleum distillates used for the process of the invention treated, the greater part of the aromatics is removed from the distillates, e.g. the polycyclic aromatics, alkylated polyoyelic aromatics and the partly aromatic, partly naphthenic pdy cyclic compounds. Particularly beneficial it is the polyoyelic and the alkylated polycyclic Remove aromatics.

The paraffinic hydrocarbons and naphthenes of petroleum distillate, which do not have an aromatic group are retained in the treated charge intended for the craok oven. The alkylbenzenes may or may not be substantially retained in the raffinate, depending on the method of separation be contained in the extract.

The separation of the aromatic compounds from the in the Distillates boiling in the area of gas oil can be carried out according to the known methods customary in petroleum refining. The separation can be carried out by solvent extraction to remove the aromatics from the distillate oil phase Transferring solvent extract phase or by means of adsorption

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through silica gel or molecular sieve adsorbents. They are different Solvent extraction processes and adsorption processes are known which, as described in detail below, can be used in accordance with the present invention. The choice of a particular procedure depends on the particular one too treating distillate, the amount and type of aromatic compounds present, on the selectivity of the desired Separation and the costs of the respective procedure chosen for a particular separation.

The separation is carried out in order to remove the greater part of the aromatic compounds which contribute little to the production of the olefins and which are the main cause of the formation of coke and high boiling tars which increase both coke separation and pollution. The feed about contains 15 - 70 wt -.% Aromatic compounds, and depending on the crude oil from which the distillate was collected and the processes to which the distillate 1st been subjected. The distillate feeds for which the process of the present invention has particular advantages are those containing about 20-60 # aromatics. Depending on the particular distillate being worked up as a feed, 50-98 weight percent of the aromatic compounds present can be removed while less than 2-20 weight percent of the non-aromatic compounds are lost. A suitable separation process can remove around 75-90% of the aromatic constituents, but only 5-10% of the non-aromatic compounds.

The particular amount of aromatic or non-aromatic compounds removed depends, as set out above, on the particular one to be treated Petroleum distillate, the dissolution and separation process and the separation conditions.

The raffinate has a considerably higher ratio of paraffinic and naphthenic hydrocarbons to aromatic hydrocarbons as compared to the untreated distillate to * The alkylbenzenes «Lt. more than one carbon atom having side chains retained in the raffinate. The extract contains aromatics and practically all of it

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the heavy aromatics and the extract is preferably free from

the paraffinic and naphthenic compounds of the distillate.

Various solvent extraction processes are known which can be used for the purposes of the invention. In general, solvents for these processes are e.g. Furfural, sulfur dioxide, phenol and dimethylformamide are used. The solvents are characteristic of the aromatics selectively.

Silica gel and molecular sieve solid absorbents can be used will. The silica gel has a preference for the aromatic components. The sieves also have a preferred one Adsorption of the aromatic constituents.

Furural is used for one of the well-known solvent extraction processes used as a solvent; this process is described in the article "Fufural as a Selective Solvent in Petroleum Refining", L.C. Kemp, Jr., G.B. Hamilton and H.H. Gross, Ind. Eng. Chen., Vol. 40, pp. 220-227 (1948). The furfural method is a countercurrent liquid-liquid extraction process, in which the petroleum distillate is the continuous phase and the furfural solvent is the discontinuous phase. The solvent is introduced into the extraction column at the top and the distillate into the column at the bottom. One of aromatics A rich solvent phase is produced at the bottom of the column and a solvent that is practically free of aromatics and a small amount of dissolved solvent containing raffinate phase is withdrawn from the top of the column. After the extraction is made by distillation from the The greater part of the solvent is recovered from the extract phase and a smaller part of the solvent is recovered from the raffinate. The ratio of solvent to petroleum distillate and the feed and outlet temperatures are controlled so that a maximum yield of raffinate is achieved with maximum selectivity and greatest removal of aromatics from the Distillate is compatible.

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ft

The treated feed, i.e. the raffinate from which virtually all aromatic compounds have been removed, is for the cracking process an improved feed for the production of olefins; this raffinate is comparable to the usual ones used lighter loads.

Another known solvent extraction process is the Redex process, which is described in the article "Redex Process Extracts Aromatics", AL Benham, MA Plummer and KW Robinson, Hydrocarbon Processing , pp. 134-1 ^ 8, VoI 46, no. 9 (Sept. 1967).

Double extraction columns are used for redex interrogation and selectively extracting aromatic compounds from these containing feeds.

An extraction solvent is used in the first column for the process and a displacement liquid is used for the second column. Suitable extraction solvents are furfural * Furfuryl alcohol-water mixtures, aqueous dimethylformamide and aqueous tetrahydrofurfuryl alcohol. Suitable displacement fluids are naphtha-xyl oil mixtures. Choosing a particular one The solvent system or displacement liquid as well as the extraction conditions depend on the particular feed and the degree of separation desired.

In the first column the solvent is fed in countercurrent to the hydrocarbon feed and from this the aromatic feed Selectively extracted compounds. The aromatic extraction phase contains practically all aromatics and the whole Solvent except for a minor amount dissolved in the non-aromatic raffinate. The extraction phase is then given to the second column in which it is countercurrent is performed with the displacement liquid. The displacer liquid removes the extracted aromatics from the solvent. The separated solvent is recycled to the first extraction column and here again used for the selective extraction of aromatic compounds. The displacer liquid containing the aromatic compounds

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speed is withdrawn and distilled to the displacer recover which is recycled back into the process. The raffinate is also distilled to produce the to remove residual solvents, which is also recycled back into the process. The ones for the operation the amounts of solvent used in the column compared to the feed and displacement liquids in relation to the aromatic extraction phase can vary within a wide range. The extraction temperatures can also fluctuate within a wide range. The respective working conditions depend on the particular distillate fed and the desired degree of separation of the aromatic compounds from the non-aromatic compounds.

A well-known process that is used for the selective removal of aromatic Compounds of non-aromatic compounds using solid adsorbents is the Unisorb process. After this Process are aromatic compounds from the liquid phase by adsorption in a fixed bed of the adsorbent removed. The process can be operated so that certain hydrocarbons from each other and / or all aromatic compounds can be separated from the non-aromatic »Because of the selectivity that the Unisorb process can bring about, it serves to selectively extract certain types of aromatic compounds while other types of aromatic Connections are rejected or also accepted. The separation or extraction conditions are set in order to Use a particular petroleum distillate as a feed to achieve the desired degree of separation.

The term raffinate refers to the portion of the treated distillate after the aromatic has been removed Connections lags. The term raffinate also includes the treated feed. The treated Feed is mixed with steam for dilution and is fed to a cra- * kiln to convert the feed into olefins and other products convict.

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The selective removal of the aromatic compounds according to the invention allows the use of conventional cracking ovens and Process at the same time as other known facilities and process steps in the part of the plant following the cracking ovens, taking into account coking and pollution comes to periods of time comparable to those when working with lighter loads, ovens and working conditions, which are similar or practically identical to those used for cracking hydrocarbon distillates in the naphtha range boiling can be used.

The usual olefin-producing / cracking distillates can be used ovens can be used. This includes the entire area, starting with of low stress, relatively long residence time and relatively low cracking temperatures high stress, short residence time and high cracking temperatures. The method of the invention improves effectiveness of all ovens when used for cracking petroleum distillates distilling in the area of the gas oil.

Vorw The ovens usually used have an insulation convection zone and a cracking zone. This convection zone and the cracking zone contain lines for heating the feed. The cracking zone has suitable burners which bring the surface of the pipes to high temperatures with an average heat flow of 5,000 - 55,000 BTU / hr. / Sq.ft. and preferably at 10,000-25,000 BTU / hr.sq.ft. This results in a maximum temperature of the metal pipes of about j60 - about 1066 ⁰ C.

The treated feed, ie the raffinate as it comes from the separation stage, is in the liquid phase and, depending on the type of separation process, can have a temperature of 21.1-95 ° C. The treated feed, however, has generally a temperature from 15.6 to 37.8 ⁰ C. before Craekung the treated feed of 15.6 - heated to a temperature WJ, 8 ⁰ C at which a substantial cracking takes place, ie to about 371 - 649 ⁰ C.

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Depending on the type of charge to be cracked, it can be completely preheated in the oven convection zone or outside of the Oven can only be partially preheated, with further heating taking place in the oven convection zone or it can be completely preheated to about J571 - 649 ° C outside the oven and immediately fed to the cracking zone of the furnace. The preheating that takes place outside the furnace can be carried out in a suitable Preheater take place and for this purpose steam of high temperature or another heating medium are used, it can be preheating but also take place in a suitable preheating furnace. The dilution steam is applied to the feed during preheating fed to one or more locations. The steam can therefore enter the oven convection zone or during the outside of the oven Preheating of the feed can be added.

Lower boiling pretreated loads can be preheated and evaporated in the convection zone. In an intermediate range boiling and higher boiling pretreated charges can be ^{preheated outside the furnace from about 15 * 6 - 57.8 0} C to a temperature of about 260 - 538 ⁰ C and steam can be added before the introduction of the charge into the convection zone of the furnace. The feed preheated in this way can be further preheated in the convection zone to a temperature of 371-649 ° C or optionally fed directly to the cracking zone of the furnace.

The pretreated charge can be steamed in a proportion from steam to feed from about 0.1-2.0, preferably from 0.5-1.5 and particularly preferably from 0.6-1.0, depending on the type of charge and the particular one Cracking conditions. The dilution vapor requires maintenance a low partial pressure of the hydrocarbons in the reaction zone and can also result in complete evaporation of the feed to lead. The preheated treated feed in admixture with the dilution steam in the vapor phase becomes the cracking zone fed into the furnace

The hydrocarbon partial pressure can be at the outlet of the cracking coil 0.42-1.41 kg / cm a and preferably 0.49-0.98 kg / cm a 27/9 -17-

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traded hydrocarbon distillate feeds in light Olefins with a maximum selectivity and highest yield under possible industrial operating conditions instead.

The hydrocarbon feed may have a temperature of about 371-649 ° C at the entrance to the cracking zone of the furnace. The feed is in the Crackungszone to a temperature of 704 - 927 ⁰ C at the heated Ausgaag the reaction zone. Preferably, the inlet temperatures are 56Ö - 621 C and the outlet temperatures are 816 - 899 ⁰ C.

The residence time of the feed in the reaction zone of the furnace can be 0.1-2.0 seconds, preferably 0.15-1 * 5 seconds and in particular 0.2-0.7 seconds.

At the high temperatures used, the cracking reactions are very rapid. In order to reduce the formation of undesirable by-products, to prevent degradation of products and the fouling of the lines lying in the direction of flow of the reaction products and one-directions to decrease, it is desirable that from the cracking zone at a temperature of 704 - flowing 927 ⁰ C. To rapidly cool gases to a temperature at which cracking reactions practically come to a standstill. This can be done by rapid cooling in a suitable heat exchanger around 37 * 8-316 ⁰ C, ie from about 704-927 ° C to about 538-770 ⁰ C. The cooling is done after the gases have left the cracking zone of the furnace, carried out very quickly by suitable coolants, e.g. in a quenching steam boiler, in order to recover heat. The quenching boilers can be used to recover heat in the form of high pressure steam. The hot gases are passed through a pipe or pipes of the quench boiler. The quenching steam boiler can have individual tubes which are surrounded by a suitable cooling jacket, or multi-tube coolers with cooling jackets or conventional multi-tube housings and tube exchangers.

The method of the present invention provides for the first time the practical application of indirect heat exchangers to heat

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recover from the gases emitted at high temperatures, to generate high pressure steam when petroleum distillate fractions, that boil in the area of the oas oil are cracked.

An embodiment of the invention for which the above device is used is described below with reference to Figures 1, 2 and 3 of the drawing.

According to FIG. 1 of the drawing, a gas oil distillate boiling in the range of about 260 316 ° C. is fed to an aromatic solvent extraction device in which furfural is used as the solvent. The aromatic compounds present in the distillate are about 20-25 percent by weight of the feed and include alkylbenzenes, indanes, tetralins, naphthalenes, alkylnaphthalenes, acenaphthenes and tricyclic aromatics. The furfural extraction may be used for the 70 volume ^ at an extraction temperature of the feed from 26.7 to 71 ⁰ C for the raffinate of the extraction column and distillate and about 23.9 to 43 ° C for the extract or the distillation residue of the extraction column be. The yield of raffinate after removal of a small amount of dissolved solvent can be 70-85 % based on the gas oil processed. The refined oil contains virtually all of the paraffins and naphthenes present in the feed and less than $ 5-25 of the aromatics originally present in the feed. The aromatic extraction phase contains about 75-95 $ of the aromatics that were in the feed and virtually all of the solvent. The treated feed is described in the flow diagram of Figure 1 with treated gas oil

The solvent is removed from the aromatic extraction phase and recycled. The aromatic extract can be treated further to separate certain aromatic compounds. The treated feed goes to the cracking furnace led, cracked at high temperature to obtain olefins, quickly cooled in an indirect heat exchanger and finally by direct contact with liquid hydrocarbons chilled "

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In the primary fractionation and heat recovery system

the extracted oil and cracked fuel oil fractions are separated from the low boiling point material. The material lighter than the fuel oil is guided to the compression and fraction system in which the lighter products offgasfraktion in a burn, the H _2, CH ^, C ₂ ^H 6 ^{and C} 3 ^H 8 ^entnSlt * ethylene, propylene , a C ^ stream and C ₅ stream can be decomposed to a 204 ° C stream. * '. *

Cracking and heat recovery are discussed below in individually described with reference to Figures 2 and 3 of the drawing.

A continuous stream of a treated feed containing about 70-85% by weight of the original petroleum distillate and boiling in the same range as the original distillate, that is, at about 260-316 ° C and substantially free of aromatic compounds with the exception of alkylbenzenes , is fed through line 1 and pump 2 and line 3 and out valve 4 to the heat exchanger 5 in which it is preheated to about 316 ⁰ C. To about 538-649 ⁰ C superheated steam vapor is introduced to hydrogen of about 0.5 0.8 and thereby vaporizes the feed and further heated to about 371 ⁰ C over the valve 7 by line 6 in a ratio. The mixture of steam and feed is passed through a valve 9 and line 8 into the preheating coils 10 of the furnace 11 and is further heated here to about 482-593 ° C. by convection. The preheated charge is passed through connecting lines 15 to the pressure zone 14.

When lighter loads are cracked, the whole takes place Preheating takes place in the preheating convection zone and steam is introduced through line 12 via valve I3.

The furnace 11 has refractories arranged within a housing 17 Walls 16 on. The burners 18, to which fuel is supplied through the distributor line 19/20, are located in the furnace walls. The mixture of steam and feed

St 27/9 -20-

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is fed into the cracking coils 21 and from about 482 - 593 ° C _r on a Schlangenauslaßtemperatur of 816 - 899 ° C heated; Within this temperature range, the cracking takes place in a dwell tent in the graying zone of the furnace for about 0.2 - 0.4 seconds. The hydrogen potential pressure at the outlet of the orifice change can be 0 * 63 - 1 * 12 kg / cm a. The lengths of cracks 21 are held by the holding devices 22. The hot combustion gases from the burner 18 stz * 8m @ n from the drainage zone 14 through the oil convection zone 23, in which the hot gases transfer heat to the pipes 10 by convection. The oven is supported by legs 24 and supports 25. The furnace is covered by the roof 26 * the hot combustion gas sts # n @ n through the chimney 27.

The hot gases pass from the furnace dureh © Ir © line 28 to a temperature of about 816 -. 899 ⁰ C in ias cooling tube 3O ₅ which has a jacket 31 »swieefeen through the annulus tube 30 and jacket 31 flows Hoohdruckkesselwassor that as coolant for dieVieifien Gase serves "The gases are quickly cooled in the bore 30 to a temperature of about 482-649 ° C." non-evaporated water is returned to the steam drum 32 through line 34. Steam at high pressure is withdrawn from this drum through line 35. Steam can be used for high-temperature boilers and, or even after overheating, to drive turbines. Through line 36 the steam drum 32 is supplied with exhausted water. The cooled gases leave the heat exchanger through line 37 and are further cooled in a suitable manner * for example by circulating water, then, as shown in FIG. 1, devices for a primary fraction and Wimegetfinnung ^ "are conducted to aezuaoheiden georaoctes fuel oil. The oases are then divided into a known compression and fractionation device, without separating out certain constituents, such as ethylene and propylene.

The invention is further illustrated in the following examples

909847/1213

example 1

This example comparatively illustrates the furnace capacity requirements for the production of light olefins by thermal cracking of (a) a typical naphtha distillate, (b) a sweet oil that has been treated to remove the aromatics, without (e) the same Qas oil that has been treated to remove the aromatics.

The cracking conditions for each of these accelerations are practically the same as the * which is the ¥ © rsfeehsnden BssshF ©! This is indicated in the exercise, namely about 0 _s 25 seconds® dwell string and an output temperature of 899 ° S ₉ Bi © results are in Table 3 below, depending on the treated gas oil, the aromatics are exfei ³ allied _s - #, based on the original charge.

Bsaehiokung

Qz--

weight

No-: τφι

0.714

Ο, 87β

Treated-

GaslJl

0.855

(£} 37.8 -
174 204 «
343 204 *
343 Ethylenauabeut®
(%) based on the
feed 30th 20th 26.4 Feeding to
Oven in kilos each
454 kg of ethylene 1,500 kg 2,270 leg 1,700 kg Ratio of steam
to hydrocarbon 0.5 1.0 0.7 Daapf amount in kilos 748 kg 2 27O kg 1,188 kg Oesantbesohiokung
of the oven in kilos 2 248 kg 4 540 kg 2,8Θ8 kg

From the table it can be seen that in ¥ ®rgl3ii0h to dl «double the furnace capacity for the ianbehaMelfeo CS- ^ sillich, while only about 1.3 faoh® furnace capacity for the treated oaa oil is required.

909847/1213

It was also found that, surprisingly, the removal the aromatic constituents of petroleum distillates lead to a considerable reduction in coke deposition and pollution leads without a decrease in the yield of olefins occurring based on the original charge.

Example 2

A boiling point in the range of 235 - 346 ° G and about 27.35 wt. West Texas gas oil containing aromatics was used for this trial used. The gas oil was as shown in Table 4 below Properties.

Table 4

Specific gravity ASTM distillation ⁰ F IBP initial boiling point

10%
PBP end boiling point

0.857 ⁰ C ⁰ p 236 457 288 549 293 561 504 579 312 594 328 622 346 655.

Analysis: ^C n ^H 2n + 2 19.01 39.31 Paraffins ^C n ^H 2n 10.08 Cycloparaffins ^C n ^H 2n-2 4.25 Dicycloparaffins ^¥ n ^H 2n-4 Tricycloparaffins 33.34 Total amount of cyclo-
paraffine 8.22 72.65 Total amount saturated
te! connections ° n ^H 2n-6 3.93 Alkylbenzenes ° 2 ^H 2n-8 Benzocycloparaffins

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Benzodiolycoparaffins ^C n ^H 2n-10 3.10 Naphthalenes ° n ^H 2n-12 7.86 Acenaphthenes ^C n ^H 2n- ¹⁴ 2.05 Dlbenzooycloparaffins ^C n ^H 2n- ¹⁶ 1.58 Tricyclic aromati cal connections ^C n ^H 2n-i8 0.61

Total aromatics 27.35

100.00

distillate
This gas oil was fed to an aromatic extraction plant and furfural was used as the solvent.The amount of furfural used in the extraction column was 72 % by volume of the feed at an extraction temperature of 62 ° C for the raffinate or distillate of the extraction column and of about 37.8 ° C for the extract or de-lambion residue. The raffinate contained practically all paraffins and cycloparaffins of the gas oil * The extract contained about .71 wt .- # of the aromatics originally contained in the gas oil. The following table 5 shows the material ratio.

Tabel Yy Specific
weight Weight #
Gas oil cc / 1OOcc
Gas oil 0.857
0.940
0.839 100.0
19.8
80.2 Gas oil distillate
extract
Raffinate 100.00
18.0
82.0

The raffinate was treated in the cracking furnace under the working conditions specified above with regard to residence time, temperature and hydrocarbon partial pressure and a high yield of olefins was obtained. For comparison, unextracted gas oil was also cracked under the same conditions except for the steam / hydrocarbon ratio. -.

The following working conditions were observed for pyrolysis and cracking.

-24-909847 / 1213

Steam was mixed with the hydrocarbon feed at a steam to hydrocarbon weight ratio of 0.6 for the run with the raffinate and 1.0 for the run with the unextracted gas oil. Each mixture was heated in the pre-heating convection zone to about 593 ° C and then heated in the cracking zone of the furnace from this temperature to about 885 ⁰ C at the outlet of the cracking coil. Each feed was cracked with a residence time of about 0.27 seconds. The gases leaving the cracking furnace were cooled in the heat exchangers, especially in Abschreok steam kettles, from about 885 ° to about 649 ° C; at this temperature the cracking reaction is practically stopped.

The partially cooled gas mixture was then further cooled by direct contact with circulating quench oil and then fractionated to obtain the various products.

In Table 6 are the amounts of the various obtained by cracking the raffinate and the untreated gas oil Products listed.

Table 6

Pyrolysis of gas oil pyrolysis of loading

_____________ acted! Qasöl

Yield in kg per yield in kg per 45.4 kfc Qaeöl 45.4 kg raffinate

Ethylene 21.8 27.2

H ₂ to 204 ° C

(fflwith the exception of ethylene) 56 * 4 65.3

204 ⁰ G +, fuel oil 21.8 7.5

It can be seen from Table 6 that the treated feed yields significantly more ethylene per raw georackter feed as well as lighter products and considerably less fuel oil.

Further advantages of the invention emerge from the following table 7, which shows the results of comparative experiments.

-25-9 (13847/1213

Example with pretreated and non-pretreated oil shows.

Tabel

Loading for the ovens

454 kg of ethylene were used each time or receive:

Feeding of gas oil extract

Raffinate

Charging of hydrocarbons for the furnaces

Dilution steam total charge for the ovens

Steam to hydrocarbon weight ratio

Cracked fuel oil in furnace effluent, wt % hydrocarbon

Required relative number of ovens of a given size

Relative amount of steam required for dilution

Relative amount for the cracking ovens required fuel

Relative length of operation of the furnace before decoking is required

Relative length of the service life of an indirect heat exchanger prior to any required cleaning

Untreated
Gas oil (without
Extraction) kg Treated
(extract
tes) gas oil kg 2 O83 2 O83 kg - 412 kg - " kg 1 672 kg 2 O83 kg 1 672 kg 2 O83 kg 1 005 kg 4 16b 2,675 1.0 0.6 21.8 7.5 1.0 0.64 1.0 0.48 1.0 0.73

1.0 1.0

2.25

2.25

Practical for the comparison tests for the cr ack stress the same for the untreated gas oil and the treated gas oil and the ethylene yield based on equivalent amounts Hydrocarbon distillate in the feed was the same as

-26V

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regardless of whether the aromatics were removed or not. In other words, of the hydrocarbons capable of conversion into ethylene, the same amount was converted into ethylene.

In some cases, however, the level of the petroleum distillate charge of aromatics in such a way that it may be necessary to crack the untreated distillate », cracking to be carried out at a significantly lower load than is appropriate for cracking the treated charge, in order to achieve a desirable long service life in which a deinking is required. Allowed in such circumstances the extraction of the aromatics means that the plant is subject to greater stress and the achievement of a higher yield of ethylene per unit of quantity on distillate feed with the same or longer operating times. In other words, an aromatic extraction is possible stronger stresses than is appropriate without extraction and thus enables higher yields of ethylene from the Distillate feed.

The above statements are intended to illustrate the invention and the advantages associated with it.

Claims

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Claims (5)

Dr. Ing. E. BERKENFELD · D ip I.-1 ng. H. B ERKEN FE LD, patent attorneys, Cologne Attachment file number on the submission of May 5, 1909 Sch / Name d. Note Stone & Webster Engineering Corporation Claims Ί. / Process for converting hydrocarbons into ole-. ine, characterized by the following process steps s (A) from a petroleum distillate W boiling in the region of the gas oil, aromatic compounds are removed in a known manner; (b) The aromatic hydrocarbon-depleted distillate is diluted and mixed with steam (c) the mixture is cracked, the cracked product is rapidly cooled and the olefinic hydrocarbons are separated. 2. The method according to claim 1, characterized in that . (a), the petroleum distillate 15-70 wt -% contains aromatic compounds; . (b) from the distillate 50-9 $ wt -% of the aromatic compounds are removed; and (c) the distillate depleted in aromatic hydrocarbons mixed with steam in a steam to hydrocarbon ratio of 0.1-2.0. 3. The method according to claim 1, characterized in that · .-; ..... the petroleum distillate contains 20 - 50 wt .- ^ aromatics. 4. The method according to claim 1, characterized in that the hydrocarbon at the outlet of the cracking zone has a partial pressure of 0.42-1.41 kg / cm ² a. 5. The method according to claim 1, characterized in that the cracked product is immediately quenched by a liquid, will. St 27/9 -28- 909847/1213 6. The method according to claim 1, characterized in that the cracked product is cooled by indirect heat exchange of the cracked product with a liquid coolant and high-pressure steam is produced" 7. The method according to claim 1, characterized in that (a), the petroleum distillate 15-60 wt -.% aromatic Verbindun-. gen contains; . (b) from the distillate 50 to 98 wt -% of the aromatic compounds are removed; (c) the distillate depleted in aromatic hydrocarbons with steam in a steam to feed ratio of 0.1-2, ο is mixed; and (d) in the cracking zone to an exit temperature of 704-927 ° C is heated; (e) the hydrocarbons dwell in the brackish zone for 0.10-2.0 seconds and (f) the hydrocarbon at the outlet of the cracking zone has a partial pressure of 0.42-1.41 kg / cm ² a. 8. Process for converting hydrocarbons into light olefins, characterized by the following process steps: .. (a) of in the range of 149 - 593 ° C boiling and 15 - 70 weight - 98 weight - - $-containing aromatic compounds petroleum distillate in a known manner be 50% aromatics selectively removed; (b) the distillate, which is substantially depleted in aromatic compounds, is steamed in a ratio of steam to hydrogen from 0.1 - 2.0 mixed; (ο) the mixture is georaokt, wherein the cracking product with the cracking zone temperature of 704 - 927 leaves ⁰ C; (d) the hydrocarbons linger in the crack zone 0.1 - 2.0 Seconds; (e) the hydrocarbon has one at the exit of the cracking zone Partialdructures of 0.4a - 1.41 kg / cm nj and (f) the craoic product is cooled quickly and the olefinic Separated hydrocarbons. m Z7 / 9 -29- 9 · The method according to claim 8, characterized in that the cracked product is rapidly cooled by indirect heat exchange with a liquid coolant and high-pressure steam is generated. 10. The method according to claim 8, characterized in that the DestillatO, 1 - 5.0 wt -.% Sulfur as sulfur and by the removal of the aromatic compounds, the sulfur content of the distillate feedstock by 40 - is lowered% - 80 wt.. 11. The method according to claim 8, characterized by a boiling 343 ° C and 20 - - in the range of 177 40 wt -.% of aromatic compounds containing petroleum distillate. 12. The method according to claim 8, characterized by a boiling point in the range of about 316-399C Petroleum distillate containing aromatics. Range of about 316 - 399 ° C boiling and about 15 - 60 wt. 1 ^ · The method of claim 8, characterized by a in the range of about 343 - 593 ° C boiling and about 15 - 70 wt -.% Aromatics-containing petroleum distillate. 14. The method according to claim 8, characterized by a Petroleum distillate, which is in the range of about 204 - 343 ° C boiling and containing about 20-60 wt .- ^ aromatic compounds has light, catalytic cycle oil. 15. The method according to claim 8, characterized by a Petroleum distillate, which has a heavy, catalytic cycle oil boiling in the range of about 232 - 454 ° C and containing about 15 - 70% by weight of aromatic compounds, 16. Process for converting hydrocarbons into light olefins, characterized by the following process step * te t ., (a) from a range from about 149-599 ⁰ C boiling and about 20 - 50 percent - of the matic compounds 90 wt .- # removed selectively - containing petroleum% aromatic compounds "are distillate in a known manner about 75 st 27/9 909 047/1213 (b) The aromatic hydrocarbon depleted distillate is steamed with steam in a steam to hydrocarbon ratio from about 0.6 - 1.0 mixed; (c) the mixture is cracked with the cracked product entering the cracking zone leaves at a temperature of about 816 - 899 ° C; (d) the hydrocarbons reside in the cracking zone for about 0.20-0.70 Seconds; (e) the hydrocarbon is at partial pressure at the outlet of the cracking zone from about 0.9-0.98 kg / cm a; and (f) the cracked product is rapidly cooled and the olefinic Separated hydrocarbons. 17 · Process for converting hydrocarbons into ethylene, characterized by the following process steps separating% of the aromatic compounds (a) in the range of about 204 - J> ^ ° C boiling and about 25 50 wt, - #-containing aromatic compounds petroleum distillate is selectively extracted by 70 - - 90 percent;. (b) the distillate depleted in hydrocarbons is steamed into a steam to hydrocarbon ratio of about 0.6-0.7 mixed; (c) the mixture is cracked and has at the outlet of the cracking zone a temperature of about 87I - 899 ° C; Crack (d) the hydrocarbons remain in the reaction zone for about 0.25-0.50 seconds; . (e) the hydrocarbon has a partial pressure of about 0.49-0.98 kg / cm ² a at the outlet of the cracking zone; (f) the cracked product becomes fast through indirect heat exchange cooled to produce high pressure steam; and (g) the ethylene is separated. 18. Process for converting hydrocarbons to olefins by cracking and reducing the dilution of the Hydrocarbons required amount of steam and the implementation the ratio of steam to hydrocarbons required for cracking, characterized by the following process steps i St 27/9 -31-. 909847/1213 (a) A petroleum distillate boiling in the range of 149-593 ° C. and containing 15-70% by weight of aromatic compounds is treated to separate 50-98 % of the aromatic compounds; (b) the hydrocarbon-depleted distillate is diluted with steam in a steam to hydrocarbon ratio of about 0.5 1.5; (c) the mixture is cracked, and at a residence time of about 0.2 - 7.0 seconds heated in the cracking zone at a temperature up to 704 927 ⁰ C at the outlet of the cracking zone; (d) the hydrocarbon is at partial pressure at the outlet of the cracking zone from about 0.42-1.41 kg / cm a; and (e) the mixture flowing out of the cracking zone is rapidly cooled and the olefinic hydrocarbons are separated off. 19. A process for converting hydrocarbons into olefins by cracking and for reducing coke deposition and contamination of the plant required to carry out the process and for achieving longer uninterrupted operation between coking and cleaning of the plant, characterized by the following process steps t (a) one boiling in the range of 149 - 593 ° C and about 15 - 70 Petroleum distillate containing aromatic compounds by weight is heated to separate $ 50-98 of the aromatic compounds; (b) the aromatic hydrocarbon depleted distillate is mixed with steam; (c) the mixture is in a cracking zone at a residence time of about 0.2 - 0.7 seconds heated up to a temperature of 704 927 ⁰ C at the outlet of the cracking zone; where the hydrocarbon has a partial pressure of 0.42-1.41 kg / cm a; (d) the mixture flowing out of the cracking zone is in an indirect Heat exchanger rapidly cooled to develop high pressure steam; and (e) the olefinic hydrocarbons are separated off. St 27/9 -32- 908847/1213