Process and a plant for the separation of a hydrocarbon mixture

The invention relates to a method and a system for separating a

Component mixture according to the preambles of the independent claims.

State of the art

Methods and devices for steam cracking from

Hydrocarbons are known and for example in the article "Ethylene" in

Ullmann's Encyclopedia of Industrial Chemistry, online since April 15, 2007, DOI

10.1002 / 14356007. a10_045.pub2.

By steam cracking, but also using other methods and

Devices, hydrocarbon mixtures are obtained. These must be at least partially separated into the components they contain. This can be done in different types of separation sequences. Corresponding separation sequences include, after prior separation of water, heavy components and acid gases, devices for demethanization, deethanization and

Depropanization (English Demethanizer, Deethanizer, Depropanizer, see

especially Section 5.3.2.2, "Hydrocarbon Fractionation Section" in the mentioned Ullmann article). The order of demethanization, deethanization and

Depropanization can vary.

A method or a system for separating a corresponding gas mixture in which a first fraction (C1 minus fraction) containing predominantly or exclusively methane and hydrogen, a fraction predominantly or exclusively containing hydrocarbons with two carbon atoms (C2 fraction) and a fraction containing predominantly or exclusively hydrocarbons with three or more carbon atoms (C3plus fraction) is illustrated in FIG. 1 and is explained below with reference to this figure. Here a demethanization follows a deethanization, whereby for both

Process steps rectification columns are used. The terms

Demethanization and deethanization are customary in the art, and devices used for demethanization and deethanization are known to the person skilled in the art.

The advantages of this process and this system are simple process management and high energy efficiency. On the other hand, the complexity of the

Deethanization with an additional so-called C3 absorber and the

Complexity of demethanization with intermediate cooler and top condenser, which are arranged above the demethanization column The latter require increased instrumentation and security effort. A method in which such a C3 absorber is used is also known from EP 0 683 146 A1.

No. 5,253,479 A discloses, according to FIG. 2, a method in which a gaseous component mixture is subjected to a first cooling at 36 bar. The first cooling takes place to -30 to -40'C. After the first cooling, a first phase separation takes place in a first container. The gas phase from the first container is subjected to a second cooling to -45 T. Subsequent to this second cooling, a second phase separation takes place in a second container. The liquid phases from the first and the second container are fed into a column which is operated at 30 bar. In a method disclosed in EP 1 215 459 A2, at least comparable pressures are used.

The present invention therefore has the object of specifying improved measures for separating corresponding gas mixtures.

Disclosure of the invention

Against this background, the invention proposes a method and a system for separating a component mixture with the respective features of

independent claims. Preferred configurations are the subject of the dependent claims and the following description.

Before explaining the features and advantages of the present invention, the fundamentals and the terms used are explained.

The present invention is used for the separation of component mixtures, which predominantly or exclusively hydrogen, methane,

Hydrocarbons with two carbon atoms (ethane, ethylene and possibly acetylene, if not already reacted in a previous hydrogenation), and

Contain hydrocarbons with three or more carbon atoms (propane, propylene, possibly methylacetylene and heavier hydrocarbons with in particular four, five, six and more carbon atoms).

In the context of the present invention, corresponding

Component mixtures formed in particular using a steam cracking process. In the steam cracking process, a so-called raw gas or

Fission gas obtained, in addition to the components mentioned, also other

Has components. These, in particular water, acid gases such as carbon dioxide and hydrogen sulfide as well as gasoline and oil-like components, can be separated off upstream of the method proposed according to the invention or a corresponding system. Further process steps can also be performed upstream of the

According to the invention proposed method or a corresponding plant are carried out, in particular a hydrogenation of acetylenes (so-called front-end hydrogenation). The component mixture processed within the scope of the present invention is typically enclosed in a compressed state

Ambient temperature.

In the specialist world, abbreviations are used for fractions that are formed in corresponding processes from the component mixtures mentioned, which indicate the number of carbon atoms of the hydrocarbons contained predominantly or exclusively. A "C1 fraction" is a fraction that predominantly or exclusively contains methane (however, according to convention, it may also contain hydrogen, then also called the "Cl minus fraction"). A "C2 fraction", however, contains predominantly or exclusively ethane, ethylene and / or acetylene. A "C3 fraction" contains predominantly propane, propylene, methylacetylene and / or propadiene. The same applies to a "C4 fraction" and the higher fractions. Several fractions can also be combined in terms of procedures and / or names. For example, a “C2plus fraction” contains predominantly or exclusively hydrocarbons with two or more and a “C2minus fraction” predominantly or exclusively hydrocarbons with one or two carbon atoms and possibly hydrogen.

As used herein, component mixtures can be rich or poor in one or more components, with "rich" for a content of at least 90%, 95%, 99%, 99.5%, 99.9%, 99.99% or 99.999 % and "poor" can mean a content of no more than 10%, 5%, 1%, 0.1%, 0.01% or 0.001% on a molar, weight or volume basis. In the terminology used here, component mixtures can also be enriched or depleted in one or more components, these terms referring to a corresponding content in another component mixture (starting mixture) from which the component mixture was obtained. The component mixture is "enriched" if this is at least 1, 1-fold, 1, 5-fold, 2-fold, 5-fold, 10-fold, 100-fold or 1,000-fold content, "

A component mixture is “derived” from or “formed” from a starting mixture if it has at least some components contained in the starting mixture or obtained from it. A component mixture derived or formed in this sense can be derived from the starting mixture by separating or branching off a partial flow or one or more components, enriching or reducing one or more components, chemical or physical conversion of one or more components, heating, cooling, pressurizing and the like obtained or formed.

The present application uses the terms "pressure level" and "temperature level" to characterize pressures and temperatures, which is intended to express that corresponding pressures and temperatures in a corresponding system do not have to be used in the form of exact pressure or temperature values to realize the inventive concept. However, such pressures and temperatures typically move in certain ranges, for example ± 1%, 5% or 10% around a mean value.

Corresponding pressure levels and temperature levels can be in disjoint areas or in areas that overlap. In particular, pressure levels include, for example, unavoidable or expected pressure losses, for example due to cooling effects. The same applies to

Temperature levels. The pressure levels specified here in bar are absolute pressures.

A “heat exchanger” is used for the indirect transfer of heat between at least two, for example, countercurrent flows to one another, for example a warmer gaseous pressure flow and one or more colder liquid flows. A heat exchanger can be formed from a single or several parallel and / or serially connected heat exchanger sections, for example from one or more plate heat exchanger blocks. A heat exchanger has "passages" which are designed as separate fluid channels with heat exchange surfaces.

In the parlance used here, a "rectification column" is a separation unit which is set up to at least partially dispense a mixture of substances (fluid) provided in gaseous or liquid or in the form of a two-phase mixture with liquid and gaseous components, possibly also in the supercritical state to separate, i.e. to generate pure substances or mixtures of substances from the mixture of substances that are enriched or depleted or rich or poor in the sense explained above with respect to the mixture of substances with regard to at least one component. Rectification columns are well known from the field of separation technology. Typically, rectification columns are designed as cylindrical metal containers with internals, for example sieve trays or ordered and unordered packings, are equipped. A rectification column is distinguished, among other things, by the fact that a liquid fraction separates out in its lower area, also known as the bottom. This liquid fraction, which is referred to here as bottom liquid, is heated in a rectification column by means of a bottom evaporator so that part of the bottom liquid continuously evaporates and rises in gaseous form in the rectification column. A rectification column is also provided with a so-called top condenser, into which at least part of a gas mixture enriching in an upper region of the rectification column or a corresponding pure gas, referred to here as top gas, is fed, partially liquefied to a condensate and as a liquid reflux at the top the A rectification column is distinguished, among other things, by the fact that a liquid fraction separates out in its lower area, also known as the bottom. This liquid fraction, which is referred to here as bottom liquid, is heated in a rectification column by means of a bottom evaporator so that part of the bottom liquid continuously evaporates and rises in gaseous form in the rectification column. A rectification column is also provided with a so-called top condenser, into which at least part of a gas mixture enriching in an upper region of the rectification column or a corresponding pure gas, referred to here as top gas, is fed, partially liquefied to a condensate and as a liquid reflux at the top the A rectification column is distinguished, among other things, by the fact that a liquid fraction separates out in its lower area, also known as the bottom. This liquid fraction, which is referred to here as bottom liquid, is heated in a rectification column by means of a bottom evaporator so that part of the bottom liquid continuously evaporates and rises in gaseous form in the rectification column. A rectification column is also provided with a so-called top condenser, into which at least part of a gas mixture enriching in an upper region of the rectification column or a corresponding pure gas, referred to here as top gas, is fed, partially liquefied to a condensate and as a liquid reflux at the top the also known as sump, separates a liquid fraction. This liquid fraction, which is referred to here as bottom liquid, is heated in a rectification column by means of a bottom evaporator, so that part of the bottom liquid continuously evaporates and rises in gaseous form in the rectification column. A rectification column is also provided with a so-called top condenser, into which at least part of a gas mixture enriching in an upper region of the rectification column or a corresponding pure gas, referred to here as top gas, is fed, partially liquefied to a condensate and as a liquid reflux at the top the also known as sump, separates a liquid fraction. This liquid fraction, which is referred to here as bottom liquid, is heated in a rectification column by means of a bottom evaporator so that part of the bottom liquid continuously evaporates and rises in gaseous form in the rectification column. A rectification column is also provided with a so-called top condenser, into which at least part of a gas mixture enriching in an upper region of the rectification column or a corresponding pure gas, referred to here as top gas, is fed, partially liquefied to a condensate and as a liquid reflux at the top the is heated in a rectification column by means of a bottom evaporator, so that part of the bottom liquid continuously evaporates and rises in gaseous form in the rectification column. A rectification column is also provided with a so-called top condenser, into which at least part of a gas mixture enriching in an upper region of the rectification column or a corresponding pure gas, referred to here as top gas, is fed, partially liquefied to a condensate and as a liquid reflux at the top the is heated in a rectification column by means of a bottom evaporator, so that part of the bottom liquid continuously evaporates and rises in gaseous form in the rectification column. A rectification column is also provided with a so-called top condenser, into which at least part of a gas mixture enriching in an upper region of the rectification column or a corresponding pure gas, referred to here as top gas, is fed, partially liquefied to a condensate and as a liquid reflux at the top the

Rectification column is abandoned. Some of the condensate contained in the top gas can be used for other purposes.

A “stripping column” differs from a rectification column essentially in the lack of an overhead condenser and the lack of use of a reflux formed from overhead gas for separation. Liquids can, however, be fed into a stripping column at different heights, which deliver a certain return flow or by means of which a run-down in the stripping column

Liquid fraction is provided, which is in exchange with a gas phase. However, a stripping column as used in the context of the present invention is an apparatus operated without its own overhead gas condensate.

For the design and specific design of rectification columns and other separation columns, reference is made to relevant textbooks (see

for example Sattler, K: Thermal separation processes: basics, design, apparatus, 3rd edition 2001, Weinheim; Wiley-VCH).

Advantages of the invention

Overall, the present invention proposes a method for separating a component mixture which contains hydrogen, methane, hydrocarbons with two carbon atoms and hydrocarbons with three or more carbon atoms. The method comprises a deethanization and a demethanization, wherein the demethanization follows the deethanization. In the process, as far as is known, at least 95%, 96%, 97%, 98% or 99% of the hydrocarbons with three or more carbon atoms are separated from at least part of the component mixture or gas mixture in the deethanization and then in the demethanization at least 95%, 96%, 97%, 98% or 99% of the methane and hydrogen are separated from the remainder. To avoid misunderstandings it should be emphasized that here under the "

Deethanizer first or front-end deethanizer method, as is basically known from the prior art.

In the context of the present invention, at least part of the

Component mixture is subjected to a first partial condensation by cooling from a first temperature level to a second temperature level at a first pressure level while obtaining a first gas fraction and a first liquid fraction. The first gas fraction and the first liquid fraction are formed purely condensatively as part of the partial condensation. A “purely condensative” formation is understood in particular to mean that, during the formation of the first gas fraction and the first liquid fraction, there is no return, that is, no absorption liquid to the

Washing out certain components is used. A total amount of the first gas fraction formed in a certain period of time and the first liquid fraction formed in the same period therefore corresponds in the context of the present invention to the amount of the component mixture that is used to form the first

Gas fraction and the first liquid fraction is used. In this point

differs the inventive method from method for

Deethanization according to the state of the art, in which so-called C3 absorbers are used. A first gas fraction and a first liquid fraction are also formed in a C3 absorber, but with the feed of a reflux in order to wash out incompletely condensed hydrocarbons with three carbon atoms from the gas phase.

That of cooling down from the first temperature level to the second

The component mixture subjected to the temperature level at the first pressure level has in particular 32 to 36 mol percent hydrogen, 5 to 8 mol percent methane, up to 57 mol percent hydrocarbons with two carbon atoms and up to 4 mol percent hydrocarbons with three or more carbon atoms. The present

The invention is therefore particularly suitable for gas mixtures that originate from methods for steam cracking of gaseous inserts. A gaseous use comprises predominantly or exclusively ethane or ethane and propane. The first gas fraction formed in the first partial condensation has in particular 43 to 47 mol percent hydrogen, 7 to 9 mol percent methane, 42 to 45 mol percent

Hydrocarbons with two carbon atoms and 0.5 to 0.7 mole percent

Hydrocarbons with three or more carbon atoms. The first liquid fraction formed in the first partial condensation has in particular 1 to 2

Mole percent hydrogen, 2 to 3 mole percent methane, 82 to 85 mole percent

Hydrocarbons with two carbon atoms and 10 to 13 mole percent

Hydrocarbons with three or more carbon atoms. In other words, the first gas fraction still contains appreciable amounts of hydrocarbons with three or more carbon atoms that have to be recovered. This takes place within the scope of the present invention as explained below.

In the context of the present invention, at least part of the first gas fraction is subjected to a second partial condensation by cooling from the second temperature level to a third temperature level at the first pressure level while obtaining a second gas fraction and a second liquid fraction. As part of the second partial condensation, those previously contained in the first gas fraction are

Hydrocarbons with three or more carbon atoms deposited up to any residual content. The second gas fraction formed in the second partial condensation has in particular 59 to 62 mol percent hydrogen, 9 to 11 mol percent methane, 29 to 31 mol percent hydrocarbons with two carbon atoms and 0.6 to 0.9 mol percent hydrocarbons with three or more carbon atoms. The second liquid fraction formed in the second partial condensation has in particular 1.5 to 2 mol percent hydrogen, 3 to 4 mol percent methane, 89 to 92 mol percent

Hydrocarbons with two carbon atoms and 2 to 3 mole percent

Hydrocarbons with three or more carbon atoms. The formation of the second gas fraction and the second liquid fraction also takes place, in particular, purely condensatively, ie without the use of absorbers as explained above.

The measures used in the context of the present invention also include that at least part of the first liquid fraction and at least part of the second liquid fraction while obtaining a third gas fraction and a third

Liquid fraction are subjected to rectification. For this rectification, a rectification column can be used, which is referred to below and in particular also in the description of the figures as a deethanization column. The terms are used synonymously here. In the swamp a corresponding

Rectification column are the hydrocarbons with three and more

Carbon atoms are essentially deposited so that the top gas of the

Rectification column, which is used to form the third gas fraction, is essentially free of such components.

The second gas fraction (after the second partial condensation from the second to the third temperature level), but also the third gas fraction (from the rectification) are formed within the scope of the present invention in such a way that they contain more than 95%, 96%, 97% , 98% or 99% hydrogen, methane and hydrocarbons with two carbon atoms. The third liquid fraction, on the other hand, is formed within the scope of the present invention in such a way that it contains more than 95%, 96%,

Has 97%, 98% or 99% hydrocarbons with three or more carbon atoms.

Two gas fractions are also formed in the course of conventional deethanization steps, which, as also illustrated in connection with FIG. 1, are drawn off here from the top of a C3 absorber and from the top of a deethanization column. The C3 absorber is not required in the context of the present invention, so that a method according to the invention can be carried out with significantly less effort. In the context of the present invention, the C3 absorber is produced by the first partial condensation in combination with the second

Partial condensation of the gas fraction formed in the process is replaced by the second to the third temperature level at the first pressure level, at which the second liquid fraction formed by the second partial condensation (instead of a material flow from a C3 absorber, as illustrated in Figure 1) is passed into the rectification and there is separated to form the third gas fraction and the third liquid fraction. The process according to the invention can be implemented without any significant changes in the process steps following the deethanization, since the heat exchangers, refrigerants, etc. used for the first and second partial condensation are already present in a corresponding process or a corresponding system and can therefore be used further.

According to the invention, the first liquid fraction or its part subjected to rectification and the second liquid fraction or its part subjected to rectification are released from the first pressure level to a second pressure level before rectification and the rectification is carried out at the second pressure level, the first pressure level at 25 to 35 bar and the second

Pressure level is 14 to 17 bar. In the context of the present invention, comparatively low pressures are used compared to the condensation steps in the rectification.

Because of the lower pressures used in the rectification for deethanization in the context of the present invention, the condensation capacity required for condensing overhead gas is much lower than at higher pressures. Therefore, within the scope of the present invention, one can work with a top capacitor attached. No reflux tank outside of the column used for rectification and no pump are required to provide a reflux for the rectification. In addition, at lower pressure, the fouling in the bottom and in the reboiler of the column used are greatly reduced.

In the context of the present invention it is also possible to provide a return for the rectification exclusively using C3 refrigeration.

According to the invention, therefore, an overhead gas formed during rectification is cooled to (only) -25 to -35 TD and partially condensed in the process, with a condensed portion of the overhead gas being used partially or completely as return flow in the rectification and a non-condensed portion of the overhead gas partially or is completely provided as the third gas fraction.

The condensed portion of the top gas is advantageously returned to the rectification column used for the rectification without the use of a reflux pump and / or an external reflux tank, and the

The top condenser is advantageously placed on the column. This means in particular that the reflux in the form of the condensed portion or a correspondingly used portion thereof is passed to the column without the use of lines which are led out of the column.

In the process according to the invention, the first pressure level is in particular 25 to 35 bar abs., Further in particular 28 to 30 bar abs., For example approx. 29 bar abs. In the context of the present invention, the second pressure level can in particular be 12 to 16 bar abs., For example approx. 14 bar abs. lie.

In the method according to the invention, the first temperature level is in particular from 0 to 50 T, further in particular from 10 to 30 TD, for example around 20 TD, that is essentially ambient temperature. In the context of the present invention, the second temperature level can be in particular from -30 to -40 TD, further in particular from -33 to -37 TD, for example approximately -35 TD. A

corresponding cooling to the second temperature level can take place in particular using a suitable C3 (propylene) refrigerant in a corresponding heat exchanger. In the context of the present invention can for

Cooling to the second temperature level can also be used in the process or material flows or component mixtures formed in downstream processes, for example one formed in the process

Component mixture of predominantly or exclusively hydrogen and methane (which is described below as a fraction containing more than 95% hydrogen and methane from a further separation apparatus) and a fraction formed in a subsequent separation step (C2 splitter) which predominantly or exclusively contains ethane.

The third temperature level can within the scope of the present invention

especially with -50 to -60 TD, further especially e with -52 to -56 TD,

for example about -54 TD. Corresponding cooling to the third temperature level can take place in particular using a suitable "high pressure" -C2 (ethylene) refrigerant in a corresponding heat exchanger. A corresponding refrigerant is in particular on one

Pressure level from 8 to 9 bar abs. in front. In the context of the present invention, for cooling to the third temperature level, material flows or streams formed in the process or in subsequent processes can also be used.

Component mixtures are used, for example the component mixture formed in the process of predominantly or exclusively hydrogen and methane and the fraction formed in the subsequent separation step (C2 splitter) which predominantly or exclusively comprises ethane. Furthermore, for cooling to the third temperature level, a separation step (demethanization) formed in the process and then carried out can be used

Component mixture which predominantly or exclusively comprises hydrocarbons with two carbon atoms can be used. The cooling to the third temperature level also takes place in particular in countercurrent to the liquid fraction already mentioned several times and formed in the second partial condensation.

In the context of the present invention, the third gas fraction is in the rectification through the use of the measures according to the invention, in particular at a temperature level of -25 to -35 T, further in particular from -28 to -32 TD,

for example about -30 TD formed. These temperatures are those that are used to condense the top gas of the corresponding column. As mentioned, this can take place in particular in connection with a condensation of top gas with a suitable C3 (propylene) refrigerant. In other words, in the context of the present invention, in particular a rectification column is used for the rectification, which is cooled with an overhead condenser operated with propylene refrigerant. The third liquid fraction is in the context of the present invention in the rectification advantageously on a

Temperature level of 65 to 75 T, further in particular 68 to 72 TD, for example approx. 70 TD, formed. This can be achieved in particular through the use of a bottom evaporator operated, for example, with low-pressure steam.

In the context of the present invention, the second gas fraction and the third gas fraction that are already in the process steps described above in

Substantially freed from hydrocarbons with three or more carbon atoms, fed to a downstream demethanization. In particular, a fraction containing more than 95%, 96%, 97%, 98% or 99% hydrogen and methane and a fraction containing more than 95% of the second gas fraction and the third gas fraction in a further separation apparatus, namely a stripping column %, 96%, 97%, 98% or 99% hydrocarbons with two

Fraction containing carbon atoms is formed. Such a separation also takes place in a particularly advantageous manner within the scope of the present invention, because in particular a separating apparatus is used in which no complex condensation of gas from the separating apparatus described above has to take place. The separation apparatus in the form of a stripping column is thus without

Head capacitor operated. The further separation apparatus is operated at the second pressure level, a specific pressure used can also be slightly, ie up to 1, 2, 3, 4 or 5 bar below the pressure used in the rectification, which is the first and second Liquid fraction are fed.

Before the second gas fraction is fed into the further separating apparatus, there can in particular also be a step-by-step cooling. In one special

Preferred embodiment of the present invention, at least part of the second gas fraction is subjected to further partial condensations by means of a step-by-step cooling via one or more intermediate temperature levels to a fourth temperature level at the first pressure level while obtaining further liquid fractions. The liquid fractions formed in each case are advantageously corresponding to their respective hydrogen, methane and

Hydrocarbons with two carbon atoms at different heights are fed into the separator, i.e. the stripping column.

Advantageously, a portion of the second gas fraction remaining in gaseous form at the fourth temperature level is expanded from the first pressure level to the second pressure level and fed into the further separating apparatus. The feed takes place advantageously above each of the other

Liquid fractions that are obtained in the further partial condensations mentioned above the several intermediate temperatures

The fourth temperature level is within the scope of the present invention

especially at -140 to -150 T, further in particular at -140 to -144 TD, for example at about -142 TD. This Temperaturni level can be achieved in particular by a material flow that is formed from overhead gas of the separator. Advantageously, the fraction containing more than 95%, 96%, 97%, 98% or 99% hydrogen and methane is taken from the further separating apparatus, relieved from the second pressure level to a third pressure level and used for gradual cooling to the fourth temperature level . The intermediate temperature level may, in particular at -70 to - 80 TD, moreover, in particular at -76 to -78 TD, for example, about -77 TD on the one hand and from -95 to -105 TD, moreover, in particular at -96 to -100 0C, on the other hand, be around -98 TD for example. These temperature levels can be set, for example, using "medium pressure" C2 (ethylene) refrigerant at a pressure level of 3 to 4 bar on the one hand and "low pressure" C2 (ethylene) refrigerant on one

On the other hand, achieve a pressure level of 1, 1 to 1, 6 bar. In appropriately used heat exchangers, the fraction from the further separation apparatus, which has been expanded to the third pressure level and previously used for cooling to the fourth temperature level and contains more than 95%, 96%, 97%, 98% or 99% hydrogen and methane, can also be used will.

With the concept described here, the

Hydrocarbons with two carbon atoms, in particular from the cracked gas of an ethylene plant with gaseous inputs such as ethane and ethane / propane, simplify the complicated deethanization and demethanization, in particular the deethanization can be carried out without a C3 absorber with a top condenser attached. The rectification used for deethanization is carried out at a low pressure, the mentioned second pressure level, so that the separation effort is reduced by more than 60%. Consequently, the deethanizer or a corresponding rectification column can be made much smaller. The swamp can with

Washing water or low pressure steam are boiled. This leads to easier operation, less instrumentation, less fouling and lower investment and operating costs. By using the present invention, a simple stripping column can also be used instead of a complicated demethanization column. This also leads to a simpler operation and less instrumentation and safety outlay. There are lower investment costs with constant energy consumption.

In a particularly preferred embodiment of the process according to the invention, the separating apparatus, that is to say the stripping column, has an internal one

Equipped with a heat exchanger, which is cooled with a refrigerant at a temperature level of -90 to -1 10 T. In particular, the "low pressure" C2 (ethylene) refrigerant already explained can be used here. This results in further advantages, in particular that the third gas fraction from the rectification for deethanization has to be cooled to a lower temperature level, namely only to the third temperature level, whereas in the absence of one

corresponding internal heat exchanger, a stronger cooling must take place. Furthermore, it is possible to dispense with subcooling of a condensate formed from the second gas fraction.

The present invention also extends to a plant for separating a component mixture that contains hydrogen, methane, hydrocarbons with two carbon atoms and hydrocarbons with three or more carbon atoms, the plant having means for deethanization and means for demethanization, the means for demethanization downstream the means to

Deethanization are arranged. As is known for deethanization and demethanization, the means for deethanization are set up for initially at least 95%, 96%, 97%, 98% or 99% of the hydrocarbons with three

and to separate more carbon atoms from at least part of the gas mixture and the means for demethanization are set up to then separate at least 95%, 96%, 97%, 98% or 99% of the methane and hydrogen from the remainder. The system has means which are set up to subject at least part of the component mixture to a first partial condensation by cooling from a first temperature level to a second temperature level at a first pressure level while obtaining a first gas fraction and a first liquid fraction, to subject at least part of the first gas fraction to a second partial condensation by cooling from the second temperature level to a third temperature level at the first pressure level while obtaining a second gas fraction and a second liquid fraction, and at least a part of the first liquid fraction and at least part of the second liquid fraction and subjected to rectification to obtain a third gas fraction and a third liquid fraction. According to the invention, means are provided for the second partial condensation which are set up to carry out the second partial condensation in such a way that the second gas fraction has more than 95%, 96%, 97%, 98% or 99% hydrogen, methane and hydrocarbons with two carbon atoms. The rectification is especially designed to

According to the invention, means are provided which are set up for the first liquid fraction or its part subjected to rectification and the second

To relax the liquid fraction or its part subjected to rectification prior to rectification from the first pressure level to a second pressure level. Corresponding means can in particular comprise expansion valves. Furthermore are

according to the invention, means are provided which are designed to carry out the rectification at the second pressure level, the first pressure level being 25 to 35 bar and the second pressure level being 14 to 17 bar. The latter means in particular comprise a column set up for rectification and set up for operation at the pressure mentioned.

Means are also provided, in particular in the form of an overhead condenser attached to the column used for rectification, which are set up to cool an overhead gas formed during rectification to -25 to -35 TD and thereby partially condense it, and a condensed portion of the overhead gas to use partially or completely as reflux in the rectification and to provide a non-condensed portion of the top gas partially or completely as the third gas fraction. These means are designed in particular without external return tanks and pumps, as explained above.

A corresponding system, which is advantageously set up to carry out a method, as previously explained in different configurations, benefits from the advantages mentioned, to which reference is therefore expressly made.

The invention is explained further below with reference to the accompanying drawings, which illustrate embodiments of the invention.

Brief description of the drawings

Figure 1 illustrates a system for separating a component mixture.

FIG. 2 illustrates a system for separating a component mixture according to an embodiment of the invention.

FIG. 3 illustrates a system for separating a component mixture according to an embodiment of the invention.

In the figures, components corresponding to one another are identical

Reference numerals indicated. Corresponding to a repeated explanation

Components are omitted for the sake of clarity. All pressure and temperature data are examples and approximate values ​​that can be in the ranges explained in more detail above.

Detailed description of the drawings

In FIG. 1, a system not according to the invention for separating a component mixture is illustrated in the form of a simplified process flow diagram and designated as a whole with 99.

The component mixture K, for example a cracked gas from a steam cracking process after drying, oil and gasoline removal, acid gas removal, compression and cracked gas hydrogenation, is initially at 20 ° C and 30 bar against a hydrogen and methane fraction H2 / CH4, one from a C2- (not shown) Splitter recirculated ethane fraction C2REC, a condensate C1 from a C3 absorber T1 and a C3 refrigerant C3R cooled in a heat exchanger E1 to -35 ° C and then fed into a lower part of the C3 absorber T1.

The C3 absorber T 1 is designed in two parts and, in addition to the lower part, has an upper part. The two parts are separated from one another by means of a liquid barrier floor. A return R1 is applied to the upper part and the aforementioned condensate C1 is drawn off from the lower part. The condensate C1 is fed into a deethanization column T2 after it has been heated in the heat exchanger E1. A liquid that collects on the liquid barrier tray of the C3 absorber T1 is also fed into the deethanization column T2. A gas stream G1 is drawn off from the upper part of the C3 absorber T1.

A gas stream G2 is withdrawn from the top of the deethanization column T2, cooled in a heat exchanger E7, for example by means of C3 refrigerant, and phase-separated in a container D1. A liquid phase precipitating in the container D1 is conveyed via a pump P1 and in the form of the aforementioned return R1 to the C3 absorber T1 and in the form of a further return R2 to the

Deethanization column T2 returned. A portion that has not condensed in the container D1 is drawn off in the form of a gas flow G3. Sump liquid of the

Deethanization column T2 is partially evaporated in a heat exchanger E8, which is operated, for example, by means of low-pressure steam, and into the

Deethanization column T2 returned. Further sump liquid is drawn off as liquid stream C3 + containing predominantly or exclusively hydrocarbons with three carbon atoms.

The gas streams G1 and G3, which are essentially freed of hydrocarbons with three carbon atoms in this way, are converted in a second heat exchanger E2 against the hydrogen and methane fraction H2 / CH4, the ethane fraction C2REC recirculated from the C2 splitter (not shown), an in the C2 splitter led fraction C2 and high pressure C2 refrigerant HP-C2R cooled. The gas stream G1 is partially condensed in this way and fed into a container D2 for phase separation. A liquid phase which separates out in the container D2 is fed in the form of a liquid stream C2 into a demethanization column T3. A portion that is not condensed in the container D2 is withdrawn as gas stream G4.

The gas stream G4 and the possibly already partially condensed gas stream G3 are cooled in a third heat exchanger E3 against the hydrogen and methane fraction H2 / CH4 and medium-pressure C2 refrigerant MP-C2R. The gas stream G4 is partially condensed in this way and fed into a container D3 for phase separation. A liquid phase which separates out in the container D3 is fed into the demethanization column T3 as liquid flow C3 after it has been combined with the condensed gas stream G3. A portion of the gas flow G4 that is not condensed in the container D3 is withdrawn in the form of a gas flow G5.

The gas flow G5 is cooled in a fourth heat exchanger E4 against low-pressure C2 refrigerant LP-C2R. The gas stream G5 is partially condensed in this way and fed into a container D4 for phase separation. A liquid phase which separates out in the container D4 is fed into the demethanization column T3 as liquid stream C4. A portion of the gas flow G5 that is not condensed in the container D4 is withdrawn as gas flow G6. The gas stream G6 is expanded in an expander Ex1 and fed into the demethanization column T3.

The demethanization column T3 is constructed in several parts and comprises a lower, a middle and an upper section. From the head of the

Demethanization column T3 or its upper section, the hydrogen and methane fraction H2 / CH4 is drawn off, expanded in an expander Ex2 and passed through heat exchangers E5 and E6 for cooling. In the heat exchangers E5 and E6, gas streams G7, G8 are withdrawn from an upper region of the lower and middle section of the demethanization column T3, at least partially condensed and as reflux to the corresponding sections of the

Demethanization column T3 returned. Sump liquid of the

Demethanization column T3 is partially evaporated in a heat exchanger E9, which is operated, for example, by means of high pressure C2 refrigerant, and is returned to the demethanization column T3. More sump liquid is withdrawn as liquid stream C2.

As mentioned, the complexity of the deethanization with the C3 absorber T 1 and the complexity of the demethanization with the intercooler in the form of the heat exchanger E6 and the heat exchangers E5 and E6 arranged above the demethanization column are disadvantageous. The latter require an increased

Instrumentation and security effort.

In FIG. 2, a system for separating a component mixture according to an embodiment of the invention is illustrated in the form of a simplified process flow diagram and denoted overall by 100.

The cooling in the first heat exchanger E1 takes place as explained for the system 99 according to FIG. Downstream of the heat exchanger E1, however, no C3 absorber T1 is provided here, but only a container D1 in which the first

Heat exchanger E1 partially condensed component mixture K is fed. A gas flow from the container D1, also referred to here as G1, therefore possibly still has residual contents of hydrocarbons with three carbon atoms. However, after further cooling, these are separated in the second heat exchanger E2, which is basically identical to that in the second heat exchanger E2 of the system 99 according to FIG. 1, and can be recovered in the liquid flow also designated here by C2. The liquid stream C2 also has primarily hydrocarbons with two and three carbon atoms and also smaller amounts of hydrogen and methane.

The liquid stream C2 is therefore returned through the second heat exchanger E2 and fed to a deethanization column, also referred to here as T2. Top gas from the deethanization column T2 in the system 100 according to FIG. 2 is, in contrast to the deethanization column T2 of the system 99 according to FIG. 1, also withdrawn in the form of the gas stream G2, cooled by means of C3 refrigerant and partially condensed; however, the condensate formed is only fed back to the deethanization column T2 itself and not to a C3 absorber. A non-condensed portion of the gas flow G2 is withdrawn in the form of the material flow G3, which is now essentially free of hydrocarbons with three carbon atoms. The material flow G3 is initially treated essentially like the material flow G3 in the system 99 according to FIG.

The gas flow G4 and the possibly already partially condensed gas flow G3 are also cooled here in a third heat exchanger E3 against the hydrogen and methane fraction H2 / CH4 and medium-pressure C2 refrigerant MP-C2R. The gas stream G4 is also partially condensed here and fed into a container D3 for phase separation. A liquid phase which separates out in the container D3 is drawn off in the form of a liquid flow C3 and a portion of the gas flow G4 which is not condensed in the container D3 is drawn off in the form of a gas flow G5.

The gas flow G5 and the liquid flow C3 are here in a fourth

Heat exchanger E4 against the hydrogen and methane fraction H2 / CH4 and

Low pressure C2 refrigerant LP-C2R cooled or subcooled. The gas stream G5 is partially condensed in this way and fed into a container D4 for phase separation. A liquid phase which separates out in the container D4 is then fed into a stripping column S1 as liquid stream C4, as is the liquid stream C3. A portion of the gas flow G5 that is not condensed in the container D4 is used as

Gas stream G6 withdrawn.

In contrast to the system 99 according to FIG. 1, the gas stream G6 is now cooled in a further heat exchanger E10, which is cooled with the depressurized top gas of the stripping column S1, ie the hydrogen and methane fraction H2 / CH4. The gas stream G6 partially condensed in this way is phase-separated in a further container D5. Only a gas phase remaining here is expanded via an expander, which is also designated here with Ex1, and fed into the stripping column S1. The liquid phase which separates out in the further container D5 is also fed into the stripping column S1 in the form of a liquid stream C5.

The stripping column S1 is designed in one piece and has only one bottom evaporator. The hydrogen and methane fraction H2 / CH4 is withdrawn from the top of the stripping column S1 and expanded in an expander also designated here as Ex2. The

Heat exchangers E5 and E6 of the system 99 according to FIG. 1 are now through the

Heat exchanger 10 replaced. The hydrogen and methane fraction H2 / CH4 is passed through the heat exchangers E10, E4, E3, E2 and E1. Bottom liquid from the stripping column S1 is partially evaporated in a heat exchanger E9, which is operated, for example, by means of a high-pressure C2 refrigerant, and is returned to the stripping column S1. More sump liquid is withdrawn as liquid stream C2.

In FIG. 3, a system for separating a component mixture according to an embodiment of the invention is illustrated in the form of a simplified process flow diagram and designated as a whole by 200.

The system 200 illustrated in FIG. 3 differs from the system 100 illustrated in FIG. 2 in particular in that there is another heat exchanger E1 1 integrated into the stripping column S1, which is cooled with low-pressure C2 refrigerant. The heat exchanger E1 1 is between the

Feed points for condensates C4 and C5 from tanks D4 and D10 are provided. With this measure, the top gas of the deethanization column T2, i.e. the gas stream G3 after cooling in the second heat exchanger E2, can be introduced directly into the stripping column S1 and the condensate from the container D3, i.e. the liquid stream C3, does not have to be subcooled in the fourth heat exchanger E4.

As a result, the consumption of medium-pressure and low-pressure C2 refrigerant in the third heat exchanger E3 and in the fourth heat exchanger E4 is greatly reduced, and thus the entire consumption of C2 refrigerant.

Claims

1. Process for the separation of a component mixture (K), the hydrogen,

Methane, hydrocarbons with two carbon atoms and hydrocarbons with three or more carbon atoms, comprising a deethanization and a demethanization, wherein in the deethanization

- At least part of the component mixture (K) is subjected to a first partial condensation by cooling from a first temperature level to a second temperature level at a first pressure level while obtaining a first gas fraction (G1) and a first liquid fraction (C1),

- At least part of the first gas fraction (G1) by cooling from the

second temperature level to a third temperature level at the first pressure level while obtaining a second gas fraction (G4) and a second liquid fraction (C2) is subjected to a second partial condensation, and

- at least part of the first liquid fraction (C1) and at least part of the second liquid fraction (C1) are subjected to rectification to obtain a third gas fraction (G3) and a third liquid fraction (C3 +),

characterized in that

- The first partial condensation is carried out in such a way that the second

Gas fraction (G2) contains more than 95% hydrogen, methane and hydrocarbons with two carbon atoms,

- the first liquid fraction (C1) or its part subjected to rectification and the second liquid fraction (C2) or its part subjected to rectification before rectification from the first pressure level to a second

Pressure level can be relaxed and rectification on the second

Pressure level is carried out, the first pressure level being 25 to 35 bar and the second pressure level being 14 to 17 bar, and

an overhead gas formed during the rectification is cooled to -25 to -35 TD and partially condensed, with a condensed portion of the

Overhead gas is partially or completely used as return flow in the rectification and a non-condensed portion of the overhead gas is partially or completely provided as the third gas fraction (G3).

2. The method according to claim 1, in which the rectification is carried out using a rectification column (T2), wherein the condensed portion of the top gas or part thereof without using a return pump and / or a return tank arranged outside the column to the

Rectification column (T2) is returned.

3. The method according to claim 1 or 2, wherein the first temperature level at 0 to 50 TD, the second temperature level at -30 to -40 T and the third

Temperature level between -50 and -60 T.

4. The method according to any one of the preceding claims, wherein the third

Liquid fraction in the rectification is formed at a temperature level of 65 to 75 TD.

5. The method according to any one of the preceding claims, in which a rectification column (T2) is used for rectification, which is cooled with a top condenser which is operated with propane and / or propylene refrigerant.

6. The method according to any one of the preceding claims, in which from at least part of the second gas fraction (G4) and the third gas fraction (G3) in a further separation apparatus (S1) a fraction containing more than 95% hydrogen and methane and a fraction containing more than 95% % Hydrocarbons containing two carbon atoms are formed.

7. The method according to claim 6, wherein the further separation apparatus (S1) on the

second pressure level is operated.

8. The method of claim 6 or 7, wherein at least part of the second

Gas fraction (G4) by means of gradual cooling via one or more intermediate temperature levels to a fourth temperature level at the first pressure level while obtaining further liquid fractions (C3, C4, C5) further

Partial condensations is subjected.

9. The method according to claim 8, wherein the further liquid fractions in the

Separation apparatus (S1) are fed.

10. The method according to claim 8 or 9, in which a portion (G9) of the second gas fraction (G4) remaining in gaseous form at the fourth temperature level is expanded from the first pressure level to the second pressure level and fed into the further separating apparatus (S1).

1 1. The method according to any one of claims 8 to 10, wherein the fourth

Temperature level is -140 to -150 T.

12. The method according to any one of claims 8 to 1 1, in which the more than 95%

Hydrogen and methane-containing fraction taken from the further separating apparatus (S1), providing cooling from the second pressure level to a third

Pressure level relaxed and for gradual cooling to the fourth

Temperature level is used.

13. The method according to any one of claims 6 to 12, wherein the separation apparatus (S1) is operated with an internal heat exchanger which is cooled with a refrigerant at a temperature level of -90 to -1 10 T.

14. Plant (100, 200) for separating a component mixture (K), the

Contains hydrogen, methane, hydrocarbons with two carbon atoms and hydrocarbons with three or more carbon atoms, the system (100, 200) having means for deethanization and means for demethanization, and wherein the means for deethanization are set up for

- To subject at least part of the component mixture (K) to a first partial condensation by cooling from a first temperature level to a second temperature level at a first pressure level while obtaining a first gas fraction (G1) and a first liquid fraction (C1), at least a part of the first gas fraction (G1) to subject (G1) to a second partial condensation by cooling from the second temperature level to a third temperature level at the first pressure level while obtaining a second gas fraction (G4) and a second liquid fraction (C2), and

- to subject at least part of the first liquid fraction (C1) and at least part of the second liquid fraction (C1) to a rectification while obtaining a third gas fraction (G3) and a third liquid fraction (C3 +),

characterized in that

- means are provided for the second partial condensation which are set up to carry out the second partial condensation in such a way that the second gas fraction (G2) has more than 95% hydrogen, methane and hydrocarbons with two carbon atoms,

Funds are provided that are set up for the first

Liquid fraction (C1) or its part subjected to rectification and the second liquid fraction (C2) or its part subjected to rectification to relax from the first pressure level to a second pressure level before rectification and the rectification to the second pressure level

to perform, the first pressure level being 25 to 35 bar and the second pressure level being 14 to 17 bar, and

Means are provided which are set up to cool an overhead gas formed during the rectification to -25 to -35 T and thereby partially condense it, and to use a condensed portion of the overhead gas partially or completely as return flow in the rectification and a non-condensed portion Provide portion of the head gas partially or completely as the third gas fraction (G3).

15. Plant (100, 200) according to claim 14, which has means which are set up for carrying out a method according to one of claims 1 to 11.