JP2011508031A - Method and apparatus for separating low boiling components from hydrocarbon mixtures - Google Patents

Abstract

  Continuous operation of the starting mixture, comprising at least one conduit for supplying one or more starting mixtures, a discharge pipe for the low-boiling fraction, a discharge pipe for the high-boiling fraction and a heating device A method and apparatus for separating a high-boiling fraction and a low-boiling fraction in a distillation apparatus operated at a distillation stage comprising a condensation stage each having at least two different temperature levels, Each condensing stage pre-connected in the direction of steam flow has a higher temperature level than each condensing stage connected after each, and a separate attachment has an intermediate connection to the condensing stage, Partial condensation proceeds in the condensation stage, and the partial quantities that have not been condensed in this way are respectively attached to the separate attached attachment or condensation stage, each having a lower temperature level. The respective fractions fed and condensed are introduced in the direction of the discharge pipe for the high-boiling fraction via a separating attachment, and the essentially vapor-like medium is condensed with the lowest temperature level. Which occurs in the stage where it is partially condensed, in which case the uncondensed part of the medium is returned to the discharge line for the low-boiling fraction, the condensed part being the condensing stage having the lowest temperature level. The condensing stage, which was returned to the range of the distillation apparatus and connected with the lowest temperature level, was high in the distillation apparatus having a temperature of −40 ° C. and operated in a continuous mode of operation. The method and apparatus as described above for separating a boiling fraction and a low boiling fraction.

Description

The present invention is, for example, when the low-boiling dehydrogenation of hydrocarbons, however, since even when the problem of another separation in the range of C ₁ -C ₄ separating the low-boiling components from the hydrocarbon stream, Koto And relates to a method and apparatus for separating the C ₂ fraction from the desired C ₃ ⁺ fraction as the desired product.

  Such separation is usually carried out by a combination of so-called “cold boxes” and distillation columns. The distillation column is operated as a Deethanizer and is so called because all substances having a boiling point below or equal to the boiling point of ethane are separated through the top of the column in the deethanizer.

  The use mixture is first cooled to about −25 ° C. before entering the cold box. The resulting condensate is introduced directly into the deethanizer. The non-condensed vapor is further cooled to about −90 ° C. in the cold box, in which case the product-rich condensate thus produced is likewise led to a deethanizer after heat exchange. The cold box is therefore a one-stage crude separation.

The remaining vapor phase containing essentially non-condensable components, such as hydrogen, is released into a stream that enters the cold box after heat exchange. In this case, based on the Joule-Thomson effect, the low boilers are cooled to about -110 ° C. This temperature level is used to partially condense the stream entering the cold box. Non-condensed low boilers are essentially free of C ₃ ⁺ components.

  Ultimately all the product-rich condensate phase is introduced into the deethanizer for inherent fine separation, in which the remaining low boilers are separated from the high boiling components. For this, a temperature of about −20 ° C. is required at the top of the column.

  Evaporable propane or propene can be used at −30 ° C. as a coolant for cooling the use mixture in front of the cold box for cold box operation and for deethanizer cooling.

  The production of coolant for this type of process is very expensive. Accordingly, it is an object of the present invention to provide a method and apparatus that can significantly reduce the amount of coolant used.

The present invention provides a starting mixture
Operated in a continuous mode of operation, comprising at least one conduit for supplying one or more starting mixtures, a discharge pipe for the low-boiling fraction, a discharge pipe for the high-boiling fraction and a heating device. Method for separating a high-boiling fraction and a low-boiling fraction in a distillation apparatus comprising a condensation stage having at least two different temperature levels,
In this case, each condensation stage pre-connected in the direction of steam flow has a higher temperature level than each of the subsequent condensation stages,
Attachments each having a separating action are intermediately connected to the condensation stage,
Partial condensation proceeds at the condensation stage,
In this case, the respective uncondensed partial quantities are fed to a separately connected attachment or condensing stage, each having a low temperature level, and each condensed partial quantity is supplied to a separate installation. Introduced in the direction of the discharge pipe for the high-boiling fraction through the product,
The essentially vaporous medium occurs in the condensation stage having the lowest temperature level, where it is partially condensed, in which case the uncondensed part of the medium is returned to the discharge line for the low-boiling fraction, The condensed portion is returned to the range of the distillation apparatus, pre-connected to the condensation stage having the lowest temperature level,
And the condensation stage having the lowest temperature level is for separating the starting mixture into a high-boiling fraction and a low-boiling fraction in a distillation apparatus operating in a continuous mode of operation, having a temperature of −40 ° C. The object is solved by the independent claims which describe the method.

  In an embodiment of the invention, it is provided that the distillation apparatus comprises 3 to 5 sequentially connected condensation stages each having a different temperature level.

  Furthermore, an embodiment of the present invention is provided that the condensation stage having the lowest temperature level has a temperature of -120 ° C. to -70 ° C. at a pressure of at least 2 MPa (absolute), in particular at least 3 MPa.

  Furthermore, in an embodiment of the present invention, the mixture leaving the distillation apparatus as a low-boiling fraction is released, wherein the mixture is further cooled using the Joule-Thomson effect, thereby lowering the lowest temperature level. It is provided that it is used for cooling of the condensing stage.

  Furthermore, embodiments of the present invention provide that the pressure relief is performed using a pressure relief turbine.

  Furthermore, embodiments of the present invention relate to the use of a suitable starting mixture, with which the process can be used with particular advantage in obtaining available products.

  Furthermore, in an embodiment of the invention, the process is used for a starting mixture which essentially comprises hydrogen, a hydrocarbon having up to 2 carbon atoms and a hydrocarbon having at least 3 carbon atoms. Is done. In the discharge tube for the low-boiling fraction, a mixture containing essentially hydrogen and a hydrocarbon having up to 2 carbon atoms results, which mixture essentially has at least 3 carbon atoms. Contains no hydrocarbons. In the discharge tube for the high-boiling fraction, a mixture containing hydrocarbons with at least 3 carbon atoms results, which mixture is essentially free of hydrogen and has up to 2 carbon atoms. Contains no hydrocarbons.

  Furthermore, in an embodiment of the invention, the process is used for starting mixtures each containing less than 2 mol% of carbon dioxide and water or water vapor.

  Furthermore, in an embodiment of the invention, the reaction mixture is used as a starting mixture for the catalytic dehydrogenation of hydrocarbons.

  Furthermore, in an embodiment of the invention, a segment of the distillation apparatus is present as the outlet of the distillation apparatus, through which a portion of the starting mixture condensed in the condensation stage having the highest temperature level is Supplied to the discharge pipe for the high-boiling fraction.

  Furthermore, in an embodiment of the invention, the starting mixture with a relatively low content of components having a low boiling point is advantageously added below the condensation stage with the highest temperature level and a relatively high content with a low boiling point. It is provided that the starting mixture with the components is preferably added above the condensation stage with the highest temperature level.

  Furthermore, in an embodiment of the invention, the condensation stage exists as a condenser.

  Furthermore, in an embodiment of the invention, the condensation stage is cooled with cooling water, evaporative ammonia, propane, propene and / or upon release of the process gas by utilizing the Joule-Thomson effect.

  Furthermore, in an embodiment of the invention, the heating device is operated using an external waste heat generator.

The present invention also provides:
One or more conduits for supplying one or more starting mixtures;
Discharge pipe for the low-boiling fraction,
Discharge pipe for the high-boiling fraction,
At least one heating device,
The problem is solved with a distillation apparatus suitable for separating the starting mixture, comprising at least two sequentially connected condensers and an attachment with a separating action intermediately connected to the condenser.

  Other selectable embodiments of the apparatus are provided in which the distillation apparatus exists in the form of a single distillation column, or the distillation apparatus exists as a cascade comprising a plurality of distillation columns. In the case of this distillation column, a condenser is provided between the distillation columns. In particular, the distillation apparatus may be provided with 3, 4 or 5 sequentially connected condensers each having a different temperature level.

  That is, what has been achieved in two process steps so far can now be realized in one step with the present invention without a pre-connected cold box, which is one advantage of the present invention.

  By utilizing a number of condensers operating at different temperature levels, depending on the method, it is not necessary to prepare all cooling amounts for condensation at the lowest temperature level and hence at the highest cost. Achieved. Instead, the intermediate condenser functions at a temperature of about + 45 ° C., + 15 ° C. or −30 ° C., which is another advantage of the present invention.

  Therefore, as long as it is used in this way, the majority of the vapor rising in the column is already condensed before reaching the top condenser and flows downward as a liquid. The cold air level required for the operation of the overhead condenser, about -80 ° C, and the required condensation efficiency can be formed by the low boiler discharge pressure in the device itself, This is another advantage of the present invention.

1 schematically shows the process according to the invention when the distillation apparatus consists of only one distillation column with a number of intermediate condensers. 1 is a schematic diagram showing a method according to the present invention when a distillation apparatus is composed of a separation unit and a concentration unit separated from each other. 1 is a schematic diagram showing the method according to the invention when the distillation apparatus consists of three sections. In this case, intermediate condensers exist between the sections.

  The invention will now be described in detail with three examples.

In all three embodiments, the vaporous use mixture 1 can first be cooled to 15 ° C., for example, in an ammonia evaporator 2. Furthermore, in the heat exchanger 3, the obtained C ₂ fraction can be further cooled to about 10 ° C., with a portion of the vapor condensing. The vapor phase 5 and the condensate 6 reach the distillation apparatus separately. Depending on the composition of the starting mixture, the task can also be carried out above the condensation process with the highest temperature level.

In the embodiment shown in FIG. 1, the liquid flows downward in the distillation column 7 and is partially evaporated again. The portion that has not evaporated is taken from the bottom of the distillation column 7 as C ₃ ⁺ product 8. The low-boiling substances rise upward as vapor and are partially condensed by the first condenser 9 formed in two divided parts existing on the charging bed. In this case, the low-boiling substances are sequentially cooled as a coolant. Water and ammonia are used. Furthermore, the rising steam is partially liquefied in the second condenser 10 operated with the coolant propane or propene, so that only a small part of the steam reaches the top condenser 11. The vapor not condensed in the top condenser 11 forms C ₂ fractions 12 and 13, which are released in the expander 14 following condensation, in which the fraction And cooled to about -125 ° C. The cooled steam 15 is used as a cooling medium on the cold side of the top condenser 11, and in this case, the temperature is raised to about -50 ° C. Subsequently, this C ₂ fraction 4 still passes through the heat exchanger 3 for cooling of the use mixture 1.

In the embodiment shown in FIG. 2, the liquid flows downward in the separation part 16 and is partially evaporated again. The portion that has not evaporated is taken out from the bottom of the separation section 16 as C ₃ ⁺ product 8. The vapor-like low boiling point substance 17 flows into the first condenser 9 formed in two parts, where a part is condensed, and at that time, cooling water and ammonia are sequentially used as a coolant. . The condensate 18 and the vapor 19 are supplied into the concentration unit 20. A part of the bottom of the concentrating part 20 is used as the top charge 21 of the separating part 16. Furthermore, the rising steam is partially liquefied in the second condenser 10 operated with the coolant propane, so that only a small part of the steam reaches the top condenser 11. Vapor that has not been condensed in the top condenser 11 forms C ₂ fractions 12 and 13, which are connected to the condensation and released in the expander 14, in which case the fractions Is cooled to about −125 ° C. The cooled steam 15 is used as a cooling medium on the cold side of the top condenser 11, and in this case, the temperature is raised to about -50 ° C. Subsequently, this C ₂ fraction 4 still passes through the heat exchanger 3 for cooling of the use mixture 1.

In the embodiment shown in FIG. 3, the liquid flows downward in the separation part 16 and is partially evaporated again. The portion that has not evaporated is taken out from the bottom of the separation section 16 as C ₃ ⁺ product 8. The vapor-like low boiling point substance 17 flows into the first condenser 9 formed in two parts, where a part is condensed, and at that time, cooling water and ammonia are sequentially used as a coolant. . The condensate 18 and the steam 19 are supplied into the first concentration unit 22. A part of the bottom of the first concentration unit 22 is used as the top charge 21 of the separation unit 16. Further, the rising vapor is partially liquefied in the second condenser 10 operated with the coolant propane or propene, and the condensate and vapor are fed into the second concentrator 23. . The bottom of the second concentrating unit 23 is used as the top charge of the first concentrating unit 22, and thus only a small amount of vapor reaches the condenser 11. Vapor that has not been condensed in the top condenser 11 forms C ₂ fractions 12 and 13, which are released in the expander 14 following condensation, in which case the fraction is And cooled to about -125 ° C. The cooled steam 15 is used as a cooling medium on the cold side of the top condenser 11, and in this case, the temperature is raised to about -50 ° C. Subsequently, this C ₂ fraction 4 still passes through the heat exchanger 3 for cooling of the use mixture 1.

  In this last variant, compared to the previous method, only the upper part of the second concentrating tower is formed at a stable low temperature and must be equipped with a stronger insulation, preventing heat absorption. This is one of the advantages of the present invention.

  In fact, in all three embodiments, a greater amount of heat is required for the operation of the evaporator compared to the prior art prior art, but this amount of heat is only required at about 75 ° C. For this purpose, waste heat from another processing position of the complex part of the apparatus is generally used, otherwise this waste heat has to be expelled by an air cooler. This is another advantage of the present invention. Moreover, overall a much larger amount of cooling performance is actually required, but heat can be derived at a more advantageous cooling level, which is another advantage of the present invention. is there.

Furthermore, the advantages of the method according to the invention compared to the method presented at the beginning according to the state of the art are as follows:
By using cooling water, it is possible to save about 25% of the ammonia cooling efficiency, so only a much smaller ammonia cooling device is required. The propane cooling efficiency is reduced by about 55%, so the compressor efficiency required for the propane cooling circuit is reduced by about 50% and the compressor can be sized accordingly.

1 Vapor use mixture, 2 Ammonia evaporator, 3 Heat exchanger, 5 Vapor phase, 6, 18 Condensate, 7 Distillation tower, 8 C ₃ ⁺ product, 9 First condenser, 10 Second condensation , 11 overhead condenser, 4, 12, 13 C ₂ fraction, 14 expander, 15, 19 steam, 16 separation part, 17 vapor-like low boiling point substance, 20 concentrating part, 21 overhead charge, 22 1st concentration part, 23 2nd concentration part

Claims (19)

Operated in a continuous mode of operation comprising at least one conduit for supplying one or more starting mixtures, a discharge pipe for the low boiling fraction, a discharge pipe for the high boiling fraction and a heating device In a process for separating a starting mixture into a high-boiling fraction and a low-boiling fraction in a distillation apparatus,
The distillation apparatus includes a condensation stage having at least two different temperature levels,
In this case, each condensation stage pre-connected in the direction of steam flow has a higher temperature level than each of the subsequent condensation stages,
The attachments, each having a separating action, are intermediately connected to the condensation stage,
Partial condensation proceeds at the condensation stage,
In this case, the respective uncondensed partial quantities are fed to a separately connected attachment or condensing stage, each having a low temperature level, and each condensed partial quantity is supplied to a separate installation. Introduced in the direction of the discharge pipe for the high-boiling fraction through the product,
The essentially vaporous medium occurs in the condensation stage having the lowest temperature level, where it is partially condensed, in which case the uncondensed part of the medium is returned to the discharge line for the low-boiling fraction, The condensed portion is returned to the range of the distillation apparatus, pre-connected to the condensation stage with the lowest temperature level,
And the condensation stage having the lowest temperature level has a high boiling fraction and a low boiling fraction in a distillation apparatus wherein the starting mixture is operated in a continuous mode of operation, characterized in that it has a temperature of −40 ° C. Way to separate.   The process according to claim 1, wherein the distillation apparatus comprises 3 to 5 sequentially connected condensation stages, each having a different temperature level.   The process according to claim 1 or 2, wherein the condensation stage having the lowest temperature level has a temperature of -120 ° C to -70 ° C at a pressure of at least 2 MPa (absolute).   The process according to claim 3, wherein the condensation stage having the lowest temperature level has a temperature of -120 ° C to -70 ° C at a pressure of at least 3 MPa (absolute).   The mixture leaving the distillation unit is released as a low-boiling fraction, where it is further cooled using the Joule-Thomson effect and thereby used for cooling the condensation stage with the lowest temperature level. The method according to any one of claims 1 to 4.   6. The method of claim 5, wherein the pressure relief is performed using a pressure relief turbine.   Using a mixture containing essentially hydrogen, a hydrocarbon having up to 2 carbon atoms and a hydrocarbon having at least 3 carbon atoms as the starting mixture, in the discharge pipe for the low-boiling fraction, A mixture containing hydrogen and a hydrocarbon having up to 2 carbon atoms is produced, essentially free of hydrocarbons having at least 3 carbon atoms, and in the discharge pipe for the high-boiling fraction, essentially 7. A mixture containing hydrocarbons having at least 3 carbon atoms, which does not contain hydrogen and which does not contain hydrocarbons having up to 2 carbon atoms, results in any one of claims 1 to 6. The method described in 1.   8. The process as claimed in claim 1, wherein the starting mixture is a mixture containing less than 2 mol% of carbon dioxide and water or water vapor.   9. A process according to any one of claims 1 to 8, wherein the reaction mixture is used as a starting mixture for the catalytic dehydrogenation of hydrocarbons.   A segment of the distillation unit exists as an outlet of the distillation unit, through which a portion of the starting mixture condensed in the condensation stage with the highest temperature level is discharged into the discharge pipe for the high-boiling fraction. 10. A method according to any one of claims 1 to 9, wherein the method is supplied to   11. The process as claimed in claim 1, wherein the starting mixture having a relatively low content of components having a low boiling point is added below the condensation stage, which preferably has the highest temperature level.   12. The process as claimed in claim 1, wherein the starting mixture having a relatively high content of components having a low boiling point is added above the condensation stage, which preferably has the highest temperature level.   13. A method according to any one of claims 1 to 12, wherein the condensation stage is present as a condenser.   Condensation stage is cooled upon release of the mixture leaving the distillation apparatus with cooling water, ammonia, propane, propene and / or as a low-boiling fraction by use of the Joule-Thomson effect. The method of any one of these.   15. A method according to any one of claims 1 to 14, wherein the one or more heating devices are operated using an external waste heatr. a) one or more conduits for supplying one or more starting mixtures;
b) discharge pipe for the low-boiling fraction,
c) discharge pipe for the high-boiling fraction,
d) at least one heating device;
16. Distillation for carrying out according to any one of the preceding claims, comprising e) at least two sequentially connected condensers and f) an attachment having a separating action intermediately connected to the condenser. apparatus.   17. An apparatus according to claim 16, wherein the distillation apparatus is present in the form of a single distillation column.   17. The apparatus according to claim 16, wherein the distillation apparatus exists as a cascade comprising a number of distillation columns, wherein a condenser is provided between each distillation column.   17. An apparatus according to claim 16, wherein the distillation apparatus has 3, 4 or 5 sequentially connected condensers each having a different temperature level.

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