Patent Application
20250171385
This patent application claims priority to European Patent Application No. 23213040.1, filed on Nov. 29, 2023, in the European Patent Office, the entire disclosure of which is hereby incorporated by reference herein.
The present invention relates to a process for separating 1-butene from a hydrocarbon stream containing at least 1-butene, 2-butene, n-butane and isobutane in a separation unit comprising at least two distillation columns DK1 and DK2, wherein the heat of condensation is recirculated into the process by optimized vapour compression in order to save energy costs and CO2 emissions.
1-Butene can be obtained in large amounts from technical C4 hydrocarbon streams, for example the C4 cut from steamcrackers or FCC units. These C4 hydrocarbon streams consist essentially of butadiene, the monoolefins isobutene, 1-butene and the two 2-butenes (cis- and trans-2-butene), and the saturated hydrocarbons isobutane and n-butane. Because of the small differences in the boiling points of the constituents, the low separation factors thereof and the formation of azeotropes, exclusively distillative workup of C4 hydrocarbon streams is difficult and uneconomic.
Typically, therefore, the butadiene is first separated off by extractive distillation or hydrogenated selectively to butenes. What remains in each case is a C4 hydrocarbon stream (called raffinate 1) containing not only the saturated hydrocarbons n-butane and isobutane but also the olefins isobutene, 1-butene and 2-butenes, while the butadiene is present in small amounts at most.
Since the boiling points of 1-butene and isobutene are close to one another, it is generally not possible to economically separate 1-butene from corresponding C4 hydrocarbon streams via simple distillation. The isobutene is therefore very substantially removed, for example by etherification with alcohols, e.g. methanol or ethanol to give MTBE or ETBE. The largely reactive removal of the isobutene gives rise to a C4 hydrocarbon stream (called raffinate 2) containing the linear butenes (1- and 2-butenes) and the saturated hydrocarbons isobutane and n-butane.
The separation of 1-butene from such C4 hydrocarbon streams is possible and is used in the chemical industry. The separation is effected in a distillation unit comprising at least two distillation columns. Isobutane and 1-butene are obtained at the top of the first distillation column and directed to the second distillation column. Then isobutane and 1-butene are separated from one another in the second distillation column. Such a process is disclosed, for example, in DE 10 2005 062 700 A1.
In the known processes, the energy needed for the separation of the C4 hydrocarbon stream is typically introduced into the bottom of the two distillation columns via heating steam. It is true that heating steam is generally available at chemical production sites. But, in the volumes needed for the separation tasks in question, the use of heating steam means a cost factor that cannot be underestimated. Furthermore, the generation of heating steam generates a large volume of CO2.
It was therefore the object of the present invention to provide a process in which energy and CO2 emissions can be saved by comparison with the known processes and which can be integrated into existing plants.
This problem is solved by the embodiment of the process proposed in the description herein. Preferred embodiments are also specified in the dependent embodiments. The process according to the invention is a process for separating 1-butene from a raffinate 2 stream containing at least 1-butene, 2-butene, n-butane, isobutene and isobutane in a separation unit comprising at least two distillation columns DK1 and DK2, wherein
the first distillation column DK1 has at least one reboiler SV1 and the second distillation column DK2 has at least one reboiler SV2;
the reboiler SV1 is fed with a stream which is withdrawn at the lower end of DK1 and, after passing through the respective reboiler, is guided back to DK1;
the reboiler SV2 is fed with a stream which is withdrawn at the lower end of DK2 and, after passing through the respective reboiler, is guided back to DK2; where the process comprises the following steps:
One advantage of the process according to the invention is that the vapour streams BS1 and BS2 obtained in the two columns DK1 and DK2 are subjected to a compression, accordingly upgraded and exploited in reboilers SV1 and SV2, and energy is thus introduced into the respective bottoms. The result of the energy transfer in the reboilers SV1 and SV2 is that significantly less heating steam, if any at all, has to be used for heating of distillation columns DK1 and DK2. It is thus possible to achieve (almost) complete electrification of the energy-intensive process, which in turn enables the use of green power. This saves energy costs and CO2 emissions.
According to the present invention, the starting stream from which the 1-butene is to be separated is a raffinate 2 stream containing at least 1-butene, 2-butene, n-butane and isobutane. Corresponding streams are available on the market, for example as a C4 cut from steamcrackers or FCC units. It has already been mentioned in the introduction that raffinate 2 is formed by removal of polyunsaturated C4 hydrocarbons, especially butadiene, and isobutene from the stream. Complete removal is not possible in many cases for economic and technical reasons. However, the amounts of polyunsaturated C4 hydrocarbons, especially butadiene, and isobutene should be at a minimum.
The raffinate 2 used preferably contains less than 2500 ppm, preferably less than 1000 ppm, more preferably less than 500 ppm, of isobutene. If higher amounts of isobutene are present in the starting stream, it would be possible for an MTBE or ETBE synthesis (methyl tert-butyl ether=MTBE/ethyl tert-butyl ether=ETBE) to be effected between the two distillation columns DK1 and DK2, in order to react the isobutene with methanol (to give MTBE) or ethanol (to give ETBE) and then to separate off the MTBE or ETBE (cf. EP 1 806 330 A1 or EP1 813 588 A1). It is thus possible to very greatly reduce the concentration of isobutene upstream of the second distillation column DK2. This is because isobutene would be obtained in the bottom in the second distillation column and hence in the 1-butene.
Further preferably, the raffinate 2 used in the process of the present invention contains less than 4% by weight of polyunsaturated C4 hydrocarbons. In a particularly preferred embodiment, the concentration of the polyunsaturated C4 hydrocarbons should be less than 500 ppm. If the streams should contain higher amounts of butadiene, it would be possible to conduct a selective hydrogenation beforehand, in which the butadiene is converted to butenes and/or butanes. Corresponding processes are known to the person skilled in the art, for example from EP 3 680 224 A1.
The raffinate 2 stream used may additionally contain certain amounts of water, especially in an amount of 150 to 4000 ppm. It is preferable that the water is at least partly separated off by the process described here. The water will accumulate in the respective vapour stream BS1 and BS2 in each of the two distillation columns DK1 and DK2 and be obtained as a second liquid phase after condensation, which can be separated off via udders in the distillate vessels of DK1 and/or DK2. The bottom products of DK1 and of DK2 feature very low contents of butadiene and water, preferably each below 100 ppm, more preferably below 5 ppm.
The process according to the invention is conducted in a separation unit comprising at least the two distillation columns DK1 and DK2. DK1 is the first distillation column and has at least one reboiler SV1. DK2 is the second distillation column and has at least one reboiler SV2. In a preferred embodiment, the distillation column has only one reboiler SV1. It is additionally preferable that the distillation column DK1 has only the one reboiler SV2. The pressures in the two distillation columns DK1 and DK2 should in particular be chosen such that the separation task is made easier by the influencing of relative volatility, but the compression of the volume flows BS1 and BS2 does not become too energy-intensive. The terms “first distillation column”, “distillation column DK1” and “DK1” should be considered to be synonymous in the context of the present invention. The terms “second distillation column”, “distillation column DK2” and “DK2” should likewise be considered to be synonymous in the context of the present invention.
The energy needed for the separation task is introduced into the first distillation column DK1 via the reboiler SV1. The reboiler SV1 is fed with a stream which is withdrawn at the lower end of DK1 and, after passing through the respective reboiler, is guided back to DK1. The stream is heated as it passes through the reboiler SV1.
The situation is comparable for the reboiler SV2 of the second distillation column DK2, by means of which energy needed for the separation task is introduced. For this purpose, the reboiler SV2 is fed with a stream which is withdrawn at the lower end of DK2 and, after passing through the respective reboiler, is guided back to DK2. The stream is heated as it passes through the reboiler SV2 and at least partly evaporates as it does so.
According to the invention, “reboilers” refer to evaporators that heat the bottom of the respective distillation column. Such a reboiler is typically disposed outside the respective distillation column. Since reboilers transfer energy, in particular heat, from one stream to another, they are heat transferrers. The stream to be evaporated is drawn off from the bottom of the distillation column via a draw and fed to the reboiler. The evaporated stream, with or without a residual proportion of liquid, is returned back to the respective distillation column in the region of the bottom via at least one feed.
Suitable evaporators that can be used as reboilers are, for example, natural circulation evaporators, forced circulation evaporators, forced circulation flash evaporators, kettle evaporators, falling-film evaporators or thin-film evaporators. Heat exchangers for the evaporator that are typically used in the case of natural circulation evaporators and forced circulation evaporators are a shell-and-tube or plate apparatus. As well as those mentioned, it is alternatively possible to use any other design of evaporator which is known to those skilled in the art and is suitable for use in a distillation column.
The raffinate 2 which is directed to the first distillation column DK1 is separated in distillation column DK1 into at least two streams, i.e. at least one vapour stream BS1 which comprises at least 1-butene and isobutane and is withdrawn at the top of DK1, and at least one bottom stream which comprises at least 1-butene and 2-butene and is withdrawn at the bottom of DK1. This bottom stream can be guided to an oligomerization (not shown). The vapour stream BS1 can also be withdrawn at the top of the distillation column in the form of multiple substreams BS1n where n is an integer and is equal to the number of substreams. The same also applies to the bottom stream. The temperature at the bottom of the first distillation column DK1 is preferably in the range from 40 to 110° C., preferably 50 to 100° C.
In principle, the raffinate 2 stream can be directed into the first distillation column DK1 via one or more feed points. If significant variations in the feed concentration are to be expected, it may be advisable to provide multiple different feed points. The optimal position thereof may be found, for example, by simulation via minimization of the energy demand. If multiple feed streams of different composition are to be processed, the optimal feed point can be determined analogously for each feed. It is also possible in principle that the raffinate 2 stream is divided into multiple substreams beforehand even in the case of identical or constant composition. In this case, the raffinate 2 stream is directed into distillation column DK1 in the form of two or more separate streams. It is advantageous here when the feed points of the individual streams are essentially at the same height on distillation column DK1.
The pressure and temperature of the vapour stream BS1 are specified hereinafter. This relates in particular to the pressure and temperature of the at least one vapour stream BS1 when it is withdrawn from distillation column DK1. The pressure of the vapour stream BS1 is especially in the range from 6 to 15 bar absolute, preferably in the range from 7.5 to 13 bar absolute. The temperature of the vapour stream BS1 is especially in the range from 45° C. to 120° C., preferably in the range from 48° C. to 100° C., further preferably in the range from 50° C. to 90° C., further preferably in the range from 55° C. to 80° C., more preferably in the range from 60° C. to 80° C.
The distillation column DK1 used for the separation of the raffinate 2 stream may be any distillation column known to the person skilled in the art. Distillation column DK1 preferably contains internals. Suitable internals are for example trays, unstructured packings (random packings) or structured packings. Trays used are typically bubble-cap trays, sieve trays, valve trays having fixed or movable valves, tunnel-cap trays or slotted trays. Unstructured packings are generally beds of random packings. Random packings used are typically Raschig rings, Pall rings, Berl saddles, Super-Rings/Super-Rings Plus or Intalox® saddles. Structured packings are sold for example under the Mellapak® trade name by Sulzer. In addition to the internals mentioned, further suitable internals are known to those skilled in the art and may likewise be used.
Preferred internals have a low specific pressure drop per theoretical plate. Structured packings and random packing elements have, for example, a significantly lower pressure drop per theoretical plate than trays. This has the advantage that the pressure drop in distillation column DK1 remains as low as possible and hence the mechanical output of the compressor and the temperature of the raffinate 2 stream to be evaporated remains low.
In a particularly preferred embodiment of the present invention, distillation column DK1 comprises a multitude of trays, preferably between 150 and 300 trays, further preferably between 170 and 220 trays.
What is meant in the context of the present invention by the withdrawal of the at least one vapour stream BS1 comprising at least 1-butene and isobutane at the top of distillation column DK1 is in particular that the at least one vapour stream BS1 is withdrawn as top stream or as side draw above the internals in distillation column DK1.
What is meant in the context of the present invention by the withdrawal of the at least one bottom stream comprising at least 1-butene and 2-butene at the bottom of distillation column DK1 is in particular that the at least one bottom stream is withdrawn directly at the bottom or at the lower tray of distillation column DK1.
Distillation column DK1 is preferably operated with reflux. What is meant by “reflux” is that the vapour stream BS1 withdrawn at the top end of distillation column DK1 is at least partly fed back to distillation column DK1. In the cases where such a reflux is established, the reflux ratio is preferably 2 to 30, more preferably 5 to 20, especially preferably 8 to 15.
A reflux can be established by mounting a condenser at the top of distillation column DK1. Vapour stream BS1 is partly condensed in the condenser and fed back to distillation column DK1. The vapour stream can also be applied as reflux to the distillation column only after compression and expansion. In general and in the context of the present invention, a reflux ratio means the ratio of the proportion of the mass flow rate withdrawn from the column (kg/h) that is returned back into the column in liquid form (reflux) to the proportion of that mass flow rate (kg/h) which is discharged from the respective column in liquid form or gaseous form.
After the withdrawal of vapour stream BS1, vapour stream BS1 is compressed, giving rise to a compressed stream VB1 relative to vapour stream BS1. It may be advantageous to heat stream BS1 prior to compression in order that no biphasic mixture is formed on compression. The heating can be conducted by means of internal (see WT1 in
The temperature of substream VB1 is preferably higher than the temperature of vapour stream BS1, and the quotient of temperature VB1/temperature BS1 (temperature in each case in K) is preferably in the range from 1.03 to 10, more preferably 1.04 to 9, more preferably 1.05 to 8, more preferably 1.06 to 7, more preferably 1.07 to 6, most preferably 1.08 to 5.
The at least one portion of vapour stream BS1 can be compressed in step (b) in any desired manner known to the person skilled in the art. For example, the compression can be performed mechanically and in a single-stage or multistage compression. What is meant by “single-stage” in this connection is that compression takes place from one pressure level to another. What is meant by “multistage” is that compression is effected first to a pressure level X and then from X to the pressure level Y. In a multistage compression, it is possible to use two or more compressors of the same type or compressors of different types. A multistage compression can preferably be effected with one compressor machine or with multiple compressor machines. The use of single-stage compression or multistage compression depends on the compression ratio and hence on the pressure to which the vapour stream BS1 is to be compressed.
A suitable compressor in the process according to the invention, especially for compression of the vapour stream BS1 to VB1, is any compressor known to the person skilled in the art, preferably mechanical compressor, with which gas streams can be compressed. Suitable compressors are, for example, single-stage or multistage geared turbocompressors, piston compressors, screw compressors, centrifugal compressors or axial compressors.
In step (c) of the process according to the invention, energy is transferred from the compressed stream VB1 to the stream in reboiler SV1. Step (c) lowers the energy of VB1, such that VB1 can be partly condensed. According to the invention, the phrase “transfer of energy” especially means “heating”, i.e. transfer of energy in the form of heat.
The transfer of energy from VB1 to the stream in the reboiler SV1, preferably the heating of the stream in the reboiler SV1 by VB1, is preferably direct. What is meant by direct transfer is that VB1 and the stream in SV1 do not come into direct contact, but energy, especially heat, is transferred from VB1 to the stream in SV1 without the presence of any additional heat transfer medium. Reboilers SV1 used may be the heat transferrers or heat exchangers that are familiar to the person skilled in the art, especially evaporators.
Before stream VB1 is guided to the second distillation column by step (d) to the second distillation column, stream VB1, in a preferred embodiment, is guided to a flash vessel and expanded therein to obtain a liquid phase FP1. The flash vessel may additionally comprise a condenser in order to condense a portion of the gaseous phase obtained.
At least a portion FP1a of the liquid phase FP1 is then directed in step (d) to distillation column DK2. For this purpose, in a particularly preferred embodiment, a pump is used. It is possible here to use pumps known to the person skilled in the art. Suitable pumps are, for example, standard chemical pumps.
It is further preferable that a portion FP1b of the liquid phase FP1 other than FP1a is returned as reflux to the first distillation column DK1. It is particularly preferable that this transfers energy from stream FP1b to the raffinate 2 stream before the raffinate 2 stream is introduced into the first distillation column DK1. This preheats the raffinate 2 stream. This is energetically advantageous because less energy has to be introduced for the separation task via the reboilers. The transfer of energy from FP1b to the raffinate 2 stream, preferably the heating of the raffinate 2 stream by FP1b, is preferably direct, i.e. without use of a (further) heat transfer medium. For this purpose, it is possible to use heat transferrers or heat exchangers that are familiar to the person skilled in the art.
Streams VB1 or FP1a are thus guided to the second distillation column DK2. If the amounts of isobutene in stream VB1 or in stream FP1a are too high to meet the specification for the 1-butene product from DK2, it is possible, as mentioned, for an additional MTBE or ETBE synthesis to be disposed between distillation columns DK1 and DK2. For this purpose, stream VB1 or stream FP1a is guided to an MTBE or ETBE synthesis, and the isobutene present is at least partly converted to MTBE or ETBE.
MTBE or ETBE synthesis is known in principle to those skilled in the art. For the preparation of MTBE or ETBE from isobutene-containing streams, it is possible in particular to use acidic ion exchange resins (sulfo groups) as heterogeneous catalysts. The MTBE or ETBE synthesis may take place in one or more series-connected reactors. The catalyst is preferably used in the form of a fixed bed catalyst. Since the formation of MTBE or ETBE is an equilibrium reaction, it may be appropriate to use at least one reactive distillation column in which the reaction and removal of the MTBE or ETBE are simultaneous. In the reactive distillation, the pressure should be in the range from 3 to 15 bar and the temperature in the reaction zone from 55 to 75° C.
After the synthesis, MTBE or ETBE is separated from stream VB1 or FP1a, preferably by distillation. This method is also known to the person skilled in the art. Only then is VB1 or FP1a guided to distillation column DK2.
In the second distillation column DK2, the streams that both respectively comprise at least isobutane and 1-butene are separated in step (d) into at least one vapour stream BS2 which comprises at least isobutane and is withdrawn at the top of DK2, and at least one product stream which comprises at least 1-butene and is withdrawn at the bottom of DK2.
The distillation column DK2 used for the separation of the raffinate 2 stream may be any distillation column known to the person skilled in the art. Distillation column DK2 preferably contains internals. Suitable internals are for example trays, unstructured packings (random packings) or structured packings. Trays used are typically bubble-cap trays, sieve trays, valve trays having fixed or movable valves, tunnel-cap trays or slotted trays. Unstructured packings are generally beds of random packings. Random packings used are typically Raschig rings, Pall rings, Berl saddles, Super-Rings/Super-Rings Plus or Intalox® saddles. Structured packings are sold for example under the Mellapak® trade name by Sulzer. In addition to the internals mentioned, further suitable internals are known to those skilled in the art and may likewise be used.
Preferred internals have a low specific pressure drop per theoretical plate. Structured packings and random packing elements have, for example, a significantly lower pressure drop per theoretical plate than trays. This has the advantage that the pressure drop in distillation column DK2 remains as low as possible and hence the mechanical output of the compressor and the temperature of the stream to be evaporated remains low.
In a particularly preferred embodiment of the present invention, the second distillation column DK2 comprises a multitude of trays, preferably between 150 and 300 trays, further preferably between 170 and 220 trays.
What is meant in the context of the present invention by the withdrawal of the at least one vapour stream BS2 comprising at least isobutane at the top of distillation column DK2 is in particular that the at least one vapour stream BS2 is withdrawn as top stream or as side draw above the internals in distillation column DK2.
What is meant in the context of the present invention by the withdrawal of the at least one product stream comprising at least 1-butene at the bottom of distillation column DK2 is in particular that the at least one product stream is withdrawn directly at the bottom or at the lower tray of distillation column DK2. The product stream preferably contains at least 99% by weight of 1-butene, further preferably at least 99.5% by weight of 1-butene, more preferably at least 99.6% by weight of 1-butene. The 1-butene is the target product of the present process, and therefore the product stream is discharged from the process. The 1-butene may be used, for example, as a comonomer in the production of polyethylene.
It should be noted here that the separation sharpness in the first distillation column DK1 ultimately determines the purity of the 1-butene in the product stream which is withdrawn from the second distillation column DK2. This is because n-butane and the 2-butenes are likewise obtained as high boilers in DK2, and therefore with the 1-butene. This would contaminate the 1-butene. It should thus be ensured that the separation of the raffinate 2 stream in DK1 is run as far as possible such that barely any n-butane gets to DK2. It is therefore preferable that the stream guided to DK2 (1a, VB1 or FP1a) contains below 1500 ppm, preferably below 1200 ppm, more preferably below 900 ppm, of n-butane, based on the total amount of the stream.
The temperature at the bottom of the second distillation column DK2 during the process according to the invention is preferably in the range from 30 to 100° C., preferably 45 to 80° C. Further preferably, the pressure at the top of the second distillation column DK2 is in the range from 3 to 12 bar absolute, preferably 5 to 10 bar absolute.
Distillation column DK2 can also be operated with reflux. What is meant by “reflux” is that the vapour stream BS2 withdrawn at the top end of distillation column DK2 is at least partly fed back to distillation column DK2. In the cases where such a reflux is established, the reflux ratio is preferably 10 to 100, especially preferably 30 to 50.
The pressure ranges for the top pressure, i.e. the pressure at the top of distillation columns DK1 and DK2, was defined in the preceding paragraphs. In principle, it would accordingly be possible for the two columns to be operated in a dual-pressure connection, i.e. at a different pressure. It is then possible to transfer energy from the high-pressure column to the low-pressure column, in addition to the vapour compression described here. However, it is preferable in accordance with the invention that distillation columns DK1 and DK2 are operated at the same top pressure or a similar top pressure, where the top pressures in the case of similar top pressures differ by not more than 20%, preferably not more than 15%. Another advantageous factor, aside from a lower apparatus complexity, is a lower energy input. Finally, relative volatility will fall with rising pressure, and the required amount of energy for the separation task to be accomplished will become much greater in at least the high-pressure column.
Subsequently, in step (e), the vapour stream BS2 is at least partly compressed, giving rise to a compressed stream VB2 relative to the vapour stream BS2. The pressure of VB2 after the compression is higher than the pressure of BS2. The exact value for the pressure of VB2 can be set by the person skilled in the art depending on the requirements in the subsequent energy transfer, provided that the condition that pressure VB2>pressure BS2 is met. The quotient of pressure VB2/pressure BS2 (pressures each in bar abs.) is preferably in the range from 1.1 to 10, more preferably 1.2 to 8, more preferably 1.25 to 7, most preferably 1.3 to 6. It may be advantageous to heat stream BS2 prior to compression in order that no biphasic mixture is formed on compression. The heating can be conducted by means of internal (see WT-2 in
The temperature of substream VB2 is especially higher than the temperature of vapour stream BS2, and the quotient of temperature VB2/temperature BS2 (temperature in each case in K) is preferably in the range from 1.03 to 10, more preferably 1.04 to 9, more preferably 1.05 to 8, more preferably 1.06 to 7, more preferably 1.07 to 6, most preferably 1.08 to 5.
The at least one portion of vapour stream BS2 can be compressed in step (e) in any desired manner known to the person skilled in the art. For example, the compression can be performed mechanically and in a single-stage or multistage compression. In a multistage compression, it is possible to use two or more compressors of the same type or compressors of different types. A multistage compression can be effected with one or more compressor machines. The use of single-stage compression or multi-stage compression depends on the compression ratio and thus on the pressure to which vapour stream BS2 is to be compressed.
A suitable compressor in the process according to the invention, especially for compression of the vapour stream BS2 to VB2, is any compressor known to the person skilled in the art, preferably mechanical compressor, with which gas streams can be compressed. Suitable compressors are, for example, single-stage or multistage turbines, piston compressors, screw compressors, centrifugal compressors or axial compressors.
In step (f) of the process according to the invention, energy is transferred from the compressed stream VB2 to the stream in reboiler SV2. Step (f) lowers the energy of VB2, such that VB2 can be at least partly condensed. According to the invention, the phrase “transfer of energy” especially means “heating”, i.e. transfer of energy in the form of heat.
The transfer of energy from VB2 to the stream in the reboiler SV2, preferably the heating of the stream in the reboiler SV2 by VB2, is preferably direct. What is meant by direct transfer is that VB2 and the stream in SV2 do not come into contact, but energy, especially heat, is transferred from VB2 to the stream in SV2 without the presence of any additional heat transfer medium. Reboilers SV2 used may be the heat transferrers or heat exchangers that are familiar to the person skilled in the art, especially evaporators.
Once stream VB2 has passed through reboiler SV2 and transferred energy to the stream present therein, VB2 can be discharged from the process as isobutane stream IB1. But before VB2 is removed from the process as IB1, stream VB2, in a preferred embodiment of the present invention, is guided to a flash vessel and expanded therein to obtain a liquid phase FP2. The flash vessel may additionally comprise a condenser in order to condense a portion of the gaseous phase obtained.
At least a portion FP2a of the liquid phase FP2 can then be discharged from the process as isobutane stream IB1. For this purpose, in a particularly preferred embodiment, a pump is used. Under some circumstances and given a sufficient pressure ratio, it would also be possible that no pump is used. If a pump is used, it is possible to use pumps known to the person skilled in the art. Suitable pumps are, for example, standard chemical pumps. It is further preferable that a portion FP2b of the liquid phase FP1 other than FP2a is returned as reflux to the first distillation column DK2.
In the basic configuration of the present invention, the two streams BS1 and BS2 are each compressed with a single compressor. In a preferred embodiment of the present invention, the two streams BS1 and BS2 are compressed in a single compressor machine, preferably in multiple stages. The number of stages needed depends on the target compression ratio for the respective vapour streams BS1 and BS2.
The thermal integration by means of the vapour compression described here would also be combinable with other measures for thermal integration. It would also be possible here to provide one or more heat pump(s).
The present invention is hereinbelow elucidated with reference to figures. The figures are for illustration but are not to be understood as limiting.
For all the examples that follow, a raffinate 2 stream of 55 t/h was used. The raffinate 2 stream has the following composition: 1-butene 45.1%/n-butane 22.4%/trans-2-butene 15.9%/cis-2-butene 8.9%/isobutane 7.4%/isobutene 300 ppm and water 590 ppm.
The amount of energy needed for operation of the plants detailed in the examples for separation of 1-butene from raffinate 2 was calculated by a simulation using Aspen V10. The physical data were validated by operational data and operational trials.
In the embodiment shown in
The second distillation column DK2 is operated in a similar manner. For separation of the 1-butene from the isobutane from the distillate stream from DK1, a heating output of 10.2 MW is introduced in the second column DK2 by heating steam in reboiler SV2. In the bottom of DK2, 11.6 t/h of product stream is drawn off with a purity of 99.6 wt % of 1-butene. 3.6 t/h is drawn off at the top of DK2. The distillate stream consists to an extent of 95% of isobutane. The column is likewise operated at a top pressure of 6 bar abs. and a top temperature of 40° C. The pressure drop for 140 vertical trays is 1000 mbar. A bottom temperature of 56.6° C. is established.
Overall, in the interconnection shown in
A further trial was conducted with the interconnection shown in
Overall, in the interconnection shown in
A further trial was conducted with the interconnection shown in
Overall, in the interconnection shown in
A further trial was conducted with the interconnection shown in
In the embodiment shown in
A further trial was conducted with the interconnection shown in
A further trial was conducted with the interconnection shown in
In this embodiment, direct heat integration is conducted between columns DK1 und DK2 (as disclosed in DE 10 2005 062 700 A1) and is supplemented in accordance with the invention with a multistage vapour compression (see
The results of Examples 1 to 7 are summarized below in Table 1.
It is found that the inventive configuration of the process for 1-butene separation has the effect that much less external heating power has to be used than in the known solution. The savings potential is thus considerable. The electrical power additionally required for operation of the compressors is much smaller and can enable CO2-neutral operation when green power is used.
It is also found that an embodiment in which the two distillation columns DK1 and DK2 are operated at different pressure is disadvantageous because it requires the use of a greater amount of electrical energy.
| Number | Date | Country | Kind |
|---|---|---|---|
| 23213040.1 | Nov 2023 | EP | regional |
