Method for separating 1-butene from hydrocarbon stream using optimized steam compression excellent in energy efficiency

Abstract

To provide a method for separating 1-butene from a hydrocarbon stream, which can reduce energy and CO2 emission.SOLUTION: In a separation unit including at least two distillation columns of a first distillation column DK1 and a second distillation column DK2, a method according to the present invention separates 1-butene from a raffinate 2 flow containing at least 1-butene, 2-butene, n-butane, isobutene and isobutane, in which there is at least one reboiler SV1 in the DK1, and there is at least one reboiler SV2 in the DK2. The method includes: the at least one reboiler SV1 is fed with a stream which is withdrawn at a lower end of the first distillation column DK1 and, after passing through each reboiler, is guided back to the first distillation column DK1; and the at least one reboiler SV2 is fed with a stream which is withdrawn at a lower end of the second distillation column DK2 and, after passing through each reboiler, is guided back to the second distillation column DK2.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a method for separating 1-butene from a hydrocarbon stream containing at least 1-butene, 2-butene, n-butane and isobutane in a separation unit including a first distillation column DK1 and a second distillation column DK2 of at least two distillation columns. The present invention provides a method for recycling the condensation heat into the process by optimized vapor compression in order to save energy costs and reduce CO 2 emissions.

Background Art

[0002] 1-Butene can be obtained in large quantities from industrial C4 hydrocarbon streams, such as the C4 cut from a steam cracker or an FCC unit. The C4 hydrocarbon stream consists essentially of butadiene, the monoolefin isobutene, 1-butene and the two 2-butenes (cis and trans-2-butene), and the saturated hydrocarbons isobutane and n-butane. Due to the small difference in the boiling points of the components, their small separation factors and the formation of azeotropic mixtures, the post-treatment of the C4 hydrocarbon stream by distillation alone is difficult and uneconomical. Therefore, usually, butadiene is first separated by extractive distillation or selectively hydrogenated to butene. In each case, a C4 hydrocarbon stream (referred to as raffinate 1) containing not only the saturated hydrocarbons n-butane and isobutane but also the olefins isobutene, 1-butene and 2-butene remains, and the amount of butadiene present is small. Since the boiling points of 1-butene and isobutene are close to each other, generally, 1-butene cannot be economically separated from the corresponding C4 hydrocarbon stream by simple distillation. Therefore, isobutene is sufficiently removed to MTBE or ETBE, for example, by etherification with an alcohol, such as methanol or ethanol. When most of the reactivity of isobutene is removed, a C4 hydrocarbon stream (referred to as raffinate 2) containing linear butenes (1-butene and 2-butene) and the saturated hydrocarbons isobutane and n-butane is produced. 1-Butene can be separated from such C4 hydrocarbon streams and the like and is used in the chemical industry. The separation is carried out in a distillation unit including at least two distillation columns. Isobutane and 1-butene are obtained at the top of the first distillation column and sent to the second distillation column. Thereafter, isobutane and 1-butene are separated from each other in the second distillation column. The method is disclosed in, for example, Patent Document 1. In known methods, the energy required for the separation of C4 hydrocarbon streams is usually sent to the bottoms of the two distillation columns via heating steam. The heating steam can generally be utilized at a chemical production site. The cost factor cannot be underestimated when using heating steam in the volume required for the separation operation in question. Furthermore, when recycling the used heating steam, it is not always simple from a logistic point of view because the steam can only be returned within specific conditions (pressure, temperature, etc.). Furthermore, when heating steam is generated, a large amount of CO 2 is generated.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Therefore, an object of the present invention was to provide a method capable of reducing energy and CO 2 emissions compared to known methods and capable of being incorporated into existing equipment.

Means for Solving the Problems

[0005] This problem is solved by the embodiments of the method proposed in claim 1 of the present application. Preferred embodiments are described in the dependent claims. The method according to the invention is a method 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 a first distillation column DK1 and a second distillation column DK2 of at least two distillation columns, comprising the following: The DK1 has at least one reboiler SV1, and the DK2 has at least one reboiler SV2, the SV1 is withdrawn at the lower end of the DK1 and a stream is supplied which, after passing through each of the reboilers, is returned to the DK1, the SV2 is withdrawn at the lower end of the DK2 and a stream is supplied which, after passing through each of the reboilers, is returned to the DK2, a method comprising, wherein the following: (a) sending the raffinate 2 stream to the DK1, in which the DK1 separates into at least one vapor stream BS1 containing at least 1-butene and isobutane and withdrawn at the top of the DK1, and at least one bottom stream containing at least 1-butene and 2-butene and withdrawn at the bottom of the DK1, (b) compressing at least a portion of the BS1 to produce a compressed stream VB1 for the BS1, (c) transferring energy from the VB1 to the stream in the SV1, (d) sending at least a portion of the VB1 to the DK2, in which the DK2 separates into at least one vapor stream BS2 containing at least isobutane and withdrawn at the top of the DK2, and at least one bottom stream containing at least 1-butene and withdrawn at the bottom of the DK2, (e) compressing at least a portion of the BS2 to produce a compressed stream VB2 for the BS2, and (f) transferring energy from the VB2 to the stream in the SV2, relates to a method comprising.

[0006] One advantage of the process according to the invention is that the vapor streams BS1 and BS2 obtained in the two columns DK1 and DK2 are subjected to compression, and accordingly are improved in quality and utilized in the reboilers SV1 and SV2, whereby energy is sent to the bottom of the column. As a result of the energy transfer in the reboilers SV1 and SV2, even if there was heating steam to be used for heating the distillation columns DK1 and DK2, it would be significantly reduced. Thus, (almost) complete electrification of the energy-intensive process can be achieved, whereby green power can be used. Thereby, a considerable amount of energy costs and CO 2 emissions are saved.

[0007] In the present invention, the starting stream from which 1-butene is separated is a raffinate 2 stream containing at least 1-butene, 2-butene, n-butane and isobutane. The corresponding stream can be obtained, for example, as a C4 cut from a steam cracker or an FCC unit. As described above, raffinate 2 is formed by removing polyunsaturated C4 hydrocarbons, especially butadiene and isobutene, from the stream. For economic and technical reasons, complete removal is often not possible. However, the amount of polyunsaturated C4 hydrocarbons, especially butadiene, and isobutene should be minimized. The raffinate 2 used preferably contains less than 2500 ppm, preferably less than 1000 ppm, particularly preferably less than 500 ppm of isobutene. When more isobutene is present in the starting stream, MTBE synthesis or ETBE synthesis (methyl-tert-butyl ether = MTBE / ethyl-tert-butyl ether = ETBE) can be carried out between the two distillation columns DK1 and DK2, and after reacting isobutene with methanol (in the case of MTBE) or ethanol (ETBE), MTBE or ETBE can be separated (European Patent Application Publication No. 1806330 or No. 1813588). Thus, the concentration of isobutene upstream of the second distillation column DK2 can be significantly reduced. This is because isobutene is obtained from the bottom of the second distillation column, i.e., from 1-butene. More preferably, raffinate 2 used in the method of the present invention contains less than 4% by mass of polyunsaturated C4 hydrocarbons. In a particularly preferred embodiment, the concentration of polyunsaturated C4 hydrocarbons should be less than 500 ppm. When the stream contains a larger amount of butadiene, selective hydrogenation to convert butadiene to butene and / or butane can be carried out in advance. A corresponding method is described for those skilled in the art, for example, in European Patent Application Publication No. 3680224. The raffinate 2 stream used may further contain a predetermined amount of water, particularly in an amount of 150 to 4000 ppm. The water is preferably at least partially separated by the method described herein. The water accumulates in the vapor streams BS1 and BS2 respectively in the two distillation columns DK1 and DK2, and is obtained as a second liquid phase after condensation, which can be separated via a pipe in the distillate vessel of the distillation column DK1 and / or DK2. The bottom products of the distillation columns DK1 and DK2 are characterized in that the contents of butadiene and water are extremely low, preferably less than 100 ppm each, more preferably less than 5 ppm each.

[0008] The method according to the present invention is carried out in a separation unit including at least two distillation columns DK1 and DK2. The distillation column DK1 is the first distillation column and has at least one reboiler SV1. The distillation column DK2 is the second distillation column and has at least one reboiler SV2. In a preferred embodiment, there is only the reboiler SV1 in the distillation column. Also, it is preferable that there is only the reboiler SV2 in the distillation column DK2. The pressures in the two distillation columns DK1 and DK2 should be selected such that the compression of the volumetric flows BS1 and BS2 is not too energy-intensive, and in particular, the separation operation is facilitated by the influence of relative volatility. The terms "first distillation column", "distillation column DK1" and "DK1" should be considered synonymous in the context of the present invention. The terms "second distillation column", "distillation column DK2" and "DK2" should also be considered synonymous in the context of the present invention. The energy required for the separation operation is sent to the first distillation column DK1 via the reboiler SV1. The reboiler SV1 is supplied with the stream withdrawn at the lower end of the distillation column DK1 and returned to DK1 after passing through each reboiler. The stream is heated when passing through the reboiler SV1. This situation is comparable to the reboiler SV2 of the second distillation column DK2, and thus the energy required for the separation operation is sent. Therefore, the reboiler SV2 is supplied with the stream withdrawn at the lower end of the distillation column DK2 and returned to the distillation column DK2 after passing through each reboiler. The stream is heated when passing through the reboiler SV2 and at least partially evaporates.

[0009] In the present invention, a "reboiler" refers to an evaporator that heats the bottom of each distillation column. The reboiler is usually arranged outside each distillation column. Since the reboiler transfers energy, particularly heat, from one stream to another, it is a heat transfer body. The stream to be evaporated is withdrawn from the bottom of the distillation column through the extraction section and supplied to the reboiler. The evaporated stream is returned to each distillation column in the bottom region via at least one supply section, regardless of the presence or absence of the liquid residue. 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 evaporators commonly used in the case of natural circulation evaporators and forced circulation evaporators are shell and tube or plate devices. In addition to the above, any other design of evaporators known to those skilled in the art and suitable for use in distillation columns may be alternatively used.

[0010] The raffinate 2 sent to the first distillation column DK1 is separated in the distillation column DK1 into at least two streams, namely, at least one vapor stream BS1 taken out at the top of the distillation column DK1, which contains at least 1-butene and isobutane, and at least one bottom stream taken out at the bottom of the distillation column DK1, which contains at least 1-butene and 2-butene. This bottom stream can introduce oligomerization (not shown). The vapor stream BS1 may be taken out at the top of the distillation column in the form of a plurality of sub-streams BS1n (n is an integer and equal to the number of sub-streams). The same applies to the bottom stream. The bottom temperature of the first distillation column DK1 is preferably in the range of 40 to 110°C, preferably 50 to 100°C. In principle, the raffinate 2 stream can be sent to the first distillation column DK1 via one or more supply points. If significant fluctuations in the feed concentration are expected, it may be desirable to provide a plurality of different supply points. The optimal position can be found, for example, by simulation via minimization of the energy requirement. When treating a plurality of feed streams with different compositions, the optimal supply point can be determined in the same way for each feed. Also, in principle, even if the raffinate 2 stream has the same or a constant composition, it may be pre-divided into a plurality of sub-streams. In this case, the raffinate 2 stream is sent to the distillation column DK1 in the form of two or more separate streams. In this case, it is advantageous if the supply locations of the individual streams are at substantially the same height on the distillation column DK1.

[0011] The pressure and temperature of the vapor stream BS1 are specified below. This relates in particular to the pressure and temperature of at least one vapor stream BS1 when at least one vapor stream BS1 is taken out from the distillation column DK1. The pressure of the vapor stream BS1 is in particular in the range of 6 to 15 bar (absolute pressure), preferably in the range of 7.5 to 13 bar (absolute pressure). The temperature of the vapor stream BS1 is in particular in the range of 45°C to 120°C, preferably in the range of 48°C to 100°C, more preferably in the range of 50°C to 90°C, even more preferably in the range of 55°C to 80°C, and most preferably in the range of 60°C to 80°C. The distillation column DK1 used for the separation of the raffinate 2 stream can be any distillation column known to those skilled in the art. The distillation column DK1 preferably includes internal structures. Suitable internal structures are, for example, trays, unstructured packings (random packings) or structured packings. The trays used are usually bubble cap trays, sieve trays, valve trays with fixed or movable valves, tunnel cap trays or slot trays. Unstructured packings are generally beds of random packings. The random packings used are usually Raschig rings, Pall rings, Berl saddles, Super-Rings / Super-Rings Plus or Intalox (registered trademark) saddles. Structured packings are sold, for example, under the trade name Mellapack (registered trademark) by Sulzer. The above internal structures and further suitable internal structures are known to those skilled in the art and can be used similarly. The specific pressure drop per theoretical stage of the preferred internal structures is low. The pressure drop per theoretical stage of structured packings and random packings is, for example, significantly lower in terms of pressure loss per theoretical stage than that of trays. This has the advantage that the pressure drop in the distillation column DK1 is kept as low as possible, so that the mechanical output of the compressor and the temperature of the raffinate 2 stream to be evaporated are kept low.

[0012] In a particularly preferred embodiment of the present invention, the distillation column DK1 includes a large number of trays, preferably 150 to 300 trays, more preferably 170 to 220 trays. In the context of the present invention, taking out at least one vapor stream BS1 containing at least 1-butene and isobutane at the top of the distillation column DK1 means, in particular, that at least one vapor stream BS1 is taken out as a top stream or as a side draw above the internal structure of the distillation column DK1. Within the scope of the present invention, taking out at least one vapor stream containing at least 1-butene and 2-butene at the bottom of the distillation column DK1 means, in particular, that at least one bottom stream is taken out directly at the bottom or bottom tray of the distillation column DK1.

[0013] The distillation column DK1 is preferably operated in reflux. "Reflux" means that the vapor stream BS1 withdrawn at the upper end of the distillation column DK1 is at least partially fed back to the distillation column DK1. The reflux ratio when establishing the reflux is preferably 2 to 30, more preferably 5 to 20, and particularly preferably 8 to 15. Reflux can be established by attaching a condenser to the top of the distillation column DK1. The vapor stream BS1 is partially condensed in the condenser and fed back to the distillation column DK1. The vapor stream can be applied as reflux to the distillation column only after compression and expansion. Generally, and in the context of the present invention, the reflux ratio means the ratio of the mass flow rate (kg / h) withdrawn from the column that is returned to the column in liquid form (reflux) to the ratio of the mass flow rate (kg / h) discharged from each column in liquid or gaseous form.

[0014] After the withdrawal of the vapor stream BS1, the vapor stream BS1 is compressed to produce a compressed stream VB1 for the vapor stream BS1. It may be advantageous to heat the stream BS1 before compression so that a two-phase mixture is not formed during compression. The heating may be carried out by an internal heat source (see WT1 in FIGS. 6 and 7 of the present application) or an external heat source. The pressure of VB1 after compression is higher than the pressure of BS1. The exact value of the pressure of VB1 can be set by those skilled in the art according to the requirements in subsequent energy transfer as long as the condition that the pressure VB1 > the pressure BS1 is satisfied. The value of the quotient of the pressure VB1 / pressure BS1 (pressure in each bar absolute) is preferably in the range of 1.1 to 10, more preferably 1.2 to 8, more preferably 1.25 to 7, and most preferably 1.3 to 6. The temperature of the sub-stream VB1 is preferably higher than the temperature of the vapor stream BS1, and the quotient of the temperature VB1 / temperature BS1 (the temperature is in K respectively) is preferably in the range of 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, and most preferably 1.08 to 5.

[0015] At least a part of the vapor stream BS1 can be compressed in any desired manner known to those skilled in the art in the above (b). For example, the compression can be carried out mechanically and in one or multiple stages. In this case, "one stage" means that the compression is carried out from one pressure level to another pressure level. "Multiple stages" means that the compression is first carried out to pressure level X and then from X to pressure level Y. In multi-stage compression, two or more compressors of the same type or different types of compressors can be used. Multi-stage compression can be carried out using one or more compressors. Whether one-stage compression or multi-stage compression is used depends on the compression ratio and thus on the pressure at which the vapor stream BS1 is compressed. In the method according to the invention, a compressor particularly suitable for compressing the vapor stream BS1 to VB1 is any compressor known to those skilled in the art that can compress a gas stream, preferably a mechanical compressor. Suitable compressors are, for example, one-stage or multi-stage geared turbocompressors, piston compressors, screw compressors, centrifugal compressors or axial flow compressors.

[0016] In the above (c) of the method according to the invention, energy is transferred from the compressed stream VB1 to the stream in the reboiler SV1. In the above (c), the energy of VB1 can be reduced to preferably at least partially condense VB1. In the present invention, the term "energy transfer (movement)" particularly means heating, i.e., the 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. Direct transfer means that VB1 does not come into direct contact with the stream in SV1, but energy, particularly heat, is transferred from VB1 to the stream in SV1 without the presence of an additional heat transfer medium. As the reboiler SV1, a heat exchanger or heat exchanger known to those skilled in the art, particularly an evaporator, can be used. In a preferred embodiment, before the stream VB1 is sent to the second distillation column according to the above (d), the stream VB1 is sent to a flash vessel where it expands to obtain a liquid phase FP1. The flash vessel may further include a condenser to condense the obtained gaseous phase portion.

[0017] Thereafter, at least a portion FP1a of the liquid phase FP1 is sent to the distillation column DK2 in the above (d). For this purpose, a pump is preferably used in a particularly preferred embodiment. Here, a pump known to those skilled in the art may be used. A suitable pump is, for example, a standard chemical pump. Furthermore, it is preferable to reflux the flow FP1b of the other portion other than FP1a of the liquid phase FP1 to the first distillation column DK1. It is particularly preferable to transfer energy from the flow FP1b of the other portion to the raffinate 2 flow before the raffinate 2 flow is sent to the first distillation column DK1. Thereby, the raffinate 2 flow is preheated. This is energetically advantageous because less energy is sent for the separation operation via the reboiler. The transfer of energy from FP1b to the raffinate 2 flow, preferably the heating of the raffinate 2 flow by FP1b, is preferably direct, that is, without using an additional heat transfer medium. For this purpose, as described above, a heat transfer device or heat exchanger known to those skilled in the art may be used. Therefore, the flow VB1 or the flow FP1a is sent to the second distillation column DK2. If the amount of isobutene in the flow VB1 or the flow FP1a is too high to meet the specifications for the 1-butene product from DK2, as described above, additional MTBE synthesis or ETBE synthesis may be arranged between the distillation columns DK1 and DK2. For this purpose, the flow VB1 or the flow FP1a is supplied to the MTBE synthesis or ETBE synthesis, and the isobutene present is at least partially converted to MTBE or ETBE. MTBE or ETBE synthesis is generally known to those skilled in the art. To produce MTBE or ETBE from an isobutene-containing stream, an acidic ion exchange resin (sulfonic group) may be used as a heterogeneous catalyst, for example. The synthesis of MTBE or ETBE can be carried out in one or more reactors connected in series. 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 the removal of MTBE or ETBE occur simultaneously. The pressure of the reactive distillation is in the range of 3 to 15 bar, and the temperature of the reaction zone should be 55 to 75 °C.

[0018] After synthesis, MTBE or ETBE is preferably separated from stream VB1 or stream FP1a by distillation. This method is also known to those skilled in the art. Only then is stream VB1 or stream FP1a sent to distillation column DK2.

[0019] In the second distillation column DK2, a stream containing at least isobutane and 1-butene each is separated into at least one vapor stream BS2, which contains at least isobutane in (d) above and is taken out at the top of distillation column DK2, and at least one product stream, which contains at least 1-butene and is taken out at the bottom of distillation column DK2. The distillation column DK2 used for the separation of the raffinate 2 stream can be any distillation column known to those skilled in the art. The distillation column DK2 preferably includes internal structures. Suitable internal structures are, for example, trays, unstructured packings (random packings) or structured packings. The trays used are usually bubble cap trays, sieve trays, valve trays with fixed valves or movable valves, tunnel cap trays or slot trays. Unstructured packings are generally beds of random packings. The random packings used are usually Raschig rings, Pall rings, Berl saddles, Super-Rings / Super-Rings Plus or Intalox (registered trademark) saddles. Structured packings are sold, for example, under the trade name Mellapack (registered trademark) by Sulzer. The above internal structures and further suitable internal structures are known to those skilled in the art and can be used similarly. The pressure drop per theoretical stage of the preferred internal structures is low. The pressure drop per theoretical stage of structured packings and random packings is significantly lower than that of trays, for example. This has the advantage that the pressure loss in the distillation column in distillation column DK2 is kept as low as possible, and thus the mechanical output of the compressor and the temperature of the stream to be evaporated are kept low.

[0020] In a particularly preferred embodiment of the present invention, the second distillation column DK2 includes a large number of trays, preferably 150 to 300 trays, more preferably 170 to 220 trays. In the context of the present invention, taking out at least one vapor stream BS2 containing at least isobutane at the top of the distillation column DK2 means, in particular, that at least one vapor stream BS2 is taken out as a top stream or as a side draw above the interior of the distillation column DK2. In the context of the present invention, taking out at least one product stream containing at least 1-butene at the bottom of the distillation column DK2 means, in particular, that at least one product stream is taken out directly at the bottom of the distillation column DK2 or at a tray below. The product stream preferably contains at least 99% by mass of 1-butene, more preferably at least 99.5% by mass of 1-butene, and even more preferably at least 99.6% by mass of 1-butene. 1-Butene is the target product of the process of the present invention and thus the product stream is discharged from the process. 1-Butene may be used, for example, as a comonomer in the production of polyethylene.

[0021] Here, it should be noted that the purification degree of the separation in the first distillation column DK1 ultimately determines the purity of 1-butene in the product stream taken out from the second distillation column DK2. This is because n-butane and 2-butene are likewise obtained as high-boiling substances in the distillation column DK2, i.e., together with 1-butene. This contaminates the 1-butene. Therefore, the separation of the raffinate 2 stream in the distillation column DK1 should be carried out reliably so that hardly any n-butane reaches the distillation column DK2. Therefore, it is preferred that the n-butane contained in the stream (1a, VB1 or FP1a) sent to the distillation column DK2 is less than 1500 ppm, preferably less than 1200 ppm, more preferably less than 900 ppm, based on the total amount of the stream. Through the process according to the present invention, the temperature at the bottom of the second distillation column DK2 is preferably in the range of 30 to 100 °C, preferably 45 to 80 °C. More preferably, the pressure at the top of the second distillation column DK2 is in the range of 3 to 12 bar (absolute pressure), preferably 5 to 10 bar (absolute pressure).

[0022] The distillation column DK2 can operate under reflux. "Reflux" means that at least part of the vapor stream BS2 withdrawn at the upper end of the distillation column DK2 is returned to the distillation column DK2. The reflux ratio when such reflux is established is preferably 10 to 80, particularly preferably 30 to 50. The top pressure, i.e., the pressure range at the top of the distillation columns DK1 and DK2, is as defined in the previous stage. Therefore, in principle, the two columns can be operated in a double-pressure connection, i.e., at different pressures. In that case, in addition to the vapor compression described here, energy can be transferred from the high-pressure column to the low-pressure column. However, in the present invention, the distillation columns DK1 and DK2 can operate at the same top pressure or similar top pressures, where the difference in top pressure is preferably 20% or less, more preferably 15% or less, when the top pressures are similar. Another advantageous factor other than the low complexity of the device is the low energy input. Finally, the relative volatility decreases with increasing pressure, and the amount of energy required for the separation operation to be achieved becomes extremely large, at least in the high-pressure column.

[0023] Thereafter, in the above (e), the vapor stream BS2 is at least partially compressed to produce a compressed stream VB2 for the vapor stream BS2. The pressure of VB2 after compression is higher than the pressure of BS2. The exact value of the pressure of VB2 can be set by those skilled in the art according to the requirements in subsequent energy transfer as long as the condition that pressure VB2 > pressure BS2 is satisfied. The value of pressure VB2 / pressure BS2 (pressures in absolute bar respectively) is preferably in the range of 1.1 to 10, more preferably 1.2 to 8, more preferably 1.25 to 7, and most preferably 1.3 to 6. It may be advantageous to heat the stream BS2 before compression so that a two-phase mixture is not formed during compression. The heating may be carried out by an internal heat source (refer to WT-2 in Figures 6 and 7 of the present application) or an external heat source. The temperature of the sub-stream VB2 is preferably higher than the temperature of the vapor stream BS2, and the value of temperature VB2 / temperature BS2 (temperatures are in K respectively) is preferably in the range of 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, and most preferably 1.08 to 5.

[0024] At least a portion of the vapor stream BS2 can be compressed in any desired manner known to those skilled in the art in said (e). For example, the compression can be carried out mechanically and in one or multiple stages. In multi-stage compression, two or more compressors of the same type or different types of compressors may be used. Multi-stage compression may be carried out using one or more compressors. Whether one-stage or multi-stage compression is used depends on the compression ratio and thus on the pressure to which the vapor stream BS2 is compressed. In the method according to the invention, a compressor particularly suitable for compressing the vapor stream BS2 to VB2 is any compressor known to those skilled in the art that can compress a gas stream, preferably a mechanical compressor. Suitable compressors are, for example, single-stage or multi-stage geared turbocompressors, piston compressors, screw compressors, centrifugal compressors or axial flow compressors.

[0025] In said (f) of the method according to the invention, energy is transferred from the compressed stream VB2 to the stream in the reboiler SV2. In said (f), the energy of VB2 can be reduced to preferably at least partially condense VB2. The term "energy transfer (transfer)" in the present invention particularly means heating, i.e., the 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. Direct transfer means that VB2 and the stream in SV2 do not come into direct contact, but energy, particularly heat, is transferred from VB2 to the stream in SV2 without the presence of an additional heat transfer medium. As the reboiler SV2, a heat exchanger or heat exchanger known to those skilled in the art, particularly an evaporator, may be used. After the stream VB2 passes through the reboiler SV2 and transfers energy to the stream present therein, VB2 can be discharged from the process as the isobutane stream IB1. However, in a preferred embodiment of the invention, before VB2 is removed from the process as IB1, the stream VB2 is sent to a flash vessel where it is expanded to obtain the liquid phase FP2. The flash vessel may further include a condenser to condense the obtained gaseous phase portion. Thereafter, at least a portion FP2a of the liquid phase FP2 can be discharged from the process as an isobutane stream IB1. For this purpose, a pump is preferably used in a particularly preferred embodiment. In certain situations, a pump may not be necessary if a sufficient pressure ratio is provided. When using a pump, a pump known to those skilled in the art may be used. A suitable pump is, for example, a standard chemical pump. Further, it is preferable to reflux the flow FP2b of the other portion of the liquid phase FP1 other than FP2a to the first distillation column DK2. In the basic configuration of the present invention, the two streams BS1 and BS2 are each compressed by a single-stage compressor. In a preferred embodiment of the present invention, the two streams BS1 and BS2 are compressed by a single-stage compressor, preferably in a plurality of stages. The number of required stages depends on the target compression ratio of the vapor streams BS1 and BS2, respectively. The heat integration by the heat pump described herein may be used in combination with other means for heat integration. Here, one or more heat pumps may be provided. The present invention will be described below with reference to the drawings. The drawings are for illustrative purposes only and should not be construed as limiting.

Brief Description of the Drawings

[0026]

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Figure 9

Mode for Carrying Out the Invention

[0027] For all of the following examples, a raffinate 2 stream of 55 t / h was used. The composition of the raffinate 2 stream was as follows: 45.1% 1-butene / 22.4% n-butane / 15.9% trans-2-butene / 8.9% cis-2-butene / 7.4% isobutane / 300 ppm isobutene and 590 ppm water. The amount of energy required for the operation of the plant described in the examples for separating 1-butene from raffinate 2 was calculated by simulation using Aspen V10. The physical data was verified by operating data and operating tests.

Example

[0028] [Example 1 (not of the present invention)] In the embodiment according to FIG. 1, raffinate 2 of the above composition is sent to distillation column DK1. The column was operated at a top pressure of 6 bar (absolute pressure). The maximum temperature is 43°C. 140 theoretical trays are included in the simulation. The stream with decreasing 1-butene (raffinate 3) is withdrawn through the bottom of the column. The bottom temperature is 62°C. A pressure drop of 1000 mbar in DK1 is included in the simulation. A distillate stream in an amount of 15.2 t / h containing about 77% by mass of 1-butene and about 22% by mass of isobutane is withdrawn through the top of the column. 15 MW of heating output is required for distillation in DK1, which is sent to the column by heating steam via reboiler SV1. The second distillation column DK2 is operated in the same way. To separate 1-butene from the isobutane in the distillate stream from DK1, 10.2 MW of heating output is sent to the second column DK2 by heating steam in reboiler SV2. At the bottom of DK2, a product stream of 11.6 t / h is withdrawn with a purity of 99.6% by mass of 1-butene. 3.6 t / h is withdrawn at the top of DK2. The distillate stream consists of 95% isobutane. The column is operated in the same way at a top pressure of 6 bar (absolute) and a top temperature of 40°C. The pressure drop of 140 vertical trays is 1000 mbar. A bottom temperature of 56.6°C is established. Overall, in the interconnection shown in FIG. 1, 25.2 MW of heating steam provided from the outside must be used.

[0029] [Example 2 (not of the present invention)] Further trials were conducted using the interconnections shown in FIG. 2. In contrast to FIG. 1 and Example 1, there is vapor compression in distillation column DK1. Therefore, the vapor stream from DK1, BS1 is compressed to 11 bar (absolute pressure) by compressor V1. As a result, a compressed vapor stream VB1 is obtained, which can be condensed in reboiler SV1. The vapor stream compressed at 11 bar (absolute pressure) condenses at 73 °C. 1.6 MW of electric power is required for the compression operation. 15 MW can be transferred via SV1. Overall, 10.2 MW of heating steam provided from the outside must be used in the interconnection shown in FIG. 2.

[0030] [Example 3 (not of the present invention)] Further trials were conducted using the interconnections shown in FIG. 3. In contrast to FIG. 1 and Example 1, there is vapor compression in distillation column DK2. Therefore, 1.0 MW of electric power is required to compress vapor BS2 to a higher pressure level of 11.7 bar (absolute pressure), and thus the heat of condensation can be utilized in SV2. 10.2 MW can be transferred. Overall, 15 MW of heating steam provided from the outside and 1.0 MW of electric power must be used in the interconnection shown in the figure.

[0031] Example 4 (the present invention) Further trials were conducted using the interconnections shown in FIG. 4. The heat integration according to the present invention is provided here to distillation columns DK1 and DK2. For this purpose, at least a two-stage single compressor can be installed, or two individual compressors can be used. Compress both vapor streams to the required pressure level to create a driving temperature difference of about 10 K and recycle the heat of condensation to the process (see Examples 2 and 3). Therefore, in the illustrated interconnection, both columns DK1 and DK2 can be fully energized. In the embodiment shown in FIG. 4, there is no need to use heating steam supplied from the outside. The electric power required for the operation of the compressor is only 2.6 MW.

[0032] Example 5 (the present invention) ​​​​Further tests were carried out using the interconnections shown in FIG. 6. The difference from FIG. 4 is that there are additional vapor streams BS1 and BS2 and preheating of the feed stream. The excess heat generated by the introduction of power does not need to be removed by additional cooling operations and is used for the vapor streams in heat exchangers WT1 and WT2 and for preheating the feed stream in preheaters VW1 and VW2. Thus, in Example 4, the power required by the compressor of 2.6 MW can be reduced to a total of 2.3 MW. Similarly, there is no need to use externally supplied heating steam.

[0033] Example 6 (the present invention) Further tests were carried out using the interconnections shown in FIG. 7. The difference from FIG. 6 was the presence of the MTBE unit. In the interconnections shown here, isobutene passes through the top of DK1 and remains at the bottom of DK2. That is, isobutene follows 1-butene and can hardly be separated from 1-butene in this interconnection. Therefore, the concentration increases. If a second MTBE stage is included between DK1 and DK2, the isobutene concentration in 1-butene can be reduced. Therefore, the separation of n-butane in column DK1 does not need to be carried out as abruptly anymore. Furthermore, more isobutane can be left in the bottom. Thus, overall, an additional 200 kW of power can be saved.

[0034] [Example 7 (not of the present invention)] ​​In this embodiment, direct heat integration is carried out between columns DK1 and DK2 (as disclosed in Patent Document 1) and complemented by multi-stage vapor compression according to the present invention (see Fig. 9). In this case, column DK1 operates at a top pressure of 11 bar and column DK2 operates at a top pressure of 7 bar. Therefore, part of the vapor stream BS1 can be used to transfer heat through the reboiler SV2a in DK2. The 4.0 MW of condensation heat from DK1 can be utilized through a single-stage vapor compression by compressor V1 and sent to DK1 through the second reboiler SV1a. For this purpose, 382 kW of electric power has to be applied to compressor V1. Furthermore, the vapor from DK2 is compressed to utilize the 9.9 MW of condensation heat from DK2 in DK1. The condensation heat increased by compressor V2 is transferred through a further reboiler SV1b. For this purpose, 2.6 MW of electric power is required. Using 2.98 MW of electrical energy, a total of 11.5 MW can be transferred through SV1b.

[0035] The results of Examples 1 to 7 are summarized in Table 1 below.

[0036]

Table 1

Claims

1. 1. 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, a first distillation column DK1 and a second distillation column DK2, the process comprising the steps of: DK1 has at least one reboiler SV1, and DK2 has at least one reboiler SV2; The SV1 is withdrawn from the lower end of the DK1 and is supplied with a stream that is returned to the DK1 after passing through the reboiler, The SV2 is withdrawn at the lower end of the DK2 and is supplied with a stream that is returned to the DK2 after each passing through the reboiler, wherein: (a) sending said raffinate 2 stream to said DK1 and separating it in said DK1 into at least one vapor stream BS1 comprising at least 1-butene and isobutane, which is withdrawn at the top of said DK1, and at least one bottom stream comprising at least 1-butene and 2-butene, which is withdrawn at the bottom of said DK1; (b) compressing at least a portion of the BS1 to produce a compressed flow VB1 relative to the BS1; (c) transferring energy from said VB1 to a flow in said SV1; (d) at least partially sending said VB1 to said DK2 and separating it in said DK2 into at least one vapor stream BS2 comprising at least isobutane, which is withdrawn at the top of said DK2, and at least one bottom stream comprising at least 1-butene, which is withdrawn at the bottom of said DK2; (e) compressing at least a portion of the BS2 to produce a compressed flow VB2 relative to the BS2; and (f) transferring energy from said VB2 to a flow in said SV2; A method comprising:

2. 2. The method of claim 1, wherein said DK1 and said DK2 operate at the same or similar maximum pressures, where the difference in the similar maximum pressures is within 20% or 15% of each other.

3. 3. The process according to claim 1 or 2, wherein an MTBE synthesis or an ETBE synthesis is arranged between DK1 and DK2, and VB1 is supplied thereto.

4. The process according to any one of claims 1 to 3, wherein the VB1 is sent to a flash vessel where it is expanded to provide a liquid phase FP1 of the VB1.

5. 5. The method according to claim 4, wherein at least a portion FP1a of the liquid phase FP1 is fed to said DK2, preferably by means of a pump.

6. 6. The method according to claim 5, wherein the other part of the liquid phase FP1, stream FP1b, is returned to said DK1 as reflux.

7. 7. The process according to any one of claims 1 to 6, wherein energy is transferred from stream FP1b to the raffinate 2 stream before the latter is sent to DK1.

8. The process according to any one of claims 1 to 7, wherein the temperature of the bottom of DK1 is in the range of 40 to 110 ° C. or 50 to 100 ° C.

9. The process according to any one of claims 1 to 8, wherein the temperature of the bottom of DK2 is in the range of 30 to 100 ° C. or 45 to 80 ° C.

10. The method of any one of claims 1 to 9, wherein said DK1 has between 150 and 300 plates.

11. The method according to any one of claims 1 to 10, wherein said DK2 has between 150 and 300 plates.

12. The method according to any one of claims 1 to 11, wherein said BS1 and said BS2 are compressed using only a single compressor.

13. The process of any one of claims 1 to 12, wherein the VB2 is expanded in a flash vessel to obtain a liquid phase FP2.

14. 13. The process according to claim 12, wherein at least a portion FP2a of the liquid phase FP2 is discharged from the process as a product stream, preferably by means of a pump.

15. 14. The process according to claim 13, wherein another portion FP2b of the liquid phase FP2 is returned to said DK2 as reflux.

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