Apparatus and method for separating and purifying styrene from crude mixture comprising styrene
By designing a connection method between a distillation tower with a specific structure and a liquid-liquid extraction washing tower, the problems of high energy consumption and large capital expenditure in the existing technology are solved, and high-purity styrene production with low energy consumption and low CAPEX is achieved.
Patent Information
- Application Number
- CN202480014710.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2023-03-08
- Filing Date
- 2024-02-26
- Publication Date
- 2025-10-03
AI Technical Summary
The existing technology has high energy requirements and capital expenditures during the separation and purification process from the crude styrene mixture and it is difficult to obtain a high-purity styrene product.
A device is used, which includes a steam generation unit, a liquid-liquid extraction washing tower and a distillation tower. The distillation tower has a specific cross-sectional area design and multiple outlet pipeline connection methods, which reduces energy consumption and equipment CAPEX, and realizes the production of high-purity styrene through the liquid-liquid extraction washing tower.
It achieves low energy consumption and low CAPEX styrene purification, producing high-purity styrene products with a content of 95% to 99%.
Smart Images
Figure CN120752076A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to an apparatus and a method for separating and purifying styrene from a crude mixture comprising styrene. Background Art
[0002] Styrene is an important building block in polymers such as polystyrene, acrylonitrile-butadiene-styrene / styrene-acrylonitrile resins, styrene-butadiene copolymer latex, unsaturated polyester resins, styrene-butadiene rubber elastomers, and latex. It is one of the most highly traded commodity chemicals; over 30% of annual styrene production is traded internationally. Styrene is primarily produced using benzene and ethylene as feedstocks, where benzene is alkylated with ethylene to form ethylbenzene, and ethylbenzene is converted to styrene via a dehydrogenation process or an ethylbenzene / styrene monomer process or a propylene oxide / styrene monomer process, respectively. Typically, styrene plants are located near ethylene crackers due to ethylene's gaseous nature, which makes it relatively difficult to transport compared to benzene.
[0003] In addition to dedicated production routes via the ethylbenzene / styrene monomer process or the propylene oxide / styrene monomer process, styrene is also present in hydrocarbon streams such as pyrolysis gasoline obtained from the steam cracking of naphtha, hydrocarbon fractions obtained from the thermal or catalytic pyrolysis of waste polystyrene, and hydrocarbon fractions obtained from the thermal or catalytic pyrolysis of various waste plastics. Styrene extraction from these hydrocarbon streams presents an economically attractive opportunity for operators due to the low cost of the raw materials. The field of styrene production from waste polystyrene has garnered particular attention due to the current global plastics recycling challenges. Waste plastics pose a significant environmental threat. However, such separation is technically difficult due to the presence of molecules with similar boiling points and impurities from the starting materials. For example, during polystyrene recycling, different types of waste polystyrene are fed into catalytic or pyrolysis reactors. Due to the contamination of waste plastics coupled with the production of other close boiling point compounds (e.g., benzene, toluene, ethylbenzene, α-methylstyrene, isopropylbenzene, n-propylbenzene, etc.) produced during the pyrolysis or catalytic steps, a reliable method is needed to purify this styrene oil to the final ASTM grade styrene specifications.
[0004] Separating and purifying styrene from a crude mixture containing styrene (such as that produced by any of the aforementioned processes) is typically performed using extractive distillation, in which the crude mixture is distilled in the presence of an extractive solvent, which is typically a miscible, relatively non-volatile component with a relatively high boiling point. To reduce the temperature required for extractive distillation, steam is often added to the distillation column as a desorbent, in addition to the crude mixture containing styrene and the extractive solvent. The extractive solvent changes the fugacity of appropriate components in the crude mixture, where fugacity is the corrected partial vapor pressure of the mixture. This facilitates the separation of substances that would be very difficult to separate using conventional distillation due to their similar boiling points. These extractive distillation-based purification processes are typically performed using two or three columns and are energy-intensive and require high capital expenditures (CAPEX).
[0005] In view of the above, an object underlying the present invention is to provide a plant for separating and purifying styrene from a crude mixture comprising styrene, which plant has only low energy requirements during its operation, requires low CAPEX and allows the production of very pure styrene compositions. Summary of the Invention
[0006] According to the present invention, this object is met by providing an apparatus, in particular for separating and purifying styrene from a crude mixture comprising styrene, wherein the apparatus comprises a steam generation unit, a liquid-liquid extraction scrubbing column and a distillation column, wherein the distillation column comprises a top section and a bottom section, wherein at least a portion of the bottom section extending over at least 10% of the height of the distillation column has a smaller cross-sectional area than the top section of the distillation column, wherein the distillation column further comprises an inlet line for feed, an inlet line for extraction solvent, an inlet line for steam connected to the steam generation unit, a top outlet line, a bottom outlet line, and a side outlet line arranged below the top outlet line and above the bottom outlet line, wherein i) the tower top outlet pipeline is directly connected to a liquid-liquid extraction washing tower, or the tower top outlet pipeline is directly or indirectly connected to a liquid-liquid separator comprising a water outlet pipeline and a hydrocarbon outlet pipeline, wherein the water outlet pipeline is connected to the liquid-liquid extraction washing tower, and ii) the side outlet pipeline is directly connected to the liquid-liquid extraction scrubber, or the side outlet pipeline is directly or indirectly connected to a liquid-liquid separator comprising a water outlet pipeline and a hydrocarbon outlet pipeline, wherein the hydrocarbon outlet pipeline is connected to the liquid-liquid extraction scrubber, and wherein the water outlet pipeline of the liquid-liquid separator leads to the steam generation unit.
[0007] This solution is based on the surprising discovery that by separating and purifying styrene from a crude mixture comprising styrene in an apparatus as described above, the apparatus being characterized in particular by using a distillation column having, in addition to a top outlet and a bottom outlet, a side outlet, wherein both the top outlet and the side outlet are connected either directly to a liquid-liquid extractive scrubber or, preferably, indirectly via a condenser and a liquid-liquid separator, and wherein the distillation column has a bottom section, at least a portion of which has a smaller cross-sectional area than the top section of the distillation column, the crude mixture can be purified with particularly low energy requirements and also with particularly low capital expenditure (CAPEX). While the particularly low energy requirements are particularly due to the relatively low steam consumption of the apparatus during operation, the particularly low CAPEX is due to the fact that the apparatus requires only one distillation column. Furthermore, the apparatus according to the present invention requires minimal floor space, particularly because, in addition to the distillation column, a further distillation column for recovering the extractive solvent from the mixture of extractive solvent and styrene is unnecessary. This allows for a reduction in the total distillation column height, i.e., the sum of the heights of all distillation columns in the apparatus. Furthermore, the apparatus according to the invention surprisingly allows the production of very pure styrene compositions, ie compositions having a styrene content of 95 to 99% by weight.
[0008] According to the present invention, the distillation column comprises a top section and a bottom section. This means that the top section is the section extending downward from the uppermost point of the distillation column, as viewed along the length direction of the distillation column (which is the vertical direction), while the bottom section is the section extending upward from the lowermost point of the distillation column. It is particularly preferred that the distillation column, as viewed from its top to its bottom, consists of the top section and the bottom section, i.e., it does not include any other section, i.e., the top section is directly connected to the bottom section.
[0009] At least a portion of the bottom section has a smaller cross-sectional area than the top section of the distillation column. This means that if the top section has the same (i.e., constant) cross-sectional area throughout its entire height, at least one subsection of the bottom section has a smaller cross-sectional area than the cross-sectional area of the top section of the distillation column. If the top section does not have a constant cross-sectional area throughout its entire height, but rather varies, at least one subsection of the bottom section has a smaller cross-sectional area than the average cross-sectional area of the top section of the distillation column. The average cross-sectional area of the top section of the distillation column can be calculated by dividing the top section along its longitudinal direction into subsections, for example, each having a length of 1 cm, measuring the cross-sectional area of each subsection, summing the cross-sectional areas of all subsections, and dividing the resulting sum by the number of subsections. If both the top and bottom sections do not have a constant cross-sectional area throughout their entire height, but rather vary, at least one subsection of the bottom section has an average cross-sectional area that is smaller than the average cross-sectional area of the top section of the distillation column.
[0010] According to the present invention, preferably, at least a portion of the bottom section extending over at least 10% of the height of the distillation column has a smaller cross-sectional area than the top section of the distillation column. This means that: if the entire bottom section has a smaller cross-sectional area, the bottom section of the distillation column extends over at least 10% of the height of the distillation column; if a portion of the bottom section has a smaller cross-sectional area, this portion of the bottom section of the distillation column extends over at least 10% of the height of the distillation column; and if two or more portions of the bottom section have smaller cross-sectional areas, the sum of these two or more portions extends over at least 10% of the height of the distillation column. Preferably, the at least one portion of the bottom section having a smaller cross-sectional area than the top section of the distillation column extends over at least 10% to 50%, and preferably 10% to 25%, of the height of the distillation column.
[0011] Preferably, the lowermost subsection of the bottom section is dome-shaped, wherein, seen in the longitudinal direction of the distillation column, the lowermost dome-shaped subsection of the bottom section extends over less than 50%, more preferably less than 30%, still more preferably less than 20% and most preferably less than 10% of the section(s) of the bottom section having a smaller cross-sectional area than the top section of the distillation column.
[0012] According to the present invention, the overhead outlet line is directly connected to the liquid-liquid extraction scrubber, or is directly or indirectly connected to a liquid-liquid separator comprising a water outlet line and a hydrocarbon outlet line, wherein the water outlet line is connected to the liquid-liquid extraction scrubber. This means that the overhead outlet line of the distillation column is directly connected to the liquid-liquid extraction scrubber, or is directly connected to the liquid-liquid separator comprising a water outlet line and a hydrocarbon outlet line, or is indirectly connected to the liquid-liquid separator comprising a water outlet line and a hydrocarbon outlet line. Indirect connection means that one or more additional devices, such as a condenser, may be arranged between the overhead outlet line of the distillation column and the inlet line of the liquid-liquid separator. Similarly, the water outlet line of the liquid-liquid extraction scrubber, which is connected to the overhead outlet line, may be directly or indirectly connected to (the inlet line of) the liquid-liquid extraction scrubber. The same applies to the side outlet line. That is, the side outlet line of the distillation column can be directly connected to the liquid-liquid extraction wash column, directly connected to a liquid-liquid separator comprising a water outlet line and a hydrocarbon outlet line, or indirectly connected to the liquid-liquid separator comprising a water outlet line and a hydrocarbon outlet line. Again, "indirect connection" means that one or more additional devices, such as a condenser, can be arranged between the side outlet line of the distillation column and the inlet line of the liquid-liquid separator. Similarly, the hydrocarbon outlet line of the liquid-liquid extraction wash column connected to the side outlet line can be connected directly or indirectly to (the inlet line of) the liquid-liquid extraction wash column.
[0013] Preferably, the top outlet pipeline of the distillation column is indirectly connected to a liquid-liquid separator comprising a water outlet pipeline and a hydrocarbon outlet pipeline. Therefore, preferably, the apparatus further comprises an overhead condenser comprising an inlet pipeline and an outlet pipeline, and the apparatus further comprises a liquid-liquid separator comprising an inlet pipeline, a water outlet pipeline, and a hydrocarbon outlet pipeline, wherein the top outlet pipeline of the distillation column is connected to the inlet pipeline of the overhead condenser, wherein the outlet pipeline of the overhead condenser is connected to the inlet pipeline of the liquid-liquid separator, and wherein the water outlet pipeline of the liquid-liquid separator is connected to the liquid-liquid extraction scrubber. The water outlet pipeline of the liquid-liquid separator may be directly or indirectly connected to the liquid-liquid extraction scrubber, and preferably, the water outlet pipeline of the liquid-liquid separator is directly connected to the liquid-liquid extraction scrubber.
[0014] In a further development of the concept of the invention, it is proposed that the hydrocarbon outlet line of the liquid-liquid separator, which is connected to the column top outlet line, be split into a discharge line and a recovery line, which is connected to the top section of the distillation column. During operation of the plant, for example, C8 raffinate can be removed via the discharge line.
[0015] According to a further preferred embodiment of the present invention, the side outlet line of the distillation column is indirectly connected to a liquid-liquid separator comprising a water outlet line and a hydrocarbon outlet line. Therefore, preferably, the apparatus further comprises a side condenser comprising an inlet line and an outlet line, and the apparatus further comprises a liquid-liquid separator comprising an inlet line, a water outlet line, and a hydrocarbon outlet line, wherein the side outlet line of the distillation column is connected to the inlet line of the side condenser, wherein the outlet line of the side condenser is connected to the inlet line of the liquid-liquid separator, and wherein the hydrocarbon outlet line of the liquid-liquid separator is connected to the liquid-liquid extraction scrubber. The hydrocarbon outlet line of the liquid-liquid separator may be directly or indirectly connected to the liquid-liquid extraction scrubber, and preferably, the hydrocarbon outlet line of the liquid-liquid separator is directly connected to the liquid-liquid extraction scrubber.
[0016] Furthermore, it is preferred that the water outlet line of the liquid-liquid separator, which is connected to the side outlet of the distillation column, opens into the steam generation unit.
[0017] The present invention is not particularly limited with respect to the locations at which the top outlet line (i) or the water outlet line (i.e., connected to the top outlet line) of the liquid-liquid separator is connected to the liquid-liquid extraction wash column, and the side outlet line (i.e., the hydrocarbon outlet line (ii) of the liquid-liquid separator is connected to the side outlet line) is connected to the liquid-liquid extraction wash column. For example, both lines (i.e., i.e., the top or bottom end) of the liquid-liquid extraction wash column, or the middle portion of the liquid-liquid extraction wash column, or both lines (i.e., i.e., i.e., i.e., ii ... Good results are particularly achieved when the top outlet line, or the water outlet line of the liquid-liquid separator connected to the top outlet line, i) is connected to one end of the liquid-liquid extraction wash column, and the side outlet line, or the hydrocarbon outlet line of the liquid-liquid separator connected to the side outlet line, ii) is connected to the opposite end of the liquid-liquid extraction wash column (i.e., during operation of the apparatus, in which the two streams are conducted in countercurrent through the liquid-liquid extraction wash column). Most preferably, the top outlet line, or the water outlet line, i) is connected to the upper part of the liquid-liquid extraction wash column, and the side outlet line, or the hydrocarbon outlet line, ii) is connected to the lower part of the liquid-liquid extraction wash column.
[0018] In addition, preferably, the liquid-liquid extraction scrubber further comprises an outlet line for purified styrene and an outlet line for a mixture of water and the extraction solvent. Preferably, the outlet line for the mixture of water and the extraction solvent leads to a steam generation unit.
[0019] In a further development of the inventive concept, it is proposed that the outlet line for the purified styrene is arranged at one end (i.e. the top end or the bottom end) of the liquid-liquid extraction washing column, and the outlet line for the mixture of water and extraction solvent is arranged at the opposite end of the liquid-liquid extraction washing column. Most preferably, the outlet line for the purified styrene is arranged at the top of the liquid-liquid extraction washing column, and the outlet line for the mixture of water and extraction solvent is arranged at the bottom of the liquid-liquid extraction washing column.
[0020] According to the present invention, at least a portion of the bottom section of the distillation column has a smaller cross-sectional area than the top section of the distillation column. Preferably, the cross-sectional area of the at least a portion of the bottom section of the distillation column is 10% to 99%, more preferably 20% to 95%, even more preferably 30% to 90%, and most preferably 40% to 60% of the cross-sectional area of the top section of the distillation column. Furthermore, it is preferred that the top section of the distillation column has an at least substantially constant cross-sectional area along its length (i.e., along the vertical axis or length axis, respectively, of the distillation column). In this context, a substantially constant cross-sectional area means that the difference between the maximum and minimum cross-sectional areas along the vertical axis is less than 10%, preferably less than 5%, more preferably less than 1%, and most preferably 0%. If the cross-sectional area of the at least one portion of the bottom section of the distillation column having a smaller cross-sectional area than the top section of the distillation column is not constant over its length, then the average cross-sectional area of the at least one portion of the bottom section of the distillation column is preferably 10% to 99%, preferably 20% to 95%, more preferably 30% to 90%, and most preferably 40% to 60% of the cross-sectional area of the top section (if the cross-sectional area of the top section is constant over its length), or the average cross-sectional area of the top section (if the cross-sectional area of the top section is not constant over its length). For example, the (average) cross-sectional area of the smaller portion of the bottom section is 30% to 70%, preferably 40% to 60%, of the (average) cross-sectional area of the top section of the distillation column. In alternative embodiments, it is preferred that the (average) cross-sectional area of the smaller portion of the bottom section is 60% to 95%, preferably 70% to 85%, of the (average) cross-sectional area of the top section of the distillation column.
[0021] As viewed from the top to the bottom of the distillation column, the bottom section of the distillation column may include: a first upper subsection having a smaller cross-sectional area than the top section of the distillation column; and a second lower subsection having a larger or smaller cross-sectional area than the first upper subsection of the bottom section. Preferably, the first upper subsection of the bottom section of the distillation column has an at least substantially constant cross-sectional area over its length, which is 10% to 99%, more preferably 20% to 95%, still more preferably 30% to 90%, and most preferably 40% to 60% of the cross-sectional area of the top section. The second lower subsection of the bottom section of the distillation column preferably has a dome shape. In this embodiment, it is preferred that the bottom section does not include any other subsections besides the first upper subsection and the second lower subsection.
[0022] Furthermore, it is possible (though less preferred) for the cross-sectional area of the first upper subsection of the bottom section of the distillation column to vary over the length of the first upper subsection. The cross-sectional area variation over the length of the first upper subsection can be up to 10%, meaning that the difference between the maximum and minimum cross-sectional areas along the vertical axis of the first upper subsection can be up to 10%. In this case, it is preferred that the average cross-sectional area of the first upper subsection of the bottom section is 10% to 99%, preferably 20% to 95%, more preferably 30% to 90%, and most preferably 40% to 60% of the average cross-sectional area of the top section.
[0023] According to a particularly preferred embodiment of the present invention, the bottom section of the distillation column, as viewed from the top to the bottom of the distillation column, comprises a first upper subsection, a second middle subsection, and a third lower subsection. Preferably, the second middle subsection has a smaller cross-sectional area than the top section. More preferably, the second middle subsection of the bottom section of the distillation column has an at least substantially constant cross-sectional area over its length, which is 10% to 99%, more preferably 20% to 95%, still more preferably 30% to 90%, and most preferably 40% to 60% of the cross-sectional area of the top section. The third lower subsection of the bottom section of the distillation column preferably has a dome shape, and preferably, as viewed from the top to the bottom of the first upper subsection, the first upper subsection tapers from the cross-sectional area of the top section of the distillation column to the cross-sectional area of the second middle subsection of the bottom section. In this embodiment, it is preferred that the bottom section does not include any further subsection other than the first upper subsection, the second middle subsection and the third lower subsection.
[0024] In a further development of the concept of the invention, it is proposed that the distillation column has a circular cross section, wherein the top of the top section of the distillation column is dome-shaped, and wherein the diameter of the subsection of the top section located below the dome-shaped top is constant over the length of the top section.
[0025] Good results are particularly achieved when an inlet line for the feed, an inlet line for the extractive solvent, and a side outlet line are connected to the top section of the distillation column, wherein the inlet line for the extractive solvent is connected to a point of the top section above the point of the top section at which the feed line is connected, wherein the feed line is connected to a point of the top section above the point of the top section at which the side outlet line is connected, and wherein the inlet line for the steam is connected to the bottom section of the distillation column.
[0026] In a further development of the concept of the invention, it is proposed that the apparatus further comprises a reboiler, wherein the lower part of the top section of the distillation column comprises an outlet line and an inlet line, both of which are connected to a recovery line leading from the outlet line to the inlet line, wherein the recovery line is connected to the reboiler.
[0027] For example, in the above-described embodiment, each of the outlet and the inlet of the lower portion of the top section of the distillation column is arranged at a position that, as seen from the bottom to the top of the top section of the distillation column, is between 0% and 25% and preferably between 1% and 15% of the distance from the bottom to the top of the top section of the distillation column.
[0028] According to a further preferred embodiment of the present invention, a (further) reboiler may be arranged in the bottom section. In this embodiment, it is preferred that the reboiler is arranged at a position that, as seen from the bottom to the top of the bottom section of the distillation column, is between 5% and 50% and preferably between 10% and 30% of the distance from the bottom to the top of the bottom section of the distillation column.
[0029] According to an alternative preferred embodiment of the present invention, the bottom section of the distillation column does not include a reboiler and is not connected to a line connected to a reboiler.
[0030] In a further development of the inventive concept, it is proposed that the steam generation unit comprises a steam generator and a solvent regenerator. When the steam generator comprises an inlet connected to a water line and an outlet for steam, the solvent regenerator comprises: an inlet connected to the steam outlet of the steam generator; a further inlet line connected to a solvent line, which is connected to the bottom outlet line of the distillation column; and an outlet connected to the steam inlet line of the distillation column. The water line of the steam generator is preferably connected to the outlet line of the liquid-liquid extraction scrubber for a mixture of water and extraction solvent and / or to the water outlet line of the liquid-liquid separator, which is connected to the side outlet line of the distillation column. Most preferably, the water line of the steam generator is preferably connected to the outlet line of the liquid-liquid extraction scrubber for a mixture of water and extraction solvent and to the water outlet line of the liquid-liquid separator, which is connected to the side outlet line of the distillation column.
[0031] According to a particularly preferred embodiment of the present invention, the apparatus comprises only the above-mentioned distillation column without another distillation column. In other words, it is particularly preferred that the apparatus consists of a distillation column, a liquid-liquid extraction washing column and a steam generation unit.
[0032] According to another particularly preferred embodiment of the present invention, the side outlet line, the condenser connected to the side outlet line, and the liquid-liquid separator connected to the side outlet line or the condenser are not (directly) connected to the reflux line leading back into the distillation column.
[0033] In another aspect, the present invention relates to a method for separating and purifying styrene from a crude mixture comprising styrene, the method comprising the steps of: a) feeding a crude hydrocarbon composition containing styrene via an inlet line for the feed, an extractive solvent via an inlet line for the extractive solvent, and a mixture comprising the extractive solvent and water vapor via an inlet line for the steam into a distillation column of the apparatus according to any of the preceding claims, b) distilling the crude hydrocarbon composition, the extractive solvent and water vapor in a distillation column, c) withdrawing the top stream via the top outlet line of the distillation column, d) withdrawing a styrene-rich composition via a side outlet line of the distillation column, e) directing the overhead stream or an aqueous stream obtained by subjecting the overhead stream to condensation and thereafter subjecting the condensed overhead stream to liquid-liquid separation in order to separate it into an aqueous stream and a hydrocarbon stream, to a liquid-liquid extraction wash column, f) conducting the styrene-rich composition directly or the hydrocarbon stream obtained by subjecting the styrene-rich composition to condensation and thereafter subjecting the condensed stream to liquid-liquid separation in order to separate it into an aqueous stream and a hydrocarbon stream, and g) A pure styrene stream is withdrawn from the liquid-liquid extraction scrubber.
[0034] During operation of the distillation column, a mixture comprising water vapor and an extractive solvent is fed into the distillation column via an inlet line for steam. However, for ease of naming, this inlet line is referred to in this application as an inlet line for steam.
[0035] Preferably, the crude hydrocarbon composition contains 10% to 80% by weight, more preferably 30% to 60% by weight, and most preferably 40% to 50% by weight of styrene, based on 100% by weight of the crude hydrocarbon composition. For example, the crude hydrocarbon composition is a hydrocarbon C8 cut of pyrolysis gasoline obtained from steam cracking naphtha or a selectively hydrotreated hydrocarbon C8 cut, a hydrocarbon cut obtained from the (thermal or catalytic) pyrolysis of waste polystyrene, an unsaturated gasoline obtained from the (thermal or catalytic) pyrolysis of various waste plastics, etc.
[0036] According to a preferred embodiment of the present invention, the crude hydrocarbon composition contains 20% to 90% by weight, preferably 40% to 70% by weight and most preferably 50% to 60% by weight of at least one compound selected from the group consisting of xylene, toluene, ethylbenzene, C 7-9 hydrocarbons, and any mixture of two or more of the above compounds, wherein C 7-9 The hydrocarbon is preferably selected from the group consisting of alkanes, cycloalkanes, aromatic hydrocarbons, alkenes, alkynes and any mixture of two or more thereof.
[0037] Good results are particularly obtained when the extraction solvent is a sulfone, such as a cyclic or acyclic sulfone, such as sulfolane.
[0038] In a further development of the inventive concept, it is suggested that the distillation is carried out at a temperature of 40 to 140° C. and at a pressure of 0.02 to 0.03 MPa and preferably at a temperature of 60 to 125° C. and at a pressure of 0.005 to 0.015 MPa.
[0039] The ratio of the extraction solvent generated in the steam generation unit is preferably 80 to 95% by weight and more preferably 85 to 95% by weight, based on the sum of the extraction solvent and water vapor in the mixture used in step a).
[0040] It is further preferred that the ratio of the crude hydrocarbon composition is 10 to 30% by weight and more preferably 15 to 20% by weight based on the sum of the crude hydrocarbon composition, the extractive solvent, and the mixture comprising the extractive solvent and water vapor fed to the distillation column in step a). BRIEF DESCRIPTION OF THE DRAWINGS
[0041] The invention is subsequently described with the aid of the accompanying drawings, which are illustrative and non-limiting, in which: Figure 1 A schematic diagram of an apparatus for separating and purifying styrene from a crude mixture including styrene according to one embodiment of the present invention is shown. DETAILED DESCRIPTION
[0042] Figure 1 The apparatus 10 for separating and purifying styrene from a crude mixture comprising styrene, shown in FIG, includes a steam generation unit 12, a distillation column 14, and a liquid-liquid extraction scrubber 16. The distillation column 14 is subdivided into a top section 18 and a bottom section 20. The top of the top section 18 of the distillation column 14 and the bottom of the bottom section 20 are both dome-shaped. More specifically, the top section of the distillation column 14 includes a first upper dome-shaped subsection 22 and a second lower subsection 24. In turn, the bottom section 20 of the distillation column 14 includes a first upper subsection 26, a second middle subsection 28 below the first upper subsection 26, and a third lower dome-shaped subsection 30 below the second middle subsection 28. The second lower subsection 24 of the top section 18 of the distillation column 14 has a constant cross-sectional area as viewed over its length, and the second middle subsection 28 of the bottom section 20 of the distillation column 14 has a constant cross-sectional area as viewed over its length, wherein the cross-sectional area of the second middle subsection 28 of the bottom section 20 of the distillation column 14 is approximately 50% of the cross-sectional area of the second lower subsection 24 of the top section 18 of the distillation column 14. In other words, the diameter of the second middle subsection 28 of the bottom section 20 of the distillation column 14 is approximately 70% of the diameter of the second lower subsection 24 of the top section 18 of the distillation column 14. As viewed from top to bottom, the first upper subsection 26 of the bottom section 20 of the distillation column 14 tapers along its length axis from the diameter of the second lower subsection 24 of the top section 18 of the distillation column 14 to the diameter of the second middle subsection 28 of the bottom section 20.
[0043] The distillation column 14 further includes: an inlet line 40 for feed, which opens into the top section 18; an inlet line 42 for extractive solvent, which opens into the top section 18 at a position above the position where the inlet line 40 for feed opens into the top section 18; an inlet line 44 for steam, which is connected to the steam generation unit 12; a top outlet line 46; a bottom outlet line 48; and a side outlet line 50, which is connected to the lower part of the second lower subsection 24 of the top section 18 of the distillation column 14. In addition, a top condenser 52 and a liquid-liquid separator 54 are provided, wherein the top outlet line 46 is connected to the top condenser 52 and is connected to the liquid-liquid separator 54 downstream thereof. Liquid-liquid separator 54 is connected to a water line 56 and to a hydrocarbon line 58, wherein water line 56 opens into liquid-liquid extraction scrubber 16, and hydrocarbon line 58 is divided into a discharge line 60 and a recovery line 62, which is connected to top section 18 of distillation column 14. In addition, a side condenser 64 and another liquid-liquid separator 66 are provided, wherein side outlet line 50 is connected to side condenser 64 and is connected downstream to liquid-liquid separator 66. Furthermore, liquid-liquid separator 66 is connected to a water line 68 and to a hydrocarbon line 70, wherein water line 68 opens into steam generation unit 12, and hydrocarbon line 70 opens into liquid-liquid extraction scrubber 16. Furthermore, the apparatus 10 includes a first reboiler 76, wherein the lower portion of the top section 18 of the distillation column 14 includes an outlet line 78 and an inlet line 80, both of which are connected to a recovery line 82 leading from the outlet line 78 to the inlet line 80, wherein the recovery line 82 is connected to the first reboiler 76. A second reboiler 84 is arranged in the second middle subsection 28 of the bottom section 20 of the distillation column 14. The second reboiler 84 allows for particularly efficient and complete desorption of the crude mixture and requires only a minimum amount of internals, such as structured packing, in the distillation column 14.
[0044] The liquid-liquid extraction wash column 16 further comprises an upper outlet line 72 for purified styrene, and a lower outlet line 74 for a mixture of water and extraction solvent.
[0045] Finally, the steam generation unit 12 includes a steam generator 86 and a solvent regenerator 88. The steam generator 86 includes an inlet 90 connected to a water line 92 into which the water lines 68 and 74 flow, and a steam outlet line 94. The solvent regenerator 88 includes an inlet 96 connected to the steam outlet line 94 of the steam generator 86, further includes an inlet line 98 connected to a solvent line 98 connected to the bottom outlet line 48 of the distillation column 14, and further includes an outlet 100 connected to the steam inlet line 44 of the distillation column 14.
[0046] During operation, a crude mixture containing styrene (e.g., a C8 fraction feed) is fed to distillation column 14 via inlet line 40, while an extractive solvent is fed via inlet line 42, and a mixture of (water) steam and extractive solvent is fed to distillation column 14 via inlet line 44. An overhead stream, comprising small amounts of non-aromatic hydrocarbons, toluene, mixed xylenes, and styrene, as well as significant amounts of water and ethylbenzene, is directed through overhead condenser 52 and liquid-liquid separator 54, where the overhead stream is condensed and separated into an aqueous stream and a hydrocarbon stream. While the aqueous stream is directed to liquid-liquid extractive scrubber 16 via line 56, the hydrocarbon stream is partially recovered to distillation column 14 via recovery line 62, while the remainder thereof is withdrawn from the apparatus via line 60, for example, as a C8 raffinate. Via bottom line 48, regenerated extractive solvent is withdrawn and partially directed to top section 18 of distillation column 14 via inlet line 42, while the remainder is directed to solvent regenerator 88 via solvent line 98. A styrene-rich stream is withdrawn from the lower portion of top section 18 of distillation column 14 via side outlet line 50, condensed in side condenser 64, and separated into an aqueous stream and a hydrocarbon stream in liquid-liquid separator 66. While the aqueous stream is directed to steam generator 86 via lines 68 and 92, the hydrocarbon stream is directed to liquid-liquid extractive scrubber 16. In liquid-liquid extractive scrubber 16, the styrene-rich hydrocarbon stream obtained in liquid-liquid separator 66 and containing the extractive solvent contacts the aqueous stream obtained in liquid-liquid separator 54 in a countercurrent direction. The extraction solvent contained in the styrene-rich hydrocarbon stream containing the extraction solvent obtained in the liquid-liquid separator 66 is thereby removed therefrom, so that pure styrene is obtained, which is withdrawn from the liquid-liquid extraction washing column 16 via the outlet line 72. In addition, a mixture of water and the extraction solvent is thereby obtained, which is withdrawn from the liquid-liquid extraction washing column 16 via the outlet line 74 and directed to the steam generator 86 via the line 92. The water is evaporated into steam in the steam generator 86 and then mixed with the solvent in the solvent regenerator 88, after which the resulting mixture of water vapor and solvent is fed to the bottom section 20 of the distillation column 14 via the line 44.
[0047] Reference numerals 10 Equipment 12 Steam generating unit 14 Distillation Tower 16 Liquid-Liquid Extraction Scrubber 18 Top section of distillation column 20 Bottom section of distillation column 22 First upper subsection of the top section of the distillation column 24 The second lower subsection of the top section of the distillation column 26 First upper subsection of the bottom section of the distillation column 28 The second middle subsection of the bottom section of the distillation column 30 The third lower subsection of the bottom section of the distillation column 40 Inlet line for feed 42 Inlet line for extraction solvent 44 Steam inlet line 46 Tower top outlet pipeline 48 bottom outlet pipeline 50 side outlet pipeline 52 Top condenser 54 Liquid-Liquid Separator 56 Water Pipeline 58 Hydrocarbon Pipeline 60 discharge line 62 Recovery pipeline 64 side condenser 66 Liquid-Liquid Separator 68 Water Pipeline 70 Hydrocarbon Pipeline 72 Upper outlet line of liquid-liquid extraction scrubber for pure styrene 74 Lower outlet pipeline of liquid-liquid extraction washing tower 76 First Reboiler 78 export pipeline 80 Inlet pipeline 82 Recovery pipeline 84 Second reboiler 86 Steam Generator 88 Solvent Regenerator 90 Steam generator inlet 92 water pipeline 94 Steam export pipeline 96 Inlet of solvent regenerator 98 solvent lines 100 Outlet of solvent regenerator.
Claims
1. A device (10) particularly for separating and purifying styrene from a crude mixture comprising styrene, wherein: The apparatus (10) comprises a steam generation unit (12), a liquid-liquid extraction washing tower (16) and a distillation tower (14), wherein the distillation tower (14) comprises a top section (18) and a bottom section (20), wherein at least a portion of the bottom section (20) extending over at least 10% of the height of the distillation tower (14) has a smaller cross-sectional area than the top section (18) of the distillation tower (14), wherein the distillation tower (14) further comprises an inlet line (40) for feed, an inlet line (42) for extraction solvent, an inlet line (44) for steam connected to the steam generation unit (12), a tower top outlet line (46), a bottom outlet line (48), and a side outlet line (50) arranged below the tower top outlet line (46) and above the bottom outlet line (48), wherein i) the tower top outlet pipeline (46) is directly connected to the liquid-liquid extraction washing tower (16), or the tower top outlet pipeline (46) is directly or indirectly connected to a liquid-liquid separator (54) comprising a water outlet pipeline (56) and a hydrocarbon outlet pipeline (58), wherein the water outlet pipeline (56) is connected to the liquid-liquid extraction washing tower (16), and ii) the side outlet pipeline (50) is directly connected to the liquid-liquid extraction washing tower (16), or the side outlet pipeline (50) is directly or indirectly connected to a liquid-liquid separator (66) comprising a water outlet pipeline (68) and a hydrocarbon outlet pipeline (70), wherein the hydrocarbon outlet pipeline (70) is connected to the liquid-liquid extraction washing tower (16), and wherein the water outlet pipeline (68) of the liquid-liquid separator (66) leads to the steam generation unit (12).
2. The device (10) according to claim 1, comprising: an overhead condenser (52) comprising an inlet line and an outlet line; and a liquid-liquid separator (54), comprising an inlet pipeline, a water outlet pipeline (56) and a hydrocarbon outlet pipeline (58), wherein the top outlet pipeline (46) of the distillation tower (14) is connected to the inlet pipeline of the top condenser, wherein the outlet pipeline of the top condenser is connected to the inlet pipeline of the liquid-liquid separator (54), and wherein the water outlet pipeline (56) of the liquid-liquid separator (54) is connected to the liquid-liquid extraction washing tower (16), wherein, preferably, the hydrocarbon outlet pipeline (58) of the liquid-liquid separator (54) is divided into a discharge pipeline (60) and a recovery pipeline (62), and the recovery pipeline is connected to the top section (18) of the distillation tower (14).
3. The device (10) according to claim 1 or 2, comprising: a side condenser (64) comprising an inlet line and an outlet line; and a liquid-liquid separator (66) comprising an inlet line, a water outlet line (68) and a hydrocarbon outlet line (70), wherein the side outlet line (50) of the distillation column (14) is connected to the inlet line of the side condenser (64), wherein the outlet line of the side condenser is connected to the inlet line of the liquid-liquid separator (66), and wherein the hydrocarbon outlet line (70) of the liquid-liquid separator (66) is connected to the liquid-liquid extraction washing column (16).
4. The device (10) according to any one of the preceding claims, wherein The top outlet pipeline (46) or the water outlet pipeline (56) of the liquid-liquid separator (54) connected to the top outlet pipeline (46) is i) connected to the end of the liquid-liquid extraction washing tower (16), and the side outlet pipeline (50) or the hydrocarbon outlet pipeline (70) of the liquid-liquid separator (66) connected to the side outlet pipeline (50) is ii) connected to the opposite end of the liquid-liquid extraction washing tower (16).
5. The device (10) according to claim 4, wherein The top outlet line (46) or the water outlet line (56) i) is connected to the upper part of the liquid-liquid extraction washing column (16), and wherein the side outlet line (50) or the hydrocarbon outlet line (70) ii) is connected to the lower part of the liquid-liquid extraction washing column (16).
6. The device (10) according to any one of the preceding claims, wherein The liquid-liquid extraction washing column (16) further comprises an outlet line (72) for purified styrene, and an outlet line (74) for a mixture of water and extraction solvent, wherein the outlet line (74) for the mixture of water and extraction solvent leads to the steam generation unit (12).
7. The device (10) according to any one of the preceding claims, wherein The cross-sectional area of the at least a portion of the bottom section (20) of the distillation column (14) is 10% to 99%, preferably 20% to 95%, more preferably 30% to 90% and most preferably 40% to 60% of the cross-sectional area of the top section (18).
8. The device (10) according to any one of the preceding claims, wherein The bottom section (20) of the distillation column (14) comprises, as seen in a direction from the top to the bottom of the distillation column (14), a first upper subsection (26) and a second lower subsection (28), wherein the first upper subsection (26) is above the second lower subsection (28), wherein the cross-sectional area of the first upper subsection (26) of the bottom section (20) is 10% to 99%, preferably 20% to 95%, more preferably 30% to 90% and most preferably 40% to 60% of the cross-sectional area of the top section (18), wherein preferably, the second lower subsection (28) of the bottom section (20) of the distillation column (14) is dome-shaped and forms the bottom.
9. The device (10) according to any one of claims 1 to 7, wherein As viewed from the top to the bottom of the distillation column (14), the bottom section (20) of the distillation column (14) includes a first upper subsection (26), a second middle subsection (28) below the first subsection, and a third lower subsection (30) below the second middle subsection (28) forming the bottom of the distillation column (14), wherein the cross-sectional area of the second middle subsection (28) of the bottom section (20) is 1 / 4 of that of the top section (18). 10% to 99%, preferably 20% to 95%, more preferably 30% to 90% and most preferably 40% to 60% of the cross-sectional area of the distillation column (14), and wherein the first upper sub-section (26) of the bottom section (20) tapers from the cross-sectional area of the top section (18) of the distillation column (14) to the cross-sectional area of the second middle sub-section (28) of the bottom section (20) of the distillation column (14) as seen in a direction from the top to the bottom of the first upper sub-section (26).
10. The device (10) according to any one of the preceding claims, wherein The feed inlet line (40), the extractive solvent inlet line (42) and the side outlet line (50) are connected to the top section (18) of the distillation column (14), wherein the extractive solvent inlet line (42) is connected to a position of the top section (18) above the position of the top section (18) connected to the feed line (40), wherein the feed inlet line (40) is connected to a position of the top section (18) above the position of the top section (18) connected to the side outlet line (50), and wherein the steam inlet line (44) is connected to the bottom section (20) of the distillation column (14).
11. The apparatus (10) according to any one of the preceding claims, further comprising a reboiler (76), wherein The lower portion of the top section (18) includes an outlet line (78) and an inlet line (80), both of which are connected to a recovery line (82) leading from the outlet line (78) to the inlet line (80), wherein the recovery line (82) is connected to the reboiler (76).
12. The device (10) according to any one of the preceding claims, wherein A reboiler (84) is arranged in the bottom section (20), wherein, as seen from the bottom to the top of the bottom section (20) of the distillation column (14), the reboiler (84) is arranged at a position between 5% and 50% and preferably between 10% and 30% of the distance from the bottom to the top of the bottom section (20).
13. The device (10) according to any one of the preceding claims, wherein The steam generating unit (12) comprises a steam generator (86) and a solvent regenerator (88), wherein the steam generator (86) comprises an inlet (90) connected to a water line (92) and an outlet (94) for steam, wherein the solvent regenerator (88) comprises: an inlet (96) connected to the outlet (94) for steam of the steam generator (86); another inlet line connected to a solvent line (98), the solvent line being connected to a bottom outlet line (48) of the distillation column (14); and an outlet connected to an inlet line (44) for steam of the distillation column (14).
14. A method for separating and purifying styrene from a crude mixture comprising styrene, the method comprising the steps of: a) feeding a crude hydrocarbon composition containing styrene via the feed inlet line (40), an extractive solvent via the extractive solvent inlet line (42), and a mixture comprising extractive solvent and water vapor via the steam inlet line (44) into a distillation column (14) of the apparatus (10) according to any one of the preceding claims, b) distilling the crude hydrocarbon composition, the extraction solvent and the water vapor in the distillation column (14), c) withdrawing a top stream via the top outlet line (46) of the distillation column (14), d) withdrawing a styrene-rich composition via a side outlet line (50) of the distillation column (14), e) directing the overhead stream or an aqueous stream obtained by subjecting the overhead stream to condensation and thereafter subjecting the condensed overhead stream to liquid-liquid separation in order to separate it into the aqueous stream and the hydrocarbon stream, to the liquid-liquid extraction wash column (16), f) directing the styrene-rich composition or a hydrocarbon stream obtained by subjecting the styrene-rich composition to condensation and thereafter subjecting the condensed stream to liquid-liquid separation in order to separate it into the aqueous stream and the hydrocarbon stream, to the liquid-liquid extraction washing column (16), and g) withdrawing a pure styrene stream from the liquid-liquid extraction scrubber (16).
15. The method according to claim 14, wherein The crude hydrocarbon composition contains 10 to 80% by weight, preferably 30 to 60% by weight, and more preferably 40 to 50% by weight, of styrene, and 20 to 90% by weight, preferably 40 to 70% by weight, and most preferably 50 to 60% by weight, of at least one compound selected from the group consisting of xylene, toluene, ethylbenzene, C 7-9 hydrocarbons, and any mixture of two or more of the above compounds, wherein the C 7-9 The hydrocarbon is preferably selected from the group consisting of alkanes, cycloalkanes, aromatic hydrocarbons, alkenes, alkynes and any mixture of two or more thereof.