Process for recovering light and heavy ends from a vapor stream

Abstract

The present invention relates to a process for recovering a light boiler and a heavy boiler from a vapour stream, wherein the process comprises the steps of: A1 ) introducing a vapour stream (1 ) comprising a light boiler and a heavy boiler into a column (2) at a point at the bottom of the column (2), A2) withdrawing a vapour stream (3) enriched in light boiler from the top of the column (2), A3) withdrawing a liquid stream (4) enriched in heavy boiler from the bottom of the column (2) and dividing stream (4) into a partial stream (5) and a partial stream (6), A4) recycling stream (5) back into column (2) at a point above column (2), wherein stream (5) remains substantially adiabatic during recycling, A5) withdrawing a stream (7) enriched in medium boiler from an intermediate section of column (2) and dividing stream (7) into a partial stream (8) and a partial stream (9), A6) cooling partial stream (9) in a heat exchanger (10) to provide a cooled stream (1 1 ) and recycling stream (1 1 ) as stream (12) back into column (2) at an introduction point below the top of column (2), and A7) withdrawing partial stream (6) enriched in heavy boiler and partial stream (8) enriched in medium boiler.

Description

[0001] The present invention relates to a process for recovering light boilers and heavy boilers from a vapor stream comprising said light boilers and said heavy boilers. In particular, the process of the present invention can improve the recovery of heavy boilers compared to prior art processes. Preferably, the present invention relates to a process for recovering acrolein and acrylic acid from a vapor comprising acrolein and acrylic acid, which improves the recovery of acrylic acid, which is formed as a by-product in the process of oxidation of propene to acrolein.

[0002] On an industrial scale, many organic products, such as ketones or aldehydes, are prepared by partial gas phase oxidation of an organic precursor compound. However, a major side reaction of the partial gas phase oxidation of organic compounds is the oxidation of the desired product to a higher oxidized by-product, in particular the oxidation of aldehydes to carboxylic acids. Therefore, the vapor stream from the oxidation reaction has to be subjected to a purification process to obtain the desired product in the desired purity. Although prior art purification processes allow the recovery of the desired product in at least an acceptable purity, they usually do not recover the by-products, in particular not in a concentration which makes their economical use attractive. However, the by-products can also be valuable materials which are lost due to the deficiencies of the prior art purification processes.

[0003] For example, on an industrial scale, acrolein is prepared by selective oxidation of propene in the gas phase in the presence of a heterogeneous catalyst. The major side reaction in this process is the oxidation of the desired product to acrylic acid. After leaving the reactor, the hot gaseous product stream is cooled with water in a quench tower. The function of the quench tower is to stop further reactions and to absorb the by-products from the gaseous product stream, thereby facilitating the separation of the high boilers, mainly water and acrylic acid, from the reaction gas. A typical prior art acrolein quench tower for the purification of acrolein is shown in the following scheme Figure 5 In the prior art typical quench tower, the hot gas from the oxidation of propene enters the quench tower in the sump section of the quench tower and is cooled by a circulating stream in a so-called sump pump-around through a heat exchanger. The thus obtained water loaded stream is fed to a stripping tower, where it is stripped with a circulating gas to recover the absorbed acrolein. The remaining water loaded stream contains about 14 to 18 wt% acrylic acid. In principle, the acrylic acid still contained in the water loaded stream represents valuable material which is worth recovering. However, the concentration of acrylic acid in said water loaded stream is relatively low. This makes the recovery of acrylic acid from the water loaded stream unattractive on an industrial scale. Therefore, the acrylic acid containing water stream is usually sent to a thermal oxidizer, however, which represents in principle a loss of valuable material.

[0004] Therefore, there is a need for an improved process which, in addition to recovering the light boiler, also improves the recovery of the heavy boiler.

[0005] It has been found that the solution to this problem is to shut off the cooling of the sump pump around reflux during the purification process so that the stream to be recycled back to the bottom of the column is essentially adiabatic. The essentially adiabatic recycling of the stream results in a higher temperature in the sump of the column compared to the prior art process. As a result, there is less condensation within the column and therefore a significantly reduced flow of condensed light and medium boilers returning to the sump of the column. This results in the heavy boiler concentrating in the sump. The lack of cooling of the sump pump around reflux is compensated by the cooling of the upper pump-around. The upper pump-around comprises withdrawing a stream (7) from an intermediate portion of the column (2), dividing the stream (7) into a withdrawn partial stream (8) and a partial stream (9), cooling the partial stream (9) in a heat exchanger (10) to provide a cooled stream (11), and recycling the stream (11) as stream (12) back into the column (2) at an introduction site below the top of the column (2).

[0006] It is therefore an object of the present invention to provide a process (A) for recovering light and heavy boilers from a vapour stream, which comprises the following steps:

[0007] A1) introducing a vapour stream (1) comprising light and heavy boilers into a column (2) at a site at the bottom of the column (2),

[0008] A2) withdrawing a vapour stream (3) enriched in light boilers from the top of the column (2),

[0009] A3) withdrawing a liquid stream (4) enriched in heavy boilers from the bottom of the column (2) and dividing the stream (4) into a partial stream (5) enriched in heavy boilers and a partial stream (6),

[0010] A4) recycling the stream (5) back into the column (2) at a site above the bottom of the column (2), wherein the stream (5) is essentially adiabatic during the recycling,

[0011] A5) withdrawing a stream (7) enriched in medium boilers from an intermediate portion of the column (2) and dividing the stream (7) into a partial stream (8) and a partial stream (9),

[0012] A6) cooling the partial stream (9) in a heat exchanger (10) to provide a cooled stream (11) and recycling the stream (11) as stream (12) back into the column (2) at an introduction site below the top of the column (2), and

[0013] A7) withdrawing the partial stream (6) enriched in heavy boilers and the partial stream (8) enriched in medium boilers.

[0014] In the context of the present application, streams (4) and (5) form the sump pump circulation reflux, and streams (7), (9), (1 1 ) and (12) form the upper pump circulation reflux.

[0015] Part stream (6) is enriched in heavy boiler. Compared to the prior art process, the process according to the present application can increase the concentration of heavy boiler, e.g. acrylic acid, in part stream (6). This is shown in the example according to the present application. Part stream (8) is enriched in medium boiler.

[0016] The process according to the present application is also shown in the following Figure 1

[0017] According to the present application, the temperature of stream (5) introduced into column (2) in step A5), i.e. the temperature of stream (5) thus circulated, is kept substantially adiabatic. Therefore, contrary to the prior art process, in the process according to the present application, the heat exchanger for the sump pump circulation reflux, in which stream (5) is circulated, is completely closed or even completely missing.

[0018] In the context of the present application, column (2) is preferably operated such that it has a quenching section at its bottom, a distillation section in its middle section, and another quenching section at its top section.

[0019] In the context of the present application, the term packing is known to the person skilled in the art of chemical engineering and denotes any type of random or structured packings, as well as plates or trays for intimate contact of the gas and liquid phases within the column.

[0020] In the context of the present application, the introduction or recirculation of a stream into a column involves the distribution of said stream, e.g. by means of a liquid distributor.

[0021] In the context of the present application, the point of withdrawal of stream (7) from column (2) is also referred to as side withdraw of stream (7).

[0022] Within column (2), the medium boiling components and the heavy boiling components condense and flow downwards to the sump of the column. Mostly, the condensation of these components takes place above the height of the packing in column (2). Therefore, stream (7) is preferably withdrawn in the middle section of the packing in column (2). This allows the use of a liquid circulating stream in the upper pump circulation reflux.

[0023] In one embodiment of the process according to the present application, stream (7) is withdrawn in the middle section of the packing in column (2). ​

[0024] The more the cooling deficit of the sump pump recycle backflow, i.e. of the stream (5), is compensated by the upper pump recycle backflow, the more the liquid portion within the column (2) is transferred to a lower amount. In other words, if the cooling deficit of the sump pump recycle backflow is not compensated by the upper pump recycle backflow, no liquid stream (4) and (6) can be withdrawn from the bottom of the column (2). However, the upper pump recycle backflow realized in steps A5) and A6) of the method according to the present application not only compensates the cooling deficit of the sump pump recycle backflow, but also allows to adjust the amount or volume of the liquid stream (6) withdrawn from the bottom of the column (2) or from the sump as partial stream. Preferably, the amount or volume of the stream (8) withdrawn as partial stream in step A7) is equal to the amount or volume of the stream (6) withdrawn in step A7).

[0025] In one embodiment of the method according to the present application, the amount of the stream (6) withdrawn in step A7) is adjusted by the amount of the stream (8) withdrawn in step A7).

[0026] The reflux of liquid, in particular of mid-boilers, but also of heavy boilers, within the column (2) can be realized in different ways. One option is that the middle section of the column (2) is provided with a liquid collector, a liquid overflow and a liquid distributor for withdrawing the stream (7) such that any condensed liquid can flow back down to the sump of the column. In addition to or as an alternative to this option, reflux can also be allowed by separating a partial stream (13) from the stream (11) and introducing said partial stream (13) into the column (2) at a point which is lower than the side reflux of the stream (7). After being introduced into the column (2), said stream (13) flows down to the sump of the column. In principle, further partial streams, which are optionally present, can also be separated from the stream (11) and introduced into the column (2) similar to the partial stream (13).

[0027] In another embodiment, also shown in the following Figure 2 The method according to the present application further comprises the following steps:

[0028] B1) separating at least one additional partial stream (13) from the stream (11), and

[0029] B2) introducing the stream (13) into the column (2) at a point which is lower than the point at which the stream (7) is withdrawn.

[0030] The streams (12) and (13) are liquid streams. Thus, they flow down through the column (2) after being introduced into said column (2).

[0031] In another embodiment of the method according to the present application, the stream (12) and / or the stream (13) is / are guided to counterflow the rising vapors after being introduced into the column (2).

[0032] In the context of the present application, the term rising vapors is used as known to experts in the field of chemical engineering and denotes rising vapors comprising mainly light boilers.

[0033] In embodiments, wherein the process according to the present application further comprises steps B1 ) and B2), stream (12) is introduced into column (2) at a point above the point of withdrawal of stream (7) and stream (13) is introduced at a point below the point of withdrawal of stream (7).

[0034] According to the present application, a liquid stream (4) enriched in heavy boilers is withdrawn from the bottom of column (2) and from said stream (4) a partial stream (6) is separated and withdrawn. In principle, the heavy boilers contained in this partial stream (6) can be further processed. However, prior to this, the partial stream (6) is preferably subjected to an additional purification step (C) in which any remaining light boilers are removed from this stream. This purification step is preferably carried out in a column (14), preferably in a stripping column, using a sweep gas stream (15) to remove any light boilers to obtain a stream (16) comprising light boilers withdrawn from column (14) and recycled back to column (2) and a light boiler depleted stream (17) which can be further processed after withdrawal from column (14).

[0035] In another embodiment, also shown in the following Figure 3 the process according to the present application further comprises the following steps:

[0036] C1 ) introducing stream (6) into column (14) at a point below the top of said column (14),

[0037] C2) stripping stream (6) within column (14) with a gas stream (15) to recover residual light boilers from stream (6),

[0038] C3) withdrawing a stream (16) comprising light boilers from the top of column (14) and introducing stream (16) into column (2) at a point above the bottom of said column (2), and

[0039] C4) withdrawing a light boiler depleted stream (17) from the bottom of column (14).

[0040] According to the present application, the stream (7) is withdrawn from the middle section of the column (2) - preferably at the height of the packing in the column (2) - and split into a partial stream (8) and a partial stream (9), wherein the latter partial stream is first cooled and then recycled back into the column at an introduction site below the top of the column. Thus, the stream (7) and the partial stream (8) typically contain the mid-boiling components of the vapor stream (1). When one or more mid-boilers represent valuable material, the partial stream (8) can be fed to another production process. However, prior to this, the partial stream (8) is preferably subjected to an additional purification step (D), wherein any remaining light boilers are removed from this stream. This purification step is preferably carried out in a column (18), preferably in a stripping column, using a sweep gas stream (19) to remove any light boilers, to obtain a stream (20) comprising light boilers withdrawn from the column (18), and a light boiler-depleted stream (21), which can be subjected to further processing after withdrawal from the column (18). The stream (20) comprising light boilers can be recycled back into the column (2) and introduced into the column at a site above the bottom of the column. Alternatively, the stream (20) can be sent to an incinerator.

[0041] In another embodiment, also shown in the following Figure 4 The method according to the present application further comprises the following steps:

[0042] D1) introducing the stream (8) into the column (18) at a site below the top of the column (18),

[0043] D2) stripping the stream (8) with a gas stream (19) within the column (18) to recover residual light boilers from the stream (8), D3) withdrawing a stream (20) comprising light boilers from the top of the column (18), and

[0044] D4) withdrawing a light boiler-depleted stream (21) from the bottom of the column (18).

[0045] In principle, the method according to the present application is not limited to the origin and composition of the vapor stream (1) of step A1), as long as the vapor stream comprises light boilers and heavy boilers.

[0046] Nevertheless, it is preferred that the vapor stream (1) is derived from the oxidation of an organic compound selected from the group consisting of olefins, fatty alcohols, fatty aldehydes, allyl alcohols, allyl aldehydes and allyl ketones.

[0047] Preferably, the vapor stream (1) is derived from the oxidation of propylene to propenal, wherein propenoic acid is the main by-product.

[0048] In one embodiment of the method according to the present application, the light boilers comprise or consist of propenal and the heavy boilers comprise or consist of propenoic acid.

[0049] In addition to the predominantly boiling propenoic acid in the context of the present application, the boiling reagent can also comprise water and other high-boiling components, however, only in small amounts, in particular allyl propenoate, allyl alcohol and acetic acid.

[0050] Before carrying out the process according to the present application, the hot vapour stream from the oxidation of propene to propenal is first cooled at the end of the reactor and, after the reactor, quenched with water in order to stop any further reactions, in particular the oxidation of the formed propenal.

[0051] In another embodiment of the process according to the present application, the vapour stream (1) also comprises water. The water condenses in the column (2), in particular at the packing height of the middle section of the column (2). It is thus also present in the stream (7).

[0052] In a preferred embodiment of the process according to the present application, the stream (7) discharged in step A5) comprises water.

[0053] In addition to water, the stream (7) can also comprise small amounts of light boilers, such as residues of propenal, formaldehyde and acetaldehyde, and small amounts of heavy boilers, such as propenoic acid.

[0054] Due to the substantially adiabatic stream (5), the process according to the present application leads to a higher temperature in the bottom or sump of the column (2) compared to the process of the prior art. For example, when the vapour stream (1) is derived from the oxidation of propene and thus comprises propenal as light boiler and propenoic acid as heavy boiler, the following temperature increase is observed in the column (2): the temperature in the bottom or sump increases from about 65°C (process of the prior art) to a temperature in the range of from about 70°C to 85°C, preferably greater than 70°C, for example greater than 70°C to 85°C, or at least 75°C, for example 75°C to 85°C, or in particular 80°C to 85°C. The temperature of the stream (4) discharged from the bottom or sump of the column (2), and of the stream (5) separated from the stream (4) and substantially adiabatic in the process of being recycled back into the column (2), is thus also in the range of from 70°C to 85°C. As a further consequence of the stream (5) being substantially adiabatic, there is also a temperature increase at the packing level in the column (2): the temperature increases from about 48°C (process of the prior art) to a temperature in the range of from 50°C to 70°C.

[0055] In a preferred embodiment of the process according to the present application, the temperature in the bottom of the column (2) is in the range of from 70°C to 85°C.

[0056] In another preferred embodiment of the process according to the present application, the temperature of the stream (5) is in the range of from 70°C to 85°C.

[0057] One would expect that the absence of cooling of the collection vessel would also lead to a significant temperature increase at the top of the column (2). However, due to the upper pumparound reflux realized in steps A5) and A6) of the process according to the application, at most only a very small temperature increase, or even no temperature increase at all, at the top of the column (2). In particular, this effect is achieved by cooling the stream (11) which is subsequently introduced as partial stream (12), preferably also as partial stream (13) and any optionally further partial streams, to a temperature of at most 20°C, preferably to a temperature in the range from 10°C to 20°C.

[0058] In another preferred embodiment of the process according to the application, the temperature of the stream (11) is at most 20°C.

[0059] Figures 1 to 5 and the examples further illustrate the process according to the application.

[0060] Figure 1 is a schematic representation of the process according to claim 1, wherein the numbers have the following meanings:

[0061] (1) a vapor stream comprising light boiler and heavy boiler,

[0062] (2) a column,

[0063] (3) a vapor stream enriched in light boiler and withdrawn from the top of the column (2),

[0064] (4) a liquid stream enriched in heavy boiler and withdrawn from the bottom of the column (2),

[0065] (5) a partial stream which is separated from stream (4) and recycled into the column (2),

[0066] (6) a partial stream which is separated from stream (4) and withdrawn from the process,

[0067] (7) a stream withdrawn from an intermediate section of the column (2),

[0068] (8) a partial stream which is separated from stream (7),

[0069] (9) a partial stream which is separated from stream (7) and sent to cooling,

[0070] (10) a heat exchanger,

[0071] (11) a cooled stream,

[0072] (12) a recycled cooled stream.

[0073] Figure 2 is a schematic representation of the process according to claim 4, wherein the numbers have the following meanings:

[0074] (1) a vapor stream comprising light and heavy ends,

[0075] (2) a column,

[0076] (3) a vapor stream enriched in light ends and withdrawn from the top of column (2),

[0077] (4) a liquid stream enriched in heavy ends and withdrawn from the bottom of column (2),

[0078] (5) a partial stream separated from stream (4) and recycled into column (2),

[0079] (6) a partial stream separated from stream (4) and withdrawn from the process,

[0080] (7) a stream withdrawn from an intermediate section of column (2),

[0081] (8) a partial stream separated from stream (7),

[0082] (9) a partial stream separated from stream (7) and sent to cooling,

[0083] (10) a heat exchanger,

[0084] (11) a cooled stream,

[0085] (12) a recycled partial stream separated from cooled stream (11),

[0086] (13) a recycled partial stream separated from cooled stream (11).

[0087] Figure 3 is a schematic representation of the process according to the embodiment of claim 7, wherein the numbers have the following meanings:

[0088] (1) a vapor stream comprising light and heavy ends,

[0089] (2) a column,

[0090] (3) a vapor stream enriched in light ends and withdrawn from the top of column (2),

[0091] (4) a liquid stream enriched in heavy ends and withdrawn from the bottom of column (2),

[0092] (5) a partial stream separated from stream (4) and recycled into column (2),

[0093] (6) a partial stream separated from stream (4) and withdrawn from the process,

[0094] (7) a stream withdrawn from an intermediate section of column (2),

[0095] (8) a partial stream which is separated from stream (7),

[0096] (9) a partial stream which is separated from stream (7) and sent to cooling,

[0097] (10) a heat exchanger,

[0098] (11) a cooled stream,

[0099] (12) a recycled partial stream which is separated from the cooled stream (11),

[0100] (13) a recycled partial stream which is separated from the cooled stream (11),

[0101] (14) a column,

[0102] (15) a gas stream for purging stream (6),

[0103] (16) a stream comprising light ends which is withdrawn from the top of column (14),

[0104] (17) a stream depleted in light ends which is withdrawn from the bottom of column (14).

[0105] Figure 4 is a schematic representation of the process according to an embodiment of claim 8, wherein the numbers have the following meanings:

[0106] (1) a vapour stream comprising light ends and heavy ends,

[0107] (2) a column,

[0108] (3) a vapour stream enriched in light ends and withdrawn from the top of column (2),

[0109] (4) a liquid stream enriched in heavy ends and withdrawn from the bottom of column (2),

[0110] (5) a partial stream which is separated from stream (4) and recycled into column (2),

[0111] (6) a partial stream which is separated from stream (4) and withdrawn from the process,

[0112] (7) a stream withdrawn from an intermediate section of column (2),

[0113] (8) a partial stream which is separated from stream (7),

[0114] (9) a partial stream which is separated from stream (7) and sent to cooling,

[0115] (10) a heat exchanger,

[0116] (11) cooled stream,

[0117] (12) a recycled partial stream separated from the cooled stream (11),

[0118] (13) a recycled partial stream separated from the cooled stream (11),

[0119] (14) a stripping column,

[0120] (15) a gas stream for purging stream (6),

[0121] (16) a stream comprising light ends, which is withdrawn from the top of the stripping column (14),

[0122] (17) a light ends depleted stream, which is withdrawn from the bottom of the stripping column (14),

[0123] (18) a stripping column,

[0124] (19) a gas stream for purging stream (8),

[0125] (20) a stream comprising light ends, which is withdrawn from the top of the stripping column (18),

[0126] (21) a light ends depleted stream, which is withdrawn from the bottom of the stripping column (14).

[0127] Figure 5 is a schematic representation of the method according to the prior art, wherein the numbers have the following meanings

[0128] (30) a vapour stream comprising light ends and heavy ends,

[0129] (31) a column,

[0130] (32) a vapour stream enriched in light ends and withdrawn from the top of the column (31),

[0131] (33) a liquid stream enriched in heavy ends and withdrawn from the bottom of the column (31),

[0132] (34) a partial stream separated from stream (33) and recycled into the column (31),

[0133] (35) a heat exchanger for cooling stream (34),

[0134] (36) a cooled stream (34),

[0135] (37) a partial stream separated from stream (33),

[0136] (38) a stripping column,

[0137] (39) a gas stream for purging stream (6),

[0138] (40) A feed stream containing light boiling matter is discharged from the top of the stripping tower (38).

[0139] (41) The stream of light boiling matter is depleted and discharged from the bottom of the stripping tower (28).

[0140] (42) The material flow discharged from the middle part of the tower (31),

[0141] (43) The portion of the material flow separated from the material flow (42),

[0142] (44) A portion of the material flow, which is separated from the material flow (42), is sent to cooling.

[0143] (45) Heat exchanger

[0144] (46) The cooled material stream,

[0145] (47) The portion of the material stream separated from the cooled material stream (42),

[0146] (48) A portion of the material stream separated from the cooled material stream (42). Example:

[0147] Use based on Figure 3 (according to an embodiment of the invention) and Figure 5 The computational model of the method shown in the (comparative example) is used to perform the embodiments of this article. Process modeling is a well-established and reliable method used by engineers to simulate complex chemical processes before building actual plants. In the context of the embodiments of this article, the commercial modeling software Aspen... (Aspen Technology, Inc., 20 Crosby Roads, Bedford, Massachusetts 01730, USA) is used in combination with physical property data from public databases.

[0148] Comparative example:

[0149] To illustrate the benefits of the method according to the present invention, for Figure 5The method illustrated in the diagram simulates the purification of a stream containing acrolein. An acrolein-containing gas stream (30) enters the collection tank section of tower (31) and is cooled by a circulation pump (containing streams 33, 34, and 36) via heat exchanger (35). Wastewater (high boiling point) and stream (37) are sent to a circulating gas stripper and a second tower (38) to recover acrolein. Wastewater and stream (41) from the circulating gas stripper are pumped (not shown) to a wastewater container. The hot gas in tower (31) is further cooled by a circulation pump (45) via an upper pump containing streams (42), (44), and (46) to (48). The acrolein-rich stream (32) is discharged from the top of the tower and sent to an absorber for further treatment (not shown). Stream (33) discharged from the bottom of tower (31) contains 18.350% by weight of acrylic acid. The overall composition of the material flow (33) is given in Table 1 below.

[0150] According to an embodiment of the present invention:

[0151] Using the modeling software Aspen Simulate the purification process of a feed stream containing acrolein, such as Figure 3 The schematic diagram is shown. A gas stream (1) containing acrolein enters the collection tank section of tower (2). In contrast to the comparative example, the collection tank pump recirculation stream (containing streams (4) and (5)) is not cooled but remains substantially adiabatic. Wastewater (high boiling point) and stream (6) are sent to the circulating gas stripping tower, the second tower (14) to recover acrolein. Wastewater and stream (17) from the circulating gas stripping tower are sent to the wastewater container by a pump (not shown). The hot gas in tower (2) is cooled by the heat exchanger (10) through the upper pump containing streams (7), (9) and (11) to (12). The acrolein-rich stream (3) is discharged from the top of the tower and sent to the absorber for further treatment (not shown). The stream (4) discharged from the bottom of tower (2) contains 51.635% by weight of acrylic acid, almost three times that of the comparative example stream (33). The overall composition of the material flow (6) is given in Table 1 below.

[0152] Table 1: Comparison of the composition of material flows (6) and (33)

[0153] Comparative Example According to an embodiment of the application Component Stream (33) [wt%] Stream (6) [wt%] Water 77.056 37.762 Acrolein 0.493 0.238 Acrylic acid 18.350 51.635 2-Ethanol 0.119 1.029 Formaldehyde 2.873 5.520 Acetaldehyde 0.013 0.004 Allyl alcohol 0.023 0.044 Allyl acrylate 0.002 0.019 Acetic acid 1.035 3.631 Other 0.036 0.118

Claims

1. A method for recovering light and dark boiling products from a steam stream, wherein the method comprises the following steps: A1) A vapor stream (1) containing light and dark boiling products is introduced into the column (2) at a point at the bottom of the column (2). A2) The steam stream (3) enriched with light boiling materials is discharged from the top of the tower (2). A3) Discharge the liquid stream (4) enriched with reboiler products from the bottom of the tower (2), and divide the stream (4) into a partial stream (5) enriched with reboiler products and a partial stream (6). A4) At a point above the bottom of tower (2), the feed stream (5) is recirculated back into tower (2), wherein the feed stream (5) remains substantially adiabatic during the recirculation process. A5) The concentrated boiling material stream (7) is discharged from the middle part of the tower (2), and the stream (7) is divided into a partial stream (8) and a partial stream (9). A6) A portion of the feed stream (9) is cooled in the heat exchanger (10) to provide a cooled feed stream (11), and the feed stream (11) is recycled back into the tower (2) as feed stream (12) at the inlet point below the top of the tower (2), and A7) Discharge the portion of the feed stream enriched with reboilerite (6) and the portion of the feed stream enriched with sinoboilerite (8). The volume of the portion of the material flow (8) is equal to the volume of the portion of the material flow (6). The light boiling product contains or is composed of acrolein, and the dark boiling product contains or is composed of acrylic acid.

2. The method according to claim 1, wherein the material flow (7) is discharged from the middle portion of the packing in the tower (2).

3. The method according to claim 1 or 2, further comprising the following steps: B1) Separate at least one additional portion of the material flow (13) from the material flow (11), and B2) Introduce the material flow (13) into the tower (2) at a point lower than the point of the discharge flow (7).

4. The method according to claim 1 or 2, wherein the feed stream (12) and / or feed stream (13) are directed to flow countercurrently to the rising steam after being introduced into the tower (2).

5. The method according to claim 3, wherein the material stream (12) is introduced into the tower (2) at a point above the discharge stream (7) and the material stream (13) is introduced at a point below the discharge stream (7).

6. The method according to claim 1 or 2, further comprising the following steps: C1) The feed stream (6) is introduced into the tower (14) at a point below the top of the tower (14). C2) The feed stream (6) is purged with airflow (15) inside the tower (14) to recover residual light boiling products from the feed stream (6). C3) Discharge the feed stream (16) containing light boiling matter from the top of the column (14) and introduce the feed stream (16) into the column (2) at a point above the bottom of the column (2), and C4) The light boiling material depleted in the feed stream (17) is discharged from the bottom of the tower (14).

7. The method according to claim 1 or 2, further comprising the following steps: D1) Introduce the feed stream (8) into the tower (18) at a point below the top of the tower (18). D2) The feed stream (8) is purged with airflow (19) inside the tower (18) to recover residual light boiling matter from the feed stream (8). D3) Discharge the feed stream (20) containing light boiling material from the top of the tower (18), and D4) Discharge the light boiling material depleted from the bottom of the tower (18) (21).

8. The method according to claim 1 or 2, wherein the vapor stream (1) originates from the oxidation of an organic compound selected from olefins, fatty alcohols, fatty aldehydes, allyl alcohols, allyl aldehydes and allyl ketones.

9. The method according to claim 1 or 2, wherein the steam stream (1) further comprises water.

10. The method of claim 8, wherein the discharge stream (7) in step A5) contains water.

11. The method according to claim 1 or 2, wherein the temperature at the bottom of the tower (2) is in the range of 70°C to 85°C.

12. The method according to claim 11, wherein the temperature of the material flow (5) is in the range of 70°C to 85°C.

13. The method according to claim 1 or 2, wherein the temperature of the material flow (11) is at most 20°C.

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