KR102579494B1 - Method for recovering aromatic hydrocarbon compound - Google Patents

Abstract

The present invention relates to a method for recovering aromatic hydrocarbon compounds, and more particularly, to a method for recovering aromatic hydrocarbon compounds, wherein a feed stream comprising a mixture of C6 to C8 hydrocarbon compounds is fed to a first column to produce a first column comprising a mixture of C6 and C7 hydrocarbon compounds. separating a column overhead stream and a first column bottoms discharge stream comprising a mixture of C8 hydrocarbon compounds; The first column overhead stream and the first solvent are fed to a second column to produce a second column overhead stream comprising a mixture of C6 and C7 non-aromatic hydrocarbon compounds, a mixture of C6 and C7 aromatic hydrocarbon compounds, and separating a second column bottoms effluent stream comprising a first solvent; The first column bottoms effluent stream and the second solvent are fed to a third column to produce a third column overhead stream comprising a mixture of C8 non-aromatic hydrocarbon compounds and the second solvent, a mixture of C8 aromatic hydrocarbon compounds, and separating a third column bottoms effluent stream comprising a second solvent; supplying the third column top discharge stream and the washing liquid to a washing tower to separate a washing tower top discharge stream containing a mixture of C8 non-aromatic hydrocarbon compounds and a washing tower bottom discharge stream containing a second solvent; Feeding the third column bottoms effluent stream to a stripper to separate a stripper top effluent stream comprising a mixture of C8 non-aromatic hydrocarbon compounds and a stripper bottoms effluent stream comprising a C8 aromatic hydrocarbon compound and a second solvent. ; Feeding the second column bottoms effluent stream and the stripper bottoms effluent stream to a fourth column, wherein the fourth column overhead stream comprises a mixture of C6 to C8 aromatic hydrocarbon compounds, and a first solvent and a second solvent. separating a fourth column bottoms discharge stream; and feeding the fourth column overhead stream to a fifth column or a seventh column, wherein the second column is an extractive distillation column and the third column is an extraction device. .

Description

Method for recovering aromatic hydrocarbon compounds {METHOD FOR RECOVERING AROMATIC HYDROCARBON COMPOUND}

The present invention relates to a method for recovering aromatic hydrocarbon compounds, and more specifically, to a method for recovering aromatic hydrocarbon compounds from pyrolysis by-products generated in a naphtha pyrolysis process.

Naphtha pyrolysis is mainly a method of supplying naphtha with steam at high temperature and applying heat of 1,000 ℃ or more to break the carbon-carbon chain at a temperature of 700 ℃ to 900 ℃, producing ethylene, propylene, butadiene, and BTX (Benzene-Toluene-Xylene) It is used to produce by-products such as mixtures.

Here, the BTX is recovered through a series of processes for recovering BTX from pyrolysis gasoline (Raw Pyrolysis Gasoline, RPG) containing hydrocarbon compounds of C5 or higher among naphtha pyrolysis products (see FIG. 1).

In this regard, during naphtha pyrolysis, the composition of the RPG produced as a by-product also changes significantly depending on changes in the composition of the feedstock or the operating conditions of the pyrolysis furnace.

In particular, in the process of recovering BTX from the RPG, in order to recover BTX, if the content of non-aromatic hydrocarbon compounds of C8 in the feed stream derived from RPG and input into the BTX recovery process increases, When separating C6 to C8 non-aromatic hydrocarbon compounds from the top of the purification column, it is difficult to separate the C8 non-aromatic hydrocarbon compounds from C6 to C8 aromatic hydrocarbon compounds, which causes the problem that the operation of the recovery process becomes unstable. .

In addition, in the above case, the non-aromatic hydrocarbon compounds of C8 are not separated like the non-aromatic hydrocarbon compounds of C6 and C7, but remain together with the aromatic hydrocarbon compounds of C6 to C8, so the C6 to C8 recovered according to the above recovery process. It causes the problem of lowering the purity of aromatic hydrocarbon compounds, especially C8 aromatic hydrocarbon compounds.

J.P. 2007-504292 A

The problem to be solved by the present invention is to improve process stability and purity of BTX when recovering BTX from pyrolysis gasoline (RPG) in order to solve the problems mentioned in the background technology of the above invention.

In other words, the present invention maintains process stability and BTX The purpose is to provide a method for recovering aromatic hydrocarbon compounds containing aromatic hydrocarbon compounds with high purity.

According to one embodiment of the present invention for solving the above problem, the present invention supplies a feed stream containing a mixture of C6 to C8 hydrocarbon compounds to a first column, thereby supplying a feed stream containing a mixture of C6 and C7 hydrocarbon compounds. separating a first column overhead stream comprising a mixture of C8 hydrocarbon compounds; The first column overhead stream and the first solvent are fed to a second column to produce a second column overhead stream comprising a mixture of C6 and C7 non-aromatic hydrocarbon compounds, a mixture of C6 and C7 aromatic hydrocarbon compounds, and separating a second column bottoms effluent stream comprising a first solvent; The first column bottoms effluent stream and the second solvent are fed to a third column to produce a third column overhead stream comprising a mixture of C8 non-aromatic hydrocarbon compounds and the second solvent, a mixture of C8 aromatic hydrocarbon compounds, and separating a third column bottoms effluent stream comprising a second solvent; supplying the third column top discharge stream and the washing liquid to a washing tower to separate a washing tower top discharge stream containing a mixture of C8 non-aromatic hydrocarbon compounds and a washing tower bottom discharge stream containing a second solvent; Feeding the third column bottoms effluent stream to a stripper to separate a stripper top effluent stream comprising a mixture of C8 non-aromatic hydrocarbon compounds and a stripper bottoms effluent stream comprising a C8 aromatic hydrocarbon compound and a second solvent. ; Feeding the second column bottoms effluent stream and the stripper bottoms effluent stream to a fourth column, wherein the fourth column overhead stream comprises a mixture of C6 to C8 aromatic hydrocarbon compounds, and a first solvent and a second solvent. separating a fourth column bottoms discharge stream; and feeding the fourth column overhead stream to a fifth column or a seventh column, wherein the second column is an extractive distillation column and the third column is an extraction device. .

According to the method for recovering aromatic hydrocarbon compounds according to the present invention, when recovering aromatic hydrocarbon compounds including BTX, even if the content of non-aromatic hydrocarbon compounds of C8 increases in pyrolysis gasoline due to changes in operating conditions of the pyrolysis furnace, the process It is possible to recover aromatic hydrocarbon compounds, including BTX, with high purity while maintaining stability, and furthermore, it is possible to recover high purity BTX, especially high purity xylene, even with low process investment costs.

Figure 1 is a process flow diagram for a general BTX purification process in the naphtha pyrolysis purification process.
Figure 2 is a process flow diagram for a method for recovering aromatic hydrocarbon compounds according to an embodiment of the present invention.
Figure 3 is a process flow diagram for a method for recovering aromatic hydrocarbon compounds according to an embodiment of the present invention.
Figure 4 is a process flow diagram for a method for recovering aromatic hydrocarbon compounds according to an embodiment of the present invention.
Figure 5 is a process flow diagram for a method for recovering aromatic hydrocarbon compounds according to a comparative example of the present invention.

Terms or words used in the description and claims of the present invention should not be construed as limited to their ordinary or dictionary meanings, and the inventor should appropriately use the concept of the term to explain his or her invention in the best way. Based on the principle of definability, it must be interpreted with meaning and concept consistent with the technical idea of the present invention.

In the present invention, the term 'hydrocarbon compound' may refer to a compound that forms a molecule using only carbon and hydrogen, and specifically, 'aromatic hydrocarbon compound' refers to a hydrocarbon that forms a molecule using only carbon and hydrogen and exhibits aromatic properties. It may refer to a compound, and 'non-aromatic hydrocarbon compound' may refer to a hydrocarbon compound that forms a molecule using only carbon and hydrogen and exhibits non-aromatic properties.

In the present invention, the term 'C number' may mean that the hydrocarbon compound has the number of carbon atoms indicated by the number.

In the present invention, the term 'stream' may refer to the flow of fluid within a process, or may also refer to the fluid itself flowing within a pipe. Specifically, the 'stream' may refer to both the fluid itself and the flow of the fluid flowing within the pipes connecting each device. Additionally, the fluid may refer to gas.

Hereinafter, the present invention will be described in more detail to facilitate understanding of the present invention.

The aromatic hydrocarbon compound recovery method according to the present invention is a part of naphtha pyrolysis, and is for recovering aromatic hydrocarbon compounds including BTX from pyrolysis gasoline (Raw Pyrolysis Gasoline, RPG) containing hydrocarbon compounds of C5 or higher among naphtha pyrolysis products. It may be a hydrocarbon compound recovery method.

According to one embodiment of the present invention, the naphtha pyrolysis includes the steps of introducing naphtha, recycled C2 and C3 hydrocarbon compounds as feedstock, and performing pyrolysis in each pyrolysis furnace (S1, not shown); Cooling the pyrolysis gas containing hydrogen and hydrocarbon compounds pyrolyzed in each pyrolysis furnace (S2, not shown); Compressing the cooled pyrolysis gas (S3, not shown); and purifying the pyrolysis compressed stream (S4, not shown).

Specifically, the thermal decomposition step (S1) may include a liquid-phase cracking process using naphtha as a feedstock, a gas-phase cracking process using recycled C2 and C3 hydrocarbon compounds such as ethane and propane as a feedstock, etc.

The cooling step (S2) may include a cooling process of cooling the pyrolysis gas generated in each pyrolysis furnace of the pyrolysis step (S1) in a cooling tower.

The compression step (S3) may include a compression process of compressing the pyrolysis stream cooled in the cooling step (S2) through multi-stage compression using two or more compressors to purify the pyrolysis stream.

The purification step (S4) may include a purification process for obtaining products and by-products from the pyrolysis compressed stream compressed and discharged in the compression step (S3).

That is, the method for recovering aromatic hydrocarbon compounds according to the present invention is a part of the refining step (S4), from pyrolysis gasoline (RPG) containing hydrocarbon compounds of C5 or higher pre-separated from the naphtha pyrolysis products in the refining step (S4). It may be a method for recovering aromatic hydrocarbon compounds including BTX.

In this regard, the process used in the recovery of aromatic hydrocarbon compounds including BTX from pyrolysis gasoline (RPG) containing hydrocarbon compounds of C5 or higher among naphtha pyrolysis products is shown in the process flow chart of FIG. 1.

According to the process flow diagram of FIG. 1, recovery of aromatic hydrocarbon compounds containing BTX from pyrolysis gasoline (RPG) involves adding hydrogen to pyrolysis gasoline (RPG) containing hydrocarbon compounds of C5 or higher, and performing a hydrogenation reaction and desulfurization reaction. separating hydrocarbon compounds of C5 and hydrocarbon compounds of C6 or higher (S5); A step (S6) of separating hydrocarbon compounds of C9 or higher from the hydrocarbon compounds of C6 or higher separated in step (S5); A step (S7) of separating C6 and C8 non-aromatic hydrocarbon compounds from the C6 to C8 hydrocarbon compounds separated in step (S6); and a step (S8) of separating benzene, toluene, and xylene from the C6 to C8 aromatic hydrocarbon compounds separated in step (S7).

Here, in carrying out the steps (S7) and (S8), according to the conventional aromatic hydrocarbon compound recovery method (M4), as shown in FIG. 5, C6 to C8 hydrocarbons separated in the (S6) step The feed stream (Feed') containing the compound is supplied to the eighth column 80 together with an extraction solvent to separate C6 to C8 non-aromatic hydrocarbon compounds and C6 to C8 aromatic hydrocarbon compounds, respectively.

The feed stream (Feed') supplied to the eighth column (80) is an eighth column bottom discharge stream (BS80) containing C6 to C8 aromatic hydrocarbon compounds and an extraction solvent, and C6 to C8 non-aromatic hydrocarbon compounds. It is separated into an eighth column overhead stream (US80) containing.

The eighth column bottom discharge stream (BS80) passes through the reboiler, and part of it is recovered in the eighth column (80), and the remainder is in the fourth 'column (40) to separate the C6 to C8 aromatic hydrocarbon compounds and the extraction solvent. '), the eighth column top discharge stream (US80) passes through a condenser and a portion is recovered to the eighth column (80), and the non-aromatic hydrocarbon compounds of C6 to C8 are discharged from the first top of the eighth column. It is discharged to stream (US81). At this time, the extraction solvent can be used by mixing water to improve the extraction performance of C6 to C8 aromatic hydrocarbon compounds, and the water in the extraction solvent is discharged in the eighth column top discharge stream (US80). The water contained in and discharged from the top discharge stream (US80) of the eighth column passes through a condenser and is separated from the non-aromatic hydrocarbon compounds of C6 to C8 in a reflux drum. 2 Discharged to the top discharge stream (US82).

The eighth column bottom discharge stream (BS80) supplied to the fourth 'column 40' is a fourth 'column top discharge stream containing C6 to C8 aromatic hydrocarbon compounds in the fourth' column 40' ( US40') and a fourth' column bottom discharge stream (BS40') containing the extraction solvent.

The fourth' column bottom discharge stream (BS40') passes through a reboiler, where a portion is recovered to the fourth' column (40') and the remainder is circulated to the eighth column (80) to reuse the extraction solvent, The 4' column overhead stream (US40') passes through a condenser and is partly recovered to the 4' column 40', and the first overhead effluent of the 4' column comprising C6 to C8 aromatic hydrocarbon compounds. The stream (US41') is supplied to the 5' column (50') to separate benzene, toluene, and xylene by the step (S8). Additionally, when the extraction solvent is mixed with water, some of the water in the extraction solvent may remain in the extraction solvent included in the eighth column bottom discharge stream (BS80). The water remaining in the extraction solvent is discharged from the 4th column 40' along with the C6 to C8 aromatic hydrocarbon compounds in the 4th column top discharge stream US40'. The water discharged from the 4th' column top discharge stream (US40') passes through a condenser and is separated from the C6 to C8 aromatic hydrocarbon compounds in a reflux drum, thereby forming the 4th' column. is discharged to a second overhead discharge stream (US42').

The first overhead stream US41 of the 4' column fed to the 5' column 50' is the 5' column overhead stream containing aromatic hydrocarbon compounds of C6 in the 5' column 50'. stream US50' and a 5' column bottoms discharge stream (BS50') containing aromatic hydrocarbon compounds of C7 and C8.

The 5' column bottom discharge stream (BS50') passes through the reboiler, and part of it is recovered in the 5th column (50'), and the remainder is sent to the 6' column (60) to separate the aromatic hydrocarbon compounds of C7 and C8. '), the 5' column top discharge stream (US50') passes through a condenser and a portion is recovered to the 5' column (50'), and the aromatic hydrocarbon compound of C6 is supplied to the first 5' column of the 5' column. It is recovered via the top discharge stream (US51').

The bottom effluent stream (BS50') of the 5' column fed to the 6' column 60' is the 6' column top effluent stream comprising aromatic hydrocarbon compounds of C7 in the 6' column 60'. (US60') and a 6' column bottoms discharge stream (BS60') containing aromatic hydrocarbon compounds of C8.

The 6' column bottom discharge stream (BS60') passes through a reboiler, a portion of which is recovered to the 6th column (60'), C8 aromatic hydrocarbon compounds are recovered from the remainder, and the 6' column top discharge stream. (US60') passes through the condenser and a portion is recovered in the 6' column (60'), and the aromatic hydrocarbon compounds of C7 are recovered through the first overhead stream (US61') of the 6' column.

Here, the eighth column uses an extractive distillation column to separate C6 to C8 aromatic hydrocarbon compounds and C6 to C8 non-aromatic hydrocarbon compounds by extractive distillation in the eighth column, The extraction solvent is used for the extractive distillation.

In this case, the extraction solvent may be a solvent that is polar and has a very high boiling point. It forms a highly non-ideal mixture with non-polar C6 to C8 non-aromatic hydrocarbon compounds, and has a polarity. It forms a near-ideal mixture with aromatic hydrocarbon compounds of C6 to C8. Therefore, in order to carry out the separation in step (S7), the C6 to C8 hydrocarbon compounds supplied to the eighth column 80 are, when the extraction solvent is added, C6 to C8 non-aromatic hydrocarbon compounds, As the relative volatility between C6 to C8 aromatic hydrocarbon compounds increases, the boiling point relationship changes as shown in Table 1 below.

boiling point Before adding extraction solvent boiling point change After adding extraction solvent lowness

↕

height C6 non-aromatic hydrocarbon compounds → C6 non-aromatic hydrocarbon compounds C6 aromatic hydrocarbon compounds C7 Non-aromatic hydrocarbon compounds C7 Non-aromatic hydrocarbon compounds C8 Non-aromatic hydrocarbon compounds C7 aromatic hydrocarbon compound C6 aromatic hydrocarbon compounds C8 Non-aromatic hydrocarbon compounds C7 aromatic hydrocarbon compound C8 aromatic hydrocarbon compounds C8 aromatic hydrocarbon compounds

Therefore, when the extraction solvent is added to the eighth column 80 and extractive distillation is performed, non-aromatic hydrocarbon compounds with low boiling points of C6 to C8 are separated into the top discharge stream (US80) of the eighth column 80. And, aromatic hydrocarbon compounds with high boiling points of C6 to C8 are separated into the bottom discharge stream (BS80) of the eighth column (80).

However, in the method of recovering aromatic hydrocarbon compounds using the eighth column 80 as described above, the present inventors have found that the composition of the feedstock for the naphtha pyrolysis in the step (S1) and the operating conditions of the pyrolysis furnace are As the content of C8 non-aromatic hydrocarbon compounds in pyrolysis gasoline (RPG) increases with change, the content of C8 non-aromatic hydrocarbon compounds in the feed stream (Feed') supplied to the eighth column (80) increases. In this case, the non-aromatic hydrocarbon compounds of C8 are not discharged to the eighth column top discharge stream (US80) together with the non-aromatic hydrocarbon compounds of C6 and C7, but are discharged to the eighth column top discharge stream (US80) together with the aromatic hydrocarbon compounds of C6 to C8. 8 is discharged to the bottom discharge stream (BS80), and when the aromatic hydrocarbon compounds of C8 are eventually recovered from the 6th column bottom discharge stream (BS60'), the non-aromatic hydrocarbon compounds of C8 remain together to form the aromatic hydrocarbon compounds of C8. It was confirmed that the purity was lowered and the process stability for the entire recovery process was also reduced.

Accordingly, as a result of repeated research, the present inventors have found that, in terms of the boiling point according to the boiling point change after adding the extraction solvent shown in Table 1, the difference between the boiling point of the C8 non-aromatic hydrocarbon compound and the boiling point of the C6 aromatic hydrocarbon compound is 15. ℃ or lower, it is difficult to separate the C8 non-aromatic hydrocarbon compound from the C6 aromatic hydrocarbon compound by extractive distillation, and as a result, the C8 non-aromatic hydrocarbon compound is separated from the C6 to C8 aromatic hydrocarbon compound together with the C6 aromatic hydrocarbon compound. It was found that discharged together with the bottom discharge stream (BS80) of column 8, and the present invention was completed to solve the above problems.

That is, the aromatic hydrocarbon compound recovery method according to the present invention maintains process stability even if the content of C8 non-aromatic hydrocarbon compounds in pyrolysis gasoline increases according to changes in the operating conditions of the pyrolysis furnace, and aromatic hydrocarbon compounds including BTX are recovered. This is an aromatic hydrocarbon compound recovery method that can recover with high purity.

The aromatic hydrocarbon compound recovery method according to the present invention may be an aromatic hydrocarbon compound recovery method for performing the steps (S7) and (S8).

Hereinafter, with reference to FIGS. 2 to 4, the aromatic hydrocarbon recovery method (M1 to M3) according to the present invention will be described in more detail.

According to one embodiment of the present invention, the aromatic hydrocarbon compound recovery method (M1 to M3) supplies a feed stream (Feed) containing a mixture of C6 to C8 hydrocarbon compounds to the first column 10, and supplies C6 and separating a first column top effluent stream (US10) comprising a mixture of hydrocarbon compounds of C7 and a first column bottom effluent stream (BS10) comprising a mixture of hydrocarbon compounds of C8 (S10); The first column overhead stream (US10) and the first solvent (Sol-1) are fed to the second column (20) to produce a second column overhead stream comprising a mixture of non-aromatic hydrocarbon compounds of C6 and C7 ( US20) and a second column bottom discharge stream (BS20) containing a mixture of aromatic hydrocarbon compounds of C6 and C7 and a first solvent (S20); The first column bottom discharge stream (BS10) and the second solvent (Sol-2) are fed to the third column (30), and the third column top discharge containing a mixture of C8 non-aromatic hydrocarbon compounds and the second solvent is produced. Separating the stream US30 and the third column bottom discharge stream BS30 comprising a mixture of aromatic hydrocarbon compounds of C8 and a second solvent (S30); The third column top discharge stream (US30) and the washing liquid (WW) are supplied to the washing tower (31) to produce a washing tower top discharge stream (US31) containing a mixture of C8 non-aromatic hydrocarbon compounds and a second solvent. Separating the washing tower bottom discharge stream (BS31) comprising (S31); The third column bottoms effluent stream (BS30) is fed to a stripper (32), wherein the stripper top effluent stream (US32) comprises a mixture of C8 non-aromatic hydrocarbon compounds, C8 aromatic hydrocarbon compounds and a second solvent. Separating the stripper bottom discharge stream (BS32) (S32); The second column bottoms effluent stream (BS20) and the stripper bottoms effluent stream (BS32) are fed to a fourth column 40 to produce a fourth column tops effluent stream (US40) comprising a mixture of C6 to C8 aromatic hydrocarbon compounds. ) and separating the fourth column bottom discharge stream (BS40) containing the first solvent and the second solvent (S40); And a step (S50) of supplying the fourth column top discharge stream (US40) to a fifth column (50) or a seventh column (70), wherein the second column (20) is an extractive distillation column (Extractive Distillation column). Column), and the third column may be an extraction device (extractor).

According to one embodiment of the present invention, in the step (S10), the difference between the boiling point of the C8 non-aromatic hydrocarbon compound and the boiling point of the C6 aromatic hydrocarbon compound in the boiling point according to the change in boiling point after the addition of the extraction solvent is 15. In order to prevent the difficulty in separating C8 non-aromatic hydrocarbon compounds and C6 aromatic hydrocarbon compounds by extractive distillation due to changes below ℃, the ratio of C8 is changed before adding the extraction solvent for extractive distillation. This may be a step to first separate the aromatic hydrocarbon compound from the C6 aromatic hydrocarbon compound. When performing the step (S10), the C6 aromatic hydrocarbon compound and the C8 non-aromatic hydrocarbon compound have already been separated prior to the addition of the extraction solvent, so when the extraction solvent for extractive distillation is added, Even if the boiling points of the C6 aromatic hydrocarbon compound and the C8 non-aromatic hydrocarbon compound change, there is an effect of being able to separate them from each other.

Meanwhile, according to one embodiment of the present invention, the first column top discharge stream (US10) is discharged from the top of the first column (10), passes through the condenser, and a portion of the first column discharge stream (US10) is recovered in the first column (10). , the remainder may be supplied to the second column 20, and the first column bottom discharge stream (BS10) is discharged from the bottom of the first column 10, passes through the reboiler, and a portion of the first column bottom discharge stream (BS10) is supplied to the first column 20. It may be recovered in (10), and the remainder may be supplied to the third column (30).

In addition, according to one embodiment of the present invention, the aromatic hydrocarbon compound recovery method including the step (S10) is a C8 non-aromatic hydrocarbon compound in a feed stream (Feed) containing a mixture of the C6 to C8 hydrocarbon compounds. When the content of the mixture is 0.5% by weight or more, 0.5% by weight to 5% by weight, or 0.76% by weight to 2.16% by weight, it can be particularly effective in recovering C8 aromatic hydrocarbon compounds with high purity.

According to one embodiment of the present invention, the step (S20) comprises a second column overhead stream (US20) comprising a mixture of non-aromatic hydrocarbon compounds of C6 and C7, from a mixture of hydrocarbon compounds of C6 and C7, and C6 And it may be a step for separating the second column bottom discharge stream (BS20) containing a mixture of aromatic hydrocarbon compounds of C7 and the first solvent.

The first solvent introduced in the step (S20) is an extraction solvent, and as shown in Table 1, by adding the first solvent, non-aromatic C6 and C7 compounds are extracted from the mixture of C6 and C7 hydrocarbon compounds. A change in the boiling point of the hydrocarbon compounds and the aromatic hydrocarbon compounds of C6 and C7 occurs, thereby enabling separation as a second column top discharge stream (US20) and a second column bottom discharge stream (BS20), respectively.

According to one embodiment of the present invention, the second column top discharge stream (US20) passes through the condenser and a portion is recovered in the second column (20), and the mixture of non-aromatic hydrocarbon compounds of C6 and C7 is It can be recovered via the first overhead stream (US21) of the second column.

At this time, the first solvent can be used by mixing water to improve the extraction performance of C6 and C7 aromatic hydrocarbon compounds, and the water in the first solvent is included in the second column top discharge stream (US20) and discharged. It can be. The water contained in and discharged from the second column top discharge stream (US20) passes through a condenser and is separated from the non-aromatic hydrocarbon compounds of C6 and C7 in a reflux drum, thereby removing the water from the second column. 2 Can be discharged to the top discharge stream (US22).

According to one embodiment of the present invention, the step (S30) comprises a third column overhead stream (US30) comprising a mixture of non-aromatic hydrocarbon compounds of C8 and a second solvent from a mixture of hydrocarbon compounds of C8, This may be a step for separating the third column bottom discharge stream (BS30) containing a mixture of aromatic hydrocarbon compounds and a second solvent.

According to one embodiment of the present invention, the step (S30) may be separated by the difference in solubility and density between the C8 non-aromatic hydrocarbon compound and the C8 aromatic hydrocarbon compound according to the addition of the second solvent, In this case, the energy consumption for operating the extraction device is lower than that of an extractive distillation column such as the second column 20, which has the effect of improving productivity. In particular, when the content of aromatic hydrocarbon compounds in the feed is small, extraction can be performed with lower operating energy compared to an extractive distillation column.

According to one embodiment of the present invention, the step (S31) may be a step for recovering the second solvent discharged together with the mixture of C8 non-aromatic hydrocarbon compounds from the third column top discharge stream (US30). Specifically, the third column top discharge stream (US30) supplied to the washing tower 31 is cleaned within the washing tower 31 by the washing liquid (WW) additionally supplied to the washing tower 31, A washing tower top discharge stream (US31) containing a mixture of non-aromatic hydrocarbon compounds and a washing tower bottom discharge stream (BS31) containing a second solvent may be separated.

According to one embodiment of the present invention, the washing liquid (WW) supplied to the washing tower 31 may be wash water. In addition, the washing liquid (WW) may be discharged together with the non-aromatic hydrocarbon compounds of C8 into the washing tower top discharge stream (US31) after washing the non-aromatic hydrocarbon compounds of C8 in the washing tower (31).

In addition, according to one embodiment of the present invention, the washing tower bottom discharge stream (BS31) containing the second solvent may be supplied to the fourth column 40, and in this case, the washing tower bottom discharge stream (BS31) may be supplied to the fourth column 40. The second solvent contained can be recovered via the fourth column bottoms discharge stream (BS40), which will be described later.

According to one embodiment of the present invention, the (S32) step is to remove C8 non-aromatic hydrocarbon compounds that may additionally remain in addition to C8 aromatic hydrocarbon compounds and the second solvent from the third column bottom discharge stream (BS30). This may be a step to separate.

According to one embodiment of the invention, the additional non-aromatic hydrocarbon compounds of C8 that may remain are discharged to the stripper top discharge stream (US32), wherein the stripper top discharge stream (US32) passes through a condenser. Part of this is recovered to the stripper 32, and the first top discharge stream US33 of the stripper containing non-aromatic hydrocarbon compounds of C8 is circulated to the third column 30, and the first top discharge stream of the stripper US33 containing the second solvent is circulated to the third column 30. The second overhead stream US34 may be fed to the fourth column 40. In this case, the C8 non-aromatic hydrocarbon compound separated from the stripper 32 can be fed back to the third column 30 and discharged to the washing tower 31 through extraction, and also discharged from the second top of the stripper. The second solvent contained in stream US34 can be recovered via the fourth column bottoms discharge stream BS40, which will be described later.

At this time, the washing tower bottom discharge stream (BS31) and the second top discharge stream (US34) of the stripper may each be supplied to the fourth column 40. As another example, the washing tower bottom discharge stream (BS31) ) and the second top discharge stream (US34) of the stripper may be mixed before being fed to the fourth column 40, in which case the mixed scrubber bottom discharge stream (BS31) and the second top discharge stream of the stripper (US34) forms a second solvent stream, which can be supplied to the fourth column 40 as one stream.

According to one embodiment of the present invention, the steps (S20) and (S30) are described sequentially for convenience of description, but may be performed independently or simultaneously. Step (S30) may be performed after step (S20), and step (S20) may be performed after step (S30).

In addition, according to one embodiment of the present invention, the steps (S31) and (S32) are described sequentially for convenience of description, but can be performed independently and simultaneously. Step (S32) may be performed after step (S31), and step (S31) may be performed after step (S32).

According to one embodiment of the present invention, in the (S40) step, the mixture of C6 to C8 aromatic hydrocarbon compounds separated in the (S20) step and (S32) step, and the first solvent and the second solvent are mixed. And, it may be a step for separating a mixture of C6 to C8 aromatic hydrocarbon compounds, and the first solvent and the second solvent.

At this time, the second column bottom discharge stream (BS20) and the stripper bottom discharge stream (BS32) each independently pass through the reboiler, and some are recovered to the second column 20 or stripper 32, respectively, and the remaining Can be supplied to the fourth column 40, and as another example, the second column bottom discharge stream (BS20) and the stripper bottom discharge stream (BS32) pass through the reboiler and a portion of the second column (20) ) or each recovered to the stripper 32, and the remainder may be mixed before being fed to the fourth column 40, in which case the mixed second column bottoms discharge stream (BS20) and third column bottoms discharge stream ( BS30) forms an aromatic hydrocarbon compound-solvent stream (ASS) and can be supplied to the fourth column 40 as one stream.

According to one embodiment of the present invention, the fourth column top discharge stream (US40) passes through the condenser, is partly recovered in the fourth column (40), and contains a mixture of C6 to C8 aromatic hydrocarbon compounds. The first overhead stream (US41) of the 4 column may be fed to the fifth column (50) or the seventh column (70) according to the step (S50) above to separate a mixture of aromatic hydrocarbon compounds of C6 to C8. . Additionally, when the first solvent is mixed with water, some of the water in the first solvent may remain in the first solvent included in the second column bottom discharge stream (BS20). The water remaining in the first solvent may be discharged from the fourth column 40 along with the C6 to C8 aromatic hydrocarbon compounds in the fourth column top discharge stream (US40). The water contained in and discharged from the fourth column top discharge stream (US40) passes through a condenser and is separated from the C6 to C8 aromatic hydrocarbon compounds in a reflux drum, thereby forming the second layer of the fourth column. It may be discharged to the top discharge stream (US42).

Additionally, according to one embodiment of the present invention, the first solvent and the second solvent used as the extraction solvent may be recovered as the fourth column bottom discharge stream (BS40).

According to one embodiment of the present invention, the aromatic hydrocarbon compound recovery method may include circulating the fourth column bottom discharge stream (BS40) to the second column 20 or the third column 30. (See Figure 3, M2). As a specific example, the fourth column bottom discharge stream (BS40) passes through the reboiler, a portion of which is recovered to the fourth column (40), and the remainder is circulated to the second column (20) and third column (30), respectively. It may include steps. As described above, when the fourth column bottoms discharge stream (BS40) is circulated to the second column 20 and/or the third column 30, the extraction solvent is recovered from the fourth column bottoms discharge stream (BS40), respectively. It is possible to reuse the first and second solvents in steps (S20) and (S30), which has the effect of improving productivity by reducing solvent costs.

In addition, according to one embodiment of the present invention, the aromatic hydrocarbon compound recovery method is to circulate the fourth column bottom discharge stream (BS40) to the second column 20 and the third column 30. It may include the step of separating the column bottom discharge stream (BS40), and the separation may be performed by a separate transfer line, or may be performed by being supplied to a drum for separation to increase separation efficiency.

According to one embodiment of the present invention, the first solvent and the second solvent are each independently sulfolane, tetraethylene glycol, dimethylsulfoxide, and N-formylphor. It may be one or more types selected from the group consisting of polyline (N-formylmorpholine). In this case, for the mixture of C6 to C8 hydrocarbon compounds, as shown in Table 1 above, a mixture of C6 and C7 non-aromatic hydrocarbon compounds, C6 and It is easy to control the boiling point of the mixture of C7 aromatic hydrocarbon compounds, and it is also easy to control the selectivity and solubility of the mixture of C8 non-aromatic hydrocarbon compounds and the C8 aromatic hydrocarbon compound, in the step (S20) It has the effect of facilitating separation by extraction distillation and extraction in step (S30).

Additionally, according to one embodiment of the present invention, the first solvent and the second solvent may be the same solvent. As a specific example, the first solvent and the second solvent may be described separately as the first solvent and the second solvent in order to distinguish the positions of the solvents introduced into the second column 20 and the third column 30, respectively. and the type may be the same solvent. In this case, it is possible to simultaneously separate the first solvent and the second solvent in the fourth column 40 for solvent separation, so there is no need to install additional columns, and it is possible to simplify the process, which has the effect of improving productivity. there is.

In addition, according to one embodiment of the present invention, the aromatic hydrocarbon compound recovery methods (M1 and M2), as shown in Figures 2 and 3, the fourth column overhead stream (US40) is passed to the fifth column (50) A step (S60) of separating the fifth column top discharge stream (US50) containing aromatic hydrocarbon compounds of C6 and the fifth column bottom discharge stream (BS50) containing aromatic hydrocarbon compounds of C7 and C8. It may include

According to one embodiment of the present invention, the fifth column top discharge stream (US50) passes through the condenser and a portion is recovered in the fifth column (50), and the aromatic hydrocarbon compounds of C6 are discharged to the first top of the fifth column. It is recovered through the discharge stream (US51), and the fifth column bottom discharge stream (BS50) passes through the reboiler, where some of it is recovered to the fifth column (50) and the remainder is a mixture of aromatic hydrocarbon compounds of C7 and C8. It can be supplied to the sixth column 60 for separation.

In addition, according to one embodiment of the present invention, the aromatic hydrocarbon compound recovery method (M1 and M2), as shown in Figures 2 and 3, the fifth column bottom discharge stream (BS50) is passed to the sixth column (60) supplying to a step (S70) of separating a sixth column top discharge stream (US60) containing aromatic hydrocarbon compounds of C7 and a sixth column bottom discharge stream (BS60) containing aromatic hydrocarbon compounds of C8. It may be.

According to one embodiment of the present invention, the sixth column top discharge stream (US60) passes through the condenser and a portion is recovered in the sixth column (60), and the aromatic hydrocarbon compounds of C7 are discharged to the first top of the sixth column. The sixth column bottom discharge stream (BS60) passes through a reboiler and is partially recovered through the sixth column (60), and the aromatic hydrocarbon compounds of C8 pass through the reboiler. It can be recovered via the remainder of the sixth column bottoms discharge stream (BS60).

In addition, according to one embodiment of the present invention, the aromatic hydrocarbon compound recovery method (M3), as shown in FIG. 4, supplies the fourth column top discharge stream (US40) to the seventh column (70), A seventh column overhead stream (US70) comprising aromatic hydrocarbon compounds from C6, a seventh column middle draw stream (MS70) comprising aromatic hydrocarbon compounds from C7, and a seventh column bottom draw comprising aromatic hydrocarbon compounds from C8. It may include a step (S80) of separating the stream (BS70).

According to one embodiment of the present invention, the seventh column top discharge stream (US70) passes through the condenser and a portion is recovered in the seventh column 70, and the seventh column bottom discharge stream (BS70) is sent to the reboiler. A portion of the C6 is recovered through the seventh column (70), the aromatic hydrocarbon compounds of C6 are recovered through the remainder of the seventh column top discharge stream (US70) that has passed through the condenser, and the aromatic hydrocarbon compounds of C7 are recovered through the seventh column. Recovered via the middle draw stream (MS70), the aromatic hydrocarbon compounds of C8 can be recovered via the remainder of the seventh column bottoms draw stream (BS70) which has passed through the reboiler.

According to one embodiment of the present invention, the seventh column 70 may be a divided wall column (DWC) for simultaneously separating three components in one column.

When recovering aromatic hydrocarbon compounds containing BTX from pyrolysis gasoline (RPG), especially pyrolysis gasoline (RPG) by naphtha pyrolysis, according to the aromatic hydrocarbon compound recovery method of the present invention described above, the operating conditions of the pyrolysis furnace Even if the content of C8 non-aromatic hydrocarbon compounds in pyrolysis gasoline increases due to changes in pyrolysis gasoline, it is possible to recover aromatic hydrocarbon compounds including BTX with high purity while maintaining process stability. Furthermore, high purity BTX is possible even at low process investment costs. , In particular, it is effective in recovering high purity xylene.

That is, when recovering an aromatic hydrocarbon compound according to the method for recovering an aromatic hydrocarbon compound of the present invention, the purity of the aromatic hydrocarbon of C8 recovered from the fifth column 50 or the seventh column 70 is 97.30% by weight or more, It may be 98% by weight or more, or 98.2% by weight or more.

In addition, when recovering aromatic hydrocarbon compounds according to the aromatic hydrocarbon compound recovery method of the present invention, it may be possible to recover not only the above-described C8 aromatic hydrocarbon compounds, but also all C6 and C7 aromatic hydrocarbon compounds with high purity. As a specific example, when recovering an aromatic hydrocarbon compound according to the method for recovering an aromatic hydrocarbon compound of the present invention, the purity of the aromatic hydrocarbon of C6 recovered from the fifth column 50 or the seventh column 70 is 99.0% by weight or more. , 99.5% by weight or more, or 99.9% by weight or more, the purity of the aromatic hydrocarbon of C7 is 99.0% by weight or more, 99.2% by weight or more, or 99.5% by weight or more, and the purity of the aromatic hydrocarbon of C8 is 97.30% by weight or more, 98 It may be more than % by weight, or more than 98.2% by weight.

Hereinafter, the present invention will be described in more detail through examples. However, the following examples are intended to illustrate the present invention, and it is obvious to those skilled in the art that various changes and modifications are possible within the scope and spirit of the present invention, and the scope of the present invention is not limited to these alone.

Experiment example

Example 1 to 3

Using the process flow diagram shown in FIG. 3, a feed stream (Feed) was supplied under the conditions shown in Table 2 below, and each column was operated to recover C6 to C8 aromatic hydrocarbon compounds, and recover C6 to C8 aromatic compounds. The purity of hydrocarbon compounds is listed in Table 2 below.

division Example One 2 3 Content of non-aromatic hydrocarbon compounds of C8 in feed (weight%) 0.76 1.22 2.16 First solvent and second solvent type Sulfolane Sulfolane Sulfolane 1st column
Driving conditions upper temperature (℃) 121.2 121.1 121.6 bottom temperature (℃) 167.8 167.5 169.6 enter kg/ ^cm2g 1.8 1.8 1.8 2nd column
Driving conditions upper temperature (℃) 87.4 87.4 87.3 bottom temperature (℃) 155.5 155.6 155.6 enter kg/ ^cm2g 0.47 0.47 0.47 3rd column
Driving conditions temperature (℃) 40 40 40 enter kg/ ^cm2g 3.9 3.9 3.9 washing tower
Driving conditions temperature (℃) 39 39 39 enter kg/ ^cm2g 3 3 3 stripper
Driving conditions upper temperature (℃) 101 101 101 bottom temperature (℃) 164 164 164 enter kg/ ^cm2g 0.9 0.9 0.9 Column 4
Driving conditions upper temperature (℃) 67.0 67.5 68.0 bottom temperature (℃) 174.5 174.5 174.5 enter kg/ ^cm2g -0.53 -0.53 -0.53 Column 5
Driving conditions upper temperature (℃) 99.6 99.6 99.6 bottom temperature (℃) 161.7 161.7 161.7 enter kg/ ^cm2g 1.96 1.96 1.96 Column 6
Driving conditions upper temperature (℃) 130.0 130.0 130.0 bottom temperature (℃) 168.1 168.1 168.1 enter kg/ ^cm2g 0.78 0.78 0.78 Purity of recovered C6 aromatic hydrocarbon compounds (weight%) 99.95 99.96 99.96 Purity of recovered aromatic hydrocarbon compounds of C7 (weight%) 99.6 99.6 99.6 Purity of recovered C8 aromatic hydrocarbon compounds (weight%) 98.5 98.3 98.2

Comparative example 1 to 3

Using the process flow diagram shown in Figure 5, a feed stream (Feed) was supplied under the conditions shown in Table 3 below, and each column was operated to recover C6 to C8 aromatic hydrocarbon compounds, and the recovered C6 to C8 aromatic The purity of the hydrocarbon compounds is listed in Table 3 below.

division Comparative example One 2 3 Content of non-aromatic hydrocarbon compounds of C8 in feed (weight%) 0.76 1.22 2.16 Solvent type Sulfolane Sulfolane Sulfolane Column 8
Driving conditions upper temperature (℃) 87.9 88.1 87.9 bottom temperature (℃) 152.0 152.0 151.3 enter kg/ ^cm2g 0.47 0.47 0.47 4th' column
Driving conditions upper temperature (℃) 66.4 66.6 56.2 bottom temperature (℃) 174.6 174.6 174.6 enter kg/ ^cm2g -0.53 -0.53 -0.53 Column 5'
Driving conditions upper temperature (℃) 98.9 98.9 98.7 bottom temperature (℃) 161.7 161.9 162.3 enter kg/ ^cm2g 1.96 1.96 1.96 Column 6'
Driving conditions upper temperature (℃) 130.0 130.1 130.0 bottom temperature (℃) 167.9 167.8 167.3 enter kg/ ^cm2g 0.78 0.78 0.78 Purity of recovered C6 aromatic hydrocarbon compounds (weight%) 99.91 99.96 99.97 Purity of recovered aromatic hydrocarbon compounds of C7 (weight%) 99.58 99.37 99.54 Purity of recovered C8 aromatic hydrocarbon compounds (weight%) 96.39 93.80 83.44

As shown in Tables 2 and 3, when recovering C6 to C8 aromatic hydrocarbon compounds according to the aromatic hydrocarbon compound recovery method of the present invention, the purity of C6 and C7 aromatic hydrocarbon compounds is recovered at high purity, and C8 It was confirmed that aromatic hydrocarbon compounds could be recovered with high purity.

In particular, according to the prior art, even though the content of non-aromatic hydrocarbon compounds of C8 in the feed stream was as low as 0.76% by weight, it was confirmed that the purity of aromatic hydrocarbon compounds of C8 was 96.39% by weight. In addition, it was confirmed that as the content of C8 non-aromatic hydrocarbon compounds in the feed stream (Feed) increased, the purity of the recovered C8 aromatic hydrocarbon compounds rapidly decreased.

However, according to the present invention, not only does the content of C8 non-aromatic hydrocarbon compounds in the feed stream (Feed) exist as low as 0.76% by weight, but even if the content of C8 non-aromatic hydrocarbon compounds in the feed stream (Feed) increases , it was possible to recover the C8 aromatic hydrocarbon compound with a purity of 98.2% by weight or more.

From the above results, the present inventors found that when recovering an aromatic hydrocarbon compound according to the present invention, when recovering an aromatic hydrocarbon compound including BTX according to the method for recovering an aromatic hydrocarbon compound according to the present invention, the operation of the thermal decomposition Even if the content of C8 non-aromatic hydrocarbon compounds in pyrolysis gasoline increases due to changes in conditions, it is possible to recover aromatic hydrocarbon compounds, including BTX, with high purity while maintaining process stability, and furthermore, it is possible to recover high-purity aromatic hydrocarbon compounds, including BTX, at low process investment costs. It was confirmed that BTX, especially high purity xylene, could be recovered.

Claims (10)

A feed stream comprising a mixture of hydrocarbon compounds C6 to C8 is fed to the first column, a first column overhead stream comprising a mixture of hydrocarbon compounds C6 and C7, and a first column overhead stream comprising a mixture of hydrocarbon compounds C8. 1 separating the column bottoms discharge stream;
The first column overhead stream and the first solvent are fed to a second column to produce a second column overhead stream comprising a mixture of C6 and C7 non-aromatic hydrocarbon compounds, a mixture of C6 and C7 aromatic hydrocarbon compounds, and separating a second column bottoms effluent stream comprising a first solvent;
The first column bottoms effluent stream and the second solvent are fed to a third column to produce a third column overhead stream comprising a mixture of C8 non-aromatic hydrocarbon compounds and the second solvent, a mixture of C8 aromatic hydrocarbon compounds, and separating a third column bottoms effluent stream comprising a second solvent;
supplying the third column top discharge stream and the washing liquid to a washing tower to separate a washing tower top discharge stream containing a mixture of C8 non-aromatic hydrocarbon compounds and a washing tower bottom discharge stream containing a second solvent;
Feeding the third column bottoms effluent stream to a stripper to separate a stripper top effluent stream comprising a mixture of C8 non-aromatic hydrocarbon compounds and a stripper bottoms effluent stream comprising a C8 aromatic hydrocarbon compound and a second solvent. ;
Feeding the second column bottoms effluent stream and the stripper bottoms effluent stream to a fourth column, wherein the fourth column overhead stream comprises a mixture of C6 to C8 aromatic hydrocarbon compounds, and a first solvent and a second solvent. separating a fourth column bottoms discharge stream; and
feeding said fourth column overhead stream to a fifth or seventh column;
The second column is an extractive distillation column,
The third column is an extraction device,
A method for recovering aromatic hydrocarbon compounds, wherein the content of the mixture of C8 non-aromatic hydrocarbon compounds in the feed stream comprising the mixture of C6 to C8 hydrocarbon compounds is 0.5% by weight or more. delete According to paragraph 1,
The method of claim 1 , wherein the second column bottoms effluent stream and the stripper bottoms effluent stream are mixed before being fed to the fourth column. According to paragraph 1,
A method of recovering aromatic hydrocarbon compounds comprising circulating the fourth column bottoms effluent stream to a second column or a third column. According to paragraph 1,
The first solvent and the second solvent are each independently a group consisting of sulfolane, tetraethylene glycol, dimethylsulfoxide, and N-formylmorpholine. A method for recovering one or more aromatic hydrocarbon compounds selected from. According to paragraph 1,
The aromatic hydrocarbon compound recovery method is,
Feeding the fourth column overhead stream to a fifth column to separate a fifth column overhead stream comprising aromatic hydrocarbon compounds of C6 and a fifth column bottom effluent stream comprising aromatic hydrocarbon compounds of C7 and C8. A method for recovering aromatic hydrocarbon compounds comprising the step: According to clause 6,
The aromatic hydrocarbon compound recovery method is,
Feeding the fifth column bottoms effluent stream to a sixth column to separate the sixth column top effluent stream comprising aromatic hydrocarbon compounds of C7 and the sixth column bottoms effluent stream comprising aromatic hydrocarbon compounds of C8. A method for recovering aromatic hydrocarbon compounds, comprising: According to paragraph 1,
The aromatic hydrocarbon compound recovery method is,
The fourth column overhead stream is fed to a seventh column to produce a seventh column overhead stream comprising aromatic hydrocarbon compounds of C6, a seventh column mid-draw stream comprising aromatic hydrocarbon compounds of C7, and aromatic hydrocarbons of C8. A method for recovering an aromatic hydrocarbon compound, comprising separating a seventh column bottoms effluent stream comprising the compound. According to paragraph 1,
A method for recovering an aromatic hydrocarbon compound, wherein the purity of the C8 aromatic hydrocarbon recovered from the fifth or seventh column is 97.30% by weight or more. According to paragraph 1,
The purity of the C6 aromatic hydrocarbon recovered from the fifth or seventh column is 99.0% by weight or more, the purity of the C7 aromatic hydrocarbon is 99.0% by weight or more, and the purity of the C8 aromatic hydrocarbon is 97.30% by weight or more. Compound recovery method.