KR101317595B1 - Method for saving energy in aromatic compounds separation from naphtha - Google Patents

Abstract

The present invention recovers the waste heat from the NHT process rerun column top product in the aromatic compound treatment process using para-xylene and benzene as main end products by treating naphtha as a raw material, and preheating NHT process stripper raw material and NHT process naphtha. The present invention relates to a process for saving energy by supplying a splitter reboiler heat source.

Description

Energy saving method in the separation process of aromatic compounds using waste heat {METHOD FOR SAVING ENERGY IN AROMATIC COMPOUNDS SEPARATION FROM NAPHTHA}

The present invention is to treat the raw material naphtha (para-xylene (PX) and benzene (benzene: BZ) in the aromatic compound treatment process, the main final product, from the NHT process rerun column top product The present invention relates to a process for recovering waste heat and saving energy by preheating the NHT process stripper raw material and supplying it to the reboiler heat source of the NHT process naphtha splitter.

In the petrochemical industry, commercial use of distillation columns is well known, and the operating principles and operating examples of commonly used distillation columns are well described by way of example in the following literature: H.Z. Kister, "Distllation-Operation," McGraw Hill, Nt, 1990; H.Z. Kister, "Distllation-Design," McGraw Hill, NY, 1992; And J.D. Seader and E. J. Henley, "Separation Process Principles," 2nd ed., Wiley, NY, 2006.

Aromatic compound treatment process (hereinafter also referred to as "aromatic process") is a process in which petrochemical plants process naphtha, a raw material, using para-xylene and benzene as main end products. In the conventional aromatic process, the main process in which the mixed xylene is produced containing para-xylene (PX), which is one of the main products, is a reformer, xylene isomerization process and 7 carbon atoms and carbon atoms Three processes of transalkylation and disproportionation of nine aromatic compounds.

Commercially used para-xylene separation processes include a simulated moving bed (SMB) process and a crystallization method, and the PMB separation process using the SMB method is performed at each stage of a multistage adsorption tower. By periodically controlling the opening and closing of the valve to be positioned, the effect is as if the adsorbent and the fluid is in countercurrent contact, effectively separating the xylene isomer, a representative example is UOP's Parex process have.

Description of this conventional Parex process is well described in Korean Patent Registration No. 10-0741752. In the Parex process, a distillation column such as an extraction column and a raffinate column is used to separate and recover the desorbent material from the xylene column which performs the adsorptive separation of PX and then the extract and raffinate streams.

A typical conventional aromatic compound treatment process is shown in FIGS. 1, 2 and 3.

According to FIG. 1, the mixture (reformer) of the raw aromatic compound injected from the reformer 1 into the splitter 2 is a mixture containing 6 aromatic compounds and 7 carbon atoms, that is, a mixture containing benzene and toluene, and heavier. Separated into aromatic mixtures (such as xylene having 8 carbon atoms), the former is introduced via line 21 into the SULFOLANE process (3), which is a benzene-toluene fractionation process and a non-aromatic removal process. It is fed to xylene column 5 via line 22. In the sulfolane process, a mixture of benzene and toluene is separated into benzene and toluene, respectively, where benzene is discharged via line 33, and toluene (TOL) is aromatic via toluene and carbon 9 aromatics via line 31. It is fed to TATORAY process (4) which is a compound disproportionation and transalkylation process. In the xylene column 5, aromatic compounds having 9 or more carbon atoms are discharged through the line 52 to the heavy aromatic column 6, and the xylene mixture having 8 carbon atoms is discharged through the line 51 to form para-xyl. It is injected into the PAREX process (8) which is a lene separation process. The xylene mixture introduced into the PAREX process 8 via line 51 is separated into para-xylene and the remaining xylene mixture, the former being discharged through line 81, the latter through line 82 It is injected into the ISOMAR process (9) which is a xylene isomerization process. The output of the ISOMAR process 9 is withdrawn via line 91 and re-introduced to the xylene column 5. The mixture of aromatic compounds having at least 9 carbon atoms fed to the heavy aromatic column (6) via line (52) is composed of aromatic compounds (A9) having at least 9 carbon atoms containing trimethylbenzene and aromatic compounds having at least 10 carbon atoms (A10 +) in the heavy aromatic column (6). ), The former is introduced via line 61 into the TATORAY process 4, which is a disproportionation and transalkylation process of toluene and an aromatic compound having 9 carbon atoms, and the latter is discharged through line 62. The aromatic compound having 9 carbon atoms introduced into the TATORAY process (4) contains para-xylene by transalkylation reaction with toluene introduced through the line 31 from the sulfolane process (3) in the TATORAY process (4). The resulting mixture is produced, which is then reintroduced into xylene process 5 via line 71.

Referring to FIG. 2, which is a schematic diagram of another embodiment of the aromatic compound treatment process, the process shown in FIG. 2 is a case where the TATORAY process in the process of FIG. 1 is replaced by a PX-Plus process and a TAC9 process. Same as the process, but different from FIG. 1 in the following matters. Toluene (TOL) separated in the sulfolane process is introduced into the PX-Plus process (4), which is a selective disproportionation process of toluene, and the TAC9 process (7), which is a transalkylation process, through the line 31, and the PX- Mixtures resulting from the selective disproportionation in Plus process (4) include aromatic compounds (A9) having 9 carbon atoms, such as benzene (A6), toluene (A7), xylene (A8) and trimethylbenzene, Among them, para-xylene is included in the xylene mixture in an amount of about 85 to 95% by weight. The resulting mixture of this PX-Plus process (4) is reintroduced to the SULFOLANE process (3) via line 41, where x8 carbon atoms and heavier trimethylbenzene are lighter components. After being separated from, it is discharged via line 32 and fed to xylene column 5 via line 22. Aromatic compound (A9) having 9 carbon atoms including trimethylbenzene separated in heavy aromatic column (6) is fed via line (61) to TAC9 process (7) which is a transalkylation process. The aromatic compound having 9 carbon atoms introduced into the TAC9 process (7) contains para-xylene by transalkylation reaction with toluene introduced through the line (31) from the sulfolane process (3) in the TAC9 process (7). The resulting mixture is produced, and the resulting mixture is reintroduced into xylene column 5 via line 71.

Referring to FIG. 3, which is a schematic diagram of another embodiment of the aromatic compound treatment process, the process shown in FIG. 3 is a case where the crystallization process is installed in the process of FIG. 2, and is basically the same as the process of FIG. 2. Xylene and heavier trimethylbenzene, etc. having 8 carbon atoms discharged from the process (3) are introduced into the crystallization process (10) via the line 32, and in this crystallization process (10), the input mixture is para-xylene and para. The process of FIG. 2 only after being separated into a xylene mixture other than xylene, the former is discharged through line 101 and the latter is discharged through line 102 and introduced into xylene column 5 There is a difference.

On the other hand, the NHT process (Naphtha Hydrotreating Process) removes C6 or less hydrocarbons above the naphtha splitter to meet the distillation range of naphtha required as a raw material of the aromatization process (reformer), and removes C10 or more hydrocarbons. The process of removing the bottom of the rerun column, which is then included in the raw naphtha to remove the impurities such as nitrogen, sulfur, etc., which may cause corrosion of the process.

In the rerun column, hydrocarbons of 10 or more carbon atoms are removed to the bottom to meet the distillation range of naphtha required as a raw material for the aromatization process (reformer). The upper product is hydrocarbon having 6 to 10 carbon atoms, which is a raw material of the reformer. In general, the top of the rerun column is not enough to be used directly as a reboiler heat source for other columns with waste heat at a temperature of 130 ° C.

In each of the existing processes, the NHT process stripper raw material preheating and the reboiler heat source of the NHT process stripper are supplied using separate steams, but in terms of energy saving, there is room for improvement to further enhance energy saving It has

An object of the present invention is to recover the waste heat from the upper product of the NHT process rerun column during the aromatic compound separation process, and to preheat the NHT process stripper raw material and supply it to the reboiler heat source of the NHT process naphtha splitter, thereby heat source during the conventional aromatic compound separation process By reducing the use of the middle pressure steam (MS) used as a, it is to significantly reduce the energy.

According to the present invention, an aromatics processing process comprising para-xylene and benzene as main end products by treating naphtha as a raw material, including the use of xylene column, extraction column, raffinate column and NHT rerun column. The waste heat from the NHT process rerun column top product is recovered and fed to the reboiler heat source of the NHT process stripper raw material preheat and the NHT process naphtha splitter to provide an energy saving method in the aromatic compound separation process.

A distillation column is generally a column for gas-liquid contact, a reboiler that boils again a liquid flowing down the column, vaporizes a portion of it, and returns it to the inside of the column, and condenses all or a portion of the gas discharged from the column top again. It is composed of a condenser returning back inside the distillation column.

As a reboiler heat source of the existing NHT process stripper raw material preheating and NHT process naphtha splitters, medium pressure steam (16-17 kg / cm ² g, steam of 280 ° C.) is mainly used. By using the waste heat from the waste as a heat source can reduce the use of the existing medium pressure steam.

According to the present invention, waste heat from the NHT process rerun column top product is recovered and replaced with the high temperature bottom material used for preheating the NHT stripper raw material and used for preheating the NHT process stripper raw material, the NHT stripper top bottom material being the NHT process. By supplying to the reboiler heat source of a naphtha splitter, energy saving can be remarkably improved through waste heat recovery compared with the conventional aromatic compound separation process.

1 is a schematic of a typical aromatics treatment process.
2 is a schematic diagram of another exemplary aromatic compound treatment process.
3 is a schematic diagram of another exemplary aromatic compound treatment process.
4 is a schematic diagram of one embodiment of an improved aromatics treatment process according to the present invention.
5 is a schematic diagram of an embodiment of a conventional aromatic compound treatment process.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the scope of the present invention is not limited by these Examples.

Example

The energy saving method in the aromatic compound separation process according to the present embodiment was realized through the establishment of four heat exchangers (EA-124, EA-138 and EA-107C / D) with reference to FIG.

As shown in FIG. 4, waste heat of the NHT process rerun column (DA-102) top product was fed to the NHT process stripper (DA-103) raw material preheat and NHT process naphtha splitter (DA-101) reboiler heat source, respectively.

By operating in this way, it was possible to save 2.1 MMKcal / hr of energy per year compared to when using MS used as a reboiler heat source for NHT process stripper raw material preheating and NHT process naphtha splitter. Savings can be achieved.

Comparative Example

In the conventional method as shown in Figure 5, by preheating the NHT process stripper raw material and supplying MS to the reboiler heat source of the NHT process naphtha splitter did not save energy as the embodiment.

SULFOLANE: Benzene-toluene fractionation process and non-aromatic removal process
TATORAY: Disproportionation and transalkylation process of toluene and aromatic compound having 9 carbon atoms
PAREX: Para-Xylene Separation Process
ISOMAR: Xylene Isomerization Process
PX-Plus: Selective Disproportionation Process of Toluene
TAC9: transalkylation process of aromatic compound having 9 carbon atoms
A6: aromatic compound having 6 carbon atoms
A7: aromatic compound having 7 carbon atoms
A8: aromatic compound having 8 carbon atoms
A9: aromatic compound having 9 carbon atoms
A10 +: aromatic compound having 10 or more carbon atoms
EA-101, EA-104, EA-107, EA-124, EA-201, and EA-138: heat exchanger
DA-102: rerun column
DA-103: naphtha splitter
FA-103: NHT reactor raw material surge drum
FA-105: NHT Reactor Effluent Separation Drum

Claims (1)

Benzene, toluene and xylene (BTX) from naphtha, including the use of xylene columns, extraction columns, raffinate columns, naphtha hydrogenation (NHT) process rerun columns, naphtha hydrogenation process strippers and naphtha hydrogenation process naphtha splitters When the separation process of the aromatic compound is carried out, the waste heat from the upper part of the naphtha hydrogenation process rerun column is recovered and fed to the reboiler heat source of the naphtha hydrogenation process stripper raw material preheating and naphtha hydrogenation process naphtha splitter Energy saving method in separation process.

Images