Process for producing liquefied petroleum gas and pentane foaming agent from light naphtha

Abstract

The invention relates to a process for producing liquefied petroleum gas and a pentane foaming agent from light naphtha. The device comprises a first dividing wall column (T1), a second rectifying column (T2), a heat exchanger (E01-09), a pump (P01-02), a storage tank (V01-05), a mixer (M01) and a flow divider (F01). A partition plate is arranged in the first dividing wall column (T1) and divides the first dividing wall column (T1) into four parts, namely a feeding side, an extraction side, a public rectifying section and a public stripping section. And the first dividing wall column (T1) and the second rectifying column (T2) are thermally integrated. Liquefied petroleum gas is extracted from the top of the first dividing wall column (T1), and a pentane foaming agent is extracted from the side line. The pentane foaming agent is extracted from the top of the second rectifying tower, and C6 and above are extracted from the bottom. Through tower system heat integration, compared with a common double-tower production process, the process saves energy by more than 15%. The process can be used for producing three types of pentane foaming agents at the same time.

Description

Technical Field

[0001] The present invention relates to a process for producing liquefied petroleum gas and pentane foaming agent from light naphtha. Background Art

[0002] In petroleum refineries, the sources of light naphtha include hydrocracked light naphtha, reforming topped light naphtha, straight-run light naphtha from atmospheric and vacuum distillation units, etc. Currently, light naphtha is mainly used as a steam cracking feedstock or a gasoline blending component. To improve the utilization value of light naphtha, liquefied petroleum gas and pentane foaming agent can be produced from light naphtha.

[0003] An internal dividing wall column designs a vertical partition inside a common distillation column. The partition can avoid backmixing of intermediate components and enable the internal dividing wall column to produce high-purity side-line products, thus reducing energy consumption.

[0004] Chinese Patent CN 111362773A uses an internal dividing wall column to separate light naphtha to produce pentane foaming agent. In terms of the column structure, the partition of the internal dividing wall column is connected to the top; in terms of product production, it cannot produce liquefied petroleum gas and pentane foaming agent simultaneously, and only one type of pentane foaming agent can be produced at the same time; in terms of process design, it does not use column system heat integration technology, resulting in high energy consumption.

[0005] Chinese Patents CN 115651704A, CN 114653319B, CN 117050774A, CN 117105739A, CN117282116A use common distillation columns to produce pentane foaming agent without using an internal dividing wall column, and the energy-saving range is limited. Summary of the Invention

[0006] The object of the present invention is to propose a process for producing liquefied petroleum gas and pentane foaming agent from light naphtha, which uses advanced internal dividing wall column technology and column system heat integration technology to reduce energy consumption during the production process and improve the production flexibility of the device.

[0007] A process for producing liquefied petroleum gas and pentane foaming agent from light naphtha proposed by the invention includes: a first internal dividing wall column (T1), a second distillation column (T2), heat exchangers (E01 - 09), pumps (P01 - 02), storage tanks (V01 - 05), a mixer (M01) and a splitter (F01).

[0008] A process for producing liquefied petroleum gas and pentane foaming agent from light naphtha proposed by the present invention. The light naphtha enters the feed side of the first dividing wall column (T1). The liquefied petroleum gas (102) is withdrawn from the top of the first dividing wall column (T1), the pentane foaming agent (103) is withdrawn from the liquid phase of the extraction side, and the components with five or more carbon atoms (104) are withdrawn from the bottom of the column. The components with five or more carbon atoms (104) enter the second distillation column (T2). The pentane foaming agent (108) is withdrawn from the top of the second distillation column (T2), and the components with six or more carbon atoms (110) are withdrawn from the bottom of the second distillation column (T2). The column systems of the first dividing wall column (T1) and the second distillation column (T2) are thermally integrated. The pentane foaming agent (105) withdrawn from the top gas phase of the second distillation column (T2) is used as the heating medium for the bottom heat exchanger (E04) of the first dividing wall column (T1).

[0009] Preferably, in the above process for producing liquefied petroleum gas and pentane foaming agent from light naphtha, the thermal integration of the column systems of the first dividing wall column (T1) and the second distillation column (T2) can be complete thermal integration or partial thermal integration. In the case of complete thermal integration, the heat exchanger (E04) is enabled, the heat exchanger (E05) is disabled, and the heat exchanger (E06) is disabled. In the case of partial thermal integration, the heat exchanger (E04) is enabled, the heat exchanger (E05) is enabled, and the heat exchanger (E06) is enabled.

[0010] Preferably, in the above process for producing liquefied petroleum gas and pentane foaming agent from light naphtha, the pentane foaming agent (103) produced by the first dividing wall column (T1) and the pentane foaming agent (108) produced by the second distillation column (T2) have different compositions. They can either be used as two types of pentane foaming agent products respectively, or be mixed and used as another type of pentane foaming agent product (113).

[0011] The process for producing liquefied petroleum gas and pentane foaming agent from light naphtha proposed by the present invention has the following advantages. The first dividing wall column (T1) in the present invention can produce liquefied petroleum gas (102) and pentane foaming agent (103) in one distillation column, reducing energy consumption and the number of equipment. The column systems of the first dividing wall column (T1) and the second distillation column (T2) are thermally integrated, reducing energy consumption. Three types of pentane foaming agents can be produced simultaneously, providing flexible production. Description of the Drawings

[0012] The above and / or additional aspects and advantages of the present invention will become apparent and be readily understood from the following description of the embodiments in conjunction with the accompanying drawings, where:

[0013] Figure 1 is a schematic diagram of an embodiment of the process for producing liquefied petroleum gas and pentane foaming agent from light naphtha of the present invention;

[0014] Figure 1Among them, T1 is the first dividing-wall column, T2 is the second rectification column, E01-E09 are heat exchangers, P01-P02 are pumps, V01-V05 are storage tanks, M01 is a mixer, and F01 is a splitter. Detailed implementation method

[0015] The process for producing liquefied petroleum gas and pentane foaming agent from light naphtha proposed by the present invention has a structure as Figure 1 shown, including a first dividing-wall column (T1), a second rectification column (T2), heat exchangers (E01-09), pumps (P01-02), storage tanks (V01-05), a mixer (M01) and a splitter (F01).

[0016] The following embodiments can enable those of ordinary skill in the art to more comprehensively understand the present invention, but do not limit the present invention in any way.

[0017] Embodiment 1

[0018] A process for producing liquefied petroleum gas and pentane foaming agent from light naphtha proposed by the present invention has a process flow as Figure 1 shown, including the following steps: Light naphtha enters the feed side of the first dividing-wall column (T1). The liquefied petroleum gas (102) is taken from the top of the first dividing-wall column (T1) and enters the liquefied petroleum gas storage tank (V01) after being cooled by the heat exchanger (E02). The pentane foaming agent (103) is taken from the liquid phase on the draw side of the first dividing-wall column (T1) and enters the pentane foaming agent storage tank 1 (V02) after being cooled by the heat exchanger (E03). The C5+ components (104) are taken from the bottom of the first dividing-wall column (T1) and enter the second rectification column (T2). The pentane foaming agent (105) taken from the top gas phase of the second rectification column (T2) enters the heat exchanger (E04) for heat transfer and cooling. After being split by the splitter (F01), a part enters the top of the second rectification column (T2) as the top reflux (107), and a part is used as the pentane foaming agent product (108) and enters the pentane foaming agent storage tank 2 (V03) after being cooled by the heat exchanger (E07). The C6+ components (110) are taken from the bottom of the second rectification column (T2) and enter the C6+ component storage tank (V05) after being cooled by the heat exchanger (E09). The first dividing-wall column (T1) and the second rectification column (T2) are fully thermally integrated. The pentane foaming agent (105) taken from the top gas phase of the second rectification column (T2) is used as the heating medium for the bottom heat exchanger (E04) of the first dividing-wall column (T1). A part (111) taken from the pentane foaming agent storage tank 1 (V02) and a part (112) taken from the pentane foaming agent storage tank 2 (V03) are mixed by the mixer (M01) and enter the pentane foaming agent storage tank 3 (V04) as another type of pentane foaming agent (113).

[0019] The composition of the light naphtha feedstock (101) in Example 1 is shown in Table 1, the composition of the liquefied petroleum gas product (102) is shown in Table 2, the composition of the pentane foaming agent products (103, 108, 113) is shown in Table 3, the parameters of the first dividing wall column (T1) are shown in Table 4, the parameters of the second distillation column (T2) are shown in Table 5, and the parameters of the heat exchanger (E04) are shown in Table 6.

[0020] Table 1 Composition of the light naphtha feedstock (101)

[0021] Component Mass fraction, wt% C3 Component 0.02 C4 Component 9.59 Isopentane 27.67 n-Pentane 31.61 Cyclopentane 2.58 Other C5 Components 0.10 C6 and Higher Components 28.43

[0022] Table 2 Composition of the liquefied petroleum gas product (102)

[0023] Item Value Vapor Pressure (37.8°C), kPa 1200 <![CDATA[(C3 + C4) hydrocarbon volume fraction, %]]> 98 <![CDATA[Volume fraction of hydrocarbons with C5 and above, %]]> 2

[0024] Table 3 Composition of the pentane foaming agent products

[0025]

[0026] Table 4 Parameters of the first dividing wall column (T1)

[0027] Number of Trays 50 Number of Trays in Common Rectifying Section 10 Number of Trays in Baffle Section 35 Number of Trays in Common Stripping Section 5 Feed Tray 30 Side Draw Tray 25 Top Pressure (kPa) 400 Reflux Ratio 13 Reboil Ratio 3 Top Temperature (°C) 50 Bottom Temperature (°C) 105

[0028] Table 5 Parameters of the second distillation column (T2)

[0029] Number of Trays 50 Feed Tray 30 Top Pressure (kPa) 1000 Reflux Ratio 6 Reboil Ratio 5 Top Temperature (°C) 120 Bottom Temperature (°C) 150

[0030] Table 6 Parameters of the heat exchanger (E04)

[0031] Cold Stream Inlet Temperature (°C) 103 Cold Stream Outlet Temperature (°C) 105 Hot Stream Inlet Temperature (°C) 122 Hot Stream Outlet Temperature (°C) 120 Log Mean Temperature Difference (°C) 17 Cold Stream Heat Absorption Load (kW) 5500 Hot Stream Heat Release Load (kW) 5500

[0032] It can be seen from the results that the composition of the liquefied petroleum gas product (102) meets that of the commercial propane-butane mixture, the pentane foaming agent product (103) of the first dividing wall column (T1) meets the pentane foaming agent of the F6 model, the pentane foaming agent product (108) of the second distillation column (T2) meets the pentane foaming agent of the F4 model, the mixed pentane foaming agent product (113) meets the pentane foaming agent of the F5 model, and the logarithmic mean temperature difference and heat load of the heat exchanger (E04) meet the complete heat integration of the first dividing wall column (T1) and the second distillation column (T2).

Claims

1. A process for producing liquefied petroleum gas and pentane foaming agent from light naphtha, comprising: The first dividing wall tower (T1), the second distillation tower (T2), the heat exchanger (E01-09), the pump (P01-02), the storage tank (V01-05), the mixer (M01) and the splitter (F01).

2. The process according to claim 1, wherein the first dividing wall tower (T1) and the second distillation tower (T2) are heat integrated, and the characteristics include: The pentane foaming agent (105) is extracted from the top gas phase of the second distillation tower (T2) as a heating medium for heating the heat exchanger (E04); When the first dividing wall tower (T1) and the second distillation tower (T2) are fully heat integrated, the heat exchanger (E04) is activated, the heat exchanger (E05) is deactivated, and the heat exchanger (E06) is deactivated; When the first dividing wall tower (T1) and the second distillation tower (T2) are partially heat integrated, the heat exchanger (E04) is activated, the heat exchanger (E05) is activated, and the heat exchanger (E06) is activated.

3. The process according to claim 1, wherein the first dividing wall column (T1) is characterized by: The first dividing wall tower (T1) is divided into a feed side and a withdrawal side by a dividing wall, and a common rectification section at the upper part of the dividing wall and a common stripping section at the lower part of the dividing wall; The feed (101) of the first dividing wall tower (T1) is light naphtha, including hydrocracked light naphtha, reformed topped light naphtha, and straight run light naphtha from atmospheric and vacuum distillation units; The feed position of the first dividing wall tower (T1) is on the dividing wall feed side; The liquefied petroleum gas (102) is extracted from the top liquid phase of the first dividing wall tower (T1), and enters the liquefied petroleum gas storage tank (V01) after being cooled by the heat exchanger (E02); Pentane foaming agent (103) is produced from the liquid phase of the extraction side of the first dividing wall tower (T1), and enters the pentane foaming agent storage tank 1 (V02) after being cooled by the heat exchanger (E03); The bottom of the first dividing wall tower (T1) produces components with carbon content of 5 or more (104); The top pressure of the first dividing wall tower (T1) is 300-1000 kPa; When the first dividing wall tower (T1) is a plate tower, the number of plates is 30-100; When the first dividing wall tower (T1) is a packed tower, the packing height is 20-80 meters.

4. The process according to claim 1, wherein the characteristics of the second distillation column (T2) include: The feed of the second distillation tower (T2) is the C5 and above components (104) extracted from the bottom of the first dividing wall tower (T1); A pentane foaming agent (105) is extracted from the top gas phase of the second distillation tower (T2); The pentane foaming agent (105) extracted from the top gas phase of the second distillation tower (T2) enters the heat exchanger (E04) for heat transfer and condensation, and is split by the splitter (F01). One part enters the top of the second distillation tower (T2) as the top reflux (107), and the other part is cooled by the heat exchanger (E07) as the pentane foaming agent product (108) and enters the pentane foaming agent storage tank 2 (V03); The carbon six and above components (110) are extracted from the bottom of the second distillation tower (T2), cooled by a heat exchanger (E09), and then enter a carbon six and above components storage tank (V05); The top pressure of the second distillation tower (T2) is 600-2000 kPa; When the second distillation tower (T2) is a plate tower, the number of plates is 40-100; When the second distillation tower (T2) is a packed tower, the packing height is 20-80 meters.

5. The process according to claim 1, wherein the characteristics of the pentane blowing agent production method include: The pentane foaming agent (103) produced by the side line of the first dividing wall tower (T1) and the pentane foaming agent (108) produced by the top of the second distillation tower (T2) have different compositions, and the two can be used as two types of pentane foaming agent products respectively; A portion (111) extracted from pentane foaming agent storage tank 1 (V02) and a portion (112) extracted from pentane foaming agent storage tank 2 (V03) are mixed through a mixer (M01) and enter pentane foaming agent storage tank 3 (V04) as another type of pentane foaming agent (113).

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