CN114053745B - Method and device for on-line separation and analysis of Fischer-Tropsch reaction products - Google Patents

Abstract

The invention relates to the technical field of material separation, in particular to a method and device for on-line separation and analysis of Fischer-Tropsch reaction products, the device for on-line separation and analysis of Fischer-Tropsch reaction products comprises: a flash separation tank connected with a Fischer-Tropsch reactor , for separating the Fischer-Tropsch reaction product into a liquid phase and a gas phase; the gas phase outlet pipeline arranged at the top of the flash separation tank is used to lead the gas phase out of the flash separation tank; it is arranged on the gas phase outlet pipeline The second valve on the upper part is used to adjust the pressure of the flash separation tank; the analysis unit arranged downstream of the second valve is used to measure the composition in the gas phase; the bottom of the flash separation tank is arranged The liquid phase collecting unit is used for collecting the liquid phase. The device of the invention prevents water from entering the gas phase, protects the analysis unit from being affected by water, ensures the accuracy of subsequent data analysis and protects the life of the analysis unit.

Description

Method and device for online separation and analysis of Fischer-Tropsch reaction products

Technical Field

The present invention relates to the technical field of material separation, and in particular to a method and device for online separation and analysis of Fischer-Tropsch reaction products.

Background Art

The Fischer-Tropsch synthesis reaction is a process that converts raw materials such as coal, natural gas and biomass into liquid fuels and high-value-added chemicals through synthesis gas. The raw materials of this process are simple, but the reaction products are relatively complex. The carbon number distribution of organic oxygen-containing compounds such as chain alkanes, olefins and alcohols is relatively wide, and the highest carbon number of the product can even reach _C70 - _C120 .

At present, the collection of Fischer-Tropsch reaction products usually adopts two-stage or even multi-stage cooling to produce wax, oil, water and tail gas, which is prone to the following problems: (1) It is difficult to control the actual separation effect of each stage during the cooling step by step, and water-oil emulsification and mutual entrainment are serious; (2) The products are collected in stages, and the subsequent sample processing for offline analysis needs to be separated and mixed again (for example, the water and oil in the cold trap and the hot trap are separated respectively, and then the water is mixed), which will add more analytical errors (weighing, volatility loss, etc.); (3) Low carbon number and volatile components will produce different degrees of flash loss during the sampling process; (4) The separation effect is poor, which makes it easy for heavy components to be entrained to the subsequent process, and then condense and cause pipeline blockage; (5) After the liquid product is collected, it needs to go through the steps of standing, separation, offline chromatographic analysis, etc., which requires a lot of manual operations and introduces many errors; (6) Flash evaporation causes the field of view near the sampling port to deteriorate, making it difficult to accurately capture the moment when the liquid sample is just emptied, resulting in gas phase components (containing CO and H ₂ ) Escape, system pressure fluctuation, air entering the system and other problems have a great impact on the circulation process; (7) Multi-stage separation leads to a higher overall layout, which squeezes the device space.

Prior art "Experimental Study on Distribution of Fischer-Tropsch Reaction Products" (Natural Gas Chemical Industry·C1 Chemistry and Chemical Engineering, Vol. 41, 2016, pp. 15-19) The reaction products enter the gas-liquid separator device (similar to the hot trap in the traditional Fischer-Tropsch device) through the reactor outlet, and the gas phase product after the separator is directly depressurized by the back pressure valve and then sent to the online chromatographic analysis, and the liquid phase product at the bottom of the separator is collected regularly and analyzed offline, eliminating the cold trap device in the traditional operation; in order to cooperate with the high-temperature online analysis of the Fischer-Tropsch synthesis gas phase product, the chromatographic inlet pipeline and components in the process are all subjected to high-temperature heating (300°C) and strict insulation, and a high-temperature resistant back pressure valve is installed. The original Agilent chromatographic valve box device is also replaced with a self-made independent heating valve box that can achieve high-temperature heating and insulation; in order to ensure that the gas phase components coming out of the separator can maintain the gaseous state and enter the gas chromatograph, the device introduces high-purity nitrogen as a diluent gas (optional use) after the gas-liquid separator to reduce the actual partial pressure of each component. This document designs a first-stage cooling and collection scheme for the Fischer-Tropsch reaction products, but this scheme requires the use of a self-made independent heating valve box that can achieve high-temperature heating and heat preservation, the replacement of a high-temperature resistant back pressure valve, and the need to ensure that the pipeline and components to the chromatographic inlet are heated at high temperature (300°C) and tightly insulated, and to introduce high-purity nitrogen as diluent gas after the gas-liquid separator. There are many overall modifications to the device and chromatogram, which is not easy to implement, and the long-term entry of a large amount of water contained in the product into the chromatogram will seriously affect the life of the chromatographic column.

Therefore, it is particularly important to develop an efficient and accurate method for online real-time analysis of Fischer-Tropsch reaction products.

Summary of the invention

The purpose of the present invention is to overcome the shortcomings of the prior art, such as poor separation effect of Fischer-Tropsch reaction products and high water content in the gas phase, and to provide a method and device for online separation and analysis of Fischer-Tropsch reaction products.

The general composition of the Fischer-Tropsch reaction product is: ① permanent gases such as H ₂ , CO, CO ₂ , CH ₄ ; ② organic substances such as alkanes, olefins, oxygen-containing compounds; ③ water. Among them, there are many organic substances with boiling points close to water (C ₅ ~ C ₈ , etc.). Gas chromatography can analyze permanent gases and low-carbon organic substances in real time online, but it cannot take in a large amount of water for a long time (damaging the chromatographic column, unstable and inaccurate analysis results), so it is necessary to collect and analyze water as much as possible as a liquid phase. However, the components of the Fischer-Tropsch reaction product are numerous, and are affected by a variety of factors such as catalyst performance, reaction conditions, separation system temperature and pressure. The composition and partial pressure of each component have a large variation range, resulting in serious water-oil emulsification and mutual entrainment of the product. The present invention intercepts water through a hydrophobic membrane to separate water from other organic gases, thereby reducing the water content in the gas phase.

The present invention provides a device for online separation and analysis of Fischer-Tropsch reaction products, the device comprising:

A flash separation tank connected to the Fischer-Tropsch reactor is used to separate the Fischer-Tropsch reaction product into a liquid phase and a gas phase; a U-shaped separation unit is further provided in the flash separation tank, and the U-shaped separation unit includes, from the inside to the outside, a hydrophobic membrane for intercepting water in the Fischer-Tropsch reaction product, a support net for fixing the hydrophobic membrane, and a liquid-blocking grid for breaking foam and diverting flow;

A first valve disposed on the connecting pipeline between the Fischer-Tropsch reactor and the flash separation tank;

A gas phase outlet pipeline disposed at the top of the flash separation tank, used to lead the gas phase out of the flash separation tank;

A second valve disposed on the gas phase outlet pipeline, used to adjust the pressure of the flash separation tank;

an analysis unit disposed downstream of the second valve, for measuring the composition of the gas phase;

The liquid phase collecting unit arranged at the bottom of the flash separation tank is used to collect the liquid phase.

The present invention also provides a method for online separation and analysis of Fischer-Tropsch reaction products, wherein the method comprises online separation and analysis of Fischer-Tropsch reaction products in the device described above.

The method comprises: flashing and separating the Fischer-Tropsch reaction products, cutting off water, breaking foam and guiding flow simultaneously to obtain a gas phase and a liquid phase;

The gas phase and the liquid phase were separately subjected to composition analysis.

Through the above technical scheme, the present invention prevents water from entering the gas phase through the U-shaped separation unit, greatly reduces the amount of water entering the gas phase, protects the analysis unit from being affected by water, and allows the high-temperature gas phase to directly enter the analysis unit for real-time analysis of the composition, thereby ensuring the accuracy of subsequent data analysis and protecting the life of the analysis unit, while avoiding a series of problems such as sample loss, environmental pollution, and system pressure fluctuations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the structure of an apparatus for online separation and analysis of Fischer-Tropsch reaction products according to a preferred embodiment of the present invention;

FIG2 is a schematic structural diagram of a U-shaped separation unit provided according to a preferred embodiment of the present invention;

FIG3 is a top view of a U-shaped separation unit provided according to a preferred embodiment of the present invention;

FIG4 is a graph showing the relationship between temperature and saturated vapor pressure of water and C ₅ -C ₉ components.

Description of Reference Numerals

1. Fischer-Tropsch reactor 2. First valve

3. Flash separation tank 4. Gas phase outlet pipeline

5. Analysis unit 6. Second valve

7. Pressure interlock unit 8. U-type separation unit

801. Hydrophobic membrane 802. Support mesh

803, Liquid-blocking grille

9. Temperature control unit 10. U-shaped conduit

11. Liquid phase receiver 12. Fourth valve

13. Gas collection unit 14. Third valve

15. Liquid phase collection tank 16. Temperature control unit

DETAILED DESCRIPTION

The endpoints and any values of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, the endpoint values of each range and the individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in this article.

Figure 1 is a schematic diagram of the structure of an apparatus for online separation and analysis of Fischer-Tropsch reaction products provided according to a preferred embodiment of the present invention; Figure 2 is a schematic diagram of the structure of a U-shaped separation unit provided according to a preferred embodiment of the present invention; Figure 3 is a top view of a U-shaped separation unit provided according to a preferred embodiment of the present invention.

According to a preferred embodiment of the present invention, the device for online separation and analysis of Fischer-Tropsch reaction products of the present invention has a structure as shown in FIG1 , specifically:

A flash separation tank 3 connected to the Fischer-Tropsch reactor 1 is used to separate the Fischer-Tropsch reaction product into a liquid phase and a gas phase; a U-shaped separation unit 8 is further provided in the flash separation tank 3, and the U-shaped separation unit 8 includes, from the inside to the outside, a hydrophobic membrane 801 for intercepting water in the Fischer-Tropsch reaction product, a support net 802 for fixing the hydrophobic membrane, and a liquid blocking grid 803 for breaking foam and diverting flow;

A first valve 2 provided on the connecting pipeline between the Fischer-Tropsch reactor 1 and the flash separation tank 3;

A gas phase outlet pipeline 4 is provided at the top of the flash separation tank 3, and is used to lead the gas phase out of the flash separation tank 3;

A second valve 6 disposed on the gas phase outlet pipeline 4 is used to adjust the pressure of the flash separation tank 3;

an analysis unit 5 disposed downstream of the second valve 6, for measuring the composition in the gas phase;

The liquid phase collecting unit arranged at the bottom of the flash separation tank 3 is used to collect the liquid phase.

The separation principle of the U-shaped separation unit 8 in the present invention is as follows: after the Fischer-Tropsch reaction product flows into the flash separation tank 3, the gas phase entrains part of the liquid phase (oil phase and water phase) and first passes through the liquid blocking grid 803 to break the foam, and the larger liquid is intercepted and guided to drip to the bottom of the flash separation tank 3. It avoids the problems of heavy components being entrained into the subsequent process and easily condensing to cause blockage, and a large amount of water entering the subsequent analysis unit to damage the chromatographic column. Under the action of the hydrophobic membrane 801, the water of the gas phase passing through the liquid blocking grid 803 is selectively intercepted, and is gradually guided and dripped to the bottom of the flash separation tank under the action of gravity. The gas phase after passing through the hydrophobic membrane 801 passes through the second valve 6 and reaches the analysis unit 5 under heating and insulation for online real-time composition analysis. By setting a U-shaped separation unit 8 in the flash separation tank 3, the liquid phase and the gas phase in the Fischer-Tropsch reaction product can be effectively separated, water can be prevented from entering the gas phase, water entrainment can be reduced, the online separation effect can be improved, and the accuracy of subsequent composition analysis can be improved. It can also prevent water from entering the analysis unit 5, so that the high-temperature gas phase can directly enter the analysis unit 5 for real-time composition analysis, thereby improving the life of the analysis unit 5 and the accuracy of the analysis, and also improving the analysis effect and efficiency.

Under preferred conditions, the analysis unit 5 is a gas chromatograph.

FIG4 is a graph showing the relationship between the temperature and saturated vapor pressure of water and _C5 - _C9 components. As can be seen from FIG4, the saturated vapor pressures of water and _C5 - _C9 organic gases at low temperatures (<100°C) are relatively close, and the water partial pressure can be made higher than the saturated vapor pressure by adjusting the pressure and temperature of the flash separation tank. In a preferred embodiment of the present invention, in order to improve the separation effect of the gas phase and the liquid phase, a first valve 2 is provided on the pipeline connecting the Fischer-Tropsch reactor 1 and the flash separation tank 3. The Fischer-Tropsch reactor 1 and the flash separation tank 3 can be separated into two independent systems by providing the first valve 2, so that the pressure and temperature of the flash separation tank 3 can be flexibly adjusted according to the test requirements. Under the condition that the separation requirements are met (the water content in the gas phase is <5wt%), the pressure of the separation system is reduced as much as possible, the gap between the flash separation tank 3 and normal temperature and pressure is reduced, and the phenomena of entrainment and emulsification are reduced. The analysis error and environmental pollution caused by the sampling flash due to the large pressure difference can also be avoided, the difficulty of sampling is reduced, the sampling loss is reduced, and the accuracy of the data is improved.

Preferably, the first valve 2 is a back pressure valve.

In a preferred embodiment of the present invention, in order to facilitate the collection of the liquid phase, preferably, the flash separation tank 3 includes a first straight cylindrical section and a first conical section arranged below the first straight cylindrical section, and the cone angle of the first conical section (the vertex of the cone and the two end points of a diameter constitute an isosceles triangle, and the vertex angle of the isosceles triangle is the cone angle) is further preferably 50-80° (for example, it can be 50°, 60°, 75°, 80° or any value in the range formed by any two of the above values), and most preferably 60°.

In the present invention, in order to further improve the gas-liquid separation effect, preferably, the first straight barrel section is divided into a cooling section and a heat preservation section, the cooling section is from the upper 1/3 of the first straight barrel section to the top part of the first straight barrel section, and the heat preservation section is from the upper 1/3 of the first straight barrel section to the bottom part of the first straight barrel section. Furthermore, a cooling unit is provided on the cooling section, and the temperature of the flash separation tank here can be controlled within 0-120°C by providing the cooling unit, and the cooling unit is preferably a circulating water cooling device. A heat preservation unit is provided on the heat preservation section, and the Fischer-Tropsch reaction product can be kept warm by providing the heat preservation unit, so that its temperature is controlled within 30-180°C.

In the present invention, in order to accurately measure the temperature of the cooling section and the insulation section, preferably, temperature sensors are respectively arranged on the cooling section and the insulation section. More preferably, the temperature sensors are respectively arranged at 1/5 and 4/5 of the first straight tube section (from top to bottom).

In the present invention, in order to increase the area of the U-shaped separation unit, extend the gas transmission path, and improve the gas-liquid separation effect, under preferred conditions, the height-to-diameter ratio of the flash separation tank 3 is 7-9:1, preferably 8:1.

In a preferred embodiment of the present invention, the hydrophobic membrane 801 can intercept moisture in the gas phase and prevent the moisture from entering the gas phase outlet pipeline 4, thereby reducing the moisture content in the gas phase. Preferably, the hydrophobic membrane 801 can adopt a membrane material made of a temperature-resistant and pressure-resistant material, and can be flexibly selected according to the water content in the gas phase and the water removal rate to be achieved. For example, it can be an inorganic _SiO2 nanofiber membrane, a high-temperature resistant hydrophobic membrane with a base material of modified epoxy resin, etc.

In the present invention, in order to reduce the gas phase transmission resistance and increase the area of the hydrophobic membrane, preferably, the hydrophobic membrane 801 includes a second straight cylindrical section and a second conical section arranged below the second straight cylindrical section, and the cone angle of the second conical section is preferably 50-80° (for example, it can be 50°, 60°, 75°, 80° or any value in the range formed by any two of the above values), and most preferably 60°.

In the present invention, by adjusting the spacing between the hydrophobic membrane, the liquid blocking grid and the flash separation tank, the gas phase can be evenly distributed and the liquid phase can be easily guided. Preferably, the ratio of the inner diameter of the second straight tube section to the inner diameter of the first straight tube section is 0.3-0.6:1, for example, it can be 0.4:1.

In the present invention, preferably, the ratio of the length of the second straight tube section to the length of the first straight tube section is 0.6-0.8:1, for example, it can be 0.7:1.

In the present invention, the support mesh 802 can support and fix the hydrophobic membrane 801 so that it does not deform or break; more preferably, the support mesh can be a stainless steel mesh or a ceramic mesh material, and further preferably, the support mesh 802 can be a single-layer structure or a multi-layer structure, and the best is a double-layer structure.

Preferably, when the support mesh 802 is a multi-layer structure, the spacing between the multi-layer support meshes can be flexibly adjusted according to the thickness of the hydrophobic film and the spacing between the hydrophobic film and the liquid-blocking grid.

In order to further improve the gas-liquid separation effect, preferably, a foam-breaking unit is provided on the side of the support net 802 adjacent to the liquid-blocking grid 803, and the foam-breaking unit is preferably a fibrous barb; the length of the fibrous barb is preferably 0.3-0.8 cm (for example, it can be 0.3 cm, 0.5 cm, 0.6 cm, 0.8 cm or any value in the range formed by any two of the above values), and is most preferably 0.5 cm. The fibrous barb can not only break the foam, but also play a role in diversion.

In the present invention, the liquid-blocking grid 803 has the functions of breaking foam and guiding flow, and can disperse the resistance of the hydrophobic membrane, thereby improving the gas-liquid separation effect. Preferably, the liquid-blocking grid 803 is made of materials such as stainless steel mesh or ceramics.

In order to further improve the foam breaking, flow diversion, gas velocity reduction and other effects of the liquid-blocking grille 803, preferably, a guide groove is provided on the inner side and/or outer side of the liquid-blocking grille 803, preferably, a plurality of spiral guide grooves forming a downward angle, more preferably, the downward angle formed by the plurality of spiral guide grooves is 30°.

In the present invention, by adjusting the distance between the liquid-blocking grid and the inner wall of the flash tank, the gas phase contacts the liquid-blocking grid in a more uniform plug flow manner, thereby reducing the gas phase transmission resistance. Preferably, the ratio of the inner diameter of the liquid-blocking grid 803 to the inner diameter of the first straight tube section is 0.4-0.8:1, and most preferably 0.6:1.

In a preferred embodiment of the present invention, the gas phase outlet pipeline 4 is further provided with:

a pressure interlock unit 7, connected to the second valve 6, and used for starting to adjust the opening of the second valve 6;

A controller is connected to the pressure interlock device 7 and the analysis unit 5 , and is used to control the pressure interlock device 7 based on the measurement result of the analysis unit 5 .

In the present invention, the pressure interlock unit 7 may be an existing pressure interlock structure, including but not limited to a pneumatic regulating valve, a stepping motor and other structures known to those skilled in the art.

In a preferred embodiment of the present invention, the liquid phase collection unit comprises: a liquid phase collection tank 15, which is connected to the flash separation tank 3 and is used to collect the liquid phase flowing out from the bottom of the flash separation tank 3. By collecting all the liquid phases in the same tank, the products of each phase are mixed more evenly, and the loss and error caused by the offline separation of the water phase and the oil phase of the cold trap and the hot trap samples, and then mixing the cold and hot trap water and the cold and hot trap oil (wax) respectively, are reduced.

In the present invention, preferably, a temperature control unit 16 is provided in the liquid phase collection tank 15 for keeping the liquid phase warm so that the liquid phase in the liquid phase collection tank 15 maintains the lowest temperature at which it can flow. The temperature control unit 16 can be set according to actual conditions, for example, it can be a heating device or a refrigeration device.

In the present invention, preferably, the height-to-diameter ratio of the liquid phase collection tank 15 is 1:1-3, and most preferably 1:2. By controlling the height-to-diameter ratio of the liquid phase collection tank 15, on the one hand, the bottom area of the liquid phase collection tank 15 can be increased, which is conducive to heating the heavy components deposited at the bottom of the liquid phase collection tank 15; on the other hand, the overall height of the device can be reduced, and the height of the flash separation tank can be increased as much as possible without changing the overall height of the device, thereby improving the flash separation effect.

In a preferred embodiment of the present invention, in order to avoid problems such as uneven components, environmental damage, and system pressure fluctuations caused by flash evaporation of light components and condensation and blockage of heavy components during the sample collection process, the liquid phase collection unit further includes:

The liquid phase receiver 11 is connected to the liquid phase collection tank 15 through the U-shaped conduit 10. Since the pressure of the liquid phase collection tank 15 is greater than that of the liquid phase receiver 11, when the two are connected through the U-shaped conduit 10, the liquid phase in the liquid phase collection tank 15 can enter the liquid phase receiver 11 by siphoning.

Preferably, a third valve 14 is provided on the pipeline connecting the flash separation tank 3 and the liquid phase collection tank 15, and a fourth valve 12 is provided on the U-shaped conduit 10. During the test, the third valve 14 is normally open; when it is necessary to perform real-time analysis on the liquid phase, the third valve 14 is closed first, and the fourth valve 12 is opened. At this time, the pressure of the liquid phase collection tank 15 is higher than the pressure of the liquid phase receiver 11, and the liquid phase automatically flows into the liquid phase receiver through the U-shaped conduit 10. By analyzing the composition of the liquid in the liquid phase receiver 11, the purpose of rapid and accurate analysis can be achieved.

Preferably, a blind hole is provided at the bottom of the liquid phase collection tank 15, and one end of the U-shaped conduit 10 is disposed in the blind hole, thereby ensuring that the liquid phase in the liquid phase collection tank 15 is completely sucked into the liquid phase receiver 11 under the siphon effect. Preferably, the blind hole has a diameter of 1 cm and a depth of 0.5 cm.

Preferably, a gas collecting unit 13 is provided on the top of the liquid phase receiver 11, and the gas collecting unit 13 can collect the gas generated by flash evaporation. More preferably, the gas collecting unit 13 is a vacuum pump, which can not only collect gas, but also generate negative pressure for the liquid phase receiver 11, thereby increasing the pressure difference between the liquid phase collecting tank 15 and the liquid phase receiver 11.

In a specific embodiment of the present invention, in order to facilitate observation of whether the liquid has been extracted, the liquid phase receiver 11 is a glass bottle, and one end of the U-shaped conduit 10 disposed in the liquid phase receiver 11 is connected to a transparent quartz glass tube.

The present invention also provides a method for online separation and analysis of Fischer-Tropsch reaction products, the method comprising online separation and analysis of Fischer-Tropsch reaction products in the device,

The method comprises: after the Fischer-Tropsch reaction product flows out of the reactor, it enters the flash separation tank 3 through the first valve 2, and after flash separation, water interception, foam breaking and flow diversion when passing through the U-shaped separation unit 8, a gas phase and a liquid phase are obtained;

The gas phase flows out through the gas phase outlet pipeline 4 and enters the analysis unit 5 through the second valve 6, and the composition analysis is performed in the analysis unit 5;

The liquid phase flows out from the bottom of the flash separation tank 3 and enters the liquid phase collection unit for composition analysis.

Preferably, the temperature of the flash separation, water interception, foam breaking and flow diversion is 0-180°C, and the pressure is 0.1-5MPa, more preferably 0.1-2MPa.

In a preferred embodiment of the present invention, the method further comprises: measuring the water content in the gas phase, and when the water content in the gas phase is higher than a predetermined value, increasing the pressure of the flash separation, water interception, foam breaking and diversion; the predetermined value is 5wt%;

Preferably, the temperature of the gas phase is 20-100°C.

In a preferred embodiment of the present invention, when the liquid phase composition needs to be analyzed, the third valve 14 is first closed and the fourth valve 12 is opened. At this time, the pressure in the liquid phase collection tank 15 is higher than that in the liquid phase receiver 11, and the liquid phase automatically flows into the liquid phase receiver 11 through the U-shaped conduit 10. Preferably, the temperature of the liquid phase is 20-60°C.

The present invention will be described in detail below through examples.

Example 1

The device for online separation and analysis of Fischer-Tropsch reaction products used in this embodiment is shown in FIG1 , and the structure of the U-shaped separation unit is shown in FIGS. 2 and 3 .

The Fischer-Tropsch reaction product flows out of the reactor and flows into the flash separation tank through the back pressure valve. After flowing into the flash separation tank, the gas phase passes through the liquid blocking grid, the hydrophobic membrane support net, and the hydrophobic membrane in sequence to simultaneously perform flash separation, water interception, foam breaking, and flow diversion, thereby separating the gas phase and the liquid phase;

After passing through the hydrophobic membrane, the gas phase passes through the second valve and is sent to the gas chromatograph for real-time composition analysis at 60°C with heating and insulation; the analysis unit on the gas phase outlet pipeline analyzes the water content of the gas phase at any time. If the water content is higher than 5wt%, the opening of the second valve is pneumatically adjusted through the pressure interlock unit to increase the pressure of the flash separation tank by 0.1MPa;

The liquid phase (water-oil mixture) enters the liquid phase collection tank from the third valve at the bottom of the flash separation tank (normally open when not sampling). When collecting liquid phase samples, close the third valve and open the fourth valve. At this time, the liquid phase automatically flows into the liquid phase receiver through the U-shaped conduit.

The parameters of the device for online separation and analysis of Fischer-Tropsch reaction products in this embodiment are as follows:

The height-to-diameter ratio of the flash separation tank is 8:1, and the cone angle of the cone-shaped part at the bottom of the flash separation tank is 60°;

The diameter of the hydrophobic membrane is 1/3 of the diameter of the straight section of the flash separation tank, the length is 70% of the straight section of the flash separation tank, and the angle of the tapered part is 60°;

The support net uses a double-layer stainless steel net to support and fix the hydrophobic membrane. The outer stainless steel net (the side adjacent to the liquid-blocking grid) is provided with fibrous barbs every 1 cm to assist in foam breaking and diversion. The barb length is 0.5 cm.

The liquid-blocking grid is made of stainless steel, with a diameter of 1/2 of the diameter of the flash separation tank. Multiple spiral guide grooves with a downward angle of 30° are arranged on the inside and outside of the grid.

The height-to-diameter ratio of the liquid phase collection tank is 1:2, the diameter of the bottom blind hole is 1 cm, and the depth is 0.5 cm.

The specific process conditions and separation results in this example are shown in Table 1.

Comparative Example 1

The method of Example 1 is followed, except that the device for online separation and analysis of Fischer-Tropsch reaction products does not include a U-type separation unit. The specific separation results are shown in Table 2.

Example 2

According to the method of Example 1, the specific process conditions and separation results are shown in Table 1.

Comparative Example 2

The method of Example 2 is followed, except that the device for online separation and analysis of Fischer-Tropsch reaction products does not include a U-type separation unit. The specific separation results are shown in Table 2.

Example 3

According to the method of Example 1, the specific process conditions and separation results are shown in Table 1.

Comparative Example 3

The method of Example 3 is followed, except that the device for online separation and analysis of Fischer-Tropsch reaction products does not include a U-type separation unit. The specific separation results are shown in Table 2.

Table 1 Separation conditions and results of Fischer-Tropsch reaction products in Examples 1-3

Table 2 Separation conditions and results of Fischer-Tropsch reaction products in comparative examples 1-3

Example 4

The method of Example 1 is followed, except that the device for online separation and analysis of Fischer-Tropsch reaction products does not include a liquid phase receiver. The specific separation results are shown in Table 3.

Comparative Example 4

The method of Example 1 is followed, except that the first valve is not included in the device for online separation and analysis of Fischer-Tropsch reaction products. The specific separation results are shown in Table 3.

Comparative Example 5

The method of Example 1 is followed, except that the device for online separation and analysis of Fischer-Tropsch reaction products does not include a U-shaped separation unit, a first valve and a liquid phase receiver. The specific separation results are shown in Table 3.

Table 3 Separation conditions and results of Fischer-Tropsch reaction products in Example 4 and Comparative Examples 4-5

In Table 1-3, _T1 is the temperature at the upper 1/4 of the first straight cylinder section of the flash separation tank, _T2 is the temperature of the gas phase entering the analysis unit, _T3 is the temperature of the liquid phase in the liquid phase collection tank, and P is the pressure of the flash separation tank.

It can be seen from the data in Tables 1-3 that the device provided by the present invention allows water to be retained in the liquid phase as much as possible, up to 99.21%, so that the water content in the gas phase is very low, with a minimum of 0.79%. Therefore, the gas phase can be directly analyzed online using a gas chromatograph for a long time.

It can be seen from the data in Table 4 that the device provided by the present invention improves the yield of the oil phase and the water phase in the liquid phase, reduces the loss of the sample, and thus improves the accuracy of the analysis;

Table 4 Liquid phase yields in Examples 1-4 and Comparative Examples 1-5

* The actual mass of the liquid sample received in Example 1 is taken as 100% as the basis; the oil phase yield is calculated based on C ₅₊ and above (the C ₅₊ components in the gas phase have been included).

By setting up the U-shaped separation unit, the moisture content in the gas phase and the light component content in the liquid phase are significantly reduced, the multiphase separation effect is significantly improved, and the problems of water-oil emulsification and mutual entrainment are avoided.

The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims (18)

1. A device for online separation and analysis of Fischer-Tropsch reaction products, characterized in that the device comprises: A flash separation tank (3) connected to the Fischer-Tropsch reactor (1) is used to separate the Fischer-Tropsch reaction product into a liquid phase and a gas phase; wherein the flash separation tank (3) is further provided with a U-shaped separation unit (8), and the U-shaped separation unit (8) comprises, from the inside to the outside: a hydrophobic membrane (801) for intercepting water in the Fischer-Tropsch reaction product, a support net (802) for fixing the hydrophobic membrane, and a liquid blocking grid (803) for breaking foam and guiding flow; A first valve (2) provided on the connecting pipeline between the Fischer-Tropsch reactor (1) and the flash separation tank (3); A gas phase outlet pipeline (4) disposed at the top of the flash separation tank (3) and used for leading the gas phase out of the flash separation tank (3); A second valve (6) disposed on the gas phase outlet pipeline (4) and used for adjusting the pressure of the flash separation tank (3); an analysis unit (5) disposed downstream of the second valve (6) for measuring the composition of the gas phase; and A liquid phase collecting unit disposed at the bottom of the flash separation tank (3) and used for collecting the liquid phase; The flash separation tank (3) has a height-to-diameter ratio of 7-9:1; the flash separation tank (3) comprises a first straight cylinder section and a first tapered section arranged below the first straight cylinder section, the tapered angle of the first tapered section is 50-80°; the hydrophobic membrane (801) comprises a second straight cylinder section and a second tapered section arranged below the second straight cylinder section, the tapered angle of the second tapered section is 50-80°; the ratio of the inner diameter of the second straight cylinder section to the inner diameter of the first straight cylinder section is 0.3-0.6:1, the ratio of the length of the second straight cylinder section to the length of the first straight cylinder section is 0.6-0.8:1, and the ratio of the inner diameter of the liquid blocking grid (803) to the inner diameter of the first straight cylinder section is 0.4-0.8:1. 2. The device according to claim 1, wherein a cooling unit is provided from the upper 1/3 of the first straight tube section to the top part of the first straight tube section, and the cooling unit is a circulating water cooling device; and/or an insulation unit is provided from the upper 1/3 of the first straight tube section to the bottom part of the first straight tube section. 3. The device according to claim 2, wherein a foam breaking unit is provided on the supporting net (802), and the foam breaking unit is a fibrous barb. 4. The device according to claim 3, wherein the length of the fibrous barbs is 0.3-0.8 cm. 5. The device according to claim 4, wherein a guide groove is provided on the inner side and/or the outer side of the liquid-blocking grid (803). The device according to claim 5 , wherein the guide groove is a plurality of spiral guide grooves forming a downward angle. 7. The device according to any one of claims 1 to 6, wherein the gas phase outlet pipeline (4) is further provided with: A pressure interlock unit (7), connected to the second valve (6), and used for starting to adjust the opening of the second valve (6); A controller is connected to the pressure interlock device (7) and the analysis unit (5), and is used to control the pressure interlock device (7) based on the measurement result of the analysis unit (5). 8. The device according to any one of claims 1 to 6, wherein the liquid phase collection unit comprises: The liquid phase collecting tank (15) is connected to the flash separation tank (3) and is used to collect the liquid phase flowing out from the bottom of the flash separation tank (3). 9. The device according to claim 8, wherein a temperature control unit (16) is provided in the liquid phase collection tank (15) for keeping the liquid phase warm; And/or, the height-to-diameter ratio of the liquid phase collection tank (15) is 1:1-3. 10. The device according to claim 8, wherein the liquid phase collection unit further comprises: The liquid phase receiver (11) is connected to the liquid phase collection tank (15) via a U-shaped conduit (10). 11. The device according to claim 10, wherein a blind hole is provided at the bottom of the liquid phase collecting tank (15), and one end of the U-shaped conduit (10) is arranged in the blind hole; and/or a gas collecting unit (13) is provided at the top of the liquid phase receiver (11). 12. The device according to claim 9, wherein the liquid phase collection unit further comprises: The liquid phase receiver (11) is connected to the liquid phase collection tank (15) via a U-shaped conduit (10). 13. The device according to claim 12, wherein a blind hole is provided at the bottom of the liquid phase collecting tank (15), and one end of the U-shaped conduit (10) is arranged in the blind hole; and/or a gas collecting unit (13) is provided at the top of the liquid phase receiver (11). 14. The device according to any one of claims 10 to 13, wherein a third valve (14) is provided on the pipeline connecting the flash separation tank (3) and the liquid phase collection tank (15); and/or The U-shaped conduit (10) is provided with a fourth valve (12). 15. A method for online separation and analysis of Fischer-Tropsch reaction products, characterized in that the method comprises online separation and analysis of Fischer-Tropsch reaction products in the device according to any one of claims 1 to 14, The method comprises: flashing and separating the Fischer-Tropsch reaction products, cutting off water, breaking foam and guiding flow simultaneously to obtain a gas phase and a liquid phase; The gas phase and the liquid phase were separately subjected to composition analysis. 16. The method according to claim 15, wherein the temperature of the flash separation, water interception, foam breaking and flow diversion is 0-180°C and the pressure is 0.1-5MPa. 17. The method according to claim 15 or 16, wherein the method further comprises: measuring the water content in the gas phase, and when the water content in the gas phase is higher than a predetermined value, increasing the pressure of the flash separation, water interception, foam breaking and diversion; And/or, the temperature of the gas phase is 20-100°C. 18. The method according to claim 15 or 16, wherein the temperature of the liquid phase is 20-60°C.

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