Systems and methods for helium extraction from natural gas and co-production of multiple products

Abstract

This invention relates to the field of natural gas processing and treatment technology, and discloses a system and method for the co-production of helium from natural gas and other products. The system includes a purification unit connected to the raw natural gas and a helium extraction tower for helium extraction. The system also includes a heat pump system comprising a mixed refrigerant compressor and a mixed refrigerant heat exchanger. The method purifies the raw natural gas to obtain purified natural gas; then, it performs helium extraction on the purified natural gas to obtain helium and product natural gas. Specifically, the mixed refrigerant is pressurized and cooled to provide a heat source for the liquid phase obtained from the helium extraction process, and the cooled mixed refrigerant provides a cold source for the gas phase obtained from the helium extraction process, which is then heated to recover the cooling energy. This invention, by installing a heat pump system outside the helium extraction tower and using the mixed refrigerant as the circulating medium, achieves cascaded energy utilization at the top and bottom of the helium extraction tower, ultimately realizing the goal of reducing energy consumption and investment in the natural gas helium extraction co-production system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of natural gas processing and treatment, in particular to a system and method for producing multiple products by extracting helium from natural gas. BACKGROUND

[0002] At present, in the field of extracting helium from natural gas, the cryogenic process is still the main choice for industrialization. As the lowest refrigeration separation temperature in the cryogenic process, the natural gas helium extraction system requires a large amount of energy consumption for unit refrigeration capacity as the refrigeration temperature continues to decrease. Although the existing industrialized natural gas helium extraction technology can rely on the co-production of ethane and other products to improve the overall project revenue, it is limited by the low refrigeration temperature and requires an additional refrigeration system to provide energy, resulting in high investment and high energy consumption.

[0003] Therefore, under the current situation of energy saving and consumption reduction, it is urgent to develop a natural gas helium extraction system and method that can significantly reduce energy consumption. SUMMARY

[0004] The purpose of the present application is to overcome the problems of high investment and high energy consumption in the prior art, and to provide a system and method for producing multiple products by extracting helium from natural gas. The system and method of the present application can significantly reduce energy consumption, thereby achieving the purposes of energy saving, carbon reduction, energy saving and investment reduction.

[0005] To achieve the above purpose, the first aspect of the present application provides a system for producing multiple products by extracting helium from natural gas, wherein the system comprises a purification unit connected to raw natural gas for purifying the raw natural gas, and a helium extraction column for extracting helium from natural gas.

[0006] The top of the helium extraction column is provided with a helium extraction column top condenser, and the bottom is provided with a helium extraction column bottom reboiler.

[0007] The system is also provided with a heat pump system comprising a mixed refrigerant compressor and a mixed refrigerant heat exchanger.

[0008] The heat pump system is indirectly heat-exchanged with the helium extraction column bottom reboiler and the helium extraction column top condenser, and is used to provide a heat source to the helium extraction column bottom reboiler and a cold source to the helium extraction column top condenser through the mixed refrigerant flowing in the heat pump system.

[0009] The second aspect of the present application provides a method for producing multiple products by extracting helium from natural gas, wherein the method comprises the following steps:

[0010] (1) purifying the raw natural gas to obtain purified natural gas;

[0011] (2) treating the purified natural gas to obtain helium and product natural gas;

[0012] The mixed refrigerant is pressurized and cooled, and then a heat source is provided for the liquid phase obtained by the helium extraction treatment, the cooled mixed refrigerant provides a cold source for the gas phase obtained by the helium extraction treatment, and the mixed refrigerant is recovered by being heated.

[0013] Through the technical scheme, the application has the following beneficial technical effects:

[0014] (1) The application sets a heat pump system outside the helium extraction column, uses the mixed refrigerant as the circulating medium, realizes the energy cascade utilization of the top and bottom of the helium extraction column, and finally realizes the purpose of reducing the energy consumption and investment of the natural gas helium extraction cogeneration system.

[0015] (2) The application avoids setting an additional refrigeration system, and compared with the conventional rectification process, the thermodynamic efficiency is increased by more than 30%, the annual operating cost is reduced by one third, and the energy consumption is about 231*10 4 kw / a.

[0016] (3) Since the helium content in natural gas is extremely low, the economic benefit of separately constructing a helium extraction device is poor, the application realizes the economic and efficient recovery of multiple products such as ethane and helium in natural gas, and simultaneously produces by-products such as LNG, liquefied petroleum gas and stable light hydrocarbons, which has great practical significance for promoting the realization of the energy saving and carbon reduction goal, improving the competitiveness of enterprises and promoting economic and social development. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 It is a system schematic diagram of natural gas helium extraction cogeneration of multiple products provided by the embodiment of the application.

[0018] REFERENCE SIGNS

[0019] 1, product natural gas export pipeline 2, refrigerant feed pipeline 3, refrigerant discharge pipeline

[0020] 4, raw material natural gas pipeline 5, C2 + mixed hydrocarbon treatment device 6, first electric ball valve

[0021] 7, product natural gas compressor 8, second electric ball valve 9, check valve

[0022] 10, expander 11, second regulating valve 12, third regulating valve 13, demethanizer 14, separator 15, first liquid level controller 16, first liquid level regulating valve 17, fourth regulating valve 18, cold box

[0023] 19, demethanizer reboiler 20, demethanizer overhead condenser 21, helium extraction column overhead condenser

[0024] 22, first regulating valve 23, helium refining device 24, fifth regulating valve 25, helium extraction column 26, sixth regulating valve 27, first liquid level controller 28, reflux tank 29, reflux pump 30, helium extraction column bottom reboiler 31, mixed refrigerant heat exchanger 32, mixed refrigerant compressor 33, seventh regulating valve DETAILED DESCRIPTION

[0025] The endpoints of the ranges and any values disclosed herein are not limited to the precise values recited as the exact dimensions are not critical to the invention. Any numerical value, however, can include any values up to the stated value, or down to the stated value, or up and down to the stated value. For ranges, the endpoints are included in the ranges. For numerical values, the endpoints are included in the numerical values.

[0026] The first aspect of the present application provides a system for helium extraction and multi-product co-production from natural gas, as shown in the accompanying drawings. Figure 1 The system for helium extraction and multi-product co-production from natural gas, as shown in the accompanying drawings, wherein the system comprises a purification unit connected to raw natural gas for purifying the raw natural gas, and a helium extraction column 25 for helium extraction from the natural gas.

[0027] The helium extraction column 25 is provided with a helium extraction column top condenser 21 at the top and a helium extraction column bottom reboiler 30 at the bottom.

[0028] The system is further provided with a heat pump system comprising a mixed refrigerant compressor 32 and a mixed refrigerant heat exchanger 31.

[0029] The heat pump system is arranged for indirect heat exchange with the helium extraction column bottom reboiler 30 and the helium extraction column top condenser 21, so as to provide a heat source for the helium extraction column bottom reboiler 30 and a cold source for the helium extraction column top condenser 21 through the mixed refrigerant flowing in the heat pump system.

[0030] In the present application, the mixed refrigerant compressor 32 is used to pressurize the mixed refrigerant, and the mixed refrigerant heat exchanger 31 is used for heat exchange between high-pressure and low-pressure mixed refrigerants.

[0031] The temperature at the bottom of the helium extraction column from natural gas is low (about -99℃), and the temperature difference between the top and the bottom is small. If a conventional rectification method is used, the energy consumption is high, and the overall operation investment of the project increases. The temperature difference between the top and the bottom of the helium extraction column from natural gas is about 10℃, which is relatively close in terms of energy grade. If heat pump rectification technology is used to improve its grade and recover the energy of the top stream, it can replace other heat sources to heat the material in the kettle, so as to realize the transfer of low-grade energy to high-grade energy and reduce the energy consumption in the rectification process.

[0032] The application of heat pump rectification technology in helium extraction from natural gas has the following adaptability:

[0033] (1) The temperature difference between the top and bottom of the helium extraction column is small (about 10 DEG C). Because the power consumption of the mixed refrigerant compressor mainly depends on the temperature difference, the greater the temperature difference, the greater the power consumption of the mixed refrigerant compressor, and only when the temperature difference is small, better economic benefits can be obtained;

[0034] (2) The temperature of the helium extraction column is much lower than the ambient temperature, and the energy required by the top and bottom of the column is all extra refrigerant, and the energy consumption is greatly reduced by using the heat pump rectification.

[0035] For the natural gas helium extraction system, the heat pump rectification technology is used in the application, the mixed refrigerant is used as the circulating medium, the mixed refrigerant is first pressurized and heated by the work of the mixed refrigerant compressor, and then is heat-exchanged with the mixed refrigerant from the top condenser of the helium extraction column to serve as the heat source of the bottom reboiler of the helium extraction column, and then serves as the cold source of the top condenser of the helium extraction column, so that the energy cascade utilization of the top and bottom of the column is realized, and thus the energy consumption is effectively reduced and the operation cost is saved.

[0036] In the application, if not particularly stated, each device can be selected from the devices commonly used in the field.

[0037] In some embodiments, the heat pump system further comprises a pipeline for conveying the mixed refrigerant to flow between the mixed refrigerant compressor 32, the mixed refrigerant heat exchanger 31, the bottom reboiler 30 of the helium extraction column and the top condenser 21 of the helium extraction column.

[0038] In some preferred embodiments, a first regulating valve 22 is arranged on the connecting pipeline between the bottom reboiler 30 of the helium extraction column and the top condenser 21 of the helium extraction column.

[0039] In the application, the first regulating valve is used for throttling and cooling the mixed refrigerant, and better provides the cold source for the top condenser of the helium extraction column.

[0040] In some embodiments, the purification unit comprises a cold box 18, a separator 14 and a demethanizer 13 connected in sequence.

[0041] The top gas phase outlet of the separator 14 is divided into two routes, one of which is connected to the demethanizer 13 through an expander 10, and the other of which is connected to the demethanizer 13 through the cold box 18; and the bottom liquid phase outlet is connected to the demethanizer 13.

[0042] The top gas phase outlet of the demethanizer 13 is connected to the helium extraction column 25 through a demethanizer top condenser 20, and the bottom liquid phase outlet is connected to a C2 + A mixed hydrocarbon treatment device 5.

[0043] In the application, the cold box is used for cooling the raw natural gas, the separator is used for gas-liquid separation of the cooled natural gas, and the demethanizer is used for demethanization treatment.

[0044] In the present application, the gas phase obtained from the top of the separator is divided into two routes, one route is introduced into the demethanizer after pressure reduction and temperature reduction by the expander, and the other route is introduced into the cold box and then into the demethanizer after recooling, the purpose is to further liquefy and reduce the temperature of the inlet tower.

[0045] In the present application, the liquid phase obtained from the bottom of the demethanizer is C2 + mixed hydrocarbon, C 2+ The mixed hydrocarbon treatment device is used for treating the mixed hydrocarbon, and products such as ethane, liquefied petroleum gas and stable light hydrocarbon can be separated and obtained.

[0046] The demethanizer 15 is further provided with a demethanizer bottom reboiler 19.

[0047] In some embodiments, the helium extraction tower 25 is further provided with a reflux tank 28 connected with the helium extraction tower top condenser 21, the top gas phase outlet of the reflux tank 28 is connected to the refined helium device 23, and the bottom liquid phase outlet is connected to the top of the helium extraction tower 25 through a reflux pump 29.

[0048] In the present application, the reflux tank is used for gas-liquid separation of the gas phase at the top of the helium extraction tower, the gas phase obtained from the top of the reflux tank is rich helium natural gas (crude helium), the helium content of which is about 70-80 mol%, which is introduced into the refined helium device for further refining, and refined helium can be obtained.

[0049] In some embodiments, the bottom liquid phase outlet of the helium extraction tower 25 is sequentially connected to the demethanizer top condenser 20, the cold box 18, the expander 10 and the product natural gas compressor 7.

[0050] In the present application, the liquid phase obtained from the bottom of the helium extraction tower is introduced into the demethanizer top condenser and the cold box after pressure reduction and temperature reduction to provide cold energy, and then is compressed to be used as product natural gas.

[0051] In some embodiments, at least two side lines are arranged in the middle of the demethanizer 13 and are connected to the cold box 18 and then are connected back to the demethanizer 13.

[0052] In the present application, at least two side lines are arranged in the middle of the demethanizer and are connected to the cold box to provide cold energy for cooling of the raw material natural gas, which can effectively realize coupling and utilization of energy.

[0053] In some preferred embodiments, the outlet of the product natural gas compressor 7 is divided into two routes, one route is connected to the product natural gas export pipeline 1, and the other route is sequentially connected to the cold box 18 and the demethanizer 13.

[0054] In the present application, the product natural gas is compressed and divided into two routes, one route is exported, and the other route is refluxed to the demethanizer through the cold box to provide mass transfer and heat transfer conditions for rectification operation.

[0055] In some preferred embodiments, the cold box 18 is further connected with a refrigerant feed pipe 2 and a refrigerant discharge pipe 3 for providing refrigerant, such as propane, into the cold box.

[0056] According to a particularly preferred embodiment of the present application, a system for co-production of helium extraction and multiple products from natural gas, the system comprises a purification unit connected with raw material natural gas, for purifying the raw material natural gas, and a helium extraction column 25 for helium extraction from the natural gas;

[0057] The purification unit comprises a cold box 18, a separator 14 and a demethanizer 13 connected in sequence;

[0058] The cold box 18 is connected with a refrigerant feed pipe 2 and a refrigerant discharge pipe 3;

[0059] The top gas phase outlet of the separator 14 is divided into two routes, one route is connected to the demethanizer 13 through an expander 10, and the other route is connected to the demethanizer 13 through the cold box 18; the bottom liquid phase outlet is connected to the demethanizer 13;

[0060] The top gas phase outlet of the demethanizer 13 is connected to the helium extraction column 25 through a demethanizer overhead condenser 20, and the bottom liquid phase outlet is connected to a C2 + The demethanizer 13 is provided with at least two side lines connected to the cold box 18 and then connected back to the demethanizer 13;

[0061] The helium extraction column 25 is provided with a helium extraction column overhead condenser 21 and a reflux tank 28 connected with the helium extraction column overhead condenser 21 at the top, and a helium extraction column bottom reboiler 30 at the bottom;

[0062] The top gas phase outlet of the reflux tank 28 is connected to a refined helium device 23, and the bottom liquid phase outlet is connected to the top of the helium extraction column 25 through a reflux pump 29;

[0063] The bottom liquid phase outlet of the helium extraction column 25 is connected to the demethanizer overhead condenser 20, the cold box 18, the expander 10 and the product natural gas compressor 7 in sequence;

[0064] The outlet of the product natural gas compressor 7 is divided into two routes, one route is connected to a product natural gas export pipe 1, and the other route is connected to the cold box 18 and the demethanizer 13 in sequence;

[0065] The system is further provided with a heat pump system comprising a mixed refrigerant compressor 32 and a mixed refrigerant heat exchanger 31;

[0066] The heat pump system is arranged for indirect heat exchange with the helium extraction column bottom reboiler 30 and the helium extraction column overhead condenser 21, for providing a heat source to the helium extraction column bottom reboiler 30 and a cold source to the helium extraction column overhead condenser 21 through the mixed refrigerant flowing in the heat pump system;

[0067] The heat pump system further comprises a pipeline for conveying the mixed refrigerant to flow between the mixed refrigerant compressor 32, the mixed refrigerant heat exchanger 31, the helium extraction column bottom reboiler 30 and the helium extraction column top condenser 21.

[0068] A first regulating valve 22 is arranged on the connecting pipeline between the helium extraction column bottom reboiler 30 and the helium extraction column top condenser 21.

[0069] The second aspect of the present application provides a method for co-producing helium and product natural gas from natural gas, wherein the method comprises the following steps:

[0070] (1) purifying raw natural gas to obtain purified natural gas;

[0071] (2) treating the purified natural gas to obtain helium and product natural gas;

[0072] The mixed refrigerant is pressurized and cooled to provide a heat source for the liquid phase obtained by the helium extraction treatment, and the cooled mixed refrigerant provides a cold source for the gas phase obtained by the helium extraction treatment, and the recovered cold energy is heated.

[0073] The method of the present application uses mixed refrigerant as the circulating medium. The mixed refrigerant is first pressurized and cooled to serve as a heat source for the liquid phase obtained by the helium extraction treatment, and then serves as a cold source for the gas phase obtained by the helium extraction treatment, thereby achieving energy cascade utilization of the column top and column bottom, effectively reducing energy consumption and saving operating costs.

[0074] In some embodiments, the mixed refrigerant is circulated to perform the steps of pressurization, cooling, providing a heat source for the liquid phase obtained by the helium extraction treatment, providing a cold source for the gas phase obtained by the helium extraction treatment, and heating.

[0075] In some preferred embodiments, after the mixed refrigerant provides a heat source for the liquid phase obtained by the helium extraction treatment, the cooled mixed refrigerant is throttled and cooled to provide a cold source for the gas phase obtained by the helium extraction treatment.

[0076] In some embodiments, the mixed refrigerant comprises the following components in mole percentage: 87-93 mol% of methane, 1-7 mol% of ethane and 1-7 mol% of nitrogen. The mixed refrigerant of the present application can meet the working conditions of small temperature difference between the column top and column bottom of the helium extraction column and meet the working conditions far below the ambient temperature.

[0077] In some preferred embodiments, the pressure of the pressurized mixed refrigerant is 2-5 MPa, preferably 3-4 MPa, and the temperature is 30-55℃, preferably 40-50℃.

[0078] In some preferred embodiments, the pressure of the mixed refrigerant after cooling is 2-5.5 MPa, preferably 2.5-4 MPa, and the temperature is -95℃ to -75℃, preferably -90℃ to -80℃.

[0079] In some preferred embodiments, the pressure of the mixed refrigerant after providing a heat source for the liquid phase obtained by the helium extraction treatment is 0.7-2.5 MPa, preferably 1-2 MPa, and the temperature is -135℃ to -100℃, preferably -120℃ to -110℃.

[0080] In some preferred embodiments, the pressure of the mixed refrigerant after cooling is 2-5.5 MPa, preferably 2.5-4 MPa, and the temperature is -95℃ to -75℃, preferably -90℃ to -80℃.

[0081] In some embodiments, the purification in step (1) comprises: cooling the raw natural gas to obtain cooled natural gas, subjecting the cooled natural gas to gas-liquid separation, dividing the obtained gas phase into two paths, one path being subjected to a pressure reduction and temperature reduction to be subjected to a demethanization treatment, and the other path being subjected to cooling to be subjected to a demethanization treatment; and subjecting the obtained liquid phase to a demethanization treatment.

[0082] The gas phase obtained after the demethanization treatment is subjected to a condensation to be subjected to a helium extraction treatment, and the liquid phase is subjected to a C2 + hydrocarbon mixing treatment.

[0083] In some embodiments, the raw natural gas has a temperature of 15-30℃, a pressure of 4-7 MPa, a methane content of 85-93 mol%, a nitrogen content of 0.13-0.73 mol%, and a helium content of 0.01-0.07 mol%.

[0084] In some preferred embodiments, the temperature of the first cooled natural gas is -40℃ to -60℃.

[0085] In some preferred embodiments, the pressure of the one path of the gas phase obtained after the gas-liquid separation of the cooled natural gas after cooling is 1.5-4.5 MPa, preferably 2-3 MPa, and the temperature is -95℃ to -75℃, preferably -85 to -80℃.

[0086] In some preferred embodiments, the temperature of the other path of the gas phase obtained after the gas-liquid separation of the cooled natural gas after cooling is 80-95℃, preferably 85-90℃.

[0087] In some preferred embodiments, the temperature of the gas phase obtained after the demethanization treatment after condensation is -115℃ to -85℃, preferably -100℃ to -90℃.

[0088] In some preferred embodiments, the temperature of the liquid phase obtained after the demethanization treatment is 2-8.5°C, preferably 4-6°C, and the pressure is 1-5 MPa, preferably 2-4 MPa.

[0089] In some embodiments, the gas phase obtained after the helium extraction treatment is condensed and subjected to gas-liquid separation to obtain crude helium gas, and the crude helium gas is subjected to helium purification treatment to obtain refined helium gas. The liquid phase obtained after the gas-liquid separation is returned to the helium extraction treatment step.

[0090] In some preferred embodiments, the crude helium gas has a pressure of 1-5 MPa, a temperature of -125°C to -140°C, a methane content of 63.2-82.3 mol%, a nitrogen content of 17-31 mol%, a helium content of 1.1-5.3 mol%, and a hydrogen content of 0.73-1.74 mol%.

[0091] In some embodiments, the liquid phase obtained after the helium extraction treatment is subjected to reboiling treatment to obtain a reboiled liquid phase, which provides condensation cooling to the gas phase obtained after the demethanization treatment and continues to provide cooling to the raw natural gas, and then is subjected to pressure reduction and cooling to obtain the product natural gas.

[0092] In some embodiments, the side line production stream obtained after the demethanization treatment provides cooling to the raw natural gas.

[0093] In some preferred embodiments, a part of the product natural gas is exported, and another part is returned to the demethanization treatment step after providing cooling to the raw natural gas;

[0094] In some preferred embodiments, the pressure of the exported product natural gas is 1.2-7.5 MPa, preferably 3-5 MPa, and the temperature is 35-65°C, preferably 40-50°C.

[0095] In some preferred embodiments, the method further comprises a cold agent providing step to provide cooling to the raw natural gas.

[0096] In some preferred embodiments, the cold agent is at least one selected from the group consisting of methane, ethylene, propane, pentane, and nitrogen.

[0097] According to a particularly preferred embodiment of the present application, a method for co-producing helium and multiple products from natural gas comprises the following steps:

[0098] S1, providing propane cold agent to cool the raw natural gas to obtain cooled natural gas, subjecting the cooled natural gas to gas-liquid separation, dividing the obtained gas phase into two parts, one part being subjected to demethanization treatment after pressure reduction and cooling, and the other part being subjected to demethanization treatment after cooling; and subjecting the obtained liquid phase to demethanization treatment;

[0099] The raw natural gas has a temperature of 15-30℃, a pressure of 4-7MPa, a methane content of 85-93mol%, a nitrogen content of 0.13-0.73mol%, and a helium content of 0.01-0.07mol%;

[0100] The cooled natural gas has a temperature of -40℃ to -60℃;

[0101] The gas phase obtained after the gas-liquid separation of the cooled natural gas has a pressure of 1.5-4.5MPa and a temperature of -95℃ to -75℃ after pressure reduction and temperature reduction;

[0102] The other route of the gas phase obtained after the gas-liquid separation of the cooled natural gas has a temperature of 80-95℃ after cooling;

[0103] The gas phase obtained after the demethanization treatment is condensed and subjected to helium extraction treatment, and the liquid phase obtained is subjected to C2 + hydrocarbon mixing treatment;

[0104] The side line production stream obtained after the demethanization treatment provides cooling capacity for the raw natural gas;

[0105] The gas phase obtained after the demethanization treatment has a temperature of -115℃ to -85℃ after condensation;

[0106] The liquid phase obtained after the demethanization treatment has a temperature of 2-8.5℃ and a pressure of 1-5MPa;

[0107] S3, the gas phase obtained after the helium extraction treatment is condensed and subjected to gas-liquid separation to obtain crude helium, the crude helium is subjected to refined helium treatment to obtain refined helium, and the liquid phase obtained after the gas-liquid separation is refluxed to the helium extraction treatment; the liquid phase obtained after the helium extraction treatment is subjected to reboiling treatment to obtain a reboiled liquid phase, which provides condensation cooling capacity for the gas phase obtained after the demethanization treatment and then continues to provide cooling capacity for the raw natural gas, and then is subjected to pressure reduction and temperature reduction and compression to obtain product natural gas; a part of the product natural gas is exported, and the other part provides cooling capacity for the raw natural gas and is refluxed to the demethanization treatment step;

[0108] The crude helium has a pressure of 1-5MPa, a temperature of -125℃ to -140℃, a methane content of 63.2-82.3mol%, a nitrogen content of 17-31mol%, a helium content of 1.1-5.3mol%, and a hydrogen content of 0.73-1.74mol%;

[0109] The exported product natural gas has a pressure of 1.2-7.5MPa and a temperature of 35-65℃;

[0110] The mixed refrigerant is pressurized and cooled, and then provides a heat source for the liquid phase obtained by the helium extraction treatment, the cooled mixed refrigerant provides a cold source for the gas phase obtained by the helium extraction treatment after throttling and cooling, and then the mixed refrigerant is recovered after being heated;

[0111] The mixed refrigerant is pressurized, cooled, provides a heat source for the liquid phase obtained by the helium extraction treatment, provides a cold source for the gas phase obtained by the helium extraction treatment, and is heated;

[0112] The mixed refrigerant comprises the following components in mole percentage: 87-93mol% of methane, 1-7mol% of ethane, and 1-7mol% of nitrogen;

[0113] The pressure of the mixed refrigerant after being pressurized and heated is 2-5MPa, and the temperature is 30-55℃;

[0114] The pressure of the mixed refrigerant after being cooled is 2-5.5MPa, and the temperature is -95℃ to -75℃;

[0115] The pressure of the mixed refrigerant after providing a heat source for the liquid phase obtained by the helium extraction treatment is 0.7-2.5MPa, and the temperature is -135℃ to -100℃;

[0116] The pressure of the cooled mixed refrigerant after providing a cold source for the gas phase obtained by the helium extraction treatment is 0.7-2.5MPa, and the temperature is -120℃ to -100℃.

[0117] The present application avoids setting an additional refrigeration system, and compared with a conventional rectification process, the thermodynamic efficiency is increased by more than 30%, and the annual operating cost is reduced by one third. The present application realizes the economic and efficient recovery of multiple products such as methane, ethane, helium and the like in natural gas by simultaneously separating the products, simultaneously produces by-products such as LNG, liquefied petroleum gas and light hydrocarbons, and the like, and has great practical significance for promoting the realization of the energy saving and carbon reduction goal, improving the competitiveness of enterprises and promoting the economic and social development.

[0118] The present application will be described in detail below through examples.

[0119] As shown in Figure 1 A method for producing multiple products by utilizing a natural gas helium extraction co-production system, comprising the following steps:

[0120] S1, providing propane refrigerant to the cold box 18 through the refrigerant feed pipeline 2, feeding the raw natural gas (temperature 15-30℃, pressure 4-7MPa, methane content 85-93mol%, nitrogen content 0.13-0.73mol%, helium content 0.01-0.07mol%) into the cold box 18 through the first electric ball valve 6, obtaining cooled natural gas (temperature -60℃ to -40℃) after cooling, carrying out gas-liquid separation in the separator 14, obtaining gas phase at the top of the separator 14 and liquid phase at the bottom of the separator 14; dividing the gas phase into two paths, one path entering the expander 10 to reduce pressure and temperature (pressure 1.5-4.5MPa, temperature -95℃ to -75℃) and then entering the demethanizer 13 for demethanization treatment, the other path entering the cold box 18 for cooling (80-95℃) and then entering the demethanizer 13 through the third regulating valve 12 for demethanization treatment; the liquid phase enters the demethanizer 13 for demethanization treatment; the propane refrigerant after providing cold energy is discharged from the refrigerant discharge pipeline 3; the propane refrigerant is provided with the fourth regulating valve 17 on the flow pipeline in the cold box 18; the bottom of the separator 14 is provided with the first liquid level controller 15 and the first liquid level regulating valve 16;

[0121] S2, after demethanization treatment in the demethanizer 13, obtaining gas phase at the top of the demethanizer 13 and liquid phase at the bottom of the demethanizer 13, condensing the gas phase through the demethanizer overhead condenser 20 (temperature -115℃ to -85℃) and then entering the helium extraction column 25 through the fifth regulating valve 24 for helium extraction treatment, and the liquid phase (temperature 2-8.5℃, pressure 1-5MPa) enters the C2 + hydrocarbon treatment device 5 for C2 + hydrocarbon treatment; the bottom of the demethanizer 13 is provided with a demethanizer bottom reboiler 19;

[0122] The middle part of the demethanizer 13 is provided with at least two side lines, and the middle product obtained by the demethanization treatment enters the cold box 18 to provide cooling cold energy for the raw natural gas, and then flows back to the demethanizer 13;

[0123] S3, after helium extraction treatment in the helium extraction column 25, obtaining gas phase at the top of the helium extraction column 25 and liquid phase at the bottom of the helium extraction column 25;

[0124] The gas phase is condensed in the helium extraction column overhead condenser 21 and enters the reflux tank 28 for gas-liquid separation. The crude helium gas (pressure 1-5 MPa, temperature -125℃ to -140℃, methane content 63.2-82.3 mol%, nitrogen content 17-31 mol%, helium content 1.1-5.3 mol%, hydrogen content 0.73-1.74 mol%) is obtained at the top of the reflux tank 28 and is sent to the refined helium device 23 for refined helium treatment to obtain refined helium. The liquid phase is obtained at the bottom of the reflux tank 28 and is refluxed to the top of the helium extraction column 25 by the reflux pump 29. The reflux tank 28 is provided with a first liquid level controller 27 and the reflux amount entering the helium extraction column 25 is controlled by the sixth regulating valve 26.

[0125] The liquid phase is subjected to reboiling treatment in the helium extraction column bottom reboiler 30 to obtain a reboiled liquid phase. The reboiled liquid phase is refluxed to the bottom of the helium extraction column 25 and then enters the demethanizer overhead condenser 20 to provide condensing cold energy, continues to enter the cold box 18 to provide cooling cold energy for the raw material natural gas, and then enters the expander 10 for pressure reduction and temperature reduction, and then enters the product natural gas compressor 7 through the check valve 9 and the second electric ball valve 8 to obtain the product natural gas. Part of the product natural gas is exported through the product natural gas export pipeline 1 (pressure 1.2-7.5 MPa, temperature 35-65℃), and the other part enters the cold box 18 to liquefy the raw material natural gas and is refluxed to the demethanizer 13 through the second regulating valve 11.

[0126] The mixed refrigerant (methane 87-93 mol%, ethane 1-7 mol%, and nitrogen 1-7 mol%) is pressurized in the mixed refrigerant compressor 32 (to a pressure of 2-5 MPa and a temperature of 30-55℃), cooled in the mixed refrigerant heat exchanger 31 (to a pressure of 2-5.5 MPa and a temperature of -95℃ to -75℃), and then heated in the helium extraction column bottom reboiler 30 by heat exchange with the liquid phase obtained from the lower part of the helium extraction column 25 (to a pressure of 0.7-2.5 MPa and a temperature of -135℃ to -100℃). After throttling and temperature reduction by the first regulating valve 22, the mixed refrigerant enters the helium extraction column overhead condenser 21 and is cooled by heat exchange with the gas phase obtained from the top of the helium extraction column 25 (to a pressure of 0.7-2.5 MPa and a temperature of -120℃ to -100℃). Then, the mixed refrigerant is heated by heat exchange with the pressurized mixed refrigerant in the mixed refrigerant heat exchanger 31 and is pressurized in the mixed refrigerant compressor 32 to continue the circulation.

[0127] The present application realizes the energy cascade utilization of the top and bottom of the helium extraction column by setting a heat pump system outside the helium extraction column and taking mixed refrigerant as the circulating medium, and finally realizes the purpose of reducing the energy consumption and investment of the natural gas helium extraction cogeneration system. The present application also realizes the economic and efficient recovery of multiple products by simultaneously separating methane, ethane, helium and other products in the natural gas, and simultaneously produces by-products such as LNG, liquefied petroleum gas and light hydrocarbons, which has great practical significance for promoting the realization of the energy saving and carbon reduction goal, improving the competitiveness of enterprises and promoting the economic and social development.

[0128] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application and belong to the protection scope of the present application.

Claims

1. A system for the coproduction of multiple products from natural gas for helium extraction, characterized in that, The system comprises a purification unit connected with raw natural gas, for purifying the raw natural gas, and a helium extraction column (25) for helium extraction of the natural gas; The top of the helium extraction column (25) is provided with a helium extraction column top condenser (21), and the bottom is provided with a helium extraction column bottom reboiler (30); a first regulating valve (22) is arranged on the connecting pipeline between the helium extraction column bottom reboiler (30) and the helium extraction column top condenser (21), and the first regulating valve (22) is used for throttling and cooling the mixed refrigerant. The system is further provided with a heat pump system comprising a mixed refrigerant compressor (32) and a mixed refrigerant heat exchanger (31); The heat pump system is arranged for indirect heat exchange with the helium extraction column bottom reboiler (30) and the helium extraction column top condenser (21), so as to provide a heat source for the helium extraction column bottom reboiler (30) and a cold source for the helium extraction column top condenser (21) through the mixed refrigerant flowing in the heat pump system.

2. The system of claim 1, wherein, The heat pump system further comprises a pipeline for conveying the mixed refrigerant to flow between the mixed refrigerant compressor (32), the mixed refrigerant heat exchanger (31), the helium extraction column bottom reboiler (30) and the helium extraction column top condenser (21).

3. The system of claim 1 or 2, wherein, The purification unit comprises a cold box (18), a separator (14) and a demethanizer (13) connected in sequence; The top gas phase outlet of the separator (14) is divided into two paths, one path is connected to the demethanizer (13) through an expander (10), and the other path is connected to the demethanizer (13) through the cold box (18); the bottom liquid phase outlet is connected to the demethanizer (13); The overhead gaseous outlet of the demethanizer (13) is connected to the helium stripper (25) via a demethanizer overhead condenser (20) and the bottom liquid outlet is connected to a C2 + hydrocarbon treating unit (5).

4. The system of claim 1 or 2, wherein, The top of the helium extraction column (25) is further provided with a reflux tank (28) connected with the helium extraction column top condenser (21), and the top gas phase outlet of the reflux tank (28) is connected to a high-purity helium device (23), and the bottom liquid phase outlet is connected to the top of the helium extraction column (25) through a reflux pump (29).

5. The system of claim 3, wherein, The bottom liquid phase outlet of the helium extraction column (25) is connected to the demethanizer top condenser (20), the cold box (18), the expander (10) and the product natural gas compressor (7) in sequence.

6. The system of claim 3, wherein, The demethanizer (13) is provided with at least two side lines connected to the cold box (18) and then connected back to the demethanizer (13).

7. The system of claim 5, wherein, The outlet of the product natural gas compressor (7) is divided into two paths, one path is connected to a product natural gas export pipeline (1), and the other path is connected to the cold box (18) and the demethanizer (13) in sequence.

8. The system of claim 5, wherein, The cold box (18) is further connected with a refrigerant feeding pipeline (2) and a refrigerant discharging pipeline (3).

9. A method for the coproduction of multiple products from natural gas for helium extraction, characterized in that, The method comprises the following steps: (1) purifying the raw natural gas to obtain purified natural gas; (2) performing helium extraction treatment on the purified natural gas to obtain helium and product natural gas; The mixed refrigerant is pressurized and cooled to provide a heat source for the liquid phase obtained by the helium extraction treatment, and the cooled mixed refrigerant is throttled and cooled to provide a cold source for the gas phase obtained by the helium extraction treatment.

10. The method of claim 9, wherein, The mixed refrigerant is pressurized, cooled, provides a heat source for the liquid phase obtained by the helium extraction treatment, provides a cold source for the gas phase obtained by the helium extraction treatment, and is heated to recover the cold energy.

11. The method of claim 9, wherein, The mixed refrigerant comprises the following components in mole percentage: 87-93 mol% of methane, 1-7 mol% of ethane and 1-7 mol% of nitrogen.

12. The method of any of claims 9-11, wherein, The pressure of the mixed refrigerant after pressurization is 2-5 MPa, and the temperature is 30-55℃.

13. The method of any of claims 9-11, wherein, The pressure of the mixed refrigerant after cooling is 2-5.5 MPa, and the temperature is -95℃ to -75℃.

14. The method of any one of claims 9-11, wherein, The pressure of the mixed refrigerant after providing heat source for the liquid phase obtained by the helium extraction treatment is 0.7-2.5 MPa, and the temperature is -135℃ to -100℃.

15. The method of any of claims 9-11, wherein, The pressure of the cooled mixed refrigerant after providing cooling source for the gas phase obtained by the helium extraction treatment is 0.7-2.5 MPa, and the temperature is -120℃ to -100℃.

16. The method of any one of claims 9-11, wherein, The purification in step (1) comprises: cooling the raw natural gas to obtain cooled natural gas, carrying out gas-liquid separation on the cooled natural gas, and dividing the obtained gas phase into two routes, one of which is subjected to a pressure reduction and temperature reduction to carry out a demethanization treatment, and the other of which is cooled to carry out a demethanization treatment; and carrying out a demethanization treatment on the obtained liquid phase. The gas phase obtained after demethanization is subjected to a helium extraction treatment after condensation, and the liquid phase obtained is subjected to a C2 + hydrocarbon mixture treatment.

17. The method of claim 16, wherein, The temperature of the raw natural gas is 15-30℃, the pressure is 4-7 MPa, the methane content is 85-93 mol%, the nitrogen content is 0.13-0.73 mol%, and the helium content is 0.01-0.07 mol%.

18. The method of claim 16, wherein, The temperature of the cooled natural gas is -60℃ to -40℃.

19. The method of claim 16, wherein, The pressure of one route of the gas phase obtained after the gas-liquid separation of the cooled natural gas is subjected to a pressure reduction and temperature reduction is 1.5-4.5 MPa, and the temperature is -95℃ to -75℃.

20. The method of claim 16, wherein, The temperature of the other route of the gas phase obtained after the gas-liquid separation of the cooled natural gas is cooled to 80-95℃.

21. The method of claim 16, wherein, The temperature of the gas phase obtained after the demethanization treatment is condensed to -115℃ to -85℃.

22. The method of claim 16, wherein, The temperature of the liquid phase obtained after the demethanization treatment is 2-8.5℃, and the pressure is 1-5 MPa.

23. The method of any one of claims 9-11, wherein, The gas phase obtained by the helium extraction treatment is condensed and subjected to a gas-liquid separation to obtain crude helium, and the crude helium is subjected to a refined helium treatment to obtain refined helium.

24. The method of claim 23, wherein, The pressure of the crude helium is 1-5 MPa, the temperature is -125℃ to -140℃, the methane content is 63.2-82.3 mol%, the nitrogen content is 17-31 mol%, the helium content is 1.1-5.3 mol%, and the hydrogen content is 0.73-1.74 mol%.

25. The method of claim 16, wherein, The liquid phase obtained by the helium extraction treatment is subjected to a reboiling treatment to obtain a reboiled liquid phase, the reboiled liquid phase provides condensing cold quantity for the gas phase obtained after the demethanization treatment and continues to provide cooling cold quantity for the raw natural gas, and then is subjected to a pressure reduction and temperature reduction to be compressed to obtain product natural gas.

26. The method of claim 16, wherein, The side line production stream obtained by the demethanization treatment provides cooling cold quantity for the raw natural gas.

27. The method of claim 25, wherein, Part of the product natural gas is exported, and the other part provides cooling cold quantity for the raw natural gas and is returned to the demethanization treatment step.

28. The method of claim 27, wherein, The pressure of the exported product natural gas is 1.2-7.5 MPa, and the temperature is 35-65℃.

29. The method of any one of claims 9-11, wherein, The method further comprises a refrigerant providing step for providing cooling cold quantity for the raw natural gas.

30. The method of claim 29, wherein, The refrigerant is at least one selected from methane, ethane, propane, pentane and nitrogen.

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