CN114314534B - Natural gas helium extraction process - Google Patents
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Abstract
The invention discloses a process for extracting helium from natural gas, which comprises the steps of pretreating the raw material gas, extracting crude helium, adding oxygen to remove hydrogen, dehydrating a system, removing nitrogen and filling helium into a natural gas raw material in sequence to obtain high-purity helium with the purity of more than 99.9999vol%, effectively realizing high helium extraction efficiency, realizing high-yield liquefied methane while obtaining helium, recycling the energy of the whole process, being efficient and environment-friendly, automatically controlling, continuously and stably operating the whole system, facilitating industrialization and having high economic value.
Description
Technical Field
The invention relates to the technical field of helium extraction, in particular to a system and a method for extracting helium from natural gas or BOG.
Background
Helium resources are extremely rare on earth and are mainly present in natural gas. Some of the natural gas found can have helium levels as high as about 8% and most levels are below 2%. Even natural gas with very low helium content is still the world's major source of helium because it is tens of millions of times higher than air.
The main methods for extracting helium from natural gas include a low-temperature condensation method, a membrane separation method, an adsorption method, an absorption method, a diffusion method, a hydrate method and the like, and the helium is widely applied to military industry, scientific research, petrifaction, refrigeration, medical treatment, semiconductor, pipeline leakage detection, superconducting experiments, metal manufacturing, deep sea diving, high-precision welding, photoelectron product production and the like. Helium can be used as a low-temperature cold source: liquid helium can be used for ultra-low temperature cooling using its low boiling point of-268.9 ℃. The ultra-low temperature cooling technology is widely applied in the field of superconducting technology and the like, superconducting materials need to show superconducting characteristics at low temperature (about 100K), and the ultra-low temperature can be realized simply only by liquid helium in most cases. The superconducting technology has great application in magnetic suspension trains in the traffic industry and nuclear magnetic resonance imaging equipment in the medical field. Helium can also be used for assay analysis: the superconducting magnet of a nuclear magnetic resonance analyzer commonly used in instrument analysis needs to be cooled by liquid helium, helium is often used as carrier gas in gas chromatography analysis, and the helium is also applied to vacuum leak detection such as a helium mass spectrometer leak detector and the like by utilizing the characteristics of good permeability and incombustibility of the helium. Helium can also be used as shielding gas: helium is commonly used as a shielding gas for welding metals such as magnesium, zirconium, aluminum, titanium and the like by utilizing the inactive chemical property of helium. Helium gas is used in other aspects: helium is used as a pressurized gas for transporting liquid propellants such as liquid hydrogen and liquid oxygen in high vacuum apparatuses and nuclear reactors in rockets and spacecraft. Helium is also used as a cleaning agent for a nuclear reactor, a gas for filling a gas thermometer in a mixed gas for breathing in the field of ocean development, and the like.
Helium is one of rare strategic materials indispensable to the development of national defense military industry and high-tech industry. The helium-containing natural gas is still the main source for industrially producing helium so far, so that the development of the natural gas helium stripping technology of China has important significance and broad prospect for ensuring the domestic helium safety and promoting the development of the natural gas helium stripping industry of China.
The prior art for extracting helium from natural gas has the following: for example, CN2021107729830, beijing china kokai hai low temperature technology limited, discloses a system and a method for extracting helium from natural gas or BOG, and the present invention relates to a system and a method for extracting helium from natural gas or BOG, which comprises a membrane separation system, a catalytic dehydrogenation unit connected to the membrane separation system, and a purification device connected to the catalytic dehydrogenation unit, wherein the membrane separation system is adopted to firstly remove the methane with the maximum content in natural gas or BOG, and then perform catalytic dehydrogenation treatment and purification treatment, so that the treatment amount of the mixed gas of the equipment behind the membrane separation system is small, which is beneficial to simplifying the whole process flow and equipment structure for extracting helium, thereby reducing the whole investment of the equipment, reducing the production cost, and the content of the methane in the gas after membrane separation is very small, and almost no by-product exists, and the whole system can continuously and stably operate, and is suitable for industrial production.
For example, in the multi-technology integrated separation process for producing high-purity helium gas from helium-rich natural gas liquefied tail gas at the university of CN 202110458339, the helium-containing tail gas from a natural gas liquefaction device enters a multistage circulating membrane separation unit for primary enrichment after cold recovery and pressurization; crude helium obtained by membrane separation enters a catalytic oxidation dehydrogenation unit after being pressurized, then enters a compression condensation and temperature swing adsorption dehydration unit, and finally enters a low-temperature pressure swing adsorption purification unit to obtain high-purity helium; the desorbed gas of the adsorption unit returns to the membrane separation unit. Through multi-technology zero-clearance matching and synergistic interaction, each impurity is removed in a proper mode, high-purity helium with the purity of 99.99vol% is obtained, the helium recovery rate is obviously improved, and the purification energy consumption is reduced. The simulation result shows that the recovery rate of the multi-technology integrated process can reach over 84.0 percent, and the unit consumption (electricity) of purification does not exceed 4.0kWh/Nm3 of helium.
As can be seen from the above document, the existing process for extracting helium from natural gas faces the following problems: the method mainly adopts a membrane process, and has high cost and difficult maintenance; (2) The efficiency of simultaneously recovering liquefied methane and helium in the gas is low; (3) The purification process comprises a low-temperature condensation method, a membrane separation method, an adsorption method, an absorption method, a diffusion method, a hydrate method and the like, but the purification process cannot effectively cooperate with each step, is only simple superposition, and cannot scientifically obtain high-purity helium.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a process for extracting helium from natural gas, which is scientifically and effectively controlled by effectively cooperating and matching with pretreatment, crude helium extraction, oxygenation dehydrogenation, a dehydration system, nitrogen removal and other processes, particularly, a self-made oxygenation dehydrogenation catalyst is adopted, the dehydrogenation efficiency is obtained at low price and high efficiency, high-purity helium is further obtained, the purity of the helium reaches up to 99.999 percent, the purity is extremely high, and the process for purifying the helium can realize industrialization.
A natural gas helium extraction process comprises the following steps:
(1) Pretreating raw material gas, wherein the raw material gas comprises methane, nitrogen and CO 2 The methane content is more than 87vol%, the helium content is less than 0.2 vol%, and the pretreatment means comprises deacidification and dehydration treatment;
(2) And (3) crude helium extraction treatment:
carrying out primary cooling, secondary cooling and tertiary cooling and sectional cooling on the raw material gas treated in the step (1), introducing the cooled raw material gas into a first helium extracting tower condenser for primary helium extracting, cooling and separating, collecting primary helium-rich gas at the upper end of the tower, collecting liquefied methane at the lower end of the tower, carrying out four-time cooling on the collected primary helium-rich gas, then carrying out secondary helium extracting, cooling and separating through a second helium extracting tower condenser to obtain secondary helium-rich gas and poor helium gas, mixing the poor helium gas with the primary helium-rich gas, and carrying out four-time cooling and secondary helium extracting and cooling treatment;
(3) Oxygen adding dehydrogenation treatment
Heating the secondary helium-rich gas to 40-80 deg.C o And C, introducing the catalyst into a catalytic oxidation dehydrogenation reactor, wherein the catalyst is foamed nickel serving as a carrier, a Pd active component is attached to the surface of the catalyst, and the catalyst is filled in the dehydrogenation reactor, and the preparation method of the catalyst comprises the following steps: carrying out surface cleaning treatment on the foamed nickel; (b) oxalic acid etching treatment; (c) Loading active components, wherein the loading amount of the active components in the catalyst is 1 to 2wt.%, the catalyst should be hexachloropalladate acid valence solution, and the gas space velocity GHSV of the secondary helium-rich gas is (4-7) × 10 6 h - The dehydrogenation reactor has at least three sections, namely three times of oxygen addition and dehydrogenation, the oxygen addition amount is sequentially decreased, and the average value of the oxygen addition amount is 0.33Nm 3 /h、0.15 Nm 3 H, and 0.05 Nm 3 And h, the hydrogen in the obtained secondary helium-rich dehydrogenation gas is less than 1ppm.
(4) And (3) dehydration treatment:
enabling helium gas subjected to the oxygen adding and dehydrogenation treatment to enter a dehydration system, wherein the dehydration system adopts a double-tower switching process, and the content of moisture in the obtained secondary helium-rich dehydrogenation gas is lower than 1ppm;
(5) Nitrogen removal treatment:
and (3) compressing the dried helium gas obtained from the dehydration treatment to 19-20MPa by a helium gas compressor in advance, then entering a buffer tank, then entering a nitrogen removal system, sequentially exchanging heat with low-temperature helium gas, low-temperature nitrogen gas and liquid nitrogen by high-pressure helium-rich gas, cooling to about-203 to-207 ℃ to realize gas-liquid separation, removing nitrogen gas, enabling the gas phase to enter a low-temperature adsorber for fine nitrogen removal, then obtaining a low-temperature helium gas product, and performing heat re-heating on the low-temperature helium gas and the high-pressure helium-rich gas to fill the gas.
Further, the main components of the primary helium-rich gas are 30-40vol% of methane, 4-4.5 vol% of helium and a hydrogen-nitrogen mixed gas.
Further, the secondary helium-rich gas has a content of main components of 35 to 40vol% of nitrogen, 59 to 62 vol% of helium, and 6 to 9vol% 2 And (3) hydrogen.
Further, the primary cooling is-45 to-50 ℃, the secondary cooling is-85 to-90 ℃, the tertiary cooling is-115 to-117 ℃, the temperature of the primary helium-rich gas is-130 to-135 ℃, and the quaternary cooling is-155 to-160 ℃.
Further, the temperature of the secondary helium-rich gas ranges from-175 ℃ to-180 ℃, the temperature of the poor helium gas ranges from-155 ℃ to-160 ℃, and the temperature of the poor helium gas is consistent with the temperature of the quartic cooling.
Further, the surface cleaning treatment of the foamed nickel is to soak and repeatedly wash the foamed nickel by using hydrochloric acid, ethanol and deionized water in sequence.
Further, the oxalic acid etching treatment is to soak the foamed nickel subjected to surface pretreatment in 5-15wt.% oxalic acid solution, heat-treat the foamed nickel at a constant pressure of 70-75 ℃ for 2-3h, and dry the foamed nickel in an inert atmosphere;
further, the active component is loaded by soaking the etched nickel in 5-7wt.% potassium hexachloropalladate solution, freezing overnight for 24h, and then placing in a vacuum condensation dryer for drying to remove water.
Further, the purity of the filled helium gas is 99.9999%.
Further, the liquefaction rate in the liquefied methane obtained in the step (2) is 95 to 96%.
Firstly, regarding the pretreatment of raw gas, namely before the gas source enters low temperature, the pretreatment of acid gas, water, mercury and the like is required to be carried out so as to avoid the impurities from being purified before entering a low temperature device and avoid the blockage, corrosion and deterioration of process conditions of pipelines, valves and equipment caused by low temperature, wherein the acid gas is carbon dioxide, hydrogen sulfide and the like, and the selected degassing method is a conventional physical degassing method.
Secondly, for crude helium extraction, the raw material gas processed in the step (1) is cooled to minus 45 to minus 50 ℃ for the first time, cooled to minus 85 to minus 90 ℃ for the second time, cooled to minus 115 to minus 117 ℃ for the third time, cooled to a segmented temperature, so that the energy consumption of equipment can be effectively reduced, impurity gas easy to condense is discharged, the cooled raw material gas is led into a first helium extracting tower condenser to carry out first helium extraction and cooling separation, primary helium-rich gas is collected at the upper end of the tower, the primary helium-rich gas mainly comprises 30 to 40vol% of methane, 4 to 4.5 vol% of helium and a hydrogen-nitrogen mixed gas, and the temperature of the primary helium-rich gas is minus 130 to minus 135 ℃.
Liquefied methane is collected at the lower end of the column, and the liquefaction rate in the liquefied methane is 95-96%.
And cooling the collected primary helium-rich gas for four times, wherein the four-time cooling is-155 to-160 ℃, then carrying out secondary helium extraction, cooling and separation by a second helium extraction tower condenser, the temperature of the secondary helium-rich gas is-175 to-180 ℃, obtaining secondary helium-rich gas and poor helium gas, mixing the poor helium gas with the primary helium-rich gas, carrying out the four-time cooling and the secondary helium extraction, and carrying out the four-time cooling and the secondary helium extraction and cooling treatment on the poor helium gas, wherein the temperature of the poor helium gas is-155 to-160 ℃, and the temperature of the poor helium gas is consistent with the four-time cooling temperature.
During the process, helium can be significantly enriched, and the secondary helium-enriched gas contains 35-40vol% of nitrogen, 59-62 vol% of helium, and 6-9vol% 2 And (3) hydrogen.
Then removing the hydrogen in the helium-rich gas, wherein the liquefaction temperature of the hydrogen is lower than-240 ℃, so that the requirement on equipment is huge if the hydrogen is continuously cooled and separated, so that the hydrogen is not suitable for cooling and removing, and the requirements on equipment, cost and maintenance are doubled if a membrane separation method is used, so that the invention adopts the oxygen-adding dehydrogenation gas, and the prior art usually has a step of removing the hydrogen by the oxygen-adding dehydrogenation, but the specific step of removing the hydrogen by the oxygen-adding dehydrogenation is adoptedThe invention discloses a spontaneously developed catalyst system, wherein the catalyst has extremely high catalytic hydrogen oxidation activity, can completely purify hydrogen in helium-rich gas at high space velocity and low temperature, can purify the hydrogen below 1ppm, the catalyst carrier is selected from foamed nickel or other foamed metals, the foam has larger pore diameter and does not generate any pressure drop, the high space velocity in the natural gas purification process is used, the mechanical strength of the foamed nickel is favorable for industrial implementation, based on the catalyst carrier, the foamed nickel is preferably used as a carrier of an oxygen addition catalyst, the foamed nickel is subjected to surface pretreatment, the surface treatment is more conventional, the surface cleaning treatment mainly comprises the steps of soaking and repeatedly washing the foamed nickel by hydrochloric acid, ethanol and deionized water in sequence, impurities, grease, dirt and oxides on the surface of a substrate are effectively removed, then the surface area of the foamed nickel is effectively increased by soaking oxalic acid treatment, the constant pressure treatment is required in the process, the surface area of the foamed nickel can be simply increased, finally, the active components are loaded, the potassium hexachloroxide precursor is adopted, the active component is a Pd, and the active component has the catalytic hydrogen addition oxidation resistance, and the Pd has the hydrogen addition oxidation resistance due to the hydrogen oxidation property of the Pd-hydrogen addition catalyst system 2 The potassium hexachloropalladate can simply and effectively meet the requirements based on the fact that the potassium hexachloropalladate can simply and effectively meet the requirements because the water resistance of the catalyst is also considered in the research and development process of the catalyst, namely K and Pd are indispensable or cannot meet the industrial requirements.
In addition, the gas space velocity GHSV of the secondary helium-rich gas is (4-7) × 10 6 h - The space velocity is high, the catalytic dehydrogenation of a single time can not meet the requirement of purification dehydrogenation, the dehydrogenation reactor of the invention has at least three sections, namely three times of oxygen addition dehydrogenation, the oxygen addition amount is sequentially decreased according to the concentration of hydrogen in the gas, and the average oxygen addition amount is 0.33Nm 3 /h、0.15 Nm 3 H, and 0.05 Nm 3 H, i.e. without introducing too much oxygenMeanwhile, the concentration of hydrogen in the helium-rich gas is effectively reduced, so that the hydrogen in the secondary helium-rich dehydrogenation gas is lower than 1ppm.
Because partial moisture is generated by the oxygen-adding dehydrogenation treatment and must enter a dehydration system, the dehydration system adopts a double-tower switching process, and the moisture content in the obtained secondary helium-rich dehydrogenation gas is lower than 1ppm.
Then, nitrogen removal treatment is carried out: and (3) compressing the dried helium gas obtained from the dehydration treatment to 19-20MPa by a helium gas compressor in advance, then entering a buffer tank, then entering a nitrogen removal system, sequentially exchanging heat with low-temperature helium gas, low-temperature nitrogen gas and liquid nitrogen by high-pressure helium-rich gas, cooling to about-203 to-207 ℃ to realize gas-liquid separation, removing nitrogen gas, enabling the gas phase to enter a low-temperature adsorber for fine nitrogen removal, then obtaining a low-temperature helium gas product, and performing heat re-heating on the low-temperature helium gas and the high-pressure helium-rich gas to fill the gas. In the process, the low-temperature helium gas and the high-pressure helium-rich gas exchange heat exchange is carried out through three times of low-temperature helium gas heat exchange, low-temperature nitrogen gas heat exchange and liquid nitrogen heat exchange stepped cooling treatment, so that the energy is effectively saved.
In addition, the invention adopts a refrigeration system that: adopts a single mixed refrigerant flow with two-stage throttling, and the refrigerant source is Xingsheng 200X 10 4 Nm 3 The outlet of the refrigerant compressor is separated into a gas phase outlet and a liquid phase outlet. The high-pressure gas-phase refrigerant enters the main heat exchanger for cooling, liquefying and supercooling and then is throttled, then enters the supercooling refrigerant separator for gas-liquid two-phase separation, and the gas phase and the liquid phase are uniformly mixed in the main heat exchanger and then are reheated, so that cold energy is mainly provided for the liquefying and supercooling section in the main heat exchanger; high-pressure liquid-phase refrigerant enters a main heat exchanger for supercooling, then throttled and enters a supercooling refrigerant separator for gas-liquid two-phase separation, gas phase and liquid phase enter a low-pressure refrigerant channel respectively, the gas phase and the liquid phase and the low-pressure refrigerant after reheating throttled by the high-pressure gas-phase refrigerant provide cold energy for a precooling section together, and then the reheating returns to a refrigerant compressor inlet of an original liquefying device.
The nitrogen refrigeration cycle mainly provides cold energy for condensation of a helium extraction tower and a denitrification tower and supercooling of liquid nitrogen, high-pressure nitrogen from a circulating nitrogen compressor unit enters a main heat exchanger for cooling, liquefaction and supercooling and then is divided into three paths, one path of the high-pressure nitrogen throttles and enters a helium extraction tower condenser to provide cold energy for the helium extraction tower condenser, the other path of the high-pressure nitrogen throttles and enters a denitrification tower subcooler to provide cold energy for the denitrification tower condenser, the other path of the high-pressure nitrogen throttles and enters a liquid nitrogen subcooler to provide cold energy for supercooling of liquid nitrogen products, nitrogen returning from the helium extraction tower condenser, the denitrification tower condenser and the liquid nitrogen subcooler is converged and then enters a main heat exchange reheating cold box, and then a nitrogen circulating compressor compresses to complete a cycle.
Helium filling system: the helium product from the denitrification system considers three modes of tube bundle vehicle transportation, single bottle filling and packaging grid filling, and is provided with a helium storage tank, a high-purity helium supercharger, a displacement vacuum pump and a helium liquefying device.
Finally, with respect to instrumentation systems: the instrument control principle adopts a basic principle that on-site monitoring is taken as auxiliary, centralized monitoring and control are taken as main, and helium extraction project equipment adopts an industrialized automatic control system to monitor conventional parameters of purity, measurement, pressure, temperature and the like of helium in raw material gas, so that a crude helium extraction system, an oxygen adding and hydrogen removing system, a dehydration system, a nitrogen removal system and a helium filling system are realized, a circulating compressor, a helium compressor, a heater and various control valves are automatically monitored, and the automatic operation of the equipment is completed. Important control loop cards, system power supplies, communication buses and redundancies of a CPU are considered in the configuration of an automatic control system. The automatic helium lifting control system is provided with a network interface communicated with an upper computer, and a set of real-time data acquisition server is arranged at the same time so as to transmit acquired data and information to a DCS (distributed control system) of a project in real time, and the original DCS carries out automatic detection and control on the whole production process in a Central Control Room (CCR). Main and important parameters in the production process of the automatic helium extraction control system are concentrated on CCR and displayed by a DCS (distributed control system); the parameters which are less important and the set values do not need to be adjusted frequently, and local display and adjustment can be adopted. The automatic helium lifting control system is connected with a management computer network of a whole plant through an upper computer while finishing process control, so that the information management of the whole plant is realized, the long-term stable operation of the process production process is ensured, the labor intensity is reduced, and the working condition is improved.
Advantageous technical effects
(1) According to the invention, a natural gas raw material is sequentially subjected to a crude helium extraction system, an oxygen adding and dehydrogenation system, a dehydration system, a nitrogen removal system and a helium filling system, so that helium in the natural gas is highly purified, and high-purity helium with the purity of more than 99.9999vol% is obtained.
(2) The invention effectively realizes extremely high helium extraction efficiency, realizes high-yield liquefied methane while obtaining helium, and can be used as a commodity.
(3) The energy source cyclic utilization, high-efficient environmental protection, automatic control, complete system can continuous stable operation, and the industrialization of being convenient for has high economic value.
(4) The K-Pd/NF catalyst has the advantages of reduced pressure, high strength, capability of completely purifying hydrogen in helium at high space velocity, and excellent water-resistant activity.
The specific implementation mode is as follows:
the following description is presented to disclose the invention so as to enable any person skilled in the art to practice the invention. The preferred embodiments in the following description are given by way of example only, and other obvious variations will occur to those skilled in the art. The basic principles of the invention, as defined in the following description, may be applied to other embodiments, variations, modifications, equivalents, and other technical solutions without departing from the spirit and scope of the invention.
Example 1
A natural gas helium extraction process comprises the following steps:
(1) Pretreating raw material gas, wherein the raw material gas comprises methane, nitrogen and CO 2 The methane content is more than 87vol%, the helium content is less than 0.2 vol%, and the pretreatment means comprises deacidification and dehydration treatment;
(2) Crude helium extraction treatment:
carrying out primary cooling, secondary cooling and tertiary cooling on the feed gas processed in the step (1) in a segmented manner, wherein the primary cooling is carried out at a temperature of-45 to-50 ℃, the secondary cooling is carried out at a temperature of-85 to-90 ℃, the tertiary cooling is carried out at a temperature of-115 to-117 ℃, and the cooled feed gas is introduced into a first helium extraction tower condenser to be fed into the first helium extraction tower condenserPerforming primary helium extraction, temperature reduction and separation, collecting primary helium-rich gas at the upper end of a tower, wherein the primary helium-rich gas mainly comprises 30-40vol% of methane, 4-4.5 vol% of helium and a hydrogen-nitrogen mixed gas, the temperature of the primary helium-rich gas is-130 to-135 ℃, collecting liquefied methane at the lower end of the tower, performing four-time temperature reduction on the collected primary helium-rich gas, performing secondary helium extraction, temperature reduction and separation by using a second helium extraction tower condenser to obtain secondary helium-rich gas and poor helium gas, mixing the poor helium gas with the primary helium-rich gas, performing four-time temperature reduction and secondary helium extraction, temperature reduction is-155 to-160 ℃, and the primary helium-rich gas mainly comprises 35-40vol% of nitrogen, 59-62% of helium and 6-9vol% of H 2 Hydrogen; the temperature of the secondary helium-rich gas ranges from-175 ℃ to-180 ℃, the temperature of the poor helium gas ranges from-155 ℃ to-160 ℃, and the temperature of the poor helium gas is consistent with the temperature of the fourth cooling.
(3) Oxygen adding dehydrogenation treatment
Heating the secondary helium-rich gas to 40-80 deg.C o And C, introducing the catalyst into a catalytic oxidation dehydrogenation reactor, wherein the catalyst is foamed nickel serving as a carrier, a Pd active component is attached to the surface of the catalyst, and the catalyst is filled in the dehydrogenation reactor, and the preparation method of the catalyst comprises the following steps: performing surface cleaning treatment on the foamed nickel: the surface cleaning treatment of the foamed nickel is to soak and repeatedly wash the foamed nickel by using hydrochloric acid, ethanol and deionized water in sequence; (b) oxalic acid etching treatment: soaking in 10wt.% oxalic acid solution, heating at 72.5 deg.C under constant pressure for 2.5h, and drying in inert atmosphere; (c) loading active components: 6wt.% potassium hexachloropalladate solution, freezing overnight for 24h, placing in a vacuum condensation drier, drying to remove water, wherein the loading amount of active components in the catalyst is 1.5wt.%, and the gas space velocity GHSV of secondary helium-rich gas is (4-7) × 10 6 h - The dehydrogenation reactor has at least three sections, namely three times of oxygen addition and dehydrogenation, the oxygen addition amount is sequentially decreased, and the average value of the oxygen addition amount is 0.33Nm 3 /h、0.15 Nm 3 H, and 0.05 Nm 3 And h, the hydrogen in the obtained secondary helium-rich dehydrogenation gas is less than 1ppm.
(4) And (3) dehydration treatment:
enabling helium gas obtained from the oxygen adding dehydrogenation treatment to enter a dehydration system, wherein the dehydration system adopts a double-tower switching process, and the content of moisture in the obtained secondary helium-rich dehydrogenation gas is lower than 1ppm;
(5) Nitrogen removal treatment:
and (3) compressing the dried helium gas obtained from the dehydration treatment to 19-20MPa by a helium gas compressor in advance, then entering a buffer tank, then entering a nitrogen removal system, sequentially exchanging heat with low-temperature helium gas, low-temperature nitrogen gas and liquid nitrogen by high-pressure helium-rich gas, cooling to about-203 to-207 ℃ to realize gas-liquid separation, removing nitrogen gas, enabling the gas phase to enter a low-temperature adsorber for fine nitrogen removal, then obtaining a low-temperature helium gas product, and performing heat re-heating on the low-temperature helium gas and the high-pressure helium-rich gas to fill the gas.
Comparative example 1:
a natural gas helium extraction process comprises the following steps:
(1) Pretreating raw material gas, wherein the raw material gas comprises methane, nitrogen and CO 2 The methane content is more than 87vol%, the helium content is less than 0.2 vol%, and the pretreatment means comprises deacidification and dehydration treatment;
(2) And (3) crude helium extraction treatment:
carrying out primary cooling, secondary cooling and tertiary cooling and segmented cooling on the feed gas processed in the step (1), wherein the primary cooling is-45 to-50 ℃, the secondary cooling is-85 to-90 ℃, the tertiary cooling is-115 to-117 ℃, the cooled feed gas is introduced into a first helium extracting tower condenser for primary helium extraction, cooling and separation, primary helium-rich gas is collected at the upper end of the tower, the main components of the primary helium-rich gas are 30-40vol% of methane, 4-4.5 vol% of helium and a hydrogen-nitrogen mixed gas, the temperature of the primary helium-rich gas is-130 to-135 ℃, liquefied methane is collected at the lower end of the tower, the collected primary helium-rich gas is cooled for four times, then secondary helium extraction and cooling and separation are carried out through a second helium extracting tower condenser, the obtained secondary helium-rich gas and poor helium gas are mixed with the primary helium-rich gas and are subjected to four-time cooling and secondary helium extraction and cooling treatment, the quartic cooling is carried out at-155 to-160 ℃, the main components of the secondary helium-rich gas are 35 to 40vol%, 59-62% of helium, and 6-9% 2 Hydrogen; the temperature of the secondary helium-rich gas is-175 to-180 ℃, and the temperature of the secondary helium-poor gas isThe temperature is-155 to-160 ℃, and the temperature of the lean helium gas is consistent with the temperature of the fourth cooling.
(3) Oxygen adding dehydrogenation treatment
Dehydrogenation is carried out by adopting a dehydrogenation tower:
the type: vertical type
The container category: class II
Temperature: 450 deg.C
Designing pressure: 2.8MPa external dimension:
Φ416×8，H=2213mm
the main material is as follows: s32168.
The dehydrogenation tower has two groups.
(4) And (3) dehydration treatment:
enabling helium gas obtained from the oxygen adding dehydrogenation treatment to enter a dehydration system, wherein the dehydration system adopts a double-tower switching process, and the content of moisture in the obtained secondary helium-rich dehydrogenation gas is lower than 1ppm;
(5) Nitrogen removal treatment:
and (3) compressing the dried helium gas obtained from the dehydration treatment to 19-20MPa by a helium gas compressor in advance, then entering a buffer tank, then entering a nitrogen removal system, sequentially exchanging heat with low-temperature helium gas, low-temperature nitrogen gas and liquid nitrogen by high-pressure helium-rich gas, cooling to about-203 to-207 ℃ to realize gas-liquid separation, removing nitrogen gas, enabling the gas phase to enter a low-temperature adsorber for fine nitrogen removal, then obtaining a low-temperature helium gas product, and performing heat re-heating on the low-temperature helium gas and the high-pressure helium-rich gas to fill the gas.
The proportion purity of the helium obtained in the embodiment 1 of the invention is high-purity helium with 99.9999%, the equipment temperature requirement is low, when the traditional dehydrogenation tower is used for treatment, the temperature is extremely high, the safety is poor, the subsequent cooling treatment is not facilitated, and the purity of the obtained helium is 98.62%, and the helium is non-high-purity helium.
The technical features of the above embodiments can be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the above embodiments are not described, but should be considered as the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above examples only express the preferred embodiments of the present invention, and the description thereof is specific and detailed, but not to be understood as the limitation of the invention patent scope. It should be noted that various changes and modifications can be made by those skilled in the art without departing from the spirit of the invention, and these changes and modifications are all within the scope of the invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (4)
1. A natural gas helium extraction process is characterized by comprising the following steps:
(1) Pretreating raw material gas, wherein the raw material gas comprises methane, nitrogen and CO 2 The methane content is more than 87vol.%, the helium content is less than 0.2 vol.%, and the pretreatment means is deacidification and dehydration treatment;
(2) And (3) crude helium extraction treatment:
carrying out primary cooling, secondary cooling and tertiary cooling and sectional cooling on the raw material gas treated in the step (1), introducing the cooled raw material gas into a first helium extracting tower condenser for primary helium extracting, cooling and separating, collecting primary helium-rich gas at the upper end of the tower, collecting liquefied methane at the lower end of the tower, carrying out four-time cooling on the collected primary helium-rich gas, then carrying out secondary helium extracting, cooling and separating through a second helium extracting tower condenser to obtain secondary helium-rich gas and poor helium gas, mixing the poor helium gas with the primary helium-rich gas, and carrying out four-time cooling and secondary helium extracting and cooling treatment;
the temperature of the primary helium-rich gas is-45 to-50 ℃, the temperature of the secondary cooling is-85 to-90 ℃, the temperature of the tertiary cooling is-115 to-117 ℃, the temperature of the primary helium-rich gas is-130 to-135 ℃, and the temperature of the quaternary cooling is-155 to-160 ℃;
the temperature of the secondary helium-rich gas ranges from-175 ℃ to-180 ℃, the temperature of the poor helium gas ranges from-155 ℃ to-160 ℃, and the temperature of the poor helium gas is consistent with the temperature of the fourth cooling;
(3) Oxygen adding dehydrogenation treatment
Heating the secondary helium-rich gas to 40-80 ℃, introducing the secondary helium-rich gas into a catalytic oxidation dehydrogenation reactor, wherein a catalyst in the reactor is foamed nickel serving as a carrier, and Pd active components are attached to the surface of the catalyst, and the secondary helium-rich gas is obtained by reacting the secondary helium-rich gas with Pd active componentsThe catalyst is filled in a dehydrogenation reactor, and the preparation method of the catalyst comprises the following steps: carrying out surface cleaning treatment on the foamed nickel; (b) oxalic acid etching treatment; (c) Loading active components, wherein the loading amount of the active components in the catalyst is 1 to 2wt.%, and the gas space velocity GHSV of the secondary helium-rich gas is 4 x 10 6 -7*10 6 h - The catalytic oxidative dehydrogenation reactor is at least three sections, namely three times of oxygen addition and dehydrogenation, the oxygen addition amount is sequentially decreased, and the average value of the oxygen addition amount is 0.33Nm 3 /h、0.15 Nm 3 H, and 0.05 Nm 3 H, the hydrogen in the obtained secondary helium-rich dehydrogenation gas is less than 1ppm;
the surface cleaning treatment of the foamed nickel is to soak and repeatedly wash the foamed nickel by using hydrochloric acid, ethanol and deionized water in sequence;
the oxalic acid etching treatment is to soak the foamed nickel subjected to surface pretreatment in 5 to 15wt.% oxalic acid solution, heat-treat the foamed nickel at a constant pressure of 70 to 75 ℃ for 2 to 3 hours, and dry the foamed nickel in an inert atmosphere;
the active component load is that the etched nickel is soaked in 5-7wt.% potassium hexachloropalladate solution, then frozen overnight for 24h, and then placed in a vacuum condensation dryer for drying to remove water;
(4) And (3) dehydration treatment:
enabling helium gas obtained from the oxygen adding dehydrogenation treatment to enter a dehydration system, wherein the dehydration system adopts a double-tower switching process, and the content of moisture in the obtained secondary helium-rich dehydrogenation gas is lower than 1ppm;
(5) Nitrogen removal treatment:
and (3) compressing the dried helium gas obtained from the dehydration treatment to 19-20MPa by a helium gas compressor in advance, then entering a buffer tank, then entering a nitrogen gas removal system, sequentially exchanging heat with low-temperature helium gas, low-temperature nitrogen gas and liquid nitrogen by using high-pressure helium-rich gas, cooling to-203 to-207 ℃, realizing gas-liquid separation, removing nitrogen gas, enabling the gas phase to enter a low-temperature adsorber for fine nitrogen removal, then obtaining a low-temperature helium gas product, and filling the low-temperature helium gas after the low-temperature helium gas exchanges heat with the high-pressure helium-rich gas for reheating, wherein the purity of the helium gas is 99.9999%.
2. The process of claim 1, wherein the primary helium-rich gas comprises methane in an amount of 30-40vol.%, helium in an amount of 4-4.5 vol.%, and a mixture of hydrogen and nitrogen.
3. The process of claim 1, wherein the secondary helium enrichment consists essentially of 35-40 vol.% nitrogen, 59-62 vol.% helium, and 6-9vol.% H 2 And (3) hydrogen.
4. The process for extracting helium from natural gas according to claim 1, wherein the liquefaction rate of the liquefied methane obtained in the step (2) is 95 to 96%.
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