CN-121988142-A - Natural gas normal temperature helium extraction system and helium extraction method

CN121988142ACN 121988142 ACN121988142 ACN 121988142ACN-121988142-A

Abstract

The application discloses a natural gas normal temperature helium extraction system and a natural gas normal temperature helium extraction method. The system comprises a first membrane separation unit, a second membrane separation unit, a catalytic cycle dehydrogenation unit, an isobaric drying unit, a first pressure swing adsorption unit, a second pressure swing adsorption unit and a purification unit which are sequentially connected, wherein the performance of the first membrane separation unit is superior to that of the second membrane separation unit. Aiming at the problems of complex process flow, more power equipment, high operation energy consumption and high comprehensive cost of helium gas extraction existing in the traditional helium extraction technology adopted by the low-grade lean helium natural gas, the application only adopts the simpler process integration technologies such as two-stage membrane separation, catalytic cycle dehydrogenation, isobaric drying, two-stage pressure swing adsorption separation and purification and the like, thereby realizing the extraction of helium gas from the natural gas with high efficiency and low cost and preparing a high-purity helium gas product.

Inventors

ZHANG ZHE
HUANG JIAN
Chen Siding
Liang Yuejiu
ZHANG LEI
WANG CHUNYAN

Assignees

中国石油天然气集团有限公司

Dates

Publication Date: 20260508
Application Date: 20241104

Claims (13)

1. The natural gas normal temperature helium extraction system is characterized by being used for extracting helium products from natural gas and comprising a first membrane separation unit, a second membrane separation unit, a catalytic cycle dehydrogenation unit, an isobaric drying unit, a first pressure swing adsorption unit, a second pressure swing adsorption unit and a purification unit which are connected in sequence; The selectivity of He relative to CH 4 and the selectivity of He relative to N 2 of the first membrane separation unit are both larger than those of the second membrane separation unit, and the helium yield is smaller than that of the second membrane separation unit; The permeate gas outlet of the first membrane separation unit is communicated with the inlet of the second membrane separation unit, the permeate gas outlet of the second membrane separation unit is communicated with the inlet of the catalytic cycle dehydrogenation unit, the non-desorption gas outlet of the first pressure swing adsorption unit is communicated with the inlet of the second pressure swing adsorption unit, and the non-desorption gas outlet of the second pressure swing adsorption unit is communicated with the inlet of the purification unit.
2. The system of claim 1, further comprising a pretreatment unit and a preheating unit, wherein the pretreatment unit, the preheating unit, and the first membrane separation unit are connected in sequence; the pretreatment unit comprises a dust filter and a gas-liquid coalescing filter.
3. The system of claim 1, wherein the first membrane separation unit has a He selectivity to CH 4 of no less than 150, a He selectivity to N 2 of no less than 50, and a helium yield of no less than 85%; The selectivity of He relative to CH 4 of the second membrane separation unit is not less than 120, the selectivity of He relative to N 2 is not less than 40, and the helium yield of the second membrane separation unit is not less than 100%.
4. The system of claim 1, wherein a first compression unit is disposed between the permeate gas outlet of the first membrane separation unit and the inlet of the second membrane separation unit, for pressurizing the permeate gas output by the first membrane separation unit and then inputting the pressurized permeate gas into the second membrane separation unit; a second compression unit is arranged between the permeate gas outlet of the second membrane separation unit and the inlet of the catalytic cycle dehydrogenation unit and is used for pressurizing the permeate gas output by the second membrane separation unit and inputting the permeate gas into the catalytic cycle dehydrogenation unit.
5. The system of claim 4, wherein the non-permeate gas outlet of the second membrane separation unit is in communication with the inlet of the first membrane separation unit, and/or, The desorption gas outlet of the first pressure swing adsorption unit is communicated with the inlet of the second compression unit, and/or, And a desorption gas outlet of the second pressure swing adsorption unit is communicated with an inlet of the second compression unit.
6. The system of claim 1, wherein the adsorbent of the first pressure swing adsorption unit is at least two of silica gel, activated carbon, molecular sieve; The molecular sieve is a calcium ion exchanged A-type molecular sieve.
7. The system of claim 1, wherein the molecular sieve adsorbent of the second pressure swing adsorption unit is a calcium ion and/or lithium ion exchanged type a, type X or type LSX molecular sieve.
8. The system of claim 1, wherein the catalytic recycle dehydrogenation unit comprises a dehydrogenation unit and a recycle cooling unit; the dehydrogenation device is used for enabling hydrogen in the input gas to react with the fed oxygen to generate water under the action of the palladium catalyst, and removing the hydrogen to be below 0.1 ppmv; the circulating cooling device is used for cooling the dehydrogenated gas to be below 45 ℃ and then inputting the dehydrogenated gas into the isobaric drying unit.
9. The system of claim 8, further comprising a recycle gas compression unit; The outlet of the circulating gas compression unit is communicated with the inlet of the catalytic circulating dehydrogenation unit, and the inlet of the circulating gas compression unit is communicated with the outlet of the catalytic circulating dehydrogenation unit.
10. The system of claim 1, wherein the molecular sieve of the drying unit is one of a 3A molecular sieve, a 4A molecular sieve, and a 13X molecular sieve.
11. The system of claim 1, wherein the purification unit utilizes coconut activated carbon to adsorb and remove nitrogen, oxygen, methane and neon from the unadsorbed gas output from the second pressure swing adsorption unit at liquid nitrogen temperature to obtain the helium product.
12. The system of claims 1-11, wherein the first membrane separation unit is configured to receive raw natural gas at a pressure of 3.0-10.0 mpa.g; the non-permeate gas outlet of the first membrane separation unit is in communication with a natural gas network.
13. A method for extracting helium from natural gas at normal temperature, which is characterized by extracting helium products from raw natural gas by using the natural gas normal temperature helium extracting system according to any one of claims 1-12.

Description

Natural gas normal temperature helium extraction system and helium extraction method Technical Field The application relates to the technical field of helium gas extraction, in particular to a natural gas normal-temperature helium extraction system and a helium extraction method. Background Helium is used as a rare gas resource and is widely applied to the fields of military industry, aerospace, medical treatment, semiconductors, scientific research, low-temperature superconductivity and the like. While the helium resources in China are extremely lean. At present, helium is extracted from natural gas as a main industrial production source, the helium extraction cost is closely related to the helium content in the natural gas, and natural gas in China basically belongs to low-grade lean helium natural gas, most of the helium content is 200-600 ppmv, and the helium amount is small, so that the direct helium extraction cost of the natural gas is extremely high. The maturity of the industrial helium separation and purification technology is higher, namely membrane separation, adsorption and low-temperature separation, more than 90% of helium in the world is obtained through natural gas low-temperature separation, and in recent years, the membrane separation and adsorption helium extraction technology also has more engineering application due to the advantages of normal temperature operation, low energy consumption, convenience in starting and stopping and the like. At present, low-temperature separation, membrane separation, adsorption separation and other technologies or combined technologies are further adopted to purify the helium to 99.999vol% aiming at BOG gas (with the helium content of 0.5-10 vol%) which is a byproduct of liquefied natural gas LNG factories at home and abroad. Helium extraction from BOG gas is undoubtedly the most economical helium extraction route for application scenarios requiring construction of LNG plants, but if cryogenic separation is employed solely for helium extraction from natural gas, the investment and operating costs for helium extraction are too high. In 2023, the natural gas yield of China is more than 2000 hundred million cubic meters, and although most of the natural gas is low-grade lean helium natural gas, the total helium contained in the natural gas is larger, and the natural gas is basically combusted and discharged into the atmosphere, so that the waste of helium resources exists. For pipeline natural gas delivery, if a direct helium extraction device is built at a natural gas pressure regulating station, natural gas after helium gas extraction returns to a pipe network, and the economic extraction of helium gas under the condition of ensuring no loss of natural gas becomes one of effective solutions for relieving the problem of helium gas supply safety in China. The biggest problem faced by directly extracting helium from the natural gas lean in the pipe is that the content of helium is too low, the concentration multiple is high, the loss of helium is as little as possible, the helium yield is ensured, and the comprehensive cost of extracting helium is reduced. According to the helium content in natural gas, the traditional technical method adopts three-level or four-level or even five-level membrane separation to carry out coarse concentration, and then adopts low-temperature separation or pressure swing adsorption, low-temperature adsorption purification and the like to obtain a high-purity helium product. The membrane material is mainly polyimide polymer material, the pretreatment requirement on raw gas is high, the investment and the operation cost of pretreatment equipment are high, the permeate gas is required to be pressurized after each stage of membrane separation and then enters the next stage of membrane separation, and the helium extraction process flow adopting the mode is relatively complex, power equipment is more, the operation energy consumption is high, the comprehensive cost for extracting helium gas of lean helium natural gas is high, and the economic benefit is poor. Disclosure of Invention In order to enrich the types of products, enrich the process routes and increase the selection space, the embodiment of the application provides a system and a method for extracting helium from natural gas at normal temperature, which realize high-efficiency and low-cost extraction of helium in natural gas and prepare a high-purity helium product. In a first aspect, an embodiment of the present application provides a helium extraction system at normal temperature for extracting helium gas from natural gas, where the helium extraction system is used for extracting helium gas product from natural gas, and the helium extraction system includes a first membrane separation unit, a second membrane separation unit, a catalytic cycle dehydrogenation unit, an isobaric drying unit, a first pressure swing adsorption unit, a second pressure swing adsorption unit and