Air Separation Unit Helium Gas Extraction Plant From Natural Gas

HE Recovery & Purification System
Helium is known as the rare earth in the gas industry and is an indispensable rare strategic resource for high-tech development. Because helium is a rare non-renewable gas, the storage volume is extremely small, the demand is increasing rapidly, and the price is rising. The helium recovery and purification system solves this problem very well, improves the utilization efficiency of helium, and at the same time removes impurities (water, carbon dioxide, nitrogen, oxygen, etc.) in helium, obtains high-purity helium, and converts helium into recycle and re-use. Save costs for customers, also have high economic value.
Technical Principle
The impurity helium that needs to be recovered, after being boosted by the compressor, removes the oil and water in it through the filter, then enters the dryer to further remove the water, carbon dioxide and oil, and then enters the purification device, to remove air components such as nitrogen and oxygen in the helium.
Through pressure swing adsorption and membrane separation technology, the impurities in helium are removed, and high-purity helium is obtained. In this way, the waste helium can be reused, which has great economic value, and can also be filled into steel cylinders or used directly.

Technical Features
1. Set the filter before the air inlet of the purification unit;
2. Set the flow meter at the outlet of the purification unit;
3. The outlet of the purification unit is equipped with a bypass valve and a loop pipeline. When the purity of the purified gas does not meet the requirements of the index, it can be purified twice through the loop pipeline;
4. The purification time of the helium purifier is short, and qualified helium can be produced in 40 minutes, and the process is fully automatic;
5. Control system: The programmable controller realizes the automatic control of the system, and sensors are installed in key parts to realize remote monitoring and control;
6. The system has a helium purity detection interface.

HE Separation & Purification
The principle of membrane separation system is to use a polymer (usually polyimide) film to select "filter" the feed gas to achieve the purpose of separation. When two or more gas mixtures pass through a polymer film, the diffusivity of each gas component in the polymer is different, resulting in different rates of penetration through the membrane wall. Thus, gases can be divided into "fast gas" (e.g. H20, H2,He, etc.) and "slow gas" (e.g. N2, CH4, etc.). When the mixed gas is under the action of the driving force and the pressure difference of the corresponding groups on both sides of the membrane, the gas with relatively high permeation rate is preferentially transmitted through the membrane wall and is enriched at the low pressure permeation side, while the gas with relatively low permeation rate is enriched at the high pressure retention side.
The membrane permeation method utilizes the different permeation properties of various gases such as helium, nitrogen, argon, and methane to the membrane to extract helium from natural gas. If there are other impurity gases in the gas, such as H2, etc., it is also necessary to use a composite process such as catalytic dehydrogenation.

Technical Principle
Although some natural gas fields in my country contain helium, the content of helium is very low, and the cost of directly extracting helium is extremely high. Through the composition test of the non-condensable gas produced during the liquefaction of natural gas and the boil-off gas (BOG, Boil off Gas) produced by the vaporization of LNG storage tanks, it was found that the content of helium in them reached more than 1%, which has economic exploitation value. To this end, our company has developed an LNG-BOG low-temperature helium extraction device, which uses the low-temperature segregation method to recover LNG and obtain high-purity helium, which is an effective means for comprehensive development of helium resources
Technical Features
The composite recovery and helium extraction process based on the coupling of various advanced technologies such as membrane separation, pressure swing adsorption, hydrogen and helium separation, catalytic dehydrogenation, and temperature swing adsorption. It has the characteristics of high adaptability and high yield for processing BOG gas and pipeline natural gas with low helium concentration.
·The purification efficiency is over 90%.
·Meet the purification requirements of the raw gas containing helium ≥ 0.3% (the pipeline natural gas needs to increase the helium concentration process), and the purity of the purified helium meets the needs of customers and the development of domestic helium resources.
·Safe explosion-proof design, cloud technology remote monitoring and operation.

The main unit of BOG cryogenic helium extraction device includes: helium liquefier, BOG compressor, BOG cold box, hydrogen removal device, control system, etc.
The BOG Cryogenic Helium Extractor utilizes a cryogenic separation method to purify and liquefy helium.
First, most of the methane is recovered by the method of low temperature rectification of BOG gas, and the remaining gas is mainly a mixture of nitrogen, helium and hydrogen. The mixed gas is cooled to a lower temperature, and most of the nitrogen is removed by condensation separation to obtain crude helium with a helium content of >75% V. The hydrogen in the crude helium is then subjected to catalytic hydrogen removal to obtain raw material helium with helium purity > 95% V, and then enters the internal purification system in the helium liquefier, and uses the method of low-temperature adsorption and separation to remove impurity gas to obtain high-purity helium. Finally, it is further liquefied in a helium liquefier to obtain liquid helium.

Helium Liquefaction Unit
The closed-cycle direct reliquefaction system is suitable for closed systems using liquid helium, and the helium gas at the outlet is of high purity (higher than 99.9995%). The liquefier is an external hanging structure, which is directly connected to the user equipment through the infusion pipe and the return gas pipeline, as shown in the figure. While achieving zero evaporation of liquid helium in the user equipment, the pressure of the user equipment is maintained within the range of 0.15psi.

Large Cryogenic Helium Liquefaction Plant/Helium Refrigerator
Large-scale cryogenic helium refrigerators/liquefaction units use helium compressors to obtain high-pressure helium gas. Part of the high-pressure helium gas is expanded and refrigerated in a turboexpander, and the rest of the high-pressure helium gas is cooled in a multi-stage heat exchanger step by step, and finally liquid helium is obtained after throttling through the throttle valve.
The obtained liquid helium can be used in two ways. One is to provide 4.5K constant temperature cooling for user equipment, and the evaporated helium gas is returned to the cold box, and the cold energy is recovered and recycled, such refrigeration equipment is called a helium refrigerator; One is to directly output the obtained liquid helium as a product, such a refrigeration equipment is called a helium liquefier. The main equipment of helium refrigerator/liquefier includes: helium compressor, helium oil filter, cold box, control system, liquid helium Dewar, coaxial transfer pipe from cold box to liquid helium dewar, helium buffer tank. Among them, the cold box is a vacuum insulated cold box, and the cold box contains a multi-stage heat exchanger, a helium turboexpander, an inner adsorption cylinder, a low temperature valve, a measuring element and other components.

The main equipment of helium refrigerator/liquefier includes: helium compressor, helium oil filter, cold box, control system, liquid helium Dewar, coaxial transfer pipe from cold box to liquid helium dewar, helium buffer tank.
Among them, the cold box is a vacuum insulated cold box, and the cold box contains a multi-stage heat exchanger, a helium turboexpander, an inner adsorption cylinder, a low temperature valve, a measuring element and other components.