Oxygen enrichment refers to the application of physical or chemical methods to collect oxygen in the air, so that the oxygen enrichment content in the collected gas is ≥ 21%.
The technology of burning carbon in oxygen rich, that is, oxygen rich combustion, is based on the existingutility boiler On the basis of the system, the combustion technology of replacing combustion air with high-purity oxygen and assisting flue gas circulation has many advantages, such as relatively low cost, easy scale, and the ability to transform existing units.
Chinese name
Oxygen enrichment
Foreign name
oxygen enrichment
Oxygen rich content
≥21%
Application
Aerospace and energy industry
Methods
Pressurization and oxygenation, chemical oxygen generation
Oxygen enrichment refers to the application of physical or chemical methods to collect oxygen in the air, so that the oxygen enrichment content in the collected gas is ≥ 21%.Oxygen enrichment methods include: pressurization and oxygenationoxygeneratorOxygen generation, chemical oxygen generation, etc.Enriched oxygen is widely used. With the continuous development of oxygen rich combustion technology, oxygen rich technology has become one of the bases of green energy.[1]
Oxygen enrichment mode
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Pressurization and oxygenation mode
Pressurization and oxygenation are mainly used on the aircraft. By increasing the pressure in the cabinAir densityAs the proportion of oxygen content in the air is certain (the volume ratio of oxygen in the air is 20 95%), after the air density increasesAbsolute massIt also increases, so as to increase oxygen.
Oxygen generation mode of oxygen generator
oxygeneratorOxygen generation is widely used in various fields. There are three types of oxygen generators. The first is to use air as raw material, and through physical methodsoxygenSeparate from the air.At 1 atmospheric pressure,Liquid oxygenThe boiling point of is - 183 ℃, whileLiquid nitrogenThe boiling point of the liquid air is - 196 ℃. When the boiling point of the liquid air is controlled below - 183 ℃ and above - 196 ℃, the liquid nitrogen will evaporate first, leaving liquid oxygen. This method can produce oxygen with high purity, and then press it into the cylinder under great pressure (generally 150 atmospheres) for storage in factories and hospitals. The oxygen stored in the cylinder can also be charged into the oxygen bag for personal or tourist use.What we usually seeOxygen bottleOxygen supply and oxygen bag supply are oxygen produced by this method.The second method is normal pressure (or low pressure) oxygen productioncompressed airThe pressure of is within 1MPa, which is a method of oxygen production developed in the past decade, also called membrane oxygen production method.Refer to the literature for the principle of membrane oxygen generation method.The third is PSAMolecular sieve oxygen productionMethod: PSA molecular sieve is used to produce oxygenPSAOxygen generation equipment, which is mainly composed of air purification system, PSA oxygen and nitrogen separation system,oxygenBuffer, detection system, etc.
Chemical oxygen generation mode
Chemical oxygen production is based onOxygenatesAs the raw material, through the reaction with the catalystoxygen。The oxygenated compound used must meet two conditions: one is that this oxygenated compound is relatively unstable and easy to decompose and release oxygen when heated;Second, the percentage of oxygen in this oxygenated compound is relatively high, which can decompose and release more oxygen.GeneralPotassium chlorate(The molecular formula is KClOthree）It contains 40% oxygen, and a small amount of blackmanganese dioxide(MnOtwo）Powder and potassium chlorate will decompose rapidly, and a large amount of oxygen will be released.Oxygen released by potassium chlorate decomposition is commonly used“Drainage and gas gathering method”Collect it for test, breathing, etc.OxylideThis principle is used to produce oxygen.[2]
Oxygen generation by membrane separation
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advantage
(1) It is convenient to increase capacity.The oxygen production of the system can be easily expanded by adding membrane modules.
(2) No special care by operators is required.
(3) Maintain less.Since there are few valves, it is unnecessary to replace the moving components regularly.
(4) Light weight, compact structure and space saving.
(5) It is easy to install and start, and the starting time shall not exceed 10 min.
(6) The oxygen enriched membrane separator has high separation coefficient and permeation rate, and the separation coefficient of oxygen/nitrogen is 5~7.
(7) No negative pressure and pressure transformation process.
(8) With full regulation function, it can greatly save energy when the oxygen production is required to be reduced.
(1) There must be a fresh and clean atmospheric environment, which cannot be guaranteed on the battlefield.
(2) Hollow fiber membranes need to be imported and cannot be manufactured in China at present.
(3) The concentration of oxygen generation is 30%~50%, which can be directly used by people, but if the oxygen bag is filled with oxygen, the oxygen content in the bag is low.
Low temperature distillation compressed oxygen
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Low temperature distillation has been used for large-scale industrial oxygen production for a hundred years, and the system composition is complex.The principle is to use different liquefaction points of different gases to produce different gases through air compression at low temperature.The main equipment includes: air purification equipment, air compressor, expander, heat exchange equipment, rectification equipmentOxygen compressor, liquid oxygen pump, etc.Although the low-temperature distillation method cannot be directly used in the project, its oxygen products can be purified through the "oxygen air separation process for compressed products in liquid oxygen pump". After meeting the medical oxygen requirements, high-pressure cylinders can be filled for standby in the project.
Pay attention to safety issues when using: First, special personnel should check the seals of steel cylinders regularly every day.Because the cylinder pressure is high, it is easy to leak after long-term storage.Second, regularly check the oxygen supply pipeline.If there are welding slag, rust, grease or other solid substances in the pipeline, when the oxygen supply is large and the flow rate is fast, these substances will be entrained and rub with the pipe wall, which will lead to combustion or explosion.The third is to eliminate the mixing of industrial oxygen.The price of industrial oxygen is low, but the quality requirements are low. It can only be used for industrial production and product processing.It containscarbon monoxide、carbon dioxide, acetylene and other impurities that are extremely harmful to human body, once the patient inhales excessively, it will cause or aggravate the disease of respiratory system, and even lead to life danger in serious cases.
Oxygen production by sodium chlorate oxygen candle
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Since the 1940s, NATO countries have generally used oxygen candles made of sodium chlorate as the basic raw material to supply oxygen.Oxygen candles can be divided into two categories according to their uses: one is startup type oxygen candles, which are used forSuperoxideThe starting device of the self rescue escape device, the starting oxygen candle has short working time and low oxygen production, generally only works for 1 min, producing about 6L of oxygen in standard state;The other is large oxygen candles, which work for a long time and are mainly used in military and aerospace fields.Due to its small mass and short service time, the start-up oxygen candle is easy to form and has a high allowable upper limit of impurities.However, large oxygen candles are of high quality and have a long service life, so there are high requirements on the formula ratio and molding process, not only to prevent flameout, collapse and other phenomena in the decomposition process, but also to try to restrain the generation of impurities.At present, the domestic research on oxygen candles is mainly focused on small start-up oxygen candles, while the research on large oxygen candles has not been in-depth.
Internationally, Western European countries and the United States have conducted more in-depth research on large-scale oxygen candles.For example, the mobile oxygen candle oxygen production device of Daimber Company in Austria, with a size of 1.5 m * 0.635 m * 0.6 m and a weight of 92 kg, has been equipped with troops.The oxygen candle oxygen generating device of IDF has been used in the French army, some former French African national armies and some hospitals.Oxygen candles are the only source of oxygen in Britain's "Dreadnought" nuclear submarine.In the aerospace fieldLithium perchlorateThe oxygen candle as raw material is used as the oxygen source of Mir space station.
There are two basic indicators for the evaluation of oxygen production technology: oxygen production and impurity gas content.So far, there are two main ways to increase oxygen production: (1) Use chlorate with high oxygen content to increase the oxygen density in the candle body.For example, the oxygen candle used by the Mir space station is made of lithium perchlorate.2) By looking for catalysts, the decomposition temperature of chlorate can be reduced, so as to reduce the use of fuel in the candle body and increase the content of chlorate.
PSA oxygen generation
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China'sPSAThe development of oxygen generation technology started early, and the 1970s was the heyday of the development of PSA separation air oxygen generation technology in China.More than ten units across the country have successively carried out experimental research on PSA oxygen production technology and established several sets of industrial test equipment.Developed during this periodPSA oxygen generation equipmentThe common points of are as follows:[3]
(1) Most of them adopt the process of adsorption and desorption at higher atmospheric pressure, and there are two to four adsorption towers;
(2) The air shall be subject to dehydration pretreatment before entering the adsorption tower;
⑶ The equipment has poor reliability and can not operate continuously and stably, leading to the scrapping of most equipment;
⑷ Technical and economic indicators are backward.
In the 1980s, the development projects of the original pressure swing adsorption oxygen generation equipment development units were suspended one after another, and the development of pressure swing adsorption oxygen generation technology in China again entered a low ebb.
In 1995,Kunshan Jinhu Machinery Co., LtdThe construction of VPSAO1000Nm3/h oxygen generator at Luoyang Iron and Steel Plant in Henan Province marks the formal entry of PSA into the industrial field in China and the rapid development of PSA in China.
The 1990s witnessed the rapid development of PSA oxygen production technology in China. PSA oxygen production technology has gradually matured, and the comprehensive technical and economic indicators of some products have approached the advanced level abroad.Years of practice shows that China's PSA oxygen generation technology has stepped out of the laboratory and into the practical stage.In the past ten years, through continuous technological upgrading and research and development, China's PSA oxygen production technology has changed with each passing day and developed rapidly, and the gap between China and the world's advanced level is narrowing.However, on the whole, China still lags behind the international advanced level in many aspects.For example, in the research of new high-performance adsorbent, improvement of adsorption process, theoretical analysis and researchmathematical model Establishment, quality control andAutomatic controlAnd many other aspects.
Oxygen enriched combustion
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Carbon capture in combustion, that is, oxygen enriched combustion technology, is based on the existingutility boiler On the basis of the system, using high-purity oxygen instead of combustion supporting air, and at the same time assisting the combustion technology of flue gas circulation, CO2 flue gas with a volume concentration of up to 80% can be obtained, thus realizing permanent storage or resource utilization of CO2 after condensation and compression at a small cost;It has many advantages such as relatively low cost, easy scale, and transformable stock units, and is considered to be one of the most likely CCUS technologies to be popularized and commercialized on a large scale.[4]
Oxygen enriched combustion technology was first proposed by Abraham in 1982 to produce COtwoIt is used to improve oil recovery (EOR).With the intensification of global warming and climate change, CO, as the main factor of greenhouse gasestwoThe issue of emissions has gradually attracted global attention.Therefore, as one of the most potential new combustion technologies to effectively reduce CO2 emissions, oxygen enriched combustion technology has become the focus of global researchers.
At present, oxygen enriched combustion technology has been valued and developed in the United States, Japan, Canada, Australia, Britain, Spain, France, the Netherlands and other countries.Major research institutions and companies include: EERC and ANL in the United States, B&W and Air Products and Alstom's U.S. branch, IHI and HITACHI in Japan, CANMET in Canada, IFRF in the Netherlands, BHP and Newcastle University in Australia, CS Energy, CIUDEN in Spain, Alstom in France, Doosan Babcock in the United Kingdom, and Vattenfall Power in Sweden.
Since 2005, the industrial demonstration of oxygen enriched combustion has made outstanding progress. In 2008, the Swedish Waterfall Power Company built the world's first full process 30MW (th) oxygen enriched combustion test device in Germany's Black Pump;In 2009, Total Lacq 30MW (th) natural gas oxygen enriched combustion demonstration system in France was put into operation;In 2011, Australia's CSEnergy Company built the world's first and largest 30MW (electricity) oxygen enriched combustion power generation demonstration power plant in Calide, and Spain's CIUDEN Technology Research and Development Center built a 20MW (th) oxygen enriched combustion power plantPulverized coal boilerAnd the world's first 30MW (th) oxygen enriched fluidized bed test device.In addition, the European Union, the United States, the United Kingdom and others have announced that they will carry out large-scale demonstration projects of oxygen enriched combustion for several power plants around 2015.In August 2010, the U.S. Department of Energy announced the launch of the Future Gen2.0 plan to achieve carbon capture based on oxygen rich combustion, and funded $1 billion (the total budget of the project is $1.3 billion) to build a 200MWe (now adjusted to 168MW (e)) commercial scale oxygen rich combustion power plant. The goal is to achieve 90% carbon capture rate and remove most of the pollutants such as SOx, NOx, Hg and particulate matter.
