Complaint
PSA full name: Pressure Swing Adsorption (PSA).PSA is a new gas separation technology, which has been developed rapidly in foreign countries since the late 1960s and early 1970s. Its principle is to separate the gas mixture by the difference of the "adsorption" performance of different gas molecules by molecular sieve. It takes air as raw material.The nitrogen and oxygen in the air are separated by the selective adsorption of nitrogen and oxygen with a high efficiency and high selection of solid adsorbent.
At present, carbon molecular sieves and zeolite molecular sieves are used more in the field of nitrogen and oxygen production.The separation of oxygen and nitrogen by molecular sieve is mainly based on the different diffusion rates of the two gases on the surface of molecular sieve. Carbon molecular sieve is a carbon-based adsorbent with some characteristics of activated carbon and molecular sieve.Carbon molecular sieves are composed of very small micropores with pore sizes ranging from 0.3nm to 1nm.The smaller diameter of the gas (oxygen) diffuses faster and more into the solid phase of the molecular sieve, so that nitrogen enrichment can be obtained in the gas phase.After a period of time, molecular sieve on oxygen adsorption balance, according to the carbon molecular sieve under different pressure on the adsorption of different gas adsorption characteristics, reduce the pressure to remove the carbon molecular sieve on oxygen adsorption, this process is called regeneration.PSA usually uses two towers in parallel, alternately pressurized adsorption and decompression regeneration to obtain a continuous flow of nitrogen.
With air as raw material, with carbon molecular sieve as adsorbent, the use of pressure change adsorption principle, the use of carbon molecular sieve on oxygen and nitrogen selective adsorption and separation of nitrogen and oxygen method, commonly known as PSA nitrogen.This method is a new technology of nitrogen production which developed rapidly in 1970s.Compared with the traditional method of nitrogen, it has simple process, high degree of automation, produce gas quickly (15 ~ 30 minutes), low energy consumption, product purity can be adjusted according to user needs in a wide range, convenient operation and maintenance, low operating cost, good adaptability device etc., in 1000 nm3 / h the following competitive in nitrogen making equipment,PSA is more and more popular among medium and small nitrogen users, and has become the choice method for medium and small nitrogen users.
Process flow and equipment introduction of PSA nitrogen making machine
1. Brief introduction to the technological process
Air through the air filter to remove dust and mechanical impurities into the air compressor, compressed to the required pressure, after strict oil removal, water removal, dust removal and purification treatment, the output of clean compressed air, the purpose is to ensure the service life of the molecular sieve adsorption tower.There are two adsorption towers with carbon molecular sieve. One tower is operated while the other tower is decompressed and desorbed.Clean air into the working adsorption tower, through the molecular sieve oxygen, carbon dioxide and water are absorbed by it, flow to the outlet end of the gas is nitrogen and trace argon and oxygen.Another tower (desorption tower) allows adsorbed oxygen, carbon dioxide and water to escape from the pores of the molecular sieve and discharge into the atmosphere.In this way, the two towers take turns to complete nitrogen and oxygen separation and continuously output nitrogen, as shown in Fig. 2.The purity of nitrogen produced by pressure change adsorption is 95%-99.9%. If higher purity nitrogen is needed, nitrogen purification equipment should be added.Psa nitrogen making machine output 95% 99.9% of the nitrogen into the nitrogen purification equipment, at the same time through the flowmeter to add just the right amount of hydrogen gas, hydrogen and nitrogen in the purification equipment of deoxidization tower of trace oxygen in catalytic reaction, and then by water to remove oxygen condenser cooling, in addition to water, water separator, and then through the depth of the dryer drying (two adsorption drying tower used interchangeably:One is adsorbed and dried for water removal, the other is heated for desorption and drainage) to obtain high purity nitrogen. At this time, the purity of nitrogen can reach 99.9995%. At present, the maximum production capacity of nitrogen production by pressure swapping adsorption in China is 3000M3N /h.
Other injection parameters are designed according to thermal recovery optimization parameters, as follows:
Injection pressure: L0 MPa
Injection temperature: above 300oC for steam
Nitrogen :20oC at room temperature
Injection rate: steam 14.6m3/h 400-600m3 /h Nitrogen
Injecting dryness: take 50% of the mixture value
In terms of cost, the on-site cost of nitrogen injection is $0.04/m3, while that of natural gas injection is $0.1/m3. The contract system of nitrogen supply after nitrogen injection is adopted, and the price is determined to be about $0.01/m3.
Other advantages of nitrogen injection are:
1. No pollution to reservoir;
2. Nitrogen supply is not restricted;
3. Nitrogen is an inert gas, which will not cause environmental pollution, flammability and corrosion;
4. Nitrogen injection can save 3965×104m3/ d of natural gas (if gas injection method is chosen), accounting for 31% of Mexico's total natural gas.
The method is gradually improved. Nitrogen is an important gas source for EOR in immiscible gas flooding because it is insoluble with oil and water and has many sources.So nitrogen application in petrochemical industry especially in the oil field system is a very wide range that can be used for 2 / tertiary oil recovery, oil and gas well protected, to maintain pressure and gas storage, container atmosphere replacement, drilling platform of inert gas protection, purging of pipeline and equipment, the protection of the atmosphere when flammable, explosive goods transport, solvent recovery, etc. [1-4].With the maturity of the membrane nitrogen technology, especially the birth of the mobile nitrogen system, it is more suitable for the flexible application of the field.It has the advantages of low investment, simple process, long life and maintenance free, low energy consumption, small volume, low nitrogen dew point, high reliability, large operation flexibility, can adapt to various harsh environments, rapid opening, concentration and flow can be online monitoring and so on.At the same time, the raw materials used are inexhaustible and inexhaustible air.Therefore, nitrogen-rich air with low price, clean, stable quality and easy control can be obtained by membrane method, and the purity of nitrogen is generally in the range of 93%-99.9% [5,6].If it is integrated with other technologies to meet any desired nitrogen purity, it will greatly enhance the market competitiveness of membrane enriched nitrogen.
1. Membrane mobile nitrogen rich system
With the continuous development of all walks of life, the demand for petrochemical products is more and more large, more and more types, and the world's major oil fields, especially heavy oil fields, now generally exists in the middle and late stage of the production of tons of oil cost rise, decline rate accelerated and other phenomena.For this reason, the development and application of oilfield nitrogen injection technology have been carried out in foreign countries since 1970s.At that time, cryogenic method, pressure swing adsorption method and liquid nitrogen injection Wells were mainly used.At the end of the 1980s, the United States first developed a successful membrane nitrogen enrichment technology, and in the middle of the 1990s, the development of mobile membrane nitrogen enrichment vehicle, successfully applied in the field of oil, the effect is very significant.
Relevant experts through the field practical demonstration: in the wellhead using mobile nitrogen-rich device for steam heat insulation and help drainage, oil recovery benefit is obvious, the construction is convenient, the cost is low, its cost is only about 1/10 of liquid nitrogen, natural gas 1/5.
Dalian institute of chemical physics, Chinese Academy of Sciences in the early 1990 s began following the world development trend of technology of nitrogen, the movable membrane technology of nitrogen vehicle tracking research, the second half of 1999 to begin the project implementation, research and development of successful domestic first vehicle-mounted mobile membrane nitrogen-rich device, driving in liaohe oilfield.The operating parameters basically meet the design requirements, and basically meet the field operation requirements of the equipment. It has experienced the severe test of high temperature of 45oC and low temperature of -35oC, which has changed the situation that such devices in China rely on imports [7].The newly developed vehicle-mounted mobile nitrogen enrichment device integrates the proprietary technology and membrane separation technology of Dalian Institute of Chemical Physics, Chinese Academy of Sciences. It changes the traditional multi-vehicle type into an integral single-vehicle type, and has the characteristics of low cost, energy saving, flexibility, high efficiency and easy operation.
Membrane method mobile nitrogen rich system is generally divided into two types: vehicle-mounted and skid-mounted;If the drive mode is divided, there are diesel engine drive and high voltage drive.In general, truck-mounted nitrogen-enriched systems have less capacity than skid-mounted systems, but they are more flexible and convenient.Membrane enrichment for mobile oil fields
