I. The basic principle of membrane separation oxygen generation
It has been more than 100 years since the study on the mass transfer process of gas in the membrane. People have done a lot of studies on the single gas transmission in the polymer and membrane, thus, it has gained better development in theory. However, the application of membrane in practice has been a matter of recent decades, and a more prominent example is the separation of isotopes from nuclear weapons. It was not until the late 1970s s that the permeability and selectivity of gas in polymer membrane had developed to be of industrial economic value that membrane was widely applied like today. Generally speaking, the membrane can permeate all the gas, but the extent of permeation is different. Gas penetrates through the hollow polymer membrane, which is a complex process. Its penetration mechanism is generally that gas molecules are first absorbed on the surface of the membrane to dissolve, and then spread in the membrane, finally, it is desorbed from the other side of the membrane, and the membrane separation technology relies on the difference of dissolution and diffusion coefficient of different gases in the membrane to realize the separation of gases.
When the mixed gas is under the action of certain driving force (pressure difference or pressure ratio on both sides of the membrane, gas with quite fast penetration rate, such as water vapor, oxygen, hydrogen, helium, hydrogen peroxide, carbon dioxide, etc., is enriched on the permeability side of the membrane after penetrating the membrane, however, gases with relatively slow penetration rate, such as nitrogen, argon, methane and carbon oxide, are retained on the retention side of the membrane and enriched to achieve the purpose of separation of mixed gases.
II. The process of membrane separation oxygen generation equipment
According to the different pressure in separation conditions, we usually divide membrane oxygen production into two different process flows, and users can choose the appropriate process according to different working conditions to achieve the purpose of minimum unit consumption.
1. High pressure flow membrane oxygen generation
Compressed air is removed from solid impurities such as oil, dust and most of the pneumatic water through the pretreatment system, and enters the membrane separator after preheating, gas with quite fast penetration rate, such as water vapor, oxygen, hydrogen, helium, hydrogen peroxide, carbon dioxide, etc., is enriched on the permeability side of the membrane after penetrating the membrane, however, the gas with relatively slow penetration rate, such as nitrogen, argon, methane and carbon oxide, is retained on the retention side of the membrane and enriched; the system can achieve continuous and stable output of oxygen under the control of PLC or DCS system.
2. Negative pressure process oxygen generationAfter the air from the air blower is purified, the dust is removed and then enters the membrane separator. The gas with relatively slow penetration rate, for example, nitrogen, argon, methane, carbon oxide and so on are detained on the retention side of the membrane, and after being enriched, they will be discharged as exhaust gas, and the oxygen-enriched air on the permeating side will be collected as product gas by vacuum pump vacuum pumping. The system can continuously obtain stable and pure oxygen under the control of PLC or DCS system.
III. Characteristics of membrane separation oxygen generation equipment
The main features of membrane oxygen-nitrogen separation equipment:
1. The equipment process is simple, the structure is compact, and the equipment investment is low
2. The device covers a small area and can be used for indoor and outdoor operations
3. The unit has a high degree of automation, and it is convenient to start and stop; the oxygen concentration can be reached within 10 minutes.
4. No moving parts such as valve switching, no need to replace wearing parts regularly, and the amount of maintenance is small.
5. By adding membrane separator, it is easy to enlarge the output of oxygen-enriched air.
6. The operating and maintenance costs of the unit are lower than those of PSA method oxygen; the purity is 25 ~ Within the range of 35%, it has superior performance-price ratio. In the aspect of combustion-supporting application, it has incomparable advantages over other air separation methods, and its operation energy consumption is relatively low.
7. The unit has strong operation independence, good stability, high reliability, and works under normal temperature and low pressure with good safety performance.
8. The scale of the unit can be from 0.2 to 50000 Nm3/h, and the purity of oxygen of the product can reach 25 to 45%;
IV. The basic composition of membrane separation oxygen generation equipment
Main components of high pressure flow equipment/components of low pressure flow equipment
1. Air compressor/1. Blower unit
2. Air source pretreatment components/2. Dust removal and cooler
3. Air buffer tank/3. Membrane separator
4. Membrane separator/4. Finished oxygen buffer tank
5. Finished oxygen buffer tank/5. Switch the valve and corresponding pipe fittings
6. Switch the valve and corresponding pipe fittings/6. Vacuum pump unit
7. Automatic control and detection system/7. Oxygen booster
8. Scalable pressurization system/8. Automatic control and detection system
V. Installation and operation conditions of membrane oxygen generation equipment
1. Installation conditions: the installation site should be clean and smooth, and the crane or forklift can be easily arrived and installed;
2. Requirements of using environment: the air around the installation site should be clean, free of oil mist and corrosive gas, and well ventilated;
3. Supporting conditions: Power supply: 380 V/50Hz/3-phase five-wire;
4. Cooling water: conform to the refrigeration and cooling water for industrial use.
VI. Matters needing attention on the selection of membrane oxygen generation equipment
1. Before the specific model selection, first confirm the requirements for the final product gas of the required oxygen equipment, and determine the process of the required equipment under the suggestions of the manufacturer;
2. Inspect the rationality of equipment design (whether the setting of each accessory is reasonable and necessary, and give full play to its maximum effect );
3. Inspect the reliability of equipment operation (verify the rationality of assurance measures in equipment design );
4. Research and development ability, manufacturing experience and level of manufacturers;
5. Comprehensively calculate the cost of oxygen generation equipment (equipment Price, necessary water, electricity, site and its cost, equipment maintenance cost, equipment service life ), not only the price of the equipment is considered.
