PSA technology (Pressure Swing Adsorption, PSA technology for short): a first 
intake of gas separation technology to the adsorbent (porous solid matter) of the interior surface of the physical adsorption of gas molecules on the basis of, at the same pressure using an adsorbent The separation of gas is achieved by the characteristics of easy absorption of high-boiling gas, difficulty of absorption of low-boiling gas, increase of adsorption of adsorbed gas under high pressure, and reduction of adsorption of adsorbed gas at low pressure. The process of adsorbing impurities under pressure and desorbing impurities under reduced pressure to regenerate the adsorbent is a pressure swing adsorption cycle.
As shown in the upper right figure, in the case of adsorption equilibrium, when the carbon molecular sieve adsorbs the same gas, the higher the gas pressure, the greater the adsorbent adsorption. Conversely, the lower the pressure, the smaller the amount of adsorption. At the same time, under a certain adsorption pressure, the adsorption of oxygen by the carbon molecular sieve is much higher than the adsorption of nitrogen.
PSA nitrogen production, also known as carbon molecular sieve air separation nitrogen, is the use of this principle, with air as raw material, carbon molecular sieve as adsorbent, the use of pressure swing adsorption principle, the use of carbon molecular sieve selective adsorption of oxygen and nitrogen, Nitrogen and oxygen in the air are separated and nitrogen is produced.
Nitrogen from PSA has simple process flow, high degree of automation, fast gas production (15 to 45 minutes), low energy consumption, high product purity, purity that can be adjusted according to user needs within a wide range, convenient operation and maintenance, and operating costs Lower, device adaptability and other characteristics. With the wide application of medium and small-scale nitrogen users under 3000Nm3/h, PSA nitrogen production has become the preferred method for users of small and medium-sized nitrogen gas.
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1, compressed air purification system Carbon molecular sieves are the key materials that determine the production capacity of nitrogen generators. Since compressed air provided by air compressors usually contains oil and water, oil and water will reduce the adsorption capacity of carbon molecular sieves, so compressed air must be removed before entering the oxygen-nitrogen separation system. Oil removes water. First, the air is compressed by the compressor to 0.75-1.0 MPa into the air purification system. Most of the water, oil and mechanical impurities are removed by the pipeline filter. Then the water is defrosted by the refrigeration dryer to make the pressure dew point reach 2°C-10°C. Again through the fine filter, ultra-fine filter, activated carbon degreasing device, get a pressure of 0.75-1.0MPa, pressure dew point of 2 °C -10 °C, oil content ≤ 0.01PPm of clean compressed air. The compressed air purification system consists of a pipeline filter, a freeze dryer, a fine filter, a superfine filter, an activated carbon degreasing device, an automatic drain valve, and a ball valve. |
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2. Air storage tank system The function of the air tank system ensures that the oxygen-nitrogen separation system uses gas smoothly, prevents the instantaneous airflow velocity from being too fast during the switching of the oxygen-nitrogen separation system, affects the air purification effect, improves the quality of compressed air entering the adsorber, and is beneficial to prolonging the life of the molecular sieve. The air tank system consists of air tanks, safety valves, globe valves, ball valves, and pressure gauges. |
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3, oxygen and nitrogen separation system Oxygen and nitrogen separation system is the core part of air separation. Its main body is two adsorption towers filled with carbon molecular sieve. When clean compressed air enters an adsorption tower, O2, CO2 and trace H2O are adsorbed by carbon molecular sieve, and nitrogen is output from the outlet. . When one tower is in the process of adsorbing nitrogen, the other tower is depressurized and the O2, CO2 and H2O that are adsorbed in the molecular sieve are discharged from the pores to achieve regeneration and desorption of the molecular sieve. The two towers alternately adsorb and regenerate and continuously output nitrogen. Oxygen and nitrogen separation system consists of an adsorption tower, carbon molecular sieve loaded inside the tower, pneumatic valve, muffler, throttle valve, pressure cylinder, pressure gauge and other components. |
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4, nitrogen buffer system The main function of the nitrogen buffer system is to equalize the pressure and purity of nitrogen separated from the nitrogen oxide separation system and to ensure continuous supply of nitrogen. At the same time, when the adsorption tower is undergoing regeneration to adsorption switching, it will store part of the qualified nitrogen gas back into the protection tower of the adsorption tower, and it will also help the adsorption tower to increase its pressure. Nitrogen buffer system consists of buffer tanks, flow meters, dust filters, pressure regulators, throttle valves, and safety valves. |
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5, electrical control system The main function of the electrical control system is the start-stop operation of the equipment, the display of the working status indicator, the audible and visual alarm indication of failure, the purity display and the actuation of the pneumatic valve according to the setting procedure. The electrical control system consists of a programmable controller CPU, gas source triple pieces, solenoid valves, indicator lights, and a micro oxygen meter, and is mainly installed in the electric control cabinet. |
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1. Excellent isofluid gas distribution technology
When the compressed air enters the adsorption tower from the pipeline, due to the small diameter of the pipeline and the coarse inner diameter of the adsorption tower, the flow rate of the compressed air in the adsorption tower is not uniform, and the gas flowing toward the inlet is rapidly flowing, and the nitrogen oxide molecules contacted by the molecular sieve are large. However, the gas flow near the inside of the adsorption tower is relatively slow, and the nitrogen and oxygen molecules contacted by the molecular sieve are relatively small, resulting in different adsorption saturation of the gas molecules by the molecular sieves at different positions. According to the comparative analysis, when the molecular sieve in the center position is working in 100% saturation, the working saturation of the molecular sieve next to the wall of the adsorption tower is only about 80%. The unsaturation of some molecular sieves directly reduces the working efficiency of the overall molecular sieve, resulting in a decrease in the ratio of nitrogen produced by the same amount of compressed air, which affects the further improvement of nitrogen production capacity per unit nitrogen.
The excellent isofluid airflow distribution device provided by Qi Hong includes a plate air distributor, a two-stage air flow buffer design, and a wide-mouth air flow collection device, so that when the compressed air enters the adsorption tower, it can be evenly distributed at an equal flow rate, ensuring the contact of each molecular sieve. The pressure is the same and the flow rate is the same to ensure that the molecular sieve is fully loaded and the maximum adsorption efficiency of the molecular sieve is used to achieve the best nitrogen production effect. At the same time, it also saves air and reduces energy consumption.
According to the actual measurement, the nitrogen generator using a gas distribution system such as aerodynamics professional has a 8% increase in nitrogen production compared to a nitrogen generator without this technology when the equivalent compressed air is consumed.
2. Unique nitrogen purging process for vent tower
In the traditional process of nitrogen production, when the adsorption tower is vented and analyzed, although the pressure in the tower is reduced to atmospheric pressure, the oxygen retained on the molecular sieve is released, and the tower remains high. Concentration oxygen. If this oxygen is not emptied, the oxygen will be adsorbed by the molecular sieve again when the tower is again in the adsorption process. The secondary adsorption of oxygen consumes the adsorption capacity of some of the carbon molecular sieves. Moreover, the high concentration of oxygen in the tower also directly reduces the nitrogen concentration in the mixed gas formed in the next step of pressure equalization in the tower, resulting in a decrease in the initial nitrogen production concentration from the adsorption column into the adsorption process and lowering the gas storage capacity. The average concentration of nitrogen. In order to increase the concentration of nitrogen production, to eliminate the negative impact of residual oxygen in the tower on the concentration of nitrogen, and to prevent repeated use of residual oxygen to consume the molecular sieve adsorption capacity. Qihong has set up a residual oxygen purging system, that is, venting the tower. After that, the vent column is purged with a suitable nitrogen gas in an adsorption tower in an adsorption state, and the oxygen in the vent column is blown out of the tower. When the air-releasing tower enters the adsorption process again, the nitrogen concentration in the tower is already high, which avoids the problem of the decrease of the initial nitrogen concentration in the adsorption tower, which increases the effective working capacity of the molecular sieve and ensures the production of high-purity nitrogen.
3. Four technical processes to ensure
high-purity nitrogen production at one time In the production process of high-purity nitrogen produced at one time, any imperfections in details will affect the production of high-purity nitrogen. Qihong Company has adopted four special technologies to study the key links in nitrogen production and ensured the high purity of nitrogen at one time. Four professional technologies are:
Equal flow gas distribution technology to improve the overall working efficiency of molecular sieves;
The pure nitrogen purge of the vent tower completely emptied the residual oxygen in the adsorption tower;
High-concentration nitrogen pressure equalization technology to increase nitrogen concentration in the adsorption tower;
Gas storage irrigation high nitrogen backfill technology to avoid unqualified nitrogen gas storage .
Note:
1. If the user has special requirements, specifications and performance parameters can be different from the specifications of this table according to the user's requirements according to the contract;
2. Nitrogen purity is oxygen-free purity, nitrogen gas contains trace amounts of helium, neon, argon and other inert gases;
3. The flow unit “Nm3/h” refers to the unit of flow at 20°C and 0.101 MPa (absolute pressure);
4. The pressure value is the gauge pressure value unless otherwise specified ;
5. The dew point value is not specified except Are dew point of normal pressure.
