In detail, the pressure swing nitrogen generator (PSA nitrogen generator) is an advanced gas separation technology which uses carbon molecular sieve as adsorbent. It has irreplaceable position in the field gas supply in the world, and is widely used in all walks of life and in hundreds of nitrogen making enterprises, How should customers choose nitrogen making machines with good performance

First, before determining the specific model and specification (i.e. hourly nitrogen output, nitrogen purity, outlet pressure, dew point), the performance and characteristics of nitrogen production machine must be comprehensively analyzed, and the existing environmental conditions must be selected correctly.

First, the comparison and analysis of nitrogen machine are made from the following aspects: a) rationality of the whole system design; b) The filling technology and compression method of carbon molecular sieve; c) Control the service life of the valve; d) Research and development, manufacturing experience and user performance; Secondly, the factors affecting the cost of nitrogen generator: 1) one-time investment of the whole system; 2) The service life of molecular sieve; 3) Service life and cost of accessories required in the process of use; 4) Operation and maintenance, maintenance cost and power and compressed air consumption;

Third, the factors that affect the stability of nitrogen generator: nitrogen generator is a high-tech product integrating machine, power and instrument. The stability of the equipment is particularly important in the long-term use. From the composition of nitrogen generator, it is easy to see that there are two factors affecting the stability: 1. control valve: for pressure swing adsorption nitrogen generator, the valve must have the following performance: good material performance, no air leakage; For the valve receiving control signal within 0.02 seconds of receiving control signal, the opening or closing action must be completed; Can bear frequent opening and closing to ensure long enough service life;

1.1 when the root cause of valve failure is in normal use, each program control valve must be switched once in each cycle (about 120 seconds), and the nitrogen generator shall be calculated for 300 working days every year, and it shall be operated continuously for 24 hours every day, and the adsorption and desorption period is 4 minutes. Each valve needs to be switched for more than 200000 times a year. One of the valves will fail to affect the normal operation of the whole equipment. Therefore, the continuous life of the gate is the most important link of the stability and reliability of the nitrogen generator.

2. Carbon molecular sieve is the core of the pressure changing nitrogen adsorber

2.1. Performance index of carbon molecular sieve:

a. Hardness

b. Nitrogen production (Nm3 / T-H)

c. Recovery (n2/air)%

d. Filling density

The above indicators have been clearly recorded by the carbon molecular sieve manufacturer at the factory, but as reference data, how to make the carbon molecular sieve to maximize efficiency is directly related to the process flow of nitrogen manufacturers and the ratio of high diameter of adsorption tower, and at the same time, it is also very important to ensure the life of molecular sieve

2.2. Carbon molecular sieve filling technology: when the carbon molecular sieve is installed in the adsorption tower, special filling technology must be available, otherwise it is easy to pulverize and cause failure. It can be found from the process that when compressed air enters from the bottom of the adsorption tower at high speed, if there is no special gas distributor, the molecular sieve will be strongly impacted and rubbed by the air flow, which will easily cause the pulverization of the molecular sieve. In addition, molecular sieve can not enter the adsorption tower absolutely tightly. After a period of time, the gap between molecular sieves will decrease and slowly sink. If there is no automatic molecular sieve filling device and compression device, there will be obvious space on the upper part of the adsorption tower. When compressed air enters the lower part of the adsorption tower, the molecular sieve will move rapidly under the impact of air flow, which will cause the molecular sieve to collide with each other, friction and impact with the wall of the adsorption tower, which will easily cause the molecular sieve pulverization failure.

2.3. The influence of oil and water in the air on molecular sieve: because there is certain water and oil vapor in the air, if it is not treated with strict air purification, the oil vapor is easily absorbed by carbon molecular sieve, and it is difficult to desorption. The pore diameter of molecular sieve is blocked, which leads to the molecular sieve poisoning failure. Therefore, before compressed air enters the adsorption tower, strict air purification device should be set up, which is an important link to ensure the service life of molecular sieve. Although water is not fatal to molecular sieve, it will increase the load of molecular sieve adsorption, that is, the ability of O2 and CO2 adsorption. Therefore, drying and removing compressed air is an important problem to improve the adsorption capacity and stability of molecular sieve.

3. Analysis of the scheme

In view of the above problems, sap has carried out special research and development, so a complete nitrogen manufacturing system is designed and arranged carefully. The complete nitrogen manufacturing unit consists of the following parts.

3.1. air compressor is the main component of air supply. Compressed air first removes water and oil through compressed air purification parts, and then enters air purification parts.

3.1.2 air purification device consists of high efficiency filter, freeze dryer, precision filter, ultra precision filter, catalyst oil remover, etc. Compressed air enters the pipeline filter for removal >1 μ M particles and most of the water ensure the normal use of the freeze dryer and the rear filter. The freeze dryer forced cooling to about 5 ℃, so that the water vapor in the air condenses into water. After separation and filtration of water separation filter, the discharge valve will be discharged, and the dew point of compressed air reaches to -10 ℃, and the precision filter filter will filter more than 0.01 μ M of particles and oil and water, then into ultra precision filter filter oil and water. Filter accuracy >0.001 μ m. Through the adsorption of residual oil mist by activated carbon in the oil remover, clean compressed air is obtained and enters the nitrogen and oxygen separation system through the pipeline to ensure the service life of the molecule.

3.1.3 the air storage tank assembly and air storage tank are used to ensure the stable use of air, reduce air flow pulsation, play a buffer role, reduce system pressure fluctuation, stabilize compressed air through compressed air purification system, fully remove oil and water impurities, and reduce the load of subsequent PSA oxygen nitrogen separation device. Meanwhile, during the cycle operation switching of the oxygen nitrogen separation system, a large amount of compressed air is provided for the oxygen nitrogen separation system to boost the pressure rapidly in a short time, so that the adsorption pressure in the adsorption tower rises to the working pressure rapidly, so as to ensure the stable operation of the equipment.

3.1.4 oxygen nitrogen separation system is the core part of nitrogen generator, which consists of two adsorption towers, compression device, program control valve and other components. Our hospital adopts high-quality imported valves, without leakage and service life of more than 3 million times. It provides reliable performance for the whole device.

3.1.5 nitrogen buffer tank. Nitrogen buffer tank is mainly composed of buffer tank, dust filter, flowmeter, pressure regulating and throttle valve, which provides stable nitrogen source for users. Conclusion: through the analysis of the above scheme, we can have a certain understanding of the structure and composition of nitrogen generator, but for different environmental conditions and different process conditions, the equipment will have certain choice in configuration.