Pressure Swing Adsorption (PSA nitrogen generator) is a kind of advanced gas separation technology using carbon molecular sieve as adsorbent, which has an irreplaceable position in today's world of on-site gas supply, and is commonly used in various industries. In the existing hundreds of nitrogen enterprises, customers how to choose a nitrogen generator with good performance is the first choice for many customers to face the problem, for a nitrogen generator selection involves more problems, but as long as we carefully analyze, compare, grasp the key, you can get satisfactory results.
First of all, before determining the specific model specifications (i.e., hourly nitrogen production, nitrogen purity, outlet pressure, dew point), we should focus on the performance of the nitrogen generator and the characteristics of a comprehensive comparative analysis, and at the same time, we need to make the right choice for our existing environmental conditions.
First, compare and analyze the nitrogen generator from the following aspects:
a) the rationality of the whole system design;
b) the carbon molecular sieve filling technology and compression mode;
c) the service life of the control valve;
d) the research and development, manufacturing experience, and the performance of the users;
The second factor affecting the cost of the nitrogen generator:
The second factor affecting the cost of the nitrogen generator:
The second factor affecting the cost of the nitrogen generator is as follows Factors affecting the cost of nitrogen generator:
1) one-time investment in the whole system;
2) the service life of molecular sieve;
3) the service life and cost of spare parts required in the process of using;
4) the operation and maintenance cost and the consumption of electricity, water and compressed air;
Thirdly, the factors affecting the stability of the nitrogen generator:
Nitrogen generator is the first one which involves the integration of machine, electricity and instrumentation, which is the most important factor in the development of nitrogen generation system. The nitrogen generator is a high-tech product involving machine, electricity and instrumentation, and the stability of the equipment is especially important in long-term use. It is not difficult to see from the composition of the nitrogen generator, affecting the stability of the following two points:
1, control valves:
For the pressure adsorption nitrogen generator, the valves must have the following properties:
a) good material performance, absolutely no air leakage;
b) in the acceptance of control signals in 0.02 seconds to complete the opening or closing action;
c) can withstand the frequent use of nitrogen generator;
Control valve:
This is the most important factor that affects the stability of the nitrogen generator, which is a high-tech product involving machine, electricity and instrumentation. c) can withstand frequent opening and closing, to ensure long enough service life;
1.1, the root cause of valve failure
Normal use, each programmable valve must be switched on and off once in each cycle (120 seconds), according to the nitrogen generator 300 workdays per year, 24 hours per day, continuous action, adsorption and desorption cycle of 4 minutes, then each valve needs to be opened and closed more than 200,000 times per year. Each valve needs to be opened and closed more than 200,000 times a year. And as long as one of the valve failure will affect the whole equipment. Therefore, the continuous service life of the valve is the most important part of the stability and reliability of the nitrogen generator.
2, carbon molecular sieve is the core of variable pressure nitrogen generator:
2.1, carbon molecular sieve performance indicators:
a. Hardness
b. Nitrogen production (Nm3/T-h)
c. Recovery (N2/Air)
d. Filling density
Above the indicators of the carbon molecular sieve manufacturers have been The above indexes have been indicated by the carbon molecular sieve manufacturers in the factory, but they can only be used as the reference data, how to make the carbon molecular sieve play the maximum performance, which is directly related to the process flow and adsorption tower height and diameter ratio of each nitrogen manufacturer, and at the same time, to ensure that the service life of the molecular sieve is very important:
2.2, Carbon molecular sieve filling technology:
Carbon molecular sieve must be equipped with the specialized filling technology when it is loaded into the adsorption tower, otherwise it will be easily pulverized and lead to the failure. Extremely easy to pulverize and lead to failure, we can find from the process, when the compressed air from the bottom of the adsorption tower at high speed into, if there is no special gas distributor, molecular sieve by the strong impact of the airflow, friction, easy to cause the pulverization of molecular sieve. In addition molecular sieve filled into the adsorption tower is not absolutely tight, after a period of time, the gap between the molecular sieve in the reduction, slowly sinking, if there is no molecular sieve automatic filling device and compression device, the upper part of the adsorption tower there will be obvious space. When the compressed air into the lower part of the adsorption tower, the molecular sieve will be under the impact force of the airflow, in a short period of time, rapid displacement occurs, resulting in molecular sieve collision with each other, friction and impact with the wall of the adsorption tower, which will be easy to make the molecular sieve pulverization failure.
2.3, air oil, water on the molecular sieve effect:
Since the air contains certain water and oil vapor, after the compressor, if not through strict air purification, oil vapor is easy to be adsorbed by the carbon molecular sieve, and it is difficult to adsorb, fill the molecular sieve aperture, resulting in the molecular sieve "poisoning" failure. Therefore, in the compressed air into the adsorption tower before setting strict air purification device is to ensure that the molecular sieve service life is an essential part. Although water is not fatal to the molecular sieve, but will make the molecular sieve adsorption "load" increase, that is, affecting its adsorption of O2, CO2 ability, so the compressed air drying in addition to water, is to improve the adsorption capacity of molecular sieve and the stability of the problem can not be ignored.
3.Program Analysis
Aiming at the above problems, Sapo has made special research and development, for which the whole set of nitrogen production system has been carefully designed and arranged, and the whole set of nitrogen production device contains the following parts.
3.1System flow chart
3.1.1Air compressor
The air compressor is the main part of the air source, and the compressed air firstly passes through the compressed air purification component to remove water and oil, and then enters into the air purification component. filter, ultra-fine filter, catalyst degreaser and other components, compressed air into the pipeline filter to remove ＞1μm particles and most of the water, to ensure the normal use of the freeze dryer and the post-filter, the freeze dryer so that the forced cooling to about 5 ℃, so that the water vapor in the air condenses into water, through the separation of water filters and filtration, by the sewage valve, so that the dew point of compressed air to reach -10 ℃ The compressed air is filtered by the fine filter >0.01μm particles and oil and water, and then enter the ultra-fine filter to filter oil and water; the filtration precision >0.001μm, the residual trace of oil mist adsorbed by the activated carbon in the degreaser, and the clean compressed air is piped into the nitrogen-oxygen separation system, which ensures that the molecules are used for a long life.
3.1.3 Air storage tank components
The role of the air storage tank is to ensure the smooth use of the system, reduce the airflow pulsation, play a buffer role in reducing system pressure fluctuations, so that compressed air through the compressed air purification system, in order to adequately remove oil and water impurities, to reduce the load of the subsequent PSA oxygen and nitrogen separation device. At the same time, when the oxygen-nitrogen separation system carries out cycle work switching, it also provides the oxygen-nitrogen separation system with a large amount of compressed air required for a short period of time to rapidly increase the pressure, so that the adsorption pressure in the adsorption tower rises to the working pressure very quickly to ensure the stable operation of the equipment.
3.1.4 Oxygen-Nitrogen Separation System
Oxygen-Nitrogen Separation System is the core part of the nitrogen generator, which consists of two adsorption towers, compression device, programmable control valves and other components, and the institute adopts high-quality imported valves, which have a service life without leakage of more than three million times, providing a reliable performance for the whole set of devices.
3.1.5 Nitrogen buffer tank
Nitrogen buffer tank mainly consists of buffer tank, dust filter, flow meter, regulator, throttle valve, etc., to provide a stable source of nitrogen at the site of the user. Summary: Through the above program analysis, we can have a certain knowledge and understanding of the structure and composition of the nitrogen generator, but for different environmental conditions as well as different process conditions of use, the equipment in the configuration will have a certain selectivity.