Hospital construction in my country is in a period of rapid development. In the construction of domestic medical gas, this part has long been not given enough attention, the overall investment is relatively small, and the construction level is somewhat different from the international common practice. In order to meet the needs of hospital construction in my country, change the backward appearance of hospitals, and meet the needs of modernization, medical oxygen production systems have begun to be widely promoted and applied, and have developed rapidly throughout the country, and have become an indispensable facility for hospital modernization.
Development History of Medical Oxygen Supply System
The hospital oxygen supply system has gone through a long development process, starting with the first generation of direct oxygen supply from steel cylinders. Due to the high pressure and heavy weight of the oxygen cylinders, it is difficult to carry, inconvenient and unsafe to use, and prone to accidents, affecting the normal operation of medical and rescue work. It was gradually replaced by the second generation of liquid oxygen tanks. Liquid oxygen will absorb heat from the environment and quickly vaporize, and its volume will increase greatly, thereby increasing the pressure in the closed pipeline section and causing danger. Since the current liquid oxygen interface specifications are the same as those of liquid nitrogen and other liquids, there is a risk of misconnection and misinstallation. Such accidents have occurred in China, so liquid oxygen tanks have gradually been eliminated. Up to now, the third generation has been oxygenated by oxygen generators based on the principle of PSA (pressure swing adsorption) . The PSA process is a simple oxygen production method that uses air as the main component. Raw materials, energy consumption is only the electricity consumed by air compressors, oxygen generators and other auxiliary equipment, with the advantages of low operating cost, low energy consumption and high efficiency.
PSA Oxygen Generator
PSA Oxygen Plant
99% PSA Oxygen Generator
PSA Oxygen Generator
Composition of PSA oxygen generator
PSA medical oxygen generator can be roughly divided into two parts: ① oxygen production module; ② analysis and control module. The oxygen generation module is what we often call the molecular sieve tower. It is the core component of the oxygen generator and the main component of the PSA (pressure swing adsorption) oxygen production principle. A large amount of molecular sieves are filled in the molecular sieve tower. The molecular sieve has the structure and characteristics of a crystal, with a solid skeleton on the surface and the pores inside that can adsorb molecules. There are channels connecting the pores, and molecules pass through the channels. Due to the clean nature of the pores, the pore size distribution of the molecular sieve is very uniform. Molecular sieves selectively adsorb molecules based on the size of the pores inside their crystals, that is, based on the different sizes of the molecules of oxygen, nitrogen, carbon dioxide and other rare gases in the air, they adsorb molecules of a certain size and reject molecules of larger substances.
The adsorption effect of zeolite molecular sieves has two characteristics: ① The Lewis center on the surface is very polar; ② The size of the cage or channel in the zeolite is very small, which makes the gravitational field therein very strong. Therefore, its adsorption capacity for adsorbate molecules far exceeds that of other types of adsorbents. Even if the partial pressure (or concentration) of the adsorbate is very low, the adsorption amount is still considerable. The adsorption separation effect of zeolite molecular sieves is not only related to the size and shape of the adsorbate molecules, but also to their polarity. Therefore, zeolite molecular sieves can also be used to separate substances of similar size.
The analysis and control module is mainly composed of CPU controller, electrochemical analyzer, pneumatic valve, relay, pilot valve, pressure switch, back pressure regulator and other components. The CPU controller mainly has a robust programmable logic controller (PLC) which can automatically control and monitor all parameters of the oxygen generator and implement the molecular sieve tower intake, oxygen production, balance, nitrogen exhaust and other work processes through these parameters.
Working principle of PSA oxygen production technology
The oxygen generator separates air mainly by two adsorption towers filled with molecular sieves. Under normal temperature conditions, the compressed air is filtered, dehydrated, deoiled and purified before entering the adsorption tower. In the adsorption tower, nitrogen and other gases in the air are adsorbed by the molecular sieve, and oxygen is enriched. It flows out from the outlet and is stored in the oxygen buffer tank. In the other tower, the molecular sieve that has completed adsorption is rapidly depressurized to analyze the adsorbed components. The two towers are alternately circulated to obtain cheap oxygen with a purity of ≥90%. The automatic switching of valves in the entire system is automatically controlled by a computer.
When the molecular sieve tower A produces oxygen, valve a opens (valves b and c are closed) and clean compressed air enters the molecular sieve tower. When the internal pressure of the molecular sieve tower reaches the rated working pressure, valve a closes, valves c and m open, and the generated oxygen enters the oxygen storage tank. When the pressure in tower A drops to the rated pressure, valve m closes, valve f of tower B opens (valves d and e are closed), and the oxygen generated by tower A enters tower B, making the internal pressure of tower A and tower B balanced (purpose: to increase the oxygen production concentration of tower B and protect the molecular sieve at the same time). When the pressure of the two towers is balanced, valve c of tower A closes, valve b opens, and the exhaust is discharged. The remaining nitrogen in the tower is discharged, and the working process of tower B is the same as that of tower A. The two-stage molecular sieve towers A and B work alternately to increase the oxygen production and oxygen concentration.
Conclusion
PSA oxygen generator has the advantages of long life, stable operation, low energy consumption, low noise, etc., and gradually replaces the traditional oxygen supply method. However, if regular daily maintenance and maintenance are not done well, it will cause damage to the molecular sieve inside the oxygen generator, reduce the performance of the oxygen generator (oxygen production, concentration), and even shorten and damage the service life of the oxygen generator itself. Therefore, a set of management systems for oxygen generators is specially formulated to facilitate the maintenance of oxygen generators, so that the oxygen generators can operate in a good and stable state for a long time.
