20 May 2022
Oxygen is an indispensable medical material in modern hospitals, and plays an important role in life support, critical rescue and rehabilitation physiotherapy. With the continuous progress of preparation technology, hospital oxygen supply has been developed from cylinder oxygen supply, liquid oxygen centralized oxygen supply to molecular sieve oxygen concentrator oxygen supply.
1. Cryogenic oxygen production technology
Cylinder oxygen supply and liquid oxygen centralized oxygen supply generally use cryogenic oxygen production technology. The preparation principle is as follows: air is used as raw material, and impurities such as dust and water vapor are removed through pretreatment, and then the air is cooled by heat exchange to turn the air into liquid air. , using the principle of different boiling points of nitrogen and oxygen, depressurizing and heating up to vaporize nitrogen to obtain liquid oxygen. Cylinder oxygen supply is to put the prepared liquid oxygen into steel cylinders of different capacities under normal temperature and high pressure after vaporization, and transport it to various departments for use. The liquid oxygen centralized oxygen supply technology is to fill the liquid oxygen into the special liquid oxygen storage tank installed in the hospital, and then transport it to the clinical departments through the special oxygen pipeline after decompression and vaporization. Due to factors such as cost, technology, site, safety and labor, ordinary hospitals cannot perform cryogenic oxygen production. Usually, liquid oxygen must be regularly purchased from liquid oxygen manufacturers and sent to hospitals for filling by special liquid oxygen transport vehicles.
2. Molecular sieve oxygen production technology
2.1 Molecular sieve oxygen production principle
Molecular sieve pressure swing adsorption (PSA) gas purification and separation technology is a technology developed with pollution control and environmental protection after the 1960s. Molecular sieve is a crystalline aluminosilicate compound with a porous cage skeleton structure, which has good adsorption selectivity and high-efficiency adsorption capacity. At this time, molecular sieves preferentially adsorb gas molecules, while oxygen molecules are rarely adsorbed. According to the unique selective adsorption characteristics of the molecular chapter, it is possible to use molecular sieves to produce oxygen. When the temperature remains unchanged, the adsorption capacity of molecular sieves for chlorine increases with With the change of pressure, the pressure increases and the adsorption capacity increases; the pressure decreases and the adsorption capacity decreases. Through this feature, the process of pressurized adsorption and decompression release of gas can be realized.
2.2 Molecular sieve oxygen concentrator working process
The ambient air passes through the coarse filter to remove large particles of solid impurities, and then enters the air compressor. The temperature of the compressed air rises. The high-temperature air first enters the air buffer tank, and then enters the freeze dryer after cooling to cool down and remove moisture. And then through the precision filter to remove dust, that is, to obtain dry and clean air. The treated air is pressurized into the adsorption tower, the chlorine gas is adsorbed, the oxygen flows into the oxygen buffer tank, and then decompressed, transported to the ward by the pipeline, and the separated chlorine gas is discharged outdoors. In order to continuously provide oxygen, molecular sieve oxygen concentrators are generally installed with more than 2 adsorption towers, which work alternately in the process of pressurized adsorption of chlorine gas and reduced pressure release of chlorine gas.
3. Advantages of molecular sieve oxygen concentrator
Cylinder oxygen supply method The compressed oxygen pressure in the bottle is extremely high. During the process of transportation, handling and storage, improper operation and management are prone to explosion and high risk. Liquid oxygen centralized oxygen supply method Liquid oxygen is extremely low temperature, and accidental contact during vaporization will cause serious injury to personnel; the oxygen storage capacity of the liquid oxygen tank is very large. , the explosion risk is great; in addition, the liquid oxygen tank needs to be evacuated regularly, and the operator is at great risk. Molecular sieve oxygen concentrator works at normal temperature and low pressure. There are situations such as transportation, filling and storage, and the safety is high.
In the oxygen supply of steel cylinders, the amount of oxygen stored in a single cylinder is small, and the oxygen cylinders need to be replaced frequently. The purchase, transportation, storage and custody are complicated and cumbersome, and consume a lot of manpower and material resources. Liquid oxygen centralized oxygen supply requires regular purchase of liquid oxygen from professional oxygen producers, and transportation and filling by special high-pressure tank trucks. Therefore, the procurement cycle takes 5 to 7 days; the oxygen station needs to be equipped with more management and maintenance personnel. In the above two oxygen supply methods, oxygen preparation is not completed in the hospital. It takes a certain time from purchase to use, and is affected by weather and traffic. It is easy to cause difficulties in hospital oxygen use in case of emergencies. The molecular sieve oxygen concentrator is installed in the hospital and uses air as the raw material. It is convenient and fast to operate, and it is self-produced and used. Especially in small and medium-sized cities that lack liquid oxygen manufacturers, it is more convenient. The equipment is controlled by a microcomputer, and the operation is simple and convenient. It only requires less management personnel. Multiple adsorption towers work in turn. The failure of one of them does not affect the overall oxygen supply, which can save a lot of manpower and material resources.
4. The development prospect of molecular sieve oxygen concentrator
As a new type of oxygen production technology, molecular sieve oxygen concentrator is an energy-saving gas separation technology with low energy consumption and fast regeneration, especially suitable for applications in areas with inconvenient transportation and energy shortages. With the advancement of science and technology, molecular sieve oxygen concentrators can be further developed in the following aspects.
4.1 Oxygen concentration
The oxygen concentration obtained by the molecular sieve oxygen production mechanism is (96±3)%. Compared with the 99.5% oxygen concentration of the cryogenic oxygen production technology, the oxygen concentration of molecular sieve oxygen production is somewhat lacking. With the development of the material industry and the application of new adsorption materials, the adsorption performance of molecular sieves will be improved, and the oxygen concentration produced will be higher and higher, making it possible to reach the oxygen concentration produced by the cryogenic oxygen production technology.
4.2 Molecular sieve life
The molecular sieve oxygen concentrators generally use zeolite molecular sieves as adsorbents. The service life of zeolite molecular sieves is 1 to 2 years, and it is particularly sensitive to moisture. The amount of water in the air will directly affect its service life. Although manufacturers generally promise to replace molecular sieves free of charge within 10 years, the development of molecular sieve materials with long service life and high adaptability will certainly greatly promote the development and application of the molecular sieve oxygen concentrators.
Compared with the centralized oxygen supply of liquid oxygen, the installed capacity and area of the molecular sieve oxygen concentrator have been greatly reduced, but it still needs to be placed in a special machine room, occupying a certain area. At present, the domestic molecular sieve oxygen concentrators on the market are highly portable, but the oxygen concentration level can only reach about 80%, which cannot meet the medical requirements of the molecular sieve oxygen concentration level of 90%. Therefore, the molecular sieve oxygen concentrator with high portability is one of the development directions of the future.
5. The outlook for oxygen concentrator
Molecular sieve pressure adsorption and purification technology is a great revolution of oxygen production technology, which is developing rapidly and will be widely used in the future. Compared with traditional cylinder oxygen supply and liquid oxygen centralized oxygen supply, molecular sieve oxygen production technology is safe, easy to operate, less economic investment and high degree of automation. With the development of science and technology, molecular sieve oxygen production technology will continue to develop and improve, making the oxygen concentration level is higher, more pure, longer equipment life, higher degree of automation, better portability, to provide better support for modern hospital construction.
Keywords: oxygen concentrator
Originally published 20 May 2022, updated 20 May 2022.