What are the methods of air separation.
Answer: The main components in the air are oxygen and nitrogen, which respectively exist in molecular state. Molecules maintain their original properties
The smallest particle, whose diameter is in the order of magnitude of 10-8 cm, and the number of molecules is very large, and it keeps doing irregular movement, therefore, molecules such as oxygen and nitrogen in the air are mixed evenly with each other, so it is difficult to separate them. Currently, there are mainly three separation methods.
(1) low temperature method
First, the air is compressed, expanded and cooled down until the air is liquefied, and then the gasification temperature (boiling point) of oxygen and nitrogen is different (in
Under atmospheric pressure, the boiling point of oxygen is 90 K, and the boiling point of nitrogen is 77 K). Nitrogen with low boiling point is easier to gasification compared with oxygen.
In the distillation column, let the steam with higher temperature keep in touch with the liquid with lower temperature, and the nitrogen in the liquid will steam more
The oxygen in the gas condenses more, which makes the nitrogen content in the rising steam increase continuously and the oxygen content in the downstream liquid increase continuously.
Big, so as to realize the separation of air. To liquefied the air, it is necessary to cool the air to a temperature below 100 k, which is called deep freezing; while the process of separating the liquid-air by using boiling point difference is called rectification process. realizing Air separation by low temperature method is the combination of cooling and rectification, and it is the most widely used method of air separation at present.
(2) absorption method
It allows air to pass through the absorption tower filled with some kind of porous substance which is divided into sieve, and utilizes molecular sieve to divide different parts
The molecule has the characteristic of selective adsorption, and some molecular sieves (such as 5A, I SMC, etc.) have relatively strong adsorption performance on nitrogen, allowing oxygen molecules to pass through, thus obtaining oxygen with higher purity; some molecular sieves (carbon molecular sieves, etc.) have relatively strong adsorption performance on oxygen, allowing nitrogen molecules to pass through, so that nitrogen with relatively high purity can be obtained. Due to the limited adsorption capacity of the adsorbents, when the adsorption of a certain molecule reaches saturation, there is no ability to continue the adsorption, and the adsorbated substance needs to be driven away to recover the adsorption capacity. This process is called "regeneration ". Therefore, in order to ensure continuous gas supply, more than two absorption towers need to be used alternately. The method of regeneration can adopt the method of heating and increasing temperature (TSA), or the method of reducing pressure (PSA ).
The process of this method is simple, the operation is convenient, and the operation cost is low. However, it is difficult to get high-purity products, and the oxygen purity of the products is about 90%. Moreover, it is only suitable for separation devices with small capacity (less than 4000 m 3/h.
(3) membrane separation method
It utilizes the permeability selectivity of some organic polymer membrane, when the air passes through the membrane (0. L μm) or hollow fiber membrane, oxygen
The speed of gas penetrating through the film is about 4 to 5 times of nitrogen, so as to realize the separation of oxygen and nitrogen. This method has simple device, convenient operation, fast start-up and less investment, but the oxygen concentration is generally suitable for 28-3 s intestines, and the scale is only medium or small, so it is only suitable for oxygen burning, health care and other aspects. At present, the glass kiln towel has been applied practically.
2. What types of oxygen generator (air separation plant) are there?
Answer: oxygen generator is also called air separation equipment (referred to as air separation equipment), which has many types. According to different classification methods, there are many different types
According to the difference of product purity, it can be divided into high-purity oxygen devices whose gas purity is over 99.2%; low-purity oxygen devices whose oxygen purity is about 95% (also called process oxygen; A device for producing oxygen-enriched (also called liquefied air) with a purity lower than 35%.
According to different kinds of products, it can be divided into single-high product device which only produces high-purity oxygen; double-high product device which produces high-purity oxygen and high-purity nitrogen at the same time; attached with extraction device or full extraction device which extracts rare gas.
According to the form of the product, it can be divided into devices for producing gas products: Devices for producing liquid products and devices for producing gas products at the same time,
Devices of liquid products.
According to the different quantity of products, it can be divided into small equipment under 800 m 3/h; medium equipment 1000 ---- 6000 m 3/h;
10000rn 3/h 8: large equipment above.
According to different separation methods, it can be divided into low temperature rectification method; molecular sieve absorption method and membrane infiltration method.
According to the working pressure, the pressure can be divided into 10. 0 --- 20.0MPa high pressure device; working pressure is 1. 0 --- 5.0MPa medium pressure device; pressure is 0. 5-0. Full low pressure device of 6MPa.
The classification method is artificial, and there can be other classification methods
