DEAR Liquid air separation unit.The temperature of compressed air will rise. In order to reduce the energy consumption of compression, the temperature rise should be minimized. The air is usually cooled by an intercooler, and further compressed after the temperature is lowered. Generally, the temperature of air drops from about 150 ℃ to 40 ~ 50 ℃ after cooling, while the temperature of cooling water only rises about 10 ℃ after absorbing heat.Oxygen blowing in EAF steelmaking can accelerate the melting of burden and oxidation of impurities, save power consumption, and gradually become a fixed oxygen user. Oxygen enriched blast in blast furnace ironmaking can increase pulverized coal injection, save coke and reduce fuel ratio. Although the purity of rich oxygen is not high (oxygen content is 24% - 25%), the oxygen consumption is considerable due to the large amount of blast, which is close to one third of the oxygen used in steelmaking. Therefore, it has also become a major oxygen user.DEAR Liquid air separation unit.When the temperature of sewage nitrogen in the cold end is reduced, the temperature difference in the hot end will be enlarged, so that the insufficient reheating will increase the cold loss, the expansion will increase, and the product quantity will decrease; liquid hammer may occur, and the automatic valve will be easily damaged. In a word, air liquefaction at the cold end is harmful but not beneficial, and the expansion of temperature difference at the cold end is the most harmful.
DEAR Liquid air separation unit.There are two ways to express the content of a substance in gaseous mixture, one is called mass fraction, the other is called volume fraction. Mass fraction refers to the percentage of the mass of a certain component in the total mass of the mixture; volume fraction refers to the percentage of the volume of a certain component in the total volume of the mixture. For the same content, the values of the two fractions are different.The change of temperature working condition of accumulator (or switching heat exchanger) is generally caused by the change of positive and return gas flow or its inlet temperature. For example, with the increase of positive air flow, the amount of backflow gas and its cold end inlet temperature remain unchanged, then the cooling capacity is insufficient and the air cannot be cooled to the original required temperature. That is to say, the outlet temperature of air at the cold end will rise, and the temperature difference at the cold end will expand.
Some molecular sieves (such as carbon molecular sieves) have strong adsorption properties for oxygen, so that nitrogen molecules can pass through, so nitrogen with high purity can be obtained. Due to the limited adsorption capacity of adsorbent, when the adsorption of a certain molecule reaches saturation, there is no ability to continue adsorption. It is necessary to drive away the adsorbed substances in order to restore the adsorption capacity. This process is called regeneration.The main fault in the valve body is that the sealing surface between the valve top and the valve seat is not tight, which causes the valve not to close. The most common is the O-ring rubber seal off. This is mainly related to the uncleanness of the bonding surface and the poor quality of the adhesive. In addition, there are foreign matters at the valve seat; the concave convex spherical washers at both ends of the valve stem and the valve top are too tight or too loose; the fixed nut is not tightened, resulting in the loosening of the valve top; the bending of the valve stem may cause the valve to close loosely.
It can be divided into three stages: cooling equipment, liquid accumulation and rectification condition adjustment. Compared with the start-up mode of switching process, it can be called "overall cooling method" or "one-time cooling method". Attention should be paid to the following points during the start-up operation: the molecular sieve used for the first time should be activated and regenerated to remove the water and carbon dioxide absorbed in the transportation and filling process.DEAR Liquid air separation unit.When the air volume is reduced or the product throughput is increased, the temperature difference at the cold end will be reduced, the temperature difference at the hot end will be enlarged, and the temperature at the outlet of the circulation (or the middle extraction) will be reduced. Therefore, when increasing the air throughput or reducing the product throughput, we should pay attention to the expansion of the temperature difference between the cold end and the middle; when reducing the air throughput or increasing the product throughput, we should pay attention to the cold loss at the hot end. If necessary, it should be supplemented by circulation regulation.
