When the boiling point difference between rare gases is very large, the components with high boiling point can be condensed and frozen out. When separating neon and helium, because neon is frozen at 24.3k and the liquefying temperature of helium is 4.178k, liquid hydrogen can be used as the cold source to separate neon and helium.DEAR Air separation unit.If the liquefier appears liquid too early, it means that the liquefier is connected too early. If there is liquid in the liquefier before the temperature condition of the switching heat exchanger is established, the amount of backflow gas in the switching heat exchanger will be reduced due to the generation of liquid, so that the self cleaning can not be guaranteed.Air is a mixed gas, and the gas separation process cannot be spontaneous. In order to achieve the separation of oxygen and nitrogen, work must be consumed. If the separation process is reversible, that is, without any energy loss, the work consumed is the minimum, which is called the separation minimum work.
DEAR Air separation unit.When the processing air volume and compressed temperature of the air compressor are fixed, if the processing air is compressed to 1MPa (gauge pressure) and 2MPa (gauge pressure) respectively, the absolute pressure of the former is almost half that of the latter, that is, the volume is almost twice as large as that of the latter, the mass of the moisture content will also be nearly doubled.When the gas expands in the expander, only the enthalpy drop caused by external work is considered in calculating the refrigeration capacity of the expander. In fact, when the pressure decreases, the molecular potential energy also increases, so a part of the throttling effect should be produced, which should be the cooling capacity. This part of refrigerating capacity is not calculated separately, but the total throttling effect refrigerating capacity of the unit is expressed by the total enthalpy difference between the low-pressure gas at the time of leaving the unit and the pressure gas at the time of entering the unit. When the refrigeration capacity of expander is adjusted, the refrigeration capacity of throttling effect is not affected.
In the liquid accumulation stage, in order to accelerate the accumulation of liquid, it is necessary to give full play to the maximum refrigeration potential of the expander and run several expanders in full capacity. In order not to make the expander temperature too low, the method of increasing the central suction or circulating current is adopted to increase the temperature in front of the expander.DEAR Air separation unit.The common cases of water inflow into the accumulator (or switching heat exchanger) are as follows: the automatic water level regulation system of the air cooling tower of the nitrogen water precooling system fails, which makes the water level too high. Or improper operation, such as unreasonable start-up of air cooling tower or sudden drop of air separation tower pressure, resulting in a large number of water inflow accidents.There are three types of fins commonly used: straight, serrated and multi hole. Straight fins are rectangular fins with smooth walls. The main function of this kind of fin is to expand the heat transfer area, but it has little effect on promoting fluid disturbance. Therefore, its heat transfer performance is slightly worse, but its flow resistance is small. It is suitable for the case of large heat transfer temperature difference between high temperature fluid and low temperature fluid, and can also be used for the case of large heat transfer coefficient when the fluid has phase change.
