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.At the top of the upper tower, gas nitrogen and liquid nitrogen coexist in a saturated state, and they have the same saturation temperature. The absolute pressure of nitrogen out of the upper tower is about 0.13mpa, and the corresponding saturation temperature is - 193 ℃. The temperature of nitrogen saturated steam out of the tower is also at this temperature. The absolute pressure at the top of the lower tower is about 0.55mpa, and the corresponding nitrogen saturation temperature is about - 177 ℃.The backflow cryogenic gas is composed of several gases which have been separated into product oxygen, product nitrogen and waste nitrogen. When calculating the heat exchange incomplete loss, the total heat exchange incomplete loss should be calculated separately and then added up. Because of the largest amount of polluted nitrogen, the temperature difference at the hot end has the greatest influence on the incomplete heat exchange loss.
DEAR Air separation plant.The purification effect of molecular sieve purification system affects the operation cycle of the device. For the same equipment, improper operation may also affect the purification effect. During the operation, the following problems should be paid attention to: the installation requirements of molecular sieve adsorber: carefully check whether the upper and lower screens are damaged and whether the fixation is firm;In the ideal case, the work done by expansion can be equal to the work consumed by compression. It is a reversible adiabatic expansion process, and the entropy value before and after expansion remains unchanged, which is called isentropic expansion. The actual expander expansion will have loss, which is also an irreversible process, and the entropy also increases.Generally, the amount of hydrogenation should be increased by 1% excess hydrogen according to the amount of hydrogen required for complete reaction of hydrogen and oxygen. The purpose is to make the oxygen in the crude argon react fully and further improve the purity of the refined argon. According to the calculated amount of hydrogenation and start hydrogenation, the process should be slow.
DEAR Air separation plant.From the safety point of view, it is required that the vaporization rate at the outlet of the evaporation channel should not be greater than 4%, that is, the liquid circulation rate should be greater than 25. If the height diameter ratio of the channel is too large, it is good for heat transfer, but the vaporization rate of liquid oxygen in the channel also increases, which makes people uneasy from the safety point of view.The method is to observe the "sweating" or "frosting" parts on the wall of the cold box. At this time, attention should be paid to the leakage of low-temperature liquid, and the "frosting" part is below the leakage point.DEAR Air separation plant.In argon production, part of liquid air and liquid nitrogen in the main tower need to be pumped as cold source. At the same time, due to the increase of equipment, the cold loss increases correspondingly. Therefore, more cooling capacity is required to keep the balance of cooling capacity. For medium pressure device, high pressure should be increased.
