DEAR Liquid air separation unit.When the absolute pressure is increased from 0.55mpa to 0.6MPa, the liquefaction temperature can be increased by about 1 ℃, and the cooling capacity difference needed to condense 1kg air is about 2kJ. At this time, the bypass valve from the air to the waste nitrogen pipeline should be closed to increase the downtower pressure. Of course, there is a limit to the increase of pressure.DEAR Liquid air separation unit.When the temperature of the cold end of the switching heat exchanger reaches - 60 ～ - 150 ℃, the circulation can be used. The function of the circulation is to reduce the temperature difference at the cold end. When passing through the water freezing stage before - 60 ℃, it is easy to ensure the temperature difference of water self-cleaning (between 12 ℃ and 28 ℃), so the circulating current can not be used. In particular, the central cooling method can accelerate the cooling of the cold end of the switched heat exchanger.DEAR Liquid air separation unit.The middle pumping volume should be small at the beginning. For the 6000m3 / h oxygen generator, 200m3 / h can be pumped first. With the continuous decrease of the temperature of the intermediate extraction, the gas extraction volume is gradually increased. Increase 500m3 / h each time, so that the temperature at the bottom of the accumulator does not rise sharply and the outlet temperature of the expander is not lower than - 180 ℃.
DEAR Liquid air separation unit.The greater the pressure difference of molecular sieve switching, the greater the pressure on the sieve bed, which will be detrimental to the safety of molecular sieve bed. Therefore, we should pay close attention to the molecular sieve heating, cold blowing and other processes. It is disadvantageous to take too long and too short time to equalize and relieve pressure.The thermometer is directly installed on the outer wall of the pipe, and the temperature measuring part is not in contact with the medium; although the thermometer joint is inserted into the fluid pipe, the temperature measuring part still can not contact with the medium; the thermometer itself is not accurate, the temperature of the backflow gas is higher than that of the air, and the temperature difference at the hot end is negative, and no problem is found;DEAR Liquid air separation unit.When the air passes through the throttle valve, the total enthalpy remains unchanged and the temperature and pressure decrease. As for whether liquid is produced before and after throttling, it depends on the state before throttling and the pressure after throttling. It can be seen from the thermodynamic properties of air that there is a saturation curve as the boundary of state.
In tube test of heat exchanger. Close the high pressure air throttle valve and the high pressure air inlet valve of the expander, install the high pressure gauge and open the valve. Open one blow off valve of the lower tower and one blow off valve of the upper tower, and the gas source is introduced from the blow off-2 valve. Open the blow off-1 valve to check whether the gas is discharged, and then close it. When the pressure of the heat exchanger rises to 1MPa, stop the air intake and check whether there is air leakage at the external connection.DEAR Liquid air separation unit.When blowing out the oil and water at all levels of the air compressor, we can see that there is always a large amount of water blowing out from the separator. Where does the water come from? This is because the amount of water that can be contained in every cubic meter of air mainly depends on the temperature, but has little to do with the total air pressure. For example, at 30 ℃ and 0.1MPa pressure, the saturated moisture content in the air is 30.3g/m3.
DEAR Liquid air separation unit.If the refrigerating capacity is too much, for example, when the working pressure of the medium pressure device is too high, the moisture content of the air entering the lower tower will increase, the heat load of the main cooler will decrease, the evaporation capacity of liquid oxygen will decrease, and the liquid oxygen level will rise. Therefore, whether the cooling capacity of the device is balanced or not is first reflected in the change of the main cooling liquid level.DEAR Liquid air separation unit.In the air separation unit with air expansion and full low pressure process, the expanded air directly enters the upper column to participate in distillation. The more the amount of expanded air entering the upper tower, the lower the average purity of nitrogen and the lower the extraction rate of oxygen. Therefore, on the premise of ensuring the required cooling capacity, trying to reduce the amount of expansion air is one of the important measures to improve the oxygen extraction rate. That is to say, under the condition of a certain amount of processing air, the oxygen production can be increased.
