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What are the restrictions on the amount of expanded air entering the upper tower of DEAR air separation unit?
2022-01-13

Attention should be paid to the following problems when using: the liquid level in the liquid oxygen tank should not be lower than 20% at any time; the acetylene content in the liquid oxygen in the tank should be analyzed according to the specified period (for example, once every half a month), and measures should be taken to solve the abnormality in time; the liquid in the tank should not be stored for a long time, and should be filled and discharged frequently, so as to avoid the concentration of acetylene and other harmful impurities.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 oxygen flow rate in the oxygen pipeline shall be in accordance with the provisions of code for design of oxygen station (GB 50030-91): when the pressure is greater than 10MPa, the oxygen flow rate shall be less than 6m / S; when the pressure is between 3Mpa and 10MPa, the oxygen flow rate shall not be greater than 10m / S; when the pressure is between 0.1MPa and 3Mpa or less, the oxygen flow rate shall not be greater than 15m / S; when the pressure is between 3Mpa and 3Mpa, the oxygen flow rate shall not be greater than;In the start-up operation, when the cold end temperature reaches - 10 ℃, circulating current is used. Using circulation in advance can not only reduce the temperature difference at the cold end, ensure self cleaning, but also make the switching heat exchanger cool evenly. When the stage cooling method is used for start-up, the use of circulating current as early as possible can also prolong the operation time of the expander under the condition of higher inlet temperature, give full play to the characteristics of large cooling capacity of the turbo expander under high temperature, and thus shorten the start-up time.
If the heat stored in the insulation layer (the cooling capacity required for cooling the insulation layer is often greater than that required for the whole liquid accumulation stage) continues to flow into the tower, the liquid level will not rise or rise slowly, prolonging the time required for this stage.The heat removed from the unit is (H ′ 4-h ′ 2), which is the cooling capacity of throttling effect at that time. This shows that the cooling capacity of throttling effect still exists in non isothermal compression, but it does not exist in the compression process. The compression process is to create conditions for throttling and cooling.Due to the hard work of valve opening and closing, the valve stem is often twisted and the hand wheel is broken. Therefore, after the maintenance of the valve, the packing should be installed evenly and tightly, and the compression nut should be tightened. During the overall leakage test of DEAR air separation unit, the leakage at the valve rod packing should also be checked, and this problem should be solved before cold start-up.
When the air volume of middle extraction or circulation is adjusted, there is a sudden change in the proportion of positive and return air volume at the outlet of middle extraction or circulation, and the change of temperature is more severe. Therefore, the central temperature is the most sensitive and representative. In operation, it is often adjusted according to the central temperature to keep the central temperature at the value corresponding to the specified temperature difference between the cold end and the hot end.Serrated fin is a kind of fin with a certain distance and a notch, which makes it protrude to the fluid. It is very effective to promote fluid disturbance and destroy laminar boundary layer, so it has good heat transfer performance. It is often used in switching heat exchanger with small temperature difference between high and low temperature fluids. On the one hand, it can strengthen the heat transfer between gases; on the other hand, it is convenient for the precipitation and removal of water and carbon dioxide.