DEAR Air separation unit.Close the oxygen regulating butterfly valve and fully open the dirty nitrogen and pure nitrogen regulating butterfly valve. Turn off steam source of steam heater. Cut off the power switch of electrical equipment and make it in the start position. After finding out the cause of the power failure and eliminating the fault, make preparations for the start-up.DEAR Air separation unit.In the actual operation, the situation is much more complicated than the design situation. The main factors affecting the operation cycle include the continuous working ability of the oxygen generator equipment and operating machinery, the quality of heating and blowing before starting, the level of operation in the starting stage and normal operation, the size of air load, etc.On the one hand, because the temperature of water is higher than that of sewage nitrogen, heat is directly transferred from water to sewage nitrogen to cool the water; on the other hand, because sewage nitrogen is relatively dry and the relative humidity is only about 30%, the molecules of water can continuously evaporate and diffuse into sewage nitrogen.
In addition to oxygen, nitrogen and argon, the air also contains a very small amount of rare gases such as neon, helium, krypton and xenon. According to the volume fraction, neon accounts for about 15 × 10-6 ~ 18 × 10-6, helium accounts for 4.6 × 10-6 ~ 5.3 × 10-6. Krypton is only 1.08 × 10-6, xenon is 0.08 × 10-6, commonly known as "gold gas". Because of their small content and complex extraction process, only when the capacity of the oxygen generator is more than 10000 m3 / h can the extraction device be considered.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;
The main way to adjust the temperature of the heat exchanger is to adjust the middle temperature and keep the deviation as small as possible. It is the most common and effective method to adjust the middle temperature by changing the ring flow (or middle pumping).It should be noted that the latent heat of evaporation of 1 kg liquid oxygen is not equal to that of condensation of 1 kg gaseous nitrogen. At the above temperature, the gasification latent heat of oxygen is 207 kJ / kg, and the condensation latent heat of nitrogen is 168 kJ / kg. Therefore, after the heat is transferred from gas nitrogen to liquid oxygen, the condensation amount of nitrogen is about 1.23 times of the evaporation amount of oxygen.In the plate type 6000m3 / h air separation plant, the air flow is only 33000m3 / h, while the annular flow is 5200m3 / h, resulting in air liquefaction at the cold end of the switching heat exchanger. When the circulating flow is reduced to 3400m3 / h, the gas distribution of each unit is reasonable, and the liquefaction phenomenon disappears. In addition, it is also related to the performance of liquid air subcooler, liquid nitrogen subcooler and liquefier.
DEAR Air separation unit.In practical work, kerosene or soapy water can be used for leak detection. First, install the automatic valve in a special tool, put in 0.6MPa pressure and stop pressure for 3min. The standard of air leakage is: no more than 6 soap bubbles with diameter of 40mm can be blown out within 3min. The automatic valve qualified by pressure test shall be equipped with split pin for standby. Special attention must be paid to the split pin must be made of low temperature resistant brass or stainless steel products, and can not be replaced by general split pin.DEAR Air separation unit.The liquid oxygen circulating adsorber is used to absorb the impurities in the liquid oxygen and switch regularly; if the acetylene or hydrocarbon content in the liquid oxygen exceeds the standard, the alarm will start. In addition to the requirement of discharging liquid oxygen equivalent to 1% of the gas oxygen output per hour, the liquid discharge shall be increased; the plate type main cooler shall adopt full immersion operation; the main cooler shall have good grounding device.
