DEAR Liquid 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.In order to realize the separation of oxygen and nitrogen in the air separation unit, it is necessary to liquefy the air, which must be reduced to the liquefying temperature. The absolute pressure of the lower column of the air separation column is about 0.6MPa, and the temperature at which the air begins to liquefy is about - 172 ℃. Therefore, in order to liquefy the air, there must be a lower temperature cold fluid to cool the air.Compared with switching purification process, the air separation unit of molecular sieve purification process has simple start-up operation and easy control because the air is adsorbed by molecular sieve to remove impurities such as water and carbon dioxide. It does not need to consider the complex effects such as the self removal of water and carbon dioxide, the precipitation of water and carbon dioxide in the expander and so on. The attention of the start-up process is mainly focused on giving full play to the refrigeration capacity of the expander, reasonably distributing the cooling capacity, and comprehensively cooling the equipment.
The design parameters of general purifier are: working pressure is 2MPa (gauge pressure), working temperature is 30 ℃, switching time is 8h. If the pressure of high-pressure air is not controlled during the heating of fractionator, the working pressure is likely to be lower than 1MPa (gauge pressure). Although the working temperature of purifier is still 30 ℃, the water brought into purifier per hour will double the design value.DEAR Liquid air separation unit.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).During the start-up of the low-pressure oxygen generator, the self-cleaning condition of the switching heat exchanger has not been established, so some water or carbon dioxide must pass through the expander. If the temperature decreases after expansion, it may precipitate in the expander and cause blockage of the expander.
DEAR Liquid air separation unit.When filling the tower with liquid oxygen, one is to pay attention to the timing. When the unit cools down to the beginning of liquid generation in the main cooling, it must be filled in again to avoid damaging the equipment due to thermal stress caused by excessive temperature difference; the other is to pay attention to the filling pressure. Because only when the pressure is higher than the bottom pressure of the upper tower, liquid oxygen can be injected, but it can not exceed the set pressure of the safety valve of the liquid oxygen storage tank, so as to avoid the action of the safety valve.Cooling capacity is a kind of idiom in the field of refrigeration. Because in order to get a lower temperature than the environment, it depends on the power consumption of refrigeration. That is to say, there is a price to be paid to remove heat from cold objects. Because its temperature is lower than the ambient temperature, it has the ability to spontaneously absorb heat from the environment.
