DEAR Air separation plant.When using air separation method to produce oxygen, we always want to separate as much oxygen as possible from the processing air as a product. In order to evaluate the perfection of separation, the concept of oxygen extraction rate was introduced.
The oxygen extraction rate is expressed by the ratio of the total oxygen in the product oxygen to the total oxygen in the air entering the tower. Namely
Where, ψ - oxygen extraction rate;
VO2, VK -- oxygen output and processing air volume, m3 / h;
Yo2, YK volume fraction of oxygen in product and air.The gas source for the test shall be oil-free, dry air or nitrogen, and the pressure shall be higher than the maximum pressure of the heat exchanger. The pressure gauge used in the test shall be calibrated accurately and avoid oil. The accuracy shall be higher than 1.5. The dial diameter shall be greater than 100 mm. The scale on the dial shall meet the requirements of measurement value (the measurement value shall be between 1 / 3 and 2 / 3 of the dial). The inlet flange of high pressure air and outlet flange of oxygen, nitrogen and fraction are sealed with blind plate, and the inlet and outlet of expander can be closed tightly with valve. Remove the safety valve and replace the plug for pressure test.
DEAR Air separation plant.The generation and accumulation of liquid in the main cooling tower depend on the liquid hollow section of the lower tower to flow into the upper tower. When liquid air appears in the lower tower and throttles to the upper tower, part of the liquid vaporizes after throttling, and the temperature further decreases. These low-temperature liquids and gases are used to cool the upper tower.DEAR Air separation plant.If the compression pressure of liquid oxygen is higher than the critical pressure (for example, the oxygen pressure for chemical industry is 6.0MPa or higher), there is no gasification stage with constant temperature in the gasification process of heat exchanger. This will affect the heat transfer performance of high-pressure heat exchanger, which should be fully considered in the design.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.
Nitrogen and a small amount of excess hydrogen are in the top of the tower after several times of partial condensation of the rising steam (the liquefaction temperature of hydrogen is lower than that of nitrogen, so it is impossible to condense), and there is still about 40% argon in it. Part of the rising gas required for distillation comes from the argon evaporated at the bottom of the column. Gas nitrogen from the lower tower is used as heat source for evaporation of liquid argon.DEAR Air separation plant.If the molecular sieve bed is uneven and the thickness of the bed through which the airflow passes is different, the maximum temperature will not be reached at the same time at the outlet. Several peaks may appear after mixing, or the whole peak may be relatively flat, the peak temperature will decrease, and the shape of the cold blowing curve will also become "short and fat". In this case, heating and cold blowing to the specified temperature often takes longer.The throttling temperature drop plays an important role in the refrigeration of small high and medium pressure oxygen generators. In the start-up stage, in order to speed up the cooling rate, the method of increasing the pressure is often used to increase the cooling capacity of throttling effect. After the normal operation of the equipment, the required cooling capacity is reduced, and then the working pressure is reduced.
