Liquefied air separation FAQ

Cavitation phenomenon of centrifugal liquid oxygen pump

Gas blockage of centrifugal liquid oxygen pump

In order to ensure the stable operation of the distillation column, the in and out material and its state of the distillation column needs to meet the material balance, component balance and energy balance. The main cooling liquid oxygen surface is an important indicator of whether the cooling capacity of the air separation plant is balanced or not. When the cooling loss of the unit is greater than the cooling capacity, the moisture content of the air entering and leaving the column (the liquid content in the saturated air) will be reduced, and the nitrogen to be condensate in main cooling needs to be condensed, the evaporation of liquid oxygen will also increase, and the surface of liquid oxygen will decrease. On the contrary, when the cooling capacity is greater than the cooling loss of the unit, the moisture content of the air entering the lower column will increase, and the amount of nitrogen to be condensed in the main cooling system will decrease, and the liquid oxygen surface wi

The lower and upper columns are the main equipment in the distillation system of cryogenic oxygen air separation plant. The lower column and the upper column separate the components of the mixture gas into different components with the required purity by using the different boiling points. The upper and lower columns are of cylindrical structure. The lower column is equipped with multi-layer sieve plates, and the sieve plate is equipped with overflow bucket. There is an overflow baffle with dense holes. The upper column is equipped with regular packing and liquid distributor. In the distillation process of the lower column, the liquid flows through each sieve plate one by one from top to bottom. Due to the effect of overflow weir, a certain height of liquid level is created on the pedal. When the gas passes through the small hole of sieve plate from bottom to top, it contacts with the liquid and produces bubbles, which increases the gas-liquid contact area and makes the heat and mass e

A user of DEAR air separation reflected that when the air separation plant was put into operation, a large liquid nitrogen storage tank was equipped for emergency backup when the air separation was stopped or export of liquid products. The value of oxygen content in nitrogen product is designed to be less than 3ppm (i.e., < 3 ×10-6) due to the high requirement of users for nitrogen purity. But in fact, the oxygen content of liquid nitrogen in the tanks had been found more than 5ppm. The substandard purity of liquid nitrogen not only affects the export of products, but also directly affects the emergency backup of liquid nitrogen backup system.

Due to the large demand for cryogenic liquid of the market, and in order to ensure the normal operation of the production line when the air separation plant stops abnormally or the air supply is interrupted due to failure, the air separation users with cryogenic liquid production capacity will maximize the production and storage of liquid products while ensuring that the gas production is not affected, and try their best to improve the production of liquid products.

Liquid air separation equipment is an air separation device that directly produces liquid oxygen, nitrogen and other liquid products. Some liquid air separation equipment not only produces liquid products, but also produces a small amount of gas products.

If the passing capacity of the liquid-air regulating valve selected in the design is too small, or it is replaced with the liquid nitrogen regulating valve incorrectly during installation, or the regulating valve, liquid-air adsorber and supercooler are blocked during operation, it can reduce the passing capacity of liquid air. Even if the regulating valve of the liquid level is opened to the maximum, the liquid level of the liquid level will continue to rise. In order to maintain the stability of the liquid level of the lower tower, we have to adopt the method of enlarging the liquid nitrogen regulating valve to reduce the reflux liquid of the lower tower, which will destroy the normal rectification working condition of the lower tower. Because the amount of liquid nitrogen is too large, the purity of liquid nitrogen decreases, and the purity of nitrogen in the upper tower also decreases, the extraction rate of oxygen decreases, and the output of oxygen decreases. At the same time,...

Besides reducing air loss as much as possible, reducing equipment resistance to increase air volume and reducing loss of running cooling, incomplete loss of heat exchange and leakage as much as possible to reduce expansion air volume, here we analyze the methods of adjusting output mainly from the angle of adjusting rectification working condition: 1) the liquid level should be stable. The stability of liquid oxygen level marks the cooling balance of the equipment. If the liquid oxygen level is high and low, it is very difficult to adjust the purity. Reasonably adjust the expansion amount and the opening degree of liquid-air and liquid-oxygen regulating valve to make the liquid-oxygen surface stable. 2) adjust the purity of liquid air and liquid nitrogen. Rectification in the lower tower is the foundation of the upper tower. The change of the amount of liquid nitrogen and liquid nitrogen will affect the purity of liquid nitrogen and the reflux ratio of the distillation section of th...

Currently, there are three types of high-pressure aerators applied in the air separation plant: 1) Water Bath type. Put the coil into water with steam flowing in. Use hot water to gasification liquid oxygen (or liquid nitrogen, liquid argon. Coil pipe adopts one or more tubes with larger diameter (for example, φ25mm×2 ~ 3mm) winding. Generally, it is made into one layer, and the upper and lower layers are equipped with confluence pipes or collectors (no single one ). Both the import and export pipes face up. The tube material should use aluminum tube or stainless steel tube. Keep the water temperature at 80 ~ 90℃. Its advantages are good heat transfer performance, small volume, light weight and safe operation. The disadvantage is that it needs to consume a certain amount of steam whose pressure is about 0.4MPa. 2) empty bath type. The heat exchanger is placed in the atmosphere, and the low temperature liquid is heated by air to make it gasification. The heat transfer pipe adopts sta...

In order to realize the separation of oxygen and nitrogen in the air separation plant, the first thing is to make the air liquefaction, which must try to reduce the air temperature to the liquefaction temperature. The absolute pressure of the lower tower of the air separation tower is about 0.6MPa. Under this pressure, the temperature at which the air begins to liquefaction is about-172 ℃. Therefore, in order to make the air liquefaction, there must be a cold fluid with lower temperature to cool the air. As we know, the air separation plant is cooled by the inflated low temperature air. If the Air wants to expand, it needs to be compressed first, and the compression needs to consume energy. Air expansion can be through throttling expansion or expansion machine expansion. However, the temperature drop of this kind of expansion is limited. For high pressure air of 20MPa ℃ and 30℃, the temperature drop is only 32℃ when throttling to 0.1MPa. In the turbine expander, the maximum temperat...