Large air separation FAQ - DEAR Air Separation

Safety measures for oxygen centrifugal compressors in large air separation units

Oxygen is a strong oxidising gas, flammable and explosive, so safety measures should be taken in its design and manufacture. When choosing materials, all metals in contact with oxygen must be chemically stable and not easily oxidised. Each component should be degreased. The shaft seal should be sealed with nitrogen pressure difference and also ensure the vacuum of the oil system. All large air separation unit parts and pipings in contact with oxygen should be earthed to prevent static electricit...

Apr 19, 2022

Why does the large air separation units liquid drain valve not close？

The acetylene content in liquid air and liquid oxygen needs to be analysed every day, so the liquid air and liquid oxygen discharge valves have to be operated every day. The problem arises when it is easy to open the valve, but difficult to close it, sometimes even a little can not be closed. This is mainly due to the presence of moisture at the valve stuffing box. When the liquid is discharged, the temperature drops and freezing occurs. In order to prevent this, the valve should be turned cont...

Apr 15, 2022

What is the principle of a self-cleaning air filter in a large air separation

The clean air chamber outlet of the self-cleaning air filter is connected to the air compressor inlet, where process air is drawn in from the atmosphere under negative pressure. The air passes through the filter cartridge and the dust is blocked by the filter media. Numerous small particles of dust form a dust film on the windward surface of the filter media. The dust film improves the filtration effect, but also increases the resistance to airflow. When the resistance increases to a high limit...

Apr 13, 2022

Daily management of circulating water system in large air separation units

1.Operators should adjust the discharge volume in time so that the concentration times are within the index. 2.Every week, a large amount of sewage should be discharged once. Discharge the sewage from the drainage pipe at the bottom of the tower. 3.Regularly analyse the calcium loss rate. Calcium loss rate is used to assess the system scaling situation, in general, calcium loss rate ≤ 20%. 4.Monitor the cooling water analysis once a week. Main analysis items: pH, conductivity, total phosph...

Apr 11, 2022

The role of pre-film of circulating water system in large air spearation units

The pre-film of circulating water system is to improve the film-forming effect of corrosion inhibitor. We often add a higher concentration of corrosion inhibitor at the beginning of the circulating water drive, and after it has formed a film, then reduce the concentration of the agent to maintain the replenishment film. This pre-film treatment is to quickly form a protective film on the metal surface, to improve the corrosion inhibitor inhibit the effect of corrosion.Practice has proved that in ...

Apr 08, 2022

Design basis for circulating water in large air separation units

According to the system water balance, water treatment to ensure that the circulating water system does not corrode and scale. Water treatment operation steps: flushing the system with clean water is to remove mechanical impurities and suspended matter from the system. When the water system is full of water, then turn on the pump to run. When the turbidity of the circulating cooling water system is high, drainage replacement is carried out. When the turbidity is below 20mg, then move on to the ...

Apr 06, 2022

Large air separation unit circulating water system scheme selection

The water quality of the cooling circulating water system is related to the safe operation of the large air separation unit. During the operation of the system, there are three major hazards commonly found in large air separation unit: scale, corrosion and biological slime, such as equipment scaling: corrosion perforation of water pipelines, scale and slime deposited on the packing that makes cooling towers work less efficiently. These hazards increase electricity consumption and also increase ...

Apr 01, 2022

Self-cleaning air filter in large air separation units

(1) In the box combination installation, the combined part of the clean air chamber should pay attention to. (2)the use of welding form, must be the net air chamber around the welding of the sealing welding (i.e. full welding), do not allow intermittent welding. (2)If the combination of gasket in the middle of the chamber is used, the bolts and nuts of the combination should be tightened. and can be sealed by injecting glass glue at the seam of the splice. (3) When installing the large a...

Mar 30, 2022

Filler liquid holding capacity of the large air separation untis

Under certain conditions, the unit volume of the packing layer, the volume of liquid accumulated on the surface of the packing and in the packing void is the liquid holding capacity of the packing. The liquid-holding capacity of the filler is related to the shape and size of the filler, the nature of the filler, the surface characteristics of the filler and so on. Also with the gas-liquid two-phase physical properties, the structure of the tower and the tower operating conditions. In practice, w...

Mar 24, 2022

Cold test of large air separation unit

1. Before the overall large air separation unit cold test. Fractionation should be fully heated and blown out. Air turbine compressor, turbine expander, air pre-cooling system, molecular sieve purification system and electrical, instrumentation and control system must be ready for operation. 2、The operation of the cold test is carried out in accordance with the operating instructions of the large air separation unit, in order to cool the distillation tower, the main condenser and othe...

Mar 23, 2022

Installation of the cold box of large air separation units

1 When installing cold box panels, the two adjacent sides can be pre-assembled on the ground as a whole or in angular form. The base frame and the skeleton section steel between with thin steel plate liner to adjust the box plate upper end surface level. 2 Cold box verticality. Verticality <1.5/1000, the total height deviation shall not be greater than 20mm 3 cold box sealing: the outer side of the skeleton between the use of full welding, intermittent welding on the inner side, to confirm ...

Mar 17, 2022

Throttle expansion versus isentropic expansion of large air separation unit

Isentropic expansion is more effective than throttle expansion in terms of temperature effect and cooling capacity. Moreover, the expander can also recover part of the expansion work, which can improve the economy of refrigeration. However, the throttling valve is simple in structure, easy to adjust and can work in the gas-liquid two-phase zone. Especially when the initial temperature is low, the cooling capacity of throttling is enhanced, isentropic expansion is weakened and the gap between the...

Mar 10, 2022

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