Large air separation FAQ

Switching purification process air separation equipment refers to self-cleaning of moisture and carbon dioxide in the passageway of switching Plate-fin Heat Exchanger (or cooler) through switching valve. Switching purification process the air separation equipment mostly adopts the method of circulation or extraction to reduce the temperature difference of the cold end of the Plate-fin Heat Exchanger (or the cooler); it adopts the expansion heat exchanger to recover the cooling, further reduce the temperature of the expansion gas; use the liquid supercooler to further reduce the liquid temperature of the throttle entering the upper tower. Therefore, when switching purification process air separation plant restarts and starts after short-term parking, attention should be paid to: 1) before recovery, the start-up circuit should be determined according to the recovery situation of cold end temperature; 2) for the air separation equipment with liquid supercooler, a part of the liquid fro...

On the one hand, the expansion heat exchanger is to reduce the temperature of the air after expansion by utilizing the cooling amount of the sewage nitrogen returned from the upper tower, so as to reduce the superheat of the air after expansion into the upper tower; on the other hand, it plays a role in distributing the cooling capacity of the upper and lower towers. Through it, the cooling amount of dirty nitrogen from the outlet supercooler to the switch-type heat exchanger (or the cooler) is partly returned to the upper tower, which improves the rectification of the upper tower. The location of the expansion heat exchanger can be placed in front of or behind the expansion machine, which is determined by the process design. The large air separation equipment in our country is often set in front of the machine, using part of the dirt nitrogen from the supercooler to cool the air in front of the expansion machine, so that the temperature behind the expansion machine is not too high,...

As the air of the air separation plant of the molecular sieve purification process removes impurities such as moisture and carbon dioxide through the adsorption of the molecular sieve, compared with switching the purification process, the start-up operation is simple and easy to control. It doesn't need to consider the complex influences such as self-cleaning of water and carbon dioxide, precipitation of water and carbon dioxide in the expansion machine, and the attention of starting process mainly focuses on giving full play to the refrigeration capacity of the expansion machine, reasonably allocate cooling capacity and fully cool the equipment. It can be divided into three stages: cooling equipment, accumulation of liquid and adjustment of rectification working condition. Compared with the start-up mode of switching process, it can be called "comprehensive cooling method" or "one-time cooling method ". The following points should be paid attention to when starting the operation: 1...

Nitrogen-water precooler is generally installed in all low-pressure air separation plant. It mainly uses the unsaturation of the water in the nitrogen to make part of the water evaporate. When the water evaporates, it absorbs the latent heat of vaporization to lower the cooling water temperature, and then uses it to cool the processed air to lower the air temperature entering the tower. Therefore, it includes air cooling tower and water cooling tower. The fundamental purpose of setting nitrogen-water precooler is to reduce the temperature of air entering the air separation tower and avoid the sharp fluctuation of the temperature entering the tower. Because the air temperature in the tower directly affects the working condition of switching heat exchanger and distillation column and the economy of the whole air separation plant. When designing, the temperature of air entering the tower is generally set at 30℃. When the inlet temperature of the tower is higher than the design index du...

Air separation plant is one of the important production devices in petrochemical, metallurgy and other industries. Due to its special structure and physical and chemical properties of media, the risk of explosion is relatively high. In recent years, due to manufacturing defects and poor management of air separation plant, there have been many explosion accidents of air separation plant. According to incomplete statistics, there have been more than 100 explosion accidents of small air separation plant all over the country, there are more than 30 accidents of large and medium-sized air separation plant, especially the explosion caused by excessive hydrocarbon substances in the evaporator of air separation main condensing is the main reason for frequent accidents in recent years, which not only affects the smooth operation of production unit, and cause great economic losses to enterprises and the country. The following is a brief discussion on the explosion mechanism and explosion-proo...

The start-up of the air separation plant includes three stages: cooling, hydrops and purification. For a certain equipment, the start-up time is roughly certain. As for the low-pressure air separation equipment, there is no room to adjust the pressure of the air compressor. Generally, it depends on two expansion machines working at the same time to increase the refrigerating capacity in the start-up stage and shorten the start-up time. Even so, according to the maximum refrigeration capacity and the cooling required by cooling and Hydrops of the device, the start-up time of the device needs to be more than 36 hours. Large air separation plants are generally equipped with liquid oxygen storage tanks as emergency standby oxygen. If necessary, can liquid oxygen be filled into the tower to shorten the start-up time of the air separation plant? Theoretically, it is completely possible. For example, if filling 1M3 liquid oxygen into the main cooling, it is equivalent to providing 0.47 × 1...

When the working condition of the air separation plant is stable, the cooling capacity of the unit keeps balance with the cooling capacity consumption, and the temperature, pressure, liquid level and other parameters of each part in the unit no longer change with time. The main cooling is the bond connecting the upper tower and the lower tower. The rising nitrogen from the lower tower is heated and condensed in the main cooling, and the reflux liquid oxygen from the upper tower is absorbed and evaporated in the main cooling. When the amount of recirculation liquid is equal to the evaporation, the liquid level remains unchanged. When the processed air enters the tower, it has certain "moisture content", that is, a small part of it is liquid. Most of the air will be liquefied in the main cooling. As for the low-pressure air separation equipment, the air going into the tower is composed of the air at the cold end of the main heat exchanger and the air passing through the liquid purifie...

The process of extracting neon and helium from the air separation plant is divided into three steps: the first step is to produce crude neon and helium; the second step is to produce pure neon and helium mixture; the third step is to separate neon and helium, and get pure neon, pure helium products. The purpose of crude neon and helium preparation is to remove nitrogen from raw materials and make them concentrated. Because the boiling points of nitrogen, neon and helium differ greatly, which is over 50 K, it can be separated in the condenser or auxiliary tower by using low pressure liquid nitrogen as cold source, make the nitrogen in the feed gas of neon and helium with the pressure of the lower tower condense, and get the content of neon and helium about 1% ~ 3%, the rest is the mixture of crude neon and helium of nitrogen, and then enter the pure neon and helium preparation process. Some processes of crude neon and helium need to go through hydrogen removal and nitrogen removal. T...

Molecular sieve is a kind of crystal of siovenate, which has many micropores with uniform aperture size. The skeleton is usually negatively charged, and there is a cation in the pore channel that balances the negative charge of the skeleton. The earliest molecular sieve found was natural zeolite. People found that the ore exploited near the crater would produce bubbles after heating, so it was called zeolite. In 1930s, United Carbide Company of the United States firstly artificially synthesized 4A and 13X molecular sieves, and applied the molecular sieves as desicides in petrochemical industry. Later United Carbon Company successively discovered Y-type molecular sieve and applied it to the catalytic field, replacing the previous application of silicon-aluminum balls, which increased the gasoline production rate by more than 15%. At that time, the world's annual crude oil consumption was 400 million tons, and generate economic benefits of 8 billion dollars. Later, a series of molecul...

The technical requirements of molecular sieve purifier include: 1. the manufacture, inspection and acceptance of the molecular sieve adsorption cylinder should comply with "pressure vessel safety technology supervision regulations" and CB 150-1998 "steel pressure vessel", it should also comply with the provisions of "The design and manufacturing technical conditions of adsorber for large and medium-sized air separation plant. 2. the molecular sieve adsorption cylinder A, B class welding joints for 100% ray detection, quality should meet the JB/t4730-2005 "pressure equipment nondestructive testing" n level requirements, the penetration test of the weld seam of the socket and the barrel head meets the level I requirement of JB/t4730-2005. 3. After the equipment is manufactured, conduct the air pressure test with 0.69MPa (gauge pressure), and then conduct the air tightness test with 0.6MPa (gauge pressure). The test method is in accordance with gb150-1998 and relevant provisions. 4....

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