Large air separation FAQ

In the main column of the air separation column, the distribution of argon varies with the position of the liquid air inlet. With the increase of liquid air inlet position, the maximum concentration of argon enrichment zone in the stripping section also increases, and the nitrogen content in the distillate can be reduced. However, the argon content in the downstream also increases. In order to ensure the purity of oxygen, more trays are needed under the extraction port of argon fraction. Therefore, in the case of producing argon, the position of liquid air supply E1 should be appropriately increased compared with the case of not producing argon. Some unit is equipped with two liquid air inlet positions to meet the conditions of argon production and non argon production respectively. In the production of argon, in order to improve the extraction rate of argon, the content of argon in oxygen and nitrogen must be reduced. When the content of argon in exhaust nitrogen is more than 0.3%

There are 10 ways to transilluminate the welding seam of air separation unit, which are suitable for different occasions. Single wall is the most commonly used transilluminating method, but when the radiation source or film cannot enter the inside small diameter vessel and pipeline, double wall transilluminating method is adopted. The selection of transillumination method should consider all factors synthetically. For example, according to the principle of selecting the transillumination method which is beneficial and improves the sensitivity, single wall transillumination should be selected as far as possible. According to the principle which is conducive to the detection of corresponding defects, the outside radiation source is preferred for the detection of cracks on the inner wall of the container.

If the temperature after the expander of the air separation unit is too low, it should find out the cause of the low temperature and take measures to increase the temperature after the expander. If the low temperature of expander is caused by liquid air in front of expander, appropriate measures should be taken to reduce the liquid air level of lower column. If it is caused by other reasons, the more effective method is generally throttling in front of the expander. Throttling will not increase the temperature in front of the expander, but throttling will reduce the pressure in front of the expander, so the pressure difference between the front and the back of the expander will be reduced, the expander will do less work and the temperature will be reduced, so the temperature at the after of the expander can be increased.

1.The purpose of purging is to purge the welding slag and dirt left in the pipeline and container. 2.The principle of purging is doing the outside columnfirstly,and the inside column after. The purging should be carried out one pipeline by one. 3.When purging the system, the filter core on the equipment inlet pipe should be removed. 4.When purging the pipe outside the cold box, all the valves connected with the cold box should be disconnected to prevent dirt from entering the valve and column. 5.The purging of each system should be repeated for many times. The purging time shall not be less than 4 hours. 6.To check whether the purging is complete, wet white filter paper or white cloth shouldbe used to placeat the outlet of purging. After 5 minutes, it is qualified if it is clean and free of obvious mechanical impurities.

1.In the process of preparation and implementation of hoisting construction, the safety and quality assurance system must ensure the normal operation,to ensure that the hoisting project meets the requirements of safety and quality. Before hoisting, safety and quality inspection must be carried out, and it must comply with the code forLifting construction of chemical engineering construction (HG20201-2000) and other regulations and specifications. 2.The crane performance shall meet the requirements of hoisting process, and the alarm and hydraulic system must be reliable. 3.Strictly implement the provisions of the technical documents attached to the crane. 4.The hoisting schedule of auxiliary crane should match that of main crane. 5.The hook deflection angle shall not be greater than 3°. 6.It is forbidden to drag the unitdirectly on the ground with crane. 7.Before unithoisting, trial hoisting shall be carried out. The clear hoisting distance and the foundation change at

1.The cold box foundation is divided into frame type and non frame type. The levelness of top surface of frame type frame shall not exceed 1 / 1000. All sections of the frame shall be placed vertically. All bottom plates of non frame type cold box shall be kept at the same level, and the levelness shall not exceed 1 / 1000.   2.When installing the cold box plate, the adjacent two sides can beassembled into a whole piece or angle type on the ground. The length error of each diagonal line a...

When the amount of processing air is reduced, the rising steam and reflux liquid in the upper column will be reduced, but the reflux ratio will not change. Therefore, the reduction of processing air in a small range will not affect the purity of oxygen and nitrogen, and the reduction of processing air volume will help to reduce the pressure of the upper and lower columns. However, according to the material balance, the production of oxygen and nitrogen will naturally decrease when the amount of processing air is reduced. If the amount of processing air is too small, there will be leakage on the tray. If the heat and mass exchange of the leaked liquid is not sufficient, the purity of oxygen and nitrogen will be greatly affected, and even the normal production can not be realized. Therefore, the minimum allowable load of distillation column is generally specified.

Air separation unit is a kind of unit that takes air as raw material, transforms air into liquid by low temperature cryogenic method which compresses and circulates air, and then gradually separates oxygen, nitrogen, argon and other inert gases from liquid air by distillation. At present, the air separation unit produced in China has many forms and types. There are unit for the production of gaseous oxygen and nitrogen, as well as unit for the production of liquid oxygen and nitrogen. However, there are four types of basic processes: high pressure, medium pressure and low pressure, and full low pressure process. The production scale of air separation unit in China has developed from the original oxygen generator which can only produce 20m³/ h (oxygen) to the current large-scale air production capacity of 20000 m³/ h, 30000 m³/ h and 50000 m³/ h (oxygen). The air separation unit can be divided into 5 basic systems in terms of process 1. Impurity purification system: the mechani

The air separation column mainly includes main heat exchanger, liquefier, distillation column, condensing evaporator, etc. The main heat exchanger, condensing evaporator and liquefier are plate type of heat exchangers. It is a new type of all aluminum metal composite partition heat exchanger. The average temperature difference is small, and the heat exchange efficiency is as high as 98-99%. Distillation column is the unit of air separation. The types of column unit are classified according to the internal parts. The sieve plate column with sieve plate, the bubble cap column with bubble cap plate, and the packed column with packing material. The sieve plate is widely used in air separation distillation column because of its simple structure, easy manufacture and high efficiency. Packed column is mainly used for distillation column with diameter less than 0.8m and height less than 7m. Bubble column is seldom used because of its complicated structure and difficult manufacture. Turbine

Special pressure-bearing equipment generally bears internal pressure, that will cause tensile stress inside the shell, which is called working stress. The working stress is directly proportional to the pressure and diameter, and inversely proportional to the vessel wall thickness. The axial stress is half of the circumferential stress. Therefore, for cylindrical vessels, the stress of longitudinal weld is twice that of girth weld. Because the geometric shape of the spherical shell is symmetrical to the spherical center, and the axial stress is equal to the circumferential stress in numerical value. Therefore, the wall thickness of the spherical vessel can be reduced by half as much as that of the cylindrical vessel under the same pressure and diameter.

When the air separation unit is in normal operation, the liquid flows down and can only flow on the tray and flow to the lower tray through the overflow bucket because the supporting force of the rising steam prevents the liquid from flowing down from the small hole of the tray. After shutdown, due to the interruption of rising gas flow, the liquid on the tray can flow from the overflow bucket to the lower tray, and also can flow through the small hole on the tray to the lower tray. This will cause the surface of liquid oxygen and liquid air rise, which may exceed the position of the expansion air outlet pipe, resulting in liquid carrying accident of the expander during restart. Therefore, pay attention to the liquid level position when stopping.

The plant operation cycle between two large heating is related to many factors. From an operational point of view, this mainly depends on when the air passage of the main heat exchanger is blocked. The main reason for the blockage is that the moisture and carbon dioxide content in the air entering the unit exceeds the standard, which accumulates and freezes in the main heat exchanger until it is blocked. The abnormal operation of molecular sieve purification system will shorten the operation cycle of the unit. It is mainly caused by the following reasons: 1. The molecular sieve adsorption bed is short circuited. In the process of operation, due to the unstable gas velocity control or switching, the pressure difference between the two tanks is too large, which will affect the bed layer, make the molecular sieve bed uneven and make the bed layer short circuit. In serious cases, the dust screen of the adsorber will break and the molecular sieve powder will enter the heat exchanger c