Large air separation FAQ

In the air separation unit of molecular sieve adsorption purification process, after the air is compressed at the last stage of the air compressor, the temperature out of the air compressor reaches 80-90 ℃. Since the adsorption capacity of molecular sieve is inversely proportional to the temperature, in order to improve the working efficiency of molecular sieve adsorber and ensure the purification effect, the compressed air from the air compressor must be cooled to reduce the temperature of the compressed air before entering the purification system.

The oxygen and nitrogen products produced by the air separation unit in the external compression process are low-pressure oxygen and nitrogen from the upper column, which are sent out of the cold box after being reheated by the heat exchanger. The product gas pressure out of the cold box is generally 0.12MPa. After being compressed to the pressure required by the user by the oxygen compressor, it is sent to the user’s pipeline. The internal compression process of oxygen is that liquid oxygen products are directly extracted from the condensing evaporator, compressed to the user's required pressure by the liquid oxygen pump in the cold box, and then sent to the user's pipeline after reheating and gasification by the heat exchanger.

1. Before hoisting, check and confirm whether the crane body, crane legs, lifting rigging and wire rope meet the safety requirements and hoisting conditions. 2. The hanging points of hoisting facilities shall be confirmed to prevent deviation and inclination; steel wire rope or sling shall be used for protection of edges and corners; sling and U-ring shall be used for lifting objects. 3. The commander shall use inter-phone for command, and special personnel shall be assigned for command, and the personnel shall stand at the position where the lifting object can be fully observed; warning isolation shall be set up in the hoisting area, and no one shall stand under the lifting object. 4. For large-scale hoisting, the hoisting safety scheme shall be formulated in combination with the company's special operation system.

1. Adhere to the electrical professionals to work with certificates, non electrical professionals are not allowed to replace or repair any electrical components. 2. Establish the temporary electricity inspection system, inspect and irregularly inspect various lines and facilities on site according to the temporary power management regulations, and archive the inspection and spot check records. 3. The inspectors and operators must wear insulating rubber shoes and gloves according to the regulations; they must use special insulating tools for electricians. 4. The temporary distribution lines must be erected according to the specifications. The overhead lines must be insulated wires, plastic flexible wires, bundles of overhead laying and surface laying along the ground. 5. The erection and use of temporary electricity on the construction site must comply with the provisions of technical code for safety of temporary electricity on construction site (JGJ46-88). 6. Constructio

1. The removal of perlite site shall be supervised by full-time personnel and guided by professionals. The principle of who organizes, who takes responsibility shall be followed. There should be a safe passage and a warning line at the removal of perlite site, and it is strictly forbidden to enter. 2. Dry air shall be used to warm the sand during the removal and knock the cold box to remove the pearlite caking, so as to prevent equipment damage caused by falling caking. 3. The removal of perlite should be carried out in layers and sand holes should be opened at different heights of the cold box. (It can be adjusted according to the site conditions) 4. In the process of removal of perlite, always supervise the caking on the top and enter the cold box for cleaning at any time. 5. In case of severe weather such as rain, snow, strong wind or sand storm danger, the construction party and the owner shall jointly confirm that the sand stripping work shall be postponed. 6. Remov

The reflux liquid in the upper column of the distillation column is throttled by the lower column to the liquid air and liquid nitrogen of the upper column, and the reflux ratio of the upper column is regulated by the liquid nitrogen throttle valve. When the liquid air and liquid nitrogen pass through the throttle valve, the pressure will decrease, and the corresponding saturation temperature will also be reduced. If the supercooling degree of liquid is not enough, some liquid will be vaporized. The higher the gasification rate is, the lower the reflux ratio of the upper column is, and the purity of nitrogen is affected. Therefore, in order to improve the supercooling degree of the liquid nitrogen in the night sky through the throttle valve, a subcooler is generally set up to increase the supercooling degree of the liquid nitrogen in the liquid air.

The pressure relief of molecular sieve in the purification system is generally rapid in the early stage, not complete and running overtime in the later stage. The pressure relief degree is adjusted by the manual stop valve in front of the pressure relief valve. Through practical adjustment, no matter how it is adjusted, the pressure relief in front is fast, or the pressure can not be exhausted. It is suggested that the valve positioner should be added to the automatic pressure relief valve, and the pressure linear adjustment should be programmed, so that the impact on molecular sieve will be much smaller.

Under the conditions of certain welding methods, welding materials, welding specification parameters and welding structure, the difficulty of obtaining high-quality welded joints is called steel weldability. Therefore, the weldability should be evaluated from two aspects of manufacturing and application. The weldability of process mainly refers to the possibility of various cracks in welded joints, which reflects the difficulty of manufacturing. Weldability of using mainly refers to the mechanical properties and special properties of heat resistance, corrosion resistance, low temperature resistance and fatigue resistance of welded joints, which reflects the reliability of use.

When the output pressure of turbine air compressor is constant, when the flow rate decreases to a certain value, surge will occur. Therefore, it is necessary to control the flow rate of the turbine air compressor and prevent its flow value from entering the surge zone. However, when the system resistance increases, the flow rate will surely decrease, which makes it possible for the flow value to enter the surge zone. Therefore, the common solution is to add a bypass valve from the outlet to the inlet or vent. When the turbine air compressor is normal, the valve is closed. The flow rate is reduced to a certain value, and then the flow through the turbine air compressor is increased.

When the same pressure is reduced, the temperature drop of throttling is far greater than that of expansion. This is because the gas does not work externally during throttling, but when the molecular spacing increases, the potential energy of molecules increases, and the kinetic energy decreases correspondingly, reflecting the decrease of temperature. The expansion refrigeration not only increases the potential energy between molecules, but also makes external work to push the impeller to rotate or push the piston to move. All these energies need to reduce the kinetic energy of molecules, so the molecular kinetic energy decreases more and the temperature drop is larger.

1.Before filling alumina and molecular sieve adsorbent into the adsorber, personnel should be arranged to enter the adsorber to check whether the screen screen is damaged. If there is any damage, it must be repaired before filling. 2.The quantity of adsorbent should be counted during loading and unloading, and the packing barrel and bag of adsorbent should be prevented from being damaged, and the adsorbent should be prevented from getting damp due to poor sealing. 3.The molecular sieve in the container should be filled in dry weather without rain. Personnel entering the container shall wear oil-free work clothes and caps and clean soft soled shoes.

The main causes are as follows: 1. The structure is unreasonable, the welding seam is concentrated and the welding joint stress is too large. 2. When welding, the molten pool is too large and overheated, and the alloy is burnt too much. 3. The arc crater is not filled due to too fast arc closing and too early wire drawing. 4. Material problems, for example, when Mg content is less than 3%, and impurities such as Fe and s exceed the standard, it is easy to cause cracks. When the melting temperature of welding wire is too high, liquefaction cracks in heat affected zone are easy to occur. Preventive measures include: 1. During the design, attention should be paid to the reasonable arrangement of welding seams, avoiding the stress concentration as far as possible, and selecting the welding sequence reasonably. 2. Reduce welding current or increase welding speed properly. 3. The arc stopping operation technology should be correct, and the arc pit should be filled by adding the ou