Large air separation FAQ

The upsizing of air separation plant has became an inevitable trend of the development of national economy. A few years ago, the domestic air separation industry had achieved the air separation performance of 100000 m³/h level, and there were more than 150000 m³/h air separation plant abroad. With the gradual increase of the scale of air separation plant, its energy consumption is also increasing. In order to save energy, reduce consumption and reduce pollution, it is of great significance to study the driving mode of compressor for large-scale air separation plants. 1. Turbine drive: Steam turbine is widely used in electric power, chemical industry, metallurgy and other industries and fields because of its axisymmetric high-speed rotation characteristics, smooth operation, small wear and long continuous operation time. However, the one-time investment of steam turbine drive is relatively large, and the requirements for heat supply pipeline and production system are high. The pla

In order to check the installation quality, deformation under low temperature and smooth condition of pipelines, valves and field installed air separation plant in air separation column, needs to be further tighten the flange bolts at low temperature. It is necessary to start freezing before filling the cold insulation box with cold insulation material, which is called naked cooling. During naked cooling, the rectification column, main condensing evaporator and other main equipment shall be cooled to the minimum temperature for 2 hours respectively, and then the whole air separation unit shall be cooled for 3 to 4 hours. The deformation and leakage of each part shall be checked in detail, and the flange bolts shall be tightened again. After defrosting, the flange shall be heated to normal temperature before gas seal test can be conducted.

When the air is out of the air compressor, due to the compression, the moisture in the air is in the saturated state. After the water cooling column decreasing the temperature, the water content in the saturated state decreases, and the excess water condenses into the water. The water volume in the air cooling column increases and the water temperature rises. But not only is the temperature of the air reduced, but also the moisture content of the air. In the water cooling column, the crude nitrogen is used to cool the water. After passing through the main heat exchanger from the fractionator, the temperature of the crude nitrogen is close to the normal temperature, but it is very dry. The dry crude nitrogen contacts with the water, and a large amount of water is evaporated into the crude nitrogen by using the unsaturation of the crude nitrogen, which absorbs the heat of the water and reduces the water temperature.

Thermodynamic energy is the sum of kinetic energy of irregular motion of molecules in matter and potential energy generated by mutual attraction between molecules. In the process of oxygen production, there are many flow processes, such as compression, expansion, heating and cooling. These processes not only involve the change of thermodynamic energy, but also involve the transformation between the flow energy and the thermodynamic energy. Enthalpy is the sum of material thermodynamic energy and material flow, so it is more convenient to study these flow processes with enthalpy.

In general, the liquefaction temperature of nitrogen is higher than that of oxygen, but why can the condensation evaporator between the upper and lower columns of the air separation column use gas nitrogen condensation to release heat to vaporize liquid oxygen? This is because we usually think that the liquefaction temperature of nitrogen is lower than that of oxygen under the same pressure. However, the pressure at the bottom of the upper column of the air separation unit is generally 0.149 MPa, and the pressure at the top of the lower column is about 0.58 MPa. The reason for the different pressure causes the inversion of the saturation temperature of oxygen and nitrogen. It is precisely by using this principle that the condensing evaporator can continuously provide liquid nitrogen for the lower column At the same time, it provides gas oxygen for the upper column as the rising gas to participate in fractionation.

In the air separation plant, the purity of oxygen is mainly determined by the working conditions of the distillation column at the upper and lower parts. In addition, the oxygen content in argon fraction, reflux ratio, number of theoretical trays and separation efficiency will have a direct impact on the purity of oxygen. The following is a brief introduction to the relationship between these factors and oxygen purity.

During the normal operation of the air separation plant, the temperature of each part of the cold box should be kept in balance. However, due to the temperature difference at the hot end of the heat exchanger and the possibility of no heat transfer between the cold box and the environment, and some large-scale air separation plants may produce a small amount of liquid products, which will cause heat loss. Therefore, to supplement the lost cooling capacity through expander and throttling, we paid electric energy to get the cooling capacity of expander. Why can throttling produce cooling capacity? This is because the pressure decreases after throttling, and the throttled liquid air and liquid nitrogen are saturated liquid. The pressure drop naturally causes the saturation temperature to decrease. In order to maintain its saturation state, part of the liquid is gasified to absorb heat.

Steam turbine is a kind of turbine mechanical equipment that converts heat energy of steam into mechanical energy. In air separation plant, steam turbine is used as power source of air compressor instead of motor, which saves a lot of power consumption for air separation users, so it is widely used in air separation field.

With the rapid development of national economy, cryogenic air separation plant has been widely used in petrochemical, glass, tire, polysilicon, carbon fiber and other industrial fields. The nitrogen production process consists of air compression and purification, air separation and liquid nitrogen vaporization.

1. Enter the work area, wear all kinds of labor protection equipment; check the surrounding working environment; confirm the tools and machines; prohibit the use of defective tools. 2.When using the sledge hammer, it is forbidden to wear gloves; it is strictly forbidden to stand in the range of before, after, up, down, left and right of the sledge hammer, and no one is allowed to stand on the opposite side to prevent injury. 3.Before welding operation, it is necessary to carefully check whether the electric welding tools used are insulated, whether the primary and secondary wires of the welding machine are damaged, and whether the grounding wire is in good condition; insulating gloves must be worn to prevent the occurrence of electric shock accidents when the welding machine stops power transmission and switches on. 4.The safety protection facilities of oxygen cylinder and acetylene cylinder should be complete and reliable. When working, the distance between oxygen cylinder an

When the new air separation plant is purged the first time, the air compressor pressure shall be increased to the quota pressure as far as possible. The purge valve should be fully opened as far as possible. Since the drain valve is connected together, the pressure is different. Therefore, when purging the drain valve, should purge one by one, and then close one after another for half an hour. After purging, do not fully close the purge and drain valves. Shut down the air compressor and wait until there is no pressure. Take all the valve bodies of the purge and discharge valves to check and clean, and then restore them. Only in this way can the purging be qualified.

Users reported that the on-line analyzer of a 30000 grade air separation plant showed that the outlet CO₂of the molecular sieve suddenly increased from the normal value of 0.43×10-6 to 120×10-6, and the temperature difference in the expansion air channel entering the two high-pressure plate fin heat exchangers began to expand. At the same time, the temperature in front of expander also decreased from - 105°C to - 132°C with liquid entrainment. After receiving the user's notice, DEAR air separation sent technical personnel to the site for observation and detection. It was found that the location of the self-cleaning filter of the equipment was close to the chemical boundary area. When the wind direction was in the downwind direction of the chemical industry boundary area, the phenomenon that the concentration of CO₂ in the air at the inlet of the self-cleaning filter of the air compressor exceeded the standard. In view of this phenomenon, the following opinions are given: 1. Sh