Large air separation FAQ

With the development trend of large-scale air separation plant, the column support of its matching cold box equipment tends to be large-scale. The traditional support structure has complex structure and poor bearing capacity. Through the use of finite element analysis software, DEAR air separation carries out finite element analysis and optimization on the commonly used experienced column of air separation plant, so as to improve the bearing capacity of support and reduce the processing difficulty, to reach the purpose of saving material cost.

Pressure swing adsorption and temperature swing adsorption of molecular sieve

1. The requirements of molecular sieve adsorber, electric heater and other equipment in place are the same as those of air cooling column of pre cooling system. 2. Process piping shall be constructed in strict accordance with relevant specifications and design and construction drawings. 3. The air tightness test shall be conducted before the valve is installed, and the test pressure and inspection standard shall be carried out according to the technical requirements of corresponding valves. 4. Pay attention to the direction of switch valve installation. V1201, V1202, V1207 and V1208 are front mounted valves, while V1203, V1204, V1205 and V1206 are reverse mounted valves. When the switch valve is installed, its shaft should be in a horizontal position, and the flange bolts should be evenly cross tightened. 5. The pipeline of pressure equalizing valve V1209 should have compensating bend.

The principle of expander with motor brake in air separation plant is to control the speed of expander by braking torque generated by motor generator braking state. Once the brake motor fails, the expander speed will lose control and overspeed will occur. At this time, it is necessary to automatically open the protection and control system. The principle is that the speed measuring motor will send out the overspeed signal to cut off the three-way solenoid valve. The three-way solenoid valve directly controls the air open pneumatic butterfly valve at the inlet of the expander, so that the butterfly valve is quickly closed and the air inlet is cut off. At the same time, the rotation of the valve rod touches the stop and limit switch, so that the power supply of the expander motor is cut off and the safe shutdown is realized.

In the operation of air separation plant, in order to ensure the accuracy of DCS control system monitoring and the safety and stability of operation, it is necessary to do well of DCS system grounding.

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.