Cryogenic air separation technology is a key process for separating components such as oxygen, nitrogen and argon from the air through a low-temperature distillation process. This technology is widely used in metallurgy, chemical industry, electronics, medical care and other fields. However, the performance of cryogenic air separation equipment is affected by a variety of factors. This article explains what factors may be received and provides support for you in combination with relevant specific data cases.
Process parameters
1. Temperature: The ambient temperature has a significant impact on equipment performance. When the ambient temperature increases, the power of the air compressor shaft increases. Under normal ambient conditions, for every 3K increase in temperature, the power of the air compressor shaft increases by about 1%. At the same time, changes in ambient temperature will directly affect the exhaust temperature of the air compressor, which in turn affects the cooling loss. The cooling loss of the air separation equipment is proportional to the difference between the temperature and the ambient temperature of the equipment. In addition, the low temperature environment inside the equipment is the key to achieving gas separation. If the liquid nitrogen temperature (-196℃) or lower is reached, it is necessary to ensure effective gas separation and liquefaction. If the temperature is improperly controlled, for example, the temperature of the cold end of the main heat exchanger is too high, the gas will be insufficiently liquefied and the separation effect will be affected.
2. Pressure: Changes in atmospheric pressure will affect the suction pressure, volume flow rate and pressure ratio of the air compressor. The atmospheric pressure is reduced by 0.01MPa, and the air compressor pressure ratio can increase by 6%-8%. For refrigeration systems, although the atmospheric pressure decreases, the liquidization temperature of air and its components decreases, making it difficult to liquefy, and the isothermal throttling effect decreases. In the distillation system, the atmospheric pressure decreases, the working pressure of the upper and lower towers also decreases, and the boiling point temperature difference increases, which is conducive to distillation. Under the same logistic conditions for entering the tower, the oxygen extraction rate will increase when the number of columns is the same, but the reduction in atmospheric pressure will increase the amount of expanded air, which will have an adverse effect on distillation.
Equipment operation
1. Raw material air compressor: As the energy input source of the system, its performance is crucial. The energy consumption of raw air compressors accounts for a high proportion of the total energy consumption of air separation. If its efficiency is reduced, it will increase the energy consumption of the entire system and the gas separation effect will also be affected. For example, it may lead to unstable air volume and pressure entering the distillation tower, affecting the purity of the product.
2. Expansion machine: It is a key component of the refrigeration system, and its efficiency is directly related to the provision of refrigeration capacity. Parameters such as the adiabatic efficiency of the expander will affect its refrigeration effect. For example, under specific operating conditions, the actual expansion and refrigeration efficiency of the low-temperature expander may be only 42%, and considering the loss of positive refrigeration resistance, the actual refrigeration efficiency of the high-temperature expander can be above 45%. If the expander fails or the efficiency decreases, it will not be possible to provide sufficient cooling for the system, affecting the liquefaction and separation of the air.
3. Molecular sieve purifier: When the molecular sieve purifier has problems such as insufficient filling amount, uneven bed layer, incomplete regeneration of molecular sieve, poor adsorption performance, and structural defects, it will lead to a short circuit in the air, affecting the adsorption of impurities such as moisture and carbon dioxide in the air, increasing the temperature difference and resistance of the main heat exchanger at the hot end, thereby affecting the overall performance of the equipment.
Environmental factors
1. Atmospheric humidity: The air humidity increases and the moisture content in the air increases. Some of the compression functions will be used to compress water vapor, resulting in an increase in the power of the air compressor shaft, increasing energy consumption, and may also affect the effect of subsequent gas drying and other links.
2. Impurities content in the air: The increase in the content of impurities in the air such as mechanical impurities, moisture, carbon dioxide, acetylene, etc. will increase the purification load of the molecular sieve adsorber. If impurities enter the air separation equipment, solid impurities will wear the device, water vapor and carbon dioxide will freeze and precipitate at low temperatures, blocking gas channels and tower screen holes, acetylene, etc. may also cause safety hazards, and will also affect the heat exchange effect and product purity.
The performance of cryogenic air separation equipment is affected by a comprehensive impact on process parameters, equipment operating conditions and environmental factors. In actual operation, these factors need to be strictly monitored and adjusted reasonably to ensure efficient and stable operation of the equipment and achieve good gas separation effect and product quality.
