DEAR Liquid air separation unit.The moisture and carbon dioxide in the gas after circulation reheating are in unsaturated state, which is also conducive to preventing moisture and carbon dioxide from separating out in the expander. In a word, it is more advantageous to use circulation in advance, and it must be used before the cold end temperature of the switching heat exchanger reaches - 150 ℃.Reducing the ring flow rate will lead to the expansion of cold end temperature difference and the rise of middle temperature. Therefore, there is also a lower limit to reduce the annular flow, to avoid the freezing of carbon dioxide in the cold section. In addition, when changing the distribution of circulation flow, it is necessary to avoid the change of total circulation flow and adjust the bypass flow rate if necessary. If it is found that the temperature in the middle of each unit is low, the temperature difference at the cold end is small, and the temperature difference at the hot end is large, it indicates that the total circulation is too large and should be reduced appropriately.
Refrigeration is to remove the heat from the device which is lower than the ambient temperature, so as to balance the heat from the outside, keep the device at low temperature, or keep the internal temperature decreasing until the low temperature liquid is accumulated. Heat can only be transferred from high-temperature objects to low-temperature objects. To remove heat from low-temperature objects, we must first use artificial methods to create a lower temperature state, so that it has the ability to absorb and take away heat. Theoretically speaking, the cooling capacity is the capacity to take away heat.Start the purification stage ahead of time. When the liquid level reaches 60% of the normal level, there is liquid on the tray, and the distillation process of gas-liquid heat and mass exchange has been carried out. Therefore, according to the previous operation experience, we can enter the purification stage ahead of time. Some plants shorten the cold start-up time to less than 20h, reduce the power consumption and provide oxygen and nitrogen products in time.
DEAR Liquid air separation unit.When the temperature of positive flow air into the accumulator (the temperature at the hot end, which is related to the cooling effect of the last stage cooler of the air compressor or nitrogen water precooler) and the temperature of return flow air into the accumulator remain unchanged, the temperature difference between the hot end and the cold end of the accumulator is interdependent. If the temperature difference at the hot end is too large, the temperature difference at the cold end must be too small; if the temperature difference at the hot end is too small, the temperature difference at the cold end must be too large. This is determined by the balance of positive and return gas cooling capacity of the accumulator.In case of temperature deviation in the middle part, it should be adjusted as soon as possible. Because when the deviation is small, as long as a little adjustment, it will soon return to normal. If the deviation develops to a large extent and measures are taken, the adjustment will become difficult. In the process of adjustment, a small number of times should be taken, that is, the amount of each adjustment should be less, but the number of times can be more, so that the middle temperature tends to be uniform smoothly. In the process of regulation to prevent irritability, so as not to produce new interference factors.
The outlet temperature of sewage nitrogen will also increase gradually, reaching the peak temperature of 160 ℃, and then decrease until normal temperature. This shows that the molecular sieve has been regenerated and ready for use. Two or three peaks may appear at the outlet temperature of sewage nitrogen in the cold blowing stage, which is often due to the uneven, thin and thick molecular sieve bed of purifier.High pressure blow off: when the purifier pressure rises to near the maximum start-up pressure, open the high-pressure air main inlet valve, and then open the air inlet valves of oxygen, nitrogen and distillate compartments intermittently and blow off repeatedly until the blown gas is clean. When the high-pressure pressure is lower than the normal working pressure, the blowing should be stopped temporarily, and the blowing should be started when it is close to the maximum starting pressure;The common phenomenon is that the purity of main cooling gas oxygen and liquid oxygen is quite different, and the concentration of gas phase is lower than that of liquid oxygen. For example, the concentration of liquid oxygen and gas oxygen in a factory was 99% and 96%, respectively. As a result, seven main cooling pipes were found leaking during maintenance.
