DEAR Air separation unit.With a large amount of oxygen condensing, the oxygen content in gas phase decreases, and the argon condensing relatively increases. Therefore, the argon content in gas phase gradually decreases, and it is only 0.0% after reaching the top of the tower. Because oxygen and argon are difficult to volatilize to nitrogen, they condense into liquid phase more than nitrogen, so the concentration of oxygen and argon in liquid phase is higher than that in gas phase.If the upper and lower correction irons outside the shell of the fractionator are broken or lost during transportation, the pearlite in the fractionator shall be unloaded, a vertical line shall be hung from the top of the upper tower to the condensing evaporator, and the distance between the vertical line and the tower body shall be measured from the top, middle and bottom, and the verticality deviation shall not be greater than 1 / 1000. Every 90 degrees, the measured values should be basically consistent. If not, the bottom of fractionator can be adjusted by adding pad iron to make it meet the requirements.
DEAR Air separation unit.However, at the beginning of the handover, it often goes up instead of down. This phenomenon is not caused by the abnormal phenomenon of the accumulator, nor by the wrong connection of the thermometer. It is often caused by the hysteresis of the platinum resistance thermometer. The length of the lag time is also related to the position of the temperature measuring point and the insertion depth of the thermometer rod. If the probe is inserted deeper, the temperature response is more sensitive. On the contrary, the lag time is longer.Under the design condition, the positive and return flow rates of the hot section of the switched heat exchanger (or cool storage) are basically equal. In the cold section, the amount of backflow air must be greater than that of positive flow air, and a certain proportion should be maintained, so that the temperature difference at the cold end is within the range required by the self removal of water and carbon dioxide, and the temperature difference at the hot end should be more appropriate.
DEAR Air separation unit.The quantity and temperature of expansion air are determined by the balance of cooling capacity of the whole unit, and adjusted by the distribution ratio of the two air volumes after the first heat exchanger. If we insist on increasing the air temperature in front of the expander, we need to increase the air flow through the second heat exchanger, which will inevitably increase the temperature after expansion and the temperature before throttling.With the decrease of the argon fraction extraction, the reflux ratio of the upper tower decreases correspondingly, and the oxygen purity increases, so the nitrogen content in the argon fraction decreases correspondingly. As a result, the temperature difference of the condensing evaporator will expand, the fraction extraction will automatically increase, and the nitrogen content in the argon fraction will increase. This repeated change makes the crude argon column unable to work normally.DEAR Air separation unit.When crude argon is extracted from a full low pressure air separation unit, due to the tight cooling capacity and excessive expansion, the upper column distillation will be adversely affected. Therefore, the extraction volume of argon fraction should not be too large, which is about 8% - 15% of the processing air volume. Therefore, the extraction rate of argon is low, the highest is only 30% - 35%.
The main way to adjust the temperature of the heat exchanger is to adjust the middle temperature and keep the deviation as small as possible. It is the most common and effective method to adjust the middle temperature by changing the ring flow (or middle pumping).In tube test of heat exchanger. Close the high pressure air throttle valve and the high pressure air inlet valve of the expander, install the high pressure gauge and open the valve. Open one blow off valve of the lower tower and one blow off valve of the upper tower, and the gas source is introduced from the blow off-2 valve. Open the blow off-1 valve to check whether the gas is discharged, and then close it. When the pressure of the heat exchanger rises to 1MPa, stop the air intake and check whether there is air leakage at the external connection.DEAR Air separation unit.The more water is allowed to evaporate, the more evaporation latent heat is absorbed, and the lower the temperature of cooling water out of the cooling tower. Therefore, the higher the temperature at the outlet of the sewage nitrogen, the better the cooling effect of the water cooling tower. Of course, the outlet temperature of sewage nitrogen can not be higher than the inlet temperature of water.
