The argon fraction is separated from oxygen and argon in a crude argon tower. The argon fraction enters from the bottom and produces crude argon containing about 95% argon at the top. Due to the close boiling points of oxygen and argon, separation is difficult, and about two-thirds of the argon is washed down. At the same time, the argon fraction enters from the bottom, and the liquid at the bottom contains high argon, which returns to the main tower for distillation. Therefore, only a portion of the argon in the argon fraction is extracted as a crude argon product, and the required argon fraction is about 35-40 times the amount of crude argon.
When extracting crude argon on a fully low-pressure air separation equipment, due to tight cooling capacity and excessive expansion, it will have adverse effects on the distillation of the upper tower. Therefore, the extraction amount of argon fraction should not be too large, which is about 8% to 15% of the processing air volume. Therefore, the extraction rate of argon is relatively low, with a maximum of only 30-35%. For high and medium pressure devices, the cooling capacity is relatively abundant, and increasing the expansion does not affect distillation. Therefore, the extraction amount of argon fraction can reach 25% to 28% of the processing air volume, and the highest extraction rate of argon can reach 60%. The maximum extraction rate of argon from molecular sieve purification and pressurized full low-pressure air separation equipment can reach 87%.
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