Questions about distillation operations
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Our factory has a new set of deamination and distillation equipment. Its main purpose is to remove ammonia contained in the production exhaust gas. The process is as follows: The tail gas passes through the deamination tower (i.e., absorption tower), and there is a spray at the top of the tower. The dilute ammonia water after deamination is pumped from the bottom of the tower to the rectification tower for concentration. The ammonia content of the finished product is required to be no less than 20%. There is no requirement for the distillate at the bottom of the rectification tower, but this part of the distillate must be cooled by a cooler and then returned to the top of the deamination tower for spray absorption. The whole process is like this, but now there are some problems, mainly concentrated on the distillation tower: First, the pressure gauge on the total condenser shell at the top of the tower now shows unstable pressure. Second, the return flow is very unstable, and sometimes there is no flow at all. Third, the steam flow rate of the reboiler is now 1200Kg/h, and the temperature difference from the bottom of the tower to the top of the tower is very small. The bottom of the tower is 108 degrees, and the temperature at the top of the tower can exceed 100 degrees during reflux hours, and can drop to about 89 degrees when the reflux flow is slightly larger. And if you touch the shell of the total condenser at the top of the tower, the temperature is not low, about 50 degrees. Fourth, when the content of light components in the overhead distillate is high, the content of the bottom distillate is sometimes high and sometimes low. Basically, there are so many questions. I hope someone who understands can help me.
First, is the pressure gauge normal?； If there is no fault, the flow of the shell medium is stable. Second, the heat load control is unstable or the ammonia flow is unstable. Third, the amount of steam added is too large or the rectification reflux is small, the gas phase is relatively excessive, the heat load is excessive, and the ammonia gas phase fails to be stripped or flashed normally. When the reflux is large, the ammonia volume in the tower kettle increases and the heat load decreases, causing the temperature at the bottom of the tower to drop. Fourth, the light component content of the top distillate is high. If it is within the normal index range, the bottom distillate content should be maintained in a normal range. ； If the content of light components in the overhead distillate is high and deviates from the normal range, and the distillation conditions are unstable, fluctuating or deteriorating, the content of the bottom distillate will definitely not be stable.