Problems with the evaporation exhaust gas scrubber tower (aqueous solution)
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In our plant, the evaporated vapor phase enters the washing tower, and after being absorbed by the second liquid stage, it goes into the ammonium carbonate solution tank (the ammonium carbonate solution tank is a combined unit with the first liquid stage); this obviously increases the hydrolysis load. There are two modification options: 1. Two-tank liquid circulation washing, with replenishment to the low-pressure absorption system. 2. Add a circulation pump and a circulation tank; when the urea content in the circulation tank reaches 20%, it is fed back into the evaporation system. Dear sea friends, which of these two options is better?
The first option is cost-effective, but it is not economical to operate； The second option requires additional equipment, but it is more energy-efficient in operation; people tend to prefer the second option
Our factory uses the second approach, which includes adding a washer and a circulation tank, but the effect is not very significant. The concentrated secondary surface liquid is fed into the evaporation system.
When I was learning * at another factory, they used the first method, but there were frequent problems with the liquid level reaching its maximum due to low pressure. The temperature of the dimethyl liquid could exceed 60 degrees; I’m not sure if this is related to a high urea content. Additionally, both their hydrolysis off-gas and reflux liquid are cooled to one degree; when the amount of hydrolysis is high, this can affect low-pressure operations, leading to overpressure in that low-pressure area and poor absorption. Would it be more effective if the reflux liquid were added back to the dimethyl liquid in the absorption tower? Because the composition of the return fluid is basically the same as that of dimethyl fluid, its temperature is much higher than that of dimethyl fluid.