Case study discussion on carbon dioxide stripping method
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Case analysis: The outlet temperature of the urea stripping tower dropped rapidly – it was normally 173 degrees, but it fell to 165 degrees within two minutes, with a further downward trend following. The stripping efficiency was low, the pressure in the high-pressure system decreased, and the gas production volume in the low-pressure vessel dropped significantly; meanwhile, the pressure in the low-pressure system increased. The outlet temperature of the high-pressure cooling unit dropped to 163 degrees, and the outlet temperature of the synthesis stream dropped to 172 degrees. Subsequently, the level of the synthesis fluid dropped to 0. It was evident that the high-pressure load was low while the low-pressure load was high. It was assumed that this was caused by air leaking into the stripping tower, but closing the valve for the tower’s outlet fluid did not help. Production was reduced. At that time, the pressure and level of the high-pressure vessel were normal. The level of the fluid in the vessel was then reduced from 50 to 10, but this had no effect. Adjustments were made throughout the day, yet it was not possible to raise the temperature for evaporation, nor could large particles be formed, and the temperature in the low-pressure distillation tower also did not increase… What could be the reason?
Check whether there is an issue with the quality of the steam – its calorific value may not be sufficient. Our factory has encountered such problems before!
It is likely that there is a carbon deficiency in the high-pressure system; check the pressure of the carbon dioxide compressor. The temperature in the high-pressure reactor is low; a drop in the temperature of the synthesis tower is definitely caused by a reduced amount of methylammonium being produced, which leads to an energy imbalance. Check whether carbon dioxide can be added. The stripper is merely a symptom of the problem; the synthesis loop has stopped functioning, the conversion rate is very low, and it’s not possible to raise the temperature of the stripper.
We also experienced a situation where the temperature of the liquid leaving the stripping tower dropped rapidly. At that time, we immediately increased the valve opening for discharging inert gases from the stripping tower, and its temperature returned to normal quite quickly. For reference only.
If there is no CO2 or little of it, the temperature of the liquid exiting the stripping tower should increase; there must be a problem with the heating steam in the ammonia system or the stripping tower.
Close the liquid outlet valve of the stripping tower; has the degree of closing this valve been properly considered? This situation is usually a sign of air leakage
Is there too much steam inert gas on the shell side of the stripping tower?