Issues with exhaust gas from the final condenser in the two-stage evaporation process for large-scale CO2 stripping of urine
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The exhaust from the second-stage final condenser is connected to the constant-absorption tower, where further absorption takes place to recover a small amount of ammonia (in normal processes, it is connected to an exhaust stack). However, there is a drawback: if production is not operating properly and the constant-absorption tower is under positive pressure, this could affect the vacuum level in the second stage. I would appreciate everyone’s insights on this matter; I am concerned about this issue.
If production is not normal and the atmospheric pressure absorption tower is under positive pressure, it will certainly affect the vacuum level in the second stage; the extent of this impact varies depending on the pressure inside the atmospheric pressure absorption tower. Its high pressure results in a significant impact ； Conversely, the impact is minimal. Therefore, it is recommended that the poster run a pipe from the exhaust of the final condenser to the vent main; when the system is not operating properly and the pressure in the atmospheric pressure absorption tower is high, the ammonia content in the exhaust gas from the final condenser is actually very low, allowing it to be discharged directly in order to ensure the proper operation of the evaporation system.
Thank you for the valuable suggestion from the second floor; we indeed plan to do this. I wonder if there are any devices in the industry that can be connected to constant suction towers, and what is the performance of such devices? This post was last edited by YHL512777 on 2009-4-28 at 13:40.]
This post was last edited by 1025199692 on 2009-5-14 07:46. We have two routes: one leads to the chimney and the other to atmospheric absorption; currently, the flow is going towards the chimney!
1# YHL512777: I’m telling you responsibly that it’s necessary to ensure that the atmospheric pressure tower remains at atmospheric pressure; otherwise, it will definitely affect the vacuum level in the second stage. Why? Imagine that for absorption, an increase of a few kilopascals in pressure has little effect, but an increase of a few kilopascals in pressure before the ejector pump can be problematic.
I have a question for everyone: what is the diameter of the exhaust and drainage pipes for the final condenser? Does the diameter of these pipes affect the level of vacuum? The final condenser discharges gas and liquid at atmospheric pressure, but the exhaust stack is also at atmospheric pressure. Since the exhaust stack is quite tall, it may draw in air from above; what impact does this have on the final condenser?
ttlkk: Both the drain pipe and the exhaust pipe are DN80 in diameter. According to the material balance calculations done by the design institute, 31.22 kilograms of ammonia are emitted per hour; could there really be that much ammonia available for recovery? I doubt it.
31.22 kilograms – does this refer to the total air intake volume of the absorption tower, or to the amount of evaporated exhaust gas? Overall, it should be more or less the same.
I agree with the view from the second floor; we also received information to that effect. The atmospheric pressure absorption tower is supposed to operate under negative pressure according to the design, but in actual production it operates under positive pressure. This is related to things such as the normal heat exchange apparatus and the vapor flow rate of the low-pressure methane cooler.
CTHIJ2007: The data on the material balance sheet of the design institute refers to the amount of ammonia in the gas exiting the final condenser and going to the absorption tower: 31.22 kilograms per hour.