Vessel V1 (1850mm ID & 5650mm height) collects low pressure steam condensate (140°C & 3.1kg/cm) from various plants and steam tracing lines. The flash steam is vented to atmosphere and the condensate is pumped to utility for re-use. The pump auto starts at 81% level (3080mm) and auto stop at 17% (520mm). In winter months , due to high condensate incoming, The pump keep running whole day and vessel starts overflowing. Hence the drain to sewer at the pump suction kept opened throughout at 30% opening. Now the pump auto stops after 25 minutes and auto start again after half an hour and gives a constant flow rate of 26 Sm/hr. Please help me to calculate the amount of condensate that is wasted in sewer?
Well, this is a real life scenario and I am from operations. I am just curious how much condensate we are wasting. Any pointers on how to solve this will be appreciated
You know the exact inflow rate.
After all it is 30min to fill the vessel from 17% to 81%. Just calculate the volume.
And you know that you are pumping (duty cycle x pump rate) 25/55 * 26 to utilities.
So the difference must be wasted.
It's a little more knarley than that. It's a two martini problem! During that 30 min. fill, the condensate is coming in and the valve is also draining. Also, the condensate is flashing to atmospheric steam. The OP has to use the data during the two states (pump on and pump off) to write two material balance equations and combine it with an energy balance. 3 equations and 3 unknowns (condensate in, flash steam out, and condensate wasted).
EDIT - Initially, I didn't bother to explain it fully either. Fixed it!
Latex, thanks for pointing that out.
I had thought of that, and then didn't bother explaining how to handle it.
To be honest if it were me, I would stand next to the vessel, override the drain valve keeping it closed, and use a stopwatch to an accurate time for the fill rate.
Or just set up both equations and solve that way.
