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# Kv calculation for depressurization valve

## Kv calculation for depressurization valve

(OP)
Hello,

I'm having some trouble with this problem. Does anybody can help me, please?

Request:
Calculate Kv (range) of a valve that has to be used to have a constant depressurization of a vessel with supercritical Co2 inside. The vent is in atmosphere.

Hypothesis:
Initial Pressure: 120 bar

Temperature: 40 °C constant (heater)

Volume vessel: 10 liters = 0.01 m^3

- What Kv formula should I use for supercritical fluid?

- If I would obtain a constant depressurization (e.g. 4 bar/min), is volumetric flow constant in all the process, right?

depressurization time = 120 bar/(4bar/min) = 30 min = 0.5 h

volumetric flow = volume (constant)/time = 0.01/0.5 = 0.02 m^3/h

- Does mass flow change because pressure change so density change, isn't it?

### RE: Kv calculation for depressurization valve

Before you get round to calculating the Kv for this depressurisation, have you done a depressure simulation to see if there is some part of this valve that will see solid CO2 at some time during this 30minute depressure?

Also account for the built up backpressure on this valve from the vent line in this simulation. To address the risk of blockage due to CO2 solids, heat tracing the valve and valve inlet line may be enough for any dead zones, since main line velocity would be too high for solids to settle down - check if this would be true for the line size you would be selecting.

The Pro/ II simulator from Simsci allows for both constant standardised flow (Sm3/hr) depressures and standard depressures, dont know about Hysis. Dont think the Pro / II simulator has a feature for constant dp/minute depressures.

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