13 replies to this topic

[Ahmadhamzahperta]

Guys i have a basic question that have been bothering me for a while now.

I know that even tho liquids are considered as incompressible that doesn’t mean that it cant be pressurized. However im confused on how do we pressurize it in industry.

Lets say i have a CSTR operating at 5 bar and lets assume that both the producs and reactants are all stable liquid with low volatility. If the feed is supplied with centrifugal pump, at startup how will the reactor be pressurized?

Please consider two cases where air exist inside reactor and where the tank is in vacuum pre-start up

[breizh]

A better description is needed.

Breizh

[Pilesar]

If there is vapor and liquid both in the vessel, the pressure comes from the vapor. The vapor pushes against the inside walls of the vessel and against the liquid also. So the pressure of the vapor and liquid are very close to the same. There will be some gradual increase in pressure toward the bottom since the bottom will have the additional weight of the fluid above.

[shvet1]

You need to feed the reactor with a gas, e.g. a source of N2@10bar. The higher gas pressure, the sooner one will achieve the pressure swing.

 

And the liquids are compressible, google "liquids bulk modulus"

[breizh]

Hi,

A good start should be to give us the chemical reaction(s) together with the operating conditions.

Breizh.

[Ahmadhamzahperta]

You need to feed the reactor with a gas, e.g. a source of N2@10bar. The higher gas pressure, the sooner one will achieve the pressure swing.


And the liquids are compressible, google "liquids bulk modulus"

Is there any other way beside supplying N2 into the reactor? I always imagine that pump would be enough to somehow pressurize it

[Ahmadhamzahperta]

If there is vapor and liquid both in the vessel, the pressure comes from the vapor. The vapor pushes against the inside walls of the vessel and against the liquid also. So the pressure of the vapor and liquid are very close to the same. There will be some gradual increase in pressure toward the bottom since the bottom will have the additional weight of the fluid above.

If for example there is no vapor inside the reactor, could we still somehow pressurize it? Can pump alone pressurize it?

[Ahmadhamzahperta]

Hi,
A good start should be to give us the chemical reaction(s) together with the operating conditions.
Breizh.

I can’t think of any chemical reactions as it was only a hypothetical scenario. But if you’re concern is whether the reaction is exothermic or not lets ignore that for now and also lets assume that no vapor are generated. What i want to understand is how liquid vessel is usually pressurize. Do we supply high pressure gas? Or does pump somehow do the work?

[Ahmadhamzahperta]

By the way thanks guys for the responds. Very much appreciate it

[breizh]

Hi,

Shvet1 gave you an answer, by adding Inert gas in the sky of the reactor. 

Pumps are not going to add pressure; it's a transfer mean.

 

Breizh

[shvet1]

If for example there is no vapor inside the reactor, could we still somehow pressurize it?

Could, but those cases are irrelevant to the topic.

 

Can pump alone pressurize it?

Given the reactor has a vapor-liquid interface, no, it can't.

[Ahmadhamzahperta]

If for example there is no vapor inside the reactor, could we still somehow pressurize it?
Could, but those cases are irrelevant to the topic.

Can pump alone pressurize it?
Given the reactor has a vapor-liquid interface, no, it can't.

Ahhh i see, thanks a lot my friend

Edited by Ahmadhamzahperta, 03 April 2025 - 12:12 PM.

[shvet1]

Given the reactor total volume is 5m3 and is filled with air @1bara.

Assume it is filled with water and all outlet connections are closed and tight (no air leaks frm the reactor).

One pumps 4m3 of water to the reactor, reactor vapor space is displaced with water and shrinkes from 5m3 to (5-4)=1m3.

As there are no air leaks, air compessibility does not chang and ignoring the temp change and assuming Henry's constant = 0, the air mass is constant and the equation looks

P*V=m/M*Z*R*T

m1=m2

Z1=Z2

T1=T2

m1/M1*Z1*R*T1=m2/M2*Z2*R*T2

P1*V1=P2*V2

P2=P1*V1/V2= 1bara * 5m3 / 1m3 = 5bara

 

Ta-da, one has pressurized the vessel with water only. A middle school level task.

Are you looking for such explanation?

Edited by shvet1, 03 April 2025 - 11:06 PM.

[Ahmadhamzahperta]

Given the reactor total volume is 5m3 and is filled with air @1bara.
Assume it is filled with water and all outlet connections are closed and tight (no air leaks frm the reactor).
One pumps 4m3 of water to the reactor, reactor vapor space is displaced with water and shrinkes from 5m3 to (5-4)=1m3.
As there are no air leaks, air compessibility does not chang and ignoring the temp change and assuming Henry's constant = 0, the air mass is constant and the equation looks
P*V=m/M*Z*R*T
m1=m2
Z1=Z2
T1=T2
m1/M1*Z1*R*T1=m2/M2*Z2*R*T2
P1*V1=P2*V2
P2=P1*V1/V2= 1bara * 5m3 / 1m3 = 5bara

Ta-da, one has pressurized the vessel with water only. A middle school level task.
Are you looking for such explanation?

Of course not, i was just wondering wheter its the pump or supply of high pressure air that are usually used in industry to pressurize a liquid vessel. So your previous have sufficed thank you