What people use as Check Valve?

[Swissgoldrefiner]

Hello,
I am using very basic NOx scrubbing system. I am passing the NOx gas trought NaOH/H2O2 liquid.
However, when the pressure become negative, if i dont care about the reaction, it will suck the liquid into the reaction.
So, i need to add a check valve in PTFE to avoid the gas/liquide to go back.
What people use as check valve?

 

[eaglekeeper]

A vacuum flask with a hose adapter you can make a suck back trap. I'm not sure if using a check valve is a good idea in some applications...like distilling nitric acid from dry reagents, solidified salts can clog up the valve closing off the system.

 

[Martijn]

Hello,
I am using very basic NOx scrubbing system. I am passing the NOx gas trought NaOH/H2O2 liquid.
However, when the pressure become negative, if i dont care about the reaction, it will suck the liquid into the reaction.
So, i need to add a check valve in PTFE to avoid the gas/liquide to go back.
What people use as check valve?

You can also use a simple air check valve to let air in the reaction vessel by using a 2-hole stopper. Overpressure goes to the scrubber, you can always put a catch bottle in between to be sure, and when negative pressure happens, the air is drawn in through the air check valve rather than from the scrubber solution.

This way you can avoid any drawback, if you keep a slight vacuum on the scrubber, slowly drawing in fresh air into the reaction vessel, (measure by counting bubbles through the scrubber) oxidizing any NO to those nice brown gases in the reaction vessel, ready to be absorbed into the scrubber solution if they make it that far and not be condensed on the flask walls.
a cooling of the reaction vessel then does not matter, you have a pressure equalizer.

I used a simple aquarium-air check valve when I was still scrubbing...
Now I digest slowly and loosely cap off the Erlenmeyer or beaker, and little to no NOx is released. Most of it condenses back on the flask walls and is reused as HNO3 in the reaction. But I have the time and no desire to create a BFRC.

 

[Swissgoldrefiner]

A vacuum flask with a hose adapter you can make a suck back trap. I'm not sure if using a check valve is a good idea in some applications...like distilling nitric acid from dry reagents, solidified salts can clog up the valve closing off the system.

How you imagine the vacuum flash with a hose adapter?

 

[Swissgoldrefiner]

You can also use a simple air check valve to let air in the reaction vessel by using a 2-hole stopper. Overpressure goes to the scrubber, you can always put a catch bottle in between to be sure, and when negative pressure happens, the air is drawn in through the air check valve rather than from the scrubber solution.

This way you can avoid any drawback, if you keep a slight vacuum on the scrubber, slowly drawing in fresh air into the reaction vessel, (measure by counting bubbles through the scrubber) oxidizing any NO to those nice brown gases in the reaction vessel, ready to be absorbed into the scrubber solution if they make it that far and not be condensed on the flask walls.
a cooling of the reaction vessel then does not matter, you have a pressure equalizer.

I used a simple aquarium-air check valve when I was still scrubbing...
Now I digest slowly and loosely cap off the Erlenmeyer or beaker, and little to no NOx is released. Most of it condenses back on the flask walls and is reused as HNO3 in the reaction. But I have the time and no desire to create a BFRC.

Do you have any draw? I didnt get well how you want do it. For moment, i am using actually "two" scrubbing system. The first one is empty and there to catch the drawback and the second one is with NaOH/H2O2 to quench the NOx.

 

[Martijn]

With draw you mean flow? Then yes. And with some flow, the check valve will not be exposed to nitric fumes very much.
I only made it a check valve to avoid any NOx flowing out at that point, but a vacuum should keep the reaction vessel at slight under pressure, so actually no check valve is needed. unless you expect a pressure surge in the reaction vessel.

 

[eaglekeeper]

I am using very basic NOx scrubbing system. I am passing the NOx gas trought NaOH/H2O2 liquid.
However, when the pressure become negative, if i dont care about the reaction, it will suck the liquid into the reaction.

Maybe I'm misunderstanding what your trying to accomplish.

Do you have any draw?

This may describe it better than I can draw it.



*edited for spelling*

 

[Martijn]

Do you have any draw? I didnt get well how you want do it. For moment, i am using actually "two" scrubbing system. The first one is empty and there to catch the drawback and the second one is with NaOH/H2O2 to quench the NOx.

You mean a drawing? Ok.

 

[Swissgoldrefiner]

You mean a drawing? Ok.

Ah yes, i like this setup. Now i got you and it's good ideal! Thank you, i will try it.

 

[Swissgoldrefiner]

Maybe I'm misunderstanding what your trying to accomplish.


This may describe it better an I can draw it.

Yes, it's the setup i was using to avoid water going into reactor.

 

[Rob2069]

With draw you mean flow? Then yes. And with some flow, the check valve will not be exposed to nitric fumes very much.
I only made it a check valve to avoid any NOx flowing out at that point, but a vacuum should keep the reaction vessel at slight under pressure, so actually no check valve is needed. unless you expect a pressure surge in the reaction vessel.

or a power outage or disruption

 

[Rob2069]

Do you have any draw? I didnt get well how you want do it. For moment, i am using actually "two" scrubbing system. The first one is empty and there to catch the drawback and the second one is with NaOH/H2O2 to quench the NOx.

Are you familiar with the snorkels that have the ball like a ping pong ball that floats to close the opening so you don't inhale a bunch of water if your snorkel is infiltrated? I have no idea what its name is but you could probably find a diagram of it online and it seems to me something like that would be easy and somewhat foolproof depending on the chemicals and composition of ball but even a ping pong ball with a very thin layer of silicone to protect it should work

 

[Rob2069]

Hello,
I am using very basic NOx scrubbing system. I am passing the NOx gas trought NaOH/H2O2 liquid.
However, when the pressure become negative, if i dont care about the reaction, it will suck the liquid into the reaction.
So, i need to add a check valve in PTFE to avoid the gas/liquide to go back.
What people use as check valve?

It'sIt's called a float valve and they're on something called a dry snorkel

 

[Swissgoldrefiner]

Are you familiar with the snorkels that have the ball like a ping pong ball that floats to close the opening so you don't inhale a bunch of water if your snorkel is infiltrated? I have no idea what its name is but you could probably find a diagram of it online and it seems to me something like that would be easy and somewhat foolproof depending on the chemicals and composition of ball but even a ping pong ball with a very thin layer of silicone to protect it should work

Yes, i saw them....it's some sort of valve that i saw...