8 replies to this topic

[prix]

I have got some basic question regarding CO2. I am pumping CO2 through syringe pump to reactor at a flowrate of 5 ml/min. Both the Pump and Co2 are at a temperature of 28C.

 

Whenever I open the outlet of the pump, the reactor pressure automatically take a spike and try to equilibrate with the pump pressure. The pressure of pump at any point displayed is vapor pressure of CO2, which makes sense.

 

But I expect the reactor to display the actual pressure. Because as I am pumping Co2 at a very low flowrate it should also go up in a slow manner, but it doesnt. It shows the vapor pressure of CO2 after equilibration.

 

I am attaching rough sketch of my system.

 

Can anyone please tell me why is this happening. I am new to this field. Your help is highly appreciated.

 

Thank You

[Art Montemayor]

Prix:

 

You failed to attach your sketch to your post.

What is a "syringe" pump?  I would assume it is a plunger-type, positive displacement pump using ball check valves and being stroked by a very slow motor of a hydraulic actuator.  Am I right?

What is the pressure and temperature inside your reactor when you introduce the CO₂?

Does the CO₂ participate in the reaction inside the reactor?

Is the reaction in the reactor a continuous one or is this a batch reaction?

Are you really pumping LIQUID CO₂ or introducing the CO₂ as a gas?

Does the CO₂ form a blanket inside the reactor or do you have to continuously add makeup CO₂ for a duration?

What is the MAWP (Maximum Allowable Working Pressure) of your reactor?

 

Await your reply (please furnish a detailed sketch of your process).

[prix]

Art Montemanyor Thank for the reply.

 

My apologies I forgot to attach the image.

 

Syringe pump is a pump where the syringe pump co2 out of the pump at a very controlled flowrate. The flowrate that I a working with is 3 ml/min which is very slow. So the pressure thats going to increase is very slow.

 

The reactor is a batch reactor with a size of around 2L. Its a research project so at present its very small.

 

I am continuously adding CO2 untill the reactor reach the desired pressure of 550 PSI.

 

The temperature of reactor and pump are the same at 28C

 

Thank You.

Attached Files

•  Pump.JPG   31.62KB   13 downloads

[Art Montemayor]

Prix:

 

Please respond to the following:

1. Is there a reaction taking place inside the reactor?  During, before, or after?  Or are you just trying to fill the reactor vessel with CO₂ gas at 550 psig?
2. If there is a reaction taking place, does the CO₂ participate in the reaction inside the reactor?
3. Are you really pumping LIQUID CO₂ or introducing the CO₂ as a gas?
4. Does the CO₂ form an inert blanket inside the reactor or do you have to continuously add makeup CO₂ for a duration?
5. What is the MAWP (Maximum Allowable Working Pressure) of your reactor?

[MrShorty]

Is the manual valve simply an on/off valve, or is it capable of regulating the flow rate? Fluids flow from high P to low P, and if there isn't any kind of regulator/needle valve/control valve between the pump and the reactor, the CO2 will flow unchecked into the reactor until the pressure of the reactor is the same as the pump.

 

I would tend to assume that, with a syringe pump, your 3 mL/min means 3 mL of liquid CO2 per minute. Any chance you are trying to deliver 3 mL of gaseous CO2 (at stp or other condition) per minute?

 

I am continuously adding CO2 untill the reactor reach the desired pressure of 550 PSI.

If I had to guess, it looks to me like you need something (regulator or other control valve) between the pumps/CO2 tank and the reactor.

[prix]

Art Montemayor:

 

1) There is no reaction happening inside the reactor

2) I assume its liquid CO2 with the CO2 coming from Liquid CO2 tank with siphon tube

3) It form inert blanket inside the reactor

4) The MAP for reactor is 2000 psi

[MrShorty]

2) I assume its liquid CO2 with the CO2 coming from Liquid CO2 tank with siphon tube

If this were my experiment, I would do something to assure myself that it was either vapor or liquid in the pump. If you are at saturation pressure, you don't know if the material in the pump is liquid or vapor or a combination of vapor and liquid.

 

If you decide you want to deliver liquid CO2, fill the pumps, then compress to a pressure well above saturation pressure (1000 psia maybe?) to be sure that the pumps are filled with liquid. Then you will need some mechanism in the delivery lines to make sure the pump pressure stays high while delivering CO2 to the reactor.

 

If you decide you want to deliver vapor to the reactor, then stop filling the pumps before they reach the saturation pressure (550 psi maybe?). Then you can run the pumps as needed to maintain pressure.

[Art Montemayor]

Knowing no more than what you have submitted:

 

"I am continuously adding CO₂ untill the reactor reach the desired pressure of 550 PSI."

And,

 

"1) There is no reaction happening inside the reactor

2) I assume its liquid CO₂ with the CO₂ coming from Liquid CO₂ tank with siphon tube

3) It form inert blanket inside the reactor

4) The MAP for reactor is 2,000 psi"

 

I am led to believe that you are doing nothing more than pressurizing the small (2 liter) “reactor” vessel.  If that is, in effect, the totality of your scope of work then I strongly urge you to cease trying to meter in liquid CO₂ into the vessel.

 

The simplest, safest, and most accurate way to pressurize any vessel with CO₂ gas is to use a conventional high pressure CO₂ cylinder (25 kg capacity) with a 2-stage regulator installed and regulate the gas flow into your vessel.  You are going to have a Joule-Thomson effect through the regulator which will yield a low temperature gas product – especially at the very outset when the pressure difference across the regulator is the greatest.  If it is important to have the regulated CO₂ gas at an ambient temperature inside the vessel, then all that is done is that the outlet of the regulator is connected to a submerged copper coil in a bath of warm water, prior to being introduced into the vessel.  I have done this operation many times in the past in industrial plants prior to startups and after shutdowns.

 

If, on the contrary, you want to establish CO₂ gas inside the vessel at its saturated pressure of 550 psig (saturated temperature = 39.7 ^oF), then that is entirely another story.  That can be done, but not with a cylinder of hp CO₂.

 

Briefly, I would not try to pressurize by pumping liquid CO₂.  I would pressurize with regulated gas.

[thorium90]

Im curious as to why is it called a "reactor" if all the OP is doing is adding stuff and then taking it out later... Its just another tank but a higher pressure tank?

Edited by thorium90, 28 March 2013 - 03:34 AM.