How Long Does It Take for CO2 to Diffuse in a Nitrogen-Filled Vessel?

In summary, the conversation discusses a problem with filling a bundle of cylinders with 30% CO2 and 70% Nitrogen to a final pressure of 200 bar. However, the analysis for CO2 often falls below the required 30% when checked immediately after filling. The speaker suggests that the diffusion rate of CO2 in Nitrogen may be causing this issue and asks for help in calculating the time it takes for CO2 to diffuse in the vessel. Possible solutions are also mentioned, such as filling a smaller vessel for analysis, increasing pump speed to raise the temperature and thus the diffusion rate, and preheating the CO2 liquid before filling.
  • #1
rad10k
61
0
Ok so I wish to try solve a problem at work I will try explain as best I can .

Problem Definition;
Filling of a bundle of cylinders 17 x 50litre ( 850 000 k/m^3). 30 % Co2 in the cyindrical vessal followed by input of Nitrogen 70% to a final pressure of 200 bar

Due to production requirements it is often required to analysis the gas straight away after filling and more often than not the analysis for CO2 is reaching only 24 - 26 % which is under spec

If the vessals were left for instance 4 hours then upon anaylsis a reading of around 30% CO2 would be found.

.
My thoughts are with the diffusion of the CO2 in nitrogen as CO2 rate of diffusion is 1.25 to n2 is this causing the CO2 to take time to uniformly distribute throughout the vessal.

I would like to know how to calculate the time it will take for the CO2 to diffuse in the vessal given the final pressure and temperature of the vessal? if possible

Solution:

My current thought on solutions;

1. Fill a much smaller vessal as well at the same time and use that for analysis since the cylinder will get hotter causing the gases to diffuse quicker.

2. Increase pump speed to increase the temperature of the 17x50 bundle which in turn will increase the rate of diffusion.

3. heat the CO2 liquid before it enters the vessal increase the rate of its diffusion once inside the vessal

Any help and advice ie am I on the right track please

thanks
 
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  • #2
I wonder how you're filling these bundles. Are they being weighed and a specific amount of CO2 added or are they filled to a specific pressure? Once filled to that limit, I assume you're adding the nitrogen.

The critical pressure and temperature of CO2 is 1071 psia and 87.9 F respectively. It's very possible the partial pressure and temperate of CO2 is below that, in which case there can be liquid CO2 in equilibrium with the gas. So if you can better define the gas mixture, it would help.
 
  • #3
Hi they are filled to pressure and temp. Liquid is cooled then vapourised. Co2 goes in first as you say then n2 upto specific pressure and temp to reach thre required final pressure (190 b)
 

1. What is diffusion?

Diffusion is the process by which molecules move from an area of high concentration to an area of low concentration. This movement occurs due to random motion and does not require any external energy.

2. How does diffusion of CO2 in nitrogen occur?

Diffusion of CO2 in nitrogen occurs due to the concentration gradient between the two gases. CO2 molecules, being smaller and lighter, move more quickly and easily than nitrogen molecules, resulting in a net movement of CO2 from areas of high concentration to areas of low concentration.

3. What factors affect the rate of diffusion of CO2 in nitrogen?

The rate of diffusion of CO2 in nitrogen can be affected by temperature, pressure, and the molecular weight of the gases involved. Higher temperatures and lower pressures can increase the rate of diffusion, while heavier molecules diffuse more slowly.

4. What is the role of diffusion of CO2 in nitrogen in the Earth's atmosphere?

The diffusion of CO2 in nitrogen plays a crucial role in maintaining the balance of gases in the Earth's atmosphere. CO2, being a greenhouse gas, helps to trap heat from the sun and regulate the Earth's temperature. Without diffusion, the distribution of CO2 in the atmosphere would not be as efficient.

5. Can diffusion of CO2 in nitrogen be manipulated or controlled?

Diffusion is a natural process and cannot be controlled or manipulated directly. However, we can indirectly control the rate of diffusion by altering the factors that affect it, such as temperature and pressure. For example, increasing the temperature or decreasing the pressure can speed up the diffusion of CO2 in nitrogen.

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