2 replies to this topic

[Geetanjali]

Hi everyone,

 

Hope you are doing well. I have to separate Hydrogen gas from a mixture of gases consisting of methane, ethane, propane, and butane. I plan to use a Pressure Swing Adsorption (PSA) unit for this purpose. Just wanted to know if my approach is correct? Asking because I want to do this correct and follow how it is done industrially i.,e. on a large scale.

 

Thank you.

Geetanjali

[Bobby Strain]

If you provide the composition, source, and pressure, then we might be able to help you.

 

Bobby

[Geetanjali]

Thanks, sure.

 

So, I am trying to convert waste plastics (polyethylene) in a hydrogenolysis reactor that uses pure H2 and a solid catalyst at 20 bar and 225 degC to make liquid alkanes (C6-C20) and gases (methane, ethane, propane, and butane). The total liquid yield is 53% and the total gases are 47%. We provide an excess of hydrogen to favor conversion and only 35% of the incoming feed is utilized. The rest comes out with the products. This is where I want to separate this hydrogen gas from the rest of the gaseous stream and recycle it back to the hydrogenolysis reactor. Please note that, this hydrogen is 11% of the total gaseous stream with rest formed by 61% methane, 19% of ethane, 6% formed by propane and 4% is butane.

 

As the hydrogenolysis reactor operates at high pressure (between 16 to 40 bar), and for this particular study I am choosing 20 bar, so the reactor outlet gases will also be at 20 bar pressure. (I did read in the literature that PSA unit operates between 10 - 40 bar), so this might be a good pressure.

 

The other alternative I was considering was some suggestions I got in this forum couple of months back regarding separation of olefins from a pyrolysis stream. So, we could let this stream pass through cold boxes and then demethanizer, deethanizer column etc. However, I' m not sure if this could fit here.

 

In an another scenario, we will be converting all this plastics into propane (and some ethane, methane) but no liquids in that case. We will still be having this extra hydrogen from the reactor outlet and we will have to separate and recycle it again. 

 

Would be helpful to get your insights.

 

Thanks

Geetanjali

Edited by Geetanjali, 30 June 2022 - 01:50 PM.