1 reply to this topic

Dear all,

So, I have this process : I'd like to liquefy phosphine (PH3) gas that contains traces of water also. I proposed a design as follows :

Phosphine gas is passed through molecular sieve to prevent clogging by water.

After that, it is compressed to 20 bar. The outlet will be divided into two flows, one is recycled to compressor and the other will be cooled until 0 deg.C.

Based on simulation I did in aspen plus, 43%-w/w of phosphine gas will be liquefied.

What do you experts think about the process? And the next question, could you give me advice which compressor vendor that is reliable for this phosphine gas?

Thanks before.

[Art Montemayor]

numb3rs:

Thank you for following my recommendation. This thread allows us all to concentrate on your specific topic and any needs or consultation that you may require.

I have designed and operated many gas liquefaction processes in my time. However, I have never liquefied Phosphine – and I’m glad I didn’t have to. It is not an “easy” gas – from the point of view of potential hazards in dealing with it. Nevertheless, it should not be a difficult thermodynamic challenge to liquefy it since it has relatively good Critical Properties:

• Critical temperature : 124.9 °F
• Critical pressure : 947.9 psia

The critical properties are even better than those of CO2, which is an easy gas to liquefy.

I know from the critical properties that this gas can be liquefied relatively easy. The main problem is obtaining the thermodynamic property values of Phosphine in order to generate the required calculations identifying the heat and mass balance around the process. Although you don’t tell us, I have to assume that you are in possession of the thermodynamic database or can generate the property values in your simulation program – with what accuracy, I don’t know. If you can obtain a Mollier Diagram for Phosphine, it would be ideal. You definitely do not need a simulation program to design the process if you have the thermodynamic values or a Mollier Diagram. It could all be done on a spreadsheet.

The next step is to develop the Process Flow Diagram (PFD) that depicts the liquefaction of Phosphine, complete with a heat and mass balance. I do not agree with what you describe as your process. I wish you could supply us with a PFD of what you think the process should be and then we could point out for you what we see as flaws or where it can be improved.

Basically, I would employ a 3-stage reciprocating compressor with a fixed-bed adsorption dryer between the 2nd and the 3rd stages of compression. I could produce either High Pressure liquid or Low Pressure liquid – whichever you desire. But you must select the type of process (HP or LP) in order to fix the way you will store and distribute the final liquefied product.

If you are located in Firenze, then you have access to one of the best and most reliable reciprocating compressor manufacturers in the world – Nuovo Pignone – right down the road from where you are. Of course, Nuovo Pignone only deals in industrial-sized compressors and may not be interested in your size of machine. But they certainly can refer you to some reputable European manufacturers of small reciprocating machines – such as Burkhardt in Germany. There are others, I know, but I can’t remember them all right now. Sulzer in Switzerland makes a great compressor – but expensive.

But the first thing is to fully develop a credible process before specifying the compressor. If you furnish us with all the details and a sample of your calculations, I can probably give you some added value to the process.

Await your reply.