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[raxza]

I want to design a LPG (Liquified Petroleum Gas) plant from natural gas. And I want to ask some questions:

1. What is the minimum capacity of LPG plant? (My gas is about 300 MMSCFD and the propane contain is about 3.7%--it is already sales gas quality)
2. What is the typical operating condition for the demethan/deethan and depropanizer, my gas have pressure about 400 psig and temperature about 95 F (is it necessary to compress the gas? Or should I reduce the pressure?)
3. What is the minimum water content for LPG process?
4. For the Column is it better if I use Packed column instead of a tray column?

-Thx!

[ShaunHill]

To answer a few of your questions:

1. I don't believe you should have a problem with minimum capacity, I've dealt with LPG production from plants that are much smaller than what you've described. Although, if the gas is already "sales quality" you might want to check the economics of recovering the liquids from that amount of gas.

2. With your gas being 400 psig, that would be on the low end for refrigeration. If you are trying to recover maximum liquids from this amount of gas you should consider a cryogenic turbo-expander, which would definately require compression. To be sure, do a phase envelope calculation and look at the dewpoint curve. Again, some of this may depend on economics

Once you have liquids and go to the de-ethanizer pressure could be around 200 psig. Pressure will be lower in de-propanizer and de-butanizer.

3. Not sure what you mean by minimum water for LPG process. I think it is preferable to have NO water (or as little as possible). Specific product specifications for propane or butane will require very low maximum water content.

4. I have seen de-ethanizers with both packed and trayed collumns and they both work. Construction costs and maintenance requirements should play a factor in selection.