Efficiencies of Large Air Liquefaction Devices

There are plenty of companies in the industrial gases business. Air Liquide, Praxair, Air Products, Linde, etc. I don't know if I would call it a Brayton cycle system, it is more of a chemical process. Unless you are talking about something that I am not familiar with.

The only real cost outside of capital is compression cost and it is a big cost. The source of "cold" to keep the plant running cryogenically is typically an expander and the resulting cold stream is passed through a heat exchanger to cool down the incoming dried and CO2 freed air. This is the only real refrigeration cycle going on in the system but it isn't really a cycle since the fluid passed through it is typically used elsewhere or vented.

There are other unit ops going on inside the plant such as dehydration, compression, distillation, etc. Depending on the product you want out of the facility, it will set what your efficiencies can be. For instance, it is a lot easier to get gaseous nitrogen out of air than it is to get liquid argon.

Thanks betomachine. My question, specifically I guess, is if the modern plant was set up to produce liquid air as defined by having it be very similar after evaporation (other than moisture removal) to the air which went in, how much horsepower (KW or whatever term you prefer) would be required to produce a given quantity of liguid air.

Liquefied air has , upon evaporation in a closed vessel, a known amount of energy which can be harvested by having the air thus compressed run an air motor. Assuming 100% effeciency of the air motor (I realize this is not realistic) how would the energy thus generated compare to the energy required to liquefy the air?

A figure such as "Plant A uses X thousand horsepower and can produce Y tons of liquid air per hour would be very useful to me.

I am not concerned with how much heat energy is required to evaporate the liquid air, as this energy is free for the taking from the atmosphere.

Is the process you are describing what I think of as "membrane filtration" as a way to separate gases from the liquid air or the type I am thinking of which utilizes different boiling points much like a an oil refinery (or at least an old oil refinery)

My goal is to prove the feasibility of liquefying air at a fixed power source and making it portable by transporting it in liquid form.

ayyon