Seeking Examples of Load Lock or Air Lock to Transfer Product out of Pressurized Process Tank

[plukens]

I'm seeking examples of a load lock or air lock to transfer batches of product out of a cryogenic process vessel with a head pressure of 20 psig. The product sits in liquid inside the vessel and is in the form of pellets approximately 1/4" in size. The main goal is to minimize the amount of process gas and liquid lost to the atmosphere as the product is transferred out of the vessel.

References to literature, patents or existing equipment would be helpful. Thanks.