Integrated system and method for providing a controlled atmosphere in a food storage facility

Claim 1

An integrated method for providing a controlled atmosphere in a food storage facility by automatically and simultaneously maintaining predetermined concentrations of component gas species carbon dioxide oxygen and nitrogen and total gas pressure in the facility relative to the atmosphere, by removing carbon dioxide by enriching and venting in a first stage membrane and by generating an appropriate quantity and composition in a second stage membrane, which process comprises: a) feeding a portion of the atmosphere from a food storage facility, said facility having carbon dioxide, oxygen and differential pressure sensors, said atmosphere containing carbon dioxide, oxygen and nitrogen, to a feed side of a semi-permeable gas membrane on a first carbon dioxide removal skid to remove carbon dioxide and to recycle oxygen and nitrogen, said membrane having higher permeability to carbon dioxide than to nitrogen, and being fluidly connected to a second skid, said second skid taking air and making a nitrogen and oxygen stream whose flow and composition when added to a recycle stream from the carbon dioxide removal skid maintains total gas pressure and concentrations of each of carbon dioxide, oxygen and nitrogen in the storage facility, each skid having one or more differential pressure sensors, said carbon dioxide skid and said make-up skid being activated to remove the majority of the carbon dioxide when the level of carbon dioxide in the storage facility is above a predetermined first carbon dioxide set point, and both of said skids being inactivated when the level of carbon dioxide in the storage facility is below a predetermined second carbon dioxide set point, said second carbon dioxide set point being lower than said first carbon dioxide set point, and wherein the carbon dioxide skid and the make-up skid are capable of being automatically and independently operated; b) recycling the carbon dioxide, oxygen and nitrogen not permeating the membrane of the carbon dioxide skid to the storage facility and venting the carbon dioxide gas permeating the membrane to the atmosphere; and c) adding the oxygen and nitrogen through said second skid as needed to maintain the concentrations of each gas species and total gas pressure in the storage facility atmosphere.