A device and a method for recovering by-product oxygen from water-electrolysis hydrogen production using a low-temperature method are provided, solving the waste problem of by-product oxygen in the green water-electrolysis hydrogen production system. The device according to the present disclosure comprises an oxygen clarifying system, a pressurizing and heat exchanging system, and a circulating gas compression and expansion refrigeration system. The recovering method according to the present disclosure comprises the following steps: first clarifying and purifying the by-product oxygen from water-electrolysis hydrogen production is to remove hydrogen, carbon monoxide, carbon dioxide, water and other impurities in the oxygen; and then, liquefying, pressurizing and heat exchanging the pure oxygen to obtain the product oxygen and liquid oxygen with required pressure. In the whole process, the cooling capacity is provided by the circulating gas expansion refrigeration system.

A device and a method for producing hydrogen and byproduct oxygen by using green electricity electrolyzed water are provided. The device comprises an oxygen purifying system, a heat exchange system, an air separation compression and expansion system, an air separation rectification system and a liquid oxygen storage system. The method comprises the following steps: first, purifying oxygen prepared by electrolyzing water by green electricity to remove impurities such as hydrogen, carbon monoxide, carbon dioxide and water in the oxygen, then feeding the pure oxygen into the heat exchange system, performing heat exchange liquefaction to obtain liquid oxygen, coupling the liquid oxygen generated by rectification of the air separation rectification system, and obtaining pressurized oxygen through the heat exchange system and the air separation compression and expansion system.

The invention relates to a method for separating gases which comprises: a first step in which a gas fuel stream comprising combustible substances that produce gas products when oxidised, and an oxygen-rich inlet stream are passed through at least two modules of oxygen-separating ceramic membranes, such that the two streams come into contact through the membranes and exchange heat; a second step of selective diffusion of oxygen from the oxygen-rich stream to the fuel stream, such that the outlet streams from the membrane modules are an oxygen-depleted or completely oxygen-free stream and a partially or completely oxidised stream; and a third step of recovery of at least two separate outlet streams of at least two gases selected from oxygen, nitrogen, carbon dioxide and hydrogen.