Provided herein is a method for improving a gas recovery rate during generation of a high-purity gas. The method includes providing three or more adsorption towers filled with an adsorbent that adsorbs an adsorption target gas. Performing a pressure lowering equalization process in a first adsorption tower in which an adsorption process has been finished, and in a source gas supply state in which a source gas is supplied to at least a second adsorption tower in which a pressure increasing equalization process has been finished and the adsorption process is to be subsequently performed; and transferring a non-adsorbed gas from an upper portion of the first adsorption tower to the upper portion of the second adsorption tower, thereby performing an adsorption and pressure lowering equalization process in the first adsorption tower and an adsorption and pressure increasing equalization process in the second adsorption tower.

A pressure swing absorption apparatus, including: at least four beds that each include an absorbent material, wherein the at least four beds are configured to rotate and are grouped such that members of one group only have fluid interconnections with members of another group; and a control system that controls a flow rate of a fluid communication between at least two of the beds by adjusting a phase angle difference between the at least two of the beds.

A method for upgrading biogas comprising methane and nitrogen, where the biogas is provided in at least one pressurized vessel at a pressure of at least 65 atm (6586 kPa). The method includes a pressure swing adsorption (PSA) cycle having a feed phase, where biogas is fed into a first adsorbent bed when the inlet end is open and the outlet end is closed, followed by a first depressurization phase, where a gas enriched in methane is withdrawn through the outlet end with the inlet end being closed. This gas enriched in methane can be pipeline quality and at pipeline pressures. A methane recovery phase is provided, which can improve methane recovery, wherein gas is withdrawn and the pressure drops to one or more lower values, and where this gas can be recycled for use in the feed phase, used in a regeneration phase, and/or fed to a second bed.

A method for upgrading biogas comprising methane and nitrogen, where the biogas is provided in at least one pressurized vessel at a pressure of at least 65 atm (6586 kPa). The method includes a pressure swing adsorption (PSA) cycle having a feed phase, where biogas is fed into a first adsorbent bed when the inlet end is open and the outlet end is closed, followed by a first depressurization phase, where a gas enriched in methane is withdrawn through the outlet end with the inlet end being closed. This gas enriched in methane can be pipeline quality and at pipeline pressures. A methane recovery phase is provided, which can improve methane recovery, wherein gas is withdrawn and the pressure drops to one or more lower values, and where this gas can be recycled for use in the feed phase, used in a regeneration phase, and/or fed to a second bed.