A method and apparatus for purifying air via a pre-purification unit (PPU) of an air separation unit (ASU) system can include passing air through a first adsorber of the PPU to purify the air for operation of the ASU system while it is at or below a first pre-selected operational capacity. In response to the operational capacity of the ASU system needing to be increased to a level above the first pre-selected operational capacity threshold, a second adsorber can be brought on-line in parallel with the first adsorber or in series with the first adsorber to provide improved purification capacity to account for the increased demand for purification capacity resulting from the increased operational capacity of the ASU system. This second adsorber can be different from the first adsorber (e.g. different in size, adsorption capacity for impurities within air, and/or configuration, etc.).

A process for separating a carbon dioxide product stream from a flue gas stream is disclosed. The process comprises passing a stream of carbon dioxide and oxygen to a regenerator to generate a catalyst stream and produce a flue gas stream comprising carbon oxides, and/or nitrogen oxides, catalyst fines, oxygen, and water. Heat is transferred to a water stream from the flue gas stream in a heat recovery unit to form a cooled flue gas stream and a steam stream. Water is removed from the cooled flue gas stream in a dehydration unit to provide a dehydrated flue gas stream. The dehydrated flue gas stream is separated into an oxygen stream and a carbon dioxide product stream.

Systems and methods are provided for recovering helium from a feed comprising helium, carbon dioxide, and at least one of nitrogen and methane. The feed is separated in a first separator to form helium-enriched stream and a CO.sub.2-enriched stream. The helium-enriched stream is separated in a pressure swing adsorption unit to form a helium-rich product stream and a helium-lean stream. At least a portion of the helium-lean stream is recycled to the first separator with the feed. In some embodiments, a membrane separation unit is used to enhance helium recovery.

A method for controlling an oxygen liquefaction device includes measuring a flow rate from an oxygen concentration subsystem to a liquefaction subsystem, comparing the flow rate to a flow rate setpoint, and adjusting a cycle timing of the oxygen concentration subsystem in accordance with the comparing. A device for producing liquid oxygen, includes an oxygen concentrator, a liquefaction system, that receives oxygen enriched gas from the concentrator, and condenses it to produce a liquid product. The device further includes a liquid product storage tank, a sensor, that measures a flow rate from the oxygen concentrator to the liquefaction system and a controller that adjusts an oxygen concentrating cycle time in response to the measured flow rate.

Processes and apparatuses for operating a centrifugal gas compressor. A storage tank containing a liquid buffer material is provided and used to offset density fluctuations in the gas stream passed to the compressor. The storage tank may contain a component of the high-pressure gas stream provided by the compressor, such as carbon dioxide.

Integrated processes for hydrogen production and carbon dioxide recovery are described. The processes use a chilling stream in a cryogenic carbon dioxide recovery unit. The chilling stream chills a working fluid which chills the hydrogen-depleted tail gas stream from a hydrogen pressure swing adsorption (PSA) unit to form a carbon dioxide product stream.

A process for separating a carbon dioxide product stream from a flue gas stream is disclosed. The process comprises passing a stream of carbon dioxide and oxygen to a regenerator to generate a catalyst stream and produce a flue gas stream comprising carbon oxides, and/or nitrogen oxides, catalyst fines, oxygen, and water. Heat is transferred to a water stream from the flue gas stream in a heat recovery unit to form a cooled flue gas stream and a steam stream. Water is removed from the cooled flue gas stream in a dehydration unit to provide a dehydrated flue gas stream. The dehydrated flue gas stream is separated into an oxygen stream and a carbon dioxide product stream.

An apparatus and process for heavy hydrocarbon (e.g., oils that include ten or more carbons, C10+ hydrocarbons, etc.) removal from a natural gas feed (e.g., a feed comprised of methane and impurities such as water and heavy hydrocarbons) can include utilization of one or more coalescing filters to provide adsorption of atomized (e.g., liquid) heavy hydrocarbons that can be present within the feed prior to the feed being fed to one or more adsorbers for adsorption of heavy hydrocarbon vapor via activated carbon beds within those adsorbers. Embodiments can be provided so that the size of downstream activated carbon bed adsorbers can be significantly reduced while also allowing such beds to have a longer life before needing to be replaced.

An adsorber for utilization in purification systems for cryogenic fluid processing can include a first layer of adsorbent material and a second layer of adsorbent material within a bed of adsorbent material within the adsorber. The first layer can include alumina or other water removal adsorbent material while the second layer can include NaMSX or other suitable molecular sieve adsorbent material. The first layer can be sized to be substantially smaller than the second layer to facilitate a pre-selected ratio of water adsorption to molecular sieve adsorption so that water can break through the first layer to the second layer during purification operations while the volume of the adsorber can be provided in a much smaller size with much less adsorbent material utilized in the bed as compared to conventional designs. Embodiments can provide an increased purification operational capacity with reduced need for adsorbent material.