Various illustrative embodiments of a system and process for recovering high-quality biomethane and carbon dioxide product streams from biogas sources and utilizing or sequestering the product streams are provided. The system and process synergistically yield a biomethane product which meets gas pipeline quality specifications and a carbon dioxide product of a quality and form that allows for its transport and sequestration or utilization and reduction in greenhouse gas emissions. The system and process result in improved access to gas pipelines for products, an improvement in the carbon intensity rating of the methane fuel, and improvements in generation of credits related to reductions in emissions of greenhouse gases.

An air separation apparatus comprises: a first rectification column, a first condensing portion, a second rectification column, a third rectification column, a second condensing portion, a fourth rectification column, a third condensing portion, and a recycling pipe for recycling a gas drawn from the third condensing portion to the second rectification column. The air separation apparatus furthermore comprises: a branch pipe branching from the recycling pipe; and a control unit for controlling opening/closing of a valve so that a gas drawn from the third condensing portion is fed to the branch pipe for a predetermined period from the start of driving of the third condensing portion, and for controlling opening/closing of the valve so that the gas drawn from the third condensing portion is fed to the recycling pipe after the predetermined period has elapsed.

A nitrogen generating device comprises: a main heat exchanger; a nitrogen distillation column; at least one nitrogen condenser; a compressor; an expansion turbine; a rotation control unit for controlling rotation with respect to a rotating shaft connecting the compressor and the expansion turbine; a pressure measuring unit for measuring a pressure value of product nitrogen gas; and an optimum rotational speed calculation command unit which inputs the pressure value measured by the pressure measuring unit into a pre-installed rotational speed calculation function to calculate the rotational speed of the rotating shaft, and issues a command to the rotation control unit.

An air separation device according to the present invention is an air separation device in which air is distilled at a low temperature, and includes a high-pressure column which separates high-pressure raw material air into high-pressure nitrogen gas and high-pressure oxygen-enriched liquefied air; a low-pressure column which separates the high-pressure oxygen-enriched liquefied air into low-pressure nitrogen gas, low-pressure liquefied oxygen, and argon-enriched liquefied oxygen; an argon column which separates the argon-enriched liquefied oxygen having a pressure higher than the pressure into argon gas and medium-pressure liquefied oxygen; a first indirect heat-exchanger which heat-exchanges between the argon gas and the low-pressure liquefied oxygen; a second indirect heat-exchanger which heat-exchanges between the high-pressure nitrogen gas and the medium-pressure liquefied oxygen; a first gas-liquid separation chamber which separates the low-pressure oxygen gas which has been vaporized by the first indirect heat-exchanger and the low-pressure liquefied oxygen which has not been vaporized; a second gas-liquid separation chamber which separates the medium-pressure oxygen gas which has been vaporized by the second indirect heat-exchanger and the medium-pressure liquefied oxygen which has not been vaporized; a first passage which communicates the gas phase of the low-pressure column and the gas phase of the second gas-liquid separation chamber; a second passage which communicates the liquid phase of the low-pressure column and the second gas-liquid separation chamber; a first opening/closing mechanism located on the first passage; and a second opening/closing mechanism located on the second passage.

A system and method for removing nitrogen from natural gas using two fractionating columns, that may be stacked, and a plurality of separators and heat exchangers, with horsepower requirements that are 50-80% of requirements for prior art systems. The fractionating columns operate at different pressures. A feed stream is separated with a vapor portion feeding the first column to produce a first column bottoms stream that is split into multiple portions at different pressures and first column overhead stream that is cooled and separated into vapor and liquid portions to control subcooling of the vapor portion prior to feeding the second column. Heat exchange between first column and second column streams provides first column reflux and reboil heat for a second column ascending vapor stream. Three sales gas streams are produced, each at a different pressure.

A method and apparatus for producing high-purity nitrogen and low-purity oxygen using three-column rectification are provided, in which: nitrogen and oxygen undergo rectification in different columns, with high-purity nitrogen and low-purity oxygen being separated out of air simultaneously, thereby overcoming the shortcomings of conventional low-purity oxygen production equipment, and also reducing equipment investment, lowering energy consumption, increasing product added value, and realizing a circular economy effect.

A nitrogen production system that can produce high purity nitrogen containing a desired concentration of oxygen and ultrahigh purity nitrogen containing a desired concentration of argon in a single rectifying column while restraining increase in electric power consumption and a production process thereof are provided. The method can include the steps of rectifying a cooled and compressed air stream in the rectifying column; withdrawing the ultrahigh purity nitrogen stream from a top portion of the nitrogen rectifying column, warming the ultrahigh purity nitrogen stream in a heat exchanger, and then recovering the ultrahigh purity nitrogen stream from the heat exchanger; and withdrawing a high purity nitrogen stream from a rectification section of the nitrogen rectifying column, warming the high purity nitrogen stream in the heat exchanger, and then recovering the high purity nitrogen stream from the heat exchanger.

Various illustrative embodiments of a system and process for recovering high-quality biomethane and carbon dioxide product streams from biogas sources and utilizing or sequestering the product streams are provided. The system and process synergistically yield a biomethane product which meets gas pipeline quality specifications and a carbon dioxide product of a quality and form that allows for its transport and sequestration or utilization and reduction in greenhouse gas emissions. The system and process result in improved access to gas pipelines for products, an improvement in the carbon intensity rating of the methane fuel, and improvements in generation of credits related to reductions in emissions of greenhouse gases.

An air separation device can include: a first compressor and a second compressor for compressing feed air; a first refrigerator and a second refrigerator for cooling the feed air; a pre-purification unit for pre-purifying the feed air; a flow rate measuring unit for measuring the flow rate of the feed air; a main heat exchanger for subjecting the feed air to heat exchange; a purification portion into which the feed air led out from the main heat exchanger is fed, and which separates and purifies product nitrogen and/or product oxygen from the feed air; and a compressor control unit for controlling the feed quantity of the feed air in accordance with an increase or decrease in the production quantity of product nitrogen and/or product oxygen.

A method for separating nitrogen from an inlet gas having less than 25 mole % nitrogen includes supplying the inlet gas having less than 25 mole % nitrogen to a nitrogen separation system configured with cryogenic refrigeration.