Systems, devices, and methods for recovering mixed refrigerant and/or nitrogen within liquefaction systems are provided. The systems, devices, and methods facilitate recovering mixed refrigerant (MR) and/or nitrogen vapor that can leak from a compressor, separating the MR from the nitrogen, and reusing the MR and/or the nitrogen within the liquefaction system. Recovering and reusing MR and/or nitrogen can minimize loss of MR and nitrogen which can lower the total operating cost of a liquefaction system. Additionally, recovering the MR, rather than burning it, can reduce environmental emissions by reducing the amount of MR that is burned.

A process for recovering valuables from vent gas in polyolefin production is disclosed. The process includes a compression cooling separation step, a heavy hydrocarbon separation step, a light hydrocarbon separation step, a N.sub.2 purification step, and a turbo expansion step in sequence. The N.sub.2 purification step comprises a membrane separation procedure. The light hydrocarbon separation step comprises at least one gas-liquid separation procedure. A first gas, which is obtained by the gas-liquid separation procedure and is heated through heat exchange with multiple streams in the light hydrocarbon separation step, enters the heavy hydrocarbon separation step and is further heated; the heated first gas then enters the N.sub.2 purification step; a first generated gas, which is obtained by the membrane separation procedure of the N.sub.2 purification step, enters the heavy hydrocarbon separation step and the light hydrocarbon separation step in sequence, and is cooled through heat exchange with multiple streams in the heavy hydrocarbon separation step and the light hydrocarbon separation step; and then the cooled first generated gas enters the turbo expansion step. The energy consumption of a compressor can be greatly reduced. An external cooling medium with a temperature lower than an ambient temperature is not needed. The purity and recovery of N.sub.2 and hydrocarbons can be improved, which can facilitate reduction of energy consumption of a whole system, an investment, and a material consumption.

Methods and systems for recovering alkene (e.g., C.sub.2-C.sub.4 alkene) gas as well as producing pressurized alkene (e.g., C.sub.2-C.sub.4 alkene) gas from process gas streams including higher concentrations of alkenes are provided herein.

Methods and systems for recovering alkenes (e.g. ethylene, propylene) from process gas streams, including multi-step condensing of the process gas stream, are provided herein.

Methods and systems for recovering nitrogen and alkenes (e.g. ethylene, propylene) from process gas streams, including multi-step condensing of the process gas stream, are provided herein.

Methods and systems for recovering alkenes (e.g. ethylene, propylene) and nitrogen from process gas streams, including multi-step condensing of the process gas stream, are provided herein.

Methods and systems for recovering alkene (e.g., C.sub.2-C.sub.4 alkene) gas as well as producing pressurized alkene (e.g., C.sub.2-C.sub.4 alkene) gas from process gas streams including lower concentrations of alkenes are provided herein.

The invention relates to a method for producing helium from a source gas stream (1) including at least helium, methane, nitrogen and hydrogen, comprising at least the following consecutive steps: step a): injecting said source gas stream (1) into at least one compressor (3); step b): eliminating the hydrogen and the methane by reacting the stream (4) obtained from step a) with oxygen; step c): eliminating at least the impurities from step b) by temperature swing adsorption (TSA); step d): partially condensing the stream (8) obtained from step c) in order to produce a stream (10) of liquid nitrogen and a gas stream (11) comprising mostly helium; step e): purifying the gas stream (11) obtained from step d) in order to increase the helium content by pressure swing adsorption (PSA) by eliminating the nitrogen and the impurities contained in the gas stream (11) obtained from step d).

A cryogenic method for capturing carbon dioxide in the gaseous emissions produced from the fossil-energy combustion of solid, liquid, or gaseous fossil fuels in a power generation installation employing an OxyFuel mode of combustion. The method includes: producing essentially pure carbon dioxide under elevated pressure and at near ambient temperatures in a Carbon-Dioxide Capture Component from the carbon-dioxide content of at least a part of the gaseous emissions produced from fossil-energy fueled combustion in the Oxyfuel mode of combustion; separating atmospheric air in an Air Separation Component into a stream of liquid nitrogen and a stream of high-purity oxygen; supplying low temperature, compressed purified air to a cryogenic air separation unit (cold box) within the Air Separation Component; collecting low temperature thermal energy from coolers employed within the Carbon-Dioxide Capture Component and the Air Separation Component; and converting the collected thermal energy to electricity within a Thermal-Energy Conversion Component.

A gas recovery system separates a mixed gas including a process gas and an inert gas. The gas recovery system includes a cooling section for cooling and liquefying the process gas contained in the mixed gas by cooling the mixed gas at a temperature higher than a condensation temperature of the inert gas and lower than a condensation temperature of the process gas, a separating section for separating the cooled mixed gas into the process gas in a liquid state and the inert gas in a gas state, and a process gas recovery line that is connected to the separating section which circulates and gasifies the liquid-state process gas and then supplies the process gas into the a compressor. The mixed gas is formed by mixing the process gas, which is compressed by the compressor, and the inert gas, which is supplied to a seal portion of the compressor.