A CO.sub.2 energy storage system includes a storage tank that stores a CO.sub.2 slurry, including dry ice and liquid CO.sub.2, at CO.sub.2 triple point temperature and pressure conditions. The storage system also includes a first pump coupled in flow communication with the storage tank. The first pump is configured to receive the CO.sub.2 slurry from the storage tank and to increase a pressure of the CO.sub.2 slurry to a pressure above the CO.sub.2 triple point pressure. The energy storage system further includes a contactor coupled in flow communication with the first pump. The contactor is configured to receive the high pressure CO.sub.2 slurry from the pump and to receive a first flow of gaseous CO.sub.2 at a pressure above the CO.sub.2 triple point pressure. The gaseous CO.sub.2 is contacted and then condensed by the melting dry ice in the slurry to generate liquid CO.sub.2

Embodiments described herein provide methods and systems for separating a mixed ethane and CO.sub.2. A method described includes generating a liquid stream including ethane and CO.sub.2. The liquid stream is flashed to form an ethane vapor stream and solid CO.sub.2. The solid CO.sub.2 is accumulated in an accumulation vessel and the gas is removed from the top of the accumulation vessel.

The present invention relates to methods of increasing the operability, capacity, and efficiency of natural gas liquefaction processes, with a focus on mixed refrigerant cycles. The present invention also relates to natural gas liquefaction systems in which the above-mentioned methods can be carried out. More specifically, a refrigerant used in a pre-cooling heat exchanger of a natural gas liquefaction plant is withdrawn from the pre-cooling heat exchanger, separated into liquid and vapor streams in a liquid-vapor separator after being cooled and compressed. The vapor portion is further compressed, cooled, and fully condensed, then returned to the liquid-vapor separator. Optionally, the fully condensed stream may be circulated through a heat exchanger before being returned to the liquid-vapor separator for the purpose of cooling other streams, including the liquid stream from the liquid-vapor separator.

The present invention is directed to a composition of solid methane gas that is stable at room temperature such that the solid methane gas is capable of storage and shipment without specialized equipment. The composition of solid methane gas is obtained by using a sophisticated apparatus and solid methane gas complexes having many different ingredients and ingenious methods. Methane gas flows through the sophisticated apparatus to be cooled and ultimately mixed with the solid methane bed complex at subzero Celsius conditions to create solid methane that is stable at room temperature. This solid methane is capable of being turned back into methane gas.

The system is provided for generating a mixed methane gas feed stream using at least one source of biogas and an alternate source of methane gas. The system includes a biogas subsystem, a control device for the methane gas from the at least one alternate source of methane gas, and a vertically-extending gas mixing vessel. A method of controlling a methane gas mass flow rate of a mixed methane gas feed stream is also disclosed. The proposed concept is particularly well adapted for situations where an uninterrupted and relatively constant input of methane gas is required to ensure an optimum operation of, for instance, a LMG production plant.

A liquid natural gas (LNG) reforming system of the present invention may include a reformer provided to receive LNG from an LNG tank; a CO2 PSA unit connected to the reformer and configured to extract carbon dioxide from off-gas generated from the reformer; a cooler connected to the CO2 PSA unit and configured to cool and liquefy the carbon dioxide extracted by the CO.sub.2 PSA unit using the LNG supplied from the LNG tank to the reformer; a storage tank connected to the cooler and provided to store liquid carbon dioxide of the cooler therein; and a circulation pump provided to pump the liquid carbon dioxide from the cooler into the storage tank and circulate a part of the liquid carbon oxide into the cooler.

A system and method for cooling and liquefying a gas in a heat exchanger that includes compressing and cooling a mixed refrigerant using first and last compression and cooling cycles so that high pressure liquid and vapor streams are formed. The high pressure liquid and vapor streams are cooled in the heat exchanger and then expanded so that a primary refrigeration stream is provided in the heat exchanger. The mixed refrigerant is cooled and equilibrated between the first and last compression and cooling cycles so that a pre-cool liquid stream is formed and subcooled in the heat exchanger. The stream is then expanded and passed through the heat exchanger as a pre-cool refrigeration stream. A stream of gas is passed through the heat exchanger in countercurrent heat exchange with the primary refrigeration stream and the pre-cool refrigeration stream so that the gas is cooled. A resulting vapor stream from the primary refrigeration stream passage and a two-phase stream from the pre-cool refrigeration stream passage exit the warm end of the exchanger and are combined and undergo a simultaneous heat and mass transfer operation prior to the first compression and cooling cycle so that a reduced temperature vapor stream is provided to the first stage compressor so as to lower power consumption by the system. Additionally, the warm end of the cooling curve is nearly closed further reducing power consumption. Heavy components of the refrigerant are also kept out of the cold end of the process, reducing the possibility of refrigerant freezing, as well as facilitating a refrigerant management scheme.

The present invention is directed to a composition of solid methane gas that is stable at room temperature such that the solid methane gas is capable of storage and shipment without specialized equipment. The composition of solid methane gas is obtained by using a sophisticated apparatus and solid methane gas complexes having many different ingredients and ingenious methods. Methane gas flows through the sophisticated apparatus to be cooled and ultimately mixed with the solid methane bed complex at subzero Celsius conditions to create solid methane that is stable at room temperature. This solid methane is capable of being turned back into methane gas.

A system and method for removing nitrogen from natural gas using two fractionating columns to achieve an ultra-low greenhouse gas content in a nitrogen vent/product stream, while also producing three sales gas streams at different pressures and with low nitrogen content within pipeline specifications. A portion of a low pressure column overhead stream may be compressed and cooled and recycled back to provide reflux to the low pressure column. A system feed stream is cooled upstream of feed a high pressure column, but preferably not separated into streams with varying compositions. A portion of the high pressure column bottoms stream and the low pressure column bottoms stream provides refrigerant to the high pressure column to produce a reflux stream. An amount of methane in a nitrogen vent/nitrogen product stream may be less than 0.01%.

Two streams containing CO.sub.2 with different purities are separated in a common distillation column, without having been compressed or purified of water together.