The present disclosure relates to a method and system for reducing propane content in a refrigerant containing propane. The refrigerant is then used for maintaining the required temperature range in a reactor. Compared to a conventional system and method, the system and method of the present disclosure are capable of reducing the propane content in a refrigerant and maintaining the required temperature range in the reactor effectively.

A ship includes: a boil-off gas heat exchanger which heat-exchanges a compressed boil-off gas (a first fluid) by means of a boil-off gas discharged from the storage tank as a refrigerant; a compressor installed on the downstream of the boil-off gas heat exchanger and compressing a part of the boil-off gas discharged from the storage tank; first and second extra compressors provided in parallel with the compressor on the downstream of the boil-off gas heat exchanger and compressing the other part of the boil-off gas discharged from the storage tank; a refrigerant heat exchanger which additionally cools the first fluid cooled by means of the boil-off gas heat exchanger; a refrigerant decompressing device which expands a second fluid, which has been sent to the refrigerant heat exchanger and cooled by means of the refrigerant heat exchanger, and then sending the expanded second fluid back to the refrigerant heat exchanger.

A method for controlling the flow of natural gas and refrigerant in the main heat exchanger of a natural gas liquefaction facility. The method provides for the automated control of a flow rate of a natural gas feed stream through a heat exchanger based on one or more process variables and set points. The flow rate of refrigerant streams through the heat exchanger is controlled by different process variables and set points, and is controlled independently of the flow rate of the natural gas feed stream.

A method for liquefying a feed gas stream. A refrigerant stream is cooled and expanded to produce an expanded, cooled refrigerant stream. Part or all of the expanded, cooled refrigerant stream is mixed with a make-up refrigerant stream in a separator, thereby condensing heavy hydrocarbon components from the make-up refrigerant stream and forming a gaseous expanded, cooled refrigerant stream. The gaseous expanded, cooled refrigerant stream passes through a heat exchanger zone to form a warm refrigerant stream. The feed gas stream is passed through the heat exchanger zone to cool at least part of the feed gas stream by indirect heat exchange with the expanded, cooled refrigerant stream, thereby forming a liquefied gas stream. The warm refrigerant stream is compressed to produce the compressed refrigerant stream.

A heat exchanger unit that comprises a heat exchanger vessel comprising a plurality of process stream conduits to receive the gaseous process stream and discharge a cooled process stream, and a plurality of refrigerant conduits to receive a pre-cooled mixed refrigerant stream and discharge a cooled mixed refrigerant stream; an expansion device to receive the cooled mixed refrigerant stream and discharge a further cooled mixed refrigerant stream, which is connected to a third and/or fourth refrigerant inlets to provide cooling to the process stream conduits and the refrigerant conduits; a refrigerant bleed vessel to receive a first refrigerant split-off stream from the cooled mixed refrigerant stream and a second refrigerant split-off stream from the pre-cooled mixed refrigerant stream; the refrigerant bleed vessel comprising a bleed outlet to discharge a bleed stream and a recycle outlet fluidly connected to the third and/or fourth refrigerant inlets.

The present invention relates to the control systems of the compression refrigerating machines, namely, to the methods of control of the natural gas liquefaction process to produce liquefied natural gas (LNG), and can be used for liquefaction and cooling of natural gas on the most major technological lines and LNG production plants, working on the mixed refrigerant (MR). The method of control of the natural gas liquefaction process on the mixed refrigerant-operating LNG production plant comprises a periodic measuring of the current parameters of the said process, and controlling composition of the mixed refrigerant entering the main cryogenic heat exchanger, in order to achieve the optimal process parameters. Carnot factor is used as an optimality criterion for parameters of the process. The mixed refrigerant composition is controlled by direct calculation on the basis of the current process parameters and equation of state (for example, Peng-Robinson equation of state) of the substance amount of the mixed refrigerant components required to obtain in the main cryogenic heat exchanger the temperature profile corresponding to the optimal process parameters, and to introduce the said components into the main cryogenic heat exchanger. The invention improves efficiency of the natural gas liquefaction process and, as a result, minimizes specific compressor power required for LNG production.

The present invention relates to the control systems of the compression refrigerating machines, namely, to the methods of control of the natural gas liquefaction process to produce liquefied natural gas (LNG), and can be used for liquefaction and cooling of natural gas on the most major technological lines and LNG production plants, working on the mixed refrigerant (MR). The method of control of the natural gas liquefaction process, on the mixed refrigerant-operating LNG production plant comprises a periodic measuring of the current parameters of the said process, and controlling composition of the mixed refrigerant entering the main cryogenic heat exchanger, in order to achieve the optimal process parameters. Carnot factor is used as an optimality criterion for parameters of the process. The mixed refrigerant composition is controlled by direct calculation on the basis of the current process parameters and equation of state (for example, Peng-Robinson equation of state) of the substance amount of the mixed refrigerant components required to obtain in the main cryogenic heat exchanger the temperature profile corresponding to the optimal process parameters, and to introduce the said components into the main cryogenic heat exchanger. The invention improves efficiency of the natural gas liquefaction process and, as a result, minimizes specific compressor power required for LNG production.

Systems and methods are provided for adjusting a composition, pressure, and/or flow rate of a mixed refrigerant (MR) fluid in a liquefaction system to provide refrigeration to natural gas (NG) feedstock to produce liquefied natural gas (LNG). The MR fluid that is in circulation within a liquefaction system can include heavy components and light components. During LNG production, heavy components and/or light components of the MR fluid can be selectively removed from, and reintroduce into the MR fluid, thereby altering the composition of the remaining MR fluid in circulation. Adjusting the composition of the MR fluid in circulation within a liquefaction system can allow the system to be optimized to maximize efficiency, LNG production, and or profitability while the system is in operation.

A refrigerant charging system includes: a reliquefaction system reliquefying boil-off gas generated in a liquefied gas storage tank by compressing the boil-off gas and subjecting the compressed boil-off gas to heat exchange with refrigerant supplied to a heat exchanger while circulating along a refrigerant circulation line; a buffer tank storing utility N.sub.2 to be supplied to the ship; a booster compressor receiving the utility N.sub.2 from the buffer tank, compressing the received N.sub.2, and supplying the compressed N.sub.2 to the refrigerant circulation line; and a first load-up line along which the N.sub.2 is supplied from the buffer tank to the refrigerant circulation line without passing through the booster compressor. Upon initial charging in a non-operation state of the reliquefaction system, the refrigerant circulation line is charged with refrigerant by supplying the N.sub.2 from by a pressure differential between the refrigerant circulation line and the buffer tank.

A ship includes: a boil-off gas heat exchanger installed on a downstream of a storage tank and heat-exchanges a compressed boil-off gas (a first fluid) by a boil-off gas discharged from the storage tank as a refrigerant, to cool the boil-off gas; a compressor installed on a downstream of the boil-off gas heat exchanger and compresses a part of the boil-off gas discharged from the storage tank; an extra compressor installed on a downstream of the boil-off gas heat exchanger and in parallel with the compressor and compresses the other part of the boil-off gas discharged from the storage tank; a refrigerant heat exchanger which additionally cools the first fluid which is cooled by the boil-off gas heat exchanger; and a refrigerant decompressing device which expands a second fluid, which is sent to the refrigerant heat exchanger, and then sends the second fluid back to the refrigerant heat exchanger.