Systems and methods are provided for the production of liquefied natural gas. At least one of the systems may include a plurality of compression assemblies in fluid communication with a precooler assembly. One compression assembly may be a part of a precooling loop and may include at least one compressor driven by a variable or fixed speed motor. Another compression assembly may be part of a liquefaction loop and may include at least one pair of compressors, each compressor driven by a respective turbine. The liquefaction loop may be fluidly coupled to a main heat exchanger utilized to liquefy at least a portion of a feed gas stream containing natural gas flowing through the main heat exchanger, thereby producing liquefied natural gas.

A method of cooling a boil-off gas (BOG) stream from a liquefied gas tank comprising at least the step of heat exchanging the BOG stream with a first refrigerant in a heat exchanger, the heat exchanger having an entry port and a warmer exit port, and comprising at least the steps of: (a) passing the first refrigerant into the entry port of the heat exchanger and into a first zone of the heat exchanger to exchange heat with the BOG stream, to provide a first warmer refrigerant stream; (b) withdrawing the first warmer refrigerant stream from the heat exchanger at an intermediate exit port between the entry port and the warmer exit port; (c) admixing the first warmer refrigerant stream with an oil-containing refrigerant stream to provide a combined refrigerant stream; (d) passing the combined refrigerant stream into the heat exchanger through an entry port located in a second zone of the heat exchanger that is warmer than the first zone; (e) passing the combined refrigerant stream out of the heat exchanger through the warmer exit port. The present invention is a modification of a refrigerant cycle for BOG cooling, and LNG re-liquefaction in particular, that allows the use of a cost-efficient oil-injected screw compressor in the refrigerant system. The present invention is also able to accommodate the possibility of different flows or flow rates of the first refrigerant stream and the oil-containing refrigerant stream, such that there is reduced or no concern by the user of the process in relation to possible oil freezing and clogging of the heat exchanger caused by variation of the flow or flow rate of the oil-containing refrigerant stream.

Provided is a method of constructing a natural gas liquefaction plant, which can shorten a construction time period by minimizing effect of a lead time for the refrigerant compressor thereon, the method including: transporting a refrigerant compression module body 175 to an installation area 85, wherein the refrigerant compression module body is provided with a frame 120 configured to allow refrigerant compressor 150 for compressing a refrigerant for cooling natural gas to be mounted therein; installing the refrigerant compression module body 175 to the installation area 85; and mounting the refrigerant compressor 150 into a mounting space 130 predefined in the frame 120 of the installed refrigerant compression module body.

The present invention relates to a method of cooling and separating a hydrocarbon stream: (a) passing an hydrocarbon feed stream (7) through a first cooling and separation stage to provide a methane enriched vapour overhead stream (110) and a methane depleted liquid stream (10); (b) passing the methane depleted liquid stream (10) to a fractionation column (200) to obtain a bottom condensate stream (210), a top stream enriched in C1-C2 (220) and a midstream enriched in C3-C4 (230), (c) cooling the upper part of the fractionation column (201) by a condenser (206), (d) obtaining a split stream (112) from the methane enriched vapour overhead stream (110) and obtaining a cooled split stream (112) by expansion-cooling the split stream (112), (e) providing cooling duty to the top of the fractionation column (201) using the cooled split stream (112).

A method for operating a main cryogenic heat exchanger for use in a natural gas liquefaction process, involves monitoring or predicting variations in the flow rate of a feed gas stream provided to the main cryogenic heat exchanger. When a variation of the flow rate exceeding a predetermined threshold value is monitored or predicted, a control scheme is started to control one or more compressor recycle valves in response to the monitored or predicted variation of the flow rate to recycle part of a compressed mixed refrigerant stream in a refrigerant loop.

A module for a natural gas liquefaction apparatus is provided to include air-cooled heat exchanger groups and another equipment group. The air-cooled heat exchanger groups another equipment group. The air-cooled heat exchanger groups are arranged side by side on an upper surface of a structure, and are each configured to cool a fluid handled in the natural gas liquefaction apparatus. The another equipment group is arranged on a lower side from an arrangement height of each air-cooled heat exchanger groups, and forms a part of the natural gas liquefaction apparatus. When equipment groups are classified into a pretreatment unit equipment group provided in a pretreatment unit configured to perform pretreatment of natural gas before being liquefed, and a liquefaction processing unit equipment group provided in a liquefaction processing unit associated with processing of liquefying the natural gas after being treated in the pretreatment unit, the another equipment group is formed of the pretreatment unit equipment group.

A split mixed refrigerant (MR) natural gas liquefication system, where low-pressure (LP) and medium pressure (MP) MR compressors are driven by a first gas turbine and a propane compressor and a high-pressure (HP) MR compressor is driven by a second gas turbine, is disclosed. The split MR liquefication system is configured to adjust the characteristics of the HP MR compressor to require less power when less power is available and more power when more power is available compared to the system's design point. Such adjustments allow for shifting the balance of power between the propane compressor and the HP MR compressor to improve LNG production efficiency.

A system and method is provided for increasing the capacity and efficiency of natural gas liquefaction processes by debottlenecking the refrigerant compression system. A secondary compression circuit comprising at least one double flow compressor is provided in parallel fluid flow communication with at least a portion of a primary compression circuit.

In a gas liquefaction plant that produces a liquefied gas by liquefying a raw gas, a pipe rack portion in which an air-cooling heat exchanging system is disposed has a rectangular shape when viewed from above. A first compressor, a precooling heat exchanging portion, an auxiliary heat exchanging portion, and a fourth compressor are arranged in this order along one long side of the pipe rack portion. A second compressor, a primary heat exchanging portion, and a third compressor are arranged in this order along the other long side of the pipe rack portion. A pipe that carries the raw gas cooled at the precooling heat exchanging portion is connected to the primary heat exchanging portion across the pipe rack portion. A pipe that carries a primary refrigerant compressed at the second and third compressors is connected to the auxiliary heat exchanging portion across the pipe rack portion.

A method and apparatus for cooling a hydrocarbon stream such as natural gas. An initial hydrocarbon stream is passed through a first separator to provide an initial overhead stream and a mixed hydrocarbon feed stream. The initial overhead stream is cooled to provide a cooled hydrocarbon stream such as LNG, and at least a C1 overhead stream and one or more C2, C3 and C4 overhead streams are separated from the mixed hydrocarbon feed stream. At least a fraction of at least one of the group comprising: the C2 overhead stream, the C3 overhead stream and the C4 overhead stream is cooled with the C1 overhead stream to provide a cooled stream, which is further cooled against at least a fraction of the cooled, preferably liquefied, hydrocarbon stream to provide an at least partly liquefied cooled stream.