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IV B. Tech. I Sem Petrochemical Engineering

LNG: Processes, Transportation & StorageUniversity College of Engineering (A) KakinadaDept. of Petroleum Engineering & Petrochemical EngineeringFPSO - LNG PROCESSESJawaharlal Nehru Technological University KakinadaProf. K. V. RaoProgramme DirectorPetroleum CoursesJNTUKLNG PROCESSES

Figure 1: LNG plant block scheme C2THE BASIC SINGLE FLOW LNG PROCESS COMPRISESA plate-fin heat exchanger set in a cold box, where the NG gas is cooled-down to LNG temperatures by a two stage single MR (Mixed Refrigerant) cycle

A separation vessel, where the MR is separated in a liquid fraction, which provides the cold temperature after expansion in a J-T (Joule-Thompson) valve for the NG precooling and liquefaction.

The gas from the separator provides the LNG subcooling temperature after J-T expansion at the bottom of the heat exchanger.

The cycle gas streams leaving the heat exchanger are recompressed in the two stage turbo compressor.

The compressed cycle gas is cooled and partly condensed against air or water.3

Figure 2 : The basic single flow LNG process4THE ADVANCED SINGLE FLOW LNG PROCESS COMPRISESA SWHE (Spiral-Wound Heat Exchanger) where the natural gas is precooled, liquefied and subcooled against various streams of a single mixed refrigerant cycle.

A medium pressure refrigerant separator, from where the liquid is used to provide the precooling temperature after J-T (Joule-Thompson) expansion to the lower section of the SWHE.

A high pressure refrigerant separator, from where the gas is cooled and partially condensed in the lower section of the SWHE.

A lower temperature refrigerant separator, from where the liquid is used to provide the natural gas liquefaction temperature after J-T expansion. The gaseous refrigerant stream from this separator is used to provide the subcooling temperature after J-T expansion in the upper section of the SWHE

The combined refrigerant cycle stream from the bottom of the SWHE is compressed in a two stage compressor with inter and aftercooling against air or water.5

Figure 3: The advanced single flow LNG process6MFC (MIXED FLUID CASCADE) PROCESSThe MFC LNG process excels by a high efficiency respectively low shaft power consumption of the three mixed refrigerant cycle compressors. The process comprises:PFHEs (Plate-Fin Heat Exchangers) for the natural gas precooling

SWHEs (Spiral-Wound Heat Exchangers) for the natural gas liquefaction and LNG subcooling

Three separate mixed refrigerant cycles, each with different compositions, which result in minimum compressor shaft power requirement

Three cold suction turbo compressors with inter and ftercooling

Up to 8 mtpa LNG can be produced in a one train unit oncerning heat exchangers and compressors.

Up to 10 mtpa LNG can be produced in a one train unit concerning the heat exchangers, however, with parallel compressors.7

Figure 4: MFC (Mixed Fluid Cascade) process8COIL-WOUND HEAT EXCHANGERThe practically unrestricted range of utilisable materials allow coil-wound heat exchangers to be used for a wide range of applications in cold, but also warm applications. The coil-wound heat exchanger is the core equipment in large base load LNG plants applying mixed refrigerant cycles for natural gas cooling and liquefaction.

Benefits

Providing a large heating surface per shell Tolerant against thermal shocks due to its robustness

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Figure 5: Manufacturing of coil-wound heat exchanger10

The coil-wound heat exchanger is the core equipment in large base load LNG plants applying mixed refrigerant cycles for natural gas cooling and liquefaction.11PLATE-FIN HEAT EXCHANGERThe vacuum brazed aluminium plate-fin heat exchangers are key components in many cryogenic process plants. They are the preferred heat exchangers in small LNG plants.BENEFITSCompactness, which saves installation space and cost

Many process streams can be treated in only one unit, thus avoiding expensive interconnecting piping of different units

Low equipment weight 12

Assembly of aluminium plate-fin heat exchangers13

Scheme of an aluminium plate-fin heat exchangerThe vacuum brazed aluminium plate-fin heat exchangers are key components in many cryogenic process plants. They are the preferred heat exchangers in small LNG plants.14UNIVERSITY OF PETROLEUM & ENERGY STUDIES, Thank You15