Liquefaction refrigeration process

Kelvin) and performed by J. P. Joule to study departures from ideal gas behavior. The Joule-Thomson expansion, as it is called, is used in the liquefaction of gases and in refrigeration processes (see Chapter 5). ... 

F rom this discussion it is apparent that conventional liquefaction installations cannot readily be converted into refrigeration units because the precooling cannot be used. Since in these installations a combination of two different processes is performed, it is practically impossible to obtain information about the quality of one of the refrigeration processes from data on the efficiency of the liquefaction process as a whole. 

FIG. L-11 An LNG feed, liquefaction, and refrigeration process system. (Source Peerless.)... 

In summary, starting with 105°F gas at atmospheric pressure, the theoretical work necessary to liquify one pound of methane is 510.8 Btu or 352 hp/MMcfd. The simplified liquefaction process, as illustrated, uses a turboexpander/compressor and a small propane refrigeration unit. The 41.25% efficiency breaks down as follows one-fourth contributed by the turboexpander/compressor at 35.8% efficiency one-sixteenth contributed by the mechanical propane refrigeration unit at 43% efficiency, at a moderate temperature where its efficiency is high and a large fraction—eleven-sixteenths—contributed at 58.2% efficiency by compression and Joule-Thomson condensation energy. 

With three or more stages for each refrigerant, the power consumption for the cascade cycle is found to compete quite favourable with other liquefaction processes, especially in arctic conditions. This is mainly because of the low flow rate of refrigerant. The cascade cycle is also more flexible in operation, since each circuit of refrigerant can be separately controlled. For the classical cascade, however, an overlap may occur of refrigerants like methane and ethylene. Thus, as methane condenses at an elevated pressure, this will inherently cause some throttling losses. 

LNG production involves cryogenic technologies that include concepts, refrigerants and process design. A state-of-the-art review of liquefaction concepts - especially on smaller scale - have been given. Cost level and relative pricing have been indicated in order to provide rough estimates. 

The industry got its start in 1895 when Dr. Carl von Linde, a pioneer in refrigeration technology, received the first patent for the liquefaction and rectification of air into its major components oxygen and nitrogen (Almqvist, E., IOMA). Georges Claude soon developed this work further in Paris, France, improving the efficiency of the liquefaction process. 

Cooling curves for natural gas liquefaction by the cascade process are shown in Fig. 7a,b. It is evident that the cascade cycle efficiency can be considerably improved by increasing the number of refrigerants or the number... 

At atmospheric pressure, H2 condenses at -423°F (-253°C). As the pressure rises, the condensation temperature also increases. The liquefaction process utilizes a number of heat pumps in series to reduce the H2 temperature from ambient to the liquefaction temperature. The efficiency of this compression-condensation process ranges from 35 to 60% as a function of size and the refrigerant used in the heat pumps. One of the most efficient refrigerants is a mixture of helium and neon (Quack cycle). The energy consumption of liquefiers theoretically ranges from 5 to 15 kWh/kg... 

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