Efficient Turbine Process for Liquefaction of Cryogens
One current process for the liquefaction of atmospheric gases (such as nitrogen, oxygen, and natural gas) uses the compressor and turbine expansion combination to develop the necessary low-temperature-level refrigeration. Sometimes the lowtemperature-level turbine-developed refrigeration is combined with higher-temperature-level refrigeration developed by Joule—Thomson expansion of an external recirculating refrigerant (such as a fluorocarbon fluid). Although the turbine cycle has many advantages, such as use of the same refrigerant fluid as that which is being liquefied, the process is relatively inefficient. Since liquefaction of atmospheric gases requires considerable refrigeration at low temperatures, the ideal minimum work (Carnot cycle) requirements for liquefaction are quite high. Thus an inefficient process has an even higher work requirement and resultant high operating costs. Apart from equipment inefficiences, the current turbine processes have irreversibilities due to heat transfer across large temperature differences. This study shows that these heat transfer irreversibilities are a major contributing factor to the poor efficiency of current turbine processes for the liquefaction of gases and discusses a method that can be used to reduce these losses. The process designer then has the flexibility to build his turbine liquefaction process for a more economically optimum balance between operating and investment costs.
KeywordsHeat Exchanger Work Requirement Efficient Turbine Carnot Cycle Liquefaction Process
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