Energy-intensive
single mixed refrigerant (SMR) cycles are employed
to produce liquefied natural gas (LNG) at small scale. The energy
required for refrigerant compression (shaft work) dominates the overall
operating costs of the LNG plant. While current methods to minimize
shaft work demand (e.g., exergy analysis) focus on the PRICO cycle,
this paper shows that structurally modifying the configuration of
SMR cycles can yield significant savings in shaft work demand with
low added complexity. The novel SMR cycle developed in this work is
based on the CryoMan SMR cycle; its benefits, in terms of energy savings,
are demonstrated through a case study for natural gas liquefaction
at small scale. The shaft work demand of the PRICO, CryoMan, and novel
SMR cycles are minimized using a genetic algorithm and nonlinear optimization.
The structural modifications applied tailor the refrigerant composition
and exploit complex trade-offs between the operating variables to
enhance the energy efficiency of the SMR cycles. The results from
the case study demonstrate that the novel SMR cycle achieves 10% savings
in shaft work demand in comparison with the PRICO SMR cycle.
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