(55b) Generalized Graphs for Minimum Compressor Duty LNG Regasification Plant

In the LNG regasification terminal, the unloading pipeline and tank vertical riser are always maintained at cryogenic conditions by recirculating some amount of send-out LNG back to the tank. Determining the required recirculation rate is an important parameter because it affects the in-tank pump operating cost and unloading line temperatures. Small recirculation flowrate decreases the pumping cost at the expense of higher recirculation line temperature. Higher recirculation line temperature may vaporize the content and cause two-phase generation in the line. If two-phase support is not available in the recirculation line, vaporization may cause the pipe to burst and jeopardize the normal operation of the regasification terminal. Thus, the minimum recirculation rate not only affects the plant economics but also its safety and finding it is of utmost importance in the regasification terminal operation. Thus, a generalized graph for obtaining minimum compressor energy corresponds to minimum recirculation rate for any combination of LNG Tank volume, send-out, recirculation pipe diameter/length/heat transfer is prepared. The graph make can help designer make informed decision without doing LNG regasification terminal simulations.