System and Method for Turndown of a Hydrogen Precooling and/or Hydrogen Liquefaction System

A method for turndown of a nitrogen-based refrigeration system in a hydrogen precooling or hydrogen liquefaction system comprising the steps of:

• (a) receiving a hydrogen feed stream at a prescribed volumetric flow;
• (b) cooling the hydrogen feed stream in a first heat exchanger or first set of heat exchanger cores via indirect heat exchange with a low pressure gaseous recycle stream and a medium pressure gaseous recycle stream to yield a cooled, hydrogen feed stream;
• (c) cooling a high pressure nitrogen refrigerant stream in the first heat exchanger or first set of heat exchanger cores and diverting a first portion of the high pressure nitrogen refrigerant stream from within the first heat exchanger or first set of heat exchanger cores to yield a first diverted stream;
• (d) expanding the first diverted stream in a warm turbine/expander to yield a warm exhaust stream that forms a part of the medium pressure gaseous recycle stream at a temperature colder than the first diverted stream;
• (e) diverting a second portion of the high pressure nitrogen refrigerant stream from within the first heat exchanger or first set of heat exchanger cores to yield a second diverted stream, wherein the second diverted stream is at a temperature colder than the first diverted stream;
• (f) expanding the second diverted stream in a cold turbine/expander to yield a cold exhaust stream that forms another part of the medium pressure gaseous recycle stream at a temperature colder than the second diverted stream;
• (g) recycling the medium pressure gaseous recycle stream through the first heat exchanger or first set of heat exchanger cores to cool the high pressure nitrogen refrigerant stream and the hydrogen feed stream;
• (h) expanding the remaining portion of the of the high pressure nitrogen refrigerant stream in an expansion valve to yield a two-phase nitrogen stream;
• (i) separating the two-phase nitrogen stream in a phase separator to yield a liquid nitrogen stream and the low pressure gaseous recycle stream;
• (j) recycling the low pressure gaseous recycle stream through the first heat exchanger or first set of heat exchanger cores to cool the high pressure nitrogen refrigerant stream and the hydrogen feed stream;
• and
• wherein, in a first operating mode, the method further comprises the steps of:
• (k) directing a prescribed volumetric flow of the liquid nitrogen from the phase separator to the second heat exchanger or second set of heat exchanger cores;
• and (l) precooling the cooled, hydrogen feed stream in a second heat exchanger or second set of heat exchanger cores via indirect heat exchange with the liquid nitrogen to yield a precooled hydrogen feed stream at a temperature of less than or equal to 80 Kelvin;
• and
• wherein, in a second operating mode, the method further comprises the steps of:
• (m) restricting the flow of the hydrogen feed stream to the first heat exchanger or first set of heat exchanger cores such that the flow is less than the prescribed volumetric flow of the hydrogen feed stream to the first heat exchanger or first set of heat exchanger cores;
• (n) restricting the flow of liquid nitrogen from the phase separator to the second heat exchanger or second set of heat exchanger cores via a control valve;
• (o) retaining a remaining portion of the liquid nitrogen in the phase separator;
• and (p) precooling the cooled, hydrogen feed stream in a second heat exchanger or second set of heat exchanger cores via indirect heat exchange with the restricted flow of liquid nitrogen to yield a precooled hydrogen feed stream at a temperature of less than or equal to 80 Kelvin.