Methods and systems for starting up and operating one or more vapor-recompression units

A method for starting up or operating at a low mass flow one or more vapor-recompression units, said method comprising:

• (a) providing a vapor recompression sub-system comprising one or more vapor-recompression units that are in vapor communication with each other, wherein said vapor recompression sub-system has a vapor inlet for a vapor and a compressed-vapor outlet for a compressed form of said vapor;
• (b) providing a means of reducing vapor density of said vapor through pressure reduction, wherein said means of reducing vapor density through pressure reduction is in vapor communication with said vapor recompression sub-system;
• (c) reducing pressure of said vapor within said vapor recompression sub-system by operating said means of reducing vapor density through pressure reduction to reach a sub-system pressure selected from about 0.1 kPa to about 1000 kPa (absolute);
• (d) before, during, or after step (c), introducing a vapor mass flow to said vapor recompression sub-system at a restricted vapor mass flow rate, wherein said vapor mass flow is a flow of said vapor;
• (e) optionally, starting up said vapor recompression sub-system while maintaining said restricted vapor mass flow rate for a start-up time period;
• (f) operating said vapor recompression sub-system at said restricted vapor mass flow rate for a low-mass-flow time period to accommodate intermittent process requirements and/or meet energy cost or availability objectives;
• and
• (g) following said low-mass-flow time period, introducing additional vapor mass flow to said vapor recompression sub-system to reach a normal vapor mass flow rate, wherein said additional vapor mass flow is a flow of said vapor,
• wherein said restricted vapor mass flow rate is selected from about 0.1% to about 90% of said normal vapor mass flow rate.