Effect count and vapour recompression: two decisions
Compare the heat arrangement against the same water-removal duty, operating hours and utility conditions.
First define the effect arrangement
An effect is an evaporation stage operating at an assigned pressure. In a multiple-effect arrangement, vapour from one effect supplies heat to another at a lower pressure. The design needs enough temperature difference across the sequence after product boiling point elevation and losses.
Then evaluate the recovery method
Steam heating, TVR and MVR describe heat supply or recovery choices. They are evaluated alongside effect count. A multi-effect TVR proposal and a single-effect MVR proposal differ along more than one dimension, so a four-column list of mutually exclusive machine types hides important assumptions.
Keep the cost boundary consistent
Request steam and electricity requirements at the same inlet temperature, outlet concentration, evaporation rate and annual hours. Include cooling, start-up, cleaning, maintenance and any preheater recovery. Keep utility quantities separate from their local prices.
Identify what the site can actually provide
For steam, specify available pressure and quality at operating load. For MVR, provide electrical service and start-up constraints. For every option, record cooling-water conditions and the permissible product temperature profile. No universal energy saving percentage is used here.
Related equipment
Vacuum & condenser package
Maintain the pressure basis used by the concentration design.
HEAT RECOVERY / TVRThermal vapour recompressor
Use motive steam to recover part of the process vapour heat.
HEAT RECOVERY / MVRMechanical vapour recompressor
Raise recovered vapour pressure using electrical drive.