Distribution, wetting & minimum load
Design for the concentrated, low-load case as carefully as the nominal feed condition.
The limiting point may be downstream
Water removal reduces the remaining liquid flow. Increasing viscosity can also change how that liquid spreads. Ask where the least favourable wetting condition occurs across all passes and effects; a single percentage of nominal plant capacity is not enough.
Prepare three operating cases
Document normal production, the lowest planned load and the transition between products. For each case give composition, flow and temperature, along with interruptions that might starve the distributor. Ask how control logic responds before heat is applied to insufficiently wetted surfaces.
Evaluate recirculation as a trade-off
Recirculation may support wetting but adds pump duty and changes the residence-time history. Request the recirculation ratio and its purpose for each case. Do not assume a recirculated design has the same thermal exposure as a once-through proposal.
Inspect what the instruments cannot see
Overall flow and pressure do not identify every blocked passage. Specify accessible distributor inspection and a method to verify coverage after cleaning or maintenance. Repeated deposits at the same location are a reason to examine distribution rather than simply intensify cleaning.