(54c) Condenser Troubleshooting in a Steam Stripping Tower with the Aid of Computational Fluid Dynamics

A shell-and-tube condenser (35-in ID) of a steam stripping tower would, at times, operate with an outlet temperature close to its maximum allowable value to minimize polymerization. A steady-state simulation of the system was put together and validated against plant data to provide the input information for a capacity rating of the condenser. Four sets of operating conditions were considered. Using a commercial exchanger rating software, an excessive overdesign (> 200%) was identified in all cases for the outlet temperature observed at the plant. Based on a pressure drop analysis, vapor maldistribution among the tubes was suspected as the culprit for the underperformance. This hypothesis was confirmed by a simulation of the vapor feed pipe and exchanger inlet region using computational fluid dynamics (CFD). Two options were investigated for solving the identified maldistribution: (i) an increase in feed pipe diameter and inlet nozzle; (ii) the use of a perforated plate in the inlet region. Design details for each option were further investigated using CFD, and the perforated plate was chosen as the best overall option to overcome the maldistribution issue.