(52g) Simulating Field Performance Data from an Ethylene Producer for a Cold Box

Plate-fin heat exchangers are key equipment used in the cold boxes of ethylene plant and other cryogenic processes.  This paper shows how the field performance data for a plate-fin heat exchanger used in hydrogen enrichment was successfully simulated.  Such simulation requires that detailed geometry of the exchanger is taken into account, and rigorous simulation of the exchanger is carried out directly in the process simulation environment.  The paper also describes various steps required to simulate field performance data, starting with the basic step of obtaining good match between the UA value used by the process simulator and that obtained by the exchanger simulation program with its built-in incremental analysis.  Detailed incremental analysis is essential because the heat exchange process involved multicomponent boiling and condensing streams, with their consequent nonlinear temperature and heat transfer coefficient profiles.  It is demonstrated that, as always, engineering judgement and process knowledge are vital to assess the relative confidence levels of different measured plant variables, so that more meaningful reconciliation of the measured data and performance predictions could be carried out.  In the step by step approach each measured plant variable is assessed and then used in the simulation as either an input item or as a target predicted item.  The final outcome of this step by step approach is rigorous simulation model of the hydrogen enrichment process, which is validated with measured field data. This type of validated model can form the basis for investigating the effect of off-design conditions on the plant operation and establishing the optimum operating conditions.