Temperature-enthalpy curve for energy targeting of distillation columns

摘要: Abstract The temperature–enthalpy ( T – H ) diagram of a distillation column at practical near-minimum thermodynamic condition (PNMTC) or the grand composite curve (CGCC) is useful representation for energy targeting studies and may be generated from converged simulation base-case design. calculation procedure CGCC involves determination net enthalpy deficit each stage by generating envelopes either condenser end (top-down approach) reboiler (bottom-up approach). However, values calculated two approaches differ stages with feeds because existing procedures generation do not consider balances feed stages. In fact, deficits both are erroneous even simplest case binary distillation. A correction (FSC) that rigorously considers mass balance equations proposed in this work to resolve discrepancy. Instead assuming compositions obtained will remain unchanged PNMTC, pinched determined intersection equilibrium q -line. Rather than perform an additional flash establish compositions, quadratic approximation developed here purposes relative volatility constant neighborhood stage. FSC ensures identical whether calculations performed top-down approach bottom-up approach. effect on targets conservation reflux modification, conditioning, introduction side reboilers/condensers discussed. As target modification pinch which typically occurs close location, significance highlighted through several including complex featuring multiple consequently points. CGCCs these computer program based single analytical equation allows every have feed, liquid product, vapor exchanger. show many cases, if ignored.