Effect of boiling point rankings and feed locations on the applicability of reactive distillation to quaternary systems

Reactive distillation (RD) offers major benefits such as costs reduction and energy saving, but the understanding and design of RD processes usually demand complex tasks that include extensive studies and rigorous simulations. To reduce this complexity and the time required, this study applies a novel mapping method to quickly provide insights into the RD applicability to reversible quaternary systems (A + B ⇌ C + D). Generic cases are used to produce applicability graphs (i.e. plots of reflux ratio vs number of theoretical stages) and multiple RD column configurations. The systems are assumed to have ideal properties and fixed key parameters (i.e. relative volatilities and chemical equilibrium constants). This study focuses on quaternary reactions considering different boiling point rankings and feed locations. Using the mapping method, quick results are achievable regarding the preliminary economic ranking of RD processes, and the optimal feed locations with reduced energy requirement (i.e. lower reflux ratio). Ultimately, this study provides a much better understanding of the effect of boiling point orders and feed locations on the RD applicability and conceptual design, being a valuable tool in early techno-economic evaluations

Heat Transfer to Sub- and Supercritical Water Flowing Upward in a Vertical Tube at Low Mass Fluxes: Numerical Analysis and Experimental Validation

Heat transfer to supercritical water (SCW) flowing upward in a vertical heated tube at low mass fluxes (<i>G</i> ≤ 20 kg/m² s) has been numerically investigated in COMSOL Multiphysics and validated with experimental data. The turbulence models, essential to describing local turbulence, in COMSOL have been checked under conditions in which empirical heat-transfer correlations are available, and it is concluded that the shear-stress transport (SST) turbulence model gives the most accurate results. The numerical results obtained show a buoyancy induced circulation of the fluid resulting from gravitational force acting on density gradients as well as a thin thermal boundary layer with a steep temperature gradient at the inner wall and a flat temperature profile in the bulk fluid. The heat-transfer coefficient of SCW is enhanced near the pseudocritical temperature (<i>T</i>_pc) and is deteriorated at temperatures above <i>T</i>_pc. A new heat-transfer correlation has been developed and validated with experimental data