Ethylene Process Optimization. Constraint Relaxation And Bounds Adjustment

Heavily constrained, mixed integer optimization problems present a difficult test for optimization algorithms. This paper examines optimization of the ethylene process (from ethane) using a flowsheet simulation model and the adaptive random search. Optimization resulted in an improvement in annual earnings of $1.15 MM over the usual ethylene process design. This process has both continuous and discrete variables and has sensitive implicit constraints in the pyrolysis furnace. The search efficiency was found to be improved by relaxing these constraints early in the search and then restoring the constraints as the optimum is approached. The search efficiency was also improved by testing each independent variable for its optimal explicit bound and using these bounds as the starting point for the optimization. Significant improvements in the economics ($0.7 MM per year) were found by examining and slightly adjusting the variable boundaries at the optimum. These results suggest that variable bounds should be established in conjunction with the optimization study. © 1979, American Chemical Society. All rights reserved

Vision, challenges and opportunities for a Plant Cell Atlas

With growing populations and pressing environmental problems, future economies will be increasingly plant-based. Now is the time to reimagine plant science as a critical component of fundamental science, agriculture, environmental stewardship, energy, technology and healthcare. This effort requires a conceptual and technological framework to identify and map all cell types, and to comprehensively annotate the localization and organization of molecules at cellular and tissue levels. This framework, called the Plant Cell Atlas (PCA), will be critical for understanding and engineering plant development, physiology and environmental responses. A workshop was convened to discuss the purpose and utility of such an initiative, resulting in a roadmap that acknowledges the current knowledge gaps and technical challenges, and underscores how the PCA initiative can help to overcome them.</jats:p