Simultaneous Dynamic Optimization Of Large-Scale Integrated Processes

MARIELA RODRIGUEZ; M. SOLEDAD DIAZ

Buenos Aires

Congreso; XXII Interamerican Congress of Chemical Engineering; 2006

In this work we address the open loop dynamic optimization of a large-scale natural gas processing plant through a simultaneous approach. Rigorous dynamic models have been developed for main units in the cryogenic sector, which includes cryogenic heat exhangers with partial phase change, high pressure separators, turboexpanders and demethanizing columns. These models render an optimization problem subject to constraints that constitute a differential algebraic equations (DAE) system. The fact that countercurrent heat exchangers have been rigorously modeled gives rise to a partial differential equation system, which is spatially discretized by applying the method of Lines. The resulting DAE system is then discretized by orthogonal collocation on finite elements and the optimization problem is solved as a large-scale nonlinear programming model. Optimal profiles are obtained for a change in natural gas feed to the sector. Numerical results show the advantage of using a simultaneous approach to solve models of highly integrated processes that include path constraints.