Optimization of Complex Column Networks with Hybrid Genetic Algorithm

Abstract Complex column networks including Petlyuk, Kaibel, divided wall columns, side-stripper and rectifiers have better energy efficiency than simple separation networks. We present automatic and systematic computer-aided design and synthesis of complex column networks with heat-integrated configurations to separate multicomponent mixtures. Automatic synthesis of complex column is a challenging problem because the rigorous mass, equilibrium, summation and heat (MESH) equations lead to non-smooth fragmented search spaces. Therefore global optimization methods involving both structural and parametric degrees of freedom can currently not handle this problem and find realizable optimal energy efficiency in practice. To tackle the network synthesis problem, we proposed the following design and optimization approaches. First we apply an inverse design methods based on temperature collocation which substantially reduces the problem dimension. This method identifies the design feasibility keeping final product purities. Second, we developed hybrid genetic algorithm, in which stochastic GA elements can be combined with a local deterministic search. At first stage, GA explores the design space until individual network solutions begin to coalesce and confines the region with niche technique. The gradient-based local optimizer refines a solution to local optimality. This hybrid scheme enables to find out all global and local solutions and thus improves computation speed and accuracy of the solutions. Our novel methods allow the global search for feasible, effective and optimal energy efficient designs of the complex distillation column network in a fully automatic fashion. We used the rigorous commercial flowsheet simulator AspenPlus to validate the result and both results are very close each other. The automatic and rigorous flowsheet synthesis is apt to systematically address industrial-size process design problems such as the synthesis of energy-efficient separation networks, layout of biorefineries with novel feedstocks or sustainable process for reduction of greenhouse gases emissions.