Geometry optimization of photochemical reactors for advanced oxidation processes

This paper studies the optimization of photochemical reactors for the production of hydroxyl radicals which can be used in advanced oxidation processes for water purification. Minimization of the energy cost of the applied UV-lamp(s) is possible via a model-based optimization of the reactor geometry. To this end, 2D reactor models are first built taking into account balance equations, reaction kinetics, reactor geometry and radiation intensity. Two tubular reactor configurations with cylinder-shaped UV-lamps are studied: a single-lamp reactor with only one lamp located at the reactor axis and a multi-lamp reactor in which the lamps are positioned symmetrically in a circular pattern. Afterwards well-posed optimization problems are formulated. For given values of the reactor volume, the flow of water to be treated and the radiation power of the UV-lamps, the aim is to minimize the average concentration of an organic pollutant at the reactor outlet. For the single-lamp reactor the optimal reactor diameter is computed, while for the multi-lamp reactor the optimal location of the lamps in the radial direction is calculated. From the results, it follows that an optimal reactor diameter (and length) exists for the single-lamp reactor (and for the multi-lamp reactor). For the multi-lamp reactor, an optimal lamp position exists. It has been shown that for the latter reactor an optimal number of lamps exists, trading off an improved radiation intensity uniformity and a decreased radiation penetration due to a lower radiation power per lamp.