LAUSR

The design and steady‐state operation of a packed bed reactor with tubular geometry is optimized. Direct optimal control methods are used. Two objective functions are considered: (i) minimization of the ammonia mass fraction at reactor outlet and (ii) minimization of the heat flux necessary to reach a predefined value of the ammonia mass fraction at reactor outlet. The optimization process is performed by using different controls, that is, the space distributions of (1) tube wall temperature Tw, (2) circular tube diameter Dtube, and (3) diameter dp of the catalyst spherical particles. Results for the first objective function are as follows. The optimal distribution of Tw along the reactor consists of a constant temperature or a U‐shaped space temperature distribution, respectively, depending on the allowed range of variation of Tw. The optimal space distribution of Dtube (or, in other words, the shape of the reactor tube) depends of Tw. For smaller values of Tw the tube is narrower at inlet and larger at outlet while the reverse situation happens for larger values of Tw. For lower Tw values, particles with smaller diameter dp are placed at reactor inlet while when higher values of Tw are considered, particles with larger dp are placed at reactor inlet. When both Dtube and dp are used as controls, the optimization results are generally different from the results obtained from one‐control optimization. Results for the second objective function are as follows. The optimal space distribution of Tw starts with high values at reactor inlet. Next, the temperature decreases abruptly towards a minimum (which is lower for longer tubes). Finally, the temperature increases smoothly towards a maximum near the reactor outlet. The required heat flux slightly decreases by increasing the tube length. The optimal Dtube ranges between its maximum allowed value (at reactor inlet) and its minimum allowed value (at reactor outlet). The best performance is obtained for catalyst particles of the smallest allowed diameter.