Simulation and control of the oxidation of sulfur dioxide in a micro-structured reactor

For producing sulfur trioxide, sulfur dioxide is oxidized to sulfur trioxide in the presence of a catalyst. Industrially, sulfur trioxide is produced by the contact process which consists of several catalytic beds and inter-cooling stages between them. This process is highly energy intense and inflexible due to long periods of start-up and shut-down caused by the thermal inertia. In order to improve the flexibility of the production process, a new approach for producing sulfur trioxide is currently being investigated. A micro-structured reactor has been constructed by the Karlsruhe Institute for Technology (KIT) which consists of only one cooling passage. In our work, a three dimensional dynamic reactor model was developed that describes the dynamic behavior of the micro-structured reactor. This model was used to simulate the efficiency and the distribution of temperature and reactants in the system and in particular for investigating the start-up of the reactor. A control strategy was developed and tested in simulations in order to react on disturbances and to improve the start-up time. The simulations showed that a conversion of approx. 98.5 % can be reached and by a suitable control strategy the start up time can be improved significantly.