Development of a Dynamic Simulation Code for a VHTR-Aided SI Process

In order to establish the optimal start-up method and to understand the dynamic behavior of the SI process coupled to a VHTR through an Intermediate Heat Exchanger (IHX), the development of a dynamic simulation code is necessary. Perturbation of the flow rate or temperature in input streams may result in various transient states. An understanding of the dynamic behavior due to these factors is very important to establish a safe operation method for a hydrogen production plant including a VHTR. Based on the mass and energy balance sheets of an electrodialysis-embedded SI process, proposed by KAERI, equivalent to a 200 MW_th VHTR, not only the establishment of a thermal pathway (draft) between the SI process and the VHTR system but also the equipment sizing required in the SI process was carried out. A dynamic simulation code for the SI –2^nd Skid (sulfuric acid concentration and decomposition part) was prepared at first for each chemical reactor. The reliability of the computer code has been confirmed by the convergence value at a steady state. This confirmation has been performed for the primary and secondary sulfuric acid distillation columns, the sulfuric acid vaporizer, the sulfuric acid decomposer, and the sulfur trioxide decomposer, respectively. An integrated computer code with a visualization function has been prepared by coupling each proven computer code, according to the thermal pathway. The dynamic behaviors of the integrated the SI-2^nd Skid according to several anticipated scenarios were evaluated and the dominant and mild factors are discussed.