A study on the dynamic behavior of a sulfur trioxide decomposer for a nuclear hydrogen production

The sulfur–iodine thermochemical water-splitting cycle (S–I cycle) is one of the most promising technologies for mass H₂ production. The S–I cycle is generally divided into three sections, one of which involves a H₂SO₄ concentration and decomposition. In the sulfuric acid processing section (Section 2), H₂SO₄ is decomposed into H₂O and SO₃, and then the produced SO₃ is further decomposed into SO₂ and O₂, which takes place in a H₂SO₄ decomposer and a SO₃ decomposer, respectively. The SO₃ decomposition requires heat of a high temperature and this suggests a heat-exchanger type reactor. To understand the temperature profiles and chemical reactions through a SO₃ decomposer, a dynamic model was developed by considering the heat and material balances in partial differential forms. A model was used to size the decomposer to a proposed design basis and it was also applied to simulate the responses corresponding to the changes of the operation conditions such as increased or decreased flow rates.