Optimization of a continuously operating rotary kiln for high temperature processes

Abstract

Renewable energies like wind energy and concentrated solar power systems have a fluctuating energy production - for example when there is no wind or sun available. But it is the approach to provide a continuous power supply. For that reason, energy storage systems have to be included. State of the art for concentrated solar power systems are molten salt storages where the heat is stored as sensible heat. A prom-ising approach is the thermochemical energy storage because it stores sensible heat and chemical energy on top of that as well. Metal oxides are used as storage medi-um due to their reversible redox reaction which offers several benefits like high stor-age capacities and a high temperature range depending on the used oxide. In this thesis a reducing reactor is both technically and thermally designed. This reac-tor operates continuously and is directly irradiated for heating a metal oxide and store the heat in a redox reaction and also as sensible heat. Firstly, the theoretical back-ground of concentrated solar power systems, heat transfer phenomena, energy stor-ages and redox reactions of metal oxides are explained. Different reactor types are introduced, but the rotary kiln is the most promising one because it offers great ver-satility. The main part of this thesis focuses on the reactor design. A morphological box is used to demonstrate the method for each feature of the kiln. Thereby, topics such as thermodynamics, mechanics and material science are considered. Every feature is discussed in detail and, if necessary, FEM analyses are performed, i.e. to evaluate the mechanical stress. A designed plant layout in form of a P&I diagram is used as reference to develop a control software and analysing all process parame-ters. Finally, preliminary experiments are conducted for providing all necessary data to perform the thermal and chemical tests.