The integration of a fixed bed thermal energy storage system into waste heat recovery systems in the iron and steel industry offers significant potential to increase process flexibility and raise the waste heat utilization efficiency from the current level of approximately 45% to up to 97%. Fixed bed thermal energy storage systems are characterized by their cost-effectiveness and the ability to use dust-laden high-temperature exhaust gases directly as a heat transfer fluid. However, the direct use of such exhaust gases to load a fixed bed storage presents specific challenges for which practical solutions must be developed.

During the charging process, dust particles accumulate at the entry surface of the bed. This dust is not completely removed by subsequent unloading with clean air, which can lead to a gradual increase in pressure loss, potentially leading to a blockage of the fixed bed. Therefore, continuous cleaning of the dust deposits is essential for long-term operation. Two approaches are suitable for this: the use of tapping or vibration mechanisms, or a continuous regeneration of the contaminated storage material. Both strategies, however, require that the bed be flowed through from the bottom up during charging and from the top down during discharging. This contrasts with the classical operating concept, where charging is from the top and discharging from the bottom to ensure the stability of the thermocline and maximize thermal efficiency.

This project develops and tests an innovative fixed bed thermal storage concept that combines effective cleaning capabilities with high thermal efficiency. The implementation is based on experimental investigations at two laboratory-scale test rigs to evaluate the technical feasibility and scalability for industrial applications. A particular focus is placed on the process design of the system as well as the analysis and evaluation of experimental data.

The characteristics and key performance indicators (KPIs) derived from the storage technology will be used for a comprehensive assessment of its potential to enhance waste heat utilization efficiency in the iron and steel industry, particularly in plants such as electric arc furnaces. The goal is to significantly increase the technological maturity of fixed bed thermal storage systems and promote their industrial application.

Functional diagram of the innovative storage configuration

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innovative storage configuration