Session: 11-01: Process Heat for Desalination and Industrial Decarbonization

Paper Number: 130277

130277 - Application of Molten Salt Thermal Energy Storage for Waste Heat Recovery in Iron and Steel Industry 

Abstract: 

The highly energy-intensive iron and steel industry contributed about 10% of the global CO₂ annual emissions when including direct and indirect emissions. The iron and steel industry has high energy consumption and abundant heat resources, but the utilization rate of waste heat recovery is low, which has a great recovery value. In this aspect, thermal energy storage technologies offer a promising approach for the recovery of massive and intermittent waste heat, which is important for energy saving and emission reduction, as well as a crucial way to realize carbon peak and carbon neutrality in the iron and steel industry. Molten salt used as sensible heat storage is the most widespread solution to improve the concentrating solar power (CSP) plant’s dispatchability, which is also suitable to be implemented into integrated steel works within different configurations, minimizing the operation costs and improving the thermal performance of the associated block. In this study, the first objective is to provide an overview of the distribution and characteristics of waste heat resources in the iron and steel industry. Once this information has been compiled, the second aim is to present the potential of integrating the molten salt thermal energy storage to production process such as iron ore sintering, steel making and by-product gas power generation in integrated steel works. The waste heat of sintering flue gas, converter flue gas and exhaust gas of the combusted by-product gas in boiler is recovered by molten salt and stored in two tanks. Those system configurations are proposed and the stored heat is further transferred to produce steam for power generation. Finally, taking a typical steel plant in China as an example, we investigated the molten salt thermal storage system design for a idle 20MW by-product gas combustion boiler from technical and economic viewpoints. An eight-hour duration thermal storage is achieved by using 1185 ton typical solar salt (60% NaNO₃ + 40% KNO₃), the heat could be released when electricity load is high and peak electricity price is expensive. By implementing four combustion furnaces with molten salt heat exchangers, 69.62 t/h superheated steam under the condition of 540℃ and 14.71 MPa could be generated. The results show that molten-salt thermal energy storage has a lot of advantages. It could not only decrease the bleeding rate of blast furnace gas and increase the power generation capabilities with high parameters, but also provide the ability to realize peak-shaving of power load and economic savings.

Presenting Author: Mingxi Zhou ShanghaiTech University

Presenting Author Biography: Mingxi Zhou received his Ph.D in energy and environment engineering from Zhejiang University in 2018. After graduation, he has worked as a Postdoctoral fellow at the State Key Laboratory of Clean Energy Utilization in Zhejiang University for three years, and worked as a technical staff in Baosteel Co., Ltd. for two years. His research interests include solar tower molten salt power generation, advanced energy storage and high efficient and clean energy utilization.

Authors:

Mingxi Zhou ShanghaiTech University
Ruochen Liu ShanghaiTech University