DESC0023883

Every year, US production of steel and aluminum accounts for more than 350 TBtu of process heating losses representing more than 2% of the total yearly process energy use in the United States. Recovering some of this waste heat presents a significant opportunity for reducing energy use in this particularly energy intensive industry. Historically, there have been numerous financial and technological challenges with collecting and reusing this energy but with the cost of energy rising and the advent of new manufacturing processes for high temperature materials, implementation of novel waste heat recovery systems is becoming more appealing for emission and cost reduction. By including thermal energy storage as part of the waste heat recovery system, heat energy can be transportable and therefore more useful in plant thermal optimization through pinch analysis of hot and cold streams.This program will address the need for high-temperature heat exchangers for industrial waste heat recovery and storage by developing an additively manufactured heat exchanger to work with reclaimed coal ash as a low-cost thermal energy storage material. The objective of the Phase I program is to integrate these two technology platforms to provide a waste heat recovery with thermal energy storage system for steelmaking furnace exhaust gases up to 870°C such as: reheat furnaces; ladle or tundish heaters; or pre-cleaned exhaust from electric arc furnaces.In the proposed program, heat exchanger designs will be generated and prototypes fabricated out of high temperature materials. The program will conclude with a laboratory demonstration of high temperature heat transfer from an exhaust gas stream to a volume of thermal energy storage particles.The applications for the additively-manufactured heat exchanger technology include regenerative heat exchangers, condensers, component cooling, and letdown heat exchangers. The design is not a one-size-fits-all scheme, but instead the general design architecture is readily tailored to purpose. This modularity is due to the parametric design, which allows capacity rate matching between streams, geometric flexibility, and different flow mediums (for example steam, liquid metal, CO2, or molten salt and water). As a heat exchanger for particle-based thermal energy storage, this design and fabrication flexibility means that devices can be scaled and optimized for every specific application without substantial re-engineering costs. This optimization improves overall system efficiency and, by extension, cost-effectiveness.