Application of Phase Change Material for Improved Energy Efficiency in Waste-to-Energy plants
Supported by: National Environmental Agency, 2017-2019
Researchers (visit the PEOPLE webpage for more infos)
Assoc. Prof. Alessandro Romagnoli, PI
Dr. Yvonne Lin, Co-PI
Miss. Haoxin Xu, PhD student
Dr. Fabio Dal Magro, Collaborator
Final achievement and status of the project
The project successfully demonstrated the buffering effects of the PCM brick technology as well as the ability to increase the steam parameter when superheated.
The project delivered a TRL 3 proof of concept (with initial lab demonstration) and it now intends to seek funding and collaboration opportunities to push the TRL from 3 to 6/7.
Description of the project
In current WtE plants, heat recovery of thermal power generated during combustion process is completely carried out by traditional steam generation boilers, which is usually composed by water-walls (i.e. radiant evaporators), evaporators, economizers and superheaters.
Although being well established, this configuration of WtE plants is subjected to a few technical limitations such as:
The limits on the maximum steam temperature, due to corrosion occurring at high metal surface temperature;
The fluctuation in steam production, due to non-homogeneous composition of waste.
These technical limitations affect the maximum net electrical efficiency achievable and the proposed project intends to offer a novel solution to solve them. In this project, we replace the existing water-wall technology with a PCM-based brick that is capable of storing a variable heat flux coming from a high temperature heat source (i.e. incineration chamber) and releasing it on demand as a steady heat flux. The proposed PCM-based brick exploits the working principle of thermal energy storage based on latent heat. This kind of heat storage system stores or releases latent heat when a PCM undergoes a phase transition from solid to liquid, or vice versa. The storage and release of heat occurs at the phase transition temperature of the PCM which can be considered to be constant. This technique for heat storage allows designing thermal energy storage systems with a high energy density capable of storing heat at high temperature (>300°C).
The proposed solution consists of replacing the typical refractory brick installed in the combustion chamber with a PCM-based refractory brick capable of storing a variable heat flux and to release it on demand as a steady heat flux. By means of this technology it is possible to mitigate steam production fluctuation, to increase temperature of superheated steam over current corrosion limits (450°C) without using coated superheaters and to increase the electrical efficiency beyond 34%.