Opportunity Issue 106
Opportunity magazine is a niche business-to-business publication that explores various investment opportunities within Southern Africa’s economic sectors. The publication is endorsed by the South African Chamber of Commerce and Industry (SACCI).
Opportunity magazine is a niche business-to-business publication that explores various investment opportunities within Southern Africa’s economic sectors. The publication is endorsed by the South African Chamber of Commerce and Industry (SACCI).
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ENERGY INNOVATION<br />
1D Simulation model of System using Flownex®.<br />
Introducing thermo-chemical heat storage<br />
In this context, a thermo-chemical heat storage system was developed.<br />
The system includes two fixed-bed regenerators that are connected<br />
to the waste hot-air stream of the high-temperature ceramic kilns. This<br />
hot air is diverted through the packed bed reactors for thermal capture<br />
and storage. This is where it gets exciting, as the heat storage material<br />
selected for this project was Zeolite 13X. Zeolites are aluminosilicate<br />
materials which consist of orderly distributed micropores. Zeolites<br />
can store heat in sensible and thermo-chemical form, with the<br />
thermo-chemical heat energy being retained independently of the<br />
temperature of the packed bed. The thermo-chemical storage capacity<br />
within Zeolites is typically four times the usable sensible heat storage<br />
capacity, making this thermal-storage material a highly attractive<br />
option. As reference, using stored thermo-chemical heat alone, just<br />
500g of charged Zeolite 13X is required to heat 100L of water by 1°C.<br />
The application<br />
The regenerators are connected to a drying chamber to use the<br />
stored heat to dry the casting moulds. The team had to design a<br />
low-cost high-temperature ceramic valve to enable cycling between<br />
the charging and discharging of the two storage vessels, so that one<br />
reactor can charge while the other discharges the heat to a drying<br />
chamber. The regenerators were designed to store more than 150kWh<br />
which is sufficient for heating two days’ worth of drying air.<br />
CFD model of packed bed reactor for thermal storage showing<br />
thermal striations.<br />
Benefits and impact<br />
The reuse of waste heat from the kiln significantly reduces the demand<br />
for electrical drying. This not only lowers manufacturing costs, but<br />
also greenhouse gas emissions.<br />
If the Zeolite bed is kept dry, standing losses are theoretically<br />
capped to the sensible-heat portion only, which amounts to a<br />
20% loss no matter how long the heat is stored. This implies that<br />
a major portion of the waste heat can be stored even during<br />
prolonged shutdowns.<br />
Zeolites like these can store heat for much longer with<br />
minimal losses compared to conventional sensible-heat storage<br />
systems, making them ideal for intermittent or batch production<br />
processes. The system not only provides hot-air, but also has<br />
the added advantage of chemically drying the process air. The<br />
steady supply of hot-air with ultra-low moisture content to the<br />
drying chambers significantly increases the control, speed and<br />
repeatability of drying processes.<br />
The performance seen in this pilot implementation at CERadvance<br />
demonstrates the tremendous potential of thermo-chemical<br />
heat storage systems. By capturing waste heat and optimising<br />
its utilisation, businesses can unlock substantial economic and<br />
environmental benefits.<br />
Contact the CSIR to explore how these technologies can propel<br />
your business forward.<br />
Authors:<br />
Tobias van Reenen: tvreenen@csir.co.za<br />
Muhammad Sheik: msheik@csir.co.za<br />
Packed bed reactors for thermal capture and storage.
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