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Author
Chela Roldán, Andrés
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Abstract
In the context of climate change, there is an increasing effort to reduce the emissions of high global warming potential (GWP) gases. The impact of fluorinated greenhouse gases (GHG) plays an important role, due to their high GWP. While the substitution of these substances is not an easy task, due to their unique properties for refrigeration, the recent Kigali Amendment to Montreal protocol, along with the strict European legislations, has driven to the study of alternatives regarding the end of F-gases lifecycle. Contemporary techniques, apart from being energy-intensive, imply a null recovery of the gas for its posterior usage.
This thesis explores the possibility of recovering the moderate-GWP gas difluoromethane (R32) from the common high-GWP blend R410A, an equimassic mixture of R32 and R125. R32 is not restricted to the new legislations, and has a very promising potential regarding the manufacturing of new refrigerant blends in combination with hydrofluoroolefins (HFOs).
In the framework of the European KET4F-Gas project, a new separation technique, based on the adsorption of F-gases in the activated carbon Anguard 5 has been modeled using new experimental data through the Aspen Adsorption® simulation tool.
Pure component isothermal data of R32 and R125 have been adjusted to fit a multi-temperature Langmuir-Freundlich isotherm model. Then, the IAST method has been performed to simulate the behavior of the R410A blend in Anguard 5. A mathematical model has been built in the software to validate experimental breakthrough curves data with a LDF mass transfer model. The created model is able to accurately reproduce the behavior of the process, facilitating the future scaling to higher productions.
The main process parameters of a new prototype designed in the context of the project have been determined by using the mathematical model developed in Aspen Adsorption. The feasibility of a continuous adsorption cycle with nitrogen entrainment has been determined by means of a process sensitivity analysis, allowing to establish the ranges of purity and recovery. Based on the results, an alternative discontinuous production cycle has been designed, at room temperature and atmospheric pressure, recirculating the regeneration stream. The redesigned process ensures a full recovery of high purity R32 at a low energy cost.
Finally, the economic viability of the process has been calculated by taking into account the capital and operational costs of the prototype.
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