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In the recent years, the demand of proDuction for energy, chemicals and transportation has seen a tremendous expansion related to a better standard living. This increase has been possible through scientific expand like technical chemistry or chemical process engineering.
Aromatic and poly-aromatic compounds are important components of fuels. They are also formed in pyrolysis reactions and in fuel rich regions of flames and other thermal systems, where they are considered important precursors and intermediates in soot and PAH formation. The decomposition products of these species in combustion and oxidation reactions involve the incorporation of oxygen through reactions with oxygenated radicals and with molecular oxygen forming species like hydroperoxides or unsaturated oxy-hydrocarbon.
Despite all the progress being made, the uncontrolled production unavoidably leads to environmental problems such as climate change or emission of toxic products (CO2, dioxins...). Because of the scarcity of experimental data, computational methods need to be employed to predict molecular properties for the species and to gain a better understanding of the formation mechanism of these systems as well as the reaction pathways.
Computational Quantum Chemistry (ab inito and DFT calculations) is used in the estimation of the thermochemical properties (enthalpy of formation, bond energies, standard entropy and heat capacity data as a function of temperature) and kinetic parameters of small and large species, including biochemicals, large aromatic intermediates in soot formation, carbon nanotubes and many other systems. These data serves the modeling communities in the area of atmospheric chemistry, combustion, industrial processes.
Within this research focus in the past the following research projects were associated:
PEGASUS will investigate a novel power cycle for renewable electricity production combining a solar centrifugal particle receiver with a sulphur storage system for baseload operation. The proposed process combines streams of solid particles as heat transfer fluid that can also be used for direct thermal energy storage, with indirect thermochemical storage of solar energy in solid sulphur, rendering thus a solar power plant capable of round-the-clock renewable electricity production.
Process scheme of the solar sulphur cycle / Image source: DLR
The overall objective of PEGASUS is the development and demonstration of an innovative solar tower system based on solid particles combined with a novel thermochemical solar energy storage technology based on elemental sulphur, to achieve dispatchable and firm renewable electricity generation with a significant cost reduction with respect to current state-of-the-art concepts. The technology will be validated under real on- sun concentrated solar irradiation in the Solar Tower Jülich (STJ) thermal plant in Germany owned by the Project Coordinator, DLR.
In this perspective, the project’s specific Technical Objectives of KIT are:
More information is published in a press-release of KIT and on the public website of the project (link below)
It has been shown that the commonly used surface radiation models without consideration of chemical reaction (combustion models) and without turbulence and soot formation models have to be re-considered. Instead, fluid dynamically driven coherent structures and CFD simulations of interacting fires have to be considered using the above mentioned sub models which partly have to be developed.
In particular, the knowledge about the interaction phenomena between two or even more pool fires will be investigated both, experimentally and numerically using CFD simulations. Additionally the knowledge about the length of the so-called clear combustion zone, which is not covered by black sooting regions, has to be deepened. Also the knowledge on the specific radiation (SEP) of single and interacting black sooting fires needs to be extended.
Of high importance and a pre-requisite for success of the above mentioned goals the knowledge on the elementary chemical reactions in peroxide pool flames has to be deepened, especially with respect to soot formation in such hydro-carbon pool flames. For this, mechanisms of soot formation will be improved and reaction mechanisms for the combustion of organic peroxides will be developed and integrated into CFD tools. Such tools can be flamelet models, which will be used int the present research work.