Bewertung von Syntheserouten auf Basis von Exergiebilanzen

• Evaluation of synthesis pathways based on exergy balances

Frenzel, Philipp; Pfennig, A. (Thesis advisor); Hillerbrand, R. (Thesis advisor); Bardow, André (Thesis advisor)

1. Aufl.. - Aachen : Apprimus Verlag (2015)
Book, Dissertation / PhD Thesis

Zugl.: Aachen, Techn. Hochsch., Diss., 2014

Abstract

The vast majority of chemical products is based on crude oil. On the one hand, crude oil is a limited resource, whose depletion will be more expensive and riskier in the future. On the other hand, using fossil raw materials is at last associated with carbon dioxide emissions. Anthropogenic emissions of greenhouse gases like carbon dioxide are responsible for the global climate change. An alternative carbon source is biomass. In contrast to crude oil, biomass is a renewable resource and it has functional groups fossil raw materials do not have. These can be used for synthesis. Therefore, biomass is an attractive feedstock for carbon based synthesis pathways.With a few exceptions, the development of bio-based synthesis pathways is currently only at the beginning. Therefore, it is interesting to know which bio-based synthesis pathways promise a high economic potential for managing research and development efforts reasonably. Due to the early stage of development of these routes, only little information about their prospective chemical processes is available. For an evaluation of such synthesis pathways - independent of the kind of feedstock -, a combination of material and exergy balances is suitable and applied in this thesis. Compared to energy balances, exergy balances have the advantage that a comparison of the quality of different forms of energy is possible, whereby the significance of the results increases.In this thesis, different approaches and structures of synthesis pathways characterised by the chemical exergy of the main components are thermodynamically evaluated and general recommendations for future bio-based synthesis pathways are derived. The examinations have shown that, from an exergetical point of view, synthesis pathways are favorable if the chemical exergy of their main components are relatively similar. Due to the high oxygen content of biomass, the chemical exergy is low compared to crude-oil. Using biomass as feedstock synthesis pathways leading to end products with a high oxygen content are promising to have low exergy losses. For a complete raw material change towards biomass, agricultural land is required to produce biomass. Because of a rising world population and a general increasing demand for agricultural products, agricultural land is a scarce resource. Thus, in this thesis the land use required for a complete raw material change is estimated under various boundary conditions. It has been shown that the structure of synthesis pathways that promise low exergy losses have a low land use as well. Since both exergy losses and land use is low, new end products with a high oxygen content and corresponding synthesis pathways should be developed if biomass is used as feedstock.