Avdelningen för Energi & material
Institutionen för Kemi och kemiteknik, Chalmers tekniska högskola
Growing energy demand worldwide has been coupled with increasing levels of fossil-CO2 emissions into the atmosphere. In order to decrease the dependency on fossil fuel and at the same time decrease the consequently emitted greenhouse gases, alternative fuels are introduced. Among the existing alternatives, biomass is considered the only one with potential to replace the fossil fuel mix used nowadays.
Gasification in fluidized bed reactors has proven to be the most energy efficient technology for thermal conversion of biomass. One of the challenges that the gasification process faces are the tars formed during the process which condense on the equipment walls and can cause costly unplanned stops. Tars is a common notation used for the complex mixture of condensable hydrocarbons, most often containing aromatic rings. If tars can be converted to CO and H2 which are the desired components of the product gas formed during gasification, the problem with tar condensation on the equipment walls would be solved. At the same time as the condensation risk is lowered, the produced gas would increase in calorific value as the chemical energy stored in the tars would be added to that of the product gas.
The most successful way used nowadays is catalytic tar conversion. The easiest way of introducing a catalyst into the system is by utilizing the bed material. As potassium has shown activity towards tar cracking, a potassium mineral, feldspar, has found recent attention. Experiments conducted in the Chalmers gasifier have shown decrease in tar levels when feldspar was applied together with additives such as calcium.
In-depth analysis of the used particles needs to be done to understand the mechanism why the particles are at certain stages of the experiment. By doing so, tailor-making catalytically active particles which are specialized for different reactor conditions would be possible.
In the proposed project, students will characterize materials sampled after biomass ash additives which have shown potential as catalysts have been introduced into GoBiGas and in the Chalmers gasifier. Based on the results from the characterized materials, design of laboratory experiments that confirm the effect of the additives will be performed.
The goal is to understand which additives have the ability to enhance the bed material and eventually have the potential to trigger complete tar conversion.
Genomförande /Viktiga moment/teknikinnehåll
Material characterization of sampled materials (Electron microscopy - SEM-EDX, X-ray diffraction - XRD, Atomic absorption - AAS, IR- spectroscopy - FTIR), followed by literature research. Design and performance of own experiments.
Speciella förkunskapskrav: Basic chemistry knowledge
Möjlig målgrupp: Kemi och Kemiteknik, Bioteknologi
Gruppstorlek: 4-6 studenter
Förslagsställare/kontaktperson/huvudhandledare: Pavleta Knutsson
Övriga handledare: Robin Faust
Ev. förslag på examinator: Britt-Marie Steenari