Production and application of sustainable metallurgical biochar pellets
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Original versionRiva, L. (2020). Production and application of sustainable metallurgical biochar pellets (Doctoral thesis). University of Agder, Kristiansand.
The effective decarbonization of our society must be boosted through the promotion of efficient alternatives to fossil fuels. This transition should take place gradually, involving a broad range of actors and technologies. The challenge is often merely perceived as the socalled green switch in producing electricity and heat. However, certain industrial branches are dependent on fossil fuels for their physio-chemical characteristics and less as fuel. For instance, the metallurgical industry (e.g. steel, silicon and manganese production) traditionally requires fossil coal and coke (thermally treated coal) as reducing agent in the reactions required to purify the metal ores. Unless going through a dramatic change in the technological process, the carbon neutrality of these systems must be reached finding a similar but renewable material. In this regard, biochar, a coal-like product of a thermal conversion of woody biomass, has been targeted as promising solution. Unfortunately, there are several barriers, which obstructs the utilization. Among them, the market price and the mechanical weakness are worth to be mentioned. In the following thesis, a method to improve the mechanical properties of biochar was developed and investigated. The method is based on the combination of pyrolysis with a consequent densification, with recovery of pyrolysis oil as binder and a further heat treatment. Besides, the economy of the process was addressed. This was done by trying to minimize the cost through a smart recovery of the byproducts and wastes. Whenever possible, the developed system was designed according to the Norwegian scenario, considering local feedstock and application. Throughout the thesis, the novel method was deeply investigated and optimized both in terms of quality of the final product and feasibility of the process. Some post-production related issues, which may limit the industrial diffusion, were pointed out and a solution was attempted. Finally, the sustainability of the process was studied. The results provided useful information about the suggested process and the related key-parameters. The novel knowledge may be used to produce fossil fuels-competitive and sustainable biochar materials and, hence, foster the renewable transition in the metallurgical industry.
Has partsPaper I: Riva, L., Surup, G. R., Buø, T. V. & Nielsen, H. K. (2019). A study of densified biochar as carbon source in the silicon and ferrosilicon production. Energy, 181, 985-996. doi: http://dx.doi.org/10.1016/j.energy.2019.06.013. Published version. Full-text is available in AURA as a separate file: http://hdl.handle.net/11250/2637238.
Paper II: Riva, L., Nielsen, H. K., Skreiberg, Ø., Wang, L., Bartocci, P., Barbanera, M., Bidini, G. & Fantozzi, F. (2019). Analysis of optimal temperature, pressure and binder quantity for the production of biocarbon pellet to be used as a substitute for coke. Applied Energy, 256: 113933. doi: http://dx.doi.org/10.1016/j.apenergy.2019.113933. Published version. Full-text is available in AURA as a separate file: https://hdl.handle.net/11250/2648997.
Paper III: Riva, L., Wang, L., Ravenni, G., Bartocci, P., Buø, T. V., Skreiberg, Ø, Fantozzi, F. & Nielsen, H. K. (Forthcoming). Considerations on factors affecting biochar densification behavior based on a multiparameter model. Energy. Author´s submitted manuscript. Full-text is not available in AURA as a separate file.
Paper IV: Riva, L., Cardarelli, A., Andersen, G. J., Buø, T. V., Barbanera, M., Bartocci, P., Fantozzi, F., Nielsen, H. K. (2020). On the self-heating behavior of upgraded biochar pellets blended with pyrolysis oil: effects of process parameters. Fuel, 278: 118395. doi: https://doi.org/10.1016/j.fuel.2020.118395. Published version. Full-text is available in AURA as a separate file: .
Paper V: Bartocci, P., Riva, L., Nielsen, H. K., Yang, Q., Yang, H., Skreiberg, Ø., Wang, L., Sorbini, G., Gul, E., Barbanera, M. & Fantozzi, F. (2020). How to produce green coke? Applied Energy Symposium. Author´s accepted manuscript. Full-text is not available in AURA as a separate file.