Developing a Tool for Techno-Economic Analysis of Pulp Mill Integrated Biorefineries
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Teknistaloudellisen kannattavuuslaskentatyökalun suunnittelu sellutehtaaseen integroitaville bioteknologioille
A kraft pulp mill forms an attractive platform for integrated biorefining due to the availability of biomass residues and access to low cost process heat. Integrating a biorefinery to a pulp mill aims to improve the overall efficiency of raw material utilization and to offer new revenue opportunities besides pulp production. Because the field of pulp mill integrated biorefining is still relatively unexplored, it is necessary to develop methods for assessing the feasibility of alternative technologies. The purpose of this thesis project was to design a techno-economic analysis tool (TEA-tool) for Valmet’s offering of pulp mill integrated biorefineries. The tool was intended to evaluate the feasibility of four different biorefinery processes from the customer point of view. The general motivation for building the tool was to improve the accessibility of techno-economical methods for users with different backgrounds and to provide an unbiased profitability model for cross-technology comparisons. The biotechnologies included in the tool were lignin extraction from black liquor by LignoBoost, black pellet production by steam explosion, bark gasification and bio oil production by integrated fast pyrolysis. The thesis project consisted of building the tool and performing a rough feasibility comparison between the included technologies. The priority task of developing the TEA-tool succeeded well, receiving a positive overall reception. The tool allowed quick and effortless comparison between the technologies in a wide range of investment scenarios. The new TEA-tool will offer a flexible platform for Valmet’s future techno-economic evaluations. In general, the analysis boosted confidence on the economic potential of biorefining. The profitability model was discovered being the most sensitive to production capacities, end product values and substitute fuel prices. The selection of process parameters and feedstock properties had significantly lower impact on the profitability estimates. From the four biotechnology alternatives, LignoBoost and gasification processes were observed being the most profitable investments. The steam explosion process was shown to be competent with these technologies, but would require large production capacities to reach the same level of returns. The integrated pyrolysis process was shown to be theoretically highly profitable in favourable operating conditions. However, the incompleteness of bio oil markets slightly lowers the attractiveness of the particular pyrolysis process. Distributing the produced bio oil to multiple mill sites would reduce the dependency on external markets.