Feasibility Assessment of an Integrated Pyrolysis-Gasification Process Combined with a Solid Oxide Fuel Cell Towards Electricity and Crude Bio-oil Production

Abstract

The core aim of this study is the process simulation and techno-economic assessment of an integrated process for the co-generation of electricity and crude fuels. The process is based on a renewable energy feedstock (olive kernel residues) and includes the consequent stages of: a) the slow pyrolysis of the olive kernel, b) the (autothermal) gasification of biochar (derived from the slow pyrolysis) to syngas and c) the direct utilisation of the gasification syngas in a solid oxide fuel cell (SOFC) system. Through the additional exploitation of the excess process heat in a two-stage Rankine cycle steam turbine, the integrated system is able to co-generate more than 13.3 GWh and more than 26.8 kt of bio-oil (crude bio-fuel), annually. The combined process was simulated by using Aspen Plus software and was based on the experimental results of a previous study. Regarding the subsequent feasibility assessment, the total fixed capital investment and the total annual operating expenses (annual production costs) were estimated at 35 M€ and 8.2 M€, respectively. Based on these values, it was found that the levelized cost of electricity (LCOE) should range between 0.8 - 0.9 €/kWh in order for the process to be feasible in a 20 y period of operation. Based on a series of energy policies (e.g. variation of olive kernel cost, possibility of EU funding, and cost escalation of the expensive SOFC system), the results revealed that the LCOE can reach values of 0.25-0.6 €/kWh, which can be (potentially) compared with the increasing electricity prices due to the fluctuating conditions with crude oil and natural gas prices worldwide.