Contents lists available at ScienceDirect Applied Energy journal homepage: www.elsevier.com/locate/apenergy Influence of controlled handling of solid inorganic materials and design changes on the product gas quality in dual fluid bed gasification of woody biomass Matthias Kuba a, ⁎ , Stephan Kraft a , Friedrich Kirnbauer a , Frank Maierhans c , Hermann Hofbauer b a Bioenergy 2020+ GmbH, Wiener Straße 49, A-7540 Güssing, Austria b TU Wien, Institute of Chemical, Environmental and Biological Engineering, Getreidemarkt 9/166, 1060 Vienna, Austria c HGA Senden, SWU Energie GmbH, Karlstraße 1, 89073 Ulm, Germany HIGHLIGHTS • Optimization of an industrial-scale dual fluidized bed gasification plant. • Design changes improving the fluidization lead to reduction of biomass tars in the product gas. • Recirculation of layered olivine particles leads to higher catalytic activity of the bed material. • A state-of-the art operation of industrial-scale dual fluidized bed gasification could be established. ARTICLE INFO Keywords: Gasification Inorganic material Bed material Dual fluidized bed Biomass tars ABSTRACT Utilizing biomass feedstock in thermal conversion technologies to reduce greenhouse gas emissions is a pro- mising way to substitute for fossil fuels. Gasification of biomass allows for the production of electricity, district heat, high-grade fuels for transportation and synthetic chemicals. Investigations at the HGA Senden industrial- scale dual fluidized bed gasification power plant have shown the potential for improving gas quality by the controlled handling of solid inorganic materials in the reactor. Two measures for optimization were im- plemented and investigated on-site. First, improving the bed material and ash loops in the system led to sig- nificant reduction of undesirable tars in the product gas. This was based on reutilizing used, layered, olivine particles with higher catalytic activity compared to that of fresh olivine. Second, improving the mixing of feedstock or char particles with catalytically active bed material in the gasification reactor, and also ensuring steam, as reaction medium, was available local to the area of the fuel input, led to further decrease of tars in the product gas. This was achieved by incorporating additional fluidization nozzles in the gasification reactor. In summary, the optimization measures for controlled handling of inorganic materials had a major influence on the product gas quality in the dual fluidized bed gasification of biomass. As a consequence, long-term op- eration at significantly higher capacity than before could be achieved at the HGA Senden industrial-scale power plant. 1. Introduction Climate change has led to strategies aiming to mitigate the increase in global average temperature. Reducing the emissions of CO 2 has been set as one of the main goals [1]. Transforming the energy supply from fossil to renewable sources is indispensable in this regard. A mix of technologies using different renewable energy sources is necessary to achieve this goal and to reduce the immense natural and social de- vastation caused by global warming [2,3]. Biomass, as feedstock for thermal conversion processes, such as pyrolysis, gasification or combustion, has the potential to play a major role in the future energy mix. Biomass is a renewable energy source that can be utilized in a wide spectrum of applications [4,5]. Utilization of biomass in thermal conversion can, for example, contribute to the generation of electricity as a net stabilizer, as biomass can be under- stood as stored energy with high energy density. On the other hand, biomass is the only renewable source of carbon that can be accessed easily [6]. Thus, conversion of biomass into a gaseous secondary energy https://doi.org/10.1016/j.apenergy.2017.11.028 Received 5 July 2017; Received in revised form 21 October 2017; Accepted 3 November 2017 ⁎ Corresponding author. E-mail address: matthias.kuba@bioenergy2020.eu (M. Kuba). Applied Energy 210 (2018) 230–240 0306-2619/ © 2017 Elsevier Ltd. All rights reserved. MARK