Strategies for Complete Recovery of Carbon in Dual Fluidized Bed Gasifiers
Doctoral thesis, 2021

To establish a circular economy and curtail our dependency on fossil resources, technologies are needed to extract carbon from biomass and plastic waste. Dual fluidized bed (DFB) gasification is a carbon-extracting technology that offers flexibility in terms of its inputs, outputs, design, and operational conditions. This thesis investigates the carbon distribution produced by DFB gasification and explores the possibilities to achieve total carbon recovery. The various configurations under which DFB gasification can be designed and operated to facilitate the total recovery of carbon are compared on a theoretical basis. Thus, insights into the carbon distribution and energy demands of each configuration are obtained. A method to increase the catalytic activity of the bed in the DFB gasifier so as to enhance the recovery of valuable forms of carbon is experimentally demonstrated, based on the use of a waste generated from the process. However, it is shown that increasing the catalytic activity is not always beneficial for carbon recovery. The development of oxygen transport along with the catalytic activity, a phenomenon that had been reported but never investigated, is here demonstrated. Taking advantage of the oxygen transport properties of certain bed materials to facilitate the total recovery of carbon is the basis for the chemical-looping gasification (CLG) technology, a DFB gasification configuration. The parameters that affect fuel conversion, an essential aspect of CLG, are investigated for a plastic waste that generates its own oxygen-carrying bed material. Oxygen transport is shown to be the most important parameter for the process. Based on these experiments, the numerous challenges associated with CLG are discussed. Finally, a process through which negative-emissions steel is produced, based on the integration of DFB gasification into a CLG configuration with direct reduction (DR) of iron, is proposed and evaluated. Compared with the traditional steelmaking route and alternative DR routes, the proposed process is found to be the most-competitive for carbon prices >60 €/tCO2, which corresponds to both the price for CO2 emissions and the revenue associated with negative emissions. Most of the data used in this work were obtained from experiments conducted at a scale relevant to the industry.

circular economy

chemical-looping

carbon

gasification

waste

dual fluidized bed

Opponent: Dr. Weihong Yang, Materials Science and Engineering, KTH Royal Institute of Technology

Author

Sébastien Pissot

Chalmers, Space, Earth and Environment, Energy Technology, Energy Technology 2

Many everyday products, most notably plastics, are made of carbon that is extracted from fossil resources. To establish a sustainable society, we must end our reliance on fossil resources. Therefore, new carbon sources, predominantly biomass and plastic waste, must be used and new technologies to extract carbon from these sources must be developed. Dual fluidized bed (DFB) gasification is a carbon-extraction technology that can convert a wide range of carbon sources into a gas from which various carbon products can be manufactured. This thesis investigates how the carbon is distributed into the various outputs of the DFB gasifier, and explores possibilities to adjust this distribution to recover as much of the carbon as possible in high-value forms, while minimizing CO2 emissions. This work emphasizes the use of waste materials in the DFB gasification process, to extend further the sustainability of this technology. Finally, a process for the production of sustainable steel that uses the DFB gasification technology is proposed and evaluated. The data used in this thesis were obtained mainly from experiments carried out at a scale relevant to the industry. This work strengthens the position and potential of DFB gasification as a carbon-extraction technology in the future society and extends its potential beyond the production of carbon-based products.

FerroSilva – production of sponge iron using biogenic reduction gas

Swedish Energy Agency (51220-1), 2021-04-01 -- 2022-09-30.

Swedish Centre for Biomass Gasification Phase 3

Swedish Energy Agency (P34721-3), 2017-04-20 -- 2021-12-31.

Driving Forces

Sustainable development

Areas of Advance

Energy

Subject Categories

Chemical Process Engineering

Infrastructure

Chalmers Power Central

ISBN

978-91-7905-545-5

Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5012

Publisher

Chalmers University of Technology

Online

Opponent: Dr. Weihong Yang, Materials Science and Engineering, KTH Royal Institute of Technology

More information

Latest update

8/31/2021