Increasing the efficiency of chemical looping combustion of biomass by a dual-stage fuel reactor design to reduce carbon
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Increasing the efficiency of chemical looping combustion of biomass by a dual-stage fuel reactor design to reduce carbon capture costs Johannes Haus 1 & Lennard Lindmüller 1 & Timo Dymala 1 & Kolja Jarolin 1 & Yi Feng 2 & Ernst-Ulrich Hartge 1 & Stefan Heinrich 1 & Joachim Werther 1 Received: 13 August 2018 / Accepted: 28 May 2020/ # Springer Nature B.V. 2020
Abstract
This paper analyzes the capabilities of a pilot-scale chemical looping combustion plant firing wood biomass in two stages to efficiently achieve negative carbon dioxide emissions. The utilized in situ gasification-chemical looping combustion (iG-CLC) process isolates the oxygen supply via air from the fuel conversion itself with the help of two separate fluidized bed reactors and an oxygen carrier to supply the necessary oxygen for the combustion. As a result, a relatively pure stream of carbon dioxide and steam is generated. Thus, the process makes capturing carbon emissions more feasible since it eliminates the need for the cost- and energy-intensive separation of the produced gases. A major issue when using biomass in a chemical looping plant is the high amount of the volatiles exiting unconverted. This problem was mitigated by using a two-stage fuel reactor system. Two bubbling fluidized beds were arranged one upon the other. The lower stage, where the fuel is introduced, is used to release the volatiles and partly convert them. The remaining volatiles rise up into the second stage and are further converted to a high degree. A series of experiments were carried out with a 25-kWth pilot plant located at the Hamburg University of Technology. Gas concentrations were continuously measured after both stages of the fuel reactor to see the gradual conversion of the fuel gases. Additionally, carbon slip at the exhaust was measured to show the effectiveness. The experiments with the reactor concept showed promising results since already at a reactor temperature of 850 °C, the total oxygen demand needed to oxidize the combustible component in the exhaust gas was well below 2%. The carbon dioxide (CO2) capture efficiency when using German hardwood slightly decreased to 93–96% compared to 97% for German lignite. In the future, the reactor design must prove that it scales and that the efficiency can be further increased. Nevertheless, firing biomass with a two-stage iG-CLC process might allow a costefficient negative carbon dioxide emission while generating heat with relatively high efficiency. Therefore, it might be a sustainable alternative to generate heat in the future. Ernst-Ulrich Hartge is deceased.
* Timo Dymala [email protected] Extended author information available on the last page of the article
Mitigation and Adaptation Strategies for Global Change
Keywords Chemical looping combustion (CLC) . Bioenergy carbon capture and storage (BECCS) . Biomass conversion . Negative CO2 emissions . Fluidized bed
1 Introduction According to the Paris Agreement (United Nations 2015), the global temperature rise during this century shall be restricted to be
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