Fluidized bed co-gasification of algae and wood pellets: gas yields and bed agglomeration analysis
2016 (English)In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 30, no 3, 1800-1809 p.Article in journal (Refereed) PublishedText
Algae utilization in energy production has gained increasing attention as a result of its characteristics, such as high productivity, rapid growth rate, and flexible cultivation environment. In this paper, three species of algae, including a fresh water macroalgae, Oedogonium sp., a saltwater macroalgae, Derbersia tenuissima, and a microalgae species, Scenedesmus sp., were studied to explore the potential of using smaller amounts of algae fuels in blends with traditional woody biomasses in the gasification processes. Co-gasification of 10 wt % algae and 90 wt % Swedish wood pellets was performed in a fluidized bed reactor. The effects of algae addition on the syngas yield and carbon conversion rate were investigated. The addition of 10 wt % algae in wood increased the CO, H2, and CH4 yields by 3–20, 6–31, and 9–20%, respectively. At the same time, it decreased the CO2 yield by 3–18%. The carbon conversion rates were slightly increased with the addition of 10 wt % macroalgae in wood, but the microalgae addition resulted in a decrease of the carbon conversion rate by 8%. Meanwhile, the collected fly ash and bed material samples were analyzed using scanning electron microscopy combined with an energy-dispersive X-ray detector (SEM–EDX) and X-ray diffraction (XRD) technique. The fly ashes of wood/marcoalgae tests showed a higher Na content with lower Si and Ca contents compared to the wood test. The gasification tests were scheduled to last 4 h; however, only wood and wood/Derbersia gasification experiments were carried out without significant operational problems. The gasification of 10 wt % Oedogonium N+ and Oedogonium N– led to defluidization of the bed in less than 1 h, and the wood/Scenedesmus (WD/SA) test was stopped after 1.8 h as a result of severe agglomeration. It was found that the algae addition had a remarkable influence on the characteristics and compositions of the coating layer. The coating layer formation and bed agglomeration mechanism of wood/macroalgae was initiated by the reaction of alkali compounds with the bed particles to form low-temperature melting silicates (inner layer). For the WD/SA test, the agglomeration was influenced by both the composition of the original algae fuel as well as the external mineral contaminations. In summary, the operational problems experienced during the co-gasification tests of different algae–wood mixtures were assigned to the specific ash compositions of the different fuel mixtures. This showed the need for countermeasures, specifically to balance the high alkali content, to reach stable operation in a fluidized bed gasifier.
Place, publisher, year, edition, pages
American Chemical Society (ACS), 2016. Vol. 30, no 3, 1800-1809 p.
IdentifiersURN: urn:nbn:se:umu:diva-112688DOI: 10.1021/acs.energyfuels.5b02291ISI: 000372562800029ScopusID: 2-s2.0-84961844576OAI: oai:DiVA.org:umu-112688DiVA: diva2:882164
Youjian Zhu is grateful for the financial support of the China Scholarship Council (CSC) and the Project of Excellent Scientist Fund in Henan (Project 12410051002). The financial support of J. Gust. Richert stiftelse is also appreciated. This research was supported by the Gasification of Algae: Swedish–Australian Research Platform (GASAR) Project funded through the Swedish Foundation for International Cooperation in Research and Higher Education (STINT), the Swedish Strategic Research Program Bio4Energy, Australian Research Council’s Linkage Projects Funding Scheme (Project LP100200616) with our industry partner SQC Pty Ltd, the Australian Government through the Australian Renewable Energy Agency (ARENA), and the Advanced Manufacturing Cooperative Research Centre (AMCRC), funded through Australian Government’s Cooperative Research Centre Scheme. Francesco G. Gentili greatly appreciates the financial support of the Swedish Energy Agency. The authors also acknowledge the support of Muradel Pty Ltd and MBD Energy. Daniel Lane at the University of Adelaide is acknowledged for help during the initial feeding tests. Dr. Britt Andersson at Umeå University is acknowledged for help during SEM/EDX analyses. Dr. Marie Magnusson at James Cook University is acknowledged for the culture and supply of algal pellets.2015-12-142015-12-142016-08-15Bibliographically approved