Fluidized bed co-gasification of algae and wood pellets: gas yields and bed agglomeration analysis

Zhu, Youjian, Piotrowska, Patrycja, van Eyk, Philip J., Bostrom, Dan, Wu, Xuehong, Boman, Christoffer, Brostrom, Markus, Zhang, Jun, Kwong, Chi Wai, Wang, Dingbiao, Cole, Andrew J., de Nys, Rocky, Gentili, Francesco G., and Ashman, Peter J. (2016) Fluidized bed co-gasification of algae and wood pellets: gas yields and bed agglomeration analysis. Energy and Fuels, 30 (3). pp. 1800-1809.

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Abstract

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, H-2, 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.

Item ID: 44052
Item Type: Article (Research - C1)
ISSN: 0887-0624
Additional Information:

5th Sino-Australian Symposium on Advanced Coal and Biomass Utilisation Technologies

Funders: China Scholarship Council (CSC), Swedish Foundation for International Cooperation in Research and Higher Education (STINT), Swedish Strategic Research Program Bio4Energy, Australian Research Council (ARC), Australian Renewable Energy Agency (ARENA), Advanced Manufacturing Cooperative Research Centre (AMCRC), Swedish Energy Agency, Muradel Pty Ltd, MBD Energy
Projects and Grants: Project of Excellent Scientist Fund in Henan (Project 12410051002), STINT Gasification of Algae: Swedish − Australian Research Platform (GASAR) Project, ARC Linkage grant LP100200616
Date Deposited: 20 Apr 2016 07:46
FoR Codes: 07 AGRICULTURAL AND VETERINARY SCIENCES > 0704 Fisheries Sciences > 070401 Aquaculture @ 50%
10 TECHNOLOGY > 1003 Industrial Biotechnology > 100302 Bioprocessing, Bioproduction and Bioproducts @ 50%
SEO Codes: 96 ENVIRONMENT > 9609 Land and Water Management > 960912 Urban and Industrial Water Management @ 50%
85 ENERGY > 8505 Renewable Energy > 850501 Biofuel (Biomass) Energy @ 50%
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