流體化床具有下列優點：高熱傳率、高效率、低污染物排放、低燃燒溫度以及燃料選擇限制較低等，並且已廣泛應用在工業及發電廠上。雙流體化床氣化爐是採用快速內循環流體化床之概念來設計，快速內循環流體化床是將流體化床分為氣化流體化床區以及燃燒流體化床區，在這兩個區域間藉由固體粒子之流動來形成一循環迴路，由於在氣化流體化床區只注入水蒸汽進行氣化反應，因此能在氣化流體化床區中得到近乎沒有氮氣之合成氣。
本研究以計算流體力學軟體ANSYS-FLUENT來進行模擬，針對雙流體化床氣化爐分別建立二維及三維多相反應流模擬分析模型，以生質燃料作為進料，並與參考文獻進行比對。在二維雙流體化床模型進行蒸汽燃料比及溫度之參數分析。在氣化模擬結果方面，固定蒸汽流量、增加燃料流量使得蒸汽燃料比下降，合成氣中之氫氣、一氧化碳和二氧化碳之含量皆上升；在溫度方面，當進入氣化爐之床砂溫度上升時一氧化碳與二氧化碳之比例也會隨之增加。在三維模型中，已成功建立床砂於雙流體化床氣化爐內之循環模式，能預測床砂之移動路徑，並將內部流場可視化，能觀察到氣體成份分佈、反應區域大小等等。模擬結果之出口合成氣體與參考文獻進行比對，模擬之二氧化碳及氫氣之含量是高於實驗值，而一氧化碳之含量則是低估，甲烷之含量則與實驗近似，此一結果推測是因為水氣轉化反應速率與實驗相比高估所致。

A fluidized-bed gasifier is characterized by the merits of high thermal conductivity, high efficiency, low pollutant emissions, and fewer fuel selection limitations. It is widely used in industries and power plants. A dual fluidized-bed gasifier was designed according to the FICFB (Fast Internal Circulating Fluidized Bed) concept, which includes two zones: the gasification zone and the combustion zone. The two zones are linked as a circulation loop by the flow of the solid particles. Only the gasification reaction occurs in the gasification zone, so the syngas produced in the gasification zone is free of nitrogen.
In this study, the CFD software, ANSYS-FLUENT, is used to simulate a dual fluidized-bed gasifier. The dual fluidized-bed gasifier is developed in 2D and 3D multiphase flow numerical models. Biomass is used as the fuel in the model, and the results are compared with the reference. In the 2D model, the SF (steam to fuel ratio) and the bed materials temperature entered into the model are tested. In gasification results, when the SF decreased, the syngas (H2, CO, and CO2) content would increase. In terms of changing bed materials temperature, when the temperature increased, the ratio of CO to CO2 would also increase. In the 3D model, the bed materials circulation is successfully built up in the dual fluidized-bed gasifier, the path of bed materials can be predicted, the flow field can be visualized, and both the gas distribution and reaction zone can be observed. Compared with the simulation results, the content of CO2 and H2 in the simulation is higher than in the experiment, the content of CO is lower than in the experiment, and the CH4 is the same as in the simulation. The difference between simulation and the reference may be overestimating the reaction rate of the water gas shift reaction.

【1】IEA, "Key World Energy Statistics 2016", 2016.
【2】經濟部能源局，"能源統計手冊"，2016.
【3】Singh R.I., Brink A. and Hupa M., "CFD Modeling to Study Fluidized Bed Combustion and Gasification", Applied Thermal Engineering, vol. 52, pp. 585-614, 2013.
【4】呂錫民，"氣化技術"，科學發展，vol. 435, pp. 62-66, 2009.
【5】錢建嵩，"流體化床焚化爐與戴奧辛控制"，科學發展，vol. 450, pp. 12-19, 2010.
【6】Hofbauer H., Rauch R., Bosch K., Koch R. and Aichernig C., "Biomass CHP Plant Güssing – A Success Story", Pyrolysis and Gasification of Biomass and Waste, 2001.
【7】Anthony D.B. and Howard J.B., "Coal Devolatilization and Hydrogasification", American Institute of Chemical Engineers, vol. 22, pp. 625-656, 1976.
【8】Agarwal P.K., "A Single Particle Model for the Evolution and Combustion of Coal Volatiles", Fuel, vol. 65, pp. 803-810, 1986.
【9】Smoot L.D. and Brown B.W., "Controlling Mechanisms in Gasification of Pulverized Coal", Fuel, vol. 66, pp. 1249-1256, 1987.
【10】Smith I.W., "The Combustion Rates of Coal Chars: A Review", In: 19th international symposium on combustion, Philadephia: The Combustion Institute, pp. 1045-1065, 1982.
【11】Yu L., Lu J., Zhang X. and Zhang S., "Numerical Simulation of the Bubbling Fluidized Bed Coal Gasification by the Kinetic Theory of Granular Flow (KTGF) ", Fuel, vol. 86, pp. 722-734, 2007.
【12】Armstrong L.M., Gu S. and Luo K.H., "CFD Modelling of the Co-Gasification of Biomass and Coal Particles in Fluidized Beds", Proceedings of the Bioten Conference on Biomass Bioenergy and Biofuels 2010, CRC Press, Birmingham, GB, 2010.
【13】Deng Z., Xiao R., Jin B., Huang H., Shen L., Song Q. and Li Q., "Computational Fluid Dynamics Modeling of Coal Gasification in a Pressurized Spout-Fluid Bed", Energy and Fuels, vol. 22, pp. 1560-1569, 2008.
【14】Gerber S., Behrendt F. and Oevermann M., "An Eulerian Modeling Approach of Wood Gasification in a Bubbling Fluidized Bed Reactor Using Char as Bed Material", Fuel, vol. 89, pp. 2903-2917, 2010.
【15】Armstrong L.M., Gu S. and Luo K.H., "Parametric Study of Gasification Processes in a BFB Coal Gasifier", Industrial and Engineering Chemistry Research, vol. 50, pp. 5959-5974, 2011.
【16】Wang Y. and Yan L., "CFD Based Combustion Model for Sewage Sludge Gasification in a Fluidized Bed", Frontiers of Chemical Engineering in China, vol. 3, pp. 138-145, 2009.
【17】He L., Schotte E., Thomas S., Schlinkert A., Herrmann A., Mosch V., Rajendran V. and Heinrich S., "Wood Gasification in a Lab-Scale Bubbling Fluidized Bed: Experiment and Simulation", Proceeding of 20th International Conference on Fluidized Bed Combustion, pp.686-692, 2010.
【18】Wang X, Jin B, and Zhong W, "Three-Dimensional Simulation of Fluidized Bed Coal Gasification", Chemical Engineering and Processing, vol. 48, pp. 695-705, 2009.
【19】Schmid J.C., Wolfesberger U., Koppatz S., Pfeifer C. and Hofbauer H., "Variation of Feedstock in a Dual Fluidized Bed Steam Gasifier-Influence on Product Gas, Tar Content, and Composition", Environmental Progress & Sustainable Energy, vol. 31, pp. 205-215, 2012.
【20】Thapa R.K., Pfeifer C. and Halvorsen B.M., "Modeling of Reaction Kinetics in Bubbling Fluidized Bed Biomass Gasification Reactor", International Journal of Energy and Environment, vol. 5, pp. 35-44, 2014.
【21】許弘德, 林士強, 林哲宇, 陳一順與邱耀平, "尤加利木屑於流體化床反應器進行氣化之研究", 第二十六屆燃燒與能源學術研討會, 2016.
【22】Kantarelis E., Donaj P., Yang W. and Zabaniotou A., "Sustainable Valorization of Plastic Wastes for Energy with Environmental Safety via High-Temperature Pyrolysis (HTP) and High-Temperature Steam Gasification (HTSG)", Journal of Hazardous Materials, vol. 167, pp. 675-684, 2009.
【23】程祖田，"流化床燃燒技術及應用"，中國電力出版社, 2013.
【24】Chejne F. and Hernandez J.P., "Modeling and Simulation of Coal Gasification Process in Fluidized Bed", Fuel, vol. 81, pp. 1687-1702, 2002.
【25】ANSYS, ANSYS FLUENT 15.0 Theory Guide, ANSYS, Inc., Southpointe, 2013.
【26】Lun C.K.K., Savage S.B., Jeffrey D.J. and Chepurniy N., "Kinetic Theories for Granular Flow: Inelastic Particles in Couette Flow and Slightly Inelastic Particles in a General Flow Field," Journal of Fluid Mechanics, vol. 140, pp. 223-256, 1984.
【27】Gidaspow D., Multiphase Flow and Fluidization: Continuum and Kinetic Theory Descriptions, Academic Press, London, 1994.
【28】Launder B.E. and Spalding D.B., Lectures in Mathematical Models of Turbulence, Academic Press, London, England, 1972.
【29】Badzioch S. and Hawksley P.G.W., "Kinetics of Thermal Decomposition of Pulverized Coal Particles", Industrial and Engineering Chemistry Process Design and Development, vol. 9, pp. 521-530, 1970.
【30】Cheng P., "Two-Dimensional Radiating Gas Flow by a Moment Method", American Institute of Aeronautics and Astronautics, vol. 2, pp. 1662-1664, 1964.
【31】Weimer A.W. and Clough D.E., "Modeling a Low Pressure Steam-oxygen Fluidized Bed Coal Gasifying Reactor", Chemical Engineering Journal, vol. 36, pp. 549-567, 1981.
【32】Klimanek A., Adamczyk W., Katelbach-Woźniak A., Węcel G. and Szlęk A., "Towards a Hybrid Eulerian–Lagrangian CFD Modeling of Coal Gasification in a Circulating Fluidized Bed Reactor", Fuel, vol. 152, pp. 131–137, 2015.
【33】Geldart D., "Types of Gas Fluidization", Powder Technology, vol. 7, pp. 285-292, 1973.
【34】Vasconcelos P.D.S. and Mesquita A.L.A., "Minimum and Full Fluidization Velocity for Alumina Used in the Aluminum Smelter", International Journal of Engineering Business Management, vol. 3, pp. 7-13, 2011.
【35】Kern S., Pfeifer C. and Hofbauer H., "Gasification of Wood in a Dual Fluidized Bed Gasifier: Influence of Fuel Feeding on Process Performance", Chemical Engineering Science, vol. 90, pp. 284-298, 2013.
【36】Koppatz S., Pfeifer C. and Hofbauer H., "Comparison of the Performance Behavior of Silica Sand an Olivine in a Dual Fluidized Bed Reactor System for Steam Gasification of Biomass at Pilot Plant Scale", Chemical Engineering Journal, vol. 175, pp. 468-483, 2011.