CFD based combustion model for sewage sludge gasification in a fluidized bed

Abstract

Gasification is one potential way to use sewage sludge as renewable energy and solve the environmental problems caused by the huge amount of sewage sludge. In this paper, a three-dimensional Computational Fluid Dynamics (CFD) model has been developed to simulate the sewage sludge gasification process in a fluidized bed. The model describes the complex physical and chemical phenomena in the gasifier including turbulent flow, heat and mass transfer, and chemical reactions. The model is based on the Eulerian-Lagrangian concept using the non-premixed combustion modeling approach. In terms of the CFD software FLUENT, which represents a powerful tool for gasifier analysis, the simulations provide detailed information on the gas products and temperature distribution in the gasifier. The model sensitivity is analyzed by performing the model in a laboratory-scale fluidized bed in the literature, and the model validation is carried out by comparing with experimental data from the literature. Results show that reasonably good agreement was achieved. Effects of temperature and Equivalence Ratio (ER) on the quality of product syngas (H₂ + CO) are also studied.

Keywords

CFD / model / sewage sludge / gasification / syngas

References

[1] Cui H, Ninomiya Y, Masui M, Mizukoshi H, Sakano T, Kanaoka C. Fundamental Behaviors in Combustion of Raw Sewage Sludge. Energy & Fuels, 2006, 20: 77-83

[2] Hartman M, Svoboda K, Pohorely M, Trnka O. Combustion of dried sewage sludge in a fluidized-bed reactor. Ind Eng Chem Res, 2005, 44: 3432-3441

[3] Midillia A, Dogrub M, Howarthb C R. Lingc M J, Ayhan T. Combustible gas production from sewage sludge with a downdraft gasifier. Energy Conversion & Management, 2001, 42: 157-172

[4] Domı´nguez A, Menéndez J A, Pis J J. Hydrogen rich fuel gas production from the pyrolysis of wet sewage sludge at high temperature. J Anal Appl Pyrolysis, 2006, 77: 127-132

[5] Ferrasse J H, Seyssiecq I, Roche N. Thermal Gasification: A Feasible Solution for Sewage Sludge Valorisation?Chemical Engineering & Technology, 2003, 26: 941-945

[6] J Manya J, Sanchez J L, Gonzalo A, Arauzo J. Air gasification of dried sewage sludge in a fluidized bed: effect of the operating conditions and in-bed use of alumina. Energy & Fuels, 2005, 19, 629-636

[7] Corella J, Toledo J M. Incineration of doped sludges in fluidized bed. Fate and partitioning of six targeted heavy metals. I. Pilot plant used and results. Journal of Hazardous Materials, 2000, B80: 81-105

[8] Shi S P, Zitney S E, Shahnam M, Syamlal M, Rogers W A. Journal of the Energy Institute, 2006, 79(4): 217-221

[9] Wang S J, Lu J D, Li W J, Hu Z J. Modeling of pulverized coal combustion in cement rotary Kiln.Energy & Fuels, 2006, 20(6): 2350-2356

[10] Chen C X, Horio M, Kojima T. Use of numerical modeling in the design and scale-up of entrained flow coal gasifiers. Fuel, 2001, 80(10): 1513-1523

[11] Vicente W, Ochoa S, Aguillon J, Barrios E. An Eulerian model for the simulation of an entrained flow coal gasifier. Applied Thermal Engineering, 2003, 23(15): 1993-2008

[12] Fletcher D F, Haynes B S, Christo F C, Joseph S D. A CFD based combustion model of an entrained flow biomass gasifier. Applied Mathematical Modelling, 2000, 24: 165-182

[13] Grammelis P, Kakaras E. Biomass Combustion Modeling in Fluidized Beds. Energy & Fuels, 2005, 19: 292-297

[14] Rostami A A, Hajaligol M R, Wrenn S E. A biomass pyrolysis sub-model for CFD applications. Fuel, 2004, 83: 1519-155

[15] Petersen I, Werther J. Experimental investigation and modeling of gasification of sewage sludge in the circulating fluidized bed. Chemical Engineering Science, 2005, 60(16): 4469-4484

[16] Khiari B, Marias F, Zagrouba F, Vaxelaire J. Use of a transient model to simulate fluidized bed incineration of sewage sludge. Journal of Hazardous Materials, 2006, 135(1-3): 200-209

[17] Petersen I, Werther J. Experimental investigation and modeling of gasification of sewage sludge in the circulating fluidized bed. Chemical Engineering and Processing, 2005, 44(7): 717-736

[18] Zarnescu V, Pisupati S V. An Integrative Approach for Combustor Design Using CFD Methods. Energy & Fuels, 2002, 16: 622-633

[19] Dixon T F, Mann A P, Plaza F, Gilfillan W N. Development of advanced technology for biomass combustion—CFD as an essential tool. Fuel, 2005, 84: 1303-1311

[20] Fluent Inc, FLUENT 6.1 User's Guide. 2003

[21] Sadakaa S S, Ghalyb A E, Sabbahc M A. Two phase bio-mass air-steam gasification model for fluidized bed reactors:Part I-model development. Biomass and Bioenergy, 2002, 22: 439-462

[22] Kee R J, Rupley F M, Miller J A. Chemkin-II: A Fortran chemical kinetics package for the analysis of gas-phase chemical kinetics. Technical Report SAND 89-8009, <OrgName>Sandia National Labs</OrgName>, 1989

[23] Filippis P D, Borgianni C, Paolucci M, Pochetti F. Prediction of syngas quality for two-stage gasification of selected waste feedstocks. Waste Management, 2004, 24: 633-639

[24] Corella J, Sanz A. Modeling circulating fluidized bed biomass gasifiers:a pseudo-rigorous model for stationary state. Fuel Processing Technology, 2005, 86(9): 1021-1053

RIGHTS & PERMISSIONS

2014 Higher Education Press and Springer-Verlag Berlin Heidelberg