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research-article

Effect of Heat Flux Distribution Profile on Hydrogen Concentration in an Allothermal Downdraft Biomass Gasification Process: Modeling Study

[+] Author and Article Information
Yuhan A. Lenis

Department of Mechanical Engineering, Universidad del Norte, km 5 vía Puerto Colombia, Barranquilla, Colombia; Department of Mechanical Engineering, Institución Universitaria Pascual Bravo, Calle 73 No. 73A - 226, Medellín, Colombia
ylenis@uninorte.edu.co

Gilles Maag

Department of Biosystems Engineering, Faculty of Animal Science and Food Engineering University of São Paulo (USP), Av. Duque de Caxias Norte 225, 13635-900, Pirassununga, SP, Brazil
gmaag@usp.br

Celso Eduardo Lins de Oliveira

Department of Biosystems Engineering, Faculty of Animal Science and Food Engineering University of São Paulo (USP), Av. Duque de Caxias Norte 225, 13635-900, Pirassununga, SP, Brazil
celsooli@usp.br

Lesme Corredor

Department of Mechanical Engineering, Universidad del Norte, Km 5 vía Puerto Colombia, Barranquilla, Colombia
lcorredo@uninorte.edu.co

Marco E. Sanjuan

Department of Mechanical Engineering, Universidad del Norte, Km 5 vía Puerto Colombia, Barranquilla, Colombia
msanjuan@uninorte.edu.co

1Corresponding author.

ASME doi:10.1115/1.4041723 History: Received May 17, 2018; Revised October 07, 2018

Abstract

Considering the potential of using concentrating solar power systems to supply the heat required for the allothermal gasification process, this study analyzes hydrogen production in such a system by assuming typical radiative heat flux profiles for a receiver of a central tower concentrated solar power (CSP) plant. A detailed model for allothermal gasification in a downdraft fixed bed tubular reactor is proposed. This considers solid and gas phases traveling in parallel flow along the reactor. Results for temperature and gas profile show a reasonable quantitative agreement with experimental works carried out under similar conditions. Aiming to maximize H2 yield, eight Gaussian flux distributions, similar to those typical of CSP systems, each with a total power of 8 kW (average heat flux 20 kW/m2), but with varying peak locations, were analyzed. The results show a maximum producer gas yield and chemical efficiency of 134.1 kmol/h and 45.9% respectively, with a molar concentration of 47.2% CO, 46.9% H2, 3.3% CH4 and 2.6% CO2 for a distribution peak at z = 1.4 m, thus relatively close to the flue gas outlet. Hydrogen production and gas yield using this configuration were 4% and 2.9% higher than the achieved using the same power but homogeneously distributed. Solar to chemical efficiencies ranged from 38.9% to 45.9%, with a minimum when distribution peak was at the reactor center. These results are due to high temperatures during the latter stage of the process favoring char gasification reactions

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