Contents lists available at ScienceDirect Energy Conversion and Management journal homepage: www.elsevier.com/locate/enconman Hydrogen production from biomass gasiﬁcation; a theoretical comparison of using diﬀerent gasiﬁcation agents E. Shayan a , V. Zare b, ⁎ , I. Mirzaee a a Department of Mechanical Engineering, University of Urmia, Urmia, Iran b Faculty of Mechanical Engineering, Urmia University of Technology, Urmia, Iran ARTICLE INFO Keywords: Hydrogen production Biomass gasiﬁcation Steam gasiﬁcation Exergy eﬃciency Uncertainty analysis NO x and SO x emissions ABSTRACT In the present paper hydrogen production from biomass gasiﬁcation using various agents is investigated and compared theoretically, from the viewpoints of the ﬁrst and second thermodynamics laws. Gasiﬁcation of wood and paper, as two types of common biomass feedstocks, is assessed using four gasiﬁcation agents namely: air, oxygen-enriched air, oxygen and steam. Thermodynamic equilibrium model is employed to simulate the gasi- ﬁcation process, the results of which are validated using available theoretical and experimental data in litera- ture. The NO x and SO x emissions from the biomass gasiﬁcation are also considered in the model and a sensitivity analysis is performed to determine the accuracy of the results regarding to the uncertainties of the input data. A parametric study is conducted to assess the eﬀects of key operating parameters on the hydrogen concentration and caloriﬁc value of producer gas, energy and exergy eﬃciencies of the process and exergy destruction rate at diﬀerent operating conditions. The results indicate that the higher values of hydrogen production is associated respectively with using steam, oxygen, oxygen-enriched air and air as the gasiﬁcation agents. Also, it is con- cluded that for the gasiﬁcation process the highest value of sensible energy eﬃciency is obtained for air gasi- ﬁcation, while the highest exergy eﬃciency, as a rational criterion, is obtained for steam gasiﬁcation for which the caloriﬁc value of the producer gas can reach to higher than 11 MJ/Nm 3 . 1. Introduction In recent years, increasing global energy demand, depletion of fossil fuels and increasing environmental concerns arising from fossil fuels have urged researchers to substitute fossil fuels with clean energies that come from renewable resources. Among the renewable energy sources, biomass and hydrogen have received signiﬁcant attention as they can increase the global energy sustainability and reduce greenhouse gas emissions [1]. Diﬀerent technologies are developed to convert biomass to producer gas, including thermochemical, biochemical and mechanical extraction methods. Thermochemical conversion methods can be classiﬁed into: combustion, gasiﬁcation, pyrolysis and liquefaction [2]. Among these methods, biomass gasiﬁcation is considered as a prominent conversion route for producing a clean feedstock for power generation and is preferred as it has lower pollutant emissions and higher eﬃciency of power and heat generation [3,4]. Various types of biomass fuels such as wood, paper, sawdust and municipal solid waste [5], are used in gasi- ﬁcation process by which biomass fuel is converted to syngas that primarily contains carbon monoxide (CO), carbon dioxide (CO 2 ), hydrogen (H 2 ), water vapor (H 2 O) and methane (CH 4 ). The composi- tion of syngas derived from biomass gasiﬁcation depends mainly on the biomass fuel, gasiﬁer type and gasiﬁcation agent [6,7]. Various gasiﬁer types for gasiﬁcation are used and the selection of the gasiﬁer type depends on the capacity of the unit [8]. Advantages and disadvantages of each gasiﬁer type can be found in Ref. [8]. In addition to diﬀerent types of the gasiﬁers, diﬀerent gasiﬁcation agents including air, oxygen, oxygen-enriched air and steam can also be employed for gasiﬁcation process, each of which brings about diﬀerent composition of the pro- duced syngas. Recent scientiﬁc literature on investigation of gasiﬁcation process includes assessment of diﬀerent aspects of the concept applied for power or hydrogen production. Seyitoglu et al. [9] developed an in- tegrated coal based gasiﬁcation system for hydrogen production and power generation. Energy and exergy analyses on their proposed system showed that the overall energy and exergy eﬃciencies of the system reaches to 41% and 36.5%, respectively. The eﬀect of biomass packing factor and employing oxygen-enriched air as gasifying agent on ﬁxed bed biomass gasiﬁcation is studied by Lenis et al. [10], who concluded that the eﬃciency slightly increases when the packing factor is https://doi.org/10.1016/j.enconman.2017.12.096 Received 15 August 2017; Received in revised form 25 December 2017; Accepted 30 December 2017 ⁎ Corresponding author. E-mail address: v.zare@uut.ac.ir (V. Zare). Energy Conversion and Management 159 (2018) 30–41 0196-8904/ © 2017 Elsevier Ltd. All rights reserved. T