Contents lists available at ScienceDirect Fuel journal homepage: www.elsevier.com/locate/fuel Full Length Article Kinetic modeling of biomass gasiﬁcation and tar formation in a ﬂuidized bed gasiﬁer using equivalent reactor network (ERN) Bijoy Das, Atmadeep Bhattacharya 1 , Amitava Datta ⁎ Department of Power Engineering, Jadavpur University, Salt Lake Campus, Kolkata 700098, India ARTICLE INFO Keywords: Biomass gasiﬁcation Pyrolysis Kinetic modeling Tar Equivalent reactor network ABSTRACT A chemical kinetic based simulation model of a bubbling ﬂuidized bed biomass gasiﬁer has been developed using an Equivalent Reactor Network (ERN). The pyrolysis zone is modeled using a thermodynamic equilibrium model and a kinetic-controlled perfectly stirred reactor (PSR) placed in succession. The gasiﬁcation zone and the freeboard are simulated as perfectly stirred reactor (PSR) and plug ﬂow reactor (PFR), respectively. A detailed chemical reaction mechanism is used to describe the chemistry of reaction during devolatilization and gasiﬁ- cation stages. The formation and evolution of gaseous and tar species in diﬀerent zones of the gasiﬁer are estimated and the major reaction paths have been identiﬁed. The inﬂuence of equivalence ratio (ER) on the gasiﬁer performance and tar species formation has been studied. Out of the three ERs considered (0.27, 0.24 and 0.19), the best performance of the gasiﬁer is exhibited at ER = 0.24 in terms of cold gas eﬃciency. 1. Introduction Biomass is a widely available, carbon–neutral energy resource that currently accounts for more than 10% of the world's total energy con- sumption [1]. One convenient way of extracting energy from the bio- mass is through its gasiﬁcation and then using the resultant fuel gas either in internal combustion engine or in gas turbine engine to produce electricity. However, as the energy content and density of the biomass feedstock are low, the cost of the biomass transportation should be considered in the economic assessment of biomass conversion tech- nologies [2]. Therefore, the power generation from gasiﬁcation of biomass in small scale decentralized units is often a more economical option than that in a large scale centralized plant [3,4]. Furthermore, the emission indices of carbon monoxide (CO) and soot from a gasiﬁer- engine combined system operating on woody biomass remains negli- gibly small [5]. Besides the gasiﬁer and reciprocating internal com- bustion engine couplings, there are a few works available in the lit- erature on the gasiﬁer and gas turbine combinations as well. Such combinations may also be used in conjunction with steam turbines in the integrated gasiﬁcation combined cycle (IGCC) plants. A detailed review of the usefulness of the IGCC technology involving biomass can be found in Parraga et al. [6]. It has been identiﬁed in this review that the biomass gasiﬁcation process is quite complex and therefore its modeling is a challenging task. The fuel gas (named producer gas or syngas), produced through gasiﬁcation of biomass in air, contains hydrogen (H 2 ), carbon monoxide (CO) and methane (CH 4 ) as the combustible components; in addition to the other non-combustible components like carbon dioxide (CO 2 ) and nitrogen (N 2 ). The syngas composition varies signiﬁcantly with the biomass feedstock, gasiﬁer type and gasiﬁer operating parameters [6]. It is an established fact that the performance of both the IC engine and the IGCC plant depends strongly on the quality of the fuel gas produced from biomass gasiﬁcation [7,8]. The producer gas also contains tar, which is a complex mixture of hydrocarbons heavier than benzene [9]. Tar is produced in the gasiﬁer primarily during the pyrolysis of bio- mass; and then it is subjected to secondary reactions. Diﬀerent com- pounds present in tar have been listed by Milne et al. [10] following the work of Evans and Milne [11]. Tar is an unwanted constituent of the producer gas, which adversely aﬀects the quality of the fuel for its use in engines and turbines. The tar constituents may condense to block the fuel lines and particle ﬁlters in engines. They also result in the increased emission of soot and UHC (unburned hydrocarbon) in the exhaust. Therefore, reduction of tar in the producer gas remains an important objective in the design and development of the biomass gasiﬁer unit. A recent review by Islam [12] has listed numerous catalytic materials that are being researched upon for the tar removal process in biomass ga- siﬁcation. Another method of reducing the quantity of tar in the producer gas https://doi.org/10.1016/j.fuel.2020.118582 Received 6 April 2020; Received in revised form 31 May 2020; Accepted 29 June 2020 ⁎ Corresponding author. E-mail address: amdatta_ju@yahoo.com (A. Datta). 1 Presently at Department of Mechanical Engineering, Aalto University, Finland. Fuel 280 (2020) 118582 0016-2361/ © 2020 Elsevier Ltd. All rights reserved. T