Evaluation of Biomass and Coal Co-Gasification of Brazilian Feedstock Using a Chemical Equilibrium Model

Abstract

-Coal and biomass are energy sources with great potential for use in Brazil. Coal-biomass cogasification enables the combination of the positive characteristics of each fuel, besides leading to a cleaner use of coal. The present study evaluates the potential of co-gasification of binary coal-biomass blends using sources widely available in Brazil. This analysis employs computational simulations using a reliable thermodynamic equilibrium model. Favorable operational conditions at high temperatures are determined in order to obtain gaseous products suitable for energy cogeneration and chemical synthesis. This study shows that blends with biomass ratios of 5% and equivalence ratios ≤ 0.3 lead to high cold gas efficiencies. Suitable gaseous products for chemical synthesis were identified at biomass ratios ≤ 35% and moisture contents ≥ 40%. Formation of undesirable nitrogen and sulfur compounds was also analyzed.

Synthesis Gas Composition Prediction for Underground Coal Gasification Using a Thermochemical Equilibrium Modeling Approach

“…The VCS algorithm has been developed for systems with constant temperature and pressure constraints and is applied in Cantera iteratively until the difference of the chemical potential between two computational steps is less than a pre-defined convergence criterion [16]. Using the previously introduced approach, the present equilibrium model allows calculating an equilibrium state with a large number of phases and chemical species [14]. A database of expected species in the solid and gaseous products must be established a priori (Table 2).…”

“…Hereby, gasification is the thermochemical conversion of carbonaceous materials (coal and/or biomass) into a high-calorific synthesis gas in the presence of an oxidizer, which may consist of air, oxygen-enriched air and/or water vapor. In the past decade, it has received increasing attention due to the growing demand for fuels and chemical feedstocks [13][14][15][16][17][18]. The chemical mechanisms of gasification are well documented and have been studied extensively, i.e., by [12,17,[19][20][21].…”

“…These models have been published using different classifications, designations and categories [13]. Gasification simulation models can be generally classified into the following three groups: thermodynamic equilibrium [14,15,17,18,[22][23][24][25][26], kinetic [27][28][29][30] and artificial neural network (ANN) models [31,32]. Guo et al [31] have shown that ANNs, which have been extensively used in the fields of pattern recognition, signal processing, function approximation and process simulation can also be applied to predict product yield and synthesis gas compositions of a gasification process.…”

“…Therefore, these characteristics provide an efficient approach, especially in cases where the form of the function is unknown or too complex to simulate and explore gasification processes [31]. In this context, kinetic models allow in some instances for a better accuracy of the estimation of the synthesis gas composition [16], but require knowledge on kinetic parameters, which are usually obtained experimentally [14]. The synthesis gas yield and composition are provided by a kinetic model for a finite time period.…”

Modeling and Parametric Study for Maximizing Heating Value of Gasification Syngas

“…A number of studies had been carried out in the past on modelling of the thermochemical conversation of various biomass materials (Muilenburg et al 2011;Bates et al 2016). Phenomenological models that represent the various chemical processes in each stage of gasification using mathematical relations (Muilenburg et al 2011;Sulaiman et al 2012;Bates et al 2016) are more commonly applied than the black box modelling approach that use Artificial Neural Network (ANN) (Puig-Arnavat et al 2013;Rodrigues et al 2016). These models can be placed into two main classes: equilibrium models that assume all major reactions of pyrolysis and gasification to reach chemical equilibrium during the gasification process, and kinetic models, which involve kinetic rate equations.…”