Elsevier

Fluid Phase Equilibria

Volume 525, 15 December 2020, 112792
Fluid Phase Equilibria

Evaluation of kinetics and thermodynamic parameters for simulation of palm oil biodiesel production

https://doi.org/10.1016/j.fluid.2020.112792Get rights and content

Abstract

Computer simulation is a powerful tool in technical, economic, and environmental assessments of processes. Some commercial simulators are available with a friendly environment and an extensive database. For some compounds, primarily biocompounds, gaps still exist in terms of their properties. In this case, predictive models are necessary, but their results are not always reliable. Hence, thermodynamic and kinetic parameters essential for the simulation of palm oil biodiesel production processes are evaluated in Aspen Plus®. Sets of parameters are tested in the prediction of liquid–liquid equilibrium, vapor–liquid equilibrium, and vapor pressure of fatty compounds. The sets of parameters previously adjusted to experimental data containing similar fatty compounds presented better results. Furthermore, kinetic parameters from literature are used in the simulation of homogeneous alkaline transesterification for palm oil biodiesel production, which yielded a good agreement between experimental results and those calculated by the simulator. It is concluded that a prior evaluation of parameters is necessary and mandatory to obtain accurate computer simulation results.

Introduction

The increase in energy demand owing to the increase in the world population has resulted in the possible depletion of fossil energy resources and high emissions of pollutants in the atmosphere, thereby causing environmental problems. Hence, studies regarding the derivation of biofuels from renewable sources have increased in recent years [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12].

In addition to reducing emissions of gaseous pollutants, the use of biofuels can generate jobs, which can increase local and regional development and promote social inclusion in rural areas [13]. Biodiesel is a biodegradable fuel produced mainly by the transesterification of triacylglycerols with short-chain alcohols in the presence of a catalyst, and it can be used as a substitute for petroleum diesel. Its production from oils and fats has grown exponentially mainly in countries receiving stimulus packages for agriculture through governmental programs [13]. Approximately 77% of biodiesel is based on vegetable oils (30% soybean oil, 25% palm oil, and 18% rapeseed oil) or waste cooking oils (22%) [14].

For biodiesel production, the raw material must be cheap and viable on a large scale [15]. Palm (Elaeis guineensis Jacq.) is the most efficient oil crop in terms of land utilization and productivity (2–8 ton of oil/ha) in addition to environmental advantages owing to the reuse and recovery of degraded areas [13]. Additionally, it is the most produced vegetable oil in the world [16]. Hence, although palm oil is edible, its advantage over other vegetable oils is guaranteed.

Methanol is an alcohol typically used for biodiesel production. However, it is toxic and produced from fossil sources; therefore, its substitution with other alcohols is worth investigating [17]. In countries such as Brazil, ethanol is mainly obtained from the alcoholic fermentation of sugars from sugarcane or molasses. Owing to its high production as a result of governmental programs, the use of ethanol in biodiesel synthesis has become more advantageous [17], thereby resulting in a fuel derived from completely biorenewable raw materials. This means that ethanol and biodiesel production processes can be integrated into a biorefinery [18].

To evaluate the viability of a process, obtain mass and energy balances, equipment dimension and study new production alternatives, computer simulations are important for research and industrial applications. However, the absence of thermophysical properties or their imprecision in the simulator databank can yield inaccurate results or compromise their reliability [19]. This applies to vegetable oils and fats, whose thermophysical properties are scarce and depend on predictive models. The use of inappropriate parameters in these models can often generate values that differ significantly from experimental ones. Hence, the goal of this study is to investigate the thermodynamic and kinetic parameters necessary for the simulation of palm oil biodiesel production using Aspen Plus® v8.8 software (AspenTech, USA).

Section snippets

Materials and methods

The methods used to evaluate the liquid–liquid equilibrium, vapor pressure of fatty compounds, vapor–liquid equilibrium, and transesterification kinetics for palm oil biodiesel production are presented below. As different fatty compounds were used in this study, their characterizations are presented separately in each evaluation.

Results and discussion

The results obtained from the evaluations of the liquid–liquid equilibrium, vapor–liquid equilibrium, vapor pressure, and transesterification kinetics for palm oil biodiesel production are presented and discussed below.

Conclusion

The relative deviations between experimental vapor pressures and those calculated using the parameters from literature were much smaller than those obtained when the Aspen Plus® parameters were used; therefore, the latter parameters should be avoided in the simulation of processes involving fatty compounds. The global root mean square deviation obtained from the analysis of the liquid–liquid equilibrium prediction indicated that the set of parameters UNIF-Hir was the most suitable for systems

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgement

This study was funded by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brazil (CAPES) - Financial Code 001, by the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) - Grant numbers 308924/2017-7, 140703/2017-9 and by Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) - Grant numbers 2014/21252-0, 2016/10636-8.

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