Simulation and optimization of biodiesel production from dimethyl carbonate in batch reactor

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Date
2016-04-01
Authors
Nur Amirah Mohd Ali
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Abstract
Simulation of biodiesel production from dimethyl carbonate (DMC) is very scarce and limited to utilization of canola oil as the raw material. In this study, a pilot scale of DMC transesterification process to produce biodiesel in a batch reactor was considered. A pilot scale operation of the batch reactor was introduced to the biodiesel production as a preparation for commercial and industrial development. A simulation of the pilot scale batch reactor for DMC transesterification reaction using Aspen Plus Version 2006 is presented in this study. The simulation model was validated with experimental results available in the literature. The simulation model was validated at temperature of 75°C which gave R2 = 0.96 and produced a similar trend of the Palm Methyl Ester (PME) concentration profile with the experimental results. From the validated simulation model, a pilot scale batch reactor operation was simulated and sensitivity studies were carried out to study the behavior of DMC transesterification process at a larger scale. A pilot scale batch reactor considered has a volume of 300 L with scaling factor of 660 from the experimental scale of operation. Based on the sensitivity studies, reactor temperature and amount of reactant were selected as variables to be optimized in the optimization study. The optimization study was carried out with three objectives which were: maximize conversion (OP1), minimize batch time (OP2), and maximize palm methyl ester (PME) and minimize waste simultaneously (OP3). The optimization study was performed using the optimizer tool in Aspen Plus which was based on the sequential xvi quadratic programming (SQP) technique. The results showed that in optimization problem (OP)1, the conversion of DMC transesterification reaction increased from 90.6% to 99.9%. In OP2, the batch time required for the reaction was shortened from 8 hours to 2.68 hours while in OP3, the PME production significantly increased from 31.05 kg to 125.99 kg and the waste decreased from 76.42 kg to 63.78 kg at the shortest batch time specified. In real situation, operational temperature of batch reactor is changing with time. Therefore, apart from optimizing temperature at single time interval, optimizing temperature at multiple time intervals was considered to obtain optimal temperature profile. By optimizing the profile, the performance of DMC transesterification process produced better results. The PME production increased while the batch time was shortened and with low amounts of waste produced. For each optimization problem, the optimum temperature profile obtained was less than the optimum temperature obtained at single time interval. In conclusion, optimization results obtained from optimal temperature profile of OP3 is the best temperature condition to be implemented in biodiesel industry since it was able to provide safer operation and produce larger biodiesel production with lower amount of waste produced at minimum batch time.
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