Operator training simulator using plantwide control for biodiesel production from waste cooking oil
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Date
2015-06-01
Authors
Dipesh Shikchand Patle
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Abstract
This study aims at developing an operator training simulator (OTS) for the complex homogeneously catalyzed two-step biodiesel process. On-job training is often costly, risky and incomplete as some emergency situations may not arise during the training session. Therefore, training using an OTS is crucial. Pertaining to the limited availability of non-renewable energy sources and the environmental concerns, biodiesel is considered as a potential alternative fuel. However, the high production cost of biodiesel limits its manufacture and utilization. One attractive option is to use waste cooking oil (WCO) as the feedstock that enables cost effective biodiesel production and also facilitates effective WCO utilization. This study considers waste cooking palm oil with 6% free fatty acids (FFA) as feedstock. Two biodiesel production processes (both involving acid esterification and alkali transesterification) are compared for economic and environmental objectives. Firstly, these processes are simulated realistically in Aspen Plus simulator. Subsequently, both the processes are optimized considering profit, heat duty and organic waste as objectives, and using an Excel-based multi-objective optimization (EMOO) program for the elitist non-dominated sorting genetic algorithm (NSGA-II). Process 1 having three transesterification reactors produces significantly lower organic waste (by 32%), requires lower heat duty (by 39%) and slightly more profitable (by 1.6%) compared to Process 2 having a single transesterification reactor and also a different separation sequence. An effective plantwide control (PWC) system is crucial for the safe, smooth, and economical operation of a biodiesel plant. Hence, a suitable PWC system is developed for the biodiesel process using the integrated framework of simulation and heuristics (IFSH). The main merits of the IFSH methodology are effective use of rigorous process simulators and heuristics in developing a PWC system and simplicity of application. Later, the performance of the developed control system is assessed in terms of settling time, deviation from the production target (DPT), and overall total variation (TV) in manipulated variables. These performance assessments and the results of dynamic simulations showed that the developed PWC system is stable, effective, and robust in the presence of several disturbances. Finally, an OTS has been developed for the biodiesel production from WCO. The developed OTS for biodiesel production process has been investigated for several abnormal process conditions. These process scenarios can be loaded and utilized at any point in time to train the new and existing operators. This is the first study to develop a complete PWC structure and OTS for a homogeneously catalyzed two-step biodiesel production from WCO.