Abstract

Good process control has been often criticized for the economic viability of large-scale production of several commercial products. In this work, the production of biodiesel from microalgae is investigated. Successful implementation of a model-based control strategy requires the identification of a model that properly captures the biochemical dynamics of microalgae, yet is simple enough to allow its implementation for controller design. This paper explores the biodiesel production in a class of continuous culture under heterotrophic conditions via closed-loop operation. A mathematical model adapted from Surisetty et al. (2010) that describe the growth of microalgae in a heterotrophic culture is studied via dynamic analysis. This model is extended to continuous operation where bifurcation analysis were carried out for the determinate the qualitative model behavior and to analyze feasible operating conditions. This project is focused on the on the use of a mixture of two substrates that are continuously fed into the reactor chamber and the continuous fermentation process is described by an unstructured mathematical model with a product inhibition on cell growth. In addition, we present the design of a nonlinear control law contains a class of bounded-type feedback of the named control error in order to regulate the substrate concentration at maximum value to lead indirectly the lipids-diesel concentration. Lipid productivity in continuous culture was 0.276 g /L d, which was an increase of 18.1% over that of the batch mode. Finally, numerical experiments proved satisfactory performance of the proposed methodology in comparison with linear PI controller.

Highlights

  • Biodiesel fuels are relatively new alternatives and environmentally sustainable sources comparing to traditional fossil fuels due to reducing greenhouse gas emission

  • Biodiesels are made from renewable biological sources such as vegetable oils, animal fats, and microalgal cultures and are prepared from lipid type acylglycerols by transesterification with short chain alcohols.[1,2]

  • Microalgae culture begins to emerge as a better option to obtain biodiesel since could accumulate much higher oil content than those of agricultural oleaginous crops

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Summary

Introduction

Biodiesel fuels are relatively new alternatives and environmentally sustainable sources comparing to traditional fossil fuels due to reducing greenhouse gas emission. Microalgae culture begins to emerge as a better option to obtain biodiesel since could accumulate much higher oil content than those of agricultural oleaginous crops. They do not require the use of crop area, can be grown in deserts or intensively in bioreactors; some cultures require only water (less than land crops for irrigation) and atmospheric CO2 coupled with sunlight. More precise models have been development including the nitrogen and carbon assimilation interactions as well.[10] Two forms of the models developed to explore the key variables of the biological process system, the bifurcation and sensitivity analyses, allow the improvement of photobioreactor lipid productivity through the study of the different culture operation conditions and the effect of parameters state values.[11] The operational condition establishment to reach the best. Several studies have been published for controlling biodiesel production,[15] we have been studied a dynamical model to predict the neutral lipid concentration changes and proposed a kinetic model extended for continuous operation to analyze the bifurcation properties considering nitrogen stress

Materials and Methods
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Results and Discussions
Conclusions
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