Case study'

The chemical industry recognizing their impact into the current state of global warming and other climate change effects has been from the last decades seeking ways to develop new technologies and to introduce new products to reduce the carbon footprint. Biodiesel production is one of such technological process that mitigates the use of fossil fuels and by extent reducing the carbon footprint.

Biodiesel can be produced from vegetable oil, microalgae oil, animal fats and other waste oil and fats from industrial processes. The process of converting these oils to biodiesel is called transesterification.

Transesterification is the technology used most widespread to produce biodiesel whether for small scale or industrial application. The purpose of the process is to lower the viscosity of the oil and has the potential to be a less expensive way of transforming the large, branched molecular structure of bio$-$oils into smaller, straight chain molecules of the type required in regular diesel combustion engines. Transesterification involves the reaction of triglycerides and an alcohol in the presence of a catalyst, that is$,$ via alkali, acid or enzymes, to produce glycerol and a mixture of fatty acid esters.

Most biodiesel is produced today by the transesterification of triglycerides of refined$/$edible type oils using methanol as the alcohol and an alkaline catalyst, sodium hydroxide or sodium methoxide due to the lower cost of both raw materials. Alkali$-$catalysis is generally preferred because alkali$-$catalyzed transesterification is carried out under low temperature and pressure conditions and the conversion rate is high with no intermediate steps. The reaction produces two distinct immiscible layers: mono$-$alkyl esters of long chain fatty acids, and glycerol at the bottom; the reaction can be seen in the equation below:

Figure $1$ General Transesterification Reaction for Triglycerides where R$1,$ R$2,$ R$3$ are Long, Fatty Acid Chains.

Enzymatic transesterification has been proven to be a more environmentally friendly and sustainable alternative to the more common alkali$-$catalyzed process. To manufacture enzymatically produced biodiesel industrially, enzymes will have to be applied to a continuous mode of production. Operating a continuous reactor under fluidized bed conditions has shown to improve the performance of packed bed columns in terms of reaction yields. Further intensification of this process has seen researchers explore binary mixtures of inert and active particles in a liquid's matrix.

The study focusses in the fluidized bed reactor using castor oil and $10\%(\frac{w}{w})$ Novozyme $435$ at $50C$ to investigate the methyl ester yield in relation to reaction time, oil to methanol ratio and addition of sand as a binary particle.

Assignment

Based on your understanding of this process and the selection of the most suitable flow diagram, see figures $2$ and $3,$ for your consideration develop the following:

Figure $$ Irauluunlat Divuleset rrucess witn an Aciulc rie$-$treatmerit step rotuweu vy Alkaline Catalysis. $($A$)$ Reactor; $($B$)$ Separation $($centrifuge or decanter$)$; $($D$)$ Product

Figure $3q,$

Draft a sketch of the fluidized continuous reactor to carry out the esterification reaction.

Identify the type of chemical reaction that you will assume will be conducted in the reactor. Select the type of catalyst.

Conducting an analysis of the process create a concept map $($cmap$)$to support the transport phenomena case to derive a model that represent the molar flux of the esters produced during the esterification reaction. Use the cmap software for this purpose$).$

Derive a mathematical model to illustrate the momentum and mass transport phenomena to optimize and simulate this reactor.

Using COMSOL Multiphysic solve the model and create a graphical representation of the fluidise bed reactor

Based on your short research of this topic, how could the process be improved.

Deliverables

Create a short technical report that will include but not limited to the following:

a$.$ Sketch of the fluidized reactor to be used to derive the model.

b$.$ Cmap of the process. Cmap file will be submitted also as individual file.

c$.$ Detailed derivation of the transport phenomena mathematical models

d$.$ COMSOL solution of the process. Use COMSOL software. Submit also the COMSOL

file.