Dynamic Modeling of a Batch Dynamic Modeling of a Batch Bioreactor for Trans-Bioreactor for Trans-esterification of Waste esterification of Waste

Vegetable OilVegetable OilProgress Report Presentation Progress Report Presentation

Nabeel A. AdeyemiNabeel A. Adeyemi Ph DPh D (Engineering) (Engineering)

G0828727G0828727

Supervisors: Prof AKM MohiuddinSupervisors: Prof AKM MohiuddinAssoc Prof Dr Tariq JameelAssoc Prof Dr Tariq Jameel

1st April 2010

• Research Overview– Introduction– Problem statement– Significance– Research Philosophy/ Hypothesis– Objective

• Progress Report November 2009-April 2010– Methodology– Results

• Discussion/ Challenges• On-going experiment • Outstanding work• Modified Work Plan /Reviewed Gantt Chart/

Milestone• Publication

Research Overview

4

Introduction

• Renewable/alternative energy sourcesRenewable/alternative energy sources– Biodiesel Biodiesel an alternative energy sourcean alternative energy source

• Similar physical & chemical properties to fuel used in Similar physical & chemical properties to fuel used in Internal Combustion enginesInternal Combustion engines

• Driving forceDriving force– Socio-politics of petro-diesel (price, Socio-politics of petro-diesel (price,

availability) availability) – Environmental effect of petro-dieselEnvironmental effect of petro-diesel

Biodiesel Production• Food Oils– Palm Oil, Soybean

– Food verse fuel debate• Non-Food Oil (Alternative source) –

WVO– Degraded culinary property– Tri, Di- and Mono-glyceride

• High Free fatty acid (FFA) >3%• High water content

Soap Formation

Introduction (Cont’d)(Cont’d)

Introduction (Cont’d)(Cont’d)

Biodiesel Generation (Reversible reaction)

TG + Alcohol DG + Fatty Acid Methyl Ester

DG + Alcohol MG + Fatty Acid Methyl Ester

MG + Alcohol G + Fatty Acid Methyl Ester

Acid / Alkali Catalyst

Alcohol

(Straight Chain)

Transesterification

Reaction stops abruptly after first few minutes and reverses, limiting conversion of TG,DG,MG to Biodiesel

Problem Statement Present Biodiesel yield from neat vegetable oil is

80-85%. It will be lower with WVO with the normal transesterification route due to FFA and moisturemass transfer and kinetics limited.

Variables investigated affecting reaction kinetics in batch reactors have been limited to temperature, catalyst ratio, alcohol type, water content and FFA. factors such as hydrodynamic effects are not considered

Laboratory kinetics data acquired from reactors cannot to translated for industrial production with reaction kinetics model alone.

Significance

Since the transesterification involves mixing, consideration of reactor hydrodynamics due to non-kinetics variables (impeller position, size, baffles etc) in relationship to the reactor, along with reaction kinetics would provide greater insight and enable exploration of the transesterification process beyond the use traditional kinetics variable.

Research Philosophy/Hypothesis

If Dynamic Modeling, which has not been extended to transesterification, is applied to waste vegetable oil transesterification, biodiesel yield can be predicted and improved.

ease the exploration of the use of non food oils for biodiesel production and establish the limitation of this approach.

With significant hydrodynamics detail and lesser experimental data, Dynamic Models can successfully determine the number of independent reactions and the corresponding stoichiometries that can show higher yields compared to purely data-driven experimental models.

Also, emphasis on analytical rather than experimental optimzation can be used successfully without extensive reaction kinetics.

ObjectiveThe broad objective is to model the transesterification

of waste vegetable oil in a batch reactor using dynamic modeling approach

Specifically to;– explore the effect due to impeller and baffle on

biodiesel yield and reaction kinetics in a 2 litre batch reactor during trans-esterification of WVO

– develop a dynamic model taking into account effect of due hydrodynamics during trans-esterification in a batch reactor

– evaluate and validate the performance of the model process with a view to optimize the process.

Progress Report

November 2009-April 2010

Methodology 1. Literature review (Jan 2009-till date)2. Characterization - WVO and

transesterification parameter.A.Collection of WVO/ FFA analysis/ Fatty Acid

profilea) titrimetric method for FFA content. The analysis was

replicated twice for three different samples of WVO. (AOCS Official Method Ca 5a-40:1)

B. Transesterification of WVO at varying impeller/baffle position• WVO:MeOH (1:6) in 2 Litre Reactor (KOH as catalyst) at

55°C, 60°C, 70°C, 600 rpm• GC-MS Analysis of transesterified WVO for TG, DG,

MG, Glyerol content

1) Develop transport and kinetics model for simulation in CFD

• Reaction transport coupling • Comparison of (3) with

transesterification process data• Evaluation/ Validation Dynamic

Model

Methodology (Cont’d)

GC-MS Configuration• The analysis was

performed on an Agilent 6890/ 5973 GC/MSD system. Automated split injection was performed using an Agilent 7683 automatic sampler.

2 minsolvent delay

250°CMS source

150°CMS quad

(40-500amu), threshold 100

MSD parameter Scan

50°C, 1 minDetector temperature AUX 2

1 minoven temperature

heliumcarrier gas

1/50split ratio

1µminjection volume

250°Cinlet temperature

Table 1. GC-MS configuration

Methodology (Cont’d)

Result-Kinetics

0.9002ARACHIDIC

NALINOLENIC

26.4377LINOLEIC

32.4711OLEIC

5.690STEARIC

1.18117PALMTIOLEIC

31.9001PALMITIC

1.59095MYRISTIC

0.7279LAURIC

%FATTY ACID

Table 2. Fatty Acid Profile using GC-MS

Fatty acid profile was obtained using a GC-MS Agilent 7683 automatic sampler with automated split injection system on a DB-Wax column. Sample preparation method was according to [2]

Source of WVOIIUM (Gombak campus) caferia between June-December 2009

Titrimetry

FFA - 1.11- 3.35%

Single step Transesterification

[1] WCO + [6]MeOH Ester + Gly (500g) (110ml)

KOH (2g)

Sample preparation for analysis was according to [2]

WVO:MeOH (1:6) in 2 Litre Reactor KOH – 2gTemperature 55°C, 60°C,

70°C, Impeller speed - 600 rpmImpeller type – RushtonImpeller bottom clearance – 15 mm

Figure 2: Fatty acid profile during Transesterification WVO at 55°C using a single Rushton Impeller with bottom clearance 15mm at 600 rpm

0

10

20

30

40

50

60

70

80

0 1 5 10 15 30 45 60 75 90 105

Th

ou

sa

nd

s

time(min)

Co

nc

en

tra

tio

n(p

pm

)

LAURIC C12:0

MYRISTIC C14:0

PALMITIC C16:0

PALMTIOLEIC C16:1

STEARIC C18:0

OLEIC C18:1 c+t

LINOLEIC C18:2 c+t

LINOLENIC C18:3n6

arachidic C20:0

Palmitic

LinoleicOleic

Result (Cont’d)

0

50

100

150

200

250

300

350

0 1 5 10 15 30 45 60 75 90

Th

ou

sa

nd

s

time(min)

Co

nc

en

tra

tio

n (

pp

m)

LAURIC C12:0

MYRISTIC C14:0

PALMITIC C16:0

PALMTIOLEIC C16:1

STEARIC C18:0

OLEIC C18:1 c+t

LINOLEIC C18:2 c+t

LINOLENIC C18:3n6

arachidic C20:0

Figure 3: Fatty acid profile during Transesterification WVO at 60°C using a single Rushton Impeller with tank bottom clearance 15mm at 600 rpm

Palmitic

Linoleic

Oleic

Result (Cont’d)

0

50

100

150

200

250

300

350

0 1 5 10 15 30 45 60 75 90 105

Th

ou

san

ds

time(min)

Co

ncen

trati

on

(pp

m)

arachidic C20:0

LINOLENIC C18:3n6

LINOLEIC C18:2 c+t

OLEIC C18:1 c+t

STEARIC C18:0

PALMTIOLEIC C16:1

PALMITIC C16:0

MYRISTIC C14:0

LAURIC C12:0

Figure 4: Fatty acid profile during Transesterification WVO at 70°C using a single Rushton Impeller with tank bottom clearance 15mm at 600 rpm

PalmiticLinoleicOleic

Result (Cont’d)

0.23T=30mmImpeller Diameter, D

48mmTotal Liquid Height, L

130mmTank diameter, T

150mmHeight, H

0.11T=15mm0.15T=20mm0.19T=25mm0.23T=30mm0.27T=35mm

impeller bottom clearance, C

600 rpm (Re=D2Nρ/μ)turbulent

Impeller speedTable 3: Stirrer reaction configuration

xyzPart1xy planeyz planezx planePartBodyPart2 (Part2.1)Part3 (Part3.1)Part3xy planeyz planezx planePartBodyPlane.1Pad.1Sketch.1Part4 (Part4.1)Part4xy planeyz plane

Results-hydrodynamic effect of impeller / baffle using COMSOL

κ-ε model - Navier-Stokes’ Equation (turbulent)WVO - Fluid• Constant Density, Viscosity• Cylindrical coordinates

.v 0∇ =

( ) ( )( ).V

V v+ v FT

U pIt

ρ η∂

+ ∇ = ∇ − + ∇ ∇ +∂

Continuity Equation

Momentum Equation

Governing Equation

the reactor-fluid was modeled as a 2D axisymmetrical body and COMSOL Multiphysics 3.5a was used to obtain the velocity profile and hydrodynamic component of the Navier Stokes’ equation. (Fig 5-8)

Boundary conditions for the tank wall, liquid surface, impeller walls were selected as in [3]

Figure 5a: axial

velocity profile present work

Figure 5b: axial velocity profile of experimentally validated model Ochieng et al, 2008 [4]

Result (Cont’d)

Figure 6: Axial velocity profile for unbaffled reactor above (x=0.35T) and below (x=0.19T) impeller at bottom distances, C (a) 0.11T (b) 0.17T (c) 0.23T

Result (Cont’d)

Figure 7: Simulated mean tangential, radial and axial velocity at impeller bottom Clearance, C= 0.11T, 0.15T, 0.19T, 0.23T and 0.27T for unbaffled

Result (Cont’d)

Simulated mean turbulent kinetic and dissipation energy rate

Figure 8b: mean turbulent kinetic at C=0.23T

Figure 8a: mean turbulent dissipation energy rate at C=0.23T

Result (Cont’d)

Discussion• FFA level low

– Adoption of single transesterification• Preliminary transesterification

– Fatty acid of ester during reaction peaked at 5 and 10 minutes for 55 and 60C respectively

– fatty acid profile cannot be used to computer reaction kinetics, however it revealed reaction trend and effect of continuous mixing

– TG, DG and MG internal standard and cool-on column add-on are Not available on GC-MS

• Simulated Hydrodynamics in 2D– 2-D CFD simulation was compared with an experimentally validated

model.– The simulation revealed that Mean turbulence and dissipative

energies peaked at impeller bottom clearance of C=0.237T for both baffled and unbaffled systems,

– The 2-D model is being improved for translation to full 3-D explicit ALE model to provided insight into the hydrodynamics in swirl flow 2 Litre reactor using WCO..

On-going experiment• Transesterification of WVO at

varying impeller/baffle position• TG, DG, MG, Glycerol estimation

Outstanding work• Transesterification at three temperature

and three reactor bottom distance • Obtain conversion of TG, DG and MG in

GC-MS (Cool-on column)• Reactive Mixing simulation• Evaluation/ validation of Dynamic Model

Modified Work Plan

CFD Modeling of the flow and reaction

WVO analysis for FFA/

Transesterification Kinetics

Hydrodynamic simulation in axi-

symmetrical 2D/3D

Start

Model

Is CFD Model comparable

to lab result ?

NoNo

Yes

Start

CFD validation

Gantt Chart/ Milestone

Publications• Investigating Hydrodynamic Effects During Mixing in a 2 L

Reactor Using CFD for Waste Cooking Oil Transesterification accepted for presentation at the Asia Modelling Symposium 2010 Kota Kinabalu, Malaysia May 26, 2010 - May 28,

• Biodiesel production: A Comparative Review submitted to the International Energy Journal

References• 1. Dias, J., M. Alvim-Ferraz, and M. Almeida, Comparison of the

performance of different homogeneous alkali catalysts during transesterification of waste and virgin oils and evaluation of biodiesel quality. Fuel, 2008.

• 2. David, F., P. Sandra, and P. Wylie, Improving the analysis of fatty acid methyl esters using retention time locked methods and retention time databases. Agilent Technologies Application Note, 2002.

• 3. Chemical Engineering Module User’s Guide Version 3.5a• 4. Ochieng, A., et al., Mixing in a tank stirred by a Rushton turbine at a low

clearance. Chemical Engineering and Processing: Process Intensification, 2008. 47(5): p. 842-851