2014
Team One – Executive Summary
The Diesel Crew
Adam Alexander, Michael Lubben
Angus Richeson, Thomas Voss
Calvin College Engineering
4/11/2014
1 Introduction
When selecting a project for this year, the team shared a desire to work with a tangible project, and
to choose a project from the area of renewable energy. The team searched through the senior design
archives and found a waste cooking oil (WCO) to biodiesel reactor built by Team Rinnova in 2008. After
some preliminary research, the team learned that many different types of reactors and reactions are
being implemented in the production of biodiesel from WCO. The team decided to investigate reaction
systems, and design, build and test an experimental biodiesel reactor system.
Much of the fall was spent in the library and on the computer researching the various components
of the reactor system. The reactor system breaks down into the following components: pre-filter and
water removal, reactor, separation train, methanol recovery, biodiesel polisher and a final filtration
system. The team determined that the focal point of the system was the reactor. Both the type of
reaction used and the type of reactor implemented would determine what was needed in the rest of the
system. First, the team decided to implement a solid catalyst reaction to allow for a continuous process,
and a microwave oven as the energy source. The team needed a method to determine the amount of
conversion achieved to better determine the requirements for the separation train. The team
determined two methods were possible for determining conversion, HPLC, and a methanol solubility
test (biodiesel is soluble in methanol, while cooking oil is not). The team met with Professor Tatko of the
Chemistry Department and were approved to borrow a HPLC unit for the year. Secondly, the team
selected a pretreatment system similar to a design from the Utah Biodiesel Supply Company. Next the
team was put into contact with a representative with the DOW Chemical company who donated a
polishing resin, AMBERLITETM BD10DRYTM, for the use of our project. After the polishing column, the last
step of the system is a final filter to remove any fine particulates from the fuel stream. The team
decided to implement a normal petrodiesel filter.
The remaining portions of the reaction system, the separation unit and methanol recovery system,
became the largest obstacles the team faced. The decision to use a solid catalyst reaction added another
requirement to the separation unit. The unit separates the biodiesel product from the glycerol
byproduct, the excess methanol, and the solid catalyst. The team is yet determining the final design of
this system, but is looking to implement a cascade system which will trap the catalyst for later removal.
This unit will be followed by a heating system to boil off the excess methanol for recovery. The team
received a large condensing unit from an old reactor system donated to Calvin College from Pfizer Inc.
The team will use this as the method of recovery for the methanol.
In addition to the design decisions, the project involves many additional choices that affect the
success of the project. First, the team asked for permission from the Chemistry Department for use of
the Advanced Organic Chemistry Lab. This space was used for all lab experiments for determining the
proper conditions of the different units. Secondly, to better control a continuous process, the team
decided to implement a control system. The Calvin Engineering Department donated LabVIEW Software
and FieldPoint control modules for the project. The team had much to learn about implementing a
control system and will provide control and sensor information for the majority of the system.
2 Project Scope
The objective of Team One’s senior design project is to construct a reaction system for producing
biodiesel from waste cooking oil (WCO), suitable for use by Calvin-sized institutions (approximately 4000
students / 8.6 gallons of WCO per day). Originally, we set out only to improve upon Rinnova’s 2008
design. As the team has progressed on the project, this goal has shifted slightly. Now, the primary
objective is not to outcompete Team Rinnova’s design, but to show the feasibility of a continuous
reactor system utilizing a solid metal catalyst for small scale biodiesel production.
TABLE 2-1: PROJECT GOALS
1
2
3
4
5
6
7
Make the new system small enough to fit through a standard doorway and easily maneuverable
Match or exceed Rinnova’s production rate of 40 gal in 16 hours (2.5 gal/hour)
Improve feedstock filtration and dewatering
Improve consistency of system operation and biodiesel product
Have a capital cost lower than $6,000 for the reactor system
Create a transparent system design, such that operation is possible by a non-professional with little training
Require infrequent operator interaction, such that the operator could work on something else while in the
same room as the system
Make the new system easily serviceable, ensuring that all consumables are easily and inexpensively replaced
Meet ASTM quality specifications for biodiesel, the industry standard
Meet and exceed all safety requirements
8
9
10
Once the team chose to use a solid catalyst rather than liquid sodium hydroxide or potassium
hydroxide, the team decided the following are not considered within the scope of The Diesel Crew’s
project:

Catalyst cleansing and recycle

Purification of glycerol byproduct

Ensure all ASTM standards of quality are met (this requires very expensive analytical equipment
not available at Calvin College)
3 Design Decisions
3.1 Process Flow Diagram
Figure 3-1 Process Flow Diagram
3.2 LabVIEW Control System
One of the original design goals for the biodiesel reactor was transparency of design and ease of
use. We have chosen to implement the LabVIEW graphical programming platform to provide a simple
and intuitive user interface for the reactor system. Calvin has supplied The Diesel Crew with several
FieldPoint control modules that establish a connection between the LabVIEW software and the various
components of the system. These FieldPoint modules will allow control of the metering pumps,
microwave power output, heating coil power output, solenoid valves, and other electrical components.
The modules will also enable monitoring of the system by way of thermocouples, pressure transducers
(used to monitor fluid level in each of the containers), and flow meters. Figure 3-2 below provides an
example of what the interface will look like. A touchscreen monitor will be used for easy user
interaction. System safety is also improved by implementing thermal shut offs and overflow protection
through LabVIEW. PID feedback controllers will be designed in LabVIEW for nearly all system variables
resulting in a reactor that will run itself requiring little to no user input.
Figure 3-2: Tank Level Measurement in LabVIEW
3.3 Dewatering System
The purpose of the dewatering system is to remove large particulates and water from the WCO.
Water is detrimental to the reaction. First, water will poison the catalyst, forming calcium hydroxide and
severely limiting the conversion. Second, the presence of water in the reaction will push side reactions
that form soap and will result in an emulsion. Finally, water present in the reaction solution can result in
the hydration of the triglycerides to FFA instead of methylating the triglycerides. The limit of FFA in the
final diesel product is very low, and thus this side reaction must be limited.
Figure 3-3: Waste Cooking Oil Dewatering System
The unit design, as seen in Figure 3-3 above, works as a small batch process before the reaction
system. Oil will be pored through a fine filter mesh, 177 micron hole width, into a 15 gallon drum. The
oil will be pumped out of the bottom of the drum past a heating coil and sprayed back into the top of
the drum. The circulatory system allows for good mixing of the oil, as well as rapid heating of the
solution. In an effort to save money, the team was able to 3-D print the spray valve from acrylic plastic.
The team tested the plastic for heat and chemical degradation in an oil bath at 110 °C. The test revealed
no signs of thermal or chemical degradation.
Finally, the team chose a heating element that worked on 120 volt power, but would heat up
the oil quickly. The team decided against a higher voltage for easier use of our reactor system at any
location. The team purchased a 2000 W heating element capable of heating 10 gallons of oil to 100 °C in
45 minutes. To ensure the safety of the system, the team chose to contain the heating element within 1
inch galvanized steel pipe.
3.4 Catalyst SelectionThe reaction to produce biodiesel from WCO and methanol is both endothermic and reversible.
A catalyst is necessary to promote the forward reaction towards biodiesel and to reduce the reaction
time required to reach sufficient conversion. Many different catalysts can be used in this process, each
with its own advantages and disadvantages. Rinnova used a solution of potassium hydroxide (KOH)
dissolved in water, which worked well, but, as a liquid, it is difficult to separate out after the reaction,
requires a water wash. This wash takes several hours, can potentially introduce water or soaps to the
fuel, and prevents catalyst recycling. In addition to a desire for further exposure to the extracurricular
topic of solids handling, The Diesel Crew chose to use a solid catalyst to eliminate the wash step and
permit catalyst recycling.
In the past five years there have been many papers published on a multitude of solid substances
used as biodiesel catalysts. Among them, several contenders rose to Team One’s attention: zirconium
oxide (ZrO2), calcium oxide (CaO), also known as quicklime, magnesium oxide (MgO), and strontium
oxide (SrO). In many ways, ZrO2 is an excellent catalyst choice. It is reportedly quite effective at the
transesterification reaction that turn oil to biodiesel, as well as a respectable catalyst of free fatty acid
(FFA) esterification, which prevents these fatty acids from impairing the transesterification in a number
of ways. ZrO2 is moderately resistant to poisoning by water in the WCO feed, can be heat-treated to
restore its catalytic activity, and has negligible solubility in the reaction mixture. Its disadvantages are its
high cost (>$1/gram), and that it requires a very small particle diameter to be effective, making it
difficult to reclaim from the reactor effluent. Since the members of The Diesel Crew are inexperienced
with solids handling, use of ZrO2 would likely inadvertently send a substantial portion of the allocated
budget literally down the drain.
Calcium oxide, on the other hand, is easily obtainable at very low costs, and can be regenerated by
roasting if needed. However, it quickly becomes poisoned by water (even water in the air) or FFA, and at
high FFA levels, soap formation can become a problem. Still, at 60°C and 1 atm, it can achieve WCO
conversion as high as 97%. MgO was rejected due to poor conversion of WCO at the desired
temperature and pressure (~60C, just under the boiling point of methanol at 1 atm), and because of its
high solubility in methanol. SrO is much more active than CaO, but is moderately soluble in methanol,
and fairly expensive. As a result, it too was rejected, resulting in calcium oxide being selected for use as
the catalyst.
3.5 Dual reactor design- CSTR into Microwave PFR
Research conducted towards the end of last semester indicated that the required level of
conversion to biodiesel, greater than 90%, would not be achieved in the desired amount of time using
our choice of CaO catalyst and a simple plug-flow or continuous-stirred tank reactor. To overcome this
short coming, many alternative reactor designs were explored and a decision matrix was used to
determine the best choice. Table 3-2 below shows the types of reactors explored, and Table 3-1
provides definitions for the abbreviations used in the decision matrix.
Table 3-1: Summary of Abbreviations for Decision Matix in Table 3-2
Criteria
Cost
Construction Difficulty
Operation costs
Operation Difficulty
Typical Fame Conversion
Reaction Time
Operating Temp
Pressure
Pretreatment of WCO
Treatment of Pdts.
Requires Catalyst
Solid Metal Catalyst
Flow Rate
Heat Transfer
Abbr.
C
CD
OC
OD
conv
t
T
P
PT
TP
Cat
SMC
FR
HT
Reactor Type
Microreactor
Acoustical Cavitation
Hydrodynamic Cavitation
Microwave Batch
Microwave Continuous
Oscillatory Baffled
Motionless Inline
Abbr.
Micro
AC
HC
MB
MC
OB
MI
Table 3-2: Decision Matrix for Reactor Type
Matrix Decisions
Criteria
C
CD
OC
OD
conv
t
T
P
PT
TP
Cat
Decision Weight
10
7
5
9
8
5
9
9
4
4
15
Reactor Type
Micro
2
8
8
8
10
10
7
10
2
2
5
AC
2
8
3
9
6
9
7
10
2
2
5
HC
4
8
5
9
8
7
7
10
2
2
5
MB
10
7
2
5
10
2
7
10
2
7
5
MC
8
6
2
9
8
7
7
10
2
7
5
OB
5
8
4
8
9
3
7
10
2
7
5
MI
8
6
7
10
9
2
7
10
2
7
5
SMC
FR
HT
Weighted Total
Normalized Score
15
5
5
110
(Higher=More Favorable)
0
1
7
3
10
5
3
8
5
7
2
10
7
8
10
7
5
5
2
8
5
602
5.5
629
5.7
655
6.0
723
6.6
771
7.0
704
6.4
688
6.3
From the above decision matrix, we determined that a microwave reactor was most suitable for
our design. The use of microwave reactors for intensified biodiesel production is an emerging
technology. The majority of journal articles found on this leading-edge technology have been published
in the last two years.
In order to test the value of the microwave, the team performed two batch reactions for one hour
with a 6:1 volume ratio of MeOH:WCO and 2wt% CaO, one heated with a mantle, one heated in a
microwave. The microwave reaction showed 38% conversion, and the conventionally heated reaction
showed only 7.7% conversion, indicating the value of using a microwave. Microwave irradiation has two
major benefits, no external heating is required and the catalyst efficiency is significantly improved.
Microwave irradiation is a highly efficient way to heat the reactor contents, eliminating the need for
another heat source. Microwave irradiation also encourages mixing on the molecular level. Small
pockets of intense heat and pressure. This promotes transesterification of triglycerides with methanol,
reaching near complete conversion depending on which catalyst is used.
After significant design calculations and considerations, the team decided that a dual reactor
scheme would be needed to achieve the high level of conversion in the given amount of time. First a
large continuously stirred tank reactor (CSTR) at 60°C with a catalyst slurry is used to achieve reasonable
conversion with a large space time. Then the reaction mixture moves to a plug flow reactor (PFR), which
is passed through the microwave to achieve the rest of the conversion. It is typically difficult to have a
catalyst slurry in a PFR, but the team overcame this challenge by finding static mixers, which cause the
slurry to be mixed as it moves through the PFR.
The team used batch testing to find the conditions for the reactor. A temperature of 60°C was
chosen, as this is near the maximum achievable temperature without MeOH boiling at atmospheric
pressure, which would cause safety and design concerns. The reaction is run with an excess of MeOH to
ensure high conversion. The optimal volume ratio of MeOH:WCO and optimal ratio of catalyst to WCO
were investigated in the lab. Results showed that using more catalyst resulted in higher conversion
(Figure 3-4).
Figure 3-4 Catalyst Ratio Determination
The results showed that a catalyst ratio of 283g CaO per L of WCO would be the best. A higher
amount of catalyst would have smaller effect on conversion and cause more difficulty in the separation
processes. The team then tested different volume ratios at this catalyst ratio (Figure 3-5).
Figure 3-5 Volume Ratio Determination
Because using the same catalyst ratio with a lower volume ratio results in a larger catalyst
concentration, lower volume ratios yielded higher conversions. The team chose a 3:1 volume ratio, as
this ratio will give high conversion without putting unnecessary strain on the separation system.
3.6 Methanol Recovery
A large volume of methanol must be recovered from the reactor stream on a continuous basis. A
desired biodiesel production rate of 2.5 gal/hour and a methanol to WCO ratio of 3:1 means that
roughly 0.125 gal/min (473mL/min) of methanol must be removed. Currently, we plan to use vacuum
distillation and possibly a heating coil to evaporate the volatile methanol off of the reactor effluent. A
water-cooled heat exchanger will then be used to condense the methanol into a collection vessel. The
effluent leaving the reactor will be just below the boiling point of methanol; therefore, only a low
vacuum, less than -5 psig, will be required for removal. The team plans to implement a large glass
condenser acquired from a Pfizer donated reactor system (Figure 3-6).
Figure 3-6 Glass condenser Available to Use for Methanol Recovery
3.7 Glycerol and Catalyst Removal
Once most of the MeOH is removed, the glycerol and biodiesel product form a two-phase liquidliquid equilibrium (LLE), making it easy to separate out the glycerol in a vertical column. This vertical
column would feature a feed at the middle, a valve to set the drip rate of glycerol at the bottom, and a
stream off the top for the biodiesel product. This design will easily be constructed and implemented, but
the glycerol may be removed elsewhere with the catalyst.
The catalyst recovery has proved to be one of the most difficult design portions of the system. The
small particle size of the CaO, which is necessary to achieve good performance, requires a very fine
mesh/filter paper for filtration, resulting in a large pressure drop. There is also a very large amount of
the catalyst, so a filter can get clogged very quickly, which is troubling in a continuous system. The CaO
could be allowed to settle out, but the CaO volume is about the same as the volume of the biodiesel
product phase, so a significant amount of biodiesel is lost if the CaO is allowed to settle out from the
liquid mixture. In a settling design, the biodiesel could be re-claimed later in a batch process or recycled
continuously. A settling design could also have the glycerol settle out with the CaO, eliminating the need
for the LLE column described earlier. Whether a settling design or filter design is used, this part of the
system is a batch process which accumulates CaO and is only implementable in a continuous design
because it takes a long time before it needs to be cleaned out.
The team has several designs for this part of the system: a large canister filter, a large flat filter
mesh, a slanted filter drum (lower pressure drop because liquid hold-up does not have to pass through
cake), and a cascade settling system before or after the MeOH recovery. The team has catalyst that is
being delivered, so testing can begin on this part of the system. If none of these designs works semicontinuously, the team may have to convert to more of a batch system.
3.8 Amberlite™ BD10DRY™ absorbent polishing column
The final step of the reactor process is the polishing column. The polishing column, otherwise
known as a purification column, consists of a large cylindrical tube filled with ion-exchange polymer
beads that prohibit the passage of various contaminates while allowing the biodiesel to pass through.
Possible contaminants include small amounts of glycerol, CaO catalyst, remaining mono-, di- and triglycerides, and any remaining free fatty acids. This is a crucial step in producing a quality biodiesel
product that meets all ASTM standards. Polishing column technology is well established and has not
changed much since Rinnova’s design. The team has chosen a very similar design to Rinnova’s polishing
column based on its effectiveness at removing most all contaminants, the ability of the column to work
in a continuous fashion, and the affordable nature of the column. There are five ion-exchange resins
commonly used for biodiesel purification, each with its pro and cons. The major design decision then
becomes which ion-exchange polymer is most suited for our specific reactor. Due to limitations of time
and money, the team has been unable to test these five polymers for their effectiveness at removing the
CaO and other contaminants. However, Professor Sykes provided The Diesel Crew with a contact at the
DOW Chemical Company who was able to supply the team with five pounds of Amberlite™ BD10Dry™ to
perform testing. This is the same ion-resin used by Team Rinnova so we expect it to work well with our
system. Bench scale testing of the ion-resin is expected to take place shortly, and final column
construction shortly thereafter.