Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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A device for the transesterification of animal and plant glycerides into fatty
acid alkyl
esters for small scale production of biodiesel and value added products
BACKGROUND OF THE INVENTION
This invention relates to a portable device for the batch transesterification
of glycerides into
fatty acid alkyl esters, particularly fatty acid methyl esters, in a small
scale system in the
general range of 50-500 L, more or less, which permits the economic production
of fatty
acid alkyl esters for various uses, including biodiesel.
Biodiesel generated from the transesterification of animal and vegetable fats
is a globally
accepted and generally ecologically sound substitute to petrodiesel in the
various
applications for which the latter is known. Of all such applications,
replacement of
petrodiesel with biodiesel in mobile engines offers the potential for a
significant impact in
the economy of remote, rural and low density areas of the world.
The use of transesterified fatty acids as fuels for diesel engines is
constrained by the
necessity of the biodiesel to meet certain standards with respect to chemical
contamination
and composition. Fatty acid esters show a bulk density which is lower than
that of glycerin,
a byproduct of transesterification. For biofuel (biodiesel) applications,
tolerance for
impurities from various sources which include but are not limited to soap,
colour, odours,
unreacted catalyst, metals and metallic compounds, free and total glycerin,
methanol,
chlorophyll, water and sediment are listed in the specifications for ASTM 6751
for North
America and European Standard EN14214 for Europe.
Fabrication of biodiesel is described in various patents, including EP 07 708
813, AU
2006100428, WO 2004053036, WO 2005JP14015 20050801 and WO 200228811, and
generally consists of a process including steps of (1) degumming, (2) acid
catalyzed
esterification of free fatty acids with methanol in the presence of sulfuric
acid, and (3)
neutralization of the acid catalyst followed by conventional base catalyzed
transesterification. The resulting diesel can then be washed with acids (WO
2004053036)
or with adsorbants (WO 2005037968). Cooke et al. (WO 2005037969) described a
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process based on the use of adsorbant materials, including magnesium silicate,
for
cleaning biodiesel to meet ASTM and EN requirements. The content of patent WO
2005037968 is hereby incorporated by reference. Cooke et al. (WO 2005037969),
however, did not address the removal of the adsorbant materials after
contacting with
biodiesel. Such removal of the adsorbant material is critical to meet fuel
standards and
prevent damages to engines by end-users.
Previous inventions dealing with the transesterification of glycerides into
biodiesel describe
methods for manufacturing of fatty acid alkyl esters through complex
continuous processes
using large scale, multi-vessels equipment which creates economical fuel only
at large
production scales. For example, patent CA 2,499,821 designed a method based on
the
continuous transesterification at large scale processes using a complex multi-
vessels
system whereby the transesterification reaction is supported by dynamic
emulsification
using cavitation, ultrasound, and/or cavitation of a two phase system.
Another example, CA 2,280,289 by Boocock and Brooke created a method based on
a
continuous single-phase production system using cosolvents which increases
phase co-
mingling as described by Fisher et al. in CA 2,499,821.
Another example, patent CA 2,515,816 describes a complex, capital-intensive,
automated,
method for refining biodiesel which includes the transesterification catalyst
to be prepared
in a base catalyst tank by spraying alkyl alcohol under pressure through jets
at metal
hydroxide pellets until the pellets have fully reacted with the alcohol. The
feedstock oil is
heated and transesterified in the presence of alkyl alcohol and the
transesterification
catalyst in a closed, recirculating transesterification flow system under
slight cavitation to
yield product alkyl ester and product glycerol. Cavitation is achieved by
permitting air to
enter the transesterification flow system through an adjustable air inlet
valve. Purification
of the product alkyl ester preferably includes subjecting the product alkyl
ester to an
overhead water mist in a wash tank with simultaneous infusion of a stream of
air bubbles.
In practice, the sophisticated levels of automation of previous arts (CA
2,499,821; CA
2,280,289; CA 2,525,816; US 2005204612; WO 2005017075) for the production of
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biodiesel do not permit them to create cost-effective fuel at the scale of
single biodiesel
users in batch sizes of 100-500 L. Indeed, the apparatus described in patents
CA
2,280,289; CA 2,499,821; CA 2,515,816; CA 2,525,816; MD 20040091; US
2005204612,
US 2005006290; WO 2003016442; WO 2005017075 necessitate significant capital
outlays
to build, sophisticated controls to operate which together with their large
sizes limit the
market potential and/or usefulness of transesterified fatty acid technologies
to large groups
of biodiesel consumers which are found in large population centers while
excluding their
application in scarcely populated or geographically isolated areas such as
rural, northern or
remote environments. This is of special significance to restaurant owners who
generate
waste vegetable oil or oilseed farmers with excess seedstocks and emphasizes
the need
for small-scale systems.
Although attention to the small-scale concept for biodiesel manufacturing has
been given in
some patents, there is a need for improvement. Patent WO 2004035396 relates to
a single
20-30 L vessel of clear or opaque plastic and uses hand shaking of the mixture
in the
vessel to produce biodiesel. The vessel is fitted with openings that allow the
input of fluids
and for the careful draining-off of stratified layers. The vessel incorporates
lined levels on
the sides of the vessel to assist the person in calibrating the amount of
feedstock and the
special blend of alcohol/catalyst (Biodiesel Converter) that will promote the
reaction to
produce biodiesel. Patent WO 2003022961 provides a description for a device
based on a
complex continuous flow and acid catalysis in the 1440 L range.
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SUMMARY OF THE INVENTION
The invention addresses the need to create a simplified small scale device for
the
transesterification of animal and vegetable fats, either virgin or used, at a
general range of
50-500 L batches and which can be operated by a minimally trained operator
without the
assistance of computer technologies and heavy infrastructure and can be easily
transported from one location to the next. As such, the small size as well as
the simplicity
of use permit to deploy this biodiesel manufacturing technology to single
users, restaurant
owners, oilseed farmers as well as remote and low density parts of the world.
The invention comprises a primary vessel, preferably made of steel, supported
on a frame.
The primary vessel is connected to a mixing chamber as well as an optional
filter assembly
also mounted on the side of the reaction tank. The device may be mounted
inside a spill
containment basin. The main reaction vessel is heated with immersion heaters,
preferably,
or other means of heating to and maintaining reaction temperature. The
invention includes
an electrical console which permits the control of the electrical equipment
which are
subcomponents of the device. Elimination of the glycerin phase resulting from
transesterification is conducted through transparent piping and facilitated by
transparent
piping serving as a manometer which is mounted on the side of main reaction
vessel.
Elimination of the lower phase is conducted through gravimetric flow and can
be aided by a
circulation pump. Purification of the remaining transesterified fatty acids is
conducted
through the addition of adsorbant material or acid washes. If adsorbant
material is used,
an optional filter housing unit can be used, preferably mounted on the side of
the main
vessel, for filtration of adsorbant particles. An embodiment of the invention
includes a spill
containment basin to prevent possible environmental contamination.
In the drawings, which form a part of this specification,
Fig. 1 is a side elevational view of the preferred embodiment of the device in
its totality;
Fig. 2 is a side elevational view of the device support stand and mounting
hoops;
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Fig. 3 is a top plan view of the device support stand and mounting hoops;
Fig. 4 is a side elevational view of the primary vessel, system pump,
associated plumbing
and support stand with mounting hoops;
Fig. 5 is a side elevational view of the filter housing, associated plumbing
and support
stand with mounting hoops;
Fig. 6 is a side elevational view of the alcohol/catalyst tank, associated
plumbing and
support stand with mounting hoops;
Fig. 7 is a longitudinal section view of the electrical console; and,
Fig. 8 is a top plan view of the device in its totality;
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1 DETAILED DESCRIPTION OF THE INVENTION
2
3 In the preferred embodiment, the primary vessel of the device described is
made of steel or
4 material which is resistant to the conditions of the primary vessel and is
fitted with two
immersion heaters and includes a circulation system made of transparent tubing
which
6 permits the operator to visually ascertain the presence of phase separation
as well as
7 facilitates the removal of the glycerin phase from the primary vessel. The
transesterified
8 fatty acids containing adsorbant material is piped to a filter housing
containing bag filters to
9 specific mesh sizes such as those described in patent US 5514275 and which
permit the
elimination of absorbent material from the biofuel. The fabrication of such
filters and filter
11 assembly is described in patent US 5514275, the contents of which are
hereby
12 incorporated by reference.
13
14 In another embodiment of the current invention, the transesterified fatty
acids are pumped
through a column packed with absorbent material which is therefore prevented
to reenter
16 the primary vessel.
17
18 In the following two examples the invention is further described for the
purpose of
19 illustrating its application but not to limit scope of the invention.
21 Example 1: Transesterification of waste vegetable oil from restaurant deep
fryers followed
22 by cleaning using magnesium silicate and filtration column
23
24 1) Preparation of the waste vegetable oil feedstock for
transesterification:
a. Titrating the waste vegetable oil feedstock to determine its free fatty
acid
26 content;
27 b. Measuring the water content of the waste vegetable oil feedstock;
28 c. Filtering the waste vegetable oil feedstock through a 100 micron
strainer and
29 into the primary vessel;
d. Circulating and heating the waste vegetable oil feedstock to 60 C;
31 e. Settling and dewatering the waste vegetable oil feedstock, if necessary;
1
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1 f. Dissolving the alkaline catalyst, particularly sodium or potassium
hydroxide,
2 in the alcohol, particularly methanol, in the alcohol/catalyst tank;
3
4 2) Performing the transesterification reaction:
a. Adding the alcohol/catalyst mixture to the waste vegetable oil feedstock.
The
6 valves are configured such that the system pump simultaneously draws
7 waste vegetable oil feedstock from the primary vessel outlet and
8 alcohol/catalyst mixture from the alcohol/catalyst tank outlet and
vigorously
9 blends the two streams inside the pump chamber. The reaction mixture is
then pumped to the vessel inlet. The rate at which the alcohol/catalyst
11 mixture is added to the waste vegetable oil feedstock is controlled by way
of
12 an in-line flowmeter.
13 b. Circulating the reaction mixture. The reaction mixture is continuously
14 pumped from the bottom of the primary vessel to the top of the primary
vessel
and the temperature of the reaction mixture is maintained at 60 C by way of
16 the immersion heaters.
17 c. Settling and draining the crude byproduct. Heat and mixing are removed
and
18 the reaction mixture is allowed to settle and separate under gravity into
its
19 two distinct phases or layers - the raw biodiesel phase and the crude
glycerin
phase. Following a settling period, the crude byproduct phase is repeatedly
21 drawn-off the bottom of the primary vessel.
22 d. Warming the raw biodiesel. Heat and mixing are re-applied to the raw
23 biodiesel to raise the temperature to 60 C prior to the addition of
magnesium
24 silicate to the primary vessel.
26 3) Purifying the biodiesel fuel:
27 a. Adding magnesium silicate. Magnesium silicate is added to the primary
28 vessel and circulated with the raw biodiesel. The amount of magnesium
29 silicate added to the raw biodiesel depends on the free fatty acid content
of
the original waste vegetable oil feedstock:
31
32
2
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Free fatty acid Amount of Free fatty acid Amount of
content of waste magnesium content of waste magnesium
vegetable oil silicate added to vegetable oil silicate added to
feedstock (% raw biodiesel (% feedstock (% raw biodiesel (%
w/w w/w w/w w/w
0.0 0.5 2.6 1.3
0.2 0.6 2.8 1.3
0.4 0.6 3.0 1.4
0.6 0.7 3.2 1.5
0.8 0.7 3.4 1.5
1.0 0.8 3.6 1.6
1.2 0.9 3.8 1.6
1.4 0.9 4.0 1.7
1.6 1.0 4.2 1.8
1.8 1.0 4.4 1.8
2.0 1.1 4.6 1.9
2.2 1.2 4.8 1.9
2.4 1.2 5.0 2.0
1
2 For example, raw biodiesel made using a waste vegetabie oil feedstock with
3 a free fatty acid content of 4.6% w/w of the waste vegetable oil feedstock
4 would receive magnesium silicate at 1.9% w/w of the waste vegetable oil
feedstock.
6 b. Removing the magnesium silicate. Mixing is removed and the mixture of
7 biodiesel and magnesium silicate is allowed to settle. The magnesium
8 silicate that has accumulated on the bottom of the primary vessel is
9 repeatedly drawn-off. Settling permits the removal of the larger magnesium
silicate particles (i.e. >100 microns), however the smaller particles must be
11 removed by filtration. In this example, the filter housing and 4 sizes of
12 polypropylene felt filter bags (i.e. 100, 50, 25 and 5 micron) are used to
13 eliminate the very fine magnesium silicate particles from the clean
biodiesel.
14 The valves are configured such that the pump delivers biodiesel containing
magnesium silicate from the primary vessel outlet to the filter housing inlet
16 and draws filtered biodiesel from the filter housing outlet and pumps it to
the
17 primary vessel inlet. The biodiesel is sent through the filter housing on
each
3
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1 filter bag. The purified biodiesel is then transferred from the primary
vessel to
2 a storage container(s).
3
4 Example 2: Transesterification of virgin vegetable oil followed by acid
washing
6 1) Preparation of the virgin vegetable oil feedstock for
transesterification:
7 a. Titrating the virgin vegetable oil feedstock to determine its free fatty
acid
8 content;
9 b. Measuring the water content of the virgin vegetable oil feedstock;
c. Filtering the virgin vegetable oil feedstock through a 100 micron strainer
and
11 into the primary vessel;
12 d. Circulating and heating the virgin vegetable oil feedstock to 60 C;
13 e. Settling and dewatering the virgin vegetable oil feedstock, if
necessary;
14 f. Dissolving the alkaline catalyst, particularly sodium or potassium
hydroxide,
in the alcohol, particularly methanol, in the alcohol/catalyst tank;
16
17 2) Performing the transesterification reaction:
18 a. Adding the alcohol/catalyst mixture to the virgin vegetable oil
feedstock. The
19 valves are configured such that the system pump simultaneously draws virgin
vegetable oil feedstock from the primary vessel outlet and alcohol/catalyst
21 mixture from the alcohol/catalyst tank outlet and vigorously blends the two
22 streams inside the pump chamber. The reaction mixture is then pumped to
23 the primary vessel inlet. The rate at which the alcohoVcatalyst mixture is
24 added to the virgin vegetable oil feedstock is controlled by way of an in-
line
flowmeter.
26 b. Circulating the reaction mixture. The reaction mixture is continuously
27 pumped from the bottom of the primary vessel to the top of the primary
vessel
28 and the temperature of the reaction mixture is maintained at 60C by way of
29 the immersion heaters.
c. Settling and draining the crude byproduct. Heat and mixing are removed and
31 the reaction mixture is allowed to settle and separate under gravity into
its
32 two distinct phases or layers - the raw biodiesel phase and the crude
glycerin
4
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1 phase. Following a settling period, the crude byproduct phase is repeatedly
2 drawn-off the bottom of the primary vessel.
3
4 4) Water-washing the biodiesel fuel:
a. Adding the wash water/mild acid. An amount of water equal/mild acid to one
6 third the volume of raw biodiesel is added to the main vessel. The wash
7 water settles as a discrete phase at the bottom of the primary vessel.
8 b. Bubbling the wash water/mild acid. Air is gently bubbled into the wash
9 water/mild acid phase by way of a ceramic air stone connected to a hose
containing compressed air. The air bubbles carry water/mild acid up through
11 the raw biodiesel phase to its upper surface where the bubbles burst. The
12 wash water/mild acid then descends through the raw biodiesel phase and
13 returns to the wash water phase. On its ascent and subsequent descent, the
14 wash water dissolves any polar compounds it encounters in the biodiesel
phase.
16 c. Removing the wash water. After bubbling the air stone is removed and the
17 wash water is allowed to settle to the bottom of the primary vessel. After
18 settling the spent wash water is drawn-off and disposed of.
19 d. The water washing process is performed 3 times.
5
