U.S. patent application number 11/481402 was filed with the patent office on 2007-02-15 for method of producing biofuels, and related apparatus.
Invention is credited to Charles David Butler.
Application Number | 20070033863 11/481402 |
Document ID | / |
Family ID | 38610141 |
Filed Date | 2007-02-15 |
United States Patent
Application |
20070033863 |
Kind Code |
A1 |
Butler; Charles David |
February 15, 2007 |
Method of producing biofuels, and related apparatus
Abstract
Methods of producing biofuels are provided herein, for example
and without limitation methods of producing biodiesel from trap
grease are provided. Systems and apparatus also are provided for
implementing, for example and without limitation, the methods
described herein.
Inventors: |
Butler; Charles David;
(Oyster Bay, NY) |
Correspondence
Address: |
JESSE A. HIRSHMAN, ESQ.
1722 MURRAY AVENUE
PITTSBURGH
PA
15217
US
|
Family ID: |
38610141 |
Appl. No.: |
11/481402 |
Filed: |
July 5, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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60697047 |
Jul 6, 2005 |
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60791771 |
Apr 13, 2006 |
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Current U.S.
Class: |
44/451 ;
44/457 |
Current CPC
Class: |
B01D 17/0208 20130101;
B01D 17/085 20130101; B01D 17/045 20130101; C10G 2300/1011
20130101; Y02P 30/20 20151101; C10L 1/026 20130101; Y02W 30/74
20150501; B01D 17/10 20130101; C11B 13/00 20130101; Y02E 50/13
20130101; B01D 17/00 20130101; B01D 17/12 20130101; C11C 3/003
20130101; Y02E 50/10 20130101; B01D 17/005 20130101; B01D 36/045
20130101 |
Class at
Publication: |
044/451 ;
044/457 |
International
Class: |
C10L 1/18 20060101
C10L001/18 |
Claims
1. A method of producing biofuel from a fatty acid
triglyceride-containing material, comprising: (a) heating the
material to a temperature greater than about 25.degree. C. to
decrease its viscosity; (b) filtering and dewatering the material
at a temperature greater than about 25.degree. C.; and (c)
converting the material to glycerol and biofuel by: i) adjusting
the pH of the starting material to about 2.5 and substantially
completely mixing the acid into the material to produce a reaction
mixture; ii) adding methanol to the reaction mixture to esterify
free fatty acids; and iii) adding sodium or potassium methylate or
hydroxide to the reaction mixture in an amount effective to bring
the pH of the reaction mixture to from about 6.2 to about 8.0,
thereby converting fatty acid acyl-glycerides to glycerol and
biofuel.
2. The method of claim 1, further comprising separating the
glycerol and biofuel and washing the methoxylated fatty acids by
mixing the methoxylated fatty acids with water and removing the
water.
3. The method of claim 2, wherein the water contains phosphoric
acid.
4. The method of claim 2, wherein the water is sprayed over the
methoyxlated fatty acids.
5. The method of claim 2, wherein the methoxylated fatty acids are
aerated during washing.
6. The method of claim 5, wherein the methoxylated fatty acids are
aerated using a limewood airstone.
7. The method of claim 2, wherein the methoxylated fatty acids are
washed at least two times with water.
8. The method of claim 2, wherein the methoxylated fatty acids are
washed three times with water.
9. The method of claim 1, comprising filtering the trap grease at a
temperature of from about 25.degree. C. to about 65.degree. C.
10. The method of claim 9, comprising filtering the trap grease at
a temperature of from about 50.degree. C. to about 55.degree.
C.
11. The method of claim 9, comprising filtering the trap grease at
a temperature of about 52.degree. C.
12. The method of claim 1, comprising filtering the trap grease in
a screen filter comprising a filter screen, a filtrate collection
container, a heater within or integral to the filtrate collection
container, a pump fluidly connected to the filtrate collection
container and a spray head fluidly attached to the pump and
directed onto the filter screen for pumping warmed filtrate onto
the screen.
13. The method of claim 12, wherein the screen is a belt.
14. The method of claim 12, wherein the screen is cylindrical, the
screen filter further comprising a screw within the cylindrical
screen for advancing material through the filter.
15. The method of claim 1, comprising adding potassium methylate to
the reaction mixture to convert fatty acid acyl-glycerides to
glycerol and biofuel.
16. The method of claim 1, comprising adding sodium methylate to
the reaction mixture to convert fatty acid acyl-glycerides to
glycerol and biofuel.
17. The method of claim 1, wherein the starting material is trap
grease.
18. The method of claim 1, comprising converting the material to
glycerol and biofuel at a temperature ranging from about 25.degree.
C. to about 65.degree. C.
19. The method of claim 18, comprising converting the material to
glycerol and biofuel at a temperature ranging from about 45.degree.
C. to about 55.degree. C.
20. The method of claim 18, comprising converting the material to
glycerol and biofuel at a temperature of about 52.degree. C.
21. The method of claim 1, wherein the filtering, dewatering and
conversion of the material to glycerol and biofuel are performed
using processing equipment configured within a commercial shipping
container.
22. The method of claim 21, wherein the container is about 40' by
about 8' by about 8'9''.
23. The method of claim 1, wherein the fatty acid
triglyceride-containing material is trap grease.
24. The method of claim 1, wherein during the heating of the
material to a temperature greater than about 25.degree. C. to
decrease its viscosity, the material is fractionated to separate
water and grease.
25. The method of claim 24, wherein the material is fractionated in
a conical-bottomed tank.
26. The method of claim 1, wherein the material is passed through
one or more self-cleaning screening devices.
27. The method of claim 26, wherein the material is passed through
two self-cleaning screening devices.
28. The method of claim 27, wherein one of the self-cleaning
screening devices is a disc filter.
29. The method of claim 28, wherein the disc filter is a vibratory
disc filter.
30. The method of claim 27, wherein one of the self-cleaning
screening devices is a liquid solid separator comprising a
cylindrical screen.
31. The method of claim 26, wherein the material is passed through
a decanter centrifuge after it is passed through the one or more
self-cleaning screening devices.
32. The method of claim 26, wherein the material is passed through,
in sequence, a vibratory disc filter, a liquid solid separator
comprising a cylindrical screen and having a finer mesh than the
disc filter, and a decanter centrifuge.
33. The method of claim 1, further comprising separating the
glycerol from the biofuel.
34. The method of claim 33, further comprising fractionating the
separated glycerol into a glycerol fraction and a residual fraction
comprising one or both of biofuel and fatty acid
acyl-glycerides.
35. The method of claim 34, wherein the fractionating is performed
by settling.
36. The method of claim 35, wherein the settling is performed in a
conical-bottom container.
37. The method of claim 34, wherein the fractionating is performed
in a centrifugal decanter.
38. The method of claim 1, further comprising dewatering the washed
biofuel.
39. The method of claim 1, wherein the washed biofuel is dewatered
in a water-oil separating coalescing filter.
40. The method of claim 1, further comprising filtering the washed
biofuel with a filter that excludes fatty acid acyl-glycerides, but
passes biofuel.
41. The method of claim 40, wherein the filter that excludes fatty
acid acyl-glycerides, but passes biofuel is a PTFE-coated filter
membrane.
42. The method of claim 41, wherein the filter is about a 2 .mu.
filter.
43. The method of claim 40, wherein the filter is about a 2 .mu.
filter.
44. The method of claim 1, further comprising filtering the washed
biofuel with, in sequence, about a 30 .mu. filter, about a 10 .mu.
filter, a water-oil separating coalescing filter and a filter that
excludes fatty acid acyl-glycerides, but passes biofuel.
45. The method of claim 1, further comprising heating the glycerol
under pressure to make propylene glycol.
46. The method of claim 45 wherein the glycerol is heated to about
200.degree. C. at about 200 psi to produce propylene glycol.
47. A biofuels processing system comprising, in sequence and
fluidly connected: a pre-filter assembly comprising one or more
self-cleaning screening devices; one or more reaction vessels
comprising a heater and a mixing subsystem; a wash tank; and one or
more of a methanol feed, an acid feed and a methylate feed fluidly
connected to the one or more heated reaction vessels and a water
feed fluidly connected to the wash tank.
48. The system of claim 47, wherein pre-filter assembly comprises
two self-cleaning screening devices.
49. The system of claim 48, wherein one of the self-cleaning
screening devices is a disc filter.
50. The system of claim 49, wherein the disc filter is a vibratory
disc filter.
51. The system of claim 48, wherein one of the self-cleaning
screening devices is a liquid solid separator comprising a
cylindrical screen.
52. The system of claim 47, further comprising a decanter
centrifuge downstream to the one or more self-cleaning screening
devices and upstream to the one or more reaction vessels.
53. The system of claim 47, the pre-filter assembly comprising in
sequence, a vibratory disc filter, a liquid solid separator
comprising a cylindrical screen and having a finer mesh than the
disc filter, and a decanter centrifuge.
54. The system of claim 47, further comprising between the
pre-filter assembly and the one or more reaction vessels two or
more filter units of differing pore size connected in series,
wherein the mesh size of the filter units decreases in a downstream
direction.
55. The system of claim 54, wherein the filter units are bag
filters.
56. The system of claim 54, comprising from three to five filter
units.
57. The system of claim 47, comprising one reaction vessel and a
methanol feed, an acid feed and a methylate feed fluidly connected
to the reaction vessel.
58. The system of claim 47, comprising a first reaction vessel
downstream to the pre-filter assembly and a second reaction vessel
downstream to the first reaction vessel.
59. The system of claim 58, in which a methanol feed and an acid
feed are fluidly connected to the first reaction vessel and a
methylate feed is fluidly connected to the second reaction
vessel.
60. The system of claim 47, comprising an acid feed fluidly
connected to the one or more reaction vessels and further
comprising a pH controller having a probe within the same reaction
vessel and a pump or solenoid fluidly connected to the acid feed
upstream of the reaction vessel under control of the pH
controller.
61. The system of claim 47, in which one or more of the methanol
feed, the acid feed, the methylate feed and the water feed are
fluidly connected to a spray head within the one or more reaction
vessels and located in a portion within the one or more reaction
vessels above where liquid collects during operation of the
system.
62. The system of claim 47, further comprising a temperature
controller having a probe within the one or more reaction
vessels.
63. The system of claim 47, housed within a commercial shipping
container.
64. The system of claim 47, wherein dimensions of the container are
about 40' by about 8' by about 8' to about 9'.
65. The system of claim 47, wherein dimensions of the container are
about 20' by about 8' by about 8' to about 9'.
66. The system of claim 47, further comprising a fractionation
container downstream to one or more of the reaction vessels to
receive glycerol from the one or more reaction vessels.
67. The system of claim 66, wherein the fractionation container is
a conical-bottom container.
68. The system of claim 47, further comprising a centrifugal
decanter downstream to one or more of the one or more reaction
vessels.
69. The system of claim 47, further comprising a dewatering device
downstream to the wash tank for dewatering the washed biofuel.
70. The system of claim 69, wherein the dewatering device is a
water-oil separating coalescing filter.
71. The system of claim 47, further comprising a filter that
excludes fatty acid acyl-glycerides, but passes biofuel downstream
to the wash tank.
72. The system of claim 71, wherein the filter that excludes fatty
acid acyl-glycerides, but passes biofuel is a PTFE-coated filter
membrane.
73. The system of claim 72, wherein the filter is about a 2 .mu.
filter.
74. The system of claim 71, wherein the filter is about a 2 .mu.
filter.
75. The system of claim 47, further comprising downstream to the
wash tank: about a 30 .mu. filter, about a 10 .mu. filter, a
water-oil separating coalescing filter and a filter that excludes
fatty acid acyl-glycerides, but passes biofuel.
76. The system of claim 47, the pre-filter assembly containing a
triglyceride.
77. A pre-filter assembly for a biofuels processing station
comprising a pre-filter assembly comprising two self-cleaning
screening devices fluidly attached.
78. The pre-filter assembly of claim 77, wherein one of the
self-cleaning screening devices is a disc filter.
79. The system of claim 78, wherein the disc filter is a vibratory
disc filter.
80. The system of claim 77, wherein one of the self-cleaning
screening devices is a liquid solid separator comprising a
cylindrical screen.
81. The system of claim 77, further comprising a decanter
centrifuge downstream to the one or more self-cleaning screening
devices and upstream to the one or more reaction vessels.
82. The system of claim 77, the pre-filter assembly comprising in
sequence, a vibratory disc filter, a liquid solid separator
comprising a cylindrical screen and having a finer mesh than the
disc filter, and a decanter centrifuge.
83. A screen filter apparatus, comprising: a filter screen, a
filtrate collection container, a heater within or integral to the
filtrate collection container, a pump fluidly connected to the
filtrate collection container and a spray head fluidly attached to
the pump and directed into the filter screen for pumping warmed
filtrate onto the screen.
84. The screen filter apparatus of claim 83, wherein the screen is
a belt.
85. The screen filter apparatus of claim 83, wherein the screen is
cylindrical, the filter further comprising a screw within the
cylindrical screen for advancing material through the filter.
86. The modified screening filter of claim 83, wherein the heater
is an electric resistance heater.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit under 35 U.S.C.
.sctn.119(e) to U.S. Provisional Patent Application Nos.
60/697,047, filed Jul. 6, 2005, and 60/791,771, filed Apr. 13,
2006, both of which are incorporated herein by reference in their
entirety.
BACKGROUND
[0002] Today, municipalities are plagued by an increasing amount of
food service generated waste oil and grease that accumulate in the
sewage network, or is dumped illegally into the ground. As a
result, in most dense urban areas, costly fees have been levied on
both the restaurants and the liquid waste haulers and carters for
the safe disposal of the waste oil and grease. Presently, liquid
waste disposal prices have increased by 800% from 2002 to 2004 for
carters. Since the waste must be carted on average 185 miles from
its point of origin, the costs are even higher. For the fiscal year
2002, restaurants were paying $65 for the disposal of 1,000 gallons
of grease. As of October 2004, the same facilities were paying as
much as $500 per 1,000 gallons.
[0003] Major metropolitan environmental and sewer authorities have
begun to require that all restaurants have approved carters for
restaurant liquid wastes. Legislation has been passed in New York
City and Long Island, with identical legislation pending in New
Jersey, Connecticut and 14 other states. Fines for failing to
comply with this law range from $250 to as high as $ 1,000 per day
in New York City. For the liquid waste carters, the cost of legal
disposal has also jumped from $30 per 1,000 gallons of grease to
$240 per 1,000 gallons. All estimates indicate a continuation of
rising disposal prices for 2005 and 2006.
[0004] This sudden increase in price coincides with an historic
rise in energy costs. Fuel costs for home heating have increased by
42% nationwide, with increases as high as 60%. Prices for motor
vehicle and machine diesel fuel have increased by 125%
nationwide.
[0005] Biodiesel is a product derived from natural oils and fatty
acids, and typically, though not exclusively, contains methoxylated
and ethoxylated free fatty acids, or more generally alkoxylated
free fatty acids (methyl, ethyl and alky esters of fatty
acids).
[0006] Biodiesel typically is made from vegetable oils, mono-, di-
and tri-glycerides (mono-, di- and tri-acylglycerides), by
transesterification whereby the glycerin is separated from the fat
or vegetable oil. The process leaves behind two products--alkyl
(for example, methyl) esters of fatty acids and glycerin. An
alcohol and a catalyst are required by traditional processes for
converting oils to biodiesel. Typical alcohols, due to their low
cost and abundance, include methanol and ethanol. Methanol is
preferred in many instances because it leads to a more robust
transesterification reaction and it is less expensive than ethanol.
Methanol, however, dissolves rubber and is toxic. Ethanol is more
expensive and often does not lead to as stable and predictable a
transesterification reaction as methanol, but it is less toxic than
methanol and typically is made from renewable resources. The most
common catalyst used in production of biodiesel is lye, or NaOH,
though KOH and H.sub.2SO.sub.4 have also been used in some
instances.
SUMMARY
[0007] Provided are methods and apparatus for producing biofuels,
for example, and without limitation, biofuels prepared from trap
grease. The methods and apparatus utilize a novel chemistry, as
well as, in the case of trap grease and other viscous, dirty
sources of fatty acid acyl glycerides, novel heating and separation
techniques designed to facilitate use of dirtier, more viscous
waste materials. In one embodiment, a fatty acid acyl
glyceride-containing material is heated, filtered, esterified with
acid and methanol and then treated with a base to transesterify the
esterified fatty acid acyl glycerides. This process differs in that
both esterification and transesterification are performed. The
process is broken in two phases. In the first, esterification phase
acid esterification is used to create an initial separation of
glycerin and to reduce total free fatty acids of the source feed
stock to less the 5%. In the second phase, fatty acid-acyl
glycerides are transesterified to produce biofuel and glycerol.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a schematic diagram a biofuels processing system
according to one embodiment of the present invention.
[0009] FIG. 2 is a schematic diagram of a cylindrical screening
device according to one embodiment of the present invention.
[0010] FIG. 3 is a schematic diagram of a screening device
according to one embodiment of the present invention.
[0011] FIG. 4 is a schematic diagram of a biofuels processing
system within a commercial shipping container according to one
embodiment of the present invention.
[0012] FIG. 5 is a schematic diagram a biofuels processing system
according to another embodiment of the present invention.
[0013] FIG. 6 is a flow chart illustrating one embodiment of a
water-grease-solids separation assembly.
DETAILED DESCRIPTION
[0014] Provided herein is a method of preparing biofuels, in one
non-limiting embodiment, from trap grease or any grease comprising
predominantly vegetable oils and free fatty acids that is viscous
at room temperature ("vegetable oil grease"). Trap grease is a
waste product generated by restaurants. Most restaurants are
required to run their waste water through a trap in which waste
organics, predominantly viscous oils, including glycerides,
predominantly triglycerides, but also containing di- and
mono-glycerides, and free fatty acids, collect. These oils are
viscous at room temperature and, thus are referred to as greases.
Due primarily to the viscosity of trap grease and the fact that it
contains significant amounts of particulate matter, it has not been
previously considered as a suitable starting material for
production of biofuels. As shown herein, use of trap grease
requires special handling.
[0015] As mentioned above, methods and apparatus are provided for
producing biofuels, for example, and without limitation, biofuels
prepared from trap grease. The methods and apparatus utilize a
novel chemistry, as well as, in the case of trap grease and other
viscous, dirty sources of fatty acid acyl glycerides, novel heating
and separation techniques designed to facilitate use of dirtier,
more viscous waste materials. In one embodiment, a fatty acid acyl
glycerides-containing material is heated, filtered, esterified with
acid and methanol and then treated with a base to transesterify the
fatty acid acyl glycerides. This process differs in that both
esterification and transesterification are performed. The process
is broken in two phases. In the first, esterification phase acid
esterification is used to create an initial separation of glycerin
and to reduce total free fatty acids of the source feed stock to
less the 5%.
[0016] Acid, for example and without limitation, H.sub.2SO.sub.4,
is introduced into the heated grease typically at a rate of from
about 1.0 ml per liter of feed stock to 1.7 ml/L to a pH of about
2.5. After acid is introduced, the mixture is agitated thoroughly
before addition or methanol in order to prevent dimethylether
creation. Methanol is then added to from about 10% to about 15% by
volume, and the mixture is agitated for about 2 hours. Glycerol is
then settled out and is removed.
[0017] Acid is then neutralized by injection of a base, preferably
KOH or Potassium methylate to reach a neutral pH of from about 6.2
to about 8.0. Use of potassium methylate or KOH is preferred Note
also in this phase that the potassium and SO.sub.4.sup.-2 combine
to form K.sub.2SO.sub.4 in suspension, which is removed in the wash
phase and which can be used as a fertilizer. In this phase (base
phase), transesterification occurs, resulting in formation of
biofuel (fatty acid methoxide) and glycerol.
[0018] FIG. 1 provides a schematic of one embodiment of a
processing system 10 suitable for preparing biofuels from trap
grease. System 10 includes fractionating tank 20 in which an
aqueous fraction 21 (graywater) is separated from organic fraction
22 (grease). Tank contains drains 23 and 24. Aqueous fraction 21 is
drained from tank 20 through drain 23, typically as waste-water to
be discarded. Organic fraction 22 is drained from tank 20 through
drain 24, fluid conduit 25 and into filter subsystem 30, which
includes a pre-filter 31 and filters 50, 51 and 52. In practice,
one or more of pre-filters 31 and filters 50, 51 and 52 may be
omitted, and additional pre-filters or filters, as are known in the
art, may be employed.
[0019] The viscosity of these greases is such that standard
biofuels processing techniques cannot be employed. Further, unlike
typical processes for producing biofuels, the trap grease contains
a good deal of particulate matter that must be filtered out of the
grease before the grease is processed into biofuel. As such, in one
non-limiting embodiment, pre-filter 31 is a modified screening
filter, such as a modified Rotomat. A modified cylindrical
screening device 131 is shown in FIG. 2. The device 131 includes a
cylindrical screen 135 through which a liquid (filtrate) can pass,
leaving within the cylindrical screen 135 any solids that could not
pass through the screen 135. Device 131 includes an inlet 136 and
an outlet 137. Solids are carried from inlet 136 to outlet 137 by
screw 139. In a typical commercial cylindrical screening device
131, such as a Rotamat, inlet 136 is lower than outlet 137. The
liquid carried along screen 135 and is scraped into trough 138, and
any materials that could not pass through the screen is carried by
screw 139 to outlet 137. Device 131 also comprises trough 140
configured to collect liquid (filtrate) that passes through screen
135. Trough 140 also comprises outlets 141 and 142 for transferring
collected filtrate out of trough 140. Trough 140 also comprises a
heater element 143, such as, without limitation, a resistance
heater for heating filtrate. A recirculation system, comprising a
conduit 146, pump 147 and spray head 148 are fluidly connected to
outlet 141, and is used to spray heated filtrate onto screen,
thereby heating un-filtered trap grease and thereby decreasing its
viscosity and dislodging particulate matter from screen 135 with
the overall effect of increasing the efficiency of separation of
particulate matter from filtrate. Outlet 142 is fluidly connected
with down-stream filter units, such as filters 50, 51 and 52 shown
in FIG. 1.
[0020] As can be appreciated, a cylindrical screening device 131,
as is shown in FIG. 2 is one of many suitable topological
configurations for a coarse filter screen. Commercial sources of
various cylindrical screening devices that can be modified with a
heater as shown in FIG. 2 are available from Huber Technology, Ltd.
of Wiltshire, England under the trade name ROTAMAT. Filter screens
of this type are typically used in waste-water treatment to remove
particulate matter from storm or sewage prior to treatment. In a
second embodiment shown in schematic in FIG. 3, device 231, shown
in cross-section, includes one or more screens 235 in the
configuration of two opposing continuous belts. Trap grease enters
inlet 236 of device 231 and particulate retentate passes through
device and exits through outlet 237. Filtrate collects in trough
240, which includes outlets 241 and 242 and heater 243.
Recirculation system 245 is provided to spray heated filtrate onto
screens 235 to heat trap grease and to dislodge particulate matter
from screens 235.
[0021] Returning to FIG. 1, trap grease is processed into a biofuel
in system 10, shown schematically. Heated trap grease filtrate
exiting from pre-filter 31, for example and without limitation, as
shown in FIGS. 2 and 3, is then filtered by one or more filter
units 50, 51 and 52. In reference to FIG. 1, three filter units 50,
51 and 52 are shown. Filter units 50, 51 and 52 may be the same or
different, but filter units are typically, sequentially from filter
50 to filter 51 to filter 52, of a finer filter size. For example
and without limitation, filter 50 is a 10-mesh filter, filter 51 is
a 20-mesh filter and filter 52 is an 80-mesh filter. Alternately
cartridge-based pool filters may be employed, such as Hayward
filters. As used herein, the terms "pore size" of a filtering
device refers to the minimum size of particles that a filter can
stop. Often, the pore size is described as a "mesh size" or in
terms of "mesh" units, though it should be recognized that "mesh
sizes" may have different values in different countries. For
example, 20 mesh refers to a 920 micron (.mu.) rating in the UK and
an 864 .mu. rating in the US. Reference to mesh size made herein
refer to the US mesh standard. It should be recognized by a person
of ordinary skill in the art that selection of filter pore size and
sequences of serial filters of differing pore size is a matter of
design preference and is based on the desired degree of particle
removal and how often the filters need to be cleaned or
replaced.
[0022] Filtrate exits filter 52 and then passes into reaction tank
55 containing stirrer 56. Reaction tank 55 includes wall 57, which
comprises a resistance heating element (not shown) under control of
programmable logic controller (PLC) 58 for controlling and
maintaining temperature within tank 55. In one non-limiting
embodiment, reaction 55 tank is a conical tank. Resistance heating
elements and temperature controllers are available from a number of
commercial sources, including, for example and without limitation,
PolyProcessing Company of Monroe, La.
[0023] Temperature, pH, conductivity and viscosity, as well as
other parameters, may be monitored within one or more reaction
vessels or transfer lines employed in the systems and processes
described herein. By "meters" (for example, and without limitation,
pH and temperature meters), it is meant a device that measures one
or more parameters. By "controllers" (for example, and without
limitation, pH and temperature controllers (e.g., thermostat)), it
is meant a device that measures one or more parameters and then can
control the operation of a device for adjusting the one or more
parameters. In the context of the systems and processes described
herein, this means that a pH controller may control, without
limitation, a pump or solenoid that controls flow of an acid or
base into a reaction vessel, and shuts the flow of the acid off if
a specified pH is reached, typically about 2.5 for the acid
addition step of the processes described herein. Useful meters and
probes for monitoring and/or controlling industrial processes are
well-known and are readily available commercially. In one
embodiment, Program Automation Controllers (PACs, also known as
Programmable Logic Controllers or PLCs) are used. In another
embodiment, redundant PACs are utilized. In one embodiment, the
PACs are Chameleon Programmable Automation Controllers,
commercially available from Fairmount Automation or Phoenixville,
Pa.
[0024] In one embodiment, conductivity of the oil- or
biofuel-containing fractions is measured to evaluate the
completeness of the separations. Prior to addition of acid,
conductivity of the fatty acid acyl-glyceride-containing
composition may be evaluated to determine the completeness of any
dewatering step. After acid and methanol treatment, subsequent
settling and removal of glycerol, the completeness of glycerol
removal can be determined by conductivity. Likewise, the
conductivity of pre-wash biofuel, post-wash biofuel and the final
product may be evaluated.
[0025] As used herein, the term "fluidly connected" means connected
by a fluid transfer conduit or any other method that permits fluid
transfer, with or without intervening elements, such as, without
limitation, containers, filters, devices, pumps, valves, etc. A
non-limiting example, two reaction vessels may be "fluidly
connected" if they are connected to each-other through a pipe or
tube, even if a pump, manifold, valve or other device is placed
in-line between the vessels. Likewise, a pre-filter assembly is
considered to be fluidly connected to a reaction vessel, even
though one or more filters lay in-line between the pre-filter and
the vessel. Two elements are considered to be "fluidly connected"
even though there is no pipe or tubing making the connection if the
fist element spills or otherwise drains, overflows, siphons or
transfers into the second element, though there may be no actual
physical connection between the two elements in the form of a pipe
or tube. In reference to a process system, the term "downstream"
means a later in the direction of general process and/or fluid flow
and "upstream" means earlier in the direction of general process
and/or flow. Thus, acid feed tanks and acid feeds are upstream of
the reaction vessel into which the acid feed drains because acid
feeds from the acid feed tank through the acid feed and into the
reaction vessel. Likewise, as shown in the figures, a pre-filter
assembly is upstream of the reaction vessel because fluid and the
overall process flows in the direction from the pre-filter assembly
to the reaction vessels.
[0026] Feed tanks 60, 65 and 70 are shown in FIG. 1. Methanol
storage tank 60 is fluidly connected to methanol transfer conduit
61 and methanol spray head 62 for delivering methanol to reaction
tank 55. Potassium methylate storage tank 65 is fluidly connected
to potassium methylate transfer conduit 66 and potassium methylate
spray head 67 for delivering potassium methylate to reaction tank
55. Sulfuric acid storage tank 70 is fluidly connected to sulfuric
acid transfer conduit 71 and sulfuric acid spray head 72 for
delivering sulfuric acid to reaction tank 55. Typically pumps (not
shown) are inserted in-line in conduits 61, 66 and 71 in order to
generate sufficient fluid pressure at spray heads 62, 67 and 72.
Alternately, tanks 60, 65 and 70 are placed above spray heads 62,
67 and 72 and the chemicals are gravity-fed. Depending on the
choice of reactants and catalysts, the feed tanks may be
substituted with feed tanks for other chemicals or compositions,
such as, without limitation, sodium hydroxide and sodium methylate,
as is applicable.
[0027] In use, filtrate is reacted with the compositions delivered
from feed tanks 60, 65 and 70, for example and without limitation,
as described herein. Reaction tank 55 comprises drain 75 connected
to four-way manifold 76. As is shown, liquid contained within
reaction tank 55, is stirred while the reaction within reaction
tank 55 proceeds. As an alternative to stirring or in addition to
stirring, for example use of stirrer 56, liquid may be recirculated
through recirculation conduit 77 by a pump, not shown. Acid,
methanol and base are added to reaction tank 55 typically in the
order of acid, methanol and base. Acid is mixed thoroughly before
addition of methanol to avoid production of hazardous dimethyl
ether. The reaction can be conducted in a single tank, as shown in
FIG. 1, or in two tanks, as shown below.
[0028] Upon completion of the conversion reaction, the reaction
mixture is allowed to settle and, first, glycerol fraction 78, is
removed through drain 75, manifold 76, and through glycerol drain
conduit 79. Once glycerol is drained, the biofuel fraction is
drained through drain 75, manifold 76 and biofuel conduit 81 and
transferred to wash tank 85. Wash tank contains inlet 86, outlet 87
aerator 88 with air supply line 89 and water supply 90 with water
spray head 91. In one embodiment, aerator is a limewood air-stone,
though it may be any air bubble source. Other air diffusers may be
employed, as are commercially available, such as, without
limitation, the Airstation products, commercially available from
Vertex water Features of Pompano Beach, Fla. After a desired length
of air-biofuel contact time, the biofuel is allowed to settle and
water is removed. This washing step may be repeated any number of
times. After washing, the biofuel is drained and is ready for
shipping.
[0029] All tanks or vessels used in the described process,
including, without limitation fractionating tank 20, reaction tank
55, wash tank 85 or any other vessels described herein may have any
physical configuration, which in many cases may be a matter of
design choice, while in other cases, facilitate the process(es)
carried out in the particular vessel. In the Figures, the vessels
are shown schematically as having cylindrical shapes. In practice,
that is but one of many possible vessel configurations. The vessels
may be cubic, conical, frustroconical, ovoid, spherical and any
combination thereof. The vessels may have, without limitation, a
tapered bottom (having a larger horizontal cross-sectional area at
the top and a smaller horizontal cross-sectional area at the bottom
as in the case of a conical or frustroconical bottom) or a flat
bottom. In practice, practical implementation of the systems and
processes described herein involves selection of vessels that are
readily available and are least expensive while retaining
functionality. Cylindrical tanks are commonly and relatively
inexpensively available as well as conical tanks having a
cylindrical upper portion and a conical lower portion. In one
non-limiting embodiment, in reference to the Figures, one or more
of fractionating tank 20, reaction tank 55, wash tank 85 have a
conical or frustroconical bottom, or a tapered bottom. Use of
vessels having a circular horizontal cross-section, such as
cylindrical, conical, frustroconical or spherical vessels may be
preferred in many instances as facilitating stirring of the
contents of the vessel. A conical, frustroconical or otherwise
tapered bottom may be preferred as facilitating the settling and
separation processes carried out in each vessel, where applicable.
The interior of the one or more vessels may contain ribs or other
protuberances in order to facilitate mixing of the liquids present
in the container. One example of a tank useful in the processes
described herein is a tank having a conical bottom is a 510 gallon,
cross-linked polyethylene, vertical, closed heard 15 degree cone
bottom tank, typically with a support stand, commercially
available, along with other suitable tank configurations, from
PolyProcessing Company of Monroe, La.
[0030] In all embodiments, fluids are transferred either by gravity
feed or by pumping. Where gravity feed is insufficient to provide
enough pressure to feed the fluid to its destination pumps are
required. For clarity, pumps are not shown in FIGS. 1 and 4, though
they may be necessary in-line in one or more feeds, including,
without limitation: chemical supply feeds, recirculation feeds (for
example, to the spray heads) and drains. Of course, the relative
configuration of the components will dictate whether a pump is
needed or if siphoning or draining is all that is needed. Factors
involved in the determination of whether a pump is needed in any
given fluid conduit and the specifications of the pump include,
without limitation: the distance between components, the fluid
conduit diameter and composition (friction), the viscosity of the
fluid to be transferred, the vertical orientation of the inlet end
of the fluid conduit relative to the outlet end of the fluid
conduit, and the required pressure at the outlet end of the fluid
conduit.
[0031] In one embodiment, shown in schematic in FIGS. 4 and 5,
system, or any suitable system, may be configured within a shipping
container, such as a standard 8'.times.8''9'.times.20' or
8'.times.8' to 9'.times.20' commercial shipping container, such as,
without limitation, a SeaLand container. Distribution of the
biofuels processing system, when configured within a commercial
transport container, as described herein may be accomplished by
standard routes. In use, one or more of the containers can be
stacked and/or lain side-by-side to produce a larger facility. The
commercial shipping container may be a stock shipping container as
are commonly available in the trade that has been retrofitted with
suitable processing equipment, or a customized or turnkey shipping
container fabricated with suitable processing equipment inside and
having the dimensions of a standard commercial shipping container,
facilitating shipment and handling by truck, train or boat.
[0032] In FIG. 4, biofuel processing system 310 is embodied within
a commercial container 390. Configuration of system 310 within a
commercial container has significant advantages, including
standardization of processes, ease of installation and ease of
moving. Moving of the processing system literally can take place
overnight. In one embodiment, in reference to FIG. 1, the shipping
container does not contain a fractionating tank 20, but includes a
coupling 395, permitting transfer of liquids into system 310. The
processing system 310 includes fluid conduits 361, 365 and 371 and
couplings at the inlet end of conduits 361, 365 and 371 that permit
fluid attachment of reactant chemicals, such as methanol, sulfuric
acid or methylate, to system 310 through conduits 361, 365 and
371.
[0033] FIG. 5 provides a second embodiment of the biofuel
processing system 410 contained within a commercial transport
container. In this embodiment, transport truck 420 delivers grease
to system 410 through fluid conduit 425. The grease is first
filtered through filters 450, 451, 452, 453 and 454. Filtrate exits
filter 454 and is transferred to heated reaction tank 455. Methanol
is transported from methanol storage tank, 460, through methanol
conduit 461, and into reaction tank 455. Pumps 496 are used to
facilitate transfer of liquids from one vessel to another. As with
methanol, sulfuric acid is transported from sulfuric acid storage
tank 465 through sulfuric acid transfer conduit 466 and into
reaction tank 455 in order to titrate the pH of the reaction
mixture. The reaction mixture within reaction tank 455 is mixed by
the circulation through circulation conduit 477.
[0034] Once the pH of the reaction mixture is adjusted within
reaction tank 455, the reaction mixture is transported through
conduit 477 and two second heated reaction tank 459. Sodium
methylate is fed from sodium methylate storage tank 470, through
sodium methylate transfer conduit 471, and into reaction tank 459.
The reaction mixture is recirculated within reaction tank 459
through recirculation conduit 477. Once the reaction with sodium
methylate is completed, glycerol is transferred from reaction tank
459 to a storage container (not shown) through conduit 479.
[0035] Raw biofuel is then transferred through conduit 481 and into
wash vessel 480. Air is forced into the biofuel mixture through
conduit 489 and water is transferred into wash vessel 480 through
conduit 490. Reaction tank 455 and 459, as well as wash vessel 480
each contain a vent 494 and one. Biofuel is transferred from
system, 410, through conduit 487.
[0036] FIG. 6 illustrates schematically an alternate embodiment of
a liquid-solids separation assembly 500 that is particularly suited
to treating trap grease or any grease product that contains
significant water and/or solids contamination. The assembly is
preceded by a fractionation 510 tank in which water settles and is
removed. Separation assembly 500 may be placed in line in a
biofuels processing system, such as, in reference to system 410
shown in FIG. 5, in line in fluid conduit 425. The fractionation
tank preferably is heated, without limitation by resistance heating
or by a water coil. In one embodiment, heated water produced from
the washing step or from other steps in the biofuel production
process is passed through the water coil in order to recycle the
heat generated in the production process. The raw grease typically
is heated to greater than 95.degree. F., and typically to about
125.degree. F. In one preferred embodiment, the fractionation tank
has a conical bottom to facilitate phase separation and, thus more
complete removal of water. Traditional fractionation tanks have
flat bottoms, which prevent good separation of the water from the
grease, and which require regular scraping to clean debris from
their bottom.
[0037] Referring again to FIG. 6, after the grease is fractionated,
the grease is separated from solids using a disc filter 520,
preferably a vibratory disc filter. An example of such a filter is
the Eco Separator, commercially available from Russell Finex, Inc.
of Pineville, N.C. Other mesh disc filters, disc screening filters
or screening filters, and preferably self-cleaning filters, for
example and without limitation, a Rotamat or like devices, are
available commercially. After the disc filter, a liquid-solid
separator 530 is employed to remove additional, smaller solids from
the grease. A non-limiting example of a liquid-solid separator is
the Russell Finex Liquid solid separator, which is a form of a
cylindrical screening device having a smaller mesh size than disc
filter 520, or other filter used as a substitute for disc filter
520, as is described in the materials. As a final step in preparing
grease for filtration and processing, the grease is passed through
a decanter centrifuge 540, for example and without limitation, from
Alfa Laval. The combination of the removal of larger particles by
the disc filter and smaller particles by the liquid solid separator
yields a clean grease product that is more amenable to filtration
using, for example and without limitation, the sequential bag
filters described above. The water-grease-solids separation
assembly 500 may be assembled from individual components, or may be
contained within a pre-assembled unit, containing the disc
separator, the liquid solids separator and the decanter centrifuge
fluidly attached in-line and ready for fluid attachment to a
fractionation tank at an inlet of the disc filter, and to
additional filters at the outlet of the decanter centrifuge. The
assembly may be housed and distributed as part of a larger
assembly, within a commercial shipping container.
[0038] As will be apparent to those of skill in the process
engineering field, a large number of commercially available
alternatives to the series of devices of assembly 500. Assembly is
intended to provide a pre-filtering system that removes solids from
the trap grease or other oil-containing materials to be filtered,
thereby taking the load off of the finer filters downstream in the
process, preferably requiring minimal human intervention in the
form of requiring cleaning of screens, etc. Disc filter 520 and
liquid solid separator 530 may be any combination of screening
filters, though self-cleaning devices are preferred. A device is
self-cleaning if it provides a method by which retained solids can
be continuously, or in batch, removed from the screen without
manual removal or cleaning of the screen. For example and without
limitation, the screen can be scraped, flushed or otherwise
de-fouled by a mechanism built into the device, such as a spray
head, screw, paddles, etc. A device is considered to be
self-cleaning if the retentate (retained solids) cleaning process
either is continuous in the separation process, automatically timed
or otherwise built into the separation process, or can be
initialized manually at a desired time, so long as the screen does
not need to be removed and manually cleaned of retentate, as is the
case with, for example, bag filters. Although the devices are
described as having "screens," this is a generic term referring to
any fixed filtering substrate, such as a screen, a perforated metal
or plastic sheet, or other porous material that generally has a
pore/hole size of larger than about 40 microns (.mu.). Equivalents
of disc filter 520 typically remove solids of 150 microns or larger
and equivalents of liquid solid separator 530 typically remove
solids of larger than about 40 .mu. to about 50 .mu..
[0039] A number of processes for production of biofuel may be
implemented favorably using the process system described herein.
For example and without limitation, biofuel production processes
utilizing methanol, lye, sulfuric acid and sodium or potassium
methylate, as are known (for example and without limitation at
www.cubiodiesel.org/howtomakebiodiesel.php and
www.journeytoforever.org) and/or as described herein. Nevertheless,
the automated processes described herein are far superior to the
manual processes described in the prior art. The prior art
processes require use of good quality vegetable oil in order to
achieve high quality conversion of the oil to biodiesel. According
to one aspect of the present invention, titration of acid addition
has the benefit of reduced requirements for acid, and less
by-product production due to imbalances in the reactants. Another
added feature according to one embodiment of the described
processes is the addition of sulfuric acid and thorough mixing of
the sulfuric acid to substantial homogeneity prior to addition of
methanol to the reaction mixture. This prevents formation of
dangerous dimethyl ether in the heated reaction mixture, which
would result if sulfuric acid were added to the mixture containing
significant amounts of methanol.
[0040] A number of additional process steps can be implemented in
order to add further value to the general biofuel production
processes described herein. Glycerol produced by the
acid/methanol/methylate treatment, as drained from the process
tanks retains a surprisingly large amount of biofuel and/or oils.
By allowing the glycerol to settle for sufficient periods of time
(typically 1 hour or more), and preferably in a conical-bottomed
tank, additional acyl-fatty acid glycerides and biofuel can be
retrieved from the glycerol fraction and circulated back into the
processing tank(s), generating higher yields of biofuel.
[0041] Glycerol can be converted to higher value propylene glycol
by heat and pressure treatment. In one embodiment, the glycerol is
converted to propylene glycol by treatment of the glycerol at
200.degree. C. at about 200 psi for a time sufficient to convert
substantially all glycerol to propylene glycol. Propylene glycol
also can be prepared from the glycerol by heating in the presence
of NaOH, followed by distillation according to known protocols.
Water (grey water) obtained from the washing step not only can be
re-circulated through a heating coil in the grease fractionation
tank, but can be used as a fertilizer due to its high
K.sub.2SO.sub.4 content.
[0042] Occasionally, the biofuel product from the above-described
process contains excess water and some triglycerides remain. This
can be remedied by additional filtration steps, such as, without
limitation, filtration through one or more filters, with the final
filter being, for example and without limitation, about a treated 2
.mu. filter. The treated filter, for example and without
limitation, treated with Teflon (polytetrafluoroethylene or PTFE),
is treated with a composition that excludes acyl-fatty acid
glycerides, yet passes biofuel. To remove water, a dewatering
device, such as, without limitation a fluid-fluid coalescing filter
(for example and without limitation, commercially available from
Racor of Modesto, Calif. or Pall Corporation of East Hills, N.Y.)
may be employed. In one embodiment, a biofuel polishing filter
assembly is provided which includes, sequentially, a 30 .mu.
filter, a 10 .mu. filter, a coalescing filter and a 2 .mu.
filter.
[0043] The examples provided below are merely exemplary and are not
intended to limit the scope of the present invention.
EXAMPLE 1
[0044] A Sealand container is provided, containing 3 large
polyethylene, resin lined reactors--Tanks 1, 2 and 3. These tanks
are rotomolded high density cross linked polyethylene, with an
embedded 120 volt, 27 amp heating mesh on tanks 1 and 2. The
heating mesh is controlled by an analog process controller, with a
high temp limit preset at 150 degrees Fahrenheit. Tanks 1 and 2 are
processing tanks; tank 3 is a wash tank. All tanks vent to an
activated carbon vapor control system. There are no atmospheric
vents. Three Hayward filters are used to filter the trap grease
prior to conversion.
[0045] The process is carried out as follows. One hundred gallons
of grease is pumped from a 10,000 gallon fractionation tank,
through five sequential Hayward bag filters and into a processing
tank. The processing tank has an electric resistance heater. The
heater on the tank then is used to heat the contents of the tank to
95.degree. F. for 2 hours. Thirty six gallons of methanol (8% by
volume) is then transferred from a 55 gallon drum into processing
tank using a pneumatic diaphragm pump. The contents of the
processing tank is then mixed for three hours at 95.degree. F. The
pH of the mixture is determined using a Hydrion pH indicator and
about 407 gallons (typical) of sulfuric acid is transferred from a
55 gallon drum using a pneumatic diaphragm (titrate to about pH
2.5). The mixture is then transferred to a second processing tank,
also having a resistance heater. Twelve gallons of pre-mixed
potassium methylate, prepared as described above, is transferred
into the mixture using a diaphragm pump. The reaction mixture is
then heated to 95.degree. F. and maintained at 95.degree. F. for
about 15 minutes. The mixture is then mixed for an additional 25
minutes. At 25 minutes mixing is halted and glycerin is drained
into storage. Mix for another ten minutes and then drain glycerol
after halting mixing. Repeat ten minute mixing and draining until
no glycerol forms. Glycerol is then shipped out for methanol
recovery.
[0046] The biodiesel is then transferred to the wash tank. Forty 40
gallons of warm water is then added through a mist system, and the
bubble aerator is turned on. The mixture is aerated for 1-2 hours
and grey water is drained. The washing step is repeated three times
and is tested for soaps and glycerol. If no soaps or glycerol is
formed, the product is finished.
EXAMPLE 2
Lye Plus Acid
[0047] The chemicals used in the process are methanol, sulfuric
acid, and sodium methoxide (Methanol premixed with lye at 33%
concentration by DOW Chemical--avoids powdered lye handling).
[0048] Chemicals are stored in original drums, in hooded spill
containment. Hooded spill containment systems are (2) drum systems,
labeled Containment 1 and Containment 2. Containment 1 contains 1
drum (55 gallons) of sodium methoxide and 1 drum (55 gallons) of
methanol. Containment 2 contains (2) drums of sulfuric acid, 66
degree Baume (93-96 percent concentration).
[0049] The process is carried out as follows. One hundred gallons
of grease is pumped from a 10,000 gallon fractionation tank,
through three sequential Hayward filters and into a processing
tank. The processing tank has an electric resistance heater. The
heater on the tank then is used to heat the contents of the tank to
95.degree. F. for 2 hours. Eight gallons of methanol is then
transferred from a 55 gallon drum into the processing tank using a
pneumatic diaphragm pump. The contents of the processing tank is
then mixed for one hour at 95.degree. F. The pH of the mixture is
determined using a Hydrion pH indicator and about three gallons
(typical) of sulfuric acid is transferred from a 55 gallon drum
using a pneumatic diaphragm (titrate to pH 2.5) The mixture is then
transferred to a second processing tank, also having a resistance
heater. Two 2 gallons of premixed sodium methoxide, prepared as
described above, is then transferred into second processing tank
using a pneumatic diaphragm pump. The reaction mixture is then
heated to 95.degree. F. and maintained at 95.degree. F. for about
15 minutes. The mixture is then mixed for an additional 25 minutes.
At 25 minutes mixing is halted and glycerin is drained into
storage. Mix for another ten minutes and then drain glycerol after
halting mixing. Repeat ten minute mixing and draining until no
glycerol forms. Glycerol is then shipped out for methanol
recovery.
[0050] The biodiesel is then transferred to the wash tank. Forty 40
gallons of warm water is then added through a mist system, and the
bubble aerator is turned on. The mixture is aerated for 1-2 hours
and grey water is drained. The washing step is repeated three times
and is tested for soaps and glycerol. If no soaps or glycerol is
formed, the product is finished.
EXAMPLE 3
[0051] The chemicals used in the process are methanol, sulfuric
acid, and potassium methoxide. Grease is filtered through five
sequential Hayward Filters ranging from 80 Mesh (US) to 1 micron
(.mu.) and into a first processing tank. The first processing tank
has an electric resistance heater. The heater on the tank then is
used to heat the contents of the tank, 400 gallons of filtered
grease, to 125.degree. F. for 1 hour. Fluid levels in the tanks are
monitored by sonar and radar and process parameters, such, without
limitation temperature and pH, are controlled and/or monitored by
redundant Chameleon Programmable Automation Controllers.
[0052] In the process, Sulfuric acid is added to the reaction
mixture until the pH reaches 2.5. Afterwards 10-15% by volume of
methanol is then transferred into the processing tank using a
pneumatic diaphragm pump. The contents of the processing tank are
then mixed by recirculation for one hour at 125.degree. F. Some
glycerol is produced by this process and can be drained from the
first processing tank. The mixture is then transferred to a second
processing tank, also having a resistance heater. Approx 20 g to pH
of about 7 gallons of premixed potassium methylate (to pH),
prepared as described above, is then transferred into second
processing tank. The reaction mixture is maintained at 125.degree.
F. for about 15 minutes. The mixture is then mixed by recirculation
for an additional 25 minutes. At 25 minutes, mixing is halted and
glycerin is drained into storage. The reaction is mixed for another
ten minutes and then glycerol is drained after halting mixing. This
mixing/glycerol draining process is repeated until no glycerol
forms.
[0053] The glycerin obtained form the first and second processing
tanks can be further settled in a conical tank to recover fuel that
is not effectively separated from the glycerol in the second
processing tank. The fuel can be added back to the first processing
tank for further processing,
[0054] Glycerol may then be shipped out for methanol recovery.
Alternately, the glycerin may be heated to about 200.degree. C. at
about 200 psi (pounds per square inch) to produce higher-value
propylene glycol, thereby producing additional value.
[0055] The biodiesel is then transferred to the wash tank. Forty 40
gallons of warm, deionized water is then added through a mist
system, and a limestone bubble aerator is turned on. The mixture is
aerated for 1-2 hours and grey water is drained. The washing step
is repeated three times and is tested for soaps and glycerol. If no
soaps or glycerol are present, the product is finished. The water
fraction contains Potassium Sulfate and can be used as a
fertilizer.
[0056] Once the biofuel is washed, it can be further refined to
remove any residual triglycerides. The fuel is filtered through a
30 .mu. KVHS filter, a 10 .mu. filter, a fluid-fluid coalescer (for
example and without limitation a PhaseSep.RTM. Coalescer from Pall
Corporation of East Hills, N.Y.) followed by a 2 .mu. coated
filter, such as a Teflon-coated filter.
[0057] Having now fully described this invention, it will be
understood to those of ordinary skill in the art that the same can
be performed within a wide and equivalent range of conditions,
formulations and other parameters without affecting the scope of
the invention or any embodiment thereof. All publications, patents
and patent applications mentioned in this specification are herein
incorporated by reference into the specification to the extent of
their technical disclosure, to the same extent as if each
individual publication, patent or patent application was
specifically and individually indicated to be incorporated herein
by reference.
* * * * *
References