U.S. patent application number 13/949029 was filed with the patent office on 2013-11-21 for methods of algae harvesting utilizing a filtering substance and uses therefor.
The applicant listed for this patent is Albert C. Rettenmaier. Invention is credited to Albert C. Rettenmaier.
Application Number | 20130305599 13/949029 |
Document ID | / |
Family ID | 44143241 |
Filed Date | 2013-11-21 |
United States Patent
Application |
20130305599 |
Kind Code |
A1 |
Rettenmaier; Albert C. |
November 21, 2013 |
METHODS OF ALGAE HARVESTING UTILIZING A FILTERING SUBSTANCE AND
USES THEREFOR
Abstract
Methods of harvesting algae, and using algae as a biofuel,
livestock feed, or food supplement are provided. The methods
comprise contacting liquid algae suspensions with a filtration
media. Depending upon the filtration media, the resulting algae and
filtration media admixture is then utilized as a biofuel, livestock
feed, food supplements, or for the extraction of algae oil.
Admixtures comprising a combustible filtration media, such as coal,
are particularly preferred. The methods are suitable for use with
any algae species. Compositions for use as a biofuel, livestock
feed, or food supplement are also provided. These compositions
comprise an admixture of algae and a filtration media.
Inventors: |
Rettenmaier; Albert C.;
(Blue Springs, MO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Rettenmaier; Albert C. |
Blue Springs |
MO |
US |
|
|
Family ID: |
44143241 |
Appl. No.: |
13/949029 |
Filed: |
July 23, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12966449 |
Dec 13, 2010 |
8518132 |
|
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13949029 |
|
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61285875 |
Dec 11, 2009 |
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Current U.S.
Class: |
44/603 ;
44/605 |
Current CPC
Class: |
C11B 13/00 20130101;
A23K 10/30 20160501; B01D 33/66 20130101; Y02C 10/02 20130101; B01D
53/84 20130101; B01D 2251/95 20130101; B01D 2257/504 20130101; Y02P
60/87 20151101; A23L 17/60 20160801; C10L 5/40 20130101; Y02E 50/10
20130101; Y02P 60/877 20151101; C10L 5/44 20130101; Y02W 30/74
20150501; Y02A 50/20 20180101; Y02E 50/30 20130101; Y02C 20/40
20200801; A23L 33/105 20160801; Y02A 50/2358 20180101 |
Class at
Publication: |
44/603 ;
44/605 |
International
Class: |
B01D 33/66 20060101
B01D033/66 |
Claims
1. A composition for use as a biofuel comprising an admixture of
algae and a filtration media.
2. The composition of claim 1, wherein said filtration media is
selected from the group consisting of carbonaceous solids, fibrous
plant materials, torrified biomass, fibrous animal waste, fibrous
industrial waste products, fibrous recyclable waste products, paper
products, and combinations thereof.
3. The composition of claim 1, wherein said filtration media is
selected from the group consisting of coal, petroleum coke,
charcoal, torrified biomass, wood, grasses, straw, leaves, hulls,
shells, bagasse, chaff, corn stover, distillers dried grains,
sawdust, ground refuse, manure, paper, paperboard, pulp, seed
cleanings, hay, ground corn, wheat, wheat middlings, soybean hulls,
oat hulls, milo, rye, oats, soybeans, alfalfa, canola meal,
safflower, safflower meal, corn gluten feed, hemp, jute, cotton,
plastics, rocks, sand, gravel, minerals, ceramic, dirt, clay,
metal, metal mesh or screens, sintered metal, pebbles, fly ash,
aluminosilicates, glass, porous glasses, lime, limestone, ash,
activated alumina, silica, zeolites, grains, chaff, flour, tires,
rubber, fabric, gauze, fiberglass, aggregate, batting, soot,
carbon, shale, activated carbon, filter membranes, magnets,
diatomaceous earth, Kieselguhr, and combinations thereof.
4. The composition of claim 1, wherein said admixture comprises
from about 0.5% by weight algae to about 90% by weight algae, based
upon the dried algae weight as a % of the total weight of the dried
algae and filtration media admixture taken as 100% by weight.
5. The composition of claim 1, wherein said admixture is dried.
6. The composition of claim 5, wherein said admixture has a
moisture content of less than about 15% by weight, based upon the
total weight of the admixture taken as 100% by weight.
7. A method of processing algae for biofuel comprising: (a)
providing an admixture comprising algae and a filtration media; (b)
heating said admixture to produce a vapor.
8. The method of claim 7, wherein said vapor comprises algae
oil.
9. The method of claim 8, further comprising: (c) collecting said
algae oil.
10. The method of claim 7, wherein said providing (a) comprises:
providing an algae suspension comprising algae dispersed in a
liquid medium; and contacting said algae suspension with a
filtration media, wherein said algae is collected by said
filtration media to yield said algae and filtration media
admixture.
11. The method of claim 10, said admixture further comprising other
organic material from said algae suspension.
12. The method of claim 10, wherein said contacting comprises
passing said algae suspension through a filtration bed comprising
said filtration media.
13. The method of claim 12, wherein said filtration media comprises
a granular, particulate, or fibrous filtering substance, said algae
being collected on said filtration media and in the interstitial
spaces or voids between said filtration media granules, particles,
or fibers.
14. The method of claim 7, wherein said filtration media is
selected from the group consisting of grains, plant materials,
biomass, fermentation byproducts, chaff, flour, and mixtures
thereof.
15. The method of claim 14, wherein said biomass is selected from
the group consisting of wood, grasses, straw, leaves, torrefied
biomass, hulls, shells, bagasse, chaff, corn stover, distillers
dried grains, sawdust, ground refuse, manure, paper, paperboard,
pulp, seed cleanings, hay, ground corn, wheat, wheat middlings,
soybean hulls, oat hulls, milo, rye, oats, soybeans, alfalfa,
canola meal, safflower, safflower meal, corn gluten feed, and
mixtures thereof.
16. The method of claim 7, wherein said heating (b) comprises
heating said admixture under vacuum.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a divisional of U.S. Ser. No.
12/966,449, filed Dec. 13, 2010, which claims the priority benefit
of U.S. Provisional Application Ser. No. 61/285,875, filed Dec. 11,
2009, both of which are incorporated by reference in their
entireties herein.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to methods of harvesting algae
for the production of biofuel, bioenergy, supplemented animal feed,
food supplements, and algae oil.
[0004] 2. Description of Related Art
[0005] Algae biomass shows great promise as a renewable fossil fuel
replacement and as a food supplement. There is need in the art for
a low cost, effective method for harvesting algae biomass and
making it available as fuel or food. However, harvesting of algae
from water or other liquids is currently a difficult process due to
the physical properties and nature of algae. Many existing methods
of harvesting algae focus on isolation of the algae itself. Thus,
when mechanical or physical methods of harvesting algae from water
are used, these processes include the additional difficult step of
further separating the algae from the filtering substances utilized
in the method. Such separation often involves the use of
undesirable solvents or detergents. Other methods of harvesting
algae utilize chemical or mechanical means of flocculation,
centrifugation, or sedimentation to facilitate skimming of algae
from the surface of the algae water or collection of algae
sediment. Some methods also produce an algae paste, which then must
be dried and re-divided for further processing. Many existing
methods also require specially cultured algae, which requires extra
nutrients and manipulation of the algae source, adding further
difficulties to the process. Thus, there remains a need in the art
for methods of harvesting algae that do not involve the drawbacks
of existing algae harvesting processes.
SUMMARY OF THE INVENTION
[0006] The present invention is broadly concerned with an algae
filtering system, which yields an algae/filtration media admixture
for further processing or combustion. The admixture comprises a
physical mixture of the filtration media and algae dispersed
therein and thereon. In general, the system uses a granular,
particulate or fibrous filtration media to recover the algae from
liquid. The algae can then be further processed, with or without
the filtration media. Further processing can include combustion of
the algae/filtration media admixture, partial combustion for
production of synthesis gas, recovery of algae or algae oil from
the algae/filtration media admixture, or the algae/filtration media
admixture can be used for livestock feed or as a food
supplement.
[0007] More specifically, in one aspect, the invention provides a
method of using algae as a biofuel. The method comprises providing
an admixture comprising algae and a filtration media and burning
the admixture to generate heat. In some embodiments, this heat can
be converted into electricity. The algae and filtration media
admixture is prepared by providing an algae suspension comprising
algae dispersed in a liquid medium, and contacting the algae
suspension with a filtration media, wherein the algae is collected
by or on the filtration media to yield the algae and filtration
media admixture. In some embodiments, a filtration bed is utilized
for contacting the algae with the filtration media.
[0008] In a further aspect, the invention provides a method of
harvesting algae for livestock feed or food supplements. The method
comprises providing an algae suspension comprising algae dispersed
in a liquid medium, contacting the algae suspension with a
filtration media, wherein the algae is collected by or on the
filtration media to yield an algae and filtration media admixture.
Then, without separating the algae from said filtration media,
using the admixture as livestock feed or a food supplement. The
filtration media is preferably selected from the group consisting
of grains, plant materials, biomass, fermentation byproducts,
chaff, flour, and mixtures thereof.
[0009] The invention also provides a composition for use as a
biofuel, livestock feed, or food supplement comprising an admixture
of algae and a filtration media. Suitable filtration media are
preferably selected from the group consisting of coal, petroleum
coke, charcoal, torrified biomass, wood, grasses, straw, leaves,
hulls, shells, bagasse, chaff, corn stover, distillers dried
grains, sawdust, ground refuse, manure, paper, paperboard, pulp,
seed cleanings, hay, ground corn, wheat, wheat middlings, soybean
hulls, oat hulls, milo, rye, oats, soybeans, alfalfa, canola meal,
safflower, safflower meal, corn gluten feed, hemp, jute, cotton,
plastics, rocks, sand, gravel, minerals, ceramic, dirt, clay,
metal, metal mesh or screens, sintered metal, pebbles, fly ash,
aluminosilicates, glass, porous glasses, lime, limestone, ash,
activated alumina, silica, zeolites, grains, chaff, flour, tires,
rubber, fabric, gauze, fiberglass, aggregate, batting, soot,
carbon, shale, activated carbon, filter membranes, magnets,
diatomaceous earth, Kieselguhr, and combinations thereof. The
admixture is preferably dried, and more preferably has a moisture
content of less than about 5% by weight, based upon the total
weight of the admixture taken as 100% by weight.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The patent or application file contains at least one drawing
executed in color. Copies of this patent or patent application
publication with color drawing(s) will be provided by the Office
upon request and payment of the necessary fee.
[0011] FIG. 1 is a diagram of one process involving combustion of
the algae and filtration media admixture according to the
invention;
[0012] FIG. 2 is a drawing (not to scale) of a preferred filtration
vessel in accordance with one embodiment of the invention;
[0013] FIG. 3 is a drawing (not to scale) of a filtration vessel in
accordance with another embodiment of the invention;
[0014] FIG. 4 is a drawing (not to scale) of a rail car filtration
vessel in accordance with another embodiment of the invention;
[0015] FIG. 5 is a drawing (not to scale) of a drum filtration
vessel in accordance with another embodiment of the invention;
[0016] FIG. 6 is a diagram of a process according to a further
embodiment of the invention involving an anaerobic digester;
[0017] FIG. 7 is a diagram of a process according to a further
embodiment of the invention involving CO.sub.2 sequestration after
combustion of the algae and filtration media admixture;
[0018] FIG. 8 is a diagram of a process according to a further
embodiment of the invention involving use of an algae source
associated with a cattle feed lot;
[0019] FIG. 9 is a photograph of the two vessel set up utilized in
Example 1;
[0020] FIG. 10 is a photograph of the unfiltered algae suspension
and resulting filtrates from Example 1;
[0021] FIG. 11 is a top-down photograph of the unfiltered algae
suspension and resulting filtrates from Example 1;
[0022] FIG. 12 is a photograph of the unfiltered algae suspension
and resulting filtrate from Example 2; and
[0023] FIG. 13 is a photograph of the algae and filtration media
admixture collected in Example 4.
DETAILED DESCRIPTION
[0024] In more detail, the invention provides methods of harvesting
algae using filtration media. Algal suspensions from a source of
algae (e.g., pond, water stream) are passed through the filtration
media, which mechanically or physically removes the algae from the
liquid suspension. That is, although adsorption (e.g., chemical
interaction) may occur in some embodiments, the methods of the
invention are concerned primarily with physical separation and may
not involve adsorption or other chemical interaction between the
filtration media and algae. The algae collects on or is collected
by the filtration media, and in some cases becomes embedded
therein. The filtrate can then be recycled back through the
filtration media until the desired level of removal is achieved, or
the filtrate can be returned to the source of algae. The filtrate
can also be used for irrigation or otherwise discharged from the
system. Unlike existing algae harvesting methods, algae collected
according to the present invention does not have to be separated
from the filtration media for use. Rather, the algae and filtration
media admixture is itself a useable product. In one aspect, the
algae and filtration media admixture can be used as a biofuel and
burned or combusted to produce heat and/or energy. A diagram of
this process is depicted in FIG. 1. In another aspect, the algae
and filtration media admixture can be used for livestock feed or as
a food supplement. It will also be appreciated that algae and/or
algal oil can also be isolated from the algae and filtration media
admixture using known methods.
[0025] Suitable sources of algae include any environment (e.g.,
liquid medium) suitable for algae growth. Specific examples include
naturally-occurring algae-laden water streams, natural or man-made
ponds and lakes (including ponds designed specifically to grow
algae), polluted water streams, cattle feed lot ponds, concentrated
animal feed operation (CAFO) ponds, algae culture vessels, algae
open ponds, algae closed ponds, algae raceway ponds, settling
basins, water troughs, water holding tanks, wastewater, seawater,
photobioreactors, anaerobic digester effluent, freshwater, salt
water, brackish water, brine, and combinations thereof. The
invention is suitable for filtering any aquatic algae species,
blends of species, natural mixtures of species, and/or genetically
engineered species. Some preferred types of algae for use in the
invention are selected from the group consisting of Diatoms,
Chlorophyta (green algae), Euglenophyta, Dinoflagellata,
Chrysophyta, Phaeophyta (brown algae), Rhodophyta (red algae), and
Cyanobacteria (blue-green algae). Particularly preferred algae
genera within the above groups include Botryococcus,
Ankistrodesmus, Chlorella, Coelastrum, Scenedesmus, Klebsormidium,
Dictyochloropsis, Kirchneriella, Phormidium, Lyngbya, Oocystis,
Oscillatoria, Cosmarium, Leptolyngbya, Monoraphidium, Phormidium,
Ulothrix, Anabaena, Uronema, Hydrodictyon, Chlorococum, Cladophora,
Lemna, and combinations thereof, with Botryococcus braunii being a
particularly preferred species. The invention is particularly
suited for filtration of microalgae (1-40 .mu.m). The invention is
suitable for filtration of brines and brackish growth media, as
well as freshwater algae suspensions (including municipal/treated
water sources). However, depending on the type of algae, the
salinity of the algae suspension will preferably range from about
0M to about 3M, more preferably from about 0M to about 0.7M, and
even more preferably from about 0M to about 0.1M. One advantage of
the present invention is that the methods can be used with native
algae sources, and do not require special cultivation procedures or
manipulation of the algae source (such as increasing salinity, or
manipulating lipid content by supplying extra or special nutrients,
or modifying growth conditions, etc.). This decreases the overall
energy input of the system and provides a more natural bioenergy
source compared to existing algae harvesting methods which often
rely on specially cultured algae sources.
[0026] Suitable filtration media will be any organic or inorganic
granular, particulate, porous, or fibrous filtering substance. It
will be appreciated that the filtration media can be ground,
crushed, or pulverized to achieve the desired particle or fiber
size prior to filtration. In one embodiment, the filtration medium
is preferably a combustible material. Examples of suitable
combustible filtration media include carbonaceous solids, fibrous
plant materials, torrified biomass, fibrous animal waste, fibrous
industrial or recyclable waste products, paper products, and
combinations thereof. Particularly preferred filtration media in
this embodiment are selected from the group consisting of coal
(e.g., fines, raw, crushed, pulverized, screened, wet or dry),
petroleum coke (e.g., fines, raw, crushed, pulverized, screened,
wet or dry), charcoal, Waffled and untorrified biomass (e.g., wood,
grasses, straw, leaves, hulls, shells, bagasse, chaff, corn stover,
distillers dried grains, sawdust, ground refuse, manure, paper,
paperboard, pulp, seed cleanings, hay, ground corn, wheat, wheat
middlings, soybean hulls, oat hulls, milo, rye, oats, soybeans,
alfalfa, canola meal, safflower, safflower meal, corn gluten feed),
hemp, jute, cotton, plastics (e.g., nylon, polyester), and mixtures
thereof. The methods can be used to enhance the combustion value of
the filtration media, and can include subsequent fermentation
processes prior to combustion. In another embodiment, the
filtration medium is a non-combustible, inert carrier, such as
rocks, sand, gravel, minerals, ceramic, dirt, clay, metal, metal
mesh or screens, sintered metal, pebbles, fly ash,
aluminosilicates, glass, porous glasses, lime, limestone, ash,
activated alumina, silica, zeolites, and mixtures thereof. In this
embodiment, the carrier component of the admixture is not actually
combusted or burned, but is instead collected or removed from the
combustion chamber, once the algae is combusted, and recycled for
use in subsequent filtration processes. Heat can also be recovered
from the carrier via heat exchange before reusing the carrier for
filtration. In a further embodiment, the methods can be used to
enhance the nutritional value of the filtration media for animal
feed or food supplements. Suitable filtration media in this
embodiment includes the grains, plant materials, and biomass,
listed above, as well as fermentation byproducts (e.g., distillers
dried grain), chaff, flour, and mixtures thereof. Other materials
that could be used as filtration media include tires, rubber,
fabric, gauze, fiberglass, aggregate, batting, soot, carbon, shale,
activated carbon, filter membranes, magnets, diatomaceous earth,
and Kieselguhr.
[0027] In one embodiment, the filtration media is paper or paper
pulp. In this embodiment, the resulting wet admixture can be used
as fuel, or dried and used as fuel. In addition, the admixture can
be pelletized or briquetted for use as fuel, such as in a wood
burning stove. Alternatively, the admixture can be treated for
recovery of algae oil, or further processed and recycled for re-use
as paper.
[0028] In a preferred embodiment, the filtration media is coal,
with the resulting algae/coal admixture being fed into a coal-fired
power plant for combustion (e.g., into a combustion chamber for
burning). The admixture is burned to generate heat, which is
converted into electricity in the power plant. Preferably, the
admixture is pulverized into a fine powder of talcum-consistency
prior to combustion, as in conventional pulverized coal power
plants. Advantageously, dried algae has roughly the same energy
output as coal. Thus, in the algae/coal admixture, the algae
displaces some of the coal used in the process, decreasing the
total amount of coal necessary for combustion, with roughly the
same total energy output. For example, a 10-lb. sample of the dried
algae/coal admixture (containing 1 lb. of algae and 9 lbs. of coal)
could be combusted to yield the same energy output as 10 lbs. of
dried coal. Accordingly, this process would be eligible for a
carbon credit, and the energy produced by the algae component of
the admixture would be renewable energy and qualify towards
Renewable Energy Portfolio Standards. The carbon dioxide generated
by the power plant could also be used as a nutrient for the algae
source, as described below. Preferred types of coal for use in the
invention are selected from the group consisting of anthracite,
lignite, sub-bituminous (e.g., Powder River Basin), bituminous
(e.g., Appalachia; Illinois), steam, cannel coal, and combinations
thereof. Coal is generally available in sizes of from about 2
inches and smaller down to the fines (which are usually less than
50 microns). Preferably, the raw coal received from the mine,
conveyor belt or rail car performs well in capturing algae "as is,"
however, if this is not the case, then the coal is preferably
crushed, pulverized, and/or screened prior to use. When used,
pulverized coal preferably has an average particle size of from
about 3 microns to about 1 mm, more preferably from about 27
microns to about 425 microns, and even more preferably from about
50 microns to about 200 microns. Crushed coal preferably has an
average particle size of from about 0.3 mm to about 25 mm, more
preferably from about 0.4 mm to about 5 mm, and even more
preferably from about 0.5 mm to about 1 mm. In some embodiments,
the combination of crushed and pulverized coal is preferred. The
term "particle size," as used herein, refers to the maximum
surface-to-surface dimension of the coal particles or pieces. The
"average" particle size refers to the size which typifies a given
sample of the coal, although it will be appreciated that some
particles or pieces in the sample will be slightly smaller or
larger than this value. It will also be appreciated that depending
upon the size of the filtration vessel, the particle size of some
of the coal pieces can be as large as 60 mm or larger in some
embodiments, such as a coal rail car.
[0029] Regardless of the embodiment, the filtration method
comprises contacting the algae suspension with the filtration
media, which generally involves collecting and pumping or otherwise
transporting the algae suspension from the source of algae and
contacting it with the filtration media. The concentration of the
algae in the natural suspension will preferably range from about
0.01% by weight to about 1% by weight, more preferably from about
0.06% by weight to about 0.5% by weight, and even more preferably
from about 0.06% by weight to about 0.2% by weight, based upon the
total weight of the suspension taken as 100% by weight. If
necessary or desired, the algae suspension can be preconcentrated
using flocculation or gravity sedimentation (e.g., centrifugation
or passive separation using settling ponds and vessels) or other
methods. Other methods for preconcentration include the use of
dewatering agents, such as flocculants, coagulants, water soluble
polymers, organopolysiloxanes, sodium hexametaphosphates,
alkylphenyolethyloxalate, electric charge manipulation, and
peptiding agents. The concentration of the algae in the
preconcentrated suspension will preferably range from about 0.2% by
weight to about 10% by weight, more preferably from about 0.5% by
weight to about 7% by weight, and even more preferably from about
1% by weight to about 5% by weight, based upon the total weight of
the suspension taken as 100% by weight. The algae concentration in
the resulting filtrate will be at least about 70% less than in the
initial algae concentration of the suspension, preferably at least
about 90% less than in the initial algae suspension, and more
preferably at least about 98% less than the initial algae
concentration of the suspension, and even more preferably about
100% less than the initial algae concentration of the
suspension.
[0030] In one aspect, the algae suspension is contacted with the
filtration media using a filtration bed. This aspect relies on a
bed of filtration media through which the algae suspension flows,
usually downward, under gravity or active pressure. The alga is
collected on the filtration media and in the interstitial spaces or
voids between the particles or granules of media throughout the
volume of the media. More specifically, a filtration vessel having
an inlet and an outlet is partially or completely filled with
filtration media to create the filtration bed. Preferably, at least
about 60% of the interior volume of the vessel is filled with the
filtration media. In some embodiments, the filtration bed comprises
layers of different filtration media or layers of the same
filtration media of different particle sizes. In general use, the
algae suspension is fed into the inlet, passed through the
filtration media in the bed, and the resulting filtrate exits the
vessel outlet. The filtrate can be recycled back through the vessel
multiple times, sent back to the algae source, collected for later
use, or simply discarded. A preferred filtration vessel is depicted
in FIG. 2. The vessel 10 is a cylindrical column oriented
vertically. It will also be appreciated that although a cylindrical
column is depicted, any suitable cross-sectional shape could be
utilized (e.g., oval, square, geometric). The inlet 12 is at the
top of the vessel 10, and the outlet 14 is at the bottom of the
vessel 10. The vessel 10 can be configured with the appropriate
valves, lockhoppers, nozzles, distributors or removable heads for
input and removal of the algae suspension and filtration media. The
vessel 10 is filled with the filtration media to form the
filtration bed 16. The algae suspension 18 is then added to the
vessel. As the suspension 18 flows through the bed 16, the algae is
collected by the filtration media and the filtrate 20 exits the
outlet. The resulting admixture 22 is removed from the vessel for
subsequent processing. It will be appreciated that the size and
dimensions of the vessel will vary greatly, depending upon a given
application of the technology (e.g., large-scale
commercial/industrial vs. small-scale operations). The length of
the vessel will generally range from about 1 ft. to about 100 ft.,
more preferably from about 10 ft. to about 100 ft., and even more
preferably, from about 30 ft. to about 70 ft. The diameter (or
width, as the case may be) of the vessel will preferably range from
about 10% of the length to about 50% of the length of the vessel,
and more preferably from about 15% of the length to about 25% of
the length of the vessel. Regardless of the shape, the interior
volume of the vessel preferably ranges from about 8 ft.sup.3 to
about 8000 ft.sup.3, and more preferably from about 100 ft.sup.3 to
about 6000 ft.sup.3. The ratio of the bed depth to diameter (or
width) is preferably from about 10:1 to about 2:1, and more
preferably from about 6:1 to about 4:1.
[0031] Although passive gravity-based filtration can be used, the
filtration system can also be employed in a closed system in which
the algae suspension is actively pumped into the vessel until the
volume of entrapped algae on the filtration media meets the desired
loading. The flow rate of the algae suspension is preferably from
about 0.5 gallons per minute (gpm) to about 100,000 gpm, more
preferably from about 100 gpm to about 75,000 gpm, and even more
preferably from about 20,000 gpm to about 30,000 gpm. The pressure
of the system preferably ranges from about 0 psig to about 200
psig, more preferably from about 0 psig to about 50 psig, and even
more preferably from about 1 psig to about 10 psig. Filtration is
preferably carried out under ambient temperature (e.g., approx.
0-40.degree. C.). Control of the algae loading can be done by
monitoring the pressure drop across the bed or the decrease in the
flow rate. In general, filtration proceeds until a pressure drop of
from about 2 psi to about 200 psi is observed, preferably from
about 10 psi to about 50 psi, and more preferably from about 2 psi
to about 10 psi. Likewise, filtration can also proceed until the
flow rate decreases by about 50%, more preferably by about 75%, and
even more preferably by about 90%. However, it will be appreciated
that these parameters will vary depending upon the filtration
media, size of the filtration bed, as well as the cell size of the
algae being filtered and concentration of the algae suspension
feed. In the case of gravity flow filtration, the harvesting
proceeds until liquid accumulates above the bed to a certain
height. This height is preferably less than about 20 ft., more
preferably less than about 10 ft., and more preferably less than
about 1 ft.
[0032] The resulting algae and filtration admixture can then be
removed from the vessel for further processing. For example, the
admixture can be dried using sunlight and wind, vacuum, forced-air
drying, steam heating, waste heat utilization, contact with a drier
substance, or other suitable methods. The dried admixture will
preferably have a moisture content of less than about 15% by
weight, more preferably less than about 5% by weight, and even more
preferably from about 0% to about 0.5% by weight, based upon the
total weight of the admixture taken as 100% by weight. The dried
admixture can then be combusted or fed to livestock to supplement
existing feed or as the feed itself. The admixture can also be
further crushed or pulverized prior to use. Vacuum pressure may
also be used to rupture the algae cells for enhanced combustion or
collection of oils and cellular by-products for food supplement
purposes. Oil can be separated from the other liquid components by
conventional means, including filtration, titration, or phase
separation. Other methods of drying the admixture, when desired,
include the use of dewatering agents, such as flocculants,
coagulants, water soluble polymers, organopolysiloxanes, sodium
hexametaphosphates, alkylphenyolethyloxalate, and peptiding agents.
Alternatively, the wet admixture can be used directly for
combustion or as a feed supplement. The admixture can also be
packaged or stored for later use. The vessel can then be refilled
with filtration media for re-use. Multiple vessels can also be used
in parallel.
[0033] In another aspect, the vessel can comprise a holding tank,
rail car, pile, slab, or trough open to the atmosphere. An example
of this embodiment is depicted in FIG. 3, with like numbering used
for like parts from FIG. 2. The vessel 10 can be filled with the
filtration media to form the filtration bed 16, followed by
applying the algae suspension 18 to the top of the bed 16. The
algae suspension 18 can be applied by spraying, pouring, doping,
dumping, distributing, pumping, or dripping the algae suspension
over the filtration media bed 16. The algae suspension 18 passes
downward through the filtration media bed 16 via gravity. The
vessel 10 can include a dumping mechanism or a screw or other
device for conveying the algae and filtration media admixture 22
out of the vessel 10. The vessel 10 can also include an outlet 14
to allow the liquid (filtrate) 20 from the algae suspension 18 to
exit the vessel 10. This embodiment is particularly suited for use
with rail cars transporting coal, as show in FIG. 4. For example,
the rail car can pass underneath a spigot or spray that can apply
the algae suspension 18 to the coal in the car. As the algae
suspension is filtered through the coal bed, the algae become
entrapped in and between the coal. The algae/coal admixture in the
rail car continues to the power plant as with conventional coal
transportation, where it is removed from the rail car, optionally
dried and/or pulverized, and fed into a combustion chamber. The
algae suspension could be applied early in the transportation
process (e.g., remote from the power plant) or immediately prior to
combustion, as in the case of an algae source (e.g., pond) on or
near the power plant property.
[0034] Another advantage of the inventive method is that the algae
suspension, once applied to the coal bed, can form a fibrous mat
that can help bind coal fines and particles in the coal bed, and/or
can bind and agglomerate the coal particles, thereby reducing the
amount of coal lost to wind erosion during transportation of the
coal in the rail car. Wind erosion coal losses from rail cars is an
increasingly significant environmental issue, as well as a safety
issue. The fouling of ballast by coal losses from rail cars has
weakened train tracks and even led to derailments.
[0035] Alternatively, the algae suspension can simply be sprayed or
poured over coal piles before loading onto the rail cars, or after
removal from the rail cars but before combustion. Another advantage
of the inventive method is that algae suspensions can be applied
for fire suppression in low rank and other coals where spontaneous
combustion can occur. The algae suspension can be used to treat hot
spots in coal piles, coal mines and other locations. Further
advantages include the suppression of oxidation of coals by coating
the coal with a film of algae.
[0036] In a further aspect, the filtration media bed can be carried
on a dewatering screen, conveyor belt, or other similar horizontal
belt filter, with the algae suspension being applied to the
filtration media as it is carried on the belt. The resulting algae
and filtration media admixture can then be conveyed directly to a
combustion chamber, if desired, or to a holding vessel for further
processing, as described herein. The admixture could also be
packaged for distribution, such as in the case of animal feed and
food supplements. The admixture can be dried on the same conveyor
or transferred to another conveyor for drying.
[0037] In another aspect, a rotary drum filter may be used as the
filtration vessel 10, as shown in FIG. 5, with like numbering being
used for like parts as in FIG. 2. In this aspect, the filtration
bed 16 and algae suspension 18 are mixed together in a trough 10
below the drum 24 forming a slurry. Half of the drum 24 is
submerged in the slurry, with the other half above it. A filter
cloth winds around the drum and, as the drum rotates, the resulting
algae and filtration media admixture 22 is sucked into the cloth
and the filtrate 20 is discarded. As the drum rotates out of the
slurry, the admixtures 22 is dried by the continuous vacuum being
drawn through the admixture in the exposed section of the drum. At
the end of each rotation cycle (approximately a three o'clock
position), the admixture 22 is discharged and the process repeats
itself. This filtration vessel 10 may incorporate a drum cloth that
is caulked onto the drum 24 itself, or it can utilize an endless
belt which tracks off and discharges away from the drum 24. In lieu
of being used as the filtration vessel, the drum filter can also be
used subsequent to one of the other filtration systems described
herein to dry the admixture.
[0038] Regardless of the embodiment, the admixture will preferably
comprise from about 0.5% by weight algae to about 90% by weight
algae, more preferably, from about 5% by weight to about 25% by
weight algae, and even more preferably from about 8% by weight to
about 12% by weight algae. The % by weight algae, as used herein,
is based upon the dried algae weight as a % of the total weight of
the dried algae and filtration media admixture taken as 100% by
weight. It will be appreciated that depending upon the source of
the algae, other organic material from the algae suspension may
also become entrapped in the filtration media. Such material is
also often suitable for combustion or further processing as
described herein.
[0039] The algae growing and harvesting process can also be
combined with an anaerobic digester. A example of this system is
depicted in FIG. 6. The digestate water (effluent) from the
anaerobic digester is sent to the algae source (e.g., pond, holding
tank, etc.). This water is rich in nutrients, which the algae
convert into useable algae fuel. Both heterotrophic and autotrophic
algae can be grown using this system. The algae suspension from
this algae source will also often contain fibrous or particulate
material (waste) from the digester effluent, which is also trapped
by the filtration media in the inventive methods and used as
biomass for combustion. For example, when coal is the filtration
media, the algae/waste/coal admixtures can be sent to the power
plant to produce power or heat in a generating plant, as described
herein. Another use involving anaerobic digesters is to use biomass
as the filtration media, and collect the algae and fibrous or
particulate material in the digester effluent. The resulting
algae/waste/biomass admixture can be further processed into compost
or fertilizer or combusted for heat recovery or power
generation.
[0040] In processes involving combustion of the algae and
filtration media admixture, the algae suspension or source can be
used as a carbon dioxide scrubber in some configurations. That is,
combustion of the admixture yields a gas stream comprising carbon
dioxide. The gas stream can be fed through the algae suspension or
source (such as a pond or other water feature near the power plant)
which scrubs (i.e., removes) at least a portion of the carbon
dioxide from the gas stream. This not only provides carbon dioxide
nutrients to the algae in the algae source, but also reduces the
carbon dioxide emissions of the power plant. Preferably, the level
of carbon dioxide is reduced by at least about 1%, more preferably
by at least about 15%, and even more preferably by at least about
25%. A diagram of this system is depicted in FIG. 7. In addition or
in lieu of the above process, the gas stream comprising carbon
dioxide can be contacted with an intermediate solvent to purify the
gas stream instead of sending the gas stream (which includes
impurities in addition to carbon dioxide) directly to the algae
suspension or source from the power plant stack. More specifically,
the solvent is contacted with the gas stream, preferably at a low
temperature, and thereby absorbs the carbon dioxide from the gas
stream. The solvent can then be regenerated, preferably by heating,
to release the absorbed carbon dioxide. The resulting purified
carbon dioxide stream can then be fed to the algae suspension or
source as a nutrient. Suitable solvents for use in this process are
selected from the group consisting of amines (e.g.,
monoethanolamine (MEA), N-methyldiethanolamine (MDEA)), carbonates
(e.g., calcium carbonate), and mixtures thereof.
[0041] Similarly, the algae and filtration media admixture can be
pulverized and slurried for feed to a gasification process that
operates with a slurry feed (like the GE Quench gasification
technology). Likewise, the algae and filtration media admixture can
be pulverized and dried for feed to a gasification process that
operates with a dry fuel feed (like the Shell SGP gasification
process). In these aspects, the filtration media is preferably
coal, petroleum coke, biomass, or other material suitable for
gasification. The admixture is partially burned (partial
combustion) to produce heat as well as synthesis gas (e.g., carbon
monoxide and hydrogen), which can be further processed to produce
energy and/or chemicals.
[0042] Similarly, an algae/coal admixture can be pulverized and
slurried to produce Coal Water Slurry for combustion. The use of
Coal Water Slurry and Coal Water Fuel has been widely investigated
and the use of the algae/coal admixture provides a renewable energy
component and increased fuel value for a given coal percentage.
[0043] As mentioned herein, the methods are also suitable for
extraction of oil from algae. The algae oil can either be extracted
by heating the algae and filtration media admixture and collecting
the oil from the resulting vapor produced, or by extraction of the
oil from the captured algae with solvent. The application of a
vacuum can be employed to reduce the boiling point of the algae oil
in this process. Vacuum pressure is also useful in rupturing the
algae cell walls, as described herein, thereby making the oil more
easily extracted or vaporized. Vacuum rupture will also release oil
that can be collected by skimming or draining off the admixture
slurry.
[0044] The invention is also suitable for use in water treatment,
and specifically the harvesting of algae from wastewater.
Advantageously, wastewater often contains a high level of nutrients
beneficial to algae growth. In this aspect, the algae consume the
nutrients in the wastewater, and the filtration media captures the
algae and any residual particulate material in the wastewater
during filtration. The resulting filtrate water is improved by the
reduction of these nutrients, and removal of particulates. The
resulting algae and filtration media admixtures can be sent on for
combustion or further processing, as described herein. Suitable
wastewaters include municipal wastewater and CAFO wastewater (FIG.
8), among others.
[0045] The invention can also be used for general algae control in
waterways, lakes, ponds and water processing facilities. The
filtering substance can be chosen depending upon the desired end
use. A combustible material, such as coal, will allow the captured
algae biomass and filtration media admixture to be combusted for
heat or power generation, as described herein.
EXAMPLES
[0046] The following examples set forth methods in accordance with
the invention. It is to be understood, however, that these examples
are provided by way of illustration and nothing therein should be
taken as a limitation upon the overall scope of the invention.
Example 1
[0047] In this Example, two filtration vessels were prepared for
filtering algae using 1.5-inch Sch. 40 PVC cut into 12-inch
lengths. The bottom of each vessel was fitted with reducing
fittings having a 0.5-inch outlet. Next, two layers of a black mesh
fabric (mesh size .about.16 mm) were placed in the bottom of each
vessel to retain the filtration media in the vessel, while allowing
the filtrate liquid to exit the vessel. The vessel for filter bed
#1 was filled with 350 ml of crushed anthracite coal with an
average particle size of 0.6-0.8 mm. The vessel for filter bed #2
was filled with the 280 ml of the crushed anthracite layered with a
layer of 70 ml of pulverized anthracite in the middle. The
pulverized anthracite was produced 70 ml at a time in a 1.25-inch
steel pipe with a cap. A 10 lb. metal bar was used to pulverize by
striking the material 22 times from a height of 8 inches. Once
filled, each vessel was capped with reduced fittings having a
1/2-inch inlet. The vessels were positioned vertically for the
downward flow of algae water through each vessel. A sump pump was
used to pump an algae suspension from a tank of algae water to the
inlet of each vessel via PVC pipe. The filtrate for each vessel was
collected for observation. A photograph of the two-vessel set up is
shown in FIG. 9.
[0048] For the tests, Botryococcus braunii was grown in a
photobioreactor comprising a 45-gallon aquarium filled with water.
Conventional plant food (Schultz's) was added to the water
periodically and light was applied to three sides of the aquarium
at a schedule of 16 hours on and 8 hours off per 24 hour cycle. The
concentration of the algae in the water at the time of testing was
estimated at 0.1 wt. %.
[0049] The algae water was first filtered through filter bed #1 at
a flow rate of approximately 0.5-1 gpm (2,000-3,800 ml/min.). The
pressure drop across the bed was 9 psi. The filtrate was collected
for observation. The optical density of the filtrate was visually
observed to be the same as the algae suspension feed. Thus, there
was no observable capture of algae. The process was repeating using
filter bed #2 at a flow rate of about 20 ml/min. (0.005 gpm) for 30
minutes. The pressure drop across the bed was 9 psi. The filtrate
from filter bed #2 was collected and observed to be clear with no
visible signs of algae, indicating near 100% capture of the algae
in the filtration media. FIG. 10 shows a photograph of unfiltered
algae water (left), filtrate #1 (middle), and filtrate #2 (right).
FIG. 11 is top-down photograph of the unfiltered algae water
(left), filtrate #1 (middle), and filtrate #2 (right).
Example 2
[0050] In this Example, another filtration bed was prepared using a
filtration vessel prepared as described above for Example 1. The
vessel was filled with filtration media comprising pulverized
anthracite coal and crushed anthracite coal (0.6-0.8 mm average
particle size). The filtration bed structure was as follows:
[0051] Bottom layer: 70 ml of 0.6-0.8 mm crushed anthracite
coal
[0052] Second layer: 35 ml of pulverized and screened (18 mesh)
anthracite coal
[0053] Third layer: 70 ml of 0.6-0.8 mm crushed anthracite coal
[0054] Fourth layer: 35 ml of lightly pulverized and screened (18
mesh) anthracite coal
[0055] Top layer: 105 ml of 0.6-0.8 mm crushed anthracite coal
Botryococcus braunii algae water was pumped through the filtration
vessel as described above, and the filtrate was collected. A higher
flow rate of approximately 240 ml/min. (0.06 gpm) was observed. It
was also observed that the algae water siphoned passively through
the filter bed with a head of about 4 feet. As shown in the
photograph in FIG. 12, the filtrate (right) was observed to be
clear with no visible signs of algae, as compared to the unfiltered
algae suspension (left).
Example 3
[0056] In this Example, additional filtration beds were prepared
using a filtration vessel prepared as described above for Example
1. For the first test run, anthracite coal was pulverized, and
screened with 84 mesh screen. Next, the filtration vessel was
filled with a layer of 140 ml of 0.6-0.8 mm crushed anthracite
coal, followed by a layer of 70 ml of the pulverized and screened
anthracite, and a final layer of 140 ml of the crushed anthracite
coal. Botryococcus braunii algae water was pumped through the
vessel as described above. The pressure of the pump was 9 psig, and
no flow was observed through the bed.
[0057] For the second test run, a second filtration bed was
prepared. The structure of bed was as follows:
[0058] Bottom layer: 50-70 ml of 0.6-0.8 mm crushed anthracite
[0059] Second layer: 5 ml of pulverized and screened (84 mesh)
anthracite
[0060] Third layer: 50-70 ml of 0.6-0.8 mm crushed anthracite
[0061] Fourth layer: 5 ml of pulverized and screened (84 mesh)
anthracite
[0062] Fifth layer: 50-70 ml of 0.6-0.8 mm crushed anthracite
[0063] Sixth layer: 5 ml of pulverized and screened (84 mesh)
anthracite
[0064] Seventh layer: 50-70 ml of 0.6-0.8 mm crushed anthracite
[0065] Eighth layer: 5 ml of pulverized and screened (84 mesh)
anthracite
Botryococcus braunii algae water was pumped through the vessel as
described above. The pressure of the pump was 9 psig, and low flow
was observed through the bed with very high capture of algae. The
filtrate was observed to be clear with no visible signs of
algae.
[0066] For the third test run, a further filtration bed was
prepared by filling the filtration vessel with filtration media
comprising approximately 70 ml crushed anthracite coal in the
bottom (0.6-0.8 mm average particle size), followed by a layer of
210 ml of pulverized anthracite, and a final layer of 70 ml of the
crushed anthracite on top. The pulverized anthracite was prepared,
as described above in Example 1, except that the material was
struck only 12 times from a height of 8 inches. Botryococcus
braunii algae water was pumped through the vessel as described
above, except that the filtrate water was re-circulated back to the
algae water tank. The initial flow rate was observed to be 240
ml/min. (0.06 gpm), which continued for 2 hours when the flow rate
was observed to drop to 120 ml/min. (0.03 gpm). At that point,
small amounts of algae were observed to begin breaking through in
the filtrate. This filtering process was run continuously for four
days. The flow rate at the end of the test was 60 ml/min. (0.015
gpm) and algae capture was still occurring. The vessel was emptied
and the resulting algae/coal admixture was analyzed. It was
calculated and observed that the percentage of algae in the
resulting algae/coal admixture was at least 10% of the admixture on
a dry weight basis.
Example 4
[0067] In this Example, a filtration bed was prepared using a
vessel according to Example 1. The bed contained 70 ml of crushed
anthracite coal (average particle size 0.6-0.8 mm) in the bottom,
followed by a layer of 70 ml of pulverized anthracite (produced as
described in Example 3, third run), a second layer of 70 ml of the
crushed anthracite coal, a second layer of 70 ml of the pulverized
anthracite, and a final layer of 70 ml of the crushed anthracite
coal on top. Algae water was circulated through the filtration
vessel for three days, with the flow rate starting out at 240
ml/min. and dropping off to 60 ml/min. at the end of the run. The
filtration vessel was emptied and the algae/coal admixture was
analyzed. FIG. 13 is a photograph of the vessel contents. The
percentage of algae in the resulting algae/coal admixture was
calculated to be greater than 10% on a dry weight basis. The sample
was dried outdoors in the sun, and the weight loss results are as
follows:
TABLE-US-00001 Time after end of run (hours) Weight of admixture
(g) 0 232 8 229 11 215 18.25 184
[0068] At 18+ hours the sample was observed to be completely dry.
The sample was then pulverized with a mortar and pestle, and
produced a fine greenish black powder of a face-powder consistency
(e.g., talcum powder consistency). This powder was easily blown
away with air, and it is proposed that this material would be
suitable as feed to a pulverized coal power plant based on these
results.
Example 5
[0069] A series of tests were conducted using outdoor, 80-gallon
algae growth vessels and various filtration bed set ups. Several
runs were made using different types of coal and different algae
strains. Coals tested: Anthracite; Powder River Basin ("PRB;"
sub-bituminous); and Illinois (bituminous). Algae tested: Chlorella
and Scenedesmus. Filtration vessels were prepared as described
above in Example 1. The use of an Optical Density (OD) Measurement
tool allowed the algae concentration in the algae feed and filtrate
to be determined.
[0070] A first filtration bed was prepared by filling the vessel
with 350 ml of PRB coal that had been pulverized and screened
through an 84-mesh screen. The OD of the Chlorella algae water to
be filtered indicated an initial algae concentration of 0.06 wt %.
The flow rate observed was approximately 4 ml/min. with a pressure
drop of 9 psi across the bed. After filtration the filtrate was
analyzed. The algae capture was nearly 100% with negligible traces
of algae in the filtrate water.
[0071] A second filtration bed was prepared by filling the vessel
with 350 ml of screened (18 mesh) Illinois coal (without
pulverization due to the high degree of fine material). Chlorella
algae water was filtered through the vessel. The flow rate observed
was 5 ml/min. and the capture of algae was observed to be near 100%
with no visible traces of algae in the filtrate. The flow dropped
off after about 30 minutes, and the test was stopped.
[0072] A third filtration bed was prepared by filling the vessel
with 200 ml of crushed anthracite coal (0.6-0.8 mm average particle
size) for the bottom layer, followed by a layer of 140 ml of
pulverized coal (as prepared above with 12-15 strikes, but no
screening), and a top layer of 35 ml of the crushed anthracite
coal. The Chlorella algae water to be filtered had an OD of 0.88
(algae concentration of 1.2 g/L). A flow rate of 40 ml/min. was
observed. The filtrate was collected and analyzed. The OD of the
filtrate was 0.121 (algae concentration of 0.067 g/L). The
harvesting efficiency was calculated to be 94% removal of
algae.
[0073] A fourth filtration bed was prepared by filling the vessel
with 70 ml of crushed anthracite coal (0.6-0.8 mm average particle
size) as the bottom layer, 210 ml of pulverized coal (as prepared
above with 12-15 strikes and no screening) as the middle layer, and
70 ml crushed anthracite coal (0.6-0.8 mm average particle size) as
the top layer. The initial algae suspension contained a mostly
Scenedesmus mix of algae with an optical density (OD) of 0.80,
which correlates to an algae concentration of 1.07 g/L. The
suspension was pumped through the vessel and a flow rate of 5
ml/min. was observed. The pressure drop across the bed was 9 psi.
The filtrate was collected and observed. The OD of the filtrate was
0.09, which corresponded to a concentration of 0.02 g/L. The
filtrate appeared clear with little visible traces of algae. The
harvesting efficiency was calculated to be 98% removal of
aglae.
Example 6
Additional Testing
[0074] In this Example, additional filtration beds were tested.
Botryococcus braunii algae water was used for all tests. Crushed
and/or pulverized anthracite coal was used. The bed structure of
the first filtration bed was as follows:
[0075] Bottom layer: 35 ml of 0.6-0.8 mm crushed anthracite
coal
[0076] Second layer: 70 ml of pulverized anthracite coal [0077] (22
strikes until puffs of coal dust seen from top of pipe)
[0078] Third layer: 70 ml of pulverized anthracite coal [0079] (26
strikes until puffs of coal dust seen from top of pipe)
[0080] Fourth layer: 70 ml of pulverized anthracite coal [0081] (20
strikes until puffs of coal dust seen from top of pipe)
[0082] Fifth layer: 70 ml of pulverized anthracite coal [0083] (17
strikes until puffs of coal dust seen from top of pipe)
[0084] Top layer: 35 ml of 0.6-0.8 mm crushed anthracite coal
The algae suspension was pumped through the vessel and a low flow
was observed. The test was stopped soon after starting.
[0085] The bed structure of the second filtration bed was as
follows:
[0086] Bottom layer: 210 ml of 0.6-0.8 mm crushed anthracite
coal
[0087] Second layer: 140 ml of pulverized anthracite [0088] (15
strikes until puffs of coal dust seen from top of pipe)
[0089] Top layer: 35 ml of 0.6-0.8 mm crushed anthracite coal
The algae suspension was pumped through the vessel and an initial
flow rate of 0.11 gpm (420 ml/min.) was observed. The initial
filtrate was observed to be clear with no visible signs of algae,
indicating a near 100% removal of algae from the feed. 80 minutes
after the flow was started, the flow was observed to drop to 0.05
gpm (200 ml/min.) and algae was observed to be breaking through the
filter bed, so the run was stopped.
* * * * *