Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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A SORBENT COMPOSITION AND APPARATUS FOR REMOVING OIL OR OILY
SUBSTANCES FROM WATER, AND PROCESS OF MANUFACTURING SAID
COMPOSITION
BACKGROUND OF THE INVENTION
Field of the Invention
This invention details a process for control and clean up of minor and massive
oil spills from
the surface of water using pre-treated peanut hulls as sorbent. Method for
producing such sorbent
and its appropriated application technique in open waters are also detailed.
Introduction
It is well lalown that oil spills in open waters produce serious ecological,
environmental and
economical damage. According to the National Research Council estimates, the
sources and
amounts of oil-related pollutants dumped into the oceans each year are:
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2
-Down the Drain: 363 million gallons, including used engine oil that
constitutes run-offfrom
land, and municipal and industrial waste.
-Routine Maintenance: 137 million gallons including bilge cleaning and other
ship releases.
-Up in smoke: 92 million gallons including air pollution, mainly from cars and
industry.
-Natural Seeps: 62 million gallons including seepage from ocean bottom and
eroding
sedimentary rocks:
-Big Spills: 37 million gallons including tanker accidents.
Large spills, even though a relatively minor source of ocean oil pollution,
can be devastating.
Only about five percent of oil pollution in oceans are due to major tanker
accidents, but one big spill
can disrupt sea and shore life for miles. The impact of oil on shorelines may
be particularly great
where large areas of rocks, sand and mud are uncovered at low tide. The
National Oceanic and
Atmospheric Administration estimates that the Eao~con Valdez accident of 1989
in Alaska spilled
around 11 million gallons of crude oil, killing 350,000 to 390,000 water fowl,
3,500 to 5,500 sea
otters, and cost more than five billion US dollars. The impact on marine life
was compounded by
toxicity and tainting effect resulting from the chemical composition of the
oil, as well as by the
diversity and variability of biological systems and their sensitively to oil
pollution. According to the
same source of information, three years later the relative percent
distribution of the oil mass released
into the environment was:
- 50% Biodegraded /Photolysed
- 20% Atmospheric photolysis
- 14% Recovered
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- 13 % Subtidal sediment
- 2% Beached
- 1% Dispersed in water
From the above results it is clear that even after catastrophic spills like
the Valdez, with
enough time natural forces act to counteract the pollution. However, the worst
immediate
consequences of a massive oil spill are due to the shock produced by the
overwhelming mass of
hazardous substances suddenly released into an environment which was not
prepared to digest it and
unable to restore itself to its original condition by itself in a short time.
Thus, we can deduct that one of the fundamental aims of oil spill response
strategies should
be to react as soon as possible with appropriate countermeasures in order to
restrict or minimize the
spread ofthe damage. With that purpose in mind, it is the aim ofthe present
invention to propose an
alternative response methodology conceived for the treatment and remedy of
extended polluted water
surfaces with celerity, bearing in mind that the areal distribution of the
injury is time dependent.
It is important to emphasize here that a sorbent composition of the present
invention is apt
and can be used with the same comparative advantages in many different
situations, such as for
treatment and remedy of routine maintenance spills, land spills and others,
and may be applied directly
on the polluted surface by any classical methodology. The preferred embodiment
mainly focuses on
an oil spill in open waters because, as it is well known to the skilled in the
art, it is probably the worst
condition to control, handle and remedy. The clean-up components are exposed
to the punishing
mercy of the elements, and are under dynamic conditions.
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4
PRIOR ART
Many compounds, apparatus and techniques were proposed by the prior art to
facilitate the
mitigation of deleterious effect or the removal of oil pollutants from water.
In a general sense, the
scope of available tools and methodologies to combat such pollution can be
summarized as follows:
Chemical Agents: elements, compounds or mixtures that coagulate, disperse,
dissolve,
emulsify, foam, neutralize, precipitate, reduce, solubilize, oxidize,
concentrate, congeal, entrap, fix,
make the pollutant mass more rigid or viscous. The above compounds include
biological additives,
dispersants, sinking agents, burning agents, but do not include solvents.
Chemical Agents have been
applied to disperse and biodegrade oil spills; however, such applications, far
from be beneficial, could
result in worse environmental damage.
Apparatus: skimmers, booms, pumps, hydrocyclones, barners, mechanical
separators,
containers, filters, bags, separators, recovery vessels, etc. Apparatus are of
limited effectiveness for
the control and recovery of extended oil spills, and are very difficult or are
unfeasible to be used under
adverse meteorological conditions.
Sorbents: essentially inert and insoluble materials that are used to remove
oil and hazardous
substances from water through adsorption and/or absorption. They include:
a) organic products (peat, moss or straw, cellulose fibers or cork, corn cobs,
chicken or duck
feathers, wood chips, cereals;
b) mineral compounds , volcanic ash or perlite, vermiculite or zeolite;
c) synthetic products (polypropylene, polyethylene, polyurethane, polyester).
Mineral sorbents are of relatively high density, and after their spread on top
of the water
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surface they sink to the bottom forming a stationary layer saturated with oil
that affects the benthos.
Synthetic sorbents are not biodegradable per se and need to be recovered and
processed by treatment
facilities for disposal. Organic sorbents, including the herein proposed
option, are biodegradable, non
toxic, effective and usually cheap.
5 There are known the following patents related to the application based on
methods of
utilization of natural organic sorbents:
US Pat. No. 3,617,564 disclosing the utilization of corncob components for the
removal of
oil spills from water and land.
US Pat. No. 3,902,998 disclosing a method for removing oil from water based on
the
utilization of rice hulls as sorbent.
US Pat. No. 4,959,154 disclosing the utilization of pre-treated wood chips for
the cleanup
of water and land oil spills.
US Pat. No. 4,969,774 disclosing the use of pre-cooked and puffed cereals as
oil spill
sorbents.
US Pat. No. 5,114,593 disclosing the application of dry and pulverized aquatic
lily plant to
the spilled oil.
US Pat. No.S,160,629 disclosing a method for removing organic substances from
bodies of
water using entire dried corn cobs in their natural state.
US Pat. No. 5,352,780 discloses a method for absorbing, removing and cleaning
up a liquid
floating in a second liquid, employing absorbent pellets made from cellulose
flakes.
Peanut shells were previously used as particulate cellulosic raw material for
the production
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of a carbonaceous residue product or char. US Pat. No.4,145,256 discloses the
procedure and
apparatus for the carry out of such an operation. Even though at first glance
some similitude exists
to the above patent with the proposed sorbent pre-treatment methodology
herein, the basic
fabrication principles and resulting final products are clearly different.
These differences will be
evident a$er a detailed examination and comparison between both technical
procedures, and can be
summarized as follows:
- in the abovementioned US patent 4,145,256, peanut shells are submitted to a
destructive
discomposure. Reaction temperatures vary between 526°C (975°F)
to 1315°C (2410°F); the result
is that the final product is a devolatilized powdered or carbonaceous residue
or char, having an
elemental carbon content in excess of about ninety percent by weight.
- in the same US patent, such high temperatures are reached by the use of a
controlled amount
of forced air introduced into the system that produces the exothermic
oxidation of the heavy tars
distilled from shells.
- in the same process, the heavier distilled tars condense on the shells in
the upper strata of
the reaction chamber; they migrate to the maximum temperature region of that
chamber whereby they
progressively fiuther discompose and carbonize to build up the final
carbonaceous residue product.
SUMMARY OF THE INVENTION
It is the aim of the present invention to provide a sorbent composition and
apparatus to
combat oil spills and other hazardous pollutants floating on or in water,
based on the utilization of
pre-treated peanut hulls as sorbent and complemented by a specific application
technique of such
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sorbent for the cleanup of such oil spills in open waters.
The selection criteria for the utilization of peanut hulls as sorbent was
found in the following
characteristics and advantages:
- peanut hulls, as a natural vegetal product, are non toxic, biodegradable and
innocuous in any
amount applied;
- as waste or byproduct of the peanut industry, the sorbent is cheap,
abundant, and their pre-
treatment is simple and economical;
- to be complementary to the proposed application technique in open waters,
the sorbent
needs to be the least dense possible; adequately pre-treated, it needs to
maintain its oleophilic
characteristics even after it has been immersed in water for a considerable
time before contact with
the oiled surface;
- under the herein proposed dosage ratio, the sorbent acts immediately and
retains the sorbed
oil with enough tenacity to minimize the tainting effect by the occasional
physical contact of the oiled
mass with any solid dry or wet surface (animal, rocks, beach, etc); it also
works satisfactorily with
crude oils of different viscosity and density;
- after the application and impregnation, the oiled sorbent forms a buoyant
rimed-like layer
that permits its control and collection by mechanical devices (booms,
skimmers, pumps, nets, etc.)
during a reasonable time, and can be subsequently introduced into a recovery
process if desired;
- some hours after its application, the oiled sorbent acts as particulate
physical dispersant, with
the advantage that. the oiled mass does not need be necessarily recovered to
mitigate the damage;
- after the oil/water saturation, the sorbent tends to reach an equilibrium
condition with a final
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apparent maximum density of about 1.27 g/cm', and behaves in that medium like
any other light
vegetal detritus, preventing the subsurface penetration of oil into cobble and
boulder beaches. The
washed-up material on shore is dry to the touch after its natural water
evaporation and drying, does
not stain, and can be easily recovered by vacuum techniques;
- with the abovementioned physical sorbent characteristics, the application
technique in open
waters can be conceived to sweep extended polluted water surfaces efficiently,
in a short time, can
be used under adverse meteorological conditions, and is apt for the cleanup of
partially ice-covered
water surfaces.
According to the National Agricultural Statistics Service, USDA, the
production of peanuts
in the US during 1998 was about 1,800,000 tons. Roughly three-quarters of the
peanuts grown are
used domestically as edible products. About one-fourth of the production is
exported to other
countries. From the approximately 1,300,000 tons consumed yearly in the US,
10% is sold as in-shell
peanuts (Valencia variety). The remaining 90% (Runner variety), about
1,170,000 tons, are
commercialized shelled.
Considering that in one pod (Runner variety), the shell represents roughly 18%
of the total
weight, the result is that about 200,000 tons of waste or by-product shells
are theoretically available
each year for diverse uses. At the present time, shells are mostly actually
used in wallboard, fire place
logs, fiber roughage for livestock and kitty litter.
BRIEF DESCRIPTION OF THE DRAWINGS:
FIG 1 illustrates a schematic way for the proposed process to produce the
sorbent according to the
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present invention.
FIG 2a illustrates schematically the top view ofthe apparatus ofthe present
invention for the cleanup
of oil spills in open waters.
Fig. 2b is a cross-sectional view of Fig. 2a.
Fig. 2c illustrates schematically the cross-sectional view of the apparatus of
the present invention for
the cleanup of oil spills in the river.
FIG 3 illustrates the experimental calve graphically showing the behaviour of
the sorbent as physical
dispersant and the expected evolution of the oil/sorbent mass in that medium
with the time.
DETAILED DESCRIPTION OF THE INVENTION
The present invention comprises two complementary sections. First and foremost
is the
sorbent composition and process ofpreparation, and secondly, the proposed
apparatus ofusing such
sorbent composition in the open waters.
Sorbent composition and process of preparation:
Peanut hulls are a natural biodegradable woody sorbent material, extremely
porous and of low
density, and endowed with intrinsic hydrophobic characteristics. Apparent
density of in-bulk dry shells
is about 160 kg/m3. Even after they have been immersed in sea water for hours,
the hulls retain their
high buoyancy owing to the spongy tissue structure. If the immersed mass is
liberated under an
aqueous medium covered by oil, it ascends immediately to the surface forming a
buoyant layer that
floats even over the crude oil. For use as a sorbent composition, raw peanut
hulls should be crushed
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to a phlrality ofparticles ofpredetermined dimensions, and pre-treated by
basic pre-treatment, which
comprises toasting in a rotary kiln at 310°C to provide oil amity. Such
pre-treated sorbent
composition allows to achieve up to 80% efficiency when applied to the oil
spills.
However, if the raw peanut hulls which were pre-treated by the basic pre-
treatment (toasting)
5 stay in the water too long previously to the contact with the oil, they
still have insuff dent oil affinity;
thus, it is necessary to add an advanced pre-treatment in order to enhance and
maintain their
oleophilic characteristics. Therefore, one aim of the present invention is to
provide a pre-treatment
methodology in order to transform the raw peanut hulls into an efficient oil
adsorbent/absorbent that
would work under any application conditions.
10 Fig. l illustrates the basic steps for the sorbent preparation process. Raw
peanut hulls are
obtained from the peanut industry as waste or by-product, crushed at the
shelling plants (step 1) and
sieved (step 2) to -4mesh, +l2mesh (USA Series); that is, - 4.75mm, +1.70mm.
From experiments,
1,000g of raw shells (Runner variety) yield approximately 780g of sieved
material. Particles under
l2mesh (about 220g) are rejected. The sieved hull particles obtained above are
mixed with 10% (by
weight) raw peanut kernels (-l2mesh) (step 3), and pass through a rotary
mixer/preheater (step 4)
where they are carefixlly mixed and dried at 120°C. The dried mass is
then passed through a rotary
kiln (5) and toasted at a temperature of about 310°C (590°F)
under restricted air flow circulation.
Under these conditions, the oily fiunes generated by the heating of the added
kernel particles adhere
to the surfaces of the hull particles forming a hydrophobic/oleophilic
protective film. It is important
to emphasize here that the advanced pre-treatment toasting process needs to be
conducted under a
controlled air flow system in order to profit as much as possible from the
generated oily fiunes.
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Comparing the technical procedure of char production as proposed by US Pat.
No. 4,145,256,
the temperature reaction in the present invention should be substantially
below the temperature of
char production, wherein the oily fumes produced by the heating are decomposed
and carbonized
completely, and the desired oily atmosphere in the kiln is destroyed. In
contrast, in the present
invention it is precisely the upkeep of the oily atmosphere, which produces
the adequate internal
conditions for the formation of a protective hydrophobic/oleophilic film on
the surface of the hull
fragments, is the important factor that creates the desired final product.
The residence time in the kiln can be estimated by means of the weight
reduction of the
original mass after the treatment. In a test laboratory 1,OOOg of dried (
110°C) crude material yields
about 700g-720g of final product after treatment, being a weight reduction of
about 28%-30%. The
final product is a scaly particle aggregate demonstrating an incipient
carbonization, a superficial oily
staining and metallized-like aspect, with an in-bulk apparent density of 140
kg/m3. The sorbent is
now ready to be utilized and can be stored in the usual way used for bulk
storage (6) used for cereals
or the like.
Sorbent annlication apparatus
The cleanup of oil spilled in open waters is one of the most troublesome tasks
to afford,
considering the natural tendency ofthe pollutant to spread as a thin layer,
and the fact that the success
of the countermeasures is always subordinated to the circumstantial
meteorological conditions. In
order to achieve such task successfully and to be operatively independent of
the mentioned climatic
factors as much as possible, we propose a specific remediation apparatus for
that scene, developed
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in accordance with the physical characteristics of the sorbent detailed above.
Regardless the type of sorbent used, one of the main factors to take into
account for an
efficient oil absorption concerns the effectiveness of the physical contact of
oil-to-sorbent. Obviously,
the more favoured the mutual physical interaction, the better the absorption.
The proposed apparatus
of the present invention is designed to make an optimum oil-to-sorbent
contact, and is primarily based
on the high buoyancy of the peanut hulls.
However, the apparatus of the present invention is not restricted to the use
of peanut hulls
as the sorbent composition, and any other sorbents having similar
characteristics could be used
instead of peanut hulls.
To illustrate the result of using the apparatus of the present invention,
similar conditions were
simulated by using a water tank, into which a pre-determined amount of sorbent
(pre-treated peanut
hulls) was placed and retained below the surface of the water by means of a
perforated container (net,
bag, etc.) in such a way that the whole mass was in direct contact with, and
saturated in the water.
A determined amount of crude oil was spilled over the water surface thus
forming a polluted layer.
When the immersed sorbent mass was liberated underwater, it ascended
immediately to the
surface due to its high buoyancy; because of the natural tendency of the
particle mass to reach an
equilibrium in the free medium, the sorbent spread abroad forming a second
layer similar to, and in
contact with, the crude oil layer. If the sorbent density is enough low, the
new solid layer (sorbent)
floats even over the previous crude oil layer, insuring an unavoidable mutual
physical contact.
The exposed idea is the basis of the herein proposed sorbent application
apparatus using
"Reverse Application" principle. Of course, the efficiency of oil
adsorption/absorption depends, at
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last, on the oil affinity and other physical characteristics of the sorbent,
which in the present case was
expressly prepared to work under such conditions. According to laboratory
experiments, a suggested
dosage ratio of sorbent-to-crude oil is 1.5:1 by weight; this was sufficient
to assure a complete oil
adsorption/absorption.
Figs. 2a and b illustrate how to put in practice the sorbent application
apparatus in a real case
for an oil spill remediation in open waters. Two cargo vessels 7 loaded with
in-bulk sorbent and
working jointly are connected by a holding means or flexible ballasted feeding
pipe 8 of appropriated
diameter which is maintained at predetermined depth below the water surface
(i.e. 4 - 12 feet)
supported by the floats 9. Each end 10 of the pipe 8 fit up on each vessel 7
to a respective sorbent
injection device 11. Injection nozzles 12 are distributed along the feeding
pipe 8 at regular intervals.
The pipe 8 is firmly attached parallel at filll length to a grip traction
cable 13. The sorbent is sucked
up from the respective cargo vessels 7 and injected under pressure with air,
water or a mixture of
both, by means of an air-compressor or water pump (not shown) from injection
device 11. The
sorbent is transported at the full length of the pipe 8 and ejected through
the nozzles 12 into the
underwater medium. As the sorbent is ejected, the polluted area is slowly
raked by the vessels 7 in
such a way as to achieve a sorbent distribution as uniform as possible. The
amount of sorbent applied
by square meter can be regulated by varying the injection pressure or the
speed of the vessels
according to the mass of pollutant to be treated.
After the underwater injection 14 (see Fig. 2b), the sorbent ascends
immediately to the surface
15, spreads abroad and in contact with the oiled surface. If the dosage ratio
of sorbent-to-oil as
suggested herein is maintained ( 1. 5:1 by weight), the final product is
attained after few minutes of
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14
natural stirring and homogenization; the product will be a rimed-like, scaly,
buoyant semi-solid layer
impregnated with oil. As the product is forming, the water surface is cleaned
up from the pollutant.
The tainting effect of the crude oil is almost completely neutralized by the
strong preferential
adsorption over the sorbent's surface.
One of the most important benefits of the underwater sorbent application
apparatus of the
present invention is that the clean-up process can be carned out
satisfactorily under relatively adverse
meteorological conditions (eg: rough seas) because the sorbent can be applied
below the wave train.
Even more, and for the same reason, the application technique could be used to
clean up partially ice-
covered water surfaces. For this purpose, the floats 9 can be removed, and
their fimction replaced by
appropriated weight balances 9a and/or hydrodynamic profile of the feeding
pipe 8 (not shown).
If the clean-up situation occurs in confined waters where the polluted water
volume has a
defined drainage direction (river, stream), the mobile vessel feeding plants 7
can be replaced by a
couple of land-based stationary or temporary feeding plants 7a (see Fig. 2c)
situated transversally to
the drainage direction, and mutually connected by the ballasted feeding pipe 8
in a similar manner as
shown on Figs. 2 (a and b). The suggested diameter of feeding pipe 8 is
between 3 and 10 inches
depending on the particular case, and suggested flexible material is synthetic
plastic or rubber.
Sorbent di~persive properties:
Fig 3 illustrates graphically the result of a laboratory test (see Test 3) to
predict the possible
time evolution of an oil and sorbent mass in sea water after the sorbent
application. During the first
18 hours (point A), the rate of sinking gradually reached 8% of the whole
mass. That is, more than
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90% ofthe total mass is accessible to be collected by mechanical devices
(pumps, skimmers, booms,
nets, etc.). From that point (point A), the slope of the curve increases and
reaches a level after 60
hours where about 75% ofthe material is sunk (point B). Between 60 hours and
120 hours, the curve
becomes more asymptotic, reaching a level where approximately 95% ofthe
initial mass is sunk (point
5 C). If we assume that the remediation process occurs in open waters under
dynamic conditions where
some free movement of the water mass exists (currents, tides), during a time
interval of about 120
hours (interval A-B-C) the sunk mass will be disseminated inside a large water
volume. In other
words, the curve interval A-B-C could be considered roughly as the time
interval in which the
impregnated sorbent acts as physical dispersant. According to our laboratory
tests, the maximum
10 relative density of the sunk mass is about 1.27 g/cm'.
It must be emphasized that if the mass which is uncollected in the first 18
hours sinks due to
the particular property of the sorbent composition of the present invention,
it will not reach the
bottom of the ocean, but will be eventually delivered by underwater streams to
the shore, where it
will dry out without damaging the surface of beaches and will remain neutral
to its surroundings until
15 it is collected.
Finally, due to a specific density of the oil-sorbent mixture of the present
invention, it will
disperse in a large area of open water, thus fulfilling the exact purpose of a
chemical dispersant
without any toxic impact on the environment.
Test 1:
Fifty grams of sorbent were introduced into a 1000 ml hermetic flask and
vigorously shaken
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for 5 minutes with 600 ml of sea water. The solid mass was then filtered out
by a kitchen colander
and transfer to an open skimmer-like, bell shaped, ballasted container. This
container was introduced
face-down into a 5-liter tank in such a way that the opening was in contact
with the bottom of the
tank. The container was maintained firmly pressed against the bottom of the
tank by means of a
stirring rod, and about 4 to 4.5 liters of sea water (at 20°C) were
added to the tank. The remaining
entrapped air bubbles retained by the sorbent were expelled by careful
movement of the plastic
container with the stirring rod, assuring that the whole sorbent mass was in
contact with the water.
This condition ofwater saturation was maintained for at least 15 minutes,
after which 34 g (~37 ml)
of crude oil density 0.91 g/cm3 was added with a syringe to the water surface.
The final dosage ratio
of sorbent-to-oil was 1.5:1 by weight. The plastic container, until now held
against the bottom, was
turned face up with the aid of two stirring rods. The liberated mass of
sorbent ascended immediately
to the water surface and contacted the oil layer as postulated in the proposed
application technique.
After a few seconds of stirring with the rod, the oil adsorption and retention
by the sorbent
was complete. The water surface showed no signs of free oil. The resulting
rimed-like scaly mass of
impregnated sorbent retained the oil firmly even after it was vigorously
shaken. All solid elements
introduced through the water surface (finger, rod, stone, etc. ) were
extracted without any oily taints.
Test 2:
The above detailed process was repeated exactly, with the only difference
being that in this
test the water medium was maintained at 4°C by means of crushed ice. In
other words, this test
attempted to reproduce the conditions of application on an ice-covered water
medium. Even though
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1~
the crude oil became thicker by the effect of the low temperature, the
adsorption efficiency was
maintained, but with a slight delay of the homogenization if compared to the
above test. The final
result was similar, as well as the clean up of the water surface and the
elimination of the tainting effect
of the oil.
Test 3:
Same conditions as Test l, variation being that there are 20 liters of sea
water at 20°C. After
application in the described way, the sunk sorbent particles were collected
with an adequate device
at regular intervals of 6 hours during a period over 120 hours, with
occasional stirring ofthe whole
mass. The collected fractions were transferred to individual aluminium
containers, dried at 95°C and
weighed. The sorbent sinking curve illustrated in Fig. 3 was prepared with the
registered time-table
and the dry weight of each fraction. It must be stated that the weight
reduction for crude oil (with
density of 0.91 g/cm3) heated for a short time at 95°C can be
considered negligible for the purposes
of present test.
Test 4: Sorbent toxicity
Two small Goldfish (Carassius auratus) were introduced in respective fish
globes, each with
about 2.5 liters of fresh water and environmental conditions similar to any
aquarium. A small net bag
with three grams of sorbent was prepared, transferred to one of the fish
globes (test globe), and
maintained totally immersed in the water by means of ballast. The other fish
globe (constant globe)
had no foreign matter such as sorbent introduced. After five days the test
globe fish appeared to be
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18
in perfect health, and an additional three grams of sorbent was added to the
water surface to
completely cover it with a sorbent layer. This condition was maintained for
another ten days. After
fifteen days, the test globe fish had a healthy appearance, with same vital
signs and reflex actions as
the constant globe fish. After this experiment, both fish were healthy and
liberated to an appropriate
natural environment.
Thus, it can be seen that the objects of the present invention have been
satisfied by the
structure presented hereinabove. While in accordance with the Patent Statutes,
only the best mode
and preferred embodiments of the present invention have been presented and
described in detail, it
is to be understood that the invention is not limited thereto or thereby.
Accordingly, for an
appreciation of the true scope and breadth of the invention, references should
be made to the
following claims.
