Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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CATALYTIC BIOCONVERSION OF PETROLEUM-CONTAMINATED
WASTES/WASTEWATERS USING KENAF CORE POWDER
FIELD OF THE INVENTION
This invention relates to processing of petroleum-contaminated
waste/wastewaters generated by the petroleum refining and/or
petrochemical industry, and more particularly to a Catalytic
Bioconversion (CB) process using kenaf core powder to promote an
environmentally friendly method to biologically treat the petroleum
contaminants in these wastes while simultaneously producing a high
energy solid fuel for use in industrial cement plants and/or power
plants.
BACKGROUND OF THE INVENTION
Certain hazardous wastes and wastewater generated by the
petroleum industry (K048, K049, K051, F037 and F038) are emulsified
mixtures of solids, water, and oil that are extremely difficult to
treat, transport, and dispose of. These wastes, in their original
state, cannot be directly used as a fuel without considerable
dewatering, nor can they be feasibly transported in conventional
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liquids tankers due to their high solids content. Costs associated
with dewatering, transporting, and disposing of these wastes are
very burdensome to the petroleum refining and petrochemical
industry. Currently, refineries and petrochemical plants are using
filter presses, high speed centrifuges, and thermal desorption to
process these wastes and waste waters. These currently used
processes involve substantial capital investments along with
exorbitant operating costs.
More importantly, they generate a
waste material that is classified as a hazardous waste and must be
incinerated and/or land-filled with a significant cost and
continued liability. Fiscal costs and future liabilities associated
with dewatering, transporting, and disposing of these wastes are
very burdensome to the petroleum and petrochemical industries.
The below discussed prior patents define preparation of fibers
for use in waste treatment and generally discuss the disadvantages
of using absorbent materials in the treatment of waste material due
to the dewatering required.
A method of separating kenaf into core and fiber has been
described in U.S. Patent 5,970,582. Disclosed is a method and
apparatus for separating kenaf into fiber and core uses a modified
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stick machine conventionally used in the cotton industry for
removing trash from unginned cotton. Lengths of kenaf are delivered
onto the periphery of a saw cylinder so the toothed wheels snag the
fiber and draw the kenaf across a grate. Core is detached from the
fiber, passes through the grate and is delivered to a core outlet.
Fiber on the toothed wheels are removed by a doffing wheel and
delivered to a fiber outlet. Multiple saw cylinder/doffing wheel
assemblies are provided.
A typical waste water sludge stabilization process is taught
in U.S. Pat. Nos. 4,781,842 and 4,902,431 wherein a sewage sludge
is stabilized and converted to fertilizer by mixing the sludge with
an alkaline material which is sufficient to raise the pH to at
least 12. The mixture is then allowed to dry for at least one day.
The alkaline material is selected from cement, kiln dust, and lime
dust, to achieve chemical stabilization. Bulking materials, such as
slag fines, fly ash, gypsum, etc. may also be added. Such a process
is primarily a drying process to eliminate offensive odors and
pathogenic microorganisms. The process is not capable of generating
a substantial amount of heat to destroy many of the contaminants
found therein.
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U.S. Patent 6,027,652 describes one process for alleviating
the environmental problems associated with the production of oil or
chemical sorbent materials is to use a sorbent system based on
natural fibers. Over the last several decades, a wide variety of
treated natural fibers have been used as sorbents of hazardous
materials. These have included tree bark, peat, wood fiber,
dealginate kelp, powdered lily, kenaf cores, puffed cereals, and a
variety of other cellulosic materials. Each of these fiber types
has disadvantages which have prevented them from becoming the
material of choice for remediation of oil and chemical spills on
land or in water. This patent states that the primary disadvantage
of most of these fiber types is that they are naturally hydrophilic
and, therefore, tend to sorb large quantities of water. Sorption of
water increases the weight of these materials and can seriously
decrease their ability to sorb the oil or hazardous chemical which
these materials are intended to recover. It is possible to reduce
or eliminate the tendency of some of these materials to sorb water
by treatment with chemical additives to increase their
hydrophobicity.
In U.S. Pat. No. 5,021,390, Hatton teaches a composition
for sorbing liquids consisting of various fibrous plant materials
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treated with the waterproofing agent sodium methyl silicate. In
U.S. Pat. No. 5,492,881, Diamond teaches a sorbent system using
finely ground cellulose treated with a hydrophobic agent such as
paraffin, other waxes, polyvinyl alcohol, hydroxyethyl cellulose or
the like. These additives add to the manufacturing expense of the
sorbent and may themselves be the source of further harm to the
environment.
Another disadvantage, as disclosed in the prior art, of
previously disclosed natural fiber based sorbents is that most are
generally only capable of sorbing 5-10 times their mass in oil or
other chemicals. Additionally, most of these natural fiber
compositions have a tendency to sink as they become saturated with
oil, water or other chemicals, making recovery of these materials
and sorbed chemical from a body of water extremely difficult or
impossible.
SUMMARY OF THE INVENTION
The invention is a Catalytic Bioconversion (CB) process using
kenaf core powder to promote an environmentally friendly method to
biologically treat the petroleum contaminants in these wastes and
waste waters while simultaneously producing a high energy solid
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fuel. The new process has very low capital and operating costs,
treats and converts hazardous waste to non-hazardous waste, and
can produce a viable solid fuel product instead of a waste.
Typically, these petroleum-contaminated waste/wastewaters undergo
some type of hydrocarbon separation and recovery via phase
separation using heat and chemical treatment in storage tanks.
The objective is to recover as much "good" hydrocarbon as
possible and recycle it back to the production process. The
material that is not recoverable, an emulsion of oil, water, and
solids must be further processed and eventually discarded.
In one embodiment there is provided a method of treating
petroleum-contaminated waste/wastewater comprising the steps of:
introducing kenaf powder into the petroleum-contaminated
waste/wastewater; processing the
petroleum-contaminated
waste/wastewater and kenaf in a bio-reactor; dewatering the
petroleum-contaminated waste/wastewater and kenaf from the bio-
reactor to produce a bio-solid material and a treated discharge
water; and recycling all of the treated discharge water to reuse
in the bioreactor.
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In the invention, kenaf core powder is introduced into the
waste/wastewater stream (after primary hydrocarbon recovery has
been attempted) with a very simple in-line eductor injection system
at a rate that can range from 100 to 5,000 mg/L. The kenaf core
powder, because of its highly absorptive characteristics,
immediately "grabs" a portion of the organic load in the petroleum-
contaminated waste/wastewater stream. The waste/wastewater and
kenaf mixture are then directed to a biological treatment system
that includes a bioreactor for organic treatment and a centrifuge
for separation of the solids.
The kenaf core powder particles
naturally contain approximately 45% glucose and 2% protein, a
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valuable source of energy for the microbes in the biological
treatment system. As a result, the kenaf core powder particles are
creating a site for the microbes that provides a rich food
consisting of the organic load that has been absorbed and the
naturally occurring glucose and protein. Furthermore, the kenaf
core powder naturally contains and provides important nutrients
(phosphorus, nitrogen, sulfur, calcium, potassium, and others) and
a significant number of indigenous microorganisms to the biological
S ystem.
The net effect on the biological system is a much healthier
and more viable microorganism population in the biological
treatment system. Consequently, the system is less vulnerable to
shock loads (swings in organic, toxic, and pH loading) and will
recover from such events much faster. During normal loading,
treatment efficiencies for pollutant removal will improve and
thereby create an opportunity to increase loading to the biological
system (provided the system can handle the additional hydraulic
load). Most importantly, expensive chemicals (pH adjustment and/or
nutrients) that are currently added to the biological system may be
reduced or eliminated.
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When the microbes assimilate the natural carbohydrate in
kenaf, a protective outer shell consisting of glycocalx is produced
by the individual bacterial cell. This protective shell is a key
factor in providing the biological population with the ability to
survive in the toxic environment that is inherent to treatment of
these wastes/wastewaters.
Organic and inorganic removal
efficiencies obtained through the CB treatment process produce
solids that are no longer classified as hazardous.
The benefits to the treatment system are not limited to the
biological treatment system (bioreactors). In addition, a portion
of the carbohydrates in the kenaf core powder consists of hemi-
cellulose. Some of the hemi-cellulose is not consumed by the
microbes in the biological system and becomes an important
substrate in the solids that are discharged from the system. These
solids will dewater better and dry faster than solids that do not
contain the hemi-cellulose, and they can be dried and pelletized
more economically. The enhanced dewatering properties of the waste
activated sludge may reduce or eliminate chemical treatment of the
solids. Also, because the solids contain the hemi-cellulose, they
now have a much greater heat energy content. The dried, pelletized
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sludge can be used as a biomass fuel in cement kilns or power
plants.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1 shows a process flow diagram illustrating the invention.
DESCRIPTION OF A PREFERRED EMBODIMENT
FIG. 1 is a flow diagram 10 of the process where kenaf powder 12
is introduced into the influent waste/wastewater stream 11 with an
in-line injection system at a rate of 100 to 5,000 mg/liter. The
flow rate of the untreated waste/wastewater stream is generally in
the range of 5 to 500 gallons per minute. The kenaf powder that is
combined with the waste/wastewater stream, and because of its
highly absorptive characteristics, will immediately "grab" a
portion of the organic load. The waste/wastewater stream and kenaf
combine and flow into a bio-reactor where microbes and other
elements break down the organics. The treated liquid is sent to a
clarifier 14 where solids are separated from the liquid. Solids 16
are pumped to a bio-solid dewatering station while a part 15 and 19
of the solids (10% to 50%) may be returned to the bio-reactor 13 for
further processing. The solids in the bio-solid dewatering station
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17 are de-watered, with the water being returned 18 to the bio-
reactor, and the dewatered solids 20 go through a solids drying
process 21. The dried solid is then processed and stored 22 for use
as a fuel.
The kenaf powder particles used in the process naturally
contain approximately 45% glucose and 2% protein, a valuable source
of energy for the microbes in the biological system. As a result,
the kenaf powder particles are creating a site for the microbes
that provides a rich food consisting of the organic load that has
been absorbed and the naturally occurring glucose and protein.
Furthermore, the kenaf powder naturally contains, and provides to
the biological system, important nutrients (phosphorus, nitrogen,
sulfur, calcium, potassium, and others) along with a significant
number of indigenous microorganisms. The net effect on the
biological system is a much healthier and more viable microorganism
population in the biological system. Consequently, the system is
less vulnerable to shock loads (swings in organic, toxic, or pH
loading) and will recover from such events much faster. During
normal loading, treatment efficiencies for pollutant removal will
improve and thereby create an opportunity to increase loading to
the system. Most importantly, costly chemicals (pH adjustment
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and/or nutrients) that are currently added to the biological system
may be reduced or eliminated.
When the microbes assimilate the natural carbohydrate in
kenaf, a protective outer shell consisting of glycocalx is produced
by the individual bacterial cell. This protective shell is a key
factor in providing the biological population with the ability to
survive in the toxic environment that is inherent to treatment of
these wastes/wastewater streams. Organic and inorganic removal
efficiencies in the bioreactor produce solids that are not
classified as hazardous wastes. The glycocalyx also functions as a
flocculant by causing the smaller suspended solids in the final
clarifier to "stick" together and form larger, heavier particles.
The larger, heavier solid particles produce a biomass sludge that
settles better and faster. Treatment systems that are utilizing
coagulants and flocculants to enhance settling may be able to
reduce dosage or even eliminate these chemicals completely.
The benefits to the wastewater treatment plant are not limited
to the biological system (bioreactors). The solids that are
discharged from the biological system dewater better and have a
much faster drying time. The enhanced dewatering and drying
properties of the solids may eliminate dewatering processes in some
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treatment plants. More importantly, because the solids now contains
kenaf powder, they can be dried and pelletized more economically,
and they contain a higher heat energy value. The dried solids can
then be shipped to cement kilns or power plants as a biomass fuel.
Cement kilns release huge quantities of CO2, one of the most
important Greenhouse Gases (GHG). CO2 emissions from the cement
manufacturing industry are released by two different processes.
First, limestone must be heated to approximately 2600 degrees F. to
produce the cement product. This requires the combustion of a
tremendous amount fossil fuel (usually coal). Second, when the
limestone is heated, it undergoes a process called calcination and
releases large quantities of CO2. Because limestone must be heated
and calcined to manufacture cement, the cement industry has very
limited options in dealing with GHG (CO2) emissions and the
reductions thereof. There is a major initiative underway in the
cement industry to find a solution to this problem.
The biomass fuel produced from the dried and pelletized solids
can provide cement plants a fuel source with CO2 credits. This
biomass fuel, because it is composed of kenaf powder and other
biomass, is renewable and sustainable. CO2 credits are created by
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replacing carbon-rich fossil fuel with biomass fuel that has
sequestered carbon from the atmosphere during the kenaf growing
season.
Another benefit of using this biomass fuel in cement kilns is
the ability of the cement kilns to utilize the inorganic solids
(ash) that are part of the combusted biomass fuel. These inorganic
solids become part of the cement manufacturing raw materials and
actually provide increased production to the cement plants.
Considering the CO2 credits and production increases, this
fuel should bring a price comparable to high-quality coal.
The kenaf core powder enhances biological activity in activated
sludge wastewater treatment, improves settling of biological solids
in the final clarifier, and improves the dewatering and drying
characteristics of the solids.
Kenaf core powder offers a natural and cost effective
alternative to expensive chemical treatment programs. The kenaf
core provides a benefit to all aspects of the biological treatment
system. Expensive chemical treatment programs for nutrient
addition, coagulant and flocculant addition, and dewatering can be
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significantly reduced or eliminated. Kenaf core powder is a natural
and environmentally safe product that is not synthetically
manufactured. It is completely biodegradable and does not introduce
chemical residues into the environment. The dried and pelletized
hemi-cellulose enhanced solids are much easier to handle and
transport. This creates a potential revenue generating product
versus a waste that must be shipped to a landfill for disposal.
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