Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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~`~, ~eE~S~ APPARATUS FOR CLEANING AN OIL CONTAMINATED
VESSEL
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FIELD OF THE INVENTION
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This invention relates to an apparatus and process for
cleaning an oil contaminated vessel having one or more
cargo compartments each containing sludge utilizing a
closed fluidized circuit.
BACKGROUND OF THE INVENTIC)N
Vessels containing oil, such as storage tanks,
tank cars, oceangoing tankers, barges, pipelines or other
structures for storlng or transporting crud~ oil or petroleum
products will over a period of time aceumulate large amounts
of sludge made up of chemical or hydrocarbon deposits which
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deposits occur particularly in crude oils or heavy oils.
Build up of such sludge over a period of time subtracts
from the load carrying or s~orage capacity of the vessel.
Further build up of sludge in oil conveying vessels such as
tank cars or trucks results in carrying excess dead weight
when the vessel is returned empty from a delivery point to
a shipping point thus increasing cost of operations.
Consequently the interiors of such vessels must be cleaned
from time to time of accumulation of sludge.
Further vessels carrying or s~oring crude oil or
other petroleum products, particularly barges and oceangoing
tankers, are often used to carry other products besides oils
or carry other grades of oils. It thus becomes necessary
to cleanse the interior of such vessels prior to being
lo~dQd with other products or higher grades of oil Vessels
of this type must be cleansed to a gas free state from time
to time so that they may be entered for periodic inspection
- or for repair in the event of damage.
Existing techniques for ~leaning oil carrying
vessels has involved the use of steam and water applied in
large volumes through spray nozzles agains~ interior side
walls of the vessels under high pressure. Occasionally
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chemicals are used in the cleaning but generally such
cleaning systems involve the use of large volumes of water.
This techique of cleaning has proved to be labor intensive,
energy intensi~e, and generally results in the Eormation of
large volumes of oil contaminated waste water. Vessels
cleaned utilizing this technique are often not completely
free of hydrocarbon deposits and are not suitable for
upgrading and carrying or storing other products without
further hand cleaning of the interior of the vessel.
It is ther~fore an object of our invention to
provide for an apparatus and process for cleaning an oil
contaminated vessel which will utilize a minimum of water
and which will substantially completely clean an oil
contaminated vessel of oil and any sludge in a comparatively
short time and at minimal expense.
It is a still further object of the invention to
provide for an apparatus and method of cleaning oil
contaminated vessels of oil and sludge by which usable oil
may be conveniently recovered for further use.
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GENERAL DESCRIPTION OF THE INVENTION
Broadly a process for cleaning an oil contaminated
vessel according to our invention involves use of a closed
recirculating fluidized system or circuit where the system
has a tank, a discharge means extending from the interior
of a compartment within the vessel to the tank and a
pressurized spray means extending from the tank to the
interior of the compartment by which the contents of the tank
may be sprayed onto the interior walls of the compartment.
The process involves the steps of treating the sludge with
a fluidizing agent to form a pool of fluidized sludge which
is then circulated through ~he system and sprayed under
pressure onto the interior walls of the compartment. When the
fluidized sludge spray contacts the walls it cleans oil from
the walls and also fluidizes any sludge thereon to increase
the size of the pool in the bottom of the compartment
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containing fluidized sludge. This fluidized sludge i8 then
discharged from the vessel to the tank where it is recir-
culated again through the pressurized spray means back to
the compartment. This recirculation is continued until the
compartment is substantially cleansed of sludge leaving onl~
a film of self emulsifiable oil.
The fluidizing agent may be initially added directly
to the compartment to form an initial pool of fluidized
sludge which is then conveyed to the tank or the agent may
be added directly to the tank after which it is circulated
~hrough the pressurized spray means onto the interior side
walls of the compartment so as to form a pool of fluidized
sludge.
Preferably the fluidized sludge is heated conven-
iently by a heat exchanger in the tank to further enhancethe cleaning action. The tank itself may act as a settling
tank to capture any large solids such as rust or sand
particles to prevent their being recirculated in the closed
system through the pressurized spray means.
Sufficient fluidizing agent is periodically added
to the system, ei~her directly to the tank or to the com-
partment being cleaned, to maintain fluidity of the sludge.
The process may include the further step of
periodically removing excess oil from the closed system and
trans~erring it to a holding tank.
The remaining film of self emulsifiable oil left in
the compartment after being sprayed with the fluidized sludge
may then be completely removed by rinsing with a small amount
of hot or cold water using a standard spray type Butterworth
wash system. The rinse water is then stripped from the
compartment and transferred to a separating tank where oil is
allowed to separate from the water. The recovered oil may
then be used as a fuel or reclaimed for refining and the rinse
water may be drawn off and used in subsequent rinsing. By
this procedure use of rinse water is minimized while at the
same time oil is recovered.
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The process described above may use water as a
component of a wash solution when the vessel being cleaned
contains low grade oil or crude oil sludge. In this case
the sludge itself may contain from 0 to 40% water as a
water in oil emulsion. The fluidizing agent serves to
invert the emulsion to orm an oil in water emulsion having
much better flow characteristics. #6 oil normally does not
contain any water such that the fluidized oil recovered will
be water free when vessels containing such oil are cleaned.
The process described above is also applicable for
use in cleaning vessels having a plurality of compartments
each containing sludge. In this instance fluidized sludge
from the first compartment cleansed is sprayed into a second
or further compartment to form an initial pool of fluidized
sludge in the second compartment which is then recirculated
through the closed fluidized system until the second
compartment is substantially cleansed of sludge.
An apparatus constructed according to our invention
comprises broadly a tank adapted to hold the fluidized sludge
or emulsion, a pressurized spray means extending from the
tank and adapted to extend into the interior of a compartment
containing sludge and a discharge means having one end
connected to the tank and an opposite end adapted to be
connected to the compartment to remove fluidized sludge or
emulsion therefrom to the tank.
The pressurized spray means preferably includes a
first pump and the discharge means a second pump with both
pumps being of equal capacity and driven by a common drive
means to assure that both operate with equal throughput.
The pumps, drive means and tank are mounted on a
common base such as a skid to form a unit which can be
conveniently lifted into position, as for example onto the
deck of a bargeO in order to clean cargo compartments.
The tank preferably has a ver~ical baffle therein
dividing the tank into a solids settling portion and into a
substantially solids free portion connected to the pressurized
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spray means.
The apparatus also preferably may include a
separating tank in which excess oil or emulsion may be
transferred from the closed fluidized circuit. Oil is
allowed to separate from the emulsion in the separating tank
where it is then removed for further use while the remaining
water is available for furthex use.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure l is a diagrammatic view of an apparatus
constructed according to the invention mounted in part on an
oil tanker having a plurality of compartments to be cleaned;
and,
Figure 2 is an enlarged sectional view of a portion
of the apparatus disclosed in Figure l.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to Figure l, there is illustrated a vessel
in the form of an oil tanker l having a plurality of-cargo
compartments 2, 3, 4 and S accessible by hatches 6.
An apparatus l0 adapted to clean the compartments
is lifted into place onto the deck of the tanker where it is
available for operation. As shown in Figure 2, the apparatus
comprises a tank 20, a discharge means 21 having one end 22
connected to the tank 20 and an opposite end 23, shown in
Figure l, adapted to extend into a pool 24 of fluidized sludge
in a compartment in order to discharge fluidized sludge or
an emulsion from the compartment into the tank 20.
The apparatus l0 also includes a pressurized spray
means 25 terminating in a spray head or nozzle 26 adapted to
extend into a compartment in order that fluidized sludge or
emulsion contained in ~he tank 20 may be sprayed under
pressure onto the interior side walls and bottom of a
compartment to clean the same of sludge.
The pressurized spray means 25 includes a first
pump 30 to convey emulsion under pressure to the nozzle 25.
- If desired, filter means 31 may be included in the pressurized
spray means to catch and fiiter any debris that might 510g
the nozzle 26.
The discharge means 21 includes a second pump 32
the intake of which is adapted to communicate with a
compartment and the outlet of which extends to the,tank 20.
Pumps 30 and 32 are of equal capacity and are
preferably driven by a common drive means 36 in the form of
an internal combustion engine or electric motor. The pumps
are coupled through independent transmissions so that they
may be operated independently or at the same speed and through
put.
The tank 20, pumps 30 and 32 as well as the common
drive means 36 are mounted on a base or skid 38 so that the
several parts making up the apparatus may be considered as
a unit which may be easily lifted onto the deck or other
portion of a vessel to be cleaned.
The tank 20 besides acting as a,holding tank also
acts as a settling tank to entrap large solids, such as sand
or rust particles, that may be circulated within the tank.
To assist in this function ,a vertically extending baffle 40
extends upwardly from the bottom of the tank about three
quarters of the height of the tank to divide the tank into a
solids settling portion 41 and a solids free portion 42. The
end 22 of the discharge means 21 discharges into the top of
the solids settling portion 41 while the intake of the pump
30 draws from the bottom of the solids free portion 42 which
further minimizes likelihood of solids being drawn into the
pump 30.
Preferably a heat transfer means in the form of
coils 45 are contained in the tank 20 to heat the circulated
emulsion to further enhar.ce cleaning action. The coils may
be connected by piping to a boiler, not shown, contained at
a convenient location, as for example an on-shore site, which
heats a heat transfer fluid, for example steam, which is
circulated through the coils. While the coils are shown in
the solids settling portion of ~he tank, they could be
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located in any portion of the closed fluidized system
defined by ~h~ discharge means 21, the ~ank 20 and the
pressurized spray mea~s 25.
The apparatus preferably also has a separating tank
50 sited on shore to which excess oil or e~ulsion is drawn
by a pump 51 through a discharge conduit 52 which as shown
e~tenas into the pool of fluidized sludge 24. The conduit
52 could just as conve~ie~tly~extend to the tank 20 or other
por~ion of the closed fluidized syst~m to withdraw excess
oi~ or e.~ulsion therefrom. Oil is separated out of the
emulsion in ~he separating ~ank 50 where i~ may be removed
~or further use, as for example, a'fuel. The remaining
water is then available to be returned by conduit 53 to a
holding tank not shown, where it is available for subse~uent
rinsing o~ a compar~ment cleaned of sludge.
The spray head or nozzle 26 preferably comprises a
jet nozzle and may be of the portable type such as a
Gunclean 270 A manufactured by Salen and Wicander Marin AB,
Gothenburg, Sweden. The nozzle is further preferably
programmable and driven by air so as to move through pre-
detenmined arcs both in ver~ical planes and in horizontal
planes to assure that a jet of fluidized sludge or emulsion
will contact those areas of a compartment to be cleaned. We
have found that in many vessels, it is not necessary to cle-n
the top of the interior of the vessel since this area does
not come in~o contact with a cargo or a stored material 50 in
suc~ ins.ances the nozzle is programmed such that the jet of
emulsion will not contac~ top interior surfaces of the
vessel.
We have found that an appara~us as desc~ibed
operates successfully where the tank 20 has a capacity of
approxim2tely 2~0 gallons ~nd pump pressure is on t~e orce-
of 100-150 psig. The pumps the~sel~es may be of a progressive
cavity type as manufac~ured by Moyno Products, Robbins &
Mye_s, Inc., Springfield, Ohio.
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The process for cleaning a vessel of contaminated
sludge utilizing the apparatus as described above is as
follows:
Approximately one fifty-five gallon drum of an
emulsifying agent is added to an end compartment of a vessel
having a plurality of compartments each having a capacity of
approximately two thousand barrels, for example, compartmen~
2 of the tanker shown in Figure 1. A hose is attached to
the suction side of the pump 32 and lowered to a pickup
point at the lowest part of the compartment, which may be
conveniently formed by ballasting to impart a list to the
tanker to lower one end.
The emulsifying agent will fluidize some of the
sludge in the tank so as to form a pool of fluidized sludge.
As the sludge becomes fluidized, it is conveyed to the tank
20 by the pump 32 where it can be heated and the fluidized
sludge or emulsion (in the case of crude oil) is then
circulated through the tank 20 into the pressurized spray
means and onto the walls of the compartment. This
recirculation of fluidized sludge or emulsion is continued
until the compartment walls have been cleansed of sludge and
all of the sludge in the bottom of the compartment has been
fluidized. During this time it may become necessary to add
further fluidizing agent to the recirculated fluidized sludge
2 or emulsion to maintain fluidity of the sludge which can be
determined by checking the fluidity in the tank 20.
When all of the sludge in the tank has been
fluidized, it is pumped into the separating tank 50 and the
nozzle 26 is moved to the next adjacent compartment 3. A
small amount of the fluidized sludge or emulsion from
compartment 2 may be used as a beginning pool of fluidized
sludge for the next adjacent compartment 3 to be cleaned.
This is accomplished by leaving the end 23 of the discharge
means in the pool 24 of compartment 2 until the nozzle 26 has
sprayed sufficient fluidized sludge or emulsion Qnto the walls
of compartment 3 to form a pool o~ fluidized sludge in that
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compartment after which the end 23 is moved to the pool in
compartment 3 such that fluidized sludge or emulsion from
that ~ompaxtment is then recirculated through the closed
fluidizing system. This procedure is repeated for cleaning
the remaining compartments.
Portions of the walls of a compartment may be
masked or shaded by interior structure from impingement by
the spray from the nozzle 26. These untouched portions may
be cleaned by a hand~held spray from the deck or by someone
entering the compartment to spray the fluidizing agent
directly onto the untouched areas followed by washing with
a hand-held water hose.
The compartment after cleaning is then rinsed with
cold water using Butterworth nozzles for approximately
fifteen to thirty minutes to form an oil water emulsion.
This emulsion is continuously removed from the compartment
during rinsing and txasferred to a holding tank, not shown.
An oil layer will form on the surface within the holding
tank after a few hours and the rinse water may be decanted
from the bottom of the tank and recycled for future rinsing.
Emulsifying agents suitable for use in the
described process are of the types disclosed in United
States Patent No.4,276,094 and those sold by Petroferm
U.S.A., Amelia Island, Florida No.'s PFC-2209, PFC-0247 or
PFC-775-
We have found that the process and apparatus asdescribed above results in much faster cleaning of oil
contaminated vessels than when compared to conventional hot
water or steam systems. Further because we utilize a closed
fluidized system through which fluidized sludge is re-
circulated, production of large amounts of waste water and
attendant disposal problems are minimized.
