Orimulsion Spill Response R&D
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Part 2 -
New
Orimulsion® Spill Response Equipment Have Been Tested
Orimulsion® is a power plant fuel
produced by Bitor (a Petroleos de Venezuela - PDVSA
affiliate) in Venezuela and shipped to terminals around the world. Although
Orimulsion® is shipped globally in double hull tankers, and the receiving
terminals have appropriate contingency plans and spill response
capabilities, there has been continued interest by Bitor and several country
agencies (such as the Canadian
Coast Guard and Environment
Canada) to further develop response technology by sponsoring specific
research and development.
The efforts have led to the introduction of new response
equipment which have been successfully tested by SAIC
in Environment Canada's test tank in Ottawa. The tests
were sponsored by the Canadian Coast Guard.
Summary
An Orimulsion® spill will behave
differently to an oil spill by initially going into suspension as
microscopic surfactant coated bitumen particles in the upper 2-3 meters
below the sea surface. In case of spills at Orimulsion® marine terminals,
or near shore, it is therefore important to be able to rapidly refloat the
bitumen. In this way the spill could be converted to and treated as a
conventional heavy oil spill, using booms and heavy oil skimmers.
Previous tests by INTEVEP
( the R&D company of Petroleos de Venezuela, PDVSA) and Bitor indicated
that agitation, air injection, and splashing are important for a rapid
formation and reflotation of bitumen droplets. This developed into the FAF
(Forced Adhesion and Flotation concept). However, besides the effect of a
centrifugal pump’s agitation, air injection received the major attention
until it was discovered that the splashing effect was as important and at
the same time more simple and less costly to employ.
As a result, the ERE PNP
Orimulsion® Refloater was developed: A floating centrifugal pump, which
sucks from beneath the water surface and with great force discharges
vertically up against a diffuser and a splash cover, from where the water
splashes back to the surface. Enhanced agitation and very strong aeration
causes a very efficient reflotation.
The PNP Refloater was in December 1999 along with three mechanical feeder
skimmers successfully tested in Environment Canada’s test tank in Ottawa.
The tests demonstrated that spilled Orimulsion® can be rapidly refloated in
a simple way, and that the mechanically refloated bitumen has properties
which will keep it buoyant as long as the duration of the succeeding
conventional containment and skimming operation - even on fresh water, where
naturally refloated bitumen would sink - thus allowing for the overall
response to an Orimulsion spill to be as efficient as the response to a
conventional oil spill.
[back]
ERE
PNP Orimulsion® Refloater
The joint Bitor, flemingCo environmental, and Environment
Recovery Equipment development and design of the ERE PNP Orimulsion®
Refloater, is based on the Forced Adhesion and Flotation (FAF) principle
which already in 1996 demonstrated its efficiency in open ocean tests off
the coast of Venezuela. The FAF principle is based on the fact that strong
agitation by a powerful centrifugal pump, combined with air injection
enhanced air adhesion to the bitumen particles, result in an efficient
reflotation of the suspended bitumen particles originating from a spill of
Orimulsion®.
The PNP Orimulsion® Refloater facilitates the fact that
efficient splashing of water with bitumen particles in suspension can cause
the same degree of aeration as air injection. This allows for a flexible
approach as the reflotation process can take place "in situ".
ERE PNP Refloater and ERE Skimmer in Environment Canada Test Tank
How the ERE
PNP Orimulsion Refloater Works
Splashing and agitation are created by a
floating submersible high output centrifugal pump, which sucks from one or
more points beneath the pump. A vertical discharge tube sends the flow
vertically up above the water surface where it violently hits a diffuser
plate, which diverts the flow to hit a splash cover over the pump. The
splash cover reflects the air / Orimulsion® / bitumen particle mixture, and
sends it splashing back down towards the water surface, still at high speed,
thus bringing lots of air into the water column.
The violent agitation and very strong
aeration causes an efficient reflotation of the suspended bitumen particles
which on the surface form a coherent layer of viscous bitumen, easy to
contain by means of conventional booms.
With the advantages of On Water Splash Reflotation OWSR, and the PNP
Refloater’s appearance and size like a traditional free floating skimmer,
a new tool for the oil spill response industry has been developed. The PNP
Refloater will as to size, weight, and hydraulic power requirements fit into
conventional oil spill equipment inventories.
The ERE PNP Orimulsion® Refloater has been designed to meet the
requirements as to reflotation of spilled Orimulsion® at a typical
Orimulsion® transfer marine terminal.
[back]
Mechanical
Feeder Skimmers
See also Tests
on Refloated Bitumen
A mechanical feeder skimmer lifts or drags - by means
of more than just adhesion - the oil out of the water to a position above
the water surface, and feeds or drops it into a collection tank or a
transfer pump. The lifting/feeding can be by
- Endless ropes of bristles or brushes, gravity/scraper feeding to a
pump or a tank (LORI, LAMOR, a.o.)
- Various open or closed structure inclined belt types, which convey the
oil to a scraper, which gravity feed into a tank or pump (Marco, ERE,
Axiom HOBS, Tar Hawg, DESMI Belt Animal a.o)
- Rotating stretch metal net drum, a "snail’s shell",
feeding - by the concentrating geometry of the stretch metal drum - into
an auger, which feeds into a pump (Unisep, WP-1, Roto 70)
- Twin counter rotating drums with positive guides, which lift and
pressure-scraper feed the oil into an auger which feeds into a pump
(KLK)
- Conveyor belt with flap cups (corn elevator type) which gravity dump
feed into a tank or a pump (EGMOPOL)
- Rotating discs with rough teeth at the perimeter of the discs,
gravity/scraper feeding to a pump (Vikoma Sea Devil)
Common for all the listed principles is that they are able to drag the
oil out of the water (with various degrees of independence of the oil’s
resistance to flow (viscosity)), based on combinations of adhering,
grabbing, trapping, and squeezing, dependent of type in question. Adhesion
is a major success factor in most types. In some cases adhesion will
positively influence performance, like in 1, 2 (less ERE), 4, and 6, while
strong adhesion will negatively influence the performance of types 3 and 5.
Skimmer Tests
on Refloated Bitumen
The Tar
Hawg skimmer was in 1996 tested with some success on refloated bitumen
originating from a test spill of Orimulsion® off the coast of Venezuela.
Tests conducted in 1999 by flemingCo
environmental on behalf of Bitor demonstrated that the Unisep
net drum skimmer has some potential and that the KLK
skimmer performs well on refloated bitumen with viscosity in the 1 million
cSt range.
Tests in 1999 at SAIC/Environment Canada’s test facility in
Ottawa, Canada, sponsored by the Canadian Coast Guard, demonstrated that
floating bitumen with a viscosity of about 2 million cSt could be recovered
by mechanical feeder skimmers. The ERE, KLK, and Axiom HOBS skimmers were
all able to recover this extremely viscous bitumen.
ERE Oriliminator Mechanical Feeder Skimmer ready to skim, and the
Oriliminator recovering extremely viscous PNP-refloated bitumen
[back]
Oil Trawls
Oil trawls are used for recovery of
floating tar balls, fuel oils, oil contaminated debris, residual tar after
oil burns, and bitumen residues from Orimulsion® spills.
Oil trawls have like mechanical feeder skimmers in tests and incidents
proved to be able to recover even very viscous oils. In tank tests (CEDRE
France, and OSRL
UK) the oil trawls have demonstrated to be able to recover extremely viscous
floating bitumen.
An oil trawl system consists of the guide booms, the entrance net, and
the detachable trawl bags. It can be very rapidly deployed with only small
work boats. No hydraulic power or heavy mechanical equipment is required -
only a simple air blower for inflation of the guide booms, or even less if
foam filled booms are used.
Two of the more well know brands are the ScanTrawl
and the Jackson Trawl
[back]
Tests
at Environment Canada/SAIC Sponsored by the Canadian Coast Guard
The primary purpose of the tests was
to determine how efficiently the PNP Refloater could refloat the suspended
bitumen particles after a simulated marine terminal spill of 17 m3
Orimulsion®. To match the dimensions of the test tank’s content of 29.5 m3
of water, the spill was scaled down to 100 L Orimulsion®.
A secondary purpose was to evaluate three mechanical feeder skimmers’
ability to recover mechanically refloated bitumen. See Mechanical
Feeder Skimmers for summary info on the test results.
Test Tank Dimensions, L x W x D = 8.53 x 3.04 x 1.14 m
Salt Water
Tests in Environment Canada/SAIC Test Tank
Table 1, Test results, EC/SAIC tests, Salt
Water
100
l Orimulsion spilled into test tank with 29.5 m3 salt
water (3%)
Reflotation in % of spill, Water temperature = 14 ° C |
| Time
after treatment |
2
min |
10
min |
30
min |
60
min |
| 17
min no action (ref) |
9.0% |
10.1% |
15.8% |
35.3% |
| 17
min PNP action |
88.7% |
90.2% |
91.5% |
91.4% |
An extremely rapid bitumen layer
development was observed, actually already significant within the first
minute after starting the PNP. Although it’s appearance was foamy, it was
very "chewing-gum-like" when trying to stir with a stick.
The EC/SAIC salt water test demonstrated that the PNP refloater rapidly
may refloat about 90% of the bitumen, which is located in the water column
after an Orimulsion spill.
[Back]
Bubbled and "chewing gum-like"
refloated bitumen
Fresh
Water Tests in Environment Canada/SAIC Test Tank
Table 2, Test results, EC/SAIC tests , Fresh Water
| 100
l Orimulsion spilled into test tank with 29.5 m3 fresh
water |
| Reflotation
in % of spill. Water temperature = 14 ° C |
| Time
after treatment |
2
min |
10
min |
30
min |
60
min |
1080
min |
17
min. no treatment
(reference spill) |
<
3% |
<
3% |
<
3% |
<
3% |
<
3% |
| 1st
17 min. PNP treatment |
24.8% |
27.2% |
27.5% |
28.9% |
N/A |
2nd
17 min. PNP treatment
(60 min. after first treatment) |
47.2% |
46.8% |
45.4% |
48.0% |
N/A |
3rd
17 min. PNP treatment
(60 min. after second treatment) |
62.2% |
61.2% |
60.1% |
61.5% |
N/A |
It was during the PNP
reflotation treatment observed that bitumen with a lot of air bubbles
rapidly formed on the water surface. However, the speed of reflotation was
lower, and the layer thickness was less than in the test in salt water.
The EC/SAIC fresh water test demonstrated that an Orimulsion spill into a
body of fresh water can be refloated to a reasonable degree, although not as
well as for salt water. The purpose of the repeated PNP treatment was to
give indications on the effect of prolonged PNP treatment of fresh water
spills and the possible effect of a higher capacity PNP refloater. The
results can be translated into the following:
- If an Orimulsion spill into a body of fresh water is treated three
times longer than would apply for the same size spill into salt water,
about 60% of the bitumen may be refloated
- If an Orimulsion spill into a body of fresh water is treated with a
three times higher PNP capacity than would apply for the same size spill
into salt water, about 60% of the bitumen may be refloated
Several factors play a role here and further research into the specific
fresh water spill conditions are required. [Back]
Regarding the density or buoyancy of the
refloated bitumen, the EC/SAIC tests demonstrated that bitumen, which has
been refloated by the PNP Orimulsion Refloater will have a lower density and
therefore be more buoyant than naturally refloated bitumen. The density of
bitumen which had been refloated from salt water was – based on the visual
fact that about 50% was floating above the water surface – estimated to
0.5 g/ml, while the bitumen which had been refloated from fresh water - by a
simple measurement of volume and weight – was estimated to 0.68 g/ml.
Normal bitumen has at the same temperature a density of 1.014 g/ml. [Back]
