Note: Descriptions are shown in the official language in which they were submitted.
. CA 02643893 2008-11-17
DUAL PURPOSE BITUMEN/DILUENT RAILROAD TANK CAR
FIELD OF THE INVENTION
This invention has to do with railcar transport of bitumen, typically from a
production site to a refining or upgrading site and the return of the railcar,
at least part
of the return trip having the railcar transporting diluent instead of
deadheading. It is
proposed that diluent would be returned from a point along the return trip
back to the
bitumen production site to aid in production, refining, as fuel, or as diluent
in dilbit for
handling or transport.
BACKGROUND OF THE INVENTION
Rail tank cars are used in bulk transportation to transfer petroleum products
from
one location to another. One skilled in the art also knows that specialized
rail cars exist
for the transport of asphalt or bitumen and specialized rail cars exist for
diluent and
similar light hydrocarbons such as gasoline ("diluent"). Asphalt is defined as
residual
crudes that have a specific gravity of about 1.04 and diluents are liquid
hydrocarbons
which have specific gravities of about .830 or less.
The approval for railroad tank car designs, materials, construction or
alteration
of tank cars are prescribed by the Executive Director Tank Car Safety, AAR
(Association of American Railroads) and the Tank Car Committee. The US
Department
of Transportation in conjunction with the AAR have classified asphalt tank
cars and
diluent tank cars as DOT 111A100W1 (AAR 211A100W1). Both asphalt tank cars and
diluent tank cars share common certification requirements for tank design and
construction, type of steel, welding, repairs, documentation, mounting,
coupler vertical
restraint systems, pressure relief devices, and markings. Both these types of
cars are
classified as general purpose non-pressure tank cars (Department of
Transportation Part
179 Specifications for Tank Cars: Subpart D ¨ Specifications for Non-Pressure
Tank
Car Tanks: Classes DOT ¨ 111AW and 115AW).
However, asphalt cars and diluent tank cars have several significant
differences:
1. Asphalt tank cars are smaller than diluent tank cars because the
density of the asphalt is much higher. The density of liquid heated asphalt
loaded into
tank cars is typically in the range of 975 kg/cubic meters. The density of
diluent
typically loaded into tank cars at ambient temperature is in the range of 675
to 830
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kg/cubic meters. Because tank cars are essentially limited to 286,000 lbs in
maximum
gross weight, and assuming that the asphalt car empty weighs 82,500 lbs, it is
not
logical to build an asphalt tank car with a shell capacity greater than about
25,500 gals
(US), with a loaded capacity of 25,000 gals (at 98% of full load). The reason
is once
25,000 gallons of 975 kg/cubic meters asphalt are placed in its tank the total
gross rail
load of the rail tank car is about 286,000 lbs.
Diluent rail cars are similar to general purpose gasoline, diesel and
ethanol rail cars for reasons of interchangeability and fungability. The tank
cars and
products are interchangeable because the density and vapour pressure of these
various
products are similar. A 286,000 lb gasoline/diluent tank car can be designed
to have a
shell capacity of around 33,000 gallons (US), with a loaded capacity of 32,300
gals (at
98% loaded) and it has a vehicle weight of 72,000 lbs when empty. If the
liquid diluent
(or similar) product with a density of about 795 kg/cubic meters is placed in
this rail
car's tank then the rail car will reach its maximum allowable weight (286,000
lbs) when
98% loaded, at 32,300 gallons of diluent. The density of gasoline is about 720
kg/cubic
meters, ethanol is 795 kg/cubic meters and diesel is about 830 kg/cubic
meters.
Diluents used for bitumen are also in this range.
This aspect, the railroad's weight restriction, is a major design factor
when designing a tank car. This restriction is known by those skilled in the
art.
2. Because asphalt does not flow efficiently at ambient temperatures,
asphalt cars are insulated and, typically, externally heat traced. Heat
tracing is almost
always done with a heat exchange system of a steam coil affixed to the tank.
Steam
lines are attached to the tank car when it reaches an unloading facility. The
steam in the
coil transfers heat to the tank and that heat radiates into the asphalt
increasing its
fluidity. The steam may be supplied from either a stationary or a portable
boiler. These
cars are called coiled, insulated, non-pressurized tank cars. Because diluent
does not
"solidify" or become viscous at even low ambient temperatures, diluent cars
are not heat
traced. These diluent cars are called non-coiled, non-insulated, non-
pressurized tank
cars.
As steam lines add significant empty weight to the tank car, they are not
installed unless required by the cargo for viscosity reduction purposes. This
is known to
one skilled in the art.
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3. The tank on a diluent tank car requires a thicker head shell made of
stronger steel, or a protective head shield to reduce the possibility of tank
rupture if the
car derails or is in collision. This requirement is set out by the DOT in
section
179.169(a) (b) (c) "Tank-head puncture resistance systems" of its
Specifications for
Tank Cars and Canada's National Transportation Act, Railway Act. Diluent tank
cars
also require the installation of a pressure relief valve (as set by the AAR
Appendix A
and DOT Section 179.15: Pressure relief devices), valve protection at the top
of the
tank (around the vacuum and safety pressure relief valves), and protective
steel around
the bottom discharge valve (DOT Specifications for Tank Cars - Section 179.200
and
AAR Specifications for Tank Cars paragraphs E9.00 and E10.00).
This requirement for added safety features for diluent railcars is known
by those skilled in the art.
4. Gasket materials must be selected from a group of materials that are
effective with the commodity being transported and not negatively affected
thereby.
The US Department of Transportation (DOT) has made these aspects a requirement
for
diluent transportation by rail.
This requirement for special gaskets, seals, tubing, and valves suitable
for use with diluent type solvents in transport is known by those skilled in
the art.
5. Asphalt is loaded and unloaded into insulated tank cars at high
temperature that the asphalt is liquefied to be pumped. The temperature of the
asphalt
during loading and unloading is typically between 300 deg F and 325 deg F (-
150 deg
C). However, diluent is placed in a tank car at ambient temperature, not
elevated
temperatures, to avoid dangerous or costly boiling/evaporation of any volatile
hydrocarbon components.
These very different loading and unloading temperatures for diluent and
asphalt or bitumen are known by those skilled in the art.
Because differences between the two types of tank cars are significant, tank
car
manufacturers do not build tank cars that meet the DOT requirements and
combine
asphalt and diluent transportation.
Prior Art
There are numerous prior patents and other publications related to railroad
tank cars
some relevant ones of which are:
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,
,
,
,
A. Tank Car design
Department of Transport (DOT) Research and Special Programs Administration,
Part
179 ¨ Specifications for Tank Cars
B. Tank structure and supports
5 2,907,284 CM Folmbee: Frameless tank car
3,336,879 SP Halcomb: Frameless tank car sill design
3,487,532 E.A. Phillips: Method of expanding the tank car
to make it larger
6,357,363 Daniel Miltaru: Frameless tank car
C. Head protection
10 4,466,356 Messersmith et al Head end shield retrofit design and
method
D. Heating methods
1,706,084 .TW Steinmeyer Tank car steam coil design
2,145,614 PH Stambaugh Method of heating and insulating
tank cars
2,545,371 T Mojonneier et al Tank car heat exchange coil
design
15 3,468,300 W.T. Geyer et al Heating mechanism for insulated tank cars
4,414,462 Price Tank Car heating system
4,603,733 Loevinger Tank car steam coil design
6,347,589 Loevinger Railway tank car having a heating
system
E. Tank design
20 1,858,610 TA Banning, Jr. Tank car for gasoline, naphtha
1,864,990 LE Endsley Tank car dome design
2,558,648 RW Gausmann Tank car insulated and heating
design
2,772,784 JF Cyphers et al Tank car for transporting
chocolate
3,742,866 Needham et al Tank car sloping bottom design
25 4,624,189 Loevinger Tank car heated Outlet valve
SUMMARY OF THE INVENTION
In today's market, there is a need for a railroad tank car which can move
bitumen (nominally heavy oil with a density of 930 to 1050 kg/cubic meters)
from
heavy oil producing areas like Alberta to terminals and refineries which have
the ability
30 to refine these very heavy crudes. However, there is also a need to
transport diluent
(such as hydrocarbons with less than a density of 830 kg/cubic meters) back to
these oil
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fields. The diluent serves two purposes. First, it is used in the production
process to
separate the heavy crudes from sand and water. Second, it is mixed with the
bitumen to
produce an oil called Dilbit or Synbit that meets or exceeds standard pipeline
specifications of viscosity and density for transport.
The traditional way to transport bitumen to market is to add a diluent to the
bitumen until the viscosity of the mixture is sufficiently reduced so that the
blend can be
transported by conventional pipeline. Often, the diluent is a lighter
hydrocarbon
(pentane, hexane or synthetic crude), within the range identified here.
This invention describes an alternative form of combined transport employing
heated, insulated rail tank cars. These cars are designed to be partially (by
volume)
filled with bitumen, typically no more than 90% but to the maximum allowable
weight
capacity of the car or the rail line. The cars then move from the field to an
unloading
facility. In a normal oil transportation service the rail cars are returned to
the oil field
empty. Rather than bringing these cars back empty, with this inventive railcar
design,
which meets or exceeds DOT safety requirements, it is possible to return the
novel cars
full (by volume) of diluent back to the bitumen source in the same car. This
requires a
rail tank car which is designed to handle both commodities, with features not
at first
obvious to one skilled in the art of rail tank car design or use.
This invention is premised on the concept that those parties manufacturing
dilbit
for pipeline transport require an external supply of diluent either for
removal of the sand
and water and/or blending dilbit for pipeline transportation. Thus, diluent is
needed in
the field and the back-haul of diluent has economic utility greater than the
cost or
inefficiency of the novel railcar design.
BRIEF DESCRIPTION OF DRAWINGS
Figure 1 is a schematic flow-diagram showing a preferred transport process of
the invention.
Figure 2 is a cross sectional side elevation of a preferred embodiment of a
railway tank car of this invention, to provide context.
DETAILED DESCRIPTION
In this invention and with reference to Figure 1, the steps expected in the
use of
the specially designed two-function railcar include:
1. Hot bitumen is transferred from a hot bitumen storage tank to
the coiled,
insulated, non-pressurized rail tank car using a standard oil pump.
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CA 02643893 2008-11-17
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2. The rail tank car is transported from the loading station, preferably at
or
near a production source, to an unloading station, preferably near a refinery.
3. Steam is injected into the tank car's heat exchanger coils to reheat the
bitumen to a temperature required to liquefy it sufficiently to enable it to
be
pumped off the tank car and unloaded.
4. The hot bitumen is transferred from the tank car to a hot bitumen
storage
tank using a standard oil pump.
5. At a diluent loading station, preferably close to the bitumen unloading
station, water is injected into the coils to cool the tank car to a
temperature
suitable to prevent flashing or guide evaporation of any significant part of
the
diluent.
6. The diluent is transferred from the storage tank to the tank car using a
standard pump.
7. The tank car is transported from the loading station to an unloading
station, preferably near a production source.
8. The diluent is transferred from the tank car to a diluent storage tank
using
a standard pump.
Because bitumen has a higher density than diluent, and the capacity of tank
cars
to carry a commodity is based on the total weight of the car plus the cargo,
the car size
and design of a dual purpose car for hauling widely disparate fluid
hydrocarbon
commodities needs to be optimized such that it maximizes the transport of the
sum of
the two commodities multiplied by the product price differential between the
producing
location and the consuming market. In practice, this involves designing a tank
car that
takes into account both volume restrictions and maximum rail car and load
weight. In
almost all rail applications, the total loaded weight of the rail car is
limited by the track
and the type of support underneath the track. In almost all rail applications,
the
maximum volume of the tank cars is limited as to height and width by factors
such as en
route bridge heights. The one variable in the tank car design process that is
not
exogenous is the tank car length, although this too can be limited by
exogenous factors
related to railroad siding length, track turning radius, and loading/unloading
rack
geometries. Certain standards have emerged with regards to tank car length.
One
observes that tank cars that carry heavy cargo such as asphalt are typically
about 53 feet
in length, medium density products such as gasoline are 60 feet in length, and
light
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products such as propane are 68 feet in length. This means that standards that
have
evolved for the two different products of asphalt and gasoline are different
with regards
to rail car length.
Any tank car designed for dual use with different density fluid hydrocarbon
5 products will inevitably be designed to be able to handle the maximum
weight of the car
in one of the directions (for example when carrying bitumen) and the maximum
volume
of the car in the other direction (when carrying diluent). Given that the
ratio between
the weight of the cargo and the weight of the steel in the tank is
approximately 7:1, an
economic optimization analysis indicates that the greatest economic benefit is
achieved
10 by designing a dual use tank car which fully loads the tank cars
volumetrically with the
lower density fluid, in this case the diluent. We have determined that this
requires a
non-pressurized, insulated, coiled tank car that meets DOT, AAR and CTC safety
requirements and has approximately 30,000 gals of capacity and is
approximately 60
feet long.
15 This novel tank car will be fully loaded with bitumen at a loading
capacity much
less than 98% by volume, the current standard. The actual loading capacity
will be
equal to the ratio between the density of the two products, the hot bitumen
and cold
diluent.
Cold diluent, using a standard 30,000 gal tank car weighing about 82,000 lbs
20 empty, has a density of approximately 830 kg/cubic meter. We have
determined that
the hot bitumen has a very narrow range of product densities, even though the
various
raw bitumens identified in nature have a very broad range of densities at
ambient
temperatures. This occurs because the main design specification will be that
the rail car
must be loaded and unloaded in a finite amount of time and the key physical
25 characteristic that affects the loading and unloading time is the
viscosity of the fluid,
which requires an elevated loading temperature of the bitumen. Through
testing, we
have identified that the heavier is the bitumen, the hotter it must be to
achieve the
viscosity specification. We have also identified that the bitumen density
drops as it heats
up (the fluid expands with increases in temperature). Therefore, the density
of the
30 bitumen as it is loaded and unloaded at a suitably elevated temperature
defines a much
narrower range of densities than is seen amongst raw bitumens at ambient
temperatures.
This is shown in the table below, where the raw bitumen at ambient (15.6 C)
describes a
3.8% range in density, while the density at 570 cP of viscosity describes a
1.2% range of
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density. The table derives from actual testing that was done on three
different bitumen
samples.
Relationship of Density to Viscosity of Three Different Bitumens
Bitumen Sample # 1 2 3
Density @ 15.6 C (kg/cubic meters) 977.9 1002.3 1015.3
Temperature @ 570 cP viscosity ( C) 49.0 68.6 90.6
Density at above temperature (kg/cubic meters) 956.3 966.7 967.3
Temperature @ 350 cP viscosity ( C) 60.0 76.0
Density at above temperature (kg/cubic meters) 949.3 961.8
It is now expected that all bitumens will show this characteristic and, having
done these novel experiments with the optimization features of this invention
as a
motivation, it is apparent that the density of hot bitumen loaded into the
more dual use
tank car of this invention will be approximately equal to 950 kg/cubic meter
at the
temperatures required to reach the bitumen viscosity required to load or
unload the car.
The volumetric analysis of a car, assuming a diluent load that will not exceed
about 830
kg/cubic meter loaded density and a hot bitumen load that will be
approximately equal
to 950 kg/cubic meter, indicates that the tank car, when loaded with bitumen,
will not
exceed a loading capacity of 87% (830/950).
Further, the car design deals with issues that can potentially arise from the
contamination of the diluent by the bitumen. This design constraint means that
virtually
all of the bitumen needs to be unloaded from the tank car before the car is
filled with
diluent. In practice, this means the bitumen will be heated to come to a high
fluidity
state during the unloading procedure. The proposed method to accomplish this
goal is
by employing steam to heat the tank car and its bitumen through heat exchanges
on or in
the car upon (and if necessary, during) the unloading process. This is
achieved by
heating the tank car using a steam coil for at least thirty minutes. This
practice involves
designing a car that is insulated to conserve the heat imparted to the bitumen
when the
tank car is loaded, then adding additional heat to raise the temperature of
the bitumen
until the bitumen has high fluidity for unloading.
After the car is emptied of bitumen, it is still hot from the unloading
process. If
diluent were placed in the hot tank car portions of it would vaporize causing
waste and
increasing hazard. We have determined that the external steam coil or heat
exchanger
on or in the car can be flushed with water at or near ambient temperature for
a
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CA 02643893 2008-11-17
reasonably short period of time to reduce the temperature of the tank to a
point it can be
loaded with diluent without having the diluent vaporize. Currently, this
cooling activity
is not done with asphalt-type tank cars because they are not loaded with
diluent-type
hydrocarbons after unloading (or at all), due to the lack of diluent style
safety features
on the asphalt car. Hence, this process step, changing the temperature state
of the tank,
is not known by or obvious to one skilled in the art.
For safety reasons, because the consequence of a bitumen spill is much less
dangerous than a diluent spill, the design of this dual-purpose car involves
designing the
car to meet the more stringent railroad safety code for diluent cars. The
preferred car
design is therefore based on an insulated rail car that can be heated upon
delivery of the
bitumen into the market, the car can then be cooled prior to introduction of
the more
volatile diluent to avoid flashing the diluent, and the rail car has the
safety features
required for diluent type cars, primarily involving a reinforced head end at
the front of
the car and safety reinforcement around the bottom and other valves of the
rail car.
The invention includes the design and manufacture of an optimized dual purpose
asphalt-diluent railroad tank car. The entire unit is self contained and no
ancillary
equipment is required for the tank car to complete the transport task for
which it was
designed. Thus this dual purpose tank car can be used anywhere there are
appropriate
loading and off-loading facilities.
The invention may be described as a railroad tank car whose tank has been
adapted to meet DOT, AAR, and CTC ("Canadian Transport Commission") safety
requirements for the purpose of transporting diluents which include: synthetic
crude,
light crude, diesel fuel, gasoline, pentane, hexane, naphtha and or blends of
these
hydrocarbons. Additionally, the tank has been insulated and a steam heat coil
has been
attached so that it may be used to transport asphalt, bitumen, bunker or any
other
hydrocarbon which requires heating so that its fluidity increases at the time
of loading
or unloading.
As the first step in the refining process of bitumen is to heat the bitumen
for
distillation, preservation of the heat energy in an insulated tank car and the
subsequent
storage (as hot bitumen) has additional economic utility.
Although there is an economic benefit in heat conservation, we have found that
there is no business case in preheating the tank car before loading the
bitumen. For
example, if the mass of the bitumen to be loaded is 198,000 lbs and its
temperature is
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CA 02643893 2008-11-17
120 C and the temperature of the railcar's 30,000 lb tank is 20 C then
(assuming the
heat capacity of the bitumen is 2 joules/gram/ C and the heat capacity of the
steel tank
is 0.5 joules/gram/ C) the temperature of the tank and bitumen after loading
and when at
equilibrium, should be about 116 C. This temperature loss is a negligible
amount
(approximately 4 C) and does not warrant the deployment of capital (a boiler,
steam
piping, etc.) required to pre-heat the car, as it does not materially affect
the loading
process or provide other utility.
In an embodiment of the process of this invention, the empty weight of a dual
purpose railroad tank car is about 82,000 lbs. The shell capacity of the tank
car is
29,200 US gallons. The tank car is capable of being fully loaded by weight by
being
partially filled by volume with hot bitumen. Because the bitumen is hot, its
density is
approximately 950 kg/cubic meters. Hence, when the tank car is filled by
weight to
286,000 lbs, approximately 25,700 gals of bitumen are placed in the tank car.
This is
88% of the tank car's volumetric capacity but 100% of its weight capacity. Of
course,
the weight of the car and load must also be tailored to the maximum weight
capacity of
the line and other similar known constraints.
The tank car is then hauled to a refinery or terminal. Steam hoses are
connected
to conventionally designed heat exchange means in or on the tank and the
temperature
of the tank and the bitumen are raised to about 100 C. A valve at the bottom
of the tank
car is opened and the hot bitumen is flowed out of the tank car and into a
hose which is
connected to a pipe. The pipe and a pump move the bitumen to a storage tank.
After the tank is drained (approximately 30 minutes), the steam hoses are
removed and they are replaced with water hoses. Alternatively, the same hoses
can be
used and the steam supply is shut off and the hoses are filled with water from
a
steam/water manifold. In either case, water is pumped through the tank car's
steam coil
and the tank is cooled to a temperature which is below the flash point of the
diluent
which will next be loaded; the water having been at a temperature to effect
this cooling,
preferably at or near ambient temperatures.
After the tank car is cooled with water, the hoses are removed and the tank
car is
filled with diluent. Because the tank car has been cooled from its heated
state at the
unloading of the bitumen stage to at or near ambient temperature, the diluent
does not
flash to form a wasteful or hazardous vapor. The tank car is then filled to 98-
99% of its
volumetric capacity with diluent. If the density of the diluent is 675
kg/cubic meters,
CA 02643893 2015-04-22
and the volume of diluent loaded in the tank car is 28,900 gallons (US), then
the weight
of the cargo is 162,750 lbs. The loaded total weight of the tank car is
244,750 lbs, equal
to approximately 85.5% of the total weight capacity of the tank car of 286,000
lbs. If the
density of the diluent is 846 kg/cubic meters, the car would be fully loaded
by weight.
This tank car is transported back to the production location. Similarly, it
may be
emptied at a terminal or refinery en route to the bitumen production area, or
may be filled
at a different loading station that at the unloading point.
With reference to Figure 2, there is depicted a railcar which is an embodiment
of
the present invention, with an insulated tank 3, protected valve housings 2,
steam tracing
or heat exchange means (dotted lines means internal to the tank) 6, saddle and
sump
protectors 5, and a hemispherical full tank head jacket 4.
In the preceding description, for purposes of explanation, numerous details
are set
forth in order to provide a thorough understanding of the embodiments of the
invention.
However, it will be apparent to one skilled in the art that these specific
details are not
required in order to practice the invention.
The above-described embodiments of the invention are intended to be examples
only. Alterations, modifications and variations can be effected to the
particular
embodiments by those of skill in the art without departing from the scope of
the
invention, which is defined solely by the claims appended hereto.
WSI,cgal\064456\00017 \11832296vI 11
