Note: Descriptions are shown in the official language in which they were submitted.
1399
The present invention relates generally to a method
and a system for transporting natural gas between a gas
well and a transmission pipeline, or other end user facility.
More particularly, it relates to such a method and system
particularly adapted to the economies involved with re-
motely located or low producing wells, where the cost of
constructing a conventional feeder pipeline from the well
head directly to a pipeline terminal or end point purchaser
is excessive.
The distribution and use of natural gas for energy
purposes is very widespread. The conventional manner for
handling the natural gas is to build a feeder pipeline
directly to the well head, which is then used to collect the
gas and transport it to a terminal on a major transmission
pipeline utilized to transport large volumes of natural
gas over long distances to remote users. While this system
has proven successful over the years in most instances,
there are some situations where the economic costs involved
are so excessive as to make use of natural gas from small
reservoirs and certain wells impractical. This is especially
true of low producing wells, and those wells that are isolated
or lo~ated in remote places.
Over the time when an abundance of natural gas wells
located in easily accessible locations existed to meet the
needs for this form of energy, the ignoring of the output
of natural gas from small reservoirs, and from low producing
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and poorly located wells, was of no great moment. But
in this time of energy shortage, particularly the short-
age of natural gas available to the major gas transmission
pipeline sys-tems, there is now a need for an economically
feasible means for making use of the natural gas available
from such wells.
Industry has previously developed special equipment
for the commercial handling of what are called specialty
gases, such as oxygen, acetylene, and in some instances,
energy fuels. The key element in such equipment is an
over-the-road motor vehicle carrying one or more pressure
vessels, designed to transport the specialty gas safely
under normal highway conditions. Among such vehicles
for transporting specialty gases will be found semi-
trailers including a plurality of cylindrical high pres-
sure vessels, and capable of transporting perhaps 200,000
cubic feet of gas under high compression.
It has also been demonstrated that natural gas
can be stored in refrigerated pressure vessels on board
a ship, under relatively low pressures and at low tempera-
tures, for transporting it over long distances across a
body of water. Such a method for the storage and trans-
portation of natural gas is described in U. S. Patent
No. 3,232,725, but has a disadvantage for large scale use`
on the land because of the need to keep the pressure vessels
under refrigeration. The method of the patent r~quires
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refrigeration equipment and insulation to hold the com-
pressed natural gas at sub-freezing temperatures, and t
such equipment and insulation occupies valuable space and
adds weight in a land vehicle with the result that haul-
ing capacity can be reduced and transportation costs in-
creased to the point where economical transport of the
natural gas cannot be accomplished.
The present invention is intended to solve the need
for economically transporting natural gas from remote
small reservoirs and low yield wells to a pipeline terminal,
or other end user facility. It is particularly designed
for economically transporting the natural gas over-
the-road, and in this embodiment makes use of the general
type of transport motor vehicles that have been developed L
for handling specialty gases, suitably modified to carry
out the method o~ the invention. At the same time, the
need for insulation and refrigeration of the cylindrical
high pressure vessels, as required in U. S. Patent No.
3,232,725, is eliminated, thereby greatly enhancing the
economics of transporting the natural gas over-the-road.
While the present invention is particularly useful
for transporting natural gas over--the-road, it can also
be adapted for use with high pressure vessels transported
by other means, such as by barge, rail or airplane. When
these transport vehicles are employed, the elimination
of the need for refrigeration equipment allows carrying
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a significantly heavier payload than in the past. More-
over, the unique loading and off-loading method and system
of the inventlon is of equal value, regardless of the kind
- of transport vehicle utili~ed for the high pressure ves-
sels.
In the method and system of the invention, a first
terminal is built at the natural gas well site, and a r
second terminal is established at a terminal on a trans-
mission pipeline, or at another end user location. rrhe
first and second terminals are especially equipped to .!
handle the loading and off-loading of natural gas, re-
spectively, the first terminal including a dehydrator unit
to remove moisture from the gas, and a compressor for
supplying it under pressure to the high pressure vessels L
carried by the transport vehicle means used to transport
the gas. The transport vehicle, whether it is an over~
the-road truck, a railroad car, a barge, or even an air-
craft, carries a specially designed manifold system to
facilitate loading and off-loading of the natural gas, r~
quickly and with safety.
At the well site, natural gas is gathered from a
plurality of gas wells through a gathering manifold system
that includes a meter foreach well, and a check valve
arrangement to prevent backflow toward the meter and its
associated well. The check valve prevents gas from flow-
ing from a gas well with a high well head pressure, into
one having a lower well head pressure. The number of gas L
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wells connected to the gathering manifold system is largely
a matter of choice, involving decisions based on
en~ineeriny and economics.
The com~ressor unit of the system is uniquely
designed and arranged both to minimize problems of
significant temperature drops normally associated with
high pressure differentials when the outpu-t of a compres-
sor unit is by-passed back to the inlet side thereof, and
to make the system fail safe. Turning to the temperature
drop problem, this is minimized in the invention by connect-
ing the by-pass from the outlet of the compressor unit to
the inlet of a pressure control valve feeding natural gas
to the compressor unit from the gathering manifold system.
This arrangement utilizes the usually relatively high
pressure within the gathering manifold to minimize the
pressure drop resulting from by-Dassing the output of the
compressor unit.
The compressor unit arrangement is made fail safe
by an over-ride switch, connected to a by-pass from the
outlet side of the compressor unit. If the by-pass valve
should fail and system pressure rise to an unacceptable
level, the over-ride switch will turn off the compressor
unit.
Once a transport vehicle has been loaded at -the r~
first terminal, it is simply driven or otherwise moved
to the second terminal at the pipeline terminal, or other
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:10733~
end user location. The natural gas is carried under
high pressure, normally in excess of 1500 p~s.i., and
under ambient temperature conditions. It has been
found that by utilizing such high pressures, usually
in the range of from 2000 to 3000 p.s.i., the natural
gas can be successfully transported uncler ambient tempera-
ture conditions, without the need to refrigerate the
pressure vessels. At the second terminal the gas is off-
loaded through a flow monitoring system and control sys-
tem, and flows into the pipeline, or a suitable storage
vessel. The cylindrical pressure vessels are each fitted
with a suction hose arranged to pick up any liquids that
have accumulated therewithin, which are entrained with
the natural gas and removed from the pressure vessels
therewith.
It has been found that in off-loading natural gas
at high pressures such as are contemplated in the inven-
tion, hydrates can form in the gas that are undesirable.
The invention contemplates that heaters can be disposed
in the off-loading system, to prevent this problem from t
occurring. This can make it possible to deliver the
natural gas in a condition ready for transmission.
The method and system of the invention for trans-
porting natural gas are at once simple and economical.
The invention thus makes it possible to utilize the many
so-called "shut in" natural gas wells to augment the
supply of natural gas energy
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Accordingly, -the invention claimed herein is the
method for transporting natural gas from a gas well (5)
location to a terminal facility located at a delivery location,
essentially including the steps of: taking the natural gas
from a gas well gathering system at said gass well(s) location;
compressin~ the natural gas to a pressure in excess of about
800 p.s.i., if it is not already at that pressure when received
from the gas well gathering system; loading the compressed
natural gas under ambient temperature conditions in-t~ a pres-
sure vessel means mounted for transporting by a -transport
vehicle, said loading being termina-ted aEter said pressure
vessel means contains a selected discrete batch of natural gas
in a relatively static confined state, compressed to a pres-
sure in excess of about 800 p.s.i.; transporting said pressure
vessel means containing said compressed, conEined discrete
batch of natural gas from said gas well(s) location to said
terminal facility located at a delivery location, said pres-
sure vessel means and said confined discrete batch of natural
gas contained therein remaining generally at ambient temperature,
and being transported under ambient temperature conditions,
without requiring refrigeration and thermal insulation of said
vessel means; and off-loading the compressed discre~e batch of
natural gas confined with.in said pressure vessel means through
conduit means, and under ambient temperature conditions.
The invention, as also herein claimed, lies in a
system for transporting discrete batches of natural gas at
high pressures ~nd under ambient tempera-ture conditions from a
gas well(s) location to a terminal facili-ty located at a
delivery location, including: pressure vessel means moun-ted
for transportation by a transport vehicle, and incl~ldi.ng:
at least one pressure vessel capable of containing a discrete
batch of na-tural gas at T
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ambien-t temperature a,nd at a press~lre in excess oE a~out 800
p.s.i.; and vehicle manifold means connected with said pressure
vessel, said vehicle manifold means being arranged and operable
to safely handle natural gas flowing therethrough at a pressure
in excess of about 800 p.s.i. and including: a manifold conduit;
means connecting said manifold conduit with said pressure
vessel; and vehicle conduit means connected with said manifold
conduit, and including ln series, moving outwardly from said
manifold conduit, flow con-trol valve means; bleed valve means;
and vehicle coupling means; a first terminal located at said gas
well location, and including: means for gathering natural gas
from a gas well(s) at said gas well(s) location; loading mani-
fold means; loading coupling means for detachably connecting
said loading ma~iEold means with said vehicle coupling means, and
including in series, moving outwardl~ from said loading mani-
foldl flow control valve means; bleed valve means; and a loading
coupling connectable with said vehicle coupling means; and
loading conduit means connecting said gathering means with said
loading manifold means, said loading conduit means including
dehydrator means connected therein; and a second terminal located
at said terminal facility at said delivery location, and
including: off-loading manifold means; off-loading coupling
means for detachably connecting said off-loading means with said
vehicle coupling means, and including in series, moving toward
said off-load.ing manifold means, an off-loading coupling con-
I nectable with said vehicle coupling means; bleed valve means;
and flow control valve means; and off-load.ing conduit means con-
nected with said off-loading man,ifold means; all of said flow
control valve means beiny operable for closing off the flow of
natural gas, and all of said bleed valve means being operable
for relieving the pressure be-tween their associated flow con-
trol valve means and coupling means af-ter such associated flow ",,
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control valve means are closed and beEore such associated
coupling means are operated, whereby to assure safe operation
of said system.
Several-objects and many of the attendant advantages
of the present invention will become apparent from the fol-
lowing descrip-tion of the preferred embodiment, when taken
in conjunction with the accompanying drawings.
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FIGURE 1 is a diagrammatic view o:E the Eirst
terminal installation located at the well head end of
the system of the invention, showing in particular the
gathering manifold system, the dehydrator and the com-
pressor arrangement utilized to prepare the natural
gas for loading on the transport vehicle means, and the
loading manifold system;
FIGURE 2 is a diagrammatic view of the second
terminal installation located at the terminal of the trans-
mission pipeline, or other end user location, utilized
for off-loading the natural gas from a transport vehicle,
and showing in particular the heater system for prevent-
ing the formation of undesirable hydrates;
FIGURE 3 is an enlarged diagrammatic view showing
in particular the ~ehicle manifold system, and the bleed
valve arrangements on both the loading and the off-
loading sides thereof; and
FIGURE 4 is a vertical sectional view taken
generally along the line 4-4 in FIGURE 3, showing the
suction hose arrangement for draining any accumulated
liquids from the bottom of the cylindrical pressure
vessels.
The method and system of the present invention are
especially effective for economically transporting natural
gas over-the-road by motor vehicle, from -the first
terminal to the second. Hence, it is this embodiment of
the invention that is described in detail herein.
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However, it is to be understood that the present
method and system can also be utilized with other trans-
port vehicles, and their associated terminals. The choice
of a transport vehicle can include motor trucks, railroad
cars, barges, aircraft, and the likel or even a combination
of these. In each instance the loading and off-loading
method and system will function in the same manner, and a
maximum payload will be carried by the high pressure vessel,
with no loss of weight or space to refrigeration equipment.
Given this explanation, it is to be understood that
where a truck terminal is referred to herein, it might
instead be a railroad terminal, or a terminal established
to handle barges or aircraft. Similarly, the pressure
vessels might be carried by some transport vehicle other
than a motor truck. At the same time, it is again emphasized
that the invention is especially useful for over-the-road
transport of natural gas.
The value of the invention for over-the-road
transport flows from several features thereof. First of
all, by eliminating the need for refrigeration equipment
associated with the high pressure vessels, valuable
weight is saved that translates into a significantly
greatex payload of natural gas per trip. This is especially
important in a motor v~hicle, where highway and bridge
weight limits must be observed. Further, the method and
system of the invention provide for the saf~ and effective
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10733~g
handling of the natural gas at truck terminals, utilizing
relatively untrained personnel. In addition, the method
and system make it possible to use the semi-trailer-carried
pressure vessels already being manufactured for hauling
certain specialty gases, with a limited amount of modifica-
tion thereto. This results in considerable economies in
carrying out the method.
Referring now to the drawings, a first truck
terminal, located at the natural gas well site, is indicated
generally at 2 in FIG. 1, and includes a gathering manifold
system 4, and a loading manifold system 6 having two
truck-loading stations 8 and 10. The terminal 2 is arranged
to load natural gas under pressure into the high pressure
vessels 12 of semi-trailer motor vehicle ~mits 14, which
are designed to be drawn by a motorized cab 16 in the
usual manner. While the loading manifold system 6 is shown
arranged to handle two semi-trailer units 14, it is to be
understood that the system could be enlarged, if desired,
to handle a greater number of such units.
The gathering manifold system 4 is designed to
gather natural gas from a plurality of gas wells 18. While
only three gas wells 18 are shown in FIG. 1, it is to be
understood that other wells can be added to the system, as
indicated by broken lines at 18', or that as few as a single
gas well might be connected thereto. A gathering manifold
20 extends to all of the gas wells 18,and each well is
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connected thereto by a conduit 22 having a flow meter 24
connected therein for measuring the amount of natural gas
taken from the well. A one-way check valve 26 is also
connected into each conduit 22, between its associated
flow meter 24 and the gathering manifold 20, the check
valves 26 functioning to prevent back-flow into the meters
24 and the gas wells 18 connected thereto. This arrange-
ment is especially designed to meet the situation where
well head pressure in one gas well is greater than that in
other gas wells, and functions to prevent flow through the
gathering manifold 20 from well to weli.
The loading manifold system 6 includes a loading
manifold 28 having a plurality of supply conduits 30
connected thereto, one for each truck loading station 8, 10.
Each supply conduit 30 has a flow control valve 32 connected
therein, and has a flexible hose 34 connected to its outer
end. The outer end of the flexible hose 34 carries one ~
half 36 of a conventional quick connect-disconnect coupling
thereon, and a bleed valve 38 is connected in the supply
conduit 30 between the coupling element 36 and the flow
control valve 32 so that pressure can be bled from the
flexible hose 34 to allow safe operation of the coupling.
If desired, pipes with suitable swivel joints can
be substituted for the flexible hoses 34. The choice of
flexible hoses or tubing, or relatively rigid pipes, can
depend on the location of the terminals and other factors.
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Referring now to ~IGS. 3 and 4, the semi-trailer
14 has a plurality of the cylindrical pressure vessels 12
mounted thereon, the number actually emPloyed being a mat-
ter of choice. Indeed, in some instances only a single
vessel 12 might be employed. A vehicle manifold system
40 is mounted on the rear end of the semi-trailer 14, and
is especially designed to handle the loading and off-loading
of natural gas. The system 40 includes a vehicle manifold
42 disposed across the ends of the pressure vessels 12,
the latter having threaded inlets 44 in their ends, each
receiving a collar fitting 46. A control valve 48 of
conventional construction is carried by each fitting 46,
and is connected to the vehicle manifold 42 by a conduit
50, which can be a flexible hose. Thus, each pressure
vessel 12 can be connected and disconnected to the vehicle
manifold 42 merely by operating its associated control
valve 48.
The vehicle manifold 42 has one end of a transfer
conduit 52 connected thereto, the other end of said trans-
fer conduit having a T-branch fitting 54 thereon. A load-
ing conduit system 56 is connected to one side of the T-
fitting 54, and an off-loading conduit system 58 is connected
to the other side thereof.
The loading conduit system 56 has a flow control
valve 60 therein, and a bleed valve 62 at its outer end.
Between the flow control valve 60 and the bleed valve 62
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10~7339~
is an inlet stub 64, carrying half 66 of a quick connect-
disconnect coupllng, which coupling half 66 is designed
to mate with the coupling half 36 carried by the flexible
hose 34. The purpose for the bleed valve 62 is to allow
all pressure to be drained from the fill conduit system
56, before the coupling halves 66 and 36 are disconnected.
Disposed between the flow control valve 60 and the
T-fitting 54 is a one-way check valve 68, designed to permit
flow only in a direction toward the T-fitting 54. Thus,
back-flow from the pressure vessels 12 cannot occur.
The off-loading conduit system 58 includes a flow
control valve 70, and has a bleed valve 72 at its outer
end. Between the valves 70 and 72 is a discharge stub 74,
carrying one-half 76 of a conventional quick connect-
disconnect coupling. The coupling halves 66 and 76 can be
of different design, to prevent the accidental coupling
of the flexible hose 34 to the discharge conduit system 58;
for example, one can be male, the other female.
Between the gathering manifold system 4 and the
20 ~ loading manifold system 6, the first terminal 2 ~ncludes
a compressor unit 78 of suitable construction, and which
preferably includes an after cooler 80. The compressor
unit 78 is connected to the gathering manifold 20 by a
conduit system 82, which includes in series a conventional
oil/gas separator unit 84, followed by a dehydration
unit 86 for removing moisture from the natural gas prior
to compression thereof. In some gas wells, where the
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natural gas is free of oil, the separator unit 84 need notbe employed in the system.
The normal standard or moisture allowable in
pipelines is 7# water/mm cubic feet of gas. Where the yas
taken from a gas well 18 exceeds this, the moisture must
be removed. This is the purpose for the dehydration unit
86.
The present invention contemplates transporting
natural gas in the pressure vessels 12 at a pressure in
excess of 1500 p.s.i., and usually within the range of from
2000 p.s.i. to 3000 p.s.i. Where well head pressure is
below this level, the purpose for the compressor unit 78
is to raise it into this range. If well head pressure
is already in this desired operational range, the compressor
unit 78 may not be initially required, but can become
necessary duringgas withdrawals when the well head pressure
falls to a more normal value.
Flow through the conduit system 82 from the ;
gathering manifold 20 is controlled by a pressure control
valve 88, supplied with line pressure by a pressure conduit
90. The pressure control valve 88 functions to establish
a relatively constant pressure in the conduit system 82
and the components thereof, regardless of the well head
pressures of the different gas wells 18. This relatively
constant system pressure offers several advantages, all
of which contribute to efficient operation of the
invention. -14-
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First of all, a relatively constant system pressure
to the dehydration unit 86 assures a constant speed on the
dehydrator pump, and relatively consistent drying of the
natural gas. Second, by supplying the compressor unit
78 with natural gas at a relatively constant pressure,
maximum operational characteristics are obtained, and a
relatively constant filling time is achieved f~ the
pressure vessels 12 on the semi-trailers 14.
A main flow control valve ~2 is connected in the
conduit system 82 before the loading manifold 28, and a
. by-pass control valve 94 is connected between the main
flow control valve 92 and the compressor unit 78. The by-
pass port of the valve 94 is connected by a by-pass con-
duit 96 to the inlet side of the pressure control valve 88.
Connecting the by-pass conduit 96 to the inlet
side of the pressure control valve 88, rather than to the
outlet side, offers unique benefits that constitute a
desirable feature of the present invention. It is known
that significant drops in temperature are associated with
corresponding decreases in gas pressure, as when high
pressure natural gas from the outlet of the compressor
unit 78 is introduced to a low pressure region On the inlet
side of the compressor unit. Given the operating pres-
sures of the invention, it is possible that this pressure
drop could result in creating temperatures in the range of
-20'~F or greater, which could cause damage to
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1073399
the materials and construction techniques utilized in
normal valve and other components.
By connecting the by-pass conduit 96 to the inlet
side of the pressure control valve 88, pressure flowing
from the compressor unit 78 is mi~ed with pressurized
natural gas from the gathering manifold system 4, which
will normaly be at a significantly greater pressu~e than
will natural gas on the outlet side of the valve 88.
When the compressor unit 78 shifts to a by-pass mode,
the pressure in the manifold gathering system 4 will
build up to the highest well head pressure 'in the system,
since there is then no flow from the manifold 20. Thus,
the pressure drop incurred by the by-passing is minimized,
as is the resultant temperature change.
In the event the temperature drop resulting from
the by-passing produces operating temperatures that are
too low, it may become necessary to put a heater on the
by-pass conduit 96. If well head pressures are sufficiently
high~ however, this should not prove necessary, with the
arrangement of the invention.
In operation, natural gas is pulled from the gas
wells 18 through the gathering manifold 20 and the
conduit system 82, by the compressor unit 78. The main L
control valve 92 is open to supply natural gas to the load-
ing manifold system 6, and from there it supplied
through the flexible conduit 34 to the pressure vessels
12. When the pressure vessels 12 are filled to the desired !~
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~3399
operating pressure, the by-pass control valve 94 opens,
and flow from the compressor unit 78 is routed by the
- by-pass conduit 96 to the inlet side of the pressure con-
trol valve 88. Thereafter, the compressor unit 78 in
effect just recirculates the same gas.
Should the pressure build up too much in the con-
duit system 82 on the compressor side of the pressure
control valve 88, pressure conducted through the conduit
90 will be effective to close the control valve. This
acts as a safety shutdown of the system.
The compressor arrangement of the invention in-
cludes a further safety feature, designed to make the
system fail safe. A high pressure over-ride switch 98
is connected to the compressor unit 78, and is operated
by a conduit 100 connected to the conduit system 82 after
the by-pass valve 94, but before the main flow control
valve 92. The high pressure over-ride switch 98 acts ~ ! '
as a compressor unit shut-down, should the by-pass
valve 94 fail to function.
As has been noted, the compressor unit 78 includes
an after cooler 80, which can be employed to increase
the density of the natural gas by lowering its temperature.
This allows a greater volume of natural gas per trailer L
load. It is to be noted, however, that the present method
and system do not contemplate keeping the gas in a
refrigerated condition during transport, which would require
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~07~39~
the use of heavy insulation and refrigera-tion systems
that would significantly lower the carrying capacity of
the semi~trailers 14. Rather, once placed in the pres-
sure vessels 12 under high pressures in excess of about
- 1500 p.s.i., it is expected that the natural gas will be
transported under ambient pressure conditions. In has
been Eound that natural gas can be effectively transported
in this manner, and that refrigeration to sub-freezing
temperatures is not necessary.
Turning now to FIG. 2, the second or off-loading
terminal of the system of the invention is shown cJenerally .;
at 102, and includes an unloading manifold 104 having a
pair of discharge conduits 106 connected thereto, one for
each of a pair of off-loading stations 108 and 110. Each
discharge conduit 106 includes a flow control valve 112,
and has a flexible hose 114 connected thereto, the
outer end of each hose 114 carrying one half 116 of a
conventional quick connect-disconnect coupling, adapted
to mate with the coupling half 76 on the semi-trailer 14.
A bleed valve 118 is positioned between the flexible 1,
hose 114 and the flow control valve 112, and is utilized
to bleed the system before the coupling valves 116
and 76 are disconnected.
As mentioned above for the flexibe hoses 34,
tubing or rigid piping with suitable swivel joints can
be used instead, if such is desired. The need is for a
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3399
movable conduit, in both cases.
Natural gas is collected from the unloading mani-
fold 104 by a conduit 120, which leads through a main
flow control valve 122 to a gas heater 124, a safety
pressure relief valve 126 being connected to the conduit
120 after the flow control valve 122. The outlet of the
gas heater 124 is connected by a conduit 128 to the lnlet
of a flow meter 130, the outlet of which is connected to
a conduit 132 leading to the gas transmission pipeline,
or possibly a storage vessel (not shown).
It has been found that when natural gas is dis-
charged at a fast rate, such as will normally occur when
releasing natural gas under high pressure from the pres-
sure vessels 12, damaging hydrates can be formed. It
has also been found that the possibility of such hydrates
forming can be eliminated by use of the gas heater 124
of the invention. Thus, the system of FIG. 2 provides
an effective means for releasing natural gas from khe
pressure vessels 12 in proper condition for its trans-
mission through a pipeline, or for other end uses. I
The temperature of the natural gas flo~ing through t
the conduit 128 is controlled by a heater temperature con-
trol unit 134, connected at one end to the conduit 128,
and at its other end to the operating chamber of a by-
pass valve 136 that is effective to channel natural gas
from the conduit 120 either through the heater 124 or into
a by-pass conduit 138. Flow through the heater 124
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339~9
and hence the conduit 128, is ultimately under the control
of a remotely operated control valve 140, controlled by
a sensing unit 142 connected across the flow meter 130.
Also connected across the meter 130 is a conventional
flow recorder 144, and by knowing the temperature and the
flow rate of the natural gas entering the conduit 128,
the amount thereof can be accurately measured.
The pressure relief valve 126 is intended to
provide emergency relief to the system. Further safety
features include a temperature control over-ride sensing
unit 1~6 and a pressure control over-ride sensing
unit 1~8, both connected to the conduit 128, and connected
through the sensing unit 142 to operate the remote flow
control valve 140.
The method of the invention includes the steps
of taking the natural gas from a gas well gathering system
at the gas well(s), compressing the gas to a pressure
in excess of 1500 p.s.i., and usually to a pressure within
the range of 2000 p.s.i. to 3000 p.s.i., loading the com~
pressed natural gas into pressure vessel means mounted
for transporting by a motor vehicle, transporting the
pressure vessel means with the compressed gas therein
at ambient temperatures to an end user terminal location,
off-loading the compressed natural gas through conduit
means, and heating the compressed natural gas as it flows
through said conduit means to prevent the formation of
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hydrates. By transporting the natural gas at the indicatedhigh pressures and under ambient pressure conditions, the
use of heavy and space-occupying refrigeration equipment
such as is required in the method of U. S. Patent
No. 3,232,725 is eliminated, with the result that natural
gas can be economically transported over the road.
The method also contemplates passing the natural
gas through a dehydration unit before it enters the
compressor unit, if needed to remove moisture therefrom.
Further, the method includes the step of passing the natural
gas through a gas/oil separator, placed before the ~ehydrator
unit, where such i5 re~uired because of the nature of the
flow from the gas well(s).
The manner in which the loading system of FIG. l
functions to carry out the first portion of the method is
believed obvious from the above description thereof.
The pressure control valve 88 functions to supply natural
gas at an even rate of flow to the separator unit 84 and the
dehydrator unit 86, and ultimately to the compressor unit
78. The compressor unit 78 includes the cooling coils
80, which act to increase the density of the compressed
gas and the flow control valve 92 controls the supply of
compressed natural gas to the manifold 28.
In order to load a semi-trailer unit 14, such is
first placed at one of the loading s-tations 8 or 10, and
the coupling halves 36 and 66 are then joined. The control
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valves ~8 and 60 are opened, and then the main flow control
valve 92 is opened to begin the flow of natural gas.
~fter the pressure vessels 12 are filled, the individual
control valves 48 thereon are closed, and the control ;
valve 60 is closed. The main control valve 92 is closed to
terminate the supply of natural ~as, and thereafter, the
bleed valves 62 and 38 are operated to relieve pressure
on the coupling elements 36 and 66. The quick connect-
disconnect coupling is then disconnected, and the loaded
semi-trailer 14 is ready for transport.
During loading of the pressure vessels 12, the
pressure within the line leading thereto will reach a
pre-determined value, causing the by-pass valve 94 to
operate, whereby the natural gas will be by-passed through
the conduit 96 to the inlet side of the pressure control
valve 88. As noted above, this point of connection of the
by-pass conduit 96 will minimize temperature changes occur-
ring from such by-pass of the compressed natural gas.
Should pressure within the line 82 build above a pre-
selected level, the pressure control valve 88 will simplyclose. In the event of component failure, the fail-
safe switch 98 will act -to close down the compressor unit
78.
Turning now to the second or off-loading terminal,
unloading of the natural gas is carried out as follows.
The coupling elements 116 and 76 are joined and the valves
48 and 70 are opened. The flow control valves
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112 and 122 are then opened, and thereafter flow is con-
trolled by the valve 140. The heater unit 124 is effective
to heat the natural gas as it is unloaded, to prevent
- the ormation of hydrates.
It has been found with the invention that some
liquids can accumulate within the pressure vessels 12.
In order to provide for removal thereof during off-
loading, the pressure vessels 12 are each provided with a
suction hose 150, shown in FIG. 4. The end of the hose
150 is secured in the fitting 46, and the other end there-
of lies on the bottom of the pressure vessel 12, where any
liquids will accumulate. As the natural gas is off-
loaded, the liquids will simply be entrained therein, and
will pass through the suction hose 150 and the conduit
system.
When off-loading is complete, the valves 122 and
112 will be closed, along with the valves 48 and 70. There- ¦
after, the bleed valves 72 and 118 will be opened to relieve
any pressure on the opposite sides of the quick connect-
disconnect coupling, and then the coupling will be
disconnected.
It is believed obvious Erom the above how the present
method and system can be adapted for use with other kinds
of transport vehicles and other kinds of vehicle terminals.
The method of the invention remains the sama, the equip-
ment is substantially identical and functions in the same
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manner, regardless of the kinds of transport vehicles or --
terminals utilized.
The present method and system fulfill all of the
objects set forth hereinabove for the invention, and make
it possible to utilize the natural gas from wells which
have heretofore been considered impossible to use. Thus,
the available supply of natural gas energy is increased
by the invention. In addition, the advantages offered
by the invention will open further opportunities for
exploring new natural gas wells, and will make it possible
to bring such wells into production long before a collector
pipeline system can be built.
Obviously, many modifications and variations oE
the present invention are possible.
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