Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INVENTION
Natural gas wells are almost always located in remote "off-grid" locations,
which are not
economical to connect to normal electrical power distribution systems. In
order to prevent the
formation of ice-like hydrate within the piping and valves (especially at
pressure-drop locations
such as the wellhead choke), free water is removed (separated), and then a
chemical (typically
methanol) is injected by pump. Other similar applications would include
injection of corrosion
inhibitor, scale inhibitor, paraffin inhibitor, biocide, demulsifier, and
others, as typically required
in both natural gas and oil production.
Common pneumatic injection pumps are typically used for this purpose, driven
by venting
some of the natural gas from the high-pressure line, into the atmosphere. In
addition to being a
gross waste of the potential heating value energy contained in the vented gas,
this has some other
negative effects, including loss of gas sales revenue, and increased
greenhouse gas emissions.
Also, in the event that sour gas (containing poisonous H2S) is the only gas
available at a given
location, venting it creates a more immediate safety hazard to all life in the
area.
Recently, some sites have started using solar photovoltaic (PV) power
generation systems,
along with electric methanol pumps using rotational-type electric motors, and
batch-injection
timers. Unfortunately, the amount of methanol injection required is usually
higher during the
winter, just at the time when solar systems produce the least power (due to
reduced daylight and
poor low-temperature battery performance). Also, since PV cells only produce
the rated power
under "peak sunlight" conditions, this means that a large number solar panels
are needed to collect
enough power to last through the night, and also a large number of batteries
must be used to store
power during the "off-peak" times. The December/January average "peak
sunlight" is limited to 2-
3 hours per day throughout Southern Alberta (even less in the north, and
British Columbia),
assuming the weather is "average". Long periods of cloud or snowfall can cause
the solar PV
system to shut down for lack of power.
If the pump stops injecting methanol, the main gas pipeline will stop flowing
due to
hydrate formation, resulting in lost production and damaged equipment. It is
not acceptable or
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economic to send equipment and personnel out to these remote locations to thaw
hydrated gas lines
on a regular basis, especially in the winter. Reliability is extremely
important.
The invention will consist of a system using an electric methanol injection
pump that is run
by reliable power, generated from the DMFC "on-demand". This will be intended
for continuous,
unattended operation in remote areas with a wide variety of weather
(specifically for winter
conditions). This type of fuel cell is distinctly advantageous from other
types, in that it converts
liquid methanol at atmospheric pressure directly into electricity, without
having to create or store
high-pressure hydrogen. Since there is usually a large tank of liquid methanol
on site already (to
inject), the system will merely use a small portion (typically 0.4%) of this
volume to create the
required power in the fuel cell (or else draw from a much smaller separate
tank). The heat by-
product will serve to keep the system and batteries warm, to improve operation
efficiency and
lifetime cycle. Optionally a hybrid power system may be used, in which power
is supplied by both
the DMFC fuel cell and PV solar panel, in order to increase the operational
lifetime of the DMFC.
For the lower-pressure injection ranges, an electromagnetic solenoid-type pump
design
appears to have great potential, in terms of being simple, economic, leak-
free, and low-
maintenance (no shaft seals). It is also uniquely easy to set a specific
constant flow rate using a
simple control panel, without having to resort to stroke counting. It is very
energy-efficient and has
a large turndown ratio (max to min flow range with a given piston size), which
works nicely with
the intended constant-delivery method. This is much better than the method of
timed batch-
injecting, followed by a long period of no flow, as is often required by
rotational-type electric
motors (hydrates can form in the pipeline before the next batch is injected).
Multiple solenoid-
pumps in series could boost pressures as needed, and there is no risk of
damage or over-pressure,
in the case where the pump stalls (i.e. valve shutoff). Normal rotational-type
electric motor pumps
(or other commercially-available pump types) may be required for the higher-
pressure ranges, or
for other circumstances.
The inherent reduction in greenhouse gas emissions provided by adopting this
technology
would provide improved air quality, while helping clients increase production
of natural gas. This
will improve public relations, especially on a "good-neighbor" scale with
local landowners who
need to be satisfied prior to drilling new gas wells. Also, governmental
legislation (or industry self-
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regulatory guidelines) may eventually lead to additional client savings in the
form of "carbon-
credits". Using this type of DMFC pump system (compared to pneumatic pump
venting natural
gas, which is mostly methane) would reduce C02-equivalent (C02e) emissions by
a ratio of about
13,650:1. This is due to the C02e (equivalent) rating of methane being 21
times higher than C02,
and also the relative energy efficiency (650 times higher) of the direct
methanol fuel cell, relative
to wasting the gas by venting.
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PRIOR ART
Chemical injection systems of various types of been known and used for many
years, some
patent applications of which are listed below.
Pneumatic (gas powered, venting):
CA2215652 MERCER, MARK A.G.
CA2411214 MCKEARY, LEONARD E.
Pneumatic (gas powered, non-venting / pipeline pressure drop required)
CA2344632 GRIMES, EDWARD C. et al
Electric (grid power, or solar powered):
CA2540400 BURNS, PATRICK J., SR. et al
CA2166076 MARSHALL, STEPHEN E. et al
Although the preceding prior art are related to the field of the invention,
none use the same
method, or necessarily meet the same design goals. To the best of the author's
knowledge, there is
no prior art for a DMFC powered pump system.
Direct methanol fuel cell power systems are already well known, and are
recently
commercially available. Similarly, electromagnetic solenoid pumps are also
known. However
neither of these devices is currently used in this well site chemical
injection application, either
separately or in combination with each other as proposed. The invention
teaches that a complete
"stand-alone" system including these items and other specially designed
components (in the
configurations claimed) provide a unique and improved solution to an existing
industrial and
environmental problem.
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SUMMARY OF THE INVENTION
The invention is a self-contained system comprised of an electric power
generating system,
an electric power storage system (batteries), and an electric chemical
injection pump system,
housed together in an insulated weatherproof enclosure. The power generating
system consists of a
direct methanol fuel cell (DMFC) alone, or else a hybrid system using both
DMFC and optional
photovoltaic (PV) solar panel in combination, plus the control systems as
needed to regulate the
power generated to match the recharging requirements of the batteries. The
electric power storage
system would typically consist of one or more common electrochemical
batteries, to provide a
power reserve and enable better matching of power generation to load (power
consumption). The
injection pump system uses this power (supplied via the recharged batteries)
to inject chemical into
a pipeline at a particular flow rate and pressure, as determined by a pump
controller. The injection
pump may be either a type that uses a conventional rotary electric motor, or
preferably an
electromagnetic linearly reciprocating solenoid type. The pump controller may
be manually
adjusted by a local operator, or else optionally controlled remotely by an
electric set-point signal.
If the injection chemical happens to be methanol of suitable quality, it may
be optionally
connected to the supply line to the DMFC in lieu of having a separate methanol
supply. Also, in
the event that the waste heat generated by the DMFC is not sufficient to keep
the inside of the
enclosure warm enough for correct operation during very cold weather, an
optional automatic
electric heater may be added.
DETAILED DESCRIPTION OF THE INVENTION
The invention is illustrated schematically in figure 1. Optional or alternate
components and
configurations are shown in the clouded areas.
The injection chemical storage tank 1 contains the liquid chemical, typically
at atmospheric
pressure in an amount suitable for sustained remote, un-attended injection
over a long period of
time (typically a month or longer). Chemical is fed to the injection pump 3
via a suction tube 2.
The injection pump 3 pumps the chemical into the high-pressure pipeline 5 via
discharge tube 4.
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Methanol of suitable quality is stored in a small methanol cartridge or
container 7, typically
at atmospheric pressure in an amount suitable for sustained remote, un-
attended operation of the
direct methanol fuel cell (DMFC) 10 over a long period of time (typically a
month or longer). If
the injection chemical happens to be methanol of suitable quality, it may be
optionally connected
to the supply line to the DMFC via tube 8, in lieu of having a separate
methanol supply. Methanol
is fed to the DMFC 10 via tube 9.
The direct methanol fuel cell (DMFC) 10 combines the liquid methanol plus
oxygen from
the air in a reaction that produces direct-current (DC) electric power, plus
by-product waste
streams that typically include water vapor, a small amount of carbon dioxide,
and hot air. It also
contains an integral charge control system (not shown) in order to determine
and control the
amount of power produced to match the demand of the batteries. The DC power is
conveyed to the
batteries 19 via an electrically conductive wiring system 18. Cold air 13 is
drawn into the insulated
enclosure 6, and into the fuel cell via a cold air inlet vent 12, under the
action of the electric fuel
cell air fan 11, which is integrated into and controlled by the fuel cell. The
waste water vapor and
carbon dioxide are conveyed to the outside of the insulated enclosure via tube
14, which preferably
exits near the warm air outlet vent 16, in order to prevent freezing off at
the tip. Hot air 15 from the
fuel cell circulates freely within the insulated enclosure, prior to exiting
via the warm air outlet
vent. This hot air also helps to keep the enclosed equipment above the minimum
operating
temperature during cold weather. A fuel cell control panel 17 on the exterior
surface of the
insulated enclosure allows for operator control and status indication without
opening the insulated
enclosure.
In the event that the waste heat generated by the DMFC is not sufficient to
keep the inside
of the enclosure warm enough for correct operation during very cold weather
(or if the ambient
weather is overly hot), an optional automatic electric heater/cooler 23 may be
added. This
heater/cooler would have a built-in thermostat, set to maintain the
temperature of the equipment
inside the insulated enclosure as needed for correct operation. It would not
consume power unless
additional heating or cooling is required.
The optional photovoltaic (PV) solar panel 24 (mounted outside the insulated
enclosure)
converts solar energy from the sun into direct-current (DC) electric power. A
solar charge control
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system 25 is optionally included in order to determine and control the amount
of power produced
to match the demand of the batteries, and set to provide as much power as the
available sunlight
conditions will allow, prior to the direct methanol fuel system having to do
so. This permits the
fuel cell system to operate only when needed, thus preserving its longevity,
increasing reliability,
and reducing methanol consumption. The DC power is conveyed to the batteries
19 via an
electrically conductive wiring system 18.
The DC electric power is conveyed from the batteries 19 to the pump controller
20 via an
electrically conductive wiring system 18. This pump controller allows for
operator control and
status indication without opening the insulated enclosure. In the case of the
pump being of an
electromagnetic linearly reciprocating solenoid type design, the pump
controller provides operator-
adjustable electrical pulse frequency modulation, in order to cause the pump
to stroke at the same
frequency, thus controlling the chemical flow rate. In the case of the pump
being a traditional
rotary electric motor pump, the pump controller provides a timer function,
such that the pump runs
at full speed for a set period of time, then shuts off for a set period of
time, thus determining the
average flow rate as required. In either case, the electrical power is
conveyed from the pump
controller to the pump via an electrically conductive wiring system 18.
Optionally the pump
controller can be set to accept a remote electric set-point signal via remote
signal wire 21, which
would over-ride the local settings and enable the pump rate to be determined
by another device or
remote operator via a communication system interface.
Surplus power may optionally be supplied to external devices in multiple
voltage levels,
via the external power receptacle 22. Similarly, power can be collected from
external power
sources if needed and available.
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