Note: Descriptions are shown in the official language in which they were submitted.
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N~TURAL G~S FILTERING ~PP~R~TUS
This invention relates to an apparatus for filtering
suspended impurities from gas and, more particularly, to a
device that may be used to filter both moisture such as
water vapour and solid particulate impurities such as sand,
wax and dirt from natural gas.
It is common in devices for filtering natural gas
to pass the gas through a filter bed thereby removing suspended
impurities. Devices of this type, however, are inefficient
because accumulated impurities tend to clog the bed thereby
inhibiting gas flow and requiring the devices to be frequently
disconnected from the gas supply in order that the bed may
be replaced or cleaned. Moreover, devices are unsatisfactory
for the removal of moisture from gas as moisture tends not
to precipitate in the filter bed. Difficulty is encountered,
in particular, with the removal of fine droplets of moisture.
Further disadvantages of known devices include low capacity,
difficulty with respect to installation, decreased Eilter
efficiency at hi~h gas pressure and a narrow range of applications
~ith respect to the type of gas filtered and the gas transportation
system to which the device may be joined.
l`he separation of suspended impurities from natural
gas is desirable so as to improve tha energy efficiency of
the gas as a fuel, improve the efficiency of the gas trans-
portation system and prevent impurity related breakdowns in
the system. In particular, the accumulation of moisture in
either the filtering device or the transportation system may
result in freeze-ups at temperatures below the freezing
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point of the moisture, thereby inhibiting gas flow and increasing the energy
required to be expended in piping the gas. Freeze-ups may also descrease fil-
tering efficiency and dam~ge both the device and transporation system.
To prevent pipe freeze-up it is known to insert alcohol or some
other liquid having a low freezing point into the gas supply so as to lower
the freezing point of the moisture. Such a method is not only expensive, but
lowers fuel efficiency without hindering pipe freeze-up to any significant
extent.
The aforementioned disadvantages may be overcome by the apparatus
of the invention which provides a device comprising both baffles and a porous
filter bed within a filter tank and means for collecting filtered impurities.
Thus, this invention provides for a gas filtering apparatus for the
removal:~rom gas of suspended impurities, selected from the group consisting
of moisture, alcohol and solid particulate impuritiesJ and preferably a member
selected from the group consisting of sand, wax and dirt particles, comprising
a filter tank having an inlet and an outlet for gas flow through the filter
tank from the inlet to the outlet, baffles within the Eilter tank at least
a majority of which the gas must flow through and positioned such that the
baffles inhibit the gas flowJ a porous filter bed within the filter tank
positioned such that the gas must flow through the filter bed and means for
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collecting the filtered impurities.
The provision of baffles within the filter tank permits the apparatus
of the invention to be used in high pressure, high volume filtering applications
`; such as those typically encountered in natural gas transportation systems. The
baffles deflect the gas flow so as to cause turbulence and assist the porous
filter bed in filtering impurities. Perforations, preferably ~" in diameter,
are placed in the baffles so as to pe:rmit gas flow through the baffles.
The provlsion of a porous filter bed, which, in a preferred embodiment
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may be comprised of particles of filter material that are resistant to
deterioration when subject to liquid or gas under pressure (such as gravel,
glass and steel and, which, in a further preferred embodiment may be
substantially comprised of particles over one inch in size, permits the
filtering of bo~h liquid and solid impurities. The filter bed need only be
replaced infrequently and is readily cleanable. Moreover, the particles of
filter materials not only filter impurities from the gas but also act as
miniature baffles deflecting the gas flow in order to cause turbulence and
enhance the filtering efficiency of the device. The provision of particles
of filter material substantially grea~er than one inch in diameter permits
the apparatus of the invention to be used in high pressure and high volume
filtering applications. A suitable filter material such as gravel is in-
expensive and readily available.
The invention also includes means for collecting the filtered impur-
ities. In a preferred embodiment, the me~ms for collecting the filtered
impurities comprises a holding tank and drainage pipe posit:ioned such that the
filtered impurities collected in the filter tank may pass
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due to gravity Erom the filter tank, through the drainage
pipe and into the holding tank. A blowout pipe and valve
connecting the holding tank with the atmosphere may be
provided so as to enable the removal of impurities collected
in the holding tank. Such a means for collecting filtered
impurities enhances filtering efficiency in that the filtered
impurities do not accumulate in the filter tank thereby
hindering gas flow through the apparatus. Liquid impurities
are readily filtered from gas as the collection of the
impurities in a separate tank prevents them from vaporizing
in the filter tank or being blown as a result of gas pressure
and volume out of the apparatus and back into the gas transportation
system. Thus, very fine droplets of liquid impurities may
be filtered. The provision of a blowout pipe and valve
attached to the holding tan~ permits the removal of the
impurities collected in the tank by allowing the collected
impurities to be blown from the apparatus by the gas pressure
when the valve is opened. Special pumping of the collected
impurities from the device is not required nor is it necessary
for the gas flow to be bypassed around the apparatus when it
is desired to remove the impurities. The apparatus of the
invention thereby permits the continuous filtering of gas.
Collected impurities need not be blown into the atmosphere
but may be collected in a suitable vessel for disposal.
Collecting the filtered impurities in a separate holding
tank also ensures that the filtering efficiency of the
apparatus remains constant.
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In a preferred embodiment of the invention, means
comprising a pipe and ~alve arXangement are provided for
bypassing the gas flow around the apparatus.
Infrequently, it may be necessary to clean the
filter or holding tanks. In a preferred embodiment, wash-
out means are provided comprising a wash-out inlet on the
filter tank, a filler line pipe connecting the filter tank
with the atmosphere and a filler line pipe valve. In conjunction
with the bypass and blow-out means, the apparatus of the
invention may be cleaned by by-passing the gas around the
apparatus by way of the bypass means, filling the apparatus
of the invention with a suitable cleansing solution by way
of the wash-out means and then blowing the cleansing solution
out of the device by opening the blow-out line and redirecting
the gas flow back through the apparat.us. The provision of
wash-out means enables the device to be cleaned and permits
the removal of any accumulated impurities that cannot be
removed by the blow-out means~
The apparatus of the invention is easily adaptable
. 20 to any type of gas supply or gas transportation system~
The device does not require the substantial alteration of
the gas supply or transportation system save for the provision
of means to direct the gas flow into the apparatus and back
` into the transportation system or gas source once the filtering
function has been completed~ Thus, the device may be easily
and quickly installed. In addition, the apparatus is
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fully reversible in that either the inlet or the outlet of the filter
tank may be used as the gas supply source. The simple design of the apparatus
ensures that the apparatus may be inexpensively manufactured and not prone
to breakdown.
The apparatus of the in~ention may be manufactured from one of
a number of materials, but preferably is manufactured from steel. The
apparatus is particularly adaptable for natural gas pipeline applications of
pressures o:f 1000 pounds per square inch and volumes of gas of 20,000 ft
per hour. Means may be provided for the prevention of the corrosion of the
apparatus as well as for the release of gas pressure in the apparatus when
the pressure becomes excessive.
An advantage of the apparatus o the invention is that the removal
of liquid impurities such as water droplets inhibits freeze-up thereby
improving the efficiency of the gas transportation system in that gas may
be transported at temperatures below the freezing point of the liquid
impurities. The apparatus may be prevented from freezing up by installing
the apparatus underground below the frost line. Moreover~ the insertion of
alcohol or some other liquid with a low freezing point into ~he gas so as
to prevent reeze-up is not required. Thus, fuel efficiency is maintained.
The prevention of pipe freeze-up also permits the uninhibited flow of gas
through the filtering and gas transportation systems thereby resulting in
substantial savings in transporting the gas. Finally the filtering
efficiency of the apparatus of the invention remains constant.
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The removal of suspended impurities f~om natural
gas improves the energy e~ficiency of the gas as a fuel,
improves the efficiency of the gas transportation system and
prevents breakdowns in the system.
Further advantages that may be achieved by use of
the invention will become apparent from the following
description of a preferred embodiment of the invention,
given by way of example only, illustrated in the accompanying
drawings.
In drawings which illustrate the preferred embodiment
of the invention;
Figure 1 is a side elevation partly in section of
the preferred embodiment.
Figure 2 is an end elevation of this embodiment.
Figure 3 illustrates a non-permeable baffle.
Figure 4 illustrates a permeable baffle.
Figure S illustrates a second permeable baffle. ~`
The apparatus illustrated comprises a filter tank
1 adapted for installation in series or in parallel on a
natural gas pipeline to provide for a flow of natural gas
; through the apparatus. The filter tank may be joined to the
gas pipeline by one of a number of means, but, in the
embodiment illustrated, is joined in parallel to the gas
pipeline by way of inlet pipe 2 and outlet pipe 3. In this
manner, gas flowing through the pipeline may pass in suc-
~ cession from the pipeline, through the inlet pipe, the
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filter tank, the outlet pipe and back into the pipeline dol~nstream from
the inlet pipe.
A porous filter bed ~ is provided within the filter tank and
positioned such that the gas must flow from the inlet pipe through the filter
bed (therein being filtered~ and into the outlet pipe. The filter bed
is composed of particles of material substantially greater than one inch in
diameter that do not or tend not to disintegrate or deteriorate when subject
to liquid or gas under pressure, preferably particles of a material selected
from the group consisting of gravel, glass and steel.
A series of baffles are arranged within the filter tank so that
the gas flow through the filter tank is deflected. In the embodiment
illustrated, however, non-permeable baffle 5, illustrated in Figure 3,
is secured to the inner wall of the filter tank near the inlet pipe. The
gas flow from the inlet pipe is directed by means of a filter tank inner
inlet pipe 6 onto the non-permeable baffle such that the gas flow is diverted
into the filter bed. Permeable baffles 7 and 8, illustrated in Figures
and 5 respectively~ are positioned within the filter tank near the inlet
end such that the gas flow passes through the baffle perforations 9.
In the embodiment illustra~ed, the baffle and pipe arrangement within the
inlet end of the filter tank is the converse of that within the outlet end
of the filter tank. The apparatus of the invention is thereby fully
reversible in that either the inlet pipe or the outlet pipe may serve as
the gas supply to the apparatus.
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A drainage pipe 10 is joined to the filter tank
such that it connects the`filter tank and a holding tank 11.
The holding tank may be secured to the filter tank in any
suitable manner so long as the ~ilter impurities collected
in the filter tank may pass due to gravity from the filter
tank through the drainage pipe and into the holding tank.
In the embodiment illustrated, the holding tank is positioned
directly below the filter tank and secured to the filter
tank by support members 12 and 13.
In the embodiment illustrated, a bypass pipe 14
connecting the inlet pipe and the outlet pipe, a blow out
pipe 15 connecting the holding tank with the atmosphere, and
a filler pipe 16 connecting the filter tank with the atmosphere,
are also provided. A lifting lug 17 is fixed to the filter
tank. All pipe junctions are secured so that the gas does
not leak from the apparatus. Valves for selectively obstructing
the gas flow are provided on all pipes. A blowout over
pressure safety valve 18 is also optionally attached to the
bypass line. This over pressure safety valve may, in a
further em~odiment, be attached to the main gas pipeline.
A number of preventative measures may be taken to
prevent the corrosion of the device, such as the installation
on the apparatus of a zinc anode, prime coating of the
apparatus or the wrapping of the apparatus with dinsul tape.
Gas flowing from the natural gas pipeline may be
; diverted from the pipeline through the inlet pipe and into
the filter tank by way of the`filter tank inner inlet pipe.
The gas flow is then inhibited and directed by the non- -
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perrrleahle baffle through the filter bed. The gas then
passes through the permeable baffles thereby further inhibiting
gas flow. Impurities are filtered from the gas by way of
the filter bed and baffles. The impurities then pass due to
gravity through the drainage pipe and into the holding tank.
The reciprocal baffl~s within the outlet end of the filter
tank also inhibit gas flow and assist in the filtering
process. The filtered gas then passes into the filter tank
inner outlet pipe 19, through the outlet pipe and then returns
to the pipeline. During the filtering operation bypass pipe
valve 20, filler pipe valve 21, and blowout pipe valve 22
remain closed such that the gas flow through those pipes is
prec].uded. Drainage pipe valve 23, inlet pipe valve 24 and
outlet pipe valve 25 are open so as to permit the passage of
gas and i.mpurities.
Irnpurities collected in the holding tank may be
removed therefrom by opening the blowout pipe valve. The
gas pressure in the apparatus thereby forces the collected
impurities through the blowout pipe and into the atmosphere
2Q or a suitable container.
The filter and holding tanks may be cleansed by
diverting the gas flow through the bypass pipe with the aid
of ~he inlet, outlet and bypass pipe valves. Alcohol, water
or some other suitable cleansinc3 solution may then be
introduced into the tanks by way of the filler pipe. The
cleaning solution and any accumulated impurities in the
apparatus may be re~oved from the apparatus by closing the
filler pipe valve, opening the blowout pipe valve and allowing
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a stream of gas under pressure to enter the apparatus. Thus, gas passes
through the inlet pipe and into the apparatus thereby forcing the collected
cleansing solution and impurities into the atmosphere by way of the blow out
pipe.
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