Note: Descriptions are shown in the official language in which they were submitted.
CA 02759967 2011-11-29
SETTLING VESSET, AND METHOD OF USE
FIELD OF THE INVENTION
The present invention relates generally to a vessel for use in removing
particulate matter from a fluid
stream. More particularly, the present invention relates to a horizontal
desander having internal baffles, ribs,
or flow barriers to assist in the removal of particulate matter from a fluid
stream.
BACKGROUND OF THE INVENTION
In oil and gas operations, sand is often present within fluid streams removed
from a wellbore. For
example, sand may be used as a proppant in fracturing operations, and as a
result, may be present in the
resulting flow-back production fluid. Further, increasing amounts of sand may
be produced as oil and gas
field production matures. As the presence of sand within well fluids may
damage or erode surface
equipment, vessels of various configuration have been developed to assist in
the removal of sand from fluids
produced from a wellbore. Such vessels are typically known as desanders, or
sand separators.
In a vertical sand trap, gravity is leveraged to effect settling of sand from
the fluid flow. That is, a
fluid stream enters a vertically oriented vessel, and sand accumulates in the
bottom of the vessel for later
removal.
In a hydrocyclone desander, one or more hydrocyclones are attached to a feed
manifold. Inflow fluid
to be desanded passes through the manifold and to the hydrocyclones, which
discharge particulates from the
bottom thereof, while overflow fluid from the hydrocyclone may be collected
and further processed in
subsequent steps.
SUMMARY OF THE INVENTION
In accordance with a first aspect of the invention, a vessel is provided for
use in separation of
particulate matter from a fluid stream, the vessel comprising; a horizontally
elongated separation chamber
comprising first and second ends, the chamber comprising walls defining a
chamber volume; a chamber inlet
and outlet, each providing an angular flowpath with respect to the elongated
axis of the chamber, the inlet
proximal to the first end of the chamber to define an inflow pathway for
delivery of a fluid stream into the
first end of the chamber, the outlet proximal to the second end of the chamber
to define an fluid outflow
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pathway from the second end of the chamber, the chamber thereby providing a
separation flowpath along the
elongated axis of the chamber from the chamber inlet to the chamber outlet;
one or more separation baffles
depending from a bottom surface of the chamber between the inlet and the
outlet to facilitate collection of
particulate matter from the fluid stream along the bottom surface of the
chamber; and an inlet baffle disposed
within the chamber and aligned with the inflow pathway to disrupt flow of the
fluid stream entering the
separation chamber.
In an embodiment, the chamber is generally cylindrical and the inlet has a
cross sectional area that is
less than a corresponding cross sectional area of the elongated separation
chamber.
In an embodiment, the vessel inlet and outlet are each oriented perpendicular
to the horizontal axis of
the vessel. The inlet baffle may be positioned at an angle to be aligned with
both the inlet of the vessel and
the elongated axis of the vessel, so as to redirect the fluid stream toward
the outlet.
In certain applications, the fluid stream may originate from a wellhead, and
may include oil, water,
and/or gas. The fluid stream may comprise sand.
In an embodiment, at least one of the ends of the chamber comprises a valve
for use in accessing the
interior of the chamber to remove particulate matter therefrom. The vessel may
further comprise a lower
drain for use in washing and/or emptying the chamber.
In an embodiment, the vessel further comprises an outlet baffle within the
chamber, the outlet baffle
proximal to the outlet for disrupting flow of fluid from the inlet to the
outlet. Generally, the inlet baffle
and/or the outlet baffle may be positioned at an angle between 30 and 60
degrees from horizontal. For
example, the inlet or outlet baffle may be positioned at 45 degrees from
horizontal.
In an embodiment, the outlet extends from the side of the chamber, and the
outlet baffle depends
from an inner side wall of the chamber. The vessel may further comprise
additional baffles extending from
an inner side wall of the chamber.
In accordance with a second aspect of the invention, there is provided a
vessel for use in separation
of particulate matter from a fluid stream, the vessel comprising; an
elongated, horizontal separation chamber
comprising first and second ends and defining a chamber volume and having a
cross sectional area; a
chamber inlet and outlet, each providing an angled flowpath with respect to
the elongated axis of the
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chamber, the inlet proximal to the first end of the chamber to define an
inflow pathway for delivery of a fluid
stream into the first end of the chamber, the outlet proximal to the second
end of the chamber to define an
fluid outflow pathway from the second end of the chamber, the chamber thereby
providing a separation
flowpath along the elongated axis of the chamber from the chamber inlet to the
chamber outlet; an inlet
baffle disposed within the chamber and aligned with the inflow pathway to
disrupt flow of the fluid stream
entering the separation chamber; and an outlet baffle within the chamber, the
outlet baffle proximal to the
outlet for disrupting flow of fluid from the inlet to the outlet.
In order to reduce the velocity of the fluid stream, the inlet may have a
cross sectional area that is
less than the cross sectional area of the chamber.
In an embodiment, the inlet baffle is positioned at an angle to be aligned
with both the inlet of the
vessel and the elongated axis of the vessel, so as to redirect the fluid
stream toward the outlet.
In an embodiment, the inlet and outlet each provide a generally perpendicular
flow pathway into or
out of the vessel, respectively.
In an embodiment, the fluid stream originates from a wellhead and may
comprise, oil, water, and/or
gas. The fluid stream may comprise sand.
In an embodiment, at least one of the first and second ends of the chamber
comprises a valve for use
in accessing the interior of the chamber to remove particulate matter
therefrom.
In an embodiment, the inlet baffle or the outlet baffle is positioned at an
angle between 30 and 60
degrees from horizontal. For example, the inlet or outlet baffle may be
positioned at 45 degrees from
horizontal.
In an embodiment, the vessel further comprises a particulate outlet in a lower
portion of the chamber.
In accordance with a third aspect of the invention, there is provided a method
for use in settling
particulate matter from a fluid stream, the method comprising the steps of:
receiving a fluid stream from a
fluid stream conduit, the fluid stream comprising fluid and particulate matter
at a first pressure; introducing
said fluid stream to a horizontally elongated vessel through a substantially
vertically oriented inlet of the
vessel, the horizontally elongated vessel further comprising a fluid outlet
distal to the vertically oriented inlet
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of the vessel; operating the vessel contents at a second pressure, the second
pressure lower than the first
pressure to facilitate settling of particulate matter within the vessel;
contacting the fluid stream with an inlet
baffle, the baffle proximal to the inlet and oriented so as to redirect the
vertical flow of the fluid stream from
the inlet along the horizontal axis of the vessel; collecting fluid from the
fluid outlet of the vessel; and
collecting settled particulate matter from the vessel.
In various embodiments, the fluid stream may contain gas and/or liquid.
In an embodiment, the particulate matter is a proppant such as sand.
In an embodiment, the fluid stream comprises wellbore production fluid and the
conduit may be a
pipeline.
In an embodiment, the fluid outlet is oriented substantially parallel to the
fluid inlet. In an
embodiment, the fluid inlet and/or outlet comprises a substantially vertically
oriented conduit extending from
the vessel. The fluid outlet may discharge fluid vertically from the vessel.
In an embodiment, the step of operating the vessel contents at a second
pressure comprises providing
a vessel having a cross sectional area greater than the cross sectional area
of the conduit from which the fluid
stream is received.
In an embodiment, the step of contacting the fluid stream with an inlet baffle
comprises installing the
inlet baffle within the vessel proximal to, and aligned with, the inlet. The
inlet baffle may be installed within
the vessel at an angle between 30 and 60 degrees from horizontal.
In an embodiment, the step of removing settled particulate matter from the
vessel comprises closing
a valve to terminate fluid communication between the conduit and the vessel.
In an embodiment, the step of removing settled particulate matter from the
vessel comprises opening
a valve at an end of the vessel. The step of removing settled particulate
matter from the vessel may comprise
collecting particulate matter from a solids discharge port in the vessel.
In an embodiment, the method further comprises the step of contacting the
horizontally redirected
fluid stream with a separation baffle along a bottom surface of the vessel. In
a further embodiment, the
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method comprised the step of contacting the horizontally redirected fluid
stream within the vessel with an
outlet baffle, the outlet baffle positioned within the vessel to interrupt
flow of the fluid stream to the outlet.
In accordance with a fourth aspect of the invention, there is provided a
method for separating
particulate matter from a fluid stream, the method comprising the steps of:
providing a separation vessel
comprising: a horizontally elongated separation chamber, an inlet defining an
inflow pathway substantially
perpendicular to the elongated axis of the vessel, and a fluid outlet distal
to the inlet, the outlet for
discharging fluid from the vessel; introducing an inflow stream comprising
fluid and particulate matter to the
inlet; providing a baffle within the vessel, the baffle positioned within the
inflow pathway and oriented to
deflect a fluid stream from the inlet toward the outlet; providing one or more
separation baffles extending
from a bottom surface of the vessel, the baffle oriented substantially
perpendicular to the elongated axis of
the vessel; providing an outlet baffle within the vessel, the outlet baffle
positioned so as to impede laminar
flow of the fluid stream from the inlet to the outlet; discharging fluid from
the outlet of the vessel; and
removing settled particulate matter from the vessel.
In an embodiment, the step of removing settled particulate matter comprises
opening a valve at one
end of the vessel to access settled particulate matter within the vessel.
In an embodiment, the method further comprises the steps of connecting the
inlet with a flow
containment system continuous with a fluid stream. For example, the flow
containment system may include a
pipeline.
Other aspects and features of the present invention will become apparent to
those ordinarily skilled
in the art upon review of the following description of specific embodiments of
the invention in conjunction
with the accompanying figures.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the present invention will now be described, by way of example
only, with
reference to the attached Figures, wherein:
Fig. 1 is a schematic cross sectional view of a separator vessel in accordance
with one
embodiment of the invention.
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DETAILED DESCRIPTION
Generally, a method and system for settling particulate matter from a fluid
stream is provided.
In a horizontal sand trap, a fluid stream generally enters an area of reduced
pressure, causing a
decrease in fluid velocity. As a result, the particulate matter falls from the
fluid and collects at the bottom of
the sand trap. With reference to Figure 1, a settling vessel 10 extends
horizontally, defining two ends 11, 12.
The vessel is constructed to be operated at pipeline pressures, for example up
to 2800 psi.
Towards the first end 11 of the vessel, an inlet 15 is provided through which
a fluid stream
containing suspended particulate matter may be introduced. The inlet provides
a generally perpendicular
(substantially vertical) flowpath for the fluid stream into the vessel.
Similarly, an outlet 16 is provided
towards the second end 12 of the vessel, through which fluid may be discharged
from the vessel. The outlet
shown in the drawing provides a generally perpendicular (or substantially
vertical) flowpath from the vessel.
Fluid streams containing gas, liquid and suspended particulate solid may all
be introduced into the
vessel inlet. For example, well production fluids may contain gas and liquid
hydrocarbons, water, and sand.
When such a fluid stream is introduced into the vessel, the sand is separated
from the fluids and accumulates
on the bottom of the vessel.
Inlet
The vessel inlet shown in Figure 1 provides a conduit extending upwardly from
the vessel. Extension
from the top of the vessel in this manner may facilitate connection of the
vessel within a facility or otherwise
space-constrained system. However, the vessel inlet may instead simply be a
port within the vessel, or may
extend from the vessel from any location or at any angle. The fluid inlet may
further be formed in the side of
the vessel. The inlet is adapted for connection to the fluid stream source,
using appropriate flanges,
couplings, etc. When the vessel is used for desanding well production fluids,
for example, the inlet would
typically be connected to a pressurized pipeline or to pressurized surface
production equipment. As such, the
inlet would be adapted for fluid-tight connection to the fluid stream source.
Typically, the conduit connected
to the inlet will have a cross sectional area that is less than the cross
sectional area of the vessel, thereby
causing a pressure drop across the vessel inlet.
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Fluid Outlet
With reference to Figure 1, the vessel includes an outlet for discharge of
fluid. The outlet shown in
Figure 1 extends vertically from the top of the vessel, however, many
alternate outlet configurations are
possible for discharge of fluid from the vessel. In most situations, an outlet
location in the upper portion of
the vessel would be suitable, to avoid resuspension of settled particulate
matter from the bottom of the vessel
as the fluid is discharged. However, a side outlet and baffle are also
specifically contemplated, as this will
again redirect the fluid stream, further interrupting laminar flow within the
vessel to facilitate settling of any
remaining particulate matter from the fluid stream prior to reaching the
outlet. This configuration is further
discussed below.
The outlet is adapted for connection to a tank, pipeline, conduit, or other
fluid storage vessel. The
outlet may contain a screen, baffle, or other flow obstructing device within
the vertically extending portion of
the outlet to promote settling of any sand that reaches the outlet.
Inlet Baffle
As the vertical introduction of fluid into a horizontal settling vessel would
generally be expected to
cause constant turbulence and erosion of the bottom surface of the vessel, a
sacrificial inlet baffle 20 is
provided, aligned with the inlet flowpath. The inlet baffle is positioned to
redirect inflow fluid from the inlet
towards the outlet. That is, the inlet baffle redirects inflow fluid parallel
to the horizontal axis of the vessel
and toward the second end 12 of the vessel. Should the inlet be provided in
the side of the vessel instead of
the top, the baffle would be appropriately positioned at an angle to direct
fluid from the side inlet.
As shown in Figure 1, the inlet baffle may be an angled plate provided within
the vessel. Such baffle
may be positioned within the vessel at an angle so as to be generally facing
both the inlet flowpath and the
horizontal axis of the vessel. The baffle should be removable, easily
replaceable, and should not interfere
with cleanout of particulate matter from the bottom of the vessel. For
example, the baffle may be a tungsten
plate hingedly attached to the vessel walls. The hinge mechanism of the baffle
shown in Figure 1 is provided
as a bar welded at each end to the interior side sides of the vessel, the bar
having a release and/or pivot point
for accessing the bar to hingedly attach the baffle. The inlet baffle has
generally flat upper and lower edges
and therefore depends from the hinge bar leaving an upper gap between the
upper edge of the baffle and the
curved top of the vessel, while the lower edge of the inlet baffle rests along
the lower portion of the curved
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walls of the vessel, leaving a lower gap between the lower edge of the baffle
and the bottom of the vessel.
The baffle is located and sized so as to rest at an angle of at least about 15
degrees from vertical. Practically,
the angle is determined by the width of the inlet. That is, the baffle should
be of a size and positioned at such
an angle so as to provide a redirection barrier between the inlet and the
bottom surface of the vessel. When
appropriately positioned, the baffle redirects the inflow fluid stream along
the horizontal axis of the vessel,
while also acting as a sacrificial surface to prevent erosive damage to the
bottom of the vessel opposite the
inlet.
As the fluid stream enters the vessel at the inlet containing fluid and
particulate matter, any
streamlined or laminar flow in the fluid stream is interrupted by the inlet
baffle. The turbulence introduced
by placement of the baffle, together with the pressure drop across the inlet
both serve to magnify the flow
characteristics between the fluid and the particulate matter suspended
therein, releasing the particulate matter
from the fluid stream to settle at the bottom of the vessel.
Testing to date has confirmed that the turbulence provided at the first end of
the vessel, by the
positioning of the inlet and the inlet baffle as discussed above, causes a
greater degree of settling towards the
first end of the vessel that has been observed in existing horizontal settling
devices without vertical
introduction of the fluid stream and without an inlet baffle as described
above.
In testing to date, the baffle has been placed at about a 45 degree angle from
horizontal, however
angles between 30 and 60 degrees would also be suitable. It is expected that
an approximately equal angle
from the inlet and from horizontal will be most efficient. That is, where the
inlet is not vertical, the angle of
the inlet should be appropriately adjusted. For example, angling the inlet at
45 degrees and the baffle at 45
degrees would result in the inflow stream contacting the baffle at 90 degrees.
This may cause excessive
turbulence, possibly resulting in backflow or excessive turbulence throughout
the vessel.
The hinged attachment of the baffle facilitates cleaning out of particulate
matter from the bottom of
the vessel as needed, upon opening of the end valves of the vessel. The
sacrificial inlet baffle may be
inspected and replaced as necessary during regularly scheduled cleanout of the
vessel to remove settled
particulate matter. Notably, when the inlet is provided within the side of the
vessel, cleanout of the
particulate matter may be further facilitated as the inlet baffle could be
positioned with a larger gap beneath
the inlet baffle
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Providing a gap between the lower edge of the inlet baffle and the bottom of
the vessel promotes
settling towards the first end of the vessel, as the settled particulate
matter can accumulate behind the inlet
baffle. Testing to date has shown that the configuration of the inlet and
inlet baffle shown in Figure provides
more settling towards the inlet end of the tank, and therefore allows a
greater time between particulate
cleanouts than in existing vessels where the fluid stream is introduced
parallel to the vessel axis without
turbulence.
Secondary inlet baffles may also be present. These secondary baffles may
extend within the vessel
from any interior vessel surface, to disrupt flow of fluid through the vessel,
thereby increasing fluid retention
time and promoting settling. Notably, baffles extending inwardly from the
sides of the vessel may be added
without complicating cleanout procedures, particularly when such side baffles
are hingedly attached and
easily moved by cleaning equipment.
Settling Baffles
As redirected fluid flows from the inlet baffle 20 toward the second end 12 of
the vessel, the fluid
stream flows at reduced velocity such that particulate matter suspended within
the fluid stream begins to fall
toward the bottom of the vessel. The settling particulate matter may continue
to be carried toward the second
end of the vessel as it falls from suspension, by fluid flowing within the
lower portion of the vessel.
Placement of settling baffles along the bottom of the vessel may therefore be
useful in halting the forward
progression of such falling particulates, trapping them along the bottom of
the vessel. An example of such
settling baffles 30 is shown in Figure 1.
Each settling baffle is configured as a rib extending across the width of the
vessel between the inlet
15 and outlet 16. In the embodiment shown in the Figure, each rib is fixed to
the bottom of the vessel and
extends generally upward from the bottom of the vessel, but not to such an
extent that would impede
cleaning out of particulate matter from one or both ends of the vessel. In
practice, a two-inch height has
provided a suitable barrier for trapping particulate matter, while not
impeding cleanout of the vessel. During
operation, particulate matter will accumulate on the inlet side of each
settling baffle, forming mounds that
may be later remove from the vessel. As mounds of settled particulate
accumulate along the bottom of the
vessel, the mounds will further act as baffles to some extent, facilitating
settling of further particulates from
the redirected fluid stream. It is noted that the settling baffles may take
any other suitable form, may be
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hingedly, pivotably, or removably attached within the vessel to facilitate
cleanout, and may extend a
significant distance across the vessel as desired.
Outlet Baffle
As a further aid to the settling of particulate matter from the fluid stream,
an outlet baffle 40 may be
placed within the vessel between the inlet and the outlet, proximal to the
outlet. The outlet baffle is generally
positioned so as to disrupt the flow of the fluid stream prior to reaching the
outlet, facilitating the settling of
further particulates from the fluid stream.
As shown in Figure 1, an outlet is provided in the top of the vessel,
extending vertically therefrom.
The outlet may or may not also extend into the vessel. An outlet baffle 40 is
positioned at an angle just
before the= outlet, to interrupt laminar flow along the horizontal axis of the
vessel. Such redirection of the
fluid stream promotes settling of any remaining particulate matter that may
remain suspended within the
fluid as it approaches the second end of the vessel.
The outlet baffle may be similar in construction, orientation, and
installation as the inlet baffle, but
will not be subject to erosive damage to the same extent as the inlet baffle
due to the lower velocity and
reduced concentration of particulate matter present in the fluid stream
adjacent the outlet, compared to the
concentration at the inlet. The outlet baffle may be fixed or hingedly
attached within the vessel, may have
generally flat upper and lower edges, and may rest at an angle, with the lower
edge of the baffle supported by
the lower portion of the vessel walls. This hinged attachment facilitates
cleanout of the vessel, and also
allows replacement of the outlet baffle as necessary. A gap above the upper
edge of the baffle and below the
lower edge of the baffle may be present. In addition, the outlet baffle may
have slots, vertical weir openings,
may be screened, or may be provided in any alternate configuration that
partially or fully redirects, or
partially obstructs flow to the outlet.
In an alternate configuration, the outlet may be provided in a first side of
the vessel, proximal to the
second end of the vessel, and one or more outlet baffles may also be attached
to the first and/or second side
of the vessel, just prior to the outlet. In this configuration, fluid would be
required to flow around the outlet
baffle(s) toward in order to reach the outlet.
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Any additional lengthening of the pathway from the inlet to the outlet, or
otherwise increasing the
fluid retention time within the vessel, for example by placement of additional
baffles, will favour further
settling of particulate matter from the fluid stream.
Particulate Removal
During initial operation of the vessel, minimal particulate matter may be
detected in the outlet fluid
stream. As operation continues, and sand or other particulate matter
accumulates along the bottom of the
vessel, some particulate matter may be more readily detectable in the outlet
fluid. Once the amount of
particulate matter present in the outlet stream becomes unacceptable, the
vessel will be taken off line for
cleanout. In the embodiment shown in Figure 1, each end of the vessel may be
opened. One or both ends may
be opened for cleaning out particulate matter from the vessel as needed.
As shown in Figure 1, the vessel includes a vent 45, pressure release valve
43, lower drain 44. End
valves 41, 42, are provided at each end of the vessel 11, 12, respectively.
The pressure release valve 43,
operates to release pressure from the vessel at a predetermined limit. For
example, if the vessel is rated for
2800 psi, the pressure release valve 43 may open when an internal pressure of
2520 psi is detected (2800 ¨
10% tolerance).
When cleanout of particulate matter or other maintenance is required, the vent
may be opened to
depressurize the vessel. Once the vessel pressure has been equalized, one or
both of the end valves 41, 42
may be opened to clean out particulate matter from the vessel as needed. A
cleaning tool, for example a
crush, scraper, or vacuum, is inserted into the open vessel and used to remove
particulate matter, deflecting
any baffles as necessary in order to access the bottom of the vessel for
removal of solids.
A lower drain 44 is provided to facilitate full drainage of the vessel when
relocation is desired.
Other Features
In Figure 1, the vessel is supported within a front and rear saddle 51, 52.
One or both of the saddles
may be adjustable to accommodate support over various surfaces and structures,
and to facilitate transport. In
the embodiment shown, the front saddle 51 is fixed to the vessel, while the
rear saddle 52 is movable beneath
the vessel.
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Operation
In operation, a fluid source/fluid stream containing particulate matter is
identified. An inflow conduit
continuous with the fluid source is attached to the vessel inlet 15. An
outflow conduit may be attached to the
outlet 16.
As the vessel is operated, receiving fluid from the fluid source via the inlet
15 proximal to the first
end 11, the fluid stream entering the vessel will contact the inlet baffle at
high velocity, causing turbulence in
the fluid stream about the inlet. Fluid will be redirected generally parallel
to the horizontal axis of the vessel,
continuing to flow toward the second end 12 of the vessel. Solids within the
fluid stream will be swept by the
turbulent fluid, promoting separation of particulates from the fluid, and
settling of same below and adjacent
the inlet. Some particulates will be carried within the fluid toward the
outlet, however as the cross sectional
area of the vessel is greater than that of the inflow conduit, the velocity of
the fluid slows and particulates are
deposited along the bottom of the vessel, halted by the settling baffle(s)
across the bottom of the vessel.
Compared with other pressurized horizontal settling vessels, a significant
degree of settling occurs
closer to the first end 11 (inlet end) of the vessel as a result of the
presence of the inlet baffle, creating
turbulence at the inlet. Moreover, as the inlet baffle redirects the fluid
stream toward the second end 12 of the
vessel, the first end of the vessel is available to collect settled solids
behind the inlet baffle. This results in
efficient utilization of the space within the vessel, and increases the amount
of particulate matter collected
within the vessel and/or the length of time between required cleanouts (before
excessive particulates can be
detected within the outlet fluid).
As necessary, the vessel may be taken off-line by closing the inlet (and
outlet). The pressurized
vessel is equalized to atmosphere via the vent 45, and one or both end valves
41, 42, may be opened for
cleanout of settled particulate matter. When the vessel is to be moved, the
interior may be washed and
drained, and the vessel may be lifted from beneath, between the saddles.
During particulate cleanout, the baffles, and vessel surfaces in general, are
inspected to determine
appropriate timing for replacement based on erosion patterns experienced
during operation. The baffles may
be engineered to withstand erosion for at least the expected time required
between cleanouts, such that no
additional shutdowns of the vessel are required to maintain the baffles or
other interior vessel surfaces.
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The above-described embodiments of the present invention are intended to
examples only.
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