Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 2723955 2017-04-21
SHATTER JET NOZZLE WITH MULTIPLE STEAM SOURCES AND METHOD
FOR DISRUPTING SMELT FLOW TO A BOILER
[0001] Continue to next paragraph.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a shatter jet
nozzle and a method for disrupting the smelt flow from a
smelt spout of a recovery boiler.
[0003] A recovery boiler, such as a soda recovery boiler,
is typically used in the chemical recovery of sulfate and
other sodium-based substances from pulp manufacturing
processes. Organic substances dissolved in the waste liquor
during digestion or other pulping processes are combusted
in the recovery boiler to melt inorganic compounds, e.g.,
ash, in the waste liquor and generate steam. The melted
inorganic compounds flow as a primarily liquid smelt to the
bottom of the recovery boiler. The smelt flows from the
bottom of the boiler along one or more cooled smelt spouts
to a dissolving tank. In the dissolving tank, the smelt is
dissolved by water or weak white liquor to produce soda
lye, e.g., green liquor.
[0004] The hot smelt flow from the spout causes "banging"
and explosions when the smelt falls into the
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cooler liquid in the dissolving tank. The temperature of
the smelt is on the order of 750 Celsius ( C) to 820 C.
In contrast, the temperature of the green liquor (or weak
white liquor) in the dissolving tank, containing mainly
water, is on the order of 70 C to 100 C. This dramatic
temperature difference belween the hot smelt flow and the
much cooler green liquor contributes to the explosions
and banging noises as the smelt hits and is instantly
cooled by the green liquor.
[0005] The intensity of the explosive reactions of the
smelt in the dissolving tank may be reduced and
controlled by disrupting the smelt flow into small
streams, droplets or pieces as the flow leaves the spout
and before it hits the liquid in the dissolving tank. It
is conventional to disrupt the smelt with jet streams,
e.g., steam jets, discharged from nozzles at low or
medium pressure steam. These nozzles are referred to as
shatter jet nozzles because they shatter the flow of the
smelt.
[0006] The shatter jet nozzle discharges a jet stream
at a specific volume and rate designed to break-up the
smelt flow expected during normal operation of the
recover boiler. The smelt flows at a relatively uniform
rate and volumetric flow during normal recovery boiler
operation. Conventional shatter jet nozzles direct a jet
stream at a rate and volume designed to disrupt the
normal uniform rate and flow of smelt. Conventional
shatter jet nozzles are coupled to a single steam source
that provides a constant flow rate of steam to the
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nozzles. The rate of steam flow to the nozzle typically
cannot be adjusted remotely, and is adjusted at or near
the nozzle.
[0007] Variations can occur in the rate and volume of
smelt flowing from a recovery boiler. During normal
operation of the recovery boiler, the normal steam jets
from the shatter jet nozzles are capable of disrupting
the smelt flow and sufficiently reducing explosions in
the dissolving tank. However, the recovery boiler may be
operated in an upset condition resulting in heavy smelt
flows. These heavy smelt flows may not be adequately
disrupted by the jets from the shatter jet nozzle and the
smelt may cause explosions from which hot smelt droplets
may splatter from the tank. These excessive explosions of
smelt can result in equipment damage and danger to
personnel safety.
BRIEF DESCRIPTION OF THE INVENTION
[0008] A shatter jet nozzle has been developed that
discharges jets to breakup a smelt flow at two or more
flow rates or pressures. The nozzle is coupled to two or
more sources of steam (or other disrupting fluid) that
provide the capacity for multiple rates or pressures of
the jets. Further, the flow rate or pressure of the jets
from the shatter jet nozzle may be manually or remotely
controlled by controlling the flow of steam from one of
the steam sources, such as by unblocking steam from a
second steam source only during heavy smelt flows. By
controlling the flow rate or pressure, the jet discharged
from the shatter jet nozzle can be adjusted to breakup
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different rates of smelt flow. For example, the volume or
pressure of the jets discharged from the shatter jet
nozzle(s) may be increased during heavy smelt flows from
the boiler and may be reduced during normal smelt flows.
[0009] An apparatus has
been conceived and is
disclosed herein to disrupt smelt flowing from a recovery
boiler to a dissolving tank, the apparatus comprising: a
shatter jet nozzle assembly arranged to direct a jet of
disrupting fluid against the smelt flowing from the
recovery boiler to the dissolving tank; a first source of
disrupting fluid coupled to the shatter jet nozzle
assembly; a second source of disrupting fluid coupled to
the shatter jet nozzle assembly, and a valve arranged at
or between the second source and the shatter jet nozzle
assembly to regulate a flow of the disrupting fluid from
the second source to a nozzle in the shatter jet nozzle
assembly, wherein the apparatus has a first operating
mode in which disrupting fluid from the first source
flows through the shatter jet nozzle assembly and forms
the jet of disrupting fluid discharged from the nozzle
while the valve prevents disrupting fluid from the second
source from being discharged from the jet, and a second
operating mode in which disrupting fluid from the first
and second sources flow through the shatter jet nozzle
assembly to form the jet of disrupting fluid while the
valve permits disrupting fluid to flow from the second
source to the shatter jet nozzle assembly.
[0010] A method has been
conceived and is disclosed
herein to disrupt a smelt flow including: arranging a
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shatter jet nozzle assembly to direct a jet of disrupting
fluid against the smelt flowing from a recovery boiler to
a dissolving tank; supplying the disrupting fluid to the
shatter jet nozzle assembly from a first source of
disrupting fluid to form the jet_ directed against the
smelt flow while a second source does not provide
disrupting fluid to the shatter jet nozzle, and supplying
the disrupting fluid from both the first source and the
second source flow to the shatter jet nozzle assembly to
form the jet of disrupting fluid directed against the
smelt flow.
[0011] A shatter jet
nozzle assembly has been conceived
and is disclosed herein forming a jet applied to a smelt
flowing from a recovery boiler and into a dissolving
tank, the assembly comprising: a first nozzle conduit
having a first discharge nozzle directed towards the
smelt flow as the flow falls from the recovery boiler to
a liquid surface in the dissolving tank, wherein the
first nozzle conduit is connectable to a first source of
disrupting fluid, wherein the disrupting fluid flows
through the first nozzle conduit and from the first
discharge nozzle to form a jet directed against the smelt
flow, and a second nozzle conduit having a second
discharge nozzle direcLed towards the smelt flow as the
flow falls from the recovery boiler to a liquid surface
in the dissolving tank, wherein the second nozzle conduit
is connectable to a second source of disrupting fluid,
wherein the disrupting fluid flows through the second
nozzle conduit and from the second discharge nozzle to
form a jet directed against the smelt flow, wherein the
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jet from the first discharge nozzle and the jet from the
second discharge nozzle merge prior to the jets impacting
the smelt flow.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIGURE 1 is a is schematic diagram showing a
side view, partially in cross-section, of a smelt hood,
smelt spout, an upper portion of a dissolving tank and a
shatter jet nozzle discharging a jet to break-up the
smelt flow from the spout.
[0013] FIGURE 2 is a schematic diagram showing a front
view of the hood, smelt spout, shatter jet nozzle and
dissolving tank, wherein Figure 2 is a view along line
2-2 in Figure 1.
[0014J FIGURE 3 is a side view of an exemplary shatter
jet nozzle having concentric passages for multiple flows
of disrupting fluid.
[0015] FIGURE 4 is another side view, shown in partial
cross section, of the shatter jet nozzle, wherein the
view is taken from a ninety degree angle from the view
shown in Figure 3.
[0016] FIGURE 5 is a cross-sectional view of the distal
end of the nozzle taken along line 5-5 in Figure 3.
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DETAILED DESCRIPTION OF THE INVENTION
[0017] FIGURES 1 and 2
show a lower section of a
recovery boiler 10 of a pulp mill. Smelt flows from the
bottom of the boiler through an opening 12 and into a
smelt spout 14. The portion of the smelt spout 14
extending outside the wall of the boiler is surrounded by
a conventional closed protecting hood 16 comprising an
upper hood portion 18 and a lower hood portion 20. The
upper hood portion 18 includes a cover 22.
[0018] The hood 16
contains the splash of liquid and
smelt as they flow through the spout 14 and contains
exhaust gases so that the gases do not discharge directly
to the environment. The lower hood portion 20 may be
connected to a conventional dissolving tank 24 disposed
under the protecting hood 16. The smelt dissolves into
Liquid in the tank 24 to produce green liquor.
[0019] Hot, liquid smelt
flows from a boiler opening 12
near the bottom of the recovery boiler to the smelt spout
14. The smelt flows along a downwardly sloped bottom 26
of the spout 14, over a free end 28 of the spout, and
into the dissolving tank 24. The smelt flow path as the
smelt falls from the free end 28 to the spout to the
liquid surface in the tank is indicated by arrows 30.
[0020] A jet 32 of steam
or other disrupzing fluid is
directed against the smelt as the smelt flows from the
free end 28 of the spout to the tank. The jet 32 disrupts
the flow of smelt into droplets, segments the flow or
otherwise breaks up the flow such that there is not a
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uniform stream of smelt entering the tank. The jet 32 is
discharged from nozzle 34 of a shatter jet nozzle
assembly 36.
[0021] The shatter jet nozzle assembly 36 may be
attached to an adjustable mounting bracket 37 fixed to
the lower portion 20 of the hood 16. The adjustable
mounting bracket allows the shatter jet nozzle assembly
to be moveably positioned to direct the jet 32 against
the flow of smelt 30. Optionally, opposite shatter jet
nozzle assemblies may be mounted to the lower portion 20
of the hood to project disrupting fluid jets from
opposite sides of the smelt flow 30 to enhance the
breakup of the smelt flow before the smelt reaches the
liquid level in the dissolving tank.
[0022] During normal operation of the recovery boiler
10, steam or other disrupting fluid is supplied to the
shatter jet nozzle assembly by a first pressurized fluid
source 38, such as a source of low pressure or medium
pressure steam. The first pressurized fluid source 38 may
a pressurized header of steam or other disrupting fluid.
Alternatively, the fluid source 38 may be a conduit with
a pump coupled to a tank, such as the dissolving tank 24
of the weak white liquor or green liquor.
[0023] The first pressurized fluid source 38 may
provide fluid, e.g., steam or other gas, to the shatter
jet nozzle assembly 36 at a first pressure level. The
pressure of the first pressurized fluid source may be
selected to be adequate to produce a jet 32 from the
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shatter jet nozzle 34 sufficient to breakup the smelt
flow during normal operation of the recovery boiler. The
volume or flow rate of disrupting fluid from the first
pressurized fluid source to the nozzle assembly 36 is
sufficient to fully supply the shatter jet nozzle
assembly with a jet 32 adequate to breakup the flow of
smelt during normal boiler operation.
[0024] A first valve
39 connected to a conduit
extending from the first pressurized fluid source 38 to
the shatter jet nozzle assembly 36 regulates the flow of
disrupting fluid, which may be a low-pressure flow, to
the nozzle assembly. The first valve 39 may be remote,
e.g., twenty feet distant, from the protective hood 16 or
the valve may be proximate to the hood. The first valve
39 may be manually operated or remotely controlled by a
solenoid affixed to the valve. The first valve
is
' typically open to a fixed position during. operation of
the recovery boiler to provide a continuous flow of
disrupting fluid to the shatter jet nozzle assembly 36.
[0025] A second source
40 of disrupting fluid may alSo
be connected to the shatter jet nozzle assembly 36. The
second source 40 provides disrupting fluid that may be at
the same or a higher pressure than the first fluid
source. The second source 40 may be disrupting fluid in a
pressurized header containing steam or other disrupting
fluid. Alternatively, the second source 40 may be
provided by a pump which pressurizes disrupting fluid,
such as liquor from the dissolving tank or water.
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[0026] The second source 40 provides supplemental
disrupting fluid that increases the volume or pressure of
the jet 32, over and above the volume or pressure of the
jet 32 when supplied solely from the first pressure
source. The high velocity and pressure jet 32 formed by
the combine flow of disrupting fluid from the first and
second sources 38, 40 may be applied to breakup heavy
smelt flows that occur during an upset condition in the
recovery boiler.
[0027] A second valve
42 is connected to a conduit
extending from the second pressurized fluid source 40 to
the shatter jet nozzle assembly 36. The second valve 42
regulates the flow of disrupting fluid, which may be a
high pressure flow, to the nozzle assembly. The second
valve 42 may be remote, e.g., twenty feet distant, from
the protective hood 16 or the valve may be proximate to
the hood. The second valve 42 may be manually operated or
remotely controlled by a solenoid affixed to the second
valve. The second valve 42 may be opened to allow flow
from the second pressurized fluid source 40 only during
extraordinary conditions, such as during heavy smelt
flows. Because the second valve is remote to the hood or
is remotely operable, the second valve may be safely
opened after heavy smelt flow begins and explosions are
occurring as the smelt flow hits the cool liquor in the
dissolving tank 24.
[0028] FIGURES 3 to 5
show an exemplary shatter jet
nozzle assembly 50 which has a generally cylindrical
metallic housing 52 which extends substantially the
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length of the assembly and provides shielding to protect
the assembly from smelt. A distal end of the assembly
includes a bell housing 54 (not shown in Figure 4) that
provides a shield to the nozzle end of the assembly.
Housed within the housings 52 and 54 are coaxial tubes 56
and 58 that define conduits for the two flows of
pressurized disrupting fluid, e.g., steam.
[0029] A center inlet 60 to a center coaxial tube 56 is
coupled to one of the sources of disrupting fluid, such
as the first steam source 38. The center inlet 60 directs
disrupting fluid from the first source into the center
coaxial tube 56 such that the fluid flows to a center
nozzle 62, which may have an oval shape in cross-section
as is shown in FIGURE 5.
[0030] A side inlet 64 to the outer coaxial tube 58 is
coupled to another source of disrupting fluid, such as
the second steam source 40. The side inlet directs
disrupting from the second source through an annular
passage between the outer and inner coaxial tubes to an
outer nozzle 66 that surrounds the center nozzle 62. The
outer nozzle 66 may have a racetrack shape such as shown
in FIGURE 5. The center nozzle 62 and outer nozzle 66 may
be coaxial and have adjacent openings at a common outlet
for the nozzle assembly.
[0031] The length of the nozzle assembly 50 is
sufficient to position the nozzles 66, 62 adjacent to the
flow of smelt from the spout. The nozzle asseMbly is
preferably mounted to the protecting hood 16, so that the
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nozzles 66, 62 may be turned and positioned properly with
respect to the smelt flow.
[0032] With
the nozzle assembly 50 disclosed herein, the
breakup of the smelt is more efficient and safer,
especially during heavy smelt flows from a recovery boiler.
The ability to discharge jets from two nozzles 62, 66 in
the nozzle assembly 50 reduces the risk of extensive
explosions in the dissolving tank and the noise level is
reduced in the vicinity of the dissolving tank even during
heavy smelt flows.
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