Note: Descriptions are shown in the official language in which they were submitted.
CA 02461607 2006-12-22
IMPROVED SEAL AND PRESSURE RELIEF FOR
STEAM INJECTION HEATER
Background of the Invention
[0002] The present invention relates to direct contact steam injection heaters
that use full
pressure steam. More particularly, the invention relates to a direct contact
steam injection heater
for heating certain types of slurries that contain abrasive material.
[00031 In direct contact steam injection heaters, steam is directly mixed into
a flowing
stock (e.g. liquid or slurry) being heated. Direct contact steam injection
heaters are very effective
at transferring heat energy to the flowing stock. They provide rapid heat
transfer with virtually
no heat loss to the atmosphere, and also transfer both the latent and the
available sensible heat of
the steam to the liquid slurry.
[00041 The present invention was developed during ongoing developmental
efforts by the
assignee in the field of direct contact steam injection heaters. U.S. Patent
No. 5,622,655 entitled
"Sanitary Direct Contact Steam Injection Heater And Method" by Bruce A.
Cincotta et al.,
issuing on April 22, 1997, U.S. Patent No. 5,842,497 entitled "Adjustable
Direct Contact Steam
Injection Heater", by Brian Drifka and Bruce A. Cincotta, issuing on December
1, 1998, and U.S.
Patent No. 6,361,025 entitled "Steam Injection Heater With Transverse Mounted
Mach
Diffuser", issuing on March 26, 2002 represent some of the prior developments
in direct contact
steam injection heaters by the assignee.
[0005] These types of direct contact steam injection heaters use full pressure
steam (i.e.
the full amount of steam pressure available), and modulate the amount of steam
added to the
flowing liquid or slurry by a nozzle and plug configuration. The steam exits
through the nozzle
under sonic choked flow conditions. The high speed steam from the nozzle
shears the flowing
liquid or slurry, and creates a homogeneous blend in a combining region
located downstream of
the nozzle. As heat is transferred, the steam condenses.
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CA 02461607 2004-03-22
~ r
[0006] Another direct contact steam injection heater was developed by the
assignee for heating purified water or other liquids in which steam bubbles
tend to
merge to create large steam bubbles prior to condensing. This direct contact
steam
injection heater is disclosed in U.S. Patent No. 6,082,712, and incorporated
herein by
reference. This direct contact steam injection heater employs a Mach diffuser.
The
Mach diffuser injects a sonic velocity steam into the liquid stock through a
plurality of
relatively small steam diffusion holes. The Mach diffuser :is generally
coaxial with the
heater body and resides within the inlet of a combining region. The purified
water or
other liquid flows in a radial direction through the inlet into the combining
region and
turns at an essentially right angle to flow through the combining region. The
steana
exits the coaxial Mach diffuser as small jets of steam injecting partially
into the axial
flow through the combining region. The velocity of the liquid flowing through
the
channel between the Mach diffuser and the combining region is maintained at a
relatively high velocity (i.e., a relatively small flow area in the channel
compared to
the downstream portion of the combining region).
[0007] Although the transverse mounted Mach diffu.ser shown and taught by
U.S. Patent No. 6,361,025 is effective and efficient for heating a flow of
slurry in an
in-line configuration to eliminate the requirement that stoc:k flow negotiates
sharp
turns, additional difficulties are presented when attempting to heat the flow
of slurry
having abrasive materials, such as fine sand particles or other similar
components.
Summary of the Invention
[0008] The invention is a direct contact steam injection heater in which steam
is
introduced into a flow of stock that is flowing axially through a pipe. The
heater is
installed in line and allows continued axial flow of the stock so the stock
flow is not
required to negotiate sharp turns when passing through the heater. That is,
the heater
includes a heater body having a flowing stock inlet and a heated stock
discharge outlet
that are aligned to provide axial flow through the pipe and the heater body.
Full
pressure steam is introduced into the stock through a Mach. diffuser that is
mounted
transverse to the axial flow through the heater body. The A/Iach diffuser has
a plurality
of steam diffusion holes through which small jets of steam are injected into
the
flowing stock. The small steam jets break apart easily in viscous slurries and
disperse
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before the steam has a chance to conglomerate into large biubbles that can
create
"steam hammers" and lead to unwanted vibration within the heating system.
Furthermore, small steam bubbles dissipate heat more efficiently and thereby
prevent
hot and cold spots in the flowing stock.
[0009] The Mach diffuser has an adjustably positionable steam-plug cover. The
adjustably positionable steam-plug cover obstructs a selected amount of the
steam
diffusion holes in order to modulate the amount of steam discharged through
the Mach
diffuser into the flow of stock. The steam-plug cover is preferably rotatable
relative to
the longitudinal axis of the transversely mounted Mach diffuser.
[0010] The Mach diffuser preferably has a diffuser tube having a cylindrical
wall containing the steam diffusion holes. The diffuser tube is preferably a
cylindrical
wall nested outside the steam-plug cover. The preferred diffuser tube has an
internal
region within the cylindrical wall that receives steam passing into the
heater. The
cylindrical wall has multiple steam openings that enable steam to flow from
the
internal region in the steam-plug cover through the exposed steam diffusion
holes in
the Mach diffuser, and into the axial flow of stock.
[0011] Preferably, there are two steam openings in the steam-plug cover, each
consisting of a longitudinal slot located on opposite sides of the steam-plug
cover.
The longitudinal slots preferably have widths that occupy less than one
quarter of the
circumference of the cylindrical wall of the steam-plug cover.
[0012] The Mach diffuser has an upstream surface area and a downstream
surface area on the cylindrical wall of the diffuser tube, each occupying less
than one
quarter of the circumference of the transversely mounted Mach diffuser. The
upstream and downstream surface areas of the diffuser tube do not contain
steam
diffusion holes. The side surface areas on the diffuser tube of the Mach
diffuser
contain the steam diffusion holes. The Mach diffuser is oriented in the heater
body
such that the upstream surface area faces into the axial flow of the stock.
This
orientation to prevents unnecessary plugging of the diffusion holes on the
upstream
surface.
[0013] Preferably, a deflector is mounted upstream of the Mach diffuser. The
deflector deflects the flow of stock around the upstream surface area on the
Mach
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diffuser and towards the side surfaces of the Mach diffuser. This prevents
flow
directly into a fluid stagnation point on the upstream surface of the Mach
diffuser.
The deflector is preferably attached to the inside wall of the heater body by
a pair of
removable connectors such that it does not become dislodged in the face of
heavy
flows of viscous slurries but cari be removed for replacement as required.
[0014] The Mach diffuser includes a pair of 0-rings, each of which surround
one of the longitudinal slots located in the steam-plug cover. The 0-rings
slightly
protrude from the otherwise cylindrical wall of the steam-plug cover and form
a seal
with the inner surface of the diffuser tube. The seal created by the 0-ring
between the
diffuser tube and the steam-plug cover prevents backflow of a fibrous slurry
or other
type of slurry into the steam-plug cover, particularly when steam is not being
supplied
to the Mach diffuser.
[0015] The amount of full pressure steam discharged through the Mach diffuser
into the axially flowing stock is modulated by adjusting the position of the
steam-plug
cover over a selected amount of steam diffusion holes. The steam-plug cover is
preferably adjustable between a fully closed position in which no steam
diffuser holes
are exposed to a fully open position where a maximum nwnber of the steam
diffusion
holes are exposed. This adjustment is preferably accomplished with a rotating
actuator having a key that engages one end of the cover. When the actuator
rotates the
key, the cover is positioned to expose a generally proportional amount of
steam
diffusion holes in the Mach diffuser. Radial jets of steam then flow through
the
exposed steam diffusion holes into the axial flow of stock.
[0016] When the steam-plug cover is in the fully closed position, the
diffusion
holes formed in each side of the diffuser tube are positioned between the pair
of 0-
rings that surround the longitudinal slots formed in the steam-plug cover.
Since the
pair of 0-rings create a seal with the inner surface of the diffuser tube, the
pair of 0-
rings prevent the slurry material from passing through the diffusion holes and
along
the outer surface of the steam-plug cover to reach the longitudinal open slots
formed in
the steam-plug cover. Since each of the longitudinal slots occupies less than
one
quarter of the outer circumference of the steam-plug cover, an 0-ring seal is
formed
on each side of the series of diffusion holes formed in the diffuser tube.
Thus, when
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CA 02461607 2006-12-22
the steam-plug cover is in the fully closed position, the pair of 0-rings
prevents the slurry from
entering into the steam-plug cover. This feature is particularly relevant when
no positive
pressure is included in the open interior of the steam-plug cover, such as
when steam is no longer
being applied to the Mach diffuser.
100171 The steam-plug cover includes a pair of pressure ports that each extend
through
the top wall of the steam-plug cover. The pair of pressure ports equalize the
pressure within the
open interior of the steam-plug cover and the rotational components for the
steam-plug cover.
The pair of pressure ports equalize the pressure, which allows the steam-plug
cover to be more
easily rotated relative to the stationary diffuser tube.
(0018] The Mach diffuser is designed for use with slurries including entrained
particulate
matter, such as sand or other solid particles. The entrained sand and
particulate matter increases
the wear on the components of the Mach diffuser and heater that directly
contact the slurry. To
address such problem, a wear coating is applied to the upstream deflector,
stationary diffuser tube
and along the inside wall of the heater body. Preferably, the wear coating is
formed from a
tungsten carbide material applied in an even thickness over the metallic outer
surface of each
component. The wear coating increases the durability of each of the parts that
are in direct
contact with the slurry passing through the heater body.
100191 It should be apparent to those skilled in the art that the use of an
actuator to rotate
the cylindrical cover for the Mach diffuser is especially accommodating for
large volume flows
through pipes having relatively large diameters. The rotatable cover allows
for generally
consistent injection of steam across the entire length of the transversely
mounted Mach diffuser.
In addition, the stroke on a linear actuator may create installation problems.
100201 Various other features, embodiments, and advantages of the invention
will be
made apparent from the following detailed description and the drawings.
Brief Description of the Drawings
100211 The drawings illustrate the best mode presently contemplated of
carrying out the
invention.
100221 In the drawings:
CA 02461607 2004-03-22
[0023] Fig. 1 is an isometric view of an installed prior art direct contact
steam
injection heater;
[0024] Fig. 2 is an assembly view of the heater shovm in Fig. 1;
[0025] Fig. 3 is a side view showing a cross-section of the prior art steam
injection heater shown in Figs. 1 and 2 as it is installed in a pipe through
which a flow
of stock flows axially;
[0026] Fig. 4 is a view taken along line 4-4 in Fig. 3;
[0027] Fig. 5 is a view of the Mach diffuser taken along line 5-5 in Fig. 3;
[0028] Fig. 6a is a view similar to Fig. 5 further showing a deflector
positioned
upstream from an upstream surface area of the Mach diffuser, and also showing
a
cover aligned so that it does not obstruct steam diffusion holes in the Mach
diffuser;
[0029] Fig. 6b is a view as shown in Fig. 6a with the cover rotated to
partially
close steam injection holes through the Mach diffuser;
[0030] Fig. 7 is an assembly view of the present, preferred embodiment of the
Mach heater that forms the present invention;
[0031] Fig. 8 is an assembly view of the Mach diffuser of the present
invention;
[0032] Fig. 9 is an end view of the direct contact steam injection heater of
the
present invention;
[0033] Fig. 10 is a section view taken along line 10-10 of Fig. 9;
[0034] Fig. 11 is a magnified view of the Mach diffuser shown in Fig. 10;
[0035] Fig. 12 is a magnified view of the Mach diffuser in which the steam
tube
assembly is rotated 90 relative to Fig. 11; and
[0036] Fig. 13 is a section view taken along line 13-13 of Fig. 9.
Detailed Description of Preferred Embodiments
[0037] The prior art steam injection heater illustrated in Figs. 1-12 is
designed
to accommodate large flows of slurries or other viscous liquids containing
materials
that tend to flocculate, such as suspended fibrous or particulate matter. In
accordance
with the invention, the heater 110 has a Mach diffuser 121 that is placed
transversely
in the heater body 112. The heater body 112 is connected in line with a stock
supply
pipe.
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[0038] As shown in Figs. 1-3, steam 120 flows into l:ieater 110 through a
steam
inlet 114, and into an intemal region 152 (Fig. 5) defined by a cover 154
located
within the Mach diffuser 121. Steam 120 enters internal region 152 through an
opening 1561ocated near steam pipe 132. Cover 154 is a cylindrical wall having
a
closed end 158 and an open end 160, Fig. 2. Steam is supplied through the
cover 154
via openings 162 (only one opening 162 is shown in Fig. 2, the other opening
is
directly opposite of the opening 162 that is shown) at esseritially the full
steam
pressure available at the heater 110.
[0039] As shown in Figs. 2 and 3, the Mach diffuser 121 includes an open end
161, a cylindrical wall 164 and a flanged base 166. An internal region within
the
Mach diffuser 121 is defined by the base 166 and the cylindrical wall 164.
Cover 154
is preferably contained within the internal region of the Mach diffuser 121.
[0040] The cylindrical wall 164 of the Mach diffuser 121 includes a plurality
of
radial steam diffusion holes 168. The size and number of t:he steam diffusion
holes is
a matter of choice depending on the size of heater 110. However, a diameter of
about
1/8 of an inch is preferred for most stocks. Such a diameter is sufficiently
small to
facilitate the creation of relatively small radial jets of steana through the
diffuser wall
164, yet is not so small as to create other problems such as plugging or
scaling. In
addition, it is preferred that the Mach diffuser 121 be made of stainless
steel, and that
the cylinder wall 164 for the Mach diffuser have a thickness sufficient to
avoid
premature deterioration as steam passes through the pluraliity of steam
diffusion holes
168 over extended periods of time.
[0041] The plurality of steam diffusion holes 168 are arranged at least in
part
longitudinally along the cylinder wall 164. In this manner, the amount of
steam
supplied through the Mach diffuser 121 into the stock 126 flowing through the
heater
body 112 can be easily modulated by moving the adjustably positionable cover
154 to
expose a selected number of steam diffusion holes 168. The pattern of steam
diffusion
holes 168 in the Mach diffuser 121 as shown in Fig. 3 includes rows of steam
diffusion holes 168, with each row 170 being offset from t:he immediately
adjacent
rows in order to provide high hole density.
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[0042] Referring now in particular to Figs. 3 and 4, Mach diffuser 121 is
attached to heater body 112 first by seating the Mach diffuser base 166 on a
rim 171
located on an outwardly extending cylindrical flange 172 extending from heater
body
112. Next, the Mach diffuser end 161 engages a seal assembly 174 located at
the
steam inlet 114, Fig. 3. Seal assembly 174 is attached to heater body 112 by
inserting
a lip 176 on the seal assembly 174 into an outwardly extending steam inlet
projection
114 of the heater body 112. The interior surface 178 of seal assembly 174 is
preferably sealed by a pair of 0-rings 180 against the end 161 of the Mach
diffuser
121, although other types of sealing arrangements may be used.
(0043] The steam pipe 132 has a radially extending flange 184 that engages a
flange 186 of seal assembly 174. Preferably, flange 184 is not flush with the
end 187
of steam pipe 132, so that end 1.87 extends slightly outward from the surface
191 of
the flange 186 on the seal assembly 174. This interface preferably forms a
stepped
seal to prevent steam from escaping. Flange 186 and flange 184 are secured
using
bolts 188 extending through holes 190, Fig. 2.
[0044] An actuator 192 drives rotation of the cover 154 by rotating an
actuator
key 194. The actuator 192 is shown in the drawings as a phantom box. One
skilled in
the art will recognize that the actuator 192 may be activated manually,
pneumatically
or electrically. Preferably, the operation of the actuator, if pneumatic or
electric, is
controlled by an electronic controller in response to a feedback signal from a
downstream temperature sensor. The preferred actuator is a quarter turn
pneumatic
actuator that provides shaft rotation of 90 . The actuator key 194 has a shank
196 and
a key head 198. The key 194 engages the output shaft of the actuator 192 using
means
appropriate for the type of actuator provided.
[0045] The actuator 192 is mounted on an actuator plate 200 that is secured to
the base 166 of the Mach diffuser. As shown in Figs. 4 and 2, the actuator 192
is
mounted to base 166 of the Mach diffuser using a pair of threaded bolts 202
that are
screwed into apertures 204 located in the base 166 and the actuator plate 200.
Openings 206 and 208 are located in the actuator plate 200 and the base 166 of
the
Mach diffuser, respectively. The openings allow passage of actuator key 194
into the
base 166 of the Mach diffuser for engagement with the cover 154. Openings 206
and
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208 are aligned with the longitudinal axis of rotation for thie cover 154. The
actuator
key head 198 engages the cover 154 at the top end 158 of the Mach diffuser
where a
key slot 210 is provided. Preferably, the key slot 210 is located in a disc-
shaped end
cap 212, Fig. 4, that is rigidly attached (e.g., welded) to the top of the
cover 154 at end
158.
[0046] As shown in Figs. 1 and 3, the heater body 112 is attached to the stock
supply pipe 151 in such a manner that the longitudinal flovv axis of heater
body 112 is
aligned with the longitudinal flow axis of the supply pipe ].51. The supply
pipe 151 is
fitted with flanges 216a, 216b that are designed to engage flanges 218a, 218b,
respectively, located on heater body 112. The flanges 216a, 216b on the pipe
extend
radially from the cylindrical surface of the pipe 151, and are preferably
welded to the
supply pipe 151. Flanges 216a, 216b and 218a, 218b preferably have a stepped
interface 120. Flanges 216a, 216b, and flanges 218a, 218b have apertures 122
provided therein through which bolts 224 are passed to secure the heater body
112 to
the pipe 151.
[0047] Fig. 5 illustrates the flow of stock 126 through the heater body 112.
Note that the flow wets the outer side surfaces of the Macli diffuser 121. In
the
embodiment shown in Fig. 5, however, there is likely to be a stagnation point
at the
upstream surface 234. The existence of a stagnation point is likely to cause
unwanted
accumulation of suspended materials on or near the Mach diffuser 121.
Therefore, it
may be desirable to use a deflector 226 positioned upstream of the Mach
diffuser, see
Figs. 6a and 6b.
[0048] Referring now to Figs. 6a and 6b, a deflector 226 is preferably located
within the heater body 112 in a position upstream from the Mach diffuser 321.
Preferably, deflector 226 is welded to inner surface 228 (Fig. 3) of the
heater body 112
in order to secure the deflector 226 in a manner that is capable of
withstanding
pressure from the stock flow through the pipe 151. The deflector 226 is
preferably
constructed from an angle-iron shaped piece of metal, such as stainless steel.
A
leading edge 230 of the deflector 226 is aligned with the central axis of the
Mach
diffuser 121. The symmetric shape of deflector 226 deflects the flow of stock
away
from the upstream surface area. 234 on Mach diffuser 121 and towards the side
surface
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CA 02461607 2004-03-22
areas 233, 235. Thus, deflector 226 helps to pcrevent mater:ials suspended in
the stock
126 from flocculating in steam diffusion holes 168 facing upstream or
partially
upstream, and also prevents the stock 126 from stagnating at the Mach diffuser
121 at
the upstream surface area 234.
[0049] The Mach diffuser 121 is mounted to the heater body 112 transversely to
the longitudinal flow axis through heater body 112. Upstream surface area 234
and
downstream surface area 236 each occupy substantially one quarter or 90 of
the
circumference of the Mach diffuser 121. Upstream surface area 234 is directly
opposite downstream surface area 236, and both are aligned so that the center
of the
90 arc defming each area is substantially aligned with the longitudinal flow
axis
through heater body 112 and the pipe 151. Steam diffusion holes are not
present in the
upstream surface area 234 and the downstream surface area 236. Steam diffusion
holes 168 are located in the arcs remaining between upstream surface area 234
and
downstream surface area 236, i.e., steam diffusion holes 168 are located in
the side
surface areas 233, 235.
[0050] The cover 154 is preferably placed concentrically inside the Mach
diffuser 121, although one skilled in the art should realize the cover 154 may
be placed
concentrically around the outside surface of Mach diffuser= 121. Like Mach
diffuser
121, cover 154 has two areas of solid wall that each compirise substantially
one quarter
or 90 of the cover 154 circumference. Preferably, two longitudinal slots 162
are
centrally positioned on each side of the cover 154. Each slot 162 has a width
substantially one quarter or 90 of the circumference of the cover 154. The
ends 158
and 160 of the cover 154 also have a solid wall around the entire
circumference. Only
the central portion 155 of the cover 154 are slotted. The perimeter defining
the slots
162 on the cover 154 is substantially coextensive with the perimeter defining
the area
of the Mach diffuser 121 having steam diffusion holes 168 when the heater is
in the
fully open position.
[00511 In operation, the cover 154 is rotated to selectively cover steam
diffusion
holes 168 in the Mach diffuser 121 either partially, or completely. Steam 120
flows
through the heater inlet 114 into an intemal region within the Mach diffuser
121
through opening 156, Fig. 3. Steam flows from the internal region within the
Mach
CA 02461607 2004-03-22
diffuser into the flow of stock 126 by passing through the uncovered steam
diffusion
holes 168 in the Mach diffuser 121. In Fig. 6a, the cover 154 is shown in a
completely
open position, and all of the steam diffusion holes 168 are open. In Fig. 6b,
the cover
154 is shown in a partially closed position so that only a portion of the
steam diffusion
holes 168 are open. When the cover 154 is fully closed (not shown), the
cylindrical
wall 165 of the cover 154 covers all of the steam diffusion holes 168 in the
Mach
diffuser wall 164, and no steam is allowed to flow through the Mach diffuser
121 into
the flow of stock 126. When the cover 154 is moved to an open or partially
open
position, steam within internal region 152 of the cover 154 flows through the
exposed
steam diffusion holes 168 of the Mach diffuser 121. Stearn flows through the
respective steam diffusion holes 168 in the form of high velocity jets of
steam 238 into
the flow of stock 126 through the heater body 112.
[0052] The inside diameter of the heater body 112 should match the inside
diameter of the stock supply pipe 151. It is desired that the velocity of the
stock be
sufficient to continually wet the outer side surfaces 233, 235 of cylindrical
wall 164 of
Mach diffuser 121, thus eliminating the likelihood that continuous large
bubbles will
generate from the small jets of steam 238 into the flow of stock 126.
[0053] The steam pressure within Mach diffuser 121 is sufficient so that the
flow of steam through the steani diffusion holes is not hindered by the flow
of stock
126. As long as there is a sufficient pressure drop across tlle open steam
holes 168,
the flow of steam 120 into stock 126 will remain stable. The flow rate of
steam 120 is
defmed by the steam pressure and the accumulated flow area of the exposed
steam
diffusion holes 168. As mentioned, the amount of steam 120 added to the
flowing
stock 126 is precisely modulated by adjusting the position of the cover 154 to
expose
the proper amount of steam diffusion holes 168.
[0054] Referring now to Fig. 7, an improved, alternate embodiment of the Mach
diffuser is shown by reference numeral 321. The Mach dij:fuser 321 includes a
steam-
plug cover 330 having a generally cylindrical outer wall 331. The cylindrical
outer
wa11331 includes a pair of longitudinal open slots 332 that each occupy less
than one
quarter of the circumference of the steam plug 330. The slots 332 provide
access to a
generally open interior 340, as shown in Fig. 11. The longitudinal slots 332
are spaced
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CA 02461607 2004-03-22
180 apart from each other along the outer circumference of the steam-plug
cover 330.
The steam-plug cover 330 receives a supply of steam through its end 334 such
that
steam is supplied into the open interior 340 defined by the steam-plug cover
330.
[0055] As illustrated in Figs. 8 and 11, the steam-plug cover 330 is received
within a diffuser tube 336 having two emitter sections 337 each having a
plurality of
diffuser holes 338. The emitter sections 337, including diffuser holes 338,
are spaced
180 apart from each other and define an area through which steam can pass
through
the otherwise cylindrical wall of the diffuser tube 336. During operation of
the Mach
diffuser 321, the steam-plug cover 330 can be rotated relative to the
stationary diffuser
tube 336 such that the longitudinal slots 332 are selectively positioned in
alignment
with the series of diffuser openings 338. Thus, when the rotatable steam-plug
cover
330 is in the fully open position shown in Fig. 11, steam can flow through
each of the
longitudinal slots 332 and out of the diffuser openings 338,When the steam-
plug
cover 330 is in the fully open position, steam from within the internal
opening 340 can
flow out of the Mach diffuser through the longitudinal slots 332 and the
diffuser
openings 338.
[0056] Referring again to Figs. 8 and 11, the outer viall of the steam-plug
cover
330 includes a pair of slots 342 and 344 that each surround one of the
longitudinal
slots 332. The slots 342 and 344 are sized to each receive an 0-ring 346 and
347.
When the steam-plug cover 330 is placed within the diffuser tube 336, the 0-
rings
346, 347 contact the inner, smooth wall 348 of the cylindrical diffuser tube
336 to
provide a liquid-tight seal therebetween.
[0057] As shown in Fig. 12, when the steam-plug cover 330 is rotated 90 to a
fully closed position, the 0-rings 346, 347 create a fluid-tight seal on each
side of the
eniitter sections 337 to prevent the slurry material from flowing through the
diffuser
openings 338 and into the longitudinal slots 332. As previously described,
each of the
longitudinal open slots 332 formed in the steam-plug coveir 330 comprise less
than one
quarter of the outer circumference of the steam-plug cover. Thus, the solid
wall
sections 349 and 351 combine to comprise more than one-half the circumference
of
the steam-plug cover 330. As can be understood in Fig. 12, the circumferential
length
of each of the emitter sections 337 formed in the diffuser tube 336 is less
than the
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CA 02461607 2004-03-22
circumferential distance of the solid wall sections 349, 351 between the pair
of 0-rings
346, 347. Thus, each of the emitter sections 337 is captureci between the pair
of O-
rings 346, 347 when the steam-plug cover 330 is rotated to the fully closed
position
shown in Fig. 12.
[0058] The use of the 0-rings 346, 347 is particularly desirable when steam
pressure is not present within the open interior 340. Without the 0-rings,
when steam
pressure is not present, the slurry of material can pass between the outer
surface of the
steam-plug cover 330 and the inner wall of the diffuser tube 336 and enter
into the
open interior 340. The 0-rings 346, 347 operate to prevent the flow of
material in
such a direction.
[0059] Referring now to Fig. 13, the steam-plug cover 330 includes a pair of
pressure ports 350 that extend from the open interior 340 of the cover 330 to
the
exterior of the stearn-plug cover 330. Each of the pressure ports 350 are
formed in a
top wall 352 of the steam-plug cover 330, as can also be seen in Fig. 8. The
pressure
relief ports 350 equalize the pressure within the open interior 340 and the
area 354
contained above the steam-plug cover 330. In a prior art system not including
the
pressure ports 350, the pressure within the open interior 340 force the entire
steam-
plug cover 330 upward. Such pressure increases the difficulty of rotating the
steam-
plug cover 330 within the stationary diffuser tube 336. The pressure ports 350
provide
pressure relief points for the cover to prevent internal steam pressure from
creating a
large force that would inhibit the free rotational movement of the steam-plug
cover
330 within the unit. The pressure ports 350 pass through the upper plug wall
352 and
allow steam pressure to release from within the open interior 340.
[0060] As mentioned previously, the Mach diffuser of the present invention is
described as being particularly useful with a slurry of material, such as
paper fiber. In
some contemplated uses of the Mach diffuser of the present invention, the
slurry
includes abrasive particles, such as sand or other solid, particulate matter.
In such a
use, the sand particles entrained within the slurry create a;great deal of
wear with any
components that are in contact with the moving slurry. As can be understood in
Fig.
10, the deflector 349, the outer surface of the diffuser tube 336 and the
inner wall 356
of the heater body 312 are in direct contact with the slurry being heated. In
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CA 02461607 2004-03-22
accordance with the present invention, each of these three components includes
a wear
coating to provide additional durability such that the heater of the present
invention
can be used in a slurry including entrained particulate matter.
[0062] Referring first to Fig. 11, the deflector 349 includes a main body 358
formed from a metallic material. The main body 358 inclucies a wear coating
360
applied over its entire surface area. In the preferred embodiment of the
invention, the
wear coating 360 is an arc welded overlay consisting of two applied layers of
material
that result in a thickness of approximately '/4 inch. In the preferred
embodiment of the
invention, the wear coating 360 is a tungsten carbide material in a nickel
silicon boron
matrix. Preferably, the wear coating 360 is applied to the nn.etallic body 358
by
GMAW welding process. Alternatively, the wear coating 360 could be a 65%
tungsten carbide weld overlay applied via plasma transfer arc welding to the
same 1/4
inch thickness. The tungsten carbide wear coating 360 provides for increased
durability of the deflector 340, which is placed directly in the flow of
slurry as
described.
[0062] Referring now to Fig. 7, the deflector 349 is mountable within the
inlet
362 to the heater body 312 by a pair of connectors 364. The mounting of the
deflector
349 by using removable and replaceable connectors 364 allows the deflector 349
to be
easily replaced upon excessive wear. Referring now to Fig. 13, the deflector
349 is
shown mounted in the inlet 362 by the pair of connectors 364.
[0063] Referring now to Fig. 11, the diffuser tube 336 also includes a wear
coating 366, since the diffuser tube 336 also contacts the slurry, which may
include
abrasive entrained particulate matter. In the embodiment of the invention
illustrated,
the wear coating 366 extends around the entire outer circumference of the
diffuser
tube 336, including the emitter sections 337 area including the plurality of
diffuser
openings 338. The diffuser openings 338 extend through t:he wear coating 366
such
that steam can escape the open interior 340 through the plurality of diffuser
openings
338.
10064] In the embodiment of the invention illustrated, the wear coating 366
applied to the diffuser is a high velocity oxy-fuel (HVOF) coating consisting
of 88%
tungsten carbide and 12% cobalt to a finished thickness of approximately 0.60
to
14
CA 02461607 2004-03-22
0.100 inches. The high velocity oxy-fuel coating allows the wear material to
be
applied to the outer surface of the diffuser tube 336 while allowing the
diffuser
openings 338 to remain open. In an alternate embodiment of the invention, the
wear
coating 366 could be 65% tungsten carbide weld applied via plasma transfer arc
welding to the same thickness of 0.60 to 0.100 inches. In either case, the
diffuser
openings 338 remain unblocked to allow steam to escape from the open interior
340.
[0065] Although not specifically shown in Fig. 10, ttie inner wall of the
heater
body 312 also includes a wear coating that is arc welded over the metal body
using
two equal passes to obtain a total thickness of approximately'/4 inch. In the
preferred
embodiment of the invention, the wear coating is a tungsteri carbide material
in a
nickel silicon boron matrix. Preferably, the weld is applied in a GMAW
process. In
an alternative embodiment of the invention, the wear coating could be a 65%
tungsten
carbide weld overlay applied via plasma transfer arc welding to the same 1/4
inch
thickness.
[0066] Various alternatives and embodiments are contemplated as being within
the scope of the following claims particularly pointing out and distinctly
claiming the
subject matter regarded as the invention.
