Note: Descriptions are shown in the official language in which they were submitted.
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AN ASSEMBLY FOR FOSSIL FUEL DISTRIBUTION
FIELD OF INVENTION
The present invention relates to the field of fossil fuel combustion
arrangement. It relates in particular to a fuel distribution assembly for
equal and
homogenous pulverized fuel distribution in pulverized fuel conduits
throughout. It
also relates to a system for providing an equal and homogenous pulverized fuel
distribution.
BACKGROUND OF THE INVENTION
Coal coming out of mines requires to be crushed first in a crushing device at
power plant yards. Crushing device crushes coal with around 2-centimeter
diameter.
This crushed coal is then pulverized to powder in coal mills. This
pulverization is
required for better burning in a boiler. Burning of coal releases heat to
produce steam
at boiler. This steam rotates turbine and alternator to produce electricity.
Pulverized coal coming out from coal mill requires to be evenly distributed in
all individual burners for better burning and desired boiler efficiency.
Otherwise it
results in unburnt coal and unequal temperature at different zones of the
boiler. In a
typical boiler, coal particle and a primary airflow are fed from a pulverizer
to the
burners through a network of fuel lines. A single large diameter main conduit
along
with further branching of numerous small diameter conduits form a fuel line.
Primary
air helps the pulverized fuel to move towards the boiler. A single conduit is
used in
carrying pulverized fuel from the coal mill and further branches into smaller
conduits
to feed burners of the boiler. At branching of single conduit into numerous
smaller
conduits a flow imbalance takes place. Many users complain about the
phenomenon
of unequal temperatures in side the boiler. Investigations revealed that
unequal flow
after the coal mill is a major cause of such imbalance.
Coal has to travel a long path sometimes about 30 to 50 meters after outlet at
coal mill. Because of differences in conduits lengths and numbers and types of
elbows
in each fuel line, the different conduits from a pulverize mill usually have
different
flow resistances.
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Sometimes an orifice is fitted in each fuel line coming out of the mill.
Orifices
help to reduce flow imbalance only. But these orifices or flow restaictors are
not
sufficient. The long travel increases possibility of unequal flow through
conduits.
Another phenomenon takes place with high velocity air (around 30 meter per
=
second) is the formation of concentrated flow in one side of large diameter
conduit,
which is called "rope formation".
Imbalances in pulverized fuel flow through conduits also lead to maintenance
problems associated with conduits erosion and /or clogging for example
excessive
localized coal accumulation, damage to burners and wind boxes, and accelerated
water wall wastage. Problems such as these reduce the operating flexibility of
the
boiler. =
Effort of equal flow to each burner thus gets impaired due to complexity of
the
situation. A burner imbalance leads to higher carbon monoxide emissions and
high
levels of unburned carbons. Large and old boilers thus suffer from lesser
effectiveness
of burners. Most of the boilers have numerous burners that are to be fed by a
single
coal mill.
Also lesser space to accommodate new device is a typical problem in existing
=
boilers. Currently there is a need for a solution in industry for removal of
imbalance in
coal flow to burners. At the same time the boilers require homogeneous flow of
pulverized fuel (crushed coal). The solution needs to be used in space
constraints and
it should be cost effective.
The problem arises when coal mill outlet branches out in several numbers of
smaller diameter conduits or ducts to reach individual burner of boiler. The
resistance
of each branches being unequal due to different lengths and varieties of
configuration
=
causes unequal output of pulverized fuel. Concentrated flow of pulverized fuel
(coal
rope) inside the conduit is another problem that causes erosion and unequal
flow.
Although here we described the problems due to coal, similar problems are also
there
when any other fuel is used.
OBJECT OF SOME EMBODIMENTS OF THE INVENTION
An object of some embodiments of the present invention may be to provide an
assembly that provides
equal pulverized fuel to the pulverized fuel conduits and homogenous flow of
pulverized fuel through out the pulverized fuel conduits.
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An object of some embodiments ofthe present invention may be to provide an
assembly that withstands
the erosion effects of coal and increases the life of pulverized fuel conduits
supplying
pulverized fuel.
An object of some embodiments of the present invention may be to provide an
assembly which
maintains sufficient pressure drop across the pulverized fuel conduits which
is
necessary for the supply of pulverized fuel.
SUMMARY
The present invention provides an assembly for pulverized fuel distribution
from a mill to a boiler comprising a support unit and a resistance unit. The
support
unit comprises at least one tube. The resistance unit is disposed inside the
at least one
tube providing resistance and orientating the pulverized fuel flow.
The support unit comprises an inner tube and an outer tube having same
central axis. The support unit holds the whole assembly .The resistance unit
comprises
at least one partition plate and at least one deflector.
The deflector comprises a first and a second tapered side walls attached to a
base structure, the deflector is positioned such that the base structure
forrns a passage
for a zig zag movement of the pulverized fuel.
The partition plate is embedded inside the inner tube and the deflector is
circumferentially distributed between the inner tube and the outer tube. The
partition
plate provides partial resistance to the flow of pulverized fuel.
The base structures are alternatively attached to an inner surface of the
outer
tube and to an outer surface of the inner tube. The base structure is angled
with
respect to the central axis of the at least one tube. The first and the second
tapered side
walls are angled alternatively towards and away respectively with respect to
the
central axis of the tube.
The partition plate is extending in a radial direction from the central axis
of the
tube.
The present invention provides a system for pulverized fuel distribution from
a
mill to a boiler comprising a heater that generates a primary air, a mill that
pulverized
the coal into pulverized fuel, the pulverized fuel being supplied with the
help of
primary air through a main pulverized fuel conduit, an assembly that provides
pulverized fuel equally and homogenously into the main pulverized fuel
conduit, a
distributor that furcates the main pulverized fuel conduit into smaller
pulverized fuel =
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duct, the smaller pulverized fuel ducts feeding equal and homogenous
pulverized fuel to the
burners of a boiler.
The assembly is embedded inside the main pulverized fuel conduit.
In another embodiment the assembly is installed between the main conduit and
the distributor.
Some embodiments of the present invention provide an assembly for
pulverized fuel distribution from a mill to a boiler comprising: an outer
tube: an inner tube
disposed within the outer tube wherein the inner tube and outer tube have a
common central
axis; and a plurality of deflectors disposed circumferentially about the
central axis between
the inner tube and outer tube to provide resistance to a pulverized fuel flow;
wherein the
pulverized fuel flow passing through the outer and the inner tube is converted
into
homogenous pulverized fuel flow prior to distribution of the pulverized fuel
to the boiler.
Some embodiments of the present invention provide a system for pulverized
fuel distribution from a mill to a boiler comprising: a heater that generates
a primary air; a
mill that pulverizes coal into pulverized fuel, the pulverized fuel being
supplied with the help
of primary air through a main pulverized fuel conduit; an assembly that
converts the
pulverized fuel into homogeneous pulverized fuel and provides the homogenous
pulverized
fuel into the main pulverized fuel conduit; the assembly including: an outer
tube: an inner tube
disposed within the outer tube wherein the inner tube and outer tube have a
common central
) axis; and a plurality of deflectors disposed circumferentially about the
central axis between
the inner tube and outer tube to provide resistance to a pulverized fuel flow;
wherein the
pulverized fuel flow passing through the outer and the inner tube is converted
into
homogenous pulverized fuel flow and a distributor that furcated the main
pulverized fuel
conduit into smaller pulverized fuel ducts, the smaller pulverized fuel ducts
feeding the
homogenous pulverized fuel to burners of the boiler.
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BRIEF DESCRIPTION OF THE DRAWINGS
The invention, its further features, nature as well as its advantages, shall
be
described in more details with the aid of accompanying drawings. Referring to
the
drawings
Fig.1 schematically shows an embodiment of an assembly installed in a power
plant,
Fig. 2 schematically shows a front exploded perspective view of an assembly,
Fig. 2a and 2b schematically shows perspective view of two embodiments of
the deflectors for the assembly,
Fig. 2c schematically shows a perspective view of partition plate of the
assembly,
Fig. 3 schematically shows a partial transverse view of an assembly,
Fig. 4 schematically shows a plan view of an assembly,
Fig. 5 schematically shows a bottom perspective view of an assembly,
DETAIL DESCRIPTION OF THE DRAWINGS AND THE INVENTION
In Fig 1, reference numeral 1 denotes a coal mill that receives primary air 2
from air heater 3 and crushed coal from a crusher device 4 through a coal
feeder 5.
The coal milli further pulverizes the coal to powder size. Pulverized fuel is
moved
with the help of primary air 2 towards a boiler 6 through a main pulverized
fuel
conduit 21. The main pulverized fuel conduit 21 is connected with the coal
mill 1.
A distributor 20 is provided for furcating the main pulverized fuel conduit 21
into a branching of smaller pulverized fuel ducts 24. The distributor 20 is
attached for
example through flange or nut bolts with the main pulverized fuel conduit 21
from
one side and to the branching of smaller pulverized fuel ducts 24 from other
side
towards the burners of the boiler 6.
An assembly 7 is embedded inside the main pulverized fuel conduit 21 in a
non-moveable way for example through welding. The assembly 7 provides equal
and
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homogenous fuel to the distributor 20 for distributing it into branching of at
least one
smaller pulverized fuel duct 24. Alternatively the assembly 7 is installed
between the
main pulverized fuel conduit 21 and distributor 20.
The branching of smaller pulverized fuel ducts 24 feeds equal and
homogenous pulverized fuel to the burners of the boiler 6. The emissions from
boiler
6 after passing through an electrostatic precipitator 8 are discharged through
a
chimney 9.
The assembly 7 comprises a support unit 22 and a resistance unit 23.The
support unit 22 is configured to hold the resistance unit 23 and provides
strength and
support to the fuel distribution assembly 7. The support unit 22 is attached
to the main
pulverized fuel conduit 21 for example through welding and flanges.
The resistance unit 23 is configured to provide resistance to the pulverized
fuel
flow so that equal pulverized fuel is supplied to the branching of smaller
pulverized
fuel ducts 24 and also orients the pulverized fuel flow into homogenous
pulverized
fuel flow through out the smaller pulverized fuel ducts 24. The resistance
unit 23 is
embedded inside and attached to the support unit 22 for example through
welding and
flanges.
The support unit 22 comprises at least one tube. In one embodiment as
represented in fig 2, the support unit comprises for example two concentric
tubes: an
outer tube 10 and an inner tube 11. The inner tube 11 provides support,
rigidity and
toughness to whole assembly 7 during the online condition when boiler 6 is
fully
operational. The outer tube 10 protects the whole assembly 7 from the
corrosion
effects, which occurs due to movement of pulverized fuel through it and holds
the
whole assembly 7. The length of outer tube 10 and the inner tube 11
corresponds to
the length of the assembly 7.
Means for attachment are provided in form of welding, flanges, zigs, fixtures
nut bolts, rivets and any other type for attaching the assembly 7 to the main
conduit
21. The outer tube 10 is attached to the main pulverized fuel conduit 21 for
example
through welding or joined by a flange.
The resistance unit 23 comprises at least one partition plate 12 attached for
example through welding or flange inside the inner tube 11 and at least one
deflector13 equally circumferentially distributed between the inner tube 11
and the
outer tube 10. The assembly for example can have only one tube 10,11 to which
for
example at least one partition plate 12 or at least one deflector 13 attached
through
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welding or flange. The partition plate 12 provides partial resistance to the
flow of
pulverized fuel. The deflectors 13 provide optimum resistance to the movement
of
pulverized fuel flow leading to accumulation of pulverized fuel downstream at
the
entry point of the assembly 7.
Each of the deflectors 13 is attached for example through welding or flange to
an outer surface 14 of the inner tube 11 and to an inner surface 16 of the
outer tube10.
The deflectors 13 and partition plates 12 may be attached directly for example
through welding or through flanges with main pulverized fuel conduit 21. Zigs,
fixtures and nut bolts can also be provided with main pulverized fuel conduit
21 for
attachment. The resistance unit 23 is disposed inside the at least one tube
for example
the partition plates 12 inside the inner tube 11 and/or the deflectors inside
the outer
tube 10.
The central axis of the tubes 10, 11 is denoted by A-A' and is parallel to the
central axis of main conduit 21.
The partition plates 12 as shown schematically in Fig 2c are flat surfaced and
rectangular in shape. The partition plates 12 are attached for example by
welding
along the circumference to an inner surface 15 of the inner tube 11 and
orthogonally
placed from each other. The partition plates 12 can have a curved surface and
any
shape including square.
The partition plates 12 are extending in a radial direction from the central
axis
A-A'.
The main conduit 21, tubes10, 11 and further smaller pulverized fuel ducts 24
can be of any shape including circular.
Fig 2a, 2b shows perspective view of two embodiments of the deflectors 13.
The two embodiments of the deflectors 13 are symmetrical. The deflectors 13
comprise a first tapered side wall 17 and a second tapered side wall 18
attached along
at one of their ends to a base structure 19 in between.
The deflectors 13 are positioned such that the base structure 19 attached to
the
first tapered side wall 17 and the second tapered sidewall 18 forms a passage
for the
movement of the pulverized fuel. The base structure 19 can have any shape
including
rectangular, square, parallelogram. The base structure 19 corresponds to the
length of
the assembly7, measured along the axis A-A'.
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The first 17 and the second 18 tapered sidewalls are angled alternatively
towards and away respectively with respect to the central axis A-A'. The
tapered
sidewalls angle a, shown in fig2 is the angle of the tapered sidewalls with
respect to
central axis A-A'. The angle a is with in range of 0 degree to 180 degrees
with
respect to the central axis or more preferably in the range of 10 to 20
degrees. The
first 17 and the second 18 tapered side walls are angled to provide optimum
resistance
in the path of pulverized fuel so that maximum amount of air and pulverized
fuel can
pass through them. This optimum resistance helps in equal and homogenous
distribution of pulverized fuel into the at least one smaller pulverized fuel
duct for
feeding the burners of the boiler 6 through the deflector 20. The first
tapered side wall
17 and the second tapered side wall 18 can have any shape including trapezium,
rectangular, square, parallelogram
The angling of first 17 and the second 18 tapered side walls also helps in
maintaining a optimum velocity and minimum pressure drop which is necessary
for
the flow of pulverized fuel, so that the assembly 7 does not become a
hindrance in
flow of pulverized fuel.
In Figure 3 angled base structures 19 are shown in a transverse partial view
of
the assembly 7.The base structures 19 angler, is the angle of the base
structure 19
with respect to central axis A-A'. The base structures 19 angle r. is with in
range of 0
degree to 90 degrees with respect to the central axis A-A' or more preferably
in the
range of 10 to 30 degrees. The angling of base structure 19 provides optimum
resistance to break the rope formation and equal distraction, which leads to
equal and
homogenous distribution of pulverized fuel in the branching of the smaller
pulverized
fuel ducts 24. The equal and homogenous pulverized fuel move upstream
homogenously in central portions of the branching of the smaller pulverized
fuel ducts
24.
The geometrically symmetrical deflectors 13 are attached for example through
welding between the inner tube 11 and the outer tube 10 in such a way that the
base
structures 19 of the deflectors 13 are alternatively attached to the inner
surface 16 of
the outer tube 10 and to the outer surface 14 of the inner tube 11. Pulverized
fuel
moves towards the central axis A-A' along the deflector13 angled towards the
central
axis A-A' through base structure 19 attached to the inner surface 16 of the
outer tube
10 or alternatively towards periphery of outer tube 10 along the deflector13
angled
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away from central axis A-A' through base structure 19 attached to the outer
surface
14 of the inner tube 11.
Means for transporting the pulverized fuel through the assembly 7 are
provided for example a main pulverized fuel conduit 21, numerous smaller
pulverized
fuel ducts 24 concentric tubes 10,11 or conveyer belt or any similar type of
arrangement.
Means for supporting the assembly 7 are provided through the support unit 22
for example concentric tubes 10,11, and any other similar arrangement.
Means for resistance are provided in form of deflector 13, tapered sidewalls
17,18 and angled base plates 19, structures, of any shape and size and any
other type
in the assembly 7 to the flow of pulverized fuel.
The assembly 7 is used for a laminar flow, a periphery flow and a turbulent
flow. Basically type of flow has no impact on the working of the assembly 7.
The
assembly 7 ensures an equal distribution of pulverized fuel and breaking of
concentrated flow of pulverized fuel to homogeneous one for any kind of flow.
The
assembly 7 provides low to high resistance through partition plates 12 and
deflectors
13 respectively. Most of the pulverized fuel having laminar flow passes
through
partition plates 12 but in case of peripheral and turbulent flow high
resistance is
provided through deflectors13 for equal distribution and breaking of rope
formation.
Due to resistance, pulverized fuel coming from coal mill 1 starts accumulating
before the assembly 7. The pulverized fuel starts moving towards deflectors
13. The
base structure 19 of the deflector 13 pushes the pulverized fuel towards the
central
axis A-A' and towards a periphery of the outer tube10. A zigzag movement
results in
of the down stream-pulverized fuel due to this particular arrangement. This
zig zag
movement leads to equal distribution of the pulverized fuel and breaks the
rope
formation to a large extent. Rope formation occurs due to high concentration
of
pulverized fuel in one side or periphery regions of the main pulverized fuel
conduit 21
supplying pulverized fuel from coal mill 1 to the assembly 7.
After passing over the assembly 7, the pulverized fuel is converted in to a
homogenous equal upstream-pulverized fuel with a desired flow pattern. This
homogenous equal upstream-pulverized fuel is supplied through the branching of
the
smaller pulverized fuel ducts 24 to the burners of the boiler 6.
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The pulverized fuel is directed preferentially towards the plurality of
partition
plates12 in case of a laminar flow. The pulverized fuel is directed
preferentially
towards the plurality of deflectors 13 in case of a periphery flow and
turbulent flow.
=
In another embodiment a system for pulverized fuel distribution from a mill to
a boiler comprising a beater that generates a primary air, a mill that
pulverized the
coal into pulverized fuel, the pulverized fuel being supplied with the help of
primary
air through a main pulverized fuel conduit, an assembly that provides
pulverized fuel
equally and homogenously into the main pulverized fuel conduit, a distributor
that
furcates the main pulverized fuel conduit into smaller pulverized fuel duct,
the smaller =
pulverized fuel ducts feeding equal and homogenous pulverized fuel to the
burners
=
of a boiler.
The assembly 7 can be applicable to other fossil fuels including gas although
the description is here regarding coal.
By using the present assembly 7 imbalances in fuel distribution have been
greatly reduced resulting in for examples with in 2% variation from mean flow.
=
The assembly 7 may be produced in any desired shape or size including
circular, elliptical and cylindrical. It may be available singly, in
multiples, or in a
=
"set" of varying sizes and shapes to suite existing layouts or the proposed
lay outs
=
according to user needs. It may vary in shape and dimensions as determined by
its
desired locality and can be designed for any length and size of the main
conduit 21 as
well as further smaller pulverized fuel ducts 24.
The assembly 7 can be placed in a "set" in multiple outlets from multiple coal
=
mills as well as in the further of the smaller pulverized fuel ducts 24.
The assembly 7 is attachable vertically along the axis of vertically placed
conduits, horizontally along the axis of horizontally placed conduits and in
inclination
=
along the axis of inclined conduits.
The assembly 7 is made of mild steel with hard faced steel conduit with
internal fitments of specific designed numbers of plates. It can also be
prepared
through any similar material including stainless steel and cast iron.
The assembly 7 is preferably light in weight and may be dismantled and
relocated in very short span of time.
Some embodiments of the assembly 7 may be inexpensive, may easily fit in the
existing systems
with minimum alteration of existing systems and may need very little space.
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Although the invention has been described and illustrated with respect to
exemplary embodiments thereof, it should be understood by those skilled in the
art
that the foregoing and various other changes, omissions and additions may be
made
therein and thereto, without parting from the scope of the present invention.
Accordingly, other embodiments are within the scope of the following claims.
