FIELD OF THE INVENTION
The present invention relates to a rigid and reliable support device tube bundles
with lower inter-spacing in a bundle chamber of fluidized bed combustion
boilers.
BACKGROUND OF THE INVENTION
In a fluidized bed combustion boiler, the heat transfer surfaces such as
Superheater, Reheater and Evaporator bundles are kept immersed inside the
inert bed material to recover the heat of the solid particles available in the bed of
the boiler. The bundles are kept inside a bundle chamber and inlet and outlet
headers of the bundles are kept outside the chamber being connected through
tubes penetrating the walls of the bundle chamber. The bundles are either
suspended from top or supported from bottom based on the coil penetration
location with respect to walls of the bundle chamber. There are a number of
tube rows or parallel flow paths with defined spacing in between the tube
elements. In specific cases, the distance between the tube elements of each
column is very less which requires different types of support . Just below the
tube bundle, air nozzles are provided on the grate for proper fluidization of the
bed material.

According to the prior art, the supports for the horizontal heat transfer surfaces
are provided in the second pass of the conventional boilers, which interalia face
only flue gas flow as the external medium. But, in case of a fluidized bed,
combustion boiler the tube bundles are in a physical contact with the agitating
solid particles since they are immersed in the fluidized bed. Hence, known
support for conventional boilers may not be adequate for a fluidized bed
environment due to dynamics of fluidization. In some cases, when the distance
between the tube elements of each column is very less, different type of support
is needed. Further, the tube bundles need to be supported inside the bundle
chamber considering the self weight of the bundle, tube thermal expansion and
the dynamic forces due to fluidization. The supports shall be sufficiently rigid
enough to take care of the above forces. Considering the harsh operating regime
inside the fluidized bundle chamber, it is necessary to develop support devices to
support the tube bundles inside the fluidized bed having less spacing between
the tube elements.
US 5943985 teaches a welded bracket for supporting SH and RG coils inside a
fluidized bed, in which one tube firmly engages with the other vertical tube. The
bracket is welded on both the tubes to prevent relative movement between the
tubes. The tubes can not move with respect to each other. The tubes have
angular surface contact with the bracket for intimate thermal contact with the
tubes.

US 4270599 discloses a support structure for supporting tube bundles in a
fluidized bed heat exchanger. A grid plate is supported in the housing for
receiving bed particulates material. A perforated support pier projects out from
the grid plate and supports the tube bundles and passes the air over the tubes. A
ladder type support structure is provided between adjacent tube sections to
support the tube sections relative to each other.
US 3530838 describes a support system for low and high temperature
superheaters. Low temperature superheater coils are directly welded to the
vertical hanger tubes whereas high temperature SH is indirectly supported from
these vertical hanger tubes. Horizontal elements rests on a support tube either
independently of in groups. Steam from drum passes through the horizontal
support tubes and acts as additional SH heat transfer surfaces.
US 4619315 describes a hot support bracket for supporting heat exchanger tubes
inside a fluidized bed furnace. It comprises a plurality of plates having openings
or cut outs at one edge for housing the tubes. Adjacent plates are connected for
stability. The vertical support plate rests on a wear channel on which the load of
the tubes are transferred and having provision for sliding.
US 3265044 teaches an arrangement for supporting a horizontal heat transfer
serpentine tube on a vertical tube with slidable arrangement. It is free to expand
without overstressing the support tube. One part of the support is welded to the
vertical tube whereas another part with groove is welded to the horizontal tube.
The sliding joints are free from jamming due to ash accumulation.

OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a rigid and reliable device to
support tube bundles with lower inter-spacing in a bundle chamber of fluidized
bed combustion boilers.
Another object of the invention is to propose a rigid and reliable device to
support tube bundles with lower inter-spacing in a bundle chamber of fluidized
bed combustion boilers which is capable to sustain harsh operating temperature
inside the bed including the thermal expansion forces and the dynamic forces of
fluidization.
SUMMARY OF THE INVENTION
Accordingly, there is provided a rigid and reliable device to support tube bundles
with lower inter-spacing in a bundle chamber of fluidized bed combustion boilers.
The fluidized bed material generally consists of inert particles and crushed coal
particles. The plurality of tubes are arranged as rows and columns with definite
spacing in between the tubes. Sometimes, the distance between the tube
elements of each column is very less which requires different type of support.
The tube elements are subjected to internal steam pressure, temperature and
other dynamic forces of fluidization. Considering this operating environment, a
cooled and rigid support device formed of a solid forged block with steam cooled
hanger tubes is provided to support the tube bundle. The tube bundles are
formed of multi loop horizontal coils.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 - shows an overview of a tube bundle forming heat transfer surface in a
fluidized bed combustion boiler.
Figure 2 - show the plan and elevational views of the tube bundle when
supported inside the combustion chamber.
Figure 3 - shows an assembled view of the support device of the invention.
Figure 4 - shows an exploded view of the support device of the invention.
DETAILED DESCRIPTION OF THE INVENTION
The attached drawing may be referred for better understanding of the invention.
A vertical steam cooled hanger tube (1) is interposed between two horizontal coil
(2) assemblies. The two horizontal coils are connected to the hanger tube
through a solid forged block (3) which also accommodates the hanger tube and
the coil assemblies. The forged block (3) is inserted into the vertical hanger
tubes (1) by shrink fit and held in position by welding with the hanger tube. A
central hold for inserting the block into the hanger tube is made to close
tolerances so that the shrink fit can be implemented between the forged block
and the hanger tube. The assembled forged blocks along with the vertical

hanger tube is inserted in between the two horizontal coil (2) assemblies. The
horizontal coil elements are pushed into a semi-circular profile available on both
sides of the forged block. The two profiled end blocks (4) are assembled from
both ends to kept the horizontal coil elements in position. The end blocks (4) are
welded with the block (3) after inserting the coils (2) into a position. It is
ensured that there is no welding over the horizontal tube element (2) so that the
tube can freely move along its length inside the block due to thermal expansion.
Similarly, each pair of the remaining horizontal coils are assembled to the
vertical hanger tubes. The number of hanger tubes per row of support is half the
number of horizontal coil assemblies since there is one hanger tube for each pair
of coil assemblies. The vertical hanger tubes (1) are suspended from the roof
casing of the bundle chamber. There are two rows of hanger tuber support for
the tube bundle to make it a simply supported configuration.

WE CLAIM :
1. A rigid and reliable device to support tube bundles with lower inter-spacing
a bundle chamber of fluidized bed combustion boilers, the tube bundle
comprising at least one vertical tube (1) having a central hole formed on the
vertical tube (1); and at least two multi loop horizontal coil assemblies, the
support device configured as a sold forged block (3) having semi-circular
profiles at both ends (4) of the block (3), the vertical tube (1) is shrink-fit
with the forged block (3) through the central hole to form a sub-assembly
(1, 3), the sub-assembly is inserted in between the at least two multi loop
horizontal coil assemblies (2) with the coil elements pushed into said semi-
circular profiles;
wherein the end blocks (4) are welded with the forged block (3) upon
insertably locating the coil elements (2) such that the horizontal tube
elements (2) remain free from welding to allow a force longitudinal
movement of the vertical tube (1) when susceptible to thermal expansion
during boiler operation and wherein the vertical tube (1) is a steam-cooled
hanger tube.
2. The device as claimed in claim 1, wherein a plurality pairs of horizontal coil
assemblies (1) are assembled to one each vertical tubes (1).

3. The device as claimed in claim 1, wherein the number of hanger tubes
per row of support is half the number of horizontal coil assemblies.

ABSTRACT

The invention relates to a rigid and reliable device to support tube bundles with
lower inter-spacing a bundle chamber of fluidized bed combustion boilers, the
tube bundle comprising at least one vertical tube (1) having a central hole
formed on the vertical tube (1); and at least two multi loop horizontal coil
assemblies, the support device configured as a sold forged block (3) having
semi-circular profiles at both ends (4) of the block (3), the vertical tube (1) is
shrink-fit with the forged block (3) through the central hole to form a sub-
assembly (1, 3), the sub-assembly is inserted in between the at least two multi
loop horizontal coil assemblies (2) with the coil elements pushed into said semi-
circular profiles; wherein the end blocks (4) are welded with the forged block (3)
upon insertably locating the coil elements (2) such that the horizontal tube
elements (2) remain free from welding to allow a force longitudinal movement of
the vertical tube (1) when susceptible to thermal expansion during boiler
operation and wherein the vertical tube (1) is a steam-cooled hanger tube.