FIELD OF THE INVENTION
The present invention is related to inter-connection of heat exchanger coils
immersed in a fluidized bed chamber. More particularly, the invention relates to a
holding device for coils assemblies to prevent vibration of the coils inside a
fluidized bed heat exchanger without restricting the free movement of the coils
during expansion.
BACKGROUND OF THE INVENTION
In a fluidized bed heat exchanger, recirculated solid particles are fluidized with
air, like a bubbling fluidized bed. Different heat transfer surfaces like
superheater, reheater and evaporator coils are kept inside the chamber to
extract from the solid particles. The coils are generally made up of plurality of
tubes placed parallel with uniform pitch. They are generally top, bottom or end
supported. Normally in large boilers, vertical tube support arrangement is
adopted for the tube surfaces provided in a fluidized bed. Vertical tubes are
connected to coils through support blocks, suitably designed to accommodate
the flexibility and thermal expansion of the tubes. The fluidization during
operation causes formation of bubbles in the bed with a low particle density
inside the bubble. These are subjected to strong hydrostatic force which causes

them to rise upwards rapidly. On reaching the surface, they burst forth like
volcanic eruption. This creates pressure fluctuations inside the chamber,
resulting in vibration of the coil tubes. With the increase in length, the coil
assemblies are more liable to vibrate. The rigidity of the coil assemblies with
vertical tubes may not be enough to keep them in position. Present invention
provides a method to interconnect the coils by making the system more rigid and
durable. Considering the operating regime inside the fluidized bed chamber, new
arrangement has been developed by stiffening the coil tubes. The method
envisages inter-connection of coils by means of steam/water cooled tubes.
EP 0492398 Bl describes the use of one second tube assembly, in the
perpendicular direction of the first tube assembly, to support the latter in a
fluidized bed boiler. The second tube assembly is made of plurality of tubes,
attached rigidly on top of each other, and the ends are supported on the walls. A
retainer lug is used in the second tube assembly to restrict the sideways
movement of the first tube assembly. It is welded to the top/bottom most tube
of the second assembly at the crossing point of first and second assemblies.
US 6244330 Bl discusses selection of plurality of tubes from the horizontal
assemblies and tying the selected tubes so as to arrest the movement of the
tubes in transverse direction, while allowing them to freely expand in longitudinal
direction. The tie includes restraints on opposite lateral side of the tubes and a
spacer is provided between the tube loops. A motion limiter is welded to at least
two of the plurality of tubes to restrict the movement of the restraints.

US 20140150735 A1 describes a fluidized bed heat exchanger, where plurality of
tubes in an assembly follow vertical boustrophedon path. Vertical tubes are used
to support the assemblies. Vertical tubes are alternatively attached with the
horizontal tubes by means of welded interference clamp support. Each horizontal
portion is preferably fixed to only one vertical tube. This allows reduction in
bending stresses in the exchanger.
IN 214945 teaches horizontal coil supports for heat recovery surface of boilers.
Horizontal tubes are supported on hanger tubes by welding vertical plate with
notches to the hanger tube. On the other side vertical plate is welded with the u-
clip. Horizontal tubes sit inside the u-clips. Another u-shaped Spacer clip is
closely fitted between the vertical plate and the horizontal tube to maintain the
position of the tubes.
However, the prior art describe the ways and means of supporting individual
tube elements, without any interconnection between the tube element
assemblies.
OBJECTS OF THE INVENTION
It is therefore an object of the invention is to propose a holding device for coils
assemblies to prevent vibration of the coils inside a fluidized bed heat exchanger
without restricting the free movement of the coils during expansion.

SUMMARY OF THE INVENTION
Accordingly, there is provided a holding device for coils assemblies to prevent
vibration of the coils inside a fluidized bed heat exchanger without restricting
the free movement of the coils during expansion, comprising a plurality of
horizontal/inclined coils assemblies disposed in pairs; a plurality of vertical tubes
each connected to each of the pair of coil assembly through a support block to
allow transfer of coil load during the fluidized bed heat exchanger; at least two
horizontal cooled tubes transversely attached to the vertical tubes above and
below the coil assemblies; and a connecting block flexibly disposed for each pair
of coil assembly joining both the vertical tubes and pair of coil assembly.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The following is the list of Figures accompanying this patent specification and
their description.
Figure 1 shows overall view of a tube bundle inside a fluidized bed combustion
boiler.
Figure 2 shows assembled view of a holding device of the invention.
Figure 3 shows elevation and plan views of the holding device of Figure 2.

DETAILED DESCRIPTION OF THE INVENTION
The attached drawing may be referred for better understanding the numbering
of components.
According to the invention, vertical tubes (1) are placed in between every two
horizontal / inclined coil assemblies (2). Two rows of vertical tubes (1) are used
to support the tube bundles. Every two coils (2) are connected to the vertical
tube (1) through a support block, to transfer the coil load during operation. Two
horizontal cooled tubes (3) are positioned on either sides of the vertical tubes
(1), in a transverse direction, above and below the coil assemblies. The cooled
tubes (3) are attached to the vertical tubes (1) by means of a connecting block
(4), every two assemblies (2) are attached together via the vertical tubes (1),
thereby holding all the vertical tubes (1) are effectively tying all the assemblies
(2) together, and enhancing the stiffness of the coil arrangement. The length of
the cooled tubes (3) depend on number of coil assemblies and their routing to
impart enough flexibility. Temperature differences causes relative movement
between the tubes (3) and the vertical tube (1), and this movement is allowed to
be unrestricted by the connecting block (4) arrangement, as it does not have any
welding with either the vertical tubes (1) or the cooled tubes (3). The purpose of
the cooled tube (3) is to inter-connect all the vertical tubes (1) so as to increase
the stiffness of the system, thus protecting the coil tubes (2) from vibration is
fluidized bed environment.

ADVANTAGES OF THE INVENTION
1. The steam/water cooled tube with connecting blocks, interconnecting
the coils enhance the stiffness of the coil arrangements, thus
preventing them from vibration.
2. Cooled tubes arrangement ensure sufficient cooling for the holding
device whereas conventional plate supports particularly when
operating in a fluidized bed environment tends to burn out quickly due
to uncooled extensions.
3. The holding device enhances the stiffness of the tubes by binding the
coils together. But, it does not impede free thermal expansion of coil
tube along the coil axis as there is no welding between them.

WE CLAIM :
1. A holding device for coils assemblies to prevent vibration of the coils
inside a fluidized bed heat exchanger without restricting the free
movement of the coils during expansion, comprising
a plurality of horizontal/inclined coils assemblies disposed in pairs;
a plurality of vertical tubes each connected to each of the pair of coil
assembly through a support block to allow transfer of coil load during the
fluidized bed heat exchanger;
at least two horizontal cooled tubes transversely attached to the vertical
tubes above and below the coil assemblies; and
a connecting block flexibly disposed for each pair of coil assembly joining
both the vertical tubes and pair of coil assembly.
2. The device as claimed in claim 1, wherein the connecting block allows
relative movement between the cooled tubes and the vertical tubes due to
temperature differential.

4. The device as claimed in claim 1, wherein the length of the at least
two cooled tubes depends on the number of coil assemblies and their
routing.
5. The device as claimed in claim 1, wherein the at least two cooled
tubes interconnect the vertical tubes.