FIELD OF INVENTION
The present invention relates to erosion control of economizer tubes in high coal
ash boilers. More particularly, the invention relates to a device provided between
two adjacent finned tube economizer in the vertical direction, i.e., along the flow
direction.
BACKGROUND OF THE INVENTION
The feed water from the high pressure heaters enters the economizer and picks
up heat from the flue gases after the low temperature super heater. Many types
of economizer are designed for picking up heat from the flue gas. These can be
classified as an 'in-line' or 'staggered' arrangement based on the selected type of
tube arrangement. The staggered arrangement is compact and occupies less
volume for the same amount of heat transfer when compared to the in-line
arrangement.
Economizers are also designed with plain tube and fined tubes. The fins can be
longitudinal. All these types are suitable for clean fuels like gas, oil, and low ash
coals. For high ash coals, only the plain tube in-line arrangement Is used. This is
mainly to reduce ash erosion and thus reduce erosion failures.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a device to reduce erosion in
economizer tubes disposed between two adjacent tubes of the economizer and
along the flue gas flow direction.
Another object of the invention is to propose a device to reduce erosion in
economizer tubes disposed between two adjacent tubes of the economizer and
along the flue gas flow direction, which regularizes the flue gas flow path with an
in-line arrangement of economizer coils of high ash coal Boiler.
A still another object of the invention is to propose a device to reduce erosion in
economizer tubes disposed between two adjacent tubes of the economizer and
along the flue gas flow direction, which controls the flow induced vibration,
occurring in the boiler second pass, in the economizer zone.
A further object of the invention is to propose a device to reduce erosion in
economizer tubes disposed between two adjacent tubes of the economizer and
along the flue gas flow direction, which enhances the heat transfer rate.
A still further object of the invention is to propose a device to reduce erosion in
economizer tubes disposed between two adjacent tubes of the economizer and
along the flue gas flow direction, which increases the Boiler economizer life.
SUMMARY OF THE INVENTION
Accordingly, there is provided a device to reduce erosition in economizer tube
bark in high coal ash boilers. The device comprises an in-line arrangement of the
economizer tube bank consisting of plain tubes with continuous flat provided
between two adjacent tubes. The flat metal strip is placed between two Boiler
economizer tubes bank and along the flow direction. The device allows alteration
between two plain economizer tubes. The continuous flat placed between two
plain economizer tubes, is used to reduce the erosion in the economizer tube
bank in high coal ash Boiler. Further, the device enables reduction in the flow
induced vibration due to alteration in Boiler economizer tube bank.
The inventive device reduces the erosion in Boiler economizer without disturbing
the flow path. Recirculation and eddies which is formed due to the intermittent
placement of the tube is reduced to a large extent by this invention, which in
turn reduces the erosion in the boiler economizer. Since the flow is streamlined
and unperturbed, reduction of flow induced vibration is also envisaged in this
Invention.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 shows an embodiment of a typical in-line arrangement (plain tube with
discontinuous flat) of economizer tube bank.
Figure 2 shows an embodiment of the inventive device to reduce erosion in
economizer tubes in high ash coal boilers.
DETAILED DESCRIPTION OF THE INVENTION
IN-LINE ARRANGEMENT OF BOILER ECONOMIZER TUBE BANKS
Figure 1 shows a typical in-line arrangement (plain tube (1) with discontinuous
flat (2) or without flat) of Boiler economizer tube bank for high coal ash Boiler. In
a typical-in-line arrangement of the economizer, the flue gas glow path (3) is not
aligned with the tube bank in the flow direction. A plain tube and/or finned tube
economizer placed in a pitch, generall produces a gap between the tubes in the
tube bundle, which gap causes the flue gas path (3) to be perturbed and to form
local eddies. Due to formation of the eddies and turbulent nature of the flow
including the angle of gas path, a changed flue gas path (4) is developed which
increases the erosion rate. The edges of the flat fins (5) are eroded in a very
short time. The turbulent nature of the flow and cross over flow behavior
generates flow induced vibration in the tube bank. These erosion behavior and
flow induced vibration greatly reduce the life of the economizer tubes.
Figure 2 shows an embodiment of the invented device which interalia constitutes
an in-line arrangement (plain tube with continuous flat (6) between two adjacent
tubes) of economizer tube bank. This flat (6) reduces the erosion in the
economizer tube bank in high coal ash Boiler, because, the device ensures that
the flue gas flow path (7) is not disturbed throughout the economizer tube bank
as shown in Figure 2. The flow induced vibration is reduced due to disposition of
the flat metal strip (6), which is of the same material as the flat fin in Boiler
economizer tube bank.
WE CLAIM
1. A device for reducing erosion in a tube bank of economizer in high ash
coal boilers, comprising:
an economizer tube bank consisting of In-line arrangement of plain
tubes;
wherein continuous flat strip members Interposed between two
adjacent tubes;
wherein the flat strip members disposed in the flow direction to ensure
an unaltered flue gas path; and
wherein the flat strip members are formed of material Identical to that
of flat fin in the economizer tube bank.
2. The device as claimed in claim 1, wherein the flat strip member Is
enabled to reduce flow induced vibration due to maintenance of
unaltered flue gas path.
3. A device for reducing erosion in a tube bank of economizer In high ash
coal boilers as substantially described and Illustrated herein with
reference to the accompanying drawings.

The invention relates to a device for reducing erosion in a tube bank of
economizer in high ash coal boilers, comprising: an economizer tube bank
consisting of in-line arrangement of plain tubes; wherein continuous flat strip
members interposed between two adjacent tubes; wherein the flat strip
members disposed in the flow direction to ensure an unaltered flue gas path;
and wherein the flat strip members are formed of material identical to that of flat
fin in the economizer tube bank.