FIELD OF INVENTION:
The present invention generally relates to Rotary Regenerative heat exchangers
normally used as Airpreheaters and more particularly to an improved airpreheater
sealing system which reduces the leakage of high pressure air stream to low
pressure gas stream during operation of the Airpreheaters.
BACKGROUND OF INVENTION;
Airpreheaters are used in Thermal power stations / Industrial applications to transfer
the heat from the flue gas leaving boiler / furnace to the entering combustion air
through regenerative heat transfer surface in a rotor which turns continuously
through the air and gas streams.
A Rotary Regenerative Airpreheater transfers heat from the flue gas leaving a boiler
to the entering combustion air through regenerative heat transfer surface in a rotor
which turns continuously through the gas and air streams. The rotor is divided into
compartments by a number of radially extending plates referred to as diaphragms.
These compartments are adapted to hold modular heat exchange baskets which
contain a mass of heat absorbent material commonly formed of stacked plate-like
elements.
In a typical Rotary Regenerative heat exchanger, the hot flue gas and the
combustion air enter the rotor shell from opposite ends and pass in opposite
directions over the heat exchange material housed within the rotor. Consequently,
the cold air inlet and the cooled gas outlet are at one end of the heat exchanger,
referred to as the cold end, and the hot gas inlet and the heated air outlet are at the
opposite end of the heat exchanger, referred to as the hot end.

The Airpreheater is divided into a flue gas side or sector and one or more
combustion air sides or sectors by the sector plates. Flexible radial seals on the
rotor, usually mounted on the top and bottom edges of the diaphragms, which are in
close proximity to these sector plates and minimize leakage of gas and air between
the sectors to separate the air and flue gas steams from each other. Likewise, a
rotor shell is mounted to the outboard ends of the diaphragms, forming the
periphery of the rotor, to prevent the air and gas steams from flowing through the
peripheral ends of the sectors and bypassing the heat transfer surface.
Circumferential seals seal the gap between the rotor and the rotor housing to
prevent bypass flow through the annulus formed between the rotor and the rotor
housing.
The Rotary Regenerative Airpreheater comprises a Rotor assembly, a rotor drive, a
support bearing assembly, a guide bearing assembly, a plurality of connecting plates
and a rotor housing. The housing surrounding the rotor is provided with duct
connections at both ends and is adequately sealed by radial and axial sealing
members. The radial seals are fixed in the diaphragm plate radial to the rotor post
along with a first seal holding bar and is touching the sector plate. Similarly, the axial
seals are fixed in the diaphragm plate axial to the rotor post along with a second
seal holding bar and is touching the axial seal plate which is mounted on the main
pedestal. The Regenerative Airpreheater is rotated by the drive system. During
operation of the Airpreheater, the rotor gets turn down which increases the gap
between the sector plate radial seals. Through this gap the high pressure air stream
leaks to the low pressure gas side. In order to reduce the leakage of high pressure
air to the low pressure gas, it is necessary to introduce a web seals in the
Airpreheater.

OBJECTS OF INVENTION:
It is therefore an object of the present invention to propose an improved
airpreheater sealing system which can be mounted between the top diaphragm and
bottom diaphragm plates axial to the rotor post.
Another object of the present invention is to propose an improved airpreheater
sealing system which is cost-effective.
A further object of the invention is to propose an improved airpreheater sealing
system which reduces the leakage of high pressure air stream to low pressure gas
stream.
A still further object of the invention is to propose an improved airpreheater sealing
system which reduces the leakage of high pressure air stream to low pressure gas
stream in the Airpreheater thereby increasing the life of heating elements of the
airpreheater.
SUMMARY OF THE INVENTION:
Accordingly thee is provided an improved airpreheater sealing system which reduces
the leakage of high pressure air stream to low pressure gas stream.
In the present invention, the diaphragm plate is split into a top diaphragm plate and
a bottom diaphragm plate and a first component of the improved sealing system is
mounted in between the top and bottom diaphragm plates radial to the rotor post in
addition to the existing radial seal fixed above the diaphragm plate. Similarly, a
second component of the improved sealing system is mounted between the top
diaphragm and bottom diaphragm plates axial to the rotor post in addition to

the existing axial seal fixed on the diaphragm plate. During operation of the
Airpreheater, the rotor gets turn down causing an increase in the gap between the
top diaphragm and the bottom diaphragm plates. Because of the provision of the
web seals, according to the invention, no passage is available for leakage of the high
pressure air stream to the low pressure gas stream and thus the leakage is reduced.
The inventive concept resides in configurating the diaphragm plates as 'the splitting
diaphragm plates' for example, the top and bottom diaphragm plates and mounting
the web seals between the top and bottom diaphragm plates. Accordingly, the web
seals function as a sealing means for the gap between the top and bottom
diaphragm plates during operation of the Airpreheater and thereby leakage of high
pressure air stream to low pressure gas stream is reduced considerably.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1(a)- shows an elevational view of an improved sealing system according to
the invention.
Figure 1(b)- shows a side view of an improved sealing system according to the
invention.
Figure 2(a)- shows a first component of the improved sealing system of the
invention disposed at the hot end of the airpreheater.
Figure 2(b)- shows a second component of the improved sealing system of the
invention disposed at a cold end of the airpreheater.

DETAILED DESCRIPTION OF THE INVENTION:
According to the present invention, the web seal is mounted between the top
diaphragm and bottom diaphragm plates radial to the rotor post in addition to the
radial seal fixed above the top diaphragm plates which minimizes the gap due to
turn down of the rotor and thus the leakage of the high pressure air to low pressure
gas stream is reduced.
Figures 1(a) & 1(b), show an improved sealing system comprising a top diaphragam
plate (01), a bottom diaphragm plate (02) and a web seal assembly (03).
As shown in figure -2(a), the improved sealing system comprises a diaphragm plate
split into a top diaphragm plate (01) and a bottom diaphragm plate (02) and a first
component of the sealing system (03) is mounted in between the top and bottom
diaphragm plates (02,03) radial to the rotor post (04). The web seal (03) is mounted
on the diaphragams (02,03) in addition to a radial seal (05) fixed above the top
diaphragm plate (01) and touching the bottom surface of the sector plate (06).
Similarly, as shown in figure 2(b), a second component of the sealing system (03) is
mounted between the top diaphragm plate (01) and bottom diaphragm plate (02)
axial to the rotor post (04) in addition to an axial seal (07) fixed on the top
diaphragm and bottom diaphragm plates (01,02). During operation of the
Airpreheater, the rotor gets turned down, due to this, the gap between the top
diaphragm (01) and the bottom diaphragm plate (02) gets increased. Because of the
provision of the web seals (03), no passage is available for leakage of the high
pressure air stream to the low pressure gas stream and thus the leakage is reduced.

WE CLAIM
1. An improved sealing system for rotary regenerative air preheaters to reduce
leakage of high pressure airstream to low pressure gas stream comprising:
- a first splitted diaphragm plate constituting a first top diaphragm plate (01)
disposed at the hot end of the air preheater;
- a second splitted diaphragm plate constituting a first bottom diaphragm plate
(02) disposed at the hot end of the airpreheater;
- a first web seal (03) constituting a first component of the sealing system
mounted between the first top and bottom diaphragm plates (01,02), and being
at a radial position in respect of a rotor post (04) at the hot end, the first web
seal (03) being accommodated in addition to a radial seal (05) fixed above the
first top diaphragm plate (01);
- a third splitted diaphragm plate constituting a second top diaphragm plate (01)
disposed at the cold end of the air preheater;
- a fourth splitted diaphragm plate constituting a second bottom diaphragm plate
(02) disposed at the cold end; and
- a second web seal (03) constituting a second component of the sealing system
mounted between the second top and bottom diaphragm plates (01, 02), and
being at a radial position in respect of a rotor post (04) at the cold end, the

second web seal (03) being accommodated in addition to an axial seal (07) fixed
on the second top and bottom diaphragm plates (01, 02);
characterized in that the web seal (03) allows a flexible movement between the
top diaphragm (01) and bottom diaphragm (02) which retain its original position
after each stage of rotation.

ABSTRACT

AN IMPROVED SEALING SYSTEM FOR ROTARY REGENERATIVE AIR
PREHEATER TO REDUCE LEAKAGE OF HIGH PRESSURE AIR STREAM TO
LOW PRESSURE GAS STREAM
An improved sealing system for rotary regenerative air preheaters to reduce
leakage of high pressure air stream to low pressure gas stream comprising;
a first web seal (03) constituting a first component of the sealing system
mounted between the first top and bottom diaphragm plates (01, 02) at the hot
end of the air preheater and being at a radial position in respect of a rotor post
(04), the first web seal (03) being accommodated in addition to radial seal (05)
fixed above the first top diaphragm plate (01);
a second web seal (03) constituting a second component of the sealing system
mounted between the second top and bottom diaphragm plates (01, 02) at the
cold end of the air preheater and being at a radial position in respect of a rotor
post (04), the second web seal (03) being accommodated in addition to an axial
seal (07) fixed on the second top and bottom diaphragm plate (01, 02) wherein
the web seal (3) causes a flexible movement of the top and bottom diaphragm
which retain its original position during rotation preventing leakage from high
pressure air stream to low pressure gas stream.