FIELD OF THE INVENTION
The present invention relates to a slow-moving ash cleaning device in a rotating
air pre-heater to clean the soot deposited on the pre-heater chamber during pre-
heating of air by passing flue gas.
BACKGROUND OF THE INVENTION
In Rotating Air preheater, air is pre-heated with the flue gas. When the flue gas
passes through the preheater, the ash deposits over the air preheater chamber
affecting subsequent flow of the flue gas resulting in loss of heat energy. In
order to increase the heat absorption rate, the deposited soot is to be cleaned.
In rotating type Air pre-heater used in boilers , swinging arm type soot blowers
are generally installed. However, for bigger sizes of air pre-heaters the swinging
arm type soot blowers are not normally used because the arm element hang like
a cantilever beam. Accordingly, the arm element of soot blowers in large air
preheater needs frequent replacement to eliminate permanent deformation to
the element which is extended inside the air preheater. The prior art swinging
arm soot blower is not applicable to meet the requirement of large preheaters,
which additionally generated high vibrations and not being effective to clean the
soot deposited.

OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a slow-moving ash cleaning
device in a rotating air pre-heater to clean the soot deposited on the pre-heater
chamber during the pre-heating of air by passing flue gas.
SUMMARY OF THE INVENTION
Accordingly, there is provided a slow-moving ash cleaning device in a rotating air
pre-heater to clean the soot deposited on the pre-heater chamber during pre-
heating of air by passing flue gas, the air pre-heater having at least a housing
with a wall box assembly, a solenoid valve, and a support assembly, the device
comprising : a lance extension pipe welded to a lance tube, the extension pipe is
supportedly disposed in the air-preheater being exposed to flue gas temperature;
a diaphragm actuated valve assembly attached to a steam pipe line a push
button assembly having one each start and retract push button allowing the
lance tube to make a to and fro movement retractable by one each front limit
switch and rear limit switch disposed at both end of the device; a motor and a
gear box to power and control movement of the lance tube, the output of the
motor being connected to a chain assembly through sprockets; the solenoid
valve upon actuation admission of air to allow opening or closing of the steam
pipe line for steam entry based on air entry to the device; the lance tube fitted
with the traveling carriage upon movement enables steam entry to the lance

tube from a feed pipe which are injected through varying diameter for cleaning
the soot; and the rear limit switch activated upon arrival of the lance tube at
end position, the solenoid valve being activated to stop supply of steam which in
turn enables the device to retract to be ready for commencement of next phase
of cleaning.
The lance tube is permanently positioned inside the air pre-heater duly
supported which eliminates the problems of overhanging and permanent
deformation. The nozzle of the lance tube is of high grade temperature resistant
material to sustaining high temperature and erosion due to velocity of steam
flow. The steam flow is only in forward direction and complete cleaning is done
in forward direction only. Steam supply pressure can be adjusted online. Speed
reduction from the power pack assembly to drive chain is done through the
sprockets.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
Figure 1 - shows a schematic representation of the ash cleaning device in an air
pre-heater according to the invention.
DETAIL DESCRIPTION OF THE INVENTION
As shown in figure 1, a slow moving ash cleaning device consists of a lance tube
assembly (1), a feed tube assembly (2), a traveling carriage assembly (3), a
diaphragm actuated valve assembly (4), a connecting tube (5), a lance extension

assembly (6), a housing assembly (7), a plurality of limit switches (8), a push
button box assembly (9), a power pack assembly (10), and a drive chain
assembly (11).
The lance extension assembly (6) is exposed to flue gas temperature and is
supported inside the air preheater with suitable supports. The lance tube (1) is
welded with the extension tube (6). The slow moving cleaning device is fixed to
the air pre-heater housing with a wall box assembly (12). The other end of the
device is fixed with a Support Assembly (13) at the rear. The diaphragm
actuated valve assembly (4) at the end of this device is fitted with a Steam pipe
line.
There exists two limit switches (8) one at the front of the device and the other at
the rear to control the travel of the lance tube (1). The device is actuated with
the push button box (9) which comprises of Start and Retract push button.
The movement of the lance tube (1) is powered with the gear box assembly
(10) driven by a motor. The diaphragm actuated valve (4) fitted with the steam
pipe line is opened and closed based on the admission of air through the
actuation of a solenoid valve. When air is admitted through DA head valve (4),
the diaphragm (4) lifts the valve steam (4) by creating steam flow path toward
the feed pipe assembly (2) fitted in the Cleaning device.
The push button box (9) which has start and retract push button used for
making the lance tube (1) of the cleaning device to move to and fro inside the
air preheater.

When the start push button is actuated the signal from the start push button
triggers the motor and rotates the motor. The solenoid valve is simultaneously
actuated to admit the steam flow. As the gear box (7) is coupled to the motor,
the output gets connected to the chain assembly (11) through the sprockets. The
traveling carriage (3) traverse speed is maintained about 90mm/min. This speed
ensures complete cleaning of soot in the air preheater.
When the lance tube (1) fitted with the traveling carriage assembly (03) starts
moving, the steam enters the lance tube (1) from the feed pipe assembly (2)
and escapes though the nozzles of varying diameters present in lance assembly
(1) which in turn cleans the soot. When the lance tube (1) of the cleaning device
goes to the end, the reverse limit switch (8) is getting activated by the roller
present in traveling carriage (03) and the lance tube (1) retracts. During this
time, the solenoid valve closes and the steam supply stops. The device starts
retracting. When the lance tube (1) comes to the home position, the stop limit
switch (8) present in the rear of the device is actuated by the roller present in
the traveling carriage assembly (3) and the signal makes the motor stop and the
device halts.

WE CLAIM:
1. A slow-moving ash cleaning device in a rotating air pre-heater to clean the
soot deposited on the pre-heater chamber during pre-heating of air by
passing flue gas, the air pre-heater having at least a housing with a wall box
assembly, a solenoid valve, and a support assembly, the device comprising :
- a lance extension pipe welded to a lance tube, the extension pipe is
supportedly disposed in the air-preheater being exposed to flue gas
temperature;
- a diaphragm actuated valve assembly attached to a steam pipe line;
- a push button assembly having one each start and retract push button
allowing the lance tube to make a to and fro movement restrictable by
one each front limit switch and rear limit switch disposed at both end of
the device;
- a motor and a gear box to power and control movement of the lance
tube, the output of the motor being connected to a chain assembly
through sprockets;

- the solenoid valve upon actuation admission of air to allow opening or
closing of the steam pipe line for steam entry based on air entry to the
device;
- the lance tube fitted with the traveling carriage upon movement enables
steam entry to the lance tube from a feed pipe which are injected through
varying diameter for cleaning the soot; and
- the rear limit switch activated upon arrival of the lance tube at end
position, the solenoid valve being activated to stop supply of steam which
in turn enables the device to retract to be ready for commencement of
next phase of cleaning.
2. The slow moving ash cleaning device in a rotating air pre-heater to clean
the soot deposited on the pre-heater chamber during pre-heating of air by
passing flue gas, substantially as herein described and illustrated with
reference to the accompanying drawings.