EXTRACTEUR DE CENTRE A RACLOIR SOUS EAU

ASH HANDLING SYSTEM WITH SUBMERGED SCRAPER

Abrégé anglais

ASH HANDLING SYSTEM
WITH SUBMERGED SCRAPER
Abstract of the Invention
Apparatus for handling ash and slag produced in the
combustion of coal or other ash-bearing fuel in the furnace (10)
of a steam generator, including an ash hopper (14) beneath the
furnace into which the ash initially falls. A pair of scraper
conveyors (30, 32) which are submerged in water are located below
the ash hopper from which the ash is continuously disposed of.
Water nozzles (40) are located in the ash hopper for cooling and
moving the ash.
C780960

Revendications

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An ash-disposal system for ashes discharged from a coal-
fired or other ash-bearing fuel-fired combustion chamber,
including an ash hopper positioned beneath the combustion chamber
into which the ash falls, spray nozzles for directing water jets
onto the falling ash, a pair of openings in opposite walls of the
ash hopper adjacent to the bottom thereof, a pair of gate valves
associated with the ash hopper openings, means for maintaining a
given water level in the ash hopper when both gate valves are in
their closed positions, a pair of tanks located beneath the ash
hopper, each being beneath the respective ash hopper openings,
means for maintaining a given level of water in each tank,
conveyor means located in each tank beneath the water level for
removing ash from the tanks, and water seal means between the
combustion chamber and the ash hopper, and between the ash hopper
and the tanks, so that the dry ash fines cannot escape to the
atmosphere, and atmospheric air cannot enter the combustion
chamber, so that if one of the tanks needs repair, its respective
gate valve can be closed, and if both tanks need repair, both gate
valves can be closed, and the ash can be temporarily stored in the
thus water-filled ash hopper.

Description

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Background of the Invention
In coal-fired steam generators, the manner in which the
ash is handled and disposed of is an item of considerable
importance. The equipment for handling the ash cannot only be
costly, but if it requires much maintenance, it can also lead to
untimely and lengthy shut-downs of the entire steam generator.
Summary of the Invention
In a broad aspect, the invention resides in an ash-
disposal system for ashes discharged from a coal-fired or other
ash-bearing fuel-fired combustion chamber, including an ash
hopper positioned beneath the combustion chamber into which the
ash falls, spray nozzles for directing water jets onto the falling
ash, a pair of openings in opposite walls of the ash hopper
adjacent to the bottom thereof, a pair of gate valves associated
with the ash hopper openings, means for maintaining a given water
level in the ash hopper when both gate valves are in their closed
positions, a pair of tanks located beneath the ash hopper, each
being beneath the respective ash hopper openings, means for main-
taining a given level of water in each tank, conveyor means
located in each tank beneath the water level for removing ash from
the tanks, and water seal means between the combustion chamber and
the ash hopper, and between the ash hopper and the tanks, so that
the dry ash fines cannot escape to the atmosphere, and atmospheric
air cannot enter the combustion chamber, so that if one of the
tanks needs repair, its respective gate valve can be closed, and
if both tanks need repair, both gate valves can be closed, and
the ash can be temporarily stored in the thus water-filled ash
hopper.

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Brief Description of the Drawing
Figure l is a cross-sectional side view of the ash
handling apparatus for the furnace of a steam generator; and
Figure 2 is a view taken on line 2-2 of Figure l.
Description of the Preferred Embodiment
Referring to Figure l, numeral lO denotes the furnace
bottom opening of a coal-fired steam generator, through which
molten ash and slag are discharged. A water seal 12 permits
thermal expansion of the top-supported furnace, while preventing
exposure of the interior of ash hopper 14 to the atmosphere. Ash
falls into the ash hopper (Figure 2), sliding down the angled
floor to one of the openings 18, 20. These openings can be closed
by gates 22, 24 when
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necessary, as later described. This hopper may or may not be refrac-
tory-lined and may or may not be water-cooled.
The ash falls through the openings 18, 20 into one or the
other of the longitudinal tanks 26, 28. Each tank contains a scraper
conveyor 30, 32, the upper runs of which are submerged, or located
beneath the water level maintained in each tank. The upper runs of
the conveyors carry the clinkers to the end of the tanks, where they
can be discharged into trucks or onto mechanical conveyors (not shown)
and transported away. A portion of the water in the tanks is con-
stantly removed and replenished to maintain the main body of waterat a temperature not exceeding 160F.
In normal operation, the conveyors are in constant opera-
tion, continuously removing ash. When one of the conveyors need
repair, its corresponding gate valve, for example 22, can be closed,
so~all of the ash is then discharged through opening 20 into tank 28.
Tank 26 can then be drained so that the conveyor 30, or other broken
equipment, can be repaired without necessitating shutdown of the steam
generator.
~f both conveyors need some minor repairs simultaneously,
~ both gate valves 22 and 24 can be closed. Water from the nozzles 40
can then be used to fill the ash hopper 14 to a given level, and the
ash can be temporarily stored in the ash hopper for a short time
while minor repair or maintenance work is done to the conveyors. An
overflow pipe 42 keeps the water at a constant level during this type
of operation.
The water nozzles 40 provide an additional function. During
normal operation, they direct jets or sprays of water onto the falling
ash, thus providing hydraulic fracturing and sluicing of large ash
particles, preventing the openings 18 and 20 from becoming clogged.
Alternatively, the gates can be kept closed, and the ash hopper nor-
mally filled with water. The gates could then be intermittently
opened to allow discharge of the ash.
From the above, it can be seen that in normal operation,
the ash is continuously removed by both of the scraper conveyors.
Falling ash from furnace 10 strikes surface 16 of the ash hopper,
preventing damage to the conveyors 30, 32. The drop from the ash
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hopper bottom to the conveyors is retatively short compared to the
height of the ash hopper. When repair work is required on one of
the conveyors, the ash is removed by the other one. This is
accomplished without the necessity of moving the tank and conveyor
and also without shutting down the steam generator. In addition,
minor maintenance can be done to both of the conveyors while the
ash is temporarily stored in the ash hopper 14. Certainly, the
length o~ time of this operation is limited by the ash storage
capacity of the hopper 14.
C78096~