Note: Descriptions are shown in the official language in which they were submitted.
~03~ ~
REMOVABLE SEAL PLATES
Background of the Invent;on
In coal-fired steam generators, the manner in which the
ash is handled and disposed of is an item of considerable importance.
One means used today for continuously removing ash and slag which
falls through an opening in the furnace bottom is a scraper conveyor
which is submerged in a tank of water. When the unit ;s shut down
~or periodic maintenance, it is desirable to be able to move the
entire scraper conveyor unit, including the tank in which 1t is
housed, from beneath the furnace so that it can be easily worked on,
and so that it can be replaced with another unit if major repair is
required.
A water seal is generally provided for preventing the
a~mosphere from being exposed to the furnace interior. This consists
of a plate extending down and surrounding the furnace bottom opening9
which plate extends into the submerged scraper conveyor tank, which
tank is filled with water, thus forming a water seal. This type of
seal is provided because it ailows the furnace to grow relative to
the submerged scraper conveyor unit caused by thermal expansion.
2~ Large furnaces are generally top supported, so that they are free
to expand in a downward direction when the unit is first started up.
This growth can be on the order of 10-12" from the cold to the ho~
condition.
The above provides the problem of how to be able to
quickly remove the submerged scraper conveyor unit ~rom beneath the
furnace when the unit is shut down for ma1ntenance. In the past9
it has been necessary to allow the unit to cool down to a point
where work~en can unbolt the seal plate from the furnace bottom.
This cooling and unbolting time is considerable and can caus~ the
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entire steam generator to be down for lengthy malntenance periods.
Summary of the Invention
In accordance with the invention, a submerged scraper
conveyor unit is provided beneath a coal-fired furnace and a water
seal is provided therebetween to prevent the furnace gases from
escaping to the atmosphere. This water seal is formed by providing
plate means extending down from the furnace bottom into the water-
filled submerged scraper conveyor tank~ The upper end of the plate
means forms a seal with the furnace bottom. The plate means are
capable of being moved upwardly and downwardly by a hydraulic or
electr;c motor so that it can be moved downwardly into sealing
relationship during operation of the furnace~ and can be moved to
its up position during a maintenance shutdown so as to permit the
submerged scraper conveyor tank to be removed from under the furnace.
Brief Description of the Drawings
Figure 1 ;s a sect;onal side view of a submerged scraper
conveyor unit and its assoc;ated furnace constructed in accordance
with the ;nvent;on; and
Figure 2 ;s a view taken on line 2-2 of F;gure 1.
9escr;pt;on of the Preferred Embodiment
Looking now to the drawings, numeral 10 des;gnates a fur-
nace or a transition chute which is attached to a furna~e of a steam
generator in wh;ch coal is burned. Molten ash and slag are dis-
charged through the Furnace bottom or trans;tion chute opening 12,
and falls into the submerged scraper conveyor unit 14. The tank 16
is filled with water 18 and contains a conveyor belt 20 with integral
scraper blades ;n the bottom thereof, by means of which the cooled
ash and slag is continuously removed from the tank (Fig.2). The
upper run of the conveyor 20 carries the cl;nkers to the end of the
tank, where they can be d;scharged ;nto trucks or onto a mechanical
conveyor (not shown) and transported away. A portion of the water
in the tank is constantly removed and replenished (wh;le maintain;ng
a g;ven water level) to ma;ntain the main body of water at a temper-
ature not exceeding 160F.
A water seal permits thermal expans;on of the top-supported
furnace 10 wh;le prevent;ng exposure of the inter;or thereof
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to the atmosphere. The water seal is formed by plate 24 which is
secured to the bottom of the furnace and extends downwardly into
the water in tank 16. The plate 24 extends around the entire peri-
phery of the opening 12, so as to completely seal the opening between
the furnace lO and the submerged scraper conveyor unit 14. Dur;ng
operation of the furnace9 the plate 24 extends downwardly into the
water in tank 16 so as to ~orm the seal. In addition, a movable
neoprene gasket 40 cooperates with the stationary metal rim 42, to
form a seal at the furnace bottom end. As in the case of plate 2~,
both the rim 42 and gasket 40 extend .around the entire periphery of
the opening 12 so as to completely seal the opening when in its
sealing position. The gasket 40 is attached to the plate 24, and
is thus movable wi~h it. Rim 42 is attached to the furnace 10 by
means of an imperforate metal skirt member 44.
The tank 16 is provided with a drain 46, so that it can
be emptied during a maintenance shutdown. The tank is also mounted
on wheels 48, so that it can be quickly moved from beneath the
furnace lO during a shutdown. The plate 24 and gasket 40 are motor
actuated, so that during furnace operation they are in the;r lower
position in sealing re1ationship with the water in tank 16, and rim
42 respecti~vely. When it is desired to move ~he tank 16, during a
maintenance shutdown, the plate 24 and gasket 40 are moved to their
upper positions, so that the plate ls located above the upper edge
of tank 16 and it will clear the plate 24 during sideways movement
in either direction.
The gasket 40 and plate 24 arè secured to a piston-cylinder
arrangement 50, 52, by rods 5~. The rods 54 are supported and guided
by lateral guide members 56 which are secured to the furnace, and
prevent any lateral movement of the various members. Hydraulic flu;d
can be pumped by pump 58 beneath the pistons 50 through valve 60 and
above the pistons through valve ~2. Fluid can return to the storage
or sump tank 64 from above and below the pistons 50 through valves
66 and 68, respectively. As shown in F;gure 2, there are two piston-
cylinder arrangements located on each of the four sides of the fur~
nace bottom, so that the gasket 40 and plate 24 move up and down
smoothly without binding. All eight of the piston~cylinders are
supplied and drained of hydraulic fluid through lines 70 and 72, which
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extend all the way around the furnace bottom.
The manner in which the water seal ;s operated should now
be apparPnt. When it is desired to move the submerged scraper
conveyor unit from beneath the furnace 10, the pump 58 is ac~uated
and valves 60 and 66 are opened. Valve 60 permits fluid to flow
through hydraulic line 70, forcing the pistons 50 upwardly. ~imit
switches (not shown) which are actuated by the plate 24 can be used
to stop the pump 58 and close the valves when the plate is 1n its
proper upper or lower position, as the case may be. When plate 16
is in sealing relat;onsh;p w;th the water 18, then intermediate seal
member or gasket 40 is in sealing engagement with rim ~2. During
the opposite operation, gasket 40 is in its up position, out of
contact with rim 42. Tank 16 is drained of water through valve 46
and the tank 16 can then be moved from beneath the furnace 10 to be
worked onO If major work is required, a second or spare tank can
be placed beneath the furnace while the other one is being fixed or
repaired.
When the unit is to be put back into operation, the tank
16 is firs' positioned beneath the furnace 10. Pump S~ is actuated~
and valves 62 and 68 are opened. ~alve 62 admits fluid to line 72,
forcing pistons 50 downwardly while fluid drains from line 70 into
the sump 64 through valve 68. Tank 16 is meanwhile being f~lled wlth
water. The furnace can thereafter be fired with coal or other ash
bearing fuel.
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