[0001] The invention relates to an ash disposal system for ash discharged from a coal-fired
combustion chamber, particularly for the pretreatment to dewater bottom ash from a
steam generator firing solid fuels.
[0002] In coal-fired steam generators, the manner inwhich the ash is disposed of is a matter
of considerable importance. The equipment for handling the ash is costly and can require
much maintenance. In prior systems, the ash is usually removed from an ash hopper
beneath the steam generator furnace along with a considerable amount of water and
allowed to settle out in dewatering bins over a long period of time, such as 18 hours.
Thus, large amounts of water have to be stored and held in reserve, not only requiring
much water but also a huge storage facility. Also, in colder climates, the dewatering
bins are subject to freezing and plugging during the lengthy dewatering period.
[0003] The invention as claimed is intended to provide a remedy. In particular, the invention
provides an ash handling system for the furnaces of steam generators, including an
ash hopper beneath the furnace, a water transport system for carrying the ash away
from the hopper, a screen arrangement for separating most of the water from the ash
so it can be recycled, and a relatively small settling bin for separating the ash
from the remainder of the water.
[0004] One way of carrying out the invention is described in detail below with reference
to the drawing, wherein the figure is a sectional side view of an ash disposal system
for the furnace of a steam generator.·
[0005] In the Figure, numeral 10 designates the furnace of a steam generator in which coal
is burned as a fuel. Slag and ash fall through the bottom opening 12 into an ash hopper
14, which is kept filled with water to a level 16 by means of pipe 18,
[0006] which continuously admits water to the hopper. An overflow pipe 20 keeps the water
level constant.
[0007] A valve 22 is periodically opened to discharge the ash. A clinker grinder 24 breaks
up the large ash particles so that they will not become jammed in the discharge opening,
and so that they may be easily transported in a stream of water away from the hopper
14. Generally, the material discharged from'the hopper 14 contains 75% solids, and
25% water. Water is added to the transport pipe 26, so that the mix transported therein
is 20% ash and 80% water. This mixture is transported to a holding or surge tank 28.
[0008] A gate valve 30 in the bottom of tank 28 can be opened at short intervals, or be
maintained in an opened position except when the equipment downstream thereof is being
repaired, to discharge the ash and water into a vibrating dewatering screen arrangement
32. A pair of screens, 34 and 36, are continuously vibrated in any well--known manner,
to separate the ash from a majority of the water. The first screen 34 can separate
out the more coarse particles, and screen 36 can remove the fines.
[0009] The screens are preferably slightly inclined, so that the solids gravitate towards
and are discharged through outlet 38. Some water will still be carried over with the
ash. The mixture being discharged through outlet 38 will be approximately 25% water
and 75% ash, and is discharged into holding tank 40. 'From here, it can be discharged
into a truck, storage pond, etc.
[0010] The water flowing through the screens is discharged through opening 42, and flows
through pipe 44 and pump 46 back to the hopper discharge to be used again as transport
water.
[0011] From the above, it can be seen that a system is provided which eliminates the need
for large settling tanks. The majority of the water can be quickly recycled, thus
reducing the requirement for large quantities of water. Also, because very little
time is involved, there are no freezing or plugging problems in the system. The majority
of the water is constantly flowing.
1. An ash disposal system for ash discharged from a coal-fired combustion chamber,
including an ash hopper (14) positioned beneath the combustion chamber (10) into which
the ash falls, means (18,20) for maintaining a given water level (16) in the ash hopper
(14), a discharge opening in the bottom of the ash hopper (14), through which the
ash is discharged, screen means (34,36) for separating ash from water, pipe means
(26) connecting the ash hopper (14) discharge opening with the screen means (32),
means for adding transport water to the pipe (26) at a point adjacent the ash hopper
(14) discharge opening, means (42-46) for recycling the water separated in the screen
means (32) back to the point adjacent the ash hopper (14) discharge opening, and means
(38) by which the separated ash can be discharged from the screen means (32).
2. An ash disposal system as set forth in Claim 1, including a holding tank (28) in
the.pipe means (26) upstream of the screen means (32).
3. An ash disposal system set forth in Claim 2, wherein the screen means (32) includes
a pair of screens (34,36), the first of which separates coarse ash particles from
the water, and the second of which separates fine ash particles from the water.
4. An ash disposal system as set forth in Claim 3, including a settling tank (40)
downstream of the screen means (32) ash discharge opening (38).
