Furnaces – Process – Treating fuel constituent or combustion product
Reexamination Certificate
1999-09-01
2001-04-17
Ferensic, Denise L. (Department: 3749)
Furnaces
Process
Treating fuel constituent or combustion product
C110S344000, C110S216000, C110S16500A, C110S16500A, C055S315000
Reexamination Certificate
active
06216612
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
This invention generally relates to the control of emissions from combustion processes such as coal-fired processes or other combustion processes that produce large quantities of solid fly ash particles. More particularly, the present invention relates to a system and method for segregating the separated fly ash particles based on particle size and collecting the segregated particles into individual storage containers. Specifically, the present invention relates to a separation system that allows ultra fine fly ash to be separately collected from a dry fly ash removal system by providing a dedicated removal system for removing fly ash particles only from the last separation device of the system.
2. Background Information
The combustion of coal and other similar fuels produces molten inorganic matter that is carried away in the exhaust gas stream as the fuel burns. The molten inorganic matter cools as the exhaust stream flows away from the combustion and coalesces into spherical or ellipsoidal ceramic particles in the general range of 0.01 to 500 microns in diameter. These combustion by-product particles are known in the art as fly ash.
Fly ash must be removed from combustion exhaust streams before the streams are exhausted to the atmosphere because of environmental concerns. Numerous methods and systems for removing fly ash are known in the art that effectively remove the fly ash from an exhaust stream. One problem common to all of these methods and systems is the cost of disposing of the collected fly ash. Although some of the fly ash may be sold for various commercial purposes such as for fillers, most fly ash must be landfilled at the expense of the company creating the fly ash. It is thus desired in the art to increase the quantity of commercially-valuable fly ash and consequently decrease the amount of fly ash that must be landfilled.
One known system that separates fly ash from a combustion exhaust stream is an electrostatic precipitator
12
depicted in
FIGS. 1 and 2
. Other systems
12
that will function with the concepts of the present invention are separation systems such as bag filters, cyclones, and others know in the art. Separation system
12
may be positioned as the final cleaning step for an exhaust stream from a coal-fired power production process. For instance, system
12
may be used in a power production process where coal is burned to create heat that produces steam to run generators. The burning coal creates an exhaust stream containing fly ash that must be substantially removed from the stream according to federal regulations. System
8
is a Fly Ash Removal System (FARS) which transports ash from the hoppers of the separation device
12
. FARS
8
transports the fly ash pneumatically to a storage facility (i.e. silo, pond, etc). The conveying air can be either a pressure or vacuum system. In the example of system
8
depicted in
FIG. 1
, the ash enters system
8
directly from an inlet conduit
10
that receives ash from electrostatic precipitator
12
positioned above conduit
10
and receives its transport air from air intake
11
.
Inlet
10
feeds a primary supply line
14
that is in communication with a plurality of separation units
16
. In this embodiment of system
8
, four separation units
16
are connected to primary supply line
14
in parallel such that each unit
16
receives substantially equal amounts of the fly ash-laden transport air. In other embodiments, a separate, individual precipitator may be used to deliver fly ash-laden transport air to each unit
16
without departing from the concepts of the present invention. Additional or fewer units
16
may be provided based on flow rate, need, and desired redundancies. Further systems
8
for one or more power producers may also utilize a silo
40
common to all systems
8
.
Each separation unit
16
includes a feed line
18
that connects primary supply line
14
to a coarse separator
20
. In this example, each coarse separator
20
includes a primary separator
22
connected to a secondary separator
24
. In the preferred embodiment of the present invention, each separator
22
and
24
is cyclone. Feed line
18
is connected to the inlet of primary separator
22
such that the fly ash-laden transport air is drawn into the separation chamber of primary separator
22
. The transport air exits primary separator
22
through an outlet
26
after at least a portion of the fly ash falls out of the transport air stream into a primary receiver
28
. The separated fly ash exists through a first gate
30
that selectively opens and closes the outlet
32
to primary receiver
28
. A storage hopper
34
is disposed below outlet
32
to collect the fly ash. The outlet
36
of storage hopper
34
is selectively opened and closed by a hopper gate
38
. Storage hopper
34
is positioned above a collection silo or storage container
40
that gathers fly ash from each separation unit
16
. A pressure equalization system
35
is provided to regulate the pressure in the system.
Outlet
26
of primary separator
22
is connected directly to the inlet
42
of secondary separator
24
. Second cyclone
24
has an outlet
44
through which the transport air is drawn and a secondary receiver
46
where the fly ash removed by secondary separator
24
is temporarily collected. The outlet
48
of secondary receiver
46
is selectively opened and closed by a secondary gate
50
that selectively opens secondary receiver
46
to storage hopper
34
.
Outlet
44
is connected to the inlet
52
of a tertiary separator
54
. Each tertiary separator
54
is preferably a bagfilter in system
8
. Other separators such as ceramic filters or other high efficiency separating devices known in the industry may also be used as the tertiary separator. Each bagfilter
54
is designed and configured to remove the smallest particles of fly ash from the transport air before it enters a vacuum pump
58
. Bagfilters
54
thus function as a final cleaning step for the transport air. A bagfilter transfer conduit
56
connects outlet
44
of each coarse separator
20
to inlet
52
of bagfilter
54
. The transport air flow is pulled through system
8
by vacuum pump
58
.
As is known in the art, bagfilter
54
may often use a collection of fabric filters, similar to common household vacuum cleaners, but at a much larger scale, to entrap air-borne particulate matter onto a filter surface, allowing the largely particulate-free air to continue through the filter surface. During operation of bagfilter
54
, particulate matter builds up on the surface of the filter. This buildup is commonly known as the bag's cake. Cakes are frequently allowed to build up to thicknesses of approximately 0.25 inch or somewhat more between intervals of cleaning. Bags in operational bagfilters are cleaned of cake buildup at periodic intervals that are determined by variables of operation and engineering design. The cleaning process often involves blowing air backwards through the bag filters, shaking the bags, or banging the tops of the bags, all of which cause a substantial portion of the filter cake to drop off the bags.
In system
8
, the bags of each bagfilter
54
are cleaned by knocking the cakes off of the bags and dumping the cake material into an open hopper
60
. First gate
61
selectively opens and closes into a transfer hopper
62
. Transfer hopper
62
is selectively opened and closed by a second gate
64
that controls access to silo
40
. The fly ash separated by bagfilter
54
is moved into hopper
62
and dumped into silo
40
. A pressure equalization system
63
is provided to control the pressure in the system because the bag filter is under vacuum and the silo is not. As such, the fly ash collected in bagfilters
54
is mixed with the fly ash collected in coarse separator
20
and is commonly disposed. Silo
40
is emptied through a rotary conditioning drum
66
and into a vehicle
68
that transports the fly ash to another location.
It has been discovered as part of the present invent
Hume John D.
Mainieri J. F.
Ridgeway R. F.
American Electric Power Service Corporation
Ferensic Denise L.
Rinehart K. B.
Sand & Sebolt
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