Combustion device

Details Combustion device Combustion device

1999-09-10

2001-07-24

Wilson, Gregory (Department: 3749)

Heating

With heating gas conveying, agitating, scattering or...

C432S015000, C432S016000, C122S00400R, C122S412000

Reexamination Certificate

active

06264465

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to combustion apparatus for use as boilers wherein refuse-derived fuel (hereinafter referred to as “RDF”) is used as the fuel for incinerators for burning municipal waste.
BACKGROUND ART
FIG. 4
shows a combustion apparatus conventionally utilized as a boiler wherein RDF is used as its fuel.
With reference to
FIG. 4
, the combustion apparatus comprises a fluidized-bed furnace
1
, a cyclone
2
(dust collector) disposed downstream from the furnace
1
for separating a free-flowing medium and a combustion residue discharged from the furnace
1
from combustion gases and collecting these solids, and a medium-residue return channel
3
provided between the cyclone
2
and the fluidized-bed furnace
1
for returning the free-flowing medium and the combustion residue collected by the cyclone
2
to the furnace
1
therethrough.
The fluidized-bed furnace
1
forms a fluidized bed from sand, or like free-flowing medium respectfully with primary air and secondary air sent from an air preheater. A multiplicity of water tubes (not shown) for a boiler are arranged within the furnace
1
to cover the inner peripheral surface thereof. These water tubes communicate at their upper ends with a steam drum
6
via an unillustrated header. RDF is supplied from an unillustrated scale conveyor to a hopper
7
in portions of predetermined quantity and placed into the fluidized-bed furnace
1
from the hopper
7
. Noncombustibles and free-flowing medium are drawn off from the lower end of the furnace
1
and separated by a separator
8
disposed below the furnace
1
, and the noncombustibles are discharged from the system, while the medium is returned to the furnace
1
by a conveyor
9
and an elevator
10
.
The medium-residue return channel
3
is bifurcated into two branches at an intermediate portion thereof. One of the branches,
3
a,
is provided at intermediate portions thereof with a flow control valve
11
and a heat recovery unit
12
which are arranged in this order downstream from the cyclone
2
. A superheater
13
for the boiler is disposed in the heat recovery unit
12
. Medium transport air is forced into the heat recovery unit
12
. The forward end of the other branch
3
b
is opened to the fluidized-bed furnace
1
at a position above the position here the hopper
7
is opened to the furnace. The free-flowing medium transported by the conveyor
9
and the elevator
10
is admitted into the branch
3
b
at an intermediate portion thereof.
A heat recovery column
14
is disposed downstream from the cyclone
2
. This column
14
has in its interior a first flue
15
for passing combustion gases, discharged from the cyclone
2
, from above downward therethrough, and a second flue
16
in communication with the lower end of the first flue
15
for passing the combustion gases from below upward therethrough. The inner peripheral surface of the first flue
15
is covered with a multiplicity of boiler water tubes (not shown), the upper ends of which also communicate with the steam drum
6
via an unillustrated header. Arranged within the second flue
16
are a boiler economizer
17
for passing therethrough water forwarded from a deaerator, and two superheaters
18
,
19
connected in series with the superheater
13
in the heat recovery unit
12
for passing steam sent from the steam drum
6
. A water injector
20
for adjusting the temperature and pressure of the steam by injecting water is disposed between the two superheaters
18
,
19
within the second flue
16
, also between the lower superheater
19
in the flue
16
and the superheater
13
in the heat recovery unit
12
.
A temperature reduction column
21
and a bag filter
22
are arranged downstream from the heat recovery column
14
. The combustion gases passing through the heat recovery column
14
are further reduced in temperature by the heat reduction column
21
. The bag filter
22
serves to collect hydrogen chloride, sulfur oxides, soot and dust from the combustion gases. Slaked lime, or like neutralizing agent, and a reaction assisting agent, are added to the combustion gases at a position upstream from the filter. After passing through the bag filter
22
, the combustion gases are released into the atmosphere through a stack.
Fly ash is discharged from the lower ends of the heat recovery column
14
, temperature reduction column
21
and bag filter
22
and sent to a fly ash treating unit (not shown).
With the combustion apparatus thus constructed, RDF is sent into the fluidized-bed furnace
1
by the hopper
7
. In the furnace
1
, the free-flowing medium is formed into a fluidized bed with primary air and secondary air, and RDF is burned in the fluidized bed. The unburned combustibles are almost completely burned until the combustion gases and the medium enter the cyclone
2
from the upper end of the furnace
1
. The medium and combustion residue discharged from the furnace
1
are separated from the combustion gases and trapped in the cyclone
2
, passed through the two branches
3
a,
3
b
of the return channel
3
and returned to the furnace
1
. While passing through the branch
3
a
having the heat recovery unit
12
, the medium and the residue have their heat transferred to steam flowing through the superheater
13
, whereby the steam is superheated. The temperature of the furnace
1
can be lowered by adjusting the amount of medium transport air to be forced in and the opening degree of the flow control valve
11
and thereby increasing the quantities of medium and residue to be passed through the branch
3
a
having the heat recovery unit
12
. Conversely, the temperature of the furnace
1
can be raised by reducing the quantities of medium and residue to be passed through the branch
3
a
having the heat recovery unit
12
.
The combustion gases flowing out of the cyclone
2
enter the heat recovery column
14
, flow down the first flue
15
first and consequently have their heat transferred to boiler water in the water tubes providing the wall of the flue, whereby the boiler water in the water tubes is heated and evaporated, and the temperature of the combustion gases is lowered. The combustion gases then flow upward through the second flue
16
and have their heat transferred to the boiler water in the water tubes constituting the wall of the flue, to the steam in the two superheaters
19
,
18
and to the water in the economizer
17
, whereby the boiler water in the water tubes is heated and evaporated, the steam is superheated, and the water in the economizer
17
is preheated to result in a drop in the temperature of the combustion gases.
The combustion gases subsequently flow into the temperature reduction column
21
and have their temperature further reduced. Slaked lime, or like neutralizing agent, and a reaction assisting agent, are thereafter added to the combustion gases, and the resulting mixture is led into the bag filter
22
, in which hydrogen chloride, sulfur oxides, soot and dust are removed. The gases separated off are then released into the atmosphere.
On the other hand, the water sent from the deaerator and preheated during passage through the economizer
17
is admitted into the steam drum
6
and thereafter further heated within the water tubes of the fluidized-bed furnace
1
and the heat recovery column
14
constituting a boiler water circulation circuit to become a steam-water mixture, which is then sent to the steam drum
6
again. The steam is separated off in the steam drum
6
, passed through the three superheaters
18
,
19
,
13
in succession and superheated with the heat of the combustion gases during passage through the superheaters
18
,
19
and with the heat of the free-flowing medium during passage through the superheater
13
. The superheated steam is sent to a steam turbine.
However, the conventional combustion apparatus has the problem that almost complete combustion of RDF in the fluidized furnace
1
increases the internal temperature of the furnace
1
to a considerably high level and necessitates supply of

Affiliated with

Also associated with

Rating

Combustion device does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Combustion device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Combustion device will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2444477