Technical Field
[0001] The present invention relates to a diffusion bleeder that combusts a coke oven gas
and diffuses the coke oven gas into the atmosphere and a coke-oven-gas combustion
method using the diffusion bleeder.
Background Art
[0002] A coke oven battery has a structure in which a heat regenerator is disposed in a
lower portion thereof and a carbonization chamber and a combustion chamber are alternately
arranged in an upper portion thereof. Here, a fuel gas is combusted in the combustion
chamber and coal is carbonized inside the carbonization chamber adjacent to the combustion
chamber, thereby obtaining coke.
[0003] A coke oven gas generated by the carbonization of the coal is gathered in an ascension
pipe set in each carbonization chamber and is collected in a gas collection pipe called
a dry main through a bend pipe. A pressure control valve is provided inside the gas
collection pipe, and the pressure inside the gas collection pipe is controlled to
be 4 to 5 mmH
2O at normal time by the pressure control valve to prevent an explosion caused by entry
of air from the outside. The coke oven gas collected in the gas collection pipe is
then sent through an intake blower to a gas purification process.
[0004] While the coke oven gas is required to be diffused into the atmosphere in emergency
time in which, for example, the intake blower stops due to a trouble such as a pressure
increase inside the gas collection pipe or a power failure, the coke oven gas contains,
as by-products of incomplete combustion, combustible gases including methane, carbon
monoxide, hydrogen, and the like in an uncombusted state and is diffused into the
atmosphere after the combustible gases contained in the coke oven gas are combusted
to be neutralized. At this time, when incomplete combustion of the combustible gases
contained in the coke oven gas occurs, black smoke is generated at the time of diffusion
into the atmosphere. Therefore, to diffuse the coke oven gas into the atmosphere,
it is required to diffuse the coke oven gas after completely combusting the combustible
gases contained in the coke oven gas.
[0005] Here, as an apparatus used for diffusion of the coke oven gas, a diffusion bleeder
is widely known. As illustrated in Fig. 5, a general diffusion bleeder 100 has a diffusion
pipe 40 formed by an outer pipe 40a and an inner pipe 40b and in which a coke oven
gas is distributed and a casing 30 in which an open valve 20a, called a flap, and
actuators 20d and 20e, such as cylinders, are provided, and includes a diffusion valve
20 that diffuses the coke oven gas inside a gas collection pipe 10 into the atmosphere.
The diffusion bleeder 100 is mounted on the upper side of the gas collection pipe
10.
[0006] In the case when the coke oven gas is required to be diffused, the diffusion valve
20 is opened by using the actuators 20d and 20e, such as cylinders, when a pressure
of the coke oven gas inside the gas collection pipe 10 has a set value, to diffuse
the coke oven gas through the diffusion pipe 40 to the outside. An upper portion of
the diffusion pipe 40 has a double structure that includes the outer pipe 40a in communication
with the atmosphere and the inner pipe 40b in communication with a source of the coke
oven gas. The coke oven gas is pressure-fed from the source into the inner pipe 40b,
and a negative pressure generated consequently is used to take in air through a gap
between the outer pipe 40a and the inner pipe 40b. In the coke oven gas, components
are not constant and calories fluctuate, and therefore, pilot light for ignition is
required to combust the coke oven gas stably. Therefore, at an upper portion of the
outer pipe 40a, there are provided an ignition-gas supplying device 60 including an
ignition-gas supply pipe 60a and an ignition-gas supply valve 60b that are used for
supplying a gas (hereinafter, referred to as "ignition gas") for pilot light, and
an ignition device 50, such as an igniter. The ignition gas is combusted to serve
as pilot light, and the combustible gases in the coke oven gas are combusted to be
neutralized. During combustion of the coke oven gas, the ignition gas is continuously
supplied to avoid extinction of fire.
[0007] The diffusion bleeder 100 illustrated in Fig. 5, however, has a problem that, since
the diffusion valve 20 is opened manually or by using the actuators 20d and 20e, such
as cylinders, after the pressure of the coke oven gas inside the gas collection pipe
10 has a set value, it takes time to actually open the diffusion valve 20 after diffusion
of the coke oven gas is required.
[0008] In addition, there is a problem that, since the gases are not sufficiently mixed
and stirred in the inside of the diffusion pipe 40 by only taking in air through the
gap between the outer pipe 40a and the inner pipe 40b, it is not possible to completely
combust the combustible gases in the coke oven gas and a large amount of the combustible
gases in an uncombusted state are diffused into the atmosphere.
[0009] Regarding such problems, PTL 1 discloses a configuration in which a counterweight
for counteracting a moment generated by the own weight of a diffusion valve is mounted
on the diffusion valve to open the valve automatically in response to an increase
in the pressure of a coke oven gas inside a gas collection pipe and diffuse the coke
oven gas into the atmosphere.
[0010] In addition, PTL 2 discloses a configuration in which an injection pipe through which
a combustion acceleration gas that accelerates combustion inside a diffusion pipe
is provided in a gap between an outer pipe and an inner pipe to accelerate combustion
of a coke oven gas.
Citation List
Patent Literature
Summary of Invention
Technical Problem
[0012] However, with the technologies disclosed in PTL 1 and PTL 2, there is a time lag
between opening of a diffusion valve and activation of an ignition device or injection
of a combustion acceleration gas, and a coke oven gas moves in the diffusion pipe
40 during the time lag is not completely combusted and is diffused as it is into the
atmosphere. Further, to combust combustible gases in a coke oven gas, it is required
at all times to continue activation of an ignition device and injection of a combustion
acceleration gas, and there is thus a problem in terms of costs related to the use
of electric power and gases.
[0013] The present invention has been made in consideration of such circumstances, and an
object of the present invention is to provide a diffusion bleeder and a coke-oven-gas
combustion method that are capable of suppressing incomplete combustion of a coke
oven gas and suppressing excessive use of electric power and gases by combusting combustible
gases contained in the coke oven gas at optimum timing in a coke oven battery.
Solution to Problem
[0014] A summary of the configuration of the present invention for solving the aforementioned
problems is as follows.
- [1] A diffusion bleeder that combusts a coke oven gas collected in a gas collection
pipe and diffuses the coke oven gas into an atmosphere, the diffusion bleeder including
a diffusion pipe connected to the gas collection pipe and through which the coke oven
gas is distributed; a diffusion valve that opens to distribute the coke oven gas from
the gas collection pipe to the diffusion pipe when a pressure of the coke oven gas
in the gas collection pipe has a set value; an ignition device that ignites the coke
oven gas; an ignition-gas supply device that supplies an ignition gas for ignition
to an inside of the diffusion pipe; a combustion-acceleration-gas supply device that
supplies a combustion acceleration gas that accelerates combustion of the coke oven
gas to the inside of the diffusion pipe; a detector that detects a start of opening
of the diffusion valve; and a control device that controls the ignition-gas supply
device, the ignition device, and the combustion-acceleration-gas supply device, in
which the control device receives a detection signal indicating that the diffusion
valve starts to open from the detector, transmits a control signal for ordering a
start of supplying of the ignition gas to the ignition-gas supply device, transmits
a control signal for ordering an ignition operation to the ignition device, receives
a detection signal indicating that the diffusion valve is fully opened, and transmits
a control signal for ordering a start of supplying of the combustion acceleration
gas to the combustion-acceleration-gas supply device.
- [2] A coke-oven-gas combustion method in which a coke oven gas collected in a gas
collection pipe is combusted in a diffusion pipe, the method including a diffusion-start
detection step in which a start of opening of a diffusion valve that is provided between
the gas collection pipe and the diffusion pipe is detected when a pressure of the
coke oven gas in the gas collection pipe has a set value; an ignition-gas supply step
in which supplying of an ignition gas for ignition to an inside of the diffusion pipe
is started; an ignition step in which the ignition gas is lit to serve as pilot light
for ignition and ignite the coke oven gas; and a combustion-acceleration-gas supply
step in which, after completion of the ignition step and after full opening of the
diffusion valve is detected, supplying of a combustion acceleration gas that accelerates
combustion of the coke oven gas to the inside of the diffusion pipe is started.
Advantageous Effects of Invention
[0015] It becomes possible by using the diffusion bleeder and the coke-oven-gas combustion
method according to the present invention to activate an ignition device, supply an
ignition gas, and supply a combustion acceleration gas in response to opening of a
diffusion valve. It is thus possible to combust a combustible gas contained in a coke
oven gas at optimum timing and possible to suppress incomplete combustion of the coke
oven gas and suppress excessive use of electric power and gases.
Brief Description of Drawings
[0016]
[Fig. 1] Fig. 1 schematically illustrates a sectional view of a heat regenerator and
a carbonization chamber of a coke oven battery.
[Fig. 2] Fig. 2 schematically illustrates an example of a configuration of a diffusion
bleeder according to an embodiment of the present invention.
[Fig. 3] Fig. 3 illustrates an example of a flowchart at the time of starting combustion
and stopping combustion in a diffusion bleeder according to an embodiment of the present
invention.
[Fig. 4] Fig. 4 is a flowchart illustrating a flow of processing in a coke-oven-gas
combustion method according to an embodiment of the present invention.
[Fig. 5] Fig. 5 schematically illustrates a configuration of a diffusion bleeder of
the related art. Description of Embodiments
[0017] A configuration of a diffusion bleeder according to an embodiment of the present
invention will be described below.
[0018] Fig. 1 is a sectional view of a heat regenerator 22 and a carbonization chamber 23
of a coke oven battery 21. In the coke oven battery 21, the heat regenerator 22 is
disposed in a lower portion of an oven body, and a combustion chamber (not illustrated)
and the carbonization chamber 23 are alternately arranged at an upper portion of the
heat regenerator 22. A coke oven gas that is generated from the carbonization chamber
23 in the process of carbonization of coal passes through an ascension pipe 24 and
a bend pipe 25 and gathers in a gas collection pipe 1, which is called a dry main.
When the pressure inside the gas collection pipe 1 is abnormality increased due to
a facility trouble or the like, a diffusion valve 2 is opened as an emergency measure,
and the coke oven gas inside the gas collection pipe 1 is diffused through a diffusion
pipe 4 into the atmosphere.
[0019] Fig. 2 schematically illustrates an example of a diffusion bleeder 12 according to
the present embodiment. As illustrated in Fig. 2, the diffusion bleeder 12 further
includes a combustion-acceleration-gas supply device 7, a detector 8, and a control
device 11, in addition to the diffusion valve 2 including a counterweight 2f, the
diffusion pipe 4, an ignition device 5, and an ignition-gas supply device 6.
[0020] On the upper side of the diffusion valve 2, the diffusion pipe 4 connected to the
gas collection pipe 1 and through which the coke oven gas is distributed is disposed.
The ignition-gas supply device 6 supplies an ignition gas to the diffusion pipe 4
and the ignition device 5. The combustion-acceleration-gas supply device 7 supplies
a gas (hereinafter referred to as "combustion acceleration gas") for accelerating
combustion of the coke oven gas. The detector 8 detects opening of the diffusion valve
2. The control device 11 controls operation of the ignition device 5, the ignition-gas
supply device 6, and the combustion-acceleration-gas supply device 7.
[0021] As in the diffusion bleeder 100 previously described with Fig. 5, the diffusion pipe
4 has a double structure that includes an outer pipe 4a in communication with the
atmosphere and an inner pipe 4b in communication with a source of the coke oven gas
through the diffusion valve 2.
[0022] The diffusion valve 2 includes a casing 3 that has an opening through which the coke
oven gas passes; an open valve 2a that opens and closes an opening 2c by rotating
about a rotary shaft 2b, the open valve 2a being called a flap; an open actuator 2d
and a close actuator 2e that rotationally drive the open valve 2a connected to the
rotary shaft 2b by a link mechanism or the like; the counterweight 2f that is located
opposite the open valve 2a in point symmetry with respect to the rotary shaft 2b and
that is provided to counteract a moment generated by the own weight of the open valve
2a; and a striker 2g that is mounted on the counterweight 2f to be interlocked with
the counterweight 2f.
[0023] The counterweight 2f is provided to counteract the moment generated by the own weight
of the open valve 2a and is configured such that, as a moment acting on the open valve
2a due to the pressure of the coke oven gas is larger than a moment due to the own
weight of the open valve 2a when the internal pressure of the gas collection pipe
1 becomes a set pressure, the open valve 2a rotates as indicated by the dotted line
in Fig. 2 without actuation of the open actuator 2d, the opening 2c is opened, and
the open valve 2a is opened. Here, the set pressure means a pressure that corresponds
to a value of a weight that is obtained by subtracting the weight of the counterweight
2f from the weight of the open valve 2a. It is also possible to rotate the open valve
2a and open the opening 2c by actuating the open actuator 2d. Then, it is possible
by actuating the close actuator 2e to rotate the open valve 2a and close the opening
2c.
[0024] The ignition device 5 is provided at an upper portion of the outer pipe 4a and is
constituted by an igniter or the like that is provided for combustion of the coke
oven gas inside the diffusion pipe 4.
[0025] The ignition-gas supply device 6 is used to supply a small amount of the coke oven
gas (ignition gas) for pilot light for ignition of the coke oven gas to the ignition
device 5 and includes an ignition-gas supply pipe 6a and an ignition-gas supply valve
6b. The ignition-gas supply pipe 6a is connected at one end thereof to the gas collection
pipe 1, and a tip portion at the other end thereof is provided on the inner side of
the outer pipe 4a to project in the vicinity of the ignition device 5. When the coke
oven gas is diffused, the ignition gas that is supplied from the tip portion through
the ignition-gas supply valve 6b disposed at an intermediate portion of the ignition-gas
supply pipe 6a is ignited and combusted by the ignition device 5 and becomes pilot
light for ignition of the coke oven gas distributed through the inside of the diffusion
pipe 4. As an alternative to the small amount of the coke oven gas, a combustible
gas, such as oxygen, may be used as the ignition gas.
[0026] The combustion-acceleration-gas supply device 7 includes a combustion-acceleration-gas
supply pipe 7a that is for supplying the combustion acceleration gas for accelerating
combustion through a gap between the outer pipe 4a and the inner pipe 4b; the combustion-acceleration-gas
supply valve 7b that is disposed at the combustion-acceleration-gas supply pipe 7a
and that opens to distribute the combustion acceleration gas; and a compressor 7c
for pressure-feeding the combustion acceleration gas. When the coke oven gas is diffused,
the combustion acceleration gas compressed by the compressor 7c flows in together
with gases (hereinafter, referred to as "accompanying gases") including a peripheral
gas such as air and the like through the gap between the outer pipe 4a and the inner
pipe 4b. The combustion acceleration gas and the accompanying gases are stirred with
the coke oven gas in the diffusion pipe 4, and complete combustion of the coke oven
gas is accelerated in the diffusion pipe 4.
[0027] While the combustion acceleration gas is not particularly limited as long as the
combustion acceleration gas is a gaseous body, the combustion acceleration gas is
preferably a non-combustible gas to prevent explosion and incomplete combustion inside
the outer pipe 4a. In particular, a non-combustible gas that contains at least one
or more of air, nitrogen gas, and water vapor is preferable. Even when the nitrogen
gas is employed as the combustion acceleration gas, complete combustion of the combustible
gas is accelerated since, as described above, oxygen that is contained in the accompanying
gases, such as air, together with the nitrogen gas reacts with the combustible gas
in the coke oven gas.
[0028] Here, the pilot light for ignition by the ignition device 5 and the ignition-gas
supply device 6 triggers the combustion of the coke oven gas in a wide range in the
inside of the diffusion pipe 4. In addition, supplying of the combustion acceleration
gas to the inside of the diffusion pipe 4 through the gap between the outer pipe 4a
and the inner pipe 4b by the combustion-acceleration-gas supply device 7 also accelerates
the combustion of the coke oven gas in a wide range in the inside of the diffusion
pipe 4. In other words, it is possible to efficiently accelerate the combustion of
the coke oven gas in a wide range in the inside of the diffusion pipe 4 by activating
the ignition device 5 and supplying the ignition gas through the ignition-gas supply
device 6 and the combustion acceleration gas through the combustion-acceleration-gas
supply device 7 to the inside of the diffusion pipe 4 before the opening 2c starts
to be opened by the rotation of the open valve 2a of the diffusion valve 2 and causes
the coke oven gas to flow from the gas collection pipe 1 to the inside of the diffusion
pipe 4.
[0029] The detector 8 detects opening and closing of the opening 2c by the open valve 2a
of the diffusion valve 2 and is constituted by a closure detector 8a that detects
a state in which the opening 2c is completely closed and an opening detector 8b that
detects a state in which the opening 2c is completely opened.
[0030] The detector 8 is installed at the counterweight 2f located opposite the open valve
2a in point symmetry with respect to the rotary shaft 2b of the diffusion valve 2
and detects the presence of the striker 2g when the striker 2g interlocked with the
counterweight 2f enters a region in which the striker 2g is detectable.
[0031] The closure detector 8a is set at a location where the closure detector 8a is able
to detect the striker 2g in a state in which the open valve 2a completely closes the
opening 2c and where the striker 2g is out of a range in which the closure detector
8a is able to detect the striker 2g when the open valve 2a starts opening of the opening
2c even slightly.
[0032] The opening detector 8b is set at a location where the opening detector 8b is able
to detect the striker 2g in a state in which the open valve 2a rotates in a direction
away from the opening 2c and reaches an ascent limit and in which the open valve 2a
is fully opened and where the striker 2g is out of a region in which the opening detector
8b is able to detect the striker 2g when the open valve 2a rotates in a direction
toward the opening 2c and is away from the ascent limit.
[0033] The closure detector 8a and the opening detector 8b each transmit a detection signal
to the control device 11 in response to detection of the striker 2g. A method of detecting
the striker 2g by the detector 8 may be either one of an optical contactless method,
such as a laser and a contact method, such as a limit switch.
[0034] The control device 11 controls the ignition-gas supply device 6, the ignition device
5, and the combustion-acceleration-gas supply device 7 and is constituted by a general-purpose
information processing device, such as a computer including a CPU and the like or
a workstation. One example of the control device 11 illustrated in Fig. 2 is constituted
by an ignition control device 11a that controls ignition and combustion of the diffusion
bleeder 12 by controlling the ignition device 5 and the ignition-gas supply device
6, and a combustion-acceleration control device 11b that controls supplying of the
combustion acceleration gas to the diffusion pipe 4 by controlling the combustion-acceleration-gas
supply device 7.
[0035] After receiving the detection signal indicating that the diffusion valve 2 starts
to open from the detector 8, the control device 11 transmits a control signal for
ordering a start of supplying of the ignition gas to the ignition-gas supply device
6 and then transmits a control signal for ordering an ignition operation to the ignition
device 5. After the ignition operation is completed and a detection signal indicating
that the diffusion valve 2 is fully opened is received, a control signal for ordering
a start of supplying of the combustion acceleration gas is transmitted to the combustion-acceleration-gas
supply device 7.
[0036] Here, a specific control processing by the control device 11 at the time of starting
of combustion in the diffusion bleeder 12 will be described with a flowchart in Fig.
3(a). The ignition control device 11a of the control device 11 receives a detection
signal indicating that opening of the diffusion valve 2 is started from the detector
8 (closure detector 8a) (S1). Next, the ignition control device 11a transmits a control
signal for ordering valve opening for starting distribution of the ignition gas (S2)
to the ignition-gas supply valve 6b of the ignition-gas supply device 6. Further,
the ignition control device 11a transmits a control signal for ordering a start of
the ignition operation (S3) to the ignition device 5. The ignition control device
11a transmits an ignition-operation completion signal (S4) to the combustion-acceleration
control device 11b. After receiving a detection signal indicating that the diffusion
valve 2 is fully opened from the detector 8 (opening detector 8b), the combustion-acceleration
control device 11b transmits a control signal for ordering activation of the compressor
7c (S5). Further, the combustion-acceleration control device 11b transmits a control
signal for ordering valve opening for starting distribution of the combustion acceleration
gas (S6) to the combustion-acceleration-gas supply valve 7b.
[0037] As described above, immediately after the opening of the diffusion valve 2 is started,
the pilot light for ignition of the coke oven gas is lit by the ignition device 5
and the ignition-gas supply device 6 in response to transmission of the control signals
by the ignition control device 11a. It is possible with this pilot light for ignition
to achieve stable ignition and combustion of the coke oven gas that flows into the
diffusion pipe 4 when the diffusion valve 2 is opened.
[0038] Furthermore, since supplying of the combustion acceleration gas by the combustion-acceleration-gas
supply device 7 is started after the diffusion valve 2 is fully opened and the combustion
of the coke oven gas is stabilized, it is possible to avoid extinction of fire due
to supplying of the combustion acceleration gas pressure-fed in a state in which combustion
of the coke oven gas is unstable, and complete combustion of the coke oven gas in
the diffusion pipe 4 is accelerated. In other words, it is possible to execute control
of the ignition device 5, the ignition-gas supply device 6, and the combustion-acceleration-gas
supply device 7 at optimum timing after detection of the start of opening of the diffusion
valve 2 based on an increase in the internal pressure of the gas collection pipe 1.
By controlling the devices at the optimum timing, it is possible to suppress a situation
in which a combustible gas contained in the coke oven gas is diffused in an incompletely
combusted state into the atmosphere.
[0039] Fig. 3(b) is a flowchart at the time of stopping combustion in the diffusion bleeder
12. The ignition control device 11a of the control device 11 receives a detection
signal indicating that the open valve 2a completely closes the opening 2c from the
detector 8 (closure detector 8a) (S11). In response to this, the ignition control
device 11a transmits a control signal for ordering valve closure for stopping distribution
of the ignition gas to the ignition-gas supply valve 6b of the ignition-gas supply
device 6 (S12). Further, the ignition control device 11a transmits a control signal
for ordering a stoppage of the ignition operation to the ignition device 5 (S13).
The ignition control device 11a transmits an ignition-operation stop signal to the
combustion-acceleration control device 11b (S14). Then, the combustion-acceleration
control device 11b transmits a control signal for ordering a stoppage of the compressor
7c (S15). Further, the combustion-acceleration control device 11b transmits, after
the stoppage of the compressor 7c, a control signal for ordering valve closure for
stopping distribution of the combustion acceleration gas to the combustion-acceleration-gas
supply valve 7b (S16).
[0040] Here, the configuration illustrated in Fig. 2 is a configuration in which the detection
signal from the detector 8 is received by the control device 11 but may be a configuration
in which the detection signal from the detector 8 is transmitted as it is to the ignition
device 5, the ignition-gas supply device 6, and the combustion-acceleration-gas supply
device 7 to control the operation of each of the devices.
[0041] In the coke-oven-gas combustion method according to the present embodiment, the coke
oven gas collected in the gas collection pipe 1 is combusted in the diffusion pipe
4 by performing the following steps. As illustrated in Fig. 4, the method includes
a diffusion-start detection step S21, an ignition-gas supply step S22, an ignition
step S23, and a combustion-acceleration-gas supply step S24. Each of these steps will
be described below.
[0042] The diffusion-start detection step S21 is a step in which a start of opening of the
diffusion valve 2 provided between the gas collection pipe 1 and the diffusion pipe
4 is detected when the pressure of the coke oven gas in the gas collection pipe 1
has a set value. In the present embodiment, the control device 11 of the diffusion
bleeder 12 executes the step S1 indicated in Fig. 3(a).
[0043] The ignition-gas supply step S22 is a step in which supplying of the ignition gas
for ignition to the inside of the diffusion pipe 4 is started. In the present embodiment,
the control device 11 of the diffusion bleeder 12 executes the step S2 indicated in
Fig. 3(a).
[0044] The ignition step S23 is a step in which the ignition gas is lit to serve as the
pilot light for ignition and ignite the coke oven gas. In the present embodiment,
the control device 11 of the diffusion bleeder 12 executes the step S3 indicated in
Fig. 3(a).
[0045] The combustion-acceleration-gas supply step S24 is a step in which supplying of the
combustion acceleration gas that accelerates the combustion of the coke oven gas to
the inside of the diffusion pipe 4 is started after completion of the ignition step
(S23) and after full opening of the diffusion valve 2 is detected. In the present
embodiment, the control device 11 of the diffusion bleeder 12 executes the steps S4,
S5, and S6 indicated in Fig. 3(a).
[0046] As described above, it is possible by using the diffusion bleeder 12 according to
the present invention to control the ignition device 5, the ignition-gas supply device
6, and the combustion-acceleration-gas supply device 7 at optimum timing in response
to the opening of the diffusion valve 2. It is thus possible to combust the combustible
gas contained in the coke oven gas at optimum timing and possible to suppress incomplete
combustion of the coke oven gas and suppress excessive use of electric power and gases.
Reference Signs List
[0047]
- 1
- gas collection pipe
- 2
- diffusion valve
- 3
- casing
- 4
- diffusion pipe
- 5
- ignition device
- 6
- ignition-gas supply device
- 7
- combustion-acceleration-gas supply device
- 8
- detector
- 11
- control device
- 12
- diffusion bleeder