Note: Descriptions are shown in the official language in which they were submitted.
-1- 1316413
INTERNAL CIRCULATING FLUIDIZED BED TYPE BOILER AND
MET~OD OF CONTROLLING THE SAME
Technical Field:
1 The present invention relates to a boiler utilizing
an apparatus for incineratiny coal, smokeless coal, coal
dressing sludge, oil coke, bark, bagasse, industrial waste,
municipal waste and other combustibles in a fluidized bed
for recovering thermal energy from the fluidized bed, and a
method of controlling the amount of diffusion gas to be
blown into a thermal energy recovery chamber and the amount
of fuel to be supplied in order to regulate the amount of
thermal energy recovered and to maintain the constant
temperature in the primary incinerating chamber of the
fluidized bed.
Brief Explanation of Drawin~s:
Figs. 1 ~nd 2 are sectional views expla~ning the
conventional fluidized bed type boiler; Fig. 3 is a
schematic illustration e~plaining the principle of the
present invention; Fig. 4 is a sectional view of an internal
circulating fluidized bed typa boiler explaining in outline
the construction according to the present invention; Fig. 5
is a graph showing the relationship between the amount of
air for fluidization ~Gmf) at the portion below the inclined
partition wall and the amount of the fluidizing medium
circulated; Fig. 6 is a graph indicating the relationship
between the amount of diffusing air (Gmf) in the thermal
energy recovery chamber and the descending rate of the
downward moving bed in the thermal energy recovery chamber;
Fig. 7 is a graph indicating the relationship between the
mass flow for fluidization (Gmf) and the overall thermal
conducting coefficient in the conventional bubbling type
boiler; Fig. 8 is a graph indicating the relationship
between the diffusion mass ilow ~Gmf) in the thermal energy
recover~ chamber and the overall thermal conducting coeffi-
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1 cient in the internal circulating fluidized bed type boiler
according to the present invention; Fig. 9 is a graph ~how-
ing the relationship between the mass flow for fluidization
and the abrasion rate of the thermal conducting conduit;
Figs. 10 and 11 show variations in the fuel feeding amount,
vapor pressure and the fluidized bed temperature relative to
the lapse of time without and with regulation of the
fluidizing mass flow for the thermal energy recovery chamber
in response to stepwise change of the vapor flow rate; Fig.
12 shows similar variations relative to the lapse of time in
response to lumpwise change of the vapor flow rate; Figs. 13
and 14 are sectional drawings explaining other embodiments
of the internal recycling type fluidized bed boiler accord-
ing to the present invention; Fig. 15 is a sectional side
view of an internal recycling type fluidized bed boiler
explaining still another embodiment of the present invention
which is particularly adapted or use as a small boiler;
Fig. 16 is a section taken in a plan view on a line shown by
the arrows A - A in the drawing of the embodiment shown in
Fig. 15 which particularly illustrates the section in plan
view of an internal recycling type fluidized bed boiler
- adapted for use in a circularly pac~aged boiler; and
Figs. 17 - 19 illustrate fluidizing patterns in a primary
fluidized bed incinerating chamber with the relationship
between the horizontal length L of the incinerator bottom
and the projection length Q of the inclined partition wall
in the horizontal directlon.
Prior Art:
With respect to a conventional f luidizing bed type
boiler, there are three kinds as noted below which can be
distinguished from each other by giving consideration to the
arrangement of the thermal conducting portion and the
incineration of minute unburnt combustibles that are
scattered from the fluidlzed bed.
(1) a fluidized bed boiler of non-recycling type
(referred to as a conventional fluidized bed boiler or
bubbling type bo~ler), and
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1 (2) a fluidized bed boiler of recycling type.
In the non-recycling type shown in Fig. 1, thermal
conducting conduits are arranged within the fluidized bed
and the heat transfer is effected under high heat transfer
efficiency by virtue of physical contact between the
conduits and the burniny substances or fuels at the high
temperature and the fluidizing medium. However, unburnt
substances are discharged outside without being burnt. In
the recycling types such as shown in Fig. 2, a part of the
~inute combustibles which are not yet burnt, as well as ash
or fluidi~ing medium (a recycling solid), merges into a flow
of combustion gas and is directed to a heat transferring
portion (external heat exchanger) provided independently of
the combustor where incineration of the unburnt substances
is continued, the solid after this heat transfer being
returned to the combustor together with a part of the
combustion gas . This type of boiler being
given on account of the kind of recycling noted above.
(3) intern~l recycling type fluidized bed boiler
As to an lnternal recycling type fluidlzed bed
boiler, a fluldized bed lncinerator provided with a
deflectlng strUCtUre pro~ecting from a wall of the furnace
for alding the circulat~on of fluidi~ing medlum and a
non-fluidlzlng thermal e~ergy recovering chamber between
~urnace walls is disclosed in the specificatlon oi U.K.
Patent No. 1604314. However, the transferring movement
o~ the fluidlzing medium ~rom the thermal ener~y recovery
chamber to the fluidiæed bed lncinerating chamber ln the
fluidlzed bed incinerator disclosed ln thls speeificatlon
ls e~ected by a feed screw at the bottom o~ the thermal
energy recovery chamber independently or by mi~lng wlth
fuel supplled from a fuel supply chamber disposed in the
lower portion o~ the thermal energ~ recovery chamber.
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/
_ 3 _ 1 31 641 3
In the fluidized bed type boiler, a variety of fuels
having different characteristics may be incinerated according to
the particular incineration process but s~veral drawbacks have
recently been noticed. In regard to the bubbling type, its
loading capacity, the complexity of the fuel feeding system, the
requirement for a large quantity of lime for denitration, and the
abrasion of thermal conducting conduits, etc. have been
recognized as drawbacks inherent thereto. It has been realized
that the recycling type is capable of solving these inherent
drawbacks. However, further technical developments remain to be
achieved with respect to maintaining proper temperatures in the
circulating system, scaling-up of the apparatus and solving the
problem of restarting a boiler once it has been stopped.
Summary of the Invention
The inventors of this application have been
investigating the above problems in order to seek appropriate
solutions thereto and have found the following matters to be
effective. That is, in a circulating fluidized bed type
incinerator, an inclined partition wall is provided on the inside
of the incinerator wall and above the end portion of the
diffusion plate to form a primary incinerating chamber of the
fluidized bed and provision for a thermal energy recovery chamber
is also made between the back side of the inclined partition wall
and the incinerator wall or between the rear sides of the two
partition walls so that the recovery chamber communicates at the
upper and lower portions thereof with the primary incinerating
chamber of the fluidized bed, thermal conducting conduits adapted
to pass heating medium therethrough being inserted into the
thermal energy recovery chamber and a diffuser for the thermal
energy recovery chamber being provided at the lower part of the
recovery
~ .,
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chamber and al~ng the back side of the partition wall. The
heated fluidizing medium introduced into the thermal energy
recovery chamber beyond the upper portion of the inclined
partition wall is subjected to the fluidizing gas blown from
the diffuser and regulated in an amount of 3 - 3 Gmf or
preferably 0 - 2 Gmf to form a static bed or a descending
moving bed of the fluidizing medium so that the thermal
energy of the fluidizing medium is recovered ky the heating
medium passing through the thermal conducting conduits. The
inventors found that, by the arrangement noted above, it is
possible to easily control the temperature of the primary
incinerating chamber of the fluidized bed in the incinerator
above explained while effectively recovering the thermal
energy by the thermal conducting conduits in the fluidized
zone where the degree of abrasion of the thermal conducting
conduits is small.
The inventors have further investigated and developed
an internal recycling type fluidized bed boiler provided
with the thermal energy recovery chamber that accompanies
the inclined partition wall and the method for recovering
thermal energy and controlling the feeding rate of the fuel
and found it possible to form an effective circulating
fluidized bed using the fluidizing medium heated in the
primary chamber and to introduce a sufficient amount of the
heated fluidizing medium re~uired in the thermal energy
recovery chamber by arranging the inclination of the
inclined partition wall to be 10 - 60 or preferably 25 -
45 relative to the horizon and the projection length of the
inclined partition wall in the hori~ontal direction on the
bottom of the incinerator to be 1/6 - 1~2 or preferably 1/4
- 1/2 of the horizontal length of the ~ottom of the incin-
erator. Also the inventors found it possible not only to
fully meet the demand from users utilizing the recovered
thermal energy but also to limit the degree of temperature
variation in the primary chamber within a small range by
controlling the amount of thermal energy recovered ~rom the
thermal energy recovery chamber by regulation of the thermal
calories of the- heating medium passed through the thermal
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1 31 641
conducting conduits, for example by regulating the flow rate,
pressure and temperature of the vapor or the temperature, etc. of
the hot water, at the same time as regulating the amount of air
blown from the diffuser in the thermal energy recovery chamber in
response to variations in the demands from the users, for Pxample
those regarding the vapor pressure and temperature and the
regulation of the amount of fuel supplied, such being determined
in response to the demands from the users or based upon the
temperature in the primary chamber.
lo The internal recycling type in this specification and
appended claims, refers to an arrangement in which a space is
provided within a combustor or incinerator so as to be separated
from a primary incinerating chamber and a thermal conducting
portion is dispersed within the space so that the recycling is
effected within the incinerator.
That is, the present invent~on is directed to an
internal recycling type fluidized bed boiler comprising: a
primary fluidized bed incinerating chamber constructed by an air
diffusion plate provided at the bottom of an incinerator and
adapted to inject fluidizing air upwardly under a mass flow that
is at least greater at one side than that at another side; and an
inclined partition wall provided above a side of said diffusion
plate where the mass flow is greater so as to interfere with the
upward flow of the fluidizing air and thereby to deflect the air
towards a portion above said another side of said diffusion plate
where the mass flow is smaller; a thermal energy recovery chamber
formed between said inclined partition wall and a side wall of
the incinerator or between the two inclined partition walls; a
heat exchanging surface means provided within said thermal energy
recovery chamber for the passage of a heat sink fluid
therethrough; and an air diffuser provided at a lower portion of
said thermal energy recovery chamber and at a back side of said
- 6 - l 31 ~4 1,
inclined partition wall; said thermal energy recovery chamber
being communicated at upper and lower portions thereof with said
primary fluidized bed incinerating chamber, said inclined
partition wall being inclined by 10-60 relative to the
horizontal and the projection length thereof in the horizontal
direction being 1/6-1/2 of the horizontal length of the
incinerator bottom, a moving bed being formed above the portion
of said diffusion plate where the injected mass flow is smaller
so that a fluidizing medium descends and diffuses within the
moving bed, and a circulating fluidized bed being formed above
the portion of said diffusion plate where the mass flow of the
fluidiæing air is greater so that said fluidizing medium is
actively fluidized and whirled towards a position above said
moving bed and a part of said fluidizing medium being introduced
into said thermal energy recovery chamber beyond an upper portion
of said inclined partition wall, the formation of said moving bed
and said whirling fluidized bed being effected by regulation of
the amount of air injected upwardly from said diffusion plate and
regulation of the amount of fluidizing air injected from said
diffuser in said thermal energy recovery chamber causing the
fluidizing medium within said recovery chamber to descend in the
state of a moving bed for circulation.
The invention is also directed to a method of
controlling an internal recycling type, fluidized bed boiler
constructed by comprising: a primary fluidized bed incinerating
chamber constructed by an air diffusion plate provided at the
bottom of an incinerator and adapted to inject fluidizing air
upwardly under a mass flow that is at least greater at one side
than that at another side; and an inclined partition wall
provided above a portion of said diffusion plate where the mass
flow is greater so as to interfere with the upward flow of the
fluidizing air and thereby to deflect the air towards a portion
above said another side of said diffusion plate where the mass
flow is smaller; thermal energy recovery chambers formed between
- 7 - 1 31641~
said inclined partition wall and a side wall of the incinerator
and between the back sides of two inclined partition walls; a
heat exchanging surface means provided within said thermal energy
recovery chamber for the passage of a heat sink fluid
therethrough; and an air diffuser provided at a lower portion of
said thermal energy recovery chamber and a back side of said
inclined partition wall; said thermal energy recovery chamber
being communicated at a upper and lower portions thereof with
said primary fluidized bed incinerating chamber; said method
comprising regulating the amount of air injected from said
diffusion plate so that a moving bed is formed above the portion
of said diffusion plate where the injected mass flow is smaller
with a fluidizing medium descending and diffusing within said
moving bed, and circulating fluidized bed is formed above the
lS portion of the diffusion plate where the mass flow of the
fluidizing air is greater with said fluidizing medium being
actively fluidized and circulated towards a position above said
moving bed and a part of said fluidizing medium being introduced
into said thermal energy recovery chamber beyond an upper portion
of said inclined partition wall, the fluidizing air being
injected from said diffuser in said recovery chamber so as to
cause said fluidizing medium within said recovery chamber to
descend and recycle in the state of a moving bed, controlling the
amount of thermal energy recovered by said thermal energy
recovery chamber by the regulation of the amount of gas injected
from said diffusor in said recovery chamber based on demands from
a user side utilizing generated vapor and hot water, and
controlling the amount of fuel supplied to the primary fluidized
bed incinerating chamber based on the temperature of said primary
fluidized bed incinerating chamber.
1316413
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Detailed Description ~f the Preferred Embodiments
1 Hereinafter, the present invention will be explained
in detail referring to the accompanying drawings.
In Fig. 3, a diffusion plate 52 is provided at the
bottom of an incinerator 51 for introducing fluidizing air
fed by a blower 57 through a fluidizing air feeding conduit
53, the diffusion plate 52 being configured in the shape of
a hill (chevron shape) approximately symmetrical about the
center line of the incinerator so that the opposite end
portions are lower than the center portion thereof. The
fluidizing air fed from the blower 57 is arranged to be
injected upwardly from the air diffusion plate 52 through
air chambers 5~, 55 and 56 and the mass flow of the fluidiz-
ing air in;ected from the opposite end air chambers 54 and
56 is arranged to be sufficient to form the fluidized bed of
the fluidizing medium within the incinerator 51, while the
mass flow of the fluidlzing air injected from the center
air chamber 55 is selected to be smaller than that from the
former.
Inclined partition walls 58 are provided above the
opposite end air chambers 54 and 56 as a deflecting wall
means designed to interfere with the upwardly directed
passage of fluidizing air and to deflect the air towards
the center of the incinerator, the whirling flows in the
directions of the arrows shown being generated due to the
presence of the inclined partition walls 5~ and the
difference in the mass flow of the inJ'ected fluidizing air.
On the other hand, thermal energy recovery chambers 59 are
formed between the back side surfaces of the inclined parti-
tion walls 5g and side walls of the inclnerator so that a
part of the fluidizing medium may be introduced during the
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1 3 1 6 4 1 3
operation into the thermal energy recovery chambers 59 beyond the
upper ends of the inclined partition walls 58.
In the present invention, the inclined portion of each
inclined partition wall 58 is arranged to incline by 10-60, or
preferably 25-45, relative to the horizontal and the projection
length thereof in the horizontal direction relative to the
incinerator bottom is arranged to be 1/6-l/2, or preferably 1/4-
l/2, of the horizontal length L of the respective half of the
incinerator bottom.
The angle of the inclination relative to the horizontal
and the projection length in the horizontal direction of the
inclined partition wall are both factors which influence the
fluidizing state of the fluidizing medium and the amount of
grains introduced into the thermal energy recovery chambers.
Incidentally, the meaning of "L" and "~" and the flowing modes of
the fluidizing medium are shown in Fig. 17.
If the angle of inclination of the inclined portion is
either smaller than 10 or greater than 60 relative to the
horizontal, a satisfactory whirling flow is not produced and the
condition under which the fuel is incinerated deteriorates. This
angle is preferably in the range between 25 and 45 and it is
particularly preferable if it is set at approximately 35.
In the case where the projection length ~ of the
inclined partition wall in the horizontal direction relative to
the incinerator bottom is greater than 1/2 of the incinerator
bottom length L as shown in Fig. 18, the amount of fluidizing
medium deflected from the inclined partition walls and caused to
fall on the center of the incinerator becomes smaller thereby
adversely affectiny the formation of the moving bed at the
incinerator center as well as the descending and diffusing mode
of the ~uel charged into the incinerator center.
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1 3 1 6~ 1 `
~ n the other hand, .in a case such as that shown in Fig.
19 where the projection length ~ of the inclined partition wall
relative to the incinerator bottom is smaller than 1/6 of the
incinerator bottom length L, the formation of the whirling flow
and particularly the forming mode of the
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moving bed at the incinerator center is caused to deterio-
rate whereby the fuel entraining effect is also affected
adversely and the deflected flow of fluidizing medium into
the recovery chamber becomes insufficient.
~t the lower portion of the thermal energy recovery
chamber 59 and the back side of the inclined partition wall
58, a diffuser 62 for the thermal energy recovery chamber is
provided for introducing gas such as air from a blower 60
through a feeding conduit 61. At the portion in the thermal
energy recovery chamber 59 adjacent to the place where the
diffuser 62 is disposed, an opening port 63 is provided and
the fluidizing medium introduced into the thermal energy
recovery chamber 59 is caused to continuously or intermit-
tently descend, depending on the operating mode, and
recycled into the incinerating portion through the opening
port 63.
Fig. 4 shows an embodiment based on the principle of
Fig. 3.
The descending amount of the fluidizing medium in the
thermal energy recovery chamber for recycling is regulated
by the amount of diffusing air for the thermal energy
recovery chamber and the amount of fluidizing air for the
incinerating portion. That is the amount of fluidizing
medium (Gl) introduced into the thermal energy recovery
chamber is increased as shown in Fig. 5 if the amount of
fluidizing air injected from the diffusion plate 52, partic-
ularly that from the end air chambers 54 and 56 which is
intended to cause fluidization at the incinerating portion,
is increased. Further, as shown in Fig. 6, the amount of
fluidizing medium descending in the thermal energy recovery
chamber is changed approximately proportional to the change
in the amount of diffusing air blown into the thermal energy
recovery chamber when in the range 0 - l Gmf and it becomes
approximately constant if the amount of diffusing air for
the thermal energy recovery chamber is increased beyond 1
Gmf. This constant amount of fluidizing medium is almost
equivalent to the amount of fluidizing medium (Gl) intro-
duced into the thermal energy recovery chamber and thus the
1 6 4 1 )
amount of fluidizing medium descending in the thermal energy
recovery chamber becomes equivalent to a value corresponding
to G,. By controlling the air amount both for the inciner-
ating portion and the recovery chamber, the descending
amount of fluidizing medium in the thermal energy recovery
chamber 59 may be regulated.
The descent of the fluidizing medium in the static
bed when in the range of O - 1 Gmf is due to the difference
in weight of the fluidizing medium (the difference in
height of the fluidized bsds) as between the thermal energy
recovery chamber and the primary fluidized bed incinerating
chamber and, in the case where the mass flow is over 1 Gmf,
the height of the moving bed portion becomes slightly higher
or approximately equal to the other. The recycling of the
fluidizing medium is assisted by a deflecting flow with a
sufficient amount of fluidizing medium brought about by the
inclined partition wall.
Now, the relationship between the height of the
fluidized bed and the recycling amount of the fluidizing
medium (the deflecting flow) will be explained in detail.
In the case where the surface of the fluidized bed is
lower than the upper end of the inclined partition wall, the
air flow moving upwardly along the inclined partition wall
is given its direction by that wall and injected along the
inclined partition wall from the fluidized bed, the fluidiz-
ing medium being accompanied therewith. The injected air
flow is put in a state different from that in the fluidized
bed and freed from the fluidizing medium with which the
fluidized bed is filled, and the sectional area of the air
flowing passage is suddenly enlarged whereby the injected
air flow is diffused and its speed is reduced to a few
meters per second, becoming a gentle flow~ and is exhausted
upwardly. Therefore, the fluidizing medium that accompanies
the injected air flow loses its kinematic energy to fall
due to gravity and the friction with the exhaust gas as the
grain size of the fluidizing medium is too large (approxi-
mately 1 mm) to be carried with the air flow.
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In the case where the surface of the fluidized bed is
higher than the upper end of the inclined partition wall, a
part of the fluidizing medium accompanied with air masses
gathered by the partition walls is injected along the
deflecting partition wall with the direction imparted in a
manner similar to that in the circulating fluidized bed type
incinerator, while the other part, due to a sudden boiling
phenomenon derived from the explosion of bubbles, is boiled
upwardly like fire works just above the upper end of the
inclined partition wall and falls all around the periphery.
Accordingly, a part of the fluidizing medium is introduced
in a large amount towards the ~ack side of the partition
wall, i.e. the thermal energy recovery chamber.
That is, the moving direction of the injected
fluidizing medium becomes closer to upright as the surface
becomes higher above the upper end of the inclined partition
wall. Therefore, the amount of fluidizing medium introduced
into the thermal energy recovery chamber becomes large in
the case where the surface is slightly above the upper end
of the inclined partition wall.
In Fig. 5 is shown the relationship between the
amount of fluidizing air in the portion below the inclined
partition wall in the primary fluidized bed incinerating
chamber and the amount of fluidizing medium recycled through
the thermal energy recovery chamber.
For example, during the operation under the state Ll,
if the height of the fluidized bed is lowered due to the
scattering of the abraded fluidizing medium, the recycling
amount of the fluidizing medium is suddenly reduced to, for
example, below l/lO of that of the former and thermal energy
recovery cannot be performed. Thus, what is important is
the amount of the fluidizing air and, if it is arranged to
be more than 4 Gmf and preferably more than 6 Gmf, the value
of Gl/Go is maintained over l and the required and suffi-
cient amount of the recycling fluidizing medium may beobtained even if the height of the fluidized bed is chang~d.
Further, by arranging the mass flow of the air
injected from the diffuser in the bottom of the thermal
1 ~ 1 6~ ~ `
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energy recovery chamber to be O - 3 Gmf, or preferably 0 -
~ Gmf, and the mass flow of the fluidizlng air in~ected from
the diffu~ion plate disposed below the inclined partition
wall to be 4 - 20 Gmf or preferably 6 - 12 Gmf, that is by
always keeping the mass flow to be larger at the incinerat-
ing chamber side than at the thermal energy recovery
chamber, the amount of fluidizing medium fed back to the
primary fluidized bed incinerating chamber from the thermal
energy recovery chamber may be adequately assured.
As to the moving bed in the thermal energy recovery
chamber, it is referred to in the academic sense as a static
bed in the case where the mass flow is O - 1 Gmf and a
fluidized bed in the case where the mass flow is over 1 Gmf
and it is commonly known that a minimum mass flow of 2 Gmf
is required for generating a stable fluidized bed. On the
other hand, in the case of the moving bed according to the
present invention which is always descending and moving, the
descending moving bed is satisfactorily formed until the
mass flow is increased to th0 order of 1.5 - 2 Gmf without
causing the destruction of the moving bed by the bubbling
phenomenon. It is assumed that the grains of the fluidizing
medium gradually descend and move under a vibrating
mode whereby the fluidiziny air is converted into small air
bubbles uniformly flowing upward towards the upper portion
2S of the fluidized bed.
Inside the thermal energy recovery chamber 59,
thermal conducting conduits 65, through which a heat sink
fluid such as vapor or water, etc. is passed, are arranged
so that the thermal energy is recovered from the fluidizing
medium by effecting a heat transfer with the fluidizing
medium downwardl~ moving in the thermal energy recovery
chamber. The thermal conducting coefficient in the thermal
energy recovering portion is greatly varied as shown in
Fig. 8 in a case where th~ amount of the diffusing air in
the thermal energy recovery chamber is changed in the range
of O - 2 Gmf.
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Now the characteristics such as the load response
characteristics brouyht about by the formation of the moving
bed in the thermal energy recovery chamber will be explained
The general relationship between the overall thermal
conducting coefficient and the mass flow for fluidization is
shown in Fig. 7. Between the values of the mass flow in the
range of 0 - l Gmf, the increase in the thermal conducting
coefficient is small and it suddenly increases when the mass
flow becomes over l Gmf. AS a method for turning down the
fluidized bed boiler utilizing the above phenomenon, the
"Wing Panel Type" was introduced in DOE Report, 6021 (2),
655 - 633 (1985) and the thermal conducting coefficient in
response to the variation of the fluidizing mass flow is
stated to be insensitive (static bed) or too sensitive
(fluidized bed).
Incidentally, upon reviewing certain foreign patent
specifications, several cases are found which seem to be
similar to the present technology in the point that the
incinerating chamber and the thermal energy recovery chamber
are separated; however, all the partitions disclosed therein
are constructed with a vertical orientation and the fluidiz-
ing medium in the thermal energy recovery chamber is in the
mode for being changed to the static bed and to the fluidiz-
ing bed, it being the static bed when the thermal energy
recovery is small in amount and the fluidizing bed in which
the medium is blown upwardly from the lower portion when the
thermal energy recovery is large iIl amount. This is because
it is difficult to produce a deflected flow with a verti-
cally oriented partition as compared to the case where the
partition is inclined. It is therefore inevitable in the
case of the vertically oriented partition that the fluidiz-
ing medium is arranged in both the incinerating chamber and
the thermal energy recovery chamber to be in a fluidized
state (similar to water) so that the fluidizing medium is
caused to flow between the two chambers.
~ he relationship between the overall thermal conduct-
ing coefficient and the mass flow for fluidization is shown
in Fig. 8. As shown in Fig. 8, it changes almost linearly
and, thus, the amount of thermal energy recovered and the
1 31 64 ~ j
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temperature of the primary fluidized bed incinerating
chamber may be controlled optionally. Further, such control
may be easily effected simply by regulation of the amount of
diffusing air in the thermal energy recovery chamber.
Also it is said that the abrasion rate of the thermal
conducting conduits in the fluidized bed is proportionate
to the cube power of the mass flow for fluidization and such
relationship is shown in Fig. 9. Accordingly, the problem
of abrasion regarding the thermal conducting conduits may be
solved by arranging the amount of diffusing air blown into
the moving bed in the thermal energy recovery chamber to be
O - 3 Gmf or preferably O - 2 Gmf.
In order to regulate the amount of thermal energy
recovered, regulation of the amount of recycling fluidizing
medium is effected, as explained before, while effecting
simultaneous regulation of the thermal conducting coeffi-
cient. That is, if the amount of fluidizing gas in the air
chambers 54 and 56 for the primary fluidized bed incinerat-
ing chamber is made constant and the amount of diffusing air
in the thermal energy recovery chamber is increased, the
amount of recycling fluidizing medium is increased and the
thermal conducting coefficient is simultaneously increased
to greatly increase the amount of thermal energy recovered
as the effect of a combination of the two factors. From the
viewpoint of the temperature of the fluidizing medium in the
fluidized bed, the above corresponds to the effect of
preventing the temperature of the fluidizing medium from
being raised above the predetermined temperature.
As a means for introducing the diffusing gas into
the thermal energy recovery chamber 59, several means may
be considered but it is generally disposed such as to be
inclined at the back side of the inclined partition wall
(the side facing the thermal energy recovery chamber) so as
to effectively utilize the thermal energy recovery chamber.
Also, in the diffuser, the open ports for injecting
the diffusing air are made smaller as their location becomes
closer to the tip end of the diffuser taS the height of the
131G~1 )
-16-
bed becomes smaller) so that the diffusing air is prevented
rom being injected in large amounts at the tip end portion.
The respective sizes of the open ports are preferably
determined so .hat an approximately uniform diffusing amount
is injected over the full length of the diffuser 62 with the
diffusing air amount being 2 Gmf. That is, when the above
is met, it is possible to obtain the maximum amount of
thermal energy recovered by all the thermal conducting
surfaces in the thermal energy recovery chamber and the
abrasion rate of the thermal conducting surfaces may be kept
small over all the surfaces.
In Fig. 4, numeral 66 is a combustible charge inlet
provided at the upper portion of the incinerator 51 and 67
is a steam drum for forming a circulating passage (not
shown) with the thermal conducting conduits 65 in the
thermal energy recovery chambers 59. Numeral 69 represents
incombustible discharge outlets coupled to the opposite end
sides of the air diffusion plate 52 in the bottom of the
incinerator 51 and 70 is a screw conveyor provided with
screws 71 each having a helex opposite to the other.
Incidentally, the location of the combustible charge
inlet is not limited to the upper portion of the incinerator
and it may be disposed at the side of the incinerator as a
spreader 56' for charging coal, etc. therethrough.
The combustibles F charged through the combustible
charge inlet 66 or 66' are whirled and incinerated in the
fluidizing medium which is circulating under the influence
of the whirling flow caused by the fluidizing air. At this
time, tha fluidizing medium at the upper center above the
air chamber 55 is not accompanied by a violent up-and-down
motion thereof and forms a descending moving bed which is in
a weak fluidizing state. The width of this moving bed is
narrow at the upper portion thereof and the trailing ends
thereof are extended in the opposite directions to reach the
portions above the air chambers 54 and 56 at the opposite
side ends, thus being subjected to the fluidizing air
injected at a greater mass flow from both air chambers and
blown upwardly. Accordingly, a portion of each trailing end
1 3 1 64 1 ,
~ 17-
is displaced and, t~us, the bed just above the air chamber
55 descends under gravity. Above this bed, the fluidizing
medium piles up having been supplemented from the fluidizing
bed, as explained later, and the fluidi~ing medium above the
air chamber 55 forms a gradually and continuously descending
moving bed with the repetition of the above modes.
The fluidizing medium moved above the air chambers 54
and 56 is blown upwardly and deflected and whirled by the
inclined partition walls 58 towards the center of the
incinerator 51 and falls on the top of the central moving
bed and is circulated again as explained before, a part of
the fluidizing medium being introduced into the thermal
energy recovery chambers 59 beyond the upper portions of the
inclined partition walls. In the case where the descending
rate of the fluidizing medium in the thermal energy recovery
chamber 59 is slow, the angle of repose for the fluidizing
medium is formed at the upper portion of the thermal energy
recovery chamber and the excess fluidizing medium falls from
the upper portion of the inclined partition wall to the
primary fluidized bed incinerating chamber.
The fluidizing medium introduced into the thermal
ener~y recovery chamber 59 forms a gradually descending
moving bed due to the gas injected from the diffuser 62 and
it is returned to the primary fluidized bed incinerating
chamber from the opening portion 63 after the thermal
transfer is effected with the thermal conducting conduits.
The mass flow of the diffusing air introduced from
the diffuser 62 in the thermal energy recovery chamber 59 is
selected from values in the ran~e of O - 3 Gmf or preferably
- 2 Gmf
The reason for the above is that, as shown in Fig. 8,
the thermal conducting coefficient varies from the minimum
to the maximum below the value of 2 Gmf and the abrasion
rate can be controlled, as shown in Fig. 9, within a small
range~
Further, the thermal energy recovery chamber is out
of the strong corrosive zone of the primary fluidized bed
incinerating chamber under the reducing atmospheres and,
-18- l 31 641 ~
thus, th~ thermal conductlng conduits ~5 are subjected to
less corrosion as compared to the conventlonal ones and the
degree of abrasion of the thermal conducting conduits 65 is
made quite small because the fluidi~ing rate in this portion
is, as explained before, low. As to the speed of air flow
in the fluidizing air mass flow range O - 2 Gmf, it is q~ite
low, such as O - 0.4 m/sec. ~superficial velocity), for
example while it practically depends on the temperature and
grain size of the fluidizing medium.
In a case where the co~bustibles are mixed with
incombustibles having a size greater than the grain size
of the fluidizing medium, the incineration residue is dis-
charged together with a part of the fluidizing medium bv the
screw conveyor 70 disposed at the bottom of the incinerator.
Regarding the thermal conduction in the thermal
energy recovery chamber 59, in addition to the thermal
conduction that takes place due to the direct contact
between the fluidizing medium and the thermal conducting
conduits 65, there is another form of thermal conduction
that utilizes the rising gas moving upwardly as the conduct-
ing media, the gas moving up with irregular vibrat~on as
the fluidizing medium moves. In the latter case, there is
substantially no boundary layer between the solid articles
prohibiting the thermal conduction, in contrast to the
ordinary contact thermal conduction between gas and solid
articles, and the fluidizing medium is well agitated so that
the thermal conduction within the grains of the fluidizing
medium may be neglegible, which fact may not be disregarded
in a case where the medium is stationary; thus, quita
substantial thermal conducting characteristics may be
obtained. Accordingly, in the thermal energy recovery
chamber according to the present invention, it is possible
to obtain a large thermal conducting coefficient almost
e~ual to ten times that obtained in the conventional
incinerating gas boiler.
~ s explained above, the thermal conducting phenomenon
that occurs between the fluidizing medium and the thermal
conducting surfaces largely depends on the strength or
, ~
~ .. .
1 3 1 64 1 7)
-19-
weakness of the fluidi~ation and the amount of recycling
fltlidizing medium can be controlled by regulating the amount
of gas introduced from the diffuser 62. Also, by arranging
the thermal energy recovery chamber 59 with its moving bed
to be independent from the primary incinerating chamber
within the incinerator, it is possible to construct a
compact thermal energy recovery apparatus in which the
turning down ratio is large and the fluidized bed may be
easily controlled.
In a boiler using combustibles having a low inciner-
ating rate su~h as coal or oil cokes as fuels therefor, it
is impossible in most cases to rapidly vary the vaporizing
amount except for varying the vaporizing amount alone in
correspondence with the incinerating rate. In a bubbling
type boiler, the situation becomes still inferior compared
to that in the former boi~er because the thermal energy
recovery is effected based on the temperature of th0
fluidized bed.
However, in the present invention the thermal
conducting amount is instantaneously varied in the range
between several times and several fractions by changing the
amount of diffusing air in the thermal energy recovery
chamber. Therefore, the variation in the thermal energy
input into the fluidized bed due to the variation in the
feeding amount of the combustibles depends on the incinera-
tion rate and causes a time lag; however, the amount of
thermal energy recovery taking place in the thermal energy
recovery chamber according to the present invention can be
rapidly varied by varying the amount of diffusing air in the
thermal energy recovery chamber and the response difference
between the thermal input and the thermal recovery can be
absorbed as a temporary change in the temperature of the
fluidizing medium due to the heat sinking capacity of the
fluidizing medium forming the fluidized bed. Accordingly,
the thermal energy can be utilized without waste thereof and
the regulation of the vaporizing amount having good response
characteristic, which cannot be achieved with a conventional
boiler such as one incinerating coal, can be obtained.
131641~,
-2Q-
Incidentally, the locations o~ the incombustibles
discharge openings 69 areJ as shown for example in the
drawing, preferably determined at positions near the opening
ports 63 and the opposite side ends of the air diffusion
plate in the incinerator 51; however, the location is not
limited to that explained above.
In Fig. 4, the air diffusion plate 52 is illustrated
as having the shape of a hill; however, if the amount of the
fluidizing air injected from the air chambers 54 and 56 is
arranged to be more than 4 Gmf, the whirling flow is formed
in the primary fluidized bed incinerating chamber due to the
effect of the inclined partition walls and, therefore, the
air diffusion plate 52 may be made a horizontal one in the
case where combustibles such as coal containing a few
incombustibles are incinerated. Also, the incombustible
discharge opening may be omitted.
As explained above, the capability of the fluidized
bed boiler according to the present invention to recover
thermal energy is quite superior. Now, the method of
controlling the boiler according to the present invention
will be explained below.
In the present invention, the amount of thermal
energy recovered from the thermal energy recovery chamber
is controlled, in response to the demands of the user
utilizing the recovered thermal energy, by regulating the
amount of gas injected from the diffuser into the thermal
energy recovery chamber. Also, the regulation of the
temperature in the primary fluidized bed incinerating
chamber is effected by controlling the fuel charging amount
based on said temperature or the vapor pressure and, in
the boiler according to the present invention, the thermal
conducting coefficient can be optionally adjusted and the
variation of the amount of thermal energy recovered in the
present invention is aksorbed as variation in the sensible
heat of the fluidizing medium whereby the boiler can be
controlled instantaneously to meet the demands of the user
and can be operated under stable conditions.
- 2l -
The explanation is made in relation to Fig. 4. For
example, in a case where the temperature of the vapor withdrawn
from the thermal conducting conduits 65 is insufficient, a
diffusing air regulating valve 93 is regulated in its opening
direction by a regulator 92 for the valve 93 based on the
temperature sensed by a thermo-sensor 91 on a vapor withdrawing
conduit 90 so as to increase the amount of diffusing air injected
so that the amount of thermal energy recovered is increased and
the vapor temperature is raised to that demanded by the user.
The temperature of the primary fluidized bed
incinerating chamber is controlled within a certain range by
regulating the amount of fuel fed to the primary fluidized bed
incinerating chamber and/or by regulating the amount of air fed
to the air chambers 54, 55 and 56 based on the fluidized bed
temperature sensed by a thermo-sensor 94.
There is another method wherein the amount of fuel fed
to the primary fluidizing bed incinerating chamber is controlled
by a pressure signal, for example in the case where the amount of
vapor demanded is varied due to a load variation on the user's
side, since vapor pressure is the factor which most rapidly
changes in response to a change in the demand.
The response characteristics are shown in Figs. 10 and
11 wherein the vapor flow rate is changed by +30% stepwise from
70% to 100%.
Fig. 10 shows test results obtained when the amount of
air from the diffuser in the thermal energy recovery chamber was
maintained constant while the vapor flow rate was varied by +30
stepwisely, and Fig. 11 shows test results obtained in a case
where the amount of diffusing air was regulated in response to
the +30% stepwise variation in the vapor flow rate. Upon
.~
- 21A 1 31 6'-~ I 3
comparing the two, it is found that the fluidized bed temperature
and the vapor flow rate are constrained to predetermined values
within a short time and the variation range is also made small in
the case (Fig. 11) where the diffusing air amount is regulated
-22- 1 31 64 1 7~
accordin~ to th~ present invention in response to the varia-
tion in the vapor flow rate, as compared with the results
for the conventional method shown in Fig. 10.
Incidentally, the variation range of the fluidized
bed temperature was approximately ~12C and that of the
vapor pressure was approximately below +0.3 kg/cm2 (0.029
MPa) in the case where the regulation was effected according
to the present invention as shown in Fig. 11.
The responding characteristics are also shown in
Fig. 12 when the vapor flow rate is varied lumpwisely by
-60~ wherein the diffusing air amount of in the thermal energy
recovery chamber is regulated in response to the above
variation in accordance with the present invention. In this
case also, it ls found that the fluidized bed temperature
is almost constant and the variation range of the vapor
pressure is small.
Next, another embodiment according to the present
invention will ba explained referring to Fig. 13. The
embodiment shown-in Fig. 13 corresponds to the case wherein
the present invention is applied to the incinerator in which
a single whirling fluidized bed is present, the reference
numerals being the same as those used in
Fig. 3 with respect to the meaning and function thereof.
Fig. 14 shows an embodiment to be used when a large
size boiler is required. The embodiment shown in Fig. 14
is constructed by combining the two internal recycling type
fluidized bed boilers shown in Fig. 4.
As shown in Figs. 4 and 14, the operation is effected
without difficulty by charging fuels from the charge inlet
provided in the ceiling~ In the case where solid fuels such
as coal having a grain size below several centimeters are
incinerated, it is preferable to charge the fuel into the
incinerating portion from a relatively low position instead
of from the ceiling and yet still higher than the surface of
the fluidized bed by using a suitabla type of equipment such
as a spreader adapted to scatter the fuel by means of a
rotary blade.
,,~^~4
-23- 1 3 ~ 6 4 1 ')
Accordingly, in a case where the apparatus is used
solely for incinerating solid fuels such as coal, it is
possible to provide the inlet at a position other than the
ceiling and simply to provide a spreader of the above type.
Also it is possible to charge combustibles containing large
size objects from the ceiling and to charge solid fuels from
the spreader just explained so as to incinerate them both
mixed together.
The internal recycling type fluidized bed boilers
herein above explained are the sort that are preferably
applied to boilers that are medium or large in size. As for
small pac~age boilers, it is desirable for them to be made
more compact and, thus, an embodiment designed to such end
is illustrated in Fig. 15. In the embodiment shown in
Fig. 15, the thermal conducting conduits 65 shown within the
bed in Fig. 4 are oriented in an almost vertical direction
and are extended to an exhaust gas heat conducting portion
provided above the thermal energy recovery chamber so that
this group of thermal conducting conduits is arranged to
also serve as means for unitarily coupling a top water
chamber 91 and a bottom water chamber 92.
By arranging the approximately vertical evaporating
conduits in a plural number in a free board at the upper
portion of the primary fluidized bed incinerating chamber
and around the thermal energy recovery chamber, it is
possible to utilize them as members for reinforcing the
boiler body as well as to eliminate the need for auxiliary
devices such as a forcible circulating pump and associated
conduits, etc. because the fluid in the thermal conducting
conduits including that in the conduits within the bed is
automatically circulated.
Further, a fluidized bed boiler and an exhaust gas
boiler can be combined as a unitarily structure so that an
internal recycling type fluidized bed boiler can be made
economically available in a small size.
The construction and function of the present inven-
tion are further described hereinbelow in detail. The
exhaust gas generated after the incineration in the primary
_~4_ 1 31 6~1 3
fluidized bed incinerating chamber is passed upwardly
through the free board at the portion above the incinerating
chamber and thence introduced into the group of thermal
conducting conduits formed around the periphery from the
upper portion of the group. It is then moved downwardly in
a flow moving in a direction that is nearly normal relative
to the thermal conducting conduits while effecting heat
transfer. At this occasion, a part of the unburnt ash
collected by means of baffle plates 93 due to the inertia-
gravity is caused to fall towards the moving bed in thethermal energy recovery chamber so that the unburnt ash is
then completely incinerated due to its long dwelling time
in that moving bed, thereby improving the incinerating
efficiency.
The above situation is particularly effective when
coal is used, the unburnt carbon of which needs a long time
to be incinerated. However, in other cases where a fuel
other than coal is employed and the unburnt ash thereof may
not scatter widely, means for recycling the unburnt ash may
not be needed,
As to the fuel charge inlet, if it is arranged, for
example as a type allowing charging from the top as
illustrated, it is preferable to blow the secondary incin-
erating air towards the primary fluidized bed incinerating
chamber. By the arrangement above, an air curtain effect
brought about the secondary air is expected to prevent fine
fuel particles such as minute powdered coal from being
scattered together with the incineration exhaust gas as well
as to perform an effective agitation and mixing operation in
the free board portion so that it may also contribute to
effect sufficient contact between oxygen in the secondary
air and the unburnt ash in the exhaust gas, thereby improv-
ing the incinerating efficiency and lowering the density of
NOx and C~, etc.
3~ Fig. 16 is a planar sectional view taken along the
line shown by the arrow A - A in Fig. 15 and it particularly
illustrates an example of a circular type boiler. In a case
` -2S- 1 316~
where it is a small size package boiler, it is not parti-
cularly necessary to make it a circular type as shown ln
Fig. 16, but manufacturing the arrangement of the thermal
conducting conduits is made easy if it is made circular.
Incidentally, in the ~mbodiments shown in Figs. 4,
13 and 14, etc., it ls preferable to arrange them in a
rectangular configuration from the construction viewpoint.
The effect and advantages of the present invention
may be summarized as noted below.
~ Because of the inclination of the partition wall,
it is possible, by controlling the amount of air inJected
from the air diffuser (62) disposed at the rear of the
partition wall of the thermal energy recovery chamber to
cause descending and circulation of the fluidizing medium
in the state o~ a moYing bed within the thermal energy
recovery chamber as well as to control the amount o~
fluidlzing medium circulatlng so as to optionally
regulate the amount of thermal energy recovered.
Also, lt is possible to put the fluldlzing ~edium
withln the thermal energy recovery chamber ln the sta-
tionary state by regulating the amount of air in~ec~ed
from the alr diffuser (62) of the thermal energy recovery
chamber so that It is zero.
~ Because of the fact that a boundary wall separat-
lng the thermal energy recovery chamber and the primary
fluldized bed lncinerating chamber ls an lnclined
partition wall and the mass flow of the fluidixing air
ln~ected from the portlon below the inclined partition
wall is large, ~t is posslble to make the amount of
fluidizing medium introduced from the primary fluidizing
bed incinerating chamber into the thermal energy recovery
chamber large.
~ Relatlve to the Gmf of the alr ln~ected from the
alr diffuser of the thermal energy recovery chamber lnto
the thermal energy recovery chamber, the Gmf of the alr
injected to the primar~ incinerating chamber at the
~`
1 3 1 6 4 1
portlon ad~acent the lower openlng of the thermal energy
recovery chamber is large, so the circulating amount o-f
the fluidiæing medium into the thermal energy recovery
chamber is adequately assured. Also, it is possible to
easily control the amount of fluldizing medium circulat-
ing in the thermal energy recovery chamber by regulating
the amount of air diffusing from the air diffuser of the
thermal energy recovery chamber.
~ Because the air diffuser of the thermal energy
recovery chamber is provided at the rear of the inclined
partition wall, the circulation of the fluidizing medium
is adequately assured and is easily controlled.
~ Because the primary fluidising bed incinerating
chamber constituted an lnternal recycling type fluidized
bed, the fluidizlng medium which is introduced from the
thermal energy recovery chamber to the primary fluidized
bed incinerating chamber after recovery of the thermal
energy therein is smoothly dlffused in the primary
incineratlng chamber, thereby being heated
instantaneously.
~ The fluidizing medium within the thermal energy
recovery chamber is caused to descend and circulate in
the state of a moving bed with difPusing air in the mass
flow range of O - 2 Gmf and, therefore, the abrasion rate
of the thermal conductlng surface is made quite small, as
is apparent from Fi~. 9, compared to a case wherein the
thermal conducting surface under whlch the heat sink
fluid is flown is dlrectly disposed within the fluidized
medium of a bubbling type boiler.
~ Since the descending rate of the thermal med~um
within the thermal energy recovery chamber is regulated
in the range of O - 2 Gmf with respect to the mass flow
of the difPusing air in the thermal energy recovery
chamber, ~he overall thermal energy transmitting coeffi-
cient is linearly changed as shown in Flg. 8, so the
regulation o~ thermal energy recovery is made easy.
-. ~
