CA1280319C - Method of stable combustion for a fluidized bed incinerator - Google Patents
Method of stable combustion for a fluidized bed incineratorInfo
- Publication number
- CA1280319C CA1280319C CA000527710A CA527710A CA1280319C CA 1280319 C CA1280319 C CA 1280319C CA 000527710 A CA000527710 A CA 000527710A CA 527710 A CA527710 A CA 527710A CA 1280319 C CA1280319 C CA 1280319C
- Authority
- CA
- Canada
- Prior art keywords
- fluidized bed
- refuse
- incinerator
- water
- air
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
- F23G5/00—Incineration of waste; Incinerator constructions; Details, accessories or control therefor
- F23G5/30—Incineration of waste; Incinerator constructions; Details, accessories or control therefor having a fluidised bed
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23L—SUPPLYING AIR OR NON-COMBUSTIBLE LIQUIDS OR GASES TO COMBUSTION APPARATUS IN GENERAL ; VALVES OR DAMPERS SPECIALLY ADAPTED FOR CONTROLLING AIR SUPPLY OR DRAUGHT IN COMBUSTION APPARATUS; INDUCING DRAUGHT IN COMBUSTION APPARATUS; TOPS FOR CHIMNEYS OR VENTILATING SHAFTS; TERMINALS FOR FLUES
- F23L7/00—Supplying non-combustible liquids or gases, other than air, to the fire, e.g. oxygen, steam
- F23L7/002—Supplying water
Abstract
ABSTRACT OF THE DISCLOSURE
A combustion method in the fluidized bed incinerator for burning and decomposing of refuse, such as municipal wastes in which the refuse is fluidized together with a fluidizing medium, such as sand, with primary air being burnt and decomposed. The pyrolysis gas produced by thermal decomposition is combusted with the secondary air supplied to the incinerator.
By controlling the temperature inside the fluidized bed in the range from 520 to 650°C by spraying water, a stable combustion is carried out, despite the change in the volume of refuse thrown onto the fluidized bed, and the unburnt pyrolysis gas and smut densities among the exhaust gas can be decreased. The combustion air ratio can be reduced because the refuse can be stably combusted, and the temperature of pyrolysis gas inside the combustion chamber can be maintained at a high level.
A combustion method in the fluidized bed incinerator for burning and decomposing of refuse, such as municipal wastes in which the refuse is fluidized together with a fluidizing medium, such as sand, with primary air being burnt and decomposed. The pyrolysis gas produced by thermal decomposition is combusted with the secondary air supplied to the incinerator.
By controlling the temperature inside the fluidized bed in the range from 520 to 650°C by spraying water, a stable combustion is carried out, despite the change in the volume of refuse thrown onto the fluidized bed, and the unburnt pyrolysis gas and smut densities among the exhaust gas can be decreased. The combustion air ratio can be reduced because the refuse can be stably combusted, and the temperature of pyrolysis gas inside the combustion chamber can be maintained at a high level.
Description
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This invention relates to a method of incinerating sub-stances such as municipal wastes and industrial wastes (called "refuse" hereinafter) inside a fluidized bed incinera-tor. More particularly, it relates to a method of stable combustion of refuse in a fluidized bed incinerator.
The fluidized bed incinerator is known for burning and decomposing refuse such as municipal wastes. With the method of incineration/disposition in this fluidized bed incinerator, refuse is burnt while fluidized in a fluidized bed incinerator.
In order to improve combustion of the refuse together with the fluidized bed, fluidizing medium, such as sand, is fed together with the refuse in the fluidized bed.
A general type of fluidized bed incinerator is equipped with a plurality of air diffuser tubes or plates (called as "air diffusers" hereinafter) supplying air down to the lower part of the incinerator body, and with a refuse feeding mechanism and a fluidizing medium feeding mechanism in the upper part.
The refuse is burnt while both the refuse and the fluidizing medium thrown onto the air diffuser tubes or pla-tes inside the incinerator body, are fluidized by the primary air hlown from the air diffusers.
~5 The refuse, such as municipal wastes, generally con-tains a variety of materials, such as low caloriP refuse, e.g.
good waste, high calorie refuse, e.g. plastics and rubber, refuse of the type shredded paper or chipped furniture, refuse of the type fragmented metallic or vitreous containers, bottles, or cans.
Of the refuse, as it is fed to the fluidized bed, the combustibles are burnt, of which substances, such as plastics undergo pyrolysis generating various pyrolysis gasss, while the incombustibles, such as metals or glasses, are left unburnt (called ~combustion residue~ hereinafter).
As the fluidizing medium is gradually fed in the fluidized bed, a moving bed of fluidizing medium is formed, descending as the fluidizing medlum is supplied continuously.
Therefore, while the combus-tibles are bùrnt and decomposed wi.khin the fluidized bed, the combustion residue passes out of the incinerator, together with the fluidizing medium, through the gaps in air diffusers at the lower section of the 1~
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fluidized bed. The fluidizing medium and the combustion residue are separated from each other, and then fluidizing medium is again fed to the fluidized bed.
The secondary air is supplied into the fluidized bed upper section of the incinerator, where the generated pyrolysis gases are burnt.
Because, in this fluidized bed incinerator, the sand which is the fluidizing medium thrown onto the fluidized bed is oscillated while descends and is heated, it promotes the agitation and dispersion of the refuse.
For this reason, the refuse thrown onto the fluidized bed is dispersed uniformly under the presence of the fluidizing medium, to be dried, ignited, burnt, and decomposed instantaneously. Further, the ashes and dust produced therein are brought to upper section the incinerator and are collected by an electric precipitator.
Consequently, the refuse thrown onto the fluidized bed is disposed of almost completely leaving behind some metallic, vitreous, or ceramic residue. The ratio of these substances to the refuse is usually 2%, meaning a fluidized bed incinerator can dispose of 98% of the refuse. This is a merit with the fluidized bed incinerator that the volume of combustion residue can be reduced to 1/3 compared with a conventional mechanical incinerator like a stoker-type combustor.
However, the refuse thrown onto the fluldized bed ls burnt and decomposed at high speed so that the refuse cannot be stably combusted. The refuse has different calorific value de-pending on the kind of refuse, and it is often difficult to always supply a cons-tant volume o~ the refuse onto the fluid1zed bed. Suppose that a large quantity vf refuse is thrown onto the fluidized bed all at once, the refuse is burn-t and decomposed ins-tantaneously and then a large amount of pyrolysis gases with lU dust is generated simultaneously. In this instance, it is not only impossible to completely combust a large amount of pyrolysis gases with the secondary air inside incinerator but it is also difficult to collect all of the large amount of smuts in exhaust gas by the ele~tric precipltator.
The present invention provides a method to slow the burning and decomposing the re~use in the fluidized bed for stable combustion.
This invention relates to a method of incinerating sub-stances such as municipal wastes and industrial wastes (called "refuse" hereinafter) inside a fluidized bed incinera-tor. More particularly, it relates to a method of stable combustion of refuse in a fluidized bed incinerator.
The fluidized bed incinerator is known for burning and decomposing refuse such as municipal wastes. With the method of incineration/disposition in this fluidized bed incinerator, refuse is burnt while fluidized in a fluidized bed incinerator.
In order to improve combustion of the refuse together with the fluidized bed, fluidizing medium, such as sand, is fed together with the refuse in the fluidized bed.
A general type of fluidized bed incinerator is equipped with a plurality of air diffuser tubes or plates (called as "air diffusers" hereinafter) supplying air down to the lower part of the incinerator body, and with a refuse feeding mechanism and a fluidizing medium feeding mechanism in the upper part.
The refuse is burnt while both the refuse and the fluidizing medium thrown onto the air diffuser tubes or pla-tes inside the incinerator body, are fluidized by the primary air hlown from the air diffusers.
~5 The refuse, such as municipal wastes, generally con-tains a variety of materials, such as low caloriP refuse, e.g.
good waste, high calorie refuse, e.g. plastics and rubber, refuse of the type shredded paper or chipped furniture, refuse of the type fragmented metallic or vitreous containers, bottles, or cans.
Of the refuse, as it is fed to the fluidized bed, the combustibles are burnt, of which substances, such as plastics undergo pyrolysis generating various pyrolysis gasss, while the incombustibles, such as metals or glasses, are left unburnt (called ~combustion residue~ hereinafter).
As the fluidizing medium is gradually fed in the fluidized bed, a moving bed of fluidizing medium is formed, descending as the fluidizing medlum is supplied continuously.
Therefore, while the combus-tibles are bùrnt and decomposed wi.khin the fluidized bed, the combustion residue passes out of the incinerator, together with the fluidizing medium, through the gaps in air diffusers at the lower section of the 1~
3~
fluidized bed. The fluidizing medium and the combustion residue are separated from each other, and then fluidizing medium is again fed to the fluidized bed.
The secondary air is supplied into the fluidized bed upper section of the incinerator, where the generated pyrolysis gases are burnt.
Because, in this fluidized bed incinerator, the sand which is the fluidizing medium thrown onto the fluidized bed is oscillated while descends and is heated, it promotes the agitation and dispersion of the refuse.
For this reason, the refuse thrown onto the fluidized bed is dispersed uniformly under the presence of the fluidizing medium, to be dried, ignited, burnt, and decomposed instantaneously. Further, the ashes and dust produced therein are brought to upper section the incinerator and are collected by an electric precipitator.
Consequently, the refuse thrown onto the fluidized bed is disposed of almost completely leaving behind some metallic, vitreous, or ceramic residue. The ratio of these substances to the refuse is usually 2%, meaning a fluidized bed incinerator can dispose of 98% of the refuse. This is a merit with the fluidized bed incinerator that the volume of combustion residue can be reduced to 1/3 compared with a conventional mechanical incinerator like a stoker-type combustor.
However, the refuse thrown onto the fluldized bed ls burnt and decomposed at high speed so that the refuse cannot be stably combusted. The refuse has different calorific value de-pending on the kind of refuse, and it is often difficult to always supply a cons-tant volume o~ the refuse onto the fluid1zed bed. Suppose that a large quantity vf refuse is thrown onto the fluidized bed all at once, the refuse is burn-t and decomposed ins-tantaneously and then a large amount of pyrolysis gases with lU dust is generated simultaneously. In this instance, it is not only impossible to completely combust a large amount of pyrolysis gases with the secondary air inside incinerator but it is also difficult to collect all of the large amount of smuts in exhaust gas by the ele~tric precipltator.
The present invention provides a method to slow the burning and decomposing the re~use in the fluidized bed for stable combustion.
2~ Further, the present invention controls the speed of the fluidized bed and to be able to carry out stable combustion despite the fluctuations in the thrown volume of re~use onto the fluid bed.
2~ The present invention also provides a method of stable combustion for the fluidized bed incinerator which is capable of reducing the volume of air SUppliPd for the re~use and of main-taining the combustion temperature of pyrolysis at high level in the combustion chamber. The present inventlon agaln provides a type of fluidized bed incinerator which is capable of stably carrying out th0 combustion of the refuse in the fluidized bed.
According to one aspect the present invention there is provided a method of stable combustion of refuse in a ~luidized 3 r bed incinerator, comprising the steps of: (a) forming a fluidized ~ _ 4 _ .~ . ' :
~ 3~ 9 bed in the incinerator by fluldizing said re~use to be lnciner-ated and an incombustible fluidizing medium as said refuse and the fluidizing medium are supplied to the fluidizing bed along with primary air~ the primary air being blown into the fluidized bed by air difEuser tubes provided in the lower part of the incinerator, the air dif~user tubes extending generally parallel to each other; tb) burning and decomposing said re~use iIl sa:ld fluidized bed, the decomposition of said refuse resulking in khe generation of pyrolysis gas; ~c) combusting said prolysls gas with secondary air supplied to an upper section of said incinera-LU tor; ~d) forming a downward flow of the combinatlon of the com-bustion residue of said refuse~and the fluidizing medium inside the fluidized bed through the air diffuser tubes, and discharging said combination from the bottom of the incinerator; (e) separat-ing the fluidizing medium from the combustion residue ln a sieve;
(f) circulating the fluidizing medium separated in step (e) back to said fluidized bed; and (g) maintaining the fluidized bed temperature in the range from 520 to 650C. by spraying water onto the fluidized bed.
2Q In the present invention the fluidized bed is formed by fluidizing the refuse and the fluidizing medlum with the primary air which is blown thereinto via the air diffuser tubes provided at a lower part of the incinerator body in parallel to each other having a large number of nozzles provided on either side.
Desirably the total volume of the primary air and secondary air is from 1.4 to 1.7 times the theoretical air volume for the refuse. More desirably primary air and secondary air are approxlmately in the ratio 1:1.
3~ In another aspect thereof the present invention provides a method performing stable combustion of re~use in a fluidized bed incinerator, comprising the steps of: (a) ~orming a fluidized b0d in said lncinerator by fluidizlng said refuse and a : fluidizing medium with primary air; (b3 burning and decomposing said refuse in sald fluidized bed; and (c) controlllng said .~ . ' . i, .,.~;
~ 2 ~ ~ 3 ~ ~
fluidized bed temperature so as to maintain said temperature in the range from 520 to 630C. by applying water onto said ~lu-idized bed. Suitably step (c) is performed by spraying sald water onto said fluidlzed bed. Desirably step ~c) is performed by mixing said water wi-th said refuse and introducing re~use having said water mixed therein into said fluidized bed~
Suitably the method includes the steps of separa~ing the combustion residue of the refuse from the fluidizing medium in the lower part of said fluidized bed, and circulating the separated fluidizing medium back to ~aid fluidizing bed, and lU wherein step (c~ is performed by cooling the fluidizlng medium circulated back to said fluidized bed.
The present invention also provides a fluidized bed incinerator having a fluidiæed bed for combusting refuse, com-prising an incinerator body; a plurality of parallel air dif-fuser tubes in a lower section of said body, each of said tubes having a plurality of openings on opposite sides thereof for supplying pr~mary co~bustion air to said fluidized bed; means for supplying said primary combustion air to said tubes; means for introducing refuse onto said fluidized bed above said tubes, the thermal decomposition of said refuse lnside fluldized bed result-in~ in the generation of pyrolysls gas; means below said tubes for removing combustion res~due and a fluidizing medium from said . lower section of said incinerator body; means for separating said 25 . . combustion residue from said fluidizing medium; means for circulating the separated fluidizing medium back to said . fluidized bed; and means for spraying water onto the upper face of said fluidized bed to control said fluidized bed temperature, . said water spraying means having at least one nozzle which has 3~ changeable orientation and which produces an essentially u~iform spray of water over said bed~ Suitably the fluldized bed in-cludes a temperature detector for detecting the fluidized bed temperature, and wherein said water spraylng means is responsive . to said temperature detector for controlling the volume o water sprayed onto said fluidlzed bed in accordance with the value of -- 6 -- .
"f~
the detected temperature. Desirably sald water spraying means includes a double tube haviny an inner tube for spraying said water and an outer tube for air cooling sald inner tube. Preferably said double tube includes a water spraying tip and extends through said incinerator body, and said water spraying means lncludes a drive mechanism connected to said double tube for moving said spraylng tip to spray water uni~ormly over said fluid~zed bed.
The present invention will be further illustrated by u way of the accompanying drawings, in which:-Fig. 1 ls schematic sectional view of a fluidized bed incinerator according to one embodiment of the present invention;
Fig. 2 is a fragmentary enlarged view of Fig. l;
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- 6a -' ~':.
Fig. 3 is a graph showing the relation be-tween the tem-perature of the fluidized bed and the combustion speed ratio of the refuse, according to the present invention;
Fig. 4 is a graph showiny the temperature of the fluidized bed and the chronolo~ical change o~ exhaust gas temper~
atures inside the incinerator when the refuse is burnt according to the present invention;
Fig. 5 is a graph showing the condition of smuts gener-ated wi-thin the exhaust gas after burning the refuse in accor-dance with the present invention;
Fig. 6 is a graph showing the tempera-ture of the fluidized bed and the chronological change of exhaust gas temper-ature at several locations in the incinerator when the refuse is burnt in accordance with the conventional method; and Fig. 7 is a graph showing the condition of exhaust gas generated when the refuse is burnt according to the conventional method.
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-~23~3~9 ~ -lereinafter, the preferred embodiment example of the method of stable combustion for the fluidized bed incinerator according to the present invention is described reEerring to attached drawings.
In Fig. 1, the re~erence numeral 10 denotes the incinerator body made up of the refractory walls 12, and comprises a rectangular top wall 14, side walls 16 and an inverted rectangular pyramid bottom wall 18 connected to with the lower section of the said side walls 16.
The side walls 16 comprise the upper wall 16a in which a combustion chamber 20, described later, is formed, the tilted wall 16b sloped inwardly from the said upper wall 16a, and the vertical side wall 16c extended vertically fro~ the lower section of said tilted wall 16b and also connected with the bottom wall 18.
An exhaust port 19 is provided in the top wall 14, and a discharge port 22 is provided at the lower center of bottom wall 18.
In the space enclosed by the vertical walls 16c, a large number of air diffuser tubes 24 are provided in parallel each other to supply the primary air to form the fluidized bed 40 described later.
3~
The tubes 24 are extended through the vertical wall 16c out of the incinerator body 10 and are connected to the Eluidizing air charging tube 26.
On either side of air diEfuser tubes 2~, the noz~le holes 25 are provided along the length direction at intervals.
The duct 30 through which the reEuge 28 is thrown onto the air diEfuser tubes 24 is connected to the upper side wall 16a of incinerator body 10, to which said precipitator 31 is further connected.
The precipitator 31 compromises a screw 36, and a casing 34 connected to the duct 30. That casing 3~ has a hopper section 38 for the refuse 28. The refuse 28 thrown into this hopper 38 is transferred into the duct 30 by the rotation of screw 36, and fed onto the air diffuser tubes 24 via the duct 30.
The upper section wall 16a of incinerator body 10 has a charging port 37 for feeding such fluidizing medium as sand into the incinerator body 10. This fluidizing medium 32 is supplied onto the air diffuser tubes 24 through the charging port 37 from the circulation unit described later.
The fluidized air charging tube 26, (not shown in the figure) is connected to the air charging source, to supply ~8~ 9 the air to each air diffuser tubes 24, from which air comes out, as shown by the arrow in the figure, from each nozzle holes 25 of the air diffuser tubes 24. The refuse 28 alony with the fluidizing medium 32 fed onto the air dillser ~ubes 24 is fluidized by the said air, forming the fluidized bed 40.
A screw conveyor 46 is connected to the discharge port 22 of the incinerator body 10 to transfer the fluidizing medium and the combustion residue among the refuse 28 which descends through the gaps among the air diffuser tubes 24.
A separator 44 contains a sieve 48 which separates the fluidizing medium 32 from the combustion residue 42. The combustion residue 42 remains on the sieve 48 and is discharged from an discharge port 45 of the separator 44.
The fluidizing medium 32, after passing through the sieve 48, is fed back to the fluidized bed 40 via the charging port 37 through a circulation l.ine 50 equipped with the vertical conveyor which is connected to the separator 44.
The secondary air is supplied into the combustion chamber (free-board) 20 in the incinerator body 10, by air intake nozzles 52 which are installed to the upper wall 16a.
A water spray 54 whose tip 54a is provided above the , ' ,' ~2~q~3~9 fluidized bed 40 is provided, which penetrates the upper section wall 16a oE incinerator body 10.
This spray 54 is connected to a water charglny line 56.
A temperature sensor 58 for the temperature of the fluidized bed 40 is provided inside the side wall 16c. The value detected by the sensor 58 is input to a control unit 62 through a signal line 60.
A control valve 66 is connected to the water charging line 56, to regulate the volume of water 64 sprayed to the fluidized bed 40 from the spray 54. Based on the value detected by the temperature sensor 58, the control unit 62 controls valve 66 through a control signal line 68 so that the temperature of the fluidized bed 40 is in the range from 520 to 650C.
Next, the method for burning the refuse in the fluidized bed incinerator will be explained.
The refuse 28 is fed onto the air diffuser tubes 24 inside incinerator body 10, via the duct 30 from the precipitator 31, and the fluidizing medium 32 is supplied through the discharging port 37 from the circulation unit 50.
On the other hand, the fluidizingair is supplied to each air diffuser tubes 24 from the fluidizing air charging tube 26, and the primary air is blown out as sllown by the arrow in figure from each nozzle 25 of the said air diffuser tubes 24.
: 10 ~28~3~9 The refuse 28 and the fluidizing medium 32 which are supplied OlltO the air diffuser tubes 2~ are fluidized by the primary air blown in from the nozzles 25.
A rlumber . of start-up burners are provided inside khe incinerator body 10 (not shown i,n the figure), and when starting the incineration operation, the refuse 28 on the Eluidized bed 40 is ignited by the Elames from these burners.
When the refuse 28 inside the fluidized bed 40 has all combusted by the fluidizing air, the ignition by burners is ceased.
SOme of refuse 28 undergo pyrolysis and generate pyrolysis gases by the combustion heat oE the refuse 28 inside the fluidized bed 40. The pyrolysis gases, containing ~l2, CO and hydrocarbonaceous gases, are burnt with the secondary air which is blown in as shown by the arror 52a from the nozzles 52 at the combustion chamber 20 on the upper part inside the incinerator body 10.
The primary air blown out of the air diffuser tubes 24 and the secondary air blown out oE nozzles 52 are adjusted to the ratio from 2:3 through 3:3, or preEerably at the ratio of 1:1, and further, the total air ratio to the theoretical air volume for combusting the reEuse is adjusted in the range from 1.4 to 1.7 times.
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The exhanst gas produced through the combustlon of refuse 2a and pyrolysis gas are exhausted out of the incinerator from the exhalls-t port 19. Containing a large quantity of heat, this exhaus-t has ls utilized to preheat the water oX the boilers etc. Since smuts are contalned in the exhaust has, 1t is removed by an electrostatic precipitator after used as the heat source.
The refuse 28 and the fluidizing medium 32 have to be fed timely to the fluidized bed 40 where the refuse is burnt and decomposed as mentioned above.
On the other hand, the fluidizing medium 32 promotes the agitation and dispersion of the refuse, and it also for1ns a moving bed descending through the fluidized bed 40.
Thereafter, the fluidizing medium 32 flows down onto the bottom wall 18 along with the combustion residue 42 within the refuse 28 from the gaps among the air diffuser tubes 24, and forms a filling bed below the air diffuser tubes 24 with the fluidizing tnedium 32 and the combustion reisdue 42 contained therin, and the said filling bed helps adjust the thickness of fluidized bed 40 which is built up above the air diffuser tubes 24. As the combustion residue increases, filling bed becomes big, so it is discharged by the screw 3~
conveyor 46 installed in a downward position. I'he screw conveyor 46 transEers the fluidizing medium 32 and the combustion residue 42 to the separator 44.
In the separator 44, the combustion residue 42 is separated from the fluidizing medium 32 by the sieve 48, then the combustion residue 42 is discharged Erom the exhaust port 45, wl~ile the fluidizing medium 42 is fed again to the fluidized bed 40 through the circulation line 50.
If the refuse 28 is usually burnt in the fluidized bed 40 as mentioned above, the temperature of that fluidized bed may reach a level from 700 to 800C. However, in this temperature range, the combustion of refuse 28 occurs so quickly that the said refuse would be instantaneously dried, ignited, burnt, and decomposed. For this reason, if a large quantity of refuse 28 is thrown at a time into the fluidized bed 40, a large quantity of pyrolysis gases and smuts will be generated. As a consequence, all the pyrolysis gases cannot be burnt with the secondary air supplied into the combustion chamber 20, and the smuts within exhaust gas coming out of the incinerator body 10 cannot get the dust completely removed by the electric precipitator.
In this embodiment, therefore, the temperature of the fluidized bed 40 is detected by the temperature sensor 58, and the control unit 62 functions to regulate the control valve 66 and control the water volume sprayed from the spray 54 so that the temperature oE the fluidized bed 40 is in the range from 520 to 650C.
Since the fluidized bed 40 is maintained in the temperature range from 520 to 650~C by the water spray, the reEuse 28 is burnt and decomposed stably. Therefore, even if the thrown volume of refuse 28 to the fluidized bed 40 fluctuates, or a large amount of refuse 28 is thrown at a time, a stable burning and decomposing occur so that pyrolysis g-as and dust are not generated in a large quantity.
Further, the total air ratio required for burning the reuse 28 is 1.7 to 2.0 conventionally to the theoretical air volume, which can however be lowered to 1.4 to 1.7 according to this invention, and the temperature inside the free-board section (combustion chamber) can also be maintained at a high level.
Fig. 2 shows the details of the water spray 54. The water spray 54 consists oE double tubes 70, which are inserted at a downward angle from the insertion hole 72 which is provided on the upper section wall 16a of the incinerator body 10 and whose tip nozzle section 71 is positioned on the upper side o the fluidized bed 40.
~286~3~
The insertion hole 72 is a cone-shaped hole which has smaller open end at the outer surface of the wall 16a and the said insertion hole 72 allows the nozzle 70a on the tip of the double tube 70 to move to the right and leEt or up and down. The basement 7~ of the double tube 70 is supported via a universal joint 78, on the supporting body 76 which is installed on the upper sec tion wall 16a. What's morel this universal joint 78 is interlocked with the linkage 801 and the nozzle 70a of the double tube 70 is moved up and down or right and left, via the said universal joint 78, by which the movement of the said linkage 80. The double tube consists of the inner tube 82 for water and the outer tube 84 for the cooling air. The basement of the inner tube 82 is connectedl via a flexible tube 86, to the water supplying line 56. The basement of outer tube 84 is connected, via another flexible tube 88, to the cooling air supplying source (not shown in the figure).
These flexible tubes 86 and 88 supply water and cooling air to the double tube 70 moving with the basement of double tube 70.
In the explanation of the aforecited embodiment, water is sprayed directly on the fluidized bed 40 to keep the fluidized bed temperature in a range from 520 to 650C, but :' .,.
' ~ -~28~t3~
this invention shalL not be limited only by this way of keeping the temperature.
As another means for keeping the ternperature oE the fluidized bed 40 in the range Erom 520 to 650C, .~.t ls ~lso acceptable, as shown by an imaginary line in Fig. 1, by providing a water spray 90 to the hopper 38 of the precipitator 31, in order to spray the water onto the refuse 28 inside the said hopper 38.
In this case too, the volume of the water from the spray go is adjusted so that the fluidized bed temperature by the temperature sensor 58 is in the range from 520 to 650C.
As another way to control the temperature, because the tempe.rature of the fluidizing medium 82 which is separated by a separator 44 and circulated to the fluidized bed 40 through the circulation line 5Q is at a considerably high level, the fluidized bed temperature can be controlled lower than 650 by providing a cooling unit 92 for the fluidizing medium 32 to the circulation line 50 to lower the temperature of the fluidizing medium 32 supplied to the fluidized bed 40.
There is one more way to control the temperature. The fluidized bed temperature can be controlled at 650C by cooling the fluidizing air which passes through the air diffuser tubes 24 and the fluidizing air tube 26.
3~9 It is also acceptable to combine these means together for controllin~ the Eluidized bed temperature.
Fig. 3 is the graph showing the relation between the temperature of the fluidized bed and the combustion speed where the combustion spee~ ratio represents the ratio oE the minimum time needed Eor burning and decomposing in a ideal condition and the time spent actually, after the refuse is thrown.
AS can be seen from this figure too, when the fluidized bed temperature is in the range from 700 to 800C, its combustion speed ratio was 0.7 to 1.0 in the past, but this speed ratio can be maintained in the range Erom 0.~ to 0.6 by keeping the temperature in the range "A", from 520 to 650C
as in this invention, and it is possible to lower the speed ratio to about 60~ of the conventional combustion speed ratio.
By burning the refuse slowly on the fluidized bed in this way, the refuse can be prevented from being burnt instantaneously, and the voluminous generation of pyrolysis gas and smuts can be suppressed.
In this case, if the temperature of the fluidized bed is lower than 520C, it i9 not favorable because the combustion of the refuse in fluidized bed becomes unstable (difficult), :
~28C~3~
and if it is higher than 650 ~c, it is not favorable either because the speed becomes hlgher and the volume to be decomposed and the volume of smuts generated are instantaneously increased even if the change of the volume and qual~ty of the refuse are relatively small.
Fig. 4 and Fig. 6 show the chrcnological changes of f.luiclized bed temperature and combustion gas temperature in the case of this invention and the conventional example.
For Fig.4 and Fig. 6, the same fluidized bed incinerator is used and the temperature is measured for 6 or hours, feecling the municipal wastes at 2.5 tons/h and Fig.
~ shows the result where the secondary combustion at the free board has been fully carried out in addition to the present invention.
As shown in Fi-g. 6, since the temperature inside the fluidized bed is not controlled in the conventional method, it can be seen that the fluidized bed temperature reaches a level higher than 650 oc, and its temperature gradually increases because inside the combustion chamber, lower section temperature 'b' is around ~50~c, upper section tempera-ture 'c' i5 around 850'c, and the temperature 'd' of combusted gas leaving the inclllarator and entering into the gas cooling unit is around 950'c.
This means that the pyrolysis gas generated by the . . .
~L28~3~L~
thermal decomposition in the fluidized bed is burnt until it enters the gas cooling unit, and that the temperature inside the combustion chamber is lowt around 800C~ and that the pyrolysis gas has not been perEectly burnt.
In contrast, in this invention as shown in Fig. ~, it can be understood that when water is sprayed onto the fluidized bed and its fluidized bed temperature "ao" is kept at 600C _ 15C, the lower section temperature "bo" of incinerator, the upper section temperature "co" as well as the temperature "do" at the entrance Q~ the gas cooling unit are all maintained at a high level oE around 900C. This explains the fact that the combustible gas which is generated is completely burnt by the secondary air inside the combustion chamber.
Fig. 5 and Fig. 7 are graphs showing the smut concentration of exhaust gas ~rom the stack, after the exhaust gas passes through the cooling unit and dust is removed by the electric precipitator, which is then measured chronologically by a Ringelman smoke density indicator.
In case oE the conventional example, the smoke with the Ringelman smoke indicator value o~ more than about 0.5, which is the critical point for vision, is discharged disorderly as : ~ .
.:
~.
~ 8~3~ ~
shown in Fig. 7, but in this invention little smoke with an indi-cated value of more than 0.5 is emitted, as shown in Fig. 5.
When controlling the -temperature of the fluidized bed, its temperature can be controlled to the desired range even by spraying water at a constant rate to the volume o the refuse without detecting the temperature.
It will be appreciated that this invention will develop following excellent effects. (1) Keeping the temperature of the fluidized bed in the range from 520 to 650C, the refuse can be slowly burnt and stable combustion can be carried out without being influenced by the change of the volume or quality of the refuse. (2) Since the refuse is burnt and decomposed slowly, pyrolysis gas or smuts does not come out in a large amount. (3) Because the air ratio for combustion can be reduced, the combus-tion chamber temperature inside incinerator can be high and the secondary combustion of pyrolysis gas can be carried out favourably.
,-
2~ The present invention also provides a method of stable combustion for the fluidized bed incinerator which is capable of reducing the volume of air SUppliPd for the re~use and of main-taining the combustion temperature of pyrolysis at high level in the combustion chamber. The present inventlon agaln provides a type of fluidized bed incinerator which is capable of stably carrying out th0 combustion of the refuse in the fluidized bed.
According to one aspect the present invention there is provided a method of stable combustion of refuse in a ~luidized 3 r bed incinerator, comprising the steps of: (a) forming a fluidized ~ _ 4 _ .~ . ' :
~ 3~ 9 bed in the incinerator by fluldizing said re~use to be lnciner-ated and an incombustible fluidizing medium as said refuse and the fluidizing medium are supplied to the fluidizing bed along with primary air~ the primary air being blown into the fluidized bed by air difEuser tubes provided in the lower part of the incinerator, the air dif~user tubes extending generally parallel to each other; tb) burning and decomposing said re~use iIl sa:ld fluidized bed, the decomposition of said refuse resulking in khe generation of pyrolysis gas; ~c) combusting said prolysls gas with secondary air supplied to an upper section of said incinera-LU tor; ~d) forming a downward flow of the combinatlon of the com-bustion residue of said refuse~and the fluidizing medium inside the fluidized bed through the air diffuser tubes, and discharging said combination from the bottom of the incinerator; (e) separat-ing the fluidizing medium from the combustion residue ln a sieve;
(f) circulating the fluidizing medium separated in step (e) back to said fluidized bed; and (g) maintaining the fluidized bed temperature in the range from 520 to 650C. by spraying water onto the fluidized bed.
2Q In the present invention the fluidized bed is formed by fluidizing the refuse and the fluidizing medlum with the primary air which is blown thereinto via the air diffuser tubes provided at a lower part of the incinerator body in parallel to each other having a large number of nozzles provided on either side.
Desirably the total volume of the primary air and secondary air is from 1.4 to 1.7 times the theoretical air volume for the refuse. More desirably primary air and secondary air are approxlmately in the ratio 1:1.
3~ In another aspect thereof the present invention provides a method performing stable combustion of re~use in a fluidized bed incinerator, comprising the steps of: (a) ~orming a fluidized b0d in said lncinerator by fluidizlng said refuse and a : fluidizing medium with primary air; (b3 burning and decomposing said refuse in sald fluidized bed; and (c) controlllng said .~ . ' . i, .,.~;
~ 2 ~ ~ 3 ~ ~
fluidized bed temperature so as to maintain said temperature in the range from 520 to 630C. by applying water onto said ~lu-idized bed. Suitably step (c) is performed by spraying sald water onto said fluidlzed bed. Desirably step ~c) is performed by mixing said water wi-th said refuse and introducing re~use having said water mixed therein into said fluidized bed~
Suitably the method includes the steps of separa~ing the combustion residue of the refuse from the fluidizing medium in the lower part of said fluidized bed, and circulating the separated fluidizing medium back to ~aid fluidizing bed, and lU wherein step (c~ is performed by cooling the fluidizlng medium circulated back to said fluidized bed.
The present invention also provides a fluidized bed incinerator having a fluidiæed bed for combusting refuse, com-prising an incinerator body; a plurality of parallel air dif-fuser tubes in a lower section of said body, each of said tubes having a plurality of openings on opposite sides thereof for supplying pr~mary co~bustion air to said fluidized bed; means for supplying said primary combustion air to said tubes; means for introducing refuse onto said fluidized bed above said tubes, the thermal decomposition of said refuse lnside fluldized bed result-in~ in the generation of pyrolysls gas; means below said tubes for removing combustion res~due and a fluidizing medium from said . lower section of said incinerator body; means for separating said 25 . . combustion residue from said fluidizing medium; means for circulating the separated fluidizing medium back to said . fluidized bed; and means for spraying water onto the upper face of said fluidized bed to control said fluidized bed temperature, . said water spraying means having at least one nozzle which has 3~ changeable orientation and which produces an essentially u~iform spray of water over said bed~ Suitably the fluldized bed in-cludes a temperature detector for detecting the fluidized bed temperature, and wherein said water spraylng means is responsive . to said temperature detector for controlling the volume o water sprayed onto said fluidlzed bed in accordance with the value of -- 6 -- .
"f~
the detected temperature. Desirably sald water spraying means includes a double tube haviny an inner tube for spraying said water and an outer tube for air cooling sald inner tube. Preferably said double tube includes a water spraying tip and extends through said incinerator body, and said water spraying means lncludes a drive mechanism connected to said double tube for moving said spraylng tip to spray water uni~ormly over said fluid~zed bed.
The present invention will be further illustrated by u way of the accompanying drawings, in which:-Fig. 1 ls schematic sectional view of a fluidized bed incinerator according to one embodiment of the present invention;
Fig. 2 is a fragmentary enlarged view of Fig. l;
.
- 6a -' ~':.
Fig. 3 is a graph showing the relation be-tween the tem-perature of the fluidized bed and the combustion speed ratio of the refuse, according to the present invention;
Fig. 4 is a graph showiny the temperature of the fluidized bed and the chronolo~ical change o~ exhaust gas temper~
atures inside the incinerator when the refuse is burnt according to the present invention;
Fig. 5 is a graph showing the condition of smuts gener-ated wi-thin the exhaust gas after burning the refuse in accor-dance with the present invention;
Fig. 6 is a graph showing the tempera-ture of the fluidized bed and the chronological change of exhaust gas temper-ature at several locations in the incinerator when the refuse is burnt in accordance with the conventional method; and Fig. 7 is a graph showing the condition of exhaust gas generated when the refuse is burnt according to the conventional method.
~ ~ 6b -' ' ' ' ' '~ ':
.
-~23~3~9 ~ -lereinafter, the preferred embodiment example of the method of stable combustion for the fluidized bed incinerator according to the present invention is described reEerring to attached drawings.
In Fig. 1, the re~erence numeral 10 denotes the incinerator body made up of the refractory walls 12, and comprises a rectangular top wall 14, side walls 16 and an inverted rectangular pyramid bottom wall 18 connected to with the lower section of the said side walls 16.
The side walls 16 comprise the upper wall 16a in which a combustion chamber 20, described later, is formed, the tilted wall 16b sloped inwardly from the said upper wall 16a, and the vertical side wall 16c extended vertically fro~ the lower section of said tilted wall 16b and also connected with the bottom wall 18.
An exhaust port 19 is provided in the top wall 14, and a discharge port 22 is provided at the lower center of bottom wall 18.
In the space enclosed by the vertical walls 16c, a large number of air diffuser tubes 24 are provided in parallel each other to supply the primary air to form the fluidized bed 40 described later.
3~
The tubes 24 are extended through the vertical wall 16c out of the incinerator body 10 and are connected to the Eluidizing air charging tube 26.
On either side of air diEfuser tubes 2~, the noz~le holes 25 are provided along the length direction at intervals.
The duct 30 through which the reEuge 28 is thrown onto the air diEfuser tubes 24 is connected to the upper side wall 16a of incinerator body 10, to which said precipitator 31 is further connected.
The precipitator 31 compromises a screw 36, and a casing 34 connected to the duct 30. That casing 3~ has a hopper section 38 for the refuse 28. The refuse 28 thrown into this hopper 38 is transferred into the duct 30 by the rotation of screw 36, and fed onto the air diffuser tubes 24 via the duct 30.
The upper section wall 16a of incinerator body 10 has a charging port 37 for feeding such fluidizing medium as sand into the incinerator body 10. This fluidizing medium 32 is supplied onto the air diffuser tubes 24 through the charging port 37 from the circulation unit described later.
The fluidized air charging tube 26, (not shown in the figure) is connected to the air charging source, to supply ~8~ 9 the air to each air diffuser tubes 24, from which air comes out, as shown by the arrow in the figure, from each nozzle holes 25 of the air diffuser tubes 24. The refuse 28 alony with the fluidizing medium 32 fed onto the air dillser ~ubes 24 is fluidized by the said air, forming the fluidized bed 40.
A screw conveyor 46 is connected to the discharge port 22 of the incinerator body 10 to transfer the fluidizing medium and the combustion residue among the refuse 28 which descends through the gaps among the air diffuser tubes 24.
A separator 44 contains a sieve 48 which separates the fluidizing medium 32 from the combustion residue 42. The combustion residue 42 remains on the sieve 48 and is discharged from an discharge port 45 of the separator 44.
The fluidizing medium 32, after passing through the sieve 48, is fed back to the fluidized bed 40 via the charging port 37 through a circulation l.ine 50 equipped with the vertical conveyor which is connected to the separator 44.
The secondary air is supplied into the combustion chamber (free-board) 20 in the incinerator body 10, by air intake nozzles 52 which are installed to the upper wall 16a.
A water spray 54 whose tip 54a is provided above the , ' ,' ~2~q~3~9 fluidized bed 40 is provided, which penetrates the upper section wall 16a oE incinerator body 10.
This spray 54 is connected to a water charglny line 56.
A temperature sensor 58 for the temperature of the fluidized bed 40 is provided inside the side wall 16c. The value detected by the sensor 58 is input to a control unit 62 through a signal line 60.
A control valve 66 is connected to the water charging line 56, to regulate the volume of water 64 sprayed to the fluidized bed 40 from the spray 54. Based on the value detected by the temperature sensor 58, the control unit 62 controls valve 66 through a control signal line 68 so that the temperature of the fluidized bed 40 is in the range from 520 to 650C.
Next, the method for burning the refuse in the fluidized bed incinerator will be explained.
The refuse 28 is fed onto the air diffuser tubes 24 inside incinerator body 10, via the duct 30 from the precipitator 31, and the fluidizing medium 32 is supplied through the discharging port 37 from the circulation unit 50.
On the other hand, the fluidizingair is supplied to each air diffuser tubes 24 from the fluidizing air charging tube 26, and the primary air is blown out as sllown by the arrow in figure from each nozzle 25 of the said air diffuser tubes 24.
: 10 ~28~3~9 The refuse 28 and the fluidizing medium 32 which are supplied OlltO the air diffuser tubes 2~ are fluidized by the primary air blown in from the nozzles 25.
A rlumber . of start-up burners are provided inside khe incinerator body 10 (not shown i,n the figure), and when starting the incineration operation, the refuse 28 on the Eluidized bed 40 is ignited by the Elames from these burners.
When the refuse 28 inside the fluidized bed 40 has all combusted by the fluidizing air, the ignition by burners is ceased.
SOme of refuse 28 undergo pyrolysis and generate pyrolysis gases by the combustion heat oE the refuse 28 inside the fluidized bed 40. The pyrolysis gases, containing ~l2, CO and hydrocarbonaceous gases, are burnt with the secondary air which is blown in as shown by the arror 52a from the nozzles 52 at the combustion chamber 20 on the upper part inside the incinerator body 10.
The primary air blown out of the air diffuser tubes 24 and the secondary air blown out oE nozzles 52 are adjusted to the ratio from 2:3 through 3:3, or preEerably at the ratio of 1:1, and further, the total air ratio to the theoretical air volume for combusting the reEuse is adjusted in the range from 1.4 to 1.7 times.
- ~ :
~2~1~3~
The exhanst gas produced through the combustlon of refuse 2a and pyrolysis gas are exhausted out of the incinerator from the exhalls-t port 19. Containing a large quantity of heat, this exhaus-t has ls utilized to preheat the water oX the boilers etc. Since smuts are contalned in the exhaust has, 1t is removed by an electrostatic precipitator after used as the heat source.
The refuse 28 and the fluidizing medium 32 have to be fed timely to the fluidized bed 40 where the refuse is burnt and decomposed as mentioned above.
On the other hand, the fluidizing medium 32 promotes the agitation and dispersion of the refuse, and it also for1ns a moving bed descending through the fluidized bed 40.
Thereafter, the fluidizing medium 32 flows down onto the bottom wall 18 along with the combustion residue 42 within the refuse 28 from the gaps among the air diffuser tubes 24, and forms a filling bed below the air diffuser tubes 24 with the fluidizing tnedium 32 and the combustion reisdue 42 contained therin, and the said filling bed helps adjust the thickness of fluidized bed 40 which is built up above the air diffuser tubes 24. As the combustion residue increases, filling bed becomes big, so it is discharged by the screw 3~
conveyor 46 installed in a downward position. I'he screw conveyor 46 transEers the fluidizing medium 32 and the combustion residue 42 to the separator 44.
In the separator 44, the combustion residue 42 is separated from the fluidizing medium 32 by the sieve 48, then the combustion residue 42 is discharged Erom the exhaust port 45, wl~ile the fluidizing medium 42 is fed again to the fluidized bed 40 through the circulation line 50.
If the refuse 28 is usually burnt in the fluidized bed 40 as mentioned above, the temperature of that fluidized bed may reach a level from 700 to 800C. However, in this temperature range, the combustion of refuse 28 occurs so quickly that the said refuse would be instantaneously dried, ignited, burnt, and decomposed. For this reason, if a large quantity of refuse 28 is thrown at a time into the fluidized bed 40, a large quantity of pyrolysis gases and smuts will be generated. As a consequence, all the pyrolysis gases cannot be burnt with the secondary air supplied into the combustion chamber 20, and the smuts within exhaust gas coming out of the incinerator body 10 cannot get the dust completely removed by the electric precipitator.
In this embodiment, therefore, the temperature of the fluidized bed 40 is detected by the temperature sensor 58, and the control unit 62 functions to regulate the control valve 66 and control the water volume sprayed from the spray 54 so that the temperature oE the fluidized bed 40 is in the range from 520 to 650C.
Since the fluidized bed 40 is maintained in the temperature range from 520 to 650~C by the water spray, the reEuse 28 is burnt and decomposed stably. Therefore, even if the thrown volume of refuse 28 to the fluidized bed 40 fluctuates, or a large amount of refuse 28 is thrown at a time, a stable burning and decomposing occur so that pyrolysis g-as and dust are not generated in a large quantity.
Further, the total air ratio required for burning the reuse 28 is 1.7 to 2.0 conventionally to the theoretical air volume, which can however be lowered to 1.4 to 1.7 according to this invention, and the temperature inside the free-board section (combustion chamber) can also be maintained at a high level.
Fig. 2 shows the details of the water spray 54. The water spray 54 consists oE double tubes 70, which are inserted at a downward angle from the insertion hole 72 which is provided on the upper section wall 16a of the incinerator body 10 and whose tip nozzle section 71 is positioned on the upper side o the fluidized bed 40.
~286~3~
The insertion hole 72 is a cone-shaped hole which has smaller open end at the outer surface of the wall 16a and the said insertion hole 72 allows the nozzle 70a on the tip of the double tube 70 to move to the right and leEt or up and down. The basement 7~ of the double tube 70 is supported via a universal joint 78, on the supporting body 76 which is installed on the upper sec tion wall 16a. What's morel this universal joint 78 is interlocked with the linkage 801 and the nozzle 70a of the double tube 70 is moved up and down or right and left, via the said universal joint 78, by which the movement of the said linkage 80. The double tube consists of the inner tube 82 for water and the outer tube 84 for the cooling air. The basement of the inner tube 82 is connectedl via a flexible tube 86, to the water supplying line 56. The basement of outer tube 84 is connected, via another flexible tube 88, to the cooling air supplying source (not shown in the figure).
These flexible tubes 86 and 88 supply water and cooling air to the double tube 70 moving with the basement of double tube 70.
In the explanation of the aforecited embodiment, water is sprayed directly on the fluidized bed 40 to keep the fluidized bed temperature in a range from 520 to 650C, but :' .,.
' ~ -~28~t3~
this invention shalL not be limited only by this way of keeping the temperature.
As another means for keeping the ternperature oE the fluidized bed 40 in the range Erom 520 to 650C, .~.t ls ~lso acceptable, as shown by an imaginary line in Fig. 1, by providing a water spray 90 to the hopper 38 of the precipitator 31, in order to spray the water onto the refuse 28 inside the said hopper 38.
In this case too, the volume of the water from the spray go is adjusted so that the fluidized bed temperature by the temperature sensor 58 is in the range from 520 to 650C.
As another way to control the temperature, because the tempe.rature of the fluidizing medium 82 which is separated by a separator 44 and circulated to the fluidized bed 40 through the circulation line 5Q is at a considerably high level, the fluidized bed temperature can be controlled lower than 650 by providing a cooling unit 92 for the fluidizing medium 32 to the circulation line 50 to lower the temperature of the fluidizing medium 32 supplied to the fluidized bed 40.
There is one more way to control the temperature. The fluidized bed temperature can be controlled at 650C by cooling the fluidizing air which passes through the air diffuser tubes 24 and the fluidizing air tube 26.
3~9 It is also acceptable to combine these means together for controllin~ the Eluidized bed temperature.
Fig. 3 is the graph showing the relation between the temperature of the fluidized bed and the combustion speed where the combustion spee~ ratio represents the ratio oE the minimum time needed Eor burning and decomposing in a ideal condition and the time spent actually, after the refuse is thrown.
AS can be seen from this figure too, when the fluidized bed temperature is in the range from 700 to 800C, its combustion speed ratio was 0.7 to 1.0 in the past, but this speed ratio can be maintained in the range Erom 0.~ to 0.6 by keeping the temperature in the range "A", from 520 to 650C
as in this invention, and it is possible to lower the speed ratio to about 60~ of the conventional combustion speed ratio.
By burning the refuse slowly on the fluidized bed in this way, the refuse can be prevented from being burnt instantaneously, and the voluminous generation of pyrolysis gas and smuts can be suppressed.
In this case, if the temperature of the fluidized bed is lower than 520C, it i9 not favorable because the combustion of the refuse in fluidized bed becomes unstable (difficult), :
~28C~3~
and if it is higher than 650 ~c, it is not favorable either because the speed becomes hlgher and the volume to be decomposed and the volume of smuts generated are instantaneously increased even if the change of the volume and qual~ty of the refuse are relatively small.
Fig. 4 and Fig. 6 show the chrcnological changes of f.luiclized bed temperature and combustion gas temperature in the case of this invention and the conventional example.
For Fig.4 and Fig. 6, the same fluidized bed incinerator is used and the temperature is measured for 6 or hours, feecling the municipal wastes at 2.5 tons/h and Fig.
~ shows the result where the secondary combustion at the free board has been fully carried out in addition to the present invention.
As shown in Fi-g. 6, since the temperature inside the fluidized bed is not controlled in the conventional method, it can be seen that the fluidized bed temperature reaches a level higher than 650 oc, and its temperature gradually increases because inside the combustion chamber, lower section temperature 'b' is around ~50~c, upper section tempera-ture 'c' i5 around 850'c, and the temperature 'd' of combusted gas leaving the inclllarator and entering into the gas cooling unit is around 950'c.
This means that the pyrolysis gas generated by the . . .
~L28~3~L~
thermal decomposition in the fluidized bed is burnt until it enters the gas cooling unit, and that the temperature inside the combustion chamber is lowt around 800C~ and that the pyrolysis gas has not been perEectly burnt.
In contrast, in this invention as shown in Fig. ~, it can be understood that when water is sprayed onto the fluidized bed and its fluidized bed temperature "ao" is kept at 600C _ 15C, the lower section temperature "bo" of incinerator, the upper section temperature "co" as well as the temperature "do" at the entrance Q~ the gas cooling unit are all maintained at a high level oE around 900C. This explains the fact that the combustible gas which is generated is completely burnt by the secondary air inside the combustion chamber.
Fig. 5 and Fig. 7 are graphs showing the smut concentration of exhaust gas ~rom the stack, after the exhaust gas passes through the cooling unit and dust is removed by the electric precipitator, which is then measured chronologically by a Ringelman smoke density indicator.
In case oE the conventional example, the smoke with the Ringelman smoke indicator value o~ more than about 0.5, which is the critical point for vision, is discharged disorderly as : ~ .
.:
~.
~ 8~3~ ~
shown in Fig. 7, but in this invention little smoke with an indi-cated value of more than 0.5 is emitted, as shown in Fig. 5.
When controlling the -temperature of the fluidized bed, its temperature can be controlled to the desired range even by spraying water at a constant rate to the volume o the refuse without detecting the temperature.
It will be appreciated that this invention will develop following excellent effects. (1) Keeping the temperature of the fluidized bed in the range from 520 to 650C, the refuse can be slowly burnt and stable combustion can be carried out without being influenced by the change of the volume or quality of the refuse. (2) Since the refuse is burnt and decomposed slowly, pyrolysis gas or smuts does not come out in a large amount. (3) Because the air ratio for combustion can be reduced, the combus-tion chamber temperature inside incinerator can be high and the secondary combustion of pyrolysis gas can be carried out favourably.
,-
Claims (17)
1. A method of stable combustion of refuse in a fluidized bed incinerator, comprising the steps of: (a) forming a fluidized bed in the incinerator by fluidizing said refuse to be incinerated and an incombustible fluidizing medium as said refuse and the fluidizing medium are supplied to the fluidizing bed along with primary air, the primary air being blown into the fluidized bed by air diffuser tubes provided in the lower part of the incinerator, the air diffuser tubes extending generally parallel to each other; (b) burning and decomposing said refuse in said fluidized bed, the decomposition of said refuse resulting in the generation of pyrolysis gas; (c) combusting said pyrolysis gas with secondary air supplied to an upper section of said incinerator; (d) forming a downward flow of the combination of the combustion residue of said refuse and the fluidizing medium inside the fluidized bed through the air diffuser tubes, and discharging said combination from the bottom of the incinerator; (e) separating the fluidizing medium from the combustion residue in a sieve; (f) circulating the fluidizing medium separated in step (e) back to said fluidized bed; and (g) maintaining the fluidized bed temperature in the range from 520° to 650°C. by spraying water onto the fluidized bed.
2. The method of claim 1, wherein said fluidizing medium consists of sand.
3. The method of claim 1, wherein step (g) is performed by sensing the fluidized bed temperature and spraying water onto said fluidized bed.
4. The method of claim 1, wherein the total volume of the primary air and secondary air is from 1.4 to 1.7 times the theoretical volume of air required to combust said refuse.
5. The method of claim 4, wherein the ratio of the volume of the primary air to that of the secondary air is approximately 1:1
6. A method performing stable combustion of refuse in a fluidized bed incinerator, comprising the steps of: (a) forming a fluidized bed in said incinerator by fluidizing said refuse and a fluidizing medium with primary air; (b) burning and decomposing said refuse in said fluidized bed;
and (c) controlling said fluidized bed temperature so as to maintain said temperature in the range from 520° to 630° C.
by applying water onto said fluidized bed.
and (c) controlling said fluidized bed temperature so as to maintain said temperature in the range from 520° to 630° C.
by applying water onto said fluidized bed.
7. The method of claim 6, wherein step (c) is performed by spraying said water onto said fluidized bed.
8. The method of claim 6, wherein step (c) is performed by mixing said water with said refuse and introducing refuse having said water mixed therein into said fluidized bed.
9. The method of claim 6, including the steps of separating the combustion residue of the refuse from the fluidizing medium in the lower part of said fluidized bed, and circulating the separated fluidizing medium back to said fluidizing bed, and wherein step (c) is performed by cooling the fluidizing medium circulated back to said fluidized bed.
10. A fluidized bed incinerator having a fluidized bed for combusting refuse, comprising: an incinerator body; a plurality of parallel air diffuser tubas in a lower section of said body, each of said tubes having a plurality of openings on opposite sides thereof for supplying primary combustion air to said fluidized bed; means for supplying said primary combustion air to said tubes; means for introducing refuse onto said fluidized bed above said tubes, the thermal decomposition of said refuse inside fluidized bed resulting in the generation of pyrolysis gas; means below said tubes for removing combustion residue and a fluidizing medium from said lower section of said incinerator body;
means for separating said combustion residue from said fluidizing medium; means for circulating the separated fluidizing medium back to said fluidized bed; and means for spraying water onto the upper face of said fluidized bed to control said fluidized bed temperature, said water spraying means having at least one nozzle which has changeable orientation and which produces an essentially uniform spray of water over said bed.
means for separating said combustion residue from said fluidizing medium; means for circulating the separated fluidizing medium back to said fluidized bed; and means for spraying water onto the upper face of said fluidized bed to control said fluidized bed temperature, said water spraying means having at least one nozzle which has changeable orientation and which produces an essentially uniform spray of water over said bed.
11. The fluidized bed incinerator of claim 10, including a temperature detector for detecting the fluidized bed temperature, and wherein said water spraying means is responsive to said temperature detector for controlling the volume of water sprayed onto said fluidized bed in accordance with the value of the detected temperature.
12. The fluidized bed incinerator of claim 10, wherein said water spraying means includes a double tube having an inner tube for spraying said water and an outer tube for air cooling said inner tube.
13. The fluidized bed incinerator of claim 12, wherein said double tube includes a water spraying tip and extends through said incinerator body, and said water spraying means includes a drive mechanism connected to said double tube for moving said spraying tip to spray water uniformly over said fluidized bed.
14. A fluidized bed incinerator having a fluidized bed for combusting refuse, comprising: an incinerator body having an upper section and a lower section; means for forming a fluidized bed in said lower section of said incinerator body using said refuse, a fluidizing medium and primary combustion air; means for feeding said refuse to said fluidized bed; and means for spraying water including a water nozzle shiftably mounted on said incinerator body and means connected to said water nozzle for shifting said nozzle, in order to spray water essentially uniformly over said fluidized bed and to maintain the fluidized bed temperature within a preselected temperature range irrespective of the rate at which said refuse is fed to said fluidized bed by said refuse feeding means, whereby to achieve stable combustion of said refuse.
15. The fluidized bed incinerator of claim 14, wherein said water spraying means includes means for detecting the temperature of said fluidized bed and means responsive to the value of the temperature detected by said detecting means for controlling the volume of water to be sprayed over said fluidized bed by said water spraying means.
16. The fluidized bed incinerator of claim 14, wherein said water spraying means includes a double tube having an inner tube adapted to be coupled with a source of water for spraying water, and an outer air tube containing air for cooling said inner tube.
17. The fluidized bed incinerator of claim 14, including:
means for separating combustion residue of said refuse from the fluidizing medium derived from a lower portion of said fluidized bed; and means for circulating the separated fluidizing medium back to said fluidized bed, and wherein said temperature maintaining means includes means for cooling the separated fluidizing medium which is fed back to said fluidized bed.
means for separating combustion residue of said refuse from the fluidizing medium derived from a lower portion of said fluidized bed; and means for circulating the separated fluidizing medium back to said fluidized bed, and wherein said temperature maintaining means includes means for cooling the separated fluidizing medium which is fed back to said fluidized bed.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP61008945A JPH0799257B2 (en) | 1986-01-21 | 1986-01-21 | Stable combustion method of fluidized bed furnace |
| JP8945/1986 | 1986-01-21 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1280319C true CA1280319C (en) | 1991-02-19 |
Family
ID=11706805
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000527710A Expired - Fee Related CA1280319C (en) | 1986-01-21 | 1987-01-20 | Method of stable combustion for a fluidized bed incinerator |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US4757771A (en) |
| EP (1) | EP0235531B1 (en) |
| JP (1) | JPH0799257B2 (en) |
| CA (1) | CA1280319C (en) |
| DE (1) | DE3760188D1 (en) |
Families Citing this family (22)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0656256B2 (en) * | 1989-01-31 | 1994-07-27 | 繁 齋藤 | Incinerator |
| US4979448A (en) * | 1990-01-08 | 1990-12-25 | International Paper Company | Apparatus and method for recovery of constituents and heat from fluidized bed combustion |
| US5012750A (en) * | 1990-01-08 | 1991-05-07 | International Paper Company | Apparatus for recovery of constituents and heat from fluidized bed combustion |
| CA2036747C (en) * | 1990-02-22 | 1995-10-31 | Yasuaki Harada | Fluidized bed combustion method for burning wastes |
| US4974531A (en) * | 1990-05-22 | 1990-12-04 | Donlee Technologies, Inc. | Method and apparatus for incinerating hazardous waste |
| US5101742A (en) * | 1990-06-22 | 1992-04-07 | Energy Products Of Idaho | Fluidized bed combustion |
| US5060584A (en) * | 1990-06-22 | 1991-10-29 | Energy Products Of Idaho | Fluidized bed combustion |
| FR2682459B1 (en) * | 1991-10-09 | 1997-11-21 | Stein Industrie | METHOD AND DEVICES FOR REDUCING THE NITROGEN PROTOXIDE CONTENT OF THE GASES OF AN OXIDIZING COMBUSTION OF A FLUIDIZED BED REACTOR. |
| TW235335B (en) * | 1991-11-05 | 1994-12-01 | Mitsubishi Heavy Ind Ltd | |
| US6119607A (en) * | 1997-05-09 | 2000-09-19 | Corporation De L'ecole Polytechnique | Granular bed process for thermally treating solid waste in a flame |
| FI110026B (en) | 1997-09-12 | 2002-11-15 | Foster Wheeler Energia Oy | Fluidized bed boiler grate structure |
| US6808390B1 (en) * | 1999-05-04 | 2004-10-26 | Commonwealth Scientific And Industrial Research Organization | Process for carbonizing wood residues and producing activated carbon |
| SE0103822D0 (en) * | 2001-11-16 | 2001-11-16 | Ecomb Ab | Combustion optimization |
| KR20040078985A (en) * | 2003-03-05 | 2004-09-14 | (주) 우리에너텍 | Gas generator of waste tire and waste compose resin pyrolysis and terminal ash treatment system |
| EP1946006B1 (en) * | 2005-09-27 | 2009-08-19 | Dall Energy Holding ApS | Method and system for heating of water based on hot gases |
| EP1921380A1 (en) * | 2006-11-10 | 2008-05-14 | Lentjes GmbH | Method and Apparatus for Reducing NOx in Exhaust Gases of Fluidized Bed Incinerators |
| WO2009060885A1 (en) * | 2007-11-07 | 2009-05-14 | Metawater Co., Ltd. | Fluidized-bed incinerator and method of fluidized-bed incineration of sludge with the same |
| US9371487B2 (en) * | 2007-12-12 | 2016-06-21 | Outotec Oyj | Process and plant for producing char and fuel gas |
| AU2009242253B2 (en) * | 2008-04-29 | 2013-08-01 | Clean Fuels B.V. | Method of converting a raw material stream into a product stream using a fluidized bed and apparatus for use in said method |
| US20110272389A1 (en) * | 2010-05-10 | 2011-11-10 | Tyl Thomas W | Heating and fluidization system for air fluidized sand beds |
| JP2020148437A (en) * | 2019-03-15 | 2020-09-17 | 荏原環境プラント株式会社 | Incineration ash discharge device and incineration ash discharge method |
| CN112856440A (en) * | 2021-01-12 | 2021-05-28 | 查昀 | Prevent high-efficient waste incinerator of type of going out |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1448898A (en) * | 1965-06-16 | 1966-08-12 | Charbonnages De France | Improved process for the thermal treatment of partially combustible products in the form of or packaged in the form of sludge and device implementing said process |
| US3397657A (en) * | 1965-11-01 | 1968-08-20 | Tada Mitsuru | Apparatus for continuously burning wastes |
| GB1561237A (en) * | 1976-09-22 | 1980-02-13 | Ahlstroem Oy | Method of treating materials in a fluidized bed reactor |
| JPS54141071A (en) * | 1978-04-24 | 1979-11-01 | Babcock Hitachi Kk | Moving layer incinerator control |
| DK310979A (en) * | 1978-08-04 | 1980-02-05 | Energy Equip | PROCEDURE FOR CONTROLING THE OPERATION OF A FLUIDIZED BOTTLE LIFTING PLANT AND USING MEASURES IN THE IMPLEMENTATION OF THE PROCEDURE |
| US4291635A (en) * | 1979-08-20 | 1981-09-29 | The Quaker Oats Company | Apparatus for feeding fluidized bed incinerator, and method of autogenic operation of same |
| DE3003245A1 (en) * | 1980-01-30 | 1981-11-12 | Deutsche Babcock Ag, 4200 Oberhausen | METHOD AND DEVICE FOR BURNING SUBSTANCES WITH HEAVY BURNING INGREDIENTS |
| US4397267A (en) * | 1981-08-03 | 1983-08-09 | Conco Inc. | Technique and apparatus for solids circulation control in the solids circulating boiler |
| FR2526182B1 (en) * | 1982-04-28 | 1985-11-29 | Creusot Loire | METHOD AND DEVICE FOR CONTROLLING THE TEMPERATURE OF A FLUIDIZED BED |
| AU563279B2 (en) * | 1982-06-22 | 1987-07-02 | Lawrence Waldemar Ihnativ | Processing waste materials |
| US4543894A (en) * | 1983-05-17 | 1985-10-01 | Union Oil Company Of California | Process for staged combustion of retorted oil shale |
| DE3347056A1 (en) * | 1983-12-24 | 1985-07-04 | Johann Dipl.-Ing. 4005 Meerbusch Roos | METHOD FOR PROCESSING HOUSEHOLE AND / OR HOUSEHOLD SIMILAR COMMERCIAL MATERIAL FOR PRODUCING A FUEL, AND COMBUSTION OVEN |
-
1986
- 1986-01-21 JP JP61008945A patent/JPH0799257B2/en not_active Expired - Lifetime
-
1987
- 1987-01-20 CA CA000527710A patent/CA1280319C/en not_active Expired - Fee Related
- 1987-01-20 EP EP87100736A patent/EP0235531B1/en not_active Expired
- 1987-01-20 US US07/005,177 patent/US4757771A/en not_active Expired - Fee Related
- 1987-01-20 DE DE8787100736T patent/DE3760188D1/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| EP0235531A1 (en) | 1987-09-09 |
| JPS62169921A (en) | 1987-07-27 |
| DE3760188D1 (en) | 1989-06-29 |
| JPH0799257B2 (en) | 1995-10-25 |
| US4757771A (en) | 1988-07-19 |
| EP0235531B1 (en) | 1989-05-24 |
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Legal Events
| Date | Code | Title | Description |
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| MKLA | Lapsed |