CN111878801A - Fly ash circulating device and circulating fluidized bed boiler comprising same - Google Patents
Fly ash circulating device and circulating fluidized bed boiler comprising same Download PDFInfo
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- CN111878801A CN111878801A CN202010898018.3A CN202010898018A CN111878801A CN 111878801 A CN111878801 A CN 111878801A CN 202010898018 A CN202010898018 A CN 202010898018A CN 111878801 A CN111878801 A CN 111878801A
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- 239000010881 fly ash Substances 0.000 title claims abstract description 118
- 239000002956 ash Substances 0.000 claims abstract description 54
- 239000003245 coal Substances 0.000 claims abstract description 51
- 239000000428 dust Substances 0.000 claims abstract description 42
- 238000004064 recycling Methods 0.000 claims description 9
- 230000001105 regulatory effect Effects 0.000 claims description 6
- 238000000034 method Methods 0.000 claims description 4
- 238000007599 discharging Methods 0.000 claims description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 abstract description 22
- 229910052799 carbon Inorganic materials 0.000 abstract description 22
- 230000008901 benefit Effects 0.000 abstract description 12
- 230000007613 environmental effect Effects 0.000 abstract description 5
- 239000003570 air Substances 0.000 description 29
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 10
- 235000011114 ammonium hydroxide Nutrition 0.000 description 10
- 239000004744 fabric Substances 0.000 description 9
- 238000012360 testing method Methods 0.000 description 9
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 8
- 239000000463 material Substances 0.000 description 8
- 238000012986 modification Methods 0.000 description 8
- 229910052760 oxygen Inorganic materials 0.000 description 8
- 239000001301 oxygen Substances 0.000 description 8
- 238000002485 combustion reaction Methods 0.000 description 7
- 230000004048 modification Effects 0.000 description 7
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 6
- 239000002245 particle Substances 0.000 description 6
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 239000003546 flue gas Substances 0.000 description 5
- 238000012546 transfer Methods 0.000 description 5
- 238000005516 engineering process Methods 0.000 description 4
- 230000009466 transformation Effects 0.000 description 4
- 229910021529 ammonia Inorganic materials 0.000 description 3
- 239000000446 fuel Substances 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- 239000012716 precipitator Substances 0.000 description 3
- 238000013461 design Methods 0.000 description 2
- 239000012717 electrostatic precipitator Substances 0.000 description 2
- 238000004134 energy conservation Methods 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 239000007921 spray Substances 0.000 description 2
- 239000012080 ambient air Substances 0.000 description 1
- RHZUVFJBSILHOK-UHFFFAOYSA-N anthracen-1-ylmethanolate Chemical compound C1=CC=C2C=C3C(C[O-])=CC=CC3=CC2=C1 RHZUVFJBSILHOK-UHFFFAOYSA-N 0.000 description 1
- 239000003830 anthracite Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000000567 combustion gas Substances 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 238000003306 harvesting Methods 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000002407 reforming Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 238000004088 simulation Methods 0.000 description 1
- 239000000779 smoke Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
Images
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN A CARRIER GAS OR AIR
- F23C10/00—Fluidised bed combustion apparatus
- F23C10/02—Fluidised bed combustion apparatus with means specially adapted for achieving or promoting a circulating movement of particles within the bed or for a recirculation of particles entrained from the bed
- F23C10/04—Fluidised bed combustion apparatus with means specially adapted for achieving or promoting a circulating movement of particles within the bed or for a recirculation of particles entrained from the bed the particles being circulated to a section, e.g. a heat-exchange section or a return duct, at least partially shielded from the combustion zone, before being reintroduced into the combustion zone
- F23C10/08—Fluidised bed combustion apparatus with means specially adapted for achieving or promoting a circulating movement of particles within the bed or for a recirculation of particles entrained from the bed the particles being circulated to a section, e.g. a heat-exchange section or a return duct, at least partially shielded from the combustion zone, before being reintroduced into the combustion zone characterised by the arrangement of separation apparatus, e.g. cyclones, for separating particles from the flue gases
- F23C10/10—Fluidised bed combustion apparatus with means specially adapted for achieving or promoting a circulating movement of particles within the bed or for a recirculation of particles entrained from the bed the particles being circulated to a section, e.g. a heat-exchange section or a return duct, at least partially shielded from the combustion zone, before being reintroduced into the combustion zone characterised by the arrangement of separation apparatus, e.g. cyclones, for separating particles from the flue gases the separation apparatus being located outside the combustion chamber
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN A CARRIER GAS OR AIR
- F23C10/00—Fluidised bed combustion apparatus
- F23C10/18—Details; Accessories
- F23C10/24—Devices for removal of material from the bed
- F23C10/26—Devices for removal of material from the bed combined with devices for partial reintroduction of material into the bed, e.g. after separation of agglomerated parts
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES
- F23J15/00—Arrangements of devices for treating smoke or fumes
- F23J15/02—Arrangements of devices for treating smoke or fumes of purifiers, e.g. for removing noxious material
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES
- F23J15/00—Arrangements of devices for treating smoke or fumes
- F23J15/02—Arrangements of devices for treating smoke or fumes of purifiers, e.g. for removing noxious material
- F23J15/022—Arrangements of devices for treating smoke or fumes of purifiers, e.g. for removing noxious material for removing solid particulate material from the gasflow
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Fluidized-Bed Combustion And Resonant Combustion (AREA)
Abstract
The invention provides a fly ash circulating device and a circulating fluidized bed boiler comprising the same, wherein the fly ash circulating device comprises: the device comprises an intermediate ash bin, a feeder and a pneumatic conveying device; the middle ash bin is used for containing fly ash to be circulated, an inlet of the middle ash bin is connected with the dust remover, and an outlet of the middle ash bin is connected with a coal supply port of the hearth through a fly ash circulation pipeline; the feeding machine is arranged on the fly ash circulating pipeline and is used for providing fly ash from the intermediate ash bin to the hearth; the pneumatic conveying device is arranged on the fly ash circulating pipeline and is used for conveying the fly ash provided by the feeding machine to the hearth. The invention can reduce the carbon content of the fly ash and improve the economic benefit and the environmental protection benefit.
Description
Technical Field
The invention belongs to the technical field of boilers, and particularly relates to a fly ash circulating device and a circulating fluidized bed boiler comprising the same.
Background
The Circulating Fluidized Bed (CFB) boiler has the advantages of wide fuel adaptability, good environmental protection and the like, and is developed rapidly in China. After the fire coal is burned in the hearth, the generated high-temperature flue gas, ash and carbon particles enter a cyclone separator for separation, wherein the larger particles are captured by the separator and enter a vertical pipe and a return feeder to return to the hearth, and the small-particle fly ash enters a dust remover from a central cylinder of the separator and then is sent to an ash storehouse from the dust remover.
At present, most fluidized bed boilers have the conditions that the deviation between the actually operated coal quality and the initially designed coal quality is large and the proportion of mixed combustion gas is large, the ash content in the actually operated coal quality cannot reach the ash content of the designed coal quality, so that the quantity of circulating ash in the boiler is insufficient, the circulating multiplying power of the ash cannot reach the designed value (the designed value is generally 20-30), the operation essence of the fluidized bed boilers is mass transfer and heat transfer, the mass transfer process cannot be realized due to the quantity of the circulating ash, the heat transfer of a material layer cannot be carried out during the operation of the boiler, and the following hazards can be caused to the operation of the boiler: the bed temperature of a hearth is over high, the outlet temperature of the hearth is low, the temperature difference between the upper part and the lower part of the hearth is large, the bed temperature is over-temperature, and the load capacity of a boiler is poor; the carbon content of the fly ash is always high, the carbon content of the fly ash determines the mechanical incomplete combustion heat loss of the boiler and is an important part of the combustion efficiency of the boiler, the carbon content of the fly ash is generally between 5 and 20 percent, the carbon content of a part of fluidized bed boilers is even more than 30 percent, and the integral operation economy is poor; and thirdly, because the outlet temperature of the SNCR is low and cannot reach the SNCR window temperature (850-1100 ℃ in low load, the denitration efficiency is low, and the system cannot be put into operation basically. Under the large background requirements of economic benefit and energy conservation and emission reduction, the boiler is urgently improved.
Aiming at the problems, through long-term engineering practice, a technology of re-feeding the fly ash into a hearth for secondary combustion, namely a fly ash back combustion technology, is provided in the industry to reduce the carbon content of the fly ash and integrally improve the economic effect of boiler operation.
In the prior art, fly ash is generally sent into a hearth through a secondary air pipe. However, practical application of a plurality of projects finds that the technology of feeding the fly ash into a hearth through a secondary air pipe and performing back combustion is limited by a plurality of factors, and the effect is not ideal. Firstly, the quantity of the fed-in points is not enough, and the quantity of the ash after the back combustion is far less than the quantity of the ash required by the establishment of the circulation; secondly, the feeding point position can not really enable the reburning fly ash to be well fused into the mass transfer atmosphere in the furnace; the third point is that the feeding point is connected with the secondary air pipe, which seriously influences the regulation and control function of the secondary air quantity.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a fly ash circulating device which can effectively reduce the carbon content of fly ash and improve the operation condition of a boiler.
In order to achieve the above object, in one aspect, the present invention provides a fly ash circulation device, including: the device comprises an intermediate ash bin, a feeder and a pneumatic conveying device;
the middle ash bin is used for containing fly ash to be circulated, an inlet of the middle ash bin is connected with the dust remover, and an outlet of the middle ash bin is connected with a coal supply port of the hearth through a fly ash circulation pipeline;
the feeding machine is arranged on the fly ash circulating pipeline and is used for providing fly ash from the intermediate ash bin to the hearth;
the pneumatic conveying device is arranged on the fly ash circulating pipeline and is used for conveying the fly ash provided by the feeding machine to the hearth.
In some embodiments, the feeder is a variable frequency feeder.
In some embodiments, the pneumatic conveying device is a roots blower.
In some embodiments, a flow regulating valve is arranged on the fly ash circulating pipeline, and preferably, the flow regulating valve is a gate valve.
In some embodiments, the furnace includes a plurality of coal feed ports, and the fly ash circulation duct is divided into a plurality of branch ducts at an end adjacent to the furnace, each branch duct being connected to one of the coal feed ports.
In some embodiments, a top dust collector is disposed at the top of the intermediate ash bin, and is used for discharging air in the fly ash from the dust collector and collecting the fly ash in the air into the intermediate ash bin.
In some embodiments, the top hopper is connected to an air reservoir for containing compressed air for removing fly ash attached to the filter bags in the top hopper.
In some embodiments, a level gauge is disposed at the top of the intermediate ash bin.
In another aspect, the invention also provides a circulating fluidized bed boiler comprising the fly ash circulating device.
In another aspect, the present invention provides a method for improving the efficiency of a circulating fluidized bed boiler, which comprises circulating fly ash collected by a dust collector into a furnace chamber through a coal supply port.
Compared with the prior art, the fly ash circulating device has the following beneficial effects:
1. under the condition that the fixed carbon of the coal as fired is relatively stable, the carbon content of the fly ash is reduced;
2. the economic benefit and the environmental protection benefit are obvious. The coal consumption and the power consumption are obviously reduced, the flue gas index is better controlled, and the amount of the externally transported ash is reduced;
3. data comparison is carried out, the operation condition of the modified boiler is improved, the bed temperature is reduced, and the adjustment space is larger;
4. the outlet temperature of the hearth is improved, the SNCR operation is met, and the low-load NOx emission is ensured to reach the standard. Meanwhile, the consumption of ammonia water can be reduced.
Drawings
The drawings are only for purposes of illustrating and explaining the present invention and are not to be construed as limiting the scope of the present invention. Wherein:
FIG. 1 is a schematic view of a fly ash recycling apparatus according to an embodiment of the present invention;
FIG. 2 is a graph showing the relationship between the volatile matter of coal before and after modification and the carbon content of fly ash in the embodiment of the present invention;
FIG. 3 is a relation between the feeder frequency and the main steam flow in the embodiment of the invention;
FIG. 4 is a relation between the frequency of the feeding machine and the circulating temperature of the material in the embodiment of the invention;
FIG. 5 is a relation between the feeder frequency and the temperature difference of the hearth outlet in the embodiment of the invention.
Detailed Description
In order to make the aforementioned features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below, but the present invention is not limited thereto.
In the description of the present invention, reference to "one embodiment" means that a particular feature, structure, or parameter, step, or the like described in the embodiment is included in at least one embodiment according to the present invention. Thus, appearances of the phrases such as "in one embodiment," "in one embodiment," and the like in this specification are not necessarily all referring to the same embodiment, nor are other phrases such as "in another embodiment," "in a different embodiment," and the like. Those of skill in the art will understand that the particular features, structures or parameters, steps, etc., disclosed in one or more embodiments of the present description may be combined in any suitable manner.
In the description of the present invention, it is to be noted that, unless otherwise explicitly specified or limited, the terms "connected" and "connected" are to be interpreted broadly, e.g., as being fixed or detachable or integrally connected; may be directly connected or indirectly connected through an intermediate. The specific meaning of the above terms in the present invention can be understood as appropriate by those of ordinary skill in the art.
Aiming at the problems in the prior art, the inventor finds that the special effect is achieved after the furnace inlet point of the fly ash circulating device is adjusted by improving a plurality of engineering practice technologies and combining numerical simulation of a flow field in the furnace. After the fly ash circulating device is adopted by three 130t/h CFB boilers of a certain power plant, the fly ash circulating pipeline is connected to the coal feeding port, the return ash can be well fed into the boiler, the carbon content of the fly ash is obviously reduced, the steam yield per ton of coal can also be increased, the bed temperature of the boiler is reduced, the operation adjustment ratio of the boiler is better controlled, and the operation adjustment space is larger; the fuel can be saved to a certain extent, the power consumption of the fan can be reduced, and the economic benefit and the environmental protection benefit are obvious.
In the embodiment of the invention, the fly ash circulating device sends a part of fine ash captured by the dust collector back to the hearth through the Roots blower, the feeder, the ash conveying pipeline and other conveying equipment, firstly, unburned carbon particles in the fly ash are continuously combusted, the carbon content of the fly ash is reduced from 16.13% to 12.18%, and the furnace efficiency is improved; meanwhile, the boiler is helped to establish good ash circulation, the heat exchange in the boiler is enhanced, the temperature difference between the upper part and the lower part of a hearth is reduced, and the load capacity of the boiler is improved; and thirdly, the temperature of the hearth outlet is increased, and the reaction efficiency of the SNCR system is improved, thereby achieving multiple purposes.
As shown in fig. 1, the circulating fluidized bed boiler of the present invention includes a furnace 1, a separator 2, a heat exchanger 3, a dust collector 4 and a fly ash circulating device 5, wherein a coal feed port 101 is provided at the lower end of the furnace 1, one or more coal feeders 102 convey pulverized coal into the furnace 1 through the coal feed port 101, an outlet of the furnace 1 is connected to the separator 2, a solid particle outlet 201 at the lower end of the separator is connected to a return port 103 of the furnace 1 through a return pipe 202, an exhaust port 203 of the separator 2 is connected to the heat exchanger 3, flue gas enters the dust collector 4 through the heat exchanger 3, the dust collector 4 is used for collecting fly ash in the flue gas, and the fly ash circulating device 5 is connected to the dust collector 4 and is used for conveying fly ash collected by the dust collector 4 back to the furnace 1.
According to one embodiment of the present invention, the dust removing device 4 comprises an electrostatic precipitator 401, a precipitator ash bin 402 is arranged at the lower end of the electrostatic precipitator 401, and fly ash in the precipitator ash bin 402 is transported to a fly ash silo by a precipitator bin pump 403.
The fly ash circulating device 5 comprises an intermediate ash bin 501, fly ash collected in the electrostatic dust collector 401 can be conveyed into the intermediate ash bin 501 by a dust collector bin pump 402, and an outlet at the lower end of the intermediate ash bin 501 is connected with the coal supply port 101 of the hearth 1 through a fly ash circulating pipeline. The fly ash circulating pipeline is provided with a variable frequency feeder 502 and a Roots blower 503, and the Roots blower 503 is positioned at the downstream of the variable frequency feeder 502 and is used for conveying the fly ash provided by the variable frequency feeder 502 to the hearth 1.
As shown in fig. 1, in one embodiment, three coal feeders 102 feed pulverized coal into the furnace 1 through three coal feeding ports 101, respectively, and the fly ash circulation duct is divided into three branch ducts at the end, which are connected to the three coal feeding ports 101, respectively.
In a preferred embodiment, the fly ash circulation duct is provided with a first gate valve 504 near the outlet of the intermediate ash bin for regulating the flow of fly ash to the variable frequency feeder 502. The fly ash circulation pipeline is provided with a second gate valve 505 at a position close to the coal feeding port, and is used for adjusting the flow rate of fly ash entering the hearth 1.
The top of the intermediate ash bin 501 may be provided with a level gauge 506 for detecting the level of fly ash therein. The middle ash bin 501 is also provided with a bin top dust remover 507, mainly for pressure relief and no ash leakage. When the dust collector bin pump 402 delivers dust to the intermediate dust bin 501 by compressed air, the intermediate dust bin 501 discharges excess air through the bin top dust collector 507 and collects fly ash in the air back to the intermediate dust bin 501, and the bin top dust collector 507 includes the dust removal fan 508.
An air storage tank 509 above the middle ash bin 501 can be used for storing compressed air from the air compression station 510 and providing the compressed air to the top ash bin 507, and an electromagnetic pulse valve on a pipeline receives a control signal to enable the blown compressed air to sequentially clean ash of filter bags in the top ash bin 507, so that the resistance of the top ash bin 507 is kept within a set range.
According to one embodiment of the invention, the dust-containing gas enters the box body of the bin top dust collector 507 from the air inlet, and fine dust particles are blocked on the outer wall of the cloth bag due to the blockage of the cloth bag. The purified gas is discharged through the air outlet of the box body on the cloth bag. With the increase of the service time, the dust adsorbed on the surface of the cloth bag increases, the air permeability of the cloth bag is weakened, and the resistance of the bin top dust remover 507 is increased continuously. In order to ensure that the resistance of the bin top dust collector 507 is controlled within a limited range, a pulse controller sends out signals, electromagnetic pulse valves are opened sequentially, compressed air in an air storage tank 509 is sprayed to a corresponding venturi tube (called primary air) through each spray hole of a spray pipe, and ambient air (called secondary air) which is several times of the primary air is induced to enter a cloth bag when high-speed airflow passes through the venturi tube, so that the cloth bag is expanded rapidly, and the cloth bag is contracted rapidly due to the fact that the impact effect of reverse pulse airflow disappears rapidly, and therefore dust on the outer wall of the cloth bag is removed. The falling dust enters the intermediate dust bin 501 to ensure the processing capacity and the dust removal efficiency of the top dust remover 507.
In one embodiment according to the present invention, a 130t/h CFB boiler was subjected to an economic and technical analysis after being equipped with the fly ash recycling device of the present invention. Before transformation, the fly ash is sent into the hearth through a secondary air pipe, and after the transformation, the fly ash is sent into the hearth through a coal feeding port. As a result, it was found that, when the fly ash circulating apparatus of the present invention was used, the temperature at the outlet of the furnace was increased, the temperature at the outlet of the separator was increased, the differential pressure in the furnace was increased, and NO was producedXAnd the denitration efficiency is improved. The fly ash circulating device can improve the material circulating multiplying power and the temperature of the outlet of the hearth, meet the requirement of SNCR operation and ensure low-load NOXThe emission reaches the standard, and the coal consumption can be reduced at the same time.
The boiler is a YG-130/9.8-M type high-temperature and high-pressure steam boiler produced by the Minnan boiler plant, and adopts a single-steam-drum, natural circulation and circulating fluidized bed combustion mode. The design coal type of the boiler is shown in table 1, and the boiler parameters are shown in table 2.
Table 1 design of coal types
TABLE 2 boiler parameters
The actual operation coal quality is greatly different from the designed coal type, and is mainly reflected in low ash content, high fixed carbon content and high heat value of the actual operation coal quality, and the coal quality test is shown in a table 3.
TABLE 3 coal quality test
The test records of the coal as fired and the fly ash before and after the fly ash circulating device of the invention is added are shown in tables 4 and 5.
TABLE 4 coal as fired and fly ash test record table before reforming boiler
TABLE 5 coal as fired and fly ash test record table after boiler transformation
As shown in fig. 2, the comparison of the carbon content of fly ash under the same volatile matter content of coal before and after modification shows that:
the change of the content of volatile matters in the coal has obvious influence on the carbon content of the fly ash. When the volatile matter is low, the burnout degree of the coal is reduced, and the carbon content of the fly ash is increased. When the volatile matter is high, the burnout degree of the coal is improved, and the carbon content of the fly ash is obviously reduced. Comparing the carbon content of the fly ash when the weighted average value of the volatile matters before and after modification is 18%, 19% and 20%, the carbon content of the fly ash after modification is lower than that before modification, and particularly when coal with lower volatile matters is combusted, the carbon content of the fly ash is greatly reduced, and the energy-saving and consumption-reducing effects after modification are obvious.
TABLE 6 typical working condition parameter recording table after reconstruction
| |
1 | 2 | 3 | ||
| Main steam flow | t/ |
110 | 115 | 120 | |
| Temperature of main steam | ℃ | 529 | 535 | 534 | |
| Pressure of main steam | MPa | 9.38 | 9.23 | 9.19 | |
| Total command for regulating coal feeder | ％ | 46 | 57 | 61 | |
| Total coal supply | t/h | 10.23 | 14.7 | 16.6 | |
| Gas quantity | m3/h | 400 | 0 | 0 | |
| Total amount of hot primary air | m3/h | 68721 | 68302 | 68574 | |
| Post-superheater oxygen amount A | ％ | 3.1 | 1.9 | 2.2 | |
| Post-superheater oxygen amount B | ％ | 2.7 | 2.2 | 2.5 | |
| Flue gas NOX | mg/ |
31 | 33 | 32 | |
| Amount of ammonia water | m3/h | 0.39 | 0.47 | 0.67 | |
| Input amount of inlet ammonia gun | Branch stand | 6 | 6 | 6 | |
| Number of ammonia guns put into the outlet | Branch stand | 4 | 4 | 4 | |
| Upper secondary air door | ％ | 100 | 100 | 100 | |
| Opening degree of lower secondary | ％ | 100 | 100 | 100 | |
| Smoke recirculation baffle | ％ | 65 | 61 | 70 | |
| Oxygen content of hot primary air | ％ | 16.6 | 16.19 | 15.49 | |
| Ash bin level | ％ | 1.4 | 1.3 | 60 | |
| Roots blower current | A | 9.2 | 10.1 | 10.2 | |
| Roots blower wind pressure | KPa | 5.9 | 13.4 | 14.3 | |
| Frequency of the feeder | Hz | 40.8 | 45.9 | 46 | |
| Temperature of material bed | ℃ | 954 | 978 | 970 |
As can be seen from Table 6, after the fly ash circulating device of the present invention is adopted, the CFB boiler can continuously operate with high load, the main parameters of the boiler such as steam temperature, steam pressure, bed temperature, etc. are all in normal ranges, NO isXThe emission value is continuously and stably controlled below 45mg/Nm3 to reach NOXUltra-low emission requirements.
TABLE 7 boiler efficiency test Table
As can be seen from Table 7, the boiler efficiency at the load of 122t/h is 91.26%, and the boiler efficiency at the load of 109t/h is 91.63%; the coal consumption of the boiler after being reformed is reduced by about 1.6 percent, under the condition of full load and the same fuel, the coal consumption of the boiler is about 18t/h, the cost of the anthracite is about 600 yuan/ton, the coal-saving cost is 1.6 percent multiplied by 8000 multiplied by 600 multiplied by 18 to 1382400 yuan/year according to 8000 hours of the whole year operation of the boiler, namely, the coal-saving cost is 1382400 yuan per year through the transformation of a fly ash circulating device.
The stable operation of the boiler is ensured when the adjustment test of the fly ash circulating device is carried out, the output forces of the variable frequency feeder are adjusted to be 0Hz, 25Hz, 35Hz and 40Hz respectively, the bed temperature of the dense phase region, the outlet temperature of the hearth and the temperature of the material returning device are observed (the test parameters are shown in the table 8), and when the temperature deviation at each position reaches the minimum, the material concentration in the boiler can be determined to be enough and the fly ash recycling amount is the best.
Table 8 test parameter table of fly ash circulation device
| Feeder frequency (Hz) | 0Hz | 25Hz | 35Hz | 40Hz |
| Main steam flow (t/h) | 86 | 88 | 105 | 110 |
| Coal feeder control gross (%) | 35.5 | 35.1 | 34 | 33 |
| Post-superheater oxygen (%) | 2.3 | 2.3 | 1.8 | 1.7 |
| Level in the Ash storehouse (%) | 0 | 53 | 50 | 20 |
| Roots blower current (A) | 0 | 9.4 | 9.3 | 9.9 |
| Roots blower wind pressure (KPa) | 0 | 12.5 | 12.2 | 15.8 |
| Bed temperature (. degree. C.) | 948 | 945 | 969 | 976 |
| Furnace exit temperature (C)) | 882 | 889 | 935 | 945 |
| Return feeder temperature (. degree. C.) | 872 | 883 | 940 | 943 |
| Temperature difference (DEG C) between material layer and |
66 | 56 | 34 | 31 |
As can be seen from Table 8 and FIGS. 2-4, when the frequency of the fly ash feeder is 0Hz, the boiler load is 86t/h, the boiler oxygen amount is 2.3%, and the temperature difference between the bed temperature and the hearth outlet is 66 ℃; when the frequency of the fly ash feeder is 25Hz, the load of a boiler is 88t/h, the oxygen content of the boiler is 2.3 percent, and the temperature difference between the bed temperature and the outlet of a hearth is 56 ℃; when the frequency of the fly ash feeder is 35Hz, the load of a boiler is 105t/h, the oxygen content of the boiler is 1.8 percent, and the temperature difference between the bed temperature and the outlet of a hearth is 34 ℃; when the frequency of the fly ash feeder is 40Hz, the load of a boiler is 110t/h, the oxygen content of the boiler is 1.7 percent, and the temperature difference between the bed temperature and the outlet of the hearth is 31 ℃. In conclusion, as the frequency of the fly ash feeder is gradually increased, the circulating ash amount in the furnace is gradually increased, the bed temperature in the dense-phase region is stably controlled to fluctuate up and down at 970 ℃, the temperature at the outlet of the furnace chamber is gradually increased, the temperature difference between the bed temperature and the outlet of the furnace chamber is reduced from 66 ℃ to 31 ℃, which shows that the external circulating ash plays a role in uniformly distributing the heat in the furnace, the bed temperature in the dense-phase region is reduced after the high-temperature dense-phase region is mixed with the fly ash, the temperature is increased after the circulating ash concentration in the upper part of the furnace chamber and the material returning device is increased, the.
Fluidized bed boiler is commonControl of NO with excess ammonia injectionXAnd the emission increases the running cost and the operation difficulty of the power plant. The improvement of the fly ash circulating device reduces NO in the furnaceXAnd the generation is realized, the outlet temperature of the hearth is improved, the denitration efficiency of the SNCR is improved, and the combined denitration mode of 'firstly lowering and then removing' saves more denitration cost for the power plant.
Boiler outlet NO before modificationXThe emission is controlled at 70mg/m3About 0.8m of ammonia water under full load3About/h, the cost of each ton of ammonia water is about 815 yuan/ton, 1m3The weight of ammonia water is 1 ton, calculated according to 8000 hours of boiler operation all year round, the cost of inputting ammonia water is 0.8X 8000X 815 ═ 5216000 yuan/year.
NO at outlet of improved boilerXThe emission is controlled at 50mg/m3When the amount of ammonia water is 0.47m3About/h, and the NO at the outlet of the modified boilerXThe emission is controlled at 35mg/m3When the amount of ammonia water is 0.67m3About/h, the cost of ammonia water can be saved by 2151600 yuan/year and 847600 yuan/year respectively.
By modifying the fly ash circulating device of the CFB boiler, NO can be realizedXThe method meets the requirement of ultra-low emission, reduces the consumption of ammonia water, realizes the double harvest of economic benefit and environmental protection benefit, and makes positive contribution to the realization of the aim of energy conservation and emission reduction in China.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A fly ash recycling apparatus, comprising: the device comprises an intermediate ash bin, a feeder and a pneumatic conveying device;
the middle ash bin is used for containing fly ash to be circulated, an inlet of the middle ash bin is connected with the dust remover, and an outlet of the middle ash bin is connected with a coal supply port of the hearth through a fly ash circulation pipeline;
the feeding machine is arranged on the fly ash circulating pipeline and is used for providing fly ash from the intermediate ash bin to the hearth;
the pneumatic conveying device is arranged on the fly ash circulating pipeline and is used for conveying the fly ash provided by the feeding machine to the hearth.
2. A fly ash circulation device according to claim 1, wherein the feeder is a variable frequency feeder.
3. A fly ash circulation device as claimed in claim 1, wherein the pneumatic transport device is a roots blower.
4. A fly ash circulation device according to claim 1, wherein a flow regulating valve is provided on the fly ash circulation pipe, preferably the flow regulating valve is a gate valve.
5. A fly ash recycling device according to claim 1, wherein the furnace comprises a plurality of coal feed ports, and the fly ash recycling duct is divided into a plurality of branch pipes at an end adjacent to the furnace, each branch pipe being connected to one of the coal feed ports.
6. A fly ash recycling apparatus according to claim 1, wherein a top dust collector is provided at the top of the intermediate ash bin for discharging air from the fly ash in the dust collector and collecting the fly ash in the air into the intermediate ash bin.
7. A fly ash recycling device according to claim 6, wherein the top dust collector is connected to an air tank for containing compressed air for removing the fly ash attached to a filter bag in the top dust collector.
8. A fly ash recycling device according to claim 1, wherein a level gauge is provided at the top of the intermediate ash bin.
9. A circulating fluidized bed boiler comprising a fly ash circulation device according to any of claims 1 to 8.
10. A method for improving the efficiency of circulating fluidized bed boiler includes circulating the fly ash collected by dust collector to furnace cavity via coal feeding port.
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| JPH06307606A (en) * | 1993-04-23 | 1994-11-01 | Ishikawajima Harima Heavy Ind Co Ltd | Grain size classifying-type ash recirculation device |
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Application publication date: 20201103 |