CN115264490A - Circulating fluidized bed boiler with bed temperature adjusting device and temperature adjusting method - Google Patents
Circulating fluidized bed boiler with bed temperature adjusting device and temperature adjusting method Download PDFInfo
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- CN115264490A CN115264490A CN202210910509.4A CN202210910509A CN115264490A CN 115264490 A CN115264490 A CN 115264490A CN 202210910509 A CN202210910509 A CN 202210910509A CN 115264490 A CN115264490 A CN 115264490A
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- 238000000034 method Methods 0.000 title claims abstract description 18
- 239000010881 fly ash Substances 0.000 claims abstract description 65
- 239000000463 material Substances 0.000 claims abstract description 59
- 238000010438 heat treatment Methods 0.000 claims abstract description 50
- 238000005243 fluidization Methods 0.000 claims description 20
- 230000033228 biological regulation Effects 0.000 claims description 11
- 238000010521 absorption reaction Methods 0.000 claims description 10
- 239000002956 ash Substances 0.000 claims description 8
- 238000009826 distribution Methods 0.000 claims description 7
- 239000000446 fuel Substances 0.000 claims description 7
- 239000002245 particle Substances 0.000 claims description 5
- 238000005192 partition Methods 0.000 claims description 5
- 230000001105 regulatory effect Effects 0.000 claims description 4
- 238000000926 separation method Methods 0.000 claims description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 3
- 230000009471 action Effects 0.000 claims description 2
- 238000012546 transfer Methods 0.000 claims description 2
- 239000003245 coal Substances 0.000 description 19
- 238000002485 combustion reaction Methods 0.000 description 16
- 238000006477 desulfuration reaction Methods 0.000 description 14
- 230000023556 desulfurization Effects 0.000 description 10
- 239000003344 environmental pollutant Substances 0.000 description 8
- 231100000719 pollutant Toxicity 0.000 description 8
- 238000005516 engineering process Methods 0.000 description 7
- 238000013461 design Methods 0.000 description 6
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 4
- 238000005299 abrasion Methods 0.000 description 4
- 230000007613 environmental effect Effects 0.000 description 4
- 239000003546 flue gas Substances 0.000 description 4
- 238000011160 research Methods 0.000 description 4
- 230000008901 benefit Effects 0.000 description 3
- 230000005587 bubbling Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000005265 energy consumption Methods 0.000 description 3
- 238000011161 development Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000010248 power generation Methods 0.000 description 2
- 239000011819 refractory material Substances 0.000 description 2
- 235000019738 Limestone Nutrition 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
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- 239000002803 fossil fuel Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000011031 large-scale manufacturing process Methods 0.000 description 1
- 239000006028 limestone Substances 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 238000005065 mining Methods 0.000 description 1
- IJGRMHOSHXDMSA-UHFFFAOYSA-N nitrogen Substances N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 1
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- 239000007787 solid Substances 0.000 description 1
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Classifications
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- 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
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- 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
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- 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
- F23C10/20—Inlets for fluidisation air, e.g. grids; Bottoms
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- 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
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- 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
- F23C10/28—Control devices specially adapted for fluidised bed, combustion apparatus
- F23C10/30—Control devices specially adapted for fluidised bed, combustion apparatus for controlling the level of the bed or the amount of material in the bed
- F23C10/32—Control devices specially adapted for fluidised bed, combustion apparatus for controlling the level of the bed or the amount of material in the bed by controlling the rate of recirculation of particles separated from the flue gases
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Fluidized-Bed Combustion And Resonant Combustion (AREA)
Abstract
The invention discloses a circulating fluidized bed boiler with a bed temperature adjusting device and a temperature adjusting method, wherein the circulating fluidized bed boiler comprises a hearth, a horizontal flue, a separator and a tail flue which are sequentially communicated, wherein the bottom surface of the horizontal flue is provided with a horizontal flue ash falling vertical pipe and the bed temperature adjusting device, two ends of the horizontal flue ash falling vertical pipe are respectively communicated with the bed temperature adjusting device and comprise a cavity, a heating surface and a fluidized air system which are vertically arranged, and two ends of the horizontal flue ash falling vertical pipe are respectively communicated with the horizontal flue and the cavity; the fluidized air system comprises a heat exchange area fluidizing air chamber and a material returning area fluidizing air chamber which are arranged below the bed temperature adjusting device, and a material returning opening communicated with the hearth is formed in the bottom of the cavity; the bed temperature adjusting means of the circulating fluidized bed boiler is increased, the bed temperature adjusting method is enriched, the bed temperature can be locally adjusted in different regions, multi-region and overall adjustment of the bed temperature can also be realized, the flexibility of bed temperature adjustment is increased, and the system is simple and the operation difficulty is low compared with the traditional external bed heat exchanger.
Description
Technical Field
The invention belongs to the technical field of energy conservation and environmental protection of coal-fired circulating fluidized bed boilers, and particularly relates to a circulating fluidized bed boiler with a bed temperature adjusting device and a temperature adjusting method.
Background
The technical basis of circulating fluidized bed boilers is fluidization, which originally originates from fluidization reactors in chemical production. The fluidized bed combustion technology was introduced in the 50 s of the 20 th century, and in the early 60 s, small-sized bubbling fluidized bed BFB boilers began to emerge and developed. The bubbling fluidized bed is limited by the problems of large incomplete combustion loss of solids, low desulfurization efficiency, serious abrasion of a heating surface of a buried pipe, difficulty in large-scale production and the like when burning inferior fuels, and the combustion technology of the circulating fluidized bed boiler is generated. At the initial stage of the research of the circulating fluidized bed in China, technologists do not realize that the fluidizing states of a bubbling fluidized bed boiler and a circulating fluidized bed boiler in a combustion chamber are completely different, so that the problems that the circulating fluidized bed boiler developed at the early stage is insufficient in material circulation, cannot run at full load and the like are caused.
The real engineering applications of circulating fluidized bed boilers began in the late 70 s and early 80 s of the 20 th century. In 1979, the first 20t/h commercial circulating fluidized bed boiler developed by Ahlstrom, oslo, finland was put into operation [20]. In 1982, the first circulating fluidized bed boiler for steam production and heat supply in the world developed by Lurgi, germany was built and put into operation at 84 MW. At present, nearly one hundred circulating fluidized bed boilers with the capacity of 300-600 MW in the world are put into operation, wherein the first supercritical circulating fluidized bed boiler is manufactured by Forster-While company in America, is installed in a 460MW supercritical circulating fluidized bed boiler of a Lagisza power plant of Bolang Waki Sand, and is put into operation in 3 months in 2009.
Since the first 35t/h circulating fluidized bed boiler is put into operation in 11 months in 1989, 3000 circulating fluidized bed boilers are put into commercial operation. The circulating fluidized bed boiler of 20-690 t/h is developed by national institutes of research and development, such as the western-safety thermal research institute, the Chinese scientific and research engineering thermophysical institute, the Qinghua university and the like, and by each boiler manufacturer in turn. A300 MW circulating fluidized bed boiler of an exemplary power plant of Sichuan white horse is introduced into French ALSTOM company equipment by the nation through technical trade combination, and is built and put into operation in 4 months in 2006. Due to the complex structure and flow of the introduced technology, the adaptability to Chinese fuel is poor, and the problems promote the development of the simple design meeting the Chinese condition. Since 2008, the first 300MW simple circulating fluidized bed boiler was successfully put into operation in Baolihua power plants, and rapidly occupied the domestic market due to simple flow, reliable operation, convenient operation and maintenance and low cost, the first domestic 330MWCFB boiler developed by cooperation of the Western Ann thermal research institute and the Harbin boiler plant was successfully put into operation in the power plants in 1 month of 2009 in the Jiangxi province.
The energy structure mainly based on fire coal, the economic policy of the thermal power plant using inferior coal as much as possible, the increasingly declining coal quality and the continuously improved thermal power peak regulation requirement, the fluctuation of the coal quality entering the plant caused by the purchase of the commercial coal, the serious atmospheric pollution brought in the coal mining and using process and the requirements of sustainable development and comprehensive resource utilization all urgently need a novel efficient coal-burning technology which can efficiently burn various low-heat fuels and has low pollution and good peak regulation capability. Driven by this market demand, circulating fluidized bed coal burning technology has come into force. Compared with the traditional coal-fired boiler, the circulating fluidized bed boiler has the advantages of wide coal type adaptability, stable combustion, less pollutant discharge amount, easy control, good load regulation and the like, and the power generation cycle efficiency of the power plant is remarkably improved due to higher steam parameters, so that the circulating fluidized bed boiler is widely popularized and applied.
Circulating fluidized bed boilers have certain advantages over conventional combustion methods. The circulating fluidized bed boiler adopts low combustion temperature of 850-920 ℃ and air staged combustion, has low NOx generation amount and certain SO self-desulfurization capacity2Is lower than the actual amount of SO calculated as total sulfur2Theoretical yield; circulating fluidized bed boilerThe furnace can effectively remove 90 percent or more of SO by adding a certain amount of limestone particles into the furnace through dry desulfurization in the furnace2(ii) a The circulating fluidized bed boiler has excellent fuel adaptability, and almost any fossil fuel can be designed and used; the circulating fluidized bed boiler has good peak regulation capacity and can stably burn without oil feeding under the rated load of 30 percent. Therefore, the circulating fluidized bed boiler technology is rapidly developed in China during the last two decades, and the middle coal plastic 2 x 660MW supercritical circulating fluidized bed boiler unit is commercially operated.
The circulating fluidized bed boiler is used as environment-friendly combustion equipment to realize low-nitrogen combustion by adopting a low-temperature, low-oxygen and air classification mode, and the generation amount of NOx is lower than that of a pulverized coal boiler. Low temperature combustion is favorable for SO2The control of the generated amount has high self-desulfurization efficiency and improves the dry desulfurization efficiency in the furnace. The NOx emission value of the circulating fluidized bed boiler is generally 150-300 mg/m according to the difference of coal types and the change of combustion conditions3In the meantime. The self-desulfurization efficiency in the furnace is 10-40%, and the dry desulfurization efficiency in the furnace is 70-95%. Bed temperature is the main influencing factor in combustion conditions. Most circulating fluidized bed boiler units can meet the requirement of NOx emission limit without adopting flue gas denitration before the new thermal power plant atmospheric pollutant emission standard is implemented in 2011.
Along with the increase of the comprehensive treatment strength of the atmospheric pollutants in China and the implementation of the ultra-low emission requirement. Most circulating fluidized bed boilers need to be provided with a flue gas denitration device to meet the requirement of ultralow emission of NOx, and secondary flue gas desulfurization such as wet desulfurization or semidry desulfurization systems is added to meet the requirement of SO2Ultra low emission requirements. However, according to the guidance and suggestions of related environmental protection technologies, the circulating fluidized bed boiler should fully exert the advantage of low pollutant generation of the boiler, and on the basis, the effective control of pollutant emission is realized by combining the improvement of environmental protection facilities.
The design of the circulating fluidized bed boiler is based on the design coal quality parameters, and the combustion efficiency, NOx and SO of the boiler are comprehensively considered2When the pollutants are discharged, the operating bed temperature of the selected boiler is generally 850-920 ℃. Therefore, the boiler can be ensured to have good combustion efficiency, and the low-temperature combustion of the circulating fluidized bed boiler can be exertedLow pollutant emission value caused by burning and high desulfurization efficiency in the furnace. However, because the coal market in China changes rapidly, the difference between actual coal and designed coal of many coal-fired power generation enterprises is large, and when the variation range of parameters such as the calorific value of coal as fired and ash content is large, a series of problems such as bed temperature increase, NOx generation increase, in-furnace desulfurization efficiency decrease, the operation load of a flue gas desulfurization and denitrification system is increased, and safety, stability and economy are reduced can be caused.
Due to the importance of bed temperature control in the operation of circulating fluidized bed boilers, operating bed temperature regulation measures are taken into account in the boiler design phase. For example: the material thickness of the bed layer is increased within a certain range during operation; the primary air quantity is increased to cool the bed material; the large circulating fluidized bed boiler is also provided with an external bed heat exchanger for adjusting the bed temperature. These bed temperature control methods can provide a certain degree of bed temperature control, but also have some adverse effects. The energy consumption of an induced draft fan and a primary air fan can be increased by increasing the thickness of the bed material; the increase of the primary air volume can improve the abrasion rate of the heating surface of the boiler; the external bed heat exchanger has a complex structure, is generally applied to a large circulating fluidized bed boiler unit, and has the problem of high failure rate in operation. The design of an external bed heat exchanger of a circulating fluidized bed boiler with the level of 300MW or below is cancelled by various domestic large boiler design and manufacturing enterprises.
Disclosure of Invention
In order to solve the problems in the prior art, the invention discloses a circulating fluidized bed boiler with a bed temperature adjusting device, wherein the bed temperature adjusting device is additionally arranged on the basis of the conventional circulating fluidized bed boiler, so that not only can the overall adjustment of the bed temperature be realized, but also the regional local adjustment of the bed temperature can be realized, the bed temperature is controlled within a target range, and the uniformity of the bed temperature distribution is improved.
In order to achieve the purpose, the invention adopts the technical scheme that: a circulating fluidized bed boiler with a bed temperature adjusting device comprises a hearth, a horizontal flue, a separator and a tail flue which are sequentially communicated, wherein the bottom surface of the horizontal flue is provided with a horizontal flue ash falling vertical pipe and the bed temperature adjusting device, two ends of the horizontal flue ash falling vertical pipe are respectively communicated with the bed temperature adjusting device and comprise a cavity, a heating surface and a fluidized air system which are vertically arranged, and two ends of the horizontal flue ash falling vertical pipe are respectively communicated with the horizontal flue and the cavity; the fluidized air system comprises a heat exchange area fluidized air chamber and a material returning area fluidized air chamber which are arranged below the bed temperature adjusting device, an air distribution plate is arranged at the top ends of the heat exchange area fluidized air chamber and the material returning area fluidized air chamber, a plurality of air caps are arranged on the air distribution plate, and a material returning port communicated with a hearth is formed in the bottom of the cavity; the heat transfer area fluidization air chamber and the material returning area fluidization air chamber are connected with a fluidization fan unit through fluidization air pipes, and fluidization air pipe valves are arranged on the fluidization air pipes.
The inside of the bed temperature adjusting device is a heat exchange area and a material returning area, the material returning area is positioned at the bottom of the bed temperature adjusting device, the heat exchange area is positioned in an area provided with a heating surface, a partition wall is arranged between the heat exchange area and the material returning area for separation, a fluidization air chamber of the heat exchange area is arranged below the heat exchange area, and a fluidization air chamber of the material returning area is arranged below the material returning area.
When the separator is provided with a plurality of separators, a bed temperature adjusting device is arranged below each horizontal flue, and all the bed temperature adjusting devices form a bed temperature adjusting system.
The heating surface is composed of a group of tube banks, working media in the heating surface are water or steam, heating surface pipeline collecting boxes are arranged at an inlet and an outlet of the heating surface and comprise an inlet collecting box and an outlet collecting box, the working media are distributed to all pipelines of the heating surface by the inlet collecting box, the outlet collecting box is used for collecting the working media after heat exchange, and parameters of the heating surface tube banks are selected by combining the parameters of the working media and the requirements of heat absorption capacity.
The working area of the fluidizing air chamber of the heat exchange area is larger than that of the fluidizing air chamber of the material returning area.
The number of hoods is proportional to the size of the top section of the fluidizing plenum.
The invention relates to a temperature adjusting method of a circulating fluidized bed boiler, when the boiler is in operation and bed temperature adjusting is required, fly ash formed by burning fuel in a hearth enters a high-temperature cyclone separator through a horizontal flue, the fly ash which is separated and is larger than a set particle size range is returned to the hearth, the fly ash which is smaller than the set particle size enters a tail flue, and the fly ash and a heated surface arranged in the tail flue complete heat exchange and then are discharged out of the boiler;
the fly ash in the horizontal flue enters a heat exchange area of the temperature adjusting device from an ash falling vertical pipe of the horizontal flue, and the fly ash flows out of a material returning opening through a material returning area under the action of airflow and enters a hearth after heat exchange is carried out on the fly ash and a heating surface; the heat absorption capacity of the working medium is adjusted by changing the flow and the flow speed of the working medium on the heating surface.
The temperature of the fly ash is controlled by adjusting the residence time of the fly ash in the system and the heat absorption capacity of the working medium on the heating surface; the residence time of the fly ash in the temperature adjusting device is adjusted through different proportions of the fluidized air quantity of the heat exchange area and the material returning area, namely, the residence time of the fly ash is adjusted through adjusting the proportions of the fluidized air quantity of the material returning area and the fluidized air quantity of the heat exchange area.
One group of bed temperature adjusting devices operates or a plurality of groups of bed temperature adjusting devices operate in a combined way.
The grade of the working medium after heat exchange is improved, and the working medium is conveyed to a boiler to generate a working medium with the same grade according to the temperature and pressure parameters of a designed outlet, and further participates in heat exchange and work application or is output as industrial steam.
Compared with the prior art, the invention at least has the following beneficial effects: based on the device, bed temperature adjusting means of the circulating fluidized bed boiler can be added, and bed temperature adjusting methods are enriched; the bed temperature can be locally adjusted in different areas, multi-area and overall adjustment of the bed temperature can be realized, and the flexibility of bed temperature adjustment is improved. Compared with a method for adjusting the bed temperature by running wind, the method does not increase the abrasion of the heating surface of the hearth and does not influence the energy consumption of the fan. Compared with the traditional external bed heat exchanger, the system is simple, and the operation difficulty is small; the fly ash is cooled by a heating surface arranged in the bed temperature adjusting system, and the grade of the working medium is improved after heat exchange, so that the working medium can be further recycled.
The fly ash temperature returned to the hearth is controlled by adjusting the residence time of the fly ash in the system and the heat absorption capacity of the working medium on the heating surface. The residence time of the fly ash in the system is realized by adjusting the matching relation of fluidized air in the heat exchange area and the material returning area, and the heat absorption capacity of the working medium on the heating surface is realized by adjusting the parameters of the temperature, the pressure, the flow speed, the flow and the like of the working medium.
Furthermore, a set of bed temperature adjusting device is arranged below a horizontal flue at the inlet of each high-temperature separator of the boiler, the fly ash on the horizontal flue enters the bed temperature adjusting device through a vertical ash falling pipe of the horizontal flue, and the fly ash after heat exchange is returned to the hearth through a material returning port.
Furthermore, the inside of the bed temperature adjusting device is divided into a heat exchange area and a material returning area, and the two areas are separated by a partition wall laid by wear-resistant refractory materials.
Furthermore, the flow and the temperature of the fly ash returned to the hearth are controlled by adjusting the residence time of the fly ash in the bed temperature adjusting device and the heat absorption capacity of the working medium on the heating surface.
Furthermore, the bed temperature adjusting device can be operated independently to realize the regional local adjustment of the bed temperature, and a plurality of sets of bed temperature adjusting devices can be put into operation simultaneously to realize the multi-region and overall adjustment of the hearth bed temperature.
Furthermore, the fly ash is cooled by a heating surface arranged in the bed temperature adjusting system, and the grade of the working medium is improved after heat exchange, so that the working medium can be further recycled, and the running economy of the system is improved.
Drawings
FIG. 1 is a schematic view of the present invention.
FIG. 2 is a schematic view of a partial structure of the bed temperature adjusting device of the present invention.
The device comprises a hearth 1, a horizontal flue 2, a separator 3, a tail flue 4, a horizontal flue ash falling vertical pipe 5, a bed temperature adjusting device 6, a heating surface 7, a heat exchange zone 8, a hood 9, a heating surface pipeline header 10, an air distribution plate 11, a heat exchange zone fluidizing air chamber 12, a material returning zone fluidizing air chamber 13, a material returning port 14, a material returning zone 15, a partition wall 16, a fluidizing air pipeline valve 17, a fluidizing air pipeline 18 and a fluidizing air blower 19.
Detailed Description
The invention is further described with reference to the following drawings and detailed description.
The method for adjusting the operating bed temperature of the circulating fluidized bed boiler can be roughly divided into two methods, namely operation air adjustment and circulating material adjustment. The operation air regulation mainly comprises the adjustment of the total air quantity, the primary air quantity, the secondary air quantity, the proportion of the primary air quantity and the secondary air quantity and the like in the operation of the boiler. As the temperature of the secondary air is mostly between 180 and 230 ℃, parameters such as the quantity ratio of the running air entering the hearth and the like can play a role in adjusting the bed temperature. The circulating material is adjusted by changing parameters such as the quantity of the circulating material entering a hearth, the temperature of the material and the like to adjust the operating bed temperature of the boiler, and because the heat exchange in the circulating fluidized bed boiler mainly heats the circulating material by burning coal, the heat exchange between the circulating material and a heating surface is completed, and the addition of the coal only accounts for 5-8% of the material in the hearth. Therefore, the temperature of the operating bed of the boiler can be effectively adjusted by changing the circulating material quantity and the material temperature. The circulating material temperature regulation also overcomes the defects of high energy consumption level of a fan, aggravation of abrasion of a heating surface of a hearth and the like caused by operation air regulation.
Referring to fig. 1 and 2, the circulating fluidized bed boiler with bed temperature adjusting device provided by the invention comprises a hearth 1, a horizontal flue 2, separators 3 and a tail flue 4, wherein a set of bed temperature adjusting device is arranged below the horizontal flue at the inlet of each separator 3 of the boiler, and fly ash at the upper part of the horizontal flue 2 is introduced into the bed temperature adjusting device through a horizontal flue ash dropping vertical pipe 5; the bottom of the separator 3 is communicated with the hearth 1; all the bed temperature adjusting devices form a bed temperature adjusting system. The inner part of each set of bed temperature adjusting device 6 is a heat exchange area 8 and a material returning area 15, the two areas are separated by a partition wall built by wear-resistant refractory materials, the fly ash carries out heat exchange with the arranged heating surface 7 in the heat exchange area 8, and the fly ash flows out of a material returning opening 14 through the material returning area 15 to enter the hearth 1 after being cooled.
The bed temperature adjusting device comprises an air cap 9, an air distribution plate 11, a heat exchange area fluidization air chamber 12, a material returning area fluidization air chamber 13, a fluidization air pipeline valve 17 and a fluidization air unit 19, and is used for controlling the flow rate and the flow speed of fly ash, and the temperature of returned material ash is not lower than 600 ℃.
The separator 3 is a high-temperature cyclone separator.
The operation control of the bed temperature adjusting device mainly comprises two aspects: on one hand, the flow rate of the fly ash is controlled, the residence time of the fly ash in the device is controlled, and on the other hand, the operation parameters of working media in the heating surface are controlled; the two aspects of operation control achieve the effects of reducing the temperature of the fly ash and ensuring the parameters of the working medium at the outlet of the heating surface. The specific adjustment method is as follows:
(1) The flow rate and residence time of the fly ash are adjusted by pneumatic adjustment, i.e. the flow rate and flow speed of the fly ash are controlled by the blown air to drive the fly ash. The air quantity ratio of the heat exchange area 8 and the material returning area 15 can adjust the retention time of the fly ash; generally, the air volume of the heat exchange area 8 maintains the fly ash in a fluidized state, and the air volume of the material returning area 15 can adjust the flow speed of the fly ash. The air quantity of the material returning area 15 is in direct proportion to the flowing speed of the fly ash.
(2) The air quantity of the heat exchange area 8 and the material returning area 15 can be adjusted by changing the opening degree of the fluidized air pipeline valve 17.
(3) During the operation of the boiler, the opening of the valve 17 of the fluidizing air pipeline is controlled according to the changes of parameters such as the load of the boiler, the coal type and the like, so that the flow and the flow speed of the fly ash are adjusted.
(4) If the fluidizing blower is a Roots blower, a main fluidizing air pipe, a hot primary air connecting pipe and a control valve are preferably arranged for adjusting the total amount of fluidizing air. For example: and a control valve of the hot primary air communication pipe is opened, so that a part of fluidized air can be conveyed to the hot primary air system, the total amount of the fluidized air is reduced, and vice versa.
(5) The heat absorption capacity of the working medium is adjusted by changing parameters such as the flow rate, the flow speed and the like of the working medium on the heating surface of the hot zone 8. Generally, a regulating valve is arranged behind the outlet header of the heating surface to realize the functions. For example: when the flow and the flow speed of the fly ash of the bed temperature adjusting device are constant, the opening degree of the adjusting valve is reduced, the temperature and the pressure of the working medium in the heating surface can be increased along with the opening degree, and the outlet flow of the working medium is reduced. The adjustment of the returned ash temperature and the parameters of the working medium at the outlet of the heating surface is realized by the cooperative control of the parameters of the fly ash and the working medium at the heating surface.
(6) The enthalpy value of the working medium after absorbing heat is improved, the grade is increased, and the working medium can be further utilized.
The bed temperature adjusting devices can independently operate to realize the local bed temperature adjustment of the hearth, and the bed temperature adjusting devices jointly operate to realize the multi-zone and overall adjustment of the bed temperature.
When the circulating fluidized bed boiler with the bed temperature adjusting system is in operation, fly ash formed by burning fuel in a hearth enters the separator 3 through the horizontal flue 2, the fly ash with the granularity larger than a set granularity after separation is returned to the hearth 1, fine ash enters the tail flue 4, and the fine ash is discharged out of the boiler after heat exchange with the heating surface 7 arranged in the tail flue 4 is completed. When the boiler is in operation and needs bed temperature regulation, the fly ash on the horizontal flue 2 enters a heat exchange area 8 of the temperature regulation device from the horizontal flue ash falling vertical pipe 5, and the fly ash and the heating surface 7 exchange heat and then flow out of a return port 14 through a return area 15 to enter the hearth 1. The working medium in the heating surface 7 can be water or steam, a heating surface pipeline header 10 is arranged at an inlet and an outlet of the heating surface 7, and the heating surface pipeline header 10 comprises an inlet header and an outlet header; the inlet header distributes the working medium to each pipeline of the heating surface, and the outlet header collects the working medium after heat exchange. The grade of the working medium after heat exchange is improved, and the working medium can be further utilized. The fly ash cooled by the bed temperature adjusting system has lower temperature and can achieve the effect of adjusting the bed temperature after entering the hearth.
In summary, the circulating fluidized bed boiler with the bed temperature adjusting device of the invention cools the fly ash with a set amount through the bed temperature adjusting device, and returns the fly ash to the furnace chamber to adjust the operating bed temperature of the boiler. Through the reasonable control of bed temperature, guarantee that the boiler has higher combustion efficiency, reduce NOx's formation volume simultaneously, improve the self-desulfurization efficiency of boiler and stove dry process denitration efficiency, reduce the operating pressure and the running cost of environmental protection facilities such as SOx/NOx control system, promote the stability and the economic nature of the ultralow emission of pollutant.
Claims (10)
1. The utility model provides a circulating fluidized bed boiler with bed temperature adjusting device which characterized in that: the device comprises a hearth (1), a horizontal flue (2), a separator (3) and a tail flue (4) which are sequentially communicated, wherein the bottom surface of the horizontal flue (2) is provided with a horizontal flue ash falling vertical pipe (5) and a bed temperature adjusting device (6), two ends of the horizontal flue ash falling vertical pipe (5) are respectively communicated with the bed temperature adjusting device (6) and comprise a vertically arranged cavity, a heating surface (7) and a fluidized air system, and two ends of the horizontal flue ash falling vertical pipe (5) are respectively communicated with the horizontal flue (2) and the cavity; the fluidized air system comprises a heat exchange area fluidizing air chamber (12) and a material returning area fluidizing air chamber (13) which are arranged below a bed temperature adjusting device (6), an air distribution plate (11) is arranged at the top ends of the heat exchange area fluidizing air chamber (12) and the material returning area fluidizing air chamber (13), a plurality of air caps (9) are arranged on the air distribution plate (11), and a material returning port (14) is formed in the bottom of the cavity and communicated with the hearth (1); the heat transfer area fluidization air chamber (12) and the material return area fluidization air chamber (13) are connected with a fluidization air unit (19) through a fluidization air pipe (18), and a fluidization air pipeline valve (17) is arranged on the fluidization air pipe (18).
2. The circulating fluidized bed boiler with a bed temperature adjusting device according to claim 1, characterized in that: the inside of the bed temperature adjusting device (6) is divided into a heat exchange area (8) and a material returning area (15), the material returning area (15) is positioned at the bottom of the bed temperature adjusting device (6), the heat exchange area (8) is positioned in an area provided with a heated surface (7), a partition wall is arranged between the heat exchange area (8) and the material returning area (15) for separation, a fluidizing air chamber (12) of the heat exchange area is arranged below the heat exchange area (8), and a fluidizing air chamber (13) of the material returning area is arranged below the material returning area (15).
3. The circulating fluidized bed boiler with a bed temperature adjusting device according to claim 1, wherein: when the separators (3) are provided with a plurality of separators, a bed temperature adjusting device (6) is arranged below each horizontal flue (2), and all the bed temperature adjusting devices (6) form a bed temperature adjusting system.
4. The circulating fluidized bed boiler with a bed temperature adjusting device according to claim 1, characterized in that: the heating surface (7) is composed of a group of tube banks, working media in the heating surface (7) are water or steam, a heating surface pipeline header (10) is arranged at an inlet and an outlet of the heating surface (7), the heating surface pipeline header (10) comprises an inlet header and an outlet header, the working media are distributed to each pipeline of the heating surface by the inlet header, the outlet header is used for collecting the working media after heat exchange, and parameters of the heating surface tube banks are selected by combining the parameters of the working media and the requirement of heat absorption capacity.
5. The circulating fluidized bed boiler with a bed temperature adjusting device according to claim 1, wherein the working area of the heat exchange zone fluidizing air chamber (12) is larger than that of the material returning zone fluidizing air chamber (13).
6. A circulating fluidized bed boiler with bed temperature adjusting means according to claim 1, characterized in that the number of hoods (9) is proportional to the size of the top cross section of the fluidizing plenum.
7. A method for regulating the temperature of a circulating fluidized bed boiler according to any one of claims 1 to 6, characterized in that, when there is a demand for bed temperature regulation during the operation of the boiler, fly ash formed by burning fuel in a furnace (1) is introduced into a separator (3) through a horizontal flue (2), fly ash having a particle size larger than a predetermined range after separation is returned to the furnace, fly ash having a particle size smaller than the predetermined range is introduced into a tail flue (4), and is discharged from the boiler after heat exchange with a heated surface arranged in the tail flue is completed;
fly ash in the horizontal flue (2) enters a heat exchange area (8) of the temperature adjusting device from a vertical ash falling pipe (5) of the horizontal flue, and flows out of a material returning port (14) to enter a hearth through a material returning area (15) under the action of air flow after the heat exchange between the fly ash and a heating surface (7); the heat absorption capacity of the working medium is adjusted by changing the flow and the flow speed of the working medium on the heating surface.
8. The temperature regulating method according to claim 7, wherein the control of the fly ash temperature is realized by adjusting the residence time of the fly ash in the system and the heat absorption capacity of the heating surface working medium; the residence time of the fly ash in the temperature adjusting device is adjusted through different proportions of the fluidized air quantity of the heat exchange area (8) and the material returning area (15), namely, the residence time of the fly ash is adjusted through adjusting the proportions of the fluidized air quantity of the material returning area and the fluidized air quantity of the heat exchange area.
9. The method of claim 7, wherein one set of bed temperature adjusting means is operated or a plurality of sets of bed temperature adjusting means are operated in combination.
10. The temperature regulating method according to claim 7, characterized in that the grade of the working medium after heat exchange is improved, and the working medium is delivered to a boiler to generate working medium with equivalent grade according to the temperature and pressure parameters of a designed outlet, and further participates in heat exchange and work application or is output as industrial steam.
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| US20130284120A1 (en) * | 2011-02-24 | 2013-10-31 | Kari Kauppinen | Circulating Fluidized Bed Boiler Having Two External Heat Exchangers for Hot Solids Flow |
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