CN111981473A - Slag burnout system and method of biomass boiler - Google Patents
Slag burnout system and method of biomass boiler Download PDFInfo
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- CN111981473A CN111981473A CN202010963836.7A CN202010963836A CN111981473A CN 111981473 A CN111981473 A CN 111981473A CN 202010963836 A CN202010963836 A CN 202010963836A CN 111981473 A CN111981473 A CN 111981473A
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- 239000002893 slag Substances 0.000 title claims abstract description 116
- 239000002028 Biomass Substances 0.000 title claims abstract description 58
- 238000000034 method Methods 0.000 title claims abstract description 12
- 239000000463 material Substances 0.000 claims abstract description 44
- 238000001816 cooling Methods 0.000 claims abstract description 41
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims abstract description 38
- 239000003546 flue gas Substances 0.000 claims abstract description 38
- 239000000446 fuel Substances 0.000 claims description 29
- 239000002245 particle Substances 0.000 claims description 19
- 238000004064 recycling Methods 0.000 claims description 12
- 239000007789 gas Substances 0.000 claims description 11
- 239000007921 spray Substances 0.000 claims description 8
- 238000005260 corrosion Methods 0.000 abstract description 6
- 230000007797 corrosion Effects 0.000 abstract description 6
- 230000008021 deposition Effects 0.000 abstract description 3
- 238000005243 fluidization Methods 0.000 abstract description 2
- 239000002956 ash Substances 0.000 description 93
- 230000014759 maintenance of location Effects 0.000 description 12
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 12
- 230000001965 increasing effect Effects 0.000 description 11
- 238000002156 mixing Methods 0.000 description 11
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 9
- 229910052799 carbon Inorganic materials 0.000 description 9
- 238000002485 combustion reaction Methods 0.000 description 9
- 230000006872 improvement Effects 0.000 description 7
- 239000003245 coal Substances 0.000 description 6
- 230000002035 prolonged effect Effects 0.000 description 6
- 238000006722 reduction reaction Methods 0.000 description 5
- 239000010881 fly ash Substances 0.000 description 4
- 238000004062 sedimentation Methods 0.000 description 4
- 239000000779 smoke Substances 0.000 description 4
- 239000003638 chemical reducing agent Substances 0.000 description 3
- 239000003795 chemical substances by application Substances 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
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- 239000002918 waste heat Substances 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 230000009471 action Effects 0.000 description 1
- XKMRRTOUMJRJIA-UHFFFAOYSA-N ammonia nh3 Chemical compound N.N XKMRRTOUMJRJIA-UHFFFAOYSA-N 0.000 description 1
- 230000001174 ascending effect Effects 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000010531 catalytic reduction reaction Methods 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
- F23C10/22—Fuel feeders specially adapted for fluidised bed combustion apparatus
-
- 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
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
Abstract
The invention discloses a slag burnout system and a method of a biomass boiler, which comprises the following steps: the boiler comprises a boiler body, wherein a water-cooled wall and a first superheater are arranged in the boiler body; the inlet of the cyclone separator is communicated with the exhaust port of the boiler body; a slag outlet of the cyclone separator is communicated with an air outlet of the cyclone separator communicated with the first throat structure of the boiler body through a return material pipeline, and a second superheater, an economizer and an air preheater are sequentially arranged in the flue gas pipeline along the flow direction of flue gas; the inlet of the air preheater is communicated with a blower through a blower pipeline; the outlet of the air preheater is communicated with a primary air pipeline and a secondary air pipeline; an ash cooling air pipeline; denitration equipment. According to the invention, through circulating fluidization and maintaining upward ash cooling air in the slag well, the boiler ash can be fully combusted, the sensible heat of the ash can be fully utilized, the boiler efficiency can be improved, and the ash deposition corrosion can be reduced.
Description
Technical Field
The invention belongs to the technical field of biomass fuel combustion and environmental pollution emission, and particularly relates to a slag burnout system and a method of a biomass boiler.
Background
At present, the promotion of the utilization of renewable energy sources is being advocated, biomass power generation is the key development direction of biological energy sources, and biomass power plants are being built in great force in various places. The biomass direct combustion power generation refers to that a biomass boiler utilizes heat energy generated by directly combusting biomass to generate steam and then pushes a steam turbine system to generate power, and the mode has the most mature biomass energy and the most application value prospect due to the economic and social advantages of near zero emission, agriculture and the like; the biomass grate boiler is mature in technology, large in application scale and high in market share.
At present, the structure of a biomass power generation boiler generally comprises: the device comprises a furnace body, a superheater, a coal economizer, a flue gas cooler, a dust remover, a chimney, a secondary air pipe and a feeder on the side wall of the furnace body, a slag well and a slag discharge device at the bottom of the furnace body, an ash hopper and an ash treatment device. Because the biomass boiler has small single machine capacity and low heat value of biomass fuel and generates a large amount of ash or caking after combustion, the following problems often exist after long-term use:
1) when the biomass boiler is used for deslagging, the slag still contains a large amount of high-temperature unburnt components, and the residual sensible heat of the slag is absorbed by the slag extractor and cannot be reasonably utilized, so that the thermal efficiency of the boiler is reduced; the water vapor generated in a large amount in the slag extractor is easy to corrode the bottom of the furnace body, and simultaneously, the flue gas humidity is increased, so that the corrosion of a tail flue is aggravated;
2) because the density of the biomass is low, a large amount of unburnt substances are easily entrained by the flue gas and leave the hearth, so that the ash content of a flue is too high, the equipment is seriously abraded, and the operation and maintenance cost is increased;
3) most of the existing biomass burning boiler power plants are not provided with a denitration device or use an SCR denitration device, the NOx emission is high, and the requirements of the latest standard are difficult to adapt along with the improvement of the emission standard of the nitrogen oxides in the power plants.
In summary, a new system and method for enhancing the burnout of biomass boiler ash and saving energy is needed.
Disclosure of Invention
The invention aims to provide a slag burnout system and a method of a biomass boiler, which aim to solve the technical problems that the existing biomass boiler has large amount of ash and slag, the ash and slag are dispersed in a hearth and a flue and are difficult to collect, the ash and slag waste heat is high, the heat efficiency is low, and the tail flue is accumulated with ash and corroded. According to the invention, through circulating fluidization and maintaining upward ash cooling air in the slag well, the boiler ash can be fully combusted, the sensible heat of the ash can be fully utilized, the boiler efficiency can be improved, and the ash deposition corrosion can be reduced.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention relates to a slag burnout system of a biomass boiler, which comprises:
the boiler comprises a boiler body, a boiler body and a heat exchanger, wherein the boiler body is provided with a feeding hole, a slag well and an exhaust hole; a water-cooled wall and a first superheater are arranged in the boiler body; the boiler body is a double-throat configuration, comprising: the first necking structure is arranged below the second necking structure;
the cyclone separator is provided with an inlet, an air outlet and a slag outlet; the inlet of the cyclone separator is communicated with the exhaust port of the boiler body; a slag outlet of the cyclone separator is communicated with the first throat structure of the boiler body through a material return pipeline; the material returning pipeline is provided with a recycling material returning fan; the gas outlet of the cyclone separator is communicated with a flue gas pipeline, and a second superheater, an economizer and an air preheater are sequentially arranged in the flue gas pipeline along the flow direction of flue gas;
the inlet of the air preheater is communicated with a blower through a blower pipeline; the outlet of the air preheater is communicated with a primary air pipeline and a secondary air pipeline; wherein, the outlet of the primary air pipeline is positioned below the feed inlet of the boiler body; the outlet of the secondary air pipeline is positioned at the first necking structure;
an inlet of the ash cooling air pipeline is arranged on the air supply pipeline, and an outlet of the ash cooling air pipeline is arranged at a slag well of the boiler body;
and the spray gun of the denitration device is arranged at the second necking structure.
The invention has the further improvement that the air inlet of the recirculation material returning fan is communicated with a flue gas pipeline between the economizer and the air preheater; the initial section of the material returning pipeline is U-shaped, and the middle part of the material returning pipeline is communicated with an air outlet of the recycling material returning fan.
The further improvement of the invention is that the width of the inner section of the hearth of the second necking structure is 1/2-2/3 of the maximum width in the hearth of the boiler body.
The invention further improves the method and also comprises the following steps: and the discharge hole of the biomass fuel feeding equipment is communicated with the feed inlet of the boiler body.
The invention has the further improvement that the outlet of the flue gas pipeline is also provided with an ash removal device and a tail gas treatment system; wherein, the flue gas of flue gas pipeline is introduced into the tail gas treatment system through the induced draft fan.
The invention is further improved in that the outlet of the return duct is above the outlet of the secondary air duct; the pipeline direction of the return pipeline is parallel to the inclined plane direction of the upper hearth of the first throat structure.
The invention has the further improvement that the ash cooling air pipeline is provided with a valve for controlling the air speed and the air quantity of the ash cooling air; wherein the wind speed is more than 12m/s, and the wind volume is less than 10% of the total wind volume.
The invention has the further improvement that a discharger is also arranged at the slag well of the boiler body; the discharger is provided with rotating blades for grinding the slag.
The invention is further improved in that a slag collecting and conveying device is arranged below the slag well of the boiler body.
The invention discloses a method for burning out slag of a biomass boiler, which is based on the system provided by the invention and comprises the following steps of:
feeding biomass fuel and primary air into a hearth of a boiler body;
the cyclone separator separates and collects ash particles discharged from an exhaust port of the boiler body, and the ash particles are mixed and fluidized through a material returning pipeline and a recycling material returning fan and are sent back to the hearth; wherein, the feeding is carried out at the first necking structure;
the slag well of the boiler body is used for collecting falling slag in the hearth, and upward ash cooling air is kept in the slag well, so that the settlement of the slag is slowed down or part of the ash rises along with air flow;
denitration treatment is carried out on the hearth flue gas through denitration equipment arranged at the second necking structure.
Compared with the prior art, the invention has the following beneficial effects:
according to the biomass boiler ash burnout system, the ash particle recycling module is formed through the cyclone separator, the recycling material returning fan and the material returning pipeline, external circulation of the slag can be achieved, part of fly ash which is not burnt and has high carbon content and leaves a hearth can be recycled and sent back to the hearth for combustion, the total amount of the ash and the ash in a tail flue are reduced, the amount of the slag in the hearth is increased, the coking corrosion problem of the tail flue is favorably reduced, and the burnout and collecting treatment efficiency of the ash and the ash are improved. In the invention, the ash cooling air pipe, the inclined plane above the slag well (the first throat structure) and the hearth throat at the position of secondary air form a slag sensible heat recovery module together, and because upward ash cooling air is provided for fuel in the furnace and slag fed back by the cyclone separator, the sedimentation of ash can be reduced, the ash with extremely small particle size and higher carbon content can be raised, the retention time is prolonged, the unburned carbon in the ash can be fully utilized, and the burnout of the ash is strengthened; the temperature of the ash cooling air is low, so that the sensible heat of the slag can be absorbed, and the heat efficiency of the boiler can be improved; and the downward return air and the upward cooling air are converged near the throat where the secondary air of the furnace wall is positioned to generate standing vortex of air flow, so that internal circulation of furnace slag is formed, ignition and mixing are further enhanced, the economical efficiency is more excellent, and the total amount of boiler ash and carbon content of the ash are further reduced. According to the invention, through the second necking of the hearth arranged above the fuel feeding equipment and below the superheater, the disturbance and the sufficient mixing of the flue gas in the upper part of the hearth, namely the heating surface area are increased, the retention time is prolonged, the incomplete combustion loss of the biomass fuel is further reduced, and a more uniform temperature concentration field is provided. In the invention, the denitration device adopts SNCR, and the spray gun is arranged at the second necking position of the hearth. The temperature space range of the common grate boiler suitable for SNCR denitration is narrower than that of a pulverized coal boiler, the most suitable temperature is 950 ℃, the ideal temperature is 850-1150 ℃, and the denitration retention time is 0.5 s. Therefore, the SNCR device is arranged at the necking part, and more uniform treatment agent mixing can be provided compared with the conventional equipment so as to ensure that the NOx reduction reaction is sufficient, thereby remarkably reducing the NOx emission of the boiler.
In the invention, the inlet of the recirculation material returning fan is connected with the flue between the economizer and the air preheater, and the flue gas extracted from the recirculation material returning fan is sent to the initial section of the material returning pipe to be mixed with ash and slag materials, thereby avoiding the ignition in the material returning pipe.
According to the invention, a variable cross-section reducing port is additionally arranged above the position of the feeding equipment and below the superheater in the hearth of the boiler, the minimum cross-section width of the reducing port is 1/2-2/3 of the maximum width of the whole hearth, and the reducing agent for SNCR denitration is sprayed from the reducing port, so that the mixing of the denitration reducing agent and flue gas is enhanced, the ash retention time in the boiler is prolonged, and the burnout rate and the denitration efficiency are improved.
In the invention, the slag well is internally provided with upward ash cooling air, so that most of particles except for little fine fly ash in the slag can fall but settle slowly, the ascending airflow speed is not lower than 12m/s, and the air volume of the cooling air is not more than 10 percent of the total air volume, thus the sensible heat of the slag leaving the fire grate is effectively utilized. Wherein, the side surface of the slag well is connected with an outlet of the ash cooling air pipe; the ash cooling air pipeline is communicated with a valve and the like and is communicated with a bypass at the outlet of the blower without passing through the air preheater. The upward cooling wind of the ash slag is kept in the slag well, so that the sedimentation of the slag is slowed down or part of the extremely fine ash rises along with the air flow, the cooling wind is heated by the sensible heat of the falling slag, and the more sufficient retention and burnout of the fuel in the furnace are ensured.
In the invention, a slag collecting and conveying device is arranged at an outlet below the slag well, a discharger with a rotating blade is arranged in front of the outlet and is used for grinding slag, so that the slag can smoothly fall and can not be blocked, and the slag is conveyed to a collecting tank for further treatment.
The method of the invention is based on the system of the invention, and can realize the improvement of the heat energy utilization efficiency and the ash recycling rate of the boiler.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art are briefly introduced below; it is obvious that the drawings in the following description are some embodiments of the invention, and that for a person skilled in the art, other drawings can be derived from them without inventive effort.
FIG. 1 is a schematic structural diagram of a slag burnout system of a biomass boiler according to an embodiment of the invention;
in the figure, 1, a primary air pipeline; 2. an ash cooling air pipeline; 3. a slag well; 4. a grate; 5. a biomass fuel feeding device; 6. a secondary air duct; 7. a boiler body; 8. denitration equipment; 9. a water cooled wall; 10. a first superheater; 11. a cyclone separator; 12. a recirculation return fan; 13. a second superheater; 14. a coal economizer; 15. an air preheater; 16. ash removal equipment; 17. a blower; 18. an induced draft fan; 19. a tail gas treatment system.
Detailed Description
In order to make the purpose, technical effect and technical solution of the embodiments of the present invention clearer, the following clearly and completely describes the technical solution of the embodiments of the present invention with reference to the drawings in the embodiments of the present invention; it is to be understood that the described embodiments are only some of the embodiments of the present invention. Other embodiments, which can be derived by one of ordinary skill in the art from the disclosed embodiments without inventive faculty, are intended to be within the scope of the invention.
Referring to fig. 1, a slag burnout system of a biomass boiler according to an embodiment of the present invention is used for enhanced burnout of ash, taking a biomass grate boiler as an example (also applicable to a fluidized bed furnace), and includes: the functional optimization module comprises a cyclone separator 11, a recycling material returning fan 12, a boiler body 7 with a double-necking structure and the like; simultaneously, still include: the device comprises a blower 17, a slag well 3, slag treatment equipment, biomass fuel feeding equipment 5, a primary air pipeline 1, a secondary air pipeline 6, a grate 4, a second superheater 13, an economizer 14, ash removal equipment 16, a tail gas treatment system 19, denitration equipment and other general devices.
Wherein, the biomass fuel feeding device 5 is positioned on the left wall of the boiler, above the starting end of the fire grate 4 and at the height position equivalent to the secondary air pipeline 6. The primary air pipeline 1 and the secondary air pipeline 6 are both communicated with the outlet of the air preheater 15, and the inlet of the air preheater 15 is communicated with the blower 17. The slag well 3 is arranged at the tail end of the grate 4 and the bottom of the slag well is lower than the bottom of the hearth. The water-cooled wall 9 is arranged in the hearth, and the plurality of first superheaters 10 and the plurality of second superheaters 13 are respectively and sequentially arranged in the hearth and the flue gas pipeline of the boiler body 7; the economizer 14 is arranged after the second superheater 13; the economizer 14 is connected to an ash removal device 16 and is sent to a tail gas treatment system 19 by an induced draft fan 17 to be discharged.
In the embodiment of the invention, the cyclone separator 11 is provided with an inlet, an air outlet and a slag hole, the inlet is connected with a flue gas outlet channel at the top of the right wall of the hearth of the boiler body 7, the air outlet is communicated with a flue gas channel going to the superheater, and the slag hole is communicated with a return material pipeline and a recirculation return material fan 12.
In the embodiment of the invention, the initial section of the material returning pipeline is U-shaped, and the middle of the material returning pipeline is connected with the air outlet of the recirculation material returning fan 12.
Preferably, the inlet of the recirculation material returning fan 12 is connected with a flue between the economizer 14 and the air preheater 15, and the flue gas extracted from the flue is sent to the initial section of the material returning pipe to be mixed with ash and slag materials, so that ignition in the material returning pipe is avoided; the outlet at the tail end of the return material pipeline is communicated to the hearth from the upper part of the secondary air pipeline 6 on the right wall of the furnace, and the pipeline direction is parallel to the hearth inclined plane direction of the first throat structure above the secondary air pipeline 6.
In the embodiment of the invention, the type of the boiler hearth body is adjusted and modified on the basis of the hearth type of the existing biomass furnace: a second throat, as shown in figure 1, is provided at an intermediate location above the boiler fuel feed means and below the superheaters in the furnace.
Preferably, the whole height of the furnace is increased by 3-4 m relative to the original furnace.
Preferably, the width of the inner section of the hearth of the second necking structure is between 1/2 and 2/3 of the maximum width in the hearth.
Preferably, the denitration device 8 is an SNCR (selective non-catalytic reduction) device, and the lance is arranged at the second throat structure position of the furnace. The temperature space range of the common grate boiler suitable for SNCR denitration is narrower than that of a pulverized coal boiler, the most suitable temperature is 950 ℃, the ideal temperature is 850-1150 ℃, and the denitration retention time is 0.5 s. Therefore, the SNCR device is arranged at the necking part, and more uniform treatment agent mixing can be provided compared with the conventional equipment so as to ensure that the NOx reduction reaction is sufficient, thereby remarkably reducing the NOx emission of the boiler.
Preferably, a slag collecting and conveying device is arranged at an outlet below the slag well 3, a discharger with rotating blades is arranged in front of the outlet and used for grinding slag, the slag falls smoothly and is not blocked, and the slag falls to a collecting tank and is conveyed for further treatment. Meanwhile, the side surface of the slag well 3 is connected with the outlet of the ash cooling air pipeline 2; the ash cooling air duct 2 communicates with a valve or the like in communication with a bypass at the outlet of the blower 17 without passing through the air preheater 15.
Preferably, the wind speed of the cooling wind rising in the slag well 3 should satisfy: if the slag can be settled except a very small amount of ash, the particles corresponding to the slag with the particle size of less than or equal to 1mm are required to be suspended, namely, the particle suspension speed is calculated to be about 12m/s according to the physical conditions of inequality (1) and corresponding Stokes formula (2) according to the parameters of density 2700kg/m3, particle size 1mm, airflow density 1.185kg/m3 and dynamic viscosity 1.835 x 10-5 Pa-s (air temperature of 25 ℃). Therefore, the wind speed should not be lower than 12m/s, and the wind quantity should not exceed 10% of the total wind quantity.
The working principle of the system of the embodiment of the invention is as follows:
the biomass furnace fuel is fed by the feeder, and along with the movement and combustion of the fire grate, the air is fed into the air preheater by the air feeder, then fed into the hearth of the boiler body from the lower part of the fire grate through the primary air pipeline, and blown upwards to the fire grate and the fuel by a plurality of strands at the bottom; the secondary air pipeline of the furnace wall provides an upper secondary air and a lower secondary air for burning out fuel; after the smoke in the hearth rises to the second throat structure at the middle upper part of the hearth body, NOx is removed by using SNCR equipment, the smoke flows out of the hearth and enters a cyclone separator, and larger particle ash and slag are settled and flow out of the bottom of the cyclone separator and are mixed and fluidized with the smoke extracted by a recirculation fan, so that ignition in a material returning pipe is avoided; the fluidized return air is returned to the hearth again, is circulated for many times to strengthen burnout, and simultaneously provides a reducing atmosphere for the hearth, thereby being beneficial to inhibiting the generation of NOx in the furnace; in addition, the outlet of the air feeder is connected with an ash cooling air pipeline through a bypass, and the ash cooling air pipeline is communicated to the side surface of the slag well, the air speed and the air volume of the ash cooling air are controlled by the valve, the air speed is not less than the suspension speed of the ash with the particle size of 1mm, namely 12m/s, the sedimentation of the slag is reduced, the retention time of unburned fuel above the slag well is prolonged, the sensible heat of the cooling air is absorbed and utilized, the thermal efficiency of the boiler is improved, and the carbon content of the ash is reduced so as to enhance the burn-out; in addition, the air flow raised by the cooling air and the return air are merged near a throat of a secondary air inlet on the right wall of the furnace to form air flow standing vortex, so that turbulent mixing is further enhanced, the residence time of fuel is increased, the complete combustion is promoted to reduce the total amount of ash slag, and finally the residual slag is crushed by a discharger and falls into a collecting and conveying device at the bottom of a slag well; the flue gas flows through the water-cooled wall in the hearth and the heating surfaces of a high-temperature superheater (a first superheater), leaves from the air outlet of the cyclone separator, sequentially flows through a second superheater and an economizer, and the residual fly ash of the flue gas is treated and collected by ash removal equipment 16. And finally, conveying the flue gas to a tail gas treatment system through a draught fan and exhausting the flue gas to the atmosphere.
According to the principle of fluid mechanics, when jet flow bypasses significant necking and bluff bodies, a deceleration diffusion flow area is formed in a downstream flow field, boundary layer separation occurs in a wake area due to the retarding effect of necking to form a low-pressure area, a backflow vortex area is formed in the wake area under the action of a counter-pressure gradient, and strong momentum, heat and mass exchange is carried out between the backflow area and a main flow area. The recirculated flue gas and the SNCR reducing agent carry out strong momentum, heat and mass exchange, show and promote the mixing effect, impel the inside concentration field of combustor, temperature field more even, improved the degree of going on of denitration reduction reaction to avoid appearing local high oxygen high-temperature region in the flame zone, reduce the formation of thermal type NOx.
Preferably, each circulating flue gas, air conveying and ash cooling air pipeline is provided with a valve, so that the circulating flue gas quantity and the air quantity can be conveniently adjusted according to needs.
The characteristics of biomass fuel and boiler types are considered in the arrangement of the SNCR spray guns, the actual operation data parameters are considered, the arrangement positions, the number and the intervals of the spray guns are determined according to the spray angles and the spray ranges of the spray guns, a temperature window is searched, and a proper ammonia nitrogen ratio is selected.
According to the biomass boiler ash burnout system provided by the embodiment of the invention, the ash particle recycling module is formed through the cyclone separator, the recycling material returning fan and the material returning pipe, so that the external circulation of the ash is realized, the fly ash which is unburned and has high carbon content and leaves the hearth can be circularly sent back to the hearth for combustion, the total amount of the ash and the ash in the tail flue are reduced, the amount of the ash in the hearth is increased, the coking corrosion problem of the tail flue is favorably reduced, and the burnout and collecting treatment efficiency of the ash are improved. The ash cooling air pipe and the inclined plane above the hearth slag well and the hearth throat at the position of the secondary air form a slag sensible heat recovery module together, and the upward ash cooling air is provided for the fuel in the furnace and the slag fed back by the cyclone separator, so that the sedimentation of the ash can be reduced, the ash with extremely small particle size and higher carbon content can be lifted, the retention time is prolonged, the unburned carbon in the ash can be fully utilized, and the burn-off of the ash is enhanced; the temperature of the ash cooling air is low, so that the sensible heat of the slag can be absorbed, and the heat efficiency of the boiler can be improved; and the downward return air and the upward cooling air are converged near the throat where the secondary air of the furnace wall is positioned to generate standing vortex of air flow, so that internal circulation of furnace slag is formed, ignition and mixing are further enhanced, the economical efficiency is more excellent, and the total amount of boiler ash and carbon content of the ash are further reduced. Through the second necking of the hearth arranged above the fuel feeding equipment and below the superheater, the disturbance and the sufficient mixing of the flue gas in the upper part of the hearth, namely the heating surface area, are increased, the retention time is prolonged, the incomplete combustion loss of the biomass fuel is further reduced, and a more uniform temperature concentration field is provided. The temperature space range of the common grate boiler suitable for SNCR denitration is narrower than that of a pulverized coal boiler, the most suitable temperature is 950 ℃, the ideal temperature is 850-1150 ℃, and the denitration retention time is 0.5 s. Therefore, the SNCR device is arranged at the necking part, and more uniform treatment agent mixing can be provided compared with the conventional equipment so as to ensure that the NOx reduction reaction is sufficient, thereby remarkably reducing the NOx emission of the boiler.
In another aspect, an embodiment of the present invention provides a method for operating the above system to enhance burnout of biomass ash and reduce NOx emission, including the following steps:
the fuel feeding equipment and the primary air pipe send the biomass fuel and the primary air into the biomass furnace, the falling slag is collected and conveyed after passing through the slag well at the tail end, and meanwhile, ash cooling is applied from the side surface of the slag well, the wind speed of the ash cooling air is kept to be not less than 12m/s, and the wind volume is not more than 10% of the total wind volume. Most of slag with the particle size of more than 1mm can be settled and settled slowly at last, and ultrafine particles can rise along with airflow, so that ash cooling air is heated by utilizing waste heat of hot slag, and the longer retention time and the burn-out rate of fuel in the furnace are ensured;
meanwhile, the cyclone separator separates and collects ash of larger particles in the flue, smoke is extracted from the flue in front of the air preheater to serve as return material fluidized air to be mixed with the return material fluidized air, and then the return material fluidized air is sent back to the hearth along the direction of the inclined plane above the secondary air of the right furnace wall, so that the retention time and the burnout of slag materials are further increased.
In addition, because the proper temperature space range of the biomass boiler is narrower than that of the pulverized coal furnace, a second necking of the hearth is additionally arranged, and the SNCR denitration device is operated to ensure more sufficient mixing and more proper temperature space conditions, thereby promoting the reduction of nitrogen oxides in the furnace. After passing through the multi-stage superheater and the economizer, the dust removal equipment removes the remaining ash particles, and the ash particles are discharged to the atmosphere by a tail gas treatment device such as a draught fan and a chimney.
In conclusion, aiming at the problems that the biomass boiler has low fuel burn-out rate, large ash amount and is dispersed in a boiler hearth and a flue, the boiler has low thermal efficiency and serious ash deposition corrosion and the problem that the emission of the boiler nitrogen oxides is difficult to reach the standard along with the increasing strictness of the NOx emission standard, the invention provides a system and a method for strengthening burn-out and energy saving of the ash of a new biomass boiler, and the heat energy utilization efficiency and the ash recycling rate of the boiler are improved; according to the invention, ash and slag are circulated outside the hearth through cyclone separation and recirculated flue gas return, and the internal circulation of the hearth of slag fuel is realized through the upward ash and slag cooling air and return air of a slag well and airflow vortex forming a first necking of a furnace wall, so that the ash and slag burnout rate is increased, and the problem of flue slagging is solved; and provides reducing atmosphere for the boiler to inhibit the generation of nitrogen oxides; and through adding the second throat of the hearth, the flue gas denitration of the biomass boiler is effectively realized by matching with the SNCR equipment, the required equipment is less, the modification amount is small, the cost is lower, and the economical efficiency and the environmental protection performance are excellent.
Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can make modifications and equivalents to the embodiments of the present invention without departing from the spirit and scope of the present invention, which is set forth in the claims of the present application.
Claims (10)
1. A slag burnout system of a biomass boiler, comprising:
the boiler comprises a boiler body (7), wherein the boiler body (7) is provided with a feeding hole, a slag well (3) and an exhaust hole; a water-cooled wall (9) and a first superheater (10) are arranged in the boiler body (7); the boiler body (7) is of a double-throat configuration, comprising: a first throat structure and a second throat structure; the first necking structure is arranged below the second necking structure;
the cyclone separator (11), the said cyclone separator (11) has inlets, air outlets and slag outlets; the inlet of the cyclone separator (11) is communicated with the exhaust port of the boiler body (7); a slag outlet of the cyclone separator (11) is communicated with a first throat structure in a hearth of the boiler body (7) through a return material pipeline; the material returning pipeline is provided with a recirculation material returning fan (12); the gas outlet of the cyclone separator (11) is communicated with a flue gas pipeline, and a second superheater (13), an economizer (14) and an air preheater (15) are sequentially arranged in the flue gas pipeline along the flow direction of flue gas;
the inlet of the air preheater (15) is communicated with a blower (17) through a blower pipeline; the outlet of the air preheater (15) is communicated with a primary air pipeline (1) and a secondary air pipeline (6); wherein the outlet of the primary air pipeline (1) is positioned below the feed inlet of the boiler body (7); the outlet of the secondary air pipeline (6) is positioned at the first necking structure;
an inlet of the ash cooling air pipeline (2) is arranged on the air supply pipeline, and an outlet of the ash cooling air pipeline (2) is arranged at a slag well (3) of the boiler body (7);
and the spray gun of the denitration device (8) is arranged at the second necking structure.
2. The slag burnout system of a biomass boiler according to claim 1, characterized in that the air inlet of the recirculation material returning fan (12) is communicated with the flue gas pipeline between the economizer (14) and the air preheater (15);
the initial section of the material returning pipeline is U-shaped, and the middle part of the material returning pipeline is communicated with an air outlet of the recycling material returning fan (12).
3. The slag burnout system of a biomass boiler according to claim 1, wherein the width of the inner cross section of the furnace of the second throat structure is 1/2-2/3 of the maximum width in the furnace of the boiler body.
4. The slag burnout system of a biomass boiler according to claim 1, further comprising:
the biomass fuel feeding device (5), the discharge hole of the biomass fuel feeding device (5) is communicated with the feed inlet of the boiler body (7).
5. The slag burnout system of a biomass boiler according to claim 1, characterized in that the outlet of the flue gas pipeline is further provided with an ash removal device (16) and a tail gas treatment system (19);
wherein, the flue gas of the flue gas pipeline is introduced into a tail gas treatment system (19) through an induced draft fan (18).
6. The slag burnout system of a biomass boiler according to claim 1, characterized in that the outlet of the return duct is above the outlet of the secondary air duct (6); the pipeline direction of the return pipeline is parallel to the inclined plane direction of the upper hearth of the first throat structure.
7. The slag burnout system of a biomass boiler according to claim 1, wherein the ash cooling air pipeline (2) is provided with a valve for controlling the air speed and the air volume of the ash cooling air; wherein the wind speed is more than 12m/s, and the wind volume is less than 10% of the total wind volume.
8. The slag burnout system of the biomass boiler according to claim 1, characterized in that a discharger is further arranged at the slag well (3) of the boiler body (7);
the discharger is provided with rotating blades for grinding the slag.
9. The slag burnout system of a biomass boiler according to claim 1, characterized in that a slag collecting and conveying device is further arranged below the slag well (3) of the boiler body (7).
10. The slag burnout method of the biomass boiler is characterized by comprising the following steps based on the system of claim 1:
biomass fuel and primary air are sent into a hearth of a boiler body (7);
the cyclone separator (11) separates and collects ash particles discharged from an exhaust port of the boiler body (7), and the ash particles are mixed and fluidized through a material returning pipeline and a recycling material returning fan (12) and are returned to the hearth; wherein, the feeding is carried out at the first necking structure;
the slag well (3) of the boiler body (7) is used for collecting falling slag in the hearth, and upward ash cooling air is kept in the slag well (3) to slow down slag settlement or make part of ash rise along with air flow;
denitration treatment is carried out on the hearth flue gas through denitration equipment (8) arranged at the second necking structure.
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| CN202010963836.7A CN111981473A (en) | 2020-09-14 | 2020-09-14 | Slag burnout system and method of biomass boiler |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112610951A (en) * | 2020-12-17 | 2021-04-06 | 烟台市红森林节能环保科技有限公司 | Multipurpose fluidized bed type fluidized bed furnace and system with fully reduced atmosphere |
| CN114738725A (en) * | 2022-05-06 | 2022-07-12 | 西安交通大学 | Coal-based solid waste preheating direct combustion and waste heat gradient utilization system and operation method |
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