CN104949149A - Rotary air preheater dust-blocking-prevention synergy sealing method and system - Google Patents
Rotary air preheater dust-blocking-prevention synergy sealing method and system Download PDFInfo
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- CN104949149A CN104949149A CN201510369487.5A CN201510369487A CN104949149A CN 104949149 A CN104949149 A CN 104949149A CN 201510369487 A CN201510369487 A CN 201510369487A CN 104949149 A CN104949149 A CN 104949149A
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E20/00—Combustion technologies with mitigation potential
- Y02E20/34—Indirect CO2mitigation, i.e. by acting on non CO2directly related matters of the process, e.g. pre-heating or heat recovery
Abstract
The invention discloses a rotary air preheater dust-blocking-prevention synergy sealing method and system. The dust-blocking-prevention synergy sealing method includes the steps that air leaked from the heat end is guided or extracted to the cold end from the heat end, and local heat exchange elements are purged and heated. The rotary air preheater dust-blocking-prevention synergy sealing system comprises a heat end primary air/smoke side sector sealing box, a heat end primary air/secondary air side sector sealing box and a cold end secondary air/smoke side sector sealing box, and further comprises a heat air leakage air flue; the heat end primary air/smoke side sector sealing box and the heat end primary air/secondary air side sector sealing box are each provided with an air inlet, one end of the heat air leakage air flue is in butt joint with the air inlets, and the other end of the heat air leakage air flue extends to a cold end secondary air highest-temperature module. By means of the rotary air preheater dust-blocking-prevention synergy sealing method and system, H2SO4 drops and liquid state NH4HSO4 are gasified while the air leaked from a preheater is reduced, and the aim of removing accumulated dust is achieved; the rotary air preheater dust-blocking-prevention synergy sealing method and system have the advantages of reducing the boiler smoke discharging temperature, restraining the accumulated dust of the preheater, reducing the air leakage rate, prolonging the service life of the heat exchange elements and the like.
Description
Technical field
The present invention relates to method and system thereof that the anti-blocking ash of a kind of rotary regenerative air preheater works in coordination with sealing, belong to air preheater accumulatingdust and air pre-heater sealing field.
Background technology
Rotary regenerative air preheater (be called for short " preheater ") is a kind of heat-exchange apparatus for large-sized station boiler, the air that it utilizes the heat of boiler smoke to come needed for heating flame, improves the efficiency of boiler with this.
The focal issue that preheater is paid close attention to mainly comprises stifled ash, air leak rate of air curtain is higher, heat transfer efficiency is low, cold end corrosion is serious, and these problems affect safety and the economical operation of equipment for a long time.
The problems referred to above are long-standing, and mutually promote, influence each other.In recent years, along with generally putting into operation of denitrating system, preheater running environment changes, and the problems referred to above are particularly outstanding, administers more difficult and complicated.
The denitrating flue gas facility that current coal-burning power plant sets up is mainly based on SCR (SCR) technology.After adopting SCR denitration technique, the part SO in flue gas
2sO will be oxidized to by denitrating catalyst
3, add SO in flue gas
3volumetric concentration, there is inevitable the escaping of ammonia phenomenon in addition, cause ammonium hydrogen sulfate (NH
4hSO
4) etc. a large amount of generations of accessory substance, and improve flue gas acid dew point temperature, cause cold end corrosion to aggravate.
Above-mentioned accessory substance ammonium hydrogen sulfate (NH
4hSO
4) be within the scope of 146 ~ 207 DEG C in temperature, in molten, air preheater heat exchange element surface can be tightly adhered to, make heat exchange element that corrosion and dust stratification occur, finally may cause stifled ash, cause very big hidden danger to the safe operation of unit.Domestic existing part power plant causes unit limited load, even by forced-stopping machine because solving or alleviate this problem.
When exhaust gas temperature is lower than acid dew point, sulfuric acid vapor will condense, and sulfuric acid droplets is attached on cold junction heat exchange element, corrosion heat exchange element.The acid dew point of flue gas is along with SO
3the rising of concentration and improving, generally reaches 130 ~ 160 DEG C.Because denitrating system adds SO
2to SO
3conversion ratio, namely improve SO in flue gas
3concentration, therefore at present the acid dew point of many power plant, generally higher than exhaust gas temperature, causes cold end corrosion (acid dew piont corrosion) to aggravate.
According to the temperature range that above-mentioned ammonium hydrogen sulfate deposition and sulfuric acid vapor are condensed, cold end corrosion generally occurs in the low-temperature zone region of heat exchange element, and ammonium hydrogen sulfate deposition generally occurs in the middle low-temperature zone region of heat exchange element, the band of position degree of overlapping that both generate is less, the most of region of ammonium hydrogen sulfate drop all on sulfuric acid droplets of generation.
Preheater is generally equipped with online steam soot blowing and the problems referred to above are dealt with in water flushing, and namely two medium blows ash, to reaching the object preventing from blocking.The general each operation class (8 hours) of online steam soot blowing is put into operation once, puts into operation 1 ~ 4 hour time at every turn; And water flushing is generally carried out under stopped status; The safe operation of online high pressure water washing to unit causes certain threat, and domestic only small part power plant attempts using, and can not ensure developing result.Operative practice shows, two medium blows ash can not reach good ash-removal effect, can not ensure the safe operation of equipment.Trace it to its cause, no matter be that online steam soot blowing or water rinse, be intermittent duty, and when flying dust sticks to heat exchange element surface because of ammonium hydrogen sulfate deposition or cold end corrosion, if clear up not in time, a large amount of dust stratifications can form lump, is difficult to remove.In addition, online steam soot blowing not only consumes a large amount of high-quality steam, causes energy loss, and unfavorable to the operation of the equipment such as the bag-type dust of device downstream, causes the resistance of dust-removal cloth-bag sharply to rise as steam parameter controls improper meeting.
The measure of conventional reply cold end corrosion also comprises to be installed steam air heater additional or adopts thermal wind sensor system, but these two kinds of technical schemes are all what to sacrifice the utilization rate of air preheater be cost, reduce the heat exchange property of preheater, cause exhaust gas temperature to raise, flue gas loss increases.And in fact, some power plant adopt above-mentioned two schemes also to fail to play the effect obviously alleviating cold end corrosion.
Although above-mentioned steam air heater technology has reclaimed partial heat, can offset the flue gas loss of part increase, but there is the problem such as fouling of heating surface, the increase of burn into resistance in longtime running.This technology only can tackle acid dew piont corrosion problem, there is no obvious benefit to alleviation or solution ammonium hydrogen sulfate deposition problems.
In addition, according to research, above-mentioned thermal wind sensor technology can alleviate cold end corrosion problem, but deposit preventing ammonium hydrogen sulfate and also there is no benefit, the ammonium hydrogen sulfate string of deposits can be made on the contrary to offset toward preheater top, closer to the most interlude of heat exchange element, and then cause steam soot blowing poor effect, increase the probability of preheater blocking.
The increasingly stringent required along with Chinese environmental protection and the reinforcement of law enforcement dynamics, the problem of flue gas NOx discharge is more and more subject to the attention of national environmental protection department and the public.Company of current Ge great electricity power group is carrying out the demonstration improvement project of large electric power plant coal-burning boiler minimum discharge, is reduced to 50mg/Nm with flue gas NOx concentration of emission
3it is below target.In order to realize above-mentioned target; major part power plant can only be forced to the technical measures taking to increase ammonia spraying amount; but this will cause amount of ammonia slip to strengthen; the cold end corrosion of aggravation air preheater and blockage problem; air preheater resistance is caused sharply to rise; and then cause boiler limited load even by forced-stopping machine, the serious threat safe operation of unit.
Except environmental requirement increasingly stringent can impel the cold end corrosion of air preheater and stifled grey problem aggravation, the expire denitration efficiency that causes of the catalyst life of assaulting the SCR system started in recent years declines, also ammonia spraying amount can be caused to increase, and then amount of ammonia slip is difficult to control within scope of design, the cold end corrosion of aggravation air preheater and blockage problem.Therefore, can predict, the cold end corrosion of following air preheater and blockage problem, by ubiquity, become a great problem of each high-power station.
Above-mentioned cold end corrosion and blockage problem make the heat transfer coefficient of heat exchange element decline to a great extent, and then exhaust gas temperature is significantly raised; And increase the pressure reduction of air preheater flue gas and air side, cause air leak rate of air preheater to rise.Increase owing to leaking out and reduce further again heat exchange element wall temperature, cold end corrosion and blockage problem aggravation can be impelled conversely.Data shows, and for 600MW grade unit, preheater air leak rate of air curtain often increases by 1%, and gross coal consumption rate increases 0.20g/kWh, station service power consumption rate increase about 0.1 ‰; Exhaust gas temperature often reduces by 1 DEG C, and net coal consumption rate declines about 0.166g/kWh.Therefore, the comprehensive regulation is leaked out, the problems such as ash, corrosion of blocking up can yet be regarded as a kind of effective means significantly improving preheater performance.
Summary of the invention
In order to the defect such as solve stifled ash that preheater in prior art exists, air leak rate of air curtain is higher, heat transfer efficiency is low, cold end corrosion is serious, the invention provides method and system thereof that the anti-blocking ash of a kind of rotary regenerative air preheater works in coordination with sealing.The present invention is particularly useful for tradition three points of storehouse air preheaters, set up localized hyperthermia and high-flow area therein in essence, from a point storehouse quantity, owing to adds additional a subregion, the air preheater of technical solution of the present invention is adopted to be defined as a kind of 3.5 points of storehouse air preheaters.
For solving the problems of the technologies described above, the technical solution adopted in the present invention is as follows:
The anti-blocking ash of rotary regenerative air preheater works in coordination with a method for sealing, guides or extracts hot junction and leak out to cold junction, purge and heat Local Heat Transfer element from hot junction.
Adopt said method, while reduction preheater leaks out, gasified H
2sO
4and NH
4hSO
4drop, reaches the object removing dust stratification.
Such scheme is easy to implement, is not only applicable to the supporting of new preheater, and is applicable to the transformation of active service preheater, has remarkable results such as reducing exhaust gas temperature, suppression dust stratification, reduction air leak rate of air curtain, prolongation heat exchange element life-span.
The application mainly comprises three parts toward leaking out of fume side: First air leaks out to carrying of fume side to directly the leaking out of fume side, Secondary Air to directly the leaking out of fume side, First air.Above-mentioned size of leaking out determines the air leak rate of air curtain index of this preheater jointly, but to the index of leaking out of thoroughly evaluating preheater, First air also can not be ignored to directly leaking out of Secondary Air.
Preferably, utilize hot junction to leak out and heat cold junction Secondary Air highest temperature module; Wherein, leak out and at least comprise heat primary air and leak out in hot junction, First air directly the leaking out and First air directly leaking out to Secondary Air to fume side namely drawn from hot junction fanning strip or extract; Cold junction Secondary Air highest temperature module refers to the module that in Secondary Air sector, temperature levels is the highest, next-door neighbour's Secondary Air/fume side fanning strip.
Said method is washed away by flying dust and keeps the clean of heat exchange element with the acting in conjunction of high-temperature gasification, adopts the means of " treatment of wastes with processes of wastes against one another " to prevent the stifled ash of preheater.
Heat exchange element in cold junction Secondary Air highest temperature module just absorbs heat from fume side, and then air side heat release is arrived, therefore in this module, the mean temperature of heat exchange element is the highest, now, the heat primary air introducing about 300 DEG C from cold junction leaks out, continue to purge the heat exchange element in this module, significantly improve the wall temperature of this module cold junction heat exchange element, reach gasification H
2sO
4drop and liquid NH
4hSO
4object, avoid dust stratification to aggravate.
The said method anti-blocking ash of rotary regenerative air preheater used works in coordination with sealing system, comprise the fan-shaped seal box of hot junction First air/fume side, hot junction First air/fan-shaped seal box in Secondary Air side and the fan-shaped seal box of cold junction Secondary Air/fume side, also comprise heat leak wind air channel, the fan-shaped seal box of hot junction First air/fume side and hot junction First air/fan-shaped seal box in Secondary Air side all offer air inlet, one end, heat leak wind air channel is docked with air inlet, and the other end extends to cold junction Secondary Air highest temperature module.
Above-mentioned air inlet runs through the upper bottom surface of fan-shaped seal box, is namely equipped with through hole at the upper bottom surface of fan-shaped seal box.The bottom surface of the fan-shaped seal box of the application refers to the one side being close to rotor, is also the fanning strip that the application mentions.
In order to avoid above-mentioned heat primary air to leak out and cold secondary air flow mixing as far as possible, preferably, the seal form of rotary regenerative air preheater is double sealing structure; Splice in the Secondary Air side of the fan-shaped seal box of cold junction Secondary Air/fume side fan-shaped bellows, the fanning strip of fan-shaped bellows and the fan-shaped seal box of cold junction Secondary Air/fume side forms local three hermetically-sealed constructions; Wherein, the fanning strip of the fan-shaped seal box of cold junction Secondary Air/fume side refers to the one side fan-shaped seal box of cold junction Secondary Air/fume side being close to rotor; Fan-shaped bellows are the body structure that side is provided with air outlet, and air outlet is located on the side of the fan-shaped bellows between the fan-shaped seal box of cold junction Secondary Air/fume side and fan-shaped bellows; One end, heat leak wind air channel is docked with air inlet, and the other end extends in fan-shaped bellows, and heat is once leaked out and to be entered in fan-shaped bellows by the guiding in heat leak wind air channel, then from air outlet discharging jet to cold junction Secondary Air highest temperature module.
Above by heat leak wind air channel, heat primary air is guided to leak out to the fan-shaped bellows of cold junction Secondary Air/fume side fanning strip side.Above-mentioned air inducing process can not need extra power (as blower fan etc.) to drive, the neous flow utilizing the pressure reduction of First air and Secondary Air can realize heat primary air to leak out.
A few hermetically-sealed construction of the application refers to correspondence at least several diaphragm seals in the course of work, namely double containment is correspondence at least two panels diaphragm seal, three hermetically-sealed constructions are correspondence at least three diaphragm seals, and namely above-mentioned three hermetically-sealed constructions are correspondence at least correspondence at least a slice diaphragm seal on two panels diaphragm seal, fan-shaped bellows on fanning strip.
Leak out from the heat primary air of fan-shaped bellows air outlet ejection and to be intercepted by diaphragm seal corresponding fan-shaped bellows, directly can not contact with cold Secondary Air, so most heat primary air is leaked out can only by Secondary Air highest temperature module.
It should be noted that, above-mentioned heat primary air leaks out can not all by Secondary Air highest temperature module, also have sub-fraction can leak from the seal clearance cool and heat ends Secondary Air/fume side fanning strip, first leak to the module be close to Secondary Air highest temperature module below this fanning strip, be defined as time high temperature module.Carry the high-temperature flue gas of mean temperature about 250 DEG C in secondary high temperature module, the heat primary air that leakage is come in leaks out and mixes with it, can maintain the temperature levels that this sector is higher, also can play gasification H
2sO
4drop and liquid NH
4hSO
4effect.Therefore, heat primary air leak out in fact at least two modules heat exchanging element carry out purging and heating.
Also it should be noted that, the mist that high-temperature flue gas in above-mentioned high temperature module and heat primary air leak out, still can leak to low-pressure side (fume side) further, leaking out of final generation essence, but because pressure reduction is less, in mist containing about air capacity only half, this part ratio accounting for share of always leaking out of leaking out is less, and therefore the economic influence of leakage to preheater at this place is less.
When heat primary air leaks out and flows through heat exchange element, temperature is higher, gasification H
2sO
4drop and liquid NH
4hSO
4effect better.Data shows, the H under preheater environment
2sO
4steam acid dew point is mostly between 130 ~ 160 DEG C, and NH
4hSO
4be liquid within the scope of 146 ~ 207 DEG C.Therefore, to reach preferably gasification result, heat primary air leaks out in the process flowing through heat exchange element, can not be cooled to less than 207 DEG C, and this just requires that heat primary air leaks out and ensures certain flow or initial temperature.
Preferably, the heat leak wind air channel between in air inlet and fan-shaped bellows is provided with takes out the blower fan that leaks out.
Preheater air leak rate of air curtain can be reduced further like this, and allow more heat primary air leak out degassing H
2sO
4drop and liquid NH
4hSO
4.
In order to provide a kind of heat primary air that regulates to leak out the method for flow, preferably, the heat leak wind air channel between the air inlet of the fan-shaped seal box of hot junction First air/fume side and fan-shaped bellows is provided with takes out the blower fan that leaks out.
Easy to maintenance in order to make to take out the blower fan that leaks out, and the flexibility keeping heat primary air to regulate, preferably, the two ends of taking out the blower fan that leaks out are parallel with bypass air channel.Like this when taking out the blower fan that leaks out and being out of service, part heat primary air leaks out and flow to Secondary Air cold junction through bypass air channel.
The heat leak wind air channel of taking out the fans entrance that leaks out is provided with takes out the fans entrance air duct isolation door that leaks out, and bypass air channel is provided with bypass air duct isolation door.When take out leak out fans entrance air duct isolation door close, bypass air duct isolation door open time, take out the blower fan that leaks out do not allow run, now heat primary air leaks out and spontaneously flow to cold junction Secondary Air side by bypass air channel; When bypass air duct isolation door close, take out the fans entrance air duct isolation door that leaks out open time, open and take out the blower fan that leaks out, now have more substantial heat primary air and leak out and flow to cold junction Secondary Air side; When two isolation doors are all opened, operation is not allowed to take out the blower fan that leaks out, otherwise blower fan short circuit, can energy waste be caused, and also there is no necessity that two isolation doors are all opened in any case; When two isolation doors are all closed, First air can not flow to cold junction Secondary Air side to leaking out of fume side, and components of system as directed is out of service.
The heat leak wind air channel of hot junction First air/between the fan-shaped seal box in Secondary Air side and fan-shaped bellows is provided with First air to Secondary Air isolation door.When only this isolation door is closed, components of system as directed is out of service.
When above-mentioned three isolation doors are all closed, system is completely out of service.
The every platform unit in general power plant arranges two preheaters, to leak out the adjustment allowance of flow to increase heat primary air further, the heat primary air of an adjacent preheater leaks out and can partly or entirely cause another preheater, switched in turn by flow divider valve, every platform preheater intermittent duty said system.
In order to reduce the crushing near air inlet as far as possible, preferably, leaking out from the heat primary air of hot junction First air/fume side fan-shaped seal box extraction is be collected to heat leak wind air channel by plural arm, then flows to cold junction Secondary Air highest temperature module.
In order to more efficiently heat heat exchange element, to ensure better gasification H
2sO
4and NH
4hSO
4effect, preferably, Secondary Air/fume side fan-shaped seal box in hot junction is also provided with air inlet, and leaking out from the heat primary air of hot junction Secondary Air/fume side fan-shaped seal box extraction is be collected to heat leak wind air channel by plural arm, then flows to cold junction Secondary Air highest temperature module.
With set up compared with duct insert heater, below hot junction Secondary Air/fume side fanning strip, extract the heat primary air heated further through heat exchange element leak out and seem more economical and safer.The design of leaking out of taking out at hot junction Secondary Air/fume side fanning strip place leaks out design class seemingly with hot junction First air/taking out of fume side fanning strip place.In fact, this design allows heat primary air leak out recirculation, increases air quantity, improves wind-warm syndrome, to reach the object of better removing heat exchange element dust stratification.
Arm is provided with arm isolation door.All arms being equipped with isolation door, being closed and opening operation by the isolation door of various combination, wind-warm syndrome that the heat primary air through taking out the blower fan that leaks out leaks out and dust content can being controlled easily.Close the isolation door of arm above more First air/fume side fanning strip, and open the isolation door of arm above Secondary Air/fume side fanning strip, wind-warm syndrome and dust content that heat primary air leaks out can be improved.
It should be added that, the above-mentioned heat primary air be actually after the heating of Secondary Air highest temperature module that leaks out extracted below hot junction Secondary Air/fume side fanning strip leaks out and the mist (causing because rotor carries flue gas) of high-temperature flue gas, and mean temperature is close to the temperature of pre-heater inlet flue gas.In addition, extract the air leak rate of air curtain that above-mentioned mist is also conducive to reducing further preheater, be expected to make the air leak rate of air curtain of preheater to be down to less than 2%.Therefore, extracting the mist below Secondary Air/fume side fanning strip, is a kind of more satisfactory selection, the high-temperature gas mixture body reclaimed can air blower of compensating energy consumption, the wind-warm syndrome that heat primary air leaks out can be improved again, and improve dust concentration, play and remove dust stratification effect more significantly.
In order to the clean of heat exchange element can be kept further, preferably, air inlet on hot junction First air/fume side fanning strip and hot junction First air/Secondary Air side fanning strip is the fan-shaped mouth along preheater rotor radial, and fan-shaped air inlet angle is 1 ~ 3 °, is arranged in the middle of fanning strip; Hot junction First air/fume side fanning strip and hot junction First air/Secondary Air side fanning strip refer to the one side fan-shaped seal box of hot junction First air/fume side and hot junction First air/fan-shaped seal box in Secondary Air side being close to rotor respectively.
The above-mentioned fanning strip be arranged in the middle of fanning strip comprises hot junction First air/fume side fanning strip and hot junction First air/Secondary Air side fanning strip.
The form fit of the fan-shaped seal box of hot junction First air/fume side and the air inlet shape in one side relative with fanning strip on hot junction First air/fan-shaped seal box in Secondary Air side and heat leak wind air inlet of air duct, to dock.
In order to ensure the structural strength of former fanning strip, fan-shaped mouth is divided into plural zonule by vertical stiffener.
In order to both ensure less leaking out, leaking out more than making again as far as possible causes cold junction Secondary Air side, and widen hot junction First air/fume side fanning strip and hot junction First air/Secondary Air side fanning strip, the angle of widening is equal with the angle of fan-shaped mouth.
Such energy ensures that the fanning strip after being split by fan-shaped mouth still can form complete double sealing structure.
In order to ensure ash-removal effect further, the air outlet on fan-shaped bellows is fan-shaped air outlet.
According to above-mentioned design, fan-shaped air inlet (the above-mentioned fan-shaped mouth mentioned) has two, and fan-shaped air outlet only has one, therefore, in order to reduce restriction loss as far as possible, the summation of the flow area of fan-shaped air outlet and two fan-shaped air inlet flow areas is suitable.
Further preferably, the angle of fan-shaped air outlet is 2 ~ 6 °.
Above-mentioned fan-shaped air outlet is arranged in the fan-shaped seal box of cold junction Secondary Air/fume side and fan-shaped bellows and splices and locate, and air outlet and fanning strip are in same plane; The sealing surface of fan-shaped bellows and the sealing surface of fanning strip are in same plane, and namely the one side of the two next-door neighbour's rotor is in same plane.
The cross section in the connection air channel between above-mentioned fan-shaped air inlet and fan-shaped air outlet can be circular, also can be square or rectangle.
It should be added that, although above-mentioned fan-shaped bellows cover the sector of the original cold Secondary Air heat absorption of a part, but the sealing sector that First air both sides fanning strip is corresponding is become heat absorption district (cold junction leaks out through heat exchange element to hot junction) of leaking out from flow dead, therefore the total endotherm area of air is the increase in.And heat primary air is when leaking out by Secondary Air highest temperature module, first heat release is absorbed heat again, and thermal discharge is less than caloric receptivity, and the temperature after heat absorption is greater than the mean temperature of hot Secondary Air.Separately consider that the heat transfer temperature difference of cold Secondary Air and heat exchange element increases, the factor such as First air flow and flow velocity all increase, technical scheme in fact of the present invention significantly improves the utilization rate of preheater.
In order to more efficiently heat heat exchange element surface, to reach better gasification H
2sO
4and NH
4hSO
4effect, need reduce the radiation loss in flowing, therefore, above-mentioned all air channels are all necessary to carry out high-efficiency insulated measure as far as possible.
In order to reduce radiation loss further, the fan-shaped bellows being exposed to cold junction Secondary Air side are also necessary to carry out Insulation.Inner at preheater, the insulation material being similar to heat-preservation cotton is inapplicable, needs to select the advanced heat preservation technologies such as spraying insulating moulding coating.
Preferably, heat leak wind air channel has two, wherein one end of one is docked with the air inlet on the fan-shaped seal box of hot junction First air/fume side, the other end extends in fan-shaped bellows, one end of another root is docked with the air inlet on hot junction First air/fan-shaped seal box in Secondary Air side, and the other end extends in fan-shaped bellows.
First air to fume side leak out and First air is cause fan-shaped bellows that cold junction Secondary Air side installs additional respectively to leaking out of Secondary Air side.Because above-mentioned two strands of static pressure leaked out are variant, therefore cause the fan-shaped bellows that cold junction Secondary Air side installs additional respectively necessary.
In order to reduce two strands leak out influence each other, fan-shaped inner bellows is provided with demarcation strip, and demarcation strip is separated fan-shaped inner bellows, allow wherein one outlet of leaking out closer to central tube, and another stock is closer to rotor maximum gauge place.Preferably, the heat primary air toward fume side leaks out closer to central tube, and leaks out closer to rotor maximum gauge place toward the heat primary air of Secondary Air side.
In order to more efficiently heat heat exchange element, to ensure H
2sO
4and NH
4hSO
4completely, as another kind of technical scheme, air channel has additional duct insert heater to heat leak wind in gasification.
Heater can be pipe burner, plasma heater etc.But whether heater is set, in conjunction with unit practical operation situation, and security and economy need be considered.
The NM technology of the present invention is all with reference to prior art.
The anti-blocking ash of rotary regenerative air preheater of the present invention works in coordination with the method for sealing and system has following beneficial effect: the air leak rate of air curtain reducing preheater; Maintain the clean of heat exchange element, significantly improve heat transfer coefficient; Flow dead becomes heat absorption district of leaking out, and adds heat exchange area; More substantial First air flows through heat exchange element, improves the utilization rate of preheater; Reduce flow resistance, decrease total power consumption of three large blower fans; Prevent cold end corrosion, extend the life-span of heat exchange element; Come into operation or do not come into operation steam soot blowing less, decreases high-quality steam consumption; Reduce exhaust gas temperature, decrease the measures such as steam soot blowing, be all directly conducive to the electric precipitation in preheater downstream or the safety of bag-type dust equipment and economical operation.Consider the problems such as current most of power plant preheater ubiquity air leak rate of air curtain is large, cold end corrosion, stifled ash, 600MW grade units technical scheme of the present invention, boiler efficiency can improve 0.5% ~ 1%, the consumption of kiloton high-quality steam can be saved every year, station service power consumption rate can decline 0.1% ~ 0.5%, and significantly can reduce the maintenance cost of relevant device.
Accompanying drawing explanation
Fig. 1 is rotary regenerative air preheater structural representation.
Fig. 2 is typical case's three points of storehouse air preheater three-dimensional structure schematic diagrames.
Fig. 3 is the STRUCTURE DECOMPOSITION figure of typical case's three points of storehouse air preheaters.
Fig. 4 is the sealing schematic diagram that typical case's three points of storehouse air preheaters circumferentially launch.
Fig. 5 is the sealing schematic diagram adopting the improved preheater of technical solution of the present invention circumferentially to launch.
Fig. 6 is for adopting technical solution of the present invention improved preheater induced draught system figure (horizontal end face).
Fig. 7 is for adopting technical solution of the present invention improved preheater induced draught system figure (vertical section).
Fig. 8 be in the embodiment of the present invention fan-shaped bellows into and out of the layout schematic diagram in air port.
Fig. 9 in the embodiment of the present invention draw heat primary air and to leak out the graph of a relation of total flow and air leak rate of air curtain.
Figure 10 is that the one of the embodiment of the present invention improves and optimizates scheme schematic diagram.
In figure, 1 is the heat smoke flow direction, and 2 is that cold air flows to, and 3 is hot junction, and 4 is cold junction, and 5 is flue gas sector, and 6 is First air sector, and 7 is Secondary Air sector, 10 is hot junction connecting plate, and 11 is hot junction connecting plate intermediate beam, and 12 is hot junction stiffening ring, 13 is transmission device, and 14 is guide bearing, and 15 is shell, 16 is arc, and 17 is rotor, and 18 is module, 19 is cold junction stiffening ring, 20 is fanning strip, cylinder centered by 21, and 22 is cold junction connecting plate intermediate beam, 23 is cold junction connecting plate, and 24 is secondary bearing, 30 is diaphragm seal, 31 is the fan-shaped seal box of cold junction Secondary Air/fume side, 32 is the fan-shaped seal box of hot junction Secondary Air/fume side, 33 is cold junction First air/fan-shaped seal box in Secondary Air side, 34 is hot junction First air/fan-shaped seal box in Secondary Air side, 35 is the fan-shaped seal box of cold junction First air/fume side, 36 is the fan-shaped seal box of hot junction First air/fume side, 37 turn to for rotor, 38 is air inlet, 39 is heat leak wind air channel, 40 for taking out the blower fan that leaks out, 41 is fan-shaped bellows, 42 is air outlet, 43 is Secondary Air highest temperature module, 44 is Secondary Air time high temperature module, 45 for taking out the fans entrance air duct isolation door that leaks out, 46 is bypass air duct isolation door, 47 is that First air is to Secondary Air isolation door, 48 fanning strips for widening, 49 is demarcation strip, 50 is vertical stiffener, 51 is cold junction Secondary Air/fume side fanning strip, 52 is hot junction Secondary Air/fume side fanning strip, 53 is cold junction First air/Secondary Air side fanning strip, 54 is hot junction First air/Secondary Air side fanning strip, 55 is cold junction First air/fume side fanning strip, 56 is hot junction First air/fume side fanning strip, 57 is arm, 58 is arm isolation door, 59 for leaking out toward the heat primary air of fume side, 60 for leaking out toward the heat primary air of Secondary Air side, 100 is flue gas, and 101 is First air, and 102 is Secondary Air, I is First air side, and II is Secondary Air side, and III is fume side.
Detailed description of the invention
In order to understand the present invention better, illustrate content of the present invention further below in conjunction with embodiment, but content of the present invention is not only confined to the following examples.
Embodiment 1
Large-sized station boiler is nearly all equipped with rotary regenerative air preheater, to reduce exhaust gas temperature, and then improves boiler efficiency.As shown in Figure 1, the rotor of preheater by rotating continuously, carries heat exchange element and rotates typical rotary regenerative air preheater lentamente, and the heat smoke and the cold air that flow into preheater complete heat exchange.Be specially heat exchange element draw heat from the heat smoke of fume side, by the rotation of rotor, energy constantly passed to by the heat exchange element that heats the cold air that air side comes in, thus add hot-air.
The flue gas of preheater and air are reverse flows, and therefore, the entrance of cold air and the exhanst gas outlet through cooling are in one end of preheater, and be generally lower surface, this end is called cold junction; And heat smoke entrance and the air outlet slit through heating are in the other end of preheater, be generally upper surface, this end is called hot junction.In cool and heat ends, relative fanning strip radially covers the upper and lower end face of rotor respectively, preheater is divided into fume side sector and air side sector.
Large-scale power station generally adopts unit pulverized-coal system, requires the hot air source of different pressures, and air side sector is divided into First air sector and Secondary Air sector by fanning strip again, and primary air pressure is higher, and Secondary Air pressure is lower.The preheater of above-mentioned typical structure is commonly referred to as three points of storehouse air preheaters, as shown in Figure 2.
Fig. 3 is the STRUCTURE DECOMPOSITION figure of typical case's three points of storehouse air preheaters, more clearly have expressed the structure composition of preheater, main building block comprises: upper and lower connecting plate (i.e. cool and heat ends connecting plate), stiffening ring (comprising cold junction stiffening ring and hot junction stiffening ring), rotor, heat exchange element, triaxial forces sensor, shell, main bearing, secondary bearing, transmission device, metal (upper and annex etc.
Cold junction connecting plate intermediate beam, main bearing and secondary bearing are the main members supporting whole preheater weight.Especially cold junction connecting plate intermediate beam, about supports the weight of whole preheater 90%.
Rotor is made up of multiple fanlike die block, and it is the important component loading heat exchange element.
Heat exchange element is thousands of, high efficiency heat transfer waveform thin plate through special processing, and fixedly formed by framework.
Triaxial forces sensor refers to that radial direction, axial and circumferential seal, and being made up of apex seal and fanning strip, axial seal sheet and axial arc and bypass seal sheet and rotor seal angle steel, is stop air to the main member of smoke spillage.
Upper and lower bearing refers to guide bearing and block bearing, transmits the radial load from rotor and gravity respectively, and produces the component of the mill sassafras that rolls.
Transmission device is the dynamic component maintaining rotor rotation.
Upper lower connecting plate, stiffening ring and shell form flue gas, air duct, prevent working medium from leaking.
Operative practice for many years shows, above-mentioned conventional pre-heater exists the problems such as bigger than normal, the cold end corrosion of leaking out.In recent years, along with thermal power plant generally adopts SCR or SNCR technology to reduce NOx emission, the cold end corrosion aggravation of active service preheater cold junction, goes back ubiquity NH
4hSO
4the problem of deposition, preheater can be caused time serious to block, and unit is forced to limited load and even shuts down.
The problem of above-mentioned preheater cold end corrosion and blocking, particularly serious when unit load is lower, be because lower flue-gas temperature causes more H on the one hand
2sO
4drop and liquid NH
4hSO
4gathering, is cause flying dust more easily to deposit because flue gas flow rate during underload reduces on the other hand; In addition, when environment temperature is lower, the heat transfer temperature difference of preheater strengthens, and the flue-gas temperature of preheater outlet also can decline, and then aggravates cold end corrosion and the blocking of preheater.
Conventional art adopts online steam soot blowing or water to rinse and deals with the problems referred to above, engineering also adopts steam air heater or thermal wind sensor technology alleviate cold end corrosion phenomenon, to reaching the object preventing from blocking.But the former intermittent duty Chang Buneng reaches good ash-removal effect, the latter is what to sacrifice the utilization rate of preheater be cost, and in thermal power plant's pollutant emission index increasingly strict today, above-mentioned conventional art can not ensure safety and the economical operation of air preheater.
Present embodiments provide a kind of brand new technical scheme that can prevent Ash Blocking in Air Preheater, the object reducing preheater air leak rate of air curtain can be reached simultaneously, compared with conventional art, there is significant economy and security advantages.
The technical thought of the present embodiment can be sketched and be: guide from hot junction or extract and leak out to cold junction, purge and heat Local Heat Transfer element, while reduction preheater leaks out, and gasification H
2sO
4and NH
4hSO
4drop, reaches the object removing dust stratification.
Such scheme is easy to implement, is not only applicable to the supporting of new preheater, and is applicable to the transformation of active service preheater, has remarkable results such as reducing exhaust gas temperature, suppression dust stratification, reduction air leak rate of air curtain, prolongation heat exchange element life-span.
Hereafter to transform the trisector air heater of a 600MW unit, describe the technical scheme of transformation in detail, and then illustrate core content of the present invention.
Certain power plant 600MW rotary regenerative air preheater that unit is joined, three points of chamber structures, totally 36 modules, each module 10 °, every block fanning strip 20 °, namely preheater seal style is double containment; Adopt fixed sealing, namely without automatic control system of leaking out (LCS).Above-mentioned fanning strip has three groups (cool and heat ends relative two pieces of fanning strips be called one group), 6 complete module can be covered, overlay area is flow dead, all the other 30 modules are media flow district, wherein, 15 module circulation flue gases, 11 module circulation Secondary Airs, 4 module circulation First air.Preheater turns to: flue gas → Secondary Air → First air.
Table 1 is the partial properties design parameter of this preheater.
Table 1 certain power plant 600MW unit air preheater partial properties design parameter
Fig. 4 is the sealing schematic diagram that this preheater circumferentially launches, and this preheater mainly comprises three parts toward leaking out of fume side: First air leaks out to carrying of fume side to directly the leaking out of fume side, Secondary Air to directly the leaking out of fume side, First air.Above-mentioned size of leaking out determines the air leak rate of air curtain index of this preheater jointly, but to the index of leaking out of thoroughly evaluating preheater, First air also can not be ignored to directly leaking out of Secondary Air.
Leaking out and heat cold junction Secondary Air highest temperature module in the present embodiment employing hot junction, is washed away keep the clean of heat exchange element with the acting in conjunction of high-temperature gasification by flying dust, adopts the means of " treatment of wastes with processes of wastes against one another " to prevent preheater stifled grey.
Leak out and at least comprise heat primary air and leak out in above-mentioned hot junction, First air directly the leaking out and First air directly leaking out to Secondary Air to fume side namely drawn from hot junction fanning strip or extract; Above-mentioned cold junction Secondary Air highest temperature module refers to the module that in Secondary Air sector, temperature levels is the highest, next-door neighbour's Secondary Air/fume side fanning strip.Heat exchange element in this module just absorbs heat from fume side, and then air side heat release is arrived, therefore in this module, the mean temperature of heat exchange element is the highest, now, the heat primary air introducing about 300 DEG C from cold junction leaks out, continue to purge the heat exchange element in this module, significantly improve the wall temperature of this module cold junction heat exchange element, reach gasification H
2sO
4drop and liquid NH
4hSO
4object, avoid dust stratification to aggravate.
Fig. 5 is the sealing schematic diagram circumferentially launched according to preheater after above-mentioned thinking transformation, and the reconstruction scope at least comprises the fan-shaped seal box of hot junction First air/fume side, hot junction First air/fan-shaped seal box in Secondary Air side, the fan-shaped seal box of cold junction Secondary Air/fume side of former preheater.Set up heat leak wind air channel, fan-shaped bellows of splicing in the Secondary Air side of the fan-shaped seal box of cold junction Secondary Air/fume side, the fanning strip of fan-shaped bellows and the fan-shaped seal box of cold junction Secondary Air/fume side forms local three hermetically-sealed constructions; Wherein, the fanning strip of the fan-shaped seal box of cold junction Secondary Air/fume side refers to the one side fan-shaped seal box of cold junction Secondary Air/fume side being close to rotor; Fan-shaped bellows are the body structure that side is provided with air outlet, and air outlet is located on the side of the fan-shaped bellows between the fan-shaped seal box of cold junction Secondary Air/fume side and fan-shaped bellows; The fan-shaped seal box of former hot junction First air/fume side and hot junction First air/fan-shaped seal box in Secondary Air side drive air port into; One end, heat leak wind air channel is docked with air inlet, the other end extends in fan-shaped bellows, heat is once leaked out and to be entered in the fan-shaped bellows of cold junction Secondary Air/fume side fanning strip side by the guiding in heat leak wind air channel, then from air outlet discharging jet to cold junction Secondary Air highest temperature module.
Splice fan-shaped bellows in the above-mentioned Secondary Air side at the fan-shaped seal box of cold junction Secondary Air/fume side, local three hermetically-sealed constructions are formed with former fanning strip, leak out from the heat primary air of fan-shaped bellows air outlet ejection and to be intercepted by diaphragm seal, directly can not contact with cold Secondary Air, and then most heat primary air is leaked out can only, by Secondary Air highest temperature module, avoid heat primary air to leak out and cold secondary air flow mixing.
The application's fanning strip refers to one side seal box being close to rotor.
Fig. 6 illustrates above-mentioned air inducing process from preheater end face.It should be noted that, above-mentioned air inducing process can not need extra power (as blower fan etc.) to drive, the neous flow utilizing the pressure reduction of First air and Secondary Air can realize heat primary air to leak out; Also can set up and take out the blower fan that leaks out, further reduce preheater air leak rate of air curtain, and allow more heat primary air leak out degassing H
2sO
4drop and liquid NH
4hSO
4.
It should be noted that, above-mentioned heat primary air leaks out can not all by Secondary Air highest temperature module, also have sub-fraction can leak from the seal clearance cool and heat ends Secondary Air/fume side fanning strip, first leak to the module be close to Secondary Air highest temperature module below this fanning strip, be defined as time high temperature module.Carry the high-temperature flue gas of mean temperature about 250 DEG C in secondary high temperature module, the heat primary air that leakage is come in leaks out and mixes with it, can maintain the temperature levels that this sector is higher, also can play gasification H
2sO
4drop and liquid NH
4hSO
4effect.Therefore, heat primary air leak out in fact at least two modules heat exchanging element carry out purging and heating.
Also it should be noted that, the mist that high-temperature flue gas in above-mentioned high temperature module and heat primary air leak out, still can leak to low-pressure side (fume side) further, leaking out of final generation essence, but because pressure reduction is less, in mist containing about air capacity only half, this part ratio accounting for share of always leaking out of leaking out is less, and therefore the economic influence of leakage to preheater at this place is less.
When heat primary air leaks out and flows through heat exchange element, temperature is higher, gasification H
2sO
4drop and liquid NH
4hSO
4effect better.Data shows, the H under preheater environment
2sO
4steam acid dew point is mostly between 130 ~ 160 DEG C, and NH
4hSO
4be liquid within the scope of 146 ~ 207 DEG C.Therefore, to reach preferably gasification result, heat primary air leaks out in the process flowing through heat exchange element, can not be cooled to less than 207 DEG C, and this just requires that heat primary air leaks out and ensures certain flow or initial temperature.
In order to provide a kind of heat primary air that regulates to leak out the method for flow, causing on the heat leak wind air channel of cold junction Secondary Air/fume side fanning strip at hot junction First air/fume side fanning strip, setting up and take out the blower fan that leaks out.
Easy to maintenance in order to make to take out the blower fan that leaks out, and the flexibility keeping heat primary air to regulate, set up bypass air channel, take out leak out blower fan and bypass air channel and be connected in parallel, when taking out the blower fan that leaks out and being out of service, part heat primary air leaks out and flow to Secondary Air cold junction through bypass air channel.
As shown in figs. 6 or 7, above-mentioned to take out on leak out fans entrance air channel and bypass air channel to arrange respectively take out leak out fans entrance air duct isolation door and bypass air duct isolation door.When take out leak out fans entrance air duct isolation door close, bypass air duct isolation door open time, take out the blower fan that leaks out do not allow run, now heat primary air leaks out and spontaneously flow to cold junction Secondary Air side by bypass air channel; When bypass air duct isolation door close, take out the fans entrance air duct isolation door that leaks out open time, open and take out the blower fan that leaks out, now have more substantial heat primary air and leak out and flow to cold junction Secondary Air side; When two isolation doors are all opened, operation is not allowed to take out the blower fan that leaks out, otherwise blower fan short circuit, can energy waste be caused, and also there is no necessity that two isolation doors are all opened in any case; When two isolation doors are all closed, First air can not flow to cold junction Secondary Air side to leaking out of fume side, and components of system as directed is out of service.
First air causes on the air channel of cold junction Secondary Air side to Secondary Air side leakage wind and also installs First air to Secondary Air isolation door, and when only this isolation door is closed, components of system as directed is out of service.
When above-mentioned three isolation doors are all closed, system is completely out of service.
In order to reduce the crushing near fan-shaped air inlet as far as possible, be collected to heat leak wind air channel by some arms from hot junction First air/heat primary air of fume side fanning strip extraction leaks out, then send to cold junction Secondary Air side, as shown in Figure 7.
Above-mentioned air inlet runs through the upper bottom surface of fan-shaped seal box, namely fresh air inlet hole is equipped with at the upper bottom surface of fan-shaped seal box, fresh air inlet shape on upper bottom surface is corresponding with heat leak wind air channel entry shape, and heat is once leaked out first through fan-shaped seal box, then flows into heat leak wind air channel.The bottom surface of the fan-shaped seal box of the application refers to the one side being close to rotor, is also the fanning strip that the application mentions.
Air inlet on described hot junction First air/fume side fanning strip and hot junction First air/Secondary Air side fanning strip is preferably the fan-shaped mouth along preheater rotor radial, and fan-shaped air inlet angle is 1 ~ 3 °, is arranged in the middle of fanning strip, in Fig. 6, this feature has been shown.
In order to ensure the structural strength of former fanning strip, fan-shaped mouth is divided into several zonules by vertical stiffener, as shown in figs. 6 or 7.
In order to both ensure less leaking out, leaking out more than making again as far as possible causes cold junction Secondary Air side, and also need to widen fanning strip, the angle of widening is suitable with the angle of fan-shaped mouth, thus ensure that the fanning strip after segmentation still can form complete double sealing structure, in Fig. 5, this feature is shown.
First air to fume side leak out and First air is cause fan-shaped bellows that cold junction Secondary Air side installs additional respectively to leaking out of Secondary Air side.Because above-mentioned two strands of static pressure leaked out are variant, therefore cause the fan-shaped bellows that cold junction Secondary Air side installs additional respectively necessary.
In order to reduce two strands leak out influence each other, adopt demarcation strip the fan-shaped inner bellows installed additional is separated, allow wherein one outlet of leaking out closer to central tube, and another stock is closer to rotor maximum gauge place, as shown in Figure 7.Preferably, the heat primary air toward fume side leaks out closer to central tube, and leaks out closer to rotor maximum gauge place toward the heat primary air of Secondary Air side.
The air outlet of above-mentioned fan-shaped bellows is fan-shaped air outlet.According to above-mentioned design, fan-shaped air inlet has two, and fan-shaped air outlet only has one, therefore, in order to reduce restriction loss as far as possible, the summation of the flow area of fan-shaped air outlet and two fan-shaped air inlet flow areas is suitable, further preferably, the angle of fan-shaped air outlet is 2 ~ 6 °.
Above-mentioned fan-shaped air outlet is arranged in the fan-shaped seal box of cold junction Secondary Air/fume side and fan-shaped bellows and splices and locate, and fan-shaped air outlet and fanning strip are in same plane, and the sealing surface of fan-shaped bellows and the sealing surface of fanning strip are in same plane, in Fig. 5, this feature have been shown.
The cross section in the connection air channel between above-mentioned fan-shaped air inlet and fan-shaped air outlet can be circular, can be also square or rectangle, when selecting the airduct of circular cross-section, and dust diameter 600 ~ 1000mm.
It should be added that, although above-mentioned fan-shaped bellows cover the sector of the original cold Secondary Air heat absorption of a part, but the sealing sector that First air both sides fanning strip is corresponding is become heat absorption district (cold junction leaks out through heat exchange element to hot junction) of leaking out from flow dead, therefore the total endotherm area of air is the increase in.And heat primary air is when leaking out by Secondary Air highest temperature module, first heat release is absorbed heat again, and thermal discharge is less than caloric receptivity, and the temperature after heat absorption is greater than the mean temperature (reaching about 350 DEG C during this unit oepration at full load) of hot Secondary Air.Separately consider that the heat transfer temperature difference of cold Secondary Air and heat exchange element increases, the factor such as First air flow and flow velocity all increase, technical scheme in fact of the present invention significantly improves the utilization rate of preheater.
In order to more efficiently heat heat exchange element surface, to ensure better gasification H
2sO
4and NH
4hSO
4effect, need reduce the radiation loss in flowing as far as possible, and therefore, above-mentioned all air channels are all necessary to carry out high-efficiency insulated measure.
In order to reduce radiation loss further, the fan-shaped bellows being exposed to cold junction Secondary Air side are also necessary to carry out Insulation.Inner at preheater, the insulation material being similar to heat-preservation cotton is inapplicable, needs to select the advanced heat preservation technologies such as spraying insulating moulding coating.
Adopt technique scheme, system architecture presses Fig. 6 or 7 design, as calculated, during unit oepration at full load, the wind-warm syndrome that the heat primary air causing cold junction Secondary Air side leaks out reaches 300 ~ 320 DEG C, total flow is adjustable between 84 ~ 168t/h, and preheater air leak rate of air curtain can decline 0.7% ~ 3.3% (calculated value under former air leak rate of air curtain 6.3% condition).
Need to further illustrate, the amplitude that above-mentioned air leak rate of air curtain declines depend primarily on join the size of taking out the blower fan that leaks out, the heat primary air of extraction leaks out more, and air leak rate of air curtain fall is larger.Under above-mentioned design condition, do not come into operation and take out the blower fan that leaks out, only utilize the pressure reduction of system self to realize flowing, the heat primary air the flowing to cold junction Secondary Air side flow that leaks out can reach 84t/h, and corresponding air leak rate of air curtain declines 0.7%; Take out when coming into operation the blower fan that leaks out, fans entrance negative pressure is maximum is designed to smoke inlet negative pressure, now, original leakage to the heat primary air of fume side leaks out and all flow to cold junction Secondary Air side, total flow can reach about maximum 168t/h, and corresponding air leak rate of air curtain can decline 3.3%, and namely preheater air leak rate of air curtain is 3%.
In above-described embodiment, linear approximate relationship is there is between the total flow that the heat primary air flowing to cold junction Secondary Air side leaks out and air leak rate of air curtain, mathematic(al) representation is: A=5.6%-(S-84)/(168-84) * 2.6%, and wherein A is air leak rate of air curtain, and S is total flow.The relation of above-mentioned total flow and air leak rate of air curtain also can represent with Fig. 9.
Also it should be noted that, the leak out amplitude of total flow random groups load variations of above-mentioned heat primary air is less, therefore regardless of unit load height, the gas flow rate change flowing through sector wind upper box part heat exchange element is little, can remain between 10 ~ 30m/s, owing to avoiding too low flow velocity, even if therefore performing low-load running of machine set, also can reach and purge effect preferably, prevent flying dust to be deposited on heat exchange element surface in a large number.
In order to more efficiently heat heat exchange element, to ensure the H that is gasified totally
2sO
4drop and liquid NH
4hSO
4, it is also a kind of alternative scheme that heat leak wind air channel is set up duct insert heater, as pipe burner, plasma heater etc.But whether heater is set, in conjunction with unit practical operation situation, and security and economy need be considered.
With set up compared with duct insert heater, below hot junction Secondary Air/fume side fanning strip, extract the heat primary air heated further through heat exchange element leak out and seem more economical and safer, as shown in Figure 10, the design of leaking out of taking out at hot junction Secondary Air/fume side fanning strip place leaks out design class seemingly with hot junction First air/taking out of fume side fanning strip place in typical design.In fact, this design allows heat primary air leak out recirculation, increases air quantity, improves wind-warm syndrome, to reach the object of better removing heat exchange element dust stratification.
Turn to as flue gas → Secondary Air → First air due to preheater, so the wind-warm syndrome size that the heat primary air extracted from the different fanning strip in three pieces, hot junction leaks out is followed successively by: Secondary Air/fume side fanning strip > First air/Secondary Air side fanning strip > First air/fume side fanning strip, high about 50 DEG C than First air/fume side fanning strip place of the temperature that the heat primary air at wherein Secondary Air/fume side fanning strip place leaks out.Meanwhile, the dust content that heat primary air leaks out also meets above-mentioned magnitude relationship.
Wind-warm syndrome is higher, heating and gasifying H
2sO
4and NH
4hSO
4the effect of drop is better; Dust content is higher, and the effect that flying dust washes away is more obvious.According to above-mentioned theory, leaked out from two bursts of different wind-warm syndrome at Secondary Air/fume side fanning strip place, the heat primary air of different dusts concentration by allotment First air/fume side fanning strip, the object regulating present system operational effect can be reached.When the long-term underrun of unit, because pre-heater inlet cigarette gentleness outlet wind-warm syndrome all declines, increase the risk of stifled ash, above-mentioned regulating measure be can yet be regarded as a kind of effective method.
In Figure 10, all arms being equipped with isolation door, being closed and opening operation by the isolation door of various combination, wind-warm syndrome that the heat primary air through taking out the blower fan that leaks out leaks out and dust content can being controlled easily.Close the isolation door of arm above more First air/fume side fanning strip, and open the isolation door of arm above Secondary Air/fume side fanning strip, wind-warm syndrome and dust content that heat primary air leaks out can be improved.
It should be added that, the above-mentioned heat primary air be actually after the heating of Secondary Air highest temperature module that leaks out extracted below hot junction Secondary Air/fume side fanning strip leaks out and the mist (causing because rotor carries flue gas) of high-temperature flue gas, and mean temperature is close to the temperature of pre-heater inlet flue gas.In addition, extract the air leak rate of air curtain that above-mentioned mist is also conducive to reducing further preheater, be expected to make the air leak rate of air curtain of preheater to be down to less than 2%.Therefore, extracting the mist below Secondary Air/fume side fanning strip, is a kind of more satisfactory selection, the high-temperature gas mixture body reclaimed can compensate a part of fan energy consumption, the wind-warm syndrome that heat primary air leaks out can be improved again, and improve dust concentration, play and remove dust stratification effect more significantly.
Summarize according to above explanation, the beneficial effect of the present embodiment is at least embodied in following eight aspects:
1) air leak rate of air curtain of preheater is reduced;
2) keep heat exchange element to clean, significantly improve heat transfer coefficient;
3) flow dead becomes heat absorption district of leaking out, and adds heat exchange area;
4) more substantial First air flows through heat exchange element, improves the utilization rate of preheater;
5) to come into operation less or the steam soot blowing that do not come into operation, decrease high-quality steam consumption;
6) reduce flow resistance, decrease total power consumption of three large blower fans;
7) prevent cold end corrosion and stifled ash, reduce steam soot blowing and the high pressure water washing frequency, be all conducive to the life-span extending heat exchange element;
8) reduce exhaust gas temperature, reduce the measures such as the steam soot blowing frequency, be all directly conducive to the electric precipitation in preheater downstream or the safety of bag-type dust equipment and economical operation.
Consider the problems such as current most of power plant preheater ubiquity air leak rate of air curtain is large, cold end corrosion, stifled ash, 600MW grade units technical scheme of the present invention, from above-mentioned eight aspects estimation benefit, boiler efficiency can improve 0.5% ~ 1%, the consumption of kiloton high-quality steam can be saved every year, station service power consumption rate can decline 0.1% ~ 0.5%, and significantly can reduce the maintenance cost of relevant device.
Claims (12)
1. the anti-blocking ash of rotary regenerative air preheater works in coordination with a method for sealing, it is characterized in that: guide or extract hot junction from hot junction and leak out to cold junction, purge and heat Local Heat Transfer element.
2. the method for claim 1, is characterized in that: utilize hot junction to leak out and heat cold junction Secondary Air highest temperature module; Wherein, leak out and at least comprise heat primary air and leak out in hot junction, First air directly the leaking out and First air directly leaking out to Secondary Air to fume side namely drawn from hot junction fanning strip or extract; Cold junction Secondary Air highest temperature module refers to the module that in Secondary Air sector, temperature levels is the highest, next-door neighbour's Secondary Air/fume side fanning strip.
3. the anti-blocking ash of rotary regenerative air preheater that method described in claim 1 or 2 is used works in coordination with sealing system, comprise the fan-shaped seal box of hot junction First air/fume side, hot junction First air/fan-shaped seal box in Secondary Air side and the fan-shaped seal box of cold junction Secondary Air/fume side, it is characterized in that: also comprise heat leak wind air channel, the fan-shaped seal box of hot junction First air/fume side and hot junction First air/fan-shaped seal box in Secondary Air side all offer air inlet, one end, heat leak wind air channel is docked with air inlet, and the other end extends to cold junction Secondary Air highest temperature module.
4. the anti-blocking ash of rotary regenerative air preheater as claimed in claim 3 works in coordination with sealing system, it is characterized in that: the seal form of rotary regenerative air preheater is double sealing structure; Splice in the Secondary Air side of the fan-shaped seal box of cold junction Secondary Air/fume side fan-shaped bellows, the fanning strip of fan-shaped bellows and the fan-shaped seal box of cold junction Secondary Air/fume side forms local three hermetically-sealed constructions; Wherein, the fanning strip of the fan-shaped seal box of cold junction Secondary Air/fume side refers to the one side fan-shaped seal box of cold junction Secondary Air/fume side being close to rotor; Fan-shaped bellows are the body structure that side is provided with air outlet, and air outlet is located on the side of the fan-shaped bellows between the fan-shaped seal box of cold junction Secondary Air/fume side and fan-shaped bellows; One end, heat leak wind air channel is docked with air inlet, and the other end extends in fan-shaped bellows, and heat is once leaked out and to be entered in fan-shaped bellows by the guiding in heat leak wind air channel, then from air outlet discharging jet to cold junction Secondary Air highest temperature module.
5. the anti-blocking ash of rotary regenerative air preheater as claimed in claim 4 works in coordination with sealing system, it is characterized in that: the heat leak wind air channel between in air inlet and fan-shaped bellows is provided with takes out the blower fan that leaks out.
6. the anti-blocking ash of rotary regenerative air preheater as claimed in claim 5 works in coordination with sealing system, it is characterized in that: the heat leak wind air channel between the air inlet of the fan-shaped seal box of hot junction First air/fume side and fan-shaped bellows is provided with takes out the blower fan that leaks out; The two ends of taking out the blower fan that leaks out are parallel with bypass air channel.
7. the anti-blocking ash of rotary regenerative air preheater as claimed in claim 6 works in coordination with sealing system, it is characterized in that: the heat leak wind air channel of taking out the fans entrance that leaks out is provided with takes out the fans entrance air duct isolation door that leaks out, and bypass air channel is provided with bypass air duct isolation door.
8. the anti-blocking ash of the rotary regenerative air preheater as described in claim 3-7 any one works in coordination with sealing system, it is characterized in that: leaking out from the heat primary air of hot junction First air/fume side fan-shaped seal box extraction is be collected to heat leak wind air channel by plural arm, then flows to cold junction Secondary Air highest temperature module.
9. the anti-blocking ash of rotary regenerative air preheater as claimed in claim 8 works in coordination with sealing system, it is characterized in that: Secondary Air/fume side fan-shaped seal box in hot junction is also provided with air inlet, leaking out from the heat primary air of the fan-shaped seal box extraction of hot junction Secondary Air/fume side flows to cold junction Secondary Air highest temperature module.
10. the anti-blocking ash of the rotary regenerative air preheater as described in claim 3-7 any one works in coordination with sealing system, it is characterized in that: the air inlet on hot junction First air/fume side fanning strip and hot junction First air/Secondary Air side fanning strip is the fan-shaped mouth along preheater rotor radial, fan-shaped air inlet angle is 1 ~ 3 °, be arranged in the middle of fanning strip, and fan-shaped mouth is divided into plural zonule by vertical stiffener; Hot junction First air/fume side fanning strip and hot junction First air/Secondary Air side fanning strip refer to the one side fan-shaped seal box of hot junction First air/fume side and hot junction First air/fan-shaped seal box in Secondary Air side being close to rotor respectively.
The anti-blocking ash of 11. rotary regenerative air preheater as claimed in claim 10 works in coordination with sealing system, it is characterized in that: widen hot junction First air/fume side fanning strip and hot junction First air/Secondary Air side fanning strip, the angle of widening is equal with the angle of fan-shaped mouth.
12. anti-blocking ashes of rotary regenerative air preheater as described in claim 4-7 any one work in coordination with sealing system, and it is characterized in that: the air outlet on fan-shaped bellows is fan-shaped air outlet, the angle of fan-shaped air outlet is 2 ~ 6 °.
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