Background technology
The dust emission of coal-fired power station boiler is the one of the main reasons for causing China's environmental pollution and haze weather.China
The cleaner of station boiler nearly all adopts electrostatic precipitator.Although in recent years many power plant are all carried out to electric dust-removing equipment
Upgrading, but the smoke dust discharge concentration of quite a lot of power plant all beyond《Generating plant pulverized coal boiler atmosphere pollutants emission standardses
(GB 13223-2011)》With regard to the limit value of dust emission standard, i.e. 20~30mg/Nm3。
With the raising of environmental requirement, State Council assigns within 2014《The General Office of the State Council is with regard to printing and distributing energy development war
Omit action plan(2014~the year two thousand twenty)Notice》(The Office of the State Council sends out [2014] No. 31), to east China area, middle part and west
Portion area requires that respectively the smoke dust discharge concentration of Thermal generation unit is basically reached or the close flue dust for reaching gas turbine group
Concentration of emission(That is 10mg/Nm3).To implement this emission request, transformation of the coal fired power plant to electric cleaner will make arduousness
Effort.
Through the research for many years of countries in the world, the Dust Characteristics of coal-fired ash content are found, mainly the ratio resistance of dust is to electricity
The efficiency of dust collection of deduster affects very big, and dust specific resistance is bigger, and the efficiency of dust collection of electric cleaner is lower, and dust emission concentration is just
It is bigger, and dust specific resistance is relevant with the temperature height of dust.
Boiler smoke handled by electric cleaner, is the flue gas temperature here by boiler air preheater exhaust pass
Degree is referred to as exhaust gas temperature.The exhaust gas temperature of China's station boiler is mostly between 120~160 DEG C.This temperature range
For the dust of most of coals, high specific resistance region is belonging to, dust collection efficiency is relatively low.Multinational research finds, if by electricity
The flue dust temperature of deduster process is reduced to 80~100 DEG C by 120~160 DEG C, because the ratio resistance of coal-fired dust significantly drops
It is low(Even up to 2 orders of magnitude), dust collection efficiency can be increased substantially, and thus propose low temperature electrostatic precipitation technology.
A key measures for realizing low temperature electrostatic precipitation technology are in boiler air preheater outlet and electric precipitation
A gas cooler is installed between device additional, so that 80~100 DEG C will be reduced to into the flue-gas temperature of electric cleaner.Flue gas is cooled down
Device is a huge heat exchanger, wherein to the medium of cooled flue gas(Or title heat transfer medium or heating agent), there is gas(Such as low temperature
Flue gas)Or liquid(Such as water).
Gas cooler is a cryogenic heat exchanger for boiler, in order to not make heat exchanger excessively huge, it is desirable to conduct heat
The temperature of medium is as more lower as possible than flue-gas temperature.But to the most of coals of China, 80~100 DEG C of temperature province is
Less than sulfureous in flue gas acid vapor(By SO3Transformation)Dew point, sulfuric acid vapor translates into liquid sulfur acid mist.In deduster not
In the flue gas of removing dust, the concentration of dust is very big, to China's coal, typically up to 10~40g/Nm3, high concentrate dust particle deposits
, a large amount of condensation nucleis are provided to the condensation of sulfuric acid vapor, so in the flue gas between gas cooler and electric cleaner,
Sulfuric acid mist is mainly condensed and is sticked on dust, rather than on smooth metal surface, and by the alkalescence in coal-fired ash content into
Part neutralizes and loses activity, and is subsequently removed by electric cleaner again.Therefore, gas cooler and electric cleaner and behind equipment
(Such as induced-draught fan)The heavy corrosion of sulfuric acid will not be subjected to.But prevent flue gas from the solidifying of water vapour occurring because temperature is too low
Knot, otherwise sulfuric acid corrosion and electrochemical corrosion are had an effect simultaneously, will greatly shorten the use of gas cooler and electric cleaner
Life-span.From the angle for preventing water recovery, it is desirable to dew point of the flue-gas temperature than water vapour in flue gas(Generally 40~50 DEG C)
It is higher by about 20~25 DEG C.Thus, the general heat medium temperature required into gas cooler is not less than 60 DEG C.
It is general to go back in addition to gas cooler is installed additional in the flue before electric cleaner in low temperature electrostatic precipitation technology
The smoke outlet of wet desulfurizer behind installs flue gas reheater additional(Smoke re-heater), desulfurizing tower out
Flue-gas temperature(The saturation temperature of water vapour in flue gas, generally 40~50 DEG C), be heated to than water vapour saturation state be higher by
Few 20~25 DEG C temperature(Some national requirements reach about 80 DEG C), to avoid desulfurizing tower after flue, booster fan and chimney
It is subjected to chemical attack Deng equipment, and around there is gypsum rain in region when can prevent chimney of electric plant discharge flue gas(This is that environment is protected
What shield was impermissible for).
Low temperature electrostatic precipitation technology has many advantages, such as:
1. relative to routine(It is 120~160 DEG C to process flue-gas temperature)Electrostatic precipitation technology is low due to processing flue-gas temperature
(80~100 DEG C), the ratio resistance of coal ash dust is little, and dust collection efficiency is higher, therefore the dust concentration of fume emission is significantly reduced.
2. for the wet desulphurization tower along flue gas flow direction device after deduster, because most of SOx is with adhesion dust
Remove from deduster, so desulfurization light load, also more conventional electric dust-removing equipment is low for flue gas SOx concentration of emissions, meanwhile, low temperature
The high-effective dust-removing of electrostatic precipitation technology, improves the quality of wet type desulfurizing technology by-produced gypsum.
3. in low temperature electrostatic precipitation technology, the flue-gas temperature into wet desulphurization tower is also low than conventional electrostatic precipitation technology,
The water consumption of desulfurization can be saved.
With the raising to environmental protection requirement, low temperature electrostatic precipitation technology is that fossil-fired unit starts nearly ten years
Existing new technology.Tested in only one or two power plant of China's Thermal Power Generation Industry according to reports;External advanced industrial country, such as day
Sheet, Germany etc., existing a number of fired power generating unit implements this technology(More using the MGGH systems of following heating agent alone cycles
System), boiler dust concentration of emission significantly declines.
Distinguish from technology enforcement or Discussion on Technology scheme, about three kinds methods.
1. only with low temperature(Or low temperature)Economizer makees gas cooler technology
The know-why of this scheme is as depicted in figs. 1 and 2.If symbol 1~4 and 20 is Steam Turbine Regenerative System in figure
Dry level heater, 1~4 is respectively the 8th~the 5th level steam turbine draws gas corresponding low-pressure heater(Or claim No. 8~No. 5 it is low plus),
20 is turbine shaft seal heater.Condensate pump 8 is by full-flow condensate(From turbine condenser, simultaneously the dead axle vapour of Jing mono- adds
Heat)Force feed is delivered to oxygen-eliminating device respectively through low-pressure heaters at different levels.9 is boiler air preheater exhaust pass in figure, here
Flue-gas temperature is referred to as exhaust gas temperature, and China's fired power generating unit is mostly in 120~160 DEG C of level.If taking no action to, flue gas is straight
Tap into into electric cleaner 11, then because cigarette temperature is higher, dust specific resistance is big in flue gas, and efficiency of dust collection is relatively low, and flue gas is discharged from chimney
When, dust emission concentration is very big, and after having installed gas cooler 10 additional, cigarette temperature can be down to 90~110 DEG C, and dust specific resistance can drop
Low 1~2 magnitude, efficiency of dust collection is greatly improved, and Jing after induced-draught fan 12, desulfurizing tower 13, booster fan 14, flue gas is from chimney 15
During discharge, its dust emission concentration can be greatly reduced.
Fig. 1 and Fig. 2 are in fact equivalents.Only it is classified as because of the limited space of arrangement gas cooler in FIG
Two-stage(10 and 21), Fig. 2 is then 1 grade of arrangement.In gas cooler, the heating agent of cooled flue gas be from it is low with No. 8 Jia 1 before and 7
It is number low Jia 2 after after main condensate two-way draws and mixes, conveyed by booster 7, in cooled flue gas after conducting self-heating, loopback
In main condensate to No. 5 low-pressure heaters 4.When valve 6 is fully closed, gas cooler and thermodynamic system of steam tur solution
Row.
This scheme has a two big defects, and first, dedusting flue gas desulfurization and is fully contacted, cigarette in wet desulphurization tower with spraying
Temperature degree is down to about 40~50 DEG C, flue thereafter, increases blower fan and chimney corrosion is more serious.Additionally, in this scheme,
The flue gas discharged by chimney 15 carries a large amount of water smokes, and the by-product generated in desulfurizing tower in wet desulphurization is also carried in flue gas
Product gypsum(CaSO4•2H2O), water smoke and gypsum can not possibly distally spread with flue gas, but occur and cigarette near chimney breast
Gas is separated, and power plant surrounding area is scattered in as gypsum rain, unfavorable in surrounding environment, is also that environmental protection is impermissible for.
Second, in this scheme, because the inlet temperature that gas cooler cools down heating agent will keep substantially 60 DEG C of temperature,
Therefore have the main condensate water intaking of plus 1 entrance low from No. 8 all the way.When low temperature electric dust removing system works, the 8th grade of steam turbine draws gas
(The minimum extracted steam from turbine of pressure)Will accordingly reduce, its result declines the generated output of steam turbine, the heat of heat regenerative system
Efficiency will be reduced accordingly.
Additionally, to prevent gas cooler heat medium temperature during underload too low, in gas cooler heating agent and entrance are exported
Hot water re-circulation system should be installed between heating agent additional.
2. MGGH systems of heating agent alone cycle
MGGH is that thermal medium type flue gas-flue gas heater english name the 1st is alphabetical referred to as, including the flue gas of boiler exhaust gas
The reheater of " clean " flue gas after cooler and dust-removal and desulfurizing, schematic diagram is as shown in Figure 3.The flue gas of this technology is cooled down and added again
Thermal medium from into a circulatory system, 16 for thermophore circulating line, thermophore cooled flue gas itself in gas cooler
After heating, as smoke re-heater thermal medium is added, itself is cooled, and Jing heating agents recirculation pump 24 is recycled to again gas cooler
In.So, MGGH systems are not in contact with any heater in Steam Turbine Regenerative System.This technology is applied to state's dispatch from foreign news agency mostly
Factory, domestic certain power plant once introduced and adopted.
Fig. 4 illustrates the somewhat detailed circulatory systems of any of MGGH.Thermophore under the driving of heating agent recirculation pump 24, in heat
It is circulated between matchmaker's circulating line 16 and gas cooler, smoke re-heater.
In underload, flue gas flow is greatly decreased boiler, and exhaust gas temperature is also decreased obviously, in MGGH systems,
Heat of the heating agent obtained in gas cooler 10, may be not enough to " clean " flue gas in flue gas heater 22 extremely
Than the temperature that water dew point in flue gas is about higher by 20~25 DEG C.In this case, should open steam control valve 28 to steam-
Heating medium for heating device 25 supplies superheated steam, to improve the Heating medium temperature of smoke re-heater 22.The Jing heating agents of superheated steam 27 add
After hot device heating, heating agent is further heated in drain cooler 26 to reduce the consumption of superheated steam.Additionally, low negative in boiler
During lotus, if " pollution " exhanst gas outlet cigarette temperature is too low(This temperature should at least be higher by 20~25 DEG C of temperature than water vapour dew point in flue gas
Degree), the heating agent bypass valve 29 of appropriate ON cycle system is answered, with short-circuit a part of heating agent.
In MGGH systems, the circulatory system of heating agent is closing, and when system starts and stops transport, heating agent specific volume becomes
Change, therefore device heating agent expansion vessel 30 is answered in system.As can be seen here, the circulatory system of MGGH and its operation are more complicated.
Because the heating agent of gas cooler and smoke re-heater is enclosed in a closed circuit, when gas cooler and cigarette
When the thermal power of gas reheater is unequal, the temperature of heating agent will change in the circulatory system, it is impossible to keep stable, be holding
Heat medium temperature is constant it is necessary to adjusting(Increase or decrease)The superheated steam amount of heating medium for heating device.So, this system needs extra
Steam energy.
3. the system that heating agent adopts " main condensate-gas cooler-smoke re-heater-main condensate "
Once a kind of investigation scheme of the low temperature electric dust removing system with main condensate as heating agent, such as Fig. 5 were reported on domestic literature
It is shown.On boiler flue gas treatment system, gas cooler was installed before electric cleaner, install dry additional after wet desulphurization tower
Neat stress reheater.Flue gas cool down and heat thermophore be main condensate, using No. 8 it is low Jia 1 before with No. 7 it is low Jia 2 after two-way
Condensate converges, and by the force feed of liter water pump 7, is introduced into gas cooler 10, conducting self-heating after cooled flue gas, then Jing pipelines send
To smoke re-heater 22, heat " clean " flue gas, after itself is cooled down, No. 6 it is low Jia 3 before return main condensate water system.
In order to ensure that the water temperature into gas cooler 10 is not less than 60~65 DEG C, employ No. 8 it is low Jia 1 before and No. 7 it is low
Two-way converges the mode of water supply after plus 2.
This system schema, due to having installed gas cooler 10 and " clean " smoke re-heater 22 additional, you can improve electricity and remove
The efficiency of dust collection of dirt device, reduces dust emission concentration, can prevent again desulfurizing tower rear pass and relevant device cold end corrosion and
The generation of gypsum rain phenomenon around chimney.
This technological system has no at home enforcement report, if it is unknown to produce a desired effect.But analyzing this is
System using main condensate as can be seen that for being introduced into gas cooler(To cool down boiler export flue gas), its own is heated
Afterwards, the scheme of " clean " smoke re-heater, gas cooler cooling water are then sent through(Main condensate)Inlet temperature, can neither be too
It is low(Cannot be below 60~65 DEG C), again should not be too high, such as cooling water temperature is too high, and the temperature difference between flue gas and cooling water is too little,
Just it is not easily accomplished the requirement that flue gas is reduced to 80~100 DEG C of temperature from about 150 DEG C.
So, system that employs all the way No. 8 it is low Jia 1 before main condensate water intaking, fetch water from here, No. 7 will be squeezed
The rate of air sucked in required for adding low with No. 8, so as to adverse effect occur to the thermal efficiency of thermodynamic cycle.
Additionally, in order to prevent heat medium temperature during underload into gas cooler too low, system should also be cooled down in flue gas
Device exports heating agent to hot water recirculation pump 19 is increased between entrance heating agent, makes system and its adjusts excessively complicated, also extra to consume
Energy.
The content of the invention
Technical problem:It is contemplated that propose a kind of simple structure, steam turbine and therrmodynamic system are run without impact, and
Can preferably improve ESP Efficiency, meet the requirement of environmental protection and be conducive to the electricity for improving therrmodynamic system thermal efficiency of cycle to remove
Dirt heat-exchange system.
Technical scheme:To solve above-mentioned technical problem, the technical solution used in the present invention is:
A kind of electric precipitation heat-exchange system, including electric cleaner, desulfurizing tower, be arranged on the electric cleaner front end flue gas it is cold
But device, the smoke re-heater for being arranged on the desulfurizing tower rear end and the heating agent circulation that is connected with steam turbine condensate system are logical
Road, the condensate system is connected in series by the condensation water channel of steam turbine heater at different levels, it is characterised in that:The heating agent is followed
Ring passage includes that exhalant canal and one end of backwater channel, the exhalant canal and backwater channel are connected to the condensate system
On, the other end of the exhalant canal is connected to the water inlet of the smoke re-heater, and the delivery port of the smoke re-heater connects
The water inlet of the cooler is connected to, the delivery port of the gas cooler is connected to the other end of the backwater channel.
One end and backwater channel that the exhalant canal is connected with the condensate system is connected with the condensate system
One end between adjacent double-bank heater.
The exhalant canal is connected in the middle of double-bank heater of the output condensate temperature between 100 DEG C~110 DEG C.
A control valve is provided with the condensate system, the control valve by main condensate electric control valve and with it is described
Main condensate electric control valve bypass valve in parallel is constituted, and the exhalant canal and backwater channel are connected to the two of the control valve
Side.
A booster is provided with the exhalant canal.
Valve is each provided with the exhalant canal and backwater channel.
The present invention adopts the low temperature of " main condensate-smoke re-heater-gas cooler-main condensate " for heating agent
The heat exchanging system of electrostatic precipitation technology, its feature is as follows.
(1) gas cooler is installed additional before electric cleaner;Install smoke re-heater additional after wet desulphurization tower;
(2) with preference temperature(95~105 DEG C)Main condensate as gas cooler and the heating agent of reheater.From steamer
The condensate that machine therrmodynamic system is extracted, is introduced into the smoke re-heater of desulfurizing tower outlet, by the temperature of flue gas to more than 80 DEG C
Degree, itself is cooled to~70 DEG C, by the power of booster, flue-gas-cooling system is delivered to, as flue gas cooling medium, flue gas
90~95 DEG C are cooled to, into electric cleaner dedusting is carried out, after itself being heated to 95~105 DEG C of temperature, return steamer
The therrmodynamic system of machine.As the main condensate of heating agent, the outlet of No. 7 low-pressure heaters is taken from, and returned before No. 6 low-pressure heaters
Return, between dry point and backwater point valve is installed additional.
(3) gas cooler and smoke re-heater adopt optimized extended surface heat exchanger.
Specific embodiment
Using certain 330MW subcritical pressure boilers coal unit as the example for implementing this low low temp. electric dust-collecting and heat exchanging system patent,
As shown in fig. 7, thermodynamic system of steam tur only illustrates No. 7 low-pressure heaters 2 to No. 6 low-pressure heaters, 3 one sections of main condensates in figure
Pipeline.
In boiler smoke flow process, between the booster fan being exported to before chimney from boiler air preheater, two need to be installed additional
Individual flue gas-main condensate heat exchanger:One heat exchanger apparatus after air preheater, before electric cleaner, referred to as gas cooler
10, another device is after wet desulphurization tower, the smoke re-heater 22 before booster fan.Main condensate is from steam turbine heating power
The outlet of No. 7 low-pressure heaters 2 of system is extracted out, and water temperature during rated load here is 103 DEG C, is conveyed by liter water pump 7 advanced
Enter smoke re-heater 22, by out, wherein water vapour is in the flue gas of saturation state from desulfurizing tower(Temperature is typically at 40~50 DEG C
Between, it is assumed here that about 45 DEG C)More than 20~25 DEG C higher than water vapour saturation temperature of temperature is heated to, main condensate is released
After heat is to flue gas, own temperature is reduced to 60~70 DEG C, then, into gas cooler 10, by flue gas from air preheater
The temperature of 130~150 DEG C of outlet is reduced to 85~95 DEG C of deduster entrance, and main condensate absorbs cigarette in gas cooler 10
After gas heat, 104 DEG C are heated to(During rated load)Temperature, be then return to(The import of No. 6 low-pressure heaters 3)Main condensate
In system.
On main condensate pipe between No. 7 low-pressure heaters and No. 6 low-pressure heaters, a set of regulating valve 17 and side are installed additional
The valve group 33 that road valve 18 is constituted, to realize that the heating agent of system with low-low temperature ESP heat exchanger is extracted out by before valve, backwater is after valve
Return;The flow proportional of system with low-low temperature ESP water consumption and straight-through main condensate is can also adjust using this group of valve, with full
To the requirement of each node flue gas and heat medium temperature in the range of sufficient full load.
The temperature of the unit each node of the system with low-low temperature ESP in rated load is also illustrated that in the figure 7.By listed
Data find out that the system fully meets the requirement of low temperature electrostatic precipitation technology, and matches with thermodynamic system of steam tur well, can
Ensure therrmodynamic system Effec-tive Function.Additionally, the system can obtain relatively low flue dust and SOx concentration of emissions, both are expected to reach
10mg/Nm3Level.
The advantage of dust pelletizing system of the present invention is:
1. the system that heating agent adopts " main condensate-smoke re-heater-gas cooler-main condensate ".Main condensate
It is introduced into after smoke re-heater and passes through gas cooler, it is desirable to extracts the higher condensate of temperature, such as condensate extraction point
After No. 7 low-pressure heaters 2, when system works, No. 8 low-pressure heaters and No. 7 low-pressure heaters are not affected, i.e., will not
Exclusion low-pressure pumping steam, is conducive to improving the thermal efficiency of cycle of therrmodynamic system;
2. with the heat medium system of conventional art(" main condensate-gas cooler-smoke re-heater-main condensate "
System, such as Fig. 1,2,3 and 5)Compare, the heating agent of the present invention can adopt diversion and all the way system of backwater all the way, compare conventional art
Two-way diversion and two-way return water system are simple, also at all unnecessary to install hot water recirculation pump additional(Such as the hot water recirculation pump 19 of Fig. 5
It is shown);So much valve need not be adjusted in boiler operatiopn(See Fig. 1, Fig. 2 and Fig. 5), only need to adjust one group of valve(Fig. 6 it
The valve group 33 of electric control valve 17 and bypass valve 18 or Fig. 7).Only need to increase during underload into the solidifying of this heat medium system
The ratio of the amount of bearing water, you can reach the requirement of parameters;
3. due to present invention employs the temperature main condensate higher than conventional art as the heating agent of heat exchanger, low
There is no concern that heat medium temperature is too low during load(Such as less than 60 DEG C)Do not reach more than water with flue gas temperature in smoke re-heater
The requirement of about 20 DEG C of temperature of dew point;
4. the heat medium system of the present invention consumes in operation, not additional energy source, it is not necessary to such as MGGH systems(Such as Fig. 4)Like that,
Consume extra superheated steam;Also as shown in Figure 1, Figure 2 with Fig. 5 like that hot water re-circulation need not be needed.Because heating agent of the present invention is from flue gas
The energy that cooler is obtained empties back into the therrmodynamic system of steam turbine, and not extra consumed energy, so, from the angle of energy efficiency
Degree, the present invention is higher than prior art.