CN112763399B - Method for detecting flue gas corrosion risk area of low-temperature heating surface of boiler - Google Patents
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- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 title claims abstract description 149
- 239000003546 flue gas Substances 0.000 title claims abstract description 149
- 238000010438 heat treatment Methods 0.000 title claims abstract description 117
- 238000005260 corrosion Methods 0.000 title claims abstract description 72
- 230000007797 corrosion Effects 0.000 title claims abstract description 72
- 238000000034 method Methods 0.000 title claims abstract description 37
- RAHZWNYVWXNFOC-UHFFFAOYSA-N Sulphur dioxide Chemical compound O=S=O RAHZWNYVWXNFOC-UHFFFAOYSA-N 0.000 claims abstract description 116
- 239000007789 gas Substances 0.000 claims abstract description 58
- 238000012546 transfer Methods 0.000 claims abstract description 48
- 238000009826 distribution Methods 0.000 claims abstract description 28
- 238000001514 detection method Methods 0.000 claims abstract description 24
- 239000002253 acid Substances 0.000 claims abstract description 19
- 239000012530 fluid Substances 0.000 claims abstract description 8
- AKEJUJNQAAGONA-UHFFFAOYSA-N sulfur trioxide Chemical compound O=S(=O)=O AKEJUJNQAAGONA-UHFFFAOYSA-N 0.000 claims description 28
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 18
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 12
- 238000004364 calculation method Methods 0.000 claims description 9
- 238000006243 chemical reaction Methods 0.000 claims description 7
- 238000004781 supercooling Methods 0.000 claims description 7
- 239000007788 liquid Substances 0.000 claims description 4
- 230000003647 oxidation Effects 0.000 claims 2
- 238000007254 oxidation reaction Methods 0.000 claims 2
- 230000000694 effects Effects 0.000 abstract description 6
- 238000013461 design Methods 0.000 abstract description 4
- 235000010269 sulphur dioxide Nutrition 0.000 description 42
- 239000000779 smoke Substances 0.000 description 8
- 239000002184 metal Substances 0.000 description 7
- 239000011248 coating agent Substances 0.000 description 6
- 238000000576 coating method Methods 0.000 description 6
- 239000003245 coal Substances 0.000 description 3
- 238000004088 simulation Methods 0.000 description 3
- 230000001590 oxidative effect Effects 0.000 description 2
- 238000011084 recovery Methods 0.000 description 2
- 239000004291 sulphur dioxide Substances 0.000 description 2
- 239000002918 waste heat Substances 0.000 description 2
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 238000005299 abrasion Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 238000005536 corrosion prevention Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000012502 risk assessment Methods 0.000 description 1
- 239000004071 soot Substances 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
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Abstract
The invention discloses a method for detecting a flue gas corrosion risk area of a low-temperature heating surface of a boiler, which comprises the following steps of firstly, detecting and acquiring boundary conditions of the low-temperature heating surface of the boiler and a flue gas heat transfer area; secondly, acquiring pressure distribution and a temperature field of the flue gas on a low-temperature heating surface of the boiler by adopting computational fluid dynamics; thirdly, acquiring the pressure distribution of sulfur dioxide gas on the low-temperature heating surface of the boiler by adopting a similar principle; fourthly, calculating the temperature distribution of the acid dew point of the flue gas on the low-temperature heating surface of the boiler according to the pressure distribution of the sulfur dioxide gas; and fifthly, determining a risk area of the low-temperature heating surface of the boiler, which is easy to generate low-temperature flue gas corrosion, by combining a temperature field of the low-temperature heating surface of the boiler, and calculating the low-temperature corrosion risk probability. The method disclosed by the invention is simple in steps, reasonable in design, convenient to implement, low in detection cost, obvious in effect and convenient to popularize, and can be effectively applied to detection of a flue gas corrosion risk area of a low-temperature heating surface of a boiler, and the probability of low-temperature corrosion risk can be quantitatively analyzed.
Description
Technical Field
The invention belongs to the technical field of low-temperature corrosion detection, and particularly relates to a detection method for a smoke corrosion risk area of a low-temperature heating surface of a boiler.
Background
The boiler flue gas waste heat recovery mainly comprises a low-temperature heating surface, such as a coal economizer, an air preheater or other waste heat recovery devices, arranged at a flue at the tail of the boiler. For coal-fired boilers, oil-fired boilers, garbage incinerators and the like, the sulfur content of fuel is high, the combustion product of the boiler is mostly sulfuric acid vapor, and when the temperature of a low-temperature heating surface is lower than the acid dew point of flue gas, the sulfuric acid vapor is condensed into acid liquor on the heated surface, so that metal corrosion is caused, which is called low-temperature corrosion, and great potential safety hazard is brought to the operation of the boiler.
Therefore, in order to slow down or prevent low-temperature corrosion, a risk area of the boiler heating surface, which is prone to low-temperature corrosion, needs to be detected, and then safety protection measures can be applied to the boiler low-temperature heating surface in different levels according to different risk areas, so that the win-win purposes of reducing the boiler corrosion prevention cost and prolonging the service life are achieved.
In the prior art, a detection method for a smoke corrosion risk area of a low-temperature heating surface of a boiler is complex, the detection cost is high, but the detection result is single, the degree of low-temperature corrosion risk on the whole low-temperature heating surface of the boiler cannot be quantitatively reflected, and the cost for applying anticorrosion measures is increased.
Disclosure of Invention
The invention aims to solve the technical problem of providing a method for detecting a flue gas corrosion risk area of a low-temperature heating surface of a boiler aiming at the defects in the prior art, which has the advantages of simple steps, reasonable design, convenient realization, low detection cost, capability of being effectively applied to detection of the flue gas corrosion risk area of the low-temperature heating surface of the boiler, capability of quantitatively analyzing the probability of the low-temperature corrosion risk, obvious effect and convenient popularization.
In order to solve the technical problems, the invention adopts the technical scheme that: a detection method for a boiler low-temperature heating surface flue gas corrosion risk area comprises the following steps:
detecting and acquiring boundary conditions of a low-temperature heating surface and a flue gas heat transfer area of a boiler;
step two, acquiring pressure distribution and a temperature field of the flue gas on a low-temperature heating surface of the boiler by adopting computational fluid dynamics;
thirdly, obtaining the pressure distribution of sulfur dioxide gas on the low-temperature heating surface of the boiler by adopting a similar principle;
fourthly, calculating the temperature distribution of the acid dew point of the flue gas on the low-temperature heating surface of the boiler according to the pressure distribution of the sulfur dioxide gas;
and step five, determining a risk area of the low-temperature heating surface of the boiler, which is easy to generate low-temperature flue gas corrosion, by combining a temperature field of the low-temperature heating surface of the boiler, and calculating the low-temperature corrosion risk probability.
In the method for detecting the flue gas corrosion risk area of the low-temperature heating surface of the boiler, in the first step, the flue gas heat transfer area is an independent area for heat exchange between the low-temperature heating surface of the boiler and flue gas, and the boundary conditions comprise geometric boundary conditions, flowing heat transfer boundary conditions and flue gas component boundary conditions.
According to the detection method for the boiler low-temperature heating surface flue gas corrosion risk area, the geometric boundary conditions comprise that the distance range between an inlet and an outlet of flue gas in a flue gas heat transfer area and the boiler low-temperature heating surface is 10-30 cm; the flowing heat transfer boundary conditions comprise the average flow velocity, the average temperature and the average pressure of the flue gas at the inlet and the outlet of the flue gas heat transfer area, the average flow velocity ranges from 3m/s to 20m/s, the average temperature ranges from 60 ℃ to 240 ℃, the average pressure is the absolute pressure, and the range is 80kPa to 105 kPa; the boundary conditions of the components of the flue gas comprise the average volume content of sulfur dioxide gas and water vapor at the inlet and the outlet of the flue gas in a flue gas heat transfer area, the average volume content of the sulfur dioxide gas ranges from 1ppm to 1000ppm, and the average volume content of the water vapor ranges from 2% to 14%.
According to the detection method for the flue gas corrosion risk area of the low-temperature heating surface of the boiler, the average flow velocity is detected through a pitot tube; the average temperature is detected by a temperature sensor; the average pressure is detected by a pressure sensor.
In the method for detecting the flue gas corrosion risk area of the low-temperature heating surface of the boiler, the computational fluid mechanics in the step two is subjected to numerical simulation calculation by adopting a steady-state method.
In the third step, the specific process of obtaining the pressure distribution of the sulfur dioxide gas on the low-temperature heating surface of the boiler by using the similarity principle includes: according to the condition that the partial pressure of the sulfur dioxide gas deviates from the average pressure thereof to a degree similar to the partial pressure of the flue gas deviates from the average pressure thereof, calculating the pressure distribution of the sulfur dioxide gas on the low-temperature heating surface of the boiler, wherein the calculation expression is
Wherein,
is the pressure of sulfur dioxide gas on the low-temperature heating surface of the boiler,
is the average pressure of sulfur dioxide gas on the low-temperature heating surface of the boiler, p is the local pressure of the flue gas on the low-temperature heating surface of the boiler,
the average pressure p of the flue gas on the low-temperature heating surface of the boilermaxThe maximum pressure p of the flue gas on the low-temperature heating surface of the boilerminIs the minimum pressure of the flue gas on the low-temperature heating surface of the boiler,
is the maximum pressure of sulfur dioxide gas on the low-temperature heating surface of the boiler,
the minimum pressure of sulfur dioxide gas on the low-temperature heating surface of the boiler。
In the fourth step, the specific process of calculating the distribution of the acid dew point temperature of the flue gas on the low-temperature heating surface of the boiler according to the pressure distribution of the sulfur dioxide gas comprises the following steps: calculating the critical temperature of the low-temperature heating surface corroded by the sulfuric acid liquid formed by sulfur trioxide gas and water vapor in the flue gas by adopting a Verhoff formula, wherein the calculation expression is
Wherein, tsldIs the flue gas acid dew point temperature of the low-temperature heating surface of the boiler,
is the partial pressure of the water vapor in the flue gas,
is the partial pressure of sulfur trioxide gas in the flue gas.
According to the method for detecting the corrosion risk area of the flue gas on the low-temperature heating surface of the boiler, the sulfur trioxide gas is formed by oxidizing the sulfur dioxide in the flue gas, and the conversion rate of the sulfur dioxide oxidized into sulfur trioxide
Wherein,
is the average volume content of sulfur dioxide gas at the inlet of the flue gas heat transfer area,
the average volume content of sulfur dioxide gas at the outlet of the flue gas heat transfer area is shown, and the conversion rate a ranges from 0% to 3%.
In the method for detecting the flue gas corrosion risk area of the low-temperature heating surface of the boiler, the temperature field of the low-temperature heating surface of the boiler is combined to determine the low-temperature stress of the boilerThe specific process of the hot surface in the risk area prone to low-temperature flue gas corrosion comprises the following steps: the risk area which is easy to generate low-temperature corrosion of the flue gas is judged through supercooling temperature difference, and the supercooling temperature difference delta t is tw-tsldWherein, twSurface temperature, t, of the low-temperature heated surface of the boilersldThe temperature is the acid dew point temperature of the flue gas on the low-temperature heating surface of the boiler, and when delta t of a local area of the low-temperature heating surface of the boiler is less than or equal to 0, the local area is judged to be a risk area which is easy to generate low-temperature corrosion of the flue gas.
In the method for detecting the flue gas corrosion risk area of the low-temperature heating surface of the boiler, in the fifth step, the low-temperature corrosion risk probability is the ratio of the area of the risk area where the low-temperature corrosion of the flue gas easily occurs to the total heat transfer area of the low-temperature heating surface of the boiler.
Compared with the prior art, the invention has the following advantages:
1. the method has simple steps, reasonable design and convenient realization.
2. According to the invention, by combining theory and experiment and adopting a similar principle method, the detection of the local distribution characteristic of trace sulfur dioxide gas in the flue gas is realized, the effective detection of the flue gas corrosion risk area of the low-temperature heating surface of the boiler is obtained by combining the calculation of the acid dew point temperature of the floating flue gas, and the reliability of the detection result is obviously improved.
3. The invention provides a concept of the low-temperature corrosion risk probability of the low-temperature heating surface of the boiler, quantitatively reflects the degree of low-temperature corrosion risk on the whole low-temperature heating surface of the boiler, provides accurate guidance basis for the protection measures of the heating surface, and can obviously reduce the cost of applying anticorrosion measures.
4. The boiler detection method based on risk analysis can judge the low-temperature corrosion risk area of the low-temperature heating surface of the boiler without depending on a large amount of detection data, can reduce the safety detection cost of the boiler, and is beneficial to the safety prevention and control of a boiler system.
5. The method can be effectively applied to detection of the flue gas corrosion risk area of the low-temperature heating surface of the boiler, has obvious effect and is convenient to popularize.
In conclusion, the method provided by the invention has the advantages of simple steps, reasonable design, convenience in implementation, low detection cost, obvious effect and convenience in popularization, can be effectively applied to detection of the flue gas corrosion risk area of the low-temperature heating surface of the boiler, and can be used for quantitatively analyzing the probability of the low-temperature corrosion risk.
The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.
Drawings
FIG. 1 is a flow chart of a method of the present invention;
FIG. 2 is a diagram for verifying the detection effect of the H-shaped finned elliptical tube heat exchanger in a low-temperature corrosion risk area in flue gas by using the method disclosed by the invention.
Detailed Description
As shown in FIG. 1, the method for detecting the flue gas corrosion risk area of the low-temperature heating surface of the boiler comprises the following steps:
detecting and acquiring boundary conditions of a low-temperature heating surface and a flue gas heat transfer area of a boiler;
step two, acquiring pressure distribution and a temperature field of the flue gas on a low-temperature heating surface of the boiler by adopting computational fluid dynamics;
thirdly, obtaining the pressure distribution of sulfur dioxide gas on the low-temperature heating surface of the boiler by adopting a similar principle;
fourthly, calculating the temperature distribution of the acid dew point of the flue gas on the low-temperature heating surface of the boiler according to the pressure distribution of the sulfur dioxide gas;
and step five, determining a risk area of the low-temperature heating surface of the boiler, which is easy to generate low-temperature flue gas corrosion, by combining a temperature field of the low-temperature heating surface of the boiler, and calculating the low-temperature corrosion risk probability.
In this embodiment, the flue gas heat transfer area in the first step is an independent area where the low-temperature heating surface of the boiler exchanges heat with flue gas, and the boundary conditions include a geometric boundary condition, a flow heat transfer boundary condition, and a flue gas component boundary condition.
In the embodiment, the geometric boundary conditions comprise that the distance range between an inlet and an outlet of the flue gas in the flue gas heat transfer area and the low-temperature heating surface of the boiler is 10-30 cm; the flowing heat transfer boundary conditions comprise the average flow velocity, the average temperature and the average pressure of the flue gas at the inlet and the outlet of the flue gas heat transfer area, the average flow velocity ranges from 3m/s to 20m/s, the average temperature ranges from 60 ℃ to 240 ℃, the average pressure is the absolute pressure, and the range is 80kPa to 105 kPa; the boundary conditions of the components of the flue gas comprise the average volume content of sulfur dioxide gas and water vapor at the inlet and the outlet of the flue gas in a flue gas heat transfer area, the average volume content of the sulfur dioxide gas ranges from 1ppm to 1000ppm, and the average volume content of the water vapor ranges from 2% to 14%.
In this embodiment, the average flow rate is detected by a pitot tube; the average temperature is detected by a temperature sensor; the average pressure is detected by a pressure sensor.
In this embodiment, the computational fluid dynamics in the second step adopts a steady-state method to perform numerical simulation computation.
In this embodiment, the specific process of obtaining the pressure distribution of the sulfur dioxide gas on the low-temperature heated surface of the boiler by using the similar principle in the third step includes: according to the condition that the partial pressure of the sulfur dioxide gas deviates from the average pressure thereof to a degree similar to the partial pressure of the flue gas deviates from the average pressure thereof, calculating the pressure distribution of the sulfur dioxide gas on the low-temperature heating surface of the boiler, wherein the calculation expression is
Wherein,
is the pressure of sulfur dioxide gas on the low-temperature heating surface of the boiler,
is the average pressure of sulfur dioxide gas on the low-temperature heating surface of the boiler, p is the local pressure of the flue gas on the low-temperature heating surface of the boiler,
the average pressure p of the flue gas on the low-temperature heating surface of the boilermaxIs flue gasMaximum pressure at the low-temperature heated surface of the boiler, pminIs the minimum pressure of the flue gas on the low-temperature heating surface of the boiler,
is the maximum pressure of sulfur dioxide gas on the low-temperature heating surface of the boiler,
the minimum pressure of sulfur dioxide gas on the low-temperature heating surface of the boiler.
In this embodiment, the specific process of calculating the temperature distribution of the dew point of the flue gas acid on the low-temperature heated surface of the boiler according to the pressure distribution of the sulfur dioxide gas in the fourth step includes: calculating the critical temperature of the low-temperature heating surface corroded by the sulfuric acid liquid formed by sulfur trioxide gas and water vapor in the flue gas by adopting a Verhoff formula, wherein the calculation expression is
Wherein, tsldIs the flue gas acid dew point temperature of the low-temperature heating surface of the boiler,
is the partial pressure of the water vapor in the flue gas,
is the partial pressure of sulfur trioxide gas in the flue gas.
When the temperature of the metal surface of a certain local area of the low-temperature heating surface of the boiler is lower than the acid dew point temperature of the flue gas of the area, the area can be condensed with the liquid sulfuric acid and can be judged as a low-temperature corrosion risk area, and the maximum value of the floating acid dew point temperature of the flue gas can be obtained through a Verhoff formula, so that the effective prediction of the low-temperature corrosion risk area can be realized.
In this exampleThe sulfur trioxide gas is formed by oxidizing sulfur dioxide in the flue gas, and the conversion rate of the sulfur dioxide to sulfur trioxide
Wherein,
is the average volume content of sulfur dioxide gas at the inlet of the flue gas heat transfer area,
the average volume content of sulfur dioxide gas at the outlet of the flue gas heat transfer area is shown, and the conversion rate a ranges from 0% to 3%.
In this embodiment, the specific process of determining the risk region of the low-temperature heating surface of the boiler, where low-temperature flue gas corrosion easily occurs, by combining the temperature field of the low-temperature heating surface of the boiler in the fifth step includes: the risk area which is easy to generate low-temperature corrosion of the flue gas is judged through supercooling temperature difference, and the supercooling temperature difference delta t is tw-tsldWherein, twSurface temperature, t, of the low-temperature heated surface of the boilersldThe temperature is the acid dew point temperature of the flue gas on the low-temperature heating surface of the boiler, and when delta t of a local area of the low-temperature heating surface of the boiler is less than or equal to 0, the local area is judged to be a risk area which is easy to generate low-temperature corrosion of the flue gas.
In this embodiment, the low-temperature corrosion risk probability in the fifth step is a ratio of a risk area where low-temperature corrosion of flue gas is likely to occur to a total heat transfer area of the low-temperature heating surface of the boiler.
In order to verify the effect of the method, the flue gas corrosion risk area is detected by aiming at a coal economizer at the tail part of a flue of a certain coal-fired boiler, the coal economizer is a tubular oval tube heat exchanger, the water supply pressure in the tube is supplied by a deaerator (104 ℃), and an H-shaped fin is welded outside the tube for strengthening heat transfer and preventing soot abrasion.
Firstly, boundary conditions of a low-temperature heating surface and a smoke heat transfer area of a boiler are obtained, and the average flow velocity of smoke at an inlet of the smoke heat transfer area is 7.4m/s and the average flow velocity of the smoke at an outlet of the smoke heat transfer area is 6.9m/s through pitot tube measurement; measuring the average temperature of the flue gas at the inlet of the flue gas heat transfer area to be 143 ℃ and the average temperature of the flue gas at the outlet of the flue gas heat transfer area to be 96 ℃ by using a temperature sensor; measuring the average pressure of the flue gas at the inlet of the flue gas heat transfer area to be 103kPa and the average pressure of the flue gas at the outlet of the flue gas heat transfer area to be 102kPa by a pressure sensor; for the detection task of the invention, only the component contents of sulfur dioxide and water vapor are needed to be obtained, the average volume content of the sulfur dioxide gas at the inlet of the flue gas heat transfer area is 106ppm and the average volume content of the sulfur dioxide gas at the outlet of the flue gas heat transfer area is 105ppm, which are measured by a flue gas analyzer, and the average volume content of the water vapor at the inlet of the flue gas heat transfer area is 6.94% and the average volume content of the water vapor at the outlet of the flue gas heat transfer area is 7.01% which are measured by a moisture meter.
And secondly, performing numerical simulation on the tube array type H-shaped elliptical finned tube heat exchanger by a computational fluid mechanics method to obtain the smoke pressure distribution and the temperature field of the metal surface of the heat exchange tube.
And thirdly, according to the similar principle provided by the invention, the sulfur dioxide gas content of all areas on the metal surface of the heat exchanger is calculated by combining the obtained flue gas pressure distribution and the measured average volume content of the sulfur dioxide gas at the inlet and the outlet of the flue gas heat transfer area. Since the content of water vapour is 4 orders of magnitude higher than the sulphur dioxide content, the local content of water vapour relative to sulphur dioxide can be considered as a constant value.
And fourthly, calculating the acid dew point temperature of the flue gas on the surface of the H-shaped elliptical finned tube, calculating the conversion rate of sulfur dioxide oxidized into sulfur trioxide to be 0.94% according to the average volume content of sulfur dioxide gas at the inlet and the outlet of the flue gas heat transfer area, further calculating the content of the sulfur trioxide gas, and calculating the acid dew point temperature on the surface of the heat exchanger through a Verhoff formula.
And fifthly, judging the risk area of the H-shaped elliptical finned tube subjected to low-temperature corrosion, and using the supercooling temperature difference parameter delta t less than or equal to 0 as the risk area for judging the low-temperature corrosion, as shown in figure 2, wherein the metal wall surface of the safe area is deleted for conveniently estimating the risk probability. As can be seen from fig. 2, the proportion of the metal surface prone to low-temperature corrosion in the entire heat transfer surface is about two thirds, and the quantified risk probability is 72.86% by statistical calculation, that is, for the economizer, at least 72.86% of the metal heat transfer surfaces are at risk of low-temperature corrosion.
When taking anticorrosion measures for the whole heat transfer surface, the risk area should be focused on, for example, through anticorrosion of the coating, the thickness of the coating in the risk area should be significantly higher than that in other areas, and for the safety area, the thickness of the coating can be reduced properly, thereby saving the cost. By adopting the method, the risk area of low-temperature corrosion is detected, the anticorrosion measures can be realized through the non-uniform coating, and about 27 percent of coating raw materials can be saved compared with the traditional uniform coating.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and all simple modifications, changes and equivalent structural changes made to the above embodiment according to the technical spirit of the present invention still fall within the protection scope of the technical solution of the present invention.
Claims (8)
1. A detection method for a boiler low-temperature heating surface flue gas corrosion risk area is characterized by comprising the following steps:
detecting and acquiring boundary conditions of a low-temperature heating surface and a flue gas heat transfer area of a boiler;
step two, acquiring pressure distribution and a temperature field of the flue gas on a low-temperature heating surface of the boiler by adopting computational fluid dynamics;
thirdly, obtaining the pressure distribution of sulfur dioxide gas on the low-temperature heating surface of the boiler by adopting a similar principle;
according to the condition that the partial pressure of the sulfur dioxide gas deviates from the average pressure thereof to a degree similar to the partial pressure of the flue gas deviates from the average pressure thereof, calculating the pressure distribution of the sulfur dioxide gas on the low-temperature heating surface of the boiler, wherein the calculation expression is
Wherein,
is the pressure of sulfur dioxide gas on the low-temperature heating surface of the boiler,
is the average pressure of sulfur dioxide gas on the low-temperature heating surface of the boiler, p is the local pressure of the flue gas on the low-temperature heating surface of the boiler,
the average pressure p of the flue gas on the low-temperature heating surface of the boilermaxThe maximum pressure p of the flue gas on the low-temperature heating surface of the boilerminIs the minimum pressure of the flue gas on the low-temperature heating surface of the boiler,
is the maximum pressure of sulfur dioxide gas on the low-temperature heating surface of the boiler,
the minimum pressure of sulfur dioxide gas on the low-temperature heating surface of the boiler;
fourthly, calculating the temperature distribution of the acid dew point of the flue gas on the low-temperature heating surface of the boiler according to the pressure distribution of the sulfur dioxide gas;
calculating the critical temperature of the low-temperature heating surface corroded by the sulfuric acid liquid formed by sulfur trioxide gas and water vapor in the flue gas by adopting a Verhoff formula, wherein the calculation expression is
Wherein, tsldIs the flue gas acid dew point temperature of the low-temperature heating surface of the boiler,
is the partial pressure of the water vapor in the flue gas,
the partial pressure of sulfur trioxide gas in the flue gas;
and step five, determining a risk area of the low-temperature heating surface of the boiler, which is easy to generate low-temperature flue gas corrosion, by combining a temperature field of the low-temperature heating surface of the boiler, and calculating the low-temperature corrosion risk probability.
2. The method for detecting the boiler low-temperature heating surface flue gas corrosion risk area according to claim 1, wherein in the step one, the flue gas heat transfer area is an independent area where the boiler low-temperature heating surface and the flue gas exchange heat, and the boundary conditions comprise geometric boundary conditions, flow heat transfer boundary conditions and flue gas component boundary conditions.
3. The method for detecting the boiler low-temperature heating surface flue gas corrosion risk area according to claim 2, wherein the geometric boundary conditions comprise that the distance between an inlet and an outlet of the flue gas in the flue gas heat transfer area and the boiler low-temperature heating surface is 10 cm-30 cm; the flowing heat transfer boundary conditions comprise the average flow velocity, the average temperature and the average pressure of the flue gas at the inlet and the outlet of the flue gas heat transfer area, the average flow velocity ranges from 3m/s to 20m/s, the average temperature ranges from 60 ℃ to 240 ℃, the average pressure is the absolute pressure, and the range is 80kPa to 105 kPa; the boundary conditions of the components of the flue gas comprise the average volume content of sulfur dioxide gas and water vapor at the inlet and the outlet of the flue gas in a flue gas heat transfer area, the average volume content of the sulfur dioxide gas ranges from 1ppm to 1000ppm, and the average volume content of the water vapor ranges from 2% to 14%.
4. The method for detecting the flue gas corrosion risk area of the low-temperature heating surface of the boiler as recited in claim 3, wherein the average flow velocity is detected by a pitot tube; the average temperature is detected by a temperature sensor; the average pressure is detected by a pressure sensor.
5. The method for detecting the flue gas corrosion risk area of the low-temperature heating surface of the boiler according to claim 1, wherein the computational fluid dynamics in the second step is numerically simulated and calculated by adopting a steady-state method.
6. The method for detecting the corrosion risk area of the flue gas on the low-temperature heating surface of the boiler as recited in claim 1, wherein the sulfur trioxide gas is formed by the oxidation of sulfur dioxide in the flue gas, and the conversion rate of the oxidation of sulfur dioxide into sulfur trioxide
Wherein,
is the average volume content of sulfur dioxide gas at the inlet of the flue gas heat transfer area,
the average volume content of sulfur dioxide gas at the outlet of the flue gas heat transfer area is shown, and the conversion rate a ranges from 0% to 3%.
7. The method for detecting the flue gas corrosion risk area of the low-temperature heating surface of the boiler according to claim 1, wherein the specific process for determining the risk area of the low-temperature heating surface of the boiler, which is prone to flue gas low-temperature corrosion, by combining the temperature field of the low-temperature heating surface of the boiler in the fifth step comprises the following steps: the risk area which is easy to generate low-temperature corrosion of the flue gas is judged through supercooling temperature difference, and the supercooling temperature difference delta t is tw-tsldWherein, twSurface temperature, t, of the low-temperature heated surface of the boilersldThe temperature is the acid dew point temperature of the flue gas on the low-temperature heating surface of the boiler, and when delta t of a local area of the low-temperature heating surface of the boiler is less than or equal to 0, the local area is judged to be a risk area which is easy to generate low-temperature corrosion of the flue gas.
8. The method for detecting the flue gas corrosion risk area of the low-temperature heating surface of the boiler according to claim 1, wherein the low-temperature corrosion risk probability in the fifth step is a ratio of an area of the risk area where low-temperature corrosion of the flue gas is prone to occur to a total heat transfer area of the low-temperature heating surface of the boiler.
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