Ammonia desulfurization ammonium salt aerosol source identification method and device

Abstract

The application provides an ammonia desulfurization ammonium salt aerosol source identification method and device. The method comprises the following steps: introducing ammonia desulfurization outlet or simulating ammonia-containing and sulfur-containing sample gas; determining sample gas dew point temperature under constant speed sampling; pre-separating and collecting flushing liquid from sample gas droplet; the first constant temperature filtration section is controlled above the sample gas dew point, and the original filterable ammonium salt particles are captured; after filtration, the sample gas is reduced below the dew point, the condensable ammonium salt is formed and captured in the condensation conversion section; the remaining gaseous ammonia is captured by series acid absorption; ammonium in each stage sample is detected, and sulfate or sulfite in droplets, the first filter membrane and the condensation captured sample is checked to calculate the contribution rate of each phase state source, the nitrogen and sulfur mass balance deviation, and the dominant source of the ammonium salt aerosol is identified when the validity check containing the nitrogen and sulfur mass balance deviation meets the conditions. The application can distinguish the droplet entrainment, the original particle, the sampling condensation conversion and the gaseous ammonia escape conversion potential, and reduce the misjudgment of the aerosol source caused by the conventional total sampling.

Description

Technical Field

[0001] This invention relates to the field of detection and evaluation of pollutants in coal-fired flue gas and optimization of ammonia-based desulfurization processes, and in particular to a method and apparatus for identifying the source of ammonium salt aerosols in ammonia-based desulfurization, specifically a method and apparatus for identifying the source of ammonium salt aerosols in ammonia-based desulfurization based on dew point-phase staged collection. Background Technology

[0002] Ammonia-based desulfurization uses ammonia water, liquid ammonia, ammonia gas, or ammonia-containing waste liquid as absorbents to absorb sulfur dioxide from coal-fired flue gas. Byproducts can be converted into ammonium sulfate or ammonium sulfite, offering advantages such as rapid absorption rate and resource utilization of byproducts. However, during the operation of ammonia-based desulfurization, the outlet wet flue gas may simultaneously contain entrained ammonium salts from liquid droplets, pre-formed filterable ammonium salt particles, condensable ammonium salt particles formed during the cooling process through the continued reaction or condensation of gaseous ammonia with acidic components, and unabsorbed gaseous ammonia.

[0003] In existing detection methods, ammonia slip detection typically focuses on determining the concentration of gaseous ammonia after it has been absorbed by acid; particulate matter sampling typically focuses on the total dust or filterable particulate matter mass; and condensable particulate matter sampling typically focuses on the total amount of particulate matter generated after condensation. While these methods can provide the total amount of a particular type of pollutant, they struggle to differentiate between droplet entrainment, native filterable particles, condensed particles, and the potential for gaseous ammonia slip transformation within the same sampling sequence.

[0004] Especially when the wet flue gas at the outlet of the ammonia-based desulfurization process is close to saturation, and the temperature of the sampling pipeline, filter, or absorption bottle is slightly lower than the dew point of the sample gas, components such as gaseous ammonia, sulfur dioxide, sulfur trioxide, ammonium bisulfite, or ammonium sulfate may continue to condense or react during the sampling process. In this case, the ammonium salts captured on the filter may be particles originally present in the flue gas, or particles that are formed secondaryly due to cooling during the sampling process, leading to misjudgments of the aerosol formation path.

[0005] Existing ammonia desulfurization aerosol control technologies primarily focus on in-tower demisting, water washing, wet electrostatic precipitators, operating parameter adjustment, or additive suppression. However, they lack graded sampling and evaluation methods that can provide source diagnosis basis for these control measures. Existing ammonia slip and particulate matter sampling devices typically do not use the sample gas dew point as a phase classification boundary, nor do they combine nitrogen-sulfur mass balance, acid absorption breakthrough, and sampling validity verification to determine the reliability of source identification results.

[0006] Therefore, there is a need for a method and device specifically for identifying the source of ammonium salt aerosols in wet flue gas from ammonia desulfurization, which can separate different sources according to phase state and dew point boundary in the same sampling process, and improve the reliability of judgment through mass balance and validity verification. Summary of the Invention

[0007] The purpose of this invention is to provide a method and apparatus for identifying the source of ammonium salt aerosols in ammonia desulfurization, so as to solve the problem that conventional total sampling is difficult to distinguish between droplet entrainment, native filterable particles, condensed particles and gaseous ammonia escape and conversion potential.

[0008] A first aspect of the present invention provides a method for identifying the source of ammonium salt aerosols from ammonia-based desulfurization processes, comprising the following steps: S1. Introduce ammonia-containing and sulfur-containing sample gas from the ammonia desulfurization outlet or simulate the ammonia desulfurization process; S2. Determine the dew point temperature T of the sample gas before it enters the staged collection link under constant velocity sampling conditions. dp And record the sampling rate deviation and the standard state sampling volume V. s ; S3, at a temperature not lower than the sample gas dew point temperature T dp Under certain conditions, the sample gas entrained droplets were pre-separated, the rinsing liquid from the pre-separation part of the droplets was collected, and the droplet phase trap was obtained. S4. The sample gas after droplet pre-separation is sent into the first isothermal filtration section, and the collection temperature T of the first isothermal filtration section is set to... H The temperature is higher than the dew point temperature T of the sample gas. dp Captures native filterable ammonium salt particles; S5. Cool the sample gas after passing through the first constant temperature filtration section to a temperature lower than the sample gas dew point temperature T. dp Condensation temperature T C The condensate is collected and the ammonium salt particles generated by the condensation are captured by a second filter. S6. Allow the sample gas after the second filter to enter at least two stages of series acid absorption sections to capture the remaining gaseous ammonia. S7. Detect the NH4+ content in the rinsing solution, the first constant-temperature filtration section trap, the condensate, the second filter trap, and the acid absorption solution, and detect the SO4 content in the rinsing solution, the first constant-temperature filtration section trap, the condensate, and the second filter trap. 2- or SO3 2- The content, m, is calculated from the test results to obtain the amount of ammonium salt entrained in the droplet. d Original filterable ammonium salt particle size (m) f The amount of ammonium salt particles generated by condensation (m) c and gaseous ammonia escape amount m n ; S8, according to m d m f m c and m n The contribution rate of each phase source was calculated using a unified denominator, and the dominant source of ammonium salt aerosols from ammonia desulfurization was identified based on the nitrogen-sulfur mass balance deviation and the sampling validity verification results.

[0009] Preferably, in step S1, the ammonia- and sulfur-containing sample gas originates from the outlet of the ammonia-based desulfurization absorption tower, the outlet of the demister, the inlet of the wet electrostatic precipitator, the outlet of the wet electrostatic precipitator, the outlet of the pilot-scale absorption reactor, or the outlet of the laboratory constant-temperature absorption reactor.

[0010] In this invention, the dew point temperature Tdp of the sample gas is used as the basis for the classification boundary in step S2 because: the wet flue gas at the outlet of the ammonia desulfurization process is usually close to the water vapor saturation state, and when the sampling link temperature is lower than Tdp... dp At this time, gaseous ammonia, acidic sulfur-containing components, and water vapor may continue to condense or react during sampling, forming secondary ammonium salt particles; when the sampling link temperature is maintained at T... dp When the above is achieved, the amount of condensed particles generated during the sampling process mixed with the original filterable particulate matter can be reduced. Therefore, the present invention uses T dp As phase classification boundaries, the objects to be captured above the dew point are limited to droplet entrainment and native filterable particles, while the objects to be captured below the dew point are limited to condensation-transformed traps formed under specified condensation conditions.

[0011] Preferably, in step S2, the constant-rate sampling condition must satisfy: The relative deviation between the sampling nozzle speed and the mainstream speed of the flue or reactor is no more than 10%. When the relative deviation exceeds 10% and the duration exceeds the preset time, the sampling is marked as a sample to be reviewed. The preset time is 1 to 5 minutes, or 5% to 10% of the total sampling time.

[0012] Preferably, in step S3, the droplet pre-separation is performed using an impactor, cyclone trap, baffle trap, or inertial separator trap, and the droplet pre-separation area is rinsed with deionized water, dilute acid, or an absorbent with a known ion background after sampling.

[0013] Preferably, in step S4, the collection temperature T of the first isothermal filtration section is... H satisfy: ; In the formula, ΔT H The temperature ranges from 10 degrees Celsius to 60 degrees Celsius, ΔT H The temperature fluctuation of the first constant temperature filtration section is determined based on the sample gas dew point measurement error, the temperature fluctuation of the first constant temperature filtration section, the temperature resistance range of the filter membrane, and the thermal stability of the ammonium salt. The temperature fluctuation of the first constant temperature filtration section is no greater than ±5 degrees Celsius, and the pore size of the filter membrane of the first constant temperature filtration section is 0.1 micrometers to 1.0 micrometers.

[0014] Preferably, in step S5, the condensation temperature T C satisfy: ; In the formula, ΔT C The temperature ranges from 10 degrees Celsius to 70 degrees Celsius, ΔTC The condensation temperature T is determined based on the sample gas moisture content, condenser heat exchange capacity, condensate load, and the integrity of condensable component capture. C The temperature ranges from 5 degrees Celsius to 45 degrees Celsius, and a second filter is installed after the condensate collector.

[0015] Specifically, the temperature margin ΔT of the first constant-temperature filtration section H Condensation temperature difference ΔT C The filter membrane pore size, acid absorption breakthrough ratio, dominant source threshold, and parallel source difference threshold can all be determined through on-site calibration or laboratory simulation calibration. During calibration, the sample gas moisture content, ammonia concentration, sulfur dioxide or sulfur trioxide concentration, absorbent pH, outlet flue gas temperature, and demisting status are changed respectively, and the NH4 content in each stage of the collected material is recorded. + SO4 2- or SO3 2- The optimal control range is defined as the range of parameters that can stably distinguish the phase source and meet the mass balance check, including content, blank value, spiked recovery rate, and repeat sampling bias.

[0016] Preferably, in step S6, the at least two-stage series acid absorption section includes: a first acid absorption bottle and a second acid absorption bottle. When the ratio of the amount of ammonia captured by the second acid absorption bottle to the amount of ammonia captured by the first acid absorption bottle exceeds a preset breakthrough ratio, the sampling is marked as an absorption breakthrough sampling. The preset breakthrough ratio is 5% to 10%, and the preset breakthrough ratio is determined based on the concentration of the acid absorption liquid, the volume of the absorption liquid, the sampling volume, and the spiked recovery result.

[0017] Preferably, in step S8, according to m d m f m c and m n The contribution rate of each phase source is calculated using a unified denominator, including: droplet entrainment contribution rate R. d Native filterable contribution rate R f Condensation generation contribution rate R c Contribution rate R of gaseous ammonia escape n : Droplet entrainment contribution rate R d Satisfy the following formula: ; Native filterable contribution rate R f Satisfy the following formula: ; Condensation generation contribution rate R c Satisfy the following formula: ; Contribution rate of gaseous ammonia escape R n Satisfy the following formula: .

[0018] R d R f R c and R n Using m d m f m c and m n The sum of these components serves as a unified denominator, enabling comparisons of droplet entrainment paths, native filterable particle paths, condensation generation paths, and gaseous ammonia escape paths under the same caliber.

[0019] Preferably, when R d R f R c and R n When the maximum value in the sample is greater than a preset dominant threshold and the sampling validity verification is qualified, the droplet entrainment path, native filterable particle path, condensation generation path, or gaseous ammonia escape path corresponding to the maximum value is identified as the dominant source; when the difference between any two contribution rates is less than a preset difference threshold, the corresponding path is identified as a parallel source; the preset dominant threshold is 0.50 to 0.70, the preset difference threshold is 0.05 to 0.15, and the preset difference threshold is determined based on parallel sampling deviation, ion detection error, or spike recovery rate.

[0020] Preferably, in step S8, the nitrogen-sulfur mass balance deviation E NS Used to verify the composition of ammonium salts, satisfying the following formula: ; In the formula, n N The sum of the molar amounts of nitrogen calculated from NH4+ in the rinsing fluid, the first isothermal filtration section trap, the condensate, and the second filter trap; n S The rinsing fluid, the product collected in the first constant-temperature filtration section, the condensate, and the product collected in the second filter contain SO4. 2- and SO3 2- The sum of the converted molar amounts of sulfur, and the NH4 in the acid absorption solution. + Used to calculate m n Excluding E NS λ is determined based on the ammonium salt species; when ammonium sulfate or ammonium sulfite is the main component, λ is 2; when ammonium acid sulfite or ammonium bisulfate is the main component, λ is 1; when it is a mixed ammonium salt, λ is a value obtained by weighting the mole fraction of different ammonium salt species.

[0021] Nitrogen-sulfur mass balance deviation E NS Used to determine whether the ammonium ions and sulfoxide anions in the collected material conform to the stoichiometric relationship of ammonium salts. When E NSA high E value indicates the possible presence of undetected non-sulfate ammonium salts, non-sulfate non-ammonium salts, impurities entrained in the absorbent, sample loss, or detection errors. Therefore, the source contribution rate should not be directly used to determine the dominant source. NS When the preset validity conditions are met, it indicates that the ammonium salt composition of each stage of the collected samples matches the selected ammonium salt species coefficient, and the R... d R f R c and R n They are comparable.

[0022] Preferably, in step S8, the ammonium salt aerosol formation index Ia is also calculated, satisfying the following formula: .

[0023] Preferably, in step S8, the sampling validity verification includes at least a nitrogen-sulfur mass balance deviation verification, and also includes at least three of the following: isochronous sampling deviation verification, first isothermal filtration section temperature deviation verification, condensation temperature deviation verification, series acid absorption breakthrough verification, blank value verification, and spiked recovery rate verification; wherein, the blank value is used to subtract the background of reagents, filter membranes, or rinsing solutions, and the spiked recovery rate is used to verify NH4. + SO4 2- or SO3 2- Extraction and recovery status.

[0024] Preferably, in step S8, when the sampling validity verification fails, the dominant source result is not output, or a verification mark is output, and sampling is performed again or at least one of the filter membrane, acid absorbent, condenser collector, and droplet pre-separation component is replaced.

[0025] Preferably, steps S1 to S8 are repeated under different absorbent pH, absorbent temperature, flue gas temperature, SO2 concentration, oxygen content, ammonium salt concentration, liquid-to-gas ratio, demister flushing intensity, or additive dosage, and according to R d R f R c R n I a and E NS Screening for operating conditions or additives that result in low aerosol generation and low ammonia slip.

[0026] A second aspect of the present invention provides an apparatus for performing the ammonia-based desulfurization ammonium salt aerosol source identification method, comprising: a sample gas introduction unit, an isokinetic sampling and dew point measurement unit, a droplet pre-separation unit, a first isothermal filtration unit, a condensation conversion and trapping unit, a series acid absorption unit, and a metering pumping unit connected sequentially along the sample gas flow direction; a data processing and source identification unit associated with data from the droplet pre-separation unit, the first isothermal filtration unit, the condensation conversion and trapping unit, the series acid absorption unit, and the metering pumping unit; and a detection data input unit or an offline detection interface; the detection data input unit or offline detection interface is used to receive NH4 from each trapped substance. + SO4 2- or SO3 2- The detection results are then sent to the data processing and source identification unit.

[0027] Preferably, the data processing and source identification unit is configured to calculate R. d R f R c R n I a and E NS And when the sampling validity check, which includes at least the nitrogen-sulfur mass balance deviation, meets the preset validity conditions, the dominant source of ammonium salt aerosols will be output.

[0028] Preferably, the first constant temperature filtration unit includes a heated sampling tube, a constant temperature filtration chamber, a first filter, a first temperature detection element, and a first temperature control element; the condensation conversion and collection unit includes a condenser, a condensate collector, a second filter, a second temperature detection element, and a second temperature control element.

[0029] The present invention has at least the following beneficial effects: (1) The present invention uses the dew point temperature of the sample gas as the grading boundary. Above the dew point, the filter is maintained to capture native filterable ammonium salt particles, and below the dew point, the condensation is induced and captured to generate ammonium salt particles, which can reduce the source confusion caused by sampling cooling.

[0030] (2) The present invention combines droplet pre-separation, constant temperature filtration above the dew point, condensation conversion and capture below the dew point and series acid absorption in sequence, so that the amount of ammonium salt entrained by droplets, the amount of native filterable ammonium salt particles, the amount of condensed ammonium salt particles and the amount of gaseous ammonia escape can be obtained in the same sampling link.

[0031] (3) The present invention introduces validity checks such as nitrogen and sulfur mass balance deviation, acid absorption breakthrough, temperature control deviation and isochronous deviation, which can avoid misjudgment of the source due to sampling distortion, absorption liquid breakthrough or temperature runaway.

[0032] (4) This invention can be used for comparative screening under different absorbent pH, absorbent temperature, SO2 concentration, ammonium salt concentration, demisting state and additive addition conditions, providing an evaluation basis for low aerosol generation and low ammonia slip operation. Attached Figure Description

[0033] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0034] Figure 1 A flowchart of the method for identifying the source of ammonium salt aerosols in ammonia desulfurization provided by the present invention; Figure 2 A structural diagram of the dew point-phase grading and collection device provided by the present invention; Figure 3 A diagram showing the correspondence between temperature ranges before and after the dew point and the target objects provided by this invention; Figure 4 The nitrogen and sulfur mass balance and source contribution calculation diagram provided by this invention; Figure 5 The flowchart for sampling validity verification and working condition or additive screening provided by the present invention.

[0035] Explanation of reference numerals in the attached figures: 10, Sample gas introduction unit; 20, Isokinetic sampling and dew point measurement unit; 30, Droplet pre-separation unit; 40, First isothermal filtration unit; 50, Condensation conversion and collection unit; 60, Series acid absorption unit; 70, Metering and extraction unit; 80, Data processing and source identification unit. Detailed Implementation

[0036] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0038] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly; for example, they may refer to a fixed connection, a detachable connection, or an integral connection; they may refer to a mechanical connection or an electrical connection; they may refer to a direct connection or an indirect connection through an intermediate medium; and they may refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0039] Example 1 like Figure 1 As shown in the figure, this embodiment provides a method for identifying the source of ammonium salt aerosols from ammonia desulfurization based on dew point-phase staged collection. The specific steps are as follows: First, ammonia- and sulfur-containing sample gas after ammonia desulfurization is introduced. The sampling speed is adjusted by isokinetic sampling and dew point measurement unit, and the dew point temperature T of the sample gas is measured. dp Then, the sample gas is pre-separated by a droplet pre-separation unit to trap entrained droplets. After sampling, the pre-separation area is rinsed to obtain droplet-phase traps. The sample gas is then fed into the first isothermal filtration unit, whose temperature is set to T. dp The above method aims to capture filterable ammonium salt particles already present in the flue gas. The sample gas, after passing through the first isothermal filtration unit, enters the condensation and conversion capture unit, where it is kept below T... dp At the condensation temperature, condensate and condensable ammonium salt particles are formed and further captured by the second filter. Finally, the sample gas after passing through the second filter enters the series acid absorption unit to capture the remaining gaseous ammonia.

[0040] like Figure 2As shown, the present invention also provides an apparatus for performing the above method, including a sample gas introduction unit 10, an isokinetic sampling and dew point measurement unit 20, a droplet pre-separation unit 30, a first isothermal filtration unit 40, a condensation conversion and collection unit 50, a series acid absorption unit 60, a metering and pumping unit 70, and a data processing and source identification unit 80.

[0041] In this embodiment, the sample gas introduction unit 10 can be connected to the outlet of the ammonia desulfurization absorption tower, the outlet of the demister, the measuring points before and after the wet electrostatic precipitator, or the outlet of the laboratory simulation reactor. The isokinetic sampling and dew point determination unit 20 includes a sampling nozzle, a differential pressure measuring element, a flow regulating valve, and a dew point sensor. The droplet pre-separation unit 30 can adopt an impact type, cyclone type, baffle type, or inertial separation structure. The first isothermal filtration unit 40 includes a heated sampling tube, an isothermal filtration chamber, and a first filter. The condensation conversion and collection unit 50 includes a condenser, a condensate collector, and a second filter. The series acid absorption unit 60 includes at least two stages of acid absorption bottles. The metering pumping unit 70 is used to record the standard state sampling volume V. s The data processing and source identification unit 80 receives NH4 through the detection data input unit or the offline detection interface. + SO4 2- or SO3 2- The detection results are used to calculate the contribution rate, mass balance deviation, and output the source identification results.

[0042] like Figure 3 As shown, the sample gas dew point temperature T dp As the boundary of phase classification. The temperature T of the first isothermal filtration unit 40. H Set to T dp +ΔT H ΔT H The temperature can range from 10 degrees Celsius to 60 degrees Celsius. ΔT H The lower limit is used to avoid secondary condensation caused by temperature fluctuations near the dew point, ΔT H The upper limit is used to avoid insufficient temperature resistance of the filter membrane material, thermal decomposition of ammonium salts, or excessive volatilization loss. The pore size of the filter membrane in the first isothermal filtration section can be from 0.1 micrometers to 1.0 micrometers to balance the efficiency of filterable particle capture and the sampling pressure drop. The condensation temperature TC of the condensation conversion capture unit 50 is set to T. dp -ΔT C ΔT C Temperatures ranging from 10°C to 70°C are used to allow condensable components to form and be collected under specified condensation conditions; T C It can be set to 5 degrees Celsius to 45 degrees Celsius to be compatible with ice water bath, circulating water bath or semiconductor cooling conditions.

[0043] ; ; The above ΔT H The criteria for selecting a temperature range of 10°C to 60°C are as follows: the lower limit of 10°C can cover the error of the dew point sensor, local heat dissipation of the sampling pipeline, and fluctuations in the control of the constant-temperature filter chamber, reducing the risk of secondary condensation near the dew point; the upper limit of 60°C is used to avoid the filter membrane, seals, or sampling pipeline being exposed to excessively high temperatures for extended periods, while also reducing sampling deviations caused by thermal decomposition, volatilization loss, or form transformation of ammonium sulfate, ammonium sulfite, or acidic ammonium salts. The temperature fluctuation of the first constant-temperature filter section should not exceed ±5°C to ensure that the actual filtration temperature is always above T. dp And allowances for control are provided.

[0044] The above ΔT C The criteria for selecting a temperature range of 10°C to 70°C are as follows: the lower limit of 10°C is used to ensure sufficient condensable components generate condensation driving force within the condensation conversion trapping unit, avoiding incomplete condensation; the upper limit of 70°C is used to limit excessive condensation, resulting in increased liquid load, pressure drop, and the risk of secondary entrainment. Condensation temperature T C The temperature range is 5°C to 45°C, covering common condensation conditions such as ice-water baths, circulating water baths, and semiconductor refrigeration, and ensuring repeatable condensation conversion boundaries for different field or laboratory measurement points. The pore size of the first isothermal filtration section is 0.1 micrometers to 1.0 micrometers, designed to control sampling resistance while capturing filterable ammonium salt particles, avoiding excessive pressure drop due to too small a pore size or penetration of fine particles due to too large a pore size.

[0045] like Figure 4 As shown, after sampling, ammonium ions were detected in the droplet rinsing solution, the first filter membrane extract, the condensate, the second filter membrane extract, and the acid absorption solution. Sulfate or sulfite ions were also detected in the droplet rinsing solution, the first filter membrane extract, the condensate, and the second filter membrane extract. The droplet rinsing solution, the first filter membrane extract, and either the condensate or the second filter membrane extract were included in the ammonium ion detection and sulfoxide anion verification. The acid absorption solution was only included in the ammonium ion detection. The condensate and the second filter membrane extract could be combined to calculate the amount of ammonium salt particles generated during condensation (m). c Alternatively, the data can be recorded separately and then summed. After the detection data is aggregated, the data processing and source identification unit 80 calculates R. d R f R c R n I a and E NS .

[0046] The amount of ammonium salt entrained in the droplet (md) and the amount of native filterable ammonium salt particles (m) f The amount of ammonium salt particles generated by condensation (m) c The NH4 in the corresponding samples + The mass was calculated and obtained through the corresponding SO4 content in the sample. 2-or SO3 2- Content verification of ammonium salt composition; gaseous ammonia escape amount m n The result is obtained by converting the mass of NH4+ in the acid absorption solution. Calculate E. NS When, n N The droplet washing solution, the first filter membrane extract, the condensate, and the second filter membrane extract contain NH4. + The sum of the converted nitrogen molar amounts, n S The above samples contain SO4 2- or SO3 2- The sum of the converted molar amounts of sulfur, and the NH4 in the acid absorption solution. + Not included in E NS .

[0047] m d m f m c and m n All measurements are based on ammonium ion mass conversion to a unified measurement standard. For the droplet phase, primary filterable particulate phase, and condensation phase, SO4 is used when the concentrations are the same. 2- or SO3 2- Composition verification was performed, and the gaseous ammonia escape amount m was calculated. n NH4 in the acid absorption solution alone + The conversion yields the result. Ammonium ions in the acid absorption solution are not included in E. NS This is because it represents residual gaseous ammonia rather than already formed ammonium salt particles; after excluding it, E NS It is mainly used to verify the consistency of ammonium salt stoichiometry of the first three types of salt-containing traps.

[0048] When R d R f R c and R n When the maximum value in the output is greater than the preset dominant threshold and the validity check is qualified, the path corresponding to that contribution rate is output as the dominant source; when two or more contribution rates are similar and the difference is less than the preset difference threshold, parallel sources are output. The preset dominant threshold can be 0.50, 0.60 or 0.70, and the preset difference threshold can be 0.05 to 0.15.

[0049] The preset dominant source threshold is set between 0.50 and 0.70 because when the contribution rate of a certain path is higher than 0.50, that path has exceeded the combined contribution of the other paths or has at least become the main source of contribution. When a more stringent distinction between dominant sources is required on-site, the threshold can be increased to 0.60 or 0.70. The preset difference threshold is set between 0.05 and 0.15 to take into account ion detection error, sample recovery rate, and relative deviation of repeated sampling. When the difference between two contribution rates is less than this range, they are classified as parallel sources, which avoids misclassifying statistically indistinguishable sources as a single dominant source.

[0050] like Figure 5 As shown, this embodiment also verifies the validity of the sampling data. Validity verification includes at least verification of nitrogen-sulfur mass balance deviation, and may further include isokinetic deviation, temperature control deviation, acid absorption breakthrough, blank value, and spiked recovery rate. The acid absorption breakthrough rate can be 5% to 10%, and the duration of isokinetic deviation exceeding the limit can be 1 to 5 minutes, or 5% to 10% of the total sampling time. If the verification fails, the sampling data will not be used for determining the primary source, and resampling or replacement of the filter membrane, absorbent, or condenser may be prompted. If the verification passes, the sampling results can be entered into the operating condition or additive screening database for comparing the differences in ammonium salt aerosol sources under different pH, temperature, SO2 concentration, ammonium salt concentration, liquid-to-gas ratio, demister flushing intensity, or additive dosage conditions.

[0051] The acid absorption breakthrough ratio is 5% to 10%, judged by the amount of acid collected in the second-stage acid absorption bottle relative to the first-stage acid absorption bottle. When the second-stage collection ratio is too high, it indicates that the first-stage absorbent may be close to saturation or the absorption efficiency is insufficient, and the remaining gaseous ammonia amount is m. n It may be underestimated. The constant velocity deviation limit and duration are used to eliminate the impact of short-term flow disturbances on the representativeness of the sampling; when the deviation lasts for 1 to 5 minutes, or reaches 5% to 10% of the total sampling time, it indicates that the sampling speed deviates from the mainstream speed and may have changed the proportion of droplets and particles entering the sampling nozzle, so it should be marked as a sample to be verified.

[0052] In field applications, the above thresholds can be calibrated using blank samples, parallel samples, spiked recovery samples, and known ammonium salt standards. The blank value is used to subtract background from reagents, filter membranes, and rinsing solutions; the spiked recovery rate is used to verify NH4. + SO4 2- or SO3 2- The extraction and recovery status were measured; parallel samples were used to determine the contribution rate difference threshold and ENS validity conditions. The calibrated threshold can be used as a preset parameter for the same device, the same measuring point, or the same type of operating conditions.

[0053] Experimental Example 1 The ammonia desulfurization process was simulated in a laboratory isothermal absorption reactor. Simulated flue gas containing SO2, O2, CO2, N2, and water vapor was used, and the pH of the absorbent was adjusted. Sample gases were collected under different pH conditions using the method of this invention. If R under a certain operating condition... c Significantly higher than R d and R f This indicates that the condensation generation pathway contributes significantly to ammonium salt aerosols, and priority should be given to reducing the coexistence of gaseous ammonia and acidic precursors in the outlet wet flue gas.

[0054] Experimental Example 2 On-site sampling was conducted at the demister outlet of the ammonia desulfurization unit. If R d If the concentration of ammonium salts in the pre-separation flushing solution is high and the proportion of ammonium salts is large, it indicates that droplet entrainment is the dominant source. In this case, priority should be given to optimizing the demister flushing, liquid-gas ratio, droplet size distribution in the tower, or the demister operating status.

[0055] Experimental Example 3 Samples were taken at both the inlet and outlet of the wet electrostatic precipitator. If the outlet R of the wet electrostatic precipitator... f Decline but R n Or R c If the level is still high, it indicates that particulate matter removal is effective, but the potential for gaseous ammonia escape or condensation still needs to be controlled. Further adjustments can be made to the absorbent pH, oxidation air volume, outlet flue gas temperature, or additive dosage.

[0056] Comparative Example 1 Sampling was performed using a conventional total particulate filter connected in series with an acid absorption bottle. This method did not determine the dew point of the sample gas, nor did it establish a stage for isothermal filtration above the dew point and condensation conversion below the dew point. Therefore, it was impossible to determine whether the ammonium salts captured on the filter were native filterable particles or particles formed by secondary condensation during the sampling process.

[0057] Comparative Example 2 A separate ammonia slip detection method is used. This method can measure the concentration of gaseous ammonia, but it cannot distinguish between ammonium salts entrained in droplets, native particles, and condensed particles, nor can it determine the direction of optimization for demisting, temperature control, humidification, or additives based on the source of the particles.

[0058] Comparative Example 3 Sampling was performed using a separate condensation method. This method can evaluate the total amount of condensable particulate matter, but without above-dew-point filtration and droplet pre-separation, droplet entrainment, primary particles, and condensation-generated particles may be mixed and measured.

[0059] Compared to the comparative examples above, this invention can identify sources by focusing on the dew point-phase classification and collection chain. This invention does not simply measure ammonia slip, sample total particulate matter, or use condensation sampling; instead, it uses the dew point as the phase classification boundary, sequentially separating the mist phase, the particulate phase above the dew point, the condensation-conversion phase below the dew point, and the remaining gaseous ammonia. The source is identified by both contribution rate and nitrogen-sulfur mass balance. Therefore, it can provide more direct diagnostic data for pH, temperature, demisting, wet electrolysis, additive dosing, and ammonia slip control in ammonia-based desulfurization absorbent.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for identifying the source of ammonium salt aerosols from ammonia desulfurization, characterized in that, Includes the following steps: S1. Introduce ammonia-containing and sulfur-containing sample gas from the ammonia desulfurization outlet or simulate the ammonia desulfurization process; S2. Determine the dew point temperature T of the sample gas before it enters the staged collection link under constant velocity sampling conditions. dp And record the sampling rate deviation and the standard state sampling volume V. s ; S3, at a temperature not lower than the sample gas dew point temperature T dp Under certain conditions, the sample gas entrained droplets were pre-separated, the rinsing liquid from the pre-separation part of the droplets was collected, and the droplet phase trap was obtained. S4. The sample gas after droplet pre-separation is sent into the first isothermal filtration section, and the collection temperature T of the first isothermal filtration section is set to... H The temperature is higher than the dew point temperature T of the sample gas. dp Captures native filterable ammonium salt particles; S5. Cool the sample gas after passing through the first constant temperature filtration section to a temperature lower than the sample gas dew point temperature T. dp Condensation temperature T C The condensate is collected and the ammonium salt particles generated by the condensation are captured by a second filter. S6. Allow the sample gas after the second filter to enter at least two stages of series acid absorption sections to capture the remaining gaseous ammonia. S7. Detect NH in the rinsing solution, the first constant temperature filter trap, the condensate, the second filter trap, and the acid absorption solution. 4+ The content of SO4 was measured, and the SO4 in the rinsing solution, the first isothermal filtration section trap, the condensate, and the second filter trap was also detected. 2- or SO3 2- The content, m, is calculated from the test results to obtain the amount of ammonium salt entrained in the droplet. d Original filterable ammonium salt particle size (m) f The amount of ammonium salt particles generated by condensation (m) c and gaseous ammonia escape amount m n ; S8, according to m d m f m c and m n The contribution rate of each phase source was calculated using a unified denominator, and the dominant source of ammonium salt aerosols from ammonia desulfurization was identified based on the nitrogen-sulfur mass balance deviation and the sampling validity verification results.

2. The method for identifying the source of ammonium salt aerosols from ammonia desulfurization according to claim 1, characterized in that, In step S1, the ammonia- and sulfur-containing sample gas comes from the outlet of the ammonia desulfurization absorption tower, the outlet of the demister, the inlet of the wet electrostatic precipitator, the outlet of the wet electrostatic precipitator, the outlet of the pilot absorption reactor, or the outlet of the laboratory constant temperature absorption reactor.

3. The method for identifying the source of ammonium salt aerosols from ammonia desulfurization according to claim 1, characterized in that, In step S2, the constant-rate sampling condition must be met: The relative deviation between the sampling nozzle speed and the mainstream speed of the flue or reactor is no more than 10%. When the relative deviation exceeds 10% and the duration exceeds the preset time, the sampling is marked as a sample to be reviewed. The preset time is 1 to 5 minutes, or 5% to 10% of the total sampling time.

4. The method for identifying the source of ammonium salt aerosols from ammonia desulfurization according to claim 1, characterized in that, In step S3, droplet pre-separation is performed using an impactor, cyclone trap, baffle trap, or inertial separator trap, and after sampling of the droplet pre-separation area, it is rinsed with deionized water, dilute acid, or an absorbent with a known ion background.

5. The method for identifying the source of ammonium salt aerosols from ammonia desulfurization according to claim 1, characterized in that, In step S4, the collection temperature TH of the first isothermal filtration section satisfies: ； In the formula, ΔT H The temperature ranges from 10 degrees Celsius to 60 degrees Celsius, ΔT H The temperature fluctuation of the first constant temperature filtration section is determined based on the sample gas dew point measurement error, the temperature fluctuation of the first constant temperature filtration section, the temperature resistance range of the filter membrane, and the thermal stability of the ammonium salt. The temperature fluctuation of the first constant temperature filtration section is no greater than ±5 degrees Celsius, and the pore size of the filter membrane of the first constant temperature filtration section is 0.1 micrometers to 1.0 micrometers.

6. The method for identifying the source of ammonium salt aerosols from ammonia desulfurization according to claim 1, characterized in that, In step S5, the condensation temperature TC satisfies: ； In the formula, ΔT C The temperature ranges from 10 degrees Celsius to 70 degrees Celsius, ΔT C The condensation temperature T is determined based on the sample gas moisture content, condenser heat exchange capacity, condensate load, and the integrity of condensable component capture. C The temperature ranges from 5 degrees Celsius to 45 degrees Celsius, and a second filter is installed after the condensate collector.

7. The method for identifying the source of ammonium salt aerosols from ammonia desulfurization according to claim 1, characterized in that, In step S6, the at least two-stage acid absorption section includes a first acid absorption bottle and a second acid absorption bottle. When the ratio of the amount of ammonia captured by the second acid absorption bottle to the amount of ammonia captured by the first acid absorption bottle exceeds a preset breakthrough ratio, the sampling is marked as an absorption breakthrough sampling. The preset breakthrough ratio is 5% to 10%, and the preset breakthrough ratio is determined based on the concentration of the acid absorption liquid, the volume of the absorption liquid, the sampling volume, and the spiked recovery result.

8. The method for identifying the source of ammonium salt aerosols from ammonia desulfurization according to claim 1, characterized in that, In step S8, according to m d m f m c and m n The contribution rate of each phase source is calculated using a unified denominator, including: droplet entrainment contribution rate R. d Native filterable contribution rate R f Condensation generation contribution rate R c Contribution rate R of gaseous ammonia escape n : Droplet entrainment contribution rate R d Satisfy the following formula: ； Native filterable contribution rate R f Satisfy the following formula: ； Condensation generation contribution rate R c Satisfy the following formula: ； Contribution rate of gaseous ammonia escape R n Satisfy the following formula: ； When R d R f R c and R n When the maximum value in the sample is greater than a preset dominant threshold and the sampling validity verification is qualified, the droplet entrainment path, native filterable particle path, condensation generation path, or gaseous ammonia escape path corresponding to the maximum value is identified as the dominant source; when the difference between any two contribution rates is less than a preset difference threshold, the corresponding path is identified as a parallel source; the preset dominant threshold is 0.50 to 0.70, the preset difference threshold is 0.05 to 0.15, and the preset difference threshold is determined based on parallel sampling deviation, ion detection error, or spike recovery rate; Nitrogen-sulfur mass balance deviation E NS Satisfy the following formula: ； In the formula, n N The rinsing fluid, the trap in the first constant temperature filtration section, the condensate, and the trap in the second filter contain NH4. + The sum of the converted molar amounts of nitrogen; n S The rinsing fluid, the product collected in the first constant-temperature filtration section, the condensate, and the product collected in the second filter contain SO4. 2- and SO3 2- The sum of the converted molar amounts of sulfur, and the NH4 in the acid absorption solution. + Used to calculate m n Excluding E NS λ is determined based on the ammonium salt species; when ammonium sulfate or ammonium sulfite is the main component, λ is 2; when ammonium acid sulfite or ammonium bisulfate is the main component, λ is 1; when it is a mixed ammonium salt, λ is a value obtained by weighting the mole fraction of different ammonium salt species. In step S8, the ammonium salt aerosol formation index Ia is also calculated, satisfying the following formula: ； The sampling validity verification includes at least a nitrogen-sulfur mass balance deviation verification, and also includes at least three of the following: isochronous sampling deviation verification, first isothermal filtration section temperature deviation verification, condensation temperature deviation verification, series acid absorption breakthrough verification, blank value verification, and spiked recovery rate verification; wherein, the blank value is used to subtract the background of reagents, filter membranes, or rinsing solutions, and the spiked recovery rate is used to verify NH4. + SO4 2- or SO3 2- The extraction and recovery status are monitored; when the sampling validity verification fails, the dominant source result is not output, or a verification mark is output, and sampling is performed again or at least one of the following is replaced: filter membrane, acid absorbent, condenser collector, and droplet pre-separator.

9. The method for identifying the source of ammonium salt aerosols from ammonia desulfurization according to claim 8, characterized in that, Repeat steps S1 to S8 under different absorbent pH, absorbent temperature, flue gas temperature, SO2 concentration, oxygen content, ammonium salt concentration, liquid-to-gas ratio, demister flushing intensity, or additive dosage, and according to R d R f R c R n I a The ENS screens for operating conditions or additive conditions with low aerosol generation and low ammonia slip.

10. An apparatus for performing the ammonia-based desulfurization ammonium salt aerosol source identification method according to any one of claims 1 to 9, characterized in that, include: The sample gas introduction unit, isokinetic sampling and dew point measurement unit, droplet pre-separation unit, first isothermal filtration unit, condensation conversion and trapping unit, series acid absorption unit, and metering pumping unit are connected sequentially along the sample gas flow direction. A data processing and source identification unit, associated with the data from the droplet pre-separation unit, first isothermal filtration unit, condensation conversion and trapping unit, series acid absorption unit, and metering pumping unit, is also included. A detection data input unit or offline detection interface is also provided. The detection data input unit or offline detection interface is used to receive NH4 from each collected sample. + SO4 2- or SO3 2- The detection results are then sent to the data processing and source identification unit, which is configured to calculate R. d R f R c R n I a and E NS And when the sampling validity check, which includes at least the nitrogen-sulfur mass balance deviation, meets the preset validity conditions, the dominant source of ammonium salt aerosols will be output.

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