CN110749481A - Sampling device and sampling method for low-concentration total particulate matters in flue gas of thermal power plant - Google Patents
Sampling device and sampling method for low-concentration total particulate matters in flue gas of thermal power plant Download PDFInfo
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/02—Devices for withdrawing samples
- G01N1/22—Devices for withdrawing samples in the gaseous state
- G01N1/2247—Sampling from a flowing stream of gas
- G01N1/2258—Sampling from a flowing stream of gas in a stack or chimney
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/02—Devices for withdrawing samples
- G01N1/22—Devices for withdrawing samples in the gaseous state
- G01N1/24—Suction devices
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
- G01N15/06—Investigating concentration of particle suspensions
- G01N15/0606—Investigating concentration of particle suspensions by collecting particles on a support
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
- G01N15/06—Investigating concentration of particle suspensions
- G01N15/0606—Investigating concentration of particle suspensions by collecting particles on a support
- G01N15/0618—Investigating concentration of particle suspensions by collecting particles on a support of the filter type
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- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N5/00—Analysing materials by weighing, e.g. weighing small particles separated from a gas or liquid
- G01N5/02—Analysing materials by weighing, e.g. weighing small particles separated from a gas or liquid by absorbing or adsorbing components of a material and determining change of weight of the adsorbent, e.g. determining moisture content
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/02—Devices for withdrawing samples
- G01N1/22—Devices for withdrawing samples in the gaseous state
- G01N1/2247—Sampling from a flowing stream of gas
- G01N2001/225—Sampling from a flowing stream of gas isokinetic, same flow rate for sample and bulk gas
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/02—Devices for withdrawing samples
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- G01N2001/2282—Devices for withdrawing samples in the gaseous state with cooling means
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Abstract
The invention provides a sampling device and a sampling method for low-concentration total particulate matters in flue gas of a thermal power plant, which are suitable for detecting the emission condition of the total particulate matters discharged by the flue gas after ultralow emission modification or flue gas plume treatment modification and detecting the particulate matter removal performance of equipment. The sampling device mainly comprises a sampling device, a condensing device, a dehumidifying device, a metering device and a sampling pump which are sequentially arranged along the flow direction of flue gas; the sampling device comprises a sampling head and a heating sampling gun; the sampling head is formed by combining a sampling nozzle and a first-stage filtering membrane; a secondary filtering membrane is also arranged between the condensing device and the dehumidifying device; the condensing device adopts a two-stage series structure, and the two-stage condensing device is respectively provided with a water bath temperature control device; and a reinforced phase change system is arranged between the two stages of condensing devices and is used for adding water vapor into the flue gas entering the rear stage condensing device, increasing the humidity of the flue gas and improving the total particulate matter trapping rate. The device can realize scientific, accurate and comprehensive test of the total particles.
Description
The technical field is as follows:
the invention relates to the field of fixed source flue gas testing, in particular to a sampling device and a sampling method for low-concentration total particulate matters in flue gas of a thermal power plant based on a source environment. Wherein the low concentration of total particulate matter means that the concentration of filterable particulate matter is 50mg/m3(containing 50 mg/m)3) The particles contained therein.
Background art:
the fine particulate matter is the pollutant that contributes most to the current regional composite atmospheric pollution. The problem of regional atmospheric environment is solved, the detailed information of generation and emission of the particulate matters must be mastered firstly, and particularly, the information of fine particulate matters emitted by important pollution sources should not be missed. The concentration of particulate matter in the scientific monitoring thermal power plant flue gas, the once particulate matter concentration level and the emission of mastering thermal power plant institute comprehensively, it is significant to regional compound atmospheric haze pollution control.
Filterable Particulate Matter (FPM) is a type of Particulate Matter that is solid or liquid within the flue and can be trapped by a sampling filter cartridge/membrane. The particulate matter in the part has definite test specifications in fixed source test standards, and the particulate matter emission data of the thermal power plant disclosed by the current environmental statistics bulletin or monitoring report refers to filterable particulate matter.
The transformation from the thermal power plant is promoted comprehensively to realize ultralow emission, the concentration of particulate matters in the flue gas is greatly reduced after the dry dust collector, and the concentration of filterable particulate matters is 50mg/m under most conditions3Within. However, both the ultra-low emission modification of flue gas desulfurization and the ultra-low emission modification of denitration are possible to increase the emission of escaping particulate matters, and the proportion of the particulate matters in the total particulate matters emitted by pollution sources is rapidly increased. Escaping particulate matter (Pe)netrating Particulate Matter (PPM) refers to a pollutant (not containing SO in flue gas) which can penetrate through a sampling filter material and escape to the atmosphere to form liquid or solid Particulate Matter in the process of sampling in exhaust gas of a fixed pollution source2Particulate matter formed by secondary conversion of gaseous pollutants such as NOx in the atmospheric environment). PPM as PM in ambient air2.5The important precursor has been proved to have important influence on haze formation under specific meteorological conditions.
Only by comprehensively testing the concentration of total particulate matters (including FPM and PPM), the environmental emission of the primary particulate matters of the coal-fired source can be completely measured and calculated, and a complete and scientific particulate matter emission list of the thermal power plant can be obtained.
In order to promote the air pollution deep treatment in the thermal power industry, the actual emission conditions of the flue gas of the power plant are also greatly changed since the wet smoke plume is treated and transformed: the concentration of filterable particles in the flue gas is further reduced after passing through the dry dust collector (most of the filterable particles are 5 mg/m)3Within); the discharge temperature of the flue gas is different from 40 ℃ to 90 ℃; the humidity of the smoke at different points also varies from 3% to 17%. The change of the actual test environment inevitably requires that the test method follow up innovation so as to compare the particulate removal effects of different pollution treatment devices.
The invention content is as follows:
the invention provides a sampling device for low-concentration total particulate matters in flue gas of a thermal power plant based on a source environment.
The invention also aims to provide a method for sampling low-concentration total particulate matters in flue gas of a thermal power plant, which is suitable for detecting the emission condition of the total particulate matters discharged by the flue gas after ultralow emission modification or flue gas plume treatment modification and detecting the particulate matter removal performance of equipment.
The specific technical scheme of the invention is as follows:
a sampling device for low-concentration total particulate matters in flue gas of a thermal power plant mainly comprises a sampling device, a condensing device, a dehumidifying device, a metering device and a sampling pump which are sequentially arranged along the flow direction of the flue gas; the sampling device comprises a sampling head and a heating sampling gun; the sampling head is formed by combining a sampling nozzle and a first-stage filtering membrane; a secondary filtering membrane is also arranged between the condensing device and the dehumidifying device; the condensing device adopts a two-stage series structure, and the two-stage condensing device is respectively provided with a water bath temperature control device; and a reinforced phase change system is arranged between the two stages of condensing devices and is used for adding water vapor into the flue gas entering the rear stage condensing device, increasing the humidity of the flue gas and improving the total particulate matter trapping rate.
Preferably, the two-stage condensing device is provided with a spiral condensing pipe and an impact bottle, wherein the spiral condensing pipe is vertically arranged above the impact bottle and is connected through a connecting pipe.
Preferably, in the two-stage condensing device, the spiral condensing pipe adopts a pump circulation mode to carry out water bath temperature control on the inner pipe, and the impact bottle adopts a water bath tank to control the temperature.
Preferably, in the two-stage condensation device, the diameter of an inner pipe of the spiral condensation pipe is 6-8 mm, and the extension length of the inner pipe is 3-5 m.
Preferably, the intensified phase change system comprises a jet mixer and a phase change chamber which are communicated with each other in a front-back mode, the jet mixer is provided with two inlets and an outlet, the two inlets are respectively used for connecting steam and a front-stage condensing device, and the phase change chamber is provided with a mixed gas outlet for connecting a rear-stage condensing device. The inlet of the steam is connected or directly connected to a steam generator. The steam of the steam generator is used for electrically heating vaporized ultrapure water, and the steam has the following quality requirements: the water used for steam is ultrapure water (the resistivity reaches 18M omega cm (25 ℃)), and the steam temperature ranges from 120 ℃ +/-2 ℃.
Preferably, the heated sampling barrel employs an outer liner heating sleeve configuration.
Preferably, the primary filter membrane is a quartz membrane or a PTFE membrane; for standard particles with a diameter of 0.3 μm, the capture efficiency of the first filter should be greater than 99.5%.
Preferably, the secondary filtering membrane adopts an inverted filtering membrane device, and the filtering membrane is made of a PTFE membrane; for standard particles with a diameter of 0.3 μm, the capture efficiency of the secondary filter should be greater than 99.5%.
Preferably, the device also comprises a nitrogen stripping device;
preferably, the metering device comprises a pressure gauge and a dry flow meter;
preferably, the impact bottles are dry spherical impact bottles.
A method for sampling low-concentration total particulate matters in flue gas of a thermal power plant mainly comprises the following steps: controlling the temperature of the device, starting a sampling pump, adding steam, stopping sampling, collecting samples, weighing and calculating;
when steam is added, the water content of the flue gas entering the rear stage condensing device is controlled to be 34g/m3～46g/m3(under dry gas conditions); the heating temperature of the heating sampling gun tube is controlled to be 120 +/-5 ℃; the water bath temperature of the preceding stage condensing device is controlled to be 60-80 ℃; the temperature of the water bath of the latter stage condensing unit is controlled to be 25-30 ℃.
The collected sample comprises the particulate matters on the primary filtering membrane and the secondary filtering membrane and the particulate matters on each connecting component between the primary filtering membrane and the secondary filtering membrane.
Preferably, the sampling is constant-speed tracking sampling, and the flow velocity of flue gas in the two-stage spiral pipe is controlled to be 2.5-3.5 m/s; the residence time of the flue gas in the strengthening phase change system is controlled to be not less than 10 seconds.
Preferably, when steam is added, the steam addition flow is controlled to be 1 g/min-10 g/min, and the steam quality requirement is as follows: the water used for steam is ultrapure water (the resistivity reaches 18M omega cm (25 ℃)), and the steam temperature ranges from 120 ℃ +/-2 ℃.
Preferably, when weighing, the particles collected on the primary and secondary filter membranes are dried in a constant temperature and humidity device to constant weight and then measured.
Preferably, in the circulating water bath system of the condensing device, the circulating water pump adopts a water pump with the maximum lift design of 3.5-4.5 meters.
When steam is added, the steam addition amount required by the reinforced phase change system is calculated according to the flue gas humidity in the tested basic flue gas parameters, so that the water content of the flue gas entering the rear-stage condensing device is controlled to be 34g/m3～46g/m3。
By designing the size of the phase change chamber, for example, the length, the width and the height of the phase change chamber are not less than 600mm 50mm, particulate matters and steam in the smoke in the phase change chamber can be fully mixed, the residence time of the smoke in the reinforced phase change system is not less than 10 seconds, and the smoke is ensured to have enough residence time to be fully condensed and grown in the reinforced phase change system.
In order to control the flow velocity of flue gas in the two-stage spiral pipes to be 2.5-3.5 m/s, the flow velocity can be controlled by controlling the diameter of the inner pipe of the spiral condensing pipe to be 6-8 mm; the extension length of the inner pipe is 3-5m, and the PPM can be fully condensed.
The filterable particulate matter concentration in the present application is at 50mg/m3The sampling of the total particulate matters (called as low-concentration total particulate matters) in the device needs to be innovated aiming at measures for avoiding escape loss caused by insufficient condensation, also needs to be innovated for taking reinforced intervention because fine particulate matters are not easy to be trapped, and also needs to optimize and innovate the structure of the device so as to meet the support requirements on the test data of the low-concentration total particulate matters in the performance test of a deep purification device of a thermal power plant and the updating of a particulate matter emission list of the thermal power plant.
Compared with the prior art, the invention has the following advantages:
1. in the prior art, SO in the flue gas is ignored3And the escape phenomenon caused by the fact that pollutants with strong hygroscopicity such as ammonium salt cannot be fully condensed under the quenching condition is ignored, the condition that the temperature meets the condensation requirement but the pollutants in the actual flue gas are not fully condensed is ignored, and the phenomenon that part of metal ions penetrate through the secondary filtering membrane is ignored. The method can be used for measuring the concentration of the low-concentration total particulate matters in source environments with different flue gas humidity and different flue gas temperature, and avoids negative errors caused by the fact that condensation temperature is controlled improperly, moisture content is low, and metal ions penetrate through a filter membrane along with water to test the total particulate matters.
2. The method is based on sampling in a flue of a source environment, the heating sampling gun is adopted to lead out flue gas, the sampling gun and the condensing device are reasonably controlled in temperature during sampling, the heating temperature is controlled to be above the dew point of the flue gas, the adsorption and loss of the escaping particulate matters are inhibited, and the adsorption loss of the diluting sampling method on the escaping particulate matters is avoided.
3. The sampling method provided by the invention condenses and traps the escaped particulate matters in a two-stage condensing device separated temperature control mode, can promote the condensation, nucleation and collision coalescence of the desulfurized and denitrified secondary particulate matters and fine particulate matters formed in the raw coal combustion process, and avoids overlarge escape amount caused by the formation of fine particles in the condensation process of the escaped particulate matters with strong hygroscopicity, thereby reducing the error of the test result.
4. The testing method of the invention adds steam into the flue gas to carry out enhanced condensation on the escaped particulate matters in the low-humidity flue gas, thereby effectively inhibiting SO caused by insufficient water vapor3、NH3And the escaping particles can not be condensed sufficiently to escape. The method can adapt to the trapping of the escaped particulate matters with different flue gas humidity and flue gas temperature under the actual flue gas condition.
5. The secondary filter membrane adopts an inverted membrane structure, adopts the PTFE membrane as the secondary filter membrane, and effectively inhibits Ca2 +、Mg2+Penetration loss of the plasma.
6. The invention adopts two groups of condensing devices to recover condensed PPM particles, and controls the pipe diameter of the inner pipe and further controls the flow velocity of flue gas in the inner pipe by reasonably designing the extension length of the inner pipe. The retention time of the sampled flue gas in the two-stage condensing device is not less than 5 seconds, and effective capture is realized.
Description of the drawings:
FIG. 1 is a schematic diagram of a sampling device for low concentration total particulate matters in flue gas of a thermal power plant in an example (also shown in the abstract);
in fig. 1: 1-an integrated sampling head; 2-heating the sampling gun; 3-a pitot tube; 4-a preceding stage spiral condenser pipe; 5-temperature control circulating water bath; 6-circulating water pump; 7-impact bottle; 8-a thermometer; 9-a steam generator; 10-strengthening of the phase change system; 11-temperature control circulating water bath; 12-a circulating water pump; 13-a later stage spiral condenser pipe; 14-impact bottle; 15-secondary filtration membrane; 16-a thermometer; 17-a dryer; 18-a pressure gauge; 19-a dry gas flow meter; 20-a sampling pump;
FIG. 2 is a diagram of a middle inverted filtering membrane device structure according to the first embodiment;
in FIG. 2, 1-inlet flue gas; 2-PPM filtering membrane; 3-a film holder; 4-outlet flue gas;
FIG. 3 is a diagram of an enhanced phase change system of example one;
in FIG. 3, 1-steam inlet connection ring; 2-a flue gas inlet connecting ring; 3-a jet mixer; 4-a phase change chamber; 5-mixed gas outlet connecting ring.
FIG. 4 shows the configuration of the nitrogen purge apparatus of example one;
in FIG. 4, 1-high purity nitrogen gas cylinder; 2-a pressure reducing valve; 3-a flow control device; 4-connecting an O-ring; 5-a spiral condenser pipe; 6-long neck impact bottle; 7-exhaust port.
The specific implementation mode is as follows:
the technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The first embodiment is as follows:
as shown in FIG. 1, the sampling device for low concentration total particulate matters in flue gas of a thermal power plant comprises a sampling device, a condensing device, a secondary filtering membrane 15(PPM filtering membrane), a dryer 17, a metering device and a sampling pump 20 which are sequentially connected along the flow of the flue gas. A pitot tube 3 is also provided in the device.
The sampling device comprises an integrated sampling head 1 and a heating sampling gun 2, wherein the integrated sampling head 1 is formed by combining a sampling nozzle and a first-order filtering membrane (FPM filtering membrane), a heating sleeve is lined outside the heating sampling gun, and the heating temperature of the heating sleeve lined outside the heating sampling gun 2 is controlled to be 120 +/-5 ℃.
Condensing equipment divide into the front and back two-stage of establishing ties, and two-stage condensing equipment all is provided with the spiral condenser pipe and strikes the bottle, and on the bottle was strikeed to the vertical setting of spiral condenser pipe, spiral condenser pipe all was equipped with water bath temperature regulating device with strikeing the bottle.
Wherein, preceding stage spiral condenser pipe 4 is vertical to be set up in impact bottle 7 top, and preceding stage spiral condenser pipe 4 accuse temperature is furnished with circulating water pump 6, and impact bottle 7 is established in accuse temperature circulating water bath 5.
The rear-stage spiral condenser pipe 13 is vertically arranged above the impact bottle 14, the rear-stage spiral condenser pipe 13 is provided with a circulating water pump 12 for controlling the temperature, and the impact bottle 14 is arranged in the temperature-controlled circulating water bath 11.
The spiral condenser pipe is divided into an inner pipe and an outer pipe, the inner pipe is a spiral pipe and used for flue gas flowing, and the outer pipe is an outer sleeve and used for water bath temperature control. The inner tube is communicated with the impact bottle, and the outer sleeve adopts circulating water circulation to carry out water bath temperature control.
The two-stage condensing device separately controls the temperature, and the temperature control is different. The pre-stage condensing device adopts a water bath to control the temperature to be 60-80 ℃; the temperature of the latter stage condensing device is controlled to be 25-30 ℃ by adopting water bath. And temperature sensors are arranged at the outlets of the dry type impact bottles of the two-stage condensing device.
And a reinforced phase change system 10 is arranged in the middle of the two-stage condensing device and is connected with the two-stage spiral condensing tube through a Teflon tube for adding steam into the rear-stage condensing device. The intensified phase change system 10 can be directly connected with a steam pipeline and can also be connected with a steam generator 9 through a steam inlet connecting ring. The internal devices of the steam generator 9 are all made of SUS304, and steam with adjustable flow and controllable temperature is generated. The water used by the steam generator 9 is ultrapure water (the resistivity reaches 18M omega cm (25 ℃)), and the steam temperature range is 120 +/-2 ℃; the jet mixer is designed by adopting a jet principle, so that the steam and the flue gas are conveniently and fully mixed; the residence time of the mixed gas in the phase change chamber is not less than 10 seconds.
The metering device includes a pressure gauge 18 and a dry gas flow meter 19. The measurement error can be within plus or minus 3 ℃ in the temperature range of 0-90 ℃ and the true value, and the volume error is within plus or minus 2 percent.
Example two:
as shown in fig. 2, in the present example, the secondary filtering membrane 15 is optionally in an inverted structure; the filtering membrane is provided with inlet flue gas 1, a PPM filtering membrane 2, a membrane support 3 and outlet flue gas 4. The inverted filter membrane of the secondary filter membrane 15 is a PTFE membrane; for standard particles with a diameter of 0.3 μm, the capture efficiency of the secondary filter should be greater than 99.5%. The first-stage filter membrane adopts a quartz membrane or a PTFE membrane; for standard particles with a diameter of 0.3 μm, the capture efficiency of the first filter should be greater than 99.5%.
Example three:
as shown in fig. 3, the intensified phase change system 10 of the present embodiment is designed as shown in the figure, and comprises a jet mixer 3 and a phase change chamber 4 which are communicated with each other, the jet mixer 3 is provided with two inlets, the two inlets are respectively used for connecting steam and a front stage condensing device, the jet mixer 3 is communicated with the phase change chamber 4, and the phase change chamber 4 is provided with a mixed gas outlet for connecting a rear stage condensing device.
The invention mixes steam and flue gas in a jet flow mode, and the mixed flue gas enters a reinforced phase change system. The length, width and height of the phase change chamber are 600mm x 50mm, so that the residence time of the smoke in the intensified phase change system is not less than 10 seconds.
Example four:
optionally, the sampling device for low-concentration total particulate matters in flue gas of a thermal power plant is further provided with a nitrogen purging device for purging during sample recovery. As shown in fig. 4, comprises a high purity nitrogen gas cylinder 1; a pressure reducing valve 2; a flow control device 3; connecting an O-shaped ring 4; a condenser pipe 5; a long neck impact bottle 6; and an exhaust port 7.
Example five:
the invention discloses a method for sampling low-concentration total particulate matters in flue gas of a thermal power plant, which comprises the following steps of:
the method comprises the following steps: preparation of a sampling device: before sampling, the integrated sampling head is cleaned by ultrasonic waves in deionized water. And cleaning for 5 minutes, then washing with deionized water, and placing in an oven for drying at 105-110 ℃ for at least 1 hour.
Baking the first-stage filter membrane and the second-stage filter membrane for 1 hour at the baking temperature of 180 ℃. And (3) placing the filter membrane in a drying dish for cooling after baking, loading the filter membrane into the integrated sampling head after cooling, and placing the integrated sampling head into constant temperature and humidity equipment for balancing for at least 24 hours. Taking out the sample after balancing, weighing for 2 times, wherein the weighing interval of 2 times is more than 1 hour, the maximum deviation between the weighing results of 2 times is within 0.02mg, otherwise, the sample is discarded; the average of 2 measurements was used as the measurement value. The secondary filtration membrane was prepared by the same treatment method as that for the primary filtration membrane.
Assembling the sampling device shown in figure 1, checking whether the system leaks air, and if the system leaks air, checking and plugging the system in sections until the system is qualified. The leak detection is in accordance with the requirement of the system on-site leak detection in GB/T16157-1996.
Step two: and testing basic smoke parameters. And testing the smoke temperature and the smoke humidity of the test section according to the regulation in GB/T16157-1996. The flue gas humidity can be used for calculating the steam addition amount of the strengthening phase change system; according to the regulation in GB/T16157-1996, the number and the positions of sampling points are determined by a grid method, and the positions of the sampling points are more than 20cm away from the flue wall, so that flue gas condensate and particulate matters on the flue wall are prevented from being trapped by mistake.
Step three: assembling the sampling device and starting temperature control. Starting a circulating water bath pump, heating the front and rear spiral condenser pipes in a water bath, and raising the temperature of the water bath to a set temperature; the water bath temperature of the preceding stage condensing device is controlled to be 60-80 ℃; controlling the temperature of the water bath of the rear-stage condensing device to be 25-30 ℃; and switching on a power supply of the heating sampling gun to enable the heating temperature of the inner tube of the heating sampling gun to rise to 120 +/-5 ℃.
Step four: and starting a sampling pump to extract the smoke in a mode of automatically tracking the flow rate of the smoke. The flue gas passes through the collection that the sampling mouth realized filterable particulate matter. Opening a steam injection valve of the reinforced phase change system to mix water vapor with the sample gas; and the mixed gas enters a steam phase change chamber, the retention time of the mixed gas in the phase change chamber is not less than 10S by controlling the flow rate of the flue gas, and the flue gas after the mixed steam enters a rear-stage condensing device. The steam adding flow rate is 1 g/min-10 g/min, and the flue gas flow rate in the phase change chamber is controlled within 0.05m/s through the size design of the phase change chamber. Adding steam to make the water content in the sample gas not less than 34g/m3(under dry gas conditions);
the time for collecting samples is not less than 60min each time; in the sampling process, the temperature of the flue gas at the outlet of the impact bottle of the secondary condensation device is not lower than 25 ℃ and not higher than 30 ℃.
Step five: after sampling is finished, the sampling pump is closed, and sampling information is recorded; then the following operations are carried out in sequence:
1) respectively collecting and numbering a primary filtering membrane (filtering membrane 1) and a secondary filtering membrane (filtering membrane 2), and sealing the primary filtering membrane by adopting a preservative film; the secondary filtering membrane is sealed and stored by a culture dish. And numbering and recording are carried out simultaneously.
2) Recovering condensate and flushing liquid:
first, the condensate in the dry shock bottle of the two-set condensing device is recovered to a long stem impact bottle.
Then, washing the particles on each connecting component (including the spiral tube inner tube of the two-stage condensing device, the dry type impact bottle, the reinforced phase change system and the connecting pipelines of all components from the integrated sampling head to the secondary filter) between the primary filter membrane and the secondary filter membrane for 2 times by using ultrapure water, and recovering the washing liquid to the long stem impact bottle; and adding ultrapure water into the long-stem impact bottle to enable the liquid level to be 5cm higher than the air guide pipe orifice of the impact bottle, and then filling the long-stem impact bottle to assemble the device shown in the figure 4.
Finally, the nitrogen purging device of fig. 4 was used to purge the condensate and rinse collected in the long stem impingement flask with high purity nitrogen at a rate of about 10 liters/minute for 30 minutes. After nitrogen purge the condensate and rinse were transferred to the sample vial. And numbering and recording are carried out simultaneously.
Step six: sample weighing and calculation.
And drying the filter membrane 1 and the filter membrane 2 in a constant temperature and humidity device to obtain the product with constant weight. The weight gain of the filter membrane 1 before and after sampling is the mass of the collected Filterable Particles (FPM) and is marked as MFPM. The weight gain of the filter membrane 2 is the mass of part of the escaped particles (PPM1) which is marked as MPPM1。
And pouring the condensate and the flushing liquid in the sample bottle into a glass evaporation dish, placing the glass evaporation dish in a 50 ℃ oven to dry until a small amount of liquid (the volume is less than 10mL) remains, then moving the glass evaporation dish into a drying dish to dry until the weight is constant, weighing, and obtaining the weight gain before and after the test of the glass evaporation dish, namely the mass of the other part of the escapeable particulate matter (PPM 2).
Total particulate matter mass: mTPM＝MFPM+MPPM1+MPPM2，
Further calculation of total particulate matter concentration:
total particulate matter concentration (M)TPM/V。
Wherein, the total particulate matter concentration, unit: mg/m3；MTPMThe unit is mg for the total particulate matter mass; v is gas production volume (standard, dry basis), unit: m is3。
The first test case:
a power plant, the 2 x 600MW boiler is a supercritical pressure, single-time intermediate reheating, single-hearth, balanced ventilation, solid slag discharge, open-air arrangement, all-steel frame structure, "W" -shaped flame combustion, vertical internal thread water-cooled wall, and pi-shaped variable pressure direct current boiler. The matched environment-friendly facility comprises an SCR denitration device, an electric dust remover, a wet desulphurization system and a wet electric dust remover.
The test load was 660MW full load at which validation tests of the trapping effect were performed at different tube lengths within the spiral condenser tube. The test position is positioned at the outlet of the desulfurizing tower. The following two sets of equipment were used in experimental validation:
the device 1 is a particle sampling device provided by American ES company and based on methods 17 and 202A, the extension lengths of inner tubes of a front-stage temperature-control spiral condenser tube and a rear-stage temperature-control spiral condenser tube are both 160cm, the diameter of the inner tube is 7mm, and the diameter of an inner tube ring is 50 mm; two-stage cooling and condensation are adopted: the water bath temperature of the front section is 65 ℃, and the water bath temperature of the rear section is 30 ℃.
The device 2 is a device for sampling low-concentration total particulate matters in flue gas of a thermal power plant, the extension lengths of a front-section spiral condenser pipe and a rear-section spiral condenser pipe are both 300cm, the diameter of an inner pipe is 7mm, and the diameter of an inner pipe ring is 50 mm; the temperature of the front-stage water bath is 65 ℃ and the temperature of the rear-stage water bath is 30 ℃.
In order to investigate the total particulate matter trapping effect of the lengths of the pipes in different spiral condensation pipes, the device is adopted to carry out verification tests. As the FPM testing method is basically consistent, in order to highlight the condensation effect under different condenser tube lengths, the PPM testing result is provided in the application and is shown in the following table.
TABLE 1 verification test results of tube length in spiral condenser tube
After having testedIn the process, the temperature of the flue gas at the outlet of the two sets of rear-stage condensing devices is reduced to 29 ℃. The verification test result shows that when the temperature control spiral condenser tube with the inner tube extension length of 160cm is adopted, the PPM mass obtained by the test is 3.43mg/m3The test result is obviously lower than that of the temperature control spiral condenser tube with the inner tube length of 300 cm; device 2 gave 22.7% higher results for PPM testing than device 1.
In comparison with the conventional patents (HuyueQi (201721111305.5) and Shenshigang (application No. 201710343942.3)), it is basically emphasized that the end point of the test control is determined when the smoke temperature reaches 30 ℃. However, in tests, the flue gas flow velocity in a sampling system is often very high due to constant-speed tracking sampling, and even reaches more than 5m/s in a local pipeline. Although the flue gas is reduced to the target temperature under the high flow speed condition, the flue gas does not actually realize the condensation effect, namely: particulate matters in the flue gas are not condensed and grow to a certain particle size and are carried out of the sampling system, which brings difficulty to subsequent trapping. The sectional design of the temperature control condenser pipe and the extension length design of the inner pipe are particularly emphasized, and the flue gas is effectively and completely condensed.
Test case two:
a boiler of a 2 x 350MW unit of a power plant B is a boiler with supercritical pressure, reheating is performed in the middle of one time, a single hearth is adopted, balanced ventilation is performed, solid-state slag discharge is performed, open-air arrangement is performed, an all-steel frame structure is adopted, and four-corner tangential firing is adopted. The matched environment-friendly facility comprises an SCR denitration device, a bag type dust collector, a wet desulphurization system and a wet electric dust collector.
And carrying out a sectional water bath temperature control verification test at a desulfurization outlet of a #2 unit of the B power plant. In experimental verification, two sets of equipment are used, the two sets of equipment are the testing devices provided by the invention, the extension lengths of the front-section spiral condenser pipe and the rear-section spiral condenser pipe are both 300cm, the diameters of the inner pipes are both 7mm, and the difference of the verification test is that the temperature is controlled by a sectional water bath, and the temperature is controlled by a water bath directly reduced to 30 ℃ which is commonly adopted at present.
The device 3 is characterized in that the water bath temperature of the front section is 65 ℃ and the water bath temperature of the rear section is 30 ℃;
in the equipment 4, the water bath temperature of the front section is 30 ℃, and the water bath temperature of the rear section is 30 ℃.
Other sampling parts, drying systems, metering devices, laboratory processing and the like are consistent. Because the FPM test method is completely consistent, for investigating the condensation effect of the sectional cooling design, PPM test data is provided in the application so as to compare the condensation effect, and the following table 2 shows.
TABLE 2 Experimental verification results of the segmented temperature reduction design
As can be seen from the above table, the test result of the equipment 3 on the escaped particulate matters is significantly higher than that of the equipment 4, and the test result of the equipment 3 on the escaped particulate matters is 29.9% higher than that of the equipment 4 under the same conditions. The most main reason is that the temperature of the flue gas from the flue gas heating gun is 120 ℃, and in the process of reducing the temperature from 120 ℃ to 30 ℃, if a direct condensation and temperature drop mode is adopted without a primary temperature control condensation process (the temperature control point is higher than the water dew point of the flue gas but lower than the acid dew point of the flue gas), a large amount of sulfuric acid mist and ammonium salt in the flue gas are inevitably consumed for water vapor, and as a result, the substances are in an aerosol state, have smaller average particle size and better followability, and are more difficult to be trapped.
The two-stage condensing device is used for controlling the temperature in a segmented manner, and is an important innovation of the application. The device 3 effectively controls the median particle size after PPM condensation through two temperature control points, namely a 65 ℃ temperature control point and a 30 ℃ temperature control point, and reduces the negative deviation of the total particulate matter concentration test result. Through the contrast above, the design of this application is better to the condensation of the particulate matter of can escaping, entrapment effect, and test total particulate matter concentration is more accurate.
Test case three:
and effect verification tests of different structures of the secondary filtering membrane are carried out at the desulfurization outlet of the #2 unit of the B power plant. Where the flue gas temperature is 51 deg.c and the flue gas moisture content is 15.2%. Two sets of equipment are used in experimental verification, and are the test devices provided by the method, and the difference is that the secondary filtration membrane is arranged, other structural designs of the test devices are the same as those of the test case I, the extension lengths of the spiral condenser pipes are 300cm, the diameter of the inner pipe is 7mm, and the diameter of the inner pipe ring is 50 mm.
The PPM filter membrane is inverted and supported by a firmware;
6, PPM filter membrane is in traditional transverse mode;
other sampling portions, drying systems, metering devices and laboratory treatments were all identical. Placing a condensing bottle of ice water bath behind the PPM filter membrane, collecting the flue gas condensate passing through the PPM filter membrane, and analyzing SO in the flue gas condensate4 2-、NO3 -、Ca2+、Mg2+Concentration (condensate to 25 mL). The results of the validation test are shown in table 3 below.
TABLE 3 PPM Filter Membrane inversion design experiment verification results
As can be seen from the above table, the ion concentration in the condensate after PPM filtration of the device 6 is significantly higher than that of the device 5, especially the metal ion Ca2+And Mg2+The concentration is significantly higher than in the device 5. Normally, the metal ion Ca2+And Mg2+The concentration should not pass through the PPM filter. As the practical operation finds that a certain amount of liquid water appears on the conventional transverse PPM membrane, the trapping efficiency of the filter membrane on the ions is greatly reduced, and a non-negligible measurement error is generated. Therefore, the invention adopts the design of the inverted PPM filtering membrane, and the measurement error is smaller.
Because the wet desulphurization process is widely applied to the desulphurization device of the thermal power plant, the moisture content in a considerable amount of flue gas of the thermal power plant is higher, and even reaches an oversaturated state. In the moisture content condition, the temperature of the flue gas is reduced to 30 ℃, and liquid water on the PPM filter membrane is caused to appear. In practical operation, the occurrence of liquid water can cause part of water-soluble ions and metal ions to penetrate through the filter membrane, so that PPM loss is caused, and negative errors are brought to PPM test.
Test case four:
in the embodiment, the verification test of the effect of the reinforced phase change system is carried out at the outlet of the flue gas reheater of the #3 unit of the power plant C entering the chimney flue. Where the flue gas temperature is 71 deg.c and the flue gas moisture content is 5.2%. Two sets of equipment are used in experimental verification, and are test devices provided by the method, and the difference is that whether a steam generator and a phase change chamber are arranged or not, and other structural designs of the test devices are the same as those of a test case I, wherein: the extension length of the spiral condenser pipe is 300cm, the diameter of the inner pipe is 7mm, and the diameter of the inner pipe ring is 50 mm.
The device 7 is provided with a reinforced phase change system between two stages of condensing devices and uses a steam generator.
The device 8 does not use a reinforced phase change system, and the flue gas directly enters a rear-stage condensation pipe from a front-stage condensation pipe.
Other sampling portions, drying systems, metering devices and laboratory treatments were all identical. As the FPM test methods are completely consistent, PPM test data are provided in the patent in order to highlight the influence of the reinforced phase change on the PPM trapping efficiency, and are shown in the following table.
Table 4 steam generator design verification results for testing particulate matter that can escape from flue gas of thermal power plant
As can be seen from the table above, the test result of the device 7 is significantly higher than that of the device 8, and the test result of the device 7 to PPM is higher than that of the device 8 by 37.0%; and trapped NH4 +、Cl-、NO3 -、SO4 2-、Ca2+Are higher than the mass concentration of the device 8. The main reason is that after the verification test position is positioned behind a flue gas reheater and a flue gas plume treatment project of firstly condensing and then heating is carried out, the moisture content in the flue gas is lower (compared with the situation that the moisture content of the flue gas is supersaturated after wet desulphurization). The flue gas in the sampling system is reduced from 120 ℃ to 30 ℃, and a great amount of sulfuric acid mist and ammonium salt in the flue gas compete for water vapor, so that the average particle size of the substances is smaller; steam is added in the device 7 through a reinforced phase change system, so that the average particle size of fine particles can be increased, and the inertial trapping of CPM in a B-section temperature control condenser pipe is greatly promoted.
Because in the current smoke plume treatment practice, part of the units are cooled by smokeThe condensing-reheating mode realizes flue gas treatment, and the result is that the humidity in the flue gas is greatly reduced, which is very unfavorable for the trapping of SO3 and ammonium salt substances with strong hygroscopicity which are greatly existed in the escaped particulate matters. The enhanced phase change design provided by the invention is another important innovation of the application. This application is through adding steam in order to realize the supersaturated steam environment, is that the mode of strengthening through the manual work realizes that vapor condenses, promotes the fine particles thing to condense to grow up on the particulate matter surface. In the test case, the fact that different amounts of steam are added according to different flue gas moisture contents is found, on one hand, the critical particle size of particles subjected to nucleation condensation is reduced, and more fine particles in the flue gas are promoted to be subjected to nucleation condensation; on the other hand, the more the amount of steam condensed on the surface of the particles is, the larger the particle diameter of the condensed and grown liquid drops is, thereby improving NH4 +、Cl-、NO3 -、SO4 2-、Ca2+And the like, and can trap condensable particulate matters originally existing in the form of liquid nuclei in the smoke.
Test case five:
the primary stage of the D power plant is 2 multiplied by 330MW, wherein a #2 boiler is a sub-critical steam drum furnace of 1025t/h, and the natural circulation, the primary intermediate reheating, the front wall and the rear wall opposed firing and the open-air arrangement are adopted. Before the test, the #2 unit is transformed by ultralow emission. The outlet smoke dust emission concentration of the electric dust collector after being reformed<40mg/Nm3(ii) a The smoke dust emission concentration at the outlet of the desulfurizing tower is less than 30mg/Nm3(ii) a Dust removal efficiency designed at outlet of wet electric dust remover>83.4%, outlet smoke emission concentration<5mg/Nm3Concentration of discharged droplets<20mg/Nm3。
The test load was 330MW full load. In experimental verification, the method is respectively based on the HJ836-2017 method and the method provided by the invention. The verification results are as follows:
TABLE 5 Total particulate matter test results of the conventional method and the inventive method
The method verifies that the same measuring hole is usedThe position is carried out, and synchronous parallel testing is carried out. But the final total particulate matter test results were more different. According to the test result of the HJ836-2017 method, the total particulate matter concentration is 3.21 +/-0.22 mg/m3(ii) a The test result of the method of the invention is 5.96 +/-0.67 mg/m3. The filterable particulate quality results for both are essentially consistent, but the difference is mainly in the fugitive particulate test. The total particulate matter mass measured according to the method of the invention is 85.7% higher than the particulate matter mass measured according to the method of HJ 836-2017. In the HJ836-2017 method, the test of the escaped particulate matters is not shown, and the part of the particulate matters is discharged into the atmosphere to directly form fine Particulate Matters (PM)2.5。
According to the scheme, the method can comprehensively and truly reflect the total particulate matter emission condition of the thermal power plant, and has better monitoring support especially for strictly controlling the fine particulate matter emission in the atmosphere key control area.
Test case six:
the invention adopts a drying constant weight design under the conditions of constant temperature and constant humidity. At present, the laboratory weighing measures for a tested sample in the detection of a fixed pollution source are mainly two:
1) the existing standard method, drying and weighing:
drying at 105 ℃ for 1h, then placing the particle sample in a dryer, cooling to normal temperature, and weighing to constant mass;
2) the application has the following drying constant weight under the constant temperature and humidity condition:
and (3) placing the particle sample in an environment with the temperature of 15-30 ℃ and the humidity (50 +/-5)% for balancing for 24 hours, and then weighing to constant weight. Since the ultrafine mode is an important occurrence of the escaped particles after condensation, drying at 105 ℃ obviously causes volatilization loss of fine particulate components. Therefore, the balance weighing is carried out in a temperature and humidity environment which is consistent before and after the balance weighing; after balancing for 24h, the weight is constant, and a drying constant weight mode is not adopted.
Those skilled in the art can make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (13)
1. A sampling device for low-concentration total particulate matters in flue gas of a thermal power plant mainly comprises a sampling device, a condensing device, a dehumidifying device, a metering device and a sampling pump which are sequentially arranged along the flow direction of the flue gas; the method is characterized in that: the sampling device comprises a sampling head and a heating sampling gun; the sampling head is formed by combining a sampling nozzle and a first-stage filtering membrane; a secondary filtering membrane is also arranged between the condensing device and the dehumidifying device; the condensing device adopts a two-stage series structure, and the two-stage condensing device is respectively provided with a water bath temperature control device; and a reinforced phase change system is arranged between the two stages of condensing devices and is used for adding water vapor into the flue gas entering the rear stage condensing device, increasing the humidity of the flue gas and improving the total particulate matter trapping rate.
2. The device for sampling the low-concentration total particulate matters in the flue gas of the thermal power plant according to claim 1, characterized in that: the two-stage condensing device is provided with a spiral condensing pipe and an impact bottle, wherein the spiral condensing pipe is vertically arranged above the impact bottle and is connected through a connecting pipe.
3. The device for sampling the low-concentration total particulate matters in the flue gas of the thermal power plant according to claim 2, characterized in that: in the two-stage condensing device, the spiral condensing pipes adopt a pump circulation mode to carry out water bath temperature control on the inner pipe, and the impact bottles adopt water bath tank temperature control.
4. The device for sampling the low-concentration total particulate matters in the flue gas of the thermal power plant according to claim 3, characterized in that: in the two-stage condensation device, the diameter of an inner pipe of the spiral condensation pipe is 6-8 mm, and the extension length of the inner pipe of each stage of spiral condensation pipe is 3-5 m.
5. The device for sampling the low-concentration total particulate matters in the flue gas of the thermal power plant according to any one of claims 1 to 4, characterized in that: the intensified phase change system comprises a jet flow mixer and a phase change chamber which are communicated from front to back, the jet flow mixer is provided with two inlets and an outlet, the two inlets are respectively used for connecting steam and a front-stage condensing device, and the phase change chamber is provided with a mixed gas outlet for connecting a rear-stage condensing device; the inlet of the steam is connected or directly connected to a steam generator.
6. The device for sampling the low-concentration total particulate matters in the flue gas of the thermal power plant according to claim 5, characterized in that: the secondary filtering membrane adopts an inverted filtering membrane device.
7. The device for sampling the low-concentration total particulate matters in the flue gas of the thermal power plant according to claim 6, characterized in that: the first-stage filter membrane is a quartz membrane or a PTFE membrane; the secondary filtering membrane is a PTFE membrane.
8. The device for sampling the low-concentration total particulate matters in the flue gas of the thermal power plant according to claim 6, characterized in that: also comprises a nitrogen stripping device.
9. The device for sampling the low-concentration total particulate matters in the flue gas of the thermal power plant according to claim 8, characterized in that: the metering device comprises a pressure gauge and a dry flowmeter; the impact bottles are dry spherical impact bottles.
10. A method for sampling low-concentration total particulate matters in flue gas of a thermal power plant by adopting the sampling device of any one of claims 1 to 9 mainly comprises the following steps: controlling the temperature of the device, starting a sampling pump, adding steam, stopping sampling, collecting samples, weighing and calculating;
when steam is added, the water content of the flue gas entering the rear stage condensing device is controlled to be 34g/m3~46g/m3(ii) a The heating temperature of the heating sampling gun tube is controlled to be 120 +/-5 ℃; the water bath temperature of the preceding stage condensing device is controlled to be 60-80 ℃; controlling the temperature of the water bath of the rear-stage condensing device to be 25-30 ℃; collecting particulate matter on a sample including a primary filtration membrane, a secondary filtration membrane, and a primary filterAnd the particles on each connecting component between the filter membrane and the secondary filter membrane.
11. The method for sampling low concentration total particulate matter in flue gas of a thermal power plant according to claim 10, wherein: the sampling is constant-speed tracking sampling, and the flow velocity of flue gas in the two-stage spiral pipes is controlled to be 2.5-3.5 m/s; the residence time of the flue gas in the strengthening phase change system is controlled to be not less than 10 seconds.
12. The method for sampling low concentration total particulate matter in flue gas of a thermal power plant according to claim 11, wherein: when steam is added, the steam addition flow is controlled to be 1 g/min-10 g/min.
13. The method for sampling low concentration total particulate matter in flue gas of a thermal power plant according to claim 11, wherein: during weighing, the particles collected on the first-stage filter membrane and the second-stage filter membrane are dried in a constant temperature and humidity device to constant weight and then are measured.
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