WO2014079212A1 - Device and method suitable for online detection of particle in gas pipeline - Google Patents

Abstract

A device and method suitable for online detection of particles in a gas pipeline, the gas pipeline being a high pressure and/or high temperature pipeline (218); the device comprises an online detection unit comprising a main sampling nozzle (1); the front end of the main sampling nozzle (1) extends into the gas pipeline (218), and the rear end is connected to a flow distributor (8) in series; the flow distributor (205) is provided with a cavity (801) having a main pass and a bypass; the main pass is connected to a secondary sampling nozzle (9), an online particle diameter spectrometer (10) and a first mass flow controller (13) in series; the bypass is connected to a second mass flow controller (18) in series; after the main sampling nozzle (1) conducts sampling, the gas diffuses into the cavity (801) of the flow distributor (8), and is then discharged via the secondary sampling nozzle (9) and a bypass outlet (804) respectively. The device further comprises an offline detection unit, a long-term online detection unit, and a preheating and purging unit. The device and method also improve an optical sensor in the online particle diameter spectrometer, to cause the optical sensor to be more suitable for high temperature and high pressure operating conditions by means of optical path adjustment, and to be able to online detect particles in a high pressure and/or high temperature gas pipeline for an extended period of time.

Description

 Device and method suitable for on-line detection of particulate matter in gas pipeline

 The invention relates to a particle collection and analysis technology in a pipeline, in particular to a device and a method suitable for on-line detection of particulate matter in a gas pipeline, and is particularly suitable for particles in a pipeline of high pressure and/or high temperature gas (for example, natural gas, flue gas, etc.). online test. Background technique

 The collection and analysis technology of particulate matter in pipelines is widely used in various gas transportation fields, and usually involves some high pressure and/or high temperature conditions.

 For example, natural gas pipelines, due to wear and corrosion of natural gas sources and natural gas pipelines, contain natural solid impurities such as black solids. The natural gas station uses filtration separation equipment to remove particulate matter from natural gas, thus ensuring the normal operation of important equipment such as compressors, meters and valves. The filtration separation equipment has certain resistance in operation and increases the energy consumption of the downstream compressor. It is necessary to select appropriate filtration separation equipment according to the actual situation of the particulate matter in the natural gas pipeline and to formulate a reasonable operation plan and the arrangement of the natural gas station site sewage discharge and customs clearance. In addition, natural gas pipelines are usually operated at high pressures. Therefore, it is meaningful to detect the concentration of particulate matter and the distribution of particle size in high-pressure natural gas pipelines.

 For example, high-temperature ceramic filter is a commonly used filtration equipment in coal chemical industry and catalytic cracking. The fracture of the filter tube is an important problem at present. Once the ceramic filter tube is broken, the concentration of particulate matter in the pipeline is rapidly increased, which is a serious hazard. The normal operation of important downstream equipment, such as blade wear of the flue gas turbine, currently lacks the technology for real-time monitoring of particulate matter concentration at the filter outlet. Therefore, it is important to evaluate the performance of particulate matter determination in the inlet and outlet of high-temperature filtration separation equipment and to monitor the change of particulate concentration in the pipeline in real time to protect important downstream equipment.

At present, the detection of particulate matter in high-pressure and/or high-temperature gas pipelines is mainly divided into off-line detection and on-line detection. Off-line detection refers to the collection of dust and other particles in the gas pipeline through a high-precision filter cartridge or filter membrane. After weighing, the concentration of particulate matter in the pipeline is calculated, and the particle size of the collected particulate matter is determined by other particle size analyzers. This off-line detection method can objectively measure the characteristics of the particles in the pipeline, but when the concentration is low, the operation time is long and the real-time performance is not good. At present, most of the online detection devices adopt optical principles and can only be tested under normal temperature and normal pressure. If the detection device is used for high temperature or high pressure operation, it is necessary to cool the high temperature gas or reduce the high pressure gas. It is detected by the instrument, and the decrease in temperature or pressure causes some gases to precipitate droplets, causing agglomeration of particles, affecting the measurement results, and the condensed droplets can also contaminate the optical lens. At present, there are also a few instruments that can be directly used for on-line measurement under high temperature or high pressure conditions. For example, CN201060152Y discloses a dust on-line detection device for high-pressure natural gas pipelines, which has a complicated structure and is too low in concentration from the field use situation. When the instrument is too high, the measurement results of the measuring instrument are not accurate. In addition, for natural gas long-distance pipelines, the particle concentration varies greatly, from a few milligrams to several hundred milligrams, and the particle size ranges from 0.3 micrometers to 100 micrometers. The current detection technology cannot yet achieve the long-term online monitoring of particulate matter concentration in high-pressure natural gas pipelines. The effect is also that the amount of droplets in the pipe cannot be measured. On the other hand, there is currently no shortage of techniques for long-term monitoring of particulate matter in the field of particulate matter collection and analysis techniques in pipelines. Summary of the invention

 In view of the shortcomings of the above-mentioned existing particle detection technology in gas pipelines, the inventor of the present invention creatively proposed a direct online detection and long-term monitoring of gas pipelines, especially high-pressure or high-temperature gases, based on relevant scientific research and field experience and expertise. Apparatus and method for particulate matter in a pipeline.

 An object of the present invention is to provide a device suitable for on-line detection of particulate matter in a gas pipeline, which has low maintenance cost and high reliability, can realize measurement of particulate matter characteristics in a high-pressure or high-temperature gas pipeline, and further realizes long-term online monitor.

 Another object of the present invention is to provide a method for on-line detection of particulate matter in a gas pipeline using the apparatus, which can be a high temperature and/or high pressure gas pipeline, without depressurizing the high pressure gas or cooling the high temperature gas. The online measurement of the characteristics of the particles in the pipeline enables further long-term online monitoring.

 In order to achieve the above object, in one aspect, the present invention provides an apparatus for on-line detection of particulate matter in a gas pipeline, the apparatus comprising:

 The online detecting unit comprises: a main sampling nozzle and a flow distributor arranged in series through a pipeline; a front end of the main sampling nozzle extends into a gas pipeline to be detected, and a gas inlet of the flow distributor is connected in series at the end; The flow distributor is provided with a cavity, a gas inlet is arranged on the front side of the cavity, two gas outlets are arranged on the rear side, and the main circuit and the bypass two pipes are separated, and the main circuit is connected in series with the secondary sampling nozzle. The on-line particle size spectrometer and the first mass flow controller bypass the second mass flow controller; after the main sampling nozzle is sampled from the gas pipeline, the gas sample is diffused into the cavity from the gas distributor inlet of the flow distributor After that, they are discharged through the secondary sampling nozzle and the bypass outlet, respectively.

 In the present invention, the direction of "front", "back" or "end" refers to the direction of the upstream and downstream of the flow of the gas, that is, the direction of the flow of the gas flows from "front" to "back" or "end".

 According to a particular embodiment of the invention, the apparatus of the invention is applicable to on-line detection of particulate matter in high pressure and/or high temperature gas conduits.

 In a specific embodiment of the present invention, the gas pipeline is a high temperature gas pipeline, and the apparatus for in-line detection of particles in the gas pipeline of the present invention further comprises:

 Preheating purging unit; the preheating purging unit is arranged in parallel on the pipeline between the main sampling nozzle and the flow distributor, and includes a heating gas storage tank and a heat preservation pipeline for purging and preheating the pipeline of the entire system. .

 Specifically, the apparatus of the present invention suitable for on-line detection of particulate matter in a high temperature gas pipeline includes:

 (1) an online detecting unit; the online detecting unit comprises a main sampling subsystem, a subsampling subsystem, a particle size online analyzer, and a first flow metering control subsystem connected in series through a pipeline; wherein:

 The main sampling subsystem includes a tubular main sampling nozzle, and a front end of the main sampling nozzle extends into a high temperature gas pipeline to be detected to introduce a high temperature gas sample containing particulate matter;

The subsampling subsystem comprises a gas flow distributor and a secondary sampling nozzle; the flow distributor is provided with a cavity, a gas inlet is arranged on the front side of the cavity, and two gas outlets are arranged on the rear side to separate the main Road and bypass two pipelines; the main road is connected in series with the secondary sampling nozzle, the particle particle size online analyzer and the first flow rate control subsystem, and the second flow metering control subsystem is bypassed; After the main sampling subsystem is sampled from the high temperature gas pipeline, the gas sample is diffused into the cavity from the gas distributor inlet, and is respectively taken out by the secondary sampling nozzle in the downstream direction and discharged from the bypass outlet;

 (2) preheating purging unit; the preheating purging unit is arranged in parallel on the pipeline between the main sampling subsystem and the subsampling subsystem, and includes a heating gas storage tank and an insulated pipeline for the pipeline of the entire system. Purge and preheat.

 In the device for on-line detection of particulate matter in a gas pipeline of the present invention, the structural design of the flow distributor can allow the airflow entering the cavity to form a turbulent flow inside the cavity, thereby uniformly mixing the particles therein. A representative sample can be obtained by satisfying the secondary sampling nozzle.

 According to a specific embodiment of the present invention, in the apparatus for on-line detection of particulate matter in a gas pipeline, the flow distributor has a cavity diameter larger than a gas inlet and a main passage outlet, and the bypass is taken from the main road. Preferably, the gas inlet, the cavity and the main road outlet are disposed on the same center line; more preferably, the center line direction of the bypass outlet is perpendicular to the direction of the gas inlet center line.

 In the present invention, the flow distributor may have a structural size as long as it allows the flow of the flow distributor chamber to form a turbulent flow inside the chamber for uniform mixing. According to a preferred embodiment of the present invention, the ratio of the diameter of the cavity of the flow distributor to the diameter of the gas inlet is 2 to 10:1; the ratio of the length of the cavity (in the direction of the sampled gas flow) to the diameter of the cavity is 0.5 to 3:1. , can be adjusted according to the gas flow rate.

 According to a particular embodiment of the invention, in the apparatus of the invention for on-line detection of particulate matter in a gas conduit, the main sampling nozzle is telescoped to a position to be measured in the gas conduit by a mechanical or hydraulic structure. The main sampling nozzle is typically a tubular sampling nozzle. Preferably, the apparatus further comprises one or more of the following devices that penetrate the main sampling nozzle into the conduit:

 A sensor that measures pressure and/or temperature, and/or a probe that measures flow rate.

 According to a specific embodiment of the present invention, in the apparatus for on-line detection of particulate matter in a gas pipeline of the present invention, the front end of the secondary sampling nozzle extends into the interior of the gas distributor to perform dust on the gas entering the flow distributor. Subsampling, the end of which is connected to the first gas outlet (main gas outlet).

 According to a preferred embodiment of the present invention, in the apparatus for on-line detection of particulate matter in a gas pipeline of the present invention, the on-line particulate particle size spectrometer of the main road and the first mass flow controller are further arranged in series The first particulate trap. In this way, the on-line detection can also be performed on off-line collection and detection of particulate matter, which can be mutually verified with the results of online detection.

 According to a particular embodiment of the invention, the apparatus of the present invention suitable for on-line detection of particulate matter in a gas conduit may further comprise:

 An off-line detection unit; the off-line detection unit includes a second particulate trap, the second particulate trap front end is connected to the pipeline between the main sampling nozzle and the flow distributor, and the rear end is connected to the bypass outlet and the second mass On the pipeline between the flow controllers. The setting of the offline detection unit is mainly used to compare the detection result with the result of the online detection to verify the reliability.

 According to a specific embodiment of the present invention, the apparatus for on-line detection of particulate matter in a gas pipeline of the present invention further includes:

Long-term online monitoring unit; the long-term online monitoring unit includes a dust concentration sensor and a computer, and the dust concentration sensor is used for detecting the dust condition in the pipeline, and converting the concentration value of the particulate matter in the pipeline into a current signal and transmitting it to a computer to realize long-term online monitoring. According to a particular embodiment of the invention, the apparatus of the invention comprises:

 The online detecting unit comprises: a main sampling nozzle connected in series through a pipeline, a first valve, a three-way ball valve and a flow distributor; one end of the main sampling nozzle extends into the gas pipeline to be detected, and the main sampling The mouth extends into the connection of the gas pipe through the pipe joint and the flange seal, and the other end of the main sampling nozzle is connected to the gas distributor of the flow distributor through the first valve and the three-way ball valve; the flow distributor is provided with a cavity and a cavity One gas inlet is arranged on one side, and two gas outlets are arranged on the other side to separate the main pipeline and the two bypass pipelines; the main pipeline is connected in series with the secondary sampling nozzle, the on-line particle size spectrometer, and the first particulate matter trapping. The first pressure reducing valve and the first mass flow controller; the bypass is connected in series with the second valve, the second pressure reducing valve and the second mass flow controller; the main sampling nozzle is sampled from the gas pipeline, and the gas is collected After being diffused into the cavity from the gas distributor of the flow distributor, the sample is discharged through the secondary sampling nozzle and the bypass outlet respectively;

 An off-line detecting unit; the offline detecting unit comprises a second particulate trap and a third valve connected in series through a pipeline, the front end of the second particulate trap is connected to the three-way ball valve, and the pipeline at the end of the third valve is connected On the line between the second valve and the second pressure reducing valve;

 Long-term online monitoring unit; the long-term online monitoring unit includes a serially connected dust concentration sensor and a computer, and the front end pipeline of the dust concentration sensor extends into the gas pipeline to be detected for detecting the dust in the pipeline, and the concentration of the particulate matter in the pipeline The value is converted to a current signal that is transmitted to a computer for long-term online monitoring. In another aspect, the present invention also provides a method for on-line detection of particulate matter in a gas pipeline by using the apparatus of the present invention to perform on-line detection of particulate matter in a gas pipeline, wherein

 The gas sample is collected from the gas pipeline by using the main sampling nozzle of the online detecting unit, and the gas sample is diffused into the cavity from the gas distributor of the flow distributor, and then enters the main road and the bypass respectively;

 The particle size and particle size of the sample taken in the secondary sampling nozzle in the main road are measured by the on-line particle size spectrometer, and the gas flow rate of the on-line particle size spectrometer is measured by the first mass flow controller. And control, using the second mass flow controller to meter and control the flow of excess gas entering the bypass to meet the requirements of the online particle size spectrometer's own flow rate and the constant sampling of the online detection unit.

 According to a specific embodiment of the present invention, when the particulate matter in the high temperature gas pipe is in-line detected by the device including the preheating purge unit, the method further comprises the steps of: first introducing the heating gas into the detection unit pipeline by using the preheating purge unit. Purge and preheat, then turn off the preheating purge unit operation; then use the online detection unit to sample.

 According to a specific embodiment of the present invention, in the method for detecting on-line particles in a gas pipeline of the present invention, the sum of the gas flow rate measured by the first mass flow controller and the gas flow rate measured by the second mass flow controller is entered into the entire online detecting unit. The gas flow rate, according to the size of the main sampling nozzle, the flow rate of the gas when entering the main sampling nozzle; when the flow rate into the main sampling nozzle is equal to the flow rate in the pipeline, the constant velocity sampling is obtained, and the representative pipeline can be collected. particulates.

According to a preferred embodiment of the present invention, the apparatus of the method of the present invention further comprises the long-term online monitoring unit, the long-term online monitoring unit includes a dust concentration sensor and a computer, and the dust concentration sensor is used for detecting dust in the pipeline. , The particle concentration value in the pipeline is converted into a current signal and transmitted to a computer to realize long-term online monitoring. The method further comprises: calculating a dust concentration C in the pipeline by using a long-term online monitoring unit, and analyzing and comparing the detection result of the online detecting unit; Calculate the dust concentration C in the pipeline according to the following formula:

 c _ a(AI + βΑΗ)

_ γ ^η

 Where: C: the concentration of dust in the pipeline;

 AI: sensor output current change value;

 ΛΗ-. Humidity change value;

 V: pipe wind speed;

 α, β, m are calibration coefficients for dust concentration sensors for specific dusts. According to a specific embodiment of the present invention, the dust concentration sensor is an electrostatic dust concentration sensor (abbreviated as an electrostatic sensor). During the specific implementation, the influence of the wind speed and humidity on the output signal of the electrostatic dust concentration sensor can be experimentally studied to further determine the calibration coefficient of the electrostatic dust concentration sensor for different dusts. For example, according to a specific embodiment of the present invention, the determined electrostatic dust concentration sensor for different dusts has a calibration coefficient of: 800 mesh talcum powder having a calibration coefficient α of 1000, β of 1032, and m of 2.18; calibration of fly ash The coefficient α is 400, which is 8.04, m is 1.88; the calibration coefficient of dust in the natural gas pipeline, α is 400, which is 6.07, and m is 2.18.

 According to the above model formula, the dust concentration can be determined by the dust concentration sensor output current change, humidity change and pipeline real-time wind speed.

 In order to verify the accuracy of the above empirical model formula of the present invention, the present invention uses 800 mesh talc as the pipeline transport medium under the experimental conditions of an ambient temperature of 15 ° C, an ambient humidity of RH 30%, and a pipeline wind speed of 6.3 m/s. conducted an experiment. The empirical model is used to calculate the dust concentration corresponding to the current output value of the dust sensor and compare it with the experimental results (online test results), as shown in Figure 1. See Table 1 for the results of the relative error analysis. It can be seen from Table 1 that the relative error between the empirical model calculated value and the experimental result of the electrostatic method for measuring 800 mesh talc concentration is less than ± 5%.

 Table 1 Relative error analysis results

In a specific embodiment of the present invention, the apparatus for on-line detection of particulate matter in a gas pipeline of the present invention comprises: an on-line detecting unit; the in-line detecting unit includes a main sampling nozzle, a first valve, and a third serially connected through a pipeline Passing ball valve and a flow distributor; one end of the main sampling nozzle extends into the gas pipeline to be detected, and the main sampling nozzle extends into the joint of the gas pipeline through the pipe joint and the flange seal, and the other end of the main sampling nozzle passes through the first valve and the three-way The ball valve is connected in series with the flow distributor gas inlet; the flow distributor is provided with a cavity, one gas inlet is arranged on one side of the cavity, and two gas outlets are arranged on the other side to separate the main circuit and the bypass two pipes; The main path is connected in series with the secondary sampling nozzle, the on-line particle size spectrometer, the first particulate trap, the first pressure reducing valve and the first mass flow controller; the bypass is connected in series with the second valve and the second decompression The valve and the second mass flow controller; after the main sampling nozzle is sampled from the gas pipeline, the gas sample is diffused into the cavity from the gas distributor of the flow distributor, and then discharged through the secondary sampling nozzle and the bypass outlet;

 An off-line detecting unit; the offline detecting unit comprises a second particulate trap and a third valve connected in series through a pipeline, the front end of the second particulate trap is connected to the three-way ball valve, and the pipeline at the end of the third valve is connected On the line between the second valve and the second pressure reducing valve;

 Long-term online monitoring unit; the long-term online monitoring unit includes a serially connected dust concentration sensor and a computer, and the front end pipeline of the dust concentration sensor extends into the gas pipeline to be detected for detecting the dust in the pipeline, and the concentration of the particulate matter in the pipeline The value is converted to a current signal that is transmitted to a computer for long-term online monitoring.

 In the above specific embodiment of the present invention, the on-line detecting unit can periodically measure the concentration and particle diameter of the particulate matter in the gas pipeline; the long-term online monitoring unit can monitor the concentration of the particulate matter in the pipeline for a long period of time. The following is an example of the detection of particulate matter in a high-pressure natural gas pipeline. (The detection of particulate matter in a high-temperature gas pipeline mainly uses the preheating purge unit to introduce the heating gas into the detection unit pipeline for purging and pre-processing. Heat, then turn off the preheating purge unit operation; then use the online detection unit to sample):

 The main sampling nozzle can be telescoped to different positions in the natural gas pipeline through a mechanical or hydraulic structure, and the form is not limited. The probe having the function of measuring the flow rate may be provided in the pipeline with the main sampling nozzle, such as a pitot tube. It can also be extended into sensors that measure pressure and temperature. The dusty natural gas enters the sampling system through the sampling nozzle for particle detection. There are two detection methods, namely (1) online detection; (2) offline detection. The two detection methods can be realized by the switching of the three-way ball valve and the opening and closing combination of the second valve and the third valve. The main purpose of offline detection is to verify the mutual verification of online results, to ensure the accuracy and reliability of the detection, and offline sampling can collect dust for further analysis, such as analysis of composition and particle size distribution.

When performing on-line inspection, the three-way ball valve is in the through state, the third valve is closed, and the second valve is open. The natural gas enters the flow distributor through the three-way ball valve, and a part of the gas (this part of the gas can be determined according to the requirements of the online testing instrument. Generally, the online monitoring instrument needs to be measured under a steady flow, so the subsampling is performed here) The secondary sampling nozzle enters the on-line particle size spectrometer to detect the particle concentration and the particle size. After the detected natural gas, the particulate matter is collected by the first particulate trap, and the gas enters the first pressure reducing valve and then enters the first mass. The flow controller measures and controls the flow of natural gas entering the particulate particle size spectrometer to meet the requirements of the online particle size spectrometer's own flow rate (the flow rate is constant). The excess gas entering the flow distributor enters the second mass flow controller through the second valve and the second pressure reducing valve, and the flow rate of the gas is metered and controlled by the second mass flow controller. By adjusting the gas flow rate entering the flow controller to meet the requirements of the constant sampling of the sampling system, the sum of the measured flow rate of the first mass flow controller and the flow measured by the second mass flow controller is the flow entering the entire sampling system. The flow rate of the gas entering the sampling nozzle can be obtained according to the size of the main sampling nozzle. When the flow rate into the main sampling nozzle is equal to the flow rate in the pipe, With constant velocity sampling, representative particles in the pipeline can be collected.

 When the sampling system is switched to off-line detection, the three-way ball valve is switched to the 90 degree direction, the third valve is opened, and the second valve is closed. The natural gas enters the second particulate trap through the three-way ball valve, where the particulate matter is trapped, and the natural gas is decompressed through the third valve and the second pressure reducing valve to enter the second mass flow controller, and then discharged to the safe area. The second mass flow controller measures and controls the sampled flow to meet the requirements for constant velocity sampling.

 The long-term online monitoring unit includes a dust concentration sensor and a computer. The dust concentration sensor detects the dust in the pipeline, and converts the concentration of the particulate matter in the pipeline into a current signal and transmits it to the computer, which enables long-term online monitoring.

 In addition, with the device of the invention, the on-line detection can also be performed on the off-line collection and detection of the particulate matter, which can be mutually verified with the results of the online detection.

 According to a specific embodiment of the present invention, the valve form in the online detecting unit and the offline detecting unit is not limited, and may be any kind that realizes the function. The online particle size spectrometer is an optical principle instrument. For example, the Palas WELAS series optical on-line particle size spectrometer can be used, and the high pressure aerosol catheter in the prior art can be used to measure at a high pressure of 12 MPa, or The use of the high temperature resistant aerosol conduit of the prior art enables safe and reliable operation at a temperature of 650 ° C and a pressure of 5 MPa.

 According to a particular embodiment of the invention, the invention also improves the optical sensor in the on-line particle size spectrometer, enabling it to be better applied to high pressure (5 = standard atmospheric pressure) and high temperature conditions (above 20 ° C) The particle size and concentration of dust-containing particles are measured online. in particular:

 The optical sensor provided by the present invention is shown in Fig. 9, which comprises an aerosol detecting catheter 101, four glass windows 102 are arranged around the aerosol detecting duct 101, and two are arranged outside the two windows which are 90 degrees apart from each other. The achromatic lenses 131 and 132, and the two achromatic lenses 131 and 132 are respectively located on the incident optical path and the receiving optical path (exit optical path) inside the optical sensor, and respectively outside the achromatic lenses 131 and 132 of the incident optical path and the receiving optical path. A small aperture stop 141 and 142 are provided, and convergent lenses (focus collimating lenses) 151 and 152 are respectively disposed outside the aperture apertures 141 and 142 of the incident optical path and the receiving optical path. The outside of the converging lens of the incident optical path is a light source, and the outside of the converging lens of the receiving optical path is a photoreceiver (photodetector) 106. Further, as shown in the figure, a plane mirror 107 is further provided on the receiving light path to reflect the light from the achromatic lens 132 to the aperture stop 142 and further through the condenser lens 152 to be detected by the photodetector. In the description of the optical sensor configuration of the present invention, the "outer" is the direction centered on the aerosol detecting conduit and away from the aerosol detecting conduit.

The dust-containing gas is introduced into the interior of the optical sensor through the aerosol conduit. The optical path inside the optical sensor is divided into two parts, that is, the incident optical path and the receiving optical path. The light emitted by the light source can enter the optical sensor through the optical fiber or other forms. The condenser lens 151, the aperture stop 141, and the focus achromatic lens 131 focus the light on the center of the channel where the dust-laden gas flows (the direction perpendicular to the paper face down), that is, the center of the aerosol detecting catheter 101, the incident light path and the receiving light path. The central position of the passage through which the apertured aperture gas passes defines a virtual optically sensitive area, referred to as optical measurement body 108, only the particles entering the optical measurement body are detected. The particles entering the optical measuring body region emit scattered light under the illumination of the light, and the scattered light is received by the receiving optical path, converted into an electrical signal by the photodetector, and each particle is transferred to an electric pulse, the particle scattering light intensity and the particle size. In accordance with Mie's law of scattering, the size and concentration of particles can be derived by measuring the number and magnitude of electrical pulses. Optical sensors commonly used for on-line detection of particle size are calibrated in a normal temperature and pressure environment. Under high temperature or high pressure conditions, the density of the dust-containing gas detected by the sensor is very different from the normal temperature and pressure. The difference in the density of the gas inside and outside the aerosol detection tube will cause the light to deflect when the beam is injected into the aerosol detection catheter. The imaging position of the reflected beam passing through the pupil deviates from the center of the aerosol catheter, so that the intensity of the light irradiated onto the particle is reduced, and directly affects the intensity of light detected in the receiving optical path, resulting in a small measurement of the particle size of the system, resulting in Large measurement error. With the improved optical sensor of the present invention, the correct measurement can be ensured by adjusting the position of the aperture stop at different temperatures and pressures, and the size of the optical measurement volume is not affected by the high pressure and high temperature conditions.

According to a specific embodiment of the present invention, when the apparatus for in-line particle size spectrometer is used for on-line detection of particles in a gas pipeline, wherein the optical path of the optical particle of the on-line particle size spectrometer is in the incident optical path and the receiving optical path The central position of the aerosol detecting catheter through which the small aperture diaphragm gas passes defines a virtual optical measuring body, and the method for performing on-line detection of the particulate matter in the gas duct further includes the following process of adjusting the optical path to correct the imaging position: The temperature and pressure of the working condition are adjusted to keep the size of the optical measuring body the same as that under normal temperature and normal pressure by adjusting the position of the small aperture stop. Specifically, the distance adjusted by the aperture stop is determined as follows: Calculating the measured temperature, the refractive index of the gas under pressure, and calculating the corrected free space image according to the optical geometric relationship between the incident optical path and the receiving optical path and the law of gas refraction Then, according to the focal length and image distance of the lens and the free-space optical imaging principle, the object distance _M of the corrected pupil distance lens is calculated, and according to the initial object distance _{M of the} aperture before the correction. It is finally determined that the aperture pupil needs to move a distance ζίΜϋβ, and a positive value indicates that it is far from the lens direction, and a negative value is close to the lens direction. A further explanation is as follows:

As shown in Fig. 10, at a high temperature or a high pressure, the size of the optical measuring body is kept the same as that under normal temperature and normal pressure by adjusting the positions of the small aperture stops 141 and 142. By theoretical calculation and the actual test instrument, the diaphragm adjustment of the gas pressure Ρ distance ζί _Μ, Gamma] temperature, under the influence of the adjustment method.

 Referring again to Figure 11, the influence model of temperature and pressure on the pupil imaging is established by analyzing the characteristics of the incident optical path. Since the optical path has symmetry, the optical path is simplified for the convenience of analysis, and only half of the optical path is analyzed. The optical path analysis is shown in Figure 11.

 Corresponding to the incident light path in Fig. 10, the center of the aperture stop is at point G, the achromatic lens is at 0, the window of glass is at the point of Ρ, and the point is the center of the aerosol catheter. For the convenience of analysis, the imaging of the pupil center is selected for analysis. When the detection is performed under normal temperature and normal pressure environment, the pupil imaging is located at point A. When the high pressure or high temperature gas is introduced into the aerosol conduit, the density of the left side of the glass window is The change directly causes the refractive index of the gas in the aerosol conduit to change, and the imaging position of the pupil changes from point A to point B. Because the image at point A is blurred, the second imaging in the exiting optical path is greatly affected. Influence, when the particles enter this area, the scattered light intensity becomes weak. At this time, the measurement result of the instrument is not accurate, and the position of the image path needs to be corrected by adjusting the optical path. By changing the distance of the aperture from the lens, OG returns the image of the aperture back to point A. When the aperture is at this position and the normal temperature and pressure conditions, the image of the aperture should be at point C. Therefore, according to the geometric relationship of the light in Fig. 11, the distance of the pupil adjustment can be calculated according to the geometrical optics and the law of refraction.

 The specific calculation process is as follows:

The diameter of the lens is 2DO=D. Under the normal temperature and pressure, the radius of the glass window covered by the beam is EP. Let DI=JT;, DH=J HI=J, glass window and lens spacing PO= correct front pupil imaging position and glass window spacing AP=/. The radius of the optical window covered by the beam is EP=R; the corrected pupil imaging position and the glass window spacing CP=/;, the radius of the optical window covered by the beam FP=R &. Correct the incident angle of the most edge imaging beam at normal temperature and pressure before the ZDEH=ZJAO = a ₀ , the refraction angle ZJBP = β ₀ ; the incident angle ZKCO = ο of the most edge imaging beam at normal temperature and pressure, and the refraction angle ΖΚΑΡ = β! . The thickness of the glass window is h, the refraction angle of the light entering the glass window is ZMEJ=oc _fl ', ZNFK=a, and the refractive index of the glass window is n _glass , ignoring its influence by high pressure and high temperature, according to the optical geometric relationship,

 The following equation can be obtained by correcting the optical path before the trigonometric function relationship:

t _ar , „ _ -y _a _RS ₀ -h*tana ₀ '

m ^na . —— "-" (1) According to the law of gas refraction:

« ₀ *sin« ₀ =^ _tes *sin« ₀ ' (2) . XU ⁱⁿ A) (3) Where: It is the refractive index of air at normal temperature and normal pressure is about equal to 1, which is the refractive index of dusty gas under high temperature and high temperature conditions. From the above formula, the angle oc can be calculated. , α ₀ ', and Α).

 After the optical path is corrected, the following method can be used to obtain the following formula:

_ RS _{ -y _x _ RS ₀ — * (tan ₁ - tan ₀ ) - * tan α _χ '

^o^sin^ =« _g/ _*sina ₁ ' (5) * ^sin = ^sin A (6) The same method, through the above three formulas, plus the trigonometric formula, can be obtained separately "m; and ^^;, According to the geometric relationship, 0 ₄ <0, ₀ <[ , the angles _αι , α , Άβ can be determined.

 What I finally want to solve is:

RS _X - y _x RS ₀ — * (tan a - tan α ₀ ) - z * tan a[

 'l— — ( / 1 tan^ tan^

 The effect of refractive index at high temperatures and pressures can be calculated in the following ways:

 Usually, the components of the dust-containing gas measured at the industrial site are mostly mixed components. According to the gas component and the corresponding refractive index of each gas, the effective refractive index of the mixed gas is obtained by the Lorentz-Lorenz equation:

(8) n -2

Where _ni is the refractive index of the one component gas, φι is the volume fraction of each component

 Then derived from the equation of compressible gas state:

n ² -1 p pT ₀ Z ₀

 (9)

«ο -1 Ρο Ρο ^ΤΖ

 among them". For the refractive index of the gas, ρ« is the density under the standard condition, Ρ is the absolute pressure under the working condition, and the absolute pressure is under the standard condition.

Γ is the absolute temperature under working conditions, r _fl is the absolute temperature under standard conditions, and 3⁄4^BZ is the compression factor under standard conditions and working conditions. Through the formula (1 (6), we can first determine the ^ and oc; size, and then calculate the distance of the imaging offset and the radius R& of the optical window covered by the corrected beam, and then calculate according to the geometric relation (7). After the instrument is corrected, the distance from the window to the normal temperature and normal pressure conditions can be calculated. The image distance of the corrected free space can be calculated as 0 = +, and the focal length of the lens before and after the correction of the instrument is unchanged. Then, according to the principle of free space optical imaging:

丄(10) Calculate the corrected object distance _Ul , according to the initial object distance M of the diaphragm before correction. Finalize the exit pupil needs to move distance

Au=u _r u ₀ , a positive sign indicates that it is far from the lens, and a negative sign is near the lens. According to the above calculation, the relationship between the temperature of the gas and the adjustment distance of the pupil is obtained, and the image can be ensured to have the same position under normal temperature and pressure under the conditions of high temperature and high pressure.

 A specific example will now be given to illustrate the calculation process.

 The diameter of the achromatic lens is 7.6mm. The distance between the glass window at normal temperature and pressure is from i3⁄4=6.5mm, the distance between the window glass and the lens is 10.1mm, and the focal length of the lens is 15.1mm. The radius of the optical window covered by the beam is R = 1.5 mm. At this time, the image distance is! 3⁄4=16.5mm, the object distance is 1811∞«, when the gas in the aerosol conduit is 5Mpa, the natural gas at 13 °C can calculate the refractive index of natural gas according to formulas (8) and (9). n is 1.0034.

According to equation (7), ο3⁄4« 13 ° , oc/«13.02° , ^«12.95°, RS _; = 1.497mm, / =6.476mm and image offset distance Δν«20μηι can be obtained, and used in optical sensors. The size of the optical measuring body of the particle measurement is only 50μηιχ70μηιχ70μηι size, and the distance from the image shift distance has been enough to affect the optical measuring body size, and the measurement result is inaccurate.

The focal length of the lens and then the image distance w = L + + h, and the formula (10) can be calculated from the distance of the lens aperture _Ul case is 185.2mm. Thus, the distance that the aperture is adjusted away from the direction of the achromatic lens is _M = M _r M _fl = 4.2 mm.

 Since the optical path is reversible, the outgoing optical path of the optical sensor can also be adjusted as described above. According to a specific embodiment of the present invention, the first mass flow controller and the second mass flow controller may be an instrument integrating mass flow measurement and flow control, or may be a valve and flow measurement with flow control function. A combination of functional instrument combinations.

According to a particular embodiment of the invention, the dust concentration sensor of the long term online monitoring unit is an electrostatic dust concentration sensor of the prior art, and the computer can be replaced by any instrument having a real time display function. In summary, the present invention provides a device and method suitable for on-line detection of particulate matter in a gas pipeline. The device has a simple structure, low maintenance cost, and high reliability, and it is not necessary to depressurize the high pressure gas or cool the high temperature gas. The determination of the characteristics of the particles in the pipeline can further realize long-term online monitoring. It has been proved by practice that the technology of the present invention is used for detecting particulate matter in a natural gas long-distance pipeline, particulate matter in a high-temperature flue gas pipeline, etc., and the particle concentration varies widely, from several milligrams to several hundred milligrams, and the particle diameter ranges from 0.3 micrometers. Up to 100 microns, all can be accurately measured, and offline sampling while online detection, the results can be consistent. In long-term online monitoring, measurements can still be made when the pipe concentration is as low as 1 mg/m ³ or less.

Compared with the prior art, the invention has the following features and advantages: 1. It can be directly used in high pressure natural gas pipeline without stepping down. The concentration and particle size of the particles are measured. The maximum working pressure can reach 12 MPa, which can avoid the precipitation of high pressure natural gas and cause the droplets to precipitate and affect the particle measurement. It can be directly used for the determination of particles in high temperature gas pipelines without cooling. The maximum working temperature can be Up to 650 ° C, to avoid the high temperature gas cooling caused by some analysis to affect the particle measurement; 2. Integrated online detection and offline detection in one, two detection methods can be switched; 3. While online detection can also be The particulate matter is collected offline and can be mutually verified with the results of online testing. 4. The long-term online monitoring of dust concentration can be realized, and the maintenance cost is low. DRAWINGS

 Fig. 1 is a comparison diagram of experimental results and calculation results for verifying the accuracy of the formula for calculating the dust concentration C in the pipe of the present invention. 2 is a schematic structural view of an on-line detecting device for particulate matter in a gas pipe according to the present invention.

 Figure 3 is a schematic view showing the structure of a flow distributor in the apparatus of the present invention.

 4 is a comparison diagram of Coulter measurement results and online measurement results in Embodiment 1 of the present invention.

 Fig. 5 is a structural schematic view showing an on-line detecting device for particulate matter in a high temperature gas pipe according to Embodiment 2 of the present invention.

 Figure 6 is a graph showing the particle size distribution of the catalyst measured by the Coulter analyzer in Example 2 of the present invention.

 Figure 7 is a graph showing the particle size distribution of a catalyst measured by an in-line analyzer in Example 2 of the present invention.

 Figure 8 is a photograph showing the microstructure of the catalyst downstream of the filter of Example 2 of the present invention.

 Figure 9 is a schematic diagram of the optical sensor of the present invention.

 Figure 10 is a schematic diagram of the optical path adjustment of the optical sensor of the present invention.

 Fig. 11 is a view showing an optical path adjustment analysis of the optical sensor of the present invention. detailed description

 In order to more clearly understand the technical features, objects and effects of the present invention, the features of the measuring method of the present invention and the technical effects thereof will be further described in detail with reference to the accompanying drawings, but the present invention is not limited thereby. Example 1

 Referring to FIG. 2, the present embodiment mainly performs on-line detection of particulate matter in a high-pressure natural gas pipeline, and the apparatus includes an online detection unit I and a long-term online monitoring unit II. among them:

 The on-line detection I unit mainly comprises a main sampling nozzle 1, a pipe connecting pipe 2, a flange 3, a first valve 4, a three-way ball valve 5 and a flow distributor 8 which are serially connected in series through a pipeline (in this embodiment, pressure is also provided) Transmitter 6, temperature transmitter 7 to monitor the temperature and pressure in the flow distributor 8), two pipelines are separated from the flow distributor 8, one pipeline is connected in series to the secondary sampling nozzle 9, and the particle size of the on-line particles Spectrometer 10 (using the Palas WELAS optical on-line particle size spectrometer, which can be measured at a high pressure of 12 MPa using a high pressure aerosol catheter of the prior art), a first particulate trap 11, a first pressure reducing valve 12, and a A mass flow controller 13 is connected to the second valve 16, the second pressure reducing valve 17, and the second mass flow controller 18 in sequence.

For the specific structure of the flow distributor 8, please refer to FIG. 3, which is provided with a cavity 801, a gas inlet 802 is arranged on the front side of the cavity, and two gas outlets are arranged on the rear side (main road outlet 803, bypass outlet 804). And dividing the main line and the bypass two pipelines; wherein, the cavity 801 of the flow distributor has a larger diameter than the gas inlet 802 and the main road outlet 803, and the bypass is taken from the main road The branch line of the outlet; the gas inlet 802, the cavity 801 and the main road outlet 803 are disposed on the same center line; the center line direction of the bypass outlet 804 is perpendicular to the center line direction of the main road exit 803. By adopting the structural design of the flow distributor 8, the airflow entering the cavity can be formed into a turbulent flow inside the cavity, so that the particles in the cavity are uniformly mixed to satisfy the secondary sampling nozzle and a representative sample can be obtained.

 Further, the apparatus of this embodiment further includes an offline detection pipeline including a second particulate trap 14 and a third valve 15 connected in series by a pipeline, and the other end of the second particulate trap 14 The three-way ball valve 5 is connected, and the other end of the third valve 15 is connected to a line between the second valve 16 and the second pressure reducing valve 17.

 The main sampling nozzle 1 can be inserted into the natural gas pipeline for collecting particulate matter samples in high-pressure natural gas. The connection method of the sampling nozzle and the pipeline can be flanged, threaded, etc., and the form is not limited. The figure shows that the pipe is connected through the pipe 2 and the method. Lan 3, the natural gas in the pipeline is sealed, and the sampling nozzle can be mechanically or hydraulically inserted into different positions in the sampling pipe. The first valve 4 is disposed between the sampling nozzle 1 and the three-way ball valve 5 for controlling opening or closing of the main sampling nozzle 1.

 The dusty natural gas enters the sampling system through the sampling nozzle 1 for particle detection. There are two detection methods, namely (1) online detection and (2) offline detection. The two detection methods can be realized by the switching of the three-way ball valve 5 and the opening and closing combination of the third valve 15 and the second valve 16.

 When the online detection is performed, the three-way ball valve 5 is in a through state, and the third valve 15 is closed, and the second valve 16 is opened. The natural gas enters the flow distributor 8 through the three-way ball valve 5, and a part of the gas enters the on-line particle size spectrometer 10 through the secondary sampling nozzle 9 to detect the particle concentration and the particle size, and the detected natural gas particles pass through the particulate trap 1 1 To collect, further gas enters the first pressure reducing valve 12 and then enters the first mass flow controller 13 to measure and control the flow of natural gas entering the particulate particle size spectrometer 10 to meet the flow rate of the online particle size spectrometer. Requirements (the flow is constant at this time). The excess gas entering the flow distributor 8 passes through the second valve 16, the second pressure reducing valve 17 enters the second mass flow controller 18, and the flow of the gas is metered and controlled by the second mass flow controller 18. The flow rate of the gas entering the flow controller is adjusted to meet the requirements of the constant sampling of the sampling system. The flow measured by the first mass flow controller 13 and the flow measured by the second mass flow controller 18 are the flows entering the entire sampling system. According to the size of the main sampling nozzle 1, the flow rate of the gas entering the sampling nozzle can be obtained. When the flow rate into the sampling nozzle is equal to the flow rate in the pipe, that is, the constant velocity sampling is reached, and representative particulate matter in the pipeline can be collected. During on-line detection, the particles are collected by the first particle trap 1 1 after being detected by the line particle size analyzer 10, and can be taken offline while being detected online.

 When the sampling system is switched to off-line detection, the three-way ball valve 5 is switched to the 90 degree direction, the valve 15 is opened, and the valve 16 is closed. The natural gas enters the second particulate trap 14 through the three-way ball valve 5, where the particulate matter is trapped, and the natural gas is decompressed via the valve 15, the pressure reducing valve 17, and then enters the second mass flow controller 18, and then discharged to the safe area. . The second mass flow controller 18 meters and controls the sampled flow to meet the requirements for constant velocity sampling.

 The long-term online monitoring unit II includes an electrostatic dust concentration sensor 19 and a computer 20. The dust concentration sensor detects the dust in the pipeline, and converts the concentration of the particulate matter in the pipeline into a current signal and transmits it to the computer. The relationship between the dust concentration C in the pipeline, the change in the output current of the sensor ^/, the humidity change value H and the wind speed of the pipeline is as follows:

 c _ a(A7 + βΑΗ)

_ v ^m α, β, ηι are coefficients, which can realize long-term online monitoring of dust concentration.

 According to the above relationship, the dust current can be determined by the dust sensor output current change, humidity change and pipeline real-time wind speed.

 Further, the on-line detecting system further includes a heat tracing device, for example, wound around the pipeline by using a heating cable or the like, which can further prevent the droplets from being deposited when the dust is detected on-line, thereby improving the detection accuracy.

 Using the high-pressure on-line detecting device of this embodiment, the dust content in the inlet pipe of a cyclone separator was measured at a natural gas station in China. The experimental operating pressure was 5 MPa and the temperature was 20 °C. The experiment was conducted simultaneously with online detection and offline capture. In order to further verify the reliability of the online results, the online measurement results and the measurement results switched to the offline detection line (offline detection results are obtained by weighing the particles collected by the second particulate trap 14 to calculate the concentration, and The particle size distribution was analyzed by a Coulter particle size analyzer, and other particle size analyzers were also available, and the type of analytical instrument was not limited. As shown in Figure 4. The figure shows the cumulative curve of the particle size distribution, and the two curves are basically the same.

 Example 2

 Referring to Fig. 5, the present embodiment is for on-line detection of particulate matter in a high temperature gas pipeline, and the apparatus used includes an on-line detection section I and a long-term on-line monitoring section II. among them:

 (1) On-line detection unit; the on-line detection unit mainly comprises a main sampling subsystem (including a tubular main sampling nozzle 217 in the figure) connected in series through a pipeline, and a subsampling subsystem (including a gas flow distributor in the figure) 205 and subsampling nozzle 214), particle size on-line analyzer (online particle size spectrometer) 207 and first flow metering control subsystem (including first flow meter 209, first flow regulating valve 210 shown in the figure) ) ; specifically:

 The on-line detecting unit comprises a tubular main sampling nozzle 217, a first valve 201, a second valve 204 and a flow distributor 205 which are sequentially connected in series through a pipeline; the front end of the tubular main sampling nozzle 217 extends into the high-temperature gas pipeline to be detected. In 218, the tubular main sampling nozzle 217 extends into the junction of the high temperature gas pipe and can be sealed by a thread, or through a pipe joint and a flange seal, and the tubular main sampling nozzle 217 is downstream through the first valve 201 (the first valve 201 can be used for The opening or closing of the sampling nozzle 217 is controlled, and the second valve 204 is connected in series with the flow distributor 205 (a pressure sensor can be set, and the temperature sensor monitors the temperature and pressure in the flow distributor 205). The main circuit and the bypass two pipelines are separated from the flow distributor 205; the main circuit is connected in series with the secondary sampling nozzle 214, the third valve 206, the particulate particle size online analyzer 207, and the first particulate trapping subsystem. 208 and the first flow meter 209, the first flow regulating valve 210; the bypass sequentially connects the fourth valve 219 and the second flow meter 215, the second flow regulating valve 216 (the second flow meter 215, the second flow regulating valve 216) Forming a second flow rate control subsystem).

 The specific structure of the flow distributor 205 is the same as that of the flow distributor of the first embodiment.

 (2) an offline detecting unit; the offline detecting unit includes a fifth valve 211, a second particulate matter trapping subsystem 212, and a sixth valve 213 which are sequentially connected in series by a pipeline, and the upstream of the fifth valve 211 is connected to the first valve On the line between the 201 and the second valve 204, the downstream end of the sixth valve 213 is connected to the line between the fourth valve 219 and the second flow meter 215.

(3) preheating the purging unit; the preheating purging unit includes a heated purge gas storage tank 202, and is connected to the pipeline between the first valve 201 and the second valve 204 through the seventh valve 203 and the heat retention pipeline. For purging the gas storage tank 202 prior to testing The gas inside is introduced into the pipeline of the detecting unit for purging and preheating;

 (4) Long-term online monitoring unit; the long-term online monitoring unit includes a serially connected electrostatic dust concentration sensor 220 and a computer 221, and the front end pipeline of the electrostatic dust concentration sensor 221 extends into the high temperature gas pipe 218 to be detected for detecting the pipeline In the case of dust inside, the particulate matter concentration value in the pipeline is converted into a current signal and transmitted to the computer 221 to realize long-term online monitoring.

 When the device of the embodiment is used for detecting, the valves of the respective pipes are first opened, and the inert gas in the heated purge gas storage tank 202 is used to purge and preheat the respective pipes by using the preheating purge unit. Preventing the cooling of the sampled gas to agglomerate the particles in the gas affects the measurement result. The heating temperature of the purge gas is as close as possible to the temperature of the sampled gas in the main pipe, and the problem of preheating the pipes is as close as possible to the sampled gas in the main pipe. temperature. After warming up, close the seventh valve 203 and transfer to the formal inspection procedure.

 The dusty high temperature gas enters the main sampling system through the main sampling nozzle 217 for detection. Detection methods are divided into online detection and offline detection. The two detection methods can be realized by switching and opening and closing of each valve.

 In this embodiment, online detection and off-line sampling detection can be performed. The online detection implementation manner is: closing the fifth valve 21 1 and the sixth valve 213, opening the first valve 201, the second valve 204, the third valve 206, and the fourth valve 219 After the gas containing the particulate matter enters the subsampling subsystem, a part of the gas enters the main path, and is sampled by the secondary sampling nozzle 214 into the particle size online analyzer 207 for detecting the particle concentration and the particle diameter, and the detected high temperature gas. The particulate matter is collected by the first particulate trapping subsystem 208, and the further gas is vented after passing through the first flow meter 209 and the first flow regulating valve 210, and the first flow meter 209 and the first flow regulating valve 210 can enter the particulate matter. The gas flow rate of the on-line analyzer 207 is metered and controlled to meet the flow rate requirement of the particle size online analyzer 207 (the flow rate is constant at this time). The excess gas entering the flow distributor 205 enters the bypass, enters the second flow meter 215 and the second flow regulating valve 216 through the fourth valve 219, and is vented, and the flow of the gas passes through the second flow meter 215 and the second flow regulating valve 216. To measure and control. The sum of the main path gas flow and the bypass flow is the flow into the entire sampling system. According to the size of the tubular main sampling nozzle 217, the flow rate of the gas entering the sampling nozzle can be obtained. When the flow rate into the tubular main sampling nozzle is equal to the flow rate in the high temperature flue gas duct, the constant velocity sampling is achieved, and representative particulate matter in the pipeline can be collected.

 During on-line detection, the particulate matter is collected by the particulate matter online analyzer 207 and collected by the first particulate trapping subsystem 208, and offline sampling can also be performed offline. The particles collected offline can be analyzed. For example, the particle concentration can be calculated, the scanning electron microscope image can be taken, or the particle size and particle size can be analyzed by other particle size analyzers. The results can be compared with the online test results. Guarantee the accuracy of the results.

 When the sampling system is switched to off-line detection, the second valve 204, the fourth valve 219 are closed, and the fifth valve 21 1 and the sixth valve 213 are opened. The high temperature gas is sampled by the tubular main sampling nozzle 217 and then enters the second particulate matter trapping subsystem 212 via the fifth valve 21 1 , where the particulate matter is trapped, and further the gas sample enters the second flow meter 215 and the second through the sixth valve 213 . The second flow regulating valve 216 is then discharged to a safe area. The second flow meter 215 and the second flow regulating valve 216 meter and control the sampled flow to meet the requirements for constant sampling.

The long-term online monitoring unit II includes an electrostatic dust concentration sensor 220 and a computer 221. The dust concentration sensor detects the dust in the pipeline, and converts the concentration value of the particulate matter in the pipeline into a current signal and transmits it to the computer, which can realize long-term online monitoring. In this embodiment, the relationship between the dust concentration C in the pipeline, the sensor output current change value/, the humidity change value H, and the pipeline wind speed is as follows: _c _ a(AI + βΑΗ)

_ γ ^η

 α, β, ιη are calibration coefficients, and the calibration coefficients of different dusts are determined as described above. This embodiment can realize long-term online monitoring of dust concentration. Using the device of the present embodiment, a high-temperature flue gas filtering platform was built on a petrochemical company catalytic cracking device, and the prior art high-temperature aerosol catheter was applied to the Palas WELAS series optical on-line particle size spectrometer to detect high temperature smoke. The particle size and concentration of the flue gas after the gas filter were compared with the results of the isokinetic sampling of the off-line line, and the two were in good agreement. Optical on-line inspection instruments using high-temperature aerosol catheters can be safely and reliably measured under high temperature conditions, and the measurement results are accurate.

 Operating conditions: Operating pressure 0.21 MPa, off-line equal motion downstream of the filter (constant speed) Sampling temperature 550 °C. The measurement results of the downstream catalyst particle concentration measured by the on-line measuring instrument and the off-line method are shown in Table 2.

 Table 2 Comparison of offline online measurement results

 It can be seen from the above table that the results of on-line detection and off-line detection differed little, with a deviation of less than ±5%. Catalyst particle size distribution measured by off-line method and on-line method:

 The Coulter particle size analyzer (Multisizer 3) was used to analyze the catalyst particles obtained by off-line isokinetic sampling, and the multiple measurement results were averaged to obtain the measurement results of the catalyst particle size distribution. As shown in Figure 6. The filter exit particle size range is between 0.7μηι and 4μηι, with a median particle size of 1.2μηι. The high temperature flue gas filter is capable of removing catalyst particles of 5 μηη or more.

 The experimental results of the on-line measurement are shown in Figure 7: The on-line detection particle size distribution is between 0.4μηι and 3.5μηι, and the median particle size is 1.3μηι. It can be seen from Fig. 6 and Fig. 7 that the particle size distribution obtained by the on-line detection method is very different from that of the Coulter analyzer. The particle size distribution of the catalyst obtained by the Coulter analyzer is better than that of the on-line detection method. The accuracy of the distribution measurement, the difference between the two is also due to the difference in the measurement principle of the two instruments. Scanning electron microscopy (SEM) was used to observe the microstructure of the catalyst particles downstream of the filter by off-line method. It can also be seen from Fig. 8 that the overall particle size distribution of the particles is small, less than 5μηι, which is consistent with the results of online detection. And the results of offline detection, once again verified the reliability of online test results. The above is only the exemplary embodiments of the present invention and is not intended to limit the scope of the present invention. Equivalent changes and modifications made by those skilled in the art without departing from the spirit and scope of the invention are intended to be included within the scope of the invention.

Claims

Claim

1. A device suitable for on-line detection of particulate matter in a gas pipeline, the device comprising:

 The online detecting unit comprises: a main sampling nozzle and a flow distributor connected in series through a pipeline; a front end of the main sampling nozzle extends into a gas pipeline to be detected, and a gas inlet of the flow distributor is connected in series at the end; The flow distributor is provided with a cavity, a gas inlet is arranged on the front side of the cavity, two gas outlets are arranged on the rear side, and the main circuit and the bypass two pipes are separated, and the main circuit is connected in series with the secondary sampling nozzle. An on-line particle size spectrometer and a first mass flow controller, bypassing the second mass flow controller;

 After the main sampling nozzle is sampled from the gas pipeline, the gas sample is diffused into the cavity from the gas distributor of the flow distributor, and then discharged through the secondary sampling nozzle and the bypass outlet.

 2. Apparatus according to claim 1 wherein the gas conduit is a high pressure and/or high temperature gas conduit.

 3. The device according to claim 1, wherein the gas pipeline is a high temperature gas pipeline, and the apparatus for on-line detection of particulate matter in the gas pipeline further comprises:

 Preheating the purging unit; the preheating purging unit is arranged in parallel on the pipeline between the main sampling nozzle and the flow distributor, and includes a heating gas storage tank and a heat preservation pipeline for purging and preheating the pipeline of the entire system. .

 4. A device suitable for on-line detection of particulate matter in a high temperature gas pipeline, the device comprising:

 (1) an online detecting unit; the online detecting unit comprises a main sampling subsystem, a secondary sampling subsystem, a particle particle size online analyzer, and a first flow rate control subsystem connected in series through a pipeline; wherein:

 The main sampling subsystem includes a tubular main sampling nozzle, and the front end of the main sampling nozzle extends into a high temperature gas pipeline to be detected to introduce a high temperature gas sample containing particulate matter;

 The subsampling subsystem comprises a gas flow distributor and a secondary sampling nozzle; the flow distributor is provided with a cavity, a gas inlet is arranged on the front side of the cavity, and two gas outlets are arranged on the rear side to separate the main Road and bypass two pipelines; the main road is connected in series with the secondary sampling nozzle, the particle particle size online analyzer and the first flow rate control subsystem, and the bypass is connected to the second flow rate control subsystem;

 After the main sampling subsystem is sampled from the high temperature gas pipeline, the gas sample is diffused into the cavity from the gas distributor inlet, and is respectively taken out by the secondary sampling nozzle in the downstream direction and discharged from the bypass outlet;

 (2) preheating purging unit; the preheating purging unit is arranged in parallel on the pipeline between the main sampling subsystem and the subsampling subsystem, and includes a heating gas storage tank and an insulated pipeline for the pipeline of the entire system. Purge and preheat.

 The device according to any one of claims 1 to 4, wherein a diameter of a cavity of the flow distributor is larger than a gas inlet and a main outlet, and the bypass is a branch pipeline drawn from the main road; The gas inlet, the cavity and the main road outlet are disposed on the same center line; more preferably, the center line direction of the bypass outlet is perpendicular to the direction of the gas inlet center line.

6. The apparatus according to any one of claims 1 to 4, wherein the main sampling nozzle is telescoped to a position to be tested in the gas pipeline by a mechanical or hydraulic structure; preferably, the apparatus further comprises a deep pipeline along with the main sampling nozzle One or more of the following devices Kind:

 A sensor that measures pressure and/or temperature, and/or a probe that measures flow rate.

 The apparatus according to any one of claims 1 to 4, wherein the front end of the secondary sampling nozzle extends into the interior of the gas distributor, and the dust in the gas entering the flow distributor is sub-sampled, the end of which is Connected to the main gas outlet.

 The apparatus according to any one of claims 1 to 4, wherein a first particulate matter trap is disposed in series between the online particulate particle size analyzer of the main path and the first mass flow controller.

 9. The apparatus according to any one of claims 1 to 4, further comprising:

 An off-line detection unit; the off-line detection unit includes a second particulate trap, the second particulate trap front end is connected to the pipeline between the main sampling nozzle and the flow distributor, and the rear end is connected to the bypass outlet and the second mass On the pipeline between the flow controllers.

 10. The apparatus according to any one of claims 1 to 4, further comprising:

 Long-term online monitoring unit; The long-term online monitoring unit includes a dust concentration sensor and a computer. The dust concentration sensor is used to detect the dust in the pipeline, and converts the concentration of the particulate matter in the pipeline into a current signal and transmits it to a computer for long-term online monitoring.

 1 1. The device according to any one of claims 1 to 4, comprising:

 The online detecting unit comprises: a main sampling nozzle, a first valve, a three-way ball valve and a flow distributor connected in series through a pipeline; one end of the main sampling nozzle extends into a gas pipeline to be detected, and the main sampling The mouth extends into the connection of the gas pipe through the pipe joint and the flange seal, and the other end of the main sampling nozzle is connected to the gas distributor of the flow distributor through the first valve and the three-way ball valve; the flow distributor is provided with a cavity and a cavity One gas inlet is arranged on one side, and two gas outlets are arranged on the other side to separate the main pipeline and the two bypass pipelines; the main pipeline is connected in series with the secondary sampling nozzle, the on-line particle size spectrometer, and the first particulate matter trapping. , the first pressure reducing valve and the first mass flow controller; the bypass sequentially connects the second valve, the second pressure reducing valve and the second mass flow controller; the main sampling nozzle is sampled from the gas pipeline, and the gas is collected After being diffused into the cavity from the gas distributor of the flow distributor, the sample is discharged through the secondary sampling nozzle and the bypass outlet respectively;

 An off-line detecting unit; the offline detecting unit comprises a second particulate trap and a third valve connected in series through a pipeline, the front end of the second particulate trap is connected to the three-way ball valve, and the pipeline at the end of the third valve is connected On the line between the second valve and the second pressure reducing valve;

 Long-term online monitoring unit; the long-term online monitoring unit includes a serial dust concentration sensor and a computer, and the front end of the dust concentration sensor extends into the gas pipeline to be detected for detecting dust in the pipeline, and the concentration of particulate matter in the pipeline The value is converted to a current signal that is transmitted to a computer for long-term online monitoring.

12. The apparatus according to claim 1, wherein said on-line particulate particle size spectrometer comprises an optical sensor comprising an aerosol detecting conduit, four glass windows being arranged around the aerosol detecting conduit, Two achromatic lenses are arranged outside the two windows that are 90 degrees apart from each other, and the two achromatic lenses are respectively located on the incident optical path and the receiving optical path inside the optical sensor, and are respectively disposed outside the achromatic lens of the incident optical path and the receiving optical path. Have a small aperture, at incident light A condenser lens is disposed outside the aperture aperture of the path and the receiving optical path; the outside of the convergence lens of the incident optical path is a light source, and the outside of the convergence lens of the receiving optical path is an optical receiver.

 13. A method for on-line detection of particulate matter in a gas pipeline, the method comprising the apparatus of any one of claims 1 to 12 for performing on-line detection of particulate matter in a gas pipeline, wherein

 The gas sample is collected from the gas pipeline by using the main sampling nozzle of the online detecting unit, and the gas sample is diffused into the cavity from the gas distributor of the flow distributor, and then enters the main road and the bypass respectively;

 The particle size and particle size of the sample taken in the secondary sampling nozzle in the main road are measured by the on-line particle size spectrometer, and the gas flow rate of the on-line particle size spectrometer is measured by the first mass flow controller. And control, using the second mass flow controller to meter and control the flow of excess gas entering the bypass to meet the requirements of the online particle size spectrometer's own flow rate and the constant sampling of the online detection unit.

 14. The method according to claim 13, wherein the method of claim 12 is used for on-line detection of particulate matter in a gas conduit, wherein an incident optical path and a receiving optical path of the optical sensor of the online particulate particle size spectrometer The central position of the aerosol detecting catheter through which the small aperture diaphragm gas passes defines a virtual optical measuring body, and the method for performing on-line detection of the particulate matter in the gas pipeline further includes the following process of adjusting the optical path to correct the imaging position: According to the temperature and pressure of the measured working condition, the size of the optical measuring body is kept the same as that under normal temperature and normal pressure by adjusting the position of the small aperture stop;

Specifically, the distance adjusted by the aperture stop is determined as follows: Calculating the measured temperature, the refractive index of the gas under pressure, calculating the corrected free space according to the optical geometric relationship between the incident optical path and the receiving optical path, and the law of gas refraction Image distance, then calculate the object distance _U1 of the corrected pupil distance lens according to the focal length and image distance of the lens and the free-space optical imaging principle, and according to the initial object distance M of the aperture before the correction. It is finally determined that the aperture pupil needs to move distance = U factory U ₀ , the positive value indicates that it is far from the lens direction, and the negative value is close to the lens direction.

 15. A method according to claim 13 which utilizes the apparatus of claim 4 or 11 for on-line detection of particulate matter in a high temperature gas conduit, comprising the steps of:

 The preheating purge unit is used to introduce the heating gas into the detection unit line for purging and preheating, and then the preheating purge unit is turned off;

 The gas sample is collected from the high temperature gas pipeline by using the tubular main sampling nozzle of the online detecting unit, and the gas sample is diffused into the cavity from the gas distributor inlet, and then enters the main road and the bypass respectively;

 The particle size distribution analyzer is used to measure the concentration and particle size of the particles in the sample taken in the secondary sampling nozzle in the main path, and the gas flow rate of the on-line analyzer entering the particle particle size is performed by the first flow rate control subsystem. Metering and Control, using the second flow metering control subsystem to meter and control the flow of excess gas entering the bypass to meet the requirements of the particle size online analyzer's own flow rate and the on-line sampling unit's constant velocity sampling requirements.

 16. The method according to claim 13 or 14 or 15, wherein

The sum of the measured gas flow rate of the first mass flow controller and the gas flow rate measured by the second mass flow controller is the gas flow rate entering the entire in-line detecting unit, and the flow rate of the gas entering the main sampling nozzle is obtained according to the size of the main sampling nozzle; When entering the main When the flow rate at the sampling nozzle is equal to the flow velocity in the pipeline, the constant velocity sampling is achieved, and representative particulate matter in the pipeline can be collected.

17. The method according to claim 13 or 14 or 15, wherein the device further comprises a long-term online monitoring unit, the long-term online monitoring unit comprises a dust concentration sensor and a computer, and the dust concentration sensor is used for detecting dust in the pipeline. The method further comprises: converting the dust concentration C in the pipeline by using a long-term online monitoring unit to analyze and compare the detection result of the online detecting unit; among them,

 Calculate the dust concentration in the pipeline according to the following formula:

 c _ a(AI + βΑΗ)

_ γ ^η

 Where: C: the concentration of dust in the pipeline;

 ΔΙ-. sensor output current change value;

 ΛΗ-. Humidity change value;

 V: pipe wind speed;

 α, β, m are the calibration coefficients of the dust concentration sensor for specific dust; for example, the calibration coefficient α of 800 mesh talcum powder is 1000, which is 10.32, w is 2.18; the calibration coefficient α of fly ash is 400, which is 8.04, w is 1.88 ; The calibration coefficient of dust in natural gas pipelines, α is 400, and β is 'w is 2.18.