CN102967541B - Device and method suitable for on-line detection of particulate matters in high-temperature gas pipeline - Google Patents

Abstract

The invention provides a device and a method suitable for on-line detection of particulate matters in a high-temperature gas pipeline. The device comprises an on-line detection unit and a preheating sweeping unit, wherein the on-line detection unit comprises a main sampling subsystem, a secondary sampling subsystem, a particle matter grain size on-line analyzer and a first flow measurement control subsystem, which are connected in series; the secondary sampling subsystem comprises a gas flow distributor and a secondary sampling nozzle; the gas flow distributor is provided with a cavity and two gas outlets and is divided into a main path and a side path; the main path is connected with the secondary sampling nozzle, the particle matter grain size on-line analyzer and the first flow measurement control subsystem sequentially in series, and the side path is connected with a second flow measurement control subsystem in series; and the preheating sweeping unit is connected onto the pipeline between the main sampling subsystem and the secondary sampling subsystem in parallel and used for sweeping and preheating the pipeline of the whole system. The device further can comprise an off-line detection unit and a long-term on-line monitoring unit. According to the device, the long-term on-line detection of the particulate matters in the high-temperature gas pipeline can be realized.

Description

Device and method suitable for on-line detection of particulate matter in high-temperature gas pipelines

technical field

The invention relates to a collection and analysis technology for particulate matter in pipelines, in particular to a device and method suitable for on-line detection of particulate matter in high-temperature gas pipelines.

Background technique

High-temperature ceramic filter is a commonly used filter 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 will increase rapidly and seriously endanger the downstream. The normal operation of the equipment, for example, causes the wear of the blades of the flue gas turbine, etc., but currently there is a lack of real-time monitoring technology for the concentration of particulate matter at the filter outlet. Therefore, it is of great significance to measure the particulate matter at the inlet and outlet of high-temperature filtration and separation equipment to evaluate its performance and monitor the change of particulate matter concentration in the pipeline in real time to protect important downstream equipment.

At present, the following offline detection and online detection are usually used for the measurement of particulate matter in high-temperature gas pipelines. Off-line detection refers to collecting the dust in the gas pipeline through a high-precision filter cartridge or filter membrane, and calculating the particle concentration in the pipeline after weighing it, and then measuring the particle size of the collected particles with the help of other particle size analyzers. This off-line detection method can objectively measure the characteristics of particulate matter 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 the optical principle and can only detect under normal temperature and pressure. If the detection equipment is used in high-temperature conditions, it needs to cool down the high-temperature gas and then pass the instrument for detection. The reduction of temperature will make some Some gases will precipitate liquid droplets, causing particles to agglomerate, affecting the measurement results, and the condensed droplets will also pollute the optical lens. At present, there are also a few instruments that can be directly used for direct measurement under high temperature conditions, but from the field use situation, the measurement results of the measuring instruments are not accurate when the concentration is too low or too high. And there is still a lack of long-term monitoring of particulate matter in this field, such as monitoring the concentration of particulate matter at the outlet of high-temperature filtration and separation equipment to evaluate the performance of separation and filtration equipment.

Contents of the invention

In view of the shortcomings of the above-mentioned existing particle detection technology in gas pipelines, the inventor of this case actively improved and innovated based on relevant scientific research, on-site experience and professional knowledge, in order to achieve a direct online detection and long-term monitoring of high-temperature gas pipelines. Apparatus and methods for particulate matter.

An object of the present invention is to provide a device suitable for on-line detection and long-term monitoring of particulate matter in high-temperature gas pipelines. The device has low maintenance cost and high reliability, can realize the measurement of the characteristics of particulate matter in pipelines, and can further enable long-term online monitoring.

Another object of the present invention is to provide a method for on-line detection of particulates in high-temperature gas pipelines by using the device, which can realize online measurement of the characteristics of particulates in pipelines without cooling the high-temperature gas, and can further realize long-term online monitoring.

In order to achieve the above purpose, on the one hand, the present invention proposes a device suitable for on-line detection of particulate matter in high-temperature gas pipelines, which includes:

(1) On-line detection unit; the on-line detection unit includes a main sampling subsystem, a secondary sampling subsystem, an on-line particle size analyzer and a first flow metering control subsystem connected in series through pipelines; wherein:

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

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

After the main sampling subsystem samples from the high-temperature gas pipeline, the sampled gas is diffused into the chamber from the gas inlet of the flow distributor, and is collected by the secondary sampling nozzle in the downstream direction and discharged from the bypass outlet;

(2) Preheating and purging unit; the preheating and purging unit is installed in parallel on the pipeline between the main sampling subsystem and the secondary sampling subsystem, including the heating gas storage tank and the insulation pipeline, which is used to clean the pipeline of the whole system Purge and warm up.

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

In the device of the present invention suitable for on-line detection of particulates in high-temperature gas pipelines, the structural design of the flow distributor can make the air flow entering the cavity form a turbulent flow inside the cavity, and then the particulates in the cavity can be mixed evenly. To meet the secondary sampling nozzle can take a representative sample. Moreover, in the present invention, the preheating and purging unit is used to purge and preheat the pipelines of the whole system in advance, which can effectively prevent the particles in the gas from agglomerating after sampling and affecting the measurement results due to the cooling of the gas after sampling. According to a specific embodiment of the present invention, the temperature of the heating gas in the preheating purge unit is as close as possible to the temperature of the sampled gas in the main pipeline, and the detection pipeline is heated to the same temperature as the gas in the high-temperature gas pipeline to be detected. .

According to a specific embodiment of the present invention, in the device of the present invention suitable for on-line detection of particulate matter in high-temperature gas pipelines, the cavity diameter of the flow distributor is larger than the gas inlet and the outlet of the main road, and the bypass is drawn from the main road The branch pipeline; preferably, the gas inlet, the cavity and the outlet of the main road are arranged on the same centerline; more preferably, the direction of the centerline of the bypass outlet is perpendicular to the direction of the centerline of the gas inlet.

In the present invention, the structural size of the flow distributor only needs to achieve the purpose of making the air flow in the cavity of the flow distributor form a turbulent flow and mix uniformly inside the cavity. According to a preferred solution 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 (along the direction of the sampling air flow) to the diameter of the cavity is 0.5 to 3:1 , can be properly adjusted according to the gas flow rate.

According to a specific embodiment of the present invention, in the device suitable for on-line detection of particulate matter in high-temperature gas pipelines of the present invention, the tubular main sampling nozzle of the main sampling subsystem expands and contracts to the high-temperature gas pipeline to be detected through a mechanical or hydraulic structure. Position; Preferably, the main sampling subsystem also includes one or more of the following devices that extend into the high-temperature gas pipeline to be detected along with the tubular main sampling nozzle:

Sensors capable of measuring pressure and/or temperature, and/or probes capable of measuring flow rate.

According to a specific embodiment of the present invention, in the device suitable for on-line detection of particulate matter in high-temperature gas pipelines of the present invention, a second flowmeter is connected in series between the on-line particle size analyzer of the on-line detection unit and the first flow metering control subsystem. A particle capture subsystem. In this way, the particulate matter is collected by the first particulate matter collection subsystem, and the particulate matter can also be collected and detected offline during the online detection, which can be mutually verified with the result of the online detection.

According to a specific embodiment of the present invention, the device suitable for on-line detection of particulate matter in high-temperature gas pipelines of the present invention may further include:

(3) Off-line detection unit; the off-line detection unit includes a second particle capture subsystem, one end of the second particle capture subsystem is connected to the pipeline between the main sampling subsystem and the secondary sampling subsystem, and the other end is connected to On the pipeline between the bypass outlet of the flow distributor and the second flow metering control subsystem. The setting of the offline detection unit is mainly used to compare its detection results with the online detection results to verify the reliability.

According to a specific embodiment of the present invention, the device suitable for on-line detection of particulate matter in high-temperature gas pipelines of the present invention may further include:

(4) 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 situation in the high-temperature gas pipeline to be detected, and converts the particle concentration value in the pipeline into a current signal and transmits it to the Computer for long-term online monitoring. The long-term online monitoring unit and the online detection unit are arranged in parallel.

According to the specific embodiment of the device of the present invention, the device suitable for on-line detection of particulates in high-temperature gas pipelines of the present invention may also include: valves for controlling the switches of each pipeline, temperature sensors, pressure sensors, etc. for monitoring.

On the other hand, the present invention also provides a method for on-line detection of particulate matter in a high-temperature gas pipeline, the method is to use the device described in the present invention to perform on-line detection of particulate matter in a high-temperature gas pipeline, mainly including steps:

Use the preheating purge unit to introduce the heating gas into the pipeline of the detection unit for purging and preheating, and then close the preheating purge unit for operation;

Use the tubular main sampling nozzle of the online detection unit to collect gas samples from the high-temperature gas pipeline. The gas samples are diffused into the cavity from the gas inlet of the flow distributor, and then enter the main road and bypass respectively;

Use the particle size online analyzer to measure the concentration and particle size of the particles in the gas sample collected by the secondary sampling nozzle in the main path, and use the first flow metering control subsystem to measure the gas flow entering the particle size online analyzer Metering and control, using the second flow metering control subsystem to measure and control the flow of excess gas entering the bypass to meet the flow requirements of the particle size online analyzer itself and the isokinetic sampling requirements of the online detection unit.

According to a specific embodiment of the present invention, in the method for online detection of particulate matter in a high-temperature gas pipeline of the present invention, the sum of the gas flow measured by the first flow metering control subsystem and the gas flow measured by the second flow metering control subsystem is The gas flow rate of the online detection unit is obtained according to the size of the caliber of the tubular main sampling nozzle when the gas flow rate enters the tubular main sampling nozzle; when the flow velocity entering the tubular main sampling nozzle is equal to the flow velocity in the high-temperature gas pipeline to be detected, it reaches constant velocity Sampling can collect representative particles in the high-temperature gas pipeline to be detected.

According to a specific embodiment of the present invention, the device for on-line detection of particulate matter in a high-temperature gas pipeline of the present invention also includes a long-term on-line monitoring unit, the long-term on-line monitoring unit includes a dust concentration sensor and a computer, and the dust concentration sensor is used to detect the high-temperature gas pipeline to be detected Dust situation in the pipeline, the particle concentration value in the pipeline is converted into a current signal and transmitted to the computer to realize long-term online monitoring; the method also includes: using the long-term online monitoring unit to calculate the dust concentration C in the pipeline, and the detection result of the online detection unit Analyze and compare; among them,

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

$\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&Delta;I</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&beta;\&Delta;H</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; V</span>}}^{\mathrm{<span\; class="notranslate">\; m</span>}}}$

In the formula, C: dust concentration in the pipeline;

ΔI: sensor output current change value;

ΔH: humidity change value;

V: pipe wind speed;

α, β, m are the calibration coefficients of the dust concentration sensor for specific dust. 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 specific implementation, the influence of wind speed and humidity on the output signal of the electrostatic dust concentration sensor can be studied experimentally, and the calibration coefficient of the electrostatic dust concentration sensor for different dusts can be further determined. For example, according to the specific embodiment of the present invention, the determined calibration coefficients of the electrostatic dust concentration sensor for different dusts are: the calibration coefficient α of 800 mesh talcum powder is 1000, β is 10.32, and m is 2.18; the calibration coefficient of fly ash The coefficient α is 400, β is 8.04, and m is 1.88; the calibration coefficient of dust in the natural gas pipeline is 400, β is 6.07, and m is 2.18.

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

The derivation and verification of above-mentioned model formula of the present invention are as follows:

1. The influence of wind speed on the output signal of the electrostatic sensor

Under the experimental conditions of an ambient temperature of 15°C and an ambient humidity of RH40%, 800 mesh talcum powder, fly ash and natural gas pipeline dust were used as pipeline transport media to study the influence of different pipeline wind speeds on the output value of the electrostatic dust concentration sensor. See Figure 1A, Figure 1B and Figure 1C for measurement results. Among them, Fig. 1A, Fig. 1B and Fig. 1C are the measurement results for talcum powder, fly ash and natural gas pipeline dust respectively. It can be seen from the figure that the change of wind speed has a significant impact on the measurement results, and the three different dust media show the same measurement law.

2. The influence of humidity on the output current of the electrostatic sensor

800-mesh talcum powder, fly ash, and natural gas pipeline dust were selected as measurement objects. Under the conditions of RH25%, RH44%, RH53%, and RH76%, respectively, the wind speed in the pipeline was kept at 9.5m/s, and different dust concentrations corresponded to The output value of the electrostatic sensor is shown in the figure below. See Figure 2A, Figure 2B and Figure 2C for the measurement results. Among them, Fig. 2A, Fig. 2B and Fig. 2C are the measurement results for talcum powder, fly ash and natural gas pipeline dust respectively. It can be seen from the figure that the humidity change has a significant impact on the measurement results, and the three different dust media show the same measurement law. As the ambient humidity increases, the dust charge decreases. From RH25% to RH53%, the dust charge decreases uniformly, but when the humidity exceeds a certain value, the dust charge is very weak.

Under the same concentration, the relationship between the wind speed and the output current value of the electrostatic dust sensor can be expressed as

ΔI=K ₁ V ^m (1)

Among them, ΔI is the net current output of the electrostatic sensor (that is, the difference between the output value I and the initial value), K ₁ is the coefficient, and V is the wind speed of the pipeline.

make

$\mathrm{<span\; class="notranslate">\; A</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&Delta;I</span>}}{{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; V</span>}}^{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

Then the ratio of lnA to lnV is the value of m when other experimental conditions remain unchanged.

$\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; ln</span>}\mathrm{<span\; class="notranslate">\; A</span>}}{\mathrm{<span\; class="notranslate">\; ln</span>}\mathrm{<span\; class="notranslate">\; V</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

The value of the coefficient _K1 should be determined according to the different factors such as the sensor amplifier circuit and dust charging capacity. Under different wind speeds, _K1 is iterated with a certain step size. The initial value of K1 is set to 0.001, and the step size is 0.001. R is the linear correlation number of the straight line formed by lnA and lnV. When R>0.95, it is considered that m The value is the slope of the line formed by lnP and lnV.

Because the current output of the sensor has a linear relationship with the dust concentration.

ΔI＝kC (4)

k is the slope of the dust concentration and current output curve, and C is the dust concentration. Putting Equation 4 into Equation 2 and introducing the coefficient α, we can get:

$\mathrm{<span\; class="notranslate">\; \&Delta;I</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; cv</span>}}^{\mathrm{<span\; class="notranslate">\; m</span>}}}{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

For the change of the current output of the electrostatic sensor caused by humidity, the coefficient β is introduced as:

ΔI _H = βΔH (7)

ΔI _H is the change of current output caused by humidity, and ΔH is the change of humidity.

Considering the influence of wind speed and humidity on the output value of the electrostatic sensor, the dust concentration C can be expressed as:

$\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&Delta;I</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&beta;\&Delta;H</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; V</span>}}^{\mathrm{<span\; class="notranslate">\; m</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; .</span>$

In addition, pipeline pressure and temperature have little effect on the results of the above empirical model formulas.

In order to verify the accuracy of the above-mentioned empirical model formula of the present invention, the present invention is carried out with 800 mesh talcum powder as the pipeline transport medium under the experimental conditions that the ambient temperature is 15°C, the ambient humidity is RH30%, and the pipeline wind speed is 6.3m/s. experimented. Use the empirical model to calculate the dust concentration corresponding to the dust sensor current output value and compare it with the experimental results (on-line detection results), as shown in Figure 3. The relative error analysis results are shown in Table 1. It can be seen from Table 1 that the relative error between the calculated value of the empirical model and the experimental result of measuring the concentration of 800 mesh talcum powder by the electrostatic method is less than ±5%.

Table 1 Relative error analysis results

In a specific embodiment of the present invention, the device suitable for on-line detection of particulate matter in high-temperature gas pipelines of the present invention includes:

(1) On-line detection unit; the on-line detection unit includes a tubular main sampling nozzle, a first valve, a second valve and a flow distributor connected in series through pipelines; the front end of the tubular main sampling nozzle extends into the high temperature to be detected In the gas pipeline, the joint where the tubular main sampling nozzle extends into the high-temperature gas pipeline is sealed by the pipe adapter and the flange, and the downstream of the tubular main sampling nozzle is connected in series with the gas inlet of the flow distributor through the first valve and the second valve; the flow distributor There is a cavity, a gas inlet is set on one side of the cavity, and two gas outlets are set on the other side to separate the main road and the bypass two pipelines; the main road is connected in series with the secondary sampling nozzle, the third valve, On-line particle size analyzer, the first particle collection subsystem and the first flow metering control subsystem; the bypass is connected in series with the fourth valve and the second flow metering control subsystem; the tubular main sampling nozzle samples from the high-temperature gas pipeline Afterwards, the collected gas samples are diffused into the cavity from the gas inlet of the flow distributor, and are collected by the secondary sampling nozzle in the downstream direction and discharged from the bypass;

(2) Off-line detection unit; the off-line detection unit includes the fifth valve, the second particle collection subsystem and the sixth valve connected in series through pipelines, and the upstream of the fifth valve is connected to the first valve and the second valve On the pipeline between, the downstream end of the sixth valve is connected to the pipeline between the fourth valve and the second flow metering control subsystem;

(3) Preheating and purging unit; the preheating and purging unit includes a heating gas storage tank, which is connected to the pipeline between the first valve and the second valve through the seventh valve and the insulation pipeline, for The gas in the hot gas storage tank is introduced into the pipeline of the detection unit for purging and preheating;

(4) Long-term on-line monitoring unit; this long-term on-line monitoring unit includes a dust concentration sensor and a computer connected in series. The particle concentration value in the instrument is converted into a current signal and transmitted to the computer to realize long-term online monitoring.

In this specific embodiment of the present invention, the online detection unit can periodically accurately measure the concentration and particle size of the particulate matter in the high-temperature gas pipeline; the long-term online monitoring unit can monitor the concentration of particulate matter in the pipeline for a long time. The following takes the detection of particulate matter in the high-temperature flue gas pipeline as an example for specific instructions:

Open the valves of each pipeline first, and use the preheating purge unit to purge and preheat each pipeline with the heated purge gas (inert gas) to prevent the particles in the gas from being agglomerated due to the cooling of the sampled gas. According to the measurement results, the heating temperature of the purge gas should be the same as the temperature of the sampled gas in the main pipeline as much as possible, and the temperature of the sampled gas in the main pipeline should be as close as possible to the temperature of the sampled gas in the main pipeline after each pipeline is preheated. After preheating, close the preheating purge unit (close the seventh valve), and open the detection system.

The tubular main sampling nozzle can be stretched to different positions in the high-temperature flue gas pipeline through a mechanical or hydraulic structure. The form is not limited, and sensors for measuring pressure and temperature can also be inserted.

Dust-laden high-temperature flue gas enters the sampling system through the tubular main sampling nozzle for particle detection. There are two detection methods, namely (1) online detection; (2) offline detection. The two detection methods can be realized through the switching and opening and closing combination of each valve. The main purpose of offline testing is to verify the results of online testing to ensure the accuracy and reliability of testing, and offline sampling can collect dust for further analysis, such as analysis of composition and particle size distribution.

When performing on-line detection, open the first valve, the second valve, the third valve and the fourth valve, and the fifth, sixth and seventh valves are in the closed state. Dust-laden high-temperature flue gas enters the flow distributor through the first valve and the second valve, and a part of the gas (the specific amount of this part of gas can be determined according to the requirements of the particle size online analyzer. Generally, the particle size online analyzer needs to be in a stable Measure under the flow rate, so the secondary sampling subsystem is set in the present invention to carry out secondary sampling) enter the particle size online analyzer through the secondary sampling nozzle to detect the particle concentration and particle size, and the particles in the high-temperature flue gas after detection It is collected by the first particle collection subsystem, and the gas is further measured and controlled by the first flow metering control subsystem to measure and control the flow of high-temperature flue gas entering the particle size online analyzer to meet the requirements of the particle size online analyzer itself. Flow requirements (the flow is constant at this time). The excess gas entering the flow distributor enters the second flow metering control subsystem through the fourth valve and is discharged to a safe area, and the gas flow is metered and controlled by the second flow metering control subsystem. By adjusting the gas flow rate entering the flow controller to meet the requirements of constant-speed sampling in the entire sampling system, the sum of the flow rate measured by the first flow metering control subsystem and the flow rate measured by the second flow metering control subsystem is the flow rate entering the entire sampling system Flow rate, according to the diameter of the tubular main sampling nozzle, the flow rate of the gas entering the sampling nozzle can be obtained. When the flow velocity entering the tubular main sampling nozzle is equal to the flow velocity in the high-temperature flue gas pipeline, constant-velocity sampling is achieved, and representative particles in the pipeline can be collected.

When the sampling system is switched to offline detection, the second valve and the fourth valve are closed, and the fifth valve and the sixth valve are opened. After being sampled by the tubular main sampling nozzle, the high-temperature flue gas enters the second particle capture subsystem through the fifth valve, where the particles are captured, and further gas samples enter the second flow metering control subsystem through the sixth valve, and then discharged to safe area. The second flow measurement control subsystem measures and controls the sampling flow to meet the requirements of 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, converts the particle concentration value in the pipeline into a current signal and transmits it to the computer, which can realize long-term online monitoring.

In addition, with the device of the present invention, offline collection and detection of particulate matter can also be performed while online detection is performed, and the results of online detection can be mutually verified.

According to a specific embodiment of the present invention, the forms of the valves are not limited, and may be of any type that realizes the functions described above. The particle size on-line analyzer is an instrument using optical principles. For example, Palas company WELAS series optical on-line particle size spectrometer can be used, and the high temperature resistant aerosol conduit in the prior art can be used to achieve a temperature of 650 ° C and a pressure of 5 MPa. safe and reliable operation. The particulate matter trapping subsystem can also use any particulate matter trap in the prior art that can realize the function of collecting particulate matter.

According to a specific embodiment of the present invention, the first flow metering control subsystem and the second flow metering control subsystem may be an instrument integrating mass flow measurement and flow control, or a valve with flow control function and Combination device for meter combination with flow measurement function.

According to a specific embodiment of the present invention, the dust concentration sensor of the long-term online monitoring unit is an electrostatic dust concentration sensor in the prior art, and the computer can be replaced by any instrument with real-time display function.

In addition, according to a specific embodiment of the present invention, in the on-line detection device for particulate matter in high-temperature pipelines of the present invention, the gas flow distributor may be further provided with temperature and pressure sensors to monitor the temperature and pressure in the gas flow distributor.

In summary, the present invention provides a device and method suitable for on-line detection of particulates in high-temperature gas pipelines. The device has simple structure, low maintenance cost, and high reliability, and can be directly used for the determination of particulates in high-temperature gas pipelines without cooling , and further can realize long-term online monitoring. It has been verified by practice that the technology of the present invention is used to detect particulate matter in high-temperature flue gas pipelines, and it is suitable for large changes in particle concentration, ranging from several milligrams to hundreds of milligrams, and the particle size ranges from 0.3 microns to 100 microns, all of which can be accurately measured. And offline sampling is carried out while on-line detection, and the results of the two can be consistent. During long-term on-line monitoring, it can still be measured when the pipeline concentration is as low as 1mg/m ³ or less.

Compared with the prior art, the present invention has the following characteristics and advantages: 1. It can be directly used for the determination of particulate matter in high-temperature gas pipelines without cooling down, and the maximum working temperature can reach 650°C, which avoids the precipitation of some components caused by cooling down the high-temperature gas Affect particle measurement; 2. Integrate online detection and offline detection in one, the two detection methods can be switched, and the two detection methods can be mutually verified; 3. Offline collection of particulate matter can also be carried out while online detection, which can be used with online The detection results are mutually verified; 4. Long-term online monitoring of dust concentration can be realized, and the maintenance cost is low.

Description of drawings

Figure 1A, Figure 1B and Figure 1C are the results of studying the influence of different wind speeds on the dust concentration measured by electrostatic method. Among them, Fig. 1A, Fig. 1B and Fig. 1C are the measurement results for talcum powder, fly ash and natural gas pipeline dust respectively.

Fig. 2A, Fig. 2B and Fig. 2C are for studying the effect of environmental humidity on the output current of the electrostatic sensor. Among them, Fig. 2A, Fig. 2B and Fig. 2C are the measurement results for talcum powder, fly ash and natural gas pipeline dust respectively.

Fig. 3 is a comparison diagram of experimental results and calculation results verifying the accuracy of the formula for calculating the dust concentration C in the pipeline in the present invention.

Fig. 4 is a schematic structural diagram of the on-line detection device for particulate matter in a high-temperature gas pipeline according to the present invention. Among them, 1-first valve; 2-purge gas storage tank; 3-seventh valve; 4-second valve; 5-flow distributor; 6-third valve; 7-on-line particle size analyzer; 8 - the first particle capture subsystem; 9 - the first flow meter; 10 - the first flow regulating valve; 11 - the fifth valve; 12 - the second particle capture subsystem; 13 - the sixth valve; 14 - secondary Sampling nozzle; 15-second flow meter; 16-second flow regulating valve; 17-main sampling nozzle; 18-high temperature gas pipeline; 19-fourth valve; 20-electrostatic dust concentration sensor; 21-computer.

Fig. 5 is a schematic structural view of the flow distributor 5 in the device of the present invention. Among them, 501-cavity; 502-gas inlet; 503-main road outlet; 504-bypass outlet.

Fig. 6 is a particle size distribution diagram of a catalyst measured by a Coulter analyzer in a specific embodiment of the present invention.

Fig. 7 is a particle size distribution diagram of the catalyst measured by an online analyzer in a specific embodiment of the present invention.

Fig. 8 is a photograph of the microstructure of the catalyst downstream of the filter in a specific embodiment of the present invention.

Detailed ways

In order to have a clearer understanding of the technical characteristics, purposes and effects of the present invention, the characteristics and technical effects of the assay method of the present invention will be further described in detail with reference to the accompanying drawings, but the present invention is not limited thereby.

Example 1

Please refer to FIG. 4 , the on-line detection device for particulate matter in a high-temperature gas pipeline according to the present invention includes an on-line detection part I and a long-term on-line monitoring part II. in:

(1) On-line detection unit; the on-line detection unit mainly includes the main sampling subsystem (including the tubular main sampling nozzle 17 in the figure) connected in series through pipelines, the secondary sampling subsystem (including the gas flow distributor in the figure) 5 and secondary sampling nozzle 14), particle size online analyzer 7 and the first flow measurement control subsystem (comprising the first flow meter 9 shown in the figure, the first flow regulating valve 10); specifically:

The online detection unit includes a tubular main sampling nozzle 17, a first valve 1, a second valve 2, and a flow distributor 5 connected in series through pipelines; the front end of the tubular main sampling nozzle 17 extends into the high-temperature gas pipeline to be detected 18, the tubular main sampling nozzle 17 stretches into the joint of the high-temperature gas pipeline and can be sealed by thread, or through the pipeline connection and flange sealing (any feasible sealing method in the prior art can be used, for example, one end of the pipeline connection is fixed Connected to the outside of the sampling port on the measured high-temperature gas pipeline, the main sampling nozzle extends into the high-temperature gas pipeline through the pipeline adapter; the flange is connected to the other end of the pipeline adapter, and the flange sleeve It is arranged on the outside of the sleeve, the sleeve is inserted into the pipe connection, the main sampling nozzle and the return pipeline are passed through and fixed on the sleeve, and the flange can be slidably fixed Sleeved on the outer wall of the casing), the downstream of the tubular main sampling nozzle 17 passes through the first valve 1 (the first valve 1 can be used to control the opening or closing of the sampling nozzle 17), and the second valve 4 is connected in series for flow distribution Device 5 (a pressure sensor and a temperature sensor can be set to monitor the temperature and pressure in the flow distributor 5). Two pipelines, the main road and the bypass, are separated from the flow distributor 5; the main road is sequentially connected in series with the secondary sampling nozzle 14, the third valve 6, the particle size online analyzer 7, and the first particle collection subsystem 8 and the first flow meter 9, the first flow regulating valve 10; the bypass is connected in series with the fourth valve 19 and the second flow meter 15, the second flow regulating valve 16 (the second flow meter 15, the second flow regulating valve 16 Composition of the second flow metering control subsystem).

Please refer to Fig. 5 for the specific structure of the flow distributor 5, which is provided with a cavity 501, a gas inlet 502 is set on the front side of the cavity, and two gas outlets are set on the rear side (the main path outlet 503, the bypass outlet 504 ) and separate the main road and the bypass two pipelines; wherein, the diameter of the cavity 501 of the flow distributor is larger than the gas inlet 502 and the main road outlet 503, and the bypass is a branch pipeline drawn from the main road; The gas inlet 502 , the cavity 501 and the main road outlet 503 are arranged on the same centerline; the centerline direction of the bypass outlet 504 is perpendicular to the centerline direction of the main road outlet 503 . Utilizing the structural design of the flow distributor 5, the airflow entering the cavity can form a turbulent flow inside the cavity, so that the particles in the cavity can be mixed evenly, so that the secondary sampling nozzle can collect representative samples.

(2) Off-line detection unit; the off-line detection unit includes a fifth valve 11, a second particle collection subsystem 12 and a sixth valve 13 connected in series through pipelines, and the upstream of the fifth valve 11 is connected to the first valve On the pipeline between 1 and the second valve 4, the downstream end of the sixth valve 13 is connected to the pipeline between the fourth valve 19 and the second flowmeter 15.

(3) Preheating and purging unit; the preheating and purging unit includes a heated purge gas storage tank 2, which is connected to the pipeline between the first valve 1 and the second valve 4 through the seventh valve 3 and the insulation pipeline , which is used to introduce the gas in the purge gas storage tank 2 into the pipeline of the detection unit for purging and preheating before detection;

(4) Long-term on-line monitoring unit; this long-term on-line monitoring unit includes the electrostatic dust concentration sensor 20 and computer 21 of serial connection, and the front end pipeline of electrostatic dust concentration sensor 21 stretches in the high-temperature gas pipeline 18 that needs to detect and is used for detecting pipeline The dust situation in the pipeline, and the concentration value of the particulate matter in the pipeline is converted into a current signal and transmitted to the computer 21 to realize long-term online monitoring.

When utilizing the device of the present invention to detect, first open the valves of each pipeline, and use the preheating purge unit to purge and preheat each pipeline with the inert gas in the purge gas storage tank 2 after heating, so as to prevent The cooling of the gas after sampling makes the particles in the gas agglomerate and affects the measurement results. The heating temperature of the purge gas should be the same as the temperature of the sampled gas in the main pipeline as much as possible. temperature. After preheating, close the seventh valve 3, and transfer to the formal testing procedure.

Dust-laden high-temperature gas enters the main sampling system through the main sampling nozzle 17 for detection. The detection methods are divided into online detection and offline detection. The two detection methods can be realized through the switching and opening and closing combination of each valve.

The present invention can carry out on-line detection and off-line sampling detection. The implementation mode of on-line detection is: close the fifth valve 11 and the sixth valve 13, open the first valve 1, the second valve 4, the third valve 6 and the fourth valve 19, including After the particulate gas enters the secondary sampling subsystem, a part of the gas enters the main path, and is sampled through the secondary sampling nozzle 14 and enters the particle size online analyzer 7 to detect the particle concentration and particle size. Particulate matter is collected by the first particulate matter collection subsystem 8, and further gas is emptied after passing through the first flow meter 9 and the first flow regulating valve 10. The first flow meter 9 and the first flow regulating valve 10 can measure the particle size of the incoming particle The gas flow rate of the analyzer 7 is measured and controlled to meet the requirements of the particle size online analyzer 7's own flow rate (at this time, the flow rate is constant). The excess gas entering the flow distributor 5 enters the bypass, enters the second flow meter 15 and the second flow regulating valve 16 through the fourth valve 19 and then vents, and the flow of gas passes through the second flow meter 15 and the second flow regulating valve 16 to measure and control. The sum of the main gas flow rate and the bypass flow rate is the flow rate entering the entire sampling system. According to the size of the caliber of the tubular main sampling nozzle 17, the gas flow rate when entering the sampling nozzle can be obtained. When the flow rate entering the tubular main sampling nozzle is equal to the flow rate in the high-temperature flue gas pipeline, constant-velocity sampling is achieved, and representative particles in the pipeline can be collected.

During online detection, the particles are detected by the particle size online analyzer 7 and then collected by the first particle collection subsystem 8. Offline sampling can also be performed during the online detection. The particles collected off-line can be used for other analysis, such as calculating the particle concentration, taking scanning electron microscope pictures, and analyzing the composition and particle size of the particles with the help of other particle size analyzers. The results can be compared with the online detection results, and further Guarantee the accuracy of the results.

When the sampling system is switched to offline detection, the second valve 4 and the fourth valve 19 are closed, and the fifth valve 11 and the sixth valve 13 are opened. The high-temperature gas is sampled through the tubular main sampling nozzle 17 and then enters the second particle collection subsystem 12 through the fifth valve 11, where the particles are captured, and further gas samples enter the second flow meter 15 and the second flow meter through the sixth valve 13. flow regulating valve 16, then vent to a safe area. The second flow meter 15 and the second flow regulating valve 16 measure and control the sampling flow to meet the requirement of isokinetic 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, converts the particle concentration value in the pipeline into a current signal and transmits it to the computer, which can realize long-term online monitoring.

The long-term online monitoring unit II includes an electrostatic dust concentration sensor 20 and a computer 21 . The dust concentration sensor detects the dust in the pipeline, converts the particle concentration value in the pipeline into a current signal and transmits it to the computer, which can realize long-term online monitoring. In the present invention, the relationship between the dust concentration C in the pipeline, the sensor output current change value ΔI, the humidity change value ΔH and the pipeline wind speed V is obtained based on a large number of experiments. As shown in the following formula:

$\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&Delta;I</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&beta;\&Delta;H</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; V</span>}}^{\mathrm{<span\; class="notranslate">\; m</span>}}}$

α, β, m are the calibration coefficients, and the calibration coefficients of different dusts can be determined by referring to the above. The invention can realize long-term on-line monitoring of dust concentration.

According to the above relationship, the real-time display of the dust concentration in the pipeline can be determined through the change of the output current of the dust sensor, the change of humidity and the real-time wind speed of the pipeline.

Using the device in this example, a high-temperature flue gas filtration platform was built on a catalytic cracking unit of a petrochemical company, and the high-temperature aerosol conduit of the prior art was applied to the WELAS series optical on-line particle size spectrometer of Palas Company to detect the high-temperature flue gas The particles and concentration of the flue gas after the gas filter were compared with the results of isokinetic sampling switched to offline pipelines, and the two were in good agreement. The optical on-line detection instrument using the high-temperature aerosol conduit can safely and reliably measure under high-temperature conditions, and the measurement results are accurate.

Test operating conditions: operating pressure 0.21MPa, off-line isokinetic (constant velocity) sampling temperature 550°C downstream of the filter. The downstream catalyst particle concentration measured by the online measuring instrument and the measurement results of the offline method are shown in Table 2.

Table 2 Comparison of offline and online measurement results

It can be seen from the above table that the difference between the results of online detection and offline detection is very small, and the deviation is less than ±5%.

Catalyst particle size distribution measured by off-line method and on-line method:

The catalyst particles obtained by off-line isokinetic sampling were analyzed using a Coulter particle size analyzer (Multisizer3), and the measurement results of the catalyst particle size distribution were obtained by taking the average value of the multiple measurement results. As shown in Figure 6. The filter outlet particle size ranges from 0.7 μm to 4 μm, with a median particle size of 1.2 μm. The high-temperature flue gas filter can remove catalyst particles larger than 5 μm.

See Figure 7 for the experimental results of online measurement: the online detection particle size distribution is between 0.4 μm and 3.5 μm, and the median particle size is 1.3 μm.

It can be seen from Figure 6 and Figure 7 that the difference between the particle size distribution obtained by the online detection method and the measurement result of the Coulter analyzer is very small. The accuracy of the distribution measurement, the difference between the two is also caused by the different measurement principles of the two instruments. Using a scanning electron microscope (SEM) to observe the microstructure of the catalyst particles downstream of the filter obtained by the off-line method isokinetic sampling, it can also be seen from Figure 8 that the overall particle size distribution of the particles is small, all less than 5 μm, which is in line with the online detection results And the results of offline detection, once again verified the reliability of the online detection results.

The above descriptions are only illustrative specific implementations of the present invention, and are not intended to limit the scope of the present invention. Any equivalent changes and modifications made by those skilled in the art without departing from the concept and principle of the present invention shall fall within the protection scope of the present invention.

Claims (10)

1. be applicable to the online device detecting of hot-gas channel endoparticle thing, this device comprises:

(1) online detection unit; This online detection unit comprises main sampled subsystem, double sampling subsystem, particle particle diameter in-line analyzer and the first flow measure control subsystem being connected in series successively by pipeline; Wherein:

Described main sampled subsystem comprises the main sampling mouth of tubulose, and this main sampling mouth front end stretches in the hot-gas channel that needs to detect, to introduce the high-temperature gas sample that contains particle;

Described double sampling subsystem comprises gas flow divider and a double sampling mouth; Described flow distributor is provided with a cavity, and cavity front side arranges a gas feed, and rear side arranges two gas vents and separates main road and two pipelines of bypass; Main road is connected in series double sampling mouth, particle particle diameter in-line analyzer and first flow measure control subsystem successively, and bypass is connected in series the second flow measure control subsystem;

Main sampled subsystem is sampled in hot-gas channel, institute's gas production sample, is discharged by the double sampling mouth extraction of downstream direction and from bypass outlet respectively from flow distributor gas feed after diffusing into cavity;

(2) pre-thermal purging unit; This pre-thermal purging unit parallel connection is located on the pipeline between main sampled subsystem and double sampling subsystem, comprises heated air storage tank and hot insulated line, for the pipeline of whole system is purged and preheating.

2. device according to claim 1, wherein, the cavity diameter of described flow distributor is greater than gas feed and main road outlet, the branch line of described bypass for drawing from main road; Gas feed, cavity and main road outlet are arranged on same center line; Centerline direction and the gas feed centerline direction of bypass outlet are vertical setting.

3. device according to claim 1, wherein, the main sampling mouth of the tubulose of main sampled subsystem is retractable to the position to be measured in the hot-gas channel that needs to detect by machinery or hydraulic structure; Described main sampled subsystem also comprises with the main sampling mouth of tubulose and stretches into one or more in the following equipment in the hot-gas channel need detecting:

The sensor of energy gaging pressure and/or temperature, and/or there is the probe of measuring flow rate function;

Between the particle particle diameter in-line analyzer of online detection unit and first flow measure control subsystem, be also serially connected with the first particle collection subsystem.

4. device according to claim 1, this device also comprises:

(3) offline inspection unit; This offline inspection unit comprises the second particle collection subsystem, this the second particle collection subsystem one end is connected on the pipeline between main sampled subsystem and double sampling subsystem, and the other end is connected in the bypass outlet and the pipeline between the second flow measure control subsystem of described flow distributor.

5. according to the device described in claim 1 or 4, this device also comprises:

(4) long-term on-line monitoring unit; This long-term on-line monitoring unit comprises sensor of dust concentration and computing machine, dust situation in the hot-gas channel that sensor of dust concentration detects for detection of need, by the particle concentration value in pipeline change into current signal transfer to computing machine to realize long-term on-line monitoring.

6. device according to claim 1, this device comprises for controlling the valve of each pipeline switch.

7. device according to claim 1, this device comprises:

(1) online detection unit; This online detection unit comprises the main sampling mouth of the tubulose being connected in series successively by pipeline, the first valve, the second valve and flow distributor; The front end of the main sampling mouth of described tubulose stretches in the hot-gas channel that needs to detect, the main sampling mouth of tubulose stretches into the junction of hot-gas channel and takes over and flange seal by pipeline, the main sampling mouth of tubulose downstream the first valve, the second valve serial connection flow distributor gas feed; Described flow distributor is provided with a cavity, and cavity one side arranges a gas feed, and opposite side arranges two gas vents and separates main road and two pipelines of bypass; Main road is connected in series double sampling mouth, the 3rd valve, particle particle diameter in-line analyzer, the first particle collection subsystem and first flow measure control subsystem successively; Bypass is connected in series the 4th valve and the second flow measure control subsystem successively; The main sampling mouth of tubulose is sampled in hot-gas channel, institute's gas production sample from flow distributor gas feed after diffusing into cavity, respectively by the double sampling mouth extraction of downstream direction and discharge from bypass;

(2) offline inspection unit; This offline inspection unit comprises the 5th valve, the second particle collection subsystem and the 6th valve being connected in series successively by pipeline, the upstream of the 5th valve is connected on the pipeline between the first valve and the second valve, and the downstream end of the 6th valve is connected on the pipeline between the 4th valve and the second flow measure control subsystem;

(3) pre-thermal purging unit; This pre-thermal purging unit comprises heated air storage tank, by the 7th valve, hot insulated line, is arranged on the pipeline between the first valve and the second valve, for the gas in hot gas storage tank being introduced to the pipeline of detecting unit before detection, purges and preheating;

(4) long-term on-line monitoring unit; This long-term on-line monitoring unit comprises sensor of dust concentration and the computing machine of serial connection, sensor of dust concentration front end pipeline stretches in the hot-gas channel need detecting for detection of the dust situation in pipeline, and by the particle concentration value in pipeline change into current signal transfer to computing machine to realize long-term on-line monitoring.

8. hot-gas channel endoparticle thing is carried out to the online method detecting, the method is to utilize the device described in claim 1～4,6 any one to detect online hot-gas channel endoparticle thing, comprises step:

Utilize pre-thermal purging unit that heated air is introduced to detecting unit pipeline and purge and preheating, close afterwards pre-thermal purging cell operation;

Utilize the main sampling mouth of tubulose of online detection unit to gather gas sample in hot-gas channel, institute's gas production sample after diffusing into cavity, enters respectively main road and bypass from flow distributor gas feed;

Utilize particle particle diameter in-line analyzer to measure concentration and the particle diameter of particle in double sampling mouth institute gas production sample in main road, and utilize first flow measure control subsystem to measure and control entering the gas flow of particle particle diameter in-line analyzer, utilize the second flow measure control subsystem metering and control the flow of the unnecessary gas that enters bypass, to meet the requirement of particle particle diameter in-line analyzer self flow and online detection unit isokinetic sampling's requirement.

9. method according to claim 8, wherein,

It is the gas flow that enters whole online detection unit that first flow measure control gas flow that subsystem is surveyed and the second flow measure control subsystem are surveyed gas flow sum, the flow velocity of gas while obtaining entering the main sampling mouth of tubulose according to the size of the main sampling mouth of tubulose bore; In entering the hot-gas channel that the flow velocity at the main sampling mouth of tubulose place equals need to detect, during flow velocity, reach isokinetic sampling, can collect representative particle in the hot-gas channel that needs to detect.

10. method according to claim 8 or claim 9, wherein, described device also comprises long-term on-line monitoring unit, this long-term on-line monitoring unit comprises sensor of dust concentration and computing machine, dust situation in the hot-gas channel that sensor of dust concentration detects for detection of need, by the particle concentration value in pipeline change into current signal transfer to computing machine to realize long-term on-line monitoring; Described method also comprises: utilize long-term on-line monitoring unit to calculate dust concentration C in pipeline, analyze relatively with the testing result of online detection unit; Wherein,

According to following formula, calculate dust concentration C in pipeline:

$C=\frac{\mathrm{\&alpha;}(\mathrm{\&Delta;I}+\mathrm{\&beta;\&Delta;H})}{V^m}$

In formula, C: dust concentration in pipeline;

Δ I: current output sensor changing value;

Δ H: humidity changing value;

V: air velocity duct;

α, β, m are the sensor of dust concentration calibration coefficient for concrete dust; Wherein, the talcous calibration coefficient α of 800 order is that 1000, β is that 10.32, m is 2.18; The calibration coefficient α of flying dust is that 400, β is that 8.04, m is 1.88; The calibration coefficient of dust in natural gas line, α is that 400, β is that 6.07, m is 2.18.