CN202256201U - Device for measuring concentration of coal powder and phase distribution in pneumatic transmission pipeline in real time - Google Patents

Abstract

The utility model discloses a real-time measuring device for coal powder concentration and phase distribution in a pneumatic conveying pipeline, which belongs to the gas-solid two-phase flow detection equipment range. The sensor pipe section of the measuring device is connected to the pipe under test through a flange, the point gamma ray source protrudes from the side wall of the measuring pipe section to the edge of the flow field in the pipe, the scintillation probe array and the amplifier array are arranged on the periphery of the sensor pipe, and the thickness of the shielding lead plate is selected , so that the gamma rays outside the annular shielding cover are within a safe range. The point gamma ray source and detector array divide the measurement space into n measurement elements invisibly, and the gamma ray intensity attenuated by each measurement element is received by the corresponding scintillation probe array, and all the microelements in the measurement field are The arithmetic mean of the volume concentration in the unit; meanwhile, the phase distribution of the pulverized coal on the cross-section of the measurement space is also obtained. The space occupied by the measuring device of the utility model is obviously reduced, the manufacturing cost of the sensor is reduced, and the gamma ray protection requirement is obviously reduced.

Description

A real-time measuring device for pulverized coal concentration and phase distribution in a pneumatic conveying pipeline

technical field

The utility model belongs to the scope of gas-solid two-phase flow detection equipment, in particular to a real-time measurement device for coal powder concentration and phase distribution in a pneumatic conveying pipeline.

technical background

The real-time detection of air-powder two-phase flow parameters in the pneumatic conveying pipeline of coal-fired power plants is directly related to the safety and economy of boiler operation. measurement methods, including heat balance method, pressure drop method, electrical capacitance tomography, Venturi tube method, microwave method, electrostatic method, capacitance method, etc., but these sensors are all "soft field sensing type", and the concentration of pulverized coal The measurement is affected by changes in factors such as temperature, humidity, pressure, coal type, continuous phase flow rate, discrete phase distribution, etc., and it is impossible to achieve absolute measurement of pulverized coal concentration. Among the above methods, only electrical capacitance tomography (ECT) can be used to detect the distribution of pulverized coal phase on the cross-section of the pipeline. At the same time, it is noted that the phase distribution is very important for judging whether the powder delivery wind speed in the primary air pipeline is appropriate and whether the powder delivery is uniform. And whether the operation of the pneumatic conveying pipeline is safe is of great significance, but there is still a lack of effective means to obtain phase distribution information.

A known technology "I.R.Barratt, Y.Yan, B.Byrne, M.S.A.Bradley.Massflow measurement of pneumatically conveyed solids using radiometricsensor.Flow Measurement and Instrumentation 11(2000) 223-235" proposed a gamma-ray-based In order to ensure that the gamma beams are parallel to each other in the method of measuring the solid phase concentration of gas-solid two-phase flow by the absorption method, it is required that the linear radiation source, source collimator, gamma ray detector collimator, and ray detection array in the scheme must be in one Arranged on a straight line perpendicular to the measured pipeline, coupled with the radiation shield, the installation space occupied by the equipment is very large, and the application of this measuring device in engineering is limited by the site conditions.

Utility model content

The purpose of this utility model is to propose a real-time measuring device for coal powder concentration and phase distribution in a pneumatic conveying pipeline in view of the limitation that the existing radiation sensor occupies a large installation space.

The real-time measuring device is composed of gamma ray source, collimator, sensor pipe section, scintillation probe array, amplifier array, gamma ray shielding cover and microcomputer signal processing system. Measured on the pneumatic conveying pipeline; the integrated γ-ray source 1 and collimator 2 are placed in the Al ₂ O ₃ wear-resistant ceramic casing 3, the Al ₂ O ₃ ceramic bottom cover 4 and the Al ₂ O ₃ wear-resistant ceramic casing 3 threaded connection, extend the Al ₂ O ₃ wear-resistant ceramic cladding from the side wall of the sensor pipe section into the flow field of the measured pneumatic conveying pipeline 12, insert the γ-ray source collimator 2 in the side wall of the sensor pipe section and the sensor pipe section The side wall is threaded; the exit port of the gamma-ray source collimator 2 protrudes into the edge of the flow field inside the side wall of the sensor pipe section, and the scintillation probe array 13 and the corresponding amplifier array 14 surround the outer layer of the sensor pipe section and are arranged in a ring The array adopts an annular lead shielding cover 15 to cover the periphery of the amplifier array 14 and the gamma ray source 1 .

The gamma source 1 emits a narrow beam of gamma light at a plane angle of 180° through the collimator 2, and the emission plane is perpendicular to the axis of the sensor pipe section.

The sensor pipe section is a composite pipe section with an Al ₂ O ₃ ceramic lining and a Kovar alloy shell.

The collimator is made of Kovar alloy.

The beneficial effects of the utility model are as follows: a point-shaped gamma-ray source is adopted, the collimator emits at a plane angle of 180°, the scintillation probe array and the amplifier array sensor pipeline are arranged in an arc shape, and the ring-shaped gamma-ray shielding cover is fixed on the periphery of the amplifier array, so that The on-site space occupied by the sensor equipment is significantly reduced, the manufacturing cost of the sensor is reduced, and the requirements for gamma ray protection are reduced.

Description of drawings

Figure 1 is a schematic diagram of the longitudinal section of the measuring pipe section of the γ-ray absorption method measuring device.

FIG. 2 is a schematic cross-sectional view along line B-B of FIG. 1 .

Detailed ways

The utility model provides a real-time measuring device for coal powder concentration and phase distribution in a pneumatic conveying pipeline of a power plant boiler, which greatly reduces the occupied space of sensor equipment and is hardly affected by site conditions. Limitations, the utility model will be further described below in conjunction with the accompanying drawings and the best implementation examples.

In Figures 1 and 2, the sensor sensor pipe section is composed of Al ₂ O ₃ ceramic lining 6 and Kovar alloy shell 7. The sensor sensor pipe section passes through the sensor pipe section flange 9, the sealing gasket 10, and the pipe connection flange 11 under test. Realize the connection with the measured pipeline 12; the γ-ray source 1 and the collimator 2 are manufactured as one, placed in the Al ₂ O ₃ wear-resistant ceramic shell 3, and the Al ₂ O ₃ ceramic bottom cover 4 is screwed on the Al ₂ O 3 ₃ On the wear-resistant ceramic cladding 3, the Al ₂ O ₃ wear-resistant ceramic cladding 3 extends into the pipeline from the side wall of the sensor pipe section, and is connected with the side wall of the sensor pipe section by thread 5, so that the exit port of the collimator 2 protrudes appropriately And enter the flow field inside the side wall of the sensor pipe section; the scintillation probe array 13 and the corresponding amplifier array 14 surround the outer layer of the sensor pipe section, arranged in an annular array, and the cylindrical lead shielding cover 15 is used to cover the amplifier array 14 and γ The periphery of the ray source 1. The collimator 2 is made of Kovar alloy. The gamma-ray source 1 of the sensor is a point source. Straightener 2 transmits Al ₂ O ₃ wear-resistant ceramic cladding 3 in the form of narrow beam rays, then irradiates wind powder two-phase fluid 8 in the sensor tube section, and passes through Al ₂ O ₃ ceramic lining 6 and Kovar alloy shell 7 The compound composite passes through the side wall of the sensor pipe section, and the gamma rays reach the ring array formed by the scintillation probe array 13 and the amplifier array 14 . The γ-ray source 1 and n scintillation probe arrays 13 invisibly divide the cross-section of the sensor pipe section into n measurement cells with different areas, which constitute the measurement field of coal powder volume concentration and phase distribution; each scintillation probe array Receive the γ-ray intensity transmitted in the corresponding micro-element. Obviously, the larger n is, the more micro-elements will be divided into the measured section, and the smaller the area of each micro-element will be. The phases are considered to be uniformly distributed and measured separately, thereby reducing the measurement error and improving the measurement accuracy; the annular γ-ray lead shielding cover 15 shields the γ-rays penetrating the detector, and the appropriate shielding cover is selected according to the γ-ray intensity The thickness of the lead plate makes the γ-ray intensity in the environment outside the shielding cover within the standard range stipulated by the state; the electric pulse signal output by the scintillation probe array becomes a measurable pulse after being amplified, and the pulse is counted, and the count rate can represent the incident gamma-ray intensity.

The working principle of the pulverized coal phase concentration measuring device is as follows:

While the γ-rays penetrate the sensor pipeline, they also pass through the air-powder two-phase flow in the pipeline. The absorption coefficient of the powder-transporting hot air to γ-rays is very small compared with coal powder, which can be ignored. The law of interaction between rays and matter is as follows:

${\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&mu;</span>}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

(1) In the formula, I ₀ -the gamma-ray intensity received by the scintillation probe array when the sensor tube section is space-time; I _i (t)-t time, when there is coal powder in the sensor tube section, the gamma-ray received by the i-th scintillation probe array Intensity; at time _xi (t)-t, the equivalent thickness of pulverized coal in the i-th measurement element in the sensor space; μ-the linear absorption coefficient of pulverized coal.

At time t, the volume concentration β(t) of pulverized coal in the i-th measurement element in the sensor space is expressed as follows:

${\mathrm{<span\; class="notranslate">\; \&beta;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}\mathrm{<span\; class="notranslate">\; \&mu;</span>}}\mathrm{<span\; class="notranslate">\; ln</span>}\frac{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

(2) In the formula, H _i - the equivalent chord length of the γ-ray passing through the i-th microelement in the sensor space.

The pulverized coal volume concentration β(t) in the sensor measurement space is:

$\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; [</span>{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span>{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</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>$

This scheme divides the cross-section of the pipeline under test into n parts, and measures the concentration value in each micro-element separately, and β _i (t) (i=1, 2,...n) represents the average Coal powder concentration, then β ₁ (t), β ₂ (t) ... β _i (t) ... β _n (t) characterizes the distribution information of coal powder phase on the cross section of the sensor pipe section, the computer system can be based on β ₁ (t), β ₂ (t) ... β _i (t) ... β _n (t) to reconstruct the distribution image of pulverized coal on the sensor pipeline section, which can not only obtain the phase distribution information, but also obviously overcome the flow pattern and Effect of Phase Distribution Variations on Coal Concentration Measurements.

The point-shaped γ-ray source of the utility model is arranged on the pipe wall of the sensor pipe section, and the scintillation probe array is surrounded outside the pipe section of the sensor pipe to form a measurement section. The detector side does not need to use a collimator, so that the space occupied by the sensor equipment is significantly reduced, and Sensor manufacturing costs are reduced, and gamma-ray protection requirements are significantly reduced.

Claims (3)

1. A real-time measuring device for pulverized coal concentration and phase distribution in a pneumatic conveying pipeline, the real-time measuring device is composed of gamma-ray source, collimator, sensor pipe section, scintillation probe array, amplifier array, gamma-ray shielding cover and microcomputer signal processing The composition of the system is characterized in that: the sensor pipe section is connected to the measured pneumatic conveying pipeline through flanges and sealing gaskets; the integrated γ-ray source and collimator are placed in the Al ₂ O ₃ wear-resistant ceramic cladding, and the Al ₂ The O ₃ ceramic bottom cover is threadedly connected with the Al ₂ O ₃ wear-resistant ceramic casing, and the Al ₂ O ₃ wear-resistant ceramic casing is inserted into the side wall of the measured pneumatic conveying sensor pipe section from the side wall of the sensor pipe section, and inserted into the side of the sensor pipe section The γ-ray source collimator in the wall is threadedly connected with the side wall of the sensor pipe section; the exit port of the γ-ray source collimator protrudes to the edge of the flow field inside the side wall of the sensor pipe section, and the scintillation probe array and the corresponding amplifier array surround it The outer layer of the sensor pipe section is arranged in a circular array, and the ring-shaped lead shielding cover is used to cover the periphery of the amplifier array and the γ-ray source. 2. The real-time measuring device for coal powder concentration and phase distribution in the pneumatic conveying pipeline according to claim 1, characterized in that: the gamma-ray source emits a narrow beam of gamma light at a plane angle of 180° through a collimator, and the emitted The plane is perpendicular to the axis of the sensor pipe section. 3. The real-time measurement device for coal powder concentration and phase distribution in the pneumatic conveying pipeline according to claim 1, characterized in that: the collimator is made of Kovar alloy. the

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