Non-throttle method. It consists of three categories: direct measurement of solid particle mass flow, concentration measurement and velocity measurement. This paper introduces the technical development level of this aspect, as well as the research, development and commercial products in this field. The measurement of mass flow concentration measurement speed 1. The University of Manchester Xie meters combines the two-dimensional finite method with the factor rotation method. The surface plate capacitive phase concentration sensor is optimized. Tsinghua University Zhang Baofen, Huang Songming and others combined the multi-electrode rotation method with the sensor structure optimization design. In addition, Northeastern University has done systematic research on capacitance tomography.
Some corresponding solid flow measuring instruments appearing on the international market are shown in Table 1. Table 1 Market Products Company National Sensors Tested Parameters UK Electrostatic Mass Flow UK Electrostatic Optical Mass Flow Concentration US Capacitor Microwave Concentration Speed ​​German Ultrasonic Concentration Acoustic Concentration Speed ​​UK Capacitance Flow imaging UK Coriolis mass flow UK impact plate mass flow 3 mass flow measurement technology 3.1 throttling method for measuring the mass of solid particles Flowmeters can be divided into throttling and non-throttle throttling flow sensors mechanical principles such as Table 2 shows. Actual field tests and studies have demonstrated that these devices are suitable for use in a variety of industrial processes. The measurement of mass flow of solids by gravity is measured by the mass flow rate of the solid, but in essence the chemical composition of the solid particle size. The change in humidity is not sensitive.
All throttling sensors have wear problems. Due to the invasiveness of sensor installation, the wear and scattering of moving particles, the compression of streamlines, and the compression of streamlines affect the accuracy of mass flow measurement of solid particles in pneumatic conveying pipes. Principle of Flow Method Sensor Coriolis Principle Coriolis Tube Thermodynamic Venturi Tube, Orifice Impact Impact Disc Weighing Spiral, Vibrating Plate, Intermittent Pulse 3.2 Non-throttle Method 3.2.1 Direct Measurement of Solid Mass Flow Measurement The non-throttle method can be divided into two main categories: direct measurement and indirect measurement. The direct solid flow meter has a direct response to the solid mass flow rate through the device. Only one single signal processing element is required to design three direct solids. The flowmeter has been tested, including thermal method, active charge detection method and passive charge detection method. The common feature is that a pair of sensitive or detecting components need to be set differentially along the axis of the pipeline to obtain the mass flow signal. However, the direct method is often used. This results in a length of the sensing head in the axial direction that is too long, but it is not suitable for large-scale production processes in the energy industry.
3.2.2 Indirect measurement Most of the proposed methods are based on the principle of indirect measurement, namely independent measurement of instantaneous volume concentration and instantaneous solid flow rate. 3.2.21 Flow rate measurement based on Doppler method, correlation method, space-connected filtering method, particle point imaging method, etc. Speed ​​sensor, as shown in Table 3 Table 3 solid flow rate measurement principle sensor Doppler method laser, microwave correlation method capacitance, acoustic, electrostatic, optical, radiation spatial filtering acoustic, capacitance, electrostatic, optical, microwave particle imaging optics By using the Doppler method, the microwave sensor can be used to roughly estimate the solid flow rate, and the laser sensor can be used to obtain the accurate result of the fixed point in the flow pattern.
Related speeds provide a better way than the Doppler method.
Electrical sensors (electrostatic and capacitive) have advantages over attenuation methods in terms of price, maintenance, and suitability, but capacitance and attenuation methods are susceptible to flow pattern changes. In-depth theoretical research and field experiments have found that electrostatic-type speedometers are superior to other related measuring equipments. The spatial filtering method is a new method. In general, the sensors used in spatial filtering are more complicated in design and structure than related sensors. However, signal processing equipment is relatively simple. Spatial filtering can extract more information from the particle stream, and when combined with effective signal processing techniques, more accurate results can be obtained.
The particle imaging method can not only use the advantages of its visual measurement to conduct on-line monitoring, observe the flow pattern, calculate the phase content rate, but also extract the flow pattern, phase content and other information from its direct measurement signal.
3.2.22 Concentration Measurements Solid concentration measurements are performed in a variety of ways and progress is not the same. There are many problems with the measurement of the dilute phase and cause great measurement errors, but the two methods of passive charge detection and optical attenuation are suitable for dilute phase detection. Furthermore, the uneven solid distribution leads to additional operational errors because The sensors all show a certain degree of non-uniform spatial sensitivity. For a more uniform sensitive field, a larger physical size sensor head must be used, such as a thicker wall or a longer axial length. The combination of multi-sensor fusion and new signal processing techniques can effectively solve this problem. The difference in particle size of the problem affects the operation of most sensors, while the sensor based on the principle of capacitance and radiation is not affected by this. Therefore, the calibration of the concentration measurement of particles of a specific size does not need to transmit particles of different size distribution. Many sensors include all based on Sensors for electrical and resonant methods rely on the chemical nature of the solid. When using a capacitive sensor or the like to measure the concentration, the difference in humidity and material type causes a large error. Therefore, the sensor based on the principles of electricity, resonance and attenuation must be calibrated with a specific measured solid. Table 4 Solid concentration measurement principle sensor Electrical capacitance, electrostatic resonance acoustics, microwave, nuclear magnetic, electromagnetic attenuation lasing acoustics, microwave, optical, radiation tomography acoustics, capacitance, electrostatic, optical, radiation resin solution, quantitatively add different proportions of phenolic resin solution, and mix evenly; Infrared scanning was performed as a series of standard samples in the range of 2000-800 cm-1. The absorbance of the quantitative peaks was read by the baseline method, and the ratio of A1740/A916 was calculated. The percentage of the phenolic resin was plotted on the abscissa, corresponding A1740/ The ratio of A916 is plotted as the ordinate, and the standard curve is drawn. 2.4 Samples are taken and dissolved in xylene. After smearing, the sample is evaporated under infrared light to form a film. The ratio of A1740/A916 is determined under the same experimental conditions. Percentage of phenolic resin 3 Results and discussion 3.1 Precision of measurement results for phenolic resin: ring The resin was fed in two samples of 3 7 and 46, and repeated experiments were carried out. The thickness of the film was as large as possible. The measurement of the content of the phenolic resin was measured. The ratio of the content of the phenolic resin was shown in Table 2. The sample was made to be a quantitative sample (30% phenolic resin) (40% phenolic resin), and the standard deviation was calculated. The results are shown in Table 1. For samples with the same composition content and different film thickness, the results are shown in Table 23.2. The relevant curves for drawing phenolic resin and epoxy resin are based on the sample of the ester resin on the phenolic resin and the epoxy resin at 916 cm-1. The peak is a quantitative peak but the peak is relatively small, so there is a certain error in the measurement when the epoxy resin content is small. However, it can be found from the standard curve that the linear relationship between the phenolic resin content of 20% and 70% is within the error range. This method is feasible. There are some differences in the measurement of different film thickness samples, so it is necessary to control the film thickness as much as possible. Consistency.
According to this method, when an independent absorption peak representing each resin is found, it can be applied to quantitative determination of other types of coating blend resins. In the case where an independent absorption peak cannot be found in the infrared spectrum, an infrared spectroscopy computer multi-component simultaneous quantitative analysis method can be employed.
4 Conclusion Infrared spectroscopy proportional method can accurately and quickly quantitatively analyze the blending film-forming resin in complex coating system, and obtain the relative content of each component. The method is simple and reproducible. The monitoring and evaluation of coating quality has great application value. .
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