![<?echo $_SERVER['SERVER_NAME'];?>](/template/twentyseventeen/skin/images/header.jpg)
As a new type of particle size testing instrument, laser particle size analyzer has been widely used in other powder processing and application fields. It is characterized by fast test speed, good repeatability, good accuracy and easy operation. It is of great significance to improve product quality and reduce energy consumption.
1. The principle of laser particle size analyzer
The laser particle size analyzer tests the particle size distribution based on the physical phenomenon that the particles can cause the laser light to scatter. Because the laser has good monochromaticity and strong directionality, the laser will radiate to infinity in an infinite space without obstruction, and there will be little divergence during propagation.
The Mie scattering theory shows that when the beam meets the particle blocking, part of the light will be scattered, and the direction of the scattered light will form an angle θ with the direction of the main beam. The angle θ is related to the size of the particle. The larger, the smaller the θ angle of the generated scattered light; the smaller the particles, the larger the θ angle of the generated scattered light. That is, the scattered light at a small angle (θ) is caused by large particles; the scattered light at a large angle (θ1) is caused by small particles, as shown in FIG. 2. Further research shows that the intensity of scattered light represents the number of particles of this size. In this way, by measuring the intensity of the scattered light at different angles, the particle size distribution of the sample can be obtained.
In order to measure the intensity of scattered light at different angles, it is necessary to use optical means to process the scattered light. We place a Fourier lens in the appropriate position in the beam, and place a group of multi-element photodetectors on the back focal plane of the Fourier lens. The optical signal will be converted into an electrical signal and transmitted to the computer, and these signals will be processed through the dedicated software, and the particle size distribution will be accurately obtained.
2. Features of coal water slurry and its particle size distribution
As a clean, alternative fuel with fluidity, coal-water slurry has the advantages of high concentration, fine particle size, good fluidity, high combustion efficiency, environmental protection, energy saving, and storage safety. It has been widely used in industrial boilers, power station boilers and industrial furnaces. In addition to large-scale combustion equipment of power plants, steel mills, refineries and other enterprises, more and more small and medium-sized boilers (below 20 tons) have also begun to burn coal-water slurry. Taking into account China's energy structure and actual national conditions, the government is vigorously encouraging the development of the coal-water slurry industry. The State Planning Commission's "China Clean Coal Technology" Ninth Five-Year Plan "and the 2010 Development Outline" Both the "Tenth Five-Year Plan" and the "National Environmental Protection" Tenth Five-Year Plan "of the State Environmental Protection Administration have listed the application and promotion of coal-water slurry technology as a priority, with preference given to industrial policies. Therefore, the production and marketing prospect of coal water slurry is very broad.
As far as the particle size testing of coal water slurry is concerned, there are the following three special problems that must be solved:
1. High concentration. In the coal water slurry, the proportion of coal is 65% -70%, the proportion of water is 35% -30%, and there are a small amount of additives.
Because the proportion of coal is large and it is in a viscous state, and the laser particle size analyzer requires particle size testing at a low concentration (less than 0.5%), the circulation system of the laser particle size analyzer is required to have a large volume and convenience In order to ensure that the test sample concentration is controlled within a reasonable range, the test can be carried out smoothly.
2. Wide particle size distribution. At present, the average particle size of coal water slurry is generally around 50um, with a minimum particle size of 1um and a maximum particle size of 600um. In other words, the particle size range of coal water slurry is 1-600um. In such a wide particle size range, to obtain accurate particle size distribution results, the first requirement is that the range of the laser particle size analyzer is greater than the particle size range of coal water slurry; the second photodetector must have high sensitivity and stability. Only in this way can the repeatability and accuracy of the granularity test be guaranteed.
3. The particles have strong light absorption characteristics. The particles of coal water slurry are black, and the shape of the particles is also very complex, which has strong absorption characteristics for the laser, and the scattered light as an effective signal is relatively weak. Therefore, a high-power, high-brightness laser needs to be equipped to increase the effectiveness. Signal to improve the signal-to-noise ratio.
4. Need precise automatic adjustment system and long-life laser. Laser particle size analyzer is a precise optical instrument. Since coal water slurry is continuously produced and used, the particle size test as a quality control method also needs to be carried out continuously along with the production process. Therefore, it is necessary to increase the degree of automation of the instrument, increase the use rate of the instrument, and reduce manual maintenance and adjustment time. To reduce the failure rate of the instrument.
3. Development of laser particle size analyzer for coal water slurry
According to the special situation of coal water slurry particle size testing, combined with many years of manufacturing experience of laser particle size instruments, the National Coal Water Slurry Engineering Technology Center and Dandong Baite Instrument Co., Ltd. have cooperated after more than a year of hard work and hundreds of thousands of In the experiment, in the second half of 2002, the first domestic laser particle size analyzer for coal water slurry was successfully developed. The successful development of the instrument ended the history that the coal water slurry particle size test completely relied on imports. Since then, domestic coal water slurry users can use the laser particle size analyzer with excellent performance, low price, timely service, and adequate supply of spare parts. Its comprehensive performance index has reached the advanced level of similar foreign instruments.
1. Large-capacity, large-flow circulating dispersion system. The circulation dispersion system is an important device in the laser particle size analyzer system, which includes a peristaltic circulation pump, an ultrasonic disperser, an agitator, a test window assembly, a pool and a discharge device. The peristaltic circulation pump is a kind of sample that is made by alternately squeezing and recovering the silicone rubber tube with excellent elasticity. Since the external force does not directly contact the particles during the cycle, it will not cause any impact on the particles. Its flow rate reaches 2000ml / min, and the largest coal water slurry particles will not settle in the pipeline. The ultrasonic disperser is directly fixed on the bottom of the pool with a volume of 800ml. It is equipped with a drive circuit with a power of 50W and a frequency of 40KHZ. In just three minutes, the coal water slurry particles will be in a good dispersion state.
A stirrer composed of a DC motor and special blades will keep the samples in the pool in a uniformly suspended state at all times, ensuring that the samples delivered to the instrument are uniform and consistent. The test window is made of quartz glass, which has good optical characteristics, wear resistance and corrosion resistance, and is very convenient for disassembly and installation. The discharge device is composed of a specially designed control valve and corresponding pipeline, which is convenient to operate, safe and reliable, and never leaks.
2. Broaden the testing range of the instrument. The testing range of common laser particle size analyzers is generally below 300um. With the trend of ultra-fine powders increasing, the testing range of laser particle size analyzers is also developing in the ultra-fine direction. The main contradiction in the test range of the coal water slurry laser particle size analyzer is just the opposite. To ensure effective measurement of coarse-end particles, the upper limit of the test must be greater than 700um. Through trial and error and calculation, we have designed a large-aperture, long-focal-length Fuchs lens and folding optical system, so that the test range reaches 0.68-951um, and the scattered signals within this range can be effectively received. The particle size test of coal water slurry is required.
3. High-power laser and high-sensitivity photodetector array. Since the water-coal slurry particles have strong light absorption characteristics and weak scattering signals, in order for the scattered signals to reach a certain intensity and be effectively received, the intensity of incident light must be increased and the sensitivity of the photodetector must be increased. For this reason, we have selected a high-power semiconductor laser, which has five times the power of a laser used in a general laser particle size analyzer.
At the same time, a highly sensitive photodetector array with 76 photodetectors was successfully developed. The device uses a large-scale integrated circuit manufacturing process, which is formed by multiple photolithography on the same silicon wafer, which not only ensures the sensitivity of the photodetector, but also the linearity of each photodetector in the linear range . Not only that, because of the use of up to 76 photoelectric receiver arrays, the resolution of the instrument is greatly improved.
Our outdoor hammock is with its global pioneering design, breaking through convention, utilizing textilene boldly, Sevenze`s garden hammock receives rich reputation. Meanwhile, hard work on hammock stand brings its gorgeous appearance and outstanding quality. Each hammock set, through strict safety test before reaching customer,is safe, reliable, and permanently guaranteed.
Hammock Bed,Indoor Hammock,Chair Hammock,Camping Hammock
SEVENZE INDUSTRAL CO.,LIMITED , http://www.sevenze.com