Application of the hottest radar level meter in bl

2022-08-03
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The application of radar level meter in blast furnace

introduction

Liuzhou Iron and Steel Co., Ltd. now has 8 sets, with an annual output of about 6million tons of molten iron. Most blast furnaces use the bell less top mode. In the production of blast furnaces, blast furnace charge level, blast furnace distribution bin level and torpedo tank level are very important data, which play a very important role in ensuring the smooth operation of blast furnace conditions, improving production efficiency and improving production safety. Because the temperature in the blast furnace is very high (generally more than 300 ℃), it is always a difficult problem to measure the material level in the blast furnace. In the past, the material level of blast furnace was measured mechanically, which was complex to install, difficult to maintain, and the measurement data accuracy was not accurate enough. With the application of some new technologies, some iron and steel companies have been committed to finding an economic solution with long service life, reliable performance, low maintenance and high measurement accuracy. In the production of blast furnace, in order to ensure the safety of torpedo tank and railway, It is also necessary to measure the molten iron level of the torpedo tank car, so that the operator can always master the capacity of molten iron in the torpedo tank

after several years of practice, the blast furnace production of Liugang has gradually adopted a variety of radar level meters to measure the material level and molten iron tank level, and achieved good measurement results. Taking Siemens' SITRANS lr400 radar level meter as an example, this paper introduces the application of radar level meter in Liugang blast furnace

1. Composition of blast furnace level measurement system

blast furnace level measurement has three parts, as shown in Figure 1

(1) blast furnace level measurement. It is necessary to use a level meter to measure the mineral materials to be added to the blast furnace, which is very important for designing safe and reliable products. The level control needs to ensure that the level is maintained at a certain height. The maximum measurement range required for this measurement point is about 5~6m

(2) the main difficulty in measuring the slag level in the blast furnace distribution bin is that the temperature at the top of the bin is very high, generally more than 600 ℃, and the thickness of the top of the bin is large, about 1~1.5m

(3) measurement of molten iron in torpedo tank. The temperature of molten iron is above 1000 ℃. The measured medium is liquid, so the main problem is how to solve the problem of high temperature

2 measurement principle

the liquid level measurement of Liugang torpedo tank adopts Siemens' SITRANS lr400 radar level meter, which is a non-contact radar level meter specially developed for the measurement characteristics of powdery solids. 24GHz microwave is used as the measurement signal. Its wavelength is much shorter than that of radar wave in other frequency bands. Generally speaking, the shape of the solid material surface is inclined and rough. A small wavelength can ensure that the emitted radar wave can be reflected back to the radar probe to the greatest extent on the rough solid surface

the FMCW continuous frequency modulation mode is adopted, as shown in Figure 2. Its basic measurement principle is that the probe simultaneously transmits and receives radar waves, similar to "full duplex" in communication; The lr400 uses sawtooth shaped microwave. A phase difference is generated between the transmitted wave and the echo formed by the reflection of the solid surface. After the phase difference is converted by fast Fourier transform, a spectrum is formed. This spectrum has a linear relationship with the distance measured by the radar level meter. Therefore, a high-precision level signal can be obtained by detecting the sawtooth phase. According to the FMCW measurement principle, the radar wave can continuously "shoot" to the measurement medium, so that its anti-jamming ability is strengthened, and the possibility of "missing wave" is minimized, thus improving its reliability

four wire system design is adopted. The four wire system design ensures that the instrument has enough power to emit enough energy to meet the harsh measurement conditions. The lr400 can measure media with a dielectric constant as low as 1.5 (the dielectric constant of most media in nature is greater than 1.5), and the maximum range is 50m

due to the use of high-frequency signals, the minimum transmission angle can reach 8 °, which can avoid the influence of fixed interference to the greatest extent

the newly launched solid-state lr400 radar has made many improvements on the basis of the past. These improvements are:

⑴ new sight, which is the standard configuration of the new solid-state radar. The sight can ensure that the chemical powder with low dielectric constant can get a strong signal even when the lr400 is used under the condition of large inclination angle of the dielectric surface

⑵ three different sizes of horn antennas (2 ", 3", 4 "(5.8,7.62,10.16 cm) are provided to meet different site requirements

⑶ the solid-state algorithm of lr400 is improved, which can be specially applied to various complex solid-state measurements

⑷ a new algorithm is adopted, and the guided wave performance is greatly improved. In addition, the blending of glass fiber and inorganic fillers and the option of extension tube (antenna design up to 592mm) are added, so that it can meet some installation conditions of long installation riser and thick silo top

⑷ a new PTFE plane dust-proof window is designed, which can work stably under the condition of very large dust blowing

it is worth mentioning that the working conditions on the site are relatively bad, and ores often fall on the site. Since lr40 has 107 kinds of plastic materials that can be in direct contact with food, the standard configuration of 0 is a solid aluminum shell design, so lr400 can work normally even under bad site conditions

3 application effect on blast furnace

as shown in Figure 1, there are mainly three material level measurement points in blast furnace: blast furnace charge level measurement; Material level measurement of blast furnace distribution bin; The liquid iron level of torpedo tank is thus helpful to make space shuttle measurement with lighter weight and stronger damage resistance. Taking the liquid iron level measurement of torpedo tank as an example, the measurement effect is good

at this measuring point, Siemens radar level meter was used to try three different methods to solve the problem of high temperature, and good results were achieved

(1) install a nitrogen channel on the extended installation riser and inject nitrogen to reduce the process temperature of the horn antenna port of the radar level gauge

(2) adopt the design of guided wave elbow to avoid the ultra-high temperature caused by radiation. Using the guided wave characteristics of lr400, the guided wave elbow is designed and manufactured to avoid the high-temperature gas at the installation outlet of the silo top; In order to reduce the influence of heat conduction, the length of the entire waveguide tube is more than 2m, so that the high-temperature gas in the tube can be sufficiently reduced. After installing the guided wave elbow, the temperature of the installation flange is less than 100 ℃. After 2~3 weeks of field use, the material level measurement results are basically accurate

(3) since lr400 has a very small transmission angle (8 °), the horn antenna of lr400 shall be kept at a certain distance from the installation port to reduce the ultra-high temperature in the process

4 scheme optimization

in the measurement of molten iron level in torpedo tank, due to the small visible area after slagging at the tank mouth, the waveguide cannot be aligned with the tank mouth for measurement; In addition, the dust raised by the feeding port of torpedo tank car is easy to adhere to the nozzle of the guided wave elbow, resulting in signal drift and high-level alarm after the instrument is used for a period of time

theoretically, the above problems can be solved if a guided wave bend with a large bell mouth is made, but it is difficult to make a guided wave bend with a substitute bell mouth (no obvious welds are allowed) and the cost is high

therefore, through the understanding of Siemens SITRANS series radar level gauge, Siemens radar level gauge integrates the most advanced acoustic intelligent echo processing technology, which can eliminate the interference of clutter by correcting complex echo. Therefore, it can be considered to directly install a radar level meter on the dust cover, eliminate the interference echo from the probe to the tank mouth through the Siemens PDM software, and directly read the waveform below the tank mouth for measurement. This optimized scheme is relatively low in both use and installation cost; No compressed gas purging is required, which improves the reliability of the system

5 conclusion

the measurement of blast furnace level is special. Many units have used different measurement methods. From the measurement effect of Liugang, the application of radar level meter in blast furnace can give full play to the characteristics of solid radar, reduce maintenance workload and ensure the safe production of blast furnace. (end)

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