Baicun Village, Ganzi Prefecture, Sichuan Province, is located in Mawei Township, Changtai District, Baiyu County, Ganzi Prefecture, Sichuan Province. The currently proven ore reserves are 7.81 million tons, including 1865.53 tons of silver and 80,900 tons of copper. Lead 400,900 tons, zinc 651,900 tons, gold
5.198 tons. The potential value of resources is more than RMB 20 billion, and the long-term reserve of the mine is also very impressive. It is hailed as one of the "three pearls" of the national polymetallic ore. The mine was developed by Xinyuan Company, consisting of 6 shareholders including Western Mining Corporation, China North China Metallurgical Construction Corporation, Ganzi Prefecture Yufa Mining Co., Ltd., and Sichuan Emeishan 403 Construction Engineering Company. And in August 2006 officially completed and put into production (Figure 1).
The completion of the mine's production marks the gradual progress of the western mining industry in the province, which will play a positive role in accelerating economic development, providing employment opportunities, and developing related industries in ethnic regions.
First, the challenge
Due to the high elevation of the location of the Yucun Silver Polymetallic Mine, the China Construction Group Corporation China Huaye Group has always been concerned about whether various instruments can work properly to overcome the impact of altitude. The level meter used to measure various mineral silos is important for the entire system – it is necessary to control the height of the silo through stable and accurate level measurement to improve production efficiency; also need to pass the level measurement To achieve the purpose of asset management.
China Huaye previously used Siemens various level gauges and is familiar with the performance of Siemens's level gauges, and is also relatively relieved. Therefore, China Huaye once again found Siemens to seek a solution for its level. After confirming with the technicians, we learned that the Siemens radar level gauge had been used for 3 years at a cement plant with an elevation of 3,950 meters in Tibet. The work has been normal; but it is not certain whether the ultrasonic level meter can be used normally at such a high altitude. : After all, the high altitude air is relatively thin and the temperature is low. The work of the ultrasonic level meter will be affected by the environment. According to investigations, the highest altitude used by ultrasonic level meters is about 2000m, and has never been used at an altitude of nearly 4000m.
To use the level meter to measure the level of various silos in the Xuncun silver polymetallic ore, in addition to overcoming the acoustic energy loss caused by the diffuse reflection formed by the irregular material surfaces of various silos, it is necessary to overcome the high altitude. The influence of the thin air on the speed of sound, and the test of the instrument at low temperatures.
Second, the solution
The final solution is to use a combination of ultrasonic material level meter and radar level gauge to solve the level measurement of silos of different properties: For silos with a height of 15 meters and a large particle size, Multiranger ultrasonics are used. The position meter (as shown in Fig. 2) and various ultrasonic transducers of different ranges; and for applications with a large range (above 15 meters) or dust lifting, Siemens solid-state radar LR400 was selected.
Ultrasonic level measurement solution.
Siemens ultrasonic level measurement technology has always been a leader in the world, it has many unique technical features and patented technology.
Sound resistance matching technology.
Unlike other companies' products, Siemens uses a sound-resistance matching technology as the main technology for measuring solid material levels. The low-density medium is closely attached to the surface of the ultrasonic emission surface to reduce the acoustic resistance of the ultrasonic probe and minimize the occurrence of ultrasonic energy attenuation. This is also the lowest cost, highest reliability, and most widely used technology in all ultrasonic solid-state measurement technologies. According to tests, the performance of ultrasonic probes using acoustic impedance matching technology is 5 to 6 times higher than that of ordinary ultrasonic probes.
Matrix sound source system.
As the range increases, the transmitted energy of the ultrasonic probe also needs to be greatly increased. At the same time, it is also necessary to reduce the transmission frequency to reduce the attenuation of ultrasonic energy in long-distance transmission. However, using the above techniques will also bring about some “side effectsâ€: the increase of beam angle; the divergence of ultrasonic energy; the “self-cleaning†function of the probe surface is not obvious, and it is easy to bond materials; the lower emission frequency is easily interfered by natural noise. A series of problems such as low accuracy.
Siemens uses a matrix sound source system to overcome the shortcomings of the above technologies. It chose to use multiple (not a) crystals as the emission source; it has a higher emission frequency, a smaller beam angle (up to 6o), and a higher surface vibration energy than conventional ultrasonic probes. "Self-cleaning" The effect is more pronounced; the ability to resist environmental noise is also stronger.
Two-wire connection method.
Siemens ultrasound probes generally use two-wire mode, in addition to transmission and identification of ultrasonic probe pulse signal, but also the temperature signal transmission to achieve temperature compensation. Different from the common three-wire mode, the two-wire mode can use twisted-pair shielded cable as the transmission cable or coaxial cable with stronger anti-interference ability. Its advantages are: the maximum transmission distance of up to 365m, the largest degree of multi-point measurement; the most effective way to overcome the noise from the environment, so that the echo signal is more reliable and stable.
Sound smart echo processing technology.
Siemens' patented acoustic intelligence technology is currently the most advanced echo processing technology.
Due to the high altitude of Yucun Silver Polymetallic Ore, which has the characteristics of thin air and low temperature, the use of acoustic intelligence technology has the function of temperature compensation for sound velocity (built-in high-precision temperature sensor), which can overcome the low environmental impact of low temperatures. At the same time, due to the thin air, the change of the sound speed will eventually lead to inaccurate readings. For sound intelligence, only a simple calibration is required. Fine adjustment of the sound speed according to the actual value can be a good solution to this problem. 5).
Of course, the sound intelligence technology also includes various filters, TVT (echo suppression curve), ALF selection algorithm and other functions can be solved due to the wall fixed (if people ladder, structural beams, etc.), irregular material surface caused Multiple echoes such as static or dynamic interferences.
Radar Level Measurement Solution
Siemens' LR400 solid-state radar is widely used in cement, mining, iron and steel, electric power and other silos, especially in level measurement applications for measuring powders with very high dust levels. Good reputation (Figure 6). LR400 has the main features:
n non-contact measurement principle, basic maintenance-free;
n Using 24GHz high-frequency signals, shorter wavelengths can easily form good echo signals on rough solid surfaces. Compared to many 6G and 10GHz radars, their measurement reliability, stability and accuracy are good. many.
n 
FMCW (Continuous Frequency Modulation) operating principle and four-wire power supply design; ensure that the LR400 can provide more reliable measurement echoes and greater power to ensure noise interference in harsh operating conditions;
n All-aluminum housing ensures that the instrument is not easily damaged in the harsh environment, which greatly extends the life of the instrument;
n The standard sight and smaller antenna size make installation easier and more convenient;
n Built-in solid-state radar algorithms integrated with tens of thousands of application experiences provide different measurement modes for fine powder solids and bulk solids.
Third, the use of the results
After technical exchanges and confirmation, China Huaye accepted Siemens' material level solution and purchased it for use in the ore silo and other solid silos of the Xicun Silver Polymetallic Mine (Figure 7). In the nearly one year since its use in 2006, the ultrasonic and radar level meters provided by Siemens have performed satisfactorily, completely overcoming the effects of high altitude and low temperature, and due to the use of non-contact measurement methods, debugging No maintenance has ever been performed since the installation was completed.
The "Use it and forget it" that Siemens's level gauges advocated (it does not need to care about it) was perfectly reflected at an altitude of 3,990 meters and was also considered as a contribution to the development of the west.