First, the significance of detection
Detection is an indispensable means for human beings to understand the essence of things. Through detection, people can get the concept of qualitative and quantitative things, and discover the inherent laws of things. Without accurate detection methods, there is no development of science and technology. The development of science and technology and the development of detection technology are complementary. Modern science and technology are inseparable from testing. Therefore, the use of advanced testing technology is an important symbol of the modernization of science and technology.
Mineral processing detection is an important means to understand and control the mineral processing process. The beneficiation process is a complex, multi-parameter, multi-variable comprehensive process. In this process, there are not only a large number of static geometric quantities, such as material level, liquid level, particle size, etc., but also with the development of production technology. More and more dynamic physical quantities are detected, such as flow rate, flow rate, displacement, concentration, temperature, pressure, and the like. These inspections must be carried out frequently and repeatedly in order to keep abreast of the changes in various factors in the process, to make timely adjustments and controls, to keep various process factors stable within the specified range, or to make the mechanical equipment according to regulations. The system performs the work and controls the entire process under normal operating conditions for normal operation. Ensure that the products of each operation meet the specified technical and economic indicators, so that the ore dressing process is of high quality, high yield, low consumption, and maximize economic benefits.
The mineral processing process detection includes manual detection and automatic detection. Manual testing is still the main testing method for most of the selected plants in China. For example, using the concentration pot to check the graded overflow concentration, the concentration of the slurry in the sorting operation, the concentration of the concentrated product and the concentration of the filtered feed, etc., the size and grade of the crushed product are checked by the sieve. The particle size, the size of the selected product, etc., and the quality of the raw materials and products are examined by chemical analysis methods. The accuracy of manual detection is greatly influenced by subjective factors and method factors. There is a difference between the quality of each operator and the accuracy of each inspection method, which has certain influence on the accurate adjustment and control of the beneficiation process.
With the advancement of science and technology, the development of the electronics industry, and the emergence of various instrumentation, in the 1960s, some factories in China gradually used automatic detection instead of manual detection. Especially since the 1980s, most of the plants in China have adopted automatic detection. Technologies such as electromagnetic flow meters, ultrasonic particle size meters, gamma ray concentration meters, electronic belt scales, and isotope online grade analyzers have been used for production. The main advantages of automatic detection: can eliminate the influence of subjective factors on the beneficiation process, significantly reduce the number of operators, increase the possibility of multi-machine care; can obtain reliable information on process factors changes, reflect the process and equipment operation, timely Guide manual adjustment or automatic adjustment of the production process, able to comply with the operating system specified in the process, thereby improving the technical and economic indicators and productivity of the plant, saving raw materials and pharmaceutical consumption.
Second, the content of the test
The purpose of the mineral processing process is to obtain quantitative results and mathematical characterization of the process, providing a reliable basis for controlling the production process.
The content of the mineral processing process is determined by the beneficiation method and also determined by the beneficiation process. The process of re-election, flotation and magnetic separation plants is different, and the test parameters are also different, but the most important test items are common. If necessary, the raw material and product weight, material level and liquid level, product particle size, slurry concentration, slurry flow rate, slurry flow rate, raw material and product grade must be tested. The details of the specific tests are listed in the table below.
Table  Mineral processing process test content
process | Election coal plant | Concentrator |
Coarse | 1. ash;. 2 through the crushed material in the bulk content;. Metal was 3 | 1. ore; 2. bin material level;. 3 and broken into pieces after granularity;. Metal object 4; 5 magnet mineral content; 6 crushers clogging. |
Medium crush | 1. mineral amount; 2. grain position in the bin; 3. particle size; 4. crusher productivity | |
magnetic separation | 1. Productivity; 2. Magnetite content; 3. Particle size; 4. Concentration | |
Flotation | 1. the amount of minerals; 2. concentration; 3. ash; 4. dosage; 5. liquid level | 1. Mineralization; 2. Foam and slurry surface; 3. pH; 4. Concentration and dosage of the agent; 5. Ionic composition; 6. Temperature; 7. Product grade; 8. Foam strength |
Dehydration, filtration | 1. Moisture; 2. Easy to teach points; 3. Solid content of filtrate, oversized particles; 4. Liquid level; 5. Pressure; 6. Vacuum degree; 6. Filter aid concentration and dosage | 1. slurry concentration; 2. moisture; 3. filter liquid level; 4. vacuum degree; 5. mineral amount; 6. filter aid concentration and dosage |
concentrate | 1. concentration; 2. overflow turbidity | 1. Concentrator truss overload; 2. Product concentration, density; 3. Overflow turbidity; 4. Clarity level; 5. Coagulant dosage |
Centrifugal dewatering machine | Moisture | |
dry | 1. amount of treatment; 2. moisture; 3. temperature; 4. air consumption | 1. treatment volume; 2. moisture; 3. temperature |
Grinding and grading | 1. The amount of coal entering the sieve; 2. The amount of the mixture on the sieve; 3. The amount of the mixture under the sieve | 1. Feeding particle size and particle size composition; 2. Productivity according to the specified particle size; 3. Mineral amount; 4. Gradation overflow concentration; 5. Grading overflow density; 6. Grinding machine filling rate; 7. Grading product size Composition; 8. cyclic load |
Jigging | 1. Feeding amount and product quantity; 2. Mixing of heavy products; 3. Ash; 4. Moisture; 5. Particle size; 6. Bed looseness; 7. Circulating water (flow, solid content); 8. Compressed air (flow, pressure) | 1. The amount of water under the sieve; 2. Product density (or mixed product of heavy products); 3. Bed thickness and looseness |
Heavy medium | 1. Mixture of light and heavy products; 2. Density; 3. Viscosity; 4. Liquid level; 5. Selected medium (media loss, density, muddyness); 6. Concentration | 1. Inclusion amount; 2. Density; 3. Viscosity; 4. Yield; 5. Metal content (grade) |
Third, the classification of detection methods
The detection method is very important for the detection work, and it is related to whether the detection task can be completed. Therefore, it is necessary to carry out serious analysis on the specific conditions of different detection tasks, find out practical and feasible detection methods, and then, according to the detection methods, select appropriate detection technology tools to form a detection system for actual detection. On the other hand, if the detection method is not correct, even if the selected technical tools (related instruments, instruments, equipment, etc.) are advanced, there will be no good detection results.
For the detection method, there are different classification methods from different perspectives. According to the inspection procedures, it can be divided into: direct detection, indirect detection and simultaneous detection; according to the detection method, it can be divided into: deviation detection, zero detection and differential detection. In addition, there are many other classification methods, for example, according to whether the sensing sensor is in contact with the measured medium, it can be divided into contact detection and non-contact detection; according to whether the detection system applies energy to the object to be measured, it can be divided. For active detection and passive detection.
1. Direct detection, indirect detection and simultaneous detection
(1) Direct detection When using the meter for detection, the meter reading can be directly represented by the operation without any calculation, which is called direct detection. For example, a magnetoelectric ammeter is used to detect a branch current of a circuit, and a spring tube type pressure gauge is used to detect a boiler pressure. The advantage of direct detection is that the detection process is simple and rapid, and the disadvantage is that the detection accuracy is not very high. This method of detection is a method that is widely used in engineering.
(2) Indirect detection When using the meter for detection, several measured values ​​should be measured separately. Then, according to a certain physical law, the detected value is substituted into a certain function relationship, and the required result is obtained through calculation, which is called indirect. Detection. At this time, the measured physical quantity cannot be immediately obtained by a simple measurement, because it is a function of several measured physical quantities. Therefore, these several measurements must be measured and substituted into the relevant formula, and the final result is calculated. Indirect testing is mostly used for laboratory testing in scientific experiments, and this method is sometimes applied to engineering testing.
(3) Simultaneous detection (also called combined detection) When applying the instrument for detection, the measured physical quantity must be solved by solving the simultaneous equations to obtain the final result, that is, the directly detected data is substituted into the formula to form a group of cubics. Cheng, such a test is called simultaneous detection. In the case of simultaneous detection, it is generally necessary to change the test conditions in order to obtain the data required for a set of simultaneous equations.
For example, the detection of the coefficient of the standard resistance coil resistance temperature. For an electric coil, the relationship between its resistance value R t and temperature t is given by: R t =R 20 +a(t-20)+ β(t-20) 2 , where a, β is the temperature coefficient of resistance of the resistance coil, and R 20 is the resistance value of the resistance coil at 20 °C.
In order to measure the a and β values ​​of the resistance coil, only the temperature conditions of the test are changed, and at the three temperatures t 1 , t 2 , t 3 , the corresponding resistance values ​​R t1 , R t2 , R t3 are respectively measured, and then Substituting the above formula can get a set of simultaneous equations:
R t1 =R 2 0+a(t 1 -20)+ β(t 1 -20) 2
R t2 =R 2 0+a(t 2 -20)+ β(t 2 -20) 2
R t3 =R 2 0+a(t 3 -20)+ β(t 3 -20) 2
After solving the simultaneous equations, a, β, and R 20 can be obtained to obtain the final desired results a and β.
2. Deviation detection method, zero detection method and differential detection method
(1) Deviation detection method In the detection process, the method of measuring the displacement (ie, deviation) of the instrument pointer is used, which is called the deviation detection method. When using this method for testing, the standard gauge is not installed in the meter, but the gauge is calibrated in advance using a standard gauge; then, at the time of measurement, the input is measured, according to the indication of the gauge pointer on the scale and ruler. The value to be measured is determined, which is an indirect way of comparing the measured quantity with the standard quantity. For example, a magnetoelectric ammeter is used to detect the current of a branch in the circuit, and a magnetoelectric voltmeter is used to detect the voltage across the electrical component. Using this method for detection, the detection process is relatively simple and rapid, but the accuracy of the detection results is low. This detection method is widely used in engineering inspection.
(2) Zero-position detection method (also known as compensation type or balanced type detection method) In the detection process, the zero position indication of the zero-point meter is used to detect the balance state of the measurement system. When the measurement system reaches equilibrium, the known method is used. The reference quantity determines the detection method of the unknown quantity to be measured, which is called the zero position detection method. When using this method for testing, the standard measuring instrument is installed in the meter. During the testing process, the standard quantity is directly compared with the measured quantity. When detecting, the standard quantity is adjusted, that is, the balancing operation is performed until the measured quantity is equal to the standard quantity. , that is, the zero meter returns to zero.
(3) Differential detection method The differential detection method is a detection method that combines the advantages of the deviation detection method and the zero position detection method. In this method, the unknown quantity to be measured is compared with a known standard quantity, and the difference is obtained, and then the difference is obtained by the deviation type detection method. When using this method, the standard measuring instrument is installed in the instrument. During the detection process, the standard quantity is directly compared with the measured quantity. Since the values ​​of the two are very close, the standard quantity is not required to be adjusted during the detection process, but the measurement is needed. The difference between the two.
Let N be the standard quantity, X be measured, and Δ be the difference between the two. Obviously, the relationship Δ=XN is established. After the shift, it becomes X=N+Δ, that is, the measured quantity is the standard quantity and deviation. Sum.
N is a standard quantity, and its error is very small. Since Δ < <N , it is possible to measure △ with a high-sensitivity deviation meter, even if the accuracy of the measurement is low, because Δ < <x , the total measurement is accurate. The degree is still high.
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