An Automatic Calibration Method and System for an Online Differential Pressure Type Pulp Density Meter

Abstract

The present invention relates to the technical field of automatic calibration of pulp density meters, and specifically to an online differential pressure type pulp density meter automatic calibration method and system. According to the liquid pressure formula, combined with the process characteristics of the production pulp pipeline in the concentrator being one in use and one in reserve, when the pulp pipeline is switched to standby and there is no pulp in the pipeline, the values of the upper and lower two sensors are obtained, and the drift deviation is obtained by subtracting the values of the upper and lower two sensors when the pulp pipeline was switched to standby last time. Then, the pressure compensation is corrected, and then when the pulp pipeline is switched to normal use, the automatic calibration of the pulp density is completed. The present invention can automatically complete the online calibration of the density meter. Each time the concentrator switches between the working pipeline and the standby pipeline, the system will automatically perform a calibration process, and it is applicable to all models of pressure transmitters on the market.

Description

Technical Field

[0001] The present invention relates to the technical field of automatic calibration of pulp density meters, and specifically to an online differential pressure type pulp density meter automatic calibration method and system. Background Art

[0002] The pulp density is an important judgment basis and reference index in the ore dressing process. During the ore dressing process, the pulp density needs to be frequently measured in the grinding and magnetic separation, flotation, concentrate and tailing processes of the ore dressing plant. According to the density index, the subsequent production process is adjusted. Accurately and timely online measurement of the pulp density is of crucial significance for a series of operations such as grinding and flotation.

[0003] At present, the online differential pressure type pulp density meter has been applied to a certain extent in the ore dressing plant. After calibration by comparing with the manual sampling data, the accuracy also meets the needs of general ore dressing plant process control. However, as the use time prolongs, the error of the data measured by the density meter begins to increase, and it is necessary to re-compare with the manual sampling data for calibration to correct the error, and the operation is cumbersome.

[0004] In the prior art, in the controller of the automatic zero drift correction system of the pressure transmitter, the measured pressure value is automatically subtracted from the above-mentioned memorized zero drift value, so as to achieve the purpose of automatically correcting the zero drift of the pressure transmitter. It can be realized after the transformation of the pressure transmitter body, but the user who uses the pressure transmitter cannot do it, and there is no calibration. After running for a period of time, errors occur and manual sampling is required for calibration work. Summary of the Invention

[0005] In order to solve the above technical problems, the purpose of the present invention is to provide an online differential pressure type pulp density meter automatic calibration method and system, which can automatically complete the online calibration of the density meter, will not affect the measurement accuracy of the pulp density due to the zero drift of the sensor, and ensure that the density meter always maintains a small error.

[0006] The technical solution adopted by the present invention to achieve the above purpose is: an online differential pressure type pulp density meter automatic calibration method, including the following steps:

[0007] When the pulp pipeline is switched to standby and there is no pulp in the pipeline, obtain the values of the first pressure sensor and the second pressure sensor arranged vertically from bottom to top in the vertical pipeline;

[0008] According to the values of the first pressure sensor and the second pressure sensor, and the values of the first pressure sensor and the second pressure sensor when the pulp pipeline was last switched to standby, obtain the drift deviation of the first pressure sensor and the drift deviation of the second pressure sensor;

[0009] Correct the pressure compensation according to the drift deviation of the first pressure sensor and the drift deviation of the second pressure sensor.

[0010] The pipeline is vertically arranged to make the pulp in the pipeline flow from bottom to top, and the distance between the first pressure sensor and the second pressure sensor is greater than 1 m.

[0011] The drift deviation is obtained based on the values of the two pressure sensors and the values of the two sensors when the pulp pipeline was switched to standby last time, and the pressure compensation is corrected according to the drift deviation, including the following steps:

[0012] 1) The current values of the first pressure sensor and the second pressure sensor are P′ 1 、P′ 2 ;

[0013] The current values of the two sensors are compared with the values P″ 1 、P″ 2 of the first pressure sensor and the second pressure sensor when the pulp pipeline was switched to standby last time to obtain the drift deviation ΔP′:

[0014] ΔP′ 1 = P′ 1 - P″ 1

[0015] ΔP′ 2 = P′ 2 - P″ 2

[0016] ΔP′ = ΔP′ 1 - ΔP′ 2

[0017] where ΔP′ 1 、ΔP′ 2 are the drift deviations of the first pressure sensor and the second pressure sensor respectively;

[0018] 2) Subtract the previous pressure compensation from the drift deviation ΔP′, and use the difference as the current pressure compensation to achieve the correction of the pressure compensation:

[0019] ΔP = ΔP - ΔP′

[0020] ΔP represents the pressure compensation;

[0021] 3) When the pulp pipeline is switched to normal use, the automatic calibration of the pulp density is achieved. At the same time, the values P′ 1 、P′ 2 of the first pressure sensor and the second pressure sensor in the state without pulp this time are used to replace the values P″ 1 、P″ 2 of the first pressure sensor and the second pressure sensor when the pulp pipeline was switched to standby last time for the next correction.

[0022] When the pulp pipeline is switched to normal and there is pulp in the pipeline, the pulp density is obtained according to the corrected pressure compensation and the current values of the first pressure sensor and the second pressure sensor:

[0023]

[0024] Among them, ρ 浆 is the pulp density, P 1 is the current pressure value of the first sensor, P 2 is the current pressure value of the second sensor, g is the acceleration due to gravity, and h is the distance between the first pressure sensor and the second pressure sensor.

[0025] An online differential pressure type pulp density meter automatic calibration system includes:

[0026] A first pressure sensor, arranged on a vertical pipeline;

[0027] A second pressure sensor, arranged on the vertical pipeline and above the first pressure sensor;

[0028] A CPU module, configured to obtain the drift deviation of the first pressure sensor and the drift deviation of the second pressure sensor according to the values of the first pressure sensor and the second pressure sensor and the values of the first pressure sensor and the second pressure sensor when the pulp pipeline was switched to standby last time; correct the pressure compensation according to the drift deviation of the first pressure sensor and the drift deviation of the second pressure sensor.

[0029] The CPU module is configured to obtain the pulp density according to the corrected pressure compensation and the current values of the first pressure sensor and the second pressure sensor when the pulp pipeline is switched to normal and there is pulp in the pipeline.

[0030] The present invention has the following beneficial effects and advantages:

[0031] 1. Each time the working pipeline and the standby pipeline are switched in the concentrator, the system will automatically perform a calibration process without manual intervention, ensuring the long-term measurement accuracy of the density meter;

[0032] 2. The present invention can automatically complete the online calibration of the density meter. Each time the working pipeline and the standby pipeline are switched in the concentrator, the system will automatically perform a calibration process, and is applicable to all models of pressure transmitters on the market. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a schematic structural diagram of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0034] The present invention will be further described in detail below with reference to the drawings and embodiments.

[0035] An automatic calibration method for an online differential pressure type pulp density meter. According to the liquid pressure formula, combined with the process characteristics of the production pulp pipeline in the concentrator being one in use and one in reserve, when the pulp pipeline is switched to the standby state and there is no pulp in the pipeline, the values of the upper and lower two sensors are obtained, and the drift deviation is obtained by subtracting the values of the upper and lower two sensors when the pulp pipeline was switched to the standby state last time. Then, the pressure compensation is corrected. And then when the pulp pipeline is switched to normal use, the automatic calibration of the pulp density is completed.

[0036] The specific liquid pressure formula is as follows:

[0037]

[0038] Among them, ρ 浆 is the pulp density kg / m 3 , P 1 is the absolute pressure value of the lower sensor Pa, P 2 is the absolute pressure value of the upper sensor Pa, g is the gravitational acceleration N / kg, and h is the distance between the two sensors, with the unit m.

[0039] The fact that the pulp pipeline is one in use and one in reserve is determined by the on-site process of the concentrator. Because of reasons such as maintenance and faults during production, the pipelines of key processes are all designed in a mode where one is in normal use and the other is in reserve, ensuring the continuity of production.

[0040] The so-called pressure compensation means that in the on-site production of the concentrator, the pulp in the pipeline is flowing rather than static. Coupled with factors such as the pulp temperature being higher than the ambient temperature and the frictional force generated by the non-smooth inner wall of the pipeline, the pulp density calculated by the liquid pressure formula (1) has errors. In order to eliminate the errors, the liquid pressure formula becomes:

[0041]

[0042] Among them, ΔP is the pressure compensation, with the unit Pa.

[0043] For the so-called pressure compensation, when there is pulp in the pipeline, after manually analyzing the pulp concentration and comparing it with the density meter value, it is calculated and determined. Since after the upper and lower two sensors have been used for a period of time, the values when there is no pulp in the pipeline are not zero, the pressure compensation needs to be corrected.

[0044] The correction of the pressure compensation specifically includes the following steps:

[0045] 1) When the pulp pipeline is switched to the standby state and there is no pulp in the pipeline, obtain the values P′ 2 , P′ 1 of the upper and lower two sensors at this time;

[0046] 2) Subtract the values P″ of the upper and lower sensors when the pulp pipeline was switched to standby last time 2 and P″ 1 to obtain the drift deviation ΔP′:

[0047] ΔP′ 1 = P′ 1 - P″ 1 (3)

[0048] ΔP′ 2 = P′ 2 - P″ 2 (4)

[0049] ΔP′ = ΔP′ 1 - ΔP′ 2 (5)

[0050] 3) Calibrate the pressure compensation:

[0051] ΔP = ΔP - ΔP′ (6)

[0052] 4) When the pulp pipeline is switched to normal use, the automatic calibration of the pulp density is completed. At the same time, use the values P′ 2 and P′ 1 of the upper and lower sensors in the state without pulp this time to 2 replace the values P″ 1 of the upper and lower sensors when the pulp pipeline was switched to standby last time, so as to facilitate the next calibration, that is:

[0053] P″ 1 = P′ 1 (7)

[0054] P″ 2 = P′ 2 (8)

[0055] As Figure 1 shown, an automatic calibration system for an on-line differential pressure type pulp density meter, characterized by comprising a CPU module 1, an analog input / output module 2, a signal cable 3, an upper sensor 4, a lower sensor 5, and a pulp pipeline 6.

[0056] The CPU module 1 is used to calculate the pulp concentration and correct the pressure compensation; the analog input / output module 2 is used to receive the data of the upper and lower sensors; the signal cable 3 is used to connect the sensors and the analog input / output module; the upper sensor 4 is used to obtain the pressure value at the upper installation position; the lower sensor 5 is used to obtain the pressure value at the lower installation position; when the pulp pipeline 6 is in normal use, there is pulp flowing from bottom to top inside, and when it is in standby state, there is no pulp inside the pipeline and it is directly connected to the atmosphere.

[0057] Experimental Example 1:

[0058] An on-line differential pressure type pulp density meter was installed in a concentrator. The CPU module model is FX3UC-16MR / D-T; the analog input / output module model is FX2N-5A; the signal cable model is RVVP shielded cable with 2 cores and 1.0 square, which is used to transmit 4-20 mA signals; the upper sensor model is WIA-PA-SWPU1000D, which is used to measure the absolute pressure in the pipeline at the installation position; the lower sensor model is WIA-PA-SWPU1000D, which is used to measure the absolute pressure in the pipeline at the installation position; the distance between the upper and lower sensors is 3.3 m; when initially installed, both the upper and lower sensors were zero-adjusted, that is:

[0059] h = 3.3 (9)

[0060] P″ 1 = 0 (10)

[0061] P″ 2 = 0 (11)

[0062] After the pipeline was switched to the working state, through manual sampling and comparison, the pressure compensation was determined, that is:

[0063] ΔP = 3000 (12)

[0064] At a certain moment, the values of the upper and lower sensors were obtained as follows:

[0065] P 1 = 1015100 (13)

[0066] P 2 = 963558 (14)

[0067] Taking g = 9.8, the calculated pulp density result is:

[0068]

[0069] At this time, the pulp density is 1501 kg / m 3 .

[0070] After the pipeline was switched to the standby state, the values of the upper and lower sensors were obtained as follows:

[0071] P′ 1 = -1800 (16)

[0072] P′ 2 = -900 (17)

[0073] The drift deviation ΔP′ was obtained:

[0074] ΔP′1 = P' 1 - P'' 1 = -1800 (18)

[0075] ΔP' 2 = P' 2 - P'' 2 = -900 (19)

[0076] ΔP' = ΔP' 1 - ΔP' 2 = -1800 - (-900) = -900 (20)

[0077] Calibrate the pressure compensation:

[0078] ΔP = ΔP - ΔP' = 3000 - (-900) = 3900 (21)

[0079] After the pipeline is switched back to the normal use state, the upper and lower sensor values obtained are:

[0080] P 1 = 984954 (22)

[0081] P 2 = 936591 (23)

[0082] The calculated result of the pulp density after calibrating the pressure compensation is:

[0083]

[0084] The result of the pulp density without calibrating the pressure compensation is:

[0085]

[0086] There is an error of 28 kg / m 3 between them.

[0087] After on-site verification, the calculated pulp density after calibrating the pressure compensation is closer to the actual value.

[0088] The above are only the preferred embodiments of the present invention and are not intended to limit the idea of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An automatic calibration method for an online differential pressure type pulp density meter, characterized in that, it includes the following steps: When the pulp pipeline is switched to standby and there is no pulp in the pipeline, obtain the values of the first pressure sensor and the second pressure sensor arranged vertically from bottom to top in the vertical pipeline; According to the values of the first pressure sensor and the second pressure sensor, and the values of the first pressure sensor and the second pressure sensor when the pulp pipeline was last switched to standby, obtain the drift deviation of the first pressure sensor and the drift deviation of the second pressure sensor; 1) The current values of the first pressure sensor and the second pressure sensor are P′ 1 and P′ 2 respectively; Compare the current values of the two sensors with the values P″ 1 and P″ 2 of the first pressure sensor and the second pressure sensor when the pulp pipeline was switched to standby last time, to obtain the drift deviation ΔP′: ΔP′ 1 = P′ 1 - P″ 1 ΔP′ 2 = P′ 2 - P″ 2 ΔP′ = ΔP′ 1 -ΔP′ 2 where, ΔP′ 1 and ΔP′ 2 are the drift deviations of the first pressure sensor and the second pressure sensor, respectively; 2) Subtract the previous pressure compensation from the drift deviation ΔP′, and use the difference as the current pressure compensation to achieve the correction of the pressure compensation: ΔP = ΔP - ΔP′ ΔP represents the pressure compensation; 3) When the pulp pipeline switches to normal use, automatic calibration of the pulp density is achieved. At the same time, the values P' 1 and P' 2 of the first pressure sensor and the second pressure sensor in the state without pulp this time are respectively used to replace the values P″ 1 and P″ 2 of the first pressure sensor and the second pressure sensor when the pulp pipeline switched to standby last time, so as to facilitate the next calibration; Correct the pressure compensation according to the drift deviation of the first pressure sensor and the drift deviation of the second pressure sensor.

2. The automatic calibration method for an online differential pressure type pulp density meter according to claim 1, characterized in that, the pipeline is vertically arranged so that the pulp in the pipeline flows from bottom to top, and the distance between the first pressure sensor and the second pressure sensor is greater than 1 m.

3. The automatic calibration method for an online differential pressure type pulp density meter according to claim 1, characterized in that, When the pulp pipeline is switched to normal and there is pulp in the pipeline, obtain the pulp density according to the corrected pressure compensation and the current values of the first pressure sensor and the second pressure sensor; Among them, ρ 浆 is the pulp density, P 1 is the current pressure value of the first sensor, P 2 is the current pressure value of the second sensor, g is the acceleration due to gravity, and h is the distance between the first pressure sensor and the second pressure sensor.

4. The calibration system for the automatic calibration method for an online differential pressure type pulp density meter according to claim 1, characterized in that, it includes: a first pressure sensor arranged on the vertical pipeline; a second pressure sensor arranged on the vertical pipeline and above the first pressure sensor; a CPU module for obtaining the drift deviation of the first pressure sensor and the drift deviation of the second pressure sensor according to the values of the first pressure sensor and the second pressure sensor, and the values of the first pressure sensor and the second pressure sensor when the pulp pipeline was last switched to standby; correcting the pressure compensation according to the drift deviation of the first pressure sensor and the drift deviation of the second pressure sensor.

5. The calibration system for the automatic calibration method for an online differential pressure type pulp density meter according to claim 4, characterized in that, the CPU module is used to obtain the pulp density according to the corrected pressure compensation and the current values of the first pressure sensor and the second pressure sensor when the pulp pipeline is switched to normal and there is pulp in the pipeline.

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