Coal dust concentration on-line calibration system and method for on-line detecting coal dust concentration

Abstract

The online coal powder concentration calibration system of the present invention includes: a coal mill feed rate detector, a primary air flow rate detector, a data acquisition and processing unit, and an electrostatic sensor. A coal inlet pipe and an air inlet pipe are installed at the inlet of the coal mill. The coal feeder delivers coal to the coal inlet pipe, and the primary air blower delivers air to the air inlet pipe. A coal outlet pipe is installed at the outlet of the coal mill. The coal mill feed rate detector is installed on the coal feeder, and the primary air flow rate detector is installed on the air inlet pipe. An electrostatic sensor is installed on the wall of each coal outlet pipe. The output terminals of each electrostatic sensor, the coal mill feed rate detector, and the primary air flow rate detector are connected to the input terminal of the data acquisition and processing unit. The data acquisition and processing unit calculates and outputs the coal powder concentration of each coal outlet pipe. The method of the present invention for online detection of coal powder concentration in the coal outlet pipe includes: acquiring the original signal, determining the total coal powder quantity, and the data acquisition and processing unit calculating the coal powder concentration of each coal outlet pipe.

Description

Technical Field

[0001] This invention relates to the field of thermal power generation technology, specifically to an online calibration system for pulverized coal concentration and a method for online detection of pulverized coal concentration in a boiler pulverizing system. Background Technology

[0002] In thermal power plants, the combustion efficiency of boilers is closely related to the uniformity of pulverized coal distribution. Currently, large thermal power units generally adopt medium-speed coal mill direct-fired pulverizing systems, with one coal mill typically corresponding to 4-6 pulverized coal pipelines to deliver pulverized coal into the burner.

[0003] Currently, the measurement of pulverized coal concentration in pulverized coal pipelines is in a "black box" state. Existing online pulverized coal measurement devices (such as microwave methods and electrostatic methods) have significant limitations in practical applications. Due to variations in the composition, moisture, fineness, and type of pulverized coal, these measuring devices have large absolute errors, and these errors drift with changes in operating conditions. This makes it impossible for operators to accurately determine the true amount of pulverized coal in each pipeline, hindering combustion adjustments and easily leading to problems such as unstable combustion, increased NOx emissions, or localized coking on water-cooled walls.

[0004] Chinese patent CN215768146U discloses a coal powder concentration measurement and air-powder flow rate adjustment device based on charge induction analysis. It includes a measurement and control host, electrostatic sensors, a data acquisition card, a resistance regulating valve, and an actuator. The electrostatic sensors are arranged in pairs, parallel to each other, with one end placed upstream and downstream of the primary air-powder duct at a distance L. The other end of each electrostatic sensor is connected to the measurement and control host via the data acquisition card. The resistance regulating valve is connected to the actuator, and the actuator is connected to the measurement and control host. This invention offers the advantages of stable and high-precision air-powder velocity measurement.

[0005] Chinese patent CN104316720A discloses an adaptive flow velocity change-based charge-inductive online dust detection device and method, comprising a signal measurement module and a calculation module. The signal measurement module includes several metal probes and DC signal measurement circuits and AC signal measurement circuits connected to the metal probes, used to collect DC and AC signals generated during dust flow and transmit them to the calculation module. The calculation module is used to select the DC and AC signals, perform cross-correlation operations on multiple AC signals, compensate the signals based on the selection results and cross-correlation results, and output the results after calibration. Using this invention, all information contained in the original signal can be fully utilized, making the measurement of particulate matter flow rate and concentration unaffected by flow velocity changes, thereby expanding the application scope of particulate matter electrostatic measurement technology. Summary of the Invention

[0006] This invention aims to overcome the shortcomings of existing technologies and solve the problems of large absolute errors and inaccurate measurements caused by changes in coal quality in existing coal powder concentration measuring devices. It provides an online calibration system for coal powder concentration and a method for online detection of coal powder concentration.

[0007] The core idea of ​​this invention is to take advantage of the fact that the physical properties (composition, moisture, etc.) of the coal powder in each powder pipe at the outlet of the same coal mill are almost the same. The relative proportion of coal powder concentration in each pipe is obtained by electrostatic measurement technology. Then, combined with the total primary air volume and coal feed rate at the inlet of the coal mill, the absolute coal powder concentration of each pipe is deduced.

[0008] To achieve the purpose of this invention, the following technical solution is adopted:

[0009] This invention discloses an online coal powder concentration calibration system, comprising: a coal mill feed rate detector, a primary air flow rate detector, a data acquisition and processing unit, and an electrostatic sensor. A coal inlet pipe and an air inlet pipe are installed at the inlet of the coal mill. The coal feeder delivers coal to the coal inlet pipe, and the primary air blower delivers air to the air inlet pipe. At least four coal outlet pipes are installed at the outlet of the coal mill. The coal mill feed rate detector is installed on the coal feeder, and the primary air flow rate detector is installed on the air inlet pipe. An electrostatic sensor is installed on the wall of each of the above-mentioned coal outlet pipes. The output terminals of each electrostatic sensor, the coal mill feed rate detector, and the primary air flow rate detector are respectively connected to the input terminal of the data acquisition and processing unit. The data acquisition and processing unit calculates and outputs the coal powder concentration of the above-mentioned coal outlet pipes.

[0010] The present invention provides an online coal powder concentration calibration system, wherein: there are 4 to 6 coal inlet pipes, which are evenly distributed along the circumference of the coal mill.

[0011] The present invention discloses an online coal powder concentration calibration system, wherein: an air damper is also installed on the coal outlet pipe upstream of the electrostatic sensor, and the output end of the data acquisition and processing unit is connected to the air damper of the corresponding coal outlet pipe.

[0012] The present invention provides a method for online detection of coal powder concentration in a coal inlet pipe using a coal powder concentration online calibration system, comprising the following steps:

[0013] (a) Acquisition of raw signals:

[0014] The data acquisition and processing unit obtains the raw measurement values ​​of each coal outlet pipe from the aforementioned electrostatic sensors, which are respectively... The data acquisition and processing unit normalizes the data and calculates the total electrostatic signal. :

[0015]

[0016] Then calculate the pulverized coal content ratio coefficient for each coal outlet pipe. :

[0017] at this time, ;

[0018] (II) Determination of total pulverized coal quantity:

[0019] The data acquisition and processing unit obtains the total amount of pulverized coal at the inlet of the coal mill from the aforementioned coal mill feed rate detector. (kg / h) Total pulverized coal output at the coal mill outlet (kg / h) is calculated using the following formula:

[0020] in, For the separator efficiency of the coal mill;

[0021] The data acquisition and processing unit obtains the primary air volume at the inlet of the coal mill from the aforementioned primary air flow detector. (m) 3 / h);

[0022] (III) Data acquisition and processing unit for coal powder concentration at each coal outlet pipe Calculation: For the i-th coal outlet pipe, its actual pulverized coal flow rate (kg / h) is:

[0023] The coal powder concentration of the coal outlet pipe is then... (kg / m 3 ):

[0024]

[0025] Where n is the number of coal outlet pipes, the data acquisition and processing unit calculates and outputs the coal powder concentration of each coal outlet pipe. .

[0026] The present invention relates to a method for online detection of pulverized coal concentration in a coal feed pipe using an online pulverized coal concentration calibration system, wherein: the separator efficiency of the coal mill... The value ranges from 95% to 99%.

[0027] The present invention relates to a method for online detection of coal powder concentration in a coal inlet pipe using a coal powder concentration online calibration system, wherein: the coal powder concentration output by the data acquisition and processing unit for each coal outlet pipe is... It controls the opening degree of the damper.

[0028] The online coal powder concentration calibration system and online coal powder concentration detection method of the present invention have the following advantages compared with the prior art:

[0029] 1. Eliminate the influence of coal quality:

[0030] By utilizing the principle of "same machine, same quality" and calculating relative proportions, the interference of changes in coal type, moisture and ash content on measurement accuracy is effectively eliminated, solving the problem of large absolute error in traditional electrostatic sensors.

[0031] 2. Achieve precise allocation:

[0032] It can accurately calculate the absolute amount of pulverized coal produced by each coal outlet pipe, providing reliable data support for operators to make air-coal balance adjustments, which helps to reduce the carbon content of fly ash, reduce NOx emissions, and prevent boiler coking.

[0033] 3. Multi-source data fusion:

[0034] By deeply integrating local measurement signals (electrostatics) with DCS system signals (coal feed rate, air volume), a measurement effect of 1+1>2 is achieved. This is an innovative application of soft measurement technology in the thermal power field. This method can greatly improve the accuracy of the feedback signal to the damper, and further improve the control accuracy of the entire boiler. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the connection relationship of the online coal powder concentration calibration system of the present invention.

[0036] exist Figure 1 In the middle; No. 1 is the coal feeder; No. 2 is the primary air fan; No. 3 is the data acquisition and processing unit; No. 4 is the coal mill; No. 5 is the coal inlet pipe; No. 6 is the coal mill feed rate detector; No. 7 is the air inlet pipe; No. 8 is the primary air flow detector; No. 9 is the electrostatic sensor; No. 10 is the coal outlet pipe; No. 11 is the air damper. Detailed Implementation

[0037] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0038] like Figure 1 As shown, this embodiment takes a coal mill as an example, and the outlet of the coal mill is connected to 4 coal outlet pipes 10.

[0039] The online coal powder concentration calibration system of the present invention includes: a coal mill feed rate detector 6, a primary air flow rate detector 8, a data acquisition and processing unit 3, and an electrostatic sensor 9. A coal inlet pipe 5 and an air inlet pipe 7 are respectively installed at the inlet of the coal mill 4. The coal feeder 1 feeds coal into the coal inlet pipe 5, and the primary air fan 2 feeds air into the air inlet pipe 7. Four coal outlet pipes 10 are evenly distributed along the circumference of the coal mill 4 at the outlet of the coal mill 4. The coal mill feed rate detector 6 is installed on the coal feeder 1, and the primary air flow rate detector 8 is installed on the air inlet pipe 7. An electrostatic sensor 9 is installed on the pipe wall of each of the above-mentioned coal outlet pipes 10. The output terminals of each of the above-mentioned electrostatic sensor 9, coal mill feed rate detector 6, and primary air flow rate detector 8 are respectively connected to the input terminal of the data acquisition and processing unit 3. The data acquisition and processing unit 3 calculates the coal powder concentration of the above-mentioned coal inlet pipe 10 and outputs it.

[0040] An air damper 11 is also installed on the coal outlet pipe 10 upstream of the electrostatic sensor 9, and the output terminal of the data acquisition and processing unit 3 is connected to the air damper 11 of the corresponding coal outlet pipe 10.

[0041] use Figure 1 The online coal powder concentration calibration system shown includes the following steps for online detection of coal powder concentration:

[0042] (a) Acquisition of raw signals:

[0043] The data acquisition and processing unit 3 obtains the raw measurement values ​​of each coal outlet pipe 10 from the electrostatic sensor 9, which are respectively The data acquisition and processing unit 3 normalizes the data and calculates the total electrostatic signal. :

[0044]

[0045] Then calculate the pulverized coal content ratio coefficient for each coal outlet pipe 10. :

[0046] at this time, ;

[0047] (II) Determination of total pulverized coal quantity:

[0048] Data acquisition and processing unit 3 obtains the total amount of pulverized coal at the inlet of coal mill 4 from the coal feed rate detector 6 of the aforementioned coal mill 4. (kg / h), total pulverized coal output at the outlet of coal mill 4 (kg / h) is calculated using the following formula (4):

[0049] in, The separator efficiency of coal mill 4 depends on the specific conditions of the coal mill. The value is 98%; the data acquisition and processing unit 3 obtains the primary air volume at the inlet of the coal mill 4 from the primary air flow detector 8. (m) 3 / h);

[0050] (III) Data acquisition and processing unit 3 collects coal powder concentration data from each coal outlet pipe 10. Calculation: For the i-th coal outlet pipe 10, its actual pulverized coal flow rate (kg / h) is:

[0051] The coal powder concentration of the coal outlet pipe 10 is then... (kg / m 3 ):

[0052]

[0053] Where n is the number of coal outlet pipes 10, in this case n=4. The data acquisition and processing unit 3 calculates and outputs the coal powder concentration of each coal outlet pipe 10. .

[0054] The calculated pulverized coal concentration of the four coal outlet pipes 10 The data is displayed in real time on the screen of the data acquisition and processing unit 3 and serves as a feedback signal for the automatic adjustment of the damper 11.

[0055] Through the above steps, even if the type of coal is changed, it will only cause the basic signal of the electrostatic sensor 9 to be amplified or reduced overall. The data acquisition and processing unit 3 will recalculate the scaling factor based on the signal detected by the electrostatic sensor 9 in real time. Combining total coal volume and primary air volume Afterwards, the calculated coal powder concentration is still used to maintain the accuracy of the coal output from the coal outlet pipe 10 by controlling the damper 11.

[0056] Compared with Chinese Patent CN215768146U, the online calibration system and method for online detection of pulverized coal concentration in this invention rely solely on electrostatic sensors for velocity and concentration measurements, failing to address the impact of coal quality variations on measurement accuracy. This application, by constructing a soft measurement model based on "proportional allocation + total mass balance," achieves online calibration of pulverized coal concentration for the first time, significantly improving measurement accuracy and adaptability to different operating conditions.

[0057] Compared with Chinese Patent CN104316720A, the online calibration system and method for online detection of pulverized coal concentration of this invention have achieved a technological breakthrough: while Chinese Patent CN104316720A can measure concentration distribution, its system is complex, costly, and poses radiation risks. This application adopts an electrostatic sensing + data fusion approach, achieving a simplified system, safety and environmental protection, and strong engineering applicability while ensuring measurement accuracy.

[0058] This application represents a significant technological advancement and inventiveness compared to Chinese Patent CN215768146U and Chinese Patent CN101430269A, primarily in the shift from "direct measurement" to "soft measurement calibration" and from "single signal" to "multi-source fusion." These innovations were not disclosed or implied by the aforementioned patents and thus possess inventiveness in the sense of patent law.

[0059] The technical content of the present invention has been described above, but the scope of protection of the present invention is not limited to the described content. Within the scope of knowledge possessed by those skilled in the art, various changes can be made to the technical content of the present invention without departing from the spirit of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A coal concentration on-line calibration system comprising: The coal mill has a coal feed rate detector (6), a primary air flow detector (8), a data acquisition and processing unit (3), and an electrostatic sensor (9). A coal inlet pipe (5) and an air inlet pipe (7) are installed at the inlet of the coal mill (4). The coal feeder (1) feeds coal into the coal inlet pipe (5), and the primary air blower (2) feeds air into the air inlet pipe (7). At least four coal outlet pipes (10) are installed at the outlet of the coal mill (4). The coal mill feed rate detector (6) is installed on the coal feeder (1), the primary air flow detector (8) is installed on the air inlet pipe (7), and an electrostatic sensor (9) is installed on the pipe wall of each of the above coal outlet pipes (10). The output terminals of each of the above electrostatic sensor (9), the coal feed rate detector (6), and the primary air flow detector (8) are connected to the input terminal of the data acquisition and processing unit (3). The data acquisition and processing unit (3) calculates the coal powder concentration of the above coal outlet pipes (10) and outputs it.

2. The on-line coal concentration calibration system of claim 1, wherein: There are 4 to 6 coal outlet pipes (10), which are evenly distributed along the circumference of the coal mill (4).

3. The online coal powder concentration calibration system as described in claim 2, characterized in that: An air damper (11) is also installed on the coal outlet pipe (10) upstream of the electrostatic sensor (9), and the output end of the data acquisition and processing unit (3) is connected to the air damper (11) of the corresponding coal outlet pipe (10).

4. A method for online detection of pulverized coal concentration using the pulverized coal concentration online calibration system as described in claim 3, characterized in that: It includes the following steps: (a) Acquisition of raw signals: The data acquisition and processing unit (3) obtains the original measurement values ​​of each coal outlet pipe (10) from the electrostatic sensor (9) mentioned above. These values ​​are respectively ; The data acquisition and processing unit (3) normalizes the data and calculates the total electrostatic signal. : ， Then calculate the pulverized coal ratio coefficient for each coal outlet pipe (10). : ， at this time, ; (II) Determination of total pulverized coal quantity: The data acquisition and processing unit (3) obtains the total amount of pulverized coal at the inlet of the coal mill (4) from the coal feed rate detector (6) of the coal mill. (kg / h), total pulverized coal output at the outlet of the coal mill (4) (kg / h) is calculated using the following formula (4): ， in, The separator efficiency of the coal mill (4); The data acquisition and processing unit (3) obtains the primary air volume at the inlet of the coal mill (4) from the primary air flow detector (8). (m) 3 / h); (iii) Data acquisition and processing unit (3) for coal powder concentration of each coal outlet pipe (10) Calculation: For the i-th coal outlet pipe (10), its actual pulverized coal flow rate (kg / h) is: ， The coal powder concentration of the coal outlet pipe (10) is then... (kg / m 3 ): ， Where n is the number of coal outlet pipes (10), and the data acquisition and processing unit (3) calculates and outputs the coal powder concentration of each coal outlet pipe (10). .

5. The method as described in claim 4, characterized in that: The separator efficiency of the coal mill (4) The value ranges from 95% to 99%.

6. The method as described in claim 5, characterized in that: The data acquisition and processing unit (3) outputs the coal powder concentration of each coal outlet pipe (10). It controls the opening degree of the damper (11).

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