Online filtering method for pH value data of wet desulphurization slurry

Abstract

The invention discloses a wet desulphurization slurry pH value online data filtering method. According to the method, output values of the two pH meters and increments of the two pH meters in two continuous adjacent time intervals are compared with a fixed state value, and the states of the pH meters are judged. When the pH value is smaller than a verification process state constant value, the verification process is judged; the pH value increments in two continuous adjacent time intervals are both higher than the constant value of the flushing starting state, and it is judged that flushing starting is conducted; when the pH value is higher than a flushing process state constant value, judging as a flushing process; and judging that the flushing is finished when the increments in two continuous adjacent time intervals are both smaller than the constant value of the flushing finishing state. When any one pH meter judges the four states, directly replacing the value of the pH meter with the result output by the other pH meter; otherwise, the pH value is not treated. The finally output pH value is a mean value of the two pH meters after data filtering. The output result of the pH meter is filtered on line by judging the running state of the pH meter in real time, and the automatic control level of wet desulphurization is effectively improved.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental protection and relates to an online filtering method for pH value data of wet desulfurization slurry. Background Art

[0002] Wet flue gas desulfurization equipment is widely used in the power, steel, and chemical industries, especially large coal-fired thermal power units are equipped with limestone gypsum wet flue gas desulfurization equipment. As an important parameter for the operation and control of wet flue gas desulfurization equipment, two sets of pH meters are usually installed on the wet flue gas desulfurization absorption tower to improve the reliability of the measurement of the pH value of the desulfurization circulating slurry. In order to make the measurement results representative, the pH value of the slurry during normal operation is the average of the two pH meters. Since the wet flue gas desulfurization circulating slurry contains solid limestone, gypsum, calcium sulfite and other substances, in order to avoid the pH meter being blocked by the slurry or the pH meter electrode scaling during long-term operation, the pH meter needs to be flushed regularly. In addition, in order to ensure the long-term stability and reliability of the pH meter, the pH meter needs to be calibrated regularly with a standard solution. During the flushing and calibration process, the output of the pH meter quickly deviates from the true pH value of the circulating slurry. Therefore, the flushing and calibration of the two pH meters are usually carried out separately to keep one pH meter in normal operation. During this process, the controller manually switches the output of the pH meter to ensure that the operation control can always obtain the normal pH value of the slurry. However, the manual switching operation of the above-mentioned pH meter requires coordination between the control room operator and the on-site inspection, and reliability is difficult to ensure. Untimely or premature switching operations often occur, which has a great impact on the automatic control operation mode of wet flue gas desulfurization, which takes the pH value of the circulating slurry as the primary control indicator. Great disturbances are generated during the flushing and calibration of the pH meter, which seriously affects the system's automation control level.

[0003] In summary, the industry urgently needs an online filtering method for wet desulfurization slurry pH data to solve the current problem of rapid fluctuations in the output value of the wet desulfurization pH meter during flushing and calibration, which seriously interferes with automatic control and improves the level of wet desulfurization automation control. Summary of the invention

[0004] The technical problem to be solved by the present invention is that the flushing and calibration of the pH meter of the wet desulfurization system seriously interfere with the automatic control of the desulfurization system.

[0005] In order to achieve the above-mentioned purpose, the present invention provides an online data filtering method for pH value of wet flue gas desulfurization slurry. The online data filtering method for pH value determines the state of pH meter by comparing the pH value output by two pH meters and the increment of the pH value in two consecutive adjacent time intervals: the pH value at the current moment is less than the state value of the verification process, which is determined as the verification process; the increments in two consecutive adjacent time intervals are all higher than the state value of the flushing start state, which is determined as the flushing start; the pH value at the current moment is higher than the state value of the flushing process, which is determined as the flushing process; the increments in two consecutive adjacent time intervals are all less than the state value of the flushing end state, which is determined as the flushing end. The increment of the pH value in two consecutive time intervals is: the increment of the slurry pH value in the time interval from the delay of 2t seconds to the delay of t seconds and the increment of the slurry pH value in the time interval from the delay of t seconds to the current moment. If the state judgment result of any one of the two pH meters is the above four states, the result output by the other pH meter directly replaces the value of the pH meter; otherwise, the pH value is not processed. The final output result of the pH value participating in the automatic control of wet flue gas desulfurization is the average value of the two pH meters after data filtering. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0007] Figure 1 The present invention is a flow chart of the online filtering method of the online data of pH value of wet desulfurization slurry.

[0008] Figure 2 This is a flow chart for determining the flushing start-up status of the wet desulfurization pH meter of the present invention.

[0009] Figure 3 This is a flow chart for determining the flushing completion state of the wet desulfurization pH meter of the present invention.

[0010] Figure 4 The present invention is a flow chart of the status determination process of the wet desulfurization pH meter flushing and calibration. DETAILED DESCRIPTION

[0011] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings:

[0012] The present invention relates to an online filtering method for pH value data of wet desulfurization slurry, such as Figure 1 As shown, the method includes the following steps.

[0013] 1. Obtain the real-time online output pH value data of slurry pH meter 1 and slurry pH meter 2, which are recorded as pH1 and pH2 respectively.

[0014] 2. Set the pH delay time to 2t seconds and t seconds, where 2t and t are pH delay times in seconds, and the value of 2t is twice the value of t.

[0015] 3. Calculate the increment of pH1 and pH2 with a delay of 2t seconds and the increment of pH1 and pH2 with a delay of t seconds respectively. The increment of pH1 and pH2 with a delay of 2t seconds is: the increment of pH1 and pH2's corresponding pH value in the time period from the delay of 2t seconds to the delay of t seconds; the increment of pH1 and pH2 with a delay of t seconds is: the increment of pH1 and pH2's corresponding pH value in the time period from the delay of t seconds to the current moment.

[0016] 4. If Figure 2 , Figure 3 and Figure 4 As shown in the figure, the pH meter has four states, namely calibration process, flushing start, flushing process and flushing end. Set the calibration process state constant, denoted as pHc, and its value range is pHc=(4.0~4.8); set the flushing start state constant, denoted as ΔpHb, and its value range is ∆pHb= (-0.01~-0.002)×t; set the flushing process state constant, denoted as pHf, and its value range is pHf= (6.0~8.0); set the flushing end state constant, denoted as ΔpHe, and its value range is ∆pHe= (0.002~0.01)×t. In the formula, t is the delay time, in seconds.

[0017] 5. According to the results of step 3 and step 4, the status of the two pH meters are determined respectively: if the current pH value is less than pHc, it is determined as a calibration process; if the current pH value delay 2t seconds increment and delay t seconds increment are both less than ΔpHb, it is determined as flushing start; if the current pH value is greater than pHf, it is determined as a flushing process; if the current pH value delay 2t seconds increment and delay t seconds increment are both greater than ΔpHe, it is determined as flushing end.

[0018] 6. For any pH meter, when the state judgment result is one of the above four states, the pH value output by another pH meter will directly replace the value of the pH meter; otherwise, the output pH value will not be processed.

[0019] 7. Calculate the average pH value after filtering the output data of the two pH meters, and assign the calculation result to the pH value involved in the automatic control of wet flue gas desulfurization, that is, pH = (pH1 + pH2) / 2.

Claims

1. A method for online filtering of pH value data of wet desulfurization slurry, characterized in that: The method compares the output values ​​of two pH meters and their increments in two consecutive time intervals with the state constant value to determine whether the pH meter is in the four states of calibration process, flushing start, flushing process and flushing end; when the state determination result of any pH meter is one of the four states, the pH value result output by the other pH meter directly replaces the value of the pH meter; otherwise, the output pH value is not processed.

2. The increment of pH value in two consecutive time intervals as claimed in claim 1, characterized in that pH1 and pH2 are the increase in the corresponding pH values ​​of pH1 and pH2 during the time period from 2t seconds to t seconds. pH1 is the pH value output by pH meter 1; pH2 is the pH value output by pH meter 2; 2t and t are both pH value delay times, in seconds, and the value of 2t is twice the value of t.

3. The method for determining whether the pH meter is in the four states of calibration process, flushing start, flushing process and flushing end as claimed in claim 1, characterized in that The determination method is: the current pH value is less than the calibration process state value, which is determined as the calibration process; the current pH value delay 2t seconds increment and delay t seconds increment are both less than the flushing start state value, which is determined as flushing start; the current pH value is greater than the flushing process state value, which is determined as the flushing process; the current pH value delay 2t seconds increment and delay t seconds increment are both greater than the flushing end state value, which is determined as flushing end.

4. The state setting value according to claim 3, characterized in that: The range of the verification process state constant is 4.0~4.8; the range of the flushing start state constant is (-0.01~-0.002)×t; the range of the flushing process state constant is 6.0~8.0; the range of the flushing end state constant is (0.002~0.01)×t; where t is the delay time, in seconds.

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