Online real-time calculation method for limestone slurry supply flow

Abstract

The invention discloses an online calculation method for limestone slurry supply flow, which comprises the following steps of: solving coefficients a, b and c in a function relational expression by taking the function relational expression delta Q = a + b * delta pH + c * delta SO2 as a calculation basis according to the total SO2 removal amount, the increment of a circulating slurry pH value and the total limestone slurry supply amount in a valuing time period; then calculating the total SO2 removal amount and the increment of the pH value of the circulating slurry in a control time period in real time, and calculating the total limestone slurry supply amount in the control time period in real time by utilizing the function relation expression; and finally, calculating the limestone slurry supply flow according to the total limestone slurry supply amount and the set control time period. According to the method, the limestone slurry supply flow required for controlling the pH value of the desulfurization circulating slurry is calculated in real time, the aim of accurately and rapidly controlling the pH value of the desulfurization circulating slurry can be achieved, and materials and energy consumption of a desulfurization system are saved.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental protection and relates to an online real-time calculation method for limestone slurry supply flow. Background Art

[0002] In recent years, all large coal-fired power generation units have been equipped with limestone gypsum wet desulfurization systems to remove SO2 pollutants from flue gas. 2 The traditional limestone gypsum wet flue gas desulfurization operation control mode is to fix the pH value of the circulating slurry, and the limestone slurry supply flow is controlled by PID mode. 2 This control method can fully meet the operation requirements under the condition of stable concentration. However, with the continuous advancement of the flexibility transformation of coal-fired power generation units, the operation mode of the power generation units has changed from the traditional base load to the flexible peak load regulation, and the unit load changes rapidly. Therefore, the traditional fixed circulating slurry pH value operation mode of the limestone gypsum wet desulfurization system supporting the power generation unit can no longer adapt to the current operation mode, resulting in the desulfurization circulating slurry pH value fluctuating in a large range during operation, and the desulfurization outlet SO 2 The concentration is controlled at a low level, significantly lower than the emission limit, which is very unfavorable to the energy-saving operation of the limestone gypsum wet flue gas desulfurization system. Based on the above reasons, the industry has proposed the concept of wet flue gas desulfurization variable pH value control, that is, to adjust the pH value of the circulating slurry to operate within a reasonable range and maintain the desulfurization outlet SO 2 The concentration is close to the emission limit, which can effectively reduce the energy consumption of the wet flue gas desulfurization system.

[0003] The above wet flue gas desulfurization circulating slurry variable pH value control concept controls the target pH value in real time through a model or other method, and the pH value is adjusted by changing the amount of limestone supplied to the slurry. Since limestone is slightly soluble in the desulfurization tower slurry pool, the pH value of the circulating slurry is related to the limestone content in the slurry. The correlation is affected by factors such as the concentration of impurity ions in the slurry, the slurry concentration, and the quality of limestone. The limestone content in the slurry is also related to the supply flow rate, density, circulating slurry concentration, SO 2 The relationship between the pH value of the circulating slurry and the amount of limestone slurry supplied and other factors cannot be expressed by theoretical formulas. Therefore, after the control target pH value is given, how to quickly calculate the amount of limestone slurry supplied has become the core problem of system operation control in the limestone gypsum wet flue gas desulfurization industry.

[0004] Therefore, the industry urgently needs an online real-time calculation method for limestone slurry supply flow to achieve accurate and rapid control of the pH value of the desulfurization circulating slurry and achieve SO 2 Stable and standard-compliant emissions are of great significance to energy conservation and consumption reduction in coal-fired power plants. Summary of the invention

[0005] The technical problem to be solved by the present invention is that the existing technology cannot meet the accurate and rapid control target of the desulfurization circulating slurry with variable pH value operation.

[0006] In order to achieve the above-mentioned object, the present invention provides an online real-time calculation method for limestone slurry supply flow rate, which converts the functional relationship ΔQ=a+b×ΔpH+c×ΔSO 2 In the functional relationship, ΔQ is the total amount of limestone slurry supplied in the corresponding time period; ΔpH is the increment of the pH value of the circulating slurry in the corresponding time period; ΔSO 2 SO in the corresponding time period 2 Total removal; a, b and c are coefficients. First, calculate the SO in no less than 3 time periods in real time online. 2 The total amount of removal, the increment of the pH value of the circulating slurry and the total amount of limestone slurry supplied are used to establish an equation group according to the functional relationship or use a data fitting method to solve the values ​​of coefficients a, b and c; then the SO 2 The total amount of removal and the increment of the pH value of the circulating slurry are calculated online and in real time according to the functional relationship and the values ​​of the coefficients a, b and c obtained by solving them; finally, the limestone slurry supply flow rate required for the desulfurization circulating slurry pH value control is calculated online and in real time according to the calculated total amount of limestone slurry supply in the control time period and the set control time period. The increment of the pH value of the circulating slurry in the control time period is the difference between the control target slurry pH value and the current circulating slurry pH value. During operation: the coefficients a, b and c are recalculated online and in real time at regular intervals; the limestone slurry supply flow rate required for the desulfurization circulating slurry pH value control is calculated online and in real time according to the functional relationship and the values ​​of the coefficients a, b and c obtained by the latest calculations. DETAILED DESCRIPTION

[0007] The invention relates to an online real-time calculation method for limestone slurry supply flow rate, which comprises the following steps.

[0008] 1. Set the time period for online operation data acquisition starting from the current time.

[0009] 2. Calculate the SO value within the time period 2 The total amount removed is recorded as ΔSO 2。

[0010] 3. Calculate the increment of the pH value of the circulating slurry during the sampling time period, recorded as ΔpH.

[0011] 4. Calculate the total flow rate of limestone slurry supply during the sampling time period, recorded as ΔQ.

[0012] 5. Repeat steps 1), 2), 3) and 4) for no less than 2 times to obtain no less than 3 sets of ΔSO 2 , Δ pH and ΔQ data.

[0013] 6. According to the functional relationship ΔQ=a+b×ΔpH+c×ΔSO 2 With the data set obtained in steps 1) to 5), establish a system of equations or use data fitting methods to solve the values ​​of coefficients a, b and c.

[0014] 7. Set the limestone slurry supply control time period.

[0015] 8. Calculate the SO during the control period 2 The total amount removed is recorded as ΔSO 2。

[0016] 9. Calculate the difference between the target pH value of the slurry and the current pH value of the circulating slurry, recorded as ΔpH.

[0017] 10. Calculate the total limestone slurry supply ΔQ required to be supplied during the control time period according to the functional relationship described in step 6 and the coefficients a, b and c determined in step 6.

[0018] 11. Based on the total supply amount of limestone slurry calculated in step 10 and the set control time period, the limestone slurry supply flow rate required for controlling the pH value of the desulfurization circulating slurry is finally calculated.

[0019] 12. During operation: Repeat steps 1 to 6 regularly and recalculate coefficients a, b and c; based on the latest calculated values ​​of coefficients a, b and c, calculate the limestone slurry supply flow required for desulfurization circulating slurry pH value control online in real time.

Claims

1. A method for online real-time calculation of limestone slurry supply flow, characterized in that The functional relationship ΔQ=a+b×ΔpH+c×ΔSO2 is used as the basis for calculation. In the formula, ΔQ is the total supply of limestone slurry in the corresponding time period; ΔpH is the increment of the pH value of the circulating slurry in the corresponding time period; ΔSO2 is the total amount of SO2 removed in the corresponding time period; a, b and c are coefficients. The total amount of SO2 removed, the increment of the pH value of the circulating slurry, and the total amount of limestone slurry supplied in the value-taking time period are calculated online in real time, and the coefficients a, b and c in the functional relationship are solved; then the total amount of SO2 removed and the increment of the pH value of the circulating slurry in the control time period are calculated online in real time, and the total amount of limestone slurry supplied in the control time period is calculated online in real time using the above functional relationship; finally, according to the total amount of limestone slurry supply and the set control time period, the calculation of the limestone slurry supply flow is completed online in real time.

2. The method of controlling the pH increment of the circulating slurry within a time period as claimed in claim 1, characterized in that The increment of the circulating slurry pH value is the difference between the controlled target slurry pH value and the current circulating slurry pH value.

3. The coefficients a, b and c of the functional relationship according to claim 1, characterized in that The coefficients a, b and c are recalculated periodically.

4. The timed recalculation coefficients a, b and c as claimed in claim 3, characterized in that The scheduled recalculation period is 1 minute to 1 day.

5. The method for solving the coefficients a, b and c in the functional relationship according to claim 1, characterized in that Solve by establishing a set of equations or using data fitting methods.

6. The calculation method of the total amount of SO2 removed, the increment of the pH value of the circulating slurry, and the total amount of limestone slurry supplied within the time period as claimed in claim 1, characterized in that The data are calculated for no less than 3 groups.