JPH03249918A - Method and device for controlling wet waste gas desulfurization equipment - Google Patents

Abstract

PURPOSE:To reduce the power consumption and to prevent a decrease in the desulfurization efficiency by providing a fuzzy-inference computing element and calculating the coefficient for distributing the demands for the flow rate of the circulating adsorbent slurry by the control for fixing the outlet SO2 concn. and desulfurization efficiency in accordance with the actual condition. CONSTITUTION:The demand for the circulating liq. adsorbent flow rate for fixing the outlet SO2 concn. is obtained by a computing element 2 based on the output signals of the computing element 1 for on-line-identifying the desulfurizing performance, inlet SO2 concn. meter 10, adsorbent pH meter 11 and outlet SO2 concn. setting device 9. The demand for the circulating flow rate for fixing the desulfurization efficiency is obtained by a computing element 3 based on the output signals of the computing element 1, inlet SO2 densitometer 10, adsorbent pH meter 11 and desulfurization efficiency setting device 14. The demands for the circulating adsorbent flow rates of the computing elements 2 and 3 are distributed by a fuzzy computing element 4 based on the output signal of the outlet SO2 densitometer 8 and desulfurization efficiency signal 15, the flow rates are added, and the demand for the circulating adsorbent flow rate is obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a control device and a control method for a wet exhaust gas desulfurization device, and in particular, a method for controlling a constant outlet SO concentration control and a constant desulfurization rate control in a ratio according to priority. The present invention relates to a control device and a control method for a wet exhaust gas desulfurization device.

[Conventional technology]

As shown in FIG. 6, the wet flue gas desulfurization equipment brings the inlet flue gas 30 into gas-liquid contact in the absorption tower 32 with an absorption liquid supplied from the absorption liquid circulation line 33 and sprayed in the tower, thereby removing SO2 in the flue gas. is fixed in the absorption liquid in the form of sulfite,
Exhaust gas is discharged from the chimney through an exhaust line 31.

The absorption liquid that has absorbed SO□ flows down from the tower section to the tank 35.

Absorbent is supplied to the tank 35 through an absorbent slurry flow rate adjustment valve 36, and the liquid whose SO2 absorption performance has been restored is supplied to the absorption tower 32 by an absorption tower circulation pump 41. A portion of the circulating liquid is discharged through a withdrawal line 34 1, and in a subsequent step the sulfites in the absorption liquid are oxidized and recovered in plaster.

A related control system for this type of wet flue gas desulfurization apparatus includes, for example, Japanese Patent Application Laid-open No. 110320/1983. In this control method, the optimum PH value multiplication signal 0 of the absorption liquid circulating in the absorption tower and the absorption tower circulation pump 4
Set the optimum operating number signal 39 of 1, and when the load is stable,
Set the number by subtracting 1 from the optimal number of operating units, add a certain increment to the above-mentioned optimal pH 4M, use this as the pH setting value, and use the simulation model 38 to determine if the desulfurization rate satisfies the target value. However, the amount of absorbent supplied and the number of pumps are controlled based on the changed set values.

However, this control method cannot support pump rotational speed control using fluid couplings, etc., and is essentially a constant desulfurization rate control, and the outlet SOz concentration fluctuates due to load changes, etc., so the outlet SOz concentration is constant. No consideration was given to the fact that it would not be possible to respond to

Furthermore, a method for controlling the outlet SO□ concentration to be constant is shown in FIG. 7 (Japanese Patent Application No. 1-265224). In Figure 7,
57 is an online desulfurization performance identifier, which performs the following calculations. The desulfurization rate η has the following causal relationship with the operating conditions.

77*=1 exp(BTU-RTUpH-RTUt
zc.

・RTU 30! ' ) ・−” (1) η=
(SO□・-5O□')/SO2''...(2) RTU
ps=f, (PH), RTUL/G=fz (
L/G) RTUsoz-r, (SCz5) ...... (3) Here, η: desulfurization rate, η*: calculated desulfurization rate, BTU: parameter, pH: absorption liquid pH value, L /G: liquid-gas ratio (
ratio of absorption liquid volume to exhaust gas volume), SO2: inlet SO□ concentration,
SO7: If the outlet SO□ concentration η-η*, then BTU=-1n (So z' / SOz' ) /
(RTLl, H・RTU 302' HRTTJL/
G) - (4) Therefore, the parameter BTU of equation (1) is identified from equation (4). The parameter signal 64, which is the output signal of the online desulfurization performance identifier 57, is filtered to remove noise by a filter 58.
is input.

In addition, in (4) 2, the inlet/outlet SO□ concentration, pH, and L/G on the right side are the inlet SO, concentration meter 51, and outlet SO
These are output signals of the z concentration meter 52, absorption liquid pH meter 53, circulation flow meter 54, and exhaust gas flow meter 55, and are measured online. The liquid-gas ratio L/G is determined from the ratio of the output signal of the circulation flowmeter 54 and the output signal of the exhaust gas flowmeter 55.

Next, the circulating flow rate demand calculator 59 performs the following calculations.

In order to maintain the outlet SO2 concentration at the set value, So2'
=S,,, ・−・・−(5) Here,
5sat: Outlet SO2 concentration set value η=η*
...... (6) Therefore, (1) ~ (
6) From the formula, RTUL/G = ffn (Ss*t /302
)/(BTU-RTUpH-RTUSOz')
...... (7) Therefore, L d = f (RTUL/G) ・Gg ・
...(8) Here, Ld: Circulation flow rate demand, G
g: Exhaust gas flow rate Note that the parameter BTU in equation (7) uses a parameter correction signal 65 obtained by passing the calculation result of equation (4) through a filter.

In this way, the absorption ? The output signal of the F1 pH meter 53, the output signal of the inlet SO□ concentration meter 51, and the output signal of the outlet S
Output signal of O2 concentration setting device 56, parameter correction signal 6
5 is used to output a circulating flow rate demand signal 66.

The subtracter 60 calculates the deviation between the circulation flow rate demand signal 66 and the output signal of the circulation flowmeter 54, and this deviation signal is processed by the controller 61. By controlling the rotation speed, the circulation flow rate is regulated.

That is, by adjusting the liquid-gas ratio L/G in response to changes in operating conditions, the outlet SOz concentration is maintained at the set value.

In other words, we have created a model that can calculate the desulfurization performance and predict the outlet SO□ concentration, and installed an online desulfurization performance identifier that can identify the model parameters so that the calculation results of this model match the outlet SO2 concentration that can be measured online. , a circulation flow rate demand calculator is provided which calculates the demand for the absorption liquid circulation amount based on the identification parameter which is this output signal, and the absorption liquid pH1 inlet SO concentration and outlet SO□ concentration which are online measurement signals. This is a control method in which the rotation speed of the absorption tower circulation pump is controlled by a fluid coupling or the like based on the above, and the circulation amount is adjusted.

[Problem to be solved by the invention]

Among the above-mentioned prior arts, constant desulfurization rate control has problems such as a small effect of reducing the power of the absorption tower circulation pump, and because the number of pumps is controlled, extremely fine control is difficult. In addition, although the above problem is solved by constant output SO□ concentration control, the total amount of inlet SO□ decreases at low load, and the desulfurization rate decreases because the outlet SO□ concentration is the same as at high load. There is a point.

An object of the present invention is to solve the problems of each control method by combining the above two control methods.

[Means for Solving the Problems] The above purpose is to provide a control device for a wet flue gas desulfurization equipment that absorbs and removes sulfur oxides in flue gas using an absorbing liquid.
a computing unit 1 that identifies desulfurization performance online based on the output signals of the meter and the absorption liquid v11 reflux meter, the output signals of the computing unit 1, the output signals of the inlet SO2 concentration meter and the absorption liquid pH meter, and the outlet A computing unit 2 calculates the demand for the absorption liquid circulation flow rate to keep the outlet SO2 concentration constant based on the output signal of the SO□ concentration setting device, and the output signal of the computing unit 1, the inlet S Oz concentration meter and the absorption liquid pH meter A calculator 3 that calculates the demand for the circulating flow rate to keep the desulfurization rate constant based on each output signal and the output signal of the desulfurization rate setting device, and the outlet SO□
a computing unit 4 which calculates the demand for the absorption liquid circulation flow rate by distributing and adding the demand for the absorption circulation flow rate, which is the output signal of the computing units 2 and 3, based on the output signal of the concentration meter and the desulfurization rate signal; and a means for operating an absorption tower circulation pump based on the output signal of the arithmetic unit 4. In a method of controlling a wet flue gas desulfurization equipment that absorbs and removes by
A process for online identification of desulfurization performance based on the inlet and outlet SOx concentrations, exhaust gas flow rate, absorption liquid pH value, and absorption liquid circulation flow rate, and output signals from the same process, inlet SOx concentration, absorption liquid pH value, and outlet SOx concentration setting. a step of calculating an absorption i circulation flow rate demand LdI for setting the outlet SOX concentration to a predetermined value based on the output signal from the identification step, the inlet SOx concentration, the absorption liquid PH value, and the desulfurization rate setting value. A step of calculating the absorption liquid circulation flow rate demand Ldz for setting the desulfurization rate to a predetermined value, and calculating the absorption liquid circulation flow rate demand Ldl based on the outlet 5Ox1 degree and the desulfurization rate.
This is achieved by a method for controlling a wet exhaust gas desulfurization apparatus, which is characterized by having a step of determining the absorption liquid circulation flow rate by adjusting and adding the distribution ratio of Ldz and Ldz.

[Function] The circulating flow rate demand calculators 2 and 3 are equipped with an online identifier, so that they can determine the outlet SO2 concentration and desulfurization rate based on the calculation model, and the outlet SO□ measured online.
Since the model parameters are automatically corrected so that the concentration and desulfurization rate always match, each circulating flow rate demand calculator can adjust the set value of the desulfurization rate and the outlet SO□
Outputs the appropriate circulation flow rate demand for the concentration setting value.

The fuzzy inference calculator comprehensively calculates the priority of constant output SO, It is possible to make judgments (fuzzy reasoning).

Therefore, when the inlet SO□ concentration is high, priority is given to constant outlet SO2 concentration control, and when the desulfurization rate is low, priority is given to constant desulfurization rate control. Flow rate demand can be output.

[Example] A specific example of the present invention is shown in FIG. In FIG. 1, 1 is an online desulfurization performance identifier, and its output signal, the identification signal 16, is the circulating flow rate demand calculator (1) 2.
and is input to the circulating flow rate demant calculator (2) 3.

The circulating flow rate demand calculator (1) 2 receives the output signal of the absorption tower pH meter 11 measured online, the output signal of the inlet SO2 concentration meter 10, the output signal of the exhaust gas flow meter 12, and the output signal of the outlet SO2 concentration setting device 9. Using the output signal, the identification signal 16 from the online identifier 1, the circulating flow rate demand signal 17
Output. (Details of the calculations in the online identifier 1 and circulating flow rate demand calculator (1) 2 have been explained in the prior art.) This circulating flow rate demand signal 17 is a demand signal for maintaining the outlet 5O2fi degree at the set value. becomes.

In addition, the circulating flow rate demant calculator (2) 3 uses the output signal of the absorption tower pH meter 11 measured online, the inlet SO2
Output signal of concentration meter 10, output signal of exhaust gas flow meter 12,
Using the output signal of the desulfurization rate setting device 14 and the identification signal 16 from the online identifier 1, a circulating flow rate demand signal 18 is output. Here, the online identifier 1 is the same calculation method as the online desulfurization performance identifier 57 in FIG. 7, which is the prior art, and the circulating flow rate demand calculator (2) 3 is the same as the circulating flow rate demand calculator 59 in FIG. has.

This circulation flow rate demand signal 18 becomes a demand signal for maintaining the desulfurization rate at a set value.

The output signal from the outlet SO, S concentration meter 8 is converted from the output signal from the inlet SO□ concentration meter 10 into a desulfurization rate signal 15 by a subtracter 6 and a divider 7, and the output signal is converted into a desulfurization rate signal 15 by an online identifier 1 and a fuzzy inference calculation. The signal is input to the device 4.

The fuzzy inference calculator 4 outputs a circulating flow rate demand signal 17 for maintaining the outlet SO concentration at the set value, a circulating flow rate demand signal 18 for maintaining the desulfurization rate at the set value, a desulfurization rate signal 15, and the outlet SO□ concentration. A total of 8 output signals are input, and a desulfurization rate signal 15 and an inlet SO□ concentration meter 1 are input.
The circulating flow demand signal 17.
18 is calculated again using fuzzy inference and output as a circulating flow rate demand signal 19.

The subtracter 21 calculates the deviation between the circulation flow rate demand signal 19 and the output signal of the circulation flowmeter 13, and the controller 5 processes this deviation signal to control the rotation speed of the absorption tower circulation pump 20. This controls the circulation flow rate.

Here, the operation of the fuzzy inference calculator 4 shown in FIG. 1 will be explained.

First, Tables 1 and 2 show examples of control rules used in fuzzy inference.

No. table In other words, the following six control rules are used.

1: If the desulfurization rate η is low, α is decreased.

2: If the desulfurization rate η is medium, set α to medium.

3: If the desulfurization rate η is high, increase α.

4: Outlet SO2 concentration SO□. If °″ is low, reduce α.

5: If outlet SO2 concentration S○ out is medium, set α to medium.

6: If the outlet SO□ concentration 302out is high, increase α.

Here, α is the circulation flow rate demand l” (L d,), which is the output signal from the circulation flow rate demand calculator (1) for maintaining the outlet SO□ concentration constant in FIG. 3
The demand for the circulating flow rate (L
d2) as shown in the following equation.

Ld-α*Ld+ ±(1-α)*Ldz...(1)
Here, Ld is the demand signal 19 of the circulating flow rate which is the output signal from the fuzzy inference calculator shown in FIG. In other words, the above six rules are such that when the desulfurization rate is low, α is made small to prioritize constant desulfurization rate control, and when the outlet SO2 concentration is high, priority is given to constant outlet SO□ concentration control.

Next, an example of the Menharshimbu function used in the antecedent part of the control rules 1 to 3 above is shown in Figure 2, and an example of the Menharshimbu function used in the antecedent part of the control rules 4 to 6 above is shown in Figure 2.
An example is shown in FIG. 3, and an example of the Menharsisop function used in the consequent part of control rules 1 to 6 is shown in FIG.

FIG. 5 shows the operation of fuzzy inference using the above control rules and member functions. For ease of understanding, as an example, the input of desulfurization rate η is 87% and the output SO2 is 87%.
Consider the case where the input of concentration 3 Q 2out is 300 ppm. From this input signal, four of the six control rules, rule l, 2.4.5, are selected, and the degree of the antecedent part (η and So, "t) of each rule is determined (in the case of rule 1 Then, the degree = 0.7).The degree of the consequent part (α) is calculated for each rule based on the degree (hunting part in the figure).Finally, 4
The MAX of the area of the consequent part (α) of the two rules is calculated, and its center of gravity (α-0,2 in FIG. 5) is calculated, and this is used as the calculation result of fuzzy inference.

In the fuzzy computing unit shown in FIG. 1, α obtained by fuzzy inference is substituted into the above-mentioned equation (1) together with Ld, , Ld2, and Ld, which is the demand for the circulating flow rate, is obtained as the output of the fuzzy computing unit 4. In the case of Figure 5, exit SO
□Ld, which is the demand for circulation flow rate for constant concentration control
, is 0.2, and the ratio of L d z, which is the demand for the circulation flow rate for constant desulfurization rate control, is 0.8. In other words, the input signal (η, SO□out) indicates that the desulfurization rate is lower than normal (bad condition) and the outlet SO□ concentration is lower than normal (good condition), so as a result of fuzzy inference, desulfurization Demand for circulating flow rate for constant rate control (L
The reasoning is that dZ) should be given priority.

In this way, fuzzy inference is performed using the desulfurization rate and outlet SO2 concentration as inputs for the antecedent part of the control rule, and the circulating flow rate demand signal is determined by two control methods (constant desulfurization rate control and constant outlet SO□ concentration control). By determining the distribution coefficient, when the desulfurization rate is lower than normal, priority is given to the circulating flow rate demand signal L d z due to constant desulfurization rate control, and when the outlet SO□ concentration is higher than normal, the output SO
□The circulating flow rate demand signal Ld based on constant concentration control is the control method that takes priority. In other words, it is possible to compensate for the shortcomings of each control method and calculate the optimal demand signal Ld for the circulating flow rate depending on the situation at the time.

[Effects of the invention] As mentioned above, each of the control methods, constant outlet SO However, according to the present invention, by providing a fuzzy inference calculator, the coefficients for distributing the demand for the circulation flow rate of the absorbent slurry due to each control method can be calculated at the present time. status (desulfurization rate and outlet SO□ concentration)
Therefore, it is possible to perform control using only the good points of both control methods.

[Brief explanation of drawings]

Fig. 1 is a system diagram of the control system of the wet exhaust gas desulfurization equipment according to the present invention, and Figs. 2, 3, and 4 are explanatory diagrams of membership functions used in the fuzzy inference calculator used in the embodiments of the present invention. , Fig. 5 is an explanatory diagram of the operation of the fuzzy inference calculator used in the actual flow of the present invention, Fig. 6 is an explanatory diagram of the prior art, and Fig. 7 is an unknown prior art system related to the application by the present inventors. times. 1... Online identifier, 2... Circulating flow rate demand calculator 1.3... Circulating flow rate demand calculator 2.4...
・Fuzzy inference calculator, 5...Controller, 6...Subtractor, 7...Divider, Digit...Exit 5Oza degree meter, 9...
・Outlet SO□ concentration setting device, 10... Inlet SO2 concentration meter, 11... Absorption tower pH meter, 12... Exhaust gas flow meter,
13... Circulating flow meter, 14... Desulfurization rate setting device, 15
...Desulfurization rate signal, 16...Desulfurization performance identification signal, 17
... Circulating flow rate demand signal Ld, 18... Circulating flow rate demand signal Ldz, 19... Circulating flow rate demand signal Ld, 20... Circulating pump, 21... Subtractor. Partition coefficient d(-) Figure 0 SO2 concentration meter logo concentration meter absorption liquid pH meter circulation flow meter gas flow meter output r'''] SO2 concentration setter online desulfurization performance identifier filter circulation flow rate demand calculator Calculator Controller Fluid Stepchild Absorption Tower Circulation Pump Parameter Signal Parameter

Claims (3)

[Claims] (1) In a control device for a wet flue gas desulfurization equipment that absorbs and removes sulfur oxides in flue gas using an absorbing liquid, each output signal of the inlet and outlet SO_2 concentration meters, flue gas flow meter, absorbing liquid pH meter, and absorbing liquid circulation flow meter A computing unit 1 identifies the desulfurization performance online based on the output signal of the computing unit 1, each output signal of the inlet SO_2 concentration meter and the absorption liquid pH meter, and the output signal of the outlet SO_2 concentration setting device. A computing unit 2 that calculates the demand for the absorption liquid circulation flow rate to keep constant the output signal of the computing unit 1 and the inlet SO
A calculator 3 that calculates the demand for the circulating flow rate to keep the desulfurization rate constant based on the output signals of the _2 concentration meter and the absorption liquid pH meter and the output signal of the desulfurization rate setting device, and the output signal of the outlet SO_2 concentration meter and the desulfurization rate. The arithmetic unit 2 based on the signal
and an arithmetic unit 4 which calculates the demand for the absorption liquid circulation flow rate by distributing and adding the demands of the absorption liquid circulation flow rate, which are the output signals of the three output signals, and an absorption tower circulation pump based on the output signal of the arithmetic unit 4. 1. A control device for a wet exhaust gas desulfurization device, characterized in that a control device for a wet exhaust gas desulfurization device is provided. (2) In claim (1), the arithmetic unit 4 is the outlet SO_2
A control device for a wet exhaust gas desulfurization device, characterized in that it is a fuzzy calculator that calculates based on concentration and desulfurization rate. (3) In a control method for a wet flue gas desulfurization equipment that absorbs and removes sulfur oxides (SO_x) in flue gas with an absorbing liquid, the inlet and outlet SO_x concentrations, the flue gas flow rate, the absorbing liquid p
The process of online identification of desulfurization performance based on the H value and absorption liquid circulation flow rate, the output signal from the same process, and the inlet SO
a step of calculating an absorbent circulation flow rate demand Ld_1 for setting the outlet SO_x concentration to a predetermined value based on the _x concentration, the absorbent pH value, and the outlet SO_x concentration setting value, and the output signal from the identification step, the inlet SO_x concentration, absorption liquid pH value,
A step of calculating an absorbent circulation flow rate demand Ld_2 for setting the desulfurization rate to a predetermined value based on the desulfurization rate setting value, and adjusting the distribution ratio of the absorbent circulation flow rates Ld_1 and Ld_2 based on the outlet SO_x concentration and the desulfurization rate. 1. A method for controlling a wet exhaust gas desulfurization apparatus, comprising the step of determining an absorption liquid circulation flow rate by adding