JPH02180617A - Control of waste gas desulfurization apparatus - Google Patents

Abstract

PURPOSE:To make it possible to carry out predictive control agreeable to actual operation by computing desulfurization efficiency after a certain time by setting scheduled waste gas flow rate and concentration of SO2 at an inlet based on the present operation data as well as the load of a boiler. CONSTITUTION:Predictive simulation computation of desulfurization ability is carried out by a computer 27 based on scheduled waste gas flow rate and SO2 concentration at an inlet, which are set depending on scheduled load alteration obtained from present waste gas flow rate and present SO2 concentration at the inlet and the relations between the load and waste gas flow rate in the inlet and between the load and the SO2 concentration at the inlet based on the present load, as well as present operation data such as waste gas flow rate at the inlet of an absorption tower 1, pH of an absorbent solution 2, the concentration of an absorbent in the absorbent solution 2, the concentrations of SO2 at the inlet 8 and outlet 9, the number of driving circulation pumps 6, etc. Then, the computed desulfurization efficiency after (t) hours and set desulfurization efficiency are compared each other and the operation conditions at the time of small deviation between both is stored and the supply of the absorbent is predictively controlled by the stored operation conditions.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a flue gas desulfurization device that absorbs and removes SO2 from the flue gas by introducing the flue gas into an absorption tower and bringing it into contact with an absorption liquid. The present invention relates to a control method for a flue gas desulfurization device used to predict and control the future.

[Prior Art] A flue gas desulfurization device that absorbs and desulfurizes 802 in the flue gas from a boiler is designed so that the boiler flue gas is introduced through a gas inlet pipe connected at the bottom and discharged through a gas outlet pipe at the top. A liquid storage tank is installed at the bottom of the absorption tower.
The absorption liquid in the liquid storage tank is guided to the upper spray stage through a plurality of circulation pumps and circulation lines, and the absorption liquid is jetted out from the spray nozzle of the spray stage and brought into contact with the exhaust gas, thereby eliminating S02 in the exhaust gas. The gas after desulfurization was absorbed by the absorbent in the absorption liquid and discharged from the gas outlet pipe at the top of the tower.Meanwhile, the absorbent slurry that had absorbed S02 was oxidized with air in a sump tank to form gypsum slurry. There is also known an i♀-type limestone method flue gas desulfurization equipment that recovers gypsum as gypsum.

In the control method of such a wet lime plaster method smoke desulfurization equipment, predictive control of the absorbent supply source and the number of circulation pumps in operation has not been carried out so as to optimize the desulfurization rate after a period of time from the current point in time. . Conventional control methods are based on the flow rate of exhaust gas entering the absorption tower, the degree of SO□Q in the exhaust gas entering the absorption tower (inlet 3021aA degree), and the degree of S in the exhaust gas exiting from the absorption tower.
Supply of absorbent to the absorption tower from current data such as 02 concentration (outlet S O > 11 degrees) and pH 1 of the circulating absorbent
and determine the number of circulating pumps to operate.
It controls the desulfurization rate, Q degree (absorbent in the absorption liquid),
In particular, the number of operating circulation pumps is determined by the absorption tower outlet S.
This is done with the help of a worker while monitoring the O2'tH level.

[Problems to be Solved by the Invention] The conventional control method for flue gas desulfurization equipment described above does not attempt to find the optimal operating conditions by determining the desulfurization rate based on current operating data. However, since it does not perform predictive control, optimal control could not be achieved.

Therefore, the present invention can perform predictive control that matches the actual situation by determining the desulfurization rate after a certain period of time based on the current operating data and setting the planned exhaust gas flow rate and inlet SO2 concentration based on the boiler load. This is what we are trying to do.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention aims to improve the flow rate of exhaust gas entering the absorption tower, absorption liquid 1) absorbent concentration in the H1 absorption liquid, S02 concentration at the absorption tower inlet and exit, and circulation. A model formula for the desulfurization rate is set by a computer based on current operating data such as the number of pumps in operation, while the planned exhaust gas flow rate and planned inlet are calculated based on the current load, current exhaust gas flow rate, and current inlet SO2 concentration. S.O.
ziM degree is set, and the desulfurization rate after 1 hour is calculated by taking the above planned exhaust gas flow rate and planned inlet S02'a degree according to the desulfurization rate model formula, and then, the desulfurization rate after 1 hour obtained by the calculation is Compare with the set desulfurization rate, and if the deviation is large, change the calculated operating conditions and recalculate. If the deviation becomes small, the operating conditions at that time are stored and predictive control is performed according to the memorized operating conditions. method.

[Function] Set the planned exhaust gas flow rate and planned inlet 5o2s degrees from the current operating data, especially the exhaust gas flow rate at the absorption tower/inlet, the inlet SC 1 degree, the current boiler load, and the planned boiler load. Since this is used as the basis for predictive simulation calculations, it is possible to easily predict the inlet exhaust gas flow range and the inlet S02 concentration after a certain period of time, and accordingly, the number of operating circulation pumps for supplying the absorbent can be predictively controlled.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

Figure 1 does not show the outline of the flue gas desulfurization equipment used to carry out the method of the present invention.
Spray stages 3 having spray nozzles 4 are arranged in multiple stages on the upper part of the absorption tower 1 configured to store water, and a plurality of circulation lines are provided for guiding the absorption liquid 2 from the liquid storage tank to each spray stage 3. Circulation pumps 6 are installed in the middle of each of the pumps 5, and the absorption liquid 2 is guided to the spray stage 3 and sprayed from the spray nozzle 4 by operation of the plurality of circulation pumps 6. On the other hand, a gas inlet pipe 8 is connected to a position between the liquid level of the absorption liquid 2 in the absorption tower 1 and the spray stage 3 so as to introduce exhaust gas from the boiler 7, and a gas outlet pipe 9 is connected to the top of the tower. The boiler exhaust gas, which has been pressurized by a booster fan 10 installed in the middle of the gas inlet pipe 8, is brought into contact with the absorption liquid 2 spouted from the spray nozzle 4 of each spray stage 3, and the S02 in the exhaust gas is The gas is absorbed by the absorbent in the absorption liquid, and is discharged from the gas outlet pipe 9. Sα reacts with cacO3 as the absorbent and enters the absorption liquid 2 as calcium sulfite. An air blowing pipe 11 having an air blowing port 12 is disposed in the air blowing pipe 11, an air supply pipe 13 is connected to the air blowing pipe 11, and a line 1 supplies CaCo3 as an absorbent into the absorbing liquid 2.
4 is connected to the lower part of the absorption tower 1, and a liquid extraction pipe 15 is connected near the bottom of the absorption tower 1. Further, in the middle of the gas inlet pipe 8, an exhaust gas flow meter 16 for detecting the flow rate of exhaust gas,
Inlet 5O2a degree meter 17 for detecting S02 concentration in exhaust gas
and SO in the gas discharged to the gas outlet pipe 9.
An outlet SO2 concentration meter 18 for detecting 2m degrees is provided, and further,
In the circulation line 5, there is a pH π119 line for detecting the pH of the absorption liquid.
An absorbent concentration meter 20 is provided to detect the absorbent concentration in the absorbent liquid. 21 is the value from the exhaust gas flow 8116 and the inlet 80
21a Multiply the S02 concentration value from the degree meter 17 to obtain S02
22 is an adder, 23 is a flow meter that adjusts the amount of absorbent supplied by the absorbent supply line 14, and 24 is a control valve that is adjusted by the flow meter 23. , 25 is a flow m controller that adjusts the amount of absorption liquid discharged from the absorption liquid discharge pipe 15, and 26 is the flow♀ regulator 2.
This is a control valve regulated by 5.

In the present invention, in addition to the above configuration, current operation data,
Based on the planned inlet exhaust gas flow m determined in relation to the boiler's current or planned load, and the planned inlet SO2 concentration, a predictive simulation calculation of the desulfurization rate is performed to determine the desulfurization rate for one hour, and the operating conditions at that time are calculated. The calculator 27 is used to store the current operating data, and the current operating data includes the current exhaust gas flow rate from the exhaust gas flow meter 16, the current inlet SO2 concentration of the inlet SO2m degree meter 1 change, and the outlet S02 concentration.
Current outlet 5O2iIa degrees from O2 concentration meter 18, l)
In order to use the current absorbent pH from the H meter 19, the current absorbent concentration from the absorbent concentration meter 20, and the current number of circulating pumps in operation, these data are electrically connected to be input into the calculator 27. .

FIG. 2 shows an example of the internal configuration of the computer 27.
8 is the desulfurization efficiency η and absorption liquid 1) from the current operating data.
A model formula setting section 29 calculates the relationship between the boiler load and the inlet exhaust gas flow rate, the boiler load and the Create a relationship with the inlet 5 OJ 1 degree, and compare this relationship with the planned exhaust gas flow port G based on changes in the planned load.
30 is the desulfurization rate η calculated by the model equation setting unit 28 and the planned exhaust gas flow from the setting unit 29 at the above-mentioned planned exhaust gas outlet and planned inlet 302 m degrees. 31 is the calculated 1
A comparison section 33 compares the desulfurization rate η1 after time and the set desulfurization rate η8 from the desulfurization rate setting device 32, and 33 is the result of comparison in the comparison unit 31.
34 is the value of the planned absorbent (CaCa) supply amount, and 35 is the value of the planned number of operating circulation pumps.

Further, 36 is an operation instruction for storing the operating conditions at this time when the comparing section 31 compares the desulfurization rate η1 after one hour with the set desulfurization rate η8 and the deviation becomes small and η1>η. It is a storage device.

Now, the exhaust gas from the boiler 7 passes through the gas inlet pipe 8, is pressurized by the booster fan 10, and is introduced into the absorption tower 1. In the absorption tower 1, the spray stage 3 is
Since the absorption liquid 2 is ejected from the spray nozzle 4, the exhaust gas that has entered the absorption tower 1 is brought into countercurrent contact with the absorption liquid 2, and the S02 in the exhaust gas is mixed with the absorbent (CaCa) in the absorption liquid. ), the gas is discharged from the gas outlet pipe 9, and the absorption liquid is recycled. The absorbent that has absorbed S02 in the exhaust gas reacts with S02 to form absorbent liquid 2.
Here, it is oxidized by the air blown into it, and is discharged from the liquid extraction pipe 15 as a 6-blue slurry.

Inside the absorption tower 1, S02 in the exhaust gas that is sequentially introduced
The desulfurization effect is carried out by absorption of Model formula setting part 28 in Toni calculation m27
Create a simulation model of desulfurization efficiency η using
Planned exhaust gas flow rate and planned inlet 5 based on current operating data, current boiler load, and planned boiler load changes.
o2iU degree is set, a prediction simulation is calculated based on this, the desulfurization rate η after 1 hour is determined, and the desulfurization rate η is calculated based on this.
The operating conditions under which the ratio η1 is optimal are stored and predictive control is performed.

To be more specific, as shown in Fig. 2, the current operating data includes the current exhaust gas flow rate, absorbent p11, absorbent concentration in the absorbent, number of circulating pumps in operation, inlet 5 o 2 f 4 degrees, and outlet 5.
The O2iH degree is input to the model formula setting unit 28, and the desulfurization efficiency η and the absorption liquid pH are calculated according to the model formula. In other words, the desulfurization efficiency η is: Pn: Number of operating circulation pumps G
: Inlet exhaust gas flow rate Y : Inlet S02 hotness C : Absorbent concentration in absorption liquid V : Liquid reservoir tank capacity S : Absorbed SO2 amount (100-η) = a-G-Y・100 PC: Absorbent supply mount B : After-drain liquid ■ In this case, the relationship between the desulfurization efficiency and the number of circulation pumps in operation is as shown in FIG. 3, and the desulfurization efficiency improves as the number of circulation pumps in operation increases. In the figure, ■ is a curve when the exhaust gas flow m is small, ■ is a curve when the exhaust gas flow m is large, and ■ is a curve when the exhaust gas flow rate is in the middle of the above. In addition, the relationship between desulfurization efficiency and absorption liquid pH is as shown in Figure 4.
The relationship between H and the absorbent concentration in the absorbent liquid is as shown in Figure 5. Once the absorbent concentration in the absorbent liquid is determined, the absorbent liquid pH
The relationship is determined by In Figure 5, E' is when the amount of absorbed S02 is small, ■' is when the amount of absorbed S02 is intermediate, and ■
' is each curve when absorption 5o2ffl is large.

Next, the setting unit 29 sets the planned exhaust gas ωG and the planned inlet S02 concentration Y, which are the basis of the calculation in the calculation unit 30 of the prediction simulation. In this case, the setting unit 29 creates a relationship between the boiler load and the exhaust gas flow, and a relationship between the boiler load and the inlet SO□ vigor, based on the current inlet S 02 concentration, the current exhaust gas flow rate, and the current boiler load. This is set based on the planned load change. Above boiler load and exhaust gas flow d
The relationship between the ratios was found to be as shown in Figure 6 as a result of experiments, and the relationship between boiler load and inlet s02yA degree was found to be as shown in Figure 7 as a result of experiments. . The inlet exhaust gas flow rate ratio on the vertical axis in Figure 6 is based on the inlet exhaust gas flow rate at 100% boiler load (1,0
) is the ratio of the inlet exhaust gas flow rate at each load, and the inlet 5O2vA degree ratio on the vertical axis in Fig. 7 is:
Based on 3028 degrees at 100% boiler load (1,0)
This is the ratio of S 02 concentration at each load when By storing the relationships shown in FIGS. 6 and 7 in the setting section 29, it is possible to easily predict to what value the inlet exhaust gas flow rate and inlet S02 concentration will reach with respect to the scheduled boiler load. That is, by finding the relationships shown in Figures 6 and 7, if the current boiler load is 50% and the boiler load reaches 100% after 1 hour, the inlet exhaust gas flow d ratio will be 0.75. to 1.0, entrance 50
It is found that the 2m degree ratio increases from 0.77 to 1.0, and the boiler load change after this time, the inlet exhaust gas flow rate at that time, and the inlet 5O2I! It is possible to predict and measure the degree of

When the planned inlet exhaust gas flow rate and the planned inlet 5o2i degree are set based on the planned load of the boiler one hour from now, the desulfurization performance simulation unit 30 calculates the desulfurization rate η1 for one hour. Then, the comparison section 31 compares the desulfurization rate η1 after one hour obtained by the calculation with the desulfurization rate η3 set from the desulfurization rate setting device 32. If the deviation between the above-calculated desulfurization rate η1 after 1 hour and the set desulfurization rate η3 is large, especially when η1 is less than η3, an instruction to change the calculated operating conditions is issued and the planned absorbent supply stage is changed. The value 34 and the value 35 of the planned number of operating circulation pumps are input into the calculation unit 30 to recalculate the desulfurization rate η1 after one hour, and when the deviation between η1 and η3 becomes small, especially when η1>η, Operating conditions such as the planned absorbent supply amount and the planned number of circulating pumps to be operated at this time are stored in the operating instruction storage device 36, and when performing predictive control after a certain period of time, the operating conditions are stored in the operating instruction storage device 36. Control commands are sent to the flow control valve 23 on the absorbent supply line 14 and the circulation pump 6 in accordance with the operating conditions set, thereby changing the amount of absorbent supplied and the number of operating circulation pumps. This allows optimal predictive control for one hour later.

[Effects of the Invention] As described above, according to the control method of the flue gas desulfurization equipment of the present invention, based on the current operation data, the inlet exhaust gas flow ω, the inlet S Ch 18 degrees, and the current boiler load, Boiler load and inlet exhaust gas flow, boiler load and inlet S 02I
Create a relationship between the JA degree and set the planned inlet exhaust gas flow m and the planned inlet S02 concentration from this and the planned boiler load,
The desulfurization performance prediction simulation is calculated based on the set scheduled inlet exhaust gas flow rate and the scheduled inlet of 502 m degrees, and predictive control is performed one hour from the current time, so the inlet exhaust gas flow rate and inlet S02
Compared to the case of setting 'a degree, since we start from the current operating conditions, we can make predictions that actually match. Therefore, by knowing the change in the scheduled load after the specified time, it is possible to make predictions and avoid operating under optimal conditions, which is an excellent effect.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing an example of the flue gas desulfurization equipment used to carry out the method of the present invention, Fig. 2 is a block diagram showing an example of the internal configuration of a computer not shown in Fig. 1, and Fig. 3 is a diagram showing desulfurization efficiency. Figure 4 shows the relationship between desulfurization efficiency and the number of operating circulation pumps.
Figure 5 is a diagram showing the relationship between the absorption liquid DH and absorbent concentration in the absorption liquid, Figure 6 is a diagram showing the relationship between the boiler load and the exhaust gas flow rate ratio at the inlet of the absorption tower, and Figure 7 is a diagram showing the relationship between the absorption liquid DH and the absorbent concentration in the absorption liquid. Load and inlet S
It is a figure showing the relationship with O2 concentration ratio. DESCRIPTION OF SYMBOLS 1... Absorption tower, 2... Absorption liquid, 3... Spray stage, 5... Circulation line, 6... Circulation pump, 8...
Gas inlet pipe, 9... Gas outlet pipe, 14... Absorbent supply line, 16... Exhaust gas flow meter, 17... Inlet S
O2 concentration meter, 18... Outlet S 02Ia degree meter, 19.
...pH meter, 20...Absorbent concentration h1.27...Calculator, 29...Planned exhaust gas flow rate and inlet S02'a
degree setting section, 30... desulfurization performance prediction simulation calculation section, 31... comparison section, 32... desulfurization rate setting section,
36... Driving instruction storage device.

Claims (1)

[Claims] (1) Current operating data such as the inlet exhaust gas flow rate to the absorption tower, absorption liquid pH, absorbent concentration in the absorption liquid, SO_2 concentration at the absorption tower inlet and outlet, number of circulation pumps in operation, current inlet exhaust gas flow rate, current The planned inlet exhaust gas flow rate and planned inlet SO_2 are set based on the current load, the load and the inlet exhaust gas flow rate, and the relationship between the load and the inlet SO_2 concentration, and are set based on the planned load change.
A predictive simulation of the desulfurization performance is calculated using the concentration as a base, and then the desulfurization rate after t time obtained by the calculation is compared with the set desulfurization rate, and the operating conditions are determined when the deviation between the two is small. 1. A method of controlling a flue gas desulfurization equipment, which comprises storing the operating conditions and predicting and controlling the amount of absorbent supplied, etc. based on the stored operating conditions.