JPH0714454B2 - Control method of flue gas desulfurization equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a flue gas desulfurization device for absorbing and removing SO ₂ in exhaust gas by putting the exhaust gas into an absorption tower and contacting with the absorbing liquid. The present invention relates to a control method of a flue gas desulfurization device used for predicting and controlling after a certain period of time.

[Prior Art] As a flue gas desulfurization device that absorbs SO ₂ in exhaust gas from a boiler and desulfurizes it, the exhaust gas of the boiler, which has flowed in through a gas inlet pipe connected to the lower part, is discharged through a gas outlet pipe at the top. A liquid storage tank is installed in the lower part of the absorption tower, and 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 from the spray nozzle of the spray stage. by so as to contact with the exhaust gas, the gas after desulfurization by absorbing the sO ₂ in the flue gas in the absorption agent in the absorbing fluid is discharged from the top of the gas outlet pipe, while the absorbent that has absorbed sO ₂ There is known a flue gas desulfurization apparatus of the wet lime gypsum method in which gypsum slurry is obtained by oxidizing the slurry with air in a liquid storage tank to obtain gypsum slurry.

In such a method for controlling a wet lime gypsum flue gas desulfurization device, predictive control of the supply amount of the absorbent and the number of circulating pumps has been conventionally performed so that the desulfurization rate after a certain time from the present time becomes optimum. Absent. Conventional control method, exhaust gas flow rate entering the absorption tower, SO ₂ concentration (the inlet SO ₂ concentration) in the exhaust gas entering the absorption tower, SO ₂ concentration in the exhaust gas leaving the absorption tower (outlet SO ₂ concentration), is circulated The desulfurization rate and the concentration of absorbent in the absorbent are controlled by adjusting the amount of absorbent supplied to the absorption tower based on the current data such as the pH of the absorbent, etc., and by determining the number of operating circulating pumps. Especially, the number of operating circulation pumps is determined by the operator's intuition while observing the SO ₂ concentration at the outlet of the absorption tower.

[Problems to be Solved by the Invention] In the above conventional control method for a flue gas desulfurization device, not only is the desulfurization rate calculated based on the current operation data to find an optimum operating condition, Since it is not a predictive control, the optimum control could not be performed.

Therefore, the present invention is based on the present operation data, and the predicted exhaust gas flow rate and the inlet SO ₂ concentration are set from the load of the boiler to obtain the desulfurization rate after a certain time, and the predictive control actually matched. It is intended to be possible.

[Means for Solving the Problems] In order to solve the above problems, the present invention is directed to a flow rate of exhaust gas entering an absorption tower, a pH of an absorbent, an absorbent concentration in the absorbent, a SO ₂ concentration at an inlet and an outlet of the absorbent, a circulation. A model formula of desulfurization rate is set by a computer based on the current operation data such as the number of pumps operating, while the current load, the current exhaust gas flow rate, the current inlet
Relationship between load and exhaust gas flow rate based on SO ₂ concentration, load and inlet S
O ₂ irradiation to planned exhaust gas flow to the load change events from the present time to make a concentration of relationship until after t time, scheduled inlet SO ₂ set concentration, the expected exhaust gas flow rate in accordance with the desulfurization rate model formula will inlet SO ₂ The concentration is taken in to calculate the desulfurization rate after t hours, and then the desulfurization rate after t hours obtained by the calculation is compared with the set desulfurization rate. If the deviation is large, the operating conditions for calculation are changed to calculate. Again, when the deviation becomes small, the operating condition at that time is stored, and the predictive control is performed according to the stored operating condition.

[Operation] Of the current operation data, set the exhaust gas flow rate at the inlet of the absorption tower, the SO ₂ concentration at the inlet, the current boiler load, and the planned exhaust gas flow rate and the planned SO ₂ concentration from the planned boiler load. , This is the basis of the predictive simulation calculation, so the inlet exhaust gas flow rate after t hours from the present time, the inlet
The SO ₂ concentration can be easily predicted, and the absorbent supply amount and the number of circulating pumps can be predicted and controlled accordingly.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an outline of a flue gas desulfurization apparatus used for carrying out the method of the present invention.
A plurality of spray stages 3 each having a spray nozzle 4 are arranged on the upper part of the absorption tower 1 configured to store the liquid, and a plurality of circulation lines for guiding the absorption liquid 2 of the liquid storage tank to the spray stages 3 of the respective stages. A circulation pump 6 is installed in the middle of each of 5 so that the absorption liquid 2 is guided to the spray stage 3 and ejected from the spray nozzle 4 by the operation of the plurality of circulation pumps 6. On the other hand, a gas inlet pipe 8 is connected between the liquid surface of the absorbing liquid 2 and the spray stage 3 in the absorption tower 1 so as to introduce the exhaust gas from the boiler 7, and a gas outlet pipe 9 is provided at the top of the tower. The boiler exhaust gas pressurized by a pressure booster 10 installed in the middle of the gas inlet pipe 8 is brought into contact with the absorbing liquid 2 ejected from the spray nozzle 4 of each spray stage 3, and SO ₂ in the exhaust gas is discharged. Is absorbed by the absorbent in the absorbent, the gas is discharged from the gas outlet pipe 9, and SO ₂ reacts with CaCO ₃ as the absorbent to form calcium sulfite as the absorbent 2.
Further, an air blow-in pipe 11 having an air blow-in port 12 is disposed in the lower part of the absorption tower 1 so that the air blow-in pipe 11 can be inserted.
Is connected to the air supply pipe 13, a line 14 for supplying CaCO ₃ as an absorbent into the absorption liquid 2 is connected to the lower part of the absorption tower 1, and a liquid withdrawal pipe 15 is provided near the bottom of the absorption tower 1. Connecting. Further, an exhaust gas flow meter 16 for detecting the flow rate of the exhaust gas and an inlet SO ₂ concentration meter 17 for detecting the SO ₂ concentration in the exhaust gas are provided in the middle of the gas inlet pipe 8, and the gas outlet pipe 9 is provided. An outlet SO ₂ concentration meter 18 for detecting the concentration of SO ₂ in the discharged gas is provided, and a pH for detecting the pH of the absorbing liquid is further provided in the circulation line 5.
Total 19 and absorbent concentration meter 20 to detect the concentration of absorbent in the absorbent
To provide. 21 is a multiplier for obtaining the amount of SO ₂ by multiplying the value from the exhaust gas flow meter 16 and the SO ₂ concentration value from the inlet SO ₂ concentration meter 17, 22 is an adder, and 23 is supplied by the absorbent supply line 14. Flow controller for adjusting the supply amount of the absorbent, 24 is a control valve adjusted by the flow controller 23, and 25 is a flow controller for adjusting the amount of the absorption liquid extracted from the absorption liquid extraction pipe 15. Total,
Reference numeral 26 is a control valve controlled by the flow rate controller 25.

In the present invention, in addition to the above configuration, current operation data and
A desulfurization rate for t hours is calculated by performing a predictive simulation calculation of the desulfurization rate based on the planned inlet exhaust gas flow rate and the planned inlet SO ₂ concentration determined in relation to the present or planned load of the boiler, and the operating conditions at that time Is used, and the current exhaust gas flow rate from the exhaust gas flow meter 16 and the inlet SO ₂ are used as the current operation data.
Current absorption liquid p from the current inlet SO ₂ concentration, the current outlet SO ₂ concentration, pH meter 19 from the outlet SO ₂ concentration meter 18 from densitometer 17
Since H, the current absorbent concentration from the absorbent densitometer 20, and the current number of circulating pumps in operation are used, these data are electrically connected so as to be input to the computer 27.

FIG. 2 shows an example of the internal configuration of the computer 27, where 28 is a model formula setting unit that calculates desulfurization efficiency η and absorption liquid pH from the current operation data, and 29 is the current operation data among the current operation data. Based on the exhaust gas flow rate, the current inlet SO ₂ concentration and the current boiler load, the relationship between the boiler load and the inlet exhaust gas flow rate and the relationship between the boiler load and the inlet SO ₂ concentration are created, and this relationship is compared with the changes in the planned load. A setting unit for setting the planned exhaust gas flow rate G and the planned inlet SO ₂ concentration Y, and 30 is a desulfurization rate η calculated by the model setting unit 28 and the above-mentioned planned exhaust gas flow rate and planned inlet SO ₂ concentration setting unit 29. Planned exhaust gas flow rate from the planned entrance S
A calculation unit that calculates a desulfurization performance prediction simulation based on the O ₂ concentration and calculates a desulfurization rate η _t in t hours, 31
Is a comparing section for comparing the calculated desulfurization rate η _t after t hours with the desulfurization rate η _s set by the desulfurization rate setting unit 32, and 33 is a comparing section 31.
As a result, the calculated operating conditions are changed according to the instruction when the deviation between the desulfurization rate η _t after the above t hours and the set desulfurization rate η _S is large, and 34 is the planned absorbent (CaC
O ₃ ) Supply amount value, 35 is the value of planned circulation pump operation number. Further, 36 is a comparison unit 31 which compares the desulfurization rate η _t after t hours with the set desulfurization rate η _s , and when the deviation is small and η _t > η _s , the operating condition at this time is stored. This is a storage device for storing driving instructions.

Now, the exhaust gas from the boiler 7 passes through the gas inlet pipe 8 and is boosted by the booster fan 10 and put into the absorption tower 1. In the absorption tower 1, the plurality of circulation pumps 6 are operated to guide the spray to the spray stage 3, and the spray nozzle 4 ejects the absorption liquid 2. Therefore, the exhaust gas entering the absorption tower 1 is brought into countercurrent contact with the absorption liquid 2. The SO ₂ in the exhaust gas is absorbed by the absorbent (CaC
O ₃ ) is absorbed and removed, the gas is discharged from the gas outlet pipe 9, and the absorbing liquid is circulated and used. The absorbent that has absorbed SO ₂ in the exhaust gas reacts with SO ₂ and enters the absorption liquid 2, where it is oxidized by the blown air and extracted from the liquid extraction pipe 15 as gypsum slurry. Become.

In the absorption tower 1, desulfurization is performed by absorption of SO _{2 in} the exhaust gas that is sequentially introduced, but a book that optimizes predictive control after a certain time (t hours) from the present time In the method of the invention, a simulation model of the desulfurization efficiency η is created by the model formula setting unit 28 in the computer 27 based on the data obtained from the current (current time) operation, and further, the current operation data, the current boiler load, A planned exhaust gas flow rate and a planned inlet SO ₂ concentration are set based on the planned boiler load change, and a predictive simulation is calculated based on this to determine the desulfurization rate η _t after t hours, and the desulfurization rate η _t The operating conditions at which is optimal are stored for predictive control.

More specifically, as the current operation data, as shown in Fig. 2, the exhaust gas flow rate, the absorption liquid pH, the concentration of the absorbent in the absorption liquid, the number of operating circulation pumps, the inlet SO ₂ concentration, and the outlet SO ₂ concentration are set as model equations as shown in Fig. 2. It is input to the unit 28 and the desulfurization efficiency η and the absorption liquid pH are calculated according to the model formula. That is, the desulfurization efficiency η
Is η = 100 {1-exp (-K ・ Pn ^a・ G ^-b・ exp (pH−α ・
Y) · C ^e } The absorption liquid pH is However, K, Kc, a to h: Constant Pn: Number of circulating pumps operating G: Inlet exhaust gas flow rate Y: Inlet SO ₂ concentration C: Absorbent concentration in absorbing liquid V: Liquid tank capacity S: Absorbed SO ₂ amount Pc: Absorbent supply amount B: Extracted liquid amount In this case, the relationship between the desulfurization efficiency and the number of operating circulation pumps is as shown in Fig. 3, and the desulfurization efficiency improves as the number of operating units increases. In the figure, I is a curve when the exhaust gas flow rate is low, II is a curve when the exhaust gas flow rate is high, and III is a curve when the exhaust gas flow rate is in the middle of the above. The relationship between desulfurization efficiency and absorption liquid pH is as shown in Fig. 4.
The relationship between and the concentration of the absorbent in the absorbent is as shown in FIG. 5, and if the concentration of the absorbent in the absorbent is determined, the pH of the absorbent is determined. In Fig. 5, I'is when the absorbed SO ₂ amount is small, II 'is when the absorbed SO ₂ amount is intermediate, and III' is the absorbed SO _{2 amount.}
The curves are for large quantities.

Next, the planned exhaust gas amount G and the planned inlet SO ₂ concentration Y, which are the basis of the calculation in the calculation unit 30 of the prediction simulation, are set in the setting unit 2
Set with 9. In this case, in the setting unit 29, the current entrance SO ₂
Based on the concentration, the current exhaust gas flow rate, the current boiler load, the relationship between the boiler load and the exhaust gas flow rate, the boiler load and the inlet
Create a relationship of SO ₂ concentration and set this in light of the planned load change. As a result of the experiment, the relationship between the boiler load and the exhaust gas flow rate ratio was found to be as shown in FIG. 6, and the relationship between the boiler load and the SO ₂ concentration at the inlet was the same as the result of the experiment.
It turned out that there is a relationship as shown in the figure. The inlet exhaust gas flow rate ratio on the vertical axis in FIG. 6 is the ratio of the inlet exhaust gas flow rate at each load when the inlet exhaust gas flow rate when the boiler load is 100% is taken as the base (1.0). The inlet SO ₂ concentration ratio is the ratio of SO ₂ concentration at each load when the SO ₂ concentration at 100% boiler load is used as the base (1.0). By storing the relationships shown in FIG. 6 and FIG. 7 in the setting unit 29, it becomes possible to easily predict what values the inlet exhaust gas flow rate and the inlet SO ₂ concentration will reach with respect to the planned boiler load. That is, if the current boiler load is 50% and the boiler load reaches 100% after t hours by finding the relationship between FIG. 6 and FIG. 7, the inlet exhaust gas flow rate ratio increases from 0.75 to 1.0, SO ₂ concentration ratio is from 0.77
It can be seen that the value rises to 1.0, which means that the boiler load change after a certain time, the inlet exhaust gas flow rate, and the inlet SO ₂
The concentration can be predicted.

When the planned inlet exhaust gas flow rate and the planned inlet SO ₂ concentration are set in light of the planned load of the boiler after t hours from the present time,
The desulfurization rate η _t after t hours is calculated by the calculation unit 30 of the desulfurization performance simulation, and the desulfurization rate η _t after t hours obtained by the calculation.
And the desulfurization rate η _s set by the desulfurization rate setting unit 32 are compared by the comparison unit 31. The deviation between the calculated desulfurization rate η _t after t hours and the set desulfurization rate η _s is large, and particularly when η _t <η _s , a calculation operating condition change instruction is issued and the planned absorption The value 34 of the agent supply amount and the value 35 of the planned number of circulating pumps are input to the calculation unit 30 to recalculate the desulfurization rate η _t after t hours, and the deviation between the above η _t and η _s becomes small. η _t ＞ η _s
Then, the operating conditions such as the planned supply amount of the absorbent and the planned number of circulating pumps at this time are stored in the operation instruction storage device 36, and when the predictive control after t hours is performed, the operation instruction storage device is used. According to the operating condition stored in 36, a control command is sent to the flow rate control valve 23 and the circulation pump 6 on the absorbent supply line 14 to change the absorbent supply amount and the number of operating circulation pumps. As a result, the predictive control after t time can be optimally performed.

[Effects of the Invention] As described above, according to the control method of the flue gas desulfurization apparatus of the present invention, the inlet exhaust gas flow rate and the inlet are included in the present operation data.
Based on the SO ₂ concentration and the current boiler load, the relationship between the boiler load and the inlet exhaust gas flow rate, the boiler load and the inlet SO ₂ concentration is created, and the planned inlet exhaust gas is compared with the planned load change of the boiler after t hours from the present time. The flow rate and the planned inlet SO ₂ concentration are set, the desulfurization performance prediction simulation is calculated based on the set planned inlet exhaust gas flow rate and the planned inlet SO ₂ concentration, and the predictive control is performed after t hours from the present time. As a result, compared to the case where the inlet exhaust gas flow rate and the inlet SO ₂ concentration are set for each fuel, it is possible to make a prediction that actually matches from starting from the current operating conditions, and the load of the boiler and the inlet exhaust gas flow rate. Yu relationship, since the obtained relation load and inlet sO ₂ concentration of the boiler can be operated under optimum conditions and be predicted by the change in the scheduled load after a certain time is known, that And it can achieve the effect.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of a flue gas desulfurization apparatus used for carrying out the method of the present invention, FIG. 2 is a block diagram showing an internal configuration example of the computer shown in FIG. 1, and FIG. Fig. 4 shows the relationship between the number of circulating pumps, Fig. 4 shows the relationship between desulfurization efficiency and absorption liquid pH, Fig. 5 shows the relationship between absorption liquid pH and absorbent concentration in absorption liquid, and Fig. 6 shows boiler load. And the absorption tower inlet exhaust gas flow rate ratio, and FIG. 7 is a diagram showing the relationship between the boiler load and the inlet SO ₂ concentration ratio. 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 SO ₂ concentration meter, 18 …… Outlet SO ₂ concentration meter, 19 …… pH meter, 20 …… Absorption Agent concentration meter, 27 …… Calculator,
29 …… Scheduled exhaust gas flow rate and inlet SO ₂ concentration setting part, 30…
… Calculation part of desulfurization performance prediction simulation, 31 …… Comparison part, 32 …… Desulfurization rate setting part, 36 …… Operation instruction storage device.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location B01D 53/34 125 E

Claims (1)

[Claims] 1. Current operating data such as the flow rate of exhaust gas at the inlet to the absorption tower, the pH of the absorbent, the concentration of the absorbent in the absorbent, the SO ₂ concentrations at the inlet and outlet of the absorbent, and the number of circulating pumps operating, and the current exhaust gas at the inlet. A planned inlet set based on the flow rate, the current inlet SO ₂ concentration, the current load, and the relationship between the load and the inlet exhaust gas flow rate, the load and the inlet SO ₂ concentration, and set in light of the planned load change after t hours from the present time. The desulfurization performance prediction simulation is calculated based on the exhaust gas flow rate and the planned inlet SO ₂ concentration, and then the desulfurization rate after t hours obtained by the calculation is compared with the set desulfurization rate, and the deviation between the two is calculated. A method for controlling a flue gas desulfurization apparatus, characterized in that the operating conditions when the value is small are stored, and the absorbent supply amount and the like are predicted and controlled under the stored operating conditions.