JPH0427417A - Method for controlling wet-type stack gas desulfurizer - Google Patents

Abstract

PURPOSE:To accurately recognize the concentration of the component in an absorbent slurry for which continuous measurement is not available by correcting the calculating results of the calculated concentration of the component from the sampling to the present time by using the manual analysis data sampled from absorbent slurry and manually analyzed as an initial data. CONSTITUTION:The various process data such as a flow rate signal 27 from a gas flow meter 22, a concentration signal 28 from inlet SO2 concentration meter 23, a concentration signal 29 from outlet SO2 concentration meter 24, a flow rate signal 30 from the flow meter of the absorbent slurry 25 and a flow rate signal 31 from the flow meter of outlet of an absorbent tower 26 are inputted into an arithmetic unit. These process data (signals 27-31) are recorded into the prescribed address of the data file 42 at every minute time DELTAt (within several second), and the amount of variation of composition is calculated. On the other hand, the analytical data of respective ingredients by manual analysis 40 is inputted into liquid arithmetic unit 39. Also, the concentration of components at the present time is accurately recognized by re-calculating the variation with the lapse of time of the concentration of the component using the analytical data by the manual analysis of the component at sampling time as the initial data.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to a wet flue gas flue gas system that removes sulfur oxides in flue gas discharged from a combustion device such as a boiler for thermal power generation by bringing it into contact with an absorbent slurry. The present invention relates to a desulfurization device, and particularly to a method for controlling an absorbent slurry in the desulfurization device.

[Background Art] In recent years, as the demand for power generation has increased, boiler devices that use fossil fuel as the main fuel have also become larger, and the influence of power generation boilers on air pollution is also increasing.

Emission regulations for sulfur oxide (SOx), which accounts for a large proportion of the pollutants that increase air pollution, are becoming stricter year by year. Under these circumstances, since the second oil crisis, Japan's power generation industry, which has been using oil as its main fuel, is switching to coal, which is cheaper and has a more stable supply source.

Furthermore, this coal is now being imported from a large number of countries and producing areas for the purpose of ensuring long-term stable supply and alleviating trade imbalances, and dozens of types of coal are used in one power plant. There are also examples.

It goes without saying that the combustion characteristics in the boiler will differ due to the differences in the properties of the coal, but the desulfurization characteristics will also vary greatly depending on the properties of the combustion exhaust gas discharged from the boiler.

In addition, as boiler equipment becomes larger, boiler equipment is started and stopped (DSS, WSS) on a daily or weekly basis to perform frequent load fluctuations in response to power generation demand in order to reduce power generation costs. is being repeated.

As a feature of recent electricity demand, as the use of nuclear power generation increases, the difference between the maximum and minimum power loads also increases, and there is a tendency to shift boilers for thermal power generation from base load use to load** use.

As the types of coal used in the boiler equipment described above increase, operational changes expand, and speeds increase, the flue gas desulfurization equipment that processes the exhaust gas from the boiler equipment also follows the changes in the operating conditions of the boiler and is capable of changing its performance in each operating state. It has become necessary to aim for optimal operation that minimizes the negative impact.

[Problem to be solved by the invention] Wet flue gas desulfurization equipment is installed at thermal power plants.

Using a slurry-like absorbent slurry containing calcium envyate [CaC0a], calcium hydroxide [Ca (OH) oxidized calcium sulfite to form calcium sulfate.

In other words, the common method is to recover it as gypsum.

The schematic structure of the wet flue gas desulfurization equipment using this limestone is explained in the third section.
As shown in the figure.

In the figure, 1 is an absorption tower, 2 is an untreated gas, 3 is a demister, 4 is a treated gas, 5 is an absorbent slurry, 6 is an absorption tower circulation tank, 7 is an absorption tower circulation pump, 8 is air, and 9 is an absorption Tower extraction piping, 10 is a relay tank, 11 is a wastewater treatment device,
12 is a slurry pump, 13 is a conduit, 14 is Shirafuna, 1
5 separator.

16 is a conveyor, 17 is plaster, 18 is a filtered water conduit, 19
is a filtered water tank, and 20 is a blow water control valve.

21 is a blow water conduit, 22 is a gas flow meter, 23 is an inlet S
24 is an outlet SOx concentration meter, 25 is an absorbent slurry flowmeter, 26 is an absorption tower extraction flowmeter, and 27 is an absorption liquid tank.

As shown in the figure, the untreated gas 2 is introduced into the absorption tower 1 and comes into gas-liquid contact with the calcium-based absorbent slurry 5 in the absorption tower 1, so that the sulfur dioxide gas contained in the untreated gas 2, Dust, HCjl and HF are removed. The purified gas is discharged to the atmosphere as a process gas 4 after entrained mist is removed by a demister 3. On the other hand, the required amount of the absorbent slurry 5 is sent to the head of the absorption tower 1 by the absorption tower circulation pump 7, and is dispersed to absorb sulfur dioxide gas and the like.

The absorbent slurry 5, which has become calcium sulfite through this absorption reaction, returns to the absorption tower circulation tank 6.

Then, air 8 is supplied into the tank, and calcium sulfite is oxidized to become gypsum.

A part of the circulating absorbent slurry 5 is extracted from the absorption tower extraction pipe 9 to the relay tank 10. The absorbent slurry 5 in the relay tank 10 is led to Shirafuna 14 through a slurry pump 12 and a conduit 13, and after being concentrated to a predetermined concentration, it is applied to a separator 15, where the gypsum 17 is dehydrated and recovered as a solid. Ru. Shirafuna 14 supernatant liquid (filtrated water)
is stored in a filtered water tank 19 through a filtered water conduit 18.

A portion of the filtrated water is discharged to the wastewater treatment device 11 through the blow water control valve 20 in order to maintain the concentration of impurities such as chlorine ions in the system below a certain value. The remaining filtered water is sent to the absorption liquid tank 45 or the like and reused within the system.

In such a system, when the gas conditions flowing into the desulfurization device change, the liquid properties of the absorbent slurry also change.

Some of the components contained in the absorbent slurry have a large effect on the performance of the desulfurization equipment, so accurately understanding the concentration of each component is essential for optimal operation that reduces the needs of the desulfurization equipment. important to do.

For example, CaC0, since the concentration controls the desulfurization rate.

The absorbent slurry is supplied to the absorption tower so that the CaCO5 concentration can be maintained above the specified value. Furthermore, the exhaust gas contains ICΩ, and HCl1 is absorbed by the desulfurization device and accumulated as chlorine ions. If this chlorine ion concentration increases, it will cause corrosion of the equipment and will also have a negative effect on the desulfurization rate, so it is necessary to adjust the chlorine ion concentration so that it is below a specified value.

However, with conventional measurement techniques, CaC in absorbent slurry
0, concentration, chloride ion concentration, etc., cannot be measured continuously and accurately. Therefore, from the mass balance calculation of the desulfurization equipment, CaC0, concentration in the absorbent slurry,
Predictive calculations were made of the concentration of each component, such as chloride ion concentration.

Next, this predictive calculation will be explained using an example of CaC0a concentration with reference to FIGS. 3 and 4.

A flow rate signal 27 from a gas flow meter 22 provided at the inlet of the desulfurization equipment, a concentration signal 28 from an inlet So, and a concentration meter 23.
The concentration signal 29 from the outlet SO8 concentration meter 24, the flow rate signal 30 from the absorbent slurry flow meter 25, and the flow rate signal 31 from the absorption tower extraction flow meter 26 are sent to a computing device 32, respectively.
is input.

Based on these signals, the concentration of CaC0a in the absorbent slurry can be determined by the following formula. In addition, since a large amount of absorbent slurry is held in the absorption tower,
Time delays due to volume effects must be taken into account.

V-dCi/dt=Fco-FCi-(1) V: Absorption tower retained slurry amount C1: CaC0 in absorbent slurry, concentration CO: Apparent CaC0 flowing into the absorption tower, concentration F: Absorption tower withdrawal flow rate Co = ([30] XKI-[27] X ([2
g]-[29]1 xK2>/[31F...
・(2) [27F: Inlet gas flow rate [28]: Inlet SO, concentrated gas flow rate [29]: Inlet/outlet SO, concentrated gas flow rate [301: Absorbent slurry amount [31]: 1 Nislurry for absorption tower withdrawal amount CaC0 in, concentration conversion factor 2: absorption S
Conversion coefficient for converting the amount of O into the equivalent amount of CaC It is inevitable that it will occur,
For this reason, it is necessary to periodically perform manual analysis and compare it with calculated values. However, it usually takes 3 to 4 days for the results of this manual analysis to be available, so at the time the analysis results are obtained, the slurry composition in the device is different from the composition at the time of sampling, and the values calculated by the manual analysis result are different from the composition at the time of sampling. It is difficult to fix.

The purpose of the present invention is to eliminate such drawbacks of the prior art,
It is an object of the present invention to provide a control method for a wet flue gas desulfurization device that can accurately grasp the concentration of components in an absorbent slurry that cannot be measured continuously.

[Means for Solving the Problems] In order to achieve the above-mentioned objects, the present invention provides a wet flue gas desulfurization device that removes sulfur oxides in flue gas discharged from a combustion device by contacting with an absorbent slurry. A calculation means is provided for calculating the component concentration in the absorbent slurry based on the process data of the wet flue gas desulfurization equipment, and the current calculation result calculated by the calculation means is
This method is characterized in that the manual analysis value obtained by sampling and manually analyzing the absorbent slurry in use is used as the initial value at the sampling time, and is corrected by the calculation result of calculating the component concentration from sampling to the present time.

[Operation] By inputting the result obtained by manual analysis at the sampling time, that is, by recalculating the temporal change in component concentration using the hand-analyzed value of component concentration at the sampling time as the initial value, The concentration of the components can be accurately determined.

[Embodiments of the invention] Next, examples of the present invention will be described.

FIG. 1 is a block diagram of a control device according to an embodiment of the present invention;
Fig. 2 is an explanatory diagram showing a method for correcting calculation results in the present invention, Fig. 3 is a schematic configuration of a wet flue gas desulfurization device, Fig. 4 is a functional explanatory diagram of the arithmetic unit, and Fig. 5 is a flowchart of the arithmetic unit. No. 6 is a flowchart of the liquid property calculation device.

As shown in FIG. 1, the control device according to the embodiment is as shown in FIG.

It mainly consists of a calculation device 32, a data file 42, and a liquid property calculation device 39.

The arithmetic unit 5I32 includes a flow rate signal 27 from the gas flow meter 22, a concentration signal 28 from the inlet SO8 concentration meter 23, a concentration signal 29 from the outlet SO8 concentration meter 24, a flow rate signal 30 from the absorbent slurry flow meter 25, In addition, process data such as a flow rate signal 31 from the absorption tower outlet flow meter 26 are inputted. In addition, these process data (signal 2
7 to 31) are recorded at predetermined addresses of the data file 42 at every minute time Δt (for example, several seconds or several minutes).

FIG. 5 is a flowchart of the arithmetic unit 32.

As shown in the figure, the amount of composition change ΔC is calculated by sibling the above-mentioned process data for each time and using Δ as a time mass balance calculation.

Then, with the concentration Ci at time t as an initial value, time t
The component concentration CiB at time 0 B (see FIG. 2) for determining the concentration C1==Ci+ΔC at 1Δt is calculated based on the component concentration CiA at time A as an initial value.

As shown in Figure 1, the liquid property calculation system! 139, manual analysis data 40 of each component is input. This manual analysis is performed, for example, once a week by withdrawing a portion of the circulating absorbent slurry, and one manual analysis typically takes 3 to 4 days. In addition to manual analysis data 40, this liquid property calculation device i39 contains gas flow rate signals 34. Input So, concentration signal 35, output So, concentration signal 36, absorbent slurry flow rate signal 37. and absorption tower outlet flow meter No. 3
Process data such as 8 (time series data between times A-+B) is input.

FIG. 6 is a flowchart of this liquid property calculation unit w39. The calculation method is performed using the calculation device 13 explained in FIG.
It is almost the same as 2.

The difference from this calculation device E32 is that one analysis value CiA' (the manual analysis data 40) is used as the initial value at one time t.

In addition, process data between time A18 is stored in data file 4.
2, the simulation calculation is performed, and the component concentration CiB' at time B is determined.

The component concentration C4B' calculated in this manner is inputted to the calculation device 32 as a corrected concentration signal 41 as shown in FIG. Then, in the arithmetic unit [32], the component concentration CiB calculated using the component concentration CiA at time A as an initial value as described above is replaced with the component concentration CiB', and the component concentration is corrected.

21st! 1 is a diagram showing a method of correcting this component concentration, where the vertical axis shows time and the horizontal axis shows component concentration. A curve 43 in the figure is an online calculation signal before correction calculated by the calculation device 32, and a curve 44 is a correction calculation signal calculated by the liquid property calculation device 139.

As mentioned above, the component concentration Ci is calculated in the calculation device 11132.
After replacing B with the component concentration CiB', the calculation device! 3
In 2, prediction calculations are repeated based on that table.

A component concentration calculation result signal 33 is output from the calculation device [32].

7th vA is a schematic diagram of an operation support system for a wet flue gas desulfurization apparatus equipped with a control device according to an embodiment of the present invention.

This operation support system has a desulfurization performance prediction control function. This function uses online simulation to calculate the composition of absorbent slurry that cannot be automatically analyzed from the current boiler load, coal type, and desulfurization process amount, and uses the calculated values to calculate the optimal setting values for operating factors related to desulfurization performance. It sends commands to the desulfurization control device, and has the following functions.

(Function 1) By predicting desulfurization performance, determining the absorption tower circulation amount necessary to maintain the desired desulfurization rate, determining the number of absorption*wi ring pumps in operation, and stopping unnecessary pumps. , aiming to reduce the amount of electricity used by the absorption tower circulation pump.

The absorption tower circulation pump is driven by a high-voltage electric motor, and since there are limits to the time and number of times it can go from stop to start, a motor start/stop limit circuit and a motor selection priority circuit are installed to protect the motor. .

(Function 2) Predictably calculates the concentration of limestone slurry in the absorption tower and adjusts it to the desired pH.
The optimum amount of limestone slurry required to maintain the value is calculated and controlled.

(Function 3) Simulate the oxidation reaction within the absorption tower, calculate and control the required amount of oxidizing air.

(Function 4) In order to prevent the influence of HF and HCl1 in the exhaust gas on the desulfurization performance, the optimum amount of caustic soda supply is calculated and controlled.

(Function 5) In order to reduce the amount of wastewater, calculate and control the amount of wastewater that can maintain a constant chlorine concentration in the absorption system.

In order to improve the accuracy of this online simulation, the following auxiliary functions are provided.

■0 manual analysis correction function As mentioned above, this is a function that corrects the predicted calculated value of each component concentration in the absorbent slurry, which cannot be measured online, using manual analysis values.A trace that can be entered back to the sampling time for 1 manual analysis. It has a back function.

■Simulation automatic correction function This function automatically corrects the simulation model when a discrepancy occurs between the calculated value obtained in online simulation and the process amount due to changes in exhaust gas composition, etc.

■Offline simulation function This function has the same model as the online simulation model, sets operating conditions, and calculates optimal operating values.

[Effects of the Invention] The present invention has the above-described configuration, in which the results obtained by manual analysis are inputted at the sampling time,
That is, by recalculating the temporal change in the component concentration using the manually analyzed value of the component concentration at the sampling time as an initial value, it is possible to accurately grasp the component concentration at the present time. From this, it is possible to provide a highly reliable control method for a wet flue gas desulfurization device.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a control device according to an embodiment of the present invention; FIG. 2 is an explanatory diagram showing a method for correcting calculation results in the present invention; FIG. 3 is a schematic configuration of a wet flue gas desulfurization device; FIG. 4 is a functional explanatory diagram of a conventional calculation device, FIG. 5 is a flowchart of the calculation device, FIG. 6 is a flowchart of a liquid property calculation device, and FIG. 7 is a control device according to an embodiment of the present invention. 1 is a schematic configuration diagram of an operation support system for a wet flue gas desulfurization device equipped with the following. 1... is an absorption tower, 2... is an untreated gas,
3... Demister, 4... Processing gas, 5
...Absorbent stripe 1 Halo ...Absorption tower circulation tank, 7 ...Absorption tower circulation pump, 8 ...
... Air, 9 ... Absorption tower extraction piping. 22...Gas flow meter, 23...Inlet S
Ox concentration meter. 24... Outlet SOx concentration meter, 25...
Absorbent slurry flow meter, 26... Absorption tower extraction flow meter, 27... Flow rate signal from gas flow meter 22, 28... Concentration from inlet SO1 concentration meter 23 Signal, 29... Concentration signal from outlet SOx concentration meter 24, 30... Flow rate signal from absorbent slurry flow meter 25, 31... Absorption tower extraction flow meter Flow rate signal from 26, 32... calculation device, 33...
...Component concentration calculation result signal, 34...Gas flow rate signal, 35...Input So, concentration signal, 36.
... Outlet So3 concentration signal, 37 ... Absorbent slurry flow rate signal, 38 ... Absorption tower extraction flow rate signal, 39 ... Liquid property calculation device, 40.・・・・・・
Manual analysis data. 41...Corrected density signal, 42...Data file, 43...Arithmetic device! Online calculation signal before correction calculated in 32, 44... Corrected calculation signal calculated in liquid property calculation device M39. Figure 2 Figure 3 Figure 5

Claims (1)

[Claims] In a wet flue gas desulfurization device that removes sulfur oxides in flue gas discharged from a combustion device by contacting it with an absorbent slurry, A calculation means is provided that performs calculations based on the process data of the device, and the current calculation result calculated by the calculation means is
A wet flue gas desulfurization device characterized in that the manual analysis value obtained by sampling and manually analyzing the absorbent slurry in use is used as the initial value at the sampling time, and is corrected by the calculation result of calculating the component concentration from sampling to the present time. Control method.