JPH0258528B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a soot blower control method, and particularly to a soot blower control method suitable for application to a boiler used in a thermal power plant.

In boiler equipment used in thermal power plants, soot and ash are generated in steam due to the combustion of fuel, and these adhere to heat transfer surfaces and accumulate over time. When such deposits occur, the efficiency of the boiler deteriorates, so cleaning is carried out periodically by blowing steam onto the deposited surface using a plurality of soot blowers.

FIG. 1 is a block diagram schematically showing a soot blower control system.

A heat exchanger 2 is installed within the boiler 1, and a flue 3 is provided at the upper end of the boiler. Heat transfer device 2
A soot blower 4 is provided adjacent to the soot blower 4, and this blower 4 is controlled by a data processing device 10.
The heat transfer device 2 is an assembly of a large number of tubes arranged to efficiently exchange heat with the combustion gas in the furnace of the boiler, and is usually composed of 3 to 10 heat transfer devices. The soot blower 4 is three-dimensionally arranged to correspond to the heat transfer tube in order to thoroughly clean the heat transfer surface. Data processing device 10
are the output signals of the flue 3 temperature (or steam temperature in the draft or heat transfer device) detector 5 and the temperature in the boiler 1 (or the steam temperature in the draft or heat transfer device) detector 6 and the soot blower. The soot blower 4 is controlled based on the operation information of 4, and its configuration consists of a data input/output section 11, a memory section 12, and a data processing section 13. Data input/output unit 11 inputs and outputs various information from the boiler side and control (drive) signals for controlling the soot blower 4.
The data is stored in the memory section 12. The data processing program stored in the memory section 12 is processed by the data processing section 13, and is again output from the data input/output section 12 to the soot blower 4, where required control is performed.

The operation of the soot blower 4 is to prevent the deterioration of the heat exchange performance of the heat transfer device by cleaning the heat transfer surface as described above, but with the introduction of large coal-fired power plants, the number of soot blowers has increased. With the increase in demand, it has become necessary to efficiently operate the boiler, improve boiler efficiency, and reduce the burden on operators. The conventional soot blower sequence is to summarize the boiler characteristics regarding dirt on the heat transfer surface from experimental data or calculated values,
The equipment was operated by creating judgment data for determining the allowable limit for contamination on heat transfer surfaces. However, in this case, it is not possible to quantitatively understand the improvement in boiler efficiency, and the criteria for determining the degree of contamination lacks objectivity and is not accurate.
Since it is not necessarily optimal, it has not been put into practical use.

An object of the present invention is to provide a soot blower control method that allows soot blower control to be performed in an optimal sequence.

In order to achieve this objective, the present invention evaluates the optimal blow sequence based on the optimal sequence in which the amount of steam consumed by the soot blower blow in the sequence is constant and the boiler thermal efficiency is maximized under this condition. The boiler thermal efficiency is set at a point where the boiler thermal efficiency is maximized when the amount of steam consumed by blowing by the soot blower in one cycle sequence is changed.

FIG. 2 is an explanatory diagram for explaining the principle of the present invention. In FIG. 2, the horizontal axis V represents the amount of steam consumed by blowing, which is the total amount of steam when a plurality of soot blowers sequentially perform one cycle of blowing. Here, one cycle sequence refers to starting each soot blower only once and completing one cycle of blowing. FIG. 4a shows an example of a driving pattern. The vertical axis ψ is the boiler thermal efficiency,
This is the average value for one cycle. The boiler thermal efficiency ψH is the maximum boiler thermal efficiency curve at each blow steam amount determined by the optimal blow sequence search procedure described below. Next, the search procedure for the optimal blow sequence will be explained. Note that ~ in the figure corresponds to ~ described below.

A test sequence for determining the optimum sequence pattern of the soot blower is prepared, and the boiler efficiency ψ ₁ at the blown steam amount V ₁ is determined by conducting several tests on an actual boiler using the data processing device 10. In other words, it is determined by test runs during boiler installation, etc.

The test sequence is shown in Figure 4a, which will be described later.
The soot blower groups A to C provided corresponding to each heat transfer surface are arranged in ascending order of soot blower numbers A1 → A2 according to the flow of combustion gas.
→ A3 → A4 (same for B and C groups), one cycle operation is performed sequentially once with a constant blowing time length and time interval.

Further, the boiler thermal efficiency ψ is determined by inputting boiler inputs such as fuel, air, water supply, etc. and boiler outputs such as main steam, combustion gas flow rate, enthalpy, etc. to the data processing device 10. In addition, the blown steam is branched from the middle of the heat exchanger, which has several stages, and is blown as fuel gas by the soot blower.
It is discharged.

Next, with the blow steam amount V ₁ constant and the test sequence partially changed, tests are conducted several times in an actual boiler, and the significance of the change is determined from a statistical test of the boiler efficiency ψ ₁ ′. .
Here, the statistical test of boiler thermal efficiency ψ ₁ ′ is
If the test sequence is partially changed and the boiler efficiency ψ ₁ ′ increases after several confirmation tests on the actual boiler, the test sequence after the change is good, and conversely the boiler thermal efficiency ψ ₁ ′ decreases. In this case, the test sequence before the change was better.

As a partial change in the sequence pattern, the details will be described later, but as a specific example, as shown in Fig. The blow steam flow rate FH' is divided by the average blow steam flow rate FA, and the fact that this is the minimum indicates that the blow steam flow rate is averaged and there is little disturbance as described later due to blowing.), and when the blow starts. Averaging the end time (both times are placed at appropriate positions at equal intervals) As shown in Figure 7a, the operating frequency and blowing time length of each soot blower should be adjusted to correspond to the dirt on each heat transfer surface. This is what we aim to do.

We repeatedly change the sequence pattern partially as shown in the figure below, and modify the sequence more appropriately while evaluating the blowing effect of the change based on the boiler thermal efficiency ψ′, ψ″ obtained through several tests on the actual boiler. and create an optimal sequence.This is an example where the boiler thermal efficiency ψ ₁ ″ is worse than the boiler thermal efficiency ψ ₁ in the test sequence.

Next, the blow steam amount is set to V ₂ , the injection time of each soot blower is lengthened by the increased flow rate ratio as shown in Fig. 9a, and the sequence is modified to improve the boiler efficiency to ψ _2. Test.

Once confirmed, further increase the blow steam amount, shorten the injection interval of each soot blower by the increased flow rate ratio, and modify the sequence.
Repeat the test to see if the boiler efficiency improves.

If the boiler thermal efficiency is decreasing as shown in ψ ₄ , on the other hand, reduce the amount of blown steam, shorten the injection time length of each soot blower by the amount of the reduced flow rate, and correct the sequence to maximize the boiler efficiency. Determine the optimal blow sequence.

The above search is performed under the conditions that the operation of the boiler load, the fuel, etc. are constant, and the conditions other than the soot blower, which determines the boiler efficiency, are constant. Blow flow rate
If the blow is less than Fo, the blow is not sufficient and the heat exchange performance of the heat transfer surface is not fully developed.On the other hand, if the blow is excessive, the effect of the blow is saturated and the blow steam is There is a tendency for it to be consumed excessively, which contributes to a decline in the actual boiler effectiveness. According to one embodiment of the present invention, it is possible to select the optimum blowing sequence in each load zone.

FIG. 3 shows an example of a flowchart when the above principle is carried out by the data processing device 10. The numbers in the figure correspond to the above-mentioned processing items.

First, an initial test sequence is defined (S=S ₁ ), then an initial blow is performed, and the amount of steam consumption V is confirmed (V=V ₁ ). Next, the boiler thermal efficiency is checked to find a sequence that can further improve efficiency. After creating a suitable test sequence, update the steam consumption of the soot blower (V=V ₁ +ΔV), further modify the test sequence, perform a test blow, and check the efficiency at this time. Thereafter, the above-described processes are executed, and if the improvement in efficiency is within the error range, all processes are terminated.

Next, as an example of a procedure for partially changing the sequence pattern, we will explore an optimal sequence that minimizes the inequality rate and averages the blow start and end times from the test sequence, which is a conventional blow sequence. The details will be explained below.

Figures 4a and 4b show one cycle of the blowing operation program based on models of four soot blowers in each of the three soot blower groups A to C provided corresponding to the heat transfer surface as shown in Figure 1. The minutes are arranged in chronological order, and the vertical axis shows the blow steam flow rate F. In this case, the operation will be as follows.

(a) One cycle sequence starts at time Ts in Fig. 4b, and the maximum blowing steam flow rate F _H is suddenly blown, and this continues until T _1. (b) At time T ₂ , the blowing suddenly starts. It became zero and continued until T ₃ , causing the following problems due to the blow.

(c) The reduction in _NO
It has a similar effect of reducing _NOx . Also,
On the other hand, as a way to suppress _NOx in the combustion gas of the boiler due to the rise _{in NOx} due to the stoppage of blowing, there is a method of suppressing the amount of air, which is the input amount to the boiler, to completely suppress combustion. As shown in Fig. 4b, rapid steam blowing such as when three soot blowers are activated simultaneously causes the _NOx value to fluctuate, changing the combustion state and causing disturbance.

(d) As shown in Fig. 4b, the interior of the heat exchanger is cleaned and the heat exchange performance is restored by rapid blowing such as starting three soot blowers at the same time. As a result, heat transfer from the combustion gas becomes more efficient, and the steam temperature within the heat exchanger rises rapidly beyond a limited value, necessitating an unnecessary emergency cooling spray operation. On the other hand, if blowing is not performed for a long time, such as from time T ₂ to _{T 3} , soot will accumulate on the heat exchanger surface and heat exchange performance will decrease. When the steam temperature falls below the set value, the combustion gas will be removed. Insufficient heat transfer will result in a starved fuel injection operation. These emergency cooling spray operations and fuel injection operations reduce the thermal efficiency of the boiler, resulting in disturbances in the steam temperature.

(e) If rapid blowing is performed, such as starting three soot blowers at the same time as shown in Figure 4b, if the supply limit of the auxiliary steam source for the soot blowers of the boiler is exceeded, the amount of consumed steam will be insufficient. leading to pressure drop. Therefore, in such a case, it is necessary to increase the amount of steam generated by the boiler. On the other hand, if the blowing suddenly stops, the amount of steam consumed becomes unnecessary and the pressure increases rapidly. This causes a disturbance to the auxiliary steam pressure control.

(f) Decreased boiler efficiency due to disturbances in (c) to (e). These problems can be solved by eliminating sudden blow changes when creating programs, but in reality, the blow blow of nearly 300 soot blowers time,
It is a heavy burden on the operator to consider and create the blow steam amount.

The sequence of the present invention, which will be explained below, has been proposed as a solution to this problem.
Fig. 6b shows a principle diagram, and Fig. 6 shows an example of a processing flowchart.

F _A is the same value as the average blow consumption of the program of FIG. 4, but the maximum blow steam flow rate is reduced to F _H ' and the blow is averaged. Next, the procedure for creating this blow sequence will be explained.

The blowing time lengths T _A to T _C and the blowing steam flow rates F _A to F _C of the soot blowers A ₁ to C 4 in FIG. ₄ are determined by the data processing device 10 by actually starting the programmed test sequence.

Next, based on this data, the start time of blowing for each soot blower is changed so that the unequal rate of steam consumption due to blowing is minimized.

Furthermore, the optimum sequence is determined by averaging so that the start and end of blowing of each soot blower do not overlap.

The flowchart in FIG. 6 shows an example of processing the above principle using the data processing device 10. A test sequence as shown in FIGS. The entire process is completed by reading the various quantities _A to T _C and the blow steam flow rates F _A to F _C , selecting the minimum sequence with the inequality rate, averaging the blow start and end times, and determining the optimal sequence.

The above is a job of the data processing device 10, so it does not impose a burden on the operator. In this case, in the final sequence of Figure 5a and b, the soot blower
A1 → C1 → B1 → starts at time T _S , T ₄ , T ₁ in the order,
Stops in the order of A2→C2→B at times T ₁ , T ₅ , and T ₈ . Furthermore, even if the frequency of operation of each soot blower is the same, the higher the frequency of operation of the soot blowers as a whole (the more one soot blower is always blowing), the lower the degree of contamination. 45-28324,
The blowing averaging method described above can achieve more completeness, reducing the frequency of blowing operations and improving the thermal efficiency of the boiler.

Next, as part 2 of the procedure example of partially changing the sequence pattern, the operating frequency and blowing time length of each soot blower can be optimized based on the blow sequence shown in Figure 5 to correspond to the dirt on the heat exchanger surface. The details of the means for finding a sequence will be explained.

Figures 7a and b have the same average blow steam flow rate F _A and maximum blow steam flow rate F _H ' as the blow sequences in Figures 5 a and b, and the specific change in the sequence pattern is the operation of the B1 soot blower in one cycle. The point that changed from 1 time to 2 times and A1, A2, B1 to B4
The blowing time was shortened or lengthened in response to contamination on the heat transfer surface. (Although the actual time length adjustment is not as different for each soot blower as in this example, it is clearly described for the purpose of explaining the procedure.)
Contamination on the heat transfer surface varies to some extent depending on the installation position in the boiler 1 and the flow condition of combustion gas, and the number of blowing times and length of operation of the soot blower that is affected by the contamination on the heat transfer surface is This results in effective blowing. This specific processing is performed by the data processing device 10, and an example of this is shown in a flowchart in FIG. Next, the procedure for creating this blow sequence will be explained.

The test sequence in which the blow time length T _A - T _C and the blow steam flow rate F _A - F _C of the target soot blower A ₁ - C ₄ in FIG. The blow steam amount V is determined and used as the reference value.

V ₁ = 4 (F _A × T _A + F _B × T _B + F _C × T _C ) ………(1) Read process information for determining the contamination characteristics of the blowing heat exchanger surface of each soot blower.
Specific contamination determination information includes the gas temperature in the flue 3 (or the steam temperature in the draft or heat exchanger) detector 5 and the gas temperature in the boiler 1 (or the steam temperature in the draft or heat exchanger) detector 6. There is an output signal of the soot blower 4 and operation information of the soot blower 4, and a detector 6 installed between the soot blowers after blowing.
The change in heat exchange characteristics (degree of contamination) is comprehensively determined from the gas temperature difference (draft difference or steam temperature difference in the heat transfer device), etc., and the cumulative blowing time length of each soot blower is determined. (There may be as many as 300 soot blowers in practice, and if it is not possible to provide a detector for each soot blower, the soot blowers should be rationally divided into groups and the detectors should be placed appropriately.) As the degree of contamination of the heating device surface increases, the gas temperature difference in the detector 6 installed between the soot blowers rapidly decreases, the gas draft difference increases, and the steam temperature difference in the heat transfer device decreases.

Compare the cumulative blowing time of each soot blower determined by the above with the actual blowing time _length T _A to T _C confirmed in the test sequence. The blow time length of T _A1
shall be. ta ₁ =T _A1 (b) From the cumulative blow time length ta ₂ of one cycle of the similar soot blower A2, let T _A2 be the time length of one blow. ta ₂ = T _A2 , the blowing time length T _A of the soot blower A1 to A4 in Figure 5
and 2T _A = T _A1 + T _A2 (2), so that the total blowing time length of A1 and A2, that is, the amount of blowing steam, does not change.

(c) In group B of soot blowers,
B1 soot blower is very dirty, so
From the cumulative blow time length t _b1 of the cycle, divide it into two blows and calculate the blow time length for one time.
Let T _B ′. t _b1 =2T _B ′ (d) According to (c), the time length of one blow of B2 to B4 was set as T _B ′. In addition, B1 to B4 in Figure 5
The blowing time length T _B of the soot blower is 4T _B =5T _B ′ (3), so that the blowing time length of the B group, that is, the blowing steam amount does not change.

As described above, the number of blowing times (frequency) in one cycle of each soot blower and the length of one blowing time are determined by (a) to (c), and the optimum sequence is determined (updated). The blowing time of the soot blower is adjusted by changing the power supply voltage or frequency of the soot blower motor and changing the rotation speed.

Next, a third example of the procedure for partially changing the sequence pattern is shown in FIGS. 9 and 10. This figure changes the average blow steam flow rate F _A to F _A ′ from the blow sequence in Figure 7, that is, changes the blow steam consumption.
This is a detailed explanation of means for searching for an optimal sequence by setting V ₁ to V ₂ (V ₃ to _{V 4} , V ₀ ) and lengthening the blowing time length of each soot blower by the increased flow rate ratio.

In step 2 of partially changing the sequence pattern, given blow steam consumption
The purpose of this change was to find out how to allocate V ₁ to each soot blower according to the degree of contamination on the heat transfer surface to achieve effective blowing. The aim is to find out how to blow the most effective amount of steam from each soot blower depending on the situation. FIG. 10 shows this flowchart, and the procedure for creating this blow sequence will be explained.

In the test sequence of FIG. 7, the blow steam amount V ₁ of one cycle is updated by an appropriate amount ΔV, and the next time is also set to the reference blow steam amount _Ve .

V ₂ =V ₁ +ΔV (4) Next, the cumulative blowing time length of each soot blower is updated based on this updated reference blow steam amount V ₂ . Basically, the cumulative blowing time length of each soot blower is lengthened by the updated blow steam amount ratio (ΔV/V ₁ ).

Based on the next updated cumulative blowing length of each soot blower, if the blowing time length for one blow is too long, divide the number of blowing times (frequency) into two or three times, and Determine the time length and determine (update) the optimal sequence.

In the example of FIG. 9, since the soot blower groups A and B are already blowing continuously and alternately, an example is shown in which the blowing time length of each soot blower in the C soot blower group is updated from T _C →T _C '. There is.

ΔV=4(T _C ′−T _C )×F _C (5) As is clear from the above, according to the present invention, it is possible to select the optimal blow sequence, thereby reducing the cost spent on blowing. This also makes it possible to reduce the burden on the operator.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the outline of the soot blower control system, Fig. 2 is an explanatory diagram for explaining the principle of the present invention, Fig. 3 is a flowchart showing an embodiment of the present invention, and Figs. 4 a and b. 5, 7 and 9 are diagrams of the sequence principle of the present invention, and Figures 6, 8 and 10 are flowcharts showing other embodiments (parts 1 to 3) of the present invention. It is. 1...boiler, 2...heat transferr, 3...flue, 4
... Soot blower, 5, 6 ... Temperature detector (or draft detector), 10 ... Data processing device, 1
1...Data input/output section, 12...Memory section, 13
...Data processing section.

Claims (1)

[Claims] 1. A soot blower control method for controlling a plurality of soot blowers provided corresponding to each heat transfer surface of a boiler, comprising: sequentially operating each of the soot blowers at predetermined blowing time lengths and time intervals. 1 sequence is initialized, each soot blower is operated according to the first sequence, and the steam consumption amount is determined.
Using the steam consumption value in the first sequence, the blow steam amount of each soot blower, operating frequency,
updating at least one of the blowing times to set a second sequence, and operating each soot blower according to the second sequence;
A second step of detecting the boiler thermal efficiency at that time, and updating and setting the steam consumption in the second sequence, and among the operating frequency and blowing time of each soot blower according to the update of the steam consumption.
at least one modification, and the modified second
and a third step of executing the operation according to the sequence of and detecting the thermal efficiency of the boiler at that time, and the third step is performed until the boiler thermal efficiency reaches the desired value.
A soot blower control method characterized by repeating the steps.