CN108488831B - Boiler combustion control system and method - Google Patents
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- 238000002485 combustion reaction Methods 0.000 title claims abstract description 88
- 238000000034 method Methods 0.000 title claims abstract description 22
- 238000012545 processing Methods 0.000 claims abstract description 21
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 claims description 33
- 239000002956 ash Substances 0.000 claims description 20
- 239000003245 coal Substances 0.000 claims description 12
- 239000002893 slag Substances 0.000 claims description 12
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims description 11
- 239000003546 flue gas Substances 0.000 claims description 11
- 239000010881 fly ash Substances 0.000 claims description 11
- 238000012937 correction Methods 0.000 claims description 7
- 239000000126 substance Substances 0.000 claims description 7
- 239000007789 gas Substances 0.000 claims description 6
- 239000007787 solid Substances 0.000 claims description 6
- 238000001514 detection method Methods 0.000 claims description 4
- 230000017525 heat dissipation Effects 0.000 claims description 4
- 239000000779 smoke Substances 0.000 claims description 3
- 238000004364 calculation method Methods 0.000 description 6
- 238000005457 optimization Methods 0.000 description 5
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 4
- 230000006870 function Effects 0.000 description 4
- 239000001301 oxygen Substances 0.000 description 4
- 229910052760 oxygen Inorganic materials 0.000 description 4
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- 230000008859 change Effects 0.000 description 2
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- 230000000694 effects Effects 0.000 description 2
- 239000000446 fuel Substances 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
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- 238000013473 artificial intelligence Methods 0.000 description 1
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- 238000006243 chemical reaction Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
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- 238000012546 transfer Methods 0.000 description 1
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N3/00—Regulating air supply or draught
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N2900/00—Special features of, or arrangements for controlling combustion
- F23N2900/05003—Measuring NOx content in flue gas
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Abstract
The invention provides a boiler combustion control system and method, and belongs to the technical field of boiler combustion control. The boiler combustion control system includes: the receiving module is used for receiving the pressure difference between a hearth and an air box of the boiler and the load of a combustion unit of the boiler; the processing module is used for obtaining a compensation value of the opening degree of each layer of secondary air door according to the pressure difference and the load; and the control module is used for adjusting the opening degree of each layer of secondary air door according to the compensation value. According to the invention, the compensation value of the opening degree of each layer of secondary air door is obtained according to the pressure difference between the hearth and the air box of the boiler and the load of the combustion unit of the boiler, and the opening degree of each layer of secondary air door of the boiler is adjusted according to the compensation value, so that the problems of low thermal efficiency and large pollution of the thermal power station boiler are solved.
Description
Technical Field
The invention relates to a boiler combustion control technology, in particular to a boiler combustion control system and a boiler combustion control method.
Background
At present, the thermal power station boiler in China mainly takes subcritical and supercritical large-capacity boilers as main parts, and mainly has the problems of low thermal efficiency, large pollution and the like, so that the research on the development and application of the combustion optimization technology of the power station boiler is of great significance, resources can be effectively saved, the thermal efficiency is improved, and the pollution of coal generated in the combustion process can be reduced. The utility boiler combustion is a complex physical and chemical process, and relates to the fields of combustion science, hydromechanics, thermodynamics, heat and mass transfer science and the like. The boiler combustion optimization control is to ensure that the fuel fed into the boiler furnace is combusted safely, stably and continuously in time by adjusting the fuel supply and air distribution parameters of the boiler, changing the control mode of the boiler, and the like, and to obtain the optimal combustion condition on the premise of meeting the load change requirement of a unit.
A large power station generally adopts a Distributed Control System (DCS) to realize automatic control of power production, and the combustion process in a furnace involves complex physical and chemical reaction processes, so that at present, the mechanism of the combustion process is not completely understood, the factors influencing the pulverized coal combustion process in the furnace are more (including various factors such as coal types, boiler loads, air distribution modes, hearth negative pressure, coal mill combination modes and the like), and the factors are nonlinear and strongly coupled, so that the modeling of boiler combustion optimization control is greatly challenged.
Disclosure of Invention
The invention aims to provide a boiler combustion control system and a boiler combustion control method, which are used for solving the problem of automatically and effectively controlling boiler combustion.
In order to achieve the above object, the present invention provides a boiler combustion control system, comprising: the receiving module is used for receiving the pressure difference between a hearth and an air box of the boiler and the load of a combustion unit of the boiler; the processing module is used for obtaining a compensation value of the opening degree of each layer of secondary air door according to the pressure difference and the load; and the control module is used for adjusting the opening degree of each layer of secondary air door according to the compensation value.
Optionally, the processing module includes: the difference value calculating module is used for calculating the difference between the received differential pressure and the preset differential pressure to obtain a deviation value; and the fuzzy compensation module is used for obtaining a compensation value of the opening degree of each layer of secondary air door through a fuzzy rule according to the deviation value and the received load.
Optionally, adjusting the opening degree of the secondary air door of each floor according to the compensation value comprises: and under the condition that the compensation value is greater than the compensation threshold value, adjusting the compensation threshold value for the opening degree of each layer of secondary air door, otherwise, adjusting the compensation value for each layer of secondary air door.
Optionally, the system further comprises: a combustion efficiency prediction module for predicting the combustion efficiency of the boiler; the detection module is used for detecting the content of nitrogen oxides in the flue gas of the boiler; and the processing module obtains a compensation value of the opening degree of each layer of secondary air door according to the pressure difference and the load under the condition that the combustion efficiency is lower than the preset efficiency or the content of the nitrogen oxide is higher than the preset content, and the control module adjusts the opening degree of each layer of secondary air door according to the compensation value.
Optionally, the system further comprises: the presetting module is used for storing a pressure difference typical value of the pressure difference between a hearth and an air box of the boiler, a load typical value of the load of a boiler combustion unit and an opening typical value of the opening of each layer of secondary air doors corresponding to the pressure difference typical value and the load typical value; and the control module controls the opening of each layer of secondary air door according to the corresponding opening typical value obtained by the processing module.
Correspondingly, the invention also provides a boiler combustion control method, which comprises the following steps: receiving the pressure difference between a hearth and an air box of the boiler and the load of a combustion unit of the boiler; obtaining a compensation value of the opening degree of each layer of secondary air door according to the pressure difference and the load; and adjusting the opening degree of each layer of secondary air door according to the compensation value.
Optionally, the obtaining a compensation value of the opening degree of each layer of secondary air door according to the pressure difference and the load comprises: calculating a difference between the received differential pressure and a predetermined differential pressure to obtain a deviation value; and obtaining a compensation value of the opening degree of each layer of secondary air door according to the deviation value and the received load through a fuzzy rule.
Optionally, adjusting the opening degree of the secondary air door of each floor according to the compensation value comprises: and under the condition that the compensation value is greater than the compensation threshold value, adjusting the compensation threshold value for the opening degree of each layer of secondary air door, otherwise, adjusting the compensation value for each layer of secondary air door.
Optionally, the method further comprises: predicting a combustion efficiency of the boiler; detecting the content of nitrogen oxides in the flue gas of the boiler; and under the condition that the combustion efficiency is lower than the preset efficiency or the content of the nitrogen oxides is higher than the preset content, obtaining a compensation value of the opening of each layer of secondary air door according to the pressure difference and the load, and adjusting the opening of each layer of secondary air door according to the compensation value.
Optionally, the method further comprises: storing a pressure difference typical value of the pressure difference between a hearth and an air box of the boiler, a load typical value of the load of a boiler combustion unit and an opening typical value of the opening of each layer of secondary air doors corresponding to the pressure difference typical value and the load typical value; and controlling the opening degree of the secondary air door of each floor according to the corresponding opening degree typical value in the case that the received pressure difference and the load are the pressure difference typical value and the load typical value, respectively.
According to the technical scheme, the compensation value of the opening degree of each layer of secondary air door is obtained according to the pressure difference between the hearth and the air box of the boiler and the load of the combustion unit of the boiler, and the opening degree of each layer of secondary air door of the boiler is adjusted according to the compensation value, so that the problems of low thermal efficiency and high pollution of the thermal power station boiler are solved.
Additional features and advantages of embodiments of the invention will be set forth in the detailed description which follows.
Drawings
The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the embodiments of the invention without limiting the embodiments of the invention. In the drawings:
FIG. 1 is a block diagram of a boiler combustion control system provided by the present invention;
FIG. 2 is a flow chart of an embodiment of boiler combustion control provided by the present invention; and
FIG. 3 is a flow chart of a boiler combustion control method provided by the present invention.
Detailed Description
The following detailed description of embodiments of the invention refers to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating embodiments of the invention, are given by way of illustration and explanation only, not limitation.
The basic starting point of the artificial intelligence technology is to simulate human intelligence to realize effective modeling and control of a complex uncertainty system, has the capability of self-learning and adapting to the environment from the environment, has the capability of automatically processing information to reduce uncertainty of the information, and can plan, generate and safely and reliably execute control action. Aiming at the condition that the existing DCS system is operated in a power plant, the invention changes the combustion efficiency of the boiler and the emission of NOx by adjusting the compensation value of the opening of the secondary air quantity on the premise of not influencing the production.
FIG. 1 is a block diagram of a boiler combustion control system provided by the present invention, as shown in FIG. 1, including a receiving module 101, a processing module 102, and a control module 103. The receiving module 101 is used for receiving the pressure difference between a hearth and an air box of the boiler and the load of a combustion unit of the boiler; the processing module 102 is used for obtaining a compensation value of the opening degree of each layer of secondary air door according to the pressure difference and the load; the control module 103 is used for adjusting the opening of each layer of secondary air door according to the compensation value.
The processing module 102 may obtain a compensation value of the opening degree of the secondary damper of each floor according to the pressure difference between the furnace and the windbox of the boiler and the load of the combustion unit of the boiler by using a fuzzy rule established by expert fuzzy experience. It will be appreciated by those skilled in the art that the compensation value for the opening of the secondary damper for each level may also be derived from the pressure differential and the load according to other neural network algorithms established in advance.
It should be understood by those skilled in the art that the opening degree of each layer of the secondary damper may be the same or different, so the compensation value of the opening degree of each layer of the secondary damper obtained by the processing module 102 is respectively corresponding to the opening degree of each layer of the secondary damper, that is, the processing module 102 outputs a plurality of values, that is, there is one compensation value respectively corresponding to each layer of the secondary damper, that is, the processing module 102 actually obtains a plurality of compensation values, and one compensation value corresponds to one secondary damper.
The processing module 102 may include a difference calculating module and a fuzzy compensation module, wherein the difference calculating module is configured to calculate a difference between the received differential pressure and a predetermined differential pressure to obtain a deviation value; and the fuzzy compensation module is used for obtaining a compensation value of the opening degree of each layer of secondary air door according to the deviation value and the received load through a fuzzy rule.
The deviation value is a received pressure difference between a furnace and a windbox of the boiler, and here, a compensation value of the opening degree of the secondary air door of each layer is obtained according to the deviation value and the received load of the combustion unit of the boiler, and the control module 103 adjusts the opening degree of the secondary air door of each layer according to the compensation value.
It will be appreciated that if the offset is too large, i.e. there is too much adjustment of the opening of the secondary damper at a time, which may result in excessive adjustment, then adjustment back may be required, e.g. assuming that there is 20% adjustment of the opening of the secondary damper at a time, there is a high possibility that there will be a 10% adjustment back again, i.e. an adjustment of-10%, which-10% may be excessive if desired, so that if this adjustment is repeated, it will be difficult to achieve a satisfactory result, and so it is recommended that there is not too much adjustment.
Adjusting the opening degree of each layer of secondary air door according to the compensation value comprises the following steps: and under the condition that the compensation value is greater than the compensation threshold value, adjusting the compensation threshold value for the opening degree of each layer of secondary air door, otherwise, adjusting the compensation value for each layer of secondary air door. That is, a compensation threshold is set, and if the compensation value obtained by the processing module 102 is greater than the compensation threshold, the compensation threshold is adjusted only for the opening degree of the secondary damper, so that the overcompensation condition does not occur.
For example, the compensation threshold may be set to 5%, and assuming that the compensation value currently obtained by the processing module 102 is 20%, the control module only adjusts the opening degree of the secondary damper for each floor by 5%, and if the opening degree is still not appropriate, the adjustment is continued for the next time.
Fig. 2 is a flowchart of an embodiment of the boiler combustion control provided by the present invention, as shown in fig. 2, the flowchart includes:
And step 202, obtaining a compensation value of the opening of each layer of secondary air door according to the pressure difference between the hearth and the air box of the boiler and the load of a combustion unit of the boiler.
In step 203, it is determined whether the compensation value obtained in step 202 is greater than a predetermined compensation threshold, if so, step 205 is executed, otherwise, step 204 is executed.
And step 204, adjusting the opening degree of each layer of secondary air door by using the compensation value.
In step 205, the opening degree of the secondary damper for each floor is adjusted by using the compensation threshold.
The boiler combustion control system further comprises a combustion efficiency prediction module and a detection module. The combustion efficiency prediction module is used for predicting the combustion efficiency of the boiler; the detection module is used for detecting the content of nitrogen oxides in the flue gas of the boiler; the processing module obtains a compensation value of the opening degree of each layer of secondary air door according to the pressure difference and the load under the condition that the combustion efficiency is lower than the preset efficiency or the content of the nitrogen oxide is higher than the preset content, and the control module adjusts the opening degree of each layer of secondary air door according to the compensation value. The model is also called as a soft measurement model of the boiler efficiency, can effectively predict the combustible substances of the fly ash and the slag which can not be measured in real time in the boiler, can represent the combustion economy in the boiler in real time, and provides a basis for the compensation value of the air door opening of the boiler.
Specifically, the processing module needs to determine whether the following conditions are satisfied: first, the combustion efficiency is lower than a predetermined efficiency; second, the nitrogen oxide content is higher than the predetermined content. The above-described technology of the present invention is required to be performed if one of the two conditions is not satisfied, that is, if the combustion efficiency is lower than the predetermined efficiency or if the nox content is higher than the predetermined content, it indicates that the opening degree of the secondary damper needs to be adjusted, and thus the processing module obtains a compensation value for the opening degree of the secondary damper for each floor according to the pressure difference and the load and the control module performs the adjustment of the opening degree of the secondary damper for each floor.
The boiler combustion control system further comprises a presetting module, wherein the presetting module is used for storing a pressure difference typical value of the pressure difference between a hearth and an air box of the boiler, a load typical value of the load of a boiler combustion unit and an opening typical value of the opening of each layer of secondary air doors corresponding to the pressure difference typical value and the load typical value; and the control module controls the opening of each layer of secondary air door according to the corresponding opening typical value obtained by the processing module.
The typical values of pressure difference and load in the presetting module are the optimal operation parameters of the opening degree of the secondary air door of each layer of the boiler under the typical load working condition. However, those skilled in the art will appreciate that the pressure differential and load do not remain constant at all times, and therefore, it is necessary to constantly compensate for the opening of the secondary dampers for each floor.
The invention is explained by combining the specific examples, the deviation value is taken as input, and the compensation value of the opening degree of each layer of secondary air door is output by utilizing a fuzzy rule table established by expert fuzzy experience. Those skilled in the art will appreciate that the secondary dampers of the boiler include auxiliary dampers and burnout dampers. The opening of the auxiliary air door is adjusted to maintain a required static pressure difference between the furnace and the secondary windbox, and the opening of the burnout air door is adjusted to reduce NOx and provide boiler combustion efficiency.
For the auxiliary damper, the total opening is:
in formula (1), Σ x1To assist the total opening of the damper, x1For the opening degree typical value stored in the presetting module, i.e. the control module compensates the opening degree of the secondary air door based on the typical value of the pressure difference, Deltax1To compensate for opening, x, of auxiliary dampers1nThe opening degree of the nth sub-damper is expressed by equation (1) for 7 sub-dampers.
For the auxiliary damper, the total opening is:
∑x2＝x2+Δx2(n＝8…14) (2)
in the formula (2), Σ x2For total opening of the burn-out damper, x2For the opening degree typical value, Δ x, stored in the presetting module2In order to compensate the opening degree of the burnout damper, 7 auxiliary dampers from the 8 th layer to the 14 th layer are expressed in equation (2). In general, the opening degree of each layer in the burnout damper is the same, so Σ x in expression (2)2I.e. the opening degree of each layer of the overfire air.
The combustion efficiency prediction module in the present invention predicts the boiler efficiency by the following formula (3):
η＝100-q2-q3-q4-q5-q6 (3)
where eta is called boiler efficiency-meal equilibrium thermal efficiency (i.e., boiler efficiency), q2To the rate of loss of smoke, q3The heat loss rate of incomplete combustion of combustible gas, q4Is the rate of heat loss due to incomplete combustion of solids, q5To obtain the heat dissipation loss rate, q6Is the physical heat loss rate of ash (including slag and fly ash).
Q in the following formula (3)2、q3、q4、q5、q6The calculation of (a) is explained in detail.
Loss rate q of exhaust gas2The calculation is as follows:
q2＝(3.55×αpy+0.44)×(tpy-t0)/100×(100-q4)/100％ (4)
in the formula (4), αpyIs the excess air factor at the location of the exhaust fumes, tpyIs the exhaust gas temperature, t0Is the reference temperature.
Incomplete combustion heat loss rate q of combustible gas3The calculation is as follows:
q3＝0.032×αpy×co×100％ (5)
in formula (5), αpyCO is the volume fraction of CO in the flue gas, which is the excess air factor at the flue gas (same as in equation (4)).
Heat dissipation loss rate q5The calculation is as follows:
in the formula (6), DedAnd D is the actual evaporation capacity of the boiler.
Physical heat loss rate q of ash (including slag and fly ash)6The calculation is as follows:
in the formula (7), AarReceiving basic ash, Q, for coal combustionrFor low calorific value of coal, alphahzThe ash quantity accounts for the mass share of the total ash (C theta)hz1kg of ash at a temperature thetahzSpecific enthalpy of mass, thetahzAs 600 deg.C, look-up table (C theta)hz＝560。
Heat loss rate q of incomplete combustion of solid4The calculation is as follows:
in formula (8), αlzThe mass portion of the slag ash in the total ash is,Clzis the content of combustible substances in the slag, alphafhThe mass fraction of fly ash in the total ash content, CfhIs the content of combustible substance in fly ash, AarReceiving basic ash, Q, for coal combustionrIs the lower calorific value of the coal, wherein alphalz+αfhAs a rule of thumb, α is given as 1fh＝0.9，αlz＝0.1。
The following explains beta in the formula (8), where beta is a correction coefficient, and the correction coefficient beta is added to accurately calculate the carbon content of fly ash and slag in consideration of the influence of different flue gas oxygen contents on the combustible content of fly ash and slag under the condition of constant load. The correction factor β expert empirical fuzzy rule is shown in table 1
TABLE 1
| Oxygen content of flue gas | Is very low | Is low in | Is moderate | Is higher than | Is very high |
| Correction factor | Is very high | Height of | Is moderate | Is lower than | Is very low |
The weighted average rice fuzzification by fuzzy rule is calculated as follows:
in the formula (9), z1Is the oxygen content of the flue gas,
is the point, μ, corresponding to the jth rule when the fuzzy membership function takes the maximum valueAMembership function as a fuzzy rule, i.e. z1Membership function of (c). As can be seen from table 1, in this embodiment, the oxygen content of the flue gas is divided into 5 levels, which are very low, moderate, high, and very high, respectively, and the correction coefficient is correspondingly divided into 5 levels, which are very high, moderate, low, and very low, respectively, according to the embodiment described in table 1, M in equation (9) is 5. Those skilled in the art will appreciate that while the 5 levels in table 1 are described literally, e.g., lower, higher, etc., they are substantially calculated using numerical range values. The above-mentioned membership functions, fuzzy rules and other specialized vocabularies are commonly used in the art and are not described herein.
Fig. 3 is a flowchart of a boiler combustion control method provided by the present invention, as shown in fig. 3, the method including:
step 301, receiving the pressure difference between a hearth and an air box of the boiler and the load of a combustion unit of the boiler.
And step 302, obtaining a compensation value of the opening degree of each layer of secondary air door according to the pressure difference and the load.
And step 303, adjusting the opening degree of each layer of secondary air door according to the compensation value.
It should be noted that the specific details and benefits of the boiler combustion control method provided by the present invention are similar to those of the boiler combustion control system provided by the present invention, and are not described herein again.
Although the embodiments of the present invention have been described in detail with reference to the accompanying drawings, the embodiments of the present invention are not limited to the details of the above embodiments, and various simple modifications can be made to the technical solutions of the embodiments of the present invention within the technical idea of the embodiments of the present invention, and the simple modifications all belong to the protection scope of the embodiments of the present invention.
The technical scheme provided by the invention has the advantages that the algorithm is relatively simple, the online optimization speed is greatly improved, the calculated amount and the storage amount are reduced, the effect is obvious, and the method is very suitable for the real-time combustion optimization control of a large boiler. The fuzzy control is designed based on heuristic knowledge and language decision rules, simulates the process and method of operating personnel on the site of boiler operation, converts a large amount of on-site operation experience into reliable fuzzy rules, and enhances the adaptability of the control system, so that the control system has certain intelligent level. Meanwhile, the robustness is strong, the influence of interference and parameter change on the control effect is greatly weakened, and the method is suitable for the control of a nonlinear, time-varying and pure hysteresis system.
It should be noted that the various features described in the above embodiments may be combined in any suitable manner without departing from the scope of the invention. In order to avoid unnecessary repetition, the embodiments of the present invention do not describe every possible combination.
Those skilled in the art will understand that all or part of the steps in the method according to the above embodiments may be implemented by a program, which is stored in a storage medium and includes several instructions to enable a single chip, a chip, or a processor (processor) to execute all or part of the steps in the method according to the embodiments of the present application. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.
In addition, any combination of various different implementation manners of the embodiments of the present invention is also possible, and the embodiments of the present invention should be considered as disclosed in the embodiments of the present invention as long as the combination does not depart from the spirit of the embodiments of the present invention.
Claims (6)
1. A boiler combustion control system, characterized in that the system comprises:
the receiving module is used for receiving the pressure difference between a hearth and an air box of the boiler and the load of a combustion unit of the boiler;
a combustion efficiency prediction module to predict a combustion efficiency of the boiler by:
η＝100-q2-q3-q4-q5-q6
wherein q is2To the rate of loss of smoke, q3The heat loss rate of incomplete combustion of combustible gas, q4Is the rate of heat loss due to incomplete combustion of solids, q5To obtain the heat dissipation loss rate, q6Is the physical heat loss rate of the ash slag,
and calculating the rate of heat loss q from incomplete combustion of the solid by the following formula4：
Where β is the correction coefficient and αlzThe mass fraction of the slag ash in the total ash content, ClzIs the content of combustible substances in the slag, alphafhThe mass fraction of fly ash in the total ash content, CfhIs the content of combustible substance in fly ash, AarReceiving basic ash, Q, for coal combustionrIs the lower calorific value of the coal, wherein alphalz+αfh＝1；
The detection module is used for detecting the content of nitrogen oxides in the flue gas of the boiler;
the processing module comprises a difference value calculating module and a fuzzy compensating module, the difference value calculating module is used for obtaining a deviation value according to the difference between the pressure difference and the preset pressure difference under the condition that the combustion efficiency is lower than the preset efficiency or the content of the nitrogen oxides is higher than the preset content, and the fuzzy compensating module is used for obtaining a compensation value of the opening degree of each layer of secondary air doors through a fuzzy rule according to the deviation value and the received load by utilizing a fuzzy rule table established based on expert fuzzy experience; and
and the control module is used for adjusting the opening degree of each layer of secondary air door according to the compensation value of the opening degree of the secondary air door.
2. The system of claim 1, wherein adjusting the secondary damper opening per tier as a function of the compensation value comprises:
and under the condition that the compensation value is greater than the compensation threshold value, adjusting the compensation threshold value for the opening degree of each layer of secondary air door, otherwise, adjusting the compensation value for each layer of secondary air door.
3. The system of claim 1, further comprising:
the presetting module is used for storing a pressure difference typical value of the pressure difference between a hearth and an air box of the boiler, a load typical value of the load of a boiler combustion unit and an opening typical value of the opening of each layer of secondary air doors corresponding to the pressure difference typical value and the load typical value;
and the control module controls the opening of each layer of secondary air door according to the corresponding opening typical value obtained by the processing module.
4. A method for controlling combustion in a boiler, the method comprising:
receiving the pressure difference between a hearth and an air box of the boiler and the load of a combustion unit of the boiler;
predicting the combustion efficiency of the boiler by:
η＝100-q2-q3-q4-q5-q6
wherein q is2To the rate of loss of smoke, q3The heat loss rate of incomplete combustion of combustible gas, q4Is the rate of heat loss due to incomplete combustion of solids, q5To obtain the heat dissipation loss rate, q6Is ash slagThe rate of physical heat loss is,
and calculating the rate of heat loss q from incomplete combustion of the solid by the following formula4：
Where β is the correction coefficient and αlzThe mass fraction of the slag ash in the total ash content, ClzIs the content of combustible substances in the slag, alphafhThe mass fraction of fly ash in the total ash content, CfhIs the content of combustible substance in fly ash, AarReceiving basic ash, Q, for coal combustionrIs the lower calorific value of the coal, wherein alphalz+αfh＝1；
Detecting the content of nitrogen oxides in the flue gas of the boiler;
under the condition that the combustion efficiency is lower than the preset efficiency or the content of the nitrogen oxides is higher than the preset content, obtaining a deviation value according to the difference between the pressure difference and the preset pressure difference, and obtaining a compensation value of the opening degree of each layer of secondary air doors through a fuzzy rule according to the deviation value and the received load by utilizing a fuzzy rule table constructed based on expert fuzzy experience; and
and adjusting the opening degree of each layer of secondary air door according to the compensation value.
5. The method of claim 4, wherein adjusting the secondary damper opening per tier as a function of the compensation value comprises:
and under the condition that the compensation value is greater than the compensation threshold value, adjusting the compensation threshold value for the opening degree of each layer of secondary air door, otherwise, adjusting the compensation value for each layer of secondary air door.
6. The method of claim 4, further comprising:
storing a pressure difference typical value of the pressure difference between a hearth and an air box of the boiler, a load typical value of the load of a boiler combustion unit and an opening typical value of the opening of each layer of secondary air doors corresponding to the pressure difference typical value and the load typical value; and
in the case where the received pressure difference and load are a pressure difference typical value and a load typical value, respectively, the opening degree of the secondary damper for each floor is controlled according to the corresponding opening degree typical value.
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| CN112413634B (en) * | 2020-10-22 | 2022-09-20 | 中国大唐集团科学技术研究院有限公司西北电力试验研究院 | Secondary air control method for front-back wall hedging coal-fired power station boiler |
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