CN115681947A - Power plant's boiler flue gas waste heat recovery controlling means - Google Patents
Power plant's boiler flue gas waste heat recovery controlling means Download PDFInfo
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Abstract
The invention relates to the technical field of boiler flue gas waste heat utilization, and discloses a power plant boiler flue gas waste heat recovery control device, which comprises: the economizer is communicated with the flue gas channel; an air preheater, a flue gas heat exchanger, an induced draft fan, a desulfurizing tower and a chimney are sequentially arranged on the flue gas channel along the flow direction of flue gas; a circulating booster pump, a low-pressure heater group and a deaerator are sequentially arranged on the cooling water branch in the flow direction of the cooling water; the circulating heat exchange loop is used for absorbing the waste heat of the flue gas; the ultrasonic soot blowing system is arranged on the flue gas side of the flue gas heat exchanger; a detection device; the controller is used for controlling the ultrasonic soot blowing system to clean the flue gas heat exchanger; the flow rate and pressure of the cooling water are adjusted. The invention realizes the recovery of the waste heat of the flue gas, carries out soot blowing cleaning on the flue gas heat exchanger, avoids the accumulation of dust to block the flue gas heat exchanger, and avoids low-temperature corrosion of equipment by adjusting the flow and the pressure of cooling water.
Description
Technical Field
The invention relates to the technical field of boiler flue gas waste heat utilization, in particular to a power plant boiler flue gas waste heat recovery control device.
Background
The coal-fired power plant boiler in China provides most of electric energy output for the society, and simultaneously consumes a large amount of coal resources and industrial water resources. The exhaust gas temperature of a common boiler is usually higher, tail flue gas is directly sent into a desulfurizing tower after being dedusted, is discharged into the atmosphere after being cooled by spray and desulfurized by a wet method, and a large amount of exhaust gas waste heat is not utilized, so that waste heat is caused. With the upgrading of energy conservation and emission reduction and the development of energy conservation technology, the deep cooling and utilization of the tail flue gas of the boiler become important measures for reducing the temperature of the flue gas of the boiler and improving the economic benefit at present.
The flue gas at the tail part of the boiler can exchange heat by using a flue gas heat exchanger, and the heat exchange efficiency of the heat exchanger is influenced by dust deposition.
Disclosure of Invention
The invention provides a control device for recovering flue gas waste heat of a power plant boiler, which realizes flue gas heat exchange and flue gas temperature control by controlling the flow and pressure of cooling water and can effectively avoid the low-temperature corrosion phenomenon of equipment; the smoke side of the smoke heat exchanger is provided with an ultrasonic soot blower system for blowing soot at fixed time during operation, so that the occurrence of soot deposition is reduced;
in order to achieve the purpose, the invention provides the following scheme: the invention provides a flue gas waste heat recovery control device of a power plant boiler, which comprises:
the coal economizer is communicated with the flue gas channel; an air preheater, a flue gas heat exchanger, a dust remover, an induced draft fan, a desulfurizing tower and a chimney are sequentially arranged on the flue gas channel along the flow direction of flue gas;
the cooling water branch is used for circulating cooling water, and a water pump, a low-pressure heater group and a deaerator are sequentially arranged on the cooling water branch along the flowing direction of the cooling water;
the circulating heat exchange loop is used for absorbing the waste heat of the flue gas; the circulating heat exchange loop is communicated with the flue gas heat exchanger and the cooling water branch, and a pipeline circulating booster pump is arranged on the circulating heat exchange loop;
the ultrasonic soot blowing system is arranged on the flue gas side of the flue gas heat exchanger and is used for cleaning accumulated soot on the flue gas heat exchanger;
the detection device is used for detecting the temperature, flow speed and pressure of the flue gas and the cooling water and also used for detecting the dust deposition degree of the flue gas heat exchanger;
the controller is used for controlling the ultrasonic soot blowing system to clean the flue gas heat exchanger;
the controller is used for adjusting the flow of the cooling water to reduce the temperature of the flue gas.
In one embodiment, the low pressure heater group comprises a first low pressure heater, a second low pressure heater, a third low pressure heater and a fourth low pressure heater; and the first low-pressure heater, the second low-pressure heater, the third low-pressure heater and the fourth low-pressure heater are sequentially arranged on the cooling water branch in the flow direction of cooling water.
In one embodiment, the circulating heat exchange loop comprises a water inlet branch and a water outlet branch, wherein the water inlet end of the water inlet branch is communicated with the cooling water branch between the first low-pressure heater and the second low-pressure heater, and the water outlet end of the water inlet branch is communicated with the water inlet of the flue gas heat exchanger; the circulating booster pump is arranged on the water inlet branch;
and the water inlet end of the water outlet branch is communicated with the water outlet of the flue gas heat exchanger, and the water outlet end of the water outlet branch is communicated with the cooling water branch between the second low-pressure heater and the third low-pressure heater.
In one embodiment, the detection device comprises a flow meter, a speed sensor, a temperature measuring element and a video detection device;
the water outlet end of the water inlet branch, the water inlet end of the water outlet branch, the smoke inlet of the smoke heat exchanger and the smoke outlet of the smoke heat exchanger are respectively provided with the temperature measuring element;
the flow meter and the speed sensor are arranged on the water inlet branch, the water outlet branch and the flue gas channel;
the video detection device is used for detecting the accumulated dust of the flue gas heat exchanger.
In one embodiment, the controller is used for controlling the ultrasonic soot blowing system to clean the flue gas heat exchanger, and includes:
establishing a cleaning model of the flue gas heat exchanger;
determining the cleanliness degree of the flue gas heat exchanger according to the cleaning model;
setting soot blowing grades according to the relation between the cleanliness degrees and each preset cleanliness degree;
and adjusting the ultrasonic soot blowing system to clean the flue gas heat exchanger according to the soot blowing grade.
In one embodiment, establishing a cleaning model of the flue gas heat exchanger comprises:
calculating the total heat exchange coefficient value K of the flue gas heat exchanger according to the logarithmic mean temperature difference method of the heat exchanger;
calculating the total heat exchange coefficient value K of the flue gas heat exchanger under the cleaning working condition when the flow speed of the fluid at the hot side and the inlet and outlet temperatures are kept constant ch ；
According to the total heat exchange coefficient value K of the flue gas heat exchanger and the total heat exchange coefficient value K of the flue gas heat exchanger under the clean working condition ch Establishing a cleaning model of the flue gas heat exchanger;
the cleaning model of the flue gas heat exchanger is as follows:
wherein R is sf The thermal resistance of dirt before and after dust deposition of a flue gas heat exchanger under the same flue gas flow velocity is as follows: m is a unit of 2 K/W; said R is sf The size of the gas inlet pipe reflects the cleanliness of the flue gas side of the heat exchanger;
K sf actually measuring the total heat exchange coefficient of the flue gas heat exchanger, wherein the unit is as follows: w/m 2 ·K；
K s Under the same actual measurement flue gas flow velocity, the total heat exchange coefficient of the flue gas heat exchanger under the cleaning working condition is as follows: w/m 2 ·K。
In one embodiment, the setting of the soot blowing level according to the relationship between the cleanliness degrees and the preset cleanliness degrees includes:
presetting a preset cleaning degree matrix Q0, and setting Q0= (Q1, Q2, Q3, Q4), wherein Q1 is a first preset cleaning degree, Q2 is a second preset cleaning degree, Q3 is a third preset cleaning degree, and Q4 is a fourth preset cleaning degree, wherein Q1 is more than Q2 and less than Q3 and less than Q4;
presetting a preset soot blowing level matrix G0, and setting G0= (G1, G2, G3, G4), wherein G1 is a first preset soot blowing level, G2 is a second preset soot blowing level, G3 is a third preset soot blowing level, G4 is a fourth preset soot blowing level, and G1 is greater than G2 and greater than G3 and less than G4;
and setting a soot blowing grade G according to the relation between the cleanliness degree Q and each preset cleanliness degree:
when Q is less than Q1, selecting the first preset soot blowing level G1 as a soot blowing level G;
when Q1 is more than or equal to Q and less than Q2, selecting the second preset soot blowing level G2 as a soot blowing level G;
when Q2 is more than or equal to Q and less than Q3, selecting the third preset soot blowing level G3 as a soot blowing level G;
and when Q3 is not more than Q and is less than Q4, selecting the fourth preset soot blowing level G4 as a soot blowing level G.
In one embodiment, the controller is used for adjusting the flow rate and pressure of the cooling water, and comprises:
acquiring parameter data in a power plant boiler flue gas waste heat recovery process, and classifying and refining the parameter data to extract each basic characteristic data;
determining a frequency value of a frequency converter of the circulating booster pump, an opening value of an electric adjusting door at a water side inlet of the flue gas heat exchanger and an opening value of an electric adjusting door at a water side outlet of the flue gas heat exchanger based on the basic characteristic data and a preset relation model; the preset relation model is obtained by training according to a plurality of sample data based on a mixed type dynamic recurrent neural network;
and adjusting the frequency of the frequency converter of the circulating booster pump, the opening degree of the cold side inlet electric regulating valve of the flue gas heat exchanger and the opening degree of the cold side outlet electric regulating valve of the flue gas heat exchanger based on the determined frequency value of the frequency converter of the circulating booster pump, the opening degree of the water side inlet electric regulating valve of the flue gas heat exchanger and the opening degree of the cold side outlet electric regulating valve of the flue gas heat exchanger.
In one embodiment, the controller is further configured to establish the preset relationship model, including:
defining an input layer and an output layer, selecting optimized calculation values of flue gas heat exchanger outlet smoke temperature, unit load, flue gas heat exchanger inlet smoke temperature, flue gas heat exchanger water supply inlet temperature, flue gas heat exchanger water supply outlet temperature and flue gas acid dew point as input variables, and inputting dimension m =6; taking the frequency value of a frequency converter of the circulating booster pump, the opening value of the water side inlet electric regulating gate of the flue gas heat exchanger and the opening value of the water side outlet electric regulating gate of the flue gas heat exchanger as output variables, wherein the output dimension n =3;
selecting the number of hidden layers and the number of hidden layer units, adopting a single hidden layer, and determining the number of hidden layer nodes to be 7 according to an exhaustion method.
In one embodiment, the controller is further configured to optimize the established preset relationship model, including: and training the hybrid dynamic recurrent neural network based on the PSO algorithm.
The invention has the technical effects that: the cooling water flowing through the circulating heat exchange loop exchanges heat with the flue gas flowing through the flue gas heat exchanger, so that the waste heat recovery of the flue gas is realized, the flue gas temperature is reduced, the boiler efficiency is improved, the steam extraction quantity of a steam turbine regenerative system is reduced, and the coal consumption for power generation is reduced; the controller cleans the flue gas heat exchanger by controlling the ultrasonic soot blowing system, so that dust accumulation is avoided to block the flue gas heat exchanger, and the heat exchange efficiency is reduced; through the flow and the pressure of adjusting the cooling water, the water temperature of the cooling water at the inlet of the flue gas heat exchanger is not lower than the preset water temperature and then enters the flue gas heat exchanger, and low-temperature corrosion of equipment is avoided.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a schematic diagram of a flue gas waste heat recovery control device of a power plant boiler provided by an embodiment of the invention;
FIG. 2 is a schematic diagram of a cyclical heat exchange loop provided by an embodiment of the present invention;
FIG. 3 is a flow chart of cleaning a flue gas heat exchanger according to an embodiment of the present invention;
FIG. 4 is a flow chart for regulating the flow and pressure of cooling water provided by an embodiment of the present invention;
FIG. 5 is a schematic structural diagram of a hybrid dynamic recurrent neural network provided by an embodiment of the present invention;
wherein, 1, a coal economizer; 2. a flue gas channel; 3. an air preheater; 4. a flue gas heat exchanger; 5. a dust remover; 6. an induced draft fan; 7. a desulfurizing tower; 8. a chimney; 9. an ultrasonic soot blowing system; 10. a cooling water branch; 11. a water pump; 12. a first low pressure heater; 13. a second low pressure heater; 14. a third low pressure heater; 15. a fourth low pressure heater; 16. a deaerator; 17. a water inlet branch; 18. a water outlet branch; 19. a circulating booster pump; 20. a flow meter; 21. a speed sensor; 22. a temperature measuring element; 23. a video detection device; 24. an electric gate.
Detailed Description
The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.
In the description of the present application, it is to be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience in describing the present application and simplifying the description, but do not indicate or imply that the referred device or element must have a particular orientation, be constructed in a particular orientation, and be operated, and thus should not be construed as limiting the present application.
The terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present application, the meaning of "a plurality" is two or more unless otherwise specified.
In the description of the present application, it is to be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present application can be understood in a specific case by those of ordinary skill in the art.
With the rapid development of economy and the improvement of environmental protection requirements in China, more and more factory enterprises (coal, gas and oil) boilers are put into use; as diesel oil and gasoline resources are increasingly tense and the cost is continuously increased, the fuel cost of users is greatly increased, and the efficiency of boilers is increasingly improved. Energy conservation and environmental protection are important issues of global attention in the modern times, and people are more and more conscious of saving energy and improving energy utilization rate. Due to the requirement of boiler engineering design, the exhaust gas temperature can reach 160-500 ℃, the high-temperature exhaust gas not only causes heat waste, but also has great harm to environment pollution caused by the discharge of waste heat. The part of energy is fully utilized to utilize waste heat air and water, the air temperature and the water supply temperature are improved, and the fuel utilization efficiency can be improved to a certain extent. However, the flue gas at the tail of the boiler exchanges heat by using the flue gas heat exchanger 4, and the heat exchange efficiency of the heat exchanger is influenced by the surface dust deposition.
As shown in fig. 1, this embodiment discloses a power plant boiler flue gas waste heat recovery controlling means, includes: the economizer 1 is communicated with the flue gas channel 2; an air preheater 3, a flue gas heat exchanger 4, a dust remover 5, an induced draft fan 6, a desulfurizing tower 7 and a chimney 8 are sequentially arranged on the flue gas channel 2 along the flow direction of flue gas;
the cooling water branch is used for circulating cooling water, and a water pump 11, a low-pressure heater group and a deaerator 16 are sequentially arranged on the cooling water branch along a cooling water flowing method;
the circulating heat exchange loop is used for absorbing the waste heat of the flue gas; the circulating heat exchange loop is communicated with the flue gas heat exchanger 4 and the cooling water branch, and a pipeline circulating booster pump 19 is arranged on the circulating heat exchange loop;
the ultrasonic soot blowing system 9 is arranged on the flue gas side of the flue gas heat exchanger 4 and is used for cleaning accumulated soot on the flue gas heat exchanger 4;
the detection device is used for detecting the temperature, flow speed and pressure of the flue gas and the cooling water and also used for detecting the dust deposition degree of the flue gas heat exchanger 4;
the controller is used for controlling the ultrasonic soot blowing system to clean the flue gas heat exchanger 4;
the controller is also used to regulate the flow and pressure of the cooling water.
Specifically, the cooling water can be condensed water or demineralized water, the cooling water can absorb the heat of exhaust smoke in the smoke heat exchanger 4 of the device, the cooling water returns to the low-pressure heater group for utilization after the temperature is raised, the exhaust smoke temperature is reduced, the boiler efficiency is improved, the steam extraction amount of a turbine regenerative system is reduced, and the coal consumption of power generation is reduced.
Specifically, the flue gas heat exchanger 4 can be installed at any position behind the air preheater and in front of the dust removal system, and the installation direction can be horizontally arranged or vertically arranged; the heat exchange tube of the flue gas heater adopts a thick-wall steel tube with the diameter of 38cm and strong wear resistance, and two layers of dummy tubes can be arranged at the front end of the windward side of the heat exchange tube bank in order to improve the wear resistance of the heat exchange tube of the flue gas heater, so that the wear of the heat exchange tube bank at the front end is reduced, and the reliability of equipment is improved. For example, a stainless steel wear-resistant cover tile with the thickness of 2mm is additionally arranged on the first row of heat exchange tubes along the flue gas direction, so that the abrasion of the front-end heat exchange tube row is further reduced, and the reliability of the equipment is improved.
It can be understood that, in the above embodiment, the cooling water flowing through the circulating heat exchange loop exchanges heat with the flue gas flowing through the flue gas heat exchanger 4, so as to realize waste heat recovery of the flue gas, reduce the temperature of the flue gas, improve the boiler efficiency, reduce the steam extraction amount of the turbine regenerative system, and reduce the coal consumption of power generation; the controller cleans the flue gas heat exchanger 4 by controlling the ultrasonic soot blowing system, so that dust accumulation and blockage of the flue gas heat exchanger 4 are avoided, and the heat exchange efficiency is reduced; through the flow and the pressure of adjusting the cooling water, the temperature of the cooling water at the inlet of the flue gas heat exchanger 4 is not lower than the preset temperature and then enters the flue gas heat exchanger 4, and low-temperature corrosion of equipment is avoided.
In some embodiments of the present application, the low pressure heater group comprises a first low pressure heater 12, a second low pressure heater 13, a third low pressure heater 14 and a fourth low pressure heater 15; a first low pressure heater 12, a second low pressure heater 13, a third low pressure heater 14 and a fourth low pressure heater 15 are installed on the cooling water branch in sequence along the flow direction of the cooling water.
In some embodiments of the present application, the circulating heat exchange loop includes a water inlet branch 17 and a water outlet branch 18, a water inlet end of the water inlet branch 17 is communicated with the cooling water branch between the first low-pressure heater 12 and the second low-pressure heater 13, and a water outlet end of the water inlet branch 17 is communicated with a water inlet of the flue gas heat exchanger 4; a circulating booster pump 19 is arranged on the water inlet branch 17;
the water inlet end of the water outlet branch 18 is communicated with the water outlet of the flue gas heat exchanger 4, and the water outlet end of the water outlet branch 18 is communicated with the cooling water branch between the second low-pressure heater 13 and the third low-pressure heater 14.
It can be understood that, in the above embodiment, the efficiency of the low-pressure heater absorbing the heat of the heated cooling water is improved by reasonably planning the installation position of the circulating heat exchange loop.
In some embodiments of the present application, the sensing devices include a flow meter 20, a speed sensor 21, a temperature sensing element 22, and a video sensing device;
the water inlet branch 17, the water outlet branch 18 and the flue gas channel are respectively provided with a flowmeter 20 and a speed sensor 21;
the video detection device 23 is used for detecting the dust deposition degree of the flue gas heat exchanger 4.
It is understood that, in the above embodiments, the detected data includes: outlet flue gas temperature x of flue gas heat exchanger 4 1 (t) condensing temperature t of hot side of flue gas heat exchanger 4 s And the temperature x of the smoke at the inlet of the smoke heat exchanger 4 3 (t), the temperature x of the water supply inlet of the flue gas heat exchanger 4 4 (t) inlet temperature t of the cold side of the flue gas heat exchanger 4 c1 Temperature x of water supply outlet of flue gas heat exchanger 4 5 (t) outlet temperature t of the cold side of the flue gas heat exchanger 4 c2 Cold side cooling water flow velocity v c The flow rates of the water inlet branch 17, the water outlet branch 18 and the flue gas channel, the pressure of the water inlet branch 17 close to the flue gas heat exchanger 4, and the like.
As shown in fig. 3, in some embodiments of the present application, the controller is configured to control the ultrasonic soot blowing system to clean the flue gas heat exchanger 4, and includes:
step S110, establishing a cleaning model of the flue gas heat exchanger 4;
step S120, determining the cleanliness of the flue gas heat exchanger 4 according to the cleaning model;
step S130, setting soot blowing grades according to the relation between the cleanliness degrees and the preset cleanliness degrees;
and step S140, adjusting the ultrasonic soot blowing system to clean the flue gas heat exchanger 4 according to the soot blowing grade.
It can be understood that, in the above embodiments, the soot blowing level is set according to the relationship between the cleanliness degrees and the preset cleanliness degrees, so that the soot blowing efficiency can be improved, and the problems of unclean cleaning or excessive cleaning, consuming time, power and energy, and energy consumption can be avoided.
In some embodiments of the present application, a cleaning model of the flue gas heat exchanger 4 is established, comprising: calculating the total heat exchange coefficient value K of the flue gas heat exchanger 4;
when the flow speed of the fluid at the hot side and the inlet and outlet temperature are kept constant, the total heat exchange coefficient value K of the flue gas heat exchanger 4 under the clean working condition is calculated ch ；
According to the total heat exchange coefficient value K of the flue gas heat exchanger 4 and the total heat exchange coefficient value K of the flue gas heat exchanger 4 under the cleaning working condition ch Establishing a cleaning model of the flue gas heat exchanger 4;
the cleaning model of the flue gas heat exchanger 4 is as follows:
wherein R is sf The thermal resistance of dirt before and after dust deposition of a flue gas heat exchanger 4 under the same flue gas flow velocity is as follows: m is 2 ·K/W；R sf The size of the gas inlet pipe reflects the cleanliness of the flue gas side of the heat exchanger;
K sf actually measuring the total heat exchange coefficient of the flue gas heat exchanger 4, unit: w/m 2 ·K；
K s Under the same actually measured flue gas flow velocity, the total heat exchange coefficient of the flue gas heat exchanger 4 under the cleaning working condition is as follows: w/m 2 ·K。
Specifically, the total heat exchange coefficient value K of the flue gas heat exchanger 4 is calculated by using the detected flow rate of the cold side (i.e., the cooling water side), the inlet temperature and the outlet temperature of the cold side, and the condensation temperature (i.e., the temperature at the smoke outlet of the flue gas heat exchanger 4) of the hot side (i.e., the flue gas side), by using a logarithmic mean temperature difference method, and is calculated by the following formula:
wherein, Q: total heat of the flue gas heat exchanger 4, unit: w;
a is the heat exchange area of the flue gas heat exchanger 4, unit: m2;
Δ tm the mean logarithmic temperature difference of the flue gas heat exchanger 4, in units: DEG C;
wherein: the average logarithmic temperature difference can be further written as:
wherein: t is t s : condensation temperature of the hot side of the flue gas heat exchanger 4, unit: DEG C;
t c1 : inlet temperature at the cold side of the flue gas heat exchanger 4, unit: DEG C;
t c2 : outlet temperature at the cold side of the flue gas heat exchanger 4, unit: DEG C;
the total heat exchange coefficient value K of the flue gas heat exchanger 4 under the current condition can be calculated by the formulas (1) and (2).
According to the flow of the cold side, the convective heat transfer coefficient of the cold side under the cleaning working condition can be calculated through the heat transfer performance of the cold side of the flue gas heat exchanger 4, and during flue gas-water heat exchange, the relationship between the total heat transfer coefficient of the flue gas heat exchanger 4 without cleaning and the convective heat transfer coefficients of fluids at two sides is as follows:
K ch : the total heat exchange coefficient of the flue gas heat exchanger 4 during flue gas-water heat exchange, unit: w/(m) 2 ·K)；
h c : the convective heat transfer coefficient of the cold side fluid during flue gas-water heat transfer of the flue gas heat exchanger 4 is as follows, unit: w/(m) 2 ·K)；
R w : thermal resistance of the wall of the flue gas heat exchanger 4 during flue gas-water heat exchange of the flue gas heat exchanger 4, unit: w/(m) 2 ·K)；
h h : the heat convection coefficient of the hot side fluid during flue gas-water heat exchange of the flue gas heat exchanger 4 is as follows, unit: w/(m) 2 ·K)；
Also, because the convective heat transfer coefficient can be expressed as a 0.8 th power relation to the flow velocity, i.e.
In the formula, a c Is a constant coefficient;
and make an order
When the flow rate of the fluid at the hot side and the temperature of the inlet and the outlet are almost unchanged, b is a constant;
finishing into the following components:
to obtain
In the formula, v c -cold side cooling water flow rate, m/s;
therefore, a relational expression between the flow rate of the cold side and the total heat exchange coefficient of the heat exchanger is obtained when the hot side fixes the flow rate during the smoke-water heat exchange of the smoke heat exchanger 4.
The condensation heat exchange coefficient of the flue gas side can be calculated through the flue gas side heat transfer performance of the flue gas heat exchanger 4, and therefore the total heat exchange coefficient of the flue gas heat exchanger 4 under the clean working condition can be calculated.
Wherein R is sf The thermal resistance of dirt before and after dust deposition of a flue gas heat exchanger 4 under the same flue gas flow velocity is as follows: m is 2 ·K/W；R sf The size of the gas inlet pipe reflects the cleanliness of the flue gas side of the heat exchanger;
K sf actually measuring the total heat exchange coefficient of the flue gas heat exchanger 4, unit: w/(m) 2 ·K)；
K s In factMeasuring the total heat exchange coefficient under the cleaning working condition of the flue gas heat exchanger 4 at the same flue gas flow velocity, unit: w/(m) 2 ·K)。
It can be understood that, in the above embodiment, through establishing the clean model of gas heater 4, the clean degree that reflects gas heater 4 that can be accurate improves the accuracy of cleaning the deposition on gas heater 4, avoids the deposition to pile up, influences heat exchange efficiency, causes the waste of flue gas waste heat.
In some embodiments of the present application, the setting of the soot blowing level according to the relationship between the degree of cleanliness and each preset degree of cleanliness includes:
presetting a preset cleaning degree matrix Q0, and setting Q0= (Q1, Q2, Q3, Q4), wherein Q1 is a first preset cleaning degree, Q2 is a second preset cleaning degree, Q3 is a third preset cleaning degree, and Q4 is a fourth preset cleaning degree, wherein Q1 is more than Q2 and less than Q3 and less than Q4;
presetting a preset soot blowing level matrix G0, and setting G0= (G1, G2, G3, G4), wherein G1 is a first preset soot blowing level, G2 is a second preset soot blowing level, G3 is a third preset soot blowing level, G4 is a fourth preset soot blowing level, and G1 is greater than G2 and greater than G3 and less than G4;
setting a soot blowing grade G according to the relation between the cleanliness degree Q and each preset cleanliness degree:
when Q is less than Q1, selecting a first preset soot blowing level G1 as a soot blowing level G;
when Q1 is not more than Q and less than Q2, selecting a second preset soot blowing level G2 as a soot blowing level G;
when Q2 is not less than Q and is less than Q3, selecting a third preset soot blowing level G3 as a soot blowing level G;
and when Q3 is not less than Q and is less than Q4, selecting a fourth preset soot blowing level G4 as a soot blowing level G.
In particular, because R sf The size of (2) reflects the cleanness of the flue gas side of the heat exchanger, and R is more than 0 sf < 1, so a predetermined cleanliness matrix Q0 is predetermined, Q0= (0.2, 0.4,0.6, 0.8) is set, wherein 0.2 is a first predetermined cleanliness level, 0.4 is a second predetermined cleanliness level, 0.6 is a third predetermined cleanliness level, and 0.8 is a fourth predetermined cleanliness level, wherein 0 < 0.2 < 0.4 < 0.6 < 0.6 <0.8；
Presetting a preset soot blowing level matrix G0, and setting G0= (G1, G2, G3, G4), wherein G1 is a first preset soot blowing level, G2 is a second preset soot blowing level, G3 is a third preset soot blowing level, G4 is a fourth preset soot blowing level, and G1 is greater than G2 and greater than G3 and less than G4;
and setting a soot blowing grade G according to the relation between the cleanliness degree Q and each preset cleanliness degree:
when Q is more than 0 and less than 0.2, selecting a first preset soot blowing level G1 as a soot blowing level G;
when Q is more than or equal to 0.2 and less than 0.4, selecting a second preset soot blowing level G2 as a soot blowing level G;
when Q is more than or equal to 0.4 and less than 0.6, selecting a third preset soot blowing level G3 as a soot blowing level G;
and when Q is more than or equal to 0.6 and less than 0.8, selecting a fourth preset soot blowing level G4 as a soot blowing level G.
It can be understood that, in the above embodiment, the soot blowing level G is set according to the relationship between the cleanliness degree Q and each preset cleanliness degree, and the accuracy of setting the soot blowing level G is improved.
It should be noted that the above solution of the preferred embodiment is only one specific implementation proposed in the present application, and those skilled in the art may select other cleanliness degree matrices Q0 and the preset soot blowing level matrix G0 according to practical situations, for example, set Q0= (Q1, Q2, Q3, Q4, Q5), set G0= (G1, G2, G3, G4, G5), which does not affect the protection scope of the present application.
As shown in fig. 4, in some embodiments of the present application, the controller is used to regulate the flow and pressure of the cooling water, including:
s210, acquiring parameter data in the flue gas waste heat recovery process of the power plant boiler, and classifying and refining the parameter data to extract each basic characteristic data;
step S220, determining a frequency value of a frequency converter of the circulating booster pump 19, an opening value of an electric adjusting door 24 at a water side inlet of the flue gas heat exchanger 4 and an opening value of an electric adjusting door 24 at a water side outlet of the flue gas heat exchanger 4 based on each basic characteristic data and a preset relation model; the preset relation model is obtained by training according to a plurality of sample data based on a mixed type dynamic recurrent neural network;
and step S230, adjusting the frequency of the frequency converter of the circulating booster pump 19, the opening degree of the inlet electric regulating door 24 at the cold side of the flue gas heat exchanger 4 and the opening degree of the outlet electric regulating door 24 at the cold side of the flue gas heat exchanger 4 based on the determined frequency value of the frequency converter of the circulating booster pump 19, the opening degree of the inlet electric regulating door 24 at the water side of the flue gas heat exchanger 4 and the opening degree of the outlet electric regulating door 24 at the cold side of the flue gas heat exchanger 4.
Specifically, the sample data includes input data and output data having a correspondence relationship; the basic feature data can be preprocessed before the step S220, so that the problems of poor effect, unstable accuracy and the like caused by too many correlation samples in the subsequent step of constructing the preset relationship model are avoided.
It can be understood that, in the above embodiment, the frequency of the frequency converter of the circulating booster pump 19, the opening degree of the electric water inlet regulating gate 24 of the flue gas heat exchanger 4, and the opening degree of the electric water outlet regulating gate 24 of the flue gas heat exchanger 4 are adjusted based on the determined frequency value of the frequency converter of the circulating booster pump 19, the opening degree of the electric water inlet regulating gate 24 of the flue gas heat exchanger 4, and the opening degree of the electric water outlet regulating gate 24 of the cold side of the flue gas heat exchanger 4, so as to adjust the flow rate and pressure of the cooling water, so that the water temperature of the cooling water at the inlet of the flue gas heat exchanger is not lower than the preset water temperature and then enters the flue gas heat exchanger, thereby avoiding low-temperature corrosion of the equipment.
As shown in fig. 5, in some embodiments of the present application, the controller is further configured to establish a preset relationship model, including:
defining an input layer and an output layer, selecting an outlet smoke temperature of the smoke heat exchanger 4, a unit load, an inlet smoke temperature of the smoke heat exchanger 4, a water supply inlet temperature of the smoke heat exchanger 4, a water supply outlet temperature of the smoke heat exchanger 4 and an optimized calculation value of a smoke acid dew point as input variables, and inputting the dimension m =6; taking the frequency value of a frequency converter of the circulating booster pump 19, the opening value of an inlet electric regulating gate 24 at the water side of the flue gas heat exchanger 4 and the opening value of an outlet electric regulating gate 24 at the water side of the flue gas heat exchanger 4 as output variables, wherein the output dimension n =3;
selecting the number of hidden layers and the number of hidden layer units, adopting a single hidden layer, and determining the number of hidden layer nodes to be 7 according to an exhaustion method.
It is understood that, in the above embodiment, the hybrid dynamic recurrent neural network (MDRNN) is used to construct the preset relationship model.
Specifically, the MDRNN consists of three layers of grids: an input layer, a hidden layer and an output layer.
The input variable is 6, namely the smoke temperature x at the outlet of the smoke heat exchanger 4 1 (t) Unit load x 2 (t) flue gas temperature x at inlet of flue gas heat exchanger 4 3 (t) feed water inlet temperature x of flue gas heat exchanger 4 4 (t) temperature x of water supply outlet of flue gas heat exchanger 4 5 (t) flue gas acid dew point optimization calculated value x 6 (t), thus the input dimension m =6; determining the number of nodes of the hidden layer to be 7 by an exhaustion method according to the training sample set; the control quantity of the output layer is 3, namely the frequency u of a frequency converter of the 19 circulating booster pump 1 (t) 24-degree of opening u of water side inlet electric control door of flue gas heat exchanger 4 2 (t), 24-degree opening u of the water side outlet electric regulating valve of the flue gas heat exchanger 4 3 (t) of (d). The frequency of the frequency converter of the circulating booster pump 19, the opening degree of the inlet electric regulating valve 24 at the water side of the flue gas heat exchanger 4 and the opening degree of the outlet electric regulating valve 24 at the water side of the flue gas heat exchanger 4 are regulated by regulating the frequency of the frequency converter of the circulating booster pump 19, the opening degree of the inlet electric regulating valve 24 at the cold side of the flue gas heat exchanger 4 and the opening degree of the outlet electric regulating valve 24 at the cold side of the flue gas heat exchanger 4, so that the flow and the pressure of cooling water entering the flue gas heat exchanger 4 are controlled, and the outlet flue gas temperature of the flue gas heat exchanger 4 is controlled.
In some embodiments of the present application, the controller is further configured to optimize the established preset relationship model, including: and training the hybrid dynamic recurrent neural network based on the PSO algorithm.
It can be understood that, in the above embodiment, the improved ant colony optimization algorithm is used to train the neural network sample data and optimize the calculation network weights so as to better reduce the error between the neural network model output and the actual output of the flue gas heat exchanger 4 system.
Six main influence parameters of the current flue gas heat exchanger 4 device can be comprehensively learned by utilizing PSO-MDRNN optimization control, the minimum difference between the flue gas temperature at the outlet of the flue gas heat exchanger 4 and the flue gas acid dew point is used as a training signal, the actual flue gas temperature at the outlet of the flue gas heat exchanger 4 is used as a feedback signal for network learning, the control effect can be enhanced, the optimal condensate flow and pressure are obtained to be used as real-time action instructions of an electric regulating valve, and the optimization control of regulating the flue gas temperature drop at the outlet of the flue gas heat exchanger 4 is realized.
Specifically, the PSO algorithm training neural network comprises the following steps:
step1, initial time t =0, initializes all sets I pi Setting the maximum iteration number to Nmax, making pheromone of each element in the set and residual pheromone delta tau j (I pi ) =0, place all ants in ant nest.
And Step2, starting all ant groups, selecting paths by the ant k according to the equation, and selecting elements in the set by adopting a wheel disc method.
And Step3, dynamically adjusting pheromones of all ants according to an equation (9) and an equation (10), obtaining chaotic disturbance variables by using an equation (11), and adding chaotic disturbance to avoid a local trap area.
z j，i+1 ＝4z j，i (1-z j，i )，i＝0，1，2...(11)
Step4, repeat Step2 until all ants reach the food source.
Step5, letting t = t + l and N = N +1, calculating the output and error of the model according to the weight selected by each ant, and recording the current optimal solution. Where l is the elapsed time unit.
And Step6, when the optimal solution does not change for N1 times continuously, finishing the coarse search, enabling r = r +1, carrying out scale transformation near the current optimal solution according to an equation (12), and carrying out fine search by using a linear combination obtained by the equation (13) as a chaotic variable to guide the ant colony to accelerate the search speed.
And Step7, making N = N +1, and ending when the optimization result is kept unchanged when repeating steps 6 to N2 iterations.
And Step8, when the overall evolutionary trend is not obvious or N = Nmax, the iteration is ended, and the optimal solution is output. Otherwise, step2 is switched.
In conclusion, the control device for recovering the flue gas waste heat of the power plant boiler, provided by the invention, can adjust the heat exchange amount and control the flue gas temperature by controlling the frequency conversion of the circulating booster pump 19 and the opening degree of the water side inlet electric regulating door 24 of the flue gas heat exchanger 4 and the opening degree of the water side outlet electric regulating door 24 of the flue gas heat exchanger 4, so that the water temperature of the inlet of the heat exchanger in the flue gas is increased, and the low-temperature corrosion of equipment is avoided. Determining the cleaning degree of the flue gas heat exchanger 4 by establishing a cleaning model of the flue gas heat exchanger 4; and setting a soot blowing grade according to the relation between the cleanliness degrees and the preset cleanliness degrees, and performing soot blowing cleaning.
It should be understood that, although the steps in the flowcharts of the embodiments of the present invention are shown in sequence as indicated by the arrows, the steps are not necessarily performed in sequence as indicated by the arrows. The steps are not performed in the exact order shown and described, and may be performed in other orders, unless explicitly stated otherwise. Moreover, at least a portion of the steps in various embodiments may include multiple sub-steps or multiple stages that are not necessarily performed at the same time, but may be performed at different times, and the order of performance of the sub-steps or stages is not necessarily sequential, but may be performed in turn or alternately with other steps or at least a portion of the sub-steps or stages of other steps.
Those of ordinary skill in the art will understand that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that modifications may be made to the embodiments described above, or equivalents may be substituted for elements thereof. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. The utility model provides a power plant's boiler flue gas waste heat recovery controlling means which characterized in that includes:
the coal economizer is communicated with the flue gas channel; an air preheater, a flue gas heat exchanger, a dust remover, an induced draft fan, a desulfurizing tower and a chimney are sequentially arranged on the flue gas channel along the flow direction of flue gas;
the cooling water branch is used for circulating cooling water, and a water pump, a low-pressure heater group and a deaerator are sequentially arranged on the cooling water branch along the flowing direction of the cooling water;
the circulating heat exchange loop is used for absorbing the waste heat of the flue gas; the circulating heat exchange loop is communicated with the flue gas heat exchanger and the cooling water branch, and a circulating booster pump is arranged on the circulating heat exchange loop;
the ultrasonic soot blowing system is arranged on the smoke side of the smoke heat exchanger and is used for cleaning accumulated soot on the smoke heat exchanger;
the detection device is used for detecting the temperature, flow speed and pressure of the flue gas and the cooling water and also used for detecting the dust deposition degree of the flue gas heat exchanger;
the controller is used for controlling the ultrasonic soot blowing system to clean the flue gas heat exchanger;
the controller is also used for adjusting the flow and pressure of the cooling water.
2. A power plant boiler flue gas waste heat recovery control device as claimed in claim 1, wherein the low pressure heater group comprises a first low pressure heater, a second low pressure heater, a third low pressure heater and a fourth low pressure heater; and the first low-pressure heater, the second low-pressure heater, the third low-pressure heater and the fourth low-pressure heater are sequentially arranged on the cooling water branch in the flow direction of the cooling water.
3. A power plant boiler flue gas waste heat recovery control device according to claim 2, wherein the circulating heat exchange loop comprises a water inlet branch and a water outlet branch, a water inlet end of the water inlet branch is communicated with the cooling water branch between the first low-pressure heater and the second low-pressure heater, and a water outlet end of the water inlet branch is communicated with a water inlet of the flue gas heat exchanger; the circulating booster pump is arranged on the water inlet branch;
and the water inlet end of the water outlet branch is communicated with the water outlet of the flue gas heat exchanger, and the water outlet end of the water outlet branch is communicated with the cooling water branch between the second low-pressure heater and the third low-pressure heater.
4. The power plant boiler flue gas waste heat recovery control device according to claim 3, wherein the detection device comprises a flow meter, a speed sensor, a temperature measuring element and a video detection device;
the temperature measuring elements are arranged at the water outlet end of the water inlet branch, the water inlet end of the water outlet branch, the smoke inlet of the smoke heat exchanger and the smoke outlet of the smoke heat exchanger;
the flow meter and the speed sensor are arranged on the water inlet branch, the water outlet branch and the flue gas channel;
the video detection device is used for detecting the accumulated dust of the flue gas heat exchanger.
5. A power plant boiler flue gas waste heat recovery control device as claimed in claim 1, wherein the controller is configured to control the ultrasonic soot blowing system to clean the flue gas heat exchanger, and comprises:
establishing a cleaning model of the flue gas heat exchanger;
determining the cleanliness degree of the flue gas heat exchanger according to the cleaning model;
setting soot blowing grades according to the relation between the cleanliness degrees and each preset cleanliness degree;
and adjusting the ultrasonic soot blowing system to clean the flue gas heat exchanger according to the soot blowing grade.
6. The power plant boiler flue gas waste heat recovery control device of claim 5, wherein the establishing of the cleaning model of the flue gas heat exchanger comprises:
calculating the total heat exchange coefficient value K of the flue gas heat exchanger according to the logarithmic mean temperature difference method of the heat exchanger;
calculating the total heat exchange coefficient value K of the flue gas heat exchanger under the cleaning working condition when the flow speed of the fluid at the hot side and the inlet and outlet temperatures are kept constant ch ；
According to the total heat exchange coefficient value K of the flue gas heat exchanger and the total heat exchange coefficient value K of the flue gas heat exchanger under the clean working condition ch Establishing a cleaning model of the flue gas heat exchanger;
the cleaning model of the flue gas heat exchanger is as follows:
wherein R is sf The thermal resistance of dirt before and after dust deposition of a flue gas heat exchanger under the same flue gas flow velocity is as follows: m is 2 K/W; the R is sf The size of the gas inlet pipe reflects the cleanliness of the flue gas side of the heat exchanger;
K sf actually measuring the total heat exchange coefficient of the flue gas heat exchanger, wherein the unit is as follows: w/(m) 2 ·K)；
K s Under the same actual measurement flue gas flow velocity, the total heat exchange coefficient of the flue gas heat exchanger under the cleaning working condition is as follows: w/(m) 2 ·K)。
7. A power plant boiler flue gas waste heat recovery control device as claimed in claim 5, wherein the setting of soot blowing levels according to the relationship between the cleanliness degrees and the respective preset cleanliness degrees comprises:
presetting a preset cleaning degree matrix Q0, and setting Q0= (Q1, Q2, Q3, Q4), wherein Q1 is a first preset cleaning degree, Q2 is a second preset cleaning degree, Q3 is a third preset cleaning degree, and Q4 is a fourth preset cleaning degree, wherein Q1 is more than Q2 and more than Q3 and more than Q4;
presetting a preset soot blowing level matrix G0, and setting G0= (G1, G2, G3, G4), wherein G1 is a first preset soot blowing level, G2 is a second preset soot blowing level, G3 is a third preset soot blowing level, G4 is a fourth preset soot blowing level, and G1 is more than G2 and more than G3 and more than G4;
setting a soot blowing grade G according to the relation between the cleanliness degree Q and each preset cleanliness degree:
when Q is less than Q1, selecting the first preset soot blowing level G1 as a soot blowing level G;
when Q1 is more than or equal to Q and less than Q2, selecting the second preset soot blowing level G2 as a soot blowing level G;
when Q2 is not less than Q and is less than Q3, selecting the third preset soot blowing level G3 as a soot blowing level G;
and when Q3 is more than or equal to Q and less than Q4, selecting the fourth preset soot blowing level G4 as a soot blowing level G.
8. The power plant boiler flue gas waste heat recovery control device of claim 1, wherein the controller is used for adjusting the flow and pressure of cooling water, and comprises:
acquiring parameter data in a power plant boiler flue gas waste heat recovery process, and classifying and refining the parameter data to extract each basic characteristic data;
determining a frequency value of a frequency converter of the circulating booster pump, an opening value of an inlet electric regulating gate at the water side of the flue gas heat exchanger and an opening value of an outlet electric regulating gate at the water side of the flue gas heat exchanger based on the basic characteristic data and a preset relation model; the preset relation model is obtained by training according to a plurality of sample data based on a mixed type dynamic recurrent neural network;
and adjusting the frequency of the frequency converter of the circulating booster pump, the opening degree of the cold side inlet electric regulating valve of the flue gas heat exchanger and the opening degree of the cold side outlet electric regulating valve of the flue gas heat exchanger based on the determined frequency value of the frequency converter of the circulating booster pump, the opening degree of the water side inlet electric regulating valve of the flue gas heat exchanger and the opening degree of the cold side outlet electric regulating valve of the flue gas heat exchanger.
9. A power plant boiler flue gas waste heat recovery control device as claimed in claim 8, wherein the controller is further configured to establish the preset relationship model, including:
defining an input layer and an output layer, selecting an optimized calculation value of the outlet smoke temperature of the smoke heat exchanger, the unit load, the inlet smoke temperature of the smoke heat exchanger, the water supply inlet temperature of the smoke heat exchanger, the water supply outlet temperature of the smoke heat exchanger and the acid dew point of smoke as input variables, and inputting the dimension m =6; taking the frequency value of a frequency converter of the circulating booster pump, the opening value of an inlet electric regulating gate at the water side of the flue gas heat exchanger and the opening value of an outlet electric regulating gate at the water side of the flue gas heat exchanger as output variables, wherein the output dimension n =3;
selecting the number of hidden layers and the number of hidden layer units, adopting a single hidden layer, and determining the number of hidden layer nodes to be 7 according to an exhaustion method.
10. A power plant boiler flue gas waste heat recovery control device as claimed in claim 9, wherein the controller is further configured to optimize the established preset relationship model, including: and training the hybrid dynamic recurrent neural network based on the PSO algorithm.
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