Burning in circulating fluid bed boiler process optimization control system
(1) technical field
The present invention relates to a kind of control system, especially burning in circulating fluid bed boiler process optimization control system.
(2) background technology
Combustion technology of circulating fluidized is a kind of coal combustion technology of efficient, cleaning, is subjected to paying attention to widely in worldwide.Appearance along with oil crisis; shift from fuel oil and natural gas the energy resource structure ratio countries in the world to fire coal; but fire coal can bring serious environmental to pollute, therefore the combustion technology of a new generation---have high-efficiency low-pollution, Combustion technology of circulating fluidized that coal adaptability is good is arisen at the historic moment.
The combustion system of CFBB has reflected the design feature of recirculating fluidized bed than the concentrated area, and there is bigger difference its combustion chamber with the burner hearth of conventional pulverized-coal fired boiler.Typical CFBB is divided into upper and lower two parts, the top of combustion chamber is the oxidizing fire district, the bottom mainly is reduction burning and Gu Liuqu, is made up of air-distribution device, emulsion zone (suspension section), bed internal heating surface, gas-solid material separation device, solid material EGR parts such as (feeding back devices).Its combustion process is: after coal and desulfurizing agent are admitted to burner hearth, the a large amount of inertia high-temperature materials that existed in the burner hearth rapidly surround, and fire burns, and desulphurization reaction takes place, and under the ascending air effect, move to upper furnace, to other heating surface heat release of arranging in water-cooling wall and the stove.Oversize grain constantly slows down under gravity and other external force effect and departs from primary air, and finally form attached wall decline particle flux after being brought into the floating zone by ascending air.The solids that are entrained with burner hearth enter high-temperature separator with air-flow, and a large amount of solid materials comprise coal dust and desulfurizing agent, are separated and send burner hearth back to, carry out circulating combustion and desulfurization.Not separated superfine particle enters back-end ductwork with flue gas, further to heat releases such as heating surface, air preheater cooling, behind deduster, sends into chimney by air-introduced machine and enters atmosphere.
More existing companies have researched and developed the control scheme of boiler control system.Wherein have: propositions such as Wang Dewen are applied in fuzzy control in the coal-air ratio control of combustion system of circulating fluidized bed boiler, promptly adopt the steam coal amount of unit interval than calculating efficiency of combustion, utilize this efficient from seeking best coal-air ratio (Wang Dewen, Li Wentian, Liu Jincheng, etc., the application of fuzzy control in the burning in circulating fluid bed boiler control system. electric power information, 1997,4:47~50).Propositions such as Yu Haibin adopt expert system that CFBB is controlled, wherein total blast volume (air output) feedforward unit circuit controls is adopted in combustion chamber draft control, carbonated drink control scheme and the conventional similar (Yu Haibin of three momentums control, Chu builds, Zhang Baili, etc., 75t/ CFBB CFBB expert control system, chemical process automation and instrument, 1999,26 (1): 14~18; Based on the CFBB automatic control system of expert intelligence, generating equipment, 1999,4:14~21).Guo Shuan etc. propose fuzzy control to the combustion system of CFBB, employing be that the proportioning of a secondary wind realizes (Guo Shuan, Bian Lixiu, Zhang Yuping, electric power information, the combustion control system of CFBB, 2000,4:8~10).Yi Yang etc. propose fuzzy control to recirculating fluidized bed, employing be bed temperature-coal-supplying amount cascade control system (easily raise, Yi Fei, Lang Wenpeng, etc., boiler technology, the fuzzy control research of CFBB bed temperature, 2000,31 (1)).In intellectual education the application of expert control system in boiler combustion process proposed, by rule base 1, adjusting coal supply, wind, secondary wind and a secondary returning charge are controlled bed temperature (in intellectual education, the application of JX-300X expert control system in boiler combustion process, Shandong metallurgy, Vol.24, No.3:65~67).Yang Lin etc. propose the fuzzy control of Circulating Fluidized Bed Temperature, mainly regulate by coal-supplying amount and control bed temperature (Yang Lin, Xu Maosheng, the fuzzy control of CFBB bed temperature, Northern Transportation University's journal, 2002.26 (6)).Niu Peifeng proposes adaptive decoupling control to the temperature of CFBB, mainly controls superheater steam exit temperature (Niu Peifeng, automation journal, 1999,25 (1)) by feedwater flow.Alsthom Power Co. discloses the patent application (number of patent application: 97180932) of the control of the steam generator that relates to boiler.Wu Yuerong etc. propose fuzzy logic from adjusting P temperature measuring equipment coal-supplying amount controller complex control algorithm at CFBB, control fire box temperature (Wu Yuerong by the adjusting of a wind, yellow Yunan, the design of burning in circulating fluid bed boiler control system, Maritime Affairs University Of Dalian's journal, 1999, (1)).Horse bezoar duckweeds etc. propose the Circulating Fluidized Bed Temperature Fuzzy control system based on genetic algorithm, proposition is the reference frame of bed temperature control with the furnace outlet temperature, adopt the coarse adjustment primary air flow, the scheme of fine setting fuel quantity realizes (horse bezoar duckweed, department's wind fine jade, Xu Zhigao, Deng, based on the Circulating Fluidized Bed Temperature Fuzzy control system of genetic algorithm, Chinese engineering journal, 2001 (11)).Tsing-Hua University (Tsing-Hua University's journal, 2002,42 (5): 665-668) utilize generalized predictive control to realize that bed temperature is regulated and the coordination control of main steam pressure control.Mainly be to utilize dynamic model prediction bed temperature and main steam pressure, produce the given of bed temperature and main steam pressure by given generator then, realize that bed temperature is regulated and control is coordinated in the decoupling zero of main steam pressure control.
In sum, existing CFBB control scheme mainly contains following type:
1, confluent control is controlled with vapor (steam) temperature: confluent is controlled the main steam water-level three momentums control of adopting, and this also is present maturation and successful control scheme the most.Main steam temperature-desuperheating water tandem control also is the control scheme that extensively adopts.
2, air quantity control: generally adopt air inducing control combustion chamber draft, also have some reports to adopt wind, secondary wind and a primary and secondary air ratio to regulate the material bed tempertaure.As the scheme of Wu Yuerong etc., characteristics are 1) adopt coal-supplying amount control steam pressure, 2) adopt and regulate air quantity and control material bed tempertaure and coal-air ratio simultaneously.This also is present more common control scheme.Scheme in intellectual education adopts expert control system, and by rule base, adjusting coal supply, wind, a secondary wind are controlled bed temperature.
3, coal-supplying amount control: mainly contain three class schemes, 1) control bed temperature with coal-supplying amount, 2) control steam pressure with coal-supplying amount, 3) the coordination control (Tsing-Hua University's scheme) of steam pressure, bed temperature and coal supply.
(3) summary of the invention
The present invention aims to provide the smooth combustion of a kind of energy and improves the burning in circulating fluid bed boiler process optimization control system of efficiency of combustion.
The present invention is provided with the actuator of optimal controller, particle concentration controller, blast volume controller, coal-supplying amount controller, particle concentration controller, the actuator of blast volume controller, actuator, boiler combustion process measurement mechanism, particle concentration prediction device and the bed temperature prediction device of coal-supplying amount controller.
Wherein optimal controller is a calculation element that is used to export the optimization set-point of particle concentration controller, blast volume controller and coal supply controller, can use computer (single-chip microcomputer, PC etc.) to constitute, its set-point input is can be by the device of artificial setting numerical value, as instrument face plate or computer keyboard, in order to accept the boiler output products that operating personnel provide according to arts demand---the technology rated value of the pressure and temperature of superheated steam, and export above-mentioned optimization set-point according to an intelligent decision system that constitutes by computer software.The output of its manipulated signal input termination boiler combustion process measurement mechanism, the given control signal output of optimal controller connects the manipulated signal set-point input of particle concentration controller, blast volume controller, coal-supplying amount controller respectively.
Particle concentration prediction device and material bed tempertaure prediction device are real-time calculation elements, and available computers adds software systems and constitutes.The input of particle concentration prediction device and material bed tempertaure prediction device all inserts the output of boiler combustion process measurement mechanism, the output of particle concentration controller and the output of coal-supplying amount controller, and output in real time characterizes the characteristic of boiler furnace particle concentration and the discreet value of material bed tempertaure respectively.
Above-mentioned optimal controller, particle concentration prediction device and material bed tempertaure prediction device can be realized with same calculation element, also can use independently calculation element realization.
The discreet value output of the manipulated signal input termination particle concentration prediction device of particle concentration controller.
The manipulated signal input of blast volume controller connects the control signal output of coal-supplying amount controller and the output of boiler combustion process measurement mechanism respectively.
The material bed tempertaure discreet value output of the manipulated signal input termination bed temperature prediction device of coal-supplying amount controller.
The control signal output of particle concentration controller connects the input of the input of actuator of particle concentration controller and particle concentration prediction device, bed temperature prediction device respectively.
The give a dinner for a visitor from afar input of actuator of amount controller of the control signal output of blast volume controller.
The control signal output of coal-supplying amount controller inserts the input of the input of actuator of coal amount controller and particle concentration prediction device, bed temperature prediction device respectively.
Above-mentioned controller can be intelligence instrument, PLC (Programmable Logic Controller) or computer system.
The actuator of particle concentration controller, blast volume controller, coal-supplying amount controller is connected to CFBB respectively.The detection signal input of boiler combustion process measurement mechanism is connected to CFBB respectively.
Above-mentioned actuator can be frequency converter, control valve or magnetic valve.
Said boiler combustion process measurement mechanism is measurement mechanisms such as temperature, pressure and pressure reduction, air quantity, oxygen content of smoke gas.
As everyone knows, energy and environment are two large problems of current social development.China is producing coal and uses coal big country, and coal accounts for 76% in the primary energy consumption at present, and wherein 84% is used for direct burning, but efficiency of combustion is not high enough, and the atmosphere pollution that burning produces is not controlled effectively yet.China enters 87%SO in the atmosphere every year
2With 67% O
XAll from the direct burning of coal, also can produce a large amount of harmful materials if coal combustion is insufficient in addition, so adopt clean coal power generation technology, be the inevitable requirement of the strategy of sustainable development to power industry.China has classified clean coal power generation technology as the emphasis of medium-term and long-term program for the development of science and technology, is one of cross-centennial five big scientific and technological guides, and CFBB has been taken this task.The commercialized development of CFBB is had higher requirement to its operation automation, but because the burning in circulating fluid bed boiler process is a complex process with non-linear, large time delay, multiple coupled characteristic, the source and the quality that add coal are changeable, and its automatic control is a difficult point always.At present domestic have hundreds of platform boiler to put into operation, though great majority all adopt computer control systems such as coal-supplying amount controller, blast volume controller, the rate that comes into operation of robot control system(RCS) is all very low.It is the temperature of superheated steam and the rated value of pressure that the optimal control system that the present invention proposes sets boiler product according to arts demand, reaches the target of control boiler furnace particle concentration, smooth combustion and control boiler material bed and fire box temperature by the optimal control system.
Especially the present invention has caught the key issue of boiler combustion process particle concentration control, makes burning in circulating fluid bed boiler stable, and can optimize combustion process, improves efficiency of combustion.This control system has following characteristic: the characteristic that 1) obtains to characterize the boiler furnace particle concentration by soft measurement mechanism.2) set-point of the best particle concentration of exporting by optimal controller, material bed tempertaure and air quantity so forms an on-line optimization tandem system.3) be incorporated into particle concentration prediction device and bed temperature prediction device by output with particle concentration controller and coal-supplying amount controller, make soft measurement mechanism have the function of estimating simultaneously, in order to solve pure hysteresis and the coupled problem that particle concentration controller and coal-supplying amount controller exist.
Experiment showed, that the present invention has good feasibility.In the combustion process of CFBB, the particle concentration of burner hearth is the important parameter that characterizes combustion position, and suitable particle concentration is the key factor that guarantees high burning efficiency; Particle concentration also is the key factor that influences the heating surface heat transfer efficiency simultaneously.Therefore, the control particle concentration can be described as the key of having caught the burning in circulating fluid bed boiler process.But particle concentration can not be surveyed, so the present invention at first provides the characteristic that characterizes particle concentration by soft measurement estimating device, is used for representing particle concentration.According to the setting value and the optimal controller of superheated steam pressure and temperature, provide the best set-point of current particle concentration controller in real time simultaneously, realize the control of two-stage on-line optimization, reach smooth combustion and energy-conservation target.
(4) description of drawings
Fig. 1 is the composition frame chart of the embodiment of the invention.
Fig. 2 be the embodiment of the invention when implementing control changing trend diagram of main controlled variable of 8 hours.
(5) specific embodiment
Control system among the present invention as shown in Figure 1, the device A be an optimal controller, the device B, C, D are respectively particle concentration controller, blast volume controller and coal-supplying amount controller.Device E is the actuator of B controller, it can be the device of regulating the machinery and the electronic regulating unit of feed back air quantity or regulating the boiler bottom bed drain purge, device F is the actuator of C controller, in order to regulate the main air amount, device G is the actuator of D controller, in order to regulate coal-supplying amount, H is a CFBB, represent its combustion process, device I, J, K, L is respectively temperature measuring equipment, pressure and differential pressure measurement device, apparatus for measuring air quantity and oxygen content of smoke gas measurement mechanism, and they form the measuring system of boiler combustion process jointly.Device M is a boiler furnace particle concentration prediction device, and device N then is a material bed tempertaure prediction device.
In fact boiler furnace particle concentration prediction device M is soft measurement estimating device, can constitute as follows: with the various measuring-signals (temperature, pressure, pressure reduction and air quantity etc.) of boiler combustion process and the output u of particle concentration controller B
B(t), the output u of coal-supplying amount controller D
D(t) send into boiler furnace particle concentration prediction device M, and characterize the characteristic of boiler furnace particle concentration by following equation output
η(t)=f
M(ΔT(t),ΔP(t),R
a(t),u
B(t),u
D(t))
Wherein η (t) is for characterizing the characteristic of boiler furnace particle concentration, and Δ T (t) is the burner hearth temperature signal, and Δ P (t) is the burner hearth pressure difference signal, R
a(t) be the main air amount.Function f
MCan be the function of being derived by the CFBB mechanism mathematical model, also can be the function by the experimental data match.Material bed tempertaure prediction device N is an estimating device, can constitute as follows: the output u that will expect bed tempertaure measuring-signal, air quantity, pressure and differential pressure measurement signal, particle concentration controller B
B(t), the output u of coal-supplying amount controller D
D(t) send into material bed tempertaure prediction device N, according to the dynamic mathematical models of bed temperature or the discreet value of model of mind process line solver calculating acquisition material bed tempertaure.
At optimal controller A and controller B, C, among the D, the measured value or the discreet value of input port PV end input manipulated signal, the set-point of input port SV end input manipulated signal.In native system, the input signal of the SV of optimal controller A end is a boiler product---the temperature of superheated steam and the rated value T of pressure
GSAnd P
GS(can set) by arts demand, the input signal of PV end is other measuring-signal of superheat steam temperature, pressure and the combustion process of actual measurement, by system optimizing control o controller B, C, the given signal of D is sent into controller B respectively, C, the SV end of D.The PV end input signal of controller B is the characteristic η (t) of the sign boiler furnace particle concentration of particle concentration prediction device M output, calculates output control signal u through system optimizing control
B(t) deliver to the actuator E of particle concentration controller,, reach the target of control boiler furnace particle concentration at last to the combustion process generation effect of CFBB H.Blast volume controller C is a fuzzy decision system, and its PV end input signal is the output u of coal-supplying amount controller D
D(t), air quantity and oxygen content of smoke gas measuring-signal and bed temperature measuring-signal, controller carries out fuzzy decision to given signal, control signal and the measuring-signal of above-mentioned input, output control signal u
C(t), the actuator F by blast volume controller regulates the main air amount.The PV end input signal of coal-supplying amount controller D is the material bed tempertaure discreet value of bed temperature prediction device N output, calculates output control signal u through system optimizing control
D(t), by the actuator G adjusting coal-supplying amount of coal-supplying amount controller, reach the target of control boiler material bed tempertaure.Above-mentioned system optimizing control adopts no identification adaptive control algorithm in an embodiment, conventional pid algorithm or other control algolithm.
Fig. 2 provides the embodiment of the invention when implementing control 8 hours tendency chart.By the experimental result of Fig. 2 as seen, control respond wellly, bed temperature, steam pressure and temperature are all more stable.In Fig. 2, curve a is a vapor (steam) temperature, and curve b is the material bed tempertaure, and curve c is a steam flow, and curve d is a steam pressure, and curve e is an air quantity, and curve f is an oxygen content.