CN102385356B - Optimizing control method for sintering waste heat power generation system - Google Patents

Optimizing control method for sintering waste heat power generation system Download PDF

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CN102385356B
CN102385356B CN2011101921293A CN201110192129A CN102385356B CN 102385356 B CN102385356 B CN 102385356B CN 2011101921293 A CN2011101921293 A CN 2011101921293A CN 201110192129 A CN201110192129 A CN 201110192129A CN 102385356 B CN102385356 B CN 102385356B
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pressure
steam
waste heat
temperature
heat boiler
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CN2011101921293A
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CN102385356A (en
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任铁良
王春凯
方会斌
陈巍
林金柱
梁伯平
林建军
陈深灿
乐晓芳
江荣才
李志红
李宝东
蒋卫
杨懿
李鹏元
李岩
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中钢集团鞍山热能研究院有限公司
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    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00Technologies related to metal processing
    • Y02P10/25Process efficiency

Abstract

The invention relates to an optimizing control method for a sintering waste heat power generation system; the optimizing control method is characterized in that when parameters of a waste heat boiler and a steam turbine and the smoke flow and the inlet/outlet temperature of the waste heat boiler are constant, the power generation capacity of the steam turbine is only related to the pressure of middle pressure steam and low pressure steam which are output by the waste heat boiler, and the power generation capacity of the steam turbine is maximized by controlling the pressure of middle pressure steam and low pressure steam which are output by the waste heat boiler. Compared with the prior art, the optimizing control method has the beneficial effects: (1). the optimum control on a waste heat recycling system can be realized; and when external conditions change, the real-time automatic tracking is carried out and the optimal pressure value is adjusted; (2). the optimizing control method not only can be used for carrying out optimum control on the sintering waste heat power generation system put into operation, but also can be used for checking the design of the sintering waste heat power generation system and optimizing the design, thereby obtaining parameters such as the optimal outlet temperature of a preheater of the waste heat boiler, the optimal temperature of an evaporator, the optimal outlet temperature of a superheater, the optimal flow of the middle pressure steam and the low pressure steam, and the like and selecting the appropriate steam turbine.

Description

A kind of optimal control method of sintering waste heat generating system
Technical field
The present invention relates to steel enterprise sintering waste heat recovery field, relate in particular to a kind of optimal control method of sintering waste heat generating system.
Background technology
The sintering circuit energy consumption accounts for 9%~12% of iron and steel enterprise's total energy consumption at present, and the waste heat of its discharging accounts for 50% of sintering total energy consumption heat energy.Sintering deposit is in cooling procedure, and the heat of taking away by the cooler air accounts for about 30% of sintering total energy consumption, recycles this part heat energy (encircle cold or belt-cooling machine cooling air discharging), and sintering circuit energy-saving and cost-reducing had very important effect.The heat energy that accounts in addition in addition sintering total energy consumption heat energy 20% is discharged by main exhauster.
The waste heat recovery main application has: 1) be used as the combustion air of igniting, holding furnace, with gas saving; 2) be used for pre-heat mixture, to reduce coke powder consumption; 3) be used for waste heat boiler and produce steam, with Partial Replacement fuel boiler steam; 4) be used for cogeneration etc.
Most of iron and steel enterprise generally all uses the reduction that first three kind mode realizes sintering energy consumption, but also having greatly, low temperature exhaust heat does not utilize fully, and the most of supervisor of iron and steel enterprise net steam has surplus, so these enterprises are all considering further to reduce sintering energy consumption with cogeneration.
Cold or the belt-cooling machine cogeneration technology difficult point of sintered ring is:
1) the sinter cooler exhaust gas flow is very large, but, low-temperature zone (below 150 ℃) and part middle-temperature section waste gas do not have value, and high temperature section and the medial temperature that can utilize part middle-temperature section waste gas are between 300~380 ℃, affected by fall ore deposit temperature and cooler air leak rate of air curtain of sintering machine, waste heat is of low quality, and it is larger to recycle difficulty.
2) electricity generation system is higher to the quality requirements of afterheat steam in addition; because the sintering therrmodynamic system is unstable; the exhaust gas temperature fluctuation range is more than ± 100 ℃; cause the fluctuation of afterheat steam temperature to exceed standard; force the Waste Heat Power Station frequent shutdown, the security of serious threat steam turbine, stability and life-span.
Summary of the invention
The optimal control method that the purpose of this invention is to provide a kind of sintering waste heat generating system; large for sintering system exhaust gas temperature fluctuation range; thermo-power station frequent shutdown phenomenon; trace model parameter optimal value and to its On-line Control makes steam turbine change with the sintering exhaust-heat boiler parameter and automatically keeps the optimized operation state.
For solving the problems of the technologies described above, technical scheme of the present invention is:
A kind of optimal control method of sintering waste heat generating system, when waste heat boiler and steam turbine equipment parameter and exhaust-heat boiler flue gas flow and out temperature one timing, the steam turbine power generation ability only with waste heat boiler output in, low-pressure steam pressure is relevant, by in the waste heat boiler output, low-pressure steam pressure controls, can make the steam turbine power generation ability reach maximum, its control step is as follows:
1) determine the control simulated target, be simulated target to the maximum with steam turbine power generation power:
Max?W e=η eW m??(1)
In the formula: W eBe generated output, W; η eBe efficiency of generator, dimensionless;
W eBe turbine shaft output mechanical power, W;
2) set up the energy equilibrium equation of constraint
(1) steam turbine energy-balance equation
W m = η m Σ i = 1 M η c , i Δ H i - - - ( 2 )
Wherein: η c , i = 1 - T 0 T i (i=1,2,…,M)??(3)
Δ H i = L i [ 4182 ( 373.15 - T a ) + 1000 × 2256.6 + ∫ 373.15 T i C P ( T ) dT + 8314 18 ln P i 101325 ]
(i=1,2,…,M)??(4)
In the formula: η mBe steam turbine mechanical efficiency, dimensionless; η iBe Carnot Engine work efficiency corresponding to i class steam, dimensionless; T iBe steam turbine i class steam throttle (steam) temperature, K; T 0Be the exhaust temperature of steam turbine, K; Δ H iBe steam turbine i class steam unit interval admission enthalpy, J/s; L iBe steam turbine i class steam flow, kg/s; P iBe i class steam pressure, Pa; T aFor being condenser backwater (water tank) temperature, K; C P(T) be the specific heat at constant pressure of steam, relevant with temperature T, J/ (kgK);
The specific heat at constant pressure C of steam PDetermined that by following rule-of-thumb relation wherein specific heat at constant pressure unit is J, temperature unit be K (scope 298~2500K) of temperature T:
C p ( T ) = 1000 18 ( 30.00 + 10.71 × 10 - 3 T + 0.33 × 10 5 T - 2 ) - - - ( 5 )
(2) sintering exhaust-heat boiler energy-balance equation
1. superheater energy-balance equation
L i , j ∫ T p , i , j T h , i , j C P ( T ) dT = ( T y , 3 ( i - 1 ) , j - T h , i , j ) - ( T y , 3 ( i - 1 ) + 1 , j - T p , i , j ) ln T y , 3 ( i - 1 ) , j - T h , i , j T y , 3 ( i - 1 ) + 1 , j - T p , i , j R h , i , j = η j L y , j ∫ T y , 3 ( i - 1 ) + 1 , j T y , 3 ( i - 1 ) , j C Py ( T ) dT
(i=1,2,…,M;j=1,2,…,N)??(6)
In the formula: L I, jBe j platform waste heat boiler i class steam flow, kg/s; T P, i, jBe water (vapour) temperature in the j platform waste heat boiler i class pressure drum, K; T H, i, jBe j platform waste heat boiler i class pressure superheater steam exit temperature, K; T Y, 3 (i-1) jBe j platform waste heat boiler i class pressure superheater smoke inlet temperature, K; T Y, 3 (i-1)+1, jBe flue-gas temperature between j platform waste heat boiler i class pressure superheater and evaporator, K; R H, i, jBe j platform waste heat boiler i class pressure superheater thermal resistance (containing inside and outside thermal-convection resistance), K/W; η jBe the j platform waste heat boiler thermal efficiency, dimensionless; L Y, jBe j platform exhaust-heat boiler flue gas flow, kg/s; C Py(T) be the specific heat at constant pressure of flue gas, relevant with temperature T, J/ (kgK);
The specific heat at constant pressure C of flue gas PyDetermined that by following rule-of-thumb relation wherein specific heat at constant pressure unit is J, temperature unit be K (scope 298~2500K) of temperature T:
C Py ( T ) = 1000 79 × 28 + 21 × 32 [ 79 ( 27.87 + 4.28 × 10 - 3 T ) + 21 ( 29.96 + 4.18 × 10 - 3 T - 1.67 × 10 5 T - 2 ) ] - - - ( 7 )
The flow of flue gas is tried to achieve according to following theoretical relationship:
L y , j = 1000 ( 0.79 × 28 + 0.21 × 32 ) P y , j 8.314 T y , 0 , j L yv , j
In the formula: P Y, jBe j platform exhaust-heat boiler inlet flue gas pressures, Pa; L Yv, jBe j platform exhaust-heat boiler flue gas volumetric flow rate, m 3/ s;
2. evaporator energy-balance equation
L i , j h ( T ) | T = T p , i , j = ( T y , 3 ( i - 1 ) + 1 , j - T p , i , j ) - ( T y , 3 ( i - 1 ) + 2 , j - T p , i , j ) ln T y , 3 ( i - 1 ) + 1 , j - T p , i , j T y , 3 ( i - 1 ) + 2 , j - T p , i , j R p , i , j = η j L y , j ∫ T y , 3 ( i - 1 ) + 2 , j T y , 3 ( i - 1 ) + 1 , j C Py ( T ) dT
(i=1,2,…,M;j=1,2,…,N)??(8)
In the formula: T Y, 3 (i-1)+2, jBe flue-gas temperature between j platform waste heat boiler i class pressure evaporator and primary heater, K;
R P, i, jBe j platform waste heat boiler i class pressure evaporator thermal resistance, K/W; H (T) is evaporation of water latent heat, and is relevant with temperature T, J/kg;
Evaporation of water latent heat h by following rule-of-thumb relation determine (scope 0~473K) of temperature T:
h ( T ) = 1000 × 2256.6 ( 273.99 473.99 - T ) 0.38 - - - ( 9 )
3. primary heater energy-balance equation
4182 L i , j ( T p , i , j - T a ) = ( T y , 3 ( i - 1 ) + 2 , j - T p , i , j ) - ( T y , 3 ( i - 1 ) + 3 , j - T a ) ln T y , 3 ( i - 1 ) + 2 , j - T p , i , j T y , 3 ( i - 1 ) + 3 , j - T a R w , i , j = η j L y , j ∫ T y , 3 ( i - 1 ) + 3 , j T y , 3 ( i - 1 ) + 2 , j C Py ( T ) dT
(i=1,2,…,M;j=1,2,…,N)??(10)
In the formula: T Y, 3 (i-1)+3, jBe j platform waste heat boiler i class pressure primary heater exhanst gas outlet temperature, K; R W, i, jBe j platform waste heat boiler i class pressure primary heater thermal resistance (containing inside and outside thermal-convection resistance), K/W;
(3) steam energy balance equation
Δ H i + L i ∫ T i T i - Δ t i C P ( T ) dT = Σ j = 1 N L i , j [ 4182 ( 373.15 - T a ) + 1000 × 2256.6 + ∫ 373.15 T h , i , j C P ( T ) dT + 8314 18 ln P i 101325 ]
(i=1,2,…,M)??(11)
In the formula: Δ t iBe temperature drop between i class steam steam manifold and steam turbine, K;
(4) quality of steam balance equation
L i = Σ j = 1 N L i , j (i=1,2,…,M)??(12)
(5) relation equation of saturated vapour pressure and temperature
I class pressure drum steam Antoine equation:
ln P i = 23.2032 - 3826.36 T p , i , j - 45.47 (i=1,2,…,M;j=1,2,…,N)??(13)
Wherein pressure unit is Pa, and temperature unit is K (temperature applicable range 290~500K);
Above-mentioned equation (1)~(13) consist of the sintering waste heat generating system mathematical model;
3) work out corresponding computer program according to above-mentioned model algorithm, program is implanted in the host computer of the PLC of afterheat generating system or DCS;
4) flow of Real-Time Monitoring waste heat boiler circulating flue gas and import and export flue-gas temperature and output in, low-pressure steam pressure, by mathematical model in line computation, in obtaining, low-pressure steam optimum pressure value, as long as centering, low-pressure steam force value carry out automatically regulating in real time, it is in the optimum pressure scope at any time, can realizes the maximized target of generating capacity.
A kind of sintering waste heat generating system, comprise waste heat boiler, two pressure steam turbine, be provided with middle pressure steam manifold and low pressure steam manifold between waste heat boiler and the two pressure steam turbine, be provided with reheat control valve and middle pressure pressure sensor between middle pressure steam manifold and the two pressure steam turbine, be provided with low pressure modulating valve and low-pressure sensor between low pressure steam manifold and the two pressure steam turbine;
Be provided with flue gas flow meter, flue-gas temperature meter and flue gas pressures pick-up unit at the smoke inlet place of waste heat boiler, be provided with temperature-detecting device at the smoke outlet of waste heat boiler;
Described middle pressure pressure sensor, low-pressure sensor, flue gas flow meter, flue-gas temperature meter and flue gas pressures pick-up unit and temperature-detecting device are connected with PLC or DCS respectively, and PLC or DCS are connected with host computer;
PLC or DCS are connected with low pressure modulating valve with reheat control valve by actuator respectively.
Described waste heat boiler is more than one.
Compared with prior art, the invention has the beneficial effects as follows: 1) can realize the optimum control of residual neat recovering system, when external condition changes, during such as the flow of waste heat boiler input and output flue gas, temperature change, by the host computer on-line operation, draw in real time generating capacity maximized in, the low-pressure steam optimum pressure, carry out the closed loop regulating and controlling with PID, real-time automatic tracking and regulate the optimum pressure value.2) the present invention not only can carry out optimum control to the sintering waste heat generating system of having gone into operation, and can carry out verification and optimal design to the design of sintering waste heat generating system, according to the parameter of sintering waste heat thermal source obtain two the pressure (in, low pressure) or singly press (middle pressure or low pressure) steam optimum pressure parameter, and obtain waste heat boiler primary heater outlet Optimal Temperature, the evaporator Optimal Temperature, superheater outlet Optimal Temperature, in, the parameters such as low-pressure steam optimal flux are according to optimum vapor pressure and temperature and suitable two the pressure or single steam turbine of pressing of flow parameter type selecting.
Description of drawings
Fig. 1 is sintering waste heat double-pressure generating system optimal control theory block diagram of the present invention;
Fig. 2 is many multiple pressure afterheat boiler electricity-generating systems of the present invention optimum control flow chart;
Fig. 3 is many two afterheat boiler electricity-generating system structured flowcharts of pressing of the present invention.
Among the figure: FE-differential pressure measuring element FT-differential pressure transmitter PE-pressure detecting element PT-pressure unit TE-thermoelectricity is thermal resistance occasionally
Embodiment
Below in conjunction with accompanying drawing the specific embodiment of the present invention is described in further detail.
See Fig. 1, a kind of sintering waste heat generating system optimal control theory of the present invention block diagram, comprise waste heat boiler, two pressure steam turbine, be provided with middle pressure steam manifold and low pressure steam manifold between waste heat boiler and the two pressure steam turbine, be provided with reheat control valve and middle pressure pressure sensor between middle pressure steam manifold and the two pressure steam turbine, be provided with low pressure modulating valve and low-pressure sensor between low pressure steam manifold and the two pressure steam turbine;
Be provided with flue gas flow meter, flue-gas temperature meter and flue gas pressures pick-up unit at the smoke inlet place of waste heat boiler, smoke outlet at waste heat boiler is provided with temperature-detecting device, and the detection of flue gas flow realizes by differential pressure measuring element FE and differential pressure transmitter FT;
Described middle pressure pressure sensor, low-pressure sensor, flue gas flow meter, flue-gas temperature meter and flue gas pressures pick-up unit and temperature-detecting device are connected with PLC or DCS respectively, and PLC or DCS are connected with host computer;
PLC or DCS are connected with low pressure modulating valve with reheat control valve by actuator respectively.
Sintering waste heat generating system is implemented instrument check point required for the present invention and is at least 4N+M+1, and wherein flow detection point N is individual, pressure detection point N+M is individual, temperature detecting point 2N+1 is individual, reference mark M, is the motorized adjustment valve opening.M is the pressure kind of steaming of sintering exhaust-heat boiler, and N is the waste heat boiler number of units.To single pressure (middle pressure or low pressure) M=1, right, two pressures (middle pressure or low pressure) M=2.
Measure the smoke inlet position that flue gas flow (volumetric flow rate) primary detecting element is installed in every waste heat boiler, the thermoelectricity of measuring waste heat smoke inlet temperature occasionally thermal resistance is installed in the smoke inlet position of every waste heat boiler, the pressure detecting element of measuring waste heat smoke inlet pressure (negative pressure) is installed in the smoke inlet position of every waste heat boiler, the thermoelectricity of measuring waste heat exhanst gas outlet temperature occasionally (has deaerating heater such as the position before exhanst gas outlet in the thermal resistance exhanst gas outlet position that is installed in every waste heat boiler, before then temperature detecting point should be placed on flue gas and advances deaerating heater), the thermoelectricity of measuring waste heat boiler water inlet (condenser backwater) temperature occasionally thermal resistance is installed in the below (keeping suitably distance with the bottom) of water tank, and the pressure detecting element of measuring all kinds of vapor pressures is installed in all kinds of steam steam manifolds near steam outlet.The variable valve of control vapor pressure is installed in all kinds of steam steam manifold steam (vapor) outlet pipelines place, variable valve is installed in this position and not only can utilizes this point to jet chimney buffering (buffer memory) volume between steam turbine from dividing, can also avoid to greatest extent the frequent pressure adjusting of variable valve on the impact of steam turbine, make the sintering waste heat system of steaming be down to minimum to the impact of electricity generation system.
4N+M+1 instrument detection signal (simulating signal), the mould by signal transmitting device (thermopair goods thermal resistance can without temperature transmitter) access PLC or DCS enters module (or integrated circuit board); The mould of M control signal (simulating signal) access PLC or DCS goes out module (or integrated circuit board), and PLC or DCS are connected with industrial computer (host computer).
See Fig. 2, it is a kind of sintering waste heat generating system optimum control of the present invention flow chart, when waste heat boiler and steam turbine equipment parameter and exhaust-heat boiler flue gas flow and out temperature one timing, the steam turbine power generation ability only with waste heat boiler output in, low-pressure steam pressure is relevant, by in the waste heat boiler output, low-pressure steam pressure controls, can make the steam turbine power generation ability reach maximum, its control step is as follows:
At first according to the actual condition of sintering waste heat generating system, this model is simplified as follows to the actual condition of system:
A, hot device are ignored to the temperature drop of steam manifold;
B, case to steam temperature drop between steam turbine are constant;
The temperature of water in c, the device (vapour) is identical;
Water in d, the boiler drum (vapour), evaporator inlet steam, primary heater outlet coolant-temperature gage are identical;
E, boiler drum, evaporator, drum and identical with pressure in the pipeline of its connection;
F, ignore to the pressure loss between steam turbine;
G, diffuse with blowdown and ignore;
H, device low-pressure steam consumption are ignored;
I, smoke components are constituent of air;
The thermal energy transfer mode is convection heat transfer' heat-transfer by convection in j, the boiler;
K, water level keep certain, and undulate quantity is ignored in time.
1) determine the control simulated target, be simulated target to the maximum with steam turbine power generation power:
Max?W e=η eW m??(1)
In the formula: W eBe generated output, W; η eBe efficiency of generator, dimensionless;
W mBe turbine shaft output mechanical power, W;
2) set up model energy Constraints of Equilibrium equation
(1) steam turbine energy equilibrium model
W m = η m Σ i = 1 M η c , i Δ H i - - - ( 2 )
Wherein: η c , i = 1 - T 0 T i (i=1,2,…,M)??(3)
Δ H i = L i [ 4182 ( 373.15 - T a ) + 1000 × 2256.6 + ∫ 373.15 T i C P ( T ) dT + 8314 18 ln P i 101325 ]
(i=1,2,…,M)??(4)
In the formula: η mBe steam turbine mechanical efficiency, dimensionless; η iBe Carnot Engine work efficiency corresponding to i class steam, dimensionless; T iBe steam turbine i class steam throttle (steam) temperature, K; T 0Be the exhaust temperature of steam turbine, K; Δ H iBe steam turbine i class steam unit interval admission enthalpy, J/s; L iBe steam turbine i class steam flow, kg/s; P iBe i class steam pressure, Pa; T aFor being condenser backwater (water tank) temperature, K; C P(T) be the specific heat at constant pressure of steam, relevant with temperature T, J/ (kgK);
The specific heat at constant pressure C of steam PDetermined that by following rule-of-thumb relation wherein specific heat at constant pressure unit is J, temperature unit be K (scope 298~2500K) of temperature T:
C p ( T ) = 1000 18 ( 30.00 + 10.71 × 10 - 3 T + 0.33 × 10 5 T - 2 ) - - - ( 5 )
(2) sintering exhaust-heat boiler energy equilibrium model
1. superheater energy equilibrium model
L i , j ∫ T p , i , j T h , i , j C P ( T ) dT = ( T y , 3 ( i - 1 ) , j - T h , i , j ) - ( T y , 3 ( i - 1 ) + 1 , j - T p , i , j ) ln T y , 3 ( i - 1 ) , j - T h , i , j T y , 3 ( i - 1 ) + 1 , j - T p , i , j R h , i , j = η j L y , j ∫ T y , 3 ( i - 1 ) + 1 , j T y , 3 ( i - 1 ) , j C Py ( T ) dT
(i=1,2,…,M;j=1,2,…,N)??(6)
In the formula: L I, jBe j platform waste heat boiler i class steam flow, kg/s; T P, i, jBe water (vapour) temperature in the j platform waste heat boiler i class pressure drum, K; T H, i, jBe j platform waste heat boiler i class pressure superheater steam exit temperature, K; T Y, 3 (i-1), jBe j platform waste heat boiler i class pressure superheater smoke inlet temperature, K; T Y, 3 (i-1)+1, jBe flue-gas temperature between j platform waste heat boiler i class pressure superheater and evaporator, K; R H, i, jBe j platform waste heat boiler i class pressure superheater thermal resistance (containing inside and outside thermal-convection resistance), K/W; η jBe the j platform waste heat boiler thermal efficiency, dimensionless; L Y, jBe j platform exhaust-heat boiler flue gas flow, kg/s; C Py(T) be the specific heat at constant pressure of flue gas, relevant with temperature T, J/ (kgK);
The specific heat at constant pressure C of flue gas PyDetermined that by following rule-of-thumb relation wherein specific heat at constant pressure unit is J, temperature unit be K (scope 298~2500K) of temperature T:
C Py ( T ) = 1000 79 × 28 + 21 × 32 [ 79 ( 27.87 + 4.28 × 10 - 3 T ) + 21 ( 29.96 + 4.18 × 10 - 3 T - 1.67 × 10 5 T - 2 ) ] - - - ( 7 )
The flow of flue gas is tried to achieve according to following theoretical relationship:
L y , j = 1000 ( 0.79 × 28 + 0.21 × 32 ) P y , j 8.314 T y , 0 , j L yv , j
In the formula: P Y, jBe j platform exhaust-heat boiler inlet flue gas pressures, Pa; L Yv, jBe j platform exhaust-heat boiler flue gas volumetric flow rate, m 3/ s;
2. evaporator energy equilibrium model
L i , j h ( T ) | T = T p , i , j = ( T y , 3 ( i - 1 ) + 1 , j - T p , i , j ) - ( T y , 3 ( i - 1 ) + 2 , j - T p , i , j ) ln T y , 3 ( i - 1 ) + 1 , j - T p , i , j T y , 3 ( i - 1 ) + 2 , j - T p , i , j R p , i , j = η j L y , j ∫ T y , 3 ( i - 1 ) + 2 , j T y , 3 ( i - 1 ) + 1 , j C Py ( T ) dT
(i=1,2,…,M;j=1,2,…,N)??(8)
In the formula: T Y, 3 (i-1)+2, jBe flue-gas temperature between j platform waste heat boiler i class pressure evaporator and primary heater, K;
R P, i, jBe j platform waste heat boiler i class pressure evaporator thermal resistance, K/W; H (T) is evaporation of water latent heat, and is relevant with temperature T, J/kg.
Evaporation of water latent heat h by following rule-of-thumb relation determine (scope 0~473K) of temperature T:
h ( T ) = 1000 × 2256.6 ( 273.99 473.99 - T ) 0.38 - - - ( 9 )
3. primary heater energy equilibrium model
4182 L i , j ( T p , i , j - T a ) = ( T y , 3 ( i - 1 ) + 2 , j - T p , i , j ) - ( T y , 3 ( i - 1 ) + 3 , j - T a ) ln T y , 3 ( i - 1 ) + 2 , j - T p , i , j T y , 3 ( i - 1 ) + 3 , j - T a R w , i , j = η j L y , j ∫ T y , 3 ( i - 1 ) + 3 , j T y , 3 ( i - 1 ) + 2 , j C Py ( T ) dT
(i=1,2,…,M;j=1,2,…,N)??(10)
In the formula: T Y, 3 (i-1)+3, jBe j platform waste heat boiler i class pressure primary heater exhanst gas outlet temperature, K; R W, i, jBe j platform waste heat boiler i class pressure primary heater thermal resistance (containing inside and outside thermal-convection resistance), K/W.
(3) steam energy balance model
Δ H i + L i ∫ T i T i - Δ t i C P ( T ) dT = Σ j = 1 N L i , j [ 4182 ( 373.15 - T a ) + 1000 × 2256.6 + ∫ 373.15 T h , i , j C P ( T ) dT + 8314 18 ln P i 101325 ]
(i=1,2,…,M)??(11)
In the formula: Δ t iBe temperature drop between i class steam steam manifold and steam turbine, K;
(4) quality of steam balance model
L i = Σ j = 1 N L i , j (i=1,2,…,M)??(12)
(5) relational model of saturated vapour pressure and temperature
I class pressure drum steam Antoine equation:
ln P i = 23.2032 - 3826.36 T p , i , j - 45.47 (i=1,2,…,M;j=1,2,…,N)??(13)
Wherein pressure unit is Pa, and temperature unit is K (temperature applicable range 290~500K).
Above-mentioned equation (1)~(13) consist of the sintering waste heat generating system mathematical model;
3) work out corresponding computer program according to above-mentioned model algorithm, program be implanted in the host computer of the PLC of afterheat generating system or DCS the derivation algorithm of above-mentioned mathematical model:
The difference of the total variable number of model and equation of constraint number is: [M+ (MN+3M+4)+(6MN+M)]-(7MN+4M+4)=M, and identical with the independent variable number, therefore, solve M independent variable P i(i=1,2 ..., M) after, other variable can draw;
This model solution is the Conditional Extreme Value of Pluralistic Function problem that relates in the higher mathematics, because related independent variable and intermediate variable in the equation of constraint of model are all implicit function, can find the solution with lagrange's method of multipliers;
Model solution adopts the lagrange's method of multipliers step as follows:
In order respectively the C of (5) P(T) substitution (4), (6), (11), the C of (7) Py(T) substitution (6), (8), (10), the h of (9) (T) substitution (8) is respectively the η of (3) C, i(i=1,2 ..., M) substitution (2), and the L of (12) i(i=1,2 ..., M) substitution (4), (11) are respectively the Δ H of (4) i(i=1,2 ..., M) substitution (2), (11) obtain T by (13) P, i, j(i=1,2 ..., M; J=1,2 ..., N) substitution (6), (8), (10) are the W of (2) mSubstitution (1), model transferring are following form:
Objective function: Max f (x i| I=1,2 ... M+n) (14)
Equation of constraint: g j(x i| I=1,2 ..., M+n)=0 (j=1,2 ..., n) (15)
Wherein f and g represent specific known function relation, x i(i=1,2 ..., be model variable corresponding to order n), through equation of constraint number n=(7MN+4M+4)-(MN+3M+4)=6MN+M after the conversion.
(14) objective function is transformed to:
MaxF ( x i | i = 1,2 , . . . , M + n ) = f ( x i | i = 1,2 , . . . , M + n ) + Σ j = 1 n λ j g j ( x i | i = 1,2 , . . . , M + n ) - - - ( 16 )
Wherein function F and f are of equal value, λ j(j=1,2 ..., n) be constant to be asked.
Obtain (16) F to x i(i=1,2 ..., single order partial derivative M+n) also is 0:
∂ F ( x i | i = 1,2 , . . . , M + n ) ∂ x i = 0 (i=1,2 ..., M+n) namely:
∂ f ( x i | i = 1,2 , . . . , M + n ) ∂ x i + Σ j = 1 n λ j ∂ g j ( x i | i = 1,2 , . . . , M + n ) ∂ x i = 0 (i=1,2,…,M+n)??(17)
Simultaneous (15), (17) are M+2n equation altogether, comprises M independent variable and n intermediate variable and n constant λ to be asked j(j=1,2 ..., n), use Newton process of iteration computer standard program solution Nonlinear System of Equations, can obtain each variable numerical solution.
By above-mentioned afterheat generating system mathematical model, as can be known when the timing of device parameter (each position thermal resistance of waste heat boiler, steam turbine mechanical efficiency, efficiency of generator etc.) and external condition (boiler fuel flow and out temperature etc.), the cogeneration ability only with in, low-pressure steam pressure is relevant; Exist in one group of optimum, low-pressure steam pressure, make the generating capacity of system reach maximum.When external condition changes, when particularly entering kiln gas flow and temperature change, generating capacity will change thereupon, in, the low-pressure steam optimum pressure also will change.
4) flow of Real-Time Monitoring waste heat boiler circulating flue gas and import and export flue-gas temperature and output in, low-pressure steam pressure, by mathematical model in line computation, in obtaining, low-pressure steam optimum pressure value, as long as centering, low-pressure steam force value carry out automatically regulating in real time, it is in the optimum pressure scope at any time, can realizes the maximized target of generating capacity.
See Fig. 3, be that two two pressure waste heat boilers adopt parallel way to be connected in the afterheat generating system, water trap is respectively waste heat boiler and send water, the middle pressure steam of waste heat boiler output is advanced middle pressure steam manifold, the low-pressure steam of waste heat boiler output is advanced the low pressure steam manifold, be provided with reheat control valve between middle pressure steam manifold and the two pressure steam turbine, be provided with low pressure modulating valve between low pressure steam manifold and the two pressure steam turbine.Along waste heat flow of flue gas direction middle pressure superheater is installed successively in every boiler, middle pressure evaporator, middle pressure primary heater and (or) low-pressure superheater, low pressure evaporator, low pressure preheater (LPP, from every boiler, press the steam of superheater outlet to be pooled to middle pressure steam manifold, be pooled to the low pressure steam manifold from the steam of every boiler low-pressure superheater outlet, in, low-pressure steam is respectively by in the extremely two pressure steam turbines of Pipeline transport, low-pressure inlet, in, low-pressure steam expands by turbine rotor and does work, make connected generator High Rotation Speed, generator sends electric energy and delivers to electrical network.The steam that flows out from steam turbine outlet is cooled to water through condenser, after the oxygen-eliminating device deoxygenation, through water trap enter every boiler in, low pressure preheater (LPP.

Claims (1)

1. the optimal control method of a sintering waste heat generating system, it is characterized in that, when waste heat boiler and steam turbine equipment parameter and exhaust-heat boiler flue gas flow and out temperature one timing, the steam turbine power generation ability only with waste heat boiler output in, low-pressure steam pressure is relevant, by in the waste heat boiler output, low-pressure steam pressure controls, can make the steam turbine power generation ability reach maximum, its control step is as follows:
1) determine the control simulated target, be simulated target to the maximum with steam turbine power generation power:
Max W e = η e W m - - - ( 1 )
In the formula: W eBe generated output, W; η eBe efficiency of generator, dimensionless;
W mBe turbine shaft output mechanical power, W;
2) set up the energy equilibrium equation of constraint
(1) steam turbine energy-balance equation
W m = η m Σ i = 1 M η c , i ΔH i - - - ( 2 )
Wherein: η c , i = 1 - T 0 T i ( i = 1,2 , . . . , M ) - - - ( 3 )
ΔH i = L i [ 4182 ( 373.15 - T a ) + 1000 × 2256.6 + ∫ 373.15 T i C P ( T ) dT + 8314 18 ln P i 101325 ] ( i = 1,2 , . . . , M ) - - - ( 4 )
In the formula: η mBe steam turbine mechanical efficiency, dimensionless; η C, iBe Carnot Engine work efficiency corresponding to i class steam, dimensionless; T iBe steam turbine i class steam throttle (steam) temperature, K; T 0Be the exhaust temperature of steam turbine, K; ⊿ H iBe steam turbine i class steam unit interval admission enthalpy, J/s; L iBe steam turbine i class steam flow, kg/s; P iBe i class steam pressure, Pa; T aFor being the condenser return water temperature, K; C P(T) be the specific heat at constant pressure of steam, relevant with temperature T, J/ (kgK);
The specific heat at constant pressure C of steam PDetermine that by following rule-of-thumb relation wherein specific heat at constant pressure unit is J, temperature unit is K, under the scope 298~2500K of temperature T condition:
C P ( T ) = 1000 18 ( 30.00 + 10.71 × 10 - 3 T + 0.33 × 10 5 T - 2 ) - - - ( 5 )
(2) sintering exhaust-heat boiler energy-balance equation
1. superheater energy-balance equation
L i , j ∫ T p , i , j T h , i , j C P ( T ) dT = ( T y , 3 ( i - 1 ) , j - T h , i , j ) - ( T y , 3 ( i - 1 ) + 1 , j - T p , i , j ) ln T y , 3 ( i - 1 ) , j - T h , i , j T y , 3 ( i - 1 ) + 1 , j - T p , i , j R h , i , j = η j L y , j ∫ T y , 3 ( i - 1 ) + 1 , j T y , 3 ( i - 1 ) , j C Py ( T ) dT ( i = 1,2 , . . . , M ; j = 1,2 , . . . , N ) ( 6 )
In the formula: L I, jBe j platform waste heat boiler i class steam flow, kg/s; T P, i, jBe coolant-temperature gage in the j platform waste heat boiler i class pressure drum, K; T H, i, jBe j platform waste heat boiler i class pressure superheater steam exit temperature, K; T Y, 3 (i-1), jBe j platform waste heat boiler i class pressure superheater smoke inlet temperature, K; T Y, 3 (i-1)+1, jBe flue-gas temperature between j platform waste heat boiler i class pressure superheater and evaporator, K; R H, i, jBe j platform waste heat boiler i class pressure superheater thermal resistance, contain inside and outside thermal-convection resistance, K/W; η jBe the j platform waste heat boiler thermal efficiency, dimensionless; L Y, jBe j platform exhaust-heat boiler flue gas flow, kg/s; C Py(T) be the specific heat at constant pressure of flue gas, relevant with temperature T, J/ (kgK);
The specific heat at constant pressure C of flue gas PyDetermine that by following rule-of-thumb relation wherein specific heat at constant pressure unit is J, temperature unit is K, the scope 298~2500K of temperature T:
C Py ( T ) = 1000 79 × 28 + 21 × 32 [ 79 ( 27.87 + 4.28 × 10 - 3 T ) + 21 ( 29.96 + 4.18 × 10 - 3 T - 1.67 × 10 5 T - 2 ) ] - - - ( 7 )
The flow of flue gas is tried to achieve according to following theoretical relationship:
L y , j = 1000 ( 0.79 × 28 + 0.21 × 32 ) 8.314 T y , 0 , j L yv , j
In the formula: P Y, jBe j platform exhaust-heat boiler inlet flue gas pressures, Pa; L Yv, jBe j platform exhaust-heat boiler flue gas volumetric flow rate, m 3/ s;
2. evaporator energy-balance equation
L i , j h ( T ) | T = T p , i , j = ( T y , 3 ( i - 1 ) + 1 , j - T p , i , j ) - ( T y , 3 ( i - 1 ) + 2 , j - T p , i , j ) ln T y , 3 ( i - 1 ) + 1 , j - T p , i , j T y , 3 ( i - 1 ) + 2 , j - T p , i , j R p , i , j = η j L y , j ∫ T y , 3 ( i - 1 ) + 2 , j T y , 3 ( i - 1 ) + 1 , j C Py ( T ) dT ( i = 1,2 , . . . , M ; j = 1,2 , . . . , N ) - - - ( 8 )
In the formula: T Y, 3 (i-1)+2, jBe flue-gas temperature between j platform waste heat boiler i class pressure evaporator and primary heater, K;
R P, i, jBe j platform waste heat boiler i class pressure evaporator thermal resistance, K/W; H (T) is evaporation of water latent heat, and is relevant with temperature T, J/kg;
Evaporation of water latent heat h is determined by following rule-of-thumb relation, the scope 0~473K of temperature T:
h ( T ) = 1000 × 2256.6 ( 273.99 473.99 - T ) 0.38 - - - ( 9 )
3. primary heater energy-balance equation
4182 L i , j ( T p , i , j - T a ) = ( T y , 3 ( i - 1 ) + 2 , j - T p , i , j ) - ( T y , 3 ( i - 1 ) + 3 , j - T a ) ln T y , 3 ( i - 1 ) + 2 , j - T p , i , j T y , 3 ( i - 1 ) + 3 , j - T a R w , i , j = η j L y , j ∫ T y , 3 ( i - 1 ) + 3 , j T y , 3 ( i - 1 ) + 2 , j C Py ( T ) dT ( i = 1,2 , . . . , M ; j = 1,2 , . . . , N ) ( 10 )
In the formula: T Y, 3 (i-1)+3, jBe j platform waste heat boiler i class pressure primary heater exhanst gas outlet temperature, K; R W, i, jBe that j platform waste heat boiler i class pressure primary heater thermal resistance contains inside and outside thermal-convection resistance, K/W;
(3) steam energy balance equation
ΔH i + L i ∫ T i T i - Δti C P ( T ) dT = Σ j = 1 N L i , j [ 4182 ( 373.15 - T a ) + 1000 × 2256.6 + ∫ 373.15 Th , i , j C P ( T ) dT + 8314 18 ln P i 101325 ] ( i = 1,2 , . . . , M ) - - - ( 11 )
: ⊿ t in the formula iBe temperature drop between i class steam steam manifold and steam turbine, K;
(4) quality of steam balance equation
L i = Σ j = 1 N L i , j ( i = 1,2 , . . . , M ) - - - ( 12 )
(5) relation equation of saturated vapour pressure and temperature
I class pressure drum steam Antoine equation:
ln P i = 23.2032 - 3826.36 T p , i , j - 45.47 ( i = 1,2 , . . . , M ; j = 1,2 , . . . , N ) - - - ( 13 )
Wherein pressure unit is Pa, and temperature unit is K, temperature applicable range 290~500K;
Above-mentioned equation (1)~(13) consist of the sintering waste heat generating system mathematical model;
3) work out corresponding computer program according to above-mentioned model algorithm, program is implanted in the host computer of the PLC of afterheat generating system or DCS;
4) flow of Real-Time Monitoring waste heat boiler circulating flue gas and import and export flue-gas temperature and output in, low-pressure steam pressure, by mathematical model in line computation, in obtaining, low-pressure steam optimum pressure value, centering, low-pressure steam force value carry out automatically regulating in real time, it is in the optimum pressure scope at any time, to realize the maximized target of generating capacity;
Described a kind of sintering waste heat generating system comprises waste heat boiler, two pressure steam turbine, be provided with middle pressure steam manifold and low pressure steam manifold between waste heat boiler and the two pressure steam turbine, it is characterized in that, be provided with reheat control valve and middle pressure pressure sensor between middle pressure steam manifold and the two pressure steam turbine, be provided with low pressure modulating valve and low-pressure sensor between low pressure steam manifold and the two pressure steam turbine;
Be provided with flue gas flow meter, flue-gas temperature meter and flue gas pressures pick-up unit at the smoke inlet place of waste heat boiler, be provided with temperature-detecting device at the smoke outlet of waste heat boiler;
Described middle pressure pressure sensor, low-pressure sensor, flue gas flow meter, flue-gas temperature meter and flue gas pressures pick-up unit and temperature-detecting device are connected with PLC or DCS respectively, and PLC or DCS are connected with host computer;
PLC or DCS are connected with low pressure modulating valve with reheat control valve by actuator respectively.
CN2011101921293A 2011-07-08 2011-07-08 Optimizing control method for sintering waste heat power generation system CN102385356B (en)

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