Ejector control method based on waste steam utilization of steam turbine of thermoelectric unit

Abstract

The invention discloses an ejector control method based on waste steam utilization of a steam turbine of a thermoelectric unit, and belongs to the technical field of waste steam waste heat heat supply. Firstly, whether the ejector is put into operation is judged; then, the ejector power steam flow Dp and the steam turbine dead steam pressure pc are determined, and finally, the cooperative control strategy of the steam turbine dead steam pressure pc and the ejector power steam flow Dp is determined. The back pressure of the unit and the power steam flow of the ejector are adjusted and controlled in real time according to the primary heat supply network circulating water amount, the water return temperature, the power steam pressure and the unit steam exhaust amount, so that the steam ejector can keep a high ejection coefficient and a high step-up ratio when operating under variable working conditions, the purpose of maximum heat supply amount of steam exhaust waste heat of a steam turbine is achieved, and the heat supply efficiency is improved. According to the method, the engineering problem that the performance of the ejector is obviously reduced and even the operation is directly cut off during variable-working-condition operation due to lack of control strategies of the ejector is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of exhaust steam waste heat heating, and in particular relates to an ejector control method based on the utilization of exhaust steam of a steam turbine of a thermal power unit. Background Art

[0002] In the field of thermal power, steam ejectors were mostly used for vacuuming in the past. In recent years, high-performance steam ejectors with large flow rates have begun to be used in the exhaust steam heating system of thermal power plants, showing great advantages in saving coal, reducing emissions, and reducing the heating costs of power plants. Exhaust steam ejectors generally use the exhaust steam of the medium-pressure cylinder to eject the exhaust steam of the low-pressure cylinder, so that the exhaust steam of the low-pressure cylinder (i.e., the exhaust steam of the turbine) is pressurized and heated, realizing the use of exhaust steam for heating.

[0003] At present, the steam ejectors with a capacity of more than 100t / h used in China mainly use products from S&K Corporation of the United States or Körting Hannover AG of Germany. The pressure boost ratio and ejection coefficient of the ejectors under rated conditions can reach 1.7 and 1.0 respectively. The imported ejectors adopt the "needle" adjustment technology, which has good adaptability to variable conditions, and the pressure boost ratio and ejection coefficient do not decay much in a wide working range.

[0004] The operation control of the ejector is the most prominent technical problem. As long as it deviates from the design working condition, the operating performance of the ejector will be significantly reduced or even cannot be put into operation. The reason is that the variable working condition characteristics of the ejector are not clear, the operation of the ejector and the operation of the primary heating network are not considered comprehensively, and the control method of the ejector is not mastered, which greatly reduces the energy saving effect of the ejector under variable working conditions. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide an ejector control method based on the utilization of exhaust steam from a steam turbine of a thermal power unit, so as to improve the variable operating performance of the ejector and increase its energy-saving effect.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: an ejector control method based on the utilization of exhaust steam of a steam turbine of a thermal power unit, comprising: Step 1, determine whether the ejector is in operation; when Q cmax ≤ Q w1 or t c < t cmin , then the ejector operation is cut off; when Q cmax > Q w1 and t c ≥ t cmin, then the ejector is put into operation; in, Q cmax The maximum heat release of exhaust steam in the high back pressure condenser. Q w1 The heat absorbed by the circulating water in the primary heat network in the high back pressure condenser. t c is the actual exhaust steam temperature of the steam turbine, t cmin is the lowest available exhaust steam temperature of the steam turbine; Step 2: Determine the ejector steam flow rate D p and turbine exhaust steam pressure p c , the calculation methods include: a) When the ejector is in operation, the ejector power steam pressure p p When the ejector nozzle is designed, the pressure ratio ε n Calculation of turbine exhaust steam pressure p cn , if the corresponding exhaust steam temperature t cn Higher than the minimum available exhaust steam temperature required for primary heat network return water heating t cmin And lower than the maximum allowable exhaust steam temperature of the turbine t cmax , then control p c Keep the ejector nozzle at the designed pressure ratio and adjust the return water flow rate of the primary heating network. D w and temperature t h , calculate the ejector power steam flow D p ; b) When the ejector is in operation, the ejector power steam pressure p p When the pressure ratio of the ejector changes, n Calculated turbine exhaust steam temperature t cn Higher than the maximum allowable exhaust steam temperature of the turbine t cmax , then the heat load of the high back pressure condenser is designed Q gb Calculation of turbine exhaust steam pressure p c Then, the ejector power steam flow rate is calculated through the ejector variable operating condition calculation and ejector condenser heat balance. D p ; Step 3: Determine the turbine exhaust steam pressure p c and ejector power steam flow D p Cooperative control strategy; Adjust the cone displacement by adjusting the ejector s Control the ejector steam flow D p , by adjusting the operating frequency of the air cooling fan f Controlling turbine exhaust steam pressure p c .

[0007] As a preferred embodiment, in step 1, the maximum heat release of exhaust steam in the high back pressure condenser is Q cmax The calculation method is: Q cmax = ( h " c,max －h ' c,max )×( D c －D c3,min ); in, h " c,max and h ' c,max The maximum exhaust steam pressure is p cmax The saturated steam enthalpy and saturated water enthalpy under D c is the exhaust steam flow rate, D c3,min The minimum exhaust steam required for antifreeze of the air-cooled island.

[0008] As a preferred embodiment, in step 1, according to the return water temperature of the primary heating network t h , Circulating water volume D w and maximum exhaust steam pressure p cmax Calculation of heat absorption of circulating water in primary heating network in high back pressure condenser Q w1 ; Q w1 = D w · ( t cmax -2-t h ) ·4.187; Among them, the maximum allowable exhaust steam temperature of the steam turbine is: t cmax = f 1( p cmax ); Actual exhaust steam temperature of steam turbine: t c = f 1( p c ); function f 1 is the correlation function between saturated steam pressure and temperature, obtained based on steam physical property data.

[0009] As a preferred embodiment, in step 1, the minimum available exhaust steam temperature t cmin = t h +△ t hmin + δt ; Among them, △ t hmin The minimum return water temperature rise in the high back pressure condenser is 1-2℃; δt The heat transfer end difference of the high back pressure condenser is 2℃.

[0010] As a preferred implementation, in step 2, the calculation method a) includes the following steps: (1) According to the ejector power steam pressure p p and nozzle design pressure ratio ε n , calculate the ejector nozzle outlet pressure p ' cn ; p ' cn = ε n · p p ; (2) Determine the turbine exhaust steam pressure p c ; p cn = a · p ' cn ; pc = p cn ; in, a is the coefficient to consider the exhaust steam flow resistance loss; (3) Turbine exhaust steam temperature t c = f 1( p c ); when t cmin ≤ t c ≤ t cmax , then the exhaust pressure of the steam turbine is controlled in a coordinated manner p c and ejector power steam flow D p Make the ejector nozzle work under the designed pressure ratio; (4) Calculate the ejector outlet pressure based on the ejector design boost ratio p ej ; p ej = p c · m ; in, m Design the step-up ratio for the ejector; (5) Calculate the condensate temperature of the ejector condenser t ej and condensation water specific enthalpy h ' ej ; t ej = f 1( p ej ); h ' ej = f 2( p ej ); Among them, the function f 2 is the correlation function between saturated vapor pressure and saturated water specific enthalpy, obtained based on physical property data; (6) Calculate the steam flow rate at the ejector outlet D ej , Steam specific enthalpy h ej , the amount of exhaust steam used by the ejector D c2and power steam flow D p ; D ej · ( h ej －h ' ej )= D w [ t ej - 2- ( t c -2)] ·4.187; D p · h p + D c2 · h c =( D p + D c2 ) · h ej ; D p = D ej / (1+ω); D c2 = D ej - D p ; in, h p is the specific enthalpy of motive steam, according to p p and t p Check the physical properties of water vapor to obtain h c is the exhaust steam specific enthalpy of the turbine, according to the exhaust steam pressure p c Obtained by checking the physical properties of water vapor, ω is the design ejection coefficient; (7) Check the actual steam exhaust volume of the steam turbine D c Whether the exhaust steam volume calculated in step (6) is satisfied D c2 : Calculate and determine the amount of exhaust steam used by high back pressure condensers D c1 ; D c1· r ( p c )= D w ( t c - 2- t h ) ·4.187; in, r For pressure p c The corresponding latent heat of vaporization is obtained from the physical properties of water vapor; Calculate the maximum exhaust steam quantity entering the ejector D c2,max ; D c2,max = D c - D c1 - D c3,min ; If the calculated value in step (6) is D c2 ≤ D c2,max , then the exhaust steam volume of the ejector is D c2 ; If the calculated value in step (6) is D c2 > D c2,max , then let the ejector exhaust steam be D c2 = D c2,max , substitute it into the formula in step (6) and recalculate D p .

[0011] As a preferred implementation, in step 2, the calculation method b) includes the following steps: (1) If Q gb ≥ Q w1 , then the ejector operation is cut off; like Q gb < Q w1 , according to the design heat load of high back pressure condenser Q gb Calculate the exhaust steam pressure p c ; Q gb =D w ( t c - 2- t h ) ·4.187; t c = Q gb / D w / 4.187+ t h +2; Then: exhaust steam pressure p c = f 3 ( t c ); (2) The ejector coefficient under variable operating conditions is obtained through ejector variable operating condition calculation and ejector condenser heat balance calculation. oh 1 and step-up ratio m 1; oh 1= f 4( p p , t p , p c , D p ); m 1= f 5( p p , t p , p c , D p ); (3) Calculate the ejector outlet pressure p ej = p c · m 1; (4) Calculate the condensate temperature of the ejector condenser t ej and condensation water specific enthalpy h ' ej ; t ej = f 1( p ej ); h' ej = f 2( p ej ); (5) Calculate the ejector outlet steam flow rate through the ejector condenser heat balance D ej , Steam specific enthalpy h ej , the amount of exhaust steam used by the ejector D c2 and power steam flow D p ; D ej · ( h ej －h ' ej )= D w [ t ej - 2- ( t c -2)] ·4.187; D p · h p + D c2 · h c =( D p + D c2 ) · h ej ; D p = D ej / (1+ oh 1); D c2 = D ej - D p ; If the calculated value in step (5) is D c2 ≤ D c2,max , then the exhaust steam volume of the ejector is D c2 .

[0012] If the calculated value in step (5) is D c2> D c2,max , then let the ejector exhaust steam be D c2 = D c2,max , substitute it into steps (2) to (5) and recalculate D p .

[0013] As a preferred embodiment, in step 3, the ejector adjusts the cone displacement. s The calculation methods include: (1) Based on the power steam flow D p Determine the nozzle equivalent throat area A t ; ; Among them, the critical steam velocity at the nozzle throat is v t Only relevant for power steam parameters: v t = f 6 ( p p , t p ), steam density r t = f 7 ( p p , t p , f ), f is the nozzle velocity coefficient, f 7 is the correlation function, obtained based on the water vapor property data; (2) Based on the equivalent throat area A t Determine the displacement of the ejector adjustment cone s ; s = A t (s).

[0014] As a preferred embodiment, in step 3, the air cooling fan operating frequency f The calculation methods include: (1) Calculate the amount of exhaust steam discharged into the air cooling island D c3 = D c - D c1 - D c2 ; (2) Calculate the cooling air volume of the air cooling island D a ; D a · c p △ t a = D c3 · r ( p c ); (3) Determine the number of air cooling island operation rows X = D a / D a1 ;in, D a1 For the single-row design flow, X is an integer; (4) Calculate the air volume of a single air-cooling fan D a2 = D a / X / Y; where Y is the number of columns in each row of the air cooling island; (5) Control the operating frequency of the air cooling fan f = f 8( D a2 ), f 8 is the air volume of the air cooling fan D a2 With frequency f proportional function of .

[0015] The ejector control method based on the utilization of exhaust steam from the steam turbine of a thermal power unit proposed in the present invention is to adjust and control the unit back pressure and ejector power steam flow in real time according to the circulating water volume of the primary heat network, the return water temperature, the power steam pressure and the exhaust volume of the unit, so that the steam ejector can maintain a high ejection coefficient and pressure rise ratio when operating under variable operating conditions, thereby achieving the purpose of maximizing the heating capacity of the waste heat from the exhaust steam of the steam turbine. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of a heating system consisting of a high back pressure condenser, an ejector and an ejector condenser.

[0017] Figure 2 It is a schematic diagram of the structure of the ejector nozzle and the regulating cone.

[0018] In the figure, 1- ejector, 2- high back pressure condenser, 3- ejector condenser, 4- exhaust device, 5- ejector nozzle, 6- ejector regulating cone. DETAILED DESCRIPTION

[0019] In order to make those skilled in the art better understand the present invention, the present invention is further clearly and completely described below in conjunction with the accompanying drawings and embodiments. It should be noted that, in the absence of conflict, the features in the embodiments and examples of this application can be combined with each other.

[0020] This embodiment provides a new technology for efficient control of the operating performance of ejectors in thermal power plants, solving the engineering problem of significantly reducing ejector performance or even directly cutting off operation during variable operating conditions due to a lack of ejector control strategies.

[0021] The ejector control method based on the exhaust steam utilization of the steam turbine of the thermal power unit proposed in this embodiment is Figure 1 The method is implemented in the heating system composed of a high back pressure condenser 2, an ejector 1 and an ejector condenser 3 as shown.

[0022] flow D w ,temperature t h The return water of the primary heat network is heated by the exhaust steam of the steam turbine in the high back pressure condenser 2, and then heated by the steam at the outlet of the ejector 1 in the ejector condenser 3. The pressure of the steam at the outlet of the ejector 1 is p ej ,temperature t ej and flow D ej Directly affects the heating performance of the primary heating network. These parameters depend on the power steam parameters (pressure p p ,temperature p p and flow D p ) and turbine exhaust steam parameters (pressure p c ,temperature t c and flow D c2 ) and the operating performance parameters of ejector 1 (ejection coefficient and boost ratio).

[0023] The basic concept of the present invention is that when the power steam pressure of the ejector 1 p p When the operating performance of ejector 1 changes, the power steam flow of ejector 1 is controlled by coordinated D p and turbine exhaust steam pressure p c , so that the ejection coefficient and boost ratio of ejector 1 remain close to the design values ​​within a certain range of variable operating conditions, and do not attenuate much when they deviate far from the design conditions, thereby maximizing the utilization of the waste heat from the exhaust steam of the turbine.

[0024] Based on the above concept, the ejector 1 control method based on the utilization of exhaust steam from the steam turbine of a thermal power unit provided in this embodiment includes the following steps 1 to 3.

[0025] Step 1: determine whether the ejector 1 is in operation.

[0026] In this step, the maximum exhaust steam pressure allowed by the steam turbine is p cmax , Actual exhaust steam pressure p c 、Exhaust steam flow D c The minimum available exhaust steam temperature required for heating the return water of the primary heating network t cmin Determine whether ejector 1 is in operation.

[0027] (1) First, calculate the maximum heat release of exhaust steam in high back pressure condenser 2 Q cmax ; Q cmax = ( h " c,max －h ' c,max )×( D c －D c3,min ); in, h " c,max and h ' c,max The maximum exhaust steam pressure is p cmax The saturated steam enthalpy and saturated water enthalpy under p cmax Check the physical properties of water vapor to obtain; D c3,min The minimum amount of exhaust steam required for antifreeze of the air-cooled island is determined based on the design parameters.

[0028] (2) Based on the return water temperature of the primary heating network t h , Circulating water volume D w and maximum exhaust steam pressure p cmax Calculate the heat absorption of the primary heat network circulating water in the high back pressure condenser 2 Q w1 ; Qw1 = D w · ( t cmax -2- t h ) ·4.187; Among them, the maximum allowable exhaust steam temperature of the steam turbine is: t cmax = f 1( p cmax ); Actual exhaust steam temperature of steam turbine: t c = f 1( p c ); function f 1 is the correlation function between saturated steam pressure and temperature, obtained based on steam physical property data.

[0029] (3) Calculation of the minimum available exhaust steam temperature t cmin : t cmin = t h +△ t hmin + δt ; Among them, △ t hmin The minimum return water temperature rise in the high back pressure condenser 2 is 1-2℃; δt The heat transfer end difference of high back pressure condenser 2 is taken as 2℃.

[0030] when t c < t cmin , cut off the operation of high back pressure condenser 2 and ejector 1, open valves F1, F2, F3 and F7, and close valves F4, F5, F6 and F8; Q cmax ≤ Q w1 , cut off ejector 1, at this time, close F4, F5, F6 and F8.

[0031] when Q cmax > Q w1 and t c ≥ t cmin , then injector 1 is put into operation and all valves F1 to F8 are opened.

[0032] Step 2: Determine the power steam flow rate of ejector 1 D p and turbine exhaust steam pressure p c .

[0033] In the step, the ejector 1 power steam flow D p and turbine exhaust steam pressure p c There are two calculation methods: calculation method a and calculation method b.

[0034] Calculation method a: When ejector 1 is in operation, the power steam pressure of ejector 1 p p When the pressure ratio ε of the ejector nozzle 5 changes, n Calculation of turbine exhaust steam pressure p cn , if the corresponding exhaust steam temperature t cn Higher than the minimum available exhaust steam temperature required for primary heat network return water heating t cmin And lower than the maximum allowable exhaust steam temperature of the turbine t cmax , then control p c Keep the ejector nozzle 5 running at the designed pressure ratio. At the same time, according to the return water flow of the primary heating network D w and temperature t h , calculate the motive steam flow rate of ejector 1 D p ,pass p c and D p The coordinated control of the ejector 1 so that the ejection coefficient and the boost ratio are kept near the design values ​​within a certain variable operating range includes the following steps (1) to (7).

[0035] (1) Based on the power steam pressure of ejector 1 p p and nozzle design pressure ratio ε n , calculate the ejector nozzle 5 outlet pressure p ' cn ; p ' cn = ε n · p p .

[0036] (2) Determine the turbine exhaust steam pressure p c ; p cn = a · p ' cn ; p c = p cn ; in, a is the coefficient considering the exhaust steam flow resistance loss.

[0037] (3) Turbine exhaust steam temperature t c = f 1( p c ); when t cmin ≤ t c ≤ t cmax , then the exhaust pressure of the steam turbine is controlled in a coordinated manner p c and ejector 1 power steam flow D p Make the ejector nozzle 5 work under the designed pressure ratio, function f 1 is the correlation function between saturated steam pressure and temperature, obtained based on steam physical property data.

[0038] (4) Calculate the outlet pressure of ejector 1 according to the designed pressure rise ratio of ejector 1 p ej ; p ej = p c · m ; in, m Design the boost ratio for ejector 1.

[0039] (5) Calculate the condensate temperature of ejector condenser 3 t ej and condensation water specific enthalpy h ' ej ; t ej = f 1( p ej ); h ' ej = f 2( p ej ); Among them, the function f 2 is the correlation function between saturated steam pressure and saturated water specific enthalpy, which is obtained based on steam physical property data.

[0040] (6) Calculate the steam flow rate at the ejector 1 outlet D ej , Steam specific enthalpy h ej 、Amount of exhaust steam used by ejector 1 D c2 and power steam flow D p : D ej · ( h ej －h ' ej )= D w [ t ej - 2- ( t c -2)] ·4.187; D p · h p + D c2 · h c =( D p + D c2 ) · h ej ; D p = D ej / (1+ω); D c2 = D ej - D p ; in, h p is the specific enthalpy of motive steam, according to p p and t pCheck the physical properties of water vapor to obtain h c is the exhaust steam specific enthalpy of the turbine, according to the exhaust steam pressure p c Obtained by checking the physical properties of water vapor, ω is the designed ejection coefficient.

[0041] (7) Check the actual steam exhaust volume of the steam turbine D c Does the exhaust steam volume calculated in (6) meet the requirements? D c2 : First, calculate and determine the exhaust steam volume used by high back pressure condenser 2 D c1 ; D c1 · r ( p c )= D w ( t c - 2- t h ) ·4.187; in, r For pressure p c The corresponding latent heat of vaporization is obtained from the physical properties of water vapor.

[0042] Calculate the maximum exhaust steam quantity entering ejector 1 D c2,max ; D c2,max = D c - D c1 - D c3,min ; If (6) is calculated D c2 ≤ D c2,max , then the exhaust steam volume of ejector 1 is D c2 .

[0043] If (6) is calculated D c2 > D c2,max , then let the exhaust steam volume of ejector 1 be D c2 = D c2,max , substitute it into the formula in (6) and recalculate D p.

[0044] Calculation method b: When ejector 1 is in operation, the power steam pressure of ejector 1 p p When the pressure ratio ε of ejector 1 is changed, n Calculated turbine exhaust steam temperature t cn Higher than the maximum allowable exhaust steam temperature of the turbine t cmax , then according to the design heat load of high back pressure condenser 2 Q gb Calculation of turbine exhaust steam pressure p c Then, the power steam flow of ejector 1 is obtained through the calculation of ejector 1 variable operating conditions and ejector condenser 3 heat balance calculation. D p ,pass D p and p c The coordinated control to maximize the utilization of the exhaust heat of the steam turbine includes the following steps (1) to (5).

[0045] (1) If Q gb ≥ Q w1 , then the operation of ejector 1 is cut off; like Q gb < Q w1 , according to the design heat load of high back pressure condenser 2 Q gb Calculate the exhaust steam pressure p c : Q gb = D w ( t c - 2- t h ) ·4.187; t c = Q gb / D w / 4.187+ t h +2; Then: exhaust steam pressure p c = f 3 ( t c),function f 3 is the correlation function between saturated steam temperature and pressure, which is obtained based on steam physical property data.

[0046] (2) The ejector coefficient under variable operating conditions is obtained by calculating the ejector 1 variable operating conditions and the ejector condenser 3 heat balance. oh 1 and step-up ratio m 1; oh 1= f 4( p p , t p , p c , D p ); m 1= f 5( p p , t p , p c , D p ); f 4 and f 5 are the ejection coefficients oh 1 and step-up ratio m 1 and power steam pressure p p ,temperature t p , Turbine exhaust steam pressure p c and power steam flow D p The relationship function is obtained through variable operating condition performance analysis.

[0047] (3) Calculate the outlet pressure of ejector 1 p ej ; p ej = p c · m 1.

[0048] (4) Calculate the condensate temperature of ejector condenser 3 t ej and condensation water specific enthalpy h ' ej ; t ej = f 1(p ej ); h ' ej = f 2( p ej ).

[0049] (5) Calculate the steam flow rate at the ejector 1 outlet through the heat balance of ejector condenser 3 D ej , Steam specific enthalpy h ej 、Amount of exhaust steam used by ejector 1 D c2 and power steam flow D p ; D ej · ( h ej －h ' ej )= D w [ t ej - 2- ( t c -2)] ·4.187; D p · h p + D c2 · h c =( D p + D c2 ) · h ej ; D p = D ej / (1+ oh 1); D c2 = D ej - D p .

[0050] If (5) is calculated D c2 ≤ D c2,max , then the exhaust steam volume of ejector 1 isD c2 .

[0051] If (5) is calculated D c2 > D c2,max , then let the exhaust steam volume of ejector 1 be D c2 = D c2,max , substitute it into (2) to (5) and recalculate D p .

[0052] Step 3: Turbine exhaust steam pressure p c and ejector 1 power steam flow D p Implement collaborative control.

[0053] The ejector power steam flow is controlled by adjusting the displacement of the ejector regulating cone 6 D p , by adjusting the air cooling fan operating frequency to control the turbine exhaust steam pressure p c , (1) Based on the power steam flow D p Determine the nozzle equivalent throat area A t ; ; Among them, the critical steam velocity at the nozzle throat is v t Only relevant for power steam parameters: v t = f 6 ( p p , t p ), steam density r t = f 7 ( p p , t p , f ), f is the nozzle velocity coefficient, f 7 is the correlation function, obtained based on water vapor property data.

[0054] (2) Based on the equivalent throat area A t Determine the displacement of the ejector adjustment cone 6 s ; s = A t (s).

[0055] (3) Calculate the amount of exhaust steam discharged into the air cooling island D c3 ; D c3 = D c - D c1 - D c2 .

[0056] (4) Calculate the cooling air volume of the air cooling island D a ; D a · c p △ t a = D c3 · r ( p c ).

[0057] (5) Determine the number of operating rows X of the air cooling island; X= D a / D a1 ; in, D a1 For single-row design flow, X is an integer.

[0058] (6) Calculate the air volume of a single air-cooling fan D a2 ; D a2 = D a / X / Y Where Y is the number of columns in each row of the air cooling island.

[0059] (7) Control the operating frequency of the air cooling fan f ; f = f 8( D a2 ).

[0060] f 8 is the air volume of the air cooling fan Da2 With frequency f proportional function of .

[0061] The scope of protection claimed by the present invention is not limited to the above specific embodiments. For those skilled in the art, the present invention may have various deformations and changes. Any modifications, improvements and equivalent substitutions made within the concept and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An ejector control method based on the utilization of exhaust steam from a steam turbine of a thermal power unit, characterized in that: include: Step 1, determine whether the ejector is in operation; when Q cmax ≤ Q w1 or t c < t cmin , then the ejector operation is cut off; when Q cmax > Q w1 and t c ≥ t cmin , then the ejector is put into operation; in, Q cmax The maximum heat release of exhaust steam in the high back pressure condenser. Q w1 The heat absorbed by the circulating water in the primary heat network in the high back pressure condenser. t c is the actual exhaust steam temperature of the steam turbine, t cmin is the lowest available exhaust steam temperature of the steam turbine; Step 2: Determine the ejector steam flow rate D p and turbine exhaust steam pressure p c , the calculation methods include: a) When the ejector is in operation, the ejector power steam pressure p p When the ejector nozzle is designed, the pressure ratio ε n Calculation of turbine exhaust steam pressure p cn , if the corresponding exhaust steam temperature t cn Higher than the minimum available exhaust steam temperature required for primary heat network return water heating t cmin And lower than the maximum allowable exhaust steam temperature of the turbine t cmax , then control p c Keep the ejector nozzle at the designed pressure ratio and adjust the return water flow rate of the primary heating network. D w and temperature t h , calculate the ejector power steam flow D p ; b) When the ejector is in operation, the ejector power steam pressure p p When the pressure ratio of the ejector changes, n Calculated turbine exhaust steam temperature t cn Higher than the maximum allowable exhaust steam temperature of the turbine t cmax , then the heat load of the high back pressure condenser is designed Q gb Calculation of turbine exhaust steam pressure p c Then, the ejector power steam flow rate is calculated through the ejector variable operating condition calculation and ejector condenser heat balance. D p ; Step 3: Determine the turbine exhaust steam pressure p c and ejector power steam flow D p Cooperative control strategy; Adjust the cone displacement by adjusting the ejector s Control the ejector steam flow D p , by adjusting the operating frequency of the air cooling fan f Controlling turbine exhaust steam pressure p c .

2. The ejector control method based on exhaust steam utilization of a thermal power unit steam turbine according to claim 1, characterized in that: In step 1, the maximum heat release of exhaust steam in the high back pressure condenser Q cmax The calculation method is: Q cmax = （ h " c,max －h ' c,max ）×（ D c －D c3,min ）； in, h " c,max and h ' c,max The maximum exhaust steam pressure is p cmax The saturated steam enthalpy and saturated water enthalpy under D c is the exhaust steam flow rate, D c3,min The minimum exhaust steam required for antifreeze of the air-cooled island.

3. The ejector control method based on exhaust steam utilization of a thermal power unit steam turbine according to claim 2, characterized in that: In step 1, according to the return water temperature of the primary heating network t h , Circulating water volume D w and maximum exhaust steam pressure p cmax Calculation of heat absorption of circulating water in primary heating network in high back pressure condenser Q w1 ; Q w1 = D w · ( t cmax -2- t h ) ·4.187； Among them, the maximum allowable exhaust steam temperature of the steam turbine is: t cmax = f 1（ p cmax ）； Actual exhaust steam temperature of steam turbine: t c = f 1( p c ); function f 1 is the correlation function between saturated steam pressure and temperature, obtained based on steam physical property data.

4. The ejector control method based on exhaust steam utilization of a thermal power unit steam turbine according to claim 3 is characterized in that: In step 1, the lowest available exhaust steam temperature t cmin = t h +△ t hmin + δt ; Among them, △ t hmin The minimum return water temperature rise in the high back pressure condenser is 1-2℃; δt The heat transfer end difference of the high back pressure condenser is 2℃.

5. The ejector control method based on the utilization of exhaust steam from a steam turbine of a thermal power plant according to claim 1, 2, 3 or 4, characterized in that: In step 2, the calculation method a) includes the following steps: (1) According to the ejector power steam pressure p p and nozzle design pressure ratio ε n , calculate the ejector nozzle outlet pressure p ' cn ; p ' cn = e n · p p ; (2) Determine the turbine exhaust steam pressure p c ; p cn = a · p ' cn ； p c = p cn ； in, a is the coefficient to consider the exhaust steam flow resistance loss; (3) Turbine exhaust steam temperature t c = f 1( p c ); when t cmin ≤ t c ≤ t cmax , then the exhaust pressure of the steam turbine is controlled in a coordinated manner p c and ejector power steam flow D p Make the ejector nozzle work under the designed pressure ratio; (4) Calculate the ejector outlet pressure based on the ejector design boost ratio p ej ; p ej = p c · μ ； in, μ Design the step-up ratio for the ejector; (5) Calculate the condensate temperature of the ejector condenser t ej and condensation water specific enthalpy h ' ej ; t ej = f 1( p ej )； h ' ej = f 2( p ej )； Among them, the function f 2 is the correlation function between saturated vapor pressure and saturated water specific enthalpy, obtained based on physical property data; (6) Calculate the steam flow rate at the ejector outlet D ej , Steam specific enthalpy h ej , the amount of exhaust steam used by the ejector D c2 and power steam flow D p ; D ej · ( h ej －h ' ej )= D w [ t ej - 2- ( t c -2)] ·4.187； D p · h p + D c2 · h c =( D p + D c2 ) · h ej ； D p = D ej / (1+ω); D c2 = D ej - D p ； in, h p is the specific enthalpy of motive steam, according to p p and t p Check the physical properties of water vapor to obtain h c is the exhaust steam specific enthalpy of the turbine, according to the exhaust steam pressure p c Obtained by checking the physical properties of water vapor, ω is the design ejection coefficient; (7) Check the actual steam exhaust volume of the steam turbine D c Whether the exhaust steam volume calculated in step (6) is satisfied D c2 : Calculate and determine the amount of exhaust steam used by high back pressure condensers D c1 ; D c1 · r ( p c )= D w ( t c - 2- t h ) ·4.187； in, r For pressure p c The corresponding latent heat of vaporization is obtained from the physical properties of water vapor; Calculate the maximum exhaust steam quantity entering the ejector D c2,max ; D c2,max = D c - D c1 - D c3,min ； If the calculated value in step (6) is D c2 ≤ D c2,max , then the exhaust steam volume of the ejector is D c2 ; If the calculated value in step (6) is D c2 > D c2,max , then let the ejector exhaust steam be D c2 = D c2,max , substitute it into the formula in step (6) and recalculate D p .

6. The ejector control method based on exhaust steam utilization of a thermal power unit steam turbine according to claim 5, characterized in that: In step 2, the calculation method b) includes the following steps: (1) If Q gb ≥ Q w1 , then the ejector operation is cut off; like Q gb < Q w1 , according to the design heat load of high back pressure condenser Q gb Calculate the exhaust steam pressure p c ; Q gb = D w ( t c - 2- t h ) ·4.187； t c = Q gb / D w / 4.187+ t h +2； Then: Exhaust steam pressure p c = f 3 ( t c ); (2) The ejector coefficient under variable operating conditions is obtained through ejector variable operating condition calculation and ejector condenser heat balance calculation. ω 1 and step-up ratio μ 1; ω 1= f 4( p p , t p , p c , D p )； μ 1= f 5( p p , t p , p c , D p )； (3) Calculate the ejector outlet pressure p ej = p c · μ 1; (4) Calculate the condensate temperature of the ejector condenser t ej and condensation water specific enthalpy h ' ej ; t ej = f 1( p ej )； h ' ej = f 2( p ej )； (5) Calculate the ejector outlet steam flow rate through the ejector condenser heat balance D ej , Steam specific enthalpy h ej , the amount of exhaust steam used by the ejector D c2 and power steam flow D p ; D ej · ( h ej －h ' ej )= D w [ t ej - 2- ( t c -2)] ·4.187； D p · h p + D c2 · h c =( D p + D c2 ) · h ej ； D p = D ej / (1+ ω 1)； D c2 = D ej - D p ； If the calculated value in step (5) is D c2 ≤ D c2,max , then the exhaust steam volume of the ejector is D c2 ; If the calculated value in step (5) is D c2 > D c2,max , then let the ejector exhaust steam be D c2 = D c2,max , substitute it into steps (2) to (5) and recalculate D p .

7. The ejector control method based on exhaust steam utilization of a thermal power unit steam turbine according to claim 1 or 6, characterized in that: In step 3, the ejector adjusts the cone displacement s The calculation methods include: (1) Based on the power steam flow D p Determine the nozzle equivalent throat area A t ; ； Among them, the critical steam velocity at the nozzle throat is v t Only relevant for power steam parameters: v t = f 6 ( p p , t p ), steam density ρ t = f 7 ( p p , t p , φ ), φ is the nozzle velocity coefficient, f 7 is the correlation function, obtained based on the water vapor property data; (2) Based on the equivalent throat area A t Determine the displacement of the ejector adjustment cone s ; s = A t （s）。 8. The ejector control method based on exhaust steam utilization of a thermal power unit steam turbine according to claim 7, characterized in that: In step 3, the air cooling fan operating frequency f The calculation methods include: (1) Calculate the amount of exhaust steam discharged into the air cooling island D c3 = D c - D c1 - D c2 ; (2) Calculate the cooling air volume of the air cooling island D a ; D a · c p ·△ t a = D c3 · r ( p c )； (3) Determine the number of air cooling island operation rows X = D a / D a1 ;in, D a1 For the single-row design flow, X is an integer; (4) Calculate the air volume of a single air-cooling fan D a2 = D a / X / Y; where Y is the number of columns in each row of the air cooling island; (5) Control the operating frequency of the air cooling fan f = f 8( D a2 ), f 8 is the air volume of the air cooling fan D a2 With frequency f proportional function of .

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