CN111666676B - Correction calculation method for energy-saving assessment test of low-temperature economizer system - Google Patents
Correction calculation method for energy-saving assessment test of low-temperature economizer system Download PDFInfo
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Abstract
The invention disclosesA correction calculation method for a low-temperature economizer system energy saving assessment test comprises the following steps: a. respectively carrying out performance tests under the working conditions of input and exit of the low-temperature economizer according to ASME PTC6-2004 steam turbine performance test procedures; b. calculating actually measured heat consumption rate HR of steam turbine under two working conditions t (ii) a c. Adding extra sub-loop iteration to the inlet flue gas temperature T in the first class of correction calculation under the input working condition of the low-temperature economizer 7 Flow rate of flue gas M g Specific heat capacity of flue gas C g Flow F of main water supply pipe 3 Temperature T of water supply main pipe 3 Correcting; d. performing second type correction calculation to obtain the corrected heat consumption rate of the steam turbine under two working conditions; f. and calculating the difference value of the corrected heat consumption rates under the two working conditions to obtain the energy-saving effect of the low-temperature economizer. The method can correct the running boundary condition of the low-temperature economizer to the design value in the energy-saving assessment test of the low-temperature economizer system, thereby avoiding the dispute or dispute of the buyer and the seller on the result of the energy-saving acceptance test of the low-temperature economizer.
Description
Technical Field
The invention belongs to the field of thermal performance tests of generator sets, and particularly relates to a correction calculation method for an energy-saving assessment test of a low-temperature economizer system.
Background
The boiler exhaust heat loss of the coal-fired power plant is one of the heat losses of the boiler with the largest proportion, and accounts for about 60-70% of the total loss of the boiler and 5-8% of the total input heat of the boiler. The method for reducing the exhaust gas temperature and improving the unit energy efficiency is widely adopted at present by adding a waste heat utilization low-temperature economizer to a tail flue of a boiler. After the low-temperature economizer is added, the change of the unit energy efficiency is mainly reflected in that: the condensed water absorbs the waste heat of the boiler exhaust smoke to reduce the steam extraction amount of the steam extraction port of the low-pressure cylinder part of the steam turbine and increase the work.
In a thermodynamic system comprising the low-temperature economizer, the low-temperature economizer effectively reduces the steam extraction flow of the corresponding heater by heating condensed water and similar replacing the function of part of the low-pressure heater, so that the working steam flow of the low-pressure cylinder of the steam turbine is obviously increased. The operation characteristics of the low-temperature economizer are influenced by factors such as boiler coal quality change, load fluctuation and operation control, and have strong volatility, and the operation boundary conditions such as water inlet temperature, water inlet flow, heat absorption capacity, inlet flue gas temperature, inlet flue gas flow and flue gas specific heat capacity cannot be completely the same as the design conditions.
In the engineering practice of the transformation of the low-temperature economizer, the energy-saving effect of the low-temperature economizer is evaluated by respectively carrying out performance tests on the steam turbine under the two conditions of the input and the exit of the low-temperature economizer and comparing the heat consumption rate test results of the steam turbine under the two conditions. In the performance assessment test for evaluating the energy saving effect of the low-temperature economizer by using the steam turbine performance test, if the correction of the relevant operating parameters of the low-temperature economizer is not considered, the energy saving effect of the low-temperature economizer obtained through calculation only represents the energy saving effect under the test state condition, and cannot be directly compared with the energy saving effect guaranteed by the low-temperature economizer.
At present, the flue gas waste heat utilization transformation represented by a low-temperature economizer occupies a large market share in the energy-saving transformation engineering of a thermal power plant. Therefore, the method for examining and calculating the correction method of the medium-low temperature economizer system has very important significance for the energy-saving effect examination test after the low-temperature economizer is transformed.
Disclosure of Invention
The invention aims to provide a correction calculation method for an energy-saving assessment test of a low-temperature economizer system, aiming at the newly added low-temperature economizer system, the method can be used for correcting the actually measured energy-saving amount to the relevant design boundary of the low-temperature economizer in a performance assessment test for evaluating the energy-saving amount of the low-temperature economizer by using a steam turbine performance test.
In order to achieve the purpose, the invention is realized by adopting the following technical scheme:
a correction calculation method for a low-temperature economizer system energy saving assessment test comprises the following steps:
A. with reference to ASME PTC6-2004 steam turbine performance test procedure, the energy saving of the low-temperature economizer is evaluated by performing steam turbine performance tests under the conditions of input and exit of the low-temperature economizer respectively; when the performance test of the steam turbine is carried out under the working condition of the low-temperature economizer, the flow F of the water inlet main pipe of the low-temperature economizer is measured except the performance test measurement parameters of the conventional steam turbine recommended in the regulation 3 Temperature T of water inlet main pipe of low-temperature economizer 3 Pressure P of water inlet main pipe 3 Temperature T of main return water pipe 4 Pressure P of main return pipe 4 Flue gas side inlet temperature T of low-temperature economizer 7 And the temperature T of the flue gas side outlet of the low-temperature economizer 8 Measuring, and entering the step B;
B. respectively calculating the heat consumption rate of the low-temperature economizer under the actually measured state under the input working condition and the heat consumption rate of the steam turbine under the exit working condition according to ASME PTC6-2004 steam turbine performance test procedures under the input working condition and the exit working condition of the low-temperature economizer under the input working condition of the low-temperature economizer, and entering a step C;
C. the low-temperature economizer is withdrawn under the working condition, and the first operation is carried out according to ASME PTC6-2004 steam turbine Performance test SpecificationAnd calculating class correction to obtain the heat consumption rate of the steam turbine after class correction, wherein the correction items comprise: (a) feedwater heater end difference; (b) a difference of ends of a drainage cooling section of the feed water heater; (c) pressure loss and heat dissipation loss of the steam extraction pipeline; (d) system water capacity change; (e) enthalpy rise for condensate and feedwater pumps; (f) the supercooling degree of the condensed water in the condenser; (g) make-up water volume; (h) desuperheating water for controlling the steam temperature; (i) power factor; (j) the generator voltage; (k) generator hydrogen pressure; (l) generator speed; under the working condition of putting the low-temperature economizer into operation, in the first class correction calculation of the thermal performance test of the steam turbine, except for performing the first class correction project specified by ASME PTC6-2004, adding a sub-iteration cycle to finish the parameter correction of the low-temperature economizer, and after the sub-iteration cycle is added, performing the sub-iteration cycle on the temperature T of a main water inlet pipe of the low-temperature economizer 3 Flow F of water inlet main pipe of low-temperature economizer 3 Low temperature coal economizer flue gas flow F 7 Specific heat capacity C of flue gas of low-temperature economizer g And the temperature T of the inlet at the flue gas side of the low-temperature economizer 7 And performing correction, wherein in each main loop iteration of the correction calculation of the steam turbine class, a new set of iteration variable values is generated, and the set of variable values comprises: (1) Temperature T of flue gas at outlet of low-temperature economizer 8 (ii) a (2) Outlet water temperature T of low-temperature coal economizer 4 (ii) a (3) Condensation water temperature T after backwater of low-temperature economizer and main condensation water are converged 5 (ii) a (2) Condensate position F before main condensate and low-temperature economizer return water are merged 6 (ii) a (3) Water supply high-temperature water source branch flow F of low-temperature economizer 1 (ii) a (4) Low-temperature economizer water supply low-temperature water source branch flow F 2 (ii) a The group of parameters is used as a correction result of iterative calculation of the thermodynamic system sub-loop of the low-temperature economizer to participate in correction calculation of the performance result of the steam turbine, and the step D is carried out;
D. iterative convergence of the sub-loop and the main loop is carried out, the first class correction calculation under the working condition of the low-temperature economizer is finished, and the heat rate HR under the working condition of the low-temperature economizer after the first class correction calculation is respectively calculated i1c And the heat rate HR of the steam turbine under the condition of quitting o1c (ii) a According to ASME PTC6-2004 steam turbine performance test regulations, finishing the second type of correction calculation on the basis of the first type of correction calculation results, and respectivelyCalculating to obtain the heat rate HR under the input working condition of the corrected low-temperature economizer i2c And heat rate HR under exit working condition o2c Entering step F;
F. heat rate HR under condition that the low-temperature economizer is withdrawn under the condition after correction o2c And the heat rate HR under the input working condition i2c The difference value is the energy-saving effect of the low-temperature economizer.
The invention has the further improvement that in the step A, the flow F of the water inlet main pipe of the low-temperature economizer 3 Can be replaced by a low-temperature economizer water inlet branch pipe flow F 1 Or F 2 。
The invention further improves the method for calculating the measured value of the heat rate of the steam turbine in the step B, as shown in the formula (1):
in the formula: HR (human HR) t Is the measured value of the heat rate of the steam turbine, kJ/(kW.h); d m The main steam flow is t/h; d r The flow rate of the hot reheat steam is t/h; d fw The main water supply flow is t/h; d cr The flow rate of the cold reheat steam is t/h; d shs The flow rate of the temperature reduction water of the superheater is t/h; d rhs Reducing the temperature water flow of the reheater, t/h; h is m Is the main steam enthalpy, kJ/kg; h is a total of r Is the enthalpy of hot reheat steam, kJ/kg; h is fw The main water supply enthalpy, kJ/kg; h is a total of shs Reducing the enthalpy of water for the superheater, kJ/kg; h is a total of rhs Reducing the enthalpy of water for the reheater, kJ/kg; p is e And outputting power, MW, for the generator.
The invention is further improved in that in the sub-loop iteration added in the step C, the coefficient lambda is defined as the average specific heat capacity C of the low-temperature economizer on the smoke side g With mass flow of flue gas M g See formula (2):
λ＝C g ×M g (2)
in the formula: lambda is the average specific heat capacity C of the flue gas side of the low-temperature economizer g With flue gas mass flow M g kJ/(kg.s); m is a group of g Is a cigaretteGas mass flow, kg/s; c g Is the average specific heat capacity of the flue gas, kJ/(kg.K).
The invention is further improved in that in the sub-loop iteration added in the step C, the temperature T of the water inlet main pipe of the low-temperature economizer is adjusted 3 Flow F of water inlet main pipe of low-temperature economizer 3 Low temperature coal economizer flue gas flow F 7 Coefficient lambda and low-temperature economizer flue gas side inlet temperature T 7 Correcting to the design value, see formula (3) to formula (6):
T 3c ＝T 3d (3)
T 7c ＝T 7d (4)
F 3c ＝F 3d (5)
λ c ＝λ d ＝C gd ×M gd (6)
in the formula: subscript d represents design value; the subscript c represents the corrected value.
The further improvement of the invention is that in the sub-loop iteration added in the step C, the formula (7) and the formula (8) are used for calculating to obtain the formula (9) and the formula (10) by assuming that the heat exchange coefficient K of the low-temperature economizer before and after correction is unchanged:
Q＝K×A×Δt m (7)
Q＝C g ×M g ×(T 7 -T 8 )＝λ×(T 7 -T 8 ) (8)
in the formula: m g The mass flow of the flue gas is kg/s; c g Is the average specific heat capacity of the flue gas, kJ/(kg.K); a is the heat exchange area of the smoke side of the low-temperature economizer, m 2 (ii) a K is the overall heat transfer coefficient of the low-temperature economizer, kJ/(m) 2 .K)；Δt m The heat transfer logarithmic mean temperature difference of the low-temperature economizer under the test condition is DEG C; Δ t mc The corrected heat transfer logarithm average temperature difference of the low-temperature economizer is the temperature; Δ t max The maximum heat transfer temperature difference is DEG C; Δ t min Minimum heat transfer temperature difference, DEG C; t is a unit of 8c The corrected outlet flue gas temperature of the low-temperature economizer is DEG C; t is a unit of 7c The corrected inlet flue gas temperature of the low-temperature economizer is DEG C; lambda [ alpha ] t The product of the inlet flue gas temperature of the low-temperature economizer and the average specific heat capacity under the test condition is kJ/(kg.s); k represents the heat transfer coefficient of the low-temperature economizer, kJ/kg; f represents the flow rate kg/s of the working medium on the water side; q represents the heat exchange capacity of the low-temperature economizer, kW; subscript d represents a design value; subscript t represents an actual value; the subscript c represents the corrected value.
The invention is further improved in that in the sub-loop iteration added in the step C, the water outlet temperature T of the low-temperature economizer is given 4 And temperature T of exhaust gas 8 Assigning initial values, and obtaining corrected T by iterative calculation using formula (9), formula (10) and formulas (11) to (14) 4c 、T 8c 、T 5c 、F 6c 、F 1c 、F 2c ；
F 1 ×H 1 +F 2 ×H 2 ＝F 3 ×H 3 (11)
F 1 +F 2 ＝F 3 ＝F 4 ＝F 5 -F 6 (12)
Q＝(H 4 -H 3 )×F 3 (13)
F 5 ×H 5 ＝F 6 ×H 6 +F 4 ×H 4 (14)
In the formula: h represents enthalpy of the working medium, kJ/kg; f represents the flow of the working medium kg/s; q represents the heat exchange capacity of the low-temperature economizer, kW; subscript 1 indicates the branch position of the high-temperature water source for supplying water to the low-temperature economizer; subscript 2 indicates the branch position of the low-temperature water source for supplying water to the low-temperature economizer; subscript 3 indicates the low-temperature economizer feed water inlet header position; subscript 4 indicates the position of the low-temperature economizer return water outlet main pipe; subscript 5 represents the position of a condensate water main pipe after the return water of the low-temperature economizer is merged with the main condensate water; subscript 6 indicates the location of the main condensate and the low-temperature economizer return water before merging.
The invention has at least the following beneficial technical effects:
in a performance assessment test for evaluating energy saving of a low-temperature economizer by using a steam turbine performance test, for the input working condition of the low-temperature economizer, the operation boundary conditions of the low-temperature economizer, such as water inlet temperature, water inlet flow, heat absorption capacity, inlet flue gas temperature, inlet flue gas flow, flue gas specific heat capacity and the like, cannot be completely the same as the design conditions due to the influence of factors such as boiler coal quality change, load fluctuation, operation control change and the like. At the present stage, the boundary conditions are not considered to be corrected in the evaluation and calculation of the energy saving amount of the low-temperature economizer, and the calculated energy saving amount of the low-temperature economizer only represents the performance of the low-temperature economizer in the running state and cannot be directly compared with the energy saving amount of the low-temperature economizer, so that business dispute is easily caused. By adopting the method provided by the invention, the operation boundary condition of the low-temperature economizer can be corrected to the design value, so that the situation that the buyer and the seller have disputes or disputes in the energy-saving acceptance test and the test result of the low-temperature economizer is avoided.
Drawings
FIG. 1 is a diagram of a typical low-temperature economizer and turbine low-pressure heater local thermodynamic system.
FIG. 2 is a schematic flow chart of the present invention.
Detailed Description
The method for correcting and calculating the thermal performance assessment test of the steam turbine with the low-temperature economizer is further described in detail by combining the attached drawings and examples.
Fig. 1 is a diagram of a typical local thermodynamic system of a low-temperature economizer and a turbine low-pressure heater, wherein the turbine low-pressure heater comprises 4 low-pressure heaters, which are numbered #5, #6, #7 and #8. Condensed water from the shaft seal heater respectively flows to the deaerator after passing through the #8 low feeding device, the #7 low feeding device, the #6 low feeding device and the #5 low feeding device in sequence. And the drained water of the low-pressure heater is added from #5 to #8 and flows automatically step by step and finally flows to the condenser. The low-temperature economizer has two water supply sources, wherein the low-temperature water source takes water from a #8 low-filling port, and the high-temperature water source takes water from a #7 low-filling port.
In the attached figure 1, a point 1 position is a low-temperature economizer high-temperature water supply branch pipe, a point 2 position is a low-temperature economizer low-temperature water supply branch pipe, a point 3 position is a low-temperature economizer water inlet main pipe, a point 4 position is a low-temperature economizer return water main pipe, a point 5 position is a condensation water pipeline after low-temperature economizer return water and main condensation water are converged, a point 6 position is a condensation water pipeline before main condensation water and low-temperature economizer return water are converged, a point 7 position is a low-temperature economizer flue gas side inlet, and a point 8 position is a low-temperature economizer flue gas side outlet.
As shown in the flow chart of fig. 2, the energy-saving assessment test correction calculation method for the low-temperature economizer system provided by the invention comprises the following steps:
A. the energy saving of the low-temperature economizer is evaluated by referring to ASME PTC6-2004 steam turbine performance test procedures under the conditions of input and exit of the low-temperature economizer to perform steam turbine performance tests. As shown in the attached figure 2, when the performance test of the steam turbine under the working condition of the low-temperature economizer is carried out, the flow F of the water inlet main pipe of the low-temperature economizer in the figure 1 is measured in addition to the conventional measurement parameters of the performance test of the steam turbine recommended in the regulation 3 (or branch flow rate F) 1 Or F 2 ) The temperature T of a water inlet main pipe of the low-temperature economizer 3 Pressure P of water inlet main pipe 3 Temperature T of backwater main pipe 4 Pressure P of main return pipe 4 Flue gas side inlet temperature T of low-temperature economizer 7 And the temperature T of the flue gas side outlet of the low-temperature economizer 8 Measuring, and entering the step B;
B. respectively calculating the heat consumption rate of the low-temperature economizer under the actually measured state under the input working condition and the heat consumption rate of the steam turbine under the exit working condition of the low-temperature economizer according to ASME PTC6-2004 steam turbine performance test procedures, as shown in figure 2, and entering a step C; the method for calculating the measured value of the heat rate of the steam turbine is shown as a formula (1):
in the formula: HR (human HR) t Is the measured value of the heat rate of the steam turbine, kJ/(kW.h); d m The main steam flow is t/h; d r The flow rate of the hot reheat steam is t/h; d fw The main water supply flow is t/h; d cr The flow rate of the cold reheat steam is t/h; d shs Reducing the temperature and water flow rate of the superheater, t/h; d rhs The flow rate of the reheater desuperheating water is t/h; h is m Is the main steam enthalpy, kJ/kg; h is a total of r Is the enthalpy of hot reheat steam, kJ/kg; h is fw The main water supply enthalpy, kJ/kg; h is shs Reducing the enthalpy of water for the superheater, kJ/kg; h is rhs Decreasing the enthalpy of water for the reheater, kJ/kg; p is e And outputting power, MW, for the generator.
C. The low-temperature economizer exits the operating mode, as shown in fig. 2, and the heat consumption rate of the steam turbine is obtained by performing a first type of correction calculation according to ASME PTC6-2004 steam turbine performance test procedure, wherein the correction items mainly comprise: (a) feedwater heater end-to-end difference; (b) a difference of ends of a drainage cooling section of the feed water heater; (c) pressure loss and heat dissipation loss of the steam extraction pipeline; (d) system water capacity variation; (e) enthalpy rise for condensate and feedwater pumps; (f) the supercooling degree of the condensed water in the condenser; (g) make-up water volume; (h) desuperheating water for controlling steam temperature; (i) power factor; (j) the generator voltage; (k) generator hydrogen pressure; (l) the rotational speed. Under the working condition of putting the low-temperature economizer into operation, in the first type correction calculation of the thermal performance test of the steam turbine, besides a first type correction project specified by ASME PTC6-2004, a sub-iteration cycle needs to be added to finish the parameter correction of the low-temperature economizer. After the sub-loop iteration is added, the temperature T of the water inlet main pipe of the low-temperature economizer is adjusted in the sub-loop iteration 3 Flow F of water inlet main pipe of low-temperature economizer 3 Low temperature coal economizer flue gas flow F 7 Specific heat capacity C of flue gas of low-temperature economizer g And the temperature T of the inlet at the flue gas side of the low-temperature economizer 7 And performing correction, wherein in each main loop iteration of the correction calculation of the steam turbine class, a new set of iteration variable values is generated, and the set of variable values comprises: (1) Temperature T of flue gas at outlet of low-temperature economizer 8 (ii) a (2) Outlet water temperature T of low-temperature coal economizer 4 (ii) a (3) After the return water of low-temperature economizer is merged with the main condensed waterTemperature T of condensate 5 (ii) a (2) Condensate position F before main condensate and low-temperature economizer return water are merged 6 (ii) a (3) Water supply high-temperature water source branch flow F of low-temperature economizer 1 (ii) a (4) Low-temperature water source branch flow F for water supply of low-temperature coal economizer 2 . The group of parameters are used as a correction result of iterative calculation of the thermodynamic system sub-loop of the low-temperature economizer to participate in correction calculation of the performance result of the steam turbine. Entering the step D;
as shown in the attached FIG. 2, in the added sub-loop iteration, a coefficient lambda is defined as the average specific heat capacity C of the flue gas side of the low-temperature economizer g With mass flow of flue gas M g See formula (2):
λ＝C g ×M g (2)
in the formula: lambda is the average specific heat capacity C of the flue gas side of the low-temperature economizer g With mass flow of flue gas M g kJ/(kg.s); m g The mass flow of the flue gas is kg/s; c g Is the average specific heat capacity of the flue gas, kJ/(kg.K).
As shown in the attached figure 2, the temperature T of a water inlet main pipe of the low-temperature economizer is adjusted 3 Flow F of water inlet main pipe of low-temperature economizer 3 Low-temperature coal economizer flue gas flow F 7 Coefficient lambda and low-temperature economizer flue gas side inlet temperature T 7 Correcting to the design value, see formula (3) to formula (6):
T 3c ＝T 3d (3)
T 7c ＝T 7d (4)
F 3c ＝F 3d (5)
λ c ＝λ d ＝C gd ×M gd (6)
in the formula: subscript d represents design value; the subscript c represents the corrected value.
And (3) performing added sub-loop iteration, and calculating by using a formula (7) and a formula (8) to obtain a formula (9) and a formula (10) as shown in the attached figure 2 by assuming that the heat exchange coefficient K of the low-temperature economizer before and after correction is unchanged:
Q＝K×A×Δt m (7)
Q＝C g ×M g ×(T 7 -T 8 )＝λ×(T 7 -T 8 ) (8)
in the formula: m g The mass flow of the flue gas is kg/s; c g The average specific heat capacity of the smoke is kJ/(kg.K); a is the heat exchange area of the smoke side of the low-temperature economizer, m 2 (ii) a K is the overall heat transfer coefficient of the low-temperature economizer, kJ/(m) 2 .K)；Δt m The heat transfer logarithmic mean temperature difference of the low-temperature economizer under the test condition is DEG C; Δ t mc The corrected heat transfer logarithmic mean temperature difference of the low-temperature economizer is DEG C; Δ t max Maximum heat transfer temperature difference, DEG C; Δ t min Minimum heat transfer temperature difference, deg.C; t is a unit of 8c The corrected outlet flue gas temperature of the low-temperature economizer is in DEG C; t is a unit of 7c The corrected inlet flue gas temperature of the low-temperature economizer is in DEG C; lambda [ alpha ] t The product of the inlet flue gas temperature of the low-temperature economizer and the average specific heat capacity under the test condition is kJ/(kg.s); k represents the heat transfer coefficient of the low-temperature economizer, kJ/kg; f represents the flow kg/s of the working medium on the water side; q represents the heat exchange capacity of the low-temperature economizer, kW; subscript d represents design value; subscript t represents an actual value; the subscript c represents the corrected value.
As shown in FIG. 2, the added sub-loop iterates by giving the low-temperature economizer leaving water temperature T 4 And the temperature T of exhaust gas 8 Assigning initial values, and obtaining the corrected T by iterative calculation using formula (9), formula (10) and formulae (11) to (14) 4c 、T 8c 、T 5c 、F 6c 、F 1c 、F 2c 。
F 1 ×H 1 +F 2 ×H 2 ＝F 3 ×H 3 (11)
F 1 +F 2 ＝F 3 ＝F 4 ＝F 5 -F 6 (12)
Q＝(H 4 -H 3 )×F 3 (13)
F 5 ×H 5 ＝F 6 ×H 6 +F 4 ×H 4 (14)
In the formula: h represents enthalpy of the working medium, kJ/kg; f represents the flow of the working medium kg/s; q represents the heat exchange quantity of the low-temperature economizer, kW; subscript 1 represents the position of a high-temperature water source branch for supplying water to the low-temperature economizer; subscript 2 represents the position of the low-temperature water source branch of the low-temperature economizer; subscript 3 indicates the low-temperature economizer feed water inlet header position; subscript 4 indicates the position of the low-temperature economizer return water outlet main pipe; subscript 5 represents the position of a condensate water main pipe after the return water of the low-temperature economizer is merged with the main condensate water; the subscript 6 indicates the location of the main condensate and the low-temperature economizer return water prior to merging.
D. As shown in fig. 2, the sub-loop and the main loop are iteratively converged, the first type correction calculation under the low-temperature economizer input condition is finished, and the heat rate HR of the low-temperature economizer under the low-temperature economizer input condition after the first type correction calculation is respectively calculated i1c And the heat rate HR of the steam turbine under the condition of quitting o1c . According to ASME PTC6-2004 steam turbine performance test regulations, on the basis of the first correction calculation result, finishing the second correction calculation, and respectively calculating to obtain the heat rate HR (high pressure recovery) of the corrected low-temperature economizer under the input working condition i2c And heat rate HR under withdrawal condition o2c . Entering the step F;
F. according to the step D, as shown in the attached figure 2, the corrected heat rate HR under the condition that the low-temperature economizer is withdrawn o2c And the heat rate HR under the input working condition i2c The difference value is the energy-saving effect of the low-temperature economizer.
As shown in table 1, in the example, in the energy saving acceptance test of the low-temperature economizer performed on a 1000MW thermal power generating unit, the energy saving effect of the low-temperature economizer was evaluated by performing the low-temperature economizer exit and operating condition turbine tests, respectively.
If the relevant operation parameters of the low-temperature economizer are not corrected, the calculated energy-saving effect of the low-temperature economizer only represents the energy-saving amount under the test condition and cannot be directly compared with the designed energy-saving effect.
By using the correction calculation method of the invention, the product lambda of the flue gas flow and the specific heat capacity at the inlet of the low-temperature economizer is defined, and the heat transfer related formula is utilized to realize the temperature T of the flue gas at the inlet of the low-temperature economizer 7 Flow rate of flue gas M g Specific heat capacity of flue gas C g Flow F of water supply main pipe of low-temperature economizer 3 Temperature T of water supply main pipe 3 And correcting the heat absorption quantity Q of the low-temperature economizer.
In the example, the calculation result shows that if the operation parameters of the low-temperature economizer are all corrected to the design values, the energy-saving effect of the low-temperature economizer is 19.2 kJ/(kW.h), and the design value is not reached to 29.0 kJ/(kW.h).
TABLE 1 energy-saving effect assessment test calculation example of low-temperature economizer system
Claims (7)
1. A correction calculation method for a low-temperature economizer system energy saving assessment test is characterized by comprising the following steps:
A. with reference to ASME PTC6-2004 steam turbine performance test procedure, the energy saving of the low-temperature economizer is evaluated by performing steam turbine performance tests under the conditions of input and exit of the low-temperature economizer respectively; when the performance test of the steam turbine under the working condition of low-temperature economizer input is carried out, the flow F of the water inlet main pipe of the low-temperature economizer is measured except the performance test measurement parameters of the conventional steam turbine recommended in the regulations 3 The temperature T of a water inlet main pipe of the low-temperature economizer 3 Pressure P of water inlet main pipe 3 Temperature T of main return water pipe 4 Pressure P of backwater main pipe 4 Inlet temperature T of flue gas side of low-temperature economizer 7 And the outlet temperature T of the flue gas side of the low-temperature economizer 8 Measuring, and entering the step B;
B. respectively calculating the heat consumption rate of the low-temperature economizer in an actually measured state under the input working condition and the heat consumption rate of the steam turbine under the exit working condition according to ASME PTC6-2004 steam turbine performance test regulations under the input working condition and exit working condition of the low-temperature economizer, and entering a step C;
C. and (3) carrying out first-class correction calculation according to ASME PTC6-2004 steam turbine performance test procedures under the exit working condition of the low-temperature economizer to obtain a class of corrected steam turbine heat consumption rate, wherein the correction items comprise: (a) feedwater heater end difference; (b) a difference of ends of a drainage cooling section of the feed water heater; (c) pressure loss and heat dissipation loss of the steam extraction pipeline; (d) system water capacity change; (e) enthalpy rise for condensate and feedwater pumps; (f) the supercooling degree of the condensed water in the condenser; (g) make-up water volume; (h) desuperheating water for controlling the steam temperature; (i) a power factor; (j) the generator voltage; (k) generator hydrogen pressure; (l) generator speed; under the working condition of the low-temperature economizer, in the first-class correction calculation of the thermal performance test of the steam turbine, besides a first-class correction item specified by ASME PTC6-2004, a sub-iteration loop is added to finish the parameter correction of the low-temperature economizer, and after the sub-iteration loop is added, the temperature T of a main water inlet pipe of the low-temperature economizer is adjusted in the sub-iteration loop 3 Flow F of water inlet main pipe of low-temperature economizer 3 Low temperature coal economizer flue gas flow F 7 Specific heat capacity C of flue gas of low-temperature economizer g And the temperature T of the inlet at the flue gas side of the low-temperature economizer 7 And performing correction, wherein in each main loop iteration of the correction calculation of the steam turbine class, a new set of iteration variable values is generated, and the set of variable values comprises: (1) Temperature T of flue gas at outlet of low-temperature economizer 8 (ii) a (2) Leaving water temperature T of low-temperature economizer 4 (ii) a (3) Condensate temperature T after low-temperature economizer backwater and main condensate are converged 5 (ii) a (2) Condensate position F before main condensate and low-temperature economizer return water are merged 6 (ii) a (3) Water supply high-temperature water source branch flow F of low-temperature economizer 1 (ii) a (4) Low-temperature economizer water supply low-temperature water source branch flow F 2 (ii) a The set of parameters are used as the sub-loop iteration calculation of the thermodynamic system of the low-temperature economizerD, the correction result participates in the correction calculation of the performance result of the steam turbine, and the step D is carried out;
D. iterative convergence of the sub-loop and the main loop is carried out, the first class correction calculation under the working condition of the low-temperature economizer is finished, and the heat rate HR under the working condition of the low-temperature economizer after the first class correction calculation is respectively calculated i1c And the heat rate HR of the steam turbine under the condition of quitting o1c (ii) a According to ASME PTC6-2004 steam turbine performance test regulations, on the basis of the first correction calculation result, finishing the second correction calculation, and respectively calculating to obtain the heat rate HR (high pressure recovery) of the corrected low-temperature economizer under the input working condition i2c And heat rate HR under withdrawal condition o2c Entering step F;
F. heat rate HR under exit condition of corrected low-temperature economizer o2c And the heat rate HR under the input working condition i2c The difference value is the energy-saving effect of the low-temperature economizer.
2. The correction calculation method for the energy-saving assessment test of the low-temperature economizer system as claimed in claim 1, wherein in the step A, the flow F of the water inlet main pipe of the low-temperature economizer is calculated 3 Can be replaced by a low-temperature economizer water inlet branch pipe flow F 1 Or F 2 。
3. The correction calculation method for the energy-saving assessment test of the low-temperature economizer system as claimed in claim 1, wherein in the step B, the calculation method for the measured value of the heat rate of the steam turbine is as shown in formula (1):
in the formula: HR (human HR) t Is the measured value of the heat rate of the steam turbine, kJ/(kW.h); d m The main steam flow is t/h; d r The flow rate of the hot reheat steam is t/h; d fw The main water supply flow is t/h; d cr The flow rate of the cold reheat steam is t/h; d shs Reducing the temperature and water flow rate of the superheater, t/h; d rhs Reducing water flow to reheater，t/h；h m Is the main steam enthalpy, kJ/kg; h is r Is the enthalpy of hot reheat steam, kJ/kg; h is a total of fw The main water supply enthalpy, kJ/kg; h is shs The enthalpy of the desuperheated water is kJ/kg; h is rhs Decreasing the enthalpy of water for the reheater, kJ/kg; p e And outputting power, MW, for the generator.
4. The correction calculation method for the energy-saving assessment test of the low-temperature economizer system as claimed in claim 1, wherein in the sub-loop iteration added in the step C, the coefficient λ is defined as the average specific heat capacity C of the flue gas side of the low-temperature economizer g With mass flow of flue gas M g See formula (2):
λ＝C g ×M g (2)
in the formula: lambda is the average specific heat capacity C of the flue gas side of the low-temperature economizer g With mass flow of flue gas M g kJ/(kg.s); m is a group of g The mass flow of the flue gas is kg/s; c g Is the average specific heat capacity of the flue gas, kJ/(kg.K).
5. The correction calculation method for the energy-saving assessment test of the low-temperature economizer system as claimed in claim 1, wherein in the sub-loop iteration added in the step C, the temperature T of the water inlet main pipe of the low-temperature economizer is measured 3 Flow F of water inlet main pipe of low-temperature economizer 3 Low temperature coal economizer flue gas flow F 7 Coefficient lambda and low-temperature economizer flue gas side inlet temperature T 7 Correcting to the design value, see formula (3) to formula (6):
T 3c ＝T 3d (3)
T 7c ＝T 7d (4)
F 3c ＝F 3d (5)
λ c ＝λ d ＝C gd ×M gd (6)
in the formula: subscript d represents a design value; the subscript c represents the corrected value.
6. The correction calculation method for the energy-saving assessment test of the low-temperature economizer system as claimed in claim 1, wherein in the sub-loop iteration added in step C, the formula (7) and the formula (8) are used to calculate the formula (9) and the formula (10) by assuming that the heat exchange coefficient K of the low-temperature economizer before and after the correction is unchanged:
Q＝K×A×Δt m (7)
Q＝C g ×M g ×(T 7 -T 8 )＝λ×(T 7 -T 8 ) (8)
in the formula: m is a group of g The mass flow of the flue gas is kg/s; c g The average specific heat capacity of the smoke is kJ/(kg.K); a is the heat exchange area of the flue gas side of the low-temperature economizer, m 2 (ii) a K is the overall heat transfer coefficient of the low-temperature economizer, kJ/(m) 2 .K)；Δt m The heat transfer logarithmic mean temperature difference of the low-temperature economizer under the test condition is DEG C; Δ t mc The corrected heat transfer logarithmic mean temperature difference of the low-temperature economizer is DEG C; Δ t max Maximum heat transfer temperature difference, DEG C; Δ t min Minimum heat transfer temperature difference, deg.C; t is a unit of 8c The corrected outlet flue gas temperature of the low-temperature economizer is DEG C; t is a unit of 7c The corrected inlet flue gas temperature of the low-temperature economizer is DEG C; lambda [ alpha ] t The product of the inlet flue gas temperature of the low-temperature economizer and the average specific heat capacity under the test condition is kJ/(kg.s); k represents the heat transfer coefficient of the low-temperature economizer, kJ/kg; f represents the flow rate kg/s of the working medium on the water side; q represents the heat exchange capacity of the low-temperature economizer, kW; subscript d represents a design value; subscript t represents an observed value; the subscript c represents the corrected value.
7. The low-temperature economizer of claim 1The correction calculation method of the system energy-saving assessment test is characterized in that in the sub-loop iteration added in the step C, the outlet water temperature T of the low-temperature economizer is fed 4 And temperature T of exhaust gas 8 Assigning initial values, and obtaining the corrected T by iterative calculation using formula (9), formula (10) and formulae (11) to (14) 4c 、T 8c 、T 5c 、F 6c 、F 1c 、F 2c ；
F 1 ×H 1 +F 2 ×H 2 ＝F 3 ×H 3 (11)
F 1 +F 2 ＝F 3 ＝F 4 ＝F 5 -F 6 (12)
Q＝(H 4 -H 3 )×F 3 (13)
F 5 ×H 5 ＝F 6 ×H 6 +F 4 ×H 4 (14)
In the formula: h represents the enthalpy value of the working medium kJ/kg; f represents the flow of the working medium kg/s; q represents the heat exchange capacity of the low-temperature economizer, kW; subscript 1 indicates the branch position of the high-temperature water source for supplying water to the low-temperature economizer; subscript 2 represents the position of the low-temperature water source branch of the low-temperature economizer; subscript 3 indicates the low-temperature economizer feed water inlet header position; subscript 4 indicates the position of the low-temperature economizer return water outlet main pipe; subscript 5 represents the position of a condensate water main pipe after the return water of the low-temperature economizer is merged with the main condensate water; the subscript 6 indicates the location of the main condensate and the low-temperature economizer return water prior to merging.
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