CN111666676A - 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 discloses a correction calculation method for a low-temperature economizer system energy saving assessment test, which 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 regulations; b. calculating actually measured heat consumption rate HR of steam turbine under two working conditionst(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 economizer7Flow rate of flue gas MgSpecific heat capacity of flue gas CgFlow F of main water supply pipe3Temperature T of water supply main pipe3Correcting; d. performing second type correction calculation to obtain the heat consumption rate of the steam turbine after correction under two working conditions; f. calculating the difference value of the corrected heat consumption rates under 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 smoke-discharging heat loss of the coal-fired power plant is the largest specific gravity of various heat losses of the boiler, and accounts for 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 performance 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 by calculation only represents the energy saving effect under the test state condition, but 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 a low-temperature economizer system energy saving assessment test, aiming at a newly added low-temperature economizer system, and the method can be used for correcting actually measured energy saving to a related design boundary of a low-temperature economizer in a performance assessment test for evaluating the energy saving 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, evaluating the energy saving of the low-temperature economizer 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 regulations3Temperature T of water inlet main pipe of low-temperature economizer3Pressure P of water inlet main pipe3Temperature T of main return water pipe4Pressure P of main return pipe4Flue gas side inlet temperature T of low-temperature economizer7And the temperature T of the flue gas side outlet of the low-temperature economizer8Measuring, 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, and entering a step C;
C. and (3) carrying out first-class correction calculation according to ASME PTC6-2004 steam turbine performance test procedures to obtain the heat consumption rate of the steam turbine after correction, wherein the correction items comprise: (a) end difference of the feed water heater; (b) end difference of a drainage cooling section of the feed water heater; (c) pressure loss and heat dissipation loss of the steam extraction pipeline; (d) change in water storage capacity of the system; (e) enthalpy rise of the condensate pump and the feed pump; (f) supercooling degree of condensed water in the condenser; (g) supplying water quantity; (h) desuperheating water for controlling steam temperature; (i) a power factor; (j) a generator voltage; (k) hydrogen pressure of the generator; (l) The rotating speed of the generator; 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, except for performing the first type 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 economizer3Flow F of water inlet main pipe of low-temperature economizer3Low temperature coal economizer flue gas flow F7Specific heat capacity C of flue gas of low-temperature economizergAnd the temperature T of the inlet at the flue gas side of the low-temperature economizer7Making corrections, one type of turbine being corrected at each timeIn the iterative calculation of the main loop of the calculation, a new set of iteration variable values is generated, the set of variable values including: (1) temperature T of flue gas at outlet of low-temperature economizer8(ii) a (2) Outlet water temperature T of low-temperature coal economizer4(ii) a (3) Condensate temperature T after low-temperature economizer backwater and main condensate are converged5(ii) a (2) Condensate position F before main condensate and low-temperature economizer return water are merged6(ii) a (3) Water supply high-temperature water source branch flow F of low-temperature economizer1(ii) a (4) Low-temperature economizer water supply low-temperature water source branch flow F2(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 calculatedi1cAnd the heat rate HR of the steam turbine under the condition of quittingo1c(ii) a According to ASME PTC6-2004 steam turbine performance test procedure, on the basis of the first type correction calculation result, finishing the second type correction calculation, and respectively calculating to obtain the heat rate HR under the working condition of the corrected low-temperature economizeri2cAnd heat rate HR under withdrawal conditiono2cEntering step F;
F. heat rate HR under exit condition of corrected low-temperature economizero2cAnd the heat rate HR under the input working conditioni2cThe 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 economizer3Flow F of water inlet branch pipe of low-temperature economizer can be replaced1Or F2。
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)tIs the measured value of the heat rate of the steam turbine, kJ/(kW.h); dmThe main steam flow is t/h; drThe flow rate of the hot reheat steam is t/h; dfwThe main water supply flow is t/h; dcrThe flow rate of the cold reheat steam is t/h; dshsThe flow rate of the temperature reduction water of the superheater is t/h; drhsThe flow rate of the reheater desuperheating water is t/h; h ismIs the main steam enthalpy, kJ/kg; h isrIs the enthalpy of hot reheat steam, kJ/kg; h isfwThe main water supply enthalpy, kJ/kg; h isshsThe enthalpy of the desuperheated water is kJ/kg; h isrhsDecreasing the enthalpy of water for the reheater, kJ/kg; peAnd outputting power, MW, for the generator.
In a further development of the invention, in the sub-loop iteration added in step C, the coefficient lambda is defined as the mean specific heat capacity C of the flue gas side of the low-temperature economizergWith mass flow of flue gas MgSee formula (2):
λ＝Cg×Mg(2)
in the formula: lambda is the average specific heat capacity C of the flue gas side of the low-temperature economizergWith mass flow of flue gas MgThe product of (a), kJ/(kg.s); mgThe mass flow of the flue gas is kg/s; cgIs 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 adjusted3Flow F of water inlet main pipe of low-temperature economizer3Low temperature coal economizer flue gas flow F7Coefficient lambda and low-temperature economizer flue gas side inlet temperature T7Correcting to the design value, see formula (3) to formula (6):
T3c＝T3d(3)
T7c＝T7d(4)
F3c＝F3d(5)
λc＝λd＝Cgd×Mgd(6)
in the formula: subscript d represents a 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×Δtm(7)
Q＝Cg×Mg×(T7-T8)＝λ×(T7-T8) (8)
in the formula: mgThe mass flow of the flue gas is kg/s; cgThe 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, m2(ii) a K is the overall heat transfer coefficient of the low-temperature economizer, kJ/(m)2.K)；ΔtmThe heat transfer logarithmic mean temperature difference of the low-temperature economizer under the test condition is DEG C; Δ tmcThe corrected heat transfer logarithmic mean temperature difference of the low-temperature economizer is DEG C; Δ tmaxMaximum heat transfer temperature difference, DEG C; Δ tminMinimum heat transfer temperature difference, deg.C; t is8cThe corrected outlet flue gas temperature of the low-temperature economizer is DEG C; t is7cThe corrected inlet flue gas temperature of the low-temperature economizer is DEG C; lambda [ alpha ]tThe 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 given4And temperature T of exhaust gas8Assigning initial values, and obtaining the corrected T by iterative calculation using formula (9), formula (10) and formulae (11) to (14)4c、T8c、T5c、F6c、F1c、F2c；
F1×H1+F2×H2＝F3×H3(11)
F1+F2＝F3＝F4＝F5-F6(12)
Q＝(H4-H3)×F3(13)
F5×H5＝F6×H6+F4×H4(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; the subscript 6 indicates the location of the main condensate and the low-temperature economizer return water prior to merging.
The invention has at least the following beneficial technical effects:
in a performance assessment test for evaluating the energy saving performance of the 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 and flue gas specific heat capacity, cannot be completely the same as the design conditions due to the influence of factors such as boiler coal quality change, load fluctuation and operation control change. 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 flowchart 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 regulations and performing steam turbine performance tests under the conditions of input and exit of the low-temperature economizer respectively. As shown in the attached figure 2, when the performance test of the steam turbine under the working condition of putting the low-temperature economizer into operation is carried out, the flow F of the water inlet main pipe of the low-temperature economizer in the figure 1 is measured except the measurement parameters of the conventional performance test of the steam turbine recommended in the regulations3(or branch flow rate F)1Or F2) Temperature T of water inlet main pipe of low-temperature economizer3Pressure P of water inlet main pipe3Temperature T of main return water pipe4Pressure P of main return pipe4Flue gas side inlet temperature T of low-temperature economizer7And the temperature T of the flue gas side outlet of the low-temperature economizer8Measuring, and entering the step B;
B. respectively calculating the heat consumption rate of the low-temperature economizer under the actually measured state and the heat consumption rate of the steam turbine under the exit condition according to ASME PTC6-2004 steam turbine performance test procedures, as shown in figure 2, and entering the 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)tIs the measured value of the heat rate of the steam turbine, kJ/(kW.h); dmThe main steam flow is t/h; drThe flow rate of the hot reheat steam is t/h; dfwThe main water supply flow is t/h; dcrThe flow rate of the cold reheat steam is t/h; dshsThe flow rate of the temperature reduction water of the superheater is t/h; drhsThe flow rate of the reheater desuperheating water is t/h; h ismIs the main steam enthalpy, kJ/kg; h isrIs the enthalpy of hot reheat steam, kJ/kg; h isfwThe main water supply enthalpy, kJ/kg; h isshsThe enthalpy of the desuperheated water is kJ/kg; h isrhsDecreasing the enthalpy of water for the reheater, kJ/kg; peAnd 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 turbine is obtained by performing a first type of correction calculation according to ASME PTC6-2004 "turbine performance test procedure", wherein the correction items mainly include: (a) end difference of the feed water heater; (b) end difference of a drainage cooling section of the feed water heater; (c) pressure loss and heat dissipation loss of the steam extraction pipeline; (d) change in water storage capacity of the system; (e) enthalpy rise of the condensate pump and the feed pump; (f) supercooling degree of condensed water in the condenser; (g) supplying water quantity; (h) desuperheating water for controlling steam temperature; (i) a power factor; (j) a generator voltage; (k) hydrogen pressure of the generator; (l) 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 iteration3Flow F of water inlet main pipe of low-temperature economizer3Low temperature coal economizer flue gas flow F7Specific heat capacity C of flue gas of low-temperature economizergAnd the temperature T of the inlet at the flue gas side of the low-temperature economizer7And 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 economizer8(ii) a (2) Outlet water temperature T of low-temperature coal economizer4(ii) a (3) Condensate temperature T after low-temperature economizer backwater and main condensate are converged5(ii) a (2) Condensate position F before main condensate and low-temperature economizer return water are merged6(ii) a (3) Water supply high-temperature water source branch flow F of low-temperature economizer1(ii) a (4) Low-temperature economizer water supply low-temperature water source branch flow F2. 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 economizergWith mass flow of flue gas MgSee formula (2):
λ＝Cg×Mg(2)
in the formula: lambda is the average specific heat capacity C of the flue gas side of the low-temperature economizergWith mass flow of flue gas MgThe product of (a), kJ/(kg.s); mgThe mass flow of the flue gas is kg/s; cgIs 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 measured3Flow F of water inlet main pipe of low-temperature economizer3Low temperature coal economizer flue gas flow F7Coefficient lambda and low-temperature economizer flue gas side inlet temperature T7Correcting to the design value, see formula (3) -formula(6)：
T3c＝T3d(3)
T7c＝T7d(4)
F3c＝F3d(5)
λc＝λd＝Cgd×Mgd(6)
In the formula: subscript d represents a design value; the subscript c represents the corrected value.
And (3) performing added sub-loop iteration, assuming that the heat exchange coefficient K of the low-temperature economizer before and after correction is unchanged, 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:
Q＝K×A×Δtm(7)
Q＝Cg×Mg×(T7-T8)＝λ×(T7-T8) (8)
in the formula: mgThe mass flow of the flue gas is kg/s; cgThe 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, m2(ii) a K is the overall heat transfer coefficient of the low-temperature economizer, kJ/(m)2.K)；ΔtmThe heat transfer logarithmic mean temperature difference of the low-temperature economizer under the test condition is DEG C; Δ tmcThe corrected heat transfer logarithmic mean temperature difference of the low-temperature economizer is DEG C; Δ tmaxMaximum heat transfer temperature difference, DEG C; Δ tminMinimum heat transfer temperature difference, deg.C; t is8cThe corrected outlet flue gas temperature of the low-temperature economizer is DEG C; t is7cThe corrected inlet flue gas temperature of the low-temperature economizer is DEG C; lambda [ alpha ]tThe 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 low temperatureThe heat exchange capacity of the economizer, kW; subscript d represents a 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 T4And temperature T of exhaust gas8Assigning initial values, and obtaining the corrected T by iterative calculation using formula (9), formula (10) and formulae (11) to (14)4c、T8c、T5c、F6c、F1c、F2c。
F1×H1+F2×H2＝F3×H3(11)
F1+F2＝F3＝F4＝F5-F6(12)
Q＝(H4-H3)×F3(13)
F5×H5＝F6×H6+F4×H4(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; the subscript 6 indicates the location of the main condensate and the low-temperature economizer return water prior to merging.
D. As shown in the attached figure 2, the sub-loop and the main loop are iteratively converged, the first class correction calculation under the low-temperature economizer input working condition is finished, and the heat rate HR under the low-temperature economizer input working condition after the first class correction calculation is respectively calculatedi1cAnd the heat rate HR of the steam turbine under the condition of quittingo1c. According to ASME PTC6-2004 steam turbine performance test procedure, on the basis of the first type correction calculation result, finishing the second type correction calculation, and respectively calculating to obtain the heat rate HR under the working condition of the corrected low-temperature economizeri2cAnd heat rate HR under withdrawal conditiono2c. 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 withdrawno2cAnd the heat rate HR under the input working conditioni2cThe 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 inlet flue gas flow and the specific heat capacity of the low-temperature economizer is defined, and the temperature T of the inlet flue gas of the low-temperature economizer is realized by using a correlation formula of heat transfer science7Flow rate of flue gas MgSpecific heat capacity of flue gas CgFlow F of water supply main pipe of low-temperature economizer3Temperature T of water supply main pipe3And 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 19.2kJ/(kW.h), and the design value is not reached to 29.0 kJ/(kW.h).
TABLE 1 evaluation test calculation example for energy-saving effect 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, evaluating the energy saving of the low-temperature economizer 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 regulations3Temperature T of water inlet main pipe of low-temperature economizer3Pressure P of water inlet main pipe3Temperature T of main return water pipe4Pressure P of main return pipe4Flue gas side inlet temperature T of low-temperature economizer7And the temperature T of the flue gas side outlet of the low-temperature economizer8Measuring, 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, and entering a step C;
C. and (3) carrying out first-class correction calculation according to ASME PTC6-2004 steam turbine performance test procedures to obtain the heat consumption rate of the steam turbine after correction, wherein the correction items comprise: (a) end difference of the feed water heater; (b) end difference of a drainage cooling section of the feed water heater; (c) pressure loss and heat dissipation loss of the steam extraction pipeline; (d) change in water storage capacity of the system; (e) enthalpy rise of the condensate pump and the feed pump; (f) supercooling degree of condensed water in the condenser; (g) supplying water quantity; (h) desuperheating water for controlling steam temperature; (i) a power factor; (j) a generator voltage; (k) hydrogen pressure of the generator; (l) The rotating speed of the generator; 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, except for performing the first type 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 economizer3Flow F of water inlet main pipe of low-temperature economizer3Low temperature coal economizer flue gas flow F7Specific heat capacity C of flue gas of low-temperature economizergAnd the temperature T of the inlet at the flue gas side of the low-temperature economizer7Making corrections, each time the turbineIn a class of main loop iterative calculations of a modified calculation, a new set of iterative variable values is generated, the set of variable values comprising: (1) temperature T of flue gas at outlet of low-temperature economizer8(ii) a (2) Outlet water temperature T of low-temperature coal economizer4(ii) a (3) Condensate temperature T after low-temperature economizer backwater and main condensate are converged5(ii) a (2) Condensate position F before main condensate and low-temperature economizer return water are merged6(ii) a (3) Water supply high-temperature water source branch flow F of low-temperature economizer1(ii) a (4) Low-temperature economizer water supply low-temperature water source branch flow F2(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 calculatedi1cAnd the heat rate HR of the steam turbine under the condition of quittingo1c(ii) a According to ASME PTC6-2004 steam turbine performance test procedure, on the basis of the first type correction calculation result, finishing the second type correction calculation, and respectively calculating to obtain the heat rate HR under the working condition of the corrected low-temperature economizeri2cAnd heat rate HR under withdrawal conditiono2cEntering step F;
F. heat rate HR under exit condition of corrected low-temperature economizero2cAnd the heat rate HR under the input working conditioni2cThe 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 calculated3Flow F of water inlet branch pipe of low-temperature economizer can be replaced1Or F2。
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)tIs the measured value of the heat rate of the steam turbine, kJ/(kW.h); dmThe main steam flow is t/h; drThe flow rate of the hot reheat steam is t/h; dfwThe main water supply flow is t/h; dcrThe flow rate of the cold reheat steam is t/h; dshsThe flow rate of the temperature reduction water of the superheater is t/h; drhsThe flow rate of the reheater desuperheating water is t/h; h ismIs the main steam enthalpy, kJ/kg; h isrIs the enthalpy of hot reheat steam, kJ/kg; h isfwThe main water supply enthalpy, kJ/kg; h isshsThe enthalpy of the desuperheated water is kJ/kg; h isrhsDecreasing the enthalpy of water for the reheater, kJ/kg; peAnd 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 economizergWith mass flow of flue gas MgSee formula (2):
λ＝Cg×Mg(2)
in the formula: lambda is the average specific heat capacity C of the flue gas side of the low-temperature economizergWith mass flow of flue gas MgThe product of (a), kJ/(kg.s); mgThe mass flow of the flue gas is kg/s; cgIs 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 measured3Flow F of water inlet main pipe of low-temperature economizer3Low temperature coal economizer flue gas flow F7Coefficient lambda and low-temperature economizer flue gas side inlet temperature T7Correcting to the design value, see formula (3) to formula (6):
T3c＝T3d(3)
T7c＝T7d(4)
F3c＝F3d(5)
λc＝λd＝Cgd×Mgd(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 the 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×Δtm(7)
Q＝Cg×Mg×(T7-T8)＝λ×(T7-T8) (8)
in the formula: mgThe mass flow of the flue gas is kg/s; cgThe 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, m2(ii) a K is the overall heat transfer coefficient of the low-temperature economizer, kJ/(m)2.K)；ΔtmThe heat transfer logarithmic mean temperature difference of the low-temperature economizer under the test condition is DEG C; Δ tmcThe corrected heat transfer logarithmic mean temperature difference of the low-temperature economizer is DEG C; Δ tmaxMaximum heat transfer temperature difference, DEG C; Δ tminMinimum heat transfer temperature difference, deg.C; t is8cThe corrected outlet flue gas temperature of the low-temperature economizer is DEG C; t is7cThe corrected inlet flue gas temperature of the low-temperature economizer is DEG C; lambda [ alpha ]tThe inlet flue gas temperature and the average of the low-temperature economizer under the test conditionThe product of the specific heat capacities, 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.
7. The method as claimed in claim 1, wherein the step C is added to the sub-loop iteration by giving the leaving water temperature T to the low-temperature economizer4And temperature T of exhaust gas8Assigning initial values, and obtaining the corrected T by iterative calculation using formula (9), formula (10) and formulae (11) to (14)4c、T8c、T5c、F6c、F1c、F2c；
F1×H1+F2×H2＝F3×H3(11)
F1+F2＝F3＝F4＝F5-F6(12)
Q＝(H4-H3)×F3(13)
F5×H5＝F6×H6+F4×H4(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; the subscript 6 indicates the location of the main condensate and the low-temperature economizer return water prior to merging.
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