A heating capacity evaluation method for units operating with low-pressure cylinders cut off

Abstract

The present invention relates to a method for evaluating the heating capacity of a unit operating with low-pressure cylinders cut off, comprising: obtaining a maximum heating flow rate D for a low-pressure cylinder cut off operation test; correcting D for boiler desuperheating water flow rate, main steam flow rate, boiler flue gas waste heat utilization heat, and external heating steam heat, to obtain a corrected maximum heating flow rate Dc for low-pressure cylinder cut off operation; comparing Dc with the designed heating flow rate D0 to determine whether the heating capacity of the unit has reached the designed value. The beneficial effects of the present invention are: the present invention can accurately and intuitively quantitatively evaluate the heating capacity of a unit operating with low-pressure cylinders cut off, eliminating the influence of boiler desuperheating water flow rate, main steam flow rate, boiler flue gas waste heat utilization heat, and external heating steam heat on the heating capacity; and can provide an evaluation method for the assessment and acceptance of low-pressure cylinder cut off modification, as a basis for calculating the heating capacity of the unit.

Description

Technical Field

[0001] The present invention relates to the field of thermal power technology, and more specifically, to a method for evaluating the heating capacity of a unit operating with low-pressure cylinders cut off. Background Art

[0002] Low-pressure cylinder cutting operation has become an important way to improve the flexibility of current heating units, which can significantly improve the heating capacity and power peak-shaving capacity of the units.

[0003] The current low-pressure cylinder shutoff operation involves installing a hydraulic butterfly valve in the connecting pipe between the intermediate and low-pressure cylinders. This closes the butterfly valve to block steam from entering the low-pressure cylinder. Steam is extracted from the intermediate-pressure cylinder exhaust to increase the heat supply. A low-pressure cylinder cooling steam bypass is also added to ensure safety during shutoff operation.

[0004] Since the low-pressure cylinder cuts off the steam inlet, each low-pressure heater loses its heat load, and it is necessary to add heat sources such as medium-pressure cylinder exhaust steam, boiler flue gas waste heat, and external heating steam to heat the condensate, and optimize the heat recovery system to obtain higher economic benefits.

[0005] The low-pressure cylinder cutting operation system is relatively complex. During the heating capacity test, it is impossible to ensure that all parameters operate strictly according to the design values. Deviations in the boiler desuperheating water flow, main steam flow, boiler flue gas waste heat utilization heat, and external heating steam heat will affect the quantitative evaluation of the unit's heating capacity. Therefore, a new method is needed to correct the unit's maximum heating flow during the test to evaluate whether the unit's heating capacity meets the design requirements. Summary of the Invention

[0006] The purpose of the present invention is to overcome the deficiencies in the prior art and to provide a method for evaluating the heating capacity of a unit operating with low-pressure cylinders cut off.

[0007] In a first aspect, a method for evaluating the heating capacity of a unit operating with low-pressure cylinders cut off is provided, comprising:

[0008] Step 1: For the low-pressure cylinder cut-off operation unit, a heating capacity test is conducted to obtain the maximum heating flow rate D of the low-pressure cylinder cut-off operation test;

[0009] Step 2: Based on the maximum heating flow rate D of the low-pressure cylinder cutting operation test, the boiler desuperheating water flow rate, main steam flow rate, boiler flue gas waste heat utilization heat and external heating steam heat are corrected to obtain the corrected maximum heating flow rate D of the low-pressure cylinder cutting operation. c ;

[0010] Step 3: The maximum heat flow rate D after the low-pressure cylinder is cut off and operated c Based on this, it is compared with the design heating flow rate D0 to determine whether the unit's heating capacity has reached the design value.

[0011] Preferably, in step 1, the heating capacity test includes isolating the system according to the designed heat balance diagram.

[0012] Preferably, in step 1, the heating capacity test includes adjusting the main operating parameters according to design requirements to ensure that the unit is in the maximum heating flow operating condition, and the main operating parameters include main steam parameters, reheat steam parameters and condensate parameters.

[0013] Preferably, in step 1, the heating capacity test includes measuring the maximum heating flow rate of the test by a differential pressure device 20 installed in a circular cross-section pipe.

[0014] Preferably, in step 2, the correction of the boiler desuperheating water flow rate includes the correction of the superheated steam desuperheating water flow rate. The correction value of the superheated steam desuperheating water flow rate is calculated according to the first design correction curve by the deviation Δ1 between the test value of the superheated steam desuperheating water flow rate and the design value of the superheated steam desuperheating water flow rate, and is expressed as:

[0015] C1=f1(Δ1)

[0016] Among them, C1 is the correction value of the superheated steam desuperheating water flow rate, and f1 is the first design correction curve.

[0017] Preferably, in step 2, the correction of the boiler desuperheating water flow rate includes the correction of the reheated steam desuperheating water flow rate. The correction value of the reheated steam desuperheating water flow rate is calculated according to the second design correction curve by the deviation Δ2 between the test value of the reheated steam desuperheating water flow rate and the design value of the reheated steam desuperheating water flow rate, and is expressed as:

[0018] C2=f2(Δ2)

[0019] Among them, C2 is the correction value of the reheat steam desuperheating water flow rate, and f2 is the second design correction curve.

[0020] Preferably, in step 2, the correction value of the main steam flow rate is calculated based on the deviation Δ3 between the test value of the main steam flow rate and the design value of the main steam flow rate according to the third design correction curve, and is expressed as:

[0021] C3=f3(Δ3)

[0022] Among them, C3 is the correction value of the main steam flow rate, and f3 is the third design correction curve.

[0023] Preferably, in step 2, the correction value of the heat utilization of the boiler flue gas waste heat is obtained by converting the deviation Δ4 between the test value of the heat utilization of the boiler flue gas waste heat and the design value of the heat utilization of the boiler flue gas waste heat into the heating steam flow rate, and is expressed as:

[0024]

[0025] Among them, C4 is the correction value of the heat utilization of boiler flue gas waste heat, and h is the enthalpy value of heating steam.

[0026] Preferably, in step 2, the correction value of the external heating steam heat is obtained by converting the deviation Δ5 between the test value of the external heating steam heat and the design value of the external heating steam heat into the heating steam flow rate, and is expressed as:

[0027]

[0028] Among them, C5 is the correction value of the external heating steam heat, and h is the enthalpy of the heating steam.

[0029] In a second aspect, a low-pressure cylinder trimming operation unit is provided, which is applied to any of the heating capacity evaluation methods for low-pressure cylinder trimming operation units described in the first aspect, comprising: a boiler 7, a reheater 8, a high-pressure cylinder 9, an intermediate-pressure cylinder 10, a low-pressure cylinder 11, a condenser 12, a boiler flue gas waste heat-condensate heat exchanger 13, an external heating steam-condensate heat exchanger 14, a low-pressure heater 15, a deaerator 16, a feedwater pump 17, a high-pressure heater 18, a butterfly valve 19 on the intermediate and low-pressure cylinder connecting pipes, and a differential pressure device 20;

[0030] Among them, the medium-pressure cylinder 10 is connected to the low-pressure cylinder 11 through the medium- and low-pressure cylinder connecting pipe butterfly valve 19, and the differential pressure device 20 is installed in a circular cross-section pipe, which is connected to the connecting pipe between the medium-pressure cylinder 10 and the deaerator 16.

[0031] The beneficial effects of the present invention are: the present invention can accurately and intuitively quantitatively evaluate the heating capacity of the low-pressure cylinder cutting operation unit, eliminate the influence of boiler cooling water flow, main steam flow, boiler flue gas waste heat utilization heat and external heating steam heat on the heating capacity; and can provide an evaluation method for the low-pressure cylinder cutting transformation assessment and acceptance work, as a basis for the calculation of the unit's heating capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a flow chart of a method for evaluating the heating capacity of a unit operating with low-pressure cylinders cut off, provided in this application;

[0033] Figure 2 This is a schematic diagram of the structure of the low-pressure cylinder cutting operation unit provided in this application;

[0034] Explanation of the reference numerals: 1. Heating steam; 2. Superheated steam cooling water; 3. Reheated steam cooling water; 4. Main steam; 5. Heat from waste heat of boiler flue gas; 6. Heat from external heating steam; 7. Boiler; 8. Reheater; 9. High-pressure cylinder; 10. Medium-pressure cylinder; 11. Low-pressure cylinder; 12. Condenser; 13. Boiler flue gas waste heat-condensate heat exchanger; 14. External heating steam-condensate heat exchanger; 15. Low-pressure heater; 16. Deaerator; 17. Feed water pump; 18. High-pressure heater; 19. Butterfly valves connecting the medium and low-pressure cylinders; 20. Differential pressure device. DETAILED DESCRIPTION

[0035] The present invention will be further described below with reference to the following examples. The following examples are provided only to facilitate understanding of the present invention. It should be noted that, without departing from the principles of the present invention, it is possible for a person skilled in the art to make various modifications to the present invention, and such improvements and modifications fall within the scope of the claims of the present invention.

[0036] Example 1:

[0037] Aiming at the problem in the prior art that it is impossible to ensure that all parameters of the low-pressure cylinder cutting-off operation unit are strictly operated according to the design value during the heating capacity test, this application provides a heating capacity evaluation method suitable for the low-pressure cylinder cutting-off operation unit, such as Figure 1 As shown, including:

[0038] Step 1: Target Figure 2 The low-pressure cylinder cutting operation unit shown in the figure passes the heating capacity test and obtains the maximum heating flow rate D of the low-pressure cylinder cutting operation test.

[0039] The low-pressure cylinder cut-off operation unit includes: boiler 7, reheater 8, high-pressure cylinder 9, medium-pressure cylinder 10, low-pressure cylinder 11, condenser 12, boiler flue gas waste heat-condensate heat exchanger 13, external heating steam-condensate heat exchanger 14, low-pressure heater 15, deaerator 16, feedwater pump 17, high-pressure heater 18, butterfly valve 19 for the medium- and low-pressure cylinder connecting pipes, and differential pressure device 20;

[0040] Among them, the medium-pressure cylinder 10 is connected to the low-pressure cylinder 11 through the medium- and low-pressure cylinder connecting pipe butterfly valve 19, and the differential pressure device 20 is installed in a circular cross-section pipe, which is connected to the connecting pipe between the medium-pressure cylinder 10 and the deaerator 16.

[0041] In the low-pressure cylinder cutting operation unit, the heating steam 1 is extracted from the exhaust of the intermediate-pressure cylinder 10, and the steam inlet to the low-pressure cylinder 11 is blocked by closing the butterfly valve 19 connecting the intermediate and low-pressure cylinders to achieve the low-pressure cylinder 11 cutting operation.

[0042] Step 2: Based on the maximum heating flow rate D of the low-pressure cylinder cutting operation test, the boiler desuperheating water flow rate, main steam flow rate, boiler flue gas waste heat utilization heat and external heating steam heat are corrected to obtain the corrected maximum heating flow rate D of the low-pressure cylinder cutting operation. c .

[0043] There are deviations in the boiler desuperheating water flow, main steam flow, boiler flue gas waste heat utilization heat, and external heating steam heat in the heating capacity test of the low-pressure cylinder cutting operation unit. Therefore, the maximum heating flow D obtained in the low-pressure cylinder cutting operation test in step 1 cannot accurately reflect the heating capacity of the low-pressure cylinder cutting operation unit, and cannot be directly compared with the design heating flow D0 in step 3. Instead, it is necessary to correct the boiler desuperheating water flow, main steam flow, boiler flue gas waste heat utilization heat, and external heating steam heat to obtain the corrected maximum heating flow D for the low-pressure cylinder cutting operation. c .

[0044] Step 3: Run the low-pressure cylinder to cut off the cylinder and calculate the corrected maximum heating flow rate D c Based on the design heating flow rate D0, it is compared to determine whether the unit's heating capacity has reached the design value. c When it is greater than or equal to the design heating flow rate D0, it is considered that the heating capacity of the unit has reached the design value, otherwise it has not reached the design value.

[0045] In step 1, the heating capacity test includes isolating the system according to the design heat balance diagram.

[0046] In step 1, the heating capacity test includes adjusting the main operating parameters according to the design requirements. The main operating parameters include main steam parameters, reheat steam parameters and condensate parameters.

[0047] In step 1, the heating capacity test includes measuring the maximum heating flow rate of the test by using a differential pressure device 20 installed in a circular cross-section pipe.

[0048] It should be noted that the boiler desuperheating water flow rate and the main steam flow rate obtain correction values ​​through different design correction curves. Specifically, in step 2, the correction of the boiler desuperheating water flow rate includes the correction of the superheated steam desuperheating water flow rate. The correction value of the superheated steam desuperheating water flow rate is calculated based on the deviation Δ1 between the test value of the superheated steam desuperheating water flow rate and the design value of the superheated steam desuperheating water flow rate according to the first design correction curve, and is expressed as:

[0049] C1=f1(Δ1)

[0050] Among them, C1 is the correction value of the superheated steam desuperheating water flow rate, and f1 is the first design correction curve.

[0051] In step 2, the correction of the boiler attemperation water flow rate includes the correction of the reheated steam attemperation water flow rate. The correction value of the reheated steam attemperation water flow rate is calculated based on the deviation Δ2 between the test value of the reheated steam attemperation water flow rate and the design value of the reheated steam attemperation water flow rate according to the second design correction curve, and is expressed as:

[0052] C2=f2(Δ2)

[0053] Among them, C2 is the correction value of the reheat steam desuperheating water flow rate, and f2 is the second design correction curve.

[0054] In step 2, the correction value of the main steam flow rate is calculated based on the deviation Δ3 between the experimental value of the main steam flow rate and the design value of the main steam flow rate according to the third design correction curve, and is expressed as:

[0055] C3=f3(Δ3)

[0056] Among them, C3 is the correction value of the main steam flow rate, and f3 is the third design correction curve.

[0057] In step 2, the correction value of the heat utilization of the boiler flue gas waste heat is obtained by converting the deviation Δ4 between the test value of the heat utilization of the boiler flue gas waste heat and the design value of the heat utilization of the boiler flue gas waste heat into the heating steam flow rate, which is expressed as:

[0058]

[0059] Among them, C4 is the correction value of the heat utilization of boiler flue gas waste heat, and h is the enthalpy value of heating steam.

[0060] In step 2, the correction value of the external heating steam heat is obtained by converting the deviation Δ5 between the test value of the external heating steam heat and the design value of the external heating steam heat into the heating steam flow rate, which is expressed as:

[0061]

[0062] Among them, C5 is the correction value of the external heating steam heat, and h is the enthalpy of the heating steam.

[0063] In step 2, the maximum heating flow rate D after the low-pressure cylinder cut-out operation is corrected c for:

[0064] D c =D-C1-C2-C3-C4-C5

[0065] Finally, the evaluation index D of the unit's low-pressure cylinder cutting operation heating capacity is obtained c -D0. For example, in D c -D0≥0, the heating capacity of the unit's low-pressure cylinder cut-off operation reaches the design value, and the greater the absolute value, the greater the heating capacity; D cWhen -D0<0, the heating capacity of the unit's low-pressure cylinder cut-off operation does not reach the design value, and the larger the absolute value, the smaller the heating capacity.

[0066] In summary, the present invention can accurately and intuitively quantitatively evaluate the heating capacity of the unit operating with low-pressure cylinder cutting, eliminate the influence of boiler cooling water flow, main steam flow, boiler flue gas waste heat utilization heat and external heating steam heat on the heating capacity; and can provide an evaluation method for the assessment and acceptance of low-pressure cylinder cutting transformation work, which serves as the basis for calculating the unit's heating capacity.

Claims

1. A method for evaluating the heating capacity of a unit with low-pressure cylinders cut off, characterized in that: include: Step 1: For the low-pressure cylinder cut-off operation unit, a heating capacity test is conducted to obtain the maximum heating flow rate D of the low-pressure cylinder cut-off operation test; Step 2: Based on the maximum heating flow rate D of the low-pressure cylinder cutting operation test, the boiler desuperheating water flow rate, main steam flow rate, boiler flue gas waste heat utilization heat and external heating steam heat are corrected to obtain the corrected maximum heating flow rate D of the low-pressure cylinder cutting operation. c ; In step 2, the correction of the boiler desuperheating water flow rate includes the correction of the superheated steam desuperheating water flow rate. The correction value of the superheated steam desuperheating water flow rate is calculated based on the deviation Δ1 between the test value of the superheated steam desuperheating water flow rate and the design value of the superheated steam desuperheating water flow rate according to the first design correction curve, and is expressed as: C1=f1(Δ1) Wherein, C1 is the correction value of the superheated steam desuperheating water flow rate, and f1 is the first design correction curve; In step 2, the correction of the boiler attemperation water flow rate includes the correction of the reheated steam attemperation water flow rate. The correction value of the reheated steam attemperation water flow rate is calculated based on the deviation Δ2 between the test value of the reheated steam attemperation water flow rate and the design value of the reheated steam attemperation water flow rate according to the second design correction curve, and is expressed as: C2=f2(Δ2) Wherein, C2 is the correction value of the reheat steam desuperheating water flow rate, and f2 is the second design correction curve; In step 2, the correction value of the main steam flow rate is calculated based on the deviation Δ3 between the experimental value of the main steam flow rate and the design value of the main steam flow rate according to the third design correction curve, and is expressed as: C3=f3(Δ3) Among them, C3 is the correction value of the main steam flow rate, f3 is the third design correction curve; In step 2, the correction value of the heat utilization of the boiler flue gas waste heat is obtained by converting the deviation Δ4 between the test value of the heat utilization of the boiler flue gas waste heat and the design value of the heat utilization of the boiler flue gas waste heat into the heating steam flow rate, which is expressed as: Among them, C4 is the correction value of the heat utilization of boiler flue gas waste heat, and h is the enthalpy of heating steam; In step 2, the correction value of the external heating steam heat is obtained by converting the deviation Δ5 between the test value of the external heating steam heat and the design value of the external heating steam heat into the heating steam flow rate, which is expressed as: Wherein, C5 is the correction value of external heating steam heat, h is the enthalpy of heating steam; Step 3: The maximum heat flow rate D after the low-pressure cylinder is cut off and operated c Based on this, it is compared with the design heating flow rate D0 to determine whether the unit's heating capacity has reached the design value.

2. The method for evaluating the heating capacity of a unit with low-pressure cylinders cut off according to claim 1 is characterized in that: In step 1, the heating capacity test includes isolating the system according to the designed heat balance diagram.

3. The method for evaluating the heating capacity of a unit with low-pressure cylinders cut off according to claim 1 is characterized in that: In step 1, the heating capacity test includes adjusting the main operating parameters according to design requirements, and the main operating parameters include main steam parameters, reheat steam parameters and condensate parameters.

4. The method for evaluating the heating capacity of a unit with low-pressure cylinders cut off according to claim 1 is characterized in that: In step 1, the heating capacity test includes measuring the maximum heating flow rate of the test by using a differential pressure device 20 installed in a circular cross-section pipe.

5. A low-pressure cylinder cutting operation unit, characterized in that: The method for evaluating the heating capacity of a unit operating in a low-pressure cylinder cut-off state, as claimed in any one of claims 1 to 4, comprises: a boiler 7, a reheater 8, a high-pressure cylinder 9, an intermediate-pressure cylinder 10, a low-pressure cylinder 11, a condenser 12, a boiler flue gas waste heat-condensate heat exchanger 13, an external heating steam-condensate heat exchanger 14, a low-pressure heater 15, a deaerator 16, a feedwater pump 17, a high-pressure heater 18, a butterfly valve 19 for connecting pipes of the intermediate and low-pressure cylinders, and a differential pressure device 20; Among them, the medium-pressure cylinder 10 is connected to the low-pressure cylinder 11 through the medium- and low-pressure cylinder connecting pipe butterfly valve 19, and the differential pressure device 20 is installed in a circular cross-section pipe, which is connected to the connecting pipe between the medium-pressure cylinder 10 and the deaerator 16.

Images