A circulating pump scheduling method for solving critical load

Abstract

The present invention relates to the technical field of circulating water pumps in power plants, and in particular, to a circulating pump scheduling method for solving critical loads. A circulating pump scheduling method for solving critical loads, comprising: S100, obtaining the temperature rise variation coefficients of circulating water for single pumps and double pumps; S200, establishing a function of the saturated pressure change rate with exhaust steam temperature; S300, calculating the coal saving amount of the back pressure change unit and the coal consumption of the circulating pump; S310, obtaining the coal saving amount of the steam turbine back pressure change; S320, obtaining the standard coal consumption of the circulating pump power change; S400, calculating the critical electric load of the start and stop of the circulating pump. A circulating pump scheduling method for solving critical loads, which has the advantages of using experiments to measure the temperature rise variation coefficients of circulating water for single pumps and double pumps, establishing a function of the saturated pressure change rate with exhaust steam temperature to calculate the coal saving amount of the back pressure change unit and the coal consumption of the circulating pump, and calculating the critical electric load of the start and stop of the circulating pump, reduces the changes and variables of the working conditions in the test process, and is simple to calculate, and does not require professional institutions to complete.

Description

Technical Field

[0001] The invention relates to the technical field of circulating water pumps in power plants, and in particular to a circulating pump scheduling method for solving critical loads. Background Art

[0002] At present, thermal power generation occupies a dominant position among all power generation methods because of its mature technology, low cost, and easy access to raw materials required for power generation. With the growth of electricity demand, the requirements for power generation efficiency of power plants are getting higher and higher. At the same time, try to save raw materials and avoid waste of materials. According to the above requirements, the operation mode of the circulating water pump plays an important role. Cold end optimization changes the operation mode of the circulating water pump to maximize the difference between the increase in turbine power and the increase in power consumption of the circulating water pump, so as to determine the optimal condenser pressure and cooling water volume, thereby selecting the best operation mode of the circulating water pump.

[0003] The Chinese invention patent with publication number CN103063354A and a method for determining the reference back pressure of a steam turbine in the energy consumption evaluation and coal consumption determination test of a thermal power unit, using the reference back pressure to replace the rated back pressure with a large deviation, including obtaining the actual performance data of the cooling tower and the condenser through the test, obtaining the circulating water volume and temperature rise data of the condenser, and determining the reference back pressure by combining the test with the calculation method, using the data obtained in the test and the design data of other parameters, according to the general process calculation; in the test, the circulating water scheduling is based on the actual scheduling method under the annual average meteorological conditions; the back pressure data results obtained by the present invention are more real than the rated back pressure, and the randomness of the current rated back pressure data results is removed, so that the back pressure conditions and equipment status of the unit can be understood more deeply, especially convenient for comparison with other units, and the accurate reference back pressure obtained by the present invention can be used to evaluate the current energy consumption status and energy saving potential of the unit more objectively and deeply, which is of great significance. However, the patent does not solve the problem of circulating water pump regulation. Generally, the relationship between the increase in circulating pump power consumption and the increase in unit output is found through the slight increase in power method, and the circulating pump scheduling curve based on the changes in circulating water temperature and power generation load is summarized. The test process has many working conditions and variables, and needs to be completed by a professional organization. Summary of the invention

[0004] In view of the above problems, the present invention provides a method for calculating the critical load of a circulating pump scheduling. The temperature rise coefficient K1 of the circulating water of a single pump and a double pump is measured by experiment, the function K2=f(T) of the saturated pressure change rate with the exhaust temperature is established, the coal saving M1 of the back pressure change unit and the coal consumption M2 of the circulating pump are calculated, and the critical electric load of the start and stop of the circulating pump is calculated, which solves the problems of many working conditions and variables in the test process, and the need for professional institutions to complete it.

[0005] A circulating pump scheduling method for solving critical load, comprising:

[0006] S100, obtaining the temperature rise variation coefficient K1 of the circulating water of the single pump and the double pump;

[0007] K1=△T / W (1)

[0008] △T = temperature rise of circulating water with single pump T1 - temperature rise of circulating water with double pumps T2 (2);

[0009] Where, W is the unit electrical load W (MW);

[0010] S200, establishing a function K2=f(T) of the rate of change of saturated pressure as a inverse function of exhaust temperature;

[0011] According to the variation law of wet steam saturation pressure with temperature, the saturation pressure variation rate function is fitted;

[0012] S300, calculating the coal saving amount M1 of the back pressure change unit and the coal reduction amount M2 of the circulating pump power consumption;

[0013] S310, obtaining the coal saving amount M1 of the steam turbine back pressure change;

[0014] M1=W 2 *K1*C*K2 (3)

[0015] Among them, C-back pressure on power generation coal consumption difference coefficient (g / kWh / KPa)

[0016] S320, obtaining the standard coal quantity M2 converted from the circulating pump power change;

[0017] M2=1.732*U*△I*φ*b (4)

[0018] Among them, U-circulating pump motor voltage (KV), ΔI-difference between double pump and single pump circulating pump current (A), φ-circulating pump motor power factor, b-power consumption of power generation (Kg / kWh);

[0019] S400, calculating the critical electrical load of the circulation pump when starting and stopping;

[0020] When M1=M2, the corresponding electrical load is the critical electrical load of the circulation pump single pump and double pump mode; W=POWER(1.732*U*△I*φ*b / (K1*C*K2), 0.5) (5).

[0021] Furthermore, in step S100, the temperature rise of the circulating water is obtained by equation (6):

[0022] T=W * (q-3600 / ηjd) / (Q*4.2) (6)

[0023] Wherein, T is the temperature rise of circulating water in °C; W is the electrical load in MW; q is the heat consumption of steam turbine in kj / kWh; ηjd is the electromechanical efficiency in 0.985; Q is the circulating water flow in t / h; 4.2 is the specific heat of circulating water in Kj / (Kg.°C).

[0024] Furthermore, substituting formula (6) into formula (2) yields:

[0025] ΔT=(q-3600 / ηjd) / 4.2*W*(Q2-Q1) / (Q2*Q1) (7).

[0026] Furthermore, (q-3600 / ηjd) / 4.2 can be approximately considered as a constant;

[0027] (Q2-Q1) / (Q2*Q1) can be approximately considered as a constant for the two determined circulating water pump operation modes. Further, the method of obtaining K1 includes: directly obtaining it by experimentally measuring the change in circulating water temperature rise when the electrical load W remains constant, or calculating it based on the turbine heat consumption and circulating water flow rate;

[0028] The two methods can be cross-checked.

[0029] Furthermore, when the electrical load changes, the circulating water temperature rise under the single-pump and dual-pump conditions is corrected to the temperature rise under the same electrical load to obtain the K1 value.

[0030] Furthermore, in step S310, the premise for obtaining formula (2) is that the condenser end difference is the same under the single-pump and double-pump operating conditions.

[0031] Furthermore, in step S320, the method for obtaining the power generation coal consumption b of the unit includes:

[0032] b=q / 29.308 / ηgl / ηgd / 1000 (6).

[0033] Compared with the prior art, the circulating pump scheduling method for solving critical load described in the present invention has the following advantages:

[0034] The advantages of this technical solution are that it uses experiments to determine the temperature rise coefficient K1 of the circulating water with single pump and double pump, establishes the function K2=f(T) of the saturated pressure change rate with the exhaust temperature, calculates the coal saving M1 of the back pressure change unit and the coal consumption M2 of the circulating pump, and calculates the critical electric load of the starting and stopping of the circulating pump, which reduces the changes and variables of the operating conditions during the test process, is simple to calculate, and does not require a professional organization to complete. DETAILED DESCRIPTION

[0035] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0036] A circulating pump scheduling method for solving critical load, comprising:

[0037] S100, obtaining the temperature rise variation coefficient K1 of the circulating water of the single pump and the double pump;

[0038] K1=△T / W (1)

[0039] △T = temperature rise of circulating water with single pump T1 - temperature rise of circulating water with double pumps T2 (2);

[0040] Where, W is the unit electrical load W (MW);

[0041] Because the condenser temperature rise is equal to the condenser heat load divided by the circulating pipe water flow and specific heat capacity, the condenser heat load is equal to the electrical load W multiplied by the turbine heat consumption q minus the electromechanical loss, and the electromechanical efficiency ηjd is 98.5% basically constant. Under pure condensing conditions, within the normal load variation range, the turbine heat consumption changes approximately constant, which has little effect on the condenser heat load. The condenser heat load is mainly proportional to the electrical load.

[0042] That is: T=W*(q-3600 / ηjd) / (Q*4.2)(6)

[0043] Wherein, T is the temperature rise of circulating water in °C; W is the electrical load in MW; q is the heat consumption of steam turbine in kj / kWh; ηjd is the electromechanical efficiency in 0.985; Q is the circulating water flow in t / h; 4.2 is the specific heat of circulating water in Kj / (Kg.°C).

[0044] Substituting formula (6) into formula (2) we obtain:

[0045] △T=T1-T2=(q-3600 / ηjd)*W / (Q1*4.2)-(q-3600 / ηjd)*W / (Q2*4.2)

[0046] =(q-3600 / ηjd) / 4.2*W*(Q2-Q1) / (Q2*Q1)

[0047] K1=△T / W=(q-3600 / ηjd) / 4.2*W*(Q2-Q1) / (Q2*Q1) / W

[0048] Then, ΔT=(q-3600 / ηjd) / 4.2*W*(Q2-Q1) / (Q2*Q1)(7).

[0049] Among them, when calculating the temperature rise T1 of the single-pump circulating water, the corresponding Q1 is the single-pump circulating water flow rate, and when calculating the temperature rise T2 of the single-pump circulating water, the corresponding Q2 is the dual-pump circulating water flow rate.

[0050] (q-3600 / ηjd) / 4.2 can be approximately considered as a constant, and (Q2-Q1) / (Q2*Q1) can be approximately considered as a constant for the two certain operating modes of the circulating water pump.

[0051] Further, methods for obtaining K1 include: directly obtaining it by experimentally measuring the change in circulating water temperature rise when the electrical load W remains constant, or obtaining it by calculation based on the turbine heat consumption and circulating water flow rate. The two methods can be mutually verified.

[0052] Furthermore, when the electrical load changes, the circulating water temperature rise under the single-pump and dual-pump conditions is corrected to the temperature rise under the same electrical load to obtain the K1 value.

[0053] S200, establishing a function K2=f(T) of the rate of change of saturated pressure as a inverse function of exhaust temperature;

[0054] According to the variation law of wet steam saturation pressure with temperature, the saturation pressure change rate function is fitted, see Table 1.

[0055] Table 1

[0056]

[0057]

[0058] S300, calculating the coal saving amount M1 of the back pressure change unit and the coal reduction amount M2 of the circulating pump power consumption;

[0059] S310, obtaining the coal saving amount M1 of the steam turbine back pressure change;

[0060] Assuming that the condenser end difference remains unchanged under the single-pump and double-pump conditions, the change in turbine exhaust temperature is equivalent to the change in circulating water temperature rise △T=K1*W, and further derives the impact of the current exhaust temperature on the back pressure K1*W*K2, and further derives the impact of the back pressure change on the power generation coal consumption K1*W*K2*C, and further obtains the coal saving under the current load

[0061] M1=K1*W *K2*C* W=W 2 *K1*C*K2 (3)

[0062] Wherein, W is the electrical load of the unit (MW); C is the coefficient of difference in back pressure on coal consumption for power generation (g / kWh / KPa); the T value of K2 is the current exhaust steam temperature (℃).

[0063] S320, obtaining the circulating pump power change equivalent to standard coal quantity M2;

[0064] Obtain the unit’s power generation coal consumption b=q / 29.308 / ηgl / ηgd / 1000.

[0065] b-Coal consumption for power generation Kg / kWh, ηgl-boiler efficiency; ηgd-pipeline efficiency.

[0066] The power consumption of the circulating pump is equivalent to the standard coal:

[0067] M2=1.732*U*△I*φ*b (4).

[0068] Among them, U-circulating pump motor voltage (KV), ΔI-difference between double pump and single pump circulating pump current (A), φ-circulating pump motor power factor, b-power consumption of power generation (Kg / kWh);

[0069] S400, calculating the critical electrical load of the circulation pump when starting and stopping;

[0070] When M1=M2, the corresponding electrical load is the critical electrical load of the circulation pump single pump and double pump mode;

[0071] W 2 *K1*C*K2=1.732*U*△I*φ*b;

[0072] W=POWER(1.732*U*△I*φ*b / (K1*C*K2), 0.5) (5).

[0073] The following is a specific example to illustrate the circulating pump scheduling method for solving critical load of the present application.

[0074] S100. Test and determine the temperature rise variation coefficient K1 of circulating water with a single pump and dual pumps, as shown in Table 2.

[0075] Table 2

[0076] Circulation pump method unit A+B B Circulating pump current I A 435.94 217.29 Electrical load W MW 296.61 296.61 Circulating water flow Q m3 / h 36568 23936 Measured circulating water temperature rise T ℃ 8.99 13.74

[0077] K1=△T / W=(13.74-8.99) / 296.61=0.016

[0078] The heat consumption of steam turbine can be calculated from the test data.

[0079] T1=W*(q-3600 / ηjd) / (Q*4.2)

[0080] q=8.99*36568*4.2 / 296.61+3600 / 0.985=8309.87Kj / kWh

[0081] S200, using the K2 fitting function known above

[0082] K2=0.00034*T2-0.00922*T+0.20954

[0083] S300, calculate the amount of coal saved due to back pressure change M1

[0084] The consumption difference analysis constant C = 2.5g / kWh / KPa is obtained to determine the effect of the back pressure of the unit on the coal consumption for power generation. The T value of the K2 function is the current exhaust steam temperature, which is assumed to be 40°C.

[0085] M1=K1*W*K2*C*W=W 2 *K1*C*K2

[0086] =W 2 *0.016*2.5*(0.00034*power(40,2)-0.00922*40+0.20954)

[0087] S400, calculate the circulating pump power change equivalent to standard coal volume M2:

[0088] Get the coal consumption of the unit:

[0089] b=q / 29.308 / ηgl / ηgd / 1000=8309.87 / 29.308 / 0.93 / 0.99 / 1000=

[0090] 0.308kg / kWh

[0091] In the above formula, the turbine heat consumption data is obtained by reverse calculation of the circulating water flow rate. If the circulating water flow rate cannot be measured, the average power generation coal consumption of the unit under pure condensing conditions can be used. The influence of power generation coal consumption on the calculation results within the normal range can be ignored.

[0092] The circulating pump motor voltage is 6KV; the circulating pump motor power factor is 0.75;

[0093] The corresponding test values ​​of circulating pump current are I1=217.29, I2=435.94

[0094] M2=1.732*U*△I*0.75*b

[0095] =1.732*6*(435.94-217.29)*0.75*0.308=524.88kg / h

[0096] S500, calculate the critical electrical load of the circulation pump start and stop

[0097] When M1=M2,

[0098] W 2 *K1*C*K2=1.732*U*△I*0.75*b

[0099] W=POWER(1.732*U*△I*0.75*b / (K1*C*K2), 0.5)

[0100] =POWER(524.88 / (0.016*2.5*(0.00034*power(40, 2)-0.00922*40+0.20954)), 0.5)

[0101] =185MW

[0102] According to the above formula, the critical electrical load at different exhaust steam temperatures is obtained, as shown in Table 3.

[0103] Table 3

[0104]

[0105]

[0106] For the same unit, this method takes approximately constant values ​​for power generation coal consumption b and back pressure consumption difference C. Between the two determined circulating pump modes, the two main variable values ​​of circulating pump current difference △I and circulating water temperature rise change K1 remain basically unchanged. When there are high and low speed, multiple pumps and other operating modes, it is necessary to establish the K1 value and △I value between each two modes to calculate the corresponding critical electrical load W.

[0107] The K2 value is calculated using the exhaust steam temperature, which includes the influence of the ambient temperature, water tower efficiency, and condenser end difference changes on the calculation results, avoiding the influence of the above uncertain changes on the calculation, and realizing a simple calculation of the critical load with the exhaust steam temperature as the boundary.

[0108] The difference between the front and rear ends of the circulating pump and the temperature rise change will cause the exhaust steam temperature to change. In practical applications, the pump is started when the actual electrical load is greater than the critical load by 10MW-20MW, and the pump is stopped when the actual load is less than the critical load by 10-20MW.

[0109] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the claims.

Claims

1. A circulating pump scheduling method for solving critical load, characterized in that: include: S100, obtaining the temperature rise variation coefficient K1 of the circulating water of the single pump and the double pump; K1=△T / W (1) △T = temperature rise of circulating water with single pump T1 - temperature rise of circulating water with double pumps T2 (2); Wherein, W is the unit electrical load, in MW; S200, establishing a function K2=f(T) of the rate of change of saturated pressure as a inverse function of exhaust temperature; According to the variation law of wet steam saturation pressure with temperature, the saturation pressure variation rate function is fitted; S300, calculating the coal saving amount M1 of the back pressure change unit and the coal reduction amount M2 of the circulating pump power consumption; S310, obtaining the coal saving amount M1 of the steam turbine back pressure change; M1=W 2 *K1*C*K2 (3) Among them, C-back pressure to power generation coal consumption difference coefficient, unit is g / kWh / KPa S320, obtaining the circulating pump power change equivalent to standard coal quantity M2; M2=1.732*U*△I*φ*b (4) Among them, U-circulating pump motor voltage, unit is KV, ΔI-difference between the circulating pump current of double pumps and single pump, unit is A, φ-circulating pump motor power factor, b-power consumption of power generation, unit is Kg / kWh; S400, calculating the critical electrical load of the circulation pump when starting and stopping; When M1=M2, the corresponding electrical load is the critical electrical load of the circulation pump single pump and double pump mode; W=POWER(1.732*U*△I*φ*b / (K1*C*K2), 0.5) (5).

2. The circulating pump scheduling method for solving critical load according to claim 1, characterized in that: In step S100, the temperature rise of circulating water is obtained by equation (6): T=W * (q-3600 / ηjd) / (Q*4.2) (6) Among them, T is the temperature rise of circulating water, in ℃; W is the electric load, in MW; q is the heat consumption of steam turbine, in kj / kWh; ηjd is the electromechanical efficiency, the value is 0.985; Q is the circulating water flow rate, in t / h; 4.2 is the specific heat of circulating water, in Kj / (Kg·℃).

3. The circulating pump scheduling method for solving critical load according to claim 2, characterized in that: Substituting formula (6) into formula (2) we obtain: ΔT=(q-3600 / ηjd) / 4.2*W *(Q2-Q1) / (Q2*Q1) (7); Among them, when calculating the temperature rise T1 of the single-pump circulating water, the corresponding Q1 is the single-pump circulating water flow rate, and when calculating the temperature rise T2 of the single-pump circulating water, the corresponding Q2 is the dual-pump circulating water flow rate.

4. The circulating pump scheduling method for solving critical load according to claim 3 is characterized in that: (q-3600 / ηjd) / 4.2 is a constant; (Q2-Q1) / (Q2*Q1) is a constant for two certain operating modes of the circulating water pump.

5. The circulating pump scheduling method for solving critical load according to claim 4, characterized in that: Methods for obtaining K1 include: directly obtaining it by experimentally measuring the change in circulating water temperature rise when the electrical load W remains constant, or obtaining it by calculation based on the turbine heat consumption and circulating water flow rate; The two methods can be cross-checked.

6. The circulating pump scheduling method for solving critical load according to claim 5, characterized in that: When the electrical load changes, the circulating water temperature rise under single-pump and dual-pump conditions is corrected to the temperature rise under the same electrical load to obtain the K1 value.

7. The circulating pump scheduling method for solving critical load according to claim 1, characterized in that: In step S310, the premise for obtaining formula (2) is that the condenser end difference is the same under the single-pump and double-pump operating conditions.

8. The circulating pump scheduling method for solving critical load according to claim 1, characterized in that: In step S320, the method for obtaining the power generation coal consumption b of the unit includes: b=q / 29.308 / ηgl / ηgd / 1000 (6); Among them, ηgl is boiler efficiency; ηgd is pipeline efficiency.

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