Method for rapidly improving load response rate of thermal power unit based on heat storage tank

Abstract

The present invention discloses a method for rapidly improving the load response rate of a thermal power unit based on a heat storage tank. The method comprises the following steps: monitoring the unit load command and the actual load in real time, and calculating the difference between the two to obtain a power deviation value; when it is monitored that the difference between the load command and the actual load reaches a preset condition for condensate throttling, inputting the power deviation value into the condensate throttling control model of the unit to generate a condensate throttling flow rate; after the generated condensate throttling flow rate passes through high and low limit signals, adjusting the change in the condensate flow rate output by the low-pressure heater by controlling the low-temperature inlet valve of the heat storage tank, the high-temperature inlet valve of the heat storage tank, the outlet valve of the heat storage tank circulation pump, and the recirculation valve of the heat storage tank circulation pump, so as to change the extraction steam volume of the low-pressure cylinder and further change the unit power value. The present invention overcomes the limitations of the deaerator, the condenser water level, the adjustable flow rate and time of the condensate, further improves the regulation efficiency of the condensate auxiliary frequency modulation, and improves the load response rate of the unit.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal power generation, and particularly to a method capable of rapidly improving the load response rate of a thermal power unit. Background Art

[0002] In recent years, under the strong guidance of national policies, renewable energy in China has maintained a continuous and rapid development trend. With the large-scale grid connection of new energy power generation, the power system faces huge peak shaving pressure. China's power source structure determines that the flexibility of thermal power units occupies the main position of future power source flexibility. Among thermal power units, the load ramp rate of the unit is a key indicator of thermal power flexibility. Only when the thermal power unit fully responds to the volatility changes of the power system can the goal of rapid load increase and decrease be achieved. How to maximize the load response rate of thermal power units is one of the important contents of the thermal power flexibility transformation. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for rapidly improving the load response rate of a thermal power unit based on a heat storage tank, so as to overcome the limitations of the deaerator, condenser water level, adjustable condensate flow rate and time, further improve the regulation efficiency of condensate auxiliary frequency modulation, and improve the unit load response rate.

[0004] To solve the above technical problems, the following technical solutions are adopted in the present invention.

[0005] A method for rapidly improving the load response rate of a thermal power unit based on a heat storage tank, which is implemented based on the thermal power unit power generation system. The thermal power unit power generation system includes a generator set, a condenser, a condensate pump, a low-pressure heater group, a deaerator, a heat storage tank, and a heat storage tank circulation pump. The generator set is respectively connected to the condenser and the low-pressure heater group. The condenser is connected to the input end of the low-pressure heater group through the condensate pump. The output end of the low-pressure heater group is connected to the deaerator. The heat storage tank is connected in parallel at the beginning and end of the low-pressure heater group.

[0006] The outlet of the condensate pump is communicated with the lower part of the heat storage tank through the heat storage tank low-temperature inlet valve. The upper part of the heat storage tank is communicated with the outlet end of the fifth low-pressure heater through the heat storage tank high-temperature inlet valve. The inlet of the heat storage tank circulation pump is connected to the bottom of the heat storage tank. The outlet of the heat storage tank circulation pump is communicated with the bottom end of the outlet of the condensate pump through the heat storage tank circulation pump outlet valve. The outlet end of the heat storage tank circulation pump is also communicated with the outlet end of the heat storage tank inlet valve through the heat storage tank circulation pump recirculation valve.

[0007] Specifically, it includes the following steps:

[0008] S1. Real-time monitor the unit load command and the actual load, and calculate the difference between the two to obtain the power deviation value;

[0009] S2. When it is monitored that the difference between the load instruction and the actual load reaches the preset condition of condensate throttling, input the power deviation value into the unit condensate throttling control model to generate the condensate throttling flow rate;

[0010] S3. After the generated condensate throttling flow rate is judged by the high and low limit signals, adjust the condensate flow rate output by the low-pressure heater by controlling the low-temperature inlet valve of the heat storage tank, the high-temperature inlet valve of the heat storage tank, the outlet valve of the heat storage tank circulation pump, and the recirculation valve of the heat storage tank circulation pump, so as to change the extraction steam volume of the low-pressure cylinder and further change the unit power value.

[0011] For the method for quickly increasing the load response rate of a thermal power unit based on a heat storage tank described above, in step S2, the unit condensate throttling control model analyzes the energy changes of each low-pressure heater by using the equivalent enthalpy drop method, and according to the principle of energy conservation, deduces the relationship between the change in unit power and the condensate throttling flow rate.

[0012] ΔN E =k cw ΔQ cw

[0013] In the formula, ΔN E is the change in unit power, MW; k cw is the throttling gain of condensate for unit power under unit flow rate, MW·s / kg; ΔQ cw is the condensate throttling flow rate, kg / s;

[0014] The relationship between the actual load change rate and the set load change rate of the unit is

[0015]

[0016] In the formula, V1 is the actual load change rate of the unit, V is the set load change rate of the unit, MW / min; N1 is the initial value of load change, and N2 is the target value of load change, MW;

[0017] The condensate throttling flow rate can be obtained as

[0018]

[0019] For the method for quickly increasing the load response rate of a thermal power unit based on a heat storage tank described above, in step S3,

[0020] When the unit load command increases, receive the command to reduce the condensate throttle flow rate, generate the opening commands for the low-temperature inlet valve and high-temperature inlet valve of the heat storage tank, and open the low-temperature inlet valve and high-temperature inlet valve of the heat storage tank according to the opening commands, so that the low-temperature condensate enters the heat storage tank, and the high-temperature condensate in the upper part of the heat storage tank enters the deaerator through the high-temperature inlet valve of the heat storage tank, reducing the extraction steam volume of the low-pressure cylinder, increasing the unit load, and at the same time ensuring the water volume balance entering the deaerator and keeping the deaerator water level unchanged; when the load is stable, the low-temperature inlet valve and high-temperature inlet valve of the heat storage tank are closed at a set rate;

[0021] When the unit load command decreases, receive the command to increase the condensate throttle flow rate, generate the opening and closing commands for the outlet valve of the heat storage tank circulation pump, the high-temperature inlet valve of the heat storage tank, and the recirculation valve of the heat storage tank circulation pump, open the outlet valve of the heat storage tank circulation pump and the high-temperature inlet valve of the heat storage tank, and close the recirculation valve of the heat storage tank circulation pump, so that the low-temperature condensate enters the outlet of the condensate pump, increasing the condensate water flow through the low-pressure heater, increasing the extraction steam volume of the low-pressure cylinder, reducing the unit load, and at the same time ensuring the water volume balance entering the deaerator and keeping the deaerator water level unchanged; when the unit load is stable, the outlet valve of the heat storage tank circulation pump and the high-temperature inlet valve of the heat storage tank are closed at a set rate, and the recirculation valve of the heat storage tank circulation pump is opened to a preset value.

[0022] Due to the adoption of the above technical solutions, the technical progress achieved by the present invention is as follows.

[0023] The present invention is realized by applying a heat storage tank. According to the adjustment command, the flow rate of condensate water in the unit is changed through the heat storage tank, improving the adjustment efficiency of condensate water auxiliary frequency modulation. It not only overcomes the limitations of the deaerator, condenser water level, adjustable condensate water flow rate and time, improves the unit load response rate, but also improves the utilization rate of the heat storage tank during the non-heating period. Compared with the operation effect of traditional thermal power units, the unit load response rate is increased by at least 0.43 MW / min, and the improvement ratio is 7.2% (taking 350 MW as an example). At the same time, it reduces the adjustment limitations caused by the deaerator water level, condensate water hot well water level, etc. during the condensate water throttling process, improving the adjustment effect. Description of the Drawings

[0024] Figure 1 It is a structural schematic diagram of the thermal power unit power generation system described in the present invention.

[0025] Figure 2 It is a flowchart of the method described in the present invention. Detailed Embodiments

[0026] The present invention will be further described in detail below in conjunction with the drawings and specific embodiments.

[0027] During the implementation of the conventional condensate throttling process in a thermal power unit, it is necessary to ensure that the water levels in the deaerator and the hot well of the condenser fluctuate within a reasonable range, and intervene in the condensate throttling control process according to the deviation between the real-time water level and the set value of the deaerator water level, resulting in a low action rate and response efficiency of the condensate throttling frequency modulation.

[0028] With the implementation of the thermal power decoupling transformation, more and more power plants adopt the thermal power decoupling method using a heat storage tank. The construction of large heat storage tanks also creates favorable conditions for using the heat storage tank to carry out the condensate auxiliary frequency modulation technology. The heat storage tank is put into use during the heating period and will be idle during the non-heating period, causing waste of resources. In the non-heating period of the present invention, by combining the heat storage tank with the condensate throttling technology, the limitation of the water levels in the deaerator and the condenser on the condensate throttling is improved, which not only improves the utilization rate of the heat storage tank and avoids equipment idleness, but also improves the adjustment efficiency of the condensate auxiliary frequency modulation and enhances the unit load response rate.

[0029] Therefore, the present invention provides a method for quickly improving the load response rate of a thermal power unit based on a heat storage tank, which solves the restrictive factors in the condensate throttling frequency modulation process and further improves the unit load response speed.

[0030] This method is realized based on the power generation system of a thermal power unit, and the structure of the system is as Figure 1 shown, including a high-pressure cylinder 1, an intermediate-pressure cylinder 2, a low-pressure cylinder 3, a generator 4, a condenser 5, a condensate pump 6, a heat storage tank 7, a heat storage tank circulation pump 8, an eighth low-pressure heater 9, a seventh low-pressure heater 10, a sixth low-pressure heater 11, a fifth low-pressure heater 12, a deaerator 13, a heat storage tank low-temperature inlet valve 14, a heat storage tank high-temperature inlet valve 15, a heat storage tank circulation pump outlet valve 16, and a heat storage tank circulation pump recirculation valve 17. The high-pressure cylinder 1, the intermediate-pressure cylinder 2, the low-pressure cylinder 3, and the generator 4 constitute a generating set, and the eighth low-pressure heater 9, the seventh low-pressure heater 10, the sixth low-pressure heater 11, and the fifth low-pressure heater 12 constitute a low-pressure heater group.

[0031] The high-pressure cylinder 1, the intermediate-pressure cylinder 2, the low-pressure cylinder 3, and the generator 4 are coaxially arranged, on the same horizontal plane, and are connected in sequence; the inlet of the condensate pump is connected to the output end of the condenser, the outlet of the condensate pump is connected to the water-side inlet of the eighth low-pressure heater, and is sequentially connected to the seventh low-pressure heater, the sixth low-pressure heater, and the fifth low-pressure heater, and the outlet of the fifth low-pressure heater is connected to the inlet of the deaerator 13.

[0032] The outlet of the condensate pump 6 is connected to the lower part of the heat storage tank through the low-temperature inlet valve 14 of the heat storage tank. The upper part of the heat storage tank is connected to the inlet of the deaerator through the high-temperature inlet valve 15 of the heat storage tank. The inlet of the heat storage tank circulation pump 8 is connected to the bottom of the heat storage tank 7. The outlet of the heat storage tank circulation pump 8 is connected to the outlet of the condensate pump 6 through the outlet valve 16 of the heat storage tank circulation pump. The recirculation valve 17 of the heat storage tank circulation pump is connected from the outlet of the heat storage tank circulation pump 8 to the outlet of the inlet valve 14 of the heat storage tank.

[0033] In the present invention, high-temperature and high-pressure steam enters the condenser 5 after doing work in the high-pressure cylinder, intermediate-pressure cylinder, and low-pressure cylinder and condenses into water. The condensed water is heated by the eighth low-pressure heater, seventh low-pressure heater, sixth low-pressure heater, and fifth low-pressure heater in sequence and then sent to the deaerator for oxygen removal treatment before use. When the unit load in the system changes, the opening and closing states of the low-temperature inlet valve 14 of the heat storage tank, high-temperature inlet valve 15 of the heat storage tank, outlet valve 16 of the heat storage tank circulation pump, and recirculation valve 17 of the heat storage tank circulation pump can be adjusted to regulate the condensate water flow rate, and further achieve a rapid response to the unit load.

[0034] In the present invention, by adding a heat storage tank to participate in the condensate water auxiliary frequency modulation of a coal-fired unit, the process is as Figure 2 shown, and specifically includes the following steps.

[0035] S1. Monitor the unit load command and the actual load in real time, and calculate the difference between the two to obtain the power deviation value.

[0036] S2. When it is monitored that the difference between the load command and the actual load reaches the preset condition for condensate water throttling, input the power deviation value into the unit condensate water throttling control model to generate the condensate water throttling flow rate.

[0037] In this embodiment, taking a 350MW supercritical unit as an example, the preset conditions for condensate water throttling are shown in Table 1.

[0038] Table 1

[0039]

[0040] In this step, the unit condensate water throttling control model analyzes the energy changes of each low-pressure heater using the equivalent enthalpy drop method, and based on the principle of energy conservation, derives the relationship between the unit power change and the condensate water throttling flow rate:

[0041] ΔN E =k cw ΔQ cw

[0042] In the formula, ΔN E is the unit power change, MW; k cw is the throttling gain of condensate water for the unit power under unit flow rate, MW·s / kg; ΔQ cwIt is the condensate flow rate saved, kg / s.

[0043] By quantitatively analyzing the regenerative heating system of the unit under different heat consumption conditions, the corresponding relationship between the change rate of condensate flow and the unit load is obtained, and the throttling gain under different conditions is derived. Continuing with the above example, when the rated flow rate of the condensate water diversion of a 350MW supercritical unit is 520t / h, the value is 0.031, and the diversion flow rate is controlled at 30% - 100% of the rated flow rate.

[0044] The relationship between the actual load change rate of the unit and the set load change rate is

[0045]

[0046] In the formula, V1 is the actual load change rate of the unit, V is the set load change rate of the unit, MW / min; N1 is the initial value of the load change, and N2 is the target value of the load change, MW.

[0047] The condensate flow rate saved can be obtained

[0048]

[0049] After the generated condensate flow rate saved is judged by the high and low limit signals, the condensate flow rate output by the low-pressure heater is adjusted by controlling the low-temperature inlet valve of the heat storage tank, the high-temperature inlet valve of the heat storage tank, the outlet valve of the heat storage tank circulation pump, and the recirculation valve of the heat storage tank circulation pump, so as to change the extraction steam volume of the low-pressure cylinder and further change the unit power value.

[0050] In this step, when the unit load command increases, a command to reduce the condensate flow rate saved is received, and commands for the opening degrees of the low-temperature inlet valve 14 of the heat storage tank and the high-temperature inlet valve 15 of the heat storage tank are generated. According to the opening degree commands, the low-temperature inlet valve 14 of the heat storage tank and the high-temperature inlet valve 15 of the heat storage tank are opened, so that the low-temperature condensate enters the heat storage tank 7, and the high-temperature condensate in the upper part of the heat storage tank enters the deaerator 13 through the high-temperature inlet valve of the heat storage tank, reducing the extraction steam volume of the low-pressure cylinder 3, increasing the unit load, and at the same time ensuring the water volume balance entering the deaerator and keeping the water level of the deaerator unchanged; when the load is stable, the low-temperature inlet valve and the high-temperature inlet valve of the heat storage tank are closed at the set rate. During the execution of this command, the recirculation valve of the heat storage tank circulation pump remains unchanged to maintain the minimum recirculation flow rate of the circulation pump.

[0051] When the unit load command decreases, receive the command to increase the condensate throttle flow rate, generate the opening and closing commands for the outlet valve 16 of the heat storage tank circulation pump, the high-temperature inlet valve 15 of the heat storage tank, and the recirculation valve 17 of the heat storage tank circulation pump. Open the outlet valve 16 of the heat storage tank circulation pump and the high-temperature inlet valve 15 of the heat storage tank, and close the recirculation valve 17 of the heat storage tank circulation pump, so that the low-temperature condensate enters the outlet of the condensate pump, increase the condensate flow rate through the low-pressure heaters, increase the extraction steam volume of the low-pressure cylinder, reduce the unit load, and at the same time ensure the water volume balance entering the deaerator and keep the deaerator water level unchanged; when the unit load is stable, the outlet valve of the heat storage tank circulation pump and the high-temperature inlet valve of the heat storage tank are closed at a set rate, and the recirculation valve of the heat storage tank circulation pump is opened to a preset value.

[0052] Continuing the above embodiment, the original unit load change rate of the supercritical 350MW unit is 6MW / min. During the process of the unit's load decreasing from 350MW to 105MW, the condensate is diverted to the heat storage tank, and the water diversion flow rate of the heat storage tank is 520.82t / h. The average load reduction change rate of the unit is 6.43MW / min, an increase of 0.43MW / min, and the load response rate of the unit is increased by 7.2%.

[0053] The specific calculation process is shown in Table 2.

[0054] Table 2

[0055]

[0056]

Claims

1. Method for rapidly improving load response rate of thermal power unit based on heat storage tank Characterized in that: This method is implemented based on the power generation system of the thermal power unit. The power generation system of the thermal power unit includes a generator set, a condenser (5), a condensate pump (6), a low-pressure heater group, a deaerator (13), a heat storage tank (7), and a heat storage tank circulation pump (8). The generator set is respectively connected to the condenser (5) and the low-pressure heater group. The condenser (5) is further connected to the input end of the low-pressure heater group through the condensate pump (6). The output end of the low-pressure heater group is connected to the deaerator (13). The heat storage tank (7) is connected in parallel at the beginning and end of the low-pressure heater group; The outlet of the condensate pump (6) is communicated with the lower part of the heat storage tank (7) through the low-temperature inlet valve (14) of the heat storage tank. The upper part of the heat storage tank (7) is communicated with the outlet end of the fifth low-pressure heater (12) through the high-temperature inlet valve (15) of the heat storage tank. The inlet of the heat storage tank circulation pump (8) is connected to the bottom of the heat storage tank (7). The outlet of the heat storage tank circulation pump (8) is communicated with the bottom end of the condensate pump outlet through the outlet valve (16) of the heat storage tank circulation pump. The outlet end of the heat storage tank circulation pump (8) is also communicated with the outlet end of the low-temperature inlet valve (14) of the heat storage tank through the recirculation valve (17) of the heat storage tank circulation pump; The method specifically includes the following steps: S1. Monitor the unit load command and the actual load in real time, and calculate the difference between the two to obtain the power deviation value; S2. When it is monitored that the difference between the load command and the actual load reaches the preset condition of condensate throttling, input the power deviation value into the unit condensate throttling control model to generate the condensate throttling flow rate; S3. After the generated condensate throttling flow rate passes through the high and low limit signal judgment, adjust the condensate flow rate output by the low-pressure heater by controlling the low-temperature inlet valve of the heat storage tank, the high-temperature inlet valve of the heat storage tank, the outlet valve of the heat storage tank circulation pump, and the recirculation valve of the heat storage tank circulation pump, so as to change the extraction steam volume of the low-pressure cylinder and further change the unit power value.

2. The method for rapidly improving the load response rate of a thermal power unit based on a heat storage tank according to claim 1, Characterized in that: The unit condensate throttling control model described in step S2 uses the equivalent enthalpy drop method to analyze the energy changes of each low-pressure heater, and according to the principle of energy conservation, deduces the relationship between the unit power change amount and the condensate throttling flow rate. ΔN E = k cw ΔQ cw Where, ΔN E is the change in unit power of the unit, MW; k cw is the throttling gain of condensate on the unit power under unit flow, MW·s / kg; ΔQ cw is the condensate throttling flow rate, kg / s; The relationship between the actual load change rate of the unit and the set load change rate is where V1 is the actual load change rate of the unit, V is the set load change rate of the unit, MW / min; N1 is the initial value of the load change, and N2 is the target value of the load change, MW; The condensate throttling flow rate can be obtained.

3. The method for rapidly improving the load response rate of a thermal power unit based on a heat storage tank according to claim 2, Characterized in that: In step S3, When the unit load instruction increases, receive the instruction to reduce the condensate throttle flow rate, generate the opening instructions for the low-temperature inlet valve (14) and high-temperature inlet valve (15) of the heat storage tank, and open the low-temperature inlet valve (14) and high-temperature inlet valve (15) of the heat storage tank according to the opening instructions, so that the low-temperature condensate enters the heat storage tank (7), and the high-temperature condensate in the upper part of the heat storage tank enters the deaerator (13) through the high-temperature inlet valve of the heat storage tank, reducing the extraction steam volume of the low-pressure cylinder (3), increasing the unit load, while ensuring the water volume balance entering the deaerator and keeping the deaerator water level unchanged; when the load is stable, the low-temperature inlet valve and high-temperature inlet valve of the heat storage tank are closed at a set rate; When the unit load instruction decreases, receive the instruction to increase the condensate throttle flow rate, generate the opening and closing instructions for the outlet valve (16) of the heat storage tank circulation pump, the high-temperature inlet valve (15) of the heat storage tank, and the recirculation valve (17) of the heat storage tank circulation pump, open the outlet valve (16) of the heat storage tank circulation pump and the high-temperature inlet valve (15) of the heat storage tank, and close the recirculation valve (17) of the heat storage tank circulation pump, so that the low-temperature condensate enters the outlet of the condensate pump, increasing the condensate water flow through the low-pressure heater, increasing the extraction steam volume of the low-pressure cylinder, reducing the unit load, while ensuring the water volume balance entering the deaerator and keeping the deaerator water level unchanged; when the unit load is stable, the outlet valve of the heat storage tank circulation pump and the high-temperature inlet valve of the heat storage tank are closed at a set rate, and the recirculation valve of the heat storage tank circulation pump is opened to a preset value.

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