A method for optimizing and adjusting main steam temperature of a gas-steam combined cycle unit

Abstract

A kind of gas-steam combined cycle unit main steam temperature optimization adjustment method, comprising: step 1, obtaining the target value of main steam temperature optimization;Step 2, preset main steam desuperheating water flow initial value is 0 t / h;Step 3, carry out unit thermal calculation to obtain main steam temperature and steam turbine power;Step 4: when desuperheating water flow is 0 t / h, if the main steam temperature calculated in step 3 is less than the target value, then the optimal desuperheating water flow is 0 t / h, the calculated main steam temperature is the optimal value, the difference between the calculated steam turbine power and the steam turbine power before optimization is the efficiency impact brought by optimization;If the calculated main steam temperature is greater than the target value, then gradually increase the desuperheating water flow, and repeat step 3 until the deviation of main steam temperature and target value is less than 0.1℃, that is, the optimal desuperheating water flow is obtained, the target value is the optimal main steam temperature that can be achieved, and the difference between the calculated steam turbine power and the steam turbine power before optimization is the efficiency impact brought by optimization.

Description

Technical Field

[0001] This invention belongs to the field of gas-steam combined cycle units, and specifically relates to a method for optimizing and adjusting the main steam temperature of a gas-steam combined cycle unit. Background Technology

[0002] The main steam temperature at the outlet of the high-pressure superheater of the waste heat boiler in the gas-fired combined cycle unit of the power plant is mainly controlled by the operators through manually setting the target value of the main steam temperature at the outlet of the high-pressure final stage superheater.

[0003] In practice, if the target value of the main steam temperature at the outlet of the high-pressure final stage superheater of the waste heat boiler is set unreasonably, or if the main steam de-cooling process is poorly controlled, the high-pressure superheater of the waste heat boiler will de-cool excessively and will not be adjusted in time. This will cause the main steam temperature of the combined cycle unit to deviate from the optimal operating value, which will result in a loss of the operating efficiency of the waste heat boiler, a reduction in the output of the combined cycle unit, and a decrease in the unit's thermal efficiency. Summary of the Invention

[0004] The technical problem to be solved by this invention is: to accurately guide the optimization and adjustment of the main steam temperature of a combined cycle unit, this invention proposes a method for optimizing and adjusting the main steam temperature of a gas-steam combined cycle unit. This allows power plant operators to intuitively understand the performance impact caused by deviations in the main steam temperature, and proposes the optimal main steam desuperheating water flow rate to be adjusted. This guides power plant operators to pay attention to and carry out optimization and adjustment of the main steam temperature, which has a significant beneficial effect on improving the operating efficiency of the combined cycle unit.

[0005] This invention is achieved using the following technical solution:

[0006] A method for optimizing and adjusting the main steam temperature of a gas-steam combined cycle unit includes the following steps:

[0007] Step 1: Based on the historical operating data of the combined cycle unit, obtain the highest value of the main steam temperature of the waste heat boiler under the premise of ensuring the safe and stable operation of the unit, and use this main steam temperature as the target value for optimizing and adjusting the main steam temperature of the waste heat boiler.

[0008] Step 2: Set the initial value of the main steam desuperheating water flow rate of the high-pressure superheater of the combined cycle unit's waste heat boiler to 0 t / h;

[0009] Step 3: Based on the preset main steam desuperheating water flow rate, perform thermal calculations of the bottom steam cycle of the combined cycle unit to calculate the main steam temperature and turbine power under the preset main steam desuperheating water flow rate of the high-pressure superheater of the waste heat boiler.

[0010] Step 4: When the main steam desuperheating water flow rate is 0t / h, compare the main steam temperature calculated in Step 3 with the target value of the waste heat boiler main steam temperature optimization adjustment selected in Step 1 to determine the efficiency impact of the main steam temperature optimization.

[0011] A further improvement of this invention is that, in step 1, the highest value of the main steam temperature of the waste heat boiler during the set time of stable operation of the unit is taken, and this main steam temperature is used as the target value for optimizing and adjusting the main steam temperature of the waste heat boiler, as follows:

[0012] T w2,sh,hrsg,target =MAX(T) w2,sh,hrsg )

[0013] In the formula: T w2,sh,hrsg,target The target value for optimizing and adjusting the main steam temperature is ℃;

[0014] T w2,sh,hrsg Historical operating data for the main steam temperature, in °C.

[0015] A further improvement of the present invention is that, in step 1, the highest value of the main steam temperature of the waste heat boiler is taken from the unit's stable operation for more than 1 hour.

[0016] A further improvement of this invention lies in that, in step 3, the main steam temperature and turbine power are calculated under the current main steam desuperheating water flow rate of the high-pressure superheater in the waste heat boiler, i.e.

[0017] (Power ST,cal ,T w2,sh,hrsg,cal )=f ccpp (m desuper,sh )

[0018] In the formula: f ccpp A thermodynamic calculation model for the bottom-level steam cycle of a combined cycle unit;

[0019] POWER ST,cal The calculated turbine power is expressed in kW.

[0020] T w2,sh,hrsg,calt The calculated main steam temperature is in °C.

[0021] m desuper,shg The flow rate of the main steam desuperheating water in the waste heat boiler is t / h.

[0022] A further improvement of this invention is that, in step 4, if the calculated main steam temperature is less than the target value for main steam temperature optimization, then the optimal main steam desuperheating water flow rate under the current operating conditions is 0 t / h. The main steam temperature calculated in step 3 when the main steam desuperheating water flow rate is 0 t / h is the achievable optimal main steam temperature. The difference between the turbine power calculated in step 3 when the main steam desuperheating water flow rate is 0 t / h and the turbine power before main steam temperature optimization is the efficiency impact brought about by main steam temperature optimization.

[0023] A further improvement of this invention is that, in step 4, the difference between the turbine power calculated in step 3 when the main steam desuperheating water flow rate is 0 t / h and the turbine power before main steam temperature optimization is the efficiency impact brought about by the main steam temperature optimization.

[0024] Power benefits =Power ST,cal -Power ST,bo

[0025] Where: POWER ST,benefits The turbine power gain from main steam temperature optimization, in kW;

[0026] POWER ST,cal The calculated turbine power is expressed in kW.

[0027] POWER ST,bo The turbine power (kW) before main steam temperature optimization.

[0028] A further improvement of this invention is that, in step 4, if the calculated main steam temperature is greater than the target value for main steam temperature optimization, the main steam desuperheating water flow rate of the high-pressure superheater of the waste heat boiler is gradually increased, and step 3 is repeated to carry out the thermal calculation of the bottom steam cycle of the combined cycle unit until the deviation between the main steam temperature and the target value for main steam temperature optimization is less than 0.1℃. At this time, the main steam desuperheating water flow rate is the optimal main steam temperature desuperheating water flow rate. The target value for main steam temperature optimization of the waste heat boiler determined in step 1 is the achievable optimal main steam temperature. The difference between the turbine power calculated under the optimal main steam temperature desuperheating water flow rate and the turbine power before main steam temperature optimization is the efficiency impact brought about by the optimization of main steam temperature.

[0029] A further improvement of this invention is that, in step 4, step 3 is repeated to perform the thermodynamic calculation of the bottom-level steam cycle of the combined cycle unit until the deviation between the main steam temperature and the target value for optimized adjustment of the main steam temperature is less than 0.1℃, i.e.

[0030] abs(T w2,sh,hrsg -T w2,sh,hrsg,target )≤0.1.

[0031] The present invention has at least the following beneficial technical effects:

[0032] This invention provides a method for optimizing and adjusting the main steam temperature of a gas-steam combined cycle unit. Specifically, it involves calculating and analyzing the actual impact of main steam temperature changes on the efficiency of the combined cycle unit when the main steam temperature deviates from the optimal operating value, and calculating the optimal main steam temperature desuperheating water flow rate. This method guides power plant operators to optimize and adjust the main steam temperature, solving the problem that excessive desuperheating of the high-pressure superheater in the waste heat boiler without timely adjustment leads to the main steam temperature of the combined cycle unit deviating from the optimal operating value, thereby reducing the output of the combined cycle unit and lowering its thermal efficiency. Attached Figure Description

[0033] Figure 1 This is a flowchart of a method for optimizing and adjusting the main steam temperature of a gas-steam combined cycle unit according to the present invention. Detailed Implementation

[0034] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0035] like Figure 1 As shown, the present invention provides a method for optimizing and adjusting the main steam temperature of a gas-steam combined cycle unit, comprising:

[0036] Based on the analysis of historical operating data of the combined cycle unit, the highest value of the main steam temperature of the waste heat boiler after more than one hour of stable operation of the unit was obtained, under the premise of ensuring the safe and stable operation of the unit. This main steam temperature was then used as the target value for optimizing and adjusting the main steam temperature of the waste heat boiler, as follows:

[0037] T w2,sh,hrsg,target =MAX(T) w2,sh,hrsg )

[0038] In the formula: T w2,sh,hrsg,target The target value for optimizing and adjusting the main steam temperature is ℃;

[0039] T w2,sh,hrsg Historical operating data for the main steam temperature, in °C.

[0040] The initial value of the main steam desuperheating water flow rate of the high-pressure superheater in the waste heat boiler of the combined cycle unit is set to 0 t / h. Thermal calculations of the bottom-level steam cycle of the combined cycle unit are performed to obtain the main steam temperature and turbine power under the current main steam desuperheating water flow rate of the high-pressure superheater in the waste heat boiler.

[0041] (Power ST,cal ,T w2,sh,hrsg,cal )=f ccpp (m desuper,sh )

[0042] In the formula: f ccpp A thermodynamic calculation model for the bottom-level steam cycle of a combined cycle unit;

[0043] POWER ST,cal The calculated turbine power is expressed in kW.

[0044] T w2,sh,hrsg,calt The calculated main steam temperature is in °C.

[0045] m desuper,shg The flow rate of the main steam desuperheating water in the waste heat boiler is t / h.

[0046] When the main steam desuperheating water flow rate is 0t / h, the calculated main steam temperature is compared with the target value for optimizing the main steam temperature of the waste heat boiler. If the calculated main steam temperature is less than the target value for optimizing the main steam temperature, then the optimal main steam desuperheating water flow rate under the current operating conditions is 0t / h.

[0047] When the main steam desuperheating water flow rate is 0 t / h, the calculated main steam temperature is the optimal achievable main steam temperature. The difference between the calculated turbine power and the turbine power before main steam temperature optimization (turbine power gain) is the efficiency impact of main steam temperature optimization.

[0048] Power benefits =Power ST,cal -Power ST,bo

[0049] Where: POWER ST,benefits The turbine power gain from main steam temperature optimization, in kW;

[0050] POWER ST,cal The calculated turbine power is expressed in kW.

[0051] POWER ST,bo The turbine power (kW) before main steam temperature optimization.

[0052] When the main steam desuperheating water flow rate is 0 t / h, if the calculated main steam temperature is greater than the target value for optimized main steam temperature adjustment, the main steam desuperheating water flow rate of the high-pressure superheater of the waste heat boiler should be gradually increased until the deviation between the main steam temperature and the target value for optimized main steam temperature adjustment is less than 0.1℃.

[0053] abs(T w2,sh,hrsg- T w2,sh,hrsg,target )≤0.1

[0054] At this point, the main steam desuperheating water flow rate is the optimal main steam temperature desuperheating water flow rate. The difference between the turbine power at the optimal main steam temperature desuperheating water flow rate obtained by conducting thermodynamic calculations of the bottom steam cycle of the combined cycle unit and the turbine power before main steam temperature optimization (turbine power gain) is the efficiency impact brought about by main steam temperature optimization.

[0055] Example:

[0056] Analysis of historical operating data of Unit 1 of a power plant's gas-steam combined cycle unit revealed that the highest recorded main steam temperature at the outlet of the high-pressure final stage superheater was 567.5℃ (meeting the unit's operating requirements that the main steam temperature at the outlet of the high-pressure final stage superheater of the waste heat boiler should not exceed 573.9℃). Between 5 PM and 10 PM on a certain day, the steam temperature at the outlet of the high-pressure final stage superheater of the waste heat boiler fluctuated between approximately 560-564℃, and the desuperheating water flow rate of the high-pressure superheater fluctuated between 15.6-15.9 t / h. By optimizing the main steam temperature and reducing the desuperheating water flow rate to 10-13.5 t / h, the main steam temperature at the outlet of the high-pressure final stage superheater could be increased to approximately 567.4℃, resulting in a turbine power gain of approximately 530 kW. Specific results are shown in Table 1 below.

[0057] Table 1. Optimization and adjustment of main steam temperature for combined cycle units under typical operating conditions.

[0058]

[0059] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for optimizing and adjusting the main steam temperature of a gas-steam combined cycle unit, characterized in that, Includes the following steps: Step 1: Based on the historical operating data of the combined cycle unit, obtain the highest value of the main steam temperature of the waste heat boiler under the premise of ensuring the safe and stable operation of the unit, and use this main steam temperature as the target value for optimizing and adjusting the main steam temperature of the waste heat boiler, as follows: In the formula: T w2,sh,hrsg,target The target value for optimizing and adjusting the main steam temperature is ℃; T w2,sh,hrsg Historical operating data for main steam temperature, in °C; Step 2: Set the initial value of the main steam desuperheating water flow rate of the high-pressure superheater of the combined cycle unit's waste heat boiler to 0 t / h; Step 3: Based on the preset main steam desuperheating water flow rate, perform thermodynamic calculations for the bottom-level steam cycle of the combined cycle unit. Calculate the main steam temperature and turbine power under the preset main steam desuperheating water flow rate of the waste heat boiler high-pressure superheater. In the formula: f ccpp A thermodynamic calculation model for the bottom-level steam cycle of a combined cycle unit; POWER ST,cal The calculated turbine power is expressed in kW. T w2,sh,hrsg,calt The calculated main steam temperature is in °C. m desuper,shg The flow rate of the main steam desuperheating water in the waste heat boiler is t / h; Step 4: When the main steam desuperheating water flow rate is 0 t / h, compare the main steam temperature calculated in Step 3 with the target value for optimizing the main steam temperature of the waste heat boiler selected in Step 1 to determine the efficiency impact of the main steam temperature optimization. If the calculated main steam temperature is greater than the target value for optimizing the main steam temperature, gradually increase the main steam desuperheating water flow rate of the high-pressure superheater of the waste heat boiler, and repeat Step 3 to carry out the bottom steam cycle thermodynamic calculation of the combined cycle unit until the deviation between the main steam temperature and the target value for optimizing the main steam temperature is less than 0.1℃. At this time, the main steam desuperheating water flow rate is the optimal main steam temperature desuperheating water flow rate, and the target value for optimizing the main steam temperature of the waste heat boiler determined in Step 1 is the achievable optimal main steam temperature. The difference between the turbine power calculated under the optimal main steam temperature desuperheating water flow rate and the turbine power before the main steam temperature optimization is the efficiency impact of the main steam temperature optimization.

2. The method for optimizing and adjusting the main steam temperature of a gas-steam combined cycle unit according to claim 1, characterized in that, In step 1, the highest value of the main steam temperature of the waste heat boiler is taken from the unit's stable operation for more than 1 hour.

3. The method for optimizing and adjusting the main steam temperature of a gas-steam combined cycle unit according to claim 1, characterized in that, In step 4, if the calculated main steam temperature is less than the target value for main steam temperature optimization, then the optimal main steam desuperheating water flow rate under the current operating conditions is 0 t / h. The main steam temperature calculated in step 3 when the main steam desuperheating water flow rate is 0 t / h is the achievable optimal main steam temperature. The difference between the turbine power calculated in step 3 when the main steam desuperheating water flow rate is 0 t / h and the turbine power before main steam temperature optimization is the efficiency impact brought about by main steam temperature optimization.

4. The method for optimizing and adjusting the main steam temperature of a gas-steam combined cycle unit according to claim 3, characterized in that, In step 4, the difference between the turbine power calculated in step 3 when the main steam desuperheating water flow rate is 0 t / h and the turbine power before main steam temperature optimization is the efficiency impact brought about by the main steam temperature optimization. In the formula: POWER ST,benefits The turbine power gain from main steam temperature optimization, in kW; POWER ST,cal The calculated turbine power is expressed in kW. POWER ST,bo The turbine power (kW) before main steam temperature optimization.

5. The method for optimizing and adjusting the main steam temperature of a gas-steam combined cycle unit according to claim 4, characterized in that, In step 4, repeat step 3 to perform the bottom-level steam cycle thermodynamic calculation of the combined cycle unit until the deviation between the main steam temperature and the target value of the optimized main steam temperature adjustment is less than 0.1℃. 。

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