1. An operation method of a closed circulating water system of a generator set based on environmental parameters is characterized by comprising the following steps;

A. performance standard working condition test: respectively carrying out a turbine variable back pressure test, a condenser variable working condition test, a circulating water pump flow and power consumption test and a cooling tower variable working condition test to obtain performance characteristic curves of each device under different working conditions;

B. establishing a calculation model: establishing an integral calculation model containing a steam turbine, a condenser, a circulating water pump and a cooling tower by taking certain heat balance calculation software as a platform;

C. acquiring the back pressure of the unit under different environmental parameters: calculating according to the ambient dry bulb temperature, the air relative humidity and the running mode of a circulating water pump to obtain the unit back pressure under different loads;

D. calculating the back pressure of the optimal unit: according to the circulating water flow and the power consumption of the circulating water pump in different running modes, calculating the differential pressure between the generated power gain generated by the reduction of the back pressure of the unit and the power consumption increase caused by the increase of the running number of the circulating water pumps, and obtaining the optimal unit back pressure under the specific power generation load.

2. The method of claim 1, wherein the performance characteristic curve of the cooling tower in the step a comprises a relationship curve between an ambient dry bulb temperature, an air relative humidity and a circulating water flow rate and a cooling tower outlet water temperature; the performance characteristic curve of the condenser comprises a relation curve of unit load, circulating water flow, condenser inlet water temperature and unit backpressure, and particularly for a mechanical ventilation cooling tower, the heat dissipation characteristics of gas-water ratio and characteristic number under each working condition need to be obtained.

3. The method of claim 1, wherein the performance characteristic curve obtained in step B through the benchmark test performed in step a is added to the thermal balance calculation software in a customized manner to establish an overall calculation model based on the actual performance of the generator set.

4. The operating method of the closed circulating water system of the generator set based on the environmental parameters of claim 1, wherein in the step B, the relationship between the inlet water temperature and the outlet water temperature of the cooling tower is obtained through a Merkel enthalpy difference equation according to the environmental dry bulb temperature, the air relative humidity, the operating mode of the circulating water pump (i.e. different circulating water flow rates) and the characteristic number of the cooling tower:

in the formula: beta is volume bulk coefficient, kg/(m)³S); v is the water spray area, m³(ii) a Q is cooling water flow rate, kg/s; c_wThe specific heat of water, kJ/(kg. K); t is t₁、t₂The water temperature of an inlet and an outlet of the cooling tower is lower than the temperature of the water in the inlet and the outlet of the cooling tower; h ″)_tAt the water temperature tThe saturated steam specific enthalpy of (1), kJ/kg; h is_θIs the specific enthalpy of air, kJ/kg; dt is the temperature difference of the cooling water entering and exiting the unit packing, K; k is the heat dissipation coefficient of the evaporation water amount;

the left side of the formula (1) is a characteristic number of the cooling tower, which is expressed by omega ', and the relation omega' ═ A lambda is obtained by calculation through a thermal performance test of the cooling tower^m(A, m is constant, λ is gas-water ratio); the right side of the formula (1) is the cooling number of the cooling tower and is expressed by omega;

and inputting the ambient dry-bulb temperature, the air relative humidity, the circulating water flow and the cooling tower inlet water temperature in thermal balance calculation software by using a characteristic relation curve of the cooling tower obtained through a thermal performance test, and calculating the cooling tower outlet water temperature.

5. The operating method of the closed circulating water system of the generator set based on the environmental parameters as claimed in claim 1, wherein in the step C, heat balance calculation software is used as a platform, and according to the environmental dry bulb temperature, the air relative humidity and the circulating water flow, the circulating water temperatures at the inlet and the outlet of the condenser and the back pressure of the generator set under different load conditions are obtained through the variable working condition coupling calculation of the cooling tower, the condenser and the steam turbine; the essence of the coupling calculation is that the temperature of circulating water at the outlet of the condenser is taken as the temperature of water entering the cooling tower, the temperature of enthalpy rise of the circulating water after passing through the circulating water pump is taken as the temperature of the circulating water at the inlet of the condenser by taking the temperature of the water entering the cooling tower as a reference, and the backpressure of the unit is calculated through the cleaning coefficient of the condenser and the total heat exchange coefficient under the test working condition.

6. The operation method of the closed type circulating water system of the generator set based on the environmental parameters as claimed in claim 1, wherein in the step D, when a circulating water pump is added to operate or an original low-speed pump is changed into a high-speed pump to operate under a certain condition of the set load, the circulating water flow is increased, the backpressure of a condenser is reduced, the power of the turbine generator is increased, but the power consumption of the circulating water pump is also increased, and when the power Δ N of the turbine generator is increased_OPower delta N consumed more than circulating water pump_PThe difference DeltaN being maximum, i.e. the unitWhen the output net power is maximum, the back pressure of the corresponding unit is the optimal back pressure, and the operation mode is the optimal mode.

Background

The cold end system of the thermal power generator unit comprises a condenser, a cooling tower, a circulating water pump and the like, and mainly has the main function of maintaining certain vacuum, the backpressure (vacuum) of the unit is one of important performance indexes of a steam turbine and even the whole generator unit, and the backpressure (vacuum) directly determines the cold end loss ratio and the circulating heat efficiency in the Rankine cycle process of the generator unit; in addition, in order to maintain lower unit backpressure, a plurality of circulating water pumps are required to operate simultaneously to increase circulating water flow, and auxiliary machine power consumption and plant power consumption of the unit are increased, so that power supply coal consumption of the unit is increased.

Therefore, the optimal back pressure is obtained by analyzing and adjusting the running state of the circulating water system, and the method has important significance for reducing the coal consumption of the unit power supply.

For a thermal power generating set with a closed circulating water system, the optimal operation mode of the circulating water system is determined by utilizing the circulating water temperature at the inlet of the condenser, the guiding significance for the operation of the set is limited, and the method for determining the optimal operation mode of the circulating water system by utilizing 3 factors of the environmental temperature, the atmospheric relative humidity and the load of the set is more practical.

Disclosure of Invention

In order to overcome the defects in the prior art, the invention aims to provide an operation method of a closed circulating water system of a generator set based on environmental parameters, which can simulate the optimal operation mode of the closed circulating system under different environmental parameters and different loads more appropriately.

In order to achieve the purpose, the invention adopts the technical scheme that:

an operation method of a closed circulating water system of a generator set based on environmental parameters comprises the following steps;

A. performance standard working condition test:

respectively carrying out a turbine variable back pressure test, a condenser variable working condition test, a circulating water pump flow and power consumption test and a cooling tower variable working condition test to obtain performance characteristic curves of each device under different working conditions;

B. establishing a calculation model:

establishing an integral calculation model containing a steam turbine, a condenser, a circulating water pump and a cooling tower by taking certain heat balance calculation software as a platform;

C. acquiring the back pressure of the unit under different environmental parameters:

calculating according to the ambient dry bulb temperature, the air relative humidity and the running mode of a circulating water pump to obtain the unit back pressure under different loads;

D. calculating the back pressure of the optimal unit:

according to the circulating water flow and the power consumption of the circulating water pump in different running modes, calculating the differential pressure between the gain of generating power generated by the reduction of the back pressure of the unit and the increase of the power consumption caused by the increase of the running number of the circulating water pumps, and obtaining the optimal unit back pressure under the specific generating load.

The performance characteristic curve of the cooling tower in the step A comprises a relation curve between the ambient dry bulb temperature, the air relative humidity and the circulating water flow and the cooling tower outlet water temperature; the performance characteristic curve of the condenser comprises a relation curve of unit load, circulating water flow, condenser inlet water temperature and unit backpressure, and particularly for a mechanical ventilation cooling tower, the heat dissipation characteristics of gas-water ratio and characteristic number under each working condition need to be obtained.

And B, adding the performance characteristic curve obtained through the benchmark test in the step A into heat balance calculation software in a user-defined mode, and establishing an overall calculation model taking the actual performance of the generator set as the benchmark.

And in the step B, obtaining a relational expression of the inlet water temperature and the outlet water temperature of the cooling tower through a Merkel enthalpy difference equation according to the ambient dry-bulb temperature, the air relative humidity, the running modes of the circulating water pump (namely different circulating water flow rates) and the characteristic number of the cooling tower:

in the formula: beta is volume bulk coefficient, kg/(m)³S); v is the water spray area, m³(ii) a Q is cooling water flow rate, kg/s; c_wThe specific heat of water, kJ/(kg. K); t is t₁、t₂The water temperature of an inlet and an outlet of the cooling tower is lower than the temperature of the water in the inlet and the outlet of the cooling tower; h is_t"is the specific enthalpy of saturated steam at water temperature t, kJ/kg; h is_θIs the specific enthalpy of air, kJ/kg; dt is the temperature difference of the cooling water entering and exiting the unit packing, K; k is the heat dissipation coefficient of the evaporation water amount;

the left side of the formula (1) is a characteristic number of the cooling tower, which is expressed by omega ', and the relation omega' ═ A lambda is obtained by calculation through a thermal performance test of the cooling tower^m(A, m is constant, λ is gas-water ratio); the right side of the formula (1) is the cooling number of the cooling tower and is expressed by omega;

and inputting the ambient dry-bulb temperature, the air relative humidity, the circulating water flow and the cooling tower inlet water temperature in thermal balance calculation software by using a characteristic relation curve of the cooling tower obtained through a thermal performance test, and calculating the cooling tower outlet water temperature.

In the step C, heat balance calculation software is used as a platform, and according to the ambient dry bulb temperature, the air relative humidity and the circulating water flow, the circulating water temperatures at the inlet and the outlet of the condenser and the unit backpressure under different load working conditions are obtained through variable working condition coupling calculation of the cooling tower, the condenser and the steam turbine; the essence of the coupling calculation is that the temperature of circulating water at the outlet of the condenser is taken as the temperature of water entering the cooling tower, the temperature of enthalpy rise of the circulating water after passing through the circulating water pump is taken as the temperature of the circulating water at the inlet of the condenser by taking the temperature of the water entering the cooling tower as a reference, and the backpressure of the unit is calculated through the cleaning coefficient of the condenser and the total heat exchange coefficient under the test working condition.

In the step D, when the load of the unit is under a certain condition, a circulating water pump is added for operation or the original low-speed pump is changed into a high-speed pump for operation, the circulating water flow is increased, the backpressure of the condenser is reduced, the power of the steam turbine generator is improved, but the power consumption of the circulating water pump is also increased, and when the power Delta N of the steam turbine generator is increased_OPower delta N consumed more than circulating water pump_PWhen the difference value delta N is maximum, namely the output net power of the unit is maximum, the back pressure of the corresponding unit is the optimal back pressure, and the operation mode is the optimal mode;

the optimization of the circulating water system is to determine the optimal circulating water flow under different unit loads and environmental conditions, in the actual engineering, the circulating water volume flow is not a continuous variable, so the circulating water flow can be changed only by changing the number of running circulating water pumps or adjusting the rotating speed of the circulating water pumps, and the optimization of the circulating water system is to determine the optimal running mode of the circulating water pumps under different working conditions at the moment and output net power (delta N) according to the output net power (delta N)_O-ΔN_P) And whether it is greater than 0.

The invention has the beneficial effects that:

1. the invention relates to a method for determining the optimal operation mode of a circulating water system, which is different from the optimization mode of an open circulating water system, and the optimal operation mode of the circulating water system is determined by using the ambient dry bulb temperature, the atmospheric relative humidity and the unit load through the coupling calculation of the variable working conditions of a cooling tower, a condenser and a turbine instead of using the inlet circulating water temperature of the condenser as a reference, so that the method is more practical.

2. According to the invention, the relation curve of the turbine output and the back pressure, the variable working condition characteristic of the condenser and the characteristic of the cooling tower adopt performance test results, the optimization calculation result is more reliable, and the coupling calculation speed of the cooling tower, the condenser and the turbine variable working condition is faster by adopting thermal balance calculation software.

Drawings

FIG. 1 is a schematic flow chart of the present invention.

FIG. 2 is a graph of the relationship between turbine output and back pressure under different load conditions.

FIG. 3 is a relation curve of total power consumption and circulating water flow under different operation modes of the circulating water pump.

FIG. 4 is an overall computational model built on a thermal balance computation software platform.

FIG. 5 is a graph of dry bulb temperature, relative humidity, and unit backpressure.

Fig. 6 is a schematic diagram of an optimal operation mode of a circulating water system under different environmental parameters.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings.

As shown in fig. 1, the method according to the invention achieves an optimum operation of a subcritical 300MWf closed circulation water system of a power generating unit.

As shown in fig. 2, a variable back pressure test is performed on a turbine of a certain subcritical 300MW generator set, and a relationship curve between turbine output and back pressure at 50%, 60% and 70% rated loads is obtained; the back pressure does not rise by 1kPa under 50 percent of rated load, and the output of the turbine drops by 2.271 MW; when the back pressure rises by 1kPa under 60 percent of rated load, the output force of the steam turbine is reduced by 2.105 MW; for every 1kPa increase in back pressure at 70% rated load, the turbine output drops by 2.088 MW.

As shown in fig. 3, the total power consumption and the circulating water flow rate in 4 different operating modes of the circulating water pump are measured at the same time, and a relation curve between the total power consumption and the circulating water flow rate in the different operating modes of the circulating water pump is established.

The end difference and the cleaning coefficient of the condenser under 50%, 60% and 70% rated loads are obtained through a condenser variable working condition test; obtaining a relational expression of the cooling number and the air-water ratio of the mechanical ventilation cooling tower through a mechanical ventilation cooling tower variable working condition test, wherein omega is 2.60 multiplied by lambda^0.59。

As shown in fig. 4, an overall calculation model including a steam turbine, a condenser, a circulating water pump and a mechanical ventilation cooling tower is established by using certain thermal balance calculation software as a platform.

Referring to local historical meteorological parameters, the change range of the ambient dry bulb temperature is determined to be 10-30 ℃, the change range of the air relative humidity is determined to be 40% -80%, and the unit back pressure of 50% rated load under the parallel operation mode of a high-speed circulating water pump and a low-speed circulating water pump is calculated according to the ambient dry bulb temperature and the air relative humidity.

The back pressure of the circulating water pump under different operation modes (a single low-speed circulating water pump, a single high-speed circulating water pump, a high-speed low-speed circulating water pump and two high-speed circulating water pumps which are connected in parallel) when the unit is at 50% of rated load is obtained through calculation.

According to the circulating water flow and the power consumption of the circulating water pump in different running modes, calculating the differential pressure between the gain of generating power generated by the reduction of the back pressure of the unit and the increase of the power consumption caused by the increase of the running number of the circulating water pumps, and obtaining the optimal unit back pressure under the specific generating load.

As shown in fig. 6, at 50% rated load, the optimum operation mode of the circulating water pump can be obtained according to the optimum set back pressure and different ambient relative humidity and dry bulb temperature.