JPS62102085A - Control of number of operating set of pump for cooling condenser - Google Patents

Abstract

PURPOSE:To control cooling water temperature and the number of sets of operating pumps, which is capable of operating economically even when the amount of cooling water is changed, by a method wherein a heat consumption rate in accordance with the change of the vacuum degree of a condenser is compared with the change of the heat consumption rate of the power consumption of the pumps in accordance with the change of the number of operating sets of the pumps for cooling the condenser. CONSTITUTION:The vacuum degree 204 of a condenser 203, the cooling water temperature 205 of the inlet of the condenser, the cooling water temperature 206 of the outlet of the condenser, the amount of cooling water 207 of the condenser and the starting and stopping conditions of cooling pumps 201, 202 are read as data necessary for operating the optimum number of operating sets and controlling the number of operating sets of pumps. The amount of cooling water for a condenser in case the number of operating sets of cooling pumps is operated based on the amount of cooling water, which is measured at a present time. The power consumption of the pumps in case the number of operating sets of the cooling pumps is operated. The vacuum degree of the condenser in case the number of operating sets of the cooling pumps is operated from cooling water temperatures of the outlet and inlet ports of the condenser, which are measured at a present time, the amount of cooling water and the amount of cooling water after changing the number of operating sets. The change of the amount of heat consumption of turbine is obtained from the operated degree of vacuum of the condenser to operate the changing amount of an output. The change of power consumption is compared with the change of output to decide the effect of change of the number of operating sets.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method for controlling the number of operating condenser cooling pumps. In particular, the present invention relates to a method of controlling the number of operating pumps for cooling a condenser in a power generation plant where the condenser inlet cooling water temperature and the amount of cooling water change depending on the season and the degree of vacuum of the condenser.

[Background of the invention]

Due to the increasing proportion of nuclear power plants among all power plants, including thermal and hydropower, and the widening range of daily load changes, existing large-scale thermal power plants that were planned as pace-load thermal power plants have recently changed output by two parts as adjusted-load thermal power plants. Opportunities for load operation have increased significantly.

Under these circumstances, condenser cooling pumps in existing thermal power plants generally operate at 50 to 60% of their rated load.
Since two to three capacity fixed-blade mixed-flow pumps are installed, there is a growing trend to reduce the number of pumps in operation during partial load operation, reduce pump power consumption, and improve thermal efficiency. Ta.

Conventionally, condenser cooling pumps are planned as base load thermal power plants, so it is of course necessary to control the number of pumps in operation during normal operation.

This is because the operation is complicated even when starting and stopping, and in conventional technical thinking, it was thought that there were few opportunities to change the number of pumps in operation.

Existing large-scale thermal power plants are designed and manufactured in such a way that all condenser cooling pumps are operated from the start-up preparation process.

It has been reported that some plants actively working to improve efficiency are planning to change the number of units in operation based on the load (generator output) through manual operations by operators. This method is a very simple method because it attempts to change the number of operating units based only on the load (generator output), but the condenser inlet cooling water temperature and cooling water amount may change depending on the season. When changes occur over an hour, etc., simple operation based on a predetermined change point (load) K for the number of operating units may not necessarily provide the best thermal economic effect and may result in losses in terms of thermal efficiency, so improvement is desirable. It will be done.

There are no published examples of how to change the number of operating machines depending on the load, as this is a manual operation by an operator. On the other hand, regarding the constant operation of all units currently being implemented,
2nd year, VOL, 33. A3 No. 1 The paper entitled ``Planning and actual design of heated wastewater temperature control system for Akita Thermal Power Plant No. 4'' discusses this issue.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to adjust the temperature of the condenser inlet cooling water depending on the season, etc.
Alternatively, it is an object of the present invention to provide a method for controlling the number of operating pumps for cooling a condenser, which can be operated economically without causing a loss in thermal efficiency even when the amount of cooling water changes.

[Summary of the invention]

The present invention measures the current degree of vacuum in the condenser, and also measures the temperature or amount of cooling water for the condenser and inlet to estimate the degree of vacuum after changing the number of operating units, and calculates the heat consumption due to the change in the degree of vacuum. The feature is that the change in the heat consumption rate due to the change in the power consumption of the cooling pump is compared with the change in the heat consumption rate due to the change in the power consumption of the cooling pump, and the number of units in operation is controlled based on the advantages and disadvantages. In addition, in the preferred embodiment of the present invention, when the number of operating units is reduced, it is confirmed by calculation that the condensate amount ratio and the inlet cooling water temperature after the operation where one unit is reduced are below the specified values. The specified value of the cooling water temperature mentioned above is determined based on the hot water discharge limit, and is usually 6.5C to 8C.

[Embodiments of the invention]

Next, one embodiment of the present invention will be described with reference to the accompanying drawings.

The flowchart in Figure 1 shows how to apply the method of the present invention to capture the current condenser vacuum level as data, and also capture the condenser, inlet cooling water temperature, and cooling water amount as data, and after changing the number of operating units. Optimum operation is achieved by estimating the degree of vacuum of the vacuum and comparing the change in heat consumption rate due to changes in the degree of vacuum with the change in heat consumption rate due to changes in the power consumption of the cooling pump, and determining the number of pumps to operate based on the advantages and disadvantages. This shows an example of the number calculation flow. In addition, this Figure 1 shows that when the number of operating units is reduced, it is estimated from the current temperature that the temperature of the condenser and inlet cooling water after the operation is reduced to below the specified value.

The flowchart for calculating the number of vehicles in operation is also shown, which determines the number of vehicles in operation after confirmation.

As shown in Fig. 1, in step 101, the optimum number of operating units is calculated, and the data required to control the number of units is the condenser vacuum degree, condenser inlet cooling water temperature, condenser outlet cooling water. The temperature, condenser cooling water amount, and cooling pump start/stop status (ONloFF) are captured. The system diagram in Figure 2 shows these measurement points, and the cooling pump 201
, 202 are cooling pumps for the condenser 203 whose number is to be controlled, and the condenser vacuum degree is 204. Condenser inlet cooling water temperature 205. Detection points of condenser outlet cooling water temperature 206 and condenser cooling water amount 207 are respectively shown.

In step 102 in FIG. 1, the amount of cooling water in the condenser when the number of operating cooling pumps is changed is calculated based on the amount of cooling water measured at the present time.

Here, since the amount of cooling water is basically determined by the balance point (intersection) 303 between the cooling pump performance curve 301 and the system resistance curve 302 as shown in the condenser cooling water system operating curve in Figure 3, the number of operating units is There is also a method of uniquely giving it as a constant, but cooling pumps are generally mixed flow pumps that take in seawater or river water, and as shown by the dotted line 304 in the figure, the flow rate changes due to the influence of the tide level etc. By measuring the actual flow rate, it is possible to more accurately calculate the optimal number of operating units. FIG. 4 is a graph showing changes in the amount of cooling water depending on the number of cooling pumps in operation. The flow rate changes as the system resistance curve moves as shown by the dotted line 304. 'fr,! You can take it.

In step 103 of FIG. 1, the pump power consumption when the number of operating cooling pumps is changed is calculated. Figure 5 is a graph showing the change in power consumption depending on the number of cooling pumps in operation, and was created from the pump shaft power curve 306 in Figure 3.The number of units in operation changes from 2 to 1 based on the change in the amount of cooling water. Alternatively, you can read the power consumption of the pump when changing from one to two pumps.

In step 103B of Fig. 1, the condenser vacuum degree when the number of operating cooling pumps is changed is determined based on the currently measured condenser cooling water temperature, inlet cooling water temperature, cooling water amount, and step 102 of Fig. 1. Calculated from the amount of cooling water obtained after changing the number of units.

Here, a specific method for calculating the degree of vacuum of the condenser will be shown below, taking as an example a case where the number of pumps in operation is changed from one to two.

First, heat 1 exchanged in the condenser is released into the cooling water and raises the temperature of the cooling water, and the relationship is expressed by the following equation.

Q=Gw-Cp・r(tz tt) ・-
(t) Here, Q: Condenser exchange heat amount (kcat/h)G
w: Cooling water amount (m3/h) Cp: Constant pressure specific heat of cooling water (kcat/kgr) γ:
Specific weight of cooling water (kg/m3) Next, since these amounts of heat are exchanged through the surface of the cooling pipe, the following equation holds true.

Q=to-8-Q, ...(2) where k: Heat transmission coefficient (kcaj/m2h C) S: Cooling area (m2) Q, ,: Logarithmic average temperature difference (C) t,: Cooling water Inlet temperature (C) tt: Cooling water outlet temperature (C) Furthermore, the above logarithmic average temperature difference Q is the 'I!' of the condenser. ,
It is given by the triadic formula.

Here, ta: Saturated steam temperature in the condenser (C) (1)
, (2) and (3), the vacuum degree of the condenser is calculated by the saturation pressure with respect to the steam temperature given by the following equation.

Therefore, the amount of heat exchanged by the condenser Q when operating one unit is calculated from equation (1) and substituted into equation (4), and the flow rate after changing the number of GwK units in equation (4), that is, the amount of cooling water when operating two units, is calculated as follows: By substituting, it is possible to almost accurately obtain the condenser vacuum degree when changing to two units.

In equation (4), Cp, γ, and S are all constants, and k is the generally adopted American Heat Exchanger Association (HeatEx
Use the following calculation formula specified in ``change''.

k; φ2・φ3・CVv where φI: correction coefficient for cooling water inlet temperature φ2: coefficient for cleanliness of cooling pipe and coefficient for contamination of cooling pipe φ3; correction coefficient for cooling pipe material and wall thickness C: cooling pipe Constant V determined by the outer diameter: Average flow rate of cooling water in the pipe For reference, the amount of heat exchanged in the condenser under the condition that the amount of cooling water is constant,
FIG. 6 shows an example of condenser characteristics (600 MW once-through plant) showing changes in condenser vacuum degree when cooling water inlet temperature changes.

(There is a method in which the cooling water inlet temperature t1 is set as a constant in the 4-channel system, but the cooling water intake source for most power plants is seawater, and the temperature fluctuates considerably not only by the season but also by the hour.) (It varies depending on the region, but in the Kanto region during the summer, the temperature fluctuates by 2 to 3 C per day.) Only by measuring the actual temperature can an accurate calculation of the optimal number of vehicles be operated.

For reference, an example of data on the maximum daily cooling water temperature in summer is shown in Figure 7. Judging from these data comprehensively, it can be seen that if the cooling water temperature increases by 3C at the point of 100% heat exchange in Figure 6, the degree of vacuum may decrease by about 6.5 m Hg. (
This is a decrease of approximately 0.3% as an output change. ) In step 104 of FIG. 1, a change in turbine heat consumption is determined from the degree of vacuum of the condenser calculated in step 103B, and the total amount of change in output is calculated.

FIG. 8 is a graph for calculating the turbine heat consumption due to changes in the degree of vacuum of the condenser, and the amount of change in output is given by the following equation.

In step 105 in FIG. 1, the change in power consumption obtained in step 103 and the change in output obtained in step 104 are compared to determine the effect of changing the number of machines.

At step 106 in FIG. 1, it is determined whether the operation is to increase or decrease the number of operating vehicles.

In step 107 of FIG. 1, when the number of units is reduced as a result of step 105, in order to prevent the condenser amount and inlet temperature difference after the number of units reduced operation from exceeding the specified value, Calculate the outlet and inlet temperatures using equation (1). This allows the output for changing the number of operating units to be output only if the specified value is satisfied.

In the first step 108, if the results of steps 105 and 107 are effective, a change in the number of operating vehicles is output.

According to the embodiment described above, the number of operating condenser cooling pumps can be controlled by 1++ without causing a loss in thermal efficiency. For example, a condenser cooling pump designed and manufactured to operate two pumps at all times can pump depending on the situation (e.g. load factor 60
% or less and other conditions permit) 1 out of 2
The machine can be stopped, and the plant output is approximately 0.
．． A savings of 2% is possible. For example, if a 600MW class thermal power plant can save 0.2, then 120
This results in a savings of 0KW, and the economic effect is tremendous.

〔Effect of the invention〕

As detailed above, if the method of the present invention is applied, even if the cooling water temperature or amount of cooling water entering the condenser changes for one hour in a season, etc., the plant can be economically operated without causing any loss in thermal efficiency. It has an excellent practical effect in that it can be operated.

[Brief explanation of drawings]

Fig. 1 is a flowchart of one embodiment of the control method of the present invention, Fig. 2 is a system diagram of the cooling water system, Fig. 3 is a condenser cooling system operating curve diagram, and Fig. 4 is a change in the amount of cooling water due to a change in the number of operating units. Figure 5 is a diagram showing power consumption changes due to changes in the number of units in operation, Figure 6 is a condenser characteristic curve diagram, Figure 7 is a diagram showing data on the maximum daily chilled water temperature in summer, Figure 8 is a turbine exhaust pressure heat dissipation rate correction curve chart. 201.202... Condenser cooling pump, 203...
- Condenser, 204...Condenser X emptyness, 205...Condenser inlet cooling water temperature, 206...Condenser outlet cooling water temperature. 207... Condenser cooling water amount.

Claims (1)

[Claims] 1. In a method for controlling the number of operating condenser cooling pumps when operating a power generation plant equipped with a plurality of condenser cooling pumps, the degree of vacuum of the condenser is actually measured. At the same time,
The change in the degree of vacuum is estimated by calculating the degree of vacuum when the number of operating condenser cooling pumps is changed, and the change in the heat consumption rate due to the change in the degree of vacuum described above and the change in the condenser cooling A condenser cooling system characterized in that the optimum value for the number of pumps in operation is determined by comparing the change in heat consumption rate due to a change in pump power consumption due to a change in the number of pumps in operation, and the changes in both heat consumption rates. How to control the number of operating pumps. 2. The condenser cooling pump according to claim 1, wherein the degree of vacuum is estimated by actually measuring the temperature of the condenser inlet cooling water and calculating using the measured value. How to control the number of vehicles in operation. 3. The number of operating condenser cooling pumps according to claim 1, wherein the degree of vacuum is estimated by actually measuring the amount of condenser cooling water and calculating using the measured value. Control method. 4. If the above-mentioned determination of the optimum value for the number of operating units results in a decrease in the number of operating units, the judgment shall be made by confirming that the difference in cooling water temperature at the condenser outlet and inlet after the reduction in the number of operating units is below the specified value. Control of the number of operating condenser cooling pumps according to claim 1, wherein the above-mentioned cooling water temperature difference is checked using an actual measured value of the cooling water temperature. Method.