JPS6179904A - Feed pump changeover controller - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a water supply control system, and particularly relates to the control of a boiler feed water pump recirculation system that causes disturbance to ensure the minimum water supply flow rate at low flow rates. The present invention relates to a water supply flow rate control device suitable for a water supply control system.

[Background of the invention]

Conventional devices, as described in Japanese Patent Application Laid-Open No. 55-116006, suppress the amount of fluctuation when switching the water supply pump.

However, although the amount of fluctuation is not the limit value of the water supply control system, and the total water supply amount is the limit value, only a correction signal is added to the main water supply amount request signal from the boiler automatic control device located at the top of the water supply control system. The total amount of water supplied was not considered.

[Purpose of the invention]

The purpose of the present invention is to simplify the control system of boiler feed water pump recirculation valves, etc., which are subject to various restrictions as disturbances in water supply control, and to clear restrictions on the water supply flow rate from steam tank equipment, thereby improving the overall water supply control system. The purpose is to monitor and provide a stable control device.

[Summary of the invention]

Many control devices have been devised to deal with the operation of the boiler feed water pump recirculation valve, which is considered to be a major disturbance in the feed water control system, but the operation in low feed water flow areas poses a problem. The present invention is a feed water pump switching control device that detects a boiler feed water pump recirculation valve operating point, increases the feed water flow rate, and ensures the boiler minimum flow rate.

[Embodiments of the invention]

Figure 4 shows an overview of the power plant. Steam generated from steam tank equipment 1 passes through main steam pipe 2 and is led to turbine 3, which converts thermal energy into mechanical energy, rotates generator 4, and generates electricity. The steam that has released energy is condensed in the condenser 5 and returned to water. The condensate pump 6 extracts water from the condenser 5 and sends the water to the condensate boost pump 7. The water pressurized by the condensate boost pump 7 is heated by the low-pressure feed water heater 8 and sent to the deaerator 9. Furthermore, the water whose pressure has been increased by the water supply pressure boost pump 10 and the water supply pump 11 is reheated by the high pressure water supply heater 12 and is supplied to the steam tank equipment 1. The recirculation system of the water supply pump 11 is branched from the outlet piping of the water supply pump 11, and is connected to a water supply recirculation valve (BFP recirculation valve) 13.
It is connected to the deaerator 9 via. Note that a plurality of water supply pumps 11 and their recirculation systems are installed.

Figure 2 shows a detailed diagram of the water supply pump circuit. The water in the deaerator 9 is supplied to the steam tank equipment IVc by a water supply boost pump 10 and a water supply pump 11. The feed water pump has a double water system, and the other feed water boost pump 14 and feed water pump 15 are also installed in parallel, each pump has its own recirculation system, and the deaerator 9 This is the system that will be returned to. The recirculation valve is generally opened and closed by installing a flow transmitter 17, 18 on the suction side of each water pump to detect the flow rate.
It is connected to flow rate switches 19, 20, 21, 22 which output a signal when the required recirculation amount is reduced, and the valve is operated by the switch signal. Further, as a driving source for each water pump, an electric motor 23 having a capacity of 25 cm at full load is used, and a steam-driven turbine 24 is used to reduce power consumption within the station.

During the startup process when an in-house steam source is not secured, the electric motor 23V
The operation of the power plant is to supply water by the water supply pump 11 connected to the turbine 24, and then, when steam is secured, to supply water by the water supply pump 15 connected to the turbine 24. Conventionally, during the start-up process of a power plant, there is a switching operation of the feedwater pump, and the switching load is performed at the designed flow rate of the motor-driven feedwater pump. Water supply flow rate control is performed by keeping the total water supply flow rate constant at the time of switching, since there is an element of cine stability due to switching of the water supply pump.

Conventionally, the minimum flow rate value for the total water supply flow rate was set on the steam tank equipment side, and on the water supply pump side, for the purpose of economical operation, the capacity of one pump water supply was set at the equivalent of a flow rate of 25 tons, so when switching the water supply pump, The water supply pump recirculation valve that opens and closes has been replaced with a continuous control valve with a short service life, and multiple 0N-QFF valves are operated in sequence to improve the characteristics of the water supply recirculation valve, and technology for water supply control systems has been developed. As such, it is considered that protection is provided by the terminal part.

Figure 1 shows a schematic diagram of water supply flow rate control. A schematic diagram of two water supply pumps in a control system that reduces the rate of flow rate fluctuation when switching between water supply pumps is shown. Flow rate control signal 25 for each water pump
．． 26 is determined as follows. Power generation demand signal 27
, and the output signal of the fixed value signal switch 28, the rate of change limiter 2
9, a signal based on a certain limit value becomes a flow signal by a function generator 30 that converts the flow rate from the load. This signal and the signal from the boiler total feedwater flow rate transmitter 31 are calculated by the calculator 32 to become a deviation signal. The flow rate deviation signal is taken into a determination circuit 33 that determines whether automatic mode or manual mode is selected for each water supply pump, and its output signal is passed through a proportional-integral regulator 34 and becomes a water supply flow rate mask signal 35. For the water supply pump 11Vc, the signal of its own water supply flow rate transmitter 36 and the water supply flow rate master signal 35 are calculated by a calculator, the bias signal 37 is recalculated, and the deviation signal is sent to the control signal via the proportional integral regulator 38. It becomes 25. However, water supply pump A
When the terminal is manual, the control signal 25 is passed through the automatic/manual selector 39 and the switch 40. The same applies to the water supply pump 15, and a control schematic diagram is shown in which a control signal 26 is issued by a water supply flow rate transmitter 41, a bias signal 42, a proportional-integral regulator 43, an automatic/manual selector 44, a switch 45, etc.

In this way, each water pump is controlled, so that
This is a control system in which the discharge flow rate of each pump changes, the signal of the boiler total feed water flow rate transmitter 31 changes, the feed water flow rate master signal 35 changes, and is finally fed back to each feed water pump.

In the case of switching between the water supply pump 11 and the water supply pump 15, for the sake of explanation, an example will be taken where the water supply pump 11 is operating in automatic mode and the water supply pump 15 is started.

Since the water supply pump 15 is in the pump switching mode with the water supply flow rate initially at zero, the signal from the rate of change limiter 29 becomes the signal from the 25% load setting device 46, and all of the flow rate is determined by the water supply pump. 11 is secured. From this state, reduce the bias signal 42 of the water supply pump 15,
When the flow rate control signal is increased, the signal from the boiler total feed water flow rate transmitter 31 increases, so the signal from the calculator 32 becomes negative, and the feed water flow rate mask signal becomes negative, so the feed water pump 11 decreases the flow rate. After adjusting and balancing, the total boiler water supply flow rate becomes 25 inches.

By repeating this operation of the bias signal 42, when the flow rate of the pump 11 decreases to a flow rate equivalent to the opening operation of the recirculation valve, conventionally, the switching continues without changing the output signal of the fixed value signal switching 428. As a result, the flow rate of the recirculation valve is
Since fluctuations occur in the total water supply amount for 25 inches, it was necessary to take various measures on the recirculation valve side. At the flow rate corresponding to the opening operation of the recirculation valve, the flow rate of the water supply pump 11 is 6 to 7 inches, and the water supply pump 15 is in a state of supplying water at the remaining flow rate of 18 to 19 inches. is 2
It is possible to supply water up to a flow rate of 5 cm, and the signal from the 25-ch load setter 46 is equivalent to the recirculation valve opening flow rate signal to the 35-ch load setter 47.
By switching to a signal of
The objective is to provide a control system that satisfies the flow rate.

Figure 3 shows a diagram of water supply flow rate fluctuations. Switching start timing 4
8, the pump 15 flow rate 49 is increased by bias algae cultivation, and the pump 11 flow rate 50 is controlled to maintain the flow rate 2511 of the total water supply amount 52.

Therefore, the flow rate of the pump 11 corresponds to the recirculation valve opening flow rate signal 5.
1, the flow rate setting is switched, the total water supply flow rate 52 increases to 35 inches flow rate, and the pump 11 flow rate 50 also increases.

After the flow rate setting is changed, the pump 15 flow rate 49 is increased by bias operation again, the pump 11 flow rate 50 is decreased, and the recirculation valve opening timing 53 is reached. However, since the total water supply amount 52 is a 35 inch flow rate, the water supply fluctuation rate is small, the steam can minimum flow rate 54 is not exceeded, the maximum flow rate 55 of the pump 11 is satisfied, and stable control can be provided.

〔Effect of the invention〕

According to the present invention, it is possible to switch the load at a large value with the same pump specifications, and even when the recirculation valve is operating, which has high power generation efficiency, the water supply fluctuation rate (variation amount / water supply amount) is small and control is possible. The top is also good.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of water supply flow rate control according to an embodiment of the present invention;
The figure is a system diagram around a water supply pump, FIG. 3 is an explanatory diagram of fluctuations in water supply flow rate, and FIG. 4 is a schematic diagram of a power plant system to which the present invention is applied. 28... Fixed value signal switcher, 29... Rate of change limiter,
30μ・Function generator, 31...Total water supply flow rate transmitter, 3
2... Arithmetic unit, 33... Judgment circuit, 34... Proportional-integral regulator, 36... Water supply flow rate transmitter, 38... Proportional-integral regulator, 39... Automatic/manual selector , 40...
- Switching device, 41... Water supply flow rate transmitter, 43... Proportional integral regulator, 44... Automatic/manual selector, 45...
Switching device, 46...25 inches height 2 figure tilting 4- figure

Claims (1)

[Scope of Claims] 1. In equipment that supplies water to steam tank equipment using multiple systems of water supply pumps having a recirculation system, in order to reduce the fluctuation rate of the water supply flow rate due to the opening and closing operations of the recirculation valve of the water supply pump, A water supply pump switching control device, comprising means for changing the set value of the total water supply flow rate based on a prediction signal of the operation timing of the circulation valve.