JPH0333967B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the flow rate of a feed liquid when a pump that supplies the feed liquid to a vaporizer consisting of an evaporation drum and a reboiler, such as a vaporizer that supplies LPG gas to an LPG-fired boiler, trips. It is something.

A conventional method for controlling the flow rate of a feed liquid in a vaporizer will be described with reference to an embodiment shown in FIG.

The embodiment shown in FIG. 1 is applied to a vaporizer consisting of a reboiler and an evaporator drum that gasifies low-temperature LPG using a heat medium and supplies this LPG gas as fuel to an LPG-fired boiler.

A level detector 9 is provided at the bottom of the evaporating drum 1, and the output end of this level detector 9 is connected to the input end of a level controller 10. Level controller 10
The output is sent as a feedback signal (correction signal) for the drum level control system to the supply liquid amount controller 13, and the controller 13 obtains this correction signal, the supply liquid flow rate detector 11, and the converter 12. An operation signal is calculated and given to the supply liquid flow rate control valve 14 so that it matches the supply liquid flow rate detection signal,
This control valve 14 is operated according to the operation signal.

Additionally, a pressure detector 30 is installed at the top of the evaporation drum 1.
The pressure detector 30 detects the evaporating drum pressure, and the detection signal is sent to the drum pressure regulator 3.
1 input. Drum pressure regulator 3
The output of No. 1 becomes a correction signal for keeping the drum pressure at a predetermined value and is sent to the heating medium flow rate controller 34, which then uses the output signal of the drum pressure controller 31 and the heating medium flow rate detector 32. An operation signal is calculated so that the heat medium flow rate detection signal obtained by the converter 33 and the heat medium flow rate detection signal coincide with each other, and is applied to the heat medium flow rate control valve 35, which is operated in accordance with the operation signal. Ru.

On the other hand, the liquid to the supply pipe 3 is supplied by a supply liquid pump 21 driven by a driver 20. or,
Because the vaporizer that supplies fuel to the LPG-fired boiler requires a stable supply, multiple supply pumps are installed so that even if one trips, a standby unit will automatically start up. The feed liquid pump 23 driven by the driver 22 is for this purpose. That is, when an abnormality occurs in the supply liquid pump 21 such as an overcurrent or a low differential pressure of the pump, the trip detector 24 detects the abnormality, and the trip device 25 detects an abnormality in the drive unit 2.
0 (stops the supply liquid pump 21), the drive machine 22 is started by the reserve machine starting device 26, and the reserve supply liquid pump 23 is automatically started. Further, reference numeral 27 is a trip detector for the supply liquid pump 23, and 28 is a trip device for stopping the driving machine 22.

If an abnormality occurs in the supply liquid pump 21 while the load is stable and the liquid is being supplied by the supply liquid pump 21, the trip detector 24 will be activated.
The trip device 25 and driver 20 operate, and the supply liquid pump 21 is tripped.

On the other hand, since the trip detector 24 is activated, the standby machine starting device 26 is activated, the drive machine 22 is started, and the standby liquid pump 23 is started. However, during the above-mentioned automatic start-up period of the standby machine, the liquid flow rate temporarily decreases (is insufficient), so the output of the supply liquid flow rate detector 11 and further the output of the converter 12 decreases. Therefore, the supply liquid flow rate controller 13 operates the control valve 14 in the fully open direction. Therefore, when the preliminary supply liquid pump 23 is started, a large amount of liquid temporarily flows from the supply pipe 3 to the evaporation drum 1, so that the pressure in the supply pump header 29 does not recover, and the trip detector 27 of the preliminary supply liquid pump 23 (Detection based on low differential pressure) is activated, the trip device 28 is activated, and the driver 22, that is, the preliminary supply liquid pump 23 is tripped. In other words, both the feed liquid pump 21 and the preliminary feed liquid pump 23 stop at the same time, making it impossible to supply the feed liquid, causing the liquid level in the evaporator drum 1 to drop, eventually making it impossible to continue operating the vaporizer, and eventually stopping the boiler. A situation arises where they are forced to do so.

Furthermore, even if the preliminary supply liquid pump 23 can be started, the control valve is temporarily wide open, which causes disturbance to the drum level control system.
The drum level will fluctuate significantly, impairing safe driving.

Furthermore, the feed liquid is at a much lower temperature than the LPG liquid in the evaporator drum 1, and the large fluctuation in the amount of the low-temperature feed liquid causes the heat balance to collapse and the pressure in the evaporator drum 1 to fluctuate.

In order to avoid the above-mentioned phenomenon, the opening degree of the feed liquid flow control valve 14 may be maintained at the value before the feed liquid pump trip until the feed liquid pump header pressure recovers after the feed liquid pump trip.

The logic for this is simple, and the period during which the feed liquid flow control valve 14 is kept constant as described above may be short, and the effect on the evaporating drum level control system is small.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for controlling the flow rate of a feed liquid in a vaporizer that eliminates the conventional drawbacks.

According to the present invention, in a vaporizer equipped with a flow rate control valve that controls the flow rate of liquid supplied from the pump to the vaporizer according to the liquid level in the vaporizer, a trip of an arbitrary supply liquid pump is detected and a signal thereof is detected. The operation signal of the flow rate control valve is set to the value immediately before the trip in synchronization with the trip, and the value of the operation signal is held until the pump discharge side pressure recovers to a predetermined value or higher by starting the preliminary supply liquid pump. There is provided a method for controlling the flow rate of a liquid supplied to a vaporizer, characterized in that, after recovery, the operation signal of the flow control valve is returned to be controlled in accordance with the liquid level of the vaporizer.

According to the present invention, it is possible to smoothly and automatically start the preliminary supply liquid pump when the supply liquid pump trips, thereby stably supplying the flow rate of the supply liquid, thereby stabilizing the operation of the vaporizer.

In addition, since the above method is adopted, when the supply liquid pump trips, a large amount of liquid does not temporarily flow into the evaporation drum, the pressure in the supply liquid pump header quickly recovers, and the automatic start-up of the preliminary supply liquid pump is smooth. This also makes it possible to suppress fluctuations in the evaporator drum level.

A preferred embodiment of the present invention illustrated in FIG. 2 will be described in detail below. In FIG. 2, elements that are equivalent to those in FIG. 1 are designated by the same reference numerals.

In FIG. 2, reference numeral 100 is a feed liquid pump header pressure detector, and its output is sent to a feed liquid pump trip/preparation feed liquid pump activation completion judgment device 101 (hereinafter abbreviated as judgment device). The judgment device 101 outputs the drive signal of the relay 102, the mode switching signal (tracking mode/hold mode) of the analog memory 103, and the mode switching signal (automatic/manual) of the supply liquid flow rate controller 13.
It is sent to each of them for use as a.

The determination device 101 determines whether an arbitrary supply liquid pump (in the explanation of the conventional example, the supply liquid pump 23 was used as a standby machine, but the feed liquid pump 21 is operated as a standby machine) due to a decrease in the output of the feed liquid pump header pressure detector 100. ) is detected and judged, the relay 102 is switched to the analog memory 103 side, the analog memory 103 is set to the hold mode, and the opening degree of the control valve 14 is fixed at the value before the trip. Further, the supply liquid flow rate controller 13 is set to manual mode.

Further, the determination device 10 determines that the start-up of the preliminary supply pump is completed due to the recovery of the output of the supply liquid pump header pressure detector 100, and switches the relay 102 to the output side of the supply liquid flow rate controller 13, and also switches the relay 102 to the output side of the supply liquid flow rate controller 13. 13 is set to automatic. As a result, the opening degree of the supply liquid flow rate control valve 14 is determined by the analog memory 1.
The opening degree fixed by 03 is set as an initial value and the operation is changed by the correction signal from the supply flow rate controller 13, and the supply liquid flow rate control system returns to the control method before the trip. At this time, the analog memory 103
is a mode in which the output of the supply liquid flow rate controller 13 is tracked.

Now, when the load is stable and liquid is being supplied by the supply liquid pump 21, if an abnormality occurs in the supply liquid pump 21, the preliminary supply liquid pump 23 is started as in the conventional control method. At this time, the judgment device 101 determines that the opening degree of the supply liquid flow rate control valve 14 is fixed during the period when the supply liquid pump header pressure is decreasing (the period from when the supply liquid pump trips to when the pre-supply liquid pump completes startup). Therefore, a large amount of liquid does not flow into the evaporating drum 1 as in the conventional case, the pressure in the supply liquid pump header quickly recovers, and the preliminary supply liquid pump is quickly automatically started. Therefore, unlike in the past, the evaporating drum level and pressure do not fluctuate significantly, and there is no longer a situation where the vaporizer stops.

Although the preferred embodiment of the present invention has been described with respect to the case in which two supply liquid pumps are installed, the present invention is not limited to this specific embodiment, and can also be applied to the case where two or more pumps are installed. can.

In addition, in this embodiment, the determination of whether to trip the supply liquid pump or automatically start the pre-supply liquid pump was made based on the decrease and increase in the header pressure of the supply liquid pump, but the actual supply liquid pump trip signal and the automatic start-up signal of the pre-supply liquid pump are used. A similar effect can be achieved by using .

[Brief explanation of the drawing]

FIG. 1 is an explanatory view illustrating a conventional method for controlling the flow rate of a feed liquid in a vaporizer, and FIG. 2 is an explanatory view illustrating a method for controlling the flow rate of a feed liquid in a vaporizer according to the present invention. DESCRIPTION OF SYMBOLS 1... Evaporation drum, 3... Supply pipe, 4... Boiler, 9... Level detector, 10... Level controller, 11... Supply liquid flow rate detector, 12... Converter, 13... Supply Liquid flow rate controller, 14... Supply liquid flow rate control valve, 20... Drive machine, 21... Supply liquid pump, 22... Drive machine, 23... Supply liquid pump,
24... Trip detector, 25... Trip device, 26... Standby machine starting device, 27... Trip detector, 28... Trip device, 30... Pressure detector, 31... Drum pressure regulator, 32 ... Heat medium flow rate detector, 33 ... Converter, 34 ... Heat medium flow rate controller, 35 ... Heat medium flow rate control valve, 100 ... Supply liquid pump header pressure detector, 101 ... Supply liquid pump trip/spare Supply liquid pump start completion determination device, 102...Relay, 103...Analog memory.

Claims (1)

[Claims] 1. In a vaporizer equipped with a flow control valve that controls the flow rate of liquid supplied from the pump to the vaporizer according to the liquid level in the vaporizer, a trip of any supplied liquid pump is detected and the flow rate is adjusted in synchronization with the signal. The operation signal of the control valve is set to the value immediately before tripping, and the value of the operation signal is held until the pump discharge side pressure recovers to a predetermined value or higher by starting the preliminary supply liquid pump, and after recovery, the flow rate increases. A method for controlling the flow rate of a liquid supplied to a vaporizer, characterized in that the operation signal of the control valve is returned to be controlled according to the liquid level of the vaporizer.