JPH08240185A - Control method for numbr of pump in operation - Google Patents

Abstract

PURPOSE: To suppress unnecessary starting motion and/or stopping motion of a pump which is caused by disturbance at the time of a raising pattern and/or a falling-down pattern, and smooth stable correspondence with respect to increase/decrease of an original demand. CONSTITUTION: The increase/decrease possible pattern of a demand amount is set to an apparatus number control system 10, and at least one of two control methods is carried out, wherein, one is an increasing time control method for delaying, for a constant time, stop of pumps 3, 5 which exceed a stop setting value when the demand amount is in an increasing pattern in the increase/ decrease possible pattern, and the other one is a falling-down time control method for delaying, for a constant time, start of the pumps 3, 5 which exceed a start setting value when the demand amount is in a falling-down pattern in the increase/decrease possible pattern.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the number of operating pumps, which is suitable for controlling the operating number of low-temperature liquefied gas delivery pumps such as LNG.

[0002]

2. Description of the Related Art For example, various low-temperature liquefied gases such as LNG and LPG are stored in a storage tank in a liquefied state, and are discharged from the storage tank by a delivery pump according to a demand amount, and then vaporized. After being vaporized in, they are supplied for city gas, fuel for power generation equipment, or industrial use, respectively. FIG. 1 shows a schematic configuration of an LNG payout facility, which is an example of a low-temperature liquefied gas supply facility of this type. Reference numeral 1 in the figure is an LNG storage tank. Normal,
The storage tank 1 has a plurality of units (in the figure,
Two of these are shown. ) Installed and these LN
The LNG 2 stored in the G storage tank 1 includes a plurality of submerged primary pumps (dispensing pumps) 3 (three shown in the figure) disposed in each storage tank 1.
After being extracted by the high-pressure pumps (discharging pumps) 5 (..., Three pumps are shown in the figure) disposed downstream of the LNG delivery pipe 4, the vaporizer supply LN
After being transferred to the LNG vaporizer 7 via the G adjustment valve 6 and being vaporized in the LNG vaporizer 7, the gas is delivered from the gas delivery pipe 8 to a supply destination such as a power generation facility.

By the way, in such an LNG payout facility, as shown in FIG. 2, in the cycle of one day, the rising pattern 11 in which the demand amount gradually increases from the early morning, and the maximum constant amount continues in the morning thereafter. After returning to the normal pattern 12 in which the above-mentioned demand amount is once reduced in the daytime and then in the afternoon, the above-mentioned constant amount continues again, and further in the evening, the above-mentioned demand amount is gradually decreased, and from night to early morning During this period, the increase / decrease pattern of the demand amount such as the normal pattern 14 in which the constant amount with a relatively small demand amount is held is repeated. For this reason, conventionally, as shown in FIGS. 1 and 3, for example, first, two primary pumps 3 are manually started and then automatically operated, and a system for controlling the number of devices such as a DDC responds to the increase or decrease in the demand amount. By 10 the total flow rate is calculated by adding the other flow rate to the detected flow rate from the LNG flow rate detector 9 installed upstream of the carburetor supply LNG adjusting valve 6, and the total flow rate is increased or decreased. When a predetermined start set value or stop set value is reached, the additional primary pump 3 or high pressure pump 5 is started, or the already operating primary pump 3 or high pressure pump 5 is stopped, The payout amount is controlled according to the demand amount.

At this time, due to a slight fluctuation of the payout amount,
As shown in FIG. 3, in order to prevent the above starting and stopping of the primary pump 3 and the like from being frequently repeated, the stop set values S ₁ , S ₃ , and S are set rather than the start set values S ₂ , S ₄ , and S _6. Hysteresis is set so that ₅ becomes a low value. Thereby, for example, when the desired payout amount reaches S ₄ from the state where the three primary pumps 3 are operating, the fourth primary pump 3 is activated, and the payout amount is changed from this operating state. The extra play pump 3 is stopped for the first time when S _{3 is} reduced. When such a hysteresis is set, if it is set too large, the startup of the primary pump 3, which should originally be started in response to an increase in demand, is delayed, and smooth response cannot be achieved, or It is uneconomical because the unnecessary primary pump 3 continues to operate unnecessarily as the demand decreases.

[0005]

However, even in the increase / decrease pattern of the demand amount which is usually shown macroscopically in FIG.
Microscopically, as in the rising pattern 11 shown in FIG. 4, when the additionally activated primary pump 3 rises and the discharge side opening / closing valve opens, or when the high pressure pump 5 on the downstream side starts / stops. Due to the disturbance, the hunting 15 of the payout amount due to the rapid change of the discharge flow rate occurs. Therefore, conversely, if the hysteresis is reduced, the hunting 15 of the payout amount is not less than the start set value S ₄ and the stop set value S ₃ although it is advantageous in terms of operating cost as described above. When the vibration occurs in the amplitude, the primary pump 3, which originally does not need to be started and stopped, frequently repeats starting and stopping, and as a result, the viscosity of the LNG is particularly low, and the primary pump 3 concerned is low. However, there is an inconvenience such as that the bearing portion and the like are worn out at an early stage and the service life is shortened.

The present invention has been made to effectively solve the problems of the conventional method for controlling the number of operating pumps, and in particular, during the ascending pattern and / or the descending pattern, unnecessary pump start-up and It is an object of the present invention to provide a method for controlling the number of operating pumps that can suppress the stop operation and can smoothly and stably cope with an increase or decrease in the original demand amount. To do.

[0007]

According to the method for controlling the number of operating pumps according to the present invention as set forth in claim 1, demand is increased or decreased while the fluid is delivered from one or more fluid supply sources by a plurality of pumps. Then, when the start set value or stop set value set in the device number control system is reached, when starting or stopping the pump, a forecast pattern of increase / decrease in demand is set in advance in the device number control system, and the increase / decrease is set. When the demand volume is in the rising pattern in the forecast pattern, the stop of the pump when the above stop setting value is reached is delayed for a certain period of time, and after the certain time has elapsed, the pump is stopped when the demand amount is below the stop setting value. The rising control to stop and the start of the pump when the demand amount is in the decreasing pattern in the above increase / decrease forecast pattern reaches the above start set value for a certain period of time. Cast allowed, the time of descent to start controlling the pump when the demand after a lapse the predetermined time is higher than the operation setting value, is characterized in that performing at least one control.

According to a second aspect of the present invention, the hunting time width of the payout amount generated in the facility for delivering the fluid from the fluid supply source by a plurality of pumps is used for the fixed time period of the first aspect. The invention according to claim 3 is the above, and the set time for starting and / or stopping two pumps for a certain period of time according to claim 1 and / or Alternatively, it is characterized in that it is the time until the stop set value is reached.

Further, in the invention described in claim 4, in the invention described in any one of claims 1 to 3, the fluid supply source is a storage tank for low temperature liquefied gas, and the pump is the storage tank. It is a delivery pump for delivering the low temperature liquefied gas in the tank.

[0010]

According to the first aspect of the present invention, the demand amount increase / decrease forecast pattern is set in advance in the device number control system, and when the forecast demand amount is in the rise pattern, the actual payout amount is set by the ascending control. Is decreased and the set stop value is reached, the stop of the pump is delayed for a certain period of time. Then, after the lapse of a certain period of time, the payout amount is increased again, and when it is equal to or more than the stop set value, the pump does not stop, and after the certain period of time, it is still below the stop set value,
Unnecessary pumps stop for the first time. Therefore, when the expected demand amount is in the rising pattern, even if the hunting of the payout amount that the lower limit reaches the stop set value or less temporarily occurs, the pump is prevented from repeatedly stopping and starting. On the other hand, when the actual payout amount rises according to the rising pattern and reaches the start set value of the additional pump, the next pump is immediately started to respond to this.

Further, when the expected demand amount is in the descending pattern, if the actual payout amount increases and reaches the start set value by the descending control, the start of the pump is delayed by a constant time, and this constant time is set. After the lapse of time, the payout amount falls again,
The pump does not start when it is below the start set value, and the pump that is required for the first time starts when it is still above the start set value after the lapse of the certain time. As a result, even when the expected demand amount is in a downward pattern, even if hunting of the payout amount that temporarily causes the upper limit to reach the start set value or more occurs, it is possible to prevent unnecessary pumps from repeatedly stopping and starting. To be done. Then, when the actual payout amount decreases along the descending pattern and reaches an unnecessary pump stop set value, the pump is immediately stopped, and this is dealt with. From the above, it is possible to effectively suppress unnecessary start and / or stop operations of the pump due to disturbance, and to smoothly increase or decrease the original demand amount in accordance with the forecast pattern of increase or decrease in demand amount. This can be accommodated.

At this time, as the fixed time for delaying the start and / or stop of the pump, the hunting of the payout amount that can occur in the equipment in which the pump is installed is set as in the invention of claim 2. If the time width is set to be equal to or longer than the time width, it is possible to avoid the unnecessary start and stop of the pump most effectively, which is preferable. By the way, the cause of the hunting of the payout amount that can occur in the above equipment and its time width can be predicted for each equipment from the operating conditions by the arrangement of the piping system and pumps and valves in each equipment, For example, in the low-temperature liquefied gas discharge facility as in the invention described in claim 4, the cause of the hunting of the discharge amount is that when the additionally activated primary pump rises and the discharge side opening / closing valve opens. Also, there is a disturbance due to human error in operating the on-off valve that is likely to occur when starting or stopping the high-pressure pump on the downstream side or during operation.
Moreover, since the time width of the hunting caused by these is about 30 seconds to 3 minutes, when the above-mentioned low temperature liquefied gas delivery facility is applied, the above-mentioned fixed time is appropriately in the range of 1 to 5 minutes. It is preferable to set the time.

Further, the fixed time is, as in the invention described in claim 3, the time until the start set value and / or the stop set value for starting and / or stopping the second pump are reached. It is also possible to set. In this case, when the payout amount rises or falls in the descending pattern or the ascending pattern, even if the set value for starting or stopping the first pump is reached, the pump is not started or stopped. The pump is started or stopped for the first time after the rising or lowering continues until the start set value and / or the stop set value for starting and / or stopping the second pump is reached.

As described above, the invention according to any one of claims 1 to 3 is, like the invention according to claim 4, a fluid whose demand volume greatly fluctuates and is delivered particularly in one day. When used for controlling the number of operating delivery pumps in a low-temperature liquefied gas delivery facility that is a low-temperature liquefied gas such as LNG having a low viscosity, a remarkable effect is obtained.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the method for controlling the number of operating pumps of the present invention is applied to a dispensing pump in an LNG dispensing facility will be described below with reference to FIGS. 1, 2 and 4. Note that, in these drawings, since the description of each component is as described above, the same reference numerals are used below and the duplicated description is omitted. In the method for controlling the number of operating pumps in this example, the system for controlling the number of devices 10 includes the primary pumps 3 ...
And a start set value and a stop set value for starting and stopping the high-pressure pump 5 ...
A forecasted increase / decrease pattern of daily demand as shown in FIG. 2 is set in advance in the device number control system 10.

In the device number control system 10, when the demand amount is in the rising pattern 11 in the increase / decrease forecast pattern, the primary pump 3 and the high pressure pump 5 are stopped for a certain time when the stop set value is reached. When the delay time is exceeded and, after the elapse of this fixed time, the value is equal to or less than the stop set value, the rising control is first set to stop the primary pump 3 and the high-pressure pump 5. Further, when the demand amount is in the falling pattern 13 in the increase / decrease forecast pattern, the startup of the primary pump 3 and the high-pressure pump 5 when the startup set value is reached is delayed for a fixed time, and after the fixed time elapses, the startup set value is set. In the above cases, the descent control for starting the primary pump 3 and the high-pressure pump 5 is also set.

Here, in the LNG payout facility,
As a cause of hunting of the payout amount, when the additionally activated primary pump 3 rises to deliver LNG, or when the discharge side opening / closing valve is opened / closed when the high pressure pump 5 is started / stopped,
Further, there is a disturbance due to human error of the on-off valve during operation, and the time width of hunting caused by these is about 30 seconds to 3 minutes.
Set an appropriate time within the range of 5 minutes.

As a result, when LNG is paid out in the LNG payout facility, during the time when the expected demand amount is in the rising pattern 11 shown in FIG. 2, the actual payout is performed by the rising time control by the device number control system 10. When the amount decreases and reaches the stop set value, the stop of the primary pump 3 and the high-pressure pump 5 is delayed for a set fixed time. Then, when the payout amount again rises after the elapse of the certain time and is equal to or more than the stop set value, the primary pump 3 and the high-pressure pump 5 do not stop and continue to operate as they are. For some reason, if the demand volume on the day differs from the preset demand pattern and is still below the stop set value after the elapse of the certain time, the unnecessary primary pump 3 and high-pressure pump 5 are stopped. To do.

Therefore, the expected demand amount rises pattern 1.
In the time zone of 1, even if the hunting of the payout amount that the lower limit reaches the stop set value or less temporarily occurs,
It is avoided that the primary pump 3 and the high-pressure pump 5 are repeatedly stopped and started. On the other hand, in the same manner as the expected demand amount increase pattern 11, when the actual payout amount increases and reaches the start set value of the additional primary pump 3 and the high-pressure pump 5, the above-mentioned delay of the fixed time is Without being applied, the next primary pump 3 or high-pressure pump 5 is promptly activated to deal with this.

Next, when the forecast demand amount is in the descending pattern 13 shown in FIG.
When the actual payout amount increases and reaches the start set value by the descent control by 0, the start-up of the primary pump 3 and the high-pressure pump 5 is delayed for a predetermined time, and the payout amount after the predetermined time has elapsed. When it descends again and is below the above-mentioned start set value, the primary pump 3 and the high-pressure pump 5 do not start. Further, for some reason, when the demand amount on the day differs from the preset expected demand pattern and is still equal to or higher than the start set value after the elapse of the certain time, the primary pump 3 and the high-pressure pump 5 that are required for the first time are required. Will start. As a result, even when the predicted demand amount is in the descending pattern 13, even if the hunting of the payout amount that temporarily causes the upper limit to reach the start set value or more occurs, the primary pump 3 and the high-pressure pump 5, which are originally unnecessary, are Repeated stop and start is avoided.

As in the case of the predicted lowering pattern, when the actual payout amount decreases and reaches the unnecessary stop set value of the primary pump 3 and the high-pressure pump 5,
The primary pump 3 and the high-pressure pump 5 are immediately stopped to deal with this. As described above, according to the method for controlling the number of operating pumps of this example, unnecessary starting and stopping operations of the primary pump 3 and the high-pressure pump 5 due to disturbance can be effectively suppressed, and the rising pattern 11 and the descending pattern can be suppressed. With respect to the increase or decrease of the demand amount along the line 13, the primary pump 3 and the high-pressure pump 5 are immediately set by the start set value and the stop set value.
This can be dealt with smoothly by starting and stopping.

In the above embodiment, the fixed time for delaying the start-up / shutdown of the primary pump 3 and the high-pressure pump 5 is 3 to 10 minutes, which is equal to or longer than the hunting time width of the payout amount generated in the LNG payout facility. Although the case where the time is set to an appropriate time within the range has been described, the present invention is not limited to this, and the start set value and the stop set value for starting and stopping the second primary pump 3 or the high pressure pump 5 are reached. The same effect can be obtained with time.

Further, in the above embodiment, only the example in which the method for controlling the number of operating pumps of the present invention is applied to the control of the number of operating primary pumps 3 and high pressure pumps 5 in the LNG payout facility, is not limited to this. The same applies to the control of the number of operating multiple transfer pumps in other low-temperature liquefied gas delivery facilities such as LPG, and also in the delivery or transfer facility of other various fluids such as lubricating oil and fuel oil. Can be applied to.

[0024]

As described above, according to the method for controlling the number of operating pumps according to any one of claims 1 to 3, unnecessary start and stop operations of the pump due to disturbance can be effectively suppressed. In addition, when the demand amount increases or decreases during the rising pattern or the falling pattern, each pump 5 is started / started according to the start set value and the stop set value.
By stopping it, this can be dealt with smoothly. Therefore, the invention according to any one of claims 1 to 3 is, like the invention according to claim 4, a LNG in which the demand amount greatly fluctuates particularly in one day and the fluid to be transferred has a low viscosity. When used for controlling the number of operating delivery pumps in a low-temperature liquefied gas delivery facility that is a low-temperature liquefied gas such as the above, a remarkable effect is obtained.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing LNG payout equipment to which an embodiment of a method for controlling the number of operating pumps of the present invention is applied.

FIG. 2 is a graph showing a pattern of demand in the LNG payout facility of FIG.

FIG. 3 is a pump start / stop diagram showing a conventional method of controlling the number of operating pumps.

FIG. 4 is a graph showing a state of hunting in the rising pattern of the graph of FIG.

[Explanation of symbols]

1 Storage tank 2 LNG 3 Primary pump (delivery pump) 4 LNG delivery pipe 5 High pressure pump (delivery pump) 6 Vaporizer supply LNG adjustment valve 7 LNG vaporizer 8 Gas delivery pipe 9 LNG flow detector 10 Equipment number control system 11 Rise Pattern 13 Descent pattern S ₂ , S ₄ , S ₆ Start set value S ₁ , S ₃ , S ₅ Stop set value

Claims (4)

[Claims] 1. When the demand amount increases or decreases and a start set value or a stop set value set in a device number control system is reached while the fluid is delivered from a plurality of pumps from one or more fluid supply sources. In the method of controlling the number of operating pumps that starts the additional pumps or stops the pumps that are operating, the increase / decrease forecast pattern of the demand amount is set in advance in the device number control system, and the increase / decrease forecast pattern is set. When the demand amount is in the rising pattern, the stop of the pump when the stop set value is reached is delayed for a certain period of time, and when the demand amount is equal to or less than the stop set value after the certain period of time, the pump is stopped. When the ascending control to stop and the demand amount in the above increase / decrease forecast pattern are in the descending pattern,
At least one of delay control that delays the start of the pump when the start set value is reached, and starts the pump when the demand amount is equal to or more than the start set value after the certain time has elapsed, A method for controlling the number of operating pumps, which is characterized by performing control. 2. The fixed time period is equal to or longer than a time width of hunting of a payout amount generated in a facility that sends out the fluid from the fluid supply source by a plurality of the pumps. How to control the number of operating pumps. 3. The method according to claim 1, wherein the certain period of time is a time required to reach a start set value and / or a stop set value for starting and / or stopping the second pump. Of controlling the number of operating pumps. 4. The fluid supply source is a storage tank for low temperature liquefied gas, and the pump is a discharge pump for delivering the low temperature liquefied gas in the storage tank. 4. The method for controlling the number of operating pumps according to any one of 3 to 3.