JPH074600A - Method for changing over raw material - Google Patents

Abstract

PURPOSE:To provide a method for changing over raw materials which stabilizes a control action and reduce the waste of energy. CONSTITUTION:In a method for changing over one of two crude oil tanks 1A, 1B to the other, a pump 2D stopped in the change-over of a crude oil by a pump 2A is started. The pump 2A is stopped after a pump 2D rises up completely and valves 3AA, 3BA are changed over to change over the crude oil. Then, in the starting of the auxiliary pump 2D, the flow of a plurality of pumps 2A, 2B, 2C other than the pump 2D is controlled in a lump and in the stoppage of the pump 2A to be changed over, the flow of a plurality of pumps 2B, 2C, 2D is controlled in a lump to direct the control and prevent mutual interference. Similarly other pumps 2B, 2C, 2D are sequentially changed over.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for switching raw materials, and can be used for switching a plurality of crude oil tanks which are sources of crude oil as a raw material for petroleum plants.

[0002]

2. Description of the Related Art Conventionally, in a petroleum plant, a plurality of delivery pumps are provided in parallel on the downstream side of a plurality of crude oil tanks that are sources of crude oil as a raw material, and a charge pump is provided on the downstream side of these delivery pumps. A crude oil supply device is used. In such a supply device, crude oil extracted from a crude oil tank by a delivery pump is pressure-fed by a charge pump to supply the crude oil to a demineralizer or the like. In addition, a switching valve is provided between each payout pump and each crude oil tank, and different types of crude oil accumulated in each oil tank can be switched by operating each switching valve and switching the piping. It has become. A plurality of dispensing pumps are provided so that each of the pumps in operation delivers a predetermined amount of crude oil.
The flow rate is individually controlled, and at least one unit is always stopped as a backup pump. When switching crude oil,
After additionally activating the stopped standby pump, the activated delivery pumps are sequentially stopped one by one, and the switching valve of the stopped delivery pump is operated to switch the crude oil.

[0003]

However, in the conventional switching method, the switching is performed while individually controlling the flow rates of the plurality of delivery pumps. Therefore, when the standby pumps are activated, each control system is activated by the activation of the standby pumps. There is a problem that the control operation becomes unstable because the control operations interfere with each other to cause the turbulence of the flow rate and the control operation becomes unstable.In some cases, the charge pump is stopped due to the fluctuation of the suction pressure, It may be necessary to stop the dispensing pump to stop the hunting operation. On the other hand, it is possible to slow down the operation of each control system to prevent hunting operation, but if the control operation is slowed,
There is a problem that a standby pump that does not need to be normally operated has a long operating time, a wasteful power is consumed for a long time, and energy is wasted.

It is an object of the present invention to provide a raw material switching method in which the control operation is stable and energy consumption is reduced.

[0005]

According to the present invention, there are provided a plurality of systems of raw material supply sources, a plurality of delivery pumps connected in parallel to these raw material supply sources, and between each delivery pump and each raw material supply source. A raw material switching method for a raw material supply device comprising a connected switching valve and a charge pump that is provided on the discharge side of the dispensing pump and sends the raw material to another device connected to the downstream side. The control is performed so that the suction pressure of the charge pump and the total flow rate from each of the delivery pumps become a predetermined value.

[0006] Here, the procedure for switching the raw material supply source is as follows:
By operating the switching valve of the stopped delivery pump, when switching from one raw material source to the raw material of another raw material source, the additional starting pump started to stop the switching target pump Until the flow rate of the pump reaches the flow rate of the switching target pump, the flow rates of pumps other than the additional starting pump including the switching target pump are collectively controlled, and this flow rate of the predetermined starting value and the additional starting pump After the first control mode in which the flow rate is controlled so as to be equal to the difference with the flow rate is performed and the flow rate of the additional startup pump reaches the flow rate of the switching target pump, other than the switching target pump including the additional startup pump. The flow rate of the pumps is collectively controlled, and the flow rate is equal to the difference between the predetermined flow rate value and the flow rate of the switching target pump. Procedure for performing a second control mode in which flow control can be employed as. The first control mode is preferably started after the suction pressure of the charge pump rises by a predetermined value due to the start of the additional start pump.

[0007]

In the present invention as described above, the total flow rate of the flow rates from the respective discharge pumps is controlled to a predetermined value, so that the control operations do not interfere with each other and the suction pressure of the charge pump is kept constant. The operation becomes stable and the control operation becomes stable. And
Performs the first control mode that collectively controls the flow rate of multiple pumps other than the additional start pump when the additional start pump is started, and collectively controls the flow rates of multiple pumps other than the change target pump when the switch target pump is stopped. If the second control mode in which the control is performed is performed, the sum of the two flow rate values to be controlled in each mode is controlled to be the predetermined flow rate value. Controls will not be commanded and interfere with each other. When the flow rate of the additional startup pump reaches the flow rate of the switching target pump, the first
If the control mode is changed to the second control mode, it is not necessary to change the control parameters such as the target value and the set value when the mode is changed, and the mode can be switched quickly and smoothly. In the second control mode, control can be performed regardless of the operating state of the switching target pump, so that stopping the switching target pump does not cause a disturbance. For this reason, stable control can be performed all the time, and the raw material can be switched in the shortest time, thereby achieving the above object.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a crude oil supply device 1 which is a raw material supply device of this embodiment. The crude oil supply device 1 has two systems of crude oil tanks 1A and 1B, which are raw material supply sources, and supplies crude oil to a desalting device or the like connected to a downstream side via a transport line L. Four lines of series A to D are connected in parallel to each of the crude oil tanks 1A and 1B.
The series A to D are respectively connected with dispensing pumps 2A, 2B, 2C and 2D for extracting crude oil from the crude oil tanks 1A and 1B. Of the delivery pumps 2A, 2B, 2C, 2D, one of them is sequentially used as a standby pump so as to stop the operation in order, whereby the operation time is equalized.

Discharge pump 2A and each crude oil tank 1A, 1B
The switching valves 3AA and 3BA are connected between the two, and the switching valve 3A is connected between the discharge pump 2B and each crude oil tank 1A and 1B.
B, 3BB are connected between the discharge pump 2C and the crude oil tanks 1A, 1B by switching valves 3AC, 3BC, and between the discharge pump 2D and the crude oil tanks 1A, 1B by switching valves 3AD, 3BD. There is. Switching valve 3AA, 3AB, 3AC, 3AD
Are paired with switching valves 3BA, 3BB, 3BC, 3BD,
When one is open, the other is set to close,
As a result, the crude oil tanks 1A and 1B are switched.

The discharge side of each dispensing pump 2A, 2B, 2C, 2D is
Charge pump 4 that sends crude oil to a desalting device etc.
It is connected to the. A flow rate sensor 5A, 5B, 5C, 5D and a flow rate adjusting valve 6A, 6B, 6C, 6D are connected between the delivery pumps 2A, 2B, 2C, 2D and the charge pump 4, respectively. The flow rate sensors 5A, 5B, 5C, 5D consist of orifices, differential pressure transmitters, etc., and measure the instantaneous flow rate of crude oil flowing from the delivery pumps 2A, 2B, 2C, 2D. The flow rate adjusting valves 6A, 6B, 6C, 6D adjust the flow rate of crude oil flowing from the payout pumps 2A, 2B, 2C, 2D based on the signal values measured by the flow rate sensors 5A, 5B, 5C, 5D. It is a thing.

A pressure transmitter 7 is installed on the suction side of the charge pump 4, and the suction pressure of the charge pump 4 is measured. On the other hand, on the discharge side of the charge pump 4, two branch passages 8 are provided, a desalting device is connected to each branch passage 8, and in order to control the flow rate of crude oil flowing inside to a predetermined value, The flow rate sensor 8A and the flow rate adjustment valve 8B are connected. The flow rate adjustment valve
8B is a flow rate indicating controller to which the signal from the flow rate sensor 8A is input.
It is controlled by 8C.

Such a crude oil supply device 1 is controlled by an instrumentation line shown by a broken line in the figure. Next, the instrumentation system of the crude oil supply device 1 will be described. Flow sensor 5A, 5
The outputs of B, 5C and 5D are the same series of flow indicator controllers 9A, 9B and 9D.
It is connected to C and 9D respectively. Further, all of the outputs of these flow rate sensors 5A, 5B, 5C, 5D are also connected to a programmable flow rate indicating controller 10 capable of being arbitrarily programmed.

The flow rate indicating controllers 9A, 9B, 9C, 9D are regulators for individual control which respectively control the openings of the flow rate adjusting valves 6A, 6B, 6C, 6D based on one input flow rate signal. . The flow rate indicating controller 10 has two control systems, that is, a control system consisting of a designated one of the series A to D and a control system in which the other three series are combined into one. By controlling the system as a whole, the overall flow rate can be adjusted to a specified value C _Q.
Is configured to keep. For example, three series A ~
When the series D of C is designated and the crude oil flowing in the series D is increased or decreased, the flow rate indicating controller 10 adds up the amounts of the crude oil flowing in the series A to C with each other and the flow rate value which is the sum of them. In addition to obtaining Q _G , the flow rate value Q _D flowing in the series D is subtracted from the target value C _Q to obtain a difference ΔQ between them, and the flow rate adjusting valves 6A, 6B, 6C are set so that the flow rate value Q _G becomes ΔQ.
Is adjusted to control the flow rate value Q _{T to} be constant. Here, the flow rate adjusting valves 6A, 6B, 6C are
They are controlled collectively and perform the same operation.

The flow rate indicating controller 10 has two control modes, a first control mode and a second control mode, and monitors the outputs of the flow rate sensors 5A, 5B, 5C, 5D while controlling the flow rate condition. It also operates by switching the control mode. That is, the first control mode is the dispensing pumps 2A, 2
When one of the B, 2C, and 2D that was stopped as a standby pump was additionally started, the flow rates of the other three pumps were adjusted collectively in accordance with the increase in the flow rate of this additionally started pump,
It is a control mode that keeps the overall flow rate constant.
The flow is continued until the flow rate of the additionally activated standby pump reaches the flow rate of the switching target pump that is stopped for switching.

The second control mode is the dispensing pump.
When stopping the pump to be switched among 2A, 2B, 2C, 2D,
This is a control mode in which the flow rates of the other three pumps are collectively adjusted according to the decrease in the flow rate of the pump scheduled to stop so that the overall flow rate becomes constant. After reaching the flow rate of the switching target pump that is stopped due to, the switching target pump continues until it is stopped.

A signal switch 11 is connected between the flow rate adjusting valve 6A and the flow rate indicating controller 10. Signal switch 11
Is also connected to the flow rate indicating controller 9A
This is a device that switches the signal input to 6A from one of the flow rate indicating controller 9A and the flow rate indicating controller 10 to the other. A signal switch 11 is also connected between each of the other flow rate adjusting valves 6B, 6C, 6D and the flow rate indicating controller 10.

The output of the pressure transmitter 7 is the pressure indicating controller 12
Is input to the sequence controller 20. The deviation ΔP between the input pressure value and the set pressure value is output from the pressure indicating controller 12 to the sequence controller 20. The sequence controller 20 is composed of payout pumps 2A, 2B, 2C, 2D and switching valves.
3AA, 3BA… 3AD, 3BD, etc. operation and flow indicator controller
It controls the 10 control operations as a whole. That is, the sequence controller 20 includes a pressure indicating controller 12
In addition to the deviation ΔP from the operating condition signals of the discharge pumps 2A, 2B, 2C, 2D and the switching valves 3AA, 3BA ... 3AD, 3BD
The open / close status signal of is input. The sequence controller 20 outputs start / stop signals to the dispensing pumps 2A, 2B, 2C, 2D, and the switching valves 3AA, 3BA… 3AD, 3B.
An open / close signal is being output to D. In addition, pump 2
Switching valve 3AA, 3BA… 3A during A, 2B, 2C, 2D operation
An interlock is built in to prevent D and 3BD from operating. A control signal for switching the flow rate control from individual control for each series A to D to group control for collectively controlling a plurality of series A to D is output to the flow rate indicating controller 10 and the signal switcher 11. It is like this. here,
The control signals to the flow rate indicating controller 10 and the signal switch 11 are
The deviation ΔP between the suction pressure value and the set pressure value of the charge pump 4 is output after the deviation ΔP has become larger than a predetermined value, and upon receipt of this control signal, the flow rate indicating controller 10 starts the control in the first control mode. It is supposed to do. After the first control mode is started, the output of the deviation ΔP between the suction pressure value of the charge pump 4 and the set pressure value causes the flow rate indicating controller 10 to keep the overall flow rate value Q _T constant. To control.

Next, the crude oil switching procedure of this embodiment will be described with reference to FIG. In addition, the changeover of crude oil is performed by the payout pump.
2A, 2B, 2C, 2D are performed in this order, crude oil is supplied from the crude oil tank 1A, and the delivery pump 2D of the delivery pumps 2A, 2B, 2C, 2D is started in a state of being stopped as a standby pump.

First, when switching the crude oil of the dispensing pump 2A, as shown in FIG. 2, the spare pump 2D is started at time T1. When the pump 2D is activated, the suction pressure of the charge pump 4 increases and the deviation ΔP from the set value reaches a predetermined value immediately, and the flow rate indicating controller 10 starts the first control mode. In the first control mode,
As shown on the time i in FIG. 2, the pump with the 2D flow increases, pump 2A, 2B, squeezed collectively flow rate value Q _A Q _B Q _C of 2C, the overall flow rate value Q _T is the target value Control so as to be C _Q. As a result, the flow rates of the pumps 2A, 2B, 2C are collectively controlled, mutual interference of control operations is prevented, and hunting phenomenon and the like are prevented from occurring.

At time T2, the flow rate value Q _D of the pump 2D and the flow rate value Q _{A of the} pump 2A both become the value Q1, and the control mode of the flow rate indicating controller 10 changes from the first control mode to the second control mode. Transition to. In the second control mode, as shown in the time period B of FIG. 2, the flow rate values Q _B Q _C Q _D of the pumps 2B, 2C, 2D are increased in a lump as the flow rate of the pump 2A decreases, and the total flow rate is increased. The value Q _T is controlled to be the target value C _Q. As a result, the flow rates of the pumps 2B, 2C, 2D are collectively controlled, mutual interference of control operations is prevented, hunting phenomenon, etc. are prevented from occurring, and even if the pump 2A stops, the pumps 2B, 2C The total flow rate value Q _G of 2D and the total flow rate value Q _T do not deviate from the controllable range in the second control mode, and the control operation becomes stable.

With respect to each of the other dispensing pumps 2B, 2C, 2D, the crude oil switching is similarly performed, and the entire crude oil switching is completed. However, when switching the pump 2B, the backup pump is the pump 2A, when switching the pump 2C, the backup pump is the pump 2B, and when switching the pump 2D, the backup pump is the pump 2C.

According to this embodiment as described above, the following effects can be obtained. That is, the first control mode in which the flow rates of a plurality of pumps other than the standby pump are collectively controlled is performed when the standby pump is started, and the flow rates of a plurality of pumps other than the switching target pump are collectively controlled when the switching target pump is stopped. Since the second control mode for controlling is performed, and in each mode, the control is performed so that the sum of the flow rate values of the two control systems becomes a predetermined flow rate value, the control of each control system is controlled. Therefore, the control operations can be stabilized from beginning to end without interfering with each other.

Further, since the first control mode is switched to the second control mode when the flow rate of the auxiliary pump reaches the flow rate of the switching target pump, the target value and the set value are set at the time of mode transition. It is possible to switch modes quickly and smoothly without changing control parameters such as, and even if the pump to be switched is stopped, the overall flow rate value is within the controllable range in the second control mode. Since the deviation does not occur, the stop of the pump to be switched does not cause a disturbance, and the material can be switched in the shortest time.

Further, in carrying out the above-mentioned crude oil switching procedure, it is not necessary to add any new field equipment to the crude oil supply device 1, and it is sufficient to add a new regulator such as the flow rate indicating controller 10 and so on. It is possible to easily change from the switching procedure of to this switching procedure.

It should be noted that the present invention is not limited to the above-mentioned one embodiment, but also includes the following modifications and the like. That is, in the above-mentioned embodiment, the number of delivery pumps was set to four, and one of them was used as a spare, but eight small delivery pumps may be used and two of them may be used as auxiliary pumps. Can be appropriately set in consideration of the operating rate and the like.

As the flow rate sensor, various types such as an axial flow type with a built-in turbine or the like, an oval type positive displacement type, etc. can be selected, and the type of other meters can be appropriately selected. Furthermore, the present invention is not limited to the crude oil supply device, but can be widely applied to a raw material supply device for food processing industries such as dairy products and paint manufacturing industries.

[0027]

As described above, according to the present invention, it is possible to stabilize the control operation and reduce the waste of energy.

[Brief description of drawings]

FIG. 1 is an instrumentation flow chart showing an entire embodiment of the present invention.

FIG. 2 is a graph for explaining a procedure for switching crude oil according to the present invention.

[Explanation of symbols]

1A, 1B Crude oil tank which is a raw material supply source for supplying liquid raw material 2A, 2B, 2C, 2D Dispensing pump 3AA, 3BA ... 3AD, 3BD switching valve 4 Charge pump

Claims (3)

[Claims] 1. A raw material supply source of a plurality of systems, a plurality of delivery pumps connected in parallel to these raw material supply sources, a switching valve connected between each delivery pump and each raw material supply source, and A method of switching a raw material of a raw material supply device, comprising a charge pump that supplies the raw material to another device that is provided on the discharge side of the delivery pump and is connected to the downstream side,
A method for switching raw materials, characterized in that the control at the time of switching raw materials is controlled so that the suction pressure of the charge pump and the total flow rate from each of the delivery pumps become predetermined values. 2. The method of switching raw materials according to claim 1, wherein the operating delivery pumps are sequentially stopped one by one, and the switching valve of the stopped delivery pumps is operated, so that one raw material supply source is operated. When switching to the raw material of another raw material supply source, until the flow rate of the additional starting pump started to stop the switching target pump to be switched from now on reaches the flow rate of the switching target pump, Performing a first control mode of collectively controlling the flow rate of pumps other than the additional starting pump including and controlling the flow rate such that this flow rate becomes equal to the difference between the predetermined flow rate value and the flow rate of the additional starting pump. After the flow rate of the additional startup pump reaches the flow rate of the switching target pump, the pumps other than the switching target pump including the additional startup pump are operated. Of raw switching method which is characterized in that the second control mode in which flow control as this flow rate equals the difference between the flow rate of said a predetermined flow rate value switching target pump while collectively controlling the amount. 3. The raw material switching method according to claim 2, wherein the first control mode is started after the suction pressure of the charge pump is increased by a predetermined value due to the start of the additional start pump. Characteristic raw material switching method.