JPH0560077A - Control method for number of compressor in operation - Google Patents

Abstract

PURPOSE:To reduce a required power in a total range of required air amounts as small as possible in a device which supplies high and low pressure air to requirement consumption systems. CONSTITUTION:In is a control method for the number of compressor in operation, the numbers of low pressure side compressors 12A to 12C in operation and high pressure side compressor 14A to 14C in operation are are set based on consumption amounts of low and high pressure air, and the low and high pressure air are each supplied to consumption systems. In respect to a total consumption rate of the low pressure air, the number of the low pressure side compressors 12A to 12C in operation is set and the compressors 12A to 12C are operated under a load. Peficient air is supplied by reducing a pressure of the high pressure air of the high pressure side compressors 14A to 14C. One of the high pressure side compressors 14A, 14B is optionally selected, and operated under capacity control.

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 compressors for supplying high pressure and low pressure air to a consumption system.

[0002]

2. Description of the Related Art There are two types of compressor operation, load / no-load control and constant pressure / non-surge control. In this load / no-load control, air is supplied to the receiver tank, and if the pressure in the receiver tank exceeds the upper limit value, no-load operation is performed, and during that time, the air in the receiver tank does not consume the air. When the lower limit value is reached, load operation is performed and load / no-load operation is automatically switched. In constant pressure / non-surge control, 70 to 100, or 80 to 10 for full load.
During 0% operation, the valve opening of the intake valve of the compressor is controlled to control the constant pressure so that the set pressure is reached, and when the flow rate is 70 or 80% or less, the blower valve is opened to blow the compressor while blowing air. I'm driving.

By the way, 80% or 70% of the set capacity
From the viewpoint of the compressor power, the constant pressure / non-surge control and the load / no-load operation are the same in the operation above 80%, but 80
% Or 70% or less, load / no-load operation is advantageous because less power is required. Therefore, as shown in Japanese Examined Patent Publication No. 1-252020, there has been proposed a compressor capacity control device capable of reducing power in an operation up to a capacity of 0 to 100% by combining load / no-load control and constant pressure / non-surge control. This will be described with reference to FIGS. In FIG. 4, 1 is a compressor,
Reference numeral 2 is a suction line, 3 is a discharge line, 4 is a suction valve connected to the suction line 2, 5 is a pressure detection pipe connected to the discharge side of the compressor 1, and the detected pressure is input to a pressure regulator 6, The pressure detector 6 controls the opening degree of the intake valve 4 via the three-way solenoid valve SV1. 7 is a check valve connected to the discharge line 3, 8 is a receiver tank, 9 is a blow line, 1
0 is a blowoff valve connected to the line 9, FS is a flow rate detector, SV2 is a three-way solenoid valve that controls the opening and closing of the blowoff valve 10, P
S is a pressure detector and F is a filter.

In the displacement control device shown in FIG. 4, the design points of 100% pressure, 100% capacity and 100% power when the valve opening of the intake valve 4 is 100% are set to P, respectively, as shown in FIG.
₀ , Q ₀ , W ₀ , the capacity is 10 from Q ₀ to Q ₁ .
In the range of 0 to 80% capacity, constant pressure control is performed, and the discharge pressure is kept constant at point P _0, and 80 to 0% of points Q ₁ to Q ₂
When the capacity is reached, load / no-load operation is performed and the discharge pressure is set to point P.
It stays between ₀ and P ₁ . That is, during the constant pressure control, the pressure regulator 6 adjusts the valve opening of the suction valve 4 according to the fluctuation of the discharge pressure of the compressor 1 so that the discharge pressure becomes constant, and the flow rate is 80% or less. When
Switching to load / no-load operation by the flow rate detector FS and pressure detector PS. This load operation is performed by the pressure detector PS provided in the receiver tank 8. When the discharge pressure drops to the design pressure P ₁ , the valve opening degree of the intake valve 3 is set to 100%.
Alternatively, when the flow rate is decreased to the setting Q ₁ of the flow rate detector FS by adjusting the constant pressure control after performing load operation by raising it to the vicinity thereof, the intake valve 4 is closed by switching the three-way solenoid valves SV1 and SV2 ( The opening degree is about 15%), the blowoff valve 10 is opened, and no-load operation is performed, during which air is supplied by the receiver tank 8. By thus combining the load / no-load control and the constant pressure / non-surge control, the power can be reduced as much as possible in a wide range of operation from 0 to 100% in capacity.

[0005]

By the way, in recent years, in air compressor equipment, a plurality of compressors are connected in parallel with the maximum air demand value as a guide, and the number of operating machines and their capacity are controlled according to the air consumption. Is being done. In this case, one unit performs the above-mentioned capacity control, and the other compressors perform load operation near 100% capacity, so that the compressors can be efficiently operated with a small amount of power for a wide range of air usage. Being tried. That is, it is most efficient to operate the compressor at 100% load, and it is advantageous from the viewpoint of energy saving. Therefore, first determine the number of compressors that can operate at 100% load with respect to the required consumption amount. By supplementing the shortage with the supply amount based on the number of units by the capacity control operation, efficient operation with less power consumption becomes possible.

However, when the number of operating units and the capacity control are applied to the air compressor equipment using two types of air, high pressure and low pressure, the high pressure side and the low pressure side compressor facilities are usually mutually operated. The above-described number and capacity control are independently performed on the high-voltage side and the low-voltage side without performing the number and capacity control in a relational manner, and there is always a problem that efficient operation cannot be said. Particularly, low-pressure air usually consumes about twice as much as high-pressure air, and a compressor having a large discharge capacity is used. When the capacity of this compressor is controlled, power consumption becomes large, which is preferable. There is no problem.

Therefore, an object of the present invention is to solve the above-mentioned problems and to supply the required amount of high-pressure and low-pressure air to the required consumption system, respectively, by reducing the power as much as possible in the entire range of the demanded air amount including the high pressure and the low pressure. It is to provide a method of controlling the number of operating compressors that can be performed.

[0008]

In order to achieve the above object, the present invention provides a plurality of low-pressure side compressors and a plurality of high-pressure side compressors, the operating number of which depends on the low pressure and high pressure air consumption. In the method of controlling the number of operating compressors that supply low-pressure and high-pressure air to the consumption system, set the number of operating low-pressure side compressors and the low-pressure side The compressor is operated under load, the shortage is supplied by decompressing the high-pressure air of the high-pressure side compressor, and at the same time, any one of the high-pressure side compressors is capacity-controlled.

[0009].

According to the above configuration, the number of low-pressure side compressors is set so that they can be operated at almost full load, the insufficient air is decompressed from the high-pressure side and supplied, and any one of the high-pressure side compressors is supplied. By controlling the capacity, the capacity-controlled high-pressure side compressor can be operated at a high capacity, including the capacity for low pressure, resulting in high efficiency, and overall high efficiency operation with less power is possible. Become.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

In FIG. 1, 11 is, for example, 6.0 Kg /
A low pressure line for supplying air of cm ² to the consumption system, and low pressure side compressors 12A, 12B, 12C are connected to the low pressure line 11. Reference numeral 13 is a high-pressure line for supplying air of 9.0 kg / cm ² to the consumption system. The high-pressure line 13 is connected to the high-pressure side compressors 14A, 14B, 14C and the receiver tank 15.

These compressors 12A-C and 14A-C are
Although not shown in detail, as described with reference to FIG. 4, the suction valve is connected to the suction side and the blowoff line is connected to the discharge side. For example, three low pressure side compressors 12A to 12C having the same discharge capacity are connected in parallel, and the low pressure side number control device 1
In 6, the operating number is set. This low pressure side compressor 12
When A to C are operated, the capacity is 80 to 1 as described above.
Constant pressure control (or load / no-load control is also possible) is performed at a load operation of 00%, and the capacity is 80%.
In the following, the operation will be stopped. The high-pressure side compressors 14A to 14C are, for example, two compressors 14A and 14C.
The discharge capacity of B is set to be smaller than that of the other compressor 14C, and the operating number is set by the high-pressure side number control device 17, respectively. This high pressure side compressor 14A
When C to C are operated, constant pressure control (or load / no load control may be performed) is performed under load operation with a capacity of 80 to 100%, and compression of two units with a small discharge capacity is performed. The machines 14A and 14B can perform load / no-load control operation in order to control the capacity in the range of the capacity of 80 to 0%. In this case, when the set pressure is 9.0 Kg / cm ² ± 0.2 Kg / cm ² , the solenoid valve SV1, shown in FIG.
SV2 is switched and load / no-load control operation is performed.

The low-pressure line 11 and the high-pressure line 13 are connected by a connection line 18, and the connection line 18 extends from the high-pressure side to the low-pressure side to the flow meter 19 and the high-pressure side pressure transmitter 2.
0, the pressure reducing valve 21, and the low pressure side pressure transmitter 22 are connected, and these are connected to the detection / control circuit 23.

The detection / control circuit 23 receives the signals from the low selector 24 for opening and closing the pressure reducing valve 21 and the high pressure side pressure transmitter 20, and outputs the calculation result to the low selector 24. 25 and the signal from the low-pressure side pressure transmitter 22 are input, and the calculation result is input to the low selector 2
4, the low pressure side pressure indicating controller 26 and the flow meter 19
From the detected value of the flow rate instruction calculator 27 that outputs an operating number increase command to the low voltage side number control device 16 when the flow rate becomes the same as the discharge capacity when the low pressure side compressors 12A to 12C are operated under load. I have it.

Simultaneously with the input to the detection / control circuit 23, the signal of the high-pressure side pressure transmitter 20 is transmitted to the high-pressure side number controller 17 for controlling the number of units, and similarly, the signal of the low-pressure side pressure transmitter 22 is transmitted. The signal is transmitted to the low voltage side unit control device 16.

The low pressure side pressure indicating controller 26 detects that the signal from the low pressure side pressure transmitter 22, that is, the pressure in the low pressure line 11 is
For example, when it is 5.9 Kg / cm ² or more, a close signal is output to the row selector 24, and when it is 5.9 Kg / cm ² or less, an open signal is output.

The high pressure side pressure indicating controller 25 outputs an open signal to the low selector 24 when the signal from the high pressure side pressure transmitter 20, that is, when the pressure in the high pressure line 13 is 8.6 kg / cm ² or more, Is less than 8.6 Kg / cm ² , a close signal is output to the row selector 24.

The low selector 24 opens or closes the pressure reducing valve 21 by selecting one of the signals from the high-pressure side and low-pressure side pressure indicating controllers 25 and 26, whichever has the stronger demand for closing. That is, if the open / close signals of both indicating controllers 25 and 26 are the same, the low selector 24 opens and closes according to the instruction, but the high pressure is 8.6 kg / cm ² or less (close instruction) and the low pressure is 5. When the pressure becomes 9 Kg / cm ² or less (instruction to open), the pressure reducing valve 21 is closed by giving priority to the high pressure side controller signal in order to secure the high pressure, and the high pressure is 8.6 Kg / cm ² or more (open instruction), low pressure 5.9
When it becomes Kg / cm ² or more (close instruction), the pressure reducing valve 21 is controlled to be closed by giving priority to the low pressure side controller signal.

In the above, first, the high-pressure side compressors 14A to 14C of the high-pressure line 13 are operated so that the high-pressure side number control device 17 enters a set pressure of 9.0 Kg / cm ² according to the high-pressure air consumption. Set the number and operate. Further, the low pressure air consumption of the low pressure line 11 depends on the low pressure side compressor 12A.
0 ~ 8 from the discharge capacity when operating any of
When it is 0% or less, the low-pressure side unit control device 16 does not operate any of the low-pressure side compressors 12A to C, and the portion corresponding to the low-pressure side compressors 14A to 14C has a small capacity.
High pressure air from the high pressure line 13 is depressurized through the pressure reducing valve 21 via the connection line 18 by driving either B and performing capacity control, and is supplied to the low pressure line 11 as a shortage of low pressure air. At this time, the flow rate instruction calculator 27 detects the flow rate passing through the flow meter 19, and the flow rate is the flow rate (80 to 100%) during the load operation of the low pressure side compressors 12A to 12C.
When it reaches, the low-voltage side number control device 16 outputs an increase command of the operating number, and based on this, the low-voltage side number control device 16 selects the low-pressure side compressors 12A to 12C which are not in operation to load. Drive. Further, during this load operation, if the consumption amount of the low pressure line 11 decreases and the low pressure side pressure indicating controller 26 is a set value (for example, 6.2 Kg / cm ² ) or more, any of the low pressure side compressors 12A to 12C in operation. When one of them is stopped and the low pressure becomes 5.9 Kg / cm ² or less after the stop, the pressure reducing valve 21 is opened to supply the air of the high pressure line 13 to the low pressure side. When the pressure in the high pressure line 13 is 8.6 kg / cm ² or more, the low selector 24 opens the pressure reducing valve 21.

In the high pressure side compressors 14A to 14C, first, the high pressure detected by the high pressure side pressure indicating controller 26 is 8.
When the pressure is 7 Kg / cm ² or less, the high voltage side unit control device 1
7, a high-voltage side controller 14 outputs a high-voltage side controller 14 to increase the discharge amount.
Operate any of A to C or switch the operation. In addition, the compressors 14A to 14C, except for the one whose capacity is controlled, are in operation within a capacity range of 80 to 100% and have a discharge pressure of 9.0 Kg / cm ² constant pressure control (or load / non-addition control). In this case, the valve opening of the intake valve is controlled by the pressure on the discharge side of the compressor. In addition, the compressor 14A (or 1
4B), the pressure of the receiver tank 15 is 9.0 kg / cm.
² Constant pressure control with intake valve and opening controlled so that it falls within the range of ± 0.2 Kg / cm ² , and intake valve and blowoff valve are turned on
・ Combination of load and no-load control to turn off 0-1
00% capacity control operation is performed.

As described above, the low-pressure side compressors 12A to 12C perform only load operation without capacity control, and the shortage is corrected by the high-pressure line 1.
By decompressing and supplying the air of No. 3, it is sufficient to control the capacity only on the high pressure side, and efficient operation can be achieved as a whole.

Next, the difference in operating efficiency between the embodiment of the present invention shown in FIG. 1 and the conventional comparative example shown in FIG. 2 will be described.

In FIG. 2, the low pressure line 11 and the high pressure line 12 are constructed by using the low pressure side and high pressure side compressors 12A to C and 14A to C similar to those in FIG. 1, and the high pressure side compressors 14A to 14C.
And the low-pressure side compressors 12A to 12C are both controlled in number and capacity according to their air consumption. In FIG. 2, a receiver tank 30 is connected to the low pressure line 11. A connection line 18 is provided between the high pressure line 13 and the low pressure line 12 as in FIG. 1, but the communication valve 31 between them is normally closed and is not used for communication except in an emergency.

In FIGS. 1 and 2, the low pressure side compressor 12
A to C and the high pressure side compressor 14C use the same type,
Motor output 1170Kw, discharge flow rate 15000m ³ / H on low voltage side, 100% load, 10 on high voltage side (14C)
Operated under the operating conditions of 0% load, electric motor output of 1175 Kw and 100% discharge flow rate of 13000 m ³ / H, and small capacity high-pressure side compressors 14A and 14B have 100% load of electric motor output of 662 Kw and 100% discharge flow rate of 7000 m ³ / H. It was operated under the operating condition of / H.

In FIG. 1 and FIG. 2, the low pressure air consumption is 100% of the discharge amount of the low pressure compressor (15000 m ³ /
H) based on 20, 40, 80, 120, 160,
The power consumption of each compressor is shown in Tables 1 and 2 assuming that the high-pressure air always consumes 1/2 of the low-pressure air consumption at each point of 200, 240, and 280%. Further, in this case, the shaft power is 0 to 1 of the low pressure side compressor whose capacity is controlled as shown in FIG.
Shaft power characteristics at 00% capacity and high pressure side compressor 0-100
It was calculated from the shaft power characteristics in% capacity. In this case, the control pressure difference between loaded and unloaded was 0.4 Kg / cm ² , and the volume usable in the discharge line was about 90 m ³ (receiver 50 m ³ , pipe 40 m ³ ). In FIG. 3, constant pressure control (80-1
00%), the low pressure side is 948 to 1170 Kw, the high pressure side is 536 to 662 Kw, and the low pressure side is 948 to 209 Kw and the high pressure side is 536 to
It changes to 91Kw. In this load / no-load operation region, the two-dot chain line shown in the figure shows the power for the ON operation in which compressed air is actually supplied to the receiver tank, and the solid line shows the actual power in consideration of the OFF operation for the blown air. The high-pressure side compressor 14C having a large capacity is 1175 Kw at 100% load operation.

[0026]

[Table 1]

[0027]

[Table 2]

As is clear from Tables 1 and 2, low pressure 20
%, The total shaft power of 120% is about 300 Kw in the present embodiment, compared with the comparative example of Table 2, and about 150% at 40, 240%.
Kw The consumption power can be reduced.

[0029]

In summary, according to the present invention, the number of low-pressure side compressors is set so that they can be operated at almost full load, and the deficient air is decompressed from the high-pressure side and supplied. By controlling the capacity of one unit, the high-pressure side compressor for capacity control can be operated at a high capacity, including the capacity for low pressure, so efficiency is improved and overall power consumption is low and high efficiency is achieved. It becomes possible to drive.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a comparative example with respect to the embodiment of FIG.

FIG. 3 is a diagram showing shaft power characteristics of the compressors of FIGS. 1 and 2 at 0 to 100% capacity.

FIG. 4 is a diagram showing a circuit of a capacity control device that performs load / no-load control and constant pressure control.

FIG. 5 is a diagram showing the relationship among capacity, pressure and power in FIG.

[Explanation of symbols]

 11 Low Pressure Line 12A to C Low Pressure Side Compressor 13 High Pressure Line 14A to C Low Pressure Side Compressor 18 Connection Line 21 Pressure Reducing Valve

Claims (1)

[Claims] 1. A plurality of low-pressure side compressors and a plurality of high-pressure side compressors are operated by setting the number of operating units according to their respective low pressure and high pressure air consumption amounts, and low pressure and high pressure air are supplied to a consumption system. In the method for controlling the number of operating compressors to be supplied, set the operating number of low-pressure side compressors to the total consumption of low-pressure air and load-operate the low-pressure side compressors so that the shortfall is A method for controlling the number of operating compressors, characterized in that high-pressure air is decompressed and supplied and any one of the high-pressure side compressors is capacity-controlled.