JPS623198A - Capacity controller for turbocompressor - Google Patents

Abstract

PURPOSE:To prevent the delay of control operation by controlling the flow rate of each compressor according to the variation value of flow rate of a load which demands a mass flow rate and providing a master control system which compensates the variation of flow rate of the load which demands the capacity flow rate due to the variation of the pressure as the function of flow rate of the load. CONSTITUTION:A capacity controller for controlling each flow rate of compressors 1A, 1B and 1C according to the demand of loads 1, 2 and C is constituted of a master control system 4 and minor control systems 5A, 5B and 5C. Into the master control system 4, each discharge flow rate of the compressors 1A, 1B and 1C is transmitted through a minor control system, and each gas flow rate to the loads 1, 2 and 3 is transmitted through transmitters 14, 15 and 16, and each operation signal is transmitted to the minor control systems 5A, 5B and 5C from the master control system 4. Further, into the minor control systems 5A, 5B and 5C, the flow rate on each compressor discharge side is transmitted as operation signal into the suction-side vane controls 2A, 2B and 2C.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a control device for a turbo compressor, and more particularly, to a capacity control device for a plurality of turbo compressors suitable for a combination of a neuterity and a productive plant as loads. .

[Background of the invention]

There are two methods for controlling the capacity of a compressor: flow rate control and pressure control. However, due to the compressibility of gas, in a capacity process, a difference between the inflow and outflow occurs when the load fluctuates, and the pressure changes between the two. Because it affects the amount of gas, pressure control is used to control gas balance, such as compressor capacity control.

In other words, in a capacity control system process, the integral of the difference between the inflow and outflow amounts of gas is pressure, and there is self-equilibrium between pressure and flow rate, except when the flow rate is zero. Therefore, if the process pressure is kept constant, it is possible to balance the supply amount (inflow amount) corresponding to fluctuations on the load side (outflow amount).

Therefore, the conventional capacity control method of controlling the flow rate of multiple compressors according to the demand on the load side has been to use a pressure regulator to keep the discharge pressure of each compressor and the common main pipe pressure constant.
Discharge pressure control is utilized to control vane controls provided on the suction side of each compressor.

In this conventional control method, the discharge pressure of each compressor is controlled to be constant, so when the demand for any of the loads increases, the pressure drop phenomenon at the end appears on the discharge side of the compressor with a delay. This is due to the capacity of the pipes, etc.

If the pressure drop at the end is large, it is necessary to correct the target value (set value) of the pressure regulator, but it is difficult to understand the process characteristics and make accurate corrections in advance. Therefore, normally, the number of compressors is determined based on the maximum demand and the discharge pressure of the compressors is set high so that the pressure on the load side does not fall below the required value, which results in wasted power consumption. .

At the same time, increasing the set value of the pressure regulator means that the surging prevention control line Y parallel to the surging line X of the compressor and the pressure set value ( The flow rate Qs at the intersection with the target value) Ps, that is, the minimum flow rate control value Qs of each compressor for surging prevention increases.

The capacity control width becomes smaller, resulting in poor controllability.

In addition, in the case of a combination of a load that requires a volumetric flow rate and a load that requires a mass flow rate, such as a combination of a neuterity plant and a brocuty plant, the discharge pressure of the compressor is determined by the flow rate of the latter. Therefore, it is difficult to achieve optimal control using a control method that keeps the discharge pressure constant.

Incidentally, related to this type of control device is, for example, Japanese Unexamined Patent Publication No. 59-68581.

[Purpose of the invention]

The object of the present invention is to eliminate interference between loads and between controlled variables with respect to fluctuations in loads requiring volume flow or loads requiring mass flow, and to minimize pressure and flow fluctuations.
Maintaining a wide capacity control range for each compressor,
The purpose of the present invention is to provide an efficient compressor capacity control device.

[Summary of the invention]

The present invention relates to loads that require a gas volume at a predetermined pressure, that is, a volumetric flow rate, such as a demand service, as a load group connected to a plurality of compressors, and a product composition, such as a productive plant. Of the two control methods mentioned above, by adopting the flow rate control method, it is possible to reduce the pressure and flow rate to other loads in response to fluctuations in loads with different characteristics. The focus is on the ability to minimize fluctuations.

In other words, in the case of a load that requires a volumetric flow rate, a control method that keeps the discharge pressure of the compressor constant in response to load fluctuations is common; however, in the case of a load that requires a mass flow rate, Depending on the characteristics of the load (plant), the compressor discharge pressure P
There is a relationship of P=f (Q) between the flow rate Q and the flow rate Q of the load, and since a change in P is also required in response to a request for a change in Q, a control method that keeps the discharge pressure constant cannot be applied.

On the other hand, the flow rate of the compressor is controlled in accordance with the request for a change in Q, and the interference with a load requiring a volumetric flow rate due to P changing according to the relationship P=f (Q), that is.

By adding a control system that compensates for flow rate changes, P and Q can be stabilized.

In addition, by changing the flow rate control range of each compressor by P, which changes according to the relationship of P = f (Q), each pressure can be adjusted.
, the capacity control range of the compressor can be widened.

The former is controlled by a master control system common to each compressor, and the latter is controlled by a minor control system for each compressor to achieve this purpose. In order to treat the flow rate as equivalent to the mass flow rate, the temperature and pressure of the load should be used for correction and substitution.

In the master control system, the flow rate of the load group that requires volumetric flow rate is measured at a fixed sampling period, and the ratio between the sum of the flow rate change values of the load group and the sum of the capacities of the pipes, etc. corresponding to each load is determined. If a certain ratio (specified value) is exceeded, the flow rate target value of the master control system is program-controlled according to the ratio and is temporarily changed.

After this control is completed, the load group that requires volumetric flow
The target value of the master control system is changed by the sum of the control i (flow rate) of , and the load setting flow rate that requests the mass flow rate, and the capacity of each compressor is controlled as the new target value.

At the same time, in order to reduce the power consumption of a plurality of compressors and improve the overall operating efficiency, the number of compressors to be controlled is automatically selected from the total flow rate of the load group, and the priority order is determined and controlled.

In addition, in order to compensate for mutual interference between loads, pressure, and flow rate control amounts due to load fluctuations, a compressor capacity control system is added to control the flow rate of the load that requires mass flow rate to a target value. With this control system, the discharge pressure of the compressor is stabilized due to the relationship P=f(Q), and this interference can be alleviated.

On the other hand, the minor control system is provided independently for each compressor, and as shown in the compressor control limit curve in FIG. The minimum flow rate control value Q corresponding to the pressure determined from the P = f (Q) relationship of the load requiring mass flow rate is determined, the flow rate control range is varied, and the target flow rate of each compressor is When the flow rate is below Q, the output signal from the master control system is cut off and locked to the operation signal corresponding to the minimum flow rate control value Q.

If the flow rate of each compressor falls below the target value of the minor control system in the control lock state, and the deviation exceeds the specified value,
Release control lock.

Note that a load that requires a mass flow rate is a load that uses compressed gas (for example, air) as a raw material and other products (gas, liquid) due to its composition.
This is a plant that produces

In this case, the relationship between compressed gas pressure P and flow rate Q is the plant resistance curve itself, as shown in Figure 2, and P =
The relationship is f (Q).

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described based on the drawings. FIG. 1 is a control system diagram showing an embodiment of the turbo compressor capacity control device of the present invention.

The gas is compressed to a predetermined pressure by turbo compressors LA, IB, and Ic, and is branched by pipes 7, 8, 9, and 10 to load 1,
2.3.

Load 1 is a load that requires a mass flow rate, that is, a plant that uses compressed gas as a raw material, and loads 2 and 3 are loads that require a volumetric flow rate.

Load 1, 2. Compressor LA depending on the demand for C.

The capacity control devices that control the flow rates of IB and IC are a master control system 4 and minor control systems 5A and 5B.

It is composed of 5C. The discharge flow rate of the compressors IA, IB, and IC is connected to the master control system 4 via the minor control system, and the gas flow rate to the loads 1 and 2.3 is connected to the transmitters 14 and 15.
．． 16 from the master control system 4 to the minor control systems 5A and 5B.

An operation signal is being transmitted to 5C. In addition, the flow rate on the discharge side of each compressor is transmitted through transmitters 11A, IIB, and IIC, the pressure on the discharge side is transmitted through the transmitter 12, and the temperature on the discharge side is transmitted to the minor control systems 5A, 5B, and 5G. are transmitted through the minor control systems 5A, 5B, and 5C to the suction side vane controls 2A, 2B, and 2G of each compressor.
The operation signal is being transmitted to.

Next, the operation of the master control system 4 will be explained in Figures 1 and 3.
This will be explained according to the diagram.

FIG. 3 is a block diagram showing the configuration of the master control system 4. As shown in FIG. The discharge flow rates of the compressors IA, IB, and IC are sent to terminal 2 as actual measured value signals from the minor control systems 5A, 5B, and 5C.
After calculating the sum of each flow rate, the adder 31 compares the difference signal with the flow rate target value signal, and the deviation signal is sent to the proportional calculator 32 and after calculation,
The adder 33 adds the calculated signal from the integral calculator 34 and the calculated signal, and then outputs the resultant signal from terminals 25, 27, and 29 to the minor control systems 5A, 5B, and 5G.

On the other hand, the flow rates of loads 1 and 2.3 are determined by flow rate detectors 14A and 1.
Detected by 5A, 16A, transmitter 14.15.16
After signal conversion, the actual measurement signal (after temperature and pressure correction) is passed through the terminals 22, 23, and 24 to the sampling circuit 37.
are averaged to prevent the sudden input of abnormal actual measurement signals.

The averaged signal is provided to an adder 38.

The signal corresponding to the actual measurement value added by the adder 38, that is, the load 1
, 2.3 is sent to the computing unit 39A and the load distributor 39B in synchronization with the sampling period of the sampling circuit 37.

After calculating the ratio of the sum signal of the flow rates of the loads 1 and 2.3 to the preset sum of the capacitances of pipes, etc. (process capacitance) in the calculator 39A, the ratio is given to the adder 4o.

After the adder 40 compares the allowable ratio signal 41 with the ratio signal, the deviation signal is sent to the program setter 42, and the program signal adjusted according to the value of the deviation signal is sent to the adder 36.
Output to. (See Fig. 5) Adder 36 adds the sum of the flow rate setting signals Q and 6 for load 1 from adder 35 and the measured flow rate signals for loads 2 and 3 and the program signal or the signal from setting device 46. Thereafter, the corrected target value signal becomes a target value for controlling the flow rate of the compressors IA, IB', 'IC.

In addition, the flow rate signal of the load 1 given from the terminal 22 to the sampling storage calculator 43 for the purpose of interference compensation between loads and between controlled variables is calculated by the sampling storage calculator 43 after calculating the amount of change from the old and new flow values. , 6 given to adder 44
” After the adder 44 compares the allowable flow rate change value signal 45 and the change signal, the deviation signal is sent to the setting device 46, becomes a correction signal adjusted according to the value of the deviation signal, and is sent to the adder 36.
Output to.

However, while the program setting device 42 is operating, the signal switching device 5
The correction signal is blocked by o.

In addition, in the load distributor 39B, the loads 1, 1, and 1 from the adder 38 are
2.3, the compressors LA, IB, I
In addition to selecting the number of C units, the signal switching devices 47, 48, and 49 are operated according to the preset control priority order. That is, control.

A constant operation signal is sent from the load distributor 39B to the corresponding minor control system 5A for the waiting compressor.

Operate signal switch 47.48°49 to output to 5B and 5C.

Specifically, the master control system 4 changes the target value of the flow rate control system according to changes in process characteristics and demand, alleviates interference between loads and controlled variables, and minimizes pressure and flow rate fluctuations in load groups. In addition, multiple compressors can be efficiently selected and capacity controlled.

Next, the operation of the minor control systems 5A, 5B, and 5C will be explained according to FIGS. 1 and 4.

FIG. 4 is a block diagram showing the configuration of minor control systems 5A, 5B, and 5G.

The output operation signal from the master control system is sent to the output holding circuit 61 through the terminals 54 of the minor control systems 5A, 5B, and 5G.
The output is passed through a signal switch 63 to a terminal 56.
From compressors IA, IB.

IC suction side vane controls 2A, 2B.

Output to 2C and adjust the flow rate (air volume).

When the signal switch 63 is switched to the M side, the manual operation signal 62
is output to vane controls 2A, 2B, and 2G.

On the other hand, the flow rate signals detected from the discharge sides of the compressors IA, IB, and IC are sent to transmitters 11A and IIB.

After the signal is converted in step 11C, it is applied to the humidity and pressure correction calculator 66 through the terminal 51 as an actual measurement value signal.

Similarly, the pressure signal is sent to the temperature-pressure correction calculator 66 via the transmitter 12 and the terminal 52, and the temperature signal is sent to the temperature-pressure correction calculator 66 via the transmitter 13 and the terminal 53. The flow rate signals Q and I corrected for temperature, order and pressure by this calculator are applied to a terminal 55 for deviation alarms 67A, 67B, 67C and master control system 4.

In addition, the compressor discharge pressure signal determined from the resistance curve of load 1 (plant) in FIG.
As shown in Figures 6 and 7, the minimum flow rate control value signal corresponds to the pressure that changes according to the characteristics (resistance curve) of load 1 (plant) by matching the preset control line Z. After finding Q6, signal comparator 67G
sent to □received.
・Difference alarm 67G
Compare the flow rate signal Q, from the temperature and pressure correction calculator 66 with the minimum flow rate control value signal Q1, and if Q<Q, then AN
A Qo signal is sent to the D circuit 68, which is applied to the output holding circuit 61 via the OR circuit 70, cuts off the output operation signal from the master control system 4, and locks to the signal corresponding to the minimum flow rate control value signal Q3. do. This control lock is released.

Minor control system from terminal 19 of master control system 4
' The deviation alarms 64A and 64B make a judgment based on the deviation signal ΔQ between the target value and the controlled amount given through the terminals 58 of 5A, 5B, and 5G, and if ΔQ>d, the self-holding circuit 6S is reset. AND circuit 68 for the signal
The control lock of the output holding circuit 61 is released. Δ
If Q<-a, the control lock state is maintained.

(However, a and b are positive constants.) Also, a limit switch is installed at the mechanical minimum opening of the suction side vane control of the compressors LA, IB, and IC, and this limit switch operation signal is passed through the terminal 57 and
The signal is applied to circuit 69, and the control is similarly locked. This is for backup of the control lock signal.

(However, Q indicates the flow rate at the minimum opening degree.) In this way, the minor control systems 5A, 5B, and 5C are used to control the flow rate of the compressor based on the characteristics of the compressor side and the plant resistance curve CP=
By setting the minimum flow rate control value based on the pressure determined from the By correcting the target value for capacity control of the master control system 4 by considering the volume as the pressure drop in the system and using the ratio with the change in demand, control operation delays caused by process capacity can be eliminated, and the load side Pressure fluctuations can be minimized.

In addition, by using a flow rate control method as a compressor capacity control method, the flow rate fluctuations to a load that requires mass flow rate, that is, a plant whose source flow is compressed gas, can be minimized.
Mutual interference can be alleviated. In addition, by adding a function to widely adjust the capacity control width of each compressor using the minor control systems 5A and 58.5G for each compressor mentioned above,
There is no need to perform operations that allow for margins, and each compressor can be operated efficiently, which has the effect of reducing operating costs.

【Effect of the invention〕

According to the present invention, it is possible to eliminate delays in control operations caused by the process capacity of pipes, etc., to minimize load pressure fluctuations in response to fluctuations in gas demand, and to Even in cases where a plant that uses compressor as raw material is involved, it is possible to suppress mutual interference between loads with different characteristics, minimize flow fluctuations to the plant, and maintain a wide capacity control range for each compressor. .

[Brief explanation of drawings]

FIG. 1 is a control system diagram of one embodiment of the present invention, FIG. 2 is a plant resistance curve, FIG. 3 is a block diagram showing an example of the control configuration of the master control system of FIG. Figure 5 is a block diagram showing an example of the control configuration of the minor control system in Figure 3.
FIG. 6 is a P-Q characteristic diagram of the turbo compressor, and FIG. 7 is a compressor control limit curve diagram that supplements the explanation of the operation in FIG. 4. LA, IB, IC...turbo compressor, 2A, 2B. 2C... Vane control, 4... Master control system, 5A, 5B, 5C... Minor control system, IIA,
-118, IIC... Differential pressure transmitter, 12... Pressure transmitter, 13... Temperature transmitter, 14A, 15A, 1
6A...Flow rate detector, 14,15.16...Differential pressure transmitter. 3rd fig. 4

Claims (1)

[Claims] 1. In a plurality of compressors coupled to a load group requiring a volumetric flow rate and a load requiring a mass flow rate, a control line parallel to the surging line of each compressor and a flow rate function of the load requiring a mass flow rate. a minor control system that changes the flow rate control range of each compressor based on the discharge pressure of the compressor, and a minor control system that changes the flow rate control range of each compressor based on the discharge pressure of the compressor, and a minor control system that changes the flow rate control range of each compressor based on the discharge pressure of the compressor, and controlling the flow rate of the compressor discontinuously, controlling the flow rate of each compressor according to a flow rate change value of the load that requests a mass flow rate, and requesting a volumetric flow rate due to a change in pressure that is a flow rate function of the load; A capacity control device for a turbo compressor, comprising a master control system that compensates for changes in the flow rate of the load.