JPS6248999A - Method for operating compressor - Google Patents

Abstract

PURPOSE:To prevent surging and carry out safe and efficient operation by carrying out operating control while adjusting suction pressure based on the quantity of inside condition of a compressor estimated based on detected operation data or the number of revolutions, or discharge pressure. CONSTITUTION:Data from each of temp., pressure, and flow-rate indicators and a rotation number detector in each of a compressor are converted into digital signals and inputted into a central processing unit. An actual flow rate inside the compressor, discharge temperature, and discharge pressure are obtained using a pressure coefficient and an adiabatic exponent which are obtained based on operation data, and the quantity of inside condition is estimated and displayed. Based on this, a correcting operation is carried out to enable safe and efficient operation of the compressor. On carrying out the correcting operation, when the number of revolutions or discharge pressure is above the limit of control, control is carried out based on said quantity of inside condition, whereas, when it is below the limit of control, suction pressure is controlled in accordance with the number of revolutions or the discharge pressure. Thereby, a surging phenomenon which is liable to occur when the compressor is stopped can be prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to pressure 1i! Concerning how to operate the machine. For more information,
This invention relates to a method for estimating the internal state quantity of a multistage centrifugal compressor, etc., and controlling the operation while safely maintaining this internal state quantity.

[Background technology and its problems]

Conventionally, the performance of a compressor during steady operation is known.

However, during unsteady operation, for example, the rated rotation speed is 30 to 80.
It is difficult to understand the performance at % rotation, start-up, and stop. In particular, it is difficult to determine the actual flow rate, compression ratio, etc. during startup and shutdown because the temperature and pressure of the compressor are not constant.

Therefore, surging phenomenon is likely to occur especially when stopped. By the way, surging phenomenon is a phenomenon that occurs, for example, when the suction amount of a compressor is throttled below the critical point, and the wind pressure pulsates, the air volume fluctuates, and vibrations and noise are emitted, making it unusable. means.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate such drawbacks, and to reduce pressure ii without causing surging.
? An object of the present invention is to provide a method for operating a compressor that can safely control the operation of an i-machine.

[Means and actions for solving problems] Therefore,
In the present invention, the operating data of the compressor is detected, the internal state t of the compressor is determined based on this operating data, and the suction is It is characterized by controlling the operation of the compressor while correcting the pressure.

〔Example〕

FIG. 1 shows an example in which a three-stage centrifugal compressor is used in an ethylene process. In the same figure, a centrifugal compressor 10
is a three-stage type having three stages of compression sections 11, 12, and 13,
It is driven by a motor 14. The rotation speed of compression a10 is
It is constantly detected by the rotation speed detector 18.

On the inlet side of the first stage compression section 11, as shown in FIG. 2CL, there is a temperature indicator T1. and a flow rate indicator Fl. Further, on the inlet side of the second stage compression section 12, a temperature indicator T1. and a flow rate indicator FI2 are provided, respectively. Furthermore, the third stage compression section 13 has a temperature indicator Tl3i and an ml indicator F on its population side.
fffi are provided respectively, and a temperature indicator T1. . , pressure indicator P1. -0 and flow indicator Fl,. are provided for each.

Ethylene gas from the first stage drum 21 is supplied to the first stage compression section 11 via piping 15, and ethylene gas is supplied from the second stage drum 22 via piping 16 to the second stage compression section 12. However, ethylene gas from the third stage drum 23 is supplied to the third stage compression section 13 via the piping 17. The ethylene gas compressed by these compression sections 11, 12, 13 is cooled by propylene in heat exchangers HCb and HCa, and then stored in the fourth stage drum 24 and transferred to the first stage via valve V0. tram 2
Returned to 1.

Drum 2], 22.23 of each stage has a liquid level controller LCI.
, LCz, and LC3 are provided, and one end of each pipe 25, 26, 27 is connected to the bottom of the drum 22, 23, 24 of the next stage, and the other end of the pipe 25, 26, 27 is connected to the bottom of the drum 22, 23, 24 of the next stage. In the middle of the pipes 25, 26 and 27, there is the liquid level controller LC installed on the m1 stage drum 21, 22, 23.
, LC2) Liquid level control valves LV+ = LVz and LV, which are opened and closed by signals from LC8, are inserted, respectively. However, in addition to the liquid level control valve LV, the piping 27 is inserted with a heat exchanger HC4 used, for example, as a top condenser of a distillation column or for cooling raw materials. For each liquid level control valve LV, , Lv, , LVj, a heat exchanger similar to the heat exchanger IC) [Cl+HCz.

HC, and piping 28 with valves V+, Vt, V3
．． 29.30 are connected in parallel.

The drum 22.23 outlet side of the piping 16.17 and the drum 21.22 population side of the piping 25.26 are the piping 31
．． They are connected to each other via 32. Each pipe 31.
In the middle of the drum 32, there is a pressure regulating valve PV that is opened and closed by a signal from the pressure regulator PC, PO2 provided on the drum 21, 22 of the Hit stage.

, pv, are inserted respectively. Moreover, the space between the heat exchangers HC5 and HC6 and the tram 23 population side of the pipe 27 are communicated with each other via a pipe 33. In the middle of the pipe 33, a pressure regulating valve PV3 is inserted which is opened and closed by a signal from a pressure regulator PC provided in the third stage tornograph 23. Furthermore, the top of the fourth drum 24 and the inlet side of the drum 23 of the piping 27 are connected to the piping 3
They communicate with each other via 4. A pressure regulating valve PV, which is opened and closed by a pressure regulator No. 18 from a pressure regulator PCj provided on the fourth drum 24, is inserted in the middle of the piping 34.

FIG. 3 shows a data processing device. In the same figure, each indicator T+, , P provided in the first stage compression section 11 is shown.
ct , Fl, , each indicator 712 provided in the second stage compression section 12 , F Iz , third stage compression section 13
Each indicator provided in T I 3i + F l 31
゜]"Iz.', P Ixo, F Iz., and the rotation speed detector that detects the rotation speed of the compressor 1O. The detection data from the first day are selectively filtered sequentially by the multiplexer 41, and then A After being converted into a digital signal by the /D converter 42, it is taken into a central processing unit (hereinafter referred to as CPU) 43.

The CPU 43 estimates the internal state quantity of the compressor 10 based on these data and various preset constants, and displays this on the display device 44, and at the same time displays the rotation speed of the motor 14 and the pressure regulator via 11045. PC, -PCff
Correct the set pressure. In other words, while controlling the rotation of the motor 14 of the compressor 10, each drum 21, 2
2.23 pressure regulators P C+ , P Cz ,
Correct the setting value of PC3.

Next, the operation of this embodiment will be explained with reference to the flowchart shown in FIG. When the pressure tjh machine 1o is operated, the temperature indicators T I+, T Ix, T Izr, T I,
.

Temperature data from Ll+ 17. t, i-so, pressure adjustment and indicator PC,, pressure data P1 from PI3°,
P. , flow rate indicator F I+, F Iz, F Izi,
Flow rate data from F Ii; F +, F 2.
F zr, F s. The rotational speed data R detected by the rotational speed detector 18 is sequentially and selectively taken in by a multiplexer 41, then converted into a digital signal by an A/D converter 42, and then taken into the CPU 43.

The CP and U43 perform approximate calculations of physical property constants, that is, compression coefficients and shear indexes, taking advantage of the captured operating data.

In approximating the compression coefficient, the critical temperature T
Find r and critical pressure P. Now, the temperature is T and the pressure is P.
Then, the critical temperature T, ..., and the critical pressure P, are obtained from the corresponding state principle as follows: T, = T/Tc P, = p/ Pe. However, Tc is the critical temperature and PC is the critical pressure. The compression coefficient Z is obtained by substituting the above critical temperature T and critical pressure P into the following approximate equation showing the relationship between the compression coefficient, the critical temperature, and the critical pressure. That is, Z=a+b-P,+c-T,+d-p+e-T,'' where a, b, c, d, and e are constants specific to the substance.

In addition, in approximating the adiabatic index, the temperature T
and pressure P into the following approximate equation, the insulation index K
=Cp/Cv (Cp: constant pressure specific heat, CV: constant volume specific heat) is determined. That is, Cp=A+B-T+C-T"+DT'+E-T'
, then v p -Cp. However, R is a gas constant.

Next, using the compression coefficient Z and the adiabatic index K, an estimation calculation of the internal state quantity is performed for each compression section of each stage.

In the estimation calculation of the internal state c and quantity of the first stage, since the inlet temperature 1 and the inlet pressure (suction pressure) P+ are detected, ■actual flow rate, ■surging flow rate, ■weight flow rate, ■shaft horsepower, Perform estimation calculations for outlet temperature, ■flow rate ratio, and ■outlet pressure (discharge pressure).

■Actual flow rate Q is calculated as follows, where t5 is the inlet temperature of the first stage compression section and P is the population pressure. Here, the constant 0.99 is the compression coefficient in the standard state.

■For the surging flow jlQ, the design rotation speed is N9 and the rotation speed during operation is N. , surging at design rotation speed>A
When M is Qas (unit: f t' /min), it is calculated as (m' /D).

■Weight flow■W, ha, is required.

■Shaft horsepower K W + can be found as follows. Here, H8 is a polytropic head, η
, are the polytropic efficiencies, and are determined by approximate expressions obtained through experiments.

■Output temperatures t and d are found in [°C]. By the way, the above formula can be found from the polytropic compression formula. Here, L.P.

Substituting into the above equation, KZ Rη is obtained. However, Z is the average compression coefficient of suction and discharge,
m is the molecular weight of the gas (28,05), R is the gas constant (8
47).

■The baldness ratio Q+/Q+- is Q+/QC
s = Q+ / Q+sX 100 (%)
is required.

■The outlet pressure (discharge pressure) F2 is the pressure P1 of the drum 21
It is obtained by subtracting the differential pressure generated in the suction flow IFg from In other words, it is determined by P2=Pl-ΔPF2. However, ΔPFZ is the differential pressure caused by F2.

The above are the internal state quantities in the first stage compression section 11, but the internal state quantities in the second and subsequent stage compression sections are determined in the same manner. However, the inlet temperature tx after the second stage
s, ts s and the actual flow rate Q2)Q3 are determined as follows. For example, the second stage inlet temperature t2S,
How to find the actual flow 'tt Q Z is as follows: Q, = (W+ +Wz)Vz (m" /
D). Here, ■2 is the specific volume of the second stage inlet gas (
m'/T).

After the above estimation calculation is completed, the display device 44 displays the actual flow rate and pressure ratio of each stage of the compressor together with the surging curve as shown in FIG. At this time, as shown in FIG. 6, the internal shape JLift obtained by the estimation calculation can be simultaneously displayed on the screen.

In addition, in FIG. 6, data in brackets indicate values obtained by estimation calculation. Further, at the same time as the display is displayed, corrective operations are automatically executed depending on the internal situation of the compressor.

The correction operation is performed so that the actual flow rate maintains a flow rate ratio of 120% or more with respect to the surging flow rate, with emphasis on safety. Here, when moving to the stop operation, normal stop operations such as reducing the speed of the compressor and extracting the refrigerant are performed while the corrective operation is being performed.

■) In the stop operation, when the compressor rotation speed or discharge pressure is above the control limit, here the compressor rotation speed is 76
00 rpm or more, discharge pressure is 16゜0 kg/cf
l! In the above case, when the flow rate ratio of the first stage falls below 120%, the pressure of the first stage drum 21 (the set pressure of the pressure regulator PC3) is increased. The pressure of the first drum 21 is 1
, 0 kg/d, if the flow rate ratio of 120% or more cannot be maintained, reduce the pressure of the second stage drum 22 (pressure regulator PC2 set pressure) to 2.4 kg/d.
is lowered as the lower limit. This operation is performed, for example, when the pressure ratio is at point A, as shown in FIG. 7, to lower the pressure ratio and maintain a flow rate ratio of 120% or more.

2nd) Perform the same operation for the third stage.

That is, when the flow rate ratio of the second stage falls below 120%, the second stage
Pressure of drum 22 of stage (set pressure of pressure adjustment needle pc)
to rise. The pressure of the second stage drum 22 is 3.0kr
/-, if the flow rate ratio of 120% or more cannot be maintained, lower the pressure of the third stage drum 23 (set pressure of the pressure regulator pci) to 6,000 kg/cnt as the lower limit.

When the flow rate ratio of the third stage falls below 120%, the pressure of the third stage drum 23 (the set pressure of the pressure regulator PCs) is increased. Even if the pressure of the third stage drum 23 reaches 7°0 kr/-, if the flow rate ratio of 120% or more cannot be maintained, the pressure of the second stage drum 22 (set pressure of the pressure regulator PC!) is lowered to a lower limit of 2.4 kg/d.

In this way, the suction pressure of each stage is corrected so that the flow rate ratio of each stage is maintained at 120% or more.

■) In the stop operation, when the rotation speed or discharge pressure of the compressor is below the control limit, here the rotation speed of the pressure Villa is less than 760 Orpm and the discharge pressure is 16゜9 kg/
When the temperature is less than c + a, that is, when the stop process progresses and the compressor speed is lowered, the internal state quantity estimated in the steady operation region cannot be used, and by maintaining the inlet pressure corresponding to the rotation speed and discharge pressure. Maintain safe driving.

The rotational speed is reduced using the normal stopping procedure. The discharge pressure is
Determined by the rotational speed at that time and the amount of gas held in the system (No. 8
(see figure). Therefore, using the final operation value of the correction operation to maintain the flow rate ratio of 120% (rotation speed 760 orpm and pressure at each stage in Figure 8) as a reference value, the subsequent rotation speed and pressure at each stage corresponding to the discharge pressure. Find the optimal solution.

Now, assuming that the rotation speed of the compressor is N and the head is H, the following equation holds from the relationship of similarity.

H+ /Hz −(N+ /Nz)' (
1) The optimal solution for each stage pressure is found as follows.0For example, to find X in FIG. Similarly, xt to x4, ylA-y, z1 to z4 are obtained, and correction operations are performed so that these values become the set pressures for each stage.

Therefore, according to this embodiment, the internal state quantity of the compressor is estimated based on the operating data of the compressor, and correction operations are performed based on this, so that the Sho-m machine can be operated safely and efficiently. I can drive.

At this time, the estimated internal state of the compressor is displayed on the display device 44, so that it is possible to easily grasp the internal state quantity of the compressor during steady operation, during operation, and when stopped.

Moreover, in performing the correction operation, when the rotation speed or discharge pressure of the compressor is above the control limit, control is performed based on the internal state BM, while when the rotation speed or discharge pressure is below the control limit, the rotation speed or Since the suction pressure is controlled according to the discharge pressure, it is possible to prevent the surging phenomenon that tends to occur when the compressor is stopped.

In addition, according to the implementation, the pressure v? The single machine is not limited to the three-stage centrifugal type described in the above embodiment, but may be of other types.

Further, in the above embodiments, an ethylene process has been described, but the present invention is not limited to this, and can be most applicable to a system using a compressor.

〔Effect of the invention〕

As described above, according to the present invention, since the operation can be controlled while grasping the internal state quantity of the compressor, surging can be particularly prevented during stoppage, and the compressor can be operated safely.

[Brief explanation of the drawing]

Fig. 1 is a flow diagram of the method of the present invention applied to the ethylene process, Fig. 2 is a diagram showing the compressor section, Fig. 3 is a block diagram showing the internal configuration of the data processing device, and Fig. 4 is a diagram showing the compressor section. Flowchart, Figures 5 and 6 are diagrams showing examples of screen display, Figure 7 is a diagram showing the relationship between flow rate and pressure ratio, and Figure 8 is a diagram showing the relationship of each drum pressure with respect to rotation speed and discharge pressure. It is a diagram. lO... Compressor, 11.12.13... Compression section.

Claims (5)

[Claims] (1) Detect the operating data of the compressor, estimate the internal state quantity of the compressor based on this operating data, and correct the suction pressure based on the estimated internal state quantity, compressor rotation speed, or discharge pressure. A compressor operating method characterized by controlling the operation of the compressor while the compressor is being operated. (2) In claim 1, when estimating the internal state quantity of the compressor, a compression coefficient and an adiabatic index are determined based on the operating data of the compressor, and the compression coefficient and adiabatic index are used to calculate the compression coefficient and the adiabatic index. A compressor operating method characterized by determining the actual flow rate inside the machine, discharge temperature, and discharge pressure. (3) A compressor operating method according to claim 1 or 2, characterized in that an internal state quantity is displayed. (4) A compressor operating method according to claim 3, characterized in that the actual flow rate and pressure ratio are displayed together with a surging curve. (5) In any one of claims 1 to 4, when the correction is performed, the suction pressure is corrected based on the internal state quantity when the rotation speed or discharge pressure of the compressor is equal to or higher than a control limit. On the other hand, a compressor operating method characterized in that when the rotation speed or discharge pressure of the compressor is less than a control limit, the suction pressure is corrected according to the rotation speed or discharge pressure.