FR2839755A1 - INSTALLATION FOR PRODUCING A COMPRESSED GAS, AND METHOD FOR OPERATING THE SAME - Google Patents

Abstract

This compressed gas production facility comprises three compressors (4, 6, 8) connected to a compressed gas network (12, 20), for each of the compressors (4, 6, 8), a first connection line ( 26, 28, 30) to a power source (24) as well as a switch (32, 34, 36) of this line, and a variable speed drive (VAR) adapted to vary the speed of rotation of a compressors (4, 6, 8), and connected to the power source (24). The installation further comprises switches (46, 48, 50) adapted to selectively connect only one of the compressors (4, 6, 8) to the variable speed drive (VAR). Each compressor (4, 6, 8) is a compressor whose rotation speed can be continuously adjusted in a speed range between a minimum speed and a transition speed. Application to compressed air production facilities.

Description

and the level displayed by each cylinder.

  l: The present invention relates to a method for producing compressed gas

  as well as a compressed gas production installation for its covering.

  As a known compressed air production installation, there is for example that described in the article entitled: "Compressed air, feedback on a sale per m3, public in ENERGIE PLUS, n 224 of April 15, 1999, periodical from the Technical Association for Energy and Environment. Wile includes at least two compressors, the discharge side of which is connected to a compressed air network; at least one of these compressors is at fixed speed and is dimensioned in such a way that it operates continuously at 100% of its capacity; another is at a speed that is reliable and is regulated so that it makes up for the required gas flow rate. This last compressor is started or stopped according to the pressure found in the air network. When the installation includes more than two compressors,

only one has variable flow.

  However, in this type of installation, the compressors do not always operate at their set operating points; Some of them sometimes work partially in reverse mode, especially when the air flow falls below the air production capacity of the fixed compressor. This results in an unnecessary consumption of energy, which consequently results in an increase in the ratio, energy consumption per meter-cu of gas produced (specific energy)

  2 o and therefore an increase in the cost price of this cubic meter.

  In addition, this type of installation cannot be operated in an economical manner.

  than over a wide range of gas flows.

  Finally, some of the compressors are more often defective than others. The present invention aims to overcome the drawbacks mentioned, and to provide a compressed gas supply installation which is economical, in particular with regard to energy consumption. Another goal is a

  compressed gas supply system which has a low maintenance cost.

  As part of its research to achieve the above objectives, the 3rd applicant has realized that unexpectedly, it was possible to significantly improve the overall specific energy of a compressor installation by

  implementation of the device set out below.

  This is why, according to a first aspect, the subject of the invention is an installation for producing a compressed fluid, comprising: - n compressors, the discharge side of which is connected to a network of compressed fluid, n being greater than or equal to 2 - for each compressor, a first connection line with a switch allowing, individually, the establishment or [interruption of the connection of the compressor directly to the energy source, - a variable speed drive, suitable in order to vary this, the rotation speed of one of the compressors is continued as a function of a speed setpoint, and intended to be connected to the energy source, - for each of the compressors, a second connection line with a switch enabling, individually, the establishment or interruption of the connection of the compressor, via the variable speed drive, to the energy source, characterized in that it comprises: - means forming a switch, suitable for connec ter fa, con se lective, one and only one of the compressors to the variable speed drive, and ensuring the transition phases between direct connection and connection via variator, and in that: said wind switch means suitable for one at the other 2 0 of the n compressors is connected to said variator, - the compressors used in the installation object of the present invention is preferably of the "all - or - nothing" type. By compressor of the all - or nothing type, we mainly designate commercial class compressors

  in this category and more particularly screw compressors.

  The subject of the invention is in particular an installation as defined above, in which the air compressors are screw compressors, the rotational speed of which can be adjusted continuously, in a first speed range situated between a minimum speed and higher transition speed

at minimum speed.

  By compressed fluid is meant a fluid whose total pressure is greater than one atmosphere and more particularly: air, oxygen (02), nitrogen (N2), argon (Ar), dioxide carbon (CO2), carbon monoxide (CO), helium (He), nitrous oxide (N20), nitrogen monoxide (NO), mixtures of pro-nitrogen oxide and oxygen , carbon dioxide and oxygen, nitrogen and carbon monoxide, helium and oxygen, such as, for example, mixtures (50% by volume (v / v) N2O + 50% v / v 02), (5% v / v CO2, 95% v / v 02), (200 to 800 ppm NO in N2), (78% He + 22% v / v 02), (65% He + 35% 02) 80% v / v He + 20% v / v 02), mixtures of nitrogen and carbon dioxide or even gases

  refrigerants from cold stations or water vapor.

  According to a first particular aspect of the present invention, the installation

  as defined above, is a compressed air production installation.

  According to a second particular aspect of the present invention, the installation

  as defined above, includes two to six compressors.

  According to a third particular aspect of the present invention, the installation as defined above, comprises means suitable for starting the compressors one after the other via the speed controller and for stopping the compressor connected to the speed controller, when the speed reference of the compressor is located in a speed range delimited by speed 0 and the minimum speed greater than 0, and suitable for operating this compressor with the speed reference when this speed reference is greater than the minimum speed. According to a fourth particular aspect of the present invention, the installation 2 o as defined above, comprises a gas pressure sensor suitable for measuring the gas pressure prevailing in the compressed gas network, and control means suitable for controlling the switches and the means forming a switch as a function of the gas pressure measured by the pressure sensor. 2 5 According to this last particular aspect, the control means very particularly comprise means for regulating the speed setpoint continuously according to a regulation law, in particular a proportional, integral, differential law (PID; in English Proportional, Integral Differential). , eVou they wind very particularly connected to means for switching means forming com mutator, as well as to individual actuation means of each of the switches. In this case, the control means comprise exclusive connection means which are suitable for connecting a specific compressor to the variable speed drive only when the switch associated with this compressor is open and / or the control means include in particular

  selection means for selecting one of the compressors to be de-

  fed up or stopped, these selection means comprising a counter adapted to count the number of starts of each of the compressors, and means adapted to select as compressor to be started, the compressor which has the least operating time or as compressor in front of

  be stopped, the compressor with the longest operating time.

  According to a preferred mode of this particular aspect, the control means comprise a programmable automaton characterized in that it comprises a central unit, a memory and possibly means allowing its

  remote control and that it is able to function by means of a suitable prog ram

  te to regulate the variable speed drive in PID regulation mode.

  According to a fifth particular aspect of the present invention, the installation as defined above, the wind compressors connected in parallel by

  their discharge side, to a buffer reservoir of fluid compressed by means of

  diary of a first connecting pipe, said buffer tank being connected to the

  bucket of fluid compressed by a second connecting line fitted with a valve

  cutoff. The first connecting pipe is preferably provided with a filter.

  The invention also relates to a process for the production of a compressed fluid covering me the installation such as q ue defined previously, characterized in that it comprises over time, one or the other of the following operating steps: - when the pressure of the fluid in the compressed fluid network downstream of said installation is situated in a value range between a threshold of

  high pressure (hereinafter referred to as: PSH) and a low pressure threshold (desi-

  gnee hereafter by: PSL), the pressure of the fluid in said network is maintained

  in this value range by means of the compressor connects to the speed variator

  hostess; - when the pressure of the fluid in said network becomes lower than PSL for a predetermined duration, either the compressor connected to the variable speed drive is stopped, and it is in this case, started at the minimum speed; be the

  compressor connected to the variable speed drive is operated at a higher speed

  higher or equal to the minimum speed and lower than the maximum speed, and in this case its speed is brought to the maximum speed, if the compressor is connected

  the speed controller is operated at maximum speed and in this case, if the inter-

  direct connection breaker of at least one of the compressors is open, the switch means connect another compressor, the switch of which is open to the speed controller and the direct connection switch of the compressor which was previously connected to the variator is closed; - when the fluid pressure in said network becomes greater than PSH for a predetermined period, either the compressor connected to the speed controller is operated above the minimum speed, and in this case it is slowed down to the minimum speed, sot the compressor connected to the speed controller is operated at minimum speed, and in this case it is stopped, either the compressor connected to the speed controller is stopped and if the direct connection switch

  at least one of the compressors is closed, in this case open.

  According to another particular aspect of the method as defined above, it

  includes before connecting the frequency converter to one of the

  pressers, a selection step to said compressor, by which the compressor

  chosen is the one that has operated the least time over time.

  According to a last particular aspect of the process as described above.

  ment, it includes, before stopping a compressor in direct connection,

  2 o a step for selecting the compressor to be stopped, by which the compressor

  The one that has worked the longest over time.

  The process as described above is particularly suitable for

compressed air production.

  The invention will be better understood on reading the description which follows,

  2 5 given solely by way of example and made with reference to the accompanying drawings, in which: - Figure 1 is a schematic view of a compressed gas production installation according to the invention; and - Figures 2A and 2B are diagrams showing the paces of the pres

  gas over time and the corresponding regulation of a compressor.

  This installation 2 comprises compressor trots 4, 6, 8 which are connected in parallel to the inlet 10 of a buffer tank 12 of compressed gas by means of a first connecting pipe 14 provided with a filter 16. A outlet 18 of buffer tank 12 is connected to a compressed air user network (not shown) by means of a second connecting pipe 20 provided

a cutoff valve 22.

  Compressors 4, 6, 8 use lubricated screw compressors. This type of compressor allows operation within a certain range of rotational speeds. Within this range, the rotational speed can be continuously adjusted. The range is delimited by a maximum speed of rotation FMAX, 100% and a minimum speed of rotation FMIN, other than 0, which stands for example at 50% of the maximum speed of rotation FMAX. Exceptionally, compressors 4, 6, 8 can be operated, for a long stroke, at a variable speed also continuously up to a transition speed FTRA, higher than the speed

maximum FMAX.

  Below the minimum FMIN speed, the compressor 4, 6 or 8 considered must be stopped, since the lubrication of the screw is insufficient in this range of rotational speeds. The compressed air flow is substantially directly proportional to the speed of rotation. Such compressors are sold, for example, DSD 201 / 7.5 bar type compressors sold by the so

ciete KAESER.

  The installation 2 further comprises a source of electrical energy, in

  [occurrence of a three-phase power source 24.

  The installation 2 comprises trots first lines 26, 28, 30 of connection to trots firs. Each of the first connection lines 26, 28, 30 connects one of the

  compressors 4, 6, 8 at current source 24.

  Each of the first connection lines 26, 28, 30 is provided with a first switch 32, 34, 36 allowing an individual establishment or interruption of the connection between the compressors 4, 6, 8 and the current source 24. The installation 2 also includes a VAR variable speed drive connected to the current source 24 by a second connection line 44 with three steps. The variable speed drive is adapted to generate a power current whose frequency determines the speed of rotation of a compressor 4, 6, 8 connected to this VAR variator. The VAR variable speed drive is for example a variator of the type

  ATV-68 sold by the SCHNEIDER company.

  Installation 2 includes three second switches 46, 48, 50, and a third connection line 52 with three steps. The connection line 52 is subdivided into trot branches 52A, 52B, 52C, each of which connects the variable speed drive VAR to one of the compressors 4, 6, 8, in parallel with the first connection lines 26, 28, 30. Each second switches 46, 48, 50 is interposed in one of the

branches 52A, 52B, 52C.

  Each of the compressors 4, 6, 8 can therefore be connected individually

to the VAR variable speed drive.

  A gas pressure sensor 54 is located downstream of the compressors 4,

  6, 8 in the gas network, for example in the buffer tank 12.

  The installation 12 further comprises a control device, in

  The occurrence of a CMD programmable controller.

  This CMD control device comprises an inlet 56 which is connected to the pressure sensor 54 by a sensor line 58, in order to observe the pressure

  gas P established in the gas network.

  The CMD command also includes output trots 60, 62, 64 which are linked to first 66, second 68 and third 70 control lines for the first switches 32, 34, 36, and output trots 72A, 72B, 72C which are connected first 74A, second 74B and third 74C control lines of the following switches 46, 48, 50. Another output 76 of the CMD command is linked to a command line 78 of the variator VAR. The second switches 46, 48, 50 form switching means by which one of the compressors

  can be connected to the VAR variable speed drive.

  Outputs 60, 62, 64, 72A, 72B, 72C and the associated control lines 66, 68, 70, 74A, 74B, 74C are suitable for opening or closing switches 32, 34, 36, 46, 48, 50. The output 76 and the control line 78 are adapted to So to adjust the output frequency of the VAR drive. The outputs 60, 62, 64, 72A, 72B, 72C, 76 wind controlled by a central unit CPU of the CMD control according to the gas pressure P. In addition to the central unit CPU, the programmable controller CMD includes a memory MEM in which wind stores the high pressure thresholds PSH and

  low pressure PSL, and a PRG program for controlling the installation.

  In addition, the MEM memory stores, for each of the compressors 4, 6, 8, the total operating time of the associated compressor 4, 6, 8.

  The PRG program is adapted to regulate the VAR variable speed drive

  There is a regulation law, in this case in PID regulation mode when the pressure P observed is between the two pressure thresholds PSH and PSL. PID mode varies the output frequency of the drive according to the integral and

  of the difference between the actual value and the set value on an inter-

valley of predetermined time.

  The CMD control device further comprises means for

  select from the compressors whose first switch 32, 34, 36 is ou-

  green and not connected to the VAR drive, a compressor 4, 6, 8 in front

  be connected to the VAR variable speed drive according to the following condition.

  The compressor with the least total operating time.

  The PRG program implemented in the CMD command controls the first switches 32, 34, 36 and the second switches 46, 48, 50 according to an exclusive connection mode. This mode does not allow the closing of one of the second switches of a determined compressor 4, 6, 8, until the first

  switch 32, 34, 36, associated with this compressor is open.

  Furthermore, this mode does not allow the closing of one of the second inter-

  breakers 46, 48, 50 only if all the second switches 46, 48, 50 are open.

  The CMD control is furthermore provided with means for detecting one of

  2 5 bankruptcy of one of the components of the installation 2.

  These means are connected to a telephone line 80 in order to warn the

  maintenance personnel in the event of a failure.

  Figures 2A and 2B show an example of the patterns over time of the pressure P prevailing in the air network as well as of the variation of the speed.

  rotation of a compressor during operation of the installation.

  The abscissas of the two diagrams represent the time elapsed during

  fifteen phases I to XV, which are not represented on the scale.

  The ordinates of diagram 2A show the pressure P established in the re-

  air bucket and noted by the pressure sensor 54.

  The ordinates of diagram 2B indicate the rotational speed of the

  presser. On the axis of the wind ordinates marked the three determining speeds of the compressor, namely, the minimum speed FMIN (50%), the maximum speed

  (100%), as well as the FTRA transition speed (120%).

  During phase 1, the compressor is connected to the variable speed drive

  VAR and is operated under PID regulation. Due to the variation in the air flow

  prime, the rotation speed of the variable compressor is adjusted within the range between the minimum speed FMIN and the maximum speed FMAX, from

  so that the pressure P remains substantially the set pressure PREG.

  At the start of phase 11, the air demand compresses, so that the

  variable compressor is brought to its minimum FMIN speed during this phase.

  As the air flow remains falble, the pressure P rises during phase 111.

  At the end of phase 111, the pressure P reaches the high pressure threshold PSH. After

  the passage of time T5 (phase IV), during which the pressure P remains above

  above PSH, the compressor is stopped.

  During phase V, due to the decrease in the gas flow produced, the pressure P falls to the low pressure threshold PSL, and remains there for a

  time T6 (phase Vl), sufficient for the CMD command to restart the

  presser with minimum speed FMIN, after which the pressure P rises

  again up to the high pressure threshold PSH (phase Vll), and crosses this pressure

  if we. The pressure P remains above the high pressure threshold PSH and after a time T4 (phase V111), sufficient for the variable compressor to be again

  2 5 stopped, the variable compressor is then stopped.

  During phase IX, the pressure P falls below the high pressure threshold PSH before the lapse of time T7, then is below PS L. During the

  phase X, which cures time T6, the pressure P remains below the pressure threshold

  PSL low pressure and, consequently, the compressor is started at its speed

3 0 FMIN.

  Due to a large demand for gas, the pressure P remains

  below the low pressure threshold PSL during time T3 (phase Xl), and the

  compressor is set in continuous PID mode (phase Xl l) up to its maximum speed

male FMAX.

  The pressure nevertheless remains below the low pressure threshold PSL and after the delay T1 (phase X111), during phase XIV, the CMD command increases the speed of the compressor up to the transition speed FTRA, disconnected this variator compressor (DC point) and closes the switch 32, 34, 36 correspond. From the end of phase XIV, the compressor is operated in fixed mode at FMAX speed. Simultaneously with the closing of the compressor switch, the speed reference of the VAR variator is brought to 0, then another compressor is selected and is connected to the variator. Then, this compressor is started at FMIN speed. Thus, the air flow compresses product

  is increased, and consequently, the pressure P increases.

  At the end of the experiment described below, it was found that the installation according to the invention made it possible to save around 15% of energy compared to a

  installation of the state of the art.

  The specific energy is lower over a wide range of gas flows. Of

  more, this regulation leads to a falble number of starts / stops of the

  pressers, this reduces vice running times and thereby avoids

  associated energy. The service life of the compressor is increased and the

  The installation maintenance time is reduced.

  On the other hand, the installation uses only one variable speed drive or one

investment cost falble.

  Thanks to the selection process of the compressors to be stopped or started, the compressor starts are all done with the variator and the wind is distributed in a uniform manner on all the compressors, which leads to a

regular wear of these.

Claims (16)

  1. Installation for producing a compressed fluid, comprising: - n compressors whose delivery side is connected to a compressed fluid network, n being greater than or equal to 2 - for each of the compressors, a first connection line with a switch enabling, individually, the establishment or interruption of the direct compressor connection to the power source, - a speed controller, adapted to continuously vary the speed of rotation of a compressors according to a speed setpoint, and intended to be connected to the energy source, - for each of the compressors, a second connection line with a switch enabling, individually, the establishment or [' interruption of the connection of the compressor, via the speed controller, to the energy source, characterized in that it comprises: - means forming a switch, suitable for connecting in a selective manner, one and only one of the compressors to the variateu r speed, and ensuring the transition phases between direct connection and connection via variator, and enclosure: 2 0 said wind switch means adapted so that one to the other   n compressors is connected to said drive.   2. Installation as defined in claim 1, in which the wind compressors of the screw compressors whose speed of rotation can be regulated in a continuous manner in a first speed range situated between a speed   minimum and a transition speed greater than the minimum speed.   3. Installation as defined in one of claims 1 or 2, of produc compressed air.   4. Installation as defined in any one of claims 1 to 3,   characterized in that the com p makes from two to six compressors.   5. Installation as defined in any one of claims 1 to 4,   characterized in that it comprises suitable means for starting the compressors one after the other via the speed controller and stopping the compressor connected to the speed controller, when the speed setpoint of the compressor is located in one second speed range bounded by speed O and a minimum speed greater than 0, and suitable for operating this compressor with the speed reference when this speed reference is greater than the minimum speed.   6. Installation as defined in any one of claims 1 to 5,   characterized in that it comprises a gas pressure sensor adapted to measure the gas pressure prevailing in the compressed gas network, and control means suitable for controlling the switches and the switch forming means as a function of the gas pressure measured by the 1 0 pressure.   7. Installation as defined in claim 6, characterized in that the control means comprise means for regulating the set point   of continuous speed according to a regulation law.   8. Installation as defined in one of claims 6 or 7, caracteri   see in that the wind control means connected to switching means forming a switch, as well as to individual actuation means of each of the switches.   9. Installation as defined in claim 8, characterized in that the control means comprise exclusive connection means which are suitable for connecting a determined compressor to the variable speed drive only when the direct connection switch associated with this compressor is open, you have means for selecting the compressor to be started or stopped, these selection means comprising a counter adapted to count the number of starts of each of the compressors, and suitable means 2 5 for selecting as compressor to be started, the compressor which has the least operating time or as a compressor to be stopped,   the compressor with the longest operating time.   10. Installation as defined in one of claims 6 to 9, caracteri   see in that the control means comprise a programmable programmable controller comprising a central unit, a memory and possibly means allowing its remote control and which is able to operate by means of an adapted program for regulating the variable speed drive in PID regulation mode.   11. Installation as defined in one of claims 1 to 1 O. character-   see in that the wind compressors are connected in parallel by their discharge dimension-   ment, to a buffer reservoir of compressed fluid by means of a first connection pipe, said buffer reservoir being connected to the compressed fluid network by a second connection pipe provided with a cut-off valve.   12. Installation as defined in one of claims 6 to 11, character-   see in that this installation (2) comprises: - three compressors (4), (6), (8) which are connected in parallel to the inlet (10) of a buffer tank (12) of compressed gas by l 'intermediary of a first connecting line (14) provided with a filter (16), an outlet (18) of the buffer tank (12) being connected to a compressed air user network by means of a second connecting line (20) provided with a cut-off valve (22); - a three-phase power source (24); three first lines (26), (28), (30) of trot-wire connection connecting one of the compressors (4), (6), (8) to the current source (24), each of the first lines of connection (26), (28), (30) being provided with a first switch (32), (34), (36) allowing an individual establishment or interruption of the connection between the compressors (4), (6) , (8) and the current source (24); - a VAR variable speed drive connected to the current source (24) via a second connection line (44) with trots firs; - three second switches (46), (48), (50), and a third connection line (52) with trots firs, the connection line (52) being subdivided into branched trots (52A), (52B), (52C), each of which connects the VAR variable speed drive to one of the compressors (4), (6), (8), in parallel with the first connection lines (26), 2 5 (28), (30) and each of the second switches (46), (48), (50) being interposed in one of the branches (52A), (52B), (52C); - a gas pressure sensor (54) has downstream compressors (4), (6), (8) in the gas network, for example in the buffer tank (12); - a control device, in this case a CMD programmable controller comprising an input (56) connected to the pressure sensor (54) by a sensor line (58); - three outputs (60), (62), (64) connected to first (66), second (68) and three (70) control lines for the first switches (32), (34), (36), - three outputs (72A), (72B), (72C) connected to first (74A), two (74B) and three (74C) lines for controlling the second switches (46), (48), (50),   - an output (76) connected to a control line (78) of the VAR variator, the second switches (46), (48), (50) forming switching means by which one of the compressors can be connected to the variator speed control, outputs (60), (62), (64), (72A), (72B), (72C) and associated control lines (66), (68), (70), (74A ), (74B), (74C) being adapted to open or close the switches (32), (34), (36), (46), (48), (50); the output (76) and the control line (78) being adapted to adjust the output frequency of the variator VAR; the outputs (60), (62), (64), (72A), (72B), (72C), (76) being controlled by a central unit CPU of the CMD control as a function of the gas pressure P; The programmable controller CMD comprising a memory MEM in which the high pressure PSH and low pressure PSL thresholds are stored, and a pro   PRG gram of order for said installation (2).   13. Method for producing a compressed fluid using the installa   tion as defined in one of claims 1 to 12, characterized in that it   comprises, over time, one or the other of the following operating steps: - when the pressure of the fluid in the fluid network compressed downstream of said installation is situated in a value range between a pressure threshold high (hereinafter designated by: PSH) and a low pressure threshold (hereinafter designated by: PSL), the fluid pressure in said network is maintained within this value range by means of the compressor connected to the speed variator hostess; when the pressure of the fluid in said network becomes lower than PSL for a predetermined period, either the compressor connected to the variable speed drive is stopped, and it is in this case, started at the minimum speed; either the compressor connected to the variable speed drive is operated at a speed greater than or equal to the minimum speed and less than the maximum speed, and in this case its speed is brought to the maximum speed, if the compressor connected   the speed controller is operated at maximum speed and in this case, if the inter-   direct connection breaker of at least one of the compressors is open, the means forming a switch connect another compressor,   the switch is open to the speed controller and the connection switch di-   of the compressor that was previously connected to the drive is closed; - when the fluid pressure in said network becomes higher than PSH for a predetermined duration, if the compressor connected to the variable speed drive is operated above the minimum speed, and in this case it is slowed down to the minimum speed, ie the compressor connected to the speed controller is operated at minimum speed, and in this case it is stopped, if the compressor connected to the speed controller is stopped and if the direct connection switch   at least one of the compressors is closed, in this case open.   14. Method as defined in claim 13, characterized in that it comprises, prior to the connection of the speed controller to one of the compressors, a selection step for said compressor by which the compressor   selected is the one that has worked the least time over time.   15. Method as defined in claim 14, characterized in that it comprises, prior to the stopping of a compressor in direct connection, a step of selecting the compressor to be stopped, by which the compressor is selected.   2 0 is the one that has operated the longest over time.   16. Method as defined in one of claims 13 to 15 for production compressed air.