COMPRESSOR DEVICE AND METHOD FOR CONTROLLING SUCH A COMPRESSOR DEVICE

Abstract

The present invention relates to a compressor device (1) comprising: a compressor installation (2) having at least one compressor element (3a, 3b, 3c) for compressing a suctioned gas, the compressor element (3a, 3b, 3c) being driven by an electric motor (4); a heat recuperation system (6) for recuperating heat from a compressed gas resulting from the compression of the suctioned gas, the heat recuperation system (6) comprising a piping network (7) having an inlet (8) and an outlet (9) for a coolant, said piping network (7) being provided at this inlet (8) or outlet (9) with control means with a flow rate control state variable for modifying a first flow rate of the coolant in the piping network (7); and a control unit (13) which adjusts the flow rate control state variable of the control means on the basis of a drive current of the electric motor (4) or on the basis of a second flow rate of the suctioned gas such that a temperature T.sub.w,out at the outlet (9) of the piping network (7) is driven to a predefined level.

Claims

1. A compressor device, comprising a compressor installation (2) with at least one compressor element (3a, 3b, 3c) for compressing a suctioned gas, the compressor element (3a, 3b, 3c) being driven by an electric motor (4); and a heat recuperation system (6) for recuperating heat from a compressed gas resulting from the compression of the suctioned gas, the heat recuperation system (6) comprising a piping network (7) with an inlet (8) and an outlet (9) for a coolant, and the piping network (7) at the inlet (8) or outlet (9) being provided with control means having a flow rate control state variable for modifying a first flow rate of the coolant in the piping network (7), wherein the compressor device further comprises measuring means for determining an actual value for a drive current of the electric motor (4) or, respectively, a second flow rate of the suctioned gas; and the compressor device comprises a control unit (13) configured to receive the aforementioned actual value; determine, on the basis of the actual value, a desired value for the first flow rate at which a temperature T.sub.w,out of the coolant at the outlet (9) of the piping network (7) is driven to a predefined level; and, adjust the flow rate control state variable of the control means to the desired value for the first flow rate on the basis of a characteristic that provides a relationship between the flow rate control state variable of the control means and the first flow rate.

2. The compressor device according to claim 1, wherein the control means comprise an adjustable valve (12), the characteristic being a valve characteristic of the adjustable valve (12) and the flow rate control state variable being an opening position of the adjustable valve (12).

3. The compressor device according to claim 1, wherein the control unit (13) is configured so as to determine the desired value for the first flow rate on the basis of the actual value and on the basis of a relationship between the desired value for the first flow rate on the one hand, and the drive current of the electric motor (4) or the second flow rate of the suctioned gas respectively on the other hand.

4. The compressor device according to claim 3, wherein the control unit (13) is configured so as to determine the desired value for the first flow rate on the basis of the actual value and on the basis of a positive directly proportional relationship between the desired value for the first flow rate on the one hand, and the drive current of the electric motor (4) or the second flow rate of the suctioned gas respectively on the other hand.

5. The compressor device according to claim 1, wherein the compressor installation (2) is a multistage compressor installation having multiple compressor elements (3a, 3b, 3c).

6. The compressor device according to claim 5, wherein the compressor elements (3a, 3b, 3c) are driven by the electric motor (4).

7. The compressor device according to claim 5, wherein the compressor device (2) is a multistage compressor installation with multiple consecutive compressor elements (3a, 3b, 3c), wherein the consecutive compressor elements (3a, 3b, 3c) are in fluid connection with each other by means of a pipe (5) for the gas, in which pipe (5) between the consecutive compressor elements (3a, 3b, 3c) one or more intercoolers (10a, 10b) are incorporated for cooling the gas.

8. The compressor device according to claim 7, wherein the aforementioned intercoolers (10a, 10b) are mutually incorporated in parallel between the inlet (8) and the outlet (9) in the piping network (7).

9. The compressor device according to claim 7, wherein the aforementioned intercoolers (10a, 10b) are mutually incorporated in series between the inlet (8) and the outlet (9) in the piping network (7).

10. The compressor device according to claim 7, wherein downstream from the multistage compressor installation an aftercooler (11) for cooling the compressed gas is provided, the aftercooler (11) being incorporated in the piping network (7) between the inlet (8) and outlet (9) in series with respect to the intercoolers (10a, 10b).

11. The compressor device according to claim 7, wherein the multistage compressor installation comprises at least three consecutive compressor elements (3a, 3b, 3c) and, in the pipe (5) between each two directly consecutive compressor elements (3a, 3b; 3b, 3c) of these three consecutive compressor elements (3a, 3b, 3c), comprises at least one intercooler (10a, 10b).

12. The compressor device according to claim 7, wherein the multiple consecutive compressor elements (3a, 3b, 3c) are turbocompressor elements.

13. The compressor device according to claim 1, wherein the coolant is water.

14. The compressor device according to claim 1, wherein the compressor device incorporates a memory unit for storing corresponding reference values for, on the one hand, the flow rate control state variable of the control means and, on the other hand, the drive current of the electric motor (4) or the second flow rate of the suctioned gas at which the temperature T.sub.w,out at the outlet (9) of the piping network (7) is driven to the predefined level.

15. A heat recuperation system for use in a compressor device according to claim 1.

16. A method for controlling a compressor device, the compressor device comprising a compressor installation (2) having at least one compressor element (3a, 3b, 3c) for compressing a suctioned gas, the compressor element (3a, 3b, 3c) being driven by an electric motor (4); and a heat recuperation system (6) for recuperating heat from a compressed gas resulting from the compression of the suctioned gas, the heat recuperation system (6) comprising a piping network (7) having an inlet (8) and an outlet (9) for a coolant, and the piping network (7) at the inlet (8) or outlet (9) being provided with control means having a flow rate control state variable for modifying a first flow rate of the coolant in the piping network (7), wherein the method comprises the following steps: determining an actual value for a drive current of the electric motor (4) or a second flow rate of the suctioned gas respectively; determining a desired value for the first flow rate at which the coolant temperature T.sub.w,out at the the outlet (9) of the piping network (7) is driven to a predefined level on the basis of the aforementioned actual value; and adapting the flow rate control state variable of the control means to the desired value for the first flow rate on the basis of a characteristic which provides a relationship between the flow rate control state variable of the control means and the first flow rate.

17. The method according to claim 16, wherein the control means comprise an adjustable valve (12), the characteristic being a valve characteristic of the adjustable valve (12) and the flow rate control state variable being an opening position of the adjustable valve (12).

18. The method according to claim 16, wherein the desired value for the first flow rate is determined on the basis of the actual value and on the basis of a relationship between the desired value for the first flow rate on the one hand and the drive current of the electric motor (4) or the second flow rate of the suctioned gas respectively on the other hand.

19. The method according to claim 18, wherein the desired value for the first flow rate is determined on the basis of the actual value and on the basis of a positive directly proportional relationship between the desired value for the first flow rate on the one hand and the driving current of the electric motor (4) or the second flow rate of the suctioned gas respectively on the other hand.

20. The method according to claim 16, wherein the aforementioned predefined level lies between 60° C. and 90° C.

21. The method according to claim 16, wherein a temperature of the coolant at the inlet (8) of the piping network (7) lies between 5° C. and 35° C.

22. The method according to claim 16, wherein, when the electric motor (4) is driven with a certain reference drive current, or, respectively, when the compressor plant (2) suctions a certain reference flow rate of the gas, an initial reference value for the flow rate control state variable of the control means is stored when the temperature T.sub.w,out of the coolant at the outlet (9) of the piping network (7) remains within a first predefined maximum absolute deviation with respect to the predefined level during a first predefined period.

23. The method according to claim 22, wherein the first predefined period is at least 60 seconds.

24. The method according to claim 22, wherein the first predefined maximum absolute deviation is maximally 1.0° C.

25. The method according to claim 22, wherein the initial reference value for the flow rate control state variable of the control means is updated to a new reference value at predefined moments of time when, on the one hand, the temperature T.sub.w,out of the coolant at the outlet (9) of the piping network (7) remains within a second predefined maximum absolute deviation with respect to the predefined level for a second predefined period; and, on the other hand, during the second predefined period, the drive current remains within a predefined maximum absolute relative deviation with respect to the reference drive current or, respectively, the second flow rate remains within the predefined maximum absolute relative deviation with respect to the reference flow rate.

26. The method according to claim 25, wherein the second predefined period is at least 60 seconds.

27. The method according to claim 25, wherein the second predefined maximum absolute deviation is maximally 0.8° C.

28. The method according to claim 25, wherein the predefined maximum absolute relative deviation is maximally 5.0%.

Description

[0074] Hereafter, with the understanding to better demonstrate the characteristics of the invention, some preferred embodiments of a compressor device according to the invention and a method for controlling such a compressor device according to the invention are described with reference to the accompanying drawings, in which:

[0075] FIG. 1 schematically shows a compressor device according to the invention;

[0076] FIG. 2a schematically shows a heat recuperation system of the compressor device in FIG. 1;

[0077] FIG. 2b schematically shows a first variant of the heat recuperation system in FIG. 2a;

[0078] FIG. 2c schematically shows a second variant of the heat recuperation system in FIG. 2a;

[0079] FIG. 2d schematically shows a third variant of the heat recuperation system in FIG. 2a;

[0080] FIGS. 3a and 3b show a functional relationship between a relative change of the drive current, of the second flow rate of suctioned gas and of a required desired first flow rate by the adjustable valve on the one hand, and a measure for load conditions of the compressor device in FIG. 1 on the other hand.

[0081] FIG. 1 schematically represents a compressor device 1 according to the invention.

[0082] The compressor device 1 comprises a compressor installation 2, in this case a multistage compressor installation with three consecutive compressor elements 3a, 3b, 3c, in which gas sucked in by said compressor installation 2 is increasingly compressed.

[0083] Within the scope of the invention it is not excluded that said compressor installation 2 comprises another number of compressor elements.

[0084] In this case, the compressor elements 3a, 3b, 3c are turbocompressor elements.

[0085] The plurality of consecutive compressor elements 3a, 3b, 3c are driven by an electric motor 4 and are in fluid communication with each other by means of a pipe 5 for the gas.

[0086] At an inlet of a downstream first compressor element 3a, inlet vanes are provided which, upon being less or more closed, increase or decrease a second flow rate of the suctioned gas.

[0087] The compressor device 1 further comprises a heat recuperation system 6 for recuperating heat from the compressed suctioned gas.

[0088] This heat recuperation system 6 comprises a piping network 7 having an inlet 8 and an outlet 9 for a coolant.

[0089] Water, for example, can be used for the coolant, because of a relatively high specific heat capacity and relatively low-corrosive properties of water.

[0090] In the pipe 5, between each two directly consecutive compressor elements 3a, 3b and 3b, 3c, an intercooler 10a, 10b is incorporated for cooling the gas by means of heat exchange with the coolant in the piping network 7.

[0091] Besides the intercoolers 10a, 10b, downstream from the compressor installation 2, an aftercooler 11 is provided for cooling the gas compressed by a downstream last of the consecutive compressor elements 3a, 3b, 3c by means of heat exchange with the coolant.

[0092] The heat exchange between the coolant and the gas is controlled on the basis of a first flow rate of the coolant in the piping network 7 by means of an adjustable valve 12 provided at the outlet 9 of the piping network 7.

[0093] Within the scope of the invention, it is not excluded that the adjustable valve 12 is provided at the inlet 8 of the piping network 7.

[0094] Within the scope of the invention, it is also not excluded that other control means are applied for modifying the first coolant flow rate in the piping network 7, as, for example, an adjustable pump.

[0095] An opening position of the adjustable valve 12 is driven by a control unit 13 in such a way that a temperature T.sub.w,out at the outlet 9 of the piping network 7 can be driven to a predefined level.

[0096] The temperature T.sub.w,out at the outlet 9 is measured by means of a temperature sensor 14 provided at the outlet 9 of the piping network 7.

[0097] In this case, the control unit 13 receives a signal with information regarding an actual value for a drive current of the electric motor 4. Said actual value is determined in this case by means of an ammeter 15.

[0098] Based on this signal, the opening position of the adjustable valve 12 is controlled during operation of the compressor device 1.

[0099] Within the scope of the invention, the control unit 13 can alternatively or additionally receive a signal with information about an actual value for the second flow rate of the suctioned gas.

[0100] Measuring devices for directly determining the actual value of this second flow rate can be provided at the entry of the first compressor element 3a.

[0101] This actual value for the second flow rate of the suctioned gas can also be determined indirectly by means of measuring devices positioned further downstream for measuring a gas flow rate in the compressor installation 2 downstream of the entry of the first compressor element 3a. This measured gas flow rate then still has to be converted in terms of the second flow rate of the suctioned gas on the basis of the pressure ratios over the compressor elements upstream of the measuring devices positioned further downstream.

[0102] FIG. 2a schematically represents the heat recuperation system 6 of the compressor device 1 in FIG. 1.

[0103] The intercoolers 10a, 10b are incorporated mutually parallel between the inlet 8 and the outlet 9 in the piping network 7.

[0104] The aftercooler 11 is incorporated in the piping network 7 between the inlet 8 and the outlet 9 in series with respect to the intercoolers 10a, 10b.

[0105] FIG. 2b schematically represents a first variant of the heat recuperation system 6 in FIG. 2a.

[0106] The intercoolers 10a, 10b in this first variant are arranged mutually in series between the inlet 8 and the outlet 9 in the piping network 7.

[0107] Here too, the aftercooler 11 is incorporated between the inlet 8 and the outlet 9 in series with respect to the intercoolers 10a, 10b in the piping network 7.

[0108] FIG. 2c schematically represents a second variant of the heat recuperation system 6 in FIG. 2a.

[0109] Here too, the intermediate coolers 10a, 10b are mutually incorporated in parallel between the inlet 8 and the outlet 9 in the pipe network 7.

[0110] No aftercooler is incorporated in this second variant, however.

[0111] FIG. 2d schematically represents a third variant of the heat recuperation system 6 in FIG. 2a.

[0112] In this third variant, the intercoolers 10a, 10b are mutually incorporated in series between the inlet 8 and the outlet 9 in the piping network 7.

[0113] In this third variant, an aftercooler is also not incorporated.

[0114] It is not excluded within the scope of the invention that the heat recuperation system 6 comprises more than two intercoolers mutually incorporated in series and/or parallel between the inlet 8 and the outlet 9 in the piping network 7, whether or not with an aftercooler 11 incorporated in series with respect to the intercoolers in the piping network 7.

Example

[0115] In FIG. 3a, functional relationships are illustrated for the compressor device 1 in FIG. 1 between [0116] a closure ratio (IGV) of the inlet vanes provided at the entry of the first compressor element 3a on the one hand; and [0117] on the other hand, with respect to a required drive current at an inlet vane closure ratio of 75%, a relative percentage change in the drive current, represented by means of triangle symbols;
with respect to a value for the second flow rate of suctioned gas at an inlet vane closure ratio of 75%, a relative percentage change in the second flow rate of suctioned gas, represented by means of square symbols; and,
with respect to a desired value for the first flow rate through the adjustable valve 12 at an inlet vane closure ratio of 75%, a relative percentage change in the desired value for the first flow rate that should flow through the adjustable valve 12 to drive the temperature T.sub.w,out of the coolant at the outlet 9 of the piping network 7 to a predefined level, represented by means of circle symbols.

[0118] The aforementioned relative percentage change in the drive current, the second flow rate of the suctioned gas and the desired value for the first flow rate by the adjustable valve 12 are measured at values for the closure ratios of 0%, 15%, 25%, 35%, 50% and 100%.

[0119] An increase in the closing ratio of the inlet vanes at the entry of the first compressor element 3a corresponds to a reduction in the second flow rate of the gas suctioned by the compressor device 1 and, consequently, a reduction in the load conditions of the compressor device 1.

[0120] In particular, when the value of the closing ratio is equal to 0%, the compressor device 1 operates at a maximum second flow rate of suctioned gas and thus maximum load conditions.

[0121] When the value of the closing ratio is equal to 100%, the compressor device 1 operates at a zero flow rate of suctioned gas and thus minimum load conditions.

[0122] The temperature of the coolant at the inlet 8 of the piping network 7 is 25° C.

[0123] The predefined level for the temperature T.sub.w,out of the coolant at the outlet 9 is fixed at a temperature of 70° C., 80° C. or 90° C.

[0124] Each of the functional relationships in FIG. 3a corresponds to one of these temperature values, as indicated.

[0125] From the functional relationships in FIG. 3a, it can be concluded that there is a positive directly proportional relationship between, on the one hand, the drive current or the second flow rate of the suctioned gas respectively, and, on the other hand, the desired value of the first flow rate that should flow through the adjustable valve 12 to drive the temperature T.sub.w,out of the coolant at the outlet 9 of the piping network 7 to a predefined level.

[0126] FIG. 3b shows the functional relationships as in FIG. 3a, but for a temperature of the coolant at the inlet 8 of the piping network 7 that is 35° C.

[0127] To determine a proportionality constant of the aforementioned positive directly proportional relationship, an initial reference value for the opening position of the adjustable valve 12 at a reference drive current or a reference flow rate of the suctioned gas, respectively, can be determined.

[0128] In order to obtain a reliable initial reference value, the temperature T.sub.w,out of the coolant at the outlet 9 of the piping network 7 must remain within a first predefined maximum absolute deviation with respect to the predefined level during a first predefined period.

[0129] Preferably, the first predefined period should be at least 60 seconds.

[0130] Preferably, the first predefined maximum absolute deviation should be maximally 1.0° C.

[0131] The initial reference value for the opening position of the adjustable valve 12 can be updated to a new reference value at predefined moments of time, when: [0132] on the one hand, the temperature T.sub.w,out of the coolant at the outlet 9 of the piping network 7 remains within a second predefined maximum absolute deviation with respect to the predefined level during a second predefined time; and [0133] on the other hand, during the second predefined period, the drive current remains within a predefined maximum absolute relative deviation with respect to the reference drive current or, respectively, the second flow rate remains within the predefined maximum absolute relative deviation with respect to the reference flow rate.

[0134] Preferably, the second predefined period is at least 60 seconds.

[0135] Preferably, the second predefined maximum absolute deviation is maximally 0.8° C.

[0136] Preferably, the predefined maximum absolute relative deviation is maximally 5.0° C.

[0137] The positive directly proportional relationship between the drive current or the second flow rate of suctioned gas respectively on the one hand, and the desired value of the first flow rate on the other hand, can be used to control the opening position of the adjustable valve 12 based on the valve characteristic in the event of large relative changes of the drive current or the second flow rate of suctioned gas respectively.

[0138] In this context, ‘large relative changes’ means relative changes in the drive current or the second flow rate of the suctioned gas respectively which are outside twice the predefined maximum absolute relative deviation with respect to the reference drive current or the reference flow rate respectively.

[0139] For small relative changes of the drive current or, respectively, the second flow rate of the suctioned gas that fall within twice the aforementioned predefined maximum absolute relative deviation, the opening position of the adjustable valve 12 can alternatively also be controlled by means of a simple classical PI control unit based on the temperature T.sub.w,out at the outlet 9 of the piping network 7.

[0140] The present invention is by no means limited to the embodiments described as examples and shown in the figures, but a compressor device according to the invention can be implemented in all kinds of variants without departing from the scope of the invention as defined in the claims.