Compressor device, heat recovery system, and control method for compressor device

Abstract

The invention relates to a compressor arrangement (1) comprising a compressor installation (2) having at least one compressor element (3a, 3b, 3c) for compressing a suction gas, driven by an electric motor (4); and a heat recovery system (6) for recovering heat from the compressed gas resulting from the compression of the suction gas, the heat recovery system (6) comprising a piping network (7) having an inlet (8) and an outlet (9) for a coolant, the piping network (7) comprising control means having a flow control state variable for varying a first flow rate of the coolant in the piping network (7) at the inlet (8) or at the outlet (9), the compressor arrangement (1) controlling a temperature T w、out The present invention further includes a control unit (13) that adjusts a flow rate control state variable of the control means based on a drive current of the electric motor (4) or based on a second flow rate of the suction gas so as to set

Description

[Technical field]

[0001] The present invention relates to a compressor arrangement comprising a compressor installation having at least one compressor element for compressing a suction gas and a heat recovery system for recovering heat from the compressed gas resulting from the compression of the suction gas.

[0002] More specifically, the present invention relates to The compressor element is driven by an electric motor, the heat recovery system comprises a piping network having an inlet and an outlet for a coolant, the piping network also comprising control means having a flow control state variable at the inlet or outlet for modifying a first flow rate of the coolant in the piping network, the compressor device also includes a control unit for adjusting a flow control state variable of the control means based on a drive current of the electric motor or a second flow rate of the suction gas, respectively, so that the temperature of the coolant at the outlet of the piping network is at a predetermined level; Regarding the compressor device.

[0003] A "first flow rate" or a "second flow rate" is always understood within the scope of the present invention to mean a volumetric flow rate.

[0004] In this context, the "first flow rate of the coolant in the piping network" refers to the total coolant flow rate of the coolant in the piping network, and the "second flow rate of the suction gas" refers to the total gas flow rate of the suction gas. [Background technology]

[0005] Conventionally, compressor installations are known which comprise, on the one hand, a compressor installation in which a suction gas is compressed by a compressor element and, on the other hand, a heat recovery system for recovering heat generated in the compressor installation.

[0006] This heat is primarily generated as heat of compression inside the compressor element where the suction gas is compressed, in the motor driving this compressor element, and / or in the bearings of the compressor unit.

[0007] If the compressor arrangement comprises only a single compressor element, the heat of compression is extracted, for example, by an aftercooler in fluid communication with the outlet of the compressor element for the compressed gas resulting from the compression of the suction gas.

[0008] If the compressor installation comprises a number of successive compressor elements which are in fluid communication with one another by a pipeline for gas, the heat of compression is extracted, for example, by one or more intercoolers contained in the pipeline and / or by an aftercooler which is in fluid communication with the outlet of the last of the successive compressor elements.

[0009] The one or more intercoolers and / or aftercoolers comprise a coolant for extracting the heat of compression from the gas by means of a cooling circuit, in this connection the coolant can be heated to a predetermined temperature.

[0010] Additionally, the motor and / or bearings of the compressor installation are typically cooled using the same cooling circuit.

[0011] In recent years, rather than simply dissipating the heat absorbed by the refrigerant to the surroundings of the compressor plant, there has been a growing trend to utilize the heated refrigerant for various applications, such as, for example, heating a building or preheating a fluid stream in an industrial process.

[0012] To do this, the temperature of the heated coolant needs to be at a particular pre-set level with a particular level of accuracy.

[0013] The more components of a compressor plant that are cooled using a refrigeration circuit, the more difficult and less stable it becomes to control the temperature of the heated refrigerant.

[0014] Additionally, the control must also take into account changing load conditions of the compressor plant: the lower / higher the load conditions, the less / more heat of compression will be generated in a given period and the less / more heat will be absorbed by the refrigerant during that time.

[0015] The effect of low / high load conditions is typically countered by decreasing / increasing the coolant flow rate in the cooling circuit via an adjustable valve in the cooling circuit.

[0016] Conventionally, the control of this adjustable valve is based on a flow meter in the cooling circuit, however, such flow meters have the disadvantage that they are expensive. Summary of the Invention [Problem to be solved by the invention]

[0017] The present invention aims to provide a solution to at least one of the above mentioned and / or other disadvantages. [Means for solving the problem]

[0018] Therefore, the object of the invention is a compressor arrangement, comprising: a compressor installation having at least one compressor element for compressing the suction gas, the compressor element being driven by an electric motor; a heat recovery system for recovering heat from compressed gas resulting from the compression of the suction gas; Equipped with the heat recovery system includes a piping network having an inlet and an outlet for a coolant; the piping network includes a control means having a flow control state variable for varying a first flow rate of the coolant through the piping network at the inlet or outlet; The compressor arrangement further comprises measuring means for determining an actual value of the driving current of the electric motor or of the second flow rate of the suction gas, respectively; The compressor device is -Receive the actual value, -The temperature of the coolant at the outlet of the piping network T based on the actual value w、out determining a first flow rate target value that brings - adjusting the target value to the first flow rate based on a characteristic representative of a relationship between a flow control state variable of the control means and the first flow rate; The control unit is configured to:

[0019] The advantage is that by determining a target value for the first flow rate based on the driving current of the electric motor or the second flow rate of the suction gas, respectively, and adjusting the flow control state variable based on the characteristic, the piping network of the heat recovery system does not require a flow meter to drive the flow control state variable.

[0020] In a preferred embodiment of the compressor arrangement according to the invention, the control means comprises an adjustable valve, the characteristic is a valve characteristic of the adjustable valve and the flow control state variable is an opening position of the adjustable valve.

[0021] The advantage of such adjustable valves is that they can be controlled in a simple and inexpensive way and can be installed at the inlet or outlet of a piping network.

[0022] In a further preferred embodiment of the compressor arrangement of the invention, the control unit is configured to determine the setpoint value of the first flow rate based on the actual value and on the relationship between the setpoint value of the first flow rate, on the one hand, and the driving current of the electric motor or the second flow rate of the suction gas, respectively, on the other hand.

[0023] In a further preferred embodiment of the compressor arrangement of the present invention, the control unit is configured to determine the setpoint value of the first flow rate based on the actual value and on a direct proportional relationship between the setpoint value of the first flow rate, on the one hand, and the driving current of the electric motor or the second flow rate of the suction gas, respectively, on the other hand.

[0024] Such a direct proportional relationship forms a basic mathematical function that allows the first flow rate target value to be determined quickly and easily without requiring an excessive amount of computing power from the control unit.

[0025] In a further preferred embodiment of the compressor arrangement of the present invention, the compressor installation is a multi-stage compressor installation having a plurality of compressor elements.

[0026] Multi-stage compressor installations are interesting for heat recovery because the pressure ratio between input and output is generally relatively large compared to that of compressor installations with only one compressor element, and therefore the heat of compression generated is also relatively large, allowing the refrigerant in the heat recovery system to be heated to a relatively high temperature, which may be the requirement of a particular consumer of the recovered heat of compression.

[0027] In a more preferred embodiment of the compressor unit according to the invention, the compressor elements are driven by an electric motor.

[0028] By driving all compressor elements with one and the same electric motor, only one actual value of the drive current needs to be determined, limiting the costs of the measuring device.

[0029] Furthermore, the control unit only needs to receive one actual value for the drive current, which makes it possible to avoid complex control algorithms and the associated excessive computing power of the control unit.

[0030] In a further preferred embodiment of the compressor arrangement according to the invention, the compressor installation is a multi-stage compressor installation having a plurality of successive compressor elements in fluid communication with one another by piping for the gas, the piping between the successive compressor elements incorporating one or more intercoolers for cooling the gas.

[0031] The above intercoolers are installed in parallel or in series between the inlet and outlet of the piping network.

[0032] In a further preferred embodiment of the compressor arrangement according to the invention, an aftercooler for cooling the compressed gas is provided downstream of the multi-stage compressor installation, which is integrated in series with the intercooler between the inlet and the outlet of the piping network.

[0033] As a result, the heat of compression generated in the final compressor element of a multi-stage compressor installation is also used to heat the refrigerant in the piping network.

[0034] In a further preferred embodiment of the compressor arrangement according to the invention, the multi-stage compressor installation comprises at least three successive compressor elements and at least one intercooler provided in a piping between two directly successive compressor elements of the three successive compressor elements.

[0035] Such a compressor unit has at least two intercoolers and, as a result, can potentially recover more heat of compression via a heat recovery system than a compressor unit having only one intercooler.

[0036] In a further preferred embodiment of the compressor arrangement according to the invention, the compressor arrangement comprises a memory unit for storing, on the one hand, flow control state variables of the control means and, on the other hand, corresponding reference values ​​for the driving current of the electric motor or the second flow rate of the suction gas, at which the temperature of the coolant is brought to a preset level at the outlet of the piping network.

[0037] These reference values ​​then serve to determine a target value for the first flow rate based on the actual value.

[0038] Based on this pair of reference values, which correspond respectively to the flow control state variable of the control means on the one hand and the drive current of the electric motor or the second flow rate of the suction gas on the other hand, one or more parameters related respectively to the target value of the first flow rate on the one hand and the drive current of the electric motor or the second flow rate of the suction gas on the other hand can also be determined by characteristics.

[0039] In a positive proportional relationship, for example, a proportionality constant can be determined.

[0040] When the load conditions of the compressor installation, and consequently the driving current of the electric motor and the second flow rate of the suction gas change, the associated required change in the first flow rate of the coolant can be calculated to bring the temperature of the coolant at the outlet of the piping network to a preset level based on the above-mentioned positive proportional relationship with a determined proportionality constant.

[0041] An associated change in a flow control state variable of the control means may then be calculated using the characteristic based on said required change in the first flow rate of the coolant.

[0042] The invention also relates to a heat recovery system for use in a compressor unit according to one of the above embodiments.

[0043] It goes without saying that such a heat recovery system has the same advantages as the above-described embodiment of the compressor arrangement according to the invention.

[0044] Finally, the present invention also relates to a method for controlling a compressor arrangement, comprising: The compressor device is a compressor installation having at least one compressor element for compressing the suction gas, the compressor element being driven by an electric motor; a heat recovery system for recovering heat from compressed gas resulting from the compression of the suction gas; the heat recovery system comprises a piping network having an inlet and an outlet for a coolant, the piping network comprising a control means having a flow control state variable for varying a first flow rate of the coolant in the piping network at the inlet or the outlet; The method comprises: - determining an actual value of the drive current of the electric motor or of a second flow rate of suction gas, respectively; -The temperature of the coolant at the outlet of the piping network T based on the actual value w、out determining a first flow rate target value that provides a predetermined level; - adapting a flow control state variable of the control means to a target value of the first flow rate based on a characteristic describing a relationship between the flow control state variable of the control means and the first flow rate; Includes.

[0045] It goes without saying that this method has the same advantages as the above-described compressor arrangement according to the invention.

[0046] In a preferred embodiment of the method according to the invention, said preset level is between 60°C and 90°C.

[0047] This temperature level is often required by the consumer of the heat recovered from the compressed gas by the heat recovery system.

[0048] In a further preferred embodiment of the method according to the invention, the temperature of the coolant at the inlet to the pipeline is between 5°C and 35°C.

[0049] The lower the temperature of the coolant at the inlet, the faster and greater the heat exchange between the coolant and the compressed gas.

[0050] The temperature of the coolant at this inlet must of course not be selected to be so low that it freezes before it has absorbed heat from the compressed gas, which would cause blockage of the piping network and therefore failure of the heat recovery system.

[0051] In a preferred embodiment of the method according to the invention, when the electric motor is driven with a predetermined reference drive current or when the compressor installation draws in a predetermined reference flow rate of suction gas, respectively, the initial reference value of the flow control state variable of the control means is stored when the temperature of the coolant at the outlet of the piping network remains within a first preset maximum absolute deviation with respect to a preset level during a first preset period of time.

[0052] In this context, "maximum absolute deviation" means that even if the maximum absolute deviation is expressed as a maximum positive deviation, the maximum absolute deviation represents the maximum negative deviation in addition to the maximum positive deviation.

[0053] Based on the initial reference value of the flow control state variable of this control means and the reference drive current or the reference flow rate, respectively, a proportionality constant for the direct proportional relationship between, for example, the target value of the first flow rate, on the one hand, and the drive current of the electric motor or the second flow rate of the suction gas, respectively, on the other hand, can be determined by characteristics.

[0054] When the load conditions of the compressor installation, and consequently the driving current of the electric motor and the second flow rate of the suction gas change, the associated required change in the first flow rate of the coolant can be calculated to bring the temperature of the coolant at the outlet of the piping network to a preset level based on the above-mentioned positive proportional relationship with a determined proportionality constant.

[0055] An associated change in a flow control state variable of the control means may then be calculated using the characteristic based on said required change in the first flow rate of the coolant.

[0056] Preferably, the initial reference value of the flow control state variable of the control means is on the one hand, if the temperature of the coolant at the outlet of the piping network remains within a second preset maximum absolute deviation with respect to the preset level for a second preset period of time, and on the other hand, if the drive current remains within a preset maximum absolute relative deviation with respect to the reference drive current for a second preset period or if the second flow rate remains within a preset maximum absolute relative deviation with respect to the reference flow rate, respectively; The new reference value is updated at a preset instant.

[0057] As a result, the control of the control means becomes more accurate, for example by more accurately determining the proportionality constant.

[0058] In this context, "maximum relative deviation" means that the maximum deviation is expressed as a relative percentage proportion of the parameter to which the maximum deviation applies.

[0059] In order to better illustrate the features of the present invention, some preferred embodiments of a compressor arrangement according to the invention and a method for controlling such a compressor arrangement according to the invention will now be described with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0060] [Figure 1]The compressor device according to the present invention is schematically shown. [Figure 2a] Fig. 1 schematically shows the heat recovery system of the compressor device. [Figure 2b] Fig. 2a schematically shows a first modification of the heat recovery system. [Figure 2c] Fig. 2a schematically shows a second modification of the heat recovery system. [Figure 2d] Fig. 2a schematically shows a third modification of the heat recovery system. [Figure 3a] On the one hand, the relative change in the drive current, the relative change in the second flow rate of the suction gas, and the relative change in the desired first flow rate required by the adjustable valve are shown, and on the other hand, the function relationship with the degree of the load state of the compressor device of Fig. 1 is shown. [Figure 3b] On the one hand, the relative change in the drive current, the relative change in the second flow rate of the suction gas, and the relative change in the desired first flow rate required by the adjustable valve are shown, and on the other hand, the function relationship with the degree of the load state of the compressor device of Fig. 1 is shown.

Mode for Carrying Out the Invention

[0061] Fig. 1 schematically shows the compressor device 1 according to the present invention.

[0062] The compressor device 1 includes a compressor facility 2, in this case, a multistage compressor facility having three consecutive compressor elements 3a, 3b, 3c, and the gas sucked into the compressor facility 2 is gradually compressed.

[0063] Within the scope of the present invention, it is not excluded that the compressor facility 2 includes a different number of compressor elements.

[0064] In this case, the compressor elements 3a, 3b, 3c are turbo compressor elements.

[0065] The plurality of consecutive compressor elements 3a, 3b, 3c are driven by an electric motor 4 and are in fluid communication with each other through a pipe 5 for gas.

[0066] The inlet of the downstream first compressor element 3a is provided with inlet vanes which, when closed less or more, increase or decrease the second flow rate of suction gas.

[0067] The compressor arrangement 1 further comprises a heat recovery system 6 for recovering heat from the compressed suction gas.

[0068] The heat recovery system 6 comprises a piping network 7 having a coolant inlet 8 and outlet 9 .

[0069] For example, water may be used as the coolant due to its relatively high specific heat capacity and relatively low corrosiveness.

[0070] In the piping 5, between each two directly successive compressor elements 3a, 3b and 3b, 3c, intercoolers 10a, 10b are installed for cooling the gas by heat exchange with the coolant in the piping network 7.

[0071] In addition to the intercoolers 10a, 10b, an aftercooler 11 is provided downstream of the compressor installation 2 for cooling the gas compressed near the downstream rearmost of the successive compressor elements 3a, 3b, 3c by heat exchange with a coolant.

[0072] The heat exchange between the coolant and the gas is controlled based on a first flow rate of the coolant in the piping network 7 by an adjustable valve 12 provided at the outlet 9 of the piping network 7 .

[0073] Within the scope of the invention, it is not excluded that an adjustable valve 12 is provided at the inlet 8 of the pipeline network 7 .

[0074] Within the scope of the invention, it is not excluded that other control means are applied to vary the first flow rate of the coolant in the piping network 7, such as, for example, an adjustable pump.

[0075] The opening position of the adjustable valve 12 is determined by the temperature T w、outis driven by the control unit 13 so that the

[0076] Temperature T at outlet 9 w、out is measured by a temperature sensor 14 provided at the outlet 9 of the piping network 7.

[0077] In this case, the control unit 13 receives a signal which contains information about the actual value of the drive current of the electric motor 4. This actual value is determined in this case by an ammeter 15.

[0078] Based on this signal, the opening position of the adjustable valve 12 is controlled during operation of the compressor arrangement 1 .

[0079] Within the scope of the present invention, the control unit 13 can alternatively or additionally receive a signal comprising information regarding the actual value of the second flow rate of suction gas.

[0080] A measuring device for directly determining the actual value of this second flow rate can be provided at the inlet of the first compressor element 3a.

[0081] The actual value of this second flow rate of suction gas can also be determined indirectly by a measuring device arranged further downstream to measure the gas flow rate of the compressor installation 2 downstream of the inlet of the first compressor element 3a, which measured gas flow rate has to be further converted in relation to the second flow rate of suction gas based on the pressure ratio of the measuring device arranged further downstream to the upstream compressor element.

[0082] FIG. 2a shows diagrammatically a heat recovery system 6 of the compressor arrangement 1 of FIG.

[0083] The intercoolers 10 a , 10 b are installed in parallel with each other in the piping network 7 between the inlet 8 and the outlet 9 .

[0084] An aftercooler 11 is installed in the piping network 7 between the inlet 8 and the outlet 9 in series with the intercoolers 10a, 10b.

[0085] FIG. 2b shows diagrammatically a first variant of the heat recovery system 6 of FIG. 2a.

[0086] The intercoolers 10a, 10b in this first modified example are arranged in series with each other in the piping network 7 between the inlet 8 and the outlet 9.

[0087] Again, an aftercooler 11 is installed in series with the intercoolers 10a, 10b within the piping network 7 between the inlet 8 and the outlet 9.

[0088] FIG. 2c shows diagrammatically a second variant of the heat recovery system 6 of FIG. 2a.

[0089] Here too, the intermediate coolers 10 a , 10 b are installed in parallel with one another in the piping network 7 between the inlet 8 and the outlet 9 .

[0090] However, in this second variant, no aftercooler is incorporated.

[0091] FIG. 2d shows diagrammatically a third variant of the heat recovery system 6 of FIG. 2a.

[0092] In this third variant, the intercoolers 10a, 10b are installed in series with one another in the piping network 7 between the inlet 8 and the outlet 9.

[0093] In this third variant, no aftercooler is installed.

[0094] Within the scope of the present invention, it is not excluded that the heat recovery system 6 comprises three or more intercoolers integrated with each other in series and / or parallel between the inlet 8 and the outlet 9 in the piping network 7, regardless of whether or not it comprises an aftercooler 11 integrated in series with the intercoolers in the piping network 7. EXAMPLES

[0095] In FIG. 3a, for the compressor device 1 of FIG. on the one hand the closing ratio of the inlet vanes (IGV) provided at the inlet of the first compressor element 3a; on the other hand, the relative rate of change of the drive current with respect to the required drive current at an inlet vane closure ratio of 75% (represented by a triangular symbol); the relative rate of change of the second flow rate of the suction gas with respect to the value of the second flow rate of the suction gas with an inlet vane closure ratio of 75% (represented by a square symbol); the temperature T of the coolant at the outlet 9 of the pipe network 7 with respect to the set value of the first flow rate through the adjustable valve 12 with an inlet vane closure ratio of 75% w、out 1. The functional relationship between the relative rate of change (represented by the circular symbol) of the target value of the first flow rate that needs to flow through the adjustable valve 12 to bring the flow rate to a preset level is shown.

[0096] The relative rates of change of the target values ​​of the drive current, the second flow rate of suction gas, and the first flow rate through the adjustable valve 12 are measured at closure ratio values ​​of 0%, 15%, 25%, 35%, 50% and 100%.

[0097] An increase in the closing ratio of the inlet vanes at the inlet of the first compressor element 3 a corresponds to a decrease in the second flow rate of gas sucked by the compressor arrangement 1 and, consequently, to a decrease in the load condition of the compressor arrangement 1 .

[0098] In particular, when the blockage ratio value is equal to 0%, the compressor device 1 operates at the maximum second flow rate of suction gas and, consequently, at maximum load condition.

[0099] When the blockage ratio value is equal to 100%, the compressor unit 1 operates at a minimum load condition with zero suction gas flow.

[0100] The temperature of the coolant at the inlet 8 of the piping network 7 is 25°C.

[0101] Coolant temperature T at outlet 9 w、out The predetermined levels are fixed at temperatures of 70°C, 80°C or 90°C.

[0102] Each of the functional relationships in FIG. 3a corresponds to one of these temperature values, as shown.

[0103] From the functional relationship of FIG. 3a, it is possible to determine, on the one hand, the drive current or the second flow rate of the suction gas, respectively, and, on the other hand, the temperature T w、out It can be concluded that there is a direct proportional relationship between the target value of the first flow rate that needs to flow through the adjustable valve 12 to achieve a predetermined level.

[0104] FIG. 3b shows a similar relationship to FIG. 3a, but for a coolant temperature of 35° C. at the inlet 8 of the piping network 7.

[0105] To determine the proportionality constant of the above-mentioned direct positive 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 aspirated gas, respectively, can be determined.

[0106] In order to obtain a reliable initial reference value, the temperature T w、out must remain within a first preset maximum absolute deviation relative to the preset level for a first preset period of time.

[0107] Preferably, the first pre-set period should be at least 60 seconds.

[0108] Preferably, the first pre-set maximum absolute deviation should be at most 1.0°C.

[0109] The initial reference value for the opening position of the adjustable valve 12 can be updated to a new reference value at a preset instant in the following cases: On the one hand, the temperature T of the coolant at the outlet 9 of the piping network 7 w、out remains within a second preset maximum absolute deviation with respect to the preset level for a second preset time; and on the other hand, if the drive current remains within a preset maximum absolute relative deviation with respect to the reference drive current for a second preset time period or if the second flow rate remains within a preset maximum absolute relative deviation with respect to the reference flow rate, respectively; It is.

[0110] Preferably, the second preset period is at least 60 seconds.

[0111] Preferably, the second preset maximum absolute deviation is at most 0.8°C.

[0112] Preferably, the preset maximum absolute relative deviation is at most 5.0°C.

[0113] The positive proportional relationship between the drive current or the second flow rate of the suction gas, respectively, on the one hand, and the target 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 characteristics in the event of large relative changes in the drive current or the second flow rate of the suction gas, respectively.

[0114] In this context, a "large relative change" means a relative change in the drive current or the second flow rate of the aspirated gas, respectively, that deviates from twice the preset maximum absolute relative deviation relative to the reference drive current or reference flow rate, respectively.

[0115] Alternatively, for small relative changes in the drive current or the second flow rate of the suction gas, respectively, that fall within twice the above-mentioned preset maximum absolute relative deviation, the opening position of the adjustable valve 12 is adjusted to a value that is smaller than the temperature T w、out It can also be controlled by a simple standard PI control unit based on

[0116] The invention is not limited to the embodiments described by way of example and shown in the drawings, and the compressor arrangement 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.

Claims

1. 1. A compressor apparatus comprising: a compressor installation (2) having at least one compressor element (3a, 3b, 3c) for compressing the suction gas, driven by an electric motor (4); a heat recovery system (6) for recovering heat from the compressed gas resulting from the compression of said suction gas; Equipped with The heat recovery system (6) comprises a piping network (7) having an inlet (8) and an outlet (9) for a coolant, the piping network (7) is provided with a control means having a flow control state variable for varying a first flow rate of the coolant in the piping network (7) at the inlet (8) or at the outlet (9); the compressor arrangement further comprises measuring means for determining an actual value of the driving current of the electric motor (4) or of the second flow rate of the suction gas, respectively; The compressor device includes: - receiving said actual value, - the temperature T of the coolant at the outlet (9) of the pipeline (7) based on the actual value w、out determining a target value for the first flow rate that provides a predetermined level; - adjusting the flow control state variable of the control means to the target value of the first flow rate based on a characteristic describing a relationship between the flow control state variable of the control means and the first flow rate; A compressor device comprising a control unit (13) configured as described above.

2. 2. The compressor arrangement of claim 1, wherein the control means includes an adjustable valve (12), the characteristic is a valve characteristic of the adjustable valve (12), and the flow control state variable is an opening position of the adjustable valve (12).

3. 3. The compressor arrangement according to claim 1 or 2, wherein the control unit (13) is configured to determine the target value of the first flow rate on the basis of the actual value and on the basis of a relationship between the target value of the first flow rate, on the one hand, and the driving current of the electric motor (4) or the second flow rate of the suction gas, respectively, on the other hand.

4. 4. The compressor arrangement according to claim 3, wherein the control unit (13) is configured to determine the setpoint value of the first flow rate on the basis of the actual value and on the basis of a direct proportional relationship between the setpoint value of the first flow rate, on the one hand, and the driving current of the electric motor (4) or the second flow rate of the suction gas, respectively, on the other hand.

5. The compressor arrangement according to any one of claims 1 to 4, wherein the compressor installation (2) is a multi-stage compressor installation having a plurality of compressor elements (3a, 3b, 3c).

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

7. The compressor installation (2) is a multi-stage compressor installation having a plurality of successive compressor elements (3a, 3b, 3c).

7. A compressor arrangement according to claim 5 or 6, wherein the successive compressor elements (3a, 3b, 3c) are fluidly connected to one another by piping (5) for the gas, the piping (5) between the successive compressor elements (3a, 3b, 3c) incorporating one or more intercoolers (10a, 10b) for cooling the gas.

8. 8. The compressor arrangement according to claim 7, wherein the intercoolers (10a, 10b) are installed in parallel with one another between the inlet (8) and the outlet (9) of the piping network (7).

9. 8. The compressor arrangement according to claim 7, wherein the intercoolers (10a, 10b) are installed in series with one another between the inlet (8) and the outlet (9) of the piping network (7).

10. 10. The compressor arrangement according to claim 7, further comprising an aftercooler (11) for cooling the compressed gas downstream of the multi-stage compressor installation, the aftercooler (11) being integrated in series with the intercooler (10a, 10b) between the inlet (8) and the outlet (9) of the piping network (7).

11. 11. The compressor arrangement according to any one of claims 7 to 10, wherein the multi-stage compressor installation comprises at least three successive compressor elements (3a, 3b, 3c) and comprises at least one intercooler (10a, 10b) in the piping (5) between each two directly successive compressor elements (3a, 3b; 3b, 3c) of the three successive compressor elements (3a, 3b, 3c).

12. Compressor arrangement according to any one of claims 7 to 11, wherein the plurality of successive compressor elements (3a, 3b, 3c) are turbo compressor elements.

13. A compressor arrangement as claimed in any preceding claim, wherein the coolant is water.

14. The compressor unit is adapted to reduce the temperature T w、out 14. The compressor arrangement according to claim 1, further comprising a memory unit for storing corresponding reference values ​​for the flow control state variable of the control means on the one hand and the drive current of the electric motor (4) or the second flow rate of the suction gas on the other hand, at which the preset level is reached.

15. A heat recovery system for use in a compressor arrangement according to any preceding claim.

16. 1. A method for controlling a compressor arrangement, comprising: The compressor device includes: a compressor installation (2) having at least one compressor element (3a, 3b, 3c) for compressing the suction gas, driven by an electric motor (4); a heat recovery system (6) for recovering heat from the compressed gas resulting from the compression of said suction gas; Equipped with The heat recovery system (6) comprises a piping network (7) having an inlet (8) and an outlet (9) for a coolant, the piping network (7) is provided with a control means having a flow control state variable for varying a first flow rate of the coolant in the piping network (7) at the inlet (8) or at the outlet (9); The method comprises: - determining an actual value of the drive current of the electric motor (4) or of the second flow rate of the suction gas, respectively; - the temperature T of the coolant at the outlet (9) of the pipeline (7) based on the actual value w、out determining a target value for the first flow rate that provides a predetermined level; - adapting the flow control state variable of the control means to the target value of the first flow rate based on a characteristic describing a relationship between the flow control state variable of the control means and the first flow rate; A method comprising:

17. 17. The method of claim 16, wherein the control means includes an adjustable valve (12), the characteristic is a valve characteristic of the adjustable valve (12), and the flow control state variable is an opening position of the adjustable valve (12).

18. 18. The method according to claim 16 or 17, wherein the setpoint value of the first flow rate is determined on the basis of an actual value and on the basis of a relationship between the setpoint value of the first flow rate, on the one hand, and the driving current of the electric motor (4) or the second flow rate of the suction gas, respectively, on the other hand.

19. 19. The method according to claim 18, wherein the setpoint value of the first flow rate is determined based on an actual value and on a direct proportional relationship between the setpoint value of the first flow rate, on the one hand, and the driving current of the electric motor (4) or the second flow rate of the suction gas, respectively, on the other hand.

20. 20. The method of any one of claims 16 to 19, wherein the predetermined level is between 60°C and 90°C.

21. 21. The method according to any one of claims 16 to 20, wherein the temperature of the coolant at the inlet (8) of the piping network (7) is between 5°C and 35°C.

22. When the electric motor (4) is driven with a predetermined reference drive current or when the compressor installation (2) draws a predetermined reference flow rate of the gas, respectively, the initial reference value of the flow rate control state variable of the control means is the temperature T w、out is stored in a memory unit associated with the compressor arrangement if the deviation remains within a first predetermined maximum absolute deviation with respect to the preset level during a first preset period.

23. 23. The method of claim 22, wherein the first preset period is at least 60 seconds.

24. 24. The method of claim 22 or 23, wherein the first preset maximum absolute deviation is at most 1.0°C.

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

26. 26. The method of claim 25, wherein the second preset period is at least 60 seconds.

27. 27. The method of claim 25 or 26, wherein the second preset maximum absolute deviation is at most 0.8°C.

28. 28. The method of any one of claims 25 to 27, wherein the preset maximum absolute relative deviation is at most 5.0%.

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