Method for controlling a first reference temperature in a gas compression plant

Abstract

A method for controlling a first reference temperature in a gas compression plant (1), the gas compression plant (1) comprising an oil injected element (2) for compressing a gas, an oil injection piping network (6) for injecting oil into the oil injected element (2), the oil injection piping network comprising distribution means (8) for distributing the oil into a first portion and a second portion, an oil cooler (10) cooled by a fan (9) for cooling the first portion, and a bypass (11) for bypassing the second portion around the oil cooler (10), wherein first a distribution ratio of the first portion is controlled to a desired distribution ratio, and subsequently a speed of the fan (9) is optionally controlled to a desired speed based on the distribution ratio, characterized in that the distribution ratio is controlled by a control unit (15) based on a non-fuzzy logic algorithm.

Description

TECHNICAL FIELD

[0001] The present invention relates to a method for controlling a first reference temperature in a gas compression device to a desired temperature value.

[0002] A "gas compression device" herein can refer to a compressor device for compressing atmospheric gas to superatmospheric pressure and a vacuum pump device for vacuum pumping a user network or an enclosed space.

[0003] More specifically, the present invention relates to a method for controlling a first reference temperature in a device to a first desired temperature value, wherein the device comprises the following components:

[0004] an oil-injected element for compressing gas;

[0005] an oil injection network having a discharge outlet for injecting oil into the oil-injected element, the oil injection network comprising:

[0006] a distribution device for distributing the oil into a first portion and a second portion;

[0007] an oil cooler cooled by a fan for cooling the first portion; and

[0008] a bypass for bypassing the second portion around the oil cooler,

[0009] wherein first the distribution ratio of the first portion is controlled to a desired distribution ratio to direct a second reference temperature in the device to a second desired temperature value, and subsequently the speed of the fan is controlled to a desired speed to direct the first reference temperature to the first desired temperature value.

[0010] A "reference temperature in the device" herein refers to the temperature at a specific reference location in the device, for example at the outlet of the oil-injected element where the gas temperature is typically highest in the device, or at the discharge outlet of the oil injection network where the oil temperature is crucial for the cooling and lubrication of the device.

[0011] A "distribution ratio of the first portion" herein refers to the ratio of the flow or amount of the first portion to the total flow or total amount of oil. The distribution ratio can thus range from 0 to 100%. BACKGROUND

[0012] The need and methods for controlling a certain reference temperature in a gas compression device to a desired temperature value are known.

[0013] On the one hand, the reference temperature should not fall below a minimum level, for example to avoid the formation of condensate from the gas, which would negatively affect the cooling or lubrication capacity of the oil in the device and would be corrosive to the components of the device, thus shortening the lifetime. On the other hand, the reference temperature should not rise above a maximum level, for example to avoid damaging the device due to degradation of the oil quality in the device or even deformation of the components in the device.

[0014] In some existing plants having an oil-jetted element for compressing a gas and an oil injection pipe network for injecting oil into the oil-jetted element, a thermostatic control valve having a fixed temperature setpoint and a constant speed fan for cooling the oil in the oil injection pipe network are used to control the reference temperature to a desired temperature, wherein the fan is stopped when the reference temperature is below a maximum level.

[0015] Tests have shown that when using a thermostatic control valve having a fixed temperature setpoint and a fan having a fixed speed, the plant is not always energy efficient. Even if the reference temperature does not significantly exceed the maximum level, the fan will always be started at its fixed speed, which causes the reference temperature to drop quickly and also requires the fan to be stopped again quickly. In the worst case, the reference temperature drops so much that it falls below the minimum level, resulting in an increased risk of condensate formation in the plant.

[0016] Other existing plants use a thermostatic control valve controlled by a PID controller and a variable speed fan. Such a system usually has separate control circuits for controlling the thermostatic control valve and the fan, respectively.

[0017] Tests have shown that these types of plants can exhibit irregular and oscillating behavior due to interference between the individual separate control circuits. Negative consequences include that the plant can experience emergency shutdowns, mechanical parts of the plant can be damaged, and various parts of the plant can wear out prematurely.

[0018] WO2018 / 033827A1 describes a method for controlling an outlet temperature of a plant having an oil-jetted element for compressing a gas and an oil injection pipe network for injecting oil into the oil-jetted element, wherein the position of a thermostatic control valve is controlled by applying a fuzzy logic algorithm to an outlet temperature measurement, and the speed of a fan for cooling the oil is controlled by applying a fuzzy logic algorithm and further based on the position of the thermostatic control valve.

[0019] A disadvantage of using a fuzzy logic algorithm is that it is a complex "multiple input multiple output" (MIMO) calculation algorithm. SUMMARY

[0020] The present invention aims to solve at least one of the above and / or other disadvantages.

[0021] More specifically, it is an object of the present invention to provide a simple method for controlling a reference temperature in a gas compression plant to a desired temperature value, wherein, on the one hand, as many individual separate control circuits as possible are utilized having as simple calculation algorithms as possible, but, on the other hand, interference between the individual separate control circuits in the plant is as small as possible.

[0022] To this end, the present invention relates to a method for controlling a first reference temperature in a gas compression plant to a first desired temperature value,

[0023] wherein the gas compression device comprises the following components:

[0024] an oil-entraining element for drawing in gas at an inlet of the gas compression device and compressing the gas to an operating pressure at an outlet of the oil-entraining element;

[0025] an oil injection network having an outlet for injecting oil into the oil-entraining element, the oil injection network comprising:

[0026] a distribution device for distributing the oil into a first portion and a second portion;

[0027] an oil cooler cooled by a fan for cooling the first portion; and

[0028] a bypass for bypassing the oil cooler for the second portion,

[0029] wherein first:

[0030] a required distribution ratio of the first portion is determined to direct a second reference temperature in the gas compression device to a second desired temperature value; and

[0031] the distribution ratio of the first portion is controlled to the required distribution ratio,

[0032] and wherein subsequently:

[0033] a required speed of the fan is determined to direct a first reference temperature to a first desired temperature value, wherein the required speed is determined based on the second desired temperature value and the distribution ratio if the first reference temperature is identical to the second reference temperature; and

[0034] the speed of the fan is controlled to the required speed,

[0035] characterized in that the distribution ratio is controlled using a control unit based on a non-fuzzy logic algorithm with the following as input:

[0036] a first current value of the second reference temperature; and

[0037] the second desired temperature value.

[0038] This has the advantage that the distribution ratio is controlled by a standard control unit, such as a PID controller or an on-off controller. Thus, the use of the complex "multiple-input-multiple-output" calculation algorithm described in WO 2018 / 033827 A1 is avoided.

[0039] However, the device according to the invention has the same basic advantages as described in WO 2018 / 033827 A1.

[0040] More specifically, if the first reference temperature is the same as the second reference temperature, the method according to the present application also avoids any interference between the control of the distribution ratio and the control of the fan speed. This is in complete contrast with the danger of such interference explicitly warned in WO 2018 / 033827 Al page 2 lines 18-27 in the case of an apparatus using a single-input-single-output (SISO) control unit to control both the distribution ratio and the variable speed fan.

[0041] In a preferred embodiment of the method according to the present application, the second desired temperature value is determined on the basis of the highest temperature value among the group of one or more temperature values.

[0042] As a result, the second desired temperature value can be determined on the basis of a desired number of targets.

[0043] Furthermore, the second desired temperature value can be adjusted to accommodate the most relevant target depending on the operating state of the apparatus.

[0044] In a more preferred embodiment of the method according to the present application, the first temperature value among the group represents the value of the second reference temperature at which the temperature of the compressed gas at the outlet is equal to:

[0045] the first condensation temperature of the compressed gas at the outlet; or

[0046] the first condensation temperature plus a first safety margin.

[0047] In this way, when determining the second desired temperature value, the first target in terms of avoiding the formation of condensate in the apparatus is taken into account.

[0048] Preferably, in this regard, the first temperature value is limited according to a first temperature interval between a first minimum temperature limit value and a first maximum temperature limit value.

[0049] This means that:

[0050] when the first temperature value is lower than the first minimum temperature limit value, the first temperature value is set equal to the first minimum temperature limit value;

[0051] when the first temperature value is higher than the first maximum temperature limit value, the first temperature value is set equal to the first maximum temperature limit value; and

[0052] when the first temperature value is within the first temperature interval between the first minimum temperature limit value and the first maximum temperature limit value, the first temperature value is not changed.

[0053] By limiting the first temperature value to the first temperature interval, safety constraints can be taken into account, for example with respect to a minimum operating temperature and a maximum operating temperature of the apparatus.

[0054] In another more preferred embodiment of the method according to the present application, the second temperature value of the set represents a value of a second reference temperature at which a specific energy demand of the gas compression plant is at a minimum.

[0055] In this way, when determining the second desired temperature value, the second objective of minimizing the specific energy demand and thus maximizing the energy efficiency of the plant is taken into account.

[0056] Preferably, the second temperature value is determined based on at least:

[0057] a second current value representative of the working pressure; and

[0058] a third current value representative of the gas temperature at the inlet.

[0059] In the context of the present application, "a current value representative of a parameter" does not necessarily mean that the current value equals the value of the parameter, but that the current value can be derived from the value of the parameter.

[0060] In this way, the second temperature value is determined based on two standard state variables of the plant, the values of which can be reliably and easily measured using accurate, relatively inexpensive and readily available sensors.

[0061] More preferably, in case the oil injection element is driven by a variable speed motor, the second temperature value is determined further based on a tenth current value representative of a variable speed motor speed.

[0062] As a result, when determining the second temperature value, the variable speed motor speed and thus the variable power provided by the variable speed motor to the gas compression process is taken into account.

[0063] Further, alternatively or additionally, the second temperature value is preferably limited according to a second temperature interval between a second minimum temperature limit value and a second maximum temperature limit value.

[0064] This means that:

[0065] when the second temperature value is below the second minimum temperature limit value, the second temperature value is set equal to the second minimum temperature limit value;

[0066] when the second temperature value is above the second maximum temperature limit value, the second temperature value is set equal to the second maximum temperature limit value; and

[0067] when the second temperature value is within the second temperature interval between the second minimum temperature limit value and the second maximum temperature limit value, the second temperature value is not changed.

[0068] By limiting the second temperature value to the second temperature interval, safety constraints, for example with respect to a minimum working temperature and a maximum working temperature of the plant, can be taken into account.

[0069] In another more preferred embodiment of the method according to the application

[0070] controlling the second reference temperature from the old temperature value to a second desired temperature value; and

[0071] In order to determine the second desired temperature value, the highest temperature value is limited by a third temperature interval between, on the one hand, the old temperature value minus a maximum temperature decrease value and, on the other hand, the old temperature value plus a maximum temperature increase value, according to an aspect.

[0072] In this way, for example in order to take into account safety constraints related to temperature variations in the device, the variation of the second reference temperature can be limited when the second reference temperature is controlled to the second desired temperature value.

[0073] Preferably, the second reference temperature is controlled from the old temperature value to the second desired temperature value within a predetermined time interval, and the maximum temperature decrease value and the maximum temperature increase value are positively correlated with the length of the predetermined time interval.

[0074] In this way, for example in order to take into account safety constraints related to the maximum absolute temperature-time gradient in the device, the variation of the second reference temperature can be limited according to the predetermined time interval.

[0075] In another more preferred embodiment of the method according to the application, the required distribution ratio is determined according to a first ratio between the first current value and the second desired temperature value.

[0076] The first ratio is a measure of the deviation of the first current value with respect to the second desired temperature value.

[0077] If the first ratio is less than 1, this indicates that the value of the second reference temperature is too low, and the required distribution ratio should be chosen lower than the current value of the distribution ratio, if possible, in order to send less oil to the oil cooler and thereby less cooling of the oil to be sprayed, which will increase the second reference temperature.

[0078] If the first ratio is greater than 1, this indicates that the value of the second reference temperature is too high, and the required distribution ratio should be chosen higher than the current value of the distribution ratio, in order to send more oil to the oil cooler and thereby more cooling of the oil to be sprayed, which will decrease the second reference temperature.

[0079] Preferably, the required distribution ratio, between the minimum zero value and the maximum value 100%, depends on the first ratio according to a first monotonically increasing function.

[0080] In this way, when there is a large deviation between the second reference temperature and the second desired temperature value, the variation of the distribution ratio with respect to the required distribution ratio will not be small.

[0081] Alternatively, the required distribution ratio is preferably:

[0082] The required distribution ratio is the maximum value 100% when the first current value is higher than the second desired temperature value or the second desired temperature value plus the second safety margin or when the first current value is higher than the second desired temperature value or the second desired temperature value plus the second safety margin during the first period; otherwise, the required distribution ratio is the minimum zero value.

[0083] This is a simple on-off control, where the oil is completely sent to the oil cooler when there is an indication that the reference temperature is too high, more specifically higher than the second desired temperature value plus or minus the second safety margin.

[0084] By applying the first period before controlling the distribution ratio to a state where the oil is completely sent to the oil cooler, a fast and unnecessary switching of the distribution ratio from the minimum zero value to the maximum value 100% and back to the zero value can be avoided. This switching situation would occur if the second reference temperature is higher than the second desired temperature plus or minus the second safety margin only during a limited non-harmful time period which is shorter than the first period.

[0085] Thus, by applying the first period, the control dynamics of the distribution device and the plant in general do not respond or less to non-harmful short-term increases of the second reference temperature. Thus, the control dynamics are more stable than when the first period is not applied.

[0086] In another preferred embodiment of the method according to the present application, the second reference temperature:

[0087] is the temperature of the gas at the outlet of the oil injected element; or

[0088] is the temperature of the oil at the discharge outlet of the oil injection pipe network.

[0089] At the outlet of the oil injected element, the gas pressure in the plant is highest. Thus, the risk of condensate formation is also highest at this outlet. This is because the higher the gas pressure, the higher the gas condensation temperature. It must be ensured that the gas temperature at the outlet is not lower than the gas condensation temperature at the outlet. Thus, in order to avoid the formation of condensate in the plant, the gas temperature at the outlet of the oil injected element is the relevant second reference temperature in the plant.

[0090] The oil temperature at the discharge outlet of the oil injection pipe network, on the other hand, determines the cooling capacity of the oil. It must be ensured that this cooling capacity does not become too high to prevent the gas temperature at a given location in the plant from falling below the gas condensation temperature at this location. Thus, in order to avoid the formation of condensate in the plant, the oil temperature at the discharge outlet of the oil injection pipe network is also the relevant second reference temperature in the plant.

[0091] In a further preferred embodiment of the method according to the application, the required speed is determined on the basis of the highest speed value of the group consisting of the one or more speed values.

[0092] This allows the required speed to be determined on the basis of the desired number of criteria.

[0093] Furthermore, the required speed can be adjusted to the most relevant criterion depending on the device operating state.

[0094] In a more preferred embodiment of the method according to the application, the first speed value of the group represents the speed value of the fan required to achieve the second desired temperature value of the second reference temperature.

[0095] In this way, when determining the required fan speed, the first criterion in terms of achieving the second desired temperature value is taken into account. In other words, in this respect, the purpose of the fan control is the same as the purpose of the distribution ratio control as described above, and thus contributes to achieving the goal of controlling the distribution ratio.

[0096] In a further preferred embodiment of the method according to the application,

[0097] when the fourth current value of the second reference temperature is higher than a predetermined minimum temperature; and

[0098] when the fifth current value of the distribution ratio is higher than a predetermined minimum distribution ratio and the fourth current value is higher than the second desired temperature value,

[0099] the first speed value is determined based on at least:

[0100] a sixth current value representing the operating pressure; and

[0101] a seventh current value representing the gas temperature at the inlet.

[0102] In this way, the first speed value is determined on the basis of two standard state variables of the device, the values of which can be reliably and easily measured using precise, relatively inexpensive and readily available sensors.

[0103] Preferably, in the case of the oil injection element being driven by a variable speed motor, the first speed value is also determined on the basis of an eleventh current value representing the variable speed motor rotational speed.

[0104] As a result, when determining the first speed value, the rotational speed of the variable speed motor, and thus the variable power provided by this variable speed motor to the gas compression process, is taken into account.

[0105] Alternatively or additionally, preferably,

[0106] when the fourth current value is higher than the second desired temperature value plus a first tolerance value; or

[0107] when the fourth current value is lower than the second desired temperature value minus the second tolerance value during the third period,

[0108] when the fourth current value is lower than the second desired temperature value minus the second tolerance value during the third period,

[0109] when the fourth current value is lower than the second desired temperature value minus the second tolerance value during the third period,

[0110] The first speed value is also determined on the basis of at least:

[0111] a fifth current value of the distribution ratio; and

[0112] a second ratio between the fourth current value and the second desired temperature value.

[0113] By determining the first speed value on the basis of the fifth current value of the distribution ratio, the distribution ratio can be taken into account in determining the fan speed, thereby avoiding any interference between the fan speed control and the distribution ratio control.

[0114] The second ratio is a measure of the deviation of the fourth current value with respect to the second desired temperature value.

[0115] If the second ratio is less than 1, this indicates that the value of the second reference temperature is too low, and the required distribution ratio should be chosen lower than the current value of the distribution ratio, so that less oil is sent to the oil cooler and therefore the degree of cooling of the oil to be injected is less, which will increase the second reference temperature.

[0116] If the second ratio is greater than 1, this indicates that the value of the second reference temperature is too high, and the required distribution ratio should be chosen higher than the current value of the distribution ratio, so that more oil is sent to the oil cooler and therefore the degree of cooling of the oil to be injected is greater, which will decrease the second reference temperature.

[0117] More preferably, the first speed value depends on the second ratio according to a second monotonically increasing function.

[0118] In this way, when there is a large deviation between the second reference temperature and the second desired temperature value, the variation of the fan speed with respect to the first speed value will not be small.

[0119] Alternatively or additionally, more preferably, the first speed value depends on the fifth current value according to a third monotonically increasing function.

[0120] As a result, when the fan speed is controlled to the first speed value, the fan speed will never be smaller when the distribution ratio increases, and the fan speed will never be larger when the distribution ratio decreases.

[0121] This contributes to the stability of the fan speed control, since the fan speed can gradually be increased when the distribution ratio increases and the fan speed can gradually be decreased when the distribution ratio decreases. This prevents the fan from suddenly having to start at high speed from a standstill when the distribution ratio rises from zero or from suddenly going from high speed to standstill when the distribution ratio suddenly drops to zero.

[0122] In another more preferred embodiment, when the gas compression installation is provided with an aftercooler for cooling the compressed gas downstream of the oil injection element,

[0123] When the eighth current value of the minimum available temperature in the aftercooler is higher than the required minimum available temperature value, the second speed value in the group is determined based on:

[0124] the first speed value; and

[0125] a third ratio between the eighth current value and the required minimum available temperature value;

[0126] Otherwise, the second speed value is set equal to zero.

[0127] In this way, when the eighth current value of the minimum available temperature in the aftercooler is too high, the fan speed can be controlled to a second speed value that is higher than the first speed value. In this way, in addition to the oil cooler being cooled by the fan, the aftercooler can also be sufficiently cooled by the fan, so that the maximum temperature of the gas in the aftercooler can be controlled and limited to the required minimum available temperature.

[0128] Preferably, the required minimum available temperature is equal to a second condensation temperature value of the gas in the aftercooler plus a compensation amount.

[0129] By means of the compensation amount, the formation of condensate in the aftercooler can be avoided.

[0130] Alternatively or additionally, the second speed value depends on the third ratio according to a fourth monotonically increasing function.

[0131] In this case, if the minimum available temperature deviates too much above the required minimum available temperature value, the second speed value will not decrease, so that the minimum available temperature will not further deviate from the required minimum available temperature value at an accelerated rate.

[0132] In another more preferred embodiment of the method according to the application, a third speed value in the group is determined based on:

[0133] a ninth current value of the first reference temperature; and

[0134] a predetermined maximum value of the first reference temperature,

[0135] wherein the third speed value:

[0136] is equal to zero when the ninth current value is lower than a predetermined maximum value; and

[0137] is equal to a value representative of the maximum speed of the fan when the ninth current value is higher than a predetermined maximum value.

[0138] In this way, the speed of the fan can be regulated to a third speed value determined by exceeding a predetermined maximum value, for example a maximum value of the first reference temperature of the gas, which must not be higher than the maximum value for safety reasons.

[0139] The present application also relates to a computational control assembly comprising:

[0140] a first computational control unit having a control unit for controlling the second reference temperature in the gas compression plant to a second desired temperature value; and

[0141] a second computational control unit for controlling the first reference temperature in the gas compression plant to a first desired temperature value;

[0142] for carrying out the method according to any of the embodiments described above.

[0143] Finally, the present application relates to a gas compression plant equipped with such a computational control assembly according to the present application.

[0144] Obviously, such a computational control assembly and such a plant exhibit the same advantages as the method according to the embodiments of the present application described above. BRIEF DESCRIPTION OF DRAWINGS

[0145] In order to better explain the features of the present application, a plurality of preferred embodiments of the method, computational control assembly and plant according to the present application are described below with reference to the attached drawings, by way of non-limiting example, in which:

[0146] Figure 1 a plant equipped with a computational control assembly according to the present application is shown;

[0147] Figure 2 a schematic overall view of the method according to the present application is shown. DETAILED DESCRIPTION

[0148] Figure 1 A gas compression plant 1 is shown, comprising an oil injection element 2 for sucking a gas at an inlet 3 of the gas compression plant 1 and compressing it to a working pressure at an outlet 4 of the oil injection element 2.

[0149] Within the scope of the present invention, the gas compression device 1 is to be interpreted as a complete compressor or vacuum pump device, including but not limited to the oil injected element 2 in the form of a compressor element or vacuum pump element, all typical connecting pipes and valves, an optional housing of the gas compression device 1, and a first electric motor 5 for driving the oil injected element 2.

[0150] Within the context of the present invention, the oil injected element 2 is to be understood as an element housing, in which a gas is compressed by a rotating rotor motion or by a reciprocating piston motion.

[0151] In this regard, the oil injected element 2 can comprise one or more screw rotors, gear rotors, baffle plates, rotating vanes, or pistons, as non-limiting examples.

[0152] When the gas compression device 1 comprises a compressor element, the inlet 3 of the gas compression device 1 is typically fluidly connected to an atmospheric environment of the gas compression device 1. When the gas compression device 1 comprises a vacuum pump element, the inlet 3 is typically fluidly connected to a user network or an enclosed space at a pressure lower than atmospheric pressure.

[0153] Furthermore, the gas compression device 1 further comprises an oil injection pipe network 6 having a discharge outlet 7 for injecting oil into the oil injected element 2.

[0154] In this regard, it is not excluded within the scope of the present invention that the oil injection pipe network 6 comprises a plurality of discharge outlets 7 for injecting oil into the oil injected element 2.

[0155] The compression of the gas in the oil injected element 2 generates compression heat, which heats the gas. In order to keep the temperature of the compressed gas at the outlet 4 of the oil injected element 2 below a certain maximum safety limit, the temperature of the oil injected should be below a maximum level corresponding to this safety limit. On the other hand, the temperature of the compressed gas at the outlet 4 should not be lowered below the first condensation temperature of the gas at the outlet 4 or below the first condensation temperature plus a first safety margin, in order to avoid the formation of condensate at the outlet 4. Thus, the temperature of the oil injected must be above a minimum level corresponding to this first condensation temperature or this first condensation temperature plus a first safety margin. Accordingly, the temperature of the gas at the outlet 4 of the oil injected element 2 and the corresponding temperature of the oil at the discharge outlet 7 of the oil injection pipe network 6 should be controlled to values within a temperature interval defined at both ends, respectively.

[0156] To this end, the oil injection pipe network 6 comprises:

[0157] a distribution device 8 for distributing the oil into a first portion and a second portion, such as a thermostatic control valve;

[0158] an oil cooler 10 cooled by a fan 9 for cooling the first portion; and

[0159] a bypass 11 for bypassing the second portion around the oil cooler 10.

[0160] The fan 9 has a variable speed and is driven by a second electric motor 12. This makes it possible, for example, to control the cooling of the first portion of oil to be injected by adjusting the speed of the fan 9.

[0161] More generally, in the present application, the speed of the fan 9 is adjusted in such a way that a first reference temperature in the gas compression device 1 is controlled to a first desired temperature value.

[0162] The distribution device 8 and the bypass 11 are provided for bypassing the second portion of oil to be injected around the oil cooler 10, in order to more or less limit the cooling of the oil to be injected by the oil cooler 10 by controlling the distribution ratio of the first portion of oil. In this way, it is possible to control a second reference temperature in the gas compression device 1 to a second desired temperature value, wherein the second reference temperature value is, for example, the temperature of the compressed gas at the outlet 4 of the oil-injected element 2 or the temperature of the oil at the discharge outlet 7 of the oil injection network 6.

[0163] The first reference temperature controlled by the fan 9 can be identical to the second reference temperature, wherein the first desired temperature value is therefore also equal to the second desired temperature value.

[0164] In order to control the distribution ratio, the gas compression device 1 has a first calculation control unit 13. This first calculation control unit 13 comprises:

[0165] a calculation unit 14 for determining the second desired temperature value; and

[0166] a control unit 15 for adjusting the distribution ratio of the first portion on the basis of a first current value for the second reference temperature to adapt to the second desired temperature.

[0167] In this case, the control unit 15 is designed, for example, as a PID controller or an on-off controller.

[0168] In this case, the first current value for the second reference temperature is provided by using a temperature sensor measurement, for example, a first temperature sensor 16 at the outlet 4 of the oil-injected element 2 or a second temperature sensor 17 at the discharge outlet 7 of the oil injection network 6.

[0169] The second desired temperature value is determined by the calculation unit 14 at least on the basis of:

[0170] a second current value representative of the working pressure, which is provided, for example, by using a first pressure sensor 18 at the outlet 4 of the oil-injected element 2; and

[0171] a third current value representative of the temperature of the gas at the inlet 3, which third current value is provided, for example, by measuring using a third temperature sensor 19 at the inlet 3 of the gas compression device 1.

[0172] Furthermore, also a measurement of the atmospheric pressure at the inlet 3 can be taken into account, which measurement of the atmospheric pressure is provided, for example, by using a second pressure sensor 20 at the inlet 3 of the gas compression device 1. However, it is also possible to simply assume an absolute standard value of the atmospheric pressure of 1 bar or 1 atmosphere, which means that the measurement of the atmospheric pressure and thus the second pressure sensor 20 is not strictly necessary for the present application.

[0173] Likewise, also a measurement of the relative humidity at the inlet 3 can be taken into account, for example, using a humidity sensor 21 at the inlet 3. Alternatively, it is also possible to assume a worst-case value of the relative humidity of 100% for the gas at the inlet 3. In the latter case, the measurement of the relative humidity at the inlet 3 and thus the humidity sensor 21 is not strictly necessary for the present application.

[0174] On the basis of the second desired temperature value determined by the calculation unit 14 and the first current value for the second desired temperature value, the control unit 15 will determine a required distribution ratio and control the distribution ratio of the first portion of oil to this required distribution ratio.

[0175] In the case where the distribution device 8 is located downstream of the oil cooler 10 and the bypass 11, the second desired temperature value determined by the calculation unit 14 is a second reference temperature of the gas at the outlet 12 of the oil cooler 10. Figure 1 However, in the context of the present application, it is also not excluded that the distribution device 8 is located upstream of the oil cooler 10 and / or the bypass 11, for example, at the location where the conduits leading to the oil cooler 10 and the bypass 11 branch off from each other.

[0176] In order to control the speed of the fan 9, the gas compression device 1 is equipped with a second calculation control unit 22.

[0177] The second calculation control unit 22 forms, together with the first calculation control unit 13, a calculation control assembly according to the present application.

[0178] The control of the fan 9, as is the case for the control of the distribution ratio of the first portion of oil as described above, can aim at controlling a second reference temperature to a second desired temperature value. In this case, the first reference temperature will thus be identical to the second reference temperature, and the first desired temperature value will be equal to the second desired temperature value.

[0179] In this case, when the fourth current value for the second reference temperature is higher than the second desired temperature value and the fifth current value for the distribution ratio is higher than the predetermined minimum distribution ratio, the required speed of the fan 9 is then determined by the second calculation control unit 22 at least on the basis of:

[0180] a sixth current value representative of the working pressure, for example provided by measuring with a first pressure sensor 18 at the outlet 4 of the oil injected element 2; and

[0181] a seventh current value representative of the temperature of the gas at the inlet 3, for example provided by measuring with a third temperature sensor 19 accordingly.

[0182] The fourth current value can for example be provided by using the measurement of the first temperature sensor 16 or the second temperature sensor 17.

[0183] The second desired temperature value is obtained by the second calculation control unit 22 from the calculation unit 14.

[0184] Then, in order to be able to take into account the first part oil distribution ratio when controlling the speed of the fan 9, also a fifth current value for the distribution ratio can be taken into account for determining the specific value of the required speed of the fan 9. This fifth current value can be provided by using a measurement of a position or flow sensor 23 in the distribution device 8, by which the opening of the distribution device 8 and thus the first part oil distribution ratio can be measured.

[0185] Of course, in the context of the present invention, the second calculation control unit 22 can also obtain the fifth current value directly from the control unit 15 (not shown in the figure). In this case, the position or flow sensor 23 is no longer necessary and can be dispensed with. Figure 1

[0186] Figure 1 It is also shown that the gas compressed by the oil injected element 2 can flow through an oil separator 24 for example, in which the compressed gas is purified by separating the oil previously injected into the oil injected element 2 from the compressed gas, before the purified compressed gas leaves the gas compression device 1.

[0187] In this case, the oil separated in the optional oil separator 24 can be re-injected into the oil injected element 2 via the oil injection pipe network 6.

[0188] Optionally, the compressed gas, whether purified or not, can also be sent through a post-cooler 25 before leaving the gas compression device 1. The compressed gas can be cooled in this post-cooler 25 by the same fan 9 as used for the oil cooler 10. In this case, the speed of the fan 9 can be controlled so that the minimum available temperature of the gas in the post-cooler 25 is lower than the required minimum available temperature. In this case, the first reference temperature is thus equal to the minimum available temperature of the gas in the post-cooler 25. The fan 9 is controlled on the basis of the required minimum available temperature and an eighth current value for the minimum available temperature, which is for example measured with a fourth temperature sensor 26 at the appropriate location in the post-cooler 25. ​

[0189] The speed of the fan 9 can also be controlled on the basis of a predetermined maximum value for a first reference temperature, for example at a location in the gas compression plant 1 where the temperature is typically relatively high and should be kept below a maximum value for safety reasons. Here, the first reference temperature is for example the temperature of the first electric motor 5, the second electric motor 12 or the frequency converter of the gas compression plant 1. The first reference temperature can also be the temperature of the gas coming out of the aftercooler 25.

[0190] The speed of the fan 9 is then controlled using as input a ninth current value for the first reference temperature, which is for example measured using the fifth temperature sensor 27.

[0191] In the context of the present application, the fifth temperature sensor 27 can also coincide with for example the first temperature sensor 16 or the second temperature sensor 17.

[0192] If the first electric motor 5 is a variable speed motor, the tenth current value representing the rotational speed of the first electric motor 5 can also be taken into account by the calculation unit 14 when determining the second desired temperature, and the eleventh current value representing the rotational speed of the first electric motor 5 can also be taken into account by the second calculation control unit 22 when determining the required speed of the fan 9.

[0193] Figure 2 A schematic overall view of the method according to the present application is shown.

[0194] As previously mentioned, the second desired temperature value for the second reference temperature is determined in the calculation unit 14.

[0195] In this case, the second desired temperature value is determined on the basis of the highest temperature value in a group of two temperature values. This is represented in Figure 2 by a first maximization operator MAX1.

[0196] The first temperature value T1 in the group thus represents the value for which the temperature of the compressed gas at the outlet 4 of the oil injection element 2 is equal to the second reference temperature at which the first condensation temperature of the compressed gas at the outlet 4 in the oil injection element 2 or the first condensation temperature plus a first safety margin.

[0197] The first condensation temperature can be determined in a manner known to the person skilled in the art, for example as described in WO 2018 / 033827 A1.

[0198] When determining the first temperature value, the value T cond In this case, the first temperature value can still be limited according to a first temperature interval between a first minimum temperature limit T min，1 and a first maximum temperature limit T max，1 This limitation of the first condensation temperature plus or minus the first safety margin is performed in a first limitation operator LIM1.

[0199] If the second reference temperature is the gas temperature at the outlet 4 of the oil injection element 2, the first minimum temperature limit value T min，1 and the first maximum temperature limit value T max，1 may vary, for example, between 0°C and 120°C, and can be set with a precision of, for example, 1°C.

[0200] The second temperature value of the group represents the second reference temperature value T SER that makes the specific energy requirement of the gas compression plant 1 the lowest.

[0201] When the first electric motor 5 is a constant speed motor, the value of the second reference temperature T SER may be calculated as a function of a second current value a2 representing the working pressure and of a third current value a3 representing the gas temperature at the inlet 3, for example according to the following equation:

[0202] T SER = B-a3 + C-a2 + D (Equation 1)

[0203] When the first electric motor 5 is a variable speed motor, the value of the second reference temperature T SER may be calculated as a function of a second current value a2 representing the working pressure, of a third current value a3 representing the gas temperature at the inlet 3 and of a tenth current value a 10 representing the first electric motor 5 speed, for example according to the following equation:

[0204] T SER = A-a 10 + B-a3 + C-a2 + D (Equation 2)

[0205] Here, the current value a 10 is a value for the first electric motor 5 speed determined as a percentage of the maximum speed of the first electric motor 5.

[0206] In the preceding Equation 1 and Equation 2, the value of the second reference temperature T SER is expressed in °C, the second current value a2 is determined as the working pressure (unit: bar), and the third current value a3 is determined as the gas temperature at the inlet 3 (unit: °C).

[0207] If the second reference temperature is the gas temperature at the outlet 4 of the oil injection element 2, the possible value interval for the constants A, B, C and D in the preceding Equation 1 and Equation 2 is:

[0208]

[0209]

[0210]

[0211]

[0212] When determining the second temperature value T2, it can still be based on the second minimum temperature limit value T. min,2 Second maximum temperature limit T max,2 The second temperature range between them is used to limit the value T. SER The value T SER The restrictions are enforced by the second restriction operator LIM2.

[0213] If the second reference temperature is the gas temperature at the outlet 4 of the fuel injection element 2, then the second minimum temperature limit value T min,2 Second maximum temperature limit T max,2 The value can vary between, for example, 0°C and 120°C, and the value can be set to have an accuracy of, for example, 1°C.

[0214] Optionally, when the second reference temperature needs to be controlled from the old temperature value to the second desired temperature value, the highest temperature value generated by the first maximization operator MAX1 can be determined by subtracting the maximum temperature decrease value ΔT from the old temperature value. max,down And on the other hand, the old temperature value plus the maximum temperature rise ΔT max,up The third temperature range between the two reference temperatures is used to limit the temperature. This prevents the second reference temperature from being excessively lowered or increased. The limitation on the maximum temperature value is enforced by the third limiting operator LIM3.

[0215] Here, a predetermined time interval Δt can be determined for controlling the old temperature value to the second desired temperature value, where the maximum temperature decrease value ΔT max,down and the maximum temperature rise ΔT max,up It is positively correlated with the length of the predetermined time interval Δt.

[0216] Alternatively, the second desired temperature value can still be determined based on a third minimum temperature limit value T. min,3 On the other hand, the second maximum temperature limit value T max,3 The fourth temperature range between these ranges is used to limit the temperature.

[0217] If the second reference temperature is the gas temperature at the outlet 4 of the fuel injection element 2, then the third minimum temperature limit value T min,3 It can be set to a value between, for example, 20°C and 80°C, with an accuracy of, for example, 1°C, to prevent condensation from forming at outlet 4.

[0218] Alternatively, if the fuel injection network 6 is also equipped with a heat recovery system that can recover heat from the oil separated by the oil separator 24 into the heat-absorbing fluid ( Figure 1 (not shown in the image), then the third minimum temperature value T min,3may be set to a high value, for example 105°C. The third minimum temperature value T min,3 This high value of the third minimum temperature value T

[0219] The third maximum temperature limit value T max,3 may be set to a value between, for example, 100°C and 120°C, with a precision of, for example, 1°C.

[0220] The second desired temperature value thus determined in the calculation unit 14 is further used in the control unit 15 for determining a required distribution ratio on the basis of a first ratio β1 between the first current value α1 of the second reference temperature and the second desired temperature value.

[0221] The required distribution ratio can be determined as a continuous ratio between a minimum zero value and a maximum value of 100% depending on the first ratio β1 according to a first monotonically increasing function.

[0222] On the other hand, the required distribution ratio can also be determined as a binary ratio which is, during operation of the gas compression plant 1, either:

[0223] 100% when the first current value α1 is higher than the second desired temperature value or the second desired temperature value plus a second safety margin or during the first period is higher than the second desired temperature value or the second desired temperature value plus the second safety margin;

[0224] or else the binary ratio is a minimum zero value.

[0225] Here, the second safety margin can be set to a value between, for example, 0°C and 20°C, with a precision of, for example, 0.1°C.

[0226] The first period can be set to a value between, for example, 0 seconds and 255 seconds.

[0227] On the basis of the required distribution ratio determined in the control unit 15, the distribution device 8 is then driven to actually achieve the required distribution ratio.

[0228] The required speed of the fan 9 for controlling the first reference temperature to the first desired temperature value is determined using a second calculation control unit 22.

[0229] To this end, the required speed is selected from a set, in this case three speed values, as the highest speed value. This is indicated in Figure 2 by a second maximization operator MAX2.

[0230] In this case, the first speed value v1 of the set represents the speed value of the fan 9 required to achieve the second desired temperature value of the second reference temperature.

[0231] In the first operating condition of the gas compression device 1, in which the fourth current value a4 of the second reference temperature is still lower than a predetermined minimum temperature (e.g. 90°C) required to terminate the first warming-up operating condition, the first speed value v1 is equal to a zero value.

[0232] In the second operating condition of the gas compression device 1, in which the fourth current value a4 is higher than the predetermined minimum temperature, the first speed value v1 is still equal to a zero value when the distribution ratio is lower than a predetermined minimum distribution ratio or the fourth current value a4 is lower than a second desired temperature value.

[0233] For example, the predetermined minimum distribution ratio can be set to a value between, for example, 0% and, for example, 100%, with a precision of, for example, 1%.

[0234] On the other hand, in the second operating condition, when the fifth current value a5 of the distribution ratio is higher than the predetermined minimum distribution ratio and the fourth current value a4 is higher than the second desired temperature value, the first speed value v1 is determined at least on the basis of:

[0235] a sixth current value a6 representative of the working pressure; and

[0236] a seventh current value a7 representative of the gas temperature at the inlet 3.

[0237] When the first electric motor 5 is a variable speed motor, when determining the first speed value v1, a eleventh current value a 11 is also taken into account, for example according to the following equation:

[0238] v1 = v 1，raw = E · a 11 + F · a7+ G · a6+ H (Equation 7)

[0239] Here, the current value a 11 is a value for the speed of the first electric motor 5, determined as a percentage of the maximum speed of the first electric motor 5.

[0240] In the preceding Equation 7, the first speed value v1 is determined as a percentage of the maximum speed of the fan 9, the sixth current value a6 is determined as the working pressure (unit: bar), and the seventh current value a7 is determined as the gas temperature at the inlet 3 (unit: °C).

[0241] If the second reference temperature is the gas temperature at the outlet 4 of the oil injection element 2, the possible value intervals for the constants E, F, G and H in Equation 7 are:

[0242]

[0243]

[0244]

[0245]

[0246] In this case,

[0247] when the fourth current value a4 is higher than the second desired temperature value plus the first tolerance value; or

[0248] when the fourth current value a4 is higher than the second desired temperature value plus the first tolerance value during the second period; or

[0249] when the fourth current value a4 is lower than the second desired temperature value minus the second tolerance value; or

[0250] when the fourth current value a4 is lower than the second desired temperature value minus the second tolerance value during the third period;

[0251] then the first speed value vi is further determined based on at least:

[0252] a fifth current value a5 of the distribution ratio; and

[0253] a second ratio b2 between the fourth current value a4 and the second desired temperature value.

[0254] For example, the first tolerance value and the second tolerance value can be set between values of, for example, 0 °C and, for example, 20 °C, with a precision of, for example, 0.1 °C.

[0255] For example, the second interval and the third interval can be set between values of, for example, 0 seconds and, for example, 255 seconds.

[0256] In this case, the first speed value vi preferably depends on the second ratio b2 according to a second monotonically increasing function, and alternatively or additionally preferably depends on the fifth current value a5 according to a third monotonically increasing function, for example according to the following equation:

[0257] vi = v 1，raw a5P b2Z (Equation 12)

[0258] In this equation 12, the fifth current value is determined as a percentage distribution ratio of the first portion of oil.

[0259] Possible value intervals for the constants P and Z in equation 12 are:

[0260] P = 0 - 4 (Equation 13)

[0261] Z = 0 - 4 (Equation 14)

[0262] The second speed value v2 of the group is determined as follows:

[0263] When the eighth current value a8 of the minimum available temperature in the aftercooler 25 is higher than the value of the required minimum available temperature, the second speed value v2 is determined according to:

[0264] the first speed value vi; and

[0265] a third ratio β3 between the eighth current value a8 and the value of the required minimum available temperature;

[0266] Otherwise, the second speed value v2 is set equal to zero.

[0267] The required minimum available temperature is equal to the value of the second condensation temperature of the gas in the aftercooler 25 plus a compensation amount.

[0268] The second speed value v2 is preferably dependent on the third ratio β3 according to a fourth monotonic increasing function. When the eighth current value a8 of the minimum available temperature in the aftercooler 25 is higher than the value of the required minimum available temperature, the second speed value v2 is for example calculated according to the following equation:

[0269] v2 = vi - β3P (equation 15)

[0270] In the preceding equation 15, the second speed value v2 is determined as a percentage of the maximum speed of the fan 9.

[0271] The possible interval of values of the constant P has been given in equation 13.

[0272] A third speed value v3 of the group is determined on the basis of:

[0273] a ninth current value a9 of the first reference temperature; and

[0274] a predetermined maximum value of the first reference temperature,

[0275] wherein the third speed value a9:

[0276] is equal to zero when the ninth current value a9 is lower than the predetermined maximum value; and

[0277] is equal to a value representative of the maximum speed of the fan 9 when the ninth current value a9 is higher than the predetermined maximum value.

[0278] For example, the predetermined maximum value can be set between a value of for example 90 °C and for example 120 °C, with a precision of for example 1 °C.

[0279] Finally, the second electric motor 12 is driven so that the fan 9 actually works at the required speed, according to the required speed determined by the second calculation control unit 22.

[0280] The application is not limited to the embodiments described by way of example and shown in the drawings, but rather the method, the computing control device, or the apparatus according to the application can be implemented in various variants without departing from the scope of the application defined in the claims.

Claims

1. A method for controlling a first reference temperature in a gas compression device (1) to a first desired temperature value, wherein, The gas compression device (1) includes the following components: The oil-spraying element (2) is used to draw gas at the inlet (3) of the gas compression device (1) and compress the gas to the working pressure at the outlet (4) of the oil-spraying element (2); The fuel injection network (6) has an outlet (7) for injecting fuel into the fuel-injected element (2), and the fuel injection network includes: A dispensing device (8) is used to dispense oil into a first part and a second part; An oil cooler (10) cooled by a fan (9) is used to cool the first part; and Bypass (11) is used to allow the second part to bypass the oil cooler (10). First of all: Determine the required allocation ratio for the first part to guide the second reference temperature in the gas compression device (1) to the second desired temperature value; and Control the allocation ratio of the first part to the required allocation ratio. And then: Determine the required speed of the fan (9) to guide the first reference temperature to a first desired temperature value, wherein, if the first reference temperature is the same as a second reference temperature, the required speed is determined based on the second desired temperature value and the allocation ratio; and Control the speed of fan (9) to the required speed. The feature is that the control unit (15) uses a non-fuzzy logic algorithm to control the allocation ratio using the following as input: The first current value α1 of the second reference temperature; and Second desired temperature value.

2. The method of claim 1, wherein, The second desired temperature value is determined based on the highest temperature value in a group consisting of one or more temperature values.

3. The method of claim 2, wherein, The first temperature value T1 of the group represents a value T such that the temperature of the compressed gas at the outlet (4) is equal to the second reference temperature when cond : The first condensation temperature of the compressed gas at outlet (4); or First condensation temperature plus first safety margin.

4. The method of claim 3, wherein, According to a first minimum temperature limit value T min,1 and a first maximum temperature limit value T max,1 a first temperature interval between the first temperature value T1 is limited.

5. The method according to any one of claims 2 to 4, characterized in that, The second temperature value T2 in the group represents the second reference temperature value that minimizes the specific energy requirement of the gas compression device (1).

6. The method of claim 5, wherein, The second temperature value T2 is determined based on at least the following: The second current value α2 represents the work stress; and The third current value α3 represents the gas temperature at the inlet (3).

7. The method of claim 5, wherein, According to a second temperature interval between a second minimum temperature limit value T min,2 and a second maximum temperature limit value T max,2 the second temperature value T2 is limited.

8. The method according to any one of claims 2 to 4, characterized in that: Control the second reference temperature from the old temperature value to the second desired temperature value; and In order to determine the second desired temperature value, according to one aspect the old temperature value is subtracted by a maximum temperature decrease value ΔT max,down and according to another aspect the old temperature value is added by a maximum temperature increase value ΔT max,up between a third temperature interval.

9. The method of claim 8, wherein, the second reference temperature is controlled from the old temperature value to the second desired temperature value within a predetermined time interval Δt, and a maximum temperature decrease value ΔT max,down and a maximum temperature increase value ΔT max,up is positively correlated with the length of the predetermined time interval Δt.

10. The method according to any one of claims 2 to 4, characterized in that, The required allocation ratio is determined based on a first ratio β1 between the first current value α1 and the second desired temperature value.

11. The method of claim 10, wherein, The required allocation ratio between the minimum zero value and the maximum value of 100% depends on the first ratio β1 according to the first monotonically increasing function.

12. The method according to claim 10, characterized in that: When the first current value α1 is higher than the second expected temperature value or the second expected temperature value plus the second safety margin, or when the first current value α1 is higher than the second expected temperature value or the second expected temperature value plus the second safety margin during the first cycle, the required allocation ratio is the maximum value of 100%; otherwise, the required allocation ratio is the minimum value of zero.

13. The method according to any one of claims 1 to 4, characterized in that, Second reference temperature: It is the temperature of the gas at the outlet (4) of the fuel injection element (2); or It is the temperature of the oil at the outlet (7) of the fuel injection network (6).

14. The method of any one of claims 1 to 4, wherein, The required speed is determined based on the highest speed value in a group consisting of one or more speed values.

15. The method of claim 14, wherein, The first speed value v1 of the group represents a speed value of the fan (9) required to achieve a second desired temperature value of the second reference temperature.

16. The method according to claim 15, characterized in that, when a fourth current value a4 of the second reference temperature is higher than a predetermined minimum temperature; and when a fifth current value a5 of the distribution ratio is higher than a predetermined minimum distribution ratio and the fourth current value a4 is higher than the second desired temperature value, the first speed value v1 is determined based on at least: a sixth current value a6 representing the working pressure; and a seventh current value a7 representing the gas temperature at the inlet (3).

17. The method according to claim 16, characterized in that, when the fourth current value a4 is higher than the second desired temperature value plus a first tolerance value; or when the fourth current value a4 is higher than the second desired temperature value plus the first tolerance value during a second period; or when the fourth current value a4 is lower than the second desired temperature value minus a second tolerance value; or when the fourth current value a4 is lower than the second desired temperature value minus the second tolerance value during a third period, the first speed value v1 is determined based on at least: a fifth current value a5 of the distribution ratio; and a second ratio b2 between the fourth current value a4 and the second desired temperature value.

18. The method of claim 17, wherein, The first speed value v1 depends on the second ratio b2 according to a second monotonically increasing function.

19. The method of claim 17 or 18, wherein, The first speed value v1 depends on the fifth current value a5 according to a third monotonically increasing function.

20. The method of claim 15, wherein, When the gas compression plant (1) is provided with an aftercooler (25) for cooling the compressed gas downstream of the oil injection element (2), when an eighth current value a8 of the minimum available temperature in the aftercooler (25) is higher than a required minimum available temperature value, the second speed value v2 of the group is determined based on at least: the first speed value v1 ; and a third ratio b3 between the eighth current value a8 and the required minimum available temperature value; Otherwise, the second speed value v2 is set equal to zero.

21. The method of claim 20, wherein, The required minimum available temperature is equal to a second condensation temperature value of the gas in the aftercooler (25) plus a compensation amount.

22. The method of claim 20, wherein, The second speed value v2 depends on the third ratio b3 according to a fourth monotonically increasing function.

23. The method of claim 14, wherein, The third speed value v3 of the group is determined based on at least: a ninth current value a9 of the first reference temperature; and a predetermined maximum value of the first reference temperature, wherein the third speed value v3: is equal to zero when the ninth current value a9 is lower than the predetermined maximum value; and is equal to a value representing a maximum speed of the fan (9) when the ninth current value a9 is higher than the predetermined maximum value.

24. A computational control assembly comprising: a first computational control unit (13) having a control unit (15) for controlling a second reference temperature in a gas compression plant (1) to a second desired temperature value; and a second computational control unit (22) for controlling a first reference temperature in the gas compression plant (1) to a first desired temperature value; for performing the method according to any one of claims 1 to 23.

25. A gas compression plant having a computational control assembly according to claim 24.

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