Exhaust temperature control method and system of two-stage dry screw compressor

Abstract

The invention discloses an exhaust temperature control method and system of a two-stage dry screw compressor. The method comprises the step of controlling the exhaust temperature in the operation process of the two-stage dry type screw compressor, and specifically comprises the following steps: when the pressure of an interstage pipeline of the two-stage dry type screw compressor is lower than a lower limit value of a preset pressure range, controlling the exhaust temperature of the two-stage dry type screw compressor; one or more of the following multiple adjusting modes is / are adopted: reducing the opening degree of a one-return and one-backflow adjusting valve, increasing the rotating speed of a first-stage compressor, reducing the rotating speed of a second-stage compressor and increasing the opening degree of a two-return and two-circulation backflow valve; and when the pressure of the interstage pipeline is higher than the upper limit value of the preset pressure range, one or more of the following multiple adjusting modes are adopted: reducing the opening degree of the two-return and two-backflow adjusting valve, increasing the rotating speed of the second-stage compressor, reducing the rotating speed of the first-stage compressor and increasing the opening degree of the one-return and one-backflow adjusting valve. According to the invention, the exhaust temperature of the two-stage dry screw compressor can be controlled within a reasonable range.

Description

Technical Field

[0001] The invention relates to a multi-stage dry compressor operation control technology, in particular to a two-stage dry screw compressor technology. Background Art

[0002] Positive displacement compressors achieve gas compression through volume changes. In this process, as the gas pressure increases, the gas temperature will also increase accordingly. Wet compressors reduce the gas temperature by spraying liquid, while dry compressors have no effective cooling means and usually have higher exhaust temperatures. Therefore, during the operation of dry screw compressors, due to the high exhaust temperature, the rotor will undergo significant thermal expansion, resulting in changes in the meshing clearance. For high-temperature units, if the clearance is too small, rotor collisions are very likely to occur during operation; if the clearance is too large, gas is prone to leakage, affecting the operating efficiency of the compressor. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide an exhaust temperature control method and system for a two-stage dry screw compressor, which can control the exhaust temperatures of a first-stage compressor and a second-stage compressor of the two-stage dry screw compressor to be within a reasonable range.

[0004] According to a first aspect of the present invention, a method for controlling the exhaust temperature of a two-stage dry screw compressor is provided, comprising controlling the exhaust temperature during operation of the two-stage dry screw compressor, wherein the method for controlling the exhaust temperature during operation of the two-stage dry screw compressor comprises:

[0005] When the pressure of the interstage pipeline of the two-stage dry screw compressor is lower than the lower limit of the preset pressure range, one or more of the following multiple adjustment methods are used to adjust the pressure of the interstage pipeline until the pressure of the interstage pipeline is adjusted to the preset pressure range, and the multiple adjustment methods include reducing the opening of the one-return one-return regulating valve, increasing the speed of the first-stage compressor, reducing the speed of the second-stage compressor and increasing the opening of the two-return two-circulation return valve;

[0006] When the pressure of the interstage pipeline of the two-stage dry screw compressor is higher than the upper limit of the preset pressure range, one or more of the following multiple adjustment methods are used to adjust the pressure of the interstage pipeline until the pressure of the interstage pipeline is adjusted to the preset pressure range, and the multiple adjustment methods include reducing the opening of the two-return two-return regulating valve, increasing the speed of the second-stage compressor, reducing the speed of the first-stage compressor and increasing the opening of the one-return one-return regulating valve;

[0007] Among them, the one-return-one-return regulating valve and the two-return-two-return regulating valve are respectively arranged in the one-return-one-circulation return pipe and the two-return-two-circulation return pipe, the one-return-one-circulation return pipe is connected between the interstage pipe and the intake pipe of the two-stage dry screw compressor, and the two-return-two-circulation return pipe is connected between the exhaust pipe and the interstage pipe of the two-stage dry screw compressor.

[0008] The above-mentioned exhaust temperature control method of the two-stage dry screw compressor also includes controlling the exhaust temperature during the startup process of the two-stage dry screw compressor. Controlling the exhaust temperature during the startup process of the two-stage dry screw compressor includes: when the ratio of the external pressure ratio to the internal pressure ratio of each stage of the compressor exceeds a preset ratio range, adjusting the content volume ratio adjustment structure of the compressor of that stage until the ratio of the external pressure ratio to the internal pressure ratio of each stage of the compressor is adjusted to within the preset ratio range.

[0009] According to a second aspect of the present invention, there is also provided an exhaust temperature control system for a two-stage dry screw compressor, the two-stage dry screw compressor comprising a first-stage compressor, a second-stage compressor, a first driving device, a second driving device, an intake pipe, an interstage pipe, an exhaust pipe, a one-return one-circulation return pipe and a two-return two-circulation return pipe; the first driving device and the second driving device are used to drive the first-stage compressor and the second-stage compressor respectively, and can adjust the rotation speed of the first-stage compressor and the second-stage compressor; the intake pipe is connected to the inlet of the first-stage compressor, the interstage pipe is connected between the outlet of the first-stage compressor and the inlet of the second-stage compressor, and the exhaust pipe is connected to the outlet of the second-stage compressor; The one-return one-circulation return pipe is connected between the interstage pipe and the intake pipe, and the two-return two-circulation return pipe is connected between the exhaust pipe and the interstage pipe; the exhaust temperature control system of the two-stage dry compressor includes a pressure sensor PT01, a pressure sensor PT02, a pressure sensor PT03, a pressure sensor PT04, a one-return one-circulation regulating valve, a two-return two-circulation regulating valve and a controller; the pressure sensor PT01 is arranged in the intake pipe, the pressure sensor PT02 and the pressure sensor PT03 are respectively arranged in the interstage pipe, and the pressure sensor PT04 is arranged in the exhaust pipe. The pressure sensors PT01 to PT04 are used to detect the first-stage intake pressure respectively. , first-stage exhaust pressure, second-stage intake pressure and second-stage exhaust pressure; the one-return one-return regulating valve and the two-return two-return regulating valve are respectively arranged in the one-return one-circulation return pipeline and the two-return two-circulation return pipeline; the controller is used to receive the pressure detection results of the pressure sensors PT01 to PT04, and the valve state signals fed back by the one-return one-return regulating valve and the two-return two-return regulating valve. When the detection pressure of the pressure sensor PT03 or PT02 is lower than the lower limit of the preset pressure range during the operation of the two-stage dry screw compressor, one or more of the following multiple adjustment methods are adopted until the detection pressure of the pressure sensor PT03 or PT02 is within the preset pressure range The multiple adjustment methods include reducing the opening of the one-return and one-return regulating valve, increasing the rotation speed of the first-stage compressor, reducing the rotation speed of the second-stage compressor and increasing the opening of the two-return and two-circulation return valve. When the detection pressure of the pressure sensor PT03 or PT02 is higher than the upper limit of the preset pressure range during the operation of the two-stage dry screw compressor, one or more of the following multiple adjustment methods are adopted until the detection pressure of the pressure sensor PT03 or PT02 is within the preset pressure range. The multiple adjustment methods include reducing the opening of the two-return and two-return regulating valve, increasing the rotation speed of the second-stage compressor, reducing the rotation speed of the first-stage compressor and increasing the opening of the one-return and one-return regulating valve.

[0010] The present invention has at least the following advantages:

[0011] The embodiment of the present invention maintains the matching of the internal and external pressure ratios during the startup process of the two-stage dry screw compressor, and the pressure ratio distribution of the first-stage compressor and the second-stage compressor during stable operation is within the design requirement range, thereby maintaining the exhaust temperature of the first-stage compressor and the second-stage compressor of the two-stage dry screw compressor unit always stable and within a reasonable range. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 A schematic diagram of a two-stage dry screw compressor using an exhaust gas temperature control system according to an embodiment of the present invention is shown.

[0013] Figure 2 A control logic schematic diagram is shown of a specific implementation method of the present invention for controlling the exhaust temperature during the operation of a two-stage dry screw compressor. DETAILED DESCRIPTION

[0014] In actual design, the static clearance of the screw compressor is fixed, so there is a certain reasonable range of temperature corresponding to hot operation, which is usually determined by the exhaust temperature. For dry screw compressors, the exhaust temperature is directly determined by the intake temperature, pressure ratio and efficiency. If the exhaust temperature is too low, the rotor expansion is small, which will increase the leakage of the dry screw compressor and reduce the operating efficiency; if the exhaust temperature is too high, rotor collision will occur, causing the unit to shut down, resulting in equipment failure and economic losses. Therefore, too high exhaust temperature will cause more serious consequences. In actual operation, due to reasons such as fluctuating incoming gas and unstable exhaust pressure, the pressure ratio of the dry screw compressor is prone to offset, causing significant changes in exhaust temperature, especially for multi-stage compressors. Taking a two-stage dry screw compressor as an example, when the pressure at the front and rear ends of the process is stable, the interstage pressure will change due to the mismatch of the gas volume of the first compressor and the second compressor. If the interstage pressure is too high, the pressure ratio of the first compressor is too high, which will cause the first compressor to overheat. If the interstage pressure is too low, the pressure ratio of the second compressor is too high, which will cause the second compressor to overheat. Therefore, by reasonably controlling the interstage pressure and ensuring a reasonable pressure ratio distribution, the exhaust temperature of the two-stage dry screw compressor can be kept within a reasonable range, ensuring stable operation of the unit.

[0015] Figure 1 A schematic diagram of a two-stage dry screw compressor using an exhaust gas temperature control system according to an embodiment of the present invention is shown. Figure 1 The two-stage dry screw compressor includes a first-stage compressor 11, a second-stage compressor 12, a first driving device 21, a second driving device 22, an air intake pipe 31, an inter-stage pipe 32, an exhaust pipe 33, a one-return one-circulation return pipe 34, and a two-return two-circulation return pipe 35.

[0016] The first driving device 21 and the second driving device 22 are used to drive the primary compressor 11 and the secondary compressor 12 respectively, and can adjust the rotation speed of the primary compressor 11 and the secondary compressor 12. In this embodiment, the primary compressor 11 and the secondary compressor 12 are twin-screw compressors.

[0017] The intake pipe 31 is connected to the inlet of the first-stage compressor 11, the interstage pipe 32 is connected between the outlet of the first-stage compressor 11 and the inlet of the second-stage compressor 12, and the exhaust pipe 33 is connected to the outlet of the second-stage compressor 12. The one-return one-circulation return pipe 34 is connected between the interstage pipe 32 and the intake pipe 31, and the two-return two-circulation return pipe 35 is connected between the exhaust pipe 33 and the interstage pipe 32.

[0018] The exhaust temperature control system of the two-stage dry compressor of this embodiment includes pressure sensor PT01, pressure sensor PT02, pressure sensor PT03, pressure sensor PT04, a one-return one-return regulating valve PV01, a two-return two-return regulating valve PV02 and a controller (not shown in the figure).

[0019] The pressure sensor PT01 is arranged in the intake pipe 31 to detect the first-stage intake pressure (i.e., the pressure of the intake pipe 31); the pressure sensor PT02 and the pressure sensor PT03 are respectively arranged in the inter-stage pipe 32 to detect the first-stage exhaust pressure and the second-stage intake pressure respectively; the pressure sensor PT04 is arranged in the exhaust pipe 33 to detect the second-stage exhaust pressure (i.e., the pressure of the exhaust pipe 33).

[0020] The one-return-one-return regulating valve PV01 and the two-return-two-return regulating valve PV02 are respectively arranged in the one-return-one-circulation return pipeline 34 and the two-return-two-circulation return pipeline 35 to adjust the flow rate.

[0021] The controller is used to receive the pressure detection results of the pressure sensors PT01 to PT04, and the valve status signals fed back by the one-return one-return regulating valve PV01 and the two-return two-return regulating valve PV02. When the detection pressure of the pressure sensor PT03 is lower than the lower limit of the preset pressure range during the operation of the two-stage dry screw compressor, one or more of the following multiple adjustment methods are adopted until the detection pressure of the pressure sensor PT03 is within the preset pressure range. The multiple adjustment methods include reducing the opening of the one-return one-return regulating valve PV01, increasing the speed of the first-stage compressor 11, and reducing the pressure of the first-stage compressor 12. Speed, reduce the speed of the secondary compressor 12 and increase the opening of the two-return two-circulation return valve PV02. When the detection pressure of the pressure sensor PT03 is higher than the upper limit of the preset pressure range during the operation of the two-stage dry screw compressor, one or more of the following adjustment methods are adopted until the detection pressure of the pressure sensor PT03 is within the preset pressure range. The multiple adjustment methods include reducing the opening of the two-return two-circulation regulating valve PV02, increasing the speed of the secondary compressor 12, reducing the speed of the first-stage compressor 12 and increasing the opening of the one-return one-circulation regulating valve PV01.

[0022] The aforementioned preset pressure range is n1*P0~n2*P0, P0 is the design value of the pressure of the interstage pipeline 32, which is related to the structural properties of the compressor and is determined when designing the two-stage dry screw compressor, n1=0.94~0.96, n2=1.04~1.06.

[0023] In this embodiment, the first drive device 21 and the second drive device 22 both include a frequency converter and a motor, and the frequency converter is electrically connected to the controller and the motor, respectively. The speed of the primary compressor 11 and the secondary compressor 12 is adjusted by the controller controlling the frequency converter to increase or decrease the speed of the motor. Optionally, the controller adopts a PLC controller, but is not limited thereto.

[0024] Furthermore, the first-stage compressor 11 and the second-stage compressor 12 are also respectively provided with an internal volume ratio adjustment structure; the controller is used to adjust the internal volume ratio adjustment structure of the compressor at this stage when the ratio of the external pressure ratio to the internal pressure ratio of each stage of the compressor exceeds the preset ratio range during the startup of the two-stage dry screw compressor, until the ratio of the external pressure ratio to the internal pressure ratio of each stage of the compressor is adjusted to within the preset ratio range. Among them, the external pressure ratio of the first-stage compressor 11 is equal to the first-stage exhaust pressure divided by the first-stage intake pressure, and the external pressure ratio of the second-stage compressor 12 is equal to the second-stage exhaust pressure divided by the second-stage intake pressure. Optionally, the internal volume ratio adjustment structure is a sliding valve adjustment mechanism.

[0025] In this embodiment, the preset ratio range is n3-n4, n3=0.94-0.96, n4=1.05-1.15.

[0026] Furthermore, the two-stage dry screw compressor includes a two-return one-circulation return pipe 36, which is connected between the exhaust pipe 33 and the intake pipe 31, and is provided with a two-return one-circulation regulating valve PV03. The two-return one-circulation regulating valve PV03 has the function of adjusting the exhaust volume of the two-stage dry screw compressor when starting up, which is irrelevant to the technical problem to be solved by the present application and will not be described in detail here.

[0027] A circulating reflux cooler 71 is provided on the common pipe section of the two-return-one circulation return pipe 36 and the two-return-two circulation return pipe 35; preferably, the circulating reflux cooler should be able to meet 100% reflux cooling requirements and have a certain design margin. An aftercooler 73 is provided on the interstage pipe 32 to reduce the temperature of the intake air of the secondary compressor 12.

[0028] In this embodiment, the intake pipe 31 is provided with a temperature sensor TT01 for detecting the first-stage intake temperature; the inter-stage pipe 32 is provided with a temperature sensor TT02 and a temperature sensor TT03, and the temperature sensor TT02 and the temperature sensor TT03 are respectively used to detect the first-stage exhaust temperature and the second-stage intake temperature; the exhaust pipe 33 is provided with a temperature sensor TT04 for detecting the second-stage exhaust temperature. The signal output ends of the temperature sensors TT01 to TT04 are respectively connected to the input ends of the controller. The temperature sensor TT02 is as close to the exhaust port of the first-stage compressor 11 as possible, and the temperature sensor TT04 is as close to the exhaust port of the second-stage compressor 12 as possible.

[0029] During operation, the inlet medium gas passes through the primary inlet filter 81 and the primary inlet muffler 82 in sequence to enter the primary compressor 11, and after being pressurized by the primary compressor 11, it passes through the primary outlet muffler 83, the aftercooler 73, the secondary inlet filter 84, and the secondary inlet muffler 85 in sequence to enter the secondary compressor 12. After being compressed by the secondary compressor, it passes through the secondary outlet muffler 86 to the medium gas outlet.

[0030] According to another embodiment of the present invention, a method for controlling exhaust temperature of a two-stage dry screw compressor includes controlling the exhaust temperature during startup of the two-stage dry screw compressor and controlling the exhaust temperature during operation of the two-stage dry screw compressor.

[0031] When the compressor starts, the pressure at the exhaust end gradually builds up and the system external pressure ratio keeps changing. When the difference between the internal and external pressure ratios is too large, the compression operation will be unstable and the compressor will vibrate greatly. To ensure that the internal and external pressure ratios match, the compressor runs smoothly and the gas is not compressed over-temperature, each level of compressor is equipped with a content ratio adjustment mechanism to adjust the internal pressure ratio ε of the compressor.

[0032] The controller is used to adjust the content volume ratio adjustment structure of the compressor at this stage when the ratio of the external pressure ratio to the internal pressure ratio of each stage of the compressor exceeds a preset ratio range during the startup of the two-stage dry screw compressor, until the ratio of the external pressure ratio to the internal pressure ratio of each stage of the compressor is adjusted to within the preset ratio range.

[0033] Specifically, when the ratio of the external pressure ratio to the internal pressure ratio of each stage of the compressor is lower than the lower limit of the preset ratio range, the content volume ratio adjustment structure of the compressor at this stage is adjusted to reduce the internal pressure ratio of the compressor; when the ratio of the external pressure ratio to the internal pressure ratio of each stage of the compressor is higher than the upper limit of the preset ratio range, the content volume ratio adjustment structure of the compressor at this stage is adjusted to increase the internal pressure ratio of the compressor.

[0034] In this embodiment, the preset ratio range is n3-n4, n3=0.94-0.96, n4=1.05-1.15. In a specific implementation, the preset ratio range is 0.95-1.1, when the external pressure ratio of the compressor is less than 0.95*ε, it means that the ratio of the external pressure ratio of the compressor to the internal pressure ratio is lower than the lower limit of the preset ratio range, when the external pressure ratio of the compressor is greater than 1.1*ε, it means that the ratio of the external pressure ratio of the compressor to the internal pressure ratio is higher than the upper limit of the preset ratio range, when the external pressure ratio of the compressor is greater than or equal to 0.95*ε and less than or equal to 1.1*ε, it means that the internal and external pressure ratios match and no adjustment is required.

[0035] When the compressor is operating normally, the inter-stage pressure ratio distribution is controlled to ensure that the inter-stage pressure distribution is reasonable and the compression ratio of the two-stage compressor is within the design range, which can ensure that the exhaust temperature of the two-stage screw compressor does not exceed the temperature.

[0036] Controlling the exhaust gas temperature during operation of a two-stage dry screw compressor includes:

[0037] When the pressure Pj1 of the interstage pipeline 32 of the two-stage dry screw compressor is lower than the lower limit of the preset pressure range, one or more of the following multiple adjustment methods are used to adjust the pressure of the interstage pipeline until the pressure Pj1 of the interstage pipeline 32 is adjusted to the preset pressure range, and the multiple adjustment methods include reducing the opening of the one-return one-return regulating valve PV01, increasing the speed of the first-stage compressor 11, reducing the speed of the second-stage compressor 12 and increasing the opening of the two-return two-circulation return valve PV02;

[0038] When the pressure Pj1 of the interstage pipeline 32 of the two-stage dry screw compressor is higher than the upper limit of the preset pressure range, one or more of the following multiple adjustment methods are used to adjust the pressure Pj1 of the interstage pipeline until the pressure Pj1 of the interstage pipeline 32 is adjusted to the preset pressure range, and the multiple adjustment methods include reducing the opening of the two-return two-return regulating valve PV02, increasing the speed of the second-stage compressor 12, reducing the speed of the first-stage compressor 11 and increasing the opening of the one-return one-return regulating valve PV01;

[0039] Among them, the one-return-one-return regulating valve PV01 and the two-return-two-return regulating valve PV02 are respectively arranged in the one-return-one-circulation return pipe 34 and the two-return-two-circulation return pipe 35, the one-return-one-circulation return pipe 34 is connected between the interstage pipe 32 and the intake pipe 31 of the two-stage dry screw compressor, and the two-return-two-circulation return pipe 35 is connected between the exhaust pipe 33 and the interstage pipe 32 of the two-stage dry screw compressor.

[0040] In this embodiment, in the process of adjusting the pressure Pj1 of the interstage pipeline 32, only one adjustment method is used each time, and only when the adjustment method of the previous priority cannot adjust the pressure Pj1 of the interstage pipeline to the preset pressure range within a predetermined time, the adjustment method of the next priority is executed. After each adjustment, wait for a period of time until the system runs stably, and then adjust cyclically according to the pressure change of the interstage pipeline until the requirements are met.

[0041] Among them, when the pressure Pj1 of the interstage pipeline of the two-stage dry screw compressor is lower than the lower limit of the preset pressure range, the priority order of the multiple adjustment methods is: reduce the opening of the one-return and one-return regulating valve PV01, increase the speed of the first-stage compressor 11, reduce the speed of the second-stage compressor 12, and increase the opening of the two-return and two-return regulating valve PV02; when the pressure Pj1 of the interstage pipeline of the two-stage dry screw compressor is higher than the upper limit of the preset pressure range, the priority order of the multiple adjustment methods is: reduce the opening of the two-return and two-return regulating valve PV02, increase the speed of the second-stage compressor 12, reduce the speed of the first-stage compressor 11, and increase the opening of the one-return and one-return regulating valve PV01. The above priority order has the advantage of high adjustment efficiency.

[0042] The aforementioned preset pressure range is n1*P0~n2*P0, P0 is the design value of the pressure of the interstage pipeline, n1=0.94~0.96, n2=1.04~1.06. In a specific embodiment, the pressure Pj1 of the interstage pipeline 32 adopts the intake pressure of the secondary compressor 12, and P0 is set to Ps is the intake pressure design value of the two-stage dry screw compressor (i.e. the intake pressure design value of the first-stage compressor), Pd is the exhaust pressure design value of the two-stage dry screw compressor (i.e. the exhaust pressure design value of the second-stage compressor), and the controller can obtain the intake pressure of the second-stage compressor 12 by reading the detection result of the pressure sensor PT03. The preset pressure range is 0.95*P0~1.05*P0. When 0.95*P0≤Pj1≤1.05*P0, it means that no adjustment is required and the existing operating conditions can be maintained unchanged. The aforementioned preset time is 10 minutes.

[0043] In other embodiments, the pressure Pj1 of the interstage pipeline can also use the exhaust pressure of the first-stage compressor as the pressure of the interstage pipeline 32. In this case, P0 is set to c = 20kpa ~ 30kpa.

[0044] Figure 2 A control logic schematic diagram is shown of a specific implementation method of the present invention for controlling the exhaust temperature during the operation of a two-stage dry screw compressor.

[0045] When the compressor is operating normally, the pressure sensor PT03 monitors the pressure Pj1 of the interstage pipeline 32 (i.e., the pressure Pj1 of the interstage pipeline 32 is equal to the detection value of the pressure sensor PT03). The design value of the pressure of the interstage pipeline 32 is P0. In order to maintain the stable pressure distribution, the controller adopts the following method: Figure 2 The control logic shown in the figure can be divided into three working conditions according to the pressure of the interstage pipeline, and the execution steps are as follows:

[0046] Working condition 1: Pj1<0.95*P0, use the following adjustment steps for adjustment:

[0047] 1-1. If the opening of the return-to-return regulating valve PV01 can be reduced, then reduce the opening of the return-to-return regulating valve PV01 by 5% and then execute step 1-5. If not, execute step 1-2.

[0048] 1-2. If the speed of the motor M1 of the primary compressor 11 can be increased, the speed of the motor M1 of the primary compressor is increased by 3% and then step 1-5 is performed. If not, step 1-3 is performed;

[0049] 1-3. If the speed of the motor M2 of the secondary compressor 12 can be reduced, the speed of the motor M2 of the secondary compressor is reduced by 3% and then step 1-5 is performed. If not, step 1-4 is performed;

[0050] 1-4. Increase the opening of the secondary return and secondary return regulating valve PV02 by 5%;

[0051] 1-5. Wait for ten minutes and adjust the cycle according to the pressure changes in the inter-stage pipeline.

[0052] Working condition 2: Pj1>1.05*P0, use the following adjustment steps to adjust:

[0053] 2-1. If the opening of the two-return two-circulation return regulating valve PV02 can be reduced, reduce the opening of the two-return two-circulation return regulating valve PV02 by 5% and then execute step 2-5. If not, execute step 2-2;

[0054] 2-2. If the speed of the motor M2 of the secondary compressor 12 can be increased, the speed of the motor M2 of the secondary compressor 12 is increased by 3% and then step 2-5 is performed. If not, step 2-3 is performed;

[0055] 2-3. If the speed of the motor M1 of the primary compressor 11 can be reduced, the speed of the motor M1 of the primary compressor 11 is reduced by 3% and then step 2-5 is performed. If not, step 2-4 is performed.

[0056] 2-4. Increase the opening of the return flow regulating valve PV01 by 5%;

[0057] 2-5. Wait for ten minutes and adjust the cycle according to the pressure changes in the inter-stage pipeline.

[0058] Working condition 3: 0.95*P01≤Pj1≤1.05*P01, maintain the existing working conditions unchanged.

[0059] The dry screw compressor is designed to take full account of the thermal expansion during operation, and the design clearance meets the temperature adjustment range during operation. The exhaust temperature of the dry screw compressor mainly depends on the pressure ratio. After setting the design pressure ratio, through feedback adjustment, the pressure ratio distribution of the first-stage compressor and the second-stage compressor is within a reasonable range during stable operation, and the pressure ratio fluctuation range of the compressor is maintained within ±5%, thereby maintaining the stability of the exhaust temperature of the first-stage compressor and the second-stage compressor of the two-stage dry screw compressor.

[0060] The above description is only a preferred embodiment of the invention and is not intended to limit the invention. Although the invention is described in detail with reference to the above embodiments, those skilled in the art can still modify the technical solutions recorded in the above embodiments or replace some of the technical features with equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the invention shall be included in the protection scope of the invention.

Claims

1. A method for controlling exhaust temperature of a two-stage dry screw compressor, characterized in that: The exhaust temperature control during the operation of the two-stage dry screw compressor includes: When the pressure of the interstage pipeline of the two-stage dry screw compressor is lower than the lower limit of the preset pressure range, one or more of the following multiple adjustment methods are used to adjust the pressure of the interstage pipeline until the pressure of the interstage pipeline is adjusted to the preset pressure range, and the multiple adjustment methods include reducing the opening of the one-return one-return regulating valve, increasing the speed of the first-stage compressor, reducing the speed of the second-stage compressor and increasing the opening of the two-return two-circulation return valve; When the pressure of the interstage pipeline of the two-stage dry screw compressor is higher than the upper limit of the preset pressure range, one or more of the following multiple adjustment methods are used to adjust the pressure of the interstage pipeline until the pressure of the interstage pipeline is adjusted to the preset pressure range, and the multiple adjustment methods include reducing the opening of the two-return two-return regulating valve, increasing the speed of the second-stage compressor, reducing the speed of the first-stage compressor and increasing the opening of the one-return one-return regulating valve; Among them, the one-return-one-return regulating valve and the two-return-two-return regulating valve are respectively arranged in the one-return-one-circulation return pipe and the two-return-two-circulation return pipe, the one-return-one-circulation return pipe is connected between the interstage pipe and the intake pipe of the two-stage dry screw compressor, and the two-return-two-circulation return pipe is connected between the exhaust pipe and the interstage pipe of the two-stage dry screw compressor.

2. The exhaust gas temperature control method of a two-stage dry screw compressor according to claim 1, characterized in that: In the process of adjusting the pressure of the interstage pipeline, only one adjustment method is used each time, and only when the adjustment method of the previous priority cannot adjust the pressure of the interstage pipeline to the preset pressure range within a predetermined time, the adjustment method of the next priority is executed; When the pressure of the interstage pipeline of the two-stage dry screw compressor is lower than the lower limit of the preset pressure range, the priority order of the multiple adjustment methods is: reducing the opening of the one-return one-return regulating valve, increasing the speed of the first-stage compressor, reducing the speed of the second-stage compressor and increasing the opening of the two-return two-return regulating valve; When the pressure of the interstage pipeline of the two-stage dry screw compressor is higher than the upper limit value of the preset pressure range, the priority order of the multiple adjustment methods is: reducing the opening of the two-return and two-return regulating valve, increasing the speed of the second-stage compressor, reducing the speed of the first-stage compressor and increasing the opening of the one-return and one-return regulating valve.

3. The exhaust gas temperature control method of a two-stage dry screw compressor according to claim 1, characterized in that: The preset pressure range is n1*P0~n2*P0, P0 is the design value of the pressure of the inter-stage pipeline, n1=0.94~0.96, n2=1.04~1.

06.

4. The exhaust gas temperature control method of a two-stage dry screw compressor according to claim 3, characterized in that: When the inlet pressure of the two-stage compressor is used as the pressure of the interstage pipeline, When the exhaust pressure of the first-stage compressor is used as the pressure of the inter-stage pipeline, Among them, Ps is the design value of the inlet pressure of the two-stage dry screw compressor, Pd is the design value of the exhaust pressure of the two-stage dry screw compressor, and c=20kpa~30kpa.

5. The exhaust gas temperature control method of a two-stage dry screw compressor according to claim 1, characterized in that: It also includes controlling the exhaust temperature during the startup of the two-stage dry screw compressor. Controlling the exhaust temperature during the startup of the two-stage dry screw compressor includes: When the ratio of the external pressure ratio to the internal pressure ratio of each stage of the compressor exceeds the preset ratio range, the content volume ratio adjustment structure of the compressor of this stage is adjusted until the ratio of the external pressure ratio to the internal pressure ratio of each stage of the compressor is adjusted to within the preset ratio range.

6. The exhaust gas temperature control method of a two-stage dry screw compressor according to claim 5, characterized in that: The preset ratio range is n3-n4, n3=0.94-0.96, n4=1.05-1.

15.

7. The exhaust gas temperature control method of a two-stage dry screw compressor according to claim 5, characterized in that: The internal volume ratio adjustment structure is a slide valve adjustment mechanism.

8. An exhaust temperature control system for a two-stage dry screw compressor, the two-stage dry screw compressor comprising a primary compressor, a secondary compressor, a first drive device, a second drive device, an intake pipe, an interstage pipe, an exhaust pipe, a one-circulation return pipe and a two-circulation return pipe; the first drive device and the second drive device are used to drive the primary compressor and the secondary compressor respectively, and can adjust the rotation speed of the primary compressor and the secondary compressor; the intake pipe is connected to the inlet of the primary compressor, the interstage pipe is connected between the outlet of the primary compressor and the inlet of the secondary compressor, and the exhaust pipe is connected to the outlet of the secondary compressor; the one-circulation return pipe is connected between the interstage pipe and the intake pipe, and the two-circulation return pipe is connected between the exhaust pipe and the interstage pipe; characterized in that The exhaust temperature control system of the two-stage dry compressor includes a pressure sensor PT01, a pressure sensor PT02, a pressure sensor PT03, a pressure sensor PT04, a one-return one-return regulating valve, a two-return two-return regulating valve and a controller; The pressure sensor PT01 is arranged in the intake pipe, the pressure sensor PT02 and the pressure sensor PT03 are arranged in the interstage pipe respectively, and the pressure sensor PT04 is arranged in the exhaust pipe. The pressure sensors PT01 to PT04 are used to detect the first-stage intake pressure, the first-stage exhaust pressure, the second-stage intake pressure and the second-stage exhaust pressure respectively; The one-return-one-return regulating valve and the two-return-two-return regulating valve are respectively arranged on the one-return-one-circulation return pipeline and the two-return-two-circulation return pipeline; The controller is used to receive the pressure detection results of the pressure sensors PT01 to PT04, and the valve status signals fed back by the one-return one-return regulating valve and the two-return two-return regulating valve. When the detection pressure of the pressure sensor PT03 or PT02 is lower than the lower limit of the preset pressure range during the operation of the two-stage dry screw compressor, one or more of the following multiple adjustment methods are adopted until the detection pressure of the pressure sensor PT03 or PT02 is within the preset pressure range. The multiple adjustment methods include reducing the opening of the one-return one-return regulating valve, increasing the opening of the first-stage compressor, and adjusting the pressure of the pressure sensor PT03 or PT02. The speed of the machine is increased, the speed of the secondary compressor is reduced and the opening of the two-return two-circulation reflux valve is increased. When the detection pressure of the pressure sensor PT03 or PT02 is higher than the upper limit of the preset pressure range during the operation of the two-stage dry screw compressor, one or more of the following adjustment methods are adopted until the detection pressure of the pressure sensor PT03 or PT02 is within the preset pressure range. The multiple adjustment methods include reducing the opening of the two-return two-circulation regulating valve, increasing the speed of the secondary compressor, reducing the speed of the first-stage compressor and increasing the opening of the one-return one-circulation regulating valve.

9. The exhaust gas temperature control system of the two-stage dry screw compressor according to claim 8, characterized in that: The first-stage compressor and the second-stage compressor are respectively provided with an internal volume ratio adjustment structure; The controller is used to adjust the content volume ratio adjustment structure of the compressor at this stage when the ratio of the external pressure ratio to the internal pressure ratio of each stage of the compressor exceeds a preset ratio range during the startup of the two-stage dry screw compressor, until the ratio of the external pressure ratio to the internal pressure ratio of each stage of the compressor is adjusted to within the preset ratio range.

10. The exhaust gas temperature control system of the two-stage dry screw compressor according to claim 8, characterized in that: The first driving device and the second driving device both include a frequency converter and a motor, and the frequency converter is electrically connected to the controller and the motor respectively.

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