Compressed air aftertreatment system

Abstract

The invention discloses a compressed air post-processing system which comprises a variable-frequency refrigeration dryer and a controller for performing variable-frequency control on the variable-frequency refrigeration dryer, wherein the controller obtains the gas production rate of the variable-frequency air compressor and performs variable-frequency control on the variable-frequency refrigeration dryer according to the gas production rate of the variable-frequency air compressor. According to the variable-frequency refrigeration dryer, the variable-frequency control of the variable-frequency refrigeration dryer is realized by directly acquiring the gas production rate of the variable-frequency air compressor and integrating the compressed air pressure and temperature parameters, so that the variable-frequency control of the variable-frequency refrigeration dryer can change along with the change of the variable-frequency air compressor in real time, and the defect that the variable-frequency control of the variable-frequency refrigeration dryer is lagged in the prior art can be effectively avoided; therefore, the accuracy of frequency conversion control in the post-treatment process of the compressed air is improved, and the quality of the compressed air is improved.

Description

Technical Field

[0001] This invention relates to a compressed air processing system, and more specifically to a compressed air after-processing system. Background Technology

[0002] As a key component in compressed air after-treatment systems, refrigerated dryer manufacturers are gradually introducing variable frequency refrigerated dryer products to the market. A refrigerated dryer, also known simply as a refrigerated air dryer, is an air source processing element in a pneumatic system. It utilizes refrigerant to exchange heat with compressed air, reducing the compressed air temperature to a dew point range of 2–10°C. With the development of energy-saving technologies, permanent magnet variable frequency technology is increasingly widely used in the air compressor industry. The air compressor's discharge capacity can be adjusted over a wide range according to changes in the user's air load through frequency conversion control. This places higher demands on the refrigerated dryers in the after-treatment system.

[0003] Conventional fixed-frequency refrigerated dryers cannot achieve energy-saving operation by controlling the compressor output through start-stop operation. In addition, because the refrigerant evaporation rate is only adjusted within a small range using an expansion valve, it is difficult to adapt to the wide adjustment range when the compressed air volume changes. Often, when the output frequency of the front-end variable-frequency compressor is low, that is, when the compressed air volume is small, the refrigerant evaporation rate of the refrigerated dryer is too large relative to the cooling capacity, which leads to ice blockage inside the evaporator of the refrigerated dryer, causing an increase in system pressure drop, or even blockage that prevents compressed air from passing through. In more serious cases, the expansion of ice can damage the evaporator, rendering the refrigerated dryer unusable.

[0004] To address the aforementioned issues, variable frequency refrigerated air dryers, which adjust the refrigerant circulation volume according to changes in cooling demand when the compressed air load fluctuates, have become widely used for energy-saving operation. Chinese patent document CN216440310U discloses a variable frequency speed control and voltage stabilizing energy-saving device for a refrigerated air dryer. This device is used in a refrigerated air dryer comprising an air precooler, an evaporator refrigerant system assembly, and a refrigerant condenser. The device includes a variable frequency speed control system, a signal sensor, a variable frequency refrigeration compressor, an air precooler fan, and a refrigerant condenser fan. The signal sensor is connected to the evaporator refrigerant system assembly and to the variable frequency speed control system. The variable frequency speed control system has inverter a and inverter b. Inverter a is controlled by the variable frequency refrigeration compressor, and inverter b is controlled by the air precooler fan and the refrigerant condenser fan, respectively. The variable frequency refrigeration compressor is connected to the evaporator refrigerant system assembly.

[0005] Another Chinese patent document, CN206262330U, discloses a high-efficiency refrigerated dryer, including a pre-cooler, a heat exchanger, an evaporator, a gas-liquid separator, a compressor, a hot gas bypass valve, a condenser, a drying filter, and an expansion valve. The pre-cooler, heat exchanger, evaporator, and gas-liquid separator are connected in sequence, and the outlet of the gas-liquid separator is connected to the heat exchanger. The compressor, hot gas bypass valve, condenser, drying filter, expansion valve, and evaporator are connected in sequence through pipes. The compressor is a variable frequency compressor, and the expansion valve is an electronic expansion valve. The variable frequency compressor is connected to a controller, and the controller is also connected to a temperature sensor, which is located at the pipe connecting the gas-liquid separator and the evaporator.

[0006] In the aforementioned patent documents, frequency conversion adjustment of the variable frequency refrigerated dryer is achieved by obtaining the temperature or pressure of the refrigerant system to realize energy-saving operation. However, in the actual operation of variable frequency refrigerated dryers, there are still cases where the drying effect is not up to standard or ice blockage occurs. Summary of the Invention

[0007] To address the technical problems of substandard drying effect or ice blockage in variable frequency refrigerated dryers in existing compressed air post-treatment systems, this invention provides a compressed air post-treatment system, including a variable frequency refrigerated dryer and a controller for frequency conversion control of the variable frequency refrigerated dryer; wherein: the controller acquires the air output of the variable frequency air compressor and performs frequency conversion control on the variable frequency refrigerated dryer according to the air output of the variable frequency air compressor.

[0008] Currently, there are various reasons why variable frequency refrigerated dryers may fail to achieve the required drying effect or experience ice blockage, such as poor air circulation or condenser tube malfunction. However, in addition to the above-mentioned common faults, the applicant found that even with a well-functioning compressed air after-treatment system, the drying effect may still be substandard or ice blockage may occur during use. After analyzing this phenomenon, it was found that this is because variable frequency refrigerated dryers are currently used independently of the air compressor. During the operation of the variable frequency refrigerated dryer, frequency adjustment is performed based on the evaporation temperature of the evaporator or the high and low pressure status of the refrigerant system.

[0009] However, both the evaporation temperature and the high / low pressure state of the refrigerant system are only reflected in the temperature or pressure changes after the compressed air load changes, following the temperature change within the evaporator. Therefore, there is a lag in temperature or pressure changes. This lag leads to a mismatch between the actual refrigerant circulation volume and the required cooling capacity under conditions of large fluctuations in compressed air consumption. Specifically, as the compressed air load increases, the cooling capacity cannot increase in time due to control lag, resulting in a higher exhaust dew point value for the inverter refrigerated dryer and substandard drying performance. Conversely, as the compressed air load decreases, the refrigerant evaporation rate exceeds the required cooling capacity, leading to excessively low evaporation temperatures and ice blockage in the inverter refrigerated dryer. This not only fails to achieve energy-saving operation but may also affect the stability of the inverter refrigerated dryer's operation.

[0010] Therefore, in this solution, the frequency conversion control of the variable frequency refrigerated dryer is achieved by directly acquiring the air output of the variable frequency air compressor. This allows the operating status of the compressed air after-treatment system to change in real time with the air output of the variable frequency air compressor, with virtually no lag. This adapts to the real-time changes in the compressed air load in the equipment, thus avoiding problems such as substandard drying effect or ice blockage in the compressed air after-treatment system caused by lagging frequency conversion control. Furthermore, since this solution directly acquires the air output of the variable frequency air compressor, it does not require control based on the evaporation temperature of the variable frequency refrigerated dryer or the high and low pressure status of the refrigerant system collected by the original sensors in the system. The sensor data is only used for interlock control of system safety operation, thus avoiding control deviations caused by sensor failure or acquisition errors, and improving the accuracy of frequency conversion control of the compressed air after-treatment system.

[0011] Preferably, the controller obtains the air output of the variable frequency air compressor by acquiring its operating status. Since the air output of the variable frequency air compressor is directly related to its operating status, this solution obtains a relatively accurate air output by acquiring the operating status of the variable frequency air compressor, thereby ensuring accurate variable frequency control of the compressed air after-treatment system.

[0012] Preferably, the operating status acquired by the controller includes the output frequency and / or output power of the variable frequency air compressor. Since the output frequency and output power are directly related to the air production rate of the variable frequency air compressor, the higher the output frequency and / or output power, the higher the air production rate. Therefore, this solution achieves variable frequency control of the refrigerant compressor by acquiring the output frequency and / or output power of the variable frequency air compressor, resulting in faster feedback and simpler and more efficient implementation.

[0013] Preferably, the variable frequency refrigerated dryer includes a variable frequency refrigerant compressor. This solution utilizes a variable frequency refrigerant compressor to achieve the refrigerated drying operation of compressed air, enabling a wide range of load adjustments and featuring a simple structure.

[0014] Preferably, the variable frequency refrigerated dryer also includes an evaporator, and the evaporator's connecting branch is equipped with an electronic expansion valve. Considering that the air output of the variable frequency air compressor only varies within a small range, the controller is used to control the electronic expansion valve to adjust the evaporator within a small range, so that the compressed air after-treatment system can more accurately follow the changes in the air output of the variable frequency air compressor for variable frequency control, and the operation is simple.

[0015] Preferably, the variable frequency refrigerated dryer also includes a condenser, which is located in the piping between the refrigerant compressor and the evaporator. In this design, the inclusion of a condenser further improves the accuracy of the variable frequency control of the compressed air after-treatment system, and the structure is simple.

[0016] Preferably, the system also includes a purification device for preliminary treatment of the compressed air output from the variable frequency air compressor. Since the compressed air output from the variable frequency air compressor contains impurities such as moisture and oil, this solution utilizes a purification device to perform preliminary treatment on the compressed air, thereby purifying it and preventing its impact on subsequent processing equipment such as the refrigerant compressor, while also improving the purity of the compressed air.

[0017] The present invention has the following beneficial effects:

[0018] 1. In this invention, the frequency conversion control of the variable frequency refrigerated dryer is achieved by directly obtaining the air output of the variable frequency air compressor. This allows the frequency conversion control of the variable frequency refrigerated dryer to change in real time with the changes of the variable frequency air compressor, effectively avoiding the shortcomings of the lagging frequency conversion control in the prior art. This avoids the problems of substandard drying effect or ice blockage in the compressed air post-treatment system caused by lagging frequency conversion control.

[0019] 2. This invention can also avoid control deviations caused by sensor failure or acquisition errors, thus improving the accuracy of frequency conversion control in compressed air after-treatment systems. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of Embodiment 1 of the compressed air after-treatment system of the present invention;

[0021] Figure 2 This is a schematic diagram of Embodiment 2 of the compressed air after-treatment system of the present invention. Detailed Implementation

[0022] The following detailed description illustrates the specific implementation method:

[0023] 1. Definition

[0024] Variable frequency air compressor: A device used for air compression. Its working principle is similar to the energy-saving control of fan motors and water pumps. Variable frequency air compressors can control the input voltage frequency according to the load changes to maintain the stability of parameters such as pressure, flow rate, and temperature.

[0025] Refrigerated air dryer: By utilizing the principle of heat exchange between refrigerant and compressed air, it transforms humid compressed air into dry compressed air. Its working process includes compressed air entering the heat exchanger for cooling, exchanging heat with the low-temperature compressed air at the outlet to achieve initial cooling, and then entering the evaporator for further cooling. During this process, water and oil are condensed and separated by a built-in separation device to achieve the drying of compressed air.

[0026] Gas production: refers to the flow rate of gas produced by a variable frequency air compressor within a certain period of time.

[0027] Ice blockage: This refers to the situation where, during the operation of a variable frequency refrigerated dryer, the condensate on the compressed air side freezes below its freezing point due to excessively low evaporation temperature, causing internal blockage and affecting the normal operation of the equipment.

[0028] Variable frequency drive (VFD): VFD changes the power supply frequency to regulate the load, thereby reducing power consumption, minimizing losses, and extending the lifespan of equipment.

[0029] Refrigerant: A fluid used in a refrigeration cycle to absorb heat, evaporate at a low temperature, and then condense at a high temperature to release heat. It is the core medium of a refrigeration system.

[0030] 2. The reference numerals in the accompanying drawings of the instruction manual include: 1. Variable frequency air compressor; 2. Oil-gas separator; 3. Evaporator; 4. Variable frequency refrigerant compressor; 5. Condenser; 6. Electronic expansion valve.

[0031] Figure 1 and Figure 2 The dashed box in the middle represents a variable frequency refrigerated dryer.

[0032] Example 1

[0033] The basics are as follows: Figure 1 As shown: A compressed air after-treatment system includes a variable frequency refrigerated dryer and a controller for frequency conversion control of the variable frequency refrigerated dryer; the controller acquires the air output of the variable frequency air compressor 1 and performs frequency conversion control on the variable frequency refrigerated dryer according to the air output of the variable frequency air compressor 1. In this embodiment, the same controller is used to control both the variable frequency air compressor and the variable frequency refrigerated dryer.

[0034] In obtaining the air output of the variable frequency air compressor 1, the controller obtains the air output of the variable frequency air compressor 1 by means of communication or other effective means. In this embodiment, the obtained operating parameters include the output power and output frequency of the variable frequency air compressor 1. In other embodiments, the obtained operating parameters may also be the pressure or exhaust volume of the variable frequency air compressor 1.

[0035] The aforementioned variable frequency refrigerated dryer includes a variable frequency refrigerant compressor 4, an evaporator 3, an electronic expansion valve 6, and a condenser 5. The variable frequency refrigerant compressor 4 is equipped with a variable frequency motor that is controlled by a variable frequency controller. The electronic expansion valve 6 achieves a wide range of throttling regulation through precise motor control of its opening. In this embodiment, the evaporator 3 is an integrated preheating evaporator, but it can also be a separate plate heat exchanger or shell-and-tube heat exchanger. The condenser 5 is an air-cooled condenser, but it can also be a water-cooled condenser.

[0036] A purification device is also provided on the pipeline between the output end of the variable frequency air compressor 1 and the variable frequency refrigerated dryer. The purification device can perform preliminary treatment on the compressed air output by the variable frequency air compressor 1. In this embodiment, the purification device adopts an oil-gas separator 2.

[0037] Preferably, the compressed air after-treatment system also includes a temperature difference sensor capable of measuring the temperature of the airflow produced by the variable frequency air compressor and a pressure sensor capable of detecting the airflow pressure. When performing variable frequency control on the variable frequency refrigerated dryer, the variable frequency refrigerated dryer is controlled by fitting the air output of the variable frequency air compressor and the corresponding temperature and pressure parameters to the current heat load parameters.

[0038] The specific implementation process is as follows: During use, the compressed air output by the variable frequency air compressor 1 undergoes preliminary purification through the oil-gas separator 2 before entering the subsequent variable frequency refrigerated dryer for further processing to obtain dry compressed air. During the operation of the variable frequency refrigerated dryer, the controller acquires the output power and output frequency of the variable frequency air compressor 1, and then performs variable frequency control on the variable frequency refrigerated dryer based on the changes in output power and output frequency.

[0039] Under different operating conditions of reduced and increased compressed air consumption, the output frequency change ( / Hz), output power change ( / kW), frequency change time ( / s), and lag time ( / s) of the variable frequency air compressor from the frequency change to the evaporation temperature of the refrigerated dryer reaching a new equilibrium were recorded.

[0040] control group

[0041] In operation, the compressed air output from the variable frequency air compressor 1 undergoes preliminary purification in the oil-gas separator 2 before entering the subsequent variable frequency refrigerated dryer for further processing to obtain dry compressed air. Under the set inlet pressure and temperature conditions of the variable frequency refrigerated dryer, the variable frequency control is achieved by adjusting the outlet temperature of the evaporator or the refrigerant pressure inside the refrigerated dryer under different operating conditions, such as decreasing and increasing compressed air consumption. The output frequency change ( / Hz), output power change ( / kW), frequency change time ( / s), and the lag time ( / s) between the air compressor frequency change and the refrigerated dryer reaching a new equilibrium evaporation temperature are recorded.

[0042] The results are shown in the table below.

[0043]

[0044]

[0045] As can be seen from the table above, in the compressed air post-treatment process, the variable frequency control method of directly obtaining the air output of the variable frequency air compressor to realize the variable frequency control of the variable frequency refrigerated dryer can realize that the operating status of the compressed air post-treatment system changes in real time with the air output of the variable frequency air compressor, so that the refrigerant temperature does not fluctuate significantly, the outlet pressure dew point value of the variable frequency refrigerated dryer is stable, meeting the design dew point performance requirements, the drying effect meets the standard, and there will be no ice blockage in the variable frequency refrigerated dryer.

[0046] Example 2

[0047] The difference from Embodiment 1 is that in this embodiment, the variable frequency refrigerated dryer is used as an independent device. That is, the variable frequency refrigerated dryer has its own controller. The controller of the variable frequency refrigerated dryer has a reserved input interface for the status signal of the variable frequency air compressor or a reserved communication interface to collect the status parameters of the variable frequency air compressor in order to realize the joint control of the variable frequency.

[0048] The above descriptions are merely embodiments of the present invention. Commonly known structures and characteristics are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the field prior to the application date or priority date, are aware of all existing technologies in that field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can, under the guidance of this application, improve and implement this solution in combination with their own capabilities. Some typical known structures or methods should not be obstacles for those skilled in the art to implement this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention. These should also be considered within the scope of protection of the present invention, and will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A compressed air after-treatment system, comprising a variable frequency refrigerated dryer and a controller for frequency conversion control of the variable frequency refrigerated dryer; characterized in that: The controller acquires the air output of the variable frequency air compressor and performs variable frequency control on the variable frequency refrigerated dryer based on the air output of the variable frequency air compressor.

2. The compressed air aftertreatment system according to claim 1, characterized in that: The controller obtains the air output of the variable frequency air compressor by acquiring the operating status of the variable frequency air compressor.

3. The compressed air aftertreatment system according to claim 2, characterized in that: The operating status acquired by the controller includes the output frequency and / or output power of the variable frequency air compressor.

4. The compressed air aftertreatment system according to any one of claims 1-3, characterized in that: The variable frequency refrigerated dryer includes a variable frequency refrigerant compressor.

5. The compressed air aftertreatment system according to claim 4, characterized in that: The variable frequency refrigerated dryer also includes an evaporator, and the connecting branch of the evaporator is equipped with an electronic expansion valve.

6. The compressed air aftertreatment system according to claim 5, characterized in that: The variable frequency refrigerated dryer also includes a condenser, which is located in the pipeline between the variable frequency refrigerant compressor and the evaporator.

7. The compressed air aftertreatment system according to claim 6, characterized in that: It also includes a purification device for preliminary treatment of the compressed air output from the variable frequency air compressor.

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