Anticipatory controlled compressed air refrigeration dryer

Abstract

A compressed air refrigeration dryer for dehumidifying compressed air by means of a refrigerant circuit with carbon dioxide as the refrigerant, comprising at least one compressor (1), a gas cooler (3), at least one evaporator (2) configured to dehumidify compressed air passed on its secondary side at its cold surface, a refrigerant receiver (5.1, 11), an expansion valve (6) or an ejector, and a heat exchanger (8, 18) for heating the dried compressed air, which is connected downstream of the evaporator (2) at its air-side outlet, characterized in that the compressed air refrigeration dryer further comprises a control unit, at least one frequency converter connected upstream of each electrical power input of the at least one compressor (1), and a temperature sensor at a cooling water inlet of the gas cooler (3) for detecting a cooling water temperature.a temperature sensor for detecting a compressed air temperature at a compressed air inlet provided for introducing compressed air to be dehumidified into the compressed air refrigeration dryer, at least one pressure dew point sensor for detecting air humidity and a volume flow sensor for detecting a compressed air volume flow at the compressed air inlet, and at least one pressure sensor for detecting the refrigerant pressure at the compressor inlets, wherein the control unit is connected to the at least one compressor (1), the at least one frequency converter, the temperature sensors, the at least one pressure dew point sensor, the volume flow sensor and the at least one pressure sensor and is configured in such a way as tothat it can continuously read and store measured values ​​acquired by the sensors and that it can regulate the cooling capacity generated by the refrigerant circuit by controlling the at least one compressor (1) and / or the at least one frequency converter in such a way that dehumidified compressed air flowing out of the compressed air outlet of the refrigerated dryer constantly has a predetermined pressure dew point during operation of the compressed air refrigerated dryer.

Description

[0001] The invention relates to the design of the compressed air refrigeration dryer according to DE 10 2012 110 237.6, wherein the compressed air refrigeration dryer has one or more parallel-connected evaporators with superheat control (so-called dry or DX evaporation) and furthermore a control unit and at least one capacity-controllable compressor, which makes it possible to control the dehumidification capacity, corresponding to a compressed air volume flow occurring at the compressed air inlet of the compressed air refrigeration dryer, to a pressure dew point of the dehumidified compressed air that is constant during operation.

[0002] German patent application DE 10 2014 113 167 A1 describes a CO2 refrigeration machine suitable for compressed air drying, equipped with various pressure and temperature sensors and a control system. German patent application JP 2007 - 229 644 A describes a CO2 refrigeration dryer with a compression refrigeration cycle and several sensors, the measurement results of which are used for control. German patent application US 5 099 655 A describes a CO2 refrigeration dryer with a compression refrigeration cycle and a control unit.

[0003] A common control method for a compressed air refrigeration dryer to maintain a predetermined pressure dew point of the dried compressed air is achieved by measuring the pressure dew point of the dried compressed air exiting the dryer and adjusting the dehumidification capacity if the pressure dew point deviates from the setpoint. However, with this type of control, the pressure dew point of the dried compressed air is only corrected with a time delay. Therefore, deviations from the setpoint occur before and during each adjustment of the dehumidification capacity of the compressed air refrigeration dryer. This is particularly true for shell-and-tube heat exchangers, where the refrigerant flows through the tubes of the tube bundles. Consequently, a deviation from the setpoint persists for a longer period compared to flooded evaporators.This is particularly disadvantageous when rapid changes in air volume flow occur at short and irregular intervals.

[0004] A desirable feature would be a compressed air refrigeration dryer with an anticipatory, i.e., "forward-looking", control system that can adjust the dehumidification capacity accordingly before the pressure dew point deviates from a predetermined setpoint, or in the event of changes in the air volume flow at the compressed air inlet of the compressed air refrigeration dryer.

[0005] The object of the invention is to provide a compressed air refrigeration dryer, in particular a control unit for regulating a compressed air refrigeration dryer, which enables a delay-free readjustment of the dehumidification performance to maintain a constant pressure dew point of the dried compressed air during operation of the compressed air refrigeration dryer, even in the case of irregular and / or rapid changes in the air volume flow.

[0006] The solution to this problem is provided according to claim 1; a further advantageous embodiment of the invention is provided by claim 2.

[0007] The inventive design of the compressed air refrigeration dryer comprises a cooling water temperature sensor for detecting the cooling water temperature at the cooling water inlet of the gas cooler. Furthermore, it comprises a volume flow sensor, a pressure dew point sensor, and an air temperature sensor at the compressed air inlet of the compressed air refrigeration dryer for detecting the corresponding compressed air parameters (volume flow, pressure dew point, and temperature) of the compressed air to be dehumidified, which is introduced by the compressed air compressor into the air-to-air heat exchanger or air-to-refrigerant heat exchanger of the compressed air refrigeration dryer, as well as at least one pressure sensor at the refrigerant inlet of the compressor for measuring the refrigerant pressure.

[0008] Furthermore, the inventive design of the compressed air refrigeration dryer comprises one or more compressors arranged in parallel in the refrigerant circuit, at least one of which may have a frequency converter arranged at its power input. The design also includes a control unit that is connected to the temperature sensors, the volume flow sensor, the pressure dew point sensor, the compressors, and the at least one frequency converter.

[0009] The control unit is designed to calculate the cooling capacity required to dehumidify the compressed air to a predetermined pressure dew point using a stored algorithm and the actual values ​​of refrigerant pressure, compressed air volume flow, compressed air dew point, and compressed air temperature at the compressed air inlet of the compressed air dryer, as determined by the sensors. Based on this calculation, the unit can then adjust the cooling capacity supplied by the refrigerant circuit for the dehumidification process. This adjustment can be achieved, for example, by varying the electrical power supplied to one or more compressors using a frequency converter.The adjustment can also be made by switching on individual compressors, for example if the volume flow measured at the compressed air inlet increases, or by switching off a compressor, for example if the volume flow measured at the compressed air inlet falls below a threshold value specified for switching off a compressor.

[0010] With the design of the compressed air refrigeration dryer according to the invention, it is therefore possible to adjust the cooling capacity generated by the refrigerant circuit for dehumidifying the compressed air by means of parameters of the compressed air to be dehumidified, measured at the compressed air inlet of the compressed air refrigeration dryer, in such a way that the pressure dew point of the compressed air dehumidified in the compressed air refrigeration dryer remains almost constant at the compressed air outlet of the compressed air refrigeration dryer during operation.

Claims

[1] Compressed air refrigeration dryer for dehumidifying compressed air by means of a refrigerant circuit with carbon dioxide as the refrigerant, comprising at least one compressor (1), one gas cooler (3), at least one evaporator (2) configured to dehumidify compressed air passed on its cold surface on the secondary side, a refrigerant receiver (5.1, 11), an expansion valve (6) or an ejector and a heat exchanger (8, 18) for heating the dried compressed air, which is connected downstream of the evaporator (2) at its air-side outlet, characterized bythat the compressed air refrigerated dryer further comprises a control unit, at least one frequency converter, each connected upstream of an electrical power input of the at least one compressor (1), a temperature sensor at a cooling water inlet of the gas cooler (3) for detecting a cooling water temperature, a temperature sensor for detecting a compressed air temperature at a compressed air inlet provided for introducing compressed air to be dehumidified into the compressed air refrigerated dryer, at least one pressure dew point sensor for detecting humidity and a volume flow sensor for detecting a compressed air volume flow at the compressed air inlet, and at least one pressure sensor for detecting the refrigerant pressure at the compressor inlets, wherein the control unit is connected to the at least one compressor (1), the at least one frequency converter, the temperature sensors, and the at least one pressure dew point sensor.is connected to the volume flow sensor and the at least one pressure sensor and is configured in such a way that it can continuously read and store measured values ​​acquired by the sensors and that it can regulate the cooling capacity generated by the refrigerant circuit by controlling the at least one compressor (1) and / or the at least one frequency converter in such a way that dehumidified compressed air flowing out of the compressed air outlet of the refrigerated dryer constantly has a predetermined pressure dew point during operation of the compressed air refrigerated dryer. [2] Compressed air refrigeration dryer according to claim 1, characterized by , that at least one evaporator (2) is equipped with an overheating control.