Patent Application
20240295214
The present invention relates to a method for heat recovery in a compressor. The method also relates to a compressor comprising a plurality of compression stages for compressing gas; three or more heat exchangers for cooling compressed gas, each of the three or more heat exchangers comprising at least a primary part having a gas input for entering the compressed gas for cooling and a gas output for outputting the cooled gas from the primary part, and a secondary part having a coolant input for entering the coolant and a coolant output for outputting the coolant from the secondary part; the compressor further comprising a coolant circuitry for conducting flow of the coolant via the three or more heat exchangers; and a gas flow circuitry for conducting flow of gas in series via the plurality of compression stages and the heat exchangers.
Compressors typically have one or more heat exchangers for reducing temperature of gas compressed by one or more compressor stages of the compressor. Multi-stage compressors typically have heat exchangers after each compression stage to cool down gas compressed by the compression stage. Coolant inlets of the heat exchangers are usually coupled in parallel so that the coolant, such as water, is fed in parallel to each heat exchanger. This means that the temperature of the coolant is the same at each input of the heat exchangers. However, each compressor stage may not have the same operation parameters wherein the heat recovery efficiency and consequently the efficiency of each compressor stage may not be optimum.
It is known that the temperature at an inlet of a compressor stage affects the efficiency of the compressor stage. Basically, the higher the temperature of the gas at the inlet the higher is the energy needed for the compression.
Heat exchangers typically have a primary part and a secondary part. Some heat exchangers may also have a tertiary part. In compressor applications one of the parts, such as the primary part, is provided for leading compressed gas through the heat exchanger and the secondary part is provided for leading the coolant through the heat exchanger. Hence, at least a part of the heat of the compressed gas is transferred from the compressed gas to the coolant when the temperature of the compressed gas is higher than the temperature of the coolant.
Transferring heat from one substance to another substance can also be called heat recovery from one substance to another substance.
According to some embodiments of the present invention there is provided a method and a multi-stage compressor in which heat recovery efficiency and the outlet coolant temperature can be improved compared to prior art methods and compressors. One basic idea behind the invention is to arrange a coolant circuitry so that the order in which the coolant flows through different heat exchangers can be selected based on the compression parameters, either statically or dynamically, and the order of heat recovery is different from the order in which the compressed gas flows through different heat exchangers.
In a series connection of the cooling circuitry the coolant or a part of the coolant from an output of one heat exchanger is conducted to an input of another heat exchanger.
In this specification the expression “the order of the compression stages” means the order in which gas to be compressed travels through the compression stages of the compressor: a first compression stage is the compression stage to which the gas is input from outside the compressor and the last compressor stage outputs the compressed gas for further processing e.g. for utilizing in a manufacturing plant, or after treatment, filtration, drying etc. However, it may also be possible to have intermediate gas outlet(s) in a compressor from which a part of the gas can be taken out from the compressor.
According to a first aspect of the present disclosure there is provided a compressor comprising:
In accordance with an embodiment the coolant circuitry is at least partly coupled in series so that the liquid to liquid heat exchanger is the first or the second in a sequence of the series connection and at least two of the two or more compressed gas heat exchangers are in series connection, wherein the liquid to liquid heat exchanger is either in series with the compressed gas heat exchangers or in parallel with at least one of the compressed gas heat exchangers.
In accordance with an embodiment the coolant circuitry of at least three or more heat exchangers is at least partly coupled in series so that the series connection is at least partly different from the series connection between the compressor stages and different from a reversed order of the compressor stages and selected to optimize coolant temperature or energy content.
In accordance with an embodiment at least one heat exchanger is coupled with a gas output of each compression stage.
In accordance with an embodiment at least one heat exchanger is coupled with a gas output of each compression stage.
In accordance with an embodiment the amount of heat exchangers is at least one more than the amount of the compression stages.
In accordance with an embodiment the means for bypassing comprise one or more controllable valves.
According to a second aspect of the present disclosure there is provided a compressor comprising:
In accordance with an embodiment there is provided a compressor with two or more compression stages so that at least three cooling stages are in series so that the order in which coolant is provided to the at least three cooling stages is selectable based on one or more predetermined criteria.
In accordance with an embodiment there is provided a compressor with two or more compression stages so that at least three cooling stages are in series so that the order in which coolant is provided to the at least three cooling stages is selectable based on one or more predetermined criteria.
In accordance with an embodiment there is provided a compressor with two or more compression stages so that at least three cooling stages are in series so that the order in which coolant is provided to the at least three cooling stages is adjustable during operation of the compressor.
In accordance with an embodiment there can also exist a tertiary cooling circuit for transferring heat from the compressor components (i.e. not from the compressed air), said cooling circuit can be parallel to or in series with any of the compressed air cooling circuits, said circuitry can be adjustable during operation of the compressor.
In accordance with an embodiment the compressor is an air compressor.
In accordance with an embodiment there is provided an air compressor with two or more compression stages so that at least two cooling stages are at least partially in series to increase the temperature of the outgoing coolant.
In accordance with an embodiment there is provided an air compressor having one or more intercoolers between compression stages and an aftercooler after a last compression stage downstream of the gas flow, wherein the intercoolers are in the series before the aftercooler. This may prevent air from being too hot in compression process. However, the aftercooler can also be located before one or more of the intercoolers.
In accordance with an embodiment there is provided an air compressor equipped with an additional aftercooler to cool the compressed air after the compressor.
In accordance with an embodiment there is provided an air compressor in which all heat exchangers are in series.
In accordance with an embodiment there is provided an air compressor in which only some but not all of the heat exchangers are in series.
In accordance with an embodiment the coolant flow and the order of the partially or completely in series cooling stages are adjustable based on operating characteristics.
In accordance with an embodiment the logic with which the coolant flows through the heat exchangers is adjusted to optimize the coolant temperature and compression efficiency.
In accordance with an embodiment there is provided an air compressor having three separate cooling circuits so that one of the cooling circuits utilizes the heat recovered by the heat exchangers and another of the cooling circuits dissipates the heat into the atmosphere.
In accordance with an embodiment there is provided an air compressor comprising an additional aftercooler which is water cooled.
In accordance with an embodiment there is provided an air compressor comprising an additional aftercooler which is air cooled.
In accordance with an embodiment there is provided an air compressor having an air dryer, which can be of the Heat of Compression type dryer, the compressor outlet temperature is selected to optimize the efficiency of the dryer and the heat utilization of the manufacturing plant.
According to a third aspect of the present disclosure there is provided a compressor comprising:
In accordance with an embodiment at least one heat exchanger is coupled with a gas output of each compression stage.
In accordance with an embodiment the order in which the secondary parts of the heat exchangers are coupled by the coolant circuitry is selected based on one or more predetermined criteria.
In accordance with an embodiment one or more predetermined criteria is one or more of the following:
In accordance with an embodiment at least one heat exchanger is coupled with a gas output of each compression stage.
In accordance with an embodiment the amount of heat exchangers is at least one more than the amount of the compression stages.
In accordance with an embodiment the compressor comprises means for adjusting mutual connections between the three or more heat exchangers by the coolant circuitry.
In accordance with an embodiment the means for adjusting mutual connections comprise controllable valves.
In accordance with an embodiment the means for adjusting mutual connections are configured to adjust the mutual connections between the three or more heat exchangers based on operating characteristics of the compressor or the environment the compressor is operating.
In accordance with an embodiment the means for adjusting mutual connections are configured to adjust the mutual connections or at least partially bypass any of the three heat exchangers to optimize coolant temperature and compression efficiency.
In accordance with an embodiment the compressor comprises two separate cooling circuits so that one of the cooling circuits is configured to utilize the heat recovered by the heat exchangers and another of the cooling circuits is configured to dissipate heat into the atmosphere.
In accordance with an embodiment the compressor is configured to adjust the two separate cooling circuits to optimize the efficiency of a dryer and heat utilization of a manufacturing plant.
In accordance with an embodiment the heat exchangers comprise:
In accordance with an embodiment the compressor comprises an additional aftercooler, which is water cooled.
In accordance with an embodiment the coolant circuitry comprises
The present invention may improve heat recovery efficiency of the compressor inter alia due to the possibility to arrange the series connection of different heat exchangers so that the overall efficiency of the compressor can be increased and/or waste energy can be utilized at least partly. One factor which may affect the efficiency is the temperature of the coolant entering a heat exchanger. For some compression stages it may be beneficial to have a low temperature of the input gas flow which may be achieved by inputting a coolant as cold as possible to the preceding heat exchanger whereas for some other compression stages higher temperature of the input gas flow may be acceptable in view of the overall efficiency of the compressor.
In the following, some embodiments of the disclosure are described in more detail with reference to the appended drawings, in which
In the following the compressed gas heat exchangers 1.1-1.3 may also be called as heat exchangers 1.1-1.3 whereas a heat exchanger for internal cooling 17 is called as a liquid to liquid heat exchanger 2.4.
Each compression stage 1.1, 1.2, 1.3 has a gas input 1.1a, 1.2a, 1.3a and a gas output 1.1b, 1.2b, 1.3b. Each exchanger 2.1, 2.2, 2.3 has a primary part for cooling gas and a secondary part for coolant. The primary parts have a gas input 2.1a, 2.2a, 2.3a and a gas output 2.1b, 2.2b, 2.3b and the secondary parts have a coolant input 2.1c. 2.2c, 2.3c and a coolant output 2.1d, 2.2d, 2.3d.
The compressor 1 has at least one motor 3 for rotating one or more compression stages 1.1, 1.2, 1.3. In some embodiments there is only one motor 3.1 wherein each compression stage is coupled to an axis 3.1a of the motor 3 but in the example of
The compressor 1 also has a coolant circuitry 5 for conducting flow of the coolant via the secondary parts of the heat exchangers 2 and a gas flow circuitry 6 for conducting flow of gas via the compression stages 1.1, 1.2, 1.3 and the heat exchangers 2.1, 2.2, 2.3.
It should be noted that the compressor 1 may also have further components such as valves, dryers, etc. which are not shown in
In the embodiment of
Next, the flow of the coolant in the compressor 1 of
It should be noted that the series connection of the secondary parts of the heat exchangers may be different from the above, such as the third heat exchanger 2.3, the first heat exchanger 2.1 and the second heat exchanger 2.2.
In the example of
The internal components of the control unit(s) 4 and the motor(s) 3 of the compressor 1 may include, for example, integrated circuits and other semiconductors as well as other electrical components, etc. It would therefore be advantageous to maintain the temperature of at least the semiconductors well below their maximum operating temperature. This may be achieved by providing the coolant at an early stage of the coolant circuitry to the liquid to liquid heat exchanger 2.4, for example as a first heat exchanger or a second heat exchanger for cooling the internal components.
In accordance with an embodiment the same coolant, which is circulated via the heat exchangers of the compressor stages, also via the heat exchanger of the internal cooling 17. Hence, at least part of heat generated by the internal components is also utilized by the system and is not wasted to the atmosphere.
In this example embodiment there is also a fifth heat exchanger 2.5 for recovering heat from the coolant after the coolant has circulated through the first 2.1, third 2.3 and second heat exchanger 2.2 to lower the temperature of the coolant before recirculating the coolant through the heat exchangers. The coolant may further be cooled by an additional cooler 14 such as a blower, when necessary. The additional cooler 14 may be powered by a motor 15, for example.
The compressed air from the compressor 1 may also be cooled when the temperature of the compressed air should be lower at the utilization location of the compressed air. For this purpose there is another cooler 11, such as a blower and a motor 12 for powering the another cooler 11. In accordance with an example, the additional cooler 11 is a heat exchanger, such as a liquid-liquid heat exchanger.
The compressor 1 may also have a valve 13 or valves to control flow of the coolant and/or the gas. For example, a first valve 13.1 is coupled in the coolant circulation circuitry 8 so that the first valve 13.1 can adjust the flow of coolant through the secondary part of the first heat exchanger 2.1 and a second valve 13.2 can adjust the flow of coolant through the secondary part of the liquid to liquid heat exchanger 2.4. The first valve 13.1 can reduce the flow rate of the coolant through the secondary part of the first heat exchanger 2.1 when less cooling is required, and respectively, the first valve 13.1 can increase the flow rate of the coolant through the secondary part of the first heat exchanger 2.1 when more cooling is required. Similar operation can be performed by the second valve 13.2 with respect to the cooling requirements of the internal circuitry of the compressor 1.
In the example embodiment of
It should be noted that the bypass of the circulant coolant need not be at the last heat exchanger but may be located at some other heat exchanger as well. Furthermore, there may be more than one means for bypassing a heat exchanger so that none, one, or more than one of the means for bypassing may be activated according to the circumstances during operation of the compressor 1.
One purpose for such bypassing is to maintain the temperature of the coolant at the output of the compressor 1 as constant as possible so that the coolant can also be utilized in such arrangements in which the coolant is directed from the compressor 1 to the manufacturing plant 16, in which a constant temperature of the coolant is required or at least recommended. Furthermore, adjusting the way the coolant is bypassed (or not) may affect the temperature of the coolant, wherein if higher temperatures are needed, bypassing may not be used, for example.
Some heat may also be recovered by a fifth heat exchanger 2.5 for recovering heat from the compressor 1 to be utilized in a process of an end user. For example, heat is recovered to a liquid, such as a clean water, which will be used in the process. The coolant circulating in the compressor 1 may be cooled further, when necessary, by an additional cooler 14 comprising, for example, a blower and a motor 15 for powering the another cooler 14.
In the example of
The tertiary part (cooling circuit) can be used, for example, for transferring heat from the compressor components (i.e. not from the compressed air). The tertiary part can be parallel to or in series with any of the compressed air cooling circuits. Furthermore, the tertiary part can be adjustable during operation of the compressor.
The example of
In the example of
In accordance with an embodiment some or all of the circulating coolant may be bypassed outside of the compressor 1, e.g. to the atmosphere after one of the heat exchangers 2.1-2.4.
In accordance with an embodiment the order in which the coolant is flowing through the heat exchangers 2.1-2.4 is not fixed but can at least partly be amended according to one or more predetermined criteria. For example, the temperature of gas outputted by the compressing stages 1.1-1.3 can be measured and based on this the order may be changed, if necessary. Another criteria may be the efficiency of one or more compressing stages 1.1-1.3 and if the efficiency of a compression stage 1.1-1.3 should be amended, the order of the heat exchangers 2.1-2.4 can be changed to better correspond with the amended efficiency. A yet another criteria may be the temperature of the coolant wherein that compression stage from which the temperature of the gas is higher than other compression stages may cause that the heat exchanger at the output of that particular compression stage is selected to be at the beginning of the coolant circulation, for example the first in the chain of heat exchangers 2.1-2.4.
In the example of
In accordance with an embodiment the coolant is not circulated but the coolant is input from a source 8 and after the last heat exchanger in the flowing path of the coolant the coolant is provided to be utilized by an entity. An example of such arrangement is illustrated in
In the example of
In the example of
The coolant circuitry of
It should be noted that the different examples of
It should be noted that also in the embodiments presented in
In some embodiments the room where the compressor 1 or a plurality of compressors 1 are located may warm up, wherein also the room can be cooled down e.g. by a heat pump or a refrigerator.
The heat exchanger(s) which are between two compression stages can also be called as intercoolers and that heat exchanger or those heat exchangers which are after the last compression stage can also be called as aftercooler(s).
By coupling the intercoolers in series before the aftercooler may prevent air from being too hot in the compression process.
In an embodiment in which some or all the coolant can be bypassed after some of the heat exchangers 2.1-2.5 of the coolant circuitry, such as after the last heat exchanger, temperature of the bypassed coolant can be regulated by adjusting the amount of coolant to bypass. For example, the temperature may be kept at a constant value.
According to an embodiment, the bypassed coolant may be used to bring back some energy to the compressor 1, e.g. from an after cooler.
In some situations, warm outside air may be used to warm up the coolant if it is otherwise too cool to be entered to the compressor 1.
In accordance with an embodiment the compressor has two separate cooling circuits so that one of the cooling circuits utilizes the heat recovered by the heat exchangers and another of the cooling circuits dissipates the heat into the atmosphere.
In accordance with an embodiment there is provided an air compressor having an air dryer, which can be, for example, the heat of compression type dryer.
The compressor outlet temperature is selected to optimize the efficiency of the dryer and the heat utilization of the manufacturing plant. For example, when demand of heat of the dryer is higher, more heat is recovered to air flowing through the dryer and less heat is recovered to the coolant, and, respectively, when demand of heat of the dryer is smaller, more heat can be recovered to the coolant and less heat is recovered to air flowing through the dryer.
In accordance with some embodiments, the last compression stage is affected least by the temperature, wherein less cooling power may be provided for that compression stage and more cooling power may be provided to other compression stages. In other words, that heat exchanger which is after the last compression stage may receive coolant after all previous heat exchangers in the path of the coolant i.e. is the last heat exchanger downstream of the coolant.
In accordance with an embodiment the coolant flow and the order of the heat exchangers 2 which are partially or completely in series are adjustable based on operating characteristics of the compressor 1 or the environment the compressor 1 is operating.
In accordance with an embodiment the logic with which the order in which the coolant flows through the heat exchangers 2 is adjusted to optimize the coolant temperature and compression efficiency.
In accordance with an embodiment the order in which the coolant flows through the heat exchangers 2 is selected to optimize the coolant temperature and/or energy content of the coolant at the coolant output 19 from the compressor 1.
In the following some factors which may affect the order the coolant flows through the heat exchangers 2.1-2.4 are shortly provided:
It should be noted that there may also be other factors which may be taken into account when determining the path for the coolant within the compressor 1.
To determine the temperature of the coolant, incoming gas, compressed gas etc. some temperature sensors can be installed at appropriate locations in the compressor 1. Accordingly, to determine pressure inside the compressor 1, some pressure sensors can be installed at appropriate locations in the compressor 1 as well. However, these sensors are not depicted in the Figures.
In the following a method for adaptive heat recovery in the compressor 1 will be described with reference to the diagram of
The control circuitry 4 receives measurement signals from one or more temperature sensors and one or more pressure sensors (not shown) and compares the measurement signals with some predetermined criteria to determine whether the coolant flowing path should be changed. If the comparison indicates that one or more of the predetermined criteria is fulfilled, the control circuitry 4 changes states of one or more of the valves 13.1-13.6 so that the coolant flowing path corresponds the measured conditions. For example, the order in which the coolant flows through the first heat exchanger 2.1 and the second heat exchanger 2.2 may be swapped or may be changed to a parallel connection.
In accordance with an embodiment, the temperature of the coolant at the output of the compressor 1 may be much higher than in prior art compressors. As an example, when a cool tap water, the temperature of which is well below 20° C., is used as the coolant, the temperature of the coolant at the output of the compressor 1 may be over 80° C., e.g. 84° C., when the present invention is utilized.
It should be noted here that the flowing path of the coolant need not be closed so that the same coolant circulates in the coolant circuitry 5 of the compressor 1 but may also be open so that the coolant is entered to the coolant circuitry 5 from an external source (e.g. tap water), flows through the coolant circuitry 5 and exits from the coolant circuitry 5.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20215768 | Jun 2021 | FI | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/FI2022/050476 | 6/28/2022 | WO |
