Method for cooling off the compressed gas of a compressor installation and compressor installation in which this method is applied

Abstract

A compressor installation provided with one or more compressor elements and a heat recovery circuit in the form of a closed Rankine circuit in which a working medium circulates through one or more evaporators that act as a cooler for the compressed gas, and a condenser connected to a cooling circuit for cooling the working medium in the condenser, whereby an additional cooler is provided for each evaporator that is connected in series to an evaporator concerned, and which is calculated to be able to guarantee sufficient cooling by itself when the heat recovery circuit is switched off.

Claims

1. A compressor installation comprising one or more compressor elements configured to provide a cooling to cool the gas compressed by the one or more compressor elements, whereby said cooling comprises: a heat recovery circuit that is realized as a closed Rankine circuit with a pump, and a working medium that circulates in the Rankine circuit during operation of the Rankine circuit by means of the pump; one or more evaporators through which the compressed gas to be cooled is guided for cooling the compressed gas; an expander configured in a way to convert thermal energy into mechanical energy; and a condenser that is connected to a cooling circuit with a coolant that is guided through said cooling circuit to cool the working medium in the condenser, wherein the compressor installation comprises at least one additional cooler that is incorporated in series with at least one of the one or more evaporators in a gas flow direction of the compressed gas to be cooled, and wherein the one or more evaporators are in the gas flow direction of the compressed gas to be cooled upstream from the at least one additional cooler, wherein said at least one additional cooler is connected to the cooling circuit with the condenser, wherein said cooling circuit is configured so that said condenser is connected in series upstream from the at least one additional cooler so that said coolant is guided through the additional cooler without a temperature increase in the condenser and said at least one additional cooler has a cooling capacity to cool of the compressed gas, for a given cooling capacity of the cooling circuit, when the Rankine circuit is switched off.

2. The compressor installation according to claim 1, wherein the Rankine circuit is an Organic Rankine Circuit (ORC circuit), in which an organic working medium circulates.

3. The compressor installation according to claim 2, wherein the boiling temperature of the organic working medium is below 90 C.

4. The compressor installation according to claim 1, wherein the compressor installation comprises a single stage compressor with one single compressor element; wherein said at least one or more evaporators of said Rankine circuit acts as an aftercooler; and an additional aftercooler for cooling the compressed gas coming from the one compressor element.

5. The compressor installation according to claim 3, wherein the boiling temperature is below 60 C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) With the intention of better showing the characteristics of the invention, a few preferred embodiments of a compressor installation according to the invention for compressing a gas with heat recovery are described hereinafter by way of an example, without any limiting nature, with reference to the accompanying drawings, wherein:

(2) FIG. 1 schematically shows a compressor installation according to the invention;

(3) FIGS. 2 to 4 each show a different variant of the compressor installation of FIG. 1;

(4) FIGS. 5 to 11 show possible variants of a compressor installation according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

(5) In this case the compressor installation 1 shown in FIG. 1 comprises one single stage compressor with one compressor element 2 with a drive 3 in the form of a motor or similar.

(6) The compressor element 2 is provided with an inlet 4 and an outlet 5, whereby in this case the inlet 4 connects to a suction pipe 6 with an inlet valve 7 therein and a suction filter 8, while the outlet 5 connects to a pressure pipe 9 for compressed gas to which a consumer network 10 can be connected.

(7) The compressor installation 1 is further provided with a heat recovery circuit 11 in the form of a closed circuit 12 in which a working medium circulates according to an Organic Rankine Cycle, abbreviated to ORC, by means of a pump 13 that successively drives the working medium through an evaporator 14; an expander 15; a condenser 16 and thus back to the pump 13.

(8) The aforementioned expander 15 is configured such that it enables the thermal energy to be converted into mechanical energy, for example because it is constructed in the form of a turbine, with an outgoing shaft 17 that is coupled to a load, such as a generator 18 for supplying electrical energy to a consumer 19.

(9) The evaporator 14 is incorporated as a cooler in the aforementioned pressure pipe 9 in series with an additional cooler 20 for cooling the compressed gas coming from the compressor element 2. More specifically a primary section of the evaporator 14 is connected in series to a primary section 20 of the additional cooler 20.

(10) Together with the aforementioned additional cooler 20, the condenser 16 is incorporated in series in a separate cooling circuit 21 through which a different coolant to the working medium of the Rankine circuit 12, for example water or a different coolant, is guided, for example by means of a pump or similar that is not shown. More specifically a secondary section 16 of the condenser 16 is connected in series to a secondary section 20 of the additional cooler 20.

(11) The heat recovery circuit 11 and the cooling circuit 21 are preferably configured such that the direction of flow of the working medium in the evaporator 14 (in this case a secondary section of the evaporator 14) and of the coolant in the additional cooler 20 (more specifically in the secondary section 20 of the additional cooler 20) are opposite to the direction of flow of the compressed gas that flows through it (in this case through the primary section of the evaporator 14 and the primary section 20 of the additional cooler (20), which ensures an efficient heat transfer from the one medium to the other medium.

(12) Analogously the working medium and the cooling medium are guided through the condenser 16 in opposite directions. Indeed, in the example shown the working medium is guided in a first direction through the primary section 16 of the condenser 16, while the coolant is guided in a second direction through the secondary section 16 of the condenser 16, opposite to the aforementioned first direction of the working medium.

(13) The operation of the compressor installation 1 according to the invention is very simple and as follows.

(14) When the compressor element 2 is driven, a gas, for example air, is drawn in via the inlet 4 and supplied to the consumer network 10 under pressure via the pressure pipe 9.

(15) The compressed gas leaves the compressor element 2 at a high outlet temperature, which means that the compressed gas must be cooled before it is supplied to a consumer network 10 in order to prevent damage to the consumers in this consumer network 10.

(16) The compressed gas is partly cooled in the additional cooler 20 and partly in the evaporator 14 that are incorporated in series in the pressure pipe 9, at least insofar the pump 13 of the heat recovery circuit 11 makes the working medium circulate in the circuit 12. The additional cooler 20 is preferably incorporated in the pressure pipe 9 downstream from the evaporator 14.

(17) The pump 13 drives the working medium in liquid form through the evaporator 14 where the working medium is heated by the compressed gas that flows through the evaporator 14.

(18) The working medium is selected such that at a certain pressure the boiling temperature of the working medium is lower than the outlet temperature of the compressed gas so that the working medium can evaporate in the evaporator 14 and it leaves the evaporator 14 as a vapour at an increased pressure realised by the pump 13, whereby the vapour can undergo an expansion in the expander 15, such that the expander is driven and thereby also the generator 18 or another useful load.

(19) An example of a suitable organic working medium is 1,1,1,3,3-pentafluoropropane.

(20) Then the expanded working medium flows in vapour form through the condenser 16 where it comes into contact with the low temperature of the coolant, which ensures that the working medium condenses to be able to be pumped around as a liquid by the pump 13 for a subsequent cycle.

(21) The additional cooler 20 is calculated, on the basis of the available cooling capacity of the cooling circuit 21, to be able to sufficiently cool the compressed gas without the cooling action of the evaporator 14, for example when the heat recovery circuit 11 has failed due to a defect or similar, whereby the coolant is then guided through the additional cooler 20 without a temperature increase in the condenser 16.

(22) This means that the additional cooler 20 is dimensioned for a conventional operation without heat recovery and that the cooling capacity of the additional cooler 20 is then overdimensioned for operation with heat recovery, but with the great advantage that the compressor installation 1 can continue operating when the heat recovery circuit 11 fails.

(23) The best result in recovering the heat energy to a maximum is achieved when the additional cooler 20 is placed in the pressure pipe 9 downstream from the evaporator 14, and the condenser 16 is provided in the cooling circuit 21 upstream from the additional cooler 20, although other configurations are not excluded.

(24) In the example shown the condenser 16 and the additional cooler 20 are incorporated in series in a common cooling circuit 21, although this is not strictly necessary and two separate cooling circuits may also be provided.

(25) The compressor installation 1 of FIG. 2 differs from that of FIG. 1 by the ORC circuit 12 being provided with a bypass 22 that connects the input and output of the pump 13 together, and in which a non-return valve 23 is incorporated that enables a flow of the working medium from the input to the output of the pump 13 but prevents a flow in the reverse direction.

(26) This bypass 22 is used in event of a stoppage of the pump 13 to enable a natural circulation of the working medium in cases when the pump 13 does not present any leaks between the input and output when stopped.

(27) FIG. 3 shows the same compressor installation as that of FIG. 2, with the difference that the non-return valve 23 is replaced by a bypass valve 24 that is controllable or otherwise for the control of the Rankine cycle. If the bypass valve 24 is made controllable, to this end it is connected to a control unit or controller that is not shown in the drawings, either by means of an electrical connection, or by means of another form of connection that enables a control signal to be sent from the control unit to the bypass valve 24.

(28) FIG. 4 shows a variant of a compressor installation 1 according to the invention whereby in this case, with respect to the embodiment of FIG. 1, the cooling circuit 21 with a liquid coolant is replaced by a cooling circuit 21 with cooling by means of the surrounding air or another cooling gas that is blown successively over the condenser 16 and over the additional cooler 20 by means of a fan or similar, whereby to this end the condenser 16 and the additional cooler 20 are constructed as a radiator instead of a heat exchanger with a primary section through which the working medium, and the compressed gas respectively, is guided and a secondary section through which the coolant is guided.

(29) FIG. 5 shows a compressor installation 1 according to the invention that comprises a multistage compressor 1, in this case with two compressor elements 2 connected in series, respectively for a compressor element 2a of the low pressure stage and a compressor element 2b of the high pressure stage, which in this case are driven together by a common drive 3 and which are connected together by an intermediate pressure pipe 9a.

(30) In this case the ORC circuit 12 comprises two evaporators 14 to be able to extract heat, on the one hand from the compressed gas coming from the compressor element 2a and on the other hand from the compressed gas coming from the compressor element 2b, to which one evaporator 14a is incorporated in the intermediate pressure pipe 9a and the other evaporator 14b is incorporated in the pressure pipe 9b to the consumer network 10.

(31) Upstream from each evaporator 14a and 14b, an additional cooler 20 is provided, respectively cooler 20a and cooler 20b, that is incorporated in the pressure pipes 9a and 9b in series with an evaporator 14a, respectively 14b, concerned for cooling the gas that is guided through this additional cooler 20a and 20b.

(32) The evaporators 14a and 14b are incorporated in the cooling circuit 21 in parallel whereby a threeway valve 26 is provided in the circuit at the parallel input of the evaporators 14a and 14b in order to distribute the flow of the working medium coming from the pump 13 over both evaporators 14a and 14b, and this depending on the temperatures of the compressed gas at the outlet 5 of the compressor elements 2a and 2b that depend on the pressure ratios of the compressor elements 2a and 2b and/or depend on the temperatures of the working medium at the outlet of the evaporators 14a and 14b.

(33) In this case, the additional coolers 20a and 20b are connected together in parallel and incorporated in the cooling circuit 21 in series together with the condenser 16 and are so dimensioned that they can ensure sufficient cooling of the compressed gas when the ORC circuit 12 fails.

(34) It is clear that in this case only one single evaporator 14 can be used in one of the pressure pipes 9a or 9b, whereby an additional cooler 20 is provided in this pressure pipe 9a or 9b with the evaporator 14, while in the other pressure pipe without an evaporator 14 only a conventional intercooler or aftercooler 20 is provided, whereby the additional cooler 20 is then incorporated in the cooling circuit 21 in series with the condenser 16 while the conventional cooler 20 can also be connected in series in this cooling circuit 21 or in a separate circuit.

(35) FIG. 6 shows a variant whereby the threeway valve is replaced by two separate valves 27 with the same function, while in FIG. 7 instead of a threeway valve, a valve 27 and a restrictor 28 are applied.

(36) FIG. 8 shows a compressor such as that of FIG. 5, but whereby in this case the cooling circuit 21 is based on air cooling.

(37) FIG. 9 shows an identical configuration to that of FIG. 8, but whereby the coolers 20a and 20b have changed places.

(38) Each of the FIGS. 10 and 11 show a variant of FIG. 5 whereby in this case the evaporators 20a and 20b are connected in series in the heat recovery circuit 11 instead of in parallel, such that in this case no means are required either such as a threeway valve 26 or similar, in order to distribute the flow of the working medium that circulates in the heat recovery circuit 11 over the evaporators 14a and 14b.

(39) In FIG. 10 the working medium first passes through the evaporator 14a of the low pressure compressor element 2a and then through the evaporator 14b of the high pressure compressor element 2b, while this is precisely the reverse in FIG. 11.

(40) It is clear that if, in a multistage compressor such as in the case of FIGS. 5 to 11, there are no limitations with regard to maximum temperature of the compressed gas supplied to the consumer network 10, an additional aftercooler 20b may be omitted as, when the cooler function of the aftercooler 14b fails due to the failure of the heat recovery circuit 11, the temperature increase at the output of the additional aftercooler 20b is not limited.

(41) In summary the invention concerns a compressor installation for compressing a gas with heat recovery, whereby this compressor installation is provided with one or more compressor elements 2 and a heat recovery circuit 11 for the recovery of the heat of compression from the compressed gas, whereby this heat recovery circuit 11 is realised as a closed circuit with a pump 13 to enable a working medium to circulate in it according to a Rankine cycle through one or more evaporators 14 that act as a cooler for the compressed gas coming from an upstream compressor element 2 that is guided through it and in which the working medium is heated by the compressed gas; an expander 15 for converting thermal energy into mechanical energy; and a condenser 16 that is connected to a cooling circuit 21 with a coolant for cooling the working medium in the condenser 16, characterised in that the compressor installation 1 comprises an additional cooler 20 for each evaporator 14 that acts as an intercooler between two successive compressor elements 2 and/or for an evaporator 14 that acts as an aftercooler that is connected in series to an evaporator 14 concerned for cooling the gas that is guided through this evaporator 20, and that each additional cooler 20 is incorporated in the aforementioned cooling circuit 21 of the condenser 16, whereby the one or more additional coolers 20 are calculated to be able to guarantee sufficient cooling by themselves, for a given cooling capacity of the cooling circuit 21, when the heat recovery circuit 11 is switched off.

(42) The present invention is by no means limited to the embodiments described as an example and shown in the drawings, but a compressor according to the invention for compressing a gas with heat recovery can be realised in all kinds of forms and dimensions without departing from the scope of the invention, and by extension is also applicable to compressors with more than two compression stages.