WO2020126837A1

WO2020126837A1 - Thermodynamic cycle for producing compressed air

Info

Publication number: WO2020126837A1
Application number: PCT/EP2019/084932
Authority: WO
Inventors: Norbert Mittwollen; Bernd Mueller; Michael Diez; Agniva DHARA
Original assignee: Robert Bosch Gmbh
Priority date: 2018-12-19
Filing date: 2019-12-12
Publication date: 2020-06-25
Also published as: DE102018222245A1

Abstract

The invention relates to a thermodynamic cycle for producing compressed air, comprising: an evaporator, in which a working fluid is present in liquid phase and in steam phase; a steam-operated compressor, to which the working fluid in the form of steam flows from the evaporator; a condenser for cooling and liquefying the working fluid once this has left the compressor; and a feed pump, which conveys the working fluid liquefied in the condenser back to the evaporator. A preheater is arranged between the condenser and the evaporator, in which preheater heat is transferred between the compressed air generated by the compressor and the liquid working fluid.

Description

Thermodynamic cycle for the generation of compressed air

description

The invention relates to a thermodynamic cycle for producing compressed air with an evaporator, in which a working medium is in the liquid phase and in the vapor phase, with a steam-operated compressor (13), to which the working medium flows as steam from the evaporator, with a condenser for cooling and Liquefaction of the working medium after leaving the compressor and with a feed pump that conveys the working medium liquefied in the condenser back to the evaporator.

Such a thermodynamic cycle for generating compressed air is known from WO 89/08188 Al. Within the thermodynamic cycle process known from the cited document, a steam-operated double-acting compressor is used in which the interior of the housing is divided into two sections, with a first dimensionally stable piston having a section in a working chamber and in a compression chamber and a second dimensionally stable piston divides the other section into a working chamber and a compression chamber, and the two pistons are connected to one another by a piston rod which is tightly guided from one section to the other section through a central part of the housing.

In WO 89/08188 it is pointed out that the energy source for the heating can be waste heat or solar heat.

The invention has for its object to improve the known thermodynamic circular process.

The pursued goal is achieved in a thermodynamic cycle with the features mentioned at the beginning by the fact that between the condenser and the evaporator a preheater is arranged in which heat transfer from the compressed air generated by the compressor and the liquid working medium takes place. The compressed air generated is heated during compression in the compressor. The compressed and heated compressed air is led through the preheater, through which the liquid working medium conveyed by the feed pump also flows. On the one hand, the liquid working fluid is preheated in the preheater. On the other hand, the compressed air is cooled in the preheater, so that only little heat is introduced into the compressed air system.

A thermodynamic cycle according to the invention can advantageously be further developed.

The working medium is advantageously a high-molecular organic working medium whose boiling point is lower than the boiling point of water.

With a high molecular weight organic working medium, the boiling point of which is lower than the boiling point of water, it is also possible to heat the working medium above the boiling point by means of waste heat from an industrial process that only has a temperature of, for example, 80 or 100 degrees Celsius .

The preheater is advantageously arranged between the feed pump and the evaporator, since then the working medium flowing through the feed pump is still cool.

The preheater can contain a pipe coil through which the working medium flows and which is surrounded by the compressed air.

It is favorable if the compressor is a double-acting compressor with a plurality of pistons which can be moved together in a straight line relative to a housing. Compressed air is then pumped in every half movement cycle.

The pistons of the compressor can be rigid pistons or deformable membranes.

Two exemplary embodiments of a thermodynamic cycle according to the invention for generating compressed air are shown in the drawings. The invention will now be explained in more detail with reference to the figures of these drawings. Show it

Figure 1 in a highly simplified representation, the first embodiment with a compressor with dimensionally stable pistons and

Figure 2 in a highly simplified representation, the second embodiment with a compressor with flexible membranes as pistons.

The two thermodynamic cycle processes shown in the figures are shown schematically and are each a so-called Organic Rankine Cycle (ORC). The name Organic Rankine Cycle is derived from the British physicist and engineer William John Macquorn Rankine and from the use of a high-molecular organic working medium with a boiling point that is lower than the boiling point of water.

The ORC comprises an evaporator 10, in which the working medium is in the liquid phase and in the vapor phase, which is essentially above the liquid phase. The liquid phase is heated by a heat source 11, preferably by the waste heat from machines or systems, to above its boiling point, so that a pressure is established in the two phases which is above atmospheric pressure. For example, a working medium can be used whose boiling point is 45 degrees Celsius. The waste heat heats the working medium to 80 degrees Celsius, for example. In accordance with this heating to 80 degrees, a certain vapor pressure of, for example, 3 bar is established. A zigzag line indicates how the working medium rises within the evaporator. Via a pipe 12, the pressurized steam reaches a double-acting compressor 13, in which the steam does work to compress air, so that it generates compressed air and feeds it into a compressed air system. From the compressor sensor 13, the expanded steam passes through a pipe 14 to a condenser 15, in which the working medium is cooled and liquefied. A feed pump 16 conveys the liquid working medium back into the evaporator 10. The working fluid conveyed by the feed pump 16 first flows in a coil 19 through a preheater 18 and then to the evaporator 10. The preheater 18 is thus arranged between the feed pump 16 and the evaporator 10, so that the cool working medium flows through the feed pump 16.

The compressed air generated is heated during compression in the compressor. The compressed and heated compressed air is fed via a pipe 19 to the preheater 18, through which in the Pipe coil 17 also flows the liquid working medium conveyed by the feed pump 16. In the preheater 18, the compressed air flows around the coil 19 before it leaves the pre-heater 18 and arrives at a compressed air tank. On the one hand, the liquid working fluid is preheated in the preheater 18. On the other hand, the compressed air is cooled in the preheater 18, so that only a little heat is introduced into the compressed air system.

The double-acting compressor 13 according to FIG. 1 has a pressure-resistant housing 30 with a central housing part 31, the interior of which is divided into a first working chamber 33 and a second working chamber 34 by a dimensionally stable working piston 32. The working chamber 33 is via an inlet valve 35, which is closed in one position and opened in a two-th position and which can be actuated, for example, electromagnetically from a position which it assumes under the action of a spring into the other position, to one in the housing 30 extending channel connected to the tube 12. The working chamber 34 is connected via an inlet valve 36, which is formed in the same way as the inlet valve 35, to the channel connected to the tube 12. The working chamber 33 is also via a drain valve 37, which is closed in one position and opened in a second position and which, for example, can be actuated electromagnetically from a position which it assumes under the action of a spring into the other position, to an in Housing 30 extending channel connected, which is connected to the tube 14. The working chamber 34 is also connected to the channel connected to the pipe 14 via a drain valve 38, which is designed in exactly the same way as the drain valve 37.

The compressor 13 also has a first lateral housing part 39 with an interior space, which is divided into two chambers by a first dimensionally stable compressor piston 40. In addition, the compressor 13 has a second lateral housing part 41 which is opposite the housing part 39 with respect to the central housing part 31 and the interior of which is also divided into two chambers by a second rigid compression piston 42. Each of the compressor pistons 40 and 42 is fixedly connected to the working piston 32 by means of a piston rod 43 which extends from it on one side and which is sealed through the walls separating the interior spaces of the three housing parts. The piston rod 43 can be formed by two individual piston rods, which are individually firmly connected to the working piston 32, or by a one-piece piston rod which passes through the working piston and on which the working piston 32 is firmly seated. All three pistons 32, 40 and 42 can thus be moved together in the direction of the axis of the piston rod 43 in the housing. se 30 led. The two compressor pistons 40 and 42 have the same outside diameter. This is smaller than the outer diameter of the working piston 32.

Due to the described construction of the compressor 13 from FIG. 1, the chamber 44, which is located on the side of the working piston 40 remote from the piston rod 43, that is to say the outer chamber, has a circular disc-shaped cross section perpendicular to the direction of movement of the pistons, while the opposite, inner one Chamber 45 has an annular cross section. Likewise, the chamber 46, which is located on the side of the working piston 42 remote from the piston rod 43, that is to say the outer chamber, has a circular, disc-shaped cross section, while the opposite, inner chamber 47 has an annular cross section. The two outer chambers 44 and 46 are used as compression chambers. The compression chamber 44 is connected to an air inlet channel 51 via a sucking valve 50, which is designed as a check valve opening towards it, and via a pressure valve 52, which is designed as a check valve which blocks it, to an air outlet channel 53, to which the pipe 14 is connected. The Verdichterkam mer 44 is connected via a sucking valve 54, which is designed as a check valve opening towards it, to the air inlet channel 51, and via a pressure valve 55, which is designed as a check valve, which blocks it, with the air outlet channel 53. The chambers 43 and 45 are connected to atmosphere.

The two working chambers 33 and 34 each have a ring-shaped cross section in the direction of movement of the pistons, but this is larger than the cross section of the compression chambers 42 and 45.

It is initially assumed that the two inlet valves 35 and 36 and the two outlet valves 37 and 38 are closed. The pistons 32, 40 and 42 then stand still.

If the inlet valve 35 belonging to the working chamber 33 and the outlet valve 38 belonging to the working chamber 34 are opened, pressurized steam flows from the evaporator 10 and the tube 12 into the working chamber 33. The pressure generates a force on the working piston 32, which moves the working piston and with it also the two compressor pistons 40 and 42 to the right according to the view according to FIG. 1. By means of the compressor piston 42, the compressor chamber 46 is reduced and air is displaced from it via the pressure valve 55 into the pipe 17 and further into the compressed air container. The air is compressed to the pressure in the compressed air tank. In contrast to this, the volume of the compression chamber 44 is increased so that air flows in via the sucking valve 50. When the pistons have reached the end of their path, the inlet valve 35 and the outlet valve 38 are closed and the inlet valve 36 and the outlet valve 37 are opened. Pressurized steam now flows from the evaporator 10 via the tube 12 into the working chamber 34. The pressure generates a force on the working piston 32, which forces the working piston and with it also the two compressor pistons 40 and 42 according to the view according to FIG. 1 moved to the left. By means of the compressor piston 40, the compressor chamber 44 is reduced and the air previously sucked in is compressed and displaced via the pressure valve 52 into the pipe 17 and further into the compressed air tank. In contrast, the volume of the compression chamber 46 is increased so that 54 flows in through the sucking valve. The cycle described is repeated until the alternating opening and closing of valves 35, 36, 37 and 38 is omitted and at least the two inlet valves 35 and 36 are closed at the same time.

The double-acting compressor 13 according to FIG. 2 has a pressure-resistant housing 60 with a central housing part 61 and with two lateral housing parts 62 and 63 arranged in a mirror image with respect to the central housing part 61, the diameter of which is larger than the diameter of the central housing part 61. The housing parts 62 and 63 each consist of a bottom 64 and a cover 65. The interior of the housing part 62, which is formed by the bottom and cover and is circular in cross section, is inserted into a working chamber 67 adjoining the central housing part 61 and into an outer chamber by a circular membrane 66, which can be made of Teflon, a thermoplastic or rubber, for example Compressor chamber 68 divided. The circular interior formed by the bottom and cover of the housing part 63 is divided by a circular membrane 69, which is the same as the membrane 66, into a working chamber 70 adjacent to the central housing part 61 and into an external compression chamber 71. The membrane 66 is clamped with its outer edge between the lid and the bottom of the housing part 62. The membrane 69 is clamped with its outer edge between the lid and the bottom of the housing part 63. Through the respective membrane, the parting line between the bottom and the cover of a side housing part is thus sealed. In the middle, the two diaphragms 66 and 69 are each clamped between two learning clamps 72, which are held on a piston rod 73 which passes through the central housing part 61 and is guided therein in a sliding manner in its longitudinal direction. A Movement of one membrane is transmitted to the other membrane via the piston rod 73.

As with the compressor 13 according to FIG. 1, the working chamber 67 is via an inlet valve 35 which is closed in one position and opened in a second position and which is, for example, electromagnetically from a position which it takes up under the action of a spring into the other position is operable, connected to a channel running in the housing 60, which is connected to the tube 12. The working chamber 70 is connected via a flow valve 36, which is designed in the same way as the inlet valve 35, to the channel connected to the tube 12. The working chamber 67 is also via a drain valve 37, which is closed in one position and opened in a second position and which can be actuated, for example, electromagnetically from a position which it assumes under the action of a spring into the other position, to one in the housing 30 extending channel connected to the tube 14. The working chamber 70 is also connected to the channel connected to the pipe 14 via a drain valve 38, which is designed in exactly the same way as the drain valve 37.

The compression chamber 68 is connected via a sucking valve 50, which is designed as a check valve opening towards it, with an air inlet channel 51, and via a pressure valve 52, which is designed as a check valve, which blocks it, with an air outlet channel 53, to which the Tube 14 is connected. The compressor chamber 71 is connected to the air inlet channel 51 via a sucking valve 54, which is designed as a check valve opening towards it, and via a pressure valve 55, which is designed as a check valve which blocks it, with the air outlet channel 53.

The compressor 13 according to FIG. 2 is also at a standstill when the two inlet valves 35 and 36 and the two outlet valves 37 and 38 are closed.

If the inlet valve 35 belonging to the working chamber 70 and the outlet valve 38 belonging to the working chamber 67 are opened, pressurized steam flows from the evaporator 10 and the tube 12 into the working chamber 70. A pressure is generated on the membrane 69 by the pressure, which pushes the membrane 69 outward and moves it outward, so that the volume of the working chamber 70 increases and the volume of the compression chamber 71 decreases. The piston rod 73 moves according to the View to the right according to FIG. 2 and moves the membrane 66 inwards, so that the volume of the working chamber 67 is reduced and the volume of the compressor chamber 68 is increased. Air is thus displaced from the compression chamber 71 via the pressure valve 55 into the pipe 17 and further into the compressed air tank. Air flows into the enlarging compressor chamber 68 via the sucking valve 50. Are the membranes 66 and 69 at the end of theirs

On the way, the inlet valve 35 and the outlet valve 38 are closed and the inlet valve 36 and the outlet valve 37 are opened. Pressurized steam now flows from the evaporator 10 via the pipe 12 into the working chamber 67. The pressure creates a force on the membrane 66 which pushes the membrane 66 outwards and moves it outwards, so that the volume of the working chamber moves 67 increased and the volume of the compression chamber 68 reduced. The piston rod 73 moves according to the view according to FIG. 2 to the left and moves the membrane 69 inwards, so that the volume of the working chamber 70 is reduced and the volume of the compression chamber 71 is increased. Air is thus displaced from the compression chamber 68 via the pressure valve 52 into the pipe 17 and further into the compressed air tank. In the expanding compression chamber

71 flows in via the sucking valve 54.

The cycle described is repeated until the alternate opening and closing of the valves 35, 36, 37 and 38 is omitted and at least the two inlet valves 35 and 36 are closed at the same time.

Reference list

10 evaporators

11 heat source

12 pipe

13 compressor

14 pipe

15 condenser

16 feed pump

17 pipe coil

18 preheaters

19 pipe

30 flameproof housing from 13

31 middle housing part

32 working pistons

33 first working chamber

34 second working chamber

35 inlet valve of 33

36 inlet valve from 34

37 drain valve of 33

38 drain valve from 34

39 side housing part

40 compressor pistons

41 side housing part

42 compressor pistons

43 piston rod

44 compression chamber

45 chamber

46 compression chamber

47 chamber

50 nursing valve

51 air intake duct

52 pressure valve

53 air outlet duct 54 nursing valve

55 pressure valve

60 pressure-resistant housing 61 middle housing part from 60 62 side housing part from 60

63 side housing part of 60

64 bottom of 62, 63

65 covers of 62, 63

66 membrane

67 Chamber of Labor

68 compression chamber

69 membrane

70 working chamber

71 compression chamber

72 clamping plates

73 piston rod

Claims

1. Thermodynamic cycle for producing compressed air with an evaporator, in which a working medium is in the liquid phase and in the vapor phase, with a steam-operated compressor (13), to which the working medium flows as steam from the evaporator (10), with a condenser ( 15) for cooling and liquefying the working medium after leaving the compressor (13) and with a feed pump (16) which conveys the working medium liquefied in the condenser (15) back to the evaporator (10), characterized in that between the condenser (15 ) and the evaporator (10) a preheater (18) is arranged in which a heat transfer from the compressor (13) generated by the compressed air and the liquid working medium takes place.

2. Thermodynamic cycle according to claim 1, wherein the Ar beitsmedium is a high molecular weight organic working medium whose boiling point is lower than the boiling point of water.

3. Thermodynamic cycle according to a preceding patent claim, the working medium in the evaporator (10) being heated and evaporated by waste heat from an industrial process.

4. Thermodynamic cycle according to a preceding patent claim, wherein the preheater (18) between the feed pump (16) and the evaporator (10) is arranged.

5. Thermodynamic cycle according to a previous patent claim, wherein the preheater contains a coil through which the working medium flows and which is surrounded by the compressed air.

6. Thermodynamic cycle according to a preceding patent claim, wherein the compressor is a double-acting compressor (13) with a plurality of pistons (32, 40, 42; 66, 69) that can be moved together in a straight line relative to a housing (30; 60).

7. Thermodynamic cycle according to claim 6, wherein the pistons of the compressor (13) are rigid pistons (32, 40, 42).

8. Thermodynamic cycle according to claim 6, wherein the pistons of the compressor (13) are deformable membrane (66,69)