Method and system for energy conversion from pressure energy into electrical energy

Abstract

A method for energy conversion from pressure energy into electrical energy uses an expansion turbine. In the method, a pressurized, gaseous, first medium is heated before being fed into the expansion turbine. The expansion turbine drives a generator and a compressor. At least one gaseous second medium is compressed by the compressor in a heating arrangement. Heat generated by the compression and preferably also via utilization of ambient heat according to a heat exchanger principle is used for heating the gaseous first medium.

Claims

1. A method for energy conversion from pressure energy into electrical energy using an expansion turbine, comprising steps of: first heating a pressurized, gaseous, first medium; feeding the heated, pressurized, gaseous, first medium into the expansion turbine; driving a generator and a compressor by the expansion turbine; the compressor compressing a gaseous second medium in a heating arrangement for generating heat; and second heating the gaseous first medium using the heat from the heated, gaseous second medium.

2. The method according to claim 1, wherein the heating arrangement has a closed circuit in which the second medium circulates and wherein the second medium proceeds from a heating medium tank and is present in the heating medium tank in an at least partially liquid state.

3. The method according to claim 2, wherein the second medium is vaporized under the influence of external heat before being fed into the compressor.

4. The method according to claim 3, wherein an ambient temperature is determined; wherein the second medium is fed to a heat exchange with heat arrangement physical surroundings; and wherein a vaporization temperature of the second medium is below the ambient temperature in order that the second medium is completely vaporized under the influence of the ambient energy of the ambient temperature.

5. The method according to claim 1, wherein the compressing takes place in two stages.

6. The method according to claim 1, wherein the second medium transfers its heat in a first heat exchanger to a third medium, and wherein the heat transferred to the third medium is used for heating the gaseous first medium in an input heat exchanger.

7. The method according to claim 6, wherein the third medium circulates in a closed circuit, is driven by a pump and proceeds from a tank.

8. The method according to claim 1, wherein expansion of the gaseous first medium takes place in two stages; and wherein the gaseous first medium is preheated again between the two stages in an intermediate heat exchanger.

9. The method according to claim 1, wherein the pressure energy, ambient heat (W) and, optionally, waste heat from any of the steps of first heating, feeding, driving compressing and second heating is exclusively used for the energy conversion from pressure energy into electrical energy.

10. An expansion turbine system for carrying out a method according claim 1, comprising: an expansion turbine that drives the generator via a transmission; wherein the compressor is connected to the transmission and is a component of the heating arrangement for compressing the second medium; and wherein the heating arrangement further comprises an input heat exchanger in a supply line of the expansion turbine for heating the first medium.

11. A method for energy conversion from pressure energy into electrical energy, wherein a pressurized process gas is initially preheated and is subsequently expanded to release pressure energy that is converted into mechanical energy and then into electrical energy, and wherein a portion of the mechanical energy is used for operating a thermodynamic cycle, the method including the steps of: a) vaporizing a partially liquid heating medium via the introduction of external energy; b) compressing the gaseous heating medium; c) cooling and condensing the gaseous heating medium via a direct or indirect release of energy to the process gas; and d) throttling the cooling medium.

12. The method according to claim 11, wherein the heating medium does not give off its heat directly to the process gas; and wherein heat from the heating medium is used for heating a second thermodynamic cycle, the second thermodynamic cycle including the steps of: a) providing a liquid transfer medium; b) introducing mechanical work into the transfer medium; c) cooling the transfer medium by giving off thermal energy to the process gas; and d) heating the transfer medium via introduction of thermal energy from the heating medium.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG. 1 shows a method according to the invention having a process gas, a heating medium, and a transfer medium, and

[0028] FIG. 2 shows a method according to the invention having a process gas and a hot gas.

DETAILED DESCRIPTION OF THE INVENTION

[0029] The following is a detailed description of example embodiments of the invention depicted in the accompanying drawings. The example embodiments are presented in such detail as to clearly communicate the invention and are designed to make such embodiments obvious to a person of ordinary skill in the art. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present invention, as defined by the appended claims.

[0030] FIG. 1 schematically shows a process circuit diagram for the method according to the invention for energy conversion from pressure energy into electrical energy.

[0031] Therein, a pressurized process gas P, for example, natural gas, is initially heated, as the first medium, in an input heat exchanger 1 and is subsequently expanded in a first stage 2a of an expansion turbine 2 to an intermediate pressure level. The process gas P is subsequently reheated in an intermediate heat exchanger 3. A second expansion of the process gas P then takes place in a second stage 2b of the expansion turbine 2.

[0032] The mechanical energy generated by the expansion turbine 2 is used for driving an electric generator 4 via a transmission and a compressor 5 comprising a first stage 5a and a second stage 5b.

[0033] A heating medium H is provided, as the second medium, in a heating medium tank 6, wherein the heating medium H is present in the heating medium tank 6 as a two-phase, liquid/gaseous mixture. The heating medium H is withdrawn from the heating medium tank 6 in an at least partially liquid state and is fed to a vaporization arrangement 7. The vaporization arrangement 7 can consist of multiple individual vaporizers 7a, 7b, 7c, . . . , wherein the individual vaporizers 7a, 7b, 7c, . . . are connected in parallel to one another. Any energy source having a higher temperature than the vaporization temperature of the heating medium H is suitable for vaporizing the heating medium H. Propane is preferably used as the heating medium H in the example shown, since propane vaporizes at very low temperatures and can be returned to a liquid state in a simple way via compression and re-cooling. Due to the low boiling temperature of propane, vaporization can take place simply under the influence of ambient heat W. This is advantageous, in particular, when the method described herein is carried out in a system which is set up in an area having particularly high ambient temperatures. Thus, a slight heating of the now gaseous heating medium H can take place in addition to the vaporization.

[0034] After the vaporization, the heating medium H is fed to the compressor 5 which is driven by the expansion turbine 2. The compression takes place in two stages in this case. In the first stage 5a, the heating medium H is compressed to an intermediate pressure level and is subsequently fed back to the heating medium tank 6. Due to the different density ratios of liquid and gaseous heating medium H, the liquid portion settles on the bottom of the heating medium tank 6 and the gaseous portion settles in the cover region of the heating medium tank 6.

[0035] The state of matter of the heating medium H can therefore be selected depending on which removal point is selected. The heating medium H, which is at an intermediate pressure level, is withdrawn from the heating medium tank 6 again, through an opening in the cover region of the heating medium tank 6, and is fed to a second compression stage 5b of the compressor 5.

[0036] The heating medium H, which has been heated because of the pressure increase in the second stage 5b, is subsequently fed to a first heat exchanger 8, and the heat of the heating medium H is transferred to the transfer medium U as the third medium.

[0037] The first heat exchanger 8 consists of multiple connected individual heat exchangers 8a, 8b, 8c, . . . for this purpose. In addition, the thermal energy from a generator cooler 9 and the thermal energy from an oil cooler 10 are transferred to the transfer medium U.

[0038] The transfer medium U also circulates in a closed circuit and is initially stored in a transfer medium tank 11. Since heated transfer medium U is not yet present during a start-up of the expansion turbine 2 and, therefore, a preheating of the process gas P cannot take place, the transfer medium tank 11 is additionally provided with a separate heating 12, which continues to preheat the preferably liquid transfer medium to the required temperature until the required heat quantity can be provided by the compressed heating medium H.

[0039] Water is used as the transfer medium U for preheating in the example shown, where the water flows in the liquid state, via a pump 13, out of the transfer medium tank 11 and through the input heat exchanger 1 as well as the intermediate heat exchanger 3. The input heat exchanger 1 and the intermediate heat exchanger 3 are connected in parallel to one another in this case.

[0040] An arrangement also is conceivable in which the input heat exchanger 1 and the intermediate heat exchanger 3 are connected in series. The transfer medium U cools down because of the heat transfer and is subsequently heated by the heat of compression as well as by the heat from the generator cooler 9 and the oil cooler 10, and is fed back to the transfer medium tank 11.

[0041] FIG. 2 schematically shows a process circuit diagram for the method according to the invention for converting pressure energy into electrical energy in the case of an only one-stage expansion in an expansion turbine 2. The heating of the process gas P takes place by an input heat exchanger 1; since the process has only one stage, an intermediate heat exchanger 3 is not required. In addition, compression of the heating medium H takes place in only one stage of the compressor 5 which is driven by the expansion turbine 2.

[0042] The heating medium H is provided, as the second medium, in a heating medium tank 6, wherein the heating medium H is present as a two-phase, liquid/gaseous mixture in this case as well. Proceeding from an at least partially liquid state, the heating medium H is subsequently fed to a vaporization arrangement 7 consisting of multiple individual vaporizers 7a, 7b, 7c, . . . . In this case, the individual vaporizers 7a, 7b, 7c, . . . are connected in parallel to one another. As a particularity with respect to the method presented in FIG. 1, the heat from the generator cooler 9 and the oil cooler 10 are used directly for vaporizing and heating the heating medium H.

[0043] After vaporization in the vaporization arrangement 7, the heating medium H is compressed in the compressor 5 and is subsequently fed directly to the input heat exchanger 1. Therefore, no heat is transferred to a transfer medium U which has been selected as the second medium. The heating medium H cools down in the input heat exchanger 1 and at least partially condenses out as the process continues. The heating medium H is fed back to the heating medium tank 6 in this state, and therefore the process can be carried out again.

[0044] As will be evident to persons skilled in the art, the foregoing detailed description and figures are presented as examples of the invention, and that variations are contemplated that do not depart from the fair scope of the teachings and descriptions set forth in this disclosure. The foregoing is not intended to limit what has been invented, except to the extent that the following claims so limit that.