Method for converting thermal energy into mechanical work

• US 20040088980A1
• Filed: 03/04/2003
• Published: 05/13/2004
• Est. Priority Date: 08/11/2000
• Status: Active Grant

• Current Assignee: Applikations-Und Technikzentrum Fur Energieverfahrens-Umwelt Und Strmungstechnik
• Original Assignee: Applikations-Und Technikzentrum Fur Energieverfahrens-Umwelt Und Strmungstechnik
• Inventors: Stevanovic, Dragan, Emmel, Andreas
• Granted Patent: US 6,799,425 B2
• Time in Patent Office: Days
• US Class Current: 60/645
• CPC Class Codes: F01K 25/14 using industrial or other waste gases
• CPC Class Codes: F02C 1/04 the working fluid being heated indirectly in a fluidised-bed combustor F02C3/205
• CPC Class Codes: F02C 3/28 using a separate gas producer for gasifying the fuel before combustion
• CPC Class Codes: F02C 6/18 using the waste heat of gas-turbine plants outside the plants themselves, e.g. gas-turbine power heat plants using waste heat as source of energy for refrigeration plants F25B27/02; using the waste heat of a gasturbine for steam generation or in a steam cycle see F01K23/10
• CPC Class Codes: F02C 7/08 Heating air supply before combustion, e.g. by exhaust gases
• CPC Class Codes: F02C 7/141 of working fluid
• CPC Class Codes: F23L 15/02 Arrangements of regenerators
• CPC Class Codes: F28D 17/005 using granular particles
• CPC Class Codes: Y02E 20/34 Indirect CO2mitigation, i.e. by acting on non CO2directly related matters of the process, e.g. pre-heating or heat recovery
• CPC Class Codes: Y02E 50/10 Biofuels, e.g. bio-diesel

Abstract

The invention relates to a method for converting the energy into mechanical work, whereby a first (4) and a second means (9) for storing thermal energy are alternately connected into a turbine branch (T). In order to increase the efficiency of this method, the invention provides that a compressed oxidizing gas (11) is cooled to a second temperature T2 before passing through the first means (4) for storing thermal energy, and the oxidizing gas is then increased, in one step, to a third temperature T3 when passing through the first means (4) for storing thermal energy.

Claims

1. Method for converting thermal energy into mechanical work, a first (4) and a second means (9) for storing thermal energy being connected alternately into a turbine branch (T), with the following steps:

a) compressing an oxidizing gas (11), its temperature being raised from ambient temperature RT to a first temperature Ti and its pressure being raised to a first pressure P1,

b) cooling the compressed gas (11) down to a second temperature T2,

c) leading the compressed gas (11) through a first means (4) for storing thermal energy, the temperature of the gas (11) being raised to a third temperature T3 in one step,

d) expanding the first pressure P1 in a gas turbine (3) to substantially atmospheric pressure, the gas (11) being cooled down from the third temperature T3 to a fourth temperature T4,

e) feeding the gas (11, 14) to a combustion chamber (6) connected downstream,

f) burning biomass (7) together with the gas (14), and

g) leading the flue gases (19) through a second means (9) for storing thermal energy.

2. Method according to claim 1, the cooling in step b being effected by acting on the gas (11) with liquid, preferably water, or by means of a heat exchanger.

3. Method according to claim 1 or 2, the thermal energy obtained by the cooling in step b being coupled out as useful heat.

4. Method according to one of the preceding claims, a partial stream of the gas (11) being led in step c through a bypass past the means (4, 9) for storing thermal energy.

5. Method according to one of the preceding claims, part of the gas (14) being branched off after step d and being led over a heat exchanger (13) in order to couple out thermal energy.

6. Method according to one of the preceding claims, part of the gas (14) being branched off after step d and being brought into contact with the biomass (7) to be burned, in order to dry the latter.

7. Method according to one of the preceding claims, dust being separated off from the flue gases (19) formed during the combustion.

8. Method according to one of the preceding claims, the flue gases (19) being cooled down [lacuna] a temperature of less than 150°

C., preferably to 90 to 110°

C., in less than 200 ms in step g.

9. Method according to one of the preceding claims, it being true of the temperatures of the gases (11, 14) that:

T2<

T1<

T4<

T3

10. Method according to one of the preceding claims, the second temperature T2 being less than 150°

C., preferably less than 100°

C.

11. Method according to one of the preceding claims, gas and combustion gas being led alternately through the means (4, 9) for storing thermal energy, constructed as bulk material regenerators, through bulk material having a maximum grain diameter (D_max) which is accommodated in the annular chamber (12, 15) between a substantially cylindrical hot grate and a cold grate surrounding the latter, and at least one discharge opening for discharging the bulk material being provided in the bottom of the annular chamber (12, 15), a predefined quantity of bulk material being discharged while or after flue gas (19) is led through, so that a compressive stress exerted on the hot and cold grates by the bulk material is reduced.

12. Method according to claim 10, the maximum grain diameter (D_max) of the bulk material being less than 15 mm.

13. Method according to one of the preceding claims, the bulk material discharged being fed back to the [sic] by means of a transport gas into the annular chamber (12, 15).

14. Method according to one of the preceding claims, where after the bulk material has been separated from the transport gas, a dust fraction contained therein is separated off.

15. Method according to one of the preceding claims, a third means for storing thermal energy being connected into the turbine branch (T) in alternation with the first (4) or second means (9) for storing thermal energy.

17. Apparatus according to claim 15 [sic], the gas turbine (3), the compressor (1) and a generator (2) being arranged on one shaft.

16. Apparatus for converting thermal energy into mechanical work, the following being provided:

a turbine branch (T) comprising;

a compressor (1) for compressing an oxidizing gas (11) taken in,

a means (5, 16) connected downstream for cooling down the compressed gas (11),

a first bulk material generator [sic] (4) connected downstream of the cooling means (5, 16),

a gas turbine (3) connected downstream of the first bulk material generator [sic] (4), and a preheating branch (V) comprising

a combustion chamber (6) connected downstream of the first bulk material generator [sic] (4),

a second bulk material generator [sic] (9) connected downstream of the combustion chamber (6) and

a means (21, 32) for the alternate connection of the second bulk material generator [sic] (9) into the turbine branch (T) and the connection of the first bulk material generator [sic] (4) into the preheating branch (V).

18. Apparatus according to claim 16 or 17, a flue gas cleaning device (8) being connected downstream of the combustion chamber (6).

19. Apparatus according to claim 16 to 18, a heat exchanger (13) for coupling thermal energy out being connected in between the gas turbine (3) and the combustion chamber (6).

20. Apparatus according to one of claims 16 to 19, a substantially cylindrical hot grate in the bulk material regenerator (4, 9) being surrounded coaxially by a cold grate, and a bulk material with a maximum grain diameter (D_max) being accommodated in an annular chamber (12, 15) formed between the hot and the cold grates, and the hot and/or cold grates being constructed in such a way that the bulk material can expand radially when heated.

21. Apparatus according to one of claims 16 to 20, the means (4, 9) for storing thermal energy being provided with a bypass (17).

22. Apparatus according to one of claims 16 to 21, a third bulk material regenerator (20) being provided, and the means (21-32) for alternate connection also being suitable to connect the third bulk material generator [sic] (9) into the turbine branch (T) and into the preheating branch (V).