WO2009116889A1

WO2009116889A1 - Apparatus for use in a plant for generating electrical or mechanical power from waste heat and use of such an apparatus

Info

Publication number: WO2009116889A1
Application number: PCT/RU2008/000157
Authority: WO
Inventors: Norbert Huber; Viacheslav Vsevolodovich Schuchkin
Original assignee: Siemens AG; Siemens Corp
Current assignee: Siemens AG; Siemens Corp
Priority date: 2008-03-19
Filing date: 2008-03-19
Publication date: 2009-09-24
Anticipated expiration: 2010-09-19

Abstract

An apparatus for generating mechanical or electrical power from waste heat with at least one expansion turbine (10) and a thermokinetic compressor (130) following the expansion turbine (10) with a heat extraction to evaporated water is known. The invention proposes that a new thermokinetic compressor (140) has at least one additional inlet (150) which is forming a Laval nozzle for a cold gas. By accelerating and mixing the cold gas to the waste air in supersonic flow conditions the waste gas is cooled and effect of total pressure recovery from total temperature is provided.

Description

Apparatus for use in a plant for generating electrical or mechanical power from waste heat and use of such an apparatus

The invention is related to an apparatus for use in a plant for generating electrical or mechanical power, e.g. in a power plant, with at least one expansion turbine and further devices, especially a thermokinetic compressor. Further the invention is also related to the use of such an apparatus.

In US 6 935 096 B2 a device called thermokinetic compressor (TC) is suggested. This device converts waste heat from airflow at low pressure to airflow at higher pressure. The En- ergy conversion is enabled by adding water spray. The resulting device is a machine without any rotating parts.

In the technique of the state of art there are some problems . These are :

1. Huge amounts of water are needed which at least have to be recondensed in order to feed back to the process . For this purpose at least one additional apparatus is necessary. 2. A very quick water evaporation must be ensured, whereby flash boiling spray nozzles are needed.

3. The spray nozzles have to be integrated, which is an additional cost factor together with injection system, piping, etc. 4. The spray nozzle cones tend to disturb the supersonic flow and tend to cause shock waves which reduce the efficiency.

Up to now there exist no other devices of this kind. The men- tioned problems in the known thermokinetic compressor were tolerated. Therefore it is one objective of the invention to create a better thermokinetic compressor, whereby the described problems are solved or at least reduced.

The invention is defined in claim 1. Special features are given in the dependent claims . The use of such an apparatus in a plant for generating mechanical or electrical power is given in independent claims 19 and 20.

The invention creates a new thermokinetic compressor, which can be implemented in plants with at least one expansion turbine. Additional or replacing cold gas is used to either increase mass flow rate at same pressure level or to even increase pressure. In order to accelerate the cold gas to sound velocity the inlet duct (annular duct) for cooling gas injection has to be shaped according to Laval nozzle geometry. The cold gas can either be air from the environment or any other gas resulting from other processes. Such a gas could be possibly cooler than the environmental air.

In the scope of the invention lies the feature, that a natural pressure difference between atmospheric pressure and static pressure in the supersonic flow is used to accelerate atmospheric air till supersonic velocity.

The invention has some advantages and particularities in respect to the state of art, which are defined by special feature . These are :

1. It has a cooling effect through mixing with cold gas, especially air from environment.

2. It has at least one second inlet .

3. There could be additional injectors with Laval nozzle shape . 4. Spray nozzles are reduced or totally avoided and replaced by atmospheric air accelerating nozzles. 5. A water mass flow inside the compressor is avoided or at least reduced.

A power plant with turbines and the apparatus of the invention as device for waste heat recovery has much cheaper capi- tal expenditures, because no nozzles, condenser, etc. are needed. Besides there cheaper operational expenditures, because no water or at least less water is needed.

Analytical estimations show that injection of about 10÷15 % cold air, compared to the waste heat air flow, leads to a waste heat (heat above normal conditions) recovery of 9÷13 % and total temperature decrease of 6÷9 %.

The recovered total pressure value through air injection is relatively small about 30÷40 kPa but the effect is enough to compensate mixing losses and increase mass flow rate by about 10÷15 % using cooling potential of atmospheric air that is free .

If initial pressure in the exhaust gas stream from the main power plant is above atmospheric level, which is necessary to provide pressure ratio for the expansion turbine, latter effect can be used to increase gas mass flow rate by 10÷15 % and expansion turbine power by 5÷6 % or just to transfer ex- cess thermal energy to additional mass flow rate.

In prospective, a cold air thermokinetic compressor can be implemented in the last stages of turbines for interstage mass flow production by means of cold air injection to the main flow accelerated till supersonic speed, preserving value of total pressure.

More special features and advantages of the invention are shown in the description of examples in connection with the figures .

There are shown schematically Figure 1 a thermokinetic compressor in respect to the state of art,

Figure 2 the thermokinetic compressor of the invention,

Figure 3 another embodiment of the invention, Figure 4 the engineering for the thermokinetic compressor of the state of the art

Figure 5 a so called dry thermokinetic compressor,

Figure 6 a cross section of the inlet part of a new thermokinetic compressor and Figure 7 the implementation of the new apparatus in a plant for generating electrical or mechanical power.

In the figures same elements and parts have corresponding numerals .

Figure 1 presents a Scheme of a state of the art of a thermokinetic compressor. A compressor 130 has wall contour 131 and a waist 132 in the middle, which is adjustable for startup. There is an inlet 134 for waste heat of (for example from a gas turbine or other combustion process shown in figure 7, which has a high temperature T, and before the outlet a dif- fuser 135 for pressure regain of the gas stream. In the inlet part of the thermokinetic compressor 130 there is inside the channel a spray nozzle ring 133, which contour is designed to be a Laval Nozzle for air flow. There is an evaporating spray field 136, whereby cooling water is sprayed in from outside. The spray nozzles are not shown in figure 1.

In the middle line of the schematic figure there are two points with pressure levels pi and p2. At the end of the thermokinetic compressor there is the outlet pressure p_o.

Such thermokinetic compressor is implemented in an arrangement of a power plant with at least one expansion turbine, described epecially in the older, not published patent application of the applicant, File No. PCT/RU2008/... (Internal File No. 2008P02693WO) and the title "Method and plant for gener- ating mechanical or electrical power from waste heat and apparatus for a power plant". Reference to this application is made .

Figure 2 presents a new thermokinetic compressor 140 using cold gas to extract heat instead of water spraying into the waste gas. The compressor 140 has wall contour 141 like contour 131 of figure 1 and a waist 142 in the middle, which is adjustable for startup and formed like figure 1, and also a diffuser part 145. But in the first part the contour 143 (Laval Nozzle) is to accelerate the waste heat gas flow.

There is an additional Laval Nozzle 150 with a special contour to accelerate a cold gas flow. The cold gas is prefer- able cold air, which could be taken from environment.

In the inlet of the cold gas there can be an annular ring or one or several pipes at the circumference. In case of pipes they can be connected in axial direction or partially in circumferential direction. By this a swirl created inside the thermokinetic compressor 140 is possible. The waste gas in the inlet part has a high temperature T.

Figure 3 shows additional devices at the inlet of the cold gas. This can be an assisting compressor or an adjustable throttle 155 or a valve. Alternatively a compressor or a valve is possible. The operation of the compressor, throttle or valve can be different for start-up and for normal operation.

Figure 4 and 5 represent the concept of engineering realisation of new thermokinetic compressor. Figure 4 shows the state of art, whereby figure 5 using an additional cold gas for injection into the waste gas. This could be from environ- ment . There are shown a comparison with water injection concept of figure 1/4. In both figure 4 and figure 5 it is shown that the thermoki- netic compressor 130 and 140 respectively has a Geometrical Acceleration zone (GA) , a Thermal Acceleration zone (ThA) and a Geometrical Deceleration zone.

In the state of the art of figure 4 in the inlet part of the thermokinetic compressor the velocity of the hot waste gas is subsonic, e.g. the Mach-Number is M < 1. In the flow direction there is a part of geometrical acceleration, which is formed by the wall contour and an obstacle to be a Laval nozzle. The obstacle at the same time holds the water spray nozzles. The obstacle 160 could be annular formed.

In the next part in flow direction there follows the thermal accelerating zone ThA with water evaporation field 161. In this zone the Mach-Number is increasing (M > 1) .

After that there comes a geometrical deceleration zone GD. There is the function of the supersonic confuser and a sub- sonic diffuser with Mach-Number M < 1. This part is used for a pressure regain.

In the new concept of figure 5 in the inlet part of the thermokinetic compressor the velocity of the hot waste gas is subsonic, e.g. the Mach-Number is M < 1. In the flow direction there is a part of geometrical acceleration, which is formed by the wall contour and an obstacle to be a Laval nozzle. The obstacle 170 in this case carries another nozzle 175 of Laval shape which is used to inject and accelerate the cold gas flow to M = 1. The obstacle 170 could be annular formed.

In the next part in flow direction there follows the thermal accelerating zone ThA with gas diffusion and mixing. In this zone there is the Mach-Number M > 1. After that there comes a geometrical deceleration zone GD. There is the function of the supersonic confusor and a subsonic diffuser with Mach-Number M < 1. Using this arrangement the water spray nozzles from Fig. 4 can all or at least par- tially be replaced by the shown cold gas nozzles according to figures 2 or 3 of this invention.

Figure 6 shows an example for a combination of water spray nozzles with a cold gas injection. In this example six inven- tion points are use over the circumference 141 of the ther- mokinetic compressor 140 of figure 5. There are six injection points shared consistently on the circumference 141. At three injection points - signed W - water is sprayed in and at three other injection points - signed A - cold gas is in- jected, especially air of the environment.

The relation of cold gas injection to water injection can be varied whereby water spraying can be avoided at all. So a dry thermokinetic compressor could be created.

In figure 7 the use of the new apparatus is shown in a schematic: This scheme is taken from the older international patent application of the applicant, cited on page 5, and shows a waste heat generating apparatus 10, for example a gas tur- bine, an expansion turbine 20 and a thermokinetic compressor 30 with a diffuser 35, whereby in principle the thermokinetic compressor 30 could be situated upstream or downstream to the expansion turbine 20.

Figure 7 presents the new principle scheme of thermokinetic compressor implementation with a different arrangement of components: The thermokinetic compressor 30 is arranged ad- ventageously downstream to the expansion turbine 20. This scheme allows further increase of power output and essen- tially reduces the length of the device. If the thermokinetic compressor 30 is placed to the expansion turbine 20 as shon in figure 7 the temperature T at the inlet of the thermokinetic compressor 30 will be higher and the pressure ratio can potentially be increased through an in- crease of evaporated water mass flow rate Gw up to 20 % from total mass flow rate GO of the power plant. A total flow G with increased mass flow rate

G = GO + Gw and an increased total pressure p enters the extension tur- bine 20 raising its power, potentially by 100 %, compared with the case of the state of the art.

In figure 7 it is shown that the diffuser 35, which is part of the thermokinetic compressor 30, can be omitted in special cases, what is described elsewhere below. Normally there is a diffuser 35 with a length L for pressure regain, whereby the length L is dependant of the geometry, e.g. diameter, open angle, etc. The diffuser 35 can be a long part, for example in the range of meters .

Now the length L of the diffuser 35 can be varied in a wide range, for example shortened or even cancelled. If the diffuser 35 has a length L and an inner diameter D3 at its beginning, the length L of the diffuser 35 could be shortened in dependence to the diameter D3 at the basis part in respect to the relation

0 < L/D3 < 20

This means a big advantage and a remarkable gain in efficiency. List of Numbers

Figure 1 State of art

130 known Thermokinetic Compressor

131 contour

132 waist

133 spray nozzle ring

134 Evaporating spray

135 Diffuser

Figure 2 Invention

140 new Thermokinetic Compressor

141 contour

142 waist

143 spray nozzle ring

144 Evaporating spray

145 Diffuser

150 additional Laval nozzle Figure 3 Alternative/Supplemental means for figure 2

151 Valve for Laval nozzle 150 Figure 4 Geometry - State of art

160 Laval Nozzle shape obstacle 161 evaporation spray f ield GA Geometrical acceleration zone

ThA Thermal acceleration zone

GD Geometrical deceleration zone

Figure 5 Geometry - Invention

170 modified obstacle 171 evaporation spray field

175 build-in Laval nozzle (in obstaclel70)

Figure 6 Cross-section

141 Distribution of injection points over circumference

W Water injection A Air injection

Figure 7 Implementation in a gas turbine arrangement

10 Gas Turbine Unit or boiler or any other unit with waste heat

20 Expansion turbine

25 Generator

30 Thermokinetic Compressor

35 Diffuser Gw Gas mass flow rates

L2 Electrical or mechanical Power

H₂0/Air Water/Air Injection

D3 starting Diameter of diffusor

L Length of diffusor

Claims

1. An Apparatus for generating mechanical or electrical power from waste air, with at least one expansion turbine (10) and a thermokinetic compressor (130) , whereby the thermokinetic compressor (140) uses at least partly cold gas for heat extraction.

2. The Apparatus of claim I₇ whereby there are means (150, 155, 175) to bring in and accelerate the cold gas for cooling the waste air through mixing with the cold gas .

3. The Apparatus of claim 2, whereby the cooling gas for the waste air is cold air taken from environment.

4. The Apparatus of claim 2, whereby the cooling gas for the waste air is a gas resulting from other processes

5. The Apparatus of claim 4, whereby temperature of the cool- ing gas is lower than the temperature of the environmental air.

6. The Apparatus of claim 1 or claim 2, whereby the thermokinetic compressor (140) has at least one second inlet (150) for the cooling gas .

7. The Apparatus of claim 6, whereby the least one second inlet (150) for the cooling gas in the thermokinetic compressor (140) are additional injectors (150) with Laval nozzle shape .

8. The Apparatus of claim 7, whereby the at least one additional injector (150) has an additional compressor.

9. The Apparatus of claim 7, whereby the at least one additional injector (150) has an adjustable throttle.

10. The Apparatus of claim 7, whereby the at least one additional injector (150) has a valve (151) .

11. The Apparatus of claim 1 or claim 2, whereby the ther- mokinetic compressor (140) has a Laval shape with a zone of geometrical acceleration (GA) in the inlet part, a zone of further thermodynamic acceleration (ThA) and a zone of geometrical deceleration (GD) in the outlet part.

12. The Apparatus of claim 11, whereby for the geometrical acceleration (GA) in the inlet part the thermokinetic compressor (140) has at least one inside Laval shaped obstacle (170) .

13. The Apparatus of claim 12, whereby the inside obstacle (170) has another build-in Laval nozzle (175) .

14. The Apparatus of any of proceeding claims, whereby the number of spray nozzles for injecting water (H₂O) are at least reduced.

15. The Apparatus of claim 14, whereby at least half of the spray nozzles in the thermokinetic compressor (130) are substituted by Laval nozzles for cold gas.

16. The Apparatus of claim 14, whereby in the thermokinetic compressor (140) spray nozzles for water (H₂O) are avoided.

17. The Apparatus of any of proceeding claims, whereby the mass flow of water in the thermokinetic compressor (140) is at least reduced.

18. The Apparatus of claim 17, whereby a water mass flow in the thermokinetic compressor (130) is totally avoided.

19. Use of an Apparatus for generating mechanical or electrical power with the features of claim 1 or one of claims 2 to

18, whereby the expansion turbine is situated downstream to the the thermokinetic compressor (140)

20. Use of an Apparatus for generating mechanical or electrical power with the features of claim 1 or one of claims 2 to

19, whereby the apparatus the thermokinetic compressor (140) is combined with a gas turbine (10)