WO2008014568A1

WO2008014568A1 - Steam turbine

Info

Publication number: WO2008014568A1
Application number: PCT/AU2007/001096
Authority: WO
Inventors: Alan Robert Burns
Original assignee: Carnegie Corporation Ltd
Priority date: 2006-08-03
Filing date: 2007-08-03
Publication date: 2008-02-07
Also published as: WO2008014569A1; WO2008014567A1

Abstract

A steam power plant (10) comprising a steam generation apparatus (11), a steam turbine (13) and an electrical generator (15). The steam generation apparatus (11) generates superheated steam from feed water. The steam turbine (13) is driven by a working fluid comprising the superheated steam. The steam turbine (13) has a rotor (61) which incorporates a heat exchanger (62) for recovery of heat released from the working fluid in the turbine (13) to preheat the feed water.

Description

Steam Turbine

Field of the Invention

This invention relates to a steam turbine and also a steam power plant. The steam power plant may generate mechanical energy from which shaft power is used for generation of electrical energy by way of a generator.

Background Art

Steam turbines account for the majority of electricity generation plant worldwide. A power plant that is geared to the production of electricity only will exhaust steam from the turbine and the overall plant efficiency will be low as there is no means by which conventional steam turbines can recover this tow grade heat energy. This is the major drawback of conventional steam turbines. It is addressed in power plants by the addition of a bottoming cycle where the waste steam is reticulated through a heat exchanger to recover the heat energy that would otherwise be wasted. Plants configured in this way are said to operate a combined heat power (CHP) cycle, with the heat being used for plant operation, including feed water preheating, domestic heating or industrial processes if these heats sinks are located nearby.

The additional equipment in a CHP plant adds cost and complexity. Conventional steam turbines rely on a plurality of rotors on a common shaft with each set of rotors experiencing the steam sequentially from the rotor set ahead of it. Each set experiences a partial pressure drop in the working fluid and a corresponding acceleration of the steam across the rotor blades. This conversion of potential energy to kinetic energy is what drives the turbine. . There is however, no facility for recovery of remnant thermal energy.

Conventional steam turbines, while having many rows of blades, can commonly be considered to have three distinct groupfngs of blades all on a common rotor shaft. The first is the 'high pressure' region whose input is directly from the steam generator at the highest operating pressure in the plant. The pressure drop across the high pressure region comprising many blades may be say 500 psi; the steam exhausted from the high pressure region then feeds the input of the next stage or intermediate pressure region. Again the pressure drop through the series of blades in the intermediate pressure region may be 100's of psi. Steam exiting the intermediate pressure region is stili energetic and enters the final or low pressure stage.

The progression from high pressure to intermediate to low pressure is marked by an increase in turbine diameters and blade clearances to account for the volume expansion that takes place as the steam expends its potential energy to mechanical work.

Steam in the final low pressure region is able to condense to water vapour but this process must be tightly controlled as the water droplets can cause damage to the turbine blades through pitting if the condensation is excessive. Consequently, there is no facility for recovery of remnant thermal energy.

Electricity is traditionally generated by a base load power station in which steam is produced to drive a turbine which ir» turn drives a generator. The energy for generation of the steam is available from various sources including combustion of fossil fuels such as coal and gas as well as nuclear power.

Where there is a need for decentralised power generation, and also small-scale electricity generation, it is now common to utilise natural gas-fired turbines directly rather than burning the gas in a steam cycle turbine.

There are, however, locations where there is a need for small-scale electricity generation plants but there is a lack of available natural gas for operating the plants.

It would be advantageous for there to be a steam-cycle power generation system that is compact, thermodynamically efficient, environmentally friendly with zero or low emissions and adaptable to combust a variety of fuels. It is against this background that the present invention has been developed. In particular, one aspect of the present invention seeks to provide a steam turbine suitable for use in such a steam-cycle power generation system.

Disclosure of the Invention

According to a first aspect of the invention there is provided a turbine comprising a rotor onto which a working fluid can be directed to cause rotation of the rotor, and a heat exchanger associated with the rotor for recovery of heat released by the working fluid impinging upon the rotor,

In one arrangement, the heat exchanger may be incorporated in the rotor.

In another arrangement, the heat exchanger may be disposed adjacent to the rotor. The heat exchanger may, for example, be accommodated within a stationary casing within which the rotor is housed.

Preferably, the heat exchanger comprises a fluid flow path, whereby heat released by the working fluid can be transferred to fluid flowing along the fluid flow path.

Preferably, the fluid flow path comprises a plurality of tubes.

Preferably, the tubes provide for parallel fluid flow therethrough.

Preferably, the tubes are disposed in circumferential relation with respect to the rotor.

The heat recovered by the heat exchanger is preferably used for pre-heatiπg water from which steam is generated for use as working fluid for the turbine.

Preferably, the plurality of tubes are provided on the rotor for rotation therewith.

Preferably, the rotor further comprises an outer casing, the outer casing being thermally insulated from the water tubes. Preferably, a means is associated with each tube to present a surface upon which the working fluid can impinge to impart momentum to the rotor.

Preferably, each tube presents an exposed surface configured with respect to the incident working fluid such that at least a portion of the working fluid attaches itself to the exposed surface by virtue of the Coanda effect. As a consequence of such attachment, the working fluid can exert an attractive force on the exposed surface in the direction of rotation of the rotor. In this way, rotational effects imparted to the rotor by virtue of the working fluid are enhanced.

The working fluid may comprise solely steam or a mixture of steam and exhaust gases from a combustion process, typically the combustion process used for generation of the steam.

Where the working fluid comprises a mixture of steam and exhaust gases from the combustion process, the mixture is preferably created in a Coanda amplifier.

The turbine may operate in series with a further turbine on a common output shaft to provide a turbine assembly. The further turbine may comprise a turbine according to the invention or a turbine of some other form, such as for example a conventional multi-stage turbine. The may be two or more such further turbines on the common shaft.

According to a second aspect of the invention there is provided a turbine comprising a rotor and a heat exchanger incorporated in the rotor, the heat exchanger comprising a fluid flow path, wherein heat released by a working fluid impinging upon the rotor can be transferred to fluid flowing along the fluid flow path.

According to a third aspect of the invention there is provided a turbine comprising a rotor and a nozzle for directing a flow of working fluid onto the rotor to cause rotation thereof, the rotor presenting a surface configured with respect to the direction of incident working fluid such that at least a portion of the flow of the workiπg fluid attaches to the surface by virtue of the Coanda effect, thereby exerting an attractive force on the surface in the direction of rotation of the rotor.

According to a fourth aspect of the invention there is provided a steam power plant comprising apparatus for generating steam and a turbine, the turbine being adapted to be driven by a working fluid comprising steam generated by the steam generation apparatus, the turbine having a heat exchanger for using heat released in the turbine from the working fluid to preheat water from which steam is generated in the steam generation apparatus.

Preferably, the rotor comprises a fluid flow path through which water can flow in heat exchange relation with the hot working fluid issuing onto the rotor.

Preferably, the steam power plant comprises a nozzle system within the turbine for directing working fluid onto the heat exchanger.

Preferably, the nozzles are spaced axially along the rotor.

The nozzles may comprise Laval nozzles.

Brief Description of the Drawings

The invention will be better understood by reference to the following description of several specific embodiments thereof as shown in the accompanying drawings in which:

Figure 1 is a schematic diagram illustrating a steam power plant according to a first embodiment;

Figure 2 is a schematic perspective view of the steam power plant according to the first embodiment;

Figure 3 is a plan view of the steam power plant;

Figure 4 is side elevational view of the steam power plant; Figure 5 is a further side elevational view of the steam power plant;

Figure 6 is a fragmentary perspective view of the steam power plant;

Figure 7 is a fragmentary plan view illustrating in particular the burner of the steam power plant;

Figure 8 is a fragmentary plan view (on an enlarged scale) of a part of the burner;

Figure 9 is a fragmentary perspective view of a part of the burner;

Figure 10 is a fragmentary elevational view of the steam power plant;

Figure 11 is a fragmentary perspective view, partly in section, showing the turbine, generator and boiler of the steam power plant;

Figure 12 is a partly sectioned perspective view of the turbine and the generator;

Figure 13 is a side view of the turbine (in part section) and the generator;

Figure 14 is a fragmentary side view, in part section and on an enlarged scale, of the turbine;

Figure 15 is a schematic fragmentary view of part of the turbine, illustrating in particular the nozzle system and the rotor;

Figure 16 is a further fragmentary view of the turbine rotor and the nozzle system, again on an enlarged scale;

Figure 17 is a schematic fragmentary side view of the nozzie system and the rotor of the turbine; Figure 18 is a plan view of the turbine, showing in particular the nozzle system and the rotor;

Figure 19 is a schematic view illustrating steam issuing from a nozzle onto the rotoπ

Figure 20 is a fragmentary perspective view at the lower end of the boiler;

Figure 21 is a schematic perspective view of the boiler;

Figure 22 is a fragmentary view of the boiler shown in section;

Figure 23 is a view of part of the boiler shown in Figure 22 but on an enlarged scale;

Figure 24 is a view similar to Figure 23 but again on a further enlarged scale;

Figure 25 is a fragmentary perspective view of part of the boiler;

Figure 26 is a schematic diagram illustrating a steam power plant according to a second embodiment;

Figure 27 is a fragmentary elevational view of the steam power plant according to the second embodiment;

Figure 28 is a schematic diagram illustrating a steam power plant according to a third embodiment;

Figure 29 is a schematic perspective view of a steam power plant according to a third embodiment;

Figure 30 is a fragmentary side view of the steam power plant according to the third embodiment, illustrating the relationship between the boiler and a burner for generating combustion products for use in the boiler; and Figure 31 is a schematic diagram illustrating a steam power plant according to a fourth embodiment.

Best Modθ(s) for Carrying Out the Invention

Referring to Figures 1 and 2 of the drawings, the steam power plant 10 according to the first embodiment is used for generation of electricity. The steam power plant 10 comprises steam generation apparatus 11, a steam turbine 13 and an electrical generator 15.

The steam generation apparatus 11 generates superheated steam from feed water. Energy within the superheated steam (in the form of fluid pressure) is converted directly to mechanical energy in the turbine 13. Mechanical energy from the turbine 13 is transmitted by a rotary shaft to the electrical generator 15 for generation of electricity.

The steam generation apparatus 11 comprises a burner 21 having a combustion zone 22 for generating hot combustion products (gases) for production of steam. The burner 21 is adaptable to combust a variety of fuels, including coal, oil and gas. In this embodiment, the burner 21 receives fuel from a fuel tank 23 by way of a feed line 25 incorporating a fuel delivery pump 27. Combustion air is delivered to the combustion zone 22 of burner 21 via an air intake 29 incorporating an air blower 31.

From the combustion zone 22, the combustion flame and also hot combustion products are directed into two heating zones, being a first heating zone 33 and a second heating zone 35. In this embodiment, the flame and the hot combustion products are split into two portions, one of which flows through the first heating zone 33 and the other of which flow through the second heating zone 35, as will be explained in more detail later. As also will be explained later, wet steam generated from steam water passes in heat exchange relationship with the hot combustion products in the first heating zone 33 to be converted to dry steam, and the dry steam passes in heat exchange relationship with the hot combustion products in the second heating zone 35 to be converted into superheated steam. The superheated steam is superheated to a level to constitute supercritical steam.

From the two heating zones 33, 35, the hot combustion products are passed through in heat exchange relationship with the feed water in a boiler 41 to generate the wet steam. The combustion products from the first and second zones 33, 35 have separate flow paths 43, 45 passing through the boiler 41. The two flow paths 43, 45 communicate with the common outlet flow path 47 which terminates at a flue 49 at which the combustion products are discharged to atmosphere. A blower 51 is incorporated in the flow path 47 for delivery of the combustion products to the flue 49. While not shown in the drawings, there may be treatment means for treating the combustion products prior to discharge thereof to atmosphere.

Feed water for the production of steam is delivered to the boiler 41 from a feed water tank 53 by way of a feed water line 55 incorporating a feed water pump 57.

Prior to being delivered to the boiler 41 for conversion to wet steam, the feed water is preheated using heat extracted from the spent steam in the turbine 13. For this purpose, the turbine 13 has a rotor 61 which incorporates a heat exchanger 62 through which the feed water passes in heat exchange relation for preheating.

Wet steam from the boiler 41 is conveyed to heat exchanger 63 associated with the first heating zone 33 by wet steam line 64. The heat exchanger 63 converts the wet steam into dry steam.

Dry steam from the heat exchanger 63 is conveyed to heat exchanger 65 associated with the second heating zone 35 by dry steam line 66. The heat exchanger 65 converts the dry steam into superheated steam.

Superheated steam from heat exchanger 65 is conveyed to the turbine 13 by superheated steam line 67. The superheated steam drives the turbine 13, as will be explained in more detail later. The spent steam condenses and is conveyed to a first return water tank 71 via a return line 73 incorporating a return pump 75. A steam trap 77 is incorporated in the return line 73 upstream of the return pump 75.

The first return water tank 71 is coupled to a second return water tank 72 by way of a water line 74. The water line 74 passes through a heat exchanger 7$ in which the return water flowing from the first return water tank 71 to the second return water tank 72 passes in heat exchange relationship with air delivered to the burner 21 via air intake 29. With this arrangement, remnant heat contained in the water condensed from the steam can be utilised for preheating the combustion air.

Referring now to Figures 11 to 19, the turbine 13 comprises the turbine rotor 61 and a nozzle system 80 for directing the superheated steam onto the rotor 61 to cause rotation thereof.

The rotor 61 comprises a rotor body 83 mounted onto a rotor shaft 85. In this embodiment, the axis of rotation of the rotor shaft 85 is substantially vertical. The rotor shaft 85 is rotatably supported in bearings 86 and one end of the shaft is drivingly coupled to the generator 15 to transmit shaft power thereto.

The rotor body 83 comprises a plurality of tubes 87 which provide parallel flow passages within the rotor 61 for preheating the feed water. With this arrangement, the tubes 87 are incorporated in the rotor 61 and constitute part of the heat exchanger 62.

In this embodiment, the tubes 87 are disposed circumferentially around the periphery of the rotor 61 and are supported on two supports 90 mounted on the rotor shaft 65. Each support 90 comprises a disc structure 91 having an outer periphery 94 incorporating recesses 95 in which the tubes 87 are accommodated.

A casing 93 surrounds the tubes 87 to define the radial outer periphery of the rotor 61. Thβ casing 93 is thermally isolated from the tubes 87 for the purposes of minimising heat loss from the tubes through the casing. Specifically, each tube 87 is attached to the casing 93 by way of a mounting 95 configured as an elongate cowling 97. The cowling 97 is positioned longitudinally adjacent the tube 87 on the trailing side thereof with respect to the direction of rotation of the rotor 61. The cowling 97 comprises a central web 99, an inner flange 101 on one side of the central web and an outer flange 103 on the other longitudinal side of the central web, with the two flanges 101 , 103 extending to opposed sides of the web. The cowling 97 is attached at the outer flange 101 to the casing 93, and the respective tube 87 rests against the central web 99 and the inner flange 103, as best seen in Figure 19. With this arrangement, the cowling 97 provides the connection between its respective tube 87 and the casing 93. There is no direct connection between the tube 87 and the casing 93, and in fact there is a gap therebetween (which is not apparent in the drawings) to provide the thermal isolation referred to previously.

The cowlings 97 provide an enhanced surface area for the impinging steam to impart momentum to the rotor 61.

Each tube 87 has an exposed surface 111 against which steam issuing from the nozzle system 80 is directed in order to cause rotation of the rotor 61. Each exposed surface 111 is so configured with respect to the direction of incident steam such that a portion of thø steam flow attaches itself to the surface by virtue of the Coanda effect. This is illustrated schematically in Figure 19 in which the incident flow of steam is identified by reference numeral 112 and a portion 112a thereof is shown attaching itself to the surface 111. As a consequence of such attachment, the steam flow exerts an attractive force on the exposed surface in the direction of rotation of the rotor. In this way, rotational effects imparted to the rotor 61 by virtue of the steam are enhanced; that is, rotation is imparted to the rotor 61 not only as a reaction to the impingement of the steam on the rotor 61 (and more particularly the cowling 97 on the tubes 87) but also by virtue of the Coanda effect arising through attachment of the steam flow to the surface 111. While the tubes 87 in this embodiment are disposed in a circumferential arrangement adjacent the outer periphery of the rotor 61 , other arrangements are of course possible. Tubes may, for example, be disposed longitudinally within the rotor 61 at various radial distances from the axis of rotation of the rotor.

As mentioned above, the tubes 87 constitute part of the heat exchanger 62. The tubes 87 are connected at each end to a common manifold 88 which is connected into the feed water line 55 by a rotary coupling 89. In this way, the feed water flow path is incorporated into the rotating rotor 61.

The nozzle system 80 comprises a plurality of nozzles 121 each of which receives superheated steam from the superheated steam line 67. The superheated steam line 67 has a plurality of branch lines 123 each of which terminates at one of the nozzles 121. The branch lines 123 extend into the confines of the rotor 61 though the upper end thereof and the nozzles 121 are disposed within the confines of the rotor to direct superheated steam onto the tubes 87 and associated cowlings to impart momentum and thereby generate motive torque on the rotor, as previously described. '

The nozzles 121 are arranged at various spacings axially along the rotor 61. The nozzles 121 each comprise a Laval nozzle.

The superheated steam undergoes collapse or implosion upon contact with the tubes 87 and cowlings 97, imparting thermal energy thereto and thus heating the feed water flowing upwards along the tubes 87.

The collapsed steam is confined within the rotor 61 by the casing 93. Because of the vertical orientation of the rotor 61, spent steam and its condensate descend within the rotor 61 and exits through the lower end thereof. The exiting spent steam and condensate communicate with return line 73 which incorporates the steam trap 77 as previously described. As mentioned earlier, the combustfon flame and also hot combustion products from the combustion zone 22 are separated into two heating zones, being the first heating zone 33 and the second heating zone 35.

The first heating zone 33 comprises a passage 131 defined by a first flame tube 133, and the second zone comprises a passage 135 defined by a second flame tube 137. The two flame tubes 133, 137 extend from the combustion zone 22 and are in communication with each other at their inners ends, with the first flame tube

133 branching from the second flame tube, as best seen in Figure 8- A control device such as an adjustable butterfly valve 141 is provided for selectively varying the extent of separation of the combustion flame and the combustion products between the two flame tubes 133, 137.

An outer tube 143 surrounds the first flame tube 133 in spaced apart relation therewith. A longitudinal baffle structure 145 is provided in the annular space 147 defined between thθ two tubes 133, 143 to form a steam flow path 149. With this arrangement, the steam flow path 149 is in heat exchange relation with the flame and the hot combustion products contained within the ffame tube 133. The spacing of the baffle structure 145 is set according to the heat transfer necessary to achieve conversion of the wet steam into dry steam as it flows along the steam flow path 149.

Similarly, an outer tube 153 surrounds the second flame tube 137 in spaced apart relation therewith. A longitudinal baffle structure 156 is provided in the annular space 157 defined between the two tubes 137, 153 to form a steam flow path 159. With this arrangement, the steam flow path 159 is in heat exchange relation with the flame and the hot combustion products contained within the flame tube 137. The spacing of the baffle structure 155 is set according to the heat transfer necessary to achieve conversion of the dry steam into superheated steam as it flows along the steam flow path 159.

As mentioned above, the boiler 41 has separate flow paths which receive hot combustion products from the first and second heating zones 33, 35. The boiler 41 comprises an inner tube 161, an outer tube 163 spaced from the inner tube to define an annular space 164 therebetween, anά a spiralling water tube 165 accommodated within the inner tube 161 in close proximity to the sidewall thereof. The pitch of the spiral can be selected according to the characteristics of the wet steam required to be generated in the boiler 41 , along with other parameters of the boiler.

With this arrangement, the inner tube defines an inner gas flow path 168 and the annular space 164 defines outer gas flow path 169. The inner gas flow path 168 has an inlet 172 and an outlet 174. Similarly, the outer gas flow path 169 has an inlet 176 and an outlet 178.

The water tube 165 has an inlet 181 through which feed water from feed water line 55 enters the boiler 41 and an outlet 183 through which wet steam generated in the boiler 41 exits to flow along wet steam line 64.

The annular space 164 accommodates a plurality of baffles 167 disposed at intervals along the space. Each baffle 167 is configured as an annular disc 169 having a radially inner end 171 which engages the outer periphery of the inner tube 161 and a radially outer end 173 which engages the inner periphery of the outer tube 163. Each baffle 167 has a plurality of flow openings 175 formed therein, there being four such opening in each baffle in this embodiment. Each flow opening 175 is formed by cutting a flap 177 in the disc, with the cuts forming the sides of the flap extending inwardly from the radially inner end 171 of the disc, and then bending the flap to extend normally from the plane of the disc. The area of the disc from which each flap 177 provides the respective flow opening 175. The baffles 167 are butted one against another along the space 165, with the flaps 177 function as spacers between the baffles. The spacings between the baffles 167 and the flow openings in the baffles cooperate to form a tortuous flow passage 179 which along the annular space 164. Further, the flaps 177 function as turbulators for generating turbulence in flow along the flow path 179. The flow passage 179 is incorporated in flow path 43 and as such receives hot combustion products from the first heating zone 33. The inner tube 161 is incorporated in flow path 45 and as such receives hot combustion products from the second heating, zone 35. The inner tube 161 has a plurality of baffles 191 provided along its length to assist in heat transfer to the surrounding flow path 179. The baffles are accommodated within the confines of the spiral windings of the water tube 165. The baffles 191 each comprise a plate 193 having a plurality of outer flow openings 197 formed by bending potions 198 at the outer periphery to form flaps 199. The flaps 199 function as spacers between the baffles 191 and also as turbulators to assist heat transfer to the water tube 165 also accommodated within the inner tube 161.

Accordingly, there is heat transfer to the feed water from hot combustions products derived from both the first and second heating zones 33, 35. The combustion products from the second zone 35 are hotter and are therefore more effective in the heat transfer process for generation of the wet steam from the feed water.

The flow directions of the feed water are in counter flow to the flow directions of the hot combustion products in the flow paths 43, 45 in order to optimise heat transfer.

Referring now to Figures 26 and 27, the steam power plant according to the second embodiment is similar in many respects to the steam power plant of the first embodiment and so the same reference numerals are used to identify corresponding parts.

In this second embodiment, there is provision for diversion of the spent combustion products for further use and processing before being discharged to atmosphere or sequestered. In particular, a portion of the combustion products (exhaust gases) is combined with the superheated steam to form a working fluid for driving the turbine 13.

The second embodiment has a diversion line 201 for diverting the exhaust gases after having passed through the boiler 41 to a Coanda amplifier 203. Valves 205 are provided in the flow paths 43, 45 between the boiler 41 and the flue 49, and the diversion line 201 branches from the flow paths 43, 45 upstream of the valves 205. With this arrangement, closure of the valves 205 causes the exhaust gases leaving the boiler 41 to flow along the diversion line 201 to the Coanda amplifier 203. Alternatively, the valves 205 can be so set as to partially block exhaust gas flow to the flue 49, thereby causing a portion of the exhaust gases to be diverted to the Coanda amplifier 203.

In the Coanda amplifier 203, the diverted exhaust gases are mixed with the superheated steam (which is at high pressure) to form a high pressure working fluid. Specifically, the exhaust gases are accelerated in the Coanda nozzle through injection of the high pressure superheated steam in known manner.

The working fluid, which comprises the mixture of superheated steam and the exhaust gases, is then delivered to the turbine 13 to issue onto the rotor 61 through the nozzle system 80 as was the case in the first embodiment.

The spent working fluid, which comprises steam condensate and exhaust gases dissolved therein, is passed through a processing stage 211. The processing stage 211 comprises separation of solids from the condensate in separation unit

213. The processing stage 211 further comprises treatment of the gases in the condensate in treatment unit 215 for purification of undesirable components such as carbon dioxide and other greenhouse gases. Thereafter, there is separation of the gas from the water in a separation unit 217 from which the gases are vented to atmosphere or sequestered, and the water is returned to the first return water tank 71.

A particular advantage of the second embodiment is that the combustion products (exhaust gases) can be treated in a cost-effective manner using condensate from the spent steam. Further, remnant heat energy in the spent exhaust gases can be utilised in the working fluid.

In the previous embodiments, the boiler 41 generated wet steam which was converted to dry steam in heat exchanger 63 and the dried steam was converted into super-heated steam in heat exchanger 65. In other arrangements it is possible for. such a boiler to be constructed and operated to generate dry steam which can subsequently be converted to superheated steam for delivery to the turbine 13, or alternatively to generate superheated steam which can then be delivered to the turbine 13.

Referring now to Figures 28, 29 and 30, there is shown a steam power plant according to a still further embodiment which incorporates a boiler that can convert feedwater directly into superheated steam. The steam power plant according to this still further embodiment is similar in many respects to the steam power plant according to the first embodiment and so corresponding reference numerals are used to identify corresponding parts.

As alluded to above, conversion of feed water into super-heated steam in this further embodiment is performed entirely within the boiler 41 , and consequently, there is no need for the heat exchanger 63, 65.

In particularly, in this further embodiment, the steam generation apparatus 11 has the combustion zone 22 for generating hot combustion products (gases). From the combustion zone, the combustion flame and also hot combustion products are split into two portions, one of which is delivered to the inner gas flow path 168 of the boiler and the other of which is delivered to the outer gas flow path 169. In this regard, ducting 220 extends between the combustion zone 22 and the boiler ^' 41. The ducting 220 incorporates a first duct section 221 which communicates with the inner gas flow path 168 and a second duct section 222 which branches outwardly and communicates with the outer gas flow path 168, as best seen in

Figure 30. As with the first embodiment, a control device such as an adjustable butterfly valve may be provided for selectively varying the extent of separation of the combustion flame and the combustion products into the two ducts 221 , 222.

It is a feature of this embodiment that the co-axial construction of the boiler 41 assists in withstanding high internal fluid pressures required to achieve super^¬ critical steam conditions. By having such a boiler 41 which can convert feedwater into superheated steam, the steam generation apparatus 11 may be of more compact construction, as there is no requirement for the heat exchangers 63, 65. Additionally, the construction may provide easier access to the burner 21 for it to be exchanged. As alluded to earlier, the steam power plant has been devised to combust different types of fuel. A burner designed for combusting one type of fuel may be very different from that designed to combust another type of fuel. Accordingly, it is advantageous to have a construction which allows the burner to be readily exchanged.

Referring now to Figure 31 , there is shown a steam power plant according to a still further embodiment which also incorporates a boiler that can convert feedwater directly into superheated steam. The steam power plant according to this still further embodiment is similar In many respects to the steam power plant according to the second embodiment (in that there is provision for diversion of the spent combustion products for further use and processing before being discharged to atmosphere) and so corresponding reference numerals are used to identify corresponding parts.

In yet another embodiment, which is not shown, the heat exchanger 62 may be associated with the rotor 61 is some way other than being incorporated on the rotor. The heat exchanger may be disposed adjacent to the rotor. The heat exchanger may, for example, be accommodated within a stationary casing within which the rotor is housed.

The turbine 13 according to any of the earlier embodiments may operate in series with a further turbine on a common output shaft to provide a turbine assembly. The further turbine may comprise a turbine according to the invention or a turbine of some other form, such as for example a conventional multi-stage turbine (although the latter would only be appropriate in cases where the working fluid comprised solely steam). The may be two or more such further turbines on the common shaft. Qne particular arrangement may involve a conventional turbine with high pressure and intermediate pressure zones but no low pressure condensing zone, interposed between the turbine 13 and the steam generation apparatus 11. The interposed turbine and the turbine 13 share the same shaft so that each can contribute useful mechanical work. Steam exiting the conventional turbine enters the turbine 13 where the thermal energy extraction takes place in addition to conversion of pressure to mechanical work.

The function of the two-zone conventional turbine is to optimise the energy conversion of the steam at the very high pressure and temperature ranges without having to also optimise the low pressure functioning. The high and intermediate pressure turbine can be relatively compact without the need for the larger low pressure turbine section so thermal mass may be reduced leading to cost savings and improvement in thermal response times.

Another turbine assembly, which is an extension of the previous arrangement, involves, in order of decreasing pressure, a conventional turbine as above followed by turbine 13 which is in turn followed by a further turbine 13. The conventional turbine exhausts into the input of the first turbine 13 which in turn exhausts into the input of the second turbine 13. All three turbines are coupled together on a common shaft

The feature of this arrangement is that the two turbines 13 may bθ optimised over a narrower pressure range which provides better performance than a single turbine operating over the broader pressure range.

In the embodiments where there are several turbines in series on a common output shaft, it would be necessary for the turbine casings to be sealed and form a pressure vessel rated to the appropriate operating pressures.

From the foregoing, it is evident that the various embodiments can each provide a steam power plant which is particularly, although not necessarily exclusively, suitable as a relatively small scale, decentralised power plant that can use a variety of fuels including in particular coal. It is a feature of the power plant that it is designed to be entirely modular and readily transportable. As such, all components of the steam power plant are designed such that the whole unit, when disassembled, can be transported in one or more sea containers. The steam turbine 13 utilised in the steam. power plant of each embodiment has been developed in order to meet this requirement.

It should be understood that the invention is not limited to the embodiments described and that various alterations and modifications may be made without departing from the scope of the invention.

Further, various features of the embodiments, such as the turbine 13 (including in particular the construction of the turbine rotor 61 for heat exchange), as well as the construction of boiler 41 and the feature of splitting Of the flame and combustion products at the burner 21 may have applications separately of each other, including in plants and apparatus other than the steam power plants according to the embodiments described.

Throughout the specification, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

Claims

The Claims Defining the Invention are as Follows:

1. A turbine comprising a rotor onto which a working fluid can be directed to cause rotation of the rotor, and a heat exchanger associated with the rotor for recovery of heat released by the working fluid impinging upon the rotor.

2. A turbine according to claim 1 wherein, the heat exchanger may be incorporated in the rotor.

3. A turbine according to claim 1 or 2 wherein the heat exchanger comprises a fluid flow path, whereby heat released by the working fluid can be transferred to fluid flowing along the fluid flow path.

4. A turbine according to any one of the preceding claims wherein the fluid flow path comprises a plurality of tubes.

5. A turbine according to claim 4 wherein the tubes provide for parallel fluid flow therethrough.

6. A turbine according to claim 4 or 5 wherein the tubes are disposed in circumferential relation with respect to the rotor.

7. A turbine according to claim 4, 5 or 6 wherein the plurality of tubes are provided on the rotor for rotation therewith.

8. A turbine according to any one of claims 4 to 7 wherein the rotor further comprises an outer casing, the outer casing being thermally insulated from the water tubes.

9. A turbine according to any one of claims 4 to 8 further comprising a means associated with each tube to present a surface upon which the working fluid can impinge to impart momentum to the rotor.

10. A turbine according to any one of claims 4 to 9 wherein each tube presents an exposed surface configured with respect to the incident working fluid such that at least a portion of the working fluid attaches itself to the exposed surface by virtue of the Coanda effect.

11. A turbine according to any one of claims 1 to 10 wherein the working fluid comprise solely steam.

12. A turbine according to any one of claims 1 to 10 wherein the working fluid comprises a mixture of steam and exhaust gases from a combustion process.

13. A turbine according to any one of claims 1 to 10 wherein the working fluid comprises a mixture of steam and exhaust gases from a combustion process, the mixture being created in a Coanda amplifier.

14. A turbine according to claim 1 wherein the heat exchanger is disposed adjacent to the rotor.

15. A turbine according to claim 14 wherein the heat exchanger is accommodated within a stationary casing within which the rotor is housed.

16. A turbine comprising a rotor and a heat exchanger incorporated in the rotor, the heat exchanger comprising a fluid flow path, wherein heat released by a working fluid impinging upon the rotor can be transferred to fluid flowing along the fluid flow path.

17. A turbine comprising a rotor and a nozzle for directing a flow of working fluid onto the rotor to cause rotation thereof, the rotor presenting a surface configured with respect to the direction of incident working fluid such that at least a portion of the flow of the working fluid attaches to the surface by virtue of the Coanda effect, thereby exerting an attractive force on the surface in the direction of rotation of the rotor.

18. A steam-cycle power generation system comprising a turbine according to any one of the preceding claims.

19. A steam power plant comprising a turbine according to any one of claims 1 to 17.

20. A steam power plant comprising apparatus for generating steam and a turbine, the turbine being adapted to be driven by a working fluid comprising steam generated by the steam generation apparatus, the turbine having a heat exchanger for using heat released in the turbine from the working fluid to preheat water from which steam is generated in the steam generation apparatus.

21. A steam power plant according to claim 20 wherein the turbine comprises a rotor, the heat exchanger being incorporated in the rotor and defining a fluid flow path through which water can flow in heat exchange relation with the hot working fluid issuing onto the rotor.

22. A steam power plant according to claim 20 or 21 further comprising a nozzle system within the turbine for directing working fluid onto the heat exchanger.

23. A steam power plant according to claim 22 wherein the nozzle system comprises nozzles spaced axially along the rotor.

24. A turbine assembly comprising a turbine according to any one of claims 1 to 17 and a further turbine, the turbines being arranged for operation in series.

25. A turbine assembly according to claim 24 wherein the turbines have rotors mounted on a common output shaft.

26. A turbine assembly according to claim 24 or 25 wherein the further turbine comprises a turbine according to any one of claims 1 to 17.

27. A turbine assembly according to claims 24, 25 or 26 wherein the further turbine comprises a multi-stage turbine.

28. A turbine assembly according to any one of claims 24 to 27 further comprising a working fluid flow path communicating first with the further turbine and thereafter with the other turbine.

29. A turbine assembly according to claim 28 wherein the further turbine comprises a high pressure zone and an intermediate pressure zone, the arrangement being that working fluid exiting the intermediate pressure zone enters the other turbine.

30. A turbine assembly according to any one of claims 24 to 29 wherein there is a still further turbine having a rotor mounted on the common shaft. .

31. A turbine assembly according to claim 30 wherein the still further turbine comprises a turbine according to any one of claims 1 to 17 located in the working fluid path after the first-mentioned turbine.

32. A turbine substantially as herein described with reference to the accompanying drawings.

33. A steam power plant substantially as herein described with reference to the accompanying drawings.

34. A turbine assembly substantially as herein described.