GB2420382A

GB2420382A - Turbine power generating system using solid fuel

Info

Publication number: GB2420382A
Application number: GB0523516A
Authority: GB
Inventors: Robert Edward Talbolt; David Lyndon Pritchard
Original assignee: TALBOTT S HEATING Ltd
Current assignee: TALBOTT S HEATING Ltd
Priority date: 2004-11-18
Filing date: 2005-11-18
Publication date: 2006-05-24
Also published as: GB0425369D0; GB0523516D0

Abstract

A power generating system 10 includes a combustion chamber 16 for combustion of solid fuel material, a heat exchanger 18 associated with the combustion chamber 16 through which compressed fluid passes to be heated by combustion of the solid fuel material, a compressor 22 for compressing fluid to be heated in the heat exchanger 18, a turbine 14 which is arranged to be driven by the compressed and heated fluid to generate power, and a diverter arrangement 34, preferably in the form of a diverter valve 36, which is selectively operable to divert a proportion of the compressed fluid, desirably to the combustion chamber 16. In another diversion arrangement, a proportion of the air that has passed through the heat exchanger 18 may be diverted to the combustion chamber and a further diversion arrangement may be provided for diverting a proportion of the air from the compressor directly to the turbine. Another aspect of the invention relates to maintaining a negative pressure inside the combustion chamber, preferably by means of an induced draft fan 46. An air pressure sensor 47, combustion air fans 42, a solid fuel inlet 20, and an electric motor for driving the turbine during start-up, may be provided.

Description

1 2420382 Power Generating System The present invention relates to power

generating systems and to a method for operating power generating systems.

It is known to generate electrical power by combusting solid fuel materials such as biomass, combustible waste, fossil fuels and wood, to indirectly heat fluid. The heated fluid is used to drive a turbine which in turn drives a generator to generate electrical power.

In view of the combustion characteristics of solid fuel materials and the need for indirect heating of the fluid, difficulties may be encountered operating such power generating systems.

According to a first aspect of the present invention, there is provided a power generating system comprising a combustion chamber for combustion of solid fuel material, a heat exchanger associated with the combustion chamber through which compressed fluid passes to be heated by combustion of the solid fuel material, a compressor for compressing fluid to be heated in the heat exchanger, and a turbine arranged to be driven by the compressed and heated fluid to generate power, wherein the system includes a diverter arrangement selectively operable to divert a proportion of the compressed fluid.

The diverter arrangement may be selectively operable to divert a proportion of the compressed fluid away from the turbine, and may be operable to divert a proportion of the compressed fluid away from the turbine:*. * before the compressed fluid has been passed through the turbine.

The diverter arrangement may be selectively operable to divert a proportion of the compressed fluid to the combustion chamber. S..

The diverter arrangement may be selectively operable to divert a proportion of the compressed fluid to the combustion chamber prior to heating of the compressed fluid in the heat exchanger, in which case the diverter arrangement may be located upstream of the heat exchanger.

Alternatively, the diverter arrangement may be selectively operable to divert a proportion of the compressed fluid to the combustion chamber after heating of the compressed fluid in the heat exchanger, in which case the diverter arrangement may be located downstream of the heat exchanger.

The fluid may be a gas. The fluid is preferably atmospheric air. The proportion of the compressed fluid diverted to the combustion chamber preferably provides combustion air to facilitate combustion of the solid fuel material.

The diverter arrangement may be selectively operable to divert none of the compressed fluid when in a first diverting condition such that all of the compressed fluid is supplied to the turbine. The diverter arrangement may be selectively operable to direct a proportion of the compressed fluid to the turbine and to divert a remaining proportion of the compressed fluid to the combustion chamber when in a second diverting condition.

When in the second diverting condition, the diverter arrangement may be operable to direct between approximately 70% and 90% of the compressed fluid to the turbine, and to divert between approximately 10% and 30% of the compressed fluid to the combustion chamber. More preferably, when in the second diverting condition, the diverter arrangement may be operable to direct approximately 80% of the compressed fluid to the turbine, and to divert approximately 20% of the compressed fluid to the combustion: * chamber.

The power generating system may include a further diverter arrangement which may be selectively operable to divert a proportion of the compressed fluid to the turbine. The further diverter arrangement may be I...

selectively operable to divert a proportion of the compressed fluid to the * turbine prior to heating of the compressed fluid in the heat exchanger, the further diverter arrangement preferably being located upstream of the heat exchanger. The further diverter arrangement may be selectively operable to divert said proportion of the compressed fluid to a fluid inlet of the turbine.

The power generating system may include a control arrangement for controlling the operation of the diverter arrangement and/or the further diverter arrangement, and the control arrangement may be arranged to control the operation of the diverter arrangement between the first and second diverting conditions. The control arrangement may be operable to provide variable control of the diverter arrangement between the first and second diverting conditions.

The diverter arrangement and/or the further diverter arrangement may comprise a diverter valve.

The power generating system may be arranged so that the compressor is driven by the turbine. The power generating system may include external drive means which may be selectively operable to drive the turbine. The external drive means may be an electrically operated drive means, and may be an electric motor.

The power generating system may include an air feed arrangement for feeding air into the combustion chamber to facilitate combustion. The air feed arrangement may include one or more combustion air fans which may be selectively operable to feed ambient air into the combustion chamber to facilitate combustion of the solid fuel material. * , .

The air feed arrangement may further or alternatively include means for feeding heated turbine exhaust air which has been used to drive the turbine to the combustion chamber where any residual heat in the air facilitates and enhances combustion of the solid fuel material. S... C * S...

The combustion chamber may include an air control arrangement which may be operable to maintain a negative air pressure inside the combustion chamber. The air control arrangement may be operable to maintain a substantially constant negative air pressure inside the combustion chamber.

By negative air pressure is meant an air pressure which is less than atmospheric pressure.

The air control arrangement may include an air pressure sensor for monitoring the air pressure inside the combustion chamber.

The air control arrangement preferably includes at least one air drive means for evacuating air from the combustion chamber to thereby maintain a negative air pressure inside the combustion chamber. The air drive means is preferably a fan, and is desirably an induced draft fan.

The air control arrangement may be arranged to vary the speed of the air drive means whereby to vary the amount of air evacuated from the combustion chamber, preferably to maintain a substantially constant negative air pressure inside the combustion chamber. The air control arrangement may be arranged to vary the speed of the air drive means according to the amount of air fed into the combustion chamber by the air feed arrangement, and preferably according to the amount of ambient air and/or heated turbine exhaust air fed into the combustion chamber.

According to a second aspect of the present invention, there is provided a method for operating a power generating system according to the first aspect of the present invention, the method comprising: * * .....

combusting solid fuel material in the combustion chamber; activating the compressor to provide compressed fluid; and diverting a proportion of the compressed fluid. *0*.

S I..

The diverting step may comprise diverting a proportion of the * compressed fluid away from the turbine, and may comprise diverting a proportion of the compressed fluid away from the turbine before it has been used to drive the turbine.

The method may comprise initially feeding a predetermined amount of solid fuel material into the combustion chamber and may comprise igniting said predetermined amount of solid fuel material. The method may include combusting said predetermined amount of solid fuel material to raise the combustion temperature in the combustion chamber to a predetermined initial combustion temperature. The initial combustion temperature may be between approximately 350 C and 550 C.

The method may comprise feeding further solid fuel material into the combustion chamber, desirably at a controlled feed rate, to maintain combustion and raise the combustion temperature from the initial combustion temperature to a preliminary combustion temperature. The method may comprise raising the combustion temperature from the initial combustion temperature to the preliminary combustion temperature at a predetermined rate, for example a rate of between 1 and 20 C/mm, and desirably a rate of between 5 and 10 C/mm.

The method may comprise circulating ambient air into the combustion chamber to facilitate combustion of the solid fuel material.

The method may comprise activating the compressor when the combustion temperature in the combustion chamber has attained the preliminary combustion temperature. The preliminary combustion temperature may be between approximately 400 C and 800 C, and may be between:. approximately 750 C and 800 C. The step of activating the compressor may comprise activating external drive means to drive the turbine and thereby drive the compressor, desirably for an extended period of time. 0ISI

S

The method may comprise diverting a proportion of the compressed SI'' fluid to the combustion chamber. The method may comprise operating the diverter arrangement to divert said proportion of the compressed fluid to the combustion chamber.

The method may comprise operating the diverter arrangement so that no compressed fluid is diverted to the combustion chamber when the rotational speed of the turbine reaches a predetermined speed preferably at which the turbine may be driven by the compressed and heated fluid alone.

The method may comprise feeding heated fluid which has driven the turbine to the combustion chamber where any residual heat in the fluid is used to facilitate and enhance combustion in the combustion chamber.

The method may further comprise increasing the power provided to the turbine by the external drive means when the rotational speed of the turbine reaches said predetermined speed to accelerate the turbine.

The method may comprise deactivating the external drive means when the rotational speed of the turbine reaches a self-sustaining speed. The method may further comprise accelerating the turbine to a generating speed.

The method may comprise diverting a proportion of the compressed air to the combustion chamber in response to a detected increase in turbine speed above the generating speed to preferably decrease the amount of compressed air directed to the turbine and thereby preferably decrease turbine speed.

The method may comprise diverting a proportion of the compressed fluid to the turbine, and may comprise diverting said proportion of the compressed fluid to a fluid inlet of the turbine. The method may comprise S.....

operating the further diverter arrangement to direct a proportion of the: 5.5...

compressed fluid to the turbine prior to heating of the compressed fluid in the heat exchanger. .. S. *... *

S S. *

The method may comprise operating the further diverter arrangement to divert a proportion of the compressed fluid to the turbine in response to a detected increase in turbine speed above the generating speed to preferably decrease the amount of compressed heated air directed to the turbine from the heat exchanger, and thereby preferably decrease turbine speed. The method may comprise mixing the diverted air with the compressed heated air from the heat exchanger to reduce the temperature of the air fed to the turbine and thereby decrease turbine speed.

According to a third aspect of the present invention, there is provided a power generating system comprising a combustion chamber for combustion of solid fuel material, a heat exchanger associated with the combustion chamber through which air passes to be heated by combustion of the solid fuel material, a turbine arranged to be driven by the heated air to generate power, and an air feed arrangement for feeding air into the combustion chamber to facilitate combustion, the combustion chamber including an air control arrangement operable to maintain a negative air pressure inside the combustion chamber.

The air control arrangement is preferably operable to maintain a substantially constant negative air pressure inside the combustion chamber.

The air control arrangement may include an air pressure sensor for monitoring the air pressure inside the combustion chamber. The air pressure sensor is preferably located inside the combustion chamber. * .:. * S

S.....

The air control arrangement preferably includes at least one air drive: S.

....DTD: means for evacuating air from the combustion chamber to thereby maintain a negative air pressure inside the combustion chamber. The air drive means is preferably a fan, and is desirably an induced draft fan. * :: The air feed arrangement may comprise one or more combustion air fans which may be selectively operable to feed ambient air into the combustion chamber to facilitate combustion of the solid fuel material.

The air feed arrangement may further or alternatively comprise means for feeding heated turbine exhaust air which has been used to drive the turbine to the combustion chamber where any residual heat in the air facilitates and enhances combustion of the solid fuel material.

Embodiments of the present invention will now be described by way of example only and with reference to the accompanying drawings, in which: Fig. I is a schematic representation of a power generating system according to a first embodiment of the invention; Fig. 2 is a schematic representation of a power generating system according to a second embodiment of the invention; and * * * * ** Fig. 3 is a schematic representation of a power generating system according to a third embodiment of the invention. * S..... 30:

S.....

Referring to the drawings, there is shown generally a power generating system 10, 110, 210 comprising a combustion arrangement 12, 112, 212 in *.

which combustion of solid fuel material (not shown) such as combustible waste, fossil fuels and wood takes place to heat fluid, such as air, the heated fluid being used to drive a turbine 14, 114, 214 to generate power.

The power generating system 10, 110, 210 is a development of the power generating system disclosed in the applicant's earlier published international patent application no. WO 02/055855, the contents of which are incorporated herein.

In more detail and referring in particular to Fig. 1, the combustion arrangement i 2 comprises a combustion chamber 16 inside which is located a heat exchanger 18. The combustion chamber 16 includes a fuel inlet 20 which enables solid fuel material to be fed into the combustion chamber 16, preferably by an automatic fuel feed arrangement.

The power generating system 10 includes a compressor 22 which operates to compress fluid, preferably in the form of atmospheric air, and to supply this compressed air to the heat exchanger 18 for heating in the combustion chamber 16. As seen in Fig. 1, the compressed air, whose temperature may have been raised by compression, is supplied to the heat exchanger 18 along a conduit 24, and after heating in the heat exchanger 18, is supplied along a conduit 26 to the turbine 14.

The compressed and heated air is expanded through the turbine 14 to drive the turbine 14 and thereby drive a generator 28 to generate electrical power. The electrical power may be subjected to an inverter/rectifier before being outputted for further use.

S * S * * **

In order to feed air into the combustion chamber 16 to facilitate combustion of the solid fuel material, the power generating system 10 includes an air feed arrangement. The air feed arrangement comprises an air: S.... * return conduit 32 which feeds heated turbine exhaust air which has been used to drive the turbine 14 to the combustion chamber 16. Reintroduction of the *. *..

heated turbine exhaust air into the combustion chamber 16 is advantageous as this facilitates and enhances the efficiency of combustion.

The power generating system 10 includes a diverter arrangement 34, preferably in the form of a diverter valve 36 which, in the embodiment shown in Fig. 1, is located upstream of the heat exchanger 18 in the conduit 24. The diverter valve 36 is connected to the air return conduit 32 via a diverting conduit 38.

The diverter valve 36 is selectively operable to direct a proportion of the compressed air, which has been compressed by the compressor 22, along the conduit 24, through the heat exchanger 18 where it is heated, along the conduit 26 and to the turbine 14 to drive the turbine 14. The diverter valve 36 is also selectively operable to simultaneously divert a remaining proportion of the compressed air along the diverting conduit 38, into the air return conduit 32 and thereafter into the combustion chamber 16 to facilitate combustion of the solid fuel material.

One of the main advantages provided by the diverter arrangement 34 is that it enables the load on the compressor 22 to be reduced during starting of the power generating system 10, as will be explained in detail hereinafter.

The diverter valve 36 may be selectively operable between first and second diverting conditions according to the operating status of the power generating system 10, and a diverter control arrangement 40 may be provided to automatically control the operation of the diverter valve 36 between the first and second diverting conditions.

When the diverter valve 36 is in the first diverting condition, substantially none of the compressed air is diverted and instead all of the compressed air is directed along the conduit 24, through the heat exchanger S.....

18, along the conduit 26 and to the turbine 14 to drive the turbine 14. :

S

According to preferred embodiments of the invention, when the diverter: : : : valve 36 is in the second diverting condition, approximately 80% of the:. : compressed air is directed to the turbine 14 along the conduit 24, through the heat exchanger 18, and along the conduit 26, whilst the remaining approximately 20% of the compressed air is diverted along the diverting conduit 38, into the air return conduit 32 and thereafter into the combustion chamber 16 where it facilitates combustion of the solid fuel material. It will however be understood by those skilled in the art that any suitable amount of compressed air, for example between approximately 70% and 90%, may be directed to the turbine 14 and that any suitable amount of compressed air, for example between approximately 10% and 30%, may be diverted to the combustion chamber 16.

In order to supply further air to the combustion chamber 16 to facilitate combustion, for example during starting of the power generating system 10 prior to operation of the compressor 22 and turbine 14, the air feed arrangement further includes combustion air fans 42 which can be selectively operated as required.

Irrespective of the amount of air fed into the combustion chamber 16 along the air return conduit 32 from the compressor 34 (via the diverter valve 36) and/or the turbine exhaust, and/or by the combustion air fans 42, the applicant has appreciated that it is highly desirable to maintain a negative air pressure, in other words an air pressure which is less than atmospheric pressure, inside the combustion chamber 16. The power generating system therefore includes an air control arrangement 44 which is operable to maintain a negative air pressure, desirably a substantially constant negative air pressure, inside the combustion chamber 16.

The air control arrangement 44 includes air drive means in the form of an induced draft fan 46 which is operable to evacuate air from the combustion chamber 16 and thereby maintain the negative air pressure inside the S.....

combustion chamber 16. : 5ISS *

S

The amount of air which needs to be removed from the combustion..... S...

chamber 16 by the fan 46 varies according to the amount of turbine exhaust air fed into the combustion chamber 16, this being dependent upon the rotational speed of the turbine 14, and/or the amount of air diverted to the combustion chamber 16 by the diverter valve 36, and/or the amount of combustion air, if any, fed into the combustion chamber 16 by the combustion fans 42. The air control arrangement 44 therefore includes an air pressure sensor 47 which is located inside the combustion chamber 16 and which is operable to measure the air pressure inside the combustion chamber 16. The speed of the fan 46 is varied, as required, in response to the measured air pressure to maintain a substantially constant negative air pressure inside the combustion chamber 16, irrespective of the volume of air supplied into the combustion chamber 16.

A method for starting and operating the power generating system 10 described above to enable the system to generate electrical power will now be described.

Initially, a predetermined amount of solid fuel material is fed into the combustion chamber 16 via the fuel inlet 20 to enable combustion to be initiated. The combustion fans 42 are then activated to draw combustion air into the combustion chamber 16. The induced draft fan 46 is also activated to ensure that a negative air pressure is created inside the combustion chamber 16, and the air pressure sensor 47 continuously monitors this air pressure and controls the speed of the induced draft fan 46, as necessary, to maintain the air pressure inside the combustion chamber 16 substantially constant.

Once the predetermined amount of fuel has been ignited, either manually or automatically, it is combusted to raise the combustion temperature in the combustion chamber 16 to an initial combustion temperature, for example in the order of between 350 C and 550 C. Further solid fuel material is then fed into the combustion chamber 16 via the fuel inlet 20 at a substantially constant rate. This results in a gradual increase of the combustion temperature from the initial combustion temperature to a preliminary combustion temperature. For example, the temperature may increase at a rate of between 1 and 20 C/mm, and such a slow increase is advantageous in order to minimise thermal expansions of the heat exchanger 18 and restrict differential expansions and stresses. The combustion temperature in the combustion chamber 16 may be raised from the initial combustion temperature to the preliminary combustion temperature over a period of time which may, for example, be in the order of I to 2 hours. During this initial combustion period, the compressor 22 and the turbine 14, which drives the compressor 22, are desirably inoperative. The further solid fuel material is fed into the combustion chamber by a suitable automatic fuel feed mechanism (not shown), and the amount of fuel fed into the combustion chamber 16 may be controlled automatically to provide optimum combustion conditions.

When the combustion temperature in the combustion chamber 16 has risen to the preliminary combustion temperature, which may be between approximately 400 C and 800 C, the compressor 22 is activated. Since at this time there is insufficient energy in the system to drive the turbine 14 and hence the compressor 22, the power generating system 10 includes an external drive means, for example in the form of an electric motor 48, which is activated to drive the turbine 14, and thereby drive the compressor 22, for an extended period.

In order to reduce the electrical power consumed by the motor 48 to drive the turbine 14, and hence the compressor 22, the diverter control arrangement 40 operates to control the diverter valve 36 so that it is in the second diverting condition. Accordingly, as explained in detail above, only a proportion of the compressed air is directed to the turbine 14, via the heat exchanger 18, whilst the remaining proportion of the compressed air is diverted along the diverter conduit 38 and the air return conduit 32 to the combustion chamber 16. The reduction in electrical power consumption arises from the fact that not all of the compressed air is fed to the turbine 14 to be I.....

expanded through, and therefore assist with driving, the turbine 14, a proportion of the compressed air instead simply being fed to the combustion chamber 16 to facilitate combustion. Furthermore, by supplying the remaining proportion of the compressed air, whose temperature will have been raised e:. : : during compression, to the combustion chamber 16, combustion is facilitated and enhanced thus increasing the rate of combustion of the solid fuel material and thereby decreasing the start up time before the power generating system reaches its power generating condition. The combustion air fans 42 may be deactivated when sufficient compressed air from the diverter valve 36 and/or sufficient turbine exhaust air is being supplied to the combustion chamber 16 to facilitate combustion.

As the combustion temperature increases, the temperature to which the compressed air is raised by the heat exchanger 18 also increases. This results in an increase in the speed of the turbine 14, and a resultant increase in the temperature and the volume flow rate of turbine exhaust air which is reintroduced into the combustion chamber 16 along the air return conduit 32.

When the temperature of the air from the heat exchanger 18 has reached a predetermined temperature, known as the turbine lift off temperature, the diverter control arrangement 40 operates the diverter valve 36 so that it is moved from the second diverting condition to the first diverting condition in which none of the compressed air is diverted, and instead in which substantially all of the compressed air is directed solely to the turbine 14, via the heat exchanger 18. At the same time, the external power provided by the motor 48 is increased. The combined effect of all of the compressed air being directed to the turbine 14 to drive the turbine 14 and the increased external assistance from the motor 48, rapidly accelerates the turbine 14 through its critical speeds until the rotational speed reaches a self-sustaining speed at which external assistance is no longer needed. Accordingly, at this speed the motor 48 is deactivated. S * * S.

As the combustion temperature, and hence the temperature of the air heated in the heat exchanger 18, continues to increase, the turbine 14 * S.....

continues to accelerate until the rotational speed of the turbine 14 reaches a *S*.. * generating speed. The power generating system 10 is finally allowed to stabilise before a load is applied to the generator 28 to generate electrical * :: : :* power.

Once the load has been applied, the load may be varied to control the rotational speed of the turbine 14, as desired. However, prior to application of the load whilst the system 10 is being allowed to stabilise, the rotational speed of the turbine 14 may be varied by operation of the diverter valve 36. In particular, if an unwanted increase in the rotational speed of the turbine 14 is detected, for example above the generating speed, the diverter control arrangement 40 may operate the diverter valve 36 so that a proportion of the compressed air from the compressor 22 is diverted along the diverter conduit 38 and the air return conduit 32 to the combustion chamber 16. The volume flow rate of compressed air directed to the turbine 14 via the heat exchanger 18 is thus reduced and hence the speed of the turbine 14 is also reduced accordingly. An alternative embodiment of the power generating system 110 is

illustrated in Fig. 2 in which corresponding components have been given corresponding reference numerals, preceded by the numeral 1'.

The construction of the power generating system 110 is similar to the power generating system 10 except that the diverter arrangement 134 is located downstream of the heat exchanger 118, in the conduit 126. This means that when the diverter valve 136 is in the second diverting condition, the compressed air which is diverted to the combustion chamber 116 has been heated in the heat exchanger 118. Due to the increased temperature of the air which is fed into the combustion chamber 116, the rate of combustion of the solid fuel material may increase such that less time is taken before the turbine 114 reaches the generating speed. S. S * S S * S.

The power generating system 110 is started and operated using the method described above for starting and operating the power generating SSsSst system 10.

S

A further embodiment of the power generating system 210 is shown in Fig. 3 in which corresponding components have been given corresponding *:: reference numerals, preceded by the numeral 2'.

The construction and method of operation of the power generating system 210 is similar to that of the power generating system 110.

The power generating system 210 includes a further diverter arrangement 250 in the form of a further diverter valve 252 which is located upstream of the heat exchanger 218 in the conduit 224. The further diverter valve 252 is connected to an air inlet of the turbine 214 via a bypass conduit 254 and is selectively operable to divert a proportion of the compressed air from the compressor 222 to the air inlet of the turbine 214, before the remaining proportion of the compressed air is passed through, and heated by, the heat exchanger 218.

The power generating system 210 is started using the method described above for the power generating system 110, and during the start up phase, the further diverter valve 252 is operated such that none of the compressed air is diverted along the bypass conduit 254. All of the compressed air is thus directed to the heat exchanger 218.

When the turbine 214 is operating at its generating speed, the further diverter valve 252 may be used to control the speed of the turbine 214, and in particular to reduce the speed of the turbine 214 in response to a detected increase in the rotational speed of the turbine 214, for example above the generating speed. The further diverter valve 252 may be used to provide speed control in addition to, or as an alternative to, the diverter valve 36, 136 which may be used as set out above to control turbine speed. *. . * * S * ,*

By operating the further diverter valve 252 to divert compressed air to the air inlet of the turbine 214 when an increase in speed is detected, the S... p5 amount of air directed through the heat exchanger 218, and hence the amount of heated air directed to the turbine 214, is reduced. Furthermore, the * unheated, and therefore cooler, compressed air diverted along the bypass..* SSS4 conduit 254 is mixed with the heated air from the heat exchanger 218 at the turbine 214 air inlet, thus reducing the temperature of the air fed to the turbine 214 and thereby reducing turbine speed.

The power generating system 10, 110, 210 includes a master control arrangement (not shown) which is operable, in use, to monitor and automatically control the system parameters, for example including, but not limited to, the amount of solid fuel material supplied to the combustion chamber 16 via the fuel inlet 20, the diverter control arrangement 40, the combustion air fans 42, the air control arrangement 44, and the motor 48. It should of course be appreciated that the master control arrangement may be operable to monitor and control any number or combination of the system parameters as necessary to ensure that the power generating system 10, 110, 210 according to the invention can operate with no, or at least minimal, user intervention after the system 10, 110, 210 has been initially activated.

There is thus provided a power generating system 10, 110, 210 and a method for starting the power generating system 10, 110, 210 which enables the system to be started efficiently and to generate electrical power as rapidly as possible.

The provision of the diverter arrangement 34, 134, 234 is particularly advantageous since, by diverting a proportion of the compressed air away from the turbine 14, 114, 214 to the combustion chamber 16, 116, 216 and therefore by directing only a proportion of the compressed air to the turbine 14, 114, 214 the load on the compressor 22, 122, 222 is reduced. At the same time, the compressed air diverted to the combustion chamber 16, 116, 216 facilitates and enhances combustion of the solid fuel material, thereby decreasing the start up time of the system 10, 110, 210 before the system 10, 110, 210 is able to generate electrical power.

I....' 30: Sasilt The provision of the further diverter arrangement 250 is also advantageous since this permits the speed of the turbine 214 to be controlled. S... * III * S *5 5

The provision of an air control arrangement 44, 144, 244 which enables the air pressure in the combustion chamber 16, 116, 216 to be maintained at a substantially constant negative pressure is also advantageous since this ensures that any combustion products or hot gases are not expelled from the combustion chamber 16, 116, 216. This could arise in the case of a positive pressure inside the combustion chamber 16, 116, 216 and thereby present a significant heath and safety risk.

Furthermore, the negative air pressure inside the combustion chamber 16, 116, 216 tends to draw the air along the return duct 32, 132, 232 from the diverter valve 34, 134, 234 when the diverter valve 34, 134, 234 is in the second diverting condition, and also from the turbine exhaust, into the combustion chamber 16, 116, 216.

Although embodiments of the invention have been described in the preceding paragraphs with reference to various examples, it should be appreciated that various modifications to the examples given may be made without departing from the scope of the present invention, as claimed. For example, any suitable diverter arrangement 34, 134, 234 may be employed to divert the compressed air away from the turbine 14, 114, 214 and to the combustion chamber 16, 116, 216. Any suitable number of combustion air fans 42, 142, 242 may be employed. A fan other than an induced draft fan 46, 146, 246 may be employed. When the diverter valve 34, 134, 234 is in the second diverting condition, the proportion of air which is not directed to the turbine 14, 114, 214 may simply be diverted to atmosphere or to any desired location rather than being diverted to the combustion chamber 16, 116, 216.

The initial combustion temperature and the preliminary combustion temperature may be other than indicated above. The rate of temperature increase from the initial combustion temperature to the preliminary:.,:.

combustion temperature may be different, and may be dependent upon the nature of the solid fuel material that is utilised. ::;:; Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance, it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings, whether or not particular emphasis has been placed thereon. * S S * ** * S

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S **S* * 5*S * S S S. S * 20

Claims

Claims 1. A power generating system comprising a combustion chamber for

combustion of solid fuel material, a heat exchanger associated with the combustion chamber through which compressed fluid passes to be heated by combustion of the solid fuel material, a compressor for compressing fluid to be heated in the heat exchanger, and a turbine arranged to be driven by the compressed and heated fluid to generate power, wherein the system includes a diverter arrangement selectively operable to divert a proportion of the compressed fluid.
2. A power generating system according to claim 1, wherein the diverter arrangement is selectively operable to divert a proportion of the compressed fluid away from the turbine.
3. A power generating system according to claim 2, wherein the diverter arrangement is selectively operable to divert a proportion of the compressed fluid away from the turbine before the compressed fluid has been passed through the turbine.
4. A power generating system according to any of the preceding claims, wherein the diverter arrangement is selectively operable to divert a proportion of the compressed fluid to the combustion chamber.
5. A power generating system according to claim 4, wherein the diverter arrangement is selectively operable to divert a proportion of the compressed fluid to the combustion chamber prior to heating of the compressed fluid in the I.....

heat exchanger, the diverter arrangement being located upstream of the heat exchanger. *

S.....

S
6. A power generating system according to claim 4, wherein the diverter *USS arrangement is selectively operable to divert a proportion of the compressed Is. . fluid to the combustion chamber after heating of the compressed fluid in the heat exchanger, the diverter arrangement being located downstream of the heat exchanger.
7. A power generating system according to any of claims 4 to 6, wherein the proportion of the compressed fluid diverted to the combustion chamber provides combustion air to facilitate combustion of the solid fuel material.
8. A power generating system according to any of the preceding claims, wherein the fluid is a gas.
9. A power generating system according to any of the preceding claims, wherein the fluid is atmospheric air.
10. A power generating system according to any of the preceding claims, wherein the diverter arrangement is selectively operable to divert none of the compressed fluid when in a first diverting condition such that all of the compressed fluid is supplied to the turbine.
11. A power generating system according to claim 10, wherein the diverter arrangement is selectively operable to direct a proportion of the compressed fluid to the turbine and to divert a remaining proportion of the compressed fluid to the combustion chamber when in a second diverting condition.
12. A power generating system according to claim 11, wherein when in the second diverting condition, the diverter arrangement is operable to direct between approximately 70% and 90% of the compressed fluid to the turbine, and to divert between approximately 10% and 30% of the compressed fluid to a.....

the combustion chamber. * S

a.....
13. A power generating system according to any of the preceding claims, wherein the power generating system includes a further diverter arrangement S...

which is selectively operable to divert a proportion of the compressed fluid to a. . a IS.

the turbine. .. :
14. A power generating system according to claim 13, wherein the further diverter arrangement is selectively operable to divert a proportion of the compressed fluid to the turbine prior to heating of the compressed fluid in the heat exchanger, the further diverter arrangement being located upstream of the heat exchanger.
15. A power generating system according to claim 13 or claim 14, wherein the further diverter arrangement is selectively operable to divert said proportion of the compressed fluid to a fluid inlet of the turbine.
16. A power generating system according to any of the preceding claims, wherein the power generating system includes a control arrangement for controlling the operation of the diverter arrangement.
17. A power generating system according to claim 16 when dependent on any of claims 10 to 15, wherein the control arrangement is arranged to control the operation of the diverter arrangement between the first and second diverting conditions.
18. A power generating system according to claim 17, wherein the control arrangement is operable to provide variable control of the diverter arrangement between the first and second diverting conditions.
19. A power generating system according to any of claims 16 to 18 when dependent on any of claims 13 to 15, wherein the control arrangement is arranged to control the operation of the further diverter arrangement.
20. A power generating system according to any of the preceding claims, wherein the diverter arrangement comprises a diverter valve. :...:.

S.....

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21. A power generating system according to any of claims 13 to 20, S...

wherein the further diverter management comprises a diverter valve. :
22. A power generating system according to any of the preceding claims, wherein the power generating system is arranged so that the compressor is driven by the turbine.
23. A power generating system according to any of the preceding claims, wherein the power generating system includes external drive means which are selectively operable to drive the turbine.
24. A power generating system according to any of the preceding claims, wherein the power generating system includes an air feed arrangement for feeding air into the combustion chamber to facilitate combustion.
25. A power generating system according to claim 24, wherein the air feed arrangement includes one or more combustion air fans which are selectively operable to feed ambient air into the combustion chamber to facilitate combustion of the solid fuel material.
26. A power generating system according to claim 24 or claim 25, wherein the air feed arrangement includes means for feeding heated turbine exhaust air which has been used to drive the turbine to the combustion chamber where any residual heat in the air facilitates and enhances combustion of the solid fuel material.
27. A power generating system according to any of the preceding claims, wherein the combustion chamber includes an air control arrangement which is operable to maintain a negative air pressure inside the combustion chamber.

S.....
28. A power generating system according to claim 27, wherein the air control arrangement includes an air pressure sensor for monitoring the air pressure inside the combustion chamber and air drive means for evacuating:...:.

air from the combustion chamber to thereby maintain a negative air pressure S...

inside the combustion chamber. ::;:;
29. A power generating system according to claim 28, wherein the air control arrangement is arranged to vary the speed of the air drive means to vary the amount of air evacuated from the combustion chamber, to maintain a substantially constant negative air pressure inside the combustion chamber.
30. A power generating system according to any of the claims 24 to 29, wherein the air control arrangement is arranged to vary the speed of the air drive means according to the amount of air fed into the combustion chamber by the air feed arrangement.
31. A method for operating a power generating system according to any of the preceding claims, the method including: combusting solid fuel material in the combustion chamber; activating the compressor to provide compressed fluid; and diverting a proportion of the compressed fluid.
32. A method according to claim 31, wherein the diverting step comprises diverting a proportion of the compressed fluid away from the turbine.
33. A method according to claim 32, wherein the diverting step comprises diverting a proportion of the compressed fluid away from the turbine before it has been used to drive the turbine.
34. A method according to any of claims 31 to 33, wherein the method comprises initially feeding a predetermined amount of solid fuel material into the combustion chamber and igniting said predetermined amount of solid fuel S.....

material. * S

*S..S.

S
35. A method according to claim 34, wherein the method includes combusting said predetermined amount of solid fuel material to raise the combustion temperature in the combustion chamber to a predetermined initial * combustion temperature. * :. :
36. A method according to claim 35, wherein the initial combustion temperature is between approximately 350 C and 550 C.
37. A method according to claim 35 or claim 36, wherein the method comprises feeding further solid fuel material into the combustion chamber at a controlled feed rate to maintain combustion and raise the combustion temperature from the initial combustion temperature to a preliminary combustion temperature.
38. A method according to claim 37, wherein the method comprises raising the combustion temperature from the initial combustion temperature to the preliminary combustion temperature at a predetermined rate.
39. A method according to claim 38, wherein the predetermined rate is between I and 20 C/mm.
40. A method according to claim 39, wherein the predetermined rate is between 5 and 10 C/mm.
41. A method according to any of claims 34 to 40, wherein the method comprises circulating ambient air into the combustion chamber to facilitate combustion of the solid fuel material.
42. A method according to any of claims 37 to 41, wherein the method comprises activating the compressor when the combustion temperature in the combustion chamber has attained the preliminary combustion temperature.

a.....
43. A method according to claim 42, wherein the preliminary combustion temperature is between approximately 400 C and 800 C. *

I
44. A method according to claim 43, wherein the step of activating the *I*.

compressor comprises activating external drive means to drive the turbine and thereby drive the compressor for an extended period of time. :. :
45. A method according to any of claims 31 to 44, wherein the method comprises diverting a proportion of the compressed fluid to the combustion chamber.
46. A method according to claim 45, wherein the method comprises operating the diverter arrangement to divert said proportion of the compressed fluid to the combustion chamber.
47. A method according to claim 46, wherein the method comprises operating the diverter arrangement so that no compressed fluid is diverted to the combustion chamber when the rotational speed of the turbine reaches a predetermined speed at which the turbine may be driven by the compressed and heated fluid alone.
48. A method according to any of claims 31 to 47, wherein the method comprises feeding heated fluid which has driven the turbine to the combustion chamber where any residual heat in the fluid is used to facilitate and enhance combustion in the combustion chamber.
49. A method according to claim 47 or claim 48, wherein the method further comprises increasing the power provided to the turbine by the external drive means when the rotational speed of the turbine reaches said predetermined speed to accelerate the turbine.
50. A method according to claim 49, wherein the method comprises deactivating the external drive means when the rotational speed of the turbine reaches a self-sustaining speed.
51. A method according to claim 50, wherein the method further comprises accelerating the turbine to a generating speed. :...:.
52. A method according to claim 51, wherein the method comprises diverting a proportion of the compressed air to the combustion chamber in response to a detected increase in turbine speed above the generating speed to decrease the amount of compressed air directed to the turbine and thereby decrease turbine speed.
53. A method according to any of claims 31 to 52, wherein the method comprises diverting a proportion of the compressed fluid to the turbine.
54. A method according to claim 31 to 53, wherein the method comprises operating the further diverter arrangement to direct a proportion of the compressed fluid to the turbine prior to heating of the compressed fluid in the heat exchanger.
55. A method according to claim 54, wherein the method comprises operating the further diverter arrangement to divert a proportion of the compressed fluid to the turbine in response to a detected increase in turbine speed above the generating speed to decrease the amount of compressed heated air directed to the turbine from the heat exchanger, and thereby decrease turbine speed.
56. A method according to claim 55, wherein the method comprises mixing the diverted air with the compressed heated air from the heat exchanger to reduce the temperature of the air fed to the turbine and thereby decrease turbine speed.
57. A power generating system comprising a combustion chamber for combustion of solid fuel material, a heat exchanger associated with the combustion chamber through which air passes to be heated by combustion of the solid fuel material, a turbine arranged to be driven by the heated air to III...

generate power, and an air feed arrangement for feeding air into the combustion chamber to facilitate combustion, the combustion chamber including an air control arrangement operable to maintain a negative air pressure inside the combustion chamber. S... * **. * * S I. *
58. A power generating system according to claim 57, wherein the air control arrangement is operable to maintain a substantially constant negative air pressure inside the combustion chamber.
59. A power generating system according to claim 57 or claim 58, wherein the air control arrangement includes an air pressure sensor for monitoring the air pressure inside the combustion chamber.
60. A power generating system according to any of claims 57 to 59, wherein the air control arrangement includes at least one air drive means for evacuating air from the combustion chamber to thereby maintain a negative air pressure inside the combustion chamber.
61. A power generating system according to any of claims 57 to 60, wherein the air feed arrangement comprises one or more combustion air fans which are selectively operable to feed ambient air into the combustion chamber to facilitate combustion of the solid fuel material.
62. A power generating system according to any of claims 57 to 61, wherein the air feed arrangement comprises means for feeding heated turbine exhaust air which has been used to drive the turbine to the combustion chamber where any residual heat in the air facilitates and enhances combustion of the solid fuel material.
63. A power generating system according to any of claims 57 to 62, wherein the air control arrangement is arranged to vary the speed of the air drive means whereby to vary the amount of air evacuated from the S.... .

combustion chamber to maintain a substantially constant negative air pressure inside the combustion chamber. ...:.

30:...:.
64. A power generating system according to claim 63, wherein the air *0* control arrangement is arranged to vary the speed of the air drive means according to the amount of air fed into the combustion chamber by the air feed arrangement, and according to the amount of ambient air and/or heated turbine exhaust air fed into the combustion chamber.
65. A power generating system substantially as hereinbefore described and/or as shown in the accompanying drawings.
66. A method for operating a power generating system substantially as herein before described and/or as shown in the accompanying drawings.
67. Any novel subject matter or combination including novel subject matter disclosed herein, whether or not within the scope of or relating to the same invention as any of the preceding claims. * * * * S. * S

S.....

S * S * S

IS....

S S... * . S... * S., * S *

I