JPS6158652B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas turbine power plant having a pressurized fluidized bed combustion chamber, and more particularly to a control system and start-up method for such a power plant.

a gas turbine power plant having a free power turbine for driving a load and driven by gases generated in a pressurized fluidized bed combustion chamber in which pulverized fuel is burned;
For example, in US Pat. Nos. 3,791,137, 3,924,402 and 4,028,883, operational control is most difficult. This difficulty in commercial-sized power plants is due to large volumes of heated pressurized air and large amounts of fuel in the fluidized bed combustion chamber, and in power plants where the fuel is burned in the presence of pulverized dolomite. Due to the high tonnage of dolomite produced, these factors slow the power plant's response to changes in load demands.

In the start-up operation of such a power plant, this large volume and quantity of material is brought into thermodynamic equilibrium relatively slowly before the load (such as a generator) can be effectively driven. He must come. For example, it may take 3 to 4 hours to achieve proper operation of a fluidized bed combustion chamber.
When a free power turbine is used to drive a generator, as distinguished from an expander in a gas turbine engine,
Sudden and significant reductions in generator load occur in free power turbines because the operation of the gas turbine engine and fluidized bed combustion chamber cannot be changed quickly to respond to changes in speed and/or load demands on the free power turbine. may cause overspeeding and damage.

It is therefore an object of the present invention to provide a gas turbine power plant having a pressurized fluidized bed combustion chamber and a free power turbine for driving the load, in which the fluidized bed It is an object of the present invention to provide a control system that can respond quickly without disrupting the thermodynamic operation of the combustion chamber and gas turbine engine.

Another object of the invention is that in a gas turbine power plant having a pressurized fluidized bed combustion chamber and a free power turbine for driving the load, the valves are not exposed to very high temperatures;
It is therefore an object to provide a control system that does not require special valves.

Yet another object of the invention is to provide a start-up control system and method that eliminates the need for separate start-up and a primary air compressor in a gas turbine power plant having a pressurized fluidized bed combustion chamber and a free-power turbine for driving the load. It is to provide.

It was therefore contemplated by the present invention to provide a new control system and method of start-up for a gas turbine power plant.

A gas turbine power plant includes a pressurized fluidized bed combustion chamber in which a pulverized solid fuel, such as coal, is burned in the presence of crushed dolomite (limestone) to remove sulfur dioxide from the combustion gases. A heat exchanger is provided in the fluidized bed combustion chamber to control the reaction temperature, for example between 700°C and 900°C below the melting point of the fuel ash. Air compression means are provided for supplying compressed air via the first conduit means to the heat exchanger and the fluidized bed combustion chamber in a ratio of approximately 2:1. The compressed air introduced into the fluidized bed combustion chamber is used to fluidize the bed and support combustion of the fuel. The gas turbine engine has an expander connected to drive the air compression means and has a fuel combustion zone that provides exhaust air to drive the expander during start-up. Second conduit means are provided for directing the combustion gas from the fluidized bed combustion chamber into a mixture with combustion gas, if any, from the combustion zone of the gas turbine engine and from there into the expander. .
A free power turbine is connected to drive a load such as a generator, and third conduit means are provided for directing exhaust air from the expander to drive the free power turbine.

The controller includes first valve means in the first conduit means for independently controlling the flow of compressed air into the heat exchanger and into the fluidized bed. Valve-controlled bypass conduit means are provided for directing the exhaust from the expander around the free-power turbine during start-up operations and reducing the load on the free-power turbine without disrupting the thermodynamic balance between the fluidized bed combustion chamber and the gas turbine engine. Provision is made to adjust the free power turbine in response to demand. The valve controlled bypass conduit means also serves to prevent destructive overspeeding of the free power turbine upon sudden and large reductions in the load on the free power turbine. To control the flow of exhaust gas into the free power turbine and in conjunction with valve controlled bypass conduit means in the event of sudden loss of load on the free power turbine so that no gas flows through the free power turbine and the rotation Third valve means may be provided within the third conduit means to ensure that it is stopped.

The start-up method according to the invention includes the following steps. Initially, the start-up was such that the gas turbine was driven through an independent rotary power source, as is customary for conventional gas turbines, and the fuel was discharged into the combustion zone of the engine such that compressed air was generated by means for air compression. Requires to be ignited. At the same time, compressed air is prevented from flowing into the fluidized bed combustion chamber and the heat exchanger. After the gas turbine engine achieves autonomous self-operation, the independent source of rotational power is shut down. A portion of the compressed air is heated and directed to the fluidized bed combustion chamber, while a portion sustains combustion of the fuel in the turbine combustion zone. Heated compressed air is forced into the fluidized bed combustion chamber, and when the volume, temperature and pressure of this air reach levels sufficient to suspend and ignite the fuel, the pulverized coal and dolomite flow into the fluidized bed combustion chamber. The fuel is ignited. Within a first predetermined temperature range within the fluidized bed combustion chamber, compressed air is allowed to flow in increasing amounts into the heat exchanger. Exhaust air is directed around the free power turbine. Within a second predetermined temperature range in the fluidized bed combustion chamber that is higher than the first temperature range, preheating of the compressed air and ignition of the gas turbine combustion zone is stopped and diversion of the exhaust around the free power turbine is stopped, and Such gas is then directed to a free power turbine to drive it and thereby drive a load.

The invention will be more fully understood from the following description when considered in conjunction with the accompanying drawings which illustrate a control system according to the invention.

Referring now to the drawings, reference numeral 10 designates a gas turbine power plant (hereinafter referred to as a power plant) of the type having a pressurized fluidized bed combustion chamber and a control system therefor according to the invention.

The power station 10 and its control system has a pressurized fluidized bed combustion chamber 12 connected through supply means, e.g. conduits 14 and 16, to a source of pulverized fuel 18 and sulfur dioxide absorbing material, e.g. coal and ground dolomite, respectively. include. The combustion gases generated by combustion of the fuel in the fluidized bed combustion chamber 12 are conducted from there through a conduit 22 to separators 24 and 26, such as a cyclone separator for two-stage separation, and to a conduit 28.
through the expander 3 of the gas turbine engine 32
It leads to 0. The pressurized fluidized bed combustion chamber 12 is a fluidized bed 3
4 is equipped with an air cooling system to control the reaction temperature within the range of about 700°C and about 925°C.

The air cooling system includes any suitable type of heat exchanger 36 within the fluidized bed 34, which heat exchanger has tubes 38 for receiving compressed air from an air compressor 42.
and 40 to the compressor. The heat exchanger 36 is also connected to the tube 28 through an outlet tube 44 so that the heated compressed air is directed to mix with the cleaned combustion gases discharged from the fluidized bed combustion chamber 12 and into the tube 28. flows through.

Fluidized bed combustion chamber 12 is connected to the compressor via pipe 38 to receive a portion of the compressed air discharged from compressor 42. This compressed air discharged into the fluidized bed combustion chamber 12 is distributed to the fluidized bed 34 by suitable distribution means such as a porous distribution baffle 46. The compressed air serves to maintain the fuel and other particulate materials, such as dolomite, in a suspended fluid state and to provide oxygen to support combustion of the fuel.

The air compressor 42 is connected to be driven by the expander 30 of the turbine engine 32 and may be part of a gas turbine engine system or is a separate device suitably connected to be rotated by the expander 30. It may be hot. Turbine engine combustor 48 may also be an integral part of the gas turbine system or may be a separate device. The combustor 48 is connected to receive compressed air from the compressor 42 via a passage 50 and fuel from a suitable supply thereof generates combustion gases which are transferred via a passage 52 to the combustor 48 . tube 28
It is discharged to mix with the gas inside. Passage 52
Compressed air flow through is controlled by valve 51.
The combustion gases from the combustor 48 are sent to the expander 30, either alone or together with the combustion gases and heated compressed air.
It works to drive.

Exhaust air from expander 30 is directed by passageway or pipe 54 to free power turbine 56 .
Free power turbine 56 is connected to drive a load, such as a generator 58. Exhaust from free power turbine 56 is transferred to steam power generation system 61
It is discharged through the exhaust pipe 60 to the exhaust pipe 60.

Steam power generation system 61 includes a waste heat boiler 62 that receives exhaust gas from free power turbine 56 and passes the gas in indirect heat exchange relationship with water from supply pipe 54 to convert water to steam. A steam turbine 66 drives a generator 63 and an outlet pipe 7
0 to receive steam. The spent steam is passed from steam turbine 66 to steam condenser 72 where it is converted back to water and discharged through pipe 74 for recirculation to waste heat boiler 62. Water from condenser 72 and make-up water are passed through feedwater heater 76 and then routed through feedwater pipe 64 into waste heat boiler 62 .

The control system according to the present invention places the power plant in operation and provides rapid adjustment of the free power turbine 56 in response to changes in the load demand on the generator 58 as well as rapid adjustment of the free power turbine 56 in the event of a sudden loss of load demand on the generator 58. Contains several valve-controlled bypass pipes or conduits to help provide protection against overloading.

The control system more particularly includes a bypass pipe 78 arranged to interconnect a pipe 40 conducting compressed air to heat exchanger 36 with outlet pipe 44 and thereby bypassing the air around heat exchanger 36 . include. A valve 80 is disposed within bypass pipe 78 to control flow therethrough, one-way valve 82
is disposed within tube 40 to control the flow of compressed air therethrough. To bypass the compressed air entirely around the heat exchanger 36, as is done during part of the start-up period, or to maintain the fluidized bed temperature within a desired temperature range of 700°C to 925°C during operation. Valves 80 and 82 are adjustable to adjust the flow according to the temperature of fluidized bed 34. Valves 80 and 82 also work together to maintain the fluidizing air flow rate within fluidized bed 34 at a constant actual value. This subsequent function determines the temperature and pressure therein by detecting the air flow velocity in the tube downstream of the valve 82, e.g. 35, and by correlating that measurement of air velocity within the fluidized bed with the air velocity. This is accomplished by sensing as a function of velocity.

A second bypass pipe 84 in the cooling air system is provided to bypass compressed air discharged from air compressor 42 into pipe 38.
A suitable heater 86 is arranged in the bypass pipe 84 to heat the compressed air before it enters the fluidized bed combustion chamber 12. Heater 86 may be of any suitable type for heating compressed air, and may be a fuel-ignited combustion chamber as shown. Valves 88 and 90 are provided in tubes 84 and 38, respectively, to control the flow of compressed air through bypass tube 84 and tube 38.

Another bypass pipe 92 is connected at one end to pipe 54 and at the other end to exhaust pipe 60 to connect expander 30 to
Bypassing the exhaust gas from around the free power turbine 56. A valve 94 operable in response to a signal generated by a speed switch or other suitable load sensing device 96 is disposed within the bypass pipe 92 to control the flow through the bypass pipe 92. For operation under a substantially constant load on free power turbine 56, valve 94 is in the closed position. However, for start-up operation of power plant 10, valve 94 is fully open. Valve 94 also directs the torque generated by free power turbine 56 to
It serves to accommodate substantial changes in the load demands on the generator 58 and therefore the free power turbine. Additionally, in the event of a sudden loss of load demand, valve 94 opens to reduce the pressure differential across free power turbine 56 to nearly zero, thus preventing overspeeding of the free power turbine and damage resulting therefrom. The bypass 92 and valve 94 provide rapid and precise control of the free power turbine without disturbing the thermodynamic balance of the fluidized bed combustion chamber 12 therein. In order to further ensure protection of the free power turbine 56, valve means 98 are preferably provided within the tube 54.

Valve means 98 is in a normally open position and serves to shut off gas flow to free power turbine 56 in the event of a sudden rejection of the power load on the free power turbine. This sudden loss of load demand will occur when there is an electrical failure in the generator 58, a circuit break, or a drive coupling failure between the free power turbine 56 and the generator 58 driven thereby. The valve means 98 may take any suitable shape, such as a set of vanes or baffles in the inlet annulus of a free power turbine, the vanes or baffles being in the direction of gas flow relative to a normally open position. and can be aligned with and rotated by suitable linkage and tuning ring arrangements to a position in which the vanes or armor plates are in an almost perpendicular orientation to the direction of gas flow; An iris or guillotine plate can be positioned and actuated to form an annular gate valve; or in new turbine designs, the first stage vanes can be rotated to a closed position to achieve exhaust flow isolation. It can be designed as follows.

Preferably, valve means 98 is included in the control system and functions in conjunction with valve 94 in bypass pipe 92. Because in some situations,
It has been found that sufficient exhaust gas cannot be bypassed through tube 92 to reduce the power output of free power turbine 56 to zero and prevent the free power turbine from overspeeding. Valve means 98, similar to valve 94, is responsive to load sensing device 96 to control valve 94.
is connected to close while it is open. Valve means 98 also includes closed valve 94 when in the closed position.
It also serves to maintain back pressure on the gas turbine engine 32 and thus prevent it from overspeeding.

Start of operation The start of operation of the power station begins with valves 80, 82, and 8.
This is accomplished by closing valves 8, 90, and 98 and simultaneously opening valves 51 and 94. This positioning of the valve closes the flow of compressed air to the fluidized bed combustion chamber 12 and opens the bypass pipe 92 so that exhaust from the expander 30 does not enter the free power turbine 56. With valve 51 open, a suitable starting mechanism 100, such as an internal combustion engine, is operated to drive the air compressor. All compressed air discharged from air compressor 42 flows through passage 50 into combustion chamber 48 where fuel is injected and ignited to produce combustion gases. The combustion gases are conducted via passage 52 into tube 28 and thence to and drive expander 30. A check valve 102 or similar shutoff device in tube 28 prevents flow of combustion gases in a direction toward fluidized bed combustion chamber 12 .
Exhaust air from expander 30 is directed through pipe 54, bypass pipe 92 and exhaust pipe 60 to steam and power generation system 61. A check valve 104 prevents backflow of exhaust gas within the exhaust pipe 60. Once the expander 30 is activated, the self-starting mechanism 100 is deactivated and the combustor 48 is operated to heat the gas turbine engine. Once operation of the gas turbine engine is stable, a valve 88 in the bypass pipe 84 is opened to allow a portion of the compressed air to flow to the heater 86 which supports the combustion fuel and is heated with the combustion gases. The compressed air enters the fluidized bed combustion chamber 12 via pipe 38. After the heated air and combustion gases are directed into the fluidized bed combustion chamber 12 to achieve sufficient volume and pressure to support the suspended fuel and particulate material, the fuel and particulate material flow through conduits 14 and 16. It is fed into the layer combustion chamber 12. The mixture of hot combustion gases and compressed air also provides sufficient heat and oxygen to ignite the fuel within fluidized bed 34. When the fluidized bed temperature reaches approximately 750°C to 800°C as detected by temperature sensing and signaling device 106, valve 82 is gradually opened to allow compressed air to enter heat exchanger 36 via pipe 40. forgive. By gradually increasing the compressed air flow into and through the heat exchanger 36, excessive thermal shock to the heat exchanger is prevented as relatively cool compressed air begins to flow through the heat exchanger. . Fluidized bed is approximately 870℃
When a temperature within the range of 925°C to
0 opens and the amount of compressed air flowing through the heat exchanger 36 flows to a desired temperature range of approximately 870°C to 950°C by adjusting the flow through the heat exchanger and bypass pipe 78. It is controlled to maintain the layer 34. Valves 80 and 82 cooperate so that one moves to the closed position while the other moves to the open position, thereby dividing the air flow to maintain the desired fluidized bed temperature. These valves also cooperate to maintain the fluidized bed air velocity at a constant actual velocity. The gas generated in the fluidized bed combustion chamber 34 is passed through the pipes 22 and 28.
and into the expander 30 of the gas turbine engine 32. The exhaust from expander 30 is now bypassing free power turbine 56 through bypass pipe 92 . Also, the fluidized bed 34
When the temperature range of about 750° C. to 800° C. is reached and gas turbine 32 reaches a synchronous idle point, valve 88 is closed to cut off fuel to heater 86. At about the same time as valve 88 is closed, valve 90 is opened so that the compressed air now flows directly into the fluidized bed combustion chamber 12 where the fluidized bed has been brought into thermodynamic equilibrium. At this time, bypass valve 94 is closed and valve 98 is opened to direct exhaust gas from expander 30 to free power turbine 5.
6 and thereby drive its turbine. Also at this time, valve 51 is closed and fuel is cut off to combustor 48 so that expander 30 is powered only by a mixture of combustion gases and heated compressed air discharged to the expander via tubes 28 and 44. Driven. Power station 10 is now generator 58
operating with valves 94 and 98 regulating the flow through passage 54 and bypass pipe 92 to compensate for variations in load demand at full load demand above, and sudden and substantial loss of load demand. In this case, the free power turbine 56 and the expander 30 are opened and closed to prevent them from overspeeding.

This invention provides a gas turbine power plant with a fluidized bed combustion chamber with an improved and simplified start-up operation, adjustment to changes in load demands that do not disrupt the thermodynamic equilibrium of the fluidized bed combustion chamber, and sudden and It is believed that it is now readily apparent to provide a control system that can provide protection against overspeeding of free power turbines in the event of substantial loss of load demand. It is a control system in which the valves are arranged to control gas flows, when these gases are at relatively low temperatures and therefore do not require special design.

Although only one embodiment of the invention has been illustrated and described in detail, it is to be clearly understood that the invention is not limited except as described in the claims.

[Brief explanation of the drawing]

The drawing is a schematic illustration of a gas turbine power plant according to the invention. 10...Gas turbine power plant, 12...Fluidized bed combustion chamber, 18...Fuel supply device, 28...Pipe, 3
0... Expander, 32... Gas turbine engine, 34... Fluidized bed, 36... Heat exchanger, 38,
40...Pipe, 42...Air compressor, 48...Combustion zone (combustor), 50, 52, 54...Passway, 56
...free power turbine, 61 ... steam and power generation system, 62 ... waste heat boiler, 82 ... valve,
84...Second bypass pipe, 88, 90...Valve, 9
2...bypass pipe, 94...valve, 98...valve means.

Claims (1)

Claims: 1. (a) a pressurized fluidized bed combustion chamber having means for receiving therein pulverized fuel for combustion; (b) a combustion chamber within the combustion chamber for controlling the reaction temperature within said fluidized bed combustion chamber; (c) means for compressing air; (d) passing a portion of the compressed air discharged from the means for compressing air into the heat exchanger and another portion for suspending the fuel and supporting combustion of the fuel; first conduit means connecting the means for compression to the heat exchanger and the fluidized bed combustion chamber for passage to the fluidized bed combustion chamber; (e) having an expander connected to drive the means for compressing air and for connecting the means for compressing air to the fluidized bed combustion chamber; a gas turbine engine having a fuel combustion zone for providing exhaust gas for driving the panda; (f) directing combustion gases from a fluidized bed combustion chamber to mix with combustion gases from the gas turbine engine combustion zone and extracting therefrom; a gas turbine prime mover comprising: second conduit means for conducting into the expander; (g) a free power turbine connected to drive the load and to receive exhaust air from the expander to be driven therewith; wherein the control system is operable between an open position and a closed position to independently control the flow of compressed air into the heat exchanger and into the fluidized bed combustion chamber; (h-2) a first valve means in the first conduit means; a valve-controlled bypass conduit means for preventing overspeeding of the turbine in the event of a sudden and significant reduction in the amount of load on the control system; 2. A heater is located in parallel with the first conduit means and during start-up operations of the gas turbine power plant, the first conduit means is connected to the first conduit means for passing compressed air to the heater before entering the fluidized bed combustion chamber. 2. Apparatus according to claim 1, characterized in that it is provided with valve means for cooperating with a single valve means. 3 third conduit means are provided for directing exhaust gas from the expander to the free power turbine;
Valve means is included in said third conduit means to control the flow of exhaust gas into the free power turbine in inverse proportion to the amount of exhaust gas allowed to flow through said valve-controlled bypass conduit means. An apparatus according to claim 1. 4. said valve controlled bypass conduit means includes a valve actuated in response to free power turbine speed such that flow at speeds below a predetermined maximum is prevented by the valve controlled bypass conduit means and said third valve means 4. The apparatus of claim 3, wherein the apparatus operates normally to permit exhaust flow into the free power turbine at a speed below the predetermined maximum speed. 5. Means are provided for isolating the combustion zone of the gas turbine engine from the compression means and the expander, so that the expander can only be operated with combustion gas from the fluidized bed combustion chamber. An apparatus according to claim 1. 6. The gas turbine engine comprises third conduit means for guiding compressed air from the compression means to a combustion zone and third valve means for controlling the flow of compressed air to the combustion zone. The device according to scope 1. 7 a pressurized fluidized bed in which a pulverized solid fuel is burned under controlled conditions to produce combustion gases, discharging at least a portion of the compressed air discharged to entrain and support the fuel for combustion; an air compressor connected to, a gas turbine engine connected to receive combustion gases from a combustion chamber;
In a gas turbine power plant comprising a free power turbine connected to drive a load and to receive and be driven by exhaust gas from a gas turbine engine, the control system: (a) determines the load demand at the free power turbine; bypass means for directing exhaust gas around the free power turbine to prevent overspeeding of the free power turbine during decrement; (b) second valve means for controlling exhaust flow into the free power turbine; and (c) detecting the load on the free power turbine and
actuating valve means to reduce exhaust flow through the free power turbine and causing said bypass valve to increase exhaust flow through the bypass conduit, thereby causing a reduction in the amount of load on the free power turbine; A control system comprising: detection and signal generation means for preventing overspeeding of a power turbine. 8. A gas turbine engine having a combustion zone for burning fuel therein, an expander for driving air compression means driven by the exhaust gas from said combustion zone, a source of pulverized solid fuel and dolomite and means for air compression. a pressurized fluidized bed combustion chamber connected to receive at least a portion of the compressed air discharge and thereby provide a bed of floating fuel and dolomite for burning fuel, said air compressor for regulating the temperature of said bed; a heat exchanger within the combustion chamber connected to receive another portion of the compressed air discharged from the gas turbine and connected to conduct the air heated within the heat exchanger to an expander of the gas turbine; A method of controlling a gas turbine power plant comprising a free power turbine connected to receive exhaust from said expander of a gas turbine engine, comprising the steps of: (a) said gas turbine engine; (b) simultaneously driving said fluidized bed combustion by an external source of rotary power and igniting the fuel discharged into the combustion zone of said engine to start said gas turbine engine, thereby driving means for air compression; (c) After the gas turbine engine has achieved sustained self-operation, the external source of rotary power is shut off and the compressed air is preheated to form the pulverized fuel. co-directed into the fluidized bed combustion chamber with the flow of dolomite so that the fuel and dolomite are fluidized and the fuel is combusted; (d) compressed air is directed into the heat exchanger within a first predetermined temperature range within the fluidized bed combustion chamber; (e) bypassing the exhaust from the expander around the free power turbine; (f) the first predetermined portion within the fluidized bed; Within a second predetermined temperature range higher than the temperature range, preheating of the compressed air and generation of combustion gases in the gas turbine combustion zone is discontinued and diversion of said exhaust gas is discontinued and such gases drive it to a free power turbine. guided to do. 9. The first predetermined temperature range is approximately 750° to 800°C.
The method according to claim 8. 10 The second predetermined temperature range is approximately 870°C to 925°C.
9. The method according to claim 8, wherein the temperature is .degree. 11 The first and second predetermined temperatures are each about
The method according to claim 8, wherein the temperature is 700°C and 900°C. 12. The method of claim 8, further comprising the step of allowing a portion of the compressed air to bypass around a heat exchanger at or above the second predetermined temperature range. 13 automatically detecting said second predetermined temperature range within the fluidized bed combustion chamber to effect entry of compressed air into the heat exchanger, closure of the heating means and termination of exhaust flow around the free power turbine; 9. A method as claimed in claim 8 for generating a functional signal. 14. The method of claim 8, wherein the fluidizing air velocity flow into the fluidized bed combustion chamber is maintained at a constant predetermined value.