JPH05538B2 - - Google Patents

Description

Detailed Description of the Invention <Industrial Application Field> The present invention relates to a method of operating a gas turbine, and more specifically, to a method of operating a gas turbine, and more specifically, a method for generating gas for driving a turbine using a combination device of a fluidized bed boiler and a gasifier. The present invention relates to the above-mentioned operating method for generating electricity.

<Prior Art> Combustion systems using a fluidized bed as a primary heat source have been known for some time. In this device, air is directed over a bed of granular material containing a fossil fuel, such as coal, and an adsorbent for the sulfur produced by the combustion of the coal, fluidizing the bed and producing fuel at relatively low temperatures. promotes combustion. The combustor can be pressurized and the hot gas produced by the fluidized bed can be used to drive a power generation turbine.

One feature of the fluidized bed combustion process is the relatively low gas temperatures required to keep pollutant emissions low. However, this results in a compromise in the combined efficiency of the boiler-turbine cycle. This is because the turbine can be operated at gas temperatures well in excess of the maximum allowed in a fluidized bed boiler. It has therefore been proposed to gasify the feed fuel slip stream in a separate vessel in order to increase the temperature of the gas entering the turbine and improve cycle efficiency. This fuel gas stream is then combined with the flue gas from the boiler in a burner to increase the temperature of the flue gas to an acceptable level. However, the necessity of using this separate gasifier is undesirable since it makes the method of operation significantly more expensive.

<Problems to be Solved by the Invention> Accordingly, one object of the present invention is to provide a method for generating gas for driving a turbine that eliminates the cost of a separate gasifier.

Another object of the invention is to generate a gas that is partially combusted and to take out a portion of the gas so that when recombined with the flue gas from the boiler of the burner, the gas is optimized for use in the gas turbine. The object of the present invention is to provide a method of operation of the type described above, when a fluidized bed boiler is provided with a gasification section for reaching high temperatures commensurate with the operation of the fluidized bed boiler.

<Means for Solving the Problems> According to the operating method of the present invention, an amount of air that is insufficient for complete combustion of the fuel but sufficient to generate flammable off-gas is used to improve the flow of granular material containing fuel. Fluidize the bed. Extra air is added to the vessel at a relatively high point to achieve complete combustion of the gas and generate flue gas. A portion of the off-gas from the bed is removed from an outlet upstream of where this extra air is added. The entrained particulate material is separated from the flue gas and off-gas produced by combustion of the fuel, and the relatively pure gas is combusted to increase the temperature of the gas before it passes to the turbine.

Reference will now be made to the accompanying drawings, in which preferred embodiments of the invention are illustrated.

<Example> Referring to the drawings, 10 is a fluidized bed boiler, comprising a fluidized bed 12 of granular material containing fuel and an absorbent for absorbing sulfur produced by combustion of the fuel. There is. Piping 14 introduces air into the lower part of boiler 10, which passes through perforated grate plates 16 and thus forms a fluidized bed 12.
to uniformly distribute and fluidize the particulate material.
Air compressor 15 operates normally to supply compressed air to piping 14. This amount of air is insufficient to completely burn the fuel, but is sufficient to generate flammable off-gases. Branch pipe 14a extends from pipe 14 and introduces air into a location above fluidized bed 12 in an amount sufficient to complete combustion of the fuel. Not shown in the diagram are one or more delivery devices for directing excess fuel and adsorbent to bed 12 and one or more extraction devices to prevent solid products from accumulating in bed 12. , are provided as appropriate.

The uncombusted gases in the bed 12 are combined with the gaseous combustion products and the air introduced via the branch pipe 14a to form a flue gas which extends over the entire length of the boiler 10. After passing through, from the outlet of the boiler 10, the cyclone separator 20
is discharged into a pipe 18 connected to the inlet of the The discharge pipe 22 is disposed between the intake point of excess air from the branch pipe 14a and the air distribution grid plate 16, receives flammable off-gas from the outlet of the boiler 10, and is connected to the second cyclone separator. Drain it during the 24th.

The solid particulates separated from the gas in the cyclone separators 20, 24 are discharged from their lowermost portions into a line 26 which transfers the particulate material to the bed 12 via a suitable inlet of the boiler 10.
to erupt again. The separated gas from the separators 20, 24 passes via lines 28, 30 to two cleaning units 34, 36, respectively, for further separation of impurities or solid particulates from the gas.

The pipes 38 and 40 are connected to the cleaning units 34 and 36.
are each connected to a burner 42, and the burner 42 is
It operates in a conventional manner to ignite the gas in the presence of excess air in line 38 and feed the resulting gas to gas turbine 46 via line 44 .

A gas turbine 46 drives a generator 48 in a conventional manner. The gas outlet of the turbine is connected to a waste heat boiler 52 via piping 50. The water is absorbed through the pipe 54 and then to the waste heat boiler 52.
heater 58 disposed in the fluidized bed boiler 10 and the boiler 10 after being fed to the top of the boiler 10 and heated thereby.
It is supplied via piping 56 to . The heated steam from the superheater 58 is sent via piping 60 to other equipment, not shown, for reuse.

In operation, air from compressor 15 is transferred to fluidized bed 12 via piping 14 at a velocity sufficient to fluidize fluidized bed 12 in boiler 10 and facilitate combustion of particulate material in bed 12. . floor 1
The uncombusted gases at 2 are combined with the gaseous combustion products and the air introduced via pipe 14 to form flue gas, which after passing through the entire length of boiler 10 , is discharged from the outlet of the boiler 10 into the pipe 18. During this passage, the flue gas entrains relatively fine particulate material in bed 12 and passes to separator 20. As explained above, the air introduced into the lower portion of the fluidized bed 12 is carefully controlled so as to be insufficient to completely burn the fuel in the bed 12, but sufficient to generate flammable off-gases. Branch pipe 14a introduces an amount of extra air sufficient to complete combustion into the region of boiler 10 above floor 12.

Discharge pipe 22 receives off-gas at a point upstream of the point of introduction of excess air from branch pipe 14a, which off-gas passes to cyclone separator 24.

The gas in the separators 20, 24 is separated from the particulate material entrained therein, which particulate material is
6 and is ejected again onto the floor 12. Separator 20,2
Relatively clean gas from 4 passes via lines 28, 30 to cleaning units 34, 36 for further cleaning, and relatively pure gas passes via lines 38, 40 to burner 42. to move to. In burner 42, the combustible off-gas is combusted in the presence of excess air and flue gas in line 38, increasing the gas temperature. The gas then passes through piping 44 to gas turbine 46 .

The spent gas from the turbine passes through piping 50 to waste heat boiler 52 and exchanges heat with feed water passing through boiler 10 from piping 54 . Relatively hot feed water from boiler 52 passes via piping 56 to fluidized bed boiler 10 where it is converted to steam by passing through heater 58. The heated steam then passes through piping 60 to an external device (not shown).

The embodiment of FIG. 2 is similar to the embodiment of FIG. 1 and uses the same parts as the embodiment of FIG. 1, so these parts are designated by the same reference numerals. . According to the embodiment shown in FIG.
A second stage turbine 46' is disposed in series relationship with the stage turbine 46, and two burners 42, 42' are disposed, and piping 38, 4 is disposed.
0 to cleaning units 34 and 36, respectively. Piping 62 connects the burner 42' to the gas outlet of the first stage turbine 46, and piping 64 connects the burner 42' to the second stage turbine 46'. A bypass pipe 66 is provided to direct a portion of the gas from the cleaning unit 36 to the burner 42, as in the first embodiment.

Thus, according to the embodiment of FIG.
2', the spent gas from the second stage turbine 42' passes through piping 50 to the waste heat viler 52. In other respects, the operation of the embodiment of FIG. 2 is exactly the same as that of FIG.

Note that the fluidized bed boiler 10 may be of a so-called "bubbling" type or a "fast" type. In the case of the bubbling type, the bed of granular material is supported by an air distribution plate, and combustion support air is supplied to the air distribution plate through a plurality of perforations formed therein to expand the granular material; Leave it in a floating or fluidized state. The velocity of the gas is typically
By applying a velocity two to three times the rate required to produce a pressure drop supporting the weight of the bed (e.g., the minimum fluidization velocity), bubbles are generated that are forced upwardly through the bed. , giving the appearance of a boiling liquid. This floor presents a somewhat fixed upper surface. When provided with a high degree of recirculation of solids, a bubbling bed can establish its particulate content and operate as a circulating fluidized bed.

In a fast-type fluidized bed, the average gas velocity as a fraction of the minimum fluidization velocity is higher than that in a bubbling-type bed, so that the surface of the bed is more diffused and the solids from the bed are The amount carried will increase. According to this method, the density of the fluidized bed is between 5 and 20% solids by volume, which is considerably lower than the typical value of 30% by volume for bubbling fluidized beds. The formation of a low-density fast-type fluidized bed is
This is due to the small particle size and high solids throughput, which necessitates high solids recycling rates. The velocity range of fast-type fluidized beds lies between the terminal velocity or free fall velocity of the solids and the velocity above which the bed becomes a pneumatic conveying line.

The high degree of circulation of solids required by any circulating fluidized bed makes the bed insensitive to the heat release pattern of the fuel, so that changes in temperature inside the steam generator are minimized. , therefore, the amount of nitrogen oxides produced is reduced. High loading of solids also improves the efficiency of mechanical devices used to separate gas from solids for solids recycling. The resulting increase in sulfur adsorbent and fuel residence time reduces adsorbent and fuel consumption.

The method of operation of the present invention provides several advantages. As an example, a fluidized bed boiler with the above-mentioned inherent advantages is utilized, operated at an optimum temperature of (1600〓), and a separate gasifier is used to increase the temperature of the gas to the temperature required by the turbine. The need to use . This is accomplished by producing combustible off-gas in the lower part of the boiler and using this gas to increase the temperature of the flue gas leaving the boiler. Therefore, highly efficient operation is achieved.

Although preferred embodiments of the present invention have been described above, the present invention can be practiced with various modifications other than these embodiments, and the specific configurations described above are merely illustrative and do not limit the present invention. It's not something you do.

Supplementary Note (1) The operating method according to claim 1, wherein one burner is provided, and the flue gas and the off-gas are guided to this burner.

2. A method according to claim 1, wherein two burners are provided, the flue gas being directed to one burner and the off-gas being directed to the other burner.

(3) The operating method according to supplementary note (2), wherein each gas from the burner is guided to a first stage turbine and a second stage turbine, respectively.

(4) A step of increasing the temperature of the feed water by exchanging heat between the consumed gas from the turbine and the feed water, and a step of transferring the feed water to the fluidized bed boiler and converting the heated feed water into steam. The operating method according to claim 1, further comprising:

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the arrangement of each part of an apparatus for implementing an operating method according to an embodiment of the present invention, and FIG. 2 is a block diagram showing an arrangement of parts of an apparatus for implementing an operating method according to a modified embodiment of the present invention. FIG. 3 is a block diagram showing an example of the arrangement of each part of the device. 10...boiler (vessel), 12... bed of granular material, 46... gas turbine (turbine).

Claims (1)

[Claims] 1. directing air through a bed of fuel-containing particulate material disposed in a container, the air velocity being sufficient to fluidize the particulate material and facilitate combustion of the fuel; , the amount of air is insufficient to completely burn the fuel but sufficient to generate combustible off-gases, and the flue gases produced by combustion migrate along the length of the container. After entraining a portion of the granular material, it is discharged through an outlet in the upper part of the vessel, and at a point above the fluidized bed and below the outlet, extra air is added to the vessel to remove the granular material. complete combustion of the fuel and exhausting a portion of the off-gas from an outlet of the vessel upstream of the point where the excess air was added, removing entrained particulate material from the flue gas and the off-gas. A method of operating a gas turbine comprising the steps of separating, combusting the separated off-gas in the presence of the flue gas to increase the gas temperature, and transferring the hot gas to a turbine.