JPS61110806A - Combustion and heat exchanging method and facility thereof in combined-cycle facility for fluidized bed combustion - Google Patents

Abstract

PURPOSE:To obtain the optimized thermal efficiency value in performing desulpherization in the fluidized bed by a method wherein a flue-gas temperature at the entrance of a chimney is to be lowered as much as possible, and the flue-gas temperature at a outlet of freeboard is adjusted. CONSTITUTION:Without providing a combustion chamber and the second coal feeder system, a waste heat boiler 30 having an evaporator 27 and a feed water pre-heating tube 28, is provided adjoining the fluidized bed furnace 26, and an exhaust pipe of gas turbine 4 is connected to the bottom of the fluidized bed combustion furnace 26 for both purposes of fluid and combustion. On the other hand, another exhaust pipe 40 is connected to a freeboard 36 for the purpose of two stage combustion, further, the other exhaust pipe is also connected to the waste heat boiler 30 to recover the exhaust gas heat. As countermeasures to increase the temperature of the outlet at the freeboard 36, either change of particles size of solid fuels or installing of the insulating material member for convertible to take-off to cover the freeboard 36, comprising of water cooled wall 37 to absorb heat, which is used on-off basis of fixing and removing, thereby the exhaust temperature at the exit of the freeboard may be adjustable.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a combustion/heat exchange method and apparatus for a fluidized bed combustion combined cycle apparatus comprising a coal-fired fluidized bed combustion apparatus, a gas turbine, and a steam turbine.

2. Description of the Related Art In general, when combining a gas turbine and a steam turbine to increase thermal efficiency as a combined cycle device, a combined cycle device as shown in FIG. 2 is considered as a system that incorporates fluidized bed combustion.

In Fig. 2, air compressed by a compressor 1 is guided to a fluidized bed air heater 2, heated to a predetermined temperature, and then fed to a combustor 3 using fuel such as LNG or kerosene (clean 7 UEL).
is combusted to further raise its temperature, then passed through a gas turbine 4 to do expansion work, and a generator 5 to generate effective work.

A part of the exhaust gas exiting the gas turbine 4 becomes combustion and fluidizing air for the fluidized bed air heater 2, and the remainder of the exhaust gas is used as air for burning fuel in the combustion chamber 7 above the fluidized bed 6. The exhaust gas after combustion is cooled while giving heat to the evaporator tube 8, the superheating tube 10, and the water supply heating tube 11. After passing through the dust collector 12 and the induction tube 16 and supplying heat to the heating heater 14, the exhaust gas is desulfurized. After being desulfurized in the device 15, it is released into the atmosphere from the chimney 16. 17 is a steam turbine, 18 is a generator, 2
0 is a first coal feeding system, 21 is a second coal feeding system, 221 is a wind box, 23 is a condenser, and 24 is a water pump.

Problems to be Solved by the Invention Regarding the thermal efficiency of the combined cycle shown in FIG. 3, which is a simplified version of FIG. 2, let us consider the advantages and disadvantages of auxiliary combustion of fuel in the gas turbine exhaust line.

Assuming that the temperature Tg of the exhaust gas at the outlet of the boiler 25 has been lowered to an ideal value, the influence of auxiliary combustion will be examined with Tg constant. Gas turbine power generation output N8, fuel heat amount f8 in the gas turbine combustor, gas turbine exhaust temperature To, specific heat Op,
Assuming that the flow rate Go, the amount of heat for auxiliary combustion in the boiler ft1, the exhaust gas temperature at the boiler outlet Tg, the specific heat Op, and the thermal efficiency of the steam turbine plant ηat, the thermal efficiency A of the combined cycle with auxiliary combustion in the boiler is: When f, = 0, , I To compare the magnitude of A8 and A, we take the difference, and here, in general, N1=j-(0,2~0.25) f,,ls
0.3-0.4 in t, 0.3 in Ge0p (To-Tg).
Since the value is about 5 to 0.6, it is always A1 (A). That is, when the boiler exhaust gas temperature Tg is constant, the thermal efficiency is highest when there is no auxiliary combustion.

However, in general, gas turbine exhaust has a considerable amount of heat and there is a limit to how much it can be cooled with water and steam in the steam cycle, and the lower limit of boiler exhaust gas temperature Tg is determined by the pinch point ΔT shown in Figure 4. I end up.

To solve this problem, increasing the gas turbine exhaust temperature Te through auxiliary combustion, raising the temperature to To in Figure 4, and lowering the exhaust gas temperature to Pg is the best way to recover the most heat from the exhaust gas. , resulting in maximum thermal efficiency of the combined cycle device.

Based on the above principle, when considering the existing combined cycle equipment shown in Figure 2, it can be considered that a combined cycle is established when a heating heater can be used and heat can be recovered there. When it is not possible to utilize the calorific value of the exhaust gas at even lower temperatures, as discussed above, the best thermal efficiency is achieved by stopping auxiliary combustion in the boiler when the exhaust gas temperature has fallen to Pg.

The present invention was made in view of the above points, and the above exhaust gas temperature can be reduced to 70% without installing a new auxiliary combustion system on the freeboard.
The object of the present invention is to provide a combustion/heat exchange method in a fluidized bed combustion combined cycle device that can reduce the amount of heat to 1 g, and a device for the same.

Means and Effects for Solving the Problems The apparatus of the present invention will be described using the numbers shown in the drawings. The device is a coal-fired fluidized bed combustion system in which an air heater 2 for preheating gas turbine air is provided in a fluidized bed 6. It consists of a device 26, a gas turbine 4, and a steam turbine 17, and the gas turbine exhaust gas pipe is connected to the bottom of the fluidized bed combustion device and the upper side of the fluidized bed of the fluidized bed combustion device,
Connect the first coal feeding system 20.20a to the fluidized bed combustion device,
In a fluidized bed combustion combined cycle device in which the second coal feeding system 21 is provided in the combustion chamber 7 on the downstream side of the fluidized bed combustion device, a waste heat boiler 60 having an evaporation pipe and a water supply condenser tube is provided adjacent to the fluidized bed combustion device. , the gas turbine exhaust gas pipe is connected to the bottom of the fluidized bed combustion device, the upper side of the fluidized bed of the fluidized bed combustion device, and the waste heat boiler, and a combustion chamber and a second coal feeding system are not provided.

Furthermore, in order to reduce the temperature of the exhaust gas at the smoke inlet as much as possible, the method of the present invention allows a portion of the gas turbine exhaust gas, water supply, and steam drum to be used without feeding coal from the second coal feeding system to the combustion chamber 7. In addition to exchanging heat with the gas-liquid mixture, the particle size of the fuel for fluidized bed combustion supplied from the first coal feeding system 20 is changed, and/or the amount of heat absorbed by the 7 Lee board 66 is adjusted by installing or removing a heat insulating material. The feature is that the freeboard outlet exhaust gas temperature is adjusted by changing the temperature.

EXAMPLE Hereinafter, an example of the present invention will be described based on FIG. 2
Reference numeral 6 denotes a coal-fired fluidized bed combustion apparatus, which includes an air heater 2 for preheating gas turbine air within the fluidized bed 6. 4 is a gas turbine, and 17 is a steam turbine. A first coal feeding system 20.20a is connected to the fluidized bed combustion apparatus. In the conventional apparatus shown in FIG. 2, the second coal feeding system 21 was connected to the combustion chamber 7 above the fluidized bed of the fluidized bed combustion apparatus, but in the apparatus of the present invention, this combustion chamber and the second Do not install a coal feeding system.

A waste heat boiler 30 having an evaporator tube 27 and a water heating condenser tube 28 is provided adjacent to the fluidized bed combustion device 26, and a gas turbine exhaust gas pipe is connected to the bottom of the fluidized bed combustion device for the purpose of fluidization and combustion. It is connected to the free board 36 above the fluidized bed of the fluidized bed combustion apparatus for combustion, and is also connected to the waste heat boiler 30 for the purpose of recovering the heat amount of excess exhaust gas. 3
1 is a steam drum, 62 is an evaporation tube, 36 is a water supply heating tube, 6
4 is a fluidized bed exhaust gas convection section, 65 is a superheating pipe, 36 is a free board, 67 is a →Lee board water cooling pipe, 68 is a gas turbine surplus exhaust system, 40) is a fluidized bed two-stage combustion system, 41 is a fluidized bed fluidized This is a combustion air system. Other numbers are the same as in FIG.

In a fluidized bed combustion furnace, it is generally known that the temperature of the log gas exiting the freeboard 36 can be changed by changing the particle size of the supplied fuel and the heat absorption amount of the freeboard.

In the present invention, this is actively utilized, and a part of the gas turbine exhaust gas is introduced into the waste heat boiler 60 through the gas turbine surplus exhaust system 68 to exchange heat with the water supply and the gas-liquid mixture from the steam drum 31. As a means for increasing the freeboard outlet gas temperature so that the difference between the outlet gas temperature of the waste heat boiler 30 and the water supply temperature of the water supply child heat tube 28 population can be selected to be equal to the pinch gain ΔT shown in FIG. Either change the particle size of the fuel supplied to the fluidized bed 6, or
Alternatively, the temperature of the freeboard outlet exhaust gas is adjusted by changing the amount of heat absorption in the freeboard 36 made of the water-cooled wall 67 by attaching or removing a heat insulating material, or by taking both measures.

Note that the convection section 64 and the waste heat boiler 30 may mix exhaust gas to form a waste heat boiler in some cases, but in general, the excess exhaust gas of the gas turbine is clean gas, so
There is no risk of corrosion even if sufficient waste heat is recovered, so
It is advantageous to use a separate type as shown in the figure.

As described in detail, in the present invention, since the fuel is not reheated in a freeboard manner, desulfurization, which is a characteristic of a fluidized bed, can be performed within the fluidized bed. Therefore, there is no need to install a flue gas desulfurization device in the exhaust gas line, and it is possible to optimize the thermal efficiency of the combined cycle device while taking advantage of the original characteristics of fluidized bed combustion.

[Brief explanation of drawings]

Fig. 1 is a flow sheet showing an example of an apparatus for carrying out the method of the present invention, Fig. 2 is a flow sheet showing a conventional fluidized bed combustion combined cycle apparatus, and Fig. 3 is a simplified version of the apparatus shown in Fig. 2. Flow sheet, FIG. 4 is an explanatory diagram showing an example of temperature distribution in the apparatus shown in FIG. 3. 1... Compressor, 2... Fluidized bed air heater, 3
... Combustor, 4... Gas turbine, 5... Generator, 6... Fluidized bed, 7... Combustion chamber, 8... Evaporation pipe,
10... Superheating tube, 11... Water supply heating tube, 12...
Dust collector, 13... Induction fan, 14... Heater for heating, 15... Flue gas desulfurization device, 16... Chimney, 17
...Steam turbine, 18...Generator, 20.20a
...First coal feeding system, 21...Second coal feeding system, 22.
...Wind box, 26...Condenser, 24...Water pump,
25...Boiler, 26...Fluidized bed combustion device, 27.
... Evaporation tube, 28 ... Water supply heating tube, 30 ... Waste heat boiler, 61 ... Steam drum, 32 - ... Evaporation pipe, 63
... Water supply heating element tube, 64 ... Fluidized bed exhaust gas convection section, 6
5... Overheating tube, 36... Free board, 37...
Freeboard water cooling wall, 68...Gas turbine surplus exhaust system, 40...Fluidized bed two-stage combustion system, 41...Fluidized bed fluidized/combustion air system Applicant: Kawasaki Heavy Industries, Ltd. Figure 3 Figure 4 】υ

Claims (1)

[Claims] 1. A coal-fired fluidized bed combustion device comprising an air heater for preheating gas turbine air in the fluidized bed, a gas turbine, and a steam turbine, the fluidized bed combustion device including a gas turbine exhaust gas pipe. A fluidized bed combustion complex that is connected to the bottom and the upper side of the fluidized bed of the fluidized bed combustion device, the first coal feeding system is connected to the fluidized bed combustion device, and the second coal feeding system is provided in the combustion chamber downstream of the fluidized bed combustion device. In a cycle device, heat exchange is performed between part of the gas turbine exhaust gas, feed water, and the gas-liquid mixture from the steam drum without feeding coal to the second coal feed system, in order to reduce the exhaust gas temperature at the smoke inlet as much as possible. At the same time, by changing the particle size of the fuel for fluidized bed combustion supplied from the first coal feeding system and/or changing the amount of heat absorption in the freeboard by installing or removing heat insulating material, the exhaust gas at the freeboard outlet can be reduced. A combustion/heat exchange method in a fluidized bed combustion combined cycle device characterized by temperature adjustment. 2. Consisting of a coal-fired fluidized bed combustion device with an air heater for gas turbine air preheating installed in the fluidized bed, a gas turbine, and a steam turbine, the gas turbine exhaust gas pipe is connected to the bottom of the fluidized bed combustion device and the fluidized bed combustion device. In a fluidized bed combustion combined cycle device, the first coal feeding system is connected to the upper side of the fluidized bed, the first coal feeding system is connected to the fluidized bed combustion device, and the second coal feeding system is provided in the combustion chamber on the downstream side of the fluidized bed combustion device. A waste heat boiler having an evaporator tube and a water supply heating tube is provided adjacent to the bed combustion device, and a gas turbine exhaust gas pipe is connected to the bottom of the fluidized bed combustion device, the upper side of the fluidized bed of the fluidized bed combustion device, and the waste heat boiler, and the combustion chamber and a combustion/heat exchange device in a fluidized bed combustion combined cycle device, characterized in that a second coal feeding system is not provided.