JP3150359B2 - Steam temperature control method for fluidized bed boiler - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluidized bed boiler having a reheater, and more particularly to a method for controlling a steam temperature of a pressurized fluidized bed boiler.

[0002]

BACKGROUND OF THE INVENTION Pressurized fluidized bed boilers have most of the heat transfer surfaces in the fluidized bed to keep the temperature of the combustion gases sent to the gas turbine high. When a pressurized fluidized-bed boiler has a reheater in a fluidized bed, conventionally, the reheat steam temperature was controlled by a reheater spray using feed water.

[0003]

In the pressurized fluidized-bed boiler, when the reheat steam temperature is controlled by the reheater spray using the feed water as described above, the control is performed in comparison with the case where the reheat spray is not used. As a result, the thermal efficiency of the reheating cycle decreases.

An object of the present invention is to provide a method for controlling a steam temperature of a fluidized-bed boiler which can solve the above problems.

[0005]

(1) A method for controlling a steam temperature of a fluidized-bed boiler according to the present invention comprises transferring heat to a superheater and a reheater in a fluidized-bed furnace capable of controlling the bed height of a common fluidized bed. Surface, and the superheated steam temperature of the superheater is sprayed by a superheater spray, and the reheated steam temperature of the reheater is output to a bed height control device.
The method is characterized in that the bed height of the fluidized bed is changed by inserting , and each bed is controlled.

(2) The method for controlling the steam temperature of a fluidized-bed boiler according to the present invention is the same as the above (1), except that the bed height of the fluidized bed can be controlled independently of the fluidized-bed furnace. the evaporator is arranged as a heat transfer surface in the vapor of the evaporator, the bed height of the control device having a flow material of the further fluidized bed furnace out of the furnace
It is characterized in that it is controlled by changing the bed height of the fluidized bed by taking it in and out.

[0007]

On the heat transfer surface in the fluidized bed furnace, the portion inside the fluidized bed has a higher heat transfer coefficient than the portion outside the fluidized bed above the bed height of the fluidized bed. In the present invention (1), the amount of heat absorption is changed by changing the bed height of the fluidized bed in the fluidized bed furnace, and the reheat steam temperature is controlled. On the other hand, by changing the bed height of the fluidized bed, the amount of heat absorbed by the superheater also changes. By changing the amount of spray water supplied from the superheater spray, the superheated steam temperature at the superheater outlet is controlled.

Thus, in the present invention (1), the spray is not used for the reheater, and therefore, the thermal efficiency of the reheat cycle can be improved.

In the present invention (2), the present invention (1)
In addition to the action of the above, by changing the bed height of the fluidized bed in a fluidized bed furnace different from the fluidized bed furnace, the heat absorption of the evaporator changes, and the superheated steam temperature and the reheated steam temperature The amount of steam is controlled independently.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIG. Reference numeral 1 denotes a bubble type fluidized bed furnace, in which an evaporator 2 is disposed as a heat transfer surface, and the bed height of the fluidized bed is adjusted by moving a fluidized material into and out of the bed height control device 3 by known means (not shown). The height 16 of the surface of the flowing material during the flow can be controlled. Air and fuel are introduced into the fluidized bed of the fluidized bed furnace 1 by a known means (not shown) to keep the temperature of the fluidized bed constant and maintain the fluidized state. The combustion gas generated in the fluidized bed furnace 1 is sent to a gas turbine (not shown) through a duct 18, preferably after dust removal.

Reference numeral 4 denotes a bubble type fluidized bed furnace capable of controlling the bed height of the fluidized bed independently of the fluidized bed furnace 1, and has a low-temperature superheater 5, a high-temperature superheater 6, and a reheater 7 therein. Are arranged as heat transfer surfaces, and the bed height 17 of the fluidized bed can be controlled by the bed height control device 8 through which the fluidized material is taken in and out.
In the fluidized bed furnace 4, similarly to the fluidized bed furnace 1, air and fuel are charged, and the combustion gas is sent to a gas turbine (not shown) through a duct 19.

Water is supplied to the evaporator 2 by a water supply pump 9, and the water / steam mixture generated by heating by absorbing the heat of combustion of the fluidized-bed furnace 1 in the evaporator 2 is heated by a steam separator 10. The water is separated into water and steam, and the water is mixed with water supplied from the water supply pump 9 by a recirculation pump 11.

The steam separated by the steam separator 10 is heated by absorbing the heat of combustion of the fluidized-bed furnace 4 by the low-temperature superheater 5, and the steam exiting the low-temperature superheater 5 flows out of the fluidized-bed furnace 4. After passing through the placed superheater spray 12, it further enters the high-temperature superheater 6 and is heated by absorbing the combustion heat of the fluidized-bed furnace 4 in the fluidized-bed furnace 6.
The steam is sent as superheated steam through a pipe 13 to a high-pressure steam turbine (not shown). As the spray water of the superheater spray 12, a part of the feed water that exits the feed pump 9 is used. The exhaust gas of the high-pressure steam turbine is supplied to a reheater 7 in the fluidized-bed furnace 4 through a pipe 14, where the exhaust gas is heated by absorbing the combustion heat of the fluidized-bed furnace 4, and is heated as high-temperature reheated steam in the pipe 1.
5 and is sent to a medium-pressure steam turbine (not shown).

The heat transfer surfaces of the evaporator 2, the low-temperature superheater 5, the high-temperature superheater 6, and the reheater 7 in the fluidized bed are well-known tube-group heat exchangers, and may be suitably used if necessary. Abrasion protection is provided.

In a fluidized bed of a fluidized bed, the heat transfer coefficient is very high when the heat transfer surface is below the bed height of the fluidized bed as compared to when it is above the bed height. In this embodiment, by changing the bed height 16 of the fluidized bed of the fluidized bed furnace 1, the ratio of the heat transfer surface above and below the bed height of the evaporator 2 is changed, and the amount of heat absorption is changed to control the amount of evaporation. Can be.

Further, by changing the bed height 17 of the fluidized bed of the fluidized bed furnace 4, the amount of heat absorbed by the reheater 7 changes, whereby the reheat steam temperature at the outlet of the reheater can be adjusted without using a spray. Can be controlled. At this time, the low-temperature superheater 5
The amount of heat absorbed by the high-temperature superheater 6 also changes, but the superheated steam temperature at the outlet of the high-temperature superheater 6 can be controlled by changing the amount of spray water supplied from the superheater spray 12.

As described above, in this embodiment, the amount of evaporation in the evaporator 2 can be controlled by changing the bed height 16 of the fluidized bed of the fluidized By changing the layer height 17 of the layer,
The reheat steam temperature in the reheater 7 can be controlled without using a spray, and the thermal efficiency can be improved. Further, by changing the bed height 17 of the fluidized bed of the fluidized bed furnace 4, the amount of heat absorbed by the low-temperature superheater 5 and the high-temperature superheater 6 changes, but the amount of spray water supplied from the superheater spray 12 is changed. Thereby, the superheated steam temperature can be controlled.

A second embodiment of the present invention will be described with reference to FIG. In the present embodiment, in the fluidized-bed furnace 4 of the first embodiment, a load change /
An emergency time reheater spray 20 is provided.

In this embodiment, the same operation and effect as those of the first embodiment can be obtained without spraying water from the reheater spray 20 at all times. In addition to this, in this embodiment, when auxiliary auxiliary reheat steam temperature control is required transiently in an unsteady state such as when the load changes, spray water is supplied from the reheater spray 20. It is something that can be done.

In both of the above embodiments, the evaporator 2 is placed in one fluidized bed furnace 1 and the low and high temperature superheaters 5 and 6 are placed in the other fluidized bed furnace 4.
Although a part of the heat transfer surface of the low and high temperature superheater and the reheater may be provided in a common fluidized bed furnace with the evaporator, on the contrary, the heat transfer surface of the evaporator may be provided. May be provided in a common fluidized bed furnace with the low and high temperature superheater and the reheater,
It is also possible to be provided in the economizer Re not have the (feed water heater) of the fluidized bed furnace.

In the present invention, in addition to the change in bed height of the fluidized bed, a change in bed temperature of the fluidized bed can be used as an auxiliary control means. However, when a desulfurization reaction is performed in a fluidized bed furnace using limestone as a fluidized material, an optimal temperature range exists, and when the temperature in the fluidized bed is increased, ash melting occurs, and When you make this low temperature
Due to factors such as difficulty in combustion , the effect is limited as compared with the control of the bed height of the fluidized bed.

[0022]

According to the present invention, the reheat steam temperature can be controlled without using the reheater spray in the fluidized-bed boiler. Thus, the thermal efficiency of the reheating cycle can be improved.

The present invention according to claim 2 can control the amount of evaporation in the evaporator independently of the other superheated steam temperature and reheated steam temperature in addition to the above effects.

[Brief description of the drawings]

FIG. 1 is a system diagram of a first embodiment of the present invention.

FIG. 2 is a system diagram of a second embodiment of the present invention.

[Explanation of symbols]

 1,4 Fluidized bed furnace 2 Evaporator 3,8 Bed height control device 5 Low temperature superheater 6 High temperature superheater 7 Reheater 9 Feedwater pump 10 Steam separator 11 Recirculation pump 12 Superheater spray 13,14,15 Piping 18 , 19 duct

Continuation of front page (72) Inventor Ryuji Toyoda 2-5-1 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Heavy Industries, Ltd. (56) References JP-A-60-122801 (JP, A) JP-A-58-102002 ( JP, A) JP-A-1-217108 (JP, A) JP-A-1-217106 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F22B 1/02 F22G 5/12

Claims (2)

(57) [Claims] 1. A superheater and a reheater are arranged as a heat transfer surface in a fluidized bed furnace in which the height of a common fluidized bed can be controlled, and the superheated steam temperature of the superheater is measured by the superheater spray. The reheat steam temperature of the heater can be adjusted by
A method for controlling the steam temperature of a fluidized-bed boiler, wherein the bed height of the fluidized bed is changed and controlled accordingly. Wherein placing the evaporator to the fluidized bed furnace and a separate fluidized bed of bed height control another fluidized bed furnace capable as heat transfer surface, the amount of steam of the evaporator, said another flow Fluid for floor furnace
To the bed height control device provided outside the furnace.
The method according to claim 1, wherein the control is performed by changing the bed height of the fluidized bed.