JPH0517301U - Fluidized bed boiler primary combustion air temperature controller - Google Patents

Abstract

(57) [Summary] [Purpose] It is possible to adjust the primary combustion air temperature while cooling the exhaust gas to a specified temperature. A furnace 1 in which fuel is primarily burned by primary combustion air and secondary combustion is performed downstream by secondary combustion air, and an air preheater that cools exhaust gas from the furnace 1 by exchanging heat with the combustion air In a primary combustion air temperature control device including a fluidized bed boiler, the exhaust gas flow path of the air preheater 14 is exchanged with the primary combustion air in a primary side heat exchange section 18, and the secondary combustion air is exchanged. It is characterized in that it is partitioned into a secondary side heat exchange section 19 for heat exchange, and a distribution means 24 for distributing the exhaust gas is provided in the primary side heat exchange section 18 and the secondary side heat exchange section 19.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a fluidized bed boiler that burns fuel with primary and secondary combustion air, and more particularly to a primary combustion air temperature controller for a fluidized bed boiler that adjusts the temperature of the primary combustion air with an air preheater.

[0002]

[Prior Art]

 A fluidized-bed boiler supplies combustion air into the furnace to combust fuels such as coal and petroleum coke while fluidizing them with a fluidizing medium (bed material made of combustion ash etc.), and recovers combustion heat as steam. The exhaust gas from this boiler exchanges heat with the combustion air supplied to the furnace via the air preheater, cools below a prescribed temperature, and is then released from the chimney to the atmosphere.

[0003]

[Problems to be solved by the device]

 By the way, in the above fluidized bed boiler, the combustion air is separately supplied to the primary and secondary in order to reduce the nitrogen oxides (NOx) in the exhaust gas. Since it changes, it greatly affects the combustion characteristics (combustion efficiency, NOx reduction, desulfurization). Therefore, it is desirable to supply the primary combustion air to the furnace after raising it to a predetermined temperature with the air preheater, but adjusting the combustion air temperature with the air preheater may raise the temperature of the exhaust gas released to the atmosphere. As a result, the thermal efficiency deteriorates, so the temperature of the primary combustion air could not be adjusted with the air preheater.

Therefore, the present invention has been made in consideration of such circumstances, and an object thereof is to provide a primary controller for a fluidized bed boiler that enables the temperature control of the primary combustion air in an air preheater. It is to provide a combustion air temperature control device.

[0005]

[Means for Solving the Problems]

 In order to achieve the above-mentioned object, the present invention aims to achieve the above-mentioned object, in which the fuel is primarily burned by the primary combustion air, and the secondary combustion air is secondarily burned downstream thereof, and the exhaust gas from the furnace is burned to the combustion air. In a fluidized bed boiler equipped with an air preheater for heat exchange and cooling, the exhaust gas passage of the air preheater is exchanged with the primary combustion air for the primary side heat exchange section, and the secondary combustion air for In addition to partitioning into a secondary side heat exchange section for heat exchange, a distribution means for distributing the exhaust gas is provided to the primary side heat exchange section and the secondary side heat exchange section.

[0006]

[Action]

 Since the exhaust gas is distributed by the distribution means to the primary side heat exchange section and the secondary side heat exchange section, even if the distribution amount is changed, the total gas amount flowing into the air preheater may change. Absent. Therefore, it becomes possible to adjust the primary combustion air temperature while cooling the exhaust gas to a predetermined temperature or lower with the air preheater.

[0007]

【Example】

 Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

In FIG. 1, reference numeral 1 denotes a furnace of a circulation type fluidized bed boiler 2, an air dispersion plate 3 is provided below the inside thereof, and a fuel such as coal or petroleum coke is provided on the air dispersion plate 3. Fluidizing medium (bed material made of combustion ash, limestone, etc.) is supplied. A primary combustion air line 6 having a primary fan 5 is connected to the wind box 4 below the air distribution plate 3, and a secondary fan 7 is provided above the air distribution plate 3. The secondary combustion air line 8 is also connected, and the combustion air is separately supplied to the primary and secondary sides.

A cyclone 10 is provided on the upper end side of the furnace 1 through an exhaust gas duct 9, and a solid content discharge port of the cyclone 10 has an unburned solid content or scatters therein. A circulation path 11 for returning the formed bed material onto the air dispersion plate 3 is connected. A heat transfer unit 12 is connected to the gas outlet of the cyclone 10. Although not shown in the figure, the heat transfer unit 12 and the furnace 1 are provided with a economizer, a heater, a superheater, etc., and the steam obtained by these economizers, heaters, superheaters, etc. is supplied to a turbine, etc. To be supplied to.

An exhaust gas line 13 is connected to the heat transfer section 12, and the exhaust gas line 13 is connected to a chimney 17 via a steel pipe type air preheater 14, a bag filter 15 and a fan (IDF) 16.

In the air preheater 14, the exhaust gas flow path is divided into two by a partition wall 28 to form two heat exchange parts 18 and 19, and one heat exchange part (primary side heat exchange part) 1 The primary combustion air line 6 is connected to 8 and the secondary combustion air line 8 is connected to the other heat exchange section (secondary side heat exchange section) 19. The exhaust gas line 13 is branched and connected to the primary side heat exchange section 18 and the secondary side heat exchange section 19, and the gas lines 20, 21 are connected to the primary exhaust line 20 and the secondary exhaust line 21. The primary and secondary control valves 22 and 23 for adjusting the gas amount of the first and second control valves 22 and 23 constitute the distribution means 24, and the control valves 22 and 23 constitute the primary side heat exchange section 18 and the secondary side heat exchange section 19 respectively. The amount of flue gas flowing into the air is adjusted to control the primary and secondary combustion air temperatures.

Next, the operation of this embodiment will be described.

Primary combustion air having an air to fuel ratio of 1 or less is supplied into the wind box 4 of the furnace 1 from a primary combustion air line 6. As a result, the fuel on the air dispersion plate 3 is primary-combusted while being fluidized together with the bed material, and is secondary-combusted downstream from the secondary-combustion air from the secondary-combustion air line 8. The exhaust gas enters the cyclone 10 through the exhaust gas duct 9 together with the scattered unburned particles, where the unburned particles and the like are collected and returned to the air dispersion plate 3 through the circulation path 11. The gas component is cooled through the heat transfer unit 12, then enters the exhaust gas line 13, and is heat-exchanged with the combustion air in the air preheater 14 to be cooled to a predetermined temperature, and dust is removed by the bag filter 15, and then the chimney is obtained. Released into the atmosphere.

The amount of gas in the exhaust gas flowing into the air preheater 14 is controlled by the primary and secondary control valves 22 and 23 into the primary side heat exchange section 18 and the secondary side heat exchange section 19. That is, by changing the openings of the primary and secondary control valves 22 and 23, the amount of gas flowing into the primary side heat exchange section 18 is adjusted, and furthermore, the primary side heat exchange section 18 and the secondary side heat exchange section 19 are adjusted. The amount of gas distributed to the air preheater 14 hardly changes, but the amount of gas flowing into the air preheater 14 hardly changes, so the exhaust gas sufficiently exchanges heat with the combustion air, and the temperature of the exhaust gas falls below a predetermined temperature. .

Therefore, since the distribution means 24 for distributing the exhaust gas is provided to the primary side heat exchange section 18 and the secondary side heat exchange section 19 which divide the exhaust gas flow path of the air preheater 14 into two, the air preheater 14 In, the amount of gas flowing into the primary side heat exchange section 18, that is, the primary combustion air temperature can be adjusted while cooling the exhaust gas to a predetermined temperature or lower. Therefore, the temperature inside the furnace 1 is arbitrarily adjusted by controlling the primary and secondary control valves 22 and 23 according to the fuel, etc., and the combustion characteristics (combustion efficiency, NOx reduction, desulfurization) are improved. It is possible to improve. That is, the temperature range in which the combustion characteristic is good (temperature in the furnace 1) varies depending on the type of fuel in the control unit for controlling the opening degree of the control valves 22 and 23. The opening degree of the control valves 22 and 23 may be preset, and the temperature range may differ depending on the load. In that case, the opening degree of the control valves 22 and 23 may be preset depending on the load. To do. As a result, the openings of the control valves 22 and 23 are controlled according to the fuel and load, so that the temperature of the primary combustion air is adjusted appropriately and the temperature inside the furnace 1 is maintained within a range with good combustion characteristics. Therefore, the combustion characteristics are improved.

FIG. 2 is a view showing another embodiment of the present invention. The difference from the above embodiment is that a part of high temperature exhaust gas in the heat transfer section 12 is preheated with air through a primary exhaust gas line 20. The distribution means 27 has just been constructed by connecting a bypass line 26 having a bypass control valve 25 for bypassing the primary side heat exchange section 18 of the reactor 14 to the primary exhaust gas line 20.

With this configuration, the amount of gas flowing into the primary side heat exchange section 18, that is, primary combustion while cooling the exhaust gas to a predetermined temperature or less in the air preheater 14 is almost the same as in the above embodiment. The temperature of the air can be adjusted, and high-temperature exhaust gas in the middle of the heat transfer section 12 is discharged from the heat transfer section 12 by flowing into the primary side heat exchange section 18 of the air preheater 14 through the bypass line 26. Since it is possible to adjust the temperature range that cannot be raised by the discharged exhaust gas, a wide range of temperature can be adjusted.

Although the fluidized bed boiler has been described as a circulation type, the present invention is not limited to this, and the present invention can be applied to a bubbling type fluidized bed boiler.

[0019]

[Effect of the device]

 In short, according to the present invention, since the distribution means for distributing the exhaust gas to the primary side heat exchange section and the secondary side heat exchange section, which divide the exhaust gas flow path of the air preheater into two, is provided, the exhaust gas is heated to the predetermined temperature. It produces an excellent effect that the temperature of the primary combustion air can be adjusted while cooling.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram showing another embodiment of the present invention. Is.

[Explanation of symbols]

 1 Furnace 14 Air Preheater 18 Primary Side Heat Exchange Section 19 Secondary Side Heat Exchange Section 24 Distribution Means

Claims (1)

[Scope of utility model registration request] 1. A furnace for primary combustion of fuel with primary combustion air and secondary combustion with secondary combustion air downstream thereof, and an air preheater for cooling exhaust gas from the furnace by exchanging heat with the combustion air. In a fluidized bed boiler provided with, the exhaust gas flow path of the air preheater, a primary side heat exchange section for exchanging heat with the primary combustion air, and a secondary side heat exchange section for exchanging heat with the secondary combustion air. A primary combustion air temperature control device for a fluidized bed boiler, characterized in that the primary side heat exchange section and the secondary side heat exchange section are provided with a distribution means for distributing the exhaust gas.