JPH03105109A - Solid fuel dryer for boiler - Google Patents

Abstract

PURPOSE:To reduce load and hindrance to a crusher and raise the efficiency of a boiler by providing a solid fuel vessel with an injection nozzle and connecting to the nozzle an exhaust gas duct that is branched from a boiler exhaust gas duct and providing an exhaust gas duct from the upper section of the solid fuel vessel to a chimney. CONSTITUTION:The lower section of a bunker 1 is provided with a blowing-in nozzle 15. To the nozzle 15 an exahust gas duct 12 is connected which branches from a boiler exhaust gas duct 5a on the outlet side of an induced draft fan 8 and is provided with a regulation damper 20. To the exhaust gas duct 12 a temperature regulating duct 13 is connected which is connected to the outlet section of a forced draft fan 19 and provided with a regulating damper 21. Part of the exhaust gas of a boiler is blown into the bunker 1 from the nozzle 15 though the exhaust gas duct 12 and the moisture contained in the coal is evaporated by the thermal energy of the exhaust gas. The steam produced by the evaporation and the exhaust gas pass through an exhaust gas duct 14 and are led to a chimney 10. With this arrangement it is possible to evaporate and remove the moisture in the coal by the boiler exhaust gas and reduce the load and hindrance to a coal pulverizing machine and also to raise the boiler efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a solid fuel drying device for a boiler system that uses solid fuel such as coal that contains moisture or has moisture attached to it. [Prior art] Coal drying in a conventional pulverized coal combustion boiler requires air pre-treatment. The coal is only pulverized and dried in the pulverizer by receiving the drying energy from hot air from the heater, boiler exhaust gas, or gas generated from other hot gas generating furnaces; other equipment does not dry the coal. It wasn't.

Figure 2 shows the system of a conventional direct combustion type pulverized coal combustion boiler. The coal sent by a conveyor or the like and stored in the bunker 1 is supplied to the coal pulverizer 3 while its flow rate is controlled by a coal feeder 112. The pulverized coal that has been pulverized and dried in the pulverizer 3 is conveyed, sent, and supplied directly to a burner through a pulverized coal pipe 4 by primary air, and is combusted in a boiler 5. A part of the combustion air from the forced draft fan 19 is branched to the pulverized coal 813 and sent together with the primary air preheated by the regenerative air preheater 6 to transport dry air and pulverized coal.
It is also used as combustion air. In the figure, 7 is an electrostatic precipitator installed downstream of the regenerative heater 6, 8 is an induced draft fan for boiler exhaust gas installed downstream of the electrostatic precipitator, and 9 is an induced draft fan downstream of the induced draft fan. There is an exhaust P1 desulfurization device installed on the side, and 10 is a chimney. Next, Fig. 3 shows one system of the pulverized coal combustion boiler of the pulverized coal bin system. For drying the pulverized coal Ji13, the gas taken out from the inlet and outlet of the regenerative air preheater 6 is sent and used. Adjusting the amount taken out. Further, the pulverized coal and exhaust gas from the pulverized coal machine 3 are separated when passing through a cyclone 30 and a bag filter 31, and the pulverized coal is stored in a pulverized coal bin 32. The exhaust gas separated from the pulverized coal by the cyclone 30 and the bag filter 31 is returned to the outlet of the regenerative air preheater 6 by the exhaust fan 33. The pulverized coal is conveyed from the bin 32 via the pulverized coal pipe 4 to the burner inlet by the coal feeder 34, where it is mixed with primary air and combusted in the boiler 5.

[Problems to be Solved by the Invention] Coal, which is used as fuel in boiler plants such as thermal power plants, contains inherent moisture and surface moisture.

In particular, surface moisture is affected by the season and its content ranges from a few percent to several percent. Thermal coal with a high moisture content not only causes trouble during pulverization, but also causes trouble inside the boiler and a reduction in boiler efficiency. Specifically, (1) Thermal coal is not dried immediately before being carried into the pulverizer, and the amount of drying inside the pulverizer is large, increasing its load. Furthermore, it is necessary to adjust the drying air temperature in the pulverizer depending on the moisture content of the coal.

(2) When the moisture content of coal is high, steam is generated from the coal, and this steam is also circulated, resulting in large ventilation losses from the pulverizer, pulverized coal pipe, burner to the inside of the boiler, air preheater, etc. .

(3) Since there is an upper limit to the heat transfer characteristics of the air preheater when utilizing exhaust heat from boiler exhaust gas accompanied by water vapor, it is not possible to recover exhaust heat beyond that limit.

The present invention is. This is an attempt to solve the problems of the conventional devices mentioned above. [Means for Solving the Problems] The solid fuel drying device for the boiler of the present invention has the following features: (1) A blowing nozzle is provided in a solid fuel container that stores solid fuel to be supplied to a boiler via a crusher, and the blowing nozzle An exhaust gas duct branched from the boiler exhaust gas duct downstream of the air preheater provided in the boiler exhaust gas duct was connected to the exhaust gas duct, and an exhaust gas duct was provided that communicated from the upper part of the solid fuel container to the chimney.

(2) In the apparatus of (1) above, the branch part of the exhaust gas duct from the boiler exhaust gas duct is used as the outlet of the induced draft fan or flue gas desulfurization equipment for the boiler exhaust gas. (3) In the device of (1) above, a temperature control duct from an air duct having a control damper was connected to the exhaust gas duct. [Function] In the present invention (1), the boiler exhaust gas is blown into the solid fuel container in which the solid fuel is stored and sent to the boiler via the pulverizer by the blowing nozzle from the boiler exhaust gas duct downstream of the air preheater through the exhaust gas duct. The solid fuel is then dried in the same container. This allows the dried solid fuel to be sent to the pulverizer and then to the boiler, reducing the load on the pulverizer, as well as preventing problems during pulverization due to moisture contained in the solid fuel and problems inside the boiler. This prevents a decrease in efficiency. The exhaust gas from drying the solid fuel in the fixed fuel container and the water vapor evaporated from the solid fuel are discharged from the exhaust gas duct to the chimney.

Furthermore, exhaust gas is supplied to the solid fuel container from downstream of the air preheater, and the temperature of this exhaust gas is lowered, so that ignition of the solid fuel within the solid fuel container is prevented.

In the present invention (2), in addition to the effect of the present invention (1), the boiler exhaust gas is discharged from the induced draft fan outlet after its heat has been recovered, or from the wandering combustion desulfurization equipment outlet after desulfurization has been completed. The solid fuel that is blown into the solid fuel container is prevented from igniting within the solid fuel container, and the boiler exhaust gas that is not desulfurized is not discharged to the outside from the solid fuel container.

In the present invention (3), a regulated amount of air is supplied from an air duct such as a fuel air duct of a boiler to an exhaust gas duct through a 1L temperature duct with an adjustment damper, and the boiler exhaust gas is supplied to a solid fuel container. By adjusting the temperature of the solid fuel, ignition of the solid fuel is prevented.

[Example] A coal drying apparatus for a direct combustion type pulverized coal combustion boiler as an example of the present invention will be described with reference to FIG.

l is the bunker that stores the coal sent by Conhair l1, 2
5 is a coal feeder that supplies coal from the same bunker to pulverizer 3;
6 is a boiler to which pulverized coal is supplied from the pulverizer 3 to its burner via the pulverized coal pipe 4; In between, a dust collector 8 is provided in the boiler exhaust gas duct 5a on the heat exchange side, and is an induced draft fan 8 that is installed in the boiler exhaust gas duct 5a to attract the exhaust gas exiting the dust collector 7 and send it to the chimney 10. The boiler 5, pulverizer 3, etc. have a second
Similar to the conventional direct combustion type pulverized coal fuel boiler shown in the figure, combustion air or air preheated by an air preheater 6 is used.
Air, etc. is supplied.

A blowing nozzle 15 is provided at the bottom of the bunker 1,
An exhaust gas duct H2 branched from the boiler exhaust gas duct 5a on the exit side of the induced draft R day of exhaust gas and equipped with an adjustment damper 20 is connected to the same blowing nozzle 15. Further, a temperature control duct 13 connected to the outlet of the forced draft fan 19 of the combustion air duct and provided with an adjustment damper 21 is connected to the exhaust gas duct 2 .

Furthermore, a waste gas duct 14 equipped with a waste gas ventilator 18 is provided at the top of the bunker I and is connected to the chimney 10. A thermocouple temperature detector or CO
(Multiple fire forecasting devices 16 such as carbon monoxide detectors)
At the same time, a fire extinguishing system 17 capable of injecting fire extinguishing water, powder (foam) extinguishing agent, or inert gas such as N2 is installed. This fire forecasting device 16 is linked to a fire extinguishing device 17 and a regulating damper 20 of the exhaust gas duct port 2, so that when a fire occurs, the fire extinguishing device 17 is activated and the introduction of exhaust gas is stopped.

In this embodiment, a part of the exhaust gas from the boiler discharged from the induced draft fan 8 is adjusted in flow rate by the adjusting damper 20, and is guided to the bunker 1 through the exhaust gas duct 2 and then to the blowing nozzle l.
5 into the bang force i. The blown exhaust gas evaporates the moisture contained in the coal inside the bunker 1 using its thermal energy. The evaporated water vapor and waste gas are transferred to the waste gas duct 14.
The waste gas is guided by the exhaust gas ventilator 18 to the chimney IO and discharged to the atmosphere.

As explained above, in this embodiment, the moisture contained in the coal in the bunker I is evaporated and removed by the boiler exhaust gas blown from the blowing nozzle 15, thereby reducing the load and failure of the subsequent pulverizer. In addition, the boiler efficiency can be improved by reducing the water content of the coal fed into the boiler. By the way, when the moisture content of coal is lowered from 15% to 8%, the load or required power of the pulverizer can be reduced by about 5% due to the decrease in moisture, making it possible to downsize the pulverizer, and the boiler efficiency can be reduced to 0. .6 to 1% improvement.

The arrival temperature of dry coal increases as the degree of carbonization progresses. It is generally known that the water content has a particularly significant effect, and if there is a large amount of water, it becomes difficult to ignite; this is shown in Table 1.

Table 1 Coal ignition temperature (in air, oxygen concentration 21χ) Furthermore, Table 2 shows examples of ignitability tests using various air atmospheres for deposited coal.
It was shown to. Accordingly, by adjusting the temperature and amount of exhaust gas introduced into the bunker 1, ignition of coal can be prevented.

Table 2 Example of ignitability test for deposited coal ○ Ignition present × No (not conducted) In this example, the amount of exhaust gas blown into the bunker 1 by the adjustment damper 20 was adjusted, and the amount of exhaust gas blown into the bunker 1 was Air from the ventilator 19 is supplied to the exhaust gas duct 12 to adjust the temperature of the exhaust gas blown into the bunker 1, making it possible to prevent coal from igniting within the bunker 1. Further, by installing a fire forecasting device 16 and a fire extinguishing device 17 inside the bunker 1, it is possible to extinguish the fire when it ignites.

Although coal is used as the fuel in the above embodiment, the present invention can be applied to other solid fuels. In addition to the direct combustion method, it can also be applied to a pulverized coal combustion boiler of a pulverized coal bin system.

Furthermore, the location where the exhaust gas is blown is not limited to the bunker, but may also be a silo before the conveyor 11 shown in FIG. Further, in the above embodiment, the exhaust gas duct 12 branches from the boiler exhaust gas duct 5a on the outlet side of the induced draft fan 8, but as shown in FIGS. 2 and 3, an exhaust gas desulfurization device is provided. In some cases, the exhaust gas duct may be branched off from the boiler exhaust gas duct on the exit side of the flue gas desulfurization equipment. In this case, the desulfurized exhaust gas is introduced into the solid fuel container, and the exhaust gas discharged after drying the solid fuel can be kept clean. [Effects of the Invention] The present invention can have the following effects.

(1) By drying the solid fuel in the solid fuel container, the load and failure of the rice crusher can be reduced. (2) Boiler efficiency is improved by introducing dried solid fuel into the boiler. (3) By burning dried solid fuel in a boiler, the air volume and gas volume are reduced, which reduces the load on ventilators and their motors, making them more compact. (4) The boiler and crusher loads can be operated at a constant rate without being affected by seasonal changes in the moisture content of the solid fuel. (5) By supplying the boiler exhaust gas to the solid fuel container downstream of the air preheater and further from the induced draft outlet, relatively low-temperature boiler exhaust gas can be supplied to the solid fuel container and ignition can be avoided. ．． In addition, by supplying boiler exhaust gas from the outlet of the flue gas desulfurization equipment, the waste gas discharged after drying the solid fuel can be kept clean.
(6) Ignition in the solid fuel container can be prevented by lowering the temperature of the boiler exhaust gas supplied to the solid fuel container using air from the temperature control duct.

[Brief explanation of drawings]

Figure 1 is a system diagram of an embodiment of the present invention, Figure 2 is a system diagram of a conventional direct combustion type pulverized coal combustion boiler, and Figure 3 is a system diagram of a conventional pulverized coal combustion boiler with a pulverized coal bin system. be. 1... Bunker, 2... Coal feeder, 3...
Pulverized coal machine, 5...boiler. 5a... Boiler exhaust gas duct,

Claims (3)

[Claims] (1) A blowing nozzle is installed in the solid fuel container that stores the solid fuel that is supplied to the boiler via the crusher, and a blowing nozzle is installed in the blowing nozzle that branches from the boiler exhaust gas duct downstream of the air preheater installed in the boiler exhaust gas duct. A solid fuel drying device for a boiler, characterized in that an exhaust gas duct is connected to the exhaust gas duct and is connected to the chimney from the upper part of the solid fuel container. (2) A solid fuel drying device for a boiler according to claim (1), characterized in that a branching portion of the exhaust gas duct from the boiler exhaust gas duct is an outlet portion of an induced draft fan for boiler exhaust gas or an exhaust gas desulfurization device. . (3) The solid fuel drying device for a boiler according to claim (1), wherein a temperature control duct from an air duct having a control damper is connected to the exhaust gas duct.