JPS60133214A - Coal-ash treating method - Google Patents

Abstract

PURPOSE:To recover the heat of high temperature ash and to simplify the equipment for treating the high temperature ash, in a gas recirculating system, by directly introducing the high temperature coal ash, which is captured by a gas- recirculation dust collecting device, to the inlet flue of an air preheater. CONSTITUTION:Part of burned exhaust gas from a coal burning boiler is extracted from a gas recirculating fan 20 through the outlet of a coal saving device 2 and a gas-recirculation dust collecting device 18 and circulated to a boiler burning chamber 1. Ash, which is stored in a coal saving hopper 6, a denitration device hopper 22, an air preheater hopper 7 and a dust collecting device hopper 8 in the coal burning boiler, is supplied into an conveying pipe 11, which is connected to a vacuum source or a pressurizing source, from an ash supplying valves 10 provided at the lower parts of the hoppers. The ash is conveyed to a fly ash silo 12 by air. Meanwhile, the high temperature coal ash, which is captured by the gas-recirculation dust collecting device 18, is put in an ash conveying pipe 11a through an ash supplying valve 10a and a feeder tank 28. The ash is introduced into an inlet flue 31 of an air preheater 3 directly from a pressure blower 27.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is aimed at reducing the amount of coal ash produced in large quantities mainly in coal-fired boilers such as commercial thermal power plants.
IM
Z, Tom LV-1f This relates to a coal ash processing method that can prevent heat damage to transport pipe systems, bag filters, etc.

Coal ash includes talin ash, which falls into the clinker hopper at the bottom of the boiler hearth, and fly ash, which collects ash in the exhaust gas using economizer hoppers, air preheater hoppers, electrostatic precipitators, etc. The present invention relates to a method for treating high-temperature fly ash.

In a conventional general coal-fired boiler, as shown in Fig. 1, the combustion exhaust gas exiting from the boiler combustion chamber 1 is passed through the economizer 2.
It is cooled to approximately 850-400°C through heat exchange while passing through the air, and then passes through dust collection equipment such as a denitrification device (not shown), air preheater 3, electrostatic precipitator, cyclone, and bag filter.
4, and further passes through a subsequent flue gas treatment device such as a desulfurization device, and is finally discharged into the atmosphere from a chimney. A part of the coal ash generated by coal combustion falls into the chestnut 7 kahopper 5 at the bottom of the boiler combustion chamber 1, but the majority (80-90%) is accompanied by the combustion gas as fly ash and flows into the boiler combustion chamber 1. Carry over from. The plywood is mainly collected by the dust collector 4, but it also falls into the economizer hopper 6, the denitrification device hopper, the air preheater hopper 7, and the ash hopper provided in the flue in the middle. 8 is a dust collector hopper. The fly ash stored in each of these hoppers is supplied into the ash transport pipe 11 via the ash supply valve 10, and is transported to the fly ash silo 12 on an air flow.

As the air source, a vacuum source such as a vacuum blower 13 or an ejector is used, and a method of transporting using vacuum suctioned air is generally adopted. Note that there are cases where the pressure is transported using air pressurized by a pressure source such as a blower or compressor. 14
15 is an air intake valve, 15 is a cyclone, 16 is a bag filter, and 17 is an overload prevention vacuum switch.

The fly ash stored in each hopper is passed through the ash transport pipe 11 by the air flow generated by the vacuum blower 13 by opening the ash common supply valve 10, centrifuged by the cyclone 15, and stored in the fly ash silo 12. . The air containing a small amount of fly ash that has passed through the cyclone 5 is introduced into a bag filter 16, where fine particles are collected, and the purified air passes through a vacuum blower 13 and is exhausted into the atmosphere. Or it is returned to the dust collector 4 inlet. The amount of fly ash supplied to the ash transport pipe 11 is controlled by operating as follows depending on whether the amount increases or decreases from the specified value of the overload prevention vacuum switch 17 provided at the suction part of the vacuum blower 13. Let's do it. That is, when the ash supply valve 10 is opened and the fly ash in the hopper is supplied into the ash transport pipe 11, the pressure loss within the ash transport pipe 11 increases, and the larger the amount of fly ash supplied, the higher the degree of vacuum. growing. If the degree of vacuum rises above the specified value of the overload prevention vacuum switch 17 (if the pressure loss becomes large), the ash supply valve closes, temporarily stopping the supply of flybrush, or fluidizing air to the ash supply valve 1°. and reduce the fly ash supply. As a result, the resistance in the ash transport pipe 11 decreases, and if the vacuum value falls below the specified value again (if the pressure loss becomes small), the ash supply valve opens and either supplies fly ash or vents the fluidized air. Increase the amount of fly ash supplied. That is, by controlling the opening and closing of the ash supply valve 10, etc., the supply amount of fly ash is limited, and a substantially constant amount of fly ash corresponding to the specified value is supplied to the ash transport pipe 11. In other words, if the specified value of the overload prevention vacuum switch 17 is set high, a large amount of fly ash can be supplied, and if it is set low, a small amount of fly ash can be supplied. Fly ash is supplied from one hopper to another.
The process continues until all the hoppers are emptied one by one.

In the conventional device shown in Fig. 1, the temperature of the ash is kept at a relatively low temperature (approximately 150°C or less) in the air preheater 3 and dust collector 4, and at a high temperature (approximately 350°C) only in the economizer 2. However, even at high temperatures, the amount of ash is 2-5% of the total amount of fly ash.
Since the amount of ash is small, the supply time is extremely short, and the flybrush is cooled by the transport air and transport pipe, so that no heat damage to the ash transport pipe 11, bag filter 16, etc. occurs.

However, in recent years, a gas recirculation method as shown in Figure 2 has been adopted as a combustion method for coal-fired boilers. That is, a part of the coal combustion exhaust gas is passed from the outlet of the economizer 2 to the gas recirculation dust collector 18 and then to the gas recirculation fan 20.
It is extracted and recycled back to the boiler combustion chamber 1 for use in temperature control of the reheater or low NOx combustion. 21 is a denitrification device.

In this case, most of the fly ash in the recirculated gas is collected by the gas recirculation dust collector 18. A summary of the temperature and distribution amount (wt%) of fly ash stored in each hopper is as follows. In addition, the economizer hopper 6 and the denitrification device hopper 2
2. Since the amount of fly ash stored in the air preheater hopper 7 is small, the installation of these hoppers may be omitted.

Economizer hopper: 340-380°C 2-5% Denitrification device hopper: 340-380°C 1-3% Gas recirculation Dust collector hopper: 350-380°C 10-25% Air preheater hopper: 120-140'' C1-3% electrostatic precipitator hopper: 120-140°C 80-90% Although there are variations depending on the amount of gas recirculation, generally the gas recirculation precipitator hopper 23 is heated to a high temperature (350-380°C) and If a large amount of fly ash is accumulated and this fly ash is transported using a conventional low-temperature ash transport line by vacuum or pressure, as shown in Figures 3 and 4, and the transport is controlled by the same overload prevention vacuum switch. Since the same amount of high-temperature ash as the low-temperature ash is supplied into the ash transport pipe 11, the temperature of the ash transport pipe system rises, causing heat damage to the furnace cloth of the bag filter and heat damage to the backing of the ash transport pipe system. , there were problems such as thermal damage to the coating of the ash transport pipe, thermal deformation of the ash transport pipe, etc. In Figures 3 and 4, 24 is a double damper, 25 is an exhaust pipe,
26 is an inlet flue of the dust collector 4, 27 is a pressure blower, 2
8 is a new buffer tank, and 30 is a vent fan.

The present invention was made to solve the above problems,
In the gas recirculation method, the high-temperature coal ash collected by the gas recirculation dust collector is directly introduced into the inlet flue of the air preheater, thereby recovering the heat of the high-temperature ash and It is an object of the present invention to provide a method for processing coal ash that can simplify processing equipment.

Hereinafter, the configuration of the present invention will be explained based on the drawings.

5 to 7 show one embodiment of the present invention. In the method of this embodiment, as shown in FIGS. 5 to 7, the fly ash collected by the gas recirculation dust collector 18 is fed into the air preheater 30 inlet flue 31 using a pressure feeding method. be. That is, a part of the combustion exhaust gas of the coal-fired boiler is extracted from the outlet of the coal-fired boiler 2 by the gas recirculation fan 20 via the gas recirculation dust collector 18, and circulated to the boiler combustion chamber l, and the combustion exhaust gas of the coal-fired boiler is The ash stored in the hopper 6, the denitrification device hopper 22, the air preheater hopper 7, and the dust collector hopper 8 is transported from an ash supply valve 10 provided at the bottom of each hopper to an ash transport pipe 11 connected to a vacuum source or a pressure source. On the other hand, high-temperature coal ash collected by the gas recirculation dust collector 18 is passed through the ash supply valve 10a and the new buffer tank 28 to the ash transport pipe 11a. The air is directly introduced into the inlet flue 31 of the air preheater 3 by the pressure blower 27. A disperser 32 is provided at the introduction part of the air preheater inlet flue 81 so that the coal ash is uniformly dispersed within the flue 31.

8 to 10 show other embodiments of the invention. As shown in FIGS. 8 to 10, in the method of this embodiment, the fly ash collected by the Ganu recirculation dust collector 18 is continuously discharged by the rotary feeder 33, and the inlet of the air preheater 3 is It is directly injected into the flue 31. 34
3 is a dust collector inlet flue, and 35 is a dust collector outlet flue. The other configurations are the same as those shown in FIGS. 5 to 7.

As explained above, in the method of the present invention, the high-temperature coal ash collected by the gas recirculation dust collector is charged into the inlet flue of the air preheater, heat is recovered, and the coal becomes low-temperature. Since the ash is transported to the fly ash silo, it is possible to prevent heat damage and deformation of the ash transport pipe system and heat damage to the furnace cloth of the bag filter, and it is possible to downgrade the materials of these equipment. It has excellent effects such as being able to

[Brief explanation of the drawing]

Figure 1 is a systematic explanatory diagram showing a general coal ash treatment equipment, Figure 2 is a systematic explanatory diagram showing a gas recirculation type coal ash treatment equipment, and Figure 3 is a systematic explanatory diagram showing a coal ash treatment equipment using the gas recirculation method. 4 is a detailed diagram of the case in which the fly ash stored in the hopper of the gas recirculation dust collector is transported under pressure in FIG. 2; FIG. 5 is a systematic explanatory diagram showing an example of an apparatus for carrying out the method of the present invention, FIG. 6 is an explanatory diagram showing details of the Ganu recirculation dust collector hopper rotation in FIG. 5, and FIG. FIG. 6 is an enlarged view of the part surrounded by a chain line, FIG. 8 is a systematic explanatory diagram showing another example of the apparatus for carrying out the method of the present invention, and FIG. 9 is similar to FIG. 8. FIG. 10 is an explanatory view showing details of the hopper and surroundings of the gas recirculation dust collector, and is an enlarged view of the portion surrounded by the chain line in FIG. 9. 1... Boiler combustion chamber, 2... Economizer, 3... Air preheater, 4... Dust collector, 5... Clinker hopper,
6... Economizer hopper, 7... Air preheater hopper, 8
... Dust collector hopper, 10, 10a... Ash supply valve, 11, lla... Ash ft1B4't', 12...
・Flyer silo, 13... Vacuum blower, l゛4... Air suction valve, 15... Cyclone, 16...
・Bag filter, 17... Overload prevention vacuum switch 1 inch, 18... Ganu recirculation dust collector, 20... Gas recirculation fan, 21... Denitrification device, 22... Denitrification device hopper , 23... gas recirculation dust collector hopper, 24...
...Double damper, 25...Exhaust pipe, 26...Dust collector inlet flue, 27...Pressure blower, 28...New buffer cylinder, 30...Vent fan, 31...
...Air preheater inlet flue, 32...Distributor, 33...
・Rotary feeder, 34...dust collector inlet flue,
35... Dust collector outlet flue application Person Kawasaki Heavy Industries, Ltd.

Claims (1)

[Claims] 1. A coal-fired boiler economizer hopper, which extracts a part of the combustion exhaust gas from the coal-fired boiler from the economizer outlet, passes through the Ganu recirculation dust collector, and uses the Ganu recirculation fan and circulates it to the boiler combustion chamber. The ash accumulated in the recirculation dust collector hopper, denitrification equipment hopper, air preheater hopper, dust collector hopper, etc. is fed from the ash supply valve installed at the bottom of each hopper to a vacuum source or pressurized source. In the method of supplying ash into an ash transport pipe and pneumatically transporting it to a fly ash silo, etc., the feature is that the high temperature coal ash collected by the gas recirculation dust collector is directly introduced into the inlet flue of the air preheater. Coal ash treatment method.