JPH0615926B2 - Method for reburning combustion ash containing unburned matter - Google Patents

Description

TECHNICAL FIELD The present invention relates to combustion ash containing unburned matter for improving combustion efficiency by suppressing unburned matter in a boiler using a solid fuel such as coal and petroleum coke. The present invention relates to a method of reburning.

2. Description of the Related Art Recently, solid fuels such as coal and petroleum coke have been widely used as alternative fuels to petroleum due to unstable supply of petroleum and rising prices.

However, coal and petroleum coke have less volatile components than liquid fuels such as heavy oil and thus have poor combustibility, and most of them are finely pulverized and used as boiler fuel. Even so, the unburned content reaches several percent to several tens of percent, so that the combustion efficiency decreases.

In order to prevent this, a method of collecting ash collected in a hopper or the like into the furnace has been conventionally used, but the amount of recovered heat was small.

That is, FIG. 2 is a system diagram of a boiler that employs a conventional method for reburning combustion ash containing unburned matter, where 1 is a furnace, 2 is a fuel supply port, 3 is an ash hopper, and 4 is a stoker. 5 is a economizer, 6 is a hopper, 7 is a fan, 8 is an electric dust collector, 9 is a draft fan, and 10 is a chimney.

In the boiler of such a system, conventionally, the fuel supplied from the fuel supply port 2 is burned in the furnace 1, and the generated fuel gas flows upward in the furnace 1 to generate a superheater (not shown) or a node. It successively flowed into the charcoal vessel 5 part, where it exchanged heat with steam, water, etc., and was then dust-removed by the electrostatic precipitator 8 and was discharged from the chimney 10 into the atmosphere via the induced draft fan 9.

Then, the ash collected by the hopper 6 is supplied to the furnace 1 by the air flow sent from the fan 7 via the air transport pipe 11.
It was blown into the interior and was burned again. The ash collected by the electrostatic precipitator 8 was discharged to the outside of the system and discarded.

Problems to be Solved by the Invention The amount of ash recovered from the hopper 6 is about 5% of the total amount, and the amount of unburned heat contained in the ash is about 0.2% of the total amount. It only happens. Therefore, most of the unburned matter was simply discarded.

When burning solid fuel with low ash content, the heat value of the ash collected by the dust collector may still be several thousand Kcal / Kg.
It is an energy loss to discard this without collecting it.

In addition, since a large amount of unburned ash results in a large amount of collected ash, the cost required for the treatment of the collected ash is large due to pollution.

These are the biggest disadvantages when using solid fuel.

Means for Solving the Problems In order to solve the above problems, the present invention relates to a combustion apparatus in which solid fuel is pulverized into fine powder and is supplied to a furnace for combustion, and combustion ash in combustion exhaust gas is used. Is collected, and a part of the combustion ash is mixed with the fine powder, and the combustion promotion of the fine powder is measured by utilizing the catalytic action of Fe and Mg-based elements contained in the combustion ash and regenerating the combustion ash. It is designed to burn.

Action When combusting pulverized fuel, the unburned matter contained in the combustion exhaust gas is generated due to insufficient combustion time of the fixed carbon of the solid fuel, and the particle size of the collected ash depends on the fuel. It is about the same as the grain size. Therefore, when the ash in the fuel exhaust gas is collected, mixed with the fine powder fuel and re-burned, the unburned content is reduced because the combustion time is long and the Fe and Mg-based elements contained in the ash are burned. Acting as a promoter, the combustion effect of the fuel is activated, the unburned content is greatly reduced, and the energy loss can be minimized.

Embodiment One embodiment of the present invention will be described in detail below with reference to FIG. In FIG. 1, the same parts as those in FIG. 2 are designated by the same reference numerals, and the description thereof will be omitted.

In FIG. 1, 12 is a fuel hopper, 13 is a mill for crushing solid fuel such as coal or coke into fine powder, 14 is a fine powder tube, 15 is a bag filter, 16 is a bottle, 17 is a mixed fine powder tube, 18 Is an ash transport pipe, 19 is an ash bottle, 20, 2
Reference numerals 1 and 22 are ventilation fans, respectively.

Fine fuel pulverized by the mill 13 from the burner 2 is the furnace 1
It is thrown in and burned. Then, the exhaust gas generated by the combustion is introduced into the electrostatic precipitator 8, the solid content in the exhaust gas is collected, and the exhaust gas from which the solid content is removed is discharged from the chimney 10 to the atmosphere via the induced draft fan 9. To be done.

On the other hand, the solid content collected by the electrostatic precipitator 8 is ash containing unburned content, and has a particle size similar to that of the pulverized fuel. Then, this ash is merged with the fine powder pipe 14 through the ash transport pipe 18 by the blower 22 and mixed with the fine powder fuel sent from the mill 13. The mixed powder of ash and fine fuel is sucked by the fan 21 at the outlet of the bag filter 15 and stored in the bottle 16. Then, the mixed powder of ash and fine fuel stored in the bottle 16 is extruded by the primary air blower 20 and supplied to the burner 2 through the mixed fine powder tube 17 for combustion.

The amount of ash to be mixed with the pulverized fuel may be all or part of the ash collected by the electrostatic precipitator 8, so that the ash can be made to bleed into the ash bin 19. . Further, if the entire amount of ash collected by the electrostatic precipitator 8 is circulated, the amount of ash in the boiler 1 will gradually increase, so it is preferable to intermittently bleed in order to prevent this. , 20 for continuous mixing
% Ash is preferably allowed to bleed into the ash bin 19.

Effects of the Invention As described in detail above, according to the present invention, in a combustion device that pulverizes and pulverizes solid fuel and supplies it to a furnace for combustion, the combustion ash in the flue gas is collected and burned. Part of the ash is mixed with the derivative, and F contained in the combustion ash
Since the combustion of the fine powder was promoted and the combustion ash was recombusted by utilizing the catalytic action of e and Mg-based elements,
It is possible to greatly reduce the unburned content and greatly contribute to the improvement of combustion efficiency. The electric dust collector can collect 99% of ash, and even if you subtract 5% of ash accumulated in the upstream hopper, 90% or more of ash is collected and reburned.
It can be seen that the amount of heat recovered is greatly improved. In addition, the amount of ash taken out from the electrostatic precipitator will be reduced, and the efficiency of processing the ash and reducing the cost thereof can be obtained.

[Brief description of drawings]

FIG. 1 is a system diagram showing an example of a boiler for carrying out the present invention,
FIG. 2 is a system diagram of a boiler that implements a conventional method for reburning combustion ash. 1 ... Furnace, 2 ... Burner, 8 ... Electrostatic precipitator, 13 ...
… Mill, 14… Fine powder tube, 17… Mixed fine powder tube, 18…
… Ash transport tube, 19… Ash bin.

Claims (1)

[Claims] 1. A combustor in which solid fuel is pulverized into fine powder and supplied to a furnace for combustion, and the combustion ash in combustion exhaust gas is collected, and a part of the combustion ash is mixed with the fine powder. Fe, Mg contained in the combustion ash, utilizing the catalytic action of the Mg-based elements to promote the combustion of the fine powder, the combustion ash is reburned, combustion containing unburned content, How to reburn ash.