JPH0656245B2 - Combustion control method for pulverized coal combustion device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention has a small amount of unburned matter even if fuel coals of different types having different fixed carbon content ratios to volatile matter are simultaneously supplied and burned. The present invention relates to a combustion control method for a pulverized coal combustion device that can reduce nitrogen oxides (NO _x ) in the inside.

[Problems to be Solved by Prior Art and Invention]

The composition ratio of the fixed carbon content to the volatile matter in the fuel coal is called the fuel ratio, the one having a higher fixed carbon content than the volatile matter is the high fuel ratio coal, and the lower one is the low fuel ratio coal.

Since the available fuel coal is affected by supply and demand conditions, it is extremely rare to burn only one type of fuel coal, and normally different types of fuel coal are mixed and burned. However, in the conventional combustion apparatus is not suitable for reducing the occurrence of unburned and NO _X.

Therefore, by burning different kinds fuel coal simultaneously possible to reduce the unburned and NO _X, GoTsuta pulverized coal combustion apparatus to supply and demand of fuel coal is desired.

In an example of a conventional pulverized coal combustion apparatus, different types of fuel coal are uniformly mixed by a coal mixing mechanism, and then pulverized by a fine pulverizer (ball mill). The pulverized coal combustor (mixed coal combustor) is configured to supply the uniformly mixed pulverized coal to a burner by a transport mechanism to perform combustion. However, when the fuel coal is subjected to a ball mill, the high fuel ratio coal becomes pulverized coal earlier and the low fuel ratio coal becomes later. From this, it is better to make a desired amount of pulverized coal in a ball mill after mixing fuel coals with different fuel ratios than to make the same amount of pulverized coal in a ball mill separately for each type. However, there is a drawback that the power cost of the ball mill is high. Moreover, in this mixed coal combustion device,
The finer the powder having a low fuel ratio, the more rapidly it burns and the oxygen in the supplied air is consumed. Therefore, the high fuel ratio coal, which is difficult to burn, always burns in a state of insufficient oxygen.

However, in order to burn an extremely high pulverized coal with a high fuel ratio, a small amount of pulverized coal with a low fuel ratio may be mixed to accelerate ignition. This is one means, and it does not correspond to the case where different kinds of pulverized coal are burned at the same time, and the conventional drawbacks cannot be improved.

Another conventional example is a pulverized coal combustor that performs pulverized coal pulverization with a ball mill for each fuel coal with a different combustion ratio, and supplies it to the burner by the pulverized coal transport mechanism without mixing the pulverized coal (combustion combustion). Device). When burning pulverized coal having an extremely different fuel ratio, the calorific value between the burners is likely to be unbalanced. Therefore, the amount of pulverized coal supplied to each burner, the throat flow velocity of the pulverized coal, and the like must be adjusted to equalize the heat generation amount between the burners. Further, when burning a high-fuel ratio high-nitrogen content coal, it is necessary to adjust the burner air ratio, the pulverized coal charging position of the burner, and the like.

As described above, the conventional combustion apparatus not suitable reducing physicians unburnt and NO _X, even require complicated operations even in the burning in favorable conditions.

An object of the present invention is to provide a combustion control method of the exception of disadvantages, fuel ratio different even pulverized coal was simultaneously burned reduced capable pulverized coal combustion apparatus of the unburned and NO _X.

[Means for Solving the Problems]

In order to achieve this object, a combustion control method of a pulverized coal combustion apparatus of the present invention is a furnace for burning pulverized coal, a burner provided in the furnace, and a pulverized coal transfer mechanism for transferring pulverized coal to the burner. And a pulverized coal combustor including a pulverizer for producing the pulverized coal.

Further, at least a first pulverized coal supply passage and a second pulverized coal supply passage are provided in one burner, and the first pulverized coal supply passage is supplied with the fine powder supplied from the second pulverized coal supply passage. Pulverized coal (low fuel ratio pulverized coal), which has a lower ratio of fixed carbon to volatile matter than coal, is supplied together with the carrier gas and burned under conditions of low oxygen partial pressure to form a reducing flame in the furnace. Let

On the other hand, in the second pulverized coal supply passage, pulverized coal having a higher ratio of fixed carbon amount to volatile matter (high fuel ratio pulverized coal) than in the first pulverized coal supply passage is supplied. It is characterized in that it is supplied together with a carrier gas and burned under a condition of high oxygen partial pressure to form an oxidizing flame in the furnace.

[Work]

As described above, according to the present invention, since pulverized coal with a high fuel ratio which is relatively incombustible is burned under the condition of high oxygen partial pressure, the combustion state is good and the generation of unburned matter is suppressed. Further, since the NO _X generated at this time is decomposed by the reducing gas generated in the combustion region of the pulverized coal having a low fuel ratio, the NO _X can be reduced, and the unburned content and N
Emissions of O _X is small.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. Furnace 1
The burner throat 2 is formed on the wall of the. Pulverized coal supply paths 4 and 6 and air supply paths 3 and 5 are concentrically provided at the opening of the burner throat 2. A swirler 7 such as a vane is provided at the opening of the innermost pulverized coal supply path 6 on the furnace 1 side, and although not shown, a ball mill, a mixing means for mixing the exhaust gas with the air, and the mixing means A first pulverized coal supply mechanism is formed together with a conveying unit that conveys the pulverized coal to the pulverized coal supply path 6 with the generated mixed gas. A swirler 8 such as a vane is provided at the opening of the outer side pulverized coal supply path 4 on the side of the furnace 1, and although not shown, it is a mechanism similar to the first pulverized coal supply mechanism, but separately from the ball mill. A second pulverized coal supply mechanism is configured with the mixing means, the conveying means, and the like.

Air registers 9, 10 housed in a wind box (not shown) are provided near the furnace 1 side opening of the air supply path 5 and in the vicinity of the burner throat 2 of the air supply path 3.

The combustion mechanism of the pulverized coal combustion device having the above structure will be described. The low-fuel-ratio pulverized coal finely pulverized by the ball mill of the first pulverized coal supply mechanism is conveyed to the pulverized coal supply path 6 through the conveying means together with the mixed gas made of almost exhaust gas generated by the mixing means, and swirled. It is made into a vortex by the vessel 7 and supplied to the furnace 1. In the second pulverized coal supply mechanism, the pulverized high fuel ratio pulverized coal pulverized by the ball mill is not mixed with the air of the mixing means (only the air because the mixing of the exhaust gas by the mixing means is stopped) via the conveying means. Is carried to the pulverized coal supply path 4, is swirled by the swirler 8 and supplied to the furnace 1.

The combustion area 11 of pulverized coal with low fuel ratio is maintained in a reducing atmosphere such as hydrocarbon gas (reduction flame is formed) because the amount of oxygen in the mixed gas used for transportation is extremely small, and negative pressure is generated by the vortex flow. is doing. In the combustion region 12 of high fuel ratio pulverized coal,
Sufficient air is supplied by the air registers 9 and 10, and a strong vortex flow is generated particularly by the swirler 8 and the air register 9, so that rapid and efficient combustion by the oxidizing flame is performed. The combustion gas in the combustion region 12 is inevitably attracted by the negative pressure generated in the combustion region 11, NO _X is decomposed in the reducing atmosphere, and becomes an exhaust gas with a very small amount of unburned components and NO _X.

As described above, the fuel coal to be used is not always the same because it is influenced by the supply and demand situation, but in this embodiment, the oxygen amount of the mixed gas for transportation is adjusted by the mixing means of the first pulverized coal supply mechanism. It is possible to deal with the reduction of NO _X and unburned matter by simply adjusting

For example, the calorific value of the low fuel ratio pulverized coal supplied by the first pulverized coal supply mechanism is equal to the total calorific value of all the pulverized coal supplied to the furnace 1.
If it is 15% or less, pulverized coal with a low fuel ratio is conveyed only by the exhaust gas, and pulverized coal with a high fuel ratio is conveyed together with sufficient air for combustion. When the calorific value of the low fuel ratio pulverized coal is about 50% of the total calorific value of all the pulverized coal, the mixing means is adjusted so that the low fuel ratio pulverized coal is conveyed by the air, the exhaust gas and the mixed gas. Combustion is carried out by carrying with sufficient air.

Thus in some regulation, the combustion region 11, 12 is maintained at the optimum oxygen partial pressure, it is possible to reduce the unburned and NO _X.

In the above embodiment, although not shown, a flame stabilizer such as an impeller is additionally provided at the opening of the pulverized coal supply passages 4 and 6 on the furnace 1 side to stabilize the flame, and the pulverized coal supply passages are also provided. 4 and each of the air supply passage 3 and 5, are provided with a pipe to draw the exhaust gas regulating lines a connexion of high fuel ratio pulverized coal and throat velocity of feed air, to accelerate the reduction of unburned and NO _X .

Further, in the above-mentioned embodiment, the air supply passages 3 and 9 are provided in order to burn the pulverized coal having a high fuel ratio, which is difficult to burn, with high efficiency. However, if the air supply passage 3 alone can provide sufficient air supply. The pulverized coal supply passage 4 may be arranged outside the pulverized coal supply passage 6 without providing the air supply passage 5. Needless to say, the swirler 9 and the like provided in the air supply passage 5 are also excluded.

〔The invention's effect〕

As described above, according to the present invention, since pulverized coal with a high fuel ratio which is relatively incombustible is burned under the condition of high oxygen partial pressure, the combustion state is good and the generation of unburned matter is suppressed.

Further, the NO _X generated at this time is decomposed by the reducing gas generated in the combustion region of the pulverized coal with a low fuel ratio, so that the NO _X can be reduced, and the combustion control of the pulverized coal combustion device that emits less unburned components and NO _X. A method can be provided.

Further, in the conventional combustion device, a plurality of burners are provided to adjust the supply position of pulverized coal in order to obtain the denitration effect.
Since the burner according to the present invention can obtain the denitration effect while being a single body, it is possible to make the apparatus compact and improve the operability.

Further, the exhaust gas circulating equipment for the NO _X reduction measures provided in the conventional combustion device has versatility to be used as it is in the combustion device of the present invention.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of a pulverized coal combustion apparatus according to an embodiment of the present invention. 1 ... Furnace, 2 ... Burner throat, 4, 6 ... Pulverized coal supply passage, 3, 5 ... Air supply passage, 7, 8 ... Swirler,
9, 10 ...... Air register, 11 ...... Low fuel ratio pulverized coal combustion area, 12 ...... High fuel ratio pulverized coal combustion area.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hitoshi Migaki 6-9 Takara-cho, Kure-shi, Hiroshima Babkotuku Hitachi Co., Ltd. Kure Factory (72) Kiichi Itagaki 6-9 Takara-cho, Kure-shi, Hiroshima Babkotsu Hitachi Stock Company Kure Factory (72) Inventor Fumio Koda 6-9 Takara-cho, Kure City, Hiroshima Prefecture Babkotsu Hitachi Ltd. Kure Factory (56) References Japanese Patent Publication No. 61-38961 (JP, B2)

Claims (4)

[Claims] 1. A pulverized coal provided with a furnace for burning pulverized coal, a burner provided in the furnace, a pulverized coal transfer mechanism for delivering pulverized coal to the burner, and a pulverizer for producing the pulverized coal. In the combustion device, one burner is provided with at least a first pulverized coal supply passage and a second pulverized coal supply passage.
Pulverized coal supply passage is provided, and the first pulverized coal supply passage has a lower proportion of fixed carbon amount to volatile matter than the pulverized coal supplied from the second pulverized coal supply passage ( (Low fuel ratio pulverized coal) is supplied together with the carrier gas and burned under conditions of low oxygen partial pressure to form a reducing flame in the furnace, while the second pulverized coal supply path is provided with Pulverized coal with a higher ratio of fixed carbon to volatile matter (higher fuel ratio pulverized coal) than the pulverized coal supplied from the No. 1 pulverized coal supply channel is supplied together with the carrier gas under high oxygen partial pressure conditions. A combustion control method for a pulverized coal combustion apparatus, which comprises combusting to form an oxidizing flame in the furnace. 2. In the claim (1),
A combustion control method for a pulverized coal combustion apparatus, wherein at least exhaust gas is contained in the carrier gas supplied to the first pulverized coal supply passage. 3. In the claim (1),
A combustion control method for a pulverized coal combustion apparatus, characterized in that a negative pressure is generated in the reducing flame formation region. 4. In the claim (1),
A combustion control method for a pulverized coal combustion apparatus, characterized in that a strong vortex flow is generated in a region where the oxidizing flame is formed.