JP2816694B2 - Low volatile coal combustion equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to the combustion of low volatile coal, especially low volatile content suitable for obtaining stable ignition and flame holding of low volatile solid fuel such as anthracite. The present invention relates to a device for burning coal.

[Conventional technology]

In a conventional method for burning low volatile coal such as anthracite, 10 to 30% of a combustion assisting fuel (mainly oil) is used. In this case, since ignition and flame holding are stably and continuously maintained by the auxiliary fuel, no special consideration is given to the transport of anthracite and the means for charging the furnace, and usually, a slit having a shape like a tail fin of a fish is used. Flow into the furnace at a low flow rate and downward. With this method, anthracite can be used as fuel for power generation boilers and the like without hindrance, but power generation costs are affected because a large amount of expensive oil fuel is used. For this reason, recently, an attempt has been made to use a cyclone or a revolving burner.

However, due to insufficient treatment for the extremely difficult to ignite characteristics of low volatile coal, the maximum feature of the swirl burner, that is, "maintaining stable combustion flame by recirculation in the flame" is fully utilized. I didn't.

In other words, despite the fact that burning low volatile coal such as anthracite depends on how quickly the fine coal powder is heated to the ignition temperature, a technology that takes this point into full consideration has been developed. Did not.

That is, the problem of stable ignition and flame holding of anthracite is that its ignition temperature is very high, some anthracite reaches 800 ° C or more, and the ignition temperature of normal bituminous coal depends on the measurement method.
In contrast to the temperature of 400 to 450 ° C., the time to ignition (hereinafter referred to as ignition time) requires twice or more times when anthracite is put into a furnace using the same burner as bituminous coal. Therefore, the state of ignition cannot be reached in the recirculation region of the swirling burner jet, and it is extremely difficult to maintain the flame without the help of the auxiliary fuel.In order to cover the delay of the ignition time and maintain stable combustion, the oil The use of auxiliary fuels, such as, is essential for a wide range of boiler loads.

[Problems to be solved by the invention]

In the conventional method of burning low volatile coal, the ignition temperature of anthracite or the like is extremely high, and the ignition time is delayed.

An object of the present invention is to mix and supply high-temperature air with a minimum flow rate necessary for ignition to fine-particle particles of low-volatility coal, and adjust the pulverized coal concentration in a stagnant region near a burner throat. An object of the present invention is to provide an apparatus for burning low volatile coal.

[Means for Solving the Invention]

In order to achieve the above object, the low-volatile coal combustion device according to the present invention separates a mixture of pulverized coal obtained by pulverizing low-volatile coal and air for transport, and at least a part of the air. And a pipe for mixing and blowing the air-fuel mixture blown down from the cyclone with high-temperature air, and a flow path connected to the pipe and flowing to the center of the pipe. In a low-volatility coal combustion device in which a divergent sleeve is installed from the upstream side to the downstream side, the sleeve is formed at a divergent conical small sleeve that forms a stagnation region and at a divergent end of the small sleeve. A louver-shaped slit and a divergent nozzle formed through the slit.

[Action]

According to the present invention, as a method of burning low-volatile coal, by extracting extra air from the air-fuel mixture separated by a cyclone and mixing high-temperature air, the air in the air-fuel mixture has a predetermined flow rate and a predetermined temperature. It is adjusted to. The stagnation region is formed on the center axis side of the sleeve by connecting to a conduit for supplying the air-fuel mixture and providing a divergent cone-shaped sleeve on the main burner throat. On the other hand, the pulverized coal in the air-fuel mixture that has passed through the sleeve is separated and injected into the stagnation region through a slit provided in the sleeve.

That is, in the stagnation region, the flow of the air-fuel mixture is blocked by the small sleeve, and the downstream side is open, so that the inside of the small sleeve is a stagnation region. Next, in the louver-shaped slit, the collar that spreads toward the downstream side
The relatively coarse pulverized coal in the air-fuel mixture has a large inertial force, and then goes outward after hitting the brim. However, fine pulverized coal has a small inertia force and is accompanied by a part of the air that flows in because the inside of the small sleeve becomes negative pressure.
Inflow toward the center of the burner. Next, the air-fuel mixture of the fine pulverized coal and the air flows toward the center of the burner at the divergent injection port (skirt) downstream of the sleeve. Although this spout has a slit on the upstream side,
The upstream side is a stagnant area, which is a low flow velocity area because only a part of the air-fuel mixture flows from the slit. Therefore, fine coal that is easy to burn is always supplied, and high-temperature combustion gas circulates from the outer periphery of the high-velocity region into the negative pressure injection port. A flame is formed.

〔Example〕

One embodiment of the present invention will be described with reference to FIGS.

As shown in FIG. 1, a mixture of pulverized coal obtained by pulverizing low-volatile coal and air for conveyance is conveyed to a cyclone 10 via a pipe 30 and at least one of the air separated by the cyclone 10 is separated. The part is extracted via the pipe line 32 and is supplied to, for example, the pair burner 200. After the remainder is blown down to the pipe section 31, the high-temperature air 34 is mixed to adjust the flow rate and temperature of the air in the mixed air to predetermined values, and the main burner (main burner throat) is passed through the pipe 33. ) 100 is configured to feed.

Then, as shown in FIG. 2, a sleeve 600 connected to the pipe 33 for supplying the air-fuel mixture and having a flared cone shape along the central axis of the pipe 33 is disposed in the main burner throat 100, The small sleeve 600A has a stagnant area 90 of pulverized coal on the center axis side.
And a louver-shaped slit 601 communicating with the stagnation region 90 is provided, and pulverized coal in the air-fuel mixture that has passed through the injection port 600B via the slit 601 is injected downstream of the stagnation region 90.

Anthracite pulverized coal pulverized by the mill 20 is fed through the pipe 30 by low-temperature carrier air at 80 to 110 ° C. The weight ratio of the mixture of pulverized coal and air is, for example, 0.3 to 1.0 kg.
/ kg, and most of the pulverized coal is collected by the cyclone 10 installed on the downstream side.
The amount of air blown down to the pipeline 31 by a damper (not shown) installed in each of the pipelines 32 is adjusted to 5 to 30% of the transport air flowing through the pipeline 30. In this state, conduit 31
The temperature of the air-fuel mixture flowing through is 80-90 ° C, and the weight ratio of pulverized coal to air is 1.5-5.0 kg / kg. This state quantity is mill 20
And a value determined by the performance of each of the cyclones 10, and is not necessarily an appropriate state quantity in consideration of the burner turndown ratio and the optimum throat flow velocity. In order to improve this state quantity, high-temperature air from, for example, an air heater supplied from the booth-up fan 50 via the pipeline 51 becomes effective. By supplying the high-temperature air, for example, the state quantity of the air (high-temperature primary air) passing through the pipe line 33 is reduced to a temperature of 20 degrees.
0 to 300 ° C., the weight ratio of pulverized coal to air can be 0.5 to 2.0 kg / kg, and at least the main burner 100 can obtain optimum ignition conditions. On the other hand, vent air flowing through the pipe 32 is not only unnecessary for ignition, but also inhibits formation of various ignition atmospheres. For this reason, as shown in FIG. It is. The main burner 100 and the pair burner 200 are of a cell type operated in pairs, and the pair burner 2 is operated by the flame holding effect of the main burner 100.
00 flame holding is supported.

As shown in FIG. 2, the main burner 100 has a diverging conical sleeve (diverging bluff body) comprising a small sleeve 600A and an injection port 600B so as to provide a stagnation region (dead space) 90 at the center thereof. Sleeve) 600,
A louver-shaped slit (louver-type suction slit) 601,
In addition, a flame holding ring 700 is provided. In addition, since the pulverized coal particles have a phenomenon of drifting and agglomeration (force acting between particles due to static electricity or the like in a dry atmosphere) in the pipe 33, an abrasion-resistant material such as ceramic is used to disperse the particles unevenly. The formed dispersion plate 500 is installed. A turning register 70 is provided on the upper surface of the main burner throat 100, and the inner peripheral secondary air 71 and the outer peripheral secondary air 72 are separated by a guide sleeve 800 on the downstream side.

 Next, the operation of the present embodiment will be described.

First, a minimum required amount of air (primary air) is obtained by classifying and collecting in the cyclone. This flow rate is determined by the characteristics of the cyclone classification efficiency, as shown in FIGS. 3 and 4, and blows down only the minimum flow rate of air necessary for ignition of the pulverized coal particles, and the flow rate near the burner throat is reduced. By supplying the region, waste time for raising excess air to the ignition temperature of the fuel is eliminated. For this reason, the pulverized coal / air mixture (usually weight ratio <1 kg / kg) downstream of the mill is separated into gas and solid in the cyclone, and the cyclone has a good blowdown ratio of 5 to 30% with good cyclone classification efficiency. The pulverized coal particles are concentrated and separated without remaining in the inside.

Next, by adding a hot air line, the temperature of the air-fuel mixture of pulverized coal and the air for conveyance is increased, the ignition time is minimized, and the momentum of the conveyance air sufficient for the burner turndown is obtained. That is, by mixing high-temperature air of 300 ° C. or more, a high-temperature and concentrated pulverized coal-air mixture can be obtained. This operation can be conceptually explained by the following equation.

Pulverized coal particle temperature = air temperature for the transport = tp = t ₁ (initial condition) Density of specific heat = c pulverized coal particles having an average radius = gamma pulverized coal particles in the furnace gas temperature = tg pulverized coal particles = [rho pulverized coal particles Heat transfer coefficient of α pulverized coal particles = ignition temperature of t pulverized coal particles = Q, and assuming time as dz, dQ = α4πγ ² θdz (θ = tg-tp) When There d [theta] temperature rises, therefore dQ = -4 / 3πγ ³ cρdθ, thus ^{α4πγ 2 θdz = -4 / 3πγ 3} cρdθ dz = -cργ / 3α · dθ / θ, ignition time and z Although the ignition time depends on the value of γ, the transfer air temperature is 100 ° C.
It can be seen from the preceding equation that the temperature at 300 ° C. is almost halved as compared with the case of (1).

Furthermore, a stagnant region (dead space) having a divergent shape is formed on the main burner center axis side of the sleeve by forming an annular divergent injection port by a divergent cone-shaped sleeve connected to the pipeline (high-temperature primary area) 33. , A high-temperature stagnation area suitable for ignition and flame holding. Then, the fine particles separated from the louver-type suction slit can be selectively injected.

In this way, the inner peripheral air and the fine particles are mixed in the recirculation region stabilized by the action of the strong swirling secondary air swirling through the swirl register, and a stable flame is maintained.

The main burner shown in FIG. 2 is an embodiment in which the present invention is applied to a swivel burner, but can be easily extended to a conventional fishtail type inter-tube burner.

In the above embodiment, the cyclone and the burner are provided separately. However, as long as the function is not lost, the cyclone can be built in the burner.

〔The invention's effect〕

According to the low volatile coal combustion device of the present invention, by adjusting the air in the air-fuel mixture to the required minimum amount and raising the temperature, the ignition time can be reduced without using an auxiliary combustion charge,
By forming a stagnant area by a small sleeve in the main burner throat, ignition and flame holding are performed, and stable combustion is obtained.

Oilless combustion of anthracite is realized, and the piping for auxiliary fuel can be reduced, and the furnace width can be expected to be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG.
FIG. 3 is an enlarged cross-sectional view of a main part of the drawing, FIG. 3 is an external view of the cyclone shown in FIG. 1, and FIG. 4 is a graph illustrating cyclone efficiency. 10 Cyclone, 33 Pipe line (air-fuel mixture), 34 High temperature air, 90 Stagnation area, 100 Main burner, 600 Sleeve, 600A Small sleeve, 600B Spout, 601 …… Slit.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Koji Kuramasu, Inventor 6-9 Takara-cho, Kure City, Hiroshima Pref. Inside the Kure Plant of Babkotsu Hikku Co., Ltd. (56) References JP-A-62-182526 (JP, A) 62-39132 (JP, U) Japanese Utility Model Showa 62-75345 (JP, U) Japanese Utility Model Showa 63-23516 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) F23D 1/00 F23C 11/00 305 F23K 3/02 302

Claims (1)

(57) [Claims] 1. A cyclone for separating a mixture of pulverized coal obtained by pulverizing low-volatile coal and air for transportation, extracting at least a part of the air and blowing down the remainder, and a blowdown from the cyclone. A pipe for mixing the mixed gas with the high-temperature air and feeding the mixed gas, and a sleeve connected to the pipe and diverging from the upstream to the downstream of the flow of the gas mixture in the center of the pipe. In the low-volatility coal combustion device, the sleeve is formed through a divergent conical small sleeve that forms a stagnant region, a louver-shaped slit formed at the divergent end of the small sleeve, and the slit. A low volatility coal combustion apparatus characterized by comprising a divergently extending orifice.