JPH0333961B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pulverized coal combustion method and apparatus.

Recently, as a means of burning cement raw materials in a cement rotary kiln, there is a method of using pulverized coal as a fuel instead of heavy oil and burning this in the rotary kiln.

The general combustion method for this type of pulverized coal is to use a conventional heavy oil combustion device, which supplies low-temperature primary air and pulverized coal into the furnace. The combustion was carried out in the presence of high temperature secondary air supplied inside the tank.

However, in the conventional combustion method described above, primary air and pulverized coal are supplied to the nozzle of the combustion device at a relatively low temperature, and the pulverized coal and primary air are ignited in the ignition area near the nozzle by high-temperature secondary air in the furnace. Since the temperature had to be raised all at once to the combustion temperature, the ignition speed and combustion speed were slow, resulting in poor combustion efficiency, making it difficult to achieve high-load combustion.

The present invention has been made based on the above-mentioned viewpoints, and includes supplying high-temperature primary air and low-temperature primary air as primary air into a combustion device, and using the low-temperature primary air heated by the high-temperature primary air to fill the combustion device with high temperature primary air and low-temperature primary air. By gradually raising the temperature of the pulverized coal, the temperature of the pulverized coal near the nozzle of the combustion device approaches the ignition temperature, which speeds up the ignition speed and combustion speed of the pulverized coal in the ignition area of the combustion furnace, resulting in high loads. The object of the present invention is to provide a pulverized coal combustion method and combustion device for facilitating combustion.

The basic structure of the pulverized coal combustion method according to the present invention is that high-temperature primary air and low-temperature primary air, which has a higher flow rate than this high-temperature primary air, are separately fed into a combustion device, and the temperature is raised by the high-temperature primary air. The temperature of the pulverized coal in the combustion device is gradually raised by low-temperature primary air, and this low-temperature primary air is supplied to the vicinity of the pulverized coal spout.

In addition, the basic configuration of the combustion equipment for carrying out the above method is to configure each supply pipe of high temperature primary air, low temperature primary air, and pulverized coal with multiple pipes arranged concentrically, and to supply high temperature primary air. A low temperature primary air supply pipe having a smaller cross-sectional area than the high temperature primary air supply pipe is interposed between the pipe and the pulverized coal supply pipe.

Generally, low-temperature primary air has a higher air density than high-temperature primary air, but in the above configuration, the flow rate of this low-temperature primary air is increased and it is supplied near the pulverized coal injection port, so the low-temperature primary air is oxygen-rich. The pulverized coal can be combusted with air, and mixing with the pulverized coal, which cannot be supplied at such a high speed due to wear of the combustion device, is further promoted.

In addition, since the temperature of the pulverized coal is gradually raised in the combustion equipment via low-temperature primary air, it is possible to avoid a sudden temperature rise of the pulverized coal within the equipment, and the flow rate of the low-temperature primary air can be adjusted. Temperature control can also be easily performed.

On the other hand, according to the combustion apparatus according to the present invention, since the cross-sectional area of the low-temperature primary air supply pipe is formed smaller than that of the high-temperature primary air supply pipe, it is easy to increase the flow velocity of the low-temperature primary air. In addition, since the low-temperature primary air supply pipe is interposed between the high-temperature primary air supply pipe and the pulverized coal supply pipe, it is easy to mix the pulverized coal with the low-temperature primary air, and the pulverized coal is It becomes possible to gradually raise the temperature.

The temperature of the high temperature primary air used in the following examples is optimally within the range of 500 to 800°C, and the average particle size of the pulverized coal is 500°C to 800°C.
We use powder that has been crushed to about mm size.

The present invention will be described in detail below based on embodiments shown in the accompanying drawings.

FIGS. 1 and 2 show an embodiment of a combustion apparatus for carrying out the pulverized coal combustion method according to the present invention.

This combustion device 1 is composed of a cylindrical body in which primary air and pulverized coal supply pipes have a coaxial multi-pipe structure, and from the center to the outer periphery are a high temperature primary air supply pipe 2, an inner low temperature primary air supply pipe 3, a pulverized coal Supply pipe 4
and an outer low-temperature primary air supply pipe 5 in this order. Note that the low-temperature primary air supply pipes 3 and 5 have a narrower space and a smaller cross-sectional area than the high-temperature primary air supply pipe 2, so the flow rate of the low-temperature primary air flowing therethrough is greater than that of the high-temperature primary air.

At the inlet ends of the high temperature primary air supply pipe 2, the inner low temperature primary air supply pipe 3, and the outer primary air supply pipe 5, dampers 6, 7, and 8 for adjusting the supply amount are provided, respectively, to optimize the supply amount each time. adjusted to meet the conditions.

Furthermore, swirl vanes 9, 10, and 11 are provided at the end of each spout of the high-temperature primary air supply pipe 2, the inner low-temperature primary air supply pipe 3, and the pulverized coal supply pipe 4, respectively, for swirling and spouting the feed material. These swirl vanes 9, 10, 1 are provided at four locations during combustion.
By the action of 1, high temperature primary air, low temperature primary air and pulverized coal can be ejected at appropriate diffusion angles and flow rates. In addition, each swirl vane 9, 10, 11
By appropriately changing the turning angle and the number of particles, it is possible to adjust the ejection diffusion angle, diffusion speed, etc. of the primary air and pulverized coal, and change the combustion state of the pulverized coal. Note that the swirling vanes 9, 10, and 11 are not necessarily provided, and the primary air and pulverized coal may be jetted out straight. Further, reference numeral 12 in FIG. 1 is a support wall for supporting the combustion device 1.

Note that primary air and pulverized coal are supplied to each supply pipe by forced means via a transport pipe (not shown) connected to the inlet end of each supply pipe.

Therefore, when pulverized coal is burnt using a combustion device configured as described above, the temperature of the low-temperature primary air flowing around the periphery is first raised by the high-temperature primary air at the center, and then the low-temperature air after the temperature rise is raised. The primary air further gradually raises the temperature of the pulverized coal flowing around its outer periphery to an appropriate temperature, and preheats the pulverized coal particularly at the ejection port so that it approaches the ignition temperature. Therefore, in the ignition area near the injection port in the combustion furnace, preheated pulverized coal is quickly ignited by the high-temperature primary air and the high-temperature secondary air in the furnace, and because it is preheated, the combustion rate is low. At the same time, low-temperature primary air with high air density is supplied to the vicinity of the pulverized coal spout from both the inside and outside at a high velocity. Mixing with pulverized coal, which cannot be mixed, is carried out appropriately, and as a result, combustion efficiency is increased and high-load combustion is facilitated. Moreover, in the above combustion method, the pulverized coal is not directly heated with high-temperature primary air in the combustion device, but is indirectly heated via low-temperature primary air, so the temperature of the pulverized coal is gradually raised in the combustion device. This prevents pulverized coal from igniting within the combustion equipment due to a sudden temperature rise, ensuring safe and stable operation of the combustion equipment. Further, the temperature increase control of pulverized coal can be performed safely and easily by adjusting the flow rate of low-temperature primary air.

3 and 4 show other embodiments of the combustion device.

The combustion device 1 in this embodiment is composed of a cylindrical body having a coaxial multi-tube structure, similar to the previous embodiment, but unlike the previous embodiment, the combustion device 1
In order from the center to the outer circumference, an inner low-temperature primary air supply pipe 13, a pulverized coal supply pipe 14, an outer low-temperature primary air supply pipe 15, and a high-temperature primary air supply pipe 16 are arranged in this order. That is, the low temperature primary air and pulverized coal flowing inside are heated and supplied by the high temperature air flowing on the outer circumferential side. Therefore,
The diameter of each supply pipe is different from that of the embodiment described above, and the cross-sectional area is smaller than that of the inner low-temperature primary air supply pipe 13 at the center and the high-temperature primary air supply pipe 2 at the center of the combustion device 1 in the embodiment described above. The outermost high-temperature primary air supply pipe 16 has a larger supply path than the outer low-temperature primary air supply pipe 5 of the embodiment described above, so that the flow rate of low-temperature primary air can be increased. Adjusting the primary air supply amount.

In addition, an inner low-temperature primary air supply pipe 13 and an outer low-temperature primary air supply pipe 15 sandwiching the pulverized coal supply pipe 14,
Furthermore, dampers 17, 18, and 19 for adjusting the supply amount are provided at each inlet end of the outermost high-temperature primary air supply pipe 16, as in the previous embodiment, and the inner low-temperature primary air supply pipe 13 , pulverized coal supply pipe 14
Similarly to the embodiment described above, swirl vanes 20, 21, and 22 for swirling and ejecting the feed material are also provided at each outlet end of the outer low-temperature primary air supply pipe 15, respectively.

Therefore, in this embodiment, the low-temperature primary air and pulverized coal inside are heated to an appropriate temperature by the high-temperature primary air flowing through the outermost supply pipe 16 of the combustion device 1, and as in the previous embodiment, The pulverized coal is preheated at the spout so that it approaches the ignition temperature. Therefore, preheated pulverized coal, in the ignition region,
It is quickly ignited by the high-temperature primary air and the high-temperature secondary air in the furnace, and since it has been preheated, the combustion speed is accelerated, and as a result, high-load combustion is facilitated as in the previous example. be.

It should be noted that the multi-tube structure combustion device according to the present invention is of course not limited to the configuration of the above-described embodiments, and the temperature of the high-temperature primary air and the particle size of the pulverized coal are also limited to the above-mentioned values. However, if the particle size of the pulverized coal is relatively large, a slightly higher temperature primary air is supplied.

As explained above, according to the pulverized coal combustion method according to the present invention, high-temperature primary air and low-temperature primary air with a higher flow velocity are fed into the combustion device, and the low-temperature primary air heated by the high-temperature primary air is By gradually raising the temperature of the pulverized coal and supplying this low-temperature primary air to the vicinity of the pulverized coal spout,
In addition to making it possible to bring the temperature of pulverized coal near the ejection port closer to the ignition temperature, the mixing efficiency of pulverized coal and primary air can also be increased. As a result, the ignition rate and combustion rate of pulverized coal in the ignition zone in the combustion furnace are accelerated compared to conventional combustion methods, which increases combustion efficiency and facilitates high-load combustion, making it an alternative fuel for heavy oil. As a result, it became possible to use a large amount of pulverized coal. Moreover, preheating of pulverized coal by high-temperature primary air is indirect heating via low-temperature primary air, so the temperature of pulverized coal is gradually raised in the combustion device, and as a result, pulverized coal is ignited in the combustion device. Safe and stable operation of the combustion equipment is ensured without the risk of spoilage, and the temperature of the pulverized coal can be easily controlled by adjusting the flow rate of low-temperature primary air.

Further, according to the pulverized coal combustion apparatus according to the present invention, each supply pipe of high temperature primary air, low temperature primary air, and pulverized coal is configured with multiple pipes arranged concentrically, and the high temperature primary air supply pipe and the pulverized coal are Since the structure is such that a low temperature primary air supply pipe having a smaller cross-sectional area than the high temperature primary air supply pipe is interposed between the charcoal supply pipe,
The temperature of the pulverized coal can be gradually raised by the low-temperature primary air, and the temperature of the pulverized coal can also be easily controlled. The combustion device of the present invention can supply low-temperature primary air near the pulverized coal spout, and since the cross-sectional area of the low-temperature primary air supply pipe is small, low-temperature primary air with high air density can be fed at high speed. be able to.

Furthermore, since high-load combustion can be obtained, even when only pulverized coal is used as fuel, there is no need to make the combustion furnace large, and the present invention has the advantage that it can be applied to various combustion furnaces.

[Brief explanation of drawings]

Fig. 1 is a side sectional view showing one embodiment of the combustion device according to the present invention, Fig. 2 is a front view of the first embodiment, and Fig. 3 is a side sectional view showing another embodiment of the combustion device of the present invention. Figure 4 is a front view of the embodiment in Figure 3. 1... Combustion device, 2, 16... High temperature primary air supply pipe, 3, 13... Inner low temperature primary air supply pipe,
4, 14...Pulverized coal supply pipe, 5,15...Outside low temperature primary air supply pipe.

Claims (1)

[Claims] 1. High-temperature primary air and low-temperature primary air, which has a higher flow velocity than the high-temperature primary air, are separately fed into the combustion device, and the low-temperature primary air heated by the high-temperature primary air reduces the fine powder in the combustion device. A pulverized coal combustion method characterized by gradually increasing the temperature of coal and supplying this low-temperature primary air near a pulverized coal outlet. 2. Each supply pipe of high temperature primary air, low temperature primary air and pulverized coal is configured with multiple pipes arranged concentrically, and a high temperature primary air supply pipe is connected between the high temperature primary air supply pipe and the pulverized coal supply pipe. A pulverized coal combustion device characterized by interposing a low-temperature primary air supply pipe with a small cross-sectional area. 3. Claim 2 characterized in that the multiple pipes are configured in the order of a high temperature primary air supply pipe, an inner low temperature primary air supply pipe, a pulverized coal supply pipe, and an outer low temperature primary air supply pipe from the center to the outer periphery. Pulverized coal combustion equipment as described in Section 1. 4. Claim 2 characterized in that the multiple pipes are configured in the order of an inner low-temperature primary air supply pipe, a pulverized coal supply pipe, an outer low-temperature primary air supply pipe, and a high-temperature primary air supply pipe from the center to the outer periphery of the multiple pipe. Pulverized coal combustion equipment as described in Section 1.