JPS6269017A - Combustion method for boiler using nonflammable coal - Google Patents

Abstract

PURPOSE:To improve ignition and combustion properties, by a method wherein, after pulverized coal produced by a mill is separated from transporting, gas only the pulverized coal is forced into direct contact with high temperature gas to increase temperature and dehydrate, and is guided to a burner for drying and preheating. CONSTITUTION:Pulverized coal pulverized by a mill 2 is conveyed from the mill 2 by transporting, gas is separated from coal with the aid of a cyclone 3 to eliminate the possibility to cause explosion. Thereafter, only the pulverized coal is conveyed to a heat exchanger cyclone 4 through a piping 8, is forced into direct contact with high temperature gas guided from a boiler 1 to increase temperature, and a moisture content, simultaneously, is removed. The pulverized coal is guided to an ejector 5 through a piping 9, and is fed therefrom to a burner 6 through a piping 10 by means of gas from a blower 12. Since oxygen- freed gas taken out from the boiler 1 is guided to the burner 6, the pulverized coal is dried and preheated therein. This improves ignition and combustion properties of the pulverized coal immediately after the burner.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a combustion method for burning coal in a boiler, and particularly relates to a boiler combustion method for burning flame-retardant coal, which effectively burns flame-retardant coal. It is about law.

[Prior Art] Usually, coal is divided into good coal and bad coal depending on the heat generating claw, and good coal often generates the most heat but is difficult to burn.

When dealing with flame-retardant coal, which is difficult to burn, countermeasures can be taken such as changing the burner, changing the boiler structure, and reducing the particle size of the coal. There are problems with reducing unburned matter and NOx after burning, and some contain a lot of moisture and are difficult to ignite.

Conventionally, Rekinoji, which is between good coal and bad coal, has been said to be good for boiler combustion, and boilers have also been improved to make it possible to use it.

[Problems to be Solved by the Invention] Therefore, there were problems in burning flame-retardant coal in conventional boilers.

Therefore, the present invention aims to increase the temperature of the coal supplied to the burner without changing the temperature of the gas returned to the boiler, and to increase the temperature of the coal supplied to the burner without changing the temperature of the gas returned to the boiler, in order to use flame-retardant coal in boilers that have been conventionally adopted. The aim is to improve the combustibility of flame-retardant coal.

[Means for Solving the Problems] The present invention involves separating the pulverized coal obtained in a mill from a gas for transporting the pulverized coal, and then bringing only the pulverized coal into direct contact with a high-temperature gas to raise the temperature and simultaneously remove moisture. After removing the coal, the pulverized coal is introduced into a burner to be dried and preheated.

[Function] The pulverized coal is heated to a high temperature in the heat exchanger cyclone, moisture is removed at the same time, and is further dried and preheated in the burner, so that the ignition and combustibility of the pulverized coal immediately after the burner is promoted.

[Implementation example] Embodiments of the present invention will be described below with reference to the drawings.

The figure shows an outline of a device for carrying out the combustion method of the present invention. Between a pulverized coal-fired boiler 1 and a mill 2,
A cyclone 3 through which the pulverized coal obtained by pulverization in the mill 2 passes, a heat exchanger cyclone 4, and an ejector 5 are installed, and the cyclone 3 and the mill 2 are connected by a pipe 7. and the heat exchanger cyclone 4, the heat exchanger cyclone 4 and the ejector 5, and the ejector 5 and the burner 6 attached to the boiler 1 are connected by pipes 8 and 9jO, respectively.

The cyclone 3 separates the pulverized coal and the transport gas. A high temperature gas pipe 11 is connected to the heat exchanger cyclone 4 so as to directly introduce the high temperature gas taken out from the lower part of the boiler 1, and a blower 12 is connected to the gas pipe 13 to take out the gas from which moisture has been removed after heat exchange. The discharge side of the blower 12 is branched into a gas pipe 14 that connects to the upper part of the boiler 1 and a gas pipe 15 that leads to the ejector 5. A gas pipe 16 connects between the two.

On the other hand, on the downstream side of the boiler 1, there is a economizer 17, a gas/air heater 18, and an electric heater 17. The JM device 19 and the blower 20 are arranged in this order so that the exhaust gas is guided from the blower 20 to the chimney 21, and the conveying gas piping 22 is arranged so that the conveying gas is guided from the downstream side of the blower 20 to the mill 2. Further, the gas/air heater 18 and the burner 6 are provided.
A pipe 23 for guiding air for drying and preheating the pulverized coal to the burner 6 is provided between the burner 6 and the burner 6.

A conveyance gas is led to the mill 2 via a conveyance gas pipe 22, and coal C is supplied thereto. In the figure, only coal moves through the piping shown by the large solid line, only gas moves through the piping shown by the thin solid line, and a mixture of coal and gas moves through the piping shown by the double line.

Now, the pulverized coal pulverized by the mill 2 is conveyed from the mill 2 by a conveying gas. This carrier gas contains about 3% 02 as mentioned above, so first, the mill 2
The pulverized coal and conveying gas are led from the cyclone 3 to the cyclone 3, where the gas and solids, ie, coal, are separated. here,
The purpose of separating the conveying gas and the pulverized coal is to eliminate the risk of an explosion due to the approximately 3% O2 contained in the gas when the pulverized coal is heated. Next, only pulverized coal is
It is sent to the heat exchanger cyclone 4 via piping 8. The heat exchanger cyclone 4 is connected to a high temperature gas pipe 11 from the boiler 1.
Since the hot gas is led through the pulverized coal, the pulverized coal comes into direct contact with the hot gas in the heat exchanger cyclone 4. As a result, the temperature of the pulverized coal is raised and moisture is removed at the same time. In this case, it is not preferable to bring the pulverized coal into indirect contact with the high-temperature gas because the water contained in the pulverized coal cannot be removed and the temperature of the pulverized coal increases, but in the present invention, direct contact is not preferable. Therefore, such a situation will not occur.

The high-temperature gas led to the heat exchanger cyclone 4 for the above-mentioned heat exchange has its moisture removed in the moisture condensation separator 24 and is sucked by the blower 12. On the other hand, the high-temperature gas for circulation that is not used for heat exchange is It passes through the gas pipe 16, bypasses the heat exchanger cyclone 4 and the moisture condensation separator 24, and is sucked into the blower 12.

A part of the gas discharged from the blower 12 is introduced into the reboiler 1 through the gas pipe 14. Further, another part of the gas discharged from the blower 12 is guided to the ejector 5 via the gas pipe 15.

The pulverized coal that has been heated to a high temperature and treated with moisture in the heat exchanger cyclone 4 is guided through a pipe 9 to an ejector 5,
From here, the gas from the blower 12 is supplied to the burner 6 via the pipe 10. Oxygen-free gas taken out from the boiler 1 is led to this burner 6, so that the pulverized coal is dried and preheated here. This promotes ignition and combustion of the pulverized coal directly in the burner.

[Effects of the Invention] As described above, according to the combustion method of the present invention, after separating the pulverized coal from the conveying gas, the pulverized coal is brought into direct contact with the high-temperature gas to raise the temperature and at the same time remove moisture. After that, the pulverized coal is dried and preheated with a burner, making it easier to burn the flame-retardant coal and improving its combustibility.

[Brief explanation of drawings]

The figure is a III main diagram showing an embodiment of the present invention. 1 is a boiler, 2 is a mill, 3 is a cyclone, 4 is a heat exchanger cyclone, 5 is an ejector, and 6 is a burner.

Claims (1)

[Claims] 1) After separating the pulverized coal obtained in the mill from its conveying gas, only the pulverized coal is brought into direct contact with high-temperature gas to raise the temperature and at the same time remove moisture, and then lead the pulverized coal to a burner. A boiler combustion method for flame-retardant coal that is characterized by drying and preheating.