JPS62169908A - Pulverized coal combustion boiler - Google Patents

Abstract

PURPOSE:To improve combustion efficiency, to prevent exhaust of NOx, and to ensure safety of the interior of silo, by a method wherein a separating device, separating air into nitrogen and oxygen, in provided, nitrogen is fed to a pulverized coal silo, and oxygen is fed to a mixture flow transport pipe, and a secondary and a tertiary air pipe. CONSTITUTION:In a separating device 20, air is separated into nitrogen and oxygen. Pulverized coal from a pulverized coal silo 3 is fed to a furnace 1 together with air for combustion, and oxygen is fed to a mixture transport pipe 13a, a secondary air pipe 10, and a tertiary air pipe 14. In the furnace 1, control is effected so that, subsequently to a rapid ignition and temperature increase process, the furnace is brought into reduction atmosphere in a first stage combustion area, and it is brought into oxidation atmosphere in a second stage combustion area through a tertiary air nozzle 16 and the following air nozzles. This constitution enables sharp promotion of combustion, reduction of an amount of a residual unburnt content in ash to provide high combustion efficiency, and prevention of exhaust of NOx. Through utilization of nitrogen, atmosphere in the pulverized coal silo 3 is inactivated, and spontaneous ignition of pulverized coal is prevented from occurring.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a pulverized coal combustion boiler, and relates to a device that can control combustion efficiency according to the type of coal and ensure the safety of a pulverized coal silo.

[Conventional technology] In pulverized coal combustion boilers, a wide variety of coals can be burned without significantly changing the boiler structure, burner structure, etc., and NOx emissions can be suppressed with high combustion efficiency. At the same time, in the case of a storage combustion method, there is a strong demand for safety measures against spontaneous combustion of pulverized coal in pulverized coal silos.

In pulverized coal combustion, the combustion efficiency and NOx emissions are largely influenced by the type of coal, rather than by the unique properties of the coal.

In terms of combustion efficiency, coal combustibility, pulverized coal particle size,
The combustibility of coal is influenced by combustion reaction time, etc., and the combustion ratio corresponding to the degree of coal carbonization is used as an indicator.As for the particle size of pulverized coal, the amount passing through 200 mesh is 60 to 90%.
The combustion reaction time is determined by the furnace temperature, oxygen concentration in the surrounding air, pulverized coal particle size,
It is affected by the properties of fixed carbon and volatile matter.

In pulverized coal combustion, pulverized coal is burned in a furnace and discharged from the furnace after a certain residence time. Therefore, the combustion reaction must be completed within the residence time, and if the combustion reaction time is longer than the residence time depending on the type of coal, unburned matter remains in the ash, increasing the combustion efficiency (carbon reaction rate).
This will reduce the

In large-capacity pulverized coal-fired boilers, it is possible to secure a relatively long residence time in the furnace, but in medium- and small-capacity pulverized coal-fired boilers, it is difficult to secure a long residence time due to structural constraints. Therefore, it was difficult to improve combustion efficiency.

On the other hand, in terms of suppressing NOx emissions, NOx generated during pulverized coal combustion can be divided into thermal NOx and fuel NOx depending on the generation route. Thermal NOx is generated from nitrogen molecules in the air, and fuel NOx is generated from nitrogen molecules in the coal.
It is generated from N compounds, etc. NOx
As combustion technologies for suppression, staged combustion methods such as low air ratio combustion and two-stage combustion have been put into practical use. (for example,
Furthermore, in the storage combustion method, the pulverized coal stored in the pulverized coal silo is transported by primary air and burned in the furnace. Ignition, explosion, fire, etc. may occur, and 11 measures have been proposed as safety measures, including inertization of the surrounding air in the pulverized coal silo and forced cooling of the pulverized coal to prevent temperature rise. .

[Problems to be Solved by the Invention] However, in the above-mentioned conventional pulverized coal combustion boiler, it is not possible to easily adjust and control the appropriate oxygen atmosphere in the furnace according to a wide variety of coal types. In addition to being unable to maintain high combustion efficiency, thermal NOx is generated due to the use of air during combustion, which is difficult to suppress using combustion technology to suppress NOx along with fuel NOx. In addition, it is necessary to use a separate gas source from the boiler to inert the atmosphere in the pulverized coal silo, and it is difficult to easily use inert gas. There was a problem.

The present invention solves these conventional problems,
When burning pulverized coal, it is controlled to achieve high combustion efficiency according to a wide variety of coal types, suppresses NOx emissions, and at the same time inerts the surrounding air inside the pulverized coal silo, ensuring safety. The purpose is to provide a pulverized coal combustion boiler.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a separation device that separates air into nitrogen and oxygen, and a mixed flow transport pipe for pulverized coal and primary air supplied from a pulverized coal silo. is connected to a pulverized coal burner, a secondary air pipe is connected to the pulverized coal burner, a tertiary air pipe is connected to the tertiary air port of the furnace, and the nitrogen supply pipe is connected to the pulverized coal silo. , the oxygen supply pipe is connected to the mixed flow transport pipe, the secondary air pipe, and the tertiary air pipe,
A control device is provided to control the amount of oxygen supplied depending on the type of coal.

[Function] The present invention has the following effects due to the above configuration. That is, air is separated into nitrogen and oxygen in a separator, and the pulverized coal from the pulverized coal silo is supplied to the furnace together with combustion air to perform pulverized coal combustion. The above-mentioned oxygen is supplied to the pipe and the tertiary air pipe, and the oxygen flow rate is controlled according to the type of coal. Therefore, as the combustion air, an oxidizing agent having a substantially high oxygen ratio and low nitrogen ratio is utilized.

In the present invention, the oxidizing agent means a gas that is a mixture of the above-mentioned oxygen and air and has an oxygen ratio of 21% or more (volume ratio).

In the furnace, staged combustion is carried out using pulverized coal and an oxidizing agent. Following rapid ignition and temperature rise, the first stage combustion zone becomes surrounded by reducing feces, and the second stage combustion zone from the tertiary air port onwards is filled with oxidized feces. It is controlled to create a surrounding atmosphere. When the pulverized coal is ignited and heated under the oxidizing atmosphere by the oxidizing agent, it promotes and stabilizes ignition, and enables reductive combustion at high temperatures in the subsequent first stage combustion zone, as well as second stage combustion. A combustion reaction of unburned gas and unburned particles progresses in the combustion chamber.

In this way, the combustion reaction of the pulverized coal is significantly promoted and completed, so that less unburned matter remains in the ash, resulting in high combustion efficiency and suppressing NOx emissions.

Furthermore, by controlling the amount of oxygen-enriched gas supplied according to the type of coal, the amount of oxygen in the surrounding air in the combustion zone can be adjusted and controlled. It becomes possible to perform combustion control and NOx suppression.

The pulverized coal silo is connected to the nitrogen supply pipe mentioned above.
Since the nitrogen separated in the separator installed in the boiler equipment is directly used to inactivate the atmosphere inside the pulverized coal silo, it is possible to prevent spontaneous combustion of the pulverized coal.

[Example] FIG. 1 shows the configuration of an embodiment of the present invention.

In Fig. 1, 1 is the furnace of the boiler, 2 is the pulverized coal burner, 3 is the pulverized coal silo, 5 is the air preheater not closed, 4 is the feeder installed at the bottom of the pulverized coal silo 3, and the air 8 is heated by the air preheater through the forced feed mm9, and the air pipe 1
1, the pressure is increased by the primary blower 12, and the primary air pipe 1
3 and mixed with pulverized coal from the feeder 4 to form a mixed flow.
A mixed flow is ejected from the pulverized coal burner 2 to the furnace 1 through the mixed flow transport pipe 13a.

A secondary air pipe 10 is provided from the air outlet side of the air preheater 5, connected to the pulverized coal burner 2, and supplies secondary air necessary for pulverized coal combustion. In the furnace 1, a pulverized coal burner 2 forms a first stage combustion zone. Also, tertiary air port 1
Reference numeral 6 is provided in the furnace 1 and connects a tertiary air pipe 14 from the air outlet side of the air preheater 5, and supplies the tertiary air necessary for forming the second stage combustion zone with a blower 15.

Exhaust gas from the furnace 1 and a steam generator (not shown) passes through an air preheater 5 and is discharged to the outside of the system via a pipe 7 by a blower 6.

20 is a separation device for separating air into nitrogen and oxygen, 21 is air, 23 is a nitrogen supply pipe, and 24 is an oxygen supply pipe. The separation device 20 separates air into nitrogen gas and oxygen gas using a chemical adsorption method that has a simple structure and consumes less energy, unlike a liquefaction separation method. The nitrogen supply pipe 23 is connected to the pulverized coal silo 3,
The pulverized coal silo 3 is filled with nitrogen gas while maintaining a predetermined pressure to create an inert atmosphere, and because it is pressurized compared to atmospheric pressure, outside air enters the pulverized coal silo 3 and prevents it from becoming inert. This prevents interference with active feces. In this way, a sufficient inert atmosphere is formed to prevent spontaneous combustion of the pulverized coal within the pulverized coal silo 3.

25 is an oxygen tank, and 25a, 25b, and 25c are oxygen supply pipes, respectively. The oxygen supply pipe 24 is connected to the separation device 2
0 and the oxygen tank 25 are connected. Further, the oxygen supply pipes 25a, 25b and 25c are connected to the regulating valves 26a, 26b and 26c and the mixers 27a, 27b and 27c.
are attached to each other, and are connected to the mixed flow transport pipe 13a, the secondary air pipe 10, and the tertiary air pipe 14, respectively. Furthermore, the output signal of the control device 30 is the control valve 26a.
, 26b and 26c to control the amount of oxygen gas supplied according to the type of coal. The said control is by hand! It is also possible to use an III regulating valve. Thus, the combustion air flowing through the mixed flow transport pipe 13a, the secondary air pipe 10, and the tertiary air pipe 14 has different oxygen concentrations, and the oxidizing agent substantially has a high oxygen ratio and a low nitrogen ratio. In the furnace 1, the above-described staged combustion is performed, and the amount of oxygen in the surrounding air is controlled in the first and second combustion zones.

The ignition and temperature raising process of pulverized coal progresses rapidly by using an oxidizer to promote and stabilize ignition, and in the subsequent first stage combustion zone, reductive combustion at high temperatures progresses and NOx is generated. is suppressed, and the combustion reaction of unburned gas and unburned particles progresses in the second stage combustion region. In this way, the combustion reaction of pulverized coal is significantly promoted,
Because the process is completed, there is little unburned matter remaining in the ash.

Therefore, high combustion efficiency can be obtained even in pulverized coal combustion of coal with a high fuel ratio and low combustibility, and the NOx
In addition to #cp efficiency, combustion can be performed using an oxidizing agent with a low nitrogen ratio during staged combustion, resulting in the effect of suppressing NOx. Thus, as is clear from the above embodiments, in pulverized coal combustion, a wide variety of coal types can be combusted to achieve high combustion efficiency and NOx emissions can be suppressed. Thus, as is clear from the above example, by simultaneously using nitrogen gas and oxygen gas separated by the separator, the nitrogen gas inerts the surrounding air in the pulverized coal silo and is used to burn the pulverized coal. , under the safe storage and supply of pulverized coal, a wide variety of coals can be combusted using oxygen gas to achieve high combustion efficiency and NO
x emissions can be suppressed.

Therefore, in pulverized coal combustion, which is the basis for safe storage and supply of pulverized coal, unburned losses can be reduced, which makes it possible to improve boiler thermal efficiency, shorten the combustion time of pulverized coal, and increase the length of the combustion flame. Since the length can be shortened and the amount of combustion gas can be reduced, the furnace can be made smaller, and the pulverized coal combustion boiler can be made smaller.

Furthermore, since the amount of combustion gas is reduced, it is possible to reduce the size and size of processing containers such as blowers, air preheaters, dust collectors, etc., which are boiler gas processing equipment.

It should be noted that the embodiments of the present invention are of course not limited to the above-described embodiments, and many embodiments of separators, low NOx burners, similar combustion devices, etc. can be adopted.

[Effects of the Invention] As is clear from the above embodiments, the present invention simultaneously utilizes nitrogen gas and oxygen gas separated by a separation device,
During pulverized coal combustion, nitrogen gas is used to safely store and supply pulverized coal in a pulverized coal silo, and by controlling the amount of oxygen gas supplied, it is possible to safely store and supply pulverized coal in a pulverized coal silo using nitrogen gas. Since the amount of oxygen in the boiler can be adjusted and controlled, it is possible to perform optimal combustion control and NOx suppression according to the combustibility of the coal type and N content without making drastic changes to the boiler structure, burner structure, etc. The benefits include improved thermal efficiency, smaller boilers, reduced processing capacity and smaller dimensions of boiler gas processing equipment, and more.

[Brief explanation of drawings]

FIG. 1 is a schematic block diagram of a pulverized coal combustion boiler according to an embodiment of the present invention. 1... Fire furnace 2... Pulverized coal burner 10...
-Secondary air pipe 13...Secondary air pipe 13a...Mixed flow transport pipe 14...Tertiary air pipe 16...Tertiary air port 20...Separator 21...Air 2
3... Nitrogen supply pipe 24... a element supply pipe 25 a, 25 b, 25 c = oxygen supply pipe 30... control device

Claims (1)

[Claims] A separation device that separates air into nitrogen and oxygen, and a mixed flow transport pipe for pulverized coal and primary air supplied from a pulverized coal silo are connected to a pulverized coal burner, and a secondary air pipe is connected to the pulverized coal burner. The tertiary air pipe is connected to the tertiary air port of the furnace, the nitrogen supply pipe is connected to the pulverized coal silo, and the oxygen supply pipe is connected to the mixed flow transport pipe, secondary air pipe, and tertiary air pipe. A pulverized coal combustion boiler characterized by having continuous pipes and a control device for controlling the amount of oxygen supplied according to the type of coal.