JPS61175401A - Method of feeding coal to boiler - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method of feeding coal to a boiler.

(Conventional technique III) Figure 3 shows the implementation flow of the conventional technique.
Fine coal as a fuel and a desulfurizing agent are fed to the bottom of the fluidized bed combustion section 21 through a large number of coal feed pipes 4. The blown material is forcibly stirred while maintaining a fluid state with air supplied from the forced air blower 2 through the fluidized air pipe 3.
The combustion performance is extremely good.

Now, the coal feeding flow of the conventional method will be explained below.The raw coal received by the raw coal receiving bunker (not shown) is passed through a coal dryer and a crusher to a predetermined particle size.

After being adjusted to moisture content, it is stored in the fine charcoal hopper 10.

On the other hand, limestone is also processed after the same process or has a predetermined particle size.

The moisture-adjusted product is purchased and stored in the limestone hopper 9. The fine coal and limestone stored in each hopper are cut out in amounts that meet the usage conditions of the boiler, mixed, and then supplied to the primary coal feed pipe 11. On the other hand, the air sent by the booster blower 8 is supplied to the primary coal feeding pipe 11 through the header 7 and the conveying air supply pipe 6.
Pneumatically transport fine charcoal 1 limestone, etc. Note that the air transport conditions are set and controlled by the transport air amount adjusting device 12 to conditions that match the boiler usage conditions.

A fluid distributor 5 is provided between the primary coal feeding pipe 11 and the coal feeding pipe 4, and the fine coal and limestone transported through one primary coal feeding pipe are transferred to a large number of coal feeding pipes 4. are evenly distributed. The transported materials distributed into a predetermined number of distributions are blown into the bottom of the fluidized bed boiler 1 and combusted.

(Problems to be Solved by the Invention) Before explaining the problems of the prior art, the performance required of the fluid distributor 5 used in the fluidized bed boiler 1 will be explained below.

Fluidized bed boiler 1 injects fine coal, stone, and ashes at the same time.
By burning within the range of 50-850℃, NO
This is a pollution-free boiler that enables highly efficient combustion while generating x and desulfurizing sow. The conditions for achieving this purpose are that the ratio of S content and limestone in the bed granule coal in each coal feeding pipe is constant, and the mixing ratio of fine coal and transport air is 0.8 to 1.0. must be within the range.

The reason for this is that for desulfurization in a fluidized bed boiler, limestone equivalent to 50% of fine coal is required. or,
When the mixing ratio of fine coal and transport air changes, the mixture ratio of volatile combustible content in fine coal and transport air changes, and the combustion of volatile content immediately after being blown into the fluidized bed boiler causes the combustion of volatile matter in the furnace. This is because the temperature distribution is not uniform, and undesirable phenomena such as the generation of NOx (in high temperature regions) and an increase in unburned coal due to poor combustion of coal (in low temperature regions) occur.

The performance of the fluid distributor 5 influences the above phenomena.

Therefore, the fluid distributor 5 maintains the mixing ratio of fine coal and limestone at an extremely constant level and maintains the solid-air ratio (ratio of fine coal to transport air) to the required number of coal feeding pipes. Its superiority or inferiority is determined by how accurately it is distributed.

Figure 2 shows a cross-sectional view of a conventional fluid distributor.As a result of the research conducted by the present inventors, it has been found that the relationship between the dispensing accuracy and usage conditions of the conventional fluid distributor has the following tendency. Ta.

1) The faster the gas flow rate in the coal feeding pipe 33, the worse the distribution accuracy becomes.

2) The higher the average upward flow velocity of the fluid distributor inner column 32, the worse the distribution accuracy becomes.

3) The smaller the solid-gas ratio of the transported material supplied from the coal supply pipe 33 of the fluid distributor, the worse the distribution accuracy becomes.

On the other hand, the transportation solid-air ratio and pipe flow velocity of the conventional coal feeding system are
As shown in the figure, the transport air amount adjusting device 12 controls the boiler to achieve a solid-air ratio of 0.8 to 1.0 under operating conditions. In addition, the flow rate in the transport pipe is conventionally set at 20 m/s to prevent the accumulation of coal particles.
The flow rate is higher than S.

As mentioned above, although the conditions for satisfying the distribution accuracy of the fluid distributor and the conditions for use in the boiler are different, in the conventional system, the air amount adjustment device in the coal feeding system is only one set of transportation air amount adjustment device 12. Because it is not equipped with the following, the following problems arise.

(b) In order to achieve stable air transport with a solid-air ratio of 0.8 to 1.0 in the primary coal feeding pipe 11, the flow velocity in the pipe is required to be 20 m/s or more, which causes severe wear on the pipe, and the pipe has a large diameter. 1 Bi or 41 go 4111 薯 - so-called 1 win〉 and Ebi or Su V Shibi reliability is also inferior.

(b) Because the solid-air ratio in the coal feed pipe of the fluid distributor 5 is small, 1
The distributor quality is poor, and the deviation in temperature distribution within the boiler increases, the generation of Now and SOx increases, and the combustion efficiency decreases.

b) Since the solid-air ratio is between 0.8 and 1.0, the amount of air required to transport the transported object increases, and the transport equipment (pipes, valves, fluid distributors, etc.) becomes larger.

The coal feeding method of the present invention includes the primary coal feeding pipe 11. The aim is to solve the problems of the conventional system by equipping each of the four coal feed blowing pipe systems with an air amount adjustment system.

(Structure and operation of the invention) FIG. 1 shows an embodiment of a coal feeding system according to the present invention.

The configuration of the present invention is such that, in addition to the primary coal feeding pipe transportation air amount adjusting device 12 provided in the conventional system, a coal feeding pipe air amount adjusting device 13 is installed, so that the primary coal feeding pipe 11
．． Fluid distributor5. This allows the transportation conditions or distribution conditions of the coal feed blowing pipe 4 to be adjusted to the optimum point.

The functions of the present invention will be explained below.

The materials to be transported (coal, 9 coal ash, 1 limestone, etc.) that are blown into the fluidized bed boiler by the coal feed pipe 4 are transferred to a hopper (for example, a fine coal hopper 10, a limestone hopper 9, a limestone hopper, etc. shown in FIG. 3), not shown. The coal is supplied to the primary coal feed pipe 11 through the transported material supply pipe 41 by mechanical cutting or fluidized cutting from the coal.

On the other hand, the primary coal supply piping! Air for pneumatically transporting the goods supplied to the header 7 is supplied from an air source (not shown) to the header 7, and ! I2 air supply piping 6. The coal is supplied to the primary feed pipe 11 via the primary coal feed pipe transportation air amount adjusting device 12, and the transported material is pneumatically transported. The amount of air supplied at this time is to prevent wear of the primary coal feed pipe 11 and fluid distributor 5, reduce equipment costs, and lower operating costs.

Decisions can be made after comprehensive consideration of distribution performance, etc.

The primary coal feed pipe 11 is connected to a fluid distributor 5, where the transported material is evenly distributed to the required number of coal feed pipes. At this time, the flow rate at the inlet of the fluid distributor, the solid-air ratio, the average upward flow rate in the vessel, etc. to achieve the distribution performance change depending on the particle size distribution, specific gravity, etc. of the transported material. In order to optimize this condition and achieve distribution accuracy, the required solid-air ratio greatly contributes to determining the amount of air to be supplied.

Next, the transported materials uniformly distributed by the fluid distributor are blown into the fluidized bed boiler via a large number of coal feed blowing pipes 4. In the present invention, the amount of air in the coal feed pipe is Adjustment device 1
Air is injected into the boiler to adjust the solid-gas ratio to the optimum level for combustion in the fluidized bed boiler.

The amount of air blown from the coal feed pipe air amount adjustment device 13 is determined from the amount of air to achieve the optimum solid-air ratio to the primary coal feed pipe 11.
Ideally, the air amount is obtained by subtracting the air amount from the previous air amount ratio, but it may be adjusted independently if the previous air amount ratio is small and does not significantly affect the solid-air ratio of the coal feeding pipe.

In experiments conducted by the present inventors, the solid-gas ratio in the primary coal feeding pipe was 20, and therefore the solid-gas ratio in the fluid distributor was 20. The solid-air ratio of the coal feed pipe is 0.
8, the coal feeding system demonstrated stable performance. The air volume adjustment at this time is shown below, and the primary feed pipe transport air volume is:
The amount of air that would give a solid-air ratio of 20 was calculated from the weight of the object supplied from the object supply pipe 41, and a command signal was issued to the air amount adjustment device to automatically adjust it.

Next, the amount of air supplied from the coal feed blowing pipe air amount adjusting device 13 was calculated and automatically adjusted to a solid-air ratio of 0.83 based on the weight of the material to be transported from the material supply pipe.

Note that the water supply system is not one system that corresponds to all cells of the fluidized bed boiler, but one system is installed for one cell or several cells.

(Effect of the invention) According to the present invention, the primary coal feeding pipe 11 and the coal feeding pipe 4
Since the necessary air volume conditions can be set and controlled as desired, the following effects were obtained.

b) High concentration (solid-air ratio 20
) and low flow velocity (5 s/s), pipe wear is significantly reduced, the diameter of the pipe can be made smaller, the amount of air to be transported is reduced, and equipment costs and operating costs are significantly reduced. Equipment reliability was improved.

Mouth) The distribution accuracy of Ato & Shinjiko 5 is high → Negative control (No matter what, it can be achieved stably, so boiler NO!).

The amount of SOx generated stabilized at a low level, and coal combustion efficiency improved.

c) Since the optimum solid-air ratio of the coal feed pipe can be stably achieved regardless of boiler load fluctuations, boiler NO! .

The amount of SOx generated stabilized at a low level, and coal combustion efficiency improved.

2) The addition of the air volume adjustment device 13 reduces the air pressure used, and by providing each air source independently, the power consumption of the air source equipment is reduced.

[Brief explanation of drawings]

FIG. 1 shows an embodiment of a coal feeding system according to the present invention, FIG. 2 shows a conventional fluid distributor, and FIG. 3 shows an embodiment of a conventional coal feeding system. 1... Fluidized bed boiler, 2... Forced blower, 3...
Flowing air piping, 4... Coal feed blowing pipe, 5... Fluid type distributor, 6... Conveying air supply piping, 7... Header,
8... Booster blower, 9... Limestone hopper, lG
...Fine coal hopper, 11...Primary coal feeding pipe, 12
. . . Primary feed pipe transport air amount adjustment device, 13 . . . Coal feed blowing pipe air amount adjustment device, 21 .
... Boiler cell, 31 ... Cone part, 32 ... Round column part, 33 ... Coal feed pipe, 34 ... Distribution branch pipe. 35... Plate, 41... Transportation supply pipe.

Claims (2)

[Claims] (1) In a method for feeding coal to a boiler, which comprises arranging at least a primary coal feeding pipe, a fluid distributor, and a coal feeding pipe, and blowing the transported material into the boiler by fluid transport, the primary coal feeding pipe and the coal feeding pipe are A method for feeding coal to a boiler, characterized in that the amount of fluid supplied from each pipe can be adjusted independently. (2) A claim in which the amount of fluid supplied from the primary coal feeding pipe and the coal feeding pipe is adjusted to have a predetermined solid-air ratio with respect to the weight of the transported object supplied to the primary coal feeding pipe. The coal feeding method described in paragraph 1.