JPH0567847B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a coal feeding method in a boiler coal feeding system.

(Prior art) FIG. 4 shows an implementation flow of the prior art. In the fluidized bed boiler 1, materials to be transported, such as fine coal as a fuel and limestone as a desulfurizing agent, are blown into the bottom of a fluidized bed combustion section 21 through a large number of coal feed pipes 4 together with air. The blown materials are forcibly stirred while being maintained in a fluidized state by the air supplied from the forced air blower 2 through the fluidized air pipe 3, so that the combustion performance is extremely excellent.

Now, the conventional coal feeding flow will be explained below. Raw coal received in a 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, it is stored in a fine charcoal hopper 10. On the other hand, limestone is also purchased after the same process or after being adjusted to a predetermined particle size and moisture content 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 supply pipe 11 through the header 7 and the conveying air supply pipe 6, and pneumatically transports fine coal, limestone, and the like. Note that the pneumatic 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 distributes fine coal and limestone transported through one primary coal feeding pipe to a large number of coal feeding pipes 4. It is distributed evenly. 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.

The fluidized bed boiler 1 is a pollution-free boiler that enables highly efficient combustion while generating NOx and desulfurizing SOx by simultaneously injecting fine coal and limestone and burning them within the range of 850 to 950°C. The conditions for achieving this purpose are that the ratio of S content in the fine coal to limestone in each coal feed pipe is constant, and the mixing ratio of fine coal and transport air is 0.8 to 0.8.
It must be within the range of 1.0.

The reason for this is that in order to desulfurize in a fluidized bed boiler, limestone, which has a S content found in fine coal, is required. In addition, when the mixing ratio of fine coal and transport air changes, the mixing ratio of volatile combustible content in the fine coal and transport air changes, and the combustion of volatile content immediately after being blown into the fluidized bed boiler causes 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 as constant as possible, and maintains the required number of coal feeding pipes and the solid-air ratio (ratio of fine coal to transport air) to be constant. Its superiority or inferiority is determined by how precisely it is distributed.

FIG. 3 shows a cross-sectional view of a conventional fluid distributor. The relationship between the dispensing accuracy and usage conditions of conventional fluid distributors is as follows:
The results of research conducted by the present inventors revealed the following trends.

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

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

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

In addition, the transport solid-air ratio of the coal feeding system shown in Fig. 4,
The flow velocity in the pipe is controlled by the transportation air amount adjusting device 12 so that the solid-gas ratio is 0.8 to 1.0, which is the boiler operating condition.
Furthermore, the flow velocity in the transport pipe is conventionally set at a flow velocity of 20 m/s or more to prevent coal particles from accumulating.

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, the conventional system has only the transport air amount adjusting device 12 as the air amount adjusting device in the coal feeding system. Because this is not done, 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 increases the equipment cost and operation due to the large pipe diameter. The cost will also be high. Furthermore, equipment reliability is also poor.

(b) Since the solid-air ratio in the coal feed pipe of the fluid distributor 5 is low, the distribution accuracy is poor and the deviation in temperature distribution within the boiler becomes large, which increases the generation of NOx and SOx and reduces combustion efficiency.

(c) Since the solid-air ratio is between 0.8 and 1.0, the amount of air required to transport the cargo is large, and transportation equipment (piping,
valves, fluid distributors, etc.) become larger.

The coal feeding method of the present invention attempts to solve the problems of conventional systems by supplying air to the coal feeding pipe.

(Structure and operation of the invention) FIGS. 1 and 2 show 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 14 is installed, so that the fluid distributor 5, the coal feeding pipe This makes it possible to adjust the transport conditions or distribution conditions of No. 4 to the optimum point.

The functions of the present invention will be explained below.

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

On the other hand, air for pneumatically transporting the transported material supplied to the primary coal feeding pipe 11 is supplied to the header 7 from an air source (not shown), and is connected to the transport air supply pipe 6 and the primary coal feeding pipe transport air amount adjusting device 12. The coal is supplied to the primary coal feeding pipe 11 through the coal feed pipe, and the transported material is transported by pneumatic transport.

The primary coal feed pipe 11 is connected to the fluid distributor 5,
Here, the transported material is evenly distributed among the required number of coal feed blowing pipes. At this time, the flow rate at the inlet of the fluid distributor to achieve distribution performance based on the particle size distribution, specific gravity, etc. of the transported material,
The solid-gas ratio, average superficial upward flow rate in the vessel, etc. change. 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 goods uniformly distributed by the fluid distributor,
The coal is blown into the fluidized bed boiler through a large number of coal feed blowing pipes 4. In the present invention, air is supplied from the coal feed pipe air amount adjusting device 14 through the header 15 to the middle of the coal feed pipe to adjust the solid-gas ratio to be optimal for combustion in the fluidized bed boiler. The amount of air blown from the coal feed blowing pipe air amount adjusting device 14 is preferably the amount of air obtained by subtracting the amount of air in the primary coal feed pipe 11 from the amount of air for achieving the optimum solid-air ratio.

In experiments conducted by the present inventors, the coal feeding system exhibited stable performance at a solid-air ratio of 20 in the primary coal feeding pipe, a solid-air ratio in the fluid distributor of 20, and a solid-air ratio of 0.8 in the coal feeding pipe. The air amount adjustment at this time is as follows: The amount of air transported by the primary coal feeding pipe is determined by calculating the air amount that will give a solid-air ratio of 20 from the weight of the transported material supplied from the transported material supply pipe 41, and the air amount adjusting device A command signal was sent to the system to automatically adjust it.

Next, the amount of air supplied from the coal feed blowing pipe air amount adjusting device 14 was automatically adjusted by calculating the solid-air ratio to be 0.83 based on the weight of the material to be transported from the material supply pipe.

Next, the boiler cell 22 will be explained. A boiler cell is a section of the fluidized combustion section of a boiler provided to widen the load variable range of the boiler, and is divided into several cells to more than ten cells depending on the width of the load variable range. Therefore, since the cell operates or stops depending on the boiler load, the coal feeding may be in progress or stopped.

As a group of coal feed blowing pipes suitable for this operating method, the present inventors proposed that the coal feed blow pipe air amount adjusting device 14 should be installed in each cell. In this case, since the amount of supplied air varies and the distribution accuracy decreases, an air header was installed on the downstream side of the air amount adjusting device 14 to eliminate variations in the amount of supplied air.

(Effects of the invention) (a) Compared to the method of installing the air amount adjusting device 14 for each coal feed pipe by the method of the present invention, the equipment can be made very simple, and the distribution accuracy is improved because the adverse effects of interference are avoided. did.

(b) It has become possible to use high concentration (solid-air ratio 20) and low flow velocity (5 m/s) as transportation conditions for the primary coal feeding piping, which greatly reduces wear on the piping, allows the diameter of the piping to be made smaller, and transports air The amount was reduced, significantly reducing equipment and operating costs and improving equipment reliability.

C. Because the distribution accuracy of the fluid distributor 5 can be stably achieved regardless of boiler load fluctuations, the boiler
NOx and SOx emissions have stabilized at a low level, and coal combustion efficiency has improved.

D. The optimum solid-air ratio of the coal feed pipe can be stably achieved regardless of boiler load fluctuations, so the boiler
NOx and SOx emissions have stabilized at a low level, and coal combustion efficiency has improved.

E. By adding the air amount adjusting device 14, the air pressure used is reduced, and by providing each air source independently, the power consumption of the air source equipment is reduced.

[Brief explanation of drawings]

1 and 2 show an embodiment of a coal feeding system according to the present invention, FIG. 3 shows a conventional fluid distributor, and FIG. 4 shows an embodiment of a conventional coal feeding system. 1... Fluidized bed boiler, 2... Forced blower, 3...
... Fluid air piping, 4 ... Coal feed blowing pipe, 5 ... Fluid type distributor, 6 ... Conveying air supply pipe, 7 ... Header, 8 ... Booster blower, 9 ... Limestone hopper, 10 ... Thin Granulated coal hopper, 11...Primary coal feeding pipe, 12...Primary coal feeding pipe transportation air amount adjustment device,
14... Coal feed blowing pipe air amount adjustment device, 21... Fluid combustion section, 22... Boiler cell, 31... Conical part, 32... Round tower part, 33... Coal feed pipe, 34...
...Distribution branch pipe, 35...Blind plate, 41...Transportation material supply pipe.

Claims (1)

[Scope of Claims] 1. A boiler coal feeding system comprising a plurality of coal feed blowing pipes and a fluid distributor that uniformly distributes the transported material to these pipes, and which blows the transported material into the boiler by fluid transport. In the coal feeding method, the solid-air ratio up to the fluid distributor is at least higher than the optimum solid-air ratio for use in the boiler, and all the coal feeding pipes connected to the fluid distributor are connected to each other through a fluid header. A coal feeding method in a boiler coal feeding system characterized by supplying air evenly through tubes and adjusting the solid-air ratio in the boiler to the optimum solid-air ratio for use. 2. The coal feeding system according to claim 1, characterized in that air is supplied uniformly to all the coal feeding pipes connected to the fluid distributor for each boiler cell through the fluid header for each cell. Method. 3. For multiple coal feeding pipes connected to a fluid distributor provided in common for several cells, uniform air is distributed to all coal feeding pipes for each cell through the fluid header for each cell. The coal feeding method according to claim 1, characterized in that the solid-air ratio is set to the optimum solid-air ratio for use in an independent boiler for each cell.