JPH0522813B2 - - Google Patents

Description

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

(Prior art) FIG. 3 shows an implementation flow of the prior art. In the fluidized bed boiler 1, a mixture of fine coal as a fuel and coal stone as a desulfurizing agent is blown into the bottom of the fluidized bed combustion section 21 together with air through a large number of coal injection pipes 4. 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 air transport conditions are controlled by a transport air amount adjusting device 12.

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. In order to achieve this objective, it is necessary that the ratio of S content in the fine coal to limestone in each coal feed pipe be constant.

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.

The performance of the fluid distributor 5 influences the above phenomena. Therefore, the quality of the fluid distributor 5 is determined by how accurately and evenly it distributes the transported material to the required number of coal feed pipes while keeping the mixing ratio of fine coal and limestone as constant as possible.

FIG. 2 shows a cross section of a conventional fluid distributor.

The particle size distribution of transported materials is wide and it is difficult to determine the particle size when it comes to the starting speed of floating and the starting speed of conveyance, but as a result of experiments we found the following. As shown in FIG. 4, the distribution accuracy worsens as the average superficial upward flow velocity increases. This is thought to be because the surface of the suspended and flowing transport material becomes more volatile as the flow velocity increases. Conversely, if the flow rate is lowered, the distribution accuracy improves, but there is a phenomenon in which particles with large diameters accumulate inside the distributor and eventually become clogged. As a result of various studies based on this, we found that the average overhead flow velocity of the distributor was 30wt below the sieve.
It was discovered that the floating start speed of % particle size and the transport start flow speed of 10wt% flow diameter above the sieve were suitable. It was also discovered that the distribution accuracy deteriorates as the solid-air ratio decreases. On the other hand, the transport conditions for the primary coal feeding piping are preferably high concentration and low flow rate, both in terms of wear prevention and cost considerations.

As mentioned above, despite the difference between the conditions that satisfy the distribution accuracy of the fluid distributor and the transportation conditions of the primary coal feeding pipe, the air amount adjustment device in the coal feeding system is Since it is equipped with only one set of quantity adjusting device 12, it has the following problems.

The average superficial upward flow velocity of the fluid distributor 5 becomes too small, resulting in poor distribution accuracy and a large deviation in temperature distribution within the boiler, which increases the generation of NOx and SOx and reduces combustion efficiency.

The coal feeding system of the present invention attempts to solve the problems of the conventional system by equipping the fluid distributor 5 with an air amount adjustment system that newly supplies air.

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

The configuration of the present invention is to set the distribution condition of the fluid distributor 5 to the optimum point by installing a fluid distributor air amount adjusting device 13 in addition to the primary coal feeding pipe transportation air amount adjusting device 12 provided in the conventional system. This makes it possible to adjust the

The functions of the present invention will be explained below.

The transported material that is blown into the fluidized bed boiler through the coal feed pipe 4 is mechanically cut or fluidized from a hopper (not shown) (for example, the trickle coal hopper 10, limestone hopper 9, or coal ash hopper shown in FIG. 3). The coal is supplied to the primary coal feeding pipe 11 through the conveyed material supply pipe 41 by means of, for example, the transport material supply pipe 41.

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 passed through 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, and the transported material is transported pneumatically. The amount of air supplied at this time is
High concentration, low flow rate transportation is adopted because it can be decided after comprehensively considering factors such as anti-wear measures, lower equipment costs, and lower operating costs. The primary coal feed pipe 11 is connected to a fluid distributor 5, where the necessary number of coal feed pipes allows the transported material to be evenly distributed. At this time, the flow velocity at the inlet of the fluid distributor, solidification, vaporization, average upward flow velocity in the vessel, etc. to achieve distribution performance change depending on the particle size distribution and specific gravity of the transported material. A fluid distributor air amount adjusting device 13 is provided to optimize this condition and achieve distribution accuracy.
The amount of air supplied from the fluid distributor air amount adjustment device is adjusted to the amount obtained by subtracting the amount of air in the primary coal feed pipe 11 from the optimal amount of air in the fluid distributor 5.

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 experiments conducted by the present inventors, the amount of air supplied from the fluid distributor air amount adjustment device 13 is the average airflow inside the fluid distributor, which is the total amount of air supplied from the primary coal feeding pipe transportation air amount adjustment device 12. It was calculated and automatically adjusted so that the tower upward flow rate remained constant.

(Effects of the Invention) Since the necessary air amount conditions can be arbitrarily set and controlled in the fluid distributor 5, the following effects were obtained.

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

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing an embodiment of the coal feeding system according to the present invention, Fig. 2 a and b are sectional views and plan views showing a conventional fluid distributor, and Fig. 3 is a conventional coal feeding system. FIG. 2 is a system diagram showing an example. FIG. 4 is a graph showing the relationship between the average superficial upward flow velocity of the circular column section of a conventional fluid distributor and the distribution accuracy. 1... Fluidized bed boiler, 2... Forced blower, 3... Fluidized 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... Fine coal hopper, 11... Primary coal feeding pipe, 12... Primary coal feeding pipe transport air amount adjustment device, 13... Fluid Distributor air amount adjustment device, 21... fluid combustion section, 22... boiler cell,
31... Conical part, 32... Round tower part, 33... Coal feeding pipe,
34... Distribution branch pipe, 35... Blind plate, 41... Transport liquid supply pipe.

Claims (1)

[Scope of Claims] 1. A method for supplying coal to a boiler, which comprises disposing at least a primary coal supply pipe, a fluid distributor, and a coal supply blowing pipe, and injecting materials into the boiler by fluid transport, wherein the fluid distributor is provided with: A fluid volume adjustment device is connected to the coal supply pipe, and the total amount of fluid supplied to the primary coal feeding pipe and the fluid volume supplied from the fluid distributor fluid volume adjustment device is adjusted to a constant value. A method for adjusting the amount of fluid to a fluid distributor in a boiler coal feeding system.