JPS6410732B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a so-called pulverized coal distribution device that uniformly distributes the amount of pulverized coal supplied to each pulverized coal burner in a pulverized coal-fired boiler. The importance of uniformly distributing pulverized coal to each pulverized coal burner of the boiler is explained below. (1) Reducing nitrogen oxide (NOX) emissions In recent years, reducing NOX emissions has become a national issue and one of the greatest environmental concerns. The increase in NOX emissions from pulverized coal-fired boilers is due to many factors related to uneven distribution of pulverized coal, so the pulverized coal uniform distribution device of the present invention is an important environmental facility as a measure to reduce NOx in pulverized coal-fired boilers. be. (2) Improving boiler efficiency If pulverized coal is distributed unevenly, the air-fuel ratio of each burner in the boiler will be disturbed, causing some burners to burn with excess air and others to burn with insufficient air, reducing boiler efficiency. Furthermore, the amount of dust generated increases due to the disturbance in the air-fuel ratio, which increases the amount of dust that adheres to the boiler tube, which also causes a decrease in boiler efficiency. Therefore, the pulverized coal uniform distribution device of the present invention is important equipment from the standpoint of improving boiler efficiency. (3) Improving the service life of the boiler tube and parts around the burner If pulverized coal is distributed unevenly, the combustion temperature of pulverized coal will vary depending on each burner due to the disturbance in the air-fuel ratio as described in (2) above. . As a result, the service life of the boiler tube and parts surrounding the burner, which are high-temperature parts, is reduced. From this point of view, it is important to uniformly distribute pulverized coal and obtain a uniform combustion temperature. (4) Improving the service life of the refractories in the boiler For the same reason as (3) above, uneven distribution of pulverized coal significantly reduces the service life of the refractories in the boiler. Therefore, a device for uniformly distributing pulverized coal is an important piece of equipment for improving the service life of refractories. As described above, it can be seen that uniformly distributing pulverized coal to each burner of a boiler is extremely important from the viewpoints of environment, energy saving, and equipment maintenance. Note that uniform distribution here includes not only uniform distribution of weight but also uniform distribution of particle size. The pulverized coal is pulverized by a coal pulverizer (mill) until the 200-mesh under is 80% or more, and then sent by air to each burner of the boiler for pulverized coal combustion. Pulverized coal is distributed from the outlet of a coal crusher (mill) to usually two to four burners per distributor. In addition, the boiler load may be increased or decreased, or the distribution number may be increased or decreased at the time of starting or stopping. From the coal crusher (mill) to each burner, the inside of the pulverized coal pipe is usually 30~
It is pneumatically transported at a flow rate of 40 m/s. As conventional pulverized coal distributors and drift pipes, Japanese Patent Application Laid-Open No. 141232/1983 discloses a powder distribution device having a structure in which a distribution pipe is connected to a square right-angled bent pipe, and a round right-angled bent pipe. A distribution device having a structure in which a distribution pipe is connected to a distribution pipe is disclosed in Japanese Patent Application Laid-Open No. 110908/1983. In the former distribution device disclosed in Japanese Patent Application Laid-Open No. 56-141232, the deflection is caused only by the curvature of the right-angle bent pipe, and therefore the deflection is insufficient. In addition, impact wear on the intermediate wall surface of the right-angle bend pipe is large. Furthermore, in order to make it a vertical transportation route, the area after the horizontal distribution pipe is 90
There is a problem in that the bending has to be performed by degrees Celsius, which increases pressure loss and wear at the bend portion. Secondly, since the latter uses a round bent pipe, the density of the pulverized coal changes between the upper and lower halves of the circle, making it difficult to distribute the pulverized coal into multiple pieces so that the average density is the same. Furthermore, like the former, the degree of drift is small because the drift is caused only by the curvature of the bent pipe. The present invention solves these conventional problems and achieves uniform distribution by generating strong drift with a simple structure.
Moreover, it is an object of the present invention to provide a device for uniformly distributing pulverized coal in a pulverized coal-fired boiler, which is excellent in that there is little reduction in life due to pressure loss and wear. The gist of the present invention is that, in a pulverized coal-fired boiler, a rectangular bent pipe-like deflection pipe is provided in the middle of a vertical pulverized coal transport path for pneumatically transporting pulverized coal to the burner of the boiler, and two A deflector block is provided at approximately the inflection point position of the inner circumferential surface of the side wall farthest from the center of curvature of the first bend, and the pulverized coal that has drifted toward the outlet side of the drift tube is evenly divided into multiple sections by multiple partition walls. The two bends in the deflector tube and the deflector block give the pulverized coal airflow a strong flow bend, and the pulverized coal being transported is deflected by inertial force and centrifugal force, and is uniformly distributed by the distributor. The present invention provides a device for uniformly distributing pulverized coal in a pulverized coal-fired boiler. In the present invention, since a biased bent pipe is used as a biased flow pipe, the flow is vertical at both the inlet and the outlet, and vertical air transport is continued by causing a drift even in a short path. The drifted flow is caused by the two bends of the lopsided vent pipe and the deflector blocks installed at the points of inflection. Due to the presence of the deflector block, the radius of curvature of the first bend can be made smaller than the radius of curvature of the outer shape of the offset vent pipe, thereby generating a stronger drifted flow at the first bend. Also, in the second bend following this, the inner wall surface along which the pulverized coal flows is shifted to the opposite inner wall surface by this deflector block. At that time, the bend in the flow has a shorter radius of curvature, so the drift becomes extremely strong. Furthermore, since a deflector block is provided at the first bending inflection point that is susceptible to impact wear, wear and tear of the deflection tube due to abrasion is reduced and the service life can be extended. Furthermore, since the channel of the deflection tube is short, the pressure loss is also low. Examples will be described below based on the drawings. As shown in Fig. 1, the solid two-phase flow of pulverized coal and air in the pulverized coal pipe 2 at the outlet of the coal crusher (mill) 1 is a non-rectified flow such as a rotating flow, so it is rectified by the rectifier 3 and straightened. Flow. Further, since the pulverized coal pipe 2 is usually circular, a circular square pipe 4 is provided to make it a square pipe. after this
A deflection pipe 5 having an appropriate angle of 30° to 90° is provided to deflect the solid-gas two-phase flow. Since the pulverized coal in the solid gas two-phase flow has a true specific gravity of 2.0 to 2.3, which is heavier than air, the flow is biased toward the outer surface of the deflection tube 5 due to inertia and centrifugal force. This is a deflector block 10 that protrudes triangularly from the inner peripheral wall of the deflection tube 5.
This forces the drifting flow and makes it more reliable. When the pulverized coal becomes uniformly distributed, the distributor 6
will be distributed at Figure 4 shows the flow of pulverized coal and air. The number of distributions is usually 2 to 4, but FIG. 2 shows a distributor for three distributions. FIG. 3 shows a cross-sectional view of the distributor along the - line. The cut dampers 7, 8, and 9 are normally open, but one or two of the cut dampers may be closed due to boiler load fluctuations, etc. Even in this case, the distribution efficiency must be good. Next, test data on the distribution efficiency of the pulverized coal distribution device according to the present invention in the case of three distributions will be shown. (1) Distribution efficiency of 3 distribution (cut damper 7, 8, 9
full throttle)

[Table] (2) Distribution efficiency of two distributions (cut damper 7 closed, cut dampers 8 and 9 fully open)

[Table] *Distribution efficiency is defined as 100% when distribution is completely equal.
Test data on pressure loss of the pulverized coal distribution device according to the present invention is shown in the table below. (3) Three distribution pressure loss (cut damper 7, 8, 9
full throttle)

[Table] (4) Pressure loss in two distributions (cut damper 7 closed, cut dampers 8 and 9 fully open)

[Table] As described above, the pulverized coal uniform distribution device according to the present invention has the following excellent effects when compared with the conventional distribution device. (1) For example, a conventional ventilate type distribution device requires a vertical pipe section that is 10 times or more the diameter of the pulverized coal pipe, but the biased flow tube type distribution device according to the present invention does not require a straight pipe section. , which is very advantageous in terms of equipment. (2) Since the distribution device according to the present invention has a simple structure, the pressure loss is 1/2 to 1/3 lower than that of conventional types. Therefore, since the pressure of the air for transporting pulverized coal is low, large air blowing equipment is not required. (3) Regarding the distribution efficiency, compared to the conventional type which is 40 to 80%, the distribution efficiency of the distribution device according to the present invention can always maintain an efficiency of 90% or more. (4) By using a rectangular, one-sided bent tube as the deflection tube and installing a deflector block at the point of inflection, the radius of curvature of the bend in the flow is reduced, resulting in two strong deflections. This caused sufficient drift and enabled uniform distribution. Furthermore, since deflector blocks are provided at inflection points where impact wear is severe, the life of the deflection tube can be extended. Furthermore, there is an advantage that the flow can be deflected within a short path, and vertical transport can be continued with less pressure loss.

[Brief explanation of the drawing]

FIG. 1 is a front view showing an embodiment of a pulverized coal uniform distribution device in a pulverized coal-fired boiler of the present invention, FIG. 2 is an explanatory diagram showing the structure of a distributor of the same embodiment, and FIG. FIG. 4 is an explanatory diagram showing the flow of pulverized coal and air in this embodiment. 1: Coal crusher (mill), 2: Pulverized coal pipe, 3:
Rectifier, 4: Circular tube, 5: Variation tube, 6: Distributor,
7, 8, 9: Cut damper, 10: Deflector block.

Claims (1)

[Claims] 1. In a pulverized coal-fired boiler, a rectangular bent tube-shaped drift pipe is installed in the middle of the vertical pulverized coal transport path that pneumatically transports pulverized coal to the boiler's burner, and the first of the two bends of the drift pipe is A deflector block is provided at approximately the inflection point position of the inner circumferential surface of the side wall farthest from the center of curvature, and a distributor is connected to the outlet side of the deflection tube to evenly divide the deflected pulverized coal into a plurality of partition walls. The two bends of the deflector tube and the deflector block give strong flow bends to the pulverized coal airflow, and the pulverized coal being transported is deflected by inertial force and centrifugal force, and is evenly distributed by the distributor. Uniform distribution device for pulverized coal in a pulverized coal-fired boiler.