JP6845711B2 - Boiler duct structure, method for reducing solid particles contained in boiler and solid gas two-phase flow - Google Patents

Description

The present invention relates to a duct structure for flowing a solid-gas two-phase flow containing solid particles in a gas, such as combustion exhaust gas discharged from a coal-fired boiler, and a method for reducing solid particles contained in the boiler and the solid-gas two-phase flow. It is about.

In a coal-fired boiler, combustion exhaust gas is emitted from the inside of a fireplace by burning coal. In this combustion exhaust gas, although the size, composition, and physical properties of coal differ depending on the coal type, fly ash and coal ash (hereinafter referred to as "large diameter ash") called fly ash and high void ratio large diameter ash (popcorn ash) (hereinafter referred to as "large diameter ash") Solid particles) are included.
Of these, fly ash is a very fine particle having a particle size on the order of several μm. On the other hand, the large-diameter ash has a relatively large particle size of about 1 mm or more, but has a high porosity, so that the particles have a small apparent specific gravity.

Conventionally, the combustion exhaust gas discharged from the fireplace 102 of the coal-fired boiler 100 is a solid-gas two-phase flow containing coal ash (solid particles), and is formed by a duct made of an iron plate, for example, as shown in FIG. After passing through the flue 110 and performing the treatment necessary for releasing the combustion exhaust gas such as denitration into the atmosphere by the denitration device 140, it is discharged to the atmosphere from a chimney or the like (not shown).
The flue 110 has a first horizontal flue 111, a first vertical flue 112, a second horizontal flue 113, and a second vertical flue in order from the upstream side in the flow direction of the combustion exhaust gas G, that is, the fireplace 102 side. A portion 114, a third horizontal flue portion 115, and a third vertical flue portion 116 are continuously provided.

In the illustrated configuration example, the first hopper 120 and the second hopper 130 are installed at the lower ends of the first vertical flue portion 112 and the second vertical flue portion 114, respectively, and are scattered together with the combustion exhaust gas from the fireplace 102. Collect the diameter ash 150. Further, a denitration device 140 that performs a denitration treatment when passing the combustion exhaust gas G is installed in the third vertical flue portion 116.

The denitration device 140 is configured such that, for example, a denitration agent (denitration catalyst) in which vanadium dioxide is supported on a lattice-shaped titanium oxide carrier is placed in a pallet, and a large number of the pallets are arranged in the pallet.

In such a flue 110, a part of the large-diameter ash 150, which is a solid particle scattered from the fireplace 102, is not recovered by the first hopper 120 and the second hopper 130, and rides on the flow of the combustion exhaust gas G. It may reach the denitration device 140. Then, the large-diameter ash 150 gradually accumulates on the lattice-shaped denitration catalyst to cause clogging, and the effective flow path cross-sectional area of the flue 110 decreases, the pressure loss increases, and the denitration performance deteriorates. Regular inspections and maintenance work may be performed as there is a risk of deterioration.

In order to prevent such clogging of the denitration catalyst, for example, in Patent Document 1 below, in the flue on the upstream side of the denitration device, a rising duct structure in which the flow of exhaust gas changes from horizontal to vertical is provided, and the horizontal duct is provided. It is described that the cross-sectional area of the vertical duct is made larger than the cross-sectional area to slow down the flow of exhaust gas in the vertical duct portion. As a result, the dust having a large particle size can easily fall in the vertical duct portion, and the structure can be made such that the dust having a large particle size does not easily flow to the denitration device on the downstream side.
In Patent Document 2, untreated gas discharged from the boiler descends the exhaust gas inlet duct, and a part or all of the exhaust gas flows horizontally in the denitration device inlet duct, descends in the denitration reactor, and then exhaust gas. The structure that flows to the outlet duct is described.

Japanese Unexamined Patent Publication No. 2-95415 Japanese Unexamined Patent Publication No. 64-70128

In recent years, due to the increase in size of exhaust gas treatment equipment due to the increase in size of boilers, in the outlet duct of the boiler and the inlet duct of the denitration device, the arrangement of each device, the size of the denitration catalyst, the flow velocity of the circulated exhaust gas, etc. are optimized. Therefore, there are cases where the flow path is moved or the cross-sectional area of the flow path is different. Since ducts of different sizes are connected, the ducts may be partially divergent. For example, in the second horizontal flue portion 113 provided on the upstream side of the denitration device 140 shown in FIG. 11, as shown in FIG. 12, the duct is tapered to flow the combustion exhaust gas while the duct height remains constant. It is expanded toward the downstream side. The angle (enlarged angle) formed by the side wall of this duct is generally 45 ° or more and 60 ° or less in order to suppress the expansion of the structure while suppressing the separation of the flowing combustion exhaust gas from the flow path wall. Often in the range of.

In this case, a swirling flow may occur in the combustion exhaust gas flow at the extension portion of the duct. As a result, the large-diameter ash having a relatively small specific gravity does not fall to the second hopper 130, but rises in the second vertical flue portion 114 along with the combustion exhaust gas flow, and the amount reaching the denitration device 140 increases. There was found. That is, it was found that not only the flow velocity of the airflow of the combustion exhaust gas in the duct but also the generation of the swirling flow affects the transport of the large-diameter ash to the wake side.

The present invention has been made in view of such circumstances, and is a duct structure for a boiler, a boiler, and a boiler that can improve the collection rate of solid particles in a hopper and reduce the outflow of solid particles to the downstream side of the duct. It is an object of the present invention to provide a method for reducing solid particles contained in a solid air two-phase flow.

The duct structure for a boiler according to the first aspect of the present invention is provided on the downstream side of the airflow due to the combustion exhaust gas in the boiler, and the lateral duct through which the airflow flows in the horizontal direction and the flow direction of the airflow in the lateral duct. A first duct that is continuously provided at the end on the downstream side and includes a vertical duct through which the airflow flows upward in the vertical direction, and the lateral duct has a constant flow path cross-sectional area along the flow direction. The side wall provided in the vertical direction of the second duct portion has a duct portion and a second duct portion connected to the downstream side of the first duct portion and the flow path cross-sectional area expands toward the downstream side. The angle formed by the side wall provided in the vertical direction of the first duct portion is larger than 0 ° and smaller than 45 °, or larger than 70 ° and smaller than 90 °.

In the first aspect, the side wall provided in the vertical direction of the second duct portion has an angle formed by an angle of more than 0 ° and less than 35 ° with the side wall provided in the vertical direction of the first duct portion. But it may be.

In the first aspect, the horizontal width Y of the first duct portion, the vertical height Z of the first duct portion, the increase d of the horizontal width of the second duct portion with respect to the first duct portion, and , The duct enlargement ratio (d / Y) / (e / Z) represented by the horizontal depth length e of the vertical duct is
0.15 ≤ (d / Y) / (e / Z) ≤ 0.3
But it's okay.

In the first aspect, the lateral duct is connected to the first duct portion, and a third duct portion in which the flow direction of the air flow is oblique to the flow direction of the air flow in the first duct portion is further formed. The side wall provided in the vertical direction of the third duct portion may have an angle formed by the side wall provided in the vertical direction of the first duct portion of more than 0 ° and 30 ° or less.

In the first aspect, the relationship between the distance f from the entrance portion of the second duct portion to the outlet portion of the third duct portion and the horizontal width Y of the first duct portion is determined.
0.25 ≤ f / Y
It may be represented by.

The boiler according to the second aspect of the present invention includes the boiler duct structure of the first aspect.

The method for reducing solid particles contained in the solid-gas two-phase flow according to the third aspect of the present invention includes a lateral duct provided on the downstream side of the airflow due to the combustion exhaust gas in the boiler and the airflow flowing in the horizontal direction, and the above-mentioned. The lateral duct is provided continuously at the end on the downstream side in the flow direction of the airflow, and includes a vertical duct in which the airflow flows upward in the vertical direction, and the lateral duct flows along the flow direction. The second duct portion has a first duct portion having a constant road cross-sectional area and a second duct portion connected to the downstream side of the first duct portion and the flow path cross-sectional area expands toward the downstream side. The angle formed by the side wall provided in the vertical direction of the first duct portion with the side wall provided in the vertical direction is greater than 0 ° and less than 45 °, or greater than 70 ° and greater than 90 °. It is characterized in that the solid particles are excluded from the air flow by flowing a solid air two-phase flow containing the solid particles as the air flow through the duct provided with the duct structure for the boiler having a small angle.

According to the present invention, it is possible to improve the collection rate of solid particles in the hopper and reduce the outflow of solid particles to the downstream side of the duct.

It is a vertical cross-sectional view which shows the boiler which comprises the duct structure for the boiler which concerns on one Embodiment of this invention. It is a perspective view which shows the duct structure for a boiler which concerns on one Embodiment of this invention. It is sectional drawing which shows the duct structure for a boiler which concerns on one Embodiment of this invention. It is sectional drawing which shows the duct structure for a boiler which concerns on one Embodiment of this invention. It is a graph which shows the relationship between the scattering rate of large-diameter ash and the duct enlargement ratio. It is a graph which shows the relationship between the scattering rate of large-diameter ash and the enlargement angle. It is a graph which shows the relationship between the scattering rate of large-diameter ash and the straight line part before expansion. It is a graph which shows the relationship between the scattering rate of large-diameter ash and the deflection angle. This is a simulation result showing the swirling flow and the center of the swirling flow when the enlargement angle is 55 °. It is a simulation result which shows the swirling flow and the swirling flow center when the expansion angle is 90 °. It is a vertical cross-sectional view which shows the boiler which has the duct structure for a conventional boiler. It is a perspective view which shows the duct structure for a conventional boiler.

The boiler duct structure according to the embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, the flue 10 provided with the boiler duct structure according to the present embodiment, for example, converts the solid air two-phase flow combustion exhaust gas discharged from the furnace 2 of the coal-fired boiler 1 into a chimney (not shown) or the like. It is something to shed. The flue 10 forms a flow path of the combustion exhaust gas G formed by a duct made of an iron plate, and has, for example, a rectangular cross section. The combustion exhaust gas G discharged from the furnace 2 is a solid-air two-phase flow containing coal ash (solid particles) called fly ash or large-diameter ash, and is burned by the denitration device 4 when passing through the flue 10. After performing the treatment necessary for releasing the exhaust gas into the atmosphere, the exhaust gas flows as shown by an arrow in FIG. 1 and is released into the atmosphere from a chimney or the like (not shown).

In the following description, upward means vertical upward, downward means vertical downward, and each is described as upward and downward. The same applies to the upper and lower parts and the upper and lower ends.

The flue 10 has a first horizontal flue portion 11, a first vertical flue portion 12, a second horizontal flue portion (lateral duct) 13, in order from the furnace 2 side which is the upstream side in the flow direction of the combustion exhaust gas G. A second vertical flue section (longitudinal duct) 14, a third horizontal flue section 15, and a third vertical flue section 16 are continuously provided.

The flue 10 is provided with a first hopper 20 at the lower end of the first vertical flue portion 12 through which the combustion exhaust gas G having a downward velocity component flows, and further, the combustion exhaust gas G having an upward velocity component flows. 2 A second hopper 30 is installed at the lower end of the vertical flue portion 14. A denitration device 4 for passing the combustion exhaust gas G to perform the denitration treatment is installed in the third vertical flue portion 16 through which the combustion exhaust gas G having a downward velocity component flows.

The first hopper 20 and the second hopper 30 are mainly installed for the purpose of recovering large-diameter ash among the solid particles contained in the combustion exhaust gas G. For fly ash with a very small particle size, few are separated from the flow of combustion exhaust gas G. Therefore, there are few large-diameter ashs that are recovered by the first hopper 20 and the second hopper 30, and the combustion exhaust gas G is conveyed in the flue 10 by an air flow, passes through the denitration device 4, and is further burned exhaust gas G. It is removed by a dust collector (not shown) on the downstream side in the flow direction of.

The second vertical flue portion 14 is continuously provided at the terminal portion 13e on the downstream side in the flow direction of the combustion exhaust gas G in the second horizontal flue portion 13, and the combustion exhaust gas G flows upward in the vertical direction.

As shown in FIGS. 2 and 3, the second horizontal flue portion 13 has a first duct portion 17 having a constant flow path cross-sectional area along the flow direction of the combustion exhaust gas G and a downstream of the first duct portion 17. It has a second duct portion 18 and the like that are connected to the side and the cross-sectional area of the flow path expands toward the downstream side. Here, in the first duct portion 17 of the second horizontal flue portion 13, the longitudinal axis direction, which is the flow direction of the combustion exhaust gas G, is orthogonal to the x-axis direction and the x-axis direction, and the horizontal direction of the first duct portion 17 is set. The vertical vertical direction orthogonal to the y-axis direction, the x-axis direction and the y-axis direction is defined as the z-axis direction. The second duct portion 18 shown in FIG. 2 is a case where the side wall 18a is provided obliquely with respect to the first duct portion 17 only on one side in the horizontal direction (y-axis direction), and is shown in FIG. The second duct portion 18 shown is a case where the side wall 18a is provided obliquely with respect to the first duct portion 17 on both sides in the horizontal direction (y-axis direction).

The first duct portion 17 is provided with an ammonia injection nozzle 40 for denitration treatment. On the downstream side of the combustion exhaust gas G from the ammonia injection nozzle 40 in the flow direction, the cross-sectional area of the flow path is expanded according to the size of the denitration catalyst housed in the reaction vessel of the denitration device 4. At this time, the second horizontal flue portion 13 is configured so that the flow velocity (for example, 10 m / s or more) of the second vertical flue portion 14 is maintained and the drift of the flow of the combustion exhaust gas G is suppressed.

The results shown in FIGS. 5 to 10 show that the Reynolds number Re = 4 million to 8 million (turbulent flow area), the flow velocity in the duct is 10 m / s to 18 m / s, and the exhaust gas temperature is 300 ° C. by numerical analysis software (Fruent steady state analysis). It was obtained by calculation under the condition of ~ 400 ° C. As a result, for each duct portion, an appropriate range of shape that reduces the scattering rate of large-diameter ash is being investigated.
As shown in FIG. 2, assuming that the horizontal direction (y-axis direction) width of the first duct portion 17 is Y, the horizontal direction (y-axis direction) width expands to Y + d at the end of the second duct portion 18. Further, the height Z in the vertical direction (z-axis direction) of the first duct portion 17 expands the depth in the horizontal direction (x-axis direction) of the second vertical flue portion 14 to e. The vertical height of the second duct portion 18 is the same as the vertical height Z of the first duct portion 17.

The flow direction of the combustion exhaust gas G changes from the horizontal direction to the vertical vertical direction, and d is an increase in the horizontal (y-axis direction) width of the second duct portion 18 with respect to the first duct portion 17, and is the first duct portion. Vertical direction (z-axis direction) height Z, increase in horizontal (y-axis direction) width d of the second duct portion 18 with respect to the first duct portion 17, and the horizontal direction of the second vertical flue portion 14 ( x-axis direction) Depth e. At this time, the relationship of the dimensionless duct enlargement ratio is
Duct enlargement ratio: (d / Y) / (e / Z)
0.15 ≤ (d / Y) / (e / Z) ≤ 0.3
It is preferable to be in.

As the duct enlargement ratio (d / Y) / (e / Z) increases, the scattering rate of large-diameter ash increases, as shown in FIG. This is because the separation position of the flow of the combustion exhaust gas G exists near the inlet of the second duct portion 18, and when the duct expansion ratio becomes large, the separation position and the swirl formed at the inlet wake side of the second duct portion 18 This is because the center position of the flow becomes large. As a result, the swirling flow is likely to develop, and the scattering rate of large-diameter ash increases.

In order to reduce the duct enlargement ratio, it is conceivable to increase (e / Z). However, if the height Z of the first duct portion 17 in the vertical direction (z-axis direction) is small, the cross-sectional shape of the duct becomes flat and the flow path resistance increases. Further, when the horizontal direction (x-axis direction) depth e of the second vertical flue portion 14 is large, the flow velocity of the combustion exhaust gas G in the second vertical flue portion 14 decreases, and a constant flow velocity, for example, 10 m / s. The above cannot be maintained and drift is likely to occur.

Therefore, the increase d in the horizontal direction (y-axis direction) width of the second duct portion 18 with respect to the first duct portion 17 is the duct enlargement ratio (d / Y) / (based on the size of the denitration catalyst of the denitration device 4. e / Z) is set. The duct expansion ratio (d / Y) / (e / Z) is preferably 0.15 ≦ (d / Y) / (e / Z) based on the actual size of the existing denitration catalyst.

Further, since (e / Z) is limited as described above, considering the individual change range of each coefficient in the applicable range of the actual machine, (d / Y) / (e / Z) ≤ 0.3. It is preferable to do so.

By providing an increase d in the horizontal direction (y-axis direction) width of the second duct portion 18 with respect to the first duct portion 17, the position of the inlet portion of the second duct portion 18 is from the outlet portion of the second duct portion. Also (d / tan θj) exists on the upstream side in the flow direction of the combustion exhaust gas G. Here, the angle (enlargement angle) θj is an angle formed by the side wall 17a (in the present embodiment, the x-axis direction) provided in the vertical direction of the first duct portion 17.

The side wall 18a provided in the vertical direction of the second duct portion 18 has an angle (enlargement angle) θj formed with the side wall 17a provided in the vertical direction of the first duct portion 17 greater than 0 ° and smaller than 45 °. It is preferably an angle, or an angle greater than 70 ° and less than 90 °.

In the second horizontal flue portion 13, the flow velocity of the combustion exhaust gas G is slow and the pressure is high on the duct wall surfaces on both sides in the horizontal direction (y-axis direction), and the flow velocity of the combustion exhaust gas G is high and the pressure is low at the center of the duct. As a result, in the inside of the second vertical flue portion 14 on the downstream side of the inlet of the second duct portion 18 where the cross-sectional area of the flow path is expanded, a swirling flow is generated near the duct wall surface due to the difference in the flow velocity of the combustion exhaust gas G.

According to the simulation results when the increase d shown in FIGS. 9 and 10 is fixed, the separation position of the flow of the combustion exhaust gas G exists near the inlet of the second duct portion 18, and the enlargement angle θj changes. However, the central position of the swirling flow inside the second vertical flue portion 14 hardly changes. As shown in FIG. 6, the enlargement angle θj becomes large, and when θj = 55 °, the scattering rate of the large-diameter ash becomes maximum. It is considered that this is because the peeling position and the center position of the swirling flow become large, and the swirling flow easily develops.

When the angle is changed in the large and small directions around θj = 55 °, the scattering rate of the large-diameter ash decreases. Therefore, by setting the enlargement angle θj to a range excluding 45 ° ≦ θj ≦ 70 °, the scattering rate of large-diameter ash can be reduced.

In the range where the enlargement angle θj is larger than 70 ° and smaller than 90 °, the separation position of the flow of the combustion exhaust gas G, that is, the inlet of the second duct portion 18 is located on the downstream side in the flow direction of the combustion exhaust gas G. Therefore, the distance between the peeling position and the center of the swirling flow becomes small, and the outer diameter of the swirling flow also becomes small, so that the swirling flow is difficult to develop. Further, the distance (d / tanθj) from the inlet to the outlet of the second duct portion 18 is also shortened, and the portion where the cross-sectional area of the flow path is expanded is narrowed. As a result, in the range where the enlargement angle θj is larger than 70 ° and smaller than 90 °, the scattering rate of the large-diameter ash becomes small.

In the range where the enlargement angle θj is larger than 0 ° and smaller than 45 °, the separation position of the flow of the combustion exhaust gas G, that is, the inlet of the second duct portion 18 is located on the upstream side in the flow direction of the combustion exhaust gas G. Therefore, it is estimated that the distance between the peeling position and the center of the swirling flow becomes large, and the outer diameter of the swirling flow also becomes large. However, in reality, since the cross-sectional area of the flow path is gradually expanding, the flow of the combustion exhaust gas G does not separate. As a result, in the range where the enlargement angle θj is larger than 0 ° and smaller than 45 °, almost no swirling flow is generated, and the scattering rate of the large-diameter ash becomes small. Although a small swirling flow is generated in the second hopper 30 below the second vertical flue portion 14, it is considered that it hardly contributes to the increase in the scattering rate of the large-diameter ash.

In the range where the enlargement angle θj is larger than 0 ° and smaller than 35 °, the scattering rate of large-diameter ash can be further reduced. In addition, the material cost and manufacturing cost of the duct can be reduced.

As shown in FIGS. 2 and 4, the second horizontal flue portion 13 may be provided with a third duct portion 19 connected to the first duct portion 17. In the third duct portion 19, the flow direction of the combustion exhaust gas G is skewed by the deflection angle θk with respect to the flow direction of the combustion exhaust gas G in the first duct portion 17 (in the present embodiment, the x-axis direction), and the combustion exhaust gas G The center line of the flow in the x-axis direction is moved in the y-axis direction. The third duct portion 19 is provided between, for example, the first duct portion 17 on the upstream side in the flow direction of the combustion exhaust gas G and the first duct portion 17 on the downstream side. The flow path cross-sectional area of the third duct portion 19 is substantially constant.

The third duct portion 19 is the arrangement position of the second horizontal flue portion 13 and the arrangement position of the denitration device 4 (perpendicular direction in the horizontal plane with respect to the center line of the first duct portion 17 (y-axis direction in the present embodiment). ), That is, a deflection angle θk is provided and installed with respect to the first duct portion 17.

Let f be the distance from the outlet of the third duct portion 19 to the inlet of the second duct portion 18 via the first duct portion 17, and the relationship with the horizontal (y-axis direction) width Y of the first duct portion 17 is dimensionless. It is defined as the expansion front straight line portion f / Y.

The expansion front linear portion f / Y in the present embodiment is preferably 0.25 or more, and more preferably 0.25 or more and 0.5 or less.

When the expansion front straight line portion f / Y is 0.25, as shown in FIG. 7, the scattering rate of the large-diameter ash is reduced and the reduction effect is maximized.

This is because a rectifying section of the combustion exhaust gas G is provided to some extent from the outlet position of the combustion exhaust gas G of the third duct portion 19. As a result, the third duct portion 19 is oblique with respect to the flow direction of the combustion exhaust gas G in the first duct portion 17 (in the present embodiment, the x-axis direction), so that the flow of the combustion exhaust gas G is separated later. The effect on the swirling flow on the flow side is reduced.

Further, when the expansion front straight line portion f / Y exceeds 0.5, the horizontal direction (x-axis direction) depth f of the first duct portion 17 with respect to the horizontal direction (y-axis direction) width Y of the first duct portion 17 becomes long. This will increase duct materials and costs. Therefore, it is not preferable to set the linear portion f / Y before expansion to exceed 0.5.

The side wall 19a provided in the vertical direction of the third duct portion 19 has an angle (deflection angle θk) formed by the side wall 17a provided in the vertical direction of the first duct portion 17 greater than 0 ° and 30 ° or less. Is preferable.

In the third duct portion 19, there is a difference in the flow velocity of the combustion exhaust gas G on the duct wall surfaces (x-axis direction in the present embodiment) on both sides in the horizontal direction (y-axis direction). As a result, the flow velocity of the combustion exhaust gas G on the deflection direction side is slow and the pressure is high. As shown in FIG. 8, when the deflection angle θk exceeds 30 °, the flow of the combustion exhaust gas G is biased, so that the combustion exhaust gas G is separated from the outlet of the third duct portion 19 and a circulation vortex is formed on the wake side. Will be done. As a result, the circulating vortex increases the swirling flow inside the second vertical flue portion 14, and the scattering rate of the large-diameter ash increases.

As shown in FIG. 8, when the deflection angle θk is in the vicinity of 20 °, the flow velocity of the combustion exhaust gas G on the deflection direction side is accelerated, and the difference in the flow velocity from the center side of the duct becomes small. As a result, the swirling flow inside the second vertical flue portion 14 becomes small, and the scattering rate of the large-diameter ash decreases.

As described above, according to the present embodiment, the side wall 18a provided in the vertical direction of the second duct portion 18 has an angle (enlargement angle) θj of 0 with the side wall 17a provided in the vertical direction of the first duct portion 17. An angle greater than ° and less than 45 °, or an angle greater than 70 ° and less than 90 °. As a result, it is possible to suppress the generation of a swirling flow when the combustion exhaust gas G flows into the second vertical flue portion 14. Therefore, the generation of a swirling flow inside the second vertical flue portion 14 can be suppressed, and the amount of large-diameter ash scattered to the denitration device 4 can be reduced.

Further, the side wall 19a provided in the vertical direction of the third duct portion 19 has an angle (deflection angle θk) formed by the side wall 17a provided in the vertical direction of the first duct portion 17 greater than 0 ° and 30 ° or less. Is. As a result, the generation of a swirling flow of the combustion exhaust gas G inside the second vertical flue portion 14 can be suppressed, and the amount of large-diameter ash scattered to the denitration device 4 can be reduced.

Therefore, the probability that the large-diameter ash is scattered by the swirling flow of the combustion exhaust gas G from the second horizontal flue portion 13 to the second vertical flue portion 14 and is transported to the downstream side in the flow direction of the combustion exhaust gas G is low. As a result, the collection rate of the large-diameter ash in the second hopper 30 is improved, and the transfer of the large-diameter ash to the denitration device 4 on the downstream side of the flue 10 is suppressed. It is possible to reduce the accumulation of large-diameter ash.

In the above embodiment, the solid particles contained in the solid-gas two-phase flow have been described as coal ash contained in the combustion exhaust gas discharged from the furnace 2 of the coal-fired boiler 1, but the duct structure of the present embodiment is adopted. The formed duct can also be applied to a device for flowing various solid air two-phase flows including soot, iron powder, diesel exhaust particles, unburned particles and the like as solid particles, for example.

In addition, although the terms "vertical direction" and "horizontal direction" are used in this specification, they are not necessarily limited to the absolute "vertical direction" and "horizontal direction", and are general. It includes the categories of "vertical direction (vertical direction)" and "horizontal direction" in the concept.
The present invention is not limited to the above-described embodiment, and can be appropriately modified without departing from the gist thereof.

1: Coal-fired boiler 2: Fire furnace 4: Denitration device 10: Flue 11: 1st horizontal flue 12: 1st vertical flue 13: 2nd horizontal flue 13e: Terminal 14: 2nd vertical smoke Road section 15: Third horizontal flue section 16: Third vertical flue section 17: First duct section 18: Second duct section 19: Third duct section 20: First hopper 30: Second hopper 100: Coal-fired Boiler 102: Fire furnace 110: Flue 111: 1st horizontal flue 112: 1st vertical flue 113: 2nd horizontal flue 114: 2nd vertical flue 115: 3rd horizontal flue 116: Third vertical flue 120: First hopper 130: Second hopper 140: Denitration device 150: Large diameter ash

Claims (7)

A lateral duct provided on the downstream side of the airflow generated by the combustion exhaust gas in the boiler and through which the airflow flows in the horizontal direction,
In the lateral duct, a vertical duct which is continuously provided at the end portion on the downstream side in the flow direction of the air flow and in which the air flow flows upward in the vertical direction,
With
The lateral duct is connected to a first duct portion having a constant flow path cross-sectional area along the flow direction and a downstream side of the first duct portion, and the flow path cross-sectional area expands toward the downstream side. Has 2 ducts
The side wall provided in the vertical direction of the second duct portion has an angle formed by the side wall provided in the vertical direction of the first duct portion of more than 0 ° and less than 45 °, or more than 70 °. Duct structure for boilers that is large and has an angle smaller than 90 °. According to claim 1, the side wall provided in the vertical direction of the second duct portion has an angle formed by the side wall provided in the vertical direction of the first duct portion of more than 0 ° and less than 35 °. Described boiler duct structure. The horizontal width Y of the first duct portion, the vertical height Z of the first duct portion, the increase d of the horizontal width of the second duct portion with respect to the first duct portion, and the vertical duct portion. The duct enlargement ratio (d / Y) / (e / Z) represented by the horizontal depth length e is
0.15 ≤ (d / Y) / (e / Z) ≤ 0.3
The boiler duct structure according to claim 1 or 2. The lateral duct is connected to the first duct portion, and further has a third duct portion in which the flow direction of the air flow is oblique to the flow direction of the air flow in the first duct portion.
Any of claims 1 to 3, wherein the side wall provided in the vertical direction of the third duct portion has an angle formed by an angle of more than 0 ° and 30 ° or less with the side wall provided in the vertical direction of the first duct portion. The duct structure for the boiler according to item 1. The relationship between the distance f from the entrance portion of the second duct portion to the outlet portion of the third duct portion and the horizontal width Y of the first duct portion is as follows.
0.25 ≤ f / Y
The boiler duct structure according to claim 4, which is represented by. A boiler having a boiler duct structure according to any one of claims 1 to 5. The airflow is provided on the downstream side of the airflow caused by the combustion exhaust gas in the boiler, and is continuously provided at the lateral duct through which the airflow flows in the horizontal direction and at the end of the lateral duct on the downstream side in the flow direction of the airflow. Is provided with a vertical duct that flows upward in the vertical direction, and the horizontal duct is connected to a first duct portion having a constant flow path cross-sectional area along the flow direction and a downstream side of the first duct portion. It has a second duct portion whose flow path cross-sectional area expands toward the downstream side, and the side wall provided in the vertical direction of the second duct portion is a side wall provided in the vertical direction of the first duct portion. For a duct having a duct structure for a boiler in which the angle between the two is greater than 0 ° and less than 45 °, or greater than 70 ° and less than 90 °.
A method for reducing solid particles contained in a solid-gas two-phase flow, which comprises suppressing the transport of the solid particles from the airflow by flowing a solid-air two-phase flow containing the solid particles as the airflow.

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