SOLID FUEL BURNER AND COMBUSTION DEVICE USING SAME

TECHNICAL FIELD

The present invention relates to a burner that is mainly used in a thermal power generation plant and combusts a solid fuel such as pulverized coal and a combustion device using the burner.

BACKGROUND ART

In a boiler that comprises a plurality of burners that combust a solid fuel such as pulverized coal and adopts a two-stage combustion system as a measure for reducing NOx in a combustion exhaust gas of the fuel in the burners, to achieve both a reduction in air excess ratio and a reduction in emission of unburned combustible such as CO, there is known a technology (WO 2008/133051A1) that a flow rate of the solid fuel is measured in accordance with each burner and combustion air that is complementary with this rate is input from each burner or a two-stage combustion air port (which will be also referred to as an after-air port: AAP or an over-fire air port: OFA).

It is required to have the capability of measuring and adjusting a flow rate of a combustion gas accurately in accordance with each burner in order to apply the technology to an actual boiler.

On the other hand, there is known an invention (WO 2008/038426A1) that concerns a burner which has a flat cross-sectional shape orthogonal to a flow of a fluid in a fuel nozzle to suppress expansion of uncombusted region of fuel even when a capacity of each single burner is raised in accordance with an increase in capacity of the boiler.

Further, there is also known an invention (Japanese Unexamined Patent Application Publication No. 2002-147713, WO 2009/041081A1) of a burner that enables to respectively adjust a flow rate of an oxygen containing gas for combustion flowing through a plurality of divided flow paths surrounding a fuel supply nozzle of the burner to control a heat transfer amount for a fluid flowing through a boiler heat exchanger by changing a combustion position of the fuel in a furnace.

CITATION LIST
Patent Literature

Patent Literature 1: WO 2008/133051A1

Patent Literature 2: WO 2008/038426A1

Patent Literature 3: Japanese Unexamined Patent

Application Publication No. 2002-147713

Patent Literature 4: WO 2009/041081A1

SUMMARY OF THE INVENTION
Problems to be Solved by the Invention

A flow of the combustion air ejected from each burner is greatly affected by a configuration of the burner, especially a conformation of the flow path for the combustion gas.

To accurately measure and adjust a flow rate of the combustion gas in accordance with each burner, it is desirable to provide a long linear flow path in the vicinity of measuring means or adjusting means so that the combustion gas can uniformly flow. However, in an actual boiler, for the reason of the restrictions about installation that many burners must be compactly arranged while avoiding interference with structures outside a furnace, a conformation of the flow path that can uniform a flow of the combustion air cannot be necessarily adopted, drift may be locally produced, and the measurement and the adjustment of a flow rate may be affected.

In the burner having the flat cross-sectional shape orthogonal to the flow of the fluid in the fuel nozzle in particular, the drift is apt to be generated.

Furthermore, in a burner that actively adjusts each flow rate of the combustion gas flowing through divided flow paths, the number of targets is increased, and an adjustment width or an adjustment frequency is also increased, thus resulting in a highly demanding problem.

It is an object of the present invention to provide a solid fuel burner that has a relatively simple configuration, which is hardly affected by the local drift, and a flow rate of a combustion gas in accordance with each burner can be accurately measured and adjusted.

Further, it is another object of the present invention to provide a combustion device using this burner that has a simple configuration, is hardly affected by the local drive, accurately measures and adjusts a flow rate of a combustion gas in accordance with each burner, and achieves both a reduction in air excess ratio and emission of unburned combustibles such as CO.

Means for Solving the Problems

The object can be achieved by the invention described below.

According to a first aspect of the invention, there is provided a solid fuel burner comprising: a cylindrical fuel nozzle (10) that discharges a mixed fluid of a solid fuel and a carrier gas into a furnace (40) from a wall surface of the furnace (40); a cylindrical combustion gas throat (6) that is provided at an outer periphery of the fuel nozzle (10) and discharges a combustion gas into the furnace (40); a duct (2) that constitutes a flow path for the combustion gas that is connected to the combustion gas throat (6); flow rate adjusting means (1) for the combustion gas that is provided in the duct (2); and a differential pressure detection device (32, 35) that detects a pressure difference (a differential pressure) between the combustion gases flowing on the upstream side and the downstream side in the duct (2), wherein the duct (2) has an inlet opening (8) into which the combustion gas is taken from one direction orthogonal to a central axis direction of the fuel nozzle (10) and is formed in such a manner that the flow path for the combustion gas is bent at a right angle in the central axis direction of the fuel nozzle (10), the flow rate adjusting means (1) for the combustion gas is provided near the inlet opening (8) of the duct (2) on the downstream side of the inlet opening (8), the differential pressure detection device (32, 35) has an upstream-side pressure detection point (31, 33) on an inner wall of the duct (2) that is the farthest from the inlet opening (8) of the duct (2) corresponding to a stagnation region (90) of the combustion gas on a wake side of the flow rate adjusting means (1), and has a downstream-side pressure detection point (30, 34) on an outer wall of the combustion gas throat (6), and a control device (37) is provided, the control device (37) converting a value of a pressure difference at the upstream-side pressure detection point (31, 33) and the downstream-side pressure detection point (30, 34) detected by the differential pressure detection device (32, 35) into a flow rate of the combustion gas and operating the flow rate adjusting means (1) to adjust a flow rate of the combustion gas.

A second aspect of the invention provides the solid fuel burner according to the first aspect, wherein the flow path for the combustion gas in the duct (2) that is connected to the combustion gas throat (6) is divided by a partition wall (4) into a plurality of flow paths that the combustion gas does not flow from one flow path to another, and the upstream-side pressure detection point (31, 33) and the downstream-side pressure detection point (30, 34) are provided to each of the plurality of flow paths.

A third aspect of the invention provides the solid fuel burner according to in the first aspect, wherein the downstream-side pressure detection point (30, 34) is provided on the combustion gas throat (6) where an interval between the combustion gas flow paths in a radial direction becomes maximum with the central axis of the fuel nozzle (10) being determined as a reference.

A fourth aspect of the invention provides the solid fuel burner according to the first aspect, wherein the differential pressure detection device (32, 35) is configured to detect a value of a differential pressure between an upstream-side pressure and a downstream-side pressure of the combustion gas in the duct (2) through respective pressure conduits constituting the upstream-side pressure detection point (31, 33) and the downstream-side pressure detection point (30, 34).

A fifth aspect of the invention provides a combustion apparatus comprising solid fuel burners (44) according to the first aspect on a plurality of stages along an up-and-down direction and in a plurality of rows along a furnace width direction on a wall surface of a furnace (40), wherein the combustion apparatus comprises solid fuel flow rate measuring means (71) for individually adjusting and measuring flow rates of a solid fuel that flows into the plurality of solid fuel burners (44), and a control device (37) is configured to adjust an opening degree of flow rate adjusting means (1) for a combustion gas based on a combustion gas flow rate detected by a differential pressure detection device (32, 35) of each solid fuel burner (44) in accordance with a change in solid fuel flow rate measured by the solid fuel flow rate measuring means (71), and to individually control each flow rate of the combustion gas.

In the present above-mentioned invention, the stagnation region 90 (FIG. 2, FIG. 3) for the combustion gas in which each upstream-side pressure detection point 31 or 33, one of pressure detection points, is set means a region where a flow velocity of the combustion gas is nearly zero or relatively minimum in the flow path.

Specifically, a portion near the inner wall of the duct 2 which is the farthest from the inlet opening 8 of the duct 2 for the combustion gas corresponds to each upstream-side pressure detection point 31 or 33. For example, in the duct 2 shown in FIG. 2, when the flow path of the cube is constituted of a front wall 56 close to the furnace side, a rear wall 57 which is provided to be parallel to the front wall 56 at an interval and placed at a position distanced from the furnace side, and a sidewall 55 which connects ridge line portions of the front and rear walls 56 and 57, a region of the sidewall 55 that faces and is the farthest from an inlet opening surface of the duct 2 which functions as the inlet opening 8 of the combustion air corresponds to each upstream-side pressure detection point 31 or 33.

Here, when there is provided such a conformation as shown in FIG. 2 where each of the front wall 56 and the rear wall 57 is ovalized and has a U-like shape as a whole (see FIG. 2) and the sidewall 55 separates the flow path (the duct 2) for the combustion gas from the outside over linear portions and curved portions of the ridge lines of the front wall 56 and the rear wall 57, a top portion of a curved surface formed of the sidewall 55 corresponds to each of the upstream-side pressure detection points 31 or 33 (FIG. 1).

Moreover, the top portion of the curved surface formed of the sidewall 55 can function as a region where a flow path cross-sectional area of the duct 2, i.e., an area of the duct cross section orthogonal to the flow direction of the combustion gas in the straight portion of the duct 2 through which the combustion gas travels straight from the inlet opening 8 of the duct 2 approximates zero without limit.

Additionally, when the fuel nozzle 10 has a rectangular shape, an oval shape, or an elliptic shape (FIG. 1 shows an example of the oval shape) having a long-diameter portion and a short-diameter portion in a cross-sectional shape thereof orthogonal to a central axis direction (a flow direction of the fluid traveling toward the outlet portion) thereof, a region where a plane including a top portion of the long-diameter portion and the central axis of the fuel nozzle 10 (which is the same plane as a partition wall (a center partition) 4 in the conformation shown in FIG. 1) is parallel to a line crossing the sidewall 55 of the duct 2 corresponds to each upstream-side pressure detection point 31 or 33 (FIG. 1).

On the other hand, each of the downstream-side pressure detection points 30 and 34 (FIG. 1) which is the other pressure detection point is provided at a top portion of the combustion gas throat 6 that is the farthest from the partition wall (the center partition) 4 that divides the combustion gas duct 2 into upper and lower portions when the combustion gas throat 6 is arranged in a burner attachment opening 58 (FIG. 2) of the furnace 40. In the example where the cross-sectional shape of the fuel nozzle 10 depicted in FIG. 1 is the oval shape, each of these points is present in a region of the combustion gas throat 6 where a difference between the diameter of the concentrically arranged cylindrical combustion gas throat 6 and the short diameter of the fuel nozzle 100 having the oval cross-sectional shape, i.e., a cross-sectional area of the flow path of the duct 2 for the combustion gas with running through a central axis of the fuel nozzle 10 in the radial direction of the fuel nozzle 10 becomes maximum. In other words, it is present in a region where the plane including the short-diameter portion of the fuel nozzle 10 and the central axis of the fuel nozzle 10 are parallel to a line crossing the fuel gas throat 6.

The two pressure detection points (the upstream-side pressure detection point 31 and the downstream-side pressure detection point 30; and the upstream-side pressure detection point 33 and the downstream-side pressure detection point 34 in FIG. 1) are not restricted to one specific point or line, and they are the region which have a given width and more specifically, can also be defined by the following geometric numerical range.

The stagnation region 90 (FIG. 2, FIG. 3) of the combustion gas dust 2 where each upstream-side pressure detection point 31 or 33 is arranged is a region where a flow velocity of the combustion gas is substantially zero or it is relatively minimum in the duct 2, and this region is present in a region that runs through the central axis of the fuel nozzle 10 with the partition wall (the center partition) 4 that divides the downstream-side duct 2 of the duct 2 into upper and lower parts at the center and is surrounded by planes each of which is in the range of 15° on the upper or lower side.

The top portion of the combustion gas throat 6 which is the position where each of the downstream-side pressure detection points 30 and 34 is arranged is present in the range of ±2° in the circumferential direction (see FIG. 12) and on the downstream side of a half point of a throat length of the combustion gas throat 6 in the central axis direction when a position at which the difference between the diameter of the throat 6 and the diameter of the flow path of the fuel nozzle 10 becomes maximum (a perpendicular running through the central axis of the combustion gas throat 6 in FIG. 1) is determined as a reference.

(Operation)

The present invention has the following operation.

A value of a differential pressure of the combustion gas at each upstream-side pressure detection point 31 or 33 and each downstream-side pressure detection point 30 or 34 detected by each of the differential pressure detection devices 32 and 35 can be converted into a flow rate of the combustion gas when it is assigned to a predetermined conversion formula, whereby the flow rate of the combustion gas (gas such as air) each burner can be measured.

The predetermined conversion formula is as follows.

Q=C×√(OP×P)

(Q: a flow rate, C: constant, OP: a differential pressure, P: density of the fuel gas)

The combustion gas duct 2 has the inlet opening 8 into which the combustion gas is introduced from one direction orthogonal to the central axis direction (a flow direction of the fluid flowing toward the outlet opening portion on the furnace side) of the combustion gas throat 6, and it is formed so that the flow path (the duct) 2 of the combustion gas can bend at a right angle toward the central axis direction of the combustion gas throat 6.

To measure a flow rate of the combustion gas in the duct 2 by the differential pressure detection devices 32 and 35 and adjust this flow rate, the duct 2 is compactly accommodated in a wind box 41 parallel to the wall surface of the boiler furnace 40 while obtaining a duct length required to suppress an influence of drift produced in the duct 2.

The flow rate adjusting means 1 for the combustion gas is provided on an upstream-side of the installing portion for each differential pressure detection device 32 or 35 in the duct 2 for the combustion gas. As a result, since a duct length of the duct 2 from the flow rate adjusting means 1 can be assured to some extent, the flow rate adjusting means 1 can reduce a flow velocity distribution of the combustion gas in the duct cross section that is produced and is apt to increase when an opening degree of the inlet opening 8 is small.

Further, the flow rate adjusting means 1 which involves a mechanical operation such as opening/closing can be prevented from directly receiving radiant heat from the inside of the furnace 40 or from colliding with clinkers or the like falling from, e.g., the upper side of the furnace 40, and a possibility that damage or an inconvenience of an operation caused thereby can be lowered.

Since each of the differential pressure detection devices 32 and 35 determines an inner wall position of the duct 2 farthest from the inlet opening 8 of the duct 2 corresponding to the stagnation region 90 of the combustion gas on the wake side of the flow rate adjusting means 1 as each of the upstream-side pressure detection points 31 and 33, an influence of a dynamic pressure acting on each of the pressure detection points 31 and 33 is reduced, and the combustion gas flow rate can be measured without being affected by the drift of the combustion gas because the downstream-side pressure detection points 30 and 34 are arranged on the top portion wall surface and the bottom portion wall surface of the combustion gas throat 6, thereby highly accurately measuring the flow rate of the combustion gas.

The duct 2 for the combustion gas connected to the combustion gas throat 6 is divided into two portions by the partition wall (the center partition) 4, and the upstream-side pressure detection points 31 and 33 and the downstream-side pressure detection points 30 and 34 are provided to the respective divided flow paths.

As a result, the flow rates of the combustion gas flowing through the plurality of ducts 2 are deviated on upper and lower sides of the combustion air outlet opening 7 of the burner 44, accurate adjustment can be individually carried out, a flame forming position in the furnace 40 can be controlled, and NOx concentration of a nitrogen oxide in a combustion exhaust gas can be effectively reduced, or an amount of heat transfer to a heat transfer tube (not shown) installed in the boiler furnace 40 can be effectively controlled. When the duct 2 is divided into the plurality of flow paths, the number of targets of the combustion gas flow rate measurement and adjustment is increased, the flow rate is actively changed in accordance with each flow path, its span of adjustable range or frequency is thereby increased, and hence the configuration using the upstream-side pressure detection points 31 and 33 and the downstream-side pressure detection points 30 and 34 has high importance.

Furthermore, even if the shape of the cross section of the fuel nozzle 10 orthogonal to the central axis direction (the flow direction of the fluid flowing toward the outlet opening on the furnace side) in which drift of the combustion gas is apt to be generated is the rectangular shape, the oval shape, or the elliptic shape having the long-diameter portion and the short-diameter portion, when each of the downstream-side pressure detection points 30 and 34 is provided on the outer wall surface of the combustion gas throat 6 where the flow path cross-sectional area of the combustion gas in the radial direction becomes maximum with the central axis of the combustion gas throat 6 determined as the reference, the flow rate of the combustion gas can be accurately measured with being hardly affected by the drift.

When a differential pressure detection device that detects a value of a differential pressure between an upstream-side pressure and a downstream-side pressure of the combustion air through pressure conduits constituting each upstream-side pressure detection point 31 or 33 and each downstream-side pressure detection point 30 or 34 is used, each of the differential pressure detection devices 32 and 35 can be easily realized without greatly increasing facility cost.

In a combustion apparatus such as a boiler that comprises the solid fuel flow rate measuring means 71 provided in a plurality of stages in the vertical direction and a plurality of rows in the furnace width direction on the wall surface of the furnace 40 in particular and individually measure the flow rate of the solid fuel flowing into the solid fuel burner 44 and that is configured to individually control the combustion gas flow rate of each solid fuel burner 44 in accordance with a change in fuel flow rate measured by the solid fuel flow rate measuring means 71, when the flow rate of the combustion gas flowing through each of the plurality of flow paths must be individually accurately adjusted, this is important since the number of required devices is large. It is to be noted that this configuration can be applied not only the combustion device according to the present invention but also any other combustion devices using the solid fuel burner 44.

Effects of the Invention

According to the invention of the first aspect, the duct 2 of the combustion gas has the inlet opening 8 into which the combustion gas is introduced from one direction orthogonal to the central axis direction of the combustion gas throat 6, the duct 2 is formed to bend at a right angle toward the central axis direction of the combustion gas throat 6, the flow rate adjusting means 1 for the combustion gas is provided at the anterior flow portion in the duct 2 for the combustion gas, and hence the length of the duct 2 can be assured to some extent, whereby the flow rate adjusting means 1 can decrease spread of the flow velocity distribution of the combustion gas in the duct cross section for the combustion gas that is produced and apt to increase when an opening degree of the inlet opening 8 is small in particular.

Moreover, since each of the upstream-side pressure detection points 31 and 33 is provided in the stagnation region 90 of the combustion gas in the duct 2, the flow rate of the combustion gas can be highly accurately measured with being hardly affected by a dynamic pressure acting on each of the upstream-side pressure detection points 31 and 33, and assigning a value of the differential pressure detected by each of the differential pressure detection devise 32 and 35 into a predetermined conversion formula (1) enables conversion into a flow rate of the combustion gas and allows each burner to measure a flow rate of the combustion gas (gas such as air). In this manner, the combustion gas flow rate can be measured without being affected by drift of the combustion gas.

Additionally, since the combustion gas flow rate is measured by each of the differential pressure detection devices 32 and 35 and this flow rate is adjusted by the flow rate adjusting means 1, the duct 2 can be compactly accommodated in the wind boxy 41 parallel to the wall surface of the boiler furnace 40 while obtaining a duct length required for suppressing an influence of the drift produced in the duct 2 for the fuel gas.

Further, since the flow rate adjusting means 1 is provided in the duct 2, the flow rate adjusting means 1 that involves a mechanical operation such as opening/closing can be prevented from directly receiving the radiant heat from the furnace 40 or from colliding with clinkers or the like falling from, e.g., the upper side of the furnace 40, thus lowering a possibility that damage or an inconvenience of an operation caused thereby occurs.

According to the invention of the second aspect, in addition to the effect of the invention of the first aspect, when the duct 2 for the combustion gas is divided into the two combustion gas flow paths by the partition wall 4 and each upstream-side pressure detection point 31 or 33 and each downstream-side pressure detection point 30 or 34 are provided in the respective flow paths, the flow rate of the combustion gas flowing through each of the plurality of ducts 2 can be individually and accurately adjusted on the upper and lower sides, and the forming position of a flame in the furnace 40 can be controlled. When the duct 2 is divided into the plurality of flow paths, the number of targets for measurement and adjustment of the combustion gas flow rate is increased, and the flow rate can be actively changed in accordance with each flow path, whereby the flow rate can be finely adjusted.

According to the invention of the third aspect, in addition to the effect of the invention of the first aspect, even if the shape of the cross section of the fuel nozzle 10 orthogonal to the central axis direction (the flow direction of the fluid flowing toward the outlet opening on the furnace side) in which drift of the combustion gas is apt to be produced is the rectangular shape, the oval shape, or the elliptic shape having the long-diameter portion and the short-diameter portion, when each of the downstream-side pressure detection points 30 and 34 is provided on the outer wall surface of the combustion gas throat 6 where the flow path cross-sectional area of the combustion gas in the radial direction becomes maximum with the central axis of the fuel nozzle 10 determined as a reference, the flow rate of the combustion gas can be accurately measured with being hardly affected by the drift.

According to the invention of the fourth aspect, in addition to the effect of the invention of the first aspect, each of the differential pressure detection devices 32 and 35 can detect a value of the differential pressure between the upstream-side pressure and the downstream-side pressure of the combustion gas in the duct 2 through the pressure conduits connected to each upstream-side pressure detection point 31 or 33 and each downstream-side pressure detection point 30 or 34, and it can be easily realized without greatly increasing facility cost.

According to the invention of the fifth aspect, the flow rates of the solid fuel flowing into the plurality of solid fuel burners 44 in the combustion device are individually adjusted and measured by the solid fuel flow rate measuring means 71, the control device 37 adjusts an opening degree of the flow rate adjusting means 1 for the combustion gas based on each combustion gas flow rate detected by the differential pressure detection device 32 or 35 of each solid fuel burner 44 in accordance with a change in measured solid fuel flow rate, and the control device 37 individually controls each flow rate of the combustion gas, thereby rapidly coping with a change in solid fuel flow rate of each burner 44. Furthermore, adjusting the combustion gas alone can suffice, and the adjusting means can have a simpler configuration as compared with a case where the solid fuel is conveyed with use of a carrier gas. Moreover, when an amount of combustion gas is deviated depending on each of the upper and lower sides of each burner 44, flames can be changed to the upward direction or the downward direction in the furnace 40, NOx concentration of a nitrogen oxide in the combustion exhaust gas can be reduced, or an amount of heat transfer to the heat transfer tube (not shown) installed in the boiler furnace 40 can be effectively controlled.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic perspective view of a solid fuel burner according to an embodiment of the present invention;

FIG. 2 is a view showing constituent element of the burner shown in FIG. 1;

FIG. 3 is a front view of a combustion air duct seen from a boiler front side of the burner in FIG. 1;

FIG. 4 is a cross-sectional view taken along a line A-A of the burner shown in FIG. 3;

FIG. 5 is a schematic front view (FIG. 5(a)) and a side view (FIG. 5(b)) showing an example of a furnace having the burner in FIG. 1 disposed thereto;

FIG. 6 is a view for explaining drift in the burner in FIG. 1;

FIG. 7 is a view for explaining the drift in the burner in FIG. 1;

FIG. 8 is a view for explaining the drift in the burner in FIG. 1;

FIG. 9 is a view for explaining the drift in the burner in FIG. 1;

FIG. 10 is a view for explaining a relationship between a damper opening degree and a static pressure of the burner in FIG. 1;

FIG. 11 is a view for explaining positions at which downstream-side pressure detection points of the burner in FIG. 1 are disposed;

FIG. 12 is a view for explaining the positions at which the downstream-side pressure detection points of the burner in FIG. 1 are disposed;

FIG. 13 is a view for explaining an influence of the damper opening degree on the static pressure at the positions where the downstream-side pressure detection points of the burner in FIG. 1 are disposed in the direction of a central axis;

FIG. 14 is a view for explaining the influence of the damper opening degree on the static pressure at the positions where the downstream-side pressure detection points of the burner in FIG. 1 are disposed in the direction of circumference;

FIG. 15 is a schematic view of control over a supply amount of a solid fuel in a furnace using the burners in FIG. 1;

FIG. 16 is a view for explaining a general technique for measuring a combustion air (gas) flow rate; and

FIG. 17 is a view for explaining a general technique for measuring a combustion air (gas) flow rate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment according to the present invention will now be described with reference to the drawings.

In an embodiment according to the present invention described below, it is assumed that a solid fuel, especially pulverized coal, woody biomass, or a mixture of the pulverized coal and the woody biomass is combusted as a main fuel by a solid fuel burner, but a type of fuel is not necessarily restricted, and a liquid or a gas may be used as a main fuel. Further, air is assumed to be used as a combustion gas, but the air alone is not necessarily restricted, and a recirculating gas of a combustion exhaust gas, a high-oxygen concentration gas, or a mixed gas of the various kinds of gases may be used.

FIG. 1 is a schematic perspective view of a solid fuel burner according to an embodiment of the present invention, and FIG. 5 is a schematic front view (FIG. 5(a)) and a side view (FIG. 5(b)) when the solid fuel burners 44 to which the present invention is applied are incorporated in a boiler furnace 40.

Combustion air enters burners 44 from a wind box 41 provided on the outer side of a sidewall of the boiler furnace 40 shown in FIG. 5 through a combustion air duct 2 depicted in FIG. 1 and flows into the furnace 40 from a combustion air throat 6 provided at an opening portion of the sidewall of the furnace 40. Furthermore, pulverized coal and its carrier air are ejected into the furnace 40 through a solid fuel carrying tube (a fuel nozzle) 10.

The combustion air throat 6 that ejects the combustion air into the furnace 40 is provided on the outer peripheral side of the solid fuel carrying tube 10, and the combustion air is supplied into the combustion air throat 6 from the combustion air duct 2. An air inlet opening 8 into which the combustion air from the window box 41 is introduced is provided in the combustion air duct 2, an air inflow direction of the air inlet opening 8 indicated by an arrow B in FIG. 1 is provided to be parallel to a furnace wall surface on which a burner 44 is installed so that the combustion air is bent at a substantially right angle from the air inlet opening 8 and is spouted into the furnace 40 from a combustion air outlet opening 7 toward the furnace wall surface. Therefore, the combustion air duct 2 is provided at the outer peripheral portion of the solid fuel carrying tube (the fuel nozzle) 10, and the air that has flowed into the air inlet opening 8 is bent at a substantially right angle to surround the outer peripheral portion of the solid fuel carrying tube 10 and supplied to the combustion air throat 6.

Although an outlet opening portion of the solid fuel carrying tube 10 has a flow path formed into an oval configuration as seen from the inside of the furnace 40, whereas an outlet opening of the throat 6 has a gas flow path formed into a circular configuration as seen from the inside of the furnace. Therefore, the furnace outlet opening of the throat 6 has an opening portion that is large in an up-and-down direction around the outlet opening of the solid fuel carrying tube 10.

The combustion air duct 2 is divided into two parts in the up-and-down direction by a center partition 4, and upper air and lower air (combustion gas) do not become confluent in the combustion duct 2. Moreover, the combustion air inlet opening 8 of the combustion air duct 2 is divided by an upper partition 3 and a lower partition 5 and consists of four spaces in total including the spaces divided by the center partition 4, and a combustion air (combustion gas) amount adjustment damper 1 is installed in each of the spaces.

FIG. 2 is a detailed perspective view of the combustion air duct 2. The combustion air duct 2 is connected to the combustion air throat 6, and it is constituted of a U-shaped front wall 56 arranged to be parallel to a furnace wall surface on the side close to the furnace wall surface, a U-shaped rear wall 57 arranged to be parallel to the front wall 56 on the side far from the furnace wall surface on the back side of the front wall 56, and a sidewall 55 that has both end portions connected to ridge line portions of the front wall 56 and the rear wall 57 and covers the spaces of the combustion air duct 2. The front wall 56 has a circular opening portion 58 connected to the combustion air throat 6, and the sidewall member 57 has an opening 59 connected to the solid fuel carrying tube 10.

The center partition 4 is installed at a position having a height 0.5 L1 which is a center position having a height L1 of the inlet opening 8 of the combustion air duct 2, divides the combustion air inlet opening 8 into two parts in the up-and-down direction, and is joined to the front and rear walls 56 and 57 for the configuration of the duct 2, and the spaces in the combustion air duct 2 divided into two parts in the up-and-down direction by the center partition 4 are independent from each other so that the combustion air does not flow into or out from these spaces.

Additionally, in the combustion duct 2 divided into two parts in the up-and-down direction by the center partition 4, an upper partition plate 3 and a lower partition plate 5 are arranged, respectively. The upper partition plate 3 is arranged on the lower side with a height L3 from a top portion of the combustion air inlet opening 8, the lower partition plate 5 is arranged on the upper side with a height L4 from a bottom portion of the combustion air inlet opening 8, and these plates are arranged so as to be parallel to the center partition 4. Although the height L3 and the height L4 can be arbitrarily determined, they must be set not less than a length of a blade of the damper 1 in a gas flow direction.

Although a length L6 of each of the upper partition plate 3 and the lower partition plate 5 in the gas flow direction can be also arbitrarily determined, it must be less than a length L5 of the center partition 4 in order to allow the combustion air to flow out from the outlet opening 7 into the furnace 40. In this embodiment, the two partition plates, i.e., the upper partition plate 3 and the lower partition plate 5 are used as partition members, but an arbitrary number of the partition plates can be used.

FIG. 3 is a front view of the combustion air duct 2 as seen from the boiler front side (a front furnace wall of the boiler furnace 40). A curvature radius r2 of a cross-sectional semicircular portion of the sidewall 55 which is a constituent member of the combustion air duct 2 must be set larger than a radius r1 of the combustion air throat 6 (r2>r1). As a result, an effect of alleviating drift at the combustion air outlet opening 7 can be obtained.

FIG. 4 is a cross-sectional view taken along a line A-A in FIG. 3. The combustion air 20 that has flowed into the combustion air duct 2 from the combustion air (the combustion gas) inlet opening 8 bends at a right angle, flows through a space between the combustion air throat 6 and the solid fuel carrying tube 10, and flows out into the furnace 40 from the combustion air outlet opening 7. The space between the combustion air throat 6 and the solid fuel carrying tube 10 is also divided into two parts in the up-and-down direction by the center partition 4 to reach the combustion air outlet opening 7. As a result, a combustion air amount is deviated depending on each of the upper and lower sides of the combustion air outlet opening 7, and flames are changed to the upward direction or the downward direction, which is effective for a reduction in NOx concentration of a nitrogen oxide in the combustion exhaust gas or control over an amount of heat transfer to the heat transfer tube (not shown) installed in the boiler furnace 40.

The combustion air duct 2 is divided into two parts in the up-and-down direction by the center partition 4 to reach the combustion air outlet opening 7. The center partition 4 allows a combustion air amount to deviate depending on each of the upper and lower sides of the combustion air outlet opening 7, and flames are changed to the upward direction or the downward direction in the boiler furnace 40, which is effective for a reduction in NOx concentration of a nitrogen oxide in the combustion exhaust gas or control over an amount of heat transfer to the heat transfer tube (not shown) installed in the boiler furnace 40.

In regard to a flow rate of the combustion air in the combustion air duct 2 divided into the two parts in the up-and-down direction to sandwich the center partition 4 therebetween, a deviation between measured pressure values at an upstream-side pressure detection point 31 and a downstream-side pressure detection point 30 which are pressure conduits and a deviation between measured pressure values at an upstream-side pressure detection point 33 and a downstream-side pressure detection point 34 which are pressure conduits are measured, respectively.

The upstream-side pressure detection points 31 and 33 as the pressure conduits configured to measure a flow rate of the combustion air are disposed in a stagnation region 90 (FIG. 3) of the combustion air duct 2. Here, the stagnation region 90 means the region 90 represented by a filled portion in FIG. 2 and a hatched portion in FIG. 3, it is the region (a space surrounded by the front and rear walls 56 and 57 and the sidewall 55) restricted by virtual planes which run through the center of an opening portion 58 and are formed in the vertical direction at tilt angles θ₁and θ₂relative to a horizontal plane to sandwich the center partition 4 with the central axis of the combustion air throat 6 at an origin, and the upstream-side pressure detection points 31 and 33 as the pressure conduits can be arbitrarily disposed in the stagnation region 90. A value of each of the tilt angles θ₁and θ₂will be described later in detail.

Further, the downstream-side pressure detection points 30 and 34 as the other pressure conduits are respectively installed at a top portion and a bottom portion of the combustion air throat 6 that are positions at which a difference between the radius r1 of the combustion air throat 6 and an outlet radius r3 of the solid fuel carrying tube 10 becomes maximum. The downstream-side pressure detection points 30 and 34 are disposed on the wall surface of the combustion air throat 6 shown in FIG. 1 with a longitudinal direction of each of the downstream-side pressure detection points 30 and 34 being set in the vertical direction so as not to be affected by a dynamic pressure.

An upstream-side fluid pressure (a high-pressure side pressure) of the combustion air flowing through the combustion air duct 2 is led from each of the upstream-side pressure detection points 31 and 33, and a downstream-side fluid pressure (a low-pressure side pressure) of the combustion air is led from each of the downstream-side pressure detection points 30 and 34. The upstream- and downstream-side pressure detection points 30 and 31 as the pressure conduits are connected to the differential pressure detection device 32, the upstream- and downstream-side pressure detection points 33 and 34 are connected to the differential pressure detection device 35, and differential pressures obtained at these points are assigned to the predetermined flow rate conversion formula (1), thereby calculating a flow rate of the combustion air.

Although an arbitrary material or diameter can be adopted for each of the pressure conduits constituting the upstream- and downstream-side pressure detection points 30 and 31; and 33 and 34, a temperature of the combustion air (approximately 300° C.) must be taken into consideration in regard to the material. Furthermore, as to the diameter of each of the pressure conduits constituting the upstream- and downstream-side pressure detection points 30 and 31; and 33 and 34, clogging or the like by dust contained in the combustion air must be taken into consideration, and applying a purge system and the like is also effective.

FIG. 5 is a schematic view of the furnace 40 using the burners 44 in which the present invention is incorporated. The wind box 41 is installed in the furnace 40, and a plurality of two-stage combustion air (combustion gas) ports 42 and burners 44 to which the present invention is applied are disposed. A solid fuel supplied from the outside of the furnace 40 is connected to each burner 44 from the solid fuel carrying tubes 10.

FIG. 5 shows an example where the burners 44 are disposed on a boiler front side of the furnace 40, and the present invention can be also used for the opposed combustion burners installed on the boiler front side and a boiler rear side of the furnace 40. FIG. 5 shows an example where the two-stage combustion air (combustion gas) ports 42 are installed on two stages, and the number of stages may be one. The six ports 42 are installed in one row in FIG. 5, but an arbitrary number can be set.

Each of FIG. 16 and FIG. 17 shows an example of a generalized combustion air (combustion gas) flow rate measurement device. FIG. 16 shows an example of a flow rate measurement device using a pitot tube 61. The pitot tube 61 is installed in a flow path 60 with an introduction port of a total pressure detection hole 62 facing a direction opposite to a fluid flow 22. A fluid pressure detected by the total pressure detection hole 62 and a static pressure detection hole 63 is supplied to a differential pressure detection device 67 and assigned to the predetermined flow rate conversion formula (1), thereby calculating a flow rate.

FIG. 17 shows an example of a combustion air (combustion gas) flow rate measurement device using an orifice. An orifice 64 is disposed in a perpendicular direction relative to a fluid flow 22 in a flow path 60. Pressure conduits 65 and 66 are installed on the upstream side and the downstream side to sandwich the orifice 64 therebetween. A fluid pressure detected by the pressure conduits 65 and 66 is supplied to a differential pressure detection device 67 and assigned to the predetermined flow rate conversion formula (1), thereby calculating a flow rate.

In case of the pitot tube 61, a sufficient straight pipe length required in the burner 44 cannot be taken, a measurement accuracy for a fuel flow rate is low, and it may probably be influenced by drift. Although many pitot tubes 61 may be used to measure a given cross section in the flow path 60 at a plurality of positions in order to enhance the flow rate measurement accuracy, costs are disadvantageously high. Additionally, in case of using the orifice 64, unwanted pressure loss occurs because of the flow rate measurement, power for a fan or the like increases in order to supply the combustion air to each burner 44, which is not preferable.

In regard to the generalized flow rate measurement device, the flow rate measurement device according to the present invention detects pressure loss of the combustion air (gas) caused due to the burner configuration by using the upstream- and downstream-side pressure detection points 30 and 31 and the differential pressure detection device 32 or the upstream- or downstream-side pressure detection points 33 and 34 and the differential pressure detection device 35 respectively and converts the pressure loss into a combustion air (gas) flow rate, and unwanted pressure loss concerning the flow rate measurement does not occur. Further, when each appropriate differential pressure detection locus is selected, a differential pressure to be detected is not affected by a change in flow pattern due to an operation of the adjustment damper 1 or by drift, and hence highly accurate flow rate measurement can be carried out.

The drift of the burner combustion air will now be described.

FIG. 6 is a view showing the burner 44 from the boiler front side when an angle δ formed between a perpendicular 52 and the combustion air amount adjustment damper 1 is 30°, the perpendicular 52 being obtained by connecting rotary axes 1a, 1b, 1c, and 1d of a plurality of adjustment dampers 1 which are arranged in parallel near the combustion air inlet opening 8 of the combustion air duct 2, and FIG. 7 schematically shows flow rate deviations at the combustion air outlet opening 7.

In regard to the combustion air amount adjustment damper 1, the dampers 1a, 1b, 1c, and 1d are respectively disposed in a space 50a partitioned by the sidewall 55 and the upper partition 3, a space 50b partitioned by the upper partition 3 and the center partition 4, a space 50c partitioned by the center partition 4 and the lower partition 5, and a space 50d partitioned by the lower partition 5 and the sidewall 55.

In FIG. 6, the angle δ formed between the perpendicular 52 and an extended line 53 of each blade of the damper 1 is 30° (a damper opening degree 30°). A flow 21 of the combustion air in the combustion air duct 2 at this time has such a flow rate that varies as shown in FIG. 7. As shown in FIG. 7, the flow rate is high in a region B of the combustion air outlet opening 7, and the flow rate is low in a region A of the outlet opening 7. The flow rate is low in a region C of the outlet opening 7, and the flow rate is high in a region D of the outlet opening 7. This is drift of the combustion air.

FIG. 8 and FIG. 9 schematically show the burner 44 from the boiler front side when the angle δ formed between the perpendicular 52 and an extended line 53 of the combustion air amount adjustment damper 1 is 90° (a damper opening degree 90°) and flow rate deviations at the combustion air outlet opening 7. When the angle δ varies, the flow 21 of the combustion air differs from that when the damper opening degree is 30° in FIG. 6. Therefore, the flow rate deviations at the combustion air outlet opening 7 are different from those when the damper opening degree is 30°, the flow rate deviation is high in each of the region B of the combustion air outlet opening 7 and the region C of the outlet opening 7, and the flow rate deviation is low in the region A of the outlet opening 7 and the region D of the outlet opening 7.

Since the damper 1 is automatically controlled so that a burner air ratio can have a predetermined value, it is desirable to install the upstream-side and downstream-side pressure detection points 30 and 31; and 33 and 34 as the pressure conduits at positions where these points are not affected by the angle δ formed between the perpendicular 52 and the damper 1. The upstream-side pressure detection points 30 and 31; and 33 and 34 must be installed in the stagnation region 90 (FIG. 2, FIG. 3) that is not affected by a contracted flow of each damper 1.

FIG. 10 shows a result of examination obtained when a full-size model was used. An abscissa represents an opening degree (%) of the combustion air amount adjustment damper 1 relative to the perpendicular 52 in FIG. 6 and FIG. 8, and an ordinate represents a ratio (dimensionless) of a static pressure relative to burner pressure loss when the flow rate is unchanged. When the angles θ₁and θ₂assumed to represent the range of the stagnation region 90 shown in FIG. 3 fall within the range of θ₁=θ₂≦15°, a value of the static pressure/the burner pressure loss is substantially fixed in the range of the actually used angles θ₁and θ₂. That is because a flow velocity is substantially zero and the range that the angles θ₁and θ₂meet θ₁=θ₂≧15° is considered as the stagnation region 90. Therefore, the upstream-side pressure detection points 31 and 33 can be installed at arbitrary positions on the sidewall which is a constituent member of the combustion air (combustion gas) duct 2 included in this range.

Positions of the downstream-side pressure detection points 30 and 34 as the pressure conduits will now be examined. The downstream-side pressure detection points 30 and 34 must be installed in a region where these points are not affected by the drift of the combustion air (gas) shown in FIG. 6 to FIG. 9.

FIG. 11 is a schematic view showing installing positions 81 to 83 for the downstream-side pressure detection point 30 in the central axis direction of the combustion air throat 6, and FIG. 12 is a schematic view showing installing positions 84 to 87 for the downstream-side pressure detection point 30 in the circumferential direction of the throat 6. The installing positions 81 to 83 for the downstream-side pressure detection point (FIG. 11) are set on the top portion of the combustion throat 6 where the following expression becomes maximum in the radial direction, the installing position 82 for the downstream-side pressure detection point is set at a position with an intermediate length (0.5×L₁₀) of a length L₁₀of the throat 6, the installing position 81 for the downstream-side pressure detection point is set on the downstream side of the throat 6, and the installing position 83 for the downstream-side pressure detection point is set on the upstream side of the throat 6.

(The radius r1 of the throat 6)—(the radius r3 of the fuel nozzle 10)

Further, as shown in FIG. 12, each of the downstream-side pressure detection point installing positions 84, 85, 86, and 87 is set at an intermediate position of the length of the throat 6 in the central axis direction, each of the downstream-side pressure detection point installing positions 85 and 86 has a tilt angle θ₃=2° in the radial direction of the throat 6 with respect to a perpendicular running through the central axis of the throat 6, and each of the installing positions 84 and 87 for the downstream-side pressure detection point has the tilt angle θ₃=20° in the radial direction of the throat 6 with respect to the same.

Each of FIG. 13 and FIG. 14 shows a result of examination obtained when a full-size model was used. An abscissa in each of FIG. 13 and FIG. 14 represents an angle (a damper opening degree) formed between the perpendicular 52 and the combustion air (combustion gas) amount adjustment damper 1 in FIG. 6 and FIG. 8, and an ordinate in the same represents static pressure/burner pressure loss when the flow rate is unchanged.

As shown in FIG. 13, at each of the installing positions 81 and 82 for the downstream-side pressure detection point in the central axis direction of the throat 6, the static pressure is substantially fixed in the damper opening degree range to be used. As shown in FIG. 14, at each of the installing points 82, 85, and 86 for the downstream-side pressure detection point in the circumferential direction of the throat 6, the static pressure/burner pressure loss is substantially fixed in the range that is approximately 10 to 80% of the damper opening degree range to be used. Although the static pressure/burner pressure loss slightly differs in the damper opening degree range to be used, a differential pressure detected by each of the burner differential pressure detection devices 32 and 35 shown in FIG. 1 is 100 Pa or more, and hence this differential pressure only slightly affects accuracy of a flow rate measurement.

As described above, assuming that PL is an installing position, in regard to the central axis direction of the throat portion 6, the installing position of each of the downstream-side pressure detection points 30 and 34 of the burner shown in FIG. 1 is set in the range of 0.5 L₁₀≦PL≦L₁₀on the downstream side from a center point of the length L of the throat 6. In regard to the circumferential direction of the throat 6, each installing position is assumed to be set in the range of 0°≦θ₃=θ₄≦2° shown in FIG. 12.

Furthermore, FIG. 15 shows a view for explaining solid fuel measuring means, and the solid fuel is pulverized by a solid fuel pulverization device 70 (e.g., a vertical mill) until a predetermined particle diameter is obtained, and the fuel is carried to each burner 44 by a carrier gas through the solid fuel carrying tube 10. The solid fuel carrying tube 10 comprises solid fuel measuring means 71 (for example, there is a measuring instrument which is of a static charge type or a micro wave type and so forth). Therefore, flow rates of the solid fuel that flows into the plurality of solid fuel burners 44 in the combustion device are individually adjusted and measured by the solid fuel flow rate measuring means 71, the control device 37 adjusts an opening degree of the flow rate adjusting means 1 for the combustion gas and individually controls the flow rates of the combustion gas based on the combustion gas flow rates detected by the differential pressure detection devices 32 and 35 of the respective solid fuel burners 44 in accordance with a change in measured solid fuel flow rates, and hence it is possible to rapidly cope with a change in solid fuel flow rate of each burner 44.

Moreover, as to control over a burner load, adjusting the combustion gas alone can suffice, and the adjusting means and others can have simpler configurations than those in case of using the solid fuel that is carried by the carrier gas. Additionally, when a combustion gas amount is deviated depending on each of the upper and lower sides of each burner 44 in the furnace 40, flames can be changed to the upward direction or the downward direction, and NOx concentration of a nitrogen oxide in the combustion exhaust gas can be reduced, or an amount of heat transfer to the heat transfer tube (not shown) installed in the boiler furnace 40 can be effectively controlled. Further, since the combustion air outlet opening 7 is divided into the two parts in the up-and-down direction by the center partition 4, the combustion air amount is deviated depending on each of the upper and lower sides of the combustion air outlet opening 7, and the flames are changed to the upward direction or the downward direction in the boiler furnace 40, thereby effectively enabling a reduction in NOx concentration of a nitrogen oxide in the combustion exhaust gas or control over an amount of heat transfer to the heat transfer tube (not shown) installed in the boiler furnace 40.

In this embodiment, the burner configuration has been explained with use of the fuel nozzle 10 having a flat transverse cross section. In the present invention, the above-described measuring technique can be used with respect to the fuel nozzle 10 having a circular transverse cross section without being restricted to the flat shape.

When the fuel nozzle 10 has the circular transverse cross section, since the combustion air outlet opening 7 has a concentric cross-sectional shape formed of the fuel nozzle 10 and the combustion air throat 6, the drift is hardly produced as compared with the example adopting the flat shape.

However, the combustion air that has flowed in from the combustion air inlet opening 8 is not necessarily uniformly discharged from the combustion air throat 6 having the concentric shape in the combustion air duct 2.

An example where the fuel nozzle 10 is the fuel nozzle 10 having the circular transverse cross-sectional shape will be assumed and described with reference to FIG. 8. A flow of the air that has flowed in from the combustion air inlet opening 8 is disturbed by the adjustment damper 1. When the angle δ formed between the perpendicular 52 in FIG. 6 and the extended line 53 of the blade of the damper 1 is 30°, an air current flows downward along the vertical direction, and hence an air flow rate from the combustion air outlet opening 7 close to the downstream of the adjustment damper 1 increases.

As described above, the air flow rate at the combustion air outlet opening 7 is deviated when the transverse cross-sectional shape of the fuel nozzle 10 is either the flat shape or the circular shape.

A description will now be given as to installing positions of the upstream-side pressure detection points (although not shown, they correspond to the upstream-side pressure detection points 31 and 33 of the fuel nozzle 10 having the flat transverse cross-sectional shape in FIG. 1) of the fuel nozzle 10 having the circular transverse cross-sectional shape. As described above, the circular fuel nozzle 10 is affected by the drift due to an opening degree of the damper 1 like the flat fuel nozzle 10.

Since the installing positions PL for the upstream-side pressure detection points are the same as those of the flat fuel nozzle 10 in FIG. 11, a description will be given with reference to FIG. 11. To avoid an influence of an air contracted flow at the time of flowing from the combustion air duct 2 toward the combustion air throat 6 shown in FIG. 11, the range of 0.5 L₁₀≦PL≦L₁₀in the air flowing direction is preferable with respect to the length L₁₀of the throat 6, and the range of 0°≦θ₃=θ₄≦2° is preferable for the installing positions θ₃and θ₄in the circumferential direction as shown in FIG. 12. That is because the static pressure at the upstream-side pressure detection points is hardly changed in the adopted damper opening degree range. Therefore, in case of the fuel nozzle 10 having the circular transverse cross-sectional shape, it is desirable to install the upstream-side pressure detection points in the same range as the flat fuel nozzle 10.

Furthermore, the downstream-side pressure detection points (which correspond to the downstream-side pressure detection points 30 and 34 installed on the flat fuel nozzle 10 shown in FIG. 10, and hence a description will be given with reference to FIG. 1) are arranged on the top portion wall surface and the bottom portion wall surface of the combustion gas throat 6. The top portion of the combustion gas throat 6 that is a position where the downstream-side pressure detection point is arranged is determined as a reference, and the detection points are present in the range of ±2° in the circumferential direction (see FIG. 12) on the downstream side that is ½ of the throat length of the combustion gas throat 6 along the central axis direction (see FIG. 11). Moreover, since the downstream-side pressure detection points are arranged on the top portion wall surface and the bottom portion wall surface of the combustion gas throat 6, the combustion gas flow rate can be measured without being affected by the drift of the combustion gas, and the flow rate of the fuel gas can be highly accurately measured.

Additionally, in case of the fuel nozzle 10 having the circular transverse cross section, although not shown, differential pressure detection devices corresponding to the differential pressure detection devices 32 and 35 shown in FIG. 1 are provided, and a control device that converts values of pressure differences between the upstream-side pressure detection points and the downstream-side pressure detection points into the flow rates of the combustion gas and adjusts an amount of combustion air flowing into the combustion air duct based on a damper operation is also provided.

An example where the center partition 4 of a burner comprising the fuel nozzle 10 having the flat or circular transverse cross section is not provided will now be described.

In the foregoing embodiment, the combustion air duct 2 is completely divided into two parts in the up-and-down direction, and the combustion air measurement points must be installed at the two positions on the combustion air duct 2 divided into the upper and lower sides. However, when the center partition 4 is not provided, measuring points corresponding to the pressure detection points 30, 31, 33, and 34 in FIG. 1 are narrowed down to one position. The installing position for the pressure detection point should be set to a position that is not affected by the drift of the damper 1.

Here, an influence of the drift of the combustion air due to an opening degree of the damper 1 is assumed. The installing position of the downstream-side pressure detection point (which is not shown and corresponds to the downstream-side pressure detection point 30 or 34 in FIG. 1) will be examined. The left side of the combustion air outlet opening 7 like the region (B) or (C) in FIG. 9, namely, the combustion air outlet opening 7 on the side close to the combustion air inlet opening 8 is affected by the drift due to the damper 1, which is inappropriate. On the other hand, on the right side of the combustion air outlet opening 7, i.e., the side distanced from the combustion air inlet opening 8 (the region (A) or (D)), the air flow rate differs depending on an opening degree of the damper 1 due to an influence of a flow rate deviation in the region (B) or (C). On the top portion of the combustion air throat 6, there is no flow rate deviation due to the damper 1, the upper and lower sides are less unbalanced, and hence the flow rate deviation is small irrespective of the opening degree of the damper 1.

Therefore, installing the downstream-side pressure detection point (not shown) on the top portion or the bottom portion of the combustion air throat 6 can suffice. Considering the maintenance or ease of installation, it is good to install this detection point on the top portion.

Moreover, as the position at which the upstream-side pressure detection point (not shown) is installed, one position can suffice. When the center partition 4 is present, the stagnation space 90 (see FIG. 2) in the combustion air duct 2 is installed on the downmost-stream portion on each of the upper and lower sides. Even if there is no center partition 4, a large part of the combustion air flows out to the throat 6 before reaching the downmost-stream portion of the combustion air duct 2, and hence the stagnation region where there is almost no flow of the combustion air is produced. In the stagnation region, a static pressure is stable irrespective of an opening degree of the damper 1. Therefore, one downstream-side pressure detection point is installed in a region where each of the pressure detection points 30 and 34 is disposed on the downmost-stream portion of the combustion air duct 2 in FIG. 1.

When the combustion air duct 2 is divided into two parts in the up-and-down direction by the center partition 4, a duct center portion (a top part of a semicircular portion of the combustion air duct 2) at which the center partition 4 and the combustion air duct 2 cross each other is provided at the farthest position from the combustion air inlet opening 8, and a static pressure is in the most stable state in the stagnation region. Therefore, it is desirable to provide the upstream-side detection point on the top part (a position corresponding to each of the upstream-side pressure detection points 31 and 33 in FIG. 1) of the semicircular portion of the combustion air duct 2.

REFERENCE SIGNS LIST

1 combustion air flow rate adjustment damper

2 combustion air duct

3 upper partition

4 partition wall (center partition)

5 lower partition

6 combustion air throat

7 combustion air outlet opening

8 combustion air inlet opening

10 solid fuel carrying tube (fuel nozzle)

11 carried air/fuel outlet opening 20 to 22 air flow

31, 33 upstream-side pressure detection point

30, 34 downstream-side pressure detection point

32, 35 differential pressure detection device

37 control device

40 furnace

41 wind box

42 two-stage combustion air port

44 burner

50 space formed by partitioning the combustion air duct

52 perpendicular

53 extended line of a blade of the damper

55 sidewall

56, 57 front wall

58 opening for connecting a combustion air (gas) throat

59 opening for connecting a combustion carrying tube

60 flow path

61 pitot tube

62, 63, 65, 66 pressure conduit

64 orifice

67 differential pressure detection device

70 solid fuel pulverization device

71 solid fuel flow rate measuring means

81 to 87 installing position for the downstream-side pressure detection point

90 stagnation region

SOLID FUEL BURNER AND COMBUSTION DEVICE USING SAME

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CPC

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