JP2007057229A - Through-flow boiler - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a through-flow boiler having an inexpensive means which excellently maintains a combustion state by reducing the CO concentration, the unburnt content, and sticking ash in the vicinity of side walls with a simple structure. <P>SOLUTION: This through-flow boiler has a combustion chamber 13 formed of front-rear walls ( burner walls) 14a and 14b mutually opposed by arranging a plurality of stages of burners 2, 3 and 4 in at least one and the side walls 1a and 1b crossing with the burner walls 14a and 14b. A gas jetting port 6 of a jet 18 of gas including no fuel for increasing gas pressure in the vicinity of the side walls 1a and 1b in the combustion chamber 13 more than gas pressure in a central part of the combustion chamber 13, is arranged between the outermost burner and the side walls 1a and 1b in a height range of the burner stages 2, 3 and 4. Combustion gas 16 cannot approach the side walls 1a and 1b by the jet 18 of the gas. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a once-through boiler, and more particularly to a once-through boiler that is competitive in reducing CO concentration, unburned matter, and attached ash in the vicinity of a side wall of a furnace.

  In order to increase the thermal efficiency of the boiler, the carbon monoxide (CO) concentration and unburned content in the furnace must be reduced. The following methods are known in order to reduce the CO concentration and unburned content in the furnace.

  The first method is a method of adjusting operating conditions, specifically, a method of adjusting the air flow rate of the burner and the air flow rate of the two-stage combustion after-air port.

  The second method is a method of supplying air to a space where the unburned content becomes high. As an example of the second method, there is a method of flowing air along the wall of the furnace (see, for example, Patent Document 1, Patent Document 2, Patent Document 3, and Patent Document 4).

  Among these conventional examples, Patent Documents 1 to 3 disclose a once-through boiler in which an air outlet is provided below the burner stage.

  Patent Document 4 discloses a once-through boiler in which air outlets are provided on four walls of a furnace, and air outlets are provided at the upper and lower and middle heights of a plurality of burner stages.

Japanese Utility Model Publication No. 59-92346 (pages 4-6, FIGS. 4 and 5) Japanese Utility Model Publication No. 2-122909 (pages 4-7, Fig. 1) Japanese Patent Laid-Open No. 3-286918 (page 2, Fig. 1) Japanese Patent Laid-Open No. 62-131106 (Page 2, Fig. 1, Fig. 2) Japanese Patent Laid-Open No. 7-98103 (page 3 FIGS. 1 to 4)

  The inventors verified the effectiveness of the conventional first method and the second method by measuring an actual boiler, numerical analysis, and the like. As a result, even if any of these methods is adopted, at least at the height of the burner stage and in the vicinity of the side wall intersecting with the wall provided with the burner, the CO concentration and unburned content of the combustion gas are still high. It was revealed. Moreover, when coal was burned, it turned out that ash adheres to a side wall.

  The cause is that the combustion gas generated from the burner comes to the vicinity of the side wall where the burner is provided because the pressure in the vicinity of the side wall is lower than the combustion region in the center of the furnace.

  This countermeasure is disclosed in Patent Document 5. In this example, in a once-through boiler having a plurality of burners and a plurality of two-stage combustion air inlets downstream thereof, a combustion gas having an oxygen partial pressure of 10% or less between the side wall of the furnace and the burner. A structure is proposed in which an auxiliary combustion port for supplying the gas is provided, and the amount of combustion gas injected from the auxiliary combustion port and the direction of the jet flow are adjusted to prevent the burner jet from rewinding to the furnace side wall.

  However, this conventional example requires a pipe for supplying a combustion gas having an oxygen partial pressure of 10% or less to the auxiliary combustion port. A combustion gas supply pipe having a length of several tens of meters must be routed, and a significant increase in cost is inevitable.

  An object of the present invention is to provide a once-through boiler capable of suppressing combustion gas from coming near the side wall using air, oxygen, combustion exhaust gas, or the like.

  The present invention relates to a once-through boiler having a combustion chamber formed by front and rear walls and side walls intersecting with the front and rear walls, and a burner installed in a plurality of stages on at least one of the front and rear walls. In order to make the pressure higher in the vicinity of the side wall than the center of the combustion chamber, a once-through boiler is proposed in which a gas outlet is provided between the outermost burner and the side wall within the range of the height of the burner stage. .

  The present invention also provides a once-through boiler having a combustion chamber formed by front and rear walls and side walls intersecting with the front and rear walls, and a burner installed in a plurality of stages on at least one of the front and rear walls. In order to make the gas pressure in the vicinity of the side wall higher than the gas pressure in the center of the combustion chamber, a once-through boiler provided with a gas jet outlet on the side wall within the burner stage height range is provided. suggest.

  The present invention further includes a combustion chamber formed by front and rear walls and side walls intersecting with the front and rear walls, and has a plurality of burners on at least one of the front and rear walls, and two-stage combustion downstream of the burner stage. In the once-through boiler having the after-air port for the gas, the jet of the gas jet that makes the pressure of the gas in the vicinity of the side wall in the combustion chamber higher than the pressure of the gas in the center of the combustion chamber has a height of the burner stage. A once-through boiler is proposed in which at least one stage is provided between the outermost burner and the side wall within a range, and a plurality of stages are provided between the lowermost burner and the after-air port.

  In any of the above-described once-through boilers, the gas jet is provided at the same height of the front and rear walls facing each other, and the jet flow at a speed at which the gas jet from the gas jet facing the middle collides between the front and rear walls. It is desirable to provide an air supply means for ejecting the air.

  More specifically, the present invention provides means for supplying pulverized coal as fuel and air for conveying the pulverized coal to the plurality of burners, means for supplying combustion air to the plurality of burners, Means for supplying a jet gas to the gas jet port, and in any one of the once-through boilers, the flow rate of the jet from the gas jet port is controlled based on the load command of the boiler and the coal type information, Proposed a once-through boiler equipped with control means for reducing the flow rate of the jet from the gas jet port when the load on the boiler is low, increasing the load on the boiler and increasing the flow rate of the jet flow from the gas jet port To do.

  The present invention also provides means for supplying pulverized coal as fuel and air for conveying the pulverized coal to the plurality of stages of burners, means for supplying combustion air to the plurality of stages of burners, and the gas outlet Means for supplying a jet gas, and in any of the above-described once-through boilers, means for measuring a carbon monoxide (CO) concentration of combustion gas in the vicinity of the side wall, the boiler load command, the CO concentration The flow rate of the jet flow from the gas jet port is controlled based on the measurement result of the above, and when the load on the boiler is low, the flow rate of the jet flow from the gas jet port is reduced, the load on the boiler is increased and the There is proposed a once-through boiler provided with a control means for increasing the flow rate of the jet from the gas jet and reducing the flow rate of the jet from the gas jet when the CO concentration is less than or equal to a predetermined value.

  The control means may be means for increasing the flow rate of the jet as the pulverized coal has a lower fuel ratio.

  The means for supplying the jet gas to the gas jet port may branch the combustion air of the burner into the jet air. In that case, it is preferable to provide a flow rate adjusting damper in each of the combustion air flow path and the jet air flow path.

  The means for supplying the jetting gas to the gas jetting port can branch the pulverized coal transport air into the jetting air.

  When an after-air port for two-stage combustion is installed downstream of the burner stage, the means for supplying the jet gas to the gas jet outlet can branch the after air into jet air.

  In the present invention, in a once-through boiler having a combustion chamber formed by front and rear walls and side walls intersecting with the front and rear walls, and a burner installed in a plurality of stages on at least one of the front and rear walls, the gas in the combustion chamber In order to make the pressure in the vicinity of the side wall higher than the center of the combustion chamber, a gas jet is provided between the outermost burner and the side wall within the range of the height of the burner stage. , The combustion gas can be prevented from approaching the side wall, and ash adhesion due to the collision of the combustion gas, the CO concentration at the furnace outlet, and the unburned content can be reduced.

  In the present invention, the once-through boiler refers to a boiler in which combustion gas generated by the combustion of fuel flows in one direction from the fuel inlet to the furnace outlet.

  According to the present invention, in the once-through boiler having the combustion chamber formed by the front and rear walls and the side walls intersecting with the front and rear walls, and a plurality of stages of burners installed on at least one of the front and rear walls, the height of the burner stage In this range, a gas outlet is provided between the outermost burner and the side wall to inject gas into the combustion chamber, and the pressure of the gas near the side wall is higher than the pressure of the gas in the center of the combustion chamber. Gas can be prevented from approaching the side wall, and ash adhesion due to collision of combustion gas, CO concentration at the furnace outlet, and unburned content can be reduced.

  Next, an embodiment of a once-through boiler according to the present invention will be described with reference to FIGS.

  FIG. 1 is a perspective view showing a schematic structure of a furnace in Embodiment 1 of a once-through boiler according to the present invention. The furnace has a front wall 14a and a rear wall 14b, and a left side wall 1a and a right side wall 1b that intersect these walls 14a and 14b. Burners are attached to at least one of the opposed front wall 14a and rear wall 14b in a plurality of rows and a plurality of rows. In the case of Example 1, the lower burner 2, the middle burner 3, and the upper burner 4 are each composed of four rows of burners. Each burner puts fuel and combustion air into the combustion chamber 13.

  The gas outlet 6 installed according to the present invention is located between the lower burner 2 and the upper burner 4 in the height direction and between the side wall 1 and the outermost burner in the left-right direction. The gas outlet 6 of the first embodiment is formed at the same height as the middle burner 3. The gas jet 6 on the front wall 14a and the gas jet 6 on the rear wall 14b are formed so as to face the positions where the jets of the gas jet 6 collide.

  In the first embodiment, a gas not containing fuel is supplied from the gas jet 6. Gas components that do not contain fuel are air, oxygen, combustion exhaust gas, and the like. The flow speeds of the opposing jets do not have to be the same, and the position where the jets collide and the pressure at the collision position can be adjusted by changing the flow speed and flow rate of the jets.

  FIG. 2 is a cross-sectional view illustrating an example of the structure of the gas ejection port 6 in the first embodiment. FIG. 3 is a front view showing an example of the structure of the gas ejection port 6 of FIG. The shape of the gas outlet 6 is defined by a water pipe 17 that constitutes a boiler. A water pipe 17 is disposed around the gas outlet 6 in a direction parallel to the central axis of the gas outlet 6. When the water pipe 17 is arranged in this way, the attenuation of the jet 18 at the gas outlet 6 is reduced, and the pressure when the jet 18 collides can be increased. The optimum shape of the gas ejection port 6 is a cylinder and has a circular cross section. If the cross section of the gas jet port 6 is circular, the water jet 17 is easily bent to form the gas jet port 6.

  FIG. 4 is a diagram showing an outline of the flow of the combustion gas 16 and the jet 18 in the furnace of the first embodiment in which the gas outlet 6 is installed on the front wall 14a and the rear wall 14b. When the gas outlet 6 is installed, the combustion gas 16 does not approach the side walls 1 a and 1 b due to the gas jet 18 ejected from the gas outlet 6. This is because the pressure in the vicinity of the side walls 1a and 1b is increased by the gas jet 18 ejected from the gas ejection port 6.

  FIG. 5 is a front view schematically showing the flow of combustion gas in a conventional furnace in which no gas jet 6 is installed. When the gas outlet 6 is not installed, the combustion gas 16 formed by the burner stages 2, 3, 4 flows in the direction of the side walls 1a, 1b. The combustion gas 16 from the lower burner 2 is blocked by the combustion gas 16 of the middle burner 3 and the upper burner 4 and cannot rise directly above, so it flows in the direction of the side walls 1a and 1b where the pressure is low.

  Even if the gas ejection port 6 is formed not between the burner stages 2, 3 and 4 but between the bottom of the furnace and the ceiling, a temporary effect can be obtained. However, if it is installed at a location away from the burner stages 2, 3, 4 the effect is small.

  As shown in the prior art, when the gas outlet 6 is formed below the burner stages 2, 3, 4, the pressure in the vicinity of the side wall 1 at the formed height increases, but the burner stages 2, 3, At a height of 4, the pressure is low and the combustion gas 16 produced by the burners 2, 3, 4 flows in the direction of the side walls 1a, 1b.

  When the gas outlet 6 is formed on the upper side of the burner stages 2, 3, and 4, the pressure in the vicinity of the side walls 1 a and 1 b increases as compared with the case where the gas outlet 6 is not formed. However, compared with the case where the gas outlets are formed in the regions of the burner stages 2, 3 and 4, the pressure rise is small, and the combustion gas 16 generated by the burners 2, 3 and 4 flows in the direction of the side walls 1a and 1b. Cheap.

  When the jet 18 from the gas outlet 6 reaches the center of each of the side walls 1a and 1b, the object of the present invention can be satisfactorily achieved. When the jet 18 cannot reach the center of each of the side walls 1a and 1b, the combustion gas 16 tends to flow in the direction of the side walls 1a and 1b. Therefore, the jet 18 must collide with the center part of each side wall 1a, 1b. The desired flow rate of the jet 18 is in the range of 30 m / s to 90 m / s. In addition, when the gas outlet 6 is configured to supply a straight-flowing gas, the gas momentum attenuation can be made smaller than when the swirl-flowing gas is supplied. Gas can be supplied to the central portions of the side walls 1a and 1b.

  The jet 18 of the gas outlet 6 may be supplied not only vertically to the burner wall 14 but also at an arbitrary angle. When the jet 18 of the gas jet port 6 is supplied so as to face the inside of the combustion chamber 13, the combustion gas 16 is less likely to flow in the direction of the side wall 1. When the jet 18 is ejected toward the side wall 1, the gas of the jet 18 can be supplied along the side wall 1. When the combustion gas 16 approaches the side wall 1, the heat absorption of the side wall 1 increases, and the temperature of the water wall constituting the side wall 1 rises. The jet 18 at the gas outlet 6 also serves to cool the side wall 1.

  FIG. 6 is a diagram showing an outline of the flow of the combustion gas 16 and the jet 18 in the furnace of Example 2 in which the gas outlet 8 is installed on the left side wall 1a and the right side wall 1b. The configurations of the burner stages 2, 3, 4 and the front wall 14a and the rear wall 14b are the same as in the first embodiment. The gas outlet 8 need not be installed only on the front wall 14a and the rear wall 14b on which the burner stages 2, 3, and 4 are installed. Even if the gas outlet 8 is installed on the side walls 1a and 1b, the same effect as in the first embodiment can be obtained. In this case, as in the first embodiment, it is necessary to increase the pressure in the vicinity of the side walls 1a and 1b. The flow rate of the jet 18 is suitably in the range of 30 m / s to 90 m / s. In addition, the jet 18 of the gas outlet 8 may be supplied not only vertically to the front wall 14a and the rear wall 14b but also at an arbitrary angle. FIG. 6 shows an example in which the jet 18 is supplied downward. When the jet 18 is directed downward, the jet 18 and the combustion gas 16 collide with each other, increasing the pressure. As a result, the combustion gas 16 does not approach the side walls 1a and 1b.

  FIG. 7 is a perspective view showing a schematic structure of a furnace in Embodiment 3 of the once-through boiler according to the present invention. The configurations of the burner stages 2, 3, 4 and the front wall 14a and the rear wall 14b are the same as in the first embodiment. Above the burner stages 2, 3, 4, an after-air port 9 for two-stage combustion is attached. At least one stage of gas jets 6 is installed between the lower stage burner 2 and the upper stage burner 4, and a plurality of stages are installed between the lower stage burner 2 and the after-air port 9. In Example 3, it is attached to a total of three places, the same height as the middle burner 3, between the upper burner 4 and the after air port 9, and the same height as the after air port 9.

  The jets 18 from these gas jet ports 6 increase the pressure at the center of the side wall 1 and prevent the combustion gas 16 from approaching the side wall 1 as in the first embodiment. If the gas outlet 6 is installed in the burner stages 2, 3, 4, it becomes difficult for the combustion gas 16 to approach the side walls 1 a, 1 b, and at the same time, the reducing gas generated by the two-stage combustion method is oxidized to form the side walls 1 a, 1 b. The CO concentration and unburned content in the vicinity can be reduced. In addition, by installing a plurality of gas outlets 6 as shown in FIG. 7, the pressure in the vicinity of the side walls 1 a and 1 b increases, and the combustion gas 16 containing reducing gas does not easily approach the side wall 1.

  FIG. 8 is a front view showing a streamline 41 toward the left side wall 1a in the third embodiment. FIG. 9 is a diagram showing the calculation result of the CO concentration (%) at a position 10 cm from the left side wall 1a of Example 3. The numerically analyzed boiler is a boiler with a maximum output of 500 MW of pulverized coal culm and is in a state of 100% load. From the gas outlet 6, 4% of the combustion air was introduced. The ejection speed is 40 m / s.

  FIG. 10 is a front view showing a streamline 41 toward the left side wall 1a in a conventional once-through boiler. FIG. 11 is a diagram showing a calculation result of the CO concentration (%) at a position 10 cm from the left side wall 1a in FIG. The numerically analyzed boiler is a boiler with a maximum output of 500 MW of pulverized coal culm and is in a state of 100% load.

  FIG. 12 is a front view showing a streamline 41 in the direction of the left side wall 1a in a conventional once-through boiler in which a boundary air device 42 for forming an air flow along the wall is provided at the lower part of the furnace. FIG. 13 is a diagram showing a calculation result of the CO concentration (%) at a position 10 cm from the left side wall 1a in FIG. The numerically analyzed boiler is a boiler with a maximum output of 500 MW of pulverized coal culm and is in a state of 100% load. From the boundary air device 42 of FIG. 12, 8% of the combustion air is introduced as the boundary air 43.

  8, 10, and 12, when the gas outlet 6 is provided as shown in FIG. 8 according to Example 3 of the present invention, the side wall 1 a, compared with the conventional example of FIGS. 10 and 12, The flow of the combustion gas 16 in the 1b direction is small. In particular, there is almost no flow from the middle burner 3 and the upper burner 4 toward the side walls 1a and 1b. The jet 18 from the gas outlet 6 prevents the combustion gas 16 from colliding with the side wall. When the boundary air device 42 of FIG. 12 is provided, it is hardly possible to prevent the combustion gas 16 from colliding with the side walls 1a and 1b.

  The CO concentration in the vicinity 1 of the side wall in Example 3 of the present invention in FIG. 9 is 1% or less downstream of the burner stage.

  The CO concentration near the side wall 1 in the conventional boiler of FIG. 11 reaches a maximum of 10% between the upper burner 4 and the after-air port 9. Carbon monoxide in the vicinity of the side wall 1 is hardly oxidized and flows to the furnace outlet 5.

  The CO concentration in the vicinity of the side wall 1 in the conventional boiler in which the boundary air 42 in FIG. 13 is installed is 8% at the maximum, which is not much different from that in the conventional boiler in FIG. The CO concentration distribution is such that even if the boundary air 42 flows along the side wall 1, the combustion gas 16 flowing from the burners 2, 3, 4 flows toward the side wall 1 where the pressure is low, This is because it collides with the side wall 1.

  FIG. 14 shows burner A in which the NOx at the furnace outlet 5 has the lowest value when the burner air ratio is around 0.8, and burner B in which the NOx at the furnace outlet 5 has the lowest value when the burner air ratio is around 0.7. It is a figure which compares and shows a characteristic. It is desirable that the burner used in Example 3 has the characteristic that the NOx at the furnace outlet 5 is minimized under the operating condition where the burner air ratio is lower than 0.8. In order to reduce NOx at the furnace outlet 5 when the burner B is used, it is effective to lower the burner air ratio from 0.8 to 0.7. However, when the burner air ratio is lowered, the reducing gas produced in the burner stages 2, 3, and 4 flows in the vicinity of the side wall 1, thereby increasing the CO concentration and the unburned content.

  For this reason, the conventional boiler is operated with a burner air ratio of about 0.8, and the NOx at the furnace outlet 5 is almost the same between the burner A and the burner B.

  On the other hand, in the present invention, for example, when the gas outlet 6 is installed as shown in the third embodiment, the CO concentration and the unburned portion near the side wall 1 can be reduced, so that the burner air ratio is about 0.7. Thus, it becomes possible to use the burner B in which the NOx at the furnace outlet 5 has the lowest value, and the NOx at the furnace outlet 5 can be reduced as compared with the case where the burner A is used.

  FIG. 15 is a system diagram showing a configuration of a fourth embodiment of the once-through boiler according to the present invention. The fuel used is coal 23 and is stored in the coal bunker 37. Coal contained in the coal bunker 37 is pulverized by a coal pulverizer 38. Coal carrying air 33 and coal are supplied to burner 39. The air supplied from the blower 31 is heated by the combustion exhaust gas 32 and the air heater 30. The heated air is divided into coal conveying air 34, combustion air 35, and jet air 36 at the gas jet outlet 6. A damper 27 and a flow meter 26 are installed in the piping for the coal conveying air 34, the combustion air 35, and the jet air 36. The control device 20 inputs the load command 21, the coal type information 22, the coal type measurement result 24, and the flow rate signal 25 of the jet air 36, and controls the damper 27 of the jet air 36. What is necessary is just to install the gas jet nozzle 6 like Example 1 or Example 2. FIG.

  The control device 20 estimates the characteristics of the coal based on the coal type information 22 or the coal type measurement result 24, and the damper 27 according to the estimated coal characteristics, the load command 21, and the flow rate 25 of the jet air 36. The opening degree is controlled to adjust the jet 18 from the gas ejection port 6.

  FIG. 16 is a characteristic diagram showing an example of the relationship between the load and the flow rate of the jet 18 from the gas outlet 6. When the load is low, since the pressure in the combustion region in the furnace is not high, the flow rate of the combustion gas 16 flowing in the direction of the side wall 1 is small. Therefore, the flow rate of the jet 18 from the gas outlet 6 is reduced. As the load increases, the flow rate of the jet 18 from the gas outlet 6 is increased.

  FIG. 17 is a characteristic diagram showing an example of the relationship between the fuel ratio and the flow rate of the jet 18 from the gas outlet 6. In the case of coal with a low fuel ratio, the amount of reducing gas of the combustion gas 16 flowing in the side wall direction 1 increases, so that the flow rate of the jet 18 from the gas outlet 6 is increased. Conversely, in the case of coal with a high fuel ratio, combustion does not proceed and the amount of reducing gas is reduced compared with coal with a low fuel ratio, so the flow rate of the jet 18 from the gas outlet 6 is reduced.

  If the flow rate of the jet 18 at the gas outlet 6 is minimized without destroying the reduction region formed in the furnace by the control method shown in FIG. 16 or FIG. 17, the NOx concentration at the furnace outlet 5 is always minimized. Can be maintained.

  FIG. 18 is a characteristic diagram showing an example of the relationship between the CO concentration and the flow rate of the jet 18 from the gas jet 6. Even if there is no coal information 22 or coal type measurement result 24, a CO concentration measuring device 28 is attached to, for example, the side wall 1, a CO concentration signal 29 is taken in, and the flow rate of the jet 18 from the gas outlet 6 according to the CO concentration. May be controlled. In this case, as shown in FIG. 18, when the CO concentration signal 29 is about 4% or more, the damper 27 is opened to increase the flow rate of the jet 18 at the gas outlet 6. When the CO concentration 29 is 4% or less, the damper 27 is closed, and the flow rate of the jet 18 at the gas outlet 6 is decreased. As is apparent from the CO concentration distribution in FIG. 9, the CO concentration at which control should be started need not be limited to 4%. That is, if the CO concentration is 4% or less in the vicinity of the burners 2, 3, 4, it is considered that the flame does not collide with the side wall 1, so an arbitrary CO concentration between 0 and 4% can be selected.

  19, 20, and 21 are side views of the furnace showing variations of means for supplying the jet air 36 to the furnace 15.

  The jet air 36 in FIG. 19 is supplied by branching the combustion air 35 of the burner 39. Since the pressure of the combustion air 35 of the burner is high, the jet 18 can be ejected at high speed, which is suitable for increasing the pressure in the vicinity of the side wall 1.

  The jet air 36 in FIG. 20 is branched from the upstream side of the damper 27 that adjusts the air flow rate of the burner 39. When the jet air 36 is branched in this way, even if the flow rate of the combustion air to the burner 39 is changed, the pressure of the jet air 36 is hardly changed, and the jet air 36 can be ejected at a higher speed. Further, the jet air 36 and the combustion air of the burner 39 can be controlled independently.

  FIG. 21 shows an example in which, when the gas outlet 6 is close to the after air port 9, the jet air 36 is branched from the after air 45 to shorten the air pipe.

  In the conventional example disclosed in the above-mentioned Japanese Patent Laid-Open No. 7-98103, piping for supplying combustion gas having an oxygen partial pressure of 10% or less to the auxiliary combustion port is required. Therefore, a combustion gas supply pipe having a length of several tens of meters has to be routed, and a significant cost increase cannot be avoided.

  On the other hand, the means for supplying the jet air 36 to the furnace 15 of the present invention shown in FIGS. 19, 20, and 21 branches the combustion air 35 or the after air 45 piped to a very close position. All that is required is to supply the jet air 36. In particular, when the gas jet 6 is provided at the same height as the burner stages 2, 3, and 4, the gas jet 6 can be formed at the left and right ends of the wind box 40 of the burner 39. Minimize. The same applies to the case where the gas outlet 6 is provided at the same height as the after-air port 9.

1 is a perspective view showing a schematic structure of a furnace in Embodiment 1 of a once-through boiler according to the present invention. FIG. 3 is a cross-sectional view illustrating an example of a structure of a gas ejection port in the first embodiment. It is a front view which shows an example of the structure of the gas jet nozzle of FIG. It is a figure which shows the outline of the flow of the combustion gas and gas jet in the furnace of Example 1 which installed the gas jet nozzle in the front wall and the rear wall. It is a front view which shows the outline of the flow of the combustion gas in the conventional furnace which does not install a gas jet nozzle. It is a figure which shows the outline of the flow of the combustion gas and gas jet in the furnace of Example 2 which installed the gas jet nozzle in the left side wall and the right side wall. It is a perspective view which shows schematic structure of the furnace in Example 3 of the once-through boiler by this invention. 10 is a front view showing streamlines in the direction of the left side wall in Example 3. FIG. It is a figure which shows the calculation result of CO density | concentration (%) in the position of 10 cm from the left side wall of Example 3. FIG. It is a front view which shows the flow line to the left-side wall direction in the conventional once-through boiler. It is a figure which shows the calculation result of CO density | concentration (%) in the position of 10 cm from the left side wall of FIG. It is a front view which shows the flow line to the left-side wall direction in the conventional once-through boiler which provided the boundary air apparatus for forming the flow of the air along a wall in the lower part of the furnace. It is a figure which shows the calculation result of CO density | concentration (%) in the position of 10 cm from the left side wall of FIG. The figure which compares the characteristic of the burner A in which NOx in a furnace exit becomes the minimum value near the burner air ratio of 0.8, and the burner B in which the NOx at the furnace outlet reaches a minimum value in the vicinity of the burner air ratio of 0.7 It is. It is a systematic diagram which shows the structure of Example 4 of the once-through boiler by this invention. It is a characteristic view which shows an example of the relationship between a load and the flow volume of the jet flow from a gas jet nozzle. It is a characteristic view which shows an example of the relationship between a fuel ratio and the flow volume of the jet flow from a gas jet nozzle. It is a characteristic view which shows an example of the relationship between CO density | concentration and the flow volume of the jet flow from a gas jet nozzle. It is a side view of the furnace which shows the means which branches the combustion air of a burner and supplies the air for jets. It is a side view of the furnace which shows the means to supply the air for jets branched from the upstream of the damper which adjusts the air flow rate of a burner. It is a side view of the furnace which shows the example which branched the air for jets from after air and shortened air piping when a gas jet nozzle is near an after air port.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Furnace side wall 2 Lower burner 3 Middle burner 4 Upper burner 5 Furnace exit 6 Gas jet 8 Gas jet 9 After air port 13 Combustion chamber 14 Burner wall 15 Furnace 16 Combustion gas 17 Water pipe 18 Jet 20 Controller 21 Load command 22 Coal type Information 23 Coal 24 Coal species measurement result 25 Gas flow signal 26 Flow meter 27 Damper 28 CO concentration measuring device 29 CO concentration signal 30 Air heater 31 Blower 32 Combustion gas 33 Coal carrier air 34 Coal carrier air 35 Combustion air 36 For jet Air 37 Coal bunker 38 Coal crusher 39 Burner 40 Wind box 41 Streamline 42 Boundary air port 43 Boundary air 44 Flow toward side wall 45 After air

Claims (11)

In a once-through boiler having a combustion chamber formed by front and rear walls and side walls intersecting with the front and rear walls, and a burner installed in a plurality of stages on at least one of the front and rear walls,
A once-through boiler, wherein a gas outlet is provided between an outermost burner and the side wall within a range of the height of the burner stage. In a once-through boiler having a combustion chamber formed by front and rear walls and side walls intersecting with the front and rear walls, and a burner installed in a plurality of stages on at least one of the front and rear walls,
A gas jet outlet is provided on the side wall within the height of the burner stage so that the pressure of the gas in the vicinity of the side wall in the combustion chamber is higher than the pressure of the gas in the center of the combustion chamber. A once-through boiler. It has a combustion chamber formed by front and rear walls and side walls intersecting with the front and rear walls, has a plurality of burners on at least one of the front and rear walls, and has an after-air port for two-stage combustion downstream of the burner stage In the once-through boiler,
The outermost burner and the side wall within the range of the height of the burner stage are the jets of the gas jet that makes the pressure of the gas near the side wall in the combustion chamber higher than the pressure of the gas in the center of the combustion chamber. A once-through boiler, wherein at least one stage is provided between the lower burner and a plurality of stages are provided between the lowermost burner and the after-air port. In the once-through boiler according to any one of claims 1 to 3,
An air supply means for providing the gas jet at the same height of the front and rear walls facing each other and ejecting the jet at a speed at which a gas jet from the gas jet facing the middle collides between the front and rear walls. A once-through boiler characterized by being equipped. Means for supplying pulverized coal as fuel and air for conveying the pulverized coal to the plurality of burners; means for supplying combustion air to the plurality of burners; and supplying a jet gas to the gas outlet The once-through boiler according to any one of claims 1 to 4, comprising:
The flow rate of the jet flow from the gas jet port is controlled based on the boiler load command and the coal type information, and when the boiler load is low, the flow rate of the jet flow from the gas jet port is reduced, and the boiler load A once-through boiler comprising control means for increasing the flow rate of the jet flow from the gas jet port while increasing Means for supplying pulverized coal as fuel and air for conveying the pulverized coal to the plurality of burners; means for supplying combustion air to the plurality of burners; and supplying a jet gas to the gas outlet The once-through boiler according to any one of claims 1 to 4, comprising:
Means for measuring the carbon monoxide (CO) concentration of the combustion gas in the vicinity of the side wall, controlling the flow rate of the jet from the gas outlet based on the load command of the boiler, the measurement result of the CO concentration, When the boiler load is low, the flow rate of the jet from the gas jet port is decreased, the boiler load is increased, the flow rate of the jet flow from the gas jet port is increased, and the CO concentration is a predetermined value. In the following cases, the once-through boiler is provided with control means for reducing the flow rate of the jet flow from the gas jet port. In the once-through boiler according to claim 5 or 6,
The once-through boiler, wherein the control means is a means for increasing the flow rate of the jet as the pulverized coal has a lower fuel ratio. In the once-through boiler according to any one of claims 5 to 7,
The once-through boiler, characterized in that the means for supplying the jet gas to the gas outlet is means for branching the combustion air of the burner into jet air. The once-through boiler according to claim 8,
A once-through boiler, characterized in that a flow rate adjusting damper is provided in each of a combustion air flow path and a jet air flow path. In the once-through boiler according to any one of claims 5 to 7,
The once-through boiler, wherein the means for supplying the jet gas to the gas outlet is a means for branching the pulverized coal transport air into the jet air. In the once-through boiler according to any one of claims 5 to 7, an after-air port for two-stage combustion is installed downstream of the burner stage.
The once-through boiler, characterized in that the means for supplying the jet gas to the gas outlet is means for branching the after air into the jet air.

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