JP2014020711A - Cyclone and circulating fluidized-bed boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cyclone that allows a boiler to be stably operated for a long period of time irrespective of presence/absence of thermal stress, and to provide a circulating fluidized-bed boiler.SOLUTION: A cyclone 10 comprises a cyclone body 13 having a cylindrical portion 11 into which a combustion gas is introduced and a cylindrical inner cylinder 20 positioned at a center of the cylindrical portion 11 of the cyclone body 13. In the cyclone 10, an inward inner cylinder receiving portion 14 is provided in the cylindrical portion 11 of the cyclone body 13, and a plurality of outward ribs 21c that passes through a peripheral wall of the inner cylinder 20 and is mounted thereto by welding, is arranged on the inner cylinder 20 in a circumferential direction. The inner cylinder receiving portion 14 of the cyclone body 13 receives the plurality of ribs 21c of the inner cylinder 20, so that the inner cylinder 20 is supported by the cyclone body 13.

Description

  The present invention relates to, for example, a cyclone and a circulating fluidized bed boiler that collects a coarse ash contained in combustion gas and a part of a bed material that flows together with the ash in a circulating fluidized bed boiler.

As a circulating fluidized bed boiler provided with the above-mentioned cyclone, there exists a circulating fluidized bed boiler disclosed by patent document 1, for example.
This circulating fluidized bed boiler is equipped with a furnace that burns while flowing fuel such as coal and solid waste fuel and bed materials such as sand and limestone, and the cyclone is connected to the furnace outlet of this furnace. Thus, coarse ash and part of the bed material contained in the combustion gas from the furnace are collected and returned to the furnace.

  The cyclone includes a cyclone main body having a cylindrical portion and a conical portion continuous to the lower end of the cylindrical portion, and an inner cylinder disposed at the center of the cyclone main body. The cylindrical portion of the cyclone main body is provided with a gas inlet opening that opens in the circumferential tangential direction, and this gas inlet is connected to the furnace outlet of the furnace.

  In this cyclone, the combustion gas introduced from the gas inlet of the cyclone main body flows along the inner peripheral wall of the cylindrical portion, and descends in a spiral shape by receiving centrifugal force and gravity. At this time, the coarse and heavy ash and the bed material fall along the inner peripheral walls of the cylindrical portion and the conical portion, while the fine and light ash falls while spreading from the center of the cyclone body to the periphery. And the inner cylinder located in the center of a cyclone main body takes in the combustion gas containing a part of light ash, and supplies it to the rear heat-transfer part of the downstream of a cyclone.

  The inner cylinder of the cyclone is supported on the cyclone main body side by placing an outward annular flange fixed to the upper end of the cyclone on a flange receiver attached to the cyclone main body side.

Japanese Patent Laid-Open No. 10-314623

  In the cyclone of the circulating fluidized bed boiler disclosed in Patent Document 1 described above, the temperature of the combustion gas passing through the inner cylinder toward the rear heat transfer section during operation is about 900 ° C., while the cyclone supporting the inner cylinder The temperature on the main body side is about 20 ° C.

  Therefore, there is a possibility that thermal stress is generated in the welded portion between the outward annular flange for supporting the inner cylinder on the cyclone main body and the upper end of the inner cylinder, and it is difficult to generate thermal stress. Even so, it is desired to construct a support structure for the inner cylinder that does not hinder the operation of the boiler, and it has been a conventional problem to solve this problem.

  The present invention has been made paying attention to the above-described conventional problems, and provides a cyclone and a circulating fluidized bed boiler capable of performing a stable boiler operation over a long period of time regardless of the presence or absence of thermal stress. It is an object.

  In order to achieve the above-described object, the invention according to claim 1 of the present invention includes a cyclone main body having a cylindrical portion into which combustion gas is introduced, and a cylindrical inner member located at the center of the cylindrical portion of the cyclone main body. In the cyclone provided with a cylinder, the cylindrical part of the cyclone main body is provided with an inwardly facing inner cylinder receiving part, and the inner cylinder is attached to the inner cylinder by welding through a peripheral wall of the inner cylinder. A plurality of projecting bodies are arranged in the circumferential direction, and the inner cylinder is supported by the cyclone main body by receiving the plurality of projecting bodies of the inner cylinder at the inner cylinder receiving portion of the cyclone main body. The configuration of this cyclone is used as a means for solving the conventional problems described above.

  The cyclone according to claim 2 of the present invention is configured such that the plurality of projecting bodies of the inner cylinder are slidably mounted on the inner cylinder receiving portion of the cyclone main body.

  The cyclone according to claim 3 of the present invention is configured such that an opening penetrating the peripheral wall of the inner cylinder is provided between each of the plurality of projecting bodies of the inner cylinder.

  On the other hand, the invention according to claim 4 of the present invention is a furnace in which fuel is fluidized and burned together with a bed material, ash contained in combustion gas generated by combustion in the furnace, and the ash that has flowed together with the ash. In the circulating fluidized bed boiler provided with the cyclone which collects the bed material and returns it to the furnace, the cyclone according to any one of claims 1 to 3 is adopted as the cyclone.

  In the cyclone according to the present invention, since the outward projecting body for supporting the inner cylinder in the cyclone main body is attached by welding through the peripheral wall of the inner cylinder, the temperature of the cylindrical portion in the cyclone main body is low. The distance from the peripheral wall to the welded portion with the overhanging body in the inner cylinder exposed to high temperature is longer than in the conventional case, and the thermal stress in the welded portion is reduced by that amount.

  Further, in the cyclone according to the present invention, since a plurality of outwardly projecting bodies are arranged in the circumferential direction of the inner cylinder, even if a defect occurs in the welded portion of one or several projecting bodies, a plurality of If there is no problem in the welded portion of the other overhanging body, the inner cylinder can be reliably supported.

  Furthermore, in the cyclone according to the present invention, if the plurality of projecting bodies of the inner cylinder are slidably mounted on the inner cylinder receiving portion of the cyclone main body, the expansion and contraction due to heat of the inner cylinder can be absorbed. It will be.

  Furthermore, in the cyclone according to the present invention, if an opening penetrating the peripheral wall of the inner cylinder is provided between each of the plurality of projecting bodies of the inner cylinder, the combustion gas flows through the opening into and out of the inner cylinder. As a result, the thermal stress at the welded portion of the overhanging body is relieved, and ash is prevented from accumulating between the overhanging body and the inner cylinder receiving portion.

  On the other hand, in the circulating fluidized bed boiler according to the present invention, the support of the inner cylinder in the cyclone is always ensured, so that stable operation can be performed for a long time.

  The cyclone according to the present invention, when employed in a circulating fluidized bed boiler, has a very excellent effect that it is possible to realize stable boiler operation over a long period of time regardless of the presence or absence of thermal stress on the welded portion. Brought about.

It is a section explanatory view showing one embodiment of a circulating fluidized bed boiler concerning the present invention. It is front explanatory drawing which shows the inner cylinder of the cyclone of the circulating fluidized bed boiler in FIG. FIG. 2 is an enlarged cross-sectional explanatory view at the upper end of the inner cylinder showing a state where the inner cylinder of the cyclone is supported by the cyclone main body in FIG. 1. FIG. 3 is a partial plan view of the inner cylinder of the cyclone shown in FIG. 2. FIG. 3 is an enlarged explanatory view of an X portion of the inner cylinder of the cyclone illustrated in FIG. 2.

Hereinafter, a cyclone and a circulating fluidized bed boiler according to the present invention will be described with reference to the drawings.
FIG. 1 shows an embodiment of a circulating fluidized bed boiler according to the present invention, and FIGS. 2 to 5 show an embodiment of a cyclone.

  As shown in FIG. 1, the circulating fluidized bed boiler 1 is continuous through a furnace 2, a cyclone 10 extending along the vertical direction through a furnace outlet 3, and a lower end of the cyclone 10 and an ash drop pipe 4. At the same time, an external heat exchanger 6 connected to the furnace 2 via the ash return pipe 5 and a rear heat transfer section 7 having a superheater and a economizer (not shown) connected to the upper end of the cyclone 10 are provided.

  The furnace 2 is supplied with fuel, for example, solid waste fuel and bed material B, for example sand, and fluidizes and burns the fuel together with the bed material B by the air blown from the air dispersion nozzle 8 as indicated by the arrows. ing.

  The cyclone 10 includes a cyclone main body 13 having a cylindrical portion 11 and a conical portion 12 continuing to the lower end of the cylindrical portion 11, and a cylindrical inner cylinder 20 positioned at the center of the cyclone main body 13. The cylindrical portion 11 is provided with a gas inlet 11a that opens in the circumferential tangent direction, and the furnace outlet 3 is connected to the gas inlet 11a.

  In this cyclone 10, the combustion gas from the furnace 2 introduced from the gas inlet 11 a of the cyclone main body 13 flows along the peripheral wall of the cylindrical portion 11 and receives centrifugal force and gravity to form a spiral as shown by an arrow. Descent. At this time, the coarse heavy ash and the bed material B fall along the peripheral walls of the cylindrical portion 11 and the conical portion 12, while the fine light ash falls while spreading from the center of the cyclone body 13 to the periphery. To do.

  And the inner cylinder 20 located in the center of the cyclone main body 13 takes in the combustion gas containing a part of light ash and supplies it to the rear heat transfer section 7 on the downstream side of the cyclone 10 as shown by the broken arrow. It is like that.

  In this case, as shown in FIG. 2, the inner cylinder 20 has an annular projecting portion 21 at its upper end, and as shown in FIG. 3, the annular projecting portion 21 is connected to the cylindrical portion 11 of the cyclone main body 13. It is supported on the cyclone main body 13 side by being placed on the arranged inwardly facing inner cylinder receiving portion 14 via the receiving surface 15.

  At this time, the annular projecting portion 21 is slidable on the receiving surface 15 of the inner cylinder receiving portion 14, so that the expansion and contraction due to heat of the inner cylinder 20 and the annular projecting portion 21 is absorbed.

  The annular projecting portion 21 is fixed to the cylinder main body 22 by welding at a distance below the upper annular flange 21a and an upper annular flange 21a fixed outward by welding to the upper end of the cylinder main body 22 of the inner cylinder 20. A lower annular flange 21b and a rib (outwardly projecting body) 21c fixed between the annular flanges 21a and 21b by welding.

  An inward projecting piece 21d is formed integrally with the rib 21c, and the projecting piece 21d passes through an insertion hole 22a formed in the cylinder main body 22 so that the tip is exposed inside the cylinder main body 22. The exposed tip portion of the protruding piece 21d is fixed to the cylinder body 22 by welding.

  As shown in FIG. 4, a plurality of ribs 21c and insertion holes 22a are arranged at intervals in the circumferential direction, and between the adjacent ribs 21c, as shown in FIG. 5, a reinforcing plate 21e is also provided. And the opening 21f is arranged. As shown by the arrow in FIG. 3, the opening 21 f circulates combustion gas in and out of the inner cylinder 20, thereby reducing the generation of thermal stress in the annular projecting portion 21 and the inner cylinder receiving portion. The ash is prevented from accumulating between 14 and the annular projecting portion 21. In FIG. 3, the reinforcing plate 21e is omitted.

  In the cyclone 10 described above, the projecting piece 21d on the rib 21c for supporting the inner cylinder 20 in the cyclone body 13 is attached by welding through the peripheral wall of the cylinder body 22 of the inner cylinder 20, so that the cyclone body 13, the distance from the peripheral wall where the temperature of the cylindrical portion 11 is low to the welded portion with the rib 21c in the inner cylinder 20 exposed to a high temperature is longer than the conventional one, and the thermal stress in the welded portion is reduced accordingly. It will be.

  Further, in the cyclone 10 described above, a plurality of ribs 21c are arranged in the circumferential direction of the inner cylinder 20, and the upper and lower ends of these ribs 21c are fixed to the annular flanges 21a and 21b by welding, Even if a problem occurs in the welded portion of the protruding piece 21d in one or several ribs 21c, the inner cylinder 20 can be reliably supported if there is no problem in the welded portion of the other ribs 21c. It will be.

  Further, in the above-described cyclone 10, the annular projecting portion 21 having the rib 21c of the inner cylinder 20 is slidably mounted on the receiving surface 15 of the inner cylinder receiving portion 14 of the cyclone main body 13, so that the inner cylinder 20 and the expansion and contraction due to heat of the annular projecting portion 21 can be absorbed.

  Furthermore, in the above-described cyclone 10, since the opening 21f penetrating the peripheral wall of the cylinder main body 22 of the inner cylinder 20 is provided between each of the plurality of ribs 21c of the inner cylinder 20, the inner cylinder 20 is passed through the opening 21f. Combustion gas flows inside and outside. As a result, thermal stress in the welded portion of the projecting piece 21d in the rib 21c is relieved, and ash is formed between the annular projecting portion 21 having the rib 21c and the inner cylinder receiving portion 14. It will be avoided to accumulate.

  And in the circulating fluidized bed boiler 1 which has the above-mentioned cyclone 10, since the support of the inner cylinder 20 in the cyclone 10 is always ensured, a stable operation is achieved over a long period of time.

  The configurations of the cyclone and the circulating fluidized bed boiler according to the present invention are not limited to the configurations of the cyclone and the circulating fluidized bed boiler according to the above-described embodiment. As other configurations, for example, as shown in FIG. The cyclone lower inner cylinder 30 disposed at the lower end of the ash dropping pipe 4 is provided with an annular projecting portion 21 and an inner cylinder receiving portion 14 on the ash dropping pipe 4 side. Alternatively, the lower inner cylinder 30 may be supported.

DESCRIPTION OF SYMBOLS 1 Circulating fluidized bed boiler 2 Furnace 10 Cyclone 11 Cylindrical part 13 Cyclone main body 14 Inner cylinder receiving part 20 Inner cylinder 21c Rib (outward projecting body)
21f Opening 30 Cyclone lower inner cylinder B Bed material

Claims (4)

A cyclone body having a cylindrical portion into which combustion gas is introduced;
In the cyclone provided with a cylindrical inner cylinder located at the center of the cylindrical portion of the cyclone body,
The cylindrical portion of the cyclone main body is provided with an inward inner tube receiving portion,
In the inner cylinder, a plurality of outwardly extending bodies that are attached by welding through the peripheral wall of the inner cylinder are arranged in the circumferential direction,
The cyclone main body is supported by the cyclone main body by receiving the plurality of projecting bodies of the inner cylinder at the inner cylinder receiving portion of the cyclone main body. The cyclone according to claim 1, wherein the plurality of projecting bodies of the inner cylinder are slidably mounted on the inner cylinder receiving portion of the cyclone main body. The cyclone according to claim 1 or 2, wherein an opening penetrating a peripheral wall of the inner cylinder is provided between each of the plurality of projecting bodies of the inner cylinder. A furnace that fluidizes and burns fuel together with the bed material;
In the circulating fluidized bed boiler provided with a cyclone that collects the ash contained in the combustion gas generated by the combustion in the furnace and the bed material flowing along with the ash and returns the bed material to the furnace,
The circulating fluidized bed boiler, wherein the cyclone according to any one of claims 1 to 3 is adopted as the cyclone.

Images