JP2011169543A - Boiler - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a boiler which dispenses with inspection of whether a scale is accumulated or not on an inner wall by every boiler heat transfer tube and easily removing the scale, and to provide a boiler heat exchanger structure. <P>SOLUTION: In the boiler heat exchanger in which a plurality of heat transfer tubes 2 are collected, a lower section of the heat transfer tube is bent as a bent section, the bent section is inclined at an angle of 35-50° with respect to the horizontal plane, and is connected to a vertical or approximately-vertical heat transfer tube inlet header 3 at its lower end, and a scale collecting means is disposed on a lower end of the inlet header. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a boiler, and more particularly to a boiler that prevents scale (foreign matter) formed on the inner wall of a boiler heat transfer tube from accumulating in the heat transfer tube and facilitates removal of the scale.

  The boiler is provided with a heat transfer tube for generating steam in the wall of the combustion furnace or in the combustion gas flow path, and the heat of the steam flowing through the heat transfer tube through the heat transfer tube and the gas in the furnace or exhaust gas. Exchange is performed, and steam is generated and steam is overheated.

  First, the problems in the conventional structure will be described with reference to FIGS.

  The heat transfer tube 2 of the conventional structure has a vertical upper portion, an upper end connected to the heat transfer tube outlet header 1, a lower end bent into a dogleg shape, and a bent portion 2 a inclined at about 17 ° with respect to the horizontal. Have. The lower end of the heat transfer tube 2 is connected to a heat transfer tube inlet tube 3 extending in the vertical direction. In the figure, 2 indicates a state where the heat transfer tubes are gathered, and 4 indicates a heat transfer tube manifold.

  Further, each vent section 2a is provided with an orifice, and by adjusting the flow rate of steam flowing through each vent section 2a, that is, the heat transfer tube 2, the tube temperature of the heat transfer tube 2 becomes uniform. It is adjusted like this.

  Scales that are oxides are formed on the inner and outer walls of the heat transfer tube 2, particularly on the inner wall through which steam flows. Since the scale and the heat transfer tube 2 itself have different coefficients of thermal expansion, when the temperature of the heat transfer tube 2 decreases, such as when the boiler is stopped, the scale peels from the inner surface of the heat transfer tube 2.

  The peeled scale falls and accumulates on the vent portion 2a. Or it floats and flows with steam, and flows out to the turbine side. The accumulated scale hinders the flow of steam and causes the heat transfer tube 2 to overheat, or the suspended scale flows into the turbine, collides with the turbine blade, and wears the turbine blade.

  Therefore, in order to operate the boiler normally, it is necessary to inspect whether or not the scale is accumulated in the heat transfer tube, and the heat transfer tube 2 is inspected for each portion of the heat transfer tube 2 by X-ray inspection, such as the vent portion 2a. In the case of accumulation, a part of the heat transfer tube 2 was excised and the scale was sucked out.

  For this reason, it takes much time and labor to inspect and remove the scale.

JP-A-11-324616

  In view of such circumstances, the present invention provides a boiler that can omit the inspection of whether or not the scale is deposited for each heat transfer tube and can easily remove the scale.

  The present invention comprises a heat exchanger in which a plurality of heat transfer tubes are assembled, and a bent portion having a bent lower portion of the heat transfer tube, the vent portion being inclined at 35 ° to 50 ° with respect to the horizontal. The lower end of the boiler is connected to a vertical or substantially vertical inlet pipe.

  The present invention also relates to a boiler in which the flow rate of each vent section is adjusted by the thickness of each vent section, and to a boiler in which a scale collecting means is provided at the lower end of the inlet pipe. Furthermore, an inlet manifold is connected to the inlet pipe via a connecting pipe, and the connecting pipe relates to a boiler connected to the inlet pipe at a predetermined distance above the lower end of the inlet pipe.

  According to the present invention, the heat exchanger includes a heat exchanger in which a plurality of heat transfer tubes are assembled, and the lower portion of the heat transfer tube is a bent portion, and the vent portion is at least 35 ° and not more than 50 ° with respect to the horizontal. Inclined and the lower end is connected to a vertical or substantially vertical inlet header, so that the scale is not accumulated in the vent part, but is collected through the inlet header, and whether or not the scale is accumulated is checked. There is no need to perform each heat pipe, and the inspection work is greatly reduced.

  Further, according to the present invention, the flow rate of each vent portion is adjusted by the thickness of each vent portion, so that an orifice for adjusting the flow rate is not necessary, and the scale can be deposited at the orifice portion. Disappear.

  Further, according to the present invention, since the scale collecting means is provided at the lower end of the inlet pipe, the scale removing work only needs to be performed on the scale collecting means. To be reduced.

  According to the invention, an inlet manifold is connected to the inlet pipe via a connecting pipe, and the connecting pipe is connected to the inlet pipe at a predetermined distance above the lower end of the inlet pipe. The obtained scale is isolated from the above-mentioned flow, and an excellent effect is exhibited such that the collected scale is prevented from being mixed into the steam flow.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  1 and 2 show a structure to which the present invention is applied. In FIG. 1, the same components as those shown in FIGS. 7 and 8 are denoted by the same reference numerals.

  In the present invention, the inclination angle θ with respect to the horizontal of the vent portion is set to 35 ° or more and 50 ° or less, and the lower end is connected to the heat transfer pipe inlet header 3 extending in the vertical direction.

  Each of the vent portions has a different wall thickness for flow rate adjustment, and the flow passage cross-sectional area is changed by changing the wall thickness, so that the temperature of each heat transfer tube becomes uniform. Therefore, the conventional orifice is omitted.

  An inclined connecting pipe 5 is connected to a predetermined position above a lower end of the heat transfer pipe inlet pipe 3, and a heat transfer pipe inlet manifold 4 is connected to the lower end of the connecting pipe 5. Further, a scale tank 7 serving as a scale collecting means is provided at the lower end of the heat transfer pipe inlet header 3.

  The scale tank 7 will be described with reference to FIGS.

  The scale tank 7 has an axial center orthogonal to the heat transfer pipe inlet header 3 and has a cylindrical shape with both ends closed.

  A scale backflow preventing member 6 is fitted into the lower end inside the heat transfer pipe inlet header 3.

  The scale backflow prevention member 6 includes a funnel portion 6b having a small lower end portion, a flange portion 6a provided at the upper end of the funnel portion 6b, and a scale swirl flow restraining member provided at the upper end portion of the funnel portion 6b. 6c. Here, the inner diameter of the lower end portion of the funnel portion 6b is set to a sufficient size so that the scale is not caught, and the scale swirl flow restraining member 6c has a shape in which strip-shaped plate pieces are combined in a cross shape. ing.

  A scale discharge nipple 9 is provided at the lower end and the center of the scale tank 7, and an internal inspection nipple 8 is provided on the side of the scale tank 7 where the work can be easily performed, for example, an end face.

  The operation will be described below.

  First, the relationship between the scale and the inclination of the heat transfer tube was investigated by experiment.

  As shown in FIG. 5, the sample tube 10 made of SUS having an open top was held at an angle θ, and the SUS scale was dropped on the sample tube 10. The behavior (flow characteristics) of the SUS scale at this time is shown in FIG.

  Although the SUS scale flows down at θ = 30 °, it may be deposited by being affected by the properties of the inner surface of the welded joint or the like. At θ = 35 °, even if there is a welded joint or the like, it flows intermittently and does not accumulate regardless of the surface properties. When θ = 40 °, there is no deposition and the material slides smoothly regardless of the surface properties.

  Further, when the SUS scale is deposited on the horizontal sample tube 10 and then the sample tube 10 is tilted, the SUS scale crest deposited at θ = 27 ° is broken and intermittent at θ = 32 °. It flowed smoothly at θ = 38 °.

  From the above investigation, it is confirmed that the SUS scale flows smoothly at θ = 38 ° or more, and further considering the operation state of the boiler, for example, vibration of the vent portion, by setting θ = 35 ° or more, It is thought that scale accumulation at the vent can be suppressed.

  In consideration of the properties of the inner surface of the vent part, θ = 40 ° or more is preferable. Further, if the inclination angle of the vent portion becomes larger with respect to the heat transfer pipe inlet joint 3, the weldability is deteriorated, so that about θ = 50 ° is considered to be a limitation in construction. Note that the heat transfer tube inlet header 3 is not necessarily vertical but may be close to vertical.

  That is, the inclination angle θ of the vent portion is set to 35 ° to 50 °, preferably 40 ° to 50 °.

  Thus, the scale peeled off by the heat transfer tube 2 falls to the vent portion, and further flows down the vent portion, and falls vertically at the heat transfer tube inlet header 3. Therefore, the scale of the heat transfer tube 2 can be collected by the scale tank 7. Further, since the orifice for adjusting the flow rate is removed from the vent portion, the scale that flows down does not stay on the way.

  Whether or not the scale is accumulated may be determined by inspecting only the scale tank 7, and the inspection of whether or not the scale is accumulated is greatly reduced. In addition, since the scale removing operation only needs to be performed on the scale tank 7, the scale removing operation can be greatly reduced.

  Next, the operation of the scale tank 7 which is an example of the scale collecting means will be described.

  In order to confirm the storage state of the scale in the scale tank 7, the internal inspection nipple 8 is cut out and the inside of the scale tank 7 is observed.

  The scale discharge nipple 9 is excised and removed from the scale for a certain period, for example, every two years when boiler regular inspection is performed. After removing the scale, the scale discharge nipple 9 and the internal inspection nipple 8 are welded again.

  The steam flowing through the heat transfer pipe inlet manifold 4 rises from the connecting pipe 5 through the branch point O of the heat transfer pipe inlet pipe 3 to the heat transfer pipe inlet pipe 3. In the process in which the steam flows into the heat transfer pipe inlet header 3, steam wraps downward from the branch point O or sucks out from the scale tank 7. For this reason, it is assumed that the air in the scale tank 7 is disturbed, the scale rolls up, reversely flows on the steam flow, and rises at the heat transfer pipe inlet header 3.

  The scale backflow prevention member 6 prevents the scale from winding up and backflow.

  Since the funnel portion 6b has a shape in which the lower end is narrowed, the scale is prevented from flowing backward. Further, the scale swirl flow restraining member 6 c prevents the steam from flowing into the scale tank 7 as a swirl flow and the gas (air, steam) from swirling inside the scale tank 7. Therefore, the scale is prevented from floating and turning inside the scale tank 7, and the backflow of the scale is further suppressed. Further, since the turning in the scale tank 7 is suppressed, the wear on the inner surface of the scale tank 7 due to the rubbing of the scale is suppressed.

  Next, the influence of the steam flow from the connecting pipe 5 to the lower end portion of the heat transfer pipe inlet header 3 such as the introduction and suction of steam from the lower end portion of the heat transfer pipe inlet header 3 depends on the angle θ. Is done. When the angle θ is large, for example, 90 °, the influence of the vapor flow on the inside of the scale tank 7 is large, and the stored scale is wound up and the scale backflow is confirmed by experiments. It has also been confirmed that the angle θ should be small and the angle θ should be 50 ° or less. On the other hand, if the angle θ is reduced, the welding workability between the connecting pipe 5 and the heat transfer pipe inlet joint 3 is deteriorated, and θ = 90 ° or less and 40 ° or more are preferable in consideration of the welding workability. Therefore, the angle θ is preferably set in the range of 40 ° to 50 °. Further, the connection position between the communication pipe 5 and the heat transfer pipe inlet joint 3 is also set so that the influence of the steam flow to the lower end portion of the heat transfer pipe inlet joint 3 is small.

  In the embodiment described above, the scale swirl flow restraining member 6c has a cross shape, but it may have a three-forked shape, etc., so long as it prevents swirl flow and becomes an obstacle to scale drop.

It is explanatory drawing which shows the principal part of the Example of this invention. It is the A section enlarged view of FIG. It is a BB arrow line view of FIG. It is CC arrow line view of FIG. It is explanatory drawing which shows the relationship between the inclination angle of the inclined pipe | tube, and SUS scale deposition. It is a figure which shows the relationship between the inclination angle of the inclined pipe | tube, and SUS scale deposition. It is explanatory drawing of the conventional heat exchanger tube part. It is the D section enlarged view of FIG.

1 Heat transfer tube outlet tube 2 Heat transfer tube 3 Heat transfer tube inlet tube 4 Heat transfer tube inlet manifold 5 Connection tube 6 Scale backflow prevention member 6a Flange portion 6b Funnel portion 6c Scale swirl flow inhibiting member 7 Scale tank 8 Internal inspection nipple 9 Scale Nipple for discharge 10 Sample tube

Claims (4)

  A heat exchanger in which a plurality of heat transfer tubes are assembled is provided, and a lower portion of the heat transfer tube is a bent portion, the vent portion is inclined at 35 ° to 50 ° with respect to the horizontal, and a lower end is vertical Or the boiler characterized by being connected to the substantially vertical entrance pipe.   The boiler according to claim 1, wherein the flow rate of each vent portion is adjusted by the thickness of each vent portion.   The boiler according to claim 1, wherein a scale collecting means is provided at a lower end of the inlet pipe.   The boiler according to claim 1, wherein an inlet manifold is connected to the inlet pipe via a connecting pipe, and the connecting pipe is connected to the inlet pipe at a predetermined distance above a lower end of the inlet pipe.

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