JP2005156057A - Sulfuric acid dew point corrosion preventive heat exchanger and its application method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sulfuric acid dew point corrosion preventive heat exchanger capable of further extending a service life, and its application method. <P>SOLUTION: This sulfuric acid dew point corrosion preventive heat exchanger is provided with a combustion gas passage 7 for combustion gas to flow through, and a heated passage 12 for a heated fluid to flow through, in the state of being partitioned by a heat transfer wall 11. The combustion gas passage 7 side surface of the heat transfer wall 11 is provided with a heat insulating layer I for suppressing heat transfer between the combustion gas and the heated fluid, in a state of having sulfuric acid corrosion resistance, in a state of being formed to have sulfuric acid corrosion resistance by reaction to sulfuric acid, or in a state of neutralizing with sulfuric acid. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention provides a sulfuric acid dew point corrosion-prevention type heat exchange in which a combustion gas flow path for passing a combustion gas and a heated flow path for flowing a heated fluid are partitioned by a heat transfer wall The present invention relates to a container and a method for using the same.

Such a sulfuric acid dew point corrosion prevention type heat exchanger uses a combustion gas obtained by burning a fuel containing a sulfur compound as a heat source to heat a heated fluid such as water or air, and the heat transfer wall is subjected to sulfuric acid dew point corrosion. This is to prevent this.
That is, the combustion gas obtained by burning the fuel containing the sulfur compound contains sulfur dioxide (SO ₂ ) gas, and this sulfur dioxide gas is further oxidized to become sulfur trioxide (SO ₃ ) gas. When the temperature of the surface of the heat transfer wall falls below the sulfuric acid dew point (for example, about 140 ° C.), the sulfur trioxide gas reacts with the water vapor in the combustion gas and condenses as sulfuric acid on the surface of the heat transfer wall. Since the heat transfer wall is corroded by sulfuric acid, it is necessary to take measures against such sulfuric acid dew point corrosion.

  In such a heat exchanger of sulfuric acid dew point corrosion prevention type, conventionally, a heat insulating wall is provided on the surface of the heat transfer wall on the heated flow path side to suppress heat transfer between the combustion gas and the heated fluid. Due to the heat insulating action of the heat insulating layer, the surface of the heat transfer wall on the combustion gas flow path side is set to a temperature equal to or higher than the sulfuric acid dew point temperature to suppress the condensation of sulfuric acid and take measures against sulfuric acid dew point corrosion. (For example, refer to Patent Document 1).

Japanese Patent Laid-Open No. 11-351790

  Conventionally, a heat insulating layer that suppresses heat transfer between the combustion gas and the heated fluid is provided on the surface of the heat transfer wall on the heated flow path side to prevent sulfuric acid dew point corrosion, thereby preventing sulfuric acid dew point corrosion type heat exchange. Although the life of the vessel has been extended, it has been desired to further extend the life.

That is, the temperature and flow rate of the combustion gas flowing into the combustion gas flow path may fluctuate due to fluctuations in the combustion state of the combustion gas supply source, etc. The temperature and flow rate of the heated fluid that flows into the heated flow path may vary due to fluctuations in the operating state of the pump for heating and the preheated state of the heated fluid. When the temperature and flow rate of the fluid vary, the heat exchange conditions between the combustion gas and the fluid to be heated vary. Due to such fluctuations in the heat exchange conditions, even if the heat transfer wall has a heat insulating layer on the surface on the heated flow path side, the temperature of the heat transfer wall on the combustion gas flow path side is equal to or higher than the sulfuric acid dew point temperature. It may become impossible to maintain the temperature. When the temperature of the surface of the heat transfer wall on the side of the combustion gas flow path becomes lower than the sulfuric acid dew point due to fluctuations in the heat exchange conditions as described above, the surface of the heat transfer wall on the side of the combustion gas flow path is combusted. Since it is exposed to the gas flow path, the surface of the heat transfer wall on the combustion gas flow path side is corroded.
In addition, when the fluid to be heated is a liquid such as water, the heat insulating layer is easily peeled off due to the flow of the liquid, so that the durability of the heat insulating layer is likely to be lowered, and the liquid is contained in the heat insulating layer. The heat insulation performance will deteriorate, and the heat transfer wall will be easily corroded.
Therefore, conventionally, there is room for improvement in extending the life.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a sulfuric acid dew-point corrosion prevention type heat exchanger capable of further extending the life and a method of using the same.

[Sulfuric acid dew point corrosion prevention heat exchanger]
The sulfuric acid dew point corrosion prevention type heat exchanger according to the present invention is provided in a state where a combustion gas passage for passing a combustion gas and a heated passage for passing a heated fluid are partitioned by a heat transfer wall. It was
The first characteristic configuration is that a heat insulating layer for suppressing heat transfer between the combustion gas and the fluid to be heated has a sulfuric acid corrosion resistance state on the surface of the heat transfer wall on the combustion gas flow path side, sulfuric acid, It is characterized in that it is prepared in such a state that it has resistance to sulfuric acid corrosion by the above reaction or in a state in which it is neutralized with sulfuric acid.

In other words, the heat insulating layer provided on the surface of the heat transfer wall on the combustion gas flow path side suppresses heat transfer between the fluid to be heated and the combustion gas so that the surface temperature of the heat insulating layer is higher than the sulfuric acid dew point. Therefore, it is possible to prevent the sulfuric acid from condensing on the surface of the heat insulating layer.
In addition, the heat insulating layer is formed on the surface of the heat transfer wall on the side of the combustion gas flow path so as to be resistant to sulfuric acid corrosion, produced so as to be resistant to sulfuric acid corrosion by reaction with sulfuric acid, or neutralized with sulfuric acid. Therefore, even if the surface temperature of the heat insulating layer becomes lower than the sulfuric acid dew point and the sulfuric acid condenses due to fluctuations in the heat exchange conditions, the heat insulating layer is a combustion gas on the heat transfer wall. Since the sulfuric acid is condensed on the surface of the heat insulation layer while maintaining the state provided on the surface on the flow path side, the heat insulation layer prevents the sulfuric acid from directly contacting the surface of the heat transfer wall. This makes it possible to suppress the corrosion of the heat transfer wall.
In addition, even if the fluid to be heated flowing through the channel to be heated is a liquid such as water, the heat insulating layer is provided on the surface of the heat transfer wall on the combustion gas channel side, and the heat insulating layer is the fluid to be heated. Since the liquid does not come into contact, the conventional problem that has occurred when the fluid to be heated is a liquid, that is, the problem that the heat insulation layer is easily peeled off by the flow of the liquid, or that the heat insulation layer contains liquid. Thus, it is possible to avoid the problem that the heat insulating performance of the heat insulating layer is lowered.
Accordingly, it is possible to provide a sulfuric acid dew point corrosion prevention type heat exchanger capable of further extending the life.

In addition to the first feature configuration, the second feature configuration of the sulfuric acid dew point corrosion prevention type heat exchanger of the present invention is as follows:
A heat exchange tubular body having the inside of the peripheral wall as the heat transfer wall as the heated channel is provided in the combustion gas channel,
The heat insulating layer is provided on an outer peripheral surface of the peripheral wall of the cylindrical body for heat exchange, which is a surface on the combustion gas flow path side.

That is, the fluid to be heated flows through the channel to be heated inside the cylindrical body for heat exchange, the combustion gas flows through the combustion gas channel outside the cylindrical body for heat exchange, and the cylindrical body for heat exchange With the heat insulating layer provided on the outer peripheral surface of the peripheral wall, it is possible to suppress the heat transfer between the fluid to be heated and the combustion gas, and to make the surface temperature of the heat insulating layer higher than the sulfuric acid dew point, Since it is possible to prevent the sulfuric acid from condensing on the surface of the heat insulating layer, it is possible to prevent corrosion of the heat exchange tubular body.
And since a heat insulation layer is provided in the outer peripheral surface of the surrounding wall of the cylindrical body for heat exchange, a heat insulation layer can be provided easily.
Incidentally, a heat exchange cylindrical body having the inside of the peripheral wall as the heat transfer wall as the combustion gas flow path is provided in the heated flow path, and the heat insulating layer is a surface on the combustion gas flow path side. The case where it equips with the internal peripheral surface of the said surrounding wall of the said cylindrical body for heat exchange is assumed.
However, in the case where the heat insulating layer is provided on the inner peripheral surface of the peripheral wall of the heat exchanging tubular body, the method of providing the heat insulating layer becomes complicated.
Accordingly, it is possible to further extend the life while reducing the cost.

In addition to the first or second feature configuration, the third feature configuration of the sulfuric acid dew point corrosion prevention type heat exchanger of the present invention is as follows:
The heat insulating layer is formed of an inorganic compound, ceramics or paint.

That is, the durability of the heat insulating layer can be further improved by forming the heat insulating layer with an inorganic compound having excellent sulfuric acid corrosion resistance.
Further, the durability of the heat insulating layer can be further improved by forming the heat insulating layer with ceramics which are excellent in sulfuric acid corrosion resistance and can increase the strength of the forming layer.
In addition, it is possible to further improve the durability of the heat-insulating layer by forming the heat-insulating layer with a coating material that is excellent in sulfuric acid corrosion resistance and can be formed by a simple processing method such as painting. Therefore, it is possible to reduce the manufacturing cost and reduce the cost. Incidentally, the paint includes, in addition to the organic resin paint, a ceramic particle contained so that it can be applied.
Incidentally, when the heat insulating layer is formed of an inorganic compound or ceramics, the heat conductivity of the heat insulating layer can be reduced and the heat insulating ability can be increased by forming the porous layer.
In addition, when the heat insulating layer is formed of a paint, the heat conduction of the heat insulating layer is reduced by reducing the content of heat conductive materials such as metal powder that do not include metal powder or the like. The degree of heat insulation can be increased by decreasing the degree.
Accordingly, it is possible to obtain means suitable for implementing the first or second characteristic configuration.

In addition to the first or second characteristic configuration, the fourth characteristic configuration of the sulfuric acid dew point corrosion prevention type heat exchanger of the present invention is as follows.
The heat insulating layer is formed of a heat insulating layer forming material supplied into the combustion gas flow path.

That is, when the heat insulating layer forming material for forming the heat insulating layer is supplied into the combustion gas flow path, the heat insulating layer forming material contacts or adheres to the surface of the heat transfer wall on the combustion gas flow path side, A heat insulating layer having resistance to sulfuric acid corrosion is formed on the surface of the heat transfer wall on the combustion gas flow path side.
In other words, while using a heat exchanger that prevents sulfuric acid dew point corrosion, a heat insulating layer is formed by supplying the heat insulating layer forming material into the combustion gas flow path. In the process, a process for providing a heat insulating layer on the surface of the heat transfer wall on the side of the combustion gas flow path is not required, so that the manufacturing cost can be reduced and the cost can be reduced.
In addition, when starting to use a heat exchanger of the sulfuric acid dew point corrosion prevention type, a heat insulating layer forming material is supplied into the combustion gas flow path to form a heat insulating layer. If additional formation of the heat insulation layer is required due to exhaustion of the heat insulation layer, such as thinning, or changing the supply temperature of the fluid to be heated to a lower temperature, supply the material for forming the heat insulation layer into the combustion gas flow path By doing so, it becomes possible to maintain heat insulation performance as prescribed, so that the durability of the heat insulation layer can be further improved.
Accordingly, it is possible to obtain a suitable means for reducing the cost and further extending the life.

In addition to the first or second characteristic configuration described above, the fifth characteristic configuration of the sulfuric acid dew point corrosion prevention type heat exchanger of the present invention is:
The heat insulating layer is a corrosion product generated by corrosion during use of the material forming the heat transfer wall.

That is, when sulfuric acid is condensed on the surface of the heat transfer wall on the side of the combustion gas flow path during use of the heat exchanger of the sulfuric acid dew point corrosion prevention type, the material forming the heat transfer wall is corroded to form a corrosion product, The corrosion product has resistance to sulfuric acid corrosion and functions as a heat insulating layer.
In other words, the corrosion product formed on the surface of the heat transfer wall on the combustion gas flow path side is porous and has a heat insulating property. Therefore, the corrosion product can be insulated by removing it without removing the corrosion product. As a result, the surface temperature of the corrosion product can be made higher than the sulfuric acid dew point, and it is possible to prevent sulfuric acid from condensing on the surface of the corrosion product as a heat insulating layer. is there.
And, since the corrosion products generated during the use of the sulfuric acid dew point corrosion prevention type heat exchanger are left to form a heat insulating layer, in the manufacturing process of the sulfuric acid dew point corrosion prevention type heat exchanger, Since a process for providing a heat insulating layer on the combustion gas flow path side is not required, the manufacturing cost can be reduced and the cost can be reduced.
Therefore, it is possible to obtain a suitable means for reducing the cost.

In addition to the fifth characteristic configuration described above, the sixth characteristic configuration of the sulfuric acid dew point corrosion prevention type heat exchanger of the present invention is as follows.
The corrosion product is characterized in that colloidal particles constituting the corrosion product are bound by metal multivalent ions.

That is, the colloidal particles constituting the corrosion product are combined by a decrease in the zeta (ζ) potential on the particle surface due to the metal multivalent ions.
Since the colloidal particles constituting the corrosion product are bonded by metal multivalent ions (divalent or higher), the strength of the corrosion product is increased. Therefore, the durability of the heat insulating layer constituted by the corrosion product is improved. It becomes possible to improve further.
Therefore, a means suitable for further extending the life can be obtained.

In addition to any of the first to sixth feature configurations described above, the seventh feature configuration of the sulfuric acid dew point corrosion prevention type heat exchanger of the present invention is as follows:
The heat transfer wall is characterized by being formed of weathering steel containing at least one of chromium, copper, phosphorus, and nickel.

In other words, weathering steel containing at least one of chromium, copper, phosphorus, and nickel has a strong resistance to sulfuric acid corrosion. Therefore, by forming the heat transfer wall from the weather resistant steel, the heat transfer wall is made much longer. It becomes possible to extend the life.
In particular, since the corrosion product formed by the corrosion of the weathering steel has strong adhesion to the weathering steel, when the seventh characteristic configuration is implemented together with the fifth or sixth characteristic configuration, it forms as a heat insulating layer. Since the adhesion of the corrosion product to the heat transfer wall is strengthened, the durability of the heat insulating layer can be further improved.
Therefore, a means suitable for further extending the life can be obtained.

In addition to any of the first to seventh feature configurations described above, the eighth feature configuration of the sulfuric acid dew point corrosion prevention type heat exchanger of the present invention is as follows:
The surface of the heat transfer wall on the side of the combustion gas flow path is characterized in that an exfoliation preventing portion for preventing exfoliation of the heat insulating layer is provided in advance before the heat insulating layer is provided.

That is, since the peeling prevention part prevents the heat insulation layer from peeling off, the durability of the heat insulation layer can be further improved.
Therefore, a means suitable for further extending the life can be obtained.

In addition to the eighth characteristic configuration, the ninth characteristic configuration of the sulfuric acid dew point corrosion prevention type heat exchanger of the present invention is as follows.
The peeling prevention part is configured by a rod-like body provided in a state of protruding in a bowl shape from a surface of the heat transfer wall on the combustion gas flow path side so as to hold the heat insulating layer. To do.

That is, the heat insulating layer is held by the rod-shaped body, and the heat insulating layer is prevented from peeling off from the heat transfer wall.
In particular, as in the second feature configuration, when the heat exchange tubular body having the inside to be heated is provided in the combustion gas flow path, the peripheral wall of the portion along the horizontal direction of the heat exchange tubular body The sulfuric acid is likely to condense on the upper surface.
Therefore, when the bowl-shaped body is provided so as to hold the heat insulation layer provided on the upper side of the peripheral wall along the horizontal direction of the heat exchange tubular body, the heat insulation layer on the upper surface portion of the peripheral wall peels from the peripheral wall. Therefore, it is effective in preventing the condensation of sulfuric acid.
Therefore, it is possible to obtain a means suitable for implementing the eighth characteristic configuration.

In addition to the eighth feature configuration, the tenth feature configuration of the sulfuric acid dew point corrosion prevention type heat exchanger of the present invention is as follows:
The separation preventing portion is characterized in that it is composed of a plurality of protrusions provided in a dispersed state on the surface of the heat transfer wall on the combustion gas flow path side.

That is, the plurality of protrusions prevent the heat insulating layer from being peeled off from the heat transfer wall.
In other words, the adhesion area of the heat insulation layer to the heat transfer wall is increased by the cooperation of the fact that the adhesion area of the heat insulation layer to the heat transfer wall is widened by the plurality of protrusions and the heat insulation layer is held by the plurality of protrusions. Since the strength can be increased, the durability of the heat insulating layer can be further improved.
In addition, when a large number of small protrusions are formed in a dispersed state, the protrusions can act as an aggregate of the heat insulation layer, and the strength of the heat insulation layer itself can be increased. The body makes it possible to increase the adhesion strength of the heat insulating layer to the heat transfer wall, so that the durability of the heat insulating layer can be further improved.
Therefore, it is possible to obtain a means suitable for implementing the eighth characteristic configuration.

In addition to any one of the first to seventh feature configurations described above, the eleventh feature configuration of the sulfuric acid dew point corrosion prevention type heat exchanger of the present invention is as follows:
The surface of the heat transfer wall on the combustion gas flow path side is characterized in that it is formed in an uneven shape in advance before the heat insulation layer is provided.

That is, by providing a heat insulating layer on the surface of the heat transfer wall formed in a concavo-convex shape on the combustion gas flow path side, the adhesion area of the heat insulating layer to the heat transfer wall is widened, and the surface of the concavo-convex surface is convex. It is possible to increase the adhesion strength of the heat insulation layer to the heat transfer wall by cooperating that the heat insulation layer is retained by the anchor effect that the part enters the heat insulation layer and the heat insulation layer enters the concave portion of the uneven surface. Therefore, the durability of the heat insulating layer can be further improved.
Therefore, a means suitable for further extending the life can be obtained.

In addition to any of the first to seventh feature configurations described above, the twelfth feature configuration of the sulfuric acid dew point corrosion prevention type heat exchanger of the present invention is
The surface of the heat transfer wall on the combustion gas flow path side is pre-corroded before the heat insulation layer is provided.

That is, when the surface of the heat transfer wall on the side of the combustion gas flow path is corroded, the surface of the corroded layer becomes rough with innumerable fine irregularities, and a heat insulating layer is provided on the rough surface of the corroded layer. In addition, the adhesion area of the heat insulating layer to the heat transfer wall can be increased, and the adhesion strength of the heat insulating layer to the heat transfer wall can be increased by the cooperation of the heat insulating layer being held by the rough surface. Therefore, the durability of the heat insulating layer can be further improved.
Therefore, it is possible to obtain a suitable means for further extending the life.

In addition to any one of the first to twelfth feature configurations, the thirteenth feature configuration of the sulfuric acid dew point corrosion prevention type heat exchanger of the present invention,
It is characterized in that soot removing means for removing soot contained in the combustion gas supplied to the combustion gas flow path is provided.

That is, since soot contained in the combustion gas supplied to the combustion gas flow path is removed by the soot removal means, it is possible to suppress soot from adhering to the surface of the heat insulating layer.
That is, since the soot has good heat conductivity, when the soot is mixed into the heat insulating layer, the heat insulating property of the heat insulating layer is lowered.
Therefore, by removing the soot contained in the combustion gas by the soot removal means, soot is prevented from being mixed into the heat insulating layer, and the heat insulating property of the heat insulating layer is reduced due to the soot being mixed into the heat insulating layer. Since it can suppress, it becomes possible to maintain the surface temperature of a heat insulation layer at a higher temperature, and it becomes possible to prevent that a sulfuric acid condenses on the surface of a heat insulation layer.
Therefore, the lifetime can be further increased.

[How to use sulfuric acid dew point corrosion prevention heat exchanger]
The method of using the sulfuric acid dew point corrosion prevention type heat exchanger according to the present invention is a method of using the sulfuric acid dew point corrosion prevention type heat exchanger of any one of the first to thirteenth features,
The first characteristic configuration is characterized in that the heat transfer wall is washed or the heat transfer wall is not washed so as not to peel off the heat insulating layer.

That is, the heat transfer wall is washed so as not to peel off the heat insulation layer, or the heat transfer wall is washed as little as possible or not washed at all. Consumption of the heat insulating layer such as thinning or partial peeling can be suppressed.
That is, in such a sulfuric acid dew point corrosion prevention type heat exchanger, soot and the like contained in the combustion gas adhere to the heat transfer wall during use. Therefore, in order to remove the deposit from the heat transfer wall, heat transfer is usually performed. Although the wall is cleaned, the heat insulating layer may be consumed by the cleaning, so the heat transfer wall is cleaned so as not to peel off the heat insulating layer, or the heat transfer wall is not cleaned as much as possible. By not washing, it is possible to suppress the consumption of the heat insulating layer.
Accordingly, it is possible to provide a method of using a heat exchanger of the sulfuric acid dew point corrosion prevention type that can be used so as to further extend the life.

  The second characteristic configuration of the method of using the sulfuric acid dew point corrosion-preventing heat exchanger according to the present invention is characterized in that the temperature in the combustion gas flow path is gradually increased and decreased so that the heat insulating layer does not peel off. And

That is, by gradually increasing the temperature and decreasing the temperature in the combustion gas flow path, the difference in the amount of thermal expansion and contraction between the heat transfer wall and the heat insulation layer caused by the difference in the coefficient of thermal expansion is reduced. Suppresses peeling of the heat insulation layer.
Accordingly, it is possible to provide a method of using a heat exchanger of the sulfuric acid dew point corrosion prevention type that can be used so as to further extend the life.

[First Embodiment]
Hereinafter, based on the drawings, a first embodiment when the present invention is applied to a sulfuric acid dew point corrosion prevention type heat exchanger used as an economizer in an exhaust heat boiler will be described.
First, the overall configuration of the exhaust heat boiler will be described with reference to FIG.
The waste heat boiler is an economizer 3 that preheats raw water with combustion gas from the engine 1 as a combustion type prime mover, an air-water drum 4 that stores water heated by the economizer 3, and is stored in the air-water drum 4. The engine water is provided with a main heat exchanger 2 that is circulated and supplied with the raw material water and heated with the combustion gas, and a control unit 5 that performs various controls of the exhaust heat boiler. The steam generated by heating the raw water using the exhaust heat of 1 is supplied from the steam-water drum 4 to the steam consumption section (not shown) through the steam delivery path 6. The combustion gas from the engine 1 is passed through the main heat exchanger 2 and the economizer 3 in this order.

Specifically, the engine 1 is a diesel engine that uses a fuel that contains a relatively large amount of sulfur such as heavy oil, and the combustion gas discharged from the engine 1 contains sulfur dioxide gas.
Incidentally, although not shown in the figure, the engine 1 drives a generator and is operated in a power generation time zone set as a part of the time of the day.

A description will be added for each part.
As shown in FIG. 1, a long and thin heat exchange that includes a combustion gas flow path inlet 7i at one end in the longitudinal direction and a combustion gas flow path outlet 7e at the other end to form the combustion gas flow path 7 therein. The furnace casing 8 is erected in such a posture that the combustion gas flow path inlet 7i is upward and the combustion gas flow path outlet 7e is downward, and the meander is placed in the combustion gas flow path 7 formed by the heat exchanger casing 8. A main heat exchanger heat transfer tube 9 and a meandering economizer heat transfer tube 10 as the heat exchange tubular body are arranged in the combustion gas flow path 7.

  When the economizer heat transfer tube 10 is described, a cylindrical tube member is formed in a meandering shape in which a plurality of parallel straight tubular portions are connected in series at a curved tubular portion, and the serpentine tube member A plurality (only one is shown in FIG. 1) are connected in parallel by a header 10h to form the economizer heat transfer tube 10, and the economizer heat transfer tube 10 is combusted in a posture in which the straight tubular portion faces a horizontal direction. It is disposed in the gas flow path 7.

  That is, as shown in FIG. 5, a heat exchange tubular shape having a peripheral wall as a heat transfer wall 11 and a heating channel 12 through which the raw water (corresponding to a heated fluid) flows. The economizer heat transfer tube 10 as a body is provided in the combustion gas flow channel 7, and the combustion gas flow channel 7 and the economizer heat transfer tube 10 are connected to the combustion gas flow channel 7 and the economizer heat transfer tube 10. The economizer 3 as a heat exchanger of the sulfuric acid dew point corrosion prevention type according to the present invention, which is provided in a state where the heated channel 12 is partitioned by the heat transfer wall 11, is configured.

  And in this 1st Embodiment, the heat insulation which suppresses the heat transfer of combustion gas and raw material water to the outer peripheral surface of the said heat exchanger tube 10 which is the surface at the said combustion gas flow path 7 side of the said heat transfer wall 11 is carried out. Layer I is provided with sulfuric acid corrosion resistance.

  The economizer heat transfer tube 10 is formed of weathering steel containing at least one of chromium (Cr), copper (Cu), phosphorus (P), and nickel (Ni). FIG. 2 shows the composition of the weathering steel manufactured by each manufacturing company. In the present invention, the weathering steel is one of the weathering steels shown in FIG. 2 or the one shown in FIG. Other weathering steels can be used.

Returning to FIG. 1, a combustion gas supply path 13 that leads the combustion gas discharged from the engine 1 is connected to the combustion gas flow path inlet 7 i of the combustion gas flow path 7. Is provided with a combustion catalyst 14 as soot removal means for removing soot contained in the combustion gas supplied to the combustion gas passage 7, and at the combustion gas passage outlet 7 e of the combustion gas passage 7, the combustion gas A discharge path 15 is connected.
Since the combustion catalyst 14 is well known and will not be described in detail and will be briefly described, a combustion catalyst material such as platinum is supported on an air-permeable carrier such as a honeycomb-like body so as to be ventilated. It is. The combustion catalyst 14 is disposed in the combustion gas flow path 7 in a state extending across the entire flow path, and the combustion catalyst 14 causes the combustion gas flow through the combustion gas flow path 7. It is configured to remove the soot by burning the unburned content therein.

After the raw water is heated by passing through the economizer heat transfer pipe 10 of the economizer 3, a water supply path 16 is piped so as to be supplied to the bottom of the air-water drum 4, and a water supply pump is provided in the water supply path 16. 17 is provided.
Further, the raw water in the air / water drum 4 is taken out from the bottom, passed through the main heat exchanger heat transfer pipe 9 of the main heat exchanger 2, and then returned to the air / water drum 4. A circulation path 18 is piped so that the raw water in 4 is circulated with the main heat exchanger 2, and a circulation pump 19 is provided in the circulation path 18.
Further, the steam delivery path 6 is connected to the top of the steam-water drum 4, and steam separated from the steam by the steam-water drum 4 is supplied to the steam consumption section through the steam delivery path 6.

The water supply passage 16 is provided with a water supply preheating unit 20 for preheating raw water supplied to the economizer 3.
Although not shown, the feed water preheating unit 20 is configured to preheat the raw water by taking out a part of the steam from the steam drum 4 and mixing it with the raw water. The feed water preheating unit 20 may be configured to preheat the raw water by exchanging heat between the raw water and the exhaust heat of the engine 1.

A cleaning nozzle 21 is disposed in the heat exchanger casing 8 above the main heat exchanger heat transfer tube 9, a cleaning air supply path 22 is connected to the cleaning nozzle 21, and the cleaning is performed. The air supply path 22 is provided with a manual cleaning valve 23 that can freely and continuously adjust the supply of cleaning air and adjust the supply amount.
When the main heat exchanger heat transfer tube 9 and the economizer heat transfer tube 10 need to be cleaned, the cleaning valve 21 is opened to open the main heat exchanger heat transfer tube 9 and the economizer transfer by the cleaning nozzle 21. Cleaning air is ventilated from above the heat pipe 10 to clean the main heat exchanger heat transfer pipe 9 and the economizer heat transfer pipe 10.

  Further, a spray nozzle 24 is provided in the heat exchanger casing 8 above the main heat exchanger heat transfer tube 9 to supply a material for forming a heat insulating layer, which will be described later, into the combustion gas flow path 7. A spray material supply path 26 provided with a spray pump 25 is connected to the spray nozzle 24.

Next, the economizer heat transfer tube 10 will be described.
As shown in FIG. 5, the heat insulating layer I is formed of a heat insulating layer forming material supplied into the combustion gas flow path 7. Specifically, the heat insulating layer I includes It consists of a neutralized product 41 having sulfuric acid corrosion resistance formed by a neutralizing agent as a heat insulating layer forming material.
Further, as shown in FIG. 4, the outer peripheral surface of the economizer heat transfer tube 10 is provided with a peeling prevention portion P for preventing the neutralization product 41 from being peeled in advance before the neutralization product 41 is provided. The anti-separation part P is configured by a rod-like body 27 provided so as to protrude from the outer peripheral surface of the economizer heat transfer tube 10 so as to hold the neutralized product 41.

Referring to FIG. 4, the rod-like body 27 will be further described. The two elongated rod-like bodies 27 are arranged in the economizer heat transfer tube 10 with the phase shifted by 180 ° in the circumferential direction. Install along the direction. Then, the economizer heat transfer tube 10 to which the rod-like body 27 is attached is arranged in the combustion gas flow path 7 with the two rod-like bodies 27 aligned in the horizontal direction.
The rod-shaped body 27 is formed of the same weathering steel as that for forming the economizer heat transfer tube 10, and such a rod-shaped body 27 is attached to the outer peripheral surface of the economizer heat transfer tube 10 by welding, caulking, or the like. .

  Incidentally, as shown in FIG. 4, when the outer diameter D of the economizer heat transfer tube 10 is 34 mm and the thickness T of the peripheral wall is 3 mm, the economizer heat transfer tube 10 at the bottom of the bowl-shaped body 27 extends in the circumferential direction. A width W along the direction along the radial direction of the economizer heat transfer tube 10 of the economizer 27 is set to 17 mm, and the bar 27 is used as a heat transfer fin. is there.

A method for forming the neutralized product 41 as the heat insulating layer I will be described.
The economizer heat transfer tube 10 is disposed in the combustion gas flow path 7 formed in the heat exchanger casing 8 without the heat insulation layer I, and starts using the economizer 3.
At the beginning of use when the economizer 3 is started, the spray pump 25 is operated, and the spray nozzle 24 sprays the neutralizing agent as the heat insulating layer forming material into the combustion gas flow path 7. The neutralized product 41 is formed on the outer peripheral surface of the economizer heat transfer tube 10 and the neutralized product 41 functions as the heat insulating layer I. Incidentally, in this embodiment, an aqueous solution of magnesium hydroxide (Mg (OH ₂ )) is used as the neutralizing agent, and magnesium sulfate (MgSO ₄ ), which is an inorganic compound, is generated as the neutralized product. That is, the heat insulation layer I is formed of magnesium sulfate which is an example of an inorganic compound. Further, the spray nozzle 24 functions as a heat insulating layer forming material supply unit for supplying the heat insulating layer forming material into the combustion gas flow path 7.

That is, at the start of use of the economizer 3, since the heat insulating layer I is not provided on the outer peripheral surface of the economizer heat transfer tube 10, the outer peripheral surface temperature of the economizer heat transfer tube 10 is equal to or lower than the sulfuric acid dew point temperature. Sulfuric acid is condensed on the surface of the heat transfer tube 10 for the economizer.
When the neutralizing agent is sprayed and supplied into the combustion gas flow path 7 by the spray nozzle 24, the neutralizing agent is added to sulfuric acid on the surface of the economizer heat transfer tube 10, and the neutralization reaction between the sulfuric acid and the neutralizing agent is performed. Thus, the neutralized product 41 is generated on the surface of the heat transfer tube 10 for the economizer. Further, the neutralizing agent sprayed in the combustion gas passage 7 undergoes a neutralization reaction in the combustion gas, and the neutralized product adheres to the surface of the economizer heat transfer tube 10, so that the economizer heat transfer tube 10 The neutralization product 41 may be generated on the surface. And since such neutralization product 41 is porous and has low thermal conductivity, when it reaches a predetermined thickness (for example, 2 mm), the temperature of the surface of neutralization product 41 is reduced by its heat insulation action. It becomes possible to make the temperature higher than the sulfuric acid dew point.

Although details will be described later, since the economizer 3 is used so that the neutralized product 41 thus generated is not peeled off, the generation of the neutralized product 41 proceeds.
The neutralizing product 41 is formed so that the neutralizing agent is supplied by the spray nozzle 24 so as to cover substantially the entire length and the entire circumference of the portion of the economizer heat transfer tube 10 located in the combustion gas flow path 7. If the neutralized product 41 is generated as such, the supply of the neutralizing agent is stopped.

  And by providing the said economizer heat exchanger tube 10 with the above-mentioned rod-shaped body 27, the neutralized product 41 is hold | maintained with the rod-shaped body 27, and peeling of the neutralized product 41 is prevented. Can do.

  In addition, after the formation of the neutralized product 41 in the initial stage of use, the neutralized product 41 is consumed because the thickness of the neutralized product 41 is reduced or partially peeled off. Each time the neutralization product additional formation time that requires additional formation of the sum product 41 is reached, the spray pump 25 is operated and the spray nozzle 24 sprays the neutralizing agent into the combustion gas flow path 7. The neutralized product 41 as the heat insulation layer I is additionally formed.

Next, the control configuration of the control unit 5 will be described.
The control unit 1 stores the power generation time zone, a set output increase rate for slow start when the engine 1 is started, and a set output decrease rate for slow stop when the engine 1 is stopped. .
As the set output increase rate for the slow start, the temperature rise in the combustion gas passage 7 is moderated so that the layer of the neutralized product 41 formed as the heat insulation layer I does not peel off, and the economizer A moderate output increase rate is set such that the temperature of the heat transfer tube 10 can be gradually increased.
Further, as the set output reduction rate for the slow stop, the temperature drop in the combustion gas flow path 7 is moderated so that the layer of the neutralized product 41 does not peel off, and the heat exchanger tube 10 for the economizer is used. The output decrease rate is set so that the temperature can be gradually decreased.

  Then, based on the information stored in the power generation time zone, the control unit 1 increases the output of the engine 1 to a rated output at the set output increase rate for the slow start at the engine operation start time. When the engine 1 is started and the output is increased to the rated output, the feed water pump 17 and the circulation pump 19 are operated to start the operation of the exhaust heat boiler. When the engine stop time is reached, the feed water pump 17 and the circulation pump 19 are stopped to stop the exhaust heat boiler, and the output of the engine 1 is decreased at the set output decrease rate for the slow stop and stopped when the set minimum output is reached. The engine 1 is configured to be stopped.

  That is, the engine 1 is started at a slow start that gradually increases the output so as to moderate the temperature rise of the economizer heat transfer tube 10 so that the layer of the neutralized product 41 formed as the heat insulation layer I does not peel off. And, in order to moderate the temperature drop of the economizer heat transfer tube 10 so that the layer of the neutralized product 41 does not peel off, the engine 1 is stopped by a slow stop after the output is gradually decreased. It is configured.

FIG. 3 shows the tendency of the temperature rise of the economizer heat transfer tube 10 when the engine 1 is normally started and when it is slowly started as described above.
The time required for the temperature of the heat exchanger tube 10 for the economizer to reach a steady state from about 80 ° C. at the start of the engine 1 to about 180 ° C. is about 20 minutes when the engine 1 is normally started. On the other hand, when the engine is started slowly, it takes about 40 minutes. By the slow start, the temperature of the heat exchanger tube 10 for the economizer is gradually increased when the engine 1 is started.

Although illustration is omitted, when the engine 1 is stopped gently, the temperature of the economizer heat transfer tube 10 is reduced to about 80 ° C. in about 40 minutes from the steady state of about 180 ° C., The temperature drop of the economizer heat transfer tube 10 is gently performed when the engine 1 is stopped.
That is, when the temperature rise of the economizer heat transfer tube 10 at the start of the engine 1 or the temperature drop of the economizer heat transfer tube 10 at the stop of the engine 1 becomes faster, the space between the economizer heat transfer tube 10 and the heat insulating layer I is increased. The heat insulation layer I is easily peeled off due to the difference in thermal expansion coefficient between the two, so that the temperature of the economizer heat transfer tube 10 rises when the engine 1 starts and the temperature drop of the economizer heat transfer tube 10 stops when the engine 1 is stopped. Is performed gently to prevent the heat insulation layer I from peeling off.

Cleaning of the main heat exchanger heat transfer tube 9 and the economizer heat transfer tube 10 by the cleaning nozzle 21 is performed on the main heat exchanger heat transfer tube 9 and the economizer heat transfer tube 10 in the amount of deposits such as dust and soot. The neutralization by washing is performed by reducing the frequency of washing the heat transfer pipe 9 for the main heat exchanger and the heat transfer pipe 10 for the economizer so that the gap between the heat transfer pipes may become clogged. The consumption of the product 41 is prevented.
Moreover, even when the heat transfer tube 9 for the main heat exchanger and the heat transfer tube 10 for the economizer are cleaned, the cleaning valve 23 is gradually opened so that the layer of the neutralized product 41 does not peel off, and its opening degree Is reduced to reduce the ventilation rate of the cleaning air and the ventilation rate is slowed so that the cleaning air is gently ventilated.

That is, in the first embodiment, the economizer 3 is used by cleaning the economizer heat transfer tube 10 so as not to peel off the heat insulating layer I.
Further, the economizer 3 is used so that the temperature in the combustion gas passage 7 is gradually increased and decreased so that the heat insulating layer I does not peel off.

  Hereinafter, the second to eighth embodiments of the present invention will be described. In each embodiment, the overall configuration of the exhaust heat boiler is the first shown in FIG. 1 except that the configuration of the heat transfer tube 10 for the economizer is different. Since the control configuration of the control unit 5 and the method of using the exhaust heat boiler are the same as those in the first embodiment, the configuration of the economizer heat transfer tube 10 will be mainly described.

[Second Embodiment]
In the second embodiment, as shown in FIG. 7, the heat insulation layer I is a neutralized product 41 formed by a neutralizing agent as the heat insulation layer forming material, as in the first embodiment. Although the specific configuration of the peeling prevention part P is different from that of the first embodiment, the peeling prevention part P includes a plurality of (in this embodiment) provided in a dispersed state on the outer peripheral surface of the economizer heat transfer tube 10. 8) long projections 28.

The long projection 28 will be further described. As shown in FIG. 6, a plurality of rod-shaped bodies are attached to the outer peripheral surface of the economizer heat transfer tube 10 while being spaced apart in the circumferential direction, and the plurality of long projections 28 are attached by the plurality of rod-shaped bodies. The economizer heat transfer tube 10 having a plurality of elongated protrusions 28 on the outer peripheral surface is disposed in the combustion gas flow path 7.
The rod-shaped body constituting the elongated protrusion 28 is formed of the same weathering steel as that for forming the economizer heat transfer tube 10, and such a rod-shaped body is formed on the outer peripheral surface of the economizer heat transfer tube 10. It is attached by welding or caulking.

  Incidentally, as shown in FIG. 6, when the outer diameter D of the economizer heat transfer tube 10 is 34 mm and the thickness T of the peripheral wall is 3 mm, the circumference of the economizer heat transfer tube 10 at the bottom of the elongated protrusion 28 is increased. The width W in the direction along the direction is 5 mm, and the height H in the direction along the radial direction of the economizer heat transfer tube 10 of the elongated protrusion 28 is 3 mm.

  An economizer heat transfer tube 10 having a plurality of elongated protrusions 28 on the outer peripheral surface is disposed in the combustion gas flow path 7, and the heat insulating layer is formed on the outer peripheral surface of the economizer heat transfer tube 10 during use. Although the neutralized product 41 as I is formed, the formation method is the same as that of the first embodiment, and thus the description thereof is omitted.

  Then, by providing the economizer heat transfer tube 10 with the plurality of long projections 28 as described above, the adhesion area of the neutralized product 41 to the economizer heat transfer tube 10 is widened by the long projections 28. In addition, since the neutralized product 41 can be held by the elongated protrusions 28, the neutralized product 41 can be prevented from peeling off.

[Third Embodiment]
In the third embodiment, as shown in FIG. 9, the heat insulation layer I is a neutralized product 41 formed by a neutralizing agent as the heat insulation layer forming material, as in the first embodiment. Although it is configured, the specific configuration of the peeling prevention portion P is different from that of the first embodiment, and the peeling prevention portion P includes a large number of wart-shaped protrusions provided in a dispersed state on the outer peripheral surface of the economizer heat transfer tube 10. 29.

  The wart-shaped protrusion 29 will be further described. As shown in FIG. 8, a drop material is dropped into a wart shape in a state of being dispersed in a large number of places on the outer peripheral surface of the economizer heat transfer tube 10, and then cured to be dispersed, and a large number of warped protrusions 29 in a dispersed state. Form. The dripping material can be dripped in a wart shape and has resistance to sulfuric acid when cured. Incidentally, as the dripping material, a resin having resistance to sulfuric acid such as silicon resin can be used. Alternatively, as the dripping material, paste made of ceramic particles having resistance to sulfuric acid can be used.

  An economizer heat transfer tube 10 having a large number of wart-shaped protrusions 29 on its outer peripheral surface is disposed in the combustion gas flow path 7, and the heat insulating layer I is disposed on the outer peripheral surface of the economizer heat transfer tube 10 during use. The neutralized product 41 is formed as described above, and the method for forming the neutralized product 41 is the same as that in the first embodiment, and thus the description thereof is omitted.

Then, by providing the economizer heat transfer tube 10 with a large number of wart-shaped protrusions 29 as described above, the large number of wart-shaped protrusions 29 are caused to act as the aggregate of the neutralized product 41, and the neutralized product. The strength of 41 can be increased, and the neutralized product 41 can be held by a large number of wart-shaped protrusions 29, so that the neutralized product 41 can be prevented from peeling off.
Incidentally, the height of the wart-like projections 29 is sufficient to be at least about 1 to 2 mm in order for the wart-like projections 29 to act as the aggregate of the neutralized product 41. In this embodiment, 1 mm.

[Fourth Embodiment]
In the fourth embodiment, as shown in FIG. 11, the heat insulation layer I is formed by a neutralized product 41 formed by a neutralizing agent as the heat insulation layer forming material, as in the first embodiment. Although configured, the outer peripheral surface of the economizer heat transfer tube 10 which is the surface of the heat transfer wall 11 on the combustion gas flow path 7 side without providing the separation preventing portion P as in the first embodiment, Before the heat insulation layer I is provided, it is formed in an uneven shape in advance.

A method for forming the outer peripheral surface of the economizer heat transfer tube 10 in an uneven shape will be described.
As shown in FIG. 10 (a), the outer peripheral surface of the economizer heat transfer tube 10 when delivered from the manufacturer is smooth, and fine particles of iron, sand, or glass are sprayed onto the smooth outer peripheral surface. Innumerable fine irregularities are formed by blasting. That is, the outer peripheral surface of the economizer heat transfer tube 10 is formed into a rough surface 10s.

  An economizer heat transfer tube 10 having an outer peripheral surface formed into a rough surface 10s is disposed in the combustion gas flow path 7, and the medium as the heat insulating layer I is disposed on the outer peripheral surface of the economizer heat transfer tube 10 during use. Although the sum product 41 is formed, the formation method is the same as that of the first embodiment, and thus the description thereof is omitted.

  Since the outer peripheral surface of the economizer heat transfer tube 10 is formed into the rough surface 10s as described above, the adhesion strength of the neutralized product 41 to the outer peripheral surface of the economizer heat transfer tube 10 can be increased. The peeling of the sum product 41 can be prevented.

[Fifth Embodiment]
In the fifth embodiment, as shown in FIG. 13, the heat insulating layer I is formed by a neutralized product 41 formed by a neutralizing agent as the heat insulating layer forming material, as in the first embodiment. Although not configured, the outer peripheral surface of the economizer heat transfer tube 10 which is the surface of the heat transfer wall 11 on the combustion gas flow path 7 side without providing the separation preventing portion P as in the first embodiment, Before the heat insulation layer I is provided, it is pre-corroded to form a preliminary corrosion layer 42.

A method of forming the preliminary corrosion layer 42 by corroding the outer peripheral surface of the economizer heat transfer tube 10 will be described.
As shown in (a) of FIG. 12, the outer peripheral surface of the economizer heat transfer tube 10 when delivered from the manufacturer is smooth, and the outer peripheral surface of the economizer heat transfer tube 10 having such a smooth outer peripheral surface is The thin pre-corrosion layer 42 is formed by corrosion by water spraying in the atmosphere.

  As described above, the economizer heat transfer tube 10 in which the thin preliminary corrosion layer 42 is formed on the outer peripheral surface is disposed in the combustion gas flow path 7, and the heat insulation is provided on the outer peripheral surface of the economizer heat transfer tube 10 during use. Although the said neutralization product 41 as the layer I is formed, since the formation method is the same as that of 1st Embodiment, description is abbreviate | omitted.

  That is, since the surface of the preliminary corrosion layer 42 is a rough surface having innumerable fine irregularities, the preliminary corrosion layer 42 is formed on the outer peripheral surface of the economizer heat transfer tube 10 as described above, whereby the preliminary corrosion layer 42 is subjected to the preliminary corrosion. The layer 42 can increase the adhesion strength of the neutralized product 41 to the outer peripheral surface of the economizer heat transfer tube 10, and can prevent the neutralized product 41 from peeling off.

Since the control configuration of the control unit 5 of the economizer 3 of the second to fifth embodiments and the method of using the exhaust heat boiler are the same as those of the first embodiment, detailed description thereof is omitted. The control configuration at the start and stop of the engine 1 will be briefly described. The start of the engine 1 is a slow start in which the output of the engine 1 is increased to a rated output at the set output increase rate for the slow start. The engine 1 is stopped by a slow stop in which the output of the engine 1 is reduced at the set output reduction rate for the slow stop and stopped when the set minimum output is reached.
That is, the engine 1 is started at a slow start that gradually increases the output so as to moderate the temperature rise of the economizer heat transfer tube 10 so that the layer of the neutralized product 41 formed as the heat insulation layer I does not peel off. And, in order to moderate the temperature drop of the economizer heat transfer tube 10 so that the layer of the neutralized product 41 does not peel off, the engine 1 is stopped by a slow stop after the output is gradually decreased. It is configured.
In short, the economizer 3 is used by gradually increasing the temperature and decreasing the temperature in the combustion gas passage 7 so that the layer of the neutralized product 41 formed as the heat insulating layer I does not peel off. .

Further, the cleaning of the main heat exchanger heat transfer tube 9 and the economizer heat transfer tube 10 by the cleaning nozzle 21 is also performed in the same manner as in the first embodiment, and thus the description thereof is omitted.
In short, the economizer 3 is used by washing the economizer heat transfer tube 10 so as not to peel off the layer of the neutralized product 41 formed as the heat insulating layer I.

[Sixth Embodiment]
In the sixth embodiment, the heat insulating layer I is provided in a state having resistance to sulfuric acid corrosion as in the first embodiment. However, the forming method and the forming material are different from those in the first embodiment, and FIG. As shown in FIG. 6, in the sixth embodiment, the heat insulating layer I is a corrosion product 43 generated by corrosion during use of the material forming the heat transfer wall 11, that is, the economizer heat transfer tube 10. . Further, similarly to the first embodiment, the outer peripheral surface of the economizer heat transfer tube 10 is provided with a peeling prevention portion P for preventing the corrosion product 43 from peeling before the corrosion product 43 is provided. The peeling prevention part P is provided on the bowl-shaped body 27 provided in a state of protruding from the outer peripheral surface of the economizer heat transfer tube 10 so as to hold the corrosion product 43 as in the first embodiment. Configured.

  As shown in FIG. 4, as in the first embodiment, the bowl-shaped body 27 is formed in a long shape by the same weathering steel as that for forming the economizer heat transfer tube 10, and the long shape Two of the rod-shaped bodies 27 are attached to the economizer heat transfer tube 10 by welding, caulking, or the like along the longitudinal direction of the economizer with a phase shifted by 180 ° in the circumferential direction.

  Then, the economizer heat transfer tube 10 to which the rod-like body 27 is attached is arranged in the combustion gas flow path 7 in a state where the two rod-like bodies 27 are arranged along the horizontal direction. In addition, the outer peripheral surface of the economizer heat transfer tube 10 is corroded to form the corrosion product 43 having sulfuric acid corrosion resistance as the heat insulating layer I.

Hereinafter, a method for forming the corrosion product 43 as the heat insulating layer I will be described.
The economizer heat transfer tube 10 is disposed in the combustion gas flow path 7 formed by the heat exchanger casing 8 in the state without the heat insulation layer I and is provided with the economizer 3 as in the first embodiment. Start using.
Therefore, when the economizer 3 starts to be used, since the heat insulating layer I is not provided on the outer peripheral surface of the economizer heat transfer tube 10, the outer peripheral surface temperature of the economizer heat transfer tube 10 is lower than the sulfuric acid dew point temperature. Thus, sulfuric acid is condensed on the surface of the economizer heat transfer tube 10, and the weatherable steel forming the economizer heat transfer tube 10 is corroded by the sulfuric acid, and corrosion products (rust) are formed on the outer peripheral surface of the economizer heat transfer tube 10. 43 will be generated.
As will be described in detail later, since the economizer 3 is used so that the corrosion product 43 thus generated is not peeled off, the generation of the corrosion product 43 proceeds and the thickness of the corrosion product 43 is increased. At the same time, the corrosion product 43 is generated over substantially the entire length and substantially the entire circumference of the portion of the economizer heat transfer tube 10 located in the combustion gas flow path 7.

Further, while the generation of the corrosion product 43 proceeds, the spray pump 25 is operated a plurality of times at intervals of time, and the metal polyvalent ion-containing material is supplied to the combustion gas flow path by the spray nozzle 24. 7, the metal polyvalent ion-containing material is added to the corrosion product 43, the colloidal particles constituting the corrosion product 43 are combined by bonding with the metal polyvalent ions, and the corrosion product The strength of 43 can be increased. That is, the spray nozzle 24 functions as a metal multivalent ion-containing material supply unit that supplies the metal multivalent ion-containing material into the combustion gas flow path 7.
Incidentally, in this embodiment, an aqueous solution of calcium hydroxide (Ca (OH) ₂ ) is used as the metal multivalent ion-containing material, and the colloidal particles constituting the corrosion product 43 are bound by calcium ions.

  And the corrosion product 43 produced | generated as mentioned above is porous, and since thermal conductivity is small, when it becomes predetermined | prescribed thickness (for example, 2 mm), the surface of the corrosion product 43 will be according to the heat insulation action. It becomes possible to make the temperature higher than the sulfuric acid dew point, and when the surface temperature of the corrosion product 43 becomes higher than the sulfuric acid dew point temperature due to the heat insulating action of the corrosion product 43, the condensation of sulfuric acid is prevented. Thus, the corrosion by sulfuric acid of the economizer heat transfer tube 10 is stopped.

Next, the shape of the rod-like body 27 necessary for continuing the peeling preventing action of the corrosion product 43 by the rod-like body 27 will be described.
That is, as shown in FIGS. 4 and 14, the outer diameter D of the economizer heat transfer tube 10 is 34 mm, and the thickness T of the peripheral wall is 3 mm. Further, the thickness of the corrosion product 43 that enables the surface temperature to be higher than the sulfuric acid dew point temperature is set to 2 mm.

The rod-shaped body 27 is corroded from both sides in the circumferential direction of the economizer heat transfer tube 10, and in the state where the corrosion product 43 is generated on the rod-shaped body 27 until the thickness becomes 2 mm. Since the rod-like body 27 corrodes about 1 mm from the surface thereof, the rod-like body 27 is joined to the economizer heat transfer tube 10 in a state where the corrosion product 43 is produced until the thickness becomes 2 mm. In order to maintain this state, the width W in the direction along the circumferential direction of the economizer heat transfer tube 10 at the bottom of the bowl-shaped body 27 is set to 3 mm or more (5 mm in this embodiment).
Further, the height H of the rod-like body 27 along the radial direction of the economizer heat transfer tube 10 holds the corrosion product 43 having a thickness of 2 mm on the assumption that 1 mm is corroded in the radial direction. In order to maintain the action, it is necessary to make it 3 mm or more, but in this embodiment, it is 17 mm and is used as a heat transfer fin.

  By providing the economizer heat transfer tube 10 with the rod-like body 27 as described above, the corrosion product 43 is retained and retained by the rod-like body 27 even during the production of the corrosion product 43. 43, and after the corrosion product 43 is generated until the surface temperature can be raised above the sulfuric acid dew point temperature, the rod-like body 27 causes the corrosion product 43 to be removed. In response, peeling of the corrosion product 43 can be prevented.

[Seventh Embodiment]
In the seventh embodiment, unlike the first embodiment, the heat insulating layer I is composed of the corrosion product 43 similar to that of the sixth embodiment, as shown in FIG. Although the peeling prevention part P is provided similarly to the form, the specific structure of the peeling prevention part P is different from the first embodiment, and the peeling prevention part P is a heat transfer tube for an economizer as in the second embodiment. A plurality of (eight in this embodiment) long projections 28 provided in a distributed state on the outer peripheral surface 10 are configured.

  As shown in FIG. 6, as in the second embodiment, on the outer peripheral surface of the economizer heat transfer tube 10, a plurality of rod-shaped bodies formed of the same weathering steel as that for forming the economizer heat transfer tube 10 are arranged in the circumferential direction. The plurality of long projections 28 are constituted by the plurality of rod-like bodies and arranged in a state of being spaced apart by welding, caulking, and the like. The provided economizer heat transfer tube 10 is disposed in the combustion gas flow path 7.

An economizer heat transfer tube 10 having a plurality of elongated protrusions 28 on the outer peripheral surface is disposed in the combustion gas flow path 7, and the heat insulating layer is formed on the outer peripheral surface of the economizer heat transfer tube 10 during use. Although the said corrosion product 43 as I is formed, since the formation method is the same as that of 6th Embodiment, description is abbreviate | omitted.
Similarly to the sixth embodiment, while the generation of the corrosion product 43 proceeds, the metal polyvalent ion-containing material is sprayed into the combustion gas passage 7 by the spray nozzle 24, and the corrosion product is The strength of the corrosion product 43 can be increased by combining the colloidal particles constituting 43 by bonding with metal multivalent ions.

Next, the shape of the elongated protrusion 28 necessary for continuing the peeling preventing action of the corrosion product 43 by the elongated protrusion 28 will be described.
That is, as shown in FIGS. 6 and 15, the outer diameter D of the economizer heat transfer tube 10 is 34 mm, the thickness T of the peripheral wall is 3 mm, and the surface temperature can be made higher than the sulfuric acid dew point temperature. The thickness of the corrosion product 43 is assumed to be 2 mm.
In that case, the elongated protrusion 28 is corroded from both sides in the circumferential direction of the economizer heat transfer tube 10, so that the corrosion product 43 is generated until the thickness reaches 2 mm. In order to maintain the state in which the elongated protrusion 28 is joined to the economizer heat transfer tube 10, the width of the bottom portion of the elongated protrusion 28 in the direction along the circumferential direction of the economizer heat transfer tube 10 W is set to 3 mm or more (5 mm in the present embodiment).
Further, the height H of the long protrusion 28 in the radial direction of the economizer heat transfer tube 10 needs to be 3 mm or more on the assumption that 1 mm is corroded in the radial direction. In the embodiment, it is 3 mm.

  By providing the economizer heat transfer tube 10 with the long projection 28 as described above, the corrosion product 43 against the economizer heat transfer tube 10 is produced by the long projection 28 even during the production of the corrosion product 43. After the corrosion product 43 is generated until the surface temperature can be made higher than the sulfuric acid dew point temperature, it is possible to prevent the corrosion product 43 from peeling off. The long protrusions 28 can increase the adhesion strength of the corrosion product 43 to the economizer heat transfer tube 10 and prevent the corrosion product 43 from peeling off.

[Eighth Embodiment]
In the eighth embodiment, unlike the first embodiment, the heat insulating layer I is composed of the same corrosion product 43 as in the sixth embodiment, as shown in FIG. Without providing the separation preventing part P as in the embodiment, the outer peripheral surface of the economizer heat transfer tube 10 that is the surface of the heat transfer wall 11 on the combustion gas flow path 7 side is the same as in the fourth embodiment. Before the heat insulation layer I is provided, it is formed in an uneven shape in advance.

As shown in FIG. 10, as in the fourth embodiment, innumerable fine irregularities are formed on the outer peripheral surface of the economizer heat transfer tube 10 by blasting, and the outer peripheral surface of the economizer heat transfer tube 10 is roughened to 10s. To form.
An economizer heat transfer tube 10 having an outer peripheral surface formed into a rough surface 10s is disposed in the combustion gas flow path 7, and the heat insulating layer I is formed on the outer peripheral surface of the economizer heat transfer tube 10 during use. Although the said corrosion product 43 is formed, since the formation method is the same as that of 6th Embodiment, description is abbreviate | omitted.
Similarly to the sixth embodiment, while the generation of the corrosion product 43 proceeds, the metal polyvalent ion-containing material is sprayed into the combustion gas passage 7 by the spray nozzle 24, and the corrosion product is The strength of the corrosion product 43 can be increased by combining the colloidal particles constituting 43 by bonding with metal multivalent ions.

  Then, as described above, the outer peripheral surface of the economizer heat transfer tube 10 is formed on the rough surface 10s, and the corrosion product 43 is generated on the rough surface 10s, thereby generating corrosion on the outer peripheral surface of the economizer heat transfer tube 10. Since the adhesion strength of the object 43 can be increased, the corrosion product 43 can be prevented from peeling off.

  Since the control structure of the control unit 5 and the method of using the exhaust heat boiler of the sixth to eighth embodiments are the same as those of the first embodiment, the detailed description is omitted and the engine 1 is omitted. Briefly explaining the control configuration at the time of starting and stopping, the engine 1 is started by a slow start in which the output of the engine 1 is increased to a rated output at the set output increase rate for the slow start, The engine 1 is stopped by a slow stop in which the output of the engine 1 is decreased at the set output reduction rate for the slow stop and stopped when the set minimum output is reached.

That is, the engine 1 is started at a slow start that gradually increases the output in order to moderate the temperature rise of the economizer heat transfer tube 10 so that the layer of the corrosion product 43 formed as the heat insulation layer I does not peel off. In addition, in order to moderate the temperature drop of the economizer heat transfer tube 10 so that the layer of the corrosion product 43 is not peeled off, the engine 1 is stopped by a slow stop after the output is gradually decreased. It has become.
In short, the economizer 3 is used so that the temperature in the combustion gas passage 7 is gradually increased and decreased so that the layer of the corrosion product 43 formed as the heat insulating layer I does not peel off.

Further, the cleaning of the main heat exchanger heat transfer tube 9 and the economizer heat transfer tube 10 by the cleaning nozzle 21 is also performed in the same manner as in the first embodiment, and thus the description thereof is omitted.
In short, the economizer 3 is used by washing the economizer heat transfer tube 10 so as not to peel off the layer of the corrosion product 43 formed as the heat insulating layer I.

  Hereinafter, the ninth to twelfth embodiments of the present invention will be described. In each of the embodiments, the spray nozzle 24, the spray pump 25, and the spray material supply path 26 are omitted from the overall configuration of the exhaust heat boiler. Other than the above, the configuration is the same as that of the first embodiment shown in FIG. 1, and thus the description of the overall configuration of the exhaust heat boiler is omitted.

[Ninth Embodiment]
As shown in FIG. 17, in the ninth embodiment, before using the economizer 3, the heat insulating layer I is an outer peripheral surface of the peripheral wall of the economizer heat transfer tube 10 that is the surface on the combustion gas flow path 7 side. In a state having resistance to sulfuric acid corrosion.
The heat insulating layer I is formed of alumina (Al ₂ O ₃ ) which is an example of a ceramic having resistance to sulfuric acid corrosion. In order to reduce the thermal conductivity of the heat insulating layer I and increase the heat insulating capacity, Alumina is formed in a porous shape.

A method for forming the heat insulating layer I will be described.
By spraying, porous alumina is attached so as to cover the entire length and the entire circumference of the portion located in the combustion gas flow path 7 in the economizer heat transfer tube 10, and is applied to the outer peripheral surface of the economizer heat transfer tube 10. A heat insulating layer I is provided.

[Tenth embodiment]
As shown in FIG. 17, in the tenth embodiment, before using the economizer 3, the heat insulating layer I is an outer peripheral surface of the peripheral wall of the economizer heat transfer tube 10 that is the surface on the combustion gas flow path 7 side. In a state having resistance to sulfuric acid corrosion.
The heat insulation layer I is formed of a paint having resistance to sulfuric acid corrosion.
In order to provide heat resistance, the coating material for forming the heat insulation layer I uses a fluorine resin (for example, Teflon resin) paint to reduce the thermal conductivity of the heat insulation layer I and increase the heat insulation ability. The paint does not contain a metal powder or the like having high thermal conductivity.

A method for forming the heat insulating layer I will be described.
The above-mentioned fluororesin paint is applied over the entire length and the entire circumference of the portion located in the combustion gas flow path 7 of the economizer heat transfer tube 10, thereby providing a heat insulating layer I on the outer peripheral surface of the economizer heat transfer tube 10. I have it.

[Eleventh embodiment]
As shown in FIG. 17, in 11th Embodiment, before using the economizer 3, the said heat insulation layer I is an outer peripheral surface of the surrounding wall of the said heat exchanger tube 10 for economizers which is a surface by the side of the said combustion gas flow path 7. In a state having resistance to sulfuric acid corrosion.
The heat insulation layer I is formed of glass wool (aggregate of glass fibers) which is an example of an inorganic compound having resistance to sulfuric acid corrosion.
In other words, glass wool is coated over the entire length and the entire circumference of the portion located in the combustion gas flow path 7 of the economizer heat transfer tube 10, and the heat insulating layer I is formed on the outer peripheral surface of the economizer heat transfer tube 10. Is provided.

  In addition, as an example of the inorganic compound which has the sulfuric acid corrosion resistance which forms the said heat insulation layer I, calcium silicate can be used other than said glass wool, for example.

[Twelfth embodiment]
As shown in FIG. 17, in the twelfth embodiment, before using the economizer 3, the heat insulating layer I is disposed on the outer peripheral surface of the economizer heat transfer tube 10 that is the surface on the combustion gas flow path 7 side. It is prepared in a state of being produced to have sulfuric acid corrosion resistance by reaction with sulfuric acid.
The heat insulation layer I is formed of water glass in which countless ceramic particles are held in a dispersed state.

A method for forming the heat insulating layer I will be described.
Ceramic glass is held using water glass as a binder, and the water glass holding the ceramic particles in such a manner extends over the entire length and the entire circumference of the portion located in the combustion gas flow path 7 in the economizer heat transfer tube 10. A heat insulating layer I is provided on the outer peripheral surface of the economizer heat transfer tube 10 so as to be covered.
Thus, the economizer heat transfer tube 10 provided with the heat insulating layer I is disposed in the combustion gas flow path 7 and the use of the economizer 3 is started. During use, sulfuric acid is condensed on the surface of the heat insulating layer I, and the alkaline water glass forming the heat insulating layer I reacts with the condensed sulfuric acid so that the heat insulating layer I has sulfuric acid corrosion resistance. Is generated.

  That is, in this twelfth embodiment, the heat insulating layer I is provided in a state having sulfuric acid corrosion resistance on the outer peripheral surface of the economizer heat transfer tube 10 which is the surface on the combustion gas flow path 7 side, and It also describes that the heat insulating layer I is provided on the outer peripheral surface of the economizer heat transfer tube 10 on the combustion gas flow path 7 side in a state of neutralizing with sulfuric acid.

  Since the control configuration of the control unit 5 in the ninth to twelfth embodiments is the same as that of the first embodiment, detailed description thereof will be omitted. In short, the engine 1 is started and stopped. Is performed by the slow start and the slow stop, and the economizer 3 is used by gradually increasing and decreasing the temperature in the combustion gas flow path 7 so that the heat insulation layer I does not peel off. It is.

  In the ninth to twelfth embodiments, the main heat exchanger heat transfer tube 9 and the economizer heat transfer tube 10 are cleaned by the cleaning nozzle 21 in the same manner as in the first embodiment. Therefore, although detailed explanation is omitted, in short, the economizer 3 is used by cleaning the economizer heat transfer tube 10 so as not to peel off the heat insulating layer I.

〔inspection result〕
Next, a result of verifying that the surface temperature of the heat insulating layer I can be set to a temperature higher than the sulfuric acid dew point by providing the heat insulating layer I on the outer peripheral surface of the economizer heat transfer tube 10 will be described.
In each of the first to twelfth embodiments, it has been verified that the surface temperature of the heat insulating layer I can be higher than the sulfuric acid dew point. Hereinafter, the eleventh embodiment will be described as the heat insulating layer I. The case where it forms with the glass wool layer in a form is demonstrated to an example.
Incidentally, in this verification, in the economizer 3, the temperature of the combustion gas flowing through the combustion gas passage 7 is 170 ° C., and the temperature of the raw water flowing through the economizer heat transfer tube 10 is 80 ° C. .

FIG. 18 is a schematic diagram of a cross section along the longitudinal direction of the economizer heat transfer tube 10 in the verified economizer 3, and a temperature distribution in the radial direction of the economizer heat transfer tube 10, and FIG. The heat pipe 10 is provided with the heat insulation layer I on the outer peripheral surface, and (b) is the one without the heat insulation layer I.
FIG. 19 shows various conditions for the verification, and FIG. 20 shows the verification results.

As shown in FIGS. 18 and 20, the following points could be verified.
In the case where the heat insulation layer I is not provided on the outer peripheral surface of the economizer heat transfer tube 10, the surface temperature of the economizer heat transfer tube 10 is 86 ° C., which is lower than 140 ° C. corresponding to the sulfuric acid dew point, and sulfuric acid is condensed. become.
On the other hand, by providing the heat insulation layer I on the outer peripheral surface of the economizer heat transfer tube 10, the surface temperature of the heat insulation layer I can be made higher than 140 ° C. corresponding to the sulfuric acid dew point. Condensation can be prevented.

[Another embodiment]
Next, another embodiment will be described.
(1) In each of the first to fifth embodiments, the neutralizing agent sprayed into the combustion gas flow path 7 by the spray nozzle 24 is not limited to an aqueous solution of magnesium hydroxide, Various things such as an aqueous solution of calcium hydroxide, ammonia water, urea water, etc. can be used.
Further, the properties of the neutralizing agent as the heat insulating layer forming material supplied into the combustion gas flow path 7 are not limited to the aqueous solutions exemplified in the first to fifth embodiments. For example, A suspension in which particles of magnesium hydroxide or calcium hydroxide are dispersed in water may be used. In this case, the heat insulation layer forming material supply unit is configured to supply the suspension into the combustion gas flow path 7 in a state where the suspension is dispersed, and the suspension is supplied to the combustion gas flow of the heat transfer wall 11. It adheres to the surface on the side of the road 7.

(2) The heat insulating layer forming material is not limited to the neutralizing agent as exemplified in the first to fifth embodiments, and the heat insulating layer I having sulfuric acid corrosion resistance is formed. For example, a suspension of ceramic particles may be used. In this case, the suspension of ceramic particles is supplied into the combustion gas flow path 7 by the heat insulating layer forming material supply section, and adhered to the surface of the heat transfer wall 11 on the combustion gas flow path 7 side for combustion. By drying with gas, the heat insulating layer I made of ceramics is formed.

(3) In each of the sixth to eighth embodiments described above, the metal polyvalent ion-containing material supplied to be sprayed into the combustion gas flow path 7 by the spray nozzle 24 is not limited to calcium hydroxide. Various materials such as magnesium hydroxide and aluminum compounds can be used.

(4) The ceramic having resistance to sulfuric acid corrosion for forming the heat insulating layer I is not limited to the alumina exemplified in the ninth embodiment, and various ceramics such as silica can be used. Further, the method for forming the heat insulating layer I made of ceramics is not limited to the thermal spraying exemplified in the ninth embodiment. For example, a suspension of ceramic particles is applied to the combustion gas flow path 7 side of the heat transfer wall 11. Various methods such as a method of forming by drying or baking after being attached to the surface, a method of forming by PVD or CVD, and the like can be employed.

(5) The paint having resistance to sulfuric acid corrosion for forming the heat insulating layer I is not limited to the fluorine resin paint exemplified in the tenth embodiment, and a urethane resin paint, a phenol resin paint, etc. Various paints can be used.

(6) When the heat insulating layer I is constituted by the corrosion product 43 generated by the corrosion during use of the material forming the heat transfer wall 11, before the corrosion product 43 is provided, The surface of the heat transfer wall 11 on the side of the combustion gas flow path 7 is provided with a number of wart-shaped protrusions 29 as in the third embodiment, or the heat transfer as in the fifth embodiment. The pre-corrosion layer 42 may be formed by corroding the surface of the wall 11 on the combustion gas flow path 7 side.

(7) As in each of the ninth to twelfth embodiments, when the heat insulating layer I is provided on the surface of the heat transfer wall 11 on the combustion gas flow path 7 side before using the economizer 3, Before providing the heat insulation layer I, the rod-like body 27 as in the first embodiment, the plurality of elongated protrusions 28 as in the second embodiment, and the many wart-like protrusions as in the third embodiment. A body 29 may be provided. Further, before the heat insulation layer I is provided, the surface of the heat transfer wall 11 on the side of the combustion gas flow path 7 is formed in an uneven shape as in the fourth embodiment, or as in the fifth embodiment. Alternatively, the preliminary corrosion layer 42 may be formed by corroding the surface of the heat transfer wall 11 on the combustion gas flow path 7 side.

(8) When supplying the heat insulating layer forming material into the combustion gas flow path 7 and when supplying the metal multivalent ion-containing material into the combustion gas flow path 7, the supply direction is the economizer heat transfer tube 10. It is not limited to supply from one direction downward from the upper side of the economizer, downward from the upper side of the economizer heat transfer tube 10, from the side of the economizer heat transfer tube 10, from the lower side of the economizer heat transfer tube 10. You may supply from multiple directions including upward.

(9) Corrosion during use of the material forming the heat transfer wall 11 when the heat insulating layer I is formed of a material formed of the heat insulating layer forming material supplied into the combustion gas flow path 7 When the heat transfer wall 11 is configured by the corrosion product 43 generated by the above, the heat transfer wall 11 is provided with the peeling prevention portion P, the surface of the heat transfer wall 11 on the combustion gas flow path 7 side is formed in an uneven shape, The heat transfer wall 11 may be provided with the heat insulating layer I without corroding the surface of the wall 11 on the combustion gas flow path 7 side.

(10) When the surface of the heat transfer wall 11 on the side of the combustion gas flow path 7 is formed in an uneven shape, it is limited to the case where innumerable fine unevenness is formed by blasting as in the fourth embodiment. For example, the surface of the heat transfer wall 11 on the side of the combustion gas flow path 7 is formed by dispersing a plurality of recesses on the surface of the heat transfer wall 11 on the side of the combustion gas flow path 7 so that the surface of the heat transfer wall 11 on the side of the combustion gas flow path 7 is uneven. You may form in a shape.

(11) The specific configuration of the soot removal means is not limited to the combustion catalyst 14 exemplified in the above embodiment, and may be a filter, for example.

(12) In order to prevent exfoliation of the heat insulation layer I, a specific method for gradually increasing the temperature and decreasing the temperature of the heat transfer wall 11 is to adjust the output of the engine 1 exemplified in the above embodiment. It is not limited to the method performed by. For example, the operation may be performed by adjusting the supply amount of the combustion gas to the combustion gas flow path 7 with a flow rate adjusting valve while the engine 1 is operated at a constant output. That is, by gradually increasing the supply amount of the combustion gas to the combustion gas channel 7 by the flow rate adjusting valve, the temperature in the combustion gas channel 7 is gradually increased, and the temperature increase of the heat transfer wall 11 is moderated. Further, by gradually reducing the amount of combustion gas supplied to the combustion gas passage 7 by the flow rate adjusting valve, the temperature in the combustion gas passage 7 is gradually lowered, and the temperature of the heat transfer wall 11 is lowered. It will be done slowly.

(13) As a method of using a sulfuric acid dew point corrosion prevention type heat exchanger so as not to peel off the heat insulating layer I, the frequency of cleaning the heat transfer wall 11 is set as in the first to twelfth embodiments. It is not limited to the method of decreasing, You may make it not wash | clean the heat-transfer wall 11. FIG.
Incidentally, as the cleaning fluid for the heat transfer wall 11, for example, water vapor can be used in addition to the air exemplified in the above embodiment.
When steam is used as the cleaning fluid, the cleaning steam path is branched from the steam delivery path 6, the cleaning steam path is connected to the cleaning nozzle 21, and the cleaning steam path is connected to the cleaning steam path. Is provided with a manual cleaning valve capable of intermittently supplying and adjusting the supply amount of water vapor.

(14) During use of the sulfuric acid dew point corrosion prevention type heat exchanger, first, as in the sixth embodiment, the corrosion product 43 is formed on the surface of the heat transfer wall 11 on the combustion gas flow path 7 side, Further, as in the first embodiment, a neutralizing agent is supplied into the combustion gas flow path 7 to form a neutralized product 41 on the upper surface of the corrosion product 43, and the corrosion product 43 and the neutralized product 41. A heat insulating layer I composed of two layers may be provided on the surface of the heat transfer wall 11 on the combustion gas flow path 7 side.

(15) The material forming the heat transfer wall 11 is not limited to the weather resistant steel as exemplified in the above embodiment, and may be, for example, ordinary steel. However, in the sixth to eighth embodiments, since the corrosion product 43 formed on the weathering steel has high adhesion, it is preferable to form the heat transfer wall 11 from the weathering steel.

(16) The form in which the combustion gas flow path 7 and the heated flow path 12 are provided in a state of being partitioned by the heat transfer wall 11 is the form illustrated in the above embodiment, that is, the peripheral wall as the heat transfer wall 11 However, the present invention is not limited to a mode in which a heat exchange tubular body having the inside as the heated flow path 12 is provided in the combustion gas flow path 7.
For example, the form which provides the cylindrical body for heat exchange which makes the inside of the surrounding wall as the heat-transfer wall 11 the said combustion gas flow path 7 in the said to-be-heated flow path 12 may be sufficient. However, in this case, since the heat insulating layer I is provided on the inner peripheral surface of the peripheral wall of the heat exchange tubular body, the method of forming the heat insulating layer I is complicated.
Further, the heat transfer wall 11 is formed in a plate shape such as a flat plate or a corrugated plate, and the combustion gas flow path 7 and the heated flow path 12 are distributed on both sides of the plate-shaped heat transfer wall 11. A form in which a partition is formed may be used.

  (17) The range in which the heat insulating layer I in the economizer heat transfer tube 10 is provided is not limited to the entire range of the portion located in the combustion gas flow path 7. For example, the temperature is low and the sulfuric acid dew point temperature is low. You may form partially corresponding to the range which becomes easy to become below.

(18) In each of the above embodiments, the case where the engine 1 is started and stopped by the slow start and the slow stop is exemplified. However, the strength of the heat insulating layer I itself is prevented so that the heat insulating tank I is not peeled off. When the adhesion strength of the heat insulating layer I to the economizer heat transfer tube 10 can be sufficiently increased, it is not always necessary to start and stop the engine 1 by slow start and slow stop. It is possible to perform the operation at a normal stop.
That is, in the normal start, the output of the engine 1 is increased to the rated output at a normal set output increase rate larger than the set output increase rate for the slow start, and in the normal stop, the output of the engine 1 is increased to the rated output. The engine 1 is stopped at a normal set output decrease rate that is larger than the set output decrease rate for slow stop, and the engine 1 is stopped when the output reaches the set minimum output.

(19) The application of the heat exchanger of the sulfuric acid dew point corrosion prevention type according to the present invention is not limited to the economizer of the exhaust heat boiler exemplified in the above embodiment, but combustion for hot water heaters, waste incinerators, etc. It can be used in various applications where sulfuric acid dew point corrosion caused by SOx in the gas is a problem.
Moreover, the specific example of the to-be-heated fluid can be changed according to the use of the sulfuric acid dew point corrosion prevention type heat exchanger, and various fluids such as water vapor and air can be used in addition to water.

Block diagram showing the overall configuration of the exhaust heat boiler Diagram showing the composition of various weathering steels The figure which shows the temperature rise of the heat transfer tube when starting the engine The perspective view which shows the principal part of the heat exchanger tube for economizers concerning 1st and 6th embodiment. The perspective view which shows the principal part of the heat exchanger tube for economizers which concerns on 1st Embodiment. The perspective view which shows the principal part of the heat exchanger tube for economizers concerning 2nd and 7th embodiment. The perspective view which shows the principal part of the heat exchanger tube for economizers concerning 2nd Embodiment. The perspective view which shows the principal part of the heat exchanger tube for economizers concerning 3rd Embodiment. The perspective view which shows the principal part of the heat exchanger tube for economizers concerning 3rd Embodiment. The perspective view which shows the principal part of the heat exchanger tube for economizers concerning 4th and 8th embodiment. The perspective view which shows the principal part of the heat exchanger tube for economizers concerning 4th Embodiment. The perspective view which shows the principal part of the heat exchanger tube for economizers which concerns on 5th Embodiment. The perspective view which shows the principal part of the heat exchanger tube for economizers which concerns on 5th Embodiment. The perspective view which shows the principal part of the heat exchanger tube for economizers concerning 6th Embodiment The perspective view which shows the principal part of the heat exchanger tube for economizers concerning 7th Embodiment The perspective view which shows the principal part of the heat exchanger tube for economizers concerning 8th Embodiment. The perspective view which shows the principal part of the heat exchanger tube for economizers concerning 9th thru | or 12th embodiment. Schematic diagram of the main parts of an economizer heat transfer tube explaining heat transfer Diagram showing verification test conditions The figure which shows the result of the verification test

Explanation of symbols

7 Combustion gas flow path 10 Heat exchange tubular body 11 Heat transfer wall 12 Heated flow path 14 Soot removal means 27 Soot body 28, 29 Protrusion I Heat insulation layer P Peeling prevention part

Claims (15)

A sulfuric acid dew-point corrosion prevention type heat exchanger provided with a combustion gas flow path for passing a combustion gas and a heated flow path for allowing a heated fluid to flow partitioned by a heat transfer wall. ,
A heat insulating layer that suppresses heat transfer between the combustion gas and the fluid to be heated on the surface of the heat transfer wall on the combustion gas flow path side has a sulfuric acid corrosion resistance, sulfuric acid corrosion resistance by reaction with sulfuric acid A heat exchanger of a sulfuric acid dew point corrosion prevention type that is provided in a state where it is generated so as to have or a state where it is neutralized with sulfuric acid. A heat exchange tubular body having the inside of the peripheral wall as the heat transfer wall as the heated channel is provided in the combustion gas channel,
2. The sulfuric acid dew point corrosion prevention type heat exchanger according to claim 1, wherein the heat insulating layer is provided on an outer peripheral surface of the peripheral wall of the cylindrical body for heat exchange, which is a surface on the combustion gas flow path side.   The sulfuric acid dew-point corrosion prevention type heat exchanger according to claim 1 or 2, wherein the heat insulating layer is formed of an inorganic compound, ceramics or paint.   3. The sulfuric acid dew point corrosion-preventing type heat exchanger according to claim 1, wherein the heat insulating layer is formed of a heat insulating layer forming material supplied into the combustion gas passage.   3. The sulfuric acid dew-point corrosion prevention type heat exchanger according to claim 1, wherein the heat insulating layer is a corrosion product generated by corrosion during use of the material forming the heat transfer wall.   6. The sulfuric acid dew point corrosion prevention type heat exchanger according to claim 5, wherein the corrosion product is obtained by binding colloidal particles constituting the corrosion product with metal multivalent ions.   The sulfuric acid dew point corrosion prevention type | formula of any one of Claims 1-6 in which the said heat-transfer wall is formed with the weathering steel containing at least one of chromium, copper, phosphorus, and nickel. Heat exchanger.   The peeling prevention part for preventing peeling of the heat insulation layer is previously provided in the surface at the side of the combustion gas channel of the heat transfer wall before the heat insulation layer is provided. A heat exchanger of the sulfuric acid dew point corrosion prevention type as described in the section.   The said peeling prevention part is comprised with the hook-shaped body provided in the state which protruded in the hook shape from the surface by the side of the said combustion gas flow path of the said heat transfer wall so that the said heat insulation layer may be hold | maintained. Heat exchanger with anti-sulfur dew point corrosion prevention.   The sulfuric acid dew point corrosion prevention type heat exchanger according to claim 8, wherein the peeling prevention unit is configured by a plurality of protrusions provided in a dispersed state on a surface of the heat transfer wall on the combustion gas flow path side.   The heat of the sulfuric acid dew point corrosion prevention type according to any one of claims 1 to 7, wherein a surface of the heat transfer wall on the combustion gas flow path side is formed in an uneven shape before the heat insulating layer is provided. Exchanger.   The sulfuric acid dew point corrosion prevention type heat exchanger according to any one of claims 1 to 7, wherein a surface of the heat transfer wall on the combustion gas flow path side is corroded in advance before the heat insulation layer is provided.   The sulfuric acid dew point corrosion prevention type heat exchanger according to any one of claims 1 to 12, further comprising soot removing means for removing soot contained in the combustion gas supplied to the combustion gas flow path. It is a usage method of the heat exchanger of the sulfuric acid dew point corrosion prevention type of any one of Claims 1-13,
A method of using a sulfuric acid dew-point corrosion prevention type heat exchanger that cleans the heat transfer wall so as not to peel off the heat insulating layer or does not clean the heat transfer wall. It is a usage method of the heat exchanger of the sulfuric acid dew point corrosion prevention type of any one of Claims 1-13,
A method of using a sulfuric acid dew point corrosion prevention type heat exchanger that gradually increases and decreases the temperature in the combustion gas flow path so that the heat insulating layer does not peel off.

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