JP6526763B2 - Boiler plant and boiler plant operation method - Google Patents

Description

  The present invention relates to a boiler plant and a boiler plant operation method.

As a boiler plant, by exchanging heat between the combustion gas and the feed water, the economizer heats the feed water and supplies it to the boiler, and the feed water from the deaerator is heated by the boiler combustion gas and returned to the deaerator ( A device having a "dual economizer" (hereinafter referred to as "dual economizer") has been developed (Patent Documents 1 and 2). The dual economizer is provided, for example, on the downstream side of the combustion gas than the placement position of the economizer. The circulation heating of the water supply by the dual economizer recovers more exhaust heat discharged from the boiler.
Since the internal pressure of the deaerator is constant, the temperature of the feed water circulating through the deaerator and the dual economizer is constant, that is, the saturation temperature of the internal pressure.

In addition, boilers have also been developed which switch between heavy oil fuel containing sulfur and gas fuel not containing sulfur. Such a boiler is designed based on the acid dew point temperature corresponding to the use of heavy oil fuel in order to prevent sulfuric acid corrosion due to sulfur in the fuel. That is, the boiler equipped with the dual economizer is designed such that the outlet gas temperature of the dual economizer exceeds the acid dew point temperature.
In the boiler design corresponding to the use of such heavy oil fuel, the outlet gas temperature of the dual economizer can not be made equal to or lower than the acid dew point temperature even when using a sulfur-free gas fuel, so the heat recovery is limited Was provided.

  In Patent Document 2, although the dual economizer is not provided, the temperature of the exhaust gas at the outlet of the exhaust heat recovery boiler main body is lowered when introducing the exhaust gas after burning the fuel containing no sulfur to generate steam. A waste heat recovery boiler is disclosed that increases the thermal efficiency of the waste heat recovery boiler body.

JP, 2012-177519, A Unexamined-Japanese-Patent No. 9-33004

  However, as disclosed in Patent Document 2, when the temperature of the exhaust gas at the outlet of the exhaust heat recovery boiler main body is lowered, depending on the switching timing of burning the fuel containing sulfur, sulfuric acid corrosion due to the sulfur of this fuel Can occur.

  The present invention has been made in view of such circumstances, and can improve heat recovery of combustion gas generated by a boiler that switches between heavy oil fuel and gas fuel and can prevent sulfuric acid corrosion more reliably. It is an object of the present invention to provide a boiler plant and a boiler plant operation method.

  In order to solve the above-mentioned subject, a boiler plant and a boiler plant operation method of the present invention adopt the following means.

A boiler plant according to a first aspect of the present invention switches a gas fuel and a heavy oil fuel for combustion, generates a steam by heating feed water with the generated combustion gas, and the combustion gas generated by the boiler An economizer for heating the water supply by heat exchange with the water supply temperature control unit for adjusting the temperature of the water supply to be sent to the economizer so as to attain a target temperature according to the type of fuel burned in the boiler; and a removal soot device for removing blown off powder adhering to the inside of the said economizer, the water supply temperature adjustment unit, the removal of soot device is driven for a predetermined time if the previous SL fuel is switched from heavy oil fuel to gas fuel The temperature of the water supplied to the economizer later is adjusted to a target temperature according to the gas fuel, which is lower than when heavy oil fuel is used .

  The boiler plant according to the present invention switches between gas fuel and heavy oil fuel for combustion, and heats the feed water in the boiler with the generated combustion gas.

  Also, the economizer supplies heat to the boiler by heat exchange with the combustion gas generated by the boiler.

  Then, the temperature of the feed water to be sent to the economizer is adjusted by the feed water temperature adjustment unit so as to be the target temperature according to the type of fuel burned in the boiler. For example, in the case of heavy oil fuel, the temperature of the water supply is raised such that the exit gas temperature of the economizer exceeds the acid dew point temperature. On the other hand, in the case of gas fuel, the temperature of the water supplied to the economizer is lowered so that heat recovery can be performed more by the economizer.

Then, when the fuel is switched from heavy oil fuel to gas fuel, the temperature of the water supplied to the economizer after the removing device is driven for a predetermined time is lower than that when heavy oil fuel is used by the water supply temperature control unit. Adjusted to the target temperature according to.
If the fuel switch from heavy oil fuel to gas fuel, the temperature adjustment of the feed water, the outlet gas temperature of the economizer, changes transiently with the temperature above the acid dew point temperature below the temperature and the acid dew point temperature. For this reason, when the fuel switches from heavy oil fuel to gas fuel so that sulfuric acid corrosion does not occur in the economizer due to a change in outlet temperature of the economizer due to temperature control of water supply , the scrubber is driven for a predetermined time and then sent to the economizer The temperature of the water supply is adjusted to a target temperature according to the gas fuel which is lower than when heavy oil fuel is used .
Therefore, the present configuration can improve the heat recovery of the combustion gas generated by the boiler that switches between heavy oil fuel and gas fuel, and can prevent sulfuric acid corrosion more reliably.

In the state where heavy oil fuel is used as the fuel, powder such as soot containing sulfur content adheres to the inside of the economizer. In such a state, the temperature of the water supplied to the economizer is switched from heavy oil fuel to gas fuel, and the temperature of the outlet gas of the economizer becomes lower than the acid dew point temperature. Corrosion can occur.
Therefore, according to the present configuration, even if the fuel oil is switched to the gas fuel, the temperature of the water supplied to the economizer is maintained at the target temperature according to the fuel oil while the scrubbing device is driven for a predetermined time. And after predetermined time progress, the temperature of the water supply sent to an economizer is adjusted to the target temperature according to gas fuel.
Therefore, this configuration lowers the temperature of the water supplied to the economizer, and even if the gas temperature at the outlet of the economizer is lowered, the powder containing soot and the like that causes sulfuric acid corrosion is removed. Occurrence is suppressed.

  In the first aspect, it is preferable that the supply amount of the combustion air supplied to the boiler is increased in the predetermined time when the air removal apparatus is driven.

According to this configuration, the temperature of the combustion gas rises due to the increase of the combustion air, so the moisture in the powder such as soot evaporates and it is easy to peel off from the adhering point.
Therefore, the present configuration can further enhance the removal effect of the powder by the removing apparatus.

A boiler plant according to a second aspect of the present invention switches a gas fuel and a heavy oil fuel for combustion, heats a feed water with the generated combustion gas to generate steam, and the combustion gas generated by the boiler An economizer for heating the water supply by heat exchange with the water supply temperature control unit for adjusting the temperature of the water supply to be sent to the economizer so as to attain a target temperature according to the type of fuel burned in the boiler; And the feed water temperature control unit adjusts the temperature of the feed water to be sent to the economizer at a higher speed than when the fuel is switched from gas fuel to heavy fuel as compared to when the fuel is switched from heavy fuel to gas fuel . When the fuel is switched from heavy oil fuel to gas fuel, the temperature of the water supplied to the economizer is compared to when heavy oil fuel is used. Ku adjust.

  According to this configuration, when the fuel is heavy oil fuel, soot and the like containing sulfur are generated, so that the temperature of the water supplied to the economizer is adjusted at a high speed as compared with the case where the fuel oil is switched to the gas fuel. , The occurrence of sulfuric acid corrosion is suppressed.

In the second aspect, it is preferable to adjust the temperature of the water supplied to the economizer so that the temperature of the combustion gas that has passed through the economizer exceeds the acid dew point temperature.

  According to this configuration, the occurrence of sulfuric acid corrosion is more reliably suppressed.

A boiler plant operation method according to a third aspect of the present invention includes a combustion gas generation step of switching gas fuel and heavy oil fuel for combustion, heating feed water with generated combustion gas to generate steam, and generating the combustion gas The temperature of the feedwater is adjusted so that the target temperature corresponds to the type of fuel used in the feedwater heating step of heating the feedwater by heat exchange with the combustion gas generated in the step and the fuel used in the combustion gas generation step while, if the removal of soot apparatus before Symbol fuel removed blown off powder adhering in the water supply heating step when switching from heavy oil fuel to gas fuel the temperature of the feedwater after driving a predetermined time heavy fuel oil used And a feed water temperature adjustment step of adjusting the temperature to a target temperature according to the gas fuel .
A boiler plant operation method according to a fourth aspect of the present invention includes a combustion gas generation step of switching gas fuel and heavy oil fuel for combustion, heating feed water with generated combustion gas to generate steam, and generating the combustion gas The temperature of the feedwater is adjusted so that the target temperature corresponds to the type of fuel used in the feedwater heating step of heating the feedwater by heat exchange with the combustion gas generated in the step and the fuel used in the combustion gas generation step The temperature of the feed water is adjusted at a faster speed than when fuel is switched from heavy fuel to fuel when the fuel is switched from gas fuel to heavy fuel, and the fuel is switched from heavy fuel to gas fuel. And a feed water temperature control step of adjusting the temperature of the feed water to be lower than when heavy oil fuel is used.

  ADVANTAGE OF THE INVENTION According to this invention, while improving the heat recovery of the combustion gas produced | generated with the boiler which switches and uses heavy oil fuel and gas fuel, it has the outstanding effect that sulfuric acid corrosion can be prevented more reliably.

It is a block diagram showing composition of a boiler plant concerning an embodiment of the present invention. It is a functional block diagram showing composition of a valve opening degree control device concerning an embodiment of the present invention. It is the schematic diagram which showed the example of temperature control of the water supply sent to the dual economizer which concerns on embodiment of this invention. It is a flow chart which shows a flow of gas fuel change processing concerning an embodiment of the present invention.

Below, the boiler plant 10 which concerns on embodiment of this invention is demonstrated with reference to FIG. The boiler plant 10 may be for propulsion or for power generation.
FIG. 1 is a block diagram showing the configuration of a boiler plant 10 according to the present embodiment. The boiler plant 10 is mounted on, for example, an LNG carrier and uses heavy oil or gas as fuel.

The boiler plant 10 includes a marine boiler 12, a steam turbine 14 that is rotationally driven using steam generated by the marine boiler 12, and a feed water system 16 through which feed water flows.
The steam turbine 14 includes, as one example, a high pressure turbine 14A, an intermediate pressure turbine 14B, and a low pressure turbine 14C. In addition, the steam turbine 14 is illustrated as what utilizes steam, and is not limited to this, Moreover, the steam turbine 14 may have a turbine for reverse travel. Thus, the steam turbine 14 is for propulsion.
Furthermore, part of the steam supplied to the steam turbine 14 is supplied to the power generation turbine 18 and used for power generation.

The marine boiler 12 is provided with a burner not shown. The burner burns the fuel with the combustion air introduced via the air piping to produce a high temperature combustion gas. As fuel, gas fuel such as LNG and heavy oil fuel are appropriately switched and used.
The combustion gas exchanges heat with the feedwater flowing in the downstream heat exchanger, and heats the feedwater to become steam. The steam is supplied to the steam turbine 14 to provide rotational power to the steam turbine 14. On the other hand, the combustion gas which has completed the heat exchange with the feed water is exhausted out of the system through the combustion gas flow passage 20.

  The water supply system 16 is provided with a main condenser 22, a deaerator 24, a first economizer 26, and a dual economizer 28.

  The main condenser 22 cools and condenses (condenses) the exhaust steam of the steam turbine 14.

  The deaerator 24 physically separates and removes the dissolved gas (air, particularly oxygen) in the feedwater condensed from the steam turbine 14.

  The first economizer 26 is supplied with feed water from the deaerator 24 by the liquid feed pump 30, heats the feed water by heat exchange with the combustion gas passing through the combustion gas flow passage 20, and supplies the feed water to the marine boiler 12.

The dual economizer 28 is disposed downstream of the combustion gas channel 20 with respect to the placement position of the first economizer 26, and is connected to the deaerator 24 by the circulation channel 32.
The dual economizer 28 is fed with feed water from the deaerator 24 by the circulation pump 34, heats the feed water by heat exchange with the combustion gas passing through the combustion gas flow passage 20, and returns it to the deaerator 24. The dual economizer 28 exchanges heat between the hot water (liquid) and the combustion gas (gas), so a high heat transmission coefficient can be obtained, so the structure is simple and the size can be reduced.
The combustion gas flow passage 20 is provided with a temperature sensor 36 for measuring the temperature of the combustion gas (hereinafter referred to as “gas outlet temperature”) after passing through the dual economizer 28.

  The main condenser 22, the deaerator 24, the first economizer 26, the dual economizer 28 and the like are connected by a water supply system 16.

  Further, downstream of the water supply outlet of the main condenser 22, a condensate boost pump 38 is provided which boosts the condensate from the main condenser 22 to a necessary pressure.

A ground condenser 40, a spill steam condenser 42 and a low pressure feed water heater 44 are provided downstream of the condensate boost pump 38.
The spill steam condenser 42 is supplied with leaked steam from the steam turbine 14 through the ground packing receiver 46 and condenses the leaked steam.
The low pressure feed water heater 44 heats the feed water with the steam extracted from, for example, the low pressure turbine 14 C of the steam turbine 14. In addition, the low pressure feed water heater 44 also has a function to heat the generated fresh water (pure water) separately.

Further, the steam extracted from, for example, the medium pressure turbine 14B of the steam turbine 14 is supplied to the deaerator 24 and an air heater 48 which heats and heats the combustion air. The steam supplied to the air heater 48 is sent to the low pressure feed water heater 44 and used for heat exchange.
The steam sent to the low pressure feed water heater 44 and used for heat exchange is sent to the drain tank.

  Furthermore, in the water supply system 16, the temperature of the water supplied to the dual economizer 28 (hereinafter referred to as “inlet water temperature”) is adjusted to the target temperature according to the type of fuel burned in the marine boiler 12. A unit 50 is provided.

  The feed water temperature adjustment unit 50 measures a temperature measured by the heater 52 that heats and returns part of the feed water supplied to the deaerator 24, a temperature sensor 54 that measures the inlet water temperature of the dual economizer 28, and a temperature sensor 54 A flow control valve 56 is provided to adjust the flow rate of the water supplied to the heater 52 based on the target temperature. Further, the feed water temperature adjustment unit 50 includes a flow control valve 57 that adjusts the flow rate of the feed water sent from the low pressure feed water heater 44 to the deaerator 24.

Therefore, on the upstream side of the deaerator 24, a circulation flow path 58 is provided which is heated by the heater 52 and returned to the water supply system 16 after a part of the water supply flowing through the water supply system 16 is branched. That is, the heater 52 is a heat exchanger that exchanges heat between the water supplied to the dual economizer 28 and the water supplied through the circulation passage 58.
The temperature sensor 54 measures the temperature of the feed water after passing through the heater 52.

  The flow control valve 56 and the flow control valve 57 have their degrees of opening determined in accordance with the temperature measured by the temperature sensor 54. The flow control valve 57 operates reverse to the flow control valve 56. Specifically, when the opening degree of the flow rate adjusting valve 56 is 100%, the opening degree of the flow rate adjusting valve 57 is 0%, and when the opening degree of the flow rate adjusting valve 56 is 0%, the flow rate adjusting valve 57 is opened. The degree is 100%.

FIG. 2 is a functional block diagram showing a configuration of a valve opening degree control device 60 that controls the opening degree of the flow rate adjustment valve 56. As shown in FIG.
The valve opening control device 60 is configured of, for example, a central processing unit (CPU), a random access memory (RAM), a computer readable recording medium, and the like. A series of processes for realizing various functions are, for example, recorded in the form of a program on a recording medium etc. The CPU reads this program into a RAM etc. and executes information processing / calculation processing Thus, various functions are realized.

  The valve opening control device 60 is provided, for example, in a boiler plant control device 62 that controls the entire boiler plant 10. The boiler plant control device 62 also has other control functions such as a fuel switching instruction unit 64 and a suit blower control unit 66.

  The fuel switching instruction unit 64 generates a fuel switching instruction based on a fuel switching instruction by the driver of the boiler plant 10. The fuel switching command indicates either a command to switch the fuel used in the marine boiler 12 from gas fuel to heavy oil fuel, or a command to switch from heavy oil fuel to gas fuel. When the fuel switching instruction is output, the fuel supplied to the marine boiler 12 is switched.

The suit blower control unit 66 generates a control command for controlling the suit blower 68 and outputs the control command to the suit blower 68. The suit blower 68 is a dust removal device for removing powder such as soot adhered in the dual economizer 28 by blowing it off with compressed air or steam, for example.
The suit blower control unit 66 receives a fuel switching instruction from the fuel switching instruction unit 64.

The valve opening control device 60 includes a water supply temperature setting unit 70 and a valve opening calculation unit 72.
When the fuel switching instruction from the fuel switching instruction unit 64 is input, the feed water temperature setting unit 70 outputs the target temperature according to the fuel used by the marine boiler 12 to the flow rate adjustment valve 56. The target temperature is a target temperature of the inlet water temperature of the dual economizer 28, and is stored in advance in the water supply temperature setting unit 70.
The valve opening degree calculation unit 72 receives the temperature measured by the temperature sensor 54, calculates a valve opening degree command value according to the difference between the target temperature and the measurement temperature, and outputs the calculated value to the flow rate adjusting valve 56.
Note that the valve opening degree computing unit 72 adjusts the temperature of the water supplied to the economizer at a faster speed than when the fuel is switched from heavy fuel to heavy fuel when the fuel is switched from heavy fuel to heavy fuel. When switching from heavy oil fuel to gas fuel , the valve opening degree command value is calculated so as to adjust the temperature of the feed water to be sent to the economizer lower than in the case where heavy oil fuel is used .

  Hereinafter, the operation of the boiler plant 10 according to the present embodiment configured as described above will be described.

The exhaust of the steam turbine 14 is cooled by the main condenser 22 and condensed. Condensate water is ground capacitor 40, the spill scan team condenser 42 and low-pressure feed water heater 44, for example, are heated to about 90 ° C.. The hot water is heated by the steam extracted from the steam turbine 14 in the deaerator 24 and is further converted to high temperature hot water and supplied to the marine boiler 12. The hot water is further heated by the combustion gas passing through the combustion gas flow passage 20 by the first economizer 26 and supplied to the marine boiler 12.

At the same time, the circulation pump 34 operates, and the hot water (water supply) in the deaerator 24 is introduced into the circulation flow path 32 provided with the dual economizer 28 and circulates in the circulation flow path 32. When passing through the dual economizer 28, the circulating warm water exchanges heat with the combustion gas passing through the combustion gas flow passage 20 and returns to the deaerator 24.
The circulation heating of the water supply by the dual economizer 28 as described above recovers more exhaust heat discharged from the marine boiler 12.

  Then, the inlet water temperature of the dual economizer 28 is adjusted by the feed water temperature adjustment unit 50 to a target temperature according to the type of fuel used in the marine boiler 12. For example, in the case of heavy oil fuel, the temperature of the water supply is raised so that the outlet gas temperature of the dual economizer 28 exceeds the acid dew point temperature. On the other hand, in the case of gas fuel, the temperature of the water supply is lowered so that the dual economizer 28 performs more heat recovery.

  FIG. 3 is a schematic view showing an example of temperature control of the inlet water temperature of the dual economizer 28. As shown in FIG. Arrows shown by double lines in FIG. 3 indicate the flow direction of the feed water, and alternate long and short dashed lines passing through the dual economizer 28 indicate the flow direction of the combustion gas. The upper part of each temperature is the case where the fuel is heavy oil fuel, and the lower part shown in parentheses is the case where the fuel is a gas fuel. In addition, the temperature shown by FIG. 3 is an example, is not a constant value, but may have a certain extent of width.

The temperature of the water supplied to the deaerator 24 and the heater 52, the temperature of the water supplied circulating through the deaerator 24 and the heater 52, and the temperature of the water supplied from the dual economizer 28 back to the deaerator 24 are the types of fuels. It is the same regardless of Also, the temperature of the combustion gas at the inlet of the dual economizer 28 is the same regardless of the type of fuel.
On the other hand, the temperature of the water supplied from the heater 52 to the dual economizer 28 differs between the heavy oil fuel and the gas fuel.

Here, when the fuel is heavy oil fuel, the valve opening control device 60 sets the target temperature of the water supply after passing through the heater 52 to, for example, 130 ° C. On the other hand, when the fuel is a gas fuel, the valve opening control device 60 sets the target temperature of the water supply after passing through the heater 52 to, for example, 110 ° C.
The valve opening degree control device 60 generates a valve opening degree command value and outputs it to the flow control valve 56 and the flow control valve 57 so that the temperature of the feedwater after passing through the heater 52 becomes the target temperature. The flow rate adjusting valve 56 and the flow rate adjusting valve 57 open and close the opening degree of the valve according to the valve opening degree command value to adjust the flow rate of the water supply. When the fuel is a gas fuel, the opening degree of the flow rate adjustment valve 56 is made larger than in the case of a heavy oil fuel, and more feed water flows to the heater 52.

As a result, the temperature of the feed water after passing through the heater 52 is 130 ° C. in the case of heavy oil fuel and 110 ° C. in the case of gas fuel.
And by heat exchange with the dual economizer 28, the outlet gas temperature of the dual economizer 28 is 140 ° C. in the case of heavy oil fuel and 120 ° C. in the case of gas fuel.
As described above, when the fuel is heavy oil fuel, the outlet gas temperature is 140 ° C., which is equal to or higher than the acid dew point temperature, so that sulfuric acid corrosion in the dual economizer 28 is prevented. Also, if the fuel is a gas fuel, the outlet gas temperature will be lower, 120 ° C., so more heat recovery will be performed with the dual economizer 28.

Furthermore, when the fuel switches from gas fuel to heavy oil fuel, the temperature of the water supplied to the economizer is adjusted at a faster rate than when fuel oil is switched to gas fuel, and the economizer is switched when fuel switches from heavy oil fuel to gas fuel. The temperature of the feed water to be sent to it is adjusted to be lower than when heavy fuel oil is used .
When the fuel switches from gas fuel to heavy oil fuel or from heavy oil fuel to gas fuel, the outlet gas temperature of the dual economizer 28 exceeds the acid dew point temperature from the temperature below the acid dew point temperature as described above by adjusting the temperature of the feed water. It changes excessively between temperatures. Therefore, when the fuel is switched from the gas fuel to the heavy oil fuel according to the switching of the fuel so that the sulfuric acid corrosion does not occur in the dual economizer 28 due to the change in the outlet temperature of the dual economizer 28 due to the temperature control of the water supply The temperature of the water supplied to the economizer is adjusted at a faster speed than when switching to the gas fuel, and the temperature of the water supplied to the economizer when the fuel switches from heavy oil fuel to the gas fuel is compared to when heavy oil fuel is used Will be adjusted low .

  Below, the case where fuel is switched from heavy oil fuel to gas fuel is demonstrated.

  In the state where heavy oil fuel is used as fuel, powder such as soot containing sulfur content adheres to the outer surface of the heat transfer pipe in which the water supply flows in the dual economizer 28. In such a state, when the fuel oil is switched from heavy oil fuel to gas fuel, the inlet water temperature of the dual economizer 28 decreases, and the outlet gas temperature of the dual economizer 28 becomes lower than the acid dew point temperature, powder such as sulfur containing sulfur is used. Sulfuric acid corrosion may occur.

  Therefore, when switching the fuel from heavy oil fuel to gas fuel, the gas plant switching process shown in FIG. 4 is executed by the boiler plant control device 62.

  First, in step 100, a fuel switching command value indicating that fuel is switched from heavy oil fuel to gas fuel is generated by the fuel switching instruction unit 64, and the fuel switching command value is sent to the valve opening control device 60 and the suit blower control unit 66. It is input.

  In the next step 102, the suit blower control unit 66 outputs a control signal for driving the suit blower 68 to the suit blower 68. The driving of the suit blower 68 is thereby started.

  In the next step 104, it is determined whether or not the drive of the suit blower 68 has reached a predetermined time. If the determination is affirmative, the process proceeds to step 106. If the determination is negative, the suit blower 68 is Continue to drive. The predetermined time is a time when the soot is removed from the dual economizer 28 by the suit blower 68, and is set in advance.

In step 106, the valve opening control device 60 starts temperature adjustment of the water supply according to the gas fuel. That is, the feed water temperature adjustment unit 50 reduces the inlet water temperature of the dual economizer 28 from 130 ° C. to 110 ° C. in accordance with the target temperature 110 ° C. of the gas fuel.
Further, based on the outlet gas temperature of the dual economizer 28 which is the temperature measured by the temperature sensor 36, the inlet water temperature of the dual economizer 28 is adjusted so that the outlet gas temperature of the dual economizer 28 does not decrease excessively.

As described above, the boiler plant 10 according to the present embodiment targets the inlet water temperature of the dual economizer 28 according to the heavy oil fuel in a state where the suit blower 68 is driven for a predetermined time even after switching from heavy oil fuel to gas fuel. Leave at temperature. By driving the suit blower 68 for a predetermined time, the powder containing soot and the like is removed from the marine boiler 12.
Then, after the predetermined time has elapsed, the inlet water temperature of the dual economizer 28 is adjusted to the target temperature according to the gas fuel.

  Thereby, the boiler plant 10 according to the present embodiment reduces the inlet water temperature of the dual economizer 28, and even if the outlet gas temperature of the dual economizer 28 decreases, the powder including the soot that causes sulfuric acid corrosion is Since it is removed, the occurrence of sulfuric acid corrosion of the dual economizer 28 is suppressed.

Further, the boiler plant 10 according to the present embodiment increases the supply amount of the combustion air supplied to the marine boiler 12 in the predetermined time driven by the suit blower 68.
When the temperature of the combustion gas rises due to the increase of the combustion air, the moisture in the powder such as soot evaporates and becomes easy to peel off from the adhering point. Therefore, the boiler plant 10 according to the present embodiment can further enhance the removal effect of the powder by the suit blower 68.

  Next, the case where the fuel is switched from gas fuel to heavy oil fuel will be described.

  Even if gas fuel is used as fuel, there is no adhesion of soot or the like on the marine boiler 12. On the other hand, when heavy oil fuel is used as fuel, soot and the like containing sulfur starts to be generated, which causes sulfuric acid corrosion.

Therefore, when the fuel switches from gas fuel to heavy oil fuel, the feed water temperature adjustment unit 50 according to the present embodiment adjusts the inlet water temperature of the dual economizer 28 at a faster speed than when switching from heavy oil fuel to gas fuel. . That is, the inlet water temperature of the dual economizer 28 is rapidly raised from 110 ° C. to 130 ° C.
As a result, when the fuel becomes heavy oil fuel, the generation of soot and the like containing sulfur is suppressed, and as a result, the generation of sulfuric acid corrosion of the dual economizer 28 is suppressed.

Further, the feed water temperature adjustment unit 50 adjusts the inlet water temperature of the dual economizer 28 so that the temperature measured by the temperature sensor 36 exceeds the acid dew point temperature.
As a result, since the outlet gas temperature of the dual economizer 28 exceeds the acid dew point temperature, the occurrence of sulfuric acid corrosion is more reliably suppressed.

As described above, the boiler plant 10 according to the present embodiment heats the water supplied from the deaerator 24 by heat exchange with the combustion gas from the marine boiler 12 and returns the dual economizer 28 to the deaerator 24. Prepare. The boiler plant 10, such that the target temperature according to the type of fuel used in marine boiler 12, when adjusting the inlet water temperature of the dual economizer 28, when the fuel is switched to the oil fuel from the gas fuel The temperature of the feed water to be sent to the economizer is adjusted at a faster speed than when the fuel oil is switched to the gas fuel, and the temperature of the feed water to be sent to the economizer is used when the fuel is switched from the fuel oil to the gas fuel Adjust lower than .
Therefore, the boiler plant 10 according to the present embodiment can improve the heat recovery of the combustion gas generated by the marine boiler 12 which switches between heavy oil fuel and gas fuel, and can prevent sulfuric acid corrosion more reliably.

  As mentioned above, although this invention was demonstrated using the said embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. Various changes or improvements can be added to the above-described embodiment without departing from the scope of the invention, and a form to which the changes or improvements are added is also included in the technical scope of the present invention. Also, a plurality of the above embodiments may be combined.

10 Boiler plant 12 Marine boiler (boiler)
26 1st economizer (economizer)
28 Dual economizer (economizer)
50 water supply temperature control unit 68 suit blower (removing device)

Claims (6)

A boiler that switches between a gas fuel and a heavy oil fuel to burn and heats the feed water with the generated combustion gas to generate steam;
An economizer heating the feed water by heat exchange with the combustion gas generated by the boiler;
A feed water temperature adjustment unit that adjusts the temperature of the feed water to be sent to the economizer so that the target temperature corresponds to the type of fuel burned in the boiler;
A dust removal device for blowing away and removing the powder adhering to the inside of the economizer;
Equipped with
The water supply temperature adjustment unit is lower the feedwater temperature before Symbol fuel the removal soot device when switching from heavy oil fuel to gas fuel is delivered to the economizer after driving a predetermined time as compared with the case where the heavy oil fuel used Boiler plant that adjusts to the target temperature according to the gas fuel . Wherein the predetermined time, the boiler plant of claim 1, wherein the supply amount of combustion air supplied to the boiler is increased to the removal of soot device is driven. A boiler that switches between a gas fuel and a heavy oil fuel to burn and heats the feed water with the generated combustion gas to generate steam;
An economizer heating the feed water by heat exchange with the combustion gas generated by the boiler;
A feed water temperature adjustment unit that adjusts the temperature of the feed water to be sent to the economizer so that the target temperature corresponds to the type of fuel burned in the boiler;
Equipped with
The water supply temperature adjustment unit, when the fuel is switched to the oil fuel from the gas fuel, as compared with the case of switching from the heavy oil fuel to gas fuel, by adjusting the temperature of the water supply to be sent to the economizer at a faster rate, said fuel The boiler plant which adjusts the temperature of the said feed water sent to the said economizer low, compared with the case where heavy fuel oil is used, when switching from heavy fuel oil to gas fuel . The boiler plant according to claim 3, wherein the temperature of the water supplied to the economizer is adjusted so that the temperature of the combustion gas having passed through the economizer exceeds an acid dew point temperature. A combustion gas generation step of switching between gas fuel and heavy oil fuel for combustion and heating feed water with the generated combustion gas to generate steam;
A feed water heating step of heating the feed water by heat exchange with the combustion gas generated in the combustion gas generation step;
It said to be the target temperature according to the type of fuel used in the combustion gas generating step, thereby adjusting the temperature of the water supply, before Symbol fuel deposited in the water supply heating step when switching from heavy oil fuel to gas fuel A feed water temperature adjustment step of adjusting the temperature of the feed water to a target temperature according to the gas fuel lower than that when heavy oil fuel is used after driving the removing device for blowing off and removing powder for a predetermined time ;
Method of operating a boiler plant comprising: A combustion gas generation step of switching between gas fuel and heavy oil fuel for combustion and heating feed water with the generated combustion gas to generate steam;
A feed water heating step of heating the feed water by heat exchange with the combustion gas generated in the combustion gas generation step;
In the case where the temperature of the feed water is adjusted so that the target temperature corresponds to the type of fuel used in the combustion gas generation step, and when the fuel switches from gas fuel to heavy oil fuel, it switches from heavy oil fuel to gas fuel A feed water temperature adjusting step of adjusting the temperature of the feed water at a high speed compared to the feed water temperature adjustment step and adjusting the temperature of the feed water lower when the fuel is switched from heavy oil fuel to gas fuel as compared to when heavy oil fuel is used;
Method of operating a boiler plant comprising:

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