JP5478997B2 - Combustion device operation control method and combustion device - Google Patents

Description

  The present invention relates to an operation control method and a combustion apparatus for a combustion apparatus using petroleum-based residue as fuel, and in particular, to reduce ash adhesion in a heat transfer tube of the combustion apparatus.

A combustion apparatus (boiler) that uses petroleum residue (eg, petroleum coke) as fuel has a problem that ash adheres to the furnace and inhibits heat transfer in the cooling pipe.
For this reason, conventionally, for example, a magnesium compound (MgO), an iron-based compound (for example, Fe ₂ O ₃ ), CaCO ₃ , Na ₂ CO ₃ , an organic additive, or the like is supplied into the furnace as a fuel additive. Therefore, reduction of adhesion ash was aimed at (patent documents 1-3).

In addition, vanadium contained in petroleum-based residual fuel takes a plurality of oxidation states, and the maximum oxidation number of pentavalent oxide (V ₂ O ₅ ) has a low melting point of about 680 ° C., but as a fuel additive, for example It is known that the MgO additive increases its melting point.

JP-A 62-45691 Japanese Patent Laid-Open No. 4-13798 JP-A-11-94234 JP 2008-240102 A

  By the way, when heavy oil is used as the fuel for the combustion apparatus, the amount of vanadium is small (about 200 ppm or less), and in the combustion apparatus having a high oxygen concentration in the furnace, the oxidation state of vanadium is pentavalent. Addition of MgO additive can suppress the adhesion of ash, but the amount of vanadium in the petroleum-based residual fuel is larger than that of heavy oil (500-1500 ppm). In order to perform denitration, a reducing atmosphere is used, and in the furnace, the oxidation state of vanadium is not the maximum oxidation number of pentavalent, but is almost tetravalent.

This tetravalent vanadium has a high melting point (about 1400 ° C.) as a single compound, but the petroleum residue (eg, petroleum coke), which is a fuel, comes into contact with seawater during transportation, for example, and Na is mixed in. In this case, when it burns, it becomes a complex compound of Na and V (vanadyl / vanadate (mNa ₂ O · (np) V ₂ O ₅ · pV ₂ O ₄ )) (Patent Document 4), Since it becomes easy to produce | generate, there exists a problem that ash adhesion in a furnace generate | occur | produces more than usual.

FIG. 8 shows a relationship diagram in which the softening point (° C.) of ash decreases when Na is added to petroleum coke. As shown in FIG. 8, it can be seen that in the reducing atmosphere (CO / CO ₂ = 60% / 40%), the ash softening point decreases as Na is added.

That is, in the case of fly ash accompanied by ordinary gas, it flows to the downstream side together with the gasification gas and is collected by a dust removing device (for example, an electrostatic precipitator) installed on the downstream side. When a part of the ash melts, if it adheres to the furnace, the temperature inside the furnace rises due to heat transfer inhibition, and the proper operation of the combustion apparatus may not be possible.
It should be noted that mixing into the petroleum-based residual fuel such as Na cannot be avoided easily during transportation on the sea, and therefore, effective countermeasures are desired when burning the petroleum-based residual fuel.

  This invention makes it a subject to provide the operation control method and combustion apparatus of the combustion apparatus which uses petroleum residue as a fuel in view of the said problem.

A first invention of the present invention for solving the above-described problem is a method for controlling the operation of a combustion apparatus using petroleum residue as fuel, and after a predetermined period of time, the load factor is changed from the rated operation to 80 of the rated operation. % Of the combustion apparatus is changed to a low load operation that can be operated at the minimum, and in the low load operation, the furnace is in an oxygen-rich state, and Na and V in the heat transfer tube of the furnace wall An operation control method for a combustion apparatus is characterized in that ash adhesion based on a complex compound is reduced.

  A second aspect of the present invention is the combustion apparatus according to the first aspect, wherein the low load operation is performed at or after a command to a temperature reducing device for reducing the temperature by supplying spray water to superheated steam. It is in the operation control method.

  A third invention is the operation control method for a combustion apparatus according to the first or second invention, wherein a fuel additive is added to the fuel.

  According to a fourth aspect of the invention, there is provided an operation control method for a combustion apparatus according to the third aspect of the invention, wherein a fuel additive is added to the fuel in a gradient distribution.

  According to a fifth invention, in any one of the first to fourth inventions, the fuel supply burner blows fuel and air along the furnace wall surface to form a region having a high oxygen concentration in the vicinity of the furnace wall. It is in the operation control method of the combustion apparatus characterized.

  A sixth invention is the operation control method for a combustion apparatus according to any one of the first to fifth inventions, wherein solid matter is added to the furnace to relatively reduce the ash melting ratio. .

  According to a seventh aspect of the invention, in the sixth aspect of the invention, the solid substance is at least one of coal ash, an iron-based additive, a silica-based additive, or a magnesium-based additive. It is in.

  According to an eighth aspect of the invention, in any one of the first to seventh aspects, the operation control of the combustion apparatus is characterized in that the low oxygen operation is performed from the initial operation of the rated operation and the proportion of unburned ash is increased. Is in the way.

A ninth invention is a combustion apparatus that uses petroleum residue as fuel, a combustion apparatus that uses petroleum residue as fuel, and a plurality of fuel supply burners that supply fuel into a furnace in a reducing atmosphere; Control means for instructing the fuel supply burner to change from a rated operation to a low-load operation in which the load factor is 80% or less of the rated operation and the lowest possible operation of the combustion device after a predetermined period of time has elapsed. Thus, in the low-load operation, the combustion apparatus is characterized in that the inside of the furnace is in an oxygen-rich state and ash adhesion based on a composite compound of Na and V in the heat transfer tube on the furnace wall is reduced.

  A tenth aspect of the invention is the combustion apparatus according to the ninth aspect of the invention, wherein the low-load operation is performed at the time of a command of a temperature reducing device that reduces the temperature by supplying spray water to the superheated steam.

  An eleventh invention is the combustion apparatus according to the ninth or tenth invention, further comprising an oxygen supply nozzle for additionally supplying oxygen into the furnace on the downstream side of the fuel supply burner.

  A twelfth aspect of the invention is a combustion apparatus according to any one of the ninth to eleventh aspects, wherein the fuel supply burner blows along the furnace wall surface.

  A thirteenth aspect of the invention is a combustion apparatus according to any one of the ninth to twelfth aspects of the invention, wherein a solid substance is added to the furnace.

  A fourteenth invention is characterized in that, in any one of the ninth to thirteenth inventions, the solid is at least one of coal ash, an iron-based additive, a silica-based additive, or a magnesium-based additive. In the combustion device.

  A fifteenth aspect of the invention is the combustion apparatus according to any one of the ninth to fourteenth aspects, wherein the control means performs control to perform a low oxygen operation from the initial operation of the rated operation.

  According to the present invention, ash adhesion inside the furnace can be reduced and proper operation of the combustion facility can be achieved by changing the rated operation to the low load operation after the predetermined operation.

FIG. 1 is a schematic diagram of a combustion apparatus using petroleum residue as fuel. FIG. 2 is a flowchart of superheated steam. FIG. 3 is a diagram showing how ash adheres to the water-cooled tube on the wall surface of the furnace. FIG. 5 is a correlation diagram in which each of vanadium oxides having an oxidation number of 3, 4, 5 is changed from a solid state to a molten slag 45 by a temperature and an oxygen partial pressure. FIG. 5 is a diagram showing a change in the behavior of the oxidation state of vanadium oxide in each part of the combustion apparatus. FIG. 6 is a graph showing the relationship between the melting ratio (wt%) and the ash adhesion (g / cm ² ) due to the addition of additives. FIG. 7 is a schematic cross-sectional view of a furnace. FIG. 8 is a graph showing the relationship between the ratio of adding Na content (Nacl) to petroleum coke and the softening point (° C.) of ash.

  Hereinafter, the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. In addition, constituent elements in the following embodiments include those that can be easily assumed by those skilled in the art or those that are substantially the same.

A combustion apparatus operation control method and combustion apparatus using petroleum residue as fuel according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram of a combustion apparatus using petroleum residue as fuel. As shown in FIG. 1, a combustion apparatus 10 that uses petroleum residue as fuel according to this embodiment is a combustion apparatus that uses petroleum residue as fuel, and supplies fuel 12 into a furnace 11 in a reducing atmosphere. A plurality of fuel supply burners 13 (upper burner 13a, middle burner 13b, lower burner 13c) and control means (not shown) for executing an instruction to change from rated operation to low load operation after a predetermined period of time, During the low load operation, the inside of the furnace 11 is brought into an oxygen-rich state to reduce ash adhesion on the heat transfer tubes on the furnace wall.

  Here, in the furnace 11 of the combustion apparatus 10, a plate-type superheater 21, a secondary superheater 22, a tertiary superheater 23, a primary superheater 24, and a economizer 25 are disposed on the exit side of the combustion region 15. It arranges in order in the flue, and superheated steam is obtained by superheating saturated steam in the flue. Note that a molten slag receiving portion 26 is provided on the furnace bottom 11 a side of the furnace 11.

FIG. 2 is a flow chart of saturated steam, and the saturated steam 30 from the water-cooled pipe on the furnace wall sequentially passes through the primary superheater 24, the plate-type superheater 21, the secondary superheater 22, and the tertiary superheater 23 to superheat. Steam 31 is supplied to the turbine side.
Here, in FIG. 2, a temperature reducer 32 is provided to protect the superheater when the temperature in the furnace rises abnormally. The spray valve 33 is adjusted as necessary to overheat the water 34. The temperature is reduced by supplying it into the steam.

Therefore, when the superheated steam temperature rises above a predetermined temperature and an instruction to adjust the spray valve 33 is given from the control device, it is determined that the temperature inside the furnace 11 has increased, and at the time of the determination or after a predetermined period of time Then, an instruction to switch from the rated operation to the low load operation is performed to reduce the amount of ash adhesion and return to the proper combustion region 15.
Instead of the opening of the spray valve, it may be determined by detecting the steam temperature increase ΔT of the superheater (for example, the plate-type superheater 21) installed at the furnace combustion zone 15 outlet.

FIG. 3 shows how ash adheres to the water-cooled tube 40 on the wall surface of the furnace 11.
In FIG. 3, water (about 330 ° C.) 41 flows inside the water-cooled tube 40 and cools the furnace 11. A part of the fly ash 42 generated when the petroleum-based residue is burned as fuel is melted and adhered to the inside of the furnace of the water-cooled tube 40 as adhered ash 43.

When the furnace 11 is in a reducing atmosphere (for example, CO / CO ₂ = 60% / 40%), vanadium oxide in the fly ash 42 is solid in a tetravalent state, but contains Na, for example. When the fuel is combusted, the melting point decreases from 1400 ° C., so that a part thereof is in a molten state. As a result, a part of the fly ash 41 is in a molten state and adheres to the attached ash 43, whereby ash growth 44 occurs and grows into the growth ash 44 having a predetermined thickness D.

Here, the mechanism by which the ash deposits melt when the load reducing operation is performed will be described.
During rated normal operation, vanadium in the attached ash is dominated by tetravalent vanadium because the inside of the furnace 11 is in a reducing atmosphere.
Therefore, vanadium in the attached ash is also tetravalent.
On the other hand, by performing the load reducing operation, the reducing atmosphere is changed to an oxygen-rich atmosphere, and the vanadium in the attached ash is changed from tetravalent to pentavalent vanadium. Since pentavalent vanadium has a melting point of 680 ° C., the portion of the growth ash 45 on the furnace wall is melted to form running slag, which flows down smoothly into the slag receiving portion 26 (see FIG. 1).

FIG. 4 is a correlation diagram in which each of trivalent, tetravalent, and pentavalent vanadium oxides changes from a solid state to a molten slag 45 depending on temperature and oxygen partial pressure (oxygen concentration).
Here, each point of (1) to (6) in FIG. 4 is a result of a softening and melting test using a tetravalent vanadium reagent in a reducing atmosphere. (1) is 1210 ° C. in N ₂ (inert) atmosphere, (2) is 1% O ₂ atmosphere (N ₂ Balance) 1250 ° C., (3) is 0.01% O ₂ atmosphere (N ₂ Balance) 1590 ° C. , (4) 0.1% O ₂ atmosphere (N ₂ balance) 1590 ° C., (5) 0.5% O ₂ atmosphere (N ₂ balance) 1300 ° C., (6) 1% O ₂ atmosphere (N ₂ balance) shows the molten state between solids at 1300 ° C.

As shown in FIG. 4, the fly ash partially melts and becomes adhering ash when the temperature decreases, but when the oxygen concentration increases (O ₂ concentration 1%), it enters a molten state.

FIG. 5 is a diagram showing a change in the behavior of the oxidation state of vanadium oxide in each part of the combustion apparatus 10.
The horizontal axis shows the location of the furnace bottom, lower burner, upper burner, plate-type superheater, economizer, and electrostatic precipitator (EP), and dissolved in the adhering ash and ash sulfuric acid solution at each location. This is a measurement of the redox potential of the solution.
During operation of the furnace, tetravalent vanadium was dominant in the region of the lower burner to the upper burner, and the presence of pentavalent vanadium was confirmed after the plate superheater. It turns out that it becomes easy to become pentavalent vanadium after a superheater.
Here, at the furnace bottom, the oxidation-reduction potential is 0.86 V and the vanadium oxidation number indicates the pentavalent state, which is measured with respect to the ash obtained when the furnace is stopped. When the furnace is stopped, the adhering ash is exposed to a low temperature and high oxygen state, so the oxidation number of vanadium tends to be pentavalent.

  Here, in the present invention, the load factor of the load reduction operation is 80% (80 MW) or less, preferably 60 to 70% (60 to 70 MW) or less, assuming that the rated operation (for example, 100 MW) is 100%. . In addition, the lower limit value is set to a load that allows the minimum operation of the combustion apparatus. For example, a load factor of about 30% is used as the minimum operable load of the combustion apparatus.

  In addition, as the load reduction operation time, for example, the load reduction operation may be executed once a week (at night, for example, about 7 to 10 hours).

An example of periodically performing a load reduction operation will be described.
In general, when the temperature inside the furnace rises, in order to prevent the temperature of the superheater from rising, the temperature reducer 32 shown in FIG. 2 is activated (the spray valve 33 is activated to supply water 34 into the temperature reducer 32). Reduce the superheated steam temperature) and start the control to protect the superheater. In this case, it indicates that the furnace temperature is higher than normal, and the thickness of the grown ash deposit exceeds the allowable value, and the furnace temperature is rising. .

In such a state, the grown ash that has grown may be removed in a molten state by a load reducing operation.
That is, the control device issues a command to perform a load reduction operation based on the opening information of the spray valve from the control device, thereby reliably acquiring the ash adhesion information and reducing the ash adhesion of the combustion device. Can do.

In addition, when supplying the fuel additive (MgO) from the fuel supply burner 13, it is only necessary to perform an inclined distribution input. Inclination distribution is inclined to the wake side.
As an example of the slant distribution input of the fuel additive (MgO), the upper burner 13a is added at a rate of 1, the middle burner 13b to 0, and the lower burner 13c to 0, or the upper burner 13a is set to 0.8. There is a method of adding 0.1 from the burner 13b and 0.1 from the lower burner 13c.
As a result, an increase in the melting point of vanadium due to the fuel additive is suppressed.
The reason why the fuel additive MgO is supplied at a molar ratio of 1 or more in the V ₂ O ₅ ratio is to prevent corrosion (pentavalent vanadium) of the member on the downstream side of the boiler furnace with MgO. This is to prevent an increase in the melting point of vanadium.

Here, examples of the fuel additive in the present invention include magnesium compounds such as magnesium hydroxide (Mg (OH) ₂ ) and magnesium carbonate (MgCO ₃ ) in addition to magnesium oxide (MgO).

  In addition, when operating at rated power, a fuel additive (MgO) is introduced together with air from an air supply nozzle (not shown) that additionally supplies air provided on the upper stage of the upper burner 13a. Also good.

  In the first embodiment, the ash adhesion is surely reduced by performing the low load operation after a predetermined period of time in the rated operation. In the second embodiment, however, the load is periodically reduced in the summer, for example. This is a measure for temporary operation when the system cannot be implemented.

In Example 2, in the rated operation (100% load operation), for example, 0.5 to 5% of a solid matter of high melting point coal ash is added to the fuel additive to dilute the melt. is there.
Since the ash content in petroleum residue fuel is as low as about 0.5%, the ash adhesion is reduced by diluting with solid coal ash. As a result, the period of growth of attached ash becomes longer than when nothing is added.
Note that the amount of the solid substance added is regulated as described above because if it exceeds 5% by weight, the original combustion of the petroleum residue fuel will be adversely affected, while 0.5% by weight. This is because the effect of addition is not manifested at less than the above.

FIG. 6 is a graph showing the relationship between the melting ratio (wt%) and the ash adhesion (g / cm ² ) due to the addition of additives. In FIG. 6, quartz powder is added as powder, and when the melting ratio in the case where there is no chemical reaction with quartz powder decreases, the adhesion of ash decreases.
That is, the melting rate is determined by (melting amount) / (solid matter amount + melt amount), and the melting rate can be relatively decreased by increasing the solid matter amount.

Thereby, ash adhesion can be suppressed without lowering the rated operation.
Therefore, in the case of large electric power demand in summer, during a predetermined period (about 2 to 3 weeks), the attached ash is suppressed by supplying solids when performing rated operation without performing load reduction operation.

Further, the molar ratio (to V ₂ O ₅ ) of the fuel additive MgO may be increased (molar ratio: 1 to 3).
Further, as an additive, an iron-based additive and a silica-based additive may be added (molar ratio: 1 to 10) to prevent adhesion growth.

Further, instead of separately supplying solid matter, low oxygen operation may be performed from the beginning of operation to increase the unburned content in the ash. That is, by adjusting the combustion conditions to achieve low oxygen operation, the unburned ratio increases and the molten ash is diluted.
Therefore, it is not necessary to separately supply a solid material, the rated operation period can be extended, and as a result, the number of times of low load operation can be reduced.

In the first embodiment, the ash adhesion is surely reduced by performing the low load operation after a predetermined period of time in the rated operation, but in the third embodiment, the burner shape is changed in the existing combustion apparatus. By replacing it, the rated operation period is extended.
FIG. 7 is a schematic cross-sectional view of a furnace.
As shown in FIG. 7, the arrangement of the burner for the fuel supplied to the inside of the furnace 11 is installed in the vicinity of the corner, and the fuel supply for supplying fuel and air along the wall surface from the vicinity of each corner of the furnace 11 Burners 13a-1 to 13a-4 are used.

As a result, a region 50 having a high oxygen concentration is formed on the furnace wall surface, and even in a reducing atmosphere, the oxygen concentration in the furnace wall portion is increased to convert vanadium in the deposited ash into pentavalent oxide (V ₂ O). _It is changed to ₅ ) to generate downflow slag.

  As described above, according to the combustion apparatus of the present invention, the ash adhesion inside the furnace can be reduced and the proper operation of the combustion facility can be achieved by changing the rated operation to the low load operation after the predetermined operation. be able to.

DESCRIPTION OF SYMBOLS 10 Combustion apparatus 11 Furnace 12 Fuel 13 Fuel supply burner 15 Combustion area

Claims (15)

An operation control method for a combustion apparatus using petroleum residue as fuel,
After a predetermined period of time, the operation is changed from the rated operation to a low load operation in which the load factor is 80% or less of the rated operation and the minimum operation of the combustion device,
An operation control method for a combustion apparatus, characterized in that, during the low load operation, the furnace is in an oxygen-rich state to reduce ash adhesion based on a complex compound of Na and V in a heat transfer tube on the furnace wall. In claim 1,
An operation control method for a combustion apparatus, wherein the low-load operation is performed at or after a command to a temperature reducing device for reducing temperature by supplying spray water into superheated steam. In claim 1 or 2,
A method for controlling the operation of a combustion apparatus, comprising adding a fuel additive to a fuel. In claim 3,
An operation control method for a combustion apparatus, characterized by adding a fuel additive to a fuel in an inclined distribution. In any one of Claims 1 thru | or 4,
A combustion apparatus operation control method, wherein a fuel supply burner blows fuel and air along a furnace wall surface to form a region having a high oxygen concentration in the vicinity of the furnace wall. In any one of Claims 1 thru | or 5,
An operation control method for a combustion apparatus, characterized in that solid materials are added into a furnace to relatively reduce the ash melting ratio. In claim 6,
The operation control method of a combustion apparatus, wherein the solid is at least one of coal ash, iron-based additive, silica-based additive, or magnesium-based additive. In any one of Claims 1 thru | or 7,
An operation control method for a combustion apparatus, characterized in that low oxygen operation is performed from the initial operation of rated operation, and the proportion of unburned ash is increased. A combustion device using petroleum residue as fuel,
A plurality of fuel supply burners for supplying fuel into a reducing atmosphere furnace;
Control means for instructing the fuel supply burner to change from a rated operation to a low-load operation in which the load factor is 80% or less of the rated operation and the lowest possible operation of the combustion device after a predetermined period of time has elapsed. And
A combustion apparatus characterized in that, during the low-load operation, the furnace is in an oxygen-rich state to reduce ash adhesion based on a complex compound of Na and V in a heat transfer tube on the furnace wall. In claim 9,
The combustion apparatus characterized in that the low-load operation is performed in response to a command from a temperature reducing device that reduces the temperature by supplying spray water into superheated steam. In claim 9 or 10,
A combustion apparatus comprising an air supply nozzle for additionally supplying air into a furnace on a downstream side of a fuel supply burner. In any one of Claims 9 thru | or 11,
A combustion apparatus, wherein a fuel supply burner blows along a furnace wall surface. In any one of claims 9 to 12,
A combustion apparatus characterized by adding solid matter in a furnace. In any one of Claims 9 thru | or 13,
The combustion apparatus, wherein the solid is at least one of coal ash, iron-based additive, silica-based additive, or magnesium-based additive. In any one of Claims 9 thru | or 14,
The combustion apparatus characterized in that the control means performs control to perform low oxygen operation from the initial operation of rated operation.

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