JP5822540B2 - Boiler structure and boiler modification method - Google Patents

Description

  The present invention relates to a boiler structure for burning a solid fuel such as cheap petroleum coke and a method for remodeling the boiler.

  Fuels supplied to boilers such as power plants include solid fuels such as coal, liquid fuels such as heavy oil, and gaseous fuels such as liquefied natural gas. Recently, however, crude oil prices have risen and greenhouse gas emissions are regulated. As a result, cheap and low pollution liquefied natural gas is becoming the mainstream of boiler fuel. On the other hand, petroleum coke has attracted attention as a solid fuel that can coexist with heavy oil and the like. Petroleum coke is the residue when pyrolysis is carried out by treating asphalt-class heavy oil from an oil refining unit at about 600 ° C in a coking unit, etc., and the main component is a solid substance of carbon. is there.

  Up until now, petroleum coke has been difficult to use as fuel because it is extremely difficult to burn, and it has been used only for limited applications such as electrodes for refining aluminum, and it has been difficult to process. Therefore, since petroleum coke is inexpensive as a fuel and a strong thermal power can be obtained if the ignition conditions and combustion conditions are adjusted, the applicants of the present invention have been researching to use petroleum coke as boiler fuel since the 1980s. At the end, as disclosed in Patent Documents 1 and 2, etc., an innovative boiler capable of directly burning petroleum coke and the like was developed and put to practical use. Along with this, petroleum coke is being studied as a boiler fuel to replace heavy oil at power plants in various places.

  In general, in a boiler that burns solid fuel, in order to discharge ash after combustion, for example, as disclosed in Patent Document 3, a hopper-like bottom ash treatment facility is installed at the bottom of the furnace. This furnace bottom ash treatment facility needs a predetermined capacity in order to enable continuous operation for about six months, for example. Since petroleum coke is also a solid fuel, it is necessary to install a bottom ash treatment facility when building a new oil coke-fired boiler. For this reason, a corresponding space in the height direction is required below the furnace bottom of the boiler.

JP 2010-91235 A JP 2008-209062 A JP 58-88527 A

  Since the structure of the furnace excluding the burner is similar to that of a heavy oil fired boiler, the oil coke fired boiler has been changed to a heavy oil fired boiler burner (solid fuel combustion burner). If the bottom ash treatment facility is added, it can be converted into an oil coke-fired boiler.

  However, in order to add bottom ash treatment equipment to a heavy oil fired boiler, the space where the furnace is installed is dug down to form a space for installing the bottom ash treatment equipment, or the whole furnace is lifted to raise the bottom ash Processing equipment will be installed, and in any case, technical and cost hurdles are high. Since the greatest purpose of using petroleum coke as boiler fuel is to reduce the cost of the fuel, if the cost of remodeling into a petroleum coke-fired boiler increases, an immediate cost reduction effect cannot be expected.

  On the other hand, instead of adding furnace bottom ash treatment equipment, it may be possible to periodically remove the ash deposited on the bottom of the furnace, but this removal work must be done frequently, Since the operation must be stopped, continuous operation for a long time (tens of days to several months or more) is difficult. For this reason, it is not practical in a boiler that must be operated day and night like a power plant.

  The reliability of the bottom ash treatment equipment is not limited to a heavy oil fired boiler, even if a specific bottom ash treatment equipment is provided, such as when a new oil coke fired boiler is built. There was a problem that it was difficult to secure and that it required time and effort for operation and maintenance.

  The present invention has been made in view of the above problems, and can reduce the operating cost by using an inexpensive solid fuel such as petroleum coke with a simple and compact configuration without providing a bottom ash treatment facility. It is another object of the present invention to provide a boiler structure and a boiler remodeling method that can easily convert a heavy oil or gas fired boiler into a solid fuel fired boiler.

In order to solve the above problems, the present invention employs the following means.
That is, the first aspect of the boiler structure according to the present invention includes a furnace having a furnace wall part and a furnace bottom part, a furnace wall tube arranged to cool the furnace wall part and the furnace bottom part, and the furnace A solid fuel combustion burner installed on the wall, and a heat insulating material laid on the furnace bottom so as to insulate the combustion chamber of the furnace with respect to the furnace wall tube for cooling the furnace bottom, When the ash of the solid fuel supplied to the solid fuel combustion burner is deposited on the heat insulating material, the vertical height from the lower end of the solid fuel combustion burner to the surface of the heat insulating material in contact with the combustion chamber Furthermore, the solid fuel combustion burner is set to a height at which at least a part of the ash is kept at a melting temperature or higher and volatilizes and is reduced by the flame of the solid fuel combustion burner .

  As described above, the ash of the solid fuel deposited on the bottom of the furnace wall tube is formed by laying the heat insulating material on the bottom of the furnace to insulate between the furnace wall tube disposed at the bottom of the furnace and the combustion chamber of the furnace. It is kept in a high temperature state without being cooled by. This ash continues to be heated by the solid fuel combustion burner and is maintained in a molten state. In this way, the burned solid fuel ash is kept warm by the heat insulating material and heated by the burner to be kept at the melting temperature, so the unburned carbon in the ash collected at the bottom of the furnace is in a steamed state. Reacts with oxygen and disappears as carbon monoxide or carbon dioxide. The remaining ash is a compound containing vanadium as a main component and components such as sodium and potassium, and gradually volatilizes by being kept in a molten state. Therefore, the amount of ash accumulated and the amount of ash disappearing can be balanced.

  For this reason, even if the boiler is operated for a long time using solid fuel such as petroleum coke, it prevents the accumulation of a large amount of ash on the bottom of the boiler furnace, and the furnace equipped in a normal solid fuel fired boiler It is possible to provide a boiler capable of continuous operation for a long time while having a simple configuration in which the bottom ash treatment facility is omitted. In addition, since the furnace bottom ash treatment facility need not be provided, the dimensions of the boiler, particularly in the height direction, can be made compact.

  According to a second aspect of the boiler structure of the present invention, in the first aspect, the solid fuel is petroleum coke.

  Thus, by using petroleum coke as the fuel, the fuel cost can be reduced and the operating cost of the boiler can be reduced.

  Moreover, the 3rd aspect of the boiler structure which concerns on this invention is the said 1st or 2nd aspect. WHEREIN: The said furnace bottom part is an inclined surface which descends toward the center part from the outer edge part, The inclination | tilt angle is The minimum angle at which the ash can flow to the center of the furnace bottom in a melted state.

  According to the above configuration, the ash of the solid fuel that accumulates on the heat insulating material laid on the bottom of the furnace is collected at the center of the bottom of the furnace by gravity. For this reason, generally, the flames of the solid fuel combustion burners that are installed in the furnace wall and face each other can heat the solid fuel ash collected at the center of the furnace bottom well, as described above. The effect | action which lose | disappears ash can be heightened.

  In addition, since the inclination angle of the furnace bottom is the minimum angle at which the molten ash can flow to the center of the furnace bottom, the height dimension of the furnace bottom can be reduced, and thereby the height direction of the boiler The dimensions can be made compact.

  Moreover, the 4th aspect of the boiler structure which concerns on this invention is a perpendicular direction from the lower end of the said solid fuel combustion burner to the surface which contact | connects the said combustion chamber of the said heat insulating material in the said any 1st-3rd aspect. It is characterized by having burner height adjusting means for adjusting the height of the burner.

  According to the above configuration, the height in the vertical direction from the lower end of the solid fuel combustion burner to the surface in contact with the combustion chamber of the heat insulating material can be adjusted by the burner height adjusting means. By adjusting the height of the solid fuel combustion burner, the ash deposited on the furnace wall (heat insulating material) can be heated at an optimum temperature. This eliminates problems such as heating more than necessary to heat the ash into a molten state, reducing boiler efficiency, or causing the ash to accumulate in the furnace bottom without being heated into the molten state. can do.

The boiler remodeling method according to the present invention includes a furnace having a furnace wall portion and a furnace bottom portion, a furnace wall tube disposed in the vicinity of the furnace wall portion and the furnace bottom portion, and installed in the furnace wall portion. And a liquid or gas fuel combustion burner for heating the furnace wall tube, wherein the liquid or gas fuel combustion burner is replaced with a solid fuel combustion burner and a heat insulating material is laid at the bottom of the furnace By doing so, the combustion chamber of the furnace is insulated from the furnace wall tube arranged to cool the bottom of the furnace, and the surface of the heat insulating material that contacts the combustion chamber from the lower end of the solid fuel combustion burner the vertical way height direction of up, the when the ash of the solid fuel supplied to the solid fuel-fired burner has been deposited on the heat insulating material, by the flame of the solid fuel-fired burner, at least a portion of the ash and but kept above the melting temperature Issued, and sets the height to continue to lose weight.

  According to this boiler remodeling method, an existing heavy oil-fired or gas-fired boiler can be easily remodeled into a solid fuel-fired boiler. Furthermore, even after remodeling into a solid fuel fired boiler in this way, if the solid fuel combustion burner is replaced with a liquid fuel combustion burner or a gas fuel combustion burner, it can be easily returned to a heavy oil or gas fired boiler again. . Therefore, the fuel used according to the fuel procurement situation in the boiler plant can be changed flexibly, and an economical boiler plant can be obtained.

  As described above, according to the boiler structure and the boiler remodeling method according to the present invention, an inexpensive solid fuel such as petroleum coke can be used with a simple and compact configuration without providing a bottom ash treatment facility. The operating cost can be reduced, and a heavy oil or gas fired boiler can be easily converted to a solid fuel fired boiler.

It is a schematic block diagram of the boiler plant which can apply the boiler structure which concerns on this invention. It is the longitudinal cross-sectional view which expands the II section of FIG. 1 and shows the boiler structure which concerns on one Embodiment of this invention. It is a longitudinal cross-sectional view of the furnace wall part which follows the III-III line of FIG. It is a longitudinal cross-sectional view of the furnace bottom part along the IV-IV line of FIG.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a schematic configuration diagram of a boiler plant to which a boiler structure according to the present invention can be applied. A boiler 1 of this boiler plant includes a furnace 4 having a furnace wall portion 2 and a furnace bottom portion 3 and having a bottomed box shape extending in the vertical direction. A solid fuel combustion burner 5 is installed in the lower part of the furnace 4, and a flue 7 is connected to the upper part of the furnace 4. From the upper part of the furnace 4 to the flue 7, devices such as a superheater 8, a reheater 9, a denitration device 11, and an economizer 12 are incorporated.

  The interior of the furnace 4 is a combustion chamber 14 (see FIG. 2), and an air supply pipe 15 that supplies combustion air to the combustion chamber 14 is provided outside the furnace 4. The air supply pipe 15 is arranged in line with the downstream portion of the flue 7, and an air preheater 16 is provided across the flue 7 and the air supply pipe 15. Further, a steam drum 18 is installed at the upper part of the furnace 4, and a water drum (header) 19 is installed at the lower part of the furnace 4. The above-described configuration and the function of each part are the same as those of a known boiler.

  The solid fuel used in the present invention is mainly composed of carbon, has an ash content of 4.0% by weight or less, and has an ash content of a high melting point element such as Si of less than half. Among these, petroleum coke is most preferable for achieving the object of the present invention. Moreover, when the solid fuel which exceeded the conditions is used, since the quantity of ash increases and the quantity of the ash 45 deposited on the furnace bottom part 3 mentioned later increases, it is not preferable.

  Petroleum coke is stored in a hopper 22 of a mill device 21 installed in the vicinity of the furnace 4, and is pulverized into a fine powder by the mill device 21 and supplied to the solid fuel combustion burner 5 together with compressed air. On the other hand, an electric dust collector 25, an induction ventilator 26, and a desulfurization device 27 are connected to an exhaust pipe 24 extending from the end portion of the flue 7, and the exhaust pipe 24 is connected to a chimney 28.

  The furnace wall 2 and the furnace bottom 3 constituting the furnace 4 are generally protected from the high heat generated by the solid fuel combustion burner 5 and for the purpose of evaporating water by effectively using the high heat in the combustion chamber 14. A water-cooled furnace wall as shown in FIGS. 3 and 4 is employed. The furnace wall 2 has a structure in which a large number of furnace wall tubes 31 are densely arranged inside the furnace outer plate 30. The furnace wall tube 31 is formed in a wall shape with a connection plate 32 connected between the furnace wall tube 31 and water and steam flowing through the interior of the furnace wall tube 31 and the high heat in the combustion chamber 14 are heat-exchanged to form a furnace. The wall 2 is cooled.

  Further, the furnace bottom portion 3 is constituted by a furnace wall tube 31 formed in a wall shape like the furnace wall portion 2, and is an inclined surface that descends from the outer edge portion toward the center portion, and a bottom plate 33 of the furnace 4. It is supported from below by a support member 34 extending from the bottom. As will be described later, the inclination angle of the furnace bottom portion 3 is a minimum that can flow to the central portion that is the lowest portion of the furnace bottom portion 3 when the ash 45 of petroleum coke is melted by the heat of the solid fuel combustion burner 5. The angle may be 5 ° or more, and is preferably about 15 °. In particular, in order to make the dimension of the boiler 1 in the height direction compact, it is desirable to set it to 60 ° or less. As shown in FIG. 2, a header pipe 36 extends from each furnace wall pipe 31 and is connected to a water drum 19 installed below the furnace bottom 3. As shown in FIG. 1, the water drum 19 and the steam drum 18 are connected by a steam pipe 37.

  A heat insulating material 40 having predetermined heat resistance is laid on the upper surface of the wall-shaped furnace wall tube 31 constituting the furnace bottom portion 3. An example of the heat insulating material 40 is refractory bricks, but other materials may be used. The heat-resistant temperature of the heat insulating material 40 needs to be higher than the maximum temperature (for example, 1600 ° C.) at which the solid fuel combustion burner 5 is generated. Further, the thickness T (see FIG. 4) of the heat insulating material 40 is set to a dimension that can reliably insulate the combustion chamber 14 from the furnace wall tube 31 within the maximum temperature generated by the solid fuel combustion burner 5. The furnace wall 2 is provided with a manhole 43 at a position higher than the furnace bottom 3.

  On the other hand, the solid fuel combustion burner 5 is attached to the furnace wall 2 via a burner height adjusting mechanism 46 (burner height adjusting means). The vertical height dimension H from the lower end of the solid fuel combustion burner 5 to the surface of the heat insulating material 40 in contact with the combustion chamber 14 is such that coal coke supplied to the solid fuel combustion burner 5 is burned and the ash 45 is insulated. It is necessary to set the height at which the ash 45 is maintained at the melting temperature or higher when it falls on the material 40. Further, the height dimension H is the height at which the ash 45 is maintained at the melting temperature or higher, at any position on the lower surface of the burner 5 and the surface of the heat insulating material 40 in contact with the combustion chamber 14. good. This height dimension H can be adjusted by the burner height adjusting mechanism 46 in the vertical direction only within the range of the dimension S.

  In the boiler 1 configured as described above, the petroleum coke pulverized by the mill device 21 and supplied to the solid fuel combustion burner 5 together with the compressed air is combusted in the combustion chamber 14, and the ash 45 is supplied to the furnace. It falls on the heat insulating material 40 at the bottom 3. The dropped ash 45 is kept in a high temperature state without being cooled by the furnace wall tube 31 by the heat insulating action of the heat insulating material 40. The ash 45 is continuously heated by the solid fuel combustion burner 5 and kept in a molten state. In this way, the burned ash 45 is kept warm by the heat insulating material 40 and is heated by the solid fuel combustion burner 5 to be kept at the melting temperature, so that the unburned carbon content in the ash 45 accumulated in the furnace bottom 3 is It reacts with oxygen in a steaming state, becomes carbon monoxide or carbon dioxide, is discharged from the flue 7 together with the combustion gas, and disappears.

  For example, when petroleum coke is used as fuel, the ash 45 left in the furnace bottom 3 after the disappearance of unburned carbon as described above contains vanadium as a main component and components such as sodium and potassium. Become a compound. As this compound is stored in the furnace bottom 3 and kept in a molten state, the ash 45 gradually escapes into the gas phase and decreases in weight. Thus, by keeping the ash 45 in a high-temperature molten state, the amount of ash 45 deposited on the furnace bottom portion 3 and the amount of ash 45 disappearing can be balanced.

  Therefore, even if the boiler 1 is operated for a long time using a solid fuel such as petroleum coke, a large amount of ash is prevented from accumulating in the furnace bottom 3, and the furnace bottom equipped in a normal solid fuel-fired boiler is prevented. A boiler capable of continuous operation for a long time can be provided while having a simple configuration without ash treatment equipment. In addition, since the furnace bottom ash treatment facility need not be provided, the size of the boiler 1 in particular in the height direction can be made compact. Furthermore, the boiler 1 can be constructed at a low cost, and the running cost generated for processing industrial waste becomes unnecessary.

  Further, by using inexpensive petroleum coke as the fuel, the fuel cost can be reduced and the operating cost of the boiler 1 can be drastically reduced. The combustion gas discharged from the flue 7 is attracted by the induction fan 26 and passes through the electric dust collector 25 provided in the exhaust pipe 24, where unburned carbon powder is recovered, The sulfur content is removed by the desulfurization device 27 and discharged from the chimney 28 to the outside. Note that limestone and oxidizing air are supplied to the desulfurization device 27, and instead, gypsum and desulfurization waste water are generated.

  The furnace bottom portion 3 of the boiler 1 is an inclined surface that descends from the outer edge portion toward the center portion, and the inclination angle is the minimum that can flow to the center portion of the furnace bottom portion 3 in a state where the ash 45 of petroleum coke is melted. Since the angle is limited, petroleum coke ash 45 deposited on the heat insulating material 40 laid on the furnace bottom 3 is collected in the center of the furnace bottom 3 by gravity. For this reason, the flame of the solid fuel combustion burner 5 installed facing the furnace wall 2 can heat the ash 45 collected at the center of the furnace bottom 3 well, and the ash 45 disappears as described above. It is possible to enhance the action.

  And since the inclination-angle of the furnace bottom part 3 is shallow, the height dimension of the furnace bottom part 3 can be made small, and the dimension of the height direction of the boiler 1 can be made compact by this. In general boilers that use solid fuel, in order to improve the discharge of ash produced in large quantities, the inclination angle of the bottom of the furnace must be deepened to form a hopper shape, which increases the height of the boiler. It was bigger. In addition, since it was necessary to provide a bottom ash treatment facility below the bottom of the furnace, if the boiler has the same amount of heat, it is much larger than the boiler 1 of the present embodiment.

  Further, the boiler 1 has a burner height adjusting mechanism 46 that can adjust the vertical height H from the lower end of the solid fuel combustion burner 5 to the surface of the heat insulating material 40 that contacts the combustion chamber 14. Since the height of the solid fuel combustion burner 5 can be changed, the petroleum coke ash 45 deposited on the furnace bottom 3 (heat insulating material 40) can be heated at an optimum temperature. For this reason, the heat | fever more than necessary to heat the ash 45 to a molten state is consumed, and boiler efficiency falls, or the ash 45 cannot be heated to a molten state, but accumulates on the furnace wall part 3. Can be eliminated. Moreover, since the height of the solid fuel combustion burner 5 can be adjusted as appropriate according to the type and properties of the solid fuel, the amount of ash of petroleum coke, which tends to be unstable in properties, can always be minimized. Moreover, not only petroleum coke but other solid fuels can be adapted.

  The burner height adjusting mechanism 46 is preferably operable even during operation of the boiler 1. Thus, the solid fuel combustion burner 5 can be set to an optimum height while maintaining the state of the ash 45 while confirming the molten state of the ash 45 by remote monitoring means or the like without stopping the operation of the boiler 1.

Next, a boiler remodeling method according to the present invention will be described.
A common heavy oil-fired or gas-fired boiler furnace has the same structure as the furnace 4 of the oil coke-fired boiler 1 shown in FIG. In addition to the solid fuel combustion burner 5, a liquid or gaseous fuel combustion burner is provided.

Therefore, there are the following three items for remodeling oil-fired coke-fired boilers.
(1) Replace the liquid or gas fuel combustion burner with the solid fuel combustion burner 5.
(2) The heat insulating material 40 is laid on the upper surface of the wall-shaped furnace wall tube 31 constituting the furnace bottom portion 3 to insulate the combustion chamber 14 from the furnace wall tube 31.
(3) When the height C in the vertical direction from the lower end of the solid fuel combustion burner 5 to the surface of the heat insulating material 40 in contact with the combustion chamber 14 is deposited on the heat insulating material 40, the ash Set to a height that keeps above the melting temperature.

  According to this boiler remodeling method, an existing heavy oil-fired or gas-fired boiler can be easily remodeled into a solid fuel-fired boiler. Furthermore, even after remodeling into a solid fuel-fired boiler as described above, if the solid-fuel combustion burner 5 is replaced with a liquid fuel combustion burner or a gas fuel combustion burner, it can be easily returned to a heavy oil or gas fired boiler again. it can. At that time, it is not necessary to remove the heat insulating material 40 laid on the furnace bottom 3. Therefore, the fuel used according to the fuel procurement situation in the boiler plant can be changed flexibly, and an economical boiler plant can be obtained.

  In addition, this invention is not limited to said each embodiment, In the range which does not deviate from the summary of this invention, it can change suitably. For example, in the above description, the height dimension H is the height at which the lower end of the burner 5 is in contact with the combustion chamber 14 of the heat insulating material 40 as long as the ash 45 is maintained at the melting temperature or higher. However, the height dimension H between the lower end of the solid fuel combustion burner 5 and the surface of the heat insulating material 40 in contact with the combustion chamber 14 may be set to be the largest. By setting the height dimension H to be the largest, the ash 45 can be reliably kept at the melting temperature or higher regardless of where the ash 45 falls on the furnace bottom 3 side.

DESCRIPTION OF SYMBOLS 1 Boiler 2 Furnace wall part 3 Furnace bottom part 4 Furnace 5 Solid fuel combustion burner 14 Combustion chamber 31 Furnace wall pipe 40 Thermal insulation material 45 Solid fuel ash 46 Burner height adjustment mechanism (burner height adjustment means)

Claims (5)

A furnace having a furnace wall and a furnace bottom;
A furnace wall tube arranged to cool the furnace wall and the furnace bottom;
A solid fuel combustion burner installed on the furnace wall;
A heat insulating material laid on the furnace bottom so as to insulate the combustion chamber of the furnace with respect to the furnace wall tube that cools the furnace bottom,
When the ash of the solid fuel supplied to the solid fuel combustion burner is deposited on the heat insulating material, the vertical height from the lower end of the solid fuel combustion burner to the surface of the heat insulating material in contact with the combustion chamber Furthermore, the boiler structure is characterized in that at least a part of the ash is kept at a melting temperature or higher by the flame of the solid fuel combustion burner and is volatilized and reduced in weight .   The boiler structure according to claim 1, wherein the solid fuel is petroleum coke.   The furnace bottom part is an inclined surface that descends from the outer edge part toward the center part, and the inclination angle is a minimum angle that can flow to the center part of the furnace bottom part when the ash is melted. The boiler structure according to claim 1 or 2.   4. The burner height adjusting means for adjusting a vertical height from a lower end of the solid fuel combustion burner to a surface of the heat insulating material in contact with the combustion chamber. 5. The boiler structure described in 1. A furnace having a furnace wall and a furnace bottom;
A furnace wall tube disposed in proximity to the furnace wall and the furnace bottom;
In a boiler remodeling method comprising a liquid or gaseous fuel combustion burner installed on the furnace wall and heating the furnace wall tube,
Replacing the liquid or gaseous fuel combustion burner with a solid fuel combustion burner;
Insulating the combustion chamber of the furnace with respect to the furnace wall tube arranged to cool the furnace bottom by laying a heat insulating material on the furnace bottom,
The vertical way height direction from the lower end of the solid fuel-fired burner to a surface in contact with the combustion chamber of the heat insulating material, ash of the solid fuel supplied to the solid fuel-fired burner has been deposited on the heat insulating material In this case, the boiler is remodeled by setting the height so that at least a part of the ash is volatilized by the flame of the solid fuel combustion burner and is volatilized and reduced .

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