JP2017190908A - Boiler operation method and boiler equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a boiler operation method which can suppress lowering of the heat absorption rate of a furnace.SOLUTION: The present invention provides a boiler operation method for a boiler that burn a plurality of kinds of solid fuel by blending them comprises the steps of: acquiring a content of an ash component in the plurality of kinds of solid fuels and a content of mullite in the ash component; and determining a blending ratio of the plurality of kinds of solid fuels so that the content of the mullite in the ash component in a mixture of the plurality of kinds of solid fuels is equal to or lower than a reference value as a whole on the basis of the content of the ash component and the content of the mullite of the plurality of kinds of solid fuels acquired in the acquiring step. It is preferable that the reference value is 33 mass%. The solid fuels may be coals.SELECTED DRAWING: Figure 1

Description

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

  For example, a boiler that burns solid fuel such as coal generally includes a furnace that burns solid fuel using, for example, a burner, and a plurality of heat transfer tubes that are disposed in the furnace in the vertical direction to exchange heat. For example, in a boiler used in a thermal power plant, the heat transfer tube is disposed in the primary heater, the primary reheater, and the economizer in the lower part of the furnace, and in the upper part of the furnace. A secondary heater, a tertiary heater, a final heater, and an upper heat transfer section that exchange heat in the secondary reheater.

  Among such boilers, for example, in pulverized coal boilers using coal as a solid fuel, slagging and fouling occurs in which ash in the combustion gas generated by the combustion of coal adheres to the furnace walls and heat transfer tubes of the furnace and accumulates, An ash adhesion layer may be formed. When such ash adhesion occurs, the heat recovery rate at the heat transfer surface of the heat transfer tube is likely to be greatly reduced. Further, when the ash (clinker) adhering to the furnace wall becomes enormous, it may fall from the furnace wall or the like, resulting in a significant fluctuation in the furnace pressure, damage to the heat transfer tube, blockage of the gas flow path, or the like.

  In particular, the upper heat transfer section has a structure in which the combustion gas flows between the heat transfer tubes arranged at a narrower interval than the lower heat transfer section to exchange heat, so that ash is formed in the upper heat transfer section. If it adheres, a large fluctuation of the furnace pressure and a blockage of the gas flow path are likely to occur, and the stable operation of the boiler is hindered. Further, in the vicinity of the burner, the temperature in the vicinity of the furnace wall becomes high due to the radiant heat of the pulverized coal combustion flame, so that ash tends to melt and adhere to a relatively low temperature heat transfer tube, and the heat recovery rate of the furnace tends to decrease.

  Then, the possibility of this ash adhesion occurring is expressed as an index, and a boiler operating method that suppresses ash adhesion based on the index has been proposed (Japanese Patent No. 5342355). In this conventional operation method, focusing on slag, which is a component adhering to the furnace wall and heat transfer tube group, based on the slag ratio calculated for each solid fuel and the composition of the ash component, the mixing ratio of multiple types of solid fuel Is determined. Specifically, in the conventional boiler operation method, a reference value for the slag ratio is determined so that the ash adhesion rate is low, and the mixing ratio of a plurality of types of solid fuels is set so that the slag ratio is less than this reference value. By determining, adhesion of ash is suppressed.

  However, in the above conventional boiler operating method, the heat recovery rate of the furnace may be lowered despite the suppression of ash adhesion. Therefore, a new boiler operation method that can suppress a decrease in the heat recovery rate of the furnace is desired.

Japanese Patent No. 5342355

  This invention is made | formed based on the above situations, and makes it a subject to provide the operating method and boiler equipment of a boiler which can suppress the fall of the heat recovery rate of a furnace.

  The present inventors pay attention to the fact that the degree of reduction in the heat recovery rate varies depending on the composition of the ash even if the mass of the ash adhering to the heat transfer tube is the same. As a result, it was confirmed that as the ash mullite content increases, the porous ash adheres and the reduction in the heat recovery rate increases. And based on this knowledge, the inventors determined the mixing ratio of multiple types of solid fuel so that the mullite content of the generated ash is below the reference value, thereby suppressing the decrease in furnace heat recovery rate. As a result, it was found that the boiler can be stably operated, and the present invention was completed.

  The invention made in order to solve the above-mentioned problems is a boiler operating method for mixing and burning a plurality of types of solid fuels, wherein the ash content in the plurality of types of solid fuels and the mullite in the ash content Based on the ash content and the mullite content of each of the multiple types of solid fuel obtained in the acquisition step, and the ash content of the entire mixture of the multiple types of solid fuel And a step of determining a mixing ratio of the plurality of types of solid fuels so that the content of mullite is not more than a reference value.

  The boiler operating method includes the steps of acquiring the ash content in the plurality of types of solid fuel and the mullite content in the ash, and each of the plurality of types of solid fuel obtained in the acquisition step. Based on the ash content and the mullite content, the mixing ratio of the multiple types of solid fuel is determined so that the mullite content in the ash content of the mixture of the multiple types of solid fuel is below the reference value. Therefore, it is possible to suppress the mullite content of the ash generated by the combustion of the solid fuel to a certain value or less, and to suppress the adhesion of the porous ash to the heat transfer tube. Thereby, since the heat insulation property of adhesion ash is reduced, the operation method of the said boiler can suppress the fall of a furnace heat recovery rate.

  As said reference value, 33 mass% is preferable. Thus, the fall of the furnace heat recovery rate can be suppressed more reliably by setting the reference value to 33% by mass.

  The solid fuel may be coal. In boilers using coal as solid fuel, the furnace heat recovery rate tends to decrease. For this reason, the operating method of the said boiler which can suppress the fall of a furnace heat recovery rate can be used suitably.

  The operation method of the boiler may be used for a thermal power plant. Thus, by using the operation method of the boiler for the thermal power plant, it is possible to suppress the decrease in the furnace heat recovery rate and supply power stably.

  Another invention made to solve the above problems is a boiler facility for mixing and burning a plurality of types of solid fuels, each of which includes a plurality of mechanisms for supplying different types of the solid fuels, and A mechanism for mixing a plurality of types of solid fuel supplied from the supply mechanism, a mechanism for pulverizing the solid fuel mixed by the mixing mechanism, a boiler for burning the solid fuel pulverized by the pulverization mechanism, and the plurality of Based on the ash content of each type of solid fuel and the content of mullite in the ash, the mullite content in the ash of the mixture of the multiple types of solid fuel is less than the reference value. A mechanism for determining the mixing ratio of the different types of solid fuels, and the above-described compound introduced from the supply mechanism to the mixing mechanism so as to be the mixing ratio of the plurality of types of solid fuels determined by the determining mechanism. A boiler equipment, characterized in that it comprises a mechanism for adjusting the kind of the solid fuel respective supply amounts.

  Since the boiler equipment includes a mechanism for determining the mixing ratio of the plurality of types of solid fuel so that the content of the mullite in the ash content of the mixture of the plurality of types of solid fuel is equal to or less than a reference value, Ash adhesion can be suppressed. Thereby, since the heat insulation of adhesion ash is reduced, the said boiler installation can suppress the fall of a furnace heat recovery rate.

Here, the “ash content” is a value measured according to JIS-M8812 (2006). “Mullite” means an aluminosilicate (Al ₆ Si ₂ O ₁₃ ) having a single chain structure. Further, the “content of mullite in the ash” refers to the ash obtained in the measurement of the ash content, that is, the solid fuel ashed in an electric furnace in accordance with JIS-K0131 (1996). It is a value quantified by analyzing by line diffraction analysis.

  As described above, the boiler operating method and boiler equipment of the present invention can suppress a decrease in the furnace heat recovery rate.

It is a key map showing boiler equipment of one embodiment of the present invention. It is a flowchart which shows the procedure of the operating method of the boiler of one Embodiment of this invention. It is a graph which shows the relationship between the mullite content rate in ash, and a furnace heat recovery rate.

  Hereinafter, an embodiment of a boiler operating method and boiler equipment according to the present invention will be described using a thermal power plant.

  The thermal power plant includes the boiler equipment, the steam turbine generator equipment, and the condensate water supply equipment.

<Boiler equipment>
The boiler facility shown in FIG. 1 is a boiler facility that mixes and burns a plurality of types of solid fuels. The boiler equipment includes a hopper 1, a mixer 2, a pulverizer 3, a boiler 4, a calculator 5, and a supply amount adjusting device 6.

(hopper)
The hopper 1 is a mechanism that supplies solid fuel. The boiler facility includes a plurality of hoppers 1 for supplying different types of solid fuel to supply a plurality of types of solid fuel. Although FIG. 1 shows a case where two hoppers 1 are provided, three or more kinds of solid fuels may be used. In that case, the boiler equipment includes the same number of hoppers 1 as the type of solid fuel.

  The hopper 1 has a storage tank for storing the solid fuel, and the solid fuel can be dropped and taken out from a bottom-open funnel-shaped mouth at the bottom of the storage tank.

(Mixer)
The mixer 2 is a mechanism for mixing the solid fuel supplied from the hopper 1. As the mixer 2, for example, a known drum mixer or the like can be used.

(Crusher)
The pulverizer 3 is a mechanism for pulverizing the solid fuel mixed in the mixer 2. As the pulverizer 3, a known vertical roller mill or the like can be used.

  The particle size of the solid fuel after pulverization is not particularly limited. For example, the solid fuel can be pulverized so that the proportion of the solid fuel having a particle size of 75 μm or less is 75% by mass or more and 90% by mass or less.

(boiler)
The boiler 4 burns the solid fuel pulverized by the pulverizer 3. The boiler 4 mainly includes a burner 7, a furnace, a heat transfer tube, and a chimney. The boiler 4 burns solid fuel blown together with air in a furnace by means of a burner 7, and performs heat exchange using a large number of heat transfer tubes arranged in the vertical direction in the furnace. By this heat exchange, water supplied to the heat transfer tube is heated and pressurized to generate steam. Moreover, the combustion gas generated by the combustion is discharged from the chimney.

  The heat transfer tube is appropriately configured according to the required steam temperature and pressure, for example, a lower heater including a primary heater, a primary reheater, and a economizer disposed in the lower part of the furnace, It can comprise with the upper heat-transfer part provided with the secondary heater, the tertiary heater, the final heater, and the secondary reheater which are arrange | positioned at the furnace upper part. The lower heat transfer section mainly preheats the feed water supplied to the boiler 4, and the upper heat transfer section mainly generates high-temperature and high-pressure steam. In addition, the reheater reheats the steam that has worked in the steam turbine or the like, and creates steam that rotates the reheat cycle turbine. Further, the economizer preheats the feed water of the boiler 4 with the heat of the exhausted combustion gas.

(Calculator)
The calculator 5 is a mechanism that determines the mixing ratio of the above-described plural types of solid fuels. Specifically, based on the ash content of each of the plurality of types of solid fuels and the mullite content in the ash (hereinafter sometimes referred to simply as mullite content), a mixture of the plurality of types of solid fuels The mixing ratio of the plurality of types of solid fuels is determined so that the content of mullite in the ash in the entire ash is equal to or less than the reference value.

  The calculator 5 calculates the mixing ratio of the plurality of types of solid fuels in the mixing ratio determining step (S2) of the boiler operating method described later. In addition, the calculator 5 controls the supply amount adjusting device 6 based on the calculated mixing ratio.

(Supply amount adjustment device)
The supply amount adjusting device 6 adjusts the supply amount of each of the plurality of types of solid fuel introduced from the hopper 1 to the mixer 2 so that the mixing ratio of the plurality of types of solid fuel determined by the calculator 5 is obtained. It is a mechanism to do. That is, the boiler equipment includes a supply amount adjusting device 6 having the same number as the type of solid fuel, one for each pipe connected to the mixer 2 from each of the same number of hoppers 1 as the type of solid fuel. The supply amount adjusting device 6 is not particularly limited, and for example, a chain conveyor that conveys solid fuel from the hopper 1 to the mixer 2 can be used. In this case, the supply amount is adjusted by adjusting the moving speed of the conveyor.

<How to operate the boiler>
FIG. 2 shows a procedure of a boiler operating method using the boiler apparatus. The boiler operation method is a boiler operation method in which a plurality of types of solid fuels are mixed and burned. The boiler operating method includes the step of acquiring the ash content in the plurality of types of solid fuel and the mullite content in the ash (S1: content acquisition step) and the above obtained in the acquisition step. Based on the ash content and the mullite content of each of a plurality of types of solid fuel, the plurality of types of solids so that the mullite content in the ash content of the entire mixture of the plurality of types of solid fuel is less than or equal to a reference value. A step of determining a mixing ratio of fuel (S2: mixing ratio determining step), a step of mixing the plurality of types of solid fuels based on the determined mixing ratio and supplying them to a furnace (S3: mixing supply step); Is provided.

  The solid fuel used for the operation method of the boiler is not particularly limited as long as it is a fuel used for the boiler, and examples thereof include coal, sludge carbide, biomass fuel, and the like. Among them, coal that generates a large amount of heat and is preferably used in a thermal power plant or the like is preferable.

  The type of coal is not particularly limited. In the operation method of the boiler, since the mixing ratio of the plurality of types of solid fuels is determined so that the mullite content is less than or equal to a reference value, it is possible to suppress a decrease in furnace heat recovery rate caused by adhesion of porous ash. In other words, the boiler operation method uses a solid fuel having a relatively large mullite content and easily reducing the furnace heat recovery rate mixed with a solid fuel having a relatively small mullite content and hardly reducing the furnace heat recovery rate. Therefore, it is possible to suppress a decrease in the furnace heat recovery rate.

  Therefore, the operation method of the boiler can use coal or the like having a relatively high mullite content as part of the solid fuel. Examples of such coal having a relatively high mullite content include anthracite, bituminous coal, subbituminous coal, lignite, high silica coal, and high calcium coal.

(Content acquisition process)
In the content acquisition step (S1), the ash content of each of the plurality of types of solid fuel and the mullite content in the ash are acquired. The acquisition of the ash content in the content acquisition step and the mullite content in the ash does not necessarily require analysis of solid fuel, but the ash content measured in advance and the ash content in the ash The content rate of mullite may be referred to or input by an operator from a storage device or the like.

  Although it does not specifically limit as a measuring method of the content rate of ash content of each solid fuel, For example, the measuring method based on JIS-M8812 (2006) can be used. The ash content may be the same base value as the mixing ratio described later, and may be an anhydrous base or a water-containing base, but is preferably an anhydrous base that facilitates calculation of the mixing ratio.

  In addition, the method for measuring the mullite content is not particularly limited, but the solid fuel ashed in an electric furnace or the like is measured by, for example, an X-ray diffraction analysis method based on JIS-K0131 (1996). Can do. Specifically, an external standard method is used to calculate from the peak ratio of the solid fuel ash spectrum obtained under the same conditions by an X-ray diffractometer and the spectrum of a mullite standard material (for example, JCRM-R041 certified by the Japan Ceramic Society). It can be used to quantify the content of mullite in ash.

  In addition, in the content rate acquisition step (S1), in addition to the measurement of the ash content, it is preferable to acquire a measurement value of the calorific value of each solid fuel. By obtaining the calorific value of each solid fuel in this way, in the mixing and supplying step (S3) to be described later, the solid fuel is supplied so that the heat amount of the mixed solid fuel charged into the boiler becomes a desired amount. Since the amount is easy to adjust, the boiler can be operated efficiently. Here, the calorific value of the solid fuel is a value measured by burning the solid fuel in accordance with, for example, a measurement method based on JIS-M8814 (2003).

  Further, the ash content of each solid fuel, the mullite content, the calorific value of the solid fuel, and the like are preferably recorded and stored as data in, for example, a storage device. By storing the data in this way, the data can be used thereafter.

(Mixing ratio determination process)
In the mixing ratio determination step (S2), based on the ash content and the mullite content of each of the plurality of types of solid fuel obtained in the acquisition step, the ash content in the mixture of the plurality of types of solid fuel The mixing ratio of the plurality of types of solid fuels is determined so that the mullite content is less than or equal to a reference value. This step is performed by the calculator 5 of the boiler facility.

  Assuming that the mass content of ash in each solid fuel is Wi, the mass content of mullite in the ash is Mi, and the mass ratio to the entire fuel is Xi, the content of Mi in the ash in the entire mixture is It can be calculated by equation (1). In addition, the unit of the said ash content rate Wi, the mullite content rate Mi, and the mass ratio Xi should just be unified between fuels, and as shown to following formula (1), the unit of the mullite content rate M is each solid. The unit is the same as the content ratio Mi of mullite in the ash content of the fuel.

  In the mixing ratio determining step (S2), the mixing ratio of the plurality of types of solid fuels is determined so that the mullite content M is not more than a reference value. The operation method of the boiler can suppress the reduction in the furnace heat recovery rate by setting the mullite content M to a reference value or less.

  Here, the reason why the reduction in the furnace heat recovery rate can be suppressed by setting the mullite content M below the reference value will be described in more detail.

  Among the components of solid fuel, the component that generates mullite at the time of ashing (combustion) contains crystal water, and it is considered that ash is made porous by releasing crystal water when generating mullite. . For this reason, the porous ash with a high mullite content adheres to the heat transfer tube of the boiler, thereby inhibiting the heat transfer and lowering the furnace heat recovery rate. On the other hand, if the mullite content M is set to a reference value or less, the heat insulating property of the attached ash is reduced, so that it is considered that the reduction in the furnace heat recovery rate can be suppressed.

  The reference value of the mullite content M of the mixed coal solid fuel is preferably 33% by mass, more preferably 30% by mass, further preferably 28% by mass, and particularly preferably 26% by mass. When making the said reference value larger than the said value, since a furnace heat-recovery rate falls too much, there exists a possibility that the fall of a furnace heat-recovery rate cannot fully be suppressed.

  On the other hand, the lower limit of the mullite content M of the blended solid fuel is preferably 15% by mass, more preferably 18% by mass, and even more preferably 20% by mass. When the mullite content M is less than the above lower limit, the solid fuel that can be used is limited, so that the fuel cost may increase unnecessarily.

(Mixed supply process)
In the mixing and supplying step (S3), the plurality of types of solid fuels are mixed and pulverized based on the mixing rate determined in the mixing rate determining step (S2), and then supplied to the furnace. Specifically, the supply amount adjusting device 6 is controlled by the calculator 5 of the boiler facility to adjust the amount of solid fuel sent from the hopper 1 to the mixer 2. The mixed solid fuel is pulverized by the pulverizer 3 and then blown into the boiler 4 together with air to be burned.

(advantage)
Since the operation method of the boiler determines the mixing ratio of a plurality of types of solid fuel so that the mullite content M is not more than the reference value, the heat insulation property of the ash adhering to the heat transfer tube is reduced. A decrease in heat rate can be suppressed.

<Steam turbine generator equipment>
The steam turbine generator facility mainly includes a steam turbine and a generator.

  The steam turbine is an external combustion engine that converts steam energy into rotational motion via a turbine (impeller) and a shaft, and is driven by steam generated by the boiler equipment.

  Although the said steam turbine is not specifically limited, For example, it can be comprised with a high temperature high pressure turbine, a high temperature reheat turbine, and a low pressure turbine. In this case, the steam generated in the boiler facility first drives the high temperature and high pressure turbine. By driving the high-temperature high-pressure turbine, the steam that has lost its energy and dropped in temperature and pressure is heated again by the reheater of the boiler equipment. The high-temperature reheat turbine is driven by the high-temperature steam heated by the reheater. Further, the steam whose temperature and pressure have been lost due to the driving of the high-temperature reheat turbine is guided to the condensate water supply facility after driving the low-pressure turbine.

  The power of the high-temperature high-pressure turbine, high-temperature reheat turbine, and low-pressure turbine driven by the steam drives the generator to obtain an electrical output.

<Condensate water supply equipment>
The condensate water supply facility mainly includes a condenser, a pump, a heater, and a deaerator.

  The condensate water supply facility cools the steam that drives the steam turbine with a condenser and collects it as condensate. This condensate is pressurized by a pump, heated by a heater, and deaerated by a deaerator. The pressurized and heated condensate is supplied to the economizer of the boiler facility as water supply for the boiler facility.

<Advantages>
Since the thermal power plant using the boiler equipment uses the operation method of the boiler, the furnace heat recovery rate is unlikely to decrease. For this reason, the thermal power plant using the boiler equipment is easy to operate stably.

[Other Embodiments]
The said embodiment does not limit the structure of this invention. Therefore, in the above-described embodiment, the components of each part of the above-described embodiment can be omitted, replaced, or added based on the description and common general knowledge of the present specification, and they are all interpreted as belonging to the scope of the present invention. Should.

  The boiler facility and the operation method of the boiler facility may be applied to a boiler facility used other than a thermal power plant.

  Moreover, in the boiler facility, the configuration of the boiler may be different from that of the above embodiment.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

(Solid fuel)
First, three types of coal were prepared as solid fuels, and a small amount of each was sampled to measure the content of ash and the content of mullite in the ash. In addition, the content rate of the ash content of coal was performed by the measuring method based on JIS-M8812 (2006), and the value of the water content base was computed. Moreover, the mullite content rate was performed by the X-ray-diffraction analysis method based on JIS-K0131 (1996). The results are shown in Table 1.

(No. 1 to No. 7)
Next, among these three types of coal, two or three types of coal were used. 1-No. The coal mixing ratio (water-containing base) 7 was selected, and the mullite content in the ash was calculated. In addition, using a coal mixture in which coal is mixed so as to have the mixing ratio shown in Table 2, a thermal boiler of a thermal power plant with a power generation capacity of 700 MW was operated for a certain period, and the average value of the furnace heat recovery rate within that period was obtained. . The results are shown in Table 2.

  In Table 2, the furnace heat recovery rate is No. It is the value normalized in terms of the ratio of 1 to the furnace heat recovery rate.

  FIG. 3 is a graph showing the results of Table 2. As shown in the figure, regardless of the type of coal to be mixed, the mullite content in the ash and the furnace heat recovery rate are highly correlated, and the reduction in the furnace heat recovery rate can be suppressed by making the mullite content below the reference value. I understand.

  Moreover, No. whose mullite content rate in ash is 33 mass% or less. 1-No. No. 6 has a furnace heat recovery rate exceeding 0.95, whereas the mullite content rate exceeds 33% by mass. In 7, the furnace heat recovery rate is less than 0.95. From this, it can be seen that by setting the reference value of the mullite content rate to 33% by mass, a high furnace heat recovery rate of 0.95 or more can be obtained.

  As described above, the boiler operating method of the present invention can suppress a decrease in the furnace heat recovery rate. Therefore, the boiler equipment using the boiler operating method is easy to operate stably. Moreover, the boiler using the operating method of the said boiler is used suitably for a thermal power plant.

DESCRIPTION OF SYMBOLS 1 Hopper 2 Mixer 3 Crusher 4 Boiler 5 Calculator 6 Supply amount adjusting device 7 Burner

Claims (5)

A method of operating a boiler that mixes and burns multiple types of solid fuel,
Acquiring the ash content in the plurality of types of solid fuel and the mullite content in the ash; and
Based on the ash content and the mullite content of each of the plurality of types of solid fuel obtained in the acquisition step, the content of the mullite in the ash content of the whole mixture of the plurality of types of solid fuel is a standard. And a step of determining a mixing ratio of the plurality of types of solid fuels so as to be equal to or lower than a value.   The boiler operating method according to claim 1, wherein the reference value is 33% by mass.   The method for operating a boiler according to claim 1 or 2, wherein the solid fuel is coal.   The boiler operating method according to claim 1, 2 or 3, which is used in a thermal power plant. A boiler facility that mixes and burns multiple types of solid fuel,
A plurality of mechanisms for supplying different types of the above solid fuels;
A mechanism for mixing a plurality of types of solid fuel supplied from the plurality of supply mechanisms;
A mechanism for pulverizing the solid fuel mixed by the mixing mechanism;
A boiler for burning the solid fuel pulverized by the pulverization mechanism;
Based on the ash content of each of the multiple types of solid fuel and the mullite content in the ash, the mullite content in the ash of the entire mixture of the multiple types of solid fuel is less than the reference value. A mechanism for determining a mixing ratio of the plurality of types of solid fuels;
A mechanism for adjusting the supply amount of each of the plurality of types of solid fuel introduced from the supply mechanism to the mixing mechanism so as to obtain a mixing ratio of the plurality of types of solid fuel determined by the determination mechanism. Boiler equipment.

Images