JP7514807B2 - Evaluation method for ash adhesion inhibitors - Google Patents

Description

This disclosure relates to a method for evaluating ash adhesion inhibitors.

If ash produced by fuel combustion adheres to equipment that makes up combustion facilities (boilers, combustion furnaces, etc.), it may impede heat transfer in the equipment or cause corrosion in the equipment.

Patent Document 1 describes supplying a corrosion inhibitor that has the property of attracting corrosive particles in the combustion ash of the boiler into the exhaust gas passage of the boiler in order to suppress corrosion due to ash adhesion to the heat transfer tubes installed in the exhaust gas passage of the boiler. In the method described in Patent Document 1, the corrosion inhibitor is supplied into the exhaust gas passage to cause the corrosive particles in the combustion ash to adhere to the corrosion inhibitor, thereby reducing the contact area between the corrosive particles and the heat transfer tube when ash containing the corrosive particles adheres to the heat transfer tube, thereby suppressing corrosion of the heat transfer tube.

International Publication No. 2014/192313

By using a chemical agent for suppressing ash adhesion (ash adhesion inhibitor), ash adhesion to equipment constituting the combustion equipment can be suppressed, thereby suppressing the inhibition of heat transfer and the occurrence of corrosion in the equipment caused by ash adhesion. If the effect of ash adhesion inhibition by an ash adhesion inhibitor could be evaluated using a simple method, it would be useful for selecting an ash adhesion inhibitor according to the type of fuel and for determining the amount of ash adhesion inhibitor to be used.

In view of the above circumstances, at least one embodiment of the present invention aims to provide a method for evaluating an ash adhesion inhibitor that can easily evaluate the effect of the ash adhesion inhibitor.

A method for evaluating an ash adhesion inhibitor according to at least one embodiment of the present invention includes the steps of:
A method for evaluating an ash adhesion inhibitor used in a combustion facility, comprising:
heating a fuel containing a volatile component at a first temperature to obtain a first incinerated ash containing the volatile component;
a high-temperature treatment step of heating the mixture of the first incinerated ash and the ash adhesion inhibitor at a second temperature higher than the first temperature;
a contacting step of contacting a gas produced in the high temperature treatment step with a first object made of quartz;
an evaluation step of evaluating the ash adhesion inhibitor based on a degree of devitrification caused in the first object in the contact step;
Equipped with.

According to at least one embodiment of the present invention, a method for evaluating an ash adhesion inhibitor is provided that allows the effect of the ash adhesion inhibitor to be evaluated in a simple manner.

FIG. 1 is a schematic diagram of an example of a combustion facility. 2 is a flowchart of an evaluation method for an ash deposition inhibitor according to one embodiment. 1 is a photograph showing an example of a quartz tube including a devitrified region. 1 is a graph showing an example of the weight loss rate of first incineration ash during high-temperature heat treatment. 1 is a table showing an example of the composition of first incineration ash.

Below, several embodiments of the present invention will be described with reference to the attached drawings. However, the dimensions, materials, shapes, relative positions, etc. of the components described as the embodiments or shown in the drawings are not intended to limit the scope of the present invention and are merely illustrative examples.

(Example of combustion equipment configuration)
Fig. 1 is a schematic diagram of an example of a combustion facility using an ash deposition inhibitor to which an evaluation method according to some embodiments is applied. The combustion facility 100 shown in Fig. 1 includes a boiler 10 that uses solid fuel as a main fuel.

The boiler 10 of this embodiment is a boiler that can burn pulverized solid fuel with a burner and exchange the heat generated by this combustion with feed water or steam to generate superheated steam. As the solid fuel, biomass fuel, waste fuel, coal, etc. are used alone or in combination.

The boiler 10 has a furnace 11, a combustion device 20, and a combustion gas passage 12. The furnace 11 has a hollow rectangular cylinder shape and is installed vertically. The furnace wall 101 that constitutes the inner wall surface of the furnace 11 is composed of multiple heat transfer tubes and fins that connect the heat transfer tubes to each other, and recovers the heat generated by the combustion of pulverized fuel by heat exchange with water and steam flowing inside the heat transfer tube, while suppressing the temperature rise of the furnace wall 101.

The combustion device 20 is installed in the lower region of the furnace 11. In this embodiment, the combustion device 20 has a plurality of burners 21A, 21B, 21C, 21D, 21E, and 21F (hereinafter, they may be collectively referred to as "burners 21") attached to the furnace wall 101. The burners 21 are arranged in a plurality of stages along the vertical direction, with each set being arranged at equal intervals along the circumferential direction of the furnace 11 (for example, four burners installed at each corner of the rectangular furnace 11). Note that, for convenience of illustration, only two burners of one set are shown in FIG. 1, and each set is given the reference numerals 21A, 21B, 21C, 21D, 21E, and 21F. The shape of the furnace, the number of burner stages, the number of burners in one stage, the arrangement of the burners, and the like are not limited to this embodiment.

Burners 21A, 21B, 21C, 21D, 21E, and 21F are connected to fuel supply units 31A, 31B, 31C, 31D, 31E, and 31F (hereinafter, sometimes collectively referred to as "fuel supply unit 31") via multiple pulverized fuel supply pipes 22A, 22B, 22C, 22D, 22E, and 22F (hereinafter, sometimes collectively referred to as "pulverized fuel supply pipes 22"). The fuel supply unit 31 may include a mill (crusher) for pulverizing the solid fuel. The mill is, for example, a vertical roller mill in which a crushing table (not shown) is supported inside so as to be driven and rotatable, and multiple crushing rollers (not shown) are supported above the crushing table so as to be rotatable in conjunction with the rotation of the crushing table. The solid fuel pulverized by the cooperation of the pulverizing roller and the pulverizing table is transported to a classifier (not shown) equipped in the mill by primary air (carrier gas, oxidizing gas) supplied to the mill. In the classifier, the fuel is classified into fine pulverized fuel with a particle size smaller than that suitable for combustion in the burner 21 and coarse pulverized fuel with a larger particle size. The fine pulverized fuel passes through the classifier and is supplied to the burner 21 together with the primary air via the fine pulverized fuel supply pipe 22. The coarse pulverized fuel that does not pass through the classifier falls onto the pulverizing table by its own weight inside the mill and is pulverized again.

An air register 23 is provided on the outside of the furnace 11 at the installation position of the burner 21, and one end of an air duct 24 is connected to the air register 23. A forced draft fan (FDF) 32 is connected to the other end of the air duct 24. The air supplied from the forced draft fan 32 is heated by an air preheater 42 installed in the air duct 24, and is supplied to the burner 21 via the air register 23 as secondary air (combustion air, oxidizing gas), and is introduced into the furnace 11.

The combustion gas passage 12 is connected to the vertical upper part of the furnace 11. The combustion gas passage 12 is provided with superheaters 102A, 102B, and 102C (hereinafter, sometimes collectively referred to as "superheaters 102"), reheaters 103A and 103B (hereinafter, sometimes collectively referred to as "reheaters 103"), and a coal economizer 104 as heat exchangers for recovering heat from the combustion gas, and heat is exchanged between the combustion gas generated in the furnace 11 and the feed water or steam flowing inside each heat exchanger. The arrangement and shape of each heat exchanger are not limited to the form shown in FIG. 1.

The flue 13 is connected downstream of the combustion gas passage 12, and discharges the combustion gas whose heat has been recovered by the heat exchanger. An air preheater (air heater) 42 is provided between the flue 13 and the wind duct 24, and heat is exchanged between the air flowing through the wind duct 24 and the combustion gas flowing through the flue 13. By heating the primary air supplied to the fuel supply unit 31 (for example, the mill mentioned above) and the secondary air supplied to the burner 21, further heat is recovered from the combustion gas after heat exchange with water and steam.

Further, a denitration device 43 may be provided in the flue 13 at a position upstream of the air preheater 42. The denitration device 43 supplies a reducing agent having an effect of reducing nitrogen oxides, such as ammonia or urea water, to the combustion gas flowing through the flue 13, and promotes a reaction between the nitrogen oxides (NOx) in the combustion gas to which the reducing agent has been supplied and the reducing agent by the catalytic action of a denitration catalyst provided in the denitration device 43, thereby removing and reducing the nitrogen oxides in the combustion gas.
A gas duct 41 is connected to the flue 13 downstream of the air preheater 42. The gas duct 41 is provided with environmental equipment such as a dust collector 44 such as an electric dust collector for removing ash and the like from the combustion gas, a desulfurization equipment 46 for removing sulfur oxides, and an induced draft fan (IDF) 45 for directing the exhaust gas to these environmental equipment. The downstream end of the gas duct 41 is connected to a chimney 47, and the combustion gas treated in the environmental equipment is discharged to the outside of the system as exhaust gas.

In the boiler 10, fuel from the fuel supply section 31 (e.g., pulverized fuel crushed and classified by a mill) is supplied to the burner 21 together with primary air via the pulverized fuel supply pipe 22. Secondary air heated by the air preheater 42 is supplied to the burner 21 from the air duct 24 through the wind box 23. The burner 21 blows a pulverized fuel mixture of pulverized fuel and primary air into the furnace 11, and also blows secondary air into the furnace 11. The pulverized fuel mixture blown into the furnace 11 ignites and reacts with the secondary air to form a flame. A flame is formed in the lower region of the furnace 11, and high-temperature combustion gas rises inside the furnace 11 and flows into the combustion gas passage 12. In this embodiment, air is used as the oxidizing gas (primary air, secondary air), but it may be a gas with a higher or lower oxygen content than air, and stable combustion can be achieved in the furnace 11 by adjusting the ratio of the amount of oxygen to the amount of fuel supplied within an appropriate range.

The combustion gas that flows into the combustion gas passage 12 exchanges heat with water and steam in the superheater 102, reheater 103, and economizer 104 arranged inside the combustion gas passage 12, and is then discharged into the flue 13, where nitrogen oxides are removed in the denitration device 43, and the gas exchanges heat with primary air and secondary air in the air preheater 42, before being discharged into the gas duct 41, where ash and other particles are removed in the dust collector 44, and sulfur oxides are removed in the desulfurization device 46, before being discharged from the chimney 47 to the outside of the system. Note that the arrangement of each heat exchanger in the combustion gas passage 12 and each device from the flue 13 to the gas duct 41 does not necessarily have to be in the order described above with respect to the combustion gas flow.

In the above-described embodiment, the boiler of the present invention has been described as a boiler that uses solid fuel as fuel. The solid fuel used in the boiler may be coal, biomass fuel, petroleum coke (PC) fuel, petroleum residue, or the like.
The fuel for the boiler is not limited to solid fuels, but can also be petroleum such as heavy oil, light oil, and heavy oil, liquid fuels such as industrial wastewater, etc. Also, gaseous fuels such as natural gas, various petroleum gases, and by-product gases generated in the steelmaking process can also be used.
Furthermore, the present invention can be applied to a multi-fuel boiler that uses a combination of these various fuels.

The fuel supplied from the fuel supply unit 31 to the furnace 11 may be a fuel containing an alkali metal (such as sodium (Na) or potassium (K)) or a heavy metal (such as zinc (Zn) or lead (Pb)). The fuel may be a biomass fuel containing biomass, or a waste fuel containing waste such as urban waste and building materials. The fuel may also be coal, or a mixed fuel containing two or more of biomass, waste, and coal.

In the furnace 11, combustion gas and ash are generated by the combustion of fuel. Some of the ash accumulates at the bottom of the furnace 11 and is discharged to the outside of the furnace 11 via an ash discharge section (not shown). In addition, some of the ash is entrained in the combustion gas as fly ash and is guided to the fuel gas passage 12 and the flue 13.

The ash adhesion inhibitor to which the evaluation method according to some embodiments is applied may be supplied to the furnace 11 together with the fuel from the fuel supply unit 31 or the like in the combustion equipment 100, or the ash adhesion inhibitor may be supplied to a position other than the fuel supply position (e.g., inside the furnace 11, the combustion gas passage 12, or the flue 13).

(Flow of evaluation method for ash adhesion inhibitors)
Next, a method for evaluating an ash adhesion inhibitor according to some embodiments will be described with reference to Fig. 2. Fig. 2 is a flow chart of a method for evaluating an ash adhesion inhibitor according to one embodiment.

In the method for evaluating an ash adhesion inhibitor shown in the flowchart in Figure 2, first, a fuel containing volatile components is heated at a first temperature to obtain a first incinerated ash containing volatile components such as alkali metal compounds or heavy metal compounds (S2).

The fuel containing volatile components used in step S2 is a fuel that is assumed to be used in a combustion facility together with the ash adhesion inhibitor to be evaluated. The volatile components contained in the fuel are components that cause the ash generated when the fuel is burned to adhere to the equipment of the combustion facility (for example, the heat transfer tubes constituting the above-mentioned superheater 102, reheater 103, or economizer 104, and the heat transfer tubes constituting the furnace wall 101, etc.). The volatile components may include metal element compounds. Examples of volatile components include alkali metal (sodium (Na) or potassium (K) etc.) compounds, or heavy metal (zinc (Zn) or lead (Pb) etc.) compounds. An example of a fuel that relatively generates alkali metal compounds as volatile components is biomass fuel containing biomass (woody biomass etc.). An example of a fuel that relatively generates heavy metal compounds as volatile components is waste fuel containing waste (waste plastic, urban waste, building materials etc.).

The first temperature in step S2 is a temperature at which the fuel can be heated while suppressing the volatilization of the volatile components contained in the fuel, and incinerated ash that retains the volatile components can be obtained. By heating the fuel at such a first temperature to obtain first incinerated ash that contains the volatile components, the effect of the ash adhesion inhibitor in suppressing the volatilization of alkali metals during fuel combustion (i.e., the effect of suppressing ash adhesion in combustion equipment) can be appropriately evaluated by performing the subsequent steps (high-temperature treatment, contact, and evaluation steps).

Note that the first temperature does not necessarily refer to the temperature at one point. In other words, while the fuel is being heated in step S2, the first temperature may fluctuate within a certain temperature range (e.g., within a range of several degrees Celsius to several tens of degrees Celsius).

If the fuel is a biomass fuel, the first temperature may be between 500° C. and 650° C. If the fuel is a waste-derived fuel, the first temperature may be between 500° C. and 650° C.

Next, the mixture of the first incinerated ash and the ash adhesion inhibitor obtained in step S2 is heated at a second temperature higher than the first temperature (S4; high temperature treatment step). In step S4, the first incinerated ash is heated at a temperature close to the temperature of the combustion equipment, simulating the reaction between the incinerated ash and the ash adhesion inhibitor that occurs in the combustion equipment.

The ash adhesion inhibitor used in step S4 has the function of suppressing the evaporation of volatile components during the combustion of fuel in the combustion equipment.

When the fuel used in step S2 contains an alkali metal element as a volatile component, or when the fuel used in step S2 is a biomass fuel, the above-mentioned ash adhesion inhibitor may be, for example, an aluminum-containing silicate compound such as kaolinite, halloysite, or bentonite, or silica.

When the fuel used in step S2 contains heavy metal elements as volatile components, or when the fuel used in step S2 is waste fuel, the ash adhesion inhibitor may be, for example, a sulfur-containing substance. The sulfur-containing substance may be sulfur or a sulfur compound. The sulfur compound may be, for example, a sulfuric acid-containing substance such as sulfuric acid or fuming sulfuric acid, or a sulfate such as iron sulfate, aluminum sulfate, ammonium sulfate, or ammonium hydrogen sulfate.

The second temperature in step S4 is a high temperature close to the temperature at a location inside the combustion equipment where ash adhesion problems may occur (for example, the heat transfer tubes constituting the above-mentioned superheater 102, reheater 103, or economizer 104, or the heat transfer tubes constituting the furnace wall 101) or a location upstream of the location, and is a temperature at which the soundness of the quartz object used in step S6 described below can be guaranteed (for example, a temperature at which devitrification due to high temperatures is unlikely to occur). The second temperature may be, for example, 1300°C or higher and 1500°C or lower. Note that the second temperature does not necessarily refer to the temperature at one point. In other words, during the heating of the mixture in step S4, the second temperature may fluctuate within a certain temperature range (for example, within a range of several degrees Celsius to several tens of degrees Celsius).

Next, in step S4, the mixture of the first ashing ash and the ash adhesion inhibitor is heated at the second temperature to produce a gas, which is then brought into contact with the first object made of quartz (S6; contact step).

The shape of the first object is not particularly limited. The first object may have a shape such as a tube with openings at both ends, a test tube, a crucible, a beaker, a dish, a rectangular container, a plate, a cell, etc.

Depending on the shape of the first object, steps S4 and S6 may be performed as follows. In one embodiment, with the above-mentioned mixture placed inside the first object or with the mixture placed on the first object, the first object and the mixture may be heated at the second temperature while the gas generated by heating is brought into contact with the first object (i.e., steps S4 and S6 may be performed simultaneously). Alternatively, in one embodiment, the mixture may be placed in a container (such as a melting crucible) separate from the first object and heated at the second temperature (step S4), and the gas generated thereby may be guided to the first object and brought into contact with the first object (step S6).

Next, the ash adhesion inhibitor is evaluated based on the degree of devitrification that occurred in the first object in step S5 (S8; evaluation step).

The inventors have found that the degree of devitrification that occurs in quartz when the gas produced by high-temperature treatment of a mixture of incinerated fuel ash and an ash adhesion inhibitor acts on quartz varies depending on the mixture ratio of the fuel and the ash adhesion inhibitor or on the type of fuel.

The mechanism of ash adhesion in combustion equipment discovered by the inventors is as follows. That is, volatile components contained in the fuel (alkali metal elements, heavy metal elements, etc.) volatilize from the fuel or combustion ash as, for example, hydroxides during combustion of the fuel in the combustion equipment, and then condense in the form of, for example, carbonates on the surface of equipment (heat transfer tubes, etc.) at relatively low temperatures in the combustion equipment to form an initial adhesion layer. The surface of the initial adhesion layer is then exposed to high temperatures and melts, and ash adheres to this molten part. The surface temperature increases as the thickness of the attached ash increases, and the surface part melts, accelerating the adhesion of ash. In this way, the ash adhesion layer grows. That is, the volatilization of volatile components contained in the fuel (alkali metals, heavy metals, etc.) in the combustion equipment can be a factor in ash adhesion to the equipment.

Here, the relationship between the effect of the ash adhesion inhibitor in suppressing ash adhesion and the devitrification of quartz can be explained as follows. The occurrence of devitrification in quartz by contacting the gas generated in the above-mentioned high-temperature treatment step (S4; a step of treating a mixture of fuel incineration ash and ash adhesion inhibitor at high temperature) simulating the phenomenon in a combustion facility with quartz indicates that the volatile components in the fuel (in the incineration ash) volatilized and acted on the quartz. This is thought to be because, although the devitrification of quartz occurs due to a change in the crystal structure, the action of the volatile components (alkali metal compounds or heavy metal compounds, etc.) evaporated on the surface of the quartz promotes the change in the crystal structure of the quartz.

On the other hand, the small degree of devitrification of the quartz caused by contacting the gas generated in the same step (high-temperature treatment step) with the quartz indicates that the volatilization of the volatile components in the fuel (in the incinerated ash) was suppressed by the ash adhesion inhibitor. Therefore, it is believed that the smaller the degree of devitrification of the quartz, the more the ash adhesion inhibitor can suppress the volatilization of the volatile components when the target fuel is used, and the greater the ash adhesion suppression effect can be obtained.

Therefore, according to the method of steps S1 to S8 described above, the ash adhesion inhibition effect of the ash adhesion inhibitor when the fuel is used in a combustion facility can be appropriately evaluated in a simple manner based on the degree of devitrification that occurs in the first substance made of quartz when the gas produced by high-temperature treatment of the mixture of the first incinerated ash obtained by heating the fuel and the ash adhesion inhibitor acts on the first substance.

In step S8, the ash adhesion suppression effect of the ash adhesion suppression agent may be evaluated based on the size of the devitrified region of the first object. In this case, for example, the smaller the devitrified region that occurs in the first object, the higher the ash adhesion suppression effect of the ash adhesion suppression agent can be evaluated.

The size of the devitrified region may be measured visually, for example, using a measuring instrument such as a scale or a caliper. Alternatively, the size of the devitrified region may be measured by applying known optical measurement techniques, such as measuring absorbance by absorptiometry or measuring scattered light intensity by irradiating a laser beam.

In step S8, the ash adhesion suppression effect of the ash adhesion suppression agent may be evaluated based on the transmittance of the devitrified region of the first object. In this case, for example, the ash adhesion suppression effect of the ash adhesion suppression agent can be evaluated as being higher the greater the transmittance of the devitrified region generated in the first object.

The transmittance of the devitrified region may be measured, for example, visually. Alternatively, the transmittance of the devitrified region may be measured by applying known optical measurement techniques, such as measuring absorbance by absorptiometry or measuring scattered light intensity by irradiating the region with laser light.

The method for evaluating an ash adhesion inhibitor according to some embodiments further includes a step of heating a reference fuel different from the above-mentioned fuel (the fuel heated in step S2) at a third temperature to produce a second incinerated ash, and then heating the second incinerated ash at a fourth temperature higher than the third temperature to produce a gas, which is then brought into contact with a second object made of quartz. Then, in step S8 (evaluation step), the ash adhesion inhibitor is evaluated based on a comparison between the degree of devitrification caused in the first object in step S6 and the degree of devitrification caused in the second object.

According to the above-described embodiment, by comparing the degree of devitrification that occurs in a second object made of quartz due to contact between the gas produced by high-temperature treatment of incinerated ash of a reference fuel that has a proven track record of being less prone to ash adhesion in combustion equipment and the second object, and the degree of devitrification that occurs in a first object through the procedure of steps S2 to S6, it is possible to easily and appropriately determine whether or not the fuel used in step S2 and/or the ash adhesion inhibitor used together with the fuel can be used in a combustion equipment.

That is, the degree of devitrification caused in the second object by the high-temperature treatment of the incinerated ash of the reference fuel according to the above-mentioned procedure serves as a criterion for determining whether the fuel and/or ash adhesion inhibitor to be evaluated (the fuel and/or ash adhesion inhibitor used in steps S2 to S6) is suitable for use in a combustion facility. For example, if the degree of devitrification caused in the first object is equal to or less than the degree of devitrification in the second object, it can be determined that the fuel and/or ash adhesion inhibitor to be evaluated is suitable for use in a combustion facility. If the degree of devitrification caused in the first object is greater than the degree of devitrification in the second object, it can be determined that the fuel and/or ash adhesion inhibitor to be evaluated is unsuitable for use in a combustion facility.

The shape of the second object may be the same as the shape of the first object. In this case, it becomes easier to compare the degree of devitrification that has occurred in the first object with the degree of devitrification that has occurred in the second object.

(Example)
The above steps S1 to S6 were carried out using the following amounts of biomass fuel and ash adhesion inhibitor (Examples 1 to 3). Note that the biomass fuel and ash adhesion inhibitor used in Examples 1 to 3 were the same.
Example 1...Biomass fuel: A, ash adhesion inhibitor = 0
Example 2...Biomass fuel: A, ash adhesion inhibitor = B
Example 3...Biomass fuel: A, ash adhesion inhibitor = twice the amount of B in Example 2

Specifically, the following procedure was performed for each of Examples 1 to 3. First, the biomass fuel was heated at 600°C to obtain the first incinerated ash. Next, the first incinerated ash was mixed with a predetermined amount of ash adhesion inhibitor, placed in a quartz tube, and heated at 1300°C to 1500°C (high-temperature treatment step). The gas generated in the quartz tube was brought into contact with the inner wall surface of the quartz tube (contact step). Note that in Example 1, in the high-temperature treatment step, the ash adhesion inhibitor was not mixed in, and only the first incinerated ash was placed in the quartz tube and heated at 1300°C to 1500°C.

Figure 3 is a photograph showing the results of carrying out the above procedure for Examples 1 to 3. From Figure 3, it can be seen that in each of Examples 1 to 3, devitrification (devitrified regions R1 to R3 that appear white) occurred in the originally transparent quartz tube.

When comparing the lengths of the devitrification regions R1 to R3 (lengths in the longitudinal direction of the quartz tube) of Examples 1 to 3 measured on a scale, when the length of the devitrification region R1 of Example 1 is taken as 1, the length of the devitrification region R2 of Example 2 is 0.77, and the length of the devitrification region R3 of Example 3 is 0.24. In other words, among Examples 1 to 3, Example 1, which does not use an ash adhesion inhibitor, has the greatest degree of devitrification, and Example 3, which uses the greatest amount of ash adhesion inhibitor, has the smallest degree of devitrification. This shows that the ash adhesion inhibitor suppresses the devitrification of the quartz tube (i.e., suppresses the volatilization of volatile components during biomass fuel combustion). It can also be seen that the effect of suppressing devitrification can change depending on the amount of ash adhesion inhibitor. These facts show that the effect of the ash adhesion inhibitor can be evaluated based on the size of the devitrification region.

When comparing the transmittance of the devitrified regions R1 to R3 of Examples 1 to 3 with the naked eye, the transmittance of the devitrified region R1 of Example 1 and the devitrified region of Example 2 is relatively low, while the transmittance of the devitrified region R3 of Example 3 is relatively high. In other words, among Examples 1 to 3, the degree of devitrification of Examples 1 and 2 is relatively large, while the degree of devitrification of Example 3, which uses the largest amount of ash adhesion inhibitor, is relatively small. This shows that the ash adhesion inhibitor suppresses the devitrification of the quartz tube (i.e., suppresses the volatilization of volatile components during biomass fuel combustion). It is also clear that the effect of suppressing devitrification can change depending on the amount of ash adhesion inhibitor. These facts show that the effect of the ash adhesion inhibitor can be evaluated based on the transmittance of the devitrified region.

Figure 4 is a graph showing the weight loss of biomass fuel before and after the high-temperature treatment step (a step in which the mixture of the first incineration ash and/or the ash adhesion inhibitor is heated at 1300°C to 1500°C in a quartz tube) for each of Examples 1 to 3. Figure 5 is a table showing the composition of the first incineration ash (Examples 1 to 3) before the high-temperature treatment step is performed.

4, the weight loss from the first incineration ash was 43.5 wt % in Example 1, 22.6 wt % in Example 2, and 11.1 wt % in Example 3. Therefore, it can be seen that the amount of components volatilized in the high-temperature treatment step was greatest in the order of Example 1, Example 2, and Example 3.

Furthermore, among the components of the incinerated ash shown in the table of Fig. 5, the total concentration of _SO3 , _Na2O , _K2O , carbonate, moisture and other components that are considered to be volatile components is 47.3 wt%. This value is similar to the weight loss (43.5 wt%) of the biomass fuel in Example 1 shown in the graph of Fig. 4. From this, it is considered that in Example 1, the alkali metal (Na and K) compounds were volatilized by performing the high-temperature treatment step. Furthermore, in Examples 2 and 3, it is considered that not all of the alkali metal (Na and K) compounds were volatilized even after the high-temperature treatment step.

These findings indicate that there is a correlation between the degree of devitrification of the quartz tube and the effect of the ash adhesion inhibitor in inhibiting the evaporation of volatile components (i.e., the ash adhesion inhibition effect).

The contents described in each of the above embodiments can be understood, for example, as follows:

(1) A method for evaluating an ash adhesion inhibitor according to at least one embodiment of the present invention includes the steps of:
A method for evaluating an ash adhesion inhibitor used in a combustion facility (100), comprising:
A step (S2) of heating the fuel containing the volatile components at a first temperature to obtain a first incinerated ash containing the volatile components;
a high-temperature treatment step (S4) of heating the mixture of the first incinerated ash and the ash adhesion inhibitor at a second temperature higher than the first temperature;
A contacting step (S6) of contacting the gas generated in the high-temperature treatment step with a first object made of quartz;
an evaluation step (S8) of evaluating the ash adhesion inhibitor based on the degree of devitrification caused in the first object in the contact step;
Equipped with.

The inventors have found that the degree of devitrification that occurs in quartz when the gas produced by high-temperature treatment of a mixture of incinerated fuel ash and an ash adhesion inhibitor acts on quartz varies depending on the mixture ratio of the fuel and the ash adhesion inhibitor or on the type of fuel.

The relationship between the effect of ash adhesion inhibitors in suppressing ash adhesion and devitrification of quartz can be explained as follows. In other words, the volatile components contained in fuel evaporate during combustion of the fuel in the combustion equipment and then solidify on the surface of the equipment (heat transfer tubes, etc.), which can cause ash adhesion to the equipment. Here, the occurrence of devitrification in quartz by contacting the gas generated in the high-temperature treatment step (a step in which a mixture of fuel incineration ash and ash adhesion inhibitor is treated at high temperature) that simulates the phenomenon in the combustion equipment with quartz indicates that the volatile components in the fuel (in the incineration ash) volatilized and acted on the quartz. On the other hand, the small degree of devitrification that occurred in quartz by contacting the gas generated in the same step with quartz indicates that the volatilization of the volatile components in the fuel (in the incineration ash) was suppressed by the ash adhesion inhibitor. Therefore, it is considered that the smaller the degree of devitrification of quartz, the more the ash adhesion inhibitor suppresses the volatilization of volatile components during use of the target fuel, and the higher the ash adhesion suppression effect can be obtained.

According to the method (1) above, the ash adhesion suppression effect of the ash adhesion suppression agent when the fuel is used in a combustion facility can be appropriately evaluated in a simple manner based on the degree of devitrification that occurs in the first substance made of quartz when the gas generated by high-temperature treatment of a mixture of incinerated ash of the fuel and the ash adhesion suppression agent acts on the first substance.

(2) In some embodiments, in the method of (1),
The volatile component includes an alkali metal,
The ash adhesion inhibitor includes an aluminum-containing silicate compound.

Alkali metals (alkali metal compounds), which are relatively abundant in biomass fuels, etc., can be a cause of ash adhesion to equipment by volatilizing during combustion of the fuel and then solidifying on the surface of the equipment. In this regard, according to the method (2) above, the ash adhesion inhibition effect of the ash adhesion inhibitor containing an aluminum-containing silicate compound when the fuel is used in a combustion facility can be appropriately evaluated in a simple manner based on the degree of devitrification that occurs in a first substance made of quartz when the first substance is subjected to the gas generated by high-temperature treatment of a mixture of incinerated ash of the fuel and an ash adhesion inhibitor containing an aluminum-containing silicate compound.

(3) In some embodiments, in the method of (1) or (2),
The volatile component includes an alkali metal,
The ash adhesion inhibitor includes kaolinite, halloysite, pyrophyllite, bentonite or silica.

Alkali metals (alkali metal compounds) contained in relatively large amounts in biomass fuels, etc., can be a cause of ash adhesion to equipment by volatilizing during combustion of the fuel and then solidifying on the surface of the equipment. In this regard, according to the method of (3) above, the ash adhesion inhibition effect of the ash adhesion inhibitor containing the above-mentioned substance when the fuel is used in a combustion facility can be appropriately evaluated in a simple manner based on the degree of devitrification that occurs in a first substance made of quartz when the first substance is subjected to the gas generated by high-temperature treatment of a mixture of incinerated ash of the fuel and an ash adhesion inhibitor containing kaolinite, halloysite, bentonite or silica.

(4) In some embodiments, in the method of (1),
The volatile components include heavy metals,
The ash deposition inhibitor includes a sulfur-containing substance.

Heavy metals (heavy metal compounds) contained in relatively large amounts in waste fuels, etc., can become a cause of ash adhesion to equipment by volatilizing during combustion of the fuel, etc., and then solidifying on the surface of the equipment. In this regard, according to the method of (4) above, the ash adhesion inhibition effect of the ash adhesion inhibitor containing a sulfur-containing substance when the fuel is used in a combustion facility can be appropriately evaluated in a simple manner based on the degree of devitrification that occurs in a first substance made of quartz when the first substance is subjected to the gas generated by high-temperature treatment of a mixture of incinerated ash of the fuel and an ash adhesion inhibitor containing a sulfur-containing substance.

(5) In some embodiments, in any of the methods (1) to (4) above,
In the evaluation step, the ash adhesion inhibitor is evaluated based on the size of the devitrified regions (R1 to R3) of the first object.

According to the method of (5) above, the ash adhesion suppression effect of the ash adhesion inhibitor when the fuel is used in a combustion facility can be appropriately evaluated in a simple manner based on the size of the devitrified region that occurs in the first object made of quartz. For example, it can be evaluated that the smaller the devitrified region that occurs in the first object, the higher the ash adhesion suppression effect of the ash adhesion inhibitor.

(6) In some embodiments, in any of the methods (1) to (5) above,
In the evaluation step, the ash adhesion inhibitor is evaluated based on the transmittance of the devitrified regions (R1 to R3) of the first object.

According to the method (6) above, the ash adhesion suppression effect of the ash adhesion inhibitor when the fuel is used in a combustion facility can be appropriately evaluated in a simple manner based on the transmittance of the devitrified region that occurs in the first object made of quartz. For example, it can be evaluated that the ash adhesion suppression effect of the ash adhesion inhibitor is higher when the transmittance of the devitrified region that occurs in the first object is higher.

(7) In some embodiments, in any of the methods (1) to (6) above,
the fuel comprises biomass;
The first temperature is not less than 500° C. and not more than 650° C.

According to the method (7) above, biomass fuel, which generally contains a relatively large amount of alkali metals, is heated in a temperature range of 500°C to 650°C to obtain incinerated ash, so that the volatilization of alkali metals during heating is suppressed and incinerated ash that retains alkali metal compounds (volatile components) can be obtained. Therefore, by performing the subsequent steps (high-temperature treatment, contact, and evaluation steps), the effect of the ash adhesion inhibitor in suppressing the volatilization of alkali metal compounds during fuel combustion (i.e., the effect of suppressing ash adhesion in combustion equipment) can be evaluated.

(8) In some embodiments, in any of the methods (1) to (7) above,
The method includes a step of heating a reference fuel different from the fuel at a third temperature to obtain a second incinerated ash, and heating the second incinerated ash at a fourth temperature higher than the third temperature to produce a gas, and contacting the gas with a second object made of quartz;
In the evaluation step, the ash adhesion inhibitor is evaluated based on a comparison between a degree of devitrification caused in the first object and a degree of devitrification caused in the second object.

According to the method (8) above, by comparing the degree of devitrification that occurs in a second object made of quartz due to contact between the gas produced by high-temperature treatment of incinerated ash of a reference fuel that has a proven track record of being less prone to ash adhesion in combustion equipment and the second object, with the degree of devitrification that occurs in a first object by the procedure (1) above, it is possible to easily and appropriately determine the suitability of using the fuel used in the procedure (1) above and/or the ash adhesion inhibitor used together with the fuel in a combustion equipment.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and also includes variations on the above-described embodiments and appropriate combinations of these embodiments.

In this specification, expressions expressing relative or absolute configuration, such as "in a certain direction,""along a certain direction,""parallel,""orthogonal,""center,""concentric," or "coaxial," do not only strictly express such a configuration, but also express a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained.
For example, expressions indicating that things are in an equal state, such as "identical,""equal," and "homogeneous," not only indicate a state of strict equality, but also indicate a state in which there is a tolerance or a difference to the extent that the same function is obtained.
Furthermore, in this specification, expressions describing shapes such as a rectangular shape or a cylindrical shape do not only refer to shapes such as a rectangular shape or a cylindrical shape in the strict geometric sense, but also refer to shapes that include uneven portions, chamfered portions, etc., to the extent that the same effect can be obtained.
In addition, in this specification, the expressions "comprise,""include," or "have" a certain element are not exclusive expressions that exclude the presence of other elements.

10 Boiler 11 Furnace 12 Combustion gas passage 12 Fuel gas passage 13 Flue 20 Combustion device 21, 21A to 21F Burner 22, 22A to 22F Pulverized fuel supply pipe 23 Wind box 24 Wind duct 31, 31A to 31F Fuel supply section 32 Forced draft fan 41 Gas duct 42 Air preheater 43 Denitrification device 44 Device 46 Desulfurization device 47 Chimney 100 Combustion equipment 101 Furnace wall 102, 102A to 102C Superheater 103, 103A to 103B Reheater 104 Economizer R1 to R3 Devitrification area

Claims (8)

A method for evaluating an ash adhesion inhibitor used in a combustion facility, comprising:
heating a fuel containing a volatile component at a first temperature to obtain a first incinerated ash containing the volatile component;
a high-temperature treatment step of heating the mixture of the first incinerated ash and the ash adhesion inhibitor at a second temperature higher than the first temperature;
a contacting step of contacting a gas produced in the high temperature treatment step with a first object made of quartz;
an evaluation step of evaluating the ash adhesion inhibitor based on a degree of devitrification caused in the first object in the contact step;
A method for evaluating an ash deposition inhibitor comprising the steps of: The volatile component includes an alkali metal,
The method for evaluating an ash deposition inhibitor according to claim 1 , wherein the ash deposition inhibitor comprises an aluminum-containing silicate compound. The volatile component includes an alkali metal,
The method for evaluating an ash adhesion inhibitor according to claim 1 or 2, wherein the ash adhesion inhibitor contains kaolinite, halloysite, bentonite or silica. The volatile components include heavy metals,
The method for evaluating an ash deposition inhibitor according to claim 1 , wherein the ash deposition inhibitor contains a sulfur-containing substance. The method for evaluating an ash adhesion inhibitor according to claim 1 , wherein in the evaluation step, the ash adhesion inhibitor is evaluated based on a size of a devitrified region of the first object. The method for evaluating an ash adhesion inhibitor according to claim 1 , wherein in the evaluation step, the ash adhesion inhibitor is evaluated based on a transmittance of a devitrified region of the first object. the fuel comprises biomass;
The method for evaluating an ash deposition inhibitor according to any one of claims 1 to 6, wherein the first temperature is 500°C or higher and 650°C or lower. The method includes a step of heating a reference fuel different from the fuel at a third temperature to obtain a second incinerated ash, and heating the second incinerated ash at a fourth temperature higher than the third temperature to produce a gas, and contacting the gas with a second object made of quartz;
The evaluation method for an ash adhesion inhibitor according to any one of claims 1 to 7, wherein in the evaluation step, the ash adhesion inhibitor is evaluated based on a comparison between a degree of devitrification caused in the first object and a degree of devitrification caused in the second object.

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