JP7653099B2 - How to detect the risk of malfunctions in incinerators - Google Patents

Description

The present invention relates to a method for detecting the risk of malfunction in an incinerator, which detects the risk of exhaust gas duct blockage and poor fluidization of a fluidized bed caused by the adhesiveness of incineration ash generated in a sewage sludge incinerator that incinerates sewage sludge.
The present invention also relates to a method for detecting the risk of incinerator malfunctions, which detects the risk of exhaust gas duct blockage and poor fluidization of a fluidized bed caused by adhesion of incineration ash generated in a waste incinerator that incinerates waste.

Sewage sludge generated during purification of sewage in sewage treatment plants is dehydrated and then incinerated in a sewage sludge incinerator. In the incinerator that incinerates sewage sludge, incineration ash may adhere to the exhaust gas duct, heat exchanger, etc. of the incinerator.
In addition, in a fluidized incinerator, the incineration ash adheres to the fluidized sand that forms the fluidized bed of the incineration plant.
The adhesion of this incineration ash can cause blockages in exhaust gas ducts and heat exchangers, or can cause incomplete combustion due to poor fluidity caused by clinker, which is formed when the fluidized sand in the fluidized bed adheres to each other and swells, causing serious problems in the operation of the incinerator.

In recent years, there has been an increase in problems (hereinafter, problems) occurring in sewage sludge incinerators, such as clogging of exhaust gas ducts and poor fluidization in fluidized beds, caused by the adhesiveness of incineration ash.
The cause of this is thought to be that the advanced treatment of sewage increases the concentration of phosphorus in the sludge, which in turn promotes the adhesion of incineration ash.
To address this problem, some sewage sludge incinerators add inorganic chemicals (such as hydrated lime, calcium carbonate, polyferric sulfate, polyaluminum chloride, etc.) to the sludge to suppress the adhesion of the incineration ash.

The main cause of the above problem is that ash becomes more adhesive at high temperatures. This is because components contained in ash partially melt at high temperatures to generate a liquid phase, which forms liquid bridges between ash particles, increasing the adhesiveness of the ash.
Therefore, ash, which becomes more adhesive at high temperatures, is at high risk of causing problems.

As a countermeasure against defects, a method for predicting adhesion of incineration ash in a sewage sludge incinerator has also been disclosed.
For example, Japanese Patent Application Laid-Open No. 2010-12425 discloses a technology in which _the content of _each of _the components _Fe2O3 , CaO, _Na2O , _K2O , MgO, _SiO2 , _Al2O3 , _TiO2 , and _P2O5 in incineration ash obtained by incineration in an oxidizing atmosphere is identified, and an index is calculated using a specific formula based on the elemental composition of each identified incineration ash component (see Patent Document 1).
However, the calculated index (numerical value) does not have a clear meaning, and no method is disclosed for predicting adhesion of incineration ash using "adhesive strength (tensile strength/kPa)," an index with a clear meaning (unit) as in the present invention. Also, no technology is disclosed for calculating adhesiveness (adhesive strength) using the particle size of incineration ash as a factor.

JP 2010-12425 A

There are several conventional devices for measuring the adhesive strength of a powder layer, but all of them employ a method in which a powder sample is collected and measured using an analytical device at room temperature (around 10 to 30°C), and it has not been possible to directly measure the adhesive strength of a powder layer in a high-temperature environment such as the exhaust gas duct of an incineration facility or the fluidized bed of a fluidized incinerator.
In addition, although the technology of Patent Document 1 is an index used as one of the methods for predicting the adhesion of incineration ash, as described in [0027], the briquette test is performed at 1100 degrees, and the ash adhesion is evaluated by evaluating the melting and softening property of the ash surface of the briquette. This is far from the ash adhesion environment of a sewage sludge incinerator, which is usually in the temperature range of around 800 degrees, and is considered to be unsuitable for predicting ash adhesion in a sewage sludge incinerator.

The present invention has been made in consideration of the above problems, and its object is to provide a method for detecting the risk of malfunction in an incinerator, capable of evaluating the adhesion of ash in the high-temperature environment of a sewage sludge incinerator, and detecting the risk of blockage of the incinerator's exhaust gas duct and poor fluidization of the fluidized bed.
In addition, the present invention provides a technology for detecting the risk of blockage of exhaust gas ducts and poor fluidization of the fluidized bed of sewage sludge incinerators using an adhesion prediction formula derived by multiple regression analysis using four factors that affect the adhesion of incineration ash generated in sewage sludge incinerators: phosphorus concentration, potassium concentration, iron concentration, and particle size.
In the present invention, the exhaust gas duct means a passage through which the combustion gas (exhaust gas) is discharged from the chimney, and includes passages for the combustion gas in various facilities, such as heat exchangers in incineration facilities.

〔２〕前記付着力予測式が、複数の異なる焼却灰に基づいて導出した付着力予測式（式２）であることを特徴とする〔１〕に記載の焼却炉の不具合発生危険性察知方法。

〔３〕廃棄物焼却炉で発生した焼却灰の付着力に影響を与えるリン濃度、カリウム濃度、鉄濃度及び粒子径の４つの因子を用いて、重回帰分析により導出した付着力予測式（式１）により焼却灰の付着性に起因した廃棄物焼却炉の排気ガスダクトの閉塞及び流動床の流動不良の危険性を察知することを特徴とする焼却炉の不具合発生危険性察知方法。

In order to achieve the above object, the present inventors have solved the above problems by the following means.
[ 1 ] A method for detecting the risk of malfunction in an incinerator, comprising the steps of: detecting the risk of blockage of the exhaust gas duct of a sewage sludge incinerator and poor fluidization of the fluidized bed caused by the adhesiveness of incineration ash by using an adhesive force prediction formula (Formula 1) derived by multiple regression analysis using four factors that affect the adhesive force of incineration ash generated in a sewage sludge incinerator, namely phosphorus concentration, potassium concentration, iron concentration, and particle size.

[ 2 ] The method for detecting the risk of malfunction in an incinerator described in [1] , characterized in that the adhesion prediction formula is an adhesion prediction formula (Formula 2) derived based on a plurality of different incineration ashes.

[ 3 ] A method for detecting the risk of malfunction in an incinerator, characterized in that the method detects the risk of blockage of the exhaust gas duct of a waste incinerator and poor fluidization of the fluidized bed caused by the adhesiveness of incineration ash by using an adhesive force prediction formula (Formula 1) derived by multiple regression analysis using four factors that affect the adhesive force of incineration ash generated in a waste incinerator, namely phosphorus concentration, potassium concentration, iron concentration, and particle size.

According to the present invention, it is possible to directly evaluate the adhesion of ash in a high-temperature environment in a sewage sludge incinerator, and therefore it is possible to effectively detect the risk of blockage of the exhaust gas duct of the sewage sludge incinerator and poor fluidization of the fluidized bed when incinerating sewage sludge.
In addition, by measuring the four factors of phosphorus concentration, potassium concentration, iron concentration and particle size contained in the incineration ash generated in a sewage sludge incinerator and using an adhesion force prediction equation, it is possible to effectively detect the risk of blockage of the exhaust gas duct of the sewage sludge incinerator and poor fluidization of the fluidized bed.
Furthermore, according to the present invention, the risk of clogging of the exhaust gas duct and poor fluidization of the fluidized bed of a waste incinerator having a higher combustion temperature range than that of a sewage sludge incinerator can be effectively detected.

Figure showing the adhesive strength measurement results of the incineration ash of the sample A diagram showing the relationship between the concentration of components contained in the sample and adhesive strength A diagram showing the relationship between particle size and adhesive strength of incineration ash A graph showing the relationship between the measured adhesion value of the sample and the adhesion predicted value based on the adhesion prediction formula.

The adhesion evaluation method of the present invention will be described with reference to FIGS.
Figure 1 shows the results of measuring the adhesive force of a sample incineration ash, Figure 2 shows the relationship between the concentration of components contained in the sample (percentage of the dry weight of the sample, in wt%) and adhesive force (tensile strength), Figure 3 shows the relationship between the particle size of the incineration ash and adhesive force, and Figure 4 shows the relationship between the actual adhesive force of the sample and the predicted adhesive force value based on the adhesive force prediction formula.

In order to identify factors that contribute to the clogging of exhaust gas ducts and poor fluidity in fluidized beds caused by incineration ash generated when sewage sludge is incinerated in a sewage sludge incinerator, the inventors measured the adhesion of the incineration ash of each sample using a high-temperature hanging adhesion measuring device (Hosokawa Micron Corporation, ARF1110-300-Toku KHC) for 43 samples, which were made by adding JIS test powder to 40 samples of incineration ash generated from sludge incinerators at multiple locations.

FIG. 1 is a diagram showing the results of measuring the adhesive strength of the incineration ash of the 43 samples, with the horizontal axis showing the sample name and the vertical axis showing the tensile strength (kPa).
Regarding the evaluation of the adhesion of the 43 samples, the adhesive strength of the ash powder layer at high temperatures was derived from the chemical and physical properties of the sewage sludge incineration ash by the following procedure.
The adhesive strength is expressed as tensile strength (kPa), and the temperature at which the adhesive strength was measured was 800°C, which was determined based on the general temperature inside an actual sludge incinerator. The elemental composition of each sample was measured using a fluorescent X-ray analyzer (RIX3100) manufactured by Rigaku Corporation, and the particle size (median size) was measured using a laser diffraction/scattering particle size distribution analyzer (LA-950ND) manufactured by Horiba, Ltd.

In high-temperature environments, the low-melting-point eutectic on the surface of ash particles melts, generating a liquid phase that forms liquid bridges between particles. This liquid bridge (force) is one of the factors that increases the adhesive strength of the ash powder layer, and the melting temperature varies depending on the individual components and their proportions.

On the other hand, alkali metals such as Na and K are known to be adhesion factors of incineration ash in the fields of pulverized coal-fired power generation, biomass power generation, and the like.
In order to identify the components that affect adhesion, we verified whether the adhesion of more than 20 types of elements, such as P, K, Fe, Al, Na, Cu, Zn, Ba, Ca, and Mg, contained in each sample depended on the concentration of the components.
Specifically, a graph was created in which the component concentration of each sample was plotted on the horizontal axis and the adhesive strength (tensile strength) of each sample was plotted on the vertical axis, and the verification was performed.

FIG. 2 shows the concentration dependence of adhesion on phosphorus, potassium and iron.
The figure plots the component concentration of each sample on the horizontal axis and the adhesive strength (tensile strength) of each sample on the vertical axis, and shows the concentration dependence of the adhesive strength of phosphorus, potassium, and iron.
(A) in the figure shows phosphorus, (B) shows potassium, and (C) shows iron.
As is clear from (A) and (B) of the same figure, there is a tendency for the adhesive strength of phosphorus and potassium to increase as the concentration of the components increases.
From these results, it is considered that both phosphorus and potassium are factors that increase the adhesive strength of ash.

As is clear from FIG. 1C, there is a tendency for the adhesive strength of iron to decrease as the component concentration increases.
From these results, it is considered that iron is a factor that inhibits the adhesion of ash.
In addition, except for phosphorus, potassium, and iron, which affect adhesion, it was confirmed that other components such as Al, Na, and Cu do not affect the adhesive strength of incineration ash, so these figures have been omitted.

In the case of ash powder layers, adhesion can be influenced not only by chemical factors (elemental composition) but also by physical factors (particle size and porosity).
Therefore, the adhesion strength of the ash, particle size, and porosity were also graphed and analyzed to verify the influence of physical factors.

FIG. 3 is a diagram showing the adhesive force depending on the particle size of incineration ash, which is thought to be an influencing factor of the adhesiveness of the ash powder layer.
The figure shows the dependence of particle size (median size) of incineration ash.
The figure shows that the adhesive strength tends to decrease as the particle size increases. A similar verification was also conducted for the porosity, but no clear tendency was observed.

From the above, it appears that the factors affecting ash adhesion are phosphorus, potassium, iron and particle size.
Based on this, a formula for predicting the adhesive force of incineration ash was derived using multiple regression analysis.
Regarding the adhesive strength prediction formula, a spreadsheet software with multiple regression analysis function (Microsoft Excel) was used, and the objective variable was the adhesive strength (tensile strength) of the 43 samples, and the explanatory variables were the phosphorus, potassium, and iron concentrations (wt%) of the 43 samples and the particle diameter (median diameter) of the incineration ash.
Specifically, the explanatory variables (phosphorus concentration, potassium concentration, iron concentration, and particle size) for each sample No. (1 to 43) were organized as shown in each column of Table 1, and the values in Table 1 were used to determine the horizontal axis plots of the graphs in Figures 2 and 3. The relationship with the measured adhesive force values on the vertical axis was then organized, and the adhesive force predictions described below were performed.

A multiple regression analysis was performed using the phosphorus, potassium, and iron component concentrations conceptually shown in Table 1 and the explanatory variables of particle size.
As a result, a multiple regression equation, that is, an adhesive force prediction equation (Equation 2) was obtained.

FIG. 4 is a graph in which the horizontal axis represents the actual values of adhesion measured for 43 samples using a high-temperature hanging adhesion measuring device, and the vertical axis represents the predicted values calculated from the adhesion prediction formula.
As shown in the figure, the correlation coefficient between the two was 0.82, which indicates a high correlation, and therefore the above adhesion prediction formula is valid.

As described above, according to the present invention, it is possible to evaluate the adhesion of ash in a high-temperature field of about 800 degrees in a sewage sludge incinerator, and therefore it is possible to effectively detect the risk of clogging of the exhaust gas duct of the sewage sludge incinerator and poor fluidization of the fluidized bed when incinerating sewage sludge. Furthermore, the present invention can be applied to waste incinerators and the like that have a higher combustion temperature range than sewage sludge incinerators by changing the measurement temperature range of the high-temperature hanging adhesion measuring device to a higher temperature range and evaluating the ash adhesion. Furthermore, it is also possible to apply the present invention to biomass power generation facilities and the like.

Claims (3)

A method for detecting the risk of malfunctions in an incinerator, characterized by detecting the risk of blockage of the exhaust gas duct and poor fluidization of the fluidized bed of a sewage sludge incinerator caused by the adhesiveness of incineration ash using an adhesive force prediction formula (Formula 1) derived by multiple regression analysis using four factors that affect the adhesive force of incineration ash generated in a sewage sludge incinerator: phosphorus concentration, potassium concentration, iron concentration, and particle size.

The method for detecting the risk of malfunction in an incinerator according to claim 1 , characterized in that the adhesion prediction formula is an adhesion prediction formula (Formula 2) derived based on a plurality of different incineration ashes.

A method for detecting the risk of malfunction in an incinerator, characterized by detecting the risk of blockage of the exhaust gas duct of a waste incinerator and poor fluidization of the fluidized bed caused by the adhesiveness of incineration ash using an adhesive force prediction formula (Formula 1) derived by multiple regression analysis using four factors that affect the adhesive force of incineration ash generated in a waste incinerator, namely phosphorus concentration, potassium concentration, iron concentration, and particle size.

Images