JP2005195270A - Operation method of fluidized bed incinerator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an operation method of a fluidized bed incinerator, preventing the occurrence of flowing failure due to fixing of mutual bed materials to decrease the frequency of stopping operation in incinerating waste containing a large quantity of alkaline metals and cleaning in the incinerator, and continuing stable operation. <P>SOLUTION: The temperature in the bed of the incinerator body 1 for burning the waste 6 while being fluidized with the bed material 2 is controlled to a target temperature or lower to prevent the occurrence of flowing failure due to fixing of mutual bed materials 2, that is, about 600°C. Inorganic chemical compound additive such as dolomite, magnesium hydroxide or limestone is added to the bed material 2 to use sand having high thermal crush resistance as the bed material 2. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for operating a fluidized bed incinerator.

  Conventionally, fluidized bed incinerators have been used as means for incinerating waste.

In the fluidized bed incinerator, waste material is supplied to the fluidized bed from a dust feeder in a state where a fluidized bed is formed by bubbling a bed material such as silica sand (SiO ₂ ) with air blown from a diffuser tube. The waste is combusted while being fluidized together with the bed material.

Patent Document 1 is an example of a fluidized bed boiler operating method related to the fluidized bed incinerator as described above.
JP 2003-240210 A

  However, in the fluidized bed incinerator as described above, when the waste to be incinerated contains a large amount of alkali metals (sodium and potassium), the bed materials adhere to each other and flow failure occurs. It had the disadvantage that cleaning of the incinerator was forced.

  For this reason, wastes with a high alkali metal concentration can only be incinerated or mixed with other wastes in small amounts and incinerated.

  In view of such circumstances, the present invention can prevent the occurrence of poor flow due to the sticking of bed materials when incinerating waste containing a large amount of alkali metal, and the frequency of shutdown and incinerator cleaning. It is an object of the present invention to provide a method for operating a fluidized bed incinerator capable of reducing the amount of heat and continuing stable operation.

  The present invention controls a fluidized bed incinerator operating method in which waste is combusted while being fluidized together with a bed material, and the temperature in the bed is controlled to be equal to or lower than a target temperature capable of preventing the occurrence of a flow failure due to adhesion between the bed materials. The present invention relates to a method for operating a fluidized bed incinerator.

  In the operation method of the fluidized bed incinerator, the target temperature capable of preventing the occurrence of flow failure due to the fixation of the bed materials can be set to about 600 [° C.].

  According to the above means, the following operation can be obtained.

When the waste to be incinerated contains a large amount of alkali metals (sodium and potassium), the alkali metal compounds produced in the fluidized bed are sodium carbonate (Na ₂ CO ₃ ), sodium sulfate (Na ₂ SO). ₄ ), sodium chloride (NaCl), potassium carbonate (K ₂ CO ₃ ), potassium sulfate (K ₂ SO ₄ ), potassium chloride (KCl), etc., these alkali metal compounds react with each other and have a low melting point. After the compound is formed and melted around 650 [° C.] and adhered to the bed material surface, it reacts with the silicon dioxide (SiO ₂ ) on the bed material surface to form a low melting point silicate compound, and the surface melts The inventors of the present invention have clarified that the bed materials are bonded together and agglomerate to cause a flow failure, but as described above, the in-layer temperature is reduced due to the adhesion between the bed materials. When the temperature is controlled below the target temperature at which generation can be prevented, that is, about 600 [° C.] or less, the eutectic compound having a low melting point formed by the reaction of the alkali metal compound does not melt and hardly adheres to the bed material surface. Since the low melting point silicate compound is not formed, the bed materials are not joined together to become agglomerated and no flow failure occurs, so that it is not necessary to stop the operation and frequently clean the incinerator.

  Moreover, in the operation method of the fluidized bed incinerator, it is desirable to add an inorganic compound-based additive to the bed material. As the inorganic compound-based additive, for example, dolomite, magnesium hydroxide, limestone can be selected. When such an inorganic compound-based additive is added to the bed material, the aggregation of alkali metal compounds and the reaction between the bed material and the alkali metal compound are suppressed, while the melting temperature of the combustion ash increases, It becomes effective by preventing the material from agglomerating.

  Further, in the operation method of the fluidized bed incinerator, it is desirable to use sand having high heat-breaking resistance as the bed material, and in this way, the sand having high heat-breaking resistance is not easily crushed and pulverized by heat. Since the generation of a low melting point silicate compound is suppressed, it helps to prevent the bed materials from sticking and agglomerating.

  According to the operation method of the fluidized-bed incinerator according to claims 1 to 7 of the present invention, when incinerating waste containing a large amount of alkali metal, it is possible to prevent the occurrence of fluid failure due to adhesion between bed materials. The frequency of stoppage of operation and cleaning of the incinerator can be reduced, and an excellent effect that stable operation can be continued can be achieved.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is an example of an embodiment for carrying out the present invention. Reference numeral 1 denotes an incinerator main body that forms a fluidized bed 4 by bubbling a bed material 2 such as silica sand (SiO ₂ ) with air blown from an air diffuser 3. Yes, waste 6 is supplied from the dust feeder 5 to the fluidized bed 4 of the incinerator body 1, the waste 6 is combusted while being fluidized together with the bed material 2, and the combustion exhaust gas 7 is transferred to the waste heat boiler 8. After the ash 9 contained in the combustion exhaust gas 7 that has been guided and recovered by heat and is recovered by the waste heat boiler 8 is collected by the dust collector 10, the combustion exhaust gas 7 from which the ash 9 has been removed by the dust collector 10 is induced. The air is discharged from the chimney 12 into the atmosphere via the machine 11. The boiler dust 13 collected in the waste heat boiler 8 and the ash 9 collected by the dust collector 10 are sent to an ash storage tank.

  Here, the present inventors first elucidated the generation mechanism of the flow failure due to the fixation of the bed materials 2 and examined the prevention measures.

That is, when the waste 6 to be incinerated contains a large amount of alkali metals (sodium and potassium), the alkali metal compounds produced in the fluidized bed 4 are sodium carbonate (Na ₂ CO ₃ ) and sodium sulfate. (Na ₂ SO ₄ ), sodium chloride (NaCl), potassium carbonate (K ₂ CO ₃ ), potassium sulfate (K ₂ SO ₄ ), potassium chloride (KCl), etc. A low-melting silicate compound that forms a low-eutectic eutectic compound, melts around 650 [° C.], adheres to the surface of the bed material 2 and further reacts with silicon dioxide (SiO ₂ ) on the surface of the bed material 2 It was found that the bed materials 2 that were melted on the surface were bonded together and agglomerated to cause poor flow.

  For this reason, a temperature detector 14 for detecting the temperature in the fluidized bed 4 is provided as a first preventive measure against flow failure due to adhesion between the bed materials 2, and the temperature in the layer detected by the temperature detector 14 is set. In addition, the temperature is controlled to be equal to or lower than a target temperature at which occurrence of poor flow due to adhesion between bed materials can be prevented, that is, about 600 [° C.] or lower. In order to control the temperature in the bed below the target temperature (about 600 [° C.]), for example, from the dust feeder 5 to the incinerator main body 1 based on the temperature in the bed detected by the temperature detector 14. The amount of waste supplied to the fluidized bed 4 may be adjusted. Alternatively, water spray on the fluidized bed 4 may be performed.

  As described above, when the temperature in the layer is controlled to be equal to or lower than the target temperature at which the occurrence of flow failure due to adhesion between the bed materials can be prevented, that is, about 600 [° C.] or lower, the melting point formed by the reaction of the alkali metal compound is low. Since the eutectic compound does not melt, it becomes difficult to adhere to the surface of the bed material 2, the low melting point silicate compound is not formed, the bed materials 2 are not bonded together and agglomerated, and no flow failure occurs, It is not necessary to stop the operation and clean the incinerator frequently.

In addition, as a second countermeasure against flow failure due to adhesion between the bed materials 2, for example, dolomite (CaCO ₃ .MgCO ₃ ), magnesium hydroxide (Mg (OH) ₂ ), limestone (CaCO ₃ ) ) And other inorganic compound additives.

Here, FIG. 2 is an experimental data diagram showing the relationship between the additive concentration and rattra strength (adhesion degree) when an inorganic compound-based additive (dolomite, magnesium hydroxide, limestone) is added to the bed material 2. Based on the investigation of the properties of the clinker in the fluidized bed 4 of the actual machine, a sample obtained by adding the inorganic compound-based additive to dredged sand containing 3 [%] Na + 3 [%] K as an alkali concentration close to the clinker property It is the experimental result which measured Latra intensity | strength in the state returned to normal temperature, after cooling to 850 [degreeC] for 3 hours, allowing to cool in a desiccator, and returning to normal temperature. The Ratra strength refers to a sample heat-treated in an electric furnace placed in a rotary rod of a Ratra tester, and a predetermined rotation speed (80 [rpm] in this experiment) and a predetermined number of rotations (250 in this experiment). When rotating, the sample collapses and falls due to the rotation of the rotating rod, and the weight decreases.
Ratra strength = defined as the weight of the sample after the ratra test / the weight of the sample before the ratra test. That is, the lower the Ratra strength, the weaker the bed material 2 is, the more easily broken it is, and the bed material 2 is less likely to be agglomerated, but as is apparent from the experimental data diagram of FIG. When the inorganic compound-based additive is not added to the bed material 2, the Latra strength is about 0.8, whereas when the inorganic compound-based additive is added to the bed material 2, the additive concentration is 3 [%]. It was confirmed that the Latra strength was reduced to about 0.4 when the Latra strength was about 0.5 and the additive concentration was 6%.

  Thus, for example, when an inorganic compound-based additive such as dolomite, magnesium hydroxide, or limestone is added to the bed material 2, aggregation of alkali metal compounds and reaction between the bed material 2 and the alkali metal compound are suppressed. On the other hand, the melting temperature of the combustion ash rises and becomes effective by preventing the bed material 2 from being agglomerated.

  Furthermore, sand having high heat-resistant crushing property is used as the bed material 2 as a third measure for preventing the flow failure due to the adhesion between the bed materials 2. This is because sand that is easily crushed produces many fine particles and reacts with an alkali metal to produce a low melting point silicate compound, which leads to adhesion between the sands.

  Here, Fig. 3 shows the change over time in the average particle size of sand from different production areas (sand from Mizunami, Gifu Prefecture, sand from Iwaki City, Fukushima Prefecture, and sand from Oishida, Yamagata Prefecture). It is an experimental data diagram showing the change over time of the ratio (fine powder ratio) in the entire sand having a particle size (710 μm) or less, and the average particle size is the sand from “Mizunami, Gifu Prefecture” at the beginning of operation, The sand from "Iwaki City, Fukushima Prefecture" and the sand from "Oishida Yamagata Prefecture", both of which were about the same at about 1000 [μ], were sanded from Mizunami, Gifu Prefecture and "Iwaki City, Fukushima Prefecture" The sand produced in “Iwaki City, Fukushima Prefecture” began to decrease sharply immediately after the start, and subsequently decreased, but the sand produced in “Iwaki City, Fukushima Prefecture” did not decrease until after 50 hours, It gradually became smaller. As for the fine powder ratio, at the beginning of operation, sand produced in Mizunami, Gifu Prefecture was 4.4%, sand produced in Iwaki City, Fukushima Prefecture was 13.4%, and Oishida, Yamagata Prefecture. Although the percentage of sand was 3.7 [%], after the start of operation, the proportion of fine powder from Mizunami in Gifu Prefecture increased to about 20 [%], which is about 5 times after 50 [hr]. The proportion of fine sand in Yamagata Prefecture Oishida has increased to over 70%, which is about 20 times after 50 hours, whereas the amount of sand produced in Iwaki City, Fukushima Prefecture has increased. The fine powder ratio increased to 19.6 [%], which is about 1.5 times after 50 [hr], and then gradually increased. As a result of comprehensive determination of the change over time in the average particle size and the change over time in the fine powder ratio, sand from Mizunami, Gifu Prefecture, sand from Iwaki City, Fukushima Prefecture, and sand from Oishida, Yamagata Prefecture Among them, sand produced in Iwaki City, Fukushima Prefecture is the most heat-resistant crushing sand and can be said to be suitable for the bed material 2.

  As described above, when the bed material 2 is sand having high heat-breaking resistance such as sand produced in Iwaki City, Fukushima Prefecture, the heat-resistant breaking sand is not easily crushed and pulverized by heat. Since the generation of a low melting point silicate compound is suppressed, it is useful for preventing the bed materials 2 from adhering to each other.

  In this way, when incinerating the waste 6 containing a large amount of alkali metal, it is possible to prevent the occurrence of poor flow due to the fixing of the bed materials 2 to each other, reducing the frequency of shutdown and cleaning of the incinerator, and stable operation. Can continue.

  The operation method of the fluidized bed incinerator of the present invention is not limited to the illustrated example described above, and it is needless to say that various changes can be made without departing from the gist of the present invention.

1 is an overall schematic configuration diagram of an example of an embodiment for carrying out the present invention. It is an experimental data diagram showing the relationship between the additive concentration and rattra strength (adhesion degree) when an inorganic compound-based additive (dolomite, magnesium hydroxide, limestone) is added to the bed material. It is an experimental data diagram showing the time-dependent change of the average particle diameter of sand having different production areas and the time-dependent change of the ratio of the sand having a predetermined particle diameter or less.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Incinerator main body 2 Bed material 3 Aeration pipe 4 Fluidized bed 5 Dust feeder 6 Waste 14 Temperature detector

Claims (7)

  In a fluidized bed incinerator operation method in which waste is combusted while fluidizing with a bed material, the temperature in the bed is controlled to be equal to or lower than a target temperature capable of preventing the occurrence of flow failure due to adhesion between the bed materials. To operate a fluidized bed incinerator.   The method of operating a fluidized bed incinerator according to claim 1, wherein a target temperature capable of preventing the occurrence of flow failure due to adhesion between bed materials is set to about 600 [° C].   The method for operating a fluidized bed incinerator according to claim 1 or 2, wherein an inorganic compound-based additive is added to the bed material.   The operation method of a fluidized bed incinerator according to claim 3, wherein the inorganic compound-based additive is dolomite.   The operation method of a fluidized bed incinerator according to claim 3, wherein the inorganic compound-based additive is magnesium hydroxide.   The operation method of a fluidized bed incinerator according to claim 3, wherein the inorganic compound-based additive is limestone.   The fluidized bed incinerator operating method according to any one of claims 1 to 6, wherein sand having high heat-resistant crushability is used as the bed material.

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