JP6552502B2 - Method of detoxifying rice husk combustion ash and combustion equipment of rice husk - Google Patents

Description

  The present invention relates to a method of treating combustion waste of organic waste, and more particularly to a method of detoxifying combustion ash of organic waste used as fuel for power generation and combustion equipment of organic waste. is there.

  A system that generates power by burning organic waste (biomass) such as rice husks and using the heat of combustion has attracted attention.

  For example, Japanese Patent Application Laid-Open No. 2014-81187 (Patent Document 1) generates combustion heat using a rice husk combustion apparatus, heats the water using this combustion heat into steam, and uses a steam turbine or a steam turbine for steam. It discloses a power generation method to rotate.

  Unexamined-Japanese-Patent No. 2014-114427 (patent document 2) is disclosing effective utilization of agricultural products and agricultural waste as a fuel for small sized thermal power plants.

JP, 2014-81187, A JP, 2014-114427, A

  Organic waste such as rice husks can be expected as one of the future biomass energy, but the treatment of a large amount of combustion ash has become a problem. Ash produced by burning organic waste is highly crystalline cristobalite (highly crystalline silica) containing about 2% residual carbon but having a purity of 92% by mass or more.

  According to the International Agency for Research on Cancer (IARC), cristobalite, which is a type of insoluble crystalline silica, is pointed out to be carcinogenic. Therefore, when organic waste is used as fuel for power generation, the treatment of the combustion ash becomes a problem.

  The present invention has been made to solve the above-mentioned problems, and an object thereof is to provide a method for harmlessizing combustion ash of organic waste and a combustion facility for organic waste.

The organic waste combustion ash detoxification method according to the present invention includes the following steps.
(A) The process of collect | recovering the combustion ash which burned organic waste and was made cristobalite.
(B) The process of grind | pulverizing the combustion ash of the collect | recovered organic waste to make a fine powder.
(C) A step of amorphizing the fine particles of combustion ash by injecting and melting the fine particles into the flame in the furnace.

  Preferably, the oxygen concentration in the combustion-supporting gas during the flame treatment is 40% by volume or more. More preferably, the oxygen concentration in the support gas during the flame treatment is 60% by volume or more.

  The temperature of the inner wall of the furnace during the flame treatment is preferably 1100 ° C. or higher. The preferred flame temperature is 1750 ° C to 2500 ° C.

  The particle size of the fine particles of organic waste obtained after pulverization is preferably 15 μm or less. Further, the particle size of the amorphized fine powder after flame treatment is preferably 20 μm or less.

  Preferably, the amorphization rate of the fine powder after the flame treatment is 80% or more.

  In a preferred embodiment, the step of burning the organic waste comprises preparing the organic waste as a fuel for power generation, and burning the organic waste and generating electricity using combustion heat.

  Organic waste is preferably rice husk, rice straw, rice bran, straw, wood, thinned wood, construction waste, sawdust, bark, bagasse, corn, sugar cane, sweet potato, soybean, peanut, cassava, eucalyptus, fern, pineapple, It is any one selected from the group consisting of bamboo, rubber and used paper.

  Combustion facility for organic waste according to the present invention includes a combustion furnace for burning organic waste, and a pulverizer for crushing cristobaliteized organic waste combustion ash recovered from the combustion furnace into fine powder And a flame treatment machine for amorphizing the fine particles of the combustion ash by injecting and melting the fine particles into the flame.

  According to the present invention, the combustion ash that has been converted to cristobalite is made amorphous by the flame treatment, so that the treatment of the combustion ash can be performed safely. In addition, if necessary, the amorphized silica powder after flame treatment can be used for various applications.

FIG. 5 illustrates the steps of a method according to an embodiment of the present invention. It is a figure showing the combustion device of the organic waste concerning one embodiment of the present invention. It is a figure which shows the relationship of the oxygen concentration and the average particle diameter in support gas with respect to a rice husk ash with a particle diameter of 5 micrometers. It is a figure which shows the relationship of the oxygen concentration and the amorphization rate in supporting gas with respect to a rice husk ash with a particle size of 5 micrometers. It is a figure which shows the X-ray-diffraction result (XRD) with respect to the rice husk ash with a particle size of 5 micrometers. It is a figure which shows the relationship of the oxygen concentration and the average particle diameter in support gas with respect to rice husk ash with a particle diameter of 10 micrometers. It is a figure which shows the relationship of the oxygen concentration and the amorphization rate in supporting gas with respect to a rice husk ash with a particle size of 10 micrometers. It is a figure which shows the X-ray-diffraction result (XRD) with respect to the rice husk ash with a particle size of 10 micrometers. It is a figure which shows the relationship of the oxygen concentration and the average particle diameter in support gas with respect to a rice husk ash with a particle size of 15 micrometers. It is a figure which shows the relationship of the oxygen concentration and the amorphization rate in supporting gas with respect to a rice husk ash with a particle size of 15 micrometers. It is a figure which shows the X-ray-diffraction result (XRD) with respect to the rice husk ash with a particle size of 15 micrometers.

  FIG. 1 shows in order the processing steps of the method according to an embodiment of the present invention. In the method according to the embodiment of the present invention, first, organic waste is prepared, and the organic waste is burned to recover the combustion ash. The pulverized combustion ash is pulverized into fine particles, and then the fine particles are subjected to flame treatment to become amorphous.

  FIG. 2 is an illustrative view of an organic waste combustion apparatus according to an embodiment of the present invention. The combustion apparatus 1 includes a combustion furnace 10 that burns organic waste such as rice husks, a pulverizer 20 that crushes the combustion ash of cristobaliteized organic waste recovered from the combustion furnace 10 into fine powder, A flame treatment machine 30 that amorphizes the fine powder of combustion ash by injecting powder into the flame and melting it.

  Each step will be described in detail below.

[Preparation of organic waste]
Organic waste is preferably rice husk, rice straw, rice bran, straw, wood, thinned wood, construction waste, sawdust, bark, bagasse, corn, sugar cane, sweet potato, soybean, peanut, cassava, eucalyptus, fern, pineapple, It is selected from the group consisting of bamboo, rubber and waste paper, but is typically rice husk. Rice husks are available in a wide range of areas. The present inventors conducted experiments of the present invention using rice husks that are easily available and easy to handle as a representative example of organic wastes, but the same applies to other organic wastes. Can be expected.

[Combustion of organic waste and recovery of combustion ash]
The rice husk is used as a fuel for power generation, for example. The rice husk is burned to generate electricity using the heat of combustion, and the burned rice husk ash is recovered. The combustion temperature of rice husk is 750 ° C. to 1300 ° C., and after being burned, it becomes combustion ash by slow cooling. The combustion ash is silica having a purity of 92% by mass or more, but is cristobalite. Therefore, if the combustion ash converted to cristobalite is discarded as it is or used for other purposes, there is a concern about adverse effects on the human body.

[Combustion of combustion ash]
Therefore, in the method according to the embodiment of the present invention, first, the combustion ash is pulverized into a fine powder. The particle size (maximum length) of the combustion ash of the rice husk before pulverization corresponds to the particle size (maximum length) of the raw rice husk and is about several mm to 10 mm. Moreover, since rice husk ash is porous, the energy required for pulverization to obtain fine particles of 15 μm or less is very small. The reason why the rice husk ash is made into a fine powder of about 15 μm or less is that it is considered that the rice husk ash is immediately melted by being injected into the flame in the subsequent flame treatment.

[Flame treatment and amorphization of fine powder]
The fine powder is amorphized by being injected into a flame in the furnace and melted. If the oxygen concentration in the furnace is low and the temperature in the furnace is low, the amorphization rate becomes low. In order to obtain a good amorphization rate, it is necessary to increase the oxygen concentration in the furnace to raise the temperature in the furnace and to rapidly cool it.

  A flame is formed by a combustion gas containing oxygen, nitrogen and a small amount of argon. The oxygen concentration in the combustion supporting gas at the time of flame treatment is preferably 40% by volume or more, more preferably 60% by volume or more. The temperature of the inner wall of the furnace during the flame treatment is preferably 1100 ° C. or higher. In order to efficiently melt the fine powder to make it amorphous, it is preferable to set the flame temperature during the flame treatment to 1750 ° C. to 2500 ° C. The amorphization rate of the fine powder after the flame treatment is preferably 80% or more.

  Generally, the average particle size of spherical silica particles melted and spheroidized by flame treatment is increased as compared with the average particle size of silica fine particles before being introduced into a flame burner. One reason for the increase in the average particle size is that a plurality of silica fine particles are spheroidized in an aggregated state due to static electricity or intermolecular attractive force. When the average particle size is increased, the inside can not be rapidly quenched and it crystallizes. It should be noted here that when the organic fine particles derived from the organic waste are melt-spheronized, it is found that the increase in particle size is suppressed as compared with the fine particles derived from mineral. The reason for this has not been fully elucidated yet, but it is conceivable that the surface area is large, the surface tension is high, and that there are voids inside because the organic fine particles derived from organic waste are porous.

  If the increase in the average particle diameter of the particles at the time of the melt-spheroidization treatment using a flame can be suppressed, the crushed size of the raw material silica (ground silica) can be made closer to the spheroidized product after the flame treatment. Therefore, it is not necessary to finely pulverize the particles until the average particle size is expected to increase. Preferably, the particle size of the fine powder powder made amorphous by the melt-spheronization treatment using a flame is 20 μm or less.

  The amorphized silica fine powder may be disposed of for disposal, and may be used for other applications such as reinforcing materials such as metal materials, rubber, concrete and the like, food and drug additives and the like.

  When the amorphous silica fine powder is used for other purposes, it is preferable to remove impurities in organic waste such as rice husk before combustion. Specifically, the organic waste as a starting material is immersed in an acid solution or warm water and stirred to remove impurities from the raw material and increase the silica purity. The acid is preferably a carboxylic acid having a hydroxyl group, more preferably citric acid.

[Flame treatment for rice husk ash with a particle size of 5 μm]
Rice husk ash was pulverized to an average particle size of 5.7 μm, and flame treatment was carried out using the pulverized chaff fine powder as a raw material. In the flame treatment, rice husk ash fine powder is injected into a flame in a furnace and melted to obtain a spheroidized silica powder. The experiments were conducted in a dedicated test furnace, using 13A city gas as the flame fuel and air plus oxygen as the combustion oxidant.

  The average particle size and amorphization rate of the fine powder after the flame treatment were measured by changing the oxygen concentration in the support gas and the furnace temperature. The results are shown in Table 1.

  Five tests were conducted by changing the oxygen concentration in the fuel gas. FIG. 3 shows the relationship between the oxygen concentration in the combustion supporting gas and the average particle size of the treated fine particles in the flame treatment performed on rice husk ash fine particles having a particle diameter of 5 μm. The average particle size was measured using a CILAS 1090L (laser diffraction / scattering method) particle size distribution analyzer. A sample was prepared using water as a solvent, and was subjected to dispersion treatment using ultrasonic waves and a stirrer for 1 minute.

  FIG. 4 shows the relationship between the oxygen concentration in the supporting gas and the amorphization ratio in the flame treatment performed on the rice husk ash fine powder having a particle size of 5 μm. FIG. 5 shows the X-ray diffraction results (XRD) for the raw rice husk ash fine powder and the fine powder after the flame treatment.

  The amorphization ratio was determined as follows. Using a powder X-ray diffractometer "Ultima IV" manufactured by RIGAKU CO., LTD., X-ray diffraction analysis of the sample was performed in the range of 2 ° of CuKα ray of 3 degrees to 90 degrees. In the case of cristobalite, a main peak exists at 22.0 degrees, but as amorphization (detoxification) progresses, the peak intensity present at this position gradually weakens. Therefore, the cristobalite content ratio (X-ray diffraction intensity of cristobalite recovered material / X-ray diffraction intensity of cristobalite raw material) was calculated from the ratio of X-ray diffraction intensity of recovered powder cristobalite to X-ray diffraction intensity of raw material cristobalite. The amorphization ratio was determined by the following equation.

Amorphization rate (%) = (1−cristobalite content) × 100
The X-ray diffraction intensity of the raw material cristobalite and the recovered powder cristobalite are obtained by subtracting the X-ray diffraction base intensity from the peak intensity.

  If the amorphization ratio is "100%", it means that all the fine particles are amorphous, and if it is "95%", 95% of the fine particles are amorphous and the rest It means that 5% of is not amorphized. The higher the amorphization rate, the higher the detoxification rate.

  From the results shown in Table 1 and FIG. 3, it is recognized that the higher the oxygen concentration in the combustion-supporting gas, the more the increase in the average particle size of the fine particles after the flame treatment is suppressed. Further, from the results shown in Table 1, FIG. 4 and FIG. 5, it is recognized that the higher the oxygen concentration in the combustion support gas, the higher the amorphization rate of the fine particles after the flame treatment.

[Flame treatment for rice husk ash with a particle size of 10 μm]
Rice husk ash was ground to an average particle diameter of 9.4 μm (test 6) or 11.1 μm (test 7 to 10), and flame treatment was performed using the ground rice husk ash fine particles as a raw material. In the flame treatment, rice husk ash fine powder is injected into a flame in a furnace and melted to obtain a spheroidized silica powder. The experiments were conducted in a dedicated test furnace, using 13A city gas as the flame fuel and air plus oxygen as the combustion oxidant.

  The average particle size and amorphization rate of the fine powder after the flame treatment were measured by changing the oxygen concentration in the support gas and the furnace temperature. The results are shown in Table 2.

  Five tests were conducted by changing the oxygen concentration in the fuel gas. FIG. 6 shows the relationship between the oxygen concentration in the supporting gas and the average particle size of the fine powder after the treatment in the flame treatment performed on the rice husk ash fine powder having a particle size of 10 μm. FIG. 7 shows the relationship between the oxygen concentration in the supporting gas and the amorphization ratio in the flame treatment performed on the rice husk ash fine powder having a particle size of 10 μm. FIG. 8 shows the results of X-ray diffraction (XRD) of rice husk ash fine powder as raw material and fine powder after flame treatment.

  From the results shown in Table 2 and FIG. 6, it is recognized that the higher the oxygen concentration in the combustion-supporting gas, the more the increase in the average particle size of the fine particles after the flame treatment is suppressed. Further, from the results shown in Table 2, FIG. 7 and FIG. 8, it is recognized that the higher the oxygen concentration in the combustion support gas, the higher the amorphization rate of the fine particles after the flame treatment.

[Flame treatment for rice husk ash with a particle size of 15 μm]
Rice husk ash was ground to an average particle diameter of 15.5 μm (test 11 to 13) or 15.7 μm (test 14 to 15), and flame treatment was carried out using the crushed rice husk ash fine particles as a raw material. In the flame treatment, rice husk ash fine powder is injected into a flame in a furnace and melted to obtain a spheroidized silica powder. The experiments were conducted in a dedicated test furnace, using 13A city gas as the flame fuel and air plus oxygen as the combustion oxidant.

  The average particle size and amorphization rate of the fine powder after the flame treatment were measured by changing the oxygen concentration in the support gas and the furnace temperature. The results are shown in Table 3.

  Five tests were conducted by changing the oxygen concentration in the fuel gas. FIG. 9 shows the relationship between the oxygen concentration in the supporting gas and the average particle size of the fine powder after the treatment in the flame treatment performed on the rice husk ash fine powder having a particle size of 15 μm. FIG. 10 shows the relationship between the oxygen concentration in the supporting gas and the amorphization rate in the flame treatment performed on the rice husk ash fine powder having a particle size of 15 μm. FIG. 11 shows the X-ray diffraction results (XRD) for the raw rice husk ash fine powder and the fine powder after the flame treatment.

  From the results shown in Table 3 and FIG. 9, it is recognized that the increase in the average particle diameter of the fine particles after the flame treatment is suppressed as the oxygen concentration in the support gas is higher. Further, from the results shown in Table 3, FIG. 10, and FIG. 11, it is recognized that the higher the oxygen concentration in the combustion support gas, the higher the amorphization rate of the fine particles after the flame treatment. In addition, it is recognized that even if the average particle size of the raw material powder is about 15 μm, it can be made sufficiently amorphous by air cooling.

  In the test conducted this time, rice husk ash was used as the raw material, but the same effect can be expected even if combustion ash of other organic wastes is used as the raw material ash.

  Although the present invention has been described above based on the embodiment, the present invention is not limited to the embodiment, and various modifications and changes can be made within the same scope or equivalent scope as the invention described in the claims. Is possible.

  INDUSTRIAL APPLICABILITY The present invention can be advantageously used as a method for detoxifying combustion ash from organic waste used as a fuel for power generation and a combustion facility.

1 Organic waste combustion equipment, 10 combustion furnace, 20 pulverizer, 30 flame treatment machine.

Claims (4)

Preparing rice husk as fuel for power generation;
Burning the rice husk and generating power using combustion heat;
Recovering a cristobalite-formed porous rice husk combustion ash having a particle diameter of several mm to 10 mm generated by the combustion of the rice husk;
Pulverizing the recovered rice husk combustion ash into fine particles having a particle size of 15 μm or less;
And a step of amorphizing the fine powder of rice husk combustion ash by injecting and melting the fine powder into a flame in a furnace having an inner wall temperature of 1100 ° C. or higher,
The oxygen concentration in the combustion-supporting gas during the flame treatment is 40% by volume or more,
The temperature of the flame is 1750 ° C. to 2500 ° C.
The detoxification method of rice husk combustion ash whose amorphization rate of the fine particle powder after the said flame processing is 80% or more.   The method for detoxifying rice husk combustion ash according to claim 1, wherein the oxygen concentration in the combustion-supporting gas during the flame treatment is 60% by volume or more. The method for detoxifying rice husk combustion ash according to claim 1 or 2 , wherein a particle size of the amorphized fine powder after the flame treatment is 20 µm or less. A combustion furnace for burning rice husks to generate electricity using combustion heat;
A crusher for crushing cristobalite-formed porous rice husk combustion ash having a particle diameter of several mm to 10 mm, which is recovered after combustion in the combustion furnace, to fine particles having a particle diameter of 15 μm or less;
And a flame processor for setting the amorphization ratio of the fine powder of rice husk combustion ash to 80% or more by injecting and melting the fine particles of rice husk combustion ash into a flame,
The flame processing machine supplies a temperature of the flame of 1750 ° C. to 2500 by supplying a flame treatment furnace whose inner wall temperature is set to 1100 ° C. or more, and a combustion supporting gas having an oxygen concentration of 40 vol% Combustion equipment for rice husks, including supporting gas supply means for bringing to ℃.

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