JP2006026511A - Method for treating boron-containing combustion ash - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To treat boron-containing combustion ash by a simple and inexpensive method instead of a complicated and troublesome method such as a cement solidification method and a melt/solidification method, so that the elution of boron is restrained, and to utilize the treated combustion ash as a soil conditioner which does not hinder the growth of a farm product. <P>SOLUTION: The boron-containing combustion ash is obtained by treating the exhaust gas, which is produced when coal, RPF (Refused Paper and Plastics Fuel), paper-maker's sludge, or the like, is burned, by using an electrostatic precipitator, a bag filter, or the like. Starch or its processed goods and water are added to/mixed with the boron-containing combustion ash to insolubilize the boron contained in the combustion ash so that the amount of eluted boron is ≤1.0 mg/liter when the boron contained in the combustion ash is eluted by the elution testing method based on announcement No.18 of the Environment Agency in 2003. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a treatment agent and a treatment method for boron-containing combustion ash. More specifically, the present invention conforms to the elution standard value of boron, which is a regulated substance in the Soil Contamination Countermeasures Law enacted in February 2003 by the Environment Agency. It is related with the processing method of combustion ash which makes the elution amount of the boron contained in the combustion ash into 1.0 mg / L or less by adding and mixing a product and water.

Boron is a basic material widely used in the production of surface treatments such as plating, glass, disinfectants, resins, chemicals, and fertilizers. As health effects, cases such as vomiting, diarrhea and nausea due to high concentration intake have been reported, and it is said that suppression of fetal weight gain was observed in teratogenicity tests in rats. In order to prevent these influences, boron insolubilization technology plays an important role.

Boron is also contained in combustion ash from household waste incineration ash, coal combustion ash (coal ash) from thermal power plants, sewage sludge incineration ash, and various industrial wastes. The content of boron or boron compounds is high because boron is originally contained in coal by several to several hundred mg / kg. In addition, since most of the combustion ash is used as a soil conditioner or backfill material, there is a concern that it will elute due to rain and cause groundwater contamination. In addition, since there is also a shortage of landfills where the combustion ash is reclaimed, it is desired to make effective use by making boron in the combustion ash non-eluting.

As methods for detoxifying harmful substances in combustion ash, melt solidification methods, cement solidification, addition of lime, etc., extraction treatment with acids or other solvents, and the like have been proposed.

In the melt-solidification method (for example, Patent Document 1), the waste is heated to a high temperature of 1400 to 1600 ° C., thereby decomposing the organic matter and sealing and fixing the slag to produce boron and heavy metals. . Although this method is said to have the highest safety, it has drawbacks such as the problem of fly ash treatment that contains newly generated higher concentrations of harmful substances, and the highest processing cost is also a problem. ing.

The treatment method of solidifying boron in soil or incinerated ash with blast furnace cement (for example, Patent Document 2), even if solidified due to the properties of ash, the solidified product may not be durable. These components are eluted and contamination by this is considered. In order to solidify the ash and fall below the environmental standard value for boron, a curing time of about one week is required.

In the method of insolubilizing by adding only lime as a boron elution inhibitor in combustion ash (for example, Patent Document 3), it is possible to make it below the landfill standard, but it is insufficient to below the soil environment standard value.

Also, in the method of kneading lime, coal combustion ash and gypsum in the sludge in the presence of water (for example, Patent Document 4 and Non-Patent Document 1), the amount of boron elution is one week after adjustment until the soil environmental standard value is below And is subject to limitations such as requiring an ash storage place after the same treatment as above.

Boron removal by extraction of acids such as acids (for example, Non-Patent Document 2) takes water and time for treatment, and also requires incidental facilities such as treatment of wastewater containing boron. In other words, the equipment cost is enormous and unsuitable for practical use.

On the other hand, as a detoxifying agent for harmful substances of incineration ash, there is a technique using starch alone or a mixture of starch and a chelating agent (for example, Patent Documents 5 and 6), but this method detoxifies heavy metals such as lead. No knowledge about the effect of boron insolubilization has been shown or even suggested.

In addition, when using combustion ash as a snow melting agent or a soil conditioner used to improve acidic soil, as a banking or landfill for construction work, there are limited methods for suppressing boron elution. The method of using cannot be used. Furthermore, there should be no restriction that the processing requires a lot of time and place, and further, it must respond to fluctuations in the boron content in the combustion ash and exert its suppression effect. As described in detail above, no satisfactory ash treatment means has been proposed.
Japanese Patent Laid-Open No. 9-271738 JP 2001-310175 A JP 2003-136035 A JP 2002-346595 A JP 2001-225038 A JP 2003-113362 A Obayashi Institute of Technology Report No. 66 2003 P89-94 Obayashi Institute of Technology Report No. 65 2002 P95-100

The present invention relates to a method for suppressing elution of boron from ash discharged from an incinerator such as a boiler or paper sludge using coal or RPF as a fuel, a complicated and time-consuming method such as cement solidification or melting as described above, Provides a simple and inexpensive method to replace the time-consuming treatment agent addition method, and suppresses boron elution to remove combustion ash that does not cause soil contamination and water contamination, improving soil and grassland It is intended to be used effectively for various uses such as wood, backfill, and embankment.

(1) The present invention is a method for suppressing the elution of boron contained in combustion ash, and includes the following inventions in order to solve the above technical problems.
Coal, RPF (Refused Paper & Plastics Fuel), paper sludge, etc. are burned, the exhaust gas is treated with an electrostatic precipitator, bag filter, etc., and the resulting combustion ash is mixed with starch or its chemicals and water. By treating, boron contained in the combustion ash is eluted by a dissolution test method based on the Environmental Agency Notification No. 18 of 2003, and the amount of the boron-containing combustion ash is 1.0 mg / L or less. Processing method.

(2) The starch used for the treatment of combustion ash or its chemical product is any one of starch obtained from wheat, rice, potato, corn, sweet potato, tapioca, etc. or a chemical product obtained by chemically and chemically processing these starches. Or the combination of arbitrary ratios, or the processing method of the boron containing combustion ash as described in (1) which is the milling prepared by grind | pulverizing starch raw materials, such as cereals and potatoes.
(3) The method for treating boron-containing combustion ash according to (1), wherein the starch or a chemical product thereof is added in a range of 0.5 mass% to 10 mass% with respect to the boron-containing combustion ash.

The present invention provides a method for suppressing elution of boron from ash discharged from an incinerator such as a boiler or papermaking sludge using coal or RPF as a fuel, such as cement solidification, melting, and addition of a treatment agent as described above. Provides a simple and inexpensive method to replace the method that takes time and the addition of a treatment agent that takes time to develop the effect, and improves soil by reducing the boron elution and reducing combustion ash without the risk of causing soil and water pollution Can be used as wood, grassland improvement material, backfill material, embankment, etc. without adverse environmental impact.

The present invention will be specifically described below.
The insolubilization mechanism of boron contained in combustion ash is not clear at present, but starch is considered to have a helical structure with six glucose groups as a unit, and is considered to have a helical structure as in the present invention. When starch or its chemicals and water are added as treatment agents, boron is considered to be incorporated into the helical structure of this starch, and surprisingly, it has the effect of insolubilizing boron in only a few hours after treatment. I found it.

The ash applied to the present invention is combustion ash generated when combusting coal, RPF (Refused Paper & Plastics Fuel), papermaking sludge, and the like. Specifically, the gas discharged when these are combusted is collected by electricity. Ash collected by a duster (EP), a bag filter or the like (EP ash or bag ash, respectively).

The starch or processed product thereof used in the present invention needs to incorporate boron and boron compounds in the combustion ash into the crystal structure. For that purpose, starch or processed product thereof includes starch obtained from wheat, rice, potato, corn, sweet potato, tapioca, etc. Ammonium persulfate modified starch, enzyme modified starch, acid modified starch, pregelatinized starch, dextrin, oxidized starch, etherified starch, esterified starch, crosslinked starch, acetylated starch, phosphate esterified starch, cationized starch, grafted starch In order to suppress boron elution, it is necessary to use any one of these, or a combination of any ratio, or milling prepared by pulverizing starch raw materials such as cereals and potatoes. Is preferable.

The mass ratio when the combustion ash is treated with starch or a chemical product thereof and water is preferably within a range of 0.5% by mass to 10%, more preferably from 1% by mass with respect to the combustion ash. 5% by mass is good. If the mass ratio is less than 0.5% by mass, boron cannot be sufficiently immobilized. Conversely, if the mass ratio exceeds 10% by mass, the absolute amount of ash after treatment increases, and there is a limitation in use, and the cost is also low. It is not practical because it increases.

It is preferable to stir well after adding starch or its chemicals and water to the combustion ash. By stirring, the additives are more evenly dispersed in the combustion ash, and boron is fixed in a minimum amount. Is called. As the stirrer, a commercially available general one is used, but it is not particularly limited. It is an extremely safe technique because no odor or heat is generated during processing.

Combustion ash treated according to the present invention has a boron elution amount of about 2 to 3 mg / L in the case of untreated by the elution test method based on the Environmental Agency Notification No. 18 of 2003. After 3 hours, it is about 0.1 to 0.3 mg / L and significantly lower than the soil environmental standard (1.0 mg / L). At the same time, it has the effect of suppressing elution of heavy metals such as lead other than boron. The form after the treatment is not solidified and is easy to handle because it is in a wet state, and can be used for various applications such as a soil improvement material, a grassland improvement material, a backfill material, and embankment.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is of course not limited to these examples, and the embodiments thereof are not limited to the scope of the present invention. Can be changed.

In addition, the combustion ash used as a boron elution suppression sample in the following examples and comparative examples is EP ash captured by an electric dust collector (EP) of a stalker furnace using coal as fuel. The chemical composition, boron content, and elution amount are as shown in Table 1 below.

1) Boron Elution Method In each of the following examples and comparative examples, the boron elution test was conducted in accordance with Notification No. 18 of the 2003 Environment Agency. In other words, the fly ash collected by the electric dust collector (EP) in the flues of stalker furnaces and pulverized coal furnaces is air-dried, and untreated or treated ash samples are removed except for small pebbles and wood chips. After the grains are pulverized, they are passed through a non-metallic sieve having an opening of 2 mm and mixed well. 50 g of this sample is taken in a 1000 cc polyethylene container with a lid, and 500 cc of pure water (pH 5.8 to 6.3) is added. This prepared sample solution was shaken continuously (shaking width: 4 to 5 cm, vibration frequency: 200 times / min) at room temperature and atmospheric pressure using an industrial waste elution shaker (manufactured by Taitec Corporation) for 6 hours. This solution was allowed to stand for 30 minutes and then centrifuged at about 3000 rpm for 20 minutes. The supernatant was filtered through a membrane filter having a pore size of 0.45 μm, the filtrate was taken, the amount required for quantification was accurately measured, and this was used as a test solution.

2) Method for measuring boron The test solution was analyzed with ICP-OES (inductively coupled plasma optical emission spectrometer, Rigaku / Spectoro, CIROS-120 type), and the amount of boron eluted was quantified.

Example 1
Weigh 500 g of coal boiler EP ash in a vinyl bag, add 10 g of corn starch (manufactured by Oji Cornstarch Co., Ltd.) and stir well, then spray 125 ml of pure water uniformly with a spray and stir well . The curing days were 3 hours, 1 day, 3 days, 5 days, and 10 days, and analysis was performed by the above-described elution method and measurement method for each curing day to obtain the boron elution amount. The results are shown in Table 2.

Example 2
Weigh 500 g of coal boiler EP ash in a vinyl bag, add 35 g of corn starch (manufactured by Oji Cornstarch Co., Ltd.) and stir well, then spray 125 ml of pure water uniformly with a spray and stir well. . The curing days were 3 hours, 1 day, 3 days, 5 days, and 10 days, and analysis was performed by the above-described elution method and measurement method for each curing day to obtain the boron elution amount. The results are shown in Table 2.

Example 3
Weigh 500 g of coal boiler EP ash in a vinyl bag, add 10 g of dextrin (product name: Amirets 8099, manufactured by Oji Cornstarch Co., Ltd.), stir well, and then spray 125 ml of pure water uniformly with a spray. Stir well. The curing days were 3 hours, 1 day, 3 days, 5 days, and 10 days, and analysis was performed by the above-described elution method and measurement method for each curing day to obtain the boron elution amount. The results are shown in Table 2.

Example 4
Weigh 500 g of coal boiler EP ash in a vinyl bag, add 10 g of pregelatinized starch (product name: Konlets 100, manufactured by Oji Cornstarch Co., Ltd.) and stir well. And stirred well. The curing days were 3 hours, 1 day, 3 days, 5 days, and 10 days, and analysis was performed by the above-described elution method and measurement method for each curing day to obtain the boron elution amount. The results are shown in Table 2.

Comparative Example 1
500 g of EP ash of a coal boiler was weighed into a vinyl bag, and 125 ml of pure water was sprayed uniformly so as to be sufficiently stirred. The curing days were 3 hours, 1 day, 3 days, 5 days, and 10 days, and analysis was performed by the above-described elution method and measurement method for each curing day to obtain the boron elution amount. The results are shown in Table 2.

Comparative Example 2
500 g of EP ash of a coal boiler was weighed into a vinyl bag, 15 g of quick lime was added and sufficiently stirred, and then 125 ml of pure water was sprayed uniformly with a spray and sufficiently stirred. The curing days were 3 hours, 1 day, 3 days, 5 days, and 10 days, and analysis was performed by the above-described elution method and measurement method for each curing day to obtain the boron elution amount. The results are shown in Table 2.

Comparative Example 3
Weigh 500g of EP ash from a coal boiler into a vinyl bag, add 15g of quicklime, and add 27g of calcium sulfate hemihydrate as calcium sulfate to 5% by mass of ash, and then spray 123ml uniformly with spray. It sprayed so that it might become, and fully stirred. The curing days were 3 hours, 1 day, 3 days, 5 days, and 10 days, and analysis was performed by the above-described elution method and measurement method for each curing day to obtain the boron elution amount. The results are shown in Table 2.

 As is apparent from Table 2, in Examples 1, 3, and 4, only 2% of corn starch, dextrin, and pregelatinized starch and water were added to coal EP ash, and added for only 3 hours after the treatment. Significantly lower than the soil soil environmental standards. Furthermore, as shown in Example 2, when 7% of starch was added, boron elution suppression could be achieved almost completely after 3 hours from the treatment.

On the other hand, when the coal EP ash is humidified only with water as in Comparative Example 1, the amount of boron elution can be slightly reduced as compared with the dry ash, but the soil environment standard value cannot be cleared. In Comparative Example 2, addition of quicklime can suppress elution of boron below the reference value, but it takes 5 days or more. In Comparative Example 3, when gypsum was added in order to accelerate the boron elution suppression effect by the addition of quicklime, both elution amounts of boron can be suppressed to 0.9 mg / L or less after one day, but the same as in the example, The amount of elution is high with the number of days of curing, and it takes 3 to 5 days to reach the same value as in the examples, and it takes time to suppress elution.

As described above, starch or its chemicals and water are added to the combustion ash, and after stirring, the dissolution of boron in the combustion ash is suppressed within 3 hours, and it is kept below the standard value of the Soil Contamination Countermeasures Law. It can be seen that the present invention is a simple effective means in a short time.

It is possible to detoxify the ash discharged from coal boilers and RPF boilers that use RPF as fuel by adding them at the flue and outlet, and the resulting ash is not solidified. Is an inexpensive method that can be used effectively for soil improvement materials, grassland improvement materials, backfill materials, banking, and the like.

Claims (3)

Starch or its chemicals and water are added to boron-containing combustion ash obtained by treating exhaust gas from burning coal, RPF (Refused Paper & Plastics Fuel) and paper sludge with an electric dust collector or bag filter. The boron elution amount when the boron contained in the combustion ash is eluted by the dissolution test method based on Notification No. 18 of the Environment Agency in 2003 is 1.0 mg / L or less. A method for treating insoluble boron-containing combustion ash. The starch used for the treatment of combustion ash or its chemical product is any one of starch obtained from wheat, rice, potato, corn, sweet potato, tapioca, etc. Or the processing method of the boron containing combustion ash of Claim 1 which is the milling prepared by grind | pulverizing starch raw materials, such as combination of arbitrary ratios, or cereals and potatoes. 2. The method for treating boron-containing combustion ash according to claim 1, wherein the starch or the chemical product thereof is added in an amount of 0.5% by mass to 10% by mass with respect to the boron-containing combustion ash.