JP6788414B2 - Manufacturing method of soil property adjusting material and soil property adjusting material - Google Patents

Description

In the present invention, when iron powder is added to a contaminated soil containing a pollutant and the iron powder adsorbed by the pollutant is recovered and removed from the contaminated soil by dry magnetic separation, the iron powder is added to the contaminated soil to obtain the contaminated soil. The present invention relates to a method for producing a soil property adjusting material used for adjusting physical properties, and a soil property adjusting material.

Conventionally, the residual soil generated by road construction and tunnel construction has been treated at a predetermined residual soil treatment facility or used for other purposes, but these methods are used for contaminated soil containing pollutants. Not applicable to.

As a method for treating contaminated soil containing such pollutants, the following Patent Document 1 includes an iron powder addition step of adding iron powder to contaminated soil containing pollutants such as arsenic and selenium, and contamination before magnetic separation. Contamination including a water content adjusting step of adjusting the water content of soil to 36% by mass or less and a dry magnetic sorting step of collecting and removing iron powder from contaminated soil having a water content of 36% by mass or less by dry magnetic separation. The detoxification treatment method for soil is described.

This method utilizes the property that heavy metals such as arsenic and selenium are adsorbed on iron powder. Iron powder is added to contaminated soil to adsorb heavy metals in contaminated soil, and the iron powder is drummed. Pollutants are removed from the contaminated soil by magnetically sorting with a type magnetic separator or the like. However, if the water content of the contaminated soil is large, it becomes difficult to separate iron powder from the soil by a drum-type magnetic separator or the like. Therefore, in order to adjust the water content of the contaminated soil before magnetic separation, for example, gypsum such as hemihydrate gypsum or anhydrous gypsum is added to the contaminated soil for magnetic selection (dry magnetic selection). In addition, since plaster is hygroscopic and has a smaller average particle size than contaminated soil, adding plaster to contaminated soil reduces the water content of contaminated soil and reduces the average particle size of contaminated soil. Make it smaller to make it easier to select magnetically.

By the way, when sewage dewatered sludge is incinerated, incineration ash is generated. In Patent Document 2 below, the exhaust gas from a sludge incinerator is supplied to a high-temperature ceramic filter at 700 ° C. or higher to collect high-temperature dust-collecting ash, and the collected high-temperature dust-collecting ash is classified into coarse-grained ash and fine-grained ash. A method for collecting dust from sludge incinerator exhaust gas is described, and in the embodiment, incineration ash (particularly coarse-grained ash) can be used as a cement material or an additive for solidifying cement. It is described (paragraph 0016 of Patent Document 2).

Japanese Patent No. 5647371 Japanese Unexamined Patent Publication No. 2008-221206

However, in the detoxification treatment method for contaminated soil of Patent Document 1, since it is necessary to add a large amount of gypsum for adjusting the water content of the contaminated soil to the contaminated soil, the treated soil after magnetic selection is often used. As a result, the soil storage facility was oversized and the amount of soil transported after treatment increased. Therefore, there has been a demand for a material that can replace gypsum and can be used to control the water content of contaminated soil before magnetic separation.

Applicants have found that the incineration ash produced by the incineration of organic waste has a smaller average particle size than the contaminated soil and is dry when recovered from the incineration facility, so it can be used to adjust the physical properties of the contaminated soil such as moisture. Found to be available.

However, when incineration ash is used to adjust the physical properties of contaminated soil, the particle size, composition, moisture absorption, etc. of the incineration ash are suitable as a soil property adjustment material, and the incineration ash itself is a prescribed soil contamination countermeasure method. It was necessary to comply with the standards for contamination status (hereinafter referred to as the standards for contamination status) stipulated in.

Therefore, an object of the present invention is to provide a soil property adjusting material that can be suitably used for adjusting the physical properties of contaminated soil in a detoxification treatment method for contaminated soil including a dry magnetic separation step.

In order to achieve the above object, one of the present inventions is to add iron powder to a contaminated soil containing a pollutant, and to recover and remove the iron powder adsorbing the pollutant from the contaminated soil by dry magnetic separation. A method for producing a soil property adjusting material used for adjusting the physical properties of the contaminated soil by adding it to the contaminated soil. Organic waste is put into a flow furnace having a furnace temperature of 500 to 900 ° C. An organic waste incineration step of incinerating the organic waste while blowing air into the flow furnace, and a high temperature generated by incineration of the organic waste in the organic waste incineration step. It is characterized by including a dust collecting step of supplying exhaust gas to a cyclone type dust collector having an internal temperature of 500 ° C. to 900 ° C. and recovering incineration ash contained in the high temperature exhaust gas.

Since the above-mentioned soil property adjusting material has a moisture absorption property equal to or higher than that of gypsum and is composed of incineration ash recovered from high-temperature exhaust gas, the concentration of heavy metals having a low boiling point (eg, arsenic, selenium, etc.) is usually incinerated. It is lower than ash and can easily meet the criteria for pollution status. Then, by adding this soil property adjusting material to the contaminated soil to which iron powder is added and mixed, the soil property adjusting material absorbs the moisture in the contaminated soil, and it becomes difficult for the aggregate structure of the contaminated soil to be formed. , The particle size of contaminated soil can be reduced. Thereby, the recovery rate of iron powder from the contaminated soil by the dry magnetic selection can be increased.

In the method for producing a soil physical property adjusting material according to the present invention, it is preferable to incinerate the organic waste while blowing air having an air ratio of 1.0 or less in the organic waste incineration step. According to this aspect, it is possible to obtain a soil property adjusting material in which carbon is contained in the incineration ash and the average particle size thereof is smaller. Further, since the carbon component has a high hygroscopicity, when a soil conditioner containing carbon is mixed with the soil, it comes into contact with the soil particles, and the hygroscopicity of water contained in the soil can be enhanced. As a result, when added to the contaminated soil, the moisture of the contaminated soil can be effectively absorbed and the particle size of the contaminated soil can be made smaller.

In the method for producing a soil physical property adjusting material according to the present invention, it is preferable that the air ratio m in the organic waste incineration step is 0.6 to 0.9. According to this aspect, at the time of incineration, it is possible to add a certain carbon content to the incineration ash with a small amount of fuel used so that the hygroscopic effect is further enhanced.

In the method for producing a soil physical property adjusting material according to the present invention, it is preferable to set the separation limit particle diameter of the cyclone type dust collector in the range of 5 to 20 μm in the dust collecting step. According to this aspect, the average particle size of the collected dust ash can be reduced, and when added and mixed with the contaminated soil, the moisture absorption property of the water contained in the contaminated soil can be increased, and the average grain size of the soil can be increased. The diameter can be reduced.

In the method for producing a soil physical property adjusting material according to the present invention, it is preferable to add a Ca source to the organic waste in the organic waste incineration step. According to this aspect, in the organic waste incineration step, by adding a Ca source such as CaCO ₃ , CaO, Ca (OH) ₂ to the organic waste to be incinerated, sulfur derived from the organic waste is added. SO _X generated from (S) is, is furnace desulfurization, and turned in the ash gypsum mineral neutral (hemihydrate gypsum _{(CaSO 4 · 1 / 2H 2} O) and anhydrite (CaSO ₄₎ As it is contained, it increases the components that have the ability to adsorb water in the incineration ash, making it easier to absorb the water in the contaminated soil, and without changing the pH of the contaminated soil. Available.

Another aspect of the present invention is to add iron powder to the contaminated soil containing the pollutant, and add the iron powder adsorbing the pollutant from the contaminated soil to the contaminated soil when recovering and removing the iron powder by dry magnetic separation. It is a soil property adjusting material used for adjusting the physical properties of the contaminated soil, and is characterized by being composed of organic waste incineration ash containing 5 to 40% by mass of carbon.

According to the above invention, the soil property adjusting material is composed of organic waste incineration ash containing 5 to 40% by mass of carbon. Therefore, by adding and mixing this soil property adjusting material to the contaminated soil, the water content of the contaminated soil Efficiently absorbs moisture to reduce the water content of contaminated soil, suppress soil agglomeration, reduce the average particle size of contaminated soil, and when magnetically selecting contaminated soil, contaminated soil It is possible to increase the recovery rate of iron powder when recovering iron powder to which pollutants are attached by dry magnetic separation.

The soil physical property adjusting material according to the present invention preferably has an average particle size of 100 μm or less. According to this aspect, when added and mixed with the contaminated soil, it is easy to be mixed uniformly with the soil particles, the hygroscopic effect can be enhanced, and the soil particles can be made finer.

According to the present invention, since the incineration ash contained in the high-temperature exhaust gas is recovered, it is possible to produce a soil physical property adjusting material having a hygroscopicity equal to or higher than that of gypsum and easily satisfying a standard regarding a pollution state. .. By adding this soil property conditioner to the contaminated soil to which iron powder is added and mixed, the soil property conditioner absorbs the moisture in the contaminated soil, making it difficult to form the aggregate structure of the contaminated soil and contaminating the soil. The average particle size of the soil can be reduced, and the recovery rate of iron powder when the iron powder to which pollutants are attached from the contaminated soil is recovered by dry magnetic separation can be increased.

It is a flow chart of the treatment method of the contaminated soil which uses the soil property conditioner which concerns on this invention. It is explanatory drawing of the manufacturing method of the soil physical property adjusting material which concerns on this invention. It is explanatory drawing of the cyclone type dust collector used in the manufacturing method of the soil property conditioner. It is a graph which shows the relationship between the particle diameter, the frequency, and the integration of passages in the cyclone type dust collector. In the method of manufacturing the same soil properties adjusting material, a formation reaction diagram gypsum (hemihydrate gypsum _{(CaSO 4 · 1 / 2H 2} O) and anhydrite (CaSO _4). It is explanatory drawing of the sludge incineration method in the comparative example 1. FIG. It shows the test result of the hygroscopicity test, and is a graph which shows the relationship between the elapsed days and the amount of moisture absorption. It is a graph which shows the test result of the magnetic separation effect confirmation test, and shows the relationship between the average particle diameter and the amount of magnetic deposit recovery. (A) is a photograph of the soil to which the soil property adjusting material is not added and dried, and (b) is a photograph of the soil to which the hemihydrate gypsum is added, separated by magnetic selection and dried. , (C) are photographs in which the soil physical property adjusting material of Example 3 in the present invention was added to the soil, and the soil was magnetically separated.

Hereinafter, an embodiment of the method for producing a soil physical property adjusting material according to the present invention will be described with reference to the drawings.

The soil property adjusting material of the present invention is applied to, for example, a method for treating contaminated soil as shown in FIG. That is, the method for treating the contaminated soil is a step of adding and mixing iron powder or an acid such as sulfuric acid to the contaminated soil (step S1), and adding a soil property adjusting material to the contaminated soil mixed with iron powder. The step of adding and mixing to adjust the physical properties (moisture, particle size, etc.) of the contaminated soil (step S2) and the step of magnetically selecting the contaminated soil whose physical properties have been adjusted by a drum-type magnetic separator (step S3) are performed. It includes.

Then, by the magnetic separation step of step S3, arsenic, lead, hexavalent chromium, cadmium, selenium, mercury, cyanide, fluorine and boron, and harmful substances including their compounds are magnetically selected by a magnetic separator together with iron powder. It is recovered as a magnetic substance. This magnetic material is treated by a predetermined treatment method (landfill or the like). On the other hand, the non-magnetic deposit that has not been magnetically selected is used as purified soil for civil engineering work and the like.

In the method for producing a soil property adjusting material of the present invention, organic waste such as sludge is put into a flow furnace having a furnace temperature of 500 to 900 ° C., and the organic waste is blown into the flow furnace while the organic waste is blown into the flow furnace. A cyclone type in which the internal temperature is set to 500 ° C to 900 ° C for the organic waste incineration step of incinerating things and the high temperature exhaust gas generated by the incineration of the organic waste in the organic waste incineration step. It includes a dust collection process of supplying incineration ash contained in high temperature exhaust gas by supplying it to a dust collector.

FIG. 2 shows an example of a manufacturing apparatus for carrying out the above manufacturing method. This manufacturing apparatus passes through a flow furnace 10 for incinerating organic waste, a cyclone type dust collector 15 for recovering incineration ash contained in high temperature exhaust gas generated from the flow furnace 10, and the cyclone type dust collector 15. A heat exchanger 20 that exchanges heat from the high-temperature exhaust gas, and a filtration-type dust collector 25 (bug filter) for collecting incineration ash that could not be collected by the cyclone-type dust collector 15 from the exhaust gas that passed through the heat exchanger 20. Etc.) and a scrubber 30 (scrubber or the like) for removing harmful gas from the low temperature exhaust gas that has passed through the filtration type dust collector 25. The flow furnace 10 and the cyclone type dust collector 15 are connected by the pipe L1, the cyclone type dust collector 15 and the heat exchanger 20 are connected by the pipe L2, and the heat exchanger 20 and the filtration type dust collector 25 are connected by the pipe L3. The filtration type dust collector 25 and the cleaning tower 30 are connected by a pipe L4.

Next, an embodiment of the method for producing the soil physical property adjusting material of the present invention using the above-mentioned production apparatus will be described.

First, an organic waste incineration process using the flow furnace 10 will be described. A sand layer 3 is deposited on the bottom of the fluidized furnace 10, and air is blown into the sand layer 3 by a blower 5 to make it in a fluidized state (fluidized bed), and the temperature inside the furnace is 500 to 900. It is kept at ° C. Then, when the organic waste is put into the flow furnace 10, the organic waste is agitated and mixed with the sand layer 3 in the fluid state, and the organic waste is incinerated. ..

In this embodiment, sludge generated from sewage treatment or the like is adopted as the organic waste, but wood waste, food waste, human waste sludge, or the like can also be adopted.

The temperature inside the flow furnace 10 is set to 500 to 900 ° C, but is preferably 750 to 850 ° C. If the temperature inside the flow furnace 10 is less than 500 ° C, the organic waste cannot be sufficiently incinerated or gasified, or if it exceeds 900 ° C, the ash content melts and causes the formation of clinker. ..

Further, the air ratio m of the air blown by the blower 5 is preferably 1.0 or less. Here, the air ratio m is actually calculated when the amount of air required for complete combustion of organic waste is the theoretical amount of air A ₀ and the amount of air actually blown into the flow furnace 10 is the actual amount of air A. It is obtained by the amount of air A / the theoretical amount of air A ₀ . By setting the air ratio m to 1.0 or less, the air in the flow furnace 10 is in a so-called incomplete combustion state, and the incineration ash can contain carbon having a large surface area and high moisture absorption performance. Furthermore, since carbon has a relatively small particle size, the inclusion of such carbon in the incineration ash provides dust collection ash with a small particle size in the next dust collection step of the organic waste incineration step. Can be done.

By the way, in a carbonization furnace for the purpose of obtaining carbides, the air ratio m is generally 0.5 or less. However, when the soil property adjusting material is produced, if the air ratio m is 0.5 or less, the amount of carbides tends to be too large, and the amount of auxiliary fuel used tends to be excessive. In addition, it is difficult to keep the inside of the furnace at a high temperature, the recovery temperature of carbides tends to be low, and it becomes difficult to sufficiently remove heavy metals. Therefore, the air ratio m is preferably larger than 0.5 and preferably 1.0 or less.

The air ratio m is preferably 0.6 to 0.9, more preferably 0.8 to 0.9. When the air ratio m is 0.6 to 0.9, the incineration ash can contain an appropriate amount of carbon so as to have properties suitable for adjusting the water content of the contaminated soil.

In the present invention, the carbon content contained in the soil physical property adjusting material is preferably 5 to 40% by mass, more preferably 5 to 20% by mass by adjusting the air ratio m. By setting the carbon content in the above range, the hygroscopicity of the soil property adjusting material is increased, the particle size of the soil property adjusting material is reduced, and the soil is granulated when added to the contaminated soil. Can be promoted more.

Further, in this embodiment, as shown in FIG. 2, a Ca source is added to the organic waste in the organic waste incineration step.

Explaining with reference to FIG. 5, by adding Ca sources such as CaCO ₃ (lime gypsum), CaO, and Ca (OH) ₂ into the flow furnace 10, SO _{2 and the} like derived from organic waste can be produced. SOx reacts with Ca source is added in a furnace, hemihydrate gypsum _{(CaSO 4 · 1 / 2H 2} 0) or, gypsum etc. anhydrite (CaSO ₄₎ is generated.

For example, when CaCO ₃ is added as a Ca source, CO ₂ is separated at around 850 ° C. as shown in the following reaction formula (1).

CaCO ₃ → CaO + CO ₂ ... (1)

Then, CaO is the SO ₂ from organic waste, and reacts as following reaction formula, hemihydrate gypsum _{(CaSO 4 · 1 / 2H 2} O) or anhydrite (CaSO ₄₎ is generated.

CaO + SO ₂ + 1 / 2O ₂ → CaSO ₄ ... (2)
_{CaSO 4 + 1 / 2H 2 O} → CaSO 4 · 1 / 2H 2 O ····· (3)

In this way, the gypsum produced in the flow furnace 10 is sent to the cyclone type dust collector 15 as a composition component of the high temperature exhaust gas, and is recovered by the cyclone type dust collector 15. Since gypsum is a substance having hygroscopicity, the components having hygroscopicity in the collected dust ash increase, and the hygroscopicity of the dust collecting ash as a soil physical property adjusting material is increased.

However, in the present invention, it is not essential to add a Ca source to the organic waste in the organic waste incineration step.

Next, the dust collection process will be described.

The high-temperature exhaust gas generated by incinerating the organic waste in the dust collecting step is supplied to the cyclone type dust collector 15 via the pipe L1. Since this type of cyclone type dust collector 15 has a conventionally known structure, detailed description thereof will be omitted. However, as shown in FIG. 3, the cyclone type dust collector 15 in this embodiment includes a cylindrical main body 16 and a cylindrical main body 16. It has a conical hopper 17 that is connected below the main body 16 and is gradually reduced in diameter.

Further, on the outer periphery of the main body 16, an inflow port 18 extending in the tangential direction of the main body 16 and communicating with the internal space of the main body 16 is provided. The inflow port 18 is connected to the flow furnace 10 via a pipe L1, and high-temperature exhaust gas containing incineration ash generated in the above-mentioned organic waste incineration step flows into the main body 16 from the inflow port 18. It is designed to do.

Further, from the upper center of the main body 16, a tubular discharge portion 19 communicating with the internal space of the main body 16 is erected, and exhaust gas from which some incineration ash components are separated is discharged. ing. The discharge unit 19 is connected to the heat exchanger 20 used in the next process via the pipe L2, and the exhaust gas is supplied to the heat exchanger 20.

Then, the high-temperature exhaust gas containing the incineration ash that has flowed into the main body 16 from the inflow port 18 through the pipe L1 collides with the cylindrical inner wall of the main body 16 and swirls, whereby the incineration ash larger than the predetermined particle size is formed. The components of incineration ash smaller than a predetermined particle size are discharged from the discharge unit 19 together with the exhaust gas, and are supplied to the heat exchanger 20 in the next heat exchange step via the pipe L2. To.

The particle size (separation limit particle size δmin (μm)) that can be separated by the cyclone type dust collector 15 can be calculated by the following mathematical formula (1).

In the above formula (1), μ is the viscosity (Pa · S) of the high temperature exhaust gas (here, incineration ash), b is the inlet width (mm) of the inflow port 18, n is the number of swirls of the high temperature exhaust gas, and ρ _s is the particle. Density (kg / m ³ ), ui is the inlet velocity of the cyclone (velocity at inlet 18: m / s). That is, the separation limit particle diameter δmin can be defined by the inlet width b and the inlet velocity ui, and a substance having a particle size larger than the separation limit particle diameter δmin can be collected.

FIG. 4 shows the relationship between the particle size (horizontal axis: μm), the frequency (vertical axis on the left side:%), and the integrated passage amount (vertical axis on the right side:%) in the cyclone type dust collector 15. However, it means that substances having a particle size in the range on the right side of the figure can be collected from the design points A, B, C, and D having a separation limit particle diameter of δmin indicated by the vertical line of the broken line. For example, at design point D, it means that a substance having a particle size of 100 μm or more can be collected, and the average particle size of the collected incineration ash is 150 μm. Similarly, at design point C, it means that a substance having a particle size of 60 μm or more can be collected, and the average particle size of the collected incineration ash is 100 μm, and at design point B, the particle size is 30 μm or more. It means that the substance can be collected and the average particle size of the collected incineration ash is 80 μm. Therefore, for example, by making the design point of the separation limit particle diameter δmin smaller than C, incineration ash having an average particle diameter of 100 μm or less can be collected.

In the present invention, the separation limit particle size δmin (μm) is preferably set in the range of 5 to 60 μm, and more preferably set in the range of 5 to 20 μm.

In the present invention, it is preferable that the separation limit particle size δmin (μm) is set to the above range so that the average particle size of the soil property adjusting material composed of incinerated ash recovered from the high temperature exhaust gas is 100 μm or less. , 50 μm or less is more preferable. By reducing the average particle size of the soil property adjusting material as described above, it is possible to further promote the fine graining of the soil when it is added to the contaminated soil.

In the present invention, the average particle size indicates the median particle size D ₅₀ , and is obtained from the particle size distribution in the aggregated state of the soil. That is, for example, it means the particle size defined by measuring the frequency distribution on a mass basis using a standard sieve in a state where the soil is as it is and obtaining the particle size (D ₅₀ ) at the 50% classification point.

Further, the internal temperature of the cyclone type dust collector 15 is set to 500 to 900 ° C, but is preferably 750 to 850 ° C. If the internal temperature of the cyclone type dust collector 15 is 500 to 900 ° C, for example, Notification No. 19 of the Ministry of the Environment (hereinafter referred to as "Notification No. 19") on March 6, 2003 or March 6, 2003. When measured by the analysis method of Ministry of the Environment Notification No. 18 (hereinafter referred to as "Notification No. 18"), it is higher than the boiling point of some of heavy metals and their compounds regulated by the standards for pollution status. , Those heavy metals and their compounds can be reduced to make it easier to meet the criteria for contamination status.

Incidentally, the boiling points of heavy metals and their compounds regulated by the above-mentioned standards for pollution status are as shown in Table 1 below.

If the internal temperature of the cyclone type dust collector 15 is less than 500 ° C, it becomes difficult to sufficiently remove the pollutants specified in the above-mentioned standards for the contaminated state, and if it exceeds 900 ° C, a part of the ash content is removed. It melts and easily produces clinker.

Further, in this embodiment, a heat exchange step is provided as a step following the above-mentioned dust collecting step. This heat exchange step has a well-known heat exchanger 20, and the exhaust gas separated from the incineration ash by the dust collection step is supplied to the heat exchanger 20 via the pipe L2, which is not shown. It exchanges heat with a fluid to be heated such as water supplied through it, and the temperature drops, resulting in low-temperature exhaust gas.

Further, in this embodiment, a low temperature dust collecting step is provided as a step following the heat exchange step. This low-temperature dust collector has a well-known filter-type dust collector 25 such as a so-called bag filter, and exhaust gas having a predetermined temperature by the heat exchange step is supplied to the filter-type dust collector 25 via the pipe L3. It is separated into low-temperature dust collecting ash containing a predetermined pollutant and low-temperature exhaust gas. The low-temperature dust ash is collected and processed by landfill, etc., and the low-temperature exhaust gas is discharged as it is.

In this embodiment, a gas cleaning step may be included as a step following the above-mentioned low-temperature dust collecting step. This gas cleaning step has a well-known scrubber or the like cleaning tower 30, and the low-temperature exhaust gas separated by the low-temperature dust collecting step is supplied to the cleaning tower 30 via the pipe L4, and before that. It is possible to remove harmful substances such as SOx that could not be collected in the process. However, in this embodiment, in the organic waste incineration step, the organic waste is desulfurized by adding a Ca source, so that the scrubber 30 is unnecessary, or even if it is necessary, it may have a low load. ..

The soil property adjusting material produced by the above-mentioned production method is used in the method for treating contaminated soil by dry magnetic selection as shown in FIG. 1 described above.

Next, the action and effect of the method for producing a soil property adjusting material comprising the above steps will be described.

That is, in this manufacturing method, as shown in FIG. 2, organic waste is put into a flow furnace 10 having a furnace temperature of 500 to 900 ° C., and air is blown into the flow furnace 10 for organic waste. It has an incineration process that incinerates things. At this time, as a preferred embodiment of the present invention, the high-temperature ash gas supplied from the flow furnace 10 has a large surface area and absorbs moisture by incinerating the organic waste while blowing air having an air ratio of 1.0 or less. It can contain carbon with high performance.

Further, since carbon has a relatively small particle size, the high-temperature exhaust gas containing this carbon is supplied to the cyclone type dust collector 15 in the dust collection process, and some incineration ash components are separated from the exhaust gas by centrifugal force. By recovering as incineration ash, incineration ash with a small particle size can be obtained. As a result, it is possible to produce a soil property adjusting material composed of incineration ash containing carbon and having a small particle size. In addition, since this soil property conditioner is composed of dust collected ash collected at high temperature, the concentration of low boiling point heavy metals (eg, arsenic, selenium, etc.) is lower than that of ordinary incinerated ash. It is possible to easily meet the criteria regarding the state of contamination when analyzed in No. 19 and No. 18 of the Circulation.

By adding the soil property conditioner produced in this way to the contaminated soil to which iron powder is added and mixed, the soil property conditioner absorbs the moisture in the contaminated soil, making it difficult for the aggregate structure of the contaminated soil to be formed. Since the average particle size of the contaminated soil can be reduced, the recovery rate of the iron powder can be increased when the iron powder to which the pollutants are attached from the contaminated soil is recovered by the dry magnetic separation.

Further, when the air ratio of air in the organic waste incineration step is set to 0.8 to 0.9, the carbon content contained in the incineration ash can be adjusted so as to enhance the hygroscopic effect, and at the same time. Since the amount of fuel added for incineration is small, the production cost of the soil property adjusting material can be suppressed.

Further, in the dust collection step, when the separation limit particle size of the cyclone type dust collector 15 was set in the range of 5 to 20 μm, the average particle size of the collected dust collector ash was reduced and added to and mixed with the contaminated soil. At the same time, it is possible to increase the hygroscopicity of water contained in the contaminated soil and reduce the average particle size of the soil.

Further, in this embodiment, in the organic waste incineration step, Ca sources such as CaCO ₃ , CaO, and Ca (OH) ₂ are added to the organic waste to be incinerated to derive from the organic waste. by reaction with SO _X and the high temperatures generated from the sulfur (S), hygroscopic, gypsum (hemihydrate gypsum _{(CaSO 4 · 1 / 2H 2} O) and anhydrous gypsum (CaSO ₄₎₎ is generated, It is contained in incineration ash. Therefore, the composition of the soil property adjusting material itself is adjusted, and the inclusion of hemihydrate gypsum or anhydrous gypsum makes it easier to absorb the water content of the contaminated soil.

Next, one embodiment of the soil physical property adjusting material according to the present invention will be described.

This soil property conditioner adjusts the physical properties of the contaminated soil by adding iron powder to the contaminated soil containing pollutants and adding the iron powder to the contaminated soil when recovering and removing the iron powder from the contaminated soil by dry magnetic separation. It is made of incineration ash of organic waste containing 5 to 40% by mass of carbon.

Since this soil property adjusting material is composed of incineration ash of organic waste containing 5 to 40% by mass of carbon, the water content of the contaminated soil is added and mixed with the soil property adjusting material. Efficiently absorbs moisture to reduce the water content of contaminated soil, suppress soil agglomeration, reduce the average particle size of contaminated soil, and when magnetically selecting contaminated soil, contaminated soil It is possible to increase the recovery rate of iron powder when recovering iron powder to which pollutants are attached by dry magnetic separation. As described above, the carbon content is more preferably 5 to 20% by mass.

Further, as described above, the average particle size of the soil property adjusting material is preferably 100 μm or less, and more preferably 50 μm or less. According to this aspect, when added and mixed with the contaminated soil, it is easy to be mixed uniformly with the soil particles, the hygroscopic effect can be enhanced, and the soil particles can be made finer.

Further, as described above, this soil property adjusting material is produced by adding a Ca source in the organic waste incineration step, and by chemically reacting the Ca source and the organic waste with the SOx generated in the incineration under high temperature conditions. It may contain the formed gypsum. According to this aspect, the hygroscopicity of the produced soil property adjusting material is increased, and the moisture of the contaminated soil can be more easily absorbed.

The present invention is not limited to the above-described embodiments, and various modified embodiments are possible within the scope of the gist of the present invention, and such embodiments are also included in the scope of the present invention. ..

1. 1. Preparation of Samples Under the conditions shown in Table 2 below, the soil property adjusting materials of Examples 1 to 3 and Comparative Examples 1 and 2 according to the present invention were produced.

Examples 1 to 3 are incineration ash collected by the cyclone type dust collector 15 using the manufacturing apparatus shown in FIG. 2, and the carbon content is adjusted by adjusting the air ratio in the organic waste incineration step. It was manufactured by changing.

In Comparative Example 1, in the manufacturing apparatus shown in FIG. 6, that is, the manufacturing apparatus shown in FIG. 2, the flow furnace 10 and the heat exchanger 20 are connected to each other via the pipe L1 without providing the cyclone type dust collector 15. It is composed of incineration ash collected at a low temperature collected by a filtration type dust collector 25 using an apparatus.

Comparative Example 2 is hemihydrate gypsum.

2. 2. Hygroscopicity test Using 10 g of each of the soil property adjusting materials of Example 3 and Comparative Examples 1 and 2, their hygroscopicity was tested. The test method was carried out in accordance with the former JIS M881 1-1976 "Sampling method for limes and cokes and total water / moisture measurement method".

The results of this hygroscopicity test are shown in FIG. 7 and Table 3 below. As shown in FIGS. 7 and 3, the soil property adjusting material of Example 3 has a larger amount of moisture absorption and a faster moisture absorption rate than the soil property adjusting materials of Comparative Examples 1 and 2 (particularly 1). It was found that the rate of moisture absorption after the lapse of days is fast).

3. 3. Magnetic Separation Effect Confirmation Test Each sample of Example 1, Example 2, and Comparative Example 2 was added to contaminated soil in the amount (mass%) added as shown in FIG. 8 and mixed, and then a well-known rotary drum type magnetic separator was used. It was measured how much was recovered when magnetized by. The average particle size of the recovered magnetic material was also measured.

The result is shown in FIG. As shown in FIG. 8, it was found that the magnetic substance tends to increase as the average particle size becomes smaller. Further, in the case of Example 2 containing carbon, in particular, the case where the amount of carbon added to the contaminated soil is 3% by mass has a finer granulation effect of the magnetic substance as compared with Example 1 and Comparative Example 2. It was found that it was the highest and the amount of magnetic material recovered was also large.

4. Relationship between each sample and contaminants In Examples 1 to 3 and Comparative Example 1, it was confirmed to what extent contaminants such as cadmium and hexavalent chromium remained in the sample before addition to the soil.

The results are shown in Table 4 below.

As shown in Table 4, it can be seen that the high-temperature dust collection Examples 1 to 3 satisfy all the criteria regarding the contaminated state when analyzed by Circular No. 19 and Circular No. 18. Therefore, it was found that a soil property conditioner that easily meets the criteria for pollution status can be obtained.

On the other hand, although Comparative Example 1 of low-temperature dust collection satisfied the standard value of soil content, it can be seen that the values of selenium, arsenic, and boron did not satisfy the standard value of soil elution amount.

5. About the effect of suppressing the formation of aggregates in the soil Fig. 9 (a) shows a photograph of the soil to which the soil property conditioner was not added, and Fig. 9 (b) shows the soil to which hemihydrate gypsum was added. A separated photograph is shown, and FIG. 9 (c) shows a photograph obtained by adding the soil property adjusting material of Example 3 in the present invention to the soil and magnetically separating the soil. As shown in these, when the soil property adjusting material in the present invention is used, it can be seen that the soil is separated into pieces and the particle size is reduced.

3 Sand layer 5 Blower 10 Flow furnace 15 Cyclone type dust collector 16 Main body 17 Hopper 18 Inflow port 19 Discharge part 20 Heat exchanger 25 Filtration type dust collector 30 Scrubber L1, L2, L3, L4 Piping

Claims (5)

When iron powder is added to contaminated soil containing pollutants and the iron powder adsorbing pollutants is recovered and removed from the contaminated soil by dry magnetic separation, it is added to the contaminated soil to adjust the physical properties of the contaminated soil. In the method of manufacturing the soil property conditioner used for
An organic waste incineration step in which organic waste is put into a flow furnace having a furnace temperature of 500 to 900 ° C. and air is blown into the flow furnace to incinerate the organic waste.
The high-temperature exhaust gas generated by incineration of the organic waste in the organic waste incineration step is supplied to a cyclone-type dust collector having an internal temperature of 500 ° C. to 900 ° C. and incinerated ash contained in the high-temperature exhaust gas. A dust collection process that collects incineration ash contained in high-temperature exhaust gas,
Only including,
A method for producing a soil physical property adjusting material , which comprises incinerating the organic waste while blowing air having an air ratio of 1.0 or less in the organic waste incineration step . The air ratio of the air in the organic waste incineration process, and 0.6 to 0.9 The method of soil properties adjusting material according to claim 1, wherein. The method for producing a soil property adjusting material according to claim 1 or 2 , wherein in the dust collecting step, the separation limit particle diameter of the cyclone type dust collector is set in the range of 5 to 20 μm. The method for producing a soil physical property adjusting material according to any one of claims 1 to 3 , wherein a Ca source is added to the organic waste in the organic waste incineration step. When iron powder is added to contaminated soil containing pollutants and the iron powder adsorbing pollutants is recovered and removed from the contaminated soil by dry magnetic separation, it is added to the contaminated soil to adjust the physical properties of the contaminated soil. In the soil property conditioner used for
By putting organic waste into a flow furnace having a furnace temperature of 500 to 900 ° C. and incinerating the organic waste while blowing air having an air ratio of 1.0 or less into the flow furnace. A soil physical property adjusting material obtained , which is made of organic waste incineration ash containing 5 to 40% by mass of carbon and has an average particle size of 100 μm or less.