JP2022097374A - Manufacturing method of ground improver, and ground improving method - Google Patents

Abstract

To provide a ground improving agent excellent in ground improving performance by efficiently utilizing a sulfur-containing material remaining after a waste gas is desulfurized as a resource and a method of improving the ground.SOLUTION: A manufacturing method of a ground improving agent is characterized by comprising: a desulfurizing process for desulfurizing by charging a desulfurizing agent to an exhaust gas to desulfurize in dry; a recovery process for recovering the desulfurizing agent used in the desulfurization process; and an addition process for making the used desulfurizing agent recovered in the recovery process contain in a ground improving agent made of materials containing cement clinker and gypsum. It is a ground improvement method characterized by mixing the ground improving agent obtained in this manufacturing method and the object soil.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for producing a ground improving material and a method for improving the ground.

Conventionally, in order to strengthen the roadbed, secure the workability of heavy machinery and transport vehicles at construction work sites, and strengthen the ground at the construction site of buildings, cement-based solidifying material is used to mix with the target soil for the purpose. Improvements are being made to the ground to meet the needs.

However, the cement-based solidifying material produced from natural resources contains a very small amount of heavy metal, which is a natural mineral that is widely present in nature. Heavy metals may elute at concentrations exceeding soil environmental standards.

In relation to such a problem, for example, in Patent Documents 1 to 3, the sulfite gas contained in the exhaust gas from the fired portion of the cement clinker is absorbed in a slurry containing a calcium compound and mixed with the cement raw material. It is described that the cement composition effective for reducing the elution of hexavalent chromium can be obtained by obtaining the cement composition.

On the other hand, Patent Document 4 describes that the cement hardening system waste material such as lightweight aerated concrete is effectively utilized and dry-typed into the exhaust gas discharged from the cement kiln facility to perform desulfurization treatment.

Japanese Unexamined Patent Publication No. 2020-1963 Japanese Unexamined Patent Publication No. 2020-23415 Japanese Unexamined Patent Publication No. 2020-23416 Japanese Unexamined Patent Publication No. 2019-141795

However, in the techniques of Patent Documents 1 to 3, since the slurry-like material remaining after the exhaust gas is desulfurized in a wet manner is used as a raw material for the cement composition, energy for removing water is required. Further, in Patent Document 4, it has not been focused on recycling sulfur-containing substances remaining after desulfurization treatment of exhaust gas.

An object of the present invention is to provide a ground improvement material and a ground improvement method having excellent ground improvement performance by effectively utilizing the sulfur-containing substances remaining after desulfurization treatment of exhaust gas as resources.

In order to achieve the above object, the present invention is based on the first aspect.
A desulfurization process in which a desulfurizing agent is added to the exhaust gas and desulfurized in a dry manner,
A recovery step for recovering the desulfurization agent used in the desulfurization step, and a recovery step.
The present invention provides a method for producing a ground improving material, which comprises an addition step of incorporating the used desulfurizing agent recovered in the recovery step into a ground improving material made of a material containing cement clinker and gypsum.

According to the method for producing a ground improving material according to the present invention, the used desulfurizing agent remaining after the exhaust gas is desulfurized by a dry method is recovered and contained in the ground improving material made of a material including cement clinker and gypsum. It is possible to obtain a ground improvement material having excellent ground improvement performance.

In the above manufacturing method, it is preferable that the used desulfurizing agent recovered in the recovery step is contained in the ground improving material together with chlorine bypass dust. According to this, since the ground improving material contains chlorine bypass dust together with the used desulfurizing agent, it is possible to produce a ground improving material having further excellent performance. In this case, the chlorine concentration of the ground improving material obtained after the addition step is preferably 500 ppm to 6,000 ppm.

The manufacturing method further includes an SO ₃ concentration measuring step for measuring the SO ₃ concentration contained in the used desulfurizing agent between the recovery step and the adding step, and the SO contained in the used desulfurizing agent. It is preferable to select the desulfurizing agent whose ₃ concentration is increased by 3% by mass or more as compared with that before use and use it in the addition step. According to this, it is possible to produce a ground improvement material having higher productivity and excellent performance by using a used desulfurizing agent having a sufficient amount of _SO3 .

In the above manufacturing method, between the recovery step and the addition step, the SO ₃ concentration measuring step for measuring the SO ₃ concentration contained in the used desulfurizing agent and the water content of the used desulfurizing agent are measured. A step of measuring the water content is further included, and the SO ₃ concentration contained in the used desulfurizing agent is increased by 3% by mass or more as compared with that before use, and the water content is less than 40% by mass. It is preferable to sort and use it in the addition step. According to this, it is possible to produce a ground improvement material with higher productivity and excellent performance by using a used desulfurizing agent having a sufficient amount of SO3 _, and the water content is poor and the water content is 40. It is possible to produce a more stable and excellent ground improvement material by avoiding the mass% or more. In this case, based on the measurement in the water content measuring step, when the water content of the used desulfurizing agent is 40% by mass or more, it is dried until the water content becomes less than 40% by mass. , It is preferable to use it in the addition step. According to this, the used desulfurizing agent that has sufficiently stored SO ₃ is not excluded under the condition of water content, but is dried to adjust the water content and to produce the ground improvement material without waste. Can be used.

In the above manufacturing method, it is preferable that the desulfurizing agent charged into the exhaust gas in the desulfurization step contains at least one selected from cement hardening system waste materials, alkali metal compounds, and alkaline earth metal compounds. According to this, sulfur content can be efficiently recovered from exhaust gas by the desulfurization action of these desulfurizing agents to obtain a used desulfurizing agent having a sufficient amount of SO3 _, which can be used for manufacturing a ground improvement material. .. In particular, when the cement hardening system waste material is used, the running cost related to the desulfurizing agent is low.

In the above manufacturing method, it is preferable that the exhaust gas and the used desulfurizing agent are produced in a cement manufacturing facility. According to this, as a used desulfurizing agent after treating the exhaust gas, it is easy to obtain a used desulfurizing agent having a component suitable for exhibiting the ground improvement performance, and this can be used for manufacturing the ground improvement material.

On the other hand, from the second aspect, the present invention provides a ground improvement method characterized by mixing the ground improvement material obtained by the above-mentioned production method with the target soil.

According to the ground improvement method according to the present invention, by mixing the ground improvement material obtained by the above-mentioned production method with the target soil, the ground containing the soil can be improved.

According to the present invention, it is possible to provide a ground improvement material and a ground improvement method having excellent ground improvement performance by effectively utilizing the sulfur-containing substances remaining after desulfurization treatment of exhaust gas as resources.

It is a flow chart explaining one Embodiment of the manufacturing method of the ground improvement material which concerns on this invention. It is a flow figure explaining another embodiment of the manufacturing method of the ground improvement material which concerns on this invention. It is a flow diagram explaining another embodiment of the manufacturing method of the ground improvement material which concerns on this invention. It is a flow figure explaining still another embodiment of the manufacturing method of the ground improvement material which concerns on this invention. It is a schematic block diagram explaining one Embodiment which uses the exhaust gas and the used desulfurizing agent produced in the cement manufacturing equipment in the manufacturing method of the ground improvement material which concerns on this invention. It is a schematic block diagram explaining the structure of the blow-in type desulfurization equipment as a dry-type desulfurization apparatus. It is a schematic block diagram explaining another embodiment which uses the exhaust gas produced in the cement manufacturing equipment and the used desulfurizing agent in the manufacturing method of the ground improvement material which concerns on this invention. In Test Example 2, the desulfurizing agent B having a water content of 40% by mass (notation: B-3) was 1 day, 7 days, 14 days, 28 days, and 56 days at room temperature from the day of adjusting the water content. It is a chart which shows the result of having investigated the existence form of the calcium component by the XRD method (X-ray diffraction method) after the storage for each period. The sample was stored in a closed container so that the water did not volatilize during the storage period. In Test Example 2, the desulfurizing agent B having a water content of 30% by mass (notation: B-3') was 1 day, 7 days, 14 days, 28 days, and 56 at room temperature from the day of adjusting the water content. It is a chart which shows the result of having investigated the existence form of the calcium component by the XRD method (X-ray diffraction method) after the storage for each period of a day. The sample was stored in a closed container so that the water did not volatilize during the storage period.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings.

FIG. 1 shows a flow chart illustrating an embodiment of a method for manufacturing a ground improvement material according to the present invention. The solid arrows in FIG. 1 indicate the flow of substances brought into each process (hereinafter, the same applies to FIGS. 2 to 4).

As shown in the embodiment of FIG. 1, the method for producing a ground improving material according to the present invention is used in a desulfurization step of adding a desulfurizing agent M1 to exhaust gas G1 and desulfurizing in a dry manner, and a desulfurization step thereof. It is provided with a recovery step of recovering the desulfurizing agent M2 and an addition step of incorporating the recovered used desulfurizing agent M3 into a ground improving material made of a material M4 containing a cement clinker and gypsum.

Dry desulfurization of exhaust gas is, for example, one or more selected from cement hardening system waste materials, alkali metal compounds such as sodium hydroxide and potassium hydroxide, and alkaline earth metal compounds such as calcium hydroxide and magnesium hydroxide as desulfurizing agents. It can be done by using the one containing. Further, as the exhaust gas, chlorine bypass exhaust gas extracted from the cement kiln of the cement manufacturing facility can be preferably exemplified. As shown in the test examples described later, sulfites such as sulfite hemihydrate gypsum ₍ CaSO _3.0.5H2O ) contribute to solidification of soil and suppression of elution of hexavalent chromium, but any combination thereof may be used. For example, the desulfurization reaction efficiently produces such sulfites.

In particular, when the cement hardening system waste material is used, the running cost related to the desulfurizing agent is low. The case where a cement hardening system waste material is used as a desulfurizing agent will be described in detail below. However, the desulfurizing agent used in the present invention is not limited to those containing cement hardening system waste materials.

(Cement hardening system Desulfurizing agent made of waste material)
Examples of the cement hardening system waste material include waste materials such as a cement paste hardened body, a mortar hardened body, and a concrete hardened body. The main constituent phases of these waste materials are cement hydrates such as CSH (calcium silicate hydrate), CAH (calcium aluminate hydrate), and calcium hydroxide as their constituent components. It is a solid body and is a porous body having a predetermined amount of pores of nm size to μm size.

Since the surface of the cement hardening system waste material used as a desulfurization agent becomes an adsorption site and adsorption of sulfur oxides and the like occurs, the cement hardening system waste material having a large number of pores and a large specific surface area has better desulfurization performance. ing. Therefore, for example, the BET specific surface area of the cement hardening system waste material is preferably 5 m ² / g or more, more preferably 6 m ² / g or more, and even more preferably 7 m ² / g or more. Further, the upper limit value is not particularly limited, but is typically 40 m ² / g or less, for example. The BET specific surface area means a value obtained by applying the BET formula to the adsorption isotherm of the cement hardening system waste material obtained by the nitrogen adsorption method.

The porosity of the cement hardening system waste material is preferably 20% by volume or more, more preferably 25% by volume or more, and even more preferably 30% by volume or more. Further, the upper limit value is not particularly limited, but is typically 70% by volume or less, for example. The porosity means a value measured by a mercury intrusion porosity meter.

Further, the cement hardening system waste material has a total pore volume Vt (cm ³ / g) with a pore diameter of 3 nm to 2000 nm and a pore volume Va (cm ³ / g) with a pore diameter of 50 nm to 2000 nm by a mercury intrusion type porosimeter. The ratio Va / Vt is preferably 0.85 or less, more preferably 0.8 or less, and even more preferably 0.75 or less.

Aggregate (for example, coarse aggregate having a particle size of more than 5 mm), reinforcing bars, wood chips, and other contaminants contained in the cement hardening system waste material hardly contribute to desulfurization performance, and are therefore removed by appropriate means. Is preferable. From the viewpoint of handling as a desulfurizing agent, the particle size of the cement hardening system waste material is preferably adjusted to, for example, 20 μm to 22.4 mm, more preferably 20 μm to 16 mm, and even more preferably 20 μm. It is ~ 11.2 mm.

More specifically, when the desulfurizing agent is retained in the desulfurization tank and used in contact with the exhaust gas, the particle size of the cement hardening system waste material is adjusted to, for example, 2.8 mm to 22.4 mm. It is preferably 4 mm to 16 mm, and even more preferably 4 mm to 11.2 mm. When the desulfurizing agent is sprayed onto the exhaust gas flowing in the air supply pipe and used, the particle size of the cement hardening system waste material is preferably adjusted to, for example, 20 μm to 90 μm, more preferably 20 μm to 90 μm. It is 75 μm, and even more preferably 20 μm to 50 μm.

Here, the particle size of the cement hardening system waste material refers to the nominal opening of the sieve specified in JIS Z 8801 "Test Sieve" used in the sieve test. Further, when the particle size is on the order of μm, the value may be a value specified by a general-purpose particle size distribution measuring device such as a laser diffraction type particle size distribution measuring device.

As the cement hardening system waste material, for example, lightweight cellular concrete (ALC) waste material can be preferably used. The lightweight aerated concrete is a lightweight aerated concrete obtained by autoclaving curing (for example, curing at 180 ° C. and 1 MPa with high pressure steam for 10 hours) of silica stone, Portland cement, fresh lime, gypsum, aluminum powder and the like, and is usually 30 m ² It has a specific surface area of / g or more. Further, in the case of general lightweight cellular concrete (ALC) waste material (cured at 180 ° C. for 10 hours with high pressure steam of 1 MPa), it usually does not contain coarse aggregate, has a BET specific surface area of 20 m ² / g or more, and has a porosity. Is 40% by volume or more, and the pore volume ratio Va / Vt is 0.65 or less.

However, the desulfurization effect is small in the dry cement hardening system waste material, and a simple method is performed by the presence of water as a film on the surface of the cement hardening system waste material or by the presence of pore water in the pore structure. Although it is the desulfurization agent obtained in the above, it is possible to exhibit the same desulfurization effect as the so-called wet desulfurization method (for example, a method in which the desulfurization agent is made into a slurry and brought into contact with the exhaust gas). This is a chemical reaction in the liquid phase part existing on the surface of the waste material of the cement hardening system. It is considered that this is because sulfur oxides in the exhaust gas can be immobilized in the waste material of the cement hardening system by producing the solid sulfide of the above. Therefore, for example, the water content of the cement hardening system waste material is preferably 10% by mass or more, more preferably 12.5% by mass or more, and even more preferably 15% by mass or more. The upper limit of the water content is preferably 55% by mass or less, more preferably 50% by mass or less, still more preferably 45% by mass or less from the viewpoint of realizing a dry desulfurization method that is easy to handle. be. The water content may be adjusted by immersing the cement hardening system waste material in water, sprinkling water on the cement hardening system waste material, and if necessary, draining the cement hardening system waste material with a trommel or a sieve after the immersion or watering.

FIG. 2 shows a flow chart illustrating another embodiment of the method for manufacturing a ground improving material according to the present invention.

In the embodiment shown in FIG. 2, the embodiment described in FIG. 1 further includes an SO ₃ concentration measuring step for measuring the SO ₃ concentration contained in the used desulfurizing agent M3. Then, the desulfurizing agent is selected based on the amount of increase in the SO ₃ concentration with respect to the amount of the used desulfurizing agent M3 before use, and the desulfurizing agent M5 selected according to the SO ₃ concentration is used for the production of the ground improvement material. According to this, for example _, a desulfurizing agent whose SO3 concentration contained in the desulfurizing agent used for desulfurization treatment of exhaust gas does not increase so much as compared with that before use is re-used as a desulfurizing agent to be added to the next exhaust gas. While it can be used, for example, a used desulfurizing agent that has increased by ₃ % by mass or more compared to before use and has a sufficient amount of SO3 can be used to obtain a more productive and excellent ground improvement material. Can be manufactured.

In the present invention and the description of the present specification _, the measurement of the SO3 concentration of the desulfurizing agent is performed by sampling a part of the desulfurizing agent used for the desulfurization treatment and the desulfurizing agent used for the desulfurization treatment of the exhaust gas. For example, a general quantitative analysis method of SO ₃ such as a gravimetric method by forming a barium sulfate precipitate may be used. From the viewpoint of convenience, the measurement method using a fluorescent X-ray analyzer (FP method: fundamental parameter method) is preferable for measuring the _SO3 concentration of the desulfurizing agent. Further, for comparison with the SO ₃ concentration of the desulfurizing agent before use, the SO 3 concentration of the newly supplied desulfurizing agent may be measured and, for example, whether or not the SO ₃ concentration is increased by 3% by mass or more may be evaluated. Alternatively, the average or standard SO ₃ concentration of the desulfurizing agent before use is measured or set in advance, or a corresponding threshold value (value of 3% by mass increase) is set, and based on the value, for example. It may be evaluated whether or not the increase is 3% by mass or more.

FIG. 3 shows a flow chart illustrating another embodiment of the method for manufacturing a ground improving material according to the present invention.

In the embodiment shown in FIG. 3, in the embodiment described with reference to FIG. 1 or 2, the SO ₃ concentration measuring step for measuring the SO ₃ concentration contained in the used desulfurizing agent M3 and the water content of the used desulfurizing agent M3 It is further provided with a water content measuring step for measuring the water content. Then, the desulfurizing agent is selected based _on the amount of increase in SO3 concentration of the used desulfurizing agent M3 with respect to the amount before use, and the desulfurizing agent M6 is selected based on the water content of the used desulfurizing agent M3. Is used for the production of ground improvement materials. According to this, for example _, a desulfurizing agent in which the SO3 concentration contained in the used desulfurizing agent does not increase so much as compared with that before use can be reused as a desulfurizing agent to be added to the next exhaust gas. By using a used desulfurizing agent that has increased by, for example, 3% by mass or more compared to before use and has a sufficient amount of SO3 _, it is possible to produce a ground improvement material having higher productivity and excellent performance. In addition, if the water content is, for example, 40% by mass or more, the stability of the sulfite is poor. Therefore, avoid this and use a material with a water content of less than 40% by mass to obtain a more stable and excellent ground improvement material. Can be manufactured.

In the present invention and the description of the present specification, the measurement of the water content of the desulfurizing agent is performed by sampling a part of the desulfurizing agent used for the desulfurization treatment and the desulfurizing agent used for the desulfurization treatment of the exhaust gas. For example, it can be carried out by obtaining the mass reduction rate from room temperature when the amount becomes constant at a drying temperature of 200 ° C. Further, the mass reduction rate at a drying temperature of 200 ° C. is the weight at 200 ° C. at a heating rate of 10 ° C./min or less in thermal analysis using a general-purpose thermal analyzer such as thermogravimetric analysis (TG). It may be replaced by the rate of decrease.

In another aspect of the present invention, which is not limited to the above, it may be determined whether or not to perform the other step based on the measurement result in either the SO ₃ concentration measuring step or the water content measuring step. For example, if the SO ₃ concentration is not satisfied, it may be decided not to use the desulfurizing agent in the production of the ground improvement material without measuring the water content. According to this, unnecessary measurement can be omitted.

FIG. 4 shows a flow chart illustrating still another embodiment of the method for manufacturing a ground improving material according to the present invention.

In the embodiment shown in FIG. 4, in the embodiment described in FIG. 3, when the water content of the used desulfurizing agent is 40% by mass or more based on the measurement in the water content measuring step, the water content is increased. After drying to less than 40% by mass, a desulfurizing agent M7 selected according to the above SO ₃ concentration and water content is obtained, and this is used for producing a ground improvement material. According to this, for example, a used desulfurizing agent that has increased by ₃ % by mass or more compared to before use and has a sufficient amount of SO3 is used to produce a ground improvement material having higher productivity and excellent performance. be able to. In addition, when the water content is, for example, 40% by mass or more, the stability of the sulfite is poor. Therefore, it is improved by drying, and the one having a water content of less than 40% by mass is used for more stability and excellent performance. It is possible to manufacture ground improvement materials. Then, it can be used for producing a ground improving material without waste after adjusting the water content by drying without excluding it under the condition of the water content.

In another aspect of the present invention, which is not limited to the above, the desulfurizing agent M6 selected according to the SO ₃ concentration and the water content is obtained without going through the drying step, and the desulfurizing agent M6 is obtained through the drying step according to the SO ₃ concentration and the water content. The selected desulfurizing agent M7 may be obtained, and both of them may be used in the production of the ground improving material. For example, in the supply flow of the used desulfurizing agent at a certain timing _, the requirement that the water content is less than 40% by mass is satisfied. Since it is stored in a predetermined tank or the like by the route and the supply flow of the used desulfurizing agent at other timings does not meet the requirement of the water content of less than 40% by mass, the water content of less than 40% by mass is passed through the drying process. Even if the desulfurizing agent M7 selected according to the _SO3 concentration and the water content is obtained so as to satisfy the requirements, the desulfurizing agent M7 is mixed with the selected desulfurizing agent M6, and this is used for the production of the ground improvement material. good. According to this, even if the water content of the used desulfurizing agent varies _, the used desulfurizing agent that has a sufficient amount of SO3 is not excluded under the condition of the water content, but is dried to contain water. After adjusting the rate, it can be used for the production of ground improvement materials without waste.

In another aspect of the present invention, the recovered used desulfurizing agent M3 may be contained in a ground improving material made of a material M4 containing cement clinker and gypsum together with chlorine bypass dust. Generally, a chlorine bypass system is adopted for the treatment of chlorine that causes problems such as blockage of a preheater in a cement manufacturing facility. The chlorine bypass system extracts a part of the combustion gas from the kiln exhaust gas flow path from the kiln kiln of the cement kiln to the bottom cyclone of the preheater in the cement kiln facility, and then removes chlorine from the extracted gas to cement. It removes chlorine existing in the kiln system from the outside. Chlorine contained in the extracted gas moves to the solid phase together with the dust contained in the extracted gas (chlorine bypass dust) due to condensation due to cooling, etc., so the chlorine content is relatively low and it becomes a cement kiln type. The coarse powder of dust that can be returned is separated by a classifier such as a cyclone, and then the dust containing fine powder having an increased chlorine content is separated and collected by a solid gas separation device such as a bag filter. Although some of the chlorine bypass dust has been recycled as a raw material for cement in the finishing process of cement manufacturing, the amount of chlorine bypass dust generated is superior to the amount processed, which is one of the causes of the cost increase. Therefore, it is preferable to include it in the ground improvement material because it can be used as a resource.

Further, according to the examples described later, when water is mixed with the ground improving material, the addition of the desulfurizing agent tends to cause a decrease in fluidity in some cases, so that the ground improving material further contains chlorine bypass dust. This has the effect of suppressing the decrease in fluidity, and in turn, it is possible to prevent the workability when the ground improvement material is used from being impaired.

FIG. 5 shows a schematic configuration explanatory diagram illustrating an embodiment in which the exhaust gas produced in the cement manufacturing facility and the used desulfurizing agent are used. In FIG. 5, the solid line arrow indicates the flow of a solid such as desulfurizing agent, the dotted line arrow indicates the flow of gas such as combustion exhaust gas from the firing kiln of the cement facility, and the chain line indicates the flow of the desulfurizing agent used for desulfurization of the exhaust gas. A part of them is sampled to represent a route for performing a predetermined measurement (hereinafter, the same applies to FIGS. 6 to 7).

FIG. 5 shows a kiln combustion exhaust gas system 10 of a cement manufacturing facility. In the kiln combustion exhaust gas system 10 shown in this embodiment, the above-mentioned chlorine bypass system is adopted for the treatment of chlorine that causes problems such as blockage of the preheater in the cement manufacturing facility. That is, in the kiln combustion exhaust gas system 10 shown in this embodiment, dust containing fine powder having an increased chlorine content after separating coarse dust powder that can be returned to the cement kiln system by a classifier 1 such as a cyclone. (Chlorine bypass dust M8) is separated and collected by a solid air separating device 2 such as a bag filter to remove chlorine from the extracted gas.

Since the chlorine bypass exhaust gas discharged from the kiln combustion exhaust gas system 10 using the chlorine bypass system contains high-concentration sulfur oxides, the exhaust gas after chlorine removal cannot be discharged to the outside of the system as it is, and the preheater. It was necessary to return to the cement kiln system such as. However, returning the chlorine bypass exhaust gas to the preheater, etc. results in promoting the concentration of sulfur in the cement kiln system, causing sulfur-derived coating troubles in the cement kiln and preheater, which in turn leads to stable production of cement. There was the problem of becoming difficult.

Therefore, in the embodiment shown in FIG. 5, an exhaust gas desulfurization system 20 including a water-containing treatment device 3 and a dry desulfurization device 4 is provided.

In the water-containing treatment apparatus 3, the desulfurizing agent is provided to the dry desulfurization apparatus 4 by immersing the desulfurizing agent in water, sprinkling the desulfurizing agent, and if necessary, draining the desulfurizing agent with a trommel or a sieve after the dipping and sprinkling. To adjust the water content of the desulfurizing agent M1 (including the newly supplied desulfurizing agent M1a and / or the reused desulfurizing agent M1b in FIG. 5; the same shall apply hereinafter unless otherwise specified). I am trying to do it. The water content of the desulfurizing agent M1 used in the dry desulfurization apparatus 4 may or may not be adjusted as necessary.

In the water-containing treatment device 3, water is brought into contact with the desulfurizing agent M1 provided in the dry desulfurization device 4, and the water content is preferably 10% by mass or more and 55% by mass or less. The water content is the mass difference ₍ W2 _- W ₁ ) between the dry mass W1 of the desulfurizing agent M1 which became constant at _a drying temperature of 200 ° C. and the mass W2 of the desulfurizing agent M1 at room temperature, and the mass at room temperature. It is a value obtained by a percentage with W ₂ (W ₂ -W ₁ ) / W ₂ × 100.

Specifically, the water-containing treatment device 3 can be composed of a simple device such as a sprinkler spray or a dipping basin for immersing the desulfurizing agent M1 in water. Here, when the desulfurizing agent M1 contains fine powder, the wettability with water and the dispersibility in water may decrease, so it is efficient to use a dipping basin or the like provided with a stirring blade. As the stirring blade, for example, a general screw or ribbon may be used. Further, as a means for removing excess water, a drainer or a drainer with a sieve may be used. As the water supplied to the water-containing treatment apparatus 3, tap water, industrial water, and process water in a cement manufacturing plant can be used, and the temperature thereof is not limited.

The dry desulfurization apparatus 4 is an apparatus in which the desulfurization agent M1 is charged into the exhaust gas G1 discharged from the kiln combustion exhaust gas system 10 to perform the desulfurization treatment by the dry type.

FIG. 6 shows an example of the configuration of the blow-in type desulfurization equipment as the dry-type desulfurization apparatus 4. In the blow-in desulfurization equipment shown in this embodiment, a part of the air supply pipe 11 through which the exhaust gas G1 flows constitutes a desulfurization tower 12 for performing a dry desulfurization treatment of the exhaust gas G1. Further, as a transport device for transporting the newly supplied desulfurizing agent M1a and / or the reused desulfurizing agent M1b, a pressure feed pipe 13 for pneumatically feeding the desulfurizing agent together with the gas from a blower (not shown) is provided. I'm using it. Then, the pressure feed pipe 13 penetrates from the side wall of the air supply pipe 11 into the inside thereof, and the desulfurizing agent is sprayed onto the exhaust gas G1 flowing in the air supply pipe 11 through the pressure feed pipe 13, and the exhaust gas G1 becomes the desulfurization agent M1a. And / or contact with the desulfurizing agent M1b. Further, as a means for recovering the used desulfurizing agent M2, a recovery solid air separating device 14 arranged so that the exhaust gas G2 desulfurized through the desulfurization tower 12 is introduced through the air supply pipe 11 is used. ..

The drywall desulfurization apparatus 4 is not limited to the configuration of the blow-in desulfurization equipment, and may be configured as, for example, a facility in which the exhaust gas G1 continuously ventilates the inside of the filling tank filled with the desulfurization agent.

Here, the general exhaust gas from the chlorine bypass system has a temperature of 100 ° C. to 250 ° C., an SO ₂ concentration of 500 ppm to 10000 ppm, and an exhaust gas flow rate of 2.5 m ³ N / s to 25 m ³ N / s. In this embodiment, such exhaust gas corresponds to exhaust gas G1. Further, the inner diameter of a general exhaust pipe of an exhaust path from a chlorine bypass system is 600 mm to 1300 mm. In this embodiment, the exhaust pipe of such an exhaust path corresponds to the air supply pipe 11.

Then, in the desulfurization tower 12 composed of a part of the air supply tube 11, the desulfurizing agent M1a and / or the desulfurizing agent M1b and the exhaust gas G1 come into contact with each other and elute into the liquid phase in the desulfurizing agent M1a and / or the desulfurizing agent M1b. The calcium component reacts with the sulfur oxide (SO ₂ ) in the exhaust gas G1 and immediately reacts with dihydrate gypsum (CaSO _{4.2H 2} O) and / or desulfurization hemihydrate gypsum (CaSO _{3.0.5H 2} ). Solid sulfides such as O) are produced. As a result, the sulfur oxide in the exhaust gas G1 is removed as a solid so that the exhaust gas can be desulfurized.

FIG. 6 shows the fixed positional relationship between the pressure feed pipe 13 and the air supply pipe 11. In FIG. 6, α is an acute angle (°) formed by the inner walls of the pressure feed pipe 13 and the air supply pipe 11.

Generally, when the spray direction of the desulfurizing agent M1a and / or the desulfurizing agent M1b is on the downstream side of the exhaust gas G1, that is, on the recovery solid air separating device 14, the desulfurizing agent M1a and / or the desulfurizing agent M1b and the exhaust gas G1 flow in parallel. Therefore, the desulfurization effect may be reduced because the desulfurization agent M1a and / or the desulfurization agent M1b and the exhaust gas G1 are not sufficiently mixed.

Therefore, in the embodiment shown in FIG. 6, the pressure feed pipe 13 is fixed to the air supply pipe 11 in a state of being tilted upstream with respect to the gas flow of the exhaust gas G1 in the air supply pipe 11. That is, an example shown in FIG. 6 is a case where the desulfurization tower 12 is installed in the vertical portion (rising duct) of the air supply pipe 11, but the fixed position of the pressure supply pipe 13 to the air supply pipe 11 is the air supply pipe of the pressure supply pipe 13. The tip side through which 11 is passed is arranged downward so as to flow toward the exhaust gas G1 flowing upward in the air supply pipe 11. With such a fixed positional relationship, the desulfurizing agent M1a and / or the desulfurizing agent M1b and the exhaust gas G1 can be sufficiently mixed, and thus the solid sulfide formation reaction can be more efficiently generated. can.

The amount of the desulfurizing agent M1a and / or the desulfurizing agent M1b pumped into the air supply tube 11 is contained in the CaO equivalent amount of the calcium component eluted in the liquid phase portion of the desulfurizing agent M1a and / or the desulfurizing agent M1b and the exhaust gas G1. The molar ratio CaO / SO ₂ of the sulfur oxide to be formed is preferably 1.5 to 4.0, more preferably 3.0 to 4.0. Usually, by setting such a molar ratio range, 80% or more of the sulfur oxide contained in the exhaust gas G1 can be changed to solid sulfide (gypsum dihydrate, gypsum sulfite, etc.).

When the desulfurizing agent M1a and / or the desulfurizing agent M1b that have been pumped and reached the air supply pipe 11 adhere to the inner wall of the air supply pipe 11, they form a coating of cement hardening system waste material in the air supply pipe 11 and flow of the exhaust gas G1. Leads to inhibition. Therefore, the desulfurizing agent M1a and / or the desulfurizing agent M1b ejected in the air supply pipe 11 can optimize the fixed positional relationship between the pressure supply pipe 13 and the air supply pipe 11 so as not to reach the inner wall of the air supply pipe 11. preferable.

Specifically, the fixed positional relationship between the pressure feed pipe 13 and the air supply pipe 11 preferably has the following relationship.
β <α + β ≦ 90 °, and α is on the side flowing toward the exhaust gas G1.
α: Acute angle (°) formed by the inner walls of the pressure pipe 13 and the air pipe 11.
β: Spray angle (°) of desulfurizing agent M1a and / or desulfurizing agent M1b

That is, the desulfurizing agent M1a and / or the desulfurizing agent M1b is contained in the exhaust gas G1 in the range from the direction parallel to the inner wall surface of the air supply pipe 11 forming an acute angle with the pressure feeding pipe 13 to the direction perpendicular to the inner wall surface. It is preferable to spray in the direction of countercurrent flow.

Further, the spray speed V _D (m / s) of the desulfurizing agent M1a and / or the desulfurizing agent M1b from the pressure feeding pipe 13 into the air feeding pipe 11 and the flow velocity V _G (m / s) of the exhaust gas G1 flowing in the air feeding pipe 11. The V _D / _VG ratio is preferably 1.0 to 4.0, and more preferably 1.0 to 2.0. Within this range, the desulfurizing agent M1a and / or the desulfurizing agent M1b and the exhaust gas G1 are sufficiently mixed, so that the solid sulfide formation reaction can be generated more efficiently.

The smaller the particle size _RD (μm) of the desulfurizing agent M1a and / or the desulfurizing agent M1b ejected into the air supply pipe 11, the better the reaction for producing the solid sulfide, and as a result, the better the desulfurization efficiency. Specifically, the particle size _RD (μm) of the desulfurizing agent M1a and / or the desulfurizing agent M1b is preferably 90 μm or less, more preferably 75 μm or less, still more preferably 50 μm or less. On the other hand, when the particle size _RD of the desulfurizing agent M1a and / or the desulfurizing agent M1b exceeds 90 μm, for example, when the fixed positional relationship between the pressure feed pipe 13 and the air supply pipe 11 is α + β = 90 °, or the position thereof. In cases where the relationship is close, the desulfurizing agent M1a and / or the desulfurizing agent M1b may reach the inner wall facing the air supply pipe 11.

As the solid air separation device 14 for recovery, a general dust collector such as a centrifugal force type, a filtration type, or an electrostatic type can be used, but a bug filter (filtration type) is preferable from the viewpoint of operability and the like. The desulfurizing agent M2 used is provided with a transport means (not shown), a belt conveyor, a pneumatic feed, a screw conveyor, etc. for reuse, thereby carrying a pressure feed pipe for transporting the above-mentioned reused desulfurization agent M1b. I try to return it to 13. At this time, the desulfurizing agent M1b to be reused may be returned to the pumping pipe 13 after being subjected to the adjustment of the water content by the water content treatment apparatus 3, and the pumping pipe 13 may be returned to the pumping pipe 13 without adjusting the water content. You may try to return to.

In the embodiment shown in FIG. 5, the desulfurization agent after being used for the desulfurization treatment of the exhaust gas G1 is recovered in the dry desulfurization apparatus 4, and the SO ₃ concentration contained in the used desulfurization agent M 3 is measured by the SO ₃ concentration measuring apparatus. I am trying to measure at 5. For the recovery of the used desulfurization agent M3, for example, via the solid air separation device 14 for recovery in the blow-in desulfurization equipment described with reference to FIG. You can do it. Then, it is determined whether or not the used desulfurizing agent M3 has increased by 3% by mass or more as compared with that before use, and if it has increased by 3% by mass or more, it can be used as a raw material for the ground improvement material as the used desulfurizing agent M5. It is made to be used, and if it is not increased by 3% by mass or more, it can be returned to the route of the desulfurizing agent M1b to be reused, for example, without using it as a raw material of the ground improvement material. As described above _, the SO3 concentration of the desulfurizing agent may be measured by sampling a part of the desulfurizing agent used for the desulfurizing treatment and the desulfurizing agent used for the desulfurizing treatment of the exhaust gas. As the SO ₃ concentration measuring device 5, a fluorescent X-ray analyzer is preferable from the viewpoints of quantitative analysis accuracy, operability, time required for analysis, and expandability to online analysis. Further, for comparison with the SO ₃ concentration of the desulfurizing agent before use, the SO 3 concentration of the newly supplied desulfurizing agent may be measured and, for example, whether or not the SO ₃ concentration is increased by 3% by mass or more may be evaluated. Alternatively, the average or standard SO ₃ concentration of the desulfurizing agent before use is measured or set in advance, or a corresponding threshold value (value of 3% by mass increase) is set, and based on the value, for example. It may be evaluated whether or not the increase is 3% by mass or more.

FIG. 7 shows a schematic configuration explanatory diagram illustrating another embodiment using the exhaust gas produced in the cement manufacturing facility and the used desulfurizing agent.

In the embodiment shown in FIG. 7, the water content measuring device 6 is further provided in the embodiment described in FIG. Then, the used desulfurizing agent M5 sorted according to the SO ₃ concentration is sorted based on its water content. Then, it is determined whether or not the water content of the used desulfurizing agent M3 is less than 40% by mass, and if it is less than 40% by mass, it is used as the used desulfurizing agent M6 as a raw material for the ground improvement material. If it is 40% by mass or more, it can be returned to the path of the desulfurizing agent M1b to be reused, for example, without using it as a raw material for the ground improvement material. As described above, the water content of the desulfurizing agent may be measured by sampling a part of the desulfurizing agent used for the desulfurizing treatment and the desulfurizing agent used for the desulfurizing treatment of the exhaust gas. As the water content measuring device 6, a capacitance type or high frequency type moisture meter device is preferable from the viewpoints of quantitative analysis accuracy, operability, required time for analysis, and expandability to online analysis.

Further, as described above, in another aspect of the present invention without limitation, when the water content of the used desulfurizing agent M3 is 40% by mass or more based on the measurement by the water content measuring device 6, the water content thereof is contained. After drying until the ratio becomes less than 40% by mass _, the desulfurizing agent M7 selected according to the SO3 concentration and the water content may be obtained and used for producing the ground improvement material. The drying device 7 is used in the embodiment shown in FIG. 7. Specifically, the drying apparatus 7 preferably has a configuration in which exhaust gas such as exhaust gas from the preheater outlet and exhaust gas from the waste heat boiler is sprayed onto the used desulfurizing agent 3 at a temperature of 200 to 400 ° C. .. According to this, since waste heat energy is used, energy efficiency is good. Further, since the exhaust gas is usually low in oxygen ( _O2 concentration is about 3 to 6%), a component that contributes to solidification of soil and suppression of elution of hexavalent chromium, for example, sulfite hemihydrate gypsum (CaSO _3.0 ). It does not oxidize sulfites such as .5H ₂ O).

In another aspect of the present invention, as described in the flow chart of FIG. ₄ , the desulfurizing agent M6 sorted by the SO3 concentration and the water content is obtained without going through the drying step in the drying apparatus 7, and the desulfurizing agent M6 is obtained. The desulfurizing agent M7 selected according to the SO ₃ concentration and the water content may be obtained through the drying step in the drying apparatus 7, and both of them may be used for producing the ground improving material. For example, in the supply flow of the used desulfurizing agent at a certain timing _, the requirement that the water content is less than 40% by mass is satisfied. Since it is stored in a predetermined tank or the like along the route and the supply flow of the used desulfurizing agent at another timing does not meet the requirement that the water content is less than 40% by mass, the water content 40 is passed through the drying step in the drying device 7. A desulfurizing agent M7 sorted according to the _SO3 concentration and water content is obtained so as to satisfy the requirement of less than mass%, and then mixed with the sorted desulfurizing agent M6 and used for producing a ground improvement material. You may do so. According to this, even if the water content of the used desulfurizing agent M3 varies _, the used desulfurizing agent having a sufficient amount of SO3 is not excluded under the condition of the water content, but is dried to obtain water. After adjusting the content, it can be used for the production of ground improvement materials without waste.

In another aspect of the present invention without limitation, chlorine bypass dust may be contained in the ground improving material as described above. In this case, chlorine bypass dust M8 can be separated and recovered from the kiln combustion exhaust gas system described in FIGS. 5 and 7 through the solid air separation device 2, and this is preferably used.

In the present invention, the used desulfurizing agent obtained as described above is contained in a predetermined amount in a ground improving material made of a material containing cement clinker and gypsum to obtain a ground improving material having excellent performance. be. The ground improving material to which the present invention can be applied may be any material containing cement clinker and gypsum (for example, a cement-based solidifying material), and is not particularly limited. The content of the used desulfurizing agent contained in the ground improving material is not particularly limited, but from the viewpoint of improving the performance of the ground improving material, it is preferably 1% by mass or more and 50% by mass or less, and 3% by mass. It is more preferably% or more and 30% by mass or less, and even more preferably 5% by mass or more and 15% by mass or less.

Further, when chlorine bypass dust is contained, the content to be contained in the ground improvement material is not particularly limited, but from the viewpoint of improving the performance of the ground improvement material, the chlorine concentration of the ground improvement material may be set. It is preferably 500 ppm or more and 6,000 ppm or less, more preferably 1,000 ppm or more and 5,000 ppm or less, and most preferably 1,500 ppm or more and 3,000 ppm or less. The content of chlorine bypass dust contained in the ground improvement material is preferably 0.1% by mass or more and 5% by mass or less, and more preferably 0.3% by mass or more and 3% by mass or less. , 0.5% by mass or more and 1.5% by mass or less is most preferable.

On the other hand, the present invention can provide a ground improvement method from another viewpoint. That is, the ground improvement material obtained as described above and the target soil can be mixed to improve the ground containing the soil. That is, for example, it is suitably used for strengthening the roadbed, ensuring the workability of heavy machinery and transport vehicles at a construction work site, and strengthening the ground of a construction site of a structure or a building. Although not particularly limited, in that case, it is preferable to mix 50 kg or more and 600 kg or less per 1 m ³ of the target soil, more preferably 100 kg or more and 500 kg or less, and further more preferably 150 kg or more and 400 kg or less. preferable. Further, when converted into the amount of the used desulfurizing agent, it is preferable to mix 0.5 kg or more and 300 kg or less per 1 m ³ of the target soil, more preferably 3 kg or more and 150 kg or less, and 4.5 kg or more and 60 kg or less. It is even more preferable to do so.

Hereinafter, the present invention will be described in more detail with reference to test examples. However, these test examples do not limit the scope of the present invention at all.

[1. Desulfurizer]
-Desulfurizing agent A: Slaked lime (manufactured by Okutama Kogyo Co., Ltd.) (BET specific surface area: 44 m ² / g, pore volume: 0.2 mL / g, apparent density: 0.4 g / mL)
Desulfurizing agent B: Light-weight cellular concrete (ALC) scraps crushed and passed through a sieve with a nominal opening of 1 mm (BET specific surface area: 25 m ² / g, porosity: 59% by volume)

[2. Dry desulfurization]
Desulfurizing agent A or desulfurizing agent B was added to the exhaust gas of the cement factory in a dry manner and used for the desulfurization treatment of the exhaust gas.

Tables 1 and 2 summarize the results of measuring the compositional components of the desulfurizing agent for each usage state by a fluorescent X-ray apparatus (FP method: fundamental parameter method).

[3. Moisture adjustment of used desulfurizing agent]
The water content of the desulfurizing agent B after use (notation: B-3) was measured by an infrared moisture meter (FD-720) and found to be 40% by mass. A part of it was subjected to nitrogen drying treatment to prepare a product having a water content of 30% by mass (notation: B-3').

[4. Chlorine Bypass Dust]
Chlorine bypass dust recovered by the chlorine bypass system of the cement manufacturing facility was used. Table 4 shows the results of measuring the composition components by a fluorescent X-ray apparatus (FP method: fundamental parameter method).

[5. test〕
<Test Example 1>
Blast furnace type B cement, which is the base material of the cement-based solidifying material, was prepared, and various used desulfurization agents and chlorine bypass dust prepared above were added and mixed to prepare a ground improvement material.

(material)
・ Solidified material base: Blast furnace type B cement (ordinary Portland cement 60% by mass: blast furnace slag 40% by mass) (Cl concentration 190ppm)
-Used desulfurization agent (notation: A-1, B-1, B-2, B-3, B-3')
・ Chlorine bypass dust (notation: KP)
・ Ground improvement material: solidifying material base ± used desulfurizing agent ± chlorine bypass dust ・ Co-test soil: soil (Kanto loam, wet density 1.508 g / cm ³ )

(Evaluation 1)
The soil solidification performance and elution characteristics of hexavalent chromium and the like were evaluated for the various ground improvement materials prepared. Specifically, a specimen was prepared by kneading with soil as follows, and a test was conducted by a standard method.

(How to make a specimen)
The test piece was prepared according to JGS 0821 "Method for preparing a test piece without compacting the stabilized soil", which was carried out by adding 300 kg of the ground improvement material to 1 m ³ of the test soil. Specifically, the mixture prepared by kneading under the following conditions was packed in three layers using a rammer in a cylindrical frame having a diameter of 50 mm and a height of 100 mm, and then sealed and cured at 20 ° C. until the age of 7 days. Specimens of each level were prepared.
・ Mixing environment: 20 ° C
・ Mixing procedure: Ground improvement material + sample soil → kneading 5 minutes → scraping → kneading 5 minutes → specimen / kneading means: 5L soil mixer (A120T manufactured by Hobert)
・ Amount used per batch: Ground improvement material amount 300g, test soil 1,508g

The compressive strength (7 days) of JIS A 1216 was measured on the 7th day from the day when the specimen was prepared. In addition, the elution test of hexavalent chromium, fluorine, and selenium was conducted in accordance with the Environmental Agency Notification No. 46 test. For analysis of the test solution, hexavalent chromium is JIS K 0102 "factory wastewater test method 65.2.1 diphenylcarbazide absorptiometry", fluorine is Environmental Agency Notification No. 59 Appendix Table 7 ion chromatograph method, and selenium is JIS K. Analysis was performed by 0102 "Factory effluent test method 67.4 ICP mass spectrometry".

(Evaluation 2)
The prepared ground improvement material was evaluated for its fluidity when a slurry with water was prepared. Specifically, for each sample, a slurry having a water-cement ratio (W / C) of 60% was prepared in an environment of 30 ° C. The flow time (seconds) was measured using a compact flow cone (P-slurry) specified in "Method (method by P-slurry)". The flow time was measured after 90 minutes of continuous stirring.

(Evaluation results)
Table 5 shows the internal division mixing ratio (mass%) of each material to the solidifying material base for each level, the 7-day age strength (kN / m ² ) and hexavalent chromium (Cr ⁶⁺ ) according to the above evaluation 1. The results of the elution amount (mg / L) of fluorine (F) and selenium (Se) and the flow time (seconds) according to the above evaluation 2 are summarized.

As a result, the following became clear.
(1) From the comparison between the blank and levels 1 to 3, when chlorine bypass dust is mixed in the solidifying material base at a ratio of 0.5 to 3% by mass, a slurry with water is produced as compared with the case where chlorine bypass dust is not added. It was clarified that the fluidity when formed was improved. However, no improvement was observed in the soil solidification performance and the elution characteristics of hexavalent chromium and the like.
(2) From the comparison between the blank and level 4, when the desulfurizing agent A made of slaked lime is used for dry desulfurization and then mixed with the solidifying material base at a ratio of 10% by mass, compared with the case where the used desulfurizing agent is not added. Therefore, it was clarified that the soil solidification performance was increased and the elution amount of hexavalent chromium was reduced. However, the fluidity when slurried in water tended to decrease with the addition of a desulfurizing agent.
(3) From the comparison between Level 4 and Levels 5 to 7, water and slurry were formed by mixing chlorine bypass dust at a ratio of 0.5 to 3% by mass in addition to the used desulfurizing agent in the solidifying material base. It became clear that the liquidity of the time was improved. At that time, the effect of reducing the elution amount of hexavalent chromium by adding the desulfurizing agent could be maintained, and the effect of increasing the soil solidification performance by adding the desulfurizing agent could be almost maintained.
(4) From the comparison between the blank and level 8, level 12, level 16, or level 20, desulfurization agent B made of crushed scraps of lightweight cellular concrete (ALC) is used for dry desulfurization and then solidified material. When mixed with the base at a ratio of 10% by mass, the elution amount of hexavalent chromium was reduced as compared with the case where the used desulfurizing agent was not added. Further, at level 20, the soil solidification performance was increased.
(5) From the comparison of Level 8, Level 12, Level 16, or Level 20, the larger the amount of sulfite (SO ₃ ) contained in the used desulfurizing agent, the higher the soil solidification performance and hexavalent chromium. There was a tendency for the effect of reducing the amount of elution to be higher.
(6) From the comparison of levels 9 to 11 for level 8, levels 13 to 15 for level 12, levels 17 to 19 for level 16, and levels 21 to 23 for level 20, solidifying material. It was clarified that when chlorine bypass dust was mixed in a ratio of 0.5 to 3% by mass in addition to the used desulfurizing agent in the base, the fluidity when forming a slurry with water was improved. At that time, the effect of reducing the elution amount of hexavalent chromium by adding the desulfurizing agent could be maintained, and the effect of increasing the soil solidification performance by adding the desulfurizing agent could be almost maintained.
(7) From the comparison of level 20 with respect to level 16, level 21 with respect to level 17, level 22 with respect to level 18, and level 23 with respect to level 19, the scraps of lightweight cellular concrete (ALC) It is better to use the desulfurizing agent B made of crushed material having a water content of 30% by mass (B-3') than to use the desulfurizing agent B having a water content of 40% by mass (B-3). The solidification effect was enhanced, and the effect of reducing the elution amount of hexavalent chromium was enhanced.

From the above, it was clarified that by incorporating the desulfurizing agent used for dry desulfurization in a predetermined ratio in the cement-based solidifying material, the performance of solidifying the soil and the performance of reducing the elution amount of hexavalent chromium are further improved. ..

<Test Example 2>
8 and 9 show the water content of the desulfurizing agent B having a water content of 40% by mass (notation: B-3) and a water content of 30% by mass (notation: B-3'). The results of examining the existence form of the calcium component by the XRD method (X-ray diffraction method) after storage for each period of 1, 7, 14, 28, and 56 days at room temperature from the day of adjustment are shown. The sample was stored in a closed container so that the water did not volatilize during the storage period.

As a result, as shown in FIG. 8, in the case of the one having a water content of 40% by mass, the peak of the sulfite hemihydrate gypsum (CaSO _3.0.5H2O ) becomes smaller with the passage of time, and instead, the _dihydrate gypsum (Casso 3.0.5H2O) becomes smaller. The peak of CaSO _{4.2H 2} O) has come to be detected. On the other hand, as shown in FIG. 9, in the case of a water content of 30% by mass, the peak of sulfite hemihydrate gypsum (CaSO ₃ : 0.5H ₂ O) does not decrease with the passage of time, and dihydrate gypsum (CaSO). _The peak of _4.2H2O ) was not detected either.

From the above, in Test Example 1, the desulfurizing agent B having a water content of 30% by mass has a higher soil solidification performance and a higher effect of reducing the elution of hexavalent chromium than the desulfurizing agent B having a water content of 40% by mass. When the water content of the desulfurizing agent is 40% by mass or more, the sulfite hemihydrate gypsum (CaSO _{3.0.5H 2} O) in the desulfurizing agent B is likely to change to dihydrate gypsum (CaSO _{4.2H 2} O). It was considered that this is because the amount of gypsum sulfate, which effectively works on the soil solidification performance and the effect of reducing the elution of hexavalent chromium, is reduced by the time the test is conducted.

1 ... classifier, 2 ... solid air separation device, 3 ... water content treatment device, 4 ... dry desulfurization device, 5 ... SO ₃ concentration measuring device, 6 ... water content measuring device, 7 ... drying device, 10 ... kiln combustion exhaust gas System, 11 ... air supply pipe, 12 ... desulfurization tower, 13 ... pressure feed pipe, 14 ... solid air separation device for recovery, 20 ... exhaust gas desulfurization system, M1 ... desulfurization agent, M1a ... newly supplied desulfurization agent, M1b ... re- Desulfurizing agent used, M2 ... Desulfurizing agent used, M3 ... Used desulfurizing agent, M4 ... Material including cement scrubber and gypsum, Desulfurizing agent selected by M5 ... SO ₃ concentration, M6, M7 ... SO ₃ concentration And desulfurizing agent selected by water content, M8 ... chlorine bypass dust, G1 ... exhaust gas, G2 ... desulfurized exhaust gas

Claims (9)

A desulfurization process in which a desulfurizing agent is added to the exhaust gas and desulfurized in a dry manner,
A recovery step for recovering the desulfurization agent used in the desulfurization step, and a recovery step.
A method for producing a ground improvement material, which comprises an addition step of incorporating the used desulfurizing agent recovered in the recovery step into a ground improvement material made of a material containing cement clinker and gypsum. The method for producing a ground improving material according to claim 1, wherein the used desulfurizing agent recovered in the recovery step is contained in the ground improving material together with chlorine bypass dust. The method for producing a ground improvement material according to claim 2, wherein the chlorine concentration of the ground improvement material obtained after the addition step is 500 ppm or more and 6,000 ppm or less. Between the recovery step and the addition step, an SO ₃ concentration measuring step for measuring the SO ₃ concentration contained in the used desulfurizing agent is further included, and the SO ₃ concentration contained in the used desulfurizing agent is before use. The method for producing a ground improving material according to any one of claims 1 to 3, wherein the desulfurizing agent having an increase of 3% by mass or more is selected and used in the addition step. Between the recovery step and the addition step, a SO ₃ concentration measuring step for measuring the SO ₃ concentration contained in the used desulfurizing agent and a water content measuring step for measuring the water content of the used desulfurizing agent are further performed. The desulfurizing agent containing, the SO ₃ concentration contained in the used desulfurizing agent has increased by 3% by mass or more as compared with that before use, and the water content is less than 40% by mass, is selected, and the addition step is performed. The method for producing a ground improving material according to any one of claims 1 to 4, which is used in 1. Based on the measurement in the water content measuring step, when the water content of the used desulfurizing agent is 40% by mass or more, it is dried until the water content becomes less than 40% by mass, and then it is added to the addition step. The method for producing a ground improving material according to claim 5, which is used. The desulfurization agent added to the exhaust gas in the desulfurization step includes at least one selected from cement hardening system waste materials, alkali metal compounds, and alkaline earth metal compounds, according to any one of claims 1 to 6. The method for manufacturing the ground improvement material described. The method for producing a ground improving material according to any one of claims 1 to 7, wherein the exhaust gas and the used desulfurizing agent are produced in a cement manufacturing facility. A method for improving ground, which comprises mixing the target soil with the ground improving material obtained by the production method according to any one of claims 1 to 8.

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