JP6977788B2 - Cement composition manufacturing method and cement composition manufacturing system - Google Patents

Description

The present disclosure relates to a method for producing a cement composition and a system for producing a cement composition.

Cement clinker is manufactured using limestone, clay, silica stone, iron oxide and the like as main raw materials. In the production of cement clinker, in addition to these main raw materials, various industrial by-products and industrial wastes are effectively used as raw materials and fuels. However, depending on the selection of raw materials, a small amount of heavy metals such as cadmium, chromium, lead, and molybdenum derived from various raw materials and fuels may be mixed in the cement clinker.

Among heavy metals, hexavalent chromium, unlike other heavy metals, present in the form of a stable oxo anions such chromate ions (CrO 4 ^_2-), even at high pH conditions hardly soluble Does not form hydroxides. For this reason, hexavalent chromium is classified as a heavy metal whose elution countermeasures are relatively difficult. It is known that the elution amount of hexavalent chromium increases especially when volcanic ash cohesive soil such as Kanto Loam is targeted for ground improvement.

Cement clinker and cement may also be used as raw materials for ground improvement materials. The amount of hexavalent chromium eluted from the ground-improved soil is limited to 0.05 mg / L or less according to the soil environmental standard. In Patent Document 1, a reducing gypsum composition obtained by drying a slurry containing calcium sulfite hemihydrate and dihydrate gypsum obtained in a flue gas desulfurization step is blended with a cement-based solidifying material to obtain hexavalent chromium. A technique has been proposed in which the soil is reduced to trivalent chromium to detoxify the solidified gypsum.

Japanese Unexamined Patent Publication No. 2007-246306

Since commercially available sulfites such as calcium sulfite are expensive, the manufacturing cost of cement compositions increases when commercially available products are used. On the other hand, as in Patent Document 1, the use of a reducing gypsum composition for the cement-based solidifying material is effective in reducing the elution of hexavalent chromium from the solidified soil, but the reducing gypsum composition can be obtained. It will be necessary to produce. Therefore, the present disclosure provides a method for producing a cement composition and a system for producing a cement composition, which can easily produce a cement composition effective for reducing the elution of hexavalent chromium.

The method for producing a cement composition according to one aspect of the present disclosure includes a mixing step of blending a cement clinker and a sulfite composition and pulverizing the mixture to obtain a cement composition. In this production method, since the sulfite composition and the cement clinker are mixed and pulverized to obtain a cement composition, the cement composition can be easily produced. Since this cement composition contains a sulfite composition, it is excellent in pulverizability and can reduce the elution of hexavalent chromium when used as a solidifying material, for example.

In the mixing step, it is preferable to further add gypsum to obtain a cement composition. Thereby, the composition of the cement composition can be easily adjusted.

In the mixing step, the solid content containing the sulfite composition is blended as a sulfite slurry dispersed in a solvent containing water, and the concentration of the solid content in the sulfite slurry is preferably 0.1 to 90% by mass. .. The content of sulfite in the solid content is preferably 1% by mass or more. As a result, a sulfite slurry having good handleability can be used, and an appropriate amount of water is mixed with the cement clinker, so that pulverization can be facilitated. In addition, it is possible to produce a cement composition that suppresses the gypsum contained in the cement composition from being excessively converted into hemihydrate gypsum, has excellent fluidity and strength development, and is difficult to solidify even when stored for a long period of time. Such a cement composition can sufficiently reduce the elution of hexavalent chromium when used as a solidifying material.

The above-mentioned production method reduces the water content from the sulfite slurry in which the solid content containing the sulfite composition is dispersed in a solvent containing water, and produces a powdery or cake-like solid having a solid content concentration of 90% by mass or more. It is preferable that the sulfite composition has a water content adjusting step to obtain, the sulfite content in the solid content is 1% by mass or more, and the sulfite composition is blended as a solid in the mixing step. Thereby, even if the content of the sulfite composition in the sulfite slurry is small, the content of the sulfite composition in the cement composition can be sufficiently increased. In addition, transportation by a belt conveyor or the like and temporary storage are facilitated, and handleability can be improved.

The calcium sulfite composition preferably contains at least one selected from the group consisting of calcium sulfite, a compound salt of calcium sulfite and calcium sulfate, and calcium sulfite. Further, the solid content containing the sulfite composition preferably contains at least one selected from the group consisting of calcium sulfate, calcium hydroxide, calcium carbonate, and magnesium hydroxide. By containing such a component, a cement composition capable of further reducing the elution of hexavalent chromium can be obtained.

The calcium sulfite contained in the sulfite composition has the lengths of the major axis and the minor axis of the main surface of 1 to 500 μm and 0.5 to 300 μm, respectively, and the thickness is 50% or less of the length of the major axis. It preferably contains flaky crystals. By containing such flaky crystals, it is possible to produce a cement composition which is excellent in pulverizability and can easily increase the specific surface area.

The sulfite composition contains at least one salt of calcium sulfite and calcium sulfite, and in the above mixing step, the compounding ratio of the sulfite composition to 100 parts by mass of the cement clinker is the total of the salts in terms of anhydride (that is, , The sum of calcium sulfite and calcium sulfite in terms of anhydride) is preferably 0.1 to 20 parts by mass. This makes it possible to carry out pulverization sufficiently smoothly while maintaining the elution of hexavalent chromium at a sufficiently low level.

The above-mentioned manufacturing method is a group consisting of exhaust gas generated when manufacturing a cement clinker, exhaust gas generated in a thermal power generation facility, a combustion gas obtained by burning sulfur, and a heat-decomposed gas obtained by heat-decomposing a sulfur compound. A gas containing sulfurous acid gas, which comprises at least one selected from the above, and a raw material slurry containing an alkaline earth metal and / or a compound having an alkali metal are brought into contact with each other, and the solid content containing the sulfurous acid composition is water. It is preferable to have a slurry preparation step of obtaining a sulfurous acid sulfate slurry dispersed in a solvent containing. The alkali metal and the alkaline earth metal may be contained in the raw material slurry as a carbonate and / or a hydroxide. Thereby, the manufacturing cost of the cement composition can be sufficiently reduced.

The above manufacturing method preferably includes an bleeding step of extracting gas between the kiln bottom of the cement kiln portion and the bottom cyclone of the preheater portion to obtain exhaust gas. This makes it possible to prepare a sulfite composition by utilizing the bypass portion in the existing cement clinker manufacturing facility. However, this disclosure does not exclude the establishment of new cement clinker manufacturing equipment.

The manufacturing method includes a cooling step of cooling the exhaust gas to obtain dust particles containing a chlorine compound before bringing the exhaust gas into contact with the raw material slurry, and a collection of dust particles from which at least a part of the dust particles is removed from the exhaust gas at a dust collecting portion. It is preferable to have a dust process. This makes it possible to efficiently produce a sulfite composition in which unnecessary components are reduced.

The gas in contact with the raw material slurry is generated when a combustion gas obtained by burning sulfur and / or a heat-decomposed gas obtained by heat-decomposing a sulfur compound is used to produce air and / or a cement clinker. It is preferable to include a mixed gas obtained by diluting with exhaust gas. Thereby, the concentration of the sulfurous acid gas and the temperature of the exhaust gas can be adjusted in a suitable range, and the sulfurous acid gas contained in the exhaust gas can be efficiently made into a sulfite composition.

The brain specific surface area of the cement composition ^{is preferably 2500 to 10000 cm 2} / g. Since the sulfite composition is excellent in pulverizability, a cement composition having such a brain specific surface area can be smoothly produced.

The cement composition manufacturing system according to one aspect of the present disclosure includes a mixing portion in which a cement clinker and a sulfite composition are mixed and pulverized to manufacture a cement composition. Since this production system includes a mixing unit in which the sulfite composition is mixed with cement clinker and pulverized, the cement composition can be easily produced. Since this cement composition contains a sulfite composition, it is excellent in pulverizability and can reduce the elution of hexavalent chromium when used as a solidifying material, for example.

In the above mixing portion, the solid content containing the sulfite composition is blended as a sulfite slurry dispersed in a solvent containing water, and the concentration of the solid content in the sulfite slurry is 0.1 to 90% by mass and is solid. The content of sulfite in the minute is preferably 1% by mass or more. As a result, a sulfite slurry having good handleability can be used, and an appropriate amount of water is mixed with the cement clinker, so that pulverization can be facilitated. In addition, it is possible to produce a cement composition that suppresses the gypsum contained in the cement composition from being excessively converted into hemihydrate gypsum, has excellent fluidity and strength development, and is difficult to solidify even when stored for a long period of time. Such a cement composition can sufficiently reduce the elution of hexavalent chromium when used as a solidifying material.

The above manufacturing system includes a cement kiln section for calcining a raw material containing sulfur to obtain a cement clinker, and a preheater section provided with a cyclone for contacting the raw material with a gas containing exhaust gas from the cement kiln section to preheat the raw material. , A bypass section that draws exhaust gas containing sulfite gas from between the kiln bottom of the cement kiln section and the bottom cyclone of the preheater section, and the gas containing the exhaust gas and at least one carbonate of alkaline earth metal and alkali metal and / or It is preferable to provide a slurry preparation unit for contacting a raw material slurry containing a hydroxide to obtain a sulfite slurry in which the solid content containing the sulfite composition is dispersed in a solvent containing water. As a result, the existing cement clinker manufacturing equipment can be utilized, and the equipment configuration can be simplified while sufficiently reducing the manufacturing cost of the cement composition. However, this disclosure does not exclude the establishment of new cement clinker manufacturing equipment.

In the above manufacturing system, the exhaust gas containing sulfurous acid gas is removed by removing at least a part of the dust particles contained in the exhaust gas and the cooling unit that cools the exhaust gas from the cement kiln to generate dust particles containing chlorine compounds that aggregate. It is preferable to provide a dust collecting unit for obtaining the above. This makes it possible to efficiently produce a slurry in which unnecessary components are reduced.

The manufacturing system includes a sulfur furnace that burns sulfur and / or a heating furnace that heats and decomposes sulfur compounds, a combustion gas obtained in the sulfur furnace, and / or a gas containing a heating decomposition gas obtained in the heating furnace. , Alkaline earth metal and a raw material slurry containing at least one carbonate and / or hydroxide of alkali metal are brought into contact with each other to obtain a sulfur sulfate slurry in which the solid content containing the sulfurous acid composition is dispersed in a solvent containing water. It is preferable to provide a slurry preparation unit for obtaining. This makes it possible to easily prepare a slurry containing a high content of sulfites.

The manufacturing system includes a gas mixing section that mixes combustion gas and / or heat decomposition gas with air and / or exhaust gas from the cement kiln section, and the slurry preparation section contains the mixed gas obtained in the gas mixing section. It is preferable to bring the gas and the raw material slurry into contact with each other to obtain a sulfite slurry. Thereby, the concentration of the sulfurous acid gas and the temperature of the gas can be adjusted in a suitable range, and the sulfurous acid gas can be efficiently made into a sulfite composition.

The manufacturing system preferably includes a control unit that adjusts the compounding ratio of the sulfite composition to the cement clinker according to the chromium content of the cement clinker. Thereby, the sulfite composition can be effectively utilized while sufficiently reducing the elution of hexavalent chromium.

According to the present disclosure, it is possible to provide a method for producing a cement composition and a system for producing a cement composition, which can easily produce a cement composition effective for reducing the elution of hexavalent chromium.

FIG. 1 is a schematic diagram showing an example of flaky crystals. 1 (A) is a plan view of a flaky crystal, and FIG. 1 (B) is a side view of the flaky crystal. FIG. 2 is a diagram showing an example of a cement composition manufacturing system. FIG. 3 is a diagram showing another example of a cement composition manufacturing system. FIG. 4 is a diagram showing an apparatus used as a slurry preparation unit in the examples. 5 (A) and 5 (B) are SEM (scanning electron microscope) photographs of the sulfite composition of Example 1-1. FIG. 6 is a graph in which the results of Examples and Comparative Examples are plotted with the horizontal axis representing the crushing time and the vertical axis representing the brain specific surface area.

Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings as the case may be. However, the following embodiments are examples for explaining the present disclosure, and are not intended to limit the present disclosure to the following contents. In the description, the same reference numerals are used for the same elements or elements having the same function, and duplicate description may be omitted in some cases. In addition, the positional relationship such as up, down, left, and right shall be based on the positional relationship shown in the drawings unless otherwise specified. Further, the dimensional ratio of each element is not limited to the ratio shown in the figure.

The method for producing a cement composition according to an embodiment of the present disclosure includes a mixing step of blending a cement clinker and a solid content containing a sulfite composition and pulverizing the mixture to obtain a cement composition. As an example, in the mixing step, a cement clinker and a slurry in which a solid content containing a sulfite composition is dispersed in a solvent containing water may be blended, and then the obtained formulation may be pulverized to obtain a cement composition. good. As another example, in the mixing step, the mixing of the cement clinker and the slurry in which the solid content containing the sulfite composition is dispersed in the solvent containing water may be performed at the same time. As yet another example, in the mixing step, after crushing the cement clinker to some extent, a slurry in which the solid content containing the sulfite composition is dispersed in a solvent containing water is mixed, and the obtained combination is further crushed. May be good. In any of the above-mentioned mixing steps, gypsum may be blended at the same time or later to obtain a cement composition.

In the present disclosure, the sulfite composition includes a sulfite, a sulfite, or a double salt containing one or both of them. Examples of the sulfurous acid salt include sulfurous acid salts of alkali metals and alkaline earth metals, ammonium sulfite, copper sulfite, iron sulfite, zinc sulfite, aluminum sulfite and the like. The calcium sulfite preferably contains, for example, at least one selected from the group consisting of calcium sulfite, a compound salt of calcium sulfite and calcium sulfate, calcium sulfite, and magnesium sulfite. "Calcium sulfite" in the present disclosure is a hemihydrate unless otherwise specified. However, the sulfite may contain a hydrate other than the hemihydrate, such as a tetrahydrate other than the calcium sulfite hemihydrate and an anhydrous sum.

Calcium sulfite contains flaky crystals having a major axis length and a minor axis length of 1 to 500 μm and 0.5 to 300 μm, respectively, and a thickness of 50% or less of the length of the major axis. Is preferable. Such calcium sulfite has excellent reactivity because of its small crystal size. Since the flaky crystals are excellent in pulverizability, a highly reactive sulfite composition can be easily produced. The length and thickness of the major axis and the minor axis of the main surface of the flaky crystal can be measured based on the observation image by SEM.

FIG. 1 is a schematic diagram showing an example of flaky crystals included in an observation image by SEM. 1A is a plan view of the flaky crystal 61, and FIG. 1B is a side view of the flaky crystal 61. The length of the major axis 64 of the main surface 62 of the flaky crystal 61 is two different positions selected on the outer edge of the main surface of the plate-like crystal (the surface having the plane having the largest area). It is the maximum distance among the distances connecting points. The length of the minor axis 66 of the main surface 62 is the maximum distance among the distances connecting two points at different positions selected on the outer edge of the main surface 62 in the direction orthogonal to the major axis 64 of the main surface 62. Is. For example, if the main surface is square, the lengths of the main axis and the minor axis are both equal to the length of the diagonal line. The thickness of the flaky crystal is the maximum length along the direction orthogonal to the main plane. In FIG. 1B, the thickness of the flaky crystal 61 is T.

The length of the major axis 64 of the main surface 62 is preferably 1 to 500 μm, more preferably 3 to 300 μm, still more preferably 5 to 150 μm, and most preferably 10 to 100 μm. The length of the minor axis 66 of the main surface 62 is preferably 0.5 to 300 μm, more preferably 1 to 150 μm, and further preferably 5 to 50 μm. The thickness T of the flaky crystal 61 is preferably 50% or less, more preferably 30% or less, still more preferably 10% or less, and particularly preferably 10% or less, with respect to the length of the major axis 64 of the main surface. It is preferably 5% or less, and most preferably 1% or less. Specifically, the thickness T may be, for example, 30 μm or less, 10 μm or less, or 1 μm or less.

In the present disclosure, a slurry in which a solid content containing a sulfite composition is dispersed in a solvent may be referred to as a “sulfite slurry”. In the present disclosure, the raw material slurry is a slurry in which an alkaline earth metal and / or a compound having an alkali metal is dispersed in a solvent. Examples of such compounds include alkali earth metals and at least one carbonate and / or hydroxide of alkali metals. Specifically, it may be a calcium compound such as calcium carbonate and calcium hydroxide. However, the raw material slurry may contain components other than the calcium compound. Examples of such a component include magnesium hydroxide. The content of the calcium compound in the raw material slurry can be adjusted in consideration of the flow rate of the exhaust gas, the concentration of sulfur oxides in the exhaust gas, the size of the absorption equipment, and the like. From the viewpoint of maintaining good fluidity of the raw material slurry, the concentration of the solid content of the calcium compound or the like in the raw material slurry may be, for example, 1 to 90% by mass.

The solvent of the sulfite slurry and the raw material slurry may be water or a liquid containing water as a main component. The slurry (sulfite slurry and raw material slurry) in the present disclosure includes a granular solid and a solvent containing water as a main component. The slurry of the present disclosure may be a suspension or a fluid having a fluidity similar to that of sludge.

The solid content containing the sulfite composition is used when synthesizing sulfates such as gypsum, alkali metals, alkaline earth metals, iron, copper, aluminum and zinc, and sulfite compositions in addition to the sulfite compositions. Unreacted alkaline components (alkali metals such as slaked lime and hydroxides of alkaline earth metals, alkali metals such as calcium carbonate and carbonates of alkali metals, etc.) and other impurity components (sodium chloride, potassium chloride, chloride, etc.) It may contain chlorides such as calcium and magnesium chloride; alkali metals such as calcium sulfide and sulfides of alkaline earth metals; silicate compounds such as calcium silicate; oxides such as iron). The solid content preferably contains at least one selected from the group consisting of calcium sulfate dihydrate, calcium hydroxide, calcium carbonate, and magnesium hydroxide.

_{The sulfite slurry can be obtained by contacting a sulfur oxide (SO 2} , SO _3, etc.) contained in the exhaust gas of a sulfur-containing fuel such as coal, petroleum, coal coke, and petroleum coke with a raw material slurry. can. The contact method is not particularly limited, and for example, the two may be brought into contact with each other by bubbling the exhaust gas in the raw material slurry.

Examples of the exhaust gas containing sulfur oxides include exhaust gas from a boiler installed in a thermal power generation facility using coal or petroleum, exhaust gas from a cement kiln, and the like. In a thermal power generation facility, a sulfite slurry may be obtained by a flue gas desulfurization step by a lime / gypsum method. Further, instead of or together with the exhaust gas, a combustion gas obtained in a sulfur furnace that burns sulfur and / or a heat decomposition gas obtained in a heating furnace that heats and decomposes a sulfur compound such as gypsum may be used. The gas containing sulfur oxide may be used as a mixed gas obtained by mixing two or more kinds, or may be diluted with air to adjust the sulfur oxide and the temperature. However, the means for obtaining the sulfite slurry is not limited to the above.

For example, the exhaust gas from the cement kiln contains sulfur oxides generated from raw materials containing sulfur. Therefore, the sulfite slurry containing the sulfite composition can be efficiently produced by bringing the exhaust gas from the cement kiln portion into contact with the raw material slurry. In particular, the gas between the kiln butt of the cement kiln and the calcination furnace contains a large amount of sulfur oxides, so if the exhaust gas during this period is used, a sulfite slurry containing a large amount of sulfites can be produced with sufficiently high efficiency. can do. Chlorine bypass is often installed as a facility to extract exhaust gas from the kiln butt of the cement kiln to the calcination furnace. Therefore, a suitable sulfite slurry can be obtained by performing an bleeding step of extracting gas from a chlorine bypass to obtain exhaust gas and bringing the exhaust gas into contact with the raw material slurry.

Further, for example, an aqueous solution containing magnesium sulfite discharged from the desulfurization step by the magnesium hydroxide method may be treated with calcium to obtain a sulfite slurry. Further, industrial wastewater containing a water-soluble sulfite containing at least one of an alkali metal and an alkaline earth metal generated in a chemical factory or the like may be treated with calcium to obtain a sulfite slurry. One kind of the sulfite slurry thus obtained may be used alone or in combination of a plurality of kinds.

The content of sulfite in the solid content contained in the sulfite slurry is, for example, 1% by mass or more, preferably 10% by mass or more, more preferably 30% by mass or more, still more preferably 50% by mass or more. , Particularly preferably 70% by mass or more. The sulfite slurry may contain a component other than the sulfite composition as a solid content. Examples of such a component include calcium hydroxide, calcium carbonate, magnesium hydroxide, calcium sulfate and the like. Calcium sulfate may contain any of dihydrate (dihydrate gypsum), hemihydrate (hemihydrate gypsum), and anhydride (anhydrous gypsum). When the sulfite slurry contains an appropriate amount of calcium sulfate, the compounding of gypsum in the mixing step can be reduced or omitted. The content of calcium sulfate / dihydrate in the sulfite slurry is, for example, 30% by mass or less with respect to the total solid content. From the viewpoint of preparing a sulfite slurry containing each of the above components in a suitable range, the pH thereof is preferably 3.0 to 11.0, more preferably 4.0 to 9.0, and 5.0 to 7 .0 is even more preferred.

The concentration of the solid content in the sulfite slurry is, for example, 0.1 to 90% by mass, preferably 1 to 70% by mass, more preferably 3 to 50% by mass, and further preferably 5 to 40% by mass. %. Within such a range, the mixing of the sulfite slurry and the cement composition can be sufficiently uniform while maintaining the handleability of the sulfite slurry at a high level.

The type of cement clinker is not particularly limited, and may be any of various Portland cements specified in JIS R 5210: 2003 “Portland cement”. According to the cement composition of the present embodiment, the elution of hexavalent chromium can be sufficiently suppressed. The total amount of chromium in the cement clinker may be, for example, 20 to 250 mg / kg, 80 to 200 mg / kg, or 100 to 150 mg / kg. The amount of water-soluble hexavalent chromium of the cement clinker measured according to the method described in Cement Association Standard Test Method I-51-1981 may be, for example, 3 to 40 mg / kg, and may be 10 to 40 mg / kg. It may be 20 to 30 mg / kg.

The cement composition produced by the production method of the present embodiment can be the Portland cement specified in JIS R 5210 “Portland cement”. Examples of such Portland cement include ordinary Portland cement, early-strength Portland cement, moderate heat Portland cement, and low heat Portland cement. Further, at least one selected from blast furnace slag, fly ash and siliceous material may be added to these Portland cements to make mixed cements.

In the mixing step, a cement clinker, a sulfite slurry and gypsum may be mixed and pulverized to obtain a cement composition. The gypsum to be blended may be in any form of dihydrate gypsum, hemihydrate gypsum and anhydrous gypsum. Each form of gypsum may be blended alone or in combination of a plurality of types. The order of blending the cement clinker, the sulfite slurry and the gypsum is not particularly limited, and two of them may be blended first and then the remaining one may be blended, or three of them may be blended at the same time. good. The blending amount of gypsum may be about 3 to 10% by mass in terms of _{SO 3 with respect to the cement clinker.}

The pulverization in the mixing step may be performed by a finishing mill such as a ball mill or a vertical mill. A cement clinker, a sulfite slurry, gypsum, a pulverizing aid, and the like are added to the finishing mill and mixed while being pulverized to produce a cement composition. The cement composition thus obtained contains sulfites. Therefore, the content of hexavalent chromium in the cement composition can be reduced. The content of sulfite in the cement composition is, for example, preferably 0.1 to 15% by mass, more preferably 0.5 to 10% by mass, still more preferably 1 to 5% by mass.

The brain specific surface area of the cement composition obtained by the pulverization treatment is, for example, 2500 to 10000 cm ² / g, preferably 3000 to 8000 cm ² / g, more preferably 3500 to 7000 cm ² / g, and further preferably. Is 4300 to 6000 cm ² / g, and most preferably 5000 to 6000 cm ² / g. When the brain specific surface area is 2500 cm ² / g or more, it becomes easy to achieve excellent strength development. On the other hand, when the brain specific surface area is 10,000 cm ² / g or less, it is easy to control the viscosity when used as a concrete or solidifying material slurry within a suitable range.

The form of gypsum contained in the cement composition is preferably dihydrate gypsum or anhydrous gypsum (type II). The proportion of hemihydrate gypsum in the gypsum contained in the cement composition is preferably 50% by mass or less, more preferably 30% by mass or less, and more preferably 20% by mass with respect to the total amount of dihydrate gypsum and anhydrous gypsum. It is more preferably mass% or less.

By blending the sulfurous acid slurry containing the sulfurous acid composition obtained by contacting the sulfurous acid gas contained in the exhaust gas, the combustion gas, and / or the heat decomposition gas generated from various facilities with the raw material slurry into the cement clinker as it is. It is possible to easily produce a cement composition capable of reducing the elution of hexavalent chromium without installing a large-scale new facility. The sulfite slurry also contributes to the desulfurization of exhaust gas, combustion gas, and / or heat decomposition gas, and since the sulfite is used as the slurry without drying, a series of processes for desulfurization and production of the cement composition can be carried out. Can be simplified. In addition, since the sulfite slurry can be used instead of water injection at the time of crushing the cement composition, and the sulfite composition and the cement clinker can be uniformly mixed by utilizing the existing equipment, the manufacturing process can be shortened and the equipment can be shortened. In addition to simplification, it has the advantage of significantly reducing the manufacturing cost of a cement composition that is effective in reducing the elution of hexavalent chromium.

In the above embodiment, the sulfite slurry and the cement clinker are blended, but in the modified example, the water content is reduced from the sulfite slurry, and the solid content is 90% by mass or more, which is a powdery or cake-like solid. It has a water content adjusting step for obtaining a product, and a mixing step for obtaining a cement composition by blending a cement clinker and a solid material containing a sulfite composition and pulverizing the mixture. In this mixing step, gypsum may be blended at the same time or later to obtain a cement composition.

In the moisture adjusting step, a solid substance may be obtained by dehydration and dry powdering. For example, the desulfite composition may be powdered by drying under reduced pressure while applying shear to the cake obtained by dehydration. The concentration of the solid content in the solid matter may be 90% by mass or more, 95% by mass or more, or 98% by mass or more. In the mixing step, a solid material such as a cake or powder containing a sulfite composition and a cement clinker are mixed to obtain a cement composition. Gypsum may also be added. The cement composition may contain, for example, 0.1 to 20 parts by mass of sulfites based on solid content, or 2 to 20 parts by mass with respect to 100 parts by mass of cement clinker.

In the mixing step, the cake or powder containing the sulfite composition, the cement clinker and the gypsum may be introduced into a pulverizer (for example, a mill) sequentially or simultaneously, and mixed while pulverizing to prepare a cement composition. If a cake containing a solid content containing a high-temperature cement clinker and a sulfite composition is introduced into a crusher, the cement composition can be produced by performing drying, mixing and pulverization in parallel.

The cement composition obtained in each of the above examples may be used as it is as a soil conditioner, or may be blended with gypsum to form a soil conditioner. The soil-improved soil may be prepared by blending the soil to be improved, the cement composition and gypsum.

The method for producing the cement composition of the present embodiment may be carried out using the cement composition manufacturing system described below, or may be carried out using other cement composition manufacturing systems. The description of the cement composition manufacturing system described below can be applied to the cement composition manufacturing method of the present embodiment.

The cement composition manufacturing system according to the embodiment of the present disclosure includes a mixing unit in which a cement clinker and a slurry containing a sulfite are mixed and pulverized to manufacture a cement composition. This manufacturing system may or may not include a cement clinker manufacturing apparatus. The sulfite slurry containing the sulfite composition may be obtained by contacting the Ca-based slurry with the exhaust gas discharged from a cement clinker manufacturing apparatus using a sulfur-containing raw material, a thermal power generation facility, or the like.

FIG. 2 is a diagram showing an example of a cement composition manufacturing system. The cement composition manufacturing system 100 is extracted from a cement clinker manufacturing apparatus 70 having a cement kiln section 10 for producing a cement clinker by firing a raw material containing sulfur and a bypass section 12 for extracting exhaust gas, and a bypass section 12. A cooling unit 17 that cools the exhaust gas to generate dust particles containing a chlorine compound that aggregates, and a dust collecting unit 19 that removes at least a part of the dust particles contained in the exhaust gas to obtain an exhaust gas containing sulfurous acid gas. A slurry preparation unit 30 for contacting the exhaust gas with a raw material slurry containing a calcium compound to obtain a sulfurous acid sulfate slurry containing calcium sulfite as a sulfurous acid salt is provided.

The cement clinker manufacturing apparatus 70 includes a preheater unit (not shown) for preheating the raw material by contacting a raw material containing sulfur with the exhaust gas from the cement kiln unit 10, and a kiln tail of the cement kiln unit 10, which includes a plurality of cyclones. A bypass section 12 for extracting exhaust gas containing sulfite gas from between the bottom cyclone of the preheater section (the cyclone at the bottom) or the calciner is provided. The bypass portion 12 may be a chlorine bypass portion of the cement clinker manufacturing apparatus 70.

In the cement kiln portion 10, coal, petroleum coke and the like are burned to generate exhaust gas containing sulfur dioxide. The gas extracted from the bleeding pipe constituting the bypass portion 12 is used as the exhaust gas between the kiln butt of the cement kiln portion 10 and the bottom cyclone or the calcining furnace (not shown). The concentration of sulfur dioxide in the exhaust gas from the bypass portion 12 may be, for example, about 100 to 5000 ppm on a volume basis (standard temperature). Exhaust gas is extracted from the bypass portion 12 (bleeding process). The extracted exhaust gas is cooled to, for example, about 100 to 200 ° C. by the cooling unit 17 (cooling step). The cooling in the cooling unit 17 may be performed by mixing the exhaust gas with outside air (air) or the like, or may be performed by a cooler using heat with cooling water or air or the like.

By cooling the exhaust gas, volatile chlorine compounds and the like aggregate on the surface of the dust particles originally contained in the exhaust gas. At least a part of such dust particles is removed by the dust collecting unit 19 (dust collecting step). The dust collector 19 has, for example, a bug filter. If the exhaust gas may contain dust particles, the dust collecting unit 19 may be bypassed.

The exhaust gas from which at least a part of the dust particles has been removed in the dust collecting unit 19 is introduced into the slurry preparing unit 30. The slurry preparation unit 30 includes, for example, a bubbling tank for storing a raw material slurry containing a calcium compound. Exhaust gas is introduced into the raw material slurry and bubbling to bring them into contact with each other (slurry preparation step). As a result, sulfur dioxide is incorporated into the raw material slurry to obtain a sulfite slurry. In addition, it is possible to effectively utilize sulfur dioxide whose release into the atmosphere is restricted. In this way, the slurry preparation unit 30 also functions as a flue gas desulfurization unit. The means of contact between the raw material slurry and the exhaust gas is not limited to bubbling.

Air may be introduced into the slurry preparation unit 30. Thereby, a part of calcium sulfite may be oxidized to obtain a dihydrate of calcium sulfate. Thereby, a sulfite slurry containing calcium sulfite and a dihydrate of calcium sulfate can be obtained. By containing the dihydrate of calcium sulfate in the sulfite slurry, the amount of gypsum compounded in the compounding portion 51 can be reduced or eliminated. The content of sulfite in the solid content contained in the sulfite slurry is, for example, 1% by mass or more, preferably 10% by mass or more, more preferably 30% by mass or more, still more preferably 50% by mass or more. , Particularly preferably 70% by mass or more. The content of each sulfite can be determined, for example, by thermogravimetric analysis as shown in Examples, or by the XRD Rietveld method. The sulfite slurry may contain a component other than the sulfite composition as a solid content. Examples of such a component include calcium hydroxide, calcium carbonate, magnesium hydroxide, calcium sulfate and the like.

The sulfite slurry obtained in the slurry preparation unit 30 and the cement clinker are introduced into the compounding unit 51 in the mixing unit 50. The cement clinker may be one temporarily stored in the silo 18, or the cement clinker obtained in the cement kiln portion 10 may be used as it is. The sulfite slurry is introduced into the compounding section 51 via the liquid feeding section.

In the compounding section 51, gypsum may be compounded as needed. The sulfite slurry may contain at least one salt of calcium sulfite and calcium sulfite. The compounding ratio of the sulfite slurry to 100 parts by mass of the cement clinker is preferably 0.1 to 20 parts by mass, more preferably 0.15 to 15 parts by mass, and further, in terms of the total amount of the salts in terms of anhydride. It is preferably 0.2 to 10 parts by mass, and particularly preferably 0.25 to 5 parts by mass. Thereby, the compound can be smoothly pulverized while maintaining the content of the sulfite composition in the obtained cement composition. The compounding ratio of gypsum to 100 parts by mass of cement clinker may be about 1.5 to 20 parts by mass in terms of _{SO 3.}

The formulation containing cement clinker, sulfites and gypsum is introduced into the finishing mill 52. The finishing mill 52 may be a ball mill or a vertical mill. The temperature of the finishing mill 52 tends to rise due to frictional heat during grinding. Water is sprinkled into the finishing mill 52 so that the temperature inside the finishing mill 52 does not rise excessively. Therefore, when the sulfite slurry contains water, it is possible to suppress an excessive temperature rise in the finishing mill 52. Therefore, blending the sulfite in the form of a slurry also contributes to reducing the amount of water sprinkled into the finishing mill 52.

The temperature of the finishing mill 52 is preferably 20 ° C to 180 ° C, more preferably 40 ° C to 130 ° C, and even more preferably 70 ° C to 110 ° C. When the temperature of the finishing mill 52 is lower than 80 ° C., the water content of the sulfite slurry tends to cause a hydration reaction with the cement composition. On the other hand, when the temperature exceeds 180 ° C., calcium sulfite tends to be oxidized and changed to calcium sulfate. That is, by setting the finishing mill 52 in the above temperature range, the drying of the formulation proceeds at a sufficient rate while suppressing the oxidation of calcium sulfite. In addition, cement clinker, calcium sulfite and gypsum can be mixed sufficiently uniformly (mixing step).

The cement composition thus obtained capable of reducing the elution amount of hexavalent chromium may be stored in a silo 60. In this example, the mixing section 50 includes, but is not limited to, a blending section 51 and a finishing mill 52. For example, in the modification of this example, the cement clinker, the sulfite slurry and the gypsum to be blended as needed may be directly charged into the finishing mill 52 and blended and pulverized in the finishing mill 52. Further, the cement clinker and gypsum are blended in the compounding section 51, and the sulfite slurry is sprayed on the compounding portion on a belt conveyor for transporting the compounding obtained from the compounding section 51 to the finishing mill 52, and crushed by the finishing mill 52. May be done.

In another modification, at least a part of the sulfite slurry prepared by the slurry preparation unit 30 may be introduced into the water content adjustment unit. The water content adjusting unit is configured to be able to adjust the solid content concentration in the sulfite slurry by dehydration or water addition. The solid content concentration in the sulfite slurry may be 0.1 to 95% by mass. In the slurry concentration adjusting unit, the sulfite slurry may be dehydrated and / or dried to obtain a dehydrated cake-like or powdery solid substance. Thereby, even if the content of the sulfite composition in the sulfite slurry is small, the content of the sulfite composition in the cement composition can be sufficiently increased. In addition, transportation by a belt conveyor or the like and temporary storage are facilitated, and handleability can be improved. The concentration of the solid content in the solid matter may be 90% by mass or more, 95% by mass or more, or 98% by mass or more.

In yet another modification, a control unit may be provided that adjusts the compounding ratio of the sulfite slurry to the cement clinker according to the chromium content of the cement clinker derived from the cement kiln unit 10. The chromium content of the cement clinker may be measured by sampling from the silo 18 at a predetermined frequency, or may be calculated from the chromium content contained in the raw material introduced into the cement clinker manufacturing apparatus 70.

The control unit calculates the amount of the sulfite slurry (sulfite composition) to be blended in the cement clinker based on the input value of the chromium content of the cement clinker obtained as described above. The control unit may have table data showing the relationship between the cement chromium content and the amount of the sulfite slurry blended, or may have correlation data between the two. The control unit calculates the blending amount of the sulfite slurry using such data. Based on the calculation result, the control unit controls, for example, a flow rate control valve that adjusts the flow rate of the sulfite slurry. In this way, the compounding ratio of the sulfite slurry to the cement clinker can be adjusted. Such control can be easily realized because the slurry has fluidity.

The cement composition manufacturing system 100 and its modification are to manufacture a cement composition that can reduce the elution of hexavalent chromium by using the existing cement clinker manufacturing equipment without installing large-scale new equipment. Can be done. In addition to being able to manufacture sulfite slurry and desulfurize exhaust gas at the same time, it is possible to install dehydration equipment for the slurry, and a dedicated tank, weighing machine, and transportation equipment for the solid matter after dehydration. Is no longer necessary. Therefore, the introduction cost and the operation cost of the equipment can be sufficiently reduced.

FIG. 3 is a diagram showing another example of a cement composition manufacturing system. The manufacturing system 110 of FIG. 3 is different from the manufacturing system of FIG. 2 in that the exhaust gas of the boiler 40 is used instead of the exhaust gas from the cement clinker manufacturing apparatus 70. Other points are the same as the manufacturing system 100 of FIG. Here, the points different from the manufacturing system 100 will be mainly described.

The boiler 40 is, for example, a boiler provided in a thermal power generation facility. The exhaust gas from the boiler 40 contains sulfur dioxide. The exhaust gas is introduced into the slurry preparation unit 30A. The slurry preparation unit 30A has the same configuration and function as the slurry preparation unit 30. Therefore, in the slurry preparation unit 30A, sulfur dioxide can be incorporated into the raw material slurry to obtain a sulfite slurry. In addition, it is possible to effectively utilize sulfur dioxide whose release into the atmosphere is restricted.

When the boiler 40 is installed away from the cement clinker manufacturing apparatus 70 and the crushing equipment, the sulfite slurry obtained by contacting the exhaust gas from the boiler 40 with the raw material slurry is produced by a pipeline, a tank lorry car, or a ship. It may be transported.

If the cement composition production system 110 is used, sulfur dioxide contained in the exhaust gas can be utilized to produce a cement composition capable of reducing the elution of hexavalent chromium.

The cement composition production system of the present embodiment may be performed by using the above-mentioned cement composition production method, or may be performed by other cement composition production methods. The above-mentioned description of the cement composition manufacturing method can also be applied to the cement composition manufacturing system of the present embodiment.

Although one embodiment of the present disclosure has been described above, the present disclosure is not limited to the above embodiment. For example, a sulfur furnace that burns sulfur may be used instead of the boiler 40, or a heating furnace that heats and decomposes sulfur compounds such as gypsum may be used. A combustion gas obtained by burning sulfur in a sulfur furnace and / or a heat-decomposed gas obtained by decomposing a sulfur compound such as gypsum in a heating furnace is introduced into a slurry preparation unit 30 (30A) to form a sulfite composition. A sulfite slurry containing a substance may be prepared. The combustion gas and / or the heat-decomposed gas may be a mixed gas whose sulfur dioxide concentration and temperature are adjusted by diluting with another gas (exhaust gas) in the gas mixing section. Such a mixed gas may be introduced into the slurry preparation unit 30 (30A) alone or together with other exhaust gases. The other gas may be air or exhaust gas extracted from the chlorine bypass portion of the cement clinker manufacturing apparatus.

The contents of the present disclosure will be described in more detail with reference to Examples and Comparative Examples, but the present disclosure is not limited to the following examples.

(Examples 1-1 to 1-9)
[Preparation of sulfite slurry]
A manufacturing apparatus as shown in FIG. 4, which has a function as a slurry preparation unit, was used. The manufacturing apparatus 31 of FIG. 4 is led out from the absorption tower 81 for preparing the sulfite slurry containing the sulfurous acid composition, the raw material slurry tank 90 for supplying the raw material slurry to the absorption tower 81, and the lead-out line 85 from the absorption tower 81. A sulfurous acid slurry tank 92 for storing the sulfurous acid slurry, a water content adjusting unit 94 for reducing the water content contained in the sulfurous acid slurry, and a cooling unit 95 for cooling the sulfurous acid slurry are provided. The sulfite slurry 98 staying at the bottom of the absorption tower 81 is cooled by heat exchange with the heat exchanger 96 to which the cooling liquid is supplied from the cooling unit 95.

A part of the sulfite slurry retained at the bottom of the absorption tower 81 is circulated in the upper part of the absorption tower 81 by the circulation line 82, and is sprayed into the absorption tower 81 by the nozzle 84. The other part of the sulfite slurry staying at the bottom of the absorption tower 81 is led out to the sulfite slurry tank 92 via the lead-out line 85.

The raw material gas containing the exhaust gas obtained by extracting the gas between the kiln bottom of the cement kiln section and the bottom cyclone of the preheater section was introduced from the gas introduction section 86 into the absorption tower 81 at about 200 ° C. Further, the raw material slurry containing calcium carbonate was introduced from the raw material slurry tank 90 into the absorption tower 81. While adjusting the pH of the sulfite slurry 98 collected in the bottom of the absorption tower 81 to 5.50 to 5.80, as shown in Table 1, by changing the SO ₂ concentration in the feed gas, contained in the sulfite slurry The sulfite slurry of Examples 1-1 to 1-9 having different solid content compositions was produced. The temperature of the sulfite slurry 98 at the bottom of the absorption tower 81 in each example was as shown in Table 1.

[Analysis of solid content concentration in sulfite slurry]
The sulfite slurry was dried in air at 100 ° C., and the solid content concentration was measured from the amount of mass loss. The specific calculation formula is as follows. The solid content concentration of each example was as shown in Table 1.
-Solid content concentration (mass%) = (mass of sulfite slurry-mass reduction amount) / mass of sulfite slurry x 100

[Solid composition analysis]
The sulfite slurry was filtered and dehydrated to obtain a cake. This cake was dried in air at 60 ° C. to obtain a solid content. The powder XRD analysis of the obtained solid content was performed, and it was confirmed that only calcium sulfite / hemihydrate, calcium carbonate, and dihydrate gypsum were detected. Then, thermogravimetric analysis was performed to determine the content (% by mass) of calcium sulfite hemihydrate, calcium carbonate, and dihydrate gypsum in the solid content. The results are as shown in Table 1. The analysis conditions are as follows.

<Powder XRD analysis>
An X-ray diffractometer (manufactured by Bruker AXS Co., Ltd., acceleration voltage: 30 kV, current: 10 mA, tube: Cu) was used.

<Thermogravimetric analysis>
Using a commercially available thermogravimetric analyzer, the change in thermogravimetric analysis when heated to 200 ° C., 600 ° C. and 900 ° C. was measured. At 200 ° C, the dihydrate gypsum dehydrates. Calcium sulfite oxidizes at 600 ° C. Calcium carbonate decomposes at 900 ° C. Using the change in mass at each temperature, the contents of dihydrate gypsum, calcium sulfite and calcium carbonate were calculated based on the following formulas. The sample mass is the mass of the solid content used in the thermogravimetric analysis. It should be noted that the holding at each heating temperature was set until the weight change disappeared. The holding time at each heating temperature was 1 hour. In addition, the atmosphere at the time of heating was air.

-Content rate of dihydrate gypsum (mass%) = mass reduction amount until the mass change disappears after heating from room temperature to 200 ° C. x ([Molecular weight of dihydrate gypsum] / [Crystal water contained in dihydrate gypsum] Molecular weight]) / sample mass x 100
-Calcium carbonate content (mass%) = (mass of sample after heating to 900 ° C and no change in mass) x [mass of sample after heating to -600 ° C and no change in mass) x [CaCO ₃ Molecular weight] / [Molecular weight of CO ₂ ] / Mass of sample x 100
-Calcium sulfite content (mass%) = 100- (dihydrate gypsum content + calcium carbonate content)

As shown in Table 1, all of Examples 1-1 to 1-9 contain calcium sulfite / hemihydrate, calcium carbonate and dihydrate gypsum in the solid content, and calcium sulfite / hemihydrate. The content of the substance was 30% by mass or more.

5 (A) and 5 (B) are SEM (scanning electron microscope) photographs of the sulfite composition of Example 1-1. FIG. 5A is an SEM photograph enlarged from FIG. 5B. The crystals of calcium sulfite / hemihydrate contained in the sulfite composition have a minor axis length of 10 to 30 μm on the main surface, a major axis length of 15 to 100 μm on the main surface, and a thickness of 1 μm. It was confirmed that it was a thin plate-like crystal. Such crystals are easily crushed and can be easily made into fine particles of less than 1 μm without using a crusher.

(Examples 2-1 to 2-5, Comparative Examples 2-1 to 2-4)
[Preparation of cement composition]
The sulfite slurry of Example 1-9 was dried in air at 40 ° C. to prepare a powdery solid (moisture content: <1% by mass) containing a sulfite composition. This solid substance and / or flue gas desulfurization gypsum and ordinary Portland cement clinker were put into a ball mill with the formulations shown in Table 2 and pulverized for a predetermined time to obtain a cement composition. The degree of powderiness of the cement composition thus obtained was evaluated. The evaluation method is as follows. The flue gas desulfurization gypsum used here is a dihydrate gypsum produced by a thermal power generation facility that is desulfurized by the lime-gypsum method (hereinafter referred to as flue gas desulfurization gypsum).

[Evaluation of powderiness of cement composition]
The degree of powderiness of the cement composition was evaluated by the specific surface area of the brain and the residue of 45 μm. The brain specific surface area was measured according to JIS R5201: 2015 “Physical test method for cement”. The 45 μm residue was measured in accordance with JCAS K-02-2004 “Cement Powder Degree Test Method Using 45 μm Net Sieve”. The results of these measurements are shown in Table 2.

[Evaluation result of crushability of cement composition]
The cement compositions of Example 2-1 and Example 2-2 containing a solid substance containing a sulfite composition were compared with the cement composition of Comparative Example 2-1 containing no sulfite composition. The brain specific surface area became 4420-4470 cm ² / g in a short grinding time.

FIG. 6 is a graph in which the results of Table 2 are plotted with the horizontal axis representing the crushing time and the vertical axis representing the brain specific surface area. In FIG. 6, black circles are data when the blending ratio of the solid matter containing the sulfite composition is 15.5% by mass (Examples 2-2, 2-5), and black squares are the sulfite composition. It is the data (Examples 2-1, 2-3, 2-4) that the blending ratio of the solid matter containing is 4% by mass and the blending ratio of the drained sulfurous acid gypsum is 11.5% by mass. On the other hand, the white triangles are data in which the sulfite composition is not blended and the blending ratio of the drained dihydrate gypsum is 15.5% by mass (Comparative Examples 2-1 to 2-4). As shown in FIG. 6, it was confirmed that the brain specific surface area can be increased in a short time by blending a solid substance containing a sulfite composition. As described above, the pulverization efficiency of the cement composition can be improved by blending the sulfite composition containing calcium sulfite / hemihydrate.

(Example 3-1)
[Manufacturing of cement composition]
Using a ball mill commonly used for cement production, a sulfite slurry containing ordinary Portland cement clinker, dihydrate gypsum and sulfite composition is mixed and pulverized to produce the cement composition of Example 3-1. did.

As the sulfite slurry, a sulfite slurry prepared in the same manner as in Examples 1-1 to 1-9 was used. A dehydrated cake having a water content of 60% by mass was prepared by dehydrating a sulfite slurry having a solid content concentration of 6% by mass, and then put into a ball mill. The solid content of the sulfite slurry was 78.1% by mass of calcium sulfite / hemihydrate, 16.3% by mass of dihydrate gypsum, and 5.6% by mass of calcium carbonate.

The content of calcium sulfite / hemihydrate in the cement composition calculated from the composition of the solid content and the compounding ratio was 3.48% by mass. The brain specific surface area of the cement composition was 5050 cm ² / g. Compared with the case where the sulfite slurry containing the sulfite composition was not added, the milling amount of the cement composition per unit time was improved by up to 60%. Therefore, it was possible to increase the production of the cement composition.

[Evaluation of solidified soil]
Using the cement composition of Example 3-1 the soil ground was improved in the following manner, and its performance was evaluated. Kanto Loam (wet density: 1.36 cm ³ / g) was prepared as the soil to be treated. The processed soil to the cement composition of Example 3-1, in proportions of 300 kg / m ^3, were mixed using a Hobart mixer to obtain a mixture.

The prepared mixture 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 to prepare solidified soil. The prepared solidified soil was subjected to an elution test in accordance with Environmental Standards Notification No. 46 (August 23, 1991), and the elution amount of hexavalent chromium [Cr (VI)] was determined. The amount satisfied the standard value (0.05 mg / L or less) of the soil environmental standard.

According to the present disclosure, it is possible to provide a method for producing a cement composition and a system for producing a cement composition, which can easily produce a cement composition effective for reducing the elution of hexavalent chromium.

10 ... Cement kiln part, 12 ... Bypass part, 17 ... Cooling part, 18 ... Silo, 19 ... Dust collection part, 30, 30A ... Slurry preparation part, 31 ... Manufacturing equipment, 40 ... Boiler, 50 ... Mixing part, 51 ... Blending part, 52 ... mill, 60 ... silo, 61 ... flaky crystal, 62 ... main surface, 64 ... long axis, 66 ... short axis, 70 ... cement clinker manufacturing equipment, 81 ... absorption tower, 82 ... circulation line, 84 ... Nozzle, 85 ... Derivation line, 86 ... Gas introduction section, 90 ... Raw material slurry tank, 92 ... Sulfuric acid slurry tank, 94 ... Moisture control section, 95 ... Cooling section, 96 ... Heat exchanger, 98 ... Sulfate slurry, 100 ... Manufacturing system.

Claims (22)

Cement clinker, a sulfite composition, was to crushed formulation containing calcium sulfite, have a mixing step of obtaining a cement composition,
The calcium sulfite contains flaky crystals having a major axis length and a minor axis length of 1 to 500 μm and 0.5 to 300 μm, respectively, and a thickness of 50% or less of the length of the major axis. A method for producing a cement composition. The method for producing a cement composition according to claim 1, wherein in the mixing step, gypsum is further blended to obtain the cement composition. In the mixing step, the solid content containing the sulfite composition is blended as a sulfite slurry dispersed in a solvent containing water.
The concentration of the solid content in the sulfite slurry is 0.1 to 90% by mass, and the concentration is 0.1 to 90% by mass.
The method for producing a cement composition according to claim 1 or 2, wherein the content of calcium sulfite in the solid content is 1% by mass or more. Moisture adjustment to reduce the water content from the sulfite slurry in which the solid content containing the sulfite composition is dispersed in a solvent containing water to obtain a powdery or cake-like solid material having a solid content concentration of 90% by mass or more. Have a process,
The content of calcium sulfite in the solid content is 1% by mass or more, and the content is 1% by mass or more.
The method for producing a cement composition according to any one of claims 1 to 3, wherein the sulfite composition is blended as the solid substance in the mixing step. The flaky crystal according to any one of claims 1 to 4, wherein the lengths of the major axis and the minor axis of the main surface are 15 to 100 μm and 10 to 30 μm, respectively, and the thickness is 1 μm. How to make a cement composition. The method for producing a cement composition according to any one of claims 1 to 5, wherein the content of the flaky crystals of calcium sulfite in the solid content containing the sulfite composition is 30% by mass or more. The solid content containing the sulfite composition contains at least one selected from the group consisting of calcium sulfate, calcium hydroxide, calcium carbonate, and magnesium hydroxide.
The method for producing a cement composition according to any one of claims 1 to 6, wherein in the mixing step, the cement clinker and the solid content are mixed and pulverized to obtain the cement composition. Prior Symbol mixing step, the mixing ratio of the sulfite composition to the cement clinker 100 parts by weight, the from 0.1 to 20 parts by weight anhydrous Mono換calculation of calcium sulfite, any one of claims 1 to 7, The method for producing a cement composition according to item 1. At least selected from the group consisting of exhaust gas generated when manufacturing the cement clinker, exhaust gas generated in a thermal power generation facility, combustion gas obtained by burning sulfur, and heat decomposition gas obtained by heat-decomposing a sulfur compound. A gas containing sulfurous acid gas, including one, and
Any one of claims 1 to 8, comprising a slurry preparation step of contacting a raw material slurry containing a calcium compound with a sulfurous acid slurry in which the solid content containing the sulfurous acid composition is dispersed in a solvent containing water. The method for producing a cement composition according to a section. The method for producing a cement composition according to claim 9, further comprising an bleeding step of extracting gas between the kiln bottom of the cement kiln portion and the bottom cyclone of the preheater portion to obtain the exhaust gas. Before contacting the exhaust gas with the raw material slurry,
A cooling step of cooling the exhaust gas to obtain dust particles containing chlorine compounds,
The method for producing a cement composition according to claim 9, further comprising a dust collecting step of removing at least a part of the dust particles from the exhaust gas at the dust collecting unit. The gas in contact with the raw material slurry is generated when a combustion gas obtained by burning sulfur and / or a heat-decomposed gas obtained by heat-decomposing a sulfur compound is produced in the air and / or in the production of the cement clinker. The method for producing a cement composition according to any one of claims 9 to 11, which comprises a mixed gas obtained by diluting with the exhaust gas. The method for producing a cement composition according to any one of claims 1 to 12, wherein the brain specific surface area of the cement composition is 2500 to 10000 cm ^{2 / g.} A mixing portion for producing a cement composition by blending and pulverizing a cement clinker and a sulfite composition containing calcium sulfite is provided.
The calcium sulfite contains flaky crystals having a major axis length and a minor axis length of 1 to 500 μm and 0.5 to 300 μm, respectively, and a thickness of 50% or less of the length of the major axis. A cement composition manufacturing system. In the mixing portion, the solid content containing the sulfite composition is blended as a sulfite slurry in which a solvent containing water is dispersed.
The concentration of the solid content in the sulfite slurry is 0.1 to 90% by mass, and the concentration is 0.1 to 90% by mass.
The system for producing a cement composition according to claim 14, wherein the content of calcium sulfite in the solid content is 1% by mass or more. The cement composition according to claim 14 or 15, wherein the flaky crystals have a major axis length and a minor axis length of 15 to 100 μm and 10 to 30 μm, respectively, and a thickness of 1 μm. Manufacturing system. The system for producing a cement composition according to any one of claims 14 to 16, wherein the content of the flaky crystals of calcium sulfite in the solid content containing the sulfite composition is 30% by mass or more. A cement kiln portion that obtains the cement clinker by firing a raw material containing sulfur, and
A preheater unit provided with a cyclone to preheat the raw material by bringing the raw material into contact with a gas containing exhaust gas from the cement kiln portion.
A bypass section for extracting exhaust gas containing sulfurous acid gas from between the kiln bottom of the cement kiln section and the bottom cyclone of the preheater section.
A slurry preparation unit for contacting the gas containing the exhaust gas with the raw material slurry containing calcium carbonate and / or calcium hydroxide to obtain a sulfite slurry in which the solid content containing the sulfite composition is dispersed in a solvent containing water. The system for producing a cement composition according to any one of claims 14 to 17, comprising the above. A cooling unit that cools the exhaust gas from the cement kiln unit to generate dust particles containing chlorine compounds that aggregate.
The cement composition manufacturing system according to claim 18 , further comprising a dust collecting unit for removing at least a part of the dust particles contained in the exhaust gas to obtain the exhaust gas containing sulfite gas. A sulfur furnace that burns sulfur and / or a heating furnace that heats and decomposes sulfur compounds,
The sulfurous acid composition is obtained by contacting the combustion gas obtained in the sulfur furnace and / or the gas containing the heat-decomposed gas obtained in the heating furnace with the raw material slurry containing calcium carbonate and / or calcium hydroxide. The system for producing a cement composition according to any one of claims 14 to 19, further comprising a slurry preparation unit for obtaining a sulfite slurry in which the solid content contained is dispersed in a solvent containing water. The slurry preparation section includes a gas mixing section that mixes the combustion gas and / or the heat-decomposed gas with air and / or the exhaust gas from the cement kiln section, and the slurry preparation section contains the mixed gas obtained in the gas mixing section. The cement composition manufacturing system according to claim 20 , wherein the gas and the raw material slurry are brought into contact with each other to obtain the sulfite slurry. The production of the cement composition according to any one of claims 14 to 21 , comprising a control unit for adjusting the compounding ratio of the sulfite composition with respect to the cement clinker according to the chromium content of the cement clinker. system.

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