JP2020176057A - Manufacturing method of cement composition, and manufacturing system of cement composition - Google Patents

Abstract

To provide a manufacturing system of a cement composition capable of manufacturing easily a cement composition effective for elution reduction of hexavalent chromium.SOLUTION: A manufacturing system 100 of a cement composition includes a cement clinker firing part 70 for obtaining cement clinker by firing a raw material, a desulfurization part 60 for obtaining slurry containing a sulfite compound by allowing raw material slurry to absorb sulfurous acid gas contained in exhaust gas from the cement clinker firing part 70, and a pulverization part 50 for obtaining the cement composition by pulverizing a compound containing cement clinker and slurry.SELECTED DRAWING: Figure 1

Description

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

Cement clinker is produced 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, heavy metals such as cadmium, chromium, and lead derived from various raw materials may be mixed in the cement clinker in a very small amount.

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 or cement may also be used as a raw material for ground improvement materials. The amount of hexavalent chromium eluted from soil improvement soil is limited to 0.05 mg / L or less by 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 make the solidified soil harmless.

JP-A-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 as a cement-based solidifying material is effective in reducing the elution of hexavalent chromium from the solidified soil, but the reducing gypsum composition can be used. It is necessary to produce. Therefore, the present disclosure provides a method and a production system for a cement composition capable of easily producing 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 is a cement clinker manufacturing process in which a raw material is fired to produce a cement clinker, and a sulfite gas contained in exhaust gas generated in the cement clinker manufacturing process is absorbed in a raw material slurry. It has a desulfurization step of obtaining a slurry containing a sulfite compound, and a crushing step of crushing a compound containing a cement clinker and the above slurry to obtain a cement composition.

In this production method, a slurry containing a sulfurous acid compound is obtained from sulfurous acid gas generated when a cement clinker is produced from a raw material. Then, the compound containing the cement clinker and this slurry is pulverized to obtain a cement composition. As described above, since the sulfite compound effective for reducing the elution of hexavalent chromium is obtained from the exhaust gas generated in the cement clinker manufacturing process, it is possible to easily produce a cement composition effective for reducing the elution of hexavalent chromium. Can be done.

In the pulverization step, it is preferable to mix gypsum to obtain a cement composition. This makes it easy to adjust the composition of the cement composition.

It is preferable to have a slurry concentration adjusting step of adjusting the ratio of the solid content in the slurry to 0.1 to 95% by mass. As a result, the handleability of the slurry can be maintained well, and an appropriate amount of water is mixed with the cement clinker, so that pulverization can be facilitated. Further, it is possible to produce a cement composition in which the gypsum contained in the cement composition is suppressed from being excessively converted into hemihydrate gypsum, has excellent fluidity and strength development, and is hard to solidify even when stored for a long period of time.

The above slurry is at least one sulfite compound selected from the group consisting of a hemihydrate of calcium sulfite, calcium bicarbonate (Ca (HSO ₃ ) ₂ ), and a compound salt of calcium sulfite and calcium sulfate as solid content. And at least one salt selected from the group consisting of calcium sulfate dihydrate, 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 produced. From the same viewpoint, the sulfite slurry preferably contains a double salt of calcium sulfite and calcium sulfate.

When the cement composition is 100 parts by mass, it is preferable to add 0.1 to 20 parts by mass of the slurry to the cement clinker in terms of anhydride of the sulfite compound. As a result, pulverization can be sufficiently smoothly performed while maintaining the elution of hexavalent chromium at a sufficiently low level.

In the desulfurization step, it is preferable to obtain a slurry containing calcium sulfite by treating at least a part of the exhaust gas generated in the cement clinker manufacturing step by the lime method. As a result, a slurry containing calcium sulfite can be obtained in a simple process.

In the desulfurization step, it is preferable that the sulfurous acid gas is absorbed in an aqueous solution containing an alkaline earth metal different from Ca and / or a salt of the alkali metal, and then a calcium compound is mixed to obtain a slurry containing calcium sulfite. This can reduce the effects of scaling by calcium sulfite and improve process stability.

The raw material slurry contains an inorganic powder containing a calcium compound generated in the cement clinker production process, and preferably contains 10 to 98% by mass of the calcium compound as CaO with respect to the entire inorganic powder. This makes it possible to simplify the preparation of a slurry containing a sulfite compound. In addition, the production cost of the cement composition can be sufficiently reduced.

In some embodiments, the above-mentioned production method comprises fine particle powder containing CaCO ₃ as a main component generated when crushing a clinker raw material, and dust particles containing CaO and / or Ca (OH) ₂ generated in a chlorine bypass portion. , One or more selected from the group consisting of water-washed dust particles obtained by washing dust particles with water, and sludge containing cement and / or cement hydrate (for example, raw conslurry obtained at a ready-mixed concrete factory). It is preferable to have a raw material slurry preparation step for preparing the raw material slurry using the material. Thereby, the production cost of the cement composition can be sufficiently reduced.

The SO ₂ concentration of the exhaust gas is preferably 500 to 10000 ppm. As a result, a sufficient amount of sulfurous acid compound can be obtained from the exhaust gas. Further, the SO ₂ concentration of the exhaust gas may be controlled to 500 to 10000 ppm by adjusting the sulfur content of the raw material. Thereby, the SO ₂ concentration of the exhaust gas can be controlled by a simple method. The raw material may contain a sulfur-containing raw material containing at least one selected from the group consisting of waste gypsum board, waste tires and desulfurized slag.

The solid content concentration of the above slurry is adjusted based on at least one of the temperature of the cement clinker obtained in the cement clinker manufacturing process, the temperature of the cement composition at the outlet of the cement mill, and the ignition loss of the cement composition. It is preferable to have an adjustment step. As a result, a cement composition with reduced variation in properties can be stably produced.

Even if the exhaust gas contains a gas of 700 to 1200 ° C. extracted from the kiln tail of the cement kiln between the calcining furnaces and has a cooling step of cooling the exhaust gas to 400 ° C. or lower before the desulfurization step. Good. As a result, the sulfurous acid compound can be efficiently obtained from the exhaust gas having a high sulfur concentration.

The exhaust gas obtained in the desulfurization step after at least a part of the sulfur dioxide gas has been absorbed may be introduced into the cement kiln. As a result, the waste heat can be effectively utilized and the production cost of the cement composition can be reduced. Moreover, the release of NOx and the like can be further reduced.

In the cement composition manufacturing system according to one aspect of the present disclosure, a cement clinker firing section for obtaining a cement clinker by firing a raw material and a sulfite gas contained in exhaust gas from the cement clinker firing section are absorbed into the raw material slurry. It includes a desulfurization section for obtaining a slurry containing a sulfite compound, and a crushing section for crushing a formulation containing cement clinker and the slurry to obtain a cement composition.

In the above production system, a slurry containing a sulfurous acid compound is obtained from sulfurous acid gas generated when cement clinker is produced from a raw material. Then, the compound containing the cement clinker and this slurry is pulverized to obtain a cement composition. As described above, since the sulfite compound effective for reducing the elution of hexavalent chromium is obtained from the exhaust gas generated in the cement clinker firing section, it is possible to easily produce a cement composition effective for reducing the elution of hexavalent chromium. Can be done.

The manufacturing system preferably includes a slurry concentration adjusting unit that adjusts the proportion of solids in the slurry to 0.1 to 95% by mass. As a result, the handleability of the slurry can be maintained well, and an appropriate amount of water is mixed with the cement clinker, so that pulverization can be facilitated. In addition, this prevents the gypsum contained in the cement composition from becoming excessively semi-hydrated gypsum, and produces a cement composition having excellent fluidity and strength development and which is difficult to solidify even after long-term storage. it can.

The above slurry is at least one sulfite compound selected from the group consisting of a hemihydrate of calcium sulfite, calcium bicarbonate (Ca (HSO ₃ ) ₂ ), and a compound salt of calcium sulfite and calcium sulfate as solid content. And at least one salt selected from the group consisting of calcium sulfate dihydrate, 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 produced. From the same viewpoint, the sulfite slurry preferably contains a double salt of calcium sulfite and calcium sulfate.

The desulfurous acid section is a first preparation section in which sulfite gas is absorbed in an aqueous solution containing an alkaline earth metal different from Ca and / or a salt of an alkali metal to obtain a sulfite compound different from calcium sulfite, and a sulfite compound and calcium. It is preferable to have a second preparation part, which is mixed with a compound to obtain a slurry containing calcium sulfite. This can reduce the effect of scaling by calcium sulfite and improve the stability of the manufacturing system.

In the desulfurization part, fine particle powder containing CaCO ₃ as a main component, dust particles containing CaO and / or Ca (OH) ₂ generated in the chlorine bypass part, and dust particles generated when the raw material is crushed are washed with water. It is preferable to provide a raw material slurry preparation unit for preparing a raw material slurry using at least one selected from the group consisting of the obtained water-washed dust particles and sludge containing cement and / or cement hydrate. Thereby, the production cost of the cement composition can be sufficiently reduced.

It is preferable that the manufacturing system includes a first control unit that adjusts the sulfur content of the raw material to control the SO ₂ concentration of the exhaust gas to 500 to 10,000 ppm. As a result, a sufficient amount of sulfurous acid compound can be obtained from the exhaust gas.

The production system controls the solid content concentration of the slurry based on at least one of the temperature of the cement clinker obtained in the cement clinker firing section, the outlet temperature of the cement mill, and the ignition loss of the cement composition. It is preferable to provide a portion. As a result, a cement composition with reduced variation in properties can be stably produced.

In the above manufacturing system, it is preferable that the exhaust gas contains a gas extracted from the kiln bottom of the cement kiln between the calcining furnaces and has a cooling unit for cooling the exhaust gas to 400 ° C. or lower. As a result, the sulfurous acid compound can be efficiently obtained from the exhaust gas having a high sulfur concentration.

The manufacturing system preferably includes a flow path for introducing the exhaust gas obtained in the desulfurization section after absorption of at least a part of the sulfur dioxide gas into the cement kiln. As a result, the waste heat can be effectively utilized and the production cost of the cement composition can be reduced. Moreover, the release of NOx and the like can be further reduced.

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

It is a figure which shows an example of the manufacturing system of a cement composition. It is a figure which shows another example of the manufacturing system of a cement composition.

Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings in some cases. 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. 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 is a cement clinker manufacturing process in which a raw material containing sulfur is fired to produce a cement clinker, and a sulfite gas contained in exhaust gas generated in the cement clinker manufacturing process. It has a desulfurization step of absorbing it into a raw material slurry to obtain a slurry containing a sulfite compound, and a crushing step of crushing a compound containing a cement clinker and a slurry to obtain a cement composition. As an example, in the pulverization step, a slurry containing a cement clinker and a sulfite compound and gypsum may be blended, and then the formulation containing these may be pulverized to obtain a cement composition. As another example, in the pulverization step, the slurry containing the cement clinker and the sulfite compound and gypsum may be blended and pulverized at the same time. As yet another example, in the pulverization step, the cement clinker may be pulverized to some extent, and then a slurry containing a sulfite compound and gypsum may be blended, and the obtained formulation may be further pulverized.

Examples of the raw material include a sulfur-containing raw material and a clinker raw material. However, it is not essential to use a sulfur-containing raw material, and the fuel may contain sulfur. A slurry containing a sulfurous acid compound (hereinafter, also referred to as “sulfurous acid slurry”) contains, for example, calcium sulfite as a sulfurous acid compound. For example, an exhaust gas containing sulfurous acid gas is generated from a cement clinker manufacturing process in which a cement clinker is manufactured using a raw material containing sulfur. By bringing this exhaust gas into contact with the raw material slurry, the sulfurous acid slurry can be efficiently produced. In particular, since the gas between the kiln end of the cement kiln and the calcining furnace contains a large amount of sulfur oxides, 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. be able to. In the present disclosure, "between the kiln butt and the calcining furnace" includes the kiln butt, the calcining furnace, and the space between them.

When the chlorine bypass section is installed as a facility for extracting the exhaust gas from the kiln end of the cement kiln section to the calcining furnace, the gas may be extracted from the chlorine bypass section to obtain the exhaust gas. Further, the exhaust gas may be extracted from the kiln butt of the cement kiln. Since such exhaust gas has a high temperature (for example, 700 to 1200 ° C.), it may have a cooling step for cooling the exhaust gas to 400 ° C. or lower. Sulfurous acid slurry can be efficiently prepared by bringing such exhaust gas into contact with the raw material slurry. A sulfurous acid slurry may be obtained by a lime method using a raw material slurry containing lime.

In the production method of the present embodiment, the raw material slurry is made of water, fine particle powder containing CaCO ₃ as a main component generated when the clinker raw material is crushed, CaO and / or Ca (OH) ₂ generated in the chlorine bypass portion. Raw material slurry prepared using one or more selected from the group consisting of dust particles containing dust particles, water-washed dust particles obtained by washing the dust particles with water, and sludge containing cement and / or cement hydrate. It may have a preparation step. The raw material slurry preferably contains 10 to 98% by mass of the calcium compound as CaO with respect to the entire inorganic powder containing the calcium compound.

Examples of the sulfite compound contained in the sulfite slurry include calcium sulfite (for example, hemihydrate), calcium sulfite (Ca (HSO ₃ ) ₂ ), a double salt of calcium sulfite and calcium sulfate, and magnesium sulfite. The content of the sulfurous acid compound (anhydrous equivalent) in the sulfurous acid slurry is preferably 5% by mass or more, more preferably 30% by mass or more, still more preferably 50% by mass or more, particularly preferably 50% by mass or more, based on the total solid content. It is preferably 70% by mass or more.

The sulfurous acid slurry may contain components other than the sulfurous acid compound. Examples of such a component include calcium hydroxide, calcium carbonate, magnesium hydroxide, calcium sulfate and the like. It may contain at least one of these components. Calcium sulfate may contain any of dihydrate (dihydrate gypsum), hemihydrate (hemihydrate gypsum), and anhydrous (anhydrous gypsum).

When the sulfite slurry contains an appropriate amount of calcium sulfate, the compounding of gypsum in the pulverization 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 obtaining a sulfite slurry containing each of the above components in a suitable range, the pH is preferably 3.0 to 11.0, more preferably 4.0 to 9.0, and 5.0 to 7. 0 is more preferred.

In one example, the slurry concentration adjusting step for adjusting the ratio of the solid content in the sulfite slurry to 0.1 to 95% by mass may be provided. The proportion of the solid content in the sulfurous acid slurry is 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 mixture of the sulfurous acid slurry and the cement composition can be sufficiently made uniform while maintaining a high level of handleability of the sulfurous acid slurry.

The solid content concentration of the slurry is determined by the temperature Tr of the cement clinker obtained in the cement clinker manufacturing process, the temperature of the cement composition at the outlet of the cement mill (Tm, 40 to 140 ° C.), and the ignition loss of the cement composition (Ig, It may be adjusted based on at least one of (ig. Loss) (slurry concentration adjusting step). Thereby, the temperature at the time of pulverization in the cement mill can be controlled in a suitable range (40 to 140 ° C.), and a cement composition having stable quality can be produced while reducing the amount of water sprinkled on the cement mill. it can.

The exhaust gas obtained in the desulfurization step after at least a part of the sulfurous acid gas is absorbed in the sulfurous acid slurry may be introduced into the cement kiln via a cooler part, a preheater part or a calcining furnace of a cement clinker. .. As a result, the sulfurous acid gas that has not been absorbed by the sulfurous acid slurry can be recovered as exhaust gas again, and the sulfur content can be effectively used. Further, by performing heat recovery, the production cost of the cement composition can be reduced. Further, when the exhaust gas contains a trace amount of NOx (nitrogen oxide), the amount of NOx released can be further reduced.

The type of cement clinker obtained in the cement clinker manufacturing process 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 mg / kg to 250 mg / kg, 80 mg / kg 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 the Cement Association Standard Test Method JCAS I-53-2018 may be, for example, 3 to 40 mg / kg, and may be 10 to 40 mg / kg. It may be kg or 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 pulverization step, a cement clinker, a sulfite slurry and, if necessary, gypsum may be blended and pulverized to obtain a cement composition. The gypsum to be blended may be in any form of dihydrate gypsum, semi-hydrated gypsum and anhydrous gypsum. Each form of gypsum may be blended alone or in combination of two or more. The order of blending the cement clinker, the sulfite slurry and the gypsum is not particularly limited, and two of these may be blended first and then the remaining one may be blended, or three thereof may be blended at the same time. .. 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 gypsum may be prepared by oxidizing and dehydrating a part of the sulfite slurry.

The crushing in the crushing 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 a sulfite compound. Therefore, the content of hexavalent chromium in the cement composition can be reduced. The content of the sulfite compound 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 preferably 2500 to 6000 cm ² / g, and more preferably 3000 to 5000 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 6000 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 ratio of hemihydrate gypsum to the gypsum contained in the cement composition may be 98% by mass or less, preferably 0.1 to 95% by mass, based on the total amount of dihydrate gypsum and anhydrous gypsum. It is more preferably 5 to 85% by mass, and even more preferably 10 to 30% by mass.

The raw material slurry may be prepared by recovering the inorganic compound generated in the cement clinker manufacturing process. Examples of such an inorganic compound include fine particle powder containing CaCO ₃ as a main component generated when crushing a clinker raw material, dust particles containing CaO and / or Ca (OH) ₂ generated in a chlorine bypass portion, and the dust. Examples thereof include water-washed dust particles obtained by washing the particles with water. The raw material slurry may be prepared by blending sludge containing cement and / or cement hydrate. Examples of sludge include raw cons sludge obtained at a raw con factory.

The raw material slurry may contain an inorganic powder containing a calcium compound. It is preferable that the calcium compound is contained in an amount of 10 to 98% by mass as CaO with respect to the entire inorganic powder contained in the raw material slurry. As a result, sulfur dioxide gas can be sufficiently absorbed in the desulfurization step. Examples of the calcium compound include calcium carbonate and lime (slaked lime and quick lime).

The SO ₂ concentration (Sg) of the exhaust gas is preferably 500 to 10000 ppm, more preferably 1000 to 8000 ppm, and further preferably 2000 to 6000 ppm. This makes it possible to obtain a sufficient amount of sulfite compound from the exhaust gas while maintaining the stability of the process. The SO ₂ concentration (Sg) of the exhaust gas may be controlled by changing the amount of the sulfur-containing raw material used to adjust the sulfur content of the raw material. Examples of the sulfur-containing raw material include waste gypsum board, waste tire, desulfurized slag, gypsum, coke, sulfur-containing waste and sulfur-containing by-products. The SO ₂ concentration of the exhaust gas may be controlled by adjusting the ratio of the sulfur-containing raw material to the total raw material. In addition, in this embodiment, the waste gypsum board may contain the paper component adhering to the surface of the gypsum board.

The SO ₂ concentration of the exhaust gas has a good correlation with the SO ₃ concentration of the powder sampled from the bottom cyclone provided in the preheater section. Therefore, the SO ₂ concentration of the exhaust gas may be controlled (feedforward control) by adjusting the sulfur content of the raw material based on the SO ₃ concentration. Further, the control based on the SO ₃ concentration of the bottom cyclone powder and the control based on the SO ₂ concentration of the exhaust gas may be combined.

In the manufacturing method of the present embodiment, the sulfite slurry obtained by absorbing the sulfite gas contained in the exhaust gas generated from the cement clinker manufacturing process into the raw material slurry can be directly blended into the cement clinker, so that a large-scale new facility can be installed. A cement composition capable of reducing the elution of hexavalent chromium can be easily produced without this. The sulfurous acid slurry also contributes to desulfurization of exhaust gas, and since the sulfurous acid compound is used as a slurry without drying, a series of processes of desulfurization and production of a cement composition can be simplified. In addition, since the sulfite slurry can be used instead of water injection when the cement composition is crushed, and because it is in the form of a slurry, the mixing property of the sulfite compound and the cement clinker is improved, and the manufacturing process is shortened and the equipment is simplified. Not only that, there is an advantage that the production cost of a cement composition effective for reducing the elution of hexavalent chromium can be significantly reduced.

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.

FIG. 1 is a diagram showing an embodiment of a cement composition manufacturing system. The cement composition manufacturing system 100 includes a cement kiln section 10 for producing cement clinker by firing a sulfur-containing raw material and a clinker raw material, a bypass section 12 for extracting exhaust gas, and a preheater section 16 having one or more cyclones. A formulation containing cement clinker firing section 70, desulfurization section 60 for absorbing sulfite gas contained in exhaust gas from cement clinker firing section 70 into a raw material slurry to obtain sulfite slurry containing calcium sulfite, and cement clinker and sulfite slurry. Is provided with a crushing section 50 for obtaining a cement composition.

The preheater section 16 brings the raw material into contact with the exhaust gas from the cement kiln section 10 to preheat the raw material. The bypass section 12 extracts exhaust gas containing sulfurous acid gas from between the kiln bottom 10a of the cement kiln section 10 and the bottom cyclone (the cyclone at the bottom) or the calcining furnace (not shown) of the preheater section 16. The bypass portion 12 may be a chlorine bypass portion. The cement clinker produced in the cement kiln section 10 is cooled to 40 to 220 ° C. in the cooling section 11 and introduced into the silo 18.

The desulfurization unit 60 cools the exhaust gas extracted from the bypass unit 12 and the exhaust gas extracted from the kiln tail 10a to, for example, 400 ° C. or lower, preferably 100 to 200 ° C. to generate dust particles containing a chlorine compound that aggregates. Sulfurous acid compound by contacting the cooling unit 17 to remove at least a part of the dust particles contained in the exhaust gas to obtain the exhaust gas containing sulfurous acid gas, and the raw material slurry containing the exhaust gas and the calcium compound. A slurry preparation unit 30 for obtaining a sulfurous acid slurry containing calcium sulfite and a raw material slurry preparation unit 34 for preparing a raw material slurry are provided.

In the cement kiln portion 10, coal, petroleum coke, and the like are burned and the raw materials react to generate exhaust gas containing sulfur dioxide. The gas extracted from the bleeding pipe forming the bypass portion 12 is recovered as exhaust gas between the kiln tail 10a of the cement kiln portion 10 and the preheater portion 16. 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 state). Unless otherwise specified, the concentration of sulfur dioxide in the present disclosure is a volume-based (standard state) concentration.

The exhaust gas may be extracted from the kiln bottom 10a. The temperature of the exhaust gas extracted from the kiln tail 10a is, for example, 700 to 1200 ° C., and the concentration of sulfur dioxide may be 500 to 10000 ppm. The exhaust gas extracted from the kiln tail 10a and the exhaust gas from the bypass unit 12 are merged or individually introduced into the cooling unit 17 and cooled to, for example, about 100 to 200 ° C. (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. When the exhaust gas may contain dust particles, the exhaust gas may be introduced directly into the slurry preparation unit 30 by bypassing the dust collecting unit 19.

The dust particles collected by the dust collecting unit 19 are washed with water by the water washing unit 31 to reduce the salt content. The water-washed dust particles whose salt content is reduced in the water-washed portion 31 contain, for example, CaO and / or Ca (OH) ₂ . These water-washed dust particles are introduced into the raw material slurry preparation unit 34 and are effectively utilized as a raw material for calcium sulfite as well as desulfurization of exhaust gas. The dust particles collected by the dust collecting unit 19 may be directly introduced into the raw material slurry preparing unit 34 without being washed with water.

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 is, for example, a bubbling tank, and brings the raw material slurry into contact with the exhaust gas. 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 regulated. In this way, the slurry preparation unit 30 also functions as a flue gas desulfurization unit. The means of contacting the raw material slurry and the exhaust gas is not limited to bubbling, and a method of spraying the raw material slurry may be used.

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. When the sulfite slurry contains a dihydrate of calcium sulfate, the amount of gypsum compounded in the compounding portion 51 can be reduced or eliminated.

The raw material slurry preparation unit 30 is continuously or intermittently supplied with the raw material slurry from the raw material slurry preparation unit 34. The raw material slurry preparation unit 34 is supplied with fine particle powder containing CaCO ₃ as a main component generated in the crushing unit 82 that pulverizes water and a clinker raw material (for example, limestone). Further, sludge containing cement or cement hydrate may be introduced into the raw material slurry preparation unit 34 in addition to the above-mentioned dust particles and washing dust particles. Examples of sludge include raw cons sludge obtained at a ready-mixed factory (raw material slurry preparation step).

The exhaust gas desulfurized in the slurry preparation unit 30 is introduced into the cooling unit 11 and flows through a flow path that exchanges heat with the cement clinker, and is introduced into the cement kiln unit 10. As a result, the sulfur dioxide gas remaining in the exhaust gas can be effectively utilized. Further, when the exhaust gas contains NOx, it is possible to suppress the release of NOx into the atmosphere. Further, a part of the exhaust gas in which the dust particles are reduced in the dust collecting section 19 may be introduced into the cement kiln section 10 by a flow path passing through the cooling section 11 by bypassing the slurry preparing section 30.

At least a part of the sulfite slurry prepared by the slurry preparation unit 30 is introduced into the slurry concentration adjustment unit 36. The slurry concentration adjusting unit 36 is configured so that the solid content concentration in the sulfite slurry can be adjusted by dehydration or water addition. The solid content concentration in the sulfite slurry may be 0.1 to 95% by mass. The content of the sulfurous acid compound (in terms of anhydride) in the sulfurous acid slurry with respect to the total solid content is, for example, 5% by mass or more, preferably 10% by mass or more, more preferably 15% by mass or more, still more preferably 20% by mass. It is mass% or more.

In the oxidation treatment unit 42, a part of the sulfite slurry prepared by the slurry preparation unit 30 is oxidized. The oxidation treatment is performed, for example, by bubbling air. In this way, a gypsum slurry containing gypsum can be obtained from a sulfite slurry containing calcium sulfite. The gypsum slurry is dehydrated in the dehydration section 44 to obtain gypsum. The gypsum thus obtained is introduced into the compounding section 51.

The solid content concentration in the sulfite slurry in the slurry concentration adjusting unit 36 is in the above concentration range based on the temperature Tr of the cement clinker, the temperature Tm of the cement composition derived from the cement mill 52, and the ignition loss Ig of the cement composition. Is controlled by. Specifically, the measured values of the temperature Tr of the cement clinker, the temperature Tm of the cement composition, and the ignition loss Ig of the cement composition are input to the control unit 38 as input signals. The control unit 38 selects one of the three input signals and outputs a control signal regarding the target value of the solid content concentration in the sulfite slurry to the slurry concentration adjusting unit 36. The control unit 38 may select the signal that adjusts the solid content concentration most among the plurality of input signals. The slurry concentration adjusting unit 36 adjusts the solid content concentration in the sulfite slurry based on the control signal from the control unit 38. The control unit 38 may have table data showing the relationship between the above-mentioned three measured values and the solid content concentration of the sulfite slurry, or may have correlation type data.

It is not essential that the slurry preparation unit 30 and the slurry concentration adjustment unit 36 are provided separately. In another embodiment, the slurry preparation unit 30 may adjust the solid content concentration. In this case, the control signal from the control unit 38 may be input to the slurry preparation unit 30. The measured value input to the control unit 38 is any one selected from the temperature Tr of the cement clinker, the temperature Tm of the cement composition derived from the cement mill 52, and the ignition loss Ig of the cement composition. There may be two or two.

The sulfurous acid slurry whose solid content concentration has been adjusted and the cement clinker stored in the silo 18 are introduced into the compounding section 51 in the crushing section 50. The cement clinker may be introduced after being temporarily stored in the silo 18, or may be introduced directly from the cooling unit 11. The temperature Tr of the cement clinker introduced into the compounding section 51 is, for example, 40 to 220 ° C.

In the compounding section 51, gypsum may be compounded if necessary. The sulfite slurry contains at least one sulfite compound selected from the group consisting of a hemihydrate of calcium sulfite, calcium heavy sulfite (Ca (HSO ₃ ) ₂ ), and a double salt of calcium sulfite and calcium sulfate. Is preferable. In this case, when the cement composition is 100 parts by mass, the sulfite slurry is preferably 0.1 to 20 parts by mass in terms of anhydrous (or calcium sulfite) in the cement clinker. It is preferably blended in an amount of 0.15 to 15 parts by mass, more 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 sulfurous acid compound in the obtained cement composition. When a double salt of calcium sulfite and calcium sulfate is contained, calcium sulfite in the double salt may be contained in the above-mentioned mass ratio. The mixing ratio of gypsum to cement clinker 100 parts by weight may be about 1.5 to 20 parts by weight converted to SO _3.

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

The temperature Tm of the cement composition at the outlet of the cement mill 52 may be 20 ° C. to 180 ° C., preferably 40 ° C. to 150 ° C., more preferably 50 ° C. to 140 ° C., and further preferably 60 to 60 ° C. It is 95 ° C. If the temperature Tm becomes too low, the water content of the sulfite slurry tends to cause a hydration reaction with the cement composition. On the other hand, when the temperature Tm becomes too high, calcium sulfite tends to be oxidized and changed to calcium sulfate. That is, by setting the temperature Tm to the above-mentioned 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.

The cement composition thus obtained capable of reducing the elution amount of hexavalent chromium is housed in the silo 54. The ignition loss Ig (ig. Loss) of the cement composition may be, for example, 1.0 to 8.0% by mass.

Downstream of the particulate collection portion 19, measuring device for measuring the SO ₂ concentration Sg of the exhaust gas is installed. Moreover, the kiln inlet 10a, meter is installed to measure the SO ₃ concentration Sp in the dust. The SO ₂ concentration Sg is controlled to 500 to 10000 ppm by adjusting the sulfur content of the raw material. The sulfur content of the raw material may be adjusted by changing the supply amount of the sulfur-containing raw material, or by changing the sulfur concentration in the sulfur-containing raw material.

Specifically, the measured values of the SO ₂ concentration Sg of the exhaust gas and the SO ₃ concentration Sp in the dust are input to the control unit 84 as input signals. Control unit 84 selects one of two input signals, the supply amount controller 86 of the sulfur-containing feedstock, and outputs a control signal related to the target value of the SO ₂ concentration Sg of the exhaust gas. The control unit 84 may derive a control signal related to the target value based on the respective input signals of the SO ₂ concentration Sg and the SO ₃ concentration Sp. The supply amount adjusting unit 86 adjusts the supply amount of the sulfur-containing raw material based on the control signal from the control unit 84. The control unit 84 may have table data showing the relationship between the above two measured values and the supply amount of the sulfur-containing raw material, or may have correlation type data. The control unit 84 may adjust the supply amount of the sulfur-containing raw material based on either the SO ₂ concentration Sg of the exhaust gas or the SO ₃ concentration Sp in the dust.

In the present embodiment, the crushing unit 50 includes a compounding unit 51 and a cement mill 52, but is not limited thereto. For example, in the modified example, the cement clinker, the sulfite slurry and the gypsum to be blended as needed may be directly charged into the cement mill 52 and blended and pulverized in the cement 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 cement mill 52, and pulverized by the cement mill 52. You may go.

In another modification, a control unit may be provided that adjusts the mixing 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 firing unit 70.

The control unit calculates the amount of sulfite slurry 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 equation 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. Since such a control is a slurry having fluidity, it can be carried out with a simple facility.

The cement composition manufacturing system 100 and its modifications may be used based on the contents of the above-mentioned cement composition manufacturing method. Therefore, the contents described in the method for producing a cement composition also apply to a system for producing a cement composition. Further, the description of the manufacturing system 100 and its modification is also applied to the above-mentioned method for manufacturing a cement composition. The cement composition manufacturing system of the present disclosure can simultaneously manufacture sulfite slurry and desulfurize exhaust gas, and also provide a slurry dehydration facility or a dedicated tank for solids after dehydration. , It is no longer necessary to install weighing machines and transportation equipment. Therefore, the introduction cost and the operation cost of the equipment can be sufficiently reduced. However, this disclosure does not exclude those equipped with such equipment.

FIG. 2 is a diagram showing another embodiment of a cement composition manufacturing system. In this embodiment, the cement composition production system 101 prepares an aqueous solution or slurry containing magnesium sulfite in place of the slurry preparation unit 30 for preparing a sulfite slurry containing calcium sulfite, and the first preparation unit 30A and the first preparation. It differs from the cement composition production system 100 in that it includes a second preparation part 32 for preparing a sulfite slurry containing calcium sulfite by mixing an aqueous solution or slurry containing magnesium sulfite prepared in part 30A with a calcium compound. There is. Since the other elements are the same as those of the cement composition manufacturing system 100, the differences from the cement composition manufacturing system 100 will be described.

In the first preparation unit 30A, the exhaust gas containing sulfurous acid gas is absorbed by the aqueous solution containing magnesium hydroxide. As a result, an aqueous solution or slurry containing magnesium sulfite is obtained. Since magnesium sulfite has a higher solubility in water than calcium sulfite, it is possible to suppress clogging of solid content in the first preparation unit 30A. To the aqueous solution or slurry prepared by the first preparation unit 30A, the raw material slurry is added from the raw material slurry preparation unit 34 in the second preparation unit 32 provided on the downstream side of the first preparation unit 30A. The raw material slurry is, for example, washed with water of fine particle powder containing CaCO ₃ as a main component, dust particles containing CaO and / or Ca (OH) ₂ generated in a chlorine bypass portion, which are generated when crushing a clinker raw material. Includes at least one selected from the group consisting of the washed dust particles thus obtained and sludge containing cement and / or cement hydrate. As a result, the second preparation unit 32 can obtain a sulfurous acid slurry containing calcium sulfite.

The first preparation unit 30A needs to maintain a certain degree of airtightness in order to suppress the exhaust gas from being released to the outside. Therefore, it is preferable to reduce the maintenance frequency. In the present embodiment, among the sulfites, magnesium sulfite having a higher solubility in water than calcium sulfite is first produced, and then a sulfite slurry containing calcium sulfite is prepared by the second preparation unit 32. Therefore, it is possible to reduce the maintenance frequency of the first preparation unit 30A by scaling calcium sulfite and improve the stability of the process.

In the present embodiment, magnesium hydroxide is used in the first preparation unit 30A, but the present invention is not limited to this, and a salt capable of producing a sulfite compound having a higher solubility in water than calcium sulfite can be used. it can. As such a salt, an alkaline earth metal or a salt of an alkali metal different from Ca and Mg can be used, and examples thereof include potassium hydroxide and calcium hydroxide.

Although some embodiments have been described above, the present disclosure is not limited to the above-described embodiments. For example, it is not essential to provide the control units 38 and 84, and the operator may manually perform these controls.

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

(Example 1)
A commercially available CaCO ₃ powder and water were mixed to prepare a raw material slurry (0.4 L) having a solid content ratio of 3% by mass. Extracted gas was collected from the chlorine bypass part of the cement composition manufacturing apparatus. The collected bleed gas was cooled to about 200 ° C., and then dust particles were removed with a bug filter. The concentration of sulfur dioxide in the extracted gas after removing the dust particles was 1500 ppm (volume basis). This extracted gas was blown into the raw material slurry for bubbling, and the sulfur oxide in the extracted gas was absorbed by the raw material slurry. As a result, a sulfite slurry containing calcium sulfite was obtained. The solid content of the obtained slurry was about 10% by mass.

The sulfite slurry was filtered to recover the solid content. The recovered solid content was dried in an air atmosphere of about 40 ° C. The X-ray pattern of the obtained solid content was measured using an X-ray diffractometer (manufactured by Bruker AXS Co., Ltd., accelerating voltage: 30 kV, current: 10 mA, tube: Cu). X-ray pattern analysis software performs Rietveld analysis using (manufactured by Bruker AXS _{Inc., Topas (R)), CaCO} 3, Ca (OH) 2, CaSO 3 · 0.5H 2 O, and were quantified CaSO ₄ · 2H ₂ O. The analysis results are as shown in Table 1.

(Example 2)
A sulfurous acid slurry was obtained in the same manner as in Example 1 except that a raw material slurry was prepared using Ca (OH) ₂ powder instead of CaCO ₃ powder. The obtained sulfite slurry was subjected to X-ray diffraction in the same manner as in Example 1. The analysis results are as shown in Table 1.

As shown in Table 1, in Examples 1 and 2, calcium sulfite hemihydrate was detected in an amount of 9% by mass and 23% by mass, respectively. From this result, it was confirmed that the sulfurous acid slurry after contacting the exhaust gas containing sulfurous acid contains calcium sulfite. By using the sulfite slurry thus obtained in the pulverization step, it is possible to produce a cement composition capable of reducing the elution of hexavalent chromium.

According to the present disclosure, there is provided a method and a production system for a cement composition capable of easily producing a cement composition effective for reducing the elution of hexavalent chromium.

10 ... Cement kiln part, 10a ... Kiln butt, 11, 17 ... Cooling part, 12 ... Bypass part, 17 ... Cooling part, 16 ... Preheater part, 18 ... Silo, 19 ... Dust collecting part, 30 ... Slurry preparation part, 31 ... Washing section, 30A ... 1st preparation section, 32 ... 2nd preparation section, 34 ... Raw material slurry preparation section, 36 ... Slurry concentration adjusting section, 38, 84 ... Control section, 50 ... Grinding section, 51 ... Mixing section, 52 ... Cement mill, 54 ... Silo, 60 ... Desulfurization section, 70 ... Cement clinker firing section, 82 ... Grinding section, 86 ... Supply amount control section, 100, 101 ... Manufacturing system.

Claims (24)

The cement clinker manufacturing process, which manufactures cement clinker by firing raw materials,
A desulfurization step of absorbing sulfur dioxide gas contained in the exhaust gas generated in the cement clinker manufacturing step into the raw material slurry to obtain a slurry containing a sulfur dioxide compound, and
A method for producing a cement composition, which comprises a pulverization step of pulverizing a formulation containing the cement clinker and the slurry to obtain a cement composition. The method for producing a cement composition according to claim 1, wherein in the crushing step, gypsum is blended to obtain the cement composition. The method for producing a cement composition according to claim 1 or 2, further comprising a slurry concentration adjusting step of adjusting the ratio of the solid content in the slurry to 0.1 to 95% by mass. The slurry is used as a solid content.
At least one sulfite compound selected from the group consisting of a hemihydrate of calcium sulfite, calcium heavy sulfite (Ca (HSO ₃ ) ₂ ), and a double salt of calcium sulfite and calcium sulfate.
The cement composition according to any one of claims 1 to 3, which contains at least one salt selected from the group consisting of calcium sulfate dihydrate, calcium hydroxide, calcium carbonate, and magnesium hydroxide. How to make things. According to any one of claims 1 to 4, when the cement composition is 100 parts by mass, the cement clinker is blended with 0.1 to 20 parts by mass of the slurry in terms of anhydride of the sulfite compound. The method for producing a cement composition according to the above. The cement composition according to any one of claims 1 to 5, wherein in the desulfurization step, the slurry containing calcium sulfite is obtained by treating at least a part of the exhaust gas generated in the cement clinker manufacturing step by a lime method. Manufacturing method of things. In the desulfurization step, the sulfurous acid gas is absorbed in an aqueous solution containing an alkaline earth metal different from Ca and / or a salt of the alkali metal, and then a calcium compound is mixed to obtain the slurry containing calcium sulfite. The method for producing a calcium composition according to any one of claims 1 to 6. The raw material slurry contains an inorganic powder containing a calcium compound generated in the cement clinker manufacturing process.
The method for producing a cement composition according to any one of claims 1 to 7, wherein the calcium compound is contained in an amount of 10 to 98% by mass as CaO with respect to the entire inorganic powder. Fine particle powder containing CaCO ₃ as a main component generated when crushing a clinker raw material, dust particles containing CaO and / or Ca (OH) ₂ generated in a chlorine bypass portion, and washing dust obtained by washing the dust particles with water. Any of claims 1 to 8, which comprises a raw material slurry preparation step of preparing the raw material slurry using one or more selected from the group consisting of particles and sludge containing cement and / or cement hydrate. The method for producing a cement composition according to item 1. The method for producing a cement composition according to any one of claims 1 to 9, wherein the SO ₂ concentration of the exhaust gas is 500 to 10000 ppm. The method for producing a cement composition according to any one of claims 1 to 10, wherein the sulfur content of the raw material is adjusted to control the SO ₂ concentration of the exhaust gas to 500 to 10000 ppm. The method for producing a cement composition according to any one of claims 1 to 11, wherein the raw material contains a sulfur-containing raw material containing at least one selected from the group consisting of waste gypsum board, waste tire and desulfurized slag. .. The method for producing a cement composition according to any one of claims 1 to 12, wherein the exhaust gas contains a gas extracted from a chlorine bypass portion. The exhaust gas contains a gas of 700 to 1200 ° C. extracted from the kiln butt of the cement kiln between the calcining furnaces.
The method for producing a cement composition according to any one of claims 1 to 13, further comprising a cooling step of cooling the exhaust gas to 400 ° C. or lower before the desulfurization step. The method for producing a cement composition according to any one of claims 1 to 14, wherein the exhaust gas obtained in the desulfurization step after absorption of at least a part of sulfur dioxide gas is introduced into a cement kiln. A cement clinker firing part that fires raw materials to obtain cement clinker,
A desulfurization section that absorbs sulfurous acid gas contained in the exhaust gas from the cement clinker firing section into the raw material slurry to obtain a slurry containing a sulfurous acid compound.
A cement composition manufacturing system comprising a pulverized portion for pulverizing a formulation containing the cement clinker and the slurry to obtain a cement composition. The cement composition manufacturing system according to claim 16, further comprising a slurry concentration adjusting unit for adjusting the ratio of the solid content in the slurry to 0.1 to 95% by mass. The slurry is used as a solid content.
At least one sulfite compound selected from the group consisting of a hemihydrate of calcium sulfate, calcium sulfite (Ca (HSO ₃ ) ₂ ), and a double salt of calcium sulfite and calcium sulfate,
The system for producing a cement composition according to claim 16 or 17, which comprises at least one salt selected from the group consisting of a dihydrate of calcium sulfate, calcium hydroxide, calcium carbonate, and magnesium hydroxide. The desulfurized part is
The first preparation part, which obtains a sulfurous acid compound different from calcium sulfite by absorbing the sulfurous acid gas into an aqueous solution containing an alkaline earth metal different from Ca and / or a salt of the alkali metal.
The system for producing a cement composition according to any one of claims 16 to 18, further comprising a second preparation unit for mixing the sulfite compound and a calcium compound to obtain the slurry containing calcium sulfite. The desulfurized part is
Fine particle powder containing CaCO ₃ as a main component generated when the raw material is crushed, dust particles containing CaO and / or Ca (OH) ₂ generated in a chlorine bypass portion, and water washing obtained by washing the dust particles with water. The invention according to any one of claims 16 to 19, further comprising a raw material slurry preparation unit for preparing a raw material slurry using at least one selected from the group consisting of dust particles and sludge containing cement and / or cement hydrate. Cement composition manufacturing system. The production of the cement composition according to any one of claims 16 to 20, further comprising a first control unit that adjusts the sulfur content contained in the raw material to control the SO ₂ concentration of the exhaust gas to 500 to 10000 ppm. system. The cement clinker firing section is provided with a chlorine bypass section.
The system for producing a cement composition according to any one of claims 16 to 21, wherein the exhaust gas contains a gas extracted from the chlorine bypass. The exhaust gas contains gas extracted from the kiln butt of the cement kiln between the calciners.
The system for producing a cement composition according to any one of claims 16 to 22, which has a cooling unit for cooling the exhaust gas to 400 ° C. or lower. The production of the cement composition according to any one of claims 16 to 23, which comprises a flow path for introducing the exhaust gas obtained in the desulfurization section after absorption of at least a part of sulfur dioxide gas into a cement kiln. system.

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