JP5135675B2 - Method for producing inorganic particles - Google Patents

Description

The present invention relates to sludge reuse, and relates to inorganic particles made from sludge having suitability as a coating pigment or papermaking filler, a method for producing the same, and paper using the same.

In recent years, it has been forced to reduce industrial waste from activities associated with production from the viewpoint of environmental conservation. Even in the paper industry, the treatment of paper sludge has become a problem. Paper sludge is a solid raw material that is mixed with wastewater without being used in fibers such as pulp, which is a papermaking material, organic substances mainly composed of starch and synthetic adhesives, and inorganic substances mainly composed of white pigments. Consists of lignin washed out in the pulping process, fine fibers, or waste paper-derived filler, printing ink adhering thereto, and excess sludge resulting from the biological wastewater treatment process. The main sources of paper sludge other than excess sludge generated in the biological wastewater treatment process are (1) those that flowed out through the wire during paper making, (2) contamination removal in the waste paper treatment process, deinking treatment, etc. Waste generated in the washing process and (3) generated in the washing process in the pulping process. The waste water containing these solids is solidified by a solids separation device using precipitation or flotation. It is separated and recovered, and then subjected to biological treatment such as activated sludge treatment if necessary, and then discharged. Solid sludge separated and recovered by such treatment and excess sludge generated by the final biological treatment of wastewater become paper sludge.

Furthermore, in recent years, with the increase in the waste paper utilization rate, paper sludge derived from the waste ink deinking process has increased. It is coming. Among them, used newspapers and high-quality used papers contain less inorganic substances (inorganic pigments) in the used papers, so the amount of paper sludge generated is relatively low and the utilization rate is high. As a result, the amount of paper sludge generated increases. This contributes to the low utilization rate of used magazine paper compared to used newspaper and high-quality used paper. In the future, in order to further promote the use of waste paper, it will be necessary to improve the utilization rate of magazine waste paper. However, if the utilization rate increases, there will be a new problem that the amount of paper sludge generated will increase.

Conventionally, paper sludge generated from paper mills has often been landfilled as industrial waste, but recently, organic substances in sludge are burned in incinerators such as fluidized bed furnaces and stoker furnaces. At the same time, the volume of paper sludge is reduced. However, since paper sludge contains inorganic substances, there is a problem that a large amount of residue (incinerated ash) remains after combustion. At present, some of the incineration ash is mixed with cement, used as an antioxidant for iron making, and a soil conditioner, but most of it is landfilled as industrial waste. In the future, as waste paper is reused, the amount of paper sludge will become extremely large, and waste disposal is expected to become increasingly difficult. For this reason, environmental problems of local governments as well as the paper industry that recycles used paper are extremely serious, and their effective use is strongly demanded as part of the countermeasures.
For this reason, if paper sludge incineration ash (inorganic matter) can be reused as a papermaking material for coating pigments and papermaking fillers, it not only reduces industrial waste, but also improves the wastepaper utilization rate. It can be linked and environmental problems can be solved.

Due to such a social background, a method of reusing paper sludge for papermaking materials has been studied, and the method can be roughly divided into two types. (1) A method of reusing paper sludge incineration ash as it is, and (2) A method of reusing the paper sludge incineration ash after performing some kind of treatment to impart specific properties.

As the former method, organic components in paper sludge are incinerated to form incinerated ash, which is crushed and dispersed (Patent Documents 1 and 2), paper sludge is fired by multistage oxidation (Patent Document 3), whiteness In order to improve the above, a method of adding and adding phosphoric acid to paper sludge and baking (Patent Document 4) and a method of reacting incinerated ash with calcium carbonate (Patent Document 5) have been proposed. Moreover, in order to suppress decomposition | disassembly of a calcium carbonate, the method (patent document 6) which blows in a carbon dioxide during baking is also proposed. These methods are compatible with the conflicting quality such as high whiteness and low wear, so the firing temperature is set as high as possible within the temperature range where the inorganic components in the sludge are not decomposed or hardened, or re-combustion or multi-stage combustion. In some cases, a large amount of cost and energy is required because measures are taken to prevent or crush during combustion. Moreover, in the process of firing paper sludge, decomposition of calcium carbonate is inevitable, and it is decomposed into calcium oxide by decarboxylation. For this reason, when these incineration ash is made into aqueous suspension, it becomes a high alkali, and there exists a problem that handling property, such as a raise of slurry viscosity and poor dispersion | distribution, is inferior. As a method for lowering the pH of the highly alkaline fired product suspension, a method of adding and neutralizing carbon dioxide (Patent Documents 7 and 8) has been proposed, but carbon dioxide is actively used. Rather, the effect of calcium oxide may remain somewhat.

As the latter method, paper sludge containing silica or a compound thereof is incinerated, incinerated ash is mixed and fired with an alkali metal compound, and the mixed fired product is acid-treated to produce amorphous silica fine particles (Patent Document 9). ) Has been proposed. A method (Patent Document 10) for producing a white carbon-like substance by immersing incinerated ash in an alkali solution containing silicic acid and neutralizing it with an acid has been proposed. A method for producing a functional substance containing zeolite by subjecting paper sludge incineration ash to alkali treatment using sodium hydroxide has been proposed (Patent Document 11). By converting the incinerated ash into a functional material, it can be reused, but it does not reach a large amount of paper sludge, and the amount of waste treatment cannot be significantly reduced. As a method of reusing a large amount of paper sludge, light sludge is produced by incinerating paper sludge, adding incineration ash to the calcium hydroxide suspension and mixing it, and blowing carbon dioxide into the mixed suspension. (Patent Documents 12 and 13) have been proposed. However, the coating of light calcium carbonate with these incineration ash as the core requires sophisticated and complicated operation and management. In addition, there is a problem that the quality of the final product changes due to the influence of the incinerated ash as a raw material, and the quality is not stable.

A product obtained by reusing these paper sludges may require a lot of cost and energy, and often does not reach the quality as a papermaking material. The current situation is that there is not much merit in producing products by applying these technologies other than from the viewpoint of promoting environmental activities of companies. In addition, there is no technology or product for reusing a large amount of paper sludge as a papermaking material, particularly as a coating pigment.

JP 2001-262002 A JP 2002-167523 A JP 2001-26727 A JP 2003-278092 A JP 2005-53985 A JP 2004-262701 A JP-A-10-29818 JP 2004-176208 A JP 2001-348510 A JP 2003-71404 A JP 2004-182538 A Japanese National Patent Publication No. 11-502877 JP 2000-178024 A

An object of the present invention is to provide a method in which paper sludge discharged from a paper mill can be reused as a coating pigment or paper filler as a paper material.

The present invention is a method for producing inorganic particles using paper sludge containing calcium carbonate as a raw material, and a heat treatment step for heat treating the paper sludge, a fired product obtained in the heat treatment step, and an aqueous aluminum sulfate solution are mixed. And an aluminum sulfate mixing step.
In this method, the baked product obtained in the heat treatment step may be further mixed and stirred with water to further provide a baked product suspension step.
In this method, the aluminum sulfate mixing step may be performed by a continuous addition method in which an aluminum sulfate aqueous solution is continuously added. Furthermore, the aluminum sulfate mixing step may be performed by a multi-stage method in which an aluminum sulfate aqueous solution is added over a plurality of stages.
In the present method, the pulverization step may be provided before the aluminum sulfate mixing step and / or after the aluminum sulfate mixing step.
Furthermore, in this method, you may provide the carbonation process which makes a carbon dioxide contact after the aluminum sulfate mixing process.
In this method, a heat treatment process may be processed at 550-900 degreeC.
The pH of the inorganic particles produced in the present invention may be 12.0 or less. Further, the produced inorganic particles may contain at least calcium trisulfoaluminate.
Paper using the inorganic particles as a filler is preferred. A coated paper using the inorganic particles as a pigment is also preferable.

The inorganic particles regenerated from the paper sludge according to the present invention can be mixed in the coating solution as a coating pigment, and can also be used as a papermaking filler.

The basic flow of the manufacturing method of the present invention will be described with reference to the drawings. FIG. 1 is a view showing a basic flow sheet A of a method for producing inorganic particles using sludge as a reference example . The basic flow sheet A will be described below.

[Sludge]
Sludge is a raw material for the inorganic particles used in the present invention. The sludge may be any sludge containing calcium carbonate, and paper sludge discharged from a paper mill, sludge generated from sewage, factory waste water, or the like can be used. Apart from sludge, RPF (Refused Paper & Plastic Fuel) mainly composed of low-grade waste paper that is difficult to reuse as a papermaking material and its associated plastic can also be used as a raw material.
In addition, when calcium carbonate is not contained in the sludge, since the calcium carbonate is not decomposed to become calcium oxide, the incinerated ash can be dispersed at a high concentration, and as it is as a papermaking material without using the process of the present invention. Can be reused.

The calcium carbonate content in the sludge can be obtained from the diffraction peak intensity or diffraction peak area of each inorganic particle, using an X-ray diffractometer (XRD) for sludge incinerated products obtained by burning the sludge at 350 ° C. for 2 hours. it can.
(1) Measure sludge ash by XRD to determine the identification of inorganic particles and the diffraction peak intensity or diffraction peak area. The diffraction peak positions of the main inorganic particles are calcium carbonate: 29.5 degrees, kaolin: around 24.95 degrees, and talc: around 9.55 degrees.
(2) The intensity ratio or area ratio of each inorganic particle is determined based on the diffraction peak intensity or diffraction peak area of calcium carbonate.
(3) The composition ratio of the inorganic particles is determined from the strength ratio or area ratio of each inorganic particle, and the calcium carbonate content is determined.

Paper sludge is a mixture of organic substances such as cellulose and starch and inorganic particles such as calcium carbonate, kaolin, and talc contained in the squeezed white water that has been dehydrated in the used paper pulp manufacturing process and papermaking process. More specifically, contaminants removed in the waste paper processing process, those generated during the deinking process and washing process, those generated during the washing process in the pulping process, and organic substances that flowed into the white water through the wire during paper making And a mixture of inorganic particles can be used. By collecting sludge from white water in the disaggregation process, which is the first stage of the deinking process in the used paper recycling process, the burden on the deinking process, bleaching process, and washing process in the used paper recycling process is reduced, and the used paper processing cost is reduced. In addition, the load of wastewater treatment can be reduced, which is preferable.
In particular, in the used paper recycling process, a large amount of inorganic particles derived from the used paper material flows out into the white water. The white water can be agglomerated to recover inorganic particles efficiently. For example, it can be obtained from a normal waste paper pulp manufacturing process, and if it is a disaggregation treatment, water can be used from either a conventionally known low-concentration pulper or high-concentration pulper. For the deinking treatment of waste paper, any conventionally known method can be used, and squeezing from a washing machine in each step can also be used. In addition, in the case of white water obtained from used paper raw materials with low whiteness, it is preferable to remove ink particles from white water by white water flotation treatment.

Since the solid content concentration in the sludge varies depending on the capacity of the dehydrator, it is usually 5 to 60% by mass. However, from the viewpoint of reducing the heat energy required for incineration of sludge and from the viewpoint of shortening the processing time in the furnace, the solid content concentration of the sludge is preferably as high as possible, and preferably 40 to 60% by mass. Those having a solid content concentration exceeding 60% by mass are difficult to achieve with the capacity of the current dehydrator or concentrator.

In the present invention, it is possible to perform granulation before the heat treatment step of sludge. By this granulation treatment, the fine particles are integrated, the scattering of the fine particles can be prevented, and the yield after the heat treatment can be improved. In addition, the variation in size is reduced, the heat treatment efficiency is increased, the organic matter is thermally decomposed with good yield, and the equipment can be downsized. Although the water-containing sludge can be granulated by a rolling granulation method, a stirring granulation method, or the like, a method of compression-molding the dried sludge is preferable because it can save heat energy in the heat treatment step.
As a dry granulation method, it is preferable to use a compression molding machine such as a briquette machine or a roller compactor. These compression molding machines can perform compression molding by forcibly pushing sludge between two pressurized rolls with a screw and rotating the rolls.

[Heat treatment process]
The heat treatment step of the present invention is carried out in an air (oxygen) atmosphere, and the heat treatment temperature is not particularly limited as long as it is a temperature sufficient to burn ink pigments such as carbon black in sludge and organic substances such as fibers and polymers. . In order to burn organic matter, it is preferable to set the temperature to 550 ° C. or higher. If it is less than 550 degreeC, an organic substance may not burn completely. Furthermore, from the viewpoint of whiteness, the treatment temperature is preferably set to 600 ° C. or higher. However, if the temperature is too high, inorganic particles in the sludge change and the fired product becomes hard, which is preferable as a papermaking material. Absent.
The inorganic particles in the sludge are mainly calcium carbonate, kaolin, talc, and titanium dioxide. Calcium carbonate begins to be decarboxylated from around 600 ° C., and at least part of it begins to be decomposed into calcium oxide, and completely decomposes into calcium oxide at 900 ° C. Talc does not change its crystal structure up to 900 ° C. Titanium dioxide is stable and does not change at all. Kaolin is crystal water desorbed from around 400 ° C. and exists as amorphous metakaolin up to 500 to 850 ° C. This amorphous metakaolin is called calcined kaolin, and is an inorganic particle that is bulky, has good opacity, and is excellent in smoothness. When the temperature exceeds 900 ° C., γ-alumina and mullite are generated. Since these γ-alumina and mullite are very hard, wire wear and coating blade wear are deteriorated, which is not preferable as a papermaking material. Further, when calcium oxide decomposed from amorphous metakaolin and calcium carbonate is present at a temperature exceeding 800 ° C., hard and unsuitable galenite is generated by a chemical reaction. Therefore, in the heat treatment step of the present invention, it is preferable that kaolin is not sintered or fused and exists as amorphous metakaolin, and calcium carbonate is decomposed and present in calcium oxide, so the upper limit of the heat treatment temperature is 900 ° C. More preferably, it is 800 ° C. or lower.
Therefore, the heat treatment temperature in the heat treatment step of the present invention is preferably 550 ° C. or higher and 900 ° C. or lower, and more preferably 600 ° C. or higher and 800 ° C. or lower.
The temperature shown here is the atmosphere temperature in the incinerator, and may be slightly different from the sludge combustion temperature.

The heat treatment step of the present invention can be performed in multiple stages within the above temperature range. For example, the baking time can be shortened by drying the sludge at a temperature of 100 ° C. or higher and removing the moisture completely and then performing the baking treatment. The heat treatment time is not particularly limited, but is usually about 1 to 24 hours. Although heat treatment can be performed in an oxygen-free atmosphere, the heat treatment time becomes longer and the energy cost becomes higher, which is not preferable in practice.

As the incinerator used in the heat treatment step of the present invention, for example, a commonly used incinerator such as a rotary kiln, a fluidized bed furnace, a floating furnace, a stoker furnace or the like can be used. In particular, a furnace that can be rotated or fluidized has better heat transfer to the sludge, and after the outer layer of the molded body burns and ashes, the ash part falls off the molded body. Since a new unburned part comes out on the surface, it burns efficiently, and carbonization and firing can be avoided at an excessive temperature, which is preferable. Since a sludge incineration facility is preferably as simple as possible from the viewpoint of maintaining the facility, a rotary kiln that can be dried, carbonized, and fired in one facility is preferable as the type of furnace.

[Aluminum sulfate mixing step-1]
This mixing step is a step of mixing the calcined product obtained in the heat treatment step with an aluminum sulfate aqueous solution in order to react or neutralize calcium oxide decomposed from the calcium carbonate present in the calcined product. In simple terms, a method of gradually adding an aqueous aluminum sulfate solution into the fired product, or gradually adding a fired product into the aluminum sulfate aqueous solution, is not practical in the following respects. When the aqueous solution of aluminum sulfate is gradually added to the baked product, mixing and stirring cannot be performed immediately, and the aqueous solution of aluminum sulfate is localized and becomes excessive, so that calcium trisulfoaluminate and by-product calcium sulfate are obtained. This will produce aluminum oxide. Further, when the baked product is gradually added to the aqueous aluminum sulfate solution, the aqueous aluminum sulfate solution becomes excessive, and calcium trisulfoaluminate and by-products calcium sulfate and aluminum oxide are similarly produced. Therefore, in order to efficiently produce calcium trisulfoaluminate, it is preferable to add a [calcined product suspension step] described later.

In the present invention, the aqueous aluminum sulfate solution to be mixed with the fired product may have a reaction molar ratio of calcium oxide to aluminum sulfate of CaO / Al ₂ O ₃ = 5.5 to 8.0. It suffices if the alkalinization due to can be prevented. By preventing high alkalinity, it is possible to disperse at a higher concentration than the inorganic particles obtained only by the conventional heat treatment step, and it is possible to reduce the dispersant.

The amount of the aluminum sulfate aqueous solution to be mixed is calculated from the number of moles of calcium oxide in the fired product.
(1) Calcium carbonate decomposition rate after heat treatment step (%) = (1− (b2 / b1)) * 100
b1: Calcium carbonate diffraction peak intensity of incinerated sludge before firing after burning at 350 ° C. for 2 hours b2: Calcium carbonate diffraction peak intensity of calcined sludge (2) Calcium oxide content (%) = (A / 100) * (B / 100) * 100
A: Calcium carbonate content in sludge (%)
B: Calcium carbonate decomposition rate (%) in (1) above
(3) Calcium oxide mole number = (calcined product weight (g) * (calcium oxide content of (2) / 100)) / 56.1

[Dehydration and dispersion process]
In the present invention, a dehydration step of dehydrating the composition after the aluminum sulfate mixing step to obtain a dehydrated composition, and a dispersion step of adding water to the dehydrated composition obtained by the dehydration step to obtain a slurry-like dispersion composition It is preferable to comprise. The dehydration step can be performed by operations such as filtration, centrifugation, pressure dehydration, and pressing. The dispersion process may be any process in which water is added to the dehydrated composition obtained by the dehydration process obtained by the dehydration process to obtain a slurry-like dispersion composition. It is preferable to add a dispersing agent in addition to moisture during the dispersing step because inorganic particles made from sludge can be favorably dispersed.

Another flow of the production method of the present invention is shown in FIG. FIG. 2 is a view showing another flow sheet B of the method for producing inorganic particles using the sludge of the present invention as a raw material. The manufacturing method of the present flow sheet B is characterized in that the [baked product suspension step] and the [aluminum sulfate mixing step] different from the basic flow sheet A are added to the basic flow sheet A, and other steps. Is the same as the basic flow sheet A.
[Firing product suspension process]
The calcined product after the heat treatment step may be mixed with the aluminum sulfate aqueous solution as it is in the form of calcined ash, but the calcined product is mixed with water and stirred, and the suspension process to obtain a calcined product suspension is performed after the heat treatment step. It is preferable to provide it. By providing a suspension step, an aqueous aluminum sulfate solution can be mixed and added to the fired product suspension, so that an excessive state of the aqueous aluminum sulfate solution can be prevented and calcium trisulfoaluminate is generated. be able to. This calcium trisulfoaluminate is a white pigment having a needle-like crystal state, and by blending it in a pigment coating solution used for coated paper production, it has excellent smoothness, white paper gloss, whiteness and opacity. It is an excellent pigment that can be applied. Therefore, it is preferable to mix calcium sulfate aqueous solution with the calcined product suspension to produce calcium trisulfoaluminate rather than mixing the calcined product into the aluminum sulfate aqueous solution, when used as a coating pigment.

[Aluminum sulfate mixing step-2]
As a method of mixing and adding the calcined product suspension obtained in the calcined product suspension step and the aqueous aluminum solution, an aqueous aluminum sulfate solution is added to a predetermined amount of the calcined product suspension (calcium hydroxide suspension). There is a “batch” method and a “continuous addition” method in which an aqueous aluminum sulfate solution is continuously added to a baked product suspension (calcium hydroxide suspension) that is continuously transferred. Either method may be used, but the “continuous addition” method is preferred from the viewpoint of the uniformity of the particle size of the calcium trisulfoaluminate produced.

The aluminum sulfate aqueous solution added to the fired product suspension may be added in a predetermined amount or divided into a plurality of stages, but the fired product suspension reacts with the aluminum sulfate aqueous solution. Thus, in order to produce calcium trisulfoaluminate without producing a by-product, it is preferable to add in multiple stages.
The aqueous aluminum sulfate solution becomes calcium trisulfoaluminate by reacting with calcium hydroxide. Of these, aluminum sulfate is completely dissolved in water to form an aqueous solution, and the entire amount is ready to react, whereas calcium hydroxide as the other reaction raw material has a water solubility of 0. Since the suspension is in a very low state of 2% and hardly dissolves in water, the total amount is not ready for immediate reaction. For this reason, a predetermined amount of aqueous aluminum sulfate solution is not added at once to a calcium hydroxide suspension with low reactivity, but the amount of aluminum sulfate sufficient to meet the amount of calcium hydroxide that can be reacted immediately. By adding a predetermined amount of aluminum sulfate in multiple stages within the range, it avoids excessive aluminum sulfate in the reaction system and suppresses the generation of reaction byproducts of aluminum oxide and calcium sulfate. To do.

When adding multiple stages of aluminum sulfate aqueous solution to the fired product suspension, at least one of the multiple stage additions is continuously added to the fired product suspension that is continuously transferred It may be performed by continuous addition.
For the addition of the aqueous aluminum sulfate solution divided into a plurality of stages, a “batch” method may be performed, but regarding the fine and uniform control of the particle size of the calcium trisulfoaluminate to be produced. Since the “continuous addition” method is superior to the “batch” method, the addition by the “continuous addition” method is at least the minimum in any of the aluminum sulfate aqueous solutions performed in multiple stages. It is preferable to carry out once.

Regarding the addition of the aqueous aluminum sulfate solution by the “continuous addition” method, the addition of the first step of the addition of the aqueous aluminum sulfate solution divided into a plurality of stages can be a “continuous addition” method, Of the addition of the aqueous aluminum sulfate solution divided into a plurality of stages, all the additions except the final addition may be a “continuous addition” method. It should be noted that all additions including the final addition may be a “continuous addition” method.

In addition, when adding an aqueous aluminum sulfate solution divided into a plurality of stages to the fired product suspension, the reactivity of calcium hydroxide in the fired product is restored to produce an appropriate calcium trisulfoaluminate reaction. In order to maintain a predetermined time interval from the addition immediately before the subsequent addition, the subsequent aluminum sulfate aqueous solution is added, and the time required for stabilization depends on the state of the mixed composition. Depending on the situation, it should be 15 seconds or longer.

Further, in this method, of the addition of the aqueous aluminum sulfate solution divided into the plurality of stages, the subsequent addition, which is the second or subsequent stage addition, is a composition in which the aqueous aluminum sulfate solution is added in the subsequent addition. It is preferable to carry out at a pH of 10.0 or higher.
“Subsequent addition” as used herein refers to each of the aqueous aluminum sulfate aqueous solutions performed in the second stage to the final stage when the aqueous aluminum sulfate solution is added in multiple stages to the fired product suspension. Refers to addition.
The “composition to which an aluminum sulfate aqueous solution is added in the subsequent addition” is a mixture of a fired product suspension and an aluminum sulfate aqueous solution, and a predetermined amount (total amount) of the aluminum sulfate aqueous solution is still mixed. This is a composition that has not been added (ie, the final stage has not been added) and immediately before the addition of the aqueous aluminum sulfate solution by the subsequent addition. This indicates a composition in which calcium aluminate and unreacted calcium hydroxide remain.

In the subsequent addition, the significance that the pH of the composition to which the aqueous aluminum sulfate solution is added is 10.0 or more is considered as follows.
Regarding the production of calcium trisulfoaluminate, as described above, it is important to maintain and recover the reactivity of calcium hydroxide as a raw material when adding an aqueous aluminum sulfate solution. By observing the fluctuation state of the pH of the mixed composition obtained by mixing the aqueous solution of aluminum sulfate with the suspension, it is possible to grasp the recovery state of the reactivity of calcium hydroxide in the mixed composition, In the mixed composition, it is essential to sufficiently recover the reactivity (= recovery of the increase in pH) before adding aluminum sulfate. When the pH of the mixed composition before adding aluminum sulfate is less than 10.0, there is a high possibility that the reactivity recovery of calcium hydroxide in the mixed composition is insufficient, and the mixed composition in this state If an aqueous aluminum sulfate solution is additionally added, it is difficult to carry out the formation reaction of calcium trisulfoaluminate in an appropriate and stable manner, and a large amount of reaction by-products such as aluminum oxide and calcium sulfate are generated.

In the present invention, the aluminum sulfate aqueous solution to be mixed and added when producing calcium trisulfoaluminate may be a ratio of CaO / Al ₂ O ₃ = 5.5 to 8.0. In order to prevent high alkalinity due to the influence of calcium oxide, CaO / Al ₂ O ₃ = 7.0 or less is preferable, and more preferable is a range of CaO / Al ₂ O ₃ = 5.5 to 6.0. It is. When CaO / Al ₂ O ₃ = less than 5.5, a large amount of by-products are generated, which is not preferable.

Here, as a measuring method of “pH of the composition containing calcium trisulfoaluminate”, at least 10 minutes or more after the final addition of the aqueous aluminum sulfate solution is completed in order to stabilize the state of the remaining calcium hydroxide. The pH measurement is preferably performed after 5 hours or more have elapsed, and for the pH measurement, it is preferable to use a pH meter calibrated with a pH standard calibration solution at least once on the day of measurement. For example, the pH of a composition containing calcium trisulfoaluminate at 25 ° C. after 24 hours from the end of the final addition of the aluminum sulfate aqueous solution may be measured. As a measuring instrument, a Lacom tester pH meter (pHScanWPBN type / manufactured by ASONE) is used, and the pH electrode is immersed directly in a dispersion of the composition containing calcium trisulfoaluminate to adjust the pH of the composition. taking measurement. In addition, about the pH meter used for pH measurement, after performing pH calibration using NIST reference | standard calibration liquid (pH 6.86 and two types of pH 9.18), pH measurement is performed.

In this method, at least one of the concentration of the fired product suspension and the concentration of the aluminum sulfate aqueous solution is preferably 12% by mass or less, and more preferably at least one is 6% by mass or less. The concentration of the fired product suspension and the concentration of the aluminum sulfate aqueous solution are both most preferably 6% by mass or less.

And, in order to mix the reaction raw materials instantaneously and uniformly and stably carry out the formation reaction of calcium trisulfoaluminate, the concentration of each reaction raw material is preferably as low as possible, as described above. When the concentration of the raw material is extremely low, the amount of the reaction solution to be handled becomes enormous and it is necessary to install a production facility having an extremely large processing capacity. Therefore, it is not preferable to reduce the concentration of the raw material more than necessary.
Therefore, at least one of the concentration of the fired product suspension and the concentration of the aluminum sulfate aqueous solution is preferably 0.1% by mass or more, and at least one is particularly preferably 1% by mass or more.

The multi-stage “continuous addition” process of the aluminum sulfate mixing process will be described.
In this method, in order to control the particle shape of calcium trisulfoaluminate finely and uniformly, the reaction raw materials are mixed by the “continuous addition” method, and after adding an aqueous aluminum sulfate solution, a predetermined time interval is added. Is provided to restore the reactivity of calcium hydroxide, and for this reason, mixing means for continuously mixing the reaction raw materials to form a mixed composition, and the mixing means generated by the mixing means An intermediate tank is provided for continuously receiving the mixed composition and retaining it for a predetermined time.
In addition, as an intermediate tank provided for continuously receiving the mixed composition and retaining it for a predetermined time to recover the reactivity of calcium hydroxide, any intermediate tank can be used as long as it can be retained for a predetermined time. (It is only necessary to provide a predetermined time interval until the next addition of the aluminum sulfate aqueous solution), and there is no particular limitation. Therefore, it may be a storage tank or tank having a volume capable of storing the mixed composition, or may be a pipe having the same volume as the storage tank or tank and provided with the same predetermined time interval.

In this method, the predetermined time is 15 seconds or more from the addition of the aluminum sulfate aqueous solution to the addition of the aluminum sulfate aqueous solution in the addition step immediately after the addition. May be determined to be
This is to provide a sufficient predetermined time interval between the additions of aluminum sulfate in order to recover the reactivity of calcium hydroxide before reacting with the aqueous aluminum sulfate solution. As already described in detail in the method, a time interval of 15 seconds or more is preferably provided, a time interval of 5 minutes or more is more preferable, and a time interval of 30 minutes or more is particularly preferable. Further, a time interval of 5 hours or more may be provided between the additions of aluminum sulfate, but it is considered that the reactivity recovery of calcium hydroxide is sufficient if a time interval of about 5 hours (300 minutes) is provided. It is not preferable to leave a time interval of 5 hours or more because it takes too much time to complete the reaction of calcium trisulfoaluminate formation.

In this system, the mixing means has a main body having an internal space through which a mixture of the fired product suspension and the aqueous aluminum sulfate solution is continuously circulated, and stirring that moves in contact with the mixture in the internal space. May be included.
As the main body portion having an internal space through which the mixture of the fired product suspension and the aluminum sulfate aqueous solution is continuously circulated, there is no particular limitation as long as it has an internal space through which the mixture can circulate, For example, what has shapes, such as cylinder shape, tank shape, and tower shape, can be mentioned as an example. And what combined two or more types of these shapes can also be used.
The stirring unit is not particularly limited as long as it moves in contact with the mixture in the internal space. For example, a propeller type, a paddle type, a turbine type, a ribbon screw type, a single cone type, a double type One type of stirring device such as a cone type or a combination of two or more types may be used.
By doing so, the mixture that continuously flows through the internal space of the main body can be reliably mixed by moving while the stirring unit is in contact with the mixture in the internal space.

Various types of ready-made mixing means including such a main body part and a stirring part are also known. As an example of such mixing means, a trademark name pipeline homomixer manufactured by Tokushu Kika Kogyo Co., Ltd. (Turbo-type rotating stirring unit is built in a narrow cylindrical main body, which is a so-called in-line mixer.), Trade name Homomic Line Flow (turbine-type rotating in a wide tank-shaped main body) This is a so-called reaction tank type in-line mixer with a built-in stirrer.), Trade name “L-mixII” (manufactured by Nippon Chemical Machinery Manufacturing Co., Ltd.) A so-called multistage reaction column type in-line mixer having a built-in vertical motion stirring unit, etc.).

Another flow of the manufacturing method of the present invention is shown in FIG. FIG. 3 is a view showing another flow sheet C of the method for producing inorganic particles using the sludge of the present invention as a raw material. The manufacturing method of the present flow sheet C is characterized in that the [fired product pulverization step] is added to the flow sheet B described above, and the other steps are the same as the flow sheet B. Similarly, FIG. 4 shows another flow of the production method of the present invention to which a pulverization step is added. FIG. 4 is a view showing another flow sheet D of the method for producing inorganic particles using the sludge of the present invention as a raw material. The manufacturing method of the present flow sheet D is characterized in that the [product pulverization step] is added to the flow sheet B described above, and the other steps are the same as the flow sheet B. The pulverization process of the above flow sheets C and D will be described together.
[Crushing process]
In the present invention, the grinding treatment step may be provided before the aluminum sulfate mixing step (calcined product grinding step) and / or after the aluminum sulfate mixing step (product grinding step). By carrying out the pulverization treatment, the particle diameter of the regenerated inorganic particles can be reduced, and the smoothness is improved, which is preferable. Moreover, by providing the calcined product pulverization step, it is possible to refine the calcium oxide in the calcined product, increase the reactivity with aluminum sulfate, and produce calcium trisulfoaluminate with a more uniform particle size. This is preferable. The calcined product pulverization step may be provided before or after the calcined product suspension step.
Furthermore, it is more preferable that the regenerated inorganic particles can be further refined by performing a pulverization treatment before and after the aluminum sulfate mixing step. Thus, another flow of the manufacturing method of this invention provided with a baked product grinding | pulverization process and a product grinding | pulverization treatment process was shown in FIG. FIG. 5 is a view showing another flow sheet E of the method for producing inorganic particles using the sludge of the present invention as a raw material.
Examples of pulverizers used in such pulverization processes include roller mills, jet mills, dry ball mills, impact pulverizers and other dry pulverizers, sand mills, wet ball mills, vibration mills, stirring tank mills, flow pipe mills, coball mills and the like. A wet pulverizer can be used.

Another flow of the manufacturing method of the present invention is shown in FIG. FIG. 6 is a view showing another flow sheet F of the method for producing inorganic particles using the sludge of the present invention as a raw material. The manufacturing method of the present flow sheet F is characterized in that the [carbonation step] is added to the flow sheet B described above, and the other steps are the same as the flow sheet B. Similarly, another flow of the production method of the present invention to which a carbonation step is added is shown in FIG. FIG. 7 is a view showing another flow sheet G of the method for producing inorganic particles using the sludge of the present invention as a raw material. The manufacturing method of the present flow sheet G is characterized in that a carbonation step is added to the flow sheet C described above, and the other steps are the same as the flow sheet C. Furthermore, another flow of the production method of the present invention to which a carbonation step is added is shown in FIG. FIG. 8 is a view showing another flow sheet H of the method for producing inorganic particles using the sludge of the present invention as a raw material. The manufacturing method of the present flow sheet H is characterized in that a carbonation step is added to the flow sheet D described above, and other steps are the same as the flow sheet D. FIG. 9 shows another flow of the production method of the present invention to which a carbonation step is added. FIG. 9 is a view showing another flow sheet I of the method for producing inorganic particles using the sludge of the present invention as a raw material. The manufacturing method of the present flow sheet I is characterized in that a carbonation step is added to the flow sheet E described above, and other steps are the same as the flow sheet E. The carbonation process of the above flow sheets F-I is demonstrated collectively.
[Carbonation process]
In this invention, you may provide the carbonation process which makes a carbon dioxide contact after the aluminum sulfate mixing process. The carbonation step may be performed immediately after the aluminum sulfate mixing step or after the dispersion step. By providing the carbonation step, the alkalinity of the composition can be further reduced by neutralizing the alkali component (calcium oxide) in the composition containing calcium trisulfoaluminate with carbon dioxide (carbonic acid). Therefore, it is preferable. In the carbonation step, there is no particular limitation on the method of bringing carbon dioxide into contact with the mixed composition containing calcium trisulfoaluminate. For example, a method of bringing the carbon dioxide into contact with an in-line mixer (sealed system), and the gas being a coreless mixer. For example, a method of directly injecting and contacting the liquid (open system) can be exemplified.

The steps in this method require a heat treatment step and an aluminum sulfate mixing step, but the suspension step, pulverization step, carbonation step, and dehydration / dispersion step can be appropriately selected and combined.

[Slurry properties of inorganic particles from sludge]
The slurry of inorganic particles using the sludge obtained by this method as a raw material preferably has a pH of 12.0 or less, more preferably 11.0 or less, and even more preferably 10.0 or less. It is. Moreover, as a minimum of pH, it is preferable to set pH to 8.0 or more, and it is especially preferable to set it as 8.5 or more.
When the pH of the inorganic particles containing calcium trisulfoaluminate exceeds 12.0, since a large amount of unreacted calcium hydroxide remains, the inorganic particle slurry concentration cannot be increased, It is not preferable. On the other hand, when the pH is less than 8.5, the aluminum sulfate aqueous solution is added excessively beyond the reaction end point, and the crystal shape of the generated calcium trisulfoaluminate collapses, and aluminum hydroxide or calcium sulfate is lost. The reaction by-product is generated, which is not preferable.
This pH can be adjusted by the amount of aluminum sulfate aqueous solution added. Specifically, (A) the number of moles of calcium hydroxide, a, the total number of moles of added (B) aluminum sulfate aqueous solution added. The pH can be adjusted by changing the ratio (a / b) to b. If the ratio (a / b) is increased, the pH increases, and if the ratio (a / b) is decreased, the pH decreases. Therefore, if the ratio (a / b) is adjusted to a predetermined pH, Good. The pH can also be adjusted by the amount of carbon dioxide added in the carbonation step. If the added amount of carbon dioxide is increased, the pH is lowered, and conversely, if the added amount of carbon dioxide is decreased, the pH is increased.

The inorganic particles obtained by this method can be used as a coating pigment or a paper filler.

[Coated paper using inorganic particles from sludge as pigment]
A coated paper using inorganic particles made from the sludge obtained by the method of the present invention as a raw material is obtained. As pigments for such coated paper, in addition to inorganic particles containing calcium trisulfoaluminate from sludge, heavy calcium carbonate, light calcium carbonate, talc, calcium sulfate, barium sulfate, aluminum hydroxide, Inorganic pigments such as titanium dioxide, zinc oxide, alumina, magnesium carbonate, magnesium oxide, silica, alumina magnesium silicate, calcium silicate, bentonite, zeolite, sericite, and scumite, and solid, hollow, and through-hole plastic pigments It is possible to use pigments used in the ordinary coated paper field, such as organic pigments such as binder pigments, and one or two or more of these can be appropriately selected and used in combination.

A dispersion-type adhesive is usually used for the adhesive component of the coating layer containing the pigment as described above. Dispersion type adhesives include conjugated diene polymer latexes such as styrene-butadiene copolymers and methyl methacrylate-butadiene copolymers, acrylic polymer latexes, and vinyl polymer latexes such as ethylene-vinyl acetate copolymers. Etc. can be illustrated.

A small amount of water-soluble adhesive can be used in combination with the above-described dispersion type adhesive. Examples of water-soluble adhesives include various starches such as oxidized starch, esterified starch and cold water soluble starch, proteins such as casein, soy protein and synthetic protein, cellulose derivatives such as carboxymethylcellulose and methylcellulose, polyvinyl alcohol and its modified products. Etc. can be exemplified.

For the coated layer of the coated paper of the present invention, a blue or purple dye or colored pigment, a fluorescent whitening dye, a thickener, a water retention agent, an antioxidant, an anti-aging agent, a conductive material, if necessary. Various auxiliaries such as an inducer, an antifoaming agent, an ultraviolet absorber, a dispersant, a pH adjuster, a mold release agent, a water-proofing agent, and a water repellent can be appropriately blended.

The coating layer provided on the base paper is not particularly limited as to whether it is a single layer or a multilayer of two or more layers. In the case of a multilayer, it is not necessary for all to be the same, depending on the required quality level. It is possible to adjust appropriately.
Further, the coating amount of the coating layer is not particularly limited, and can be adjusted according to the blank paper quality, printing quality, etc. of the coated paper. m is ^2.

As for the coating method for providing the coating layer in the present invention, various coating apparatuses used in the ordinary coated paper manufacturing field, such as air knife coaters, various blade coaters, gate roll coaters, roll coaters. A die coater, a curtain coater, or the like can be used as appropriate.

The base paper in the present invention is not particularly limited, and the basis weight of the base paper can generally be appropriately adjusted within a range of about 30 to 400 g / m ² .

The coated paper thus obtained may be finished by passing the paper through various known and official finishing devices such as a super calender, gloss calender, soft calender, mat calender and the like.

[Paper containing inorganic particles from sludge]
The paper using the inorganic particles made from the sludge obtained by the present method as a filler is not particularly limited as long as it is a paper internally containing a conventional filler. In addition, as paper types, recording paper such as wrapping paper, paper containers, ink jet paper, PPC paper, newsprint paper, high quality paper, medium quality paper, various coating base papers, coated paper using the same, wallpaper, Examples thereof include fiberboard, photographic base paper, base paper for impregnation, and flame retardant paper.

Examples of the pulp include commonly used bleached chemical pulp such as LBKP and NBKP, ground pulp (GP), pressurized ground wood pulp (PGW), refined ground wood pulp (RGP), and thermomechanical pulp (TMP). Pulp, deinked waste paper pulp (DIP), waste paper, and the like are appropriately mixed and used. Moreover, 1 type, or 2 or more types, such as a pulp fiber obtained from non-wood fiber raw materials, such as kenaf, a synthetic pulp, an inorganic fiber, can also be mix | blended with a base paper. Mechanical pulp and DIP can be used after being bleached if necessary, and the degree of bleaching can be arbitrarily performed. For bleaching pulp, it is preferable to use a bleaching process that does not use molecular chlorine such as chlorine gas or chlorine compounds such as chlorine dioxide from the viewpoint of environmental conservation. Pulp that has undergone such bleaching process is used. Examples thereof include ECF (Elemental Chlorine Free) pulp and TCF (Totally Chlorine Free) pulp.

Examples of fillers other than inorganic particles made from sludge include heavy calcium carbonate, light calcium carbonate, calcium sulfite, gypsum, talc, kaolin, clay, calcined kaolin, white carbon, amorphous silica, delaminated kaolin, Inorganic pigments such as diatomaceous earth, magnesium carbonate, titanium dioxide, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, and zinc hydroxide, and organic pigments such as urea formalin fine particles and fine hollow particles can be used. Two or more fillers can be used in combination. The blending amount of the filler is generally added so that the paper (base paper) ash content is in the range of 3 to 20% by mass.

In addition to pulp and filler, the paper includes various types of papermaking exemplified by internally added sizing agents, anionic, nonionic, cationic or amphoteric yield improvers, drainage improvers, paper strength enhancers, etc. The internal additive aid can be added as necessary. Specific examples of the internally added sizing agent include alkyl ketene dimer, alkenyl succinic anhydride, styrene-acrylic, higher fatty acid, petroleum resin sizing agent, rosin sizing agent and the like. Specific examples of yield improvers, drainage improvers, and paper strength enhancers include, for example, polyvalent metal compounds such as aluminum (specifically, sulfate bands, aluminum chloride, sodium aluminate, basic aluminum compounds). Etc.), various starches, polyacrylamide, urea resin, polyamide / polyamine resin, polyethyleneimine, polyamine, polyvinyl alcohol, polyethylene oxide and the like.

The paper making conditions are not particularly limited, and examples of the paper machine include a commercial paper machine such as a long net paper machine, a gap former type paper machine, a circular net paper machine, and a short net paper machine. It can be appropriately selected and used according to the purpose. As the papermaking system, any system such as acidic papermaking, neutral papermaking, and weak alkaline papermaking can be used. It is also possible to perform size treatment on paper using a natural adhesive such as starch or a synthetic adhesive such as polyvinyl alcohol with various size presses and roll coaters.

Moreover, a base paper using inorganic particles made from sludge as a raw material and a coating layer containing inorganic particles made from sludge as a raw material may be combined to form a coated paper.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In addition, unless otherwise indicated, the part and% in an example show a mass part and the mass%, respectively. Moreover, the pH and X-ray diffraction measurement in an Example and a comparative example were measured with the following method.

[PH measurement method]
In the following examples and comparative examples, the pH of the calcium trisulfoaluminate slurry and the coating solution was measured by the following method.
Using a Lacom Tester pH meter (pHScanWPBN type, manufactured by ASONE), pH electrodes were directly immersed in various dispersions and coating solutions to measure the pH of the pigment dispersion and the coating solution. In addition, about the pH meter used for pH measurement, after performing pH calibration using NIST reference | standard calibration liquid (pH 6.86 and two types of pH 9.18), pH measurement was performed.

[Measurement of X-ray diffraction]
The sample was crushed in a mortar until coarse particles disappeared, and measurement was performed at a measurement condition of 40 KV, 20 mA, and a measurement range: 5 to 50 degrees using MO3XHF manufactured by Mac Science Co., Ltd.

Reference example 1
Inorganic particles were obtained according to the flow sheet A shown in FIG.
[Sludge]
Paper sludge consisting of solids and excess sludge resulting from activated sludge treatment separated by wastewater treatment clarifiers of paper mills with paper-making machines and coating machines for paper, paperboard, and deinking pulping equipment used as raw materials .
[Measurement of inorganic particle composition ratio in sludge]
The constituent components of the paper sludge were measured in advance and used as a basis for calculating the input amount in the aluminum sulfate mixing step described later. The paper sludge was dehydrated to a solid concentration of about 50% with a dehydrator and then ashed at 350 ° C. in a muffle furnace. The ashed product was measured with an X-ray diffractometer, and the composition ratio of inorganic particles in the paper sludge was determined. As a result, calcium carbonate: kaolin: talc = 50%: 45%: 5%.

[Heat treatment process]
The paper sludge was dehydrated with a dehydrator to a solid content concentration of about 50%, and then heat treated at a maximum temperature of 750 ° C. for 2 hours with a rotary kiln to prepare a fired product. The obtained incinerated product was measured by X-ray diffraction, and the decomposition rate of each inorganic particle was determined. As a result, 55% of calcium carbonate was decomposed into calcium oxide, kaolin was converted to 100% calcined kaolin, and talc was not decomposed at all.

[Aluminum sulfate mixing process]
Add 120 g of 6% aluminum sulfate aqueous solution (85% of the specified number of moles) to the Coreless mixer, stir and add 30 g of the calcined product at a rate of 1 g / min by “batch” method, and stir and mix for a total of 40 minutes As a result, a mixed-end composition was obtained.

Here, a method for calculating the reference number of moles will be briefly described.
Calcium oxide in the fired product (calcium hydroxide in the slurry) is 50% × 55% = 27.5% because 50% of calcium carbonate is decomposed in the sludge and 55% of calcium carbonate is decomposed by heat treatment.
The molecular weights of calcium oxide and aluminum sulfate are 56.1 and 342.16, respectively, and 30 × 0.275 = 8.25 g of calcium oxide is present in 30 g of the fired product. The number of moles (number of moles charged per unit time) is 8.25 / 56.1 = 0.147. Therefore, the reference number of moles which is 1/6 of the number of moles of calcium oxide is 0.147 × 1/6 = 0.0245 mol.
On the other hand, 120 g / min of 6% aqueous aluminum sulfate solution contains 120 g × 6% = 7.2 g of aluminum sulfate, which is 7.2 g × 1 / 342.16 = 0.021 in terms of moles. Mole.
Therefore, the calculation of the ratio of the aqueous aluminum sulfate solution to be mixed with respect to the reference mole number is calculated as (0.021 mol) / (0.0245 mol) = 85%.

[Dehydration and dispersion process]
The composition after mixing was dehydrated with a filter press to obtain a composition having a solid content of about 60%, and then the dehydrated composition was dispersed in water with a coreless mixer so that the solid content was 50%. At the time of dispersion, a polyacrylic acid-based dispersant (trade name: Aron T-50, the above-mentioned) is added to water in an amount of 0.5 part relative to the solid content of the composition (the dehydrated composition). Was prepared.
From the XRD measurement, it was recognized that calcium trisulfoaluminate, unreacted calcium hydroxide, and calcium sulfate as a reaction byproduct were mixed in the inorganic particles.

Reference example 2
Inorganic particles were obtained according to the flow sheet B shown in FIG. The heat treatment step, dehydration and dispersion step were performed in the same manner as in Reference Example 1.
[Firing product suspension process]
The fired product prepared in the same manner as in Reference Example 1 was mixed with water and stirred with a Coreless mixer to prepare a 6% fired product suspension.

[Aluminum sulfate mixing process-batch system]
A 6% calcined product suspension (500 g) was charged into a coreless mixer, and while stirring, 120 g of a 6% aluminum sulfate aqueous solution (85% of the specified number of moles) was added at a rate of 4 g / min by a “batch” method for a total of 40 minutes. Then, mixing and stirring were performed to obtain a mixed composition.
The mixing completion composition was prepared in the same manner as in Reference Example 1 to prepare a 50% solid content slurry.
From the XRD measurement, the presence of calcium trisulfoaluminate was observed in the inorganic particles, and about 85% of the calcium oxide was produced in calcium trisulfoaluminate.

Reference example 3
Inorganic particles were obtained according to the flow sheet B shown in FIG. The same procedure as in Reference Example 2 was performed except for the aluminum sulfate mixing step.
[Aluminum sulfate mixing process-continuous system]
For an in-line mixer rotated at 9000 rpm (trade name “TK Pipeline Homomixer”, manufactured by Tokushu Kika Kogyo Co., Ltd.), a 6% fired product suspension prepared in the same manner as in Reference Example 2 was 100 g / min. And 6% aluminum sulfate aqueous solution was simultaneously and continuously injected at a rate of 24 g / min (85% of the reference mole number), and the injection was continuously performed for 10 minutes to obtain a mixture finished composition.
The mixing completion composition was prepared in the same manner as in Reference Example 2 to prepare a 50% solid content slurry.
From the XRD measurement, the presence of calcium trisulfoaluminate was observed in the inorganic particles, and about 85% of the calcium oxide was produced in calcium trisulfoaluminate.

Reference example 4
Inorganic particles were obtained according to the flow sheet B shown in FIG. The same procedure as in Reference Example 3 was performed except for the heat treatment step.
[Heat treatment process]
In Reference Example 3, heat treatment was performed at a maximum temperature of 1000 ° C. to prepare a fired product. The obtained incinerated product was measured by X-ray diffraction, and the decomposition rate of each inorganic particle was determined. As a result, calcium carbonate was decomposed to 100% calcium oxide, kaolin was converted to 100% calcined kaolin, and talc was decomposed by 30%.
[Aluminum sulfate mixing process-continuous system]
A mixture finished composition was obtained in the same manner as in Reference Example 3 except that the 6% aluminum sulfate aqueous solution of Reference Example 3 was changed to 43 g / min (85% of the reference mole number).
The mixture completion composition was prepared in the same manner as in Reference Example 3 to prepare a 45% solid content slurry.
From the XRD measurement, the presence of calcium trisulfoaluminate was observed in the inorganic particles, and about 85% of the calcium oxide was produced in calcium trisulfoaluminate.

Reference Example 5
Inorganic particles were obtained according to the flow sheet B shown in FIG. The same procedure as in Reference Example 3 was performed except for the heat treatment step.
[Heat treatment process]
In Reference Example 3, heat treatment was performed at a maximum temperature of 550 ° C. to prepare a fired product. The obtained incinerated product was measured by X-ray diffraction, and the decomposition rate of each inorganic particle was determined. As a result, 25% of calcium carbonate was decomposed into calcium oxide, kaolin was converted to 100% calcined kaolin, and talc was not decomposed at all.
[Aluminum sulfate mixing process-continuous system]
A mixture finished composition was obtained in the same manner as in Reference Example 3 except that the 6% aluminum sulfate aqueous solution of Reference Example 3 was changed to 11 g / min (85% of the reference mole number).
The mixing completion composition was prepared in the same manner as in Reference Example 3 to prepare a 50% solid content slurry.
From the XRD measurement, the presence of calcium trisulfoaluminate was observed in the inorganic particles, and about 85% of the calcium oxide was produced in calcium trisulfoaluminate.

Example 1
Inorganic particles were obtained according to the flow sheet B shown in FIG. The same procedure as in Reference Example 2 was performed except for the aluminum sulfate mixing step.
[Aluminum sulfate mixing process-continuous and divided]
(1) Addition of first-stage aluminum sulfate aqueous solution to baked product suspension Reference example for in-line mixer (trade name “TK Pipeline Homomixer”, manufactured by Tokushu Kika Kogyo Co., Ltd.) rotated at 9000 rpm The 6% calcined product suspension prepared in the same manner as 2 was injected simultaneously and continuously at 100 g / min and 6% aqueous aluminum sulfate solution at 13 g / min (45% of the reference mole number). Performed continuously for 14 minutes. The mixed composition (composition discharged from the in-line mixer) obtained at that time was continuously received in a pH restoration tank and allowed to stand for 30 minutes to recover the pH. The pH of the mixed composition after the pH recovery (hereinafter referred to as “first composition”) was 10.5.

(2) Addition of second-stage aluminum sulfate aqueous solution In the same manner as in (1) above, for an in-line mixer (trade name “TK Pipeline Homomixer”, manufactured by Tokushu Kika Kogyo Co., Ltd.) rotated at 9000 rpm. The mixture composition (first composition) was injected simultaneously and continuously at 113 g / min and 6% aqueous aluminum sulfate solution at 10 g / min (35% of the reference mole number), and the injection was continued for 12 minutes. I did it. The mixed composition (composition discharged from the in-line mixer) obtained at that time was continuously received in a pH restoration tank and allowed to stand for 30 minutes to recover the pH. The pH of the mixed composition after pH recovery (hereinafter referred to as “second composition”) was 10.0.

(3) Addition of third-stage aluminum sulfate aqueous solution (end of reaction)
In the same manner as (2) above, 123 g of the above mixed composition (second composition) was applied to an in-line mixer (trade name “TK Pipeline Homomixer”, manufactured by Tokushu Kika Kogyo Co., Ltd.) rotated at 9000 rpm. And 6% aqueous aluminum sulfate solution was simultaneously and continuously injected at 5 g / minute (20% of the reference mole number), and the injection was continuously performed for 10 minutes (end of reaction). The mixed composition (composition discharged from the in-line mixer) obtained at that time was continuously received in a cushion tank to obtain a composition after mixing (hereinafter referred to as “mixed composition”). The pH of the composition after mixing was 9.5.
The mixing completion composition was prepared in the same manner as in Reference Example 1 to prepare a 50% solid content slurry.
From the XRD measurement, the presence of calcium trisulfoaluminate was observed in the inorganic particles, and almost 100% of the calcium oxide was produced in the calcium trisulfoaluminate.

Example 2
Inorganic particles were obtained according to the flow sheet C shown in FIG. The same procedure as in Example 1 was performed except that the grinding step was added before the aluminum sulfate mixing step.
[Calcined product grinding process]
In Example 1, a 50% solid content slurry was prepared in the same manner as in Example 1 except that it was pulverized using a sand grinder as a wet pulverizer before the aluminum sulfate mixing step.
From the XRD measurement, the presence of calcium trisulfoaluminate was observed in the inorganic particles, and almost 100% of the calcium oxide was produced in the calcium trisulfoaluminate.

Example 3
Inorganic particles were obtained according to the flow sheet I shown in FIG. It carried out like Example 2 except having added the carbonation process and the product grinding | pulverization process.
[Carbonation process]
In Example 2, for the in-line mixer (trade name “TK Pipeline Homomixer”, manufactured by Tokushu Kika Kogyo Co., Ltd.) rotated at 9000 rpm, 127 g / min of the mixture finished composition after addition of the aqueous aluminum sulfate solution, and carbonic acid The reaction was carried out in the same manner as in Example 2 except that the gas was simultaneously and continuously injected at 127 g / min (gas / liquid ratio = 1.0) and the injection was continuously performed for 10 minutes.

[Product grinding process]
A slurry with a solid content of 50% was prepared in the same manner as in Example 2 except that the composition after carbon dioxide gas injection was pulverized using a sand grinder as a wet pulverizer.
From the XRD measurement, the presence of calcium trisulfoaluminate was observed in the inorganic particles, and almost 100% of the calcium oxide was produced in the calcium trisulfoaluminate.

Comparative Example 1
[Dispersion process]
In Reference Example 1, with respect to the paper sludge fired product, water and a polyacrylic acid-based dispersant (trade name: Aron T-50, the above-mentioned) are added to the fired product in an amount of 0.5 part as a solid content. A slurry was prepared. The solid content of the slurry at this time was 40%.
From the XRD measurement, the presence of calcium trisulfoaluminate in the inorganic particles was observed.

[Quality evaluation of regenerated inorganic particles]
Regenerated inorganic particles produced from paper sludge were evaluated by the following methods.

[Measurement of whiteness]
About 10 g of a sample (dried product) was ground until coarse particles disappeared in a mortar, and then, using a powder tablet molding machine comprising a hollow cylinder and a cylinder with a diameter matching the inner diameter, 127.5 N / cm ² (13 kgf / cm ² ) for 30 seconds to mold. The cylinder is placed and operated on a strong gloss acrylic board. The whiteness is measured while the tablet-like powder is attached to the cylinder. The whiteness was measured according to JIS P8148 (2001) using a spectral whiteness colorimeter manufactured by Suga Test Instruments Co., Ltd.

[Abrasion test]
For 100 parts of inorganic particle slurry, 0.5 parts of oxidized starch (trade name: Ace B, manufactured by Oji Cornstarch), 9 parts of styrene-butadiene copolymer latex (trade name: T2628G, manufactured by JSR) (all Solid content conversion) was added, and finally a coating solution having a solid content concentration of 60% was prepared. The obtained coating solution is applied to one side of a high-quality base paper (43.0 g / m ² ) and the coating solution is applied using a blade coater so that the dry mass per side is 12 g / m ^2. Then, this was dried to provide a coating layer to obtain a coated paper.
A razor blade having a thickness of 10 μm is sandwiched between the tables and fixed. It tears at a constant speed so that the coated paper hits a fixed part of the fixed razor blade. When a predetermined length (5 m) was torn, the razor blade was removed from the table, and the amount of wear of the razor blade that had torn the coated paper was observed to evaluate the wear.
○: Abrasion is good.
Δ: Abrasion is slightly observed, but there is no practical problem.
X: Abrasion is poor and practically problematic.

[Measurement of pigment particle size by sedimentation method]
The particle size distribution of the pigment was measured using a Sedigraph 5100 manufactured by Micromeritics, USA, and the average particle size was determined by the particle size at the point where the cumulative mass from the coarse particles corresponds to 50%. The pigment dispersion used for the measurement was prepared by adding a pigment slurry prepared by adding 0.05% of a dispersant (sodium polyacrylate) to a pigment with a 0.1% aqueous solution of a phosphate dispersant (nancarin). The pigment solid content concentration was diluted to about 5%.

Table 1 shows the whiteness, the abrasion degree as a result of the abrasion test, the particle diameter, and the pH of the finally obtained inorganic particle slurry for Examples and Comparative Examples. For comparison, the values for kaolin and heavy calcium carbonate (heavy coal) as typical pigments are also shown in the table.

The figure which shows the basic flow sheet A of the manufacturing method of the inorganic particle which uses the sludge of a reference example as a raw material. The figure which shows another flow sheet B of the manufacturing method of the inorganic particle which uses the sludge of this invention as a raw material. The figure which shows another flow sheet C of the manufacturing method of the inorganic particle which uses the sludge of this invention as a raw material. The figure which shows another flow sheet D of the manufacturing method of the inorganic particle which uses the sludge of this invention as a raw material. The figure which shows another flow sheet E of the manufacturing method of the inorganic particle which uses the sludge of this invention as a raw material. The figure which shows another flow sheet F of the manufacturing method of the inorganic particle which uses the sludge of this invention as a raw material. The figure which shows another flow sheet G of the manufacturing method of the inorganic particle which uses the sludge of this invention as a raw material. The figure which shows another flow sheet H of the manufacturing method of the inorganic particle which uses the sludge of this invention as a raw material. The figure which shows another flow sheet I of the manufacturing method of the inorganic particle which uses the sludge of this invention as a raw material.

Claims (5)

A method for producing inorganic particles from a sludge containing calcium carbonate as a raw material, a heat treatment step for heat-treating the sludge, and a fired product suspension step for mixing and stirring the fired product obtained in the heat treatment step with water And an aluminum sulfate aqueous solution mixed with the calcined product suspension to form calcium trisulfoaluminate, and the aluminum sulfate aqueous mixture is added to the aluminum sulfate aqueous solution in a plurality of stages. And a mixing means for continuously mixing reaction raw materials to form a mixed composition, and an intermediate tank for continuously receiving the mixed composition generated by the mixing means and retaining for 15 seconds. A method for producing inorganic particles. The method for producing inorganic particles according to claim 1, wherein the pulverization step is provided before the aluminum sulfate mixing step and / or after the aluminum sulfate mixing step. The manufacturing method of the inorganic particle of any one of Claim 1 or 2 which further provides the carbonation process which makes a carbon dioxide contact after the said aluminum sulfate mixing process. The manufacturing method of the inorganic particle of any one of Claims 1-3 whose pH of the said inorganic particle is 12.0 or less. The manufacturing method of the inorganic particle of any one of Claims 1-4 with which the said heat processing process is processed at 550-900 degreeC.

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