JP2008207173A - Production method of inorganic particle, production plant of the same and paper and coated paper using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means for producing high-quality white inorganic particles which can be used effectively as paper making materials such as paper making filler and coating pigment, efficiently and economically on a large scale from paper sludge to be discharged from paper making plants. <P>SOLUTION: When paper sludge S being a raw material is burned in an excess air atmosphere while being transferred in a rotary drum 1 of a rotary kiln K1, the paper sludge is made to pass through a primary combustion section Z1, where the sludge temperature is kept at ≤650°C and an easy-to-burn organic component in the sludge is burned and removed, and a secondary combustion section Z2, where the sludge temperature is kept at 700-850°C and a hard-to-burn organic component in the sludge is burned and removed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention particularly relates to a method for producing white inorganic particles useful as a coating pigment or a papermaking filler, using paper sludge discharged from a paper mill as a raw material, a production plant thereof, and a paper using the inorganic particles. And coated paper.

  In recent years, there has been an increase in the use of recovered waste paper as a raw material for papermaking in the papermaking industry, and there has been an increase in the use of recovered waste as a resource from the viewpoint of environmental conservation throughout the industry. Accordingly, treatment of sludge contained in paper mill wastewater has become a major issue. This papermaking sludge can be used for pulp components such as fiber components such as pulp, organic substances mainly composed of starch and synthetic resin adhesive, inorganic substances such as pigments for coated paper, etc. It consists of generated lignin and fine fibers, waste paper-derived paper filler and printing ink, excess sludge generated from biological wastewater treatment process, etc., and recovers deinking process and paper-making materials to remove printing ink etc. in waste paper treatment process It contains solid components derived from the cleaning process.

  In the past, such paper sludge was often landfilled as industrial waste, but recently, by burning the organic components in the sludge in an incinerator such as a fluidized bed furnace or a stoker furnace, it is used as energy. The volume is reduced at the same time as the collection. However, the sludge incineration ash is generated even if the combustion treatment is performed because the papermaking sludge contains an inorganic substance in a high ratio. And a large amount of sludge incineration ash is partly reused as cement raw materials, iron manufacturing antioxidants, soil conditioners, etc., but most of them are landfilled as industrial waste. It is.

  On the other hand, recovered paper is broadly divided into two types: uncoated paper such as newspapers and high-quality paper with low inorganic content, and coated paper such as magazines with high inorganic content. In the case of non-coated paper, which is easy to recycle, the mainstream will be the mainstream, but in order to increase the utilization rate of used paper in the future, the proportion of used paper will inevitably increase. Is expected to increase rapidly. Therefore, it will become increasingly difficult to treat paper sludge and its incinerated ash as waste in the future, and processing costs that are rising year by year will put pressure on the profits of the pulp and paper industry. There is an urgent need to develop technologies that can be used efficiently at high rates.

  A promising recycling application of papermaking sludge is to recycle the sludge incineration ash mainly composed of inorganic components after the incineration treatment to papermaking materials such as papermaking fillers and coating pigments. If this reuse is realized, a large amount of sludge incineration ash can be consumed as a papermaking material, which not only reduces industrial waste, but also improves the wastepaper utilization rate, eliminating environmental problems at once. It will be.

  Therefore, various methods have already been proposed for the purpose of converting the incineration ash of the papermaking sludge into a suitable papermaking material. For example, as a method of performing carbonization treatment before the paper sludge combustion treatment, a method of carbonizing the paper sludge at about 350 to 700 ° C. and then combustion treatment at 650 to 800 ° C. (Patent Document 1), the paper sludge is subjected to low oxygen conditions. A method in which carbonization is performed at a temperature below 600 ° C. (preferably under anaerobic conditions) and then combustion treatment is performed at 600 to 800 ° C. (Patent Document 2). After pulverizing, the method of combusting organic components at 650 to 700 ° C. (Patent Document 3), the paper sludge is carbonized at 1000 ° C. or less under poor oxygen condition, and the method of combusting at 450 to 1000 ° C. (Patent Document) 4) A method in which papermaking sludge is carbonized at 400 to 700 ° C. in an oxygen-poor atmosphere and then subjected to a two-stage combustion process at 650 ° C. or more (Patent Document 5), and one papermaking sludge. In a kiln heated gradually to dry from 200 ° C., such further method for combustion treatment with to 850 ° C. Atsushi Nobori after carbonized (Patent Document 6) it has been proposed in 600 ° C..

  On the other hand, as a method for performing combustion treatment under specific conditions without carbonizing papermaking sludge, papermaking sludge is subjected to combustion treatment in two stages, the first stage combustion temperature is 750 ° C. or lower, and the second stage combustion temperature. By setting the temperature to less than 800 ° C., a method of suppressing the thermal decomposition of calcium carbonate contained in the papermaking sludge derived from the papermaking raw material to less than 50% (Patent Document 7), the deinking sludge content in the papermaking sludge is reduced. A method in which the primary combustion process uses a cyclone furnace to perform combustion treatment at 700 ° C. or less and within a combustion time of 10 seconds, and then the secondary combustion process performs combustion treatment at 700 ° C. or less (Patent Document 8). A method of burning the incinerated ash after incineration again at 500 to 1100 ° C. (Patent Document 9) has been proposed.

In addition, all of the above methods involve dry oxidation (so-called combustion) of paper sludge. As a method of combining dry oxidation and wet oxidation into sludge incinerated ash, the paper sludge is wet oxidized at 200 to 800 ° C. Then, a method of performing a dry oxidation treatment at 800 to 1100 ° C. after that, or a wet oxidation treatment after the dry oxidation treatment (Patent Document 10) has also been proposed.
JP 2005-161239 A Japanese Patent No. 3563707 JP 2001-262002 A JP 2002-308619 A JP 2004-262701 A JP 2004-176209 A Japanese Patent Laid-Open No. 10-029818 Japanese Patent No. 3831719 JP-A-11-310732 Japanese Patent Laid-Open No. 2001-026727

  However, although it is expected that paper sludge that requires processing will eventually reach several hundred tons to several thousand tons per month, each of the conventional methods for treating paper sludge has a large amount of paper sludge. In addition, it was difficult to obtain sludge incineration ash with high whiteness and high quality. The reason is presumed as follows.

  First, the sludge incineration ash to be reused for papermaking materials should have as high a whiteness as possible when blended with white paper. Therefore, unburned organic components (so-called soot soot) that cause a decrease in whiteness are desirable. It is important to remove as much carbon carbide as possible, but as the used paper utilization rate increases, the carbon black derived from the printing ink contained in the papermaking sludge increases. In addition, this carbon black derived from printing ink has been carefully carbonized so as not to leave ignitable impurities in order to eliminate the risk of ignition and explosion as a black pigment. It is more difficult to burn.

  On the other hand, a general organic component has a molecular structure mainly composed of a carbon molecular chain. If there is a functional group such as a carboxyl group, a hydroxyl group, an ester group, or an ether group in the molecular structure, this functional group portion is As a starting point (reaction starting point), thermal decomposition and combination with oxygen (ignition, oxidation, combustion) are promoted. For this reason, the organic component having the functional group ignites at a relatively low temperature, and can be easily burned and removed by supplying sufficient oxygen while maintaining the temperature. In addition, even if the majority of the organic component does not have the functional group, when the organic component having the functional group is included as a minor component such as an impurity, the functional group portion of the small amount of the organic component is Since it becomes the starting point of thermal decomposition and combustion, it is still possible to ignite at a relatively low temperature and to easily remove the organic component by supplying sufficient oxygen while maintaining the temperature.

  On the other hand, carbides typified by firewood and charcoal are obtained by baking (carbonizing) organic components in an oxygen-poor atmosphere. At that time, almost all of the carbon molecular chains are graphite with carbon double bonds. Since it changes to a structure (= C = C = C = C =), it loses most of the functional groups in the molecular structure and becomes very difficult to ignite.

  However, in the conventional method in which the carbonization treatment is performed before the paper sludge combustion treatment, in addition to the carbon black derived from the printing ink of the waste paper, organic carbon components that are easily combustible are not easily burned by the carbonization treatment. Since it is changed to a carbide, it is irrational from the viewpoint of combustion treatment, and actually it is difficult to obtain inorganic particles with high whiteness as well as poor combustion efficiency.

  Further, according to the study by the present inventors, when the organic component is rapidly raised to a temperature exceeding 650 ° C., only the functional group contained in the molecular structure and its peripheral portion are rapidly burned out first. Thus, it has been found that the organic component loses the starting point of ignition / pyrolysis and becomes very incombustible like carbide.

  Therefore, in any of the conventional methods in which the paper-making sludge is subjected to the two-stage combustion treatment without carbonizing, the first-stage combustion temperature exceeds 650 ° C. It can be said that it is irrational and inefficient.

In the Riken Dictionary 4th edition Iwanami Shoten, the thermal decomposition of pure calcium carbonate is 898 ° C (dissociation pressure 1 atm). However, according to JISP8251 (2003), it is actually known that calcium carbonate in paper undergoes thermal decomposition at a temperature exceeding about 525 ° C., which is lower than the above temperature. In addition, a method of suppressing thermal decomposition of calcium carbonate in paper sludge by a two-stage combustion process in which the first stage combustion temperature is 750 ° C. or less and the second stage combustion temperature is less than 800 ° C. is generally used. If calcium carbonate (CaCO ₃ ) has the property of releasing carbon dioxide (CO ₂ ) and converting to calcium oxide (CaO) at 525 ° C. or higher, the organic components in the sludge can be removed at a combustion temperature of 600 ° C. or higher. Since the reciprocal action of suppressing the thermal decomposition of calcium carbonate that occurs at a temperature lower than the combustion temperature (525 ° C.) is expected while removing it by combustion, it must be inefficient and desired. It is not suitable for obtaining high-quality sludge incineration ash at a high rate.

  In addition, the conventional method of performing multi-stage oxidation treatment of papermaking sludge by combining dry oxidation and wet oxidation complicates the treatment process and equipment, so that the treatment cost is very high, and it is necessary for combustion treatment of a large amount of papermaking sludge. Is unsuitable.

  In view of the above-mentioned situation, the present invention efficiently and economically produces high-quality white inorganic particles that can be effectively used as a papermaking filler or a coating pigment for papermaking materials from papermaking sludge discharged from a papermaking factory. And it aims at providing the method and plant which manufacture on a large scale, and the paper and coated paper using this inorganic particle.

  The method for producing inorganic particles according to claim 1 of the present invention is a method for producing inorganic particles by using papermaking sludge as a raw material and carrying out a combustion treatment while being transferred through a cylindrical heat treatment furnace, wherein the combustion treatment comprises: A primary combustion process in which flammable organic components in the sludge are burned and removed under an excess air atmosphere at a sludge temperature of 650 ° C. or lower, and a non-flammable organic component in the sludge is burned at a sludge temperature of 700 to 850 ° C. in an excess air atmosphere. It is characterized in that it undergoes at least two stages of combustion steps with the secondary combustion step to be removed.

  In the method for producing inorganic particles, the cylindrical heat treatment furnace is a rotary kiln furnace, the structure according to claim 2, the structure according to claim 3 in which the combustion treatment is performed by indirect heating, and the at least two-stage combustion process. The configuration according to claim 4, which is set during the transfer process of one cylindrical heat treatment furnace, the furnace air is forcibly discharged from the raw material supply port side at one end of the cylindrical heat treatment furnace, and the fired product at the other end 6. The structure of claim 5, wherein air is sucked into the furnace from the discharge port side, in addition to air suction from the fired product discharge port side, air is also sucked into the furnace at the transition from the primary combustion process to the secondary combustion process The structure of claim 6, wherein the indirect heating section for the primary combustion process and the indirect heating section for the secondary combustion process are separated from each other. The structure of claim 7, wherein the alkali metal compound is added to the raw papermaking sludge. Item 9 configuration, raw paper sludge The composition according to claim 9 formed into a granulated or lump shape, the composition according to claim 10 in which 50% or more of calcium carbonate contained in the raw papermaking sludge is decomposed by the combustion treatment, and the fired product after the combustion treatment. Mixing with water and stirring to form a suspension to make a suspension, contacting the suspension with carbon dioxide to obtain a carbonated product, and pulverizing the carbonated product Each of the configurations of the eleventh aspect including the following is a preferable aspect.

  On the other hand, the inorganic particle manufacturing plant according to claim 12 of the present invention supplies a cylindrical heat treatment furnace having one end side as a raw material supply port and the other end side as a fired product discharge port, and papermaking sludge to the raw material supply port. Raw material supply means, transfer means for transferring the supplied sludge to the fired product outlet, indirect heating means for bringing the inside of the cylindrical heat treatment furnace into a combustion state, and the inside of the cylindrical heat treatment furnace with an excess air atmosphere And a primary combustion section having a sludge temperature of 650 ° C. or lower and a secondary combustion section having a sludge temperature of 700 to 850 ° C. are formed in the cylindrical heat treatment furnace. The air inside the furnace is forcibly exhausted from the exhaust port provided in the vicinity of the raw material supply port of the mold heat treatment furnace, and air is sucked into the furnace from the air supply port provided near the fired product discharge port of the cylindrical heat treatment furnace. It is said.

  Furthermore, the paper according to the invention of claim 13 comprises inorganic particles obtained by the production method according to any of claims 1 to 11 as a filler.

  Moreover, the coated paper which concerns on Claim 14 shall contain the inorganic particle obtained by the manufacturing method in any one of Claim 1 to 11 as a pigment.

  According to the method for producing inorganic particles according to claim 1, the raw papermaking sludge is transferred in a cylindrical heat treatment furnace and burned through at least two stages of combustion processes of a primary combustion process and a secondary combustion process under specific conditions. Since it processes, a high quality white inorganic particle can be efficiently manufactured on a large scale. That is, first, in the primary combustion process, since a combustion treatment is performed at a sludge temperature of 650 ° C. or less in an excess air atmosphere, first, a readily combustible organic component in the organic components in the papermaking sludge, that is, a carboxyl group in the molecular structure, Organic components having a functional group such as hydroxyl group, ester group, ether group, etc. are combusted and disappeared efficiently without carbonization due to thermal decomposition starting from the functional group portion and promotion of ignition / combustion. Along with the combustion of the readily combustible organic component, the combustion of the incombustible organic component not having the functional group also proceeds. In the secondary combustion process, the combustion treatment is performed at a sludge temperature of 700 to 850 ° C. in an excess air atmosphere, so that it is difficult to burn such as carbon black derived from printing ink remaining at the end of the primary combustion process. The organic components are also surely burned and lost, and generation of a hard sintered product due to excessive high temperature combustion can be avoided.

  Therefore, the obtained inorganic particles do not contain carbides such as soot and charcoal, so they have high whiteness and do not contain hard sintered products, and are suitable for papermaking fillers and coating pigments that are papermaking materials. High quality. Further, such combustion process of at least two stages can provide high combustion efficiency, so that a large amount of papermaking sludge can be efficiently and economically processed.

  Moreover, in the structure of Claim 2, since a rotary kiln furnace is used as a cylindrical heat treatment furnace, the setting of the said primary and secondary combustion process becomes easy. In the configuration of claim 3, since the combustion process is performed by indirect heating, the temperature control in the primary and secondary combustion steps is facilitated. In the structure of Claim 4, since the said primary and secondary combustion process is performed within one cylindrical heat processing furnace, it is advantageous at the point of equipment efficiency and equipment cost.

  In the configuration of claim 5, since air is sucked into the furnace from the fired product discharge port side by the exhaust on the raw material supply port side of the cylindrical heat treatment furnace, the flow of air in the furnace and the flow of the processed material are reversed. Even if the unburned flame-retardant organic components are in a state of soot depending on the operation status of the furnace and sludge, they will fly into the furnace and the floating material such as soot will ride on the air flow to supply the raw material. It is returned to the mouth side, or further discharged to the outside of the cylindrical heat treatment furnace together with the exhaust, so that the unburned flame-retardant organic component is prevented from being mixed into the fired product, so that the whiteness of the resulting inorganic particles is higher Become. In the configuration of claim 6, the intake air at the transition from the primary combustion process to the secondary combustion process can easily set the excess air atmosphere of both combustion processes, and the temperature of the primary combustion process is controlled by the intake amount. it can. In the structure of Claim 7, since the indirect heating part with respect to a primary combustion process and the indirect heating part with respect to a secondary combustion process are isolate | separated, the temperature control of both combustion processes can be performed easily independently.

  In the structure of claim 8, since the alkali metal compound is added to the raw papermaking sludge, the alkali metal compound acts as a kind of catalyst in the combustion process, and the thermal decomposition and combustion of the organic component are further promoted. According to the ninth aspect of the present invention, since the raw papermaking sludge is granulated or formed into a lump shape, the contactability between the papermaking sludge and air is improved in the combustion process, and the combustion efficiency of the organic components is improved accordingly.

  In the configuration of claim 10, in the combustion treatment, 50% or more of calcium carbonate contained in the raw papermaking sludge is thermally decomposed, and therefore, the combustion removal of organic components in the sludge can be given top priority. Efficient papermaking sludge treatment can be performed.

  In the structure of Claim 11, since the post-process which suspends the baked material after a combustion process in water, blows in carbon dioxide, and carbonates is performed, when the papermaking sludge of a raw material contains a calcium carbonate, it is a combustion process. Although the calcium carbonate is thermally decomposed, the calcium component after the thermal decomposition can be returned to calcium carbonate, and various problems due to the presence of the thermally decomposed calcium component in the obtained inorganic particles can be avoided.

  On the other hand, according to the twelfth aspect of the present invention, there is provided a production plant that can be particularly preferably applied to the production of the inorganic particles.

  Furthermore, since the paper according to the invention of claim 13 contains inorganic particles obtained from papermaking sludge discharged from a papermaking factory, which has been conventionally discarded, as a raw material for papermaking, the effective use of waste and the environment In addition to contributing to conservation, the inorganic particles have excellent paper quality as a papermaking filler, and therefore have good paper quality. Further, since the coated paper according to the invention of claim 14 contains the same inorganic particles as a pigment, it also contributes to the effective use of waste and environmental conservation, and is excellent in whiteness, smoothness, opacity, and the like. It will be a thing.

  In FIG. 1, the suitable flowchart of the manufacturing method of the inorganic particle which concerns on this invention is shown. As shown in the figure, the raw material papermaking sludge is subjected to pretreatment consisting of washing, alkali metal compound addition, dehydration, drying, granulation, and at least two stages consisting of a primary combustion process and a secondary combustion process. Used for combustion treatment. And the baked product after this combustion treatment is recovered as white inorganic particles through a post-treatment comprising the steps of suspension-> carbonation-> dehydration-> dispersion-> pulverization.

  The raw material papermaking sludge, as mentioned above, is the one that has been transferred to wastewater without using fiber components such as pulp, organic substances such as starch and synthetic resin adhesives, and inorganic substances such as pigments for coated paper. Lignin and fine fibers generated in the pulping process, paper-making fillers and printing ink derived from waste paper, excess sludge from the biological wastewater treatment process, etc. It contains solid components and the like derived from the washing process of collecting and washing the papermaking raw material. In addition, a part of the paper sludge may include low-grade waste paper that is difficult to reuse and RPF (Refused Paper & Plastic Fuel) mainly made of plastics accompanying it.

  And the organic component in the papermaking sludge is derived from pulp, adhesive, RPF, etc., and easily combustible having a functional group such as carboxyl group, hydroxyl group, ester group, ether group in the molecule, Incombustible flame retardants having few functional groups such as carbon black derived from printing ink in used paper recycling are mixed. On the other hand, the inorganic component (ash content) in the papermaking sludge is a main component in which kaolin (clay) and calcium carbonate derived from papermaking filler and coated paper pigment account for about 90 to 95% by weight of the whole inorganic component. However, a small amount of talc and titanium dioxide are mixed.

  The ratio of kaolin and calcium carbonate, the main component of the inorganic component, varies somewhat depending on the type of waste paper to be treated, but is generally in the range of 30/70 to 70/30 by weight ratio of kaolin / calcium carbonate. . The ratio of the organic component and the inorganic component in the papermaking sludge varies somewhat depending on the type of used paper to be treated and the degree of the deinking process, but is generally 30/70 to 70/30 in terms of the weight ratio of the inorganic component / organic component. Range.

  In the present invention, all organic components contained in the papermaking sludge are surely burned and removed by the above-described at least two-stage combustion treatment. That is, the combustion treatment in the present invention is performed while transporting the raw papermaking sludge in the cylindrical heat treatment furnace, and the primary combustion process is performed under the excess air atmosphere under the sludge temperature of 650 ° C. or less in the secondary combustion process. Are set to combustion conditions with a sludge temperature of 700 to 850 ° C. in an excess air atmosphere. The excess air atmosphere means an air atmosphere that does not cause incomplete combustion by giving a sufficient amount of oxygen to the combustion of organic components.

  First, in the primary combustion process, the combustion conditions are relatively low in an excess air atmosphere, so the easily combustible organic components in paper sludge are easily pyrolyzed and ignited starting from the functional group in the molecule, and carbonized. It disappears without burning. In the next secondary combustion step, high-temperature combustion conditions are obtained in an excess air atmosphere, so that the non-combustible organic components remaining without being burned in the primary combustion step are also surely burned and lost. In such a two-stage combustion process, it is reasonable to burn and remove easily combustible organic components without changing them into hard-to-burn carbides, and the entire organic components in paper sludge can be burned and removed efficiently in a short time. Yes. And since the obtained baked product does not contain unburned organic components such as firewood and charcoal, it has high whiteness and can be suitably used for papermaking materials such as papermaking fillers and coating pigments.

  When the sludge temperature in the primary combustion process exceeds 650 ° C., as described above, the easily combustible organic component is carbonized and changed to a hardly combustible organic component, and the combustion efficiency is deteriorated. Further, if the combustion temperature in the primary combustion process is too low, even a readily combustible organic component is difficult to pyrolyze and ignite, and the combustion efficiency deteriorates. Therefore, the lower limit of the sludge temperature is preferably 250 ° C. Furthermore, the most suitable baking conditions of a primary combustion process are the range used as the sludge temperature of 350-630 degreeC.

  On the other hand, if the sludge temperature in the secondary combustion process is less than 700 ° C., it takes time to burn the non-combustible organic component, and the combustion efficiency deteriorates. On the other hand, when the sludge temperature becomes high temperature combustion exceeding 850 ° C., suitability as a papermaking material is impaired due to generation of a hard sintered material generally called gehlenite. In other words, when used as a paper filler or coating pigment prepared from a fired product mixed with such a hard sintered product, the manufacturing facilities such as paper making wire and coating blade are damaged. Will worsen the product quality. Thus, the most suitable firing conditions for the secondary combustion process are the ranges where the sludge temperature is 750 to 800 ° C.

  In addition to performing the combustion process in the two stages consisting of the primary and secondary combustion processes described above, the combustion process as a transition section from the primary combustion process to the secondary combustion process is sandwiched, or the primary and secondary combustion processes. One or both of these can be further divided into a plurality of combustion steps having different combustion temperatures (sludge temperatures), so that there are three or more stages.

  The combustion treatment time of the primary combustion process is preferably at least 10 minutes and within 8 hours, particularly preferably 15 minutes and within 2 hours, and if it is too short, the flammable organic components in the papermaking sludge There is a risk that the removal of combustion will be insufficient, and if it is too long, heat energy will be wasted. In any case, it is important to allow sufficient time for all flammable organic components to burn off. Further, the combustion treatment time of the secondary combustion process is preferably at least 10 minutes or longer and within 8 hours, particularly preferably 20 minutes or longer and within 2 hours, and if it is too short, it is difficult to burn in the papermaking sludge. There is a risk that the burning and removal of the organic component will be insufficient, and if it is too long, the heat energy will be wasted. And it is preferable to make the ratio of the combustion processing time of a primary combustion process and a secondary combustion process into the range of 1/10-10/1 in a primary combustion process / secondary combustion process.

  The cylindrical heat treatment furnace used for the combustion treatment includes a rotary kiln furnace called a rotary kiln and a screw kiln furnace depending on the transfer method of the object to be processed, but a rotary kiln furnace is preferable in terms of combustion efficiency. . The at least two-stage combustion treatment can be performed in a single cylindrical heat treatment furnace, or by using a plurality of cylindrical heat treatment furnaces that are different for each stage. It is more advantageous in terms of equipment efficiency and equipment cost.

  It should be noted that the temperature rising region generated between the primary combustion process and the secondary combustion process when the combustion treatment is performed using the one cylindrical heat treatment furnace, specifically, the combustion temperature is increased from 650 ° C. to 700 ° C. About the area | region to perform, it is preferable to make it as short as possible, and it is especially preferable to set it as less than 10 minutes. Thus, shortening the temperature rising region between the primary combustion process and the secondary combustion process leads to compactness by shortening the overall length of the cylindrical heat treatment furnace, which is advantageous in terms of equipment efficiency and equipment cost.

  As the heating method of the cylindrical heat treatment furnace, the indirect heating method (external heat method) is preferable to the direct heating method (internal heat method). That is, in the direct heating method, since a large amount of air (oxygen) is consumed to burn the heat source gas in the processing furnace, there is a concern that the combustion of the organic components contained in the papermaking sludge becomes incomplete due to air shortage. Furthermore, the control of the furnace temperature (sludge temperature) becomes very difficult due to the combustion of the heat source gas. On the other hand, the indirect heating method does not consume furnace air for the heat source, so that the inside of the furnace can be reliably set to an excess air atmosphere and the degree of heating from the outside can be freely changed. Control of the furnace temperature becomes extremely easy.

  As a heating means in the above indirect heating method, heating by an electric heater or induction current is possible, but from the viewpoint of energy cost, burning of kerosene, heavy oil, etc. is carried out in a heating jacket surrounding the cylindrical furnace body. A method of introducing gas, combustion exhaust gas discharged from an existing incinerator, high-temperature air, superheated steam, or the like, or spraying combustion gas from a gas burner on the peripheral wall of the processing furnace and heating is recommended. Further, high-temperature exhaust gas that has undergone combustion treatment in the furnace body and combustion exhaust gas from the pretreatment drying step can also be used as part of the heating medium or heat source of the heating means.

  In order to produce a high-quality fired product, it is recommended that the supply of combustion air into the furnace body of the cylindrical heat treatment furnace be performed from the fired product outlet side. In other words, the air supply from the fired product outlet side causes the air flow direction in the furnace body to be opposite to the transfer direction of the object to be treated (paper sludge and its fired product). Even if the non-combustible organic component of combustion is scattered in the furnace, which is in the state of soot, the floating substance such as soot is carried back to the raw material supply port side and burns on the air flow, or Further, since the exhaust gas is discharged outside the cylindrical heat treatment furnace, it is possible to prevent the black unburned, non-combustible organic component from being mixed into the fired product, thereby obtaining a fired product with high whiteness. Thus, unburned, non-combustible organic components discharged to the outside of the cylindrical heat treatment furnace accompanying the exhaust are collected and removed with a bag filter or the like, or are combusted with appropriate heating means together with the exhaust. It should be lost.

  As described above, in order to supply combustion air into the furnace main body from the fired product discharge port side, air may be blown from the fired product discharge port side, but air is sucked by exhaust on the raw material supply port side. Is preferred. That is, because the furnace is negatively exhausted by forcibly exhausting from the raw material supply port side, if an air supply port is provided in the vicinity of the fired product discharge port, air is automatically discharged from the air supply port by the negative pressure. Inhaled into the furnace. Thus, in such air supply by exhaust on the raw material supply port side, the air supply amount can be easily controlled by the exhaust amount, and air can be reliably distributed over the entire length of the long furnace body by a stable air flow. .

  The above air supply amount is an amount that gives an oxygen amount 1.1 to 5 times the theoretical oxygen amount required for complete combustion of the organic components contained in the papermaking sludge in the furnace body in an excess air atmosphere. It is preferable to set, and an amount that gives an oxygen amount 2 to 5 times is particularly desirable. If the air supply amount is too small, it becomes difficult to make the furnace body have an excess air atmosphere, and the whiteness of the fired product may be lowered by the carbide remaining due to incomplete combustion of the organic components. On the other hand, if the air supply amount is too large, the inside of the furnace will be excessively cooled by the supply air, so it is necessary to increase the degree of heating by the heating means in order to maintain the combustion temperature, and the energy cost will increase accordingly. Become. Therefore, since this combustion air only needs to contain oxygen that sufficiently burns organic components, there is no problem even if the content of carbon dioxide is larger than that of normal outside air.

  If a suitable combustion treatment state of the papermaking sludge according to the method of the present invention appears, in the primary combustion process, a large amount of easily combustible organic components, which occupy most of the organic components in the sludge, will burn in the presence of sufficient oxygen. It burns up, and this combustion is in a state that continues from 1/2 to 2/3 of the primary combustion process. Similarly, in the secondary combustion process, the remaining flame-retardant organic components are burned, but since the content is small, the flame is not raised, but the high temperature of 700 to 850 ° C keeps the sludge burning up. It will be in a state of burning.

  FIG. 2 is a vertical side view schematically showing an indirect heating type rotary kiln furnace K1 which is a first structural example of a cylindrical heat treatment furnace used in the present invention. As shown in the figure, the rotary kiln furnace K1 has an outer periphery of a horizontal cylindrical rotary drum 1 that is a furnace body surrounded by a heating jacket 2, and on the raw material supply port 1a side of one end of the rotary drum 1, A raw material input port 4 is provided at a distance from the exhaust port 3, and a raw material supply means 5 such as a screw feeder is disposed between the raw material input port 4 and the raw material supply port 1 a of the rotary drum 1. An air supply port 6 </ b> A and a fired product outlet 7 are provided facing the fired product discharge port 1 b at the other end of the rotating drum 1.

  In the heating jacket 2, hot air sent through the hot air blowers 81 is released by a plurality of indirect heating means 8A and 8B for primary combustion and secondary combustion, respectively. From the outlets 82, the front heating space 2a on the raw material supply port 1a side and the rear heating space 2b on the fired product discharge port 1b side are separately introduced. In addition, an exhaust means 9 such as an exhaust fan is interposed in the exhaust port 3, and the air in the rotary drum 1 is exhausted as shown by the broken line arrow a due to its operation, and the decompression action accompanying this exhaust is performed. Outside air is sucked into the rotary drum 1 through the air supply port 6A. Reference numeral 10 denotes an exhaust circulation blower provided on the downstream side of the exhaust port 3.

  Although the rotary cylinder 1 is not illustrated strictly, the rotary cylinder 1 is inclined to a very gentle downward slope from the raw material supply port 1a side to the fired product discharge port 1b side. As a result of the rotation, the internal workpiece is gradually moved from the raw material supply port 1a side to the fired product discharge port 1b side by gravity.

  In order to perform the combustion treatment of the papermaking sludge S by the rotary kiln furnace K1 having the above configuration, as shown by the solid line arrow b, the papermaking sludge S of the raw material charged into the raw material charging port 4 is rotated by the raw material supply means 5 by the rotating drum. In the process of feeding to the raw material supply port 1a and transferring to the fired product discharge port 1b side by the rotation of the rotary drum 1, the organic components in the sludge S are removed by indirect heating with hot air introduced into the heating jacket 2. Combustion is performed in two stages, the primary combustion process and the secondary combustion process described above.

  That is, the two-stage combustion process is performed while the entire interior of the rotary drum 1 is maintained in an excess air atmosphere by the intake of air from the air supply port 6A accompanying the exhaust from the exhaust port 3 due to the operation of the exhaust means 9. The heating degree is adjusted by the temperature and the introduction speed of the hot air introduced from the indirect heating means 8A, 8B of the system to the front heating space 2a and the rear heating space 2b in the heating jacket 2, respectively, and is represented by a virtual line c in the figure. As can be seen, the sludge temperature of 650 ° C. or less (preferably 650 ° C. or less, 250 ° C. or more, optimally 350 to 630 ° C.) is defined as a primary combustion zone Z1 corresponding to the front heating space 2a. ), And the rear region in the rotary drum 1 corresponding to the rear heating space 2b is controlled as a secondary combustion zone Z2 to a sludge temperature of 700 to 850 ° C. (preferably 750 to 800 ° C.).

  As a result, the paper-making sludge S is combusted and removed without carbonizing the easily combustible organic components contained in the process of passing through the primary combustion zone Z1, and then contained in the process of passing through the secondary combustion zone Z2. The components are burned and removed, and are discharged from the fired product discharge port 1b of the rotary drum 1 as a high-whiteness fired product that does not contain unburned organic components and hard sintered products. To be taken out.

  In addition, what is necessary is just to set the processing time (passing time) in both combustion area Z1, Z2 with the rotational speed and inclination degree of the rotary drum 1. FIG. Further, the length ratio of both combustion sections Z1 and Z2 in the rotary drum 1 is preferably in the range of 1/10 to 10/1 in the primary combustion process / secondary combustion process as described above. The indirect heating means 8A, 8B can be arbitrarily adjusted according to the relative ratio of the size of the region where hot air is introduced into the heating jacket 2 respectively. Therefore, various measuring means such as a thermocouple and an infrared temperature sensor can be used for temperature measurement for controlling the combustion temperature (sludge temperature) in both combustion sections Z1 and Z2. A thermocouple is preferable in terms of cost.

  On the other hand, since the exhaust from the exhaust port 3 is in a high temperature state due to combustion, it is sent to the hot air circulation system by the exhaust circulation blower 10 and used as a heat source in the pretreatment drying step shown in the flowchart of FIG. It is recycled as a part of the hot air or heat source of 8A and 8B. In addition, combustion exhaust gas from a pretreatment drying step or the like can be used for the hot air of the indirect heating means 8A and 8B and its heat source.

  FIG. 3 is a longitudinal side view schematically showing a rotary kiln furnace K2 of an indirect heating system which is a second configuration example of the cylindrical heat treatment furnace used in the present invention, and the first configuration shown in FIG. 2 described above. Constituent elements common to the example rotary kiln furnace K1 are denoted by the same reference numerals. The rotary kiln furnace K2 has substantially the same configuration as the rotary kiln furnace K1 of the first configuration example, but the front heating space 2a and the rear heating space 2b in the heating jacket 2 are blocked by the partition member 11. ing. In addition, as this partition member 11, what shape | molded the material which can endure the high temperature of combustion processes, such as a metal, ceramics, and bricks, into a required shape is used.

  In the rotary kiln furnace K2 of this second configuration example, hot air having a relatively low temperature introduced into the front heating space 2a in the heating jacket 2 by the indirect heating means 8A and the heating jacket 2 by the indirect heating means 8B. Since high-temperature hot air introduced into the rear heating space 2b is not mixed, it becomes easier to control the heat treatment temperatures in the primary combustion zone Z1 and the secondary combustion zone Z2 in the rotary drum 1, and both zones Z1, The temperature difference of Z2 can be stably maintained and a high-quality fired product can be obtained, and the length of the transition region in which the temperature changes between both sections Z1 and Z2 can be shortened. There is an advantage that the ratio of the area of the secondary combustion process becomes high, and the rotary drum 1 can be made compact accordingly, leading to a reduction in equipment cost.

  FIG. 4 is a longitudinal side view schematically showing an indirect heating type rotary kiln furnace K3 which is a third structural example of the cylindrical heat treatment furnace used in the present invention, and is shown in FIGS. 2 and 3 described above. Constituent elements common to the rotary kiln furnaces K1 and K2 of the first and second configuration examples are denoted by the same reference numerals. The rotary kiln furnace K3 of the third configuration example is surrounded by heating jackets 2A and 2B in which the outer periphery of the rotary drum 1 is separated into the raw material supply port 1a side and the fired product discharge port 1b side. An intermediate air supply port 6B is provided at the boundary portion.

  In this rotary kiln furnace K3, similarly to the rotary kiln furnaces K1 and K2 of the first and second configuration examples, hot air from two systems of indirect heating means 8A and 8B is supplied to each of the heating jackets 2A and 2B. By introducing the heating spaces 2a and 2b separately, the front region in the rotary drum 1 corresponding to the front heating space 2a has a sludge temperature of 650 ° C or lower (preferably 650 ° C or lower and 250 ° C or higher, optimally In the primary combustion zone Z1 of 350 to 630 ° C., the secondary combustion zone Z2 in which the rear region in the rotary drum 1 corresponding to the rear heating space 2b is sludge temperature 700 to 850 ° C. (preferably 750 to 800 ° C.). Respectively.

  However, in this rotary kiln furnace K3, the air in the rotary drum 1 is forcibly exhausted from the exhaust port 3 near the raw material supply port 1a by the exhaust means 9, and the negative generated in the rotary drum 1 as a result. Air is sucked in from the outside by pressure, and air supply ports 6A and 6B are provided at two places on the fired product discharge port 1b side and in the middle. For this reason, the air flow a2 from the air supply port 6B is added to the air flow a1 from the air supply port 6A in the rotary drum 1 at the intermediate position by the suction from both the air supply ports 6A and 6B. An air flow a3 that joins a2 passes through the primary combustion section in the rotary drum 1 and is discharged from the exhaust port 3.

  As described above, when the combustion air is supplied into the rotary drum 1 from the two locations of the air supply port 6A on the fired product discharge port 1b side and the intermediate air supply port 6B, the primary combustion process is performed. Since fresh air (outside air) sufficiently containing oxygen is supplied to the primary combustion zone Z1 in the rotary drum 1, the excess air atmosphere in the primary combustion zone Z1 is stably maintained, and is thus included in the papermaking sludge S. Easily burn and remove easily combustible organic components without carbonization. In addition, the air flow in the secondary combustion zone Z2 having a high combustion processing temperature moves to the primary combustion zone Z1, but the primary combustion is performed by supplying low temperature air (outside air) through the intermediate air supply port 6B. It becomes easy to stably maintain a relatively low combustion temperature in which the section Z1 is set. In order to stably control the combustion temperature, it is preferable that the opening degree of the air supply port can be adjusted manually or remotely.

  FIG. 5 shows an example of the structure of the rotary drum 1 in the rotary kiln furnace K3 of the third configuration example. The rotating drum 1 has a structure in which cylindrical bodies 1A and 1B having different diameters are arranged concentrically so that they partially overlap such that the small diameter cylindrical body 1A is on the raw material supply port 1a side. An annular gap formed in the overlapping portion is an intermediate air supply port 6B. In this case, the papermaking sludge S supplied to the raw material supply port 1a is sequentially moved in the small-diameter cylindrical body 1A and the large-diameter cylindrical body 1B as indicated by an arrow b by the rotation of the entire rotary drum 1. The organic component is burned and removed and discharged from the fired product outlet 1b. In addition, in the rotary drum 1, in addition to the air flow a <b> 1 from the air supply port 6 </ b> A on the fired product discharge port 1 b side by forced exhaust by the exhaust means 9 (see FIG. 4), the intermediate air supply port 6 </ b> B Fresh air is also sucked in as the air flow a2 from the air.

  Various structures other than those illustrated in FIG. 5 can be adopted for air supply from the intermediate position of the rotary drum 1 such as the rotary kiln furnace K3 of the third configuration example.

  The furnace body of the cylindrical heat treatment furnace used in the present invention is not limited to the horizontal cylindrical type such as the rotary drum 1 in the rotary kiln furnaces K1 to K3 of the first to third configuration examples described above, By providing the partition wall, it is possible to adopt a rotating cylinder having a multi-divided structure or a multi-cylinder multi-chamber structure in which the inside is divided into a plurality of compartments. Examples of the rotary cylinder having the multi-divided structure or the multi-cylinder multi-chamber structure are shown in FIGS. 6 to 8 are all cross-sectional views (radial cross-sectional views) in a direction orthogonal to the longitudinal direction of the horizontally long rotating drum, and the vertical direction of the drawings coincides with the actual vertical direction. Yes.

  6 (a) has a six-partitioned partition structure having a substantially hexagonal outer shell 12a. The partition 12b has a hexagonal section in the inside and is divided into six compartments 13 having a regular triangular section. It is divided. FIG. 6 (b) shows the state of lamination and deposition of the papermaking sludge S in each compartment 13 when the rotating cylinder 1 supplied with the granulated material of the papermaking sludge S is rotated in the direction of the arrow d. Yes.

  The rotating cylinder 1 shown in FIG. 7A has a six-cylinder multi-cylinder structure in which six pipe parts 14 are bundled in a substantially annular shape by a donut plate-like pipe part fixing member 15. A central cavity 16 surrounded by 14... Communicates in the axial direction through the center hole 15 a of the tube fixing member 15. FIG. 7 (b) shows the state of lamination / deposition of the papermaking sludge S in each pipe section 14 when the rotating cylinder 1 supplied with the granulated material of the papermaking sludge S is rotated in the direction of the arrow d. Yes.

  The rotating drum 1 shown in FIG. 8A has a 12-partitioned partition structure, and the annular space between the inner cylinder part 17a and the outer cylinder part 17b forming a double pipe is radially divided by 12 partition walls 17c. Thus, twelve compartments 18 are formed, and the inside of the inner cylindrical portion 17a forms a hollow portion 16. FIG. 8 (b) shows the state of lamination and deposition of the papermaking sludge S in each compartment 18 when the rotating cylinder 1 to which the granulated material of the papermaking sludge S has been rotated in the direction of the arrow d. Yes.

  As illustrated in FIGS. 6 to 8, if the horizontally long rotating drum 1 has a multi-divided structure or a multi-cylinder multi-chamber structure, the supplied papermaking sludge S is distributed little by little to a plurality of compartments or torso parts. Therefore, as compared with a simple horizontal cylindrical rotary drum that forms a single furnace space as a whole, deposition of objects to be treated (paper sludge S, fired product) during the transfer process in the rotary drum 1 While the thickness is remarkably reduced, the stirring action of the object to be processed accompanying the rotation of the rotary drum 1 is strengthened, and the contact efficiency between air (oxygen) for burning organic components and the object to be processed is remarkably improved. As a result, the combustion efficiency of the organic component is dramatically increased, and high-quality fired products and inorganic particles can be obtained.

  In addition, it is recommended that the number of divisions of the transfer path in such a multi-divided structure or a multi-cylinder multi-chamber structure is at least 6 or more in order to sufficiently exhibit the above-described effects. Further, the divided structure of the rotary drum is not limited to the structure illustrated in FIGS. 6 to 8, and is, for example, a multi-partition partition such as an 18-part type, a 24-part type, or a 36-part type introduced in Japanese Patent Application No. 2006-252751 Rotation of a multi-cylinder / multi-divided structure in which a partition or partition is provided for each tubular member of the multi-cylinder structure introduced in Japanese Patent Application No. 2006-279813, and the total number of divisions is 6 to 126. Various structures, such as a trunk structure, are possible. Further, in addition to the rotating drum and the structure in which the inside of the tubular member is divided into a plurality of compartments by a partition wall, a rotary stirring blade having a shape similar to the partition wall is provided in the rotating drum and the tubular member. By inserting in a non-fixed state, the inside of the rotary drum may be divided into a plurality of compartments, and the papermaking sludge S supplied into the rotary drum may be distributed to the plurality of compartments.

  As shown in FIGS. 7 and 8, when the multi-divided structure or the rotary cylinder 1 having a multi-cylinder structure provided with the cavity 16 along the axial direction is used, in addition to indirect heating from the outside, the cavity If the indirect heating is also performed from the inside (center side) using the part 16, the combustion temperature can be controlled with higher accuracy and higher heat treatment efficiency can be achieved. As the indirect heating means from the inside, various heating media and heat sources similar to the indirect heating means from the outside described above can be adopted.

  FIG. 9 is a longitudinal sectional side view schematically showing an indirect heating type rotary kiln furnace K4 which is a fourth structural example of the cylindrical heat treatment furnace used in the present invention, and is shown in FIGS. 2 to 4 described above. Constituent elements common to the rotary kiln furnaces K1 to K3 of the first to third configuration examples are denoted by the same reference numerals.

  In this rotary kiln furnace K4, the rotary drum 1 has a hollow portion 16 along the axial direction as shown in FIGS. 7 and 8, and the indirect heating means for heating from the outside of the rotary drum 1 is used. In addition to 8A and 8B, the cavity 16 is also provided with indirect heating means 8C and 8D for heating the rotary drum 1 from the inside. These indirect heating means 8C and 8D for the inside are each a plurality of discharge ports 82 of the pipes through which hot air sent through the respective hot air blowers 81 is inserted from the outside into the cavity 16 through the air supply port 6A. Thus, the front heating space 16a on the raw material supply port 1a side and the rear heating space 16b on the fired product discharge port 1b side in the hollow portion 16 are introduced separately. Thus, as divided by the phantom line c in FIG. 9, the front heating space 16a in the cavity 16 is formed into the front heating space 2a into which hot air by the indirect heating means 8A in the heating jacket 2 is introduced. Correspondingly, similarly, the rear heating space 16b corresponds to the rear heating space 2b into which hot air by the indirect heating means 8B in the heating jacket 2 is introduced.

  Therefore, in the combustion process of the papermaking sludge S by the rotary kiln furnace K4, the indirect heating means 8A, with the front region in the rotary drum 1 sandwiched between the inner and outer front heating spaces 16a and 2a as the primary combustion zone Z1, The sludge temperature is set to 650 ° C. or lower (preferably 650 ° C. or lower, 250 ° C. or higher, optimally 350 to 630 ° C.) by indirect heating from inside and outside by 8C. Similarly, the rear region in the rotary drum 1 sandwiched between the inner and outer rear heating spaces 16b and 2b is subjected to indirect heating from the inside and outside by the indirect heating means 8B and 8D as a secondary combustion zone Z2 and a sludge temperature 700. It is set to ˜850 ° C. (preferably 750 to 800 ° C.).

  In addition, as in the case of the rotary kiln furnace K4 of the fourth configuration example, when the indirect heating is performed from the inside using the hollow portion 16 along the axial direction of the rotating drum 1, the primary is applied similarly to the indirect heating on the outside. If two indirect heating means 8C and 8D for combustion and secondary combustion are employed, in addition to improving heat treatment efficiency by indirect heating from the inside, a primary combustion process (primary combustion zone Z1) and a secondary combustion process There is an advantage that the control of the combustion processing temperature in (primary combustion section Z2) becomes easier.

  In the combustion treatment as described above, calcium carbonate contained in the raw paper sludge is thermally decomposed (decarbonated), and the decomposition rate is preferably 50% or more of the total amount of calcium carbonate before the combustion treatment, In particular, the decomposition rate is preferably 90% or more, more preferably substantially 100%. In the present invention, since the calcium component after the thermal decomposition can be returned to the original calcium carbonate in the post-treatment carbonation step described later, it is not necessary to suppress the decomposition of the calcium carbonate in the combustion treatment, and thus the combustion treatment. This is because it is possible to preferentially burn and remove organic components at a temperature higher than the thermal decomposition temperature of calcium carbonate of 525 ° C. When the decomposition rate of calcium carbonate in the combustion treatment is less than 50%, as described above, the organic component in the sludge is burned and removed at the combustion temperature of 700 ° C. or higher in the secondary combustion process, and the combustion temperature is higher than the combustion temperature. However, since it is expected to have a contradictory effect of suppressing the thermal decomposition of calcium carbonate generated from a low temperature of about 525 ° C., it must be inefficient, and the desired high-grade sludge incineration ash has a high rate. It is unsuitable to get in.

  Next, various pretreatments performed on the raw paper sludge S before being subjected to the above-described combustion treatment will be described in the order of steps shown in the flowchart of FIG. In the first cleaning step, the papermaking sludge used as a raw material is washed with water.

[Raw material sludge]
First, as described above, raw paper sludge is discharged from various processes such as pulping process, paper manufacturing process, waste paper recycling process, etc., but sludge from waste paper recycling process is the first stage of deinking process. It is recommended to collect sludge from white water from a disaggregation process. This is because sludge recovery from white water in the disaggregation process reduces the load of the subsequent deinking process, bleaching process, and cleaning process, thereby reducing the waste paper processing cost in addition to reducing the waste paper processing cost. Also, when recovering sludge from wastepaper raw materials with low whiteness, the ink particles containing carbon black, which is a flame-retardant organic component, are sludged as much as possible by sufficiently performing deinking and flotation in the wastepaper recycling process. It is good to remove from.

[Alkali metal compound addition step]
This is a pretreatment technique found by the present inventors. By adding an alkali metal compound to the papermaking sludge as a raw material, the alkali metal can be used for the thermal decomposition and combustion of organic components in the subsequent combustion treatment. It acts as a kind of catalyst and improves combustion efficiency. And it has been found that such effects are effective not only for flammable organic components, but also for non-flammable organic components that lack a functional group that is the starting point of thermal decomposition and ignition. ing.

  The alkali metal compound to be added is not particularly limited, but sodium or potassium hydroxides and carbonates are preferable from the viewpoints of solubility in water and alkali metal safety (fulminant physical properties). In contrast, halides such as sodium chloride and potassium chloride, and nitrates such as sodium nitrate and potassium nitrate, and strong alkali metal salts such as sodium sulfate and potassium sulfate improve combustion efficiency as alkali metal compounds. Although effective, strong acids such as hydrogen halide (hydrogen chloride), nitric acid, and sulfuric acid are generated during the combustion treatment process, which is undesirable because it may corrode the metal material constituting the cylindrical heat treatment furnace. In addition, these alkali metal compounds may be in a granular or powdery solid form or an aqueous solution form, and may be added to wastewater containing sludge before dehydration treatment or sludge after dehydration treatment. From the viewpoint of ease of adjustment of the addition amount, a method of adding to the raw material sludge before dehydration in the form of an aqueous solution, a method of spraying on the sludge before drying, and the like are preferable.

  In the case of alkali metal hydroxide, the addition amount of the alkali metal compound to the papermaking sludge is preferably in the range of 0.001 to 5.0 parts by weight with respect to 100 parts by weight of the sludge absolutely dry weight. The range of 0.1 to 1.0 parts by weight is optimal. Therefore, if this addition amount is too small, a sufficient effect cannot be obtained. On the contrary, if the added amount is too large, it is wasted and, when the alkali metal compound is a hydroxide, the pH of the sludge becomes strong due to excess alkali, and care must be taken in handling the sludge. Therefore, it is not preferable.

[Dehydration process]
Paper sludge having a required moisture content is obtained from paper sludge-containing wastewater by filtration, centrifugation, pressure dehydration, squeezing and the like. As a suitable dehydrating apparatus, there is a pressurizing / squeezing dehydrating apparatus called a screw press and a centrifugal dehydrating apparatus called a denkater.

[Drying process]
The water content of the papermaking sludge is evaporated to increase the solid content concentration. That is, in the present invention, the solid content concentration of the papermaking sludge at the time of the combustion treatment is not particularly limited, but it is preferably as high as possible from the viewpoint of increasing thermal energy efficiency and downsizing the apparatus, and particularly 70% by mass. The above is preferable. However, although only the above-mentioned dehydration step varies depending on the capacity of the dehydrator, the solid content concentration is about 5 to 60% by mass, and therefore it is recommended to further increase the solid content concentration by drying treatment.

  The dryer used in such a drying step is not particularly limited, and for example, a direct heating rotary kiln, an indirect heating rotary kiln, an air flow dryer, a fluidized bed dryer, a rotary / aeration rotary dryer, or the like can be used. . Moreover, it is possible to reduce energy cost by using the exhaust heat of the combustion process mentioned above as a heat source of these dryers.

  The temperature of the drying process may be set to 500 ° C. or less in an apparatus that uses hot air such as an air dryer or a rotary / aeration rotary dryer to prevent sludge combustion and carbonization. It is preferably 250 ° C. or less. If this hot air temperature is too high, sludge is ignited, and if the combustion conditions at that time are not appropriate, there is a concern that the readily combustible organic component is carbonized and changed to incombustible.

[Granulation process]
The paper sludge after drying is formed into an appropriate particle size by an appropriate means. That is, the papermaking sludge used as a raw material in the present invention may be in a form and particle size that can burn organic components in contact with air (oxygen) while being transferred in a cylindrical heat treatment furnace, but if it is too fine, the deposited layer will be Density increases, making it difficult for air to enter the layer, and conversely, even if it becomes coarse like a lump, it becomes difficult for air to reach the inside of the lump, both of which deteriorate the combustibility of organic components and fire with unburned carbide In order to reduce the whiteness of the product, it is preferable to granulate to a certain size.

  Granulation means include compression molding machines such as briquette machines and roller compactors, extrusion molding machines such as disk pelleters, and general granulation methods that granulate pellets by rolling granulation method, stirring granulation method, etc. In addition, when the dehydrated water-containing papermaking sludge is put into a drying device or a cylindrical heat treatment furnace, it is granulated for transportation using a shearing device such as a screw feeder, or during the drying process It is also possible to carry out granulation using the paper sludge transporting motion in

  The granulated particle size is preferably in the range of about 2 to 30 mm in length or diameter, and more preferably in the range of 3 to 20 mm. When the particle size is out of this range, for example, about 1 mm, it cannot be sufficiently brought into contact with the surrounding air during combustion, and becomes unburned easily. Further, if it exceeds 30 mm, it becomes difficult to completely burn up to the center. The particle shape of the granulation is not particularly limited, such as a columnar shape, a spherical shape, an ellipse, a triangle, other polygonal shapes, or those having irregularities.

  Next, various post-treatments for the fired product obtained by the combustion treatment will be described in the order of steps shown in the flowchart of FIG.

[Suspension process / Carbonation process]
The fired product obtained by the combustion treatment is mixed and stirred in water to form a suspension, and carbon dioxide gas is blown into the suspension to carbonize the fired product. This is because when the raw paper sludge contains calcium carbonate, the calcium carbonate (CaCO ₃ ) is pyrolyzed in the combustion process, and the inorganic particles containing the pyrolyzed calcium component are used as paper filler, coating pigment, etc. When used in papermaking materials, there is a concern that the alkalinity will become extremely strong, increase in viscosity, poor pigment dispersion, etc., so the calcium component after combustion treatment will be converted into a hydrate by suspension. Further, the carbonic acid is treated to return to calcium carbonate.

  The suspension process is intended to convert the calcium component thermally decomposed by the combustion treatment as described above into a hydrate once before returning it to calcium carbonate. While it takes a long time to make a suspension at a temperature, the heating temperature for maintaining the temperature is high and uneconomical at a high processing temperature, so the processing temperature is preferably 20 to 80 ° C., and 40 to 60 ° C. It is particularly preferable to do this. Incidentally, if the treatment temperature is about 60 ° C., the suspension can be completed in about 60 minutes. In addition, the solid content concentration of the suspension can efficiently perform the carbonation treatment in the subsequent carbonation step, and maintain the viscosity of the suspension low to maintain good fluidity and fluidity. And it is preferable to set it as 5-20 mass%.

  In the carbonation step, carbon dioxide is blown into the suspension of the fired product. However, since high purity carbon dioxide gas is uneconomical, industrially, the carbon dioxide concentration is about 5 to 40% by volume. Preferably, about 10 to 35% by volume of carbon dioxide-containing gas is used. Examples of such carbon dioxide-containing gas include sludge combustion exhaust gas, limestone firing exhaust gas, lime firing exhaust gas, waste incineration exhaust gas, power generation boiler exhaust gas, exhaust gas from causticized calcium carbonate firing kiln used in pulp manufacturing process, etc. Various combustion exhaust gases can be used after dust removal by an appropriate means. If the carbon dioxide concentration of the blown gas is too low, carbonation takes a long time, and the productivity of inorganic particles decreases accordingly. On the other hand, a high preparation cost is required to set a high carbon dioxide concentration.

  The amount of carbon dioxide blown in the carbonation step is preferably 0.5 to 15 liters / minute as carbon dioxide gas with respect to 1 kg of pyrolyzed calcium component solids in the fired product, and is too small. Takes time to reduce the productivity of inorganic particles. On the other hand, too much carbon dioxide increases the power load for blowing and is uneconomical. Moreover, the temperature (carbonation reaction temperature) of the calcined product suspension at the time of carbonation is preferably about 30 to 80 ° C, particularly 40 to 70 ° C. On the other hand, even if it is too high, the carbon dioxide gas is not sufficiently dissolved in the suspension, leading to a reduction in the efficiency of the carbonation reaction.

  In the carbonation step, in order to make calcium carbonate to be produced into a desired crystal shape, a seed crystal of calcium carbonate having the crystal shape may be added to the fired product suspension.

  Since the carbonated product obtained by carbonating the fired product as described above is white inorganic particles having a large particle size suitable for a papermaking filler, the suspension of the carbonated product is directly used for papermaking. It can also be used as a filler for papermaking raw materials such as pulp.

[Dehydration process / Dispersion process / Crushing process]
The carbonation product obtained from the carbonation step is dehydrated and then dispersed and pulverized to obtain a high-concentration slurry of fine white inorganic particles suitable as a pigment for coated paper. In the dehydration step, as in the above-described dehydration step in the pretreatment, the carbonation-treated product having a required water content is obtained from the suspension of the carbonated treatment product by filtration, centrifugation, pressure dehydration, pressing, and the like. To do. In the next dispersion step, water is added to the dehydrated cake-like carbonated product to obtain a high-concentration slurry. The dispersion operation involves stirring, crushing, and dispersion performed in a normal dispersion process. Various methods such as can be adopted. In addition, by adding a dispersing agent during the dispersing operation, the inorganic particles are in a favorable dispersed state, and the quality and handleability as a papermaking material are improved. As such a dispersant, a general dispersant used in the production of a papermaking material can be used, and specific examples thereof include synthetic polymer dispersants such as sodium polyacrylate.

  As a dispersing apparatus that can be suitably used, it is preferable to use a dispersing machine in which a mixing container rotates and a stirring tool such as an agitator rotates by another drive, for example, an intensive mixer manufactured by Nihon Eirich. In this way, if a dispersing device that not only drives the stirring tool but also rotates the mixing container is used, the dewatered cake in the container moves in a complex manner, and intense internal shearing force is generated, so the viscosity of the dispersed slurry decreases. is assumed. In addition, it is possible to employ | adopt either the same direction as a stirring tool, or a reverse direction as the rotation direction of a mixing container. Furthermore, it is preferable to arrange a scraper in order to prevent the material from sticking inside the container.

  As a preferable dispersing method using the dispersing apparatus as described above, a dispersion slurry having a low viscosity can be obtained by kneading in a hard paste form having a high viscosity and then adding a dispersant and dilution water to form a slurry. The carbonation-treated product to be dispersed is preferably used in the form of a cake after dehydration or by adding a small amount of a dispersant. This is because it is presumed that by mixing the carbonated product in a hard state, the carbonated product is loosened by a strong shearing force from the stirring tool, and the viscosity of the slurry is further reduced. The size of the cake-like carbonated product is not a problem as long as it can be put into a dispersing device, and it is not particularly necessary to pulverize it finely with a pulverizer or the like.

  The suspension of the carbonated product that has undergone the carbonation step is preferably filtered through a sieve such as a vibrating sieve before dehydration, and further subjected to classification using a liquid cyclone before the filtration. Preferably it is done. That is, by the filtration process, particles containing silicon such as α-quartz and coarse particles mixed in the carbonized product and coarse particles are removed, so that the wear of the papermaking wire can be reduced. Moreover, if the classification process by a liquid cyclone is performed before this filtration process, there exists an advantage that clogging of the sieve of the subsequent filtration process can be prevented.

  In the pulverization step, the inorganic particles after the dispersion treatment are pulverized into fine particles, whereby the inorganic particles are made high-quality white inorganic particles suitable as a coating pigment. As a pulverizer for this pulverization step, a sand mill, a wet ball mill, a vibration mill, a stirring tank type mill, a flow tube type mill, a coball mill and the like generally used in the manufacture of papermaking materials can be used.

  The size (particle diameter) of the inorganic particles is preferably 0.1 to 20 μm as an average particle diameter (D50) by laser diffraction particle size distribution measurement, and is 0 when used as a coating pigment. .3 to 5 .mu.m, and particularly preferably 3 to 15 .mu.m when used as an internal filler.

  Inorganic particles obtained from papermaking sludge as a raw material according to the present invention have high whiteness and do not contain a hard sintered material, and thus are used as papermaking materials such as papermaking fillers and coating pigments as described above. In addition, it can be used by mixing with various inorganic pigments used as papermaking materials such as calcium carbonate, talc, kaolin, calcined kaolin, titanium dioxide, satin white, and silica.

[Use of the obtained inorganic particles]
The inorganic particles obtained by the method of the present invention (hereinafter referred to as “inorganic particles of the present invention”) are mainly composed of calcium carbonate particles newly precipitated by carbonation treatment and amorphous component particles in which kaolin is modified by heat treatment. It consists of This amorphous component shows properties similar to those of calcined kaolin. For this reason, the inorganic particles of the present invention are excellent in opacity, smoothness, high oil absorption, and ink drying, which are the characteristics of each of calcined kaolin and calcium carbonate, and are used as paper fillers, coated paper pigments, etc. It can be used as a papermaking material.

Applications that can make the most effective use of the characteristics of the inorganic particles of the present invention include various printing papers such as offset printing and gravure printing that are less likely to exhibit opacity and smoothness and that also require whiteness. Examples of the use of the inorganic particles of the present invention include (1) an internal filler for non-coated printing paper or base paper for coating having a basis weight of 75 g / m ² or less (hereinafter referred to as “first use”). (2) Pigment for coating of fine coating to light weight coated paper (A3 coated paper, B3 coated paper) coated with one layer per side having a basis weight of 75 g / m ² or less (hereinafter referred to as “No. As a paper that requires bulkiness, high coverage (smoothness), ink drying properties, etc. (3) coated paper with two layers per side (A2 coated paper) , B2 coated paper), art paper (A0 coated paper, B0 coated paper, A1 coated paper, B1 coated paper) and other coating pigments (hereinafter referred to as “third use”). Can be mentioned. Hereinafter, these three aspects will be described.

(1) First use (use as internal filler)
The inorganic particles of the present invention can be used alone or together with other paper-making fillers (hereinafter, these are collectively referred to as “the filler of the present invention”). Other fillers for papermaking include clay, calcined clay, diatomaceous earth, talc, kaolin, calcined kaolin, delaminated kaolin, heavy calcium carbonate, light calcium carbonate, calcium carbonate and magnesium carbonate produced from the causticizing step of the pulp manufacturing process. , Barium carbonate, titanium dioxide, zinc oxide, silicon oxide, amorphous silica, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide and other inorganic fillers, urea-formalin resin, polystyrene resin, phenol resin, fine Examples include organic fillers such as hollow particles. The inorganic particles of the present invention can be used with one or more fillers selected from these fillers.

  The blending amount when the inorganic particles of the present invention are used together with other papermaking fillers is not particularly limited, but is preferably 10% by mass or more based on the total amount of fillers from the viewpoint of reducing raw material costs.

  The content (ash content) in the inner paper of the filler of the present invention is not particularly limited, but if it is less than 1% by mass, the paper quality such as the target opacity may be lowered, and 30% by mass. If it exceeds 1, tear strength, interlaminar strength of paper, and paper quality such as blisters may be deteriorated. Therefore, the content of the filler of the present invention is preferably in the range of 1 to 30% by mass. Particularly preferred is 5 to 20% by mass. By containing in this range, the scattering surface area of paper can be increased and the opacity of paper can be enhanced.

  There are no particular limitations on the paper pulp raw material to which the filler of the present invention is internally added, and known paper pulps that are generally used for paper production can be used. Specifically, there are no restrictions on hardwood and softwood, and pulp obtained from both raw materials includes chemical pulp such as sulfite pulp, kraft pulp, soda pulp, groundwood pulp, refiner pulp groundwood pulp, thermomechanical pulp, chemi Deinked pulp made from raw paper such as thermo-mechanical pulp, chemi-ground pulp, semi-chemical pulp, non-wood pulp such as straw, sardine, hemp, etc., as well as waste paper such as newspaper waste, printed waste paper, magazine waste paper, and OA waste paper Can be mentioned. Paper can be made by mixing the filler of the present invention with one or more selected from these pulps.

  When adding the filler of this invention to a pulp raw material, it is preferable to add the filler for paper manufacture, fully stirring a pulp raw material. The stirring speed at that time is preferably about 100 to 5000 rpm.

  The concentration of the filler of the present invention at the time of adding to the pulp raw material may be set to a concentration that falls within the range of the inlet concentration of the paper machine since papermaking is performed after mixing with the pulp raw material. It is desirable to add the filler of the present invention to the pulp raw material as much as possible immediately before the paper machine. This prevents the flocs (aggregated particles) of the filler of the present invention formed by agglomeration by the addition of a yield improver such as a cationic polymer from being destroyed by shearing force, etc., and the paper filler is maintained in an agglomerated state. This is to add it to the paper as it is.

  In addition to the filler of the present invention, pulp raw materials include additives used in normal papermaking, such as sizing agents, antifoaming agents, slime control agents, dyes, coloring pigments, fluorescent dyes, dry paper strength enhancers, and wet paper. A force enhancer, a drainage improver, a fixing agent, a yield improver, and the like can be appropriately added as necessary.

  The paper stock thus prepared can be made by a known paper machine according to the purpose. As the wet paper machine, for example, a commercial paper machine such as a round net paper machine, a short net paper machine, a long net paper machine, or a twin wire paper machine can be used.

  Various types of starches, polyvinyl alcohols, polyacrylamides, various surfaces generally used for improving or improving paper strength, coating suitability, printability, etc. It is also possible to apply a coating liquid mainly composed of a sizing agent or the like.

  For the above coating solutions, various pigments commonly used for coating include heavy calcium carbonate, light calcium carbonate, talc, clay, kaolin, titanium dioxide, synthetic silica, aluminum hydroxide, etc. One or more inorganic pigments and synthetic polymer fine particles such as polystyrene resin and urea formaldehyde resin can be blended as necessary. In addition, it is also possible to mix | blend the inorganic particle of this invention.

The basis weight of the paper internally added with filler of the present invention is not particularly limited, the desired effect is exerted is in the range of about 40~200g / m ^2. In particular, the effect of the present invention becomes remarkable when the range is about 40 to 75 g / m ² . However, it can of course be added to cardboard such as paperboard and card exceeding this range.

  Since the paper thus produced contains the inorganic particles of the present invention, the paper is excellent in whiteness, opacity and smoothness, and is directly uncoated such as printing paper, writing paper and office paper. In addition to being usable as a working paper, it can also be suitably used as a base paper for coating.

(2) Second application (application as a pigment for coating)
The inorganic particles of the present invention can be used alone or together with other coating pigments as a coating pigment (hereinafter collectively referred to as “the pigment of the present invention”). Other coating pigments include heavy calcium carbonate, light calcium carbonate, calcium carbonate produced from the causticizing step of the pulp manufacturing process, kaolin, calcined kaolin, satin white, talc, titanium oxide, aluminum hydroxide, alumina, Examples thereof include inorganic pigments such as zeolite, silica, zinc oxide, activated clay, diatomaceous earth, barium sulfate, and calcium sulfate, and various plastic pigments such as solid type, hollow type, bowl type, and donut type, and binder pigments. The inorganic particles of the present invention can be used with one or more selected from these pigments.

  The blending amount when the inorganic particles of the present invention are used together with other papermaking pigments is not particularly limited. However, from the viewpoint of reducing raw material costs, it is preferable that the amount is 10% by mass or more in the total amount of the pigment. .

  In the pigment of the present invention, a general adhesive for coated paper is added to form a coating liquid for coated paper, but this adhesive is not particularly limited, and for example, as a dispersion type adhesive Copolymer latexes such as acrylic, styrene-acrylic, styrene-butadiene, vinyl acetate-acrylic, butadiene-methylmethacrylate, vinyl acetate-butylacrylate, water-soluble adhesives, oxidized starch, ether Examples thereof include various modified starches such as modified starch, esterified starch and enzyme-modified starch, casein, polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, hydroxymethyl cellulose, polyacrylic acid, and polyacrylamide. One or more selected from these adhesives can be used.

  The adhesive is preferably contained in an amount of 5 to 50 parts by mass per 100 parts by mass of the pigment of the present invention. When the blending amount of the adhesive is less than 5 parts by mass per 100 parts by mass of the pigment of the present invention, the strength of the pigment coating layer is lowered, causing problems such as streak, scratch, and picking. On the other hand, when the blending amount of the adhesive exceeds 50 parts by mass, the strength of the pigment coating layer is sufficiently expressed, but problems such as a decrease in smoothness and a deterioration in ink drying property occur. A more preferable blending amount of the adhesive is 8 to 30 parts by mass per 100 parts by mass of the pigment of the present invention.

  In the coating liquid for the coated paper, a sizing agent, a dye, a thickener, a water retention agent, a flow modifier, a water resistance agent, a pH adjuster, an erasing agent are used as long as the effects of the present invention are not impaired. Commonly used additives such as a foaming agent, a lubricant, a preservative, a surfactant, a conductive agent, and a release agent may be added.

When preparing the coated paper of 1 layer coating per single side | surface with a basic weight of 75 g / m < ² > or less using the pigment of this invention, a normal coating system can be used. Coating methods include, for example, two roll size presses, gate roll size press coaters, metering size press coaters, transfer roll coaters such as shim sizers, air knife coaters, blade coaters, bar coaters, curtain coaters, die coaters, spray coaters. Etc. In particular, the transfer roll coater method is employed, which is a coating method in which a coating liquid is transferred to an applicator roll through a plurality of rolls and a predetermined amount of the coating liquid adhered to the applicator roll is applied to the surface of the base paper. preferable.

  The transfer roll coater is also called a pre-metering coating method, and is characterized by adjusting the coating liquid to a predetermined amount before coating on the base paper. For this reason, compared to blade coaters and bar blade coaters that use a coating method (post-measuring coating method) to scrape off the coating liquid adhering to the base paper, it is easier to set the coater conditions and wear the blades, etc. There is no need to replace parts. For this reason, since stable coating conditions can be achieved, stable operation for a long time is possible. In addition, there are advantages such as few streak defects, high-speed coating at 1000 m / min or more, and the ability to provide coating layers on both sides of the base paper at the same time, greatly improving productivity. Coated paper can be manufactured at low cost.

  There are various types of transfer roll coaters, an on-machine coater and an off-machine coater, and any method may be adopted. An on-machine coater is a type of coater that is installed on a base paper production machine (such as a paper machine) and applied on the same line as the base paper. The off-machine coater is a base paper production machine. This is an installation type in which a base paper that has been separately installed and manufactured is once wound up and then coated with a coater installed in a separate line. In terms of improving production efficiency and reducing costs, it is preferable to use an on-machine type transfer roll coater.

  The viscosity of the coating paper coating solution is preferably 5 to 30 mPa · s. If the Hercules viscosity of the coating solution is less than 5 mPa · s, there is a possibility that a sufficient coating amount cannot be obtained. This is because there is a problem that the coating liquid called “Scatter” is scattered, and for example, streaks may occur during coating with a blade coater, resulting in poor coating.

  The Hercules viscosity is the viscosity of a fluid when a high shear rate is applied to the fluid (coating liquid). In this specification, a Hercules viscometer (rotor: F Bob) conforms to Tappi T648. ) And the viscosity measured under the condition of a rotational speed of 8800 rpm. When the Hercules viscosity of the coating paper coating solution is in the above range, high-speed coating with a transfer roll coater can be stably performed.

  As a method for adjusting the Hercules viscosity, for example, adjustment of the average particle diameter and concentration of each pigment used in the coating paper coating solution, adjustment of the blending amount of the adhesive added to the coating paper coating solution, Examples include thickeners, water retention agents, flow modifiers, and the like, and adjustment of the blending amount. Any of these may be adopted.

The coating amount (coating amount after drying) of the coating paper coating solution is preferably ² to 7 g / m ² per side of the base paper. When the coating amount is less than 2 g / m ² , coating unevenness occurs, and it is difficult to form a coating layer uniformly on the surface of the base paper. When the coating amount exceeds 7 g / m ² , the drying load becomes excessive. This is because the operability may be reduced.

  When coating by a transfer roll coater, the solid content concentration in the coating paper coating solution is preferably 10 to 60%. If the solid content concentration in the coating paper coating liquid is less than 10%, a sufficient coating amount may not be ensured. If it exceeds 60%, the coating paper coating liquid is used. This is because there is a possibility that practical problems such as an excessively high viscosity and difficulty in controlling the coating amount may occur. A particularly preferred solid content concentration range is 30 to 50%.

  As the base paper for the coated paper, a general base paper for coating made of wood cellulose fiber can be used. Pulp for papermaking can be used as the wood cellulose used for the base paper for coating. Specifically, there are no restrictions on hardwood materials and softwood materials, and pulps obtained from both raw materials include sulfite pulp, kraft pulp, soda. Pulp and other chemical pulp, groundwood pulp, refiner pulp groundwood pulp, thermomechanical pulp, chemithermomechanical pulp, chemical pulp such as semi-chemical pulp, non-wood pulp such as straw, miso, hemp, etc. Examples include deinked pulp made from used paper such as used printed paper, magazine used paper, and OA used paper, and base papers made from the above-mentioned various pulps alone or in combination of two or more types can be used.

  To the base paper for coating, various fillers usually used as the filler of the present invention or the above-mentioned papermaking filler can be added, and the above-mentioned additives used in the papermaking of normal base paper for coating Can be added as needed.

In the present invention, the basis weight of the coated paper for the second use using the coating pigment containing inorganic particles is not particularly limited, but the covering property, surface smoothness, bulkiness, glossiness, ink drying property, etc. The effect of is remarkable when the range is about 40 to 75 g / m ² .

  After the coating liquid for coating is applied to the base paper, the coating layer is dried to obtain a coated paper. As the drying method, for example, a normal method such as a steam heater, a gas heater, an infrared heater, an electric heater, a hot air heater, a microwave, or a cylinder dryer can be arbitrarily selected and used. The coated paper, after drying, may be finished as a rolled product or a single-wafer product after being subjected to pressure smoothing so as to have the desired surface quality and white paper gloss as post-processing, if necessary. Good. As the pressure smoothing method, a super calendar, gloss calendar, mat calendar, soft calendar, etc. can be arbitrarily selected and used.

(3) Third use (use as a coating pigment)
In addition to whiteness, smoothness and opacity, various performances such as bulkiness, high coverage (smoothness), and ink drying properties are required for coated paper and art paper with single-sided two-layer coating. In order to satisfy these performances, the pigment of the present invention can be blended in one or both of the undercoat layer and the overcoat layer. In particular, it is preferable to mix in the undercoat layer. This is because the inorganic particles of the present invention have properties similar to those of calcined kaolin, and when these inorganic particles are blended in the pigment coating layer, the bulkiness, ink absorbability and ink drying properties of the coated paper are improved. In particular, by blending the present inorganic particles with an undercoat layer close to the base paper surface, the above effect can be remarkably and effectively exhibited.

  In both the undercoat layer and the overcoat layer, the blending amount of the inorganic particles of the present invention with respect to the total amount of pigment is the same as in the second application. However, as a pigment used for the undercoat layer, it is preferable that a pigment having an average particle diameter of 1.2 μm or more is contained in an amount of 40% by mass or more based on the total amount of the pigment. This is because when the blending amount of the pigment having an average particle diameter of 1.2 μm or more with respect to the total amount of the pigment in the undercoat layer is less than 40% by mass, the smoothness of the undercoat layer becomes too high and streaks may be induced. In addition, if the average particle diameter of the pigment is too large, desired smoothness, white paper gloss, and the like are difficult to be exhibited. Therefore, it is preferable to use a pigment having an average particle diameter of 5 μm or less.

  The kind of the adhesive added to the pigment of the topcoat layer and the undercoat layer and the blending amount of the adhesive added to the pigment of the topcoat layer are the same as in the second application. Further, as in the case of the second application, an auxiliary agent such as a sizing agent can be added to the coating paper coating solution. However, the blending amount of the water-soluble adhesive added to the pigment of the undercoat layer is preferably 6 parts by mass or less per 100 parts by mass of the pigment of the present invention. When blended beyond this, the water-soluble adhesive is buried in the connected portion of the coating layer gap formed by the pigment of the present invention, the absorption by the coating layer gap is hindered, the ink absorbability, the ink drying property, etc. It is because there exists a possibility that it may fall.

  The coating method for the undercoat layer is the same as in the second application. However, regarding the coating method of the topcoat layer, it is particularly preferable to employ the blade coater method among the coating methods listed in the second application. By adopting the transfer roll coater method in the undercoat layer, as described above, it is possible to improve the productivity and operability of the coated paper while maintaining the smoothness of the undercoat layer. By using it, the smoothness of the overcoat layer can be expressed to the maximum, and these can improve the glossiness of blank paper, the uniformity of printing, the print reproducibility, and the like.

  The viscosity of the coating paper coating solution for both the undercoat layer and the overcoat layer is preferably set to a Hercules viscosity (8800 rpm) of 5 to 30 mPa · s, as in the second application. The reason is also as described above.

The coating amount of the coating paper coating solution (dry coating amount) for each of the undercoat layer and the topcoat layer is ² to 12 g / m ² per one side of the base paper, and is applied to at least one side of the base paper by the two-layer coating. It is preferable to apply and dry so that the dry coating amount (total coating amount per side) is 4 to 24 g / m ² . When the coating amount of each coating layer is less than 2 g / m ² , coating unevenness occurs, and it is difficult to form the coating layer uniformly. When the coating amount of each coating layer exceeds 12 g / m ² , the coating layer is dried. This is because the operability may be reduced due to an excessive load.

  About the solid content concentration in the coating liquid for coated paper when the undercoat layer is applied by a transfer roll coater, it is preferably 10 to 60% as in the second application. However, it is preferable that the solid content concentration of the coating liquid for coating paper when the topcoat layer is applied by a blade coater is 30 to 65%. If the solid content concentration in the coating paper coating solution is less than 30%, a sufficient coating amount may not be secured, and sufficient smoothness may not be exhibited. This is because the viscosity of the pigment coating solution becomes excessive, which may cause practical problems such as streak generation and difficulty in controlling the coating amount. Particularly preferred is 40 to 60%.

The raw material of the base paper for coated paper, the filler added internally, and the auxiliary agent are the same as in the case of the second application. In the present invention, the basis weight of the coated paper using the coating pigment containing inorganic particles is not particularly limited, but the desired effect is exhibited in a range of about 40 to 200 g / m ^2. . In particular, when the range is about 40 to 100 g / m ² , the effect of the present invention becomes remarkable. However, it can of course be added to cardboard such as paperboard and card exceeding this range.

[Examples and Comparative Examples]
EXAMPLES The present invention will be specifically described below with reference to examples and comparative 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 mass%, respectively.

Example 1
Paper sludge consisting of solids and surplus sludges such as activated sludges obtained by separating wastewater from paper mills with paper and paperboard machines and coating machines, as well as paper mills with deinking pulping equipment, using a wastewater treatment clarifier The raw material is dehydrated to about 50% solids using a dehydrator, dried to a solid content of about 75% using a dryer, and then about 5 mm in diameter and about 15 mm in length using a disk pelleter. The pellets were granulated and formed, and the pretreatment was finished. Then, the paper sludge granulated product after the pretreatment is a rotary kiln furnace K2 (Takasago Kogyo Co., Ltd., externally heated rotary kiln, diameter of rotary cylinder 300 mm, length 2400 mm) shown in FIG. Was used for combustion treatment.

  In this combustion process, raw material papermaking sludge granulated material is supplied from a raw material input port 4 at a supply rate of 3.5 Kg / h by using a hopper, and a raw material supply port of the rotary drum 1 by a screw feeder as a raw material supply means 5. The two-stage combustion process was performed in the primary combustion zone Z1 and the secondary combustion zone Z2 while being fed into 1a and transferred through the rotary drum 1. In both combustion sections Z1 and Z2, the combustion gas from the combustion boiler (not shown) is used as a heat source to the front and rear heating spaces 2a and 2b of the heating jacket 2 by the indirect heating means 8A and 8B. The heat treatment temperature is controlled by the amount introduced, the treatment time in the primary combustion zone Z1 is 600 ° C. and the treatment time (sludge residence time) is about 40 minutes, and the treatment time in the secondary combustion zone Z2 is 800 ° C. and the treatment time is about 90 minutes. Set. On the other hand, combustion exhaust gas is exhausted from the rotary drum 1 by the exhaust fan of the exhaust means 9 at 100 L / min (air temperature converted to 20 ° C.), and the same amount of outside air as exhaust gas exhausted from the exhaust port 3 due to the decompression action associated therewith. Was sucked from the air supply port 6A, and the entire inside of the rotary drum 1 was always maintained in an excess air atmosphere.

  As a result of examining the composition of the fired product obtained by this combustion treatment by X-ray diffraction, the hard high-temperature sintered product (Gerenite) was not included, and the calcium carbonate contained in the papermaking sludge before the combustion treatment was All were disassembled. Moreover, in the components other than calcium carbonate, kaolin was all changed to amorphous, but talc was not changed at all.

  Next, the fired product obtained by the combustion treatment was mixed with warm water at 60 ° C. using a suspension tank (dissolving tank), and stirred for 60 minutes while maintaining the temperature of the suspension tank at 60 ° C. Thus, a fired product suspension having a solid concentration of about 12% was prepared. Then, 10 kg of the calcined product suspension was charged into a carbonation reaction tank, and while maintaining the temperature of the carbonation reaction tank at 60 ° C., 25 vol% carbon dioxide-containing gas was added to the suspension at 20 liter / min. The carbonation was carried out by stirring for 60 minutes while blowing. As a result of examining the composition of the inorganic particles after the carbonation treatment by X-ray diffraction, the total amount of calcium components decomposed by the combustion treatment was converted to calcium carbonate.

  Next, the suspension of the carbonation-treated product obtained by the carbonation treatment is dehydrated with a filter press, and the cake-like carbonation-treated product having a solid content concentration of about 48% is put into a coreless mixer. By dispersing in water, a white inorganic particle slurry having a solid content concentration of about 46% was prepared. In addition, in this water to disperse, a polyacrylic acid type dispersing agent (trade name: Aron T-50, manufactured by Toa Gosei Co., Ltd.) is used as a dispersing agent in an amount of 1.0 with respect to 100 parts by weight of the solid content of the carbonized product. Part by weight was added. Finally, the above inorganic particle slurry was wet-ground using a sand grinder to obtain fine white inorganic particles suitable for a coating pigment.

Example 2
White inorganic particles were obtained in the same manner as in Example 1 except that the sludge temperature in the primary combustion zone Z1 in the combustion treatment was 450 ° C.

Example 3
White inorganic particles were obtained in the same manner as in Example 1 except that the raw paper sludge was granulated and formed into pellets having a diameter of about 15 mm and a length of about 15 mm.

Example 4
Except for adding about 0.01 part of sodium hydroxide to 100 parts of sludge solid content by adding sodium hydroxide to the papermaking sludge before drying treatment, the same as in Example 1 above. White inorganic particles were obtained.

Example 5
By adding sodium hydroxide to the papermaking sludge before drying, about 1 part of sodium hydroxide is added to 100 parts of sludge solids, and the primary combustion zone Z1 and secondary combustion zone in the combustion treatment White inorganic particles were obtained in the same manner as in Example 1 except that each treatment time of Z2 was shortened to 30 minutes and 70 minutes, respectively.

Example 6
White inorganic particles were obtained in the same manner as in Example 1 except that the cake-like carbonated product that had been dehydrated with a filter press was dispersed with an intensive mixer (manufactured by Japan Eirich Co., Ltd.).

Comparative Example 1
Except that the sludge temperature in the primary combustion zone Z1 and the secondary combustion zone Z2 in the combustion process is both 600 ° C. and that the entire combustion process is performed in one stage (130 minutes as the combustion processing time), the same as in Example 1 above. White inorganic particles were obtained.

Comparative Example 2
Except that the sludge temperature in the primary combustion zone Z1 and the secondary combustion zone Z2 in the combustion process is both 700 ° C., and the entire combustion process is performed in one stage (the combustion process time is 130 minutes), the same as in Example 1 above. White inorganic particles were obtained.

Comparative Example 3
Except for setting the sludge temperature in the primary combustion zone Z1 and the secondary combustion zone Z2 in the combustion process to 800 ° C. and making the entire combustion process one stage (130 minutes as the combustion process time), the same as in Example 1 above. White inorganic particles were obtained.

Comparative Example 4
Except that both the sludge temperature in the primary combustion zone Z1 and the secondary combustion zone Z2 in the combustion processing are set to 900 ° C. and the entire combustion processing is performed in one stage (combustion processing time is 130 minutes), the same as in the first embodiment. White inorganic particles were obtained.

Comparative Example 5
White inorganic particles were obtained in the same manner as in Example 1 except that the sludge temperature in the primary combustion zone Z1 in the combustion treatment was 200 ° C.

Comparative Example 6
White inorganic particles were obtained in the same manner as in Example 1 except that the sludge temperature in the primary combustion zone Z1 in the combustion treatment was 660 ° C.

Comparative Example 7
In the combustion process, the primary combustion process and the secondary combustion process are separately performed using two rotary kiln furnaces. In the primary combustion process, the air supply to the rotary drum of the rotary kiln furnace is stopped and the atmosphere is in an oxygen-poor atmosphere. White inorganic particles were obtained in the same manner as in Example 1 except that the combustion treatment (carbonization treatment) was performed.

Reference example 1
White inorganic particles were obtained in the same manner as in Example 1 except that the raw paper sludge was granulated and formed into pellets having a diameter of about 1 mm and a length of about 5 mm.

Reference example 2
White inorganic particles were obtained in the same manner as in Example 1 except that the raw paper sludge was granulated and formed into pellets having a diameter of about 30 mm and a length of about 30 mm.

  About the above examples, comparative examples, and reference examples, the whiteness of the fired product obtained in the primary combustion process of the combustion treatment, the whiteness of the fired product obtained in the secondary combustion process, and the presence or absence of unburned carbide, are finally obtained. The results of examining the whiteness of the inorganic particles, the presence or absence of the hard sintered product, the slurry viscosity, and the comprehensive evaluation are shown in Table 1 below together with each processing condition. In addition, measurement and evaluation of each item are as follows.

[Whiteness]
About 10 g of the fired product obtained by the combustion treatment is ground in a mortar until there are no coarse particles, and then pressed for 30 seconds at a pressure of 100 kN using a powder tablet molding machine (Cata9302 / 30 type, manufactured by RIKEN ELECTRIC CO., LTD.). Molded. Subsequently, the whiteness of this molded sample was measured based on JIS P8148 (2001) using a spectral whiteness colorimeter (SC-10WT type, manufactured by Suga Test Instruments Co., Ltd.).

[Presence of unburned carbide]
In the measurement of the whiteness, the fired product was pulverized. The remaining state of unburned carbide before pulverization of the fired product was visually observed and evaluated in the following three stages.
○: There is no unburned carbide in the inner and outer parts of the fired particles. △ ... Unburned carbide remains in the inner part of the fired particles. Unburned carbide remains in both the external and external parts

[With or without hard sintered product]
A sample of inorganic particles ground in a mortar until no coarse particles disappeared, measured using an X-ray diffractometer (MO3XHF, supra) under the conditions of 40 KV, 20 mA, diffraction angle measurement range: ˜50 degrees, and hard sintered product The presence or absence of (Gerlenite) was examined. “None” of this hard sintered product is excellent in quality, and “Yes” is inferior in quality.

[B type viscosity measurement]
The prepared slurry was stirred with a stirrer and allowed to stand for 30 seconds, and then a viscosity at 60 rotations was measured using a B-type rotational viscometer BM type (manufactured by Tokyo Keiki Co., Ltd.).

〔Comprehensive evaluation〕
About the inorganic particle of the sample, the quality as a papermaking material was comprehensively evaluated in the following three stages from the data on the whiteness and the presence or absence of a hard sintered product. The whiteness is less than 78% at the stage of the finally obtained inorganic particles.
○ ・ ・ ・ Whiteness is sufficiently high and hard sintered material is not included △ ・ ・ ・ Whiteness is slightly low, but hard sintered material is not included × ・ ・ ・ Whiteness is insufficient or hard sintered One or both of the inclusions

  From the results shown in Table 1, the inorganic particles obtained by the production method of the present invention using papermaking sludge as a raw material are subjected to a two-stage combustion treatment under specific conditions. It is clear that it has a high quality that can be sufficiently reused as papermaking materials such as industrial pigments and papermaking fillers. In contrast, inorganic particles obtained through a one-stage combustion process at various temperatures (Comparative Examples 1-4), inorganic particles obtained through a combustion process in which the heat treatment temperature in the primary combustion process is too low or too high in two stages (Comparative Examples 5 and 6) In inorganic particles (Comparative Example 7) obtained through a combustion process in which the primary combustion process in two stages is performed in an oxygen-poor atmosphere, the whiteness is low or a hard sintered material is included. It turns out that it is difficult to use as a papermaking material. Moreover, when the granulated material of the papermaking sludge used as a raw material is too small (reference example 1), and conversely too large (reference example 2), it results in inferior quality of the obtained inorganic particles. It is also suggested.

[Calcium carbonate decomposition rate after combustion treatment]
Next, as evaluations other than the items listed in Table 1, for each example, the decomposition rate of calcium carbonate after the combustion treatment is determined by the following steps i) to vi) and the calcium carbonate in the papermaking sludge before the combustion treatment. The amount of calcium carbonate remaining in the fired sludge was determined and evaluated. As a result, no calcium carbonate peak was observed in the X-ray diffraction measurements of all the examples, and all the calcium carbonate in the sludge fired product was decomposed in the combustion treatment step. For this reason, the amount of calcium carbonate (A) in the sludge fired product in all examples obtained based on the following procedure is 0.0 g (0% by mass) per 1 g of the sludge fired product. In all the obtained examples, the decomposition rate of calcium carbonate after the combustion treatment was 100%.

i) Preparation of calibration curve for calcite calcium carbonate Zinc oxide (reagent special grade made by Kishida Chemical Co., Ltd.) as an internal standard substance with respect to calcium carbonate having a crystal structure of calcite (Tama Pearl 222H made by Okutama Kogyo Co., Ltd.) : 5, 1: 1, 5: 1. Next, after each mixture was sufficiently ground using a mortar, it was measured using an X-ray diffractometer (MO3XHF manufactured by Max Science) under the conditions of 40 KV, 20 mA, and a diffraction angle measurement range of 5 to 50 degrees. Based on the X-ray diffraction 100% peak areas of calcium calcite and zinc oxide, a calibration curve of calcium calcite was prepared.

ii) Preparation of calibration curve of aragonite calcium carbonate Calibration of aragonite calcium carbonate was carried out in the same manner as the calibration curve of calcite calcium carbonate except that calcium carbonate having a crystal structure of aragonite (Tama Pearl 123 manufactured by Okutama Kogyo Co., Ltd.) was used. Created a line.

iii) Quantification of calcium carbonate in papermaking sludge before combustion treatment Weighed zinc oxide (reagent grade above) was added and mixed to the weighed absolute dry papermaking sludge. Next, the mixture was sufficiently ground using a mortar, then measured using an X-ray diffractometer (MO3XHF, supra) at 40 KV, 20 mA, a diffraction angle measurement range of 5 to 50 degrees, and oxidized. X-ray diffraction 100% peak areas of calcium calcite carbonate and aragonite calcium carbonate with respect to zinc were determined, and the amount of calcium carbonate (g) contained in 1 g of papermaking sludge was calculated based on the calibration curve of each calcium carbonate described above. .

iv) Measurement of ash content of paper sludge Burned sludge fired product obtained by burning the weighed dry paper sludge using a muffle furnace so as to be the same as each combustion treatment condition of the rotary kiln furnace in the examples. The ash content (%) of sludge was measured by the following formula.
Ash content (%) = (weight of sludge burned product / weight of paper drying sludge) × 100

v) Quantitative determination of calcium carbonate in the calcined sludge The weighed sludge calcined product was added and mixed with a weighed zinc oxide (reagent special grade mentioned above). Next, the mixture was sufficiently ground using a mortar, then measured using an X-ray diffractometer (MO3XHF, supra) at 40 KV, 20 mA, a diffraction angle measurement range of 5 to 50 degrees, and oxidized. Obtain 100% peak area of X-ray diffraction of calcium calcite carbonate and aragonite calcium carbonate with respect to zinc, and calculate the amount of calcium carbonate (g) contained in 1 g of the sludge fired product based on the calibration curve of each calcium carbonate described above. did.

vi) Decomposition rate of calcium carbonate after combustion treatment The amount of calcium carbonate (g) in 1 g of the sludge fired product is A, the amount of calcium carbonate (g) in 1 g of papermaking sludge is B, and the ash content (%) is C. The decomposition rate of calcium carbonate after the combustion treatment was calculated by the following equation.
Calcium carbonate decomposition rate (%) = 100− [A × (C / 100)] ÷ B × 100

[Presence / absence of unregenerated calcium carbonate]
Furthermore, as an evaluation other than the items listed in Table 1, the inorganic particles finally obtained in each example were ground in an mortar until coarse particles disappeared, and an X-ray diffractometer (MO3XHF ) Was used under the conditions of 40 KV, 20 mA, and diffraction angle measurement range of 5 to 50 degrees, and the presence or absence of calcium oxide and calcium hydroxide assumed to be calcium carbonate unregenerated was examined. As a result, it was found that the inorganic particles of all the examples did not contain the unregenerated product of calcium carbonate, and all were excellent in quality.

  In order to confirm the effect when the white inorganic particles of the present invention were used as a filler for papermaking, the following experiment was conducted.

Example 7
30% inorganic particles (average particle size 12.8 μm) obtained in Example 6 and 70% light calcium carbonate (trade name: TP-121, manufactured by Okutama Kogyo Co., Ltd., average particle size 6 μm) before mixing were mixed. Thus, a filler suspension having a solid content concentration of 10% was prepared.

On the other hand, a mixed pulp slurry (pulp concentration of 2.5%) composed of 60% hardwood bleached kraft pulp (LBKP) and 40% recycled recycled paper pulp was prepared. Subsequently, as an addition amount per pulp dry mass, 0.8 parts of cationized starch (trade name: Oji Ace K100, manufactured by Oji Cornstarch Co., Ltd.), aluminum sulfate (Al ₂ (SO ₄ ) ₃ · 18H ₂ O) 0.5 Parts of the alkyl ketene dimer (trade name: SPK903, manufactured by Arakawa Chemical Industries) and the pulp slurry so that the amount of filler added as base paper ash is about 13% by mass. On the other hand, the pulp slurry was sequentially added every 2 minutes with stirring and mixed well, and then the pulp slurry was diluted to a solid content concentration of 0.5% to prepare a sample.

Next, this sample was used to make a sheet with an air-dry basis weight of 69 g / m ² using a laboratory square hand-made sheet machine (manufactured by Tozai Seiki Co., Ltd.) and then dried with a cylinder dryer at a temperature of 100 ° C. Was prepared. The hand-sheet is conditioned at 23 ° C and 50% RH for 24 hours, and then finished once with a laboratory calender (manufactured by Kumagai Riki Kogyo Co., Ltd.) at a linear pressure of 10 kg / cm. Thus, an inorganic particle-containing paper was obtained.

Reference example 3
As in Example 7, except that a light calcium carbonate (trade name: TP-121, manufactured by Okutama Kogyo Co., Ltd., average particle diameter of 6 μm) was used as a filler suspension prepared to a solid content concentration of 10%. Thus, an inorganic particle-containing paper was obtained.

Reference example 4
A filler suspension having a solid content concentration of 10% was prepared as 100% talc (trade name: SK-2, manufactured by Toyo Kasei Co., Ltd., average particle diameter: 12.8 μm). In Reference Example 4, hand-filled filler-added paper was not prepared, and only the wire wear degree of the filler dispersion was measured.

  About Example 7 and Reference Examples 3 and 4, the wire abrasion degree of the filler dispersion, paper ash content, basis weight, thickness, density, smoothness, whiteness and opacity were investigated by the following methods. The results are shown in Table 2.

[Wire wear degree of filler dispersion]
Using a wire abrasion tester (manufactured by Oji Koei Co., Ltd.) and pumping a filler dispersion with a solid content of 5%, the test conditions (weight = 650 g, wire = plastic wire / SS-40, manufactured by Nippon Filcon Co., Ltd.) Use, test time = 3 hours), the wear degree test was performed, and the weight (mg) of the reduced wire was used as the wire wear degree. It shows that wire abrasion property is so large that a numerical value is large.

[Paper ash]
The ash content of the paper was measured according to ISO2144.

[Basis weight of paper]
The basis weight of the paper was measured according to ISO536.

[Paper thickness and density (strength)]
According to ISO534, the thickness and density (tensity) of the paper were measured.

[Smoothness of paper (PPS smoothness)]
Using a Parker Print Surf (PPS) surface smoothness tester (model name: MODEL M-569, manufactured by Messmer Buchel, UK), smoothing 5 times under the conditions of backing disk: soft rubber, clamping pressure: 0.98 MPa Was measured and the average value was determined.

[Whiteness of paper]
The whiteness of the paper was measured according to ISO 2470.

[Opacity of paper]
The opacity of the paper was measured according to ISO 2471.

  As shown in Table 2, the inorganic particle-containing paper of Example 7 was bulky and had good opacity as compared with the inorganic particle-added paper of Reference Example 3.

  In order to confirm the effect when the white inorganic particles of the present invention were used as a pigment for lightweight coated paper, the following experiment was conducted.

Example 8
40% inorganic particles (average particle size 1.5 μm) obtained in Example 6, 20% kaolin (trade name: Milagros J, manufactured by Engelhard) with an average particle size of 0.3 μm and an average particle size of 1.3 μm Polyacrylic acid sodium dispersant (trade name: Aron T50, manufactured by Toa Gosei Co., Ltd.) with respect to 100 parts of pigment containing 40% of heavy calcium carbonate (trade name: Hydrocurve K-9, manufactured by Bihoku Powder) Was added in an amount of 0.05 parts, and the pigment was dispersed in water with a Coreless disperser to obtain a pigment slurry. 10 parts (solid name) of styrene-butadiene copolymer latex (trade name: OJ1000, manufactured by JSR), pregelatinized oxidized starch (trade name: Oji Ace B, manufactured by Oji Corn Starch) ) 6 parts (solid content) was added and mixed and stirred to finally prepare a light weight coated paper pigment coating solution having a solid content concentration of 56% and a Hercules viscosity of 17 mPa · s.

This light-weight coated paper pigment coating solution is applied to both sides of a high-quality base paper having a basis weight of 52 g / m ² at a coating speed of 600 m / min using a gate roll coater and dried to obtain a double-side coated paper. Obtained. The coating amount (solid content) was 7 g / m ² per side. The obtained coated paper was further subjected to a super calendar process to obtain a double-sided, one-layer lightweight coated paper.

Reference Example 5
A pigment comprising 50% kaolin (trade name: Milagros J, supra) with an average particle size of 0.3 μm and 50% heavy calcium carbonate (trade name: Hydrocurve K-9, supra) with an average particle size of 1.3 μm 1 was used in the same manner as in Example 8 except that a light-weight coated paper pigment coating solution having a solid content concentration of 59% and a Hercules viscosity of 20 mPa · s was prepared. A layer lightweight coated paper was obtained.

About Example 8 and Reference Example 5, the basis weight, thickness, density, smoothness, whiteness and opacity of the paper were investigated by the above method, and the Hercules viscosity of the pigment coating solution was further determined by the following method. In addition, the white paper glossiness, printing glossiness, printing strength, and ink drying properties of the paper were examined.
The results are shown in Table 3.

[Hercules viscosity of pigment coating solution]
Using a Hercules high shear viscometer (manufactured by Kumagai Riki Kogyo Co., Ltd.), the viscosity (mPa · s) with F Bob at 8800 rpm was measured.

[Blank gloss of paper]
In accordance with ISO 8254-1 Part 1 (1999) (JIS P8142), the glossiness (blank paper glossiness) of the white paper surface at 75 degrees was measured.

[Paper glossiness of paper]
Using a RI-II type printing tester (Meiji Seisakusho) and 0.7cc of offset printing ink (trade name: Fusion-G ink S type, manufactured by Dainippon Ink & Chemicals) on each lightweight coated paper Printing was performed, and the printed material was left to dry for 24 hours. Then, based on JIS Z8741, the glossiness (printing glossiness) at 60 degree | times of the printing surface of each lightweight coated paper was measured.

[Paper printing strength]
Using an RI printing tester, printing was carried out using 0.6 cc of printing ink (trade name: SD50 for paper testing, manufactured by Toyo Ink Co., Ltd.), and the degree of picking on the printed surface was visually evaluated. However, the meaning of each symbol in the table is as follows.
○: Picking does not occur at all and the surface strength is good.
Δ: A little picking occurs, and the surface strength is slightly inferior.
X: A lot of picking occurs and the surface strength is considerably inferior.

[Ink dryness of paper]
Using an RI printing tester, printing was performed using 1.0 cc of printing ink (trade name: Fusion-G black S type, supra), and a blank sheet (trade name: YUPO FPG-80, YUPO Corporation) after 3 minutes. The printed surface was overlapped, and the print surface was nipped again with an RI printing tester, and the density of ink transferred to white paper (back-off stain) was visually evaluated. However, the higher the ink density (transfer stain) transferred to the white paper, the slower the ink drying property of the paper. The meaning of each symbol in the table is as follows.
○: There is almost no set-off stain on the white paper, and the ink drying property is good.
Δ: Slightly transferred to the white paper, and the ink drying property is slightly inferior.
X: A lot of set-off stains on white paper is generated, and the ink drying property is considerably inferior.

  As shown in Table 3, the light-weight coated paper of Example 8 is less viscous than the light-weight coated paper of Reference Example 5, has high smoothness and opacity, and is ink-dried. The property was also good.

  In order to confirm the effect when the white inorganic particles of the present invention were used as a pigment for a two-layer coated paper, the following experiment was conducted.

Example 9
30% of inorganic particles (average particle size of 1.5 μm) obtained in Example 6 and 70% of heavy calcium carbonate having an average particle size of 2.0 μm (trade name: Hydrocurve K-6, manufactured by Bihoku Powdered Company) 0.05 parts of sodium polyacrylate dispersant (trade name: Aron T50, manufactured by Toa Gosei Co., Ltd.) is added to 100 parts of the pigment blended with the above, and the pigment is dispersed in water with a Coreless disperser. A slurry was obtained. To 100 parts of this pigment slurry, 6 parts of styrene-butadiene copolymer latex (trade name: OJ1000, supra) (solid content), pre-gelatinized oxidized starch (trade name: Oji Ace B, manufactured by Oji Corn Starch) 4 parts (solid content) was added, mixed and stirred, and finally a coating solution for an undercoat layer having a solid content concentration of 59% and a Hercules viscosity of 21 mPa · s was prepared.

  On the other hand, from heavy calcium carbonate having an average particle size of 1.3 μm (trade name: Hydrocurve K-9, supra) and kaolin having an average particle size of 0.3 μm (trade name: Milagros J, supra) from 60% 0.05 part of a sodium polyacrylate dispersant (trade name: Aron T50, manufactured by Toa Gosei Co., Ltd.) is added to 100 parts of the resulting pigment, and the pigment is dispersed in water with a Coreless disperser to obtain a pigment slurry. It was. For 100 parts of this pigment slurry, 11 parts of styrene-butadiene copolymer latex (trade name: OJ1000, supra) (solid content), pre-gelatinized oxidized starch (trade name: Oji Ace B, manufactured by Oji Corn Starch) 2 parts (solid content) was added and mixed and stirred to finally prepare a top layer coating solution having a solid content concentration of 62% and a Hercules viscosity of 23 mPa · s.

The undercoat layer coating solution was applied to both surfaces of a high-quality base paper having a basis weight of 52 g / m ² using a gate roll coater at a coating speed of 600 m / min and dried to obtain a double-sided coated paper. The coating amount (solid content) was 7 g / m ² per side. Next, a coating speed of 600 m / min is applied to the coated paper coated with the undercoat coating liquid using a blade coater so that the dry coating amount per side is 9 g / m ^2. After coating and drying one side at a time, super calendering was performed to prepare a double-sided two-layer coated paper.

Reference Example 6
Using a pigment made of 100% heavy calcium carbonate (trade name: Hydrocurve K-6) with an average particle size of 2.0 μm, the solid content concentration is finally 61% and the Hercules viscosity is 22 mPa · s. A double-sided two-layer coated paper was obtained in the same manner as in Example 9 except that the undercoat layer coating solution was prepared.

For Example 9 and Reference Example 6, Hercules viscosity of pigment coating solution, basis weight of paper, thickness, density, smoothness, white paper gloss, whiteness and opacity, print gloss, print strength by the above methods In addition, the ink drying property was investigated. The results are shown in Table 4.

  As shown in Table 4, the double-sided, two-layer coated paper of Example 9 has a low tension and high smoothness, glossiness and opacity compared to the double-sided, two-layer coated paper of Reference Example 6. Moreover, the ink drying property was also good.

The flowchart which shows an example of the manufacturing method of the inorganic particle which concerns on this invention. The schematic longitudinal cross-sectional side view which shows the 1st structural example of the rotary kiln furnace used for this invention. The model longitudinal cross-sectional side view which shows the 2nd structural example of the rotation kiln furnace. The model longitudinal cross-sectional side view which shows the 3rd structural example of the rotation kiln furnace. The model perspective view which shows the structural example of the rotating drum in the same 3rd structural example. The longitudinal cross-sectional front view which shows the rotary trunk | drum of 6 division partition structure used for the same rotation kiln furnace. The longitudinal cross-sectional front view which shows the rotary cylinder of the 6 cylinder type multi-cylinder structure used for the same rotation kiln furnace. The longitudinal cross-sectional front view which shows the rotary drum of the 12 division | segmentation partition structure used for the rotation kiln furnace. The model longitudinal cross-sectional side view which shows the 4th structural example of the rotation kiln furnace.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Rotary cylinder 1A ... Small diameter cylindrical body 1B which comprises the rotary cylinder 1 ... Large diameter cylindrical body 1a which comprises the rotary cylinder 1 ... Raw material Supply port 1b ··· Fired product discharge port 2 ··· Heating jacket 2A ··· Separated heating jacket (for front heating)
2B: Separate heating jacket (for rear heating)
2a ... front heating space 2b ... rear heating space 3 ... exhaust port 4 ... raw material inlet 5 ... raw material supply means 6A, 6B: Air supply port 7: Burned product outlet 8A, 8C: Indirect heating means (for primary combustion)
8B, 8D ... Indirect heating means (for secondary combustion)
81 ... Hot air blower 82 ... Hot air discharge port 9 ... Exhaust means 10 ... Exhaust circulation blower 11 ... Partition member 12a ... Outer shell 12b ··· Partition 13 ··· Division chamber 14 ··· Pipe portion 15 ··· Tube portion fixing member 15a ··· Center hole 16 ··· Hollow portion 16a ··· ··· Front heating space 16b in the cavity portion 16 ··· Rear heating space 17a in the cavity portion 16 ··· Inner tube portion 17b ··· Outer tube portion 17c ··· Partition wall a ··· ... Air flow direction a1 ... Air flow a2 from air supply port 6A ... Air flow from air supply port 6B a3 ... Air combined with airflows a1 and a2 Flow b ··· Direction of papermaking sludge c ··· Virtual line d ··· Rotation direction K1 K4 ··· rotary kiln furnace S ······ paper sludge Z1 ····· primary combustion zone Z2 ····· secondary combustion zone

Claims (14)

A method for producing inorganic particles by using papermaking sludge as a raw material and performing a combustion treatment while being transferred in a cylindrical heat treatment furnace,
The combustion treatment includes a primary combustion step in which flammable organic components in the sludge are burned and removed in an excess air atmosphere at a sludge temperature of 650 ° C. or less, and a difficult combustion in the sludge in an excess air atmosphere at a sludge temperature of 700 to 850 ° C. A method for producing inorganic particles, wherein the method comprises at least two stages of combustion steps, including a secondary combustion step of burning and removing volatile organic components.   The method for producing inorganic particles according to claim 1, wherein the cylindrical heat treatment furnace is a rotary kiln furnace.   The manufacturing method of the inorganic particle of Claim 1 or 2 which performs a combustion process by indirect heating.   The method for producing inorganic particles according to any one of claims 1 to 3, wherein the at least two stages of combustion processes are set during a transfer process of one cylindrical heat treatment furnace.   5. The air according to claim 1, wherein air in the furnace is forcibly discharged from the raw material supply port side at one end of the cylindrical heat treatment furnace, and air is sucked into the furnace from the fired product discharge port side at the other end. The manufacturing method of the inorganic particle as described in claim | item.   6. The method for producing inorganic particles according to claim 5, wherein air is sucked into the furnace at the transition from the primary combustion step to the secondary combustion step in addition to air suction from the fired product discharge port side.   The method for producing inorganic particles according to any one of claims 3 to 6, wherein an indirect heating part for the primary combustion process and an indirect heating part for the secondary combustion process are separated.   The method for producing inorganic particles according to any one of claims 1 to 7, wherein an alkali metal compound is added to the raw papermaking sludge.   The method for producing inorganic particles according to any one of claims 1 to 8, wherein the raw papermaking sludge is granulated or formed into a lump shape.   The method for producing inorganic particles according to any one of claims 1 to 9, wherein 50% or more of calcium carbonate contained in the raw papermaking sludge is decomposed by the combustion treatment.   A suspension process for mixing the fired product after the combustion treatment with water and stirring to obtain a suspension; a carbonation treatment process for obtaining a carbonated product by bringing carbon dioxide into contact with the suspension; and The manufacturing method of the inorganic particle as described in any one of Claim 1 to 10 including the crushing process of grind | pulverizing a carbonation processed material. A cylindrical heat treatment furnace having one end side as a raw material supply port and the other end side as a fired product discharge port, raw material supply means for supplying papermaking sludge to the raw material supply port, and transferring the supplied sludge to the fired product discharge port side Transfer means, indirect heating means for bringing the inside of the cylindrical heat treatment furnace into a combustion state, and air supply means for making the inside of the cylindrical heat treatment furnace an excess air atmosphere,
In the cylindrical heat treatment furnace, a primary combustion section having a sludge temperature of 650 ° C. or less and a secondary combustion section having a sludge temperature of 700 to 850 ° C. are configured,
The air supply means forcibly exhausts the air in the furnace from an exhaust port provided in the vicinity of the raw material supply port of the cylindrical heat treatment furnace, so that air is supplied from an air supply port provided in the vicinity of the fired product discharge port of the cylindrical heat treatment furnace. A plant for producing inorganic particles that is used to inhale the gas into the furnace.   A paper comprising inorganic particles obtained by the production method according to any one of claims 1 to 11 as a filler.   A coated paper comprising inorganic particles obtained by the production method according to any one of claims 1 to 11 as a pigment.

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