JP2007112681A - Method of manufacturing inorganic particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing inorganic particles by which the uniform inorganic particles are manufactured by carrying out uniform firing using deinking froth as a main raw material. <P>SOLUTION: The method of manufacturing the inorganic particles uses the deinking froth as the main raw material and has a drying step and a firing step. In the drying step before the deinking froth is fired in the firing step, the deinking froth is dried to have 2-20 mass% water content in the drying step and the inorganic particles having 355-2,000 μm particle diameters are ≥70 mass% in the outlet of the drying step. In the firing step, the firing is carried out at 500-750°C firing temperature in a stage that unfired portion is 5-30% to obtain the inorganic particle F. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing inorganic particles for papermaking or plastics obtained by firing using deinking floss as a main raw material, and more specifically, firing deinking floss under main conditions under a predetermined condition. In addition, the present invention relates to a method for producing inorganic particles having porosity, affinity with various papermaking chemicals, and low wear, and can be suitably used as a filler for papermaking or plastics.

  Paper sludge discharged from various processes in a pulp and paper mill contains a large proportion of inorganic fillers and inorganic pigment particles. These paper sludge is collected and recovered in incinerators such as fluidized bed furnaces and stalker furnaces. The organic matter inside is burned to reduce the volume of papermaking sludge and is recovered as energy.

  However, since papermaking sludge contains a large amount of inorganic substances, a large amount of combustion ash (inorganic substances) remains even after combustion, and there is a limit to volume reduction. Thus, efforts have been made to utilize the combustion ash as an auxiliary material for cement raw materials and as a soil conditioner. However, the amount of incineration ash used as an auxiliary for these cement raw materials and soil conditioners is very small, and in the end, most of the combustion ash is landfilled.

  For this reason, in addition to recovering energy from incineration, the reuse of inorganic materials in incineration ash as fillers for papermaking, pigments, fillers for plastics, etc. is related to environmental problems as well as improving the utilization of used paper in the papermaking industry. This is an important improvement issue. However, the incineration ash of papermaking sludge contains organic substances that remain without being burned as carbon, so the whiteness is low, or the sintering of inorganic substances progresses, the particle size is uneven and large, and it remains as it is However, it is not suitable for use as a filler for paper, a pigment for coating, a filler for plastics, and the like.

  Therefore, Patent Document 1 discloses a method of using combustion ash (incineration ash) after reburning and improving the whiteness.

  However, in the method of recombusting the incinerated ash of Patent Document 1, it is necessary to set the recombustion temperature to 500 to 900 ° C. in order to completely burn the unburned carbon, and the whiteness of the incinerated ash is about 50%. It has been found that it is not suitable for use as a paper filler or coating pigment. It has also been found that when the reburning temperature is set to over 900 ° C., the burning ash (inorganic material) is sintered and melted and becomes extremely hard. Also, when reburned ash is used as a filler, this reburned ash has very hard properties, so the papermaking wire wears out quickly and the life of the papermaking wire becomes very short, so it can be used in actual operations. It wasn't. Further, when the reburned ash is used as a coating pigment, the reburned ash has a very hard property, so that there arises a problem that the smoothness of the surface of the coating layer is inferior even when the calendar treatment is performed.

  In this regard, it is conceivable to grind the reburned ash and reduce its particle size to reduce wear and improve smoothness, but when used as an internal filler, the yield during paper making is low. Since the combustion ash itself is extremely hard, the energy cost for pulverization is extremely high.

  Moreover, in patent document 2, papermaking sludge is supplied in the reactor which inject | poured oxygen-containing gas, and it oxidizes for 0.25-5 hours under the heating pressurization about 250-300 degreeC and 3000 psig, and in papermaking sludge A method of regenerating the inorganic material as a papermaking pigment has been proposed.

  However, since this method is based on wet air oxidation treatment of papermaking sludge, organic matter removal is not sufficient, and the obtained pigment has low whiteness and uneven particle size, and papermaking fillers and pigments. This is unsuitable for use as a reaction product, and has a problem that the reaction operation is complicated and expensive.

  On the other hand, Patent Document 3 proposes a method in which after making papermaking sludge into PS charcoal, it is further incinerated with a kiln to produce white clay as a papermaking raw material. However, this method has a great demerit that not only energy cannot be effectively extracted from the papermaking sludge but also input energy is required because the papermaking sludge is fried. Further, the generated white clay also has a large particle size and has a problem that it cannot be used as a papermaking pigment.

  Further, as in Patent Document 4, a method is known in which wastewater treatment sludge is continuously dried, carbonized, and fired in a rotary kiln. In this method, granulation and shaping are performed prior to firing in order to perform firing uniformly. The solid content concentration described in the embodiment is 40 to 60% (in other words, moisture content is 60 to 40). %) In the rotary kiln continuously, the sludge particles are forcibly processed by the rotation of the kiln regardless of the dry state or carbonized state. Therefore, if the drying is inadequate, a large amount of unburned matter remains inside the particles, resulting in incomplete firing, resulting in a decrease in whiteness. Invited, the resulting inorganic particles have a high hardness, and the use of these inorganic particles causes problems such as wire wear in a paper machine and cutter blade wear when cutting paper.

  The biggest problem when using papermaking sludge described in the preceding Patent Documents 1 to 4 as a raw material is that the papermaking sludge used as a raw material flows out through the wire in the papermaking process, and the washing process in the pulping process Collected from wastewater containing solids generated in wastewater, separated and recovered by solids separation equipment using precipitation or flotation, etc., in wastewater treatment process, removed foreign matter in wastepaper treatment process It is a point where various sludges such as are mixed.

  Among these sludges, for example, those that flow out through the wire in the paper making process are mixed with a paper strength agent or the like, and quality changes due to changes in the paper made in the paper making process.

  In the case of drainage sludge, a flocculant is mixed, and furthermore, large fluctuations occur due to papermaking in the whole factory, fluctuations in production volume, or in-process washing of production facilities.

  In papermaking sludge generated from the washing process in the pulping process, various materials that cannot be used as fillers and pigments are mixed, such as fluctuations in chip moisture and pulp production conditions, and quality fluctuations occur. Therefore, if all the papermaking sludge is used without selection, the quality of the papermaking filler / pigment is greatly deteriorated, and the quality fluctuation is extremely large and unstable.

That is, the inorganic particles obtained by a conventionally known method are not suitable for use as a filler for papermaking inorganic particles or plastics, and lack quality stability.
JP-A-11-310732 Japanese Examined Patent Publication No. 56-27638 Japanese Patent Laid-Open No. 54-14367 JP 2004-176208 A

  The main problem to be solved by the present invention is that the quality required for inorganic particles can be stably and mass-produced, and the manufacturing cost can be kept low, and the optimum filler for papermaking and the like for practical use. An object of the present invention is to provide a method for producing inorganic particles that can be used as a filler for pigments, plastics, and the like.

The present invention that has solved this problem is as follows.
[Invention of Claim 1]
Deinking floss separated from pulp fibers in the deinking process for producing waste paper pulp,
A method for producing inorganic particles, wherein the main raw material is subjected to a dehydration step, a drying step, a firing step, and a pulverization step, to obtain inorganic particles,
In the drying process of the raw material after the dehydration process, the moisture content is 2 to 20% by mass,
The firing step includes at least a first-stage combustion firing furnace having an inlet at an upper portion and a vertically oriented first-stage combustion firing furnace and a second-stage combustion firing furnace having a temperature in the furnace lower than that of the upper end portion of the first-stage combustion firing furnace. It consists of a two-step firing process.
A method for producing inorganic particles that can be used as a filler or pigment for papermaking.

[Invention of Claim 2]
The particle size of the inorganic particles before the firing step by the first-stage combustion firing furnace is 70% by mass or more from 355 to 2000 μm.
The manufacturing method of the inorganic particle of Claim 1.

[Invention of Claim 3]
Combusted and fired in the first stage firing furnace, unburned content is 5-30%,
Through a firing step of burning and firing in a second-stage combustion firing furnace following the first-stage combustion firing furnace,
The manufacturing method of the inorganic particle of Claim 1 or Claim 2.

[Invention of Claim 4]
The temperature of the second stage combustion firing furnace is lower than the temperature of the upper end of the first stage combustion firing furnace,
And the temperature of the said 2nd stage combustion baking furnace shall be 500-700 degreeC,
The manufacturing method of the inorganic particle of any one of Claims 1-3.

[Invention of Claim 5]
As a drying means in the drying step, at least a pair of rolls for scooping up the raw material, and hot air blowing means for blowing hot air upward are provided.
The manufacturing method of the inorganic particle of any one of Claims 1-4.

  According to the present invention, the quality required for inorganic particles can be stably and mass-produced, and the manufacturing cost can be kept low. The manufacturing method of the inorganic particle which can be provided as can be provided.

Next, an example of an embodiment of the present invention will be described with reference to the drawings.
〔Overview〕
The manufacturing flow of the inorganic particles of this embodiment has a dehydration process, a drying process, a combustion firing process, and a pulverization process, but further includes a deinking floss agglomeration process, a granulation process, a classification process provided between each process, and the like. It may be provided.

  In FIG. 1, the example of a partial structure of the manufacturing equipment flow of the inorganic particle of this form was shown. This equipment is equipped with various sensors, and controls the state of processing objects, equipment, processing speed, and so on.

  Moreover, various flow paths such as a transfer flow path, a supply flow path, a discharge flow path, a circulation flow path, and a return flow path shown in the following specific description can be constituted by, for example, a pipe, a duct, or the like.

  In the present embodiment, the case where the deinking floss S is used as a raw material will be exemplified below, but other papermaking sludge such as papermaking sludge in the papermaking process can be appropriately used with the deinking floss as a main raw material.

〔material〕
In the used paper pulp manufacturing process, in order to continuously produce used paper pulp of stable quality, used paper is selected and selected, and used paper of a certain quality is used.

  For this reason, the types, ratios, and amounts of inorganic substances brought into the used paper pulp manufacturing process are basically constant. Moreover, even when waste paper contains plastics such as vinyl and film, which cause unburned materials to fluctuate in the method of producing inorganic particles, these foreign substances are before the deinking process to obtain deinking floss. Can be removed in stages. Accordingly, the deinking floss is a raw material for producing inorganic particles with extremely stable quality as compared with sludge generated in other processes such as a factory drainage process and a papermaking raw material adjustment process.

  The deinking floss referred to in the present invention refers to what is separated from the pulp fiber in the deinking process for removing ink adhering to the used paper in the used paper processing process for producing the used paper pulp.

[Dehydration process]
For further dehydration of the deinking floss S, known dehydration means can be used as appropriate. In one example of this embodiment, the deinking floss S is dehydrated by separating water from the deinking floss S by a rotary screen 14 serving as a dehydrating unit. In the rotary screen 14, the deinking floss S dehydrated to 95 to 98% of the moisture can be suitably sent to, for example, the screw press 15 and further dehydrated to 40% to 70%.

  As described above, if the deinking floss S is dehydrated in a multi-stage process and abrupt dehydration is avoided, the outflow of the inorganic substance can be suppressed and there is no possibility that the flocs of the deinking floss S will become too hard. In the dehydration treatment, an auxiliary agent for improving the dehydration efficiency such as a flocculant for aggregating the deinking froth S may be added, but it is preferable to use a coagulant that does not contain iron. When iron is contained, it causes a problem of lowering the whiteness of the inorganic particles due to oxidation of the iron.

  The deinking process of the deinking froth S is preferably adjacent to the inorganic particle manufacturing process in the present invention from the viewpoint of production efficiency, but is equipped with a facility adjacent to the waste paper pulp manufacturing process in advance to transport the dehydrated product. It is also possible to do.

[Drying process]
The dehydrated product D obtained by dehydrating the deinking floss S is transported to the constant supply unit 16 by transporting means such as a truck and a belt conveyor, and supplied from the constant supply unit 16 to the drying unit 17.

  The drying means 17 includes a drying container 17b to which a dehydrated product D is supplied, a pair of rolls 17a and 17a that scrapes the supplied dehydrated product D provided at the bottom of the drying container 17b, and the pair of rolls 17a and 17a. Hot air blowing means that blows hot air upward from the middle, mainly. Further, the hot air blowing means is configured such that a feeding flow path 56 is connected to the bottom of the drying container 17 b and hot air is blown into the drying container 17 b through the feeding flow path 56.

  That is, the main drying means 17 loosens the dehydrated product D weakly and finely by a tangible means such as a pair of rolls 17a and 17a, and loosely and loosely by an intangible means such as hot air. Thus, the moisture content of the dehydrated product D having various properties such as large, small, hard and soft can be controlled and the grain size can be stably controlled.

  In particular, when the dehydrated product D supplied into the drying container 17b is dehydrated to a moisture content of 40 to 70% by mass, the temperature of the hot air is preferably 100 to 200 ° C, and is preferably 120 to 180 ° C. Is more preferable, and 130 to 170 ° C. is particularly preferable. When the moisture content of the dehydrated product D is 40 to 60% by mass, it can be sufficiently dried even with hot air at 100 ° C. On the other hand, the temperature of the hot air is preferably 200 ° C. or lower. When the temperature of the hot air exceeds 200 ° C, the drying proceeds faster than the particle alignment of the dehydrated material D having various properties such as large, small, hard, and soft, so the difference in moisture content between the particle surface and the inside It is difficult to make the amount uniform.

  It is preferable to dry the above dehydrated product D so that the moisture content of the dried product K before the firing step is 2 to 20% by mass, and the moisture content of the dried product K is 3 to 15% by mass. It is more preferable to dry it so that the moisture content of the dried product K is 3 to 10% by mass. When the dehydrated product D is dried to a range where the moisture content is less than 2% by mass, a problem of over-burning occurs in the subsequent baking. On the other hand, when the dehydrated product D is dried in a range where the moisture content exceeds 20% by mass, it is difficult to reliably perform subsequent firing.

  The particle size of the dried product K is preferably adjusted so that the particle size of 355 to 2000 μm is 70% by mass or more, and adjusted so that the particle size of 355 to 2000 μm is 75% by mass or more. More preferably, it is particularly preferable to adjust the particle size of 355 to 2000 μm so that it is 80% by mass or more.

  Further, when the dried product K is produced so that the particles having a particle diameter of 355 μm to 2000 μm or more are 70% by mass or more, that is, when the dried product K of small-sized particles is removed, partial over-burning is prevented and firing is performed. It becomes uniform. Therefore, it is useful for practical application in terms of making the quality of the obtained inorganic particles uniform. Furthermore, when the classification is after drying as in the present embodiment, the dried product K of small-diameter particles can be reliably removed, and the processing efficiency is improved.

[Baking process]
The dried material K that has fallen to the bottom in the cyclone 18 is increased in vigor by the exhaust fan H provided in the transfer flow path 58 and in the middle of the transfer flow path 58, and constitutes the first firing stage of the cyclone type. 1 is sent to the combustion firing furnace 21.

  In the first combustion firing furnace 21, the dried material K is swirled and dropped to suppress particle refinement, and in this process, firing is performed to adjust the unburned content.

  Firing in the first combustion firing furnace 21 is preferably performed such that the unburned rate is 5 to 30% by mass, more preferably 8 to 25% by mass, and 10 to 20% by mass. It is particularly preferable to carry out the above. If the unburned rate is less than 5% by mass in the first combustion firing, the particle surface is overfired in the firing, the surface becomes hard, the internal oxygen is insufficient, and the whiteness of the inorganic particles is lowered. On the other hand, if the unburned rate exceeds 30% by mass in the first combustion firing, the problem remains that the unburned portion remains after the second combustion firing that follows, and further to prevent the unburned portion from remaining. There is a problem that the surface of the inorganic particles is hardened by burning and burning until the particle surface is overfired.

  Although the form of the 1st combustion baking furnace 21 is not specifically limited, It is preferable that it is a cyclone type. According to the cyclone type, as described above, the unburned rate can be adjusted uniformly and reliably by suppressing the refinement of the particles.

  The firing temperature range is preferably in the range of 510 to 750 ° C., and the first stage combustion firing is performed at a temperature of the upper end of the first combustion firing furnace 21 of 510 to 750 ° C. and the temperature in the second combustion firing furnace 25. Is preferably 500 to 700 ° C. lower than the temperature at the upper end of the first combustion firing furnace 21, the temperature at the upper end of the first combustion firing furnace 21 is set to 550 to 730 ° C., and the temperature in the second combustion firing furnace 25 is Is more preferably 510-680 ° C., which is lower than the temperature at the upper end of the first combustion firing furnace 21, the temperature at the upper end of the first combustion firing furnace 21 is 580-700 ° C., and the temperature in the second combustion firing furnace is It is particularly preferable to set the temperature to 550 to 660 ° C., which is lower than the temperature at the upper end of the firing furnace 21. When the temperature of the upper end of the first combustion firing furnace 21 is 600 to 680 ° C., and the temperature in the second combustion firing furnace 25 is 580 to 650 ° C. lower than the temperature of the upper end of the first combustion firing furnace 21, paper is manufactured. The fine particles for use are suitable for use as recycled fillers or pigments.

  By making the temperature in the second combustion firing furnace 25 lower by 10 to 50 ° C. than the temperature at the upper end of the first combustion firing furnace 21, the unburned material is burned while preventing overheating of the surface of the fine particles for papermaking. Can do.

  The fired product obtained in the first combustion firing furnace 21 is sent to the second combustion firing furnace 25, which is the second firing stage, and is fired and fired. As the second combustion firing furnace 25, a known apparatus such as a rotary kiln furnace, a fluidized bed furnace, a stalker furnace, a cyclone furnace, a semi-dry distillation / negative pressure combustion furnace, etc. can be used. A rotary kiln furnace is preferred as a measure that can be uniformly burned with stirring without applying excessive physical pressure in the environment.

[Crushing process]
In the method for producing inorganic particles based on the present invention, if necessary, further known dispersion and pulverization steps are provided, and finely granulated to a necessary particle size as appropriate, as a pigment for coating and a filler for internal addition. Can be used.

  In one example, the fine particles obtained after firing are pulverized using a dry pulverizer such as a jet mill or a high-speed rotary mill, or a wet pulverizer such as an attritor, a sand grinder, or a ball mill. For use in fillers and pigments, it is necessary to make the particle size uniform and fine, but it is optimal for fillers, pigments, etc. using fine inorganic particles obtained by the production method according to the present invention. As for the fine particle diameter and pigment diameter, the fine particles of this embodiment have primary particles with an average particle diameter of 0.01 to 0.1 μm, and secondary particles in which the primary particles are aggregated have an average particle diameter of 0.1 to 10 μm. Is preferred.

[Attached process]
In this production facility, in order to further stabilize the quality, it is preferable to classify the inorganic particles in order to make the particle size uniform in each step, and the quality can be improved by feeding back coarse particles and fine particles to the previous step. Can be stabilized.

  In addition, it is preferable to granulate the deinked floss that has been subjected to dehydration in the previous stage of the drying process, and it is more preferable to classify the granulated product to have a uniform particle size. It is possible to further stabilize the quality by feeding back the granulated particles to the previous process. In granulation, a known granulation facility can be used, and facilities such as a rotary type, a stirring type and an extrusion type are suitable.

  In this production facility, it is preferable to remove foreign matters other than fine particles. For example, sand, plastic foreign matters, metals, etc. are removed with a pulper, a screen, a cleaner, etc. before reaching the deinking step of the used paper pulp manufacturing process. Is preferable in terms of removal efficiency. In particular, iron contamination is a substance that reduces the whiteness of fine particles due to oxidation, so it is recommended to avoid iron contamination and selectively remove it. Design or lining each process with materials other than iron, It is preferable to prevent iron from being mixed into the system due to abrasion or the like, and to further remove iron selectively by installing a high magnetic material such as a magnet in the drying / classifying equipment.

  Furthermore, the inorganic particle aggregate obtained by the method for producing inorganic particles according to the present invention has a ratio of calcium, silica, and aluminum of 30 to 82: 9 to 35: in terms of oxide in elemental analysis of fine particles by an X-ray microanalyzer. It is preferable to contain by the mass ratio of 9-35, More preferably, it is the mass ratio of 40-82: 9-30: 9-30, More preferably, it is the ratio of 60-82: 9-20: 9-20. .

  By including calcium, silica, and aluminum in a mass ratio of 30 to 82: 9 to 35: 9 to 35 in terms of oxides, the specific gravity is light and excessive aqueous solution absorption can be suppressed, so that the dehydrating ability in the dehydration process can be reduced. It is good, and not only the moisture adjustment in the drying process is easy, but also the ratio of unburned substances in the firing process and the possibility of excessive hardness due to sintering can be reduced.

  As a method for adjusting the ratio of the present invention in the firing process, the main point is to adjust the raw material composition in the deinking floss, but in the drying process and the firing process, the origin of the coating floss and the adjustment process are clear. It is also possible to adjust by means of containing floss in the process by spraying or the like, or means of containing incinerator scrubber lime.

  For example, using deinked floss as the main raw material, neutral papermaking wastewater sludge and wastewater sludge from the coated paper manufacturing process are used to adjust calcium in the inorganic particle aggregate, and opacity is used to adjust silica. Newspaper manufacturing wastewater sludge, which is added in large quantities as an improver, papermaking wastewater sludge that uses sulfuric acid bands such as acidic papermaking to adjust aluminum, and wastewater in the high quality papermaking process that often uses talc Sludge can be used.

The Example and comparative example of this invention are shown.
When the quality of the obtained inorganic particles was examined by changing various factors, the results shown in Table 1 were obtained.
The quality was evaluated as follows.
(Productivity evaluation): Evaluate the dehydration efficiency of raw materials, productivity, and power required for pulverization in four stages. ◎ is the most efficient condition, ◯ is the best, water efficiency, productivity, pulverization The problem was found as △, and the actual operation difficult as x.
(Wire wear degree): Measured at a plastic wire wear degree (manufactured by Nippon Filcon, 3 hours) and a slurry concentration of 2% by weight.
(Quality stability): The degree of variation is measured for each item of the whiteness, particle size, and production amount at a fixed time interval of the fine particles obtained by a predetermined method, and ranked in the order of small variation. ◎ up to the rank, ◯ from the 6th to 10th, △ from the 11th to the 13th, and x below.
(Appearance): The color of the inorganic particles was visually judged and classified into white and gray.
(Mass ratio): A mass ratio exceeding 2000 μm was assumed with a 4.7 mesh sieve, and a mass ratio less than 355 μm was assumed with a 42 mesh sieve.
(Particle diameter): Measured with an X-ray microanalyzer.

  The present invention is applicable as a method for producing inorganic particles by firing papermaking sludge.

It is a manufacturing equipment flowchart of the filler for paper manufacture.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 16 ... Constant quantity feeder, 17 ... Drying means, 21 ... Firing furnace, 23 ... Heat exchanger, 25 ... Combustion calcination furnace, D ... Dehydrated matter, F ... Ground material, J ... Firing material, K ... Dry material, S ... Deinking floss.

Claims (4)

  A method for producing inorganic particles having a deinking floss as a main raw material, a dehydration step, a drying step, a baking step, and a pulverization step, wherein the moisture content of the raw material before the baking step is 2 to 20% by mass A method for producing inorganic particles.   The method for producing inorganic particles according to claim 1, wherein the particle diameter of the inorganic particles before the baking step is 70 mass% or more of particles having a particle size of 355 to 2000 µm.   A method for producing inorganic particles having a deinking floss as a main raw material, a dehydration step, a drying step, a firing step, and a pulverization step, wherein the firing step has at least two stages of firing steps before reaching the final firing step. In this step, the method for producing inorganic particles is characterized by passing through a firing step for reducing the unburned content to 5 to 30%.   The method for producing inorganic particles according to claim 3, wherein in the firing step for reducing unburned content according to claim 3 to 5 to 30%, the firing temperature is 500 to 750 ° C.

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