JP2008127704A - Method for producing recycled particle aggregate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably produce a recycled particle aggregate having necessary properties especially as a papermaking filler or a coating pigment. <P>SOLUTION: The method for producing the recycled particle aggregate includes using a deinked floss as a main raw material separated from a pulp fiber in the deinking process of wastepaper treatment facilities for producing a wastepaper pulp, and obtaining the recycled particle aggregate from the main raw material through a dehydration, a drying, a burning and a grinding operations. The drying and the burning operations have at least two stages of burning operations with a previous first combustion furnace 14 for carrying out the drying and burning in series of the raw material after the dehydration and a subsequent second combustion furnace 32 for re-burning the deinked floss burned in the first combustion furnace 14 and then grinding the re-burned product to obtain the recycled particle aggregate. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a regenerated particle aggregate that obtains a regenerated particle aggregate using deinked floss as a main raw material.

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 incinerated ash (inorganic substances) remains even after combustion, and there is a limit to volume reduction. Therefore, efforts have been made to use this incinerated ash as an auxiliary agent for cement raw materials and as a soil conditioner. However, the amount of incineration ash used as an auxiliary to these cement raw materials and soil conditioners is very small, and in the end, most of the incineration ash is landfilled.
Therefore, not only recovering as thermal energy by incineration, but also reusing inorganic substances in paper sludge as paper fillers, pigments, plastic fillers, etc. is related to environmental problems as well as improving the waste paper utilization rate in the paper industry. This is an important improvement issue.
However, the incineration ash of papermaking sludge contains organic matter that remains without being burned as carbon, so the whiteness is low, or the sintering of inorganic matter proceeds, the particle size is uneven and large, and as it is It is not suitable for use as a filler for papermaking, a pigment for coating, or a filler for plastics.

Therefore, Patent Document 1 discloses a method of using after incineration ash is reburned to improve 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 filler for papermaking or as a pigment for coating. It was also found that when the re-combustion temperature was set to over 900 ° C., the incineration ash (inorganic material) was sintered and melted and became extremely hard. In addition, when reincinerated ash is used as a filler, this reincinerated ash has very hard properties, so the progress of wear of the papermaking wire is fast and the life of the papermaking wire is very short. It wasn't. In addition, when this re-incinerated ash is used as a coating pigment, the re-incinerated ash is very hard, which causes damage to the coating equipment due to wear. The problem of poor smoothness arises.
In this regard, it may be possible to pulverize the re-incinerated ash and reduce its particle size to reduce wear and improve smoothness. However, when used as an internal filler, the yield during papermaking is low. Since the incinerated ash itself is extremely hard, the energy cost for pulverization becomes extremely high.

In Patent Document 2, papermaking sludge is supplied into a reactor into which an oxygen-containing gas has been injected, and is oxidized at 250 to 300 ° C. under a heating and pressurization of about 3000 psig for 0.25 to 5 hours. Has been proposed to recycle as a pigment for papermaking.
However, since this method is based on wet air oxidation treatment with the paper sludge remaining in the liquid phase, organic matter removal is not sufficient, and the resulting pigment has low whiteness and uneven particle size, making papermaking This is unsuitable for use as a filler or pigment, 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 in an internal heat kiln furnace 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. In addition, by smoldering, the volatile matter is removed and the organic matter is difficult to burn (oxidize), so-called “residual carbon”, which makes it difficult to burn in the post-process and has a long combustion time due to the residual carbon. It is difficult to obtain high whiteness unless it is applied, and the generated clay is also large due to irregular particle sizes. Also, contamination from carbon and sulfur oxides from heavy oil burners used in internal heat kilns occurs. There is a problem that it cannot be used as a papermaking pigment.

  As disclosed in Patent Document 4, a method is known in which wastewater treatment sludge is continuously dried, carbonized, and burned in a rotary kiln furnace. Since the wastewater treatment sludge used in this method is composed of sludge having various sources, there is a problem that the resulting granulated / molded material also fluctuates due to fluctuations in the source and amount generated. In this patent document, granulation and shaping prior to combustion are considered to be performed for uniform combustion, but the solid content concentration described in the embodiment is 40 to 60% (in other words, If the moisture content is 60-40%), the sludge particles are forced by the rotation of the kiln regardless of the dry or carbonized state of the sludge. The process will continue. Therefore, if the drying is insufficient, a large amount of unburned matter remains inside the particles, resulting in incomplete combustion and a decrease in whiteness.On the other hand, overdrying results in complete combustion but overburning. As a result, the hardness of the obtained regenerated particle aggregate increases, and when this regenerated particle aggregate is used, there is a problem that wire wear in a paper machine and cutter blade wear when cutting paper are likely to occur.

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 sedimentation 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 papermaking sludges, for example, those that flow out through the wire in the papermaking process are mixed with a paper strength agent and the quality varies due to changes in the papermaking product in the papermaking process. In addition, the papermaking sludge collected from the wastewater treatment process is mixed with a flocculant, and a large fluctuation occurs due to papermaking products in the whole factory, fluctuations in production volume, or in-process washing of production facilities.
In the papermaking sludge generated from the washing process in the pulping process, fluctuations occur in chip moisture and pulp production conditions, and various fillers and substances that cannot be made into pigments are mixed, resulting in quality fluctuations. Therefore, if all the papermaking sludge is used without selection, the quality as a papermaking filler or coating pigment is greatly reduced, and the quality fluctuation is extremely large and unstable.
That is, the regenerated particles obtained by a conventionally known method are not suitable for use as fillers for papermaking, pigments for coating, plastics, etc., and lack quality stability.
JP-A-11-310732 Japanese Examined Patent Publication No. 56-27638 Japanese Patent Laid-Open No. 54-14367 Registration No. 3812900

  A main problem to be solved by the present invention is to stably produce a regenerated particle aggregate having characteristics necessary particularly as a filler for papermaking or a pigment for coating.

The present invention that has solved this problem is as follows.
[Invention of Claim 1]
Using the deinked floss separated from the pulp fiber in the deinking process of the used paper processing equipment for manufacturing used paper pulp, the main material is subjected to dehydration, drying, combustion and pulverization operations to obtain recycled particle aggregates. A method for producing an aggregate, comprising:
The drying and combustion operation re-combusts the first combustion furnace that performs a series of drying and combustion of the material after dehydration, and the deinking floss burned in the first combustion furnace, and the second combustion after the second. Having a furnace, having at least two stages of drying and burning operations;
A method for producing a regenerated particle aggregate, which is then pulverized to obtain a regenerated particle aggregate.

[Invention of Claim 2]
The first combustion furnace is an internal heat kiln furnace in which a main body is placed horizontally and rotates around a central axis, and a moisture content of the raw material after dehydration to be input into the internal heat kiln furnace is less than 50%. A method for producing regenerated particle aggregates.

[Invention of Claim 3]
The method for producing a regenerated particle aggregate according to claim 1 or 2, wherein hot air of 500 ° C to 650 ° C is blown so that the oxygen concentration in the internal heat kiln furnace is 0.2 to 20%.

[Invention of Claim 4]
The second combustion furnace is an external heat kiln furnace in which the main body is placed horizontally and rotates around a central axis. In the external heat kiln furnace, the combustion product from the internal heat kiln furnace is at a temperature of 550 ° C. to 750 ° C. The manufacturing method of the regenerated particle aggregate of any one of Claims 1-3 which burn.

  According to the present invention, it is possible to stably produce a regenerated particle agglomerate having characteristics necessary as a filler for papermaking or a pigment for coating.

Next, prior to the description of the embodiments of the present invention, the positioning of the present invention will be described.
For example, when papermaking sludge is combusted, (1) in the invention described in Japanese Patent Application Laid-Open No. 2003-119695, the dried product is poor in that oxygen is not substantially present so that the oxygen concentration in the furnace is 0.1% by volume or less. In an oxygen state, specifically, drying and carbonization are performed by an indirect heating furnace (external heat combustion furnace). Next, a method has been proposed in which carbon derived from an organic substance contained in a carbide is oxidized and decarbonized, specifically, a whitening treatment is performed using an indirect heating furnace. The invention also teaches the use of an internal heat rotary kiln furnace for the latter whitening treatment.
On the other hand, the present applicant also teaches (2) JP 2002-275785 to use a rotary kiln furnace for recombustion after carbonization.
Further, the present applicant, as (3) Patent No. 3808852, “Deinking sludge is used as raw material sludge and dried, and the dried deinking sludge is removed from the upper part of the cyclone combustion furnace. A primary combustion step of obtaining a primary combustion product containing unburned content by being supplied to the inside and swirling and descending, and a primary combustion product communicating with the cyclone-type combustion furnace and containing unburned content from the lower end thereof And a secondary combustion step of burning until a predetermined whiteness is obtained using the heat of combustion of the primary combustion step while promoting contact with oxygen by mechanical stirring. A method for producing a white pigment or a white filler from sludge "was proposed.
In addition, in (4) Japanese Patent Application Laid-Open No. 2004-176208, when the filler is produced from “the wastewater treatment sludge in the coated paper manufacturing process”, the formed sludge is “dried, carbonized and burned in one rotary kiln furnace”. Propose that.

The above (1), (2) and (4) do not use deinking floss separated from pulp fibers in the deinking process of the used paper processing equipment for producing used paper pulp, but mainly use the above-mentioned papermaking sludge. It is a raw material. The obtained regenerated particles are considered to be different from the regenerated particles “aggregates” as in the present invention.
On the other hand, according to the method (3), regenerated particle aggregates similar to those obtained by the present invention can be obtained. However, in this method, a cyclone fluidized combustion furnace is used to burn dry matter, followed by secondary combustion.
However, in this case, drying and combustion are performed by separate apparatuses, which not only increases the equipment cost, but is considered to be derived from the form of the cyclonic fluidized combustion furnace itself. Micron raw material and air are supplied from the supply port as a swirling flow and burned while being effectively mixed with air by the swirling action of the air, so that the fine particles contained in the raw material are discharged out of the system together with the exhaust gas, and the product yield is increased. Decreased problem, deinking floss that is the main raw material has a short combustion time (heating time), and unburned matter is likely to occur, and the quality (particularly shape) of the final combustion product is not constant It has been found that the whiteness of the combustion product may also vary.

Therefore, the present invention uses a first combustion furnace in which the raw material after dehydration is dried and burned in series and the combustion time (residence time) in the primary combustion furnace exceeds 30 minutes, preferably the main body is placed horizontally. The combustion time (residence time) in which the raw material after dehydration is dried and burned by an internal heat (direct heating) kiln furnace that rotates around the central axis in the above, and then the combustion product obtained from the first combustion furnace is burned again. ) Using a second combustion furnace of 10 minutes or more, preferably an externally heated (indirect heating) kiln furnace in which the main body is placed horizontally and rotates around the central axis, particularly an externally heated electric furnace whose combustion temperature can be easily adjusted, The method of burning is adopted.
Further, in this drawing, the first combustion furnace is selected as an internal heat kiln furnace, and the second combustion furnace is selected as an external heat kiln furnace. However, the first combustion furnace is preferably performed with internal heat, A known combustion furnace can be used as long as the second combustion furnace is an at least two-stage combustion furnace that performs external heat. Further, as described above, the internal combustion furnace in which the combustion time (residence time) in the primary combustion furnace is 30 minutes or more, and the external heat combustion furnace in which the combustion time (residence time) in the second combustion furnace exceeds 10 minutes. If so, a known combustion method such as a fluidized bed incinerator as an internal heat combustion furnace and an indirect heating type combustion furnace using heavy oil as a heat source as an external heat combustion furnace is employed.
According to the internal heat kiln furnace suitably used as the first combustion furnace, drying and combustion can be performed in one furnace, and the drying and combustion proceed slowly and stably from the supply port to the discharge port. And the pulverization of the combustion product is suppressed. Moreover, when combusted in an external heat kiln furnace that is suitably used as the second combustion furnace, the combusted material can be discharged from the end of the combusted material with a constant residence time through the discharge port of the other end, and further uniformed by the external heat. Since the heat is applied, the combustion becomes uniform and the combustion does not vary. Furthermore, the combustion product is gently agitated by friction caused by the rotation of the inner wall of the kiln furnace, so that it is difficult to produce fine powder. As a result, the quality and shape of the final combustion product become stable.
As described above, the drying and combustion operations are performed in the first combustion furnace and the second combustion furnace, preferably in the internal heat kiln furnace and the external heat kiln furnace, using at least two stages of combustion furnaces. By carrying out, uniform and stable regenerated particle aggregates can be obtained.
The internal heat or external heat kiln furnace used as a suitable combustion furnace can lift and agitate the combusted material without slipping by making the internal refractory into a hexagonal or octagonal shape instead of a circumferential shape. By not providing a lifter for stirring a product, generation of dust can be suppressed, dust can be prevented from being mixed into exhaust gas, and product yield can be improved.

Here, the selection of the combustion furnace most focused on when the present inventors obtain a suitable regenerated particle aggregate will be described.
Conventionally used combustion furnaces can be broadly divided into four types: stalker furnaces (fixed bed), fluidized bed furnaces, cyclone furnaces, and kiln furnaces. After repeated examination of the production of aggregates,
・ For the stalker furnace (fixed bed), it is difficult to adjust the degree of combustion of the deinking floss, the combustion products are not uniform, and combustion of the deinked floss with a lot of ash causes dust to fall from the clearance between the grate. Therefore it is not suitable. Since air is blown up and burned under the combustion material through the grate, calcium carbonate or the like becomes fly ash and is sent to the exhaust gas facility together with the exhaust gas.
-As for the fluidized bed furnace, since a particulate fluid medium such as silica sand is used as the fluid medium in the furnace, there is a problem that the silica sand is mixed into the recycled filler and the quality is deteriorated. Uniform stirring is not possible. After the cinnabar sand is mixed in a fluidized bed and combusted, the cinnabar sand and the burned material are separated, and the cinnabar sand is returned to the combustion furnace, and only the burned material is taken out. Since combustion is performed in a floating state with dredged sand, it is difficult to adjust the degree of combustion, resulting in variations in quality. Since the combustion furnace is burned while passing through the stoker (stepped shape) of the combustion furnace with a predetermined width, the ash is not sufficiently stirred and the combustion varies in the width direction.
In addition, the combustibles are pulverized by friction and collision with high hardness silica sand and are discharged as fly ash, which decreases the yield.
・ As for the cyclone furnace, the fixed carbon in the combusted material cannot be burned sufficiently because it passes through the furnace in an instant, leading to a decrease in whiteness.Further, fine particles are not separated by the cyclone and are combined with exhaust gas. Since the process goes to the exhaust gas treatment process, the yield decreases.
As a result of intensive studies on the above problems, the combustion furnace is selected as the most suitable combustion means for combustion in the kiln furnace. Further, the first combustion furnace is the internal heat kiln, and the subsequent combustion furnace for the following reasons. It has been found that the second combustion furnace is preferably an external heat kiln.
Since the external heat kiln furnace has a configuration in which heating equipment is provided outside the kiln furnace, the structure of the kiln furnace becomes complicated, and a large amount of heat source is required because the combustion products are dried and burned indirectly. When the external heat kiln furnace is used as the first combustion furnace for the drying and combustion treatment of the raw material having a high water content after dehydration according to the present invention, the drying / combustion efficiency is lowered and the productivity is poor. The temperature control becomes difficult and requires a large energy cost, and the cost effectiveness is extremely low.
In addition, when the internal heat kiln furnace is used as a secondary combustion furnace, a large amount of diluted air is required to adjust the furnace temperature when the remaining carbon is burned. Since it is difficult to uniformly transmit heat into the internal heat kiln furnace, and furthermore, it is difficult to suppress fluctuations in the furnace temperature, there is a problem in that overburning of combustion products and uneven combustion are likely to occur.
In addition, heavy oil combustion residual carbon and sulfur oxides from heavy oil burners used for normal heating cause contamination, resulting in a decrease in whiteness and variability at the product stage, making it difficult to equalize the quality of the resulting combustion products. Problems arise.
The inventors have completed the present invention as a result of finding out the above problems and intensively studying means for solving the problems.

Next, an example of an embodiment of the present invention will be described with reference to the drawings.
〔Overview〕
The production facility flow of the regenerated particle aggregate of this embodiment has a dehydration process, a drying / combustion process, and a pulverization process. In addition, a deinking floss agglomeration process or granulation process and a classification process are provided between the processes. May be.
FIG. 1 shows a partial configuration example (an example of equipment including a drying / combustion process and a combustion process) of a production facility flow of regenerated particle aggregates. This equipment is equipped with various sensors, and controls the state of combustibles, equipment, and processing speed.
The deinking floss separated from the pulp fiber in the deinking process for producing waste paper pulp (not shown) is dehydrated by a dehydration facility (not shown) through various operations. The material after dehydration preferably has a moisture content of less than 50%, particularly 25 to 45%.
The material 10 after such dehydration is desirably pulverized to a particle size of 40 mm or less by a pulverizer (or pulverizer). The raw material 10 is cut out from the storage tank 12 and charged by a charging machine 15 from one side of the first combustion furnace 14. An exhaust gas chamber 16 is provided on one side of the first combustion furnace 14, and an exhaust chamber 18 is provided on the other side. Hot air is blown from the other side of the first combustion furnace 14 through the discharge chamber 18, charged from the one side, and sequentially transferred to the other side as the first combustion furnace 14 rotates. It is designed to dry and burn.
Here, it is desirable that the hot air blown into the first combustion furnace 14 has an oxygen concentration of 0.2 to 20%. As temperature, 500 to 650 degreeC is desirable. Hot air is blown from a hot air generating furnace 20 provided with a burner 20A.
From the exhaust gas chamber 16, exhaust gas subjected to drying and combustion is sent into the recombustion chamber 22. The fine powder of the combustion material contained in the exhaust gas is discharged from the lower part of the exhaust gas chamber 16 and reused. The exhaust gas is recombusted by the burner in the recombustion chamber 22, precooled by the precooler 24, passed through the heat exchanger 26, and discharged from the chimney 30 by the induction fan 28. Here, after raising the temperature of the outside air, the heat exchanger 26 is sent to the hot air generating furnace 20 and used for the hot air blown from the first combustion furnace 14 to recover the heat of the exhaust gas from the exhaust gas chamber 16. It is like that. The treatment of exhaust gas is effective for removing harmful substances contained in the exhaust gas.
Combustion products that have been dried and burned in the first combustion furnace 14 are charged into the second combustion furnace 32. The particle size of the combusted material to be charged is preferably 20 mm or less. As a heat source in the second combustion furnace 32, it is preferable to use an electric adjustment that allows easy temperature control in the second combustion furnace 32 and easy temperature control in the longitudinal direction. Therefore, the first combustion is indirectly performed by an electric heater. It is desirable that the second combustion furnace 32 be of an external heating type in which the combustion product obtained from the furnace is burned again.
In the second combustion furnace 32, it is desirable to burn so that the oxygen concentration is 5 to 20%. As temperature, 550 degreeC-750 degreeC are desirable. Further, the residence time in the second combustion furnace is preferably 10 minutes to 60 minutes in order to completely burn the remaining carbon.
The regenerated particle aggregate after the completion of combustion is cooled by a cooler 34, and then sorted by a particle size sorter 36 such as a vibration sieve, and adjusted to a target particle size in a pulverization process using a wet pulverizer or the like. The burned product is temporarily stored in the combustion product silo 38 and is sent to the application destination of the pigment and filler.
In addition, although the case where deinking floss was used as a raw material was illustrated, even if it is a combustion thing which used as a raw material what mixed other papermaking sludges, such as papermaking sludge in a papermaking process, with deinking floss as a main raw material Good.

Although the outline has been described above, details and application examples thereof will be described below.
〔material〕
In the used paper pulp manufacturing process, for the purpose of continuously producing used paper pulp with stable quality, used paper is selected and selected and used with a certain quality.
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 plastics such as vinyl and film, which cause unburned substances in the recycled particle agglomerate production method, are contained in the waste paper, these foreign substances are used in the deinking process to obtain deinking floss. It can be removed at the previous stage. Accordingly, the deinking floss is a raw material for producing regenerated particle aggregates having extremely stable quality as compared with papermaking 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, known dehydration means can be used as appropriate. In one example of the present embodiment, the deinking floss is dehydrated by separating water from the deinking floss by a screen serving as a dewatering unit. In the screen, it is preferable that the deinking floss dehydrated to 90% to 97% is sent to, for example, a screw press and further dehydrated to 50% or less.
If the moisture content exceeds 50%, the temperature of the drying / combustion process in the first combustion furnace is lowered, energy loss due to heating increases, and uneven combustion of the raw material is likely to occur, thereby promoting uniform combustion. I want to. Further, there are problems that the moisture in the exhaust gas to be discharged increases, the recombustion treatment efficiency is reduced in dioxin countermeasures, and the load on the exhaust gas treatment facility is increased. In addition, although lowering the moisture content of the raw material facilitates uniform combustion, dehydrating the moisture content of the raw material to less than 25% increases the size of the dehydration equipment and significantly increases the energy of dehydration treatment. Have the problem.
As described above, if the deinking floss 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 deinking floss floc becomes too hard. In the dehydration treatment, an auxiliary agent for improving the dehydration efficiency such as an aggregating agent for aggregating the deinking floss may be added, but it is preferable to use an aggregating agent that does not contain iron. When iron is contained, it causes a problem of lowering the whiteness of the regenerated particle aggregate due to oxidation of iron.
The deinking process of deinking floss is preferably adjacent to the production process of the regenerated particle aggregate in the present invention in terms of production efficiency. It can also be transported, and it is transported to a fixed amount feeder by a transport means such as a truck or a belt conveyor, and supplied to the drying / combustion process from this constant amount feeder.
In the operation of supplying the raw material 10 after dehydration to the first combustion furnace, it is desirable that the average particle size is preferably adjusted to a particle size of 40 mm or less by a pulverizer (or a pulverizer), more preferably the average particle size. It is preferable to adjust so that the average particle diameter is in the range of 3 to 30 mm, and more preferably in the range of 5 to 25 mm, and it is preferably pulverized so that the ratio of the particle diameter is 50 mm or less is 70% by weight or more. Things are more preferable. In order to achieve a combustion treatment that does not cause a heat change of the calcium carbonate contained in the deinking floss, it is preferable that the particle diameter of the raw material is uniform. However, if the average particle diameter is less than 3 mm, overcombustion tends to occur. This is because an average particle size exceeding 50 has a problem that it is difficult to uniformly burn the raw material core.
In the present invention, the ratio between the average particle size and the particle size was measured using a sample solution sufficiently dispersed by a stirring type disperser.
The particle diameter in each combustion stroke was measured with a metal plate sieve based on JIS Z8801-2: 2000.

[First combustion process] (Drying and combustion process)
The raw material 10 is cut out from the storage tank 12 and supplied to the first combustion furnace. The first combustion furnace has an internal heat kiln furnace system in which a main body is placed horizontally and rotates around a central axis, and is charged from one side of the internal heat kiln furnace 14 by a charging machine 15. The internal heat kiln furnace heating means feeds hot air generated in the hot air generation furnace from the discharge port side of the internal heat kiln furnace so as to counter-flow with the flow of the dehydrated product. An exhaust gas chamber 16 is provided on one side of the internal heat kiln furnace 14, and an exhaust chamber 18 is provided on the other side. Hot air is blown from the other side of the internal heat kiln furnace 14 through the discharge chamber 18, charged from the one side, and sequentially transferred to the other side as the internal heat kiln furnace 14 rotates. It is designed to dry and burn.
That is, in this drying / combustion process, the dehydrated product is dried and burned by a tangible means such as an internal heat kiln furnace in which the main body is placed horizontally and rotates around the central axis, thereby reaching the discharge port from the supply port. Until then, drying and combustion of organic components can be performed gently, pulverization of the combusted matter can be suppressed, and the degree of combustion and particle size of the dehydrated product having various properties such as hard and soft can be controlled stably. Further, the drying can be divided into separate steps and a blow-up type dryer can be inserted.
Here, the hot air blown into the internal heat kiln furnace 14 preferably has an oxygen concentration of 0.2 to 20%, more preferably 1 to 15%, and most preferably 5 to 12%.
Since the oxygen concentration is consumed by the combustion (oxidation) of the raw material, the oxygen concentration varies depending on the state of combustion. If the oxygen concentration is less than 0.2%, it is difficult to achieve sufficient combustion. Oxygen in the combustion furnace is consumed due to the combustion of raw materials and the like, and the oxygen concentration decreases.However, the oxygen concentration is reduced by blowing or exhausting oxygen-containing gas such as air by a hot air generator for combustion. Further, the temperature in the combustion furnace can be finely adjusted by blowing or exhausting the oxygen-containing gas, and the raw material can be burned uniformly without unevenness.
As temperature of a 1st combustion furnace, 500 to 650 degreeC, More preferably, 510 to 620 degreeC, Especially preferably, 530 to 600 degreeC is desirable. In the first combustion furnace, it is preferable to combust at a combustion temperature range of 500 ° C. to 650 ° C. for the purpose of gradually burning easily combustible organic substances and suppressing generation of residual carbon that is difficult to burn, If the temperature is less than 650 ° C., the combustion of the organic matter is insufficient. If the temperature exceeds 650 ° C., overcombustion occurs, and calcium oxide is easily generated due to decomposition of calcium carbonate. Further, when the temperature of the hot air exceeds 650 ° C., the drying and combustion progress locally faster than the particle alignment of the burned material having various properties such as hard and soft, so that the unburned particles on the particle surface and inside are not burned. It becomes difficult to make the difference in rate small and uniform.
Hot air is blown from a hot air generating furnace 20 provided with a burner 20A.
From the exhaust gas chamber 16, exhaust gas subjected to drying and combustion is sent into the recombustion chamber 22. The fine powder is discharged from the lower part of the exhaust gas chamber 16 and is mixed with the raw material and reused.
The exhaust gas is recombusted by the burner in the recombustion chamber 22, precooled by the precooler 24, passed through the heat exchanger 26, and discharged from the chimney 30 by the induction fan 28. Here, after raising the temperature of the outside air, the heat exchanger 26 is sent to the hot air generating furnace 20 and is used for hot air blown from the internal heat kiln furnace 14 to recover the heat of the exhaust gas from the exhaust gas chamber 16. It is like that.
The first combustion furnace preferably burns with a residence time of 30 to 90 minutes under the above conditions in order to slowly burn the easily combusted organic substances contained in the deinking floss and suppress the formation of residual carbon. Is preferred. More preferably, 40 minutes to 80 minutes is preferable in terms of combustion of organic matter and production efficiency. Most preferably, a range of 50 minutes to 70 minutes is preferred in order to ensure constant quality. If the combustion time is less than 30 minutes, sufficient combustion is not performed and the proportion of remaining carbon increases. When the burning time exceeds 90 minutes, thermal decomposition of calcium carbonate occurs due to overburning of the raw material, and the resulting regenerated particle aggregate becomes extremely hard.
In particular, it is preferable to dry and burn the unburned rate of the combustion product supplied in the second combustion step of the next step to 2 to 20% by mass, more preferably the unburned rate is set to 2 to 15% by mass. Preferably, the unburned rate is 2 to 10% by mass.
By setting the unburned rate to 2 to 20% by mass, the combustion in the second combustion step can be efficiently performed in a short time, and the hardness is low and the whiteness is 80 by stable heating in the external heating furnace. %, At least 70% or more of high whiteness combustion products can be obtained. If the unburned material is less than 2% by mass, the energy cost in the first primary combustion furnace is high, and the hardness of the combustion product may be relatively high. In some cases, the quality may be degraded.

[Second combustion process]
Combustion products that have undergone drying and combustion treatment in the internal heat kiln furnace 14 are loaded into an external heat kiln furnace 32 that corresponds to a second combustion furnace having an external heat jacket 31 that rotates horizontally about the central axis through a transfer channel. Entered.
In this combustion furnace, the combustion product is gently stirred by friction caused by rotation of the inner wall of the kiln furnace while being heated by external heat, thereby suppressing particle refinement and further burning the unburned matter more uniformly.
In the combustion in the second combustion furnace, the residual organic matter that could not be combusted in the first combustion furnace, such as residual carbon, is burned, so that the particle diameter is adjusted to be smaller than the particle diameter of the raw material supplied in the first combustion furnace. It is preferable to use a combustion product. The particle size of the burned product after the drying / combustion step is preferably adjusted so that the average particle size is 5 to 30 mm, more preferably adjusted so that the average particle size is 5 to 18 mm. The average particle diameter is particularly preferably adjusted to 8 to 15 mm.
If the average particle diameter at the inlet of the second combustion furnace is less than 5 mm, there is a risk of overcombustion, and if the average particle diameter exceeds 30 mm, it is difficult to burn the remaining carbon and combustion does not proceed to the core. This causes a problem that the whiteness of the regenerated particle aggregate is reduced. In order to ensure stable production in the second combustion furnace, it is preferable to adjust the particle size so that the combustion product having an average particle size of 5 to 30 mm is 70% or more. Therefore, it is beneficial to the possibility of practical use in terms of making the quality of the regenerated particle aggregate obtained uniform. Furthermore, when the classification is performed after drying as in this embodiment, the combustion product of small-diameter particles can be surely removed, and the processing efficiency is improved.
As an external heat source in the external heat kiln furnace 32, an electric heating type electric furnace in which temperature control in the external heat kiln furnace 32 is easy and temperature control in the longitudinal direction is easy is preferable. A kiln furnace 32 is desirable.
By using electricity for external heat, the temperature can be finely adjusted and the internal temperature can be controlled uniformly, and the control of the degree of burning of dehydrated products with various properties, such as hard and soft, and stable particle alignment are possible. It can be carried out.
Furthermore, the electric furnace can be provided with a temperature gradient arbitrarily by providing a plurality of electric heaters in the flow direction of the furnace, and can maintain the temperature of the combustion product for a certain period of time. Residual organic content in the combustion product that has passed through one combustion furnace, especially residual carbon, can be brought to zero as much as possible without causing decomposition of calcium carbonate in the second combustion furnace. A whiteness regenerated particle aggregate can be obtained.
In the external heat kiln furnace 32, it is desirable that the oxygen concentration be 5 to 21%, more preferably 10 to 21%, and most preferably 15 to 21%.
When the oxygen concentration in the external heat kiln furnace is less than 5%, there arises a problem that the remaining carbon that is difficult to burn does not burn.
As temperature, 550 degreeC-750 degreeC, More preferably, 600 degreeC-725 degreeC, Especially preferably, 650-710 degreeC is desirable.
As described above, the second combustion furnace is preferably burnt at a higher temperature than the first combustion furnace because it is necessary to burn residual organic matter, particularly residual carbon, that could not be burned in the first combustion furnace. When the combustion temperature is less than 550 ° C., it is difficult to sufficiently burn the residual organic matter, and when the combustion temperature exceeds 750 ° C., the oxidation of calcium carbonate in the combustion product proceeds and the particles become hard. Arise.
The residence time is 10 to 60 minutes, more preferably 15 to 45 minutes, and particularly preferably 20 to 40 minutes. In particular, the remaining carbon must be burnt slowly at a high temperature that does not cause decomposition of calcium carbonate as much as possible. If the residence time is less than 10 minutes, the remaining carbon is burned in a short time and 60 minutes. If it exceeds 1, the problem of decomposition of calcium carbonate occurs.
Furthermore, it is preferable that combustion be performed in a residence time of 10 minutes or more in order to prevent overcombustion and secure productivity in order to ensure stable production of combusted materials.
The particle size of the combustion product discharged from the external heat kiln furnace 32 is preferably adjusted to 20 mm or less, more preferably the average particle size is 5 to 18 mm or less, and most preferably the average particle size is 8 to 15 mm. is there.
The regenerated particle agglomerated after the combustion is cooled by the cooler 34, and then a particle having a target particle size is temporarily stored in the combustion product silo 38 by a particle size sorter 36 such as a vibration sieve, so that the pigment and filler It is sent to the use destination.
In addition, although the case where deinking froth was used as a raw material was illustrated, it may be a combustible product obtained by appropriately mixing other papermaking sludge such as papermaking sludge in the papermaking process with deinking floss as the main raw material.

[Crushing process]
In the method for producing a regenerated particle aggregate according to the present invention, a known dispersion / pulverization step is further provided as necessary, and the pigment for coating is used by appropriately finely pulverizing to a necessary particle size. Can be used as a filler.
In one example, after combustion, the obtained particles 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. Regarding the optimum particle size for fillers, pigment applications, etc., the regenerated particle aggregate of this embodiment preferably has an average particle size of 0.1 to 10 μm.
The particle diameter of the regenerated particle aggregate after the pulverization step was measured by a volume average particle diameter using a particle size distribution measuring device (laser type microtrack particle size analyzer: manufactured by Nikkiso).

[Attached process]
In this manufacturing facility, in order to obtain more stable quality, it is preferable to classify the particle size of the regenerated particle aggregates uniformly in each step, and feed back coarse and fine particles to the previous step. In this way, quality can be further 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 make the particle diameter uniform, and the The quality can be further stabilized by feeding back the fine 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.
As raw materials for this production method, it is preferable to remove in advance those that can be used as raw materials for the regenerated particle agglomerates. For example, with a pulper, screen, cleaner, etc. in the previous stage leading to the deinking process of the used paper pulp manufacturing process It is preferable in terms of removal efficiency to remove sand, plastic foreign matter, metal and the like. 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 regenerated particle aggregate produced by the method for producing a regenerated particle agglomerate according to the present invention has a ratio of calcium, silica, and aluminum of 30 to 82: 9 in terms of oxides in elemental analysis of fine particles using an X-ray microanalyzer. It is preferable to contain in the mass ratio of 35: 9-35, More preferably, the mass ratio of 40-82: 9-30: 9-30, More preferably, the ratio of 60-82: 9-20: 9-20 It is.
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 can reduce the proportion of unburned matter in the drying / combustion process and the risk of excessive hardness due to sintering in the combustion process.
As a method for adjusting the ratio of the present invention, the main ingredient is to adjust the raw material composition in the deinking floss, but in the drying / combustion process and the combustion process, a coating floss and an adjustment process floss with a clear origin are used. It is also possible to adjust by means of containing in the process by spray or the like, or means of containing incinerator scrubber lime.
For example, using deinked floss as the main raw material, neutral papermaking drainage sludge or drainage sludge from the coated paper manufacturing process is used to adjust calcium in the recycled particle aggregate, and opacity is used to adjust silica. Newspaper production wastewater sludge with a large amount of white carbon added as an improver, papermaking wastewater sludge that uses acid bands such as acidic papermaking to adjust aluminum, and high quality papermaking that uses talc Wastewater sludge in the process can be used.
Further, the regenerated particle aggregate obtained by the present production method has a weight loss (rate) of 50 in the decomposition (change to calcium oxide) of calcium carbonate occurring at around 700 ° C. in the differential thermal analysis using the differential thermothermal gravimetric simultaneous measurement apparatus. It is preferable to control the combustion of the deinking froth based on the present invention so as to be at least%, since the progress of oxidation of the calcium component can be suppressed more accurately and the particles can be prevented from becoming hard.

The Example and comparative example of this invention are shown.
When the quality of the obtained regenerated particle aggregate was examined by changing various factors, the results shown in Table 1 and Table 2 were obtained. The results show that the method of the present invention is superior to the comparative example.
The quality was evaluated as follows.
(Unburnt rate): After heating the electric muffle furnace to 600 ° C. in advance, the sample was put in a crucible and completely burned in about 3 hours, and the unburned content was calculated from the change in weight before and after burning.
(Wire wear degree): Measured with a plastic wire wear degree (manufactured by Nippon Filcon, 3 hours) and a slurry concentration of 2% by weight.
(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.
(Quality stability): For each item of whiteness, particle diameter, and production amount at a certain time interval of fine particles obtained by a predetermined method, the degree of fluctuation is measured and ranked in the order of the smallest fluctuation. ◎ from 10th to 20th, △ from 21st to 25th, and x from there.
(Appearance): The color of the regenerated particle aggregate was compared and judged visually, and was classified into white and gray.

  The present invention is applicable as a method for producing a regenerated particle aggregate by burning deinked floss as a main raw material.

It is a schematic diagram of the manufacturing equipment concerning the present invention.

Explanation of symbols

  10 ... Raw materials, 14 ... Internal heat kiln furnace (first combustion furnace), 32 ... External heat kiln furnace (second combustion furnace).

Claims (4)

Using the deinked floss separated from the pulp fiber in the deinking process of the used paper processing equipment for manufacturing used paper pulp, the main material is subjected to dehydration, drying, combustion and pulverization operations to obtain recycled particle aggregates. A method for producing an aggregate, comprising:
The drying and combustion operation re-combusts the first combustion furnace that performs a series of drying and combustion of the material after dehydration, and the deinking floss burned in the first combustion furnace, and the second combustion after the second. Having a furnace, having at least a two-stage combustion operation;
A method for producing a regenerated particle aggregate, which is then pulverized to obtain a regenerated particle aggregate.   The first combustion furnace is an internal heat kiln furnace in which a main body is placed horizontally and rotates around a central axis, and a moisture content of the raw material after dehydration to be input into the internal heat kiln furnace is less than 50%. A method for producing regenerated particle aggregates.   The method for producing a regenerated particle aggregate according to claim 1 or 2, wherein hot air of 500 ° C to 650 ° C is blown so that the oxygen concentration in the internal heat kiln furnace is 0.2 to 20%.   The second combustion furnace is an external heat kiln furnace in which the main body is placed horizontally and rotates around a central axis. In the external heat kiln furnace, the combustion product from the internal heat kiln furnace is at a temperature of 550 ° C. to 750 ° C. The method for producing a regenerated particle aggregate according to any one of claims 1 to 3, which burns.

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