FI126056B

FI126056B - Procedure and process for treating sludge, product and its use

Info

Publication number: FI126056B
Application number: FI20125724A
Authority: FI
Inventors: Nina Pykäläinen
Original assignee: Upm Kymmene Corp
Priority date: 2012-06-26
Filing date: 2012-06-26
Publication date: 2016-06-15
Also published as: FI20125724A; EP2864257A1; EP2864257A4; WO2014001641A1

Description

A METHOD AND PROCESS FOR TREATING SLUDGE, A PRODUCT AND ITS USE

FIELD OF THE INVENTION

The invention relates to a method and a process for treating sludge. Further, the invention relates to a product formed from the sludge. Further, the invention relates to a use of the product.

BACKGROUND OF THE INVENTION

Known from prior art are different residue sludges in the paper manufacturing. Typically the sludges are waste, and they are incinerated or are disposed.

OBJECTIVE OF THE INVENTION

The objectives of the invention are to disclose a new method for treating sludges from a waste paper treatment and/or a paper mill reject and/or bio sludge and for manufacturing a new type product which can be utilized.

SUMMARY OF THE INVENTION

The method for treating a sludge according to the present invention is characterized by what is presented in claim 1.

The process for treating a sludge according to the present invention is characterized by what is presented in claim 7.

The product according to the present invention is characterized by what is presented in claim 11.

The use of the product according to the present invention is characterized by what is presented in claim 13.

BRIEF DESCRIPTION OF THE FIGURES

The accompanying figures, which are included to provide a further understanding of the invention and constitutes a part of this specification, illustrate some embodiments of the invention and together with the description help to explain the principles of the invention. In the figures:

Fig. 1 is a flow chart illustration of a method according to one embodiment of the present invention in which the separation of the fractions is carried out in one separation step,

Fig 2 is a flow chart illustration of a method according to another embodiment of the present invention in which the separation of the fractions is carried out in two separation steps,

Fig 3 is a flow chart illustration of a method according to another embodiment of the present invention in which the separation of the fractions is carried out in three separation steps, and

Fig 4 is a flow chart illustration of a waste paper treatment.

DETAILED DESCRIPTION OF THE INVENTION

In the present invention a product is formed from a sludge 1 which contains reject from a waste paper treatment and/or a paper mill and/or a waste water treatment plant. The sludge 1 is treated by drying in at least one drying step 2, and at least two fractions 10, lla-c, 12, 13 are recovered from the dried sludge 3 in at least one separation step 4 so that the first fraction 10 includes at least fibers and the second fraction 11a includes at least minerals. A process of the present invention is presented in figure 1.

In this context, the sludge 1 contains rejects, such as sludges, rejects and residues, a waste paper treatment and/or a paper mill and/or a waste water treatment plant. In one embodiment the sludge 1 contains at least rejects, such as sludges, rejects and residues, from a waste paper treatment, e.g. RCF sludge. In one embodiment the sludge contains mainly rejects from a waste paper treatment, e.g. RCF sludge. A typical waste paper treatment process is presented in figure 4. Further, the sludge may include rejects, such as sludges, rejects and residues, from a paper mill. Typically, these paper mill rejects do not include bio-sludge. Further, the sludge may include rejects, such as sludges, from a waste water treatment plant, e.g. primary sludge and/or bio sludge. Further, the sludge may include rejects, such as sludges, rejects and residues, from any paper industry process. Further, the sludge may also include sludges and rejects from other processes. In this context, RCF sludge means any RCF reject or any combination of different RCF rejects from RCF process, i.e. from recirculated fiber plant, in which waste paper is treated. The sludge may include minerals used in paper coating, filler and printing inks, and fibers, fines, sticky materials like starch, latex and adhesive, and other inorganic components and/or small amount of other components, preferably other reject components. Preferably the sludge is high solid sludge in which dry solid content can be about 50 - 70 %. Preferably, the sludge can be dewatered to form the high solid sludge before a use as the sludge in the method of the present invention. In one embodiment, the sludge may be treated in the dewatering by means of a gravitation table, disc filter and/or screw press or the like before the method of the present invention.

In one embodiment the sludge includes 50 - 100 % rejects from a waste paper treatment. In one embodiment the sludge includes 80 - 100 % rejects from a waste paper treatment. In one embodiment the sludge includes over 80 %, preferably over 90 % rejects from a waste paper treatment. In one embodiment the sludge contain over 80 % RCF sludge, in one embodiment over 90 % RCF sludge. In one embodiment the sludge includes 80 - 100 % RCF sludge. In one embodiment the sludge includes below 50 %, preferably below 40 %, more preferable below 30 and most preferable below 20 % rejects from a paper mill, in one embodiment below 10 % re jects from a paper mill. In one embodiment the sludge includes below 50 %, preferably below 40 %, more preferable below 30 and most preferable below 20 % sludges from a waste water treatment plant, in one embodiment below 10 % sludges from a waste water treatment plant. In one embodiment the sludge includes below 50 %, preferably below 40 % and more preferable below 30 %, rejects from a paper mill and sludges from a waste water treatment plant. In one embodiment the sludge includes below 20 % rejects from a paper mill and sludges from a waste water treatment plant. In one embodiment the sludge includes 50 - 100 % rejects from a paper mill. In one embodiment the sludge includes below 50 % rejects from a waste paper treatment.

The sludge is fed to the process.

A technical effect of the invention is that different rejects from a waste paper treatment and/or a paper mill and/or waste water treatment plant can be utilized. An additional technical effect of the invention is that different fractions are easy to separate from the sludge. Further, the separation efficiency of the different fractions is good. The materials of the fractions can be reused and then environmental load decreases .

The drying can be carried out in one or more drying steps 2. In preferred embodiment the drying is made in one step. In one embodiment the drying is made in at least two drying steps. Preferably, after the drying moisture content of the dried sludge is below 15 %, more preferable below 10 % and most preferable below 5 % or most preferable below 4 % or most preferable below 3 % or most preferable below 2 % or most preferable below 1 %.

The drying can be made by means of drying device selected from the group: indirect dryer, direct sludge dryer, paddle dryer, flash dryer, fluidized bed dryer, cyclone dryer, air dryer, air grinder, rotor mill, centrifugal mill, air turbulence mill, air turbulence dryer and other suitable dryers and other suitable mills, and their combinations. Preferably the drying is carried out by such air dryer or air grinder in which particles can be separated one from the other. Also other drying devices are possible. In one embodiment a drying device can also act as a grinder. In one embodiment a grinder can act as a drying device. In a preferred embodiment, low temperature can be used in the drying. In one embodiment the sludge is dried at temperature between 25 to 170 °C, preferably between 25 to 100 °C or between 100 to 170 °C, more preferable between 25 to 60 °C or between 50 to 100 °C or between 100 to 160 °C. It is important that temperature is selected so that organic components are not damaged. Further, residue heat, e.g. from a mill, can be used in the process of the present invention.

In one embodiment the dried sludge can be crushed before the separation of the fractions. In one embodiment the method comprises additional step for separating or disintegrating agglomerates after the drying of the sludge. The disintegration of the ag glomerates can be made any disintegrating or crushing device known per se.

In one embodiment of the invention, the sludge can be crushed in the connection with the drying. In one embodiment agglomerates are broken during the drying, and then separate crushing steps are not needed.

In one embodiment the method comprises pretreatment step for crushing the sludge before the drying. The crushing can be made by any crushing device known per se.

In one embodiment, moisture content of the dried sludge is analyzed, e.g. by an on-line measurement or by a laboratory analysis, after the drying. The drying can be adjusted based on measurement results .

One technical effect is that dry content of the sludge may be increased so that DS increases from about 40 - 70 % to 80 - 99 % during the drying. DS means dry solids content.

Preferably, the sludge is fed rapidly from the drying to the separation step, for example in a closed process.

In this context, separation means any separation, fractionation and/or screening.

The first fraction 10 is preferably a fiber fraction. The first fraction may also include other components, such as minerals, adhesives, latex, starch and/or other components. In one embodiment the fiber fraction includes fibers and minerals.

In one embodiment of the invention, the second fraction lla-c includes at least minerals, but it may include other substances, such as fines, latex, adhesives, starch and/or other components. In one embodiment, the second fraction 11a contains minerals and fines. The second fraction may also include other components .

In one embodiment of the invention, the recovering of fractions is carried out in one separation step 4. In one embodiment the fractions are recovered in more than one separation steps 4,5,6. In one embodiment the fractions are recovered in two separation steps 4,5. In one embodiment the fractions are recovered in three separation steps 4,5,6. In one embodiment the fractions are recovered in more than three separation steps.

In one embodiment of the invention, the first fraction 10 is firstly separated from the dried sludge 3 before the recovering of the second fraction 11a.

In one embodiment of the invention, three fractions are recovered from the dried sludge 3 so that the first fraction 10 includes fibers, the second fraction lib includes minerals and the third fraction 12 includes fines. The fractions 10, lib, 12 may also include other components. In one embodiment, the first fraction 10 is firstly separated from the dried sludge 3, after that the third fraction 12 is separated from the dried sludge 3 and finally the second fraction lib is recovered. In one embodiment the recovering of fractions is carried out in two separation steps 4, 5. A process of the present invention is presented in figure 2 .

In one embodiment the second fraction lib consisting of minerals is divided into two or more mineral fractions which may include same or different mineral components. The each mineral fraction may include one mineral component or more than one mineral component, e.g. CaCo3, clay, talc or similar. In one embodiment, the mineral fractions are separated based on mineral components, e.g. mineral component A and mineral component B. In one embodiment, the mineral fractions are separated based on particle size, e.g. small particles and big particles. The mineral fractions may include other components.

In one embodiment, more than three fractions are recovered from the dried sludge 3. For example, four fractions are recovered so that the first fraction 10 includes fibers, the second fraction 11c includes minerals and the third fraction 12 includes fines and the fourth fraction 13 includes minerals. The fractions 10, 11c, 12, 13 may also include other components. In one embodiment, the first fraction 10 is firstly separated from the dried sludge 3, after that the third fraction 12 is separated from the dried sludge 3 and finally the second 11c and fourth 13 fractions are separated and recovered. In one embodiment the recovering of fractions is carried out in three separation steps 4, 5, 6. A process of the present invention is presented in figure 3 .

In one embodiment of the invention, after the recovering of the fractions the dried sludge comprises a residue. The residue may contain fibers, minerals, stickies, inks, fines and the like. In one embodiment, the fractions can be recovered totally to be utilized from the dried sludge without residue.

The separation can be made by means of separation technique and/or device selected from the group dry separation, wet separation, mechanical screening, vibrating screen, oscillation screen, rotary classifier, air classifier, centrifuge, separation based on density differences, separation based on particle size and their combinations. Also other separation methods can be used. Preferably, the separation device is suitable for screening the dried sludge into desired fractions.

In one embodiment process conditions in the separation are analyzed, e.g. by on-line measurements or by laboratory analysis after the separation. The separation step can be adjusted and/or controlled based on measurement results.

In one embodiment of the invention, the fraction 10, 12 is pelletized after the separation in or- der to form a pelletized product 15,16, such as pellets. In one embodiment, the first fraction 10 is pelletized. In one embodiment, the third fraction 12 is pelletized.

In this context, pellet means any pellet, granulate, briquette, agglomerate and their combinations. The pelletizing can be carried out by means of any suitable pelletizing technique and/or apparatus known to a man skilled in the art, e.g. pelletizing, granulation and their combinations.

The process according to the invention can be a continuous and/or batch process.

In one embodiment of the present invention the product formed is selected from the group: a product comprising fibers, a product comprising fines, a product comprising minerals, a product comprising desired mineral component or product comprising minerals and fines. Each product may include also other components .

The product of the invention is used as a material component in a final product. The product can be used in different embodiments. In one embodiment the product according to the invention can be used as a material component in composites and papers. In one embodiment the product, specially the fiber containing fraction, according to the present invention can be used as fuel for producing energy.

In the present invention, different fractions can be recovered and they can be utilized. The present invention provides products with good or adequate quality. The method of the present invention offers a possibility to prepare the products from the sludge cost-effectively and energy-effectively. The present invention provides an industrially applicable, simple and affordable way of treating sludges and making the products from sludges and rejects. The method accord- ing to the present invention is easy and simple to realize as a production process.

The method according to the present invention is suitable for use in the manufacture of the different products from different sludges containing organic and/or inorganic components.

EXAMPLES

The invention is described in more detail by the following examples with reference to accompanying figures .

Example 1

In this example, which is shown in figure 2, a product is formed from a high solid sludge 1 comprising over 80 % RCF reject from a waste paper treatment and below 20 % paper mill sludge.

The sludge 1 is fed to the process, and the sludge is dried in the drying step 2, and desired fractions are recovered in the separation steps 4 and 5.

The drying is made in one drying step 2 in order to form the dried sludge 3. A moisture content of the dried sludge 3 is below 10 %. DS may be in creased from about 40 - 70 % to 95 - 99 %

In the first separation step 4 the first fraction 10 containing mainly fibers is separated from the dried sludge 3. The first fraction product 10 is pelletized in the pelletizing step 8 to form the first product pellets 15. In the second separation 5 the third fraction 12 containing mainly fines is separated from the second fraction lib containing mainly minerals. The third fraction product 12 is pelletized in the pelletizing step 9 to form the second product pellets 16.

Example 2

In this example, which is shown in figure 3, a product is formed from a high solid sludge 1 comprising about 80 % RCF reject from a waste paper treatment and about 10 % reject from a paper mill and about 10 % bio-sludge from a waste water treatment plant.

The sludge 1 is fed to the process, and the sludge is dried in the drying step 2, and desired fractions are recovered in the separation steps 4, 5 and 6 .

The drying is made in one drying step 2 in order to form the dried sludge 3. A moisture content of the dried sludge 3 is below 10 %. DS may be increased from about 40 - 70 % to 95 - 99 %

In the first separation step 4 the first fraction 10 containing mainly fibers is separated from the dried sludge 3. The first fraction product 10 is pelletized in the pelletizing step 8 to form the first product pellets 15. In the second separation 5 the third fraction 12 containing mainly fines is separated from the second fraction lib containing mainly minerals. The third fraction product 12 is pelletized in the pelletizing step 9 to form the second product pellets 16. In the third separation 6 the second fraction lib containing mainly mineral components is divided into two fractions so that the second fraction 11c includes mainly mineral component A and the fourth fraction 13 includes mainly mineral component B.

Example 3

In this example, which is shown in figure 2, a product was formed from a high solid sludge 1 comprising over 80 % RCF reject from a waste paper treatment and below 20 % paper mill sludge.

The sludge 1 included about 30 w-% component containing fibers, fines and stickies, about 54 w-% calcium, about 14 w-% clay and about 2 w-% other inorganic components. The stickies contained latex, starch and adhesives.

The sludge 1 was fed to the process, and the sludge was dried in the one drying step 2 in which the sludge was dried by rotor mill.

Process conditions of the drying are presented in table 1.

Table 1

The first and second fractions were separated by vibration screen so that the first fraction included mainly fibers and the second fraction included mainly minerals and fines. The sizes of screens were 0.2 mm and 1.9 mm.

In this test the second fraction contained under 0.2 mm material components including minerals, fines and stickies. The first fraction contained material components between 0.2 - 1.9 mm and over 1.9 mm including fibers, and a little minerals, fines and stickies.

In the tests it was observed that high or adequate quality products can be manufactured from the separated fractions. Further, it was observed that using residue heat from a mill in the drying efficiency and economy in the process can be improved.

The products according to the present invention are suitable in different embodiments to be used in different final products. The method according to the present invention is suitable in different embodiments to be used for manufacturing the most different kinds of products.

The invention is not limited merely to the example referred to above; instead many variations are possible within the scope of the inventive idea defined by the claims.

Claims

A process for treating a slurry, characterized in that the process comprises: - drying the slurry containing the waste paper treatment, paper mill and / or waste water treatment plant to produce a dried slurry in at least one drying step, - the slurry comprising at least RCF slurry from a recycled fiber plant; and treating the waste paper, and recovering at least two fractions from the dried slurry in at least one separation step such that the first fraction contains at least the fibers and the second fraction contains at least the minerals.

Process according to claim 1, characterized in that the second fraction contains minerals and fines.

Process according to claim 1 or 2, characterized in that three fractions of the dried slurry are recovered in at least two separation steps such that the first fraction contains fibers, the second fraction contains minerals and the third fraction contains fines.

Process according to one of Claims 1 to 3, characterized in that four fractions of the dried slurry are recovered in at least three separation steps such that the first fraction contains fibers, the second fraction contains minerals, the third fraction contains fines and the fourth fraction contains minerals.

Process according to one of Claims 1 to 4, characterized in that the fraction is pelleted to form a product.

Method according to one of Claims 1 to 5, characterized in that the sludge contains a waste paper treatment reject and a paper mill reject and / or sewage treatment plant sludge.

A process for treating sludge, characterized in that the process comprises: - a feeder for feeding the sludge (1) to the process, - at least one drying step (2) comprising a drying device for sludge (1) containing the waste paper treatment, paper mill and / or sewage treatment plant reject forming a dried slurry (3), and the slurry (1) comprising at least RCF slurry from a recycled fiber plant treating the waste paper, and - at least one separation step (4,5,6) comprising at least two fractions (10, 11a-c, 12) of the separation device. 13) for recovering from the dried slurry (3) such that the first fraction (10) contains at least fibers and the second fraction (IIa-c) contains at least minerals.

A process according to claim 7, characterized in that the process comprises two separation steps (4,5) comprising separation means for recovering three fractions (10, 11a-b, 12) from the dried slurry (3) so that the first fraction (10) ) containing the fibers are recovered in a first separation step (4) and a second fraction (11b) containing minerals and a third fraction (12) containing fines is recovered in a second separation step (5).

A process according to claim 7 or 8, characterized in that the process comprises three separation steps (4,5,6) comprising separation means for recovering four fractions (10, 11a-c, 12,13) from the dried slurry (3) so that: the first fraction (10) containing the fibers is recovered in the first separation step (4), the third fraction (12) containing the fines is recovered in the second separation step (5) and the second fraction (11c) containing minerals and the fourth fraction (13) containing minerals is recovered in the third separation step.

Process according to one of Claims 7 to 9, characterized in that the process comprises at least one pelleting device (8,9) for pelleting at least one fraction (10,12) to form the product (15,16).

11. A product characterized in that the product is formed from a slurry comprising a waste paper treatment, paper mill and / or waste water treatment plant reject, containing at least RCF slurry from a recycled fiber plant treating the waste paper, and the slurry being treated by drying the slurry containing the waste paper. a rejection of a treatment, paper mill and / or sewage treatment plant containing at least one RCF slurry in at least one drying step to form a dried slurry, and - recovering at least two fractions of the dried slurry in at least one separation step such that the first fraction contains fibers;

Product according to Claim 11, characterized in that the product is in the form of pellets.

Use of a product obtained by a process according to any one of claims 1 to 6, wherein the product is used as a material component in the final product.

Use according to claim 13, wherein the product is used as a material component in composites and papers.