JP2000176499A - Dehydration of inorganic oil-containing sludge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To always obtain an efficiently stabilized dehydration treatment by flocculating inorganic oil-containing sludge with a high polymer coagulant, then dehydrating it with a screw press type dehydrator. SOLUTION: The inorganic oil-containing sludge is added the high polymer coagulant consisting of a polymer of tertiary salt or quartenary salt of dimethylaminoethyl (meth)acrylate, etc., to coagulate the sludge and produce a block. The sludge formed the block is transferred to a force-feeding piping 1 through a shoot, and is charged into a porous punching plate 3 as a strainer through the piping 1. The sludge just after it was charged is dehydrated through numerous holes of the gravity filtering zone and is further dehydrated at the compressed zone under a grinding effect between the block themselves. Next, the sludge is converted into a dehydrated cake with press-forces of screw blades 2a at the compressed zone, and the taper corn 6 at a screw shaft 2 and through numerous holes of a punching plate 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for dehydrating an inorganic oil-containing sludge containing an inorganic component such as metal powder generated from industries such as metal polishing and machining.

[0002]

2. Description of the Related Art Conventionally, as a method of dehydrating an inorganic oil-containing sludge containing an inorganic component such as metal powder generated from industries such as metal polishing and machining (hereinafter, simply referred to as “inorganic oil-containing sludge”), A method of adding a chemical such as a polymer or inorganic flocculant to the sludge to perform flocculation treatment, performing solid-liquid separation by flotation separation or sedimentation separation, and treating the resulting sludge as industrial waste has been carried out. . In addition, since the volume reduction of industrial waste is insufficient in the above method, after a method of dehydrating with a filter press dehydrator without chemical injection without using a flocculant or after flocculating using a polymer flocculant, , Belt press type dehydrator, centrifugal dehydrator,
A method of dehydrating with a multi-disc dehydrator has been used.

[0003]

However, among the above-mentioned dewatering treatment methods, in a filter cloth-type press dewatering such as when a belt press type dehydrator or a filter press type dehydrator is used,
Dewatering efficiency is reduced due to filter cloth clogging due to filter cloth contamination by the oil content of the inorganic oil-containing sludge, and stable dewatering is difficult.In particular, it responds to changes in properties such as the oil content of the inorganic oil-containing sludge. It was difficult to stably dehydrate.

[0004] On the other hand, mechanical dehydration of a type that does not use a filter cloth, such as a centrifugal dehydrator or a multi-disc dehydrator, is effective for oil-containing sludge, but sludge containing inorganic components such as metal powder. Was not effective. For example, in the case of a centrifugal dehydrator, wear of the dehydrator due to high-speed rotation of about 1000 to 3000 rpm, and in the case of a multi-disc dehydrator,
There is a drawback that sludge solids adhere to the disk portion, causing troubles such as inability to dewater.

[0005] An object of the present invention is to solve the above-mentioned disadvantages of the prior art and to provide an efficient method for dehydrating inorganic oil-containing sludge.

[0006]

As a method for improving these disadvantages of the prior art, various treatment methods for efficiently dehydrating inorganic oil-containing sludge were examined.
The present inventors can solve the disadvantages of the prior art by coagulating inorganic oil-containing sludge using a polymer coagulant, and then dewatering using a screw press type dewatering machine, and can always be efficient. It has been found that a dehydration process that is stable in a short time can be realized.

That is, the present invention provides a method for dewatering inorganic oil-containing sludge, which comprises coagulating inorganic oil-containing sludge using a polymer flocculant and then dehydrating using a screw press type dewatering machine. Is what you do.

Hereinafter, the present invention will be described in more detail. The inorganic oil-containing sludge to be treated according to the present invention is generated from industries such as metal polishing and machining, and the hexane extract (n-hexane extract) is 50 mg / L (“liter”, the same applies hereinafter) or more. And suspended solids
In general, ignition loss ("volati") is generally referred to as "SS".
le suspended solids ", usually abbreviated as" VSS "). Here, “hexane extract” is one index indicating the oil content, and “VSS”
Is an index of the organic matter content in SS.

The polymer flocculant used in the present invention will be described. The polymer flocculant includes a polymer flocculant having a cationic group, an anionic polymer flocculant and the like, and these are used alone or in combination depending on the properties of the sludge to be treated.

The polymer flocculant having a cationic group that can be used in the present invention will be described in detail. The polymer flocculant having a cationic group used in the present invention is a polymer flocculant containing a functional group having a cationic property in a molecular structure. For example, a tertiary salt of dimethylaminoethyl (meth) acrylate and / or Polymers of quaternary salts (for example, methyl chloride quaternary salt), tertiary and / or quaternary salts of dimethylaminoethyl (meth) acrylate (for example, methyl chloride
Grade salt) and acrylamide copolymer or N-vinylacrylamidine salt unit-containing polymer flocculant (for example, JP-A-5-192513, JP-A-8-155500, JP-A-8-243600) JP-A-9-8
Cationic polymer coagulants such as the polymer coagulant disclosed in JP-A-7323 and the like, and tertiary and / or quaternary salts of dimethylaminoethyl (meth) acrylate (for example, quaternary methyl chloride). Or an amphoteric copolymer of acrylamide with at least one or more anionic monomers such as acrylic acid and salts thereof, and at least one or more anionic monomers such as 2-acrylamido-2-methylpropanesulfonate. Examples thereof include a polymer flocculant, but are not particularly limited thereto. The molecular weight of the polymer flocculant having a cationic group is 1,000,000 or more, and is preferably in the range of 1,000,000 to 30,000,000 from the viewpoint of the effect. These polymer flocculants having a cationic group can be used alone or as a mixture. The above-mentioned polymer flocculant containing N-vinylacrylamidine salt units means that the polymer flocculant finally obtained by synthesis contains N-vinylacrylamidine salt units. N
Preferred examples of the polymer flocculant containing a vinyl acrylamidine salt unit include acrylamide unit, acrylonitrile unit, N-vinylacrylamidine hydrochloride unit, N
-A copolymer comprising vinyl acrylamide units, vinylamine hydrochloride units, and N-vinylformamide units.

The amount of the polymeric flocculant having a cationic group to be added is not particularly limited, and the appropriate amount varies depending on the type of the flocculant and the type and properties of the sludge to be treated. 0.1 to 1 per SS of sludge to be treated
An addition amount of 0.0% by weight is preferred.

The anionic polymer flocculant which may be used in the present invention will be described. Examples of the anionic polymer flocculant that can be used in the present invention include a polymer of acrylic acid and / or a salt thereof, acrylic acid and / or
Or a copolymer of a salt thereof and acrylamide, a copolymer of acrylamide and 2-acrylamido-2-methylpropanesulfonate, acrylic acid and / or a salt thereof and acrylamide and 2-acrylamido-2-methylpropanesulfonate Ternary (or quaternary) copolymers and partial hydrolysates of polyacrylamide, but are not particularly limited thereto. The range of the molecular weight of the anionic polymer flocculant is not particularly limited, but is preferably in the range of 5,000,000 to 20,000,000. These anionic polymer flocculants can be used alone or as a mixture.

The amount of the anionic polymer flocculant to be added is not particularly limited, and the appropriate amount varies depending on the type of the flocculant and the type and properties of the sludge to be treated. 0.1-3.0% by weight of sludge per SS
Is preferred.

In the present invention, when a polymer flocculant having a cationic group and an anionic polymer flocculant are used in combination, the order of adding each flocculant is not particularly limited, but the polymer flocculant having a cationic group is added first. Is preferred. In the case of these combined use, a cross-linked polyion complex (fibrous or other shape) is formed by the reaction between the coagulants, and it has an effect of supplementing the floc strength of the hardly dewaterable sludge, which is preferable.

The inorganic coagulant that may be used in the present invention will be described. Examples of the inorganic coagulant that can be used in the present invention include, for example, aluminum sulfate, polyaluminum chloride, aluminum chloride, ferrous sulfate, ferric sulfate, polyferrous sulfate, ferrous chloride, ferric chloride, and the like. Examples thereof include polyvalent metal salts, but are not particularly limited thereto.

The amount of the inorganic coagulant added is not particularly limited either.
The appropriate amount of addition varies depending on the type of the flocculant, the type and properties of the sludge to be treated, but from the viewpoint of effect and economy, 0.1 to 20% by weight of SS as the metal salt per SS of the sludge to be treated.
Is preferred.

When a plurality of coagulants are used in the present invention, an appropriate order of addition of each coagulant may be determined by a jar test described later. When the inorganic coagulant and the polymer coagulant are used in combination, it is preferable to add the inorganic coagulant before adding the polymer coagulant, but the present invention is not limited thereto.

The screw press type dewatering machine used in the present invention refers to a coagulated sludge introduced into a cylindrical strainer (filtration tube) composed of a perforated punching plate, a slit-shaped wedge wire, or the like, at an extremely low speed (0.1 to 0.1). 2.0 rp
This is a dehydrator of the type that performs squeezing and dehydration while being conveyed by a specially shaped screw shaft rotating in m).
Therefore, for dehydration treatment with a screw press dehydrator,
It is required that the floc diameter is larger than the hole or slit width of the strainer, and that the floc is strong and hard to break because the coagulated sludge is transported and squeezed by the screw for a long time and twisted.

The screw press mechanism that may be used in the present invention will be described in detail. As a method of introducing coagulated sludge to a screw press, a method of collecting coagulated sludge from a mixing tank via a chute into a screw press input hopper and introducing the same under its own weight, or a method of feeding coagulated sludge through a closed mixing tank and a feeding pressure of a sludge pump. For example, but there is no limitation thereto.

As a method of solid-liquid separation of the introduced coagulated sludge, there is a method of solid-liquid separation by a strainer comprising a long, straight cylindrical, porous punching plate provided in the horizontal direction, or a long, straight cylindrical shape provided in the horizontal direction. And a solid-liquid separation method using a strainer made of a wedge wire having a large number of slit-like holes, but is not limited thereto.

As a method for washing the surface of the strainer of the screw press type dehydrator, a washing header is incorporated on the outer periphery of the strainer drum and high-pressure water washing is performed at regular time intervals. There is a method of washing the strainer from the outside, such as a method of supplying water with pressure, but the method is not limited thereto. For example, drill a hole for water supply in the screw shaft,
Although a method of washing the strainer from the inside can be adopted, a method of washing the strainer from the outside which does not require a hole in the screw shaft is preferable from the viewpoint of the strength of the screw shaft. In addition, a method of performing high-pressure water supply cleaning at regular intervals using a cleaning header is preferable from the viewpoint of cleaning efficiency.

As a method of squeezing at the outlet of the screw press, there is a method of squeezing by pressing with a taper cone provided at a dewatering cake outlet at the tip of the screw. As the type of the taper cone, a type in which the dewatered cake is cut simultaneously by pressing (hydraulic) so that the taper cone itself opens and closes completely with respect to the strainer drum at the exit of the screw press (JP-A-6-30836), Also, a spring is built inside the casing,
By pressing the taper cone with a constant pressure against the strainer drum at the exit of the screw press via the rod, the dewatering cake sent by the screw shaft is cut off intermittently. There are, but not limited to, squeezing types.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.

[0024] At least the object of the present invention can be achieved by adding a polymer flocculant to the inorganic oil-containing sludge and dehydrating with a screw press type dehydrator. The order of adding the flocculant is preferably that a polymer flocculant having a cationic group is added to the inorganic oil-containing sludge, and then an anionic polymer flocculant is added and used, thereby greatly improving the dewatering property of the flocculant sludge. I do. Furthermore, it is preferable to add an inorganic coagulant in a step before adding a polymer coagulant having a cationic group, but it is not limited thereto.

The above-mentioned optimum type and amount of each coagulant are determined by changing the type and amount of each coagulant, and when a plurality of coagulants are used in combination, by changing the order of addition and the like. The determination may be made based on results such as the floc diameter, the floc strength, and the water content of the dewatered cake.

The method of the present invention is characterized in that the temperature of the inorganic oil-containing sludge is zero.
Although it can be applied in the range of -70 ° C, the range of 20-40 ° C is more preferable.

In the present invention, it is usual that the sludge which has generated flocs is directly dewatered with a screw press type dehydrator. However, a pretreatment for separating and condensing the flocs is carried out, and then the sludge is dehydrated with a screw press type dehydrator. Is also good. Examples of the pretreatment include, but are not limited to, flotation separation, precipitation separation, and filtration separation using a vibrating sieve. For example, if the floc contains air bubbles and is light, a flotation device may be used. On the other hand, if the floc has a large density and a large particle size and has good sedimentation, a flocculation and sedimentation device may be used.

In the present invention, a screw press type dewatering machine is used to dewater sludge obtained by condensing floc as it is or by flotation or flocculation by flocculation and sedimentation. An example of the dehydrator will be described with reference to FIG. FIG. 1 is a partially cutaway side view of an example of a screw press type dewatering machine preferably used in the present invention. In addition, although the case where the sludge which generated the floc is sent to the screw press type dehydrator as it is will be described, it goes without saying that the same applies to the case of sludge.

From the mixing tank (not shown), the sludge which has generated flocs is sent to a press-fitting pipe 1 via a chute (not shown), and is put into a perforated punching plate 3 as a strainer through this pipe. The punching plate 3 incorporates a screw shaft 2 having a screw blade 2a. Screw shaft 2 from a drive source (not shown) via a chain or belt
The driving force is transmitted to the sprocket 21 on the right end of the screw shaft 2 and the screw shaft 2 rotates. By this rotation, the introduced sludge is pumped rightward in FIG. 1 by the screw blade 2a of the screw shaft 2.

The inside of the punching plate 3 can be divided into three zones, that is, a gravity filtration zone, a consolidation zone, and a compression zone in the order toward the right in FIG. Dewatering of the sludge immediately after the introduction proceeds through the innumerable holes of the punching plate 3 mainly by its own weight in the gravity filtration zone. The sludge that has been dehydrated to some extent by gravity filtration is further dewatered through the innumerable holes of the punching plate 3 in the consolidation zone due to the rubbing effect between the flocks. Then, the dewatered sludge is
In the squeezing zone, the pressing force of the screw blade 2a and the tapered cone 6 on the right end of the screw shaft 2 and the squeezing force further dehydrate the water through the innumerable holes of the punching plate 3 to form a dewatered cake. The tapered cone 6 opens and closes completely in the left and right directions with the right end (screw press outlet) of the punching plate 3 by hydraulic drive, and when squeezing the dewatered cake when closed to the left. The filtrate dripping into the filtrate receiving tray 4 through the innumerable holes of the punching plate 3 is subjected to an appropriate treatment as required, and then discharged out of the system. The dehydrated cake cut by the tapered cone 6 is also discharged out of the system. Is discharged.

A large number of holes are opened in the inner pipe wall of the annular cleaning header 5, and high-pressure cleaning water sent from a water supply rubber hose 51 is jetted toward the punching plate 3.
The leaked sludge that is trying to close the holes of the punching plate 3 is washed away with high-pressure washing water and discharged through the filter pan 4, thus effectively preventing clogging. The cleaning header 5 is reciprocated in the left-right direction by the guide chain 52 to prevent the entire punching plate 3 from being clogged.

According to the present invention, it is possible to generate a floc having sufficient strength for dehydrating an inorganic oil-containing sludge with a screw press type dehydrator, and to efficiently produce a floc with the screw press type dehydrator. Can be dehydrated. As a result, the water content of the dewatered sludge (dewatered cake) can be dramatically reduced.

[0033]

EXAMPLES Next, the present invention will be described in detail with reference to examples, but the present invention is not limited to the following examples unless departing from the gist thereof. In the table below,
A simple "%" indicates "% by weight".

Examples 1 to 22 and Comparative Examples 1 to 38 The polymer flocculant (V) containing an N-vinylacrylamidine salt unit used in the following Examples and Comparative Examples,
Table 1 shows the monomer compositions of the cationic polymer flocculant (C), the amphoteric polymer flocculant (R) and the anionic polymer flocculant (A). The inorganic flocculants used were polyaluminum chloride (PAC) and ferric polysulfate (polyiron).
And ferric chloride (iron salt). Further, Table 2 shows the properties of the inorganic oil-containing sludge used in the following Examples.

[0035]

[Table 1]

[0036]

[Table 2]

In the examples, the floc-formed sludge was coagulated with the inorganic oil-containing sludge shown in Table 2 using the polymer flocculant shown in Table 1, and then the screw press type dehydrator [trade name] "SPS-305CPHS": Dehydration treatment was performed using a strainer having a diameter of φ300 mm and L / D (length / diameter) = 5, manufactured by Organo Corporation.
In the comparative example, the inorganic oil-containing sludge was subjected to (coagulation) and dehydration treatment by a conventional method. Table 3 summarizes the temperature in the flocculation treatment, the number of rotations of the stirring and the centrifugal treatment, and the stirring time after the addition of each flocculant in relation to the type of dehydrator.

[0038]

[Table 3]

That is, in each of Examples and Comparative Examples, each coagulant was added to the inorganic oil-containing sludge and to the addition order and amount shown in Tables 4, 5, 6, and 7 (however, in the case of a filter press dehydrator, , A flocculant was not added), and the suspended solids in the sludge were flocculated under the conditions shown in Table 3, and a dehydration test was performed using various dehydrators. The results are also shown in Tables 4, 5, 6, and 7. In addition, the display of the dehydration property in the table is a determination result evaluated according to the following criteria. ◎ ・ ・ ・ very good ○ ・ ・ ・ good △ ・ ・ ・ Somewhat bad × ・ ・ ・ bad

[0040]

[Table 4]

[0041]

[Table 5]

[0042]

[Table 6]

[0043]

[Table 7]

As is clear from Tables 4 and 6, Example 1 in which a floc was formed according to the method of the present invention and a polymer flocculant having a cationic group was added during the dehydration treatment with a screw press type dehydrator. , 2 and 9, 10 and Examples 3 to 8 and 11 to 13 to which a polymer flocculant having a cationic group and an anionic polymer flocculant were added, and
Examples 14 to 22 in which an inorganic flocculant and a polymer flocculant were used in combination
In, the results of good dewatering properties were obtained for any of the inorganic oil-containing sludges, and the water content of the dewatered cake was drastically reduced, so that stable and efficient dewatering treatment could be performed.

On the other hand, as is apparent from Tables 5 and 7, filter cloth dehydrators such as belt press dehydrators and filter press dehydrators and screw presses such as multi-disc dehydrators and centrifugal dehydrators. In Comparative Examples 1 to 38 in which dehydration treatment was performed mechanically with a dehydrator other than the mold dehydrator, the dehydration properties and the water content of the dehydrated cake were inferior to Examples 1 to 22, and it was difficult to always maintain stable dehydration properties. there were. In the case of the centrifugal dehydrator, abrasion was observed. The examples of the present invention have a good dehydration property and a good water content of the dewatered cake for any inorganic oil-containing sludge as compared with any of the above comparative examples, and a continuously stable dehydration treatment is possible. there were.

Table 8 shows the amount of cake generated in the existing treatment using a belt press type dehydrator or centrifugal dehydrator (Comparative Examples 4 and 24) and the screw press dehydration treatment according to the present invention (Example 10). 20) is shown. Table 8
The amount of cake generated (%) is shown as the rate of occurrence in the screw press (SP) dewatering process with respect to the amount generated in the existing process,
“(SP / existing)” in Table 8 indicates this.

[0047]

[Table 8]

As is clear from Table 8, when a polymer flocculant was added to any of the sludges according to the method of the present invention and dewatered by a screw press type dehydrator, the water content of the cake was drastically reduced. In addition, the amount of cake generated can be reduced.

[0049]

According to the method of the present invention, flocs having sufficient strength for dehydrating an inorganic oil-containing sludge with a screw press type dehydrator can be produced by coagulation treatment, and the inorganic oil-containing sludge can be efficiently produced. The sludge can be dewatered. As a result, the water content of cake in the dewatered sludge can be drastically reduced, and the amount of cake generated can be reduced.

[Brief description of the drawings]

FIG. 1 is a partially cutaway side view of an example of a screw press type dewatering machine preferably used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Press-fitting pipe 2 Screw shaft 3 Perforated punching plate 4 Filtrate tray 5 Washing header 6 Taper cone

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B30B 9/14 B30B 9/14 G F-term (Reference) 4D015 BA04 BA06 BB12 CA06 CA17 DA04 DA05 DA13 DA15 DA16 DB03 DB07 DC07 DC08 EA39 FA19 4D059 AA10 BE26 BE55 BE56 BE57 BE59 BE60 CB17 DA16 DA17 DA23 DA24 DB21 DB24 DB25 DB28

Claims (5)

[Claims] 1. A method for dewatering an inorganic oil-containing sludge, comprising coagulating inorganic oil-containing sludge using a polymer flocculant and then dehydrating using a screw press type dewatering machine. 2. The method according to claim 1, wherein the polymer flocculant is a polymer flocculant having a cationic group and an anionic polymer flocculant. 3. The method for dewatering an inorganic oil-containing sludge according to claim 1, wherein the polymer flocculant and the inorganic flocculant are used in combination. 4. The dehydration of an inorganic oil-containing sludge according to claim 1, wherein the polymer flocculant is a polymer flocculant containing an N-vinylacrylamidine salt unit. Method. 5. The inorganic oil-containing sludge according to claim 1, wherein the screw press type dehydrator is a screw press type dehydrator having a mechanism for washing a strainer from outside. Dehydration method.