JPS58186413A - Dehydration of suspension - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for dewatering an aqueous suspension of slag particles.
ring ) method.

When ash-containing fuel is sufficiently combusted, slag is obtained as a by-product. This combustion takes place in a reactor and the resulting slag enters a water bath, generally located at the bottom of the reactor. Slag in slurry form is relatively easy to transport.

Slag is also produced in the case of partial combustion (incomplete combustion) of ash-containing fuels such as coal, lignite, beet, etc.

Again, the resulting slag is generally placed in a water bath to form an aqueous suspension.

This aqueous suspension is then drained from the water bath.

Since the inside of the reactor is preferably kept under high pressure, a sluice system'('5lui
ce system) is used. A method suitable for this purpose is described in US Pat. No. 3, Tata 4T702.

Since it is generally not possible to treat or dispose of the aqueous suspension directly, it is highly desirable to dewater the suspension. The slag particles obtained can then be reprocessed or used for other purposes, for example for road construction. The clarified water can be discharged without worrying about environmental pollution.

The suspension is dehydrated using a sieving unit (screen unit).
In the case of using a sieving unit, small slag particles in the suspension are not caught in the mesh of the sieving unit and flow out together with the aqueous phase. On the other hand, when a filter (filtration device) is used, the filter may become clogged with small slag particles. It is possible to flocculate fine particles using flocculants to produce larger particles. However, in this case the large particles also react with the flocculant. It is therefore necessary to add a relatively large amount of flocculant to the suspension in order to completely flocculate (agglomerate) all the small particles. However, this is uneconomical.

For this reason, the method of the invention divides the slag particles into groups according to their diameter. That is, the present invention provides a method for dewatering an aqueous suspension of slag particles, in which the suspension is divided into a plurality of different fractions each containing coarse particles, medium particles, and fine particles.
The present invention relates to a dehydration method characterized by dividing the water into two parts and dehydrating both parts separately.

In the method of the invention, the most effective dehydration technique can be selected for each fraction. This is because particle size has a significant influence on this selection. In the method of the invention, the separation of coarse particles and medium particles is 0. ! ;
It is preferable to use a particle diameter within the range of -, 2 tmn as a boundary, and it is more preferable to use a particle diameter/fIII++ as a boundary. The separation between medium and fine particles is 0.
It is preferable to carry out the process at a certain particle diameter within the range of O/-θ', /w+, and it is more preferable to carry out the process at a particle diameter of 0.0 or less. Therefore, a preferred coarse particle-containing fraction is a fraction containing particles with a diameter substantially larger than θ, /■, a preferred fraction containing medium particles is a fraction containing particles with a diameter substantially larger than θ The preferred fine particle-containing fraction contains substantially 0.
．． This is the fraction containing particles with a particle diameter smaller than 0Awn.

The order in which the suspension is divided into two parts is not critical. The fine particles can be first separated from the coarse and medium particles, and then the remaining suspension can be divided into a fraction containing coarse particles and a fraction containing medium particles. However, it is generally preferred to first separate the coarse particles from the suspension.

Various types of separators (semi-9ators) can be used to separate coarse particles from the suspension. Seven of the factors to be considered in selecting the type of separator to be used are the erosive or abrasive effects of the slag particles.

For example, hydrocyclones can be seriously damaged. For this reason, the separation of the coarse particle-containing fraction from the suspension and the dewatering of this fraction is advantageously carried out using one or more sieving units.

In a preferred embodiment of the invention, a static sieve is used to effect the separation of relatively large amounts of water from the suspension and the separation of coarse particles, and then a vibrating sieve is used for the separation of residual water. However, as a result of this, the coarse particle-containing fraction is sufficiently dehydrated. The separated coarse particles are discharged together for further processing.

Afterwards a residual suspension containing medium and fine particles! Divide into two parts. For this purpose the suspension/
or a higher classification unit. Various classification units can be used advantageously. For example, a classification screw or a classification rake can be used. Also, a No-Idro classification unit or a conventional classification cone can be used. However, the separation of medium and fine particles is preferably carried out in a hydrocyclone of /''! or more. The erosive or abrasive effect of medium and fine particles is greater than that of coarse particles. Therefore, by providing a suitable protective lining on the inside surface of the hydrocyclone, the risk of damage to the hydrocyclone is further reduced.The hydrocyclone is a fairly economical device, since it is very This is because selective separation is performed, that is, only a relatively small amount of fine particles are mixed in both portions containing medium-sized slag particles.

The fraction containing medium particles is then dehydrated. For this purpose, various types of separators are used.
can be used to advantage. Suitable separators are dewatering sieve units (e.g. Foder Technique screens and Elliptex dehydrators; see also: L. S. Grubski, "Solid-liquids, 7) and Rations", Buttertooth Tins. , 7979, pp. 1 Otsu-j - 1 Otsu 7). Various types of filtration units and dewatering screens are also suitable.

Preferably, the coarse particle-containing fraction is dehydrated using a dehydrating lake/or larger dehydrating lake. This unit is the cheapest and most reliable.

During this dehydration treatment, separation of fine particles and medium particles mixed in the coarse particles is also carried out. The aqueous phase obtained here still contains small amounts of substantially fine slag particles, which are absorbed by the classification unit (in particular the hydrocyclone).
Preferably, it is recycled. This ensures that contaminant-free water can be released into the surrounding environment.

The particulate-containing fraction discharged from the classification unit is transferred to one or more settling basins.
) (This sedimentation tank is also called a “sedimentation tank”).
). The concentrate obtained is /-! It is best to pass it through a filter press of at least one filter press, where it can be further dehydrated.

The sedimentation rate of fine particles in the settling tank is low. This is because the particle size is very small. Particles of colloidal size will not precipitate at all.

Therefore, it is preferable to add a flocculant to the fraction containing fine particles. The flocculant may be added to the settling tank or at a location upstream thereof. Since a significant portion of the slag particles have already been separated from the suspension, relatively small additions of flocculant are sufficient. Suitable flocculants are various types of cationic and/or anionic polymers.

The water discharged from the settling tank, i.e. the overflow, is clear and the amount of slag particles in this water is f Opp
It is only less than m. This overflow can be discharged into surface water without worrying about environmental pollution. Also, at least a portion of this O-G-flow can be recycled to the various equipment used in the method and used as wash water and/or transport medium. The F solution of the filter press still contains a small amount of slag particles. Since it is desirable to separate this small amount of particles from the suspension (ie, F liquid), the liquid is preferably recycled to the settling tank.

Specific examples of the present invention will be described in detail with reference to the accompanying drawings. However, the invention is by no means limited to this specific example. The attached drawings are schematic diagrams, and the description of the compressor, valves, control device, etc. is omitted.

The aqueous suspension of slag particles is passed through a tube/stationary sieve! Pass it through. Here, the fraction containing coarse particles is separated and dehydrated. The coarse particles are passed through a gutter 3 to a vibrating screen j, where they are further dehydrated. The dehydrated coarse slag particles are discharged to the outside of the yarn by the gutter 7 and the conveyor bell 14. The water separated as described above contains medium particles and fine particles, and this water is sent from the static sieve 2 to the tube via tube ≠, and the water from the vibrating sieve j is sent to the tube via tube B. send to This water is then sent from the pipe via pipe 10 to Hydrosylon//, where medium particles and fine particles are separated from each other. A suspension containing substantially medium particles is discharged from said cyclone through pipes /, 2 and conveys this suspension via pipes /2 to a dewatering rake /≠. In this dewatering unit, medium particles are separated from the suspension and discharged out of the system via gutter 15 and conveyor belt/B. The aqueous suspension containing fine particles passes through pipe No. 7 to pipe 9f, and then passes through pipe IO to the hydrocyclone/
recirculate to /.

From the hydrocyclone //, an aqueous suspension containing fine slag particles is discharged via pipe /3. In tube /3 the flocculant is added to the suspension from the container, 25, via tube 2O. The suspension to which the flocculant has been added is introduced into the settling tank/9 via tube/♂. The concentrated suspension is piped from the bottom of the sedimentation tank. Pass through filter press 2 through 0. The dehydrated slag particles are discharged from the system through a pipe 23.

The F liquid in filter breath 22 is recirculated via tube, 2tl, and combined with the suspension in tube/3.

The overflow (clear water) from settling tank /9 is discharged through pipe 2/. A portion of this clarified water is sent through a pipe 27 to a vibrating sieve j, where it is used as washing water. The remaining clear water is discharged out of the system through pipe 2g.

Although not shown in this figure, fluctuations in the feed fluid supplied to the various continuously operating devices described above are known.
tion) or to serve as storage tanks for the feed liquid supplied to units operated in batch mode, the method of the invention uses a plurality of buffer tanks (buffer tanks) installed. It is also possible. Suitable locations for installing this buffer tank are upstream of the hydrocyclone, between the hydrocyclone and the settling tank, and between the settling tank and the filter breath.

Example The following experiment was conducted using the apparatus described in the attached drawings.

3 μg of water and slag particles/ through the pipe /
, 4' 3 g Kg/s.

The coarse slag particles obtained after separation on a static sieve λ were washed on a vibrating sieve with 11 tKv/S of water and soil from tube 27.

The resulting flow has a coarse slag particle size of 0.70,!
i'Kg/s and water 0.236Kg/s, which was discharged through gutter 7 and conveyor belt ♂ for subsequent treatment.

The suspensions passing through tube ≠ and tube 6, respectively, were combined in a tube, and inside the tube there was a water droplet of 0. Evening 9 Kv's and 0.73 Kg/a of slag particles passed through. Water 3.7 Kv/s and slag particles 0. / g
A stream containing gKms was passed through and this was added to the tube stream. After separation in the hydrocyclone// water 3. ♂7 Ki8 and slag 0. ≠30Kg
The stream containing //s is discharged via pipe 7.2 to the dewatering rake /4? where it is sent to the water 0. ／ ／ OK
Coarse slag particles containing 0.2≠2 Kv's were separated.

The flow in pipe /3 was composed of water 4t □, 411 Kms and fine slag particles o, tl-g♂Kg/s, but this flow, through pipe 21I-, contained water≠0Kg
/s and slag 0.027 Kms is added, and also via pipe 2, water 0.0/KV'
s and a stream containing flocculant 0,0002 Kv's 'e is also added, thus through the pipe/g, the drain j Kg
/s1 sung 0, 3; /'3; Kg/s and flocculant 0. The flow containing θ002 Kg/a is in the sedimentation tank/9
was supplied to. tube! Water ≠ 37Kg//s through 0, slag 0, j/! r Kis and flocculant 0,000
．． The flow consisting of 2 Kg/s is filter press, 2
It was supplied to No.

So solid o containing 0.330 Kg/s of moisture, +
gg, 2KThs were isolated. The p-liquid was recirculated via tube, 2≠.

Clear water tio, iot Kg+/s is piped from sedimentation tank/9, 2
It was discharged through /. A portion of this clear water is left≠Kg//
S was supplied to vibrating sieve j through tube-27. Therefore, 34,422 kg/s of clear water was discharged to the outside of the system through 2 g of pipe.

[Brief explanation of the drawing]

The accompanying drawings are schematic illustrations of equipment used in one embodiment of the method of the invention. /... Raw material suspension supply pipe; No... Stationary sieve: j...
Vibration sieve; g and /otsu... Conveyor belt: //...
・No Hydrocyclone;／≠・・・Dehydration rake：／
9... Sedimentation tank (pond); 22... Filter press:
2j...Flocculant storage tank.

Claims (9)

[Claims] (1) In a method for dewatering an aqueous suspension of slag particles, the suspension is divided into a plurality of mutually different fractions each containing coarse particles, medium particles, and fine particles, and these two fractions are separated separately. A dehydration method characterized by dehydration. (2) The coarse particle-containing fraction substantially contains particles with a diameter larger than
The method described in section 1). (3) Claims (1) or (2), wherein the fraction containing medium particles substantially contains particles with a diameter of 0.0-/mI. Method described. (4) The fine particle-containing fraction is substantially 0. The method according to any one of claims (1) to (3), which contains particles having a diameter smaller than θ6. (5) Any one of claims (1) to (4), characterized in that the coarse particle-containing fraction is separated from the suspension and dehydrated using/or more sieving units. The method described in. (6) Any one of claims (1) to (5), characterized in that the coarse particle-containing fraction is sequentially separated from the suspension and dehydrated using a static sieve and a vibrating sieve. The method described in. (7) Claims (1) to (6) characterized in that the operation of separating medium particles and fine particles from each other is carried out using/or more hydrocyclones.
The method described in any of the paragraphs. (8) According to any one of claims (1) to (7), characterized in that both portions containing medium particles are dehydrated with/or more dehydrating lakes. the method of. (9) Claim No. 7 characterized in that the aqueous phase is recycled from the dewatering rake to the hydrocyclone.
) or the method described in paragraph (8). (Claim (1)) characterized in that the fraction containing 11 fine particles is concentrated in 7 or more sedimentation tanks and/or dehydrated in 7 or more filter presses.
A method according to any of paragraph (9). 0]) The method according to any one of claims (1) to 01, characterized in that a flocculant is added to the fine particle-containing fraction. Claims (1) to (1υ) characterized in that the entire 0→F liquid is recirculated from the filter press to the settling tank.
The method described in any of the paragraphs.