DE102020109403A1 - Process for removing very fine particles from waste water streams - Google Patents

Abstract

The invention relates to a novel method for removing very fine particles from waste water streams during the treatment of mineral substances by means of centrifugal separators in conjunction with a linear oscillator arrangement.

Description

The invention relates to a method for removing very fine particles from waste water streams during the treatment of mineral substances by means of centrifugal separators according to claim 1.

From the US 7 514 011 B2 a system for separating solids from a liquid stream is known. The system comprises a first separation device which is fixed to a container. The container comprises a settling chamber and a baffle module, the settling chamber receiving the liquid from the first separation device. The separation device comprises a linear vibrator. Another separation device works together with a combination of a cyclone separator and a further linear vibrator.

In the case of the transportable apparatus for separating and recovering fine particles according to US 2017/151573 A1 there is an inlet cyclone separator attached to a transportable frame. In addition, the device comprises a sieve device which removes larger particles from the underflow stream of the cyclone.

the US 2019/351429 A1 shows a device for washing and sorting sand or sand-containing materials, comprising a first vibrating screen with a cover which is provided for receiving a feed material. Oversized material runs over the deck of a first vibrating screen to be collected. Undersize material and water are collected in a pump sump and then enter a hydrocyclone. Another vibrating screen is connected to the underflow of the cyclone, with the overflow reaching a settling tank. A water reservoir collects the water overflowing from the settling tank, while sludge residues are collected and removed at the bottom of the tank. Vibrating screens provided are used to wash and clean the sand material.

It is therefore known from the prior art to clean and fractionate materials containing sand. Wastewater gets into a thickener in the usual way or is led into a settling pond. In particular, if for various, in particular environmental reasons, no flocculation aids may be used, there is a risk that sedimentation ponds will silt up very quickly.

For this reason, as much as possible of fine sand, silt and clay particles should be removed from a waste water stream, for example from a company that processes mineral substances.

To this extent, it is also known to provide a cyclone stage with a separating cut d ₅₀ in the waste water flow based on particles with a density of 2650 kg / m ³ of approximately 40 μm. Cyclones with a diameter between 150 mm and 300 mm are used here.

The separating cut d ₅₀ is defined as the grain size that can reach both the underflow and the overflow of a separator with a probability of 50%. Particles that are finer than the specified separating cut mainly end up in the overflow. Particles that are coarser than the specified separating cut mostly end up in the underflow.

According to the state of the art, however, the problem of fine particles remains, that is to say portions with grain sizes 8 to approx. 10 μm. So far, conventional means have not been successful in detaching such fine fractions from a waste water stream or a suspension and thickening or dewatering them in a satisfactory manner.

From the above, it is therefore the object of the invention to provide a further developed method for removing very fine particles from waste water streams in the treatment of mineral substances by means of centrifugal separators, which meets the technical requirements and which can be implemented with a manageable technical-technological effort.

The object of the invention is achieved by a method as defined in claim 1, the subclaims representing at least useful embodiments and developments.

The method according to the invention for removing very fine particles from wastewater streams in the treatment of mineral substances initially relies on centrifugal separators known per se in connection with a linear oscillator.

On the process side, the wastewater to be treated, containing fine particles of essentially <250 μm grain size, is first collected or discharged in a first pump sump.

The contents from the first container are then passed to a first centrifugal separator for classification with a separation cut d ₅₀ of substantially 8th - 10 µm grain size conveyed.

The underflow product from the first centrifugal separator is transferred to a second sump tank.

The overflow product from the first centrifugal separator reaches a known thickener or is placed in a settling pond.

The content from the second container is conveyed to a second centrifugal separator for thickening, whereby the underflow product reaches a linear oscillator to complete the thickening by means of residual dewatering.

The overflow product from the second centrifugal separator is returned to the first container.

In addition, the linear oscillator cycle is introduced into the second container.

In a further development of the invention, a partial flow of the overflow from the second centrifugal separator is fed into the second container to control the pump sump.

Also in a further development and optionally, a partial flow of the overflow of the first centrifugal separator can be fed into the first container to control the pump sump.

This reliably prevents the pump belonging to the centrifugal separator in question from running dry.

The linear oscillator used has wedge wire screens and electric motor drives to generate unbalance vibrations, whereby according to the invention the unbalance frequency can optionally be set or regulated in order to optimize the dwell time of the particles on the linear oscillator so that there is a sufficient possibility of water release.

The product obtained on the linear vibrator is therefore a fine sand fraction with a grain size ≥ 8 µm, which, if necessary, can be subjected to further dewatering.

The invention is to be explained in more detail below with reference to a figure which represents a system scheme.

The waste water flow containing very fine particles, for example from a company for the treatment of mineral substances, reaches a first container B01 . In this regard, the wastewater has particles with a grain size of ≤ 250 µm.

Via a pump P01 at the pump sump of the tank B01 is connected, the wastewater enters a first centrifugal separator F01 .

The overflow of the first centrifugal separator F01 containing a fraction of particles is sent to a settling pond or thickener.

A partial flow can be used to regulate the pump sump.

The corresponding control unit with float and valve is included RE1 marked in the scheme.

The underflow of the first centrifugal separator F01 enters a second container B02 with corresponding pump sump and connected pump P02 .

By means of the pump P02 becomes the second centrifugal separator F02 loaded.

With the help of the second centrifugal separator F02 a further thickening of the abandoned material takes place.

The underflow of the second centrifugal separator F02 is on the linear transducer F03 given up.

The linear oscillator F03 can be equipped with a frequency converter control in order to optimize the vibration behavior of the wedge wire screen implemented here.

The overflow of the second centrifugal separator stage F02 , which still contains fines under section d ₅₀ , would go to the first container P01 returned, similar to the principle of countercurrent washing.

A partial flow of the overflow is in turn used to increase the level of the upstream pump sump in the tank B02 to regulate by means of the control unit RE2.

In the second container B02 The entire sieve penetration of the linear oscillator also arrives F03 back to the stage with the second centrifugal separator F02 to be able to go through again.

The starting product of the processing is a fine sand fraction of> 8 µm grain size and can be transported away by means of a conveyor belt or, if necessary, further dewatered either statically or mechanically. For this purpose, units such as belt filters or flat filters are suitable for dewatering.

According to the exemplary embodiment, due to the very high fine fraction in the waste water flow, the separating cut is significantly deeper than in the prior art. In this respect, the Wastewater flow was initially classified with 50 mm centrifugal separators in order to achieve a separating cut d ₅₀ with a grain size of approx. 8-10 µm. Then the underflow, i.e. the fine sand fraction, is thickened with a further centrifugal separator stage so that it can finally be dewatered with the aid of a linear oscillator. It has surprisingly been shown that such a fine fraction can be dewatered with a linear vibrator or a related screen arrangement.

The one at the bottom of the second centrifugal separator F02 The available mass is thickened to such an extent that there is sufficient dwell time on the linear oscillator, in particular when the unbalance oscillation generation is controlled in a manner adapted to the properties of the material to be dried.

The method according to the invention can therefore in a meaningful way supplement known systems for the treatment of waste water containing particles, and help prevent the silting up of sedimentation ponds that would otherwise occur.

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• US 7514011 B2 [0002]
• US 2017151573 A1 [0003]
• US 2019351429 A1 [0004]

Claims (5)

A method for removing very fine particles from waste water streams during the treatment of mineral substances by means of centrifugal separators, comprising the following steps: - collecting the waste water to be treated (AW), containing very fine particles of essentially ≤ 250 μm grain size, in a first pump sump container (B01); - Conveying the contents from the first container (B01) to a first centrifugal separator (F01) for classification with a separating cut (d ₅₀ ) of essentially 8-10 µm grain size; - Directing the underflow product from the first centrifugal separator (F01) into a second pump sump container (B02); - Guiding the overflow product from the first centrifugal separator (F01) to a thickener or to a settling pond (AT); - Conveying the contents from the second container (B02) to a second centrifugal separator (F02) for thickening, whereby the underflow product reaches a linear oscillator (F03) for perfecting the thickening by means of residual drainage; - Returning the overflow product from the second centrifugal separator (F02) into the first container (B01); and - introducing the linear oscillator passage into the second container (B02). Procedure according to Claim 1 , characterized in that a partial flow of the overflow from the second centrifugal separator (F02) is fed into the second container (B02) by means of a control unit (RE2) to control the pump sump. Procedure according to Claim 1 and / or 2, characterized in that a partial flow of the overflow from the first centrifugal separator (F01) is fed into the first container (B01) by means of a control unit (RE1) to control the pump sump. Method according to one of the preceding claims, characterized in that the linear oscillator (F03) has wedge wire screens and electromotive drives for generating unbalance vibrations, the unbalance frequency being regulated. Method according to one of the preceding claims, characterized in that the product obtained on the linear vibrator (F03) is a fine sand fraction (FS) with a grain size> 8 µm, which is subjected to further dewatering if necessary.

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