GB1578551A

GB1578551A - Method and a device for continuously separating the solid phase from the liquid phase of a solid-liquid mixture

Info

Publication number: GB1578551A
Application number: GB20288/77A
Authority: GB
Original assignee: REIMAN D
Current assignee: REIMAN D
Priority date: 1976-05-14
Filing date: 1977-05-13
Publication date: 1980-11-05
Also published as: FR2350865B1; SE7705587L; SE436692B; DK210477A; DE2621349A1; FR2350865A1; DE2621349C2

Description

(54) A METHOD AND A DEVICE FOR CONTINUOUSLY SEPARATING THE SOLID PHASE FROM THE LIQUID PHASE OF A SOLID-LIQUID MIXTURE (71) I, DIETER REIMANN, of Erbschloe 42 a, 5600 Wuppertal 21, Federal Republic of Germany, a German Citizen, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to a method and a device for continuously separating the solid phase from the liquid phase of a solids liquid mixture, particularly a solids liquid mixture which is precipitated in the form of slurry in municipal or industrial effluent treatment plant, by means of centrifuging.

It is known that the solid phase may be separated with difficulty from the liquid phase of a solids liquid mixture by means of centrifuging, particularly a solids liquid mixture in which the solids are present in a very finely dispersed form. In order to improve the process of separation, a flocculation agent was previously added to the solids liquid mixture. Agglomeration of the solid particles present in the solids liquid mixture should be achieved with the aid of this flocculation agent; the solid particles move through the liquid to the outside under the action of the centrifugal force, and they may then be separated easily from the liquid. As practice has shown however satisfactory results cannot be achieved with this method, particularly when the solids are present in a particularly fine suspension in the liquid and the flocculation agent is not fully effective.

The invention seeks to create a method which makes effective separation of the solid phase from the liquid phase of the solids liquid mixture possible in which the solids are present in a fine dispersion.

According to a first aspect of the invention, there is provided a method of separating solids from a liquid in a solids liquid mixture comprising feeding the mixture into a rotary drum centrifuge, adding a gaseous medium to the solids liquid mixture in the centrifuge, centrifuging the mixture and floating off the solids.

A flotation reagent may be added to the solids liquid mixture as well as the gaseous medium.

According to a second aspect of the invention, there is provided apparatus for separating solids from a liquid in a solids liquid mixture comprising a rotary drum centrifuge provided with an inlet for the solids liquid mixture,,an outlet for solids in the region of the intended liquid level in the centrifuge and means for supplying a gaseous medium into the solids liquid mixture in the centrifuge.

Almost all of the solid particles present in the liquid may be separated with the aid of the gaseous medium or the flotation reagent and gaseous medium and may be floated in a direction opposite to that of the centrifugal force acting on the liquid and separated from the liquid. By appropriate choice of the gaseous medium and the flotation reagent where present, the most effective media for flotative separation of the solids from the liquid may be used and thus optimum separation may be achieved.

In advantageous refinement of the invention an amino acid may be supplied to the solids liquid mixture as a flotation reagent and compressed air may be supplied thereto as a gaseous medium. These mediums are particularly suitable for separating solid particles, which are present in biological and industrial surplus slurries, from the liquid.

The invention will now be described in greater detail, by way of example, with reference to the drawings, the single figure of which shows, schematically, one embodiment of the invention.

This device for carrying out the method in accordance with the invention comprises a solid drum screw centrifuge 1 having a supply line 4 arranged on one side in the hollow shaft 2 of the helical conveyor 3, said supply line 4 supplying the liquid-solids mixture and the flotation reagent. The helical conveyor 3 comprises a substantially tubular hollow body 5 which is provided on the outside with helical flights 6. Opcnings 7 distributed evenly over the circumference are arranged in the region in which the supply line 4 opens into the sleeve of the hollow body 5. The hollow body 5 is also provided with a separating wall 8 in this region. Moreover, the helical conveyor 3 is mounted at both sides in a hollow shaft 9 of the centrifuge drum so as to be capable of rotation.The hollow shafts 9 of the centrifuge drum are also mounted so as to be capable of rotation in bearings 10. Openings 11 are provided on the side opposite the mixture feed side for the purpose of extracting the solids and openings 12 are provided in the end wall for the purpose of extracting the liquid.

On the outside of the hollow shaft 9 of the centrifuge drum is located a two part annular manifold 13 the outer half of which 14 is attached in fixed manner to a compressed air line 15, while the inner half 16 is in open connection with pipes 18 distributed evenly over the circumference on the inner wall of the centrifuge drum via branch lincs 17 passing radially outwards; the said pipes 18 are provided with openings which are not shown in the drawings and which are nozzle shaped and point inwards. A seal 19 is arranged between the fixed annular part 14 and the rotating part 16 through which compressed air may be prevented from escaping out of this annular manifold.

In operation of this solid sleeve screw centrifuge, the solids-liquid mixture is introduced into the centrifuge drum together with the flotation reagent (arrow 4') through the supply line 4 and the openings 7. The centrifuge drum and the helical conveyor 3 are driven at diffcrcnt speeds. At the same time the pipes 18 arranged on the inner wall of the centrifuge drum and provided with nozzle shaped openings are supplied with compressed air via the line 15, the annular line 13 and the branch lincs 17.The fine solid particles located in the liquid are floated radially inwardly along with the bubbles of air escaping from the nozzle shaped openings of the pipes 18. Adhcsion of the bubbles of air to the solid particles is enhanced effcctively and in a very advantageous manner by the flotation reagent added to the solids-liquid mix turc. The solid particles floating radially inwards cause an enrichment of the mixture more and more towards the end where the solids are extracted. so that in the end region of the flights of the screw conveyor 3 they are easily caught hold of and are removed or extracted to the outside through the open ings 11 in the direction of the arrow 20, separate from the liquid. The liquid relcased from the solids flows out of the centrifuge drum through the openings 12.The openings 12 arranged in the end wall of the centrifuge drum at its edge also make it possible, in a very advantageous manner, to completely empty the centrifuge drum if necessary of the feed mixture, without the otherwise disadvantageous out of balance vibration of the centrifuge being the result. If the discharge of liquid through the openings 12 should have a disadvantageous effect on flotation because of too great a suction being created thereby in the end region then the liquid may also be removed to the outside with the aid of a line attached to the openings 12 and passed in the direction of arrow 21 radially inwardly to approximately the level of the line separation between the liquid and the solid particles and then radially outwardly again.It is sufficient, for the purpose of extracting the solids from the centrifuge drum, for the flights of the screw conveyor 3 to be constructed so that they submerge only so far into the solidsliquid mixture that the floating solids may be caught hold of thereby. The radial dimension of ths web of the flights may therefore be kept very low. With the aid of this type of solid sleeve screw centrifuge, as shown in the drawings, the method in accordance with the invention may be carried out relatively simply and economically with optimum separation of the solid phase from the liquid phase of a solids liquid mixture, particularly a solids-liquid mixture in which the difference in specific gravity is particularly small bet ween the solids and the liquid.In many cases effective separation of the solids from the liquid even without flotation reagent may be achieved, i.e. with the aid only of gaseous medium. Thus a preliminary test only is required. Flotative separation of the solid phase from the liquid phase only with the aid of gaseous medium can be of great importance if, the solids to be separated from the liquid, are materials which are in fact food stuffs or added to food stuffs.

WHAT I CLAIM IS: 1. A method of separating solids from a liquid in a solids liquid mixture comprising feeding the mixture into a rotary drum centrifuge, adding a gaseous medium to the solids liquid mixture in the centrifuge, centrifuging the mixture and floating off the solids.

2. A method according to claim 1, wherein a flotation reagent is added to the solids liquid mixture as well as the gaseous medium.

3. A method according to claim 2, wherein an amino acid is supplied to the solids liquid mixture as a flotation reagent and compressed air is supplied thereto as a gaseous medium.

4. Apparatus for separating solids from a liquid in a solids liquid mixture comprising a rotary drum centrifuge provided with an inlet for the solids liquid mixture, an outlet for

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. line 4 supplying the liquid-solids mixture and the flotation reagent. The helical conveyor 3 comprises a substantially tubular hollow body 5 which is provided on the outside with helical flights 6. Opcnings 7 distributed evenly over the circumference are arranged in the region in which the supply line 4 opens into the sleeve of the hollow body 5. The hollow body 5 is also provided with a separating wall 8 in this region. Moreover, the helical conveyor 3 is mounted at both sides in a hollow shaft 9 of the centrifuge drum so as to be capable of rotation. The hollow shafts 9 of the centrifuge drum are also mounted so as to be capable of rotation in bearings 10.Openings 11 are provided on the side opposite the mixture feed side for the purpose of extracting the solids and openings 12 are provided in the end wall for the purpose of extracting the liquid. On the outside of the hollow shaft 9 of the centrifuge drum is located a two part annular manifold 13 the outer half of which 14 is attached in fixed manner to a compressed air line 15, while the inner half 16 is in open connection with pipes 18 distributed evenly over the circumference on the inner wall of the centrifuge drum via branch lincs 17 passing radially outwards; the said pipes 18 are provided with openings which are not shown in the drawings and which are nozzle shaped and point inwards. A seal 19 is arranged between the fixed annular part 14 and the rotating part 16 through which compressed air may be prevented from escaping out of this annular manifold. In operation of this solid sleeve screw centrifuge, the solids-liquid mixture is introduced into the centrifuge drum together with the flotation reagent (arrow 4') through the supply line 4 and the openings 7. The centrifuge drum and the helical conveyor 3 are driven at diffcrcnt speeds. At the same time the pipes 18 arranged on the inner wall of the centrifuge drum and provided with nozzle shaped openings are supplied with compressed air via the line 15, the annular line 13 and the branch lincs 17.The fine solid particles located in the liquid are floated radially inwardly along with the bubbles of air escaping from the nozzle shaped openings of the pipes 18. Adhcsion of the bubbles of air to the solid particles is enhanced effcctively and in a very advantageous manner by the flotation reagent added to the solids-liquid mix turc. The solid particles floating radially inwards cause an enrichment of the mixture more and more towards the end where the solids are extracted. so that in the end region of the flights of the screw conveyor 3 they are easily caught hold of and are removed or extracted to the outside through the open ings 11 in the direction of the arrow 20, separate from the liquid. The liquid relcased from the solids flows out of the centrifuge drum through the openings 12.The openings 12 arranged in the end wall of the centrifuge drum at its edge also make it possible, in a very advantageous manner, to completely empty the centrifuge drum if necessary of the feed mixture, without the otherwise disadvantageous out of balance vibration of the centrifuge being the result. If the discharge of liquid through the openings 12 should have a disadvantageous effect on flotation because of too great a suction being created thereby in the end region then the liquid may also be removed to the outside with the aid of a line attached to the openings 12 and passed in the direction of arrow 21 radially inwardly to approximately the level of the line separation between the liquid and the solid particles and then radially outwardly again.It is sufficient, for the purpose of extracting the solids from the centrifuge drum, for the flights of the screw conveyor 3 to be constructed so that they submerge only so far into the solidsliquid mixture that the floating solids may be caught hold of thereby. The radial dimension of ths web of the flights may therefore be kept very low. With the aid of this type of solid sleeve screw centrifuge, as shown in the drawings, the method in accordance with the invention may be carried out relatively simply and economically with optimum separation of the solid phase from the liquid phase of a solids liquid mixture, particularly a solids-liquid mixture in which the difference in specific gravity is particularly small bet ween the solids and the liquid.In many cases effective separation of the solids from the liquid even without flotation reagent may be achieved, i.e. with the aid only of gaseous medium. Thus a preliminary test only is required. Flotative separation of the solid phase from the liquid phase only with the aid of gaseous medium can be of great importance if, the solids to be separated from the liquid, are materials which are in fact food stuffs or added to food stuffs. WHAT I CLAIM IS:

1. A method of separating solids from a liquid in a solids liquid mixture comprising feeding the mixture into a rotary drum centrifuge, adding a gaseous medium to the solids liquid mixture in the centrifuge, centrifuging the mixture and floating off the solids.

solids in the region of the intended liquid level in the centrifuge and means for supplying a gaseous medium into the solids liquid mixture in the centrifuge.

5. Apparatus as claimed in claim 4, wherein the centrifuge comprises a solid drum screw centrifuge having a supply line arranged on one side in a hollow shaft of the screw conveyor, said line being provided for feeding the liquid solids mixture and a flotation reagent inho the centrifuge drum, having outlets arranged separately on the other side for the discharge of separated solids and liquid and having a two part annular manifold arranged around the hollow shaft, for the purpose of supplying the gaseous medium, the manifold having attached branch lines, which are in open connection with pipes distributed evenly over the circumference on the inner wall of the centrifuge drum, these pipes being provided with nozzle shaped openings pointing inwardly.

6. Apparatus as claimed in claim 5, wherein the flights of the screw conveyor are constructed so that they dip only partially into the solids-liquid mixture.

7. Apparatus as claimed in claim 5 or 6, wherein several openings distributed evenly and circumferentially are provided in the end wall of the centrifuge drum, for the purpose of extracting the separated liquid.

8. A method of separating solids from a liquid in a solids-liquid mixture as claimed in claim 6 and substantially as described herein.

9. Apparatus for separating solids from a liquid in a solid liquid mixture substantially as described herein with reference to the drawings. '.