DE3327033A1 - Process and apparatus for the sedimenting separation of substances of different specific gravity - Google Patents

Abstract

With the aid of tangentially adjusted agitators, producing both thrust and spin, arranged in the vicinity of the bottom of a cylindrical vessel, a flow is produced in the vessel, which rotates both about the vertical axis of the vessel and in a toroidal manner therein. Material of relatively high specific gravity is deposited in the region of the centre of the vessel bottom. From there it can be discharged downwards. The present invention is suitable in particular for the treatment of waste waters having a high level of organic pollutants.

Description

Method and device for sedi-

menting separation of substances of different specific Weight The present invention relates to a method and an apparatus for sedimenting separation of substances of different specific gravity from liquids.

Substances in particular of slightly different specific Weight is known to be difficult to separate. The difficulties that arise are caused in particular by the mechanical effect on the medium in which the particles are suspended because this mechanical action causes a high level of backmixing caused.

The present invention has set itself the task of reducing the separation effect to improve with little constructive and equipment-wise expenditure.

According to the invention, this object is achieved in one with liquid filled container with a circular cross-section.

This is done with the help of agitators arranged near the bottom of the container at the same time a tangentially acting thrust and a twist are generated, whereby a tubular circulating flow is created. This rotates around the vertical axis of the Container, as well as around the tube axis running radially around the vertical axis.

In this way one emerges constantly in oneself and at the same time essentially laminar flow rotating around its central axis.

This is preferably done so that the descending part of the container wall is assigned and the flow rises in the area around the central axis of the container.

The flow leads the particles present in the container in a double Circulation, with the relatively heavier particles in the middle of the container bottom be deposited.

In the middle area of the bath level, on the other hand, a flow-calmed one forms and thus a zone with little sediment from which liquid can be drawn off, in particular without disturbing the flow conditions within the container.

The present invention has also set itself the task of an improved process for the anaerobic biodegradation of activated sludge to create, with which it is possible to remove the inert substances from the activated sludge that arise during the degradation to separate.

This can be done using the following procedure. In one like above The reactor described is predominantly homogeneously mixed anaerobic activated sludge / water suspension filled.

As explained above, a hose flow is generated and inert and specifically heavier ones that result from biological degradation Material is deposited and discharged in the middle of the floor, whereas the sludge is is constantly carried in the cycle.

An annular zone is formed around the center of the bath level greatly reduced concentration of anaerobic activated sludge.

From this, liquid can be discharged while largely avoiding turbulence subtracted from. Raw sewage and separated from the aforementioned liquid Recirculated activated sludge is fed into the active area of the agitator elements.

In this way, active biomass becomes active in an anaerobic process enriched and degradable ingredients almost completely degraded by fermentation, without removing them when the inert substances are withdrawn.

The agitators and the thrust generated by them are around 8 to 200 tangentially employed, the axes of the organs being aligned horizontally. Depending on the container size, 3 or more agitators are symmetrical to each other around the Distributed perimeter of the reactor. They are installed near the nantel and promote from this way.

That withdrawn from the annular zone of reduced concentration Mixture of wastewater / bio sludge is separated into wastewater and return sludge with the help of separators separated.

The wastewater is drained and the sludge is returned as mentioned above.

This type of process management also makes it possible to concentrate and discharge biosludge free of inert substances (downstream behind the separators), to use it elsewhere, e.g. as a fertilizer.

The device according to the invention consists of a container with a round Cross section, an agitator and supply and discharge lines.

The agitator is designed in such a way that it is tubular in the container The flow arises both around the hose center axis and around the vertical axis of the container is running.

The flow is essentially laminar.

In the middle floor area is a sediment drain and below the Bad mirror, in the area of a concentric that forms there during operation Discharge lines are arranged in an annular area with a low concentration.

According to one embodiment, the agitator consists of at least three propellers arranged symmetrically around the circumference near the bottom of the container. Propellers and their angle of attack have proven to be particularly suitable remains constant across the leaves, which means that they are not twisted.

Such propellers generate the greatest thrust in the area of the blade ends and cause a braid-like, pear-shaped flow characteristic.

The axes of the thrust generated by the propellers intersect with the radius of the container in the container wall at an angle of 8 to 200. The dimension of the angle depends on the diameter of the container, with the angle decreases with increasing diameter.

Instead of propellers, injectors can also be used optionally have adjustable guide vanes at the injector outlet. With these a braid-like flow can also be generated.

The raw sewage can be used as the propellant for this at least in part can be used.

In both cases, however, the axis of the impeller is parallel to the bottom align and maintain a distance from the floor that is 5 to 20% of the fill level of the Corresponds to the container.

As described above, the present invention is particularly useful Way to perform anaerobic processes with it.

Anaerobic procedures are mainly used for the stabilization of the Sludge used in the field of wastewater treatment. Increasingly, organic too heavily polluted wastewater, especially from the food industry, by anaerobic Procedures dealt with.

In the fermentation or digestion of organic matter in dispersed or In the dissolved form, the bacterially degradable substances are strictly excluded from atmospheric oxygen mainly converted into carbon dioxide, methane and bacterial mass. The educated Bacterial biomass is relative to aerobic wastewater treatment methods on the COD breakdown only approx. 10%.

The organic substances are fundamentally different by 3 to 4 Groups of bacteria metabolized in a breakdown chain.

The first two groups hydrolyze the different organic ones Connections to simpler products such as organic acids, alcohols, hydrogen and carbon dioxide. Their pH optimum is in the weakly acidic range. Through the Third group of bacteria become alcohol, acids and mainly acetic acid, carbon dioxide and hydrogen reacted by the methanogenic bacteria as a fourth group finally converted to methane and carbon dioxide. the the last two groups of bacteria have their optimum pH value in the weakly alkaline Area.

The different pH value optima have led to, among other things, for certain substrates suitable for this use the anaerobic process as a two-stage process to realize, with the reactions of the 2nd stage in the weakly alkaline range be guided.

For the majority of applications of the anaerobic procedure this will be One-step process selected, the pH being in the range 6.8 to 8.0.

In practice, the population density of the bacterial biomass is determined by the auxiliary variable of the loss on ignition of the solid suspended in the anaerobic fermenter judged. In stationary anaerobic fermenters, the proportion of bacterial mass is just over half of the volatiles. The residue on ignition of the im anaerobic digester denotes suspended solids inorganic, for the anaerobic process not useful material.

In incorporated, communal digestion towers, the loss on ignition is of digested sludge 50-70%.

In the anaerobic treatment of organic substances dissolved in wastewater Depending on their concentration, substances become inorganic waste water constituents due to the special environmental conditions in the anaerobic process (single-stage reactor as well as methane reactor in the two-stage process) partially to insoluble compounds failed.

The present invention is explained in more detail with the aid of the accompanying figures explained.

Fig. 1 shows the container in section and plan view; Fig. 2 shows the resulting flow conditions in section and in plan view the sediment deposition; Fig. 3 shows the integration into an anaerobic wastewater treatment plant as a bioreactor.

Figure 1 In the container 1 agitator elements 5 are arranged near the bottom, the in the present case are shown as a propeller. These agitators are located close to the ground, at around 5 to 20% of the filling level.

The supply lines 2 open into the area of the propellers.

The axes (M) of the thrust generated by the agitators intersect in the container wall at 8 with the radius of the container at an angle 84 ß to # 20C. In the area in the middle of the floor there is a sediment outlet 10.

Discharge lines go from the bath surface or just below it 4 from. The lines themselves can also be laid upwards.

With this device two-substance suspensions can be separated.

However, it is particularly advantageous to use it as a bioreactor.

Raw sewage is fed into reactor 1 through pipes 2, A mixture of waste water / organic sludge is drawn off via the lines 4 and via the line 14 concentrated, recirculated organic sludge fed in.

The resulting from anaerobic degradation leave via line 13 Inert substances enter the reactor and, via 3, the biogas (methane) produced.

Figure 2 Figure 2 shows the principle on which the present Invention is based. With the help of the agitator, a circumferential, tubular Flow 15 generated, preferably in the wall area of the container the descending Branch is to be provided.

Sinking particles are caught in the flow in the bottom area and moved to the middle and upward to recirculate back into the descending branch to get. By largely avoiding eddies, the specifically heavier ones become Particles backmixing free from a mean induced circular flow 16 detected and due to the "teacup effect" placed in the middle of the floor, from which it is deducted can be. Lighter particles remain in the flow.

The mean flow 16 generated at the same time has an upward one directional component, which is, however, less than the descending speed of the Sediments. With the help of this and the hose flow 15 is in the bath level area a calmed mud- and especially sedimentarir #, circulating ring-shaped Zone generated from which one can hardly disturb the stationary conditions without disturbing specifically lighter component containing liquid upwards, or as in Figure 1 shown, can pull sloping downwards.

The sediment that collects on the bottom forms one above the flue 10 conical dune 17, the diameter of which also depends on the energy input by the agitator elements depends.

With the help of the 7r energy input of the agitator and the generated The conditions in the reactor can largely change the speed of the circulating flow be influenced, whereby the hose diameter and the depth of the annular flow 12 can be adapted to existing requirements with regard to the filling level and the content can.

FIG. 3 FIG. 3 shows the use of the present invention as a bioreactor for anaerobic fermentation.

In the case of anaerobic degradation of wastewater, it is desirable once Concentrate degradable sludge and on the other hand only the resulting sludge discharging inert, essentially inorganic substances that are no longer degradable, what succeeds with the present invention for the first time, whereby the yield of biogas can be increased significantly.

Fermented raw sewage is placed in container 1 and, as above described, set in motion.

A mixture of sludge and water is drawn off via the lines 4, which contains little or no inert material and supplied to separators 18. In The sludge is then concentrated and anaerobically treated wastewater is drained away 19, and thickened return sludge via line 14 into the effective area the agitator 5 returned to the reactor.

Raw sewage is also pumped into the agitator area and diluted the return sludge entered at the same time.

Biogas is drawn off at the top of the reactor.

It depends on the task at hand, i.e. on the type of sludge It is easily possible to use the process intermittently, continuously or batchwise perform.

The following implementation examples demonstrate specific applications and the desired technical progress.

1. Concentration of plastic granulates from a water / granulate mixture on the floor in the center of the container, test facility 1.1 container diameter D = 1,000 mm Filling height H = 0.57 D angle of attack ß = 100 4 propeller stirrers on the circumference, around 900 each offset, installation height h = 0.123 H, installation position horizontal circumferential speed u = 6.25 m / s granulate: PVC grains diameter d = 3 mm spec. Weight # t = 1.1 kg / l Concentration in the center of the container in the area d # 0.2 D.

1.2 Container diameter D = 1,400 mm filling height H = 0.4 D angle of attack B = 180 3 propellers on the circumference, each offset by 1200, installation height h = 0.16 H, installation position horizontal, circumferential speed u = 4.0 / 5.0 / 6.25 m / s Granulate: plastic with Diameter d 0.1 - 0.3 mm spec. Weight t = 1.018 kg / l concentration in the center of the container in the range d = 0.24 to 0.2 DA, with an increase in the energy input it decreases Diameter d.

2. Concentration of solids (calcium carbonate) from a mixture - Calcium carbonate / active biomass (anaerobic) / water on the bottom in the container center with simultaneous formation of a zone of reduced solids concentration in the Area of the liquid level, test facility, container diameter D = 1,400 mm Filling height H = 0.42 D angle of attack B = 180 3 propellers on the circumference, each offset by 1200, Installation height h = 0.15 H Installation position horizontal Circumferential speed u = 5.0 m / s 2.1 Initial solids content in the homogeneously mixed reactor: FG = 16 g / l (geometry, see above).

Solids content in the biologically active reactor volume FG = 16 g / l Solids content of the specific heavier fraction on the bottom in the center of the container FG = 70 g / l (predominantly inert substance).

Solids content in the circular clear zone between 0.1 and 0.5 container diameter FG = 1.6 g / l oxygen content against 0.

(FG = solids content) 2.2 Starting solids content in the homogeneously mixed reactor: FG = 32 g / l solids content in the biologically active Reactor volume FG = 32 g / l solids content of the specifically heavier fraction am Bottom in the center of the container FG = 148 g / l (predominantly inert substance) solids content in the circular clear zone FG = 11 g / l proportion of inert substances towards 0 (geometry w.o.) The layer thickness of the clear zone is approx. 0.034 x filling level (at the maximum).

In all cases a tubular circulating flow developed, that of the observed sediment accumulation in the middle area of the container bottom led.

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Claims (10)

Method for the sedimentation separation of substances different specific gravity, in one filled with a liquid Container with a circular cross-section, characterized in that one uses by tangentially set, close to the ground, causing thrust and twist Agitators a tubular, both around the vertical axis of the container as well essentially laminar rotating around the circular central axis of the tube Flow is generated and settling in the area of the center of the container bottom, specifically, heavier goods are withdrawn to untf. 2. The method according to claim 1, characterized in that for implementation a simultaneous anaerobic biological treatment of the containers with predominantly homogeneously mixed anaerobic activated sludge / water suspension is filled, wherein inert, essentially inorganic material is withdrawn from the soil, with the help of from in the area of the suspension level in a forming annular zone strongly reduced concentration of anaerobic activated sludge ending exhaust devices Liquid is withdrawn and recirculated while largely avoiding turbulence Feeds sludge and raw sewage into the area of activity of the agitator elements. 3. The method according to claim 1 - 2, characterized in that one with three or more agitators at an angle B of about 8 to 200 between the thrust axis of the agitator and the container radius intersecting with this in the jacket acts on the contents of the container, the agitator being arranged near the jacket and promotes away from it. 4. The method according to claim 1-3, characterized in that the from The waste water / bio sludge mixture withdrawn from the zone of reduced concentration in separators separated into wastewater and return sludge, the wastewater discharged and the return sludge is fed into the container in the area of action of the agitator. 5. Device for carrying out the method according to claim 1 - 4, consisting of a round container with an agitator, supply and discharge lines, thereby characterized in that the agitator (5) is designed such that in the container (1) one tubular, both around the tube center axis (6) and around the vertical axis (7) of the container (1) a circulating, essentially laminar flow can be generated, that in the middle floor area a sediment outlet (10) and in the area of the bath level (11) from a concentric annular surface (12) of low concentration that forms there are arranged on sediment, extraction lines (4). 6. Apparatus according to claim 5, characterized in that the agitator of at least three agitating elements arranged near the container base (9) and the wall (5) consists, the thrust axes with the container radius in the shell Cut at an angle of 8-200. 7. Apparatus according to claim 5-6, characterized in that as Stirrer elements injectors with optionally adjustable guide vanes are. 8. Apparatus according to claim 7, characterized in that the propellant raw sewage is used at least in part. 9. Apparatus according to claim 5-8, characterized in that the The agitator axis is at a distance from the container bottom which is 5 to 20% of the filling level is equivalent to. 10. Apparatus according to claim 5, 6 and 9, characterized in that that propeller stirrers are used as stirring elements.