WO2005058451A1

WO2005058451A1 - Method for mixing and subsequently separating a multiphase fluid and an arrangement for carrying out said method

Info

Publication number: WO2005058451A1
Application number: PCT/EP2004/014231
Authority: WO
Inventors: Martin Armbruster
Original assignee: Hydrograv Gmbh
Priority date: 2003-12-16
Filing date: 2004-12-14
Publication date: 2005-06-30
Also published as: EP1694418A1

Abstract

The invention relates to a method for mixing a multiphase fluid in a mixing reactor and subsequently separating different heavy phases in a reservoir usable at least intermittently in the form of a sedimentation tank and for returning the separated phases in said mixing reactor. In order to increase the load of the sedimentation tank, said invention is characterised in that a volume flow which intermittently comes from the sedimentation tank or from a return line is run towards the inlet flow of the sedimentation tank through a short flow path. The inventive arrangement for carrying out said method comprises a mixing reactor (2) and a sedimentation tank (6) arranged in such a way that the volume flow coming from the sedimentation tank (6) or from the return line (9) is guided to the inlet flow of the sedimentation tank (6) through a short flow path.

Description

Process for mixing and then separating a multi-phase fluid and plant for carrying out the process

description

The invention relates to a method for mixing a multi-phase fluid in at least one flow reactor, subsequent separation of phases of different weights in at least one sedimentation tank and extensive recycling of at least one of the separated phases into the mixture reactor. The invention further relates to a plant for carrying out the method in which an at least two-phase mixture is mixed in the mixing reactor, subsequently the phase mixture flows via a feed line or directly from the mixing reactor through a flow-through inlet area to a basin, which is used at least temporarily as a settling basin and from which at least part of a phase of the mixture separated in the settling tank is returned via a return line or in turn directly from the settling tank to the mixing reactor. In particular, this invention relates to methods and systems in which so-called settling tanks with predominantly horizontal flow are used, for which it is known that high-level inlets to such tanks in the prior art lead to poor cleaning performance. Definitions for when settling basins are considered to be predominantly horizontal can be found in the relevant design rules.

Such processes and systems are used worldwide to carry out a standard wastewater treatment process in order to biodegrade the wastewater ingredients in a technically controlled manner. Biological purification stages of sewage treatment plants often consist of aeration tanks as mixing reactors and secondary settling tanks as settling tanks. In the process, activated sludge is circulated, mixed and separated again in a sludge-water suspension between the aeration tank and the secondary clarification tank. Such a system is described for example in the patent DE 43 29 239 C2.

The primary task of the aeration tanks, which can consist of one or more chambers, as mixing reactors is to mix the biodegradable dirt load of the wastewater with dirt-decomposing bacteria in the activated sludge and by optimizing their environmental conditions, e.g. with regard to the oxygen content in the water to favorably influence the biochemical degradation process.

A volume flow flows from the aeration tank to the secondary settling tank as a settling tank. The time-variable inflow of fluid volume per unit of time that flows into the settling tank gives its current external hydraulic load. The secondary clarifier has three main tasks. First, they separate the activated sludge from the cleaned wastewater and thus enable the thickened sludge to be returned to the activation tank via the sludge return. Secondly, in periods of higher inflow to the sewage treatment plant, for example in rainy weather, its volume serves as storage for activated sludge, which is then transferred from the activation tank to the secondary settling tank due to the increased hydraulic load on the plant and the resulting increased mass transport Period of lower inflow with reduced hydraulic load to be shifted back into the aeration tanks. After all, secondary settling tanks have to ensure that as few residues as possible of activated sludge flow into nature via their course. It is known from numerous studies that secondary clarifiers only fulfill this function satisfactorily if the inlet area to the secondary clarifier is below the so-called separating mirror. The altitude is called the separating mirror, From which the concentration in the sedimentation basin increases from the supernatant of the lighter phase to the heavier phase.

The relocation of activated sludge from the activated sludge tank to the secondary settling tank in the event of higher hydraulic loads results in two serious disadvantages for the success of the process in the Teclinik stand. On the one hand, the activated sludge tanks have the least amount of degrading bacteria available during the period of the highest exposure to biodegradable dirt due to the displacement of the activated sludge. The efficiency of the biological degradation of wastewater treatment is therefore reduced at the highest pollution load. On the other hand, for the storage of the shifted sludge, the secondary settling tanks with a large and expensive storage volume have to be built.

The published patent application EP 1 354 614 AI discloses a technical solution with which the amount of sludge in the secondary clarifier can be checked or minimized for all loads with an adaptive inlet. The inlet area of the inlet structure to the secondary settling basin is optimized in different ways depending on the existing load situation so that the lowest possible energy at the inlet surface is given for each situation. This is the case if the one hand, the vertical distance of the lead-in area is small for the separation mirror and on the other hand the lead-in area has an optimum for the current load situation height hi _n. On the other hand, it is also known from Offenlegungsschrift EP 1 354 614 AI that with a given pool geometry the minimum achievable energy input is smaller the larger the inlet width B; _n is. In this way, mixing processes caused by excess energy at the inlet in the secondary clarifier and thus internal increases in the hydraulic load are minimized. Such mixing-in processes return a determinable amount of ΔQ> 0 sludge suspension that has already settled in the short circuit to the sludge that is still to be settled and thus increase the tank-internal load Q _n t = Qext + ΔQ due to fluid mechanical phenomena according to hydraulic laws with constant external load Q _ex t.

The choice of the inlet geometry determines the actual internal load by the degree of interference depending on this choice. Heavily optimized inlet geometries lead to relatively small, poorly chosen geometry to very high interference ΔQ. On the basis of this knowledge, a hydraulic efficiency ηπ = Qe _x t / Q _m t of the inlet structure to the settling tank can be defined as the ratio of the externally specified hydraulic load or Inlet quantity Q _ex t and the actual load Q m given internally at a defined point at the end of the near field of the inlet. As an alternative to the definition at a single fixed point, it is also possible to determine Q _n t along the entire course of the flow path s, but this will not be discussed further below.

The technical solution for the adaptive reduction of excess energy thus makes it possible to maximize the efficiency of sedimentation tanks for all load situations by minimizing the internal pool load. A higher efficiency of the secondary clarifier with the same external load is synonymous with a lower amount of sludge in the tank and thus also with a lower separating mirror. With an adaptive inlet structure, you can ensure that the inlet surface is only high when the separating mirror is also high. If an adaptive inlet structure is now operated in such a way that it does not maximize the efficiency of the secondary clarification tank for all external load intensities, but only for maximum external pool loads, while it sets a deteriorated efficiency with lower external loads, it can be ensured that the amount of sludge in the event of Dry weather exposure due to fluid mechanical phenomena is increased compared to a possible optimum thus the separating level is also set higher than under ideal conditions, while the amount of sludge in the sedimentation tank is optimized in the event of the highest loads, i.e. is as small as possible. Depending on the degree of deterioration of the efficiency in the event of an underload, the sludge transfer from the activated sludge tank to the secondary clarification tank can be reduced or even in the event of the highest load, the activated sludge can be moved from the secondary clarification tank to the activated sludge tank. The two serious disadvantages of a conventional biological cleaning stage can thus be overcome. The secondary clarifier is thus optimized for the highest load on the smallest necessary storage space. At the same time, the sludge transfer itself can be controlled in such a way that it occurs significantly reduced or even reverses.

However, this approach also has disadvantages, because the inlet must be arranged very deep under the separating mirror and / or h; be chosen very small. Both of these measures have a negative impact on cleaning performance.

The object of the present invention is to use a method and a system to generate a short-circuit flow for temporarily increasing the hydraulic load on the settling tank in phases of low external load which, instead of increasing the inlet energy by promoting fluid into the incoming volume flow, influences the efficiency of the settling tank , In the sedimentation basin, the vertical distance between the separating mirror and the inlet surface can be influenced via the height of the separating mirror. In the event of low external hydraulic loads, the separating mirror can be kept on a raised level by increasing the internal hydraulic load on the sedimentation tank. At the same time, the solution to this task enables the inlet area to the sedimentation basin to lie high without any variability, particularly in the upper half of the basin, for a high hydraulic load without the inlet surface necessarily lying above the separating mirror in phases of low external hydraulic load. The invention thus fulfills the task of overcoming the two serious disadvantages of shifting sludge from the mixing reactor into the settling tank and at the same time achieving the optimum cleaning effect. In combination with an inlet surface, the height of which can be changed in accordance with disclosure specification EP 1 354 614 AI, the solution enables maximum control over the sludge displacement to be achieved. This is particularly advantageous in particular because in this way flexible on z. B. Changes in the settling properties of the sludge and / or the total amount of sludge in the system can be responded to.

The object is surprisingly achieved in that the efficiency of the sedimentation basin with regard to its utilization can be reduced by technical measures in the described method by supplying the sedimentation basin to the volume flow flowing in the short circuit, that is to say on a shortened flow path, additional suspension volume flow. The volume flow in the short circuit originates from the sedimentation basin and is formed by direct removal from the sedimentation basin itself or by extraction from the return line through which fluid flows from the sedimentation basin. A shortened flow path is characterized in that the volume flow of the suspension originating from the settling tank or the return line is surely superimposed on the incoming volume flow to the settling tank at an earlier point in time than if it were to flow through the flow path of the system-internal circuit between the mixing reactor and the settling tank. The volume flow is therefore added along a shortened flow path in the supply line to the settling tank, in its inlet structure or directly into the main flow of the incoming volume flow flowing in the tank. If the mixing reactor and settling tank are arranged one inside the other, a space that is structurally delimited towards the mixing reactor and that borders directly on the settling tank can take over the function of the inlet structure. A control system can change the volume flow in the short circuit and thus to the desired total load on the sedimentation tank adjust and consequently raise the height of the separating mirror by reducing the hydraulic efficiency above its minimum achievable height. This can be done by measuring the height of the separating mirror directly adapted to it or, for example, by measuring the volume flow currently flowing into the system by indirectly adapting to the height of the separating mirror.

An advantageous solution to this problem arises if the inlet structure to the sedimentation basin has openings through which volume flow can be sucked in from the sedimentation basin or can be conveyed by technical systems such as pumps or screws.

A further advantageous solution is obtained if a partial volume flow from the return line of the separated phase is not fed to the mixing reactor, but rather to the volume flow that flows into the settling tank.

An advantageous solution also arises when technical internals which promote volume flow, for example rotors or pumps, can be used to convey additional volume flow at any point in the settling basin downstream of the inlet surface into the flow volume flow.

A particularly advantageous solution is obtained if one of the aforementioned solutions is combined with an inlet structure to form the sedimentation basin, the inlet of which is designed in such a way that the excess of the inlet energy can be controlled by variability in the height of the incoming volume flow and / or variability in the inlet area through which it flows.

A device disclosed in patent specification DE 43 29 239 C2 with lamella packets in the outlet of the mixing basin makes use of the principle of the lamella separation in order to reduce the amount of heavier particles in the suspension flowing into the sedimentation basin. This process reduces the particle load in the sedimentation tank. In phases of low hydraulic load on the system, this can lead to problems with the separation performance of the sedimentation tank. Such devices are therefore to be controlled or regulated in practice. When the hydraulic load is low, for example, individual lamella packets are bypassed by the flow, so that the particle load in the sedimentation tank rises without influencing the hydraulic load, while in high-load hydraulic phases the lamella packets are operated in an optimized manner and thus when the hydraulic flow is again unaffected Load The load on the sedimentation tank with particles to be separated decreases. In practice, lamella packets are also designed with a corresponding effect on the inlet surface or inside the sedimentation tank.

A further advantageous solution thus results from the fact that one of the aforementioned solutions is combined with a device with lamella separation or another device which influences the solids load in the sedimentation tank. A control system can adjust the total load by influencing these devices in a coordinated manner.

In the case of aeration plants in sewage treatment plants, mixing reactors are at least partially provided with devices which have a positive influence on the ambient conditions in order to increase the degradation effect. These can be surface aerators or pressure aerators, for example. Settling tanks are not provided with such devices. An increased short-circuit flow, which is not passed through the mixing reactor with such devices, can have negative biological-procedural effects for the organisms of the activation system. This possible disadvantage resulting from the use of a short-circuit flow according to the invention may need to be overcome. For this purpose, areas must be provided in the inlet structure of the sedimentation basin that short-circuit the volume flow from the sedimentation basin with the inflowing volume flow from the mixing reactor and by suitable preliminary directions, for example aerators, also offer optimized environmental conditions for the organisms of the short-circuit flow. Alternatively, the mixing basin is to be arranged entirely within the settling basin, so that it itself fulfills the additional function of an inlet structure with suitable devices for improving the environmental conditions for the organisms from the short-circuit current.

These solutions are also particularly advantageous from a hydraulic point of view, because, as is described in patent application EP 02 022 051.3, the energy excess ΔEu at the inlet to the sedimentation tank decreases as the width of the inlet increases. In the case of an intake structure within the settling basin, the circumference of the structure determines the width of the intake. The width of the inlet increases when the inlet structure is enlarged by zones with additional devices with process engineering tasks, for example the improvement of the conditions for substrate degradation through ventilation or when the entire mixing tank is arranged within the sedimentation tank. It can be physically proven that in a round sedimentation basin the absolute hydraulic load capacity of the basin, i.e. the absolute flow rate of the suspension to be separated, can be increased paradoxically with constant internal loading if the inlet structure within the sedimentation basin has a significantly larger radius Rj _n than in State of the art is built. This is due to the fact that the effect of reducing the internal load on the pool due to reduced interference for an increasing inlet width Bj _n = 2 ^■ π ^• R and thus decreasing inlet energy up to large radii has a much greater positive effect on the pool efficiency than the effect of the loss of sedimentation tank volume would have a negative impact. It can even be shown that in a settling basin through which the inside flows, the inner space of the settling basin with a radius smaller than approx. 30 to 50% of the total radius of the basin is largely useless or even counterproductive for phase separation. This is due to the particularly pronounced interference in this area. The area affected in a round basin therefore corresponds to at least 20 to 30% of the total volume. It is therefore particularly economical to use this space, which is largely useless or even counterproductive with regard to phase separation, for other purposes, for example in a tank-internal mixing reactor for substrate degradation.

A particularly advantageous solution to the problem on which the invention is based arises from a hydraulic as well as from a procedural point of view for aeration systems, if the aforementioned solutions for round secondary clarifiers are combined with larger inlet structures, which solve their interior by means of devices use tasks other than phase separation. For example, a ventilation zone and a subsequent anaerobic degassing zone can usefully be provided within the intake structure.

The basic function of the invention is independent of the geometric shape of the surface of the basin. It is also independent of whether the inlet area to the sedimentation basin is located inside the basin or on its periphery. It is independent of whether individual or all pools are structurally separate, adjoin one another or are built into one another and thus in the latter cases supply lines and / or return lines are completely or partially omitted.

Embodiments of the invention are described below with reference to the accompanying drawings. All figures show systems that consist of a mixing reactor and a settling tank. The illustrations are combinations of functional sketches and greatly simplified vertical sections. All of the sedimentation tanks outlined have a round surface. However, the function of the invention is also given for sedimentation tanks designed in a rectangular or other shape. The same elements are provided with the same reference numerals. Fig. 1 combination of mixing reactor and settling tank, in which the inlet structure has openings through which volume flow can flow from the settling tank into the inlet structure;

Fig. 2 combination of mixing reactor and settling tank with an additional line for connecting the return line and feed line;

Fig. 3 combination of the mixing reactor and settling tank with a line in the settling tank, with which volume flow can be conveyed from the settling tank into the inlet structure;

Fig. 4 combination of mixing reactor and settling tank with volume flow-promoting devices in the settling tank, which downstream of the inlet surface can convey additional volume flow inside the inflow volume flow;

Fig. 5 Combination of mixing reactor and sedimentation basin, in which the inlet structure is designed in such a way that it has openings through which volume flow can flow from the sedimentation basin into the inlet structure and, in addition, the excess of the inlet energy due to the variability in height of the inflowing volume flow and through variability the inflow area can be checked;

6 plant in which the sedimentation basin is arranged within the mixing reactor, provided with lines in the sedimentation basin with which volume flow from the area of separated phase can be conveyed into the inlet structure;

7 combination of mixing reactor and sedimentation basin, in which the inlet structure has openings through which volume flow can flow from the sedimentation basin into the inlet structure and which is equipped with additional devices, in this case ventilation;

Fig. 8 plant in which the mixing reactor is arranged within the settling tank, with additional lines for connecting the return line and the mixing reactor, the inlet of the additional line to the mixing reactor being such that parts of the flow path in the mixing reactor are bypassed.

The system shown in FIG. 1 is combined with an inlet structure 4 which has openings 10 through which a volume flow can be conveyed from the settling basin 6 into the inlet structure. If the inlet structure is designed in terms of fluid mechanics so that the openings 10 in the inlet structure have a sufficiently lower pressure than outside the inlet structure, a controlled volume flow from the sedimentation basin into the inlet structure can be initiated by checking the cross-sectional area of the openings 10 - for example, through orifices or slides become. By attaching or installing suitable volume flow-promoting devices, such as pumps or screws, the volume flow can also be conveyed mechanically. One or more openings 10 can also be combined with any other shaped, rigid or variable inlet structures within or on the periphery of a settling basin 6.

FIG. 2 shows an example of a system in which supply line 3 and return line 9 are connected by an additional line 11 through which volume flow can be branched off from the return line and conveyed into the supply line to settling tank 6.

FIG. 3 shows an example of a system in which volume flow from the settling basin 6 into the inlet structure 4 can be conveyed with a line 14 in the settling basin. The sau The end of line 14 can also advantageously end at other points in the settling tank 6. Line 14 is shown here by way of example on a peripheral inlet structure 4 which, as a ring line, runs partially or completely around the periphery of the settling tank 6. The ring line can, for. For example, it can also be designed to be displaceable in height in order to be able to additionally control the excess energy at the inlet surface. Line 14 can also be combined with any other shaped, rigid or variable inlet structures within or on the periphery of a settling basin 6.

FIG. 4 shows an example of a system in which flow-promoting apparatuses 13, such as pumps or rotors, can be used to convey volume flow in the settling basin 6 within the settling basin into the volume flow flowing through the inlet surface 5. The flow-promoting apparatuses 13 can also be combined on the suction and / or pressure side with suitable lines and / or constructions that divert the flow in order to have the least possible negative influence on the flow conditions in the settling tank and thus on the settling processes. Flow-promoting devices 13 can also be combined with any other shaped, rigid or variable inlet structures within or on the periphery of a settling basin 6.

FIG. 5 shows an example of a system in which one of the advantageous solutions of the invention, here openings 10, through which a volume flow can be conveyed from the settling basin 6 into the inlet structure 4, is combined with a central inlet structure 4 to the settling basin 6 by means of a telescopic tubular ring 14a and a height-adjustable ring plate 14b, the height of the inlet surface 5 and the cross-sectional area through which it flows can be changed in order to control the excess energy at the inlet surface.

FIG. 6 shows an example of a system in which the settling tank 6 is arranged within the mixing reactor 2, combined with one of the advantageous solutions of the invention, here a line 12 in the settling tank, by means of which volume flow can be conveyed from the settling tank 6 into the inlet structure 4.

The system shown in FIG. 7 is combined with an inlet structure 4 which has openings 10 through which a volume flow can be conveyed from the settling basin 6 into the inlet structure. Additional devices 15, in this case pressure ventilation in a ventilation zone and a mixer, are built into the intake structure. The ventilation zone can extend over a partial volume or over the entire volume of the intake structure.

FIG. 8 also shows an example of a plant in which a mixing reactor 2 with devices 15 is arranged within the settling tank 6 and thus also takes on the function as an inlet structure 4. Volume flow can be branched off from the return line through line 11. Volume flow can thus be conveyed into the central structure via a shortened flow path. Lines 9 and 11 can alternatively also pierce the partition between the mixing reactor and settling tank in a direct way.

FIG. 9 shows an example of a plant in which the settling basin 6 is arranged within the mixing reactor 2, combined with a space located between the mixing reactor and the settling basin, which functions as an inlet structure. Through line 11, volume flow can be branched off from the return line and fed to the basin, which functions as an inlet structure. Alternatively, the partition between the inlet structure and settling basin can be flowed through directly through an opening in the partition. The mixing reactor can alternatively also be arranged within the settling basin and separated from it by an intermediate space which functions as an inlet structure. Compilation of the reference numbers Supply line to the system Mixing reactor Supply line to the settling basin Inlet structure of the settling basin Inlet surface to the settling basin Sedimentation basin Separating mirror of phases of different densities in the settling basin Discharge of lighter phase from the settling basin Return line to the mixing reactor Opening in the inflow structure Additional line to divert volume flow from the return line to the settling basin, with the Volume flow from the sedimentation basin can be conveyed into the intake structure. The apparatus in the sedimentation basin 6, with which volume flow within the sedimentation basin can be conveyed into the volume flow flowing through the inflow surface 5, can be conveyed. A Telescopic tubular ringb Height-adjustable ring plate Additional facilities in the inflow structure

Claims

claims

Claim 1: Method for mixing a multi-phase fluid in at least one mixing reactor, then separating phases of different weights in at least one tank, which is used at least temporarily as a settling tank, and returning at least one of the separated phases to the mixing reactor, characterized in that the load of the sedimentation basin can be increased by temporarily supplying volume flow from the sedimentation basin or the return line to the inlet flow of the sedimentation basin on a shortened flow path.

Claim 2: Method according to claim 1, characterized in that the instantaneous load on the sedimentation basin is detected in order to increase or increase the load on the desired total load on the sedimentation basin by means of control or regulation. to be able to adjust the desired height of the separating mirror.

Claim 3: Plant for carrying out the process according to one or both of claims 1 and 2, consisting of at least one mixing reactor and at least one settling tank, which at least temporarily fulfills the task of a settling tank and can be returned to the mixing reactor from the volume flow phase, thereby characterized chnet that the volume flow originating from the settling basin or the return line can be supplied at least temporarily to the inlet flow of the settling basin on a shortened flow path.

Claim 4: System according to claim 3, characterized in that the inlet structure to the sedimentation basin can be supplied with volume flow from the sedimentation basin via at least one opening in the inlet structure.

Claim 5: System according to claim 3, characterized in that volume flows from at least one return line can be partially or completely supplied to the incoming volume flow of the settling tank.

Claim 6: System according to claim 3, characterized in that at least one tank-internal line in the settling basin can convey volume flow into an inlet line, into an inlet structure or directly into the volume flow that has already flowed in.

Claim 7: System according to claim 3, characterized gekennzei chnet that additional volume flow can be conveyed through volume-enhancing internals at any point in the settling basin downstream of the inlet surface into the volume flow that has flowed in.

Claim 8: System according to one of the preceding claims, characterized in that it is carried out with an inlet structure to the sedimentation basin, which is designed in such a way that the excess of the inlet energy can be changed by varying the height of the position of the incoming volume flow.

Claim 9: System according to one of the preceding claims, characterized in that it is carried out with an inlet structure to the sedimentation tank, which is designed in such a way that the excess of the inlet energy can be changed by changing the flow through the inlet surface. Claim 10: System according to one of the preceding claims, characterized in that it is combined with an inlet structure to form the sedimentation basin, which has additional devices for process engineering use of the volume of the inlet structure.

Claim 11: Plant according to one of the preceding claims, characterized in that the settling tank is arranged within the mixing reactor.

Claim 12: Plant according to one of claims 3 to 10, characterized in that the mixing reactor is arranged within the settling tank.

Claim 13: Plant according to one of claims 11 or 12, characterized in that a space located between the mixing reactor and settling tank functions as an inlet structure.

Claim 14: System according to one of the preceding claims, characterized in that it is combined with a device for separating lamellae.