DE20009961U1 - Dosing reactor for the treatment of raw water and plant for the treatment of drinking water - Google Patents

Description

se, 00131-DEU 6 June 2000

F & P Sorting Technology GmbH 95028 Hof

"Dosing reactor for the treatment of raw water and plant for the treatment of drinking water"

The invention relates to a dosing reactor for the treatment of raw water, consisting of a dosing unit for a chemical substance, a raw water supply, a mixing unit and at least one reaction vessel.

The invention also relates to a plant for the treatment of drinking water from raw water enriched with metals, wherein an intermediate product is produced from a first arrangement for the provision of raw water in which the metals are stored in an insoluble compound, which is then separated by means of a filter system and wherein finally the water then available is adjusted in a second arrangement so that the lime-carbonic acid equilibrium can be established.

DE 36 40 542 proposes a method and a system for the treatment of drinking water, in which the dosing and mixing unit consists of a container into which both a raw water supply and a dosing device introduce a liquid substrate. A stirring device ensures the necessary mixing.

In the bottom area, the mixture flows through a passage into an adjacent reaction vessel. There, the mixture is moved in an upward flow under the slow stirring movement of an additional stirrer and is conveyed via an overflow into another adjacent dosing and mixing zone.

In this second dosing and mixing zone, a flocculant is added in a falling manner. This second dosing and mixing unit is followed by another reaction tank. Downstream arrangements serve to free the drinking water of solid, precipitated substances.

&iacgr;&ogr; The system described here has significant disadvantages. These are that the dosed substances or liquids are not evenly distributed in the water before they have completed their chemical reaction. Substances in powder form or provided as granules cannot be dosed with such a system.

The high humidity or the mist above the mixer quickly leads to the formation of encrustations in the area of the vibrating chute or the reservoir, which often contain very hygroscopic substances, and thus to the inability to dosing. On the other hand, these substances are distributed very unevenly in the mixing container despite the mixer. Considerable amounts of this substance settle in calmer areas and form encrustations there.

Another disadvantage is that considerable amounts of energy are required for the constant movement of the water or the sometimes very viscous mixtures. The treated water is of unsatisfactory quality, which is also not equally evident in all parts.

Another system of this type has become known through DE 38 26 794. In this case too, the substance to be dosed, which in this case is a flocculant, is dosed into a mixing container into which the raw water is also pumped in a falling jet. A stirring rod at the bottom of the container is intended to ensure sufficient mixing.

From the bottom area of this first mixing reactor, the mixture is fed into a reaction vessel with the addition of further raw water, from which the treated water is fed for further use via an overflow.

&iacgr;&ogr; This arrangement also has significant disadvantages. The disadvantages described in relation to the previous literature apply here without any reservations. If a substance that reacts very quickly or even explosively is used to change the water quality, even more significant losses in quality can be seen. The reaction is then often already complete before this substance is evenly distributed in the water. Significant parts of the water are passed on untreated and can no longer be specifically changed in the subsequent process.

An older German patent application 199 15 808.8 already proposed using a mixing reactor with a continuously operating dosing device. The substance to be dosed was continuously introduced, falling freely, into an extremely turbulent flow in the center of a flat funnel that flowed towards each other in a ring shape. The resulting mixture, which is already very homogeneous, is fed into the bottom area of the reaction vessel under a slight excess pressure.

An external mixing pump sucks in the mixture still enriched with undissolved particles in this soil area, mixes it outside the

mixing reactor and returns it to the bottom area (mixing zone) of the reactor via the pressure pipe of the mixing pump. This external mixing process ensures that the solution is immediately and homogeneously distributed as the dissolving process continues.

This process is repeated until the added substances continue their reactions in a dissolved state evenly distributed in the water. The slowly rising, predominantly laminar flow in the reaction vessel is only slightly affected by this process.

The disadvantage of this arrangement is that the mechanical effort and energy required to maintain the mixing process while the dissolving process continues causes above-average costs. This is particularly the case when the water treatment only requires deacidification. The raw water provided in many cases, which is available as groundwater from a well or as spring water, usually only requires deacidification or the separation of certain metals.

The aim of the present invention is to propose a dosing or mixing reactor that uses the least amount of substances and energy and can carry out a mixing and dissolving process at low water flow rates, which allows even distribution of the dissolved substance in the water even with the shortest reaction times of the substances with the water before the substance's ability to react is complete. The conditions for effective control of the process and thus good water quality should be met.

The object is achieved in a surprisingly simple manner by the features defined as a combination in claim 1. Dosing into the ring-shaped, flat funnel guided radially inwards and downwards

Raw water flow enables the substance to be distributed extensively and homogeneously in the water before its reactivity is even nearly complete.

The proportional, continuous supply of raw water and substrate into the narrowly defined mixing zone - without any damming effect - ensures that the substance is evenly distributed immediately after it is introduced. The mixing process only requires a small difference in the height of the raw water supplied. The air above the mixing zone is free of water particles. This prevents hygroscopic substances from encrusting in the area of the dosing device. The entire process - from dosing to the discharge of the treated water - runs continuously and therefore also allows reliable control of the ratio between the amount of water and the dosed substance in all parts of the water. The result is water of the highest quality with the lowest energy consumption.

A particularly simple control of the pH value of the water is possible if - according to claim 2 - the dosing device is controlled to change the dosing quantity per unit of time.

Preferably, the oscillation range of the vibrating chute is changed according to claim 3. This prevents the separation of powdery substances of different densities in the vibrating chute of the dosing device.

According to claim 4, it is of course also possible to change the frequency of the vibrating trough in order to provide more or less substrate per unit of time. Such a regulation is useful when the substance consists of a mixture of materials of similar density and similar grain size.

The design of the reaction vessel according to claim 5 ensures

ensures that no undissolved particles of the added substance can settle in any dead spaces in the bottom area of the reactor. This design of the reaction vessel additionally promotes the homogeneity of the water provided.

If substances are used that are either in a coarser grain or in a poorly soluble form, the use of an external mixing pump according to the older proposal mentioned above is necessary. The first precipitation products can then be separated in this circuit.

&iacgr;&ogr; If the pH sensor is arranged close to the overflow edge of the reaction vessel according to claim 8, the controller is able to regulate the pH value of the water to a precisely specified target value and to maintain this pH value.

Claim 9 describes a system for treating drinking water from raw water, from which metals in different compounds are also to be separated. The expert is aware that certain metals, e.g. aluminum, are only present in an insoluble form in a narrowly limited pH range and can thus be separated. The majority of metals must have at least reached this pH value if they are present in the water in a form that can be separated.

The system is operated using the dosing reactor according to claim 1 with two different target values in two separate units. The two dosing reactors are connected in series. Between them, a filter unit ensures the separation of insoluble substances.

The first dosing reactor receives a target value, e.g. for the pH value in

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the area where aluminum can be separated. The water treated by this first dosing reactor is passed through the filter system to separate the insoluble ingredients. The water freed from the precipitated substances is passed through a second dosing reactor with a pH value as the target value that allows the lime-carbonic acid balance to be achieved with high precision.

This system makes it possible for the first time to remove aluminium (and of course other metals), which is increasingly found in our water, and to provide high-quality drinking water with extremely low investment costs.

The modifications of the system according to claims 10 and 11 ensure optimal operation of the system.

The invention will be explained in more detail below using an exemplary embodiment. The accompanying drawings show:

Fig. 1 a dosing reactor which only supplies clean raw material for deacidification

water and

Fig. 2 a plant using two dosing reactors, which are used for

Treatment of drinking water from raw water with increased metal content.

Fig. 1 shows a dosing reactor in an application position. This dosing reactor DR consists of a dosing and mixing unit DME and a dissolving and reaction unit LRE.

The dosing and mixing unit DME comprises the raw water supply 1, the dosing device 2 and the mixing zone 16. The raw water supply 1 starts in a collecting tank or storage tank 10. The raw water can also be fed directly

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from a spring or a well or even from a cistern.

In a feed line 11 there is a throttle valve 12, which is used to set the flow rate that the dosing reactor DR can easily process. This throttle valve 12 is followed by a control valve 13, which can open or close the feed line 11 when a corresponding command is given by the control system or by the operator. The feed line 11 preferably opens radially into a ring line 14, which is arranged close above a flat funnel 15. The funnel angle of the funnel 15 is selected in a range from 120° to 170°.

The ring line 14 has a gap-shaped ring-shaped opening on its underside, an annular gap 141, through which the raw water supplied is guided in a flat conical flow to the lower, central outflow opening of the funnel. An extremely turbulent mixing zone 16 is formed there, which extends a considerable distance into the downpipe 4 that follows downwards. The preferably powdery or granular substance is metered into the center of this mixing zone 16 in a largely continuous flow, falling from above.

The dosing device 2 consists of a reservoir 21, which opens into a cylindrical tube at its bottom, which extends to the ramp 23 in the vibrating trough 22. Only a narrow annular gap remains between the tube mouth and the surface of the ramp 23. If the vibrating movement is interrupted, the dosing is also terminated.

This type of design of the vibrating chute 22 with ramp 23 allows the continuously delivered dosing quantity per unit of time to be reduced to very low values. The vibrating chute 22 is assigned a vibrator 24, the

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amplitude or frequency is variable.

The substrate dosed into the center of the funnel-shaped flow, into the mixing zone 16, is immediately caught by the flow and subjected to the mixing process. Due to the negative pressure in the room immediately above this mixing zone 16, this area is free of foam, splashes, mist or even moist air. If the dosing device is located in an air-conditioned room with low humidity, then the mixing zone 16 described does not cause a partial increase in humidity there. The vibrating trough 22 remains dry on a regular basis, so that even powdery substances, which are usually highly hygroscopic, cannot settle there and form a crust.

The dissolution and reaction unit LRE begins in the mixing zone 16. It extends over the downpipe 4 and the reaction vessel 3 to the overflow edge of the same. As a rule, the dissolution and reaction process should be largely completed at the overflow edge 31. However, it cannot be ruled out that some reactions may still take place in a subsequent filter.

A short distance below the extremely turbulent flow of the mixing zone 16 in the center of the funnel 15, the flow of the raw water, now referred to as the premix, calms down in the downpipe 4. The particles of the dosed substance are evenly distributed. The flow, which is still slightly turbulent in the downward-leading downpipe 4, ensures that the substrate granules dissolving there or the substances that have just gone into solution continue to be evenly distributed in the water and immediately react chemically with the stored substances present.

The downpipe 4 extends close to the preferably internally concave

formed bottom section 32 of the reactor vessel 3, to which conical sections are connected, which in turn then merge into the cylindrical walls of the reactor 3. Any undissolved particles, which are usually heavier than water, remain in this curved bottom area 32 and are moved by the water flowing out of the downpipe 4 until they are incorporated in dissolved form into the upward flow of the reaction vessel 3.

The reaction vessel 3 has an overflow edge 31 in its head area in a predetermined section. From there, a channel or a pipe extends to the collecting tank or drinking water reservoir 8. The reaction vessel 3 is closed at its top by a lid 33.

Immediately below the overflow edge 31, a pH value sensor 51 is arranged in a protected and flow-through protective container 510, which supplies its electrical information via a line to the control unit 52, 52' of the controller 5. The control unit 52, 52' can be provided with a display 521 and with means for program input 522 (keyboard).

The control unit 52, 52' is able to vary the oscillation range or frequency of the vibrator 24 depending on the pH value of the target value and the currently measured pH value. The necessary control commands are fed to the vibrator 24 via the control line 53, 53'.

The control unit 52, 52' can also monitor, control and regulate additional functions in the usual way. For example, it can operate valves 12 and 13 if the fill level in certain containers is too low or too high. It can also shut down the dosing reactor if there is no raw water or if the drinking water reservoir 8 is full.

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The arrangement according to Fig. 1 ensures that the substance and its solution are evenly distributed without the use of any mechanical mixing devices, i.e. only by the funnel flow that generates the turbulence. In all parts of the water, the reaction can begin and be completed almost simultaneously and with the same effect, so that homogeneous drinking water of high quality can be provided.

This dosing reactor DR according to Fig. 1 works perfectly as a system if the raw water is not contaminated with unacceptable amounts of metals, e.g. aluminum, iron, manganese or arsenic. The raw water that usually occurs in nature often has pH values that are less than 6. These pH values can be easily and precisely changed to the values in the range of the lime-carbonic acid equilibrium using this system.

The separation of metals from water takes advantage of the fact that the most important metals are insoluble in certain pH ranges or can be combined in such a way. The pH value is changed step by step. In a first and/or second step, the pH value is first adjusted to such ranges one after the other and the precipitated substances are separated in between. Once this separation is complete, the lime-carbonic acid equilibrium is established in a final step for use as drinking water.

Fig. 2 shows such a system for the treatment of drinking water from raw water that also contains metal compounds (e.g. aluminum). The dosing reactor DR1 corresponds in its basic structure to the dosing reactor DR described in Fig. 1. This dosing reactor DR1 is given a pH target value for its control, which is, for example, in the range between 6.8 and 7.2.

In order to treat the contaminated raw water, in addition to those that affect the pH value, additional substances may also be added that, together with the metals, lead to insoluble compounds. These substances are sometimes less reactive than the substances that change the pH value.

For this reason, a mixing circuit 6 with a mixing pump 61 is assigned to the reaction vessel 3. The suction pipe 62 of this mixing pump 61 begins in the bottom area 32 of the reaction vessel 3. In the mixing pump 61, the dissolving process and mixing process are carried out in an extremely turbulent movement.

&iacgr;&ogr; demarcated space. The pressure pipe 63 of the mixing circuit 6 leads the now further dissolved, homogeneous mixture back into the bottom area 32 of the reaction vessel 3 and thereby ensures additional turbulence in this area. Undissolved particles sink and are repeatedly sucked into the area of the mixing pump 61. The solution which reacts with the water or with the substances stored in it rises upwards in a slow or slightly turbulent flow.

In the head area of the reaction vessel 3, the previously treated water flows over an overflow edge 31 into a suction shaft 34. In the bottom area of this suction shaft 34 begins the suction pipe of a feed pump 71, which sucks in the water treated for metal separation in the filter unit 7 and presses it through the filter unit 7.

The delivery capacity of this feed pump 71 is regulated by two level sensors 55, 56 via the control unit 52'. The purified water emerging from the filter unit 7 is fed under low pressure via the line to a second dosing reactor DR2, which has an identical structure to that described in Fig. 1. The control unit 52' can adjust the lime-carbonic acid balance in the

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water. This equilibrium is usually achieved at a pH of 8.2.

The accuracy of this pH value is guaranteed by the measured value-dependent change in the dosage amount. The drinking water produced in this way is of high quality.

The system shown here, consisting of two dosing reactors DR1, DR2 with the intermediate filter unit 7, is completely sufficient for the most important raw water supplies of the quality described above.

&iacgr;&ogr; This system can be supplemented with additional units if the available raw water requires it. For example, biological filters can be installed upstream or UV reactors can be installed downstream.

Instead of a single filter, several filters with different properties can be inserted in series or parallel to each other between the two dosing reactors DR1, DR2 as filter unit 7.

Systems of this type regularly run in an automatic process. Depending on the amount of water that is to be treated per unit of time, the amount of substance to be dosed per unit of time naturally also increases. Appropriate automated feed systems can then be assigned to the dosing device's storage unit in a conventional manner.

se, 00131-DEU 6 June 2000

List of reference symbols

1 Raw water supply 5 10 Storage 11 Supply line 12 Throttle valve 13 Control valve 14 Ring line 10 141 Annular gap 15 funnel 16 Mixed zone 2 Dosing device 21 Storage 15 Vibrating chute 23 ramp 24 vibrator 3 Reaction vessel 31 Overflow edge 20 32 Floor area 33 Lid 34 Suction shaft 4 Downpipe 5 Control unit 25 51, 51' preferably pH sensor 510 Protective container 52, 52" Control unit 521 Display 522 Keyboard ....... .....
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15

53, 53' Control cable (vibrator) 55, 56 Level sensor 6 Mixing circuit 61 Mixing pump 5 62 Intake manifold 63 Pressure pipe 64 filter 7 Filter system 71 pump 10 8 Drinking water storage DMEA Dosing and mixing unit LRE Solution and reaction unit DR Dosing reactor DR1 Dosing reactor (with mixing pump) 15 DR2 Dosing reactor

Claims (11)

1. Dosing reactor for the treatment of raw water consisting of
from a dosing and mixing unit (DME)
with a continuously flowing raw water supply ( 1 ),
with a continuously dosing device ( 2 ) for substances preferably in powder or granulate form and
with a mixing zone ( 16 ) in the centre of a flat funnel ( 15 ) in which a radially inwardly directed ring flow unites,
from a solution and reaction unit (LRE) below the dosing and mixing unit (DME), with a reaction vessel ( 3 ), the outlet of which is arranged in its head region and with a downpipe ( 4 ) between the mixing zone ( 16 ) of the dosing and mixing unit (DME) and the bottom region of the reaction vessel ( 3 ), and
from a control unit ( 5 ) with a sensor ( 51 ) for determining actual values which are largely proportional to the pH value in the outlet area of the reaction vessel ( 3 ), and with a control unit ( 52 ) for changing the ratio between the substance and the raw water depending on a predetermined pH value and the current measured value of the sensor ( 51 ). 2. Dosing reactor according to claim 1, characterized in that the control unit ( 52 ) has at least one control line to the dosing device ( 2 ) for the substance. 3. Dosing reactor according to claim 1 and 2, characterized in that the control unit ( 52 ) varies the oscillation range of the vibrating trough ( 22 ) of the dosing device ( 2 ). 4. Dosing reactor according to claim 1 and 2, characterized in that the control unit ( 52 ) varies the frequency of the vibrating trough ( 22 ) of the dosing device ( 2 ). 5. Dosing reactor according to claim 1, characterized in
that the bottom section ( 32 ) of the reaction vessel ( 3 ) is conically tapered downwards and is closed by a flat, preferably internally concave central section and
that only the outlet opening of the downpipe ( 4 ) is arranged at a short distance above the middle section. 6. Dosing reactor according to claim 1 and 5, characterized in that in the bottom region ( 32 ) of the reactor vessel ( 3 ) in addition to the downpipe ( 4 ) the suction pipe ( 62 ) and the pressure pipe ( 63 ) of a mixing pump ( 61 ) open. 7. Dosing reactor according to claim 1 and 6, characterized in that a filter ( 64 ) is inserted into the circuit ( 6 ) of the mixing pump ( 61 ). 8. Dosing reactor according to claim 1, characterized in
that the reaction vessel ( 3 ) is provided with an overflow edge ( 31 ) in the head area,
that the sensor ( 51 ) is arranged in the area near and below this overflow edge ( 31 ) in a protective container ( 510 ) through which the fluid flows at regular intervals. 9. Plant for the treatment of drinking water from raw water enriched with metals, consisting
from a first arrangement for providing raw water with a pH value deviating from the lime-carbonic acid equilibrium, in which metals (e.g. Al, Fe etc.) are present in an insoluble compound,
from a filter system, connected to the output of the first arrangement, and
from a second arrangement for providing preferably drinking water with a pH value in the range of the lime-carbonic acid equilibrium, characterized in that the first and second arrangements each consist of a dosing reactor (DR1, DR2) according to claim 1, to which different pH target values are specified via their control units ( 5 ). 10. Plant according to claim 9, characterized in that the first dosing reactor (DR1) is equipped with a mixing pump ( 61 ) whose suction and pressure pipe opens into the bottom region ( 32 ) of the reaction vessel. 11. Installation according to claim 9 or 10, characterized in that a pump is arranged upstream of the filter system ( 7 ), the suction pipe of which begins at the bottom of a suction shaft ( 34 ) which is fed via an overflow edge ( 31 ).