GB2182322A

GB2182322A - Method and apparatus for maintaining fluid-gas dispersions

Info

Publication number: GB2182322A
Application number: GB08624181A
Authority: GB
Inventors: Gerhard Velebil
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-10-09
Filing date: 1986-10-08
Publication date: 1987-05-13
Anticipated expiration: 2006-10-08
Also published as: DE3536057A1; GB8624181D0; GB2182322B; DE3536057C2

Abstract

To maintain a fluid-gas dispersion in a vertical receptacle 2, which contains a substrate such as effluent, sewage or the like to be treated with gas, an upward-directed more or less helical turbulent flow of the fluid-gas dispersion is produced in receptacle 2, so that the flow path is substantially increased compared with the height of receptacle 2 and thus the dwell time of the gas in substrate 3 is appropriately extended. This may be achieved in that inlet or inlets 4 and 5 for the gas-fluid dispersion is/are arranged eccentrically in the bottom area of the receptacle near its bottom 6. <IMAGE>

Description

SPECIFICATION Fluid-gas dispersion The invention relates to a method for maintaining a fluid-gas dispersion in a vertical receptacle which is preferably used as a reactor for biochemical processes, particularly for the treatment of waste waterorsewageorthelikewithgas, particularly air, oxygen etc., and hasinletopeningsforthefluid-gas dispersion as well as a top opening for removal ofthe used gas which comes out ofthe fluid, whereby the fluid-gas dispersion flows through the reactor charge.

The invention also relates to apparatus for maintaining a gas-fluid dispersion in particularfor the instigation of biochemical reactions, e.g. for the treatment of waste water or sewage or the like with a particularly cylindrical or approximately cylindrical vertical receptacle as the reactor, which is filled with the substrate to be treated and has at least one inlet for the gas-fluid dispersion.

Amethodandadeviceformaintaininga dispersion of gases in fluids is known from European patent specification 0102435, where the gases are put into the top part of the vertical circulation device subjectto simultaneous mechanical rotation and the micro-bubbles which occur are conveyed against their upward force into the bottom horizontal part of the device, from where they pass into a connecting part of the device which leads upwards and are there exposed to pulsations and displaced into a micrn-eddy, following which the fluid is then degassed. This means therefore that these are a method and a device of another kind.

Comparable methods and devices of the kind mentioned in the introduction hereto are also known for example from CH-PS 527773 and DE-OS 2554 440.

In CH-PS 527773 a central shaft with agitators is arranged in the receptacle, which also contains other fittings, in order to produce several toroidal fluid flows distributed over the height. Flow guiding agents are therefore required, by which the fluid will be deflected so that howeverthe gas in the dispersion can escape through friction losses and the like from the fluid. What is more the fittings in the receptacle, namely the agitators and flow deflectors are expensive.

Again in the case of DE-OS 2554440 expensive fittings are provided in a vertical receptacle, to produce rising and falling spaces, whereby only gas is fed into the fluid, so that the gas-fluid dispersion will only occur in the receptacle.

Apartfrom the expensive fittings it must be expected that part of the gas fed in will not form a dispersion, so that a gas surplus is required.

The general problem with the methods and devices described as well as many others lies in the fact that the dwell time of the gas in the substrate must be made as long as possible, in order to be able to use the gas to the best possible advantage and gain sufficient reaction time.

With the well known devices therefore, due to the rising speed ofthe gas bubbles involved in a reaction, frequently very high receptacles are used.

The task of this invention is to create a method and a device ofthe kind mentioned in the introduction, where the equipment expense is less, the reaction time or dwell time ofthe gas is however as long as possible, so that it can be used to the best possible advantage, but whereby the space requirement and in particularthe necessary height of the device can nonetheless be kept as small as possible.

To meet these requirements the method in accordance with the invention is distinguished by the fact that in the receptacle an upward-directed somewhat helical turbulent flow offluid-gas dispersion is produced, the peripheral speed of which, at least in range, isgreaterthan the rising speed ofthe gas bubbles in the dispersion and less than the centrifugal speed for a separation ofthe gas-fluid mixture orthe gas-fluid-solid mixture.

As a result ofthis measurethe path ofthe fluid-gas dispersion in the receptacle and therefore the gas bubbles is substantially reduced compared with an upward and/or a downward directed flow, so that the height of a receptacle can be much better used or can be reduced and still allows a long flow path and therefore a long dwell time.

This method can be realised in a particularly simple way if the fluid-gas dispersion is introduced eccentrically in the bottom part of the receptacle, preferably nearthe bottom. Just the very fact of the eccentric inflow means that the flow is displaced within the receptacle in a circular movement, whereby the fluid-gas dispersion which keeps on flowing in afterwardsatthesametimeensuresa certain upward thrust of this fluid, which is when the helical flow occurs. The fluid-gas dispersion may therefore be introduced and displaced laterally, more or less parallel to one diameter of the receptacle.In this case it is a good idea ifthefluid-gas dispersion is introduced nearthewall ofthe receptacle and near the bottom, more or lesstangentiallyto a line parallel to the wall of the receptacle. This ensures the best possible increase in the flow path for the gas bubbles inside the receptacle.

The fluid content of the receptacle or a receptacle content consisting of a fluid-solid mixture can be displaced into an eliptical to circularflow running around its centreline and the speed of the fluid-gas dispersion on entering the receptacle may be the same as or greaterthan the peripheral speed of the reactor content in the area of the entrance. It is therefore a good idea if the inlet speed ofthe gas-fluid dispersion is designed to be so high thatthe peripheral speed, reducing over the heightofthe receptacle, even in the top part of the receptacle, is above the rising speed of the gas bubbles in the dispersion, so that there too premature rising ofthe gas bubbles and therefore premature ineffectiveness is avoided.

The content of the receptacle can be displaced into the aforementioned eliptical to circular movement by the introduction of the gas-fluid dispersion in the direction of rotation, but it is also possible to displace the receptacle content automatically and/or mechanically into such an eliptical to circular rotation movement particularly ifthere is a relatively large receptacle cross-section.

To eliminate the gas portion after passing through the receptacle the speed of flow in the top area may be reduced below the rising speed ofthe gas for example by a cross-sectional extension, so that the gas leaves the fluid in the required way and atthe required point, when it has been consumed.

Embodiments of the method are covered by further claims.

The device of the kind mentioned in the introduction intended to meet the aforementioned requirements is distinguished by the fact that the inlet/inletsforthe gas-fluid dispersion in the bottom part of the receptacle is/are arranged eccentrically near its bottom. Compared with well-known receptacles with a central inlet opening or inlets in thetop part the gas-fluid dispersion is therefore provided at more or less the lowest point and simultaneously so that a more or less helical flow occurs because of the inlet, the path of which comparedwiththe height ofthe receptacle is therefore substantially longer, so that the required length and dwell time and the required length and maintenanceofthefluid-gas dispersion are achieved simply and without the need for any otherfittings, although the basic idea of the invention is not abandoned bythefactthatthe more or less helical flow is reinforced by guide devices or mechanical means to increase the speed offlow.

In this case the inlet may be more or less horizontal, and under appropriate circumstances rise on a slant. The horizontal introduction of the fluid dispersion gives the best possible utilisation ofthe height of the receptacle, because an inlet directed in thiswaycan be provided at a very low point immediately above the bottom of the receptacle and also allows the best possible conditions and greatest distance to the centre of the receptacle forthe production ofthe helical flow eddy. Under certain circumstances a more or less slanting rise ofthe inlet may however be used to increase the speed, if the substrate to be treated in the receptacle would seem to require this.

In this case it is a good idea if the inletforthe gas-fluid dispersion is arranged near the wall of the receptacle more or less tangentially to a line running parallel to the wall ofthe receptacle. As a result of this the required eliptical to circularflowwithin the receptacle is produced or supported in the simplest manner.

In special cases the cross-section of the receptacle may reduce over its height, as a result of which the helical flow is accelerated in the part of the receptacle where the cross-section reduces, with which it is possible to counterthe natural reduction ofthis speed as the flow moves upwards.

In each case it is possiblethatthe receptacle has no fiow-guiding fittings, and it may then have a polygonal to round, preferably circular cross-section. This is the best way of meeting the required more or less helical flow and circular movement ofthe whole content of the receptacle around its centreline.

It is clearthatwhen using the specified features or measures it may be sufficient if the height ofthe receptacle is under 10 m, preferably 8 m or even less.

A receptacle can then be made in a very space-saving manner and with a low height and may be wholly or partly sunk in the ground. Eventhediameterorthe maximum cross-sectional extension of this receptacle need only be about 5 m or less.

For receptacles of more than 8 m in height and/or more than 5 m in diameter it may be a good idea if a fluid-conveying device is fitted internally to produce a moreorlesselipticaltocircularflowaroundthe centre ofthe receptacle, because it may then be possible that the inflow energy of the gas-fluid dispersion is no longersufficientto producethis flow A device for dispersing a fluid with gas may be provided outside the receptacle on the inlet pipe or inlet pipes which has/have its ortheir own fluid inlet and/or a return pipe from thetop end ofthe receptacleforthesupply of receptacle fluid Therefore the receptacle fluid can only be introduced into the receptacle mixed several times with gas and treated or additionally or instead ofthis in each case fresh fluid mixed with gas may be used for processing the content of a receptacle. The receptacle may have a cross-sectional extension at the top for degassing the fluid, used to reduce the speed of flow of its content, and the receptacle may have at least one gas outlet opening above the cross-sectional extension.

As regards the method according to this invention it should also be pointed out that the speed of flow or the dwell time of the components involved in the reaction in the rising receptacle may be controlled by controlling the quantity of the eccentrically supplied flow of fluid-gas dispersion, so that it is possibleto adapt to the speed of reaction of the relevant reaction components.

In particularwith a combination of one or several of the methods and features of the device described it is possible to achieve in a very simple way an effective maintenance of a fluid-gas dispersion treating for example effluents or sewage, so that suitably long dwell times of the gas are achieved, without the need for very high reaction receptacles or expensive fittings and mechanical devices inside the receptacle.

The invention is described below in greater detail on the basis of the drawing in the form of an embodiment byway of example.

The sole drawing shows a vertical section through a receptaclewith supply pipe for a gas-fluid dispersion and the devices which producethis dispersion.

A device designated 1 shown in the diagram in the sole drawing is used to maintain a gas-fluid dispersion, for example, when treating effluents or sewage, so that the gas remains as long as possible in the substrate to be treated and can be used to the best possible advantage in the smallest possible amount of space.

The main part of device 1 is a more or less vertically arranged vessel 2 as a reactor, which has a circular or in some cases polygonal cross-section, which is filled with the substrate 3 to be treated and in the embodiment has two inlets 4 and 5forthe gas-fluid dispersion, which is produced outside receptacle 2.

In accordance with the invention inlets 4 and 5for the gas-fluid dispersion are arranged eccentrically in the bottom area of the receptacle, near the bottom 6 ofthe receptacle. Inlets 4 and 5 both run more or less horizontally. They are arranged near the wal 17 of receptacle 2 andtangentiallyto a line running parallel to receptaclewall 7, In otherwordsinlets4 and 5 are laterally displaced practically parallel to one diameter of receptacle 2.

This allows a method for maintaining a fluid-gas dispersion in vertical receptacle 2, for example when treating effluents or sewage, whereby the gas of the gas-fluid dispersion should be effective for as long as possible, distinguished by the fact that an upward-directed more or less helical turbulentflow ofthe gas-fluid dispersion is produced in receptacle 2, and steps are taken to ensure that its peripheral speed, at least in range, is greater than the rising speed of the gas bubbles in the dispersion and less than the centrifugal speed for a separation of the gas-fluid mixture orthe gas-fluid-solid mixture. In this way the path for the gas is substantially increased compared with the height of receptacle 2, so that the required lengthy effectiveness is achieved.This is achieved practically solely by the fact that the fluid-gas dispersion is introduced eccentrically in the bottom area of receptacle 2 near its bottom 6 and, as mentioned, displaced laterally more or less parallel to one diameter.

It is an advantage if receptacle 2 is free of flow-guiding fittings and preferably has a circular cross-section but which may also be polygonal or bent and deflected from a circular line.

In this way equipment expenditure is kept very low, although a long dwell time is achieved forthe gas. The height of receptacle 2 may in this case be kept below 10 m and for example 8 m or less.

Nonetheless the path of the gas bubbles inside the receptacle, despite the lack offlow-guiding devices, is definitely substantially longer, so that an appropriate dwell time and effectiveness on the substrate is achieved. The diameterorthe maximum cross-sectional extension of receptacle 2 is in this case about 5 m or even less, so that even the required base area is relatively small.

It should be mentioned that for receptacles 2 of more than 8 m in heightand/or more than 5 m in diameter, which are therefore suitable for a greater quantity of substrate, a fluid-conveying device for producing a more or less eliptical flow directed around the centre of the receptacle may be provided inside, and this is not shown in the embodiment.

With the method which is implemented with the device in the embodiment, the eliptical to circular flow movement of the charge in receptacle 2 is produced by the introduction of the gas-fluid dispersion. This at the same time ensures thatthe speed of the fluid-gas dispersion on entering receptacle 2 is about the same as or greaterthan the peripheral speed of reactor content 3 in the area of the inlet. In this case the inlet speed may be designed to be high enough sothatthe peripheral speed reducing over the height of receptacle 2 is still above the rising speed ofthegas bubbles, even inthetop area of the receptacle, so that premature escape of the gas inthistop area is also avoided.

The speed offlow orthe dwell time ofthe components involved in the reaction is in this case controlled in rising receptacle 2 by controlling the quantity of the eccentrically supplied flow of fluid-gas dispersion, which is also very simple and keeps the mechanical expenditure low.

In this connection it is possible to recognise outside receptacle 2 on the inlet pipes 8 devices 9 for dispersing offluid with gas. In this case it is possible that such a device 9 has its own fluid inlet 10 or has a return pipe 11 from the top end of receptacle 2 for supplying receptacle fluid. In the embodiment both possibilities are provided, whereby a further return pipe 12 is taken into inlet 10 before one of the dispersion devices 9, in order in this way too via a single device 9to be ableto mix both receptaclefluid 3 and fresh fluid with gas. This circuit may be supported by a fluid-conveying device 13.

Receptacle 2 has in the top area a cross-sectional extension l4fordegassing fluid 3, bywhich the eliptical to circularflow inside the receptacle is slowed down, so that the gas comes out here. Above the cross-sectional extension 14 it is possible to see at least one gas outlet opening 15, through which the used gas may be drawn off. In addition substrate 3 when it has been completed treated is drawn off via a side pipe 16 on the top side of the receptacle.

To eliminate the gas portion after passage through receptacle 2 the speed of flow is therefore reduced in the top area by the aforementioned cross-sectional extension to below the rising speed of the gas, so that the gas can then escape upwards.

For the implementation of the method it is a good idea if the more or less eliptical to circularflowspeed in the receptacle 2 at eccentric inlet point4orSforthe fluid-gas dispersion is selected at more or less 0.5 m/sec to 4 m/sec, preferably about 0.8 m/sec to 3 m/sec. It is also a good idea if the fluid-gas dispersion - using device 9, is produced outside receptacle 2 and fluid can even be fed to it from receptacle 2 itself and partially mixed. This contributes to limiting the height of the receptacle, for no part of the height of the receptacle need be used to produce this dispersion.In the top area of the receptacle the fluid mixture of receptacle 2 is branched off via pipe 11 or 12 as already mentioned, and mixed with fresh gas in device 9 and fed back into receptacle 2 as a fluid-gas dispersion, if treatment of substrate 3 in the receptacle has to be repeated several times. This also contributes to the possibility of limiting the height of the receptacle, because the fluid in the receptacle can as a result ofthis be exposed several times to the reaction with the gas.

On the whole this gives a simple method and also a mechanically cheap device with which, and without expensivefittingsandthe like, it is nonethelessstill possible to achieve an adequate dwell time of the gas-fluid dispersion within a substrate, so that its path is located on a more or less helical line or helical su rface, which is substantially longer than the height of the receptacle. Thus depending on the circulation quantity selected and the quantity of fresh material that is fed in the dwell time ofthe dispersion can be selected without disintegration, whereby a dwell time, depending on the taskto be carried out, and the reaction speed and fresh material composition, of 900 to 180 seconds per reactor passagewas determined as being particularly suitable.

Should it be necessary however, longer or shorter dwell times may be set. The aforementioned preferred dwell times correspond to a rotation of the reactor content of 4 to 20 vol/vol useful reactor content x hour.

As a result of the possibility of the largely free choice of dwell times in reactor receptacle 2, it is therefore possible to control the gas fed in to ensure that it is used to the best possible advantage, whereby atthe same time there is an advantage in that it is possibleto operate with any concentrations of reactive gas. It is therefore possible to feed in air or airenrichedwithoxygen or pure oxygen as the gas and by selection ofthe reaction conditions and times via quantity control and the varying flow speeds resulting from this achieve the best possible utilisation. The reduction of the peripheral speed in the receptacle upwards due to flow losses, which depend on the reactor height, the viscosity and dwell time and the bottom peripheral speed, can be selected by means of an appropriately high inlet speed in the bottom area of the reactor so that in the top end area of the receptacle it is still above the rising speed of the bubbles. Where necessary a fluid-conveying device may befitted as a back-up and/or the cross-section ofthe receptacle may be tapered upwards.

Claims

1. Amethod for maintaining afluid-gas dispersion in a vertical reactor having inlet openings forthe fluid-gas dispersion and a top opening for removal of the used gas coming out ofthefluid, whereby the fluid-gas dispersion flows through the charge in the reactor, wherein an upwardly directed somewhat helical turbulent flow ofthefluid-gas dispersion is produced in the reactor, the peripheral speed ofthe dispersion at least as regards its range being greaterthanthe rising speed of the gas bubbles in the dispersion and less thanthe centrifugal speed for a separation of the gas-fluid mixtureorthe gas-fluid-solid mixture.

2. Method according to Claim 1, in which the fluid-gas dispersion enters the reactor eccentrically in the bottom partthereof, preferably near its bottom.

3. Method according to Claim 1 or 2, in which the fluid-gas dispersion enters the reactor, laterally displaced, approximately parallel to a diameter.

4. Method according to any of Claims 1 to 3, in which the fluid-gas dispersion enters the reactor nearthewall thereof and near the bottom thereof, approximately tangential to a line parallel to the wall ofthe reactor.

5. Method according to any of Claims 1 to 4, in which the contents of the reactor are displaced in an eliptical to circularflow movement around its centre-line and in which the speed of the fluid-gas dispersion on entering the reactor is the same as or greaterthanthe peripheral speed ofthe contents of the reactorin the area of the entrance.

6. Method according to any of Claims 1 to 5, in which the entrance speed of the fl uid-gas dispersion is sufficiently high that the peripheral speed reducing over the height of the reactor is still above the rising speed of the gas bubbles in the dispersion even in the top area.

7. Method according to any of Claims 1 to 6, in which the contents of the reactor are displaced bythe entrance ofthefluid-gas dispersion in the direction of rotation in an approximately eliptical to circular movement.

8. Method according to any of Claims 1 to 7, in which the contents of the reactor are displaced mechanically and/or by engineering in an eliptical to circular movement.

9. Method according to any of Claims 1 to 8, in which to eliminate the gas portions afterflowing through the reactorthe speed offlow in the top area is reduced below the rising speed of the gas bya cross-sectional extension.

10. Method according to any of Claims 1 to 9, in which the approximately eliptical to circular speed of flow in the reactor at the eccentric point of introduction of the fluid-gas dispersion is between about 0.5 m/sec and 4 m/sec, preferably about 0.8m/sec to 3m/sec.

11. Method according to any of Claims 1 to 10, in which the fluid-gas dispersion is produced outside the reactor and when necessary fluid is fed to it or partially mixed with it from the reactoritself.

12. Method according to any of Claims 1 toll, in which the fluid mixture of the reactor is branched off in the top area thereof, provided with fresh gas and then fed back as a fluid-gas dispersion into the reactor.

13. Method according to any of Claims 1 to 12, in which a fluid-gas dispersion with both fluid from the reactor and with fresh fluid is fed into the reactor.

14. Method according to any of Claims 1 to 13,in which the speed of flow or the dwell time ofthe components involved in the reaction rising in the reactor are controlled by control of the quantity of the eccentrically introduced flow of the fluid-gas dispersion.

15. Apparatus for maintaining a fluid-gas dispersion for instigating biochemical reactions and including a cylindrical or approximately vertical reactor which is filled with the substrate to be treated and which has at least one inlet for the fluid-gas dispersion, in which the inlet or inlets forthe fluid-gas dispersion is/are arranged eccentrically in the bottom area ofthe reactor.

16. Apparatus according to Claim 15, in which the inlet runs approximately horizontally, where necessary rising on a slant.

17. Apparatus according to Claims 15 to 16, in whichtheinletforthefluid-gasdispersionis arranged nearthewall ofthereactorinan approximately tangential direction to a line running parallel to the wall of the reactor.

18. Apparatus according to any of Claims 15to 17, in which the cross-section of the reactor reduces over its height.

19. Apparatus according to any of Claims 15to 18, in which the reactor has no flow-conducting fitments and has a polygonal to round or circular cross-section.

20. Apparatus according to any of Claims 15 to 19, in which the heightofthe reactor is below 10m, and is preferably 8m or less.

21. Apparatus according to any of Claims 15 to 20, in which the diameter orthe largest cross-sectional extension of the reactor is about 5m or less.

22. Apparatus according to any of Claims 15 to 21, in which for reactors of more than 8m in height and/or less than 5m in diameterafluid-conveying device is arranged internally to produce an approximately eliptical to circular flow directed around the centre of the reactor.

23. Apparatus according to any of Claims 15 to 22, including means for dispersing a fluid with gas, the means having their own fluid inlet and/or a return pipe from the top end of the reactor to supply the reactorfluid and being mounted externally ofthe reactor on the inlet pipe or pipes.

24. Apparatus according to any of Claims 15 to 23, in which the reactor has in the top area, for degassing the fluid, a cross-sectional extension to reduce the speed of flow of its content and above the cross-sectional extension at least one gas outlet opening.