EP0333045B1 - Vacuum sewage conveying system - Google Patents

Description

Waste water evacuation systems have been known for a long time. Such waters often contain poorly resistant materials. They come in particular from water closet bowls. They circulate in the vacuum evacuation conduits in the form of bundles which occupy the entire section of the conduit and which are therefore called plugs. These plugs are followed by air masses which ensure their propulsion.

• les diamètres des conduits requis pour l'évacuation sous vide sont nettement inférieurs aux diamètres nécessaires pour l'évacuation gravitaire,
• au contraire de l'évacuation gravitaire, l'évacuation sous vide fonctionne quelle que soit la pente des conduits. Elle permet notamment de faire remonter l'écoulement sur une hauteur maximale correspondant à la valeur de la dépression exprimée en mètres de colonne d'eau,
• l'évacuation des eaux de water-closet ne requiert qu'un faible volume de chasse : moins de 1,5 litre d'eau, contre 6 à 9 litres pour les systèmes à évacuation gravitaire.

Compared to gravity evacuation, vacuum evacuation has three essential advantages:

• the diameters of the conduits required for vacuum evacuation are much smaller than the diameters necessary for gravity evacuation,
• unlike gravity evacuation, vacuum evacuation works regardless of the slope of the conduits. It makes it possible in particular to bring the flow up to a maximum height corresponding to the value of the depression expressed in meters of water column,
• the evacuation of water from a closet requires only a small volume of flushing: less than 1.5 liters of water, compared to 6 to 9 liters for gravity drainage systems.

These advantages are particularly advantageous for discharging water from water closets in surface or submarine ships.

• Une première technique connue consiste à recueillir les eaux usées dans un réservoir qui est mis sous vide au moyen d'une pompe à vide. Cette pompe n'a pour fonction que de créer et maintenir le vide dans l'installation. Elle n'aspire donc que de l'air. Pour pouvoir effectuer la vidange du réservoir sans interrompre le fonctionnement de l'installation, il faut disposer d'une autre pompe pouvant aspirer les matières sous vide, ou prévoir des systèmes de sas sophistiqués. Par ailleurs les eaux usées étant stockées sous vide, la dégradation aérobie des matières ne s'effectue pas.
• Pour pallier ces inconvénients, une seconde technique est connue par le brevet français FR-A-2 502 666 . Elle consiste à compléter l'installation avec pompe à vide par une colonne barométrique qui permet de transférer les eaux usées en continu du réseau en dépression vers un collecteur à la pression atmosphérique. Le réservoir de stockage n'est alors plus indispensable. L'inconvénient majeur de cette technique est de nécessiter une hauteur importante (de 5 à 10 m) entre le collecteur et le point bas du réseau en dépression.
• Une troisième technique connue est décrite dans le brevet français FR-A-2 308 742 et son correspondant américain US-A-4 034 421. Suivant cette technique on utilise un réservoir de stockage à la pression atmosphérique. Une pompe de circulation aspire les eaux usées stockées dans ce réservoir, et les refoule sous pression dans un éjecteur dont le divergent les restitue au réservoir. Le col de l'éjecteur est raccordé au réseau d'évacuation dans lequel il maintient le vide. Les eaux usées, l'air et les matières sont ainsi transférés du réseau sous vide au réservoir par l'intermédiaire de l'éjecteur. Cette technique présente l'intérêt de laisser le réservoir de stockage à la pression atmosphérique sans complication majeure de l'installation. Elle présente cependant l'inconvénient propre aux éjecteurs qui est un mauvais rendement, ce qui se traduit par une sur-puissance de la pompe de circulation, ou par la multiplication des groupes éjecteur/pompe. Le préambule de la revendication principale se base sur ce document.
• Enfin, une quatrième technique connue consiste à employer une pompe à vide à vis d'Archimède pour créer et maintenir le vide dans un réservoir connecté au réseau de collecte des eaux usées. Une pompe à vis spéciale capable d'aspirer des liquides et des gaz a été développée pour cette application. Cette pompe n'est cependant pas capable de faire transiter les matières solides. Le réservoir doit donc être équipé pour trier les matières et les broyer. L'installation devient alors beaucoup plus complexe.

Different techniques are known for generating the vacuum:

• A first known technique consists in collecting the waste water in a tank which is put under vacuum by means of a vacuum pump. The function of this pump is only to create and maintain a vacuum in the installation. So it only sucks air. To be able to empty the tank without interrupting the operation of the installation, another pump must be able to suck up the materials under vacuum, or provide sophisticated airlock systems. Furthermore, the wastewater being stored under vacuum, the aerobic degradation of the materials does not take place.
• To overcome these drawbacks, a second technique is known from French patent FR-A-2 502 666. It consists of completing the installation with vacuum pump by a barometric column which allows to transfer wastewater continuously from the vacuum system to a collector at atmospheric pressure. The storage tank is no longer essential. The major drawback of this technique is that it requires a significant height (5 to 10 m) between the collector and the low point of the vacuum network.
• A third known technique is described in French patent FR-A-2 308 742 and its American correspondent US-A-4 034 421. According to this technique, a storage tank is used at atmospheric pressure. A circulation pump sucks the waste water stored in this tank, and discharges it under pressure into an ejector, the divergent of which returns it to the tank. The neck of the ejector is connected to the evacuation network in which it maintains the vacuum. Wastewater, air and materials are thus transferred from the vacuum network to the tank via the ejector. This technique has the advantage of leaving the storage tank at atmospheric pressure without major complication of the installation. However, it has the disadvantage of ejectors which is poor efficiency, which results in an over-power of the circulation pump, or by the multiplication of ejector / pump groups. The preamble to the main claim is based on this document.
• Finally, a fourth known technique consists in using an Archimedes screw vacuum pump to create and maintain the vacuum in a tank connected to the wastewater collection network. A special screw pump capable of sucking liquids and gases has been developed for this application. This pump is not, however, capable of passing solids. The tank must therefore be equipped to sort the materials and grind them. Installation then becomes much more complex.

Document US-A-1,492,171 also discloses a device for discharging waste water received in a tank. These waters are expelled by an overpressure created above the wastewater in the tank thanks to a liquid ring pump serving as air compressor. This pump is not never likely to pump wastewater.

Document FR-A-2 127 865 describes a liquid ring pump which is used to compress a gas.

The document Europump Terminology 1982 Trade and Technical Press Ltd, pages 7, 9 and 17 mentions liquid ring pumps among the positive displacement pumps for pumping either gases, liquids or mixtures of the two.

Finally, the document Pumping Manual 6th Edition Trade + Technical Press Ltd. page 116 discloses a similar state of the art, adding that the liquids to be pumped may possibly contain flexible solid materials.

The object of the present invention is in particular to carry out a simple process for evacuating waste water under vacuum. It also aims to ensure that this process is energy efficient and that it allows direct connection, with or without storage tank, to a collector at atmospheric pressure, without barometric column height constraint.

These objects are achieved according to the invention by the method or system as defined by the main claim. As regards examples of preferred embodiments, reference is made to the subclaims.

Using the attached diagrammatic figures, a more specific description will now be given below, by way of nonlimiting example, how the present invention can be implemented.

Figure 1 shows an exploded perspective view of a known liquid ring pump.

Figure 2 shows a sectional view of the body of this pump in operation.

FIG. 3 shows a view of the dispenser of a modified liquid ring pump according to the invention, the drawing of suction and discharge ports of the dispenser of said known pump being shown in dotted lines.

Figure 4 shows an end view of said modified pump, the suction and delivery passages of said known pump being shown in dotted lines.

Figures 5, 6 and 7 show general views of a first, a second and a third system according to the invention.

The principle of the liquid ring pump has been known since a long time for pumping gas, in particular to create a vacuum in an enclosure. It is for example described in document FR-A-2 127 865 a liquid ring pump which is known for this use and shown in fig.1 and which comprises a rotor 11 provided with blades 11A and driven by an electric motor 10 This rotor rotates in a pump body 12 around an axis 11B parallel to the axis 12A of this body. The gas to be pumped enters through a suction flange 13 of a flange 14. It then passes into the pump body through a suction port 15 of a distributor 16 (see fig.3). The compressed gas is finally discharged by a discharge port 17 from the distributor and discharged by a discharge flange from the flange. A liquid ring 92 (see fig. 2) consists of water which has been introduced in suitable volume into the body 12 and driven in rotation by the rotor 11. It is pressed by centrifugal force against the cylindrical wall of this body and leaves a free axial volume for gas suction and compression. It constitutes for the gas a seal between the rotor blades and the wall of the pump body. Two successive blades and the liquid ring define a rotating chamber, the volume of which is large when it passes opposite the suction light 15 and small compared with the discharge light 17.

The calories produced by the compression of the gas and by friction are absorbed by the water in the liquid ring, which must therefore be renewed to avoid excessive heating. This is why a supply of water to the liquid ring is carried out permanently by means of an orifice 19 of the flange, the water then entering the pump body through a supply orifice 100 of the distributor. This excess water radially thickens the liquid ring which continuously pours the surplus through the discharge port 17. Known advantages of this type of pump are that it is robust and not very sensitive to the presence of entrained liquids or dust. by the pumped gas.

• 1) Les lumières d'aspiration 15 et de refoulement 17 du distributeur connu 16 sont remplacées par des lumières agrandies 21 et 22 comme indiqué sur la figure 3. L'objet de cet agrandissement est principalement d'éviter qu'un objet ayant pu s'introduire dans le réseau sous vide puisse se bloquer à l'entrée de la lumière d'aspiration. C'est pourquoi cette lumière est agrandie jusqu'à pouvoir contenir au minimum un cercle dont le diamètre est le diamètre intérieur de la canalisation de raccordement des water-closets, soit environ 40 mm.
• 2) Pour éviter le colmatage des conduits délimités par le flasque 14 et le distributeur 16, les brides d'aspiration 13 et de refoulement 18 sont remplacées par des brides d'aspiration 33 et de refoulement 34 présentant des orifices de diamètre plus importants percés sur la face du flasque 14, de manière que leurs axes soient parallèles aux axes 11B du rotor et 12A du corps de pompe, et qu'ils intersectent les lumières d'aspiration et de refoulement 21 et 22 dans la zone où elles ont été agrandies.

According to the invention a similar pump is used to aspirate and discharge a water-based mass. It turned out that this pump lent itself to the transit of soft materials which, entering the pump body through the suction port 15, are chopped by the blades of the rotor 11. The grinding is made possible by the robustness of the rotor which equips this type of pumps. To facilitate the transit of materials and avoid clogging of the pump, it is adapted as follows:

• 1) The suction 15 and discharge 17 lights of the known distributor 16 are replaced by enlarged lights 21 and 22 as indicated in FIG. 3. The object of this enlargement is mainly to avoid that an object having been able to s '' entering the vacuum network can be blocked at the inlet of the suction light. This is why this light is enlarged until it can contain at least one circle, the diameter of which is the inside diameter of the water-closet connection pipe, ie about 40 mm.
• 2) To avoid clogging of the conduits delimited by the flange 14 and the distributor 16, the suction 13 and discharge 18 flanges are replaced by suction 33 and discharge 34 flanges having larger diameter holes drilled on the face of the flange 14, so that their axes are parallel to the axes 11B of the rotor and 12A of the pump body, and that they intersect the suction and discharge ports 21 and 22 in the area where they have been enlarged.

FIG. 5 represents a first system in which the liquid ring pump is connected to a vacuum water collection network for wastewater. This network is shown diagrammatically by a collector 42 to which is connected a water closet bowl provided with a flush and a vacuum-tight discharge valve. This flush and this valve are of known types and are not shown. The suction flange 33 is connected to the collection network. The discharge flange 34 is connected via the pipe 41 directly to the discharge pipe or sewer 44 which is at atmospheric pressure. The operation of the liquid ring pump requires a low flow water supply, intended to maintain the volume of the liquid ring and to ensure cooling. This supply reaches the supply port 19 of the pump by means of the conduit 45, the flow rate being regulated by the valve 46.

In the system which has just been described, the liquid ring pump ensures the transfer of gases, water and solid materials from the vacuum network to the sewer 44 at atmospheric pressure, as well as the grinding of these solid materials. The advantages of the invention appear clearly since on the one hand a single rotating machine is sufficient to ensure the triple function of vacuum pump, water pump, and grinder, that on the other hand the storage tank is not essential and that finally the electrical power installed and consumed is much lower than the power required for an installation with ejectors of the same suction capacity.

According to a preferred arrangement also shown in FIG. 5, a trap is placed upstream of the liquid ring pump to retain very heavy particles, such as for example metallic objects, which could have been introduced, by accident or maliciously, into the wastewater collection system which could damage the liquid ring pump. This trap can be constituted by a simple box 51 through which the waste water transits, the inlet / outlet ports 52 and 53 being placed at the top of the box so that heavy objects fall to the bottom of the box and fail to reach the pump. The box can be emptied periodically by means of an inspection hatch 54.

According to another preferred arrangement also shown in Figure 5, it is useful to set up between the vacuum network and the liquid ring pump a check valve 55, and upstream of the valve a vacuum switch 56 capable, by via a relay 57, to start the pump on a high pressure threshold and to stop it on a low pressure threshold. Thus, when the sanitary installation is little or not used, the liquid ring pump stops when the low pressure threshold is reached, and the valve closes, thereby isolating the vacuum installation. Depending on the frequency of use of the sanitary appliances, the vacuum gradually breaks. The pump then resets to the high pressure threshold and evacuates the water and the materials accumulated in the pipes.

A disadvantage of the first system which has just been described according to the invention is the need to supply the liquid ring with clear water, which penalizes the water consumption of the entire installation. To overcome this drawback, it is preferable to introduce, between the pump and the evacuation manifold of a second system according to the invention, a storage tank 61 as indicated in FIG. 6. This tank is provided with 'a ventilation chimney 62 and a drain pipe 63 closed by a valve 64. The tank is emptied either periodically or continuously, by any means not described here, without the level falling below a minimum level located above the supply nozzle of a pipe 65 connecting the base of the tank to the suction pipe 66 of the liquid ring pump. Thus, the liquid ring can be supplied by recirculating part of the wastewater, the flow in the conduit 65 being effected without an auxiliary pump, under the effect of the vacuum created by the liquid ring pump. A supply of clear water 45 is however necessary in the start-up phase of the pump. This supply is then cut by the valve 46.

In such a system comprising a storage tank, another preferred arrangement also shown in FIG. 6 consists in extending the delivery line 71 of the liquid ring pump to the bottom of the tank. Thus, the air discharged by the pump escapes from the discharge pipe in the form of bubbles. This bubbling is conducive to aerobic degradation of the materials contained in the tank.

In a third system according to the invention shown in FIG. 7, the liquid ring pump is also used for emptying the storage tank. More particularly, here a temporary use is made of a liquid ring pump which is known in itself and according to which such a pump can operate as an air compressor. To perform a drain on closes a separation valve 81 through which the storage tank is connected to the vacuum network and an air introduction valve 82 is opened which allows communication with the atmosphere. The pump then sucks in air at atmospheric pressure which it compresses by discharging it into the tank. We also closed a valve 83 located on the tank ventilation chimney. If a tank drain valve 84 is then opened, it results in a pressure drain of the latter. It is thus possible to discharge the wastewater into a drain line 86 to a collecting duct 88 located higher than the tank.

Claims (9)

1. A process for removing sewage by suction and delivery by means of a pump, in which a tubular collector (42) is connected by a suction passage (33) to the said pump and receives the said sewage in the form of successive charges, as well as air masses following these charges and coming from the atmosphere, and the said pump sucks in these charges and these following air masses by lowering the air pressure in the said collector to a suction pressure lower than atmospheric pressure, and discharges the said sewage through a discharge passage (34) under a removal pressure greater than the said suction pressure and sufficient to allow them to be removed, characterized in that the said pump employed is a liquid ring pump (P) which is furthermore provided with a water feed passage (19) for receiving a minority flow of feed water suitable for forming and/or sustaining a liquid ring in this pump.
2. A process according to claim 1, characterized in that a tank (61) is furthermore provided, receiving and temporarily containing the said sewage under a storage pressure greater than the said suction pressure, this tank (61) being connected to the said discharge passage (34) of the said liquid ring pump.
3. A process according to claim 2, characterized in that a feed pipe (65) connects a lower part of the said tank (61) to the said suction passage (33) of the said liquid ring pump (P) so as to suck in a minority flow of sewage from this tank in order to sustain the said liquid ring, the said water feed means (46) supplying clear water and being controllable so as to be capable of ceasing to supply this clear water when this ring can be sustained by this sewage.
4. A process according to claim 2, characterized in that valves (81, 82) and a drainage pipe (86) are furthermore provided, making it possible, after a period of storage of the said sewage in the said tank, which then constitutes a storage tank (61), to drain this tank under the suction and discharge action of the said liquid ring pump.
5. A process according to claim 4, characterized in that the said valves and the said drainage pipe making it possible to drain the said tank comprise

   - an air inlet valve (82) which, when it is open, connects the said suction passage (33) of the said liquid ring pump (P) to the atmosphere, an isolating valve (81) which, when it is closed, disconnects this suction passage (33) from the said collector (42),

   - and a drainage pipe (86) connecting a lower part of the said storage tank (61) to a removal zone (88) so that, in a storage period during which this air inlet valve is closed and this isolating valve is open, this pump sucks in the said charges and the said following air masses and discharges the said sewage into the said storage tank in order to store this sewage therein, and so that, in this drainage period during which this air inlet valve is open and this isolating valve is closed, this same pump sucks in an air flow from the atmosphere and discharges this air flow into the said storage tank under a drainage pressure which constitutes the said removal pressure and which is greater than atmospheric pressure and than the said storage pressure, by virtue of which this discharged air flow itself discharges, through the said drainage pipe, the sewage which has been stored in this tank during a said preceding storage period.
6. A process according to claim 5, characterized in that the said storage tank (61) is provided with an aeration valve (83) which is closed during the drainage periods, and with a drainage valve (84) which is located on the said drainage pipe (86) and which is open during this drainage period.
7. A process according to claim 2, for the removal of sewage containing organic matter, a polluting power of which can be reduced by aeration carried out for a suitable aeration time, characterized in that the said tank is a storage tank (61) for storing the said sewage during the said aeration time, and the said discharge passage (34) communicates with this tank via a discharge conduit (71) emerging at the lower part of this tank, so that the air discharged by this pump rises in the form of bubbles through the thickness of the sewage stored in this tank.
8. A process according to claim 1, characterized in that the said liquid ring pump (P) comprises

   - a pump body (12) having a generally cylindrical peripheral wall (12B) around an axis of this body (12A),

   - a rotor (11) provided with blades (11A), having a rotor axis (11B) and rotating in this body about this axis, the latter being offset with respect to the said body axis,

   - a motor (10) for driving this rotor,

   - a distributor (16) constituting a wall in contact with the internal space of the said pump body,

   - a suction port (21) and

   - a discharge port (22) which are pierced in this distributor, the said suction port (21) being sufficiently wide to contain a circle with a diameter of approximately 40 mm, so as to facilitate suction of soft matter which may form part of the said charges,

   - and a feed passage (19) making it possible to introduce water into the said body so that the water thus introduced constitutes a liquid ring driven in rotation by the said blades of the rotor and pressed by centrifugal force against the said peripheral wall (12B) and so that separate rotating pumping chambers are constituted by these blades and this ring and so that they suck in a fluid to be pumped through the said suction port and discharge it through the said discharge port.
9. A process according to claim 8, characterized in that the axis (33A) of the said suction passage (33) and preferably the axis (34A) of the said discharge passage (34) are substantially parallel to the body (12A) and the rotor (11B) axes and in that their extensions pass substantially through the said suction (21) and discharge (22) ports, respectively.

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