WO2002062564A1

WO2002062564A1 - A self-cleaning press filter with an endless screw for separatingsolids suspended in sewage

Info

Publication number: WO2002062564A1
Application number: PCT/IT2001/000383
Authority: WO
Inventors: Alessandro Sinigaglia
Original assignee: Bimec Srl
Current assignee: Bimec Srl
Priority date: 2001-02-08
Filing date: 2001-07-18
Publication date: 2002-08-15
Anticipated expiration: 2003-08-08
Also published as: ITCR20010001A0; JP2004523361A; ITCR20010001A1

Abstract

Press filter with an endless screw for separating solids suspended in sewage, of the kind comprising: - an outer framework (1); - means (15) for feeding the sewage to be treated; - and endless screw (2) for feed and pressing of the dehydrated solid material; - motor means (9); - a cylindrical sifting container (3); - an antagonist disk (24); - means for pressing (25, 26), wherein said motor means for operating the endless screw comprise an electric engine connected with programmable control means that may be separately operated, and which may invert and restore the direction of rotation of said endless screw during the work of said press filter.

Description

A SELF-CLEANING PRESS FILTER WITH AN ENDLESS SCREW FOR SEPARATING SOLIDS SUSPENDED IN SEWAGE

A SELF-CLEANING PRESS FILTER WITH AN ENDLESS SCREW AND WITH IMPROVED EFFICIENCY, FOR SEPARATING SOLIDS SUSPENDED IN SEWAGE

The present invention concerns a self-cleaning press filter with an endless screw and with improved efficiency, for separating solids suspended in sewage.

The use of press filters with endless screw is well known for separating solids suspended in sewage, in particular in the zootechnical field.

The press filters with an endless screw actually in use mainly comprise an outer framework, with an inlet for the sewage to be treated, with an outlet for the separated liquid and with an outlet for the solid, dehydrated material. It further comprises an endless screw for the feed and pressing of the solid, dehydrated material, placed in said outer framework and operated by a motor; a cylindrical sifting container with special filters, coaxially containing the endless screw, supported by the external framework. The endless screw comprises a shaft wrapped by a propeller, and the end of said propeller reaches the inner side of the sifting container. During working, the sewage to be treated will be pumped inside the sifting container, where the endless screw pushes the suspended solid parts towards the outlet, while the liquid part drains through the filters of the sifting container, is collected in the outer framework, housing the container, and is eliminated through the special outlet. The solid material will be made compact by the push exerted by the endless screw and forms a dehydrated bung that will be ejected through the outlet. Document EP 0 367 037 shows a kind of press filter with an endless screw for separating solids suspended in sewage, in which the bung of solid dehydrated material is ejected through an annular, cylindrical fissure existing between the shaft of the endless screw and the sifting container. This mentioned solution is characterized in that the end of the shaft of the endless screw projects from the opening of the outer framework and in that said shaft has a diameter usually comprised between one and twice the thickness of the annular fissure existing between said shaft and the sifting container. Such a kind of press filter with an endless screw ftirthermore shows a number of inconveniences.

The bung of solid material has a hollow cylindrical shape, is less compact near the shaft of the endless screw and tends to favour a possibility of escape for the liquid, that may hole the bung and drain from the ejection outlet for the solid material; it is not easy to restrain the shaft of the endless screw at its end projecting from the opening of the outer framework, and therefore it is easily subject to radial bending; furthermore, if the sewage to be treated is poor in solids, the machine will not be able to realize the bung of solids at the start and will request the realization of an artificial bung.

The same applicant has filed a previous Italian patent application No. CR 99A000009, in which a different solution has been described, in which the shaft of the endless screw instead of projecting from the opening of the outer framework, ends before the final section of the sifting container and has an end tapered in a conical shape. Furthermore, this realization solution comprises an extruder pipe, placed upstream of the outlet, and an antagonist disk, placed behind said outlet and that exerts a contrasting action to the ejection of the bung of solid material and thus makes it even more compact. The surface of said antagonist disk, turned towards the extruder pipe, is convex and shaped for facilitating the disintegration of the solid material coming out from the opening in the extruder pipe. Furthermore, said disk is connected with movable counterweights or elastic means which deteπnine its pressing force onto the bung of solid material coming out from the opening. The sifting container is supported and works inside the framework with its own axis inclined upwards with respect to the sense of feeding of the solid material, so as to favour the draining of the liquid part.

Further features consist in that the shaft of the endless screw has an end with a polygonal section and is connected with the shaft driven by the motor by means of a tlireaded coupling. Therefore, it is possible to disassemble the machine simply by blocking, with a special key, the end with the polygonal section of the shaft of the endless screw, inverting the direction of rotation of the motor for unscrewing the tlireaded coupling and taking out of the outer framework the endless screw and the sifting container.

Such a realization allows to form a bung of solid, homogenous, dehydrated material, without preferential breaking ways, of a nearly perfect cylindrical shape and very compact, even if sewage is treated poor in suspended solids, and without the need of realizing an artificial bung of filtered solid material when starting the machine; furthermore, it allows an effective ejection of the solid material and a high degree of separation of the phases; at last, it allows an easy disassembling of the machine for servicing and internal cleaning. One disadvantage of mentioned solution consists in that the adjusting of the pressing force of said antagonist disk, performed by means of movable weights or elastic elements like e.g. springs, is uncomfortable, requests to put ones hands at the opening of the separator and may be perfoπned only with the machine standing still. A further disadvantage consists in that the disassembling of the machine - even if it has been simplified by above-mentioned realization - makes the cleaning operations rather long and expensive. In Italian Utility Model No. CR 99000013 of the same applicant, a further improvement has been described, mainly consisting of the operating of the antagonist disk by means of a hydraulic or pne natic operating means and of the adoption of a closing plate provided with a hole closed by a removable cap, on the outer framework.

These further improvements better the efficiency of the machine, simplify the regulation operations, make the use thereof more simple and safe, simplify the periodical servicing operations and more particularly the filter cleaning operations. The motor that operates the pressing endless screw is - in the known press filters with an endless screw - of electric or oleodynamic kind. The latter is advantageously operated by an oleodynamic central usually comprising a pump, a distributor controlled by a lever with three positions that allows to invert the direction of rotation of the motor and for unscrewing the tlireaded connection between the shaft of the endless screw and the shaft of the motor, and a regulation valve that allows to vary the revolutions of the motor, usually between 0 and 200 per minute. Said pump may be operated by an internal combustion engine or by an electric motor, or even directly through the power plug of a farm tractor. The revolution speed will be regulated according to the work load of he machine and to the composition of the sewage to be treated, so as to optimise the efficiency of the press filter and to reduce the stress onto the mechanical means, specially when starting and stopping the machine. The feeding of the sewage to be treated to the inlet of the outer framework takes place through a feeding pipe usually connected by means of a T-shaped link to a overflow pipe, that discharges the excess sewage and sends it back to the raising well. The regulation of the inlet capacity to the press filter and of the capacity discharged from the overflow pipe takes place by means of a valve of known kind, with manual or controlled operating, mounted onto the overflow pipe.

In spite of all further improvements, the press filters with endless screw of the known kind still show some disadvantages. Due to their one-way preferential direction, the solid particles tend to get stuck between the filtering meshes and to foπn encaistations that worsen the filtering efficiency and make servicing and filter cleaning necessary, which requires the disassembling of the endless screw and are therefore long lasting and expensive; ftirthermore, the oleodynamic motor has proved to be little flexible in the regulation of the speed and of the direction of rotation and does not allow an optimisation of the efficiency of the press filter according to the different working conditions; then, the oleodynamic motor has a low efficiency, in particular during the working with a partial load, with a following high energy consumption in relation to the work performed by the machine.

A further inconvenience consists in that the pressure of the sewage inside the sifting container may be subject to sudden changes or to sudden increase which detennine a reduction of the efficiency of the machine and high stress rates onto the mechanical parts. A ftirther disadvantage consists in that possible front or back movements of the antagonist disk, placed before the outlet of the solid material - due to variations of the density of the treated material - may cause a variation of the pressure in the hydraulic or pneumatic means for operating the disk. Such effect implies a variation of the pressing force applied by said disk to the solid material to be ejected, with negative effects onto the homogeneity of the solid ejected product and of the global efficiency of the machine. It is the aim of the present invention to eliminate above-mentioned inconveniences. It is the main aim of the present invention to realize a press filter with an endless screw for separating solids suspended in sewage, provided with a particular movement of the endless screw that will assure the effect of automatic cleaning of the filters, that will allow a simple and comfortable regulation of the functioning speed, for optimising the efficiency of the machine; and that will assure a high efficiency with low energy consumption in all working conditions. It is a ftirther aim of the present invention to realize a press filter with an endless screw for separating solids suspended in sewage, wherein the pressure of the sewage inside the sifting container is kept constantly equal to a value that may be regulated by the operator, without sudden changes or increases.

It is another aim of the present invention to realize a press filter with an endless screw provided with an antagonist disk before the outlet of the separated solid material that exerts a pressure force onto the solid material aside of front or back movements of said disk. The aims set forth are reached by means of a self-cleaning press filter with an endless screw and with improved efficiency, for separating solids suspended in sewage according to the present invention, of the kind comprising:

- an outer framework provided with an inlet for the sewage to be treated, with an outlet for the separated liquid and an outlet for the solid dehydrated material;

- an endless screw for feed and pressing of the dehydrated solid material, placed in said outer framework;

- motor means for operating said endless screw; - a cylindrical sifting container, supported by the external framework, which coaxially houses said endless screw;

- an antagonist disk placed before said outlet for the dehydrated solid material;

- means for pressing linked to said antagonist disks, wherein the endless screw comprises a shaft wrapped by a propeller, and the end of said propeller reaches nearly the inside side of the sifting container, characterized in that sad motor means for operating the endless screw comprise an electric engine connected with programmable control means that may be separately operated, and which may invert and restore the direction of rotation of said endless screw during the work of said press filter. Said control means advantageously comprise an inverter device, a potentiometer for regulating the rotation speed and a timer which allows controlling the variation of the direction of rotation of the endless screw at determined time intervals. For balancing possible pressure increases inside said sifting container, a counterweight automatic valve with adjustable intervention is mounted onto the overflow pipe.

At the end, for making sure that the pressing force exerted by the antagonist disk placed before the outlet opening for the separated solid material be independent from front or back movements of said disk, the same is operated by a hydraulic operating means comprising a stem connected to the disk sliding in a cylinder connected to a circuit provided with special compensation means, advantageously consisting of a pressure accumulator, which maintain constant the pressure inside said circuit.

The motor means are controlled by a device that varies the motor's speed (inverter), for avoiding absorption peaks of the electric engine at the start and the following stresses on the mechanical means. The advantages obtained by means of the present invention are mainly the following: - during the working of the machine, it is possible to periodically and for detemiined time intervals invert the direction of rotation of the endless screw, which thus exerts a scraping and cleaning action of the filters, reducing the encmstations due to the one-way motion of the solid particles;

- it is possible to program automatic cleaning cycles of the filters by inverting the direction of rotation of the endless screw, increasing the separation efficiency and reducing the need of expensive disassembling and manual cleaning operations of the machine; - the electric engine assures high efficiency in all working conditions with considerable reduction of the energy consumption for the same work done; it is possible to easily vary the rotation speed of the endless screw for adapting the machine to the different functioning conditions, with an increase global efficiency; - the possibility of easily checking the incline of acceleration and deceleration of the motor during the start and stop phase, allows to reduce the electric absorption and mechanic stress peaks and increases the reliability and duration of the machine;

- the possibility of preventing sudden pressure changes inside the sifting container and to maintain constant he pressing force of the antagonist disk allows to improve the efficiency of the machine, the production constancy, the filtering efficiency and the homogeneity features of the ejected solid product;

- at the end, the functioning of the machine is highly automated. Further features and advantages of the present invention will be described more in detail herein below relating to the enclosed drawings, in which an embodiment is shown.

Figure 1 shows a lateral view and a partial section of a press filter with an endless screw for separating solids suspended in sewage according to the present invention.

Figure 2 shows in detail the working of the automatic counterweight valve with adjustable intervention, mounted onto the overflow pipe of the machine. The continuous line in figure 2 shows the completely closed position of the valve, while the dotted line shows the completely open valve.

Figure 3 shows a scheme of the antagonist disk before the outlet opening for the solid material and the hydraulic circuit connected thereto. Relating now to the enclosed figures and to the details shown therein, the press filter with an endless screw for separating solids suspended in sewage according to the present invention mainly consists of an outer framework 1, an endless screw 2 and a sifting container 3. The external framework 1 is provided with an inlet opening 4 for the sewage to be treated, with an outlet opening 5 for the separated liquid and with an outlet opening 6 for the dehydrated solid material. The endless screw 2 for feed and pressing the solid material comprises a shaft 7 wrapped by the coils 8 of a propeller: the end of said propeller reaches the inner side of the container 3 and is operated by an electric engine 9. The sifting container 3 comprises special filters 10 and devices (not shown) for centring onto the outer framework 1. The framework 1 is held up by supports 11 and 12 of different length, so that the sifting container 3 works with its own axis slightly upwards inclined, in the direction of the feed of the solid material.

The framework 1 consists of a pre-chamber 13, advantageously having the shape of a circular section, and of a separation chamber 14, advantageously having a square or polygonal section, linked to each other by means of known flanges. The inlet opening 4 for the sewage to be treated is placed on the pre- chamber 13 and is connected with a feeding system 15. Said feeding system 15 comprises a sending pipe 16 coming from a pump placed in the basin of the sewage to be treated; an overflow pipe 17, having a T- shaped connection with pipe 16, for e return into the well of the sewage exceeding the capacity of the machine; and a valve 18 mounted onto the overflow pipe 17.

The valve 18 comprises a closing diaphragm 19 hinged onto an axis 20 and onto at least a rod 21 external to said pipe 17 and connected to said diaphragm 19 and in turn rotating around said axis 20. A sliding counterweight 22 is momited onto said rod 21, and the position of said counterweight 22 may be blocked by means of special blocking systems of known kind, not shown.

The separation chamber 14 contains the sifting container 3 and is flanged, in its front part, with an extruder pipe 23 that facilitates the compression of the dehydrated material. Before the outlet opening of the extruder pipe 23 an antagonist disk is placed, connected with a stem 25 sliding in a hydraulic cylinder 26. Said hydraulic cylinder 26 is hold up by a supporting structure 27 that may be regulated in length and that is fixed to the outer framework 1, and is connected to a hydraulic circuit 28.

The hydraulic circuit 28 mainly comprises an oil tank 29, a manual operated pump 30, a maximum valve 31, a manual gate 32, a manometer 32 and a pressure accumulator 34, advantageously with a membrane and loaded with nitrogen, or of any other known kind. The electric engine 9 is connected, by means of a reducer 35, to the shaft 7 of the endless screw 2 and is controlled by an electric control apparatus 36 comprising mainly an inverter, a potentiometer for regulating the motor's speed, one or more timers for controlling the intervals of work and counter-rotation and the duration of the counter- rotation, with the possibility of regulating and operating from the outside the various functions, an amperometer for measuring the electric current absorption, a switch and, advantageously, ftirther devices and instruments like a voltmeter, an emergency button, a remote control, warning lights, call-bells etc. When the machine is working, the operator adjusts the direction and the speed of rotation of the endless screw by means of the controls on the board 36. The operator may also prepare the timers for the machine to invert the direction of rotation of the endless screw at deteπnined intervals and time periods, thus obtaining the effect of automatic cleaning of the filters. The acceleration and deceleration times of the motor are managed by an electronic device (inverter) and may be separately programmed. The sewage to be treated, suitably pumped, flows into the machine through the inlet opening 4, flows into the pre-chamber 13 and into the separation chamber 14, into the sifting container 3.

The liquid part is separated by filters 10 of said sifting container 3, is collected in the outer framework 1 due to the inclination of the machine and is discharged through the outlet opening 5. The solid part is pushed by the rotation of the endless screw 2 towards the outlet part of said container 3. As the length of the shaft 7 of the endless screw does not exceed the one of the container 3, the solid parts naturally tend to join forming a bung of cylindrical shape that is compressed and compact while proceeding along the extruder pipe 23. The outlet opening 6 is partially closed by the antagonist disk 24 which exerts a ftirther pressing onto the solid material and at the end disintegrates the cylindrical bung allowing the discharge of the compact and dehydrated solids.

The working of said valve 18 mounted onto the overflow pipe 17 is as follows: when the machine is off, the diaphragm 19 is kept in closed position by the counterweight 22. The force perfonned by said counterweight 22 onto said diaphragm 19 depends on the position in which, along said rod 21, the counterweight 22 has been blocked, or by the lever arm of said counterweight that has been measured with respect to a pin 20. During the working of the machine, the diaphragm 19 is also subject to the push exerted by the sewage, in turn depending on the pressure of said sewage and opposed to the force exerted by the counterweight; if the push of the sewage exceeds the closing push exerted by the counterweight, the valve opens discharging a part of the sewage to the overflow pipe 17. Therefore, the diaphragm 19 assumes a position depending on the entity of the push of the sewage and on the position of the counterweight 22. Variations of the sewage pressure inside the sifting container 3 cause variations of the sewage push and therefore of the position of said diaphragm 19, with the effect of varying the capacity discharged by the overflow pipe 17 and of automatically maintaining constant - within deteπnined limits - the working pressure of said container 3. The intervention of said valve may be adjusted by moving the counterweight 22 along said rod 21. The working of the hydraulic circuit connected to the antagonist disk 24 is as follows: the operator opens the gate 32 and pressurizes the circuit operating onto the pump 30 and controlling the required pressure taken from the manometer 33. When the required pressure has been reached, he closes again said valve 32. The stem 25 is connected to said antagonist disk 24 and is sliding in said cylinder 26: should said stem move, the variation of the oil volume contained in said cylinder is balanced by said accumulator 34. Therefore, the pressure inside said circuit remains constant and, consequently, the push onto the stem 25 during the movement of the antagonist disk 24 does not vary.

Claims

1. A press filter with an endless screw for separating solids suspended in sewage, of the kind comprising: - an outer framework (1) provided with an inlet opening (4) for the sewage to be treated, with an outlet opening (5) for the separated liquid and an outlet opening (6) for the solid dehydrated material;

- means (15) for feeding the sewage to be treated, connected to said inlet opening; - an endless screw (2) for feed and pressing of the dehydrated solid material, placed in said outer framework;

- motor means (9) for operating said endless screw;

- a cylindrical sifting container (3), supported by the external framework, which coaxially houses said endless screw; - an antagonist disk (24) placed before said outlet for the dehydrated solid material; - means for pressing (25, 26) linked to said antagonist disks, wherein the endless screw comprises a shaft (7) wrapped by a propeller (8), and the end of said propeller reaches nearly the inside side of the sifting container, characterized in that said motor means for operating the endless screw comprise an electric engine connected with programmable control means that may be separately operated, and which may invert and restore the direction of rotation of said endless screw during the work of said press filter. Said control means advantageously comprise an inverter device, a potentiometer for regulating the rotation speed and a timer which allows controlling the variation of the direction of rotation of the endless screw at deteπnined time intervals.

2. A press filter with an endless screw according to claim 1, characterized in that said control means comprise means that can continuously vary the rotation speed of said endless screw.

3. A press filter with an endless screw according to claim 1, characterized in that said control means comprise electronic means for managing the functions of said electric motor.

4. A press filter with an endless screw according to claim 3, characterized in that said electronic means comprise at lease one inverter.

5. A press filter with an endless screw according to claim 1, characterized in that said control means comprise one or more timers for regulating the rotation time in the two directions of said endless screw.

6. A press filter with an endless screw according to claim 1, characterized in that said means for feeding the sewage to be treated comprise automatic devices for maintaining constant the pressure of said sewage inside said sifting container.

7. A press filter with an endless screw according to claim 6, characterized in that said automatic devices comprise one valve

(18) consisting of a closing diaphragm (19) connected with at least one counterweight (22).

8. A press filter with an endless screw according to claim 7, characterized in that said counterweight (22) is sliding onto a rod (21) hinged in a point (20), and connected to said closing diaphragm (19).

9. A press filter with an endless screw according to claim 1, characterized in that said pressing means connected to said antagonist disk comprise an operating means connected to a compensation circuit (28) that maintains the push of said operating means aside from the movements of said disk.

10. A press filter with an endless screw according to claim 9, characterized in that said operating means is of the hydraulic kind and said compensation circuit comprises a pressure accumulator

(34).