TECHNICAL AREA

The present invention refers to a device for dewatering and/or transport of liquid-containing screening or sludge material, including a chamber which is being under a reduced pressure and which is formed by walls, with an inlet and with means for continuously compression and separation of liquid from th screening material/the sludge,acting towards an outlet opening for evacuation of incoming material without equalization of air pressure.

BACKGROUND OF THE INVENTION

In purifying plants, the screening material is separated from the sewage during the cleaning process. The screening material that is separated from the sewage by different screening filters is transported with conveyors to an assembly point and has normally a dryness of approximately 5 to 15 percent. Through compression of the screening material the dryness can be increased. It is desirable to achieve as high dryness as possible, since the screening material is transported awa either for deposition or to a combustion station. The freight costs and the energy consumption by the combustion is reduced by means of a higher dryness. However, the dewatering of th screening material is difficult to achieve in an economicall advantageous way.

Conveyors and means for dewatering screening material ar difficult and expensive to produce and need regula maintenance, which work usually is considerated as dirty an awkward.

Vacuum conveyors have been used for a long time for pneumati transport of goods, preferably particle-formed goods. I general, they work intermittently with a filling phase and a

emptying phase. They are therefore not suited for continuou operation in sewage-treatment plants.

THE TECHNICAL PROBLEM

One purpose with the present invention is to achieve a simpl and efficient device for transport and dewatering of screenin material, which device enables a closed transport of screenin material along a considerable distance, without mechanica devices requiring regular maintenance.

THE SOLUTION

For this purpose the device according to the invention i characterized in, that the inlet includes a pipeline with valve which can be opened and closed for recurrent intake o a quantity of screening material in the pipeline and for direc or gradual transport of said quantity along the pipeline an into the chamber, under preservation of a varying pressure i the chamber.

DESCRIPTION OF THE DRAWINGS

The invention will be described hereinafter with reference t an embodiment that is shown in the enclosed drawings, wherein Fig. 1 is a plane view of a dewatering devic according to the invention, Fig. 2 shows the device in Fig. 1 in a side view, an

Fig. 3-5 show an intake guide plate that is part of th device in three different views.

DESCRIPTION OF EMBODIMENT The dewatering device shown in Fig. 1 and 2 includes generally cylindrical chamber 10, whose outside wall 11 i divided into one bigger and one smaller section 10a and 10 respectively. The chamber is provided with end-walls 12, 13 an an inlet 14 that is radially directed against the upper par of the chamber, in relation to the longitudinal direction o the chamber. An axially directed outlet 15 is placed in th end-wall 13.

The chamber 10 is connected to a not shown vacuum suction pump via a connection piece 16. The vacuum suction pump maintains an appropriate negative pressure in the chamber by means of a pressure control. The negative pressure is transmitted via a pipeline 17 which is connected to the inlet 14, which pipeline contains a valve 18 that can be opened. The pipeline orifice, not shown in the drawings, can reach a screening filter where sediments are taken up and dumped in a gathering trough, whereby the orifice can be located near the bottom of said trough, and in such a way that the orifice always is covered with a layer of screening material. By opening the valve 18 for a short moment and then closing it again, a determined quantity of screening material can be drawn into the pipeline via the mouthpiece. This procedure is continuously repeated with regular intervals, so that screening material gradually is transported through the pipeline 17 to the chamber 10. If the pipeline in the main runs horizontally, can it reach several hundred meters without the need of a high negative pressure.

When the screening material reaches the chamber 10, which can be vertically mounted as in Fig. 1 and 2, or with a certain inclination to the horizontal plane, the screening material is caught by an intake guide plate 20, 21 that is shown separately in Fig. 3-5. The sheet 20-21 has an U-shaped cross section and is provided with two generally parallel sides 20, and a centre portion 21 formed as a semicircle that connects both sides. A flange 22 at one end of the intake guide plate, forms a hold for mounting to the end-wall 12 by means of the screws 23. The outer edges of the sides of the plate lie loosely against the inner casing surface of the chamber, so that screening material can not pass into the remaining parts of the chamber. By the same reason the short sides opposite to the flange 22 are obliquely chamfered, for connection to a conic funnel 24, which in its turn connects with its periphery edge to the inside of the wall 11. The funnel 24 is truncated and connects with its inner edge to an extension of the outlet

15 that is directed into the chamber 10.

A transport screw 25 is rotatable arranged centrally in th chamber 10 and is driven by a motor 26 via a transmission 27 By the rotation of the screw 25 the screening material i pressed downward into the funnel 24 during simultaneou compression and dewatering. The liquid is thereby draine through slits 28, 29 in the funnel 24 and in the outlet 1 respectively.

The lower part of the chamber 10 forms a ring-shaped room fo gathering liquid. A connection piece 30 provided with non-return valve enables liquid pumping from said room by mean of a not shown pump, e.g. a piston pump. Alternatively wate can leave when the pressure is as its lowest in the chamber i.e. precisely after a completed feeding cycle.

The outlet 15 is provided with an elastic tube section 31, which section forms an opening whose cross section can b varied, so that it closes and thereby contributes to retain th negative pressure in the chamber 10, but yet allows passage o relative big lumps of compressed screening material. At th same time as compressed screening material is pressed ou through the tube section 31, liquid is sucked back into th tube section 15 by the negative pressure, so that th dewatering becomes very efficient.

The degree of dewatering depends on how high the negativ pressure is in the chamber 10, on the opening frequency of th valve 18 and on the speed of rotation of the screw 25.

The device described above works with simple mechanica components, which are not expensive and do not require an extensive service and which can be readily exchanged at an breakdown. As the dewatering occurs in a closed system, th dewatering is not dependent on the surrounding temperature an weather. Besides, less odour is admitted to the surroundin

than with a conventional system for gathering and dewatering of screening material.

The invention is not limited to the above described embodiment, instead more variants are conceivable within the scoop of the following claims. For instance the chamber 10 can be designed differently than shown. The transport screw 25 can also be replaced by a piston press.