DK146904B - DEVICE FOR THE REMOVAL OF A LIQUID PHASE, ISAIR WATER, FROM A SUSPENSION, SUCH AS SLAM - Google Patents

Description

(M)

(19) DENMARK

φ (, 2) PUBLICATION WRITE od 146904 B

DIRECTORATE OF

PATENT AND TRADEMARKET SYSTEM

(21) Patent Application No. 1660/76 (51) Int.CI.3: B 01 D 33/04 (22) Filing Date: 08 Apr 1976 (41) Alm. available: 10 Oct 1976 (44) Submitted: 06 Feb 1984 (86) International Application No: - (30) Priority: 09 Apr 1975 SE 7504075 (71) Applicant: 'REDERIAKTIEBOLAGET NORDSTJERNAN; Stockholm, SE.

(72) Inventor: Sven Anders Samuel 'Håkansson; SEE.

(74) Plenipotentiary: Lehmann & Ree_ Engineering (54) Apparatus for removing a liquid phase, especially water, from a suspension such as sludge

The invention relates to an apparatus for removing a liquid phase, in particular water, from a suspension such as sludge, which apparatus has two endless, moving wires which extend over a portion of their conveying path a common stretch having a beginning and an end. and at least one of which is liquid permeable, an intake at the beginning of the stretch for introducing the suspension between the two wires and an outlet at the end of the stretch for delivering the relatively dry suspension by means of the two wires, a first press means for exerting a q pressure on the two wires on their common stretch where they form a clamping path, for partial removal of the liquid phase from the suspension between the wires, and another press means exerting a higher ratio in three pressure, and which in the direction of movement of the two wires located along the clamp path after the first pressing means and having a pressure roller, a substantial part of whose circumference is enclosed by the two wires, wherein it is fluid permeable to the outer wire relative to the pressure roller.

It is generally known to press sludge between a wire and a roller, around a portion of which the wire lies. Also, in Swedish Patent Specification No. 364,698, an apparatus for dewatering sludge is known, in which apparatus the sludge is placed between two wires, of which the liquid phase can pass through at least one, where these wires enclose one or more drainage rollers.

The pressure exerted on the sludge according to the prior art is partly a function of the tension to which the wires can be exposed. However, the wires have a troublesome limited strength, and in particular, it is difficult to assemble the ends of the wires to form endless bands in such a way that the joints do not constitute a significantly weakened portion of the wire, viewed from a strength point of view.

The compression pressure on the sludge is also a function of the diameter of the roller which encloses the wire in such a way that a smaller diameter causes a higher pressure on the sludge. However, smaller rollers result in a shorter path and thus the period during which the sludge is subjected to increased pressure, and the time factor has some significance for the result of the dewatering, as will be described later.

It is also well known to provide higher pressure against the mud using pressure rollers or other mechanical devices which, at some point where the wires enclose a roller, press from the outside against the wire and thus against the mud, see e.g. Swedish Patent No. 109,941 and U.S. Patent No. 2,711,130.

However, the pressure thus obtained against the wire becomes extremely instantaneous, and only a small part of the water is pressed out of the sludge before the pressure is relieved again.

In addition, German Patent Specification No. 655-197 discloses a luminaire having a plurality of adjacent, narrow, endless ribbons or ropes of a highly elastic material abutting directly against a filter cake on the luminaire to be pressed. Ribbons or ropes may run close to each other or at some distance from each other on the luminaire, but as no wires occur and the dewatering occurs through the luminaire, it is not suitable for dewatering suspensions such as sludge and in particular is not suitable for produce a high dewatering effect since the sludge will be squeezed away from the press area, thereby avoiding the dewatering pressure of the tapes or ropes.

Finally, from German Patent Specification No. 716.0 9 a lithium drum is known in which the filter cake is received between the drum and a non-water-permeable band. On the outside of this belt, a number of straps, which are adjacent to one another, exert a pressure on the belt. Also in this citrole, dewatering occurs through the citrum, and since there is only one band (wire) for enclosing the filter cake against the citrum, this citrum is also not suitable for effective dewatering of suspensions such as sludge.

Therefore, no apparatus has so far existed which has been able to provide a rapid and highly effective dewatering of suspensions such as sludge. However, this is possible with the apparatus according to the invention, which apparatus is of the kind referred to in the preamble, and which apparatus is characterized in that the second pressing means has a compression belt arrangement of several spaced laterally spaced belts which are approximately enclosing. the press roller in the same way as the two wires.

Compared to the prior art, it has been found possible to obtain significantly higher solids content by means of the apparatus according to the invention. For many types of sludge from wastewater treatment plants, it has been possible to obtain dry matter content of well over $ 30. The reason for the high dewatering effect according to the invention is the combination of high pressure pressures acting along the clamping path and the long pressing time, which is made possible due to the extension of the clamping path and the possibility of running out of the extruded water. Furthermore, the advantage is obtained that, in the event of an unevenly distributed suspension layer occurring between the wires, the belts cause a full pressure to be effective, despite said unevenness, over the entire width of the suspension layer. This particular advantage is greater the less aqueous the suspension to be pressed.

As mentioned earlier, the time factor is of significant importance. It is therefore appropriate to rearrange and press against the press roll about as large a portion of the press roll as is practically possible. Therefore, a rearrangement of 18 ° or more is advantageous and the present invention permits large bypass angles.

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Preferably, further pressing with the apparatus according to the invention may be adjustable so that it can be adapted to suspensions of various kinds.

Furthermore, with the apparatus according to the invention it is possible to allow the pressing to be carried out with greater compressive pressure along the outer belts than along intermediate belts, thereby ensuring that the suspension layer usually thinned to the edges of the wires is also loaded with the necessary pressure, and thus measures have been taken to prevent that the suspension runs out towards the edges of the wires. In this way, a not insignificant problem has been solved, namely the tendency of the sludge to run towards the edges by pressing.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows the diagram of initially obtained dry matter content as a function of time; FIG. 2 is a schematic side view of a wireband press according to the invention; Figures 3 and 4 show, on a larger scale, a plan view of a portion of the wireband press and a partial sectional image to illustrate in detail the invention which is not particularly exhaustive; 5 is a side view similar to FIG. 2 of another embodiment of a webbing press according to the invention.

As mentioned above, the time factor is of some importance for the result of the catchment. It has been found that the time factor - the time to expose the sludge to a certain pressure - is of great importance to the drainage in the beginning, but the more time is extended, the less this means from a drainage point of view. This is illustrated in FIG. 1 in the drawing, where a schematic diagram of the dry matter content obtained as a function of time is shown. Curve A shows a typical dewatering process at a certain constant pressure against the sludge. If the pressure doubles, a different course is obtained, curve B. Both of these curves show a steadily decreasing dewatering, and they approach asymptotically a maximum value for the dry matter content for each pressure. If the pressure is further increased, discontinuities occur on the curve, e.g. as shown by curve C, which shows that the sludge particles at a certain pressure obviously block drainage of the water. Instead, one can proceed in such a way that one degrades only after e.g. curve B, relieves the pressure and then increases the pressure further and can then have a course, as illustrated by curve D.

In both embodiments of FIG. 2 and 5, two endless wires 1 and 2 run together along a pressing path between an inlet (illustrated by arrow I) for the suspension to be dewatered and an outlet (arrow II) for the dewatered suspension and each running around deflection rollers 4 Along the pressing path, an initial dewatering occurs by means of the intermediate suspension wires being known in a known manner to pass through a selected number of rollers 3 and partially enclosing these. The pressure applied here to the suspension depends on the voltage to which the wires are exposed and the size of which is limited. This wire tension can be regulated within certain limits, e.g. by displacing at least some of the deflection rollers 4.

As particularly characteristic of the invention, a substantially increased pressure is then applied to the suspension layer between the wires 1 and 2 with a pressing roller 5 by means of a plurality of parallel elastic straps or belts 6. The belts are thus about the same rollers 3a which control the wire belt before and after the pressing roller 5, and about a clamping roller 7, thereby causing the pressure to lie against the outside of the pressing roller 5, substantially the same length as the wires enclosing the pressing roller. The clamping roller 7, as well as the rollers 3a, may be suitably grooved to maintain parallelism between the belts. The pressure of the belts against the wires is controlled by means of the clamping roll 7 by displacing it as shown by the arrow HI, by means of springs or other mechanical devices. Pig. 3 shows, in plan view and on a larger scale, the press roll 5 and the tension roll 7 and schematic springs 8 as a device for providing the required pressure by means of the belts 6.

FIG. 4 shows a partial section of the roller 5 and shows on the surface of the roller the inner wire 2, the suspension layer 9, the outer wire 1 and the belts 6.

Finally, FIG. 5 shows an embodiment with two pressing rollers 5, which embodiment is suitably used in cases where the pressing time has to be extended without sacrificing the capacity of the belt conveyor.

As can be seen from Figures 3 and 4, the belts 6 are spaced apart. This distance should be adjusted so that it is sufficiently large that the water pressed out of the suspension can reach out during the effective pressing time, but the distance is also small enough that the outer wire between the straps remains so tight. that there is also considerable pressure on the suspension between the belts. The distance between the belts should suitably be less than $ 20 of the belt width. The straps may consist of many kinds of materials, such as e.g. rubber, plastic, the straps being reinforced or otherwise reinforced. It is advantageous that the straps have some elasticity. As indicated in FIG. 4, the suspension layer may have varying thickness along the width of the wire, and it is particularly common for the suspension layer to become thinner against the edges of the wire. With appropriate elasticity of the straps, such a thinner suspension layer will also be loaded with sufficient pressure for dewatering. However, according to the invention, it is also possible by means of extra tension rollers or other devices to impart increased tension to the outer straps, e.g. to prevent the suspension from running out toward the edges.

The friction between the belts and the outer wire is often sufficient to drive the belts. However, if desired, a separate drive may be provided appropriately for the drive, in which case this drive should be synchronized with the drive (not shown) of the wires.

In some cases, it is advantageous to provide the straps with transverse recesses to facilitate the drainage of water. In another embodiment, the belts may be provided with transverse elevations which cause a relative movement in the suspension upon application of pressure. Said recesses and / or elevations can also advantageously be applied to the surface of the press roll itself 5 · Recesses in the press roll in the form of axial grooves facilitate the flow of water through the innermost wire located against the press roll. If relatively wide bands are used, these may also be provided with holes or slots.

In order to obtain the most effective dewatering, but also for design reasons, it is appropriate to allow the straps to press against the wires over substantially the same length as the wires enclosing the press roll, i.e. As shown in Figures 2 and 5, the belts run around the same rollers which control the wire belts before and after the press roll. However, it is also possible to allow the straps to press against only a portion of the length enclosed by the wires for which separate deflection rollers for the straps are provided.

The pressure which can be obtained on the suspension alone by means of wire tension without the use of a device according to the invention is of the order of 1-2 kp / cm. By contrast, by means of the device 7 146904 according to the invention, considerably higher pressures can be obtained. For many types of sludge, a pressure of 5-10 kp / cm should be sufficient, but at considerably higher pressures, 30-35 kp / cm, it is possible to apply as needed.

Compared to prior art wire-band presses, it has been found that with a wire-band press comprising the belt press device according to the invention it is possible to obtain very high dry matter contents. For many types of sludge from wastewater treatment plants, dry matter content of substantially more than 30% has been achieved with a sludge press according to the invention. For certain types of sludge it has been possible to obtain dry matter content between M0 and 55%. The reason for this is, as mentioned earlier, a combination of high pressure with long press time and the possibility for the extruded water to run out. These values can conveniently be compared with the dry matter content obtained for similar sludge by the prior art mentioned in the introduction. Thus, approx. 20% solids content by dewatering between two wires enclosing a plurality of rollers and approx. 25%, if pressed further against the wires by means of press rollers.

No drainage water collection containers are shown in any of the figures, but such will be readily available to one skilled in the art in various ways. In order to achieve the high solids content which is becoming more and more desirable, not least for transport purposes, it is advantageous for the extruded water to be removed from the wires before the pressure relieves. This can be made more efficient by blowing or sucking water away by means of a strong air flow which is conducted over the wire between the straps.

As can be seen from the embodiments of FIG. 2 and 5, after ingestion, a pre-dewatering of the suspension occurs at the rollers 3 before the final dewatering by the press roll or rollers 5.

However, such pre-dewatering can be carried out before the intake I and here also with devices other than rollers corresponding to the rollers 3, whereby the rollers 3 can be avoided in the pressing path between the intake I and the outlet II.

The invention is not limited to the exemplary embodiments described above and shown in the drawing, but can be varied in a number of ways within the scope of the claims below to achieve the desired dewatering effect by subjecting the suspension between the wires enclosing the press roll to the additional pressing along mutually spaced apart. lanes extending over preferably the entire surrounding area. Thus, the belts may conceivably be connected to each other by means of elastic softer joints for e.g. easier to control in their lanes.