SE511130C2 - Process for preparing an absorbent in particulate form from waterworks sludge - Google Patents

Abstract

The present invention relates to a method for treatment of water works sludge. Water works sludge is a waste product that at present is returned to the recipient that the water works takes its water from. This cannot continue in the long run but the water works sludge must be taken care of. Significant for the method according to the invention is that said water works sludge (2) in the first step is dried, that the works sludge (2) in the second step is air-dried to a dry matter content of 30-80 %. According to a preferred embodiment of the invention the dried water works sludge is further processed to an absorber, especially absorbers for oil or urine from cats, said dried water works being crushed or subjected to further drying.

Description

Brief Description of the Drawings Hereinafter, embodiments of the invention will be described with reference to the accompanying drawings, in which the figures show: Fig. Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig 1A 2B 3A 3B 4A 4B SA 5B 6A 6B 7 8 a side view of a filter bed included in the equipment carrying out the method according to the invention, the filter bed being in a starting position; a plan view of the filter bed in the position according to Fig. 1A; a side view of the filter bed a plan view of a side view of the filter bed a plan view of a side view of the filter bed the filter bed is located the filter bed is located the filter bed the filter bed according to Fig. 1A, wherein in a first end position; in the position according to Fig. 1A, Fig. 2A; wherein in a second end position; in the position according to Fig. 1A, of the filter bed has been removed; a plan view of the filter bed in the position according to a side view of the filter bed according to Fig. 1A, Fig. 3A; wherein a Fig. 4A; wherein a further step in the drying process has been performed; a plan view of the filter bed in the position according to Fig. SA; a side view of a set of multi-level drying grilles; a plan view of the dryer grid assembly of Fig. 6A; a flow chart absorber a flow chart absorber for Oil; production of one and production of a cat urine.

Detailed Description of Embodiments of the Invention The present invention thus relates to a process for producing an absorbent, wherein the fox is a sludge taken out of a sedimentation basin at a waterworks, said sludge being called waterworks sludge, which is a semi-organic product which normally consists of about half of a metal hydroxide and to about half of the humus substances from the raw water source. Other compositions of the waterworks sludge are also possible within the scope of the invention.

The first step in the process according to the invention is to air dry the waterworks sludge, which is illustrated in Figs. 1A-6B. The dry content of the sludge can vary greatly from waterworks to waterworks, the thinner the sludge the easier it is to separate water from the sludge the first time in the filter bed. Normally, the waterworks sludge has a dry content of 1-4%, however, it should be pointed out that within the scope of the invention, the waterworks sludge can have dry contents outside this range.

The raw material, ie the waterworks sludge 2, is transferred, preferably by pumping, from the sedimentation basin (not shown) to a filter bed 1, the filter bed 1 comprises a rectangular cradle with bottom 4 of see Figs. 1A-5B, filter cloth 3 and a rim 5 resting on bottom 4. According to the described exemplary embodiment, the rim 5 is also made of filter cloth 3, which is mounted on a frame (not shown). Figs 1A-SA are extremely schematic, which is why said figures do not show the frame of the bottom 4 in which the filter cloth 3 is clamped.

The inverted V 9 in the middle of the underside of the filter cloth 3 symbolizes the pivot point of the filter bed / cradle 1.

When the waterworks sludge 2 has been pumped over to the cradle 1 so that about 20% of its volume is filled, the transfer of the sludge 2 is interrupted.

Already during the filling of the cradle 1, a certain dewatering of the waterworks sludge 2 takes place. In order to effectively drain the waterworks sludge 2, the cradle 1 is first tilted to the left, see Figs. 2A and 2B, to its first end position second state of mind. As can be seen in particular from Figs. 2A and 3A, the waterworks sludge 2 will be displaced from one end of the cradle to the other at said rocking. the cradle 1 is allowed to stand for a certain time in its respective end positions so that water can flow through the filter cloth 3 partly in the bottom 4 of the cradle 1 and partly in the rim 5. The above-mentioned displacement of the waterworks sludge 2 from one end to the other means that a respective end position, the filter cloth 3 is self-cleaned, this applying to both the filter cloth in the bottom 4 of the cradle 1 and the filter cloth in the rim 5. Shaking can continue for as long as water is filtered out, which can last up to an hour.

After this first dewatering step, the rim 5 is lifted up, see Figs. 4A and 4B, and the dewatered waterworks sludge is allowed to remain on the filter cloth 3 of the bottom 4 for a certain time, which normally amounts to about 3 hours. Now the waterworks sludge has reached such a dry content that it has become a sludge cake, in which it is possible to mark stripes, whereby stripes in a grid pattern, see Fig. 5B, means that a large sludge cake is divided into several smaller cube-shaped sludge cakes 2 'which may lie and dry on the filter cloth 3 for a certain time, normally about 20 hours or more. By way of example but not limitation, it is stated that the mud cake preferably has a thickness of 5-10 cm. The stripes in the large mud cake can preferably be provided with a rubber rake. The cube shape is favorable for obtaining a high dry content in a short time.

Preferably, this drying takes place in a room with a temperature just above 20 ° C, whereby a fan (not shown) blows air under the filter cloth 3 of the bottom 4.

The drying time of the cube-shaped sludge cakes 2 'is controlled by the fact that the sludge cakes 2' must be movable from the filter cloth 3 of the bottom 4 to a set of drying grids 10 in several levels.

Preferably, said transfer of the cube-shaped sludge cakes 2 'from the filter cloth 3 of the bottom 4 to the set of drying grids 10 can take place, for example, by scraping the cube-shaped sludge cakes 2' over to a conveyor belt (not shown) transporting the cube-shaped sludge cakes 2 'to the set of drying grids. cube-shaped sludge cakes 2 'are transferred from the conveyor belt to the set of drying grids 10. Preferably, each of the drying grids 10' is extendable like drawers and the drying grids 10 'have a mesh size which is adapted so that when the cube-shaped sludge cakes 2' reach a dry content of 75-80% their volume has decreased so much that they fall through the drying grid 10 'and down on a collecting plane 11, which in the embodiment shown in Fig. 6A is provided with wheels 12 and a drawbar 13, whereby a transport unit 14 for said cube-shaped sludge cakes 2' is formed, which can thereby be easily transported away. In this context, it should be pointed out that within the scope of the invention it is also possible to interrupt the drying already at a lower dry content, eg 30-50%. As will be explained below, for some applications of the invention it may be advantageous to interrupt the drying at a lower dry content. At what dry content the cube-shaped sludge cakes 2 'the drying grid 10' depends of course on the selected mesh size, whereby falls down, however, care should be taken that the mesh size is sufficiently fine to support the cube-shaped sludge cakes 2 'when transferred from the filter cloth of Figs. From this reasoning it is understood that if the drying is interrupted before the cube-shaped sludge cakes 2 'fall through the drying grid 10', said cube-shaped sludge cakes 2 'may be transferred in another way to the transport unit 14.

Preferably, this drying takes place on the set of drying grilles 10 in a room with a temperature just above 20 ° C, whereby a fan (not shown) blows air through the drying grilles 10 '.

In order not to affect too much the temperature maintenance in said premises, it can be provided with an entry and exit lock for empty and filled transport units 14. The air leaving the premises should be led down into a cinema boat for purifying said air.

The time required for the entire drying process, ie from the time the waterworks sludge 2 is pumped from the sedimentation basin until the cube-shaped sludge cakes 2 'collect on the collection plane 11 of the transport unit is about 3 days if a dry content of 75-80% is to be achieved. Within the scope of the invention, the entire drying process can be automated.

The flow chart shown in Fig. 7 illustrates how an absorbent is preferably prepared for oil, the flow chart according to Fig. 7 starting from the cube-shaped sludge cakes 2 ', the drying process of which has been described above. In the exemplary embodiment according to Fig. 7, the cube-shaped sludge cakes 2 'have a dry content of 75-80%. Said, air-dried, cube-shaped sludge cakes 2 'to be comminuted are very hard and must be crushed, in the embodiment according to Fig. 7 this is done by feeding the cube-shaped sludge cakes 2' into an electric motor-driven crusher 15, whereby an electric motor (not shown) with low energy consumption. The gravel 2 "obtained after the crushing constitutes the finished product and is collected in a storage vessel 16. In the embodiment shown WU 20 25 30 35 511 130, the finished product / gravel 2" is transferred to bags, the bag-packed product constituting the ready-to-deliver 6 product. . Of course, the bags can have different volumes depending on the customers' wishes.

The flow chart shown in Fig. 8 illustrates how a so-called cat sand, is produced, the flow chart according to Fig. 8 absorbent, preferably for cats, starting with the waterworks sludge being centrifuged, which is illustrated by the symbol 18. In the described embodiment this centrifugation increases the dry content of waterworks 2 to waterworks. 20%. Thus, within the scope of the invention, the first stage of air drying, as described above, can be replaced by centrifugation.

The centrifuged sludge is then air-dried in substantially the same manner as described above in connection with Figs. 1A-6B, the air-drying being interrupted at a dry content of 30-50%. The cube-shaped air drying is obtained by the slurry cakes 2 'can either be directly transferred to a drying oven / pelletizing plant 20, said transfer being illustrated by the arrow 21. A usually brown cat litter is obtained which has no added color. wherein the color of the cat litter depends on the composition of the waterworks sludge.

According to an alternative within the framework of the flow chart according to Fig. 8, the cube-shaped sludge cakes 2 'can be transported to a dyeing tank 22 with a stirrer 23, this transport being illustrated by the arrow 24. From the dyeing tank 22 to the drying oven / pelletizing plant 20, the cube-shaped slurry cakes 2 being transported 'illustrated by the arrow 25 in Pig 8. The reason why the cube-shaped sludge cakes 2' are colored according to an alternative, usually to a gray color tone, is that according to some expertise the color of the cat litter is extremely important for the cat litter to be accepted by the cats. Preferably, natural colors were used. In general, however, dyeing makes the end product more expensive.

The drying oven / pelletizing plant 20 according to the exemplary embodiment shown is gas or oil fired, but within the scope of the invention, for example, electric drying ovens / pelletizing plants can also be used. In the drying oven / pelletizing plant 20, the dry matter content is increased to about 75-80% while the cube-shaped sludge cakes 2 'decompose into particles which are suitable in size for use as an absorbent, especially cat litter. The particulate absorbent / cat litter 2 "emanating from the drying oven / pelletizer 20 is transferred to a storage container 26, said transfer being illustrated by the arrow 27. If a pelletizer is used, a more uniform size of the particles is obtained.

From the storage container 26, the absorbent / cat litter 2 "'is transferred to a packaging line where the absorbent / cat litter 2"' is packaged in bags 28 of different sizes. The transfer of the absorbent / cat litter 2 is illustrated by the arrow 29. from the storage container 26 to the packaging line. Possible modifications of the invention. The method described above, as well as the means for air drying of waterworks sludge 2, can be modified in various ways within the scope of the invention. General to the invention, however, is that air drying is used at some stage to increase the dry content of the waterworks sludge. In this context, it should be pointed out that no chemical thickening aids are preferably used in the air drying. The sludge cakes that are produced do not have to be cube-shaped.

In general, for the present invention, the initial stage of the drying of the waterworks sludge can be carried out in a number of different ways, air drying and centrifugation being stated above. Within the scope of the invention, however, it is conceivable to use other conventional methods for drying waterworks sludge, whereby by way of example but not limitation, mention may be made of screen belt pressing, vacuum filtration and chamber filter pressing.

Centrifugation, air drying and other methods for drying waterworks sludge can thus be combined in many ways to achieve different dry contents in addition to what has been exemplified above. Thus, for example, the flow chart shown in Fig. 7 within the scope of the invention can be started with centrifugation, or another alternative drying method, and then air drying. With regard to the flow chart according to Fig. 8, it is conceivable that the centrifugation is discontinued and that only air drying precedes the subsequent drying in a drying oven / pelletizing plant. Alternatively, it is conceivable that the centrifugation will be replaced by another accepted drying method for waterworks sludge.

Claims (9)

A process for the preparation of an absorbent in particulate form, characterized in that in a second stage water sludge is air-dried to a dry matter content of 30-80%, and that it (2) in a first step is dried, that the waterworks sludge (2) so obtained product is crushed or subjected to further drying. Method according to claim 1, characterized in that the waterworks sludge (2) is only air-dried to a dry content of 30-80%. Method according to Claim 1 or 2, characterized in that during air drying in the first step, initial dewatering takes place through a filter cloth (3). 4. A method according to claim 1, characterized in that the drying in the first step consists of centrifugation or another accepted drying method for waterworks sludge. Method according to one of Claims 1 to 4, characterized in that in the second drying step, which takes place by air drying, the waterworks sludge (2) is divided into smaller units (2 '). 6. A method according to any one of claims 1-5, characterized in that after air drying in the second step the product thus obtained is dyed. Method according to one of Claims 1 to 6, characterized in that the further drying is carried out in a drying oven or a pelletizing plant. A method according to any one of claims 1-7, characterized in that the air drying takes place at a temperature of at least 20 ° C. 511 130 Method according to one of Claims 1 to 8, characterized in that the air is controlled by means of fans during air drying.