DE102006037197A1 - Production of iron hydroxide pellets for water purification, e.g. after open-cast coal mining, involves flocculation of iron hydroxide slurry, concentration, filtration, milling, addition of hygroscopic fibres and pelletisation - Google Patents

Abstract

A process for the production of pellets from iron hydroxide slurry (I) with a high concentration of iron (as in slurry from pit water purification plants or filter mud from local waterworks), involves (a) treatment of (I) with a suitable flocculant, (b) successive concentration, (c) filtration, (d) thorough mixing of the intermediate product, combined with milling, (e) addition of at least 3 wt% hygroscopic fibres and (f) further mixing combined with pelletisation. An independent claim is included for an arrangement for carrying out this process, comprising a storage tank (1) for the slurry (I) which is connected to a metering device (2), a tank (3) for the flocculant (in parallel to (1)) with a metering device on the outlet side, a concentrator (4), a filter press (6), a thick substance feeder (7) for kneading and milling the intermediate, and a pelletising mixer (8) with a distributor for adding fibres plus a discharge conveyor (9) at the outlet.

Description

The The invention relates to a method and an assembly for the production of pellets formed from Eisenhydroxidschlämmen, and their Use.

Brown coal plays for the energy industry as well as the raw material producing industry one important role. In general, lignite is extracted by open-pit mining. Since this considerable mass movements are operated, that comes mostly soil deposited on the charred open pit side in contact with oxygen. Leading regularly for the oxidation of the stored minerals, in addition to acid in particular Form iron ions and sulfate ions.

After completion of the open pit operation and adjustment of the groundwater lowering, there is a rise in groundwater in the bulk materials. As a result, the minerals are dissolved in the water and transported to the resulting mining mines. This regularly produces sulphate concentrations which correspond to 10 to 20 times the concentration of sulphate in natural waters. The result is a hostile water quality with p _h values of 2 to 3. The resulting waters are neither water management nor touristically usable.

The Target of the use of the waters and the resulting from certain levels Connection to the outfall requires water treatment.

Generally known is the flooding with extraneous water. If there is a groundwater inflow and outflow for the lake after the end of the flood, acidification of the groundwater often leads to re-acidification. Since the available amounts of flooding water are limited, ascending groundwater dominates with its described negative properties. Nevertheless, the external flooding and the calcification of the surface water for raising the p _h value are still used on a large scale.

There has therefore been no lack of attempts to develop other methods. So will in the DE 10 2004 006 084 A1 a method and an arrangement for the treatment of acidic and sulphate-containing wastewater of mining proposed in which the contaminated water is first carried out a gypsum precipitation and resulting gypsum sludge is discharged after failures. It concludes a further treatment of the mining wastewater by reversing the Pyrite weathering by sulfate reduction by microorganisms with precipitation of solid sulfides, so that a biochemical sulfate reduction occurs. In a further stage, then, a degassing of the carbon dioxide, which escapes into the atmosphere, a biological Calcitfällung occurs. Not unproblematic are extraction and removal of the precipitated calcite.

After the U.S. Patent 6,174,444 and 5,698,107 the electrochemical neutralization is applied, whereby the contained sulfate and metal ions are precipitated. Other proposals envisage the accumulation of naturally occurring acid-decomposing bacteria in acidic wastewater ( U.S. Patent 6,325,923 ) or to inhibit oxidation-promoting microorganisms in their growth ( U.S. Patent 5,171,454 ). On the one hand, the effort is considerable if it is a multi-stage treatment, on the other hand is done in a one-step process, only an imperfect treatment.

all This procedure is peculiar to the fact that it has to be changed for those in Germany considerable amounts of water are insufficiently suitable. This is how it is predicted that in the next Years new surface waters in with a total volume of 25 000 ha, where the use of Hydraulic structures are due to the corrosive action of the contained Sulfates made difficult.

task The invention is therefore based on the knowledge that the sulphate is eliminated and a withdrawal is triggered a procedure and a purpose-built facility to help develop a product that binds to sulfide converted sulphate by bivalent iron completely and possible in one form which influences the further application favorably.

The Task is solved by first the Eisenhydroxidschlämme used as starting material of Mine water purification plants that regularly have a high iron concentration have, first be mixed with a suitable flocculant. Instead of the Eisenhydroxidschlämme from mine water purification plants can also be used in local Waterworks accumulating Filterspülschlamm be used.

The raw material originating from mine water treatment plants or local waterworks regularly has a solids content of less than 1% by mass and is subject to admixture of flocculation aids and subsequent thickening. Here, the solids content is increased to a range between 3 and 8 percent by mass. By means of a downstream filtering process, the solids content is increased to more than 25% by mass. The intermediate product present after filtering is as far as plas that it is delivered via a shredder serving for promotion. Here is not only a discharge, but at the same time breaking larger filter cake pieces. Conveniently, this crushing device serving to promote is designed as a screw conveyor.

The Intermediate is further dosed with a share of at least 3% by mass of hygroscopic fibers that are cracked so far that they are in one length of a maximum of 20 mm, preferably natural fibers, mixed and pelleted. After discharge from the pelleting process the resulting pellets subjected to intermediate drying until the solids content is at least 60% by mass. In order to the pellets are inherently stable so far that they can be used further supplied can be.

In front the initiation of the filtering process can be depending on the achieved solids concentration again the addition of flocculants done.

The used flocculants may be both cationic and also be anionic in nature.

A to implement the proposed method serving device is constructed so that first a storage tank for the Filterspülschlamm or the Eisenhydroxidschlämme is present, whose output a metering device is assigned. To the storage tank in parallel is a Ansetzbehälter for the Flocculants available, the output side also a metering device assigned. These metering devices are usually metering pumps.

Both Dosing devices are the output side with a Eindickeinrichtung connected. This is appropriate designed as a band thickener.

From the Eindickeinrichtung the conveyed material reaches a filter press. This is preferably designed as a chamber filter press.

Around The process is safe to run, preferably between Eindickeinrichtung and filter press a buffer vessel as a buffer storage tank, expediently with stirrer executed arranged. In the connecting line between buffer tanks and filter press is a junction another line present, which also has a metering device with the Ansetzbehälter for the Flocculation aid is connected to procedural if necessary to allow flocculation.

Out The filter press is a further transport of the thickened sludge via a suitable thick matter conveyor. This is preferably a screw conveyor.

Of the Auger downstream of a pelleting mixer is present, which is the thick matter conveyor leaving intermediate over a metering device is abandoned. Likewise, hygroscopic Fibers, as already described, added to the pelleting mixer.

The Advance products of high-consistency intermediate and hygroscopic fibers will be chosen according to the selected Construction and operation of the pellet mixer abandoned. This is in continuous operation regularly a simultaneous and at discontinuous mode of operation, a time sequence Give up.

To intensive mixing, the pellets leave the pellet mixer over one removal device, so that the pellets after a short intermediate drying dimensionally stable to the other Use available stand.

The waters to be purified are subjected to biochemical treatment in a bioreactor or the like by converting the sulfate into hydrogen sulfide. This process follows the formula 2 (CH ₂ O) + 2H + SO ₄ - H ₂ S + 2CO ₂ + 2H ₂ O

at the cleaning of tipping groundwater Iron (II) ions the dominant acid carrier.

The resulting pellets are used as filter material to get out the over These filters are directed as described in Biologically Treated Waters, in where sulfur is present as hydrogen sulphide, sulfur is removed by binding to these pellets, so that iron sulfide arises.

In order to Is it possible, attributed accumulated water due to a pre-mining form, so this as for a common one water management use is available. An application is that, the discharge volume flows, that is, water from the mining industry that passes to rivers and the like should be treated. After treatment with the inventive device is a water available, the quality naturally Surface waters corresponds. Of others can as well as in contaminated opencast mining polluted waters and Tilt groundwaters successively treated successfully.

In comparison, experience has shown that the use of iron hydroxide sludges is insufficient to handle sulfide due to a changing concentration. Thus, the setting of defined reaction conditions is possible only with varying success.

nevertheless can when using the prepared inventive pellets in addition to sulfur-containing also arsenic or phosphate-containing residues, the latter also at the same time, from contaminated waters be removed.

The Invention will be described in more detail below with reference to an embodiment become.

In the associated Drawing shows an example

1 the diagram of a suitably constructed according to the invention proposed method plant.

Iron hydroxide sludges originating from a mine water purification plant have the same or less 1 Percent by mass solid. You will first be a storage container 1 abandoned and trained as a metering metering device 2 discharged. Parallel to this is a Ansetzbehälter 3 for a Flockungshilfsmittel present, the output side also designed as a metering metering device 2 assigned. Both dosing devices 2 are the output side with a trained as band thickening Eindickeinrichtung 4 connected. This is expediently designed as a buffer vessel intermediate storage tank 5 downstream. To prevent settling of the intermediate, the buffer tank has 5 it is known to have an agitator. In the connecting line between buffer tanks 5 and a subsequent filter press designed as a membrane chamber filter press 6 there is an opening of another line, which also has a metering device 2 with the Ansetzbehälter 3 is connected for the flocculant, to allow flaking according to the process if necessary. The adjustment of the previous technical components during operation is such that the intermediate product before entering the filter press 6 has a solids content in a range between 3 and 8 percent by mass.

In the filter press designed as a membrane chamber filter press 6 the solids content is raised to a range of at least 25 percent by weight.

The intermediate product present after filtering is so far plastic that it can be discharged without difficulty. As a precaution, the discharge of the filter press 6 one of the promotion serving thick matter conveyor 7 downstream. Here not only a discharge, but at the same time a crushing resulting filter cake pieces. Conveniently, this thick matter conveyor 7 designed as a screw conveyor. Thus, the crushing and mixing is done with high intensity and the described and desired effects occur.

The thick matter conveyor 7 works on a pellet mixer 8th to. Parallel to the continuous feed of the thickened intermediate product, hygroscopic fibers are added to the pelleting mixer at the same time as the thickened intermediate in a proportion of at least 3% by mass.

These In particular, hygroscopic fibers are natural fibers, such as those of agricultural crops or landscape care areas and the like are obtainable or as a by-product in the extraction and processing of agricultural products and the like incurred and to the extent have been subjected to a treatment process are that they are based on a fiber length of 20 mm have been shortened by preferably tearing.

After discharge from the pellet mixer 8th the resulting pellets are supplied to a warehouse after being taken over by a conveyor 9 designed as a conveyor belt. Here they dry until solids content is at least 60% by mass. Of course it is irrelevant whether the drying takes place naturally or under further supply of energy.

To Completion of drying are the pellets in terms of their shape as far as inherently stable, that they are used in large scale as starting materials in Filters find use over which dissipates the water found in an open pit mine, the sulfide is bound and purified to such an extent that it has a mining quality.

List of used reference numeral

1

storage container

2

metering

3

batching

4

Eindickeinrichtung

5

Between storage tanks

6

filter Press

7

Density solids conveyor

8th

Pelletier mixer

9

removal device

Claims (18)

Process for producing pellets from iron hydroxide sludges, characterized in that sludges having high iron concentrations, such as the filter scavenging sludge originating from iron-mine sludges of the mine water treatment plants or local waterworks, are first mixed with a suitable flocculation aid, followed by successive thickening, the thickened sludge be subjected to a filtering process, the resulting intermediate product is subjected to mixing associated with a comminution, the resulting mass is added in a proportion of at least 3 percent by mass of hygroscopic fibers are added and before the discharge takes place further mixing associated with a pelletizing. Method according to claim 1, characterized in that that the successive thickening on a range between 3 and 8 percent by mass of solid content takes place. Method according to one of claims 1 or 2, characterized that the thickened Eisenhydroxidschlamm before the task in the Filtering process is subjected to flocculation. Method according to one of claims 1 to 3, characterized that in the filtering process, the solids content in a range above 25 percent by mass is raised. Method according to one of claims 1 to 4, characterized that the hygroscopic fibers are natural fibers. Method according to claim 5, characterized in that that the hygroscopic fibers are present in a maximum length of 20 mm. Method according to one of claims 1 to 6, characterized that after pelleting an intermediate drying to a solids content at equal or greater 60 percent by mass occurs. Method according to one of claims 1 to 7, characterized that after pelleting a screening of the final product takes place. Arrangement for carrying out the method according to claims 1 to 9, characterized in that first a storage container ( 1 ) is present for the Filterspülschlamm or Eisenhydroxidschlämme whose output is a metering device ( 2 ), parallel to the storage container a Ansetzbehälter ( 3 ) is present for a flocculation aid, the Ansetzbehälter ( 3 ) on the output side is also associated with a metering device, the output side with a Eindickeinrichtung ( 4 ), this subsequently a filter press ( 6 ), the output of this filter press ( 6 ) with a thick matter conveying device serving for kneading and comminuting the pending intermediate product ( 7 ) whose discharge with the entry of a pellet mixer ( 8th ), to the entry of which an allocation device for the addition of hygroscopic fibers is also connected and to the discharge a discharge device ( 9 ) assigned. Arrangement according to claim 9, characterized in that the kneading and crushing of the pending intermediate product serving heavy-matter conveyor ( 7 ) is designed as a screw conveyor. Arrangement according to one of claims 9 or 10, characterized in that the pellet mixer ( 8th ) downstream conveyor ( 9 ) is set up to dry the pellets to be discharged. Arrangement according to one of claims 9 to 11, characterized in that the Eindickeinrichtung ( 4 ) is designed as a band thickener. Arrangement according to one of claims 9 to 12, characterized in that the filter press ( 6 ) is designed as a chamber filter press. Arrangement according to one of claims 9 to 13, characterized in that between Eindickeinrichtung ( 4 ) and filter press ( 6 ) a buffer tank ( 5 ) is designed as a buffer, conveniently carried out with agitator. Arrangement according to one of claims 9 to 14, characterized in that in the connecting line between Eindickeinrichtung ( 4 ) and filter press ( 6 ) an opening of a further line is present, which via a metering device ( 2 ) with the Ansetzbehälter ( 3 ) for the flocculation aid. Use of according to one of claims 1 to 15 resulting pellets by these used as a filter material be flowed through by sulfide-containing water. Use of according to one of claims 1 to 15 resulting pellets by these used as a filter material be traversed by arsenic water. Use of the pellets formed according to any one of claims 1 to 15 and 17, in that they are used as filter material, that of phos is flowed through phathaltigem water.