DE3105582C1 - Method of treating raw coal - Google Patents

Abstract

In the treatment of raw coal, a very fine-grained component coming from the wet treatment is treated chemically before flotation with an organic polymeric polyelectrolyte obtained by inversion of a water-in-oil emulsion of a latex, as a result of which both the clarifying and dewatering results and also the selectivity and the carbon yield of the flotation are improved. After inversion, the polyelectrolyte has a higher activity in emulsion form than comparable polyelectrolytes which are used as solids in powdered or granulated form by dissolution in water. Figure 2 shows a flow sheet of this very fine-grain treatment. <IMAGE>

Description

It differs depending on the aging of the coal and the degree of outgassing one between different types of coal (! nkohlungsgrad), which by the constituents of volatile substances can be classified: gas flame coal 33 to 40% volatile Gas coal 28 to 35% Volatile fatty coal 18 to 30% Volatile edible coal 14 to 20% Volatile lean coal 10 to -14% Volatile anthracite 7 to 10% Volatile The gas flame coal is the youngest coal with the lowest calorific value (approx. 32 892 kJ per kg) and the Anthracite coal is the oldest coal with the highest calorific value (35 406 kJ per kg). The gas coals are called Fuel for power plants, the fat and Edible coal is processed into coking coal and the lean coal or anthracite coal into house fuel.

The guide numbers for the quality properties - the salable coals may only fluctuate within certain tolerance ranges, in particular the Ash content, the water content, the sulfur content and the degree of coalification or that Baking ability is decisive for differentiating the types of coal.

The individual types of coal are also distinguished by their different Differentiated grain sizes: Nibble or cubed coal 150 to 80 mm nut varieties I bis V 50 to 6 mm fine coal 10 mm and smaller dust and sludge coal under 0.5 mm more Processing products are the mountains or

Flotation mountains, the middle product (overgrown) and the pure coal. On average, the extracted raw coal contains the following proportions: about 30 to 50% Salvage approx. 5 to 20% middle product approx. 40 to 70% pure coal The aim of the processing consists in certain specifications of the coal through a corresponding selectivity to be observed during processing. The individual grain sizes of the sales coal should According to today's quality standards, about 5 to 9% ash (ash residue) and for coarse grain Contains 3 to 5% water (including surface moisture).

The grain mixture consists of each type of coal and coal type numerous individual pieces with different ash content. The grain mix can be analytically carried out using heavy liquids or with a small setting device break it down into different layers of different ash proportions. To one special To obtain a low ash content, the sorting step must be carried out in such a way that that the ash richer layers of coal in a middle good (overgrown, neither pure coal still pure mountains) get, which is then processed further by flotation, if necessary can be.

The sharper the cut is drawn during processing the product quality is better, but the yield is lower. With everyone The sorting process must therefore compromise between yield and product quality are closed, the primary ash content and the degree of intergrowth of the raw coal always represent the maximum limits.

Sorting the coal, i.e. H. the separation according to material properties, takes place during processing due to the differences in the physical properties the components to be separated. The greater and more pronounced these differences are, the better the separation succeeds. When processing hard coal they are optical properties (basis of reading work), the different weights (most important basis of mechanical sorting) and the surface properties (Basis of flotation and Oliffloc process) of importance. The main separation procedure the hard coal processing is the mechanical sorting due to the different Weight between coal and mountains. The specific weight of the coal is about 1.3 to 1.4 g / cm3 and the specific weight of the mountains around 1.7 to 1.8 g / cm3. The mechanical sorting of the coal takes place today almost exclusively in the water Medium, whereby the so-called typesetting machines have prevailed. Another The type of sorting is the separation into floating and sinking material in a sword be (Teska-Scheider).

When the coal is processed in an aqueous medium, one also speaks from coal washing. Modern processing plants today use a machine tree, the essentially pre-classifying sieves, sifter systems, fine-grain and coarse-grain setting machines or Schwertrübescheider (Teska), dewatering centrifuges, large-capacity flotation devices and vacuum filters are used as aggregates (see Fig. 1).

The sorting of the finest grain area of the raw coal is used in particular the flotation, whereby the different surface properties of coal and Recovery particles are used. The fine grain fractions enriched in the washing water (Coal sludge or raw sludge) are processed in the so-called fine grain processing treated separately. Finest grain processing wins within hard coal processing more and more important because the raw coal contains an increasing proportion of fine grain is contained because the ash content increases in the finest grain, because for the ballast coal the sales opportunities are getting worse and because on the consumer side Increasing quality requirements are being placed on the coal.

The proportion of the finest grain, based on the raw coal extraction, is over 10% and is used as dust or filter sludge in sales products (boiler fuel or coking coal). The fine grain fraction is less than 0.5 mm Grain size denotes (dust and sludge coal).

Due to increased dust control measures underground, the water content is the raw coal has risen, so that the dedusting of the coal by sighting becomes more and more difficult and increasingly fine grain is introduced into the wet processing process. As a result, the load on the washing water circuit has increased in all systems. If there is insufficient relief of the washing water, the fine grain passes through several times all wet-working process stages, whereby it is further and more comminuted, see above that the throughput rates of the flotation and filter units are reduced. In addition, high solids contents of the wash water lead to coal losses in the processing outlets. In practice, the flotation is now carried out as a large-capacity trough flotation or as cell flotation. For the separation of coal and mountains in the flotation systems flotation reagents, e.g. B. higher alcohols, used to serve as repellants as a sedimentation accelerator in the clarification processes or as a filter aid in the Dewatering processes that are used before or after flotation. As both Flotation reagents as well as flocculants have a direct influence on the trouble-free operation and also take care of the quality of the end product, their problem-free application is of particular importance. Especially in modern Systems with circulation of the washing water is wrong or uncontrolled Use of these resources always involves costs, malfunctions, and quality losses or Reduced performance associated.

1 percent less coal output in flotation means z. B. for the German hard coal mining a loss of about 20 million DM per year and every percent of water in the flotation concentrate means a loss of quality, loss of sales, Piling up and other costs. If one assumes that in German coal mining more than 15 million DM for operating materials such as flotation reagents and flocculants consumed and thus processed processing products valued at over DM 1 billion it becomes clear how important the resources themselves are.

It is known in the sewage processes and dewatering processes for coal processing polyelectrolytes, which are also known as flocculants, to use.

In the clarification processes, the polyelectrolytes are faster Sedimentation, a higher thickening and a better water clarification achieved. at the dewatering processes are higher throughput rates with polyelectrolytes the drainage machines and better drainage with reduced final water content achieved in drainage products.

Since the entire water system is to be understood as a cycle, get the polyelectrolytes into the flotation system via the water or adsorptively via the raw sludge. In doing so, they exert an influence on the flotation results. It is known that with increasing polymer concentration, in particular, the selectivity and the carbon yield the flotation is worsened by polyelectrolytes, see A.

Götte, W. Flöter »Studies on the Effect of Flocculants and their influence on flotation and dewatering of fine hard coal «, research report of the State of North Rhine-Westphalia, No. 1079, 1962.

A. Supp and H. Auerbach report in their article »Large-scale flotation systems in the practice of coal processing in the Ruhr area "in Erzmetall, 33 (1980), No. 9, pp. 441 to 445 that an excessive use of flocculant is unfavorable affects the quality of the flotation mountains in particular. So sank z. B. at a Increase in flocculant consumption from 100 to 200 kg / day of the ash content Flotation mountains from 70 to almost 60%. The ones previously used by the technology Polyelectrolytes for washing water clarification, for flotation clarification, for sludge coal dewatering (Flotation concentrate drainage) and the flotation mountain drainage were powders or granules in solid form, which after appropriate preparation in their aqueous Solutions were used. For the preparation of foam swimming from freshly degraded Underground coal and for foam flotation of oxidized coal is suggested been (DE-PS 2740548 and DE-OS 28 50 988) a flotation promoter on the basis to use an invertible water-in-oil emulsion of a sodium polyacrylate. The coal mined underground is characterized by the fact that its oxygen content deviates only slightly from the original oxygen content (the difference is less than 1%) and it is easily floatable per se, while with oxidized coal Increasing weathering has increased the oxygen content and the flotation ability of coal in general. Characteristic of the above procedures is the use of the flotation promoter immediately during flotation. The use is also limited to latices of sodium polyacrylates, copolymers of Acrylamides in emulsion form have not been considered for flotation up to now been.

One of the objects of the invention is an improved one Process for processing raw coal in which the coal is classified according to grain size and material properties sorted and the fine grain portion processed separately with which the use of organic polyelectrolytes within the fine grain processing should be optimized, especially if the water system is out of flotation returns to coal washing in the cycle and the return is increasing Concentration of polyelectrolyte causes.

The desired procedure should be carried out in such a way that despite increasing Polyelectrolyte concentration, the selectivity and the carbon yield of the Flotation is not worsened, but even - based on the use of Polyelectrolyte (dry substance) is improved. The procedure should further be feasible so that the consumption of flotation reagents is reduced without thus having to accept losses in terms of yield and selectivity.

To achieve the objects, the invention proposes what is specified in claim 1 Process for raw coal processing before. Preferred embodiments of this method form the subject of the dependent claims 2 to 15; provide these refinements additional advantages in one or more directions, so that their application the Flotation profitability even better.

It has been found that the treatment of raw sludge, including the flotation, can be designed and influenced extremely favorably, if in the sewage and dewatering processes, especially in the clarification of washing water or the raw sludge thickening, instead of the previously used polyelectrolytes in Powder or granular form, a chemical treatment with at least one organic polymer electrolyte is provided, which consists of a water-in-oil emulsion of a this polyelectrolyte-containing latex has been obtained.

It has been shown that when using polyelectrolytes, which after the process of emulsion polymerization and which have been prepared by Phase inversion are diluted or introduced into the aqueous medium with phase inversion and primarily to improve the sewage and drainage processes, in addition one positive and completely surprising effect in relation to the subsequent flotation and the flotation results are exercised. In practice this manifests itself positively Effect in that a higher carbon output and higher mountain ash, d. H.

a better efficiency of the flotation (selectivity), become possible and that the flotation reagent consumption can also be reduced by up to 20%.

A complete explanation for the effect obtained according to the invention on the flotation results through the (according to the invention) use of emulsion polymers before the flotation is started, especially in the case of raw sludge clarification or thickening, cannot be given yet; however, it appears that the emulsion polymers (which are also referred to below as liquid polymers) the flotation process in an extremely favorable manner and taking advantage of the Amount of polymer (based on dry substance polymer in the Emulsion) and with particular use of the hydrophobic emulsion phase control by extraordinarily favorable conditions are created on the surface of the coal particles.

It is particularly surprising that this chemical treatment, which is expediently carried out during the washing water clarification, as it were with a reverberation effect in the flotation with the result that the yield a flotation system and the selectivity of the flotation can be improved.

The processing success or the yield of a flotation plant can be calculated with the help of weight or ash information. The weight or Volume application tells you how much weight percent of the task applied as a concentrate became.

v = kg concentrate 100% kg feed%% mountain ash -% feed ash V =% # Mountain ash -% Concentrate ash 100% The organic application or coal application states what percentage by weight of the coal content of the task in the flotation concentrate was applied.

kg concentrate% concentrate charcoal% concentrate charcoal kg feed% feed charcoal 100% m = v. 100 -% concentrate ash 100 - feed ash The relation between the achieved output and the theoretically possible output is expressed by the degree of efficiency, whereby the degree of intergrowth is taken into account by the mineral factor.

AA =% feed ash KA =% concentrate ash BA =% recovery ash Also Without knowledge of the weights and volume flows, it can be determined from the ash analyzes alone Calculate the flotation success, and the operating condition and profitability easily control a system. This can be explained using the following example: task ash 21.7% concentrate ash 7.6% mountain ash 75.4% v = 75.4 - 21.7 ~ 100 = 79.2% 75.4 - 7.6 m = 79.2 ~ = 93.5% n 2 (75.4-21.7) ~ (21.7-7.6) ~ 100 = 70.7% (75.4-21.7 ) 21.7 + [(91 -21.7). (21.7-7.6)] The practical use of such calculations is shown below Example clearly.

The method of the invention creates the prerequisite for a high Coal yield, an optimal selectivity in the flotation and enables a increased flexibility and high throughput rates in the processing of fine grains. the Operating costs can accordingly be kept low and the efficiency of the Flotation can be increased.

The method of the invention envisages the use of the polyelectrolyte before flotation, preferably during the clarification and dewatering process, nevertheless the effect of this chemical treatment echoes in the positive sense in the Flotation after. It is also surprising that this effect is not only achieved with emulsion polymers is achieved on the basis of sodium polyacrylate, but that also copolymers on the basis of acrylamide-acrylate in emulsion form show this positive effect and in many cases even strengthen it. They are therefore preferred. It is also surprising that this effect is linked to the emulsion form of the polyelectrolytes and with powder or granulate forms of normal flocculants cannot be achieved can.

The invention is illustrated below with reference to the drawings and examples explained, which reproduce preferred embodiments of the method.

F i g. 1 shows the family tree of a modern processing plant for Raw coal processing in which the invention can be advantageously used; Fig.2 shows the detailed family tree of the fine grain processing within the Total preparation; Fig. 3 illustrates schematically the flotation process, the according to the invention by adding the liquid polymer to the raw sludge pulp, for thickening and / or drainage can be controlled advantageously and favorably, taking into account the use of resources.

F i g. 1 shows a diagram of the course of the raw coal through the stages of Pre-classification and sifting, the coarse and fine grain separation in the jigging machines, and the further processing of the coal aggregates into nut coal and fine coal while During the spinning process, washing water is obtained, which, like the washing water, is removed The setting machines are subjected to a washing water purification with the finest grain fractions which is then the flotation with the extraction of fine grain and separation of the fine grain in mountains and concentrate follows.

F i g. 2 shows a preferred embodiment of the method of the invention, in which the fine grain as dust or as raw sludge sludge after separation of the coarse grain and fine grains are fed to the washing water purification system and the process water is circulated to the Coal washing is recycled. When processing the finest grain the coal gets the raw sludge, which in the washing water clarification with at least an organic polymeric polyelectrolyte made from a water-in-oil emulsion originates, is treated, in the flotation plant, where the raw sludge with the help of added flotation reagents and air in flotation concentrate (fine coal) and is sorted into flotation mountains. The flotation will work better the raw sludge to a certain concentration, preferably 100 - 150 g / l, diluted with circuit water from the wash water system. The two flotation products (Mountains and concentrate) are further treated for clarification and drainage and preferably produce flotation mountains with 70-80% ash and a flotation concentrate with only 7 ~ 10% ash. The flotation expediently works as a large-volume trough flotation or as cell flotation, which are known to those skilled in the art.

The one upstream of the flotation in the process according to the invention envisaged chemical treatment with a polyelectrolyte can preferably be in the Way done that the polyelectrolyte, preferably with a molecular weight of at least 106, directly as a water-in-oil emulsion to the system for fine grain processing is added, or one first by inverting a water-in-oil emulsion an aqueous solution of this latex is produced and added to the system.

The latex can be added to the system of washing water clarification via various Mixing devices are supplied. A particularly advantageous admixture takes place with the mixing device described in US-PS 4057 223, in which the latex consisting of a right-angled mixing block with a premixing chamber, a central part with an inclined, double-acting, throttling the flow of liquid in two specific directions Valve, with outlet chamber and return line, is admixed. The dosage of the polyelectrolyte takes place depending on the types of coal to be processed, on the one used Polyelectrolyte, its composition and its molecular weight. It has has shown that a particularly favorable dosage range is about 0.5 to 100 g of polyelectrolyte (calculated as dry matter per ton of raw coal [anhydrous]) and preferably a range of about 25 to 75 g per ton based on the concentration of the polymer, that got into the flotation. The polyelectrolyte can preferably directly be added to the raw sludge before it is mixed with circulating water from the washing water system is diluted.

It is expedient, time-saving and with regard to the flotation results extremely favorable when the admixture of the polyelectrolyte under turbulent conditions Conditions takes place.

The term “polyelectrolyte” is used in the present description of the invention one or more high molecular weight compounds in their polymer chain and / or ionic and / or under the process conditions incorporated as side chain substituents contain ionizable groups whose charges in the aqueous system by dissociation, positive, negative or neutralized by protonation or similar processes could be. Examples of polyelectrolytes that can be used include the anionic ones Polyelectrolytes, such as the polymers and copolymers of the acrylic acid / acrylamide series, the polyacrylic acids, the polystyrene sulfonates and other polymers with anionically active ones Properties, the cationic polyelectrolytes and also neutral polyampholytes. In addition to the basic types of polymers, both copolymers and their modification products, which are recorded by modifying the carboxyl, amide and / or carboxylate group, can be used.

According to the invention, particularly good results are obtained with polyelectrolytes obtained, the at least one polymer from the group of acrylamide polymers or the derivatives derived therefrom. There are cationically modified Acrylamide polymers are particularly advantageous. If a polyelectrolyte is used, which is an acrylamide copolymer composed of about 5 to 95% by weight of acrylamide and 95 to 5% by weight represents one or more acrylate monomers, the method is with respect to the Described reverberation effect designed particularly favorably. of the mentioned polyelectrolytes the copolymers with about 10 to 80 wt .-% acrylic acid units and about 90 to 20% by weight of acrylic acid amide units are preferred, it being permissible that the Carboxyl groups of the acrylic acid units by alkali, alkaline earth, ammonium or amine bases are at least partially neutralized and / or that the amide groups of the acrylic acid amide units at least partially cationic, e.g. B. as Mannich products are modified.

The polyelectrolyte preferably has an average molecular weight which is in the range from 105 to 107, but preferably at least 106 target.

The chemical treatment according to the method according to the invention before According to a preferred embodiment, the flotation involves the use of at least two different polyelectrolytes, which take place simultaneously or one after the other can, at least one of these polyelectrolytes being cationically active and at least another of these polyelectrolytes is anionically active and at least one of these Polyelectrolytes, i.e. either the cationically active or the anionically active or both, made from a water-in-oil emulsion by phase inversion.

The method of the invention not only improves economy and the efficiency of the fine grain processing, it also saves time and to save organic polyelectrolyte material. It also eliminates also the disadvantages that have hitherto been caused by increasing concentrations of polyelectrolyte have occurred with regard to the selectivity and the carbon yield, if are used in particular to clarify the washing water or to work up the flotation mountains and the flotation concentrate through thickening and dewatering polyelectrolytes and these get into the flotation via the recycled wash water. In this case, the flotation results are replaced by those used according to the invention Emulsion polymers, in contrast to the powdered polymers used so far, not deteriorated, but compensated by the chemical treatment and even promoted.

Example This example serves to illustrate the effectiveness the emulsion polymers in the washing water clarification, as well as the reverberation effect taking into account the flotation by the method of the invention and the comparison of the cost factor.

From October 1980 until December 1980 for the washing water purification to compare polyelectrolytes as flocculants on the basis of polyacrylamide acrylates used in solid form and as an emulsion. The addition of the polyelectrolytes was carried out in each case to improve the clarification of the Wash water at the raw sludge thickener and the flotation mountain thickener. The thickened one Raw sludge was floated and part of the washing water clarified with polyelectrolyte also fed to the flotation as dilution water.

The polymers were each used as a dilute solution (0.3-0.6%) dosed, whereby the powdery polymer was dissolved in water by stirring and the liquid emulsion polymer by inversion in the mixing unit described has been processed. The following amounts of polymer were used for the same clarifying effect required: flocculant g polymer per to raw coal throughput based on on product polymer Tl solid polymer 6.0 g 5.7 g emulsion polymer *) 9.5 g 3.7 g *) Copolymer of about 35% acrylate / 65% acrylamide (polymer content as of the powder = 95% (remainder is water of crystallization /, polymer content IS of the emulsion = 40 ° / 3) based on Polymer TS was thus achieved the same clarifying effect with a significantly lower amount.

During the operation described were on the flotation in each Monthly average achieved the following operating results: Flotation results in % Ash flocculation raw sludge flot.- flot.-mountains medium concentrate solid polymer 34.7 11.5 64.4 Emulsion polymer 35.2 11.7 70.9 When operating with solid polymer had to approx.

400 g of flotation reagents per to of raw sludge, only for the emulsion 350 g / to can be added.

Through the calculations of the flotation success described above the following picture emerges from the ash data: solid polymer emulsion polymer % Weight yield 55.0 60.2% carbon yield 74.1 82.2% efficiency 57.3 65.2 The comparison shows that the flotation is successful through the emulsion procedure could be significantly improved. From the economic point of view is above all weight distribution is important. In the example described here, approx. 100 to raw sludge floated per hour. With a coal price of 200 DM / to and at 5000 operating hours per year: solid polymer emulsion polymer % Weight output 55.0% 60.2% to red concentrate per hour 55.0 to 60.2 to Red concentrate per year 275,000 to 301,000 to DM Revenue per year 55.0 million DM 60.2 Mill. DM DM surplus per year - 5.2 million DM Assuming that with the flotation of hard coal sludge, the output as high as possible and so does the mountain ash should be as high as possible, while the concentrate pocket is kept as low as possible is to be, it can be seen that with polymers based on powders (the are prepared by the process of solution polymerization) clearly worse Flotation results are obtained with the emulsion polymers obtained by inversion get into the system. The positive influence of the emulsion polymers compensates not only the negative influence of polyelectrolytes introduced into the washing water, but also in this case it improves the flotation results. The procedure the invention opens up the possibility of a cheaper coal preparation Use of polyelectrolytes and the use of the polyelectrolytes (related to grams of dry matter polymer) to increase significantly.

The water-in-oil emulsions used according to the invention, which before water-in-oil emulsions can enter the system through inversion during flotation be as she z. B. in DE-OS 22 26 143 or in DE-AS 21 54 081 described are stable emulsions with a content of polymers of preferably about 20 to 50 wt .-%, with an aqueous phase, which is suitably about 75 to 95% by weight of the emulsion and the polymer in a proportion of 20 to 50% by weight the emulsion and the rest contains water, as well as an oil phase, which consists of a hydrophobic Liquid and one or more water-in-oil emulsifiers is formed and about 5 to 25% by weight of the emulsion of hydrophobic liquid and about 0.1 to 30% by weight The emulsifier contains the inert hydrophobic liquid expediently one or more liquid hydrocarbons or substituted liquid hydrocarbons, which can be aromatic and / or aliphatic in nature and preferably about Contain 4 to 8 carbon atoms. Individual hydrocarbons that alone or when mixed with other hydrocarbons form the organic phase of the latex, are benzene, xylene, toluene, mineral oils, kerosene, gasolines and petroleum oils that are weak or are barely refined. The paraffins can be straight-chain or branched-chain A particularly suitable oil is that sold under the name Isopar isoparaffinic solvents. As water-in-oil emulsifiers, the z. Am the DE-OS 2226 143 mentioned emulsifiers or other water-in-oil emulsifiers, the are known to the person skilled in the art.

Claims (15)

Claims: 1. Process for processing raw coal, at which classifies the coal according to grain size and according to material properties in the aqueous Medium is sorted, with the fine grain fraction from wet processing after Wash water clarification separated by flotation into flotation concentrate and flotation mountains is marked by the fact that the washing water clarification or the raw sludge thickening chemical treatment with at least one organic polymer prior to flotation Polyelectrolyte, which consists of a water-in-oil emulsion of this polyelectrolyte containing latex. 2. The method according to claim 1, characterized in that the polyelectrolyte directly as a water-in-oil emulsion or as an aqueous solution obtained by inverting a Water-in-oil emulsion made of the latex is added. 3. The method according to claim 2, characterized in that the latex is mixed in via a mixing device that comes from a booster pump a right-angled mixing block with premixing chamber, central part with an inclined double-acting, throttling the flow of liquid in two specific directions Valve, outlet chamber and return line consists. 4. The method according to any one of claims 1 to 3, characterized in that that the polyelectrolyte is added in such an amount that the fine grain with a content of about 0.5 to 100 g / t, preferably about 25 to 75 g / t on polymer (TS) per ton of raw sludge (wf), enters the flotation. 5. The method according to any one of claims I to 4, characterized in that that the polyelectrolyte is enriched with raw sludge wash water for the purpose of Washing water clarification or raw sludge thickening is added. 6. The method according to any one of claims 1 to 5, characterized in, that the admixture of the polyelectrolyte takes place under turbulent conditions. 7. The method according to any one of claims 1 to 6, characterized in, that the polyelectrolyte in emulsion form after inversion to achieve a predetermined Clarifying and thickening effect in one amount - based on g TS polymer - used which is smaller than the necessary amount of a by dissolving in water prepared solid polymers in powder or granulate form with a comparable composition. 8. The method according to any one of claims 1 to 7, characterized in that that the polyelectrolyte is at least one polymer from the group of acrylamide polymers and derivatives derived therefrom. 9. The method according to claim 8, characterized in that the polyelectrolyte is a cationically modified acrylamide polymer. 10. The method according to claim 8, characterized in that the polyelectrolyte an acrylamide copolymer of 5 to 95% by weight of acrylamide and 95 to 5% by weight of one or more acrylate monomers. 11. The method according to claim 8, characterized in that the polyelectrolyte a copolymer of about 10 to 80 wt .-% acrylic acid units and about 90 to 20 wt .-% acrylic acid amide units and optionally the carboxyl groups through Alkali, alkaline earth, ammonium and / or amine neutralized and / or the amide groups are cationically modified. 12. The method according to any one of claims 1 to 11, characterized in, that the polyelectrolyte has an average molecular weight of at least 106. 13. The method according to any one of claims 1 to 12, characterized in that that the chemical treatment prior to flotation with at least two different Polyelectrolyte is executed and of which at least one polyelectrolyte is cationic active and at least one further polyelectrolyte is anionically active and at least one of these polyelectrolytes is produced from a water-in-oil emulsion by inversion will. 14. The method according to any one of claims 1 to 13, characterized in, that the resulting water of the washing water clarification and the clarification and drainage of the flotation concentrate and the flotation mountains back into the coal processing cycle is returned. 15. The method according to claim 14, characterized in that the in The water returned to the cycle contains polyelectrolyte, which is used during the washing water clarification and the clarification and dewatering of the flotation concentrate and / or the flotation mountains is added as an aid. The invention relates to the processing of raw coal and in particular the water clarification and sludge dewatering in washing water systems under particular Consideration of the subsequent flotation of fine coal in hard coal mining. In the state in which it is extracted, the raw coal corresponds to does not meet the requirements of the consumer. Lots of mineral additions and adhesions result in excessive amounts of ash and annoying slag, so that the raw coal for the today's technology is practically useless. To make them salable it must be processed. The aim of processing is to bring the coal into uniform grain sizes to classify and sort according to material properties (mountains, coal).