DE2916261C2 - Process for the recovery of sludge - Google Patents

Description

The invention relates to a method for recycling sludge, in particular from industrial work processes, as well as from municipal wastewater, in which the sludge is first thickened and then added an additive containing at least fine coal is conditioned to improve the sludge structure, is then further dewatered on a filter press and finally at least less than stoichiometric is incinerated.

Such a method is known from the magazine "Umschau", No. 9, 1963, pages 281-283, in which at sewage sludge from the purification of wastewater is subjected to sludge gasification. As for the Combustion of the gas generated during sludge gasification in gas engines strives for the highest possible calorific values no chemicals are used as filter aids for ash-rich sludge for dewatering, but fine coal is used to improve the sludge structure. The gasification takes place in one Gas generator of conventional design based on the counterflow principle with subsequent power generation by gas machines. From the magazine it is also known to the sludge in a vortex chamber process after Direct current principle with subsequent steam generation and conversion into electrical energy through Gasifying electric generators with steam turbines.

In the swirl chamber process, the cyclone in one of the gasification systems is generated from the Lean gas separated dust is used as the sole filter aid, especially for drainage the difficult-to-treat biological excess sludge is used.

It is the object of the present invention, in a method as described in the preamble of the above Claim 1 mentioned type a more extensive thermal treatment with a lower value, but to achieve a suitable additive for adequate conditioning.

This object is achieved in that the additive is a mixture of coal dust with a grain size of 30-120 µm, in the ratio of 0.75: 1 to 2: 1, preferably 1.5: 1, is added to the dry matter of the sludge, and ash is and that incineration combustion is at least stoichiometric

According to the invention, the thickened sludge is conditioned with a coal dust-ash mixture and after further dehydration burned at least stoichiometrically in the process according to the invention incineration thus takes place in a single process step, while in the known process one two-stage incineration in the form of sludge gasification with subsequent combustion of the generated Gas in gas engines takes place

To condition the thickened sludge with the coal dust-ash mixture, z. B. the at The fine coal accruing from classification or air sifting can be used without further processing. Of the Ash content of this coal is usually in a proportion of 20-30%. Such a procedure thus has the advantage that some of the otherwise necessary processing steps for the coal are dispensed with can.

To improve the filtering effect or, in particular, to detach the filter cake from the filter surfaces it is provided that an additive is added to the coal dust-ash mixture before or during the conditioning is added to facilitate the detachment of the filter cake formed during dewatering.

The addition of the additive has the advantage that, in the context of the subsequent conditioning, a good Muddling is guaranteed

The flue gases produced during combustion or the heat contained therein can advantageously be used to dry or warm up the coal dust-ash mixture. According to one embodiment of the invention it is provided that the coal dust-ash mixture is dried before conditioning and mixed into the sludge while it is still warm. The subsequent filtration process can be improved by the supplied heat.
An optimization of the process is possible in that the two essential components are continuously analyzed with regard to their composition, in particular with regard to the combustible components and the grain size, before conditioning. Based on this analysis, z. B. the amount or composition of the coal dust-ash mixture can be adjusted in order to achieve the best possible calorific value.

The filter cake thus obtained, i.e. H. the mixture of sludge and coal dust is then burned. This is possible without further pretreatment according to a further embodiment of the invention, by placing the filter cake on a coal bed and burning it with the coal. To this In this way, it is possible to mix the sludge-coal dust mixture on the ones intended for lump coal combustion Burn rusting. It is therefore not necessary to develop a separate, expensive combustion system or to build.

3

fi An embodiment according to the invention is turned now still in the flue gas stream from the incinerator

-p according to the drawing in the following spelling, grinds to approx. 10% residual moisture, you get an \ explained The drawing shows a process scheme for sewage sludge dust with a calorific value of 17 816 K] /

% of a system for carrying out the Kg according to the invention. Such a dust can be conveyed pneumatically and

f procedure. 5 burn in special burners without difficulty.

- At 4 a sludge feeder is shown, in which one can still put burnt lime into this sewage sludge

: Analysis device 2 is built in, with which is given in, so that the incineration of the sewage

the composition of the sludge sludge released sulfur in the form of the and e.g. the calorific value can be determined. Which is bound to the plaster of paris.

: If necessary, sludge is not shown in a sludge. If the sewage sludge treatment cannot be pre-dewatered in a sedimentation plant and then integrated into a combustion plant, the Kiärin should be pretreated in a thickener 1, which sludge treatment on the sewage treatment plants by means of a waste water conduit 3 conditioning for drainage to 30% residual moisture. After that, the mud will be subjected to a conditioning. The drying and processing unit 10 is supplied, where the sludge with the mixture of coal dust incineration plant brought in via a device to the pulverized fuel can then take place in the feed 7, since the sewage works and ash is mixed. Here too, if the sludge is not burned, there is no hot 7 an analytical device 8 provided through which the flue gases are available. This process of regular analyzes of the coal flow, special treatment of the sewage sludge, is essential. The feed 7 can then be controlled via the analysis unit 20 borrowed more effectively than a sludge dewatering device. 30% flat share.

The so conditioned sludge is then

ner filter press 12 fed and dewatered there The 1 sheet of drawings

outflowing clean water is via the sewage

pipe 13 discharged

The largely dewatered sludge-coal dust mixture can then be temporarily stored in a bunker 15 or be fed directly to the incinerator 20. The ones that arise during combustion Flue gases can then z. B. can be used to pre-dry the coal.

The invention is further explained using an example. A municipal sludge with 95% WG conditioned with a coal-ash mixture and then dewatered on chamber filter presses and then burned.

The coal-ash mixture is made up as follows:

40

Coal dust 80% ash 20% Grit 30 to 100 μ each calorific value 26 800 KJ / kg

This mixture is used in a dry matter ratio of 1: 1 for conditioning the municipal sludge used. Furthermore, an organic additive is added, which leads to a better dissolution of the filter cake from the filter cloths. The sludge is conditioned with the coal-ash mixture without prior thickening been.

After conditioning, the Schlam.Ti coal ash mixture becomes fed to a chamber filter press and treated there as usual. It turns out that the The filter cake obtained only has a water content of 30 to 35%. The calorific value of the filter cake is 13 140 KJ / kg.

The same sludge, conditioned with the well-known metal salts and lime, has left the Chamber filter press still has a water content of 55% and a calorific value of 5100 KJ / kg.

It follows that the additional costs for the coal conditioning due to the above-mentioned advantages, which enable perfect combustion of the sludge, more than can be caught.

If you go one step further and the one conditioned with the coal dust-ash mixture and sludge dewatered on filter presses

Claims (4)

Patent claims: 1. Process for the recovery of sludge,
in particular from industrial work processes, as well as from municipal wastewater, in which the mud first thickened, then by adding an additive containing at least fine coal to improve the sludge structure is conditioned, is then further dewatered on a filter press and finally is incinerated at least substoichiometrically, characterized in that the addition a mixture of coal dust with a grain size of 30-120 µm, in a ratio of 0.75: 1 to 2: 1, : 'preferably 1.5: 1, to the dry matter of the Sludge is added, and ash is and that the incineration is at least stoichiometric combustion is 2. The method according to claim 1, characterized in that the coal dust-ash mixture before or an additive during conditioning to facilitate the detachment during dehydration resulting filter cake is added. 3. The method according to claim 1, characterized in that the coal dust-ash mixture before After conditioning, it is dried and mixed into the sludge while it is still warm. 4. The method according to claim 1, characterized in that the filter cake is placed on a coal bed and burned with the kohie.