DD201878A5 - METHOD FOR RELAASING CRYSTAL CLEANERS ON FILTER PRESSES - Google Patents

Abstract

1. A multistage process for dewatering sewage sludges of which the sludge solids contain less than 70% of organic matter, and whose dewatering characteristics have been improved by adding organic flocculants, on a filter press, using inert additives, wherein the sewage sludges are concentrated, by adding an organic flocculant during thickening by gravity sedimentation, from 0.5-5.0% by weight of sludge solids to 6-14, and especially 8-12, % by weight of sludge solids, the sewage sludges are mixed with additives, such as finely divided coal or ash or mixtures thereof, in an amount of from 0.5 to 1.5 parts by weight per part by weight of sludge solids, and the sludges are treated, before, during or after admixture of the additives, with a further 2-8 kg of organic flocculant/tonne of sludge solids and are then dewatered on the filter press to produce filter cakes which can be combusted with the utilization of their calorific content.

Description

-7-

^r Process for dewatering sewage sludge on filter presses

The present invention relates to a process for dewatering sewage sludge whose organic content of sludge solids is less than 70 % and whose dewatering behavior has been improved by adding organic flocculants on a filter press.

.C

Field of application of the invention

In sewage treatment plants of industrial enterprises and in large-scale municipal sewage treatment plants of municipalities, into which larger amounts of commercial wastewater are discharged, it is increasingly necessary to eliminate the sewage sludge produced by incineration. Sewage sludges of this origin may contain substances that prevent them from being landfilled. An environmentally friendly and safe way of disposal is total ashing. Also due to greatly increased transport costs and lack of space in most landfills incineration of sewage sludge is sought.

An economical incineration "can only be achieved by concentrating the sludge solids as much as possible.The specific water content (kg water / kg sludge solids) of the sludge to be incinerated should be as low as possible. ''.

Characteristic of the known technical solutions

In known processes, the sludges are dewatered on decanters or belt presses using organic flocculants. In these cases, an energy-consuming drying must be followed for further concentration of the dewatered sewage sludge in order to carry out an economic Liehe combustion can.

- 2 -. 0.2. OO5O / O34784

Even with the most widespread dewatering process, one-stage dewatering on a chamber filter press using iron salts and lime as a drainage aid and using inert aggregates such as ash sand, stone powder, filter cakes are produced which, as such, do not burn Substantial quantities of additional fuels such as coal and / or oil have to be added and the deposits and incrustations caused by the lime on the combustion equipment are also disruptive.

After another dewatering process (DE-OS 29-20 350) a further machine dewatering of sewage sludge on chamber filter presses using organic flocculants can be achieved. The sewage sludges are pretreated under defined conditions with organic flocculants, freed from the bulk of the sludge water by gravity filtration and then subjected to pressure filtration on a chamber filter press. By previously concentrating the sludge solids to within the range of 10-20 % , the sludge flakes acquire sufficient mechanical stability for the process. The sewage sludge can be pumped without damage, pumped and subjected to pressure up to a pressure of 15 bar pressure filtration. The sludge solids obtained are in sewage sludge., Which have an organic content of the sludge solids of less than 65 % ^ so high that the calorific values of the filter cake are in the range of self-combustion. For sewage sludge with a

2Q higher content of organic matter in the sludge solid · a small addition of coal sludge is required to obtain self-combustible filter cake. In this method, it is sometimes necessary, the layer thicknesses of the filter chambers for the purpose of achieving very high

-se reduce sludge solids content.

- 3 - O.Z. OO5O / O34784

'" 1 of the invention

The object of the invention was therefore to develop a dewatering process that does not have the aforementioned disadvantages, and in which by simpler and more expedient measures, the required concentration of sludge solids can be achieved to about 10 % . The aim is therefore to produce stable mud flakes, so that the pressure filtration can be made directly on a filter press and saves the upstream gravity filtration. The filter cake should be self-combustible.

Another object of the invention is to devise a dewatering process which provides filter cake which can be converted into electricity and steam when burned in a power plant instead of prismatic energy sources.

Explanation of the essence of the invention

These objects were inventively achieved in that the sewage sludge by adding organic flocculants already in the thickening by gravity sedimentation of 0.5 to 5.0 wt - . Sludge solids to the range of 6 - 14 and especially 8-12 wt. - concentrated% sludge solids, the sewage sludges with additives, such as finely divided coal or ash or mixtures thereof, is mixed in an amount of 0.5 to 1.5 parts by weight per Gewiehtsteil sludge solids, the

3Q sewage sludge treated before, during or after the blending of the aggregates with additional amounts in the range of 2-8 kg of organic flocculant / t of sludge solids and then dewatered on the filter press.

0.2-0O5O / O34784

^r According to a particular embodiment of the invention, the treatment of sewage sludge is carried out with further amounts of organic flocculants before mixing the aggregates, in. The way that the sewage sludge in ς a stirred tank within 1-3 minutes at stirrer speeds of 5-50 min be mixed with the Plockungsmittellosung, or that the sewage sludge in static tube mixers, which have Wendeln in their inside, be brought in less than 1 minute with the Plockungsmittellosung in contact ^ q.

According to a further embodiment of the invention, the treatment of the sewage sludge with further amounts of organic flocculants can also be carried out simultaneously with the mixing in of the additives.

Impact substances in a mixer within 1-5 minutes

and at stirrer speeds of 5 to 50 minutes.

As organic flocculants for the process according to the invention flocculant mixtures are used which consist of 2Q a flocculant with 30-40 % cationic modification and a flocculant with 70-90 % cationic modification and whose mixing ratio is 1: 3 to 3: 1 preferably 1: 1 amounts to.

Sewage sludges should be understood as meaning primary sludges obtained by sedimentation in the pre-treatment stage of a sewage treatment plant, mixed sludges which are a mixture of activated sludges (excess sludges) from biological sewage treatment plants with primary sludges, sewage sludge,

2Q crystallized sludges, for example, by long-term ventilation at

Ambient temperature arise. The sludges may be of municipal, industrial or mixed origin.

This sewage sludge has a sludge solids content of 0.5 - 5.0 % at its point of origin . The organic "

- 5 - Ο · ² - ΟΟ5Ο / Ο34784

^Γ Part (oTS) of the sludge solids is usually less than 70 %. Such sludges can be prepared by organic flocculants into the region of β - 14 wt% and in particular of 8-12 -.% Solids are concentrated by gravity sedimentation in the thickeners of a sewage plant. Accordingly, not only does sedimentation acceleration take place, but also a considerable increase in the degree of thickening.

1Q Commercially available brands can be used as organic flocculants. These are water-soluble, macromolecular compounds obtained by polymerization or by copolymerization of acrylamide, of acrylic acid and / or their salts or of esters of acrylic acid or methacrylic acid, which have been specially modified via their alcohol component. These flocculants also differ by their different - electrical charge '(cationic, anionic or electroneutral) and by their degree of polymerization.

.The choice of a suitable flocculant according to type and amount is made according to known. Methods already on a laboratory scale.

For the thickening Aniohische or cationic flocculants come into consideration. They are used in an amount of 0.5-2.0 kg of active ingredient / t of sludge solids.

The pre-selection of the organic flocculating agent to be used for the major improvement of the dewatering behavior of the sludge mixtures according to the invention was carried out according to the methods that have been in the DE-OS 28 37 017.

- 6 - O.Z. OO5O / O34784

According to the object of the invention, sludge flakes, which have a particularly high mechanical stability, must be formed in the flocculation reaction.

It has surprisingly been found that mixtures of organic flocculants, which consist of a flocculant with 30-40 / Siger cationic modification and a flocculant with 70-90% cationic modification, particularly mechanically stable sludge flakes lie ¬ ^ν - '' JQ remote. The mixing ratio can vary in the range of 1: 3 to 3: 1. However, a mixing ratio of 1: 1 is preferred. The required amounts of flocculant are in the range of 2 - 8 kg / t sludge solids. They depend on the type of sludge and ... the concentration of solids.

ID

The flocculants are used in the form of their 0.05-0.2 % strength aqueous solutions. The preparation of such dilute flocculant solutions from the solid and liquid commercial products is carried out by known methods. commercially available devices.

The flocculant solutions are dosed directly into the sludge line after the sludge pump. Here -_ entry aids, such as a conical mixer or a static mixer, with a small cross-section: may be advantageous.

In the method according to the invention, thickened sewage sludge additives, such as finely divided coals and ashes, are added.

J 3

Finely divided coals may be considered: fine coals obtained by flotation and subsequent dewatering at "d" e ~ r ~ Tr & f53iyng of fine coal and gangue (mountains). Even coal schlämm ¹ ^> which corresponds at Naßaufbereitungsverfahren

· - 7 - 0.2. OO5O / O34784

Furthermore, sieve fractions of steam coal or of green coke from refineries up to a grain size of 1 mm may be used.

As further additives ashes of different origin are used. Particularly economical is the use of ashes incurred in waste incineration or incineration of sewage sludge. It should be noted that the ashes are as free of lime as possible and have a pH of β to at most 8. An ash whose pH is greater than 8 adversely affects the subsequent flocculation reaction.

The. Additional quantities of the additives depend on the respective objective. In the event that self-burning filter cakes are to be produced, the proportions of sludge solids (STS) are: carbon solid (KTS): ash (A) in the range of 1: 0.2: 0.3 to 1: 0.5 : 1.0.

If filter cakes are desired which are suitable as fuel for power plants, i. if the filter cake should have a particularly high calorific value and the specific water contents should have a minimum, then it is dispensed with an ash additive and only finely divided coal slammed. Mixing ratios in the range of STS.:KTS = 1: 1.2 to 1: 1.5 proved to be particularly favorable.

The aggregates are distributed homogeneously in the sewage sludge with the help of mixing plants. These can be operated intermittently 3Q or continuously'. The residence time in the mixers is 1 to 5 minutes. The stirrer speeds are in the range of 5 to 50 min ^λ .

The treatment of the sewage sludge with further amounts of organic flocculant can, because of the particularly high mecha-

- 8 - * O.Z. OO5O / O34784

^r African stability of the sludge flocs, which is achieved by applying the invention Plockungsmittelgemische, -bereits be performed prior to mixing of the additive. It was surprisingly found that in this procedure, the sludge mixtures obtain their highest dewaterability in the pressure filtration on the filter press. The pretreatment of the thickened sludge with the aqueous 0,05 - 0,2 Plockungsmittellösungen show, in a '/ ~ \ vertically min effected from bottom to top flow stirred tank (dynamic flocculation reactor) within 1-3 minutes at stirrer speeds of 5-50. The Plokkungsreifezeiten and the most favorable energy input can be determined according to the · in DE-OS 29 20 434 "method described.

This pretreatment can also be carried out successfully in static tube mixers which have helices in their interior. The Plockungsreifezeiten be in this case because of the special hydraulic conditions less than 1 minute. As a rule, several mixer elements are switched one behind the other. This mixing section (static f ") piling reactor) is then part of the sludge line ..

In another embodiment, the treatment of the sewage sludge with further amounts of organic flocculant may be carried out simultaneously with the mixing of the aggregates in a mixer within 1-5 minutes and at stirrer speeds of 5-50 minutes, in which case the mixer also serves as a flocculation reactor This type of pretreatment results in equally favorable blowing effects for some sludge deposits during pressure filtration on filter presses, as in the previously described mode of operation ,

- 9 - ° · ² · OO5O / O34784

^r The flocculated sludge mixtures containing the aggregates are collected in an intermediate container which serves as a volume buffer and conveyed from here into the filter presses.

As filter presses come chamber filter presses, Rahmenfilterr

press or membrane filter presses into consideration. When using aggregates in an amount of 0.5-1.5 parts by weight per part by weight of sludge solids, even in IQ larger layer thicknesses of up to 40 mm can be pressed. This is an advantage of the method according to the invention, since it is now possible to work in larger layer thicknesses even when using organic flocculants as drainage aids instead of sisal salts and lime.

The pressing times are in the range of 90-180 minutes. ss

Pressing pressures up to 15 bar are used. In compliance with the measures according to the invention, the press cake solve properly from the filter cloths, so that a self-2Q active ejection can be done.

The achieved solids contents in the press cake were surprisingly high:

_c In the procedure in which finely divided coals in the proportions of STS: KTS = 1: 1.2 to 1: 1.5 are added to the sewage sludge, solids contents in the presscake of 55-65 % can be achieved. The specific water contents of the press cake are in the range of 1.4-1.6 kg: kg STS. The calorific values are 9200 to 14600 kJ / kg (2200 - 3500 kcal / kg). Due to the high calorific values and the low specific water contents, these press cakes are suitable as fuel power plants.

·.

3 ... Ä. 9_8_7 3 - 10 - 0.2. OO5O / O34784

The particular advantages of this process variant are that, on the one hand, the finely divided coal, which initially served as a filter aid, can be used in its entirety as the primary energy carrier, but on the other hand, the entire heat content of the sewage sludge can be recovered from the organic fraction of the sludge solid (OTS) This process variant is of particular importance for large-scale municipal sewage treatment plants, as municipal sewage sludge is particularly energy-rich and provides favorable conditions for incineration.

In the process variant in which finely divided coals and ashes in the proportions of STS: KTS: A = 1: 0.2: 0.3 to 1: 0.5: 1.0 are added to the sewage sludge, solids contents in the presscake of 50 to β % are obtained. The specific water contents of the press cake are in the range of 1.3 to 1.8 kg / kg STS. The calorific values are 4600 - 6300 kJ / kg (1100 - 1500 kcal / kg). These press cakes can be burned automatically in vortex or deck ovens.

This process variant allows cost-effective disposal of sewage sludge with minimal energy input, if combustion in a power plant with energy production is not possible.

The advantage of this variant of the method according to the invention over the prior art methods is that directly self-sustaining combustible filter cakes are produced by the further mechanical dehydration. An energy-intensive drying of the dewatered sewage sludge or an addition of larger amounts of finely divided coal and / or fuel oil is therefore not

more required. By the inventive method u

- 11 - 0.2. OO5O / O34784

"" is thus a usable primary energy from the sewage sludge won or saved primary energy in the disposal of the sludge. -In the case of "combustion in vortex furnaces, a higher operational reliability is achieved by the lime-free operation." As a result of the high volume reduction, better capacity utilization is possible with the dewatering and combustion devices.

embodiments

The invention will be explained in more detail by way of examples. The percentages given there are always percentages by weight.

In Examples 1-5, a mixed sludge was used from a mechanical biological treatment plant consisting of 80 parts of activated sludge and 20 parts of primary sludge and the organic content of the sludge solids is 65 % . The mixed sludge was in a round thickener

2Q by adding a 0.2% strength aqueous solution of a flocculant with 40% anionic modification in an amount of 1 kg / t sludge solids. The solids content of the thickened mixed sludge was 9.5 % ·

Example 1 '

"" Flocculation

In the above-characterized mixed sludge was using

3Q of a cone mixer _y installed in the mud line, a 0.2% aqueous solution of a flocculant mixture consisting of equal parts of an organic flocculant with 40% cationic modification and an organic flocculant with 90% cationic modification , distributed. The whole

0.2. OO5O / O34734

Addition amount of organic flocculants was 6.6 kg / t sludge solids.

The mixed slurry containing the flocculant mixture was treated with stirring for 2 minutes in a vertical cylindrical vessel. The stirrer speed of the screw stirrer used was 20 min

"5

conditioning

Thereafter, a 50 % aqueous suspension of coal slurry and sewage sludge ash was added to the flocculated sludge in a twin-shaft mixer within 4 minutes and at a stirrer speed of 20 minutes, in the amount such that the ratio of STS: KTS: A is 1: The calorific value of the dry matter content of the cabbage oil used is 23000 kJ / kg (5500 kcal / kg) .The total solids content of this sludge mixture was 12.6

et

/ 0

20

25

pressure filtration

The flocculated and conditioned sludge is placed in a collecting tank and conveyed from there with the aid of piston diaphragm pumps into a chamber filter press whose plate spacing was 33 mm. The pressure filtration took place up to a final pressure of 15 bar. The pressing time was 150 min. The press cakes detach themselves from the filter cloths.

Data of presscake 3Q solids content:

spec. Water content:

Calorific value H

u-

58.5 %

1.35 kg water / kg STS 5605 JcJ / kg (1341 kcal / kg)

The press cakes could be burned in a vortex furnace on their own. ..

-., 13 - * ° - · ^ζ - 0050/034784

Example 2

The procedure was as in Example 1, but the addition of the 0.2 #igen aqueous flocculant solution was carried out simultaneously with the mixing of the aggregates in the twin-shaft mixer under the same conditions.

After the pressure filtration on the chamber filter press, a smooth discharge of the press cake took place.

Data of the press cake

Pesticide content: 56/2 %

spec. Water content: 1.47 kg water / kg STS

Calorific value H ^: 5321 kJ / kg (1173 kcal / kg)

The presscake could be burned in a fluidized bed without additional fuel. This example shows that even in the simplified procedure, the object can be achieved according to the invention.

Example 3

flocculation

In the mixed slurry, an O ₃ I % aqueous solution of a flocculant mixture consisting of one part of an organic flocculant with 40 % ionic cationic modification and 2 parts of an organic flocculant with 90% cationic modification was distributed by means of a cone mixer. The whole

3Q added amount of organic flocculant was 5j8 kg drug / t STS. Thereafter, the sludge containing the flocculant mixture passed through a mixing section consisting of several series-connected static tube mixers (make Kenics). The residence time in this mixing section was 30 seconds.

O. Z. OO5O / O34784

' Conditioning

. The flocculated sludge was then "placed in a double-shaft mixer within 3 minutes and at a stirrer speed of 25 min with finely divided coal, the 5 'ratio of STS.:. KTS was 1: 1.3 x The complexion-piece charcoal was a 51otationskonzentrat that has a calorific value of 31,000 kJ / kg (7400 kcal / kg).

s ~ \ The entire plague oxygen content of this slurry mixture was 13%.

pressure filtration

The pressure filtration was carried out as described in Example 1. The pressing time was 150 min. The press cakes were dry and peeled off properly from the filter cloths.

Data of the press cake

Solids content: 6l, 8 %

spec. Water content: 1.42 kg water / kg STS

Calorific value H _n : 13800 kJ / kg (3 300 kcal / kg)

The calorific value is in the range of a good brown coal (Hy: 2500 - 3500 kcal / kg). The press cakes could be fired in a power plant boiler to produce secondary energy (electricity and steam).

Example 4

The procedure was as in Example 3 except that the addition of the 0.1% aqueous flocculant solution was carried out simultaneously with the mixing of the finely divided coal in the twin-shaft mixer under the same conditions.

35

O. Z. OO5O / O34784

After pressure filtration on the chamber filter press the press cake could be dropped automatically.

Data of the presscake solids content : spec. Water content: calorific value IL:

59.2 % 1.58 kg water / kg STS 13108 kJ / kg (3136 kcal / kg)

These press cakes could also be fired in a power plant.

Ex iel 5

Plockung

In the mixed slurry, an aqueous solution of a flocculant mixture consisting of equal parts of an organic flocculant having 30% cationic modification and an organic flocculant having 90% cationic modification was spread by means of a cone mixer. The total amount of organic flocculant added was 5.5 kg / t of STS. The slurry containing the flocculant mixture was then treated with stirring for 3 minutes in a vertical cylindrical vessel. The,. Stirrer speed of Schnek-2 = kenrührers was 15 min

conditioning

Thereafter, a 50% aqueous suspension of coal slurry, which had already been used in Example 1, was added to the flocculated sludge in a twin-shaft mixer within 3 minutes and at a stirrer rotation rate of 25 minutes. that the quantitative ratio of STS: KTS = 1: 1.4.

0.2.- OO5O / O34784

The total pesticide content of the sludge mixture was 13.0 %.

pressure filtration

The pressure filtration was carried out as described in Example 1. The pressing time was ΙβΟ min. The press cakes can be thrown off automatically.

Data of the press cake content of the pesticide: spec. Water content: calorific value H ":

60.4 %

1.57 kg water / kg STS 10809 kJ / kg (2586 kcal / kg)

In order to determine the most favorable addition location of the organic flocculant for erf incur.gsgemäße drainage in La borversuch a mixed sludge was used for five consecutive days, according to origin, composition and Eindickbedingungen the mixed sludge used in Examples 1 to 5 corresponds. The pH of the thickened mixed sludge samples was in the range of 8.9 - 9.2 % and the organic content of sludge solids was in the range of 64.2 - 65.8 %.

The mud pretreatment was carried out in each case according to 3 methods:

Method A

500 ml of mixed sludge are placed in a 1 liter 3-cup glass (high mold). Then, with stirring for 50 minutes with a paddle stirrer, a 0.2% aqueous flocculant solution is added within 10 seconds. The flocculated sludge is treated for a further 120 seconds at the specified stirrer speed.

Subsequently, the stirrer speed is increased to 200 min ^ and it will be the respective aggregates (finely divided

- 17 ° · ² · OO5O / O34784

In the specified amounts within 30 seconds, the total mixing time is 3 minutes.

Method B

500 ml of mixed sludge are placed in a 1 liter beaker. Then, with stirring at a stirrer speed of 200 min ", additives and flocculant solution are added in succession within 30 seconds, the total mixing time being 3 minutes.

Method C

500 ml of mixed sludge are placed in a 1 liter beaker. With stirring at a stirrer speed of 200 minutes, the additives are added in succession within 30 seconds, the total mixing time being 3 minutes.

- 1 Thereafter, the stirrer speed is reduced to 50 "min and the flocculant solution is added within 10 seconds and the flocculated sludge mixture is treated for a further 120 seconds at the specified stirrer speed.

The stirrer speeds were increased during mixing of the additives compared to the practical tests in Examples 1 to 5 ^ so that a comparable energy input takes place.

The sludge samples which have been pre-treated according to the methods A, B and C, the pressure filtration ^ q were subjected to a laboratory press immediately. It was dehydrated for 1 minute at increasing pressure and 2 minutes at a constant pressure of 10 bar.

O. Z. OO5O / 034784

Comparative Example 1

In these experiments, finely divided coal (a coal slurry in the form of a 50% aqueous suspension) and sewage sludge ash was added to the mixed sludge samples. The quantitative ratio of STS: KTS: A was 1: 0.3: 0.6 in all cases.

The flocculant solution used was a 0.2% aqueous solution of a flocculant mixture consisting of equal parts of an organic flocculant with 40% cationic modification and an organic flocculant with 90% cationic modification. The total amount of organic flocculant added was 6.5 g of active ingredient / kg of STS.

10

The following degrees of sudwetting (solids content of the presscake) were determined after pressure filtration:

20

25

30

Method. A Method B Method C

Comparative Example 2

Mean value (x) 55.8 % 55.0 % 52.8 %

Standard deviation (s)

0.5

  1.6

2.9

In this series of experiments, a flotation concentrate was added to the mixed sludge as an additive. The quantitative ratio of STS: KTS was 1: 1.3.

The flocculant solution used was a 0.2% aqueous solution of a flocculant mixture consisting of one part of an organic flocculant with 40% cationic modification and 2 parts of an organic flocculant with 90 % cationic modification.

35

- 19 - 0.2. OO5O / O34784

^r det. The total amount of organic flocculant added was 5.8 g drug / kg STS.

The following contents of the pressed cake after pressure filtration were determined:

Mean (x) standard deviation (s) Method A 58.1 % 1.1

Method B 57.5 % 2.5

Method C ·, 5β, 2 % 2,8

Comparative Examples 1 and 2 show that in the addition of the flocculant according to the invention before or during the mixing of the aggregates the most favorable Ent-Wässerungseffekte be achieved with the lowest fluctuation ranges.

Examples β and 7

(Use of green coke and steam coal)

A mixed sludge was used, which was also used in Comparative Examples 1 and 2. The solids content of the thickened sludge was 8.9 X _1, the organic content of the sludge solids was 65.3 %.

The sludge pretreatment with the organic flocculants and the additives was carried out according to method A. The pressure filtration was carried out as indicated in comparative experiments 1 and 2.

The flocculant solution used was a 0.2% aqueous solution of a flocculant mixture consisting of equal parts of an organic flocculant with 40% cationic modification and an organic flocculant with 90% cationic modification.

Ό. Ζ. ΟΟ5Ο / Ο3-4784

"The total addition amount of organic flocculants was 6.0 g / kg STS.

Screening fractions with grain sizes smaller than 1 mm of green coke from a refinery (Example 6) and from a steam coal (Example 7) were used as aggregates. The quantitative ratio of STS to KTS was 1: 1.3 ·

The calorific values of the dry matter of the finely divided coals are: 'Green coke: H.: 35100 kJ / kg (8 400 kcal / kg)

Power coal: IL .: Esskuchen salary g STS) 29700 kJ / kg (7100 kcal / kg) Data of Pr (KJ / kg) (Kcal / kg) Example 6 Example 7 Solids content {%): (Green coke) (Steam coal spec. Water: (kg water / k 59.6 58.8 Calorific value BL: 1.56 1.61 14638 12590 3502 3012

Examples 6 and 7 show that green coke and steam coal can also be used as finely divided coals in the process according to the invention.

Comparative Example 3

In the practice of Example 1, a sample was taken from the flocculated and conditioned sludge conveyed from a sump by means of a piston diaphragm pump into a chamber filter press before and after the pump. The time was chosen when the pressing pressure had reached 15 bar.

0.2.

OO5O / O34784

Thereafter, the samples were subjected to pressure filtration in the laboratory on a laboratory press. It was dewatered for 1 minute at increasing pressure and 2 minutes at a constant pressure of 10 bar.

For comparison, a. non-inventive flocculation mixture consisting of one part of an organic flocculant with 70 % cationic modification and 2 parts of an organic flocculant with 90% cationic modification. Otherwise, the procedure was as described in Example 1 '.

Sampling and checking on the laboratory press was carried out under comparable conditions as above.

Solids content of the press cake (laboratory test )

Place of sampling: - in front of pump

Example -1 54.8 %

(with a mixture of flocculants according to the invention)

after pump 54.1 %

²⁵ Comparative Example 3 53.2 %

(with a flocculant mixture not according to the invention)

43.8 %

This comparative example shows the high mechanical strength of the sludge flakes that arise when using the flocculant mixture according to the invention and when applying the procedure according to the invention.

Claims (5)

invention claim - 1
and at Hührerdrsh numbers of ,. 5 to ^ O min ', -1 are mixed with the flocculant solution for 1 to 3 minutes at a stirrer speed of 5 to 50 minutes, that sewage sludge in static pipe mixers, the have spirals in their interior, be in contact with the blocking agent in less than 1 minute. - 1 to 3 minutes at stirrer speeds of 5 to 50 min with the flocculant solution vermishht be. - 1. A method for dewatering sewage sludge whose organic content of sludge solids is less than 70 % and whose drainage behavior is improved by adding organic flocculants on a filter press, characterized in that the sewage sludge is "already" added by adding an organic flocculant. in the thickening by gravity sedimentation of Oj5 "to 5.0 wt .- # sludge solids" up to the range of 6 "to 14 and in particular 8 to 12 wt .-? concentrated sludge solids' the sewage sludge is mixed with aggregates, such as one-part coals or ashes or mixtures thereof, in an amount of 0.5 to 1.5 parts by weight per part by weight of sludge solids, treating the sewage sludge before, during or after blending the aggregates with further amounts ranging from 2 to 8 kg of organic flocculant / t of sludge solids and then dewatered on the filter press. 2. Method according to item 1, characterized in that the treatment of the sewage sludge with further amounts of organic flocculants is carried out prior to the mixing in of the aggregates, in such a way that that the sewage sludge in a Eührbehälter within - 1 3. The method according to item 1, characterized in that the treatment of the sewage sludge with other amounts of organic flocculant before mixing the supplement 59 970 12
23 - is made in the YJs iss, that the sewage sludge in a phlhrb he holds within 4. The method according to item 1, characterized in that the
Treatment of the sewage sludge with further amounts of "organic" flocculant on the same side as the mixing in of the aggregates in a mixer within Ibis 5 ml. 5, method according to item 1 to 4, characterized- characterized in that used as organic flocculants mixtures
consisting of a flocculant with 30-40% cationic modification and a flocculant with 70-90% cationic modification
and their mixing ratio is 1: 3 to 3: 1, preferably f: 1.