Floculantes Información Praestol
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Transcript of Floculantes Información Praestol
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Flo ccula nt s fo r a ll Applicat io ns
invo lving So lid /Liq uid Sepa ra t io n
PRAESTOL
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1. Introduction
2. Mode of Action
3. Properties
4. Production of PRAESTOL Solutions
5. Dosage Quantities
6. Method of Dosage
7. Operating Reliability and Accident Prevention
8. Storage
9. Packing
10. Examples of Use and Applications of PRAESTOL Flocculants
11. PRAESTOL
Product Range
11.1 Non-ionic and Anionic PRAESTOLProducts
11.2 Cationic PRAESTOL Products
11.3 Special Products
12. PRAESTOLTR Grades for Processing Potable Water
12.1 Product Range
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Contents Page
Ashland Deutschland GmbHEnvironmental and Process SolutionsFtingsweg 20, D-47805 KrefeldP.O. Box 10 04 52, D-47704 KrefeldPhone: +49 2151 38 3555Fax: +49 2151 38 [email protected]
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Anionic
Cationic
Charge characterNon-ionic
Supply forms
Granulates
Oil-free dispersions
1. Introduction
PRAESTOL products are organic, synthetic, high molecular flocculants based on polyacryl-
amide.
Non-ionic PRAESTOL flocculant types (formula 1) are technically pure polyacrylamides. Theyexhibit neutral (i. e. non-ionic) properties in aqueous solution.
Anionic PRAESTOL flocculants (formula 2) are co-polymers of acrylamide with increasing
proportions of acrylate groups, which give the polymers negative charges, and thus anionicac-
tive character, in aqueous solution.
Cationic PRAESTOL products (formula 3) are co-polymers of acrylamide with increasing
proportions of a cationic co-monomer. The cationic groups, which are thus introduced into the
polymer, have positive charges in aqueous solution.
Emulsions
PRAESTOL flocculants are available both as granular (solid) products and in liquid form as
water-in-oil emulsions, as oil-free dispersions and as aqueous solutions.
The granular products are white, granular, free-flowing, low-dust products with a grain size
up to 1.2 mm.
The water-in-oil emulsions are viscous free-flowing gel dispersions.
The oil-free dispersions are somewhat more viscous than the water-in-oil emulsions. This higher
viscosity does not imply any disadvantages for handling the products, i. e. the advantages of
the liquid products (handling, ease of dosage) are preserved. The oil-free flocculants show very
good solubility properties in water. While special attention must be given in water-in-oil emul-
sions to the solubility properties, the so-termed reversal behavior, the oil-free dispersions
mix with water immediately, i. e. without maturing time, and produce a ready-to-use solution
for dosage. The ready-to-use solutions are gel-free.
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Viscosities
pH values
* 1 dH = 1 (German) degree of hardness = hardness due to 10 mg of lime (CaO) in 1 l of water or 17.8 mg CaCO3in 1 l of water.
Charge exchangeDestabilisation
Surface potencial
Original suspension
Effectiveness
Product properties =mean values
Bulk density
2. Mode of Action
PRAESTOLflocculants incorporate reactive groups in aqueous solution, which have a strong
affinity to the surfaces of suspended colloids or very fine particles in aqueous suspensions or
slurries. According to the ionicity of the PRAESTOL types, interactions between them and the
solid particles are based on the formation of hydrogen bonds, as is the case with the non-ionic
polymers, or on electrostatic interactions and charge exchange, resulting in the destabilization
of the particle surface; the anionic (= negatively charged) and cationic (= positively charged)
PRAESTOL products act in this way. Destabilization and coagulation of a large number of
single particles leads to the formation of voluminous macro-flocs, which are easy to separate
from the suspension.
Thus the optimum effect of a PRAESTOL polymer is mainly determined by the surface po-
tential acting on the particle. These potentials are dependent both on the particle itself and on
the conditions in the environment, i. e. on the ionic strength of the water and the properties
resulting from this, such as pH value, electrical conductivity, hardness, surfactant content.
The most suitable PRAESTOL type for a particular application can be easily determined by
carrying out relatively simple preliminary tests. It is important that these tests are carried out
on the original suspension (solids and water), under the specified operating conditions (such
as temperature, turbulence, addition of other processing aids).
PRAESTOL products, as polymeric flocculants, are able to flocculate solid particles, colloids,
hydroxides and for example, bacterial substances. In the flocculated state, the solids can be
quickly and completely separated from the surrounding water. PRAESTOL flocculants are not
used to separate dissolved ingredients from water.
PRAESTOL polymers are effective in the pH range 1 to 14, depending on the particular typeinvolved. They are also effective in systems with low electrolyte concentrations, right up to
saturated salt solutions. Furthermore they cover the complete temperature range in which the
aqueous suspension is liquid, i. e. from approx. 0 C to 100 C.
3. Properties
The numerical values for the product properties, which are given in the product overview tables
are mean values, which may vary in individual cases.
The bulk density is measured using a running out breaker. This property must be taken into
consideration when designing storage tanks and feeding equipment for dissolving plants basedon volumetric dosage.
Viscosities are determined with the Brookfield viscometer at 20 C. Solutions for viscosity
measurements are prepared in distilled or de-ionized water. The viscosities quoted thus represent
the typical value, for a particular concentration of product, which has to be considered when
designing stirrers, pumps, measuring sections etc.
The solutions for determining the pH value were prepared with Krefeld tap water (approx.
25 dH*, pH value approx. 7, electrical conductivity approx. 600 S/cm). The pH values must be
taken into account when selecting the material for dissolving and dosing equipment.
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Molecular weights
Ready-to-use solution /Stock solution
Granulates
Dispersers
The molecular weights of the anionic products are between 6 to 30 million, whereby as a general
rule the molecular weights of the granulates in the 23 series are in the lower range and those of
the granulates in the 26 series are in the upper range. The molecular weights of the non-ionic
and anionic emulsion grade polymers are in the same order of magnitude.
The molecular weights of the cationic products are about 6 to 20 million; usually granulates of
the 6 series are in the lower range and granulates of the 8 series as well as emulsion polymers
in the upper range. Cationic solution polymers have a molecular weight of approx. 1 million.
4. Production of PRAESTOLSolutions
PRAESTOL flocculants are used in highly diluted aqueous solutions (e. g. 0.1 % by weight).
To keep the dissolving time low, it is recommendable when producing the ready-to-use solution
to use a concentrated stock solution (e. g. 0.5 % by weight) first, which can be diluted later to
the required application concentration. Alternatively, the ready-to-use solution can be prepared
immediately at the desired low concentration but a longer dissolving time must be taken into
account here. Tested and proven dissolving equipment is available for preparing solutions. Both
the stock and ready-to-use solutions require a maturing time, during which time the solution
should be kept gently agitated.
In producing aqueous solutions of PRAESTOL granulates, the following points must be
observed:
When adding the PRAESTOL granulates, it is important that each single particle is
individually wetted by the water. It is therefore recommended to add the granulates
slowly into the turbulent water.
It is particularly recommended to use an auxiliary unit, e. g. a disperser.
See our special information for details.
Emulsions
The subsequent dissolving procedure is aided by a turbulent agitation of the water
(stirrer, compressed-air swirling).
The dissolving time depends on the product type and on the quality and temperature
of the solution water. It usually takes about 60 minutes for the product to develop its
effectiveness completely. This should be taken into account when designing the dissolving units.
The production of aqueous solutions from PRAESTOL emulsions can be done by carefully
pouring the product into the vigorously stirred solution water or by use of special mixing units
(in-line mixers).
To guarantee developing of the full effectiveness of the product, sufficient time
should be allowed for dissolving. A dissolving time of 5 to 20 minutes is sufficient,
depending on the concentration of the solution. With increasing concentration of
the solution the required dissolving time will decrease.
Automatic dissolving units are used specially for the continuous, operational use
of PRAESTOL emulsions.
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Fig. 4:Dependence of the rate of sedimentationon the dosage quantity for suspensionswith varying solids content
Suspension A: solids content 36 g/lSuspension B: solids content 64 g/l
5. Dosage Quantities
Owing to the very different flocculating properties of the sludges to be dewatered, the required
dosing quantities can only be determined by laboratory tests or directly by carrying out plant
trials in each individual case.
In the case of mechanical sludge dewatering of mostly inorganic solids on rotary vacuum
filters, centrifuges, belt presses, chamber filter presses, PRAESTOL flocculants can increase
the output with almost completely dry cakes. The required dosing quantities lie between 80
and 300 g/t dry substance dependent on the dewatering unit.
In mechanical dewatering of mostly organic sludge on (heavy-duty) centrifuges, belt presses,
chamber and membrane filter presses, cationic-active PRAESTOL flocculants are used negating
the need for inorganic agents such as metallic salts or lime. The addition rates of polyelectrolyteare normally between 2 and 8 kg/t dry substance.
When used to accelerate the rate of sedimentation or as a clarifying agent in settling tanks, a
dose rate of 1 to 20 g/m3of the suspension to be clarified is normally sufficient.
Higher dose rates may be necessary:
Where there is a high solids content in the suspension
With increasing fineness of the suspended solids
Where the suspension has a low temperature
Figure 4 shows the relative dependence of the sedimentation speed obtained with flocculationon the different solids contents of the respective suspension.
Aqueous solutions
Feeding and dosing
PRAESTOLproducts in the form of aqueous solutions are diluted by stirring and mixing to
the required concentration for use. A dissolving time is not necessary.
Excessively fast stirrers should not be used to produce PRAESTOL stock solutions and dur-
ing their further dilution. The stirrers maximum circumferential speed should be 10 m/s as
otherwise the effectiveness of the highly-molecular polymer will be reduced by excessive
shearing of the chain lengths.
Progressive cavity pumps and not centrifugal or gear pumps should be used to feed and dose
the PRAESTOL solutions.
Stock solutions
Sludge dewatering ofinorganic solids
Organic sludge
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Even distribution
Type and point of dosage
Non-corrosive
Danger of slipping
6. Method of Dosage
As the dosage quantities of synthetic flocculants are low, an even distribution of the PRAESTOL
solution in the suspension to be treated is a prerequisite for its optimum effect.
This even distribution can be achieved by:
Diluting the flocculant solution as much as possible
The corresponding duration and intensity of the mixture of the flocculant solution
with the suspension or thickened sludge
Multiple dosage: The total quantity of flocculant solution required is added to the
suspension to be treated at different points. In many cases, multiple dosage helps toimprove the purification of the suspension being treated.
The advantageous type and the right point for adding the PRAESTOL solution to the suspension
or sludge depends on the properties of the suspension, the type of clarification or dewatering
process and the operating result required, e. g., fast rate of sedimentation, very good clarifica-
tion, high flocculation stability.
The following points apply:
A type of dosage of the flocculant solution to the suspension or sludge must be
selected which will ensure that the solution is distributed evenly.
A dosage point must be selected which will ensure sufficient reaction time betweenthe flocculant and the solid particles to be flocculated.
Flocs already formed should have the opportunity of uniting to form larger entities.
On the other hand, the destruction of the flocs by means of gravitational forces,
e. g. because of unfavorable flow conditions, should be avoided.
7. Operating Reliability and Accident Prevention
Our experience has shown that PRAESTOL solutions are non-corrosive in contact with materi-
als used for tanks and pipes, such as fiberglass, plastics, plastic-lined materials and stainless
steel.
Owing to the properties of organic solvent in the liquid products, plastic containers (pipes,
pump components) coming into contact with the undiluted product must be made of solvent-
proof material.
Scattered granular product on a wet floor, liquid product or solution which has been spilt onto
the floor, will cause slipping.
In this case the solid product or solution can be soaked up with absorbent material, e. g. saw-
dust, sand etc. and disposed of.
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Water sensitivity
Homogenization
Storage temperature
8. Storage
Highly-molecular flocculants like PRAESTOLare basically sensitive to moisture, such as
condensation, splashes and humidity. Contact with water (droplets) can lead to local formation
of knots and lumps. The product should therefore be stored in dry, closed containers, protected
against moisture (bags, big bags, containers).
After prolonged storage emulsion grade polymers might tend to separate into layers. After
homogenization by intensive stirring, pumping or re-circulation by gas injection (nitrogen,
air) the products may be re-used without any loss in quality.
The storage temperature should not exceed 40 C for long periods.
The product viscosity of emulsion grade polymers increases at low temperatures. The product
can no longer be pumped below -10 C. After warming up to approx. 8 to 10 C and homo-
genization, however, the product can be reused without any loss in efficiency.
Storage stability under correct storage conditions:
Granulates in original packing : at least 12 months
Emulsions in original packing: at least 6 months
Oil-free dispersions: at least 3 months
The storability of the stock solution and ready-to-use solution depends on the individual product.
We refer you to the corresponding PRAESTOL technical leaflet.
9. Packing
Granular products: Paper valve bags shrink-wrapped on pallets
Big bag
Liquid products: Drum
Container
Road tanker
Storage stability
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Fields of Application
Drinking Water
Industrial Water
Mining (coal / ore / salts) Wash water
Filtration of concentrates Flotation tailings Flotation pulps Acidic brines Alkaline brines
Chemical Industry Pigments (inorganic) Pigments (organic) Leaching liquors Biotechnological suspensions
Metal Producing and Metal Processing Industry
Paper Industry Retention/White water and Waste water
Waste Water (industrial, municipal) Waste water, also after neutralization
Sludge Dewatering Raw sludge Digested sludge Surplus sludge (also thickening,
centrifuging or flotation)
Non-ionic
slightly medium strongly slightly medium strongly
Anionic Cationic
10. Examples of Use and Applications of PRAESTOLFlocculants
To select the optimum product for your process from our product range, please see the
supplementary information Laboratory Tests with PRAESTOL Flocculants.
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Polyacrylamides
Very low residualcontent of monomeracrylamide
1 Letter by WHO dated January 21, 19942 DWI, London: Water Industry Act 1991: Section 69
Water Supply (Water Quality) Regulations 1989
Water Supply (Water Quality) (Amendment) Regulations 19913 DIN EN 1407 and EN 14104 DWI, London: Regulation 25 Letter 2/2002 of November 7, 2002
12. PRAESTOLTR Grades for Processing Potable Water
The synthetic polyelectrolytes which are now increasingly used in the preparation of potable
water are mainly water-soluble polyacrylamides.
A prerequisite for the use of polyacrylamides for this purpose is that they should have a very
low residual content of monomer acrylamide.
The World Health Organization (WHO) recommends limiting the amount of monomer acryl-
amide in drinking water to less than 0.5 g/l. Thus, in consideration of all safety measures
in a daily consumption of 2 liters of drinking water the total amount of monomer acrylamide
should not exceed 0.017 mg per kilogram of body weight per day.1
A residual monomer content of 0.05 % by weight (500 ppm) and a dosage of 1 mg/l (1 ppm), as
prescribed by the Food and Drug Administration (FDA) for the USA (CFR 40, 141.111), are
already within this limit.
Regulations in other countries reflect these requirements:
Germany
In Germany the use of PRAESTOL TR grades for the preparation of potable water is controlled
under the Foodstuffs, Consumer Goods and Animal Feed Code (Lebensmittel-, Bedarfsgegen-
stnde- und Futtermittelgesetzbuch, LFGB). The LFGB requires that with appropriate use of
auxiliary agents in the processing of potable water these agents must, except for technically
unavoidable and technologically inactive residues, be removed from the potable water. Whenproperly used, the PRAESTOL TR grades meet these requirements, which are set out in the
LFGB.
In keeping with 11 of the 2001 Drinking Water Act, approved conditioning agents appear
on a list published by the Federal Ministry of Health and Social Security (Bundesministerium
fr Gesundheit und Soziale Sicherung, BMGS). Only anionic and non-ionic grades with a
residual monomer content of below 0.025 % at a polymer dosage of 0.4 mg/l (DIN EN 1407)
are approved for use.
Great Britain
As of December 2003, the amount of monomer acrylamide may not exceed 0.02 %. The
quantity of the polymer dosed may not exceed 0.5 mg/l.2,3,4
European Union
The standards EN 1407 and EN 1410 were adopted by CEN (European Standards Committee)
on March 23, 1998. They prescribe polyacrylamide for conditioning potable water with a re-
sidual monomer content of less than 0.025 % acrylamide with a polymer dosage not to exceed
0.4 mg/l. Both standards are also valid for Germany.
These standards, as well as those for Germany and Great Britain, are in compliance with EU
guidelines 98/83/EG concerning the quality of water for human consumption (EU Drinking
Water Guideline, limit: 0.1g/l in the drinking water).
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International certifyingorganizations
USA
Certification is awarded by the National Sanitation Foundation International (NSF) and con-
forms to the requirements of Standard 60 Drinking Water Treatment Chemicals - Health
Effects. A residual monomer content of < 0.05 % by weight at a dosage of not more than
1 mg/l is prescribed.
USA: National Sanitation Foundation International (NSF),Ann Arbor, Michigan
GB: Department for Environment, Food and Rural Affairs,Drinking Water Inspectorate (DWI)London
Approved for use are polymers which comply with the standards
DIN EN 1407 and EN 1410. Packaging is appropriately labeled.5
PRAESTOLTR Grades
PRAESTOL TR grades are produced using a special method and every production batch is very
carefully monitored with regard to the residual content of monomer acrylamide.
For every consignment of our PRAESTOL TR product types we guarantee a residual monomer
content of < 0.02 % (by weight) of monomer acrylamide (with reference to the polymer).
On special request we can supply the relevant certificate of analysis with every consignment
of PRAESTOL TR flocculants.
The following institutes have issued certificates declaring the PRAESTOL TR grades (shown
in the table)to be safe for use in potable water preparation:
National Sanitation Foundation International, USA
ANSI/NSF Standard 60 Drinking Water Treatment Chemicals - Health Effects
All anionic and cationic PRAESTOL TR flocculant types are certified.
Department for Environment, Food and Rural Affairs,
Drinking Water Inspectorate, Great Britain All anionic and cationic PRAESTOL TR flocculants types have been approved
for use in conditioning drinking water.
Federal Ministry of Health and Social Security, Germany
Approval for anionic and non-ionic PRAESTOL TR flocculant types.
Further fields of application for PRAESTOL TR flocculants for water treatment are lime water
production, water works sludge treatment and phosphate removal.
5 DWI, London: Regulation 25 Letter 11/2000 of September 29, 2000
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2500 TR non- 650 200 50 7 1 - 7 USAionic Great Britain
Germany
2515 TR weakly 650 3000 400 7 7 - 10 USA anionic Great Britain Germany
2530 TR medium 700 4000 500 7 6 - 10 USA 2540 TR anionic 700 5500 600 7 6 - 13 Great Britain
Germany
650 TR medium 650 700 65 7 1 - 14 USAcationic Great Britain
851 TR weakly 650 600 50 7 1 - 14 USA
cationic Great Britain
DW = De-ionized water
TW = Krefeld tap water: approx. 25 dH (German) degree of hardness, electrical conductivity approx. 600 S/cm, pH value approx. 7
12.1 Product Range
PRAESTOLTR Grades for Processing Potable Water
PRAESTOL Ionic Bulk Viscosity pH Effective in Approved inCharge Density the pH Range
0.5 % by wt. 0.1 % by wt. 0.1 % by wt.DW DW TW
approx. approx. approx. approx. kg/m3 mPa.s mPa.s
All statements, information and data presented herein are believed to be accurate and reliable but are not to betaken as a guarantee, express warranty or implied warranty of merchantability or fitness for a particular purpose,
or representation, express or implied, for which seller assumes legal responsibility, and they are offered solely
for your consideration, investigation and verification. Statements or suggestions concerning possible use of this
product are made without representation or warranty that any such use is free of patent infringement and are not
recommendations to infringe on any patent.
Ashland Deutschland GmbHEnvironmental and Process SolutionsFtingsweg 20, D-47805 KrefeldP.O. Box 10 04 52, D-47704 KrefeldPhone: +49 2151 38 3555Fax: +49 2151 38 [email protected]
egisteredtrademark,
Ashland|
2006,Ashland|December2006,V01