FR2502509A1 - PROCESS FOR DEHYDRATING SUSPENSION OF MINERAL MATERIALS - Google Patents

Abstract

PROCESS FOR DEHYDRATING SUSPENSIONS OF MINERAL MATERIALS. TO THESE SUSPENSIONS ARE ADDED SURFACTORY AGENTS WITH A HLB VALUE OF 8 TO 12 OR A HL VALUE OF 50 TO 150 IN QUANTITY OF 0.03 TO 2 DEPENDING ON THE SOLID MATERIAL CONTENT OF THE SUSPENSION AND THE MOLECULAR STRUCTURE OF THE LATTER THEN THE SUSPENSION IS DEHYDRATED IN A MANNER KNOWN IN ITSELF, FOR EXAMPLE BY FILTRATION, IF NECESSARY AFTER ADDITION OF A NON-IONIC OR CATIONIC LINEAR POLYELECTROLYTE.

Description

The present invention relates to a method of

  to dehydrate suspensions of

  ral. It relates in particular to a method

  to dehydrate the fine dispersions or suspensions

  formed in large quantities by sorting or concentrating minerals and ores, washing coal (coal sludge), purifying water

  wastewater or siltation of terrace work-

is lying.

  Dehydration and filtration operations

  on dispersions or suspensions such as

  the above mentioned in order to comply with the laws or because of storage constraints or to avoid pollution of the environment, require ever increasing expenses, a lot of time and energy. Several continuous processes are already known and

  discontinuous combined with flotation and flocculation

  and in which the filters are used.

  filters, carpet and drum filters, vacuum filters, filter presses and

  centrifuges. It has also been applied

  pity by lime or magnesia. Sometimes, we

  adds to the filter material filter additives

  such as sand and change its pH. For the filtration of iron ores, it is also used

  sulphonated organic compounds known in the indus-

textile sorting.

  Such methods are described in detail with apparatus for their implementation, for example in German Patents Nos. 2,614,260 and 1,119,826 and in United States Patents Nos. 3,398,093, 3,408,293 and US Pat.

2266954.

  These processes and devices no longer meet the current requirements of

  dehydration. They also have disadvantages

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  that they require large amounts of

  energy, that they require relatively

  complicated for dehydration. Thus,

  operating costs are relatively high. The capacity

  In the known processes, the filtration head is about 10 to 60 kg / m 2 / hour, which can pass in cases of optimum composition and particle size to about

kg / m2 / hour.

  The present invention therefore aims to overcome the disadvantages of the processes of the prior art by a dehydration process which, in

  firstly, to reduce to a certain extent

  Deploy the energy consumption.

  The process according to the invention will also have to

  enable the application of filtration techniques to

  previously known simple and, by way of

  to reduce the operating costs.

  In the course of its research to achieve the goals mentioned above, the applicant found that the difficulties encountered in the filtration of dispersions or suspensions were due to the tendency to thixotropy these dispersions or suspensions, to

  the structural viscosity resulting from this thixotropic

  as well as the high zeta potential existing between the suspended substance and the suspending medium. These

  This is due to the fact that the human content

  relatively high moisture can only be eliminated

  price of great energy consumption and at great expense.

  We can reduce or even eliminate the

  thixotropy and the high zeta potential by modifying the interfacial properties of the substance

  in suspension. This change leads to a decrease in

  both the structural water content and the solvation water of the suspension. To achieve -3-

  this result, the suspended particles must be treated

  by means of compounds covering or coating their

  terface and thus prevent the formation of the structure

  of dispersion. Indeed, this structure of

  sion retains the water by capillarity. After treatment, the suspended particles are much less

  hygroscopic or much more water-repellent than

  this property leads to a reduction in the amount of energy required for

the dehydration operation.

  The ability of various combinations to

  the hygroscopic properties of suspended particles can be established by measurement of the

  CST (Capillar Suction Time, capillary suction

  lar) of the dispersion. The procedure for this measurement is described in detail in R. S. Galle's book: Optimizing the Use of Pretreatment Chemicals (pages 40).

  at 82; Upland Press Ltd, Croydon, Great Britain 1976).

  To characterize the agent used to promote the opera-

  dehydration, a so-called HLB value is used

  (Hydrophil-Lipophil Balance, hydrophilic balance-

  lipophilic) or an H / L value (relationship between the

  hydrophilic and lipophilic portion). This last one

  tells them the ratio in percent of the two portions

  of the molecule with different character. These values can

  can be measured or calculated from the ratio of the groups contained in the molecule. A more detailed definition of these terms can be found in the following works: Griffin, W.C.:I.Soc. Cosmetic Chemists 1.311 (1949) Griffin, W.C .: I. Soc. Cosmetic Chemists 5.249 (1954) Moore, C .; Bell, M .: Soap Perfumery and Cosmetics

29,893 (1956)

  -4- Davis, I.T .: Proceedings of 2nd International Congress on Surface Activity

II I

  Juhasz, E .; Lelkesné, Eros, M .: Feliiletaktiv anyagok zsebkônyve (Editor: Miszaki Kbnyvkiado, Budapest, (1979)) The invention therefore relates first and foremost to a process for dehydrating suspensions of mineral matter, which process is characterized in that to the suspension is added surfactants or surfactant mixtures in an amount of 0.03 to 2%, depending on the content of suspended particles and the molecular structure of the suspension, the agents

  surfactants or surfactant mixtures pre-

  with an HLB value of 8 to 12 and / or an H / L value of 50 to 150%, and after this treatment the

  suspension in a manner known per se.

  It has been found that the treatment with

  compounds with the specific HLB or H / L values

  in accordance with the invention diminished

  badly and practically suppressed the tendency to

  the thixotropy of particles in suspension with

  dispersion structure and potential

  zeta of these particles. This results in a decrease in

  the adsorption capacity of the moisture of the

  suspended particles and, consequently, of the

  itself, with a clear beneficial effect on the energy consumption required for the dehydration operation. This beneficial effect can be further accentuated according to the invention by adding to the suspension, before dehydration, an ionic linear polymer polyelectrolyte or cationic nonionic linear polymer polyelectrolyte, this polyelectrolyte having in both cases a molecular weight of

500,000 or more.

  According to the invention, the surfactants can be added to the suspension or the surfactants can be mixed with the suspension using a simple mixer or a centrifugal pump, or by spraying. or by laminar contact.

  The polyelectrolyte can be added to the

  pension treated with surfactants on a

spraying chute.

  One can then proceed to effective dehydration by one of the techniques known per se, in

  a filtration chamber or in a decantation tank

  or in a co-form sedimentation vessel

  nique, preferably with a cone angle of 30 °.

  In another preferred embodiment of

  the invention, the suspension treated by the agents

  It can be transported and dehydrated on

  a sedimentation chute connected to a cyan filter

vibrating or rotating lighter.

  We will now describe in more detail the

  implementation of the method according to the invention.

  The suspension or dispersion produced in the

  course of industrial operations and which must be

  Filtration is sent to a container in

  which is added by vigorous mixing or spraying.

  tion, surfactants. In a mode of

  the particular suspension, suspension or dispersion

  by the surfactants is sent from the

  to a centrifuge or a vacuum filter on which it is dehydrated. In another embodiment,

  the dispersion or suspension treated is sent from the

  on a chute on which the poly-

  electrolyte, for example by laminar contact. The sus-

  pension from the chute runs into the tank

  see of a vacuum filter on which it is dehy-

  dratée. The dispersion or suspension coming from the trough and treated with the surfactants and the polyelectrolyte can also be sent in a

  sedimentation chute. Water, that is, the

  trat, is sucked to the end of the trough opposite the inlet end of the dispersion or suspension and recycled in the circuit. The sedimented substance

  is discharged from the bottom of the chute on a rotating filter.

  and from there on a storage place.

  The following examples illustrate the invention

  without, however, limiting its scope; in these examples, the indications of parts and percentages

  by weight unless otherwise indicated.

Example 1

  Raw material: dispersion obtained by sorting

Jordan phosphate ore.

  Composition: a few percent of crude phosphate, kaolin, halloysite, illite, clay mineral

containing montmorillonite.

  Granulometry: below 0.07 mm: 48% 0.07 to 0.1 mm: 18% 0.1 to 0.152 mm: 54% Dispersion concentration:

700 g / liter.

  Surfactant used: A mixture of an ester formed from a polyethylene glycol ether and lauric acid and an ester formed

  from octanol and maleic acid.

  Quantity: 10 kg / ton of dry matter.

  Polyelectrolyte with cationic character: polyacrylamide

  methylated molecular weight 2 to 5 million.

  Quantity: 0.25 kg / ton of dry matter.

  The additives are used in aqueous solution

is.

  The dispersion formed in the sorting operation of the phosphate ore is sent to a tank in

  which the surfactant is added by spraying

  or by intensive mixing. The dispersion is then sent to a chute on which the

  polyelectrolyte with cationic character by contact la-

  seminar. The dispersion from the chute then passes into the reservoir of a vacuum filter. The applied vacuum is LPmax = 0.9 bar. In the absence of additives, the filter capacity is 302 kg / m 2

hour, in dry matter.

  The CST value of the dispersion is 52 seconds before treatment. After treatment with the surfactants and the cationic polyelectrolyte, the CST value of the dispersion is 4 seconds and the capacity of the filter is 2.487 kg / m 2

  hour. The thickness of the filter cake is 20 mm.

  The cake from the filter is evacuated to

  using a carpet conveyor and the water is recycled.

  With the same filter, the production capacity

  is 270 kg / m2 / hour before treatment and the thick-

  cake size is 10 mm; after treatment with

  surfactant and the polyelectrolyte with

  cationic, the capacity is 2.790 kg / m 2 / hour.

  These results clearly show that the

  The filter capacity is 8 to 10 times stronger after

  by surfactants and polyelectrolyte

  lyte, and even varying the thickness of the cake.

Example 2

  We start from the same dispersion as in Example 1 which is also treated as described in Example 1, after which it is sent to a decanter

  centrifugal. The speed of rotation of the centrifugal settler

  The fuge is 1,000 rpm and the centrifugal force 67 G. The results are as follows. In the case of --8-

  the untreated dispersion, the water can not be separated

  suspended particles in 10 seconds. On the other hand, the treated dispersion is concentrated at 60%

  after 2 seconds of centrifugation. This concentration

  tion does not change even at the end of the 10th second.

  The concentrated dispersion is discharged onto a transporter

  carpet and the water is recycled in the circuit.

Example 3

  Raw material: dispersion produced in the treatment of a spoil pile of a coal mine

in Yugoslavia.

Composition: 5% coal

% of clay.

  Granulometry: below 0.07 mm: 4% 0.07 to 0.1 mm: 9% 0.1 to 0.125 mm: 23% 0.125 to 0.351 mm: 64% Dispersion concentration:

430 g / liter.

  Surfactant used: ester of a polyether ether

  ethylene glycol and fatty acids mixed together

  same as obtained by decomposition of

gétales.

  Quantity: 8 kg / ton of dry matter.

  Polyelectrolyte used: polyacrylamide, molecular weight

2 to 5 million.

  Quantity: 0.2 kg / ton of dry matter.

  The dispersion from the cyclone used for the separation of the coal is sent to a tank

  wherein the surfactant is added by pulverization

  hardening or intensive mixing. The dispersion that flows from the container is sent to a chute on

  which is added the polyelectrolyte of a

  by laminar contact. The dispersion passes from the chute into the reservoir of a vacuum filter on which it is dehydrated. The applied vacuum is APmax = 0.9 bar. The dispersion has a CST value of 80 seconds before treatment and 5 seconds after treatment. Before treatment, the capacity of the filter is 70 kg / m 2 / hour of dry matter and after treatment it is 1,400 kg / m 2 / hour of dry matter. The dispersion leaving the filter is evacuated by

  a conveyor belt and water is recycled. The thick-

  the filter cake is 20 mm.

Example 4

  Raw material: dispersion produced by treating a spoil pile of a coal mine

in Austria.

  Composition: 5% lignite% of a mixture of clay minerals

  used for the manufacture of

fine ceramics and pottery.

  Granulometry: below 0.07 mm: 18% 0.07 to 0.1 mm: 25% 0.1 to 0.15 mm: 35% 0.125 to 0.515 mm: 22% Dispersion concentration:

430 g / liter.

  Surfactant used: mixture of an ester formed from octanol and maleic acid

  and an ester formed from lauric acid

  and a polyethylene glycol ether.

  3G50 Quantity: 9 kg / ton of dry matter.

  Polyelectrolyte used: polyacrylamide methyl, weight

molecular 2 to 5 million.

  Quantity: 0.02 kg / ton of dry matter.

  The dispersion has a CST value of 180 seconds before treatment and 20 seconds after treatment.

  The dispersion is treated with the surfactant

  active and the polyelectrolyte as described in the previous exerLple and then is dehydrated on a disk filter under a vacuum of APmax = 0.9 bar. Before treatment

  filter capacity is 37 kg / m2 / hour; after treatment

  only by the surfactant it is

  kg / m2 / hour and after treatment by both

  surfactant and the polyelectrolyte, it is 250 kg / m2 / hour. The filter cake has a thickness of 20 mm. The water is recycled and the dried material is

  sent to a slag heap by means of a conveyer

udder.

Example 5

  The dispersion of the above example is treated

  dent by the surfactant or by the surfactant.

  active and the polyelectrolyte then it is sent on a

  settling chute * Water is sucked in at the end

  the chute opposite the inlet end of the dispersion, and the sediment, i.e. the concentrated dispersion, is fed from the chute foot onto a rotary filter. The dried material is sent from the filter to a slag by means of a conveyor belt. The water

is recycled in the circuit.

Example 6

  Raw material: raw dispersion from normal production of Portland cement in Labatlan, Hungary Composition: SiO2 - 20.31%

A12053 - 5.41%

  Fe205 - 3.08% CaO - 68.12% MgO - 2.66% SOc - 0.29% -11- Granulometry: below 0.01 mm: 30% 0.01 to 0.065 mm: 60% 0.065 at 0.09 mm: 10% Dispersion concentration: 1.450 g / liter. Surfactant used: mixture of two esters: a polyethylene glycol ester of acid

  myristic and hexaethylene monoleate

glycol.

  Quantity: 6 kg / ton of dry matter.

  Polyelectrolyte used: polyacrylic acid.

  Quantity: 0.2 kg / ton of dry matter.

  The flow rate of the vacuum filter used in the operation is 134 kg / m2 / hour before dispersion treatment and 555 kg / m2 / hour for dispersion

  treated. The applied vacuum is APmaX = 0.8 bar.

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Claims (5)

- CLAIMS -   1 - Process for dehydrating suspensions of mineral matter, characterized in that surfactants or mixtures of surfactants are added to the suspension in an amount of from 0.03% to 2% depending on the content of the substances in suspension and the molecular structure of the suspension, these surfactants or surfactant mixtures having an ELB value of 8 to 12 or an H / L value of 50% to 150%,   after which the suspension is dehydrated naked in itself.   2 - Process according to claim 1, characterized   in addition to the suspension,   before dehydration, a polymeric polyelectrolyte   ionic nonionic polymer or polyelectrolyte with a cationic character, this polyelectrolyte having in both cases a molecular weight of 500,000 or more.   3 - Process according to claim 2, characterized   characterized in that the surfactants or surfactant mixtures are added to the suspension by means of a simple mixer, a centrifugal pump,   by spraying or laminar contact.   4 - Process according to claim 3, characterized   in that after treatment by the agents   surfactants, the suspension is sent to a government   monkfish to which the polyelectrolyte is added by spraying. Process according to Claim 4, characterized in that the suspension is dehydrated in a filter chamber or in a settling tank or in a conical-shaped sedimentation vessel.   preferably at a cone angle of 30. -13-   6 - Process according to claim 4, characterized   characterized in that the suspension treated with the surfactants and optionally with the polyelectrolyte   and concentrated is sent and dehydrated on a   monkfish sedimentation and a vibrating cylinder filter   or rotary connected to said chute.