FI64515B - FOERFARANDE FOER BEHANDLING AV EN VATTENHALTIG RESTSLAMSSUSPENSION SOM ERHAOLLITS FRAON EN HYDROMETALLURGISK FRAMSTAELLNINGSPROCESS FOER METALLER SPECIELLT ZINK - Google Patents

Description

irr. ^ _.ι Γ.Ί ADVERTISEMENT /: ac λ c jjääfA (11) UTLÄGGNINGSSKRIFT 64515 c (45) Γ '-, - ΎΐΙ ίί cy'-hru:' -2 ^ 19:33 «UKvik ^ ci3 B 01 D 21/01, C 22 B 19/22, (51) Kv.ik.7int.ci. A 62 D 5/00) / c B 7/24 ENGLISH I - FI N LAN D C21) Pwunttlhnkemu * - PMMttfwBknlnf 702197 (22) Hikumtapilvt - AmBknlnpdag 02.08. 76 (23) AlkupUvi — Glltljh «t * d« | 02.08.76 (41) Interpreted - yeasts ofFentllf 05.02.77

National Board of Patents and Registration of Finland / 44) Nihtivikripano and kuLLulk »i * un pvm. -

Patent- och registrstyrelsen 'AiMttkM uttafd och utMkriftun puMicerad 31.0o.03 (32) (33) (31) Pyrdstty etuoikeus —Begird prlorltet Oi.08.75

France-France (FR) 7521233 (71) Shell Internationale Research Maatschappij B.V., Carel van Bylandtlaan 30,

The Hague, Netherlands-Holland (NL) (72) Robert Herment, Grand Couronne, France-France (FR) (7 * +) Oy Kolster Ab (5 * 0 Method for treating an aqueous slurry slurry obtained from a hydrometallurgical process for the production of metals, in particular zinc -Förfarande for the treatment of non-wattage suspension, with the addition of hydrometallurgical framing processes for metallic, special zinc

The invention relates to a process for treating an aqueous slurry slurry obtained from a hydrometallurgical production process of metals, in particular zinc. The method is characterized in that bitumen, in particular bitumen emulsion, is added to the suspension, the temperature Tm of the mixture of slurry and bitumen emulsion being chosen so that Tm ^ RBT-15 ° C, where RBT is the ball and ring temperature of the bitumen used, and preferably RBT RBT + 15 ° C, the resulting mixture is stirred until the particles agglomerate, the water is separated from the agglomerated fines into a putty and the pH of the suspension initially recovered from the water separated from the agglomerated fines is maximally adjusted to recover salts originally dissolved in the aqueous phase. in the water phase.

The use of a bitumen emulsion as a sludge solidifier has previously been described in DE 1 071-16.

When using the process according to the invention, the bitumen is preferably first added to the emulsifier (preferably a cationic) suspension so that the emulsion is formed in situ, the bitumen preferably being added in molten form after adjusting the pH of the emulsifier-containing emulsion.

It should be remembered that when mixing a bituminous emulsion with a suspension, the emulsified particles of bitumen are bound, like an adhesive, to the fine particles contained in the suspension. Mixing of the mixture causes the formation of an agglomerate or putty-like substance from which water has been partially removed, since the gaps between the granules of the solid material are completely or almost completely filled with bitumen.

This regeneration process is specially designed for use in the treatment of residual sludges from the metallurgical industry, which sludges often contain a large amount of granulometrically relatively small solids. In zinc plants using hydrometallurgical processes (i.e. acid treatment of ore followed by electrolysis), it is always necessary to remove the iron formed from the acid treatment of zinc ore with e.g. concentrated hot sulfuric acid. Numerous methods for removing iron are now known to give various residues, including goethite. However, iron is most often removed as an insoluble complex based on ferric sulphate, which is obtained, for example, by adding calcined concentrates and ammonia. After precipitation of this insoluble complex, filtration, massaging of the filter cake and subsequent re-filtration, a filter cake containing the formula / Fe 2 is obtained. (SO 2) ^ (OH) jarosite residues. Such a jarosite residue contains approximately 70% by weight solids and 30% by weight residual water. It should be noted that this water has a pH of the order of 3.1 and may contain, for example, about 2% by weight, based on the weight of the dry slurry, of soluble zinc salts in the form of Zn cations.

On the other hand, it is clearly important to return the residual water to a certain degree of purity for immediate re-use or disposal in the wild after it has passed through settling tanks. Therefore, it is preferable to reduce the concentration of fines to a minimum. On the other hand, it is also very important to be able to recover the largest possible amount of dissolved zinc salts from this water in order to improve the efficiency of metal production.

3,64515

The mixing of the suspension with the bitumen emulsion is preferably carried out by means of a mixing device, the drum of which is provided with mixing elements which provide a putty-like mass. In order to carry out this mixing under suitable conditions, it is absolutely necessary to avoid the use of Z-shaped mixing elements whose cross-sectional area is too small. In fact, it is necessary that during this step the actual formation of a putty-like mass takes place, whereby the fine solids and the spheres of the bitumen emulsion agglomerate to form a putty. The temperature of the mixture of slurry and bitumen emulsion must be chosen so that Tm RBT - 15 ° C, where RBT is the temperature of the ball and ring test of the bitumen used. In fact, it has been found that when the temperature Tm of the mixture was lower than the RBT of the bitumen - 15 ° C, no putty formation occurred.

The temperature Tm of the mixture is preferably greater than or equal to the RBT of the bitumen used. On the other hand, it has been found that if the temperature Tm of the mixture is higher than the RBT of the bitumen + 15 ° C, the putty becomes inextricably stuck to the blades of the mixer. The temperature Tm of the mixture is thus preferably selected such that

RBT ^ Tm ^ RBT + 15 ° C

and it has been found that the temperature Tm of the mixture is optimal when

RBT = 57 Tm ^ TRBT + 10 ° C

During mixing, some of the water evaporates, depending on the mixing time (usually 5-10 min) and the stirring temperature (usually 60-80 ° C). After putty is formed, water is separated from the putty using conventional procedures such as drying, precipitation, filtration or screening.

The putty is then preferably washed at least once with water to recover the maximum amount of soluble salts originally present in the aqueous phase of the suspension from the water removed from the agglomerated solids. It should be noted that the putty retains its cohesion during and after washing.

Numerous experiments have shown that the washing with water is preferably carried out at a temperature approximately equal to the temperature Tm of the mixture of slurry and bitumen emulsion and that each washing step preferably lasts at most about 10 seconds. It has also been found that with each washing step of about 1-3 minutes, completely satisfactory results are obtained. The pH of the wash water is preferably 3 and is preferably adjusted with sulfuric acid.

In the method, the amount of water required for each washing step is selected to be about 20 to 200 percent of the amount of water originally applied to the putty. Preferably this amount of water is 50-100%.

In general, the pH of the bitumen emulsion, if used, and the wash water are adjusted so that the salts originally dissolved in the suspension water remain dissolved in the aqueous phase. A pH of 4 is very suitable.

When applied to jarosite residues, water containing about 60% of the initially soluble zinc salts in the aqueous phase of the starting suspension is separated from the putty, the zinc salts being in the form of Zn ++ cations. The purpose of the washing steps is to increase the recovery of zinc salts to about 90%, up to 95%.

Particularly for jarosite residues, it is preferred to use bitumen having a hardness of 3-600 (0.1 mm, 25 ° C), preferably 10-15 and even more preferably 20-30. If such bitumen having a hardness of between 20 and 30 is used to form the emulsion, the wash treatments are preferably performed at a temperature of about 60 ° C. The main properties of the emulsion for these residues should be as follows: - it should be stable during storage; - it should have a rate of disintegration such that it allows agglomeration of sludges and removal of water free from solids from the suspension; - its pH should be such that the zinc salts remain dissolved in the aqueous phase to allow their recovery; - the residual amount of bitumen in the agglomerated sludge should be as close as possible to the theoretical amount; - it should be possible to obtain agglomerated sludge in pieces or particles which do not stick to each other during storage.

Based on these different requirements, the composition has been determined for a cationic (about pH 4) emulsion of hard bitumen.

The emulsion found to be most suitable for a slurry containing jarosite residues should be approximately as follows: bitumen 20/30, content: 60% by weight: DNS (Dinoram S, N-alkylpropylenediamine), concentration: 6 kg / t emulsion; HCl content (31% by weight) 4.2 kg / t emulsion; pH about 4.

The percentage of pores in the fines of these slurries is about 50% by volume, which corresponds to 24% by weight (based on the dry slurry) of bitumen to fill the pores.

This bitumen emulsion is preferably prepared under pressure from 20/30 bitumen heated to a temperature of 160-220 ° C and preferably 170 ° C, the temperature of the aqueous phase being about 60-65 ° C.

; 5,64515 Such an emulsion has proven to be sufficiently stable for storage without risk of disintegration.

The water used to form this bitumen emulsion should be of the substantially salt-free, tap water type.

The putty obtained by the above emulsion contains about 68% by weight of water. 55-65% by weight of the zinc salts in the aqueous phase of the slurry are recovered from the aqueous phase. After washing the kit by mixing it 2-3 times with water (pH value 4), the recovery ratio reaches 90-95% by weight. The recovered water can then be mixed with the zinc solution circulating in the plant.

Examples of the use of the above emulsion type.

Example 1

The jarosite slurry containing 193 g of solids, 87 g of water and 4.0 g of Zn ++ ions in the aqueous phase was mixed with a bitumen emulsion containing 54 g of bitumen and 29 g of water at 60 ° C. 73 g of water containing 2.3 g of Zn ++ ions were obtained (recovery percentage 58).

Example 2

The jarosite slurry containing 177 g of solids, 80 g of water and 3.7 g of Zn ++ ions in the aqueous phase was mixed with a bitumen emulsion containing 50 g of bitumen and 28 g of water at 60 ° C. 68 g of water containing 2.3 g of Zn ++ ions were obtained. Washing the putty with 6 # grams of water (pH 4 in all examples) for 3 minutes at 40 ° C gave 62 g of water containing 0.5 g of Zn ++ ions, which means a total recovery of 76%.

Example 3

A jarosite slurry containing 206 g of solids, 92 g of water and 4.23 g of Zn ++ ions in the aqueous phase was mixed with a bitumen emulsion containing 58 g of bitumen and 29 g of water at 60 ° C. 85 g of water containing 2.7 g of Zn ions were recovered. Washing the putty for 3 minutes with 85 g of water at 60 ° C gave 85 g of water containing 1.0 g of Zn ++ ions. The overall recovery rate was 88%.

Example 4

A jarosite slurry containing 232 g of solids, 104 g of water and 4.8 g of Zn ++ ions in the aqueous phase was mixed with a bitumen emulsion containing 65 g of bitumen and 27 g of water at 60 ° C.

+ + ·

80 g of water containing 3.2 g of Zn ions were recovered. Washing the putty with 80 g of water for 3 minutes at 60 ° C gave 78 g of water containing 1.1 g of Zn ++ ions. Repeating this step gave 78 g of water containing 0.3 g of Zn ++ ions. Kokonaistalteenottoprosentt! 89.

6,64515

Example 5

A jarosite slurry containing 193 g of solids, 86 g of water and 3.6 g of Zn ++ ions in the aqueous phase was mixed with a bitumen emulsion containing 57 g of bitumen and 32 g of water at 80 ° C. 77 g of water containing 2.09 g of Zn ++ ions were recovered. When washed twice with 77 g of water for 3 minutes at 80 ° C, the overall recovery was 85.3%.

Example 6

A jarosite slurry containing 192 g of solids, 86 g of water and 3.6 g of Zn ++ ions in the aqueous phase was mixed with a bitumen emulsion containing 57 g of bitumen and 29 g of water at 80 ° C. 80 g of water containing 2.07 g of Zn ++ ions were recovered. When washed twice with 80 g of water for 10 minutes at 80 ° C, the overall recovery was 87.5%.

Example 7

A jarosite slurry containing 6200 g of solids, 2800 g of water and 117.6 g of Zn ++ ions in the aqueous phase was mixed with a bitumen emulsion containing 1960 g of bitumen and 1100 g of water at 60 ° C. 2535 g of water containing 73.6 g of Zn ++ ions were recovered. When washed twice with 2500 g of water for 3 minutes at 60 ° C, the overall recovery was 90.9%.

Example 8

A jarosite slurry containing 195 g of solids, 88 g of water and 3.7 g of Zn ++ ions in the aqueous phase was mixed with a bitumen emulsion containing 58 g of bitumen and 22 g of water at 60 ° C. 98 g of water containing 2.55 g of Zn ++ ions were recovered. When washed three times with 49 g of water for 3 minutes at 60 ° C, the total recovery was 96%.

Bitumen emulsions with lower pH (1.6) or longer wash times (10 minutes instead of 3 minutes) or higher wash temperatures (instead of 80 ° C) did not achieve improvements in recovery percentage. By increasing the number of wash treatments, it proved possible to use a smaller total amount of wash water to achieve the same recovery percentage.

An example of the use of molten bitumen.

Example 9

The jarosite slurry containing 145.5 g of solids, 90 g of water and 3.78 g of Zn ++ ions in the aqueous phase was mixed with a 1% by weight aqueous solution of emulsifier (Dinoram S hydrochloride) 7 6451 5 at pH was * 4, such that the emulsifier was 0.1% by weight of the slurry and with 47.5 g of molten bitumen at 20/30 (160 ° C) at 60 ° C. 59.5 g of water containing 2.29 g of Zn ++ ions (60%) were obtained.

When about 0.05% by weight or more than about 0.3% by weight of emulsifier was used, the recovery percentage was only 33 and less than 43, respectively, and the water content of the putty was higher.

Thus, an amount of 0.05 to 0.3, especially 0.1% by weight of emulsifier, based on the slurry, is recommended when using molten bitumen.

The emulsifier may also be added as an aqueous dispersion if it is insoluble or molten or dispersed in the bitumen. In the latter case, longer mixing times are required (e.g. 10 minutes instead of 5 minutes) and the recovery percentage obtained is lower (e.g. 66% instead of 77%). The use of a molten emulsifier also requires extended mixing times.

After mixing the slurry with the molten bitumen or bitumen emulsion, additional slurry may be added to the prepared putty to reduce its bitumen content, e.g., from 25-26% by weight to 21-22% by weight (dry putty).

For example, after mixing for about 4-10 minutes, the kit obtained with the bitumen emulsion containing 24-26% bitumen of dry matter can be mixed with an additional amount of slurry, e.g. for 3-10 minutes at a mixing temperature preferably higher than 60 ° C, preferably about 80 ° C to reduce the bitumen content of the final putty (preferably RBT Tm RBT + 30 ° C) so as to obtain 20-22% by weight of bitumen from the dry matter of the putty. Any washes are then preferably performed after mixing the additional amount of slurry.

In this way, it is possible to use less bitumen than is required to completely or almost completely fill the pores of the solid material of the sludge.

The resulting kits, especially those obtained from sludges containing jarosite residues, can be used in particular for sealing purposes or for the production of rolled or cast bituminous mixtures for roads, car parks, factory floors, building roofs, hydraulic products and the like. In general, the type of bitumen used to make the putty depends on the end use of the putty. For example, bitumen with an penetration of between 10 and 50 (0.1 mm; at 25 ° C) is preferably selected if the putty is to be used in bituminous concrete to be cast. The necessary fillers and bitumen can be added to the kit.

8 '6451 5

The shape of the kit also depends on its use. It may be a) in lumps or granules; (b) as a finely divided powder of the filler type.

It may be advantageous to perform a heat treatment on the putty to evaporate the residual water and dry the putty and mix it with a powdered substance (e.g. filler) to prevent the ground putty from becoming pulp or clumping, c) as a molten or liquid powder. In this case, it is preferable to use an excess of bitumen to make the putty liquid. On the other hand, for long-term storage, it is necessary to use thermally insulated containers equipped with mixing devices to prevent precipitation.

The possibilities of using putties, e.g. as granules or powders, as additives in hot asphalt mixtures have been investigated. To this end, several experiments were performed with sand-bitumen-type mixtures. Composition of mixture A: - sand 96% by weight, - calcareous aggregate 4% by weight, - 20/30 bitumen 4 parts by weight.

Composition of mixture B: - sand 96% by weight, - putty (jarosite filling 4% by weight, bitumen 1.4 parts per cent), - 20/30 bitumen 2.6 parts by weight.

The concentrations of fillers and bitumen in the two compositions A and B were the same. The second composition B was obtained without difficulty using the following procedure: - cold putty in the form of granules or powder is added to the hot sand (185 ° C) - mixed for 1 minute, - hot bitumen (185 ° C) is added, - finally mixed for 1 minute.

The properties of the two compositions A and B are shown in the following table: - -----—————-------- r

Composition A Composition B

Softening point ball and ring test ° C 89, S 89

Penetration 2 at 5 ° C 0.1 mm 13 13

Penetration index 2.5 2.5

Claims (3)

9,64515 Both compositions have similar properties. The possibility of using putty as a component of cast bituminous concrete (GUSS-ASPHALT) has also been investigated. It turned out that when jarosite granules are used instead of the conventional calcareous filler, about 10% less bitumen can be used while maintaining good workability and good penetrability. Although the above examples are directed to the processing of jarosite filter cakes, this method can also be applied, e.g., to a product that has been allowed to settle only. It should also be noted that when treating sludges from blast furnaces by hydrometallurgical processes to recover the zinc they contain, the process according to the invention can also be applied to the mineral sludges thus obtained. A process for treating an aqueous slurry slurry obtained from a hydrometallurgical production process of metals, in particular zinc, characterized in that bitumen, in particular a bitumen emulsion, is added to the slurry, the temperature Tm of the slurry and bitumen emulsion mixture being selected from Tm to RBT RBT is the ball and ring temperature of the bitumen used, and preferably such that the mixture formed is mixed until the particles agglomerate, the water is separated from the fines agglomerated into putty, and the suspension of salts initially dissolved in the aqueous phase is recovered from maximum water. separated from the agglomerated fines, the pH is adjusted so that the salts remain dissolved in the aqueous phase. A method according to claim 1, characterized in that the putty is subjected to at least one washing treatment with water, the putty maintaining its cohesion during and after the washing. Method according to Claim 2, characterized in that the washing treatment (s) of the putty with water is carried out at a temperature substantially equal to the temperature Tm of the mixture of slurry and bitumen emulsion. M. A method according to any one of claims 1 to 3, characterized in that bitumen having a hardness of between 10 and SO (0.1 mm;? S ° C), determined according to ASTMd 2d3, is used.