DE2040216C3 - Use of one or more solid bowl screw centrifuges for dewatering zinc leach residues - Google Patents

Description

Embodiment

Zinc leach residues with a solids content of 640 g / l dehydrated. The one fed to the centrifuge

■ to amount of lye was 4 mVh. ^{140 g / m 2 J} Praestol 2900 (0.05% solution) was added to this liquor as a flocculant before being fed to the centrifuge. The leach residues mixed with the flocculant in this way had a density of 1.775, a pH of 5.2 and a temperature of about 22 ° C. The centrifuge was operated at 1,860 rpm. The resulting centrifugate had a solids content of 1 g / l, while the centrifuged residue only had a moisture content of 22%.

In relation to the feed item, is calculated from this Solids yield of 99.9%.

As further practical tests have shown, zinc leach residues could be used for the dewatering according to the measures according to the invention compared to the previously known methods Loss of metals, especially zinc, can be largely reduced. In addition, the The electrical energy requirement of the centrifuge is only about 30% of that of the previously used suction drum filter,

M) Since, as has been shown in the exemplary embodiment, the solids content of the centrifugal material is only one gram per liter, the centrifugate can be subjected to chemical lye cleaning, for example cementation, directly without prior cleaning.

· '"· Are thrown. When draining with the help of a Drum filter, on the other hand, has to accept a nitrogen content of 5 to 10 g / t, so that on one Post-cleaning cannot be dispensed with. the

Use of a solid bowl screw centrifuge to dewater contaminated with flocculants Zinc leach residues according to the invention is therefore considerably more economical than that previously known Process for the dewatering of zinc ore leach residues, even if the dewatering and optionally washing of zinc ore leaching residues in several series-connected Centrifuges is made.

Claims (1)

Claim: Use of one or more series-connected Solid bowl screw centrifuges for dewatering contaminated flocculants Zinc leach residues. So far, one has the incurred in the wet metallurgical processing of zinc ores by leaching Leaching residues, especially those from the leaching of dissolved zinc blends, zinc oxides and similar leach residues, thickened in large containers and then using a drum suction filter or filter presses dewatered to a water content of approx. 40%. To the losses of water soluble To keep zinc in the filter cake low, it was washed on the filter. The washing liquid then had to be concentrated by evaporation, which involved a high level of work and expense was connected. Attempts have also been made in the wet metallurgical processing of zinc ores Leaching with the help of acid leaching residues after prior thickening in one Full bowl peeler centrifuge for dewatering. It was found that due to the inhomogeneity of the in animal liquor suspended solids cause such an uneven distribution of solids in the Centrifuge comes that not only the dewatering effect is significantly impaired, but that it also leads to a one-sided burden on the Centrifuge drum comes, which leads to severe imbalance, which the operation of the centrifuge make it difficult or even impossible. Surprisingly, it has been shown that a dewatering of zinc leach residues without Difficulties and with a particularly good drainage effect can be carried out if the Zinc leach residues mixed with flocculants and the drainage in one or more series-connected solid bowl screw centrifuges is carried out. With the help of the solid bowl screw centrifuge, those mixed with flocculants can be very beneficial Zinc leach residues can be dehydrated to a water content of 20% and less without it there is one-sided loading of the centrifuge drum and the formation of imbalances. This is likely to be attributed to it be that on the one hand by the addition of flocculants to the leaching residues a homogeneous and even distribution of the solids suspended in the leaching residues in the Solid bowl screw centrifuge is achieved and that on the other hand also by the continuously operating Discharge screw a continuous discharge is guaranteed. Can be used as a flocculant for this Prestol 2900 can be used advantageously. It is known from French patent specification 3 79 939 a wet-metallurgical processing method, according to the hard-to-melt zinc and lead minerals with the help of a boiling, concentrated Ammonium salt solution are treated. The resulting mother liquor is used for regeneration subjected to filtration. Also from the French patent 13 48 073 is a method for Recovery of zinc from zinc-containing blast furnace dusts known, according to which the zinc-containing dusts dissolved by means of ammonia and ammonium carbonate and the solution with the zinc-containing solids over several, successive stages is performed. The solids are removed by filtration from the Separated mother liquor and the zinc content in the solution enriched from stage to stage. The measures according to the invention require due to the lower residual moisture content of the centrifuge residues a much smaller amount of water to wash them out. It will therefore decrease also the energy costs for evaporating this amount of water before further wet metallurgical processing of the zinc sulphate contained in the washing water. is Despite the smaller amount of washing water, they are still occurring zinc sulphate losses in the centrifugal residues as a result of the reduced final moisture content by around 50% lower than with the previously known dewatering processes. However, it is also possible to precede the centrifuge by adding water dilute and in this way the zinc sulphate content in the residual moisture of the centrifuge residue and thus to reduce zinc sulphate losses. As a result of the lower residual moisture content of the centrifuge residue In this way, a special washing stage may possibly be omitted. Eventually it surrenders in the method according to the invention due to the low residual moisture content in the event of a thermal processing of the filter residue JO requires less energy to dry this residue. Also with a wet metallurgical processing of the centrifuge residue With the help of highly concentrated sulfuric acid, the low residual moisture content of the residue is an advantage.