Improvements in copper heap leaching by addition of wetting agents

Transcription

1 IMMC 2008, October 16-18, Istanbul Improvements in copper heap leaching by addition of wetting agents A. Lützerath, M. Vest, H.-P. Seelmann-Eggebert, B. Friedrich IME Process Metallurgy and Metal RWTH Aachen Prof. Dr.-Ing. Bernd Friedrich

2 Project introduction - improving Cu heap leaching Background: annually rising demand of of copper increasing prices approx % of of primary world Cu Cu production by by heap leaching processes + SX/EW so so far far recovery of of conventional heap leaching processes range by by % of of the the ore s Cu-content during leaching periods of of several months Target: Improve productivity (recovery and and leaching kinetic) by by addition of of wetting agents

3 Heap leaching of copper ores reactor volume: 100, ,000 t t ore ore retention time time of of solution: days days leaching duration: several months

4 Heap leaching of copper ores stacker unit sprinkler system

5 Principles Model: shrinking core time time 30 mm

6 Leaching model (1) 1 st st Fick s law law dn dt Cu = A D eff dc dr Cu C A C Cu r 0 r C = acid content = leached Cu content = starting radius of particle = radius of unreacted core RIM = leached core shell

7 Leaching model (2) t(f = 1) = 3D C 2 B r A,0 5 0 n τ K r 2 K r K t p 2η γ cosθ L 1,0 0,8 t(f=1) at γ = 72 mn/m t(f=1) at γ = 42 mn/m L*t(F=1) 0,6 0,4 Δ t 1 : negative influence of γ Δ t 2 : positive influence of θ Δ t 1 Δ t 2 0,2 0, contact angle θ in

8 Requirements of wetting agents By By analysis of of the the previous attempts to to introduce wetting agents to to leaching processes the the following performance profile was was developed: Requirements for for heap leaching process: good wetting performance at at process temperature improved capillary penetration of of ores ores no no negative impact on on further processing steps (SX, (SX, EW) EW) economically acceptable concentration stable in in leaching solution low low foaming biodegradable // not not eco-toxic

9 Criteria 1 - surface tension and CMC Surfactant in Surface Tension in mn/m Air Surface water of 20 C Critical micelle concentration (CMC) Water Concentration in mg/l Determination of of the the optimum dosage concentration.

10 Criteria 2 - adsorption rate Measuring the the adsorption rate rate by by miniature column test. test. surfactant solution 100 ppm surfactant concentration in outflow / ppm 0 ore 1 ore irrigation time / h

11 Criteria 3 capillary penetration solution without surfactant solution with surfactant load in mn Measuring the ore penetration and the wetting performance. analytical balance tube with sintered glass bottom ore eluent time in s

12 Column trials at IME experimental set-up: set-up: 8 columns, H = mm, mm, D = mm mm perforated stainless steel steel base base filling filling level: level: mm mm volume: appr. appr m 3 3 ore ore weight: appr. appr kg kg // column ore: ore: origin: origin: Cerro Cerro Colorado, Chile Chile particle size: size: mm mm Cu-content: wt-% wt-%

13 Experimental set up storage vessel PE granulate sprinkler valve timing pumps

14 Experimental procedure column additive BASF lab No blank nonionic surfactant (fatty alcohol alkoxylate) nonionic surfactant (fatty alcohol alkoxylate) anionic surfactant (alkyl ether sulfate) EVD61549 RD EVD63635 conditions: test test duration: 4 weeks weeks throughput: l/h l/hcolumn (10 (10 l/h l/hper m 2 2 )) concentrations: H 2 SO 2 SO 4 : 4 : 2 % surfactant: %

15 Determination of adsorption rate with PE nets total height 215 cm filling level ore 200 cm sample A 135 cm sample B 75 cm sample C 15 cm

16 Spreading of wetting agents 120 column 3+4 column 5+6 column surfactant concentration in ppm A 100 B 50 C 0 0 position in column in cm Relatively strong adsorption of of all all wetting agents

17 Copper extraction Cu in g column 1+2 column 3+4 column 5+6 column time in d nonionic wetting agents improve Cu extraction

18 Copper recovery EVD RD EVD blank 78% 80% 82% 84% 86% 88% copper recovery improvement of of leaching efficiency up up to to 6 %

19 Summary and Outlook Summary: proof of of concept has has been successful: nonionic wetting agents may may improve the the kinetic of of leaching and and copper extraction rate rate still still too too high high adsorption rate rate for for the the nonionic wetting agents depending on on the the ore ore anonic wetting agents did did not not achieve a higher extraction rate rate Outlook: optimization in in progress with with regard to: to: wetting performance adsorption rate rate proof of of transferability to to other acid acid leaching technologies e.g. e.g. Ni Ni new new trials are are planned in in Aachen with with improved wetting agents

20 IMMC 2008, October 16-18, Istanbul Thank you for your attention. Ilginize tesekkur ederiz. IME Process Metallurgy and Metal RWTH Aachen Prof. Dr.-Ing. Bernd Friedrich