Residual amine in iron ore flotation
Geraldo M.B.Batisteli a ,Antonio E.C.Peres b,*
a Samarco Minerac ßão SA,Mina do Germano,Caixa Postal 22,35420-000Mariana,MG,Brazil b
EEUFMG,Rua Espírito Santo,35/206,30160-030Belo Horizonte,MG,Brazil
a r t i c l e i n f o Article history:
Received 27November 2007Accepted 11April 2008
Available online 22May 2008Keywords:
Flotation collectors Froth flotation
社鼠a b s t r a c t
The possibility of recovering residual amine prent in the water pha of tailings pulps of the rever cationic flotation of iron ore was investigated.The samples collected in the tailings from mechanical and tank cells and also from flotation columns were kept under rest to promote the paration between the
water and the solid particles.The water was ud for determination of the residual amine concentra-tion and for flotation tests.The residual amine concentration was determined through indirect quantita-tive analysis using a spectrophotometer.The flotation tests were performed using,parately,each tailings water and a composition of them.Four ts of tests were carried out.The first three ts indicated the strong possibility of reusing the amine prent in the water.As a conquence,the dosage of amine was reduced and the residual amine concentration of three out of four collection points was below the detection limit in the sampling for the last t.
Ó2008Elvier Ltd.All rights rerved.
社区基层治理
1.Introduction
The plant practice of the rever cationic flotation of iron ores started in Brazil in 1977.Starch is ud as depressant for iron min-erals and amine acts as quartz collector and also as frother.
Amine is an expensive reagent and its consumption tends to be higher with the increasing contents of quartz in the ores being pro-cesd.Controlling the costs related to amines reprents a major challenge for the process engineering team in charge of the iron ore concentrators.
Samarco us approximately 1500tonnes per year of amine,at a production rate of 16million tons per year of concentrate,repre-nting clo to 50%of the overall costs with reagents.The concen-trator is being refurbished to produce 24million tones per year of pellet feed fines.
Most of the amine added to the flotation circuit is discarded to tailings ponds either adsorbed onto quartz particles or dissolved in the water fractions of the tailings.The reu of part of this amine combines economical issues with environmental targets.Despite the lack of evidences of toxicity of the amines ud in ores flotation (Peres and Ciminelli,2002),reducing the prence of chemicals content in effluents is always desirable.2.Literature review
Smith and Akhtar (1976)stated that,due to the fact that the adsorption of amine onto quartz is electrostatic and involves low
heat transfer,it may be considered a reversible process.According to this reasoning,desorption of amine from quartz would be feasi-ble at strongly alkaline or acidic conditions.
Nevertheless,experimental results show that extreme condi-tions are not necessarily required for desorption.Oliveira et al.(1996)investigated the desorption of dodecyl amine from pure quartz at pH levels of 4.0and 6.4adjusted with HCl.The suspen-sion was filtered after 10min of contact and the liq
uid pha was analyd for amine.It was possible to recover 60%of the amine added to the system,2/3coming from desorbed amine and 1/3cor-responding to non-adsorbed residual amine.
而今安在哉句式
Baltar et al.(2002)reached 80%desorption of ether dodecyl amine adsorbed onto pure quartz in the size range <44l m,work-ing at pH 3.The desorbed amine was effective in pure quartz flota-tion at bench scale.
Barbato et al.(2004)investigated the adsorption of amine pres-ent in effluents from iron ores flotation onto stilbite,a mineral of the zeolites class.The target was purifying the water and there was no mention to the reu of amine.Removal levels higher than 95%were achieved.
The topic of residual amine in flotation waters was addresd by Orphan and Bayraktar (2006),but the target of the investigation was to detect its effect on the quality of a feldspar flotation concen-trate rather than the reu of residual amine.3.Methodology
The amine concentration in aqueous phas was determined as a function of the absorbance in a UV visible spectrophotometer.Two calibration curves were plotted bad on an ether monoamine
0892-6875/$-e front matter Ó2008Elvier Ltd.All rights rerved.doi:10.1016/j.mineng.2008.04.002
*Corresponding author.Tel.:+553134091717;fax:+553134091815.E-mail address:aecperes@demet.ufmg.br (A.E.C.Peres).Minerals Engineering 21(2008)
873–876
Contents lists available at ScienceDirect
Minerals Engineering
段振豪j o u r n a l h o m e p a g e :w w w.e l s e v i e r.c o m /l o
动物的眼睛cate/mineng
and an ether diamine,manufactured by Clariant and ud in the plant practice.
Tailings samples were collected in the four circuits of the con-centrator:mechanical cells(76%of the total tailings),tank cells (10%),recleaner columns(8%),and slimes columns(6%).It is worthwhile recalling that in reverflotation the tailings consist of the fraction collected at the top of the cell.
The tailings samples were left under rest for12h and then the solid liquid paration was performed via siphoning.The liquid pha was compod according to the proportions of each tailings fraction and ud in the bench scaleflotation experiments and in the residual amine concentration determinations.
The iron ore sample for the laboratoryflotation experiments was compod from the feed of thefirst stage of concentration (mechanical cells)during a three months operation period.The overall sample was homogenid and quartered.
The experiments were performed in a Wemco laboratory ma-chine,operated at1300rpm,in a3L tank.The depressant condi-tioning(5min)was carried out with a pulp containing1500g of ore and800
mL of tap water to prevent the contact of particles with water containing the collector prior to starch adsorption. After the conditioning with starch,1600mL of tailings water were added to the cell jointly with the amine dosage lected for the test.At the beginning of the test the weight percent solids of the pulp was38.5%.Amine conditioning time was t at1min.After 1min of froth collection,an extra volume of300mL of tailings water was added to the cell.The total time of froth collection was3min.
In afirst t of experiments,amine from residual water was the only source of collector.Later,experiments were performed with the addition of amine dosages of20g/t,35g/t,and50g/t.For this quence a composition water was prepared taking into account the proportion of tailings from each circuit.Another ries of experi-ments simulated an operation with the u of only residual amine in the rougherflotation and amine solution addition in a cleaner stage at dosages of20g/t,35g/t,and50g/t.
The results of the tests with water containing residual amine were compared with tho from the standard test,performed with distilled water and amine solution prepared in the laboratory.
The control parameter was silica content in the concentrate. 4.Results and discussion
The time quence of the concentration of residual amine in the tailings of each individual circuit is ill
ustrated in Fig.1.The sharp decrea obrved from11/11/2005to13/09/2006was due to v-eral factors,such as:circuit changes,increa in the throughput due to the addition of new mechanical cells,increa of the propor-tion of diamine in the collector blend,start up of an advanced con-trol system in the conventionalflotation circuit,and decrea of the specific collector dosages in all addition points.This latter fac-tor was a conquence of this study.Specific amine consumption at Samarco’s concentrator was lower than that at other plants,never-theless the detection of residual amine showed that reductions in the addition level should be carried out.
Results of standard tests,illustrating the effect of amine dosage on silica content and iron recovery in the concentrate are pre-nted in Table1.
Results of silica content in the concentrate in tests performed with residual water from the mechanical cells circuit,in the ab-nce of extra amine,are prented in Fig.2.
Results from the test carried out in July2006(residual amine dosage21.0g/t;silica content in the concentrate3.49%)are very similar to tho from the standard test(residual amine dosage 20.0g/t;silica content in the concentrate3.48%).
Results of silica content in the concentrate in tests performed with residual water from the tank cells
circuit,in the abnce of ex-tra amine,are prented in Fig.3.
The results are erratic and it is difficult to explain the lack of correlation of the results of the tests carried out in May and July 2006.All experiments were performed in duplicate and the results
Table1
Results of standard tests
Control parameter Amine dosage(g/t)
203550
%SiO2concentrate 3.48 1.97 1.67
%Fe recovery92.1988.4784.85
两个小八路读后感
874G.M.B.Batisteli,A.E.C.Peres/Minerals Engineering21(2008)873–876
are reliable.A possible explanation for the poor performance of the residual water containing73g/t residual amine is the prence of slow ttling ultrafine particles.The particles are generated in the condary grinding that precedes the tank cells circuit.The tur-bidity of this residual water is significantly higher than that of the other fractions.In the sampling of September2006,this residual water was the only one prenting amine concentration above the detection limit,despite the fact that no collector is added to the tank cells circuit.
Results of silica content in the concentrate in tests performed with residual water from the recleanerflotation columns circuit, in the abnce of extra amine,are prented in Fig.4.
A thick froth layer was obrved on the top of the tailings of the recleaner columnflotation circuit even after a12h rest period.This froth layer was not obrved in the other tailings.The results achieved with the residual water from the recleanerflotation col-umns were poor in comparison with tho from the standard test. Once more,the prence of ultrafines from the regrinding stage might be causing the poor performance.
Results of silica content in the concentrate in tests performed with residual water from the slimesflota
tion columns circuit,in the abnce of extra amine,are prented in Fig.5.
The sharp drop in the concentration of residual amine was a conquence of the decrea of the addition level of collector from 200g/t or300g/t to50g/t in September2006.At this low level,no residual amine was detected in the residual water.
The results in Fig.5prent the same trend obrved in Fig.2 (residual water from the mechanical cells circuit):higher levels of amine in the residual water led to lowerfigures of silica content in the concentrate.
The next ries of results corresponds to tests with the u of the composition water plus extra amine solution.The values plot-ted in abscissa correspond to extra amine.The results of standard tests are also plotted for the sake of comparison.Fig.6prents the results of experiments performed with water collected in Decem-ber2005.The amine content of the composition water in Decem-ber2005was13g/t.
The composition water enhances the performance of the amine solution suggesting the reu of tailings water as a route to reduce the amine dosage.
Fig.7prents the results of experiments performed with water collected in May2006.The amine content of the composition water in May2006was7.9g/t.Fig.8prents the results of exper-iments performed with water collected in July2006.The amine content of the composition water in July2006was13.4g/t.In both cas there was no indication that the u of the composition water would reduce the collector addition level.
Fig.9prents the results of experiments performed with water collected in September2006.The amine content of the composi-tion water in September2006was2.5g/t.
G.M.B.Batisteli,A.E.C.Peres/Minerals Engineering21(2008)873–876875
As expected,the very low content of residual amine in the resid-ual water did not suggest that its u would lead to a decrea in the collector addition level.
The difference in performance between the composition water collected in2005and tho collected in2006may be due to circuit changes in the concentrator.The tank cells were moved from ahead of the regrinding mills to after this stage,generating ultra-fines that were entrapped in the water pha,impairing its reu.
Fig.10reports results of tests in which only residual amine was ud in a rougher stage,followed by a cleaner stage with addition of amine solution.The results correspond to residual amine con-centrations of7.9g/t(May),13.4(July),and 2.5(September), respectively.Even a low dosage of extra amine(20g/t)was effec-tive to clean the rougher concentrates produced in May and July, despite an inversion in the results with respect to tho predicted for the two dates.Higher dosages of extra amine performed well to clean all rougher concentrates.
There is a strong indication that the addition of residual water itlf does not impair theflotation performance suggesting the possibility of reu of water from the tailings fractions,since they do not containfines from regrinding stage.
5.Conclusions
Residual amine,if prent in the water pha fromflotation tail-ings,may be reud forflotation.The eff瓜子长胖吗
ectiveness of the previ-ously ud amine depends on its concentration and is impaired by the prence of ultrafines.
The reu of water from mechanical cells tailings,even at low amine concentration,does not impair theflotation process,repre-nting a significant benefit,for this fraction contains76%of the to-tal water in tailings from different circuits.
References
Baltar, C.A.M.,Araújo,J.M.M.,Cunha, A.S.F.,2002.Study on the conditions of desorption and reu of collector in quartzflotation.In:XIX National Meeting of Mineral Processing and Extractive Metallurgy(XIX Encontro Nacional de Tratamento de Minérios e Metalurgia Extrativa).Recife,vol.I,pp.241–246(in Portugue).
Barbato, C.N.,Andrade,M.C.,Francßa,S.C.A.,Luz, A.B.,2004.Adsorption and quantifying of amines in mining effluents.In:Undergraduate Symposium–CETEM,XII.Rio de Janeiro,Brazil(in Portugue).
Oliveira,J.F.,Wilberg,K.Q.,Baltar,C.A.M.,Souza,C.C.,Araujo,A.C.1996.Recovery of amine adsorbed onto quartz and in thefloated water aiming at its reu in the rever iron oreflotation.In:I Brazilian Sy
mposium of Iron Ores: Characterisation,Processing,and Pelletising,Ouro Preto,pp.375–381(in Portugue).
Orphan,E.C.,Bayraktar,I.,2006.Amine–oleate interactions in feldsparflotation.
Minerals Engineering19(1),48–55.炒生菜的家常做法
Peres,A.E.C.,Ciminelli,V.S.T.,2002.Environmental fate of an amine ud in the concentration of Brazilian iron ores.In:TMS Annual Meeting,Poster Session.
Seattle,USA.
Smith,R.W.,Akhtar,S.,1976.Cationicflotation of oxides and silicates.In: Fuerstenau,M.C.,Flotation,A.M.(Eds.),Gaudin Memorial Volume,vol.1(c5).
Society of Mining Engineers,pp.87–133.
876G.M.B.Batisteli,A.E.C.Peres/Minerals Engineering21(2008)873–876
