flotation of spodumene beryl ores

8/10/2019 Flotation of Spodumene Beryl Ores

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FLOTATION OF SPODUMENE BERYL ORES

The

U S

Bureau of Mines has been experimenting with flotation pr oc es se s

to separate the spodumene-beryl ores mined at Kings Mountain

N C

The

succ ess to date as well as the present status of the process i s disc usse d.

Furth er experimentation i s underway and stud ies will be made on the milling

cos ts involved i n the flotation proc ess.

by James

S

Browning

T

e pegmatites of the Kings Mountain-Lincolnton,

N.C., ar ea constitute the l arg es t known domestic

re ser ve of beryl and spodumene. The reser ve i s es -

timated to contain 90 million tons of pegmatic ma te-

r i a l with 1,280,000 tons of reco ver abl e Li,O ( lith ia) as

spodurnene. The pegmatite s al so contain 0.4 to 0.5

pct beryl dissemina ted throughout the orebodies. The

pegmatites may contain a potential re se rv e of 240,-

000 tons beryl , equivalent to approximate ly 34,000

tons of BeO.

Different flotation methods for sepa rati ng bery l

from feldspar o r quartz, o r both, have been devel-

oped by various investigators .2-7 On the other hand,

published informa tion is limited on concentration of

spodumene-beryl ores. s the response of beryl and

spodumene to flotation is essentia lly the sa me , a

succ ess ful separ atio n of the two min era ls depends

upon use of a sele ctiv e depr ess ant o r a selective

collector fo r one of the mine rals .

Sev era l ye ar s ago, the U.S. Bureau of Mines, r e -

cognizing the need for developing

a

large domestic

supply of st rat egi c bery l, undertook stud ies to devel-

op improved methods of recovering this mineral.

Because of th e low be ry l content of the pegma tite s,

economic production of the be ryl entails

its

recov-

ery a s a byproduct of spodumene flotation. Thus,

the development of pr oced ures that would provide

for maximum recoveries of the spodumene,

as

well

as the beryl, was a pr ima ry objective of the studi es.

Test s w ere made on run-of-mine or e and spodumene

flotation tailing fro m the Foote Mineral Co. s spodu-

mene conce ntra tor at Kings Mountain (Fig. 1). Pe t-

rographic anal yses of the or e and flotation tailing

a r e given in Table

I.

Detailed analys es and examinations of the o r e and

tailings revealed that the beryllium was pres ent in

the form of a low-alkali beryl. The crysta ls wer e

smal l, rare ly la rger than 14-mesh diam, and were

clea r and colorless.

About 10 pc t of the Li 20 content of the o re was

pres ent in the mic a and feldspar components of the

pegmatite. In som e weathered ore s the associated

J .

S

BROWNING s Supervising Metallurgist, Tuscaloosa

Research Center, Bureau of Mines, U.S. Dept. of the Interior,

University Station, Ala . TP 61820. St. Louis Meeting, Febru-

ary 1961. Also published n MINING ENGINEERING, July

1961, pp. 706 708. Discussion of this paper, submitted in du-

plica te prior to Jul y 1, 1962, wi ll appear in AlME Transac-

tions Mining), 1962, Vol. 223.

clay s al so contained sm al l amounts of lithia. This

is typica l of pe gmatites in the Kings Mountain ar ea .

LABORATORY TESTS

In the past, a vigorous chem ical trea tme nt of the

spodumene surface s with acid or caustic soda has

been considered ess enti al for satisfactory sele ctive

flotation of the spodumene from the other mine rals

in pegmatites. Many tes ts wer e made during this in-

vestigation to determine if chemica l treatm ent of

the sp odumene could be elim inated in favor of a r e -

agent combination that would de pre ss the othe r min -

er al s while selectively floating the spodumene.

A

sim ple reagent combination and proces s was devel-

oped that gave bett er spodumene recovery and grade

of co ncentrate than the mor e elaborate acid or ca us-

tic treatment methods previously used.

The finely ground or e pulps w er e conditioned with

either a n ammonium, alkali, o r alkaline eart h lignin

sulfonate and sodium fluoride , and the spodumene

was floated and cleaned using oleic a cid a s the col-

lect or. The spodumene tailing was deslimed, con-

ditioned with sulfuric acid and coco amine acetate,

and floated to reje ct mica. The mica tailing was

thickened and conditioned with hydrofluoric acid,

then washed to rem ove the acid. The washed pulp

was conditioned with sodium hydroxide for pH co n-

tr ol , and the beryl was floated and cleaned with oleic

acid a s the collector. Table

I

summarizes the re-

sul ts of the labo rato ry tes t work.

About 77 pct of the spo dumene and 75 pct of the

beryl were recovered from the pegmatitic material.

The spodumene concentrate assaye d 6.1 pct Li20

and 0.01 pct BeO, and the beryl product as saye d 3.0

pct Li2 0 and 1.57 pct BeO. Similar r esu lts we re ob-

Table I Petrographic Analysis of Ore and Flotation

Toiling From Foote Mineral Co.

Mineral

Analysis c t

re Tailing

Spodumene

Beryl

Mica

Quartz

Feldspar

Other

Compos i te


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.

Fig I-Conc entrator at Kings Mountain N . C . w here

USBM

i s conducting re se ar ch on flotation of spodu-

m ene- bery l o re s .

t a ined in t es t s of four o ther pegm at i t es , two f rom

other de pos i t s in Nor th Caro l ina , one f rom Hi l l C i ty ,

S.D. nd anoth er f rom Val d Or , Quebec .

PILOT PLANT TESTS

Spodumene F lo ta t ion : Th e l abora to ry inves t iga t ion

was prom is ing enough to wa r ran t fu r th er t es t ing of

the spodumene f lotat ion s te p of the pro ce ss in a

smal l cont inuous f lotat ion pi lot plant wi th

a

capac i ty

of about 15 lb of d ry feed pe r hour .

T h e o r e w a s

cru she d to -1/4 in . , then wet ground cont inuous ly in

a

r o d m i l l o p e r a t i n g i n c l o s ed c i r cu i t w it h

a

r a k e

c las s i f i e r to over f low -48-mesh ma ter i a l .

T h e c l a s -

s i f ier overf low pulp was fed to

a

h y d r o s ep a r a t o r t o

remo ve c lay and th icken the pulp to 40 to 45 pc t so l -

ids

The hydro separa to r under f low was condi tioned

with

2

lb of sodium f lu or ide and l lb of lignin sulfo-

na te pe r ton of o re . The d i s chM ge f rom the f i r s t co

d i t ioner f lowed

to

a

second condi t ioner , where 0 .96

Ta bl e II. Laboratory Flota tion of Spodumen e Mica and Beryl

Product

Analysis Pct Distribution Pct

Weight

Pct L ip 0 Be0 Mica L ip0 Be0 Mica

Spodumene concentra te 19 2 6 1 0 01 0 4 77 4

3 9 2

Mica concentrate 6 0 0 9 0 01

94 5 3 6 1 3 89 0

Beryl concentrate

2 3

3 0 1 57

2 0 4 5 74 9 0 7

Beryl middling

0 9

0 6 0 28 1 0 0 3 5 2 0 1

Tail ing

1 6

0 3 0 01 0 8 14 2 14 7 9 0

omposite

100 0 1 51 0 05 6 4 100 0 100 0 100 0

Pounds per ton of ore

Spodumene Mica Bery l

Conditioner Cleaner Conditioner Cleaner Conditioner Cleaner

1st 2nd 1st 2nd 3rd 1st 2nd st 1st 2nd 1st 2nd

Lignin sulfonate

Sodium fluoride

O l e i c ac i d

Sulfuric acid

Coco amine ace tate

Hydrofluoric acid

Sodium hydroxide

Conditioning time min

Pulp pH


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Toble

I l l

Summarized Results of o Smoll-Stole

Continuous Spodumene Flotation Test

Plant to i l ing

7

Analysis Pct Distribution Pct

Weight Spodu- Spodu-

Product Pct L iz 0 Be0 mene L iz 0 Be0 mane

Spodumene con-

centrate 20.5 6.00 0.01 83.0 75.5 5.1 88.8

Flotat ion ta i l ing 71. 9 0.44 0.05 3.0 19.4 89.2 11.2

Hydro-separator

overflow 7.6 1.10 0.03 trace 5.1 5 .7

omposite

100.0 1.62 0.04 19. 1 100.0 100.0 100. 0

lb of o leic aci d per ton of or e was added as the spod-

umene collector. The pulp then was floated to r e-

cover a spodumene concentrate. The tailing fr om

the rougher cell s flowed to a single cell, operated

as a scavenger, to remove additional spodumene

from the floating tailing. The froth from this unit

was recycled through the last rougher cell. The

rougher concentrate flowed to a bank of flotation

cell s fo r three-s tage cleaning. Results of the con-

tinuous te st a r e summarized in Table

111.

The cleaner concentrate assayed 6.0 pct LizO and

accounted for a Liz recover y of

75.5

pct. The con-

centrate contained 83 pct spodumene by petrographic

analysis, represent ing a spodumene recovery of 88.8

pct. About 11 pct of the lithia

in

the or e was not

present as spodumene but was associated with the

mica, f eldspar, and clay.

Beryl Flotation: Small-scal e continuous tests were

also made to substantiate the laboratory test r esults

obtained on bery l flotation. Rather than tr ea t the

crude o re to remove the spodumene before the beryl

flotation, tes ts we re made of spodumene tailings be-

ing produced

at

Foote Co. s spodumene concentrator.

As the plant tailing contained unrecovered spodu-

mene, the purpose of the te sts was to rec over t he

bery l and spodumene together

as

a

bulk concentrate

that could be re -tre ated to produce enriched beryl

and spodumene products. This method was att rac tive

because it would enable recovery of additional spod-

umene from the pegmatite to pay par t of the re- treat -

ment cost.

A pa rt of the concentrator tail ing, containing about

150

lb of d ry feed per hour, was d iverted to the pilot

plant. The pulp was conditioned with 2 lb of hydro-

fluoric acid per ton of dr y feed for 5 min

at

a pH of

3.8. The conditioned pulp was then washed in a spiral

classifier to give a sand product for flotation and r e-

move the acid from the pulp. The washed sands were

admixed with water to produce a pulp containing

about

30

pct solids in the slu rr y; and then they wer e

conditioned with 0.9 lb of sodium silic ate, 0.3 lb of

sodium hydroxide, and 0.9 lb of o lei c acid pe r ton of

dry solids. The pH of the pulp was 7.3.

The pulp was floated to produce a rougher concen-

tr at e which was then triple-cleaned. The middling

product was retur ned countercurrently to the rougher

cells. The bery l concentrate assayed 1.25 pct Be0

and 4.45 pct LizO; about 87 pct of the beryllium and

66 pct of the lithia was recovered. The bulk concen-

tr at e also contained about 12.5 pct mica, 10.5 pct

feldspar, and 5.5 pct quartz. A simplif ied flowsheet

t

Hydrofluoric acid

Sond pump

Conditioner

Spiral classifier

Sodium sil ica te

Overflow to waste

Conditioner

Sodium hydroxide

F r

le ic ac id

1

Flotot ion ce l ls

I-stage scavenging

Flotat ion ce l ls

3-stage cleaning

L

a i l i n g

Beryl-spodumene concentrate

Fig. 2-Flowsheet fo r USBM process to recover

beryl-spodumene concentrates.

fo r reco very of the bulk beryl-spodumene concen-

trate

is shown in Fig.

2.

Batch Treatment: Because of the difficulty of pro-

ducing enough bulk spodumene-beryl concentrate

from the low-grade tailings for further continuous

cleaning tes ts, the recov ery of enriched beryl and

spodumene products was c arr ied out by batch re -

treatmen t consisting of th ree stag es, as follows: 1

rejection of the mica, 2 lotation of the spodumene

and 3 lotation of the bery l.

The bulk beryl-spodumene concentrate was con-

ditioned with 10 b of su lfur ic acid per ton of dr y

feed to remove the fatty acid collector from the

mine ral surf aces. After washing the pulp to remove

Tobl e IV. Flota tion of Mica Spodumene and

Beryl From Bulk Concentrate

Analysis Pct Distribdtion Pct

Weight

Product Pct Li z0 Be0 Mica Li10 Be0 Mica

Mica concentrate 13.1 1.89 0.28 94.5 5.6 3.3 94.2

Spodumene con-

centrate

55.7 6.60 0.33 0.5 83.6 16. 7 2.0

Beryl concentrate

13.2 2.57 6.37 2.4 7. 7 76. 1 2.4

T a i l i n g 18.0 0.76 0.24 1.0 3. 1 3.9 1.4

omposite 100.0 4.40 1.1 0 13.1 100.0 100.0 100.0


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flotation of spodumene beryl ores

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