Note: Descriptions are shown in the official language in which they were submitted.
WO 93/03812 PCr/~U92~00437
2115153
D}æWAAT13RING SI~RIISS
Thia inYen~io~ relate~ to im~ro~ed dewatering method~ a~d
agents for u~e in ~acuum filtration o~eration~ in ~ineral
S and coal ~xoce~ing. The in~ention i gener~lly a~licable
to the dewatering of 31urrie~ including tho3e encou~tered
in the ~ro~e~sing of mineral~ ~uch as alu~ina, a~ well a~
coal, but i~ i of partieular intere~t in the dewatering of
fine coal and aecording~y will be de~cribed in detail with
particular reference to the latter a~plication.
sack~round of_the In~en~ion
vacuum filtration i~ co~monly used in indu~trial. ~roce~e~
~o remove water from ~lurrie~. Vacuum disc and drum
1~ filter~ are widely u~ed, a3 well a~ ~acuum belt filter
~he e~ficiency of ~uch ~roce ~e~ de~e~ds i~ lar~e ~art upon
the ~h~ical ~ro~ertie~ of the ~lurrie~ ~o be dewa~ered,
a~d exten~i~a ~udie ha~e been carried out with a ~iew to
modifyi~g tho~e~-~hy~ic~l ~ro~ertie~ in order to o~timi~e
the effieieney of the dewatering ~roee~. The ~ro~ertie~
may be affeeted, for ex~mple, by chemical mea~ ~ueh aQ
` the u~e of ehemieal ~ddi~ve~, or by ~hy~ieal mean~ ~uch a~
the meehanieal treat~ent of the ~lurrie~ and/or the filter
eake which i~ formed i~ the ~aeuum ~iltration ~roee~. A~
the~e ~roce~se~ are earried out on a very lar~Q ~eale,
eeono~ie eonsi~eration~ are al~o important ~nd what may
a~ear to be ~all impro~ement~ ean re~ult in ~ub~tantial
eo~t ~a~
39 Coal proce~ing, ~articul~rly the treatment of
metallur~eal eoal, u~ually ineorporate~ wa~hi~g ~tep~ as
~art of the benefieiatio~ ~eh~me.
WO93/03812 PCT/AU92/00437
211~153
The coal-cleaning ~roce~s ~roduce~ coal wlth a broad range
of ~article Qize~. Coar~e coal (ie., >600 micron) a~d f~ne
coal are treated differently to dewater e~fecti~ely.
Water i~ u~ually re~o~ed from ~oar~e coal by ~creen
drainage or centrifugation and from fine coal (ie.,
flotation concentrate~ or refuse) by centri~ugation or
~acuum filtration. In ~ome ca~e~, thermal drying of fi~e
coal i employed as a nece~ary ~te~ to achie~e target
moi~ure~. Depending u~on the mining o~eration, the type
of coal treated and normal ~wîng~ in proce~ o~eration in
the ~lant, the moi~ture le~elz in the cleaned coal can ~ary
quite widely. Typical moisture le~el~ in coar~e coal
range fro~ 2-12%, while fine coal moi~tures can range from
1~-30%.
. Coal ~rocesQing ~lants often ha~e considerable trouble
meeting target moi~ture le~el~ in the ~roduc~ coal they
- . ~ell. A~ a re~ult of naw mining met~od~ employed in long-
. wall operation~, the proportion of fine coal reporting to
the washing & ~reparation pl~nt~ ha~ increa~ed
~ignific~ntly.~.Fine coal iR much more di$ficult and co~tly
~o dewatar than coar~e coal. Ona method often employed by
coal ~re~ ~lants to achieve moisture ~ecification~ i~ to
blend high-moi~ture fine coal with low-moi~ture coar~ coal
i~ ~ro~ortio~ necè~ary to ~u~t meet tar~et moi~ture.
While, in many ca~es, it would be much more co~t effactive
for a coal ~re~ ~lant;to ~imply di~card the fine~ ana mine
more coar~e coal, for rea~on~ of re~ource
management/utili~ation/con~ervat~on it i~ moxe ~rudent to
treat ~e f~no~.
Vacuum f~ltrat~on i~ the mo~t commonly u~ed mea~ of
mechanical treatment to dewater fine coal. Fine coal, in
~lurry form, reports to the filtration o~eration where the
WO 93~03B12 P~/AU92/00437
211~153
watex iR removed . Yacuum diE~c and drum f ilter~ are ~che
prir~ci~al tyl?e uQed by the coal industry to f ilter f ine
coal, althou~h increasinç~ intere~t i~3 beins~ ~hown in ~acuum
belt filter~. To a~ 3t in the efficient ol?eration o~
5 VlCUllm filters, reageslts are often added to the f~ed
~lurr~r -
It i~ known to u~e anionic and cationic f locculaxlts in the~racuum ~iltrat~on o~ fine coal. The~e reage~t~ are
10 necez~ary to "thicken" the ~3lur:ry a~ it i~ $ed to the
~vacuum filter to en~ure the l?ro~er fomlation of a filter
cake. It i~ thou~ht that the reage~ts functios~ by binding
the ~rery f isle coal particle~ to larger coal part:icle~ in a
ty~?ical flocculation ~?roc~, thu~ ~roducin~ a ~ore uniform
:LS and increa~ed ~?article ~iz~ diRtribution ~or better f ilter
cake l?ermeabiliky. Thi~ re~ult~ in 1~ "blinding" of tb~e
f ilter cloth and f il~cer cake by the ~ery f i~e coal
~ar~icl~ .
Both anionie floeeulant~ (u~ually high molecular weight
aeryl ~ ide/aerylate eo-~olymer~) and eationie floeeulants
(u~ually low ~olecular weight ~olyamines) are u~ed,
indi~idually or in combination, to Go~trol filter eake
formation. These reagents are alway~ added to the ~lurry
~eeding th~ ~aeuum filter~ (ie., slurry ~re-tr~atme~t) in a
. maDner ty~ieal of floeeulant addition in the mineral~
i~du~try.
There has al~o been eonsiderable interest by the eoal
industry in the use of ~urfaetants, in eombination with
floe~ulaGt2, to eDhaQce the dewateri~g of fine eoal.
Althou~h mA~y ~tudie~ ha~e been eonducted and e~orted,
there are widely ~arying rQsults/conclusio~. Some studie~
ha~e ~hown that surfactants do not ~i~nificantly affect
WO93/03812 PCT/~U92/00437
211Sl53 4
reQidual cake moisture, while other~ Qhow they do. Other
tudieR conclude that surfactant~ can be ef ective for
certain type3 o~ ~oal but ~o~ for other~.
S One o~ the mo~t ~ignific~nt reas ~ for the Yariatio~ in
the performance of dewatering aids for fine coal i the
~ariable c~emi~try o~ coal it~elf. ~nlike all other
mineral~, coal i an organic ~aterial. C~al~ ~ary widely
in bul~urface compo~ition, de~endin~ upon a multi~licity
of factorY ~uch a~ location of the depo~it, ranX and
mi~eral (i~orga~ic~ matter, deyree of weatheri~l~, internal
truc~ure/porosity, et~. Therefore, depending upon the
s~ecific coal ~reated, dewaterin~ aid ~erfor~ance can be
expec~e~ to ~ary widely ~i~ce both the ad~orption ta
surface chemieal ~ro~erty) and absorption (a bulk chemical
~roperty) eharaeteri~tie~ of eoal~ with re~pect to drainage
aid int~raction w~ll ~ary widely.
~. . .
The ~eci~i~ation of ~uro~ean Paten~ Ap~lieation
Publieation No. 460811 in the name of nniehema Chemie BV
de~eribe~ the ~ddition of anionic f loecula~t~ or eationic
eoagula~t~ to a eoal ~lurry prior to ~ltration in the
pre~e~ee of a dewa~ering aid. However, the ~eeifieation
state~ that the preferred point for addition of the
dewateri~g aid i~ from a po~ition within the filter eake
forming zone. W~ have now found that when an a~ionie
floeeulant i~ u~ed, the be~t ~oint for addition of the
dawatering aid i8 at or ju~t ~rior to the formation of the
~ilter eake during the f~ltration ~te~.
Sy~mary of the inve~tio~
Aeeordi~ to the ~re~ent in~ention the-e i~ pro~ided a
~ethod of dewatering an aqueou~ coal or mineral ~lurry
WO93/03~12 PCT~AU92/00437
2115153
com~ri~ing addi~ a flocculant to the ~lurry, ~ub~equently
add~g a dewa~ering aid, and filteri~g the ~lurry by mean~
of ~acuum filtra~ion to obtai~ a f ilter aake a~d a
fil~rate, characteri3ed in that the dewatering aid i~
added at ju~t ~rior to formakio~ of the ilter cake during
- the filtration ~e~
Preferably, the dewateri~g aid i~ a salt ~uch a3 a ~odium
~alt o~ a ~atty acid i~cluding fatty a~ids deri~ed from
. tall oil. The fatty acid may ha~e from B to 20 carbon
atoms. However, ~odium olea~e i~ ~articularly ~referred~
The d~waterin~ aid may also be a pota~sium or ~mmonium salt
of a fatty acid.
The dewaterinQ aid may al~o com~riae either a ~alt of a
gul~honic acid ~uch a~ dodecyl be~zene ~ul~ho~ic a~id, an
ethoxylated alcohol or a~ un~apo~i~ied fatty acid.
. The ~loeculau~ may be a~ded to the coal ~lurry ~rior to the filtration ~te~ in a.ratio in the ra~ge from-10 to 100 and
~ref~rably 20 to 50 ~m~ ~er tonna of ~i~eral:or coal
co~tained in the ~lurry. On the other hand the dewatering
aid may be added to the ~lurry in a ratio in the range from
. .02 to 1.5 and preferably D.5 to 1.5 ~g ~er tonne of
mineral or coal~
- In a.further a~ect of th~ i~ention we ha~e found that the
ex~en~e cationic flocculant~ ~re~ently u~ed may be
. re~laced by ~ery much smaller amount~ of anionic
~locculant~, without ~uffering the drawbac~ formerly
a~Roc~ate~ with the u~e of ~aid anionic flocculant8,
whereby a ~ery large ~a~ing in co~t i~ achie~ed.
WO93/03812 PCT/AU92/00437
211S153 6
In ye~ another a~ect of the inven~ion, a two-~tage ~roce~
i3 ~rovided in~ol~ing u~e of anionic flocculant~ in ~lace
of cationic ~locculant~, in combination with a~lication of
t~e dewatering aid at a particular ~ta~e of t~e ~roce3~, to
5 pro~ide a greatly impro~ed and ~uch more co~t-effective
proce~s ~or dewatering ~lurrie~ than ha~ hitherto been
con.idered fea~ible.
Detailed description of the invention
An ex~erimental rig wa~ e~tabli~hed enabling accurate
~imulation of actual plant o~erations at the Bellambi Coal
Com~any Pty ~td, South Bulli, New South Wale~, ~ustralia.
~he ~erformance of the laboratory f ilter rig wa~ correlated
wi~h the ~er~or~ance of a Delkor ~acuum ~elt .ilter at
Bel. la~bi . Current ~ractice in~.rol~e~ addition of a cationic
~locculant to the feed of the Delkor filt~r~ in order to
control the for~ation of the ~ilter cake c~n the f ilter
belt. T~i~ reagent addition re~re~ent~ a ~igni icant
20 o~erational cost but u~e of ~he cationic f locculant ha~
b~en con~idered nec~ary for adequate proce~ control and
~- s~erfcrmaslce of the Delkor filter~.
It wa~ nece~ary to accurately a~ess the performance of
the ca~ionic floc¢ulant on filter cake for~atio~ ~rior to
under~akin~ draina~e aid testwork. The amount of the
cationic flocqulant ~eeded to achie~e cake formation ~n the
teRt-rig comparable to that i~ the plant had to be
de~ermined and the effect of the cationic flocculant on
drainage aid ~erformance had to be a~certained.
WO93/03812 PCT/AU92/00437
~115153
Brief Summary~of the Dra~ing~
Figure 1 i5 a graph of filter cake moi~ture content ~r~us
cationic flocculan~ do~age at a fixed dryins time and
a~plied ~acuum. Fi~ure 2 i~ a gra~h of filter cake fo~m
time a~d a~arent a~pliad ~acuum again~t c tio~i~
floccula~t do~a~e rate, Fi~ure 3 i~ a ~raph o~ filter cake
moi~ture conte~t and fo~m ti~e ~er~u~ a~lied ~acuum at a
~ixed do~age rate of cationic flocculant, Figure 4 i~ a
gra~h of fil~er cake moiR~ure content versu~ do~3age rate of
dewa~ering aid where the dewa~ering aid i~ added at
dif~erent location~ in the filtra~ion ste~, Fi~ure 5 ia a
gra~h of filter cake form ~ime ~eraus a~ionic flocculant
do~age rate for two types o~ anio~ locculant, Figure 6
i~ a gra~h of filter ca~e moi~ture content ~er~u~ anionic
~loccula~t do~a~ rate for two type~ of anionic flocculant,
Figure 7 i~ a gra~h of f ilter eake moi~ture conte~t ~er~u~
:- do~age rate of dewaterin~ aid ~howing th~ offeet of
incorporating t~e dewateri~g aid at ~ariou~ loeations in
20 - the filtration ~te~, Fi~ur~ 8 iQ a graph of filter cake
moi~ture co~tent Yer~u~ d~watering aid do~age rate for bo~h
an anio~ic floeeulated filter eake and a eationie
floeeula~ed fllter eake; and Figure 9 i~ a ~ra~h of ~ilter
ea~e moi~ture eontent ~er~us a~ionie floceulant do~age ra~e
wit~ aQd without the add;tion of a dewatering aid.
Fi~ure 1 ~hows t~e time re ired to aehie~e f~lter eake
for~ation and the a~arent ~aeuum of the ~y~tem (at 80 kPa
a~lied ~aeuum) a~ a fun~tion of eoagula~t addition. To
mateh the f~lter-~ake formation t~me (5-60 sec) and
a~are~ ~aeuum eondition~ (70 kPa) of the Delkor #2
filter, a~ equi~alent do~age of 250 g/toDne of ~he eationie
floeeulant wa~ required ~ an addition to the teRt-rig
lurry.
WO~3/03812 PCT/AU92~00437
211~1~3
Figure 2 ~how~ the re~idual filter cake moi~ture~ achie~ed
in the lab tes~ rig a~ a function of cationic flocculant
addition. ~e of the cationi~ floccula~t at the do~a~e
rate determined above (for ~ro~er form time/a~parent
vacuum) resultQ in a re~idual moi~ure le~el of 22-23%.
This re~ult i~ identical to the re3idual moisture le~el~ of
~ample~ of ~ine-coal taken ~rom the Delkor #2 filter,
confirmi~g the ability of ~he te~t rig to accurately
~imulate B llambi ~la~t o~eration~. ~xces~i~e ~atio~ic
flocculant addition wa~ found to ha~e no detrimental effect
¦ on filter cake moiRture.
Fi~ure 3 show~ the ~ariation in ~ilter-cake moigture and
formation ti~ a~ a ~unction of the a~plied ~acuum (at a
fixed do~age of cationic floccula~t). ~he~e te~t~ were
conducted to te~t the ~e~Riti~ity of the te t rig to en~ure
that-change~ in re~idual mo~ture during the ~raluation of
the draiDage aids were due to chemical parameter~ and not
to mi~or:ch~nges ~n ~acuum which ;ne~itably occur during
teRt work (i.e., due to ~light ~ari~tion~ in ~ampling or
te~t ~rocedure). A~ ~een, form ti~e i~ ~irtually
i~de~endent of a~plied ~acuum (as expected) while moi~ture
~aris~ only ~lightly o~er the ~ariation~ in a~plied ~acuum
expected.
Te~ts o~ the~Bellambi ~y~tem indicate that a ~articular
drainage aid, namely ~odium oleate, had the mo~t
~ig~ificant ~otential to ach~e~e the cr~teria for technical
~ucces~ e~tablished prior to u~dertaking the ex~erimental
woxk.
In attem~ting to o~timî~e the ~erformance of ~odium oleate,
con~iderable effort wa~ ~pent to examine the most effecti~e
WO93/03812 PCT/AU92/00437
211~1~3
. ~
method of ~eagent addition to th~ ~acu~m-belt filter.
CGnsideration wa~ gi~en to a ~ari~ty o~ rea~ent-additio~
technique~. Fir~tly, there iQ often a detrimental effect
on cost-per~orma~ce of adding drainaye aid~ to the ~ilter
feed or to t~e ~u~ernatant liquor too early in the filter
cake formation Rtage as a re~ult o~ dilution of the reagent
in the slurry. Howe~er, a lo~ in reagent ~erformance due
to reagent dilution mu~t be wei~hed again~t the ~roblem~ of
(1) in~uffi~ient ~enetration of reagent-treated liquor into
the filter cake, ~2) a raduction in filt~r-~ake dry-time
and (3) the need to recycle filtrate if the drainage aid
reagent i~ a~plied as a wash after ~ilter cake formation
occur~.
~igure 4 ~how~ that at the preferred dose rate 0.S0
kg/tonne the mo~t effecti~e methods of reagent a~plication
are to en~ure that the reagent is a~lied to th~ ~elkor
filter ~from a trou~h or ~pray ~y~tem) at or close to the
~oint of formation of the filter cake. ~oisture reduction
of a~roximately 3 to 5% (22-23~ to 18-19%3 can be expected
if the reagent i~ ~ro~erly ap~lied.
~here is, howe~er, a ~e~re detrimental con~equence of
a~lying the drainage aid to the Delkor ~ilter~ too early
in the filter cake formation ~tage. This i~ due to a
~reci~itation reactio~ between the cationic flocculant and
specific ~omponeuts of ths drainage ~id.~ Thi~ ~roblem i~
~een clearly from the re~ults pre~e~ted in ~i~ure 4. When
ths draina~e aia iB added to the cationic-treated slurry,
prior to the slurry rQ~or~ing to the filter belt, a
dramatic increa~e ~n cake moisture is ob~erved. Thi~
~roblem i~ reduced if the reagent is added to the
~u~erDatant liquor after the ~lurry i~ on the belt.
WO93/03812 PCT/AU92/00437
21151~3
Anionic Flocculant Addition
~nfortunately, due to ~wings in Bellambi ~roces~
o~ration~, ~articularly a~ more fine~ rea h the filter due
to long-wall mining, i~ is extremely difficult ~o control
the Delkor filter3 to en~ure that the filter cake form zone
remain~ at the same ~oint during f il~ration, even with
flocculant addition. In an ef~ort to o~ercome a potential
~roce ~ control problem re~ulting f rom t~e need to a~ly
reagent at a critical ~oint in the proce~ o~eration, a
method was ~ought to elimi~ate the u~e of the cationic
floccul~nt in order to achieve rapid filter cake formation.
Te~twork wa~ conducted on ~am~les of fine-coal taken from
the plant ~rior to being treated with the cationic reagent,
u~i~q both of the liquid anionic floccula~t8 (i.e.,
acrylat~/acrylamide co~olymer~) currently u~ed by Bellambi
in other ~roce~ o~eration~. The re~ults, gi~en in Figure
. . 5,.~ho~that b~ re~laci~g the catio~ic flocculant with an
I . anionic flocculant the filter cake formation t~me can be
1 20 dramatically reduced (~rom 60 ~QC to 20 sec) u~ing 1~B~
; than one-tenth of the amount of r~agent (15 g/t a~ion~c
flocculant ~ 250 g~t ~ationic flocculant). As the C08t
~er weight unit is idQntical, the sa~ing is ~ubstantial.
T~ere iB, how~er, the ~ote~tial to o~erdo~e the fine-coal
~lurry with an anionic flocculant. Thi~ ~ay result in
~rocess ~rQblems not encountered w~th th~ use of the
cationic flocculant. As shown ~n t~e cake moi~ture ~ :
reagent do~age data gi~en in Figure~ 6 ~nd 9, o~erdo~ing
the snionic flocculant csn re~ult in an increa~ in the
filter cake moisture~. Howe~er, this ~roblem is not
unique to Bellambi. Mo~t unit operation~ in~ol~ing
floccula~t sddition, e~pecially thickaner~, have similar
problem~ if too much flocculant is added to a mineral
WO93/03812 PCT/AU92/00437
211~153
. ~
- ' 11
~lurry. Fort~nately, with pro~er control of the do~ing o
the flocculant to the ~lurry, ~hi~ potential ~roblem can be
~irtually eliminated.
Sodium oleate/Anlonic Flocculant_Performa~e
- In addition to ~o~ible ~roce~ ~a~ings by ~hanging from
the cationic flocculant to an anionic flo~culaat to control
filte~ cake for~ation, we ha~e found ~hat there are
significant benefit~ to the ~erformance of ~odium oleate
and the control of filter o~eration3.
Fir~tly, here is no danger of a ~etri~ental interaction of
the reagent with the anionic flocculant. ~nlike ~he
cata~trophic result ~how~ in Fig~re 4, addition of
dewatering aid ~o ~nionic flocculated ~lurry ~roduces no
dramatic increa~e in ilter cake moi~ture (a~ ~hown in
Figure 7). Howe~er, compa~ison of the ~oi~ture ~ reagent
- do~age ~rofile~ in Figure 7 clearly i~dicates that the
- reagent i~ be~t a~lied a~ a concentrated ~olution at or
~u~t ~rior to cak~ formation.
Secondly, a~ ~hown in Figure 8, at 0.5 k~/tonne do~age
: rate, there i~ a demon~trable impro~ment in the
performance of the reagent (i.e., 1.0-2.0 ~ impro~ement in
moi~ture reduction ca~ability) u~i~g it in con~unction with
an a~ionic flocculant rather:than with a cationic
floccula~t. Furth~rmore, the ~otential ~roblem of o~er
flocculation of the fi~e-coal ~lurry i~ eliminated with a
combination reagent/flocculant ~ro~r~mme. ~ab te~t~
indicatQ that, when u~ing ~odium ol~ate as a draiDage aid,
exce~ anionic floccula~t addition ha little effect on
r~idual f~lter cake moi~ture le~el~.
WO93/03812 PCT/AU92/00437
2115153 12
It will be a~parent that a number o~ ~roce~s benefit~ are
achieved by ~he in~ention.
Fir~ly, if the dewateri~g aid i~ 2~1ied to the filter
cake ~ia a ~ray at or jus~ ~rior to ~ake formation, thi~
I re~ults in a re~uction in the a~ount of draina~e aid
¦ required to eff~c~ a 3 to 4% dro~ in re~idual moi~ture in
I the fine coal filter cake.
; 10 Secondly, the a~plication of the drainage aid reagen~ to
the ~a~uum filter a~ a ~ilter-cake ~ray at or around the
¦ point o~ cakQ 40rmation on the filter belt/di~c enable~ an
anionic floc¢ula~t to be ~ub~tituted for a cationic
floccula~t for .ilt~r fee~ thicke~in~. Thi~ tw~-~tage
ap~roach to ~ine-coal dawaterin~ hae been fourld to
co~ple~ely eliminate ~robl~ a~Qciated with ~roce~
control if a~ anionic flocculan~ i~ u~ed to ~hicken the
filter ~eed ~lurry. ~he reaqe~t ~ray ha~ been ound to
an~ure that il~er cake ~ermeabili~y durin~ the dewaterinq
~ha~e of ~iltration (~.e., once air ba~in~ ~enetration o~
the filter cake) i~ ma~ntained re~ardle~ of ~ny ~l~ght
- o~erdo~in~ of the an~onic floccula~t due to ~roce~ ~wing~.
Thi~ permit~ an anionic f loccula~t to be aub~tituted for a
cationic flocculant with enormou~ ~rocQ~s za~ing~.
Figure 9 ~how~ the impact on f iDal ~roduct cake moi~ture
u~ an anionic ~locculant ~retreatment ~te~ ~r~or to
filtration w~th and without thQ aid o~ the a~ ed reagent.
H~g~ ~roduct cake moi~ture~ are encountered where the
~locculated pretreatment i~ too high and the corres~onding
curve ~how~ the ri~ in moi~ture after thi~ phenomenon
occurs (i.~., around 20 g/T flocculant do~e).
WO93/03812 PCT/AU92/00437
21151~3
13
~owe~er, i~ a dual floccula~t/reagent ~y~t~m, the ~roblem#
e~coun~ered with flo~culant overdo~ins a~e corre~ted by way
of a ~y~ergism with the raage~t addition.
- The e~d re~ult is a lower cake moi#tu~e with a far more
C05t effec~i~e ~retreat~ent ~te~.
s~
Although th~ experimenta work de~cribed abo~e wa~ carried
out in co~nection with the de~elo~me~t of fatty acid
deri~ati~es and particularly ~odium oleate a~ dewatering
aia~, it i~ a~arent that the conce~t of a~lyi~g a
~olutio~ of the dewateri~g aid at or about th~ ~oi~t of
for~ation of the filter cake i~ ~ombi~atio~ with u~e of a
lo~cul~nt i~ no~el ~er ~e and ge~erally a~licable u~
con~entio~al dewateri~g aid~. ~he present in~ention
there ore ~x~and~ to thi~ concept a~ a~plied to the ,~.
dewaterin~ of slurrie~ U8i~ dewatering aids other than
2Q fatty acid ~erivati~e~.
~licatio~ of thA abo~e identifiea concept enable~
~ub~titutio~ of a~ionic floccula~t, hitherto believed to be
i~practical, for the much more expe~i~e ca~ionic
~loccula~t hit~erto employed i~ ~he dewatering of Rlurrie~,
~articularly i~ the dewa~erin~ of ~i~e coal. A~ detailed
abo~e, this i~.o~ co~iderable economic ~ignificance.
It will be clearly under~tood th~t tha in~ention i~ it8
~enoral a~ect~ iR ~ot lim~tea to the particular deta~lR
~et out i~ the experimental work di~clo~ed above.
