CA2115153A1 - Dewatering slurries - Google Patents
Dewatering slurriesInfo
- Publication number
- CA2115153A1 CA2115153A1 CA002115153A CA2115153A CA2115153A1 CA 2115153 A1 CA2115153 A1 CA 2115153A1 CA 002115153 A CA002115153 A CA 002115153A CA 2115153 A CA2115153 A CA 2115153A CA 2115153 A1 CA2115153 A1 CA 2115153A1
- Authority
- CA
- Canada
- Prior art keywords
- coal
- dewatering
- slurry
- aid
- flocculant
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
- C02F1/54—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using organic material
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D37/00—Processes of filtration
- B01D37/03—Processes of filtration using flocculating agents
Abstract
The specification describes a method of dewatering mineral slurries especially slurries of a fine coal. The method involves adding an anionic flocculant to the slurry and subsequently adding a dewatering aid to the slurry at or just prior to the formation of a filter cake during a filtration step. The specification also discloses that overloading with an anionic flocculant can be avoided if a dewatering aid is used in combination with the flocculant.
Description
2 PCr/~U92~00437 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.
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 3~12 PCT~AU92/00437 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.
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.
~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 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.
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 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~.
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).
21151~3 ~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.
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.
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 3~12 PCT~AU92/00437 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.
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.
~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 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.
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 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~.
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).
21151~3 ~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.
Claims (13)
1. A method of dewatering an aqueous, coal or mineral slurry comprising adding an anionic flocculant to the slurry, subsequently adding a dewatering aid and filtering the slurry by means of vacuum filtration to obtain a filter cake and a filtrate characterized in that the dewatering aid is added at or just prior to formation of the filter cake during filtration.
2. A method according to Claim 1 wherein the dewatering aid comprises a salt of a fatty acid having from 8 to 20 carbon atoms.
3. A method according to Claim 2 wherein the salt is selected from the group consisting of sodium, potassium and ammonium salts.
4. A method according to Claim 2 wherein the fatty acid is oleic acid.
5. A method according to Claim 2 wherein the fatty acid is a tall oil fatty acid.
6. A method according to Claim 1 wherein the anionic flocculant is added to the slurry at a rate in the range from 10 to 100 grams/tonne of coal or mineral.
7. A method according to Claim 1 wherein the anionic flocculant added to the slurry at a rate in the range from 20 to 50 grams/tonne of coal or mineral.
8. A method according to Claim 1 wherein the dewatering aid is added at a rate in the range from 0.02 to 1.5 kg/tonne of coal or mineral.
9. A method according to Claim 1 wherein the dewatering aid is added at a rate in the range from 0.5 to 1.5 kg/tonne of coal or mineral.
10. A method according to Claim 1 wherein the dewatering aid comprises a salt of a sulphonic acid.
11. A method according to Claim 1 wherein the dewatering aid comprises a fatty acid having from 8 to 20 carbon atoms.
12. A method according to claim 1 wherein the dewatering aid comprises an ethoxylated alcohol.
13. A method of dewatering an aqueous mineral or coal slurry comprising adding an anionic flocculant to the slurry, subsequently adding a dewatering aid and filtering the slurry by means of vacuum filtration to obtain a filter cake and a filtrate characterized in that the dewatering aid is a salt of a fatty acid having from 8 to 20 carbon atoms.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AUPK7855 | 1991-08-20 | ||
| AUPK785591 | 1991-08-20 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2115153A1 true CA2115153A1 (en) | 1993-03-04 |
Family
ID=3775635
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002115153A Abandoned CA2115153A1 (en) | 1991-08-20 | 1992-08-19 | Dewatering slurries |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0601023A4 (en) |
| JP (1) | JPH06509975A (en) |
| CA (1) | CA2115153A1 (en) |
| WO (1) | WO1993003812A1 (en) |
| ZA (1) | ZA926247B (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9068776B2 (en) | 2009-10-30 | 2015-06-30 | Suncor Energy Inc. | Depositing and farming methods for drying oil sand mature fine tailings |
| US9404686B2 (en) | 2009-09-15 | 2016-08-02 | Suncor Energy Inc. | Process for dying oil sand mature fine tailings |
| US9909070B2 (en) | 2009-09-15 | 2018-03-06 | Suncor Energy Inc. | Process for flocculating and dewatering oil sand mature fine tailings |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US11459257B1 (en) * | 2017-05-12 | 2022-10-04 | Eco Environmental, LLC | Method of treating a liquid with nanobubbles |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4132630A (en) * | 1978-04-03 | 1979-01-02 | Gulf Research & Development Company | Method for separating solids from coal liquids |
| US4290897A (en) * | 1980-05-27 | 1981-09-22 | Dow Corning Corporation | Dewatering fine coal slurries using two types of organopolysiloxanes |
| CA1156535A (en) * | 1980-10-29 | 1983-11-08 | Dieter Frank | Hydroxylbenzyl amines as dewatering agents |
| IN172903B (en) * | 1990-05-08 | 1994-01-01 | Lever Hindustan Ltd |
-
1992
- 1992-08-19 ZA ZA926247A patent/ZA926247B/en unknown
- 1992-08-19 WO PCT/AU1992/000437 patent/WO1993003812A1/en not_active Application Discontinuation
- 1992-08-19 EP EP9292918418A patent/EP0601023A4/en not_active Withdrawn
- 1992-08-19 CA CA002115153A patent/CA2115153A1/en not_active Abandoned
- 1992-08-19 JP JP5503966A patent/JPH06509975A/en active Pending
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9404686B2 (en) | 2009-09-15 | 2016-08-02 | Suncor Energy Inc. | Process for dying oil sand mature fine tailings |
| US9909070B2 (en) | 2009-09-15 | 2018-03-06 | Suncor Energy Inc. | Process for flocculating and dewatering oil sand mature fine tailings |
| US10590347B2 (en) | 2009-09-15 | 2020-03-17 | Suncor Energy Inc. | Process for flocculating and dewatering oil sand mature fine tailings |
| US9068776B2 (en) | 2009-10-30 | 2015-06-30 | Suncor Energy Inc. | Depositing and farming methods for drying oil sand mature fine tailings |
Also Published As
| Publication number | Publication date |
|---|---|
| EP0601023A1 (en) | 1994-06-15 |
| JPH06509975A (en) | 1994-11-10 |
| WO1993003812A1 (en) | 1993-03-04 |
| ZA926247B (en) | 1993-04-22 |
| EP0601023A4 (en) | 1994-09-28 |
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