[19]
Karman
[45]
[54] THIC THICKE KENE NE [7
Inve Invent nt r:
(73]
Assignee:
CONT CONTRO RO
PROC PROCES ES
Jame Jame S. Karm Karman an Evan Evansv svil ille le
4,273,658
[11]
OR IG
yo
AT NT DOCU DOCU ENTS ENTS
OTHE OTHE
Compa Company, ny, Housto Houston, n, Tex
Jun.
PUBL PUBLIC ICAT ATIO IONS NS
te le
Sep. Sep. 25 1979 1979
1975 1975 pp 61-7 61-71. 1.
Rela Relate te U.S. U.S. Appl Applic icat atio io Data Data [63]
[57]
doned.
[51] Int. C1.3 [52] U.S. [58] d of of S [56]
C02F C02F 1/52 1/52 2101709; 210/740 ,4 Referenc References es Cited
U.S. U.S. PATE PATENT NT DOCU DOCUME MENT NT 2,338,667 3,128,786 3,281,594 3,287,263 3,834,529 4,040,954 4,159,248 4,160,734
Primary Primary ExaminerExaminer-Beno Benoit it Castel Attorn Attorney, ey, Agent, Agent, or Firm-D Firm-Dav avid id A. Roth
111944 4/1964 10/1966 1111966 9/1974 8/1977 6/1979 7/1979
t a
ABSTRACT ti
if
slur slurry ry of susp suspen ende de soli solids ds an floc floccu cula lant nt ar cont contin inuull intr introd oduc uc to ef ec para parati tion on th lurr lurr into into clar clarif ifie ie solu soluti tion on whic whic is with withdr draw aw thro throug ug an over over to is th cont contro roll lled ed by esta establ blis ishi hing ng th slim slim leve leve at poin poin near near th bott bott of th ee well well onti onti uous uously ly mo it ri th nsit nsit th ownf ownflo lo in lurr lurr with within in th well well pons pons to mall mall ha ge in th sl rr dens densit ity. y.
t a t a
12 Clai Claims ms
r -
42
Draw Drawin in Figu Figure re
FLOCCULANT
46
40
OVERFLOW
30
14
28
SLUDGE
u . s . Patent
Jun.
4,273,658
IV
/1111
ILI~ ILl I&.. ..J
..J ..J
I&..
..
IIII ::111
::I~I
::
~~III
ILl
(!)
..J
U'l
C\I
I I I ~
'It /'
IIII1 IIII1 I11II ,~,IIII
4,273,658 THICKENE
CONTRO
843,471, file Oct. 19 1977 no
PROCES ".
abandoned.
particle in th slurry or pulp to flocculate or agglomer at nd thus settle or ra idly Th ount lo cu la ic ic la rr te di tribution, th densitie
th soli
articl s, nd th
ield th In enti constant conditions th amount of flocculant needed to This inventio relate to continuous thickeners .clariie ty ti fier an simila gravitationa settling device fo 'sepa- 10 cl ri ie or th like an ge rall et rmined tria rr ri rr th io lu ge an is partic larl nc rn with meth ma ange ra idly du to ri ti in th moun nd ro in ti comp sition th li sp nd in th ed tr their efficiency. ri le ic rt Continuous thickeners clarifiers an simila gravita justment ofthe amount of flocculant or coagulan adde ti al ettlin de ic re id ly ed in th ch mi al to th system isnecessary to compensate fo thes variaan metall rgical indu trie th remo al liquid ti ta ro lurries, metall rgical ul s, wage an th io liquid-soli suspensions. Such device generall includ 20 cost within acceptable bounds by eliminatin overfloc in ic ll culation. ly It ic th in lp th ie re t' manc an to monito this leve asa mean fo determin in to in er l, th hi he th li le el th more lo la th create minimu of turbulence This make it possible is ne de is ea ur me th slim leve en erally been done manually by mean of measurin sticks le it lo pulp lurr tend to mo outw rdly ina ra ia direc- 30 It as ls en pr po ed that fl ts if re tial resti lo upwardly toward erip ra er lo ta te settle downwardly throug th slow-movin liquid an densit representing th slim leve an that change in la li this le el ed to ntro th dition of lo ul nt to co pr ss as they cumulate an re sl wl move 35 th ystem. limeleve isno irec ea ur of th to ar bottom lu is harg op ni by me ns settling characteristic ofth solids in th pulp or slurry te "bo ia in lo ra sl ge re uc it li ui co te to gr te te soli an li id haract ri tics nd th like here is than isnormall achieved inbatch sedimentatio opera- 40 normally long time la betwee change in th floccu tions. la re During th or al er ti thic ner, cl ri ie or si il onti ou ra it edim tation evic th type referred to above, series of relatively well-dero ce de ir ha ge in li le el If he ov re ti fined, vertically-space zone exis within th unit Th 45 mate or underestimates th change in rate required th liquid or clarifie solution from whic most of th solids containing suspende soli particle whic th
le
lution
th
is generall
lo layeris normally referred
la le characterize by th movement of liquid an soli partith re stream operatin
conditions an othe variables. Dur-
io ot er ri le ta la thre di ti ne ay ot exist. To achiev maximu capacity with such unit it ha nerall ee thou ht th th slim le el sh ul in lo to le an th only thin laye lari ie ol ti ho ld be maintained abov th floc layer. It is conventional to ad flocculant or coagulants to th ie re their' capacities These, materials' cause' th suspende
slim
lime leve th re re
ro id
at es
isi-
clarifie operatio and, if it increase progressively, ma thickene or clarifie ha been exceeded It is virtually el me ns co tr llin th rate fl cc la addition. thickene operatio by regulating th rate of flocculant dition re in ff ti le to ug esti th th sample regula interv ls wnstream of th poin fl cc la ad ition, th ch mple th coll te in it ra representative settling ca take place, an that th sepa rate liquid an solids phases be separately withdraw termin usti
by th
on itions
th rate of lo ul nt
sire in th thic ne oa ul nt dditio to
4,273,658 to leve of th interfac during operatio of th system it th ha been said that th rate of flocculant addition ca be is nd inta it in zone xt di ro controlled automaticall an that th flocculant consumption ca be reduce substantiall xperienc ha demonstrated however, that th system thus proposed pt osit on pa ticula th ck th li is no effective. It us ha therefor been abandoned. ca readil be determined experimentally by varyin Effort to develo other, more reliable method fo th th lime le el whil adding flocculant in response to automati contro of flocculant or coagulan addition in ch urry de ty th th ll nd ob orde to stabiliz th operatio of thickeners an clarifi- 10 rv ng th ffec ch iation on co trol of th er an reduce chemical consumptio ha in th past unit Furthe change in slim le el il normally oc bee largely unsuccessful. cur, although in some case slowly if th initia le el is to th SUMMAR OF TH INVENTIO Th slim leve in thickene or simila device ca be Th presen inventio provides an improved method 15 fo controllin thickener, clarifie or simila gravitarate to ro th de ce nc th te tiona settlin device by regulating the rat offlocculant or coagulan addition whic largel avoids th difficul sponding increase in th rate at whic clarifie solution ties outlined above. Th method of th inventio result th ra ng ther ch ttli ke it bl to ch ev gh ud de ti lowe clarified solution solidscontents decreased flocculant or coagulan consumption, increase lurr or pulp capacity an reduce unit downtime Th overal
level; hile reductio in rate il have th opposite t. th needed to permit effectiv contro in accordance it the invention can normall be establishe without diffi25 culty. thickening or clarificatio pe unit volume of slurry or Th method of th in ention requires th measurin pulp handled. of th densit of th do nflowing pulp or slurry at tw or po nt ov te th th ee th th ck ne or imil ce he nsit ue th th to of th fe ll rm le th inco in slurry or pulp an flocculant or coagulan near th bottom of th ell. th pulp or slurry oves do nwardl ithi th ell, th densit il increase trolled by establishingthe slim level withi predeterwith flocculation Th variations in densit whic thus mine distance of th bottom of th feed well monitortake plac will depend in part upon th particular liquid ty solids system bein handled, th degree of flocculation lp es ow dl th th el whic occurs an othe factors. Although thes variaju ti th te ic th fl cc nt co gu nt tion ar normally small, they ca be readil detected adde in response to these smallchange in density. Th In typica thickene operatio handling metallurgi ti ba rt up th di co er th th ca pu cont ni in al ol ds fo ex th position of th limeleve it referenc to th bottom densit of th incoming pulp in th uppe portio of th 1.043 cu tt th th th centimeter whil that of th heavil flocculate pulp in leve isa critical facto if effectivecontro isto be estab1.081 lished an maintained Once th proper slim leve ha gram pe cubi centimeter In this particular instance been obtained change in th densit of th downflow th densit span is thus abou 0.04 gram pe cubi centiin slurry or pulp provid direct easureof th effect meter. Thes values illustrate th variatio whic ma fl ccul co la diti on rt cl ttlin velocities Th monitoring of such change make limiting Th difference in densit values du to floccu possibl the stabilization of thickene or clarifie operalation ay be greate or lesstha this dependin upon tion an permit opti izatio in term of reagen con- .5 th particular liquid-solid system bein handled, th sumption, sludge density, clarified solution solids con soli particle sizes, an th like Fo most applications tent slurry or pulp volume an unit downtime despit substantia fluctuation in the fee rat to the unit, varia ff ci tl ti to detect ch ng ns ty about 0.005 gram pe cubi centimeter or smalle within th rang betwee abou 1.0 an abou 1.200grams pe presen in th incoming slurry or metallurgica pulp cubi centimeter. dicate ab ou th th po An of ariety of differen.tinstruments ha in th ti of th li th refe nc to th bott of required sensitivit ma be employed fo th detection th feed el ha marked effect upon th settling rate of densit change in carr in ou th in ention Suit within th well If th leve become to high th slimes 60 le trum nt includ tica de ic on co centration th nc nt po nt ch ng li ht tr il ty th lp or rr ti co tr such as submerged turbidimeters, sonic devices respon longer be maintained Similarly if the leve becomes too sive to change in soun transmissibility whic accomlo th el will become depleted of lime an conpany change in pulp density, an radioactiv system trol il agai be lost Th zone ithi hich th slim 65 hich detect variations in th pa sageof energy from le el must be aintaine depend in part upon th conradioactiv source to detector it ariation in pulp figuration an dimensions of th particular thickener, it po nt li r, th te oy clarifie or simila device an will vary somewhat from houl be capabl of detectin densit change hich
4,273,658 rt
it il
te
th ll ultipl so rc multiple dete tors tili lo gate or collimat ur
ange in de sity ve rr to
uc
vertic
in both or detec-
interval In iv
ente of th bottom Th is ar pe in incl de lu ro ic ni ov into isch rg line Over lo la nd 14
n-
withdr wa of lari ie li id ro th nit. re ol in rake assembly includin centra shaf 15 driven by
radiatio severa inches long Such radioactiv source detector system ar availabl from commercial source 10 ll to rt ic ur os th in ention re ls commer iall ailspider 21support th rake arms Braces 22 23 24 an 25 able. ar provided to strengthen th rake assembly Blades 26 Th densit measurin instrument employed fo pur- 15 pose of th inventio will normally be suspende in th lu in ed well th thic ne cl ri ie belo th pulp le ie lo in tt th be pr vi ed with la bott in whic se olid will from this device ispasse throug an electrical conduc la io to to to powe pply ni er th si na is amplifie that shown. he pe rt of tank 10isprovid it ee el nd se to ro id orre on in oltage whic ic pe in th ra in hi ee ll isa li ri al me ic tt ia tr It ra to eter of from abou to abou 3D of th tank diameter well to increase th efficiency of flocculation within th thickene or clarifier. This aids in securing proper distri-
30
instrument detect change in density representing vari ry le ri ic in inst ta eo ad ustm of th lo ul nt rate to counteract th change in settling rate Change in density representing reductio in settling rate produc an in reas in lo la ad itio fficie to of et nd ecreas in fl cula dditio su fi ie to ff et nd compensate fo th increase Th result isbette contro e b Experience ha show that this system provides preis lo io ry lu an composition, permit th maintenanc of substanti ll nstant li le el within th thic en or arifier result in increase thickene underflo densities, substantiall reduce thickene downtime an ha nu merous othe advantages Thes an othe advantages th st il be om more re dily ap ar ro th detail es ri tion of th re rr mbodim nt 55 th inve ti et rt belo he rawing is sc em ti re re nt ti rtith ro ry ic ro id it flocculant additio contro system constructe in accordanc with th invention.
bove th in er dg of verflo la nder 4an th hi er th th li ui le el in th ta k. At it lowe
d, ir
th to increase or decrease as desired. Th skir is attached rt ll rr
la
ll th
ve
it
li he de ic
is li ov rl adin tu
ow
re il
in of th
rm ll ha in
nit.
tt
io nt is ig
rp
sp ci ic type thicke er it il nd rstood th th inve ti is ot re tricte to this rticul para tus. It ma mplo ed with ri ty th thic ners, clarifiers an simila gravity sedimentatio device in li lu in torque thickeners tray thickeners traction thickeners upflow or siphon feed thickeners an clarifiers an th like. It ca also be utilized in conjunctio with horizontal, rather than rotary thickeners clarifiers an simila de ic uc vi ve en de cribed le th in th tech ic literature nd will ther or be miliar to th se ille in th rt Th in tr me et ti de sity an es in th sy te sh wn in th ra in ma optica or ni ha
ll
te 1wh
iv
iv
th 10
in rmillicuri cesium-13
4,273,658 availabl
from commerci
suppli rs
ay be mplo ed
If th
li
th
by
ns of
la
te uspend
be
10
te It is generall
15
thickener.
to tr tr im stant.
ll
tend
to
be lect
dr ul ca
tu te
th ju ti
nd fi
co
le
ow
uppl
un ts
th
on-sca
de
co
po ti
of th
tt
25
te
ta ti
tica
ho zont
ng is bt
th
co de
xp
30
t. to
30
flow
tr
35 ta ne
th
or
unde consta
th kene
pe t-
.0 is
In us
ti zi
th full
te ca br te
th in to ns
ti th
th qu
pa tu
it ly of ca th th cent
45 fr
ca
th
te to ju te
ou ce-d te to
un
ft to
te
cati ns
will be neces-
If
on-s th
co
di
is obta di
obta
ng
ui
50
th
th or
th
te ul
ou uffi ie
of ngth to
ju tm t, ke dens ty
om
ci ly
il bl
normally intended fo 55
te
suitable ch ssis so th ings ar
individual suppre sion an
rang
obtained
30. th
ty pplication
requirin
nt
consid ra
4,273,658 stri
position an othe operatin variable is obtained Th precis calibratio techniqu employed will depend to larg extent upon the.particular densit measurin sys-
source-detecto
su pl
ni
10
Mode LJ30-W IF
avin an ut ut of ro
to
50millivolts
rc varied as necessary, covere housings an connecte by an adjustable fram th th ly to in te in ll calibrate as describe above, th system will automatill regulate th lo cula dditio rate to maintain th slim le el within th thic en relatively consta t. 10 iz ti io in th ny vari ti in ttling rate it in th ente well to ange in fe rate fe omposition olid partiamplifie ctio th te to sy te er re la ed in ib le iz density, lurr te perature th like whic The.record ntroller unit mploye wa ti gnd alterati in th li leve il ompens te 15 fs by orrespondi ch ng in th lo uTh effect of th system of th inventio upon floccu higher sludge densities, lowe clarifie solution solids la tc nsumptio is show in th ta le comp ri on contents decrease flocculant consumption, increase slurry capacity substantiall constant slim levels an 20 io tr Il ly la peri in hi th peration as ntroIled in ac or ub ta ti im ro me in thic ne peration It wiII be ic in ti reductio in thickening cost
illustrate by th result obtained in multiuni thicken- 25 amount loccul nt re ir er to or ro ss in system used fo th separation of solids from slurry one- al un pe to nd th th us th yste of spen uraniu or particle followin th extraction th inventio er itte bsta ti redu ti in lo ra iu lu ic installatio included series of rotary thickeners simila show in th ta le ta into nsid ration ariati ns in it thus comparable Th reductio in flocculant consumpholder containing thirty-inc stri source of 100milli urie ce iu 13 hm rt Corp ration thirty-inc operating costs. TABLE Floeeulant Consumption Manua Operation Tons/Day
<325
<325
Tons/Day 3492
5728
<325 26.3
3113 26.3 3270
7,
3533
20.8
10
3379
21.3
18.7
10557 25.2 3089
9243
3154
18 19 3520 26.4 21.9 10228 26
3004
28.2 2371 2908 15.9
2916 11875
Totals
47631
4,273,658 TABLE-continued Floeeulan Consumption Manual Operation
Controlled Operation
Controlle
Operation
ays 5.58
Averages
.3209#/Ton
Note: Solids ed, b a
averages.
fee well. method as define by cl im
wh rein said slim furthe illustrate by th variations in slim leve before 15 and after installatio of the system. With manua regulain he of th boto of id fe ll tion of th amount of flocculan added, slim leve vari or 16 inches were incurred Followin installation of th system of th invention, mate radioactiv source an detector 5.A method asdefine by clai wherei ch nges in slim leve variations were routinel held to abou plus 20 or minu to inch s. Similarl thickene downtime densit of abou .005gram pe cubi centimeter within followin installation of th syst wa reduce from 0ar tected. reduction. Th averag density of th underflo sludge from th syst ls increase as th result of us of th syst of th invention. It il be pp nt th th se improvements in thickene operatio significantl re duce operatin cost an increase thickene efficiency.
25
mean ar
30
mean ar mplo to detect said change in densit 8. thod ccording to cl im hereby ultipl unit in series ar utilized 9.A method fo controllin th operatio of contin uous rotary thickene having center el into whic floc ul nt nd lu ry of uspend solids introdu to ff pa tion of th lurr into la ifie
pulp an simila slurries it should be recognized that it lize in se ag disposal pl nts, chemical plants an variet of othe facilitie requirin th us of thickeners an simila continuous gravit sedimentatio device fo th separation of liquid suspension of soli particles into Clarifie liquid an sludge phases claim: 1.A method fo controllin th op ration of contin uous gravit sedimentatio unit having feed well into ic slur of su pe de olid nd fl cc lating agen ar introduc to ff ct separation of said slurry into cl rifi solution that is recovere from said unit
35
mplo
to detect said change in densit
ov fl nd thickene sludge ic is from th bottom of th thickene co prisin
ov re th st ps
unti li le ithi bout ig te inch th bottom of said center well ha been established, measur pended solids over vertical interval within said center well with sufficent sensitivit to detect change in den-
45
from th bottom of said ni he by consumptio of floc ul ting nt is uc co prisin th st ps of establishing slim leve within predetermine opti
said change in densit to compensate fo said ch ng in said solids settling rate
density is measured by radioactiv means. in th flow te to nd from said unit detectin 50 change in th densit of th downflowin slurry ov densit is measured with sufficient sensitivit to detect vertical interval in said fe well corr lating said dendensity change of abou 0.00 gram pe cubi centimesity change in th solids settling rate within said well te ithi th ng betw bout 1.0and bo 1.20 nd continuously varyin th rate at whic said floccu gram pe cubi centimeter lating agen is introduced into said feed well in response 55 to said change in densit an hereby contro of both densit is measured by mean of collim te radioacsettling rate an slim leve is obtained tive source an detector immersed in said downflowin liquid nd susp nded solids within said center well change in densit ar detected by passin energy from '" . 60
65
