Note: Descriptions are shown in the official language in which they were submitted.
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PCT/EP 96/04960
MP 124 WO
New ~nt~ inn p~a 1, 7: 3 ~5-
Surface Filtration and Surface Filter
The ,..~ni<~n relates to a surface filter Witll the ch~e~ ics of the preamble ofPateQt Claim 1. F~lhe,~ , ~ the ill~ U~I re~ates to a process for worl~ng s~id
surface filter.
Surface filtration serves for separation of dust, i.e. separation of particles from gases.
Separation of partictes occurs mostly on the surface of a filter ~i~ fabric or needle
felting made of ~tural or synthetic fibers), which is formed, as a rule, by hose- or pocket-
shaped filter f l- . ..- - n~ A so called dust cake forms on the surface of the filter element.
It constitutes the highly eff~tive ~ . ~ layer proper, iQ which takes place nearly
total s,~A;~ n~l;Qn of particles and whicb ~,~ tbe filter ,~ from
u,~,.~blo dust ~ -.. n and thus ~u..in~, clog8ing.
A~ a rewlt of th~ of dwt layer on the surface, lou of pressure CG..I..~C~ to~e. In order to o~ain s~ble operation of the filter, the filter cake needs to be~~o~c;l ~. Q~ y. With hose ~cd filter ol~ ls, ~ om the out~ide to the
in~ide, ele~ , usually is donc in such fashion that via introd~ tiQ~ of co..~ e d air into
the inte¢ior of the filter hose, excess pr~re is ge.~. ~-led, ~. h_. ~y flow Jir~oll of
the gas ,~s itself and the dust cake located at the outside of the filter medium can be
detached. A Pro-r~ *e for this i~ that the separation forces co~ing into play between
filter ...~ . and dust cako are greator than the operative ~d'haion forces.
dunng operation of ~urface filters can, in e~ ~ ~n~r, occur under two aspects:
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- clogginK of filter me~ Jnl by mesns of irrcv.,. ~ ~ le ~ ~bc~ 1 of p~icle~This is particl~larly noted in the p~ec~ 1 ;on of fine dusts (x, l ~lm) ~ ~b:~Adwith low co.~ a n~iO~ of crude gas
removal~ , as a re~ult of finnly adhe~ing dust cakes This
effect p. .,R ~' Iy occurs in s e ~ P~ t ;or of fine and/or sticky dusts and also
when particles are separated from wet gases or with particle-droplet lluA.~unvs
A surface filter ofthe here con~.-,ed type is known from US-A-25 13 174
A vertically ~, n~,~ d filter layer is located in a ho.~on~all~ l,a~,6.~d houcing Positioned
immediately before the filter layer are ~o7~l~, which serve to jet-spray tho filter layer with
a flushing fluid Since the effect of the n~771~q, located at a short distance
in front of the filter layer, is locally restricted, a plurality of nozzles needs to be E~
Con~~ y, the de~ign ofthe filter bc~.~ s very costly, s,~,ev;l;~lly if rel~i~
Isrge filter areas must be r~ -1 ed Mofeo~er, stress is ~ due to the &ect
jet-L~ ,, so that much wear and tesr occurs (~lltin8 ill low service life)
The content~ of DE-A-27 31 755 is also part of state of the art It ~d il~s filters
with ~ central, ~ ; 'Iy arrsnged filter candle, locatet in a cylintrical h-~ .o;~g The
crude gas i8 lL~J'~AlU~ ~ nti-lly and ilows spirally around the filter cantle from the top
towards th~ bottom As a result of a high L ~ y CG~ OG~,~t - agite from
the ~edimaltation cause~d by the filter candle - a separation i8 obtained based OQ the
C~rGIOnC principle In the p~nficqtinn of flue gases, which are produced during 1 ~ ~ ~i~
of MOS2, the crude gas is sprayed with water
The pre~ent hl~e~tiOll is bll~et on the object of eyp~ the ap~ ion field of
~urface filters to include A;IT..~.~II app~ tion caseg.
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The particular benefits of the suRace filter ~ c ding to the invention and also of thc
Gp~ lh~g process are based in that prior to crude gases colliding with the filter elernents,
there occurs intensive b' ~ling of the crude gas with the d,opl~ of a finely di~per~ed
mist. Consecuently, there occurs in this region a settling of the impuritie~
on the ~Iro~ '~ . A pe~ ~ a8e of these drops no longer reaches the fitter elements,
so that there is a reductiQr. in dust a~ ~ ' ~ tion at the filter ç~ e- ~t ~ proper. Another
ge of the i,-.~.J- i1:~ contained in the crude gas, which have already been blended
with thc rnist, diroctly carries whh it the required rinsing fluid whon re ~ ~ ~E the crude gas
side ofthe filter e~ for e~umple as nl-~ ~hinG) wbich assists in fl~ 3h;-~g the filter.
Blending of the finely dispersed fluid trops with the cmto gas In the filter housing
also results in that the fluid drops cus reach all regions ofthe filter ...~A;..-.., so that
erre~ cleanin~ is gu&~lt~d. Due to the fact that E~ l'mUI~ifm of dust at the filter
e~ proper is reduced and that the~ filter elo ~ are conti~ o~ y _le d, it ispossible to ob~in stable o~aLon with long servicc life ofthe filter ~ccold,.,g to the
invention. Llt~ )tion of o~,on fior ~ ~seq of additional IJ1 g via compressed air
can bo waived, as a general rule.
The type of water ~ is of p-u L~ILr ~ C6~ th this pl ~g~, in~much ~s
r~ te and highly u..ifv.~ ~ es of filter ,.,f~i~,," must be guaranteed. ~ doing so,
fc",,,ati~,n of ~ filter calce must be pr~ tct, since ~ny potentially folu,ing filter cake
would result in a distinct il~ e in the loss of p~ 3~ C, (Capillaly F~h~q~ n) which is
1~ - ec rt-'le for ellel~_t;c reasons. The classic, cake-forming filtration, as described
above, ~ rure makesnosense~thwetopc~dtio~. Itis,lh~,fo~O,
palLcul~l~ ~p.~riate to ~rrange relatiw to a ~wfaco filter having the characteristics
i;AB to the preamble of Pstent Clsim 1, the filter e~ 1 s in tho upper srea of
thc filtor housing and to ~Tange bdow tne filter elernel~ts the nozzle(~) Imt also the orifice
of the clude gas ~upply lino.
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~d-lhi~n~lly, a certsin part of the fimction is attributablc to the rinsing fluid. w~ch is
assumed by the dust cake in the conventional Lll~ at.on operation, i.e. to produce
s~ ;o~ of the particle~ and to prevent the~r p - ave into the pure gas.
In many cases of industrial application one is faced with the object of also separa~ng
the ~,r~~o lc c~ nP- -1s in ~ition to the impurities in particle-form. This possibi~'ity
is ~u~-led with a wet v~ 4t~ surfaoe filter by sel~ 1ion of an sp~vp.;dle fluid
or by sdded dosage of suitable ~ s. If, for .~ , milk of lune
(CaO-sol~tior- in H20) is employed as nnsing ~luid, the possibility exists of also
pre~ l ;~ S02, S03, HCI or HF in e d 3 on to the dust-like particles.
~elow, several possibilities will be ~pl~ined in more detai} based on eA~,-~Jlary
d~ d in Figures 1 to 9, relative as to how the process
can be d~ od - ~ee;r~JIy how the added dosage of rinsing fluid can be envi
tal~g into ~ ~r dr~ation the de~..,.il,~,d re~ s well as naming ~d~ o
be~,fil3 and details.
-Figures 1 to 3 rep,~ ~face fi~ters ~c~ ding to the invention with
dosed filter hoses,
-Figures 4 and 5 ,~,~e3~ surface filters ~nth open filter hor,es,
-Figure 6 ~ cp.~ 9 ~ntc a su&ce fi~ter with filter c~ t,;dgc
-Figure 7 1 ~ a !~,urface fi1ter: ~e for ~ .~ of moist gases
-Figure 8 ,~pr~s ~ ~ a surface filter accG.di.lg to the invention with el~l-ic~
field s~ d ~rec;~;tation and
.Figure9 ~ ts an applirPtinn embodiment for ernploying a surface filter
desi~ed ac~,.lihlg, to the .n~ n isl a ~pray drying
inct~ll ~tiQn
~ t r r~ ~ ~ ~ v ~ _ ~ ~ u ~ r o ~ r~ ~ v
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In the ~ , embodiment ~ di.~, to Figure 1 and in all other figures, the ~urface
filter d i~ d accordi..g ~o the ~ .L.al is it~ ;r.ed with 1, its filter ho.";,~L5 with 2,
the crude gss line with 3 and the pure ga~ line with 4. For Filter 1, P ~ c r~lin~ to Figure 1,
there are provided as filter ~ , in the upper region of filter ~ JF'-~, 2, g~ do~
closed at thle bottom filter ho~es 5, which ue sprayed from bdow with nns~ng fluid.
For that pulpose there are arTanged, in the lower region of the filter hmlP;ng 27 one or
several no7~ 6 ~binary no_zle or other suitable de~icer7~, which are ~"Lul
by conveyor pump 8, ~ria line 7, with rinsing fluid and ~ia line 9 wit_ cou~ ~d ~7
(for example air). ~ me~ng- and ~ .ito.u~ truments are idc-~-;rc~
w~th 11 and 12.
During Gpe.~liOII, in the imm~i~e IJ-u~lty of the crude gas inlet 3, a very finedroplet spectrum is produ~, as ~ J~;d 3 -h ~ ;C~ y in Pigure 1. The finely
c. ucd drops (typical ~t~ -,t~, ap~u ~ ',y lOO~m) follow the fiow of gas
due to their low SPI;-..-,-~t..l;o.. velocity and reach the filter hoses 5 in the same m~nner as
the p~ L~,les which are present in the crude gElS. Due to aimultanwJs sottling of
p~li~les and water, and if fluit percentage is s~ t, a ~o~flowing suspension is
produced, which runs offthe filter hoses and can be disch~rgcd from ~ou~n~ 2 vialock gate 13. Separa~ion of solid matter from rinshg fluid takes place in a sedimeQtation
ba~n 14. The se~,~t~ rin~ng fluid is transpo ted to n~l!llDg fluld vessel 15, so that
~1~ by means of cycting i~ possi~
The ~ t benefit ofthe descri'oed process co.~ ~ in that by g~l~.alu~, the finelydi;~ L ~ ~ mist, there is assurance that the rinsing fluid, which is fdtere~ in the same
manne~ as the solid matter particles, will rea¢h those regions of the filter medium fir~t,
where locally high flow ~e~ t;~, prevait - and ttws bigh particlo flow ~ ~V;~;~5, which
require a correspondingly high supply of rindng fluid. Due to this effect, a st~h;~ of
v~ . UO r~ l~lo~slluuu r~l ;~n~rr. Dr.~~ u~ u
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OpCi.alhl~ behavior is attained. A positive effect of the a,.~ 1 of the binary nozzle 6
in the area of the crude gas inlee 3 consists in th~t here a pr~-s ~ of particles can
take place v,ia ~ 1 at drops, which will, in ap~ v~- idte size, settle down in the filter
ho-. ~\B 2, 50 that there is red~l~ion in the a~ m~ tion of dust at the filter hoses 5.
In the event that in a~ to the s~l~ tion of particlos, gP~ ~~ ~1~ofthe crude gas are also to be sc~5.~,5..l~, one snay uso an ~yl-,y~ e rinsing fluid
for ehat purpose. Anothe~ possibility consists in that ~ . are added. Such
tion may be done a .lill~.<,.lt loc~ionc It is of particular benefit if the ~d~litiQn of
t~ is done at ~he crude gas inlet 3.
In the ~ ry embodirnerlt a ~ ~ _ ~g to Figure 2,the addition of the rinsing fluid ss
made directly into the crude gas. For that purpose, a nozzle 6 with co,~e~ s~dingly
narrow S~ Llg ang~e is inct~lle~ in such fi~shion in the cnude gas ~ne 3, ~hat tho flow
of crude gas and the flow of r~llsing fluid are cou~1;Q~ql to each ~ther. This
affords the ~ ;ty of ~5_t~ acploitation of the there attaiDable high relative
V- IOf ~;- g ~h.__.. partides and ~o~l~ t-~ for 5~tl~m~ of part~cles at wster droplets.
Another v ~ on r~p~s the direct spraylng of the f~lter hoses 5, as d ~ x
scheroa~cally in Figure 3. The nozzlo~ 6 are located in tho upper region of'~he
filter housing. In such an ~u~v~,e-~ nozzles 6 of most varied c,~..~ may be
employcd ~for e~c~mplo an annular DOZZIC, en~, ,lc)~,~ the hose). Since the rinsing
fluid needs to be less findy ~ ~ tharl in the ~ e ..l.ofl; .. d~ C a cl;n~ to
Figuros 1 and 2, ulwy nozzles n~y be ~ i7~ even with lower wa~er pressure. This
has a podtive effoct upon the operating costs of thc inQt~ tic!~
In tne . ~ , " ~ ~ ~ c ~ to Figures 4 and ~, tho lower end~ of the
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filter hoses are open. In r l~iti-~r~ the filling lo~el height of the suspension comprising
rinsing fluid and so~ nt particles is COl~tl olled in such manner that the lower onds of the
filtor hoses 5 cont~ o~Qly dip into tho suspension. With a surface filter ofthiQ type.
opc. ~ e ~ in normal f~shion, where the flow through the filter hoses 5 moves from the
outside to the in_ide (Figure 4) there exists the benefit that fluid ~ m~l~ting on the l~ure
gas side Ismall ~ o~ Y of rinsing fluid or suspension) can freely flow out. In addition,
w~th a surface filter l with ~Iter hoses 5 open toward the bo~toTn there exists the
po -;bi~ of ~ .n,~, ehe direction of filtration and to ~ e the filter hoses from- the inside toward the outside, as is 3,~ lly representod bn Figure 5. Since as a result
ofthe t~E,.,t~ ;~h,j ~ ofthe hose interior there will occur no wall la~ses, o"ti...~..
on of rinsing fluid is guar~nteed. With this ~ariation it is also po~ to
t~, the use of support b~ since the filter hose~ e stabilized
by the excess pressure in the interior.
As m~ntiQ~ed initially, effoTts are made to operate Slter 1 with a'~ n-l cc,.. p.es3ed ur
cloaning. ~ this instance one is not Limited to the USUrJI hose shape ~nth respec~ to the
geo~ r of the filt~ ~ v-~ whose e ntial bene~it lies in its excellent cleaning abiLity,
for ~ by intro~hlction of a pressure thn st. A pl~lit~ of ~iations are here
conceiva~le, which c.~n be ~,~t;~ ~ with respect to degree of setimentation, pres3u~e
loss and rinsing ~uid I~Ui~ nc~
Figure 6 shows in w~mplary filshion an arr~ngemont of filter ~,e~Q 16 in cartritge
consbuction mode,. The filter housing 2 i~ fil1ed over its entire cross-~ on w~ tho filter
motia. Beneath tho filte~r olementQ there iB nozzle 6, which, as in the
, embodiment~ according to Figures 1 to 4, is 5upplied with = fluid and
co...pn --~d gas. If'n~, ~nother nozzle 18 can be arrangod ~ e the fiker
v ~ o 1 .~ . v o r A~ l ~ l U ~ ~ l l U U U r ~ l ~r c or.~ v ~ ~J
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elo~ which is operatod dther con~tantly o~ t~.lll.t~ ly. Above the filter discs
there is a droplet CollD~l~or 17, which retains entrained rinsing fluid. As ~ iol~ed carlier,
since cakc-forming filtration in wet op.,. alion is not possiblc because of c~.c. ~lic rea~ons,
it is of benefit to s~ntch over to the principle of depth filtration and to employ ~p~o~l ;ate
media. The structure ofthc individual filter c~ 16 may hcreby dii~cr in adjus~ent
to the dust con~ Lon which de~,-.,Lscs from the bottom toward the top and ~he
variable particle size ~ ib!~l;on
An~ther ~ .lio-- exists with rospect to the object of the rsnsing fluid if the purifiable gas
has ~ nt moi~re con~nt Undor the~e co~ l~;o~, it is appro~ te to arr~nge in the
gas line 3 a condcnsa~ion phase 21 (~ ~ p~ ~ Figure 7). In thiq phase, particlo ~
c~n be obta~ned by k~t~,r~ nrl~nqation. l'his of~ers b w,~s fiom two D~C
I:ir~ly, thc in~ o in partide mass produces irnpro~e.~ in particle 9~;..1~ io~ based
on higher inertia effec~. Secondly, the insing liquid demand is - .~ ' - d to the system, at
least partially, by tho particles bound within the J~ . and reaches the fflter ,..~ li.--..
directly without any wall 109s. Dcp~r.~ g upon nee4 nozzles 6 may bo ammged
n~lly to asgigt in the solid rnatter - 1 13C
It iq known from numorous tcsts that the se&~ 1 ;on boha~qor of filt-~nnG co~lectors
cam clearly be i~Uy~J.~ by ~ ti~n of electrical forces. Figure 8 .~ s
y a possibility of ho~v this can be rel';7ed w~th a wet GpL.~Icd surface filter 1
of the type ~ c ? ~;ng, to the invention. Spray cle~vdes are mowlted ~h.-e~:~ the
grounded hoses 5, at whid~, when a ~ high tensions is ~pp' ~d, ch~rge canièrs
are rele-re~, which lead~ to charging ofthe particles. The charged p~rticlcs ~ b'y
move along the fidd lines, which ~e poled from the spray elc~odc~ to the fllter hoses,
and a~e settled there .
v.~ 1 vv ~ .~ . vo r~ l~lU~ llU~ r~l J~nr~ OC.~ y v~
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A~)p~ ,t;orl possibilities for tho proceas accor~ g to thc i..~ ion ~A,xist in ~ Cth'~
where f~ne and/or sticky du~s or dust~roplet n~ u.4s must be p~ , ~ and
wbere l~tit;7A-tiQn of c~ hose filters or also wet washers is not ~ le ~a e~ use
of ~ . ~3 or ecoi~n~ c reasons. In ~ iti~n, the cO~inuous, ~ rlin~ of the filtercd by the in~on is of benefit in ~he recovery of perishsble products or in regard
to such prc ~ ~ ~ wbere ~ue.ltl~ chA~ g products are to be settled.
To cite by way of ~npl
- separation of blue vapor and con~lr~ls tion e çrcsols from the exhaust air
~om ah~dd_~, mdting r~" - e s, fuui~;cs, in the manuf~cture of
particle board sheet.
- product fec~ ;on in the ph~ --~Iti~'.PI industry or behind spray dryers in the food indus~r (cocoa, sugar, mi~ powder, etc.).
Figure g depicts in ~ p1~ y falshion a possible application of tbe i"~ lion in the
spray drying l~rc ~ ss it can be found, for ~ 4 in the prod~ on of
rniL~c powder. The spray dJyer 24 is 3~-p~ Vith the to be tried products from the
wet product c~ r rnain 25 and w~h air, passed via a gas heatcr 26. Dry protuct
is .li~h~e,_d via valve 27. The moist drying air, loaded with solid matter, ~
the down-stream filter 1 via the crude gas line 3 . As a result of the c4ntin~10~1s rinsing
of hoses 5, therc is assursncc of reliable . ---' b- ofthe sepsrated product, even with
bigh te~ of moistures, so that even with irregul~rities in the o~, nlion of the dryer,
high G~alii~ s~lfety of the filter prevail~.
U~ 0 ~ . V~ rA~ 1 ~lO~ UUU r~l i~n~nrr o~.~ v ~,v
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11
The ~lid matter which is diuharged with the rinsing flu~d csn be t~lln~h-ced inso
the pn~cess with this m~hod To that end, tho sedimen~ion basin 14 is oo~
~a line 28 to ~..~eJor pwnp 28 wish the wet product u~ tor ~nain 25. The
beneSt of this ~tep con~sts in that trea~,l.ent of discharge w~ter can be eliminated.
