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Патент USA US2106318

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Patented Jan. 25, 1938
Roy D, Elliott and MaryJJ. Elliott, Jersey City,
No Drawing. Application October 15, 1932,
Serial No. 638,029
9 Claims.
(Cl. 210-203)
This invention relates to improvements in
?ltering; and it comprises an improvement in‘
ing a ?ne turbidity. There are few turbid liq
uids from which clean sand grains will absorb
?ltering turbid liquids through pervious granu-
colloidally ?ne matter;v liquids in which these
lar ?lter beds of inert materials wherein the
1:1 granules are provided with a coating or adsorption of an adhesive foreign material having a
greater physical a?inity for the particles of the
turbidity than the a?inity of the untreated material; the coating or adsorption, in the case of
10 sand ?lters and aqueous sugar solutions, being
matters are of such character as to tend to dis
place adsorbed 'water on they surface of the sand 5
Any sand ?lter works better after a period of '
use during which the pores become clogged with
sediment to a certain extent; not enough to plug
the ?lter but enough to reduce void dimensions. 10
often composed of rosin of colloidal ?neness; all
The sediment is then the real ?ltering material
as more fully hereinafter set forth and as
and the sand is, so to speak useful asa mechani
cal support. In order to promote this type of
In ?ltration of turbid liquids through pervious plugging or stoppage of the pores, in the case of
15 granular beds, the granules are usually silica or turbid liquids carrying ?ne suspended matter, 15
a silicate; sand, sandlike pumicestone, asbestos, it is usual to employ "?lter aids”; generally
kieselguhr, etc. These are the cheapest and something of the nature of paper pulp, kiesel
most generally available materials. Kieselguhr guhr, etc.
is composed of extremely ?ne particles but, for _
In the present. invention, this defect of sand
20 the present purposes these may be considered and silicate ?lters is obviatedby providing the 20
Asbestos rock is sometimes used as
. granules carrying loose surface ?bers; and some- .
times ?bers are used in loose condition, functioning in a ?lter in the same way as granules. For
25 the purposes of the present invention, all these
materials may be called sand. Unfortunately,
silica and the silicates do not have what may be
called an attractive power or a?inity for the ?ne
solids which form the turbidity in most aqueous
30 liquids; wet sand neither discharges charged 001loid particles nor tends to pick up very ?ne suspended solids. Clean wet sand attracts and
granules with a coating or an adsorption of for
eign matter having an affinity, on the one hand,
for sand and, on the other, for the solid particles
constituting the turbidity. Sometimes, this coat
ing or adsorption carries an electrical charge; 25
either positive or negative, and opposite to that
of suspended colloid particles. In many cases
the coating or adsorption applied is of a mate
rial which is somewhat sticky or tacky but in
these cases, it is not of such a character or of 30
such an amount to produce any tendency toward
bonding the particles together. Many substances
holds with great force a thin ?lm of water - are useful in the present invention, among them
around it. Thus, in a ?lter bed composed of rosin or other resin, rubber, gum chicle, cellulose
35 clean sand, ?nely divided solids may pass en- nitrates, asphaltum, tar, etc.
tirely through the ?lter bed without contacting
For aqueous sugar solutions, it is found that
the true surface of any granule of the ?lter‘ bed. good results can generally be secured with the
After a period of running, the ?ltering surface aid of a little rosin carried by the grains. Rosin
of the sand becomes foul, ?rst with larger par- or colophony is a material of acid nature, being
40 ticles retained by the straining action of the mainly abietic anhydrid. Ordinary rosin is not
bed and gradually with smaller particles of the particularly sticky or tacky at ordinary temper
?lter residue. This deposit then constitutes the atures. In ?ltering sugar solutions, which is
true ?lter medium and the ?ltrate begins to run generally done at temperatures above 60° C.,
bright, but by this time the rate of ?ow has say, about 80° C., it becomes somewhat more
45 greatly diminished due to partial clogging of the tacky, but it is not used in any amount making
pores. In our invention the sand grains are the grains sticky as this would interfere with the
given a coating of a material having less power normal action of a granular pervious bed. A
Of attracting a ?lm of water than has Sand, and moderate amount of colloidally ?ne rosin car
thus suspended solids may more easily come into ried by sand grains, gives excellent results in
50 contact with and adhere to the surface of the ?ltering sugar solutions, even where the bulk of
?lter medium. Clean sand ?lters are most ef- the suspended turbidity is of colloidal ?neness.
fective with ?occulated turbid liquids contain-v This is particularly the case where the sugar
ing coarse turbidity or sediment which can be solutionyhas been defecated with lime and phos
mechanically held in, the intergranular spaces. phate; giving precipitates of more or less basic
55 They are of little use in clarifying liquids carry-_
The foreign material may be supplied to the
sand, etc., grains prior to use in ?ltration; or it
may be supplied simultaneously; a certain
amount of the foreign matter being added to; the
?rst portion of the turbid liquid going through
the ?lter.
uors from which it is desirable to remove all haze,
it is useful to put a little colloid rosin in the top'
laye In a boneblack ?lter with down ?ltration,
the t layer of boneblack clearly becomes ex
hausted as regards decolorizing power and it then
acts as a mechanical ?lter, while the underlying
boneblack plays its usual part. When the bone--'
In using rosin, either way is convenient. Rosin
size may be diluted with water until it exhibits _ black is regenerated by heat, the rosin disappears.
a faint milkiness and .this liquid poured through I What we claim is:— e
10 the ?lter.- The sand will pick up colloidal rosin
1. In the ?ltration of turbid liquids through 10
to an extent sumcient for the present purposes.
pervious ?lter beds oi.’ loose granular media, the
Or, if the alkalinity of the; rosin size is not un
improvement which comprises providing the
obiectionable, a little rosin size may be stirred granules with a light coating or adsorption of
into the first portion oi’ liquid to be ?ltered.
Rosin size is rosin soap with an excess of rosin an adhesive substance having an a?lnity both for
the material of the granules and for the parti 15
and this rosin precipitates on dilution. An alco
cles of the turbidity.
holic solution of rosin diluted with water is also
2. In the process of claim 1, the improvement
a convenient way of producing a coating mate
rial i'or the present purposes.‘
which comprises providing said granules with
said coating or adsorption prior to ?ltration. _
For general purposes. rosin is the best ad
,3. The improvement of claim 1' which comprises 20
sorbing material for use with sand. It is not _providing
said granules with said coating vor adg
only adsorbed by sand, but it has adsorbing power , sorption simultaneously with ?ltration.
for the usual solids or turbid aqueous solutions.
4. The process of claim 1 wherein the granules
But for other purposes, rubber applied in the
form of latex is convenient. ‘Commercial latex
is ammoniacal and‘ the contained rubber parti
cles are negatively charged. It‘ imparts a dis
tinct tackiness to the sand grains, enabling a
mechanical pick-up of solids, and it is easily ap
plied. The same considerations apply to gum
chicle. Cellulose nitrate is particularly appli
cable to certain types of colloid suspensions; be
cause it has considerable adhesive power and pos
sibly also because 'of differences in electrical
35 charge. In all cases using stationary sand ?lters,
it is the character of the surface at which the
liquid enters which controls ?ltration: and ‘in
the present invention, it is su?icient it the surface
or a top layer of the ?lter be treated. This fact
40 enables the extension of the present invention to
certain types of granular bed devices not using
The presence of adsorbed matter en
hances pick-up of turbidity. Among these other
types ‘of ?lters are the boneblack ?lters used in
decolorizing sugars. A boneblack ?lter has not
only the duty of decolorizing, but, to some ex
tent, a mechanical duty in ?ltration. In a colum
nar bone-black ?lter treating turbid sugar liq
- are oi.’ siliceous nature.
- 5. The process of claim 1 wherein
the granules 25,
6. In ?ltering turbid liquids, the process which
comprises passing such a,‘ turbid liquid through
a pervious granular bed, the individual granules
being coated with an‘ adhesive material but the 30
amount of adhesivebeing insu?lcient to admit of
substantial mutual adhesion of the granules.
»7. In ?ltering turbid liquids, the process which
comprises passing such a turbid liquid through a.
pervious granular bed, the individual granules 35
carrying a coating oi.’ adhesive organic material,
the amount of coating and its character being
such as to prevent substantial adhesion of the
granules to
each other.
. '
8. In the process of claim 1, the improvement
which comprises providing the granules with a 40
coating of a tacky substance.
9. In the process of claim 1, the improvementv
which comprises providing said granules with a
coating of rosin, the rosin being introduced in
and together with the turbid liquid.
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