Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
275
The present invention relates to the breaking of
oil-in-water emulsions.
U.S. patent 3,523,891 for "Electrolytic Sewage
Trea~ment System and Process" discloses an apparatus ln
which a batch treatment process can be carried out i~
which a aissolvable iron electrode is employed to treat
sewage waste. The system includes spaced metal electrode
plates connected to a power supply for producing multivalent
metallic ions and hydroxyl ions during treatm nt of waste
waters. The metallic and hydrox~l ions form a flock which
floats to the surface of the cell and entraps its suspende~
solids forming a supernatant, frothy sludge.
We have recently been working in the field of
electrolytic treatment of waste water containing ~tabilized
oil emulsion in an e~fort to decrease the cost and increase
the production results of such a treatment syst6m. We
have, in particular, been working on a system which is
operable on a continuous basis. We also have been inves-
kigâting various operational facets of these systems in
order to develop a process for treating such oily waste
waters which is the most eficient from the standpoint of
power consumption per rate of removal of oily materials
from waste wa~ers.
Briefly, we have developea a process for breaX-
ing an oil-in-water emulsion which may be applied on a
continuous basis. We are able to use a porous iron elec-
trode in the method as the medium by which ferrous ions
are placed uniformly in t:he emulsion to break the same.
Our concept is based on the principle of putting the
required ferrous ion concentration necessary ko break the
emulsion into the emulsion as rapidly and as uniformly as
possible. We obtain this by flowing a ixed amount o~
9~ `: - 2 -
.~
`
~,
275
emulsion through a unit area of a porous ferrous ion pro-
ducing anode. A predetermined amount of power is supplied
per unit area of the anode. Thus, as a ixed volume of
the emulsion flows through a unit area of anode, it receives
,the required amount of ferrous ion necessary to break the
emulsion almost in an instantaneous ashion.
Simultaneously, with the dissolving of the anode
there is the in situ generation o the hydroxyl ion at the
cathode where concentration is fixed by the electrochemical
reation. Air is introduced near the electrodes as air is
important for effective reaction to occur, that is, the
oxidation of ferrous ion to fQr~ic ion which is necessary
to break the emulsion~
In accordance with the broad teachings of the
method of our invention, an oil-in-water emulsion is broken
in the following manner. A porous ferrous ion producing
anode is established and a supply of the emulsion is
locàted on one side thexeof. A fixed volume of the emul-
sion is flowed through the porous anode per unit of time.
2~ Less t~an a passivating current is flowed through each
unit area of the anode per unit of time. This current
dissolves Lnto the fixed volume of the emulsion passing
through the electrode ferrous ion in su~ficient quantity
to brealc the fixed volume of the emulsion. The ferrous
ions are oxidized to ferric ions which are effective ~or
breaking the emulsion. The flowing of a fixed volume of
the emulsion through the,porous iron electrode per unit of
time and the dissolving of the ferrous ion and oxidizing
thereof results in a homogeneous dispersion of ferric ions
in the fixed volume of the emulsion.
,...
2~75
In accordance wi~h specific teachings o~ the method
of this invention, the amount of electric current passed
through the anode per unit area may be calculated by the
formula i = (N)f~Co)(10 4~ wherein: N is in the range
from 20 to 50; f is flow rate of the emulsion per unit area
of electrode in cc/minute; Co is the initial conc~ntration
of oil in the water in parts per million; and i is equal
to current per unit area of anode in milliamperes.
: The method of this invention may be applied to oil-
in~water emulsions of any general type. In particular, an
oil-in-~ater emulsion used in machining of metal articles
as a coolant and lu~ricant therefor may be treated by this
-- , . . .
.
27~
process in order to break the emulsion and remove the oil
from the water. A typical oil-in~water emulsion for a
typical cutting oil lubricant comprises, approximately, hy
weight of 79~ mineral oil, 18% of soap emulsifier and 3%
of a mixture of biocidal and stabilizing agents. This
soluble oil cutting fluid is prepared by dilu~ing the
above-described emulsion with water in a weight ratio of
at least a~out 50 to 1. This solution is directed over a
metal article upon which a cutting tool is removing
material. The cutting fluid cools the article being formed,
flushes away the chips being generated in the cutting
operation and also lubricates the surface being cut.
After a period of operative life, the cutting
oil fluid becomes unsuitable for furthex use and must be
discarded~ Being ~n emulslonr the material may not
be directly discarded because it contains oil in the water.
Therefore, b~fore the material can be discarded, it is
necessary to break the emulsion and thereby separate the
oil rom the water, permitting the clean water to be dis-
carded and the oil to be recycled or discarded in a manner
appropriate for hydrocarbon materials.
A more impor~ant use is for the clean-up of
rinse waste waters from the rinsing of machined parts in
which the water may contain a dilute concentration o~
emulsified oil generally ranging from 500 to 4000 ppm.
Our process is one which provides an economical
; and efficient method or breaking an oil-in-water emulsion.
The method of our invention will be best understood by
considering the contents of the following description
'~ .
; :
.
.
while referring to the accompanying drawings, in which:
FIGURE 1 is a drawing which depicts a schematic
outline of the system in which the ~nethod of our invention
can be practiced. FIGURE 2 is a graphical presentation
showing ~he effect of using various amounts of current in
the method o our invention.
Oily waste water from a plant, such as discarded
waste water from rinsing of parts machined using oil emul-
sion coolant is delivered by means of a pump 10 to a
storage tank 12. In this tank, heat and air are added hy
means of a heater 14 and an air delivery system 1~ ~sche-
matically represented by a plurality of arrows). Any ree
oil-which flows to the surface in the storage tank may be
skimmed of and removed. Also, in the receiving and
storage tank, the pH of the oily waste water may be
adjusted to a pH in the range of 6 ~o 10 by means of a pH
system 18. The amount of material added from the
C~ o I
pH ad~it~on system to achieve the desired pH is calculated
in normal pH calculating procedures. A small amount of
salt also may have to be added to promote ionic conduc-
tivity and prevent passivation of the electrode. The addi-
tion of heat and air to the tank is simply to keep the
system at set conditions for further treatment.
A second pump 20 continuously withdra~s a portion
of the oily waste water héld in the storage tank 12 and
delivers that oil-in-water emulsion to an eléctrolytic cell
generally indicated by the numeral 22. This cell has a
receiving æone 24 into which the ernulsion is initially
delivered. The cell also has a ferrous ion producing anode
in ~he form of an iron chip anode 26 which can be formed
from the metallic chips generated from any steel or iron
machining operation. This iron chip anode is slowly dis-
~i solved to produce ferrous ions by the passage of alectric
-. " ~''~. " '
.
;2Z~ ,
current therethrough. The rate at which the anode is
dissolved is a function of the amount of current passing
therethrough. The higher the amount of current, the more
iron is dissolved but, of course, the more power that is
used. Fresh iron chip additions from time to time to this
electrode chamber assure that the chamber contains suffi-
cient iron electrode for continuously carrying out the
process. When using the electrode we require that less
than a passivating current be passed therethrough. By
this we mean that a current density is not reached which
would result in a discontinuation of iron dissolution and
a consumption of power to decompose water instead.
The amount of power passing through the anode
controls the amount of iron which is dissolved into the
oil-in-water emulsion passing through the anode. If one
visualizes the flow of the emulsion through the anode as a
slug-type flow in which a unit volume of emulsion moves
into the anode is held therein and is treated and then
moved therethrough, then it will be easy to understand
that on one side of the iron chip anode a slug of emulsion
has no iron therein, that the iron is placed in the emul-
sion ~o a p~cular conoentra~tion a$ th~t sl~ o~ emulsion passes
thro~gh the iron chip anode and khat after passage through
the node the slug of emulsion will have a particular level
of iron therein which will general~y remain constant.
Thus, the process of iron enterin~ the emulsion is one
that occurs almost instantaneously in that the concentra-
tion of e1ectric~lly dissolved ferrous ions in the emul~
sion goes from zero on one side of the iron chip anode to
r~ .
, . ' . . . . .
1 a certain ~ixed level on the other side of the iron anode,
2 the fixed level belng determined by the amount of power
3 being used at the anode. The particular manner for con-
4 trolling the amount of power used to achieve the best
results will be discussed in greater detail hereinbelow.
6 After a slug of emulsion passes through the iron
7 chip anode 26, it passes through a cathode screen 28 at
8 which hydroxyl ions are generated to complete the electro-
9 chemical reaction as is known in the art. About this posi-
tion, air is added by an air supply system 30. The air
ll supplied is in the form of tiny bubbles in order to provide
12 for oxidization of ferrous ions to ferric ions and to
13 develop a mechanism by which the oil coming out of the
14 emulsion may be picked up and floated to the surface. The
oil waste, which is an oil-iron hydroxide sludge 32, begins
16 to ~orm on the surface of the emulsion in an emulsion
17 breaking zone 34 of the electrolytic cell 2Z. This zone
18 is sufficiently long to permit substantially full separa-
l9 tion of the oily waste from the water.
Near the end of the oil emulsion breaking zone 34
21 of the electrolytic cell 22 is provided a sludge removing
22 system generally identified by the numeral 36. This system
23 includes a conveyor 38 which transports the sludge 32 up-
24 wardly from the water and deposits it in a sludge receiving
device 40O
26 Clear water is withdrawn from the bottom oE the
27 emulsion breaking zone 34 by means of a pipe 42. The water
28 from this pipe may be pumped to a sewage system or may be
29 recycled depending upon the clarity thereof and the
7S
requirements for process water in the plant using this
system.
In accordance with the teachings of this inven-
tion,- the method of this invention is operated in the
following manner. Power is applied at the anode 26 in
accordance with the following equation. This equation is
based on a unit area of the electrode and each unit area
has the same power applied thereto.
The power applied is in accordance with the
formula i- (N)f(Co)(10 4) wherein: N is any number in the
range from 20 to 50, f is the flow rate of the emulsion
per unit area of electrode in cc/minutes; Co is the initial
concentration o~ oil in the water in parts per million;
and i is equal to the current per unit area of electrode
in milliamperes. This equation, in the form N = i(10+4)/fCo,
is shown plotted in ~IGURE 2 versus ~he final concentration
in parts per million of oil in the waste water. It should
be noted from the graph that when N is in the range rom
30 to 50, the parts per million of oil in the final product
20 i5 very low. It is also important to note that the cur~e
flattens out at about the 40 to 50 range and, thus, there
is no need o~ exceeding this amount of current. In other
words, greater amount of current representative of higher N
values do not produce any significantly greater reduction
of oil in the waters being treated. Thus, we teach that it
is not desirable to operate at an N value greater than 50
because one simply is wasting power andexperiencing no added
benefit therefrom.
.~
1 In accordance with the preferred teachings o~ the
2 method of this invention, the iron chip anode 26 is
3 operated with the power per unit area being determined in
4 accordance with the formula discussed above in which N is
in the range from 20 to 50. Operation of this cell at such
6 a power load has allowed us to process 0.2 gallons per
7 minute of a solution containing 2000 parts per million of
8 oil per square foot of elec~rode. ~enerally, the water
9 delivered through the pipe has a final concentration of
oil contained therPin of about 10 parts per million~
11 Having described our method herein, it is
12 apparent that those skilled in the art will ~ind ways of
13 modifying the method which still falls within the true
14 spirit and scope of this invention. It is intended that
all such modi~ications be included within the scope o~ the
16 appended claims.
,
`` - 10 -
- .
, , ~
