U.S. patent application number 10/662610 was filed with the patent office on 2004-04-01 for multi-stage engine coolant recycling apparatus and process.
Invention is credited to Haddock, Marvin E..
Application Number | 20040060870 10/662610 |
Document ID | / |
Family ID | 22668270 |
Filed Date | 2004-04-01 |
United States Patent
Application |
20040060870 |
Kind Code |
A1 |
Haddock, Marvin E. |
April 1, 2004 |
Multi-stage engine coolant recycling apparatus and process
Abstract
A multi-stage apparatus and a process for recycling used engine
coolant employs a combination of filtration, dissolved air
floatation, centrifugation (hydrocyclone separation),
semi-permeable nano filtration, reverse osmosis, and continuous
deionization for separating ethylene glycol, with or without
propylene glycol, and water from used engine coolant. The engine
coolant is pre-filtered through a series of filters. The filters
remove particulate contaninates. This filtered fluid is then
subjected to dissolved air floatation and/or centrifugation to
remove organic petroleum contaminants. Then, it is pressurized
prior to being passed through semi-permeable nano filtration. The
nano filtration separates the feed stream into a ultra filtration
solution and a concentrated waste solution. The concentrate
solution is returned to a centrifuged coolant tank for continuous
circulation through the nano filtration device. The ultra
filtration solution is pressurized and passed through a reverse
osmosis device, which separates the feed stream into a permeate
solution and a concentrated waste solution. The concentrated waste
solution is returned to a ultrafiltrate solution tank for
continuous circulation through the reverse osmosis device. The
permeate solution is subjected to final refining by continuous
deionization which reduces ionic contaminants. Depending upon
environmental conditions, a heater and/or heat exchanger maintain
the temperature of the process solution within an optimum
pre-established operating temperature range.
Inventors: |
Haddock, Marvin E.; (Austin,
TX) |
Correspondence
Address: |
FULBRIGHT & JAWORSKI L.L.P.
600 CONGRESS AVE.
SUITE 2400
AUSTIN
TX
78701
US
|
Family ID: |
22668270 |
Appl. No.: |
10/662610 |
Filed: |
September 15, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10662610 |
Sep 15, 2003 |
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09845099 |
Apr 27, 2001 |
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6620327 |
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09845099 |
Apr 27, 2001 |
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PCT/US99/25337 |
Oct 28, 1999 |
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PCT/US99/25337 |
Oct 28, 1999 |
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09182393 |
Oct 28, 1998 |
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6187197 |
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Current U.S.
Class: |
210/652 ;
210/221.1; 210/243; 210/259; 210/295; 210/321.6; 210/703;
210/748.01; 210/781 |
Current CPC
Class: |
F01P 2011/061 20130101;
B01D 61/022 20130101; B01D 61/04 20130101; B01D 61/025 20130101;
B01D 61/145 20130101; B01D 61/48 20130101; F01P 2011/063 20130101;
B01D 61/58 20130101; B01D 61/027 20130101; F01P 11/06 20130101 |
Class at
Publication: |
210/652 ;
210/703; 210/748; 210/781; 210/221.1; 210/243; 210/259; 210/295;
210/321.6 |
International
Class: |
B01D 061/02; B01D
036/02; B01D 021/26 |
Claims
What is claimed is:
1. A process for purifying engine coolant, comprising: a) providing
engine coolant to be purified; b) treating said coolant through a
reverse osmosis process; c) treating said coolant through a
electrolysis deionization process; and d) collecting purified
coolant.
2. The process for purifying engine coolant according to claim 1,
wherein the purified coolant meets ASTM standards.
3. The process for purifying engine coolant according to claim 1,
further comprising filtering said coolant.
4. The process for purifying engine coolant according to claim 3,
further comprising filtering said coolant prior to passing said
coolant through said reverse osmosis process.
5. The process for purifying engine coolant according to claim 3,
further comprising filtering said coolant by at least two filters
positioned in series along a flow path.
6. The process for purifying engine coolant according to claim 5
wherein the filters in series have decreasing pore size.
7. The process for purifying engine coolant according to claim 1,
further comprising subjecting said coolant to dissolved air
floatation prior to passing said coolant through said reverse
osmosis process.
8. The process for purifying engine coolant according to claim 1,
further comprising removing particulate matter from said coolant by
centrifugation.
9. The process for purifying engine coolant according to claim 8,
wherein said centrifugation occurs prior to passing said coolant
through said reverse osmosis process.
10. The process for purifying engine coolant according to claim 1,
further comprising filtering said coolant with semi-permeable nano
filtration.
11. The process for purifying engine coolant according to claim 10,
wherein said semi-permeable nano filtration occurs prior to passing
said coolant through said reverse osmosis process.
12. The process for purifying engine coolant according to claim 10,
further comprising pressurizing said coolant to a pressure of 350
to 600 psi in performing said semi-permeable nano filtration.
13. The process for purifying engine coolant according to claim 1,
further comprising pressurizing said coolant to a pressure of 50 to
300 psi prior to passing through said reverse osmosis process.
14. The process for purifying engine coolant according to claim 13,
further comprising pressurizing said coolant to a pressure of 350
to 600 psi prior to passing through said semi-permeable nano
filtration.
15. A process for purifying engine coolant comprising: a) providing
engine coolant to be purified; b) filtering said coolant; c)
subjecting said coolant to dissolved air floatation; d) removing
particulate matter from said coolant by centrifugation; e)
filtering said coolant with semi-permeable nano filtration; f)
passing said coolant through a reverse osmosis process; and g)
passing said coolant through electrolysis deionization process.
16. A process for purifying engine coolant, comprising treating
said coolant to a reverse osmosis process wherein a purified
coolant meets ASTM standards as detailed in FIG. 5.
17. An apparatus for purifying engine coolant, comprising: a) a
reverse osmosis separator through which said coolant is passed; b)
a electrolysis deionizer; and c) a purified coolant collector.
18. The apparatus according to claim 17, further comprising a
filter.
19. The apparatus according to claim 18, wherein said filter is
positioned along a flow path before said reverse osmosis
separator.
20. The apparatus according to claim 19, further comprising at
least two filters positioned in series.
21. The apparatus according to claim 20, wherein said filters in
series have decreasing pore size.
22. The apparatus according to claim 17, further comprising a
dissolved air floatation separator through which said coolant is
passed prior to passing through said reverse osmosis separator.
23. The apparatus according to claim 17, further comprising a
centrifuge through which said coolant is passed prior to passing
through said reverse osmosis separator.
24. The apparatus according to claim 17, further comprising a
semi-permeable nano filtration process through which said coolant
is passed prior to passing through said reverse osmosis
separator.
25. The apparatus according to claim 24, further comprising a
pressurizer to pressurize said coolant to 350 to 600 psi prior to
passing through said semi-permeable nano filtration process.
26. The apparatus according to claim 17, further comprising a
pressurizer to pressurize said coolant to 50 to 300 psi prior to
passing through said semi-permeable reverse osmosis process.
27. The apparatus according to claim 26, further comprising a
pressurizer to pressurize said coolant to 350 to 600 psi prior to
passing through said semi-permeable nano filtration process.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an apparatus and an
improved process for recycling used glycol-based engine
coolant.
[0003] 2. Description of Related Art
[0004] Engine coolants are used to protect internal combustion
engines from temperature extremes. The coolants employ ethylene
glycol with or without propylene glycol to lower the freezing point
and raise the boiling point of water in internal combustion
engines. These coolants also commonly employ corrosion inhibitors
to counteract the corrosion associated with engine coolants. The
coolants typically contain ethylene glycol, with or without
propylene glycol, at a concentration of about 30 to 70% by volume,
and corrosion inhibitors at approximately 1 to 3% by weight.
[0005] The American Society of Testing Materials (ASTM) sets
recognized industry standards for the components of engine
coolants, both virgin and recycled. The Maintenance Council (TMC)
of the American Trucking Association also sets recognized standards
for engine coolants.
[0006] The useful life of engine coolants is limited by the
degradation over time of the glycol and inhibitor components. The
glycol components (ethylene glycol with or without propylene
glycol) chemically break down into various undesirable organic
acids. The accumulation of these acids lowers the pH of the engine
coolant composition from an initial pH of approximately 10. When
the pH decreases below approximately 8.3, aluminum, steel and iron
corrode, weakening the components that they comprise and resulting
in eventual component functional failure. In heavy-duty
applications, the necessary and commonly practiced addition of
supplemental coolant additives (SCAs) increases the total dissolved
solids (TDS) in the coolant until a saturation threshold is
approached, at which point severe engine damage is probable.
Coolant with excessive TDS is associated with premature failure of
radiators, water pumps and other cooling system components. Copper
and brass also corrode upon extended exposure to engine coolant. In
addition, the lead solder in radiators can degrade into lead oxide,
eventually allowing leaks to develop in the coolant system heat
exchangers.
[0007] Because of the well-established corrosive effects of the
circulating coolant, initial corrosion inhibitors and SCAs are
conventionally added directly to the engine coolant. However, with
time the inhibitors are consumed, allowing the corrosive effects of
the engine coolant to damage the entire cooling system.
Implementation of certain maintenance procedures is necessary to
prevent such damage. The most common procedure is removal and
replacement of the engine coolant after a pre-established time or
service interval. In some instances cooling system additives, which
are usually alkaline and include SCAs, are directly added to the
coolant to extend the protective properties, decrease the corrosive
effects, and postpone replacement of the coolant.
[0008] Recycling used engine coolant has become increasingly
desirable due to two significant factors. First, engine coolant
frequently merits designation as a hazardous waste under the
Federal Clean Water Act. Federal and some state environmental
protection agencies have instituted strict regulation of the
disposal of used engine coolant. In some cases the disposal of
engine coolant requires imposition of waste disposal fees and
surcharges. Second, ethylene glycol, the principal cost component
of engine coolant, has become more expensive. Dramatic price
fluctuations and significant shortages in the supply of ethylene
glycol have occurred. Therefore, there are both environmental and
economic pressures to recycle engine coolant and recover the glycol
component in an efficient and cost-effective manner.
[0009] A number of processes and systems have been advanced as
possible commercially viable solutions to the problem of recycling
engine coolant. Most of the processes have employed filtration, ion
exchange or distillation techniques in various forms. Distillation
of used engine coolant alone sometimes produces an acceptable end
product; however, it is an expensive, energy consumptive, and
relatively slow process which is not suitable for many potential
users. Furthermore, distillation equipment is capital intensive and
is associated with various workplace hazards. Relatively simple
chemical and filtering techniques have been employed apart from and
in conjunction with distillation for recovering and recycling used
engine coolant. Engine manufacturers have required more thorough
purification of the fluid than can be accomplished through simple
or chemical filtration methods. This requirement has been
underlined in light of advancements in antifreeze chemical
inhibitor technologies, and requirements that all preexisting
inhibitor chemistries be removed from the used engine coolant have
been imposed.
[0010] An early system for recycling engine coolant used
"chemically assisted filtration." The concept of this system was
that aeration and pH adjustment of coolant would precipitate
contaminants, and the addition of chemical additives would restore
adequate functionality to permit extended use of the coolant. U.S.
Pat. No. 4,946,595 discloses a process for physically and
chemically treating used engine coolant of a type which contains
one or more glycol and/or alcohol based antifreeze components. The
disclosed process includes the steps of oxidation with one or more
known oxidizing agents, precipitation with one or more known salt
forming agents, and filtration. Chemical additives are added to
enhance the oxidation and precipitation. Various corrosion
inhibitors and buffering agents are also added to adjust the pH-of
the recovered solution. However, the appearance of coolant recycled
by chemically assisted filtration was commercially unacceptable in
many cases. There were also concerns that filtration alone did not
provide adequate purification of the recycled coolant.
[0011] Another method available for recycling engine coolant is the
reverse osmosis (R/O) process, which provides an intermediate fluid
that is pure and offers a production rate that is fairly
cost-effective compared to distillation (Huff 1992 SAE 921635). The
osmosis phenomenon is observed in nature as a distribution or
equalization behavior of naturally occurring chemicals. The R/O
process for recycling engine coolant has been described in detail
in the literature (Eaton et al., 1997 SAE 971773). U.S. Pat. No.
5,167,826 discloses an apparatus and a process for purification of
engine coolant by reverse osmosis, and a process for reinhibition
with anti-corrosion inhibitors and buffering agents common to
antifreeze manufacturing. Reverse osmosis is a faster and more
economical method of coolant recycling than distillation, and
provides far better purification than filtration.
[0012] There are, however, shortcomings to the RIO process for
recycling used engine coolant described in U.S. Pat. No. 5,167,826.
In particular, when oil or similar petroleum products enter the R/O
system, they coat the membranes, "blinding" them, and reducing
production of recycled coolant to a trickle. In addition, recycling
engine coolant by the R/O system alone does not decrease
conventional inhibitor anions in the coolant to a level that would
permit reinhibition of the intermediate fluid either with
traditional, inorganic technologies, or European style carboxylate
inhibitors.
[0013] Thus, there has been a need for a way to provide a highly
purified recycled engine coolant at a cost advantageous compared to
virgin coolant.
SUMMARY OF THE INVENTION
[0014] Briefly stated, the invention in a preferred form is an
apparatus and a process which is employed for recycling the glycol
and water components of used engine coolant. The used engine
coolant is treated through a sequence of purification processes to
result in a final recovered, pure fluid that consists of water,
ethylene glycol with or without propylene glycol, and less than
0.001 weight percent contaminants.
[0015] The used engine coolant is filtered to remove various
particulate substances, using one or more filters in series along a
flow path. If more than one filter is used, the filters may be of
decreasing pore size along the flow path. The filtered coolant is
then introduced into a dissolved air floatation separator, a
hydrocyclone separator, or a filter press to remove petroleum
contaminants (oils and fuels) and particulates from the filtered
coolant. The dissolved air floatation separator and hydrocyclone
separator may be used together in series. The removal of petroleum
contaminants and particulates is extremely important for
trouble-free operation for the membrane separation steps
(semi-permeable nano filtration and reverse osmosis). The fluid,
now purified of oils, grease, fuels, and larger particulates is
collected in a holding tank where it is pressurized to a pressure
in the range of 50 to 1200 psi, more particularly 100 to 800 psi,
or even more particularly 350 to 600 psi and then passed through a
semi-permeable nano filtration device whereby glycol and water are
separated from the remaining fluid by a semi-permeable nano
filtration process. The nano filtered filtrate is collected in a
permeate holding tank. The concentrate material separated from the
filtrate is returned to previous holding tank for additional
passage through the semi-permeable nano filtration device. The
filtrate in the permeate holding tank is repressurized to a
pressure in the range of 50 to 1200 psi, more particularly 50 to
800 psi, or even more particularly 50 to 300 psi, and passed
through a semi-permeable reverse osmosis device, whereby glycols
and water are further purified. Concentrate separated from the
purified glycols and water is passed back to the permeate holding
tank for additional passage through the reverse osmosis process.
The permeate is now clear in appearance, but contains anionic
contaminants from tap water (for example, chlorides) and from the
old inhibitors (for example, nitrite and borate). The recovered
glycol and water (permeate) are transported to the continuous
electrolysis deionization unit (CDI). The CDI reduces the
concentration of undesirable anions in the permeate. Trace
contaminants remaining may be removed by distillation, or
purification through a dual-bed deionization device, resulting in a
solution of 99.999% pure water/glycol coolant base fluid. The
recycled coolant is purified sufficiently to meet ASTM coolant
standards when properly reinhibited.
[0016] An object of the invention is to provide a new and improved
apparatus and process for commercial recycling of used engine
coolant.
[0017] Another object of the invention is to provide a new and
improved apparatus and process wherein used engine coolant may be
recycled in a relatively inexpensive and efficient manner.
[0018] A further object of the invention is to provide a new and
improved apparatus and process for recovering used engine coolant
which, upon addition of suitable additives, results in a recycled
coolant composition having effective corrosion inhibitor
properties, effective freeze and boil protection properties, a pH
between approximately 8.0 and 10.5, and additional properties which
satisfy standard specifications for new and recycled engine
coolant.
[0019] A further object of the invention is to advance the
purification technology of the apparatus and process to permit the
transformation of coolant inhibited with "conventional" (inorganic)
inhibitor technologies to coolant that may be inhibited either
conventionally or with carboxylate technologies often referred to
as "extended service" or "long life" inhibitor systems.
[0020] A yet further object of the invention is to provide a new
and improved apparatus and process for recycling engine coolant
which apparatus and process are capable of separating a much higher
volume of pure glycol and water from the used engine coolant and
does not require distillation or other energy consumptive
processes.
[0021] Other objects and advantages of the invention will be
apparent from the drawings and the specification.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The following drawings form part of the present
specification and are included to further demonstrate certain
aspects of the present invention. The invention may be better
understood by reference to these drawings in combination with the
detailed description of specific embodiments presented herein.
[0023] FIG. 1 is a flow diagram of an apparatus for recycling
engine coolant in accordance with the present invention.
[0024] FIG. 2 is a chart showing the percentage of contaminants
remaining in the coolant after permeating through the reverse
osmosis membrane.
[0025] FIG. 3 is a schematic drawing of a reverse osmosis device as
employed in FIG. 1.
[0026] FIG. 4 is a chart showing the percentage of petroleum
removed by the dissolved air floatation process.
[0027] FIG. 5 is a chart providing ASTM/IMC Standards and comparing
the properties of virgin coolant and coolant recycled in accordance
with the present invention.
DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0028] The following examples are included to demonstrate preferred
embodiments of the invention. It should be appreciated by those of
skill in the art that the techniques disclosed in the examples
which follow represent techniques discovered by the inventor to
function well in the practice of the invention, and thus can be
considered to constitute preferred modes for its practice. However,
those of skill in the art should, in light of the present
disclosure, appreciate that many changes can be made in the
specific embodiments which are disclosed and still obtain a like or
similar result without departing from the spirit and scope of the
invention.
EXAMPLE 1
Flow Diagram for Recycling Engine Coolant
[0029] A flow diagram for recycling engine coolant according to the
invention is illustrated in FIG. 1. Used engine coolant is received
and processed to recover ethylene glycol, with or without propylene
glycol, and water. The recovered solution may be then used as the
primary ingredient to produce a new engine coolant. The apparatus
for accomplishing purification of the used engine coolant is a
relatively large system which may require, for example, a dedicated
processing facility having significant quantities of recyclable
used engine coolant imported from waste generation locations. In
one embodiment, the apparatus is arranged in a building such that
local and other building codes are met, and adequate storage is
provided either internally or externally. A dike is constructed
around the apparatus to ensure containment of any coolant in case
of a spill.
[0030] The used engine coolant is delivered to raw storage tanks
which may be 2,000-20,000 gallon iron vessels, or similar, for
example, stainless steel, plastic, or fiberglass, plumbed together
with isolation valves between the tanks. The tanks have inlet
conduits and outlet conduits that provide fluid communication with
the processing components and delivering vehicles. The recycling
process is a continuous non-distillation separation process wherein
the ethylene glycol, with or without propylene glycol, and water
are continuously separated from the raw used coolant solution.
[0031] The flow path through the apparatus is defined by several
conduits. The outlet conduit from the raw storage tanks carries
used coolant to one or more filtration units for the initial
filtration stage. Coolant passes through the filtration unit(s) and
emerges as initial filtrate solution. In a preferred embodiment,
three filtration units are positioned in series along the flow
path. The filtration units may contain, for example, 100 micron, 50
micron and 10 micron industrial water filters. The filter porosity
may be varied based on the character of the input used engine
coolant. Filter pressure monitor gauges are interposed in the flow
path upstream and down stream from each of the filtration units to
monitor the pressure drops across the filters, so that any clogging
or defect in the filtration units can be easily detected, collected
waste materials can be appropriately removed and the filters
replaced.
[0032] During the initial filtration stage, particulate substances
having a diameter in excess of 10 microns are effectively removed
from the coolant and deposited on the filters. A low inlet pressure
switch monitors the pressure of the initial filtrate exiting the
initial filtration stage. The switch communicates with a relay
which terminates the operation if the pressure of the initial
filtrate solution exiting the initial filtration stage falls below
a certain predetermined threshold.
[0033] The initial filtrate solution is transferred via conduit to
the dissolved air floatation separator (Baryon Industries, Inc.
#CLFR-05/AD-DRM). The dissolved air floatation separator removes
the majority of petroleum based contaminants from the partially
purified coolant. Petroleum based contaminates have been shown to
drastically reduce the efficiency of membrane separation systems.
To further ensure that the membranes of the membrane separation
systems are not exposed to petroleum contaminants, the partially
purified coolant from the dissolved air floatation separator is
transferred by conduit for centrifugation in a hydrocyclone
separator (Vortiol Separation Systems, Pk-Pn separator), which
removes additional oil and other contaminants, producing
centrifuged coolant. The dissolved air floatation separator may be
eliminated and the hydrocyclone separator used alone to remove
petroleum based contaminants. A filter press, such as JWI model
J-press #2772, may be substituted for the hydrocyclone
separator.
[0034] The centrifuged coolant is collected in an intermediate
storage tank and is then pressurized to 50 to 1200 psi, more
particularly 100 to 800 psi, or even more particularly 350 to 600
psi by two centrifugal pumps operating in opposing directions (one
clockwise, the other counter-clockwise). The pressurized coolant is
passed via conduit to a semi-permeable nano filtration device
(Environmental Pro, model Delta 10, 15, or 25) for additional
purification. The coolant passes through the membranes of the
semi-permeable nano filtration device under pressure, resulting in
an ultra filtrate solution which is collected in an ultra filtrate
storage tank.
[0035] The ultra filtrate solution is pressurized to 50 to 1200
psi, more particularly 50 to 800 psi, or even more particularly 50
to 300 psi and is purified by passage through a reverse osmosis
device (Environmental Pro, model Delta 10, 15, or 25), resulting in
a reverse osmosis permeate. The original reverse osmosis device
used was the REC-1 (Recycled Engine Coolant Corp.)
[0036] The reverse osmosis permeate, which constitutes the nearly
pure recycled material, is deposited in a permeate storage tank.
The permeate tank may be 500 to 5,000 gallons and is constructed of
non-reactive material, for example, stainless steel. Permeate from
the permeate storage tank is transported by conduit to a continuous
electrolysis deionization unit (CDI) (U.S. Filter, Iron Pure CD140
or CDI H60). The solution exiting the CDI is passed to a dual bed
(cation/anion) ion exchange (D1) processing device (U.S. Filter,
models 2554 and 2555 in parallel, or model 2551). The CDI and DI
device separate any remaining impurities from the pure recycled
solution. The final, pure recycled solution obtained from the dual
bed deionization unit is delivered to a chemical mixing tank
composed of a non-reactive material, for example, stainless steel,
plastic, or fiberglass. The chemical mixing tank thus contains the
pure recycled solution which is separated by the apparatus and
forms the base fluid material for a new engine coolant.
[0037] The chemical mixing tank has a large auger-type mixing
device to prevent excessive introduction of air. Liquid or solid
additives may be added to the pure recycled solution in the
chemical mixing tank either through a conduit from an additive
storage tank, or manually through an opening in the top of the
tank, to produce the new engine coolant solution.
[0038] The recycled coolant is typically verified to meet ASTM
coolant standards at the quality control station before delivery to
the customer.
[0039] While the preferred embodiment of the foregoing invention
has been set forth for purposes of illustration, the foregoing
description should not be deemed a limitation of the invention
herein. Accordingly, various modifications, adaptations and
alternatives may occur to one skilled in the art without departing
form the spirit and the scope of the present invention.
EXAMPLE 2
Removal of Emulsified Oils
[0040] Contamination by emulsified oil in used engine coolant
significantly limits the use of reverse osmosis (R/O) in purifying
efforts. Emulsified oils are suspensions of microscopic oil
droplets in the used coolant which are created in the process of
removing, storing, transferring or disposing of the used coolant.
The emulsified oil is typically used engine (mineral) oil, but
additives consisting of mineral oil combined with petroleum
sulfonate and/or amine soaps that facilitate emulsification may
also be present. This emulsified oil coats the R/O membrane,
fouling it. When fouling occurs, production rates of purified
coolant are drastically reduced. If ignored, the membranes could
become completely coated or "blinded," requiring frequent back
flushing or some other regeneration procedure. Therefore, once this
fouling is suspected, the system must be shut down, a soap solution
mixed, and the membrane cleaned of the emulsified oil contaminates.
This is a labor-intensive and onerous procedure, thus a
pre-treatment which would eliminate emulsified oil in the coolant
prior to subjecting it to reverse osmosis was needed. Tests were
run on various pre-treatment methods, such as chemical flocculates,
clarification treatments, and dissolved air floatation (DAF).
[0041] A pre-treatment sequence was developed in which used coolant
was introduced into a large feed tank with a capacity of
approximately 20,000 liters. Some contaminates were gravity
separated and removed as sludge. The remaining used coolant was
filtered through commercial water filters rated at 50 and 10
microns, and then passed through a dissolved air floatation
separator (Baryon Industries, Inc. #CLFR-05/AD-DRM), which
efficiently removed petroleum contaminants. A series of laboratory
bench tests were conducted with representative feed samples to
determine if traces of oil remained. Test results were conclusive
that there was less than 2% of the original oil concentration
remaining. To purge the remaining oils and particulates, a
hydrocyclone separator (Vortoil Separator Systems, Pk-Pn separator)
was introduced. A filter press, such as JWI model J-press #2772,
could be used in place of the hydrocyclone separator. Tests of the
fluid, including analyses for oil, trace metals, and chloride,
showed that no trace of oil was detectable in the R/O feed stream
as it exited the hydrocyclone separator. The benefit of using the
DAF/hydrocyclone separator pretreatment was to extend the cleaning
interval of the reverse osmosis system from once every 2 days to
weekly, monthly or longer, depending upon influx of feedstock and
pretreatment. This greatly enhanced production of recycled
coolant.
EXAMPLE 3
Reverse Osmosis Process
[0042] In the R/O process, a feed stream of used coolant is pumped
through a membrane unit. The input stream is a solution, having
been treated to remove suspended matter. The pre-treated feed
stream consists of the ethylene glycol with or without propylene
glycol, water, and dissolved solids including molybdate, borate,
nitrates, nitrites, phosphate, sulfate, metal ions, carboxylates
and chloride. In addition, some dissolved low molecular weight
materials pass into the membrane under applied hydrostatic
pressure.
[0043] Two factors must be considered in selecting an appropriate
membrane for use in the R/O process: porosity and membrane
capacity. The porosity of the membrane determines the degree of
purification, thus the pore structure of the membrane chosen should
provide for complete removal of contaminants. The R/O process
membranes of the present invention were 150-300 dalton
membranes.
[0044] Membrane capacity must also be carefully considered in
designing the R/O process. Membrane capacity is determined by
multiplying the surface area by the "flux," defined as the volume
of water permeated per unit membrane area per unit time. The
standard units are GPD/ft.sup.2 (m.sup.3/m.sup.2/day). Since
capital cost and operating cost increase proportionally with
membrane area, it is highly desirable to maximize membrane flux.
The flux does not necessarily predict the volume of non-water
permeate produced per unit area per unit time; experimentation must
be performed to measure actual production for a given type of fluid
other than water. Purity and flux are inversely proportional. To
develop the commercial system, actual production rates were
measured. These rates were then compared to flux values to develop
a predictive conversion factor. The conversion factor was used to
select the size of membranes required to achieve production goals.
The present invention employed sixteen 4 inch diameter.times.40
inch length membranes. Of course, membranes of other diameters, for
example 2.5 to 40 inches, and lengths may also be used in the
present invention.
[0045] The viscosity of the input into the R/O system varies with
the type and ratio of glycol to water in the input stream.
Viscosity also increases as temperature decreases. Tests were
conducted to determine the influence of several process variables
on permeate rate of flow: feed circulation rate, feed pH, operating
temperature, operating pressures, the degree of feed concentration
and time. The data showed that productivity increased with
temperature. Therefore, it is desirable to maintain a temperature
as high as possible, but at which the membranes can operate without
either short-term failure or long-term degradation. Depending upon
local climactic conditions, a heater or heat exchanger,
appropriately sized for the tank used, may be employed to maintain
the temperature in a normal operating range of 75.degree. F. to
125.degree. F. Flux was inversely proportional to glycol
concentration and to ion concentration. Other variables did not
demonstrate significant influence upon flux. Samples were pulled at
regular intervals and chemically analyzed at independent
laboratories. These analyses were used to determine membrane
rejection efficiency on the feed concentrate contaminants. Flux
versus time was recorded. Overall performance of the system was
evaluated in terms of system productivity, permeate quality and
operating cost.
[0046] The data showed that this process recovered 96% of the
ethylene glycol, propylene glycol and water in the used coolant,
leaving 4% of the input volume as waste to be disposed of either by
incineration or contract hauling. It may be possible to further
reduce the waste volume by recovering even more of the glycol and
water through local vacuum distillation of the concentrate. About
90% of the concentrated waste consisted of glycol and water.
[0047] To improve product purity while maintaining production
rates, a two-stage membrane treatment strategy was implemented. Use
in the R/O system of a low-flux, small porosity membrane, necessary
to maximize purity, presented a severe bottleneck to system flow
when used to directly process the pretreated used coolant. The
decision was made to install two membrane systems in series, a
"two-stage" system, based on data from experimentation with various
membranes. The first stage employed semi-permeable nano filtration
membranes, somewhat more porous than true reverse osmosis
membranes, but along the same line of technology. The second stage
employed low-flux, small porosity membranes. The use of the
two-stage membrane process presented to the R/O system a nano
filtered fluid that was dramatically lower in solids content. This
prior processing of the coolant by semi-permeable nano filtration
removed a majority of contaminants and permitted optimum
productivity of permeate through the R/O membranes.
[0048] The permeate from the R/O unit was sufficiently pure to
allow it to be reused in most engine coolant applications. In fact,
it has been used very successfully and its performance has been
reported previously (Eaton, 1997). This permeate varies in
percentage of ethylene glycol depending on the percentage of
ethylene glycol in the input stream. To ensure acceptability to all
engine original equipment manufacturers (OEMs) a post-R/O polishing
process has been developed. When this step is accomplished, an
inhibitor package is added to complete the process of formulating
coolant. This formulated coolant will meet ASTM and TMC RP-329
standards.
[0049] Tests conducted by the U.S. Army confirmed that the recycled
coolant resulting from the method of the invention met all Army
requirements. The disclosed method is one of the few processes that
have been approved to recycle coolant for the U.S. Army. Detroit
Diesel Corp. has also approved of the R/O process (Detroit Diesel
Coolant Selections Guide, publication 7SE 298 9804).
[0050] Some newer cars and trucks use carboxylate inhibited
coolant. In order to make use of this inhibitor package, it is
desirable to further purify the R/O permeate, reducing chloride and
borate to less than 10 ppm. Such an extremely pure coolant will
permit the option of inhibition of recycled coolant with carboxylic
acid type inhibitors.
[0051] Continuous electrolytic dialysis (CDI) of the reverse
osmosis permeate removed ions remaining in the permeate to a total
of about 100 ppm. Dual bed deionization, cost-prohibitive on less
pure coolant, was now a cost-effective way to further purify the
CDI-processed coolant. After CDI and dual bed deionization, the
purity of the final coolant is well within ASTM standards (FIG.
5).
Example 4
Working Example of Invention
[0052] Waste coolant is typically a dark-green to light brown,
milky fluid. It contains oil, grease, glycols, glycol oxidation
products, metals and metal oxides, and a mix of worn inhibitors.
The objective is to recover the reusable water and glycols, with
maximum efficiency, while removing all of the other contaminants
and chemistry.
[0053] 1. Settling
[0054] The coolant as collected at the waste generation facility is
often contaminated with external environmental matter. In spite of
efforts to maintain the coolant separate from other waste, it is
commonly contaminated with dirt, oil, grease, nuts, fuel, bolts,
and other shop artifacts. The coolant was heated and allowed to
settle before being drawn from the holding tank to the processing
plant.
[0055] 2. Simple Filtration
[0056] The primary filtration provided separation of the gross
contaminants. The chemistry of the coolant was unchanged after
filtration. A bank of step-down filters strained the coolant of
particulates with the final filters having approximately 20 micron
ratings.
[0057] 3. Dissolved Air Floatation (DAF)
[0058] The DAF system slowly floated petroleum contaminates to the
top of the processing coolant, where the foamy oil layer was
physically removed. The processed coolant was visibly greener and
cleaner, but still contained visible traces of petroleum products.
The DAF also reduced the heavy metals content of the input stream.
Analysis of the collected sludge did not reveal any leachable
metals.
[0059] 4. Centrifugation
[0060] The coolant from the dissolved air floatation separator was
centrifuged to remove the remaining petroleum contaminants. The
centrifuged coolant had a cloudy green appearance.
[0061] The preliminary treatments prevented premature blinding of
the membranes in the semi-permeable nano filtration and/or reverse
osmosis devices.
[0062] 5. Nano Filtration
[0063] To optimize production by reducing viscosity, the coolant
was pre-heated to about 100.degree. F. The semi-permeable nano
filtration and reverse osmosis units were similar in appearance and
function. The semi-permeable nano filtration device differed from
its R/O counterpart in that it operated at a slightly lower
pressure and had a set of membranes with larger porosity, giving it
a more generous flux or rate of production. This system recovered
about 90% of the fluid introduced; the remaining 10% was returned
to the holding tank immediately preceding the semi-permeable nano
filtration device containing centrifuged coolant. The nano filtrate
was light yellow to pale green in color. Most of the metals, such
as iron aluminum, lead and copper, were removed. The ethylene
glycol concentration was compromised about 1% or 2% compared to the
input stream. The concentrate that was returned to the holding tank
was about 15% higher in ethylene glycol content than the input
stream.
[0064] 6. The High Pressure Reverse Osmosis (R/O)
[0065] Reverse osmosis addressed elimination of the
difficult-to-remove contaminates that are of concern in used
coolant. The particular R/O membranes used in this process were
selected because they produced the following stripping
efficiencies:
1 Dissolved metals: over 99% removed Formate/Glycolate approx. 75%
removed Phosphate, Silicate, Molybdate over 90% removed Sulfate
over 50% removed Nitrite, Nitrate, Borate about 70% removed
Chloride varies with the chemistry of the coolant, 40% to 70%
removed.
[0066] At this point, the coolant was clear, colorless, and had
lost about 4% of its ethylene glycol content to the membrane
selection processing. Coolant permeate of this type, with corrosion
inhibitors added, has been used with great success. It is approved
for use in warranted vehicles by multiple vehicle and/or engine
OEMs. The fluid that did not pass through the R/O process was
returned to the holding tank for the ultra filtrate solution.
[0067] 7. Continuous Electrolysis Deionization (CDI)
[0068] Limitation on chloride content in recycled coolant by the
State of California, in addition to other industry discussions,
motivated purification of recycled coolant beyond that achieved
with reverse osmosis. While R/O processed coolant can often meet
virgin coolant property specifications (i.e. 25 ppm chloride), a
badly contaminated used coolant will require several time-consuming
and expensive passes through the process in order to purify the
coolant sufficiently to meet virgin specifications.
[0069] The CDI unit has been identified as a very efficient method
of removing the low-level monovalent ions such as chloride and
nitrite that escape the R/O process. Boron, which is not removed by
the R/O process, is not a problem for coolant destined for
reinhibition with boron-buffered inhibitor packages, but conflicts
with carboxylate inhibitor chemistries. The CDI removes over 90% of
these ions. After passing through the CDI, coolant was
crystal-clear and colorless. It contained less than 150 to 200 ppm
total dissolved solids.
[0070] 8. Dual-Bed Deionization (DI)
[0071] To ensure consistent low-chloride and low-boron finished
products that satisfy the desires of GM and other engine OEMs, the
proven dual-bed deionization process was used as the final
purification step. Coolant passed over the anion and cation
exchange resins exited with less than 10 ppm TDS. The DI process
could be applied to the raw coolant as received by the plant with
excellent technical results, but the ion beds would be exhausted at
such a rapid rate as to drive the cost of recycled coolant to
several times the cost of new. As a final polishing step, however,
it contributed only pennies per gallon to the processing cost.
2 Progress of a Batch of Used Coolant Through the Process Stages
Settle Filter DAF Spin Nano R/O CDI DI Mix Lead 21 21 7 6 4 0 0 0 0
Copper 8 9 6 6 2 0 0 0 0 Iron 3 4 2 2 0 0 0 0 0 Alum. 33 30 21 19
10 0 0 0 0 Phos. (P) 1757 1769 1752 1650 925 39 4 0 0 Silicon 606
615 512 489 118 12 2 0 113 Boron 684 678 691 680 593 312 298 0 159
MbO.sub.4 381 399 391 378 129 19 2 0 0 Chloride 45 51 49 50 40 18 6
1 12 Sulfate 218 224 221 230 147 39 12 0 RA 15.2 15.0 14.5 14.3 8.1
4.1 3.0 1.9 5.7 pH 10.3 10.0 9.1 9.0 8.9 8.4 8.3 8.1 10.4 FP
.degree. F. -20 -20 -21 -20 -18 -15 -15 -14 -34 FP .degree. C. -29
-29 -29 -29 -28 -26 -26 -26 -37 Cond. * 3620 3590 3521 3412 2742
2694 1592 782 1218 NO.sub.2 2838 2840 2812 2800 1298 657 152 0 1412
NO.sub.3 347 369 327 356 156 102 60 0 389 Color Brown Brown Brown
Green Light none none none green Yellow Clarity Cloudy Cloudy Foggy
Foggy clear clear dear clear clear Odor Solv. Solv. Solv Solv
glycol glycol glycol glycol TT/EG * conductivity, in umohls, of a
solution comprised of 10 ml sample and 90 ml distilled water.
EXAMPLE 5
Mobile Engine Coolant Recycling Apparatus
[0072] In this example the apparatus is a mobile, relatively
compact system. A smaller system is mounted on a sled or skid and
is moveable to various locations, such as commercial garages,
service centers, and facilities where used engine coolant is
collected. A larger version may be mounted on a truck bed. All
parts of the apparatus as shown in FIG. 1 are present in the mobile
system, with the exception that bulk storage of coolant to be
recycled is not provided. The mobile system component parts have
the same function and employ the same technology as the system
described in Example 1. The parts themselves are on a smaller scale
than those described in Example 1. For example, the mobile system
employs one or more tanks, such as 50 gallon polyethylene drums or
larger, into which the used engine coolant remotely stored can be
placed, rather than 2,000-20,000 gallon iron vessels. The
processing steps and flow path in the mobile system are the same as
those in the stationary system described in Example 1.
[0073] All of the apparatuses and processes disclosed and claimed
herein can be made and executed without undue experimentation in
light of the present disclosure. While the apparatuses and
processes of this invention have been described in terms of
preferred embodiments, it will be apparent to those of skill in the
art that variations may be applied to the apparatuses and processes
and in the steps or in the sequence of steps of the processes
described herein without departing from the concept, spirit and
scope of the invention. More specifically, it will be apparent that
certain agents which are both chemically and physiologically
related may be substituted for the agents described herein while
the same or similar results would be achieved. All such similar
substitutes and modifications apparent to those skilled in the art
are deemed to be within the spirit, scope and concept of the
invention as defined by the appended claims.
REFERENCES
[0074] The following references, to the extent that they provide
exemplary procedural or other details supplementary to those set
forth herein, are specifically incorporated herein by
reference.
[0075] U.S. Pat. No. 4,946,595, issued Aug. 7, 1990.
[0076] U.S. Pat. No. 5,167,826, issued Dec. 1, 1992.
[0077] Eaton et al., "Modern Reverse Osmosis Recycling of Used
Engine Coolant," SAE Technical Paper Series 971773, 1997.
[0078] Eaton, "Engine Reliability Experience of Mixed Vehicle
Fleets Operating on Engine Coolant Recycled with Reverse Osmosis
Technology," SAE Technical paper Series 962239, 1996.
[0079] Huff, "Using Reverse Osmosis to Recycle Engine Coolant," SAE
Technical Paper Series 921635, 1992.
* * * * *