**DryWash**

*Los Alamos National Laboratory,*

*Hughes Environmental Systems, Inc.,*

*and Global Technologies, LLC*

From industrial laundries that service military installations to retail
dry cleaners that cater to the public, the garment-cleaning industry
affects billions of people and generates nearly \$20 billion in
worldwide revenue each year. Unfortunately, the most commonly used
dry-cleaning solvent, a chlorinated organic liquid known as
perchloroethylene (perc), poses serious health and environmental
hazards, and the costs of environmental compliance for perc have
skyrocketed to the point that many cleaners cannot afford to operate. As
a result, the dry-cleaning industry is searching for a viable
alternative.

Los Alamos National Laboratory, Hughes Environmental Systems, Inc., and
Global Technologies, LLC, have developed an innovative dry-cleaning
process that offers such an alternative. This process, called
DryWash(tm), cleans with liquid carbon dioxide (CO2) that is applied
through high-pressure fluid jets. As an odorless, nonflammable,
nonhazardous solvent, CO2 effectively removes oils, sweat, and dirt from
a wide variety of fabrics. In addition to its environmental and
performance benefits, DryWash also reduces dry-cleaning costs by
lowering energy consumption, run times, and labor costs.

**The Invention\--Characteristics and Advantages**

Carbon dioxide has been used in the past to clean a variety of
electronic, mechanical, and optical equipment, but DryWash is the first
process that uses CO2 as a cleaning solvent for fabrics. In the DryWash
system, liquid CO2 at 54°F-58°F and 700 pounds per square inch\--a
pressure comparable to that used for soft-drink units at
restaurants\--is pumped from a storage tank into the cleaning vessel,
and a recirculating loop is established.

During the cleaning cycle, the CO2 must remove CO2-soluble soil,
water-soluble soil, and pigment soil (insoluble in both CO2 and water).
The CO2-soluble soils, including body oils, dissolve in the nonpolar,
liquid CO2 and are carried from the cleaning vessel. The water-soluble
soils, such as salts, are usually removed by agitation. The most
difficult to remove are the pigment soils, which are chemically bound to
garments or mechanically trapped between adjacent fibers of the fabric.

The design of the cleaning vessel makes DryWash particularly effective
at removing pigment soils. The garments are held in a perforated basket
inside a stationary cleaning vessel. To get mechanical action equivalent
to that of the rotating basket found in conventional dry-cleaning
equipment, DryWash uses a process called hydrodynamic agitation, in
which nozzles located on the inside periphery of the basket spray
high-speed jets of liquid CO2. The jets create a vortex that causes the
clothes to spin around inside the basket. As the outermost garments pass
through the fluid jets, they momentarily stretch slightly, and once they
have moved away from the jets, they relax to their original size. This
stretch-relax cycle effectively dislodges particles. The layer of
peripheral fluid immediately carries the dislodged particles out through
the drain without penetrating the bulk of the load, minimizing the
amount of soil that is redeposited on other garments.

At the end of the cleaning cycle, the liquid CO2 drains from the
cleaning vessel and is converted to a gas in the still. The dirt carried
from the garments (the only waste generated in the DryWash process)
collects at the bottom of the still, and the clean, gasified CO2 is then
recondensed for the next cycle. Because CO2 has a low surface tension
and evaporates rapidly, only a short, \"cold\" (54°F-58°F) drying cycle
is necessary.

DryWash offers numerous benefits. It is

-   **Environmentally friendly\--**Carbon dioxide is a nonflammable,
    nontoxic, inexhaustible solvent that will not deplete the ozone or
    pollute the ground water. As a result, DryWash helps the
    dry-cleaning industry comply with federal and state environmental
    regulations because the process minimizes wastes and emissions.

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-   **Effective\--**The DryWash process greatly reduces pigment-soil
    redeposition (graying), fading, and dye transfer. Because CO2 is a
    gentle solvent, it can effectively clean materials that perc often
    damages, such as leathers, furs, and accessories with sequins. In
    addition, the low temperatures of DryWash's drying cycle minimize
    heat-set stains and wrinkles.

-   **Efficient\--**Because of its short drying cycle, the DryWash
    process is complete in half the time required for conventional
    dry-cleaning processes.

-   **Inexpensive to operate\--**At 15-40¢ per pound, CO2 is a cheaper
    solvent than perc (\$5-\$7 per pound), and DryWash minimizes the
    costs of environmental compliance, such as hazardous waste disposal
    and new emissions-control equipment. In addition, DryWash
    dramatically reduces the need for costly finishing labor and nearly
    eliminates liability costs associated with damaged garments.

**Applications**

DryWash offers an efficient and environmentally friendly replacement for
the hazardous dry-cleaning methods currently used. The process can be
used to clean almost all types of fabric encountered in the drycleaning
industry, including some that cannot be cleaned by current perc
technology. DryWash's benefits have the potential to affect billions of
people worldwide who rely on retail dry cleaners or industrial laundries
at hotels, military installations, hospitals, nursing homes, and
corporate facilities.

In the future, the DryWash system and fluid jets could be used by
industries to wash dishes and to degrease and decontaminate machined
parts. Eventually, small-scale versions of DryWash may be available for
laundry or dishwashing in the home.

**Staff Who Worked On the DryWash Project**

![](media/image1.jpeg){width="5.902777777777778in"
height="4.791666666666667in"}

Shown above are the LANL researchers who worked on the DryWash process:

(back row, left to right) Jerome Barton, W. Kirk Hollis, Dennis L.
Hjeresen, Matthew Roepcke;

(front row, left to right) Craig M. V. Taylor, Leisa B. Davenhall, Leah
D. Bustos, and L. Dale Sivils. The former principal investigator of
DryWash, W. Dale Spall, is not pictured.

**Staff Biographies**

Craig M. V. Taylor, the Los Alamos principal investigator on the DryWash
project, joined the Laboratory in 1987, where he is now the team leader
for the Supercritical Fluids Facility in the Organic Chemistry Group. He
will receive his Ph.D. in physical chemistry from the University of Utah
in 1997. Currently, his research focuses on the physical properties of
supercritical fluids as these properties pertain to cleaning,
extraction, solubility, and material modification.

W. Dale Spall received his Ph.D. in analytical chemistry from the
University of New Mexico in 1970 and joined Los Alamos in 1975. He
worked in the Organic Analytical Chemistry Group from 1986 to 1995 and
was the former principal investigator of the DryWash project. In 1995,
he left the Laboratory to become the director of Isotag Research, where
he currently oversees the development of chemical bar-coding methods and
techniques for chemically tagging consumer products.

Jerome Barton has worked as a technician at Los Alamos for 21 years and
is now the senior technician at the Supercritical Fluids Facility. His
expertise lies in mechanics, practical designs, instrumentation, and
electronics.

Leah D. Bustos holds a B.S. in biology and chemistry from the College of
Santa Fe. She has worked as an organic analytical technician at the
Laboratory since 1987.

Leisa B. Davenhall joined the Laboratory in 1993 and has worked as a
technician in the Supercritical Fluids Facility since 1995. She is
experienced in method development and technical experimentation in
dense-phase gas research.

Dennis L. Hjeresen joined the Los Alamos technical staff in 1985 after
receiving his Ph.D. in neurobiology from the University of Washington in
1984. He currently serves as the supercritical fluids program manager.

W. Kirk Hollis leads the headspace gas analysis team at Los Alamos.
Hollis, a technical staff member who joined the Laboratory in 1993,
holds a B.S. in chemistry from New Mexico Institute of Mining and
Technology.

Matthew Roepcke began working at Los Alamos as a co-op student in 1996
during his Senior year at Pojoaque High School. He will attend new
Mexico Highlands University in the fall of 1997.

L. Dale Sivils received his Ph.D. in analytical chemistry from the
University of Missouri in 1995 and has worked as a technical staff
member at Los Alamos since 1995. His current research interests include
instrumentation development and studies of supercritical fluid
properties.

**Further Information**

For more information about DryWash, please contact the Civilian and
Industrial Technology Program Office, Los Alamos National Laboratory,
P.O. Box 1663, Mail Stop C331, Los Alamos, NM 87545.

Telephone (505) 665-9090

Fax (505) 667-0603

LALP-97-143 August 1997

Los Alamos

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