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CO2 Drycleaning Technology

Kanupriya Chaudhary (09)

Somya Tewari (15)

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CO2 drycleaning technology

The CO2 process is a sub-critical carbon dioxide based garment cleaning process that has been developed for use by commercial and retail dry-cleaners. CO2 is a non-flammable, non-toxic, colorless, tasteless, odorless naturally-occurring gas that, when subjected to pressure, becomes a liquid solvent. The CO2 used in the garment cleaning process is an industrial by-product from existing operations, such as production of ethanol by fermentation and anhydrous ammonia (fertilizer) production.

This process does not produce any new CO2 and, thus, does not contribute to global warming.

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How does CO2 work? Environmentally neutral, liquid carbon dioxide

(CO2) has excellent cleaning properties. It dissolves dirt, fats and oils on all materials currently dry-cleaned. Thanks to its low surface tension and viscosity it easily penetrates garment fibres

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Procedure of cleaning using CO2?1. The laundry is placed in the washing chamber of the

machine. The chamber is emptied of air.2. The pressure in the washing chamber is raised by

injecting gaseous CO2. Then, liquid CO2 is pumped into the washing chamber.

3. Agitation is achieved by jet streams and/or by a rotating basket. The cleaning cycle lasts about 5 to 15 minutes and the whole process takes place at ambient temperature.

4. The liquid CO2 goes easily into the fibers of the clothes and dissolves dirt, fats, and oils. During the washing cycle a filter cleans particles from the liquid.

5. At the end of the cleaning process, the liquid CO2 is pumped back into the storage tank.

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Procedure of cleaning using CO2? Contd..6. With the compressor, the remaining gaseous CO2 is

pumped back into the storage tank lowering the pressure in the cleaning chamber. On its way to the storage vessel the gas is chilled and once again condensed into its liquid form.

 7. When the pressure is low enough, the remaining

CO2 is vented to the atmosphere and the door can be opened.

8. The clean garments are completely dry and at room temperature. They can be taken immediately for finishing work.

9. The CO2 is regularly cleaned by distillation.

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Machines used

Sailstar CD 60 features a fully rotating drum and an inverter

drive that allows variable wash speeds. The complete cycle, including the cleaning,

rinsing, drying and distillation takes 25-30 minutes, so it can process two full loads per hour.

That is a total production of up to 54 kg per hour, making the SailStar CO2 dry cleaning machine very cost effective to operate.

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Chemical and physical properties of CO2?

Kauri butanol value (Kb). This measures the cleaning power of the solvent. The higher the Kb, the more aggressive the solvent.

Surface Tension. This is a measure of the ability to wet a fabric. The lower the surface tension, the easier it is to wet a fabric.

Viscosity. This measures a solvent’s ability to flow. The lower the viscosity, the easier the solvent can ‘flow’ within fibres of a fabric.

Solubility in water. Generally, the more soluble a solvent is in water, the easier it is to remove water-soluble stains.

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Cost effectiveness of the process?

Is it cost effective?Since the complete cycle, including the cleaning, rinsing, drying and distillation, is faster in dry cleaning machines using traditional solvents, the CO2 Dry Cleaning machine can process two full loads per hour, making such dry cleaning machines very cost effective to operate.

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How does the cleaning performance compare with PERC? Tests run by independent agencies have

shown the cleaning performance of CO2 (Cleaning Process) with detergents to be equivalent to the cleaning performance of Perc with detergents. The only stains that showed a slight difference in cleaning performance were dirty motor oil and lipstick. However, these stains could be pre-spotted or post-spotted for complete stain removal

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Drawbacks of PERC What’s actually wrong with PERC? 

The primary concerns about PERC have been its potential toxicity to people working in the industry, to the people living above or adjacent to dry cleaning operations, to the general public that wear the dry cleaned clothes, and to groundwater contaminated with PERC. The EPA classifies PERC as being between a B and a C; that is, it is a possible carcinogen, but it is not a probable carcinogen.

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Benefits of CO2 technology Eliminates exposures to PERC. Cleans effectively with no unpleasant odors. Treats garments gently. Eliminates the risk of groundwater contamination from conventional

drycleaning solvents. Utilizes a traditional rotating basket design which is gentle to

fabrics. Eliminates the risk of heat-related damage or heat-setting of stains,

as there is no drying cycle. Costs less to operate than today's PERC systems, thereby allowing

drycleaning operators to offer the same prices to customers and improve their operating margins.

Requires a 35 to 45 minute cleaning cycle for a 60-pound load -- faster than traditional 'dry-to-dry' processes.

Eliminates the time and money that operators typically must spend to comply with environmental and safety regulations associated with the use of PERC and petroleum.

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References Professional Wet Cleaning Equipment Report

pdf http://www.textilecleaning.com/index.htm http://www.stitchworld.net/default1.asp?

nextRow=320&sPage=33&cat=3&e= http://smartconcepts0.tripod.com/id9.html http://www.epa.gov/dfe/pubs/garment/lcds/

misb.pdf