Cleaning Clothes & Fabrics with Carbon Dioxide and the Solvair Hybrid System
How the Liquid CO2 Process Works
Traditional drycleaning systems use perc or petroleum-based chemicals as the primary cleaning solvent–with additives and detergents. Wetcleaning utilizes water as its primary solvent. The liquid CO2 process employs liquid CO2 as the primary solvent, with recyclable cleaning agents.
Carbon dioxide is a naturally occurring and generally benign substance. At room temperature, CO2 can exist in the form of a gas and is therefore used to carbonate soft drinks and other beverages. In solid form, carbon dioxide is known as dry ice. At room temperature, CO2 can also exist as a liquid if kept in a closed system at an elevated pressure. Liquid CO2 has a gas-like consistency and a low surface tension allowing it to function as a very effective cleaning medium when combined with detergents.
The Micare™ system uses a large conventional rotating basket with a detergent system. The system utilizes a specially designed, 60-pound capacity MICO2™ machine that houses liquid CO2. It is similar to today’s front-load, mechanical action machines and features gentle wash and extract cycles.
A detergent system (containing patented cleaning agents) enhances the cleaning ability of the liquid CO2, allowing it to remove soils from the garments. After the cleaning cycle, the machine pulls the mixture of liquid CO2 and cleaning agents (i.e., the wash fluid) away from the clothes and then cleans and reuses the solution. The Micare™ process does not require heating of the clothes and is therefore gentle to fabric.
Specifically, the Micare™ System works in the following stepwise fashion:
- Approximately 60 pounds of garments are placed inside a large rotating basket in the MICO2™ machine and the door is closed, sealing the system. Vacuum is applied to remove the majority of the air in the system and CO2 gas is added to pressurize the wash tank.
- Liquid CO2 is then added from the storage tank along with the Micare™ detergent system in order to form the wash fluid. The clothes are agitated for a pre-set time period and with a selected degree of agitation depending on the nature of the garments (e.g., delicate, normal, and heavy cycles). Similar to perc drycleaning machines, the wash fluid is circulated out of the wash tank through a lint filter to capture loose fibers and vestige lint. It then passes through a carbon filter and returns to the wash tank. At this point, the wash cycle is complete.
- The liquid CO2 and detergent mixture (i.e., the wash fluid) is pumped out of the wash tank to the storage tank. The excess wash fluid (that fluid left clinging to the garments) is further removed by a spin extract cycle. A portion of the wash fluid is then cleaned via a distillation process that removes excess dirt and detergent. The residue from the distillation process is automatically eliminated from the machine and collected for shipment back to Micell for recycling. Carbon dioxide gas is removed from the wash tank using a compressor and the gas is sent back to the storage tank for reuse. The Micare™ system is able to efficiently convert CO2 from a gas to a liquid, thereby permitting 98 percent of the CO2 to be recycled. A nominal amount (10 lbs) of CO2 gas is then vented to the atmosphere.
- After a cycle time of 35 to 45 minutes, the cleaned garments are removed from the wash tank.
Environmental, Safety, and Health Impacts
Carbon dioxide is a naturally occurring and generally benign substance that is routinely ingested in food products such as soft drinks. The use of liquid CO2 technology allows consumers and machine operators to avoid exposure to traditional drycleaning solvents. A company named “NuCo2″ supplies liquid CO2 to Micell’s professional clothes cleaning customers. The MicareTM system uses the same beverage-grade bulk CO2 that NuCo2 delivers to more than 50,000 restaurants and other fountain beverage dispensers located across the nation.
Environmental stewardship is one of the hallmarks of the Micare™ system. The residue generated by the MicareTM system distillation process (i.e., the liquid CO2 cleaning and reuse process) is returned to Micell Technologies for recycling or recovery. Even though CO2 and the MicareTM system chemistry are environmentally benign, the MICO2™ cleaning machine has multiple safeguards and process controls that minimize the potential for leaks and spills. The Micare™ system produces no hazardous waste, eliminates exposures to traditional drycleaning solvents, and does not use ozone-depleting compounds.
Because the MicareTM system liquid CO2 is stored under pressure, the MICO2™ machine is designed and constructed in accordance with the American Society of Mechanical Engineers (ASME) code for pressurized vessels and systems. In addition, Micell has considered all applicable National Fire Protection Association (NFPA) and Occupational Safety and Health Administration (OSHA) guidelines.
All MICO2™ machine components that hold liquid CO2 over long time periods have relief devices which protect the system against over-pressurization. In addition, automated control logic maintains safe operating conditions and the MICO2™ machine is self-regulating through redundant levels of safeguards and relief devices. Operating pressure for the MICO2TM machine is actually lower than that associated with various commercial equipment such as scuba gear and welding gas systems.
Insurance underwriters have insured MicareTM systems (in commercial use) through a 100 dollar per year rider on the boiler policy. This insurance cost is lower than coverage commonly necessary for traditional drycleaning processes.
