Effects of Fluid Dynamics on Cleaning Efficacy of Supercritical Fluids
Effects of Fluid Dynamics on Cleaning Efficacy of Supercritical Fluids

Author:

Publisher:

Published: 1993

Total Pages: 18

ISBN-13:

DOWNLOAD EBOOK

Pacific Northwest Laboratory (PNL) and Boeing Aerospace Company are developing a process to clean metal parts using a supercritical solvent. This work is part of an effort to address issues inhibiting the rapid commercialization of Supercritical Fluid Parts Cleaning (SFPC). PNL assembled a SFPC test stand to observe the relationship between the fluid dynamics of the system and the mass transfer of a contaminant from the surface of a contaminated metal coupon into the bulk fluid. The bench-scale test stand consists of a Berty'' autoclave modified for these tests and supporting hardware to achieve supercritical fluids parts cleaning. Three separate sets of tests were conducted using supercritical carbon dioxide. For the first two tests, a single stainless steel coupon was cleaned with organic solvents to remove surface residue, doped with a single contaminant, and then cleaned in the SFPC test stand. Contaminants studied were Dow Corning 200 fluid (dimethylpolysiloxane) and Castle/Sybron X-448 High-temperature Oil (a polybutane/mineral oil mixture). A set of 5-minute cleaning runs was conducted for each dopant at various autoclave impeller speeds. Test results from the first two sets of experiments indicate that precision cleaning for difficult-to-remove contaminants can be dramatically improved by introducing and increasing turbulence within the system. Metal coupons that had been previously doped with aircraft oil were used in a third set of tests. The coupons were placed in the SFPC test stand and subjected to different temperatures, pressures, and run times at a constant impeller speed. The cleanliness of each part was measured by Optically Stimulated Electron Emission. The third set of tests show that levels of cleanliness attained with supercritical carbon dioxide compare favorably with solvent and aqueous cleaning levels.

Supercritical Fluid Cleaning
Supercritical Fluid Cleaning

Author: Samuel P. Sawan

Publisher: Elsevier

Published: 1998-12-31

Total Pages: 307

ISBN-13: 0815519168

DOWNLOAD EBOOK

Although supercritial fluid (SCF) technology is now widely used in extraction and purification processes (in the petrochemical, food and pharmaceuticals industries), this book is the first to address the new application of cleaning. The objective is to provide a roadmap for readers who want to know whether SCF technology can meet their own processing and cleaning needs. It is particularly helpful to those striving to balance the requirements for a clean product and a clean environment. The interdisciplinary subject matter will appeal to scientists and engineers in all specialties ranging from materials and polymer sciences to chemistry and physics. It is also useful to those developing new processes for other applications, and references given at the end of each chapter provide links to the wider body of SCF literature. The book is organized with topics progressing from the fundamental nature of the supercritical state, through process conditions and materials interactions, to economic considerations. Practical examples are included to show how the technology has been successfully applied. The first four chapters consider principles governing SCF processing, detailing issues such as solubility, design for cleanability, and the dynamics of particle removal. The next three chapters discuss surfactants and microemulsions, SCF interaction with polymers, and the use of supercritical carbon dioxide (CO2) as a cleaning solvent. The closing chapters focus on more practical considerations such as scaleup, equipment costs, and financial analysis.

Precision Cleaning with Supercritical Carbon Dioxide for the Elimination of Organic Solvents and the Reduction of Hazardous Wastes
Precision Cleaning with Supercritical Carbon Dioxide for the Elimination of Organic Solvents and the Reduction of Hazardous Wastes

Author:

Publisher:

Published: 1994

Total Pages: 16

ISBN-13:

DOWNLOAD EBOOK

Private and governmental industrial facilities use chlorofluorocarbons and chlorocarbons for the cleaning of a variety of items. The Montreal Protocol (1987) and amendments to this act will phase out the use of chlorofluorocarbons, or CFCs, by the year 2000 because they are toxic, carcinogenic, and implicated in the depletion of the Earth's ozone layer. The United States has pledged to eliminate these substances by 1995. To stay competitive in the global market, US industries require an economical replacement. Supercritical fluids, which have been used in food, fragrance, and petroleum processes for years, are attractive replacement solvents because of their low environmental impact, high diffusivities, low viscosities, and temperature-pressure dependence of solvent strengths. In the case of nontoxic and nonflammable carbon dioxide (CO2), its critical temperature and pressure are readily accessible with well-established process technology and equipment. In addition, applications using a supercritical fluid such as CO2 are generally safer and environmentally benign. Extractions using supercritical CO2 use less energy than distillation and incineration processes and are less expensive than liquid extraction processes using toxic and costly organic solvents. Finally, CO2 has a very high volatility compared to virtually any organic extractant which facilitates its separation from extract solutions for extract recovery and CO2 recycle. Data will be presented on the successful removal of cutting and machine oils, silicone oils, body oils, and hydraulic fluids from a variety of industrial substrates with supercritical CO2 to, at, or below precision cleaning levels (less than 10 micrograms of contaminant per square centimeter of surface). The applicability of this technique to commercial operations was evaluated in this area of contaminant removal, surface interactions, operational costs, and waste reduction and elimination.