2002 Progress Report: Superheated Water and Steam Degreasing of Working Stocks, Parts, and Equipment in Machining, Manufacturing and Production Processes and OperationsEPA Grant Number: R828246
Title: Superheated Water and Steam Degreasing of Working Stocks, Parts, and Equipment in Machining, Manufacturing and Production Processes and Operations
Investigators: Weber, Walter J.
Institution: University of Michigan
EPA Project Officer: Hahn, Intaek
Project Period: September 1, 2000 through August 31, 2003 (Extended to August 31, 2004)
Project Period Covered by this Report: September 1, 2001 through August 31, 2002
Project Amount: $320,000
RFA: Technology for a Sustainable Environment (1999) RFA Text | Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , Sustainability
Greases, lubricating oils, and similar organic preparations are ubiquitous in virtually all machine-element related processes and operations. Chlorinated organic solvents or extremely harsh aqueous-based reagents typically have been used for degreasing operations. They are recognized widely as hazardous to both the environment and to human health. In this project, the development of alternative degreasing methods that employ essentially pure water are being explored—specifically, the superheated liquid and steam states of water. These environmentally benign solvent media have significant potential for beneficial use in a wide variety of degreasing and decoating applications. The objectives of this research project are to: (1) evaluate the efficacy of using superheated water and steam (SHWS) for degreasing surfaces; (2) characterize and investigate the separation and recycling of water and grease; (3) investigate the use of salts, surfactants, and other complexing agents to SHWS systems; and (4) demonstrate the general applicability of the SHWS degreasing systems by evaluating their effectiveness for a wide variety of greases and materials.
A wide variety of greases have been employed to accomplish the objectives, based on their types of components (e.g., base oils and thickeners). Accomplishments include the development of a reliable analytical method to evaluate grease removal efficiency using Horizontal Attenuated Total Reflectance Fourier Transform Infrared (FTIR) spectroscopy and analyzing SHWS degreasing effectiveness for a wide variety of greases and lubricating oils. Water pressure did not exhibit a noticeable effect on the removal efficiency for grease materials tested, but increasing operating temperature remarkably improved the removal of grease materials. Because the dielectric constant decreases with increasing temperature, the water becomes similar to hydrophobic solvent, which can effectively solubilize hydrophobic grease materials. Experiments for the optimization of operation time are in progress, but preliminary data support the removal efficiencies approaching a maximum point at which no more significant increase of efficiency was observed. This observation suggests that the superheated water system needs to be optimized with respect to the operation time to obtain a process-efficient and cost-effective treatment system. Steam treatment was more or less effective than superheated water depending on characteristics and properties of base oils, thickeners, and additives of grease materials. Those results suggest the need for the optimized combination of SHWS treatments to achieve the best removal efficiency.
Experimental work in the next reporting period will be focused on Objectives 2, 3, and 4. Separation techniques such as centrifugation and flash vessels currently are being developed to separate the grease materials from water. The water and grease materials then will be analyzed either by grease manufacturers or by available analytical instruments (e.g., gas chromatography/mass spectrometry, liquid chromatography/mass spectrometry, FTIR, etc.) to determine any characteristic and property changes and the possibility of recycling. Afterwards, surfactants, salts, ethylenediaminetetraacetic acid and salts, and other complexing agents will be added to explore their effects on grease removal efficiency associated with superheated water and/or steam. Finally, various types of metal parts, such as chrome, will be examined in addition to stainless steel.