Cleaning and liquid contact with solids – Processes – With treating fluid motion
Patent
1993-12-30
1999-11-09
El-Arini, Zeinab
Cleaning and liquid contact with solids
Processes
With treating fluid motion
134 37, 134 251, 1341022, 134105, 134108, 134109, 134 11, 134 7, B08B 300
Patent
active
059806486
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for cleaning workpieces exhibiting organic residues, with the use of a fluid introduced under pressure into a pressure tank loaded with the workpieces.
In a process for cleaning workpieces of various materials contaminated with residues of oil, grease, lubricant, etc., as known from WO 90 06 189, a gas compressed to its supercritical pressure or thereabove is conducted onto the workpieces to be cleaned in a pressure tank. Subsequently, the temperature of the thus-compressed gas is varied, starting with a point in the proximity of the critical temperature, in various steps, in order to influence the dissolving properties of the gaseous phase. Before each change, the temperature is kept constant for a specific time interval. Cleaning of the workpieces can furthermore be additionally enhanced by introducing into the compressed gas a liquid, such as deionized water, a chemically reactive compound, or sound or radiation energy.
The above-described measures enhancing the cleaning of the workpieces require technically expensive extra equipment and furthermore show little effectiveness. The costs to be expended are not justified by increased cleaning efficacy.
The process according to WO 90 06 189 additionally necessitates great expenditure with respect to regulating technique. The individual steps wherein the temperature is altered succeed one another at a time interval of about 10 minutes. In the meantime, the temperature must be kept constant. Consequently, care must be taken that, within a minimum time, in each case a new temperature must be set and then maintained constant in a large pressure vessel. The expensive equipment needed for this purpose, not described in any detail in WO 90 06 189, renders such a cleaning process less than attractive for industrial application.
A further drawback of this process occurs during emptying of the pressure tank. The gas mass compressed to supercritical pressure contains the residual compounds in solution after the cleaning step. In order to avoid settling of these residual compounds in the pressure tank during the removal of this mass of gas from the pressure tank, the pressure and temperature of the mass of gas must be kept constant while it is removed. For this purpose, pure gas compressed to supercritical pressure is replenished while the contaminated gas is discharged from the pressure tank. Only after the entire content of the tank consisting of contaminated gas has thus been removed is it possible to lower the pressure and to take out the workpieces. In this process, it is highly probable that the contaminated gas mass has merely been diluted, rather than replaced, and that during lowering of the pressure the remaining, dissolved residual compounds will again be precipitated. Additionally, exchanging of the entire content of the tank after each cleaning step is not economical.
Therefore, the invention is based on the object of developing a process for cleaning workpieces contaminated with organic residues with the use of a fluid, avoiding the aforementioned disadvantages and increasing the success of the cleaning procedure in an economical fashion.
This object has been attained according to the invention by circulating the fluid in the pressure tank during the cleaning step.
The process of this invention represents a simple measure considerably enhancing the cleaning operation. The fluid, understood to mean a gaseous, liquid or also supercritical substance, is mechanically circulated in the pressure tank, for example, by the rotation of a vane-equipped impeller. The thus-initiated flow of fluid in the pressure tank brings about a continuous exchange of pure fluid and of fluid loaded with dissolved impurities. Thereby, the organic residues adhering to the workpiece surfaces can be successively removed in their entirety.
In order to vary the flow profile in the pressure tank with time, the circulating velocity is advantageously varied during the cleaning step. This change can take place, for example, by cyclically varying the number
REFERENCES:
patent: 3900551 (1975-08-01), Bardoncelli et al.
patent: 4944837 (1990-07-01), Nishikawa et al.
patent: 5174917 (1992-12-01), Monzyk
patent: 5213619 (1993-05-01), Jackson et al.
patent: 5306350 (1994-04-01), Hoy et al.
El-Arini Zeinab
Union Industrie Comprimierter Gase GmbH NFG. KG
LandOfFree
Cleaning of workpieces having organic residues does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Cleaning of workpieces having organic residues, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Cleaning of workpieces having organic residues will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1450492