Solvent-free degreaser

In its simplest form (as shown in Fig. la), a solvent vapor degreaser is a tank with a heat source to boil the solvent and a cool surface to condense the vapor in the upper section. The soiled articles are suspended in this air-free zone of solvent vapor. The hot vapor condenses onto the cool parts, dissolving oils and greases providing continuous rinse in clean solvent. 

Phosphate-Free and Solvent-Free Heavy-Duty Degreaser Composition... 

An airless enclosed vapor degreaser, where the environment is at ambient presstrre but does not contain atmospheric air (with oxygen and water), dries solvent from parts through vaporization into a solvent-free environment. 

SafeChem, a subsidiary of Dow, has developed a handling system for chlorinated solvents that allows them to be used in closed-loop degreasing systems. The Safe-Tainer system uses two dedicated double wall containers one to hold fresh solvent and the other used solvent. The containers are connected to the cleaning equipment with zero dead volume, leak-free connections that prevent spills, leaks or vapour emissions during use. Used solvent is collected for recycling and professional disposal of any residues. The system minimises solvent use and release to the environment. A study carried out by Dow during a trial in... 

Steel-sheet pressings have to be made free from organic lubricants used in the shaping process, and of iron oxides. Degreasing is effected either with solvents (c.g. trichloroethylene) or with alkaline solutions. Another method is based on annealing at about 750 C to burn off all the organic substances. 

Uses Solvent for skin care formulations, coatings, agrochems., thinners, cleaners, and degreasers extremely low surf. tens, to improve flow and wetting suitable for odorless alkyd/acrylic paints food-contact paper, rubber articles defoamer in food-contact paper/paperboard Features Minimizes VOC virtually HAPs-free Regulatory FDA 21CFR 172,882,172,884,176.180,176.210,177.2600, 178.3530, 178,3570, 178.3620(b), 178,3650, 573.680 40CFR 180.1001 (c)(e) SARA nonreportable Properties Odorless m.w. 171 sp.gr. 0.77 (15.6 C) dens. 6.40 Ib/gal (60 F) vise. 1.6 cP vapor pressure 0.8 mm Hg (20 C) b.p. 189-207 C flash... 

Of the solvent systems, trichloroethylene is the most efficient. The inserts are first tumbled in the solvent to remove the majority of the organic contaminants. To obtain a surface that is free from oils and grease, a vapour phase degrease is then used. When the inserts are flooded with vapour, the solvent immediately begins to condense on the insert surface and then run off, carrying with it in solution the last traces of organic contaminants. The volume of condensate, per insert, depends on ... 

Example 25-2 A process of degreasing metal furniture begins an operation. Initially, the air in the 20,000 dryer is free of solvent vapors. The ventilation rate in the dryer is 2,500 ft /min and there is a factor of safety K=4. The degreasing solvent evaporates at a rate 0.8ft /min. How long will it take for the concentration to reach 500 ppm ... 

But there is a "free" step in this process. It is ofvapor contact. This occurs because the parts fixtured in the basket are (probably) at ambient temperature prior to entry into the vapor degreaser. That means they are colder than the solvent in the vapor zone above the immersion sumps (see Figure 1.4). So solvent vapor condenses upon these part surfaces upon entry to this vapor zone - providing a pre-cleaning rinse. This is shown in Figure 1.17 and described in Chapter 1.6. 

But the secondary demand for cooling cannot be fulfilled with CTW. The reason is that it is not cold enough to condense any solvent (including perchloroethylene) such that air emitted at the top of the degreaser is adequately free of contamination. Refrigerated brine is necessary for the secondary cooling coil. 

The volume of solvent in the air vented from the externally sealed apparatus of Figure 2.29 is small. This is because the cleaning chamber (the volume within an open-top vapor degreaser) never releases its full contents of vapor. Only air saturated with solvent is released when the parts basket displaces it into the airlock on entry and entrains it on exit. The released volume is probably measured in cubic inches per cycle. Flowever, relative to the issues associated with solvent stability (Ref. 2, Chapter 11), it may be crucial to trouble-free operation. 

A second concern about managing adsorption beds that treat solvent-rich effluent from encbsed vapor degreasers is that the tiny vapor stream which bypasses the adsorbent granules increases the pollution level of the effluent. Bypass is also normal. It comes about because no packed bed is ever free of small channels through which vapor can exit without effectively contacting adsorbent material. Bypass is typically or more than a few percent of the volumetric flow, and may be less than 1 percent. 

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