Single solvent vapor degreaser

In a single-solvent vapor degreaser (Figure 3.14), there is fluid transfer from the rinse sump to the cleaning sump as condensate overfills the rinse sump and flows over a weir (Figures 1.3 and 1.5) into the boil sump. 

In a single-solvent vapor degreaser only one temperature is involved — the normal boiling point of the solvent — and one need not control it because it cannot be exceeded unless the boil sump is empty of fluid. 

That in the single-solvent vapor degreasing process only operates when needed (batch mode), and produces... 

Integration of the batch-use distillation column into a single-solvent vapor degreaser and the continuous-use... 

Each open sump operates as a single-sump vapor degreaser, with a heater, primary and secondary condensing coils, and a freeboard zone to contain emission of solvents and to dry parts. 

The United States uses 160 billion gal of solvent each year.2 The largest single use is for vapor degreasing, followed by dry cleaning, then by immersion cleaning of parts. 

Azeotropic Degreasing Solvent—A specific composition of two or more solvents, which does not change in the liquid and vapor phases therefore, it behaves like a single solvent in a vapor degreaser and has a constant boiling point. 

Substitute another single solvent for use in an open-top vapor degreaser. This approach is covered in detail in Ref 2, where two independent approaches are implemented. 

One reason for this situation is that less change of process equipment (Figures 3.13) is required to replace vapor degreasing using single solvents with two Class II cosolvents, than is change required to replace a single solvent with two solvents with different characteristics. 

Figure 3.14 Single Solvent Open-Top Vapor Degreaser...

A second aspect of difference between the vapor degreaser used with single solvents and that used with cosolvents is the management of fluid transfer between the two sumps. 

In vapor degreasing with a single solvent, heat energy must be supplied to heat the liqirid solvent from ambient temperature to its normal boiling point, and then to change its phase to vapor. The former is known as sensible heat the latter is known as latent heat. It s thus with Class II and III cosolvent systems. The individual properties of each solvent affect the outcome heat balance. 

For reference, total energy values for single solvents in vapor degreasing are 1530 BTU/gal (n-propyl bromide), 1690 (trichloroethylene), 1830 (perchloroethylene), 1790 (methylene chloride), and 1780 (MEK) — somewhat less than for Class II cosolvents. 

Class IV cosolvent processes are simple. Cleaning work is done with them as if only a single solvent were involved. And, the Class IV cleaning process may be conducted in a standard NESHAP-compliant open-top vapor degreaser ° . That s simple ... 

The replacement proposed in Table 3.5 includes both a change in cleaning chemicals and a change in cleaning processes. The single solvents are normally used in an open-top vapor degreaser (Chapter 1) or an enclosed machine (Chapter 2). 

The cosolvent pair which replaces the single solvents is proposed to be used in two different processes. The SA cosolvent is proposed to be used in a cold cleaning process conducted in a sump at the boiling point of the RA cosolvent. The RA cosolvent is proposed to be vaporized from another sump and used to rinse the SA cosolvent from part surfaces and dry them by evaporation as is done in an open-top vapor degreaser. The proposed process is seen in Figure 3.12. 

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