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Technical Data
| Paratherm NF® Heat Transfer Fluid For Perc Distillation Units in Dry-Cleaning
Machines |
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Many dry-cleaning machines employ internal distillation units that are designed to regenerate spent "perc" dry cleaning fluid. The perc
is continuously refreshed, with little - if any - lost to the atmosphere.
Operation
Similar in design to double boilers, these "stills" typically contain an inner and outer shell. Heat transfer fluid is placed in the
annulus, between the inner and outer shells. Electric immersion heaters are located in the bottom of the annulus in the heat transfer
fluid.
The immersion heaters heat the fluid, and the fluid in turn gently and uniformly warms the inner shell. Heat from the inner shell
evenly brings the spent perc to its boiling temperature.
As the perc slowly boils, its vapors travel through the coils and are
condensed back to liquid form, leaving dirt behind.
The rejuvenated perc can then be automatically pumped back into service.
Heater Fouling
Conventional heat transfer fluids have been reported to completely foul the still's electric immersion heaters with hard, baked-on
carbon. This fouling is due to:
High heat flux - where the amount of heat produced at the surface of the heater is higher than the heat transfer fluid can handle without
degrading, and...
Circulation - where convection currents move the heat transfer fluid too slowly past the heater's surfaces (compared with forced
circulation).
In both cases, the fluid's molecules wind up lingering too long in contact with the surfaces of the immersion heaters.
As the fluid's skin temperature begins to rise, its smaller molecules begin to boil. And as skin temperatures rise further, chemical bonds
start breaking.
As the molecules degrade, a sooty, varnishy form of carbon is produced. This sticky carbon immediately adheres to the heater and
bakes on.
Heater Burnout
The layer of carbon becomes thicker, insulating the heater from the surrounding fluid. The control unit, sensing that the fluid is
cooling off, continues to provide electricity to the heater - less and less of which gets to the perc. The still's efficiency decreases
and less fresh perc is available.
Not able to release its full heat into the fluid, the internals of the heater rods become hotter and hotter and eventually, the rods
burn out.
Paratherm NF® Fluid
Widely used in solvent distillation equipment, the Paratherm NF® non-fouling,
non-toxic fluid is highly efficient, cost effective and
thermally stable.
Rated for service to 600°F, the crystal-clear NF fluid is non-fouling. It won't coat the unit's heaters with hard, baked-on
carbon deposits when severely overheated - unlike conventional heat transfer fluids.
This is particularly important with electrical
immersion heaters used in non-forced-circulation perc stills.
Toxicity/Safe Disposal
The odorless NF fluid is also completely non-toxic (it is food-grade). Easily disposed, the
NF fluid can be gathered using the
same simple techniques for spills of light lube oils. It can be safely combined with used lube oils and sent to the local motor oil
recycler - or burned for BTU value (EPA, citation 57FR21524).
Environmentally, the NF fluid has passed Bioassay with Rainbow trout, Gulf shrimp and freshwater shrimp.
Questions? We'd like to hear from you. Call toll-free, 800-222-3611 -- or fax or e-mail.
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| Note:
The information and recommendations in this literature are made in good faith and are believed to be correct as of the below date. You, the user or specifier, should independently determine the suitability and fitness of Paratherm heat transfer fluids for use in your specific application. We warrant that the fluids conform to the specifications in Paratherm literature. Because our assistance is furnished without charge, and because we have no control over the fluid's end use or the conditions under which it will be used, we make no other warranties-expressed or implied, including the warranties of merchantability or fitness for a particular use or purpose (recommendations in this bulletin are not intended nor should be construed as approval to infringe on any existing patent). The user's exclusive remedy, and Paratherm's sole liability is limited to refund of the purchase price or replacement of any product proven to be otherwise than as warranted. Paratherm Corporation will not be liable for incidental or consequential damages of any kind.
Some product names of companies found in Paratherm literature are registered trademarks. This statement is in lieu of individually noting each.
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