When you’re extracting solvent from Nitrocellulose based waste solvent and inks, it is important to distill under a relatively low controllable temperature range, ensuring that all of the conditions of temperature and dryness needed to start an exothermic reaction are not present at the same time.
Operating temperatures are a variable in industry, as different inks and coatings are normally used and cleaned with a variety of solvents with a wide range of boiling points. Low boiling flammable solvents such as alcohols, Ethyl Acetate and MEK are commonly used. These have a boiling point of less than 200°F (93°C), while new, high boiling, low VOC alternative solvents, such as some N-Methyl Pyrrolidone (NMP) based products, can have boiling points in excess of 400°F (200°C). This wide range of operating temperatures requires a high degree of versatility in a distillation system design.
A distillation system should incorporate several interlocked features to provide a safe, economical and efficient system, ideally suited to the specific requirements of Nitrocellulose. Any system used for this type of application should be controlled by a Programmable Logic Controller (PLC) for optimal operation and safety, and should include the following features:
Steep Wall Cone Design
For optimal efficiency, ease of use and safety, we would recommend a steep cone design for your waste receptacle. A steep cone, either immersed in a large oil bath or surrounded by a recirculating hot oil jacket, provides an ideal configuration because the rate of distillation is directly related to the heat transfer surface area between the heating media and the solvent.
The design of the steep cone means it is less subject to hot spots, where possible accumulation of dried nitrocellulose residue may exceed safe temperatures and cause a decomposition reaction. As a further measure, the cone can be fitted with a large, free flowing discharge gate valve at the bottom, thus making the removal of sludge an easy, safe and routine operation.
As the largest heat transfer surface area is toward the top of the cone, where most of the heat is required for distillation, the sludge concentrates at the bottom, where the small surface area provides less heat transfer, and consequently cooler temperatures, than in conventional flat or dished bottom designs.
Automatic Vacuum System
Regardless of the solvent you are using, we’d recommend a vacuum system, but it is vital with high boiling solvents above 230°F (110°C). A high performance liquid ring vacuum pump, can be effectively used to reduce the boiling point of the solvent to operate within a safe zone. When using high boiling point solvents, the operating temperature can be reduced up to 100°F (38°C) or more depending on the chemicals.
Having the vacuum in place creates a safer operating environment and actually increases the overall efficiency of the system, is less prone to foaming and fouling and reduces the warm up and cooling cycles.
Be sure to check back for the second part of this post, and in the meantime, if you wanted to discuss your distillation system or solvent recycling needs contact us by clicking the below button
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