Nitrocellulose is chemically an ester of Cellulose with Nitric Acid, and is commonly encountered in a variety of inks and coatings used throughout industry. The amount of Nitrocellulose used in a typical ink/paint system ranges from 2 to 30%, based on total solids content.
In our last post we looked at two of the five factors in choosing a safe distillation system for nitrocellulose, below are the other three factors to consider:
The pivotal area of concern when creating a safe distillation process is the controlling of temperatures within the critical zone limit below 230°F (110°C) with both precision and consistency.
An automatic solvent distillation system should control and monitor the temperatures in the vapor space, hot oil and the sludge; By using RTD (Resistance Thermal Devices), which are accurate to within 1 degree, the process can be controlled automatically with consistent and precise results.
For Nitrocellulose, the most important temperature to control is the sludge, and by monitoring and controlling this temperature accurately, the system can automatically prevent the reaction temperature from ever being reached by the sludge.
The system’s Programmable Logic Controller (PLC) program should allow only the distillation process to operate within a specified range, to avoid accidental changes by unauthorized personnel, this range should be password protected.
In the previous post we looked a steep cone designs, which can be enhanced by the use of self adjusting, low maintenance scrapers; These scapers continually sweep the inside surfaces to help the solids fall to the bottom, therefore preventing any material build up, which unchecked, can result in an exothermic reaction. The best scarper system to avoid this, should have a hub design, which would not restrict a thickened sludge to flow freely during the discharging operation.
Since a Nitrocellulose reaction could ignite in the presence of atmospheric oxygen,
an auto cool system should be installed as part of the system. When the sludge temperature has reached the predetermined level, indicating that system is ready to discharge, the Programmable Logic Controller (PLC) should automatically start an auto cool cycle, to rapidly cool the sludge to a safe discharge temperature (around 125°F / 50°C). When the aforementioned temperature is reached, the sludge can be discharged safely and disposed or handled in accordance with local environmental regulations and safety practises.
Depending on the system you choose, water quench may be an option in the distillation system in the unlikely event of a reaction; However, the majority of distillation systems are equipped with a pressure release valve on the distillation chamber, and with the introduction of water on an exothermic reaction would likely result in pressure and steam, thus should be considered a final measure.
In certain cases, where an appropriate distillation system is not equipped with the safety features required for this, adding oil or alkali to the Nitrocellulose material may reduce the risk of decomposition. For example adding soda ash (Na₂CO₃) or caustic soda (NaOH) you can create a chemical process with the Nitrocellulose, which thereby reduces the potential of both decomposition and a reaction.
Address these factors and you will be well on your way to selecting the right distillation system for you, here at Maratek we are solvent recycling experts and to learn more or discuss your needs click the below button.
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