Double Cone (DC) vacuum dryers are batch-drying systems that are gentle on products from both a thermal and physical point of view. They are widely used for drying solids such as pharmaceuticals, metals, catalysts, polymers and even some high-value food ingredients. DC dryers are closed environments. They are inherently safe for processing toxic products and are one of the most energy-efficient forms of indirect batch drying.
DCs are ideal for processing delicate and free-flowing solids such as powders, agglomerates, and crystalline particles. DCs generally do not have any internal agitators, instead relying on the tumbling action of the double cone, which means they are relatively gentle on the product.
DC vacuum dryers are not only gentle on shear-sensitive products; they are also gentle on temperature-sensitive products. Drying is about putting energy into the water or solvent in your product so that it will evaporate, leaving only the solids behind.
DC Dryers input heat indirectly by circulating thermal fluid (oil, water, or steam) through a heating jacket. This heats the cone surfaces, which are in contact with your product. The heating fluid can be supplied either by integrating existing site sources or by a stand-alone heating and temperature control unit.
Your product may suffer from degradation beyond a certain temperature point, and as a result, the dryer will be limited in the rate of heat transfer it can achieve while remaining below this limiting temperature. This temperature limit will increase drying times. That is where the vacuum comes in. Drawing a vacuum will increase the driving force of the water or solvent to evaporate. Lower pressures in the DC, as well as the removal of the vapour, will allow you to dry at lower temperatures without requiring excessively long drying times.
Usually, a liquid-ring pump system creates a vacuum when drying water or solvents. The liquid seal will usually be water, but if the process requires it, then the sealing fluid can also be another solvent. Occasionally, a simpler dry vacuum pump system can be used, which will allow vapour to pass through without contacting or being collected by a sealing fluid.
The process may require the evaporated water or solvent to be recovered. This is often the case when the solvent is toxic or valuable. Solvent recovery requires a condenser to be placed in the vapour stream from the dryer before the vacuum system.
Among other things, customising the system for a particular process involves selecting the right materials for construction, seal type, vacuum pump type and solvent recovery requirements. Loading and discharging systems can be automated for speed, containment, and safety.