Drying In Closed Loop
The Polaris technology for drying in closed circuit is based on total or partial recycle of the gaseous stream used in the drying system, in order to optimise the recovery of the separated compounds and to minimise the flowrate of the effluent emitted by the drying system. Polaris has realised complete drying plants, in particular spray-drier for pharmaceutical industry, where particular conditions or product specifications are required (e.g. amorphous product), in presence of solvents, with integrated recovery of the separated solvents.
In other cases Polaris has realised the closed circuit and the integrated recovery system associated to an existing dryer at the customer facility. Several systems have been done on fluid bed dryers or tunnel dryers. Where possible, the achievement of the closed circuit allows less investment and operating costs. Where the system works in inert atmosphere, the closed circuit allows the almost total recovery of the nitrogen used.
Polaris has developed a process for the purification of gases at low temperature, based on distillation in two columns in series (one for more lighter compounds and the other for heavier compounds). The utilities for heating and cooling are supplied through an auxiliary nitrogen circuit, which, at different pressure levels, is condensed in the reboilers and evaporated in the condensers. The process is continuous and completely automated. The system can be combined with several typologies of pretreatment depending on the pollutants to be removed preliminarily.
Possible applications are:
- production of ultrapure gases
- argon recovery/purification
- oxygen recovery/purification
- carbon monoxide purification
- light hydrocarbons recovery/purification
Advantages of the process:
- low utilities consumption
- relatively low investment cost
- possible integration with the local existing nitrogen network
- the economicity of the system makes it applicable also for relatively low flow-rates (50 100 Nm3/h)