Polaris is leader in high performances cryogenic condensation systems, having developed an efficient and reliable technology also for complex applications, getting maximum advantages of the great potential of cryogenic treatment, thanks to proprietary patented heat exchangers which are characterised by high fractionating capacity of vapours and gases. The technology of vapor recovery is particularly suitable for Vent Gas Condensation (VGC) applications, for VOC abatement. The process is based on cooling of the effluent to very low temperatures, using liquid nitrogen or other cryogenic fluid as source of cold, separating the pollutants by decreasing the vapour pressure as function of vapour/liquid and vapour/solid equilibrium.
The effluent to be treated, polluted by more or less volatile organic/inorganic compounds, is progressively cooled in the condensers, below dew point of the mixture, where the pollutants are condensed and separated as far as physically possible. Due to the very low temperature of coolant, the skin temperature of the condenser can be lower than melting point of the compounds to be condensed, and consequently there is some formation of solid on the heat exchange surface. For this reason the condensers are designed and built with a special configuration that allows the formation of solids without any negative impact on the overall process performances. If the residual concentration of the pollutants in the effluent at condensation conditions still results more than the allowed emission limits, the cooling is carried out to lower temperature as necessary, in order to get vapor recovery and pressure reduction decrease based on sublimation equilibrium.
In cryogenic condensation conditions the surface is covered by solid organic aerosols, which are intentionally kept inside the Polaris plant in order to avoid the emission to atmosphere, that would nullify the achievement of the required purification level. After some time (6 to 12 hours usually) the heat exchange rate progressively decreases and the pressure drop increases, and the condenser must be regenerated by heating the same in order to defrost it. If the process is continuous, a second condenser must be used, already ready for service in stand-by.
The check of the system performances during the operative cycle, and consequent the effectiveness of the treatment, is ensured by the control and monitoring of the effluent temperature in condensation phase, which is verified during commissioning and validation of the system, and then kept at reasonably lower levels. The reliability of the processa, again ideal for VOCÂ abatement, is ensuredÂ by the plant control system, that can constantly check the correct process conditions, detect any malfunction and eventually promptly put in service the stand-by condensation line.