(85a) Polymer Solution Preheating to Achieve Steam Usage Reduction in Polymer Isolation By Precipitation Jets

Isolation of polymers from its solution (e.g. hydrocarbon solvents) can be achieved by direct contact with saturated steam, typically in a precipitation jet. Polymer precipitates out of the solution due to solvent evaporation by steam. During this heat exchange, steam condensation leads to a wet polymer powder. This moisture in the solid polymer needs to be removed in the subsequent drying operation to meet the finished product specifications for extrusion performance. The driving force for separating the moisture from the polymer particles is the concentration gradient with the drying medium and is controlled by the outward diffusion of the water from the powder. This makes the drying operation highly energy intensive and accounts for a major fraction of the manufacturing costs. Hence, a strong interest exists in improving the efficiency of dryers for reducing costs and carbon footprint.

In this work, we demonstrate a significant reduction in steam usage by preheating the polymer solution before feeding it into the precipitation jets. The preheating of the solution causes reduced moisture in the rein powder obtained in the precipitation jet. This moisture reduction in the polymer powder exiting the precipitation jets leads to lowering in energy requirement for powder drying in the post-drying stages. In an overall energy balance of the polymer isolation operation, we have demonstrated at least 10% reduction in energy usage through steam savings and consequently reduced the carbon footprint. Furthermore, we are able to improve the production efficiency due to the reduction in the requirement of steam/polymer weight ratio.