INDUSTRIAL CHALLENGES OF HDPE FLUID BED DRYING IN DIFFERENT GRADES

چکیده مقاله

Knowing of challenges in drying of HDPE is very essential to improve the process. In this work, the polymer in terms of production with densities of 940 kg/m3 or higher is produced by slurry polymerization technique using CSTR reactors. Raw materials include ethylene, hydrogen, hexane, butene and Ziegler-Natta catalyst. The slurry product is separated by a decanter (20-30% residual hexane) and a 2-stage fluidized bed dryer where wet powder is dried further down to 0.1% residual hexane content. Acceptable drying process needs proper fluidization wheras, study of this hydrodynamic behaviour is a complex work as such it’s understanding and mathematical modelling remains a challenge to date and it relies heavily on collection of meaningful empirical processing plant data. Drying of particles is commonly carried out using fluidized bed dryers in HDPE plants where their performance evaluation depends mainly on particles behavior and flow pattern. Understanding factors affecting gas-particle flow regime is important for reaching the process with good efficiency. Double-cyclones have commonly been employed to improve separation and prevent powder being transferred to vulnerable plant locations along the drying path including distributer plate, scrubbing tower trays and blowers impellers. This assists to describe flow patterns and further reduces particle agglomeration leading to less energy consumption in blowers. Different aspects of factors affecting the drying process in the plant capable of handling a wet feed of 56000 kg/hr (40000 kg/hr dry polymer of various grades including PE100, BL3 and EX5 and 16000 kg/hr hexane) are investigated.