Assessing operational stability in condensed-mode fluidized bed reactor for linear low density polyethylene production: Insights from a thermoregulating water valve malfunction analysis

Abstract

The reliability of thermal regulation systems is crucial for ensuring the stability of condensed-mode gas-phase fluidized bed reactors (FBRs) used in the production of linear low-density polyethylene (LLDPE). However, studies reporting on the practical industrial control engineering of such reactors relying on thermal equilibrium mechanisms are scarce. This study presents a thorough analysis of a hot thermoregulating water (TRW) valve-jamming incident and interprets the related phenomena and parameter changes. The effect of the catalyst activity and variations in the liquid-phase quantities on the TRW valve action are investigated in depth, and a general explanation is provided by analyzing typical distributed control system data trends and proven deductive reasoning. Results indicate that the polymerization stability is maintained by two thermal pathways. The first pathway is related to the latent (condensate)/sensible heat (gas) extraction and polymerization heat of the materials, and the second is associated with the TRW system, specifically the cold and hot TRW branches. These pathways exhibited synergistic bidirectional effects. Finally, a series of innovative measures are proposed for internal and external operations to fully prevent and respond to TRW valve malfunctions and maintain overall polymerization stability. This study enhances the dependability of linear low-density polyethylene production through advanced process optimization utilizing the Unipol prototype and offers perspectives on system engineering for polyethylene production processes.