Managing temperature fluctuations in a distillation column to reduce energy costs in VCM production
Challenge
The variability of final product quality in a VCM (cinyl chloride monomer) plant was being driven by fluctuations in temperature within one of the distillation columns. The regulation of temperature was managed by increasing or decreasing steam supply. However, the physical delay in the system was causing a cyclicality in temperature. The existing control system was insufficient to regulate the steam and temperature to maintain a stable final product quality, independent of plant load.
Solution
Arundo built a model that predicts the temperature in the column based on various parameters, including current temperature and steam flow. This model could then determine the correct amount of steam needed to achieve the desired temperature in the future, accounting for the physical system delay. This laid the foundation to test a Model Predictive Controller (MPC) in production, which would regulate the steam based on the desired future temperature.
Impact
The implementation of the solution resulted in an estimated USD 250,000 reduction in annual costs and significant upside benefits at a plant level. These benefits included reduced energy consumption, an increased Ethylene Dichloride (EDC) conversion rate, and a reduction in final product rework.
