464667 Flare Minimization for Simultaneous Turnaround Operations of Two Olefin Plants
When one olefin plant undergoes its shut-down operation, its flare minimization strategy is conducted as: (i) keep the minium number of furnace running by shuting down extra furnaces; meanwhile, reduce liquid inventories in tanks, drums, and columns; (ii) shut down the remaining furnaces and keep CGC (crack gas compressor) running with vapor recycles; meanwhile, vaporize liquid remains in tanks, drums, and columns; (iii) shut down CGC after recovering liquids and vapor inventory as much as possible; (iv) perform decommissioning for each facilities including left liquid discharge, vapor discharge, and nitrogen purge. For another plant performing its start-up operation, the general operating procedure includes: (i) perform nitrogen replacement with hydrocarbons; (ii) input liquids to columns to build up lthe vapor - liquid balance in various vessels; meanwhile columns are engaged in the full-reflux mode; (iii) start CGC with vapor recycles; meanwhile, precooling the chilling train and warm up columns; (iv) start up furances gradually; (v) gear up each column operation to their normal status.
In this paper, flare minimization opportunities coupling shutdown operating steps (ii) through (iv) together with start-up operating steps (ii) and (iii) are exploried. To study the feasibility of this coupling turnaround operation and calculate flare emission sources, plant-wide dynamic simulations for these two plants have been conducted. The developed duo-plant flare minimization strategy has been virtually tested and demonstrated. The obtained flare minimization strategies and simulation results provide an indepth understanding on synergies of two plant abnormal operations for flare minimization.
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